Air-void embedded GaN-based light-emitting diodes grown on laser drilling patterned sapphire substrates

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

Liu, Hao; Li, Yufeng; Wang, Shuai

Air-void structure was introduced in GaN-based blue light-emitting diodes (LED) with one-step growth on periodic laser drilling patterned sapphire substrate, which free of any photolithography or wet/dry etching process. The influence of filling factors (FF) of air-void on crystal quality and optical performance were investigate. Transmission electron microscopy images and micro-Raman spectroscopy indicated that the dislocation was bended and the partially compressed strain was released. When FF was 55.43%, compared with the LED structure grown on flat sapphire substrate, the incorporation of air-void was observed to reduce the compressed stress of ∼20% and the luminance intensity has improved by 128%.more » Together with the simulated reflection intensity enhancement by finite difference time-domain (FDTD) method, we attribute the enhanced optical performance to the combined contribution of strong back-side light reflection of air-void and better GaN epitaxial quality. This approach provides a simple replacement to the conventional air-void embedded LED process.« less

Freeze-thaw resistance of concrete with marginal air content

DOT National Transportation Integrated Search

2007-05-01

Freeze-thaw resistance is a key durability factor for concrete pavements. Recommendations for the air void system parameters are normally 6 1 percent total air and a spacing factor of : < 0.20 millimeter (mm) (0.008 inch). However, it was observed...

Freeze-thaw resistance of concrete with marginal air content : final report

DOT National Transportation Integrated Search

2006-12-01

Freeze-thaw resistance is a key durability factor for concrete pavements. Recommendations for the air : void system parameters are normally: 6 1 percent total air, and spacing factor less than 0.20 : millimeters. However, it was observed that some...

Concrete pavement quality control testing requirements needed for the super air meter : final report.

DOT National Transportation Integrated Search

2016-10-01

Concrete freeze-thaw durability is prominently linked to the air void system within the concrete. : Concrete pavements in Kansas undergo repetitive freeze-thaw cycles. Total air content measurements : currently used on fresh concrete do not provide a...

Concrete pavement quality control testing requirements needed for the super air meter : technical summary.

DOT National Transportation Integrated Search

2016-10-01

Concrete freeze-thaw durability is prominently linked to the air void system : within the concrete. Concrete pavements in Kansas undergo repetitive : freeze-thaw cycles. Total air content measurements currently used on fresh : concrete do not provide...

Direct observation of void evolution during cement hydration

DOE PAGES

Moradian, Masoud; Hu, Qinang; Aboustait, Mohammed; ...

2017-09-28

This study follows the hydration of both portland cement and tricalcium silicate pastes between 30 min and 16 h of hydration. In-situ fast X-ray Computed Tomography (fCT) was used to make direct observations of the air-filled void formation in w/s of 0.40 to 0.70 with a micron resolution. The results show that over the first hour of the acceleration period the volume of air-filled voids reaches a maximum value and then decreases during the acceleration period and stays constant. The void distribution changes from a few coarse voids to a large number of smaller and more uniformly distributed voids. Thismore » behavior is suggested to be controlled by changes in the ionic strength that cause exsolution of dissolved air from the pore solution.« less

Direct observation of void evolution during cement hydration

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

Moradian, Masoud; Hu, Qinang; Aboustait, Mohammed

This study follows the hydration of both portland cement and tricalcium silicate pastes between 30 min and 16 h of hydration. In-situ fast X-ray Computed Tomography (fCT) was used to make direct observations of the air-filled void formation in w/s of 0.40 to 0.70 with a micron resolution. The results show that over the first hour of the acceleration period the volume of air-filled voids reaches a maximum value and then decreases during the acceleration period and stays constant. The void distribution changes from a few coarse voids to a large number of smaller and more uniformly distributed voids. Thismore » behavior is suggested to be controlled by changes in the ionic strength that cause exsolution of dissolved air from the pore solution.« less

An Interlab Evaluation of the Variability in the ASTM C 457 Linear Traverse Method.

DOT National Transportation Integrated Search

2005-12-01

The vital role of air entrainment in preventing freeze-thaw damage in concrete is well known and well documented [Powers 1949]. Through the action of an air entraining agent (AEA) added to fresh concrete, an air void system comprised of various micro...

In-place voids monitoring of hot mix asphalt pavements : follow-up.

DOT National Transportation Integrated Search

2014-01-01

In order to validate the policy of allowing the adjustment of the asphalt cement to reduce the laboratory : air voids up to one percent, cores were taken over a period of four years on 19 paving projects and : tested for air voids. After being compac...

Air void characteristics of hardened concrete, 1945-1980.

DOT National Transportation Integrated Search

1985-01-01

Observations at the Research Council, coupled with the national interest in possible changes in the air void characteristics of air-entrained concretes because of the wide use of admixtures and changes in cement properties, raised a question as to wh...

Concrete pavement mixture design and analysis (MDA) : assessment of air void system requirements for durable concrete.

DOT National Transportation Integrated Search

2012-06-01

Concrete will suffer frost damage when saturated and subjected to freezing temperatures. Frost-durable concrete can be produced if a : specialized surfactant, also known as an air-entraining admixture (AEA), is added during mixing to stabilize micros...

Comparison of water and air charged transducer catheter pressures in the evaluation of cystometrogram and voiding pressure studies.

PubMed

McKinney, Timothy B; Babin, Elizabeth A; Ciolfi, Veronica; McKinney, Cynthia R; Shah, Nima

2018-04-01

Air-charged (AC) and water-perfused (WP) catheters have been evaluated for differences in measuring pressures for voiding dysfunction. Typically, a two-catheter system was used. We believe that simultaneous pressure measurements with AC and WP in a single catheter will provide analogous pressures for coughs, Valsalvas, and maximum pressures in voiding pressure studies (VPS). This IRB approved prospective study included 50 women over age 21. AC dual TDOC catheters were utilized. The water-filling channel served as the bladder filler and the water pressure readings. Patients were evaluated with empty bladders and at volumes of 50-100 mL, 200 mL, and maximum capacity with cough and Valsalva maneuvers. Comparative analysis was performed on maximum stress peak pressures. At maximum bladder capacity, VPS was done and maximum voiding pressure was recorded. Comparing coughs and Valsalva maneuvers pressures, there was significant increase in variability between AC and WP measurements with less than 50 mL volume (P < 0.001). Significant correlations were observed between AC and WP measurements for coughs and Valsalvas with bladder volume over 50 mL. Visual impression showed virtually identical tracings. Cough measurements had an average difference of 0.25 cmH 2 O (±8.81) and Valsalva measurements had an average difference of 3.15 cmH 2 O (±4.72). Thirty-eight women had usable maximum voiding pressure measurements and had a strong correlation. Cystometrogram and maximum voiding pressure measurements done with either water or air charged catheters will yield similarly accurate results and are comparable. Results suggest more variability at low bladder volumes <50 mL. © 2018 Wiley Periodicals, Inc.

Case Study of the Application of the Weapon System Warranty on the C-130 Program.

DTIC Science & Technology

1986-09-01

31 Appendix A: Air Force Contract Law Center Suggested Systems Level Warranty Clauses . . . . . 33 Appendix B: Original C-130 Warranty ClauseCs...avoidance and still protect the government’s interest can work. vii This study recommends that the Department of Defense use the Air Force Contract Law Center’s...would have had the potential For allowing Lockheed to void a system level warranty had one been in effect such as the Air Force Contract Law Center’s

Air void clustering.

DOT National Transportation Integrated Search

2015-06-01

Air void clustering around coarse aggregate in concrete has been identified as a potential source of : low strengths in concrete mixes by several Departments of Transportation around the country. Research was : carried out to (1) develop a quantitati...

Air void clustering : [technical summary].

DOT National Transportation Integrated Search

2015-06-01

Air void clustering around coarse aggregate in concrete has been : identified as a potential source of low strengths in concrete mixes by : several Departments of Transportation around the country. Research : was carried out to (1) develop a quantita...

International Space Station Urine Monitoring System Functional Integration and Science Testing

NASA Technical Reports Server (NTRS)

Rodriguez, Branelle R.; Broyan, James Lee, Jr.

2008-01-01

Exposure to microgravity during human spaceflight is required to be defined and understood as the human exploration of space requires longer duration missions. It is known that long term exposure to microgravity causes bone loss. Urine voids are capable of measuring the calcium and other metabolic byproducts in a constituent s urine. The International Space Station (ISS) Urine Monitoring System (UMS) is an automated urine collection device designed to collect urine, separate the urine and air, measure the void volume, and allow for syringe sampling. Accurate measuring and minimal cross contamination is essential to determine bone loss and the effectiveness of countermeasures. The ISS UMS provides minimal cross contamination (<0.7 ml urine) and has volume accuracy of +/-2% between 100 to 1000 ml urine voids.

International Space Station Urine Monitoring System Functional Integration and Science Testing

NASA Technical Reports Server (NTRS)

Cibuzar, Branelle R.; Broyan, James Lee, Jr.

2009-01-01

Exposure to microgravity during human spaceflight is required to be defined and understood as the human exploration of space requires longer duration missions. It is known that long term exposure to microgravity causes bone loss. Urine voids are capable of measuring the calcium and other metabolic byproducts in a constituent s urine. The International Space Station (ISS) Urine Monitoring System (UMS) is an automated urine collection device designed to collect urine, separate the urine and air, measure the void volume, and allow for syringe sampling. Accurate measuring and minimal cross contamination is essential to determine bone loss and the effectiveness of countermeasures. The ISS UMS provides minimal cross contamination (<0.7 ml urine) and has volume accuracy of +/-2% between 100 to 1000 ml urine voids.

Density of Asphalt Concrete - How Much is Needed?

DOT National Transportation Integrated Search

1990-01-01

Density is one of the most important parameters in construction of asphalt : mixtures. A mixture that is properly designed and compacted will contain enough : air voids to prevent rutting due to plastic flow but low enough air voids to : prevent perm...

Evaluation of open-graded friction course mixture : technical assistance report.

DOT National Transportation Integrated Search

2004-10-01

Open-graded friction course (OGFC) is a porous, gap-graded, predominantly single size aggregate bituminous mixture that contains a high percentage of air voids. The high air void content and the open structure of this mix promote the effective draina...

Comparison of spacing factors as measured by the air-void analyzer and ASTM C457.

DOT National Transportation Integrated Search

2015-12-01

The Kansas Department of Transportation (KDOT) began using the Air-Void Analyzer (AVA) in : 2001 and first incorporated an AVA spacing factor requirement into paving specifications beginning in late : 2002. In 2005, a statewide investigation to evalu...

Mass flow rate measurements in gas-liquid flows by means of a venturi or orifice plate coupled to a void fraction sensor

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

Oliveira, Jorge Luiz Goes; Passos, Julio Cesar; Verschaeren, Ruud

Two-phase flow measurements were carried out using a resistive void fraction meter coupled to a venturi or orifice plate. The measurement system used to estimate the liquid and gas mass flow rates was evaluated using an air-water experimental facility. Experiments included upward vertical and horizontal flow, annular, bubbly, churn and slug patterns, void fraction ranging from 2% to 85%, water flow rate up to 4000 kg/h, air flow rate up to 50 kg/h, and quality up to almost 10%. The fractional root mean square (RMS) deviation of the two-phase mass flow rate in upward vertical flow through a venturi platemore » is 6.8% using the correlation of Chisholm (D. Chisholm, Pressure gradients during the flow of incompressible two-phase mixtures through pipes, venturis and orifice plates, British Chemical Engineering 12 (9) (1967) 454-457). For the orifice plate, the RMS deviation of the vertical flow is 5.5% using the correlation of Zhang et al. (H.J. Zhang, W.T. Yue, Z.Y. Huang, Investigation of oil-air two-phase mass flow rate measurement using venturi and void fraction sensor, Journal of Zhejiang University Science 6A (6) (2005) 601-606). The results show that the flow direction has no significant influence on the meters in relation to the pressure drop in the experimental operation range. Quality and slip ratio analyses were also performed. The results show a mean slip ratio lower than 1.1, when bubbly and slug flow patterns are encountered for mean void fractions lower than 70%. (author)« less

Distribution of voids in field concrete.

DOT National Transportation Integrated Search

1978-01-01

This study was intended to evaluate the air void characteristics of concrete in an attempt to identify, quantitatively or semi-quantitatively, different types of voids and to predict their influence on strength and durability. At the outset, it was a...

Developpement d'un systeme pour la mesure du taux de vide dans un ecoulement diphasique par une methode utilisant des micro-ondes

NASA Astrophysics Data System (ADS)

Pochet, Steven

The measurement of the void fraction is an important parameter in many industrial fields. Whether it is to prevent the phenomenon of critical heat flux in heat tube of thermal power plants, the explosion of gas pockets in oil rigs’ pipes or to detect bubbles in medical catheters, the knowledge of the void fraction can be a key parameter in many diverse applications. Several invasive and non-invasive measurements techniques have been developed these last decades and are based on the difference between the physical properties of liquid and gas. Some of these techniques are not always possible to implement due to restrictions in the geometry of tubes or regulatory standards limiting their use. Throughout this work we propose a new non-invasive void fraction measurement technique based on the reflection of electromagnetic waves on the water-air interface of the mixture. The reflection of electromagnetic wave is induced by a change in the impedance of the propagation medium. The impedance is function of the dielectric properties of the medium. The characteristics of air and water being distinct, it is possible to calculate the complex reflection coefficient at the interface of a double phase mixture. To this end, mathematical modeling of the response of an electromagnetic wave in a tube containing a two phase mixture was made using the model of transmission lines, applicable to microwave frequencies we use. The effects of the amount of air in water and the position of the bubbles in the section of the tube were simulated. It was shown that the phase of the reflected wave was sensitive to the position of bubbles in the tube’s section and that the magnitude of the reflection coefficient varied with the mixture’s void fraction. Subsequently, we designed and built a six-ports reflectometer operating at 2.45 GHz. This system allows the processing and calculation of the reflected wave from the incident wave. A six-ports network, a patch antenna, a wave generator and an amplifier were simulated using HFSS and ADS software. They were then built using the technology of micro-strips on dielectric laminates and the entire system was then calibrated at 6 different frequencies near 2.45 GHz. To this end, we used 4 and 5 loads calibration algorithms that gave us calibrated results with less than 2 % errors. Afterwards, the system was implemented: the antenna was placed tangent to the wall of a vertical tube and connected to the six-ports which was connected to a computer recording and displaying the results in real time. A valve positioned under the tube allows air into the tube and to vary the flow rate. The results showed that the system was sensitive to changes in void fraction from 1% and followed the predictions of the simulated model to a void fraction of about 10%. Possibly du to a change in the structure of the flow for a void fraction of 10%, the signal no longer varies monotonically with respect to the increasing void fraction possibly because of a change in the flow’s configuration. It was shown that the Rayleigh scattering phenomena of air bubbles was involved in the reflection coefficient response. Pictures of the stream at various void fraction state were taken and confirmed a change in the flow’s configuration. By placing a Plexiglas rod to simulate a flow geometry located in the section of the tube, it was noted that the change in phase of the reflected wave was the same as the model when the rod was placed in an empty tube (very few attenuation loss environment). Hence, it is possible to determine the distance of an object in a section of tube from the measurement of the reflected wave’s phase. When the rod is in a very absorbent medium such as water, it is possible to detect a moving rod when it is sufficiently close to the antenna (less than two wavelengths) thanks again to the phase variation. However, detection is still much more difficult due to the absorption of water and can not function effectively for tubes with high diameters compared with the electromagnetic wavelength used.

Neutron imaging of diabatic two-phase flows relevant to air conditioning

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

Geoghegan, Patrick J; Sharma, Vishaldeep

The design of the evaporator of an air conditioning system relies heavily on heat transfer coefficients and pressure drop correlations that predominantly involve an estimate of the changing void fraction and the underlying two-phase flow regime. These correlations dictate whether the resulting heat exchanger is oversized or not and the amount of refrigerant charge necessary to operate. The latter is particularly important when dealing with flammable or high GWP refrigerants. Traditional techniques to measure the void fraction and visualize the flow are either invasive to the flow or occur downstream of the evaporator, where some of the flow distribution willmore » have changed. Neutron imaging has the potential to visualize two-phase flow in-situ where an aluminium heat exchanger structure becomes essentially transparent to the penetrating neutrons. The subatomic particles are attenuated by the passing refrigerant flow. The resulting image may be directly related to the void fraction and the overall picture provides a clear insight into the flow regime present. This work presents neutron images of the refrigerant Isopentane as it passes through the flow channels of an aluminium evaporator at flowrates relevant to air conditioning. The flow in a 4mm square macro channel is compared to that in a 250 m by 750 m rectangular microchannel in terms of void fraction and regime. All neutron imaging experiments were conducted at the High Flux Isotope Reactor, an Oak Ridge National Laboratory facility« less

Use of electrical resistivity to detect underground mine voids in Ohio

USGS Publications Warehouse

Sheets, Rodney A.

2002-01-01

Electrical resistivity surveys were completed at two sites along State Route 32 in Jackson and Vinton Counties, Ohio. The surveys were done to determine whether the electrical resistivity method could identify areas where coal was mined, leaving air- or water-filled voids. These voids can be local sources of potable water or acid mine drainage. They could also result in potentially dangerous collapse of roads or buildings that overlie the voids. The resistivity response of air- or water-filled voids compared to the surrounding bedrock may allow electrical resistivity surveys to delineate areas underlain by such voids. Surface deformation along State Route 32 in Jackson County led to a site investigation, which included electrical resistivity surveys. Several highly resistive areas were identified using axial dipole-dipole and Wenner resistivity surveys. Subsequent drilling and excavation led to the discovery of several air-filled abandoned underground mine tunnels. A site along State Route 32 in Vinton County, Ohio, was drilled as part of a mining permit application process. A mine void under the highway was instrumented with a pressure transducer to monitor water levels. During a period of high water level, electrical resistivity surveys were completed. The electrical response was dominated by a thin, low-resistivity layer of iron ore above where the coal was mined out. Nearby overhead powerlines also affected the results.

Hot mix asphalt research investigation for Connecticut : part C - permeability/porosity testing of HMA mix designs.

DOT National Transportation Integrated Search

2014-07-01

The presence of water in asphalt pavements is detrimental to the life of the pavement. Most construction specifications require the pavement to be compacted to a specific air void content. As an asphalt pavement's air void contents increase, the perm...

Feasibility study of in-situ characterization of size distribution of air voids in concrete pavements.

DOT National Transportation Integrated Search

2013-06-01

This report concerns a feasibility study on the use of a non-destructive and non-invasive method to determine the size distribution of air voids in fresh concrete, which will be used for laying concrete pavement. A preliminary review of different tec...

Hot mix asphalt research investigation for Connecticut, part D : evaluate the feasibility of using permeability for in-place density dispute resolution on bridge decks.

DOT National Transportation Integrated Search

2014-07-01

The presence of water in asphalt pavements is detrimental to the life of the pavement. Most : construction specifications require the pavement to be compacted to a specific air void content. As an asphalt : pavements air void content increases, th...

Dynamic void behavior in polymerizing polymethyl methacrylate cement.

PubMed

Muller, Scott D; McCaskie, Andrew W

2006-02-01

Cement mantle voids remain controversial with respect to survival of total hip arthroplasty. Void evolution is poorly understood, and attempts at void manipulation can only be empirical. We induced voids in a cement model simulating the constraints of the proximal femur. Intravoid pressure and temperature were recorded throughout polymerization, and the initial and final void volumes were measured. Temperature-dependent peak intravoid pressures and void volume increases were observed. After solidification, subatmospheric intravoid pressures were observed. The magnitude of these observations could not be explained by the ideal gas law. Partial pressures of the void gas at peak pressures demonstrated a dominant effect of gaseous monomer, thereby suggesting that void growth is a pressure-driven phenomenon resulting from temperature-dependent evaporation of monomer into existing trapped air voids.

Cellular polypropylene polymer foam as air-coupled ultrasonic transducer materials.

PubMed

Satyanarayan, L; Haberman, Michael R; Berthelot, Yves H

2010-10-01

Cellular polypropylene polymer foams, also known as ferroelectrets, are compelling candidates for air-coupled ultrasonic transducer materials because of their excellent acoustic impedance match to air and because they have a piezoelectric d(33) coefficient superior to that of PVDF. This study investigates the performance of ferroelectret transducers in the generation and reception of ultrasonic waves in air. As previous studies have noted, the piezoelectric coupling coefficients of these foams depend on the number, size, and distribution of charged voids in the microstructure. The present work studies the influence of these parameters both theoretically and experimentally. First, a three-dimensional model is employed to explain the variation of piezoelectric coupling coefficients, elastic stiffness, and dielectric permittivity as a function of void fraction based on void-scale physics and void geometry. Laser Doppler vibrometer (LDV) measurements of the effective d(33) coefficient of a specially fabricated prototype transmitting transducer are then shown which clearly indicate that the charged voids in the ferroelectret material are randomly distributed in the plane of the foam. The frequency-dependent dynamic d(33) coefficient is then reported from 50 to 500 kHz for different excitation voltages and shown to be largely insensitive to drive voltage. Lastly, two ferroelectret transducers are operated in transmit-receive mode and the received signal is shown to accurately represent the corresponding signal generated by the transmitting transducer as measured using LDV.

