Numerical simulation of magma chamber dynamics.

NASA Astrophysics Data System (ADS)

Longo, Antonella; Papale, Paolo; Montagna, Chiara Paola; Vassalli, Melissa; Giudice, Salvatore; Cassioli, Andrea

2010-05-01

Magma chambers are characterized by periodic arrivals of deep magma batches that give origin to complex patterns of magma convection and mixing, and modify the distribution of physical quantities inside the chamber. We simulate the transient, 2D, multi-component homogeneous dynamics in geometrically complex dyke+chamber systems, by means of GALES, a finite element parallel C++ code solving mass, momentum and energy equations for multi-component homogeneous gas-liquid (± crystals) mixtures in compressible-to-incompressible flow conditions. Code validation analysis includes several cases from the classical engineering literature, corresponding to a variety of subsonic to supersonic gas-liquid flow regimes (see http://www.pi.ingv.it/~longo/gales/gales.html). The model allows specification of the composition of the different magmas in the domain, in terms of ten major oxides plus the two volatile species H2O and CO2. Gas-liquid thermodynamics are modeled by using the compositional dependent, non-ideal model in Papale et al. (Chem.. Geol., 2006). Magma properties are defined in terms of local pressure, temperature, and composition including volatiles. Several applications are performed within domains characterized by the presence of one or more magma chambers and one or more dykes, with different geometries and characteristic size from hundreds of m to several km. In most simulations an initial compositional interface is placed at the top of a feeding dyke, or at larger depth, with the deeper magma having a lower density as a consequence of larger volatile content. The numerical results show complex patterns of magma refilling in the chamber, with alternating phases of magma ingression and magma sinking from the chamber into the feeding dyke. Intense mixing takes place in feeding dykes, so that the new magma entering the chamber is always a mixture of the deep and the initially resident magma. Buoyant plume rise occurs through the formation of complex convective patterns, giving origin to a density-stratified magma chamber.

Combustion performance and scale effect from N2O/HTPB hybrid rocket motor simulations

NASA Astrophysics Data System (ADS)

Shan, Fanli; Hou, Lingyun; Piao, Ying

2013-04-01

HRM code for the simulation of N2O/HTPB hybrid rocket motor operation and scale effect analysis has been developed. This code can be used to calculate motor thrust and distributions of physical properties inside the combustion chamber and nozzle during the operational phase by solving the unsteady Navier-Stokes equations using a corrected compressible difference scheme and a two-step, five species combustion model. A dynamic fuel surface regression technique and a two-step calculation method together with the gas-solid coupling are applied in the calculation of fuel regression and the determination of combustion chamber wall profile as fuel regresses. Both the calculated motor thrust from start-up to shut-down mode and the combustion chamber wall profile after motor operation are in good agreements with experimental data. The fuel regression rate equation and the relation between fuel regression rate and axial distance have been derived. Analysis of results suggests improvements in combustion performance to the current hybrid rocket motor design and explains scale effects in the variation of fuel regression rate with combustion chamber diameter.

IACP (INTEGRATED AIR CANCER PROJECT) EMISSIONS: TRANSFORMATIONS AND FATE

EPA Science Inventory

As part of the Integrated Air Cancer Project (IACP), diluted emissions from wood stoves and automobiles were injected into a Teflon smog chamber and irradiated to simulate their photochemical transformation in the atmosphere. Changes in the chemical composition and physical prope...

Numerical analysis of temperature field in the high speed rotary dry-milling process

NASA Astrophysics Data System (ADS)

Wu, N. X.; Deng, L. J.; Liao, D. H.

2018-01-01

For the effect of the temperature field in the ceramic dry granulation. Based on the Euler-Euler mathematical model, at the same time, made ceramic dry granulation experiment equipment more simplify and established physical model, the temperature of the dry granulation process was simulated with the granulation time. The relationship between the granulation temperature and granulation effect in dry granulation process was analyzed, at the same time, the correctness of numerical simulation was verified by measuring the fluidity index of ceramic bodies. Numerical simulation and experimental results showed that when granulation time was 4min, 5min, 6min, maximum temperature inside the granulation chamber was: 70°C, 85°C, 95°C. And the equilibrium of the temperature in the granulation chamber was weakened, the fluidity index of the billet particles was: 56.4. 89.7. 81.6. Results of the research showed that when granulation time was 5min, the granulation effect was best. When the granulation chamber temperature was more than 85°C, the fluidity index and the effective particles quantity of the billet particles were reduced.

WE-G-BRA-04: The Development of a Virtual Reality Dosimetry Training Platform for Physics Training.

PubMed

Beavis, A; Ward, J

2012-06-01

Recently there has been a great deal of interest in the application of Simulation methodologies for training. We have previously developed a Virtual Environment for Radiotherapy Training, VERT, which simulates a fully interactive and functional Linac. Patient and plan data can be accessed across a DICOM interface, allowing the treatment process to be simulated. Here we present a newly developed range of Physics equipment, which allows the user to undertake realistic QC processes. Five devices are available: 1) scanning water phantom, 2) 'solid water' QC block/ion chamber, 3) light/ radiation field coincidence phantom, 4) laser alignment phantom and 5) water based calibration phantom with reference class and 'departmental' ion chamber. The devices were created to operate realistically and function as expected, each has an associated control screen which provides control and feedback information. The dosimetric devices respond appropriately to the beam qualities available on the Linac. Geometrical characteristics of the Linac, e.g. isocentre integrity, laser calibration and jaw calibrations can have random errors introduced in order to enable the user learn and observe fault conditions. In the calibration module appropriate factors for temperature and pressure must be set to correct for ambient, simulated, room conditions. The dosimetric devices can be used to characterise the Linac beams. Depth doses with Dmax of 15mm/29mm and d10 of 67%/77% respectively for 10cm square 6/15MV beams were measured. The Quality Indices (TPR20/10 ratios) can be measured as 0.668 and 0.761 respectively. At a simple level the tools can be used to demonstrate beam divergence or the effect of the inverse square law; They are also designed to be used to simulate the calibration of a new ion chamber. We have developed a novel set of tools that allow education of Physics processes via simulation training in our virtual environment. Both Authors are Founders and Directors of Vertual Ltd, a spin-out company that exists to commericalise the results of the research work presented in this abstract. © 2012 American Association of Physicists in Medicine.

Atmospheric cloud physics thermal systems analysis

NASA Technical Reports Server (NTRS)

1977-01-01

Engineering analyses performed on the Atmospheric Cloud Physics (ACPL) Science Simulator expansion chamber and associated thermal control/conditioning system are reported. Analyses were made to develop a verified thermal model and to perform parametric thermal investigations to evaluate systems performance characteristics. Thermal network representations of solid components and the complete fluid conditioning system were solved simultaneously using the Systems Improved Numerical Differencing Analyzer (SINDA) computer program.

Simulation of the GEM detector for BM@N experiment

NASA Astrophysics Data System (ADS)

Baranov, Dmitriy; Rogachevsky, Oleg

2017-03-01

The Gas Electron Multiplier (GEM) detector is one of the basic parts of the BM@N experiment included in the NICA project. The simulation model that takes into account features of signal generation process in an ionization GEM chamber is presented in this article. Proper parameters for the simulation were extracted from data retrieved with the help of Garfield++ (a toolkit for the detailed simulation of particle detectors). Due to this, we are able to generate clusters in layers of the micro-strip readout that correspond to clusters retrieved from a real physics experiment.

A simulation of the atmospheric cloud physics laboratory to aid in its design and the design of the experiments within the laboratory

NASA Technical Reports Server (NTRS)

Winchester, L. W., Jr.

1980-01-01

Using the finite difference method with overrelaxation, numerical solutions of the steady-state vorticity transport equation were obtained for a continuous flow diffusion chamber of the Hudson-Squires type. The calculation neglected the effects due to temperature, gravity, and saturation. The size and shape of the manifold used to inject the aerosol laden flow were varied to obtain a design which would improve the performance of the chamber from strictly low Reynolds number (less than 20) fluid dynamical considerations.

Simulation of air-bag impact on an eye with transsclerally fixated posterior chamber intraocular lens using finite element analysis.

PubMed

Uchio, Eiichi; Kadonosono, Kazuaki; Matsuoka, Yasuhiro; Goto, Satoru

2004-02-01

To determine the physical and mechanical conditions of an impacting air bag that would rupture an eye with a transsclerally fixated posterior chamber intraocular lens (IOL). Numerical simulation study on a computer. Simulations in a model human eye were performed with a computer using the finite element analysis program PAM-CRASH (Nihon ESI). The air bag was set to impact the surface of an eye with a transsclerally fixated posterior chamber IOL at various velocities. The tensile force limit of a 10-1 polypropylene suture was assumed to be 0.16 N, which is specified in the U.S. Pharmacopeia XXII. At the lowest velocity of 20.0 m/s, 10-0 polypropylene sutures were not likely to break. Sutures fixating the IOL might break and a corneoscleral incision was likely to open after 0.3 second at the medium impacting velocity (30 m/s). Suture rupture was very likely at the highest velocity (40 m/s) since the tensile force on the sutures continuously exceeded the breaking force after the impact. In an eye with a transsclerally fixated posterior chamber IOL, severe ocular trauma can be caused by an air bag at high velocity. Small individuals such as elderly women are at greater risk for air-bag ocular injury. Further research on modifying air-bag design and deployment is important to minimize the risk for ocular injury.

CFD simulation of coaxial injectors

NASA Technical Reports Server (NTRS)

Landrum, D. Brian

1993-01-01

The development of improved performance models for the Space Shuttle Main Engine (SSME) is an important, ongoing program at NASA MSFC. These models allow prediction of overall system performance, as well as analysis of run-time anomalies which might adversely affect engine performance or safety. Due to the complexity of the flow fields associated with the SSME, NASA has increasingly turned to Computational Fluid Dynamics (CFD) techniques as modeling tools. An important component of the SSME system is the fuel preburner, which consists of a cylindrical chamber with a plate containing 264 coaxial injector elements at one end. A fuel rich mixture of gaseous hydrogen and liquid oxygen is injected and combusted in the chamber. This process preheats the hydrogen fuel before it enters the main combustion chamber, powers the hydrogen turbo-pump, and provides a heat dump for nozzle cooling. Issues of interest include the temperature and pressure fields at the turbine inlet and the thermal compatibility between the preburner chamber and injector plate. Performance anomalies can occur due to incomplete combustion, blocked injector ports, etc. The performance model should include the capability to simulate the effects of these anomalies. The current approach to the numerical simulation of the SSME fuel preburner flow field is to use a global model based on the MSFC sponsored FNDS code. This code does not have the capabilities of modeling several aspects of the problem such as detailed modeling of the coaxial injectors. Therefore, an effort has been initiated to develop a detailed simulation of the preburner coaxial injectors and provide gas phase boundary conditions just downstream of the injector face as input to the FDNS code. This simulation should include three-dimensional geometric effects such as proximity of injectors to baffles and chamber walls and interaction between injectors. This report describes an investigation into the numerical simulation of GH2/LOX coaxial injectors. The following sections will discuss the physical aspects of injectors, the CFD code employed, and preliminary results of a simulation of a single coaxial injector for which experimental data is available. It is hoped that this work will lay the foundation for the development of a unique and useful tool to support the SSME program.

The Phoretic Motion Experiment (PME) definition phase

NASA Technical Reports Server (NTRS)

Eaton, L. R.; Neste, S. L. (Editor)

1982-01-01

The aerosol generator and the charge flow devices (CFD) chamber which were designed for zero-gravity operation was analyzed. Characteristics of the CFD chamber and aerosol generator which would be useful for cloud physics experimentation in a one-g as well as a zero-g environment are documented. The Collision type of aerosol generator is addressed. Relationships among the various input and output parameters are derived and subsequently used to determine the requirements on the controls of the input parameters to assure a given error budget of an output parameter. The CFD chamber operation in a zero-g environment is assessed utilizing a computer simulation program. Low nuclei critical supersaturation and high experiment accuracies are emphasized which lead to droplet growth times extending into hundreds of seconds. The analysis was extended to assess the performance constraints of the CFD chamber in a one-g environment operating in the horizontal mode.

The Living Heart Project: A robust and integrative simulator for human heart function.

PubMed

Baillargeon, Brian; Rebelo, Nuno; Fox, David D; Taylor, Robert L; Kuhl, Ellen

2014-11-01

The heart is not only our most vital, but also our most complex organ: Precisely controlled by the interplay of electrical and mechanical fields, it consists of four chambers and four valves, which act in concert to regulate its filling, ejection, and overall pump function. While numerous computational models exist to study either the electrical or the mechanical response of its individual chambers, the integrative electro-mechanical response of the whole heart remains poorly understood. Here we present a proof-of-concept simulator for a four-chamber human heart model created from computer topography and magnetic resonance images. We illustrate the governing equations of excitation-contraction coupling and discretize them using a single, unified finite element environment. To illustrate the basic features of our model, we visualize the electrical potential and the mechanical deformation across the human heart throughout its cardiac cycle. To compare our simulation against common metrics of cardiac function, we extract the pressure-volume relationship and show that it agrees well with clinical observations. Our prototype model allows us to explore and understand the key features, physics, and technologies to create an integrative, predictive model of the living human heart. Ultimately, our simulator will open opportunities to probe landscapes of clinical parameters, and guide device design and treatment planning in cardiac diseases such as stenosis, regurgitation, or prolapse of the aortic, pulmonary, tricuspid, or mitral valve.

Use of high-volume outdoor smog chamber photo-reactors for studying physical and chemical atmospheric aerosol formation and composition

NASA Astrophysics Data System (ADS)

Borrás, E.; Ródenas, M.; Vera, T.; Muñoz, A.

2015-12-01

The atmospheric particulate matter has a large impact on climate, biosphere behaviour and human health. Its study is complex because of large number of species are present at low concentrations and the continuous time evolution, being not easily separable from meteorology, and transport processes. Closed systems have been proposed by isolating specific reactions, pollutants or products and controlling the oxidizing environment. High volume simulation chambers, such as EUropean PHOtoREactor (EUPHORE), are an essential tool used to simulate atmospheric photochemical reactions. This communication describes the last results about the reactivity of prominent atmospheric pollutants and the subsequent particulate matter formation. Specific experiments focused on organic aerosols have been developed at the EUPHORE photo-reactor. The use of on-line instrumentation, supported by off-line techniques, has provided well-defined reaction profiles, physical properties, and up to 300 different species are determined in particulate matter. The application fields include the degradation of anthropogenic and biogenic pollutants, and pesticides under several atmospheric conditions, studying their contribution on the formation of secondary organic aerosols (SOA). The studies performed at the EUPHORE have improved the mechanistic studies of atmospheric degradation processes and the knowledge about the chemical and physical properties of atmospheric particulate matter formed during these processes.

High Voltage, Sub Nanosecond Feedthrough Design for Liquid Breakdown Studies

NASA Astrophysics Data System (ADS)

Cevallos, Michael; Dickens, James; Neuber, Andreas; Krompholz, Herman

2002-12-01

Experiments in self-breakdown mode and pulsed breakdown at high over-voltages in standard electrode geometries are performed for liquids to gain a better understanding of their fundamental breakdown physics. Different liquids of interest include liquids such as super-cooled liquid nitrogen, oils, glycerols and water. A typical setup employs a discharge chamber with a cable discharge into a coaxial system with axial discharge, and a load line to simulate a matched terminating impedance, thus providing a sub-nanosecond response. This study is focused on the feed-through design of the coaxial cable into this type of discharge chamber, with the feed-through being the critical element with respect to maximum hold-off voltage. Diverse feedthroughs were designed and simulated using Maxwell 3-D Field Simulator Version 5. Several geometrically shaped feed-through transitions were simulated, including linearly and exponentially tapered, to minimize electrostatic fields, thus ensuring that the discharge occurs in the volume of interest and not between the inner and outer conductor at the transition from the insulation of the coaxial cable to the liquid. All feedthroughs are designed to match the incoming impedance of the coaxial cable. The size of the feedthroughs will vary from liquid to liquid in order to match the coaxial cable impedance of 50Ω. The discharge chamber has two main ports where the feed-through will enter the chamber. Each feed-through is built through a flange that covers the two main ports. This allows the use of the same discharge chamber for various liquids by changing the flanges on the main ports to match the particular liquid. The feedthroughs were designed and built to withstand voltages of up to 200 kV. The feedthroughs are also fitted with transmission line type current sensors and capacitive voltage dividers with fast amplifiers/attenuators in order to attain a complete range of information from amplitudes of 0.1mA to 1 kA with a temporal resolution of 300 ps.

On-chip gradient generation in 256 microfluidic cell cultures: simulation and experimental validation.

PubMed

Somaweera, Himali; Haputhanthri, Shehan O; Ibraguimov, Akif; Pappas, Dimitri

2015-08-07

A microfluidic diffusion diluter was used to create a stable concentration gradient for dose response studies. The microfluidic diffusion diluter used in this study consisted of 128 culture chambers on each side of the main fluidic channel. A calibration method was used to find unknown concentrations with 12% error. Flow rate dependent studies showed that changing the flow rates generated different gradient patterns. Mathematical simulations using COMSOL Multi-physics were performed to validate the experimental data. The experimental data obtained for the flow rate studies agreed with the simulation results. Cells could be loaded into culture chambers using vacuum actuation and cultured for long times under low shear stress. Decreasing the size of the culture chambers resulted in faster gradient formation (20 min). Mass transport into the side channels of the microfluidic diffusion diluter used in this study is an important factor in creating the gradient using diffusional mixing as a function of the distance. To demonstrate the device's utility, an H2O2 gradient was generated while culturing Ramos cells. Cell viability was assayed in the 256 culture chambers, each at a discrete H2O2 concentration. As expected, the cell viability for the high concentration side channels increased (by injecting H2O2) whereas the cell viability in the low concentration side channels decreased along the chip due to diffusional mixing as a function of distance. COMSOL simulations were used to identify the effective concentration of H2O2 for cell viability in each side chamber at 45 min. The gradient effects were confirmed using traditional H2O2 culture experiments. Viability of cells in the microfluidic device under gradient conditions showed a linear relationship with the viability of the traditional culture experiment. Development of the microfluidic device used in this study could be used to study hundreds of concentrations of a compound in a single experiment.

Development of an Efficient CFD Model for Nuclear Thermal Thrust Chamber Assembly Design

NASA Technical Reports Server (NTRS)

Cheng, Gary; Ito, Yasushi; Ross, Doug; Chen, Yen-Sen; Wang, Ten-See

2007-01-01

The objective of this effort is to develop an efficient and accurate computational methodology to predict both detailed thermo-fluid environments and global characteristics of the internal ballistics for a hypothetical solid-core nuclear thermal thrust chamber assembly (NTTCA). Several numerical and multi-physics thermo-fluid models, such as real fluid, chemically reacting, turbulence, conjugate heat transfer, porosity, and power generation, were incorporated into an unstructured-grid, pressure-based computational fluid dynamics solver as the underlying computational methodology. The numerical simulations of detailed thermo-fluid environment of a single flow element provide a mechanism to estimate the thermal stress and possible occurrence of the mid-section corrosion of the solid core. In addition, the numerical results of the detailed simulation were employed to fine tune the porosity model mimic the pressure drop and thermal load of the coolant flow through a single flow element. The use of the tuned porosity model enables an efficient simulation of the entire NTTCA system, and evaluating its performance during the design cycle.

[Development of cloud chamber having thin-film entrance windows and proposal of practical training for beginners using X-ray equipment and unsealed radioactive material].

PubMed

Konishi, Yuki; Hayashi, Hiroaki; Takegami, Kazuki; Fukuda, Ikuma; Ueno, Junji

2014-01-01

A cloud chamber is a detector that can visualize the tracks of charged particles. Hayashi, et al. suggested a visualization experiment in which X-rays generated by diagnostic X-ray equipment were directed into a cloud chamber; however, there was a problem in that the wall of the cloud chamber scattered the incoming X-rays. In this study, we developed a new cloud chamber with entrance windows. Because these windows are made of thin film, we were able to direct the X-rays through them without contamination by scattered X-rays from the cloud chamber wall. We have newly proposed an experiment in which beta-particles emitted from radioisotopes are directed into a cloud chamber. We place shielding material in the cloud chamber and visualize the various shielding effects seen with the material positioned in different ways. During the experiment, electrons scattered in the air were measured quantitatively using GM counters. We explained the physical phenomena in the cloud chamber using Monte Carlo simulation code EGS5. Because electrons follow a tortuous path in air, the shielding material must be placed appropriately to be able to effectively block their emissions. Visualization of the tracks of charged particles in this experiment proved effective for instructing not only trainee radiological technologists but also different types of healthcare professionals.

Numerical Simulation of Measurements during the Reactor Physical Startup at Unit 3 of Rostov NPP

NASA Astrophysics Data System (ADS)

Tereshonok, V. A.; Kryakvin, L. V.; Pitilimov, V. A.; Karpov, S. A.; Kulikov, V. I.; Zhylmaganbetov, N. M.; Kavun, O. Yu.; Popykin, A. I.; Shevchenko, R. A.; Shevchenko, S. A.; Semenova, T. V.

2017-12-01

The results of numerical calculations and measurements of some reactor parameters during the physical startup tests at unit 3 of Rostov NPP are presented. The following parameters are considered: the critical boron acid concentration and the currents from ionization chambers (IC) during the scram system efficiency evaluation. The scram system efficiency was determined using the inverse point kinetics equation with the measured and simulated IC currents. The results of steady-state calculations of relative power distribution and efficiency of the scram system and separate groups of control rods of the control and protection system are also presented. The calculations are performed using several codes, including precision ones.

Segmented saddle-shaped passive stabilization conductors for toroidal plasmas

DOEpatents

Leuer, James A.

1990-05-01

A large toroidal vacuum chamber for plasma generation and confinement is lined with a toroidal blanket for shielding using modules segmented in the toroidal direction. To provide passive stabilization in the same manner as a conductive vacuum chamber wall, saddle-shaped conductor loops are provided on blanket modules centered on a midplane of the toroidal chamber with horizontal conductive bars above and below the midplane, and vertical conductive legs on opposite sides of each module to provide return current paths between the upper and lower horizontal conductive bars. The close proximity of the vertical legs provided on adjacent modules without making physical contact cancel the electromagnetic field of adjacent vertical legs. The conductive bars spaced equally above and below the midplane simulate toroidal conductive loops or hoops that are continuous, for vertical stabilization of the plasma even though they are actually segmented.

Computational fluid dynamic (CFD) investigation of thermal uniformity in a thermal cycling based calibration chamber for MEMS

NASA Astrophysics Data System (ADS)

Gui, Xulong; Luo, Xiaobing; Wang, Xiaoping; Liu, Sheng

2015-12-01

Micro-electrical-mechanical system (MEMS) has become important for many industries such as automotive, home appliance, portable electronics, especially with the emergence of Internet of Things. Volume testing with temperature compensation has been essential in order to provide MEMS based sensors with repeatability, consistency, reliability, and durability, but low cost. Particularly, in the temperature calibration test, temperature uniformity of thermal cycling based calibration chamber becomes more important for obtaining precision sensors, as each sensor is different before the calibration. When sensor samples are loaded into the chamber, we usually open the door of the chamber, then place fixtures into chamber and mount the samples on the fixtures. These operations may affect temperature uniformity in the chamber. In order to study the influencing factors of sample-loading on the temperature uniformity in the chamber during calibration testing, numerical simulation work was conducted first. Temperature field and flow field were simulated in empty chamber, chamber with open door, chamber with samples, and chamber with fixtures, respectively. By simulation, it was found that opening chamber door, sample size and number of fixture layers all have effects on flow field and temperature field. By experimental validation, it was found that the measured temperature value was consistent with the simulated temperature value.

Detailed Measurement of ORSC Main Chamber Injector Dynamics

NASA Astrophysics Data System (ADS)

Bedard, Michael J.

Improving fidelity in simulation of combustion dynamics in rocket combustors requires an increase in experimental measurement fidelity for validation. In a model rocket combustor, a chemiluminescence based spectroscopy technique was used to capture flame light emissions for direct comparison to a computational simulation of the production of chemiluminescent species. The comparison indicated that high fidelity models of rocket combustors can predict spatio-temporal distribution of chemiluminescent species with trend-wise accuracy. The comparison also indicated the limited ability of OH* and CH* emission to indicate flame heat release. Based on initial spectroscopy experiments, a photomultiplier based chemiluminescence sensor was designed to increase the temporal resolution of flame emission measurements. To apply developed methodologies, an experiment was designed to investigate the flow and combustion dynamics associated with main chamber injector elements typical of the RD-170 rocket engine. A unique feature of the RD-170 injector element is the beveled expansion between the injector recess and combustion chamber. To investigate effects of this geometry, a scaling methodology was applied to increase the physical scale of a single injector element while maintaining traceability to the RD-170 design. Two injector configurations were tested, one including a beveled injector face and the other a flat injector face. This design enabled improved spatial resolution of pressure and light emission measurements densely arranged in the injector recess and near-injector region of the chamber. Experimental boundary conditions were designed to closely replicate boundary conditions in simulations. Experimental results showed that the beveled injector face had a damping effect on pressure fluctuations occurring near the longitudinal resonant acoustic modes of the chamber, implying a mechanism for improved overall combustion stability. Near the injector, the beveled geometry resulted in more acoustic energy into higher frequency modes, while the flat-face geometry excited modes closer to the fundamental longitudinal mode frequency and its harmonics. Multi-scale analysis techniques were used to investigate intermittency and the range of physical scales present in measured signals. Flame light emission measurements confirmed the presence of flame holding in the injector recess in both configurations. Analysis of dynamics in light emission signals showed flame response at the chamber acoustic resonance frequency in addition to non-acoustic modes associated with mixing shear layer dynamics in the injector recess. The first known benchmark quality data sets of such injector dynamics were recorded in each configuration to enable pressure-based validation of high fidelity models of gas-centered swirl coaxial injectors. This work presents a critical contribution to development of validated combustion dynamics predictive tools and to the understanding of gas-centered swirl coaxial injector elements.

SU-F-T-471: Simulated External Beam Delivery Errors Detection with a Large Area Ion Chamber Transmission Detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoffman, D; Dyer, B; Kumaran Nair, C

Purpose: The Integral Quality Monitor (IQM), developed by iRT Systems GmbH (Koblenz, Germany) is a large-area, linac-mounted ion chamber used to monitor photon fluence during patient treatment. Our previous work evaluated the change of the ion chamber’s response to deviations from static 1×1 cm2 and 10×10 cm2 photon beams and other characteristics integral to use in external beam detection. The aim of this work is to simulate two external beam radiation delivery errors, quantify the detection of simulated errors and evaluate the reduction in patient harm resulting from detection. Methods: Two well documented radiation oncology delivery errors were selected formore » simulation. The first error was recreated by modifying a wedged whole breast treatment, removing the physical wedge and calculating the planned dose with Pinnacle TPS (Philips Radiation Oncology Systems, Fitchburg, WI). The second error was recreated by modifying a static-gantry IMRT pharyngeal tonsil plan to be delivered in 3 unmodulated fractions. A radiation oncologist evaluated the dose for simulated errors and predicted morbidity and mortality commiserate with the original reported toxicity, indicating that reported errors were approximately simulated. The ion chamber signal of unmodified treatments was compared to the simulated error signal and evaluated in Pinnacle TPS again with radiation oncologist prediction of simulated patient harm. Results: Previous work established that transmission detector system measurements are stable within 0.5% standard deviation (SD). Errors causing signal change greater than 20 SD (10%) were considered detected. The whole breast and pharyngeal tonsil IMRT simulated error increased signal by 215% and 969%, respectively, indicating error detection after the first fraction and IMRT segment, respectively. Conclusion: The transmission detector system demonstrated utility in detecting clinically significant errors and reducing patient toxicity/harm in simulated external beam delivery. Future work will evaluate detection of other smaller magnitude delivery errors.« less

First Results from the ASIBIA (Arctic Sea-Ice, snow, Biogeochemistry and Impacts on the Atmosphere) Sea-Ice Chamber

NASA Astrophysics Data System (ADS)

Frey, M. M.; France, J.; von Glasow, R.; Thomas, M.

2015-12-01

The ocean-ice-atmosphere system is very complex, and there are numerous challenges with conducting fieldwork on sea-ice including costs, safety, experimental controls and access. By creating a new coupled Ocean-Sea-Ice-(Snow)-Atmosphere facility at the University of East Anglia, UK, we are able to perform controlled investigations in areas such as sea-ice physics, physicochemical and biogeochemical processes in sea-ice, and to quantify the bi-directional flux of gases in established, freezing and melting sea-ice. The environmental chamber is capable of controlled programmable temperatures from -55°C to +30°C, allowing a full range of first year sea-ice growing conditions in both the Arctic and Antarctic to be simulated. The sea-ice tank within the chamber measures 2.4 m x 1.4 m x 1 m water depth, with an identically sized Teflon film atmosphere on top of the tank. The tank and atmosphere forms a coupled, isolated mesocosm. Above the atmosphere is a light bank with dimmable solar simulation LEDs, and UVA and UVB broadband fluorescent battens, providing light for a range of experiments such as under ice biogeochemistry and photochemistry. Ice growth in the tank will be ideally suited for studying first-year sea-ice physical properties, with in-situ ice-profile measurements of temperature, salinity, conductivity, pressure and spectral light transmission. Under water and above ice cameras are installed to observe the physical development of the sea-ice. The ASIBIA facility is also well equipped for gas exchange and diffusion studies through sea-ice with a suite of climate relevant gas measuring instruments (CH4, CO2, O3, NOx, NOy permanently installed, further instruments available) able to measure either directly in the atmospheric component, or via a membrane for water side dissolved gases. Here, we present the first results from the ASIBIA sea-ice chamber, focussing on the physical development of first-year sea-ice and show the future plans for the facility over the coming years. The ASIBIA sea-ice facility is a key component of a 5-year ERC funded program with a long-term goal to develop parameterisations for local to global scale models based on experimental results.

Simulating Extraterrestrial Ices in the Laboratory

NASA Astrophysics Data System (ADS)

Berisford, D. F.; Carey, E. M.; Hand, K. P.; Choukroun, M.

2017-12-01

Several ongoing experiments at JPL attempt to simulate the ice environment for various regimes associated with icy moons. The Europa Penitent Ice Experiment (EPIX) simulates the surface environment of an icy moon, to investigate the physics of ice surface morphology growth. This experiment features half-meter-scale cryogenic ice samples, cryogenic radiative sink environment, vacuum conditions, and diurnal cycling solar simulation. The experiment also includes several smaller fixed-geometry vacuum chambers for ice simulation at Earth-like and intermediate temperature and vacuum conditions for development of surface morphology growth scaling relations. Additionally, an ice cutting facility built on a similar platform provides qualitative data on the mechanical behavior of cryogenic ice with impurities under vacuum, and allows testing of ice cutting/sampling tools relevant for landing spacecraft. A larger cutting facility is under construction at JPL, which will provide more quantitative data and allow full-scale sampling tool tests. Another facility, the JPL Ice Physics Laboratory, features icy analog simulant preparation abilities that range icy solar system objects such as Mars, Ceres and the icy satellites of Saturn and Jupiter. In addition, the Ice Physics Lab has unique facilities for Icy Analog Tidal Simulation and Rheological Studies of Cryogenic Icy Slurries, as well as equipment to perform thermal and mechanical properties testing on icy analog materials and their response to sinusoidal tidal stresses.

Discharge Chamber Primary Electron Modeling Activities in Three-Dimensions

NASA Technical Reports Server (NTRS)

Steuber, Thomas J.

2004-01-01

Designing discharge chambers for ion thrusters involves many geometric configuration decisions. Various decisions will impact discharge chamber performance with respect to propellant utilization efficiency, ion production costs, and grid lifetime. These hardware design decisions can benefit from the assistance of computational modeling. Computational modeling for discharge chambers has been limited to two-dimensional codes that leveraged symmetry for interpretation into three-dimensional analysis. This paper presents model development activities towards a three-dimensional discharge chamber simulation to aid discharge chamber design decisions. Specifically, of the many geometric configuration decisions toward attainment of a worthy discharge chamber, this paper focuses on addressing magnetic circuit considerations with a three-dimensional discharge chamber simulation as a tool. With this tool, candidate discharge chamber magnetic circuit designs can be analyzed computationally to gain insight into factors that may influence discharge chamber performance such as: primary electron loss width in magnetic cusps, cathode tip position with respect to the low magnetic field volume, definition of a low magnetic field region, and maintenance of a low magnetic field region across the grid span. Corroborating experimental data will be obtained from mockup hardware tests. Initially, simulated candidate magnetic circuit designs will resemble previous successful thruster designs. To provide opportunity to improve beyond previous performance benchmarks, off-design modifications will be simulated and experimentally tested.

Segmented saddle-shaped passive stabilization conductors for toroidal plasmas

DOEpatents

Leuer, J.A.

1990-05-01

A large toroidal vacuum chamber for plasma generation and confinement is lined with a toroidal blanket for shielding using modules segmented in the toroidal direction. To provide passive stabilization in the same manner as a conductive vacuum chamber wall, saddle-shaped conductor loops are provided on blanket modules centered on a midplane of the toroidal chamber with horizontal conductive bars above and below the midplane, and vertical conductive legs on opposite sides of each module to provide return current paths between the upper and lower horizontal conductive bars. The close proximity of the vertical legs provided on adjacent modules without making physical contact cancel the electromagnetic field of adjacent vertical legs. The conductive bars spaced equally above and below the midplane simulate toroidal conductive loops or hoops that are continuous, for vertical stabilization of the plasma even though they are actually segmented. 5 figs.

Technical Note: A minimally invasive experimental system for pCO2 manipulation in plankton cultures using passive gas exchange (atmospheric carbon control simulator)

NASA Astrophysics Data System (ADS)

Love, Brooke A.; Olson, M. Brady; Wuori, Tristen

2017-05-01

As research into the biotic effects of ocean acidification has increased, the methods for simulating these environmental changes in the laboratory have multiplied. Here we describe the atmospheric carbon control simulator (ACCS) for the maintenance of plankton under controlled pCO2 conditions, designed for species sensitive to the physical disturbance introduced by the bubbling of cultures and for studies involving trophic interaction. The system consists of gas mixing and equilibration components coupled with large-volume atmospheric simulation chambers. These chambers allow gas exchange to counteract the changes in carbonate chemistry induced by the metabolic activity of the organisms. The system is relatively low cost, very flexible, and when used in conjunction with semi-continuous culture methods, it increases the density of organisms kept under realistic conditions, increases the allowable time interval between dilutions, and/or decreases the metabolically driven change in carbonate chemistry during these intervals. It accommodates a large number of culture vessels, which facilitate multi-trophic level studies and allow the tracking of variable responses within and across plankton populations to ocean acidification. It also includes components that increase the reliability of gas mixing systems using mass flow controllers.

Convert Ten Foot Environmental Test Chamber into an Ion Engine Test Chamber

NASA Technical Reports Server (NTRS)

VanVelzer, Paul

2006-01-01

The 10 Foot Space Simulator at the Jet Propulsion Laboratory has been used for the last 40 years to test numerous spacecraft, including the Ranger series, several Mariner class, among many others and finally, the Spirit and Opportunity Mars Rovers. The request was made to convert this facility to an Ion Engine test facility, with a possible long term life test. The Ion engine was to propel the Prometheus spacecraft to Jupiter's moons. This paper discusses the challenges that were met, both from a procedural and physical standpoint. The converted facility must operate unattended, support a 30 Kw Ion Engine, operate economically, and be easily converted back to former operation as a spacecraft test facility.

Nuclear instrumentation in VENUS-F

NASA Astrophysics Data System (ADS)

Wagemans, J.; Borms, L.; Kochetkov, A.; Krása, A.; Van Grieken, C.; Vittiglio, G.

2018-01-01

VENUS-F is a fast zero power reactor with 30 wt% U fuel and Pb/Bi as a coolant simulator. Depending on the experimental configuration, various neutron spectra (fast, epithermal, and thermal islands) are present. This paper gives a review of the nuclear instrumentation that is applied for reactor control and in a large variety of physics experiments. Activation foils and fission chambers are used to measure spatial neutron flux profiles, spectrum indices, reactivity effects (with positive period and compensation method or the MSM method) and kinetic parameters (with the Rossi-alpha method). Fission chamber calibrations are performed in the standard irradiation fields of the BR1 reactor (prompt fission neutron spectrum and Maxwellian thermal neutron spectrum).

The Mobile Chamber

NASA Technical Reports Server (NTRS)

Scharfstein, Gregory; Cox, Russell

2012-01-01

A document discusses a simulation chamber that represents a shift from the thermal-vacuum chamber stereotype. This innovation, currently in development, combines the capabilities of space simulation chambers, the user-friendliness of modern-day electronics, and the modularity of plug-and-play computing. The Mobile Chamber is a customized test chamber that can be deployed with great ease, and is capable of bringing payloads at temperatures down to 20 K, in high vacuum, and with the desired metrology instruments integrated to the systems control. Flexure plans to lease Mobile Chambers, making them affordable for smaller budgets and available to a larger customer base. A key feature of this design will be an Apple iPad-like user interface that allows someone with minimal training to control the environment inside the chamber, and to simulate the required extreme environments. The feedback of thermal, pressure, and other measurements is delivered in a 3D CAD model of the chamber's payload and support hardware. This GUI will provide the user with a better understanding of the payload than any existing thermal-vacuum system.

Development of GEM detector for plasma diagnostics application: simulations addressing optimization of its performance

NASA Astrophysics Data System (ADS)

Chernyshova, M.; Malinowski, K.; Kowalska-Strzęciwilk, E.; Czarski, T.; Linczuk, P.; Wojeński, A.; Krawczyk, R. D.

2017-12-01

The advanced Soft X-ray (SXR) diagnostics setup devoted to studies of the SXR plasma emissivity is at the moment a highly relevant and important for ITER/DEMO application. Especially focusing on the energy range of tungsten emission lines, as plasma contamination by W and its transport in the plasma must be understood and monitored for W plasma-facing material. The Gas Electron Multiplier, with a spatial and energy-resolved photon detecting chamber, based SXR radiation detection system under development by our group may become such a diagnostic setup considering and solving many physical, technical and technological aspects. This work presents the results of simulations aimed to optimize a design of the detector's internal chamber and its performance. The study of the effect of electrodes alignment allowed choosing the gap distances which maximizes electron transmission and choosing the optimal magnitudes of the applied electric fields. Finally, the optimal readout structure design was identified suitable to collect a total formed charge effectively, basing on the range of the simulated electron cloud at the readout plane which was in the order of ~ 2 mm.

High resolution muon tracking with resistive plate chambers

NASA Astrophysics Data System (ADS)

Baesso, P.; Cussans, D.; Davies, J.; Glaysher, P.; Thomay, C.; Vassallo, C.; Velthuis, J.; Quillin, S.; Robertson, S.; Steer, C.

2012-11-01

Following their introduction in the physics community in the early '80s the use of Resistive Plate Chambers (RPCs) as charged particles detectors has constantly increased. Low cost per unit area, good time resolution and easy of operation are some of the features that contributed to such large adoption and that make RPCs interesting for several applications not necessarily related to physics. We built a prototype detector to track cosmic muons and exploit the information provided by estimating the multiple coulomb scattering angle to determine the type of materials they traversed. Simulations show that the technique could be used to inspect a cargo container in a time of the order of minutes. The detector we built consists of six planes, each one providing X-Y readout over a 50 cm × 50 cm area. The readout scheme we adopted, based on multiplexing chips used in high energy physics, allowed us to use a limited amount of electronic output channels while still obtaining a spatial resolution lower than 1 mm. An overview of the detector and of the analysis performed on the data is provided.

A new plant chamber facility PLUS coupled to the atmospheric simulation chamber SAPHIR

NASA Astrophysics Data System (ADS)

Hohaus, T.; Kuhn, U.; Andres, S.; Kaminski, M.; Rohrer, F.; Tillmann, R.; Wahner, A.; Wegener, R.; Yu, Z.; Kiendler-Scharr, A.

2015-11-01

A new PLant chamber Unit for Simulation (PLUS) for use with the atmosphere simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) has been build and characterized at the Forschungszentrum Jülich GmbH, Germany. The PLUS chamber is an environmentally controlled flow through plant chamber. Inside PLUS the natural blend of biogenic emissions of trees are mixed with synthetic air and are transferred to the SAPHIR chamber where the atmospheric chemistry and the impact of biogenic volatile organic compounds (BVOC) can be studied in detail. In PLUS all important enviromental parameters (e.g. temperature, PAR, soil RH etc.) are well-controlled. The gas exchange volume of 9.32 m3 which encloses the stem and the leafes of the plants is constructed such that gases are exposed to FEP Teflon film and other Teflon surfaces only to minimize any potential losses of BVOCs in the chamber. Solar radiation is simulated using 15 LED panels which have an emission strength up to 800 μmol m-2 s-1. Results of the initial characterization experiments are presented in detail. Background concentrations, mixing inside the gas exchange volume, and transfer rate of volatile organic compounds (VOC) through PLUS under different humidity conditions are explored. Typical plant characteristics such as light and temperature dependent BVOC emissions are studied using six Quercus Ilex trees and compared to previous studies. Results of an initial ozonolysis experiment of BVOC emissions from Quercus Ilex at typical atmospheric concentrations inside SAPHIR are presented to demonstrate a typical experimental set up and the utility of the newly added plant chamber.

Donald Glaser, the Bubble Chamber, and Elementary Particles

Science.gov Websites

Effects of Ionizing Radiation on the Formation of Bubbles in Liquids Physical Review, Vol. 87, Issue 4 , 665, August 15, 1952 Characteristics of Bubble Chambers Physical Review, Vol. 97, Issue 2, 474-479 Chambers Physical Review, Vol. 102, Issue 6, 1653-1658, June 15, 1956 Methods of Particle Detection for

Space Simulation Chamber Rescues Water Damaged Books.

ERIC Educational Resources Information Center

American School and University, 1981

1981-01-01

More than 4,000 valuable water-damaged books were restored by using a space-simulation chamber at the Lockheed Missile and Space Company. It was the fifth time that the chamber has been used for the restoration of valuable books and documents. (Author/MLF)

A new plant chamber facility, PLUS, coupled to the atmosphere simulation chamber SAPHIR

NASA Astrophysics Data System (ADS)

Hohaus, T.; Kuhn, U.; Andres, S.; Kaminski, M.; Rohrer, F.; Tillmann, R.; Wahner, A.; Wegener, R.; Yu, Z.; Kiendler-Scharr, A.

2016-03-01

A new PLant chamber Unit for Simulation (PLUS) for use with the atmosphere simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) has been built and characterized at the Forschungszentrum Jülich GmbH, Germany. The PLUS chamber is an environmentally controlled flow-through plant chamber. Inside PLUS the natural blend of biogenic emissions of trees is mixed with synthetic air and transferred to the SAPHIR chamber, where the atmospheric chemistry and the impact of biogenic volatile organic compounds (BVOCs) can be studied in detail. In PLUS all important environmental parameters (e.g., temperature, photosynthetically active radiation (PAR), soil relative humidity (RH)) are well controlled. The gas exchange volume of 9.32 m3 which encloses the stem and the leaves of the plants is constructed such that gases are exposed to only fluorinated ethylene propylene (FEP) Teflon film and other Teflon surfaces to minimize any potential losses of BVOCs in the chamber. Solar radiation is simulated using 15 light-emitting diode (LED) panels, which have an emission strength up to 800 µmol m-2 s-1. Results of the initial characterization experiments are presented in detail. Background concentrations, mixing inside the gas exchange volume, and transfer rate of volatile organic compounds (VOCs) through PLUS under different humidity conditions are explored. Typical plant characteristics such as light- and temperature- dependent BVOC emissions are studied using six Quercus ilex trees and compared to previous studies. Results of an initial ozonolysis experiment of BVOC emissions from Quercus ilex at typical atmospheric concentrations inside SAPHIR are presented to demonstrate a typical experimental setup and the utility of the newly added plant chamber.

Computational Analysis of the Combustion Processes in an Axisymmetric, RBCC Flowpath

NASA Technical Reports Server (NTRS)

Steffen, Christopher J., Jr.; Yungster, Shaye

2001-01-01

Computational fluid dynamic simulations have been used to study the combustion processes within an axisymmetric, RBCC flowpath. Two distinct operating modes have been analyzed to date, including the independent ramjet stream (IRS) cycle and the supersonic combustion ramjet (scramJet) cycle. The IRS cycle investigation examined the influence of fuel-air ratio, fuel distribution, and rocket chamber pressure upon the combustion physics and thermal choke characteristics. Results indicate that adjustment of the amount and radial distribution of fuel can control the thermal choke point. The secondary massflow rate was very sensitive to the fuel-air ratio and the rocket chamber pressure. The scramjet investigation examined the influence of fuel-air ratio and fuel injection schedule upon combustion performance estimates. An analysis of the mesh-dependence of these calculations was presented. Jet penetration data was extracted from the three-dimensional simulations and compared favorably with experimental correlations of similar flows. Results indicate that combustion efficiency was very sensitive to the fuel schedule.

Hybrid-PIC Computer Simulation of the Plasma and Erosion Processes in Hall Thrusters

NASA Technical Reports Server (NTRS)

Hofer, Richard R.; Katz, Ira; Mikellides, Ioannis G.; Gamero-Castano, Manuel

2010-01-01

HPHall software simulates and tracks the time-dependent evolution of the plasma and erosion processes in the discharge chamber and near-field plume of Hall thrusters. HPHall is an axisymmetric solver that employs a hybrid fluid/particle-in-cell (Hybrid-PIC) numerical approach. HPHall, originally developed by MIT in 1998, was upgraded to HPHall-2 by the Polytechnic University of Madrid in 2006. The Jet Propulsion Laboratory has continued the development of HPHall-2 through upgrades to the physical models employed in the code, and the addition of entirely new ones. Primary among these are the inclusion of a three-region electron mobility model that more accurately depicts the cross-field electron transport, and the development of an erosion sub-model that allows for the tracking of the erosion of the discharge chamber wall. The code is being developed to provide NASA science missions with a predictive tool of Hall thruster performance and lifetime that can be used to validate Hall thrusters for missions.

Volcano Modelling and Simulation gateway (VMSg): A new web-based framework for collaborative research in physical modelling and simulation of volcanic phenomena

NASA Astrophysics Data System (ADS)

Esposti Ongaro, T.; Barsotti, S.; de'Michieli Vitturi, M.; Favalli, M.; Longo, A.; Nannipieri, L.; Neri, A.; Papale, P.; Saccorotti, G.

2009-12-01

Physical and numerical modelling is becoming of increasing importance in volcanology and volcanic hazard assessment. However, new interdisciplinary problems arise when dealing with complex mathematical formulations, numerical algorithms and their implementations on modern computer architectures. Therefore new frameworks are needed for sharing knowledge, software codes, and datasets among scientists. Here we present the Volcano Modelling and Simulation gateway (VMSg, accessible at http://vmsg.pi.ingv.it), a new electronic infrastructure for promoting knowledge growth and transfer in the field of volcanological modelling and numerical simulation. The new web portal, developed in the framework of former and ongoing national and European projects, is based on a dynamic Content Manager System (CMS) and was developed to host and present numerical models of the main volcanic processes and relationships including magma properties, magma chamber dynamics, conduit flow, plume dynamics, pyroclastic flows, lava flows, etc. Model applications, numerical code documentation, simulation datasets as well as model validation and calibration test-cases are also part of the gateway material.

Ionization chamber correction factors for MR-linacs

NASA Astrophysics Data System (ADS)

Pojtinger, Stefan; Steffen Dohm, Oliver; Kapsch, Ralf-Peter; Thorwarth, Daniela

2018-06-01

Previously, readings of air-filled ionization chambers have been described as being influenced by magnetic fields. To use these chambers for dosimetry in magnetic resonance guided radiotherapy (MRgRT), this effect must be taken into account by introducing a correction factor k B. The purpose of this study is to systematically investigate k B for a typical reference setup for commercially available ionization chambers with different magnetic field strengths. The Monte Carlo simulation tool EGSnrc was used to simulate eight commercially available ionization chambers in magnetic fields whose magnetic flux density was in the range of 0–2.5 T. To validate the simulation, the influence of the magnetic field was experimentally determined for a PTW30013 Farmer-type chamber for magnetic flux densities between 0 and 1.425 T. Changes in the detector response of up to 8% depending on the magnetic flux density, on the chamber geometry and on the chamber orientation were obtained. In the experimental setup, a maximum deviation of less than 2% was observed when comparing measured values with simulated values. Dedicated values for two MR-linac systems (ViewRay MRIdian, ViewRay Inc, Cleveland, United States, 0.35 T/ 6 MV and Elekta Unity, Elekta AB, Stockholm, Sweden, 1.5 T/7 MV) were determined for future use in reference dosimetry. Simulated values for thimble-type chambers are in good agreement with experiments as well as with the results of previous publications. After further experimental validation, the results can be considered for definition of standard protocols for purposes of reference dosimetry in MRgRT.

Ionization chamber correction factors for MR-linacs.

PubMed

Pojtinger, Stefan; Dohm, Oliver Steffen; Kapsch, Ralf-Peter; Thorwarth, Daniela

2018-06-07

Previously, readings of air-filled ionization chambers have been described as being influenced by magnetic fields. To use these chambers for dosimetry in magnetic resonance guided radiotherapy (MRgRT), this effect must be taken into account by introducing a correction factor k B . The purpose of this study is to systematically investigate k B for a typical reference setup for commercially available ionization chambers with different magnetic field strengths. The Monte Carlo simulation tool EGSnrc was used to simulate eight commercially available ionization chambers in magnetic fields whose magnetic flux density was in the range of 0-2.5 T. To validate the simulation, the influence of the magnetic field was experimentally determined for a PTW30013 Farmer-type chamber for magnetic flux densities between 0 and 1.425 T. Changes in the detector response of up to 8% depending on the magnetic flux density, on the chamber geometry and on the chamber orientation were obtained. In the experimental setup, a maximum deviation of less than 2% was observed when comparing measured values with simulated values. Dedicated values for two MR-linac systems (ViewRay MRIdian, ViewRay Inc, Cleveland, United States, 0.35 T/ 6 MV and Elekta Unity, Elekta AB, Stockholm, Sweden, 1.5 T/7 MV) were determined for future use in reference dosimetry. Simulated values for thimble-type chambers are in good agreement with experiments as well as with the results of previous publications. After further experimental validation, the results can be considered for definition of standard protocols for purposes of reference dosimetry in MRgRT.

Modeling physical vapor deposition of energetic materials

DOE PAGES

Shirvan, Koroush; Forrest, Eric C.

2018-03-28

Morphology and microstructure of organic explosive films formed using physical vapor deposition (PVD) processes strongly depends on local surface temperature during deposition. Currently, there is no accurate means of quantifying the local surface temperature during PVD processes in the deposition chambers. This study focuses on using a multiphysics computational fluid dynamics tool, STARCCM+, to simulate pentaerythritol tetranitrate (PETN) deposition. The PETN vapor and solid phase were simulated using the volume of fluid method and its deposition in the vacuum chamber on spinning silicon wafers was modeled. The model also included the spinning copper cooling block where the wafers are placedmore » along with the chiller operating with forced convection refrigerant. Implicit time-dependent simulations in two- and three-dimensional were performed to derive insights in the governing physics for PETN thin film formation. PETN is deposited at the rate of 14 nm/s at 142.9 °C on a wafer with an initial temperature of 22 °C. The deposition of PETN on the wafers was calculated at an assumed heat transfer coefficient (HTC) of 400 W/m 2 K. This HTC proved to be the most sensitive parameter in determining the local surface temperature during deposition. Previous experimental work found noticeable microstructural changes with 0.5 mm fused silica wafers in place of silicon during the PETN deposition. This work showed that fused silica slows initial wafer cool down and results in ~10 °C difference for the surface temperature at 500 μm PETN film thickness. It was also found that the deposition surface temperature is insensitive to the cooling power of the copper block due to the copper block's very large heat capacity and thermal conductivity relative to the heat input from the PVD process. Future work should incorporate the addition of local stress during PETN deposition. Lastly, based on simulation results, it is also recommended to investigate the impact of wafer surface energy on the PETN microstructure and morphology formation.« less

Modeling physical vapor deposition of energetic materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shirvan, Koroush; Forrest, Eric C.

Morphology and microstructure of organic explosive films formed using physical vapor deposition (PVD) processes strongly depends on local surface temperature during deposition. Currently, there is no accurate means of quantifying the local surface temperature during PVD processes in the deposition chambers. This study focuses on using a multiphysics computational fluid dynamics tool, STARCCM+, to simulate pentaerythritol tetranitrate (PETN) deposition. The PETN vapor and solid phase were simulated using the volume of fluid method and its deposition in the vacuum chamber on spinning silicon wafers was modeled. The model also included the spinning copper cooling block where the wafers are placedmore » along with the chiller operating with forced convection refrigerant. Implicit time-dependent simulations in two- and three-dimensional were performed to derive insights in the governing physics for PETN thin film formation. PETN is deposited at the rate of 14 nm/s at 142.9 °C on a wafer with an initial temperature of 22 °C. The deposition of PETN on the wafers was calculated at an assumed heat transfer coefficient (HTC) of 400 W/m 2 K. This HTC proved to be the most sensitive parameter in determining the local surface temperature during deposition. Previous experimental work found noticeable microstructural changes with 0.5 mm fused silica wafers in place of silicon during the PETN deposition. This work showed that fused silica slows initial wafer cool down and results in ~10 °C difference for the surface temperature at 500 μm PETN film thickness. It was also found that the deposition surface temperature is insensitive to the cooling power of the copper block due to the copper block's very large heat capacity and thermal conductivity relative to the heat input from the PVD process. Future work should incorporate the addition of local stress during PETN deposition. Lastly, based on simulation results, it is also recommended to investigate the impact of wafer surface energy on the PETN microstructure and morphology formation.« less

Development of a pore network simulation model to study nonaqueous phase liquid dissolution

USGS Publications Warehouse

Dillard, Leslie A.; Blunt, Martin J.

2000-01-01

A pore network simulation model was developed to investigate the fundamental physics of nonequilibrium nonaqueous phase liquid (NAPL) dissolution. The network model is a lattice of cubic chambers and rectangular tubes that represent pore bodies and pore throats, respectively. Experimental data obtained by Powers [1992] were used to develop and validate the model. To ensure the network model was representative of a real porous medium, the pore size distribution of the network was calibrated by matching simulated and experimental drainage and imbibition capillary pressure‐saturation curves. The predicted network residual styrene blob‐size distribution was nearly identical to the observed distribution. The network model reproduced the observed hydraulic conductivity and produced relative permeability curves that were representative of a poorly consolidated sand. Aqueous‐phase transport was represented by applying the equation for solute flux to the network tubes and solving for solute concentrations in the network chambers. Complete mixing was found to be an appropriate approximation for calculation of chamber concentrations. Mass transfer from NAPL blobs was represented using a corner diffusion model. Predicted results of solute concentration versus Peclet number and of modified Sherwood number versus Peclet number for the network model compare favorably with experimental data for the case in which NAPL blob dissolution was negligible. Predicted results of normalized effluent concentration versus pore volume for the network were similar to the experimental data for the case in which NAPL blob dissolution occurred with time.

The Outdoor Atmospheric Simulation Chamber of Orleans-France (HELIOS)

NASA Astrophysics Data System (ADS)

Mellouki, A.; Véronique, D.; Grosselin, B.; Peyroux, F.; Benoit, R.; Ren, Y.; Idir, M.

2016-12-01

Atmospheric simulation chambers are among the most advanced tools for investigating the atmospheric processes to derive physico-chemical parameters which are required for air quality and climate models. Recently, the ICARE-CNRS at Orléans (France) has set up a new large outdoor simulation chamber, HELIOS. HELIOS is one of the most advanced simulation chambers in Europe. It is one of the largest outdoor chambers and is especially suited to processes studies performed under realistic atmospheric conditions. HELIOS is a large hemispherical outdoor simulation chamber (volume of 90 m3) positioned on the top of ICARE-CNRS building at Orléans (47°50'18.39N; 1°56'40.03E). The chamber is made of FEP film ensuring more than 90 % solar light transmission. The chamber is protected against severe meteorological conditions by a moveable "box" which contains a series of Xenon lamps enabling to conduct experiments using artificial light. This special design makes HELIOS a unique platform where experiments can be made using both types of irradiations. HELIOS is dedicated mainly to the investigation of the chemical processes under different conditions (sunlight, artificial light and dark). The platform allows conducting the same type of experiments under both natural and artificial light irradiation. The available large range of complementary and highly sensitive instruments allows investigating the radical chemistry, gas phase processes and aerosol formation under realistic conditions. The characteristics of HELIOS will be presented as well as the first series of experimental results obtained so far.

A facility for long-term Mars simulation experiments: the Mars Environmental Simulation Chamber (MESCH).

PubMed

Jensen, Lars Liengaard; Merrison, Jonathan; Hansen, Aviaja Anna; Mikkelsen, Karina Aarup; Kristoffersen, Tommy; Nørnberg, Per; Lomstein, Bente Aagaard; Finster, Kai

2008-06-01

We describe the design, construction, and pilot operation of a Mars simulation facility comprised of a cryogenic environmental chamber, an atmospheric gas analyzer, and a xenon/mercury discharge source for UV generation. The Mars Environmental Simulation Chamber (MESCH) consists of a double-walled cylindrical chamber. The double wall provides a cooling mantle through which liquid N(2) can be circulated. A load-lock system that consists of a small pressure-exchange chamber, which can be evacuated, allows for the exchange of samples without changing the chamber environment. Fitted within the MESCH is a carousel, which holds up to 10 steel sample tubes. Rotation of the carousel is controlled by an external motor. Each sample in the carousel can be placed at any desired position. Environmental data, such as temperature, pressure, and UV exposure time, are computer logged and used in automated feedback mechanisms, enabling a wide variety of experiments that include time series. Tests of the simulation facility have successfully demonstrated its ability to produce temperature cycles and maintain low temperature (down to -140 degrees C), low atmospheric pressure (5-10 mbar), and a gas composition like that of Mars during long-term experiments.

A Facility for Long-Term Mars Simulation Experiments: The Mars Environmental Simulation Chamber (MESCH)

NASA Astrophysics Data System (ADS)

Jensen, Lars Liengaard; Merrison, Jonathan; Hansen, Aviaja Anna; Mikkelsen, Karina Aarup; Kristoffersen, Tommy; Nørnberg, Per; Lomstein, Bente Aagaard; Finster, Kai

2008-06-01

We describe the design, construction, and pilot operation of a Mars simulation facility comprised of a cryogenic environmental chamber, an atmospheric gas analyzer, and a xenon/mercury discharge source for UV generation. The Mars Environmental Simulation Chamber (MESCH) consists of a double-walled cylindrical chamber. The double wall provides a cooling mantle through which liquid N2 can be circulated. A load-lock system that consists of a small pressure-exchange chamber, which can be evacuated, allows for the exchange of samples without changing the chamber environment. Fitted within the MESCH is a carousel, which holds up to 10 steel sample tubes. Rotation of the carousel is controlled by an external motor. Each sample in the carousel can be placed at any desired position. Environmental data, such as temperature, pressure, and UV exposure time, are computer logged and used in automated feedback mechanisms, enabling a wide variety of experiments that include time series. Tests of the simulation facility have successfully demonstrated its ability to produce temperature cycles and maintain low temperature (down to -140°C), low atmospheric pressure (5 10 mbar), and a gas composition like that of Mars during long-term experiments.

Monte Carlo calculation of energy deposition in ionization chambers for tritium measurements

NASA Astrophysics Data System (ADS)

Zhilin, Chen; Shuming, Peng; Dan, Meng; Yuehong, He; Heyi, Wang

2014-10-01

Energy deposition in ionization chambers for tritium measurements has been theoretically studied using Monte Carlo code MCNP 5. The influence of many factors, including carrier gas, chamber size, wall materials and gas pressure, has been evaluated in the simulations. It is found that β rays emitted by tritium deposit much more energy into chambers flowing through with argon than with deuterium in them, as much as 2.7 times higher at pressure 100 Pa. As chamber size gets smaller, energy deposition decreases sharply. For an ionization chamber of 1 mL, β rays deposit less than 1% of their energy at pressure 100 Pa and only 84% even if gas pressure is as high as 100 kPa. It also indicates that gold plated ionization chamber results in the highest deposition ratio while aluminum one leads to the lowest. In addition, simulations were validated by comparison with experimental data. Results show that simulations agree well with experimental data.

Superconducting-Magnet-Based Faraday Rotation Spectrometer for Real Time in Situ Measurement of OH Radicals at 106 Molecule/cm3 Level in an Atmospheric Simulation Chamber.

PubMed

Zhao, Weixiong; Fang, Bo; Lin, Xiaoxiao; Gai, Yanbo; Zhang, Weijun; Chen, Wenge; Chen, Zhiyou; Zhang, Haifeng; Chen, Weidong

2018-03-20

Atmospheric simulation chambers play vital roles in the validation of chemical mechanisms and act as a bridge between field measurements and modeling. Chambers operating at atmospheric levels of OH radicals (10 6 -10 7 molecule/cm 3 ) can significantly enhance the possibility for investigating the discrepancies between the observation and model predications. However, few chambers can directly detect chamber OH radicals at ambient levels. In this paper, we report on the first combination of a superconducting magnet with midinfrared Faraday rotation spectroscopy (FRS) for real time in situ measurement of the OH concentration in an atmospheric simulation chamber. With the use of a multipass enhanced FRS, a detection limit of 3.2 × 10 6 OH/cm 3 (2σ, 4 s) was achieved with an absorption path length of 108 m. The developed FRS system provided a unique, self-calibrated analytical instrument for in situ direct measurement of chamber OH concentration.

Physiological responses to simulated firefighter exercise protocols in varying environments.

PubMed

Horn, Gavin P; Kesler, Richard M; Motl, Robert W; Hsiao-Wecksler, Elizabeth T; Klaren, Rachel E; Ensari, Ipek; Petrucci, Matthew N; Fernhall, Bo; Rosengren, Karl S

2015-01-01

For decades, research to quantify the effects of firefighting activities and personal protective equipment on physiology and biomechanics has been conducted in a variety of testing environments. It is unknown if these different environments provide similar information and comparable responses. A novel Firefighting Activities Station, which simulates four common fireground tasks, is presented for use with an environmental chamber in a controlled laboratory setting. Nineteen firefighters completed three different exercise protocols following common research practices. Simulated firefighting activities conducted in an environmental chamber or live-fire structures elicited similar physiological responses (max heart rate: 190.1 vs 188.0 bpm, core temperature response: 0.047°C/min vs 0.043°C/min) and accelerometry counts. However, the response to a treadmill protocol commonly used in laboratory settings resulted in significantly lower heart rate (178.4 vs 188.0 bpm), core temperature response (0.037°C/min vs 0.043°C/min) and physical activity counts compared with firefighting activities in the burn building. Practitioner Summary: We introduce a new approach for simulating realistic firefighting activities in a controlled laboratory environment for ergonomics assessment of fire service equipment and personnel. Physiological responses to this proposed protocol more closely replicate those from live-fire activities than a traditional treadmill protocol and are simple to replicate and standardise.

Mutagenicity in Salmonella of a Simulated Urban-Smog Atmosphere Generated Using a Mobile Reaction Chamber

EPA Science Inventory

The EPA Mobile Reaction Chamber (MRC) is a 24-foot trailer containing a 14.3-m3 Teflon lined photochemical chamber used to generate simulated urban atmospheres. Photochemistry in the MRC is catalyzed by 120 fluorescent bulbs evenly mixed with black light bulbs and UV bulbs (300 &...

To Create Space on Earth: The Space Environment Simulation Laboratory and Project Apollo

NASA Technical Reports Server (NTRS)

Walters, Lori C.

2003-01-01

Few undertakings in the history of humanity can compare to the great technological achievement known as Project Apollo. Among those who witnessed Armstrong#s flickering television image were thousands of people who had directly contributed to this historic moment. Amongst those in this vast anonymous cadre were the personnel of the Space Environment Simulation Laboratory (SESL) at the Manned Spacecraft Center (MSC) in Houston, Texas. SESL houses two large thermal-vacuum chambers with solar simulation capabilities. At a time when NASA engineers had a limited understanding of the effects of extremes of space on hardware and crews, SESL was designed to literally create the conditions of space on Earth. With interior dimensions of 90 feet in height and a 55-foot diameter, Chamber A dwarfed the Apollo command/service module (CSM) it was constructed to test. The chamber#s vacuum pumping capacity of 1 x 10(exp -6) torr can simulate an altitude greater than 130 miles above the Earth. A "lunar plane" capable of rotating a 150,000-pound test vehicle 180 deg replicates the revolution of a craft in space. To reproduce the temperature extremes of space, interior chamber walls cool to -280F as two banks of carbon arc modules simulate the unfiltered solar light/heat of the Sun. With capabilities similar to that of Chamber A, early Chamber B tests included the Gemini modular maneuvering unit, Apollo EVA mobility unit and the lunar module. Since Gemini astronaut Charles Bassett first ventured into the chamber in 1966, Chamber B has assisted astronauts in testing hardware and preparing them for work in the harsh extremes of space.

A three-dimensional numerical simulation of cell behavior in a flow chamber based on fluid-solid interaction.

PubMed

Bai, Long; Cui, Yuhong; Zhang, Yixia; Zhao, Na

2014-01-01

The mechanical behavior of blood cells in the vessels has a close relationship with the physical characteristics of the blood and the cells. In this paper, a numerical simulation method was proposed to understand a single-blood cell's behavior in the vessels based on fluid-solid interaction method, which was conducted under adaptive time step and fixed time step, respectively. The main programme was C++ codes, which called FLUENT and ANSYS software, and UDF and APDL acted as a messenger to connect FLUENT and ANSYS for exchanging data. The computing results show: (1) the blood cell moved towards the bottom of the flow chamber in the beginning due to the influence of gravity, then it began to jump up when reached a certain height rather than touching the bottom. It could move downwards again after jump up, the blood cell could keep this way of moving like dancing continuously in the vessels; (2) the blood cell was rolling and deforming all the time; the rotation had oscillatory changes and the deformation became conspicuously when the blood cell was dancing. This new simulation method and results can be widely used in the researches of cytology, blood, cells, etc.

Simulation of nitrous oxide effluxes, crop yields and soil physical properties using the LandscapeDNDC model in managed ecosystem

NASA Astrophysics Data System (ADS)

Nyckowiak, Jedrzej; Lesny, Jacek; Haas, Edwin; Juszczak, Radoslaw; Kiese, Ralf; Butterbach-Bahl, Klaus; Olejnik, Janusz

2014-05-01

Modeling of nitrous oxide emissions from soil is very complex. Many different biological and chemical processes take place in soils which determine the amount of emitted nitrous oxide. Additionaly, biogeochemical models contain many detailed factors which may determine fluxes and other simulated variables. We used the LandscapeDNDC model in order to simulate N2O emissions, crop yields and soil physical properties from mineral cultivated soils in Poland. Nitrous oxide emissions from soils were modeled for fields with winter wheat, winter rye, spring barley, triticale, potatoes and alfalfa crops. Simulations were carried out for the plots of the Brody arable experimental station of Poznan University of Life Science in western Poland and covered the period 2003 - 2012. The model accuracy and its efficiency was determined by comparing simulations result with measurements of nitrous oxide emissions (measured with static chambers) from about 40 field campaigns. N2O emissions are strongly dependent on temperature and soil water content, hence we compared also simulated soil temperature at 10cm depth and soil water content at the same depth with the daily measured values of these driving variables. We compared also simulated yield quantities for each individual experimental plots with yield quantities which were measured in the period 2003-2012. We conclude that the LandscapeDNDC model is capable to simulate soil N2O emissions, crop yields and physical properties of soil with satisfactorily good accuracy and efficiency.

Hypobaric chamber for the study of oral health problems in a simulated spacecraft environment

NASA Technical Reports Server (NTRS)

Brown, L. R.

1974-01-01

A hypobaric chamber was constructed to house two marmo-sets simultaneously in a space-simulated environment for periods of 14, 28 and 56 days which coincided with the anticipated Skylab missions. This report details the fabrication, operation, and performance of the chamber and very briefly reviews the scientific data from nine chamber trials involving 18 animals. The possible application of this model system to studies unrelated to oral health or space missions is discussed.

[Development of a microenvironment test chamber for airborne microbe research].

PubMed

Zhan, Ningbo; Chen, Feng; Du, Yaohua; Cheng, Zhi; Li, Chenyu; Wu, Jinlong; Wu, Taihu

2017-10-01

One of the most important environmental cleanliness indicators is airborne microbe. However, the particularity of clean operating environment and controlled experimental environment often leads to the limitation of the airborne microbe research. This paper designed and implemented a microenvironment test chamber for airborne microbe research in normal test conditions. Numerical simulation by Fluent showed that airborne microbes were evenly dispersed in the upper part of test chamber, and had a bottom-up concentration growth distribution. According to the simulation results, the verification experiment was carried out by selecting 5 sampling points in different space positions in the test chamber. Experimental results showed that average particle concentrations of all sampling points reached 10 7 counts/m 3 after 5 minutes' distributing of Staphylococcus aureus , and all sampling points showed the accordant mapping of concentration distribution. The concentration of airborne microbe in the upper chamber was slightly higher than that in the middle chamber, and that was also slightly higher than that in the bottom chamber. It is consistent with the results of numerical simulation, and it proves that the system can be well used for airborne microbe research.