Experimental study on the void fraction of air-water two-phase flow in a horizontal circular minichannel

NASA Astrophysics Data System (ADS)

Sudarja, Indarto, Deendarlianto, Haq, Aqli

2016-06-01

Void fraction is an important parameter in two-phase flow. In the present work, the adiabatic two-phase air-water flow void fraction in a horizontal minichannel has been studied experimentally. A transparent circular channel with 1.6 mm inner diameter was employed as the test section. Superficial gas and liquid velocities were varied in the range of 1.25 - 66.3 m/s and 0.033 - 4.935 m/s, respectively. Void fraction data were obtained by analyzing the flow images being captured by using a high-speed camera. Here, the homogeneous (β) and the measured void fractions (ɛ), respectively, were compared to the existing correlations. It was found that: (1) for the bubbly and slug flows, the void fractions increases with the increase of JG, (2) for churn, slug-annular, and annular flow patterns, there is no specific correlation between JG and void fraction was observed due to effect of the slip between gas and liquid, and (3) whilst for bubbly and slug flows the void fractions are close to homogeneous line, for churn, annular, and slug-annular flows are far below the homogeneous line. It indicates that the slip ratios for the second group of flow patterns are higher than unity.

40 CFR 86.1114-87 - Suspension and voiding of certificates of conformity.

Code of Federal Regulations, 2010 CFR

2010-07-01

...-Duty Vehicles, Including Light-Duty Trucks § 86.1114-87 Suspension and voiding of certificates of... 40 Protection of Environment 19 2010-07-01 2010-07-01 false Suspension and voiding of certificates... AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND...

Air-Induced Drag Reduction at High Reynolds Numbers: Velocity and Void Fraction Profiles

NASA Astrophysics Data System (ADS)

Elbing, Brian; Mäkiharju, Simo; Wiggins, Andrew; Dowling, David; Perlin, Marc; Ceccio, Steven

2010-11-01

The injection of air into a turbulent boundary layer forming over a flat plate can reduce the skin friction. With sufficient volumetric fluxes an air layer can separate the solid surface from the flowing liquid, which can produce drag reduction in excess of 80%. Several large scale experiments have been conducted at the US Navy's Large Cavitation Channel on a 12.9 m long flat plate model investigating bubble drag reduction (BDR), air layer drag reduction (ALDR) and the transition between BDR and ALDR. The most recent experiment acquired phase velocities and void fraction profiles at three downstream locations (3.6, 5.9 and 10.6 m downstream from the model leading edge) for a single flow speed (˜6.4 m/s). The profiles were acquired with a combination of electrode point probes, time-of-flight sensors, Pitot tubes and an LDV system. Additional diagnostics included skin-friction sensors and flow-field image visualization. During this experiment the inlet flow was perturbed with vortex generators immediately upstream of the injection location to assess the robustness of the air layer. From these, and prior measurements, computational models can be refined to help assess the viability of ALDR for full-scale ship applications.

Advanced Signal Processing Techniques Applied to Terahertz Inspections on Aerospace Foams

NASA Technical Reports Server (NTRS)

Trinh, Long Buu

2009-01-01

The space shuttle's external fuel tank is thermally insulated by the closed cell foams. However, natural voids composed of air and trapped gas are found as by-products when the foams are cured. Detection of foam voids and foam de-bonding is a formidable task owing to the small index of refraction contrast between foam and air (1.04:1). In the presence of a denser binding matrix agent that bonds two different foam materials, time-differentiation of filtered terahertz signals can be employed to magnify information prior to the main substrate reflections. In the absence of a matrix binder, de-convolution of the filtered time differential terahertz signals is performed to reduce the masking effects of antenna ringing. The goal is simply to increase probability of void detection through image enhancement and to determine the depth of the void.

Actions to Void Certificates for Vehicle and Engines

EPA Pesticide Factsheets

n cases where EPA has determines that manufacturers have provided inaccurate, incomplete or falsified certification information or failed to keep required records, the Clean Air Act gives the EPA the authority to void certificates.

Improvement effect on the depth-dose distribution by CSF drainage and air infusion of a tumour-removed cavity in boron neutron capture therapy for malignant brain tumours

NASA Astrophysics Data System (ADS)

Sakurai, Yoshinori; Ono, Koji; Miyatake, Shin-ichi; Maruhashi, Akira

2006-03-01

Boron neutron capture therapy (BNCT) without craniotomy for malignant brain tumours was started using an epi-thermal neutron beam at the Kyoto University Reactor in June 2002. We have tried some techniques to overcome the treatable-depth limit in BNCT. One of the effective techniques is void formation utilizing a tumour-removed cavity. The tumorous part is removed by craniotomy about 1 week before a BNCT treatment in our protocol. Just before the BNCT irradiation, the cerebro-spinal fluid (CSF) in the tumour-removed cavity is drained out, air is infused to the cavity and then the void is made. This void improves the neutron penetration, and the thermal neutron flux at depth increases. The phantom experiments and survey simulations modelling the CSF drainage and air infusion of the tumour-removed cavity were performed for the size and shape of the void. The advantage of the CSF drainage and air infusion is confirmed for the improvement in the depth-dose distribution. From the parametric surveys, it was confirmed that the cavity volume had good correlation with the improvement effect, and the larger effect was expected as the cavity volume was larger.

Improvement effect on the depth-dose distribution by CSF drainage and air infusion of a tumour-removed cavity in boron neutron capture therapy for malignant brain tumours.

PubMed

Sakurai, Yoshinori; Ono, Koji; Miyatake, Shin-Ichi; Maruhashi, Akira

2006-03-07

Boron neutron capture therapy (BNCT) without craniotomy for malignant brain tumours was started using an epi-thermal neutron beam at the Kyoto University Reactor in June 2002. We have tried some techniques to overcome the treatable-depth limit in BNCT. One of the effective techniques is void formation utilizing a tumour-removed cavity. The tumorous part is removed by craniotomy about 1 week before a BNCT treatment in our protocol. Just before the BNCT irradiation, the cerebro-spinal fluid (CSF) in the tumour-removed cavity is drained out, air is infused to the cavity and then the void is made. This void improves the neutron penetration, and the thermal neutron flux at depth increases. The phantom experiments and survey simulations modelling the CSF drainage and air infusion of the tumour-removed cavity were performed for the size and shape of the void. The advantage of the CSF drainage and air infusion is confirmed for the improvement in the depth-dose distribution. From the parametric surveys, it was confirmed that the cavity volume had good correlation with the improvement effect, and the larger effect was expected as the cavity volume was larger.

Thermo-optic characteristics of hybrid polymer/silica microstructured optical fiber: An analytical approach

NASA Astrophysics Data System (ADS)

Sharma, Dinesh Kumar; Sharma, Anurag; Tripathi, Saurabh Mani

2018-04-01

Microstructured optical fibers (MOFs) allow a variety of advanced materials to be infiltrated in their air-voids for obtaining the increased fiber functionality, and offering a new versatile platform for developing the compact sensors devices. We aim to investigate the thermal characteristics of high-index core triangular hybrid polymer/silica MOFs with circular air-voids infused with polymer by using the analytical field model [1]. We demonstrate that infiltration of air-voids with polymer, e.g., polydimethylsiloxane (PDMS) can facilitate to tune the fundamental modal properties of MOF such as effective index of the mode, near and the far-field profiles, effective mode area and the numerical aperture over the temperature ranging from 0 °C to 100 °C, for different values of relative air-void ratios. The evolution of the mode shape for a given temperature has been investigated in transition from near-field to far-field regime. We have studied the thermal dependence of splice losses between hybrid MOF and the standard step-index single-mode optical fiber in combination with Fresnel losses. For enhancing the evanescent field interactions, we have evaluated fraction of power associated with fundamental mode of hybrid MOF. We have compared the accuracy of our results with those based on full-vector finite-difference (FD) method, as available in the literature.

Impact of hydrated cement paste quality and entrained air-void system on the durability of concrete : part B.

DOT National Transportation Integrated Search

2011-06-30

This publication is a statistical review of reported motor vehicle crashes in Maine during the five-year study period 2005 - 2009. The statistics are compiled from crash reports submitted to the Department of Transportation by the Traffic Division, D...

Resistance to Internal Damage and Scaling of Concrete Air Entrained By Microspheres

NASA Astrophysics Data System (ADS)

Molendowska, Agnieszka; Wawrzenczyk, Jerzy

2017-10-01

This paper report the test results of high strength concrete produced with slag cement and air entrained with polymer microspheres in three diameters. The study focused on determining the effects of the microsphere size and quantity on the air void structure and resistance to internal cracking and scaling of the concrete. The resistance to internal cracking was determined in compliance with the requirements of the modified ASTM C666 A method on beam specimens. The scaling resistance in a 3% NaCl solution was determined using the slab test in accordance with PKN-CEN/TS 12390-9:2007. The air void structure parameters were determined to PN-EN 480-11:1998. The study results indicate that the use of microspheres is an effective air entrainment method providing very good air void structure parameters. The results show high freeze-thaw durability of polymer microsphere-based concrete in exposure class XF3. The scaling resistance test confirms that it is substantially more difficult to protect concrete against scaling in the presence of the 3% NaCl solution (exposure class XF4). Concrete scaling is a complex phenomenon controlled by a number of independent factors.

Thermal inertia mapping of below ground objects and voids

NASA Astrophysics Data System (ADS)

Del Grande, Nancy K.; Ascough, Brian M.; Rumpf, Richard L.

2013-05-01

Thermal inertia (effusivity) contrast marks the borders of naturally heated below ground object and void sites. The Dual Infrared Effusivity Computed Tomography (DIRECT) method, patent pending, detects and locates the presence of enhanced heat flows from below ground object and void sites at a given area. DIRECT maps view contrasting surface temperature differences between sites with normal soil and sites with soil disturbed by subsurface, hollow or semi-empty object voids (or air gaps) at varying depths. DIRECT utilizes an empirical database created to optimize the scheduling of daily airborne thermal surveys to view and characterize unseen object and void types, depths and volumes in "blind" areas.

Mechanism of Void Prediction in Flip Chip Packages with Molded Underfill

NASA Astrophysics Data System (ADS)

Wu, Kuo-Tsai; Hwang, Sheng-Jye; Lee, Huei-Huang

2017-08-01

Voids have always been present using the molded underfill (MUF) package process, which is a problem that needs further investigation. In this study, the process was studied using the Moldex3D numerical analysis software. The effects of gas (air vent effect) on the overall melt front were also considered. In this isothermal process containing two fluids, the gas and melt colloid interact in the mold cavity. Simulation enabled an appropriate understanding of the actual situation to be gained, and, through analysis, the void region and exact location of voids were predicted. First, the global flow end area was observed to predict the void movement trend, and then the local flow ends were observed to predict the location and size of voids. In the MUF 518 case study, simulations predicted the void region as well as the location and size of the voids. The void phenomenon in a flip chip ball grid array underfill is discussed as part of the study.

Two reference time scales for studying the dynamic cavitation of liquid films

NASA Technical Reports Server (NTRS)

Sun, D. C.; Brewe, David E.

1991-01-01

Two formulas, one for characteristic time of filling a void with a vapor of the surrounding liquid, and one of filling the void by diffusion of the dissolved gas in the liquid, are derived. Based on this analysis, it is seen that in an oil film bearing operating under dynamic loads, the content of cavitation region should be oil vapor rather than the air liberated from solution, if the oil is free of entrained air.

Construction, testing and performance report : state study no. 137 : resin modified pavement demonstration project.

DOT National Transportation Integrated Search

2007-09-01

Resin Modified Pavement (RMP) is a composite paving material consisting of a thin layer (2 inches) : of open graded hot mix asphalt (HMA) whose internal air voids (approximately 30% voids) are : filled with a latex rubber-modified portland cement gro...

A compact x-ray system for two-phase flow measurement

NASA Astrophysics Data System (ADS)

Song, Kyle; Liu, Yang

2018-02-01

In this paper, a compact x-ray densitometry system consisting of a 50 kV, 1 mA x-ray tube and several linear detector arrays is developed for two-phase flow measurement. The system is capable of measuring void fraction and velocity distributions with a spatial resolution of 0.4 mm per pixel and a frequency of 1000 Hz. A novel measurement model has been established for the system which takes account of the energy spectrum of x-ray photons and the beam hardening effect. An improved measurement accuracy has been achieved with this model compared with the conventional log model that has been widely used in the literature. Using this system, void fraction and velocity distributions are measured for a bubbly and a slug flow in a 25.4 mm I.D. air-water two-phase flow test loop. The measured superficial gas velocities show an error within  ±4% when compared with the gas flowmeter for both conditions.

Comparison of air void content measurements in fresh versus hardened concretes.

DOT National Transportation Integrated Search

1990-01-01

This study compares the air content of freshly mixed and hardened concretes. At the fresh stage, pressure meters (Types A and B) and a volumetric meter were used to determine the air content. At the hardened stage, the air content was calculated usin...

Experimental Detection and Characterization of Void using Time-Domain Reflection Wave

NASA Astrophysics Data System (ADS)

Zahari, M. N. H.; Madun, A.; Dahlan, S. H.; Joret, A.; Zainal Abidin, M. H.; Mohammad, A. H.; Omar, A. H.

2018-04-01

Recent technologies in engineering views have brought the significant improvement in terms of performance and precision. One of those improvements is in geophysics studies for underground detection. Reflection method has been demonstrated to able to detect and locate subsurface anomalies in previous studies, including voids. Conventional method merely involves field testing only for limited areas. This may lead to undiscovered of the void position. Problems arose when the voids were not recognised in early stage and thus, causing hazards, costs increment, and can lead to serious accidents and structural damages. Therefore, to achieve better certainty of the site investigation, a dynamic approach is needed to be implemented. To estimate and characterize the anomalies signal in a better way, an attempt has been made to model air-filled void as experimental testing at site. Robust detection and characterization of voids through inexpensive cost using reflection method are proposed to improve the detectability and characterization of the void. The result shows 2-Dimensional and 3-Dimensional analyses of void based on reflection data with P-waves velocity at 454.54 m/s.

Air void analyzer for plastic concrete.

DOT National Transportation Integrated Search

2008-10-01

The two main test methods that measure the air content in plastic concrete are the pressure method and the volumetric : or roll-a-meter method. Although these methods report the total air in the concrete, they do not distinguish between : entrained a...

Method and apparatus for igniting an in situ oil shale retort

DOEpatents

Burton, Robert S.; Rundberg, Sten I.; Vaughn, James V.; Williams, Thomas P.; Benson, Gregory C.

1981-01-01

A technique is provided for igniting an in situ oil shale retort having an open void space over the top of a fragmented mass of particles in the retort. A conduit is extended into the void space through a hole in overlying unfragmented formation and has an open end above the top surface of the fragmented mass. A primary air pipe having an open end above the open end of the conduit and a liquid atomizing fuel nozzle in the primary air pipe above the open end of the primary air pipe are centered in the conduit. Fuel is introduced through the nozzle, primary air through the pipe, and secondary air is introduced through the conduit for vortical flow past the open end of the primary air pipe. The resultant fuel and air mixture is ignited for combustion within the conduit and the resultant heated ignition gas impinges on the fragmented mass for heating oil shale to an ignition temperature.

Use of an automatic resistivity system for detecting abandoned mine workings

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

Peters, W.R.; Burdick, R.G.

1983-01-01

A high-resolution earth resistivity system has been designed and constructed for use as a means of detecting abandoned coal mine workings. The automatic pole-dipole earth resistivity technique has already been applied to the detection of subsurface voids for military applications. The hardware and software of the system are described, together with applications for surveying and mapping abandoned coal mine workings. Field tests are presented to illustrate the detection of both air-filled and water-filled mine workings.

Void formation in INCONEL MA-754 by high temperature oxidation

NASA Astrophysics Data System (ADS)

Rosenstein, Alan H.; Tien, John K.; Nix, William D.

1986-01-01

Subsurface void formation in oxide dispersion strengthened MA-754 caused by high temperature oxidation was investigated at temperatures of 1100, 1150, and 1200 °C for times of 1, 10, 50, and 100 hours. Material exposed at 1200 °C was examined using microprobe, SEM, and optical microscopy techniques. After exposure in air at 1200 °C for 100 hours, chromium depletion by as much as 10 wt pct was observed near the surface, and voids of various sizes up to 15 µm in diameter were found to depths of 300 µm. The fraction of voids increases with exposure time and, with the exception of anomalous values near the surface, decreases with depth. The maximum area fraction of voids observed was approximately 8 pct. Correlation of the void area fraction profile with the measured chromium depletion through a diffusion analysis shows that void formation is due to vacancy injection. Similar void formation in Ni-Cr alloys without oxide dispersions suggests that void formation is not dependent upon the presence of oxide dispersions. The diffusion coefficient for chromium in MA-754 at 1200 °C was computed from microprobe data to be 4 × 10-10 cm2 per second.

Civil Engineering Applications of Ground Penetrating Radar in Finland

NASA Astrophysics Data System (ADS)

Pellinen, Terhi; Huuskonen-Snicker, Eeva; Olkkonen, Martta-Kaisa; Eskelinen, Pekka

2014-05-01

Ground penetrating radar (GPR) has been used in Finland since 1980's for civil engineering applications. First applications in this field were road surveys and dam inspections. Common GPR applications in road surveys include the thickness evaluation of the pavement, subgrade soil evaluation and evaluation of the soil moisture and frost susceptibility. Since the 1990's, GPR has been used in combination with other non-destructive testing (NDT) methods in road surveys. Recently, more GPR applications have been adopted, such as evaluating bridges, tunnels, railways and concrete elements. Nowadays, compared with other countries GPR is relatively widely used in Finland for road surveys. Quite many companies, universities and research centers in Finland have their own GPR equipment and are involved in the teaching and research of the GPR method. However, further research and promotion of the GPR techniques are still needed since GPR could be used more routinely. GPR has been used to evaluate the air void content of asphalt pavements for years. Air void content is an important quality measure of pavement condition for both the new and old asphalt pavements. The first Finnish guideline was released in 1999 for the method. Air void content is obtained from the GPR data by measuring the dielectric value as continuous record. To obtain air void content data, few pavement cores must be taken for calibration. Accuracy of the method is however questioned because there are other factors that affect the dielectric value of the asphalt layer, in addition to the air void content. Therefore, a research project is currently carried out at Aalto University in Finland. The overall objective is to investigate if the existing GPR technique used in Finland is accurate enough to be used as QC/QA tool in assessing the compaction of asphalt pavements. The project is funded by the Finnish Transport Agency. Further research interests at Aalto University include developing new microwave asphalt radar for the thickness evaluation of thin asphalt layers. This work benefited from networking activities carried out within the EU funded COST Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar".

Bubbling behavior of a fluidized bed of fine particles caused by vibration-induced air inflow.

PubMed

Matsusaka, Shuji; Kobayakawa, Murino; Mizutani, Megumi; Imran, Mohd; Yasuda, Masatoshi

2013-01-01

We demonstrate that a vibration-induced air inflow can cause vigorous bubbling in a bed of fine particles and report the mechanism by which this phenomenon occurs. When convective flow occurs in a powder bed as a result of vibrations, the upper powder layer with a high void ratio moves downward and is compressed. This process forces the air in the powder layer out, which leads to the formation of bubbles that rise and eventually burst at the top surface of the powder bed. A negative pressure is created below the rising bubbles. A narrow opening at the bottom allows the outside air to flow into the powder bed, which produces a vigorously bubbling fluidized bed that does not require the use of an external air supply system.

Modeling quiescent phase transport of air bubbles induced by breaking waves

NASA Astrophysics Data System (ADS)

Shi, Fengyan; Kirby, James T.; Ma, Gangfeng

Simultaneous modeling of both the acoustic phase and quiescent phase of breaking wave-induced air bubbles involves a large range of length scales from microns to meters and time scales from milliseconds to seconds, and thus is computational unaffordable in a surfzone-scale computational domain. In this study, we use an air bubble entrainment formula in a two-fluid model to predict air bubble evolution in the quiescent phase in a breaking wave event. The breaking wave-induced air bubble entrainment is formulated by connecting the shear production at the air-water interface and the bubble number intensity with a certain bubble size spectra observed in laboratory experiments. A two-fluid model is developed based on the partial differential equations of the gas-liquid mixture phase and the continuum bubble phase, which has multiple size bubble groups representing a polydisperse bubble population. An enhanced 2-DV VOF (Volume of Fluid) model with a k - ɛ turbulence closure is used to model the mixture phase. The bubble phase is governed by the advection-diffusion equations of the gas molar concentration and bubble intensity for groups of bubbles with different sizes. The model is used to simulate air bubble plumes measured in laboratory experiments. Numerical results indicate that, with an appropriate parameter in the air entrainment formula, the model is able to predict the main features of bubbly flows as evidenced by reasonable agreement with measured void fraction. Bubbles larger than an intermediate radius of O(1 mm) make a major contribution to void fraction in the near-crest region. Smaller bubbles tend to penetrate deeper and stay longer in the water column, resulting in significant contribution to the cross-sectional area of the bubble cloud. An underprediction of void fraction is found at the beginning of wave breaking when large air pockets take place. The core region of high void fraction predicted by the model is dislocated due to use of the shear production in the algorithm for initial bubble entrainment. The study demonstrates a potential use of an entrainment formula in simulations of air bubble population in a surfzone-scale domain. It also reveals some difficulties in use of the two-fluid model for predicting large air pockets induced by wave breaking, and suggests that it may be necessary to use a gas-liquid two-phase model as the basic model framework for the mixture phase and to develop an algorithm to allow for transfer of discrete air pockets to the continuum bubble phase. A more theoretically justifiable air entrainment formulation should be developed.

Airborne fibre and asbestos concentrations in system built schools

NASA Astrophysics Data System (ADS)

Burdett, Garry; Cottrell, Steve; Taylor, Catherine

2009-02-01

This paper summarises the airborne fibre concentration data measured in system built schools that contained asbestos insulation board (AIB) enclosed in the support columns by a protective steel casing. The particular focus of this work was the CLASP (Consortium of Local Authorities Special Programme) system buildings. A variety of air monitoring tests were carried out to assess the potential for fibres to be released into the classroom. A peak release testing protocol was adopted that involved static sampling, while simulating direct impact disturbances to selected columns. This was carried out before remediation, after sealing gaps and holes in and around the casing visible in the room (i.e. below ceiling level) and additionally round the tops of the columns, which extended into the suspended ceiling void. Simulated and actual measurements of worker exposures were also undertaken, while sealing columns, carrying out cleaning and maintenance work in the ceiling voids. Routine analysis of these air samples was carried out by phase contrast microscopy (PCM) with a limited amount of analytical transmission electron microscopy (TEM) analysis to confirm whether the fibres visible by PCM were asbestos or non-asbestos. The PCM fibre concentrations data from the peak release tests showed that while direct releases of fibres to the room air can occur from gaps and holes in and around the column casings, sealing is an effective way of minimising releases to below the limit of quantification (0.01 f/ml) of the PCM method for some 95% of the tests carried out. Sealing with silicone filler and taping any gaps and seams visible on the column casing in the room, also gave concentrations below the limit of quantification (LOQ) of the PCM method for 95% of the tests carried out. The data available did not show any significant difference between the PCM fibre concentrations in the room air for columns that had or had not been sealed in the ceiling void, as well as in the room. Occupant exposures during normal classroom teaching activities in areas that had undergone remediation were also monitored with much greater use of TEM analysis to determine the asbestos fibre concentration. No asbestos fibres were found in the TEM analysis of samples of classroom air from seven schools, after remediation had taken place. Occupant exposures in one school and one office building have been monitored before remediation and only one asbestos fibre was found in each set of samples analysed. The average monitored occupant exposures to asbestos in CLASP buildings was <0.00005 f/ml, an order of magnitude lower than previous measurements in UK buildings.

Bubbling behavior of a fluidized bed of fine particles caused by vibration-induced air inflow

PubMed Central

Matsusaka, Shuji; Kobayakawa, Murino; Mizutani, Megumi; Imran, Mohd; Yasuda, Masatoshi

2013-01-01

We demonstrate that a vibration-induced air inflow can cause vigorous bubbling in a bed of fine particles and report the mechanism by which this phenomenon occurs. When convective flow occurs in a powder bed as a result of vibrations, the upper powder layer with a high void ratio moves downward and is compressed. This process forces the air in the powder layer out, which leads to the formation of bubbles that rise and eventually burst at the top surface of the powder bed. A negative pressure is created below the rising bubbles. A narrow opening at the bottom allows the outside air to flow into the powder bed, which produces a vigorously bubbling fluidized bed that does not require the use of an external air supply system. PMID:23378921

Analysis of two-phase flow inter-subchannel mass and momentum exchanges by the two-fluid model approach

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

Ninokata, H.; Deguchi, A.; Kawahara, A.

1995-09-01

A new void drift model for the subchannel analysis method is presented for the thermohydraulics calculation of two-phase flows in rod bundles where the flow model uses a two-fluid formulation for the conservation of mass, momentum and energy. A void drift model is constructed based on the experimental data obtained in a geometrically simple inter-connected two circular channel test sections using air-water as working fluids. The void drift force is assumed to be an origin of void drift velocity components of the two-phase cross-flow in a gap area between two adjacent rods and to overcome the momentum exchanges at themore » phase interface and wall-fluid interface. This void drift force is implemented in the cross flow momentum equations. Computational results have been successfully compared to experimental data available including 3x3 rod bundle data.« less

Experimental study of microbubble drag reduction on an axisymmetric body

NASA Astrophysics Data System (ADS)

Song, Wuchao; Wang, Cong; Wei, Yingjie; Zhang, Xiaoshi; Wang, Wei

2018-01-01

Microbubble drag reduction on the axisymmetric body is experimentally investigated in the turbulent water tunnel. Microbubbles are created by injecting compressed air through the porous medium with various average pore sizes. The morphology of microbubble flow and the size distribution of microbubble are observed by the high-speed visualization system. Drag measurements are obtained by the balance which is presented as the function of void ratio. The results show that when the air injection flow rate is high, uniformly dispersed microbubble flow is coalesced into an air layer with the larger increment rate of drag reduction ratio. The diameter distributions of microbubble under various conditions are submitted to normal distribution. Microbubble drag reduction can be divided into three distinguishable regions in which the drag reduction ratio experiences increase stage, rapid increase stage and stability stage, respectively, corresponding to the various morphologies of microbubble flow. Moreover, drag reduction ratio increases with the decreasing pore sizes of porous medium at the identical void ratio in the area of low speeds, while the effect of pore sizes on drag reduction is reduced gradually until it disappears with the increasing free stream speeds, which indicates that smaller microbubbles have better efficiency in drag reduction. This research results help to improve the understanding of microbubble drag reduction and provides helpful references for practical applications.

Using Neutron Radiography to Quantify Water Transport and the Degree of Saturation in Entrained Air Cement Based Mortar

NASA Astrophysics Data System (ADS)

Lucero, Catherine L.; Bentz, Dale P.; Hussey, Daniel S.; Jacobson, David L.; Weiss, W. Jason

Air entrainment is commonly added to concrete to help in reducing the potential for freeze thaw damage. It is hypothesized that the entrained air voids remain unsaturated or partially saturated long after the smaller pores fill with water. Small gel and capillary pores in the cement matrix fill quickly on exposure to water, but larger pores (entrapped and entrained air voids) require longer times or other methods to achieve saturation. As such, it is important to quantitatively determine the water content and degree of saturation in air entrained cementitious materials. In order to further investigate properties of cement-based mortar, a model based on Beer's Law has been developed to interpret neutron radiographs. This model is a powerful tool for analyzing images acquired from neutron radiography. A mortar with a known volume of aggregate, water to cement ratio and degree of hydration can be imaged and the degree of saturation can be estimated.

High voltage capability electrical coils insulated with materials containing SF.sub.6 gas

DOEpatents

Lanoue, Thomas J.; Zeise, Clarence L.; Wagenaar, Loren; Westervelt, Dean C.

1988-01-01

A coil is made having a plurality of layers of adjacent metal conductor windings subject to voltage stress, where the windings have insulation therebetween containing a small number of minute disposed throughout its cross-section, where the voids are voids filled with SF.sub.6 gas to substitute for air or other gaseous materials in from about 60% to about 95% of the cross-sectional void volume in the insulation, thus incorporating an amount of SF.sub.6 gas in the cross-section of the insulation effective to substantially increase corona inception voltages.

Bubble Generation in a Flowing Liquid Medium and Resulting Two-Phase Flow in Microgravity

NASA Technical Reports Server (NTRS)

Pais, S. C.; Kamotani, Y.; Bhunia, A.; Ostrach, S.

1999-01-01

The present investigation reports a study of bubble generation under reduced gravity conditions, using both a co-flow and a cross-flow configuration. This study may be used in the conceptual design of a space-based thermal management system. Ensuing two-phase flow void fraction can be accurately monitored using a single nozzle gas injection system within a continuous liquid flow conduit, as utilized in the present investigation. Accurate monitoring of void fraction leads to precise control of heat and mass transfer coefficients related to a thermal management system; hence providing an efficient and highly effective means of removing heat aboard spacecraft or space stations. Our experiments are performed in parabolic flight aboard the modified DC-9 Reduced Gravity Research Aircraft at NASA Lewis Research Center, using an air-water system. For the purpose of bubble dispersion in a flowing liquid, we use both a co-flow and a cross-flow configuration. In the co-flow geometry, air is introduced through a nozzle in the same direction with the liquid flow. On the other hand, in the cross-flow configuration, air is injected perpendicular to the direction of water flow, via a nozzle protruding inside the two-phase flow conduit. Three different flow conduit (pipe) diameters are used, namely, 1.27 cm, 1.9 cm and 2.54 cm. Two different ratios of nozzle to pipe diameter (D(sub N))sup * are considered, namely (D(sub N))sup * = 0.1 and 0.2, while superficial liquid velocities are varied from 8 to 70 cm/s depending on flow conduit diameter. It is experimentally observed that by holding all other flow conditions and geometry constant, generated bubbles decrease in size with increase in superficial liquid velocity. Detached bubble diameter is shown to increase with air injection nozzle diameter. Likewise, generated bubbles grow in size with increasing pipe diameter. Along the same lines, it is shown that bubble frequency of formation increases and hence the time to detachment of a forming bubble decreases, as the superficial liquid velocity is in-creased. Furthermore, it is shown that the void fraction of the resulting two-phase flow increases with volumetric gas flow rate Q(sub d), pipe diameter and gas injection nozzle diameter, while they decrease with surrounding liquid flow. The important role played by flowing liquid in detaching bubbles in a reduced gravity environment is thus emphasized. We observe that the void fraction can be accurately controlled by using single nozzle gas injection, rather than by employing multiple port injection, since the later system gives rise to unpredictable coalescence of adjacent bubbles. It is of interest to note that empirical bubble size and corresponding void fraction are somewhat smaller for the co-flow geometry than the cross-flow configuration at similar flow conditions with similar pipe and nozzle diameters. In order to supplement the empirical data, a theoretical model is employed to study single bubble generation in the dynamic (Q(sub d) = 1 - 1000 cu cm/s) and bubbly flow regime within the framework of the co-flow configuration. This theoretical model is based on an overall force balance acting on the bubble during the two stages of generation, namely the expansion and the detachment stage. Two sets of forces, one aiding and the other inhibiting bubble detachment are identified. Under conditions of reduced gravity, gas momentum flux enhances, while the surface tension force at the air injection nozzle tip inhibits bubble detachment. In parallel, liquid drag and inertia can act as both attaching and detaching forces, depending on the relative velocity of the bubble with respect to the surrounding liquid. Predictions of the theoretical model compare well with our experimental results. However, at higher superficial liquid velocities, as the bubble loses its spherical form, empirical bubble size no longer matches the theoretical predictions. In summary, we have developed a combined experimental and theoretical work, which describes the complex process of bubble generation and resulting two-phase flow in a microgravity environment. Results of the present study can be used in a wide range of space-based applications, such as thermal energy and power generation, propulsion, cryogenic storage and long duration life support systems, necessary for programs such as NASA's Human Exploration for the Development of Space (HEDS).

Characterization of voids formed during liquid impregnation of nonwoven multifilament glass networks as related to composite processing

NASA Technical Reports Server (NTRS)

Mahale, Anant D.; Prudhomme, Robert K.; Rebenfeld, Ludwig

1993-01-01

A technique based on matching the refractive index of an invading liquid to that of a fiber mat was used to study entrapment of air ('voids') that occurs during forced in-plane radial flow into nonwoven multifilament glass networks. The usefulness of this technique is demonstrated in quantifying and mapping the air pockets. Experiments with a series of fluids with surface tensions varying from 28 x 10(exp -3) to 36 x 10(exp -3) N/m, viscosities from 45 x 10(exp -3) to 290 x 10(exp -3) Pa.s, and inlet flow rates from 0.15 x 10(exp -6) to 0.75 x 10(exp -6) m(exp 3)/s, showed that void content is a function of the capillary number characterizing the flow process. A critical value of capillary number, Ca = 2.5 x 10(exp -3), identifies a zone below which void content increases exponentially with decreasing capillary number. Above this critical value, negligible entrapment of voids is observed. Similar experiments carried out on surface treated nonwoven mats spanning a range of equilibrium contact angles from 20 deg to 78 deg showed that there is a critical contact angle above which negligible entrapment is observed. Below this value, there is no apparent effect of contact angle on the void fraction - capillary number relationship described earlier. Studies on the effect of filament wettability, and fluid velocity and viscosity on the size of the entrapment (voids) were also carried out. These indicate that larger sized entrapments which envelop more than one pore are favored by a low capillary number in comparison to smaller, pore level bubbles. Experiments were carried out on deformed mats - imposing high permeability spots at regular intervals on a background of low permeability. The effect of these spatial fluctuations in heterogeneity of the mat on entrapment is currently being studied.

Estimation of Soil-Water Characteristic Curves in Multiple-Cycles Using Membrane and TDR System

PubMed Central

Hong, Won-Taek; Jung, Young-Seok; Kang, Seonghun; Lee, Jong-Sub

2016-01-01

The objective of this study is to estimate multiple-cycles of the soil-water characteristic curve (SWCC) using an innovative volumetric pressure plate extractor (VPPE), which is incorporated with a membrane and time domain reflectometry (TDR). The pressure cell includes the membrane to reduce the experimental time and the TDR probe to automatically estimate the volumetric water content. For the estimation of SWCC using the VPPE system, four specimens with different grain size and void ratio are prepared. The volumetric water contents of the specimens according to the matric suction are measured by the burette system and are estimated in the TDR system during five cycles of SWCC tests. The volumetric water contents estimated by the TDR system are almost identical to those determined by the burette system. The experimental time significantly decreases with the new VPPE. The hysteresis in the SWCC is largest in the first cycle and is nearly identical after 1.5 cycles. As the initial void ratio decreases, the air entry value increases. This study suggests that the new VPPE may effectively estimate multiple-cycles of the SWCC of unsaturated soils. PMID:28774139

Correction to the gas phase pressure term in the continuum model for partially saturated granular media presented by Pietruszczak and co-workers

NASA Astrophysics Data System (ADS)

Iveson, Simon M.

2003-06-01

Pietruszczak and coworkers (Internat. J. Numer. Anal. Methods Geomech. 1994; 18(2):93-105; Comput. Geotech. 1991; 12( ):55-71) have presented a continuum-based model for predicting the dynamic mechanical response of partially saturated granular media with viscous interstitial liquids. In their model they assume that the gas phase is distributed uniformly throughout the medium as discrete spherical air bubbles occupying the voids between the particles. However, their derivation of the air pressure inside these gas bubbles is inconsistent with their stated assumptions. In addition the resultant dependence of gas pressure on liquid saturation lies outside of the plausible range of possible values for discrete air bubbles. This results in an over-prediction of the average bulk modulus of the void phase. Corrected equations are presented.

Method for Molding Structural Parts Utilizing Modified Silicone Rubber

NASA Technical Reports Server (NTRS)

Weiser, Erik S. (Inventor); Baucom, Robert M. (Inventor); Snoha, John J. (Inventor)

1998-01-01

This invention improves upon a method for molding structural parts from preform material. Preform material to be used for the part is provided. A silicone rubber composition containing entrained air voids is prepared. The silicone rubber and preform material assembly is situated within a rigid mold cavity used to shape the preform material to die desired shape. The entire assembly is heated in a standard heating device so that the thermal expansion of the silicone rubber exerts the pressure necessary to force the preform material into contact with the mold container. The introduction of discrete air voids into the silicone rubber allows for accurately controlled pressure application on the preform material at the cure temperature.

Modeling and Qualification of a Modified Emission Unit for Radioactive Air Emissions Stack Sampling Compliance.

PubMed

Barnett, J Matthew; Yu, Xiao-Ying; Recknagle, Kurtis P; Glissmeyer, John A

2016-11-01

A planned laboratory space and exhaust system modification to the Pacific Northwest National Laboratory Material Science and Technology Building indicated that a new evaluation of the mixing at the air sampling system location would be required for compliance to ANSI/HPS N13.1-2011. The modified exhaust system would add a third fan, thereby increasing the overall exhaust rate out the stack, thus voiding the previous mixing study. Prior to modifying the radioactive air emissions exhaust system, a three-dimensional computational fluid dynamics computer model was used to evaluate the mixing at the sampling system location. Modeling of the original three-fan system indicated that not all mixing criteria could be met. A second modeling effort was conducted with the addition of an air blender downstream of the confluence of the three fans, which then showed satisfactory mixing results. The final installation included an air blender, and the exhaust system underwent full-scale tests to verify velocity, cyclonic flow, gas, and particulate uniformity. The modeling results and those of the full-scale tests show agreement between each of the evaluated criteria. The use of a computational fluid dynamics code was an effective aid in the design process and allowed the sampling system to remain in its original location while still meeting the requirements for sampling at a well mixed location.

An ultrasonic investigation of the effect of voids on the mechanical properties of bread dough and the role of gas cells in determining the cellular structure of freeze- dried breadcrumb

NASA Astrophysics Data System (ADS)

Elmehdi, Hussein Mohamed

This thesis is an analysis of voids in the breadmaking process, more specifically the effect of gas cells entrapped in the dough during mixing, their expansion during fermentation, and their relationship to the breadcrumb structure in the final product. This is important to food scientists because the voids ultimately influence the structural integrity of bread and hence its quality. Understanding how voids affect the viscoelastic properties of dough is also a challenging problem in soft condensed matter physics. Longitudinal ultrasonic velocity and attenuation measurements, performed at 54 kHz, investigated changes in the mechanical properties of dough and bread as void concentration was varied. In the first part of the thesis, the effect of voids on the properties of unyeasted dough at the end of mixing was investigated. As φ is increased, the attenuation coefficient increased linearly with φ hence the change in attenuation is proportional to the number of voids, allowing the combined effects of scattering and absorption by single voids to be directly determined. By contrast, the ultrasonic velocity decreased dramatically with increasing φ in the range 0.0 12 < φ < 0.03, while at higher φ, the velocity decrease was less rapid. An effective medium model successfully modeled the viscoelastic behavior of the dough at all void fraction values, provided that the shear modulus of the matrix was permitted to vary. The same ultrasonic technique was also used to monitor the increase in gas cell size due to CO 2 production during fermentation of yeasted dough. A large decrease in velocity and an increase in the attenuation coefficient were observed as the gas cells grew. In addition, at early fermentation times, a substantial contribution to the velocity decrease arises from a reduction in the shear modulus of the dough matrix. This occurs because the pH drops as CO2 molecules dissolve in the matrix and intermolecular interactions are weakened due to protein chain charge repulsion effects. In the second part of the thesis, freeze-dried breadcrumb structure was investigated. To change the size of the air cells, the dough was proofed for various times. Ultrasonic velocity and amplitude decrease with increasing φ. The experimental data were found to be in reasonable agreement with theoretical models for the elasticity of isotropic cellular foams and tortuosity. The effects of anisotropy in breadcrumb structure were studied by compressing samples uniaxially, thereby transforming the shape of the air cells from approximately spherical to elongated ellipsoids. Ultrasonic measurements were taken in the directions parallel and perpendicular to the strain. These results indicated that the path by which sound propagates is critical. The data were interpreted using the same two theoretical models, taking into account anisotropy effects. The tortuosity model was able to interpret the void fraction dependence of the velocity along the two orthogonal directions, thus giving a way of relating changes in ultrasonic velocity to changes in breadcrumb structure. This thesis demonstrates the potential for using ultrasound as a non-destructive, cheap and accurate tool for studying the effect of voids (and their expansion) on dough properties. These ultrasonic techniques can also be used to investigate the effect of air cells on the structural integrity of breadcrumb and hence be a useful tool for quantitatively assessing bread quality.

Mechanical Properties versus Morphology of Ordered Polymers. Volume III. Part I

DTIC Science & Technology

1982-08-01

measured by wide angle x-ray scattering and differential scanning calorimetry, is unrelated to the diffuse scattered intensity [62]. Cellulose acetate which...increasing void fraction, in air swollen cellulose . Comparison of the volume fraction of voids calculated from the SAXS integrated intensity with...1964). 63. P.H. Hermans, D. Heikens, and A. Weidinger, "A Quantitative Investigation on the X-Ray Small Angle Scattering of Cellulose Fibers. Part II

Trial Maneuver Generation and Selection in the Paladin Tactical Decision Generation System

NASA Technical Reports Server (NTRS)

Chappell, Alan R.; McManus, John W.; Goodrich, Kenneth H.

1992-01-01

To date, increased levels of maneuverability and controllability in aircraft have been postulated as tactically advantageous, but little research has studied maneuvers or tactics that make use of these capabilities. In order to help fill this void, a real time tactical decision generation system for air combat engagements, Paladin, has been developed. Paladin models an air combat engagement as a series of discrete decisions. A detailed description of Paladin's decision making process is presented. This includes the sources of data used, methods of generating reasonable maneuvers for the Paladin aircraft, and selection criteria for choosing the "best" maneuver. Simulation results are presented that show Paladin to be relatively insensitive to errors introduced into the decision process by estimation of future positional and geometric data.

Trial maneuver generation and selection in the Paladin tactical decision generation system

NASA Technical Reports Server (NTRS)

Chappell, Alan R.; Mcmanus, John W.; Goodrich, Kenneth H.

1993-01-01

To date, increased levels of maneuverability and controllability in aircraft have been postulated as tactically advantageous, but little research has studied maneuvers or tactics that make use of these capabilities. In order to help fill this void, a real-time tactical decision generation system for air combat engagements, Paladin, has been developed. Paladin models an air combat engagement as a series of discrete decisions. A detailed description of Paladin's decision making process is presented. This includes the sources of data used, methods of generating reasonable maneuvers for the Paladin aircraft, and selection criteria for choosing the 'best' maneuver. Simulation results are presented that show Paladin to be relatively insensitive to errors introduced into the decision process by estimation of future positional and geometric data.

International Space Station Urine Monitoring System Functional Integration and Science Testing

NASA Technical Reports Server (NTRS)

Rodriquez, Branelle R.; Broyan, James Lee, Jr.