Mimicking Mars: a vacuum simulation chamber for testing environmental instrumentation for Mars exploration.

PubMed

Sobrado, J M; Martín-Soler, J; Martín-Gago, J A

2014-03-01

We have built a Mars environmental simulation chamber, designed to test new electromechanical devices and instruments that could be used in space missions. We have developed this environmental system aiming at validating the meteorological station Rover Environment Monitoring Station of NASA's Mars Science Laboratory mission currently installed on Curiosity rover. The vacuum chamber has been built following a modular configuration and operates at pressures ranging from 1000 to 10(-6) mbars, and it is possible to control the gas composition (the atmosphere) within this pressure range. The device (or sample) under study can be irradiated by an ultraviolet source and its temperature can be controlled in the range from 108 to 423 K. As an important improvement with respect to other simulation chambers, the atmospheric gas into the experimental chamber is cooled at the walls by the use of liquid-nitrogen heat exchangers. This chamber incorporates a dust generation mechanism designed to study Martian-dust deposition while modifying the conditions of temperature, and UV irradiated.

INVESTIGATION OF THE HUMIDITY EFFECT ON THE FAC-IR-300 IONIZATION CHAMBER RESPONSE.

PubMed

Mohammadi, Seyed Mostafa; Tavakoli-Anbaran, Hossein

2018-02-01

The free-air ionization chamber is communicating with the ambient air, therefore, the atmospheric parameters such as temperature, pressure and humidity effect on the ionization chamber performance. The free-air ionization chamber, entitled as FAC-IR-300, that design at the Atomic Energy Organization of Iran, AEOI, is required the atmospheric correction factors for correct the chamber reading. In this article, the effect of humidity on the ionization chamber response was investigated. For this reason, was introduced the humidity correction factor, kh. In this article, the Monte Carlo simulation was used to determine the kh factor. The simulation results show in relative humidities between 30% to 80%, the kh factor is equal 0.9970 at 20°C and 0.9975 at 22°C. From the simulation results, at low energy the energy dependence of the kh factor is significant and with increasing energy this dependence is negligible. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Physico-Chemical Evolution of Organic Aerosol from Wildfire Emissions

NASA Astrophysics Data System (ADS)

Croteau, P.; Jathar, S.; Akherati, A.; Galang, A.; Tarun, S.; Onasch, T. B.; Lewane, L.; Herndon, S. C.; Roscioli, J. R.; Yacovitch, T. I.; Fortner, E.; Xu, W.; Daube, C.; Knighton, W. B.; Werden, B.; Wood, E.

2017-12-01

Wildfires are the largest combustion-related source of carbonaceous emissions to the atmosphere; these include direct emissions of black carbon (BC), primary organic aerosol (POA) and semi-volatile, intermediate-volatility, and volatile organic compounds (SVOCs, IVOCs, and VOCs). However, there are large uncertainties surrounding the evolution of these carbonaceous emissions as they are physically and chemically transformed in the atmosphere. To understand these transformations, we performed sixteen experiments using an environmental chamber to simulate day- and night-time chemistry of gas- and aerosol-phase emissions from 6 different fuels at the Fire Laboratory in Missoula, MT. Across the test matrix, the experiments simulated 2 to 8 hours of equivalent day-time aging (with the hydroxyl radical and ozone) or several hours of night-time aging (with the nitrate radical). Aging resulted in an average organic aerosol (OA) mass enhancement of 28% although the full range of OA mass enhancements varied between -10% and 254%. These enhancement findings were consistent with chamber and flow reactor experiments performed at the Fire Laboratory in 2010 and 2012 but, similar to previous studies, offered no evidence to link the OA mass enhancement to fuel type or oxidant exposure. Experiments simulating night-time aging resulted in an average OA mass enhancement of 10% and subsequent day-time aging resulted in a decrease in OA mass of 8%. While small, for the first time, these experiments highlighted the continuous nature of the OA evolution as the wildfire smoke cycled through night- and day-time processes. Ongoing work is focussed on (i) quantifying bulk compositional changes in OA, (ii) comparing the near-field aging simulated in this work with far-field aging simulated during the same campaign (via a mini chamber and flow tube) and (iii) integrating wildfire smoke aging datasets over the past decade to examine the relationship between OA mass enhancement ratios, modified combustion efficiency, initial aerosol concentrations and composition, aerosol size, oxidant exposure, VOC:NOx ratios, and emissions and speciation of SOA precursors.

On the acoustic wedge design and simulation of anechoic chamber

NASA Astrophysics Data System (ADS)

Jiang, Changyong; Zhang, Shangyu; Huang, Lixi

2016-10-01

This study proposes an alternative to the classic wedge design for anechoic chambers, which is the uniform-then-gradient, flat-wall (UGFW) structure. The working mechanisms of the proposed structure and the traditional wedge are analyzed. It is found that their absorption patterns are different. The parameters of both structures are optimized for achieving minimum absorber depth, under the condition of absorbing 99% of normal incident sound energy. It is found that, the UGFW structure achieves a smaller total depth for the cut-off frequencies ranging from 100 Hz to 250 Hz. This paper also proposes a modification for the complex source image (CSI) model for the empirical simulation of anechoic chambers, originally proposed by Bonfiglio et al. [J. Acoust. Soc. Am. 134 (1), 285-291 (2013)]. The modified CSI model considers the non-locally reactive effect of absorbers at oblique incidence, and the improvement is verified by a full, finite-element simulation of a small chamber. With the modified CSI model, the performance of both decorations with the optimized parameters in a large chamber is simulated. The simulation results are analyzed and checked against the tolerance of 1.5 dB deviation from the inverse square law, stipulated in the ISO standard 3745(2003). In terms of the total decoration depth and anechoic chamber performance, the UGFW structure is better than the classic wedge design.

Construction and Characterization of an Indoor Smog Chamber for Measuring Chemical and Optical Properties of Biomass Burning Aerosols as a Function of Age

NASA Astrophysics Data System (ADS)

Smith, D. M.; Fiddler, M. N.; Sexton, K.; Bililign, S.; Dowdell, T. M.

2016-12-01

Biomass burning is recognized as one of the largest sources of absorbing aerosols in the atmosphere and significantly influences the radiative properties of the atmosphere. In the atmosphere, aerosols dynamically change in complex ways. The chemical composition and physical properties of particles evolve during their atmospheric lifetime due to condensation, oxidation reactions, etc. Changes in chemical composition due to aging is likely to change the optical properties of these particles as well. We have built a 9.01m3 indoor smog chamber made of FEP Teflon. Wood and other organic samples are burned in a tube furnace with the exhaust going directly into the chamber. The construction, characterization, and calibration of the smog chamber will be presented, along with preliminary measurements of extinction and scattering of biomass burning aerosols measured using a Cavity Ring-down and Integrating Nephelometry system. This system allows us to measure any changes in the optical properties of the soot as it ages. Injections to the chamber can be controlled to simulate various atmospheric conditions. These include clean (dry) air, laboratory (room) air, water vapor, NOX, and various biogenic and anthropogenic VOCs such as aromatic hydrocarbons. These components and some of their oxidation products can also be monitored and characterized during aging. The authors acknowledge the support from the National Science Foundation through Grant Number NSF-AGS-1555479

Reactivation of Latent Viruses in Space

NASA Technical Reports Server (NTRS)

Pierson, D. L.; Mehta, S. K.; Tyring, S. K.; Lugg, D. J.

1999-01-01

Reactivation of latent viruses is an important health risk for people working and living in physically isolated extreme environments such as Antarctica and space. Preflight quarantine does not significantly reduce the risk associated with latent viruses, however, pharmaceutical countermeasures are available for some viruses. The molecular basis of latency is not fully understood, but physical and psychosocial stresses are known to initiate the reactivation of latent viruses. Presumably, stress induced changes in selected hormones lead to alterations in the cell- mediated immune (CMI) response resulting in increased shedding of latent viruses. Limited access to space makes the use of ground-based analogs essential. The Australian Antarctic stations serve as a good stress model and simulate many aspects of space flight. Closed environmental chambers have been used to simulate space flight since the Skylab missions and have also proven to be a valuable analog of selected aspects of space flight.

Method and apparatus for simulating atomospheric absorption of solar energy due to water vapor and CO.sub.2

DOEpatents

Sopori, Bhushan L.

1995-01-01

A method and apparatus for improving the accuracy of the simulation of sunlight reaching the earth's surface includes a relatively small heated chamber having an optical inlet and an optical outlet, the chamber having a cavity that can be filled with a heated stream of CO.sub.2 and water vapor. A simulated beam comprising infrared and near infrared light can be directed through the chamber cavity containing the CO.sub.2 and water vapor, whereby the spectral characteristics of the beam are altered so that the output beam from the chamber contains wavelength bands that accurately replicate atmospheric absorption of solar energy due to atmospheric CO.sub.2 and moisture.

Method and apparatus for simulating atmospheric absorption of solar energy due to water vapor and CO{sub 2}

DOEpatents

Sopori, B.L.

1995-06-20

A method and apparatus for improving the accuracy of the simulation of sunlight reaching the earth`s surface includes a relatively small heated chamber having an optical inlet and an optical outlet, the chamber having a cavity that can be filled with a heated stream of CO{sub 2} and water vapor. A simulated beam comprising infrared and near infrared light can be directed through the chamber cavity containing the CO{sub 2} and water vapor, whereby the spectral characteristics of the beam are altered so that the output beam from the chamber contains wavelength bands that accurately replicate atmospheric absorption of solar energy due to atmospheric CO{sub 2} and moisture. 8 figs.

Evaluation of Heat Recuperation in a Concentric Hydrogen Reduction Reactor

NASA Technical Reports Server (NTRS)

Linne, Diane; Kleinhenz, Julie; Hegde, Uday

2012-01-01

Heat recuperation in an ISRU reactor system involves the recovery of heat from a reacted regolith batch by transferring this energy into a batch of fresh regolith. One concept for a hydrogen reduction reactor is a concentric chamber design where heat is transferred from the inner, reaction chamber into fresh regolith in the outer, recuperation chamber. This concept was tested and analyzed to define the overall benefit compared to a more traditional single chamber batch reactor. Data was gathered for heat-up and recuperation in the inner chamber alone, simulating a single chamber design, as well as recuperation into the outer chamber, simulating a dual chamber design. Experimental data was also used to improve two analytical models, with good agreement for temperature behavior during recuperation, calculated mass of the reactor concepts, and energy required during heat-up. The five tests, performed using JSC-1A regolith simulant, also explored the effectiveness of helium gas fluidization, hydrogen gas fluidization, and vibrational fluidization. Results indicate that higher hydrogen volumetric flow rates are required compared to helium for complete fluidization and mixing, and that vibrational fluidization may provide equivalent mixing while eliminating the need to flow large amounts of excess hydrogen. Analysis of the total energy required for heat-up and steady-state operations for a variety of conditions and assumptions shows that the dual-chamber concept requires the same or more energy than the single chamber concept. With no clear energy savings, the added mass and complexity of the dual-chamber makes it unlikely that this design concept will provide any added benefit to the overall ISRU oxygen production system.

Development of the AFRL Aircrew Perfomance and Protection Data Bank

DTIC Science & Technology

2007-12-01

Growth model and statistical model of hypobaric chamber simulations. It offers a quick and readily accessible online DCS risk assessment tool for...are used for the DCS prediction instead of the original model. ADRAC is based on more than 20 years of hypobaric chamber studies using human...prediction based on the combined Bubble Growth model and statistical model of hypobaric chamber simulations was integrated into the Data Bank. It

SU-E-T-562: Scanned Percent Depth Dose Curve Discrepancy for Photon Beams with Physical Wedge in Place (Varian IX) Using Different Sensitive Volume Ion Chambers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, H; Sarkar, V; Rassiah-Szegedi, P

2014-06-01

Purpose: To investigate and report the discrepancy of scanned percent depth dose (PDD) for photon beams with physical wedge in place when using ion chambers with different sensitive volumes. Methods/Materials: PDD curves of open fields and physical wedged fields (15, 30, 45, and 60 degree wedge) were scanned for photon beams (6MV and 10MV, Varian iX) with field size of 5x5 and 10x10 cm using three common scanning chambers with different sensitive volumes - PTW30013 (0.6cm3), PTW23323 (0.1cm3) and Exradin A16 (0.007cm3). The scanning system software used was OmniPro version 6.2, and the scanning water tank was the Scanditronix Wellhoffermore » RFA 300.The PDD curves from the three chambers were compared. Results: Scanned PDD curves of the same energy beams for open fields were almost identical between three chambers, but the wedged fields showed non-trivial differences. The largest differences were observed between chamber PTW30013 and Exradin A16. The differences increased as physical wedge angle increased. The differences also increased with depth, and were more pronounced for 6MV beam. Similar patterns were shown for both 5x5 and 10x10 cm field sizes. For open fields, all PDD values agreed with each other within 1% at 10cm depth and within 1.62% at 20 cm depth. For wedged fields, the difference of PDD values between PTW30013 and A16 reached 4.09% at 10cm depth, and 5.97% at 20 cm depth for 6MV with 60 degree physical wedge. Conclusion: We observed a significant difference in scanned PDD curves of photon beams with physical wedge in place obtained when using different sensitive volume ion chambers. The PDD curves scanned with the smallest sensitive volume ion chamber showed significant difference from larger chamber results, beyond 10cm depth. We believe this to be caused by varying response to beam hardening by the wedges.« less

Numerical Investigation of the Impact of the Compressor Operation Mode on Working Process of the Combustion Chamber

NASA Astrophysics Data System (ADS)

Orlov, M. Yu; Lukachev, S. V.; Anisimov, V. M.

2018-01-01

The method of integrated compressor/combustor simulation was used to investigate the impact of flow distortion, appeared due to compressor blades, during the combustion chamber workflow. The method was improved in terms of generating a common grid and of principles of the boundary conditions settings. The geometric model includes four geometric volume bodies: guide vanes of the penultimate stage of high-pressure compressor, the impeller and guide vanes of the last stage and the flow path of combustion chamber. The calculation was carried out for some operation mode of the engine (nominal, 0.7 of nominal and 0.5 of nominal regimes) with and without compressor. The results were compared with the results of combustion chamber simulation without the compressor. Simulations showed that blade wakes extend up to the flame tube head. These wakes influence on the flame tongue, pressure field, temperature and velocity in the recirculation-mixing zone. It can influence on combustion efficiency, ecological performance and on temperature field at the combustor outlet. Thus, the simulations, which take into account combustion chamber and compressor, are more fully represent the characteristics of the working process of the combustion chamber and increase the efficiency of the design of new products.

Mimicking Mars: A vacuum simulation chamber for testing environmental instrumentation for Mars exploration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sobrado, J. M., E-mail: sobradovj@inta.es; Martín-Soler, J.; Martín-Gago, J. A.

We have built a Mars environmental simulation chamber, designed to test new electromechanical devices and instruments that could be used in space missions. We have developed this environmental system aiming at validating the meteorological station Rover Environment Monitoring Station of NASA's Mars Science Laboratory mission currently installed on Curiosity rover. The vacuum chamber has been built following a modular configuration and operates at pressures ranging from 1000 to 10{sup −6} mbars, and it is possible to control the gas composition (the atmosphere) within this pressure range. The device (or sample) under study can be irradiated by an ultraviolet source andmore » its temperature can be controlled in the range from 108 to 423 K. As an important improvement with respect to other simulation chambers, the atmospheric gas into the experimental chamber is cooled at the walls by the use of liquid-nitrogen heat exchangers. This chamber incorporates a dust generation mechanism designed to study Martian-dust deposition while modifying the conditions of temperature, and UV irradiated.« less

Monte Carlo simulation of electron beams from an accelerator head using PENELOPE.

PubMed

Sempau, J; Sánchez-Reyes, A; Salvat, F; ben Tahar, H O; Jiang, S B; Fernández-Varea, J M

2001-04-01

The Monte Carlo code PENELOPE has been used to simulate electron beams from a Siemens Mevatron KDS linac with nominal energies of 6, 12 and 18 MeV. Owing to its accuracy, which stems from that of the underlying physical interaction models, PENELOPE is suitable for simulating problems of interest to the medical physics community. It includes a geometry package that allows the definition of complex quadric geometries, such as those of irradiation instruments, in a straightforward manner. Dose distributions in water simulated with PENELOPE agree well with experimental measurements using a silicon detector and a monitoring ionization chamber. Insertion of a lead slab in the incident beam at the surface of the water phantom produces sharp variations in the dose distributions, which are correctly reproduced by the simulation code. Results from PENELOPE are also compared with those of equivalent simulations with the EGS4-based user codes BEAM and DOSXYZ. Angular and energy distributions of electrons and photons in the phase-space plane (at the downstream end of the applicator) obtained from both simulation codes are similar, although significant differences do appear in some cases. These differences, however, are shown to have a negligible effect on the calculated dose distributions. Various practical aspects of the simulations, such as the calculation of statistical uncertainties and the effect of the 'latent' variance in the phase-space file, are discussed in detail.

LES/FMDF of turbulent jet ignition in a rapid compression machine

NASA Astrophysics Data System (ADS)

Validi, Abdoulahad; Schock, Harold; Toulson, Elisa; Jaberi, Farhad; CFD; Engine Research Labs, Michigan State University Collaboration

2015-11-01

Turbulent Jet Ignition (TJI) is an efficient method for initiating and controlling combustion in combustion systems, e.g. internal combustion engines. It enables combustion in ultra-lean mixtures by utilizing hot product turbulent jets emerging from a pre-chamber combustor as the ignition source for the main combustion chamber. Here, we study the TJI-assisted ignition and combustion of lean methane-air mixtures in a Rapid Compression Machine (RCM) for various flow/combustion conditions with the hybrid large eddy simulation/filtered mass density function (LES/FMDF) computational model. In the LES/FMDF model, the filtered form of compressible Navier-Stokes equations are solved with a high-order finite difference scheme for the turbulent velocity, while the FMDF transport equation is solved with a Lagrangian stochastic method to obtain the scalar (species mass fraction and temperature) field. The LES/FMDF data are used to study the physics of TJI and combustion in RCM. The results show the very complex behavior of the reacting flow and the flame structure in the pre-chamber and RCM.

Characteristics of the Plasma Source for Ground Ionosphere Simulation Surveyed by Disk-Type Langmuir Probe

NASA Astrophysics Data System (ADS)

Ryu, Kwangsun; Lee, Junchan; Kim, Songoo; Chung, Taejin; Shin, Goo-Hwan; Cha, Wonho; Min, Kyoungwook; Kim, Vitaly P.

2017-12-01

A space plasma facility has been operated with a back-diffusion-type plasma source installed in a mid-sized vacuum chamber with a diameter of 1.5 m located in Satellite Technology Research Center (SaTReC), Korea Advanced Institute of Science and Technology (KAIST). To generate plasma with a temperature and density similar to the ionospheric plasma, nickel wires coated with carbonate solution were used as filaments that emit thermal electrons, and the accelerated thermal electrons emitted from the heated wires collide with the neutral gas to form plasma inside the chamber. By using a disk-type Langmuir probe installed inside the vacuum chamber, the generation of plasma similar to the space environment was validated. The characteristics of the plasma according to the grid and plate anode voltages were investigated. The grid voltage of the plasma source is realized as a suitable parameter for manipulating the electron density, while the plate voltage is suitable for adjusting the electron temperature. A simple physical model based on the collision cross-section of electron impact on nitrogen molecule was established to explain the plasma generation mechanism.

Laboratory Simulations of the Solar Wind's Effect on Surface Interactions and Plasma Wakes

NASA Astrophysics Data System (ADS)

Munsat, T. L.; Ulibarri, Z.; Han, J.; Horanyi, M.; Wang, X.; Yeo, L. H.

2016-12-01

The Colorado Solar Wind Experiment (CSWE) is a new device constructed at the Institute for Modeling Plasma, Atmospheres, and Cosmic Dust (IMPACT) at the University of Colorado. This large ion source is being developed for studies of the interaction of solar wind plasma with planetary surfaces and cosmic dust, and for the investigation of plasma wake physics. With a plasma beam diameter of 12 cm at the source, ion energies of up to 1 keV, and ion flows of up to 1 mA/cm^2, a large cross-section Kaufman Ion Source is used to create steady state plasma flow to model the solar wind in an experimental vacuum chamber. Chamber pressure can be reduced to 3x10^-5 Torr under operating conditions to suppress ion-neutral collisions and create a uniform ion velocity distribution. Diagnostic instruments such as a double Langmuir probe and an ion energy analyzer are mounted on a two-dimensional translation stage that allow the beam to be characterized throughout the chamber. Initial experimental results and technical details of the device will be explained.

The INAF/IAPS Plasma Chamber for ionospheric simulation experiment

NASA Astrophysics Data System (ADS)

Diego, Piero

2016-04-01

The plasma chamber is particularly suitable to perform studies for the following applications: - plasma compatibility and functional tests on payloads envisioned to operate in the ionosphere (e.g. sensors onboard satellites, exposed to the external plasma environment); - calibration/testing of plasma diagnostic sensors; - characterization and compatibility tests on components for space applications (e.g. optical elements, harness, satellite paints, photo-voltaic cells, etc.); - experiments on satellite charging in a space plasma environment; - tests on active experiments which use ion, electron or plasma sources (ion thrusters, hollow cathodes, field effect emitters, plasma contactors, etc.); - possible studies relevant to fundamental space plasma physics. The facility consists of a large volume vacuum tank (a cylinder of length 4.5 m and diameter 1.7 m) equipped with a Kaufman type plasma source, operating with Argon gas, capable to generate a plasma beam with parameters (i.e. density and electron temperature) close to the values encountered in the ionosphere at F layer altitudes. The plasma beam (A+ ions and electrons) is accelerated into the chamber at a velocity that reproduces the relative motion between an orbiting satellite and the ionosphere (≈ 8 km/s). This feature, in particular, allows laboratory simulations of the actual compression and depletion phenomena which take place in the ram and wake regions around satellites moving through the ionosphere. The reproduced plasma environment is monitored using Langmuir Probes (LP) and Retarding Potential Analyzers (RPA). These sensors can be automatically moved within the experimental space using a sled mechanism. Such a feature allows the acquisition of the plasma parameters all around the space payload installed into the chamber for testing. The facility is currently in use to test the payloads of CSES satellite (Chinese Seismic Electromagnetic Satellite) devoted to plasma parameters and electric field measurements in a polar orbit at 500 km altitude.

Blast from pressurized carbon dioxide released into a vented atmospheric chamber

NASA Astrophysics Data System (ADS)

Hansen, P. M.; Gaathaug, A. V.; Bjerketvedt, D.; Vaagsaether, K.

2018-03-01

This study describes the blast from pressurized carbon dioxide (CO2) released from a high-pressure reservoir into an openly vented atmospheric chamber. Small-scale experiments with pure vapor and liquid/vapor mixtures were conducted and compared with simulations. A motivation was to investigate the effects of vent size and liquid content on the peak overpressure and impulse response in the atmospheric chamber. The comparison of vapor-phase CO2 test results with simulations showed good agreement. This numerical code described single-phase gas dynamics inside a closed chamber, but did not model any phase transitions. Hence, the simulations described a vapor-only test into an unvented chamber. Nevertheless, the simulations reproduced the incident shock wave, the shock reflections, and the jet release inside the atmospheric chamber. The rapid phase transition did not contribute to the initial shock strength in the current test geometry. The evaporation rate was too low to contribute to the measured peak overpressure that was in the range of 15-20 kPa. The simulation results produced a calculated peak overpressure of 12 kPa. The liquid tests showed a significantly higher impulse compared to tests with pure vapor. Reducing the vent opening from 0.1 to 0.01 m2 resulted in a slightly higher impulse calculated at 100 ms. The influence of the vent area on the calculated impulse was significant in the vapor-phase tests, but not so clear in the liquid/vapor mixture tests.

Two-statge sorption type cryogenic refrigerator including heat regeneration system

NASA Technical Reports Server (NTRS)

Jones, Jack A. (Inventor); Wen, Liang-Chi (Inventor); Bard, Steven (Inventor)

1989-01-01

A lower stage chemisorption refrigeration system physically and functionally coupled to an upper stage physical adsorption refrigeration system. Waste heat generated by the lower stage cycle is regenerated to fuel the upper stage cycle thereby greatly improving the energy efficiency of a two-stage sorption refrigerator. The two stages are joined by disposing a first pressurization chamber providing a high pressure flow of a first refrigerant for the lower stage refrigeration cycle within a second pressurization chamber providing a high pressure flow of a second refrigerant for the upper stage refrigeration cycle. The first pressurization chamber is separated from the second pressurization chamber by a gas-gap thermal switch which at times is filled with a thermoconductive fluid to allow conduction of heat from the first pressurization chamber to the second pressurization chamber.

Incremental Reactivity Effects on Secondary Organic Aerosol Formation in Urban Atmospheres with and without Biogenic Influence

NASA Astrophysics Data System (ADS)

Kacarab, Mary; Li, Lijie; Carter, William P. L.; Cocker, David R., III

2016-04-01

Two different surrogate mixtures of anthropogenic and biogenic volatile organic compounds (VOCs) were developed to study secondary organic aerosol (SOA) formation at atmospheric reactivities similar to urban regions with varying biogenic influence levels. Environmental chamber simulations were designed to enable the study of the incremental aerosol formation from select anthropogenic (m-Xylene, 1,2,4-Trimethylbenzene, and 1-Methylnaphthalene) and biogenic (α-pinene) precursors under the chemical reactivity set by the two different surrogate mixtures. The surrogate reactive organic gas (ROG) mixtures were based on that used to develop the maximum incremental reactivity (MIR) factors for evaluation of O3 forming potential. Multiple incremental aerosol formation experiments were performed in the University of California Riverside (UCR) College of Engineering Center for Environmental Research and Technology (CE-CERT) dual 90m3 environmental chambers. Incremental aerosol yields were determined for each of the VOCs studied and compared to yields found from single precursor studies. Aerosol physical properties of density, volatility, and hygroscopicity were monitored throughout experiments. Bulk elemental chemical composition from high-resolution time of flight aerosol mass spectrometer (HR-ToF-AMS) data will also be presented. Incremental yields and SOA chemical and physical characteristics will be compared with data from previous single VOC studies conducted for these aerosol precursors following traditional VOC/NOx chamber experiments. Evaluation of the incremental effects of VOCs on SOA formation and properties are paramount in evaluating how to best extrapolate environmental chamber observations to the ambient atmosphere and provides useful insights into current SOA formation models. Further, the comparison of incremental SOA from VOCs in varying surrogate urban atmospheres (with and without strong biogenic influence) allows for a unique perspective on the impacts different compounds have on aerosol formation in different urban regions.

Analyzing the Formation, Physicochemical, and Optical Properties of Aging Biomass Burning Aerosol Using an Indoor Smog Chamber

NASA Astrophysics Data System (ADS)

Smith, D. M.; Fiddler, M. N.; Bililign, S.; Spann, M.

2017-12-01

Biomass burning (BB) is recognized as one of the largest sources of absorbing aerosols in the atmosphere and significantly influences the radiative properties of the atmosphere. The chemical composition and physical properties of particles evolve during their atmospheric lifetime due to condensation, oxidation reactions, etc., which alters their optical properties. To this end, an indoor smog chamber was constructed to study aging BB aerosol in a laboratory setting. Injections to the chamber, including NOx, O3, and various biogenic and anthropogenic VOCs, can simulate a variety of atmospheric conditions. These components and some of their oxidation products are monitored during the aging process. A tube furnace is used for combustion of biomass to be introduced to the chamber, while size distributions are taken as the aerosol ages. Online measurements of optical properties are determined using a Cavity Ring-down Spectrometry and Integrating Nephelometry system. Chemical properties are measured from samples captured on filters and analyzed using Ultra-Performance Liquid Chromatography coupled in-line to both a Diode Array Detector and High-Resolution Time-of-Flight Mass Spectrometer equipped with electrospray ionization. The measured changes in the optical properties as a function of particle size, aging, and chemical properties are presented for fuel sources used in Africa.

Invention and History of the Bubble Chamber (LBNL Summer Lecture Series)

ScienceCinema

Glaser, Don [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2018-01-12

Summer Lecture Series 2006: Don Glaser won the 1960 Nobel Prize for Physics for his 1952 invention of the bubble chamber at Berkeley Lab, a type of particle detector that became the mainstay of high-energy physics research throughout the 1960s and 1970s. He discusses how, inspired by bubbles in a glass of beer, he invented the bubble chamber and detected cosmic-ray muons.

Contamination Control Assessment of the World's Largest Space Environment Simulation Chamber

NASA Technical Reports Server (NTRS)

Snyder, Aaron; Henry, Michael W.; Grisnik, Stanley P.; Sinclair, Stephen M.

2012-01-01

The Space Power Facility s thermal vacuum test chamber is the largest chamber in the world capable of providing an environment for space simulation. To improve performance and meet stringent requirements of a wide customer base, significant modifications were made to the vacuum chamber. These include major changes to the vacuum system and numerous enhancements to the chamber s unique polar crane, with a goal of providing high cleanliness levels. The significance of these changes and modifications are discussed in this paper. In addition, the composition and arrangement of the pumping system and its impact on molecular back-streaming are discussed in detail. Molecular contamination measurements obtained with a TQCM and witness wafers during two recent integrated system tests of the chamber are presented and discussed. Finally, a concluding remarks section is presented.

Atlas-Centaur Separation Test in the Space Power Chambers

NASA Image and Video Library

1963-11-21

An Atlas/Centaur mass model undergoes a separation test inside the Space Power Chambers at NASA Lewis Research Center. Lewis was in the midst of an extensive effort to prepare the Centaur second-stage rocket for its missions to send the Surveyor spacecraft to the moon as a precursor to the Apollo missions. As part of these preparations, Lewis management decided to convert its Altitude Wind Tunnel into two large test chambers—the Space Power Chambers. The conversion included the removal of the tunnel’s internal components and the insertion of bulkheads to seal off the new chambers within the tunnel. One chamber could simulate conditions found at 100 miles altitude, while this larger chamber simulated the upper atmosphere. In this test series, researchers wanted to verify that the vehicle’s retrorockets would properly separate the Centaur from the Atlas. The model was suspended horizontally on a trolley system inside chamber. A net was hung at one end to catch the jettisoned Atlas model. The chamber atmosphere was reduced to a pressure altitude of 100,000 feet, and high-speed cameras were synchronized to the ignition of the retrorockets. The simulated Centaur is seen here jettisoning from the Atlas out of view to the right. The study resulted in a new jettison method that would significantly reduce the separation time and thus minimize the danger of collision between the two stages during separation.

OVERALL MASS TRANSFER COEFFICIENT FOR POLLUTANT EMISSIONS FROM SMALL WATER POOLS UNDER SIMULATED INDOOR ENVIRONMENTAL CONDITIONS

EPA Science Inventory

Small chamber tests were conducted to experimentally determine the overall mass transfer coefficient for pollutant emissions from still water under simulated indoor-residential or occupational-environmental conditions. Fourteen tests were conducted in small environmental chambers...

V&V Of CFD Modeling Of The Argonne Bubble Experiment: FY15 Summary Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoyt, Nathaniel C.; Wardle, Kent E.; Bailey, James L.

2015-09-30

In support of the development of accelerator-driven production of the fission product Mo 99, computational fluid dynamics (CFD) simulations of an electron-beam irradiated, experimental-scale bubble chamber have been conducted in order to aid in interpretation of existing experimental results, provide additional insights into the physical phenomena, and develop predictive thermal hydraulic capabilities that can be applied to full-scale target solution vessels. Toward that end, a custom hybrid Eulerian-Eulerian-Lagrangian multiphase solver was developed, and simulations have been performed on high-resolution meshes. Good agreement between experiments and simulations has been achieved, especially with respect to the prediction of the maximum temperature ofmore » the uranyl sulfate solution in the experimental vessel. These positive results suggest that the simulation methodology that has been developed will prove to be suitable to assist in the development of full-scale production hardware.« less

Lewis Research Center R and D Facilities

NASA Technical Reports Server (NTRS)

1991-01-01

The NASA Lewis Research Center (LeRC) defines and develops advanced technology for high priority national needs. The work of the Center is directed toward new propulsion, power, and communications technologies for application to aeronautics and space, so that U.S. leadership in these areas is ensured. The end product is knowledge, usually in a report, that is made fully available to potential users--the aircraft engine industry, the energy industry, the automotive industry, the space industry, and other NASA centers. In addition to offices and laboratories for almost every kind of physical research in such fields as fluid mechanics, physics, materials, fuels, combustion, thermodynamics, lubrication, heat transfer, and electronics, LeRC has a variety of engineering test cells for experiments with components such as compressors, pumps, conductors, turbines, nozzles, and controls. A number of large facilities can simulate the operating environment for a complete system: altitude chambers for aircraft engines; large supersonic wind tunnels for advanced airframes and propulsion systems; space simulation chambers for electric rockets or spacecraft; and a 420-foot-deep zero-gravity facility for microgravity experiments. Some problems are amenable to detection and solution only in the complete system and at essentially full scale. By combining basic research in pertinent disciplines and generic technologies with applied research on components and complete systems, LeRC has become one of the most productive centers in its field in the world. This brochure describes a number of the facilities that provide LeRC with its exceptional capabilities.

Three-dimensional multi-physics coupled simulation of ignition transient in a dual pulse solid rocket motor

NASA Astrophysics Data System (ADS)

Li, Yingkun; Chen, Xiong; Xu, Jinsheng; Zhou, Changsheng; Musa, Omer

2018-05-01

In this paper, numerical investigation of ignition transient in a dual pulse solid rocket motor has been conducted. An in-house code has been developed in order to solve multi-physics governing equations, including unsteady compressible flow, heat conduction and structural dynamic. The simplified numerical models for solid propellant ignition and combustion have been added. The conventional serial staggered algorithm is adopted to simulate the fluid structure interaction problems in a loosely-coupled manner. The accuracy of the coupling procedure is validated by the behavior of a cantilever panel subjected to a shock wave. Then, the detailed flow field development, flame propagation characteristics, pressure evolution in the combustion chamber, and the structural response of metal diaphragm are analyzed carefully. The burst-time and burst-pressure of the metal diaphragm are also obtained. The individual effects of the igniter's mass flow rate, metal diaphragm thickness and diameter on the ignition transient have been systemically compared. The numerical results show that the evolution of the flow field in the combustion chamber, the temperature distribution on the propellant surface and the pressure loading on the metal diaphragm surface present a strong three-dimensional behavior during the initial ignition stage. The rupture of metal diaphragm is not only related to the magnitude of pressure loading on the diaphragm surface, but also to the history of pressure loading. The metal diaphragm thickness and diameter have a significant effect on the burst-time and burst-pressure of metal diaphragm.

Simulation, Analysis, and Design of the Princeton Adaptable Stellarator for Education and Outreach (PASEO)

NASA Astrophysics Data System (ADS)

Carlson, Jared; Dominguez, Arturo; N/A Collaboration

2017-10-01

The PPPL Science Education Department, in collaboration with IPP, is currently developing a versatile small scale Stellarator for education and outreach purposes. The Princeton Adaptable Stellarator for Education and Outreach (PASEO) will provide visual demonstrations of Stellarator physics and serve as a lab platform for undergraduate and graduate students. Based off the Columbia Non-Neutral Torus (CNT) (1), and mini-CNTs (2), PASEO will create pure electron plasmas to study magnetic surfaces. PASEO uses similar geometries to these, but has an adjustable coil configuration to increase its versatility and conform to a highly visible vacuum chamber geometry. To simulate the magnetic surfaces in these new configurations, a MATALB code utilizing the Biot Savart law and a Fourth Order Runge-Kutta method was developed, leading to new optimal current ratios. The design for PASEO and its predicted plasma confinement are presented. (1) T.S. Pedersen et al., Fusion Science and Technology Vol. 46 July 2004 (2) C. Dugan, et al., American Physical Society; 48th Annual Meeting of the Division of Plasma Physics, October 30-November 3, 2006

Two stage sorption type cryogenic refrigerator including heat regeneration system

NASA Technical Reports Server (NTRS)

Jones, Jack A. (Inventor); Wen, Liang-Chi (Inventor); Bard, Steven (Inventor)

1989-01-01

A lower stage chemisorption refrigeration system physically and functionally coupled to an upper stage physical adsorption refrigeration system is disclosed. Waste heat generated by the lower stage cycle is regenerated to fuel the upper stage cycle thereby greatly improving the energy efficiency of a two-stage sorption refrigerator. The two stages are joined by disposing a first pressurization chamber providing a high pressure flow of a first refrigerant for the lower stage refrigeration cycle within a second pressurization chamber providing a high pressure flow of a second refrigerant for the upper stage refrigeration cycle. The first pressurization chamber is separated from the second pressurization chamber by a gas-gap thermal switch which at times is filled with a thermoconductive fluid to allow conduction of heat from the first pressurization chamber to the second pressurization chamber.

CHAMBER SIMULATION OF FINE PARTICLE PENETRATION INTO HOUSES

EPA Science Inventory

the paper discusses chamber simulation of fine particle penetration into houses. (NOTE: A number of recent studies have shown a correlation of negative health effects with increases in outdoor fine particles. Since people spend up to 90% of their time indoors, the relationship be...

Geometric optimization of microreactor chambers to increase the homogeneity of the velocity field

NASA Astrophysics Data System (ADS)

Pálovics, Péter; Ender, Ferenc; Rencz, Márta

2018-06-01

In this work microfluidic flow-through chambers are investigated. They are filled with magnetic nanoparticle (MNP) suspension in order to facilitate enzymatic reactions. The enzyme is immobilized on the surface of the MNPs. These reactions have been found to be flow rate dependent. To overcome this issue various chamber geometries have been examined and optimized geometries have been designed and tested experimentally. The investigation is supported with dedicated CFD simulations using the open source software OpenFOAM. The paper presents the theoretical background and the results of the simulations. The simulations have been verified with measurements and these too are presented in the paper.

Experimental and simulation study of a Gaseous oxygen/Gaseous hydrogen vortex cooling thrust chamber

NASA Astrophysics Data System (ADS)

Yu, Nanjia; Zhao, Bo; Li, Gongnan; Wang, Jue

2016-01-01

In this paper, RNG k-ε turbulence model and PDF non-premixed combustion model are used to simulate the influence of the diameter of the ring of hydrogen injectors and oxidizer-to-fuel ratio on the specific impulse of the vortex cooling thrust chamber. The simulation results and the experimental tests of a 2000 N Gaseous oxygen/Gaseous hydrogen vortex cooling thrust chamber reveal that the efficiency of the specific impulse improves significantly with increasing of the diameter of the ring of hydrogen injectors. Moreover, the optimum efficiency of the specific impulse is obtained when the oxidizer-to-fuel ratio is near the stoichiometric ratio.

Three-dimensional numerical simulation of a continuously rotating detonation in the annular combustion chamber with a wide gap and separate delivery of fuel and oxidizer

NASA Astrophysics Data System (ADS)

Frolov, S. M.; Dubrovskii, A. V.; Ivanov, V. S.

2016-07-01

The possibility of integrating the Continuous Detonation Chamber (CDC) in a gas turbine engine (GTE) is demonstrated by means of three-dimensional (3D) numerical simulations, i. e., the feasibility of the operation process in the annular combustion chamber with a wide gap and with separate feeding of fuel (hydrogen) and oxidizer (air) is proved computationally. The CDC with an upstream isolator damping pressure disturbances propagating towards the compressor is shown to exhibit a gain in the total pressure of 15% as compared with the same combustion chamber operating in the deflagration mode.

Characterization and Simulation of a New Design Parallel-Plate Ionization Chamber for CT Dosimetry at Calibration Laboratories

NASA Astrophysics Data System (ADS)

Perini, Ana P.; Neves, Lucio P.; Maia, Ana F.; Caldas, Linda V. E.

2013-12-01

In this work, a new extended-length parallel-plate ionization chamber was tested in the standard radiation qualities for computed tomography established according to the half-value layers defined at the IEC 61267 standard, at the Calibration Laboratory of the Instituto de Pesquisas Energéticas e Nucleares (IPEN). The experimental characterization was made following the IEC 61674 standard recommendations. The experimental results obtained with the ionization chamber studied in this work were compared to those obtained with a commercial pencil ionization chamber, showing a good agreement. With the use of the PENELOPE Monte Carlo code, simulations were undertaken to evaluate the influence of the cables, insulator, PMMA body, collecting electrode, guard ring, screws, as well as different materials and geometrical arrangements, on the energy deposited on the ionization chamber sensitive volume. The maximum influence observed was 13.3% for the collecting electrode, and regarding the use of different materials and design, the substitutions showed that the original project presented the most suitable configuration. The experimental and simulated results obtained in this work show that this ionization chamber has appropriate characteristics to be used at calibration laboratories, for dosimetry in standard computed tomography and diagnostic radiology quality beams.

Physics at the Frontier HS Teacher Workshop: bringing particle physics and cloud chambers into the classroom

NASA Astrophysics Data System (ADS)

Gleason, Alyx; Bedard, Jamie; Bellis, Matthew; CMS Collaboration

2016-03-01

In the summer of 2015, we hosted 10 high school teachers for a three-day ``Physics at the Frontier'' Workshop. The mornings were spent learning about particle physics, CMS and the LHC, and radiation safety while the afternoons were spent building turn-key cloud chambers for use in their classrooms. The basic cloud chamber design uses Peltier thermoelectric coolers, rather than dry ice, and instructions can be found in multiple places online. For a robust build procedure and for easy use in the classroom, we redesigned parts of the construction process to make it easier to put together while holding costs below 200 per chamber. In addition to this new design, we also created a website with instructions for those who are interested in building their own using this design. This workshop was funded in part by a minigrant for Outreach and Education from the USCMS collaboration. Our experience with the workshop and the lessons learned from the cloud chamber design will be discussed. This work was funded in part by NSF Grants PHY-1307562 and a USCMS-administered minigrant for Outreach and Education.

Roos and NACP-02 ion chamber perturbations and water-air stopping-power ratios for clinical electron beams for energies from 4 to 22 MeV

NASA Astrophysics Data System (ADS)

Bailey, M.; Shipley, D. R.; Manning, J. W.

2015-02-01

Empirical fits are developed for depth-compensated wall- and cavity-replacement perturbations in the PTW Roos 34001 and IBA / Scanditronix NACP-02 parallel-plate ionisation chambers, for electron beam qualities from 4 to 22 MeV for depths up to approximately 1.1 × R50,D. These are based on calculations using the Monte Carlo radiation transport code EGSnrc and its user codes with a full simulation of the linac treatment head modelled using BEAMnrc. These fits are used with calculated restricted stopping-power ratios between air and water to match measured depth-dose distributions in water from an Elekta Synergy clinical linear accelerator at the UK National Physical Laboratory. Results compare well with those from recent publications and from the IPEM 2003 electron beam radiotherapy Code of Practice.

Improving Spectroscopic Performance of a Coplanar-Anode High-Pressure Xenon Gamma-Ray Spectrometer

NASA Astrophysics Data System (ADS)

Kiff, Scott Douglas; He, Zhong; Tepper, Gary C.

2007-08-01

High-pressure xenon (HPXe) gas is a desirable radiation detection medium for homeland security applications because of its good inherent room-temperature energy resolution, potential for large, efficient devices, and stability over a broad temperature range. Past work in HPXe has produced large-diameter gridded ionization chambers with energy resolution at 662 keV between 3.5 and 4% FWHM. However, one major limitation of these detectors is resolution degradation due to Frisch grid microphonics. A coplanar-anode HPXe detector has been developed as an alternative to gridded chambers. An investigation of this detector's energy resolution is reported in this submission. A simulation package is used to investigate the contributions of important physical processes to the measured photopeak broadening. Experimental data is presented for pure Xe and Xe + 0.2%H2 mixtures, including an analysis of interaction location effects on the energy spectrum.

Comprehensive modeling of a liquid rocket combustion chamber

NASA Technical Reports Server (NTRS)

Liang, P.-Y.; Fisher, S.; Chang, Y. M.

1985-01-01

An analytical model for the simulation of detailed three-phase combustion flows inside a liquid rocket combustion chamber is presented. The three phases involved are: a multispecies gaseous phase, an incompressible liquid phase, and a particulate droplet phase. The gas and liquid phases are continuum described in an Eulerian fashion. A two-phase solution capability for these continuum media is obtained through a marriage of the Implicit Continuous Eulerian (ICE) technique and the fractional Volume of Fluid (VOF) free surface description method. On the other hand, the particulate phase is given a discrete treatment and described in a Lagrangian fashion. All three phases are hence treated rigorously. Semi-empirical physical models are used to describe all interphase coupling terms as well as the chemistry among gaseous components. Sample calculations using the model are given. The results show promising application to truly comprehensive modeling of complex liquid-fueled engine systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panebianco, S.; Dore, D.; Giomataris, I.

Time Projection Chambers are widely used since many years for tracking and identification of charged particles in high energy physics. We present a new R and D project to investigate the feasibility of a Micromegas TPC for low energy heavy ions detection. Two physics cases are relevant for this project. The first is the study of the nuclear fission of actinides by measuring the fission fragments properties (mass, nuclear charge, kinetic energy) that will be performed at different installations and in particular at the NFS facility to be built in the framework of the SPIRAL2 project in GANIL. The secondmore » physics case is the study of heavy ion reactions, like ({alpha},{gamma}), ({alpha},p), ({alpha},n) and all the inverse reactions in the energy range between 1.5 and 3 AMeV using both stable and radioactive beams. These reactions have a key role in p process in nuclear astrophysics to explain the synthesis of heavy proton-rich nuclei. Within the project, a large effort is devoted to Monte-Carlo simulations and a detailed benchmark of different simulation codes on the energy loss and range in gas of heavy ions at low energy has been performed. A new approach for simulating the ion charge state evolution in GEANT4 is also presented. Finally, preliminary results of an experimental test campaign on prototype are discussed.« less

Lattice Boltzmann for Simulation of Gases Mixture in Fruit Storage Chambers

NASA Astrophysics Data System (ADS)

Fabero, J. C.; Barreiro, P.; Casasús, L.

2003-04-01

Fluid Dynamics can be modelled through the Navier-Stokes equations. This description corresponds to a macroscopic definition of the fluid motion phenomena. During the past 20 year new simulation procedures are emerging from Statistical Physics and Computer Science domains. One of them is the Lattice Gas Cellular Automata (LGCA) method. This approach, which is considered to be a microscopic description of the world, in spite of its intuitiveness and numerical efficiency, fails to simulate the real Navier-Stokes equations. Another classical simulation procedure for the fluid motion phenomena is the so called Lattice Boltzmann method [1]. This corresponds to a meso-scale description of the world [2]. Simulation of laminar and turbulent motions of fluids, specially when considering several gas species is still an ongoing research [3]. Nowadays, the use of Low Oxygen and Ultra Low Oxygen Controlled Atmospheres has been recognized as a reliable method to extend the storage life of fruits an vegetables. However, small spatial gradients in gas concentration during storage may generate internal disorders in the commodities. In this work, four different gases will be considered: oxygen, carbon dioxide, water vapor and ethylene. Physiological effects such as transpiration, which affects the level of water vapor, respiration, which modifies both oxygen and carbon dioxide concentrations, and ethylene emission, must be taken into account in the hole model. The numerical model, based on that proposed by Shan and Chen, is implemented, being able to consider the behavior of multiple mixable gas species. Forced air motion, needed to obtain a correct ventilation of the chamber, has also been modelled.

CFD Analysis of Spray Combustion and Radiation in OMV Thrust Chamber

NASA Technical Reports Server (NTRS)

Giridharan, M. G.; Krishnan, A.; Przekwas, A. J.; Gross, K.

1993-01-01

The Variable Thrust Engine (VTE), developed by TRW, for the Orbit Maneuvering Vehicle (OMV) uses a hypergolic propellant combination of Monomethyl Hydrazine (MMH) and Nitrogen Tetroxide (NTO) as fuel and oxidizer, respectively. The propellants are pressure fed into the combustion chamber through a single pintle injection element. The performance of this engine is dependent on the pintle geometry and a number of complex physical phenomena and their mutual interactions. The most important among these are (1) atomization of the liquid jets into fine droplets; (2) the motion of these droplets in the gas field; (3) vaporization of the droplets (4) turbulent mixing of the fuel and oxidizer; and (5) hypergolic reaction between MMH and NTO. Each of the above phenomena by itself poses a considerable challenge to the technical community. In a reactive flow field of the kind occurring inside the VTE, the mutual interactions between these physical processes tend to further complicate the analysis. The objective of this work is to develop a comprehensive mathematical modeling methodology to analyze the flow field within the VTE. Using this model, the effect of flow parameters on various physical processes such as atomization, spray dynamics, combustion, and radiation is studied. This information can then be used to optimize design parameters and thus improve the performance of the engine. The REFLEQS CFD Code is used for solving the fluid dynamic equations. The spray dynamics is modeled using the Eulerian-Lagrangian approach. The discrete ordinate method with 12 ordinate directions is used to predict the radiative heat transfer in the OMV combustion chamber, nozzle, and the heat shield. The hypergolic reaction between MMH and NTO is predicted using an equilibrium chemistry model with 13 species. The results indicate that mixing and combustion is very sensitive to the droplet size. Smaller droplets evaporate faster than bigger droplets, leading to a well mixed zone in the combustion chamber. The radiative heat flux at combustion chamber and nozzle walls are an order of negligible less than the conductive heat flux. Simulations performed with the heat shield show that a negligible amount of fluid is entrained into the heat shield region. However, the heat shield is shown to be effective in protecting the OMV structure surrounding the engine from the radiated heat.

Numerical Simulation of Earth Pressure on Head Chamber of Shield Machine with FEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Shouju; Kang Chengang; Sun, Wei

2010-05-21

Model parameters of conditioned soils in head chamber of shield machine are determined based on tree-axial compression tests in laboratory. The loads acting on tunneling face are estimated according to static earth pressure principle. Based on Duncan-Chang nonlinear elastic constitutive model, the earth pressures on head chamber of shield machine are simulated in different aperture ratio cases for rotating cutterhead of shield machine. Relationship between pressure transportation factor and aperture ratio of shield machine is proposed by using aggression analysis.

EMAT enhanced dispersion of particles in liquid

DOEpatents

Kisner, Roger A.; Rios, Orlando; Melin, Alexander M.; Ludtka, Gerard Michael; Ludtka, Gail Mackiewicz; Wilgen, John B.

2016-11-29

Particulate matter is dispersed in a fluid material. A sample including a first material in a fluid state and second material comprising particulate matter are placed into a chamber. The second material is spatially dispersed in the first material utilizing EMAT force. The dispersion process continues until spatial distribution of the second material enables the sample to meet a specified criterion. The chamber and/or the sample is electrically conductive. The EMAT force is generated by placing the chamber coaxially within an induction coil driven by an applied alternating current and placing the chamber and induction coil coaxially within a high field magnetic. The EMAT force is coupled to the sample without physical contact to the sample or to the chamber, by another physical object. Batch and continuous processing are utilized. The chamber may be folded within the bore of the magnet. Acoustic force frequency and/or temperature may be controlled.

Research of the rotation effect upon the hydrodynamics and heat and mass transport in a chemical reactor

NASA Astrophysics Data System (ADS)

Gicheva, Natalia I.

2017-11-01

The subject of this research is a chemical reactor for producing tungsten. A physical and mathematical model of fluid motion and heat and mass transfer in a vortex chamber of the chemical reactor under forced and free convection has been described and simulated using two methods. The numerical simulation was carried out in «vortex - stream functions and «velocity - pressure» variables. The velocity field, the mass and the temperature distributions in the reactor were obtained. The influence of a rotation effect upon the hydrodynamics and heat and mass transport was showed. The rotation is important for more uniform distribution of temperature and matter in the vortex chamber. Parametric studies on effects of the Reynolds, Prandtl and Rossbi criteria on the flow characteristics were also performed. Reliability of the calculations was verified by comparing the results obtained by the methods mentioned above. Also, the created model was applied for numerically solving of the classical test problem of the velocity distribution in an annular channel and that of a rotating infinite disk in a stationary liquid. The study findings showed a good agreement with the exact solutions.

Acoustic properties of supersonic helium/air jets at low Reynolds numbers

NASA Technical Reports Server (NTRS)

Mclaughlin, Dennis K.; Barron, W. D.; Vaddempudi, Appa R.

1992-01-01

Experiments have been performed with the objective of developing a greater understanding of the physics of hot supersonic jet noise. Cold helium/air jets are used to easily and inexpensively simulate the low densities of hot air jets. The experiments are conducted at low Reynolds numbers in order to facilitate study of the large-scale turbulent structures (instability waves) that cause most of the radiated noise. Experiments have been performed on Mach 1.5 and 2.1 jets of pure air, pure helium and 10 percent helium by mass. Helium/air jets are shown to radiate more noise than pure air jets due to the increased exit velocity. Microphone spectra are usually dominated by a single spectral component at a predictable frequency. Increasing the jet's helium concentration is shown to increase the dominant frequency. The helium concentration in the test chamber is determined by calculating the speed of sound from the measured phase difference between two microphone signals. Bleeding outside air into the test chamber controls the accumulation of helium so that the hot jet simulation remains valid. The measured variation in the peak radiated noise frequency is in good agreement with the predictions of the hot jet noise theory of Tam et al.

Manufacture of Cryoshroud Surfaces for Space Simulation Chambers

NASA Technical Reports Server (NTRS)

Ash, Gary S.

2008-01-01

Environmental test chambers for space applications use internal shrouds to simulate temperature conditions encountered in space. Shroud temperatures may range from +150 C to -253 C (20 K), and internal surfaces are coated with special high emissivity/absorptivity paints. To obtain temperature uniformity over large areas, detailed thermal design is required for placement of tubing for gaseous or liquid nitrogen and helium and other exotic heat exchange fluids. The recent increase in space simulation activity related to the James Webb Space Telescope has led to the design of new cryogenic shrouds to meet critical needs in instrument package testing. This paper will review the design and manufacturing of shroud surfaces for several of these programs, including fabrication methods and the selection and application of paints for simulation chambers.

Predicted performance of an integrated modular engine system

NASA Technical Reports Server (NTRS)

Binder, Michael; Felder, James L.

1993-01-01

Space vehicle propulsion systems are traditionally comprised of a cluster of discrete engines, each with its own set of turbopumps, valves, and a thrust chamber. The Integrated Modular Engine (IME) concept proposes a vehicle propulsion system comprised of multiple turbopumps, valves, and thrust chambers which are all interconnected. The IME concept has potential advantages in fault-tolerance, weight, and operational efficiency compared with the traditional clustered engine configuration. The purpose of this study is to examine the steady-state performance of an IME system with various components removed to simulate fault conditions. An IME configuration for a hydrogen/oxygen expander cycle propulsion system with four sets of turbopumps and eight thrust chambers has been modeled using the Rocket Engine Transient Simulator (ROCETS) program. The nominal steady-state performance is simulated, as well as turbopump thrust chamber and duct failures. The impact of component failures on system performance is discussed in the context of the system's fault tolerant capabilities.

Cardiovascular simulator improvement: pressure versus volume loop assessment.

PubMed

Fonseca, Jeison; Andrade, Aron; Nicolosi, Denys E C; Biscegli, José F; Leme, Juliana; Legendre, Daniel; Bock, Eduardo; Lucchi, Julio Cesar

2011-05-01

This article presents improvement on a physical cardiovascular simulator (PCS) system. Intraventricular pressure versus intraventricular volume (PxV) loop was obtained to evaluate performance of a pulsatile chamber mimicking the human left ventricle. PxV loop shows heart contractility and is normally used to evaluate heart performance. In many heart diseases, the stroke volume decreases because of low heart contractility. This pathological situation must be simulated by the PCS in order to evaluate the assistance provided by a ventricular assist device (VAD). The PCS system is automatically controlled by a computer and is an auxiliary tool for VAD control strategies development. This PCS system is according to a Windkessel model where lumped parameters are used for cardiovascular system analysis. Peripheral resistance, arteries compliance, and fluid inertance are simulated. The simulator has an actuator with a roller screw and brushless direct current motor, and the stroke volume is regulated by the actuator displacement. Internal pressure and volume measurements are monitored to obtain the PxV loop. Left chamber internal pressure is directly obtained by pressure transducer; however, internal volume has been obtained indirectly by using a linear variable differential transformer, which senses the diaphragm displacement. Correlations between the internal volume and diaphragm position are made. LabVIEW integrates these signals and shows the pressure versus internal volume loop. The results that have been obtained from the PCS system show PxV loops at different ventricle elastances, making possible the simulation of pathological situations. A preliminary test with a pulsatile VAD attached to PCS system was made. © 2011, Copyright the Authors. Artificial Organs © 2011, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

THE FLUIDS AND COMBUSTION FACILITY: ENABLING THE EXPLORATION OF SPACE

NASA Technical Reports Server (NTRS)

Weiland, Karen J.; Gati, Frank G.; Hill, Myron E.; OMalley, Terence; Zurawski, Robert L.

2005-01-01

The Fluids and Combustion Facility (FCF) is an International Space Station facility designed to support physical and biological research as well as technology experiments in space. The FCF consists of two racks called the Combustion Integrated Rack (CIR) and the Fluids Integrated Rack (FIR). The capabilities of the CIR and the FIR and plans for their utilization will support the President s vision for space exploration. The CIR will accommodate physical research and technology experiments that address needs in the areas of spacecraft fire prevention, detection and suppression, incineration of solid wastes, and power generation. Initial experiments will provide data to support design decisions for exploration spacecraft. The CIR provides a large sealed chamber in a near-weightless environment. The chamber supports many simulated atmospheres including lunar or Martian environments. The FIR will accommodate experiments that address needs for advanced life support, power, propulsion, and spacecraft thermal control systems. The FIR can also serve as a platform for experiments that address human health and performance, medical technologies, and biological sciences. The FIR provides a large volume for payload hardware, reconfigurable diagnostics, customizable software, active rack-level vibration isolation, and data acquisition and management in a nearly uniform temperature environment.

The Fluids and Combustion Facility: Enabling the Exploration of Space

NASA Technical Reports Server (NTRS)

Weiland, Karen J.; Gati, Frank G.; Hill, Myron E.; O'Malley Terence F.; Zurawski, Robert L.

2005-01-01

The Fluids and Combustion Facility (FCF) is an International Space Station facility designed to support physical and biological research as well as technology experiments in space. The FCF consists of two racks called the Combustion Integrated Rack (CIR) and the Fluids Integrated Rack (FIR). The capabilities of the CIR and the FIR and plans for their utilization will support the President's vision for space exploration. The CIR will accommodate physical research and technology experiments that address needs in the areas of spacecraft fire prevention, detection and suppression, incineration of solid wastes, and power generation. Initial experiments will provide data to support design decisions for exploration spacecraft. The CIR provides a large sealed chamber in a near-weightless environment. The chamber supports many simulated atmospheres including lunar or Martian environments. The FIR will accommodate experiments that address needs for advanced life support, power, propulsion, and spacecraft thermal control systems. The FIR can also serve as a platform for experiments that address human health and performance, medical technologies, and biological sciences. The FIR provides a large volume for payload hardware, reconfigurable diagnostics, customizable software, active rack-level vibration isolation, and data acquisition and management in a nearly uniform temperature environment.

Advanced Small Rocket Chambers. Basic Program and Option 2: Fundamental Processes and Material Evaluation

NASA Technical Reports Server (NTRS)

Jassowski, Donald M.

1993-01-01

Propellants, chamber materials, and processes for fabrication of small high performance radiation cooled liquid rocket engines were evaluated to determine candidates for eventual demonstration in flight-type thrusters. Both storable and cryogenic propellant systems were considered. The storable propellant systems chosen for further study were nitrogen tetroxide oxidizer with either hydrazine or monomethylhydrazine as fuel. The cryogenic propellants chosen were oxygen with either hydrogen or methane as fuel. Chamber material candidates were chemical vapor deposition (CVD) rhenium protected from oxidation by CVD iridium for the chamber hot section, and film cooled wrought platinum-rhodium or regeneratively cooled stainless steel for the front end section exposed to partially reacted propellants. Laser diagnostics of the combustion products near the hot chamber surface and measurements at the surface layer were performed in a collaborative program at Sandia National Laboratories, Livermore, CA. The Material Sample Test Apparatus, a laboratory system to simulate the combustion environment in terms of gas and material temperature, composition, and pressure up to 6 Atm, was developed for these studies. Rocket engine simulator studies were conducted to evaluate the materials under simulated combustor flow conditions, in the diagnostic test chamber. These tests used the exhaust species measurement system, a device developed to monitor optically species composition and concentration in the chamber and exhaust by emission and absorption measurements.

Modeling and simulation of flow field in giant magnetostrictive pump

NASA Astrophysics Data System (ADS)

Zhao, Yapeng; Ren, Shiyong; Lu, Quanguo

2017-09-01

Recent years, there has been significant research in the design and analysis of giant magnetostrictive pump. In this paper, the flow field model of giant magnetostrictive pump was established and the relationship between pressure loss and working frequency of piston was studied by numerical simulation method. Then, the influence of different pump chamber height on pressure loss in giant magnetostrictive pump was studied by means of flow field simulation. Finally, the fluid pressure and velocity vector distribution in giant magnetostrictive pump chamber were simulated.

Radiometric observations of the 752.033-GHz rotational absorption line of H2O from a laboratory jet. [simulation of rocket plumes

NASA Technical Reports Server (NTRS)

Dionne, G. F.; Fitzgerald, J. F.; Chang, T.-S.; Fetterman, H. R.; Litvak, M. M.

1980-01-01

With the aid of a high-resolution two-stage heterodyne radiometer, spectral absorption measurements of the 752.033 GHz line of water vapor were carried out, using a blackbody continuum as a background radiation source for investigating the absorptive properties of the H2O content of high altitude rocket plumes. To simulate this physical situation in a laboratory environment, a small steam jet was operated within a large high-vacuum chamber, with the H2O jet plume traversing the radiometer line of sight. The experiments verified that this rotational line is optically thick, with excitation temperatures below 100 K, in the downstream part of the plume, as predicted by theoretical modelling.

Performance of the Satellite Test Assistant Robot in JPL's Space Simulation Facility

NASA Technical Reports Server (NTRS)

Mcaffee, Douglas; Long, Mark; Johnson, Ken; Siebes, Georg

1995-01-01

An innovative new telerobotic inspection system called STAR (the Satellite Test Assistant Robot) has been developed to assist engineers as they test new spacecraft designs in simulated space environments. STAR operates inside the ultra-cold, high-vacuum, test chambers and provides engineers seated at a remote Operator Control Station (OCS) with high resolution video and infrared (IR) images of the flight articles under test. STAR was successfully proof tested in JPL's 25-ft (7.6-m) Space Simulation Chamber where temperatures ranged from +85 C to -190 C and vacuum levels reached 5.1 x 10(exp -6) torr. STAR's IR Camera was used to thermally map the entire interior of the chamber for the first time. STAR also made several unexpected and important discoveries about the thermal processes occurring within the chamber. Using a calibrated test fixture arrayed with ten sample spacecraft materials, the IR camera was shown to produce highly accurate surface temperature data. This paper outlines STAR's design and reports on significant results from the thermal vacuum chamber test.

The numerical modelling and process simulation for the fault diagnosis of rotary kiln incinerator.

PubMed

Roh, S D; Kim, S W; Cho, W S

2001-10-01

The numerical modelling and process simulation for the fault diagnosis of rotary kiln incinerator were accomplished. In the numerical modelling, two models applied to the modelling within the kiln are the combustion chamber model including the mass and energy balance equations for two combustion chambers and 3D thermal model. The combustion chamber model predicts temperature within the kiln, flue gas composition, flux and heat of combustion. Using the combustion chamber model and 3D thermal model, the production-rules for the process simulation can be obtained through interrelation analysis between control and operation variables. The process simulation of the kiln is operated with the production-rules for automatic operation. The process simulation aims to provide fundamental solutions to the problems in incineration process by introducing an online expert control system to provide an integrity in process control and management. Knowledge-based expert control systems use symbolic logic and heuristic rules to find solutions for various types of problems. It was implemented to be a hybrid intelligent expert control system by mutually connecting with the process control systems which has the capability of process diagnosis, analysis and control.

Coarse-grained discrete particle simulations of particle segregation in rotating fluidized beds in vortex chambers [Discrete particle simulations of particle segregation in rotating fluidized beds in vortex chambers

DOE PAGES

Verma, Vikrant; Li, Tingwen; De Wilde, Juray

2017-05-26

Vortex chambers allow the generation of rotating fluidized beds, offering high-G intensified gas-solid contact, gas-solids separation and solids-solids segregation. Focusing on binary particle mixtures and fixing the density and diameter of the heavy/large particles, transient batch CFD-coarse-grained DPM simulations were carried out with varying densities or sizes of the light/small particles to evaluate to what extent combining these three functionalities is possible within a vortex chamber of given design. Both the rate and quality of segregation were analyzed. Within a relatively wide density and size range, fast and efficient segregation takes place, with an inner and slower rotating bed ofmore » the lighter/small particles forming within the outer and faster rotating bed of the heavier/large particles. Simulations show that the contamination of the outer bed with lighter particles occurs more easily than contamination of the inner bed with heavier particles and increases with decreasing difference in size or density of the particles. Bubbling in the inner bed is observed with an inner bed of very low density or small particles. Porosity plots show that vortex chambers with a sufficient number of gas inlet slots have to be used to guarantee a uniform gas distribution and particle bed. Lastly, the flexibility of particle segregation in vortex chambers with respect to the gas flow rate is demonstrated.« less

Coarse-grained discrete particle simulations of particle segregation in rotating fluidized beds in vortex chambers [Discrete particle simulations of particle segregation in rotating fluidized beds in vortex chambers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verma, Vikrant; Li, Tingwen; De Wilde, Juray

Vortex chambers allow the generation of rotating fluidized beds, offering high-G intensified gas-solid contact, gas-solids separation and solids-solids segregation. Focusing on binary particle mixtures and fixing the density and diameter of the heavy/large particles, transient batch CFD-coarse-grained DPM simulations were carried out with varying densities or sizes of the light/small particles to evaluate to what extent combining these three functionalities is possible within a vortex chamber of given design. Both the rate and quality of segregation were analyzed. Within a relatively wide density and size range, fast and efficient segregation takes place, with an inner and slower rotating bed ofmore » the lighter/small particles forming within the outer and faster rotating bed of the heavier/large particles. Simulations show that the contamination of the outer bed with lighter particles occurs more easily than contamination of the inner bed with heavier particles and increases with decreasing difference in size or density of the particles. Bubbling in the inner bed is observed with an inner bed of very low density or small particles. Porosity plots show that vortex chambers with a sufficient number of gas inlet slots have to be used to guarantee a uniform gas distribution and particle bed. Lastly, the flexibility of particle segregation in vortex chambers with respect to the gas flow rate is demonstrated.« less

Resistive plate chambers in positron emission tomography

NASA Astrophysics Data System (ADS)

Crespo, Paulo; Blanco, Alberto; Couceiro, Miguel; Ferreira, Nuno C.; Lopes, Luís; Martins, Paulo; Ferreira Marques, Rui; Fonte, Paulo

2013-07-01

Resistive plate chambers (RPC) were originally deployed for high energy physics. Realizing how their properties match the needs of nuclear medicine, a LIP team proposed applying RPCs to both preclinical and clinical positron emission tomography (RPC-PET). We show a large-area RPC-PET simulated scanner covering an axial length of 2.4m —slightly superior to the height of the human body— allowing for whole-body, single-bed RPC-PET acquisitions. Simulations following NEMA (National Electrical Manufacturers Association, USA) protocols yield a system sensitivity at least one order of magnitude larger than present-day, commercial PET systems. Reconstruction of whole-body simulated data is feasible by using a dedicated, direct time-of-flight-based algorithm implemented onto an ordered subsets estimation maximization parallelized strategy. Whole-body RPC-PET patient images following the injection of only 2mCi of 18-fluorodesoxyglucose (FDG) are expected to be ready 7 minutes after the 6 minutes necessary for data acquisition. This compares to the 10-20mCi FDG presently injected for a PET scan, and to the uncomfortable 20-30minutes necessary for its data acquisition. In the preclinical field, two fully instrumented detector heads have been assembled aiming at a four-head-based, small-animal RPC-PET system. Images of a disk-shaped and a needle-like 22Na source show unprecedented sub-millimeter spatial resolution.

Simulation and Digitization of a Gas Electron Multiplier Detector Using Geant4 and an Object-Oriented Digitization Program

NASA Astrophysics Data System (ADS)

McMullen, Timothy; Liyanage, Nilanga; Xiong, Weizhi; Zhao, Zhiwen

2017-01-01

Our research has focused on simulating the response of a Gas Electron Multiplier (GEM) detector using computational methods. GEM detectors provide a cost effective solution for radiation detection in high rate environments. A detailed simulation of GEM detector response to radiation is essential for the successful adaption of these detectors to different applications. Using Geant4 Monte Carlo (GEMC), a wrapper around Geant4 which has been successfully used to simulate the Solenoidal Large Intensity Device (SoLID) at Jefferson Lab, we are developing a simulation of a GEM chamber similar to the detectors currently used in our lab. We are also refining an object-oriented digitization program, which translates energy deposition information from GEMC into electronic readout which resembles the readout from our physical detectors. We have run the simulation with beta particles produced by the simulated decay of a 90Sr source, as well as with a simulated bremsstrahlung spectrum. Comparing the simulation data with real GEM data taken under similar conditions is used to refine the simulation parameters. Comparisons between results from the simulations and results from detector tests will be presented.

Human Exploration Spacecraft Testbed for Integration and Advancement (HESTIA)

NASA Technical Reports Server (NTRS)

Banker, Brian F.; Robinson, Travis

2016-01-01

The proposed paper will cover ongoing effort named HESTIA (Human Exploration Spacecraft Testbed for Integration and Advancement), led at the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) to promote a cross-subsystem approach to developing Mars-enabling technologies with the ultimate goal of integrated system optimization. HESTIA also aims to develop the infrastructure required to rapidly test these highly integrated systems at a low cost. The initial focus is on the common fluids architecture required to enable human exploration of mars, specifically between life support and in-situ resource utilization (ISRU) subsystems. An overview of the advancements in both integrated technologies, in infrastructure, in simulation, and in modeling capabilities will be presented, as well as the results and findings of integrated testing,. Due to the enormous mass gear-ratio required for human exploration beyond low-earth orbit, (for every 1 kg of payload landed on Mars, 226 kg will be required on Earth), minimization of surface hardware and commodities is paramount. Hardware requirements can be minimized by reduction of equipment performing similar functions though for different subsystems. If hardware could be developed which meets the requirements of both life support and ISRU it could result in the reduction of primary hardware and/or reduction in spares. Minimization of commodities to the surface of mars can be achieved through the creation of higher efficiency systems producing little to no undesired waste, such as a closed-loop life support subsystem. Where complete efficiency is impossible or impractical, makeup commodities could be manufactured via ISRU. Although, utilization of ISRU products (oxygen and water) for crew consumption holds great promise of reducing demands on life support hardware, there exist concerns as to the purity and transportation of commodities. To date, ISRU has been focused on production rates and purities for propulsion needs. The meshing of requirements between all potential users, producers, and cleaners of oxygen and water is crucial to guiding the development of technologies which will be used to perform these functions. Various new capabilities are being developed as part of HESTIA, which will enable the integrated testing of these technologies. This includes the upgrading of a 20' diameter habitat chamber to eventually support long duration (90+ day) human-in-the-loop testing of advanced life support systems. Additionally, a 20' diameter vacuum chamber is being modified to create Mars atmospheric pressures and compositions. This chamber, designated the Mars Environment Chamber (MEC), will eventually be upgraded to include a dusty environment and thermal shroud to simulate conditions on the surface of Mars. In view that individual technologies will be in geographically diverse locations across NASA facilities and elsewhere in the world, schedule and funding constraints will likely limit the frequency of physical integration. When this is the case, absent subsystems can be either digitally or physically simulated. Using the Integrated Power Avionics and Software (iPAS) environment, HESTIA is able to bring together data from various subsystems in simulated surroundings, insert faults, errors, time delays, etc., and feed data into computer models or physical systems capable of reproducing the output of the absent subsystems for the consumption of a local subsystems. Although imperfect, this capability provides opportunities to test subsystem integration and interactions at a fraction of the cost. When a subsystem technology is too immature for integrated testing, models can be produced using the General-Use Nodal Network Solver (GUNNS) capability to simulate the overall system performance. In doing so, even technologies not yet on the drawing board can be integrated and overall system performance estimated. Through the integrated development of technologies, as well as of the infrastructure to rapidly and at a low cost, model, simulate, and test subsystem technologies early in their development, HESTIA is pioneering a new way of developing the future of human space exploration.

40 CFR 63.9375 - What definitions apply to this subpart?

Code of Federal Regulations, 2010 CFR

2010-07-01

... a series of curved vanes or blades arranged on a central spindle that rotates. Deviation means any... combustion chamber. Expansion of the hot combustion gases in the chamber rotates a shaft, either through a... source to emit a pollutant under its physical and operational design. Any physical or operational...

The atmosphere simulation chamber SAPHIR: a tool for the investigation of photochemistry.

NASA Astrophysics Data System (ADS)

Brauers, T.; Bohn, B.; Johnen, F.-J.; Rohrer, R.; Rodriguez Bares, S.; Tillmann, R.; Wahner, A.

2003-04-01

On the campus of the Forschungszentrum Jülich we constructed SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) which was accomplished in fall 2001. The chamber consists of a 280-m^3 double-wall Teflon bag of cylindrical shape that is held by a steel frame. Typically 75% of the outside actinic flux (290~nm~--~420~nm) is available inside the chamber. A louvre system allows switching between full sun light and dark within 40 s giving the opportunity to study relaxation processes of the photo chemical system. The SAPHIR chamber is equipped with a comprehensive set of sensitive instruments including the measurements of OH, HO_2, CO, hydrocarbons, aldehydes, nitrogen-oxides and solar radiation. Moreover, the modular concept of SAPHIR allows fast and flexible integration of new instruments and techniques. In this paper we will show the unique and new features of the SAPHIR chamber, namely the clean air supply and high purity water vapor supply providing a wide range of trace gas concentrations being accessible through the experiments. We will also present examples from the first year of SAPHIR experiment showing the scope of application from high quality instrument inter-comparison and kinetic studies to the simulation of complex mixtures of trace gases at ambient concentrations.

Design and laboratory testing of a chamber device to measure total flux of volatile organic compounds from the unsaturated zone under natural conditions.

PubMed

Tillman, Fred D; Smith, James A

2004-11-01

To determine if an aquifer contaminated with volatile organic compounds (VOCs) has potential for natural remediation, all natural processes affecting the fate and transport of VOCs in the subsurface must be identified and quantified. This research addresses the quantification of air-phase volatile organic compounds (VOCs) leaving the unsaturated zone soil gas and entering the atmosphere-including the additional flux provided by advective soil-gas movement induced by barometric pumping. A simple and easy-to-use device for measuring VOC flux under natural conditions is presented. The vertical flux chamber (VFC) was designed using numerical simulations and evaluated in the laboratory. Mass-balance numerical simulations based on continuously stirred tank reactor equations (CSTR) provided information on flux measurement performance of several sampling configurations with the final chamber configuration measuring greater than 96% of model-simulated fluxes. A laboratory device was constructed to evaluate the flux chamber under both diffusion-only and advection-plus-diffusion transport conditions. The flux chamber measured an average of 82% of 15 diffusion-only fluxes and an average of 95% of 15 additional advection-plus-diffusion flux experiments. The vertical flux chamber has the capability of providing reliable measurement of VOC flux from the unsaturated zone under both diffusion and advection transport conditions.

Investigation of the Effect of the Non-uniform Flow Distribution After Compressor of Gas Turbine Engine on Inlet Parameters of the Turbine

NASA Astrophysics Data System (ADS)

Orlov, M. Yu; Lukachev, S. V.; Anisimov, V. M.

2018-01-01

The position of combustion chamber between compressor and turbine and combined action of these elements imply that the working processes of all these elements are interconnected. One of the main requirements of the combustion chamber is the formation of the desirable temperature field at the turbine inlet, which can realize necessary durability of nozzle assembly and blade wheel of the first stage of high-pressure turbine. The method of integrated simulation of combustion chamber and neighboring nodes (compressor and turbine) was developed. On the first stage of the study, this method was used to investigate the influence of non-uniformity of flow distribution, occurred after compressor blades on combustion chamber workflow. The goal of the study is to assess the impact of non-uniformity of flow distribution after the compressor on the parameters before the turbine. The calculation was carried out in a transient case for some operation mode of the engine. The simulation showed that the inclusion of compressor has an effect on combustion chamber workflow and allows us to determine temperature field at the turbine inlet and assesses its durability more accurately. In addition, the simulation with turbine showed the changes in flow velocity distribution and pressure in combustion chamber.

Crew report. [on Skylab altitude simulation tests

NASA Technical Reports Server (NTRS)

Bobko, K. J.; Crippen, R. L.; Thornton, W. E.

1973-01-01

A 56-day chamber simulation of Skylab was successfully completed. The atmosphere (5 psi, 70 percent oxygen, 30 percent nitrogen, 5 mm carbon dioxide) and medical features including a 21-day pre- and 18-day post-test medical protocols were closely simulated. No apparent crew health problems were induced by the atmosphere, semiclosed environment, or other test features; and no appreciable crew degradation appeared over this period. The chamber and associated systems performed without major problems.

High-energy Physics with Hydrogen Bubble Chambers

DOE R&D Accomplishments Database

Alvarez, L. W.

1958-03-07

Recent experience with liquid hydrogen bubble chambers of 25 and 40 cm dia. in high-energy physics experiments is discussed. Experiments described are: interactions of K{sup -} mesons with protons, interactions of antiprotons with protons, catalysis of nuclear fusion reactions by muons, and production and decay of hyperons from negative pions. (W.D.M.)

Protein patterns of black fungi under simulated Mars-like conditions

NASA Astrophysics Data System (ADS)

Zakharova, Kristina; Marzban, Gorji; de Vera, Jean-Pierre; Lorek, Andreas; Sterflinger, Katja

2014-05-01

Two species of microcolonial fungi - Cryomyces antarcticus and Knufia perforans - and a species of black yeasts-Exophiala jeanselmei - were exposed to thermo-physical Mars-like conditions in the simulation chamber of the German Aerospace Center. In this study the alterations at the protein expression level from various fungi species under Mars-like conditions were analyzed for the first time using 2D gel electrophoresis. Despite of the expectations, the fungi did not express any additional proteins under Mars simulation that could be interpreted as stress induced HSPs. However, up-regulation of some proteins and significant decreasing of protein number were detected within the first 24 hours of the treatment. After 4 and 7 days of the experiment protein spot number was increased again and the protein patterns resemble the protein patterns of biomass from normal conditions. It indicates the recovery of the metabolic activity under Martian environmental conditions after one week of exposure.

Protein patterns of black fungi under simulated Mars-like conditions

PubMed Central

Zakharova, Kristina; Marzban, Gorji; de Vera, Jean-Pierre; Lorek, Andreas; Sterflinger, Katja

2014-01-01

Two species of microcolonial fungi – Cryomyces antarcticus and Knufia perforans - and a species of black yeasts–Exophiala jeanselmei - were exposed to thermo-physical Mars-like conditions in the simulation chamber of the German Aerospace Center. In this study the alterations at the protein expression level from various fungi species under Mars-like conditions were analyzed for the first time using 2D gel electrophoresis. Despite of the expectations, the fungi did not express any additional proteins under Mars simulation that could be interpreted as stress induced HSPs. However, up-regulation of some proteins and significant decreasing of protein number were detected within the first 24 hours of the treatment. After 4 and 7 days of the experiment protein spot number was increased again and the protein patterns resemble the protein patterns of biomass from normal conditions. It indicates the recovery of the metabolic activity under Martian environmental conditions after one week of exposure. PMID:24870977

Protein patterns of black fungi under simulated Mars-like conditions.

PubMed

Zakharova, Kristina; Marzban, Gorji; de Vera, Jean-Pierre; Lorek, Andreas; Sterflinger, Katja

2014-05-29

Two species of microcolonial fungi - Cryomyces antarcticus and Knufia perforans - and a species of black yeasts-Exophiala jeanselmei - were exposed to thermo-physical Mars-like conditions in the simulation chamber of the German Aerospace Center. In this study the alterations at the protein expression level from various fungi species under Mars-like conditions were analyzed for the first time using 2D gel electrophoresis. Despite of the expectations, the fungi did not express any additional proteins under Mars simulation that could be interpreted as stress induced HSPs. However, up-regulation of some proteins and significant decreasing of protein number were detected within the first 24 hours of the treatment. After 4 and 7 days of the experiment protein spot number was increased again and the protein patterns resemble the protein patterns of biomass from normal conditions. It indicates the recovery of the metabolic activity under Martian environmental conditions after one week of exposure.

Modeling Cl2/O2/Ar inductively coupled plasmas used for silicon etching: effects of SiO2 chamber wall coating

NASA Astrophysics Data System (ADS)

Tinck, S.; Boullart, W.; Bogaerts, A.

2011-08-01

In this paper, simulations are performed to gain a better insight into the properties of a Cl2/Ar plasma, with and without O2, during plasma etching of Si. Both plasma and surface properties are calculated in a self-consistent manner. Special attention is paid to the behavior of etch products coming from the wafer or the walls, and how the chamber walls can affect the plasma and the resulting etch process. Two modeling cases are considered. In the first case, the reactor walls are defined as clean (Al2O3), whereas in the second case a SiO2 coating is introduced on the reactor walls before the etching process, so that oxygen will be sputtered from the walls and introduced into the plasma. For this reason, a detailed reaction set is presented for a Cl2/O2/Ar plasma containing etched species, as well as an extensive reaction set for surface processes, including physical and chemical sputtering, chemical etching and deposition processes. Density and flux profiles of various species are presented for a better understanding of the bulk plasma during the etching process. Detailed information is also given on the composition of the surfaces at various locations of the reactor, on the etch products in the plasma and on the surface loss probabilities of the plasma species at the walls, with different compositions. It is found that in the clean chamber, walls are mostly chlorinated (Al2Cl3), with a thin layer of etch products residing on the wall. In the coated chamber, an oxy-chloride layer is grown on the walls for a few nanometers during the etching process. The Cl atom wall loss probability is found to decrease significantly in the coated chamber, hence increasing the etch rate. SiCl2, SiCl4 and SiCl3 are found to be the main etch products in the plasma, with the fraction of SiCl2 being always slightly higher. The simulation results compare well with experimental data available from the literature.

Computation of Neutral Gas Flow from a Hall Thruster into a Vacuum Chamber

DTIC Science & Technology

2002-10-18

try to quantify these effects, the direct simulation Monte Carlo method is applied to model a cold flow of xenon gas expanding from a Hall thruster into...a vacuum chamber. The simulations are performed for the P5 Hall thruster operating in a large vacuum tank at the University of Michigan. Comparison

The Interplay Between Saline Fluid Flow and Dynamic Permeability in Magmatic-Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Weis, P.

2014-12-01

Magmatic-hydrothermal ore deposits document the interplay between saline fluid flow and rock permeability. Numerical simulations of multi-phase flow of variably miscible, compressible H20-NaCl fluids in concert with a dynamic permeability model can reproduce characteristics of porphyry copper and epithermal gold systems. This dynamic permeability model incorporates depth-dependent permeability profiles characteristic for tectonically active crust as well as pressure- and temperature-dependent relationships describing hydraulic fracturing and the transition from brittle to ductile rock behavior. In response to focused expulsion of magmatic fluids from a crystallizing upper crustal magma chamber, the hydrothermal system self-organizes into a hydrological divide, separating an inner part dominated by ascending magmatic fluids under near-lithostatic pressures from a surrounding outer part dominated by convection of colder meteoric fluids under near-hydrostatic pressures. This hydrological divide also provides a mechanism to transport magmatic salt through the crust, and prevents the hydrothermal system to become "clogged" by precipitation of solid halite due to depressurization of saline, high-temperature magmatic fluids. The same physical processes at similar permeability ranges, crustal depths and flow rates are relevant for a number of active systems, including geothermal resources and excess degassing at volcanos. The simulations further suggest that the described mechanism can separate the base of free convection in high-enthalpy geothermal systems from the magma chamber as a driving heat source by several kilometers in the vertical direction in tectonic settings with hydrous magmatism. This hydrology would be in contrast to settings with anhydrous magmatism, where the base of the geothermal systems may be closer to the magma chamber.

The role of simulation chambers in the development of spectroscopic techniques: campaigns at EUPHORE

NASA Astrophysics Data System (ADS)

Ródenas, Milagros; Muñoz, Amalia; Euphore Team

2016-04-01

Simulation chambers represent a very useful tool for the study of chemical reactions and their products, but also to characterize instruments. The development of spectroscopic techniques throughout the last decades has benefited from tests and intercomparison exercises carried out in chambers. In fact, instruments can be exposed to various controlled atmospheric scenarios that account for different environmental conditions, eliminating the uncertainties associated to fluctuations of the air mass, which must be taken into account when extrapolating results to the real conditions. Hence, a given instrument can be characterized by assessing its precision, accuracy, detection limits, time response and potential interferences in the presence of other chemical compounds, aerosols, etc. This implies that the instrument can be calibrated and validated, which allows to enhance the features of the instrument. Moreover, chambers are also the scenario of intercomparison trials, permitting multiple instruments to sample from the same well-mixed air mass simultaneously. An overview of different campaigns to characterize and/or intercompare spectroscopic techniques that have taken place in simulation chambers will be given; in particular, those carried out at EUPHORE (two twin domes, 200 m3 each, Spain), where various intercomparison exercises have been deployed under the frame of European projects (e.g. TOXIC, FIONA, PSOA campaigns supported by EUROCHAMP-II). With the common aim of measuring given compounds (e.g. HONO, NO2, OH, glyoxal, m-glyoxal, etc), an important number of spectroscopic instruments and institutions have been involved in chamber experiments, having the chance to intercompare among them and also with other non-spectroscopic systems (e.g. monitors, cromatographs, etc) or model simulations.

Simulated airplane headache: a proxy towards identification of underlying mechanisms.

PubMed

Bui, Sebastian Bao Dinh; Petersen, Torben; Poulsen, Jeppe Nørgaard; Gazerani, Parisa

2017-12-01

Airplane Headache (AH) occurs during flights and often appears as an intense, short lasting headache during take-off or landing. Reports are limited on pathological mechanisms underlying the occurrence of this headache. Proper diagnosis and treatments would benefit from identification of potential pathways involved in AH pathogenesis. This study aimed at providing a simulated airplane headache condition as a proxy towards identification of its underlying mechanisms. Fourteen participants including 7 volunteers suffering from AH and 7 healthy matched controls were recruited after meeting the diagnostic and safety criteria based on an approved study protocol. Simulation of AH was achieved by entering a pressure chamber with similar characteristics of an airplane flight. Selected potential biomarkers including salivary prostaglandin E 2 (PGE 2 ), cortisol, facial thermo-images, blood pressure, pulse, and saturation pulse oxygen (SPO) were defined and values were collected before, during and after flight simulation in the pressure chamber. Salivary samples were analyzed with ELISA techniques, while data analysis and statistical tests were handled with SPSS version 22.0. All participants in the AH-group experienced a headache attack similar to AH experience during flight. The non-AH-group did not experience any headaches. Our data showed that the values for PGE 2 , cortisol and SPO were significantly different in the AH-group in comparison with the non-AH-group during the flight simulation in the pressure chamber. The pressure chamber proved useful not only to provoke AH-like attack but also to study potential biomarkers for AH in this study. PGE 2 , and cortisol levels together with SPO presented dysregulation during the simulated AH-attack in affected individuals compared with healthy controls. Based on these findings we propose to use pressure chamber as a model to induce AH, and thus assess new potential biomarkers for AH in future studies.

CFD simulations of Rapid Compression Machines using detailed chemistry: Evaluation of the ‘crevice containment’ concept

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bourgeois, Nicolas; Goldsborough, S. Scott; Jeanmart, Herve

The use of creviced pistons in Rapid Compression Machines (RCMs) has proven to be very effcient in making the temperature homogeneous inside the reaction chamber but has the disadvantage of inducing a mass transfer from the reaction chamber to the crevice, especially during the preliminary heat release of two- stage ignition processes. Aiming to mitigate this mass transfer, the technique of `crevice containment' (CC) has been proposed. It consists of a physical separa- tion between the reaction chamber and the crevice region that is engaged at the end of the compression, physically preventing any mass transfer between both parts ofmore » the geometry. In order to numerically assess this novel design concept across a broader range of conditions than previously investigated, reactive simu- lations using detailed chemical kinetic mechanisms are performed for n-heptane and iso-octane. For compressed temperatures outside of the NTC (negative temperature coeffcient) region, the CC approach is very effective in suppress- ing the influence of the crevice mass transfer and thus increases the validity of the widely-used 0-D model based on the adiabatic core assumption. Still, for most of the temperature cases inside the NTC region, the ignition appears to be precipitately initiated in the residual vortex region formed after the seal engagement, possibly inducing very significant differences with the 0-D model. The benefits of eliminating the post-compression crevice mass transfer appear to be counter-balanced by effects that have not been previously investigated in detail.« less

CFD simulations of Rapid Compression Machines using detailed chemistry: Evaluation of the ‘crevice containment’ concept

DOE PAGES

Bourgeois, Nicolas; Goldsborough, S. Scott; Jeanmart, Herve; ...

2018-01-17

The use of creviced pistons in Rapid Compression Machines (RCMs) has proven to be very effcient in making the temperature homogeneous inside the reaction chamber but has the disadvantage of inducing a mass transfer from the reaction chamber to the crevice, especially during the preliminary heat release of two- stage ignition processes. Aiming to mitigate this mass transfer, the technique of `crevice containment' (CC) has been proposed. It consists of a physical separa- tion between the reaction chamber and the crevice region that is engaged at the end of the compression, physically preventing any mass transfer between both parts ofmore » the geometry. In order to numerically assess this novel design concept across a broader range of conditions than previously investigated, reactive simu- lations using detailed chemical kinetic mechanisms are performed for n-heptane and iso-octane. For compressed temperatures outside of the NTC (negative temperature coeffcient) region, the CC approach is very effective in suppress- ing the influence of the crevice mass transfer and thus increases the validity of the widely-used 0-D model based on the adiabatic core assumption. Still, for most of the temperature cases inside the NTC region, the ignition appears to be precipitately initiated in the residual vortex region formed after the seal engagement, possibly inducing very significant differences with the 0-D model. The benefits of eliminating the post-compression crevice mass transfer appear to be counter-balanced by effects that have not been previously investigated in detail.« less

Velocity Plume Profiles for Hall Thrusters Using Laser Diagnostic

DTIC Science & Technology

2010-06-01

53 Collecting LIF Using Fiber Optics .............................................................................58 Vacuum ...54 Figure 40. Etalon Issue Through Vacuum Chamber Window [25]. ................................. 55 Figure 41. Collimator with Adapter in a...Methodology Facility Set-up Vacuum Chamber Testing took place within a vacuum chamber located at the AFIT Space Propulsion Analysis and System Simulation

46 CFR 160.028-4 - Approval and production tests.

Code of Federal Regulations, 2013 CFR

2013-10-01

... the chamber and bore dimensions is not required. (2) Inspections and tests by an independent... the chamber and bore dimensions of the pistol. (2) Fire a dummy cartridge simulating a normal signal....009 (4) Recheck the chamber and bore dimensions. (5) The pistol must fire the signal properly, must...

46 CFR 160.028-4 - Approval and production tests.

Code of Federal Regulations, 2011 CFR

2011-10-01

... the chamber and bore dimensions is not required. (2) Inspections and tests by an independent... the chamber and bore dimensions of the pistol. (2) Fire a dummy cartridge simulating a normal signal....009 (4) Recheck the chamber and bore dimensions. (5) The pistol must fire the signal properly, must...

46 CFR 160.028-4 - Approval and production tests.

Code of Federal Regulations, 2014 CFR

2014-10-01

... the chamber and bore dimensions is not required. (2) Inspections and tests by an independent... the chamber and bore dimensions of the pistol. (2) Fire a dummy cartridge simulating a normal signal....009 (4) Recheck the chamber and bore dimensions. (5) The pistol must fire the signal properly, must...

46 CFR 160.028-4 - Approval and production tests.

Code of Federal Regulations, 2012 CFR

2012-10-01

... the chamber and bore dimensions is not required. (2) Inspections and tests by an independent... the chamber and bore dimensions of the pistol. (2) Fire a dummy cartridge simulating a normal signal....009 (4) Recheck the chamber and bore dimensions. (5) The pistol must fire the signal properly, must...

Polarity effects and apparent ion recombination in microionization chambers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Jessica R., E-mail: miller@humonc.wisc.edu; Hooten, Brian D.; Micka, John A.

Purpose: Microchambers demonstrate anomalous voltage-dependent polarity effects. Existing polarity and ion recombination correction factors do not account for these effects. As a result, many commercial microchamber models do not meet the specification of a reference-class ionization chamber as defined by the American Association of Physicists in Medicine. The purpose of this investigation is to determine the cause of these voltage-dependent polarity effects. Methods: A series of microchamber prototypes were produced to isolate the source of the voltage-dependent polarity effects. Parameters including ionization-chamber collecting-volume size, stem and cable irradiation, chamber assembly, contaminants, high-Z materials, and individual chamber components were investigated. Measurementsmore » were performed with electrodes coated with graphite to isolate electrode conductivity. Chamber response was measured as the potential bias of the guard electrode was altered with respect to the collecting electrode, through the integration of additional power supplies. Ionization chamber models were also simulated using COMSOL Multiphysics software to investigate the effect of a potential difference between electrodes on electric field lines and collecting volume definition. Results: Investigations with microchamber prototypes demonstrated that the significant source of the voltage-dependent polarity effects was a potential difference between the guard and collecting electrodes of the chambers. The voltage-dependent polarity effects for each prototype were primarily isolated to either the guard or collecting electrode. Polarity effects were reduced by coating the isolated electrode with a conductive layer of graphite. Polarity effects were increased by introducing a potential difference between the electrodes. COMSOL simulations further demonstrated that for a given potential difference between electrodes, the collecting volume of the chamber changed as the applied voltage was altered, producing voltage-dependent polarity effects in the chamber response. Ionization chamber measurements and COMSOL simulations demonstrated an inverse relationship between the chamber collecting volume size and the severity of voltage-dependent polarity effects on chamber response. The effect of a given potential difference on chamber polarity effects was roughly ten times greater for microchambers as compared to Farmer-type chambers. Stem and cable irradiations, chamber assembly, contaminants, and high-Z materials were not found to be a significant source of the voltage-dependent polarity effects. Conclusions: A potential difference between the guard and collecting electrodes was found to be the primary source of the voltage-dependent polarity effects demonstrated by microchambers. For a given potential difference between electrodes, the relative change in the collecting volume is smaller for larger-volume chambers, illustrating why these polarity effects are not seen in larger-volume chambers with similar guard and collecting electrode designs. Thus, for small-volume chambers, it is necessary to reduce the potential difference between the guard and collecting electrodes in order to reduce polarity effects for reference dosimetry measurements.« less

Ballistic Deficits for Ionization Chamber Pulses in Pulse Shaping Amplifiers

NASA Astrophysics Data System (ADS)

Kumar, G. Anil; Sharma, S. L.; Choudhury, R. K.

2007-04-01

In order to understand the dependence of the ballistic deficit on the shape of rising portion of the voltage pulse at the input of a pulse shaping amplifier, we have estimated the ballistic deficits for the pulses from a two-electrode parallel plate ionization chamber as well as for the pulses from a gridded parallel plate ionization chamber. These estimations have been made using numerical integration method when the pulses are processed through the CR-RCn (n=1-6) shaping network as well as when the pulses are processed through the complex shaping network of the ORTEC Model 472 spectroscopic amplifier. Further, we have made simulations to see the effect of ballistic deficit on the pulse-height spectra under different conditions. We have also carried out measurements of the ballistic deficits for the pulses from a two-electrode parallel plate ionization chamber as well as for the pulses from a gridded parallel plate ionization chamber when these pulses are processed through the ORTEC 572 linear amplifier having a simple CR-RC shaping network. The reasonable matching of the simulated ballistic deficits with the experimental ballistic deficits for the CR-RC shaping network clearly establishes the validity of the simulation technique

Locating chambers in an Egyptian pyramid using cosmic ray muons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lynch, G.R.

From symposium on advanced technology arising from particle physics research; Argonne, Illinois, USA (17 May 1973). A brief report is given on the attempt to detect a chamber or chambers in the Second Pyramid of Chephen at Giza by using cosmic-ray muons. (WDM)

Simulating synchrotron radiation in accelerators including diffuse and specular reflections

DOE PAGES

Dugan, G.; Sagan, D.

2017-02-24

An accurate calculation of the synchrotron radiation flux within the vacuum chamber of an accelerator is needed for a number of applications. These include simulations of electron cloud effects and the design of radiation masking systems. To properly simulate the synchrotron radiation, it is important to include the scattering of the radiation at the vacuum chamber walls. To this end, a program called synrad3d has been developed which simulates the production and propagation of synchrotron radiation using a collection of photons. Photons generated by a charged particle beam are tracked from birth until they strike the vacuum chamber wall wheremore » the photon is either absorbed or scattered. Both specular and diffuse scattering is simulated. If a photon is scattered, it is further tracked through multiple encounters with the wall until it is finally absorbed. This paper describes the synrad3d program, with a focus on the details of its scattering model, and presents some examples of the program’s use.« less

Results from the Thermal Vacuum Tests of the Chinese-Brazilian Earth Resources Satellite - CBERS FM2

NASA Astrophysics Data System (ADS)

Almeida, J. S.; Garcia, E. C.; Santos, M. B.; Fu, P. Z.

2002-01-01

This paper details the approach adopted and applied on the thermal vacuum tests campaign of the CBERS Flight Model #2 spacecraft, successfully performed at the Integration and Tests Laboratory - LIT, National Institute for Space Research - INPE, in São José dos Campos, SP, from September 7th to 28th, 2001. Measuring approximately 1.8 x 2.0 x 2.2m, weighting 1,500kg and carrying three cameras as the main payload, this spacecraft is scheduled to be launched in China and it will be orbiting the Earth at 778km as part of its remote sensing mission profile. Exploring the capabilities of LIT's 3m x 3m thermal vacuum chamber in terms of appropriately selecting and adjusting its cold shroud temperatures and also some low cost heat input/sink techniques, the spacecraft was adequately disjoined at its service and payload model interface in such a way that each part could physically fit inside the T/V chamber one at a time. Assuring all the necessary functional and test cabling interconnection between the two models through the chamber walls for the proper spacecraft electrical operations as an integrated system, specific thermal test techniques were applied in order to obtain the required hot and cold acceptance levels of temperature at the spacecraft subsystems and structural surfaces, as a consequence of the simulated thermal conditioning from the distinct orbital configurations. These thermal simulation techniques consisted of a combination of skin-heaters, the thermal vacuum chamber main shrouds and dedicated LN2 cold plates, effectively leading to reliable and very satisfactory testing methodology results. Taking more than 350 hours and having 67 people directly involved, including teams from both Brazil and China, this test can be considered as a very important accomplishment in terms of distinct technique of spacecraft testing and also in terms of the satisfactory working relationship between two quite different cultures.

Electromagnetic Compatibility Testing Studies

NASA Technical Reports Server (NTRS)

Trost, Thomas F.; Mitra, Atindra K.

1996-01-01

This report discusses the results on analytical models and measurement and simulation of statistical properties from a study of microwave reverberation (mode-stirred) chambers performed at Texas Tech University. Two analytical models of power transfer vs. frequency in a chamber, one for antenna-to-antenna transfer and the other for antenna to D-dot sensor, were experimentally validated in our chamber. Two examples are presented of the measurement and calculation of chamber Q, one for each of the models. Measurements of EM power density validate a theoretical probability distribution on and away from the chamber walls and also yield a distribution with larger standard deviation at frequencies below the range of validity of the theory. Measurements of EM power density at pairs of points which validate a theoretical spatial correlation function on the chamber walls and also yield a correlation function with larger correlation length, R(sub corr), at frequencies below the range of validity of the theory. A numerical simulation, employing a rectangular cavity with a moving wall shows agreement with the measurements. The determination that the lowest frequency at which the theoretical spatial correlation function is valid in our chamber is considerably higher than the lowest frequency recommended by current guidelines for utilizing reverberation chambers in EMC testing. Two suggestions have been made for future studies related to EMC testing.

The use of decompression to simulate the effect of extravehicular activity on human lymphocyte transformation

NASA Technical Reports Server (NTRS)

Meehan, R. T.; Duncan, U.; Neale, L.; Waligora, J.; Taylor, G. R.

1986-01-01

Lymphocytes from 35 subjects participating in a chamber study simulating extravehicular activity (EVA) conditions were studied. No significant differences in H3 thymidine uptake between pre chamber and post chamber response to any mitogens autologous plasma, or among circulating mononuclear cells by flow cytometry are observed. The studies could not identify the subjects who developed venous bubbles. Data from eight subjects suggests that acute stress associated with participating in the study augments in vitro lymphocyte proliferation. Results indicate EVA exposure does not greatly influence space-flight induced alterations in immune effector cell function.

Design of a hydraulic analog of the circulatory system for evaluating artificial hearts.

PubMed

Donovan, F M

1975-01-01

A major problem in improving artificial heart designs is the absence of methods for accurate in vitro testing of artificial heart systems. A mock circulatory system has been constructed which hydraulically simulates the systemic and pulmonary circulations of the normal human. The device is constructed of 1/2 in. acrylic sheet and has overall dimensions of 24 in. wide, 16 in. tall, and 8 in. deep. The artificial heart to be tested is attached to the front of the device, and pumps fluid from the systemic venous chamber into the pulmonary arterial chamber and from the pulmonary venous chamber into the systemic arterial chamber. Each of the four chambers is hermetically sealed. The compliance of each chamber is determined by the volume of air trapped above the fluid in that chamber. The pulmonary and systemic resistances are set automatically by bellows-operated valves to simulate the barroreceptor response in the systemic arteries and the passive pulmonary resistance response in the pulmonary arteries. Cardiac output is measured by a turbine flowmeter in the systemic circulation. Results using the Kwan-Gett artificial heart show a good comparison between the mock circulatory system response and the calf response.

Astronaut Russell Schweickart inside simulator for EVA training

NASA Image and Video Library

1968-12-11

S68-55391 (11 Dec. 1968) --- Astronaut Russell L. Schweickart, lunar module pilot of the Apollo 9 (Spacecraft 104/Lunar Module 3/Saturn 504) space mission, is seen inside Chamber "A," Space Environment Simulation Laboratory, Building 32, participating in dry run activity in preparation for extravehicular activity which is scheduled in Chamber "A." The purpose of the scheduled training is to familiarize the crewmen with the operation of EVA equipment in a simulated space environment. In addition, metabolic and workload profiles will be simulated on each crewman. Astronauts Schweickart and Alan L. Bean, backup lunar module pilot, are scheduled to receive thermal-vacuum training simulating Earth-orbital EVA.

Wenckebach upper rate response in single chamber pacemaker.

PubMed

Barold, S S

2000-07-01

The Medtronic Minix pacemaker during normal function in the VVT mode was found to exhibit a Wenckenbach upper rate response similar to that of dual chamber devices. This behavior occurred only when the upper rate interval was longer than the pacemaker refractory period. In a single chamber device this response may simulate pacemaker malfunction.

The response of a scintillation counter below an emulsion chamber to heavy nucleus interactions in the chamber

NASA Technical Reports Server (NTRS)

Burnett, T. H.; Dake, S.; Derrickson, J. H.; Fountain, W. F.; Fuki, M.; Gregory, J. C.; Hayashi, T.; Hayashi, T.; Holynski, R.; Iwai, J.;

Unsteady flowfield in an integrated rocket ramjet engine and combustion dynamics of a gas turbine swirl-stabilized injector

NASA Astrophysics Data System (ADS)

Sung, Hong-Gye

This research focuses on the time-accurate simulation and analysis of the unsteady flowfield in an integrated rocket-ramjet engine (IRR) and combustion dynamics of a swirl-stabilized gas turbine engine. The primary objectives are: (1) to establish a unified computational framework for studying unsteady flow and flame dynamics in ramjet propulsion systems and gas turbine combustion chambers, and (2) to investigate the parameters and mechanisms responsible for driving flow oscillations. The first part of the thesis deals with a complete axi-symmetric IRR engine. The domain of concern includes a supersonic inlet diffuser, a combustion chamber, and an exhaust nozzle. This study focused on the physical mechanism of the interaction between the oscillatory terminal shock in the inlet diffuser and the flame in the combustion chamber. In addition, the flow and ignition transitions from the booster to the sustainer phase were analyzed comprehensively. Even though the coupling between the inlet dynamics and the unsteady motions of flame shows that they are closely correlated, fortunately, those couplings are out of phase with a phase lag of 90 degrees, which compensates for the amplification of the pressure fluctuation in the inlet. The second part of the thesis treats the combustion dynamics of a lean-premixed gas turbine swirl injector. A three-dimensional computation method utilizing the message passing interface (MPI) Parallel architecture and large-eddy-simulation technique was applied. Vortex breakdown in the swirling flow is clearly visualized and explained on theoretical bases. The unsteady turbulent flame dynamics are carefully simulated so that the flow motion can be characterized in detail. It was observed that some fuel lumps escape from the primary combustion zone, and move downstream and consequently produce hot spots and large vortical structures in the azimuthal direction. The correlation between pressure oscillation and unsteady heat release is examined by both the spatial and temporal Rayleigh parameters. In addition, basis modes of the unsteady turbulent flame are characterized using proper orthogonal decomposition (POD) analysis.

Investigation of particle and vapor wall-loss effects on controlled wood-smoke smog-chamber experiments

NASA Astrophysics Data System (ADS)

Bian, Q.; May, A. A.; Kreidenweis, S. M.; Pierce, J. R.

2015-10-01

Smog chambers are extensively used to study processes that drive gas and particle evolution in the atmosphere. A limitation of these experiments is that particles and gas-phase species may be lost to chamber walls on shorter timescales than the timescales of the atmospheric processes being studied in the chamber experiments. These particle and vapor wall losses have been investigated in recent studies of secondary organic aerosol (SOA) formation, but they have not been systematically investigated in experiments of primary emissions from combustion. The semi-volatile nature of combustion emissions (e.g. from wood smoke) may complicate the behavior of particle and vapor wall deposition in the chamber over the course of the experiments due to the competition between gas/particle and gas/wall partitioning. Losses of vapors to the walls may impact particle evaporation in these experiments, and potential precursors for SOA formation from combustion may be lost to the walls, causing underestimations of aerosol yields. Here, we conduct simulations to determine how particle and gas-phase wall losses contributed to the observed evolution of the aerosol during experiments in the third Fire Lab At Missoula Experiment (FLAME III). We use the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithm coupled with the organic volatility basis set (VBS) and wall-loss formulations to examine the predicted extent of particle and vapor wall losses. We limit the scope of our study to the dark periods in the chamber before photo-oxidation to simplify the aerosol system for this initial study. Our model simulations suggest that over one-third of the initial particle-phase organic mass (41 %) was lost during the experiments, and over half of this particle-organic mass loss was from direct particle wall loss (65 % of the loss) with the remainder from evaporation of the particles driven by vapor losses to the walls (35 % of the loss). We perform a series of sensitivity tests to understand uncertainties in our simulations. Uncertainty in the initial wood-smoke volatility distribution contributes 18 % uncertainty to the final particle-organic mass remaining in the chamber (relative to base-assumption simulation). We show that the total mass loss may depend on the effective saturation concentration of vapor with respect to the walls as these values currently vary widely in the literature. The details of smoke dilution during the filling of smog chambers may influence the mass loss to the walls, and a dilution of ~ 25:1 during the experiments increased particle-organic mass loss by 33 % compared to a simulation where we assume the particles and vapors are initially in equilibrium in the chamber. Finally, we discuss how our findings may influence interpretations of emission factors and SOA production in wood-smoke smog-chamber experiments.

Investigation of particle and vapor wall-loss effects on controlled wood-smoke smog-chamber experiments

NASA Astrophysics Data System (ADS)

Bian, Q.; May, A. A.; Kreidenweis, S. M.; Pierce, J. R.

2015-06-01

Smog chambers are extensively used to study processes that drive gas and particle evolution in the atmosphere. A limitation of these experiments is that particles and gas-phase species may be lost to chamber walls on shorter timescales than the timescales of the atmospheric processes being studied in the chamber experiments. These particle and vapor wall losses have been investigated in recent studies of secondary organic aerosol (SOA) formation, but they have not been systematically investigated in experiments of primary emissions from combustion. The semi-volatile nature of combustion emissions (e.g. from wood smoke) may complicate the behavior of particle and vapor wall deposition in the chamber over the course of the experiments due to the competition between gas/particle and gas/wall partitioning. Losses of vapors to the walls may impact particle evaporation in these experiments, and potential precursors for SOA formation from combustion may be lost to the walls, causing underestimates of aerosol yields. Here, we conduct simulations to determine how particle and gas-phase wall losses contributed to the observed evolution of the aerosol during experiments in the third Fire Lab At Missoula Experiment (FLAME III). We use the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithm coupled with the organic volatility basis set (VBS) and wall-loss formulations to examine the predicted extent of particle and vapor wall losses. We limit the scope of our study to the dark periods in the chamber before photo-oxidation to simplify the aerosol system for this initial study. Our model simulations suggest that over one third of the initial particle-phase organic mass (36%) was lost during the experiments, and roughly half of this particle organic mass loss was from direct particle wall loss (56% of the loss) with the remainder from evaporation of the particles driven by vapor losses to the walls (44% of the loss). We perform a series of sensitivity tests to understand uncertainties in our simulations. Uncertainty in the initial wood-smoke volatility distribution contributes 23% uncertainty to the final particle organic mass remaining in the chamber (relative to base-assumptions simulation). We show that the total mass loss may depend on the effective saturation concentration of vapor with respect to the walls as these values currently vary widely in the literature. The details of smoke dilution during the filling of smog chambers may influence the mass loss to the walls, and a dilution of ~ 25:1 during the experiments increased particle organic mass loss by 64% compared to a simulation where we assume the particles and vapors are initially in equilibrium in the chamber. Finally, we discuss how our findings may influence interpretations of emission factors and SOA production in wood-smoke smog-chamber experiments.

Simulations of Charged-Current Supernova νe Events in a Liquid Argon Time Projection Chamber

NASA Astrophysics Data System (ADS)

Gardiner, Steven; Grant, Christopher; Pantic, Emilija; Svoboda, Robert

2016-03-01

Although it is still in its infancy, the study of supernova neutrinos has proven to be a fertile topic for fundamental science. A mere two dozen events recorded from supernova 1987A, the only supernova neutrino source observed so far, have led to numerous publications on a wide variety of topics. This bountiful scientific harvest has prompted the neutrino physics community to prepare to make more detailed observations of the neutrinos that will be produced in the next nearby supernova. Because of their unique νe sensitivity, liquid argon time projection chamber (LArTPC) experiments such as DUNE (Deep Underground Neutrino Experiment) have the potential to make valuable contributions to this detection effort. To better understand the expected SN νe signal in a LArTPC, we have developed a Monte Carlo event generator called MARLEY (Model of Argon Reaction Low-Energy Yields) for charged-current νe reactions on argon. By combining MARLEY with LArSoft, a LArTPC simulation package, we have obtained the most detailed predictions currently available for the response of a LArTPC to supernova νe. We will discuss the implications of these results for the design and operation of LArTPCs sensitive to SN neutrinos.

Crystalline heterogeneities and instabilities in thermally convecting magma chamber

NASA Astrophysics Data System (ADS)

Culha, C.; Suckale, J.; Qin, Z.

2016-12-01

A volcanic vent can supply different densities of crystals over an eruption time period. This has been seen in Hawai'i's Kilauea Iki 1959 eruption; however it is not common for all Kilauea or basaltic eruptions. We ask the question: Under what conditions can homogenous magma chamber cultivate crystalline heterogeneities? In some laboratory experiments and numerical simulations, a horizontal variation is observed. The region where crystals reside is identified as a retention zone: convection velocity balances settling velocity. Simulations and experiments that observe retention zones assume crystals do not alter the convection in the fluid. However, a comparison of experiments and simulations of convecting magma with crystals suggest that large crystal volume densities and crystal sizes alter fluid flow considerably. We introduce a computational method that fully resolves the crystalline phase. To simulate basaltic magma chambers in thermal convection, we built a numerical solver of the Navier-Stoke's equation, continuity equation, and energy equation. The modeled magma is assumed to be a viscous, incompressible fluid with a liquid and solid phase. Crystals are spherical, rigid bodies. We create Rayleigh-Taylor instability through a cool top layer and hot bottom layer and update magma density while keeping crystal temperature and size constant. Our method provides a detailed picture of magma chambers, which we compare to other models and experiments to identify when and how crystals alter magma chamber convection. Alterations include stratification, differential settling and instabilities. These characteristics are dependent on viscosity, convection vigor, crystal volume density and crystal characteristics. We reveal that a volumetric crystal density variation may occur over an eruption time period, if right conditions are met to form stratifications and instabilities in magma chambers. These conditions are realistic for Kilauea Iki's 1959 eruption.

Monte Carlo calculations of electron beam quality conversion factors for several ion chamber types.

PubMed

Muir, B R; Rogers, D W O

2014-11-01

To provide a comprehensive investigation of electron beam reference dosimetry using Monte Carlo simulations of the response of 10 plane-parallel and 18 cylindrical ion chamber types. Specific emphasis is placed on the determination of the optimal shift of the chambers' effective point of measurement (EPOM) and beam quality conversion factors. The EGSnrc system is used for calculations of the absorbed dose to gas in ion chamber models and the absorbed dose to water as a function of depth in a water phantom on which cobalt-60 and several electron beam source models are incident. The optimal EPOM shifts of the ion chambers are determined by comparing calculations of R50 converted from I50 (calculated using ion chamber simulations in phantom) to R50 calculated using simulations of the absorbed dose to water vs depth in water. Beam quality conversion factors are determined as the calculated ratio of the absorbed dose to water to the absorbed dose to air in the ion chamber at the reference depth in a cobalt-60 beam to that in electron beams. For most plane-parallel chambers, the optimal EPOM shift is inside of the active cavity but different from the shift determined with water-equivalent scaling of the front window of the chamber. These optimal shifts for plane-parallel chambers also reduce the scatter of beam quality conversion factors, kQ, as a function of R50. The optimal shift of cylindrical chambers is found to be less than the 0.5 rcav recommended by current dosimetry protocols. In most cases, the values of the optimal shift are close to 0.3 rcav. Values of kecal are calculated and compared to those from the TG-51 protocol and differences are explained using accurate individual correction factors for a subset of ion chambers investigated. High-precision fits to beam quality conversion factors normalized to unity in a beam with R50 = 7.5 cm (kQ (')) are provided. These factors avoid the use of gradient correction factors as used in the TG-51 protocol although a chamber dependent optimal shift in the EPOM is required when using plane-parallel chambers while no shift is needed with cylindrical chambers. The sensitivity of these results to parameters used to model the ion chambers is discussed and the uncertainty related to the practical use of these results is evaluated. These results will prove useful as electron beam reference dosimetry protocols are being updated. The analysis of this work indicates that cylindrical ion chambers may be appropriate for use in low-energy electron beams but measurements are required to characterize their use in these beams.

Charge exchange molecular ion source

DOEpatents

Vella, Michael C.

2003-06-03

Ions, particularly molecular ions with multiple dopant nucleons per ion, are produced by charge exchange. An ion source contains a minimum of two regions separated by a physical barrier and utilizes charge exchange to enhance production of a desired ion species. The essential elements are a plasma chamber for production of ions of a first species, a physical separator, and a charge transfer chamber where ions of the first species from the plasma chamber undergo charge exchange or transfer with the reactant atom or molecules to produce ions of a second species. Molecular ions may be produced which are useful for ion implantation.

Spatial distribution of the RF power absorbed in a helicon plasma source

NASA Astrophysics Data System (ADS)

Aleksenko, O. V.; Miroshnichenko, V. I.; Mordik, S. N.

2014-08-01

The spatial distributions of the RF power absorbed by plasma electrons in an ion source operating in the helicon mode (ω ci < ω < ω ce < ω pe ) are studied numerically by using a simplified model of an RF plasma source in an external uniform magnetic field. The parameters of the source used in numerical simulations are determined by the necessity of the simultaneous excitation of two types of waves, helicons and Trivelpiece-Gould modes, for which the corresponding transparency diagrams are used. The numerical simulations are carried out for two values of the working gas (helium) pressure and two values of the discharge chamber length under the assumption that symmetric modes are excited. The parameters of the source correspond to those of the injector of the nuclear scanning microprobe operating at the Institute of Applied Physics, National Academy of Sciences of Ukraine. It is assumed that the mechanism of RF power absorption is based on the acceleration of plasma electrons in the field of a Trivelpiece-Gould mode, which is interrupted by pair collisions of plasma electrons with neutral atoms and ions of the working gas. The simulation results show that the total absorbed RF power at a fixed plasma density depends in a resonant manner on the magnetic field. The resonance is found to become smoother with increasing working gas pressure. The distributions of the absorbed RF power in the discharge chamber are presented. The achievable density of the extracted current is estimated using the Bohm criterion.

SU‐C‐105‐05: Reference Dosimetry of High‐Energy Electron Beams with a Farmer‐Type Ionization Chamber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muir, B; Rogers, D

2013-06-15

Purpose: To investigate gradient effects and provide Monte Carlo calculated beam quality conversion factors to characterize the Farmer‐type NE2571 ion chamber for high‐energy reference dosimetry of clinical electron beams. Methods: The EGSnrc code system is used to calculate the absorbed dose to water and to the gas in a fully modeled NE2571 chamber as a function of depth in a water phantom. Electron beams incident on the surface of the phantom are modeled using realistic BEAMnrc accelerator simulations and electron beam spectra. Beam quality conversion factors are determined using calculated doses to water and to air in the chamber inmore » high‐energy electron beams and in a cobalt‐60 reference field. Calculated water‐to‐air stopping power ratios are employed for investigation of the overall ion chamber perturbation factor. Results: An upstream shift of 0.3–0.4 multiplied by the chamber radius, r-cav, both minimizes the variation of the overall ion chamber perturbation factor with depth and reduces the difference between the beam quality specifier (R{sub 5} {sub 0}) calculated using ion chamber simulations and that obtained with simulations of dose‐to‐water in the phantom. Beam quality conversion factors are obtained at the reference depth and gradient effects are optimized using a shift of 0.2r-cav. The photon‐electron conversion factor, k-ecal, amounts to 0.906 when gradient effects are minimized using the shift established here and 0.903 if no shift of the data is used. Systematic uncertainties in beam quality conversion factors are investigated and amount to between 0.4 to 1.1% depending on assumptions used. Conclusion: The calculations obtained in this work characterize the use of an NE2571 ion chamber for reference dosimetry of high‐energy electron beams. These results will be useful as the AAPM continues to review their reference dosimetry protocols.« less

Large Eddy Simulation of a Film Cooling Technique with a Plenum

NASA Astrophysics Data System (ADS)

Dharmarathne, Suranga; Sridhar, Narendran; Araya, Guillermo; Castillo, Luciano; Parameswaran, Sivapathasund

2012-11-01

Factors that affect the film cooling performance have been categorized into three main groups: (i) coolant & mainstream conditions, (ii) hole geometry & configuration, and (iii) airfoil geometry Bogard et al. (2006). The present study focuses on the second group of factors, namely, the modeling of coolant hole and the plenum. It is required to simulate correct physics of the problem to achieve more realistic numerical results. In this regard, modeling of cooling jet hole and the plenum chamber is highly important Iourokina et al. (2006). Substitution of artificial boundary conditions instead of correct plenum design would yield unrealistic results Iourokina et al. (2006). This study attempts to model film cooling technique with a plenum using a Large Eddy Simulation.Incompressible coolant jet ejects to the surface of the plate at an angle of 30° where it meets compressible turbulent boundary layer which simulates the turbine inflow conditions. Dynamic multi-scale approach Araya (2011) is introduced to prescribe turbulent inflow conditions. Simulations are carried out for two different blowing ratios and film cooling effectiveness is calculated for both cases. Results obtained from LES will be compared with experimental results.

Combustion-chamber Performance Characteristics of a Python Turbine-propeller Engine Investigated in Altitude Wind Tunnel

NASA Technical Reports Server (NTRS)

Campbell, Carl E

1951-01-01

Combustion-chamber performance characteristics of a Python turbine-propeller engine were determined from investigation of a complete engine over a range of engine speeds and shaft horsepowers at simulated altitudes. Results indicated the effect of engine operating conditions and altitude on combustion efficiency and combustion-chamber total pressure losses. Performance of this vaporizing type combustion chamber was also compared with several atomizing type combustion chambers. Over the range of test conditions investigated, combustion efficiency varied from approximately 0.95 to 0.99.

Dead space variability of face masks for valved holding chambers.

PubMed

Amirav, Israel; Newhouse, Michael T

2008-03-01

Valved holding chambers with masks are commonly used to deliver inhaled medications to young children with asthma. Optimal mask properties such as their dead space volume have received little attention. The smaller the mask the more likely it is that a greater proportion of the dose in the VHC will be inhaled with each breath, thus speeding VHC emptying and improving overall aerosol delivery efficiency and dose. Masks may have different DSV and thus different performance. To compare both physical dead space and functional dead space of different face masks under various applied pressures. The DSV of three commonly used face masks of VHCs was measured by water displacement both under various pressures (to simulate real-life application, dynamic DSV) and under no pressure (static DSV). There was a great variability of both static and dynamic dead space among various face mask for VHCs, which is probably related to their flexibility. Different masks have different DSV characteristics. This variability should be taken into account when comparing the clinical efficacy of various VHCs.

Design and construction of Keda Space Plasma Experiment (KSPEX) for the investigation of the boundary layer processes of ionospheric depletions.

PubMed

Liu, Yu; Zhang, Zhongkai; Lei, Jiuhou; Cao, Jinxiang; Yu, Pengcheng; Zhang, Xiao; Xu, Liang; Zhao, Yaodong

2016-09-01

In this work, the design and construction of the Keda Space Plasma EXperiment (KSPEX), which aims to study the boundary layer processes of ionospheric depletions, are described in detail. The device is composed of three stainless-steel sections: two source chambers at both ends and an experimental chamber in the center. KSPEX is a steady state experimental device, in which hot filament arrays are used to produce plasmas in the two sources. A Macor-mesh design is adopted to adjust the plasma density and potential difference between the two plasmas, which creates a boundary layer with a controllable electron density gradient and inhomogeneous radial electric field. In addition, attachment chemicals can be released into the plasmas through a tailor-made needle valve which leads to the generation of negative ions plasmas. Ionospheric depletions can be modeled and simulated using KSPEX, and many micro-physical processes of the formation and evolution of an ionospheric depletion can be experimentally studied.

2D/3D fetal cardiac dataset segmentation using a deformable model.

PubMed

Dindoyal, Irving; Lambrou, Tryphon; Deng, Jing; Todd-Pokropek, Andrew

2011-07-01

To segment the fetal heart in order to facilitate the 3D assessment of the cardiac function and structure. Ultrasound acquisition typically results in drop-out artifacts of the chamber walls. The authors outline a level set deformable model to automatically delineate the small fetal cardiac chambers. The level set is penalized from growing into an adjacent cardiac compartment using a novel collision detection term. The region based model allows simultaneous segmentation of all four cardiac chambers from a user defined seed point placed in each chamber. The segmented boundaries are automatically penalized from intersecting at walls with signal dropout. Root mean square errors of the perpendicular distances between the algorithm's delineation and manual tracings are within 2 mm which is less than 10% of the length of a typical fetal heart. The ejection fractions were determined from the 3D datasets. We validate the algorithm using a physical phantom and obtain volumes that are comparable to those from physically determined means. The algorithm segments volumes with an error of within 13% as determined using a physical phantom. Our original work in fetal cardiac segmentation compares automatic and manual tracings to a physical phantom and also measures inter observer variation.

Numerical and experimental analysis of heat transfer in injector plate of hydrogen peroxide hybrid rocket motor

NASA Astrophysics Data System (ADS)

Cai, Guobiao; Li, Chengen; Tian, Hui

2016-11-01

This paper is aimed to analyze heat transfer in injector plate of hydrogen peroxide hybrid rocket motor by two-dimensional axisymmetric numerical simulations and full-scale firing tests. Long-time working, which is an advantage of hybrid rocket motor over conventional solid rocket motor, puts forward new challenges for thermal protection. Thermal environments of full-scale hybrid rocket motors designed for long-time firing tests are studied through steady-state coupled numerical simulations of flow field and heat transfer in chamber head. The motor adopts 98% hydrogen peroxide (98HP) oxidizer and hydroxyl-terminated poly-butadiene (HTPB) based fuel as the propellants. Simulation results reveal that flowing liquid 98HP in head oxidizer chamber could cool the injector plate of the motor. The cooling of 98HP is similar to the regenerative cooling in liquid rocket engines. However, the temperature of the 98HP in periphery portion of the head oxidizer chamber is higher than its boiling point. In order to prevent the liquid 98HP from unexpected decomposition, a thermal protection method for chamber head utilizing silica-phenolics annular insulating board is proposed. The simulation results show that the annular insulating board could effectively decrease the temperature of the 98HP in head oxidizer chamber. Besides, the thermal protection method for long-time working hydrogen peroxide hybrid rocket motor is verified through full-scale firing tests. The ablation of the insulating board in oxygen-rich environment is also analyzed.

KENNEDY SPACE CENTER, FLA. -- In the Space Life Sciences (SLS) Lab, Jan Bauer, with Dynamac Corp., places samples of onion tissue in the elemental analyzer, which analyzes for carbon, hydrogen, nitrogen and sulfur. The 100,000 square-foot SLS houses labs for NASA’s ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASA’s Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASA’s Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

NASA Image and Video Library

2004-01-05

KENNEDY SPACE CENTER, FLA. -- In the Space Life Sciences (SLS) Lab, Jan Bauer, with Dynamac Corp., places samples of onion tissue in the elemental analyzer, which analyzes for carbon, hydrogen, nitrogen and sulfur. The 100,000 square-foot SLS houses labs for NASA’s ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASA’s Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASA’s Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

KENNEDY SPACE CENTER, FLA. -- Sharon Edney, with Dynamac Corp., measures photosynthesis on Bibb lettuce being grown hydroponically for study in the Space Life Sciences Lab. The 100,000 square-foot facility houses labs for NASA’s ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASA’s Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASA’s Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

NASA Image and Video Library

2004-01-05

KENNEDY SPACE CENTER, FLA. -- Sharon Edney, with Dynamac Corp., measures photosynthesis on Bibb lettuce being grown hydroponically for study in the Space Life Sciences Lab. The 100,000 square-foot facility houses labs for NASA’s ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASA’s Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASA’s Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

KENNEDY SPACE CENTER, FLA. -- Sharon Edney, with Dynamac Corp., checks the roots of green onions being grown hydroponically for study in the Space Life Sciences Lab. The 100,000 square-foot facility houses labs for NASA’s ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASA’s Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASA’s Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

NASA Image and Video Library

2004-01-05

KENNEDY SPACE CENTER, FLA. -- Sharon Edney, with Dynamac Corp., checks the roots of green onions being grown hydroponically for study in the Space Life Sciences Lab. The 100,000 square-foot facility houses labs for NASA’s ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASA’s Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASA’s Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

KENNEDY SPACE CENTER, FLA. -- Lanfang Levine, with Dynamac Corp., helps install a Dionex DX-500 IC/HPLC system in the Space Life Sciences Lab. The equipment will enable analysis of volatile compounds, such as from plants. The 100,000 square-foot facility houses labs for NASA’s ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASA’s Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASA’s Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

NASA Image and Video Library

2004-01-05

KENNEDY SPACE CENTER, FLA. -- Lanfang Levine, with Dynamac Corp., helps install a Dionex DX-500 IC/HPLC system in the Space Life Sciences Lab. The equipment will enable analysis of volatile compounds, such as from plants. The 100,000 square-foot facility houses labs for NASA’s ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASA’s Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASA’s Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

KENNEDY SPACE CENTER, FLA. -- In the Space Life Sciences (SLS) Lab, Jan Bauer, with Dynamac Corp., weighs samples of onion tissue for processing in the elemental analyzer behind it. The equipment analyzes for carbon, hydrogen, nitrogen and sulfur. The 100,000 square-foot SLS houses labs for NASA’s ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASA’s Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASA’s Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

NASA Image and Video Library

2004-01-05

KENNEDY SPACE CENTER, FLA. -- In the Space Life Sciences (SLS) Lab, Jan Bauer, with Dynamac Corp., weighs samples of onion tissue for processing in the elemental analyzer behind it. The equipment analyzes for carbon, hydrogen, nitrogen and sulfur. The 100,000 square-foot SLS houses labs for NASA’s ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASA’s Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASA’s Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

KENNEDY SPACE CENTER, FLA. -- Sharon Edney, with Dynamac Corp., checks the growth of radishes being grown hydroponically for study in the Space Life Sciences Lab. The 100,000 square-foot facility houses labs for NASA’s ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASA’s Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASA’s Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

NASA Image and Video Library

2004-01-05

KENNEDY SPACE CENTER, FLA. -- Sharon Edney, with Dynamac Corp., checks the growth of radishes being grown hydroponically for study in the Space Life Sciences Lab. The 100,000 square-foot facility houses labs for NASA’s ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASA’s Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASA’s Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

Measurements of Regolith Simulant Thermal Conductivity Under Asteroid and Mars Surface Conditions

NASA Astrophysics Data System (ADS)

Ryan, A. J.; Christensen, P. R.

2017-12-01

Laboratory measurements have been necessary to interpret thermal data of planetary surfaces for decades. We present a novel radiometric laboratory method to determine temperature-dependent thermal conductivity of complex regolith simulants under rough to high vacuum and across a wide range of temperatures. This method relies on radiometric temperature measurements instead of contact measurements, eliminating the need to disturb the sample with thermal probes. We intend to determine the conductivity of grains that are up to 2 cm in diameter and to parameterize the effects of angularity, sorting, layering, composition, and eventually cementation. We present the experimental data and model results for a suite of samples that were selected to isolate and address regolith physical parameters that affect bulk conductivity. Spherical glass beads of various sizes were used to measure the effect of size frequency distribution. Spherical beads of polypropylene and well-rounded quartz sand have respectively lower and higher solid phase thermal conductivities than the glass beads and thus provide the opportunity to test the sensitivity of bulk conductivity to differences in solid phase conductivity. Gas pressure in our asteroid experimental chambers is held at 10^-6 torr, which is sufficient to negate gas thermal conduction in even our coarsest of samples. On Mars, the atmospheric pressure is such that the mean free path of the gas molecules is comparable to the pore size for many regolith particulates. Thus, subtle variations in pore size and/or atmospheric pressure can produce large changes in bulk regolith conductivity. For each sample measured in our martian environmental chamber, we repeat thermal measurement runs at multiple pressures to observe this behavior. Finally, we present conductivity measurements of angular basaltic simulant that is physically analogous to sand and gravel that may be present on Bennu. This simulant was used for OSIRIS-REx TAGSAM Sample Return Arm engineering tests. We measure the original size frequency distribution as well as several sorted size fractions. These results will support the efforts of the OSIRIS-REx team in selecting a site on asteroid Bennu that is safe for the spacecraft and meets grain size requirements for sampling.

25th Space Simulation Conference. Environmental Testing: The Earth-Space Connection

NASA Technical Reports Server (NTRS)

Packard, Edward

2008-01-01

Topics covered include: Methods of Helium Injection and Removal for Heat Transfer Augmentation; The ESA Large Space Simulator Mechanical Ground Support Equipment for Spacecraft Testing; Temperature Stability and Control Requirements for Thermal Vacuum/Thermal Balance Testing of the Aquarius Radiometer; The Liquid Nitrogen System for Chamber A: A Change from Original Forced Flow Design to a Natural Flow (Thermo Siphon) System; Return to Mercury: A Comparison of Solar Simulation and Flight Data for the MESSENGER Spacecraft; Floating Pressure Conversion and Equipment Upgrades of Two 3.5kw, 20k, Helium Refrigerators; Affect of Air Leakage into a Thermal-Vacuum Chamber on Helium Refrigeration Heat Load; Special ISO Class 6 Cleanroom for the Lunar Reconnaissance Orbiter (LRO) Project; A State-of-the-Art Contamination Effects Research and Test Facility Martian Dust Simulator; Cleanroom Design Practices and Their Influence on Particle Counts; Extra Terrestrial Environmental Chamber Design; Contamination Sources Effects Analysis (CSEA) - A Tool to Balance Cost/Schedule While Managing Facility Availability; SES and Acoustics at GSFC; HST Super Lightweight Interchangeable Carrier (SLIC) Static Test; Virtual Shaker Testing: Simulation Technology Improves Vibration Test Performance; Estimating Shock Spectra: Extensions beyond GEVS; Structural Dynamic Analysis of a Spacecraft Multi-DOF Shaker Table; Direct Field Acoustic Testing; Manufacture of Cryoshroud Surfaces for Space Simulation Chambers; The New LOTIS Test Facility; Thermal Vacuum Control Systems Options for Test Facilities; Extremely High Vacuum Chamber for Low Outgassing Processing at NASA Goddard; Precision Cleaning - Path to Premier; The New Anechoic Shielded Chambers Designed for Space and Commercial Applications at LIT; Extraction of Thermal Performance Values from Samples in the Lunar Dust Adhesion Bell Jar; Thermal (Silicon Diode) Data Acquisition System; Aquarius's Instrument Science Data System (ISDS) Automated to Acquire, Process, Trend Data and Produce Radiometric System Assessment Reports; Exhaustive Thresholds and Resistance Checkpoints; Reconfigurable HIL Testing of Earth Satellites; FPGA Control System for the Automated Test of MicroShutters; Ongoing Capabilities and Developments of Re-Entry Plasma Ground Tests at EADS-ASTRIUM; Operationally Responsive Space Standard Bus Battery Thermal Balance Testing and Heat Dissipation Analysis; Galileo - The Serial-Production AIT Challenge; The Space Systems Environmental Test Facility Database (SSETFD), Website Development Status; Simulated Reentry Heating by Torching; Micro-Vibration Measurements on Thermally Loaded Multi-Layer Insulation Samples in Vacuum; High Temperature Life Testing of 80Ni-20Cr Wire in a Simulated Mars Atmosphere for the Sample Analysis at Mars (SAM) Instrument Suit Gas Processing System (GPS) Carbon Dioxide Scrubber; The Planning and Implementation of Test Facility Improvements; and Development of a Silicon Carbide Molecular Beam Nozzle for Simulation Planetary Flybys and Low-Earth Orbit.

Numerical evaluation of static-chamber measurements of soil-atmospheric gas exchange--Identification of physical processes

USGS Publications Warehouse

Healy, Richard W.; Striegl, Robert G.; Russell, Thomas F.; Hutchinson, Gordon L.; Livingston, Gerald P.

1996-01-01

The exchange of gases between soil and atmosphere is an important process that affects atmospheric chemistry and therefore climate. The static-chamber method is the most commonly used technique for estimating the rate of that exchange. We examined the method under hypothetical field conditions where diffusion was the only mechanism for gas transport and the atmosphere outside the chamber was maintained at a fixed concentration. Analytical and numerical solutions to the soil gas diffusion equation in one and three dimensions demonstrated that gas flux density to a static chamber deployed on the soil surface was less in magnitude than the ambient exchange rate in the absence of the chamber. This discrepancy, which increased with chamber deployment time and air-filled porosity of soil, is attributed to two physical factors: distortion of the soil gas concentration gradient (the magnitude was decreased in the vertical component and increased in the radial component) and the slow transport rate of diffusion relative to mixing within the chamber. Instantaneous flux density to a chamber decreased continuously with time; steepest decreases occurred so quickly following deployment and in response to such slight changes in mean chamber headspace concentration that they would likely go undetected by most field procedures. Adverse influences of these factors were reduced by mixing the chamber headspace, minimizing deployment time, maximizing the height and radius of the chamber, and pushing the rim of the chamber into the soil. Nonlinear models were superior to a linear regression model for estimating flux densities from mean headspace concentrations, suggesting that linearity of headspace concentration with time was not necessarily a good indicator of measurement accuracy.

NSLS II Vacuum System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferreira, M.; Doom, L.; Hseuh, H.

2009-09-13

National Synchrotron Light Source II, being constructed at Brookhaven, is a 3-GeV, 500 mA, 3rd generation synchrotron radiation facility with ultra low emittance electron beams. The storage ring vacuum system has a circumference of 792 m and consists of over 250 vacuum chambers with a simulated average operating pressure of less than 1 x 10{sup -9} mbar. A summary of the update design of the vacuum system including girder supports of the chambers, gauges, vacuum pumps, bellows, beam position monitors and simulation of the average pressure will be shown. A brief description of the techniques and procedures for cleaning andmore » mounting the chambers are given.« less

KA-111, Phase C, M-1 Propellant Tests: Deflagration in Partial Confinement.

DTIC Science & Technology

1991-07-01

DNA Test Director and Mr. R. !. Flory, Washington Research Center, was Program Coordinator. The DDESB, NDCS , and SSO Technical Monitors for Phase C...to simulate the chamber and access tunnel proportions of the Shallow Underground Tunnel /Chamber Explosion Test conducted at China Lake, CA, in 1988...The chamber and access tunnel at China Lake had the following dimensions (volume, cross-sectional area and length): Chamber: V. - 331.2 m 3 Tunnel : Vt

Investigation of electron-loss and photon scattering correction factors for FAC-IR-300 ionization chamber

NASA Astrophysics Data System (ADS)

Mohammadi, S. M.; Tavakoli-Anbaran, H.; Zeinali, H. Z.

2017-02-01

The parallel-plate free-air ionization chamber termed FAC-IR-300 was designed at the Atomic Energy Organization of Iran, AEOI. This chamber is used for low and medium X-ray dosimetry on the primary standard level. In order to evaluate the air-kerma, some correction factors such as electron-loss correction factor (ke) and photon scattering correction factor (ksc) are needed. ke factor corrects the charge loss from the collecting volume and ksc factor corrects the scattering of photons into collecting volume. In this work ke and ksc were estimated by Monte Carlo simulation. These correction factors are calculated for mono-energy photon. As a result of the simulation data, the ke and ksc values for FAC-IR-300 ionization chamber are 1.0704 and 0.9982, respectively.