2011-01-01

Exposure to microgravity during human spaceflight needs to be better understood as the human exploration of space requires longer duration missions. It is known that long term exposure to microgravity causes bone loss. Measuring the calcium and other metabolic byproducts in a crew member s urine can evaluate the effectiveness of bone loss countermeasures. The International Space Station (ISS) Urine Monitoring System (UMS) is an automated urine collection device designed to collect urine, separate the urine and air, measure the void volume, and allow for syringe sampling. Accurate measuring and minimal cross-contamination is essential to determine bone loss and the effectiveness of countermeasures. The ISS UMS provides minimal cross-contamination (<0.7 mL urine) and has volume accuracy of 2% between 100 to 1000 mL urine voids. Designed to provide a non-invasive means to collect urine samples from crew members, the ISS UMS operates in-line with the Node 3 Waste and Hygiene Compartment (WHC). The ISS UMS has undergone modifications required to interface with the WHC, including material changes, science algorithm improvements, and software platform revisions. Integrated functional testing was performed to determine the pressure drop, air flow rate, and the maximum amount of fluid capable of being discharged from the UMS to the WHC. This paper will detail the results of the science and the functional integration tests.

The Effect of Tow Shearing on Reinforcement Positional Fidelity in the Manufacture of a Continuous Fiber Reinforced Thermoplastic Matrix Composite via Pultrusion-Like Processing of Commingled Feedstock

NASA Astrophysics Data System (ADS)

Warlick, Kent M.

While the addition of short fiber to 3D printed articles has increased structural performance, ultimate gains will only be realized through the introduction of continuous reinforcement placed along pre-planned load paths. Most additive manufacturing research focusing on the addition of continuous reinforcement has revolved around utilization of a prefrabricated composite filament or a fiber and matrix mixed within a hot end prior to deposition on a printing surface such that conventional extrusion based FDM can be applied. Although stronger 3D printed parts can be made in this manner, high quality homogenous composites are not possible due to fiber dominated regions, matrix dominated regions, and voids present between adjacent filaments. Conventional composite manufacturing processes are much better at creating homogeneous composites; however, the layer by layer approach in which they are made is inhibiting the alignment of reinforcement with loads. Automated Fiber Placement techniques utilize in plane bending deformation of the tow to facilitate tow steering. Due to buckling fibers on the inner radius of curves, manufacturers recommend a minimum curvature for path placement with this technique. A method called continuous tow shearing has shown promise to enable the placement of tows in complex patterns without tow buckling, spreading, and separation inherent in conventional forms of automated reinforcement positioning. The current work employs fused deposition modeling hardware and the continuous tow shearing technique to manufacture high quality fiber reinforced composites with high positional fidelity, varying continuous reinforcement orientations within a layer, and plastic elements incorporated enabling the ultimate gains in structural performance possible. A mechanical system combining concepts of additive manufacturing with fiber placement via filament winding was developed. Paths with and without tension inherent in filament winding were analyzed through microscopy in order to examine best and worst case scenarios. High quality fiber reinforced composite materials, in terms of low void content, high fiber volume fractions and homogeneity in microstructure, were manufactured in both of these scenarios. In order to improve fidelity and quality in fiber path transition regions, a forced air cooling manifold was designed, printed, and implemented into the current system. To better understand the composite performance that results from varying pertinent manufacturing parameters, the effect of feed rate, hot end temperature, forced air cooling, and deposition surface (polypropylene and previously deposited glass polypropylene commingled tow) on interply performance, microstructure, and positional fidelity were analyzed. Interply performance, in terms of average maximum load and average peel strength, was quantified through a t-peel test of the bonding quality between two surfaces. With use of forced air cooling, minor decreases in average peel strength were present due to a reduction in tow deposition temperature which was found to be the variable most indicative of performance. Average maximum load was comparable between the forced air cooled and non-air cooled samples. Microstructure was evaluated through characterization of composite area, void content, and flash percentage. Low void contents mostly between five to seven percent were attained. Further reduction of this void content to two percent is possible through higher processing temperatures; however, reduced composite area, low average peel strength performance, and the presence of smoke during manufacturing implied thermal degradation of the polypropylene matrix occurred in these samples with higher processing temperatures. Positional fidelity was measured through calculations of shear angle, shift width, and error of a predefined path. While positional fidelity variation was low with a polypropylene deposition surface, forced air cooling is necessary to achieve fidelity on top of an already deposited tow surface as evident by the fifty-six percent reduction in error tolerance profile achieved. Lastly, proof of concept articles with unique fiber paths and neat plastic elements incorporated were produced to demonstrate fiber placement along pre-planned load paths and the ability to achieve greater structural efficiency through the use of less material. The results show that high positional fidelity and high quality composites can be produced through the use of the tow shearing technique implemented in the developed mechanical system. The implementation of forced air cooling was critical in achieving fidelity and quality in transition regions. Alignment of continuous reinforcement with pre-planned load paths was demonstrated in the proof of concept article with varying fiber orientations within a layer. Combining fused deposition modeling of plastic with the placement of continuous reinforcement enabled a honeycomb composite to be produced with higher specific properties than traditional composites. Thus, the current system demonstrated a greater capability of achieving ultimate gains in structural performance than previously possible.

Space charge neutralization by electron-transparent suspended graphene

PubMed Central

Srisonphan, Siwapon; Kim, Myungji; Kim, Hong Koo

2014-01-01

Graphene possesses many fascinating properties originating from the manifold potential for interactions at electronic, atomic, or molecular levels. Here we report measurement of electron transparency and hole charge induction response of a suspended graphene anode on top of a void channel formed in a SiO2/Si substrate. A two-dimensional (2D) electron gas induced at the oxide interface emits into air and makes a ballistic transport toward the suspended graphene. A small fraction (>~0.1%) of impinging electrons are captured at the edge of 2D hole system in graphene, demonstrating good transparency to very low energy (<3 eV) electrons. The hole charges induced in the suspended graphene anode have the effect of neutralizing the electron space charge in the void channel. This charge compensation dramatically enhances 2D electron gas emission at cathode to the level far surpassing the Child-Langmuir's space-charge-limited emission. PMID:24441774

Cement-based materials' characterization using ultrasonic attenuation

NASA Astrophysics Data System (ADS)

Punurai, Wonsiri

The quantitative nondestructive evaluation (NDE) of cement-based materials is a critical area of research that is leading to advances in the health monitoring and condition assessment of the civil infrastructure. Ultrasonic NDE has been implemented with varying levels of success to characterize cement-based materials with complex microstructure and damage. A major issue with the application of ultrasonic techniques to characterize cement-based materials is their inherent inhomogeneity at multiple length scales. Ultrasonic waves propagating in these materials exhibit a high degree of attenuation losses, making quantitative interpretations difficult. Physically, these attenuation losses are a combination of internal friction in a viscoelastic material (ultrasonic absorption), and the scattering losses due to the material heterogeneity. The objective of this research is to use ultrasonic attenuation to characterize the microstructure of heterogeneous cement-based materials. The study considers a real, but simplified cement-based material, cement paste---a common bonding matrix of all cement-based composites. Cement paste consists of Portland cement and water but does not include aggregates. First, this research presents the findings of a theoretical study that uses a set of existing acoustics models to quantify the scattered ultrasonic wavefield from a known distribution of entrained air voids. These attenuation results are then coupled with experimental measurements to develop an inversion procedure that directly predicts the size and volume fraction of entrained air voids in a cement paste specimen. Optical studies verify the accuracy of the proposed inversion scheme. These results demonstrate the effectiveness of using attenuation to measure the average size, volume fraction of entrained air voids and the existence of additional larger entrapped air voids in hardened cement paste. Finally, coherent and diffuse ultrasonic waves are used to develop a direct relationship between attenuation and water to cement (w/c) ratio. A phenomenological model based on the existence of fluid-filled capillary voids is used to help explain the experimentally observed behavior. Overall this research shows the potential of using ultrasonic attenuation to quantitatively characterize cement paste. The absorption and scattering losses can be related to the individual microstructural elements of hardened cement paste. By taking a fundamental, mechanics-based approach, it should be possible to add additional components such as scattering by aggregates or even microcracks in a systematic fashion and eventually build a realistic model for ultrasonic wave propagation study for concrete.

Critical analysis of partial discharge dynamics in air filled spherical voids

NASA Astrophysics Data System (ADS)

Callender, G.; Golosnoy, I. O.; Rapisarda, P.; Lewin, P. L.

2018-03-01

In this paper partial discharge (PD) is investigated inside a spherical air filled void at atmospheric pressure using a drift diffusion model. Discharge dynamics consisted of an electron avalanche transitioning into positive streamer, in agreement with earlier work on dielectric barrier discharges. Different model configurations were utilised to test many of the concepts employed in semi-analytical PD activity models, which use simplistic descriptions of the discharge dynamics. The results showed that many of these concepts may be erroneous, with significant discrepancies between the canonical reasoning and the simulation results. For example, the residual electric field, the electric field after a discharge, is significantly lower than the estimates used by classical PD activity models in the literature.

Air Layer Drag Reduction

NASA Astrophysics Data System (ADS)

Ceccio, Steven; Elbing, Brian; Winkel, Eric; Dowling, David; Perlin, Marc

2008-11-01

A set of experiments have been conducted at the US Navy's Large Cavitation Channel to investigate skin-friction drag reduction with the injection of air into a high Reynolds number turbulent boundary layer. Testing was performed on a 12.9 m long flat-plate test model with the surface hydraulically smooth and fully rough at downstream-distance-based Reynolds numbers to 220 million and at speeds to 20 m/s. Local skin-friction, near-wall bulk void fraction, and near-wall bubble imaging were monitored along the length of the model. The instrument suite was used to access the requirements necessary to achieve air layer drag reduction (ALDR). Injection of air over a wide range of air fluxes showed that three drag reduction regimes exist when injecting air; (1) bubble drag reduction that has poor downstream persistence, (2) a transitional regime with a steep rise in drag reduction, and (3) ALDR regime where the drag reduction plateaus at 90% ± 10% over the entire model length with large void fractions in the near-wall region. These investigations revealed several requirements for ALDR including; sufficient volumetric air fluxes that increase approximately with the square of the free-stream speed, slightly higher air fluxes are needed when the surface tension is reduced, higher air fluxes are required for rough surfaces, and the formation of ALDR is sensitive to the inlet condition.

A Dual Conductance Sensor for Simultaneous Measurement of Void Fraction and Structure Velocity of Downward Two-Phase Flow in a Slightly Inclined Pipe

PubMed Central

Lee, Yeon-Gun; Won, Woo-Youn; Lee, Bo-An; Kim, Sin

2017-01-01

In this study, a new and improved electrical conductance sensor is proposed for application not only to a horizontal pipe, but also an inclined one. The conductance sensor was designed to have a dual layer, each consisting of a three-electrode set to obtain two instantaneous conductance signals in turns, so that the area-averaged void fraction and structure velocity could be measured simultaneously. The optimum configuration of the electrodes was determined through numerical analysis, and the calibration curves for stratified and annular flow were obtained through a series of static experiments. The fabricated conductance sensor was applied to a 45 mm inner diameter U-shaped downward inclined pipe with an inclination angle of 3° under adiabatic air-water flow conditions. In the tests, the superficial velocities ranged from 0.1 to 3.0 m/s for water and from 0.1 to 18 m/s for air. The obtained mean void fraction and the structure velocity from the conductance sensor were validated against the measurement by the wire-mesh sensor and the cross-correlation technique for the visualized images, respectively. The results of the flow regime classification and the corresponding time series of the void fraction at a variety of flow velocities were also discussed. PMID:28481308

Application of the ultrasonic technique and high-speed filming for the study of the structure of air-water bubbly flows

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

Carvalho, R.D.M.; Venturini, O.J.; Tanahashi, E.I.

2009-10-15

Multiphase flows are very common in industry, oftentimes involving very harsh environments and fluids. Accordingly, there is a need to determine the dispersed phase holdup using noninvasive fast responding techniques; besides, knowledge of the flow structure is essential for the assessment of the transport processes involved. The ultrasonic technique fulfills these requirements and could have the capability to provide the information required. In this paper, the potential of the ultrasonic technique for application to two-phase flows was investigated by checking acoustic attenuation data against experimental data on the void fraction and flow topology of vertical, upward, air-water bubbly flows inmore » the zero to 15% void fraction range. The ultrasonic apparatus consisted of one emitter/receiver transducer and three other receivers at different positions along the pipe circumference; simultaneous high-speed motion pictures of the flow patterns were made at 250 and 1000 fps. The attenuation data for all sensors exhibited a systematic interrelated behavior with void fraction, thereby testifying to the capability of the ultrasonic technique to measure the dispersed phase holdup. From the motion pictures, basic gas phase structures and different flows patterns were identified that corroborated several features of the acoustic attenuation data. Finally, the acoustic wave transit time was also investigated as a function of void fraction. (author)« less

Dental artifacts in the head and neck region: implications for Dixon-based attenuation correction in PET/MR.

PubMed

Ladefoged, Claes N; Hansen, Adam E; Keller, Sune H; Fischer, Barbara M; Rasmussen, Jacob H; Law, Ian; Kjær, Andreas; Højgaard, Liselotte; Lauze, Francois; Beyer, Thomas; Andersen, Flemming L

2015-12-01

In the absence of CT or traditional transmission sources in combined clinical positron emission tomography/magnetic resonance (PET/MR) systems, MR images are used for MR-based attenuation correction (MR-AC). The susceptibility effects due to metal implants challenge MR-AC in the neck region of patients with dental implants. The purpose of this study was to assess the frequency and magnitude of subsequent PET image distortions following MR-AC. A total of 148 PET/MR patients with clear visual signal voids on the attenuation map in the dental region were included in this study. Patients were injected with [(18)F]-FDG, [(11)C]-PiB, [(18)F]-FET, or [(64)Cu]-DOTATATE. The PET/MR data were acquired over a single-bed position of 25.8 cm covering the head and neck. MR-AC was based on either standard MR-ACDIXON or MR-ACINPAINTED where the susceptibility-induced signal voids were substituted with soft tissue information. Our inpainting algorithm delineates the outer contour of signal voids breaching the anatomical volume using the non-attenuation-corrected PET image and classifies the inner air regions based on an aligned template of likely dental artifact areas. The reconstructed PET images were evaluated visually and quantitatively using regions of interests in reference regions. The volume of the artifacts and the computed relative differences in mean and max standardized uptake value (SUV) between the two PET images are reported. The MR-based volume of the susceptibility-induced signal voids on the MR-AC attenuation maps was between 1.6 and 520.8 mL. The corresponding/resulting bias of the reconstructed tracer distribution was localized mainly in the area of the signal void. The mean and maximum SUVs averaged across all patients increased after inpainting by 52% (± 11%) and 28% (± 11%), respectively, in the corrected region. SUV underestimation decreased with the distance to the signal void and correlated with the volume of the susceptibility artifact on the MR-AC attenuation map. Metallic dental work may cause severe MR signal voids. The resulting PET/MR artifacts may exceed the actual volume of the dental fillings. The subsequent bias in PET is severe in regions in and near the signal voids and may affect the conspicuity of lesions in the mandibular region.

Simultaneous in vivo comparison of water-filled and air-filled pressure measurement catheters: Implications for good urodynamic practice.

PubMed

Gammie, A; Abrams, P; Bevan, W; Ellis-Jones, J; Gray, J; Hassine, A; Williams, J; Hashim, H

2016-11-01

This study aimed to evaluate whether the pressure readings obtained from air-filled catheters (AFCs) are the same as the readings from simultaneously inserted water-filled catheters (WFCs). It also aimed to make any possible recommendations for the use of AFCs to conform to International Continence Society (ICS) Good Urodynamic Practices (GUP). Female patients undergoing urodynamic studies in a single center had water-filled and air-filled catheters simultaneously measuring abdominal and intravesical pressure during filling with saline and during voiding. The pressures recorded by each system at each event during the test were compared using paired t-test and Bland-Altman analyses. 62 patients were recruited, of whom 51 had pressures that could be compared during filling, and 23 during voiding. On average, the pressures measured by the two systems were not significantly different during filling and at maximum flow, but the values for a given patient were found to differ by up to 10 cmH 2 O. This study shows that AFCs and WFCs cannot be assumed to register equal values of pressure. It has further shown that even when the p det readings are compared with their value at the start of a test, a divergence of values of up to 10 cmH 2 O remains. If AFCs are used, care must be taken to compensate for any p det variations that occur during patient movement. Before AFCs are adopted, new normal values for resting pressures need to be developed to allow good quality AFC pressure readings to be made. Neurourol. Urodynam. 35:926-933, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

A New Void Fraction Measurement Method for Gas-Liquid Two-Phase Flow in Small Channels

PubMed Central

Li, Huajun; Ji, Haifeng; Huang, Zhiyao; Wang, Baoliang; Li, Haiqing; Wu, Guohua

2016-01-01

Based on a laser diode, a 12 × 6 photodiode array sensor, and machine learning techniques, a new void fraction measurement method for gas-liquid two-phase flow in small channels is proposed. To overcome the influence of flow pattern on the void fraction measurement, the flow pattern of the two-phase flow is firstly identified by Fisher Discriminant Analysis (FDA). Then, according to the identification result, a relevant void fraction measurement model which is developed by Support Vector Machine (SVM) is selected to implement the void fraction measurement. A void fraction measurement system for the two-phase flow is developed and experiments are carried out in four different small channels. Four typical flow patterns (including bubble flow, slug flow, stratified flow and annular flow) are investigated. The experimental results show that the development of the measurement system is successful. The proposed void fraction measurement method is effective and the void fraction measurement accuracy is satisfactory. Compared with the conventional laser measurement systems using standard laser sources, the developed measurement system has the advantages of low cost and simple structure. Compared with the conventional void fraction measurement methods, the proposed method overcomes the influence of flow pattern on the void fraction measurement. This work also provides a good example of using low-cost laser diode as a competent replacement of the expensive standard laser source and hence implementing the parameter measurement of gas-liquid two-phase flow. The research results can be a useful reference for other researchers’ works. PMID:26828488

A New Void Fraction Measurement Method for Gas-Liquid Two-Phase Flow in Small Channels.

PubMed

Li, Huajun; Ji, Haifeng; Huang, Zhiyao; Wang, Baoliang; Li, Haiqing; Wu, Guohua

2016-01-27

Based on a laser diode, a 12 × 6 photodiode array sensor, and machine learning techniques, a new void fraction measurement method for gas-liquid two-phase flow in small channels is proposed. To overcome the influence of flow pattern on the void fraction measurement, the flow pattern of the two-phase flow is firstly identified by Fisher Discriminant Analysis (FDA). Then, according to the identification result, a relevant void fraction measurement model which is developed by Support Vector Machine (SVM) is selected to implement the void fraction measurement. A void fraction measurement system for the two-phase flow is developed and experiments are carried out in four different small channels. Four typical flow patterns (including bubble flow, slug flow, stratified flow and annular flow) are investigated. The experimental results show that the development of the measurement system is successful. The proposed void fraction measurement method is effective and the void fraction measurement accuracy is satisfactory. Compared with the conventional laser measurement systems using standard laser sources, the developed measurement system has the advantages of low cost and simple structure. Compared with the conventional void fraction measurement methods, the proposed method overcomes the influence of flow pattern on the void fraction measurement. This work also provides a good example of using low-cost laser diode as a competent replacement of the expensive standard laser source and hence implementing the parameter measurement of gas-liquid two-phase flow. The research results can be a useful reference for other researchers' works.

Void effect on mechanical properties of copper nanosheets under biaxial tension by molecular dynamics method

NASA Astrophysics Data System (ADS)

Yang, Zailin; Yang, Qinyou; Zhang, Guowei; Yang, Yong

2018-03-01

The relationship between void size/location and mechanical behavior under biaxial loading of copper nanosheets containing voids are investigated by molecular dynamics method. The void location and the void radius on the model are discussed in the paper. The main reason of break is discovered by the congruent relationship between the shear stress and its dislocations. Dislocations are nucleated at the corner of system and approached to the center of void with increased deformation. Here, a higher stress is required to fail the voided sheets when smaller voids are utilized. The void radius influences the time of destruction. The larger the void radius is, the lower the shear stress and the earlier the model breaks. The void location impacts the dislocation distribution.

40 CFR 86.091-7 - Maintenance of records; submittal of information; right of entry.

Code of Federal Regulations, 2013 CFR

2013-07-01

... one of the previous headings including such extraordinary events as vehicle accidents (or accidents... representative by written request for his appearance, signed by the Assistant Administrator for Air and Radiation... Assistant Administrator for Air and Radiation. (8) EPA may void ab initio a certificate of conformity for...

40 CFR 86.091-7 - Maintenance of records; submittal of information; right of entry.

Code of Federal Regulations, 2012 CFR

2012-07-01

... one of the previous headings including such extraordinary events as vehicle accidents (or accidents... representative by written request for his appearance, signed by the Assistant Administrator for Air and Radiation... Assistant Administrator for Air and Radiation. (8) EPA may void ab initio a certificate of conformity for...

40 CFR 86.091-7 - Maintenance of records; submittal of information; right of entry.

Code of Federal Regulations, 2014 CFR

2014-07-01

... one of the previous headings including such extraordinary events as vehicle accidents (or accidents... representative by written request for his appearance, signed by the Assistant Administrator for Air and Radiation... Assistant Administrator for Air and Radiation. (8) EPA may void ab initio a certificate of conformity for...

Mechanical Properties of Misers Bluff Sand.