Creating the Deep Space Environment for Testing the James Webb Space Telescope (JWST) at NASA Johnson Space Center's Chamber A

NASA Technical Reports Server (NTRS)

Homan, Jonathan L.; Cerimele, Mary P.; Montz, Michael E.; Bachtel, Russell; Speed, John; O'Rear, Patrick

2013-01-01

Chamber A is the largest thermal vacuum chamber at the Johnson Space Center and is one of the largest space environment chambers in the world. The chamber is 19.8 m (65 ft) in diameter and 36.6 m (120 ft) tall and is equipped with cryogenic liquid nitrogen panels (shrouds) and gaseous helium shrouds to create a simulated space environment. It was originally designed and built in the mid 1960 s to test the Apollo Command and Service Module and several manned tests were conducted on that spacecraft, contributing to the success of the program. The chamber has been used since that time to test spacecraft active thermal control systems, Shuttle DTO, DOD, and ESA hardware in simulated Low Earth Orbit (LEO) conditions. NASA is now moving from LEO towards exploration of locations with environments approaching those of deep space. Therefore, Chamber A has undergone major modifications to enable it to simulate these deeper space environments. Environmental requirements were driven, and modifications were funded by the James Webb Space Telescope program, and this telescope which will orbit Solar/Earth L2, will be the first test article to benefit from the chamber s new capabilities. To accommodate JWST, the Chamber A high vacuum system has been modernized, additional LN2 shrouds have been installed, the liquid nitrogen system has been modified to remove dependency on electrical power and increase its reliability, a new helium shroud/refrigeration system has been installed to create a colder more stable and uniform heat sink, and the controls have been updated to increase the level of automation and improve operator interfaces. Testing of these major modifications was conducted in August of 2012 and this initial test was very successful, with all major systems exceeding their performance requirements. This paper will outline the changes in overall environmental requirements, discuss the technical design data that was used in the decisions leading to the extensive modifications, and describe the new capabilities of the chamber.

Creating the Deep Space Environment for Testing the James Webb Space Telescope at NASA Johnson Space Center's Chamber A

NASA Technical Reports Server (NTRS)

Homan, Jonathan L.; Cerimele, Mary P.; Montz, Michael E.; Bachtel, Russell; Speed, John; O'Rear, Patrick

2013-01-01

Chamber A is the largest thermal vacuum chamber at the Johnson Space Center and is one of the largest space environment chambers in the world. The chamber is 19.8 m (65 ft.) in diameter and 36.6 m (120 ft.) tall and is equipped with cryogenic liquid nitrogen panels (shrouds) and gaseous helium shrouds to create a simulated space environment. It was originally designed and built in the mid 1960 s to test the Apollo Command and Service Module and several manned tests were conducted on that spacecraft, contributing to the success of the program. The chamber has been used since that time to test spacecraft active thermal control systems, Shuttle DTO, DOD, and ESA hardware in simulated Low Earth Orbit (LEO) conditions. NASA is now moving from LEO towards exploration of locations with environments approaching those of deep space. Therefore, Chamber A has undergone major modifications to enable it to simulate these deeper space environments. Environmental requirements were driven, and modifications were funded by the James Webb Space Telescope program, and this telescope, which will orbit Solar/Earth L2, will be the first test article to benefit from the chamber s new capabilities. To accommodate JWST, the Chamber A high vacuum system has been modernized, additional LN2 shrouds have been installed, the liquid nitrogen system has been modified to minimize dependency on electrical power and increase its reliability, a new helium shroud/refrigeration system has been installed to create a colder more stable and uniform heat sink, and the controls have been updated to increase the level of automation and improve operator interfaces. Testing of these major modifications was conducted in August of 2012 and this initial test was very successful, with all major systems exceeding their performance requirements. This paper will outline the changes in overall environmental requirements, discuss the technical design data that was used in the decisions leading to the extensive modifications, and describe the new capabilities of the chamber.

Creating the Deep Space Environment for Testing the James Webb Space Telescope at the Johnson Space Center's Chamber A

NASA Technical Reports Server (NTRS)

Homan, Jonathan L.; Cerimele, Mary P.; Montz, Michael E.

2012-01-01

Chamber A is the largest thermal vacuum chamber at the Johnson Space Center and is one of the largest space environment chambers in the world. The chamber is 19.8 m (65 ft) in diameter and 36.6 m (120 ft) tall and is equipped with cryogenic liquid nitrogen panels (shrouds) and gaseous helium shrouds to create a simulated space environment. It was originally designed and built in the mid 1960's to test the Apollo Command and Service Module and several manned tests were conducted on that spacecraft, contributing to the success of the program. The chamber has been used since that time to test spacecraft active thermal control systems, Shuttle DTO, DOD, and ESA hardware in simulated Low Earth Orbit (LEO) conditions. NASA is now moving from LEO towards exploration of locations with environments approaching those of deep space. Therefore, Chamber A has undergone major modifications to enable it to simulate these deeper space environments. Environmental requirements were driven, and the modifications were funded, by the James Webb Space Telescope program, and this telescope which will orbit Solar/Earth L2, will be the first test article to benefit from the chamber s new capabilities. To accommodate JWST, the Chamber A high vacuum system has been modernized, additional LN2 shrouds have been installed, the liquid nitrogen system has been modified to remove dependency on electrical power and increase its reliability, a new helium shroud/refrigeration system has been installed to create a colder more stable and uniform heat sink and, the controls have been updated to increase the level of automation and improve operator interfaces. Testing of these major modifications was conducted in August 2012 and this initial test was very successful, with all major systems exceeding their performance requirements. This paper will outline the changes in the overall environmental requirements, discuss the technical design data that was used in the decisions leading to the extensive modifications, and describe the new capabilities of the chamber.

Influence of ion chamber response on in-air profile measurements in megavoltage photon beams.

PubMed

Tonkopi, E; McEwen, M R; Walters, B R B; Kawrakow, I

2005-09-01

This article presents an investigation of the influence of the ion chamber response, including buildup caps, on the measurement of in-air off-axis ratio (OAR) profiles in megavoltage photon beams using Monte Carlo simulations with the EGSnrc system. Two new techniques for the calculation of OAR profiles are presented. Results of the Monte Carlo simulations are compared to measurements performed in 6, 10 and 25 MV photon beams produced by an Elekta Precise linac and shown to agree within the experimental and simulation uncertainties. Comparisons with calculated in-air kerma profiles demonstrate that using a plastic mini phantom gives more accurate air-kerma measurements than using high-Z material buildup caps and that the variation of chamber response with distance from the central axis must be taken into account.

Geant4 simulation of ion chambers response to 60Co spectrum of LNMRI/IRD Shepherd 81-14D Radiator

NASA Astrophysics Data System (ADS)

Queiroz Filho, P. P.; Da Silva, C. N. M.

2018-03-01

The National Ionizing Radiation Metrology Laboratory of the Radioprotection and Dosimetry Institute (LNMRI / IRD) has recently acquired a Shepherd 81-14D Radiator. In this work we simulate, using Geant4, the behavior with the inverse square law radiation for 3 models of PTW spherical chambers used in radioprotection, a relevant information to planning the measurements. We did the corrections for the attenuation and scattering in the air for each distance, where we used the 60Co spectrum simulated previously.

Chemical and physical transformations of organic aerosol from the photo-oxidation of open biomass burning emissions in an environmental chamber

Treesearch

C. J. Hennigan; M. A. Miracolo; G. J. Engelhart; A. A. May; A. A. Presto; T. Lee; A. P. Sullivan; G. R. McMeeking; H. Coe; C. E. Wold; W.-M. Hao; J. B. Gilman; W. C. Kuster; J. de Gouw; B. A. Schichtel; J. L. Collett; S. M. Kreidenweis; A. L. Robinson

2011-01-01

Smog chamber experiments were conducted to investigate the chemical and physical transformations of organic aerosol (OA) during photo-oxidation of open biomass burning emissions. The experiments were carried out at the US Forest Service Fire Science Laboratory as part of the third Fire Lab at Missoula Experiment (FLAME III). We investigated emissions from 12 different...

Some Consequences of Some Assumptions with Respect to the Physical Decal of a Chamber Aerosol Cloud

DTIC Science & Technology

1963-12-01

RESPECT TO THE PHYSICAL DECAY OF A CHAMBER AEROSOL CLOUD* Theodore W. Horner* Project Statistician, Booz-Allen Applied Research, Inc. 4815 Rugby Avenue...recovery percentage at time t is 0 Nf(r) h(r, t) ars (r, t) dr (1) B-(t) B1 r, t) S0 , where B’r, t) is the biological recovery percentage for

16. NBS TOPSIDE CONTROL ROOM, THE NBS HYPERBARIC CHAMBER IS ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

16. NBS TOPSIDE CONTROL ROOM, THE NBS HYPERBARIC CHAMBER IS VERY CLOSE TO THE WATER'S EDGE AND HERE FOR DIVER EMERGENCY SUPPORT. A MEDICAL STAFF IS LOCATED ON THE MARSHALL SPACE FLIGHT CENTER (MSFC) AND SUPPORTS THE NBS PERSONNEL WHEN HYPERBARIC CHAMBER OPERATION IS NECESSARY. - Marshall Space Flight Center, Neutral Buoyancy Simulator Facility, Rideout Road, Huntsville, Madison County, AL

Shock-Induced Heating In A Rocket Engine

NASA Technical Reports Server (NTRS)

Lagnado, Ronald R.; Raiszadeh, Farhad

1989-01-01

Misalignments give rise to hotspots on walls. Report discusses numerical simulation of flow in and near small, ringlike cavity in wall of Space Shuttle main engine at junction of main combustion chamber and nozzle. Purpose to study effects of misalignments between combustion chamber and nozzle on transfer of heat into surfaces chamber, cavity, and nozzle. Depending on specific misalignment flow encounters forward-or backward-facing step leaving chamber and entering nozzle. Results in serious losses of performance and excessive heating of walls.

Study of low speed flow cytometry for diffraction imaging with different chamber and nozzle designs.

PubMed

Sa, Yu; Feng, Yuanming; Jacobs, Kenneth M; Yang, Jun; Pan, Ran; Gkigkitzis, Ioannis; Lu, Jun Q; Hu, Xin-Hua

2013-11-01

Achieving effective hydrodynamic focusing and flow stability at low speed presents a challenging design task in flow cytometry for studying phenomena such as cell adhesion and diffraction imaging of cells with low-cost cameras. We have developed different designs of flow chamber and sheath nozzle to accomplish the above goal. A 3D computational model of the chambers has been established to simulate the fluid dynamics in different chamber designs and measurements have been performed to determine the velocity and size distributions of the core fluid from the nozzle. Comparison of the simulation data with experimental results shows good agreement. With the computational model significant insights were gained for optimization of the chamber design and improvement of the cell positioning accuracy for study of slow moving cells. The benefit of low flow speed has been demonstrated also by reduced blurring in the diffraction images of single cells. Based on these results, we concluded that the new designs of chamber and sheath nozzle produce stable hydrodynamic focusing of the core fluid at low speed and allow detailed study of cellular morphology under various rheological conditions using the diffraction imaging method. © 2013 International Society for Advancement of Cytometry.

Performance of nanocomposites for preservation of artistic stones

NASA Astrophysics Data System (ADS)

Giancristofaro, Cristina; D'Amato, Rosaria; Caneve, Luisa; Pilloni, Luciano; Rinaldi, Antonio; Persia, Franca

2014-06-01

In this work, the effectiveness of nanocomposite surface treatments as protective systems for artistic stones was evaluated. Pyrolitic silica and titania nanoparticles were dispersed in a commercial silicon-based polymer and applied on marble and travertine samples. Artificial aging processes, both in climatic chamber and in solar box, were carried out to simulate real degradation processes in terms of photo-thermal effects and physical-chemical damage. The performances of the nanocomposites used as consolidant were evaluated comparatively by means of diverse diagnostic techniques, namely: scanning electron microscopy (SEM), laser induced fluorescence (LIF), ultrasonic technique, colorimetry, total immersion water absorption and contact angle. The results show that some properties of conservation materials can be improved by the presences of nanoparticles because they induce substantial changes of surface morphology of the coating layer and counter the physical damage observed during artificial weathering.

Deployment and testing of a second prototype expandable surgical chamber in microgravity

NASA Technical Reports Server (NTRS)

Markham, Sanford M.; Rock, John A.

1991-01-01

During microgravity exposure, two separate expandable surgical chambers were tested. Both chambers had been modified to fit the microgravity work station without extending over the sides of the table. Both chambers were attached to a portable laminar flow generator which served two purposes: to keep the chambers expanded during use; and to provide an operative area environment free of contamination. During the tests, the chambers were placed on various parts of a total body moulage to simulate management of several types of trauma. The tests consisted of cleansing contusions, debridement of burns, and suturing of lacerations. Also, indigo carmine dye was deliberately injected into the chamber during the tests to determine the ease of cleansing the chamber walls after contamination by escaping fluids. Upon completion of the tests, the expandable surgical chambers were deflated, folded, and placed in a flattened state back into their original containers for storage and later disposal. Results are briefly discussed.

Investigation of particle and vapor wall-loss effects on controlled wood-smoke smog-chamber experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bian, Q.; May, A. A.; Kreidenweis, Sonia M.

Here, smog chambers are extensively used to study processes that drive gas and particle evolution in the atmosphere. A limitation of these experiments is that particles and gas-phase species may be lost to chamber walls on shorter timescales than the timescales of the atmospheric processes being studied in the chamber experiments. These particle and vapor wall losses have been investigated in recent studies of secondary organic aerosol (SOA) formation, but they have not been systematically investigated in experiments of primary emissions from combustion. The semi-volatile nature of combustion emissions (e.g. from wood smoke) may complicate the behavior of particle andmore » vapor wall deposition in the chamber over the course of the experiments due to the competition between gas/particle and gas/wall partitioning. Losses of vapors to the walls may impact particle evaporation in these experiments, and potential precursors for SOA formation from combustion may be lost to the walls, causing underestimations of aerosol yields. Here, we conduct simulations to determine how particle and gas-phase wall losses contributed to the observed evolution of the aerosol during experiments in the third Fire Lab At Missoula Experiment (FLAME III). We use the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithm coupled with the organic volatility basis set (VBS) and wall-loss formulations to examine the predicted extent of particle and vapor wall losses. We limit the scope of our study to the dark periods in the chamber before photo-oxidation to simplify the aerosol system for this initial study. Our model simulations suggest that over one-third of the initial particle-phase organic mass (41 %) was lost during the experiments, and over half of this particle-organic mass loss was from direct particle wall loss (65 % of the loss) with the remainder from evaporation of the particles driven by vapor losses to the walls (35 % of the loss). We perform a series of sensitivity tests to understand uncertainties in our simulations. Uncertainty in the initial wood-smoke volatility distribution contributes 18 % uncertainty to the final particle-organic mass remaining in the chamber (relative to base-assumption simulation). We show that the total mass loss may depend on the effective saturation concentration of vapor with respect to the walls as these values currently vary widely in the literature. The details of smoke dilution during the filling of smog chambers may influence the mass loss to the walls, and a dilution of ~ 25:1 during the experiments increased particle-organic mass loss by 33 % compared to a simulation where we assume the particles and vapors are initially in equilibrium in the chamber. Finally, we discuss how our findings may influence interpretations of emission factors and SOA production in wood-smoke smog-chamber experiments.« less

Study on optimization of multiionization-chamber system for BNCT.

PubMed

Fujii, T; Tanaka, H; Maruhashi, A; Ono, K; Sakurai, Y

2011-12-01

In order to monitor stability of doses from the four components such as thermal, epi-thermal, fast neutron and gamma-ray during BNCT irradiation, we are developing a multiionization-chamber system. This system is consisted of four kinds of ionization chamber, which have specific sensitivity for each component, respectively. Since a suitable structure for each chamber depends on the energy spectrum of the irradiation field, the optimization study of the chamber structures for the epi-thermal neutron beam of cyclotron-based epi-thermal neutron source (C-BENS) was performed by using a Monte Carlo simulation code "PHITS" and suitable chamber-structures were determined. Copyright © 2011 Elsevier Ltd. All rights reserved.

Simulated annealing algorithm for solving chambering student-case assignment problem

NASA Astrophysics Data System (ADS)

Ghazali, Saadiah; Abdul-Rahman, Syariza

2015-12-01

The problem related to project assignment problem is one of popular practical problem that appear nowadays. The challenge of solving the problem raise whenever the complexity related to preferences, the existence of real-world constraints and problem size increased. This study focuses on solving a chambering student-case assignment problem by using a simulated annealing algorithm where this problem is classified under project assignment problem. The project assignment problem is considered as hard combinatorial optimization problem and solving it using a metaheuristic approach is an advantage because it could return a good solution in a reasonable time. The problem of assigning chambering students to cases has never been addressed in the literature before. For the proposed problem, it is essential for law graduates to peruse in chambers before they are qualified to become legal counselor. Thus, assigning the chambering students to cases is a critically needed especially when involving many preferences. Hence, this study presents a preliminary study of the proposed project assignment problem. The objective of the study is to minimize the total completion time for all students in solving the given cases. This study employed a minimum cost greedy heuristic in order to construct a feasible initial solution. The search then is preceded with a simulated annealing algorithm for further improvement of solution quality. The analysis of the obtained result has shown that the proposed simulated annealing algorithm has greatly improved the solution constructed by the minimum cost greedy heuristic. Hence, this research has demonstrated the advantages of solving project assignment problem by using metaheuristic techniques.

A large high vacuum, high pumping speed space simulation chamber for electric propulsion

NASA Technical Reports Server (NTRS)

Grisnik, Stanley P.; Parkes, James E.

1994-01-01

Testing high power electric propulsion devices poses unique requirements on space simulation facilities. Very high pumping speeds are required to maintain high vacuum levels while handling large volumes of exhaust products. These pumping speeds are significantly higher than those available in most existing vacuum facilities. There is also a requirement for relatively large vacuum chamber dimensions to minimize facility wall/thruster plume interactions and to accommodate far field plume diagnostic measurements. A 4.57 m (15 ft) diameter by 19.2 m (63 ft) long vacuum chamber at NASA Lewis Research Center is described. The chamber utilizes oil diffusion pumps in combination with cryopanels to achieve high vacuum pumping speeds at high vacuum levels. The facility is computer controlled for all phases of operation from start-up, through testing, to shutdown. The computer control system increases the utilization of the facility and reduces the manpower requirements needed for facility operations.

Shielding Effectiveness in a Two-Dimensional Reverberation Chamber Using Finite-Element Techniques

NASA Technical Reports Server (NTRS)

Bunting, Charles F.

2006-01-01

Reverberation chambers are attaining an increased importance in determination of electromagnetic susceptibility of avionics equipment. Given the nature of the variable boundary condition, the ability of a given source to couple energy into certain modes and the passband characteristic due the chamber Q, the fields are typically characterized by statistical means. The emphasis of this work is to apply finite-element techniques at cutoff to the analysis of a two-dimensional structure to examine the notion of shielding-effectiveness issues in a reverberating environment. Simulated mechanical stirring will be used to obtain the appropriate statistical field distribution. The shielding effectiveness (SE) in a simulated reverberating environment is compared to measurements in a reverberation chamber. A log-normal distribution for the SE is observed with implications for system designers. The work is intended to provide further refinement in the consideration of SE in a complex electromagnetic environment.

Nuclear physics experiments with low cost instrumentation

NASA Astrophysics Data System (ADS)

Oliveira Bastos, Rodrigo; Adelar Boff, Cleber; Melquiades, Fábio Luiz

2016-11-01

One of the difficulties in modern physics teaching is the limited availability of experimental activities. This is particularly true for teaching nuclear physics in high school or college. The activities suggested in the literature generally symbolise real phenomenon, using simulations. It happens because the experimental practices mostly include some kind of expensive radiation detector and an ionising radiation source that requires special care for handling and storage, being subject to a highly bureaucratic regulation in some countries. This study overcomes these difficulties and proposes three nuclear physics experiments using a low-cost ion chamber which construction is explained: the measurement of 222Rn progeny collected from the indoor air; the measurement of the range of alpha particles emitted by the 232Th progeny, present in lantern mantles and in thoriated welding rods, and by the air filter containing 222Rn progeny; and the measurement of 220Rn half-life collected from the emanation of the lantern mantles. This paper presents the experimental procedures and the expected results, indicating that the experiments may provide support for nuclear physics classes. These practices may outreach wide access to either college or high-school didactic laboratories, and the apparatus has the potential for the development of new teaching activities for nuclear physics.

Engineering verification of the biomass production chamber

NASA Technical Reports Server (NTRS)

Prince, R. P.; Knott, W. M., III; Sager, J. C.; Jones, J. D.

1992-01-01

The requirements for life support systems, both biological and physical-chemical, for long-term human attended space missions are under serious study throughout NASA. The KSC 'breadboard' project has focused on biomass production using higher plants for atmospheric regeneration and food production in a special biomass production chamber. This chamber is designed to provide information on food crop growth rate, contaminants in the chamber that alter plant growth requirements for atmospheric regeneration, carbon dioxide consumption, oxygen production, and water utilization. The shape and size, mass, and energy requirements in relation to the overall integrity of the biomass production chamber are under constant study.

The Other Shoe: An Early Operant Conditioning Chamber for Pigeons.

PubMed

Sakagami, Takayuki; Lattal, Kennon A

2016-05-01

We describe an early operant conditioning chamber fabricated by Harvard University instrument maker Ralph Gerbrands and shipped to Japan in 1952 in response to a request of Professor B. F. Skinner by Japanese psychologists. It is a rare example, perhaps the earliest still physically existing, of such a chamber for use with pigeons. Although the overall structure and many of the components are similar to contemporary pigeon chambers, several differences are noted and contrasted to evolutionary changes in this most important laboratory tool in the experimental analysis of behavior. The chamber also is testimony to the early internationalization of behavior analysis.

Recent Results on Microstrip Gas Chambers at Purdue

NASA Astrophysics Data System (ADS)

Menon, Naresh; Shipsey, Ian

1997-04-01

The performance of Micrstrip Gas Chambers fabricated on polymide, with a segmented backplane providing two-dimensional position information, will be presented. MSGC Research at Purdue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sadoulet, B.

The use of drift chambers in the field of high energy physics is reviewed including existing apparatus, plans and dreams. Comments are made especially on low cost large area drift chambers, use of pulse height information and high spatial resolution applications. (auth)

Response of the first wetted wall of an IFE reactor chamber to the energy release from a direct-drive DT capsule

DOE Office of Scientific and Technical Information (OSTI.GOV)

Medin, Stanislav A.; Basko, Mikhail M.; Orlov, Yurii N.

2012-07-11

Radiation hydrodynamics 1D simulations were performed with two concurrent codes, DEIRA and RAMPHY. The DEIRA code was used for DT capsule implosion and burn, and the RAMPHY code was used for computation of X-ray and fast ions deposition in the first wall liquid film of the reactor chamber. The simulations were run for 740 MJ direct drive DT capsule and Pb thin liquid wall reactor chamber of 10 m diameter. Temporal profiles for DT capsule leaking power of X-rays, neutrons and fast {sup 4}He ions were obtained and spatial profiles of the liquid film flow parameter were computed and analyzed.

From diffusion pumps to cryopumps: The conversion of GSFC's space environment simulator

NASA Technical Reports Server (NTRS)

Cary, Ron

1992-01-01

The SES (Space Environmental Simulator), largest of the Thermal Vacuum Facilities at The Goddard Space Flight Center, recently was converted from an oil diffusion pumped chamber to a Cryopumped chamber. This modification was driven by requirements of flight projects. The basic requirement was to retain or enhance the operational parameters of the chamber such as pumping speed, ultimate vacuum, pump down time, and thermal system performance. To accomplish this task, seventeen diffusion pumps were removed and replaced with eight 1.2 meter (48 inch) diameter cryopumps and one 0.5 meter (20 inch) turbomolecular pump. The conversion was accomplished with a combination of subcontracting and in-house efforts to maximize the efficiency of implementation.

Effect of trichlorofluoromethane and molecular chlorine on ozone formation by simulated solar radiation

NASA Technical Reports Server (NTRS)

Bittker, D. A.; Wong, E. L.

1977-01-01

Mixtures of air with either Cl2 or CFCl3 were photolyzed in a reaction chamber by simulated solar radiation. Ozone formation was temporarily inhibited by Cl2 and permanently inhibited by CFCl3. A chemical mechanism including gas phase and wall reactions is proposed to explain these results. The CFCl3 is assumed to be adsorbed on the chamber walls and to poison the sites for Cl destruction.

Dosimetry in MARS spectral CT: TOPAS Monte Carlo simulations and ion chamber measurements.

PubMed

Lu, Gray; Marsh, Steven; Damet, Jerome; Carbonez, Pierre; Laban, John; Bateman, Christopher; Butler, Anthony; Butler, Phil

2017-06-01

Spectral computed tomography (CT) is an up and coming imaging modality which shows great promise in revealing unique diagnostic information. Because this imaging modality is based on X-ray CT, it is of utmost importance to study the radiation dose aspects of its use. This study reports on the implementation and evaluation of a Monte Carlo simulation tool using TOPAS for estimating dose in a pre-clinical spectral CT scanner known as the MARS scanner. Simulated estimates were compared with measurements from an ionization chamber. For a typical MARS scan, TOPAS estimated for a 30 mm diameter cylindrical phantom a CT dose index (CTDI) of 29.7 mGy; CTDI was measured by ion chamber to within 3% of TOPAS estimates. Although further development is required, our investigation of TOPAS for estimating MARS scan dosimetry has shown its potential for further study of spectral scanning protocols and dose to scanned objects.

Multi-injector modeling of transverse combustion instability experiments

NASA Astrophysics Data System (ADS)

Shipley, Kevin J.

Concurrent simulations and experiments are used to study combustion instabilities in a multiple injector element combustion chamber. The experiments employ a linear array of seven coaxial injector elements positioned atop a rectangular chamber. Different levels of instability are driven in the combustor by varying the operating and geometry parameters of the outer driving injector elements located near the chamber end-walls. The objectives of the study are to apply a reduced three-injector model to generate a computational test bed for the evaluation of injector response to transverse instability, to apply a full seven-injector model to investigate the inter-element coupling between injectors in response to transverse instability, and to further develop this integrated approach as a key element in a predictive methodology that relies heavily on subscale test and simulation. To measure the effects of the transverse wave on a central study injector element two opposing windows are placed in the chamber to allow optical access. The chamber is extensively instrumented with high-frequency pressure transducers. High-fidelity computational fluid dynamics simulations are used to model the experiment. Specifically three-dimensional, detached eddy simulations (DES) are used. Two computational approaches are investigated. The first approach models the combustor with three center injectors and forces transverse waves in the chamber with a wall velocity function at the chamber side walls. Different levels of pressure oscillation amplitudes are possible by varying the amplitude of the forcing function. The purpose of this method is to focus on the combustion response of the study element. In the second approach, all seven injectors are modeled and self-excited combustion instability is achieved. This realistic model of the chamber allows the study of inter-element flow dynamics, e.g., how the resonant motions in the injector tubes are coupled through the transverse pressure waves in the chamber. The computational results are analyzed and compared with experiment results in the time, frequency and modal domains. Results from the three injector model show how applying different velocity forcing amplitudes change the amplitude and spatial location of heat release from the center injector. The instability amplitudes in the simulation are able to be tuned to experiments and produce similar modal combustion responses of the center injector. The reaction model applied was found to play an important role in the spatial and temporal heat release response. Only when the model was calibrated to ignition delay measurements did the heat release response reflect measurements in the experiment. While insightful the simulations are not truly predictive because the driving frequency and forcing function amplitude are input into the simulation. However, the use of this approach as a tool to investigate combustion response is demonstrated. Results from the seven injector simulations provide an insightful look at the mechanisms driving the instability in the combustor. The instability was studied over a range of pressure fluctuations, up to 70% of mean chamber pressure produced in the self-exited simulation. At low amplitudes the transverse instability was found to be supported by both flame impingement with the side wall as well as vortex shedding at the primary acoustic frequency. As instability level grew the primary supporting mechanism shifted to just vortex impingement on the side walls and the greatest growth was seen as additional vortices began impinging between injector elements at the primary acoustic frequency. This research reveals the advantages and limitations of applying these two modeling techniques to simulate multiple injector experiments. The advantage of the three injector model is a simplified geometry which results in faster model development and the ability to more rapidly study the injector response under varying velocity amplitudes. The possibly faster run time is offset though by the need to run multiple cases to calibrate the model to the experiment. The model is also limited to studying the central injector effect and lacks heat release sources from the outer injectors and additional vortex interactions as shown in the seven injector simulation. The advantage of the seven injector model is that the whole domain can be explored to provide a better understanding about influential processes but does require longer development and run time due to the extensive gridding requirement. Both simulations have proven useful in exploring transverse combustion instability and show the need to further develop subscale experiments and companions simulations in developing a full-scale combustion instability prediction capability.

TH-CD-BRA-07: MRI-Linac Dosimetry: Parameters That Change in a Magnetic Field

DOE Office of Scientific and Technical Information (OSTI.GOV)

O’Brien, D. J.; Sawakuchi, G. O.

Purpose: In MRI-linac integrated systems, the presence of the magnetic (B-)field has a large impact of the dose-distribution and the dose-responses of detectors; yet established protocols and previous experience may lead to assumptions about the commissioning process that are no longer valid. This study quantifies parameters that change when performing dosimetry with an MRI-linac including beam quality specifiers and the effective-point-of-measurement (EPOM) of ionization chambers. Methods: We used the Geant4 Monte Carlo code for this work with physics parameters that pass the Fano cavity test to within 0.1% for the simulated conditions with and without a 1.5 T B-field. Amore » point source model with the energy distribution of an MRI-linac beam was used with and without the B-field to calculate the beam quality specifiers %dd(10)× and TPR{sup 20}{sub 10}, the variation of chamber response with orientation and the how the B-field affects the EPOM of ionization chambers by comparing depth-dose curves calculated in water to those generated by a model PTW30013 Farmer chamber. Results: The %dd(10)× changes by over 2% in the presence of the B-field while the TPR{sup 20}{sub 10} is unaffected. Ionization chamber dose-response is known to depend on the orientation w.r.t. the B-field, but two alternative perpendicular orientations (anti-parallel to each other) also differ in dose-response by over 1%. The B-field shifts the EPOM downstream (closer to the chamber center) but it is also shifted laterally by 0.27 times the chamber’s cavity radius. Conclusion: The EPOM is affected by the B-field and it even shifts laterally. The relationship between %dd(10)× and the Spencer-Attix stopping powers is also changed. Care must be taken when using chambers perpendicular to the field as the dose-response changes depending on which perpendicular orientation is used. All of these effects must be considered when performing dosimetry in B-fields and should be accounted for in future dosimetry protocols. This project was partially funded by Elekta Ltd.« less

Progress Towards a Thermo-Mechanical Magma Chamber Forward Model for Eruption Cycles, Applied to the Columbia River Flood Basalts

NASA Astrophysics Data System (ADS)

Karlstrom, L.; Ozimek, C.

2016-12-01

Magma chamber modeling has advanced to the stage where it is now possible to develop self-consistent, predictive models that consider mechanical, thermal, and compositional magma time evolution through multiple eruptive cycles. We have developed such a thermo-mechanical-chemical model for a laterally extensive sill-like chamber beneath free surface, to understand physical controls on eruptive products through time at long-lived magmatic centers. This model predicts the relative importance of recharge, eruption, assimilation and fractional crystallization (REAFC, Lee et al., 2013) on evolving chemical composition as a function of mechanical magma chamber stability regimes. We solve for the time evolution of chamber pressure, temperature, gas volume fraction, volume, elemental concentration in the melt and crustal temperature field that accounts for moving boundary conditions associated with chamber inflation (and the possibility of coupled chambers at different depths). The density, volume fractions of melt and crystals, crustal assimilation and the changing viscosity and crustal properties of the wall rock are also tracked, along with joint solubility of water and CO2. The eventual goal is to develop an efficient forward model to invert for eruptive records at long-lived eruptive centers, where multiple types of data for eruptions are available. As a first step, we apply this model to a new compilation of eruptive data from the Columbia River Flood Basalts (CRFB), which erupted 210,000 km3 from feeder dikes in Washington, Oregon and Idaho between 16.9-6Ma. Data include volumes, timing and geochemical composition of eruptive units, along with seismic surveys and clinopyroxene geobarometry that constrain depth of storage through time. We are in the process of performing a suite of simulations varying model input parameters such as mantle melt rate, emplacement depth, wall rock compositions and rheology, and volatile content to explain volume, eruption timescales, and chemical trace aspects of CRFB eruptions. We are particularly interested in whether the large volume eruptions of the main phase Grande Ronde basalts were made possible due to the development of shallow crustal storage.

An investigation of air inlet velocity in simulating the dispersion of indoor contaminants via computational fluid dynamics.

PubMed

Lee, Eungyoung; Feigley, Charles E; Khan, Jamil

2002-11-01

Computational fluid dynamics (CFD) is potentially a valuable tool for simulating the dispersion of air contaminants in workrooms. However, CFD-estimated airflow and contaminant concentration patterns have not always shown good agreement with experimental results. Thus, understanding the factors affecting the accuracy of such simulations is critical for their successful application in occupational hygiene. The purposes of this study were to validate CFD approaches for simulating the dispersion of gases and vapors in an enclosed space at two air flow rates and to demonstrate the impact of one important determinant of simulation accuracy. The concentration of a tracer gas, isobutylene, was measured at 117 points in a rectangular chamber [1 (L) x 0.3 (H) x 0.7 m (W)] using a photoionization analyzer. Chamber air flow rates were scaled using geometric and kinematic similarity criteria to represent a full-sized room at two Reynolds numbers (Re = 5 x 10(2) and 5 x 10(3)). Also, CFD simulations were conducted to estimate tracer gas concentrations throughout the chamber. The simulation results for two treatments of air inlet velocity (profiled inlet velocity measured in traverses across the air inlet and the assumption that air velocity is uniform across the inlet) were compared with experimental observations. The CFD-simulated 3-dimensional distribution of tracer gas concentration using the profiled inlet velocity showed better agreement qualitatively and quantitatively with measured chamber concentration, while the concentration estimated using the uniform inlet velocity showed poor agreement for both comparisons. For estimating room air contaminant concentrations when inlet velocities can be determined, this study suggests that using the inlet velocity distribution to define inlet boundary conditions for CFD simulations can provide more reliable estimates. When the inlet velocity distribution is not known, for instance for prospective design of dilution ventilation systems, the trials of several velocity profiles with different source, air inlet and air outlet locations may be useful for determining the most efficient workroom layout.

Wireless transmission of biosignals for hyperbaric chamber applications

PubMed Central

Perez-Vidal, Carlos; Gracia, Luis; Carmona, Cristian; Alorda, Bartomeu; Salinas, Antonio

2017-01-01

This paper presents a wireless system to send biosignals outside a hyperbaric chamber avoiding wires going through the chamber walls. Hyperbaric chambers are becoming more and more common due to new indications of hyperbaric oxygen treatments. Metallic walls physically isolate patients inside the chamber, where getting a patient’s vital signs turns into a painstaking task. The paper proposes using a ZigBee-based network to wirelessly transmit the patient's biosignals to the outside of the chamber. In particular, a wearable battery supported device has been designed, implemented and tested. Although the implementation has been conducted to transmit the electrocardiography signal, the device can be easily adapted to consider other biosignals. PMID:28296900

Modelling the effect of diffuse light on canopy photosynthesis in controlled environments

NASA Technical Reports Server (NTRS)

Cavazzoni, James; Volk, Tyler; Tubiello, Francesco; Monje, Oscar; Janes, H. W. (Principal Investigator)

2002-01-01

A layered canopy model was used to analyze the effects of diffuse light on canopy gross photosynthesis in controlled environment plant growth chambers, where, in contrast to the field, highly diffuse light can occur at high irradiance. The model suggests that high diffuse light fractions (approximately 0.7) and irradiance (1400 micromoles m-2 s-1) may enhance crop life-cycle canopy gross photosynthesis for hydroponic wheat by about 20% compared to direct light at the same irradiance. Our simulations suggest that high accuracy is not needed in specifying diffuse light fractions in chambers between approximately 0.7 and 1, because simulated photosynthesis for closed canopies plateau in this range. We also examined the effect of leaf angle distribution on canopy photosynthesis under growth chamber conditions, as these distributions determine canopy extinction coefficients for direct and diffuse light. We show that the spherical leaf angle distribution is not suitable for modeling photosynthesis of planophile canopies (e.g., soybean and peanut) in growth chambers. Also, the absorption of the light reflected from the surface below the canopy should generally be included in model simulations, as the corresponding albedo values in the photosynthetically active range may be quite high in growth chambers (e.g., approximately 0.5). In addition to the modeling implications, our results suggest that diffuse light conditions should be considered when drawing conclusions from experiments in controlled environments.

Technical Note: Intercomparison of formaldehyde measurements at the atmosphere simulation chamber SAPHIR

NASA Astrophysics Data System (ADS)

Wisthaler, A.; Apel, E. C.; Bossmeyer, J.; Hansel, A.; Junkermann, W.; Koppmann, R.; Meier, R.; Müller, K.; Solomon, S. J.; Steinbrecher, R.; Tillmann, R.; Brauers, T.

2008-04-01

The atmosphere simulation chamber SAPHIR at the Research Centre Jülich was used to test the suitability of state-of-the-art analytical instruments for the measurement of gas-phase formaldehyde (HCHO) in air. Five analyzers based on four different sensing principles were deployed: a differential optical absorption spectrometer (DOAS), cartridges for 2,4-dinitrophenylhydrazine (DNPH) derivatization followed by off-line high pressure liquid chromatography (HPLC) analysis, two different types of commercially available wet chemical sensors based on Hantzsch fluorimetry, and a proton-transfer-reaction mass spectrometer (PTR-MS). A new optimized mode of operation was used for the PTR-MS instrument which significantly enhanced its performance for online HCHO detection at low absolute humidities. The instruments were challenged with typical ambient levels of HCHO ranging from zero to several ppb. Synthetic air of high purity and particulate-filtered ambient air were used as sample matrices in the atmosphere simulation chamber onto which HCHO was spiked under varying levels of humidity and ozone. Measurements were compared to mixing ratios calculated from the chamber volume and the known amount of HCHO injected into the chamber; measurements were also compared between the different instruments. The formal and blind intercomparison exercise was conducted under the control of an independent referee. A number of analytical problems associated with the experimental set-up and with individual instruments were identified, the overall agreement between the methods was fair.

Application test of a Detection Method for the Enclosed Turbine Runner Chamber

NASA Astrophysics Data System (ADS)

Liu, Yunlong; Shen, Dingjie; Xie, Yi; Yang, Xiangwei; Long, Yi; Li, Wenbo

2017-06-01

At present, for the existing problems of the testing methods for the key hidden metal components of the turbine runner chamber, such as the poor reliability, the inaccurate locating and the larger detection blind spots of the detection device, under the downtime without opening the cover of the hydropower turbine runner chamber, an automatic detection method based on real-time image acquisition and simulation comparison techniques was proposed. By using the permanent magnet wheel, the magnetic crawler which carry the real-time image acquisition device, could complete the crawling work on the inner surface of the enclosed chamber. Then the image acquisition device completed the real-time collection of the scene image of the enclosed chamber. According to the obtained location by using the positioning auxiliary device, the position of the real-time detection image in a virtual 3D model was calibrated. Through comparing of the real-time detection images and the computer simulation images, the defects or foreign matter fall into could be accurately positioning, so as to repair and clean up conveniently.

Note: The design of thin gap chamber simulation signal source based on field programmable gate array.

PubMed

Hu, Kun; Lu, Houbing; Wang, Xu; Li, Feng; Liang, Futian; Jin, Ge

2015-01-01

The Thin Gap Chamber (TGC) is an important part of ATLAS detector and LHC accelerator. Targeting the feature of the output signal of TGC detector, we have designed a simulation signal source. The core of the design is based on field programmable gate array, randomly outputting 256-channel simulation signals. The signal is generated by true random number generator. The source of randomness originates from the timing jitter in ring oscillators. The experimental results show that the random number is uniform in histogram, and the whole system has high reliability.

Note: The design of thin gap chamber simulation signal source based on field programmable gate array

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Kun; Wang, Xu; Li, Feng

The Thin Gap Chamber (TGC) is an important part of ATLAS detector and LHC accelerator. Targeting the feature of the output signal of TGC detector, we have designed a simulation signal source. The core of the design is based on field programmable gate array, randomly outputting 256-channel simulation signals. The signal is generated by true random number generator. The source of randomness originates from the timing jitter in ring oscillators. The experimental results show that the random number is uniform in histogram, and the whole system has high reliability.

Performance of a transpiration-regenerative cooled rocket thrust chamber

NASA Technical Reports Server (NTRS)

Valler, H. W.

1979-01-01

The analysis, design, fabrication, and testing of a liquid rocket engine thrust chamber which is gas transpiration cooled in the high heat flux convergent portion of the chamber and water jacket cooled (simulated regenerative) in the barrel and divergent sections of the chamber are described. The engine burns LOX-hydrogen propellants at a chamber pressure of 600 psia. Various transpiration coolant flow rates were tested with resultant local hot gas wall temperatures in the 800 F to 1400 F range. The feasibility of transpiration cooling with hydrogen and helium, and the use of photo-etched copper platelets for heat transfer and coolant metering was successfully demonstrated.

Intercomparison of standards of absorbed dose between the USSR and the UK

NASA Astrophysics Data System (ADS)

Berlyand, V. A.; Bregadze, J. I.; Burns, J. E.; Dusautoy, A. R.; Sharpe, P. H. G.

1991-05-01

A comparison of national standards of absorbed dose was carried out between the All-Union Research Institute for Physical Technical and Radiotechnical Measurements (VNIIFTRI), USSR, and the National Physical Laboratotry (NPL), UK (United Kingdom). Absorbed dose to water for cobalt 60 gamma radiation was compared by means of Fricke dosimeters and ionization chambers in 1985 and 1986. The primary standards used to derive absorbed dose to water were cavity ionization chambers at NPL and a graphite calorimeter at VNIIFTRI. The ratio of absorbed dose to water, NPL to VNIIFTRI, using Fricke dosimeters was 1.008; using ionization chambers it was 1.007. This agreement is within the estimated uncertainties of the standards and measurement methods.

Atmospheric cloud physics laboratory project study

NASA Technical Reports Server (NTRS)

Schultz, W. E.; Stephen, L. A.; Usher, L. H.

1976-01-01

Engineering studies were performed for the Zero-G Cloud Physics Experiment liquid cooling and air pressure control systems. A total of four concepts for the liquid cooling system was evaluated, two of which were found to closely approach the systems requirements. Thermal insulation requirements, system hardware, and control sensor locations were established. The reservoir sizes and initial temperatures were defined as well as system power requirements. In the study of the pressure control system, fluid analyses by the Atmospheric Cloud Physics Laboratory were performed to determine flow characteristics of various orifice sizes, vacuum pump adequacy, and control systems performance. System parameters predicted in these analyses as a function of time include the following for various orifice sizes: (1) chamber and vacuum pump mass flow rates, (2) the number of valve openings or closures, (3) the maximum cloud chamber pressure deviation from the allowable, and (4) cloud chamber and accumulator pressure.

An economical model for simulating droplet spectrum evolution in turbulent cloud chambers and wind tunnels

NASA Astrophysics Data System (ADS)

Krueger, Steven; Cantrell, W.; Niedermeier, D.; Shaw, R.; Stratmann, F.

2017-11-01

Although airborne instruments provide detailed information about the microphysical structure of clouds, the measurements provide only a few snapshots of each cloud. Deducing the droplet spectrum evolution from such measurements is next to impossible. We are using two alternative approaches: laboratory studies and numerical simulations. The former relies on a new turbulent cloud chamber (the Pi Chamber) at Michigan Technical University, as well as the first humid turbulent wind tunnel (LACIS-T) at the Leibniz Institute for Tropospheric Research. Both produce conditions for droplet growth (i.e., supersaturation) by mixing saturated vapor at different temperatures. The Pi Chamber produces turbulence by inducing Rayleigh-Bénard convection, while the wind tunnel generates turbulence with a grid. We are using the Explicit Mixing Parcel Model (EMPM) to numerically simulate droplet spectrum evolution in these flows. The EMPM explicitly links turbulent mixing and droplet spectrum evolution by representing a turbulent flow in a 1D domain with the linear eddy model. The EMPM can economically span scales from those of the smallest turbulent eddies to those of the largest. The EMPM grows or evaporates thousands of individual cloud droplets according to their local environments.

Peltier-based cloud chamber

NASA Astrophysics Data System (ADS)

Nar, Sevda Yeliz; Cakir, Altan

2018-02-01

Particles produced by nuclear decay, cosmic radiation and reactions can be identified through various methods. One of these methods that has been effective in the last century is the cloud chamber. The chamber makes visible cosmic particles that we are exposed to radiation per second. Diffusion cloud chamber is a kind of cloud chamber that is cooled by dry ice. This traditional model has some application difficulties. In this work, Peltier-based cloud chamber cooled by thermoelectric modules is studied. The new model provided uniformly cooled base of the chamber, moreover, it has longer lifetime than the traditional chamber in terms of observation time. This gain has reduced the costs which spent each time for cosmic particle observation. The chamber is an easy-to-use system according to traditional diffusion cloud chamber. The new model is portable, easier to make, and can be used in the nuclear physics experiments. In addition, it would be very useful to observe Muons which are the direct evidence for Lorentz contraction and time expansion predicted by Einsteins special relativity principle.

Investigation of Shock Diffusers at Mach Number 1.85. 1 - Projecting Single Shock Cones

DTIC Science & Technology

1947-06-17

cylindrical simulated combustion chamber was used to vary the outlet area of the flow through the diffuser. The pitot -static rake , located as shown in the...Simulated combustion u chamber A 90° W •—Conical damper S Static-pressure orifice ps pitot -static "" rake ’ NATIONAL ADVISORY...recoveries were obtained with subsonic entrance flow. INTRODCJCTION For efficient conversion of the kinetic energy of a supersonic air stream into ram

Interstellar and Planetary Analogs in the Laboratory

NASA Technical Reports Server (NTRS)

Salama, Farid

2013-01-01

We present and discuss the unique capabilities of the laboratory facility, COSmIC, that was developed at NASA Ames to investigate the interaction of ionizing radiation (UV, charged particles) with molecular species (neutral molecules, radicals and ions) and carbonaceous grains in the Solar System and in the Interstellar Medium (ISM). COSmIC stands for Cosmic Simulation Chamber, a laboratory chamber where interstellar and planetary analogs are generated, processed and analyzed. It is composed of a pulsed discharge nozzle (PDN) expansion that generates a free jet supersonic expansion in a plasma cavity coupled to two ultrahigh-sensitivity, complementary in situ diagnostics: a cavity ring down spectroscopy (CRDS) system for photonic detection and a Reflectron time-of-flight mass spectrometer (ReTOF-MS) for mass detection. This setup allows the study of molecules, ions and solids under the low temperature and high vacuum conditions that are required to simulate some interstellar, circumstellar and planetary physical environments providing new fundamental insights on the molecular level into the processes that are critical to the chemistry in the ISM, circumstellar and planet forming regions, and on icy objects in the Solar System. Recent laboratory results that were obtained using COSmIC will be discussed, in particular the progress that have been achieved in monitoring in the laboratory the formation of solid particles from their gas-phase molecular precursors in environments as varied as circumstellar outflow and planetary atmospheres.

Brayton Cycle Power System in the Space Power Facility

NASA Image and Video Library

1969-07-21

Set up of a Brayton Cycle Power System test in the Space Power Facility’s massive vacuum chamber at the National Aeronautics and Space Administration’s (NASA) Plum Brook Station in Sandusky, Ohio. The $28.4-million facility, which began operations in 1969, is the largest high vacuum chamber ever built. The chamber is 100 feet in diameter and 120 feet high. It can produce a vacuum deep enough to simulate the conditions at 300 miles altitude. The Space Power Facility was originally designed to test nuclear-power sources for spacecraft, but it was never used for that purpose. The Space Power Facility was first used to test a 15 to 20-kilowatt Brayton Cycle Power System for space applications. Three different methods of simulating solar heat were employed during the tests. Lewis researchers studied the Brayton power system extensively in the 1960s and 1970s. The Brayton engine converted solar thermal energy into electrical power. The system operated on a closed-loop Brayton thermodynamic cycle with a helium-xenon gas mixture as its working fluid. A space radiator was designed to serve as the system’s waste heat rejecter. The radiator was later installed in the vacuum chamber and tested in a simulated space environment to determine its effect on the power conversion system. The Brayton system was subjected to simulated orbits with 62 minutes of sun and 34 minutes of shade.

Influence of physical properties and operating parameters on hydrodynamics in Centrifugal Partition Chromatography.

PubMed

Adelmann, S; Schembecker, G

2011-08-12

Besides the selection of a suitable biphasic solvent system the separation efficiency in Centrifugal Partition Chromatography (CPC) is mainly influenced by the hydrodynamics in the chambers. The flow pattern, the stationary phase retention and the interfacial area for mass transfer strongly depend on physical properties of the solvent system and operating parameters. In order to measure these parameters we visualized the hydrodynamics in a FCPC-chamber for five different solvent systems with an optical measurement system and calculated the stationary phase retention, interfacial area and the distribution of mobile phase thickness in the chamber. Although inclined chambers were used we found that the Coriolis force always deflected the mobile phase towards the chamber wall reducing the interfacial area. This effect increased for systems with low density difference. We also have shown that the stability of phase systems (stationary phase retention) and its tendency to disperse increased for smaller values of the ratio of interfacial tension and density difference. But also the viscosity ratio and the flow pattern itself had a significant effect on retention and dispersion of the mobile phase. As a result operating parameters should be chosen carefully with respect to physical properties for a CPC system. In order to reduce the effect of the Coriolis force CPC devices with greater rotor radius are desirable. Copyright © 2011 Elsevier B.V. All rights reserved.

Environmental fog/rain visual display system for aircraft simulators

NASA Technical Reports Server (NTRS)

Chase, W. D. (Inventor)

1982-01-01

An environmental fog/rain visual display system for aircraft simulators is described. The electronic elements of the system include a real time digital computer, a caligraphic color display which simulates landing lights of selective intensity, and a color television camera for producing a moving color display of the airport runway as depicted on a model terrain board. The mechanical simulation elements of the system include an environmental chamber which can produce natural fog, nonhomogeneous fog, rain and fog combined, or rain only. A pilot looking through the aircraft wind screen will look through the fog and/or rain generated in the environmental chamber onto a viewing screen with the simulated color image of the airport runway thereon, and observe a very real simulation of actual conditions of a runway as it would appear through actual fog and/or rain.

Numerical studies of wall–plasma interactions and ionization phenomena in an ablative pulsed plasma thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Lei; School of Astronautics, Beihang University, Beijing 100191; Zeng, Guangshang

2016-07-15

Wall–plasma interactions excited by ablation controlled arcs are very critical physical processes in pulsed plasma thrusters (PPTs). Their effects on the ionization processes of ablated vapor into discharge plasma directly determine PPT performances. To reveal the physics governing the ionization phenomena in PPT discharge, a modified model taking into account the pyrolysis effect of heated polytetrafluoroethylene propellant on the wall–plasma interactions was developed. The feasibility of the modified model was analyzed by creating a one-dimensional simulation of a rectangular ablative PPT. The wall–plasma interaction results based on this modified model were found to be more realistic than for the unmodifiedmore » model; this reflects the dynamic changes of the inflow parameters during discharge in our model. Furthermore, the temporal and spatial variations of the different plasma species in the discharge chamber were numerically studied. The numerical studies showed that polytetrafluoroethylene plasma was mainly composed of monovalent ions; carbon and fluorine ions were concentrated in the upstream and downstream discharge chamber, respectively. The results based on this modified model were in good agreement with the experimental formation times of the various plasma species. A large number of short-lived and highly ionized carbon and fluorine species (divalent and trivalent ions) were created during initial discharge. These highly ionized species reached their peak density earlier than the singly ionized species.« less

Long term performance studies of large oil-free bakelite resistive plate chamber

NASA Astrophysics Data System (ADS)

Ganai, R.; Roy, A.; Shiroya, M. K.; Agarwal, K.; Ahammed, Z.; Choudhury, S.; Chattopadhyay, S.

2016-09-01

Several high energy physics and neutrino physics experiments worldwide require large-size RPCs to cover wide acceptances. The muon tracking systems in the Iron calorimeter (ICAL) experiment in the India based Neutrino Observatory (INO), India and the near detector in Deep Underground Neutrino Experiment (DUNE) at Fermilab are two such examples. A single gap bakelite RPC of dimension 240 cm × 120 cm, with gas gap of 0.2 cm, has been built and tested at Variable Energy Cyclotron Centre, Kolkata, using indigenous materials procured from the local market. No additional lubricant, like oil has been used on the electrode surfaces for smoothening. The chamber is in operation for > 365 days. We have tested the chamber for its long term operation. The leakage current, bulk resistivity, efficiency, noise rate and time resolution of the chamber have been found to be quite stable during the testing peroid. It has shown an efficiency > 95% with an average time resolution of ~ 0.83 ns at the point of measurement at ~ 8700 V throughout the testing period. Details of the long term performance of the chamber have been discussed.

Venturi vacuum systems for hypobaric chamber operations.

PubMed

Robinson, R; Swaby, G; Sutton, T; Fife, C; Powell, M; Butler, B D

1997-11-01

Physiological studies of the effects of high altitude on man often require the use of a hypobaric chamber to simulate the reduced ambient pressures. Typical "altitude" chambers in use today require complex mechanical vacuum systems to evacuate the chamber air, either directly or via reservoir system. Use of these pumps adds to the cost of both chamber procurement and maintenance, and service of these pumps requires trained support personnel and regular upkeep. In this report we describe use of venturi vacuum pumps to perform the function of mechanical vacuum pumps for human and experimental altitude chamber operations. Advantages of the venturi pumps include their relatively low procurement cost, small size and light weight, ease of installation and plumbing, lack of moving parts, and independence from electrical power sources, fossil fuels and lubricants. Conversion of three hyperbaric chambers to combined hyper/hypobaric use is described.

Experimental and numerical studies of a microfluidic device with compliant chambers for flow stabilization

NASA Astrophysics Data System (ADS)

Iyer, V.; Raj, A.; Annabattula, R. K.; Sen, A. K.

2015-07-01

This paper reports experimental and numerical studies of a passive microfluidic device that stabilizes a pulsating incoming flow and delivers a steady flow at the outlet. The device employs a series of chambers along the flow direction with a thin polymeric membrane (of thickness 75-250 µm) serving as the compliant boundary. The deformation of the membrane allows accumulation of fluid during an overflow and discharge of fluid during an underflow for flow stabilization. Coupled fluid-structure simulations are performed using Mooney-Rivlin formulations to account for a thin hyperelastic membrane material undergoing large deformations to accurately predict the device performance. The device was fabricated with PDMS as the substrate material and thin PDMS membrane as the compliant boundary. The performance of the device is defined in terms of a parameter called ‘Attenuation Factor (AF)’. The effect of various design parameters including membrane thickness, elastic modulus, chamber size and number of chambers in series as well as operating conditions including the outlet pressure, mean input flow rate, fluctuation amplitude and frequency on the device performance were studied using experiments and simulations. The simulation results successfully confront the experimental data (within 10%) which validates the numerical simulations. The device was used at the exit of a PZT actuated valveless micropump to take pulsating flow at the upstream and deliver steady flow downstream. The amplitude of the pulsating flow delivered by the micropump was significantly reduced (AF = 0.05 for a device with three 4 mm chambers) but at the expense of a reduction in the pressure capability (<20%). The proposed device could potentially be used for reducing flow pulsations in practical microfluidic circuits.

Anthropomorphic cardiac ultrasound phantom.

PubMed

Smith, S W; Rinaldi, J E

1989-10-01

A new phantom is described which simulates the human cardiac anatomy for applications in ultrasound imaging, ultrasound Doppler, and color-flow Doppler imaging. The phantom consists of a polymer left ventricle which includes a prosthetic mitral and aortic valve and is connected to a mock circulatory loop. Aerated tap water serves as a blood simulating fluid and ultrasound contrast medium within the circulatory loop. The left ventricle is housed in a Lexan ultrasound visualization chamber which includes ultrasound viewing ports and acoustic absorbers. A piston pump connected to the visualization chamber by a single port pumps degassed water within the chamber which in turn pumps the left ventricle. Real-time ultrasound images and Doppler studies measure flow patterns through the valves and within the left ventricle.

Method and apparatus for simulating gravitational forces on a living organism

NASA Technical Reports Server (NTRS)

Thornton, W. E. (Inventor)

1983-01-01

A method and apparatus for simulating gravitational forces on a living organism wherein a series of negative pressures are externally applied to successive length-wise sections of a lower limb of the organism. The pressures decreasing progressively with distance of said limb sections from the heart of the organism. A casing defines a chamber adapted to contain the limb of the organism and is rigidified to resist collapse upon the application of negative pressures to the interior of the chamber. Seals extend inwardly from the casing for effective engagement with the limb of the organism and, in cooperation with the limb, subdivide the chamber into a plurality of compartments each in negative pressure communicating relation with the limb.

Documentation of the Recirculation in a Closed-Chamber Rotor Hover Test

NASA Technical Reports Server (NTRS)

McCoy, Miranda; Wadcock, Alan J.; Young, Larry A.

2016-01-01

A rotor hover test was performed inside the JPL 25-foot-diameter Space Simulator. The 40-inch-diameter rotor was tested at two locations in the chamber-on the chamber centerline and 2m off-axis. The rotor was tested in both upright and inverted configurations for 500 < RPM < 2000. Fluorescent tufts were used to identify regions of recirculation. Velocities on the entrainment side of the rotor were measured. Tabulated values for the mean entrainment velocity components and the corresponding root mean square velocity fluctuations are provided. Unsteady velocity measurements provide a description of the turbulence ingested into the rotor plane and quantify the unsteady velocity field that the Mars Scout Helicopter can expect to encounter during free flight inside the Space Simulator.

A high-efficiency acoustic chamber and the anomalous sample rotation

NASA Technical Reports Server (NTRS)

Wang, Taylor G.; Allen, J. L.

1992-01-01

A high efficiency acoustic chamber for the levitation and manipulation of liquid or molten samples in a microgravity environment has been developed. The chamber uses two acoustic drivers that are mounted at opposite corners of the chamber; by driving these at the same frequency, with 18-deg phase shifts, an increase in force of a factor of 3-4 is obtainable relative to the force of a single-driver system that is operated at the same power level. This enhancement is due to the increased coupling between the sound driver and the chamber. An anomalous rotation is noted to be associated with the chamber; this is found to be eliminated by a physically as-yet inexplicable empirical solution.

High Accuracy, Two-Dimensional Read-Out in Multiwire Proportional Chambers

DOE R&D Accomplishments Database

Charpak, G.; Sauli, F.

1973-02-14

In most applications of proportional chambers, especially in high-energy physics, separate chambers are used for measuring different coordinates. In general one coordinate is obtained by recording the pulses from the anode wires around which avalanches have grown. Several methods have been imagined for obtaining the position of an avalanche along a wire. In this article a method is proposed which leads to the same range of accuracies and may be preferred in some cases. The problem of accurate measurements for large-size chamber is also discussed.

In Situ Fiber-Optic Reflectance Monitor

NASA Technical Reports Server (NTRS)

Linton, Roger C.; Gray, Perry A.

1996-01-01

In situ fiber-optic reflectance monitor serves as simple means of monitoring changes in reflectance of specimen exposed to simulated outerspace or other environments in vacuum chamber. Eliminates need to remove specimen from vacuum chamber, eliminating optical changes and bleaching such removal causes in coatings.

IDENTIFICATION OF AN IDEAL REACTOR MODEL IN A SECONDARY COMBUSTION CHAMBER

EPA Science Inventory

Tracer analysis was applied to a secondary combustion chamber of a rotary kiln incinerator simulator to develop a computationally inexpensive networked ideal reactor model and allow for the later incorporation of detailed reaction mechanisms. Tracer data from sulfur dioxide trace...

Performance of nanocomposites for preservation of artistic stones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giancristofaro, Cristina; Pilloni, Luciano; Rinaldi, Antonio

2014-06-19

In this work, the effectiveness of nanocomposite surface treatments as protective systems for artistic stones was evaluated. Pyrolitic silica and titania nanoparticles were dispersed in a commercial silicon-based polymer and applied on marble and travertine samples. Artificial aging processes, both in climatic chamber and in solar box, were carried out to simulate real degradation processes in terms of photo-thermal effects and physical-chemical damage. The performances of the nanocomposites used as consolidant were evaluated comparatively by means of diverse diagnostic techniques, namely: scanning electron microscopy (SEM), laser induced fluorescence (LIF), ultrasonic technique, colorimetry, total immersion water absorption and contact angle. Themore » results show that some properties of conservation materials can be improved by the presences of nanoparticles because they induce substantial changes of surface morphology of the coating layer and counter the physical damage observed during artificial weathering.« less

Experimental study of the intraventricular filling vortex in diastolic dysfunction

NASA Astrophysics Data System (ADS)

Santhanakrishnan, Arvind; Samaee, Milad; Nelsen, Nicholas

2016-11-01

Heart failure with normal ejection fraction (HFNEF) is a clinical syndrome that is prevalent in over half of heart failure patients. HFNEF patients typically show diastolic dysfunction, caused by a decrease in relaxation capability of the left ventricular (LV) muscle tissue and/or an increase in LV chamber stiffness. Numerous studies using non-invasive medical imaging have shown that an intraventricular filling vortex is formed in the LV during diastole. We conducted 2D particle image velocimetry and hemodynamics measurements on a left heart simulator to investigate diastolic flow under increasing LV wall stiffness, LV wall thickness and heart rate (HR) conditions. Flexible-walled, optically clear LV physical models cast from silicone were fitted within a fluid-filled acrylic chamber. Pulsatile flow within the LV model was generated using a piston pump and 2-component Windkessel elements were used to tune the least stiff (baseline) LV model to physiological conditions. The results show that peak circulation of the intraventricular filling vortex is diminished in conditions of diastolic dysfunction as compared to the baseline case. Increasing HR exacerbated the circulation of the filling vortex across all cases.

Aerothermal environment induced by mismatch at the SSME main combustion chamber-nozzle joint

NASA Technical Reports Server (NTRS)

Mcconnaughey, H. V.; O'Farrell, J. M.; Olive, T. A.; Brown, G. B.; Holt, J. B.

1990-01-01

The computational study reported here is motivated by a Space Shuttle main engine hardware problem detected in post-flight and post-test inspections. Of interest are the potential for hot gas ingestion into the joint (G15) at the main combustion chamber-to-nozzle interface and the effect of particular goemetric nonuniformities on that gas ingestion. The flowfield in the G15 region involves supersonic flow past a rounded forward facing step preceded by a deep narrow cavity. This paper describes the physical problem associated with joint G15 and computational investigations of the G15 aerothermal environment. The associated flowfield was simulated in two and three space dimensions using the United Solutions Algorithm (USA) computational fluid dynamics code series. A benchmark calculation of experimentally measured supersonic flow over of a square cavity was performed to demonstrate the accuracy of the USA code in analyzing flows similar to the G15 computational flowfield. The G15 results demonstrate the mechanism for hot gas ingestion into the joint and reveal the sensitivity to salient geometric nonuniformities.

Highly dexterous 2-module soft robot for intra-organ navigation in minimally invasive surgery.

PubMed

Abidi, Haider; Gerboni, Giada; Brancadoro, Margherita; Fras, Jan; Diodato, Alessandro; Cianchetti, Matteo; Wurdemann, Helge; Althoefer, Kaspar; Menciassi, Arianna

2018-02-01

For some surgical interventions, like the Total Mesorectal Excision (TME), traditional laparoscopes lack the flexibility to safely maneuver and reach difficult surgical targets. This paper answers this need through designing, fabricating and modelling a highly dexterous 2-module soft robot for minimally invasive surgery (MIS). A soft robotic approach is proposed that uses flexible fluidic actuators (FFAs) allowing highly dexterous and inherently safe navigation. Dexterity is provided by an optimized design of fluid chambers within the robot modules. Safe physical interaction is ensured by fabricating the entire structure by soft and compliant elastomers, resulting in a squeezable 2-module robot. An inner free lumen/chamber along the central axis serves as a guide of flexible endoscopic tools. A constant curvature based inverse kinematics model is also proposed, providing insight into the robot capabilities. Experimental tests in a surgical scenario using a cadaver model are reported, demonstrating the robot advantages over standard systems in a realistic MIS environment. Simulations and experiments show the efficacy of the proposed soft robot. Copyright © 2017 John Wiley & Sons, Ltd.

Characterization of air temperature in modern ion chambers due to phantom geometry and ambient temperature changes.

PubMed

Saenz, Daniel L; Kirby, Neil; Gutiérrez, Alonso N

2016-07-01

Temperature and pressure corrections are necessary to account for the varying mass of air in the sensitive volume of a vented ionization chamber (IC) when performing absolute dose measurements. Locations commonly used to measure the presumed IC air temperature may not accurately represent the chamber cavity air temperature, and phantoms undergoing temperature changes further compound the problem. Prior studies have characterized thermal equilibrium in separate phantoms for Farmer chambers alone. However, the purpose of this study was to characterize the cavity air temperature dependence on changes in the ambient temperature and phantom geometry configuration for a wider and more modern variety of chambers to determine if previously published wait times apply to these chambers as well. Thermal conduction properties were experimentally investigated by modifying a PTW 0.3 cm(3) Semiflex IC with a thermocouple replacing the central electrode. Air cavity temperature versus time was recorded in three phantom geometries characteristic of common absolute dose measurements. The phantoms were (15 ± 1) °C before measurement with an IC at the treatment vault temperature of (21 ± 1) °C. Simulations were conducted to provide a theoretical basis for the measurements and to simulate temperature response of a PTW PinPoint® and Farmer chamber. The simulation methods were first validated by comparison with measured Semiflex chamber thermal response curves before extension to the other chambers. Two thermal equilibria curves were recorded on different time scales. IC temperature initially dropped to the colder phantom temperature but subsequently increased as the phantom itself equilibrated with the warmer room temperature. In a large phantom of dimensions (25.5 × 25.5 × 23.4) cm(3), 3 min was required before the IC temperature reached within 0.5 °C of its equilibrium within the phantom. Similarly, wait times of 2 min were needed for 7.5 and 2 cm slab phantoms. Recording of temperature in the phantom was deemed far more accurate than measurement in ambient air due to the air cavity thermally equilibrating with phantom temperature instead of the vented ambient air. Wait times of 3 and 2 min are needed for a cube and 7.5 cm slab phantom, respectively, to achieve 0.2% dosimetric accuracy (temperature accuracy of 0.5 °C). Chamber volume alone did not determine wait times, as a 0.3 cm(3) IC required a longer wait time than a Farmer chamber, suggesting wall thickness as an important variable as well.

Characteristics of Perforated Diffusers at Free-Stream Mach Number 1.90

DTIC Science & Technology

1950-05-08

deg) Subscripts: 0 free stream 1 inlet entrance 2 Inlet throat 3 pitot -static rake in simulated combustion chamber 4 outlet of simulated...consisted of a 40-tube pitot -static survey rake located 0.55 combust Ion-chamber diameter downstream of the outlet of the subsonic diffuser (fig. 8(b...The rake was so designed that eaoh pitot -static tube was located at the oentroid of one of the forty equal area segments Into which the combustion

Evaluating the efficacy of a thermal exposure chamber designed for assessing workers' thermal hazard.

PubMed

Tsai, Perng-Jy; Lo, Chuh-Lun; Sun, Yih-Min; Juang, Yow-Jer; Liu, Hung-Hsin; Chen, Wang-Yi; Yeh, Wen-Yu

2003-05-01

This study was conducted on a thermal exposure chamber designed for assessing workers' thermal hazard. In order to assess the efficacy of the studied chamber, three environmental conditions were selected to simulate high, middle and low thermal impact situations, with air temperatures (Ta) of 43.12, 36.23 and 25.77 masculine C, globe temperatures (Tg) of 44.41, 41.07 and 29.24 masculine C, relative humidity (RH) of 77, 59 and 39%, and air flow velocities (Va) of 1.70, 0.91 and 0.25 m/s, respectively. For the three specified thermal impact conditions, results show that the coefficients of variation (CVs) for Ta, Tg, RH and Va measured in the chamber studied were consistently less than 10%, except for Va under the low thermal impact condition (=50%). For each specified thermal impact condition, we generated 1,000 environmental combinations by using the Monte Carlo simulation approach according to the variations obtained from the four environmental factors. We directly adopted the ISO 7933 approach to estimate the allowable exposure time (AET) for each simulated environmental condition. This study yielded a range in the 95% confidence interval (95% CI) of the estimated AETs for the three specified thermal impact conditions which were consistently less than 5 min. We further conducted the sensitivity analysis to examine the effect of the four environmental factors on estimating AETs. We found Va was the least important factor in estimating AETs for any specified thermal impact condition. In conclusion, although Va was found with great variation for the chamber specified in the low thermal impact condition, the exposure chamber studied can still be regarded as a feasible one for assessing workers' thermal hazard.

Indian LSSC (Large Space Simulation Chamber) facility

NASA Technical Reports Server (NTRS)

Brar, A. S.; Prasadarao, V. S.; Gambhir, R. D.; Chandramouli, M.

1988-01-01

The Indian Space Agency has undertaken a major project to acquire in-house capability for thermal and vacuum testing of large satellites. This Large Space Simulation Chamber (LSSC) facility will be located in Bangalore and is to be operational in 1989. The facility is capable of providing 4 meter diameter solar simulation with provision to expand to 4.5 meter diameter at a later date. With such provisions as controlled variations of shroud temperatures and availability of infrared equipment as alternative sources of thermal radiation, this facility will be amongst the finest anywhere. The major design concept and major aspects of the LSSC facility are presented here.

Laboratory simulation of cratering on small bodies

NASA Technical Reports Server (NTRS)

Schmidt, Robert M.

1991-01-01

A new technique using external pressure was developed to simulate the lithostatic pressure due to self-gravity of small bodies. A 13-in. diameter cylindrical test chamber with L/D of 1 was fabricated to accommodate firing explosive charges with gas overpressures of up to 6000 psi. The chamber was hydrotested to 9000 psi. The method allows much larger scale factors that can be obtained with existing centrifuges and has the correct spherical geometry of self gravity. A simulant for jointed rock to be used in this fixture was developed using weakly cemented basalt. Various strength/pressure scaling theories can now be examined and tested.

Simulation and measurements of the response of an air ionisation chamber exposed to a mixed high-energy radiation field.

PubMed

Vincke, Helmut; Forkel-Wirth, Doris; Perrin, Daniel; Theis, Chris

2005-01-01

CERN's radiation protection group operates a network of simple and robust ionisation chambers that are installed inside CERN's accelerator tunnels. These ionisation chambers are used for the remote reading of ambient dose rate equivalents inside the machines during beam-off periods. This Radiation Protection Monitor for dose rates due to Induced Radioactivity ('PMI', trade name: PTW, Type 34031) is a non-confined air ionisation plastic chamber which is operated under atmospheric pressure. Besides its current field of operation it is planned to extend the use of this detector in the Large Hadron Collider to measure radiation under beam operation conditions to obtain an indication of the machine performance. Until now, studies of the PMI detector have been limited to the response to photons. In order to evaluate its response to other radiation components, this chamber type was tested at CERF, the high-energy reference field facility at CERN. Six PMI detectors were installed around a copper target being irradiated by a mixed hadron beam with a momentum of 120 GeV c(-1). Each of the chosen detector positions was defined by a different radiation field, varying in type and energy of the incident particles. For all positions, detailed measurements and FLUKA simulations of the detector response were performed. This paper presents the promising comparison between the measurements and simulations and analyses the influence of the different particle types on the resulting detector response.

Influence of heat and particle fluxes nonlocality on spatial distribution of plasma density in two-chamber inductively coupled plasma sources

NASA Astrophysics Data System (ADS)

Kudryavtsev, A. A.; Serditov, K. Yu.

2012-07-01

This study presents 2D simulations of the two-chamber inductively coupled plasma source where power is supplied in the small discharge chamber and extends by electron thermal conductivity mechanism to the big diffusion chamber. Depending on pressure, two main scenarios of plasma density and its spatial distribution behavior were identified. One case is characterized by the localization of plasma in the small driver chamber where power is deposed. Another case describes when the diffusion chamber becomes the main source of plasma with maximum of the electron density. The differences in spatial distribution are caused by local or non-local behavior of electron energy transport in the discharge volume due to different characteristic scale of heat transfer with electronic conductivity.

Simulation of Layered Magma Chambers.

ERIC Educational Resources Information Center

Cawthorn, Richard Grant

1991-01-01

The principles of magma addition and liquid layering in magma chambers can be demonstrated by dissolving colored crystals. The concepts of density stratification and apparent lack of mixing of miscible liquids is convincingly illustrated with hydrous solutions at room temperature. The behavior of interstitial liquids in "cumulus" piles…

USING 14 C METHODOLOGY IN SMOG CHAMBER RESEARCH

EPA Science Inventory

Smog chambers are large enclosures (~ 10-200 m³) that are used to perform laboratory simulations of atmospheric reactions. By dealing with simple systems in which the number of reactants is limited and the conditions are strictly controlled, insights on how reactions ...

Simulation of SiO2 etching in an inductively coupled CF4 plasma

NASA Astrophysics Data System (ADS)

Xu, Qing; Li, Yu-Xing; Li, Xiao-Ning; Wang, Jia-Bin; Yang, Fan; Yang, Yi; Ren, Tian-Ling

2017-02-01

Plasma etching technology is an indispensable processing method in the manufacturing process of semiconductor devices. Because of the high fluorine/carbon ratio of CF4, the CF4 gas is often used for etching SiO2. A commercial software ESI-CFD is used to simulate the process of plasma etching with an inductively coupled plasma model. For the simulation part, CFD-ACE is used to simulate the chamber, and CFD-TOPO is used to simulate the surface of the sample. The effects of chamber pressure, bias voltage and ICP power on the reactant particles were investigated, and the etching profiles of SiO2 were obtained. Simulation can be used to predict the effects of reaction conditions on the density, energy and angular distributions of reactant particles, which can play a good role in guiding the etching process.

Simulated space environment tests on cadmium sulfide solar cells

NASA Technical Reports Server (NTRS)

Clarke, D. R.; Oman, H.

1971-01-01

Cadmium sulfide (Cu2s - CdS) solar cells were tested under simulated space environmental conditions. Some cells were thermally cycled with illumination from a Xenon-arc solar simulator. A cycle was one hour of illumination followed immediately with one-half hour of darkness. In the light, the cells reached an equilibrium temperature of 60 C (333 K) and in the dark the cell temperature dropped to -120 C (153 K). Other cells were constantly illuminated with a Xenon-arc solar simulator. The equilibrium temperature of these cells was 55 C (328 K). The black vacuum chamber walls were cooled with liquid nitrogen to simulate a space heat sink. Chamber pressure was maintained at 0.000001 torr or less. Almost all of the solar cells tested degraded in power when exposed to a simulated space environment of either thermal cycling or constant illumination. The cells tested the longest were exposed to 10.050 thermal cycles.

Computer code for the prediction of nozzle admittance

NASA Technical Reports Server (NTRS)

Nguyen, Thong V.

1988-01-01

A procedure which can accurately characterize injector designs for large thrust (0.5 to 1.5 million pounds), high pressure (500 to 3000 psia) LOX/hydrocarbon engines is currently under development. In this procedure, a rectangular cross-sectional combustion chamber is to be used to simulate the lower traverse frequency modes of the large scale chamber. The chamber will be sized so that the first width mode of the rectangular chamber corresponds to the first tangential mode of the full-scale chamber. Test data to be obtained from the rectangular chamber will be used to assess the full scale engine stability. This requires the development of combustion stability models for rectangular chambers. As part of the combustion stability model development, a computer code, NOAD based on existing theory was developed to calculate the nozzle admittances for both rectangular and axisymmetric nozzles. This code is detailed.

One Dimensional Analysis Model of a Condensing Spray Chamber Including Rocket Exhaust Using SINDA/FLUINT and CEA

NASA Technical Reports Server (NTRS)

Sakowski, Barbara; Edwards, Daryl; Dickens, Kevin

2014-01-01

Modeling droplet condensation via CFD codes can be very tedious, time consuming, and inaccurate. CFD codes may be tedious and time consuming in terms of using Lagrangian particle tracking approaches or particle sizing bins. Also since many codes ignore conduction through the droplet and or the degradating effect of heat and mass transfer if noncondensible species are present, the solutions may be inaccurate. The modeling of a condensing spray chamber where the significant size of the water droplets and the time and distance these droplets take to fall, can make the effect of droplet conduction a physical factor that needs to be considered in the model. Furthermore the presence of even a relatively small amount of noncondensible has been shown to reduce the amount of condensation [Ref 1]. It is desirable then to create a modeling tool that addresses these issues. The path taken to create such a tool is illustrated. The application of this tool and subsequent results are based on the spray chamber in the Spacecraft Propulsion Research Facility (B2) located at NASA's Plum Brook Station that tested an RL-10 engine. The platform upon which the condensation physics is modeled is SINDAFLUINT. The use of SINDAFLUINT enables the ability to model various aspects of the entire testing facility, including the rocket exhaust duct flow and heat transfer to the exhaust duct wall. The ejector pumping system of the spray chamber is also easily implemented via SINDAFLUINT. The goal is to create a transient one dimensional flow and heat transfer model beginning at the rocket, continuing through the condensing spray chamber, and finally ending with the ejector pumping system. However the model of the condensing spray chamber may be run independently of the rocket and ejector systems detail, with only appropriate mass flow boundary conditions placed at the entrance and exit of the condensing spray chamber model. The model of the condensing spray chamber takes into account droplet conduction as well as the degrading effect of mass and heat transfer due to the presence of noncondensibles. The one dimension model of the condensing spray chamber makes no presupposition on the pressure profile within the chamber, allowing the implemented droplet physics of heat and mass transfer coupled to the SINDAFLUINT solver to determine a transient pressure profile of the condensing spray chamber. Model results compare well to the RL-10 engine pressure test data.

Dosimetry in small-animal CT using Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Lee, C.-L.; Park, S.-J.; Jeon, P.-H.; Jo, B.-D.; Kim, H.-J.

2016-01-01

Small-animal computed tomography (micro-CT) imaging devices are increasingly being used in biological research. While investigators are mainly interested in high-contrast, low-noise, and high-resolution anatomical images, relatively large radiation doses are required, and there is also growing concern over the radiological risk from preclinical experiments. This study was conducted to determine the radiation dose in a mouse model for dosimetric estimates using the GEANT4 application for tomographic emission simulations (GATE) and to extend its techniques to various small-animal CT applications. Radiation dose simulations were performed with the same parameters as those for the measured micro-CT data, using the MOBY phantom, a pencil ion chamber and an electrometer with a CT detector. For physical validation of radiation dose, absorbed dose of brain and liver in mouse were evaluated to compare simulated results with physically measured data using thermoluminescent dosimeters (TLDs). The mean difference between simulated and measured data was less than 2.9% at 50 kVp X-ray source. The absorbed doses of 37 brain tissues and major organs of the mouse were evaluated according to kVp changes. The absorbed dose over all of the measurements in the brain (37 types of tissues) consistently increased and ranged from 42.4 to 104.0 mGy. Among the brain tissues, the absorbed dose of the hypothalamus (157.8-414.30 mGy) was the highest for the beams at 50-80 kVp, and that of the corpus callosum (11.2-26.6 mGy) was the lowest. These results can be used as a dosimetric database to control mouse doses and preclinical targeted radiotherapy experiments. In addition, to accurately calculate the mouse-absorbed dose, the X-ray spectrum, detector alignment, and uncertainty in the elemental composition of the simulated materials must be accurately modeled.

Urban Biometeorology: analysis of the air pollution and climate change on cognition and physical abilities of geriatric population of São Paulo City

NASA Astrophysics Data System (ADS)

Teixeira Gonçalves, Fabio Luiz; Jacob, Wilson; Alucci, Marcia; Busse, Alexandre; Duarte, Denise; Monteiro, Leonardo; Trezza, Beatriz; Tribess, Arlindo; Batista, Rafael; Ambrizzi, Tercip

2013-04-01

This is a multidisciplinary Project, which emphasizes geriatric population impacts, i. e., over 65 years old, of meteorological variables and air pollutants (such as particulate matter) associated to human health, and concerning to the real climatology and climate change in the Metropolitan Region of São Paulo. This is a biometeorological study, human subdivision, based on ISB (International Society of Biometeorology). According to the society, the environmental effects are considered meteorotropics where one or more environmental variables (meteorological or climatic even air pollution) affect one or more individuals of a population. Atmospheric pollution will be analyzed using a personal particulate matter multi-collector, concerning the impact of unfavorable meteorological conditions where the impacts will be evaluated comparing the test results during dry season (high air pollutant concentrations) and wet season (low pollutant concentrations). Therefore, the aim of this study will be to evaluate the cognitive and physical performance of a geriatric population in a pre-selected group of aged people which are considered as capable (healthy). This performance is affected by environmental conditions which thermal comfort (where meteorological variables act together) and air pollution are the meteorotropic ones. Consequently, one of the aims of the study is to establish a human thermal comfort index for geriatric populations. Architectural premises (thermal performance and ergonomics) will be also developed. An acclimatized chamber will be used to simulate the extremes of São Paulo climate and to propose a thermal comfort index. Indoors (chamber) and outdoors will be used in order to compare the impact on the selected aged people. Finally, the climate change will be based on GCM's global models which show the meteorological variations in order to calculate their impact on a comfort index. The physical and cognitive performances and architectural premises (thermal performance and ergonomics) will be analyzed inside of the climatic chamber. The preliminary results for future (climate change for 2070-2100) comfort indexes present a reasonable impact for heat discomfort during the summer and less cold discomfort during wintertime.

Experimental and Numerical Research of a Novel Combustion Chamber for Small Gas Turbine Engines

NASA Astrophysics Data System (ADS)

Tuma, J.; Kubata, J.; Betak, V.; Hybl, R.

2013-04-01

New combustion chamber concept (based on burner JETIS-JET Induced Swirl) for small gas turbine engine (up to 200kW) is presented in this article. The combustion chamber concept is based on the flame stabilization by the generated swirl swirl generated by two opposite tangentially arranged jet tubes in the intermediate zone, this arrangement replaces air swirler, which is very complicated and expensive part in the scope of small gas turbines with annular combustion chamber. The mixing primary jets are oriented partially opposite to the main exhaust gasses flow, this enhances hot product recirculation and fuel-air mixing necessary for low NOx production and flame stability. To evaluate the designed concept a JETIS burner demonstrator (methane fuel) was manufactured and atmospheric experimental measurements of CO, NOx for various fuel nozzles and jet tubes the configuration were done. Results of these experiments and comparison with CFD simulation are presented here. Practical application of the new chamber concept in small gas turbine liquid fuel combustor was evaluated (verified) on 3 nozzles planar combustor sector test rig at atmospheric conditions results of the experiment and numerical simulation are also presented.

Bayesian Modeling of Exposure and Airflow Using Two-Zone Models

PubMed Central

Zhang, Yufen; Banerjee, Sudipto; Yang, Rui; Lungu, Claudiu; Ramachandran, Gurumurthy

2009-01-01

Mathematical modeling is being increasingly used as a means for assessing occupational exposures. However, predicting exposure in real settings is constrained by lack of quantitative knowledge of exposure determinants. Validation of models in occupational settings is, therefore, a challenge. Not only do the model parameters need to be known, the models also need to predict the output with some degree of accuracy. In this paper, a Bayesian statistical framework is used for estimating model parameters and exposure concentrations for a two-zone model. The model predicts concentrations in a zone near the source and far away from the source as functions of the toluene generation rate, air ventilation rate through the chamber, and the airflow between near and far fields. The framework combines prior or expert information on the physical model along with the observed data. The framework is applied to simulated data as well as data obtained from the experiments conducted in a chamber. Toluene vapors are generated from a source under different conditions of airflow direction, the presence of a mannequin, and simulated body heat of the mannequin. The Bayesian framework accounts for uncertainty in measurement as well as in the unknown rate of airflow between the near and far fields. The results show that estimates of the interzonal airflow are always close to the estimated equilibrium solutions, which implies that the method works efficiently. The predictions of near-field concentration for both the simulated and real data show nice concordance with the true values, indicating that the two-zone model assumptions agree with the reality to a large extent and the model is suitable for predicting the contaminant concentration. Comparison of the estimated model and its margin of error with the experimental data thus enables validation of the physical model assumptions. The approach illustrates how exposure models and information on model parameters together with the knowledge of uncertainty and variability in these quantities can be used to not only provide better estimates of model outputs but also model parameters. PMID:19403840

KENNEDY SPACE CENTER, FLA. -- In the Space Life Sciences Lab, Lanfang Levine, with Dynamac Corp., transfers material into a sample bottle for analysis. She is standing in front of new equipment in the lab that will provide gas chromatography and mass spectrometry. The equipment will enable analysis of volatile compounds, such as from plants. The 100,000 square-foot facility houses labs for NASA’s ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASA’s Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASA’s Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

NASA Image and Video Library

2004-01-05

KENNEDY SPACE CENTER, FLA. -- In the Space Life Sciences Lab, Lanfang Levine, with Dynamac Corp., transfers material into a sample bottle for analysis. She is standing in front of new equipment in the lab that will provide gas chromatography and mass spectrometry. The equipment will enable analysis of volatile compounds, such as from plants. The 100,000 square-foot facility houses labs for NASA’s ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASA’s Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASA’s Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

Challenges Surrounding the Injection and Arrival of Targets at LIFE Fusion Chamber Center

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miles, R; Spaeth, M; Manes, K

2010-12-01

IFE target designers must consider several engineering requirements in addition to the physics requirements for successful target implosion. These considerations include low target cost, high manufacturing throughput, the ability of the target to survive the injection into the fusion chamber and arrive in a condition and physical position consistent with proper laser-target interaction and ease of post-implosion debris removal. This article briefly describes these considerations for the Laser Inertial Fusion-based Energy (LIFE) targets currently being designed.

Analysis of the laser ignition of methane/oxygen mixtures in a sub-scale rocket combustion chamber

NASA Astrophysics Data System (ADS)

Wohlhüter, Michael; Zhukov, Victor P.; Sender, Joachim; Schlechtriem, Stefan

2017-06-01

The laser ignition of methane/oxygen mixtures in a sub-scale rocket combustion chamber has been investigated numerically and experimentally. The ignition test case used in the present paper was generated during the In-Space Propulsion project (ISP-1), a project focused on the operation of propulsion systems in space, the handling of long idle periods between operations, and multiple reignitions under space conditions. Regarding the definition of the numerical simulation and the suitable domain for the current model, 2D and 3D simulations have been performed. Analysis shows that the usage of a 2D geometry is not suitable for this type of simulation, as the reduction of the geometry to a 2D domain significantly changes the conditions at the time of ignition and subsequently the flame development. The comparison of the numerical and experimental results shows a strong discrepancy in the pressure evolution and the combustion chamber pressure peak following the laser spark. The detailed analysis of the optical Schlieren and OH data leads to the conclusion that the pressure measurement system was not able to capture the strong pressure increase and the peak value in the combustion chamber during ignition. Although the timing in flame development following the laser spark is not captured appropriately, the 3D simulations reproduce the general ignition phenomena observed in the optical measurement systems, such as pressure evolution and injector flow characteristics.

Use, Assessment, and Improvement of the Loci-CHEM CFD Code for Simulation of Combustion in a Single Element GO2/GH2 Injector and Chamber

NASA Technical Reports Server (NTRS)

Westra, Douglas G.; Lin, Jeff; West, Jeff; Tucker, Kevin

2006-01-01

This document is a viewgraph presentation of a paper that documents a continuing effort at Marshall Space Flight Center (MSFC) to use, assess, and continually improve CFD codes to the point of material utility in the design of rocket engine combustion devices. This paper describes how the code is presently being used to simulate combustion in a single element combustion chamber with shear coaxial injectors using gaseous oxygen and gaseous hydrogen propellants. The ultimate purpose of the efforts documented is to assess and further improve the Loci-CHEM code and the implementation of it. Single element shear coaxial injectors were tested as part of the Staged Combustion Injector Technology (SCIT) program, where detailed chamber wall heat fluxes were measured. Data was taken over a range of chamber pressures for propellants injected at both ambient and elevated temperatures. Several test cases are simulated as part of the effort to demonstrate use of the Loci-CHEM CFD code and to enable us to make improvements in the code as needed. The simulations presented also include a grid independence study on hybrid grids. Several two-equation eddy viscosity low Reynolds number turbulence models are also evaluated as part of the study. All calculations are presented with a comparison to the experimental data. Weaknesses of the code relative to test data are discussed and continuing efforts to improve the code are presented.

Bayesian inversion of data from effusive volcanic eruptions using physics-based models: Application to Mount St. Helens 2004--2008

USGS Publications Warehouse

Anderson, Kyle; Segall, Paul

2013-01-01

Physics-based models of volcanic eruptions can directly link magmatic processes with diverse, time-varying geophysical observations, and when used in an inverse procedure make it possible to bring all available information to bear on estimating properties of the volcanic system. We develop a technique for inverting geodetic, extrusive flux, and other types of data using a physics-based model of an effusive silicic volcanic eruption to estimate the geometry, pressure, depth, and volatile content of a magma chamber, and properties of the conduit linking the chamber to the surface. A Bayesian inverse formulation makes it possible to easily incorporate independent information into the inversion, such as petrologic estimates of melt water content, and yields probabilistic estimates for model parameters and other properties of the volcano. Probability distributions are sampled using a Markov-Chain Monte Carlo algorithm. We apply the technique using GPS and extrusion data from the 2004–2008 eruption of Mount St. Helens. In contrast to more traditional inversions such as those involving geodetic data alone in combination with kinematic forward models, this technique is able to provide constraint on properties of the magma, including its volatile content, and on the absolute volume and pressure of the magma chamber. Results suggest a large chamber of >40 km3 with a centroid depth of 11–18 km and a dissolved water content at the top of the chamber of 2.6–4.9 wt%.

Liquid Behavior at Critical and Supercritical Conditions

NASA Technical Reports Server (NTRS)

Chiu, Huei-Huang; Gross, Klaus W.

1989-01-01

At a JANNAF workshop, the issue of fluids at and above the critical point was discussed to obtain a better understanding of similar conditions in combustion chambers of rocket engines. Invited experts from academic, industrial, and government institutions presented the most recent physical, numerical, and experimental advances. During the final discussion period, it was agreed that: (1) no analytical capability exists to simulate subject conditions; (2) mechanisms reflected by opalescence, the solubility of gases, other interfacial phenomena listed, and fluorescence diagnostics are new and important; (3) multicomponent mixtures, radiation, critical fluctuation, and other recorded ones pose unknown effects; and (4) various identified analytical and experimental actions must be initiated in a mutually supporting sequence.

Precise mapping of the magnetic field in the CMS barrel yoke using cosmic rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatrchyan, S.; et al.,

2010-03-01

The CMS detector is designed around a large 4 T superconducting solenoid, enclosed in a 12000-tonne steel return yoke. A detailed map of the magnetic field is required for the accurate simulation and reconstruction of physics events in the CMS detector, not only in the inner tracking region inside the solenoid but also in the large and complex structure of the steel yoke, which is instrumented with muon chambers. Using a large sample of cosmic muon events collected by CMS in 2008, the field in the steel of the barrel yoke has been determined with a precision of 3 tomore » 8% depending on the location.« less

Carbon Deposition Model for Oxygen-Hydrocarbon Combustion, Volume 2

NASA Technical Reports Server (NTRS)

Hernandez, R.; Ito, J. I.; Niiya, K. Y.

1987-01-01

Presented are details of the design, fabrication, and testing of subscale hardware used in the evaluation of carbon deposition characteristics of liquid oxygen and three hydrocarbon fuels for both main chamber and preburner/gas generator operating conditions. In main chamber conditions, the deposition of carbon on the combustion chamber wall was investigated at mixture ratios of 2.0 to 4.0 and at chamber pressures of 1000 to 1500 psia. No carbon deposition on chamber walls was detected at these main chamber mixture ratios. In preburner/gas generator operating conditions, the deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60 and at chamber pressures of 720 to 1650 psia. The results of the tests showed carbon deposition rate to be a strong function of mixture ratio and a weak function of chamber pressure. Further analyses evaluated the operational concequences of carbon deposition on preburner/gas generator performance. This is Volume 2 of the report, which contains data plots of all the test programs.

Concepts for dose determination in flat-detector CT

NASA Astrophysics Data System (ADS)

Kyriakou, Yiannis; Deak, Paul; Langner, Oliver; Kalender, Willi A.

2008-07-01

Flat-detector computed tomography (FD-CT) scanners provide large irradiation fields of typically 200 mm in the cranio-caudal direction. In consequence, dose assessment according to the current definition of the computed tomography dose index CTDIL=100 mm, where L is the integration length, would demand larger ionization chambers and phantoms which do not appear practical. We investigated the usefulness of the CTDI concept and practical dosimetry approaches for FD-CT by measurements and Monte Carlo (MC) simulations. An MC simulation tool (ImpactMC, VAMP GmbH, Erlangen, Germany) was used to assess the dose characteristics and was calibrated with measurements of air kerma. For validation purposes measurements were performed on an Axiom Artis C-arm system (Siemens Medical Solutions, Forchheim, Germany) equipped with a flat detector of 40 cm × 30 cm. The dose was assessed for 70 kV and 125 kV in cylindrical PMMA phantoms of 160 mm and 320 mm diameter with a varying phantom length from 150 to 900 mm. MC simulation results were compared to the values obtained with a calibrated ionization chambers of 100 mm and 250 mm length and to thermoluminesence (TLD) dose profiles. The MCs simulations were used to calculate the efficiency of the CTDIL determination with respect to the desired CTDI∞. Both the MC simulation results and the dose distributions obtained by MC simulation were in very good agreement with the CTDI measurements and with the reference TLD profiles, respectively, to within 5%. Standard CTDI phantoms which have a z-extent of 150 mm underestimate the dose at the center by up to 55%, whereas a z-extent of >=600 mm appears to be sufficient for FD-CT; the baseline value of the respective profile was within 1% to the reference baseline. As expected, the measurements with ionization chambers of 100 mm and 250 mm offer a limited accuracy, whereas an increased integration length of >=600 mm appeared to be necessary to approximate CTDI∞ in within 1%. MC simulations appear to offer a practical and accurate way of assessing conversion factors for arbitrary dosimetry setups using a standard pencil chamber to provide estimates of CTDI∞. This would eliminate the need for extra-long phantoms and ionization chambers or excessive amounts of TLDs.

Parametric investigation of secondary injection in post-chamber on combustion performance for hybrid rocket motor

NASA Astrophysics Data System (ADS)

Cai, Guobiao; Cao, Binbin; Zhu, Hao; Tian, Hui; Ma, Xuan

2017-11-01

The objective of this effort is to study the combustion performance of a hybrid rocket motor with the help of 3D steady-state numerical simulation, which applies 90% hydrogen peroxide as the oxidizer and hydroxyl-terminated polybutadiene as the fuel. A method of secondary oxidizer injection in post-chamber is introduced to investigate the flow field characteristics and combustion efficiency. The secondary injection medium is the mixed gas coming from liquid hydrogen peroxide catalytic decomposition. The secondary injectors are uniformly set along the circumferential direction of the post-chamber. The simulation results obtained by above model are verified by experimental data. Three influencing parameters are considered: secondary injection diameter, secondary injection angle and secondary injection numbers. Simulation results reveals that this design could improve the combustion efficiency with respect to the same motor without secondary injection. Besides, the secondary injection almost has no effect on the regression rate and fuel sueface temperature distribution. It is also presented that the oxidizer is injected by 8 secondary injectors with a diameter of 7-8 mm in the direction of 120°in post-chamber is identified as the optimized secondary injection pattern, through which combustion efficiency, specific impulse efficiency as well as utilization of propellants are all improved obviously.

Effects of the Canopy and Flux Tube Anchoring on Evaporation Flow of a Solar Flare

NASA Astrophysics Data System (ADS)

Unverferth, John; Longcope, Dana

2018-06-01

Spectroscopic observations of flare ribbons typically show chromospheric evaporation flows, which are subsonic for their high temperatures. This contrasts with many numerical simulations where evaporation is typically supersonic. These simulations typically assume flow along a flux tube with a uniform cross-sectional area. A simple model of the magnetic canopy, however, includes many regions of low magnetic field strength, where flux tubes achieve local maxima in their cross-sectional area. These are analgous to a chamber in a flow tube. We find that one-third of all field lines in a model have some form of chamber through which evaporation flow must pass. Using a one-dimensional isothermal hydrodynamic code, we simulated supersonic flow through an assortment of chambers and found that a subset of solutions exhibit a stationary standing shock within the chamber. These shocked solutions have slower and denser upflows than a flow through a uniform tube would. We use our solution to construct synthetic spectral lines and find that the shocked solutions show higher emission and lower Doppler shifts. When these synthetic lines are combined into an ensemble representing a single canopy cell, the composite line appears slower, even subsonic, than expected due to the outsized contribution from shocked solutions.

HABEBEE: habitability of eyeball-exo-Earths.

PubMed

Angerhausen, Daniel; Sapers, Haley; Citron, Robert; Bergantini, Alexandre; Lutz, Stefanie; Queiroz, Luciano Lopes; da Rosa Alexandre, Marcelo; Araujo, Ana Carolina Vieira

2013-03-01

Extrasolar Earth and super-Earth planets orbiting within the habitable zone of M dwarf host stars may play a significant role in the discovery of habitable environments beyond Earth. Spectroscopic characterization of these exoplanets with respect to habitability requires the determination of habitability parameters with respect to remote sensing. The habitable zone of dwarf stars is located in close proximity to the host star, such that exoplanets orbiting within this zone will likely be tidally locked. On terrestrial planets with an icy shell, this may produce a liquid water ocean at the substellar point, one particular "Eyeball Earth" state. In this research proposal, HABEBEE: exploring the HABitability of Eyeball-Exo-Earths, we define the parameters necessary to achieve a stable icy Eyeball Earth capable of supporting life. Astronomical and geochemical research will define parameters needed to simulate potentially habitable environments on an icy Eyeball Earth planet. Biological requirements will be based on detailed studies of microbial communities within Earth analog environments. Using the interdisciplinary results of both the physical and biological teams, we will set up a simulation chamber to expose a cold- and UV-tolerant microbial community to the theoretically derived Eyeball Earth climate states, simulating the composition, atmosphere, physical parameters, and stellar irradiation. Combining the results of both studies will enable us to derive observable parameters as well as target decision guidance and feasibility analysis for upcoming astronomical platforms.

Three-dimensional particle simulation of back-sputtered carbon in electric propulsion test facility

NASA Astrophysics Data System (ADS)

Zheng, Hongru; Cai, Guobiao; Liu, Lihui; Shang, Shengfei; He, Bijiao

2017-03-01

The back-sputtering deposition on thruster surface caused by ion bombardment on chamber wall material affects the performance of thrusters during the ground based electric propulsion endurance tests. In order to decrease the back-sputtering deposition, most of vacuum chambers applied in electric propulsion experiments are equipped with anti-sputtering targets. In this paper, a three-dimensional model of plume experimental system (PES) including double layer anti-sputtering target is established. Simulation cases are made to simulate the plasma environment and sputtering effects when an ion thruster is working. The particle in cell (PIC) method and direct simulation Monte Carlo (DSMC) method is used to calculate the velocity and position of particles. Yamamura's model is used to simulate the sputtering process. The distribution of sputtered anti-sputtering target material is presented. The results show that the double layer anti-sputtering target can significantly reduce the deposition on thruster surface. The back-sputtering deposition rates on thruster exit surface for different cases are compared. The chevrons on the secondary target are rearranged to improve its performance. The position of secondary target has relation with the ion beam divergence angle, and the radius of the vacuum chamber. The back-sputtering deposition rate is lower when the secondary target covers the entire ion beam.

LETS: Lunar Environments Test System

NASA Technical Reports Server (NTRS)

Vaughn, Jason A.; Schneider, Todd; Craven, Paul; Norwood, Joey

2008-01-01

The Environmental Effects Branch (EM50) at the Marshall Space Flight Center has developed a unique capability within the agency, namely the Lunar Environment Test System (LETS). LETS is a cryo-pumped vacuum chamber facility capable of high vacuum (10-7 Torr). LETS is a cylindrical chamber, 30 in. (0.8 m) diameter by 48 in. (1.2 m) long thermally controlled vacuum system. The chamber is equipped with a full array of radiation sources including vacuum ultraviolet, electron, and proton radiation. The unique feature of LETS is that it contains a large lunar simulant bed (18 in. x 40 in. x 6 in.) holding 75 kg of JSC-1a simulant while operating at a vacuum of 10-7 Torr. This facility allows three applications: 1) to study the charging, levitation and migration of dust particles, 2) to simulate the radiation environment on the lunar surface, and 3) to electrically charge the lunar simulant enhancing the attraction and adhesion of dust particles to test articles more closely simulating the lunar surface dust environment. LETS has numerous diagnostic instruments including TREK electrostatic probes, residual gas analyzer (RGA), temperature controlled quartz crystal microbalance (TQCM), and particle imaging velocimeter (PIV). Finally, LETS uses continuous Labview data acquisition for computer monitoring and system control.

Characterization of Gas Transport Properties of Fractured Rocks By Borehole and Chamber Tests.

NASA Astrophysics Data System (ADS)

Shimo, M.; Shimaya, S.; Maejima, T.

2014-12-01

Gas transport characteristics of fractured rocks is a great concern to variety of engineering applications such as underground storage of LPG, nuclear waste disposal, CCS and gas flooding in the oil field. Besides absolute permeability, relative permeability and capillary pressure as a function of water saturation have direct influences to the results of two phase flow simulation. However, number of the reported gas flow tests for fractured rocks are limited, therefore, the applicability of the conventional two-phase flow functions used for porous media, such as Mualem-van Genuchten model, to prediction of the gas transport in the fractured rock mass are not well understood. The authors conducted the two types of in-situ tests, with different scales, a borehole gas-injection test and a chamber gas-injection test in fractured granitic rock. These tests were conducted in the Cretaceous granitic rocks at the Namikata underground LPG storage cavern construction site in Ehime Prefecture in Japan, preceding to the cavern scale gas-tightness test. A borehole injection test was conducted using vertical and sub-vertical boreholes drilled from the water injection tunnel nearly at the depth of the top of the cavern, EL-150m. A new type downhole gas injection equipment that is capable to create a small 'cavern' within a borehole was developed. After performing a series of preliminary tests to investigate the hydraulic conductivity and gas-tightness, i.e. threshold pressure, gas injection tests were conducted under different gas pressure. Fig.1 shows an example of the test results From a chamber test using a air pressurizing chamber with volume of approximately166m3, the gas-tightness was confirmed within the uncertainty of 22Pa under the storage pressure of 0.7MPa, however, significant air leakage occurred possibly through an open fracture intersecting the chamber just after cavern pressure exceeds the initial hydrostatic pressure at the ceiling level of the chamber. Anomalies were detected in the data of the pore pressure as well as AE monitoring around the chamber. Results from the above two tests were simulated using a multi-phase transport simulator, TOUGH2, developed at Lawrence Berkeley National Laboratory. Fig.2 shows the model and an example of the simulation.

Sea spray as a source of ice nucleating particles - results from the AIDA Ocean03 campaign

NASA Astrophysics Data System (ADS)

Salter, M. E.; Ickes, L.; Adams, M.; Bierbauer, S.; Bilde, M.; Christiansen, S.; Ekman, A.; Gorokhova, E.; Höhler, K.; Kiselev, A. A.; Leck, C.; Mohr, C.; Mohler, O.; Murray, B. J.; Porter, G.; Ullrich, R.; Wagner, R.

2017-12-01

Clouds and their radiative effects are one of the major influences on the radiative fluxes in the atmosphere, but at the same time they remain the largest uncertainty in climate models. This lack of understanding is especially pronounced in the high Arctic. Summertime clouds can persist over long periods in this region, which is difficult to replicate in models based on our current understanding. The clouds most often encountered in the summertime high Arctic consist of a mixture of ice crystals and super-cooled water droplets, so-called mixed-phase clouds. This cloud type is sensitive to the availability of aerosol particles, which can act as cloud condensation nuclei and ice nuclei. However, since the high Arctic is a pristine region, aerosol particles are not very abundant, and the hypothesis of open leads in the Arctic as a potentially important source of cloud and ice nucleating particles via bubble bursting has emerged. In this context, we have conducted a series of experiments at the AIDA chamber at KIT, designed to investigate the mechanisms linking marine biology, seawater chemistry and aerosol physics/potential cloud impacts. During this campaign, two marine diatom species (Melosira arctica and Skeletonema marinoi) as well as sea surface microlayer samples collected during several Arctic Ocean research cruises were investigated. To aerosolize the samples, a variety of methods were used including a sea spray simulation chamber to mimic the process of bubble-bursting. The ice nucleating efficiency (mixed-phase cloud regime) of the samples was determined either directly in the AIDA chamber during adiabatic expansions, or using the INKA continuous flow diffusion chamber, or a cold stage. Results from the campaign along with the potential implications are presented.

Chamber measurement of surface-atmosphere trace gas exchange: Numerical evaluation of dependence on soil, interfacial layer, and source/sink properties

NASA Astrophysics Data System (ADS)

Hutchinson, G. L.; Livingston, G. P.; Healy, R. W.; Striegl, R. G.

2000-04-01

We employed a three-dimensional finite difference gas diffusion model to simulate the performance of chambers used to measure surface-atmosphere trace gas exchange. We found that systematic errors often result from conventional chamber design and deployment protocols, as well as key assumptions behind the estimation of trace gas exchange rates from observed concentration data. Specifically, our simulations showed that (1) when a chamber significantly alters atmospheric mixing processes operating near the soil surface, it also nearly instantaneously enhances or suppresses the postdeployment gas exchange rate, (2) any change resulting in greater soil gas diffusivity, or greater partitioning of the diffusing gas to solid or liquid soil fractions, increases the potential for chamber-induced measurement error, and (3) all such errors are independent of the magnitude, kinetics, and/or distribution of trace gas sources, but greater for trace gas sinks with the same initial absolute flux. Finally, and most importantly, we found that our results apply to steady state as well as non-steady-state chambers, because the slow rate of gas diffusion in soil inhibits recovery of the former from their initial non-steady-state condition. Over a range of representative conditions, the error in steady state chamber estimates of the trace gas flux varied from -30 to +32%, while estimates computed by linear regression from non-steady-state chamber concentrations were 2 to 31% too small. Although such errors are relatively small in comparison to the temporal and spatial variability characteristic of trace gas exchange, they bias the summary statistics for each experiment as well as larger scale trace gas flux estimates based on them.

FULL-SCALE CHAMBER INVESTIGATION AND SIMULATION OF AIR FRESHENER EMISSIONS IN THE PRESENCE OF OZONE

EPA Science Inventory

The paper discusses results of tests, conducted in the EPA large chamber facility, determining emissions and chemical degradation of volatile organic compounds (VOCs) from one electrical plug-in type pine-scented air freshener in the presence of ozone supplied by a device markete...

Hadrons registration in emulsion chamber with carbon block

NASA Technical Reports Server (NTRS)

Tomaszewski, A.; Wlodarczyk, Z.

1985-01-01

Nuclear-electro-magnetic cascade (NEC) in X-ray emulsion chambers with carbon block, which are usually used in the Pamir experiment, was Monte-Carlo simulated. Going over from optical density to Summary E sub gamma is discussed. The hole of NEC in the interpretation of energy spectra is analyzed.

Evaluating the storage environment in hypobaric chambers used for disinfesting fresh fruits

USDA-ARS?s Scientific Manuscript database

Low pressure (LP) treatment has potential as an alternative non-chemical postharvest disinfestation method for fresh fruits. A validated computer simulation model was used to determine the thickness of insulation foam needed to cover the hypobaric chamber walls in order to stabilize the air temperat...

EMISSIONS OF TRACE PRODUCTS OF INCOMPLETE COMBUSTION FROM A PILOT-SCALE INCINERATOR SECONDARY COMBUSTION CHAMBER

EPA Science Inventory

Experiments were performed on a 73 kW rotary kiln incinerator simulator equipped with a 73 kW secondary combustion chamber (SCC) to examine emissions of products of incomplete combustion (PICs) resulting from incineration of carbon tetrachloride (CCl₄) and dichlorometh...

Is Climate Simulation in Growth Chambers Necessary?

Treesearch

Z.M. Wang; K.H. Johnsen; M.J. Lechowicz

1999-01-01

In the expression of their genetic potential as phenotypes, trees respond to environmental cues such as photoperiod, temperature and soil and atmospheric water. However, growth chamber experiments often utilize simple and standard environmental conditions that might not provide these important environmental signals. We conducted a study to compare seedling growth in...

Seed Planting in Veggie Pillows

NASA Image and Video Library

2017-08-08

Water and nutrients are being added to plants in the Veggie hardware in NASA Kennedy Space Center's ISS environment simulator chamber. Mizuna mustard, Outredgeous lettuce and Waldmann's green lettuce are growing in Veggie. Growth in the chamber mimics the growth of plant experiments in the Veggie plant growth system on the International Space Station.

Extraction of Thermal Performance Values from Samples in the Lunar Dust Adhesion Bell Jar

NASA Technical Reports Server (NTRS)

Gaier, James R.; Siamidis, John; Larkin, Elizabeth M. G.

2008-01-01

A simulation chamber has been developed to test the performance of thermal control surfaces under dusty lunar conditions. The lunar dust adhesion bell jar (LDAB) is a diffusion pumped vacuum chamber (10(exp -8) Torr) built to test material samples less than about 7 cm in diameter. The LDAB has the following lunar dust simulant processing capabilities: heating and cooling while stirring in order to degas and remove adsorbed water; RF air-plasma for activating the dust and for organic contaminant removal; RF H/He-plasma to simulate solar wind; dust sieving system for controlling particle sizes; and a controlled means of introducing the activated dust to the samples under study. The LDAB is also fitted with an in situ Xe arc lamp solar simulator, and a cold box that can reach 30 K. Samples of thermal control surfaces (2.5 cm diameter) are introduced into the chamber for calorimetric evaluation using thermocouple instrumentation. The object of this paper is to present a thermal model of the samples under test conditions and to outline the procedure to extract the absorptance, emittance, and thermal efficiency from the pristine and sub-monolayer dust covered samples.

Extraction of Thermal Performance Values from Samples in the Lunar Dust Adhesion Bell Jar

NASA Technical Reports Server (NTRS)

Gaier, James R.; Siamidis, John; Larkin, Elizabeth M. G.

2010-01-01

A simulation chamber has been developed to test the performance of thermal control surfaces under dusty lunar conditions. The lunar dust adhesion bell jar (LDAB) is a diffusion pumped vacuum chamber (10(exp -8) Torr) built to test material samples less than about 7 cm in diameter. The LDAB has the following lunar dust simulant processing capabilities: heating and cooling while stirring in order to degas and remove adsorbed water; RF air-plasma for activating the dust and for organic contaminant removal; RF H/He-plasma to simulate solar wind; dust sieving system for controlling particle sizes; and a controlled means of introducing the activated dust to the samples under study. The LDAB is also fitted with an in situ Xe arc lamp solar simulator, and a cold box that can reach 30 K. Samples of thermal control surfaces (2.5 cm diameter) are introduced into the chamber for calorimetric evaluation using thermocouple instrumentation. The object of this paper is to present a thermal model of the samples under test conditions and to outline the procedure to extract the absorptance, emittance, and thermal efficiency from the pristine and sub-monolayer dust covered samples.

Evaluation of radioisotope tracer and activation analysis techniques for contamination monitoring in space environment simulation chambers

NASA Technical Reports Server (NTRS)

Smathers, J. B.; Kuykendall, W. E., Jr.; Wright, R. E., Jr.; Marshall, J. R.

1973-01-01

Radioisotope measurement techniques and neutron activation analysis are evaluated for use in identifying and locating contamination sources in space environment simulation chambers. The alpha range method allows the determination of total contaminant concentration in vapor state and condensate state. A Cf-252 neutron activation analysis system for detecting oils and greases tagged with stable elements is described. While neutron activation analysis of tagged contaminants offers specificity, an on-site system is extremely costly to implement and provides only marginal detection sensitivity under even the most favorable conditions.

CFD Simulation on the J-2X Engine Exhaust in the Center-Body Diffuser and Spray Chamber at the B-2 Facility

NASA Technical Reports Server (NTRS)

Wang, Xiao-Yen; Wey, Thomas; Buehrle, Robert

2009-01-01

A computational fluid dynamic (CFD) code is used to simulate the J-2X engine exhaust in the center-body diffuser and spray chamber at the Spacecraft Propulsion Facility (B-2). The CFD code is named as the space-time conservation element and solution element (CESE) Euler solver and is very robust at shock capturing. The CESE results are compared with independent analysis results obtained by using the National Combustion Code (NCC) and show excellent agreement.

A full scale hydrodynamic simulation of pyrotechnic combustion

NASA Astrophysics Data System (ADS)

Kim, Bohoon; Jang, Seung-Gyo; Yoh, Jack

2017-06-01

A full scale hydrodynamic simulation that requires an accurate reproduction of shock-induced detonation was conducted for design of an energetic component system. A series of small scale gap tests and detailed hydrodynamic simulations were used to validate the reactive flow model for predicting the shock propagation in a train configuration and to quantify the shock sensitivity of the energetic materials. The energetic component system is composed of four main components, namely a donor unit (HNS + HMX), a bulkhead (STS), an acceptor explosive (RDX), and a propellant (BKNO3) for gas generation. The pressurized gases generated from the burning propellant were purged into a 10 cc release chamber for study of the inherent oscillatory flow induced by the interferences between shock and rarefaction waves. The pressure fluctuations measured from experiment and calculation were investigated to further validate the peculiar peak at specific characteristic frequency (ωc = 8.3 kHz). In this paper, a step-by-step numerical description of detonation of high explosive components, deflagration of propellant component, and deformation of metal component is given in order to facilitate the proper implementation of the outlined formulation into a shock physics code for a full scale hydrodynamic simulation of the energetic component system.

A two dimensional finite difference time domain analysis of the quiet zone fields of an anechoic chamber

NASA Technical Reports Server (NTRS)

Ryan, Deirdre A.; Luebbers, Raymond J.; Nguyen, Truong X.; Kunz, Karl S.; Steich, David J.

1992-01-01

Prediction of anechoic chamber performance is a difficult problem. Electromagnetic anechoic chambers exist for a wide range of frequencies but are typically very large when measured in wavelengths. Three dimensional finite difference time domain (FDTD) modeling of anechoic chambers is possible with current computers but at frequencies lower than most chamber design frequencies. However, two dimensional FDTD (2D-FTD) modeling enables much greater detail at higher frequencies and offers significant insight into compact anechoic chamber design and performance. A major subsystem of an anechoic chamber for which computational electromagnetic analyses exist is the reflector. First, an analysis of the quiet zone fields of a low frequency anechoic chamber produced by a uniform source and a reflector in two dimensions using the FDTD method is presented. The 2D-FDTD results are compared with results from a three dimensional corrected physical optics calculation and show good agreement. Next, a directional source is substituted for the uniform radiator. Finally, a two dimensional anechoic chamber geometry, including absorbing materials, is considered, and the 2D-FDTD results for these geometries appear reasonable.

Analysis of Heat Stress and the Indoor Climate Control Requirements for Movable Refuge Chambers

PubMed Central

Hao, Xiaoli; Guo, Chenxin; Lin, Yaolin; Wang, Haiqiao; Liu, Heqing

2016-01-01

Movable refuge chambers are a new kind of rescue device for underground mining, which is believed to have a potential positive impact on reducing the rate of fatalities. It is likely to be hot and humid inside a movable refuge chamber due to the metabolism of trapped miners, heat generated by equipment and heat transferred from outside. To investigate the heat stress experienced by miners trapped in a movable refuge chamber, the predicted heat strain (PHS) model was used to simulate the heat transfer process between the person and the thermal environment. The variations of heat stress with the temperature and humidity inside the refuge chamber were analyzed. The effects of air temperature outside the refuge chamber and the overall heat transfer coefficient of the refuge chamber shell on the heat stress inside the refuge chamber was also investigated. The relationship between the limit of exposure duration and the air temperature and humidity was numerically analyzed to determine the upper limits of temperature and humidity inside a refuge chamber. Air temperature of 32 °C and relative humidity of 70% are recommended as the design standard for internal thermal environment control of movable refuge chambers. PMID:27213422

Analysis of Heat Stress and the Indoor Climate Control Requirements for Movable Refuge Chambers.

PubMed

Hao, Xiaoli; Guo, Chenxin; Lin, Yaolin; Wang, Haiqiao; Liu, Heqing

2016-05-20

Movable refuge chambers are a new kind of rescue device for underground mining, which is believed to have a potential positive impact on reducing the rate of fatalities. It is likely to be hot and humid inside a movable refuge chamber due to the metabolism of trapped miners, heat generated by equipment and heat transferred from outside. To investigate the heat stress experienced by miners trapped in a movable refuge chamber, the predicted heat strain (PHS) model was used to simulate the heat transfer process between the person and the thermal environment. The variations of heat stress with the temperature and humidity inside the refuge chamber were analyzed. The effects of air temperature outside the refuge chamber and the overall heat transfer coefficient of the refuge chamber shell on the heat stress inside the refuge chamber was also investigated. The relationship between the limit of exposure duration and the air temperature and humidity was numerically analyzed to determine the upper limits of temperature and humidity inside a refuge chamber. Air temperature of 32 °C and relative humidity of 70% are recommended as the design standard for internal thermal environment control of movable refuge chambers.

2D convolution kernels of ionization chambers used for photon-beam dosimetry in magnetic fields: the advantage of small over large chamber dimensions

NASA Astrophysics Data System (ADS)

Khee Looe, Hui; Delfs, Björn; Poppinga, Daniela; Harder, Dietrich; Poppe, Björn

2018-04-01

This study aims at developing an optimization strategy for photon-beam dosimetry in magnetic fields using ionization chambers. Similar to the familiar case in the absence of a magnetic field, detectors should be selected under the criterion that their measured 2D signal profiles M(x,y) approximate the absorbed dose to water profiles D(x,y) as closely as possible. Since the conversion of D(x,y) into M(x,y) is known as the convolution with the ‘lateral dose response function’ K(x-ξ, y-η) of the detector, the ideal detector would be characterized by a vanishing magnetic field dependence of this convolution kernel (Looe et al 2017b Phys. Med. Biol. 62 5131–48). The idea of the present study is to find out, by Monte Carlo simulation of two commercial ionization chambers of different size, whether the smaller chamber dimensions would be instrumental to approach this aim. As typical examples, the lateral dose response functions in the presence and absence of a magnetic field have been Monte-Carlo modeled for the new commercial ionization chambers PTW 31021 (‘Semiflex 3D’, internal radius 2.4 mm) and PTW 31022 (‘PinPoint 3D’, internal radius 1.45 mm), which are both available with calibration factors. The Monte-Carlo model of the ionization chambers has been adjusted to account for the presence of the non-collecting part of the air volume near the guard ring. The Monte-Carlo results allow a comparison between the widths of the magnetic field dependent photon fluence response function K M(x-ξ, y-η) and of the lateral dose response function K(x-ξ, y-η) of the two chambers with the width of the dose deposition kernel K D(x-ξ, y-η). The simulated dose and chamber signal profiles show that in small photon fields and in the presence of a 1.5 T field the distortion of the chamber signal profile compared with the true dose profile is weakest for the smaller chamber. The dose responses of both chambers at large field size are shown to be altered by not more than 2% in magnetic fields up to 1.5 T for all three investigated chamber orientations.

Study of the effective point of measurement for ion chambers in electron beams by Monte Carlo simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, L. L. W.; Rogers, D. W. O.

In current dosimetry protocols for electron beams, for plane-parallel chambers, the effective point of measurement is at the front face of the cavity, and, for cylindrical chambers, it is at a point shifted 0.5r upstream from the cavity center. In this study, Monte Carlo simulations are employed to study the issue of effective point of measurement for both plane-parallel chambers and cylindrical thimble chambers in electron beams. It is found that there are two ways of determining the position of the effective point of measurement: One is to match the calculated depth-ionization curve obtained from a modeled chamber to amore » calculated depth-dose curve; the other is to match the electron fluence spectrum in the chamber cavity to that in the phantom. For plane-parallel chambers, the effective point of measurement determined by the first method is generally not at the front face of the chamber cavity, which is obtained by the second method, but shifted downstream toward the cavity center by an amount that could be larger than one-half a millimeter. This should not be ignored when measuring depth-dose curves in electron beams. For cylindrical chambers, these two methods also give different positions of the effective point of measurement: The first gives a shift of 0.5r, which is in agreement with measurements for high-energy beams and is the same as the value currently used in major dosimetry protocols; the latter gives a shift of 0.8r, which is closer to the value predicted by a theoretical calculation assuming no-scatter conditions. The results also show that the shift of 0.8r is more appropriate if the cylindrical chamber is to be considered as a Spencer-Attix cavity. In electron beams, since the water/air stopping-power ratio changes with depth in a water phantom, the difference of the two shifts (0.3r) will lead to an incorrect evaluation of the water/air stopping-power ratio at the point of measurement, thus resulting in a systematic error in determining the absorbed dose by cylindrical chambers. It is suggested that a shift of 0.8r be used for electron beam calibrations with cylindrical chambers and a shift of 0.4r-0.5r be used for depth-dose measurements.« less

Study of the effective point of measurement for ion chambers in electron beams by Monte Carlo simulation.

PubMed

Wang, L L W; Rogers, D W O

2009-06-01

In current dosimetry protocols for electron beams, for plane-parallel chambers, the effective point of measurement is at the front face of the cavity, and, for cylindrical chambers, it is at a point shifted 0.5r upstream from the cavity center. In this study, Monte Carlo simulations are employed to study the issue of effective point of measurement for both plane-parallel chambers and cylindrical thimble chambers in electron beams. It is found that there are two ways of determining the position of the effective point of measurement: One is to match the calculated depth-ionization curve obtained from a modeled chamber to a calculated depth-dose curve; the other is to match the electron fluence spectrum in the chamber cavity to that in the phantom. For plane-parallel chambers, the effective point of measurement determined by the first method is generally not at the front face of the chamber cavity, which is obtained by the second method, but shifted downstream toward the cavity center by an amount that could be larger than one-half a millimeter. This should not be ignored when measuring depth-dose curves in electron beams. For cylindrical chambers, these two methods also give different positions of the effective point of measurement: The first gives a shift of 0.5r, which is in agreement with measurements for high-energy beams and is the same as the value currently used in major dosimetry protocols; the latter gives a shift of 0.8r, which is closer to the value predicted by a theoretical calculation assuming no-scatter conditions. The results also show that the shift of 0.8r is more appropriate if the cylindrical chamber is to be considered as a Spencer-Attix cavity. In electron beams, since the water/air stopping-power ratio changes with depth in a water phantom, the difference of the two shifts (0.3r) will lead to an incorrect evaluation of the water/air stopping-power ratio at the point of measurement, thus resulting in a systematic error in determining the absorbed dose by cylindrical chambers. It is suggested that a shift of 0.8r be used for electron beam calibrations with cylindrical chambers and a shift of 0.4r-0.5r be used for depth-dose measurements.

Pulsed fusion space propulsion: Computational Magneto-Hydro Dynamics of a multi-coil parabolic reaction chamber

NASA Astrophysics Data System (ADS)

Romanelli, Gherardo; Mignone, Andrea; Cervone, Angelo

2017-10-01

Pulsed fusion propulsion might finally revolutionise manned space exploration by providing an affordable and relatively fast access to interplanetary destinations. However, such systems are still in an early development phase and one of the key areas requiring further investigations is the operation of the magnetic nozzle, the device meant to exploit the fusion energy and generate thrust. One of the last pulsed fusion magnetic nozzle design is the so called multi-coil parabolic reaction chamber: the reaction is thereby ignited at the focus of an open parabolic chamber, enclosed by a series of coaxial superconducting coils that apply a magnetic field. The field, beside confining the reaction and preventing any contact between hot fusion plasma and chamber structure, is also meant to reflect the explosion and push plasma out of the rocket. Reflection is attained thanks to electric currents induced in conductive skin layers that cover each of the coils, the change of plasma axial momentum generates thrust in reaction. This working principle has yet to be extensively verified and computational Magneto-Hydro Dynamics (MHD) is a viable option to achieve that. This work is one of the first detailed ideal-MHD analysis of a multi-coil parabolic reaction chamber of this kind and has been completed employing PLUTO, a freely distributed computational code developed at the Physics Department of the University of Turin. The results are thus a preliminary verification of the chamber's performance. Nonetheless, plasma leakage through the chamber structure has been highlighted. Therefore, further investigations are required to validate the chamber design. Implementing a more accurate physical model (e.g. Hall-MHD or relativistic-MHD) is thus mandatory, and PLUTO shows the capabilities to achieve that.

Assessment of ionization chamber correction factors in photon beams using a time saving strategy with PENELOPE code.

PubMed

Reis, C Q M; Nicolucci, P

2016-02-01

The purpose of this study was to investigate Monte Carlo-based perturbation and beam quality correction factors for ionization chambers in photon beams using a saving time strategy with PENELOPE code. Simulations for calculating absorbed doses to water using full spectra of photon beams impinging the whole water phantom and those using a phase-space file previously stored around the point of interest were performed and compared. The widely used NE2571 ionization chamber was modeled with PENELOPE using data from the literature in order to calculate absorbed doses to the air cavity of the chamber. Absorbed doses to water at reference depth were also calculated for providing the perturbation and beam quality correction factors for that chamber in high energy photon beams. Results obtained in this study show that simulations with phase-space files appropriately stored can be up to ten times shorter than using a full spectrum of photon beams in the input-file. Values of kQ and its components for the NE2571 ionization chamber showed good agreement with published values in the literature and are provided with typical statistical uncertainties of 0.2%. Comparisons to kQ values published in current dosimetry protocols such as the AAPM TG-51 and IAEA TRS-398 showed maximum percentage differences of 0.1% and 0.6% respectively. The proposed strategy presented a significant efficiency gain and can be applied for a variety of ionization chambers and clinical photon beams. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Creating the Thermal Environment for Safely Testing the James Webb Space Telescope at the Johnson Space Center's Chamber A

NASA Technical Reports Server (NTRS)

Homan, Jonathan L.; Lauterbach, John; Garcia, Sam

2016-01-01

Chamber A is the largest thermal vacuum chamber at the Johnson Space Center and is one of the largest space environment chambers in the world. The chamber is 19.8 m (65 ft) in diameter and 36.6 m (120 ft) tall and is equipped with cryogenic liquid nitrogen panels (shrouds) and gaseous helium shrouds to create a simulated space environment. The chamber was originally built to support testing of the Apollo Service and Command Module for lunar missions, but underwent major modifications to be able to test the James Webb Space Telescope in a simulated deep space environment. To date seven tests have been performed in preparation of testing the flight optics for the James Webb Space Telescope (JWST). Each test has had a uniquie thermal profile and set of thermal requirements for cooling down and warming up, controlling contamination, and releasing condensed air. These range from temperatures from 335K to 15K, with tight uniformity and controllability for maintining thermal stability and pressure control. One unique requirement for two test was structurally proof loading hardware by creating thermal gradients at specific temperatures. This paper will discuss the thermal requirements and goals of the tests, the original requirements of the chamber thermal systems for planned operation, and how the new requirements were met by the team using the hardware, system flexiblilty, and engineering creativity. It will also discuss the mistakes and successes to meet the unique goals, especially when meeting the thermal proof load.

Secondary organic aerosol formation from isoprene photo-oxidation during cloud condensation-evaporation cycles (CUMULUS project)

NASA Astrophysics Data System (ADS)

Brégonzio-Rozier, Lola; Siekmann, Frank; Giorio, Chiara; Temime-Roussel, Brice; Pangui, Edouard; Morales, Sébastien; Gratien, Aline; Ravier, Sylvain; Monod, Anne; Doussin, Jean-Francois

2014-05-01

It is acknowledged that atmospheric photo-oxidation of Volatile Organic Compounds (VOC) leads to the formation of less volatile oxidized species. These compounds can undergo gas-to-particle conversion, leading to the formation of Secondary Organic Aerosols (SOA) in the atmosphere. Nevertheless, some of these oxidized species are water soluble and could also partition into cloud droplets. Higher molecular weight and less volatile compounds could be produced in the aqueous phase and remain in the particle phase after water evaporation (Ervens et al., 2011). The aim of the present work is to study SOA formation in the presence of cloud droplets during isoprene photo-oxidation. To this end, an original multiphase approach in a simulation chamber was set up in order to investigate the chemistry occurring in the gaseous, particulate and aqueous phases, and the exchange between these phases. Experiments were performed, within the CUMULUS project (CloUd MULtiphase chemistry of organic compoUndS in the troposphere), in the CESAM chamber (Wang et al., 2011). This chamber was designed to investigate multiphase processes under realistic actinic flux, and accurate control of both temperature and relative humidity. A specific protocol was set up to produce cloud events in the simulation chamber exhibiting a significant lifetime in the presence of light (10-12 minutes). By using this protocol, many clouds could be generated in a single experiment. In each experiment, around 800 ppb of isoprene was injected in the chamber together with HONO under dry conditions before irradiation. A Fourier Transform Infrared Spectrometer (FTIR), a Proton Transfer Reaction Mass Spectrometer (PTR-TOF-MS) and NOx and O3 analyzers were used to analyze gas-phase composition. Dried SOA size distributions and total concentrations were measured by a Scanning Mobility Particle Sizer (SMPS). An Aerodyne High Resolution Time-Of-Flight Aerosol Mass Spectrometer (HR-TOF-AMS) was also used to investigate aerosol composition. Cloud droplets size distributions were measured by a white light Optical Particle Counter (OPC). In all experiments, the dissolution of gaseous oxidation products into aqueous phase and SOA production have been observed during isoprene photo-oxidation in the presence of a cloud event. The overall results in additional SOA mass production and the dynamic of gaseous oxidation products and SOA mass concentrations will be presented. Ervens, B. et al. (2011). Atmospheric Chemistry and Physics 11(21): 11069-11102. Wang, J. et al. (2011). Atmospheric Measurement Techniques 4(11): 2465-2494.

Whistler wave propagation in the antenna near and far fields in the Naval Research Laboratory Space Physics Simulation Chamber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blackwell, David D.; Walker, David N.; Amatucci, William E.

2010-01-15

In previous papers, early whistler propagation measurements were presented [W. E. Amatucci et al., IEEE Trans. Plasma Sci. 33, 637 (2005)] as well as antenna impedance measurements [D. D. Blackwell et al., Phys. Plasmas 14, 092106 (2007)] performed in the Naval Research Laboratory Space Physics Simulation Chamber (SPSC). Since that time there have been major upgrades in the experimental capabilities of the laboratory in the form of improvement of both the plasma source and antennas. This has allowed access to plasma parameter space that was previously unattainable, and has resulted in measurements that provide a significantly clearer picture of whistlermore » propagation in the laboratory environment. This paper presents some of the first whistler experimental results from the upgraded SPSC. Whereas previously measurements were limited to measuring the cyclotron resonance cutoff and elliptical polarization indicative of the whistler mode, now it is possible to experimentally plot the dispersion relation itself. The waves are driven and detected using balanced dipole and loop antennas connected to a network analyzer, which measures the amplitude and phase of the wave in two dimensions (r and z). In addition the frequency of the signals is also swept over a range of several hundreds of megahertz, providing a comprehensive picture of the near and far field antenna radiation patterns over a variety of plasma conditions. The magnetic field is varied from a few gauss to 200 G, with the density variable over at least 3 decades from 10{sup 7} to 10{sup 10} cm{sup -3}. The waves are shown to lie on the dispersion surface for whistler waves, with observation of resonance cones in agreement with theoretical predictions. The waves are also observed to propagate without loss of amplitude at higher power, a result in agreement with previous experiments and the notion of ducted whistlers.« less

An experimental investigation of the angular scattering and backscattering behaviors of the simulated clouds of the outer planets

NASA Technical Reports Server (NTRS)

Sassen, K.

1984-01-01

A cryogenic, 50 liter volume Planetary Cloud Simulation Chamber has been constructed to permit the laboratory study of the cloud compositions which are likely to be found in the atmospheres of the outer planets. On the basis of available data, clouds composed of water ice, carbon dioxide, and liquid and solid ammonia and methane, both pure and in various mixtures, have been generated. Cloud microphysical observations have been permitted through the use of a cloud particle slide injector and photomicrography. Viewports in the lower chamber have enabled the collection of cloud backscattering data using 633 and 838 nm laser light, including linear depolarization ratios and complete Stokes parameterization. The considerable technological difficulties associated with the collection of angular scattering patterns within the chamber, however, could not be completely overcome.

WE-DE-201-05: Evaluation of a Windowless Extrapolation Chamber Design and Monte Carlo Based Corrections for the Calibration of Ophthalmic Applicators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, J; Culberson, W; DeWerd, L

Purpose: To test the validity of a windowless extrapolation chamber used to measure surface dose rate from planar ophthalmic applicators and to compare different Monte Carlo based codes for deriving correction factors. Methods: Dose rate measurements were performed using a windowless, planar extrapolation chamber with a {sup 90}Sr/{sup 90}Y Tracerlab RA-1 ophthalmic applicator previously calibrated at the National Institute of Standards and Technology (NIST). Capacitance measurements were performed to estimate the initial air gap width between the source face and collecting electrode. Current was measured as a function of air gap, and Bragg-Gray cavity theory was used to calculate themore » absorbed dose rate to water. To determine correction factors for backscatter, divergence, and attenuation from the Mylar entrance window found in the NIST extrapolation chamber, both EGSnrc Monte Carlo user code and Monte Carlo N-Particle Transport Code (MCNP) were utilized. Simulation results were compared with experimental current readings from the windowless extrapolation chamber as a function of air gap. Additionally, measured dose rate values were compared with the expected result from the NIST source calibration to test the validity of the windowless chamber design. Results: Better agreement was seen between EGSnrc simulated dose results and experimental current readings at very small air gaps (<100 µm) for the windowless extrapolation chamber, while MCNP results demonstrated divergence at these small gap widths. Three separate dose rate measurements were performed with the RA-1 applicator. The average observed difference from the expected result based on the NIST calibration was −1.88% with a statistical standard deviation of 0.39% (k=1). Conclusion: EGSnrc user code will be used during future work to derive correction factors for extrapolation chamber measurements. Additionally, experiment results suggest that an entrance window is not needed in order for an extrapolation chamber to provide accurate dose rate measurements for a planar ophthalmic applicator.« less

Design of the free-air ionization chamber, FAC-IR-150, for X-ray dosimetry

NASA Astrophysics Data System (ADS)

Mohammadi, Seyed Mostafa; Tavakoli-Anbaran, Hossein

2018-03-01

The primary standard for X-ray dosimetry is based on the free-air ionization chamber (FAC). Therefore, the Atomic Energy Organization of Iran (AEOI) designed the free-air ionization chamber, FAC-IR-150, for low and medium energy X-ray dosimetry. The purpose of this work is the study of the free-air ionization chamber characteristics and the design of the FAC-IR-150. The FAC-IR-150 dosimeter has two parallel plates, a high voltage plate and a collector plate. A guard electrode surrounds the collector and is separated by an air gap. A group of guard strips is used between up and down electrodes to produce a uniform electric field in all the ion chamber volume. This design involves introducing the correction factors and determining the exact dimensions of the ionization chamber by using Monte Carlo simulation.

Free-air ionization chamber, FAC-IR-300, designed for medium energy X-ray dosimetry

NASA Astrophysics Data System (ADS)

Mohammadi, S. M.; Tavakoli-Anbaran, H.; Zeinali, H. Z.

2017-01-01

The primary standard for X-ray photons is based on parallel-plate free-air ionization chamber (FAC). Therefore, the Atomic Energy Organization of Iran (AEOI) is tried to design and build the free-air ionization chamber, FAC-IR-300, for low and medium energy X-ray dosimetry. The main aim of the present work is to investigate specification of the FAC-IR-300 ionization chamber and design it. FAC-IR-300 dosimeter is composed of two parallel plates, a high voltage (HV) plate and a collector plate, along with a guard electrode that surrounds the collector plate. The guard plate and the collector were separated by an air gap. For obtaining uniformity in the electric field distribution, a group of guard strips was used around the ionization chamber. These characterizations involve determining the exact dimensions of the ionization chamber by using Monte Carlo simulation and introducing correction factors.

Pediatric personalized CT-dosimetry Monte Carlo simulations, using computational phantoms

NASA Astrophysics Data System (ADS)

Papadimitroulas, P.; Kagadis, G. C.; Ploussi, A.; Kordolaimi, S.; Papamichail, D.; Karavasilis, E.; Syrgiamiotis, V.; Loudos, G.

2015-09-01

The last 40 years Monte Carlo (MC) simulations serve as a “gold standard” tool for a wide range of applications in the field of medical physics and tend to be essential in daily clinical practice. Regarding diagnostic imaging applications, such as computed tomography (CT), the assessment of deposited energy is of high interest, so as to better analyze the risks and the benefits of the procedure. The last few years a big effort is done towards personalized dosimetry, especially in pediatric applications. In the present study the GATE toolkit was used and computational pediatric phantoms have been modeled for the assessment of CT examinations dosimetry. The pediatric models used come from the XCAT and IT'IS series. The X-ray spectrum of a Brightspeed CT scanner was simulated and validated with experimental data. Specifically, a DCT-10 ionization chamber was irradiated twice using 120 kVp with 100 mAs and 200 mAs, for 1 sec in 1 central axial slice (thickness = 10mm). The absorbed dose was measured in air resulting in differences lower than 4% between the experimental and simulated data. The simulations were acquired using ˜1010 number of primaries in order to achieve low statistical uncertainties. Dose maps were also saved for quantification of the absorbed dose in several children critical organs during CT acquisition.