DTIC Science & Technology

1986-09-01

in Chapter 4. 4 .7 Y~ e -~1 % CHAPTER 2 LABORATORY TESTS 2.1 CONVENTIONAL SOIL TESTS Samples of MB sand were split from the available supply of...air Va , and void ratio e (the ratio of void volume to solid volume). These composition data are listed in Table 2.1 for each test. 5 2.3 MECHANICAL...and diameter changes are made. The data can be plotted as principal stress difference versus axial strain, the slope of which is Young’s modulus E

Radioisotope measurement of selected parameters of liquid-gas flow using single detector system

NASA Astrophysics Data System (ADS)

Zych, Marcin; Hanus, Robert; Jaszczur, Marek; Mosorov, Volodymyr; Świsulski, Dariusz

2018-06-01

To determine the parameters of two-phase flows using radioisotopes, usually two detectors are used. Knowing the distance between them, the velocity of the dispersed phase is calculated based on time delay estimation. Such a measurement system requires the use of two gamma-ray sealed sources. But in some situations it is also possible to determine velocity of dispersed phase using only one scintillation probe and one gamma-ray source. However, this requires proper signal analysis and prior calibration. This may also cause larger measurement errors. On the other hand, it allows measurements in hard to reach areas where there is often no place for the second detector. Additionally, by performing a previous calibration, it is possible to determine the void fraction or concentration of the selected phase. In this work an autocorrelation function was used to analyze the signal from the scintillation detector, which allowed for the determination of air velocities in slug and plug flows with an accuracy of 8.5%. Based on the analysis of the same signal, a void fraction with error of 15% was determined.

An initial study of void formation during solidification of aluminum in normal and reduced-gravity

NASA Technical Reports Server (NTRS)

Chiaramonte, Francis P.; Foerster, George; Gotti, Daniel J.; Neumann, Eric S.; Johnston, J. C.; De Witt, Kenneth J.

1992-01-01

Void formation due to volumetric shrinkage during aluminum solidification was observed in real time using a radiographic viewing system in normal and reduced gravity. An end chill directional solidification furnace with water quench was developed to solidify aluminum samples during the approximately 16 seconds of reduced gravity (+/- 0.02g) achieved by flying an aircraft through a parabolic trajectory. Void formation was recorded for two cases: first a nonwetting system; and second, a wetting system where wetting occurs between the aluminum and crucible lid. The void formation in the nonwetting case is similar in normal and reduced gravity, with a single vapor cavity forming at the top of the crucible. In the wetting case in reduced gravity, surface tension causes two voids to form in the top corners of the crucible, but in normal gravity only one large voids forms across the top.

Two reference time scales for studying the dynamic cavitation of liquid films

NASA Technical Reports Server (NTRS)

Sun, D. C.; Brewe, D. E.

1992-01-01

Two formulas, one for the characteristic time of filling a void with the vapor of the surrounding liquid, and one of filling the void by diffusion of the dissolved gas in the liquid, are derived. By comparing these time scales with that of the dynamic operation of oil film bearings, it is concluded that the evaporation process is usually fast enough to fill the cavitation bubble with oil vapor; whereas the diffusion process is much too slow for the dissolved air to liberate itself and enter the cavitation bubble. These results imply that the formation of a two phase fluid in dynamically loaded bearings, as often reported in the literature, is caused by air entrainment. They further indicate a way to simplify the treatment of the dynamic problem of bubble evolution.

A Factorial Design Approach to Analyse the Effect of Coarse Recycled Concrete Aggregates on the Properties of Hot Mix Asphalt

NASA Astrophysics Data System (ADS)

Tanty, Kiranbala; Mukharjee, Bibhuti Bhusan; Das, Sudhanshu Shekhar

2018-06-01

The present study investigates the effect of replacement of coarse fraction of natural aggregates by recycled concrete aggregates on the properties of hot mix asphalt (HMA) using general factorial design approach. For this two factors i.e. recycled coarse aggregates percentage [RCA (%)] and bitumen content percentage [BC (%)] are considered. Tests have been carried out on the HMA type bituminous concrete, prepared with varying RCA (%) and BC (%). Analysis of variance has been performed on the experimental data to determine the effect of the chosen factors on various parameters such as stability, flow, air void, void mineral aggregate, void filled with bitumen and bulk density. The study depicts that RCA (%) and BC (%) have significant effect on the selected responses as p value is less than the chosen significance level. In addition to above, the outcomes of the statistical analysis indicate that interaction between factors have significant effects on void mineral aggregate and bulk density of bituminous concrete.

A Factorial Design Approach to Analyse the Effect of Coarse Recycled Concrete Aggregates on the Properties of Hot Mix Asphalt

NASA Astrophysics Data System (ADS)

Tanty, Kiranbala; Mukharjee, Bibhuti Bhusan; Das, Sudhanshu Shekhar

2018-02-01

The present study investigates the effect of replacement of coarse fraction of natural aggregates by recycled concrete aggregates on the properties of hot mix asphalt (HMA) using general factorial design approach. For this two factors i.e. recycled coarse aggregates percentage [RCA (%)] and bitumen content percentage [BC (%)] are considered. Tests have been carried out on the HMA type bituminous concrete, prepared with varying RCA (%) and BC (%). Analysis of variance has been performed on the experimental data to determine the effect of the chosen factors on various parameters such as stability, flow, air void, void mineral aggregate, void filled with bitumen and bulk density. The study depicts that RCA (%) and BC (%) have significant effect on the selected responses as p value is less than the chosen significance level. In addition to above, the outcomes of the statistical analysis indicate that interaction between factors have significant effects on void mineral aggregate and bulk density of bituminous concrete.

Detection of underground voids in Tahura Japan Cave Bandung using ground penetrating radar

NASA Astrophysics Data System (ADS)

Azimmah, Azizatun; Widodo

2017-07-01

The detection of underground voids is important due to their effects on subsidence higher risk. Ground Penetrating Radar is one of geophysical electromagnetic methods that has been proven to be able to detect and locate any void beneath the surface effectively at a shallow depth. This method uses the contrasts of dielectric properties, resistivity and magnetic permeability to investigate and map what lies beneath the surface. Hence, this research focused on how GPR could be applied for detecting underground voids at the site of investigation, The Japan Cave in Taman Hutan Raya located in Dago, Bandung, Indonesia. A 100 MHz GPR shielded antenna frequency were used to measure three >80 meters long measurement lines. These three GPR profiles were positioned on the surface above the Japan Cave. The radargram results showed existences of different amplitude regions proven to be the air-filled cavities, at a depth of <10 meters, and interfaces between the underneath layers.

Refractive index dependence of Papilio Ulysses butterfly wings reflectance spectra

NASA Astrophysics Data System (ADS)

Isnaeni, Muslimin, Ahmad Novi; Birowosuto, Muhammad Danang

2016-02-01

We have observed and utilized butterfly wings of Papilio Ulysses for refractive index sensor. We noticed this butterfly wings have photonic crystal structure, which causes blue color appearance on the wings. The photonic crystal structure, which consists of cuticle and air void, is approximated as one dimensional photonic crystal structure. This photonic crystal structure opens potential to several optical devices application, such as refractive index sensor. We have utilized small piece of Papilio Ulysses butterfly wings to characterize refractive index of several liquid base on reflectance spectrum of butterfly wings in the presence of sample liquid. For comparison, we simulated reflectance spectrum of one dimensional photonic crystal structure having material parameter based on real structure of butterfly wings. We found that reflectance spectrum peaks shifted as refractive index of sample changes. Although there is a slight difference in reflectance spectrum peaks between measured spectrum and calculated spectrum, the trend of reflectance spectrum peaks as function of sample's refractive index is the similar. We assume that during the measurement, the air void that filled by sample liquid is expanded due to liquid pressure. This change of void shape causes non-similarity between measured spectrum and calculated spectrum.

Recalls of Vehicles and Engines

EPA Pesticide Factsheets

n cases where EPA has determines that manufacturers have provided inaccurate, incomplete or falsified certification information or failed to keep required records, the Clean Air Act gives the EPA the authority to void certificates.

46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam, and...

46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam, and...

46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam, and...

46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam, and...

46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam, and...

Heat Transfar Properties of Flat-Panel Evacuated Porous Insrlators

NASA Astrophysics Data System (ADS)

Yoneno, Hirosyi; Yamamoto, Ryoichi

Flat Panel evacuated porous insulators have been produced by filling powder or fiber (such as perlite powder, diatomaceous earth powder, silica aerogel powder, g lass fiber and ceramic fiber) in film-like laminated plastic container and by evacuating to form vacuum in it is interior. Heat transfer properties of these evacuated insulators have been studied under various conditions (such as particle diameter, surface area, packing density, solid volume fraction and void dimension). The apparent mean thermal conductivity has been measured for the boundary surface temperature at cold face temperature 13°C and hot face temperature 35°. The effect of air pressure ranging from 1 Pa to one atomosphere (105 Pa) was examined. The results were as follows. (1) For each powder the apparent mean thermal conductivity decreases with decreasing residual air pressure, and at very low pressure bellow 1 -103 Pa the conductivity becomes indeqendent of pressure. The thermal conductivity at 1.3Pa is 0.0053 W/mK for perlite powder, 0.0048W/mK for diatomaceous earth powder, 0.0043 W/mK for silica aerogel powder and 0.0029W/mK for glass fiber. (2) With decreasing particle size, the apparent mean thermal conductivity is constant independent of residual air pressure in higher pressure region. It is that void dimension continues to decrease with particle size and the mean free path of air becomes comparable with void dimension. (3) In the range of minor solid volume fraction, the apparent mean thermal conductivity at very low precreases with decreasing particle size. This shows the thermal contact resistance of the solid particle increases with decreasing particle size.

Application of 3D Electrical Resistivity Tomography As A Tool for Mapping Subsurface Cavities in a Kaolin Mining Site at Kankara in North Central Nigeria.

NASA Astrophysics Data System (ADS)

Eshimiakhe, D.; Jimoh, R.

2017-12-01

A Kaolin mining site at Dajin Gwanma in north central Nigeria was investigated to determine the possibility of using 3D ERT to detect subsurface voids created due to mining of kaolin deposit and to perhaps suggest areas prone to subsidence. This study was undertaken on conceptual resistivity model that subsurface voids characterized by higher or lower resistivity than the host, depending on weather the void is in-filled water or not. The data collection was carried out with Terrameter SAS 4000 and ES 464 electrode selector equipment. Dipole-dipole configuration at electrode spacing of 5m was used to acquire the data along parallel profiles laid at equal interval in the study area. While the acquired data along each profile were inverted with 2D algorithm, a script file was created to collate the 2D data set into a 3D format and subsequently inverted using 3D algorithm. A volumetric resistivity model block of the study area was also created using the voxler 4 software. The results show that the voids are characterized by high resistivity (950Ωm-2500Ωm) at depth of between 0-4m and low resistivity (10Ωm-100Ωm) at a depth of 5-30m indicating both air-filled and water-filled voids respectively. The study shows that the voids increase in dimension with depth in NW-SE direction, suggesting that the voids are trending most probably along vertical bedrock joints. It also suggest that voids may overtime grow large enough that the overlying top soil can no longer bridge it, leading to its collapse.

Analysis of Ground Penetrating Radar’s Capability for Detecting Underground Cavities: A Case Study in Japan Cave of Taman Hutan Raya, Bandung

NASA Astrophysics Data System (ADS)

Azimmah, Azizatun; Widodo

2017-04-01

Underground cavities or voids detection is essential especially when it comes to building construction. By knowing the presence of void lying underground, one could consider whether the subsidence is likely to be prevented or not. Ground penetrating radar is a high-frequency electromagnetic sounding technique that has been developed to investigate the shallow subsurface using the contrast of dielectric properties. This geophysical method is suitable to be used to detect and locate voids beneath the surface especially those that lie in shallow depth. This research focused on how GPR could be implemented as void detector using model simulation or forward modelling. The models applied in the forward modelling process are to be made as similar as the real condition in the case study location which took place in Tahura Japan Cave, Bandung, Indonesia. Forward modelling needs to be done so in the future, we might use the modelling results as the references in measuring real GPR data in the location. We used three models that we considered fairly representative to prove that GPR is capable of detecting and locating voids underneath the ground. This research resulted in the different amplitude region around the considerably homogeneous region. The different amplitude region is characterized having an arc shape and is considered to be air which is known as the key component of voids.

Practical Aerobic Oxidations of Alcohols and Amines with Homogeneous Cu/TEMPO and Related Catalyst Systems

PubMed Central

Ryland, Bradford L.; Stahl, Shannon S.

2014-01-01

Alcohol and amine oxidations are common reactions in laboratory and industrial synthesis of organic molecules. Aerobic oxidation methods have long been sought for these transformations, but few practical methods exist that offer advantages over traditional oxidation methods. Recently developed homogeneous Cu/TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidinyl-N-oxyl) and related catalyst systems appear to fill this void. The reactions exhibit high levels of chemoselectivity and broad functional-group tolerance, and they often operate efficiently at room temperature with ambient air as the oxidant. These advances, together with their historical context and recent applications, are highlighted in this minireview. PMID:25044821

Galaxy evolution in extreme environments: Molecular gas content star formation and AGN in isolated void galaxies

NASA Astrophysics Data System (ADS)

Das, Mousumi; Iono, Daisuke; Saito, Toshiki; Subramanian, Smitha

Since the early redshift surveys of the large scale structure of our universe, it has become clear that galaxies cluster along walls, sheet and filaments leaving large, empty regions called voids between them. Although voids represent the most under dense parts of our universe, they do contain a sparse but significant population of isolated galaxies that are generally low luminosity, late type disk galaxies. Recent studies show that most void galaxies have ongoing star formation and are in an early stage of evolution. We present radio, optical studies of the molecular gas content and star formation in a sample of void galaxies. Using SDSS data, we find that AGN are rare in these systems and are found only in the Bootes void; their black hole masses and radio properties are similar to bright spirals galaxies. Our studies suggest that close galaxy interactions and gas accretion are the main drivers of galaxy evolution in these systems despite their location in the underdense environment of the voids.

Via fill properties of organic BARCs in dual-damascene application

NASA Astrophysics Data System (ADS)

Huang, Runhui

2004-05-01

With the introduction of copper as the interconnect metal, the Dual Damascene (DD) process has been integrated into integrated circuit (IC) device fabrication. The DD process utilizes organic bottom anti-reflective coatings (BARCs) not only to eliminate the thin film interference effects but also to act as via fill materials. However, three serious processing problems are encountered with organic BARCs. One is the formation of voids, which are trapped gas bubbles (evaporating solvent, byproduct of the curing reaction and air) inside the vias. Another problem is non-uniform BARC layer thickness in different via pitch areas. The third problem is the formation of fences during plasma etch. Fences are formed from materials that are removed by plasma and subsequently deposited on the sidewall surrounding the via openings during the etching process. Voids can cause variations in BARC top thickness, optical properties, via fill percentage, and plasma etch rate. This study focuses on the factors that influence the formation of voids and addresses the ways to eliminate them by optimizing the compositions of formulations and the processing conditions. Effects of molecular weight of the polymer, nature of the crosslinker, additives, and bake temperature were examined. The molecular weight of the polymer is one of the important factors that needs to be controlled carefully. Polymers with high molecular weights tend to trap voids inside the vias. Low molecular weight polymers have low Tg and low viscosity, which enables good thermal flow so that the BARC can fill vias easily without voids. Several kinds of crosslinkers were investigated in this study. When used with the same polymer system, formulations with different crosslinkers show varying results that affect planar fill, sidewall coverage, and, in some cases, voids. Additives also can change via fill behavior dramatically, and choosing the right additive will improve the via fill property. Processing conditions such as bake temperature also greatly affect via fill. Depending on the polymer thermal property and crosslinking reaction, varying the bake temperature can change the via fill behavior of the BARC. By understanding the nature of the polymer, the crosslinking reaction, and the processing conditions, we are able to design BARCs with better flow property to provide planar topography without voids inside the vias.

Analysis of the Hydrodynamics and Heat Transfer Aspects of Microgravity Two-Phase Flows

NASA Technical Reports Server (NTRS)

Rezkallah, Kamiel S.

1996-01-01

Experimental results for void fractions, flow regimes, and heat transfer rates in two-phase, liquid-gas flows are summarized in this paper. The data was collected on-board NASA's KC-135 reduced gravity aircraft in a 9.525 mm circular tube (i.d.), uniformly heated at the outer surface. Water and air flows were examined as well as three glycerol/water solutions and air. Results are reported for the water-air data.

Clogging evaluation of porous asphalt concrete cores in conjunction with medical x-ray computed tomography

NASA Astrophysics Data System (ADS)

Su, Yu-Min; Hsu, Chen-Yu; Lin, Jyh-Dong

2014-03-01

This study was to assess the porosity of Porous Asphalt Concrete (PAC) in conjunction with a medical X-ray computed tomography (CT) facility. The PAC was designed as the surface course to achieve the target porosity 18%. There were graded aggregates, soils blended with 50% of coarse sand, and crushed gravel wrapped with geotextile compacted and served as the base, subbase, and infiltration layers underneath the PAC. The test site constructed in 2004 is located in Northern of Taiwan in which the daily traffic has been light and limited. The porosity of the test track was investigated. The permeability coefficient of PAC was found severely degraded from 2.2×10-1 to 1.2×10-3 -cm/sec, after nine-year service, while the permeability below the surface course remained intact. Several field PAC cores were drilled and brought to evaluate the distribution of air voids by a medical X-ray CT nondestructively. The helical mode was set to administrate the X-ray CT scan and two cross-sectional virtual slices were exported in seconds for analyzing air voids distribution. It shows that the clogging of voids occurred merely 20mm below the surface and the porosity can reduce as much about 3%. It was also found that the roller compaction can decrease the porosity by 4%. The permeability reduction in this test site can attribute to the voids of PAC that were compacted by roller during the construction and filled by the dusts on the surface during the service.

Evaluation of self-consolidating concrete.

DOT National Transportation Integrated Search

2003-01-01

Conventional concrete tends to present a problem with regard to adequate consolidation in thin sections or areas of congested reinforcement, which leads to a large volume of entrapped air voids and compromises the strength and durability of the concr...

Jetting and flooding of granular backfill materials : [summary].

DOT National Transportation Integrated Search

2015-03-01

Granular backfill materials on highway projects are often compacted by mechanical methods. : This requires the contractor to place backfill material into loose lifts of varying thickness : and use compaction equipment to reduce air voids and increase...

[Comparison of new portable home electronic uroflowmeter with Laborie uroflowmeter].

PubMed

Guan, Zhi-chen; Deng, Xiao-lin; Zhang, Qian

2011-08-18

To design a new portable home electronic uroflowmeter and compare it with traditional methods. The system consists of collectors, urine conducting apparatus, intelligent cell phone, wireless network communication technology, computer analysis and drawing, and data storage technology, etc., and can automatically collect voiding information from patients with lower urinary tract symptoms(LUTS) Through Bluetooth, the voiding information was sent to the patient's intelligent cell phone from the collector, then stored directly by intelligent cell phone and wirelessly transmitted to the workstation in hospital. The system was primarily tested with regard to accuracy of measurement of the voided volume. Multiple doses with known volume were introduced in the system and Laborie uroflowmeter. Furthermore, 38 outpatients who had LUTS were tested simultaneously with the system and Laborie uroflowmeter. The statistical method for assessing agreement between the two methods of clinical measurement was Bland-Altman analysis. Among the subjects, there were 22 male patients and 16 female patients, ranging from 21 to 37 years old, with an average age of 25.5 years, of whom, 19 were tested once and 19 patients twice, equaling to 57 tests. The system could accurately collect and analyze voiding time, uroflowmetry, voided volume, and automatically provide uroflowmetry parameters. The measurement error of 100, 200, 300, 500 and 800 mL is less than 5%. 12.28%, 5.26% and 3.51% of the Qmax, Qave and voided volume points were beyond the 95% limits of agreement. The maximum absolute values of the Qmax, Qave and voided volume difference were 0.38 mL/s, 0.70 mL/s and 2.90 mL, respectively.They agreed with the recommendation of Standardization International Continence Society. The new portable home electronic uroflowmeter has good agreement with Laborie uroflowmeter,and is a new LUTS monitoring system integrated with correct, reliable, real-time, convenient and easy-managing advantages. It is as noninvasive and reliable as traditional methods, and its portable feature facilitates application out of hospitals. It can also record voiding diaries.

Development of an Inline Urine Monitoring System for the International Space Station

NASA Technical Reports Server (NTRS)

Broyan, James Lee, Jr.; Cibuzar, Banelle R.

2008-01-01

Human exposure to microgravity during spaceflight causes bone loss. Calcium and other metabolic byproducts are excreted in urine voids. Frequent and accurate measurement of urine void volume and constituents is essential to determining crew bone loss and the effectiveness of countermeasures. Previous US Space Shuttle (SS) Urine Monitoring System (UMS) technology was unable to accurately measure urine void volumes due to cross contamination between users and fluid system instabilities. Currently, urine voids must be collected manually in a flexible plastic bag containing a known tracer quantity. The crew member must completely mix the bag then withdraw a representative syringe sample for later ground analysis. The current bag system accuracy is highly dependent on mixing technique. The International Space Station (ISS) UMS has been developed as an automated device that collects urine from the Waste and Hygiene Compartment (WHC) urinal funnel interface, separates the urine, measures the void volume, and allows for syringe sampling. After operations, the ISS UMS delivers the urine to the WHC for normal processing then flushes its plumbing with a small water volume. The current ISS UMS design incorporates an innovative rotary separator that minimizes foaming, greatly reduces cross contamination between urine voids (< 0.5 ml urine), and provides accurate volume measurements (< +/- 2% error for 100 to 1000 ml void volumes). The system performance has been validated with extensive ground tests and reduced gravity aircraft flights. The lockersized ISS UMS is currently being modified to interface with the ISS Node 3 WHC Russian ACY hardware. The operation principles, characteristics, and results are outlined in the paper.

Two-phase flow measurements with advanced instrumented spool pieces and local conductivity probes

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

Turnage, K.G.; Davis, C.E.

1979-01-01

A series of two-phase, air-water and steam-water tests performed with instrumented spool pieces and with conductivity probes obtained from Atomic Energy of Canada, Ltd. is described. The behavior of the three-beam densitometer, turbine meter, and drag flowmeter is discussed in terms of two-phase models. Application of some two-phase mass flow models to the recorded spool piece data is made and preliminary results are shown. Velocity and void fraction information derived from the conductivity probes is presented and compared to velocities and void fractions obtained using the spool piece instrumentation.

Application of imaging technology to improve the laboratory and field compaction of HMA.

DOT National Transportation Integrated Search

2009-04-01

Field compaction of asphalt mixtures is an important process that influences performance of asphalt : pavements. This study evaluates the relationship between different field compaction patterns and the : uniformity of air void distribution in asphal...

Issues pertaining to the permeability characteristics of coarsegraded Superpave mixes

DOT National Transportation Integrated Search

2002-07-01

In order to evaluate the relationships between in-place air voids, lift thickness, and permeability, 23 on-going HMA construction projects were visited and field permeability tests conducted. Field permeability tests were conducted at 15 randomly det...

Closed-system freezing of soils in linings and earth embankment dams

NASA Astrophysics Data System (ADS)

Jones, C. W.

1981-03-01

A brief review of studies of closed-system freezing (no source of water except that in voids) of compacted soil canal linings, laboratory and field test results show that under certain soil and temperature conditions, freezing decreases soil density near the surface, but increases density at depth. In two linings, the average density increased slightly during a 20-year period. Frost penetration measurements made during the 1978-79 winter on a 1,5-thick reservoir lining, on three earth dams under construction, and on the Teton Dam remnant are shown along with associated soil conditions, air freezing indexes, and insulating effects of snow and, for one dam, a loose soil cover.

Experimental study of void formation during aluminum solidification in reduced gravity. Ph.D. Thesis - Toledo Univ.

NASA Technical Reports Server (NTRS)

Chiaramonte, Francis Paul, III

1993-01-01

Void formation due to volumetric shrinkage and liquid/vapor reorientation during aluminum solidification was observed in real time by using a radiographic viewing system in normal and reduced gravity. An end-chill directional solidification furnace with water quench was designed and constructed to solidify aluminum samples during the approximately 16 sec of reduced gravity (+/-0.02g) achieved by flying an aircraft through a parabolic trajectory. In the first series of tests the aluminum was contained in a vacuum sealed, pyrolytic boron nitride crucible. An ullage space was present during each test. Void formation was recorded for two cases: a nonwetting system, and a wetting system where wetting occurred between the aluminum and the crucible lid. The void formation in the nonwetting case was similar in normal and reduced gravity, with a single vapor cavity forming at the top of the crucible. In the wetting case during reduced gravity surface tension caused two voids to form in the top corners of the crucible, but during normal gravity only one large void formed across the top. In the second series of tests the aluminum was contained in a pyrolytic boron nitride crucible that was placed in a stainless steel container and sealed in an environment of argon plus 4 percent hydrogen. An ullage space was present during each test. Void formation was recorded for two cases: a nonwetting system, and a wetting system where wetting occurred between the aluminum and one side wall and the lid. The void for nation in the nonwetting case was similar in normal and reduced gravity, with a single vapor cavity forming at the top of the crucible, although the meniscus became more convex in reduced gravity. In the wetting case the aluminum did not climb up the corners in 1g, and one large symmetric void resulted at the top when the aluminum had solidified. In the wetting case during reduced gravity the molten aluminum was drawn up the wetted wall and partially across the lid by a capillary underpressure; however, on the nonwetting wall the aluminum moved down. One void resulted along the nonwetting side of the container continuing to the top on the same side.

Probability of detection of internal voids in structural ceramics using microfocus radiography

NASA Technical Reports Server (NTRS)

Baaklini, G. Y.; Roth, D. J.

1986-01-01

The reliability of microfocous X-radiography for detecting subsurface voids in structural ceramic test specimens was statistically evaluated. The microfocus system was operated in the projection mode using low X-ray photon energies (20 keV) and a 10 micro m focal spot. The statistics were developed for implanted subsurface voids in green and sintered silicon carbide and silicon nitride test specimens. These statistics were compared with previously-obtained statistics for implanted surface voids in similar specimens. Problems associated with void implantation are discussed. Statistical results are given as probability-of-detection curves at a 95 precent confidence level for voids ranging in size from 20 to 528 micro m in diameter.

Probability of detection of internal voids in structural ceramics using microfocus radiography

NASA Technical Reports Server (NTRS)

Baaklini, G. Y.; Roth, D. J.

1985-01-01

The reliability of microfocus x-radiography for detecting subsurface voids in structural ceramic test specimens was statistically evaluated. The microfocus system was operated in the projection mode using low X-ray photon energies (20 keV) and a 10 micro m focal spot. The statistics were developed for implanted subsurface voids in green and sintered silicon carbide and silicon nitride test specimens. These statistics were compared with previously-obtained statistics for implanted surface voids in similar specimens. Problems associated with void implantation are discussed. Statistical results are given as probability-of-detection curves at a 95 percent confidence level for voids ranging in size from 20 to 528 micro m in diameter.

Structural analyses of a rigid pavement overlaying a sub-surface void

NASA Astrophysics Data System (ADS)

Adam, Fatih Alperen

Pavement failures are very hazardous for public safety and serviceability. These failures in pavements are mainly caused by subsurface voids, cracks, and undulation at the slab-base interface. On the other hand, current structural analysis procedures for rigid pavement assume that the slab-base interface is perfectly planar and no imperfections exist in the sub-surface soil. This assumption would be violated if severe erosion were to occur due to inadequate drainage, thermal movements, and/or mechanical loading. Until now, the effect of erosion was only considered in the faulting performance model, but not with regards to transverse cracking at the mid-slab edge. In this research, the bottom up fatigue cracking potential, caused by the combined effects of wheel loading and a localized imperfection in the form of a void below the mid-slab edge, is studied. A robust stress and surface deflection analysis was also conducted to evaluate the influence of a sub-surface void on layer moduli back-calculation. Rehabilitative measures were considered, which included a study on overlay and fill remediation. A series regression of equations was proposed that provides a relationship between void size, layer moduli stiffness, and the overlay thickness required to reduce the stress to its original pre-void level. The effect of the void on 3D pavement crack propagation was also studied under a single axle load. The amplifications to the stress intensity was shown to be high but could be mitigated substantially if stiff material is used to fill the void and impede crack growth. The pavement system was modeled using the commercial finite element modeling program Abaqus RTM. More than 10,000 runs were executed to do the following analysis: stress analysis of subsurface voids, E-moduli back-calculation of base layer, pavement damage calculations of Beaumont, TX, overlay thickness estimations, and mode I crack analysis. The results indicate that the stress and stress intensity are, on average, amplified considerably: 80% and 150%, respectively, by the presence of the void and more severe in a bonded pavement system compared to an un-bonded system. The sub-surface void also significantly affects the layer moduli back-calculation. The equivalent moduli of the layers are reduced considerably when a sub-surface void is present. However, the results indicate the back-calculated moduli derived using surface deflection, and longitudinal stress basins did not yield equivalent layer moduli under mechanical loading; the back-calculated deflection-based moduli were larger than the stress-based moduli, leading to stress calculations that were lower than those found in the real system.

Laboratory test investigations on soil water characteristic curve and air permeability of municipal solid waste.

PubMed

Shi, Jianyong; Wu, Xun; Ai, Yingbo; Zhang, Zhen

2018-05-01

The air permeability coefficient has a high correlation with the water content of municipal solid waste. In this study, continuous drying methodology using a tension meter was employed to construct the soil water characteristic curve of municipal solid waste (M-SWCC). The municipal solid waste air permeability test was conducted by a newly designed apparatus. The measured M-SWCC was well reproduced by the van Genuchten (V-G) model and was used to predict the parameters of typical points in M-SWCC, including saturated water content, field capacity, residual water content and water content at the inflection point. It was found that the M-SWCC was significantly influenced by void ratio. The final evaporation and test period of M-SWCC increase with the increase in void ratio of municipal solid waste. The evolution of air permeability coefficient with water content of municipal solid waste depicted three distinct characteristic stages. It was observed that the water contents that corresponded to the two cut-off points of the three stages were residual water content and water content at the inflection point, respectively. The air permeability coefficient of municipal solid waste decreased with the increase of the water content from zero to the residual water content. The air permeability coefficient was almost invariable when the water content increased from residual water content to the water content at the inflection point. When the water content of municipal solid waste exceeded the water content at the inflection point, the air permeability coefficient sharply decreased with the increase of water content.

An experimental study of permeability within an out-of-autoclave vacuum-bag-only CFRP laminate

NASA Astrophysics Data System (ADS)

Wallace, Landon F.

The out-of-autoclave vacuum-bag-only (OOA-VBO) manufacturing process is a process that eliminates an autoclave when manufacturing aerospace quality carbon fiber reinforced plastics (CFRP). OOA-VBO pre-impregnated resin tow systems rely on air channel networks that guide unwanted voids out of the laminate. The air path networks can be characterized by measuring the permeability of a pre-cured laminate. Permeability results were successfully obtained for a laminate with a compaction similar to that found in a typical vacuum bagging setup. A study was done to find the relationship between compaction of the laminate and permeability. Permeability was measured as the laminate cured, using a constant temperature ramp rate. An experimental nodal analysis was performed to find the permeability at the midpoint of the in-plane direction.

Evaluation of pavement permeability in Mississippi.

DOT National Transportation Integrated Search

2003-07-01

The proper compaction of hot mix asphalt (HMA) pavements is vital for a stable and durable pavement. For dense-graded mixtures, it has been recommended that the initial in-place air voids at the time of construction should not be below 3 percent or a...

Modeling of hot-mix asphalt compaction : a thermodynamics-based compressible viscoelastic model

DOT National Transportation Integrated Search

2010-12-01

Compaction is the process of reducing the volume of hot-mix asphalt (HMA) by the application of external forces. As a result of compaction, the volume of air voids decreases, aggregate interlock increases, and interparticle friction increases. The qu...

Simulation, imaging, and mechanics of asphalt pavement (SIMAP) initiative

DOT National Transportation Integrated Search

1998-07-01

Asphalt concrete is a complex material that consists of aggregates, asphalt, and air voids. Aggregates are held together by asphalt and form a skeleton to support the weight of vehicles. The stiffer the asphalt, the tighter the aggregates are held to...

Evaluation of non-destructive technologies for construction quality control of HMA and PCC pavements in Louisiana.

DOT National Transportation Integrated Search

2013-11-01

Current roadway quality control and quality acceptance (QC/QA) procedures for the Louisiana Department of Transportation and : Development (LADOTD) include coring for thickness, density, and air voids in hot mix asphalt (HMA) pavements and thickness ...

Addressing safety through evaluation and optimization of permeable friction course mixtures.

DOT National Transportation Integrated Search

2010-01-01

Permeable friction course (PFC) mixtures are a special type of hot mix asphalt characterized by a : high total air voids content to guarantee proper functionality and stone-on-stone contact of the coarse : aggregate fraction to ensure adequate mixtur...

Illegal Immigration in the United States: Implications for Rule of Law and National Security

DTIC Science & Technology

2012-02-15

AIR WAR COLLEGE AIR UNIVERSITY ILLEGAL IMMIGRATION IN THE UNITED STATES: IMPLICATIONS FOR RULE OF LAW AND NATIONAL SECURITY By Paul A...government’s failure to strictly enforce immigration laws presents national security vulnerabilities and is subversive to the rule of law . Without...the rule of law , serious social tensions will occur that impel states and localities to fill the void left by the lack of immigration enforcement. In

Comparison of air-charged and water-filled urodynamic pressure measurement catheters.

PubMed

Cooper, M A; Fletter, P C; Zaszczurynski, P J; Damaser, M S

2011-03-01

Catheter systems are utilized to measure pressure for diagnosis of voiding dysfunction. In a clinical setting, patient movement and urodynamic pumps introduce hydrostatic and motion artifacts into measurements. Therefore, complete characterization of a catheter system includes its response to artifacts as well its frequency response. The objective of this study was to compare the response of two disposable clinical catheter systems: water-filled and air-charged, to controlled pressure signals to assess their similarities and differences in pressure transduction. We characterized frequency response using a transient step test, which exposed the catheters to a sudden change in pressure; and a sinusoidal frequency sweep test, which exposed the catheters to a sinusoidal pressure wave from 1 to 30 Hz. The response of the catheters to motion artifacts was tested using a vortex and the response to hydrostatic pressure changes was tested by moving the catheter tips to calibrated heights. Water-filled catheters acted as an underdamped system, resonating at 10.13 ± 1.03 Hz and attenuating signals at frequencies higher than 19 Hz. They demonstrated significant motion and hydrostatic artifacts. Air-charged catheters acted as an overdamped system and attenuated signals at frequencies higher than 3.02 ± 0.13 Hz. They demonstrated significantly less motion and hydrostatic artifacts than water-filled catheters. The transient step and frequency sweep tests gave comparable results. Air-charged and water-filled catheters respond to pressure changes in dramatically different ways. Knowledge of the characteristics of the pressure-measuring system is essential to finding the best match for a specific application. Copyright © 2011 Wiley-Liss, Inc.

Two-phase flow characterization based on advanced instrumentation, neural networks, and mathematical modeling

NASA Astrophysics Data System (ADS)

Mi, Ye

1998-12-01

The major objective of this thesis is focused on theoretical and experimental investigations of identifying and characterizing vertical and horizontal flow regimes in two-phase flows. A methodology of flow regime identification with impedance-based neural network systems and a comprehensive model of vertical slug flow have been developed. Vertical slug flow has been extensively investigated and characterized with geometric, kinematic and hydrodynamic parameters. A multi-sensor impedance void-meter and a multi-sensor magnetic flowmeter were developed. The impedance void-meter was cross-calibrated with other reliable techniques for void fraction measurements. The performance of the impedance void-meter to measure the void propagation velocity was evaluated by the drift flux model. It was proved that the magnetic flowmeter was applicable to vertical slug flow measurements. Separable signals from these instruments allow us to unearth most characteristics of vertical slug flow. A methodology of vertical flow regime identification was developed. Supervised neural network and self-organizing neural network systems were employed. First, they were trained with results from an idealized simulation of impedance in a two-phase mixture. The simulation was mainly based on Mishima and Ishii's flow regime map, the drift flux model, and the newly developed model of slug flow. Then, these trained systems were tested with impedance signals. The results showed that the neural network systems were appropriate classifiers of vertical flow regimes. The theoretical models and experimental databases used in the simulation were reliable. Furthermore, this approach was applied successfully to horizontal flow identification. A comprehensive model was developed to predict important characteristics of vertical slug flow. It was realized that the void fraction of the liquid slug is determined by the relative liquid motion between the Taylor bubble tail and the Taylor bubble wake. Relying on this understanding and experimental results, a special relationship was built for the void fraction of the liquid slug. The prediction of the void fraction of the liquid slug was considerably improved. Experimental characterization of vertical slug flows was performed extensively with the impedance void-meter and the magnetic flowmeter. The theoretical predictions were compared with the experimental results. The agreements between them are very satisfactory.

The study of voids in the AuAl thin-film system using the nuclear microprobe

NASA Astrophysics Data System (ADS)

de Waal, H. S.; Pretorius, R.; Prozesky, V. M.; Churms, C. L.

1997-07-01

A Nuclear Microprobe (NMP) was used to study void formation in thin film gold-aluminium systems. Microprobe Rutherford Backscattering Spectrometry (μRBS) was utilised to effectively obtain a three-dimensional picture of the void structure on the scale of a few nanometers in the depth dimension and a few microns in the in-plane dimension. This study illustrates the usefulness of the NMP in the study of materials and specifically thin-film structures.

Closeup oblique view of the forward and starboard sides of ...

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

Close-up oblique view of the forward and starboard sides of the Orbiter Discovery in the Vehicle Assembly Building at NASA's Kennedy Space Center. The view shows the void created by the removal of the Forward Reaction Control System Module. The void has a clear flexible covering to maintain positive pressure in the void to minimize foreign object contamination possibilities in the orbiter. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

Closeup view of the forward and starboard sides of the ...

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

Close-up view of the forward and starboard sides of the Orbiter Discovery in the Vehicle Assembly Building at NASA's Kennedy Space Center. The view shows the void created by the removal of the Forward Reaction Control System Module. The void has a clear flexible covering to maintain positive pressure in the void to minimize foreign object contamination possibilities in the orbiter. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

The Kirkendall and Frenkel effects during 2D diffusion process

NASA Astrophysics Data System (ADS)

Wierzba, Bartek

2014-11-01

The two-dimensional approach for inter-diffusion and voids generation is presented. The voids evolution and growth is discussed. This approach is based on the bi-velocity (Darken) method which combines the Darken and Brenner concepts that the volume velocity is essential in defining the local material velocity in multi-component mixture at non-equilibrium. The model is formulated for arbitrary multi-component two-dimensional systems. It is shown that the voids growth is due to the drift velocity and vacancy migration. The radius of the void can be easily estimated. The distributions of (1) components, (2) vacancy and (3) voids radius over the distance is presented.

Bubble Augmented Propulsor Mixture Flow Simulation near Choked Flow Condition

NASA Astrophysics Data System (ADS)

Choi, Jin-Keun; Hsiao, Chao-Tsung; Chahine, Georges

2013-03-01

The concept of waterjet thrust augmentation through bubble injection has been the subject of many patents and publications over the past several decades, and computational and experimental evidences of the augmentation of the jet thrust through bubble growth in the jet stream have been reported. Through our experimental studies, we have demonstrated net thrust augmentation as high as 70%for air volume fractions as high as 50%. However, in order to enable practical designs, an adequately validated modeling tool is required. In our previous numerical studies, we developed and validated a numerical code to simulate and predict the performance of a two-phase flow water jet propulsion system for low void fractions. In the present work, we extend the numerical method to handle higher void fractions to enable simulations for the high thrust augmentation conditions. At high void fractions, the speed of sound in the bubbly mixture decreases substantially and could be as low as 20 m/s, and the mixture velocity can approach the speed of sound in the medium. In this numerical study, we extend our numerical model, which is based on the two-way coupling between the mixture flow field and Lagrangian tracking of a large number of bubbles, to accommodate compressible flow regimes. Numerical methods used and the validation studies for various flow conditions in the bubble augmented propulsor will be presented. This work is supported by Office of Naval Research through contract N00014-11-C-0482 monitored by Dr. Ki-Han Kim.

Void fraction and velocity measurement of simulated bubble in a rotating disc using high frame rate neutron radiography.

PubMed

Saito, Y; Mishima, K; Matsubayashi, M

2004-10-01

To evaluate measurement error of local void fraction and velocity field in a gas-molten metal two-phase flow by high-frame-rate neutron radiography, experiments using a rotating stainless-steel disc, which has several holes of various diameters and depths simulating gas bubbles, were performed. Measured instantaneous void fraction and velocity field of the simulated bubbles were compared with the calculated values based on the rotating speed, the diameter and the depth of the holes as parameters and the measurement error was evaluated. The rotating speed was varied from 0 to 350 rpm (tangential velocity of the simulated bubbles from 0 to 1.5 m/s). The effect of shutter speed of the imaging system on the measurement error was also investigated. It was revealed from the Lagrangian time-averaged void fraction profile that the measurement error of the instantaneous void fraction depends mainly on the light-decay characteristics of the fluorescent converter. The measurement error of the instantaneous local void fraction of simulated bubbles is estimated to be 20%. In the present imaging system, the light-decay characteristics of the fluorescent converter affect the measurement remarkably, and so should be taken into account in estimating the measurement error of the local void fraction profile.

Optimizing laboratory mixture design as it relates to field compaction to improve asphalt mixture durability.

DOT National Transportation Integrated Search

2015-11-01

Most departments of transportation, including Indiana, currently use the Superpave mixture design method to design asphalt mixtures. : This method specifies that the optimum asphalt content for a given gradation be selected at 4 percent air voids. Du...

Evaluation of non-destructive technologies for construction quality control of HMA and PCC pavements in Louisiana : [tech summary].

DOT National Transportation Integrated Search

2013-11-01

Current roadway quality control and quality acceptance (QC/QA) procedures for the Louisiana Department of Transportation and Development : (LADOTD) include coring for thickness, density, and air voids in hot mix asphalt (HMA) pavements and thickness ...

Compaction and measurement of field density for Oregon open-graded (F-MIX) asphalt pavement

DOT National Transportation Integrated Search

1999-06-01

A research project conducted by Oregon State University (OSU) and the Oregon Department of Transportation (ODOT) investigated compaction of Oregon F-mix asphalt pavement, an open-graded mix with 25-mm maximum size aggregate and air voids typically in...

Implementation of ASTM C157: testing of length change of hardened concrete : technical summary.

DOT National Transportation Integrated Search

2016-09-01

The Kansas Department of Transportation (KDOT) has a history of using : tests such as concrete strength, permeability, and air void structure as design : and acceptance criteria on concrete paving and bridge deck projects. In 2012, : the KDOT Concret...

The cosmic web in CosmoGrid void regions

NASA Astrophysics Data System (ADS)

Rieder, Steven; van de Weygaert, Rien; Cautun, Marius; Beygu, Burcu; Portegies Zwart, Simon

2016-10-01

We study the formation and evolution of the cosmic web, using the high-resolution CosmoGrid ΛCDM simulation. In particular, we investigate the evolution of the large-scale structure around void halo groups, and compare this to observations of the VGS-31 galaxy group, which consists of three interacting galaxies inside a large void. The structure around such haloes shows a great deal of tenuous structure, with most of such systems being embedded in intra-void filaments and walls. We use the Nexus+} algorithm to detect walls and filaments in CosmoGrid, and find them to be present and detectable at every scale. The void regions embed tenuous walls, which in turn embed tenuous filaments. We hypothesize that the void galaxy group of VGS-31 formed in such an environment.