GEMS X-ray Polarimeter Performance Simulations

NASA Technical Reports Server (NTRS)

Baumgartner, Wayne H.; Strohmayer, Tod; Kallman, Tim; Black, J. Kevin; Hill, Joanne; Swank, Jean

2012-01-01

The Gravity and Extreme Magnetism Small explorer (GEMS) is an X-ray polarization telescope selected as a NASA small explorer satellite mission. The X-ray Polarimeter on GEMS uses a Time Projection Chamber gas proportional counter to measure the polarization of astrophysical X-rays in the 2-10 keV band by sensing the direction of the track of the primary photoelectron excited by the incident X-ray. We have simulated the expected sensitivity of the polarimeter to polarized X-rays. We use the simulation package Penelope to model the physics of the interaction of the initial photoelectron with the detector gas and to determine the distribution of charge deposited in the detector volume. We then model the charge diffusion in the detector,and produce simulated track images. Within the track reconstruction algorithm we apply cuts on the track shape and focus on the initial photoelectron direction in order to maximize the overall sensitivity of the instrument, using this technique we have predicted instrument modulation factors nu(sub 100) for 100% polarized X-rays ranging from 10% to over 60% across the 2-10 keV X-ray band. We also discuss the simulation program used to develop and model some of the algorithms used for triggering, and energy measurement of events in the polarimeter.

A stable and convenient protein electrophoresis titration device with bubble removing system.

PubMed

Zhang, Qiang; Fan, Liu-Yin; Li, Wen-Lin; Cong, Feng-Song; Zhong, Ran; Chen, Jing-Jing; He, Yu-Chen; Xiao, Hua; Cao, Cheng-Xi

2017-07-01

Moving reaction boundary titration (MRBT) has a potential application to immunoassay and protein content analysis with high selectivity. However, air bubbles often impair the accuracy of MRBT, and the leakage of electrolyte greatly decreases the safety and convenience of electrophoretic titration. Addressing these two issues a reliable MRBT device with modified electrolyte chamber of protein titration was designed. Multiphysics computer simulation was conducted for optimization according to two-phase flow. The single chamber was made of two perpendicular cylinders with different diameters. After placing electrophoretic tube, the resident air in the junction next to the gel could be eliminated by a simple fast electrolyte flow. Removing the electrophoretic tube automatically prevented electrolyte leakage at the junction due to the gravity-induced negative pressure within the chamber. Moreover, the numerical simulation and experiments showed that the improved MRBT device has following advantages: (i) easy and rapid setup of electrophoretic tube within 20 s; (ii) simple and quick bubble dissipates from the chamber of titration within 2 s; (iii) no electrolyte leakage from the two chambers: and (iv) accurate protein titration and safe instrumental operation. The developed technique and apparatus greatly improves the performance of the previous MRBT device, and providing a new route toward practical application. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effect of individual variation on the structure and function of interaction networks in harvester ants

PubMed Central

Pinter-Wollman, Noa; Wollman, Roy; Guetz, Adam; Holmes, Susan; Gordon, Deborah M.

2011-01-01

Social insects exhibit coordinated behaviour without central control. Local interactions among individuals determine their behaviour and regulate the activity of the colony. Harvester ants are recruited for outside work, using networks of brief antennal contacts, in the nest chamber closest to the nest exit: the entrance chamber. Here, we combine empirical observations, image analysis and computer simulations to investigate the structure and function of the interaction network in the entrance chamber. Ant interactions were distributed heterogeneously in the chamber, with an interaction hot-spot at the entrance leading further into the nest. The distribution of the total interactions per ant followed a right-skewed distribution, indicating the presence of highly connected individuals. Numbers of ant encounters observed positively correlated with the duration of observation. Individuals varied in interaction frequency, even after accounting for the duration of observation. An ant's interaction frequency was explained by its path shape and location within the entrance chamber. Computer simulations demonstrate that variation among individuals in connectivity accelerates information flow to an extent equivalent to an increase in the total number of interactions. Individual variation in connectivity, arising from variation among ants in location and spatial behaviour, creates interaction centres, which may expedite information flow. PMID:21490001

Three dimensional CFD modeling and experimental validation of a single chamber solid oxide fuel cell fed by methane

NASA Astrophysics Data System (ADS)

Nguyen, H. T.; Le, M. V.; Nguyen, T. A.; Nguyen, T. A. N.

2017-06-01

The solid oxide fuel cell is one of the promising technologies for future energy demand. Solid oxide fuel cell operated in the single-chamber mode exhibits several advantages over conventional single oxide fuel cell due to the simplified, compact, sealing-free cell structure. There are some studies on simulating the behavior of this type of fuel cell but they mainly focus on the 2D model. In the present study, a three-dimensional numerical model of a single chamber solid oxide fuel cell (SOFC) is reported and solved using COMSOL Multiphysics software. Experiments of a planar button solid oxide fuel cell were used to verify the simulation results. The system is fed by methane and oxygen and operated at 700°C. The cathode is LSCF6482, the anode is GDC-Ni, the electrolyte is LDM and the operating pressure is 1 atm. There was a good agreement between the cell temperature and current voltage estimated from the model and measured from the experiment. The results indicate that the model is applicable for the single chamber solid oxide fuel cell and it can provide a basic for the design, scale up of single chamber solid oxide fuel cell system.

Poster - 19: Investigation of Electron Reference Dosimetry Based on Optimal Chamber Shift

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhan, Lixin; Jiang, Runqing; Liu, Baochang

An addendum/revision to AAPM TG-51 electron reference dosimetry is highly expected to meet the clinical requirement with the increasing usage of new ion chambers not covered in TG-51. A recent study, Med. Phys. 41, 111701, proposed a new fitting equation for the beam quality conversion factor k’{sub Q} to a wide spectrum of chambers. In the study, an optimal Effective Point of Measurement (EPOM) from Monte Carlo calculations was recommended and the fitting parameters to k’{sub Q} was based on it. We investigated the absolute dose obtained based on the optimal EPOM method and the original TG-51 method with k’{submore » R50} determined differently. The results showed that using the Markus curve is a better choice than the well-guarded chamber fitting for an IBA PPC-05 parallel plate chamber if we need to strictly follow the AAPM TG-51 protocol. We also examined the usage of the new fitting equation with measurement performed at the physical EPOM, instead of the optimal EPOM. The former is more readily determined and more practical in clinics. Our study indicated that the k’{sub Q} fitting based on the optimal EPOM can be used to measurement at the physical EPOM with no significant clinical impact. The inclusion of Farmer chamber gradient correction P{sub gr} in k’{sub Q}, as in the mentioned study, asks for the precise positioning of chamber center at dref. It is not recommended in clinics to avoid over-correction for low electron energies, especially for an institute having matching Linacs implemented.« less

Marine Fog Studies - Fog Simulation Program.

DTIC Science & Technology

1981-06-01

ratio as small as possible. Special insulating techniques are required for this type of chamber. I This method was employed by Findeisen (61 in 1939...and later by R. Gunn [141 in 1952 and was also employed by ,J. I’odzimck S[15] in 1964 who operated a modified Findeisen low-pressure chamber. In spite

Nondestructive test of regenerative chambers

NASA Technical Reports Server (NTRS)

Malone, G. A.; Stauffis, R.; Wood, R.

1972-01-01

Flat panels simulating internally cooled regenerative thrust chamber walls were fabricated by electroforming, brazing and diffusion bonding to evaluate the feasibility of nondestructive evaluation techniques to detect bonds of various strength integrities. Ultrasonics, holography, and acoustic emission were investigated and found to yield useful and informative data regarding the presence of bond defects in these structures.

Evaluation of Aromatic Oxidation Reactions in Seven Chemical Mechanisms with an Outdoor Chamber

EPA Science Inventory

Simulations using seven chemical mechanisms are intercompared against O₃, NO_x and hydrocarbon data from photooxidation experiments conducted at the University of North Carolina outdoor smog chamber. The mechanisms include CB4–2002, CB05, CB05-TU, a CB05 vari...

Seed Planting in Veggie Pillows

NASA Image and Video Library

2017-08-08

Outredgeous red leaf lettuce, Mizuna mustard and Waldmann's green lettuce are growing in the Veggie control system in the ISS environment simulator chamber in the Space Station Processing Facility at NASA's Kennedy Space Center in Florida. Growth in the chamber mimics the growth of plant experiments in the Veggie plant growth system on the International Space Station.

Seed Planting in Veggie Pillows

NASA Image and Video Library

2017-08-08

NASA interns Jessica Scotten, left, and Ayla Grandpre water plants in the Veggie hardware in NASA Kennedy Space Center's ISS environment simulator chamber. Mizuna mustard, Outredgeous lettuce and Waldmann's green lettuce are growing in Veggie. Growth in the chamber mimics the growth of plant experiments in the Veggie plant growth system on the International Space Station.

Research on stability of nozzle-floating plate institution

NASA Astrophysics Data System (ADS)

Huang, Bin; Tao, Jiayue; Yi, Jiajing; Chen, Shijing

2016-01-01

In this paper, air hammer instability of nozzle-floating plate institution in gas lubricated force sensor were studied. Through establishment of the theoretical model for the analysis of the nozzle-floating plate institution stability, combined with air hammer stability judgment theorems, we had some simulation research on the radius of the nozzle, the radius of the pressure chamber, pressure chamber depth, orifice radius and the relationship between air supply pressure and bearing capacity, in order to explore the instability mechanism of nozzle-floating plate institution. For conducting experimental observations for the stability of two groups nozzle-floating plate institution, which have typical structural parameters conducted experimental observations. We set up a special experimental device, verify the correctness of the theoretical study and simulation results. This paper shows that in the nozzle-floating plate institution, increasing the nozzle diameter, reduced pressure chamber radius, reducing the depth of the pressure chamber and increase the supply orifice radius, and other measures is conducive to system stability. Results of this study have important implications for research and design of gas lubricated force sensor.

Thermal System Upgrade of the Space Environment Simulation Test Chamber

NASA Technical Reports Server (NTRS)

Desai, Ashok B.

1997-01-01

The paper deals with the refurbishing and upgrade of the thermal system for the existing thermal vacuum test facility, the Space Environment Simulator, at NASA's Goddard Space Flight Center. The chamber is the largest such facility at the center. This upgrade is the third phase of the long range upgrade of the chamber that has been underway for last few years. The first phase dealt with its vacuum system, the second phase involved the GHe subsystem. The paper describes the considerations of design philosophy options for the thermal system; approaches taken and methodology applied, in the evaluation of the remaining "life" in the chamber shrouds and related equipment by conducting special tests and studies; feasibility and extent of automation, using computer interfaces and Programmable Logic Controllers in the control system and finally, matching the old components to the new ones into an integrated, highly reliable and cost effective thermal system for the facility. This is a multi-year project just started and the paper deals mainly with the plans and approaches to implement the project successfully within schedule and costs.

Testing fireproof materials in a combustion chamber

NASA Astrophysics Data System (ADS)

Kulhavy, Petr; Martinec, Tomas; Novak, Ondrej; Petru, Michal; Srb, Pavel

This article deals with a prototype concept, real experiment and numerical simulation of a combustion chamber, designed for testing fire resistance some new insulating composite materials. This concept of a device used for testing various materials, providing possibility of monitoring temperatures during controlled gas combustion. As a fuel for the combustion process propane butane mixture has been used and also several kinds of burners with various conditions of inlet air (forced, free) and fuel flows were tested. The tested samples were layered sandwich materials based on various materials or foams, used as fillers in fire shutters. The temperature distribution was measured by using thermocouples. A simulation of whole concept of experimental chamber has been carried out as the non-premixed combustion process in the commercial final volume sw Pyrosim. The result was to design chamber with a construction suitable, according to the international standards, achieve the required values (temperature in time). Model of the combustion based on a stoichiometric defined mixture of gas and the tested layered samples showed good conformity with experimental results - i.e. thermal distribution inside and heat release rate that has gone through the sample.

Space simulation facilities providing a stable thermal vacuum facility

NASA Technical Reports Server (NTRS)

Tellalian, Martin L.

1990-01-01

CBI has recently constructed the Intermediate Thermal Vacuum Facility. Built as a corporate facility, the installation will first be used on the Boost Surveillance and Tracking System (BSTS) program. It will also be used to develop and test other sensor systems. The horizontal chamber has a horseshoe shaped cross section and is supported on pneumatic isolators for vibration isolation. The chamber structure was designed to meet stability and stiffness requirements. The design process included measurement of the ambient ground vibrations, analysis of various foundation test article support configurations, design and analysis of the chamber shell and modal testing of the chamber shell. A detailed 3-D finite element analysis was made in the design stage to predict the lowest three natural frequencies and mode shapes and to identify local vibrating components. The design process is described and the results are compared of the finite element analysis to the results of the field modal testing and analysis for the 3 lowest natural frequencies and mode shapes. Concepts are also presented for stiffening large steel structures along with methods to improve test article stability in large space simulation facilities.

Caldera subsidence and magma chamber depth of the Olympus Mons volcano, Mars

NASA Technical Reports Server (NTRS)

Zuber, M. T.; Mouginis-Mark, P. J.

1992-01-01

An axisymmetric finite element model is constructed to calculate elastic stresses in a volcanic edifice to examine the relationship between surface tectonism, caldera subsidence, and the physical characteristics of Olympus Mons' magmatic reservoir. Model results indicate that the surface stress state is not strongly sensitive to the aspect ratio or pressure distribution of the magma chamber, or to the contrast in stiffness between the magma chamber and surroundings, but is strongly dependent on the depth and width of the chamber. A gross similarity is suggested between the configurations of the magmatic plumbing systems of Olympus Mons and several well-studied terrestrial volcanoes such as the Hawaiian shields.

A new gun facility dedicated to performing shock physics and terminal ballistics experiments

NASA Astrophysics Data System (ADS)

Zakraysek, Alan J.; Sutherland, Gerrit T.; Sandusky, Harold D.; Strange, David

2000-04-01

A new building has been constructed to house various powder and single-stage and two-stage gas guns at the Naval Surface Warfare Center, Indian Head Division. Guns previously located at the Naval Research Laboratory and the former White Oak Site of the Naval Surface Warfare Center have been relocated here. Most of the guns are mounted on moveable pedestals to allow them to be shot into various chambers. The facility includes a concrete blast chamber, a target chamber/catch tank for flyer plate experiments, and a target chamber outfitted for terminal ballistics measurements. This paper will discuss the capabilities of this new facility.

Numerical analysis of whole-body cryotherapy chamber design improvement

NASA Astrophysics Data System (ADS)

Yerezhep, D.; Tukmakova, A. S.; Fomin, V. E.; Masalimov, A.; Asach, A. V.; Novotelnova, A. V.; Baranov, A. Yu

2018-05-01

Whole body cryotherapy is a state-of-the-art method that uses cold for treatment and prevention of diseases. The process implies the impact of cryogenic gas on a human body that implements in a special cryochamber. The temperature field in the chamber is of great importance since local integument over-cooling may occur. Numerical simulation of WBC has been carried out. Chamber design modification has been proposed in order to increase the uniformity of the internal temperature field. The results have been compared with the ones obtained for a standard chamber design. The value of temperature gradient formed in the chamber containing curved wall with certain height has been decreased almost twice in comparison with the results obtained for the standard design. The modification proposed may increase both safety and comfort of cryotherapy.

The NASA Constellation University Institutes Project: Thrust Chamber Assembly Virtual Institute

NASA Technical Reports Server (NTRS)

Tucker, P. Kevin; Rybak, Jeffry A.; Hulka, James R.; Jones, Gregg W.; Nesman, Tomas; West, Jeffrey S.

2006-01-01

This paper documents key aspects of the Constellation University Institutes Project (CUIP) Thrust Chamber Assembly (TCA) Virtual Institute (VI). Specifically, the paper details the TCA VI organizational and functional aspects relative to providing support for Constellation Systems. The TCA VI vision is put forth and discussed in detail. The vision provides the objective and approach for improving thrust chamber assembly design methodologies by replacing the current empirical tools with verified and validated CFD codes. The vision also sets out ignition, performance, thermal environments and combustion stability as focus areas where application of these improved tools is required. Flow physics and a study of the Space Shuttle Main Engine development program are used to conclude that the injector is the key to robust TCA design. Requirements are set out in terms of fidelity, robustness and demonstrated accuracy of the design tool. Lack of demonstrated accuracy is noted as the most significant obstacle to realizing the potential of CFD to be widely used as an injector design tool. A hierarchical decomposition process is outlined to facilitate the validation process. A simulation readiness level tool used to gauge progress toward the goal is described. Finally, there is a description of the current efforts in each focus area. The background of each focus area is discussed. The state of the art in each focus area is noted along with the TCA VI research focus in the area. Brief highlights of work in the area are also included.

Uniform, stable supply of medium for in vitro cell culture using a robust chamber

NASA Astrophysics Data System (ADS)

Wei, Juan; Liu, Chong; Jiang, Yang; Liu, Tao; Chen, Li; Liu, Bo; Li, Jingmin

2018-06-01

A uniform, stable supply of medium is important for in vitro cell culture. In this paper, a microfluidic device is presented for culturing cells inside a robust chamber with continuous perfusion of medium. The device consists of a main channel, two bifurcated channels and a culture chamber. The culture chamber connects to the bifurcated channels via multiple paths, and distributes symmetrically on the main channel, to improve the efficiency of medium exchange. Furthermore, regular polygonal chambers with various numbers of edges have been designed, to study the effects of chamber shape on flow fields. The finite element method has been employed to predict the effects of multiple paths on the uniformity and stability of flow fields in the culture chamber. Particle tracking technology has been used to evaluate the flow fields in the chambers, and PC-12 cells have been cultured using the microfluidic device, to test its validity. The results of simulation and experiment indicate that the microfluidic design could provide a continuous interstitial-like flow microenvironment, with a relatively stable and uniform supply of medium.

Simulation and experimental verification of silicon dioxide deposition by PECVD

NASA Astrophysics Data System (ADS)

Xu, Qing; Li, Yu-Xing; Li, Xiao-Ning; Wang, Jia-Bin; Yang, Fan; Yang, Yi; Ren, Tian-Ling

2017-02-01

Deposition of silicon dioxide in high-density plasma is an important process in integrated circuit manufacturing. A software named CFD-ACE was used to simulate the mechanism of plasma in the chamber of plasma enhanced chemical vapor deposition (PECVD) system, and the evolution of the feature profile was simulated based on CFD-TOPO. Simulation and experiment of silicon dioxide that deposited in SiH4/N2O mixture by PECVD system was researched. The particle density, energy and angular distribution in the chamber were simulated and discussed. We also studied how the depth/width ratio affected the step coverage of the trench and analyzed the deposition rate of silicon dioxide on the feature scale. X-ray photoelectron spectroscopy (XPS) was used to analyze the elemental composition of thin films. Images of the feature profiles were taken by scanning electron microscope (SEM). The simulation results were in good agreement with experimental, which could guide the semiconductor device manufacture.

Effect of decompression drying treatment on physical properties of solid foods.

PubMed

Morikawa, Takuya; Takada, Norihisa; Miura, Makoto

2017-04-01

This study used a decompression drying instrument to investigate the effects of a drying treatment on the physical properties of solid foods. Commercial tofu was used as a model food and was treated at different temperature and pressure conditions in a drying chamber. Overall, high temperatures resulted in better drying. Additionally, pressure in the chamber influenced the drying conditions of samples. Differences in physical properties, such as food texture, shrinkage, and color were observed among some samples, even with similar moisture content. This was caused by differences in moisture distribution in the food, which seems to have manifested as a thin, dried film on the surfaces of samples. It caused inefficient drying and changes in physical properties. Control of the drying conditions (i.e. pressure and heat supply) has relations with not only physical properties, but also the drying efficiency of solid foods.

EUPHORE: Research facility to study tropospheric transformation processes

NASA Astrophysics Data System (ADS)

Wirtz, K.

2003-04-01

The EUPHORE simulation chamber consists of two half-spherical Teflon bags, each with a volume of 200 m^3 and a base diameter of 9.2 m. The FEP Teflon has a transmission of about 75% at 280 nm and of more than 80% above 300 nm. Purified and dried ambient air is used to fill the chamber and flush it between experiments. The humidity in the chamber is measured by a dew point hygrometer, and the temperature is monitored by several thermocouples located at different positions inside the chamber. The solar flux is monitored with spectral resolution in the photochemically active spectral region. The simulation chamber is equipped with a number of analytical instruments for the measurement of single VOC components, NO, NO_2, O_3 and other species. In-situ measurements in the ppb range are performed using long-path absorption spectroscopy, in the UV/VIS by DOAS and in the IR by FT-IR. A GC-MS system is used for the sensitive analysis of a variety of reaction products. A newly installed LIF technique allows the in situ measurement of OH and HO_2 radicals during the reaction processes. The technological concept and the organisation structure of the EUPHORE facility will be presented. The integration of quality control measures is an obvious and necessary second step for the successful exploitation of the technically advanced outdoor smog chamber EUPHORE as a research tool. This will underline the leadership of the European scientific community in the important research areas of investigating transformation processes in the troposphere and tracking the influence of human activities on photooxidant formation and its interaction with processes related to global change. In the coming years the main scientific focus will be on testing chemical mechanisms in order to improve the models which describe the atmospheric processes of complex chemical systems. The collaborative work at the EUPHORE outdoor simulation chamber will provide all the users of the installation with a basic platform to exchange analytical technology, sampling procedures, methods of data treatment, and know-how that can also be applied in field campaigns.

Three-dimensional numerical and experimental studies on transient ignition of hybrid rocket motor

NASA Astrophysics Data System (ADS)

Tian, Hui; Yu, Ruipeng; Zhu, Hao; Wu, Junfeng; Cai, Guobiao

2017-11-01

This paper presents transient simulations and experimental studies of the ignition process of the hybrid rocket motors (HRMs) using 90% hydrogen peroxide (HP) as the oxidizer and polymethyl methacrylate (PMMA) and Polyethylene (PE) as fuels. A fluid-solid coupling numerically method is established based on the conserved form of the three-dimensional unsteady Navier-Stokes (N-S) equations, considering gas fluid with chemical reactions and heat transfer between the fluid and solid region. Experiments are subsequently conducted using high-speed camera to record the ignition process. The flame propagation, chamber pressurizing process and average fuel regression rate of the numerical simulation results show good agreement with the experimental ones, which demonstrates the validity of the simulations in this study. The results also indicate that the flame propagation time is mainly affected by fluid dynamics and it increases with an increasing grain port area. The chamber pressurizing process begins when the flame propagation completes in the grain port. Furthermore, the chamber pressurizing time is about 4 times longer than the time of flame propagation.

Preliminary Measurements of Thin Film Solar Cells

NASA Image and Video Library

1967-06-21

George Mazaris, works with an assistant to obtain the preliminary measurements of cadmium sulfide thin-film solar cells being tested in the Space Environmental Chamber at the National Aeronautics and Space Administration (NASA) Lewis Research Center. Lewis’ Photovoltaic Fundamentals Section was investigating thin-film alternatives to the standard rigid and fragile solar cells. The cadmium sulfide semiconductors were placed in a light, metallized substrate that could be rolled or furled during launch. The main advantage of the thin-film solar cells was their reduced weight. Lewis researchers, however, were still working on improving the performance of the semiconductor. The new thin-film solar cells were tested in a space simulation chamber in the CW-6 test cell in the Engine Research Building. The chamber created a simulated altitude of 200 miles. Sunlight was simulated by a 5000-watt xenon light. Some two dozen cells were exposed to 15 minutes of light followed by 15 minutes of darkness to test their durability in the constantly changing illumination of Earth orbit. This photograph was taken for use in a NASA recruiting publication.

Development of a Test Facility for Air Revitalization Technology Evaluation

NASA Technical Reports Server (NTRS)

Lu, Sao-Dung; Lin, Amy; Campbell, Melissa; Smith, Frederick; Curley, Su

2007-01-01

Development of new air revitalization system (ARS) technology can initially be performed in a subscale laboratory environment, but in order to advance the maturity level, the technology must be tested in an end-to-end integrated environment. The Air Revitalization Technology Evaluation Facility (ARTEF) at the NASA Johnson Space Center serves as a ground test bed for evaluating emerging ARS technologies in an environment representative of spacecraft atmospheres. At the center of the ARTEF is a hypobaric chamber which serves as a sealed atmospheric chamber for closed loop testing. A Human Metabolic Simulator (HMS) was custom-built to simulate the consumption of oxygen, and production of carbon dioxide, moisture and heat of up to eight persons. A multitude of gas analyzers and dew point sensors are used to monitor the chamber atmosphere upstream and downstream of a test article. A robust vacuum system is needed to simulate the vacuum of space. A reliable data acquisition and control system is required to connect all the subsystems together. This paper presents the capabilities of the integrated test facility and some of the issues encountered during the integration.

Assesment of PM2.5 emission from corn stover burning determining in chamber combustion

NASA Astrophysics Data System (ADS)

Hafidawati; Lestari, P.; Sofyan, A.

2018-04-01

Chamber measurement were conducted to determine Particulate Matter (PM2.5) emission from open burning of corn straw at Garut District, West Java. The of this study is to estimate the concentration of PM2.5 for two types of corn (corncobs and cornstover) for five varieties (Bisma, P29, NK, Bisma, NW). Corn residues were collected and then burned in the chamber combustion. The chamber was designed to simulate the burning in the field, which was observed in the field experiment that meteorological condition was calm wind. The samples were collected using a minivol air sampler. The assessment results of PM2.5 concentrations (mg/m3) from open burning experiment in the chamber for five varieties of corn cobs (Bisma, P29, NK, Bisi, NW) was 9.187; 2.843; 7.409; 3.781; 1.895 respectively. Concentration for corn stover burn was 2.060; 5.283; 4.048; 5.306 and 5.697 respectively. Fluctuations in the value of concentration among these varieties reflect variations in combustion conditions (combustion efficiency) and other parameters including water content, biomass conditions and the meteorological conditions. The combustion efficiency (MCE) of the combustion chamber simulation of corncobs ia lower than the MCE of corn stover, that the concentration PM2.5 more emitted from the burning of corn stover. The results of this study presented provide useful information for the development of local emission factors for PM2.5 from open burning of corn stover in Indonesia.

Fuel Combustion Laboratory | Transportation Research | NREL

Science.gov Websites

detection of compounds at sub-parts per billion by volume levels. A high-performance liquid chromatograph ) platform; a high-pressure (1,200- bar) direct-injection system to minimize spray physics effects; and an combustion chamber. A high-speed pressure transducer measures chamber pressure to detect fuel ignition. Air

Structural Changes and Material Transport in Al2O3-Supported Cu/Fe Spinel Particles in a Simulated Chemical Looping Combustion Environment

NASA Astrophysics Data System (ADS)

Nealley, W. H. Harrison; Nakano, Anna; Nakano, Jinichiro; Bennett, James P.

2018-05-01

Alumina-supported Cu/Fe spinel particles were exposed to oxidation/reduction atmospheres at 800°C. Structural changes of the particles subjected to gas cycles between air and 10 vol.% CO-90 vol.% Ar were studied from physical data and real-time images collected using a confocal scanning laser microscope equipped with a heating chamber. Overall particle volume slowly expanded with cycles while surface roughness decreased. Cross-sections of the exposed particles showed segregation of Cu and Fe to the edges of inner grains, which may have acted as oxygen carriers during the exposures. The particles remained whole during the cyclic exposures without any noticeable structural breakdown.

Use of cryopumps on large space simulation systems

NASA Technical Reports Server (NTRS)

Mccrary, L. E.

1980-01-01

The need for clean, oil free space simulation systems has demanded the development of large, clean pumping systems. The assurance of optically dense liquid nitrogen baffles over diffusion pumps prevents backstreaming to a large extent, but does not preclude contamination from accidents or a control failure. Turbomolecular pumps or ion pumps achieve oil free systems but are only practical for relatively small chambers. Large cryopumps were developed and checked out which do achieve clean pumping of very large chambers. These pumps can be used as the original pumping system or can be retrofitted as a replacement for existing diffusion pumps.

Alpha LAMP Integration Facility

NASA Technical Reports Server (NTRS)

Oshiro, Richard; Sowers, Dennis; Gargiulo, Joe; Mcgahey, Mark

1994-01-01

This paper describes the activity recently completed to meet the simulated space environment requirements for the ground-based testing of an integrated Space Based Laser (SBL) system experiment. The need to maintain optical alignment in the challenging dynamic environment of the pressure recovery system required to simulate space dominated the design requirements. A robust system design was established which minimized the total program costs, most notably by reducing the cost of integrating the components of the experiment. The components of the experiment are integrated on an optical bench in a clean area adjacent to the vacuum chamber and moved on air bearings into the chamber for testing.

Numerical Simulation of Flow in the Chamber of the Water-Argon Plasma Generator

NASA Astrophysics Data System (ADS)

Hlbočan, Peter; Varchola, Michal; Knížat, Branislav; Mlkvik, Marek; Olšiak, Róbert

2012-12-01

The paper describes the CFD simulation of the flow of gas and plasma in a plasma generator with a hybrid stabilization of the electric arc. The momentum equations of the model also take Lorentz forces into account. In the energy equation, Joule heat is introduced as an energy source. The introduction of boundary conditions is also explained, as along with plasma transport properties and a method of solution. The paper presents selected results of pressure and velocity fields in the chamber of the plasma generator.

Left ventricular filling under elevated left atrial pressure

NASA Astrophysics Data System (ADS)

Gaddam, Manikantam; Samaee, Milad; Santhanakrishnan, Arvind

2017-11-01

Left atrial pressure (LAP) is elevated in diastolic dysfunction, where left ventricular (LV) filling is impaired due to increase in ventricular stiffness. The impact of increasing LAP and LV stiffness on intraventricular filling hemodynamics remains unclear. We conducted particle image velocimetry and hemodynamics measurements in a left heart simulator (LHS) under increasing LAP and LV stiffness at a heart rate of 70 bpm. The LHS consisted of a flexible-walled LV physical model fitted within a fluid-filled chamber. LV wall motion was generated by a piston pump that imparted pressure fluctuations in the chamber. Resistance and compliance elements in the flow loop were adjusted to obtain bulk physiological hemodynamics in the least stiff LV model. Two LV models of increasing stiffness were subsequently tested under unchanged loop settings. LAP was varied between 5-20 mm Hg for each LV model, by adjusting fluid level in a reservoir upstream of the LV. For constant LV stiffness, increasing LAP lowered cardiac output (CO), while ejection fraction (EF) and E/A ratio were increased. For constant LAP, increasing LV stiffness lowered CO and EF, and increased E/A ratio. The implications of these altered hemodynamics on intraventricular filling vortex characteristics will be presented.

Analytical and computational studies on the vacuum performance of a chevron ejector

NASA Astrophysics Data System (ADS)

Kong, F. S.; Jin, Y. Z.; Kim, H. D.

2016-11-01

The effects of chevrons on the performance of a supersonic vacuum ejector-diffuser system are investigated numerically and evaluated theoretically in this work. A three-dimensional geometrical domain is numerically solved using a fully implicit finite volume scheme based on the unsteady Reynolds stress model. A one-dimensional mathematical model provides a useful tool to reveal the steady flow physics inside the vacuum ejector-diffuser system. The effects of the chevron nozzle on the generation of recirculation regions and Reynolds stress behaviors are studied and compared with those of a conventional convergent nozzle. The present performance parameters obtained from the simulated results and the mathematical results are validated with existing experimental data and show good agreement. Primary results show that the duration of the transient period and the secondary chamber pressure at a dynamic equilibrium state depend strongly on the primary jet conditions, such as inlet pressure and primary nozzle shape. Complicated oscillatory flow, generated by the unsteady movement of recirculation, finally settles into a dynamic equilibrium state. As a vortex generator, the chevron demonstrated its strong entrainment capacity to accelerate the starting transient flows to a certain extent and reduce the dynamic equilibrium pressure of the secondary chamber significantly.

CFD Modelling of a Quadrupole Vortex Inside a Cylindrical Channel for Research into Advanced Hybrid Rocket Designs

NASA Astrophysics Data System (ADS)

Godfrey, B.; Majdalani, J.

2014-11-01

This study relies on computational fluid dynamics (CFD) tools to analyse a possible method for creating a stable quadrupole vortex within a simulated, circular-port, cylindrical rocket chamber. A model of the vortex generator is created in a SolidWorks CAD program and then the grid is generated using the Pointwise mesh generation software. The non-reactive flowfield is simulated using an open source computational program, Stanford University Unstructured (SU2). Subsequent analysis and visualization are performed using ParaView. The vortex generation approach that we employ consists of four tangentially injected monopole vortex generators that are arranged symmetrically with respect to the center of the chamber in such a way to produce a quadrupole vortex with a common downwash. The present investigation focuses on characterizing the flow dynamics so that future investigations can be undertaken with increasing levels of complexity. Our CFD simulations help to elucidate the onset of vortex filaments within the monopole tubes, and the evolution of quadrupole vortices downstream of the injection faceplate. Our results indicate that the quadrupole vortices produced using the present injection pattern can become quickly unstable to the extent of dissipating soon after being introduced into simulated rocket chamber. We conclude that a change in the geometrical configuration will be necessary to produce more stable quadrupoles.

TH-E-BRE-09: TrueBeam Monte Carlo Absolute Dose Calculations Using Monitor Chamber Backscatter Simulations and Linac-Logged Target Current

DOE Office of Scientific and Technical Information (OSTI.GOV)

A, Popescu I; Lobo, J; Sawkey, D

2014-06-15

Purpose: To simulate and measure radiation backscattered into the monitor chamber of a TrueBeam linac; establish a rigorous framework for absolute dose calculations for TrueBeam Monte Carlo (MC) simulations through a novel approach, taking into account the backscattered radiation and the actual machine output during beam delivery; improve agreement between measured and simulated relative output factors. Methods: The ‘monitor backscatter factor’ is an essential ingredient of a well-established MC absolute dose formalism (the MC equivalent of the TG-51 protocol). This quantity was determined for the 6 MV, 6X FFF, and 10X FFF beams by two independent Methods: (1) MC simulationsmore » in the monitor chamber of the TrueBeam linac; (2) linac-generated beam record data for target current, logged for each beam delivery. Upper head MC simulations used a freelyavailable manufacturer-provided interface to a cloud-based platform, allowing use of the same head model as that used to generate the publicly-available TrueBeam phase spaces, without revealing the upper head design. The MC absolute dose formalism was expanded to allow direct use of target current data. Results: The relation between backscatter, number of electrons incident on the target for one monitor unit, and MC absolute dose was analyzed for open fields, as well as a jaw-tracking VMAT plan. The agreement between the two methods was better than 0.15%. It was demonstrated that the agreement between measured and simulated relative output factors improves across all field sizes when backscatter is taken into account. Conclusion: For the first time, simulated monitor chamber dose and measured target current for an actual TrueBeam linac were incorporated in the MC absolute dose formalism. In conjunction with the use of MC inputs generated from post-delivery trajectory-log files, the present method allows accurate MC dose calculations, without resorting to any of the simplifying assumptions previously made in the TrueBeam MC literature. This work has been partially funded by Varian Medical Systems.« less

Research of working pulsation in closed angle based on rotating-sleeve distributing-flow system

NASA Astrophysics Data System (ADS)

Zhang, Yanjun; Zhang, Hongxin; Zhao, Qinghai; Jiang, Xiaotian; Cheng, Qianchang

2017-08-01

In order to reduce negative effects including hydraulic impact, noise and mechanical vibration, compression and expansion of piston pump in closed volume are used to optimize the angle between valve port and chamber. In addition, the mathematical model about pressurization and depressurization in pump chamber are analyzed based on distributing-flow characteristic, and it is necessary to use simulation software Fluent to simulate the distributing-flow fluid model so as to select the most suitable closed angle. As a result, when compression angle is 3°, the angle is closest to theoretical analysis and has the minimum influence on flow and pump pressure characteristic. Meanwhile, cavitation phenomenon appears in pump chamber in different closed angle on different degrees. Besides the flow pulsation is increasingly smaller with increasing expansion angle. Thus when expansion angle is 2°, the angle is more suitable for distributing-flow system.

Around Marshall

NASA Image and Video Library

2002-10-01

This is a ground level view of Test Stand 300 at the east test area of the Marshall Space Flight Center. Test Stand 300 was constructed in 1964 as a gas generator and heat exchanger test facility to support the Saturn/Apollo Program. Deep-space simulation was provided by a 1960 modification that added a 20-ft thermal vacuum chamber and a 1981 modification that added a 12-ft vacuum chamber. The facility was again modified in 1989 when 3-ft and 15-ft diameter chambers were added to support Space Station and technology programs. This multiposition test stand is used to test a wide range of rocket engine components, systems, and subsystems. It has the capability to simulate launch thermal and pressure profiles. Test Stand 300 was designed for testing solid rocket booster (SRB) insulation panels and components, super-insulated tanks, external tank (ET) insulation panels and components, Space Shuttle components, solid rocket motor materials, and advanced solid rocket motor materials.

Developing a Webcam-Based Data Logger to Analyze Cosmic Rays in a Cloud Chamber

NASA Astrophysics Data System (ADS)

Nealon, Kelly; Bellis, Matt

2015-04-01

Muons from secondary cosmic rays provide students with an opportunity to interact with a natural phenomenon that relies both on special relativity and fairly sophisticated particle physics knowledge. In many physics departments, undergraduate students set up a pair of scintillators in coincidence to measure the rate of these muons and in some cases, measure their angular dependence, but this requires specialized and potentially expensive equipment. We have spent the past year formalizing a design of a cloud chamber that relies not on dry ice, but Peltier thermoelectric coolers, that can be built for about one hundred dollars worth of equipment. With this design we can see the tracks left by cosmic rays, however to turn it into a useful undergraduate physics lab requires some sort of data logger. This poster details our efforts to use an off-the-shelf webcam to trigger on the change in image when a cosmic ray track appears in the chamber. We use this to estimate the rate and angular dependence and compare our results to other measurements. The successes and limitations of this approach will be discussed.

Emergence of metapopulations and echo chambers in mobile agents

NASA Astrophysics Data System (ADS)

Starnini, Michele; Frasca, Mattia; Baronchelli, Andrea

2016-08-01

Multi-agent models often describe populations segregated either in the physical space, i.e. subdivided in metapopulations, or in the ecology of opinions, i.e. partitioned in echo chambers. Here we show how both kinds of segregation can emerge from the interplay between homophily and social influence in a simple model of mobile agents endowed with a continuous opinion variable. In the model, physical proximity determines a progressive convergence of opinions but differing opinions result in agents moving away from each others. This feedback between mobility and social dynamics determines the onset of a stable dynamical metapopulation scenario where physically separated groups of like-minded individuals interact with each other through the exchange of agents. The further introduction of confirmation bias in social interactions, defined as the tendency of an individual to favor opinions that match his own, leads to the emergence of echo chambers where different opinions coexist also within the same group. We believe that the model may be of interest to researchers investigating the origin of segregation in the offline and online world.

IMPACT OF AN OZONE GENERATOR AIR CLEANER ON STYRENE CONCENTRATIONS IN AN INDOOR AIR QUALITY RESEARCH CHAMBER

EPA Science Inventory

The paper gives results of an investigation of the impact of an ozone generator air cleaner on vapor-phase styrene concentrations in a full-scale indoor air quality test chamber. The time history of the concentrations of styrene and ozone is well predicted by a simulation model u...

Sealed Plant-Growth Chamber For Clinostat

NASA Technical Reports Server (NTRS)

Brown, Christopher S.; Dreschel, Thomas W.

1993-01-01

Laboratory chamber for growing plants used to measure photosynthesis and respiration in simulated microgravity. Holds plant specimens while rotated on clinostat, see article, "Clinostat Delivers Power To Plant-Growth Cabinets" (KSC-11537). Provides way of comparing gas-exchange rates of plants rotated horizontally on clinostat with those of stationary or vertically rotated plants. Gas extracted for analysis without stopping clinostat. Chamber includes potlike base and cylindrical cover, both made of transparent acrylic pipe. Gasket forms seal between cover and bottom plate of base. Cover bolted to pot baseplate, which in turn bolted to clinostat.

KSC-04PD-0003

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. -- Sharon Edney, with Dynamac Corp., checks the growth of radishes being grown hydroponically for study in the Space Life Sciences Lab. The 100,000 square-foot facility houses labs for NASAs ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASAs Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASAs Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

KSC-04PD-0007

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. -- In the Space Life Sciences (SLS) Lab, Jan Bauer, with Dynamac Corp., places samples of onion tissue in the elemental analyzer, which analyzes for carbon, hydrogen, nitrogen and sulfur. The 100,000 square-foot SLS houses labs for NASAs ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASAs Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASAs Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

KSC-04PD-0002

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. -- Sharon Edney, with Dynamac Corp., checks the roots of green onions being grown hydroponically for study in the Space Life Sciences Lab. The 100,000 square-foot facility houses labs for NASAs ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASAs Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASAs Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

KSC-04PD-0001

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. -- Sharon Edney, with Dynamac Corp., measures photosynthesis on Bibb lettuce being grown hydroponically for study in the Space Life Sciences Lab. The 100,000 square-foot facility houses labs for NASAs ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASAs Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASAs Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

Evaluation of SSME test data reduction methods

NASA Technical Reports Server (NTRS)

Santi, L. Michael

1994-01-01

Accurate prediction of hardware and flow characteristics within the Space Shuttle Main Engine (SSME) during transient and main-stage operation requires a significant integration of ground test data, flight experience, and computational models. The process of integrating SSME test measurements with physical model predictions is commonly referred to as data reduction. Uncertainties within both test measurements and simplified models of the SSME flow environment compound the data integration problem. The first objective of this effort was to establish an acceptability criterion for data reduction solutions. The second objective of this effort was to investigate the data reduction potential of the ROCETS (Rocket Engine Transient Simulation) simulation platform. A simplified ROCETS model of the SSME was obtained from the MSFC Performance Analysis Branch . This model was examined and tested for physical consistency. Two modules were constructed and added to the ROCETS library to independently check the mass and energy balances of selected engine subsystems including the low pressure fuel turbopump, the high pressure fuel turbopump, the low pressure oxidizer turbopump, the high pressure oxidizer turbopump, the fuel preburner, the oxidizer preburner, the main combustion chamber coolant circuit, and the nozzle coolant circuit. A sensitivity study was then conducted to determine the individual influences of forty-two hardware characteristics on fourteen high pressure region prediction variables as returned by the SSME ROCETS model.

Hot Jet Ignition Delay Characterization of Methane and Hydrogen at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Tarraf Kojok, Ali

This study contributes to a better understanding of ignition by hot combustion gases which finds application in internal combustion chambers with pre-chamber ignition as well as in wave rotor engine applications. The experimental apparatus consists of two combustion chambers: a pre chamber that generates the transient hot jet of gas and a main chamber which contains the main fuel air blend under study. Variables considered are three fuel mixtures (Hydrogen, Methane, 50% Hydrogen-Methane), initial pressure in the pre-chamber ranging from 1 to 2 atm, equivalence ratio of the fuel air mixture in the main combustion chamber ranging from 0.4 to 1.5, and initial temperature of the main combustion chamber mixture ranging from 297 K to 500 K. Experimental data makes use of 4 pressure sensors with a recorded sampling rate up to 300 kHz, as well as high speed Schlieren imaging with a recorded frame rate up to 20,833 frame per seconds. Results shows an overall increase in ignition delay with increasing equivalence ratio. High temperature of the main chamber blend was found not to affect hot jet ignition delay considerably. Physical mixing effects, and density of the main chamber mixture have a greater effect on hot jet ignition delay.

HNBody: A Simulation Package for Hierarchical N-Body Systems

NASA Astrophysics Data System (ADS)

Rauch, Kevin P.

2018-04-01

HNBody (http://www.hnbody.org/) is an extensible software package forintegrating the dynamics of N-body systems. Although general purpose, itincorporates several features and algorithms particularly well-suited tosystems containing a hierarchy (wide dynamic range) of masses. HNBodyversion 1 focused heavily on symplectic integration of nearly-Kepleriansystems. Here I describe the capabilities of the redesigned and expandedpackage version 2, which includes: symplectic integrators up to eighth order(both leap frog and Wisdom-Holman type methods), with symplectic corrector andclose encounter support; variable-order, variable-timestep Bulirsch-Stoer andStörmer integrators; post-Newtonian and multipole physics options; advancedround-off control for improved long-term stability; multi-threading and SIMDvectorization enhancements; seamless availability of extended precisionarithmetic for all calculations; extremely flexible configuration andoutput. Tests of the physical correctness of the algorithms are presentedusing JPL Horizons ephemerides (https://ssd.jpl.nasa.gov/?horizons) andpreviously published results for reference. The features and performanceof HNBody are also compared to several other freely available N-body codes,including MERCURY (Chambers), SWIFT (Levison & Duncan) and WHFAST (Rein &Tamayo).

The dynamics of magma chamber refilling at the Campi Flegrei caldera.

NASA Astrophysics Data System (ADS)

Montagna, Chiara Paola; Vassalli, Melissa; Longo, Antonella; Papale, Paolo; Giudice, Salvatore; Saccorotti, Gilberto

2010-05-01

The volcanologic and petrologic reconstructions of several eruptions during the last tens of thousand years of volcanism at the Campi Flegrei caldera show that in most cases a small, chemically evolved, partially degassed magma chamber was refilled by magma of deeper origin shortly before the eruption. New magma input in a shallow chamber is revealed from a variety of indicators, well described in the literature, that include major-trace element and isotope heterogeneities, and crystal-liquid disequilibria (e.g., Arienzo et al., Bull. Volcanol., 2009). In the case of the 4100 BP Agnano Monte Spina eruption, representing the highest intensity and magnitude event of the last epoch of activity, it has been suggested that the refilling occurred within a few tens of hours from the start of the eruption. Notably, in such a case the two end-member magmas that mixed shortly before eruption onset are not recognized as individual members in the deposits, rather, their composition and characteristics are reconstructed from small scale disequilibria, revealing that a relatively short time was sufficient for efficient mixing of the liquid components. In order to investigate the dynamics of magma chamber refilling and mixing at Campi Flegrei we have applied the GALES code (Longo et al., Geophys. Res. Lett., 2006) in a series of numerical simulations. The initial and boundary conditions have been defined in the frame of two subsequent projects coordinated by INGV and funded by the Italian Civil Protection Department, that gather a large number of experts on Campi Flegrei, and are consistent with the bulk of knowledge on the deep magmatic system. In all cases an initial compositional interface is placed at a certain depth, with non-degassed, buoyant magma placed below. The simulations investigate both the dynamics in a very large, 8 km deep reservoir revealed by seismic tomography (Zollo et al., Geophys. Res. Lett., 2008), and those in shallower and smaller chamber systems connected by dykes and representative of pre-eruptive conditions. The numerical results reveal the complex dynamics of magma mixing, dominated by the interplay between buoyant magma rise and dense magma sinking. In all simulated cases efficient mixing takes place at dyke levels, the buoyant magma entering the chamber is already a mixture of the two initial end-members, and the initial deep magma is never found as an individual component in the chamber. Over the time scale of our longest simulation (about 8 hours of real time), and with reference to the spatial resolution of our simulations (max 1 m), the magma chamber is occupied by a nearly homogeneous mixture of the two initial end-members, with minor but still visible density stratification continuously perturbed by the rise of small buoyant plumes. Consistent with the observations, an eruption occurring a few tens of hours after new magma ingression would be characterized by a magmatic composition intermediate between the two initial end-members, that can therefore be revealed only from small-scale heterogeneities and possibly from crystal-liquid disequilibria.

CFD Analysis of Evaporation-Condensation Phenomenon In an Evaporation Chamber of Natural Vacuum Solar Desalination

NASA Astrophysics Data System (ADS)

Ambarita, H.; Ronowikarto, A. D.; Siregar, R. E. T.; Setyawan, E. Y.

2018-01-01

Desalination technologies is one of solutions for water scarcity. With using renewable energy, like solar energy, wind energy, and geothermal energy, expected will reduce the energy demand. This required study on the modeling and transport parameters determination of natural vacuum solar desalination by using computational fluid dynamics (CFD) method to simulate the model. A three-dimensional case, two-phase model was developed for evaporation-condensation phenomenon in natural vacuum solar desalination. The CFD simulation results were compared with the avalaible experimental data. The simulation results shows inthat there is a phenomenon of evaporation-condensation in an evaporation chamber. From the simulation, the fresh water productivity is 2.21 litre, and from the experimental is 2.1 litre. This study shows there’s an error of magnitude 0.4%. The CFD results also show that, vacuum pressure will degrade the saturation temperature of sea water.

Microgravity Simulation Facility (MSF)

NASA Technical Reports Server (NTRS)

Richards, Stephanie E. (Compiler); Levine, Howard G.; Zhang, Ye

2016-01-01

The Microgravity Simulator Facility (MSF) at Kennedy Space Center (KSC) was established to support visiting scientists for short duration studies utilizing a variety of microgravity simulator devices that negate the directional influence of the "g" vector (providing simulated conditions of micro or partial gravity). KSC gravity simulators can be accommodated within controlled environment chambers allowing investigators to customize and monitor environmental conditions such as temperature, humidity, CO2, and light exposure.

Palaeonummulites venosus: Natural growth rates and quantification by means of CT investigation

NASA Astrophysics Data System (ADS)

Kinoshita, Shunichi; Eder, Wolfgang; Woeger, Julia; Hohenegger, Johann; Briguglio, Antonino

2016-04-01

Symbiont-bearing larger benthic Foraminifera (LBF) are long-living marine (possibly >1 year), single-celled organisms with complex calcium carbonate shells. Reproduction period, longevity and chamber building rate of LBF are important for population dynamics studies. It was expected that growth experiments in laboratory cultures cannot be used for estimation of chamber building rates and longevity studies although the laboratory conditions were simulated to natural conditions. Therefore, it is necessary to study individual and population growth under natural conditions for getting natural information. Therefore, the 'natural laboratory' method was developed to calculate the averaged chamber building rate and averaged longevity of species based on monthly sampling at fixed sampling stations and to compare with laboratory cultures simulating environmental conditions as close as possible to the natural environment. Thus, in this study, samples of living individuals were collected in 16 monthly intervals at 50m depth in front of Sesoko Island, Okinawa, Japan. We used micro-computed tomography (microCT) to investigate the chamber number of every specimen from the samples immediately dried after sampling. Single non dried specimens were cultured and the time of chamber building was obtained using microphotographs counted for every specimen at 2 to 4 days time intervals. The investigation using the natural laboratory method of Palaeonummulites venosus is based on the decomposition of the monthly frequency distributions into normally distributed components. Then the shift of the component parameters mean and standard deviation was used to calculate the necessary character of maximum chamber number and the Michaelis Menten function was applied to estimate the chamber building rate under natural conditions. This resulted in two reproduction periods, the first starting in May and the second in September, both showing the same chamber building rates, where the first shows a slightly stronger increase in the initial part. Longevity seems to be round about one year. Due to the several reproduction periods, the existence of small and large specimens in the same sample and the bimodal distributions can be explained. The cultured individuals shows a much lower chamber building rate, often demonstrating a longer period with no chamber production just after sampling, the results of sampling shock. This is the first time that it can be shown that chamber building rates and longevities cannot be based on laboratory investigations.

[Effect of 2000 m descent simulated in a hyperbaric chamber on arterial blood oxygen saturation and sleep quality in workers of a gold mine situated at an altitude of 3800-4200 m above sea level].

PubMed

Przybyłowski, Tadeusz; Ashirbaev, Aibek; Le Roux, Johannes; Zieliński, Jan

2003-01-01

Acute mountain sickness can become life threatening to people traveling at high altitude. Simulated descent with a hyperbaric chamber is a widely accepted way to treat this condition. The aim of this study was to analyze the influence of simulated descent to 2000 m on arterial oxygen saturation (SaO2), periodic breathing and sleep quality in a group of workers of a gold mine situated at 3800 m. Sleep studies were performed twice in stationary hyperbaric chamber with a portable system--MESAM IV in 20 workers. During the first study the chamber was not pressurized and on the second night the barometric pressure was set to mimic descent to 2000 m. During second study, a significant decrease in ODI (Oxygen Desaturation Index), from 9.7 +/- 6/h to 1.8 +/- 3.4/h (p < 0.0001), was noticed; mean SaO2 increased from 84.3 +/- 3.2% do 92.7 +/- 2.8% (p < 0.0001), significant changes in percentage of study time in individual SaO2 ranges were also noticed. The number (12.7 +/- 8.4 vs. 7.5 +/- 5; p < 0.05) and index of changes in body position were decreased (2.0 +/- 1.5 vs. 1.2 +/- 0.9/h; p < 0.05) as well. Simulated descent to 2000 m causes a decrease in number of desaturations, improvement in mean SaO2 during sleep, decrease in heart rate and these data suggest a decrease in periodic breathing during sleep. A decrease in number and index of body position changes suggests improved sleep quality.

An Analytic Model for the Compression of Plasma Toroids

DTIC Science & Technology

1990-10-01

chamber are only 18 cm apart in the formation section, and the total chamber length can be several meters. The concept is to form a confined plasma ring , and...Focusing of Magnetically Confined Plasma Rings ," Physical Review Letters, Vol. 61, No. 25, pp.2843-2846, 19 December 1988. 2. Turner, W. C., Goldenbaum, G

The Dartmouth Elephant plasma facility

NASA Astrophysics Data System (ADS)

Lynch, K. A.

2017-12-01

The Elephant facility in the Dartmouth Dept of Physics and Astronomyis a 1m by 2m chamber with a microwave-resonant plasma source togetherwith a higher energy electron/ion electrostatic gun. In this chamber weaim to re-create features of the auroral ionosphere including both thethermal plasma background, and the precipitating energetic auroral beam.We can manipulate the position and attitude of various sensors withinthe chamber and monitor their response to the various sources. Recentefforts have focussed on the sheath environment near and around thermalion RPA sensors and the small payloads which carry them into theionosphere.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowman, Adam J.; Scherrer, Joseph R.; Reiserer, Ronald S., E-mail: ron.reiserer@vanderbilt.edu

We present a simple apparatus for improved surface modification of polydimethylsiloxane (PDMS) microfluidic devices. A single treatment chamber for plasma activation and chemical/physical vapor deposition steps minimizes the time-dependent degradation of surface activation that is inherent in multi-chamber techniques. Contamination and deposition irregularities are also minimized by conducting plasma activation and treatment phases in the same vacuum environment. An inductively coupled plasma driver allows for interchangeable treatment chambers. Atomic force microscopy confirms that silane deposition on PDMS gives much better surface quality than standard deposition methods, which yield a higher local roughness and pronounced irregularities in the surface.

Base pressure and heat transfer tests of the 0.0225-scale space shuttle plume simulation model (19-OTS) in yawed flight conditions in the NASA-Lewis 10x10-foot supersonic wind tunnel (test IH83)

NASA Technical Reports Server (NTRS)

Foust, J. W.

1979-01-01

Wind tunnel tests were performed to determine pressures, heat transfer rates, and gas recovery temperatures in the base region of a rocket firing model of the space shuttle integrated vehicle during simulated yawed flight conditions. First and second stage flight of the space shuttle were simulated by firing the main engines in conjunction with the SRB rocket motors or only the SSME's into the continuous tunnel airstream. For the correct rocket plume environment, the simulated altitude pressures were halved to maintain the rocket chamber/altitude pressure ratio. Tunnel freestream Mach numbers from 2.2 to 3.5 were simulated over an altitude range of 60 to 130 thousand feet with varying angle of attack, yaw angle, nozzle gimbal angle and SRB chamber pressure. Gas recovery temperature data derived from nine gas temperature probe runs are presented. The model configuration, instrumentation, test procedures, and data reduction are described.

Low-pressure electrical discharge experiment to simulate high-altitude lightning above thunderclouds

NASA Technical Reports Server (NTRS)

Jarzembski, M. A.; Srivastava, V.

1995-01-01

Recently, extremely interesting high-altitude cloud-ionosphere electrical discharges, like lightning above thunderstorms, have been observed from NASA's space shuttle missions and during airborne and ground-based experiments. To understand these discharges, a new experiment was conceived to simulate a thundercloud in a vacuum chamber using a dielectric in particulate form into which electrodes were inserted to create charge centers analogous to those in an electrified cloud. To represent the ionosphere, a conducting medium (metallic plate) was introduced at the top of the chamber. It was found that for different pressures between approximately 1 and 300 mb, corresponding to various upper atmospheric altitudes, different discharges occurred above the simulated thundercloud, and these bore a remarkable similarity to the observed atmospheric phenomena. At pressures greater than 300 mb, these discharges were rare and only discharges within the simulated thundercloud were observed. Use of a particulate dielectric was critical for the successful simulation of the high-altitude lightning.

Cell proliferation of Paramecium tetraurelia under simulated microgravity

NASA Astrophysics Data System (ADS)

Sawai, S.; Mogami, Y.; Baba, S. A.

Paramecium is known to proliferate faster under microgravity in space and slower under hypergravity Experiments using axenic culture medium have demonstrated that the hypergravity affected directly on the proliferation of Paramecium itself Kato et al 2003 In order to assess the mechanisms underlying the physiological effects of gravity on cell proliferation Paramecium tetraurelia was grown under simulated microgravity performed by clinorotation and the time course of the proliferation was investigated in detail on the basis of the logistic analysis P tetraurelia was cultivated in a closed chamber in which cells were confined without air babbles reducing the shear stresses and turbulence under the rotation The chamber is made of quartz and silicone rubber film the former is for the optically-flat walls for the measurement of cell density by means of a non-invasive laser optical-slice method and the latter for gas exchange Because the closed chamber has an inner dimension of 3 times 3 times 60 mm Paramecium does not accumulate at the top of the chamber despite its negative gravitactic behavior We measured the cell density at regular time intervals without breaking the configuration of the chamber and analyzed the proliferation parameters by fitting the data to a logistic equation Clinorotation had the effects of reducing the proliferation of P tetraurelia It reduced both the saturation cell density and the maximum proliferation rate although it had little effect on the

Investigation on the electron flux to the wall in the VENUS ion source

NASA Astrophysics Data System (ADS)

Thuillier, T.; Angot, J.; Benitez, J. Y.; Hodgkinson, A.; Lyneis, C. M.; Todd, D. S.; Xie, D. Z.

2016-02-01

The long-term operation of high charge state electron cyclotron resonance ion sources fed with high microwave power has caused damage to the plasma chamber wall in several laboratories. Porosity, or a small hole, can be progressively created in the chamber wall which can destroy the plasma chamber over a few year time scale. A burnout of the VENUS plasma chamber is investigated in which the hole formation in relation to the local hot electron power density is studied. First, the results of a simple model assuming that hot electrons are fully magnetized and strictly following magnetic field lines are presented. The model qualitatively reproduces the experimental traces left by the plasma on the wall. However, it is too crude to reproduce the localized electron power density for creating a hole in the chamber wall. Second, the results of a Monte Carlo simulation, following a population of scattering hot electrons, indicate a localized high power deposited to the chamber wall consistent with the hole formation process. Finally, a hypervapotron cooling scheme is proposed to mitigate the hole formation in electron cyclotron resonance plasma chamber wall.

Modernization of NASA's Johnson Space Center Chamber: A Payload Transport Rail System to Support Cryogenic Vacuum Optical Testing of the James Webb Space Telescope (JWST)

NASA Technical Reports Server (NTRS)

Garcia, Sam; Homan, Jonathan; Speed, John

2016-01-01

NASA is the mission lead for the James Webb Space Telescope (JWST), the next of the "Great Observatories", scheduled for launch in 2018. It is directly responsible for the integration and test (I&T) program that will culminate in an end-to-end cryo vacuum optical test of the flight telescope and instrument module in Chamber A at NASA Johnson Space Center. Historic Chamber A is the largest thermal vacuum chamber at Johnson Space Center and one of the largest space simulation chambers in the world. Chamber A has undergone a major modernization effort to support the deep cryogenic, vacuum and cleanliness requirements for testing the JWST. This paper describe the challenges of developing, integrating and modifying new payload rails capable of transporting payloads within the thermal vacuum chamber up to 65,000 pounds. Ambient and Cryogenic Operations required to configure for testing will be explained. Lastly review historical payload configurations stretching from the Apollo program era to current James Webb Space Telescope testing.

Carbon deposition model for oxygen-hydrocarbon combustion, volume 1

NASA Technical Reports Server (NTRS)

Hernandez, R.; Ito, J. I.; Niiya, K. Y.

1987-01-01

Presented are details of the design, fabrication, and testing of subscale hardware used in the evaluation of carbon deposition characteristics of liquid oxygen and three hydrocarbon fuels for both main chamber and preburner/gas generator operating conditions. In main chamber conditions, the deposition of carbon on the combustion chamber wall was investigated at mixture ratios of 2.0 to 4.0 and at pressures of 1000 to 1500 psia. No carbon deposition on the chamber walls was detected at these main chamber mixture ratios. In preburner/gas generator operating conditions, the deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60 and at chamber pressures of 720 to 1650 psia. The results of the tests showed carbon deposition rate to be a strong function of mixture ratio and a weak function of chamber pressure. Further analyses evaluated the operational consequences of carbon deposition on preburner/gas generator performance. The report is in two volumes, of which this is Volume 1 covering the main body of the report plus Appendixes A through D.

Characteristics Air Flow in Room Chamber Test Refrigerator Household Energy Consumption with Inlet Flow Variation

NASA Astrophysics Data System (ADS)

Susanto, Edy; Idrus Alhamid, M.; Nasruddin; Budihardjo

2018-03-01

Room Chamber is the most important in making a good Testing Laboratory. In this study, the 2-D modeling conducted to assess the effect placed the inlet on designing a test chamber room energy consumption of household refrigerators. Where the geometry room chamber is rectangular and approaching the enclosure conditions. Inlet varied over the side parallel to the outlet and compared to the inlet where the bottom is made. The purpose of this study was to determine and define the characteristics of the airflow in the room chamber using CFD simulation. CFD method is used to obtain flow characteristics in detail, in the form of vector flow velocity and temperature distribution inside the chamber room. The result found that the position of the inlet parallel to the outlet causes air flow cannot move freely to the side of the floor, even flow of air moves up toward the outlet. While by making the inlet is below, the air can move freely from the bottom up to the side of the chamber room wall as well as to help uniform flow.

Absolute dose calculations for Monte Carlo simulations of radiotherapy beams.

PubMed

Popescu, I A; Shaw, C P; Zavgorodni, S F; Beckham, W A

2005-07-21

Monte Carlo (MC) simulations have traditionally been used for single field relative comparisons with experimental data or commercial treatment planning systems (TPS). However, clinical treatment plans commonly involve more than one field. Since the contribution of each field must be accurately quantified, multiple field MC simulations are only possible by employing absolute dosimetry. Therefore, we have developed a rigorous calibration method that allows the incorporation of monitor units (MU) in MC simulations. This absolute dosimetry formalism can be easily implemented by any BEAMnrc/DOSXYZnrc user, and applies to any configuration of open and blocked fields, including intensity-modulated radiation therapy (IMRT) plans. Our approach involves the relationship between the dose scored in the monitor ionization chamber of a radiotherapy linear accelerator (linac), the number of initial particles incident on the target, and the field size. We found that for a 10 x 10 cm2 field of a 6 MV photon beam, 1 MU corresponds, in our model, to 8.129 x 10(13) +/- 1.0% electrons incident on the target and a total dose of 20.87 cGy +/- 1.0% in the monitor chambers of the virtual linac. We present an extensive experimental verification of our MC results for open and intensity-modulated fields, including a dynamic 7-field IMRT plan simulated on the CT data sets of a cylindrical phantom and of a Rando anthropomorphic phantom, which were validated by measurements using ionization chambers and thermoluminescent dosimeters (TLD). Our simulation results are in excellent agreement with experiment, with percentage differences of less than 2%, in general, demonstrating the accuracy of our Monte Carlo absolute dose calculations.

Salt weathering in Egyptian limestone after laboratory simulations with continuous flow of salt solutions at different temperatures

NASA Astrophysics Data System (ADS)

Aly, Nevin; Gomez-Heras, Miguel; Hamed, Ayman; Alvarez de Buergo, Monica

2013-04-01

weathering in Egyptian limestone after laboratory simulations with continuous flow of salt solutions at different temperatures Nevin Aly Mohamed (1), Miguel Gomez - Heras(2), Ayman Hamed Ahmed (1), and Monica Alvarez de Buergo(2). (1) Faculty of Pet. & Min. Engineering- Suez Canal University, Suez, Egypt, (2) Instituto de Geociencias (CSIC-UCM) Madrid. Spain. Limestone is one of the most frequent building stones in Egypt and is used since the time of ancient Egyptians and salt weathering is one of the main threats to its conservation. Most of the limestone used in historical monuments in Cairo is a biomicrite extracted from the Mid-Eocene Mokattam Group. During this work, cylindrical samples (2.4 cm diameter and approx. 4.8 cm length) were subjected, in a purpose-made simulation chamber, to simulated laboratory weathering tests with fixed salt concentration (10% weight NaCl solution), at different temperatures, which were kept constant throughout each test (10, 20, 30, 40 oC). During each test, salt solutions flowed continuously imbibing samples by capilarity. Humidity within the simulation chamber was reduced using silica gel to keep it low and constant to increase evaporation rate. Temperature, humidity inside the simulation chamber and samples weight were digitally monitored during each test. Results show the advantages of the proposed experimental methodology using a continuous flow of salt solutions and shed light on the effect of temperature on the dynamics of salt crystallization on and within samples. Research funded by mission sector of high education ministry, Egypt and Geomateriales S2009/MAT-1629.

Accurate condensed history Monte Carlo simulation of electron transport. II. Application to ion chamber response simulations.

PubMed

Kawrakow, I

2000-03-01

In this report the condensed history Monte Carlo simulation of electron transport and its application to the calculation of ion chamber response is discussed. It is shown that the strong step-size dependencies and lack of convergence to the correct answer previously observed are the combined effect of the following artifacts caused by the EGS4/PRESTA implementation of the condensed history technique: dose underprediction due to PRESTA'S pathlength correction and lateral correlation algorithm; dose overprediction due to the boundary crossing algorithm; dose overprediction due to the breakdown of the fictitious cross section method for sampling distances between discrete interaction and the inaccurate evaluation of energy-dependent quantities. These artifacts are now understood quantitatively and analytical expressions for their effect are given.

Intercomparison of OH Radical Measurements by Long-Path Absorption and Laser Induced Fluorescence in the Atmosphere Simulation Chamber SAPHIR

NASA Astrophysics Data System (ADS)

Dorn, H.-P.; Brauers, T.; Greif, J.; Häseler, R.; Hofzumahaus, A.; Holland, F.; Rupp, L.

2003-04-01

A striking advantage of the SAPHIR chamber is the availability of two spectroscopic detection instruments for OH radicals: Laser-Induced Fluorescence Spectroscopy (LIF) and Long-Path Differential Optical Laser Absorption Spectroscopy (DOAS). Both instruments have already been compared in 1994 during the field measurement campaign POPCORN. They agreed well with a correlation coefficient of r=0.90 and a weighted linear fit with a slope of 1.09 +- 0.12. However, OH measurements in the simulation chamber differ significantly from measurements in ambient air. While DOAS measures OH as an integral value along the central longitudinal axis of SAPHIR, LIF samples the air locally and close (2 cm) to the floor of the chamber. Thus, the LIF measurements might be possibly affected by local concentration gradients caused by insufficient mixing of the chamber air or by deposition to the wall. On the other hand, if turbulent mixing of the chamber air is weak and high concentrations of ozone are used in experiments, the DOAS instrument might be subject to artificial formation of OH radicals in the air volume which is illuminated by the detection laser. This interference results from laser induced photolysis of ozone and the subsequent reaction of water vapor with the excited oxygen atoms formed. Thus it is of decisive importance to compare OH measurements from both instruments in order to investigate potential disturbing effects due to the specific sampling properties of both instruments within SAPHIR. We report on OH measurements accomplished simultaneously with both instruments using different trace gas compositions and experimental conditions.

Partitioning an Artificial Anterior Chamber With a Latex Diaphragm to Simulate Anterior and Posterior Segment Pressure Dynamics: The "DMEK Practice Stage," Where Surgeons Can Rehearse the "DMEK Dance".

PubMed

Sáles, Christopher S; Straiko, Michael D; Fernandez, Ana Alzaga; Odell, Kelly; Dye, Philip K; Tran, Khoa D

2018-02-01

To present a novel apparatus for simulating the anterior and posterior segment pressure dynamics involved in executing Descemet membrane endothelial keratoplasty (DMEK) surgery when using a chamber-shallowing technique. An artificial anterior chamber (AAC), 18-mm trephine, latex glove, two 3-mL syringes, and one donor cornea comprising an intact corneoscleral cap from which a DMEK tissue was peeled and punched are required for the model. After making the corneal incisions with the corneoscleral cap mounted on the AAC in the usual fashion, the corneoscleral cap is remounted onto the dried AAC over an 18-mm latex diaphragm. The space between the latex diaphragm and the cornea is filled with saline to pressurize the anterior chamber, and the posterior segment is pressurized with air from a syringe. The resulting apparatus comprises a posterior segment and anterior chamber that exert pressure on each other by way of a distensible latex diaphragm. A novice and experienced DMEK surgeon and 2 eye bank technicians were able to assemble the apparatus and perform the routine steps of a DMEK procedure, including maneuvers that require shallowing the anterior chamber and lowering its pressure. Only one cornea was required per apparatus. We present a novel in vitro model of the human eye that more closely mimics the anterior and posterior segment pressure dynamics of in vivo DMEK surgery than average human and animal cadaveric globes. The model is easy to assemble, inexpensive, and applicable to a range of teaching environments.

[Ability of typical greenery shrubs of Beijing to adsorb and arrest PM2.5 ].