Practical aerobic oxidations of alcohols and amines with homogeneous copper/TEMPO and related catalyst systems.

PubMed

Ryland, Bradford L; Stahl, Shannon S

2014-08-18

Oxidations of alcohols and amines are common reactions in the synthesis of organic molecules in the laboratory and industry. Aerobic oxidation methods have long been sought for these transformations, but few practical methods exist that offer advantages over traditional oxidation methods. Recently developed homogeneous Cu/TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidinyl-N-oxyl) and related catalyst systems appear to fill this void. The reactions exhibit high levels of chemoselectivity and broad functional-group tolerance, and they often operate efficiently at room temperature with ambient air as the oxidant. These advances, together with their historical context and recent applications, are highlighted in this Minireview. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Improving adsorption cryocoolers by multi-stage compression and reducing void volume

NASA Technical Reports Server (NTRS)

Bard, S.

1986-01-01

It is shown that the performance of gas adsorption cryocoolers is greatly improved by using adsorbents with low void volume within and between individual adsorbent particles (reducing void volumes in plumbing lines), and by compressing the working fluid in more than one stage. Refrigerator specific power requirements and compressor volumetric efficiencies are obtained in terms of adsorbent and plumbing line void volumes and operating pressures for various charcoal adsorbents using an analytical model. Performance optimization curves for 117.5 and 80 K charcoal/nitrogen adsorption cryocoolers are given for both single stage and multistage compressor systems, and compressing the nitrogen in two stages is shown to lower the specific power requirements by 18 percent for the 117.5 K system.

Materials characterization of free volume and void properties by two-dimensional positron annihilation lifetime spectroscopy

NASA Astrophysics Data System (ADS)

Chen, Hongmin; Van Horn, J. David; Jean, Y. C.; Hung, Wei-Song; Lee, Kueir-Rarn

2013-04-01

Positron annihilation lifetime spectroscopy (PALS) has been widely used to determine the free volume and void properties in polymeric materials. Recently, a two dimensional positron annihilation lifetime spectroscopy (2DPALS) system has been developed for membrane applications. The system measures the coincident signals between the lifetime and the energy which could separate the 2γ and 3γ annihilations and improve the accuracy in the determination of the free volume and void properties. When 2D-PALS is used in coupling with a variable mono-energy slow positron beam, it could be applied to a variety of material characterization. Results of free volumes and voids properties in a multi-layer polymer membrane characterized using 2D-PALS are presented.

Autonomous selection of PDE inpainting techniques vs. exemplar inpainting techniques for void fill of high resolution digital surface models

NASA Astrophysics Data System (ADS)

Rahmes, Mark; Yates, J. Harlan; Allen, Josef DeVaughn; Kelley, Patrick

2007-04-01

High resolution Digital Surface Models (DSMs) may contain voids (missing data) due to the data collection process used to obtain the DSM, inclement weather conditions, low returns, system errors/malfunctions for various collection platforms, and other factors. DSM voids are also created during bare earth processing where culture and vegetation features have been extracted. The Harris LiteSite TM Toolkit handles these void regions in DSMs via two novel techniques. We use both partial differential equations (PDEs) and exemplar based inpainting techniques to accurately fill voids. The PDE technique has its origin in fluid dynamics and heat equations (a particular subset of partial differential equations). The exemplar technique has its origin in texture analysis and image processing. Each technique is optimally suited for different input conditions. The PDE technique works better where the area to be void filled does not have disproportionately high frequency data in the neighborhood of the boundary of the void. Conversely, the exemplar based technique is better suited for high frequency areas. Both are autonomous with respect to detecting and repairing void regions. We describe a cohesive autonomous solution that dynamically selects the best technique as each void is being repaired.

Evaluation of non-destructive technologies for construction quality control of HMA and PCC pavements in Louisiana : [research project capsule].

DOT National Transportation Integrated Search

2009-07-01

Current roadway quality control and quality acceptance (QC/QA) procedures : for Louisiana include coring for thickness, density, and air void checks in hot : mix asphalt (HMA) pavements and thickness and compressive strength for : Portland cement con...

40 CFR 85.2217 - Loaded test-EPA 91.

Code of Federal Regulations, 2010 CFR

2010-07-01

....2217 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED... determinations is a simple running average of the measurements taken over five seconds. (2) Pass/fail... measurements are voided if the measured concentration of CO plus CO2 falls below six percent or the vehicle's...

Impact of Various Compaction Equipment on Hot-Mix Asphalt (HMA) Design in Ohio.

DOT National Transportation Integrated Search

1998-09-01

The study was initiated to examine the effect of different laboratory compaction devices on density, air voids, and optimum asphalt binder content for mixes designed for heavy volume traffic that are currently used in Ohio. A total of six and twelve ...

Development of a 4.75-mm (No. 4) NMS mixture : research project capsule.

DOT National Transportation Integrated Search

2017-08-01

The objective of this project is to develop a 4.75-mm NMAS asphalt mixture for Louisiana roads, which will involve establishing target criteria for aggregate gradations, volumetric properties (e.g., air voids, VMA, VFA, and dust-to-binder ratio) and ...

Newtonian self-gravitating system in a relativistic huge void universe model

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

Nishikawa, Ryusuke; Nakao, Ken-ichi; Yoo, Chul-Moon, E-mail: ryusuke@sci.osaka-cu.ac.jp, E-mail: knakao@sci.osaka-cu.ac.jp, E-mail: yoo@gravity.phys.nagoya-u.ac.jp

We consider a test of the Copernican Principle through observations of the large-scale structures, and for this purpose we study the self-gravitating system in a relativistic huge void universe model which does not invoke the Copernican Principle. If we focus on the the weakly self-gravitating and slowly evolving system whose spatial extent is much smaller than the scale of the cosmological horizon in the homogeneous and isotropic background universe model, the cosmological Newtonian approximation is available. Also in the huge void universe model, the same kind of approximation as the cosmological Newtonian approximation is available for the analysis of themore » perturbations contained in a region whose spatial size is much smaller than the scale of the huge void: the effects of the huge void are taken into account in a perturbative manner by using the Fermi-normal coordinates. By using this approximation, we derive the equations of motion for the weakly self-gravitating perturbations whose elements have relative velocities much smaller than the speed of light, and show the derived equations can be significantly different from those in the homogeneous and isotropic universe model, due to the anisotropic volume expansion in the huge void. We linearize the derived equations of motion and solve them. The solutions show that the behaviors of linear density perturbations are very different from those in the homogeneous and isotropic universe model.« less

Remote sensing of land-based voids using computer enhanced infrared thermography

NASA Astrophysics Data System (ADS)

Weil, Gary J.

1989-10-01

Experiments are described in which computer-enhanced infrared thermography techniques are used to detect and describe subsurface land-based voids, such as voids surrounding buried utility pipes, voids in concrete structures such as airport taxiways, abandoned buried utility storage tanks, and caves and underground shelters. Infrared thermography also helps to evaluate bridge deck systems, highway pavements, and garage concrete. The IR thermography techniques make it possible to survey large areas quickly and efficiently. The paper also surveys the advantages and limitations of thermographic testing in comparison with other forms of NDT.

Maintaining Low Voiding Solder Die Attach for Power Die While Minimizing Die Tilt

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

Hamm, Randy; Peterson, Kenneth A.

2015-10-01

This paper addresses work to minimize voiding and die tilt in solder attachment of a large power die, measuring 9.0 mm X 6.5 mm X 0.1 mm (0.354” x 0.256” x 0.004”), to a heat spreader. As demands for larger high power die continue, minimizing voiding and die tilt is of interest for improved die functionality, yield, manufacturability, and reliability. High-power die generate considerable heat, which is important to dissipate effectively through control of voiding under high thermal load areas of the die while maintaining a consistent bondline (minimizing die tilt). Voiding was measured using acoustic imaging and die tiltmore » was measured using two different optical measurement systems. 80Au-20Sn solder reflow was achieved using a batch vacuum solder system with optimized fixturing. Minimizing die tilt proved to be the more difficult of the two product requirements to meet. Process development variables included tooling, weight and solder preform thickness.« less

Oil field management system

DOEpatents

Fincke, James R.

2003-09-23

Oil field management systems and methods for managing operation of one or more wells producing a high void fraction multiphase flow. The system includes a differential pressure flow meter which samples pressure readings at various points of interest throughout the system and uses pressure differentials derived from the pressure readings to determine gas and liquid phase mass flow rates of the high void fraction multiphase flow. One or both of the gas and liquid phase mass flow rates are then compared with predetermined criteria. In the event such mass flow rates satisfy the predetermined criteria, a well control system implements a correlating adjustment action respecting the multiphase flow. In this way, various parameters regarding the high void fraction multiphase flow are used as control inputs to the well control system and thus facilitate management of well operations.

Spatial development of transport structures in apple (Malus × domestica Borkh.) fruit

PubMed Central

Herremans, Els; Verboven, Pieter; Hertog, Maarten L. A. T. M.; Cantre, Dennis; van Dael, Mattias; De Schryver, Thomas; Van Hoorebeke, Luc; Nicolaï, Bart M.

2015-01-01

The void network and vascular system are important pathways for the transport of gases, water and solutes in apple fruit (Malus × domestica Borkh). Here we used X-ray micro-tomography at various spatial resolutions to investigate the growth of these transport structures in 3D during fruit development of “Jonagold” apple. The size of the void space and porosity in the cortex tissue increased considerably. In the core tissue, the porosity was consistently lower, and seemed to decrease toward the end of the maturation period. The voids in the core were more narrow and fragmented than the voids in the cortex. Both the void network in the core and in the cortex changed significantly in terms of void morphology. An automated segmentation protocol underestimated the total vasculature length by 9–12% in comparison to manually processed images. Vascular networks increased in length from a total of 5 m at 9 weeks after full bloom, to more than 20 m corresponding to 5 cm of vascular tissue per cubic centimeter of apple tissue. A high degree of branching in both the void network and vascular system and a complex three-dimensional pattern was observed across the whole fruit. The 3D visualizations of the transport structures may be useful for numerical modeling of organ growth and transport processes in fruit. PMID:26388883

Detection of underground voids in Ohio by use of geophysical methods

USGS Publications Warehouse

Munk, Jens; Sheets, R.A.

1997-01-01

Geophysical methods are generally classified as electrical, potential field, and seismic methods. Each method type relies on contrasts of physical properties in the subsurface. Forward models based on the physical properties of air- and water-filled voids within common geologic materials indicate that several geophysical methods are technically feasible for detection of subsurface voids in Ohio, but ease of use and interpretation varies widely between the methods. Ground-penetrating radar is the most rapid and cost-effective method for collection of subsurface data in areas associated with voids under roadways. Electrical resistivity, gravity, or seismic reflection methods have applications for direct delineation of voids, but data-collection and analytical procedures are more time consuming. Electrical resistivity, electromagnetic, or magnetic methods may be useful in locating areas where conductive material, such as rail lines, are present in abandoned underground coal mines. Other electrical methods include spontaneous potential and very low frequency (VLF); these latter two methods are considered unlikely candidates for locating underground voids in Ohio. Results of ground-penetrating radar surveys at three highway sites indicate that subsurface penetration varies widely with geologic material type and amount of cultural interference. Two highway sites were chosen over abandoned underground coal mines in eastern Ohio. A third site in western Ohio was chosen in an area known to be underlain by naturally occurring voids in lime stone. Ground-penetrating radar surveys at Interstate 470, in Belmont County, Ohio, indicate subsurface penetration of less than 15 feet over a mined coal seam that was known to vary in depth from 0 to 40 feet. Although no direct observations of voids were made, anomalous areas that may be related to collapse structures above voids were indicated. Cultural interference dominated the radar records at Interstate 70, Guernsey County, Ohio, where coal was mined under the site at a depth of about 50 feet. Interference from overhead powerlines, the field vehicle, and guardrails complicated an interpretation of the radar records where the depth of penetration was estimated to be less than 5 feet. Along State Route 33, in Logan County, Ohio, bedding planes and structures possibly associated with dissolution of limestone were profiled with ground-penetrating radar. Depth of penetration was estimated to be greater than 50 feet.

Demonstration and implementation recommendations to integrate the United States Road Assessment Program into existing Kansas highway safety programs : technical summary.

DOT National Transportation Integrated Search

2016-09-01

The Kansas Department of Transportation (KDOT) has a history of using : tests such as concrete strength, permeability, and air void structure as design : and acceptance criteria on concrete paving and bridge deck projects. In 2012, : the KDOT Concret...

Void Growth and Coalescence in Dynamic Fracture of FCC and BCC Metals - Molecular Dynamics Study

NASA Astrophysics Data System (ADS)

Seppälä, Eira

2004-03-01

In dynamic fracture of ductile metals, the state of tension causes the nucleation of voids, typically from inclusions or grain boundary junctions, which grow and ultimately coalesce to form the fracture surface. Significant plastic deformation occurs in the process, including dislocations emitted to accommodate the growing voids. We have studied at the atomistic scale growth and coalescence processes of voids with concomitant dislocation formation. Classical molecular dynamics (MD) simulations of one and two pre-existing spherical voids initially a few nanometers in radius have been performed in single-crystal face-centered-cubic (FCC) and body-centered-cubic (BCC) lattices under dilational strain with high strain-rates. Million atom simulations of single void growth have been done to study the effect of stress triaxiality,^1 along with strain rate and lattice-structure dependence. An interesting prolate-to-oblate transition in the void shape in uniaxial expansion has been observed and quantitatively analyzed. The simulations also confirm that the plastic strain results directly from the void growth. Interaction and coalescence between two voids have been studied utilizing a parallel MD code in a seven million atom system. In particular, the movement of centers of the voids, linking of the voids, and the shape changes in vicinity of the other void are studied. Also the critical intervoid ligament distance after which the voids can be treated independently has been searched. ^1 E. T. Seppälä, J. Belak, and R. E. Rudd, cond-mat/0310541, submitted to Phys. Rev. B. Acknowledgment: This work was done in collaboration with Dr. James Belak and Dr. Robert E. Rudd, LLNL. It was performed under the auspices of the US Dept. of Energy at the Univ. of Cal./Lawrence Livermore National Laboratory under contract no. W-7405-Eng-48.

Tapioca starch graft copolymers and Dome Matrix® modules II. Effect of modules assemblage on riboflavin release kinetics.

PubMed

Casas, Marta; Strusi, Orazio Luca; Jiménez-Castellanos, M Rosa; Colombo, Paolo

2011-01-01

This paper studies the Riboflavin release from systems made of assembled modules of Dome Matrix® technology using tapioca starch-ethylmethacrylate (TSEMA) and tapioca hydroxypropylstarch-ethylmethacrylate (THSEMA) graft copolymers produced by two different drying methods. Two different shape modules were manufactured for this study, i.e., female and male modules, in order to facilitate their assemblage in "void configuration", a system with an internal void space. Drug release studies on void configurations based on THSEMA show faster releases than TSEMA; HPMC systems used as a comparative reference showed intermediate release. Moreover, using void configurations made with one module of TSEMA and the other of THSEMA is possible to average the drug release, without difference between the drying methods used for the polymers. With respect to the floatation characteristics, all the void configurations floated immediately and, due to the mass center of the system, the floatation position of the system was always axial with the female module up and the male down. The drug release studies performed with a sinker to force the immersion of the systems in the medium did not show differences with respect to the dissolution test without a sinker. The combination of floatation capability of the assembled modules and the prolonged drug release provided with the graft copolymers make these assembled modules candidates as controlled release gastro-retentive dosage forms. Copyright © 2010 Elsevier B.V. All rights reserved.

Fracture Toughness Properties of Gd123 Superconducting Bulks

NASA Astrophysics Data System (ADS)

Fujimoto, H.; Murakami, A.

Fracture toughness properties of melt growth GdBa2Cu3Ox (Gd123) large single domain superconducting bulks with Ag2O of 10 wt% and Pt of 0.5 wt%; 45 mm in diameter and 25 mm in thickness with low void density were evaluated at 77 K through flexural tests of specimens cut from the bulks, and compared to those of a conventional Gd123 with voids. The densified Gd123 bulks were prepared with a seeding and temperature gradient method; first melt processed in oxygen, then crystal growth in air; two-step regulated atmosphere heat treatment. The plane strain fracture toughness, KIC was obtained by the three point flexure test of the specimens with through precrack, referring to the single edge pre-cracked beam (SEPB) method, according to the JIS-R-1607, Testing Methods for Fracture Toughness of High Performance Ceramics. The results show that the fracture toughness of the densified Gd123 bulk with low void density was higher than that of the standard Gd123 bulk with voids, as well as the flexural strength previously reported. We also compared the fracture toughness of as-grown bulks with that of annealed bulks. The relation between the microstructure and the fracture toughness of the Gd123 bulk was clearly shown.

Comprehensive Understanding of Ductility Loss Mechanisms in Various Steels with External and Internal Hydrogen

NASA Astrophysics Data System (ADS)

Takakuwa, Osamu; Yamabe, Junichiro; Matsunaga, Hisao; Furuya, Yoshiyuki; Matsuoka, Saburo

2017-11-01

Hydrogen-induced ductility loss and related fracture morphologies are comprehensively discussed in consideration of the hydrogen distribution in a specimen with external and internal hydrogen by using 300-series austenitic stainless steels (Types 304, 316, 316L), high-strength austenitic stainless steels (HP160, XM-19), precipitation-hardened iron-based super alloy (A286), low-alloy Cr-Mo steel (JIS-SCM435), and low-carbon steel (JIS-SM490B). External hydrogen is realized by a non-charged specimen tested in high-pressure gaseous hydrogen, and internal hydrogen is realized by a hydrogen-charged specimen tested in air or inert gas. Fracture morphologies obtained by slow-strain-rate tensile tests (SSRT) of the materials with external or internal hydrogen could be comprehensively categorized into five types: hydrogen-induced successive crack growth, ordinary void formation, small-sized void formation related to the void sheet, large-sized void formation, and facet formation. The mechanisms of hydrogen embrittlement are broadly classified into hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP). In the HEDE model, hydrogen weakens interatomic bonds, whereas in the HELP model, hydrogen enhances localized slip deformations. Although various fracture morphologies are produced by external or internal hydrogen, these morphologies can be explained by the HELP model rather than by the HEDE model.

Sulfur Impurities and the Microstructure of Alumina Scales

NASA Technical Reports Server (NTRS)

Smialek, James L.

1997-01-01

The relationship between the microstructure of alumina scales, adhesion, and sulfur content was examined through a series of nickel alloys oxidized in 1100 to 1200 deg. C cyclic or isothermal exposures in air. In cyclic tests of undoped NiCrAl, adhesion was produced when the sulfur content was reduced, without any change in scale microstructure. Although interfacial voids were not observed in cyclic tests of NiCrAl, they were promoted by long-term isothermal exposures, by sulfur doping, and in most exposures of NiAl. Two single crystal superalloys, PWA 1480 and Rene' N5, were also tested, either in the as-received condition or after the sulfur content had been reduced to less than 1 ppmw by hydrogen annealing. The unannealed alloys always exhibited spalling to bare metal, but interfacial voids were not observed consistently. Desulfurized PWA 1480 and Rene' N5 exhibited remarkable adhesion and no voidage for either isothermal or cyclic exposures. The most consistent microstructural feature was that, for the cases where voids did form, the scale undersides exhibited corresponding areas with ridged oxide grain boundaries. Voids were not required for spallation nor were other microstructural features essential for adhesion. These observations are consistent with the model whereby scale spallation is controlled primarily by interfacial sulfur segregation and the consequent degradation of oxide-metal bonding.

Reactivity effects of moderator voids

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

Ahlfeld, C.E.; Pryor, R.J.

1975-01-01

Reactivity worths for large moderator voids similar to those produced by steaming in postulated reactor transients were measured in the Process Development Pile (PDP) reactor. The experimental results were compared to the computed void worths obtained from techniques currently used in routine safety analyses. Neutron energy spectrum measurements were used to verify a modified lattice pattern that correctly computed the measured spectrum, and consequently, improved macroscopic cross sections. In addition, a special two-dimensional transport calculation was performed to obtain an axially defined diffusion coefficient for the void region. The combination of the modified lattice calculations and the axial diffusion coefficientmore » yielded void reactivity worths which agreed very well with experiment. It was concluded that the computational modules available in the JOSHUA system (GLASS, GRIMHX) would yield accurate void reactivity worths in SLR--SRP safety analysis studies, provided the above mentioned modifications were made.« less

Quantifying Void Ratio in Granular Materials Using Voronoi Tessellation

NASA Technical Reports Server (NTRS)

Alshibli, Khalid A.; El-Saidany, Hany A.; Rose, M. Franklin (Technical Monitor)

2000-01-01

Voronoi technique was used to calculate the local void ratio distribution of granular materials. It was implemented in an application-oriented image processing and analysis algorithm capable of extracting object edges, separating adjacent particles, obtaining the centroid of each particle, generating Voronoi polygons, and calculating the local void ratio. Details of the algorithm capabilities and features are presented. Verification calculations included performing manual digitization of synthetic images using Oda's method and Voronoi polygon system. The developed algorithm yielded very accurate measurements of the local void ratio distribution. Voronoi tessellation has the advantage, compared to Oda's method, of offering a well-defined polygon generation criterion that can be implemented in an algorithm to automatically calculate local void ratio of particulate materials.

Nondestructive Evaluation of Foam Insulation on the Space Shuttle External Tank

NASA Technical Reports Server (NTRS)

Richter, Joel; Walker, James L.

2006-01-01

Foam loss on the External Tank (ET) during launch can be caused by a number of factors. Voids are the best understood mechanism of foam loss, although it is known that delaminations, cracks and crushed foam can also lead to liberation of foam. Shortly after the Columbia accident, work began on non-destructive evaluation of foam targeted at finding voids and delaminations. After several months of searching for candidate methods capable of inspecting ET foam, the five most promising techniques were taken through a blind test and narrowed down to two methods to develop and use for inspection of the ET. These methods were backscatter radiography and terahertz imaging. The backscatter radiography system measures a test part by detecting Compton backscattered x-ray energy generated by a collimated beam of x-rays directed at the test subject. This collimated beam is scanned across the subject, recording scatter intensity data one pixel at a time until the area of interest is covered. The resulting data can be used to generate an image similar to a radiograph. Some depth information can be gathered utilizing apertures or collimation on the detectors. The detectors are located around the collimated source, making this a single sided inspection. The void detection limit with the currently utilized system is around 0.5 inches in diameter by 0.2 inches high. The terahertz imaging system inspects a test part by utilizing a transceiver to emit a pulse focused at the aluminum skin of the ET, which reflects it back to the transceiver where it is analyzed. The transceiver is scanned across the area of interest until a measurement has been taken at every location. Amplitude, time delay and frequency content are examined to note any discontinuities which may be the result of a void or other type of defect. The pulse currently utilized is in the millimeter wave regime. The void detection limit with this system is around 0.5 inches in diameter by 0.2 inches high. With increased interest in other causes of foam loss following the flight of Discovery in July 2005, laser shearography was added to the techniques used for inspecting ET foam. The shearography method records a sheared image of a laser speckle pattern projected on a test part before And after some sort of excitation. The resultant fringe pattern allows the slope of the out of plane displacement to be measured. For crushed and delaminated foam applications, a non-contact air coupled acoustic force is used to excite the surface of the foam. Regions without defects tend to respond differently to the sound energy than do regions with defects, generating a map of the foam integrity. Foam crushed to a depth of about 0.1 inches is detectable with shearography even after it has relaxed to its original shape.

An investigation of voids formation mechanisms and their effects on freeze and thaw processes of lithium and lithium fluoride

NASA Technical Reports Server (NTRS)

El-Genk, Mohamed S.; Yang, Jae-Young

1991-01-01

The mechanisms of void formation during the cooldown and freezing of lithium coolant within the primary loop of SP-100 type systems are investigated. These mechanisms are: (1) homogeneous nucleation; (2) heterogeneous nucleation; (3) normal segregation of helium gas dissolved in liquid lithium; and (4) shrinkage of lithium during freezing. To evaluate the void formation potential due to segregation, a numerical scheme that couples the freezing and mass diffusion processes in both the solid and liquid regions is developed. The results indicated that the formation of He bubbles is unlikely by either homogeneous or heterogeneous nucleation during the cooldown process. However, homogeneous nucleation of He bubbles following the segregation of dissolved He in liquid lithium ahead of the solid-liquid interface is likely to occur. Results also show that total volume of He void is insignificant when compared to that of shrinkage voids. In viewing this, the subsequent research focuses on the effects of shrinkage void forming during freezing of lithium on subsequent thaw processes are investigated using a numerical scheme that is based on a single (solid/liquid) cell approach. The cases of lithium-fluoride are also investigated to show the effect of larger volume shrinkage upon freezing on the freeze and thaw processes. Results show that a void forming at the wall appreciably reduces the solid-liquid interface velocity, during both freeze and thaw, and causes a substantial rise in the wall temperature during thaw. However, in the case of Li, the maximum wall temperature was much lower than the melting temperature of PWC-11, which is used as the structure material in the SP-100 system. Hence, it is included that a formation of hot spots is unlikely during the startup or restart of the SP-100 system.

Force measurement-based discontinuity detection during friction stir welding

DOE PAGES

Shrivastava, Amber; Zinn, Michael; Duffie, Neil A.; ...

2017-02-23

Here, the objective of this work is to develop a method for detecting the creation of discontinuities ( i.e., voids, volume defects) during friction stir welding. Friction stir welding is inherently cost effective, however, the need for significant weld inspection can make the process cost prohibitive. A new approach to weld inspection is required in which an in situ characterization of weld quality can be obtained, reducing the need for postprocess inspection. To this end, friction stir welds with subsurface voids and without voids were created. The subsurface voids were generated by reducing the friction stir tool rotation frequency andmore » increasing the tool traverse speed in order to create “colder” welds. Process forces were measured during welding, and the void sizes were measured postprocess by computerized tomography ( i.e., 3D X-ray imaging). Two parameters, based on frequency domain content and time-domain average of the force signals, were found to be correlated with void size. Criteria for subsurface void detection and size prediction were developed and shown to be in good agreement with experimental observations. Furthermore, with the proper choice of data acquisition system and frequency analyzer the occurrence of subsurface voids can be detected in real time.« less

Force measurement-based discontinuity detection during friction stir welding

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

Shrivastava, Amber; Zinn, Michael; Duffie, Neil A.

Here, the objective of this work is to develop a method for detecting the creation of discontinuities ( i.e., voids, volume defects) during friction stir welding. Friction stir welding is inherently cost effective, however, the need for significant weld inspection can make the process cost prohibitive. A new approach to weld inspection is required in which an in situ characterization of weld quality can be obtained, reducing the need for postprocess inspection. To this end, friction stir welds with subsurface voids and without voids were created. The subsurface voids were generated by reducing the friction stir tool rotation frequency andmore » increasing the tool traverse speed in order to create “colder” welds. Process forces were measured during welding, and the void sizes were measured postprocess by computerized tomography ( i.e., 3D X-ray imaging). Two parameters, based on frequency domain content and time-domain average of the force signals, were found to be correlated with void size. Criteria for subsurface void detection and size prediction were developed and shown to be in good agreement with experimental observations. Furthermore, with the proper choice of data acquisition system and frequency analyzer the occurrence of subsurface voids can be detected in real time.« less

Evaluation of permafrost conditions in non-alpine scree slopes in Central Europe by geophysical methods

NASA Astrophysics Data System (ADS)

Gude, M.; Hauck, C.; Kneisel, C.; Krause, S.; Molenda, R.; Ruzicka, V.; Zacharda, M.

2003-04-01

Many slope sections covered with blocky material situated in Central European highlands display special microclimatic conditions that resemble those of high latitude or high altitude periglacial areas. In some of these screes even permafrost-like conditions are detected although they are located on elevations fairly below 1000 m a.s.l. These conditions are accompanied by a circulation of air through the open void system, which effects a formation of an ice body during winter by re-sublimation of air humidity, supported by refreezing water from snow melt and precipitation. This ice body is assumed to prevail during the entire summer. Population genetic investigations on alpine and polar beetle species that inhabit the screes proof the continuous existence of the extraordinary cool conditions with probable permafrost throughout the Holocene - i.e. these periglacial-like condition are relatively stable despite all Holocene climatic variations. Observations of summer ice and numerous temperature measurements lead to the assumption of permafrost with enduring ice in the open voids as an integral factor of the microclimatic system. To evaluate its existence the underground was investigated in seven European screes by means of DC resistivity and refraction seismic in early summer. In order to solve the multi-phase subsurface structures, tomographic survey and inversion techniques are necessary, as 1-dimensional plane layer approximations are usually invalid. The results clearly reveal seismic and resistivity anomalies e.g. in the Klic scree (50°49'N, 14°04'E, base at 524 m a.s.l.) in Northern Bohemia. Within a blocky layer of about 10 m high thickness velocity anomalies (2000-3000 m/s) indicate the existence of a small ground ice body, which is confirmed by the synchronous detection of resistivity anomalies in the same place. These conditions are confined to steep scree slopes in regions with thin winter snow cover to enable air circulation. It is probable, that these effects are also found in alpine regions, where they cause a significant depression of the current lower permafrost limit.

Development of an In-line Urine Monitoring System for the International Space Station

NASA Technical Reports Server (NTRS)

Broyan, James Lee, Jr.; Cibuzar, Branelle R.

2009-01-01

Exposure to microgravity during space flight causes bone loss when calcium and other metabolic by-products are excreted in urine voids. Frequent and accurate measurement of urine void volume and constituents is thus essential in determining crew bone loss and the effectiveness of the countermeasures that are taken to minimize this loss. Earlier space shuttle Urine Monitoring System (UMS) technology was unable to accurately measure urine void volumes due to the cross-contamination that took place between users, as well as to fluid system instabilities. Crew urine voids are currently collected manually in a flexible plastic bag that contains a known tracer quantity. A crew member must completely mix the contents of this bag before withdrawing a representative syringe sample for later ground analysis. The existing bag system accuracy is therefore highly dependent on mixing technique. The International Space Station (ISS) UMS has been developed as an automated device that collects urine from the Waste and Hygiene Compartment (WHC) urinal funnel interface, separates the urine, measures void volume, and allows for syringe sampling. After the ISS UMS has been used by a crew member, it delivers urine to the WHC for normal processing. The UMS plumbing is then flushed with a small volume of water. The current ISS UMS design incorporates an innovative rotary separator that minimizes foaming, consequently greatly reducing cross-contamination among urine voids (less than 0.5 mL urine) while also providing accurate volume measurements (less than 2 percent error for 100 to 1,000 mL void volumes). ISS UMS performance has been validated through extensive ground tests and reduced-gravity aircraft flights. The locker-sized ISS UMS is currently undergoing a design modification that will permit it to interface with the ISS Node 3 WHC Russian toilet (ACY) hardware. The operating principles, characteristics, and results of this design modification are outlined here.

Lidar point density analysis: implications for identifying water bodies

USGS Publications Warehouse

Worstell, Bruce B.; Poppenga, Sandra K.; Evans, Gayla A.; Prince, Sandra

2014-01-01

Most airborne topographic light detection and ranging (lidar) systems operate within the near-infrared spectrum. Laser pulses from these systems frequently are absorbed by water and therefore do not generate reflected returns on water bodies in the resulting void regions within the lidar point cloud. Thus, an analysis of lidar voids has implications for identifying water bodies. Data analysis techniques to detect reduced lidar return densities were evaluated for test sites in Blackhawk County, Iowa, and Beltrami County, Minnesota, to delineate contiguous areas that have few or no lidar returns. Results from this study indicated a 5-meter radius moving window with fewer than 23 returns (28 percent of the moving window) was sufficient for delineating void regions. Techniques to provide elevation values for void regions to flatten water features and to force channel flow in the downstream direction also are presented.

Flow void of cerebrospinal fluid in idiopathic normal pressure hydrocephalus of the elderly: can it predict outcome after shunting?

PubMed

Krauss, J K; Regel, J P; Vach, W; Jüngling, F D; Droste, D W; Wakhloo, A K

1997-01-01

We investigate the predictive value of cerebrospinal fluid (CSF) flow void on outcome after shunting in a prospective series of patients with idiopathic normal pressure hydrocephalus (NPH). The degree and extension of CSF flow void were examined on T2-weighted magnetic resonance imaging scans of 37 elderly patients with idiopathic NPH who underwent subsequent shunting. The degree of flow void was assessed in comparison with the signal of large cerebral arteries. The extension was evaluated via the calculation of sum scores for the occurrence of flow void in different locations of the ventricular system. Those parameters were not considered in the decision to perform shunting. CSF flow void in the aqueduct and the adjacent third and fourth ventricles of the 37 patients with idiopathic NPH was compared with that of 37 age-matched control patients. CSF flow void scores in patients with idiopathic NPH were investigated for correlations between postoperative outcome scores and ventricular width indices. No difference was found between the occurrence of aqueductal CSF flow void in patients with idiopathic NPH and the control group. A significant difference, however, was noted for the extension of the CSF flow void, which was greater in the NPH group. Postoperative improvement was found in 33 of 37 patients with idiopathic NPH at a mean follow-up of 15.6 months. Only small, statistically not significant correlations were found between CSF flow void and postoperative outcome. Flow void sum scores, however, correlated significantly with ventricular width indices. The degree and extension of CSF flow void on T2-weighted magnetic resonance imaging scans have little predictive value for outcome after shunting in patients with idiopathic NPH. The greater extension of the CSF flow void in patients with NPH is most likely related to increased ventricular width. It is not useful to consider CSF flow void findings on conventional magnetic resonance imaging scans in making the decision to offer shunting in patients with idiopathic NPH.

Eddy-Current Inspection of Ball Bearings

NASA Technical Reports Server (NTRS)

Bankston, B.

1985-01-01

Custom eddy-current probe locates surface anomalies. Low friction air cushion within cone allows ball to roll easily. Eddy current probe reliably detects surface and near-surface cracks, voids, and material anomalies in bearing balls or other spherical objects. Defects in ball surface detected by probe displayed on CRT and recorded on strip-chart recorder.

Industrial waste utilization for foam concrete

NASA Astrophysics Data System (ADS)

Krishnan, Gokul; Anand, K. B.

2018-02-01

Foam concrete is an emerging and useful construction material - basically a cement based slurry with at least 10% of mix volume as foam. The mix usually containing cement, filler (usually sand) and foam, have fresh densities ranging from 400kg/m3 to 1600kg/m3. One of the main drawbacks of foam concrete is the large consumption of fine sand as filler material. Usage of different solid industrial wastes as fillers in foam concrete can reduce the usage of fine river sand significantly and make the work economic and eco-friendly. This paper aims to investigate to what extent industrial wastes such as bottom ash and quarry dust can be utilized for making foam concrete. Foam generated using protein based agent was used for preparing and optimizing (fresh state properties). Investigation to find the influence of design density and air-void characteristics on the foam concrete strength shows higher strength for bottom ash mixes due to finer air void distribution. Setting characteristics of various mix compositions are also studied and adoption of Class C flyash as filler demonstrated capability of faster setting.

Velocity and void distribution in a counter-current two-phase flow

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

Gabriel, S.; Schulenberg, T.; Laurien, E.

2012-07-01

Different flow regimes were investigated in a horizontal channel. Simulating a hot leg injection in case of a loss of coolant accident or flow conditions in reflux condenser mode, the hydraulic jump and partially reversed flow were identified as major constraints for a high amount of entrained water. Trying to simulate the reflux condenser mode, the test section now includes an inclined section connected to a horizontal channel. The channel is 90 mm high and 110 mm wide. Tests were carried out for water and air at ambient pressure and temperature. High speed video-metry was applied to obtain velocities frommore » flow pattern maps of the rising and falling fluid. In the horizontal part of the channel with partially reversed flow the fluid velocities were measured by planar particle image velocimetry. To obtain reliable results for the gaseous phase, this analysis was extended by endoscope measurements. Additionally, a new method based on the optical refraction at the interface between air and water in a back-light was used to obtain time-averaged void fraction. (authors)« less

Freeze-thaw durability of microwave cured air-entrained concrete

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

Pheeraphan, T.; Leung, C.K.Y.

1997-03-01

The strength development of concrete can be greatly accelerated by curing with microwave energy. Microwave curing can therefore be beneficial to construction operations such as concrete precasting and repair. To provide freeze-thaw durability for infrastructure applications, air entrainment has to be introduced. In this investigation, the freeze-thaw resistance of microwave cured air-entrained concrete is measured, and compared to that of air-entrained concrete under normal curing. Their compressive strength at 14 days and air-void characteristics are also measured and compared. The test results indicate that microwave curing can impair the freeze-thaw durability of high w/c concrete but not for low w/cmore » concrete. Also, under microwave curing, the decrease in strength due to air entrainment becomes more significant. Based on these observations, it is recommended that for microwave cured air-entrained concrete, a low w/c ratio should be employed.« less

Blood Pump Bearing System

NASA Technical Reports Server (NTRS)

Aber, Gregory S. (Inventor)

1999-01-01

Methods and apparatus are provided for a blood pump bearing system within a pump housing to support long-term high-speed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the shaft to support high speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.

Blood Pump Bearing System

NASA Technical Reports Server (NTRS)

Aber, Gregory S. (Inventor)

2000-01-01

An apparatus is provided for a blood pump bearing system within a pump housing to support long-term highspeed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the Ir shaft to support big speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.

Voxel based parallel post processor for void nucleation and growth analysis of atomistic simulations of material fracture.

PubMed

Hemani, H; Warrier, M; Sakthivel, N; Chaturvedi, S

2014-05-01

Molecular dynamics (MD) simulations are used in the study of void nucleation and growth in crystals that are subjected to tensile deformation. These simulations are run for typically several hundred thousand time steps depending on the problem. We output the atom positions at a required frequency for post processing to determine the void nucleation, growth and coalescence due to tensile deformation. The simulation volume is broken up into voxels of size equal to the unit cell size of crystal. In this paper, we present the algorithm to identify the empty unit cells (voids), their connections (void size) and dynamic changes (growth and coalescence of voids) for MD simulations of large atomic systems (multi-million atoms). We discuss the parallel algorithms that were implemented and discuss their relative applicability in terms of their speedup and scalability. We also present the results on scalability of our algorithm when it is incorporated into MD software LAMMPS. Copyright © 2014 Elsevier Inc. All rights reserved.

Voids at the tunnel-soil interface for calculation of ground vibration from underground railways

NASA Astrophysics Data System (ADS)

Jones, Simon; Hunt, Hugh

2011-01-01

Voids at the tunnel-soil interface are not normally considered when predicting ground vibration from underground railways. The soil is generally assumed to be continuously bonded to the outer surface of the tunnel to simplify the modelling process. Evidence of voids around underground railways motivated the study presented herein to quantify the level of uncertainty in ground vibration predictions associated with neglecting to include such voids at the tunnel-soil interface. A semi-analytical method is developed which derives discrete transfers for the coupled tunnel-soil model based on the continuous Pipe-in-Pipe method. The void is simulated by uncoupling the appropriate nodes at the interface to prevent force transfer between the systems. The results from this investigation show that relatively small voids ( 4 m×90∘) can significantly affect the rms velocity predictions in the near-field and moderately affect predictions in the far-field. Sensitivity of the predictions to void length and void sector angle are both deemed to be significant. The findings from this study suggest that the uncertainty associated with assuming a perfect bond at the tunnel-soil interface in an area with known voidage can reasonably reach ±5 dB and thus should be considered in the design process.

Ultraviolet-enhanced photodetection in a graphene/SiO{sub 2}/Si capacitor structure with a vacuum channel

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

Kim, Myungji; Kim, Hong Koo, E-mail: hkk@pitt.edu

2015-09-14

We report photodetection properties of a graphene/oxide/silicon capacitor structure with a nanoscale vacuum channel. The photogenerated two-dimensional electron gas (2DEG) inversion charges at SiO{sub 2}/Si interface are extracted out to air and transported along the void channel at low bias voltage (<5 V). A monolayer graphene, placed on top of SiO{sub 2} and suspended on the void channel, is utilized as a photon-transparent counter-electrode to the 2DEG layer and a collector electrode for the out-of-plane transported electrons, respectively. The photocurrent extracted through a void channel reveals high responsivity (1.0 A/W at 633 nm) as measured in a broad spectral range (325–1064 nm), especially demonstratingmore » a UV-enhanced performance (0.43 A/W responsivity and 384% internal quantum efficiency at 325 nm). The mechanisms underlying photocarrier generation, emission, and transport in a suspended-graphene/SiO{sub 2}/Si structure are proposed.« less

An Efficient Modelling Approach for Prediction of Porosity Severity in Composite Structures

NASA Technical Reports Server (NTRS)

Bedayat, Houman; Forghani, Alireza; Hickmott, Curtis; Roy, Martin; Palmieri, Frank; Grimsley, Brian; Coxon, Brian; Fernlund, Goran

2017-01-01

Porosity, as a manufacturing process-induced defect, highly affects the mechanical properties of cured composites. Multiple phenomena affect the formation of porosity during the cure process. Porosity sources include entrapped air, volatiles and off-gassing as well as bag and tool leaks. Porosity sinks are the mechanisms that contribute to reducing porosity, including gas transport, void shrinkage and collapse as well as resin flow into void space. Despite the significant progress in porosity research, the fundamentals of porosity in composites are not yet fully understood. The highly coupled multi-physics and multi-scale nature of porosity make it a complicated problem to predict. Experimental evidence shows that resin pressure history throughout the cure cycle plays an important role in the porosity of the cured part. Maintaining high resin pressure results in void shrinkage and collapse keeps volatiles in solution thus preventing off-gassing and bubble formation. This study summarizes the latest development of an efficient FE modeling framework to simulate the gas and resin transport mechanisms that are among the major phenomena contributing to porosity.

Detecting self-ion irradiation-induced void swelling in pure copper using transient grating spectroscopy

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

Dennett, C. A.; So, K. P.; Kushima, A.

Irradiation-induced void swelling remains a major challenge to nuclear reactor operation. Swelling may take years to initiate and often results in rapid material property degradation once started. Alloy development for advanced nuclear systems will require rapid characterization of the swelling breakaway dose in new alloys, yet this capability does not yet exist. In this paper, we demonstrate that transient grating spectroscopy (TGS) can detect void swelling in single crystal copper via changes in surface acoustic wave (SAW) velocity. Scanning transmission electron microscopy (STEM) links the TGS-observed changes with void swelling-induced microstructural evolution. Finally, these results are considered in the contextmore » of previous work to suggest that in situ TGS will be able to rapidly determine when new bulk materials begin void swelling, shortening alloy development and testing times.« less

Detecting self-ion irradiation-induced void swelling in pure