PubMed

Liang, Dan; Wang, Bin; Wang, Yun-qi; Zhang, Hui-lan; Yang, Song-nan; Li, Ang

2014-09-01

Four typical types of green shrubs of Beijing (Euonymus japonicus, Buxus microphylla, Berberis thunbergii cv. atropurpurea, Taxus cuspidate cv. nana) were selected to study their capacities in adsorbing and arresting PM2.5 using both field observations and air chamber simulations. Concurrently, in order to analyze the pollution characteristics of Beijing in winter and spring, the PM2.5 concentrations of December 2012 to May 2013 were collected. Experimental results showed that: From the gas chamber experiments, the ability to adsorb and arrest PM2.5 was in the order of Berberis thunbergii cv. atropurpurea > Buxus microphylla > Taxus cuspidate cv. nana > Euonymus japonicus, mainly due to the differences in leaf characteristics; Outside measurement results showed that the ability to adsorb and arrest PM2.5 was ranked as Buxus microphylla > Berberis thunbergii cv. atropurpurea > Taxus cuspidate cv. nana > Euonymus japonicus. Chamber simulation and outdoor observation showed that Buxus microphylla and Berberis thunbergii cv. atropurpurea had strong ability to adsorb and arrest PM2.5; Meanwhile, the slight differences between the chamber simulation and outdoor observation results might be related to plant structure. Compared to tree species, the planting condition of shrub species was loose, and it greened quickly; By analyzing the Beijing PM2.5 concentration values in winter and spring, it was found that the PM2.5 concentration was particularly high in the winter of Beijing, and evergreen shrubs maintained the ability to adsorb and arrest PM2.5.

Full-scale chamber investigation and simulation of air freshener emissions in the presence of ozone.

PubMed

Liu, Xiaoyu; Mason, Mark; Krebs, Kenneth; Sparks, Leslie

2004-05-15

Volatile organic compound (VOC) emissions from one electrical plug-in type of pine-scented air freshener and their reactions with O3 were investigated in the U.S. Environmental Protection Agency indoor air research large chamber facility. Ozone was generated from a device marketed as an ozone generator air cleaner. Ozone and oxides of nitrogen concentrations and chamber conditions such as temperature, relative humidity, pressure, and air exchange rate were controlled and/or monitored. VOC emissions and some of the reaction products were identified and quantified. Source emission models were developed to predict the time/concentration profiles of the major VOCs (limonene, alpha-pinene, beta-pinene, 3-carene, camphene, benzyl propionate, benzyl alcohol, bornyl acetate, isobornyl acetate, and benzaldehyde) emitted bythe air freshener. Gas-phase reactions of VOCs from the air freshener with O3 were simulated by a photochemical kinetics simulation system using VOC reaction mechanisms and rate constants adopted from the literature. The concentration-time predictions were in good agreement with the data for O3 and VOCs emitted from the air freshener and with some of the primary reaction products. Systematic differences between the predictions and the experimental results were found for some species. Poor understanding of secondary reactions and heterogeneous chemistry in the chamber is the likely cause of these differences. The method has the potential to provide data to predict the impact of O3/VOC interactions on indoor air quality.

Sliding Mode Control of a Thermal Mixing Process

NASA Technical Reports Server (NTRS)

Richter, Hanz; Figueroa, Fernando

2004-01-01

In this paper we consider the robust control of a thermal mixer using multivariable Sliding Mode Control (SMC). The mixer consists of a mixing chamber, hot and cold fluid valves, and an exit valve. The commanded positions of the three valves are the available control inputs, while the controlled variables are total mass flow rate, chamber pressure and the density of the mixture inside the chamber. Unsteady thermodynamics and linear valve models are used in deriving a 5th order nonlinear system with three inputs and three outputs, An SMC controller is designed to achieve robust output tracking in the presence of unknown energy losses between the chamber and the environment. The usefulness of the technique is illustrated with a simulation.

Experimental investigation of the effect of air cavity size in cylindrical ionization chambers on the measurements in 60Co radiotherapy beams

NASA Astrophysics Data System (ADS)

Swanpalmer, John; Johansson, Karl-Axel

2011-11-01

In the late 1970s, Johansson et al (1978 Int. Symp. National and International Standardization of Radiation Dosimetry (Atlanta 1977) vol 2 (Vienna: IAEA) pp 243-70) reported experimentally determined displacement correction factors (pdis) for cylindrical ionization chamber dosimetry in 60Co and high-energy photon beams. These pdis factors have been implemented and are currently in use in a number of dosimetry protocols. However, the accuracy of these factors has recently been questioned by Wang and Rogers (2009a Phys. Med. Biol. 54 1609-20), who performed Monte Carlo simulations of the experiments performed by Johansson et al. They reported that the inaccuracy of the pdis factors originated from the normalization procedure used by Johansson et al. In their experiments, Johansson et al normalized the measured depth-ionization curves at the depth of maximum ionization for each of the different ionization chambers. In this study, we experimentally investigated the effect of air cavity size of cylindrical ionization chambers in a PMMA phantom and 60Co γ-beam. Two different pairs of air-filled cylindrical ionization chambers were used. The chambers in each pair had identical construction and materials but different air cavity volume (diameter). A 20 MeV electron beam was utilized to determine the ratio of the mass of air in the cavity of the two chambers in each pair. This ratio of the mass of air in each pair was then used to compare the ratios of the ionizations obtained at different depths in the PMMA phantom and 60Co γ-beam using the two pairs of chambers. The diameter of the air cavity of cylindrical ionization chambers influences both the depth at which the maximum ionization is observed and the ionization per unit mass of air at this depth. The correction determined at depths of 50 mm and 100 mm is smaller than the correction currently used in many dosimetry protocols. The results presented here agree with the findings of Wang and Rogers' Monte Carlo simulations and show that the normalization procedure employed by Johansson et al is not correct.

Georges Charpak, Particle Detectors, and Multiwire Chambers

Science.gov Websites

particle detectors used throughout experimental particle physics. In 1968, he invented and developed the the 2005 International Year of Physics (video) Top Some links on this page may take you to non-federal

Two Simulated-Smog Atmospheres with Different Chemical Compositions Produce Contrasting Mutagenicity in Salmonella.

EPA Science Inventory

Ozone (O3), particulate matter (PM), and nitrogen dioxide (NO2) are criteria pollutants used to evaluate air quality. Using a 14.3-m3 Teflon-lined smog chamber with 120 UV bulbs to simulate solar radiation, we generated 2 simulated-smog atmospheres (SSA-1 & SSA-2) with differ...

Simulating Pressure Profiles for the Free-Electron Laser Photoemission Gun Using Molflow+

NASA Astrophysics Data System (ADS)

Song, Diego; Hernandez-Garcia, Carlos

2012-10-01

The Jefferson Lab Free Electron Laser (FEL) generates tunable laser light by passing a relativistic electron beam generated in a high-voltage DC electron gun with a semiconducting photocathode through a magnetic undulator. The electron gun is in stringent vacuum conditions in order to guarantee photocathode longevity. Considering an upgrade of the electron gun, this project consists of simulating pressure profiles to determine if the novel design meets the electron gun vacuum requirements. The method of simulation employs the software Molflow+, developed by R. Kersevan at the Organisation Europ'eene pour la Recherche Nucl'eaire (CERN), which uses the test-particle Monte Carlo method to simulate molecular flows in 3D structures. Pressure is obtained along specified chamber axes. Results are then compared to measured pressure values from the existing gun for validation. Outgassing rates, surface area, and pressure were found to be proportionally related. The simulations indicate that the upgrade gun vacuum chamber requires more pumping compared to its predecessor, while it holds similar vacuum conditions. The ability to simulate pressure profiles through tools like Molflow+, allows researchers to optimize vacuum systems during the engineering process.

Simulating and explaining passive air sampling rates for semi-volatile compounds on polyurethane foam passive samplers

PubMed Central

Petrich, Nicholas T.; Spak, Scott N.; Carmichael, Gregory R.; Hu, Dingfei; Martinez, Andres; Hornbuckle, Keri C.

2013-01-01

Passive air samplers (PAS) including polyurethane foam (PUF) are widely deployed as an inexpensive and practical way to sample semi-volatile pollutants. However, concentration estimates from PAS rely on constant empirical mass transfer rates, which add unquantified uncertainties to concentrations. Here we present a method for modeling hourly sampling rates for semi-volatile compounds from hourly meteorology using first-principle chemistry, physics, and fluid dynamics, calibrated from depuration experiments. This approach quantifies and explains observed effects of meteorology on variability in compound-specific sampling rates and analyte concentrations; simulates nonlinear PUF uptake; and recovers synthetic hourly concentrations at a reference temperature. Sampling rates are evaluated for polychlorinated biphenyl congeners at a network of Harner model samplers in Chicago, Illinois during 2008, finding simulated average sampling rates within analytical uncertainty of those determined from loss of depuration compounds, and confirming quasi-linear uptake. Results indicate hourly, daily and interannual variability in sampling rates, sensitivity to temporal resolution in meteorology, and predictable volatility-based relationships between congeners. We quantify importance of each simulated process to sampling rates and mass transfer and assess uncertainty contributed by advection, molecular diffusion, volatilization, and flow regime within the PAS, finding PAS chamber temperature contributes the greatest variability to total process uncertainty (7.3%). PMID:23837599

Pre-launch simulation experiment of microwave-ionosphere nonlinear interaction rocket experiment in the space plasma chamber

NASA Astrophysics Data System (ADS)

Kaya, N.; Tsutsui, M.; Matsumoto, H.; Kimura, I.

1980-09-01

A pre-flight test experiment of a microwave-ionosphere nonlinear interaction rocket experiment (MINIX) has been carried out in a space plasma simulation chamber. Though the first rocket experiment ended up in failure because of a high voltage trouble, interesting results are observed in the pre-flight experiment. A significant microwave heating of plasma up to 300% temperature increase is observed. Strong excitations of plasma waves by the transmitted microwaves in the VLF and HF range are observed as well. These microwave effects may have to be taken into account in solar power satellite projects in the future.

Preacclimatization in hypoxic chambers for high altitude sojourns.

PubMed

Küpper, Thomas E A H; Schöffl, Volker

2010-09-01

Since hypoxic chambers are more and more available, they are used for preacclimatization to prepare for sojourns at high altitude. Since there are different protocols and the data differ, there is no general consensus about the standard how to perform preacclimatization by simulated altitude. The paper reviews the different types of exposure and focuses on the target groups which may benefit from preacclimatization. Since data about intermittent hypoxia for some hours per day to reduce the incidence of acute mountain sickness differ, it is suggested to perform preacclimatization by sleeping some nights at a simulated altitude which follows the altitude profile of the "gold standard" for high altitude acclimatization.

Note: Design of transverse electron gun for electron beam based reactive evaporation system.

PubMed

Maiti, Namita; Barve, U D; Bhatia, M S; Das, A K

2011-05-01

In this paper design of a 10 kV, 10 kW transverse electron gun, suitable for reactive evaporation, supported by simulation and modeling, is presented. Simulation of the electron beam trajectory helps in locating the emergence aperture after 90° bend and also in designing the crucible on which the beam is finally incident after 270° bend. The dimension of emergence aperture plays a vital role in designing the differential pumping system between the gun chamber and the substrate chamber. Experimental validation is done for beam trajectory by piercing a stainless steel plate at 90° position which is kept above the crucible.

Modeling and Simulation of Upset-Inducing Disturbances for Digital Systems in an Electromagnetic Reverberation Chamber

NASA Technical Reports Server (NTRS)

Torres-Pomales, Wilfredo

2014-01-01

This report describes a modeling and simulation approach for disturbance patterns representative of the environment experienced by a digital system in an electromagnetic reverberation chamber. The disturbance is modeled by a multi-variate statistical distribution based on empirical observations. Extended versions of the Rejection Samping and Inverse Transform Sampling techniques are developed to generate multi-variate random samples of the disturbance. The results show that Inverse Transform Sampling returns samples with higher fidelity relative to the empirical distribution. This work is part of an ongoing effort to develop a resilience assessment methodology for complex safety-critical distributed systems.

Feasibility of an orbital simulator of stratospheric photochemistry

NASA Technical Reports Server (NTRS)

Matloff, G. L.; Hoffert, M. I.

1978-01-01

It is proposed that a stratospheric photochemistry simulator could be created in sun-synchronous orbit, so that diffusion and photochemistry could be decoupled and uncertainties in photochemical reaction rates could be substantially reduced. The proposed test chamber is described, and it is suggested that the technology of superpressure balloons seems to be the best short-term solution to the construction of the proposed facility. Both unreinforced polyester films and gelatin films are considered as candidate chamber coatings. It is noted that the experiments can be performed early in the space-manufacturing era and that at least three dedicated Shuttle launches will be required to establish the proposed facility.

Extraction of Thermal Performance Values from Samples in the Lunar Dust Adhesion Bell Jar

NASA Technical Reports Server (NTRS)

Gaier, James R.; Siamidis, John; Larkin, Elizabeth M.G.

2008-01-01

A simulation chamber has been developed to test the performance of thermal control surfaces under dusty lunar conditions. The lunar dust adhesion bell jar (LDAB) is a diffusion pumped vacuum chamber (10-8 Torr) built to test material samples less than about 7 cm in diameter. The LDAB has the following lunar dust stimulant processing capabilities: heating and cooling while stirring in order to degas and remove absorbed water; RF air-plasma for activating the dust and for organic contaminant removal; RF H/He-plasma to simulate solar wind; dust sieving system for controlling particle sizes; and a controlled means of introducing the activated dust to the samples under study. The LDAB is also fitted with an in situ Xe arc lamp solar simulator, and a cold box that can reach 30 K. Samples of thermal control surfaces (2.5 cm diameter) are introduced into the chamber for calorimetric evaluation using thermocouple instrumentation. The object of this paper is to present a thermal model of the samples under test conditions, and to outline the procedure to extract the absorptance, emittance, and thermal efficiency from the pristine and sub-monolayer dust covered samples

Simulation of the High Performance Time to Digital Converter for the ATLAS Muon Spectrometer trigger upgrade

NASA Astrophysics Data System (ADS)

Meng, X. T.; Levin, D. S.; Chapman, J. W.; Zhou, B.

2016-09-01

The ATLAS Muon Spectrometer endcap thin-Resistive Plate Chamber trigger project compliments the New Small Wheel endcap Phase-1 upgrade for higher luminosity LHC operation. These new trigger chambers, located in a high rate region of ATLAS, will improve overall trigger acceptance and reduce the fake muon trigger incidence. These chambers must generate a low level muon trigger to be delivered to a remote high level processor within a stringent latency requirement of 43 bunch crossings (1075 ns). To help meet this requirement the High Performance Time to Digital Converter (HPTDC), a multi-channel ASIC designed by CERN Microelectronics group, has been proposed for the digitization of the fast front end detector signals. This paper investigates the HPTDC performance in the context of the overall muon trigger latency, employing detailed behavioral Verilog simulations in which the latency in triggerless mode is measured for a range of configurations and under realistic hit rate conditions. The simulation results show that various HPTDC operational configurations, including leading edge and pair measurement modes can provide high efficiency (>98%) to capture and digitize hits within a time interval satisfying the Phase-1 latency tolerance.

Diaphragm correction factors for the FAC-IR-300 free-air ionization chamber.

PubMed

Mohammadi, Seyed Mostafa; Tavakoli-Anbaran, Hossein

2018-02-01

A free-air ionization chamber FAC-IR-300, designed by the Atomic Energy Organization of Iran, is used as the primary Iranian national standard for the photon air kerma. For accurate air kerma measurements, the contribution from the scattered photons to the total energy released in the collecting volume must be eliminated. One of the sources of scattered photons is the chamber's diaphragm. In this paper, the diaphragm scattering correction factor, k dia , and the diaphragm transmission correction factor, k tr , were introduced. These factors represent corrections to the measured charge (or current) for the photons scattered from the diaphragm surface and the photons penetrated through the diaphragm volume, respectively. The k dia and k tr values were estimated by Monte Carlo simulations. The simulations were performed for the mono-energetic photons in the energy range of 20 - 300keV. According to the simulation results, in this energy range, the k dia values vary between 0.9997 and 0.9948, and k tr values decrease from 1.0000 to 0.9965. The corrections grow in significance with increasing energy of the primary photons. Copyright © 2017 Elsevier Ltd. All rights reserved.

Influence of vapor wall loss in laboratory chambers on yields of secondary organic aerosol

PubMed Central

Zhang, Xuan; Cappa, Christopher D.; Jathar, Shantanu H.; McVay, Renee C.; Ensberg, Joseph J.; Kleeman, Michael J.; Seinfeld, John H.

2014-01-01

Secondary organic aerosol (SOA) constitutes a major fraction of submicrometer atmospheric particulate matter. Quantitative simulation of SOA within air-quality and climate models—and its resulting impacts—depends on the translation of SOA formation observed in laboratory chambers into robust parameterizations. Worldwide data have been accumulating indicating that model predictions of SOA are substantially lower than ambient observations. Although possible explanations for this mismatch have been advanced, none has addressed the laboratory chamber data themselves. Losses of particles to the walls of chambers are routinely accounted for, but there has been little evaluation of the effects on SOA formation of losses of semivolatile vapors to chamber walls. Here, we experimentally demonstrate that such vapor losses can lead to substantially underestimated SOA formation, by factors as much as 4. Accounting for such losses has the clear potential to bring model predictions and observations of organic aerosol levels into much closer agreement. PMID:24711404

Measured and Monte Carlo calculated k{sub Q} factors: Accuracy and comparison

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muir, B. R.; McEwen, M. R.; Rogers, D. W. O.

2011-08-15

Purpose: The journal Medical Physics recently published two papers that determine beam quality conversion factors, k{sub Q}, for large sets of ion chambers. In the first paper [McEwen Med. Phys. 37, 2179-2193 (2010)], k{sub Q} was determined experimentally, while the second paper [Muir and Rogers Med. Phys. 37, 5939-5950 (2010)] provides k{sub Q} factors calculated using Monte Carlo simulations. This work investigates a variety of additional consistency checks to verify the accuracy of the k{sub Q} factors determined in each publication and a comparison of the two data sets. Uncertainty introduced in calculated k{sub Q} factors by possible variation ofmore » W/e with beam energy is investigated further. Methods: The validity of the experimental set of k{sub Q} factors relies on the accuracy of the NE2571 reference chamber measurements to which k{sub Q} factors for all other ion chambers are correlated. The stability of NE2571 absorbed dose to water calibration coefficients is determined and comparison to other experimental k{sub Q} factors is analyzed. Reliability of Monte Carlo calculated k{sub Q} factors is assessed through comparison to other publications that provide Monte Carlo calculations of k{sub Q} as well as an analysis of the sleeve effect, the effect of cavity length and self-consistencies between graphite-walled Farmer-chambers. Comparison between the two data sets is given in terms of the percent difference between the k{sub Q} factors presented in both publications. Results: Monitoring of the absorbed dose calibration coefficients for the NE2571 chambers over a period of more than 15 yrs exhibit consistency at a level better than 0.1%. Agreement of the NE2571 k{sub Q} factors with a quadratic fit to all other experimental data from standards labs for the same chamber is observed within 0.3%. Monte Carlo calculated k{sub Q} factors are in good agreement with most other Monte Carlo calculated k{sub Q} factors. Expected results are observed for the sleeve effect and the effect of cavity length on k{sub Q}. The mean percent differences between experimental and Monte Carlo calculated k{sub Q} factors are -0.08, -0.07, and -0.23% for the Elekta 6, 10, and 25 MV nominal beam energies, respectively. An upper limit on the variation of W/e in photon beams from cobalt-60 to 25 MV is determined as 0.4% with 95% confidence. The combined uncertainty on Monte Carlo calculated k{sub Q} factors is reassessed and amounts to between 0.40 and 0.49% depending on the wall material of the chamber. Conclusions: Excellent agreement (mean percent difference of only 0.13% for the entire data set) between experimental and calculated k{sub Q} factors is observed. For some chambers, k{sub Q} is measured for only one chamber of each type--the level of agreement observed in this study would suggest that for those chambers the measured k{sub Q} values are generally representative of the chamber type.« less

Scaling behavior of columnar structure during physical vapor deposition

NASA Astrophysics Data System (ADS)

Meese, W. J.; Lu, T.-M.

2018-02-01

The statistical effects of different conditions in physical vapor deposition, such as sputter deposition, have on thin film morphology has long been the subject of interest. One notable effect is that of column development due to differential chamber pressure in the well-known empirical model called the Thornton's Structure Zone Model. The model is qualitative in nature and theoretical understanding with quantitative predictions of the morphology is still lacking due, in part, to the absence of a quantitative description of the incident flux distribution on the growth front. In this work, we propose an incident Gaussian flux model developed from a series of binary hard-sphere collisions and simulate its effects using Monte Carlo methods and a solid-on-solid growth scheme. We also propose an approximate cosine-power distribution for faster Monte Carlo sampling. With this model, it is observed that higher chamber pressures widen the average deposition angle, and similarly increase the growth of column diameters (or lateral correlation length) and the column-to-column separation (film surface wavelength). We treat both the column diameter and the surface wavelength as power laws. It is seen that both the column diameter exponent and the wavelength exponent are very sensitive to changes in pressure for low pressures (0.13 Pa to 0.80 Pa); meanwhile, both exponents saturate for higher pressures (0.80 Pa to 6.7 Pa) around a value of 0.6. These predictions will serve as guides to future experiments for quantitative description of the film morphology under a wide range of vapor pressure.

In Vitro Culturing and Live Imaging of Drosophila Egg Chambers: A History and Adaptable Method.

PubMed

Peters, Nathaniel C; Berg, Celeste A

2016-01-01

The development of the Drosophila egg chamber encompasses a myriad of diverse germline and somatic events, and as such, the egg chamber has become a widely used and influential developmental model. Advantages of this system include physical accessibility, genetic tractability, and amenability to microscopy and live culturing, the last of which is the focus of this chapter. To provide adequate context, we summarize the structure of the Drosophila ovary and egg chamber, the morphogenetic events of oogenesis, the history of egg-chamber live culturing, and many of the important discoveries that this culturing has afforded. Subsequently, we discuss various culturing methods that have facilitated analyses of different stages of egg-chamber development and different types of cells within the egg chamber, and we present an optimized protocol for live culturing Drosophila egg chambers.We designed this protocol for culturing late-stage Drosophila egg chambers and live imaging epithelial tube morphogenesis, but with appropriate modifications, it can be used to culture egg chambers of any stage. The protocol employs a liquid-permeable, weighted "blanket" to gently hold egg chambers against the coverslip in a glass-bottomed culture dish so the egg chambers can be imaged on an inverted microscope. This setup provides a more buffered, stable, culturing environment than previously published methods by using a larger volume of culture media, but the setup is also compatible with small volumes. This chapter should aid researchers in their efforts to culture and live-image Drosophila egg chambers, further augmenting the impressive power of this model system.

In vitro culturing and live imaging of Drosophila egg chambers: A history and adaptable method

PubMed Central

Peters, Nathaniel C.; Berg, Celeste A.

2017-01-01

Summary/Abstract The development of the Drosophila egg chamber encompasses a myriad of diverse germline and somatic events, and as such, the egg chamber has become a widely used and influential developmental model. Advantages of this system include physical accessibility, genetic tractability, and amenability to microscopy and live culturing, the last of which is the focus of this chapter. To provide adequate context, we summarize the structure of the Drosophila ovary and egg chamber, the morphogenetic events of oogenesis, the history of egg-chamber live culturing, and many of the important discoveries that this culturing has afforded. Subsequently, we discuss various culturing methods that have facilitated analyses of different stages of egg-chamber development and different types of cells within the egg chamber, and we present an optimized protocol for live culturing Drosophila egg chambers. We designed this protocol for culturing late-stage Drosophila egg chambers and live imaging epithelial tube morphogenesis, but with appropriate modifications it can be used to culture egg chambers of any stage. The protocol employs a liquid-permeable, weighted, “blanket” to gently hold egg chambers against the coverslip in a glass-bottomed culture dish so the egg chambers can be imaged on an inverted microscope. This setup provides a more buffered, stable culturing environment than previously published methods by using a larger volume of culture media, but the setup is also compatible with small volumes. This chapter should aid researchers in their efforts to culture and live image Drosophila egg chambers, further augmenting the impressive power of this model system. PMID:27557572

Arrhythmia discrimination by physician and defibrillator: importance of atrial channel.

PubMed

Diemberger, Igor; Martignani, Cristian; Biffi, Mauro; Frabetti, Lorenzo; Valzania, Cinzia; Cooke, Robin M T; Rapezzi, Claudio; Branzi, Angelo; Boriani, Giuseppe

2012-01-26

Many ICD carriers experience inappropriate shocks, but the relative merits of dual- /single-chamber devices for arrhythmia discrimination still remain unclear. We explored possible advantages of the atrial data provided by dual-chamber implantable defibrillators (ICD) for discrimination of real-life supraventricular/ventricular tachyarrhythmias (SVT/VT). 100 dual-chamber traces from 24 ICD were blindly reviewed in dual-chamber and simulated single-chamber (with/without discriminator data) reading modes by five electrophysiologists who determined chamber of origin and provided Likert-scale "confidence" ratings. We assessed 1) intra/interobserver concordance; 2) diagnostic accuracy, using expert diagnoses as a reference standard; 3) ROC curves of sensitivity/specificity of "likelihood perception" scores, generated by combining chamber-of-origin diagnostic judgments with Likert-scale "confidence" ratings. We also assessed diagnostic accuracy of automated discrimination by all possible dual-/single-chamber algorithm configurations. Interobserver concordance was "substantial" (modified Cohen kappa-test values for dual-/single-chamber, 0.79/0.68); intraobserver concordance "almost complete" (kappa ≥ 0.89). Dual-chamber mode provided best diagnostic sensitivity/specificity (99%/92%) and highest reader confidence (p<0.001). Area under ROC curves of sensitivity/specificity values for the "likelihood perception" score (representing electrophysiologists' perceptions of the likelihood that an episode was of ventricular origin) was highest in dual-chamber mode (0.98 vs. 0.93 for both single-chamber modes; p<0.001). Regarding automated discrimination, all four dual-chamber configurations conferred 100% sensitivity (specificity values ranged 39%-88%), whereas single-chamber configurations appeared inferior (best sensitivity/specificity combination, 89%/64%). Availability of the atrial channel helps in reducing inappropriate ICD therapies by providing relevant advantages in terms of both appropriate cardiologist's post-hoc discrimination of SVT/VT (improving program tailoring) and automated arrhythmia discrimination. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Simulating Electrophoresis.

ERIC Educational Resources Information Center

Moertel, Cheryl; Frutiger, Bruce

1996-01-01

Describes a DNA fingerprinting simulation that uses vegetable food coloring and plastic food containers instead of DNA and expensive gel electrophoresis chambers. Allows students to decipher unknown combinations of dyes in a method similar to that used to decipher samples of DNA in DNA fingerprint techniques. (JRH)

Reactor for simulation and acceleration of solar ultraviolet damage

NASA Technical Reports Server (NTRS)

Laue, E.; Gupta, A.

1979-01-01

An environmental test chamber providing acceleration of UV radiation and precise temperature control (+ or -)1 C was designed, constructed and tested. This chamber allows acceleration of solar ultraviolet up to 30 suns while maintaining temperature of the absorbing surface at 30 C - 60 C. This test chamber utilizes a filtered medium pressure mercury arc as the source of radiation, and a combination of selenium radiometer and silicon radiometer to monitor solar ultraviolet (295-340 nm) and total radiant power output, respectively. Details of design and construction and operational procedures are presented along with typical test data.

Almond Test Body. [for microwave anechoic chambers

NASA Technical Reports Server (NTRS)

Dominek, Allen K. (Inventor); Wood, Richard M. (Inventor); Gilreath, Melvin C. (Inventor)

1989-01-01

The invention is an almond shaped test body for use in measuring the performance characteristics of microwave anechoic chambers and for use as a support for components undergoing radar cross-section measurements. The novel aspect of this invention is its shape, which produces a large dynamic scattered field over large angular regions making the almond valuable for verifying the performance of microwave anechoic chambers. As a component mount, the almond exhibits a low return that does not perturb the measurement of the component and it simulates the backscatter characteristics of the component as if over an infinite ground plane.

APOLLO 16 COMMANDER JOHN YOUNG ENTERS ALTITUDE CHAMBER FOR TESTS

NASA Technical Reports Server (NTRS)

1971-01-01

Apollo 16 commander John W. Young prepares to enter the lunar module in an altitude chamber in the Manned Spacecraft Operations Building at the spaceport prior to an altitude run. During the altitude run, in which Apollo 16 lunar module pilot Charles M. Duke also participated, the chamber was pumped down to simulate pressure at an altitude in excess of 200,000 feet. Young, Duke and command module pilot Thomas K. Mattingly II, are training at the Kennedy Space Center for the Apollo 16 mission. Launch is scheduled from Pad 39A, March 17, 1972.

T-Violation experiment using polarized Li-8 at TRIUMF

NASA Astrophysics Data System (ADS)

Murata, Jiro; MTV Collaboration

2014-09-01

The MTV experiment searching T-Violating electron transverse polarization in polarized nuclear beta decay at TRIUMF is running. The main electron tracking detector as a Mott polarimeter was upgraded from a planer drift chamber to a cylindrical drift chamber (CDC), which has been commissioned and tested. In this talk, preparation status of the next physics production using the CDC will be presented.

Neodymium:YAG laser cutting of intraocular lens haptics.

PubMed

Gorn, R A; Steinert, R F

1985-11-01

Neodymium:YAG laser cutting of polymethylmethacrylate and polypropylene anterior chamber and posterior chamber intraocular lens haptics was studied in terms of ease of transection and physical structure of the cut areas as seen by scanning electron microscopy. A marked difference was discovered, with the polymethylmethacrylate cutting easily along transverse planes, whereas the polypropylene resisted cutting along longitudinal fibers. Clinical guidelines are presented.

Elimination of Lifetime Limiting Mechanism of Hall Thrusters

NASA Technical Reports Server (NTRS)

Jacobson, David T. (Inventor); Manzella, David H. (Inventor)

2009-01-01

A Hall thruster includes inner and outer electromagnets, with the outer electromagnet circumferentially surrounding the inner electromagnet along a centerline axis and separated therefrom, inner and outer poles, in physical connection with their respective inner and outer electromagnets, with the inner pole having a mostly circular shape and the outer pole having a mostly annular shape, a discharge chamber separating the inner and outer poles, a combined anode electrode/gaseous propellant distributor, located at an upstream portion of the discharge chamber and supplying propellant gas and an actuator, in contact with a sleeve portion of the discharge chamber. The actuator is configured to extend the sleeve portion or portions of the discharge chamber along the centerline axis with respect to the inner and outer poles.

Theoretical modeling of a gas clearance phase regulation mechanism for a pneumatically-driven split-Stirling-cycle cryocooler

NASA Astrophysics Data System (ADS)

Zhang, Cun-quan; Zhong, Cheng

2015-03-01

The concept of a new type of pneumatically-driven split-Stirling-cycle cryocooler with clearance-phase-adjustor is proposed. In this implementation, the gap between the phase-adjusting part and the cylinder of the spring chamber is used, instead of dry friction acting on the pneumatically-driven rod to control motion damping of the displacer and to adjust the phase difference between the compression piston and displacer. It has the advantages of easy damping adjustment, low cost, and simplified manufacturing and assembly. A theoretical model has been established to simulate its dynamic performance. The linear compressor is modeled under adiabatic conditions, and the displacement of the compression piston is experimentally rectified. The working characteristics of the compressor motor and the principal losses of cooling, including regenerator inefficiency loss, solid conduction loss, shuttle loss, pump loss and radiation loss, are taken into account. The displacer motion was modeled as a single-degree-of-freedom (SDOF) forced system. A set of governing equations can be solved numerically to simulate the cooler's performance. The simulation is useful for understanding the physical processes occurring in the cooler and for predicting the cooler's performance.

Prediction of SFL Interruption Performance from the Results of Arc Simulation during High-Current Phase

NASA Astrophysics Data System (ADS)

Lee, Jong-Chul; Lee, Won-Ho; Kim, Woun-Jea

2015-09-01

The design and development procedures of SF6 gas circuit breakers are still largely based on trial and error through testing although the development costs go higher every year. The computation cannot cover the testing satisfactorily because all the real processes arc not taken into account. But the knowledge of the arc behavior and the prediction of the thermal-flow inside the interrupters by numerical simulations are more useful than those by experiments due to the difficulties to obtain physical quantities experimentally and the reduction of computational costs in recent years. In this paper, in order to get further information into the interruption process of a SF6 self-blast interrupter, which is based on a combination of thermal expansion and the arc rotation principle, gas flow simulations with a CFD-arc modeling are performed during the whole switching process such as high-current period, pre-current zero period, and current-zero period. Through the complete work, the pressure-rise and the ramp of the pressure inside the chamber before current zero as well as the post-arc current after current zero should be a good criterion to predict the short-line fault interruption performance of interrupters.

Numerical Simulation of Flow Through an Artificial Heart

NASA Technical Reports Server (NTRS)

Rogers, Stuart E.; Kutler, Paul; Kwak, Dochan; Kiris, Cetin

1989-01-01

A solution procedure was developed that solves the unsteady, incompressible Navier-Stokes equations, and was used to numerically simulate viscous incompressible flow through a model of the Pennsylvania State artificial heart. The solution algorithm is based on the artificial compressibility method, and uses flux-difference splitting to upwind the convective terms; a line-relaxation scheme is used to solve the equations. The time-accuracy of the method is obtained by iteratively solving the equations at each physical time step. The artificial heart geometry involves a piston-type action with a moving solid wall. A single H-grid is fit inside the heart chamber. The grid is continuously compressed and expanded with a constant number of grid points to accommodate the moving piston. The computational domain ends at the valve openings where nonreflective boundary conditions based on the method of characteristics are applied. Although a number of simplifing assumptions were made regarding the geometry, the computational results agreed reasonably well with an experimental picture. The computer time requirements for this flow simulation, however, are quite extensive. Computational study of this type of geometry would benefit greatly from improvements in computer hardware speed and algorithm efficiency enhancements.

Phase B-final definition and preliminary design study for the initial Atmospheric Cloud Physics Laboratory (ACPL). A spacelab mission payload

NASA Technical Reports Server (NTRS)

1976-01-01

Progress in the development of the Atmospheric Cloud Physics Laboratory is outlined. The fluid subsystem, aerosol generator, expansion chamber, optical system, control systems, and software are included.

On the p(dis) correction factor for cylindrical chambers.

PubMed

Andreo, Pedro

2010-03-07

The authors of a recent paper (Wang and Rogers 2009 Phys. Med. Biol. 54 1609) have used the Monte Carlo method to simulate the 'classical' experiment made more than 30 years ago by Johansson et al (1978 National and International Standardization of Radiation Dosimetry (Atlanta 1977) vol 2 (Vienna: IAEA) pp 243-70) on the displacement (or replacement) perturbation correction factor p(dis) for cylindrical chambers in 60Co and high-energy photon beams. They conclude that an 'unreasonable normalization at dmax' of the ionization chambers response led to incorrect results, and for the IAEA TRS-398 Code of Practice, which uses ratios of those results, 'the difference in the correction factors can lead to a beam calibration deviation of more than 0.5% for Farmer-like chambers'. The present work critically examines and questions some of the claims and generalized conclusions of the paper. It is demonstrated that for real, commercial Farmer-like chambers, the possible deviations in absorbed dose would be much smaller (typically 0.13%) than those stated by Wang and Rogers, making the impact of their proposed values negligible on practical high-energy photon dosimetry. Differences of the order of 0.4% would only appear at the upper extreme of the energies potentially available for clinical use (around 25 MV) and, because lower energies are more frequently used, the number of radiotherapy photon beams for which the deviations would be larger than say 0.2% is extremely small. This work also raises concerns on the proposed value of pdis for Farmer chambers at the reference quality of 60Co in relation to their impact on electron beam dosimetry, both for direct dose determination using these chambers and for the cross-calibration of plane-parallel chambers. The proposed increase of about 1% in p(dis) (compared with TRS-398) would lower the kQ factors and therefore Dw in electron beams by the same amount. This would yield a severe discrepancy with the current good agreement between electron dosimetry based on an electron cross-calibrated plane-parallel chamber (against a Farmer) or on a directly 60Co calibrated plane-parallel chamber, which is not likely to be in error by 1%. It is suggested that the influence of the 60Co source spectrum used in the simulations may not be negligible for calculations aimed at an uncertainty level of 0.1%.

Monte Carlo calculations of k{sub Q}, the beam quality conversion factor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muir, B. R.; Rogers, D. W. O.

2010-11-15

Purpose: To use EGSnrc Monte Carlo simulations to directly calculate beam quality conversion factors, k{sub Q}, for 32 cylindrical ionization chambers over a range of beam qualities and to quantify the effect of systematic uncertainties on Monte Carlo calculations of k{sub Q}. These factors are required to use the TG-51 or TRS-398 clinical dosimetry protocols for calibrating external radiotherapy beams. Methods: Ionization chambers are modeled either from blueprints or manufacturers' user's manuals. The dose-to-air in the chamber is calculated using the EGSnrc user-code egs{sub c}hamber using 11 different tabulated clinical photon spectra for the incident beams. The dose to amore » small volume of water is also calculated in the absence of the chamber at the midpoint of the chamber on its central axis. Using a simple equation, k{sub Q} is calculated from these quantities under the assumption that W/e is constant with energy and compared to TG-51 protocol and measured values. Results: Polynomial fits to the Monte Carlo calculated k{sub Q} factors as a function of beam quality expressed as %dd(10){sub x} and TPR{sub 10}{sup 20} are given for each ionization chamber. Differences are explained between Monte Carlo calculated values and values from the TG-51 protocol or calculated using the computer program used for TG-51 calculations. Systematic uncertainties in calculated k{sub Q} values are analyzed and amount to a maximum of one standard deviation uncertainty of 0.99% if one assumes that photon cross-section uncertainties are uncorrelated and 0.63% if they are assumed correlated. The largest components of the uncertainty are the constancy of W/e and the uncertainty in the cross-section for photons in water. Conclusions: It is now possible to calculate k{sub Q} directly using Monte Carlo simulations. Monte Carlo calculations for most ionization chambers give results which are comparable to TG-51 values. Discrepancies can be explained using individual Monte Carlo calculations of various correction factors which are more accurate than previously used values. For small ionization chambers with central electrodes composed of high-Z materials, the effect of the central electrode is much larger than that for the aluminum electrodes in Farmer chambers.« less

LETTER TO THE EDITOR: On the pdis correction factor for cylindrical chambers

NASA Astrophysics Data System (ADS)

Andreo, Pedro

2010-03-01

The authors of a recent paper (Wang and Rogers 2009 Phys. Med. Biol. 54 1609) have used the Monte Carlo method to simulate the 'classical' experiment made more than 30 years ago by Johansson et al (1978 National and International Standardization of Radiation Dosimetry (Atlanta 1977) vol 2 (Vienna: IAEA) pp 243-70) on the displacement (or replacement) perturbation correction factor pdis for cylindrical chambers in 60Co and high-energy photon beams. They conclude that an 'unreasonable normalization at dmax' of the ionization chambers response led to incorrect results, and for the IAEA TRS-398 Code of Practice, which uses ratios of those results, 'the difference in the correction factors can lead to a beam calibration deviation of more than 0.5% for Farmer-like chambers'. The present work critically examines and questions some of the claims and generalized conclusions of the paper. It is demonstrated that for real, commercial Farmer-like chambers, the possible deviations in absorbed dose would be much smaller (typically 0.13%) than those stated by Wang and Rogers, making the impact of their proposed values negligible on practical high-energy photon dosimetry. Differences of the order of 0.4% would only appear at the upper extreme of the energies potentially available for clinical use (around 25 MV) and, because lower energies are more frequently used, the number of radiotherapy photon beams for which the deviations would be larger than say 0.2% is extremely small. This work also raises concerns on the proposed value of pdis for Farmer chambers at the reference quality of 60Co in relation to their impact on electron beam dosimetry, both for direct dose determination using these chambers and for the cross-calibration of plane-parallel chambers. The proposed increase of about 1% in pdis (compared with TRS-398) would lower the kQ factors and therefore Dw in electron beams by the same amount. This would yield a severe discrepancy with the current good agreement between electron dosimetry based on an electron cross-calibrated plane-parallel chamber (against a Farmer) or on a directly 60Co calibrated plane-parallel chamber, which is not likely to be in error by 1%. It is suggested that the influence of the 60Co source spectrum used in the simulations may not be negligible for calculations aimed at an uncertainty level of 0.1%.

Beam quality corrections for parallel-plate ion chambers in electron reference dosimetry

NASA Astrophysics Data System (ADS)

Zink, K.; Wulff, J.

2012-04-01

Current dosimetry protocols (AAPM, IAEA, IPEM, DIN) recommend parallel-plate ionization chambers for dose measurements in clinical electron beams. This study presents detailed Monte Carlo simulations of beam quality correction factors for four different types of parallel-plate chambers: NACP-02, Markus, Advanced Markus and Roos. These chambers differ in constructive details which should have notable impact on the resulting perturbation corrections, hence on the beam quality corrections. The results reveal deviations to the recommended beam quality corrections given in the IAEA TRS-398 protocol in the range of 0%-2% depending on energy and chamber type. For well-guarded chambers, these deviations could be traced back to a non-unity and energy-dependent wall perturbation correction. In the case of the guardless Markus chamber, a nearly energy-independent beam quality correction is resulting as the effects of wall and cavity perturbation compensate each other. For this chamber, the deviations to the recommended values are the largest and may exceed 2%. From calculations of type-B uncertainties including effects due to uncertainties of the underlying cross-sectional data as well as uncertainties due to the chamber material composition and chamber geometry, the overall uncertainty of calculated beam quality correction factors was estimated to be <0.7%. Due to different chamber positioning recommendations given in the national and international dosimetry protocols, an additional uncertainty in the range of 0.2%-0.6% is present. According to the IAEA TRS-398 protocol, the uncertainty in clinical electron dosimetry using parallel-plate ion chambers is 1.7%. This study may help to reduce this uncertainty significantly.

Analysis And Validation of the Field Coupled Through an Aperture in an Avionics Enclosure

NASA Astrophysics Data System (ADS)

Bakore, Rahul

This work focused on accurately predicting the current response of an equipment under test (EUT) to a random electromagnetic field representing a threat source to model radio frequency directed energy weapons (RFDEWs). The modeled EUT consists of a single wire attached to the interior wall of a shielding enclosure that includes an aperture on one face. An in-house computational electromagnetic (CEM) code based on method of moments (MOM) and accelerated by the multi-level fast multipole algorithm (MLFMA), was enhanced through the implementation of first order vector basis functions that approximates the EUT surface current. The electric field integral equation (EFIE) is solved using MOM/MLFMA. Use of first-order basis functions gives a large savings in computational time over the previous implementation with zero-order Rao-Wilton-Glisson basis functions. A sample EUT was fabricated and tested within an anechoic chamber and a reverberation chamber over a wide frequency band. In the anechoic chamber measurements, the current response on the wire within the EUT due to a single uniform plane wave was found and compared with the numerical simulations. In the reverberation chamber measurements, the mean current magnitude excited on the wire within the EUT by a mechanically stirred random field was measured and compared with the numerical simulations. The measured scattering parameter between the source antenna and the EUT measurement port was used to derive the current response on the wire in both chambers. The numerically simulated currents agree very well with the measurements in both the anechoic and reverberation chambers over the measured frequency band, confirming the validity of the numerical approach for calculating EUT response due to a random field. An artificial neural network (ANN) was trained that can rapidly provide the mean induced current response of an EUT due to a random field under different aperture configurations arbitrarily placed on one face of an EUT. However, ANN proved no better than simple linear interpolation in approximating the induced currents on EUTs that give strong resonances and nulls in the response.

Demonstration of a light-redirecting skylight system at the Palm Springs Chamber of Commerce

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, E.S.; Beltran, L.O.; Selkowitz, S.E.

1996-05-01

As part of a demonstration project to provide a comprehensive energy upgrade to a 294 m{sup 2} (3168 ft{sup 2}) commercial building, an advanced skylight design was developed using optical light control materials and geometry to provide daylight to two adjoining offices. The skylight system was developed using outdoor physical model tests and simulation tools Limited on-site measurements and occupant polls were conducted. Market issues were addressed. The skylight systems were found to improve lighting quality and to control excessive daylight illuminance levels compared to a conventional diffusing bubble skylight. Daylighting principles developed in earlier work for vertical glazing systemsmore » (light shelves and light pipes) were shown to be applicable in skylight designs at full-scale.« less

Contamination concerns in the modular containerless processing facility

NASA Technical Reports Server (NTRS)

Seshan, P. K.; Trinh, E. H.

1989-01-01

This paper describes the problems of the control and management of contamination in the Modular Containerless Processing Facility (MCPF), that is being currently developed at the JPL for the Space Station, and in the MCPF's precursor version, called the Drop Physics Module (DPM), which will be carried aboard one or more Space Shuttle missions. Attention is given to the identification of contamination sources, their mode of transport to the sample positioned within the chamber, and the protection of the sample, as well as to the mathematical simulatiom of the contaminant transport. It is emphasized that, in order to choose and implement the most appropriate contamination control strategy for each investigator, a number of simplified mathematical simulations will have to be developed, and ground-based contamination experiments will have to be carried out with identical materials.

The role of logistic constraints in termite construction of chambers and tunnels.

PubMed

Ladley, Dan; Bullock, Seth

2005-06-21

In previous models of the building behaviour of termites, physical and logistic constraints that limit the movement of termites and pheromones have been neglected. Here, we present an individual-based model of termite construction that includes idealized constraints on the diffusion of pheromones, the movement of termites, and the integrity of the architecture that they construct. The model allows us to explore the extent to which the results of previous idealized models (typically realised in one or two dimensions via a set of coupled partial differential equations) generalize to a physical, 3-D environment. Moreover we are able to investigate new processes and architectures that rely upon these features. We explore the role of stigmergic recruitment in pillar formation, wall building, and the construction of royal chambers, tunnels and intersections. In addition, for the first time, we demonstrate the way in which the physicality of partially built structures can help termites to achieve efficient tunnel structures and to establish and maintain entrances in royal chambers. As such we show that, in at least some cases, logistic constraints can be important or even necessary in order for termites to achieve efficient, effective constructions.

Solution-limited time stepping method and numerical simulation of single-element rocket engine combustor

NASA Astrophysics Data System (ADS)

Lian, Chenzhou

The focus of the research is to gain a better understanding of the mixing and combustion of propellants in a confined single element rocket engine combustor. The approach taken is to use the unsteady computational simulations of both liquid and gaseous oxygen reacting with gaseous hydrogen to study the effects of transient processes, recirculation regions and density variations under supercritical conditions. The physics of combustion involve intimate coupling between fluid dynamics, chemical kinetics and intense energy release and take place over an exceptionally wide range of scales. In the face of these monumental challenges, it remains the engineer's task to find acceptable simulation approach and reliable CFD algorithm for combustion simulations. To provide the computational robustness to allow detailed analyses of such complex problems, we start by investigating a method for enhancing the reliability of implicit computational algorithms and decreasing their sensitivity to initial conditions without adversely impacting their efficiency. Efficient convergence is maintained by specifying a large global CFL number while reliability is improved by limiting the local CFL number such that the solution change in any cell is less than a specified tolerance. The magnitude of the solution change is estimated from the calculated residual in a manner that requires negligible computational time. The method precludes unphysical excursions in Newton-like iterations in highly non-linear regions where Jacobians are changing rapidly as well as non-physical results during the computation. The method is tested against a series of problems to identify its characteristics and to verify the approach. The results reveal a substantial improvement in convergence reliability of implicit CFD applications that enables computations starting from simple initial conditions. The method is applied in the unsteady combustion simulations and allows long time running of the code without user intervention. The initial transient leading to stationary conditions in unsteady combustion simulations is investigated by considering flow establishment in model combustors. The duration of the transient is shown to be dependent on the characteristic turn-over time for recirculation zones and the time for the chamber pressure to reach steady conditions. Representative comparisons of the time-averaged, stationary results with experiment are presented to document the computations. The flow dynamics and combustion for two sizes of chamber diameters and two different wall thermal boundary conditions are investigated to assess the role of the recirculation regions on the mixing/combustion process in rocket engine combustors. Results are presented in terms of both instantaneous and time-averaged solutions. As a precursor to liquid oxygen/gaseous hydrogen (LO2/GH 2) combustion simulations, the evolution of a liquid nitrogen (LN 2) jet initially at a subcritical temperature and injected into a supercritical environment is first investigated and the results are validated against experimental data. Unsteady simulations of non-reacting LO2/GH 2 are then performed for a single element shear coaxial injector. These cold flow calculations are then extended to reacting LO2/GH 2 flows to demonstrate the capability of the numerical procedure for high-density-gradient supercritical reacting flows.

Free radical development in phacoemulsification cataract surgery.

PubMed

Takahashi, Hiroshi

2005-02-01

Phacoemulsification and aspiration (PEA) has become the most popular cataract surgery, due to the establishment of safe surgical techniques and development of associated instruments. However, corneal endothelial damage still represents a serious complication, as excessive damage can lead to irreversible bullous keratopathy. In addition to causes such as mechanical or heat injuries, free radical formation due to ultrasound has been posited as another cause of corneal endothelium damage in PEA. Ultrasound in aqueous solution induces cavitation, directly causing water molecule disintegration and resulting in the formation of hydroxylradicals, the most potent of the reactive oxygen species. Considering the oxidative insult to endothelial cells caused by free radicals, their presence in the anterior chamber may represent one of the most harmful factors during these procedures. Indeed, some researchers have recently started to evaluate PEA from the perspective of oxidative stress. Conversely, the major ingredient in ophthalmic viscosurgical devices (OVDs), which are indispensable for maintaining the anterior chamber in PEA surgery, is sodium hyaluronate, a known free radical scavenger. OVDs can thus be expected to provide some anti-free radical effect during PEA procedures. In addition, since commercially available OVDs display different properties regarding retention in the anterior chamber during PEA, the anti-free radical effect of OVDs is likely to depend on behavior during irrigation and aspiration. The present study followed standard PEA procedures in an eye model and measured hydroxylradicals in the anterior chamber using electron spin resonance. The kinetics of free radical intensity and effects of several OVDs during clinical PEA were also demonstrated. These studies may be of significance in re-evaluating OVDs as a chemical protectant for corneal endothelium, since the OVD has thus far only been regarded as a physical barrier. In addition, many reports about corneal endothelium damage during PEA have been published, but objective evaluation of various damaging factors has been difficult. The present assay of free radicals in a simulation of clinical PEA offers the first method to quantitatively assess stress on the corneal endothelium.

[Modification of the pattern of fatty acids of erythrocytes’ membranes due to the acetone intoxication].

PubMed

Momot, T V; Kushnerova, N F; Rakhmanin, Yu A

Results of the study of the impact of acetone intoxication on the fatty acids pattern of the general lipids of erythrocytes’ membranes in rats are presented. The inhalation exposure of acetone was carried out in the inoculation chamber with the volume of 100 liters. The chamber was designed for the type of B.A. Kurlyandsky with self-contained system of purification and air regeneration and specified parameters of temperature (20-22С) and air humidity. The flow rate of the air and aerosolized acetone passed through the chamber accounted of 10 liters/min. Concentration of acetone in the chamber was sustained at the level of 206 ± 3,9 mg/m that corresponds to maximum permissible concentration for acetone vapor in the air of a working area. The time of exposure was 6 hours per day for 3 weeks in a monotonous mode, excluding weekend, and was based upon specific parameters of environment simulation in industry. The acetone impact was shown to be accompanied by the gain in the quantity of all kinds of saturated fatty acids and the fall of unsaturated fatty acids in general lipids of erythrocytes ’ membranes in rats and in the structure ofphospholipid fractions. In the content of phosphatydilcholine and phosphatydilethanolamine, as a basic structural phospholipids of biological membranes, there was noted the increase in palmitic and stearic acids. In the range offatty acids of the n-6 family the amount of linoleic and arachidonic acids decreased. In the array of fatty acids of the n-3 family the content of linolenic, eicosapentaenoic and docosahexaenoic acids (n-3 family) declined. Redistribution of fatty acids in the erythrocytes membrane towards to such alteration in quantity as the increasing of saturation and decreasing of the unsaturated fatty acids supposes the change of its physical and chemical properties, permeability, lability and complexity of passing erythrocyte via microcircular channels.

Improved thermoelectrically cooled quartz crystal microbalance

NASA Technical Reports Server (NTRS)

Mckeown, W. E.; Corbin, W. E., Jr.; Fox, M. G.

1974-01-01

Design changes in the thermoelectrically-cooled quartz microbalance, which is used to monitor surface contamination in space simulation chambers, is described in terms of its extended temperature range, increased temperature control, mass sensitivity, and cooling power. The mass sensor uses 20 MHz quartz crystals having a sensitivity of 8.8 x 10 to the minus tenth power g/sq cm - Hz. The crystals are optically polished, metal plated, and overplated with magnesium fluoride to simulate an optical surface. The microbalance temperature circuitry is designed to readout and control surface temperature between 100 C and minus 59 C to plus or minus 0.5 C, and readout only temperature between minus 60 C and minus 199 C using auxiliary liquid nitrogen cooling. Data is included on the measurement of oil contamination of surfaces as a function of temperature in space simulation chambers.

Radiation Effects on Flow Characteristics in Combustion Chambers

NASA Technical Reports Server (NTRS)

Brewster, M. Q.; Gross, Klaus W.

1989-01-01

A JANNAF sponsored workshop was held to discuss the importance and role of radiative heat transfer in rocket combustion chambers. The potential impact of radiative transfer on hardware design, reliability, and performance was discussed. The current state of radiative transfer prediction capability in CFD modeling was reviewed and concluded to be substantially lacking in both the physical models used and the radiative property data available. There is a clear need to begin to establish a data base for making radiation calculations in rocket combustion chambers. A natural starting point for this effort would be the NASA thermochemical equilibrium code (CEC).

Hybrid Modeling for Testing Intelligent Software for Lunar-Mars Closed Life Support

NASA Technical Reports Server (NTRS)

Malin, Jane T.; Nicholson, Leonard S. (Technical Monitor)

1999-01-01

Intelligent software is being developed for closed life support systems with biological components, for human exploration of the Moon and Mars. The intelligent software functions include planning/scheduling, reactive discrete control and sequencing, management of continuous control, and fault detection, diagnosis, and management of failures and errors. Four types of modeling information have been essential to system modeling and simulation to develop and test the software and to provide operational model-based what-if analyses: discrete component operational and failure modes; continuous dynamic performance within component modes, modeled qualitatively or quantitatively; configuration of flows and power among components in the system; and operations activities and scenarios. CONFIG, a multi-purpose discrete event simulation tool that integrates all four types of models for use throughout the engineering and operations life cycle, has been used to model components and systems involved in the production and transfer of oxygen and carbon dioxide in a plant-growth chamber and between that chamber and a habitation chamber with physicochemical systems for gas processing.

Analysis of the Variable Pressure Growth Chamber using the CASE/A simulation package

NASA Technical Reports Server (NTRS)

Mcfadden, Carl D.; Edeen, Marybeth A.

1992-01-01

A computer simulation of the Variable Pressure Growth Chamber (VPGC), located at the NASA Johnson Space Center, has been developed using the Computer Aided Systems Engineering and Analysis (CASE/A) package. The model has been used to perform several analyses of the VPGC. The analyses consisted of a study of the effects of a human metabolic load on the VPGC and a study of two new configurations for the temperature and humidity control (THC) subsystem in the VPGC. The objective of the human load analysis was to study the effects of a human metabolic load on the air revitalization and THC subsystems. This included the effects on the quantity of carbon dioxide injected and oxygen removed from the chamber and the effects of the additional sensible and latent heat loads. The objective of the configuration analysis was to compare the two new THC configurations against the current THC configuration to determine which had the best performance.

Output factor determination based on Monte Carlo simulation for small cone field in 10-MV photon beam.

PubMed

Fukata, Kyohei; Sugimoto, Satoru; Kurokawa, Chie; Saito, Akito; Inoue, Tatsuya; Sasai, Keisuke

2018-06-01

The difficulty of measuring output factor (OPF) in a small field has been frequently discussed in recent publications. This study is aimed to determine the OPF in a small field using 10-MV photon beam and stereotactic conical collimator (cone). The OPF was measured by two diode detectors (SFD, EDGE detector) and one micro-ion chamber (PinPoint 3D chamber) in a water phantom. A Monte Carlo simulation using simplified detector model was performed to obtain the correction factor for the detector measurements. About 12% OPF difference was observed in the measurement at the smallest field (7.5 mm diameter) for EDGE detector and PinPoint 3D chamber. By applying the Monte Carlo-based correction factor to the measurement, the maximum discrepancy among the three detectors was reduced to within 3%. The results indicate that determination of OPF in a small field should be carefully performed. Especially, detector choice and appropriate correction factor application are very important in this regard.

Space environment simulation and sensor calibration facility

NASA Astrophysics Data System (ADS)

Engelhart, Daniel P.; Patton, James; Plis, Elena; Cooper, Russell; Hoffmann, Ryan; Ferguson, Dale; Hilmer, Robert V.; McGarity, John; Holeman, Ernest

2018-02-01

The Mumbo space environment simulation chamber discussed here comprises a set of tools to calibrate a variety of low flux, low energy electron and ion detectors used in satellite-mounted particle sensors. The chamber features electron and ion beam sources, a Lyman-alpha ultraviolet lamp, a gimbal table sensor mounting system, cryogenic sample mount and chamber shroud, and beam characterization hardware and software. The design of the electron and ion sources presented here offers a number of unique capabilities for space weather sensor calibration. Both sources create particle beams with narrow, well-characterized energetic and angular distributions with beam diameters that are larger than most space sensor apertures. The electron and ion sources can produce consistently low fluxes that are representative of quiescent space conditions. The particle beams are characterized by 2D beam mapping with several co-located pinhole aperture electron multipliers to capture relative variation in beam intensity and a large aperture Faraday cup to measure absolute current density.

Space environment simulation and sensor calibration facility.

PubMed

Engelhart, Daniel P; Patton, James; Plis, Elena; Cooper, Russell; Hoffmann, Ryan; Ferguson, Dale; Hilmer, Robert V; McGarity, John; Holeman, Ernest

2018-02-01

The Mumbo space environment simulation chamber discussed here comprises a set of tools to calibrate a variety of low flux, low energy electron and ion detectors used in satellite-mounted particle sensors. The chamber features electron and ion beam sources, a Lyman-alpha ultraviolet lamp, a gimbal table sensor mounting system, cryogenic sample mount and chamber shroud, and beam characterization hardware and software. The design of the electron and ion sources presented here offers a number of unique capabilities for space weather sensor calibration. Both sources create particle beams with narrow, well-characterized energetic and angular distributions with beam diameters that are larger than most space sensor apertures. The electron and ion sources can produce consistently low fluxes that are representative of quiescent space conditions. The particle beams are characterized by 2D beam mapping with several co-located pinhole aperture electron multipliers to capture relative variation in beam intensity and a large aperture Faraday cup to measure absolute current density.

Programmable prostate palpation simulator using property-changing pneumatic bladder.

PubMed

Talhan, Aishwari; Jeon, Seokhee

2018-05-01

The currently available prostate palpation simulators are based on either a physical mock-up or pure virtual simulation. Both cases have their inherent limitations. The former lacks flexibility in presenting abnormalities and scenarios because of the static nature of the mock-up and has usability issues because the prostate model must be replaced in different scenarios. The latter has realism issues, particularly in haptic feedback, because of the very limited performance of haptic hardware and inaccurate haptic simulation. This paper presents a highly flexible and programmable simulator with high haptic fidelity. Our new approach is based on a pneumatic-driven, property-changing, silicone prostate mock-up that can be embedded in a human torso mannequin. The mock-up has seven pneumatically controlled, multi-layered bladder cells to mimic the stiffness, size, and location changes of nodules in the prostate. The size is controlled by inflating the bladder with positive pressure in the chamber, and a hard nodule can be generated using the particle jamming technique; the fine sand in the bladder becomes stiff when it is vacuumed. The programmable valves and system identification process enable us to precisely control the size and stiffness, which results in a simulator that can realistically generate many different diseases without replacing anything. The three most common abnormalities in a prostate are selected for demonstration, and multiple progressive stages of each abnormality are carefully designed based on medical data. A human perception experiment is performed by actual medical professionals and confirms that our simulator exhibits higher realism and usability than do the conventional simulators. Copyright © 2018 Elsevier Ltd. All rights reserved.

Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: Explicit modeling of SOA formation from alkane and alkene oxidation

DOE PAGES

La, Y. S.; Camredon, M.; Ziemann, P. J.; ...

2016-02-08

Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kinetics of the Organics in the Atmosphere (GECKO-A) modeling tool, which explicitly represents SOA formation and gas–wall partitioning. The model was compared with 41 smog chambermore » experiments of SOA formation under OH oxidation of alkane and alkene series (linear, cyclic and C 12-branched alkanes and terminal, internal and 2-methyl alkenes with 7 to 17 carbon atoms) under high NO x conditions. Simulated trends match observed trends within and between homologous series. The loss of organic vapors to the chamber walls is found to affect SOA yields as well as the composition of the gas and the particle phases. Simulated distributions of the species in various phases suggest that nitrates, hydroxynitrates and carbonylesters could substantially be lost onto walls. The extent of this process depends on the rate of gas–wall mass transfer, the vapor pressure of the species and the duration of the experiments. Furthermore, this work suggests that SOA yields inferred from chamber experiments could be underestimated up a factor of 2 due to the loss of organic vapors to chamber walls.« less

Design and analysis of a double superimposed chamber valveless MEMS micropump.

PubMed

Zordan, E; Amirouche, F

2007-02-01

The newly designed micropump model proposed consists of a valveless double chamber pump completely simulated and optimized for drug delivery conditions. First, the inertia force and viscous loss in relation to actuation, pressure, and frequency is considered, and then a model of the nozzle/diffuser elements is introduced. The value of the flowrate obtained from the first model is then used to determine the loss coefficients starting from geometrical properties and flow velocity. From the developed model IT analysis is performed to predict the micropump performance based on the actuation parameters and no energy loss. A single-chamber pump with geometrical dimensions equal to each of the chambers of the double-chamber pump was also developed, and the results from both models are then compared for equally applied actuation pressure and frequency. Results show that the proposed design gives a maximum flow working frequency that is about 30 per cent lower than the single chamber design, with a maximum flowrate that is 140 per cent greater than that of the single chamber. Finally, the influences of geometrical properties on flowrate, maximum flow frequency, loss coefficients, and membrane strain are examined. The results show that the nozzle/ diffuser initial width and chamber side length are the most critical dimensions of the design.

A Study of Mars Dust Environment Simulation at NASA Johnson Space Center Energy Systems Test Area Resource Conversion Test Facility

NASA Technical Reports Server (NTRS)

Chen, Yuan-Liang Albert

1999-01-01

The dust environment on Mars is planned to be simulated in a 20 foot thermal-vacuum chamber at the Johnson Space Center, Energy Systems Test Area Resource Conversion Test Facility in Houston, Texas. This vacuum chamber will be used to perform tests and study the interactions between the dust in Martian air and ISPP hardware. This project is to research, theorize, quantify, and document the Mars dust/wind environment needed for the 20 foot simulation chamber. This simulation work is to support the safety, endurance, and cost reduction of the hardware for the future missions. The Martian dust environment conditions is discussed. Two issues of Martian dust, (1) Dust Contamination related hazards, and (2) Dust Charging caused electrical hazards, are of our interest. The different methods of dust particles measurement are given. The design trade off and feasibility were studied. A glass bell jar system is used to evaluate various concepts for the Mars dust/wind environment simulation. It was observed that the external dust source injection is the best method to introduce the dust into the simulation system. The dust concentration of 30 Mg/M3 should be employed for preparing for the worst possible Martian atmosphere condition in the future. Two approaches thermal-panel shroud for the hardware conditioning are discussed. It is suggested the wind tunnel approach be used to study the dust charging characteristics then to be apply to the close-system cyclone approach. For the operation cost reduction purpose, a dehumidified ambient air could be used to replace the expensive CO2 mixture for some tests.

Absolute dose calculations for Monte Carlo simulations of radiotherapy beams

NASA Astrophysics Data System (ADS)

Popescu, I. A.; Shaw, C. P.; Zavgorodni, S. F.; Beckham, W. A.

2005-07-01

Monte Carlo (MC) simulations have traditionally been used for single field relative comparisons with experimental data or commercial treatment planning systems (TPS). However, clinical treatment plans commonly involve more than one field. Since the contribution of each field must be accurately quantified, multiple field MC simulations are only possible by employing absolute dosimetry. Therefore, we have developed a rigorous calibration method that allows the incorporation of monitor units (MU) in MC simulations. This absolute dosimetry formalism can be easily implemented by any BEAMnrc/DOSXYZnrc user, and applies to any configuration of open and blocked fields, including intensity-modulated radiation therapy (IMRT) plans. Our approach involves the relationship between the dose scored in the monitor ionization chamber of a radiotherapy linear accelerator (linac), the number of initial particles incident on the target, and the field size. We found that for a 10 × 10 cm2 field of a 6 MV photon beam, 1 MU corresponds, in our model, to 8.129 × 1013 ± 1.0% electrons incident on the target and a total dose of 20.87 cGy ± 1.0% in the monitor chambers of the virtual linac. We present an extensive experimental verification of our MC results for open and intensity-modulated fields, including a dynamic 7-field IMRT plan simulated on the CT data sets of a cylindrical phantom and of a Rando anthropomorphic phantom, which were validated by measurements using ionization chambers and thermoluminescent dosimeters (TLD). Our simulation results are in excellent agreement with experiment, with percentage differences of less than 2%, in general, demonstrating the accuracy of our Monte Carlo absolute dose calculations.

Application of Chaboche Model in Rocket Thrust Chamber Analysis

NASA Astrophysics Data System (ADS)

Asraff, Ahmedul Kabir; Suresh Babu, Sheela; Babu, Aneena; Eapen, Reeba

2017-06-01

Liquid Propellant Rocket Engines are commonly used in space technology. Thrust chamber is one of the most important subsystems of a rocket engine. The thrust chamber generates propulsive thrust force for flight of the rocket by ejection of combustion products at supersonic speeds. Often double walled construction is employed for these chambers. The thrust chamber investigated here has its hot inner wall fabricated out of a high thermal conductive material like copper alloy and outer wall made of stainless steel. Inner wall is subjected to high thermal and pressure loads during operation of engine due to which it will be in the plastic regime. Main reasons for the failure of such chambers are fatigue in the plastic range (called as low cycle fatigue since the number of cycles to failure will be low in plastic range), creep and thermal ratcheting. Elasto plastic material models are required to simulate the above effects through a cyclic stress analysis. This paper gives the details of cyclic stress analysis carried out for the thrust chamber using different plasticity model combinations available in ANSYS (Version 15) FE code. The best model among the above is applied in the cyclic stress analysis of two dimensional (plane strain and axisymmetric) and three dimensional finite element models of thrust chamber. Cyclic life of the chamber is calculated from stress-strain graph obtained from above analyses.

Investigation on the electron flux to the wall in the VENUS ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thuillier, T.; Angot, J.; Benitez, J. Y.

The long-term operation of high charge state electron cyclotron resonance ion sources fed with high microwave power has caused damage to the plasma chamber wall in several laboratories. Porosity, or a small hole, can be progressively created in the chamber wall which can destroy the plasma chamber over a few year time scale. Here, a burnout of the VENUS plasma chamber is investigated in which the hole formation in relation to the local hot electron power density is studied. First, the results of a simple model assuming that hot electrons are fully magnetized and strictly following magnetic field lines aremore » presented. The model qualitatively reproduces the experimental traces left by the plasma on the wall. However, it is too crude to reproduce the localized electron power density for creating a hole in the chamber wall. Second, the results of a Monte Carlo simulation, following a population of scattering hot electrons, indicate a localized high power deposited to the chamber wall consistent with the hole formation process. Finally, a hypervapotron cooling scheme is proposed to mitigate the hole formation in electron cyclotron resonance plasma chamber wall.« less

Investigation on the electron flux to the wall in the VENUS ion source

DOE PAGES

Thuillier, T.; Angot, J.; Benitez, J. Y.; ...

2015-12-01

The long-term operation of high charge state electron cyclotron resonance ion sources fed with high microwave power has caused damage to the plasma chamber wall in several laboratories. Porosity, or a small hole, can be progressively created in the chamber wall which can destroy the plasma chamber over a few year time scale. Here, a burnout of the VENUS plasma chamber is investigated in which the hole formation in relation to the local hot electron power density is studied. First, the results of a simple model assuming that hot electrons are fully magnetized and strictly following magnetic field lines aremore » presented. The model qualitatively reproduces the experimental traces left by the plasma on the wall. However, it is too crude to reproduce the localized electron power density for creating a hole in the chamber wall. Second, the results of a Monte Carlo simulation, following a population of scattering hot electrons, indicate a localized high power deposited to the chamber wall consistent with the hole formation process. Finally, a hypervapotron cooling scheme is proposed to mitigate the hole formation in electron cyclotron resonance plasma chamber wall.« less

Investigation on the electron flux to the wall in the VENUS ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thuillier, T., E-mail: thuillier@lpsc.in2p3.fr; Angot, J.; Benitez, J. Y.

The long-term operation of high charge state electron cyclotron resonance ion sources fed with high microwave power has caused damage to the plasma chamber wall in several laboratories. Porosity, or a small hole, can be progressively created in the chamber wall which can destroy the plasma chamber over a few year time scale. A burnout of the VENUS plasma chamber is investigated in which the hole formation in relation to the local hot electron power density is studied. First, the results of a simple model assuming that hot electrons are fully magnetized and strictly following magnetic field lines are presented.more » The model qualitatively reproduces the experimental traces left by the plasma on the wall. However, it is too crude to reproduce the localized electron power density for creating a hole in the chamber wall. Second, the results of a Monte Carlo simulation, following a population of scattering hot electrons, indicate a localized high power deposited to the chamber wall consistent with the hole formation process. Finally, a hypervapotron cooling scheme is proposed to mitigate the hole formation in electron cyclotron resonance plasma chamber wall.« less

Dosimetry for electron Intra-Operative RadioTherapy: Comparison of output factors obtained through alanine/EPR pellets, ionization chamber and Monte Carlo-GEANT4 simulations for IORT mobile dedicate accelerator

NASA Astrophysics Data System (ADS)

Marrale, Maurizio; Longo, Anna; Russo, Giorgio; Casarino, Carlo; Candiano, Giuliana; Gallo, Salvatore; Carlino, Antonio; Brai, Maria

2015-09-01

In this work a comparison between the response of alanine and Markus ionization chamber was carried out for measurements of the output factors (OF) of electron beams produced by a linear accelerator used for Intra-Operative Radiation Therapy (IORT). Output factors (OF) for conventional high-energy electron beams are normally measured using ionization chamber according to international dosimetry protocols. However, the electron beams used in IORT have characteristics of dose per pulse, energy spectrum and angular distribution quite different from beams usually used in external radiotherapy, so the direct application of international dosimetry protocols may introduce additional uncertainties in dosimetric determinations. The high dose per pulse could lead to an inaccuracy in dose measurements with ionization chamber, due to overestimation of ks recombination factor. Furthermore, the electron fields obtained with IORT-dedicated applicators have a wider energy spectrum and a wider angular distribution than the conventional fields, due to the presence of electrons scattered by the applicator's wall. For this reason, a dosimetry system should be characterized by a minimum dependence from the beam energy and from angle of incidence of electrons. This become particularly critical for small and bevelled applicators. All of these reasons lead to investigate the use of detectors different from the ionization chamber for measuring the OFs. Furthermore, the complete characterization of the radiation field could be accomplished also by the use of Monte Carlo simulations which allows to obtain detailed information on dose distributions. In this work we compare the output factors obtained by means of alanine dosimeters and Markus ionization chamber. The comparison is completed by the Monte Carlo calculations of OFs determined through the use of the Geant4 application "iort _ therapy" . The results are characterized by a good agreement of response of alanine pellets and Markus ionization chamber and Monte Carlo results (within about 3%) for both flat and bevelled applicators.

Documenting Surface and Sub-surface Volatiles While Drilling in Frozen Lunar Simulant

NASA Technical Reports Server (NTRS)

Roush, T. L.; Cook, A. M.; Colaprete, A.; Bielawski, R.; Fritzler, E.; Benton, J.; White, B.; Forgione, J.; Kleinhenz, J.; Smith, J.;

CFD simulation of a dry scroll vacuum pump with clearances, solid heating and thermal deformation

NASA Astrophysics Data System (ADS)

Spille-Kohoff, A.; Hesse, J.; Andres, R.; Hetze, F.

2017-08-01

Although dry scroll vacuum pumps (DSPV) are essential devices in many different industrial processes, the CFD simulation of such pumps is not widely used and often restricted to simplified cases due to its complexity: The working principle with a fixed and an orbiting scroll leads to working chambers that are changing in time and are connected through moving small radial and axial clearances in the range of 10 to 100 μm. Due to the low densities and low mass flow rates in vacuum pumps, it is important to include heat transfer towards and inside the solid components. Solid heating is very slow compared to the scroll revolution speed and the gas behaviour, thus a special workflow is necessary to reach the working conditions in reasonable simulation times. The resulting solid temperature is then used to compute the thermal deformation, which usually results in gap size changes that influence leakage flows. In this paper, setup steps and results for the simulation of a DSVP are shown and compared to theoretical and experimental results. The time-varying working chambers are meshed with TwinMesh, a hexahedral meshing programme for positive displacement machines. The CFD simulation with ANSYS CFX accounts for gas flow with compressibility and turbulence effects, conjugate heat transfer between gas and solids, and leakage flows through the clearances. Time-resolved results for torques, chamber pressure, mass flow, and heat flow between gas and solids are shown, as well as time- and space-resolved results for pressure, velocity, and temperature for different operating conditions of the DSVP.

Observational Simulation of Icing in Extreme Weather Conditions

NASA Astrophysics Data System (ADS)

Gultepe, Ismail; Heymsfield, Andrew; Agelin-Chaab, Martin; Komar, John; Elfstrom, Garry; Baumgardner, Darrel

2017-04-01

Observations and prediction of icing in extreme weather conditions are important for aviation, transportation, and shipping applications, and icing adversely affects the economy. Icing environments can be studied either in the outdoor atmosphere or in the laboratory. There have been several aircraft based in-situ studies related to weather conditions affecting aviation operations, transportation, and marine shipping that includes icing, wind, and turbulence. However, studying severe weather conditions from aircraft observations are limited due to safety and sampling issues, instrumental uncertainties, and even the possibility of aircraft producing its own physical and dynamical effects. Remote sensing based techniques (e.g. retrieval techniques) for studying severe weather conditions represent usually a volume that cannot characterize the important scales and also represents indirect observations. Therefore, laboratory simulations of atmospheric processes can help us better understand the interactions among microphysical and dynamical processes. The Climatic Wind Tunnel (CWT) in ACE at the University of Ontario Institute of Technology (UOIT) has a large semi-open jet test chamber with flow area 7-13 m2 that can precisely control temperatures down to -40°C, and up to 250 km hr-1 wind speeds, for heavy or dry snow conditions with low visibility, similar to ones observed in the Arctic and cold climate regions, or at high altitude aeronautical conditions. In this study, the ACE CWT employed a spray nozzle array suspended in its settling chamber and fed by pressurized water, creating various particle sizes from a few microns up to mm size range. This array, together with cold temperature and high wind speed, enabled simulation of severe weather conditions, including icing, visibility, strong wind and turbulence, ice fog and frost, freezing fog, heavy snow and blizzard conditions. In this study, the test results will be summarized, and their application to aircraft icing will be provided in detail. Overall, based on these results, scientific challenges related to icing environments will be emphasized for Arctic and cold environments in future projects in the ACE CWT.

[A new two-chamber model for examination and demonstration of transdural fluid leakage after spinal anesthesia].

PubMed

Enk, D; Enk, E

1995-11-01

Various in vitro models have been introduced for comparative examinations of post-dural-puncture trauma and measurement of liquor leakage through puncture sites. These models allow simulation of subarachnoid, but not of peridural, pressure. A new two-chamber-model realizes the simulation of both subarachnoid and peridural pressure and allows observation of in vitro punctures with video-documentation. Frame grabbing and (computer-aided) image analysis show new aspects of spinal puncture effects. Therefore, post-dural-puncture trauma and retraction can be objectively visualized by this method, which has not previously been demonstrated. Two-chamber-model consists of two short aluminium cylinders. Native human dura patches (8X8 mm) from fresh cadavers are put (correctly oriented) between two special polyamide seals. Mounted between the upper and lower cylinder, these seals stretch the dura patch, which remains flexible and even in all directions. After filling of the lower (subarachnoid) and upper (peridural) chamber with Ringer lactate solution, positive or negative physiological pressure can be adjusted by way of two (Ringer lactate solution filled) infusion lines in each chamber. Puncturing is performed at an angle of 57 degrees to the dura. The model allows examination with epi-illumination and transmitted (polarized) light. In vitro punctures are observed through an inverted camera lens with an CCD-Hi8 video camera (Canon UC1HI) looking into the peridural chamber and documented by means of an S-VHS video recorder (Panasonic NV-FS200EG). After true-colour frame grabbing by a video digitizer (Fast Screen Machine II), single video frames can be optimized and analysed with a 486-66 MHz computer and conventional software (Corel Draw 3.0, Photostyler 1.1a, DDL Aequitas 1.00b). Punctures demonstrated in this paper have been done under simulation of a transdural gradient of 20 cm water similar to the situation of a recumbent patient (15 cm water in the subarachnoid and -5 cm water in the peridural chamber). The punctures were followed by short-time observation for up to 10 minutes. By making it possible to obtains a picture of the puncture site at 20-ms intervals (because of the PAL norm of 50 half-frames/s), video-documentation has become accepted as superior to conventional photography. When the Ringer lactate solution in the subarachnoid chamber is stained with methylene blue, transdural leakage can easily be observed. The result of this documentation technique demonstrate that not dural puncture can be atraumatic, when a 29-G Quincke needle is used. Calculation on the difference between a digitized video frame before and after the puncture clearly illustrates the dural trauma. Owing to their non-cutting tip, as expected, pencil-point needles leave diffuse changes across the dura patch, whereas a more local trauma was observed after puncturing with cutting-tip needles. The same computer calculation between two video frames allows examination of post-puncture-dural retraction of the puncture site. In this connection, we found that relevant dural retraction is a phenomenon limited to the first minute after puncture. Thin spinal needles with so-called modern tips (e.g. Whitacre, Atraucan) can minimize the post-dural-puncture trauma, whereas thicker, conventional, spinal needles (Quincke) leave considerable dural defects. The two-chamber-model presented allows easy simulation of physiological subarachnoid and peridural pressure. The Ringer lactate solution in the subarachnoid chamber corresponds to the liquor, whereas that in the peridural chamber corresponds to the intercellular (peridural) space. The tension of the dural patch between the polyamide seals is similar to the situation in an anotomical model observed by spinaloscopy (in an earlier study). With the video documentation and computer-aided analysis technique introduced, dural trauma and retraction of the puncture site can be examined and demo

Johnson Space Center's regenerative life support systems test bed

NASA Technical Reports Server (NTRS)

Henninger, Donald L.; Tri, Terry O.; Barta, Daniel J.; Stahl, Randal S.

1991-01-01

The Regenerative Life Support System (RLSS) Test Bed at NASA's Johnson Space Center is an atmospherically closed, controlled environment facility for the evaluation of regenerative life support systems using higher plants in conjunction with physicochemical life support systems. When completed, the facility will be comprised of two large scale plant growth chambers, each with approximately 10 m(exp 2) growing area. One of the two chambers, the Variable Pressure Growth Chamber (VPGC), will be capable of operating at lower atmospheric pressures to evaluate a range of environments that may be used in Lunar or Martian habitats; the other chamber, the Ambient Pressure Growth Chamber (APGC) will operate at ambient atmospheric pressure. The root zone in each chamber will be configurable for hydroponic or solid state media systems. Research will focus on: (1) in situ resource utilization for CELSS systems, in which simulated lunar soils will be used in selected crop growth studies; (2) integration of biological and physicochemical air and water revitalization systems; (3) effect of atmospheric pressure on system performance; and (4) monitoring and control strategies.

A novel miniaturized PCR multi-reactor array fabricated using flip-chip bonding techniques

NASA Astrophysics Data System (ADS)

Zou, Zhi-Qing; Chen, Xiang; Jin, Qing-Hui; Yang, Meng-Su; Zhao, Jian-Long

2005-08-01

This paper describes a novel miniaturized multi-chamber array capable of high throughput polymerase chain reaction (PCR). The structure of the proposed device is verified by using finite element analysis (FEA) to optimize the thermal performance, and then implemented on a glass-silicon substrate using a standard MEMS process and post-processing. Thermal analysis simulation and verification of each reactor cell is equipped with integrated Pt temperature sensors and heaters at the bottom of the reaction chamber for real-time accurate temperature sensing and control. The micro-chambers are thermally separated from each other, and can be controlled independently. The multi-chip array was packaged on a printed circuit board (PCB) substrate using a conductive polymer flip-chip bonding technique, which enables effective heat dissipation and suppresses thermal crosstalk between the chambers. The designed system has successfully demonstrated a temperature fluctuation of ±0.5 °C during thermal multiplexing of up to 2 × 2 chambers, a full speed of 30 min for 30 cycle PCR, as well as the capability of controlling each chamber digitally and independently.

KSC-99pp0229

NASA Image and Video Library

1999-02-23

KENNEDY SPACE CENTER, FLA. -- In the Operations and Checkout Building's high bay, the Rotation Handling Fixture (RHF), with a simulated module attached, is lowered by crane into the altitude chamber below during a test. Under normal operation, the RHF will hold a pressurized module intended for the International Space Station, depositing it into the altitude chamber for leak testing. The chamber was recently reactivated after a 24-year hiatus. Originally, two chambers were built to test Apollo Program flight hardware. They were last used in 1975 during the Apollo-Soyuz Test Project. In 1997, in order to increase the probability of successful missions aboard the ISS, NASA decided to perform leak tests on ISS pressurized modules at the launch site. After installation of new vacuum pumping equipment and controls, a new control room, and a new rotation and handling fixture, the chamber again became operational in February 1999. The chamber, which is 33 feet in diameter and 50 feet tall, is constructed of stainless steel. The rotation handling fixture is aluminum. The first module that will be tested for leaks is the U.S. Laboratory. No date has been determined for the test

KSC-99pp0230

NASA Image and Video Library

1999-02-23

KENNEDY SPACE CENTER, FLA. -- Viewed from inside the altitude chamber in the Operations and Checkout Building's high bay, the Rotation Handling Fixture (RHF), with a simulated module attached, is lowered during a test. Under normal operation, the RHF will hold a pressurized module intended for the International Space Station, depositing it into the altitude chamber for leak testing. The chamber was recently reactivated after a 24-year hiatus. Originally, two chambers were built to test Apollo Program flight hardware. They were last used in 1975 during the Apollo-Soyuz Test Project. In 1997, in order to increase the probability of successful missions aboard the ISS, NASA decided to perform leak tests on ISS pressurized modules at the launch site. After installation of new vacuum pumping equipment and controls, a new control room, and a new rotation and handling fixture, the chamber again became operational in February 1999. The chamber, which is 33 feet in diameter and 50 feet tall, is constructed of stainless steel. The rotation handling fixture is aluminum. The first module that will be tested for leaks is the U.S. Laboratory. No date has been determined for the test

Design and landing dynamic analysis of reusable landing leg for a near-space manned capsule

NASA Astrophysics Data System (ADS)

Yue, Shuai; Nie, Hong; Zhang, Ming; Wei, Xiaohui; Gan, Shengyong

2018-06-01

To improve the landing performance of a near-space manned capsule under various landing conditions, a novel landing system is designed that employs double chamber and single chamber dampers in the primary and auxiliary struts, respectively. A dynamic model of the landing system is established, and the damper parameters are determined by employing the design method. A single-leg drop test with different initial pitch angles is then conducted to compare and validate the simulation model. Based on the validated simulation model, seven critical landing conditions regarding nine crucial landing responses are found by combining the radial basis function (RBF) surrogate model and adaptive simulated annealing (ASA) optimization method. Subsequently, the adaptability of the landing system under critical landing conditions is analyzed. The results show that the simulation effectively results match the test results, which validates the accuracy of the dynamic model. In addition, all of the crucial responses under their corresponding critical landing conditions satisfy the design specifications, demonstrating the feasibility of the landing system.

Experimental determination of the effect of detector size on profile measurements in narrow photon beams.

PubMed

Pappas, E; Maris, T G; Papadakis, A; Zacharopoulou, F; Damilakis, J; Papanikolaou, N; Gourtsoyiannis, N

2006-10-01

The aim of this work is to investigate experimentally the detector size effect on narrow beam profile measurements. Polymer gel and magnetic resonance imaging dosimetry was used for this purpose. Profile measurements (Pm(s)) of a 5 mm diameter 6 MV stereotactic beam were performed using polymer gels. Eight measurements of the profile of this narrow beam were performed using correspondingly eight different detector sizes. This was achieved using high spatial resolution (0.25 mm) two-dimensional measurements and eight different signal integration volumes A X A X slice thickness, simulating detectors of different size. "A" ranged from 0.25 to 7.5 mm, representing the detector size. The gel-derived profiles exhibited increased penumbra width with increasing detector size, for sizes >0.5 mm. By extrapolating the gel-derived profiles to zero detector size, the true profile (Pt) of the studied beam was derived. The same polymer gel data were also used to simulate a small-volume ion chamber profile measurement of the same beam, in terms of volume averaging. The comparison between these results and actual corresponding small-volume chamber profile measurements performed in this study, reveal that the penumbra broadening caused by both volume averaging and electron transport alterations (present in actual ion chamber profile measurements) is a lot more intense than that resulted by volume averaging effects alone (present in gel-derived profiles simulating ion chamber profile measurements). Therefore, not only the detector size, but also its composition and tissue equivalency is proved to be an important factor for correct narrow beam profile measurements. Additionally, the convolution kernels related to each detector size and to the air ion chamber were calculated using the corresponding profile measurements (Pm(s)), the gel-derived true profile (Pt), and convolution theory. The response kernels of any desired detector can be derived, allowing the elimination of the errors associated with narrow beam profile measurements.

Convolutional neural networks applied to neutrino events in a liquid argon time projection chamber

NASA Astrophysics Data System (ADS)

Acciarri, R.; Adams, C.; An, R.; Asaadi, J.; Auger, M.; Bagby, L.; Baller, B.; Barr, G.; Bass, M.; Bay, F.; Bishai, M.; Blake, A.; Bolton, T.; Bugel, L.; Camilleri, L.; Caratelli, D.; Carls, B.; Castillo Fernandez, R.; Cavanna, F.; Chen, H.; Church, E.; Cianci, D.; Collin, G. H.; Conrad, J. M.; Convery, M.; Crespo-Anadón, J. I.; Del Tutto, M.; Devitt, D.; Dytman, S.; Eberly, B.; Ereditato, A.; Escudero Sanchez, L.; Esquivel, J.; Fleming, B. T.; Foreman, W.; Furmanski, A. P.; Garvey, G. T.; Genty, V.; Goeldi, D.; Gollapinni, S.; Graf, N.; Gramellini, E.; Greenlee, H.; Grosso, R.; Guenette, R.; Hackenburg, A.; Hamilton, P.; Hen, O.; Hewes, J.; Hill, C.; Ho, J.; Horton-Smith, G.; James, C.; de Vries, J. Jan; Jen, C.-M.; Jiang, L.; Johnson, R. A.; Jones, B. J. P.; Joshi, J.; Jostlein, H.; Kaleko, D.; Karagiorgi, G.; Ketchum, W.; Kirby, B.; Kirby, M.; Kobilarcik, T.; Kreslo, I.; Laube, A.; Li, Y.; Lister, A.; Littlejohn, B. R.; Lockwitz, S.; Lorca, D.; Louis, W. C.; Luethi, M.; Lundberg, B.; Luo, X.; Marchionni, A.; Mariani, C.; Marshall, J.; Martinez Caicedo, D. A.; Meddage, V.; Miceli, T.; Mills, G. B.; Moon, J.; Mooney, M.; Moore, C. D.; Mousseau, J.; Murrells, R.; Naples, D.; Nienaber, P.; Nowak, J.; Palamara, O.; Paolone, V.; Papavassiliou, V.; Pate, S. F.; Pavlovic, Z.; Porzio, D.; Pulliam, G.; Qian, X.; Raaf, J. L.; Rafique, A.; Rochester, L.; von Rohr, C. Rudolf; Russell, B.; Schmitz, D. W.; Schukraft, A.; Seligman, W.; Shaevitz, M. H.; Sinclair, J.; Snider, E. L.; Soderberg, M.; Söldner-Rembold, S.; Soleti, S. R.; Spentzouris, P.; Spitz, J.; St. John, J.; Strauss, T.; Szelc, A. M.; Tagg, N.; Terao, K.; Thomson, M.; Toups, M.; Tsai, Y.-T.; Tufanli, S.; Usher, T.; Van de Water, R. G.; Viren, B.; Weber, M.; Weston, J.; Wickremasinghe, D. A.; Wolbers, S.; Wongjirad, T.; Woodruff, K.; Yang, T.; Zeller, G. P.; Zennamo, J.; Zhang, C.

2017-03-01

We present several studies of convolutional neural networks applied to data coming from the MicroBooNE detector, a liquid argon time projection chamber (LArTPC). The algorithms studied include the classification of single particle images, the localization of single particle and neutrino interactions in an image, and the detection of a simulated neutrino event overlaid with cosmic ray backgrounds taken from real detector data. These studies demonstrate the potential of convolutional neural networks for particle identification or event detection on simulated neutrino interactions. We also address technical issues that arise when applying this technique to data from a large LArTPC at or near ground level.

ACE: AMY CDC (central drift chamber) fast track finder

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mori, T.

1988-01-01

The central drift chamber (CDC) of the AMY detector at the TRISTAN e/sup /+//e/sup /-// collider features its fine granularity and multi-band structure. The tracking software named ACE which makes the most of these features shows an excellent performance for reconstruction of high multiplicity events with highly collimated jets. The obtained reconstruction efficiency is 97% for the particles coming from within 5 cm of the primary vertex with p/sub t/ /approx gt/ 500 MeVc in the simulated hadronic events. The processing time is on average less than 300 ms per hadronic event (simulated or real) on a FACOM M-382 computer.more » 3 refs., 5 figs.« less

A Transonic and Surpersonic Investigation of Jet Exhaust Plume Effects on the Afterbody and Base Pressures of a Body of Revolution

NASA Technical Reports Server (NTRS)

Andrews, C. D.; Cooper, C. E., Jr.

1974-01-01

An experimental aerodynamic investigation was conducted to provide data for studies to determine the criteria for simulating rocket engine plume induced aerodynamic effects in the wind tunnel using a simulated gaseous plume. Model surface and base pressure data were obtained in the presence of both a simulated and a prototype gaseous plume for a matrix of plume properties to enable investigators to determine the parameters that correlate the simulated and prototype plume-induced data. The test program was conducted in the Marshall Space Flight Center's 14 x 14-inch trisonic wind tunnel using two models, the first being a strut mounted cone-ogive-cylinder model with a fineness ratio of 9. Model exterior pressures, model plenum chamber and nozzle performance data were obtained at Mach numbers of 0.9, 1.2, 1.46, and 3.48. The exhaust plume was generated by using air as the simulant gas, or Freon-14 (CF4) as the prototype gas, over a chamber pressure range from 0 to 2,000 psia and a total temperature range from 50 to 600 F.

Improving the accuracy of ionization chamber dosimetry in small megavoltage x-ray fields

NASA Astrophysics Data System (ADS)

McNiven, Andrea L.

The dosimetry of small x-ray fields is difficult, but important, in many radiation therapy delivery methods. The accuracy of ion chambers for small field applications, however, is limited due to the relatively large size of the chamber with respect to the field size, leading to partial volume effects, lateral electronic disequilibrium and calibration difficulties. The goal of this dissertation was to investigate the use of ionization chambers for the purpose of dosimetry in small megavoltage photon beams with the aim of improving clinical dose measurements in stereotactic radiotherapy and helical tomotherapy. A new method for the direct determination of the sensitive volume of small-volume ion chambers using micro computed tomography (muCT) was investigated using four nominally identical small-volume (0.56 cm3) cylindrical ion chambers. Agreement between their measured relative volume and ionization measurements (within 2%) demonstrated the feasibility of volume determination through muCT. Cavity-gas calibration coefficients were also determined, demonstrating the promise for accurate ion chamber calibration based partially on muCT. The accuracy of relative dose factor measurements in 6MV stereotactic x-ray fields (5 to 40mm diameter) was investigated using a set of prototype plane-parallel ionization chambers (diameters of 2, 4, 10 and 20mm). Chamber and field size specific correction factors ( CSFQ ), that account for perturbation of the secondary electron fluence, were calculated using Monte Carlo simulation methods (BEAM/EGSnrc simulations). These correction factors (e.g. CSFQ = 1.76 (2mm chamber, 5mm field) allow for accurate relative dose factor (RDF) measurement when applied to ionization readings, under conditions of electronic disequilibrium. With respect to the dosimetry of helical tomotherapy, a novel application of the ion chambers was developed to characterize the fan beam size and effective dose rate. Characterization was based on an adaptation of the computed tomography dose index (CTDI), a concept normally used in diagnostic radiology. This involved experimental determination of the fan beam thickness using the ion chambers to acquire fan beam profiles and extrapolation to a 'zero-size' detector. In conclusion, improvements have been made in the accuracy of small field dosimetry measurements in stereotactic radiotherapy and helical tomotherapy. This was completed through introduction of an original technique involving micro-CT imaging for sensitive volume determination and potentially ion chamber calibration coefficients, the use of appropriate Monte Carlo derived correction factors for RDF measurement, and the exploitation of the partial volume effect for helical tomotherapy fan beam dosimetry. With improved dosimetry for a wide range of challenging small x-ray field situations, it is expected that the patient's radiation safety will be maintained, and that clinical trials will adopt calibration protocols specialized for modern radiotherapy with small fields or beamlets. Keywords. radiation therapy, ionization chambers, small field dosimetry, stereotactic radiotherapy, helical tomotherapy, micro-CT.

Comparison Between Numerically Simulated and Experimentally Measured Flowfield Quantities Behind a Pulsejet

NASA Technical Reports Server (NTRS)

Geng, Tao; Paxson, Daniel E.; Zheng, Fei; Kuznetsov, Andrey V.; Roberts, William L.

2008-01-01

Pulsed combustion is receiving renewed interest as a potential route to higher performance in air breathing propulsion systems. Pulsejets offer a simple experimental device with which to study unsteady combustion phenomena and validate simulations. Previous computational fluid dynamic (CFD) simulation work focused primarily on the pulsejet combustion and exhaust processes. This paper describes a new inlet sub-model which simulates the fluidic and mechanical operation of a valved pulsejet head. The governing equations for this sub-model are described. Sub-model validation is provided through comparisons of simulated and experimentally measured reed valve motion, and time averaged inlet mass flow rate. The updated pulsejet simulation, with the inlet sub-model implemented, is validated through comparison with experimentally measured combustion chamber pressure, inlet mass flow rate, operational frequency, and thrust. Additionally, the simulated pulsejet exhaust flowfield, which is dominated by a starting vortex ring, is compared with particle imaging velocimetry (PIV) measurements on the bases of velocity, vorticity, and vortex location. The results show good agreement between simulated and experimental data. The inlet sub-model is shown to be critical for the successful modeling of pulsejet operation. This sub-model correctly predicts both the inlet mass flow rate and its phase relationship with the combustion chamber pressure. As a result, the predicted pulsejet thrust agrees very well with experimental data.

Pulsation damping of the reciprocating compressor with Helmholtz resonator

NASA Astrophysics Data System (ADS)

Wang, W.; Zhang, Y.; Zhou, Q.; Peng, X.; Feng, J.; Jia, X.

2017-08-01

Research presented in this paper investigated the mounting of a Helmholtz resonator near the valve chamber of a reciprocating compressor to attenuate the gas pulsation in the valve chamber as well as the pipeline downstream. Its attenuation characteristics were simulated with the plane wave theory together with the transfer matrix method, and the damping effect was checked by comparing the pressure pulsation levels before and after mounting the resonator. The results show that the Helmholtz resonator was effective in attenuating the gas pulsation in the valve chamber and piping downstream, and the pulsation level was decreased by 40% in the valve chamber and 30% at maximum in the piping downstream. The damping effect of the resonator was sensitive to its resonant frequency, and various resonators working simultaneously didn’t interfere with each other. When two resonators were mounted in parallel, with resonant frequencies equal to the second and fourth harmonic frequencies, the pressure pulsation components corresponding to the resonant frequencies were remarkably decreased at the same time, while the pulsation levels at other harmonic frequencies kept almost unchanged. After a series of simulations and experiments a design criterion of chock tube and volume parameter has been proposed for the targeted frequencies to be damped. Furthermore, the frequency-adjustable Helmholtz resonator which was applied to the variable speed compressor was investigated.

Laser-filament-induced snow formation in a subsaturated zone in a cloud chamber: experimental and theoretical study.

PubMed

Ju, Jingjing; Sun, Haiyi; Sridharan, Aravindan; Wang, Tie-Jun; Wang, Cheng; Liu, Jiansheng; Li, Ruxin; Xu, Zhizhan; Chin, See Leang

2013-12-01

1 kHz, 2 mJ, 45 fs, 800 nm laser pulses were fired into a laboratory diffusion cloud chamber through a subsaturated zone (relative humidity ∼73%, T ∼ 4.3 °C). After 60 min of laser irradiation, an oval-shaped snow pile was observed right below the filament center and weighed ∼12.0 mg. The air current velocity at the edge of the vortices was estimated to be ∼16.5 cm/s. Scattering scenes recorded from the side show that filament-induced turbulence were formed inside the cloud chamber with two vortices below the filament. Two-dimensional simulations of the air flow motion in two cross sections of the cloud chamber confirm that the turbulent vortices exist below the filament. Based upon this simulation, we deduce that the vortices indeed have a three-dimensional elliptical shape. Hence, we propose that inside vortices where the humidity was supersaturated or saturated the condensation nuclei, namely, HNO(3), N(2)(+), O(2)(+) and other aerosols and impurities, were activated and grew in size. Large-sized particles would eventually be spun out along the fast moving direction towards the cold plate and formed an oval-shaped snow pile at the end.

Modelling the contribution of biogenic volatile organic compounds to new particle formation in the Jülich plant atmosphere chamber

NASA Astrophysics Data System (ADS)

Roldin, P.; Liao, L.; Mogensen, D.; Dal Maso, M.; Rusanen, A.; Kerminen, V.-M.; Mentel, T. F.; Wildt, J.; Kleist, E.; Kiendler-Scharr, A.; Tillmann, R.; Ehn, M.; Kulmala, M.; Boy, M.

2015-09-01

We used the Aerosol Dynamics gas- and particle-phase chemistry model for laboratory CHAMber studies (ADCHAM) to simulate the contribution of BVOC plant emissions to the observed new particle formation during photooxidation experiments performed in the Jülich Plant-Atmosphere Chamber and to evaluate how well smog chamber experiments can mimic the atmospheric conditions during new particle formation events. ADCHAM couples the detailed gas-phase chemistry from Master Chemical Mechanism with a novel aerosol dynamics and particle phase chemistry module. Our model simulations reveal that the observed particle growth may have either been controlled by the formation rate of semi- and low-volatility organic compounds in the gas phase or by acid catalysed heterogeneous reactions between semi-volatility organic compounds in the particle surface layer (e.g. peroxyhemiacetal dimer formation). The contribution of extremely low-volatility organic gas-phase compounds to the particle formation and growth was suppressed because of their rapid and irreversible wall losses, which decreased their contribution to the nano-CN formation and growth compared to the atmospheric situation. The best agreement between the modelled and measured total particle number concentration (R2 > 0.95) was achieved if the nano-CN was formed by kinetic nucleation involving both sulphuric acid and organic compounds formed from OH oxidation of BVOCs.

Ethylene Decomposition Initiated by Ultraviolet Radiation from Low Pressure Mercury Lamps: Kinetics Model Prediction and Experimental Verification.

NASA Astrophysics Data System (ADS)

Jozwiak, Zbigniew Boguslaw

1995-01-01

Ethylene is an important auto-catalytic plant growth hormone. Removal of ethylene from the atmosphere surrounding ethylene-sensitive horticultural products may be very beneficial, allowing an extended period of storage and preventing or delaying the induction of disorders. Various ethylene removal techniques have been studied and put into practice. One technique is based on using low pressure mercury ultraviolet lamps as a source of photochemical energy to initiate chemical reactions that destroy ethylene. Although previous research showed that ethylene disappeared in experiments with mercury ultraviolet lamps, the reactions were not described and the actual cause of ethylene disappearance remained unknown. Proposed causes for this disappearance were the direct action of ultraviolet rays on ethylene, reaction of ethylene with ozone (which is formed when air or gas containing molecular oxygen is exposed to radiation emitted by this type of lamp), or reactions with atomic oxygen leading to formation of ozone. The objective of the present study was to determine the set of physical and chemical actions leading to the disappearance of ethylene from artificial storage atmosphere under conditions of ultraviolet irradiation. The goal was achieved by developing a static chemical model based on the physical properties of a commercially available ultraviolet lamp, the photochemistry of gases, and the kinetics of chemical reactions. The model was used to perform computer simulations predicting time dependent concentrations of chemical species included in the model. Development of the model was accompanied by the design of a reaction chamber used for experimental verification. The model provided a good prediction of the general behavior of the species involved in the chemistry under consideration; however the model predicted lower than measured rate of ethylene disappearance. Some reasons for the model -experiment disagreement are radiation intensity averaging, the experimental technique, mass transfer in the chamber, and incompleteness of the set of chemical reactions included in the model. The work is concluded with guidelines for development of a more complex mathematical model that includes elements of mass transfer inside the reaction chamber, and uses a three dimensional approach to distribute radiation from the low pressure mercury ultraviolet tube.

Design of an Experiment to Measure ann Using 3H(γ, pn)n at HIγS★

NASA Astrophysics Data System (ADS)

Friesen, F. Q. L.; Ahmed, M. W.; Crowe, B. J.; Crowell, A. S.; Cumberbatch, L. C.; Fallin, B.; Han, Z.; Howell, C. R.; Malone, R. M.; Markoff, D.; Tornow, W.; Witała, H.

2016-03-01

We provide an update on the development of an experiment at TUNL for determining the 1S0 neutron-neutron (nn) scattering length (ann) from differential cross-section measurements of three-body photodisintegration of the triton. The experiment will be conducted using a linearly polarized gamma-ray beam at the High Intensity Gamma-ray Source (HIγS) and tritium gas contained in thin-walled cells. The main components of the planned experiment are a 230 Ci gas target system, a set of wire chambers and silicon strip detectors on each side of the beam axis, and an array of neutron detectors on each side beyond the silicon detectors. The protons emitted in the reaction are tracked in the wire chambers and their energy and position are measured in silicon strip detectors. The first iteration of the experiment will be simplified, making use of a collimator system, and silicon detectors to interrogate the main region of interest near 90° in the polar angle. Monte-Carlo simulations based on rigorous 3N calculations have been conducted to validate the sensitivity of the experimental setup to ann. This research supported in part by the DOE Office of Nuclear Physics Grant Number DE-FG02-97ER41033

Evaluation of Impact Damage to the Burster Detonation Vessel Caused by Fragments from a Drained M121A1 Chemical Munition Detonated with an Initiation Charge

DOE Office of Scientific and Technical Information (OSTI.GOV)

KIPP, MARLIN E.

2001-12-01

Explosive charges placed on the fuze end of a drained chemical munition are expected to be used as a means to destroy the fuze and burster charges of the munition. Analyses are presented to evaluate the effect of these additional initiation charges on the fragmentation characteristics for the M121A1 155mm chemical munition, modeled with a T244 fuze attached, and to assess the consequences of these fragment impacts on the walls of a containment chamber--the Burster Detonation Vessel. A numerical shock physics code (CTH) is used to characterize the mass and velocity of munition fragments. Both two- and three-dimensional simulations ofmore » the munition have been completed in this study. Based on threshold fragment velocity/mass results drawn from both previous and current analyses, it is determined that under all fragment impact conditions from the munition configurations considered in this study, no perforation of the inner chamber wall will occur, and the integrity of the Burster Detonation Vessel is retained. However, the munition case fragments have sufficient mass and velocity to locally damage the surface of the inner wall of the containment vessel.« less

The FIRST experiment at GSI

NASA Astrophysics Data System (ADS)

Pleskac, R.; Abou-Haidar, Z.; Agodi, C.; Alvarez, M. A. G.; Aumann, T.; Battistoni, G.; Bocci, A.; Böhlen, T. T.; Boudard, A.; Brunetti, A.; Carpinelli, M.; Cirrone, G. A. P.; Cortes-Giraldo, M. A.; Cuttone, G.; De Napoli, M.; Durante, M.; Fernández-García, J. P.; Finck, C.; Golosio, B.; Gallardo, M. I.; Iarocci, E.; Iazzi, F.; Ickert, G.; Introzzi, R.; Juliani, D.; Krimmer, J.; Kurz, N.; Labalme, M.; Leifels, Y.; Le Fevre, A.; Leray, S.; Marchetto, F.; Monaco, V.; Morone, M. C.; Oliva, P.; Paoloni, A.; Piersanti, L.; Quesada, J. M.; Raciti, G.; Randazzo, N.; Romano, F.; Rossi, D.; Rousseau, M.; Sacchi, R.; Sala, P.; Sarti, A.; Scheidenberger, C.; Schuy, C.; Sciubba, A.; Sfienti, C.; Simon, H.; Sipala, V.; Spiriti, E.; Stuttge, L.; Tropea, S.; Younis, H.; Patera, V.

2012-06-01

The FIRST (Fragmentation of Ions Relevant for Space and Therapy) experiment at the SIS accelerator of GSI laboratory in Darmstadt has been designed for the measurement of ion fragmentation cross-sections at different angles and energies between 100 and 1000 MeV/nucleon. Nuclear fragmentation processes are relevant in several fields of basic research and applied physics and are of particular interest for tumor therapy and for space radiation protection applications. The start of the scientific program of the FIRST experiment was on summer 2011 and was focused on the measurement of 400 MeV/nucleon 12C beam fragmentation on thin (8 mm) graphite target. The detector is partly based on an already existing setup made of a dipole magnet (ALADiN), a time projection chamber (TP-MUSIC IV), a neutron detector (LAND) and a time of flight scintillator system (TOFWALL). This pre-existing setup has been integrated with newly designed detectors in the Interaction Region, around the carbon target placed in a sample changer. The new detectors are a scintillator Start Counter, a Beam Monitor drift chamber, a silicon Vertex Detector and a Proton Tagger scintillator system optimized for the detection of light fragments emitted at large angles. In this paper we review the experimental setup, then we present the simulation software, the data acquisition system and finally the trigger strategy of the experiment.

Evolution of Combustion-Generated Particles at Tropospheric Conditions

NASA Technical Reports Server (NTRS)

Tacina, Kathleen M.; Heath, Christopher M.

2012-01-01

This paper describes particle evolution measurements taken in the Particulate Aerosol Laboratory (PAL). The PAL consists of a burner capable of burning jet fuel that exhausts into an altitude chamber that can simulate temperature and pressure conditions up to 13,700 m. After presenting results from initial temperature distributions inside the chamber, particle count data measured in the altitude chamber are shown. Initial particle count data show that the sampling system can have a significant effect on the measured particle distribution: both the value of particle number concentration and the shape of the radial distribution of the particle number concentration depend on whether the measurement probe is heated or unheated.

Broadband impedance calculations and single bunch instabilities estimations of of the HLS-II storage ring

NASA Astrophysics Data System (ADS)

Zhang, Qing-Kun; Wang, Lin; Li, Wei-Min; Gao, Wei-Wei

2015-12-01

The upgrade project of the Hefei Light Source storage ring is under way. In this paper, the broadband impedances of resistive wall and coated ceramic vacuum chamber are calculated using the analytic formula, and the wake fields and impedances of other designed vacuum chambers are simulated by CST code, and then a broadband impedance model is obtained. Using the theoretical formula, longitudinal and transverse single bunch instabilities are discussed. With the carefully-designed vacuum chamber, we find that the thresholds of the beam instabilities are higher than the beam current goal. Supported by Natural Science Foundation of China (11175182, 11175180)

Challenges to validation of a complex nonsterile medical device tray.

PubMed

Prince, Daniel; Mastej, Jozef; Hoverman, Isabel; Chatterjee, Raja; Easton, Diana; Behzad, Daniela

2014-01-01

Validation by steam sterilization of reusable medical devices requires careful attention to many parameters that directly influence whether or not complete sterilization occurs. Complex implant/instrument tray systems have a variety of configurations and components. Geobacillus stearothermophilus biological indicators (BIs) are used in overkill cycles to to simulate worst case conditions and are intended to provide substantial sterilization assurance. Survival of G. stearothermophilus spores was linked to steam access and size of load in the chamber. By a small and reproducible margin, it was determined that placement of the trays in a rigid container into minimally loaded chambers were more difficult to completely sterilize than maximally loaded chambers.

Saturn Apollo Program

NASA Image and Video Library

1963-01-01

Smokeless flame juts from the diffuser of a unique vacuum chamber in which the upper stage rocket engine, the hydrogen fueled J-2, was tested at a simulated space altitude in excess of 60,000 feet. The smoke you see is actually steam. In operation, vacuum is established by injecting steam into the chamber and is maintained by the thrust of the engine firing through the diffuser. The engine was tested in this environment for start, stop, coast, restart, and full-duration operations. The chamber was located at Rocketdyne's Propulsion Field Laboratory, in the Santa Susana Mountains, near Canoga Park, California. The J-2 engine was developed by Rocketdyne for the Marshall Space Flight Center.

Transient Three-Dimensional Side Load Analysis of a Film Cooled Nozzle

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Guidos, Mike

2008-01-01

Transient three-dimensional numerical investigations on the side load physics for an engine encompassing a film cooled nozzle extension and a regeneratively cooled thrust chamber, were performed. The objectives of this study are to identify the three-dimensional side load physics and to compute the associated aerodynamic side load using an anchored computational methodology. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and a transient inlet history based on an engine system simulation. Ultimately, the computational results will be provided to the nozzle designers for estimating of effect of the peak side load on the nozzle structure. Computations simulating engine startup at ambient pressures corresponding to sea level and three high altitudes were performed. In addition, computations for both engine startup and shutdown transients were also performed for a stub nozzle, operating at sea level. For engine with the full nozzle extension, computational result shows starting up at sea level, the peak side load occurs when the lambda shock steps into the turbine exhaust flow, while the side load caused by the transition from free-shock separation to restricted-shock separation comes at second; and the side loads decreasing rapidly and progressively as the ambient pressure decreases. For the stub nozzle operating at sea level, the computed side loads during both startup and shutdown becomes very small due to the much reduced flow area.

Process of electrolysis and fractional crystallization for aluminum purification

DOEpatents

Dawless, R.K.; Bowman, K.A.; Mazgaj, R.M.; Cochran, C.N.

1983-10-25

A method is described for purifying aluminum that contains impurities, the method including the step of introducing such aluminum containing impurities to a charging and melting chamber located in an electrolytic cell of the type having a porous diaphragm permeable by the electrolyte of the cell and impermeable to molten aluminum. The method includes further the steps of supplying impure aluminum from the chamber to the anode area of the cell and electrolytically transferring aluminum from the anode area to the cathode through the diaphragm while leaving impurities in the anode area, thereby purifying the aluminum introduced into the chamber. The method includes the further steps of collecting the purified aluminum at the cathode, and lowering the level of impurities concentrated in the anode area by subjecting molten aluminum and impurities in said chamber to a fractional crystallization treatment wherein eutectic-type impurities crystallize and precipitate out of the aluminum. The eutectic impurities that have crystallized are physically removed from the chamber. The aluminum in the chamber is now suited for further purification as provided in the above step of electrolytically transferring aluminum through the diaphragm. 2 figs.

Process of electrolysis and fractional crystallization for aluminum purification

DOEpatents

Dawless, Robert K.; Bowman, Kenneth A.; Mazgaj, Robert M.; Cochran, C. Norman

1983-10-25

A method for purifying aluminum that contains impurities, the method including the step of introducing such aluminum containing impurities to a charging and melting chamber located in an electrolytic cell of the type having a porous diaphragm permeable by the electrolyte of the cell and impermeable to molten aluminum. The method includes further the steps of supplying impure aluminum from the chamber to the anode area of the cell and electrolytically transferring aluminum from the anode area to the cathode through the diaphragm while leaving impurities in the anode area, thereby purifying the aluminum introduced into the chamber. The method includes the further steps of collecting the purified aluminum at the cathode, and lowering the level of impurities concentrated in the anode area by subjecting molten aluminum and impurities in said chamber to a fractional crystallization treatment wherein eutectic-type impurities crystallize and precipitate out of the aluminum. The eutectic impurities that have crystallized are physically removed from the chamber. The aluminum in the chamber is now suited for further purification as provided in the above step of electrolytically transferring aluminum through the diaphragm.

Designing efficient nitrous oxide sampling strategies in agroecosystems using simulation models

Treesearch

Debasish Saha; Armen R. Kemanian; Benjamin M. Rau; Paul R. Adler; Felipe Montes

2017-01-01

Annual cumulative soil nitrous oxide (N2O) emissions calculated from discrete chamber-based flux measurements have unknown uncertainty. We used outputs from simulations obtained with an agroecosystem model to design sampling strategies that yield accurate cumulative N2O flux estimates with a known uncertainty level. Daily soil N2O fluxes were simulated for Ames, IA (...

Thin-thick hydrogen target for nuclear physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gheller, J.-M.; Juster, F.-P.; Authelet, G.

In spectroscopic studies of unstable nuclei, hydrogen targets are of key importance. The CHyMENE Project aims to provide to the nuclear physics community a thin and pure solid windowless hydrogen or deuterium target. CHyMENE project must respond to this request for the production of solid Hydrogen. The solid hydrogen target is produced in a continuous flow (1 cm/s) by an extrusion technique (developed with the PELIN laboratory) in a vacuum chamber. The shape of the target is determined by the design of the nozzle at the extrusion process. For the purpose, the choice is a rectangular shape with a widthmore » of 10 mm and a thickness in the range of 30-50 microns necessary for the physics objectives. The cryostat is equipped with a GM Cryocooler with sufficient power for the solidification of the hydrogen in the lower portion of the extruder. In the higher part of the cryostat, the hydrogen gas is first liquefied and partially solidified. It is then compressed at 100 bars in the cooled extruder before expulsion of the film through the nozzle at the center of the reaction vacuum chamber. After the previous step, the solid hydrogen ribbon falls by gravity into a dedicated chamber where it sublimes and the gas is pumped and evacuated in a exhaust line. This paper deals with the design of the cryostat with its equipment, with the sizing of the thermal bridge (Aluminum and copper), with the results regarding the contact resistance as well as with the vacuum computations of the reaction and recovery hydrogen gas chambers.« less

Design verification of large time constant thermal shields for optical reference cavities.

PubMed

Zhang, J; Wu, W; Shi, X H; Zeng, X Y; Deng, K; Lu, Z H

2016-02-01

In order to achieve high frequency stability in ultra-stable lasers, the Fabry-Pérot reference cavities shall be put inside vacuum chambers with large thermal time constants to reduce the sensitivity to external temperature fluctuations. Currently, the determination of thermal time constants of vacuum chambers is based either on theoretical calculation or time-consuming experiments. The first method can only apply to simple system, while the second method will take a lot of time to try out different designs. To overcome these limitations, we present thermal time constant simulation using finite element analysis (FEA) based on complete vacuum chamber models and verify the results with measured time constants. We measure the thermal time constants using ultrastable laser systems and a frequency comb. The thermal expansion coefficients of optical reference cavities are precisely measured to reduce the measurement error of time constants. The simulation results and the experimental results agree very well. With this knowledge, we simulate several simplified design models using FEA to obtain larger vacuum thermal time constants at room temperature, taking into account vacuum pressure, shielding layers, and support structure. We adopt the Taguchi method for shielding layer optimization and demonstrate that layer material and layer number dominate the contributions to the thermal time constant, compared with layer thickness and layer spacing.

Evaluation of an Air Quality Health Index for Predicting the Mutagenicity of Simulated Atmospheres

EPA Science Inventory

No study has evaluated the mutagenicity of atmospheres with a calculated air quality health index (AQHI). Thus, we generated in a UV-light-containing reaction chamber two simulated atmospheres (SAs) with similar AQHIs but different proportions of criteria pollutants and evaluated...

Infrared Spectral Observations While Drilling into a Frozen Lunar Simulant

NASA Technical Reports Server (NTRS)

Roush, Ted L.; Colaprete, Anthony; Thompson, Sarah; Cook, Amanda; Kleinhenz, Julie

2014-01-01

Past and continuing observations indicate an enrichment of volatile materials in lunar polar regions. While these volatiles may be located near the surface, access to them will likely require subsurface sampling, during which it is desirable to monitor the volatile content. In a simulation of such activities, a multilayer lunar simulant was prepared with differing water content, and placed inside a thermal vacuum chamber at Glenn Research Center (GRC). The soil profile was cooled using liquid nitrogen. In addition to the soil, a drill and infrared (IR) spectrometer (1600-3400 nm) were also located in the GRC chamber. We report the spectral observations obtained during a sequence where the drill was repeatedly inserted and extracted, to different depths, at the same location. We observe an overall increase in the spectral signature of water ice over the duration of the test. Additionally, we observe variations in the water ice spectral signature as the drill encounters different layers.

Investigation of different modeling approaches for computational fluid dynamics simulation of high-pressure rocket combustors

NASA Astrophysics Data System (ADS)

Ivancic, B.; Riedmann, H.; Frey, M.; Knab, O.; Karl, S.; Hannemann, K.

2016-07-01

The paper summarizes technical results and first highlights of the cooperation between DLR and Airbus Defence and Space (DS) within the work package "CFD Modeling of Combustion Chamber Processes" conducted in the frame of the Propulsion 2020 Project. Within the addressed work package, DLR Göttingen and Airbus DS Ottobrunn have identified several test cases where adequate test data are available and which can be used for proper validation of the computational fluid dynamics (CFD) tools. In this paper, the first test case, the Penn State chamber (RCM1), is discussed. Presenting the simulation results from three different tools, it is shown that the test case can be computed properly with steady-state Reynolds-averaged Navier-Stokes (RANS) approaches. The achieved simulation results reproduce the measured wall heat flux as an important validation parameter very well but also reveal some inconsistencies in the test data which are addressed in this paper.

Changes of catecholamine excretion during long-duration confinement.

PubMed

Kraft, N; Inoue, N; Ohshima, H; Sekiguchi, C

2002-06-01

Simulation studies have become the main source of data about small group interactions during prolonged isolation, from which it should be possible to anticipate crew problems during actual space missions. International Space Station (ISS) astronauts and cosmonauts will form one international crew, although living in different national modules. They will have joint flight protocols, and at the same time, fulfill a number of different tasks in accord with their national flight programs. Consistent with these concepts, we studied two simultaneously functioning groups in a simulation of ISS flight. The objective of this study was to investigate physiological parameters (such as catecholamine excretions) related to long-duration confinement in the hermetic chamber, simulating International Space Station flight conditions. We also planned to evaluate the relationship between epinephrine/norepinephrine with group dynamics and social events to predict unfavorable changes in health and work capability of the subjects related to psychological interaction in the isolation chamber.

Optical system for determining physical characteristics of a solar cell

DOEpatents

Sopori, Bhushan L.

2001-01-01

The invention provides an improved optical system for determining the physical characteristics of a solar cell. The system comprises a lamp means for projecting light in a wide solid-angle onto the surface of the cell; a chamber for receiving the light through an entrance port, the chamber having an interior light absorbing spherical surface, an exit port for receiving a beam of light reflected substantially normal to the cell, a cell support, and an lower aperture for releasing light into a light absorbing baffle; a means for dispersing the reflection into monochromatic components; a means for detecting an intensity of the components; and a means for reporting the determination.

Semi-automated operation of Mars Climate Simulation chamber - MCSC modelled for biological experiments

NASA Astrophysics Data System (ADS)

Tarasashvili, M. V.; Sabashvili, Sh. A.; Tsereteli, S. L.; Aleksidze, N. D.; Dalakishvili, O.

2017-10-01

The Mars Climate Simulation Chamber (MCSC) (GEO PAT 12 522/01) is designed for the investigation of the possible past and present habitability of Mars, as well as for the solution of practical tasks necessary for the colonization and Terraformation of the Planet. There are specific tasks such as the experimental investigation of the biological parameters that allow many terrestrial organisms to adapt to the imitated Martian conditions: chemistry of the ground, atmosphere, temperature, radiation, etc. MCSC is set for the simulation of the conduction of various biological experiments, as well as the selection of extremophile microorganisms for the possible Settlement, Ecopoesis and/or Terraformation purposes and investigation of their physiological functions. For long-term purposes, it is possible to cultivate genetically modified organisms (e.g., plants) adapted to the Martian conditions for future Martian agriculture to sustain human Mars missions and permanent settlements. The size of the chamber allows preliminary testing of the functionality of space-station mini-models and personal protection devices such as space-suits, covering and building materials and other structures. The reliability of the experimental biotechnological materials can also be tested over a period of years. Complex and thorough research has been performed to acquire the most appropriate technical tools for the accurate engineering of the MCSC and precious programmed simulation of Martian environmental conditions. This paper describes the construction and technical details of the equipment of the MCSC, which allows its semi-automated, long-term operation.

Hydrocarbon Fuel Thermal Performance Modeling based on Systematic Measurement and Comprehensive Chromatographic Analysis

DTIC Science & Technology

2016-07-31

fueled liquid rocket engine, enthalpy is removed from the combustion chamber by a regenerative cooling system comprising a series of passages through... rocket engine, enthalpy is removed from the combustion chamber by a regenerative cooling system comprising a series of passages through which fuel flows...the unprecedented correlation of comprehensive two-dimensional gas chromatographic (GC×GC) rocket fuel data with physical and thermochemical

Charged particle transport in magnetic fields in EGSnrc.

PubMed

Malkov, V N; Rogers, D W O

2016-07-01

To accurately and efficiently implement charged particle transport in a magnetic field in EGSnrc and validate the code for the use in phantom and ion chamber simulations. The effect of the magnetic field on the particle motion and position is determined using one- and three-point numerical integrations of the Lorentz force on the charged particle and is added to the condensed history calculation performed by the EGSnrc PRESTA-II algorithm. The code is tested with a Fano test adapted for the presence of magnetic fields. The code is compatible with all EGSnrc based applications, including egs++. Ion chamber calculations are compared to experimental measurements and the effect of the code on the efficiency and timing is determined. Agreement with the Fano test's theoretical value is obtained at the 0.1% level for large step-sizes and in magnetic fields as strong as 5 T. The NE2571 dose calculations achieve agreement with the experiment within 0.5% up to 1 T beyond which deviations up to 1.2% are observed. Uniform air gaps of 0.5 and 1 mm and a misalignment of the incoming photon beam with the magnetic field are found to produce variations in the normalized dose on the order of 1%. These findings necessitate a clear definition of all experimental conditions to allow for accurate Monte Carlo simulations. It is found that ion chamber simulation times are increased by only 38%, and a 10 × 10 × 6 cm(3) water phantom with (3 mm)(3) voxels experiences a 48% increase in simulation time as compared to the default EGSnrc with no magnetic field. The incorporation of the effect of the magnetic fields in EGSnrc provides the capability to calculate high accuracy ion chamber and phantom doses for the use in MRI-radiation systems. Further, the effect of apparently insignificant experimental details is found to be accentuated by the presence of the magnetic field.

Experimental investigation of a solid rocket combustion simulator

NASA Technical Reports Server (NTRS)

Frederick, Robert A., Jr.

1991-01-01

The response of solid rocket motor materials to high-temperature corrosive gases is usually accomplished by testing the materials in a subscale solid rocket motor. While this imposes the proper thermal and chemical environment, a solid rocket motor does not provide practical features that would enhance systematic evaluations such as: the ability to throttle for margin testing, on/off capability, low test cost, and a low-hazards test article. Solid Rocket Combustion Simulators (SRCS) are being evaluated by NASA to test solid rocket nozzle materials and incorporate these essential practical features into the testing of rocket materials. The SRCS is designed to generate the thermochemical environment of a solid rocket. It uses hybrid rocket motor technology in which gaseous oxygen (Gox) is injected into a chamber containing a solid fuel grain. Specific chemicals are injected in the aft mixing chamber so that the gases entering the test section match the temperature and a non-dimensional erosion factor B' to insure similarity with a solid motor. Because the oxygen flow can be controlled, this approach allows margin testing, the ability to throttle, and an on/off capability. The fuel grains are inert which makes the test article very safe to handle. The objective of this work was to establish the baseline operating characteristics of a Labscale Solid Rocket Combustion Simulator (LSRCS). This included establishing the baseline burning rates of plexiglass fuels and the evaluation of a combustion instability for hydroxy-terminated polybutadyene (HTPB) propellants. The scope of the project included: (1) activation of MSFC Labscale Hybrid Combustion Simulator; (2) testing of plexiglass fuel at Gox ranges from 0.025 to 0.200 lb/s; (3) burning HTPB fuels at a Gox rate of 0.200 lb/s using four different mixing chamber configurations; and (4) evaluating the fuel regression and chamber pressure responses of each firing.

Methodology for the in vitro evaluation of the delivery efficiency from valved holding chambers with facemasks.

PubMed

Xu, Zhen; Hsu, Wenchi; von Hollen, Dirk; Viswanath, Ashwin; Nikander, Kurt; Dalby, Richard

2014-08-01

In vitro performance studies of valved holding chamber (VHC)-facemask systems are a cost-effective means of circumventing potentially confounding clinical variables. This article reports results of an in vitro investigation into VHC-facemask performance, using three age-specific soft anatomical model (SAM) faces, under clinically relevant conditions. A potentially standardized method was developed to assess VHC-facemask seal leakage, and evaluate the in vitro delivery efficiency of conventional and antistatic VHC-facemask systems. A custom-built test rig and VHC cradles were used to position the VHC-facemask systems against the SAM faces, with a constant, reproducible force. A standardized simulated pediatric breathing pattern (tidal volume = 155 mL; inhalation:exhalation ratio = 40:60; 25 breaths/min) was utilized. Percent facemask seal leakage, percent delivered dose, and the effect of different numbers of simulated breaths (2 to 8) were investigated. Of the VHC-facemask systems tested, the OptiChamber Diamond VHC with LiteTouch facemask (Diamond) system had the lowest percent seal leakage with each SAM face. Percent seal leakage from the other VHC-facemask systems was similar with SAM0 and SAM2 faces; the AeroChamber Plus Z-Stat VHC with ComfortSeal facemask (AC Z-Stat) system had a substantially greater percent seal leakage with the SAM1 face. Regardless of the number of simulated breaths, the Diamond system delivered the greatest mean percent delivered dose, with the lowest coefficient of variation, with each SAM face. Percent delivered dose did not correlate well with seal leakage, particularly for VHC-facemask systems with high seal leakage. The electrostatic properties of the VHCs appeared to influence drug delivery. This study describes a potentially standardized method for the evaluation of VHC-facemask systems. Use of this method enabled a comprehensive investigation into the influence of clinically relevant variables, including age-specific facial anatomy, number of simulated breaths, and seal leakage, on the delivery efficiency of several commercially available VHC-facemask systems.

SU-E-T-155: Calibration of Variable Longitudinal Strength 103Pd Brachytherapy Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reed, J; Radtke, J; Micka, J

Purpose: Brachytherapy sources with variable longitudinal strength (VLS) allow for a customized intensity along the length of the source. These have applications in focal brachytherapy treatments of prostate cancer where dose boosting can be achieved through modulation of intra-source strengths. This work focused on development of a calibration methodology for VLS sources based on measurements and Monte Carlo (MC) simulations of five 1 cm {sup 10} {sup 3}Pd sources each containing four regions of variable {sup 103}Pd strength. Methods: The air-kerma strengths of the sources were measured with a variable-aperture free-air chamber (VAFAC). Source strengths were also measured using amore » well chamber. The in-air azimuthal and polar anisotropy of the sources were measured by rotating them in front of a NaI scintillation detector and were calculated with MC simulations. Azimuthal anisotropy results were normalized to their mean intensity values. Polar anisotropy results were normalized to their average transverse axis intensity values. The relative longitudinal strengths of the sources were measured via on-contact irradiations with radiochromic film, and were calculated with MC simulations. Results: The variable {sup 103}Pd loading of the sources was validated by VAFAC and well chamber measurements. Ratios of VAFAC air-kerma strengths and well chamber responses were within ±1.3% for all sources. Azimuthal anisotropy results indicated that ≥95% of the normalized values for all sources were within ±1.7% of the mean values. Polar anisotropy results indicated variations within ±0.3% for a ±7.6° angular region with respect to the source transverse axis. Locations and intensities of the {sup 103}Pd regions were validated by radiochromic film measurements and MC simulations. Conclusion: The calibration methodology developed in this work confirms that the VLS sources investigated have a high level of polar uniformity, and that the strength and longitudinal intensity can be verified experimentally and through MC simulations. {sup 103}Pd sources were provided by CivaTech Oncology, Inc.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji, Yanfeng; Hui, Fei; Shi, Yuanyuan

The atomic force microscope is one of the most widespread tools in science, but many suppliers do not provide a competitive solution to make experiments in controlled atmospheres. Here, we provide a solution to this problem by fabricating a fast-response and user-friendly environmental chamber. We corroborate the correct functioning of the chamber by studying the formation of local anodic oxidation on a silicon sample (biased under opposite polarities), an effect that can be suppressed by measuring in a dry nitrogen atmosphere. The usefulness of this chamber goes beyond the example here presented, and it could be used in many othermore » fields of science, including physics, mechanics, microelectronics, nanotechnology, medicine, and biology.« less

Pixel response-based EPID dosimetry for patient specific QA.

PubMed

Han, Bin; Ding, Aiping; Lu, Minghui; Xing, Lei

2017-01-01

Increasing use of high dose rate, flattening filter free (FFF), and/or small-sized field beams presents a significant challenge to the medical physics community. In this work, we develop a strategy of using a high spatial resolution and high frame rate amorphous silicon flat panel electronic portal imaging device (EPID) for dosimetric measurements of these challenging cases, as well as for conventional external beam therapy. To convert a series of raw EPID-measured radiation field images into water-based dose distribution, a pixel-to-pixel dose-response function of the EPID specific to the linac is essential. The response function was obtained by using a Monte Carlo simulation of the photon transport in the EPID with a comprehensive calibration. After the raw image was converted into the primary incident photon fluence, the fluence was further convolved into a water-based dose distribution of the dynamic field by using a pregenerated pencil-beam kernel. The EPID-based dosimetric measurement technique was validated using beams with and without flattening filter of all energies available in Varian TrueBeam STx™. Both regularly and irregularly shaped fields measured using a PTW 729 ion chamber array in plastic water phantom. The technique was also applied to measure the distribution for a total of 23 treatment plans of different energies to evaluate the accuracy of the proposed approach. The EPID measurements of square fields of 4 × 4 cm 2 to 20 × 20 cm 2 , circular fields of 2-15 cm diameters, rectangular fields of various sizes, and irregular MLC fields were in accordance with measurements using a Farmer chamber and/or ion chamber array. The 2D absolute dose maps generated from EPID raw images agreed with ion chamber measurements to within 1.5% for all fields. For the 23 patient cases examined in this work, the average γ-index passing rate were found to be 99.2 ± 0.6%, 97.4 ± 2.4%, and 72.6 ± 8.4%, respectively, for criterions of 3 mm/3%, 2 mm/2%, and 1 mm/1%. The high spatial resolution and high frame rate EPID provides an accurate and efficient dosimetric tool for QA of modern radiation therapy. Accurate absolute 2D dose maps can be generated from the system for an independent dosimetric verification of treatment delivery. © 2016 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Edge-localized-modes in tokamaks

DOE PAGES

Leonard, Anthony W.

2014-09-11

Edge-localized-modes (ELMs) are a ubiquitous feature of H-mode in tokamaks. When gradients in the H-mode transport barrier grow to exceed the MHD stability limit the ELM instability grows explosively rapidly transporting energy and particles onto open field lines and material surfaces. Though ELMs provide additional particle and impurity transport through the H-mode transport barrier, enabling steady operation, the resulting heat flux transients to plasma facing surfaces project to large amplitude in future low collisionality burning plasma tokamaks. Measurements of the ELM heat flux deposition onto material surfaces in the divertor and main chamber indicate significant broadening compared to inter-ELM heatmore » flux, with a timescale for energy deposition that is consistent with sonic ion flow and numerical simulation. Comprehensive ELM simulation is highlighting the important physics processes of ELM transport including parallel transport due to magnetic reconnection and turbulence resulting from collapse of the H-mode transport barrier. As a result, encouraging prospects for ELM control and/or suppression in future tokamaks include intrinsic modes of ELM free operation, ELM triggering with frequent small pellet injection and the application of 3D magnetic fields.« less

3D simulation of electron and ion transmission of GEM-based detectors

NASA Astrophysics Data System (ADS)

Bhattacharya, Purba; Mohanty, Bedangadas; Mukhopadhyay, Supratik; Majumdar, Nayana; da Luz, Hugo Natal

2017-10-01

Time Projection Chamber (TPC) has been chosen as the main tracking system in several high-flux and high repetition rate experiments. These include on-going experiments such as ALICE and future experiments such as PANDA at FAIR and ILC. Different R&D activities were carried out on the adoption of Gas Electron Multiplier (GEM) as the gas amplification stage of the ALICE-TPC upgrade version. The requirement of low ion feedback has been established through these activities. Low ion feedback minimizes distortions due to space charge and maintains the necessary values of detector gain and energy resolution. In the present work, Garfield simulation framework has been used to study the related physical processes occurring within single, triple and quadruple GEM detectors. Ion backflow and electron transmission of quadruple GEMs, made up of foils with different hole pitch under different electromagnetic field configurations (the projected solutions for the ALICE TPC) have been studied. Finally a new triple GEM detector configuration with low ion backflow fraction and good electron transmission properties has been proposed as a simpler GEM-based alternative suitable for TPCs for future collider experiments.

Edge-localized-modes in tokamaksa)

NASA Astrophysics Data System (ADS)

Leonard, A. W.

2014-09-01

Edge-localized-modes (ELMs) are a ubiquitous feature of H-mode in tokamaks. When gradients in the H-mode transport barrier grow to exceed the MHD stability limit the ELM instability grows explosively, rapidly transporting energy and particles onto open field lines and material surfaces. Though ELMs provide additional particle and impurity transport through the H-mode transport barrier, enabling steady operation, the resulting heat flux transients to plasma facing surfaces project to large amplitude in future low collisionality burning plasma tokamaks. Measurements of the ELM heat flux deposition onto material surfaces in the divertor and main chamber indicate significant broadening compared to inter-ELM heat flux, with a timescale for energy deposition that is consistent with sonic ion flow and numerical simulation. Comprehensive ELM simulation is highlighting the important physics processes of ELM transport including parallel transport due to magnetic reconnection and turbulence resulting from collapse of the H-mode transport barrier. Encouraging prospects for ELM control and/or suppression in future tokamaks include intrinsic modes of ELM free operation, ELM triggering with frequent small pellet injection and the application of 3D magnetic fields.

KSC-04PD-0008

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. -- In the Space Life Sciences (SLS) Lab, Jan Bauer, with Dynamac Corp., weighs samples of onion tissue for processing in the elemental analyzer behind it. The equipment analyzes for carbon, hydrogen, nitrogen and sulfur. The 100,000 square-foot SLS houses labs for NASAs ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASAs Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASAs Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

KSC-04PD-0005

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. -- Lanfang Levine, with Dynamac Corp., helps install new equipment for gas chromatography and mass spectrometry in the Space Life Sciences Lab. The equipment will enable analysis of volatile compounds, such as from plants. The 100,000 square-foot facility houses labs for NASAs ongoing research efforts, microbiology/microbial ecology studies and analytical chemistry labs. Also calling the new lab home are facilities for space flight-experiment and flight-hardware development, new plant growth chambers, and an Orbiter Environment Simulator that will be used to conduct ground control experiments in simulated flight conditions for space flight experiments. The SLS Lab, formerly known as the Space Experiment Research and Processing Laboratory or SERPL, provides space for NASAs Life Sciences Services contractor Dynamac Corporation, Bionetics Corporation, and researchers from the University of Florida. NASAs Office of Biological and Physical Research will use the facility for processing life sciences experiments that will be conducted on the International Space Station. The SLS Lab is the magnet facility for the International Space Research Park at KSC being developed in partnership with Florida Space Authority.

Conference on Real-Time Computer Applications in Nuclear, Particle and Plasma Physics, 6th, Williamsburg, VA, May 15-19, 1989, Proceedings

NASA Technical Reports Server (NTRS)

Pordes, Ruth (Editor)

1989-01-01

Papers on real-time computer applications in nuclear, particle, and plasma physics are presented, covering topics such as expert systems tactics in testing FASTBUS segment interconnect modules, trigger control in a high energy physcis experiment, the FASTBUS read-out system for the Aleph time projection chamber, a multiprocessor data acquisition systems, DAQ software architecture for Aleph, a VME multiprocessor system for plasma control at the JT-60 upgrade, and a multiasking, multisinked, multiprocessor data acquisition front end. Other topics include real-time data reduction using a microVAX processor, a transputer based coprocessor for VEDAS, simulation of a macropipelined multi-CPU event processor for use in FASTBUS, a distributed VME control system for the LISA superconducting Linac, a distributed system for laboratory process automation, and a distributed system for laboratory process automation. Additional topics include a structure macro assembler for the event handler, a data acquisition and control system for Thomson scattering on ATF, remote procedure execution software for distributed systems, and a PC-based graphic display real-time particle beam uniformity.

Construction of a Lower Body Negative Pressure Chamber

ERIC Educational Resources Information Center

Esch, Ben T. A; Scott, Jessica M.; Warburton, Darren E. R.

2007-01-01

Lower body negative pressure (LBNP) is an established and important technique used to physiologically stress the human body, particularly the cardiovascular system. LBNP is most often used to simulate gravitational stress, but it has also been used to simulate hemorrhage, alter preload, and manipulate baroreceptors. During experimentation, the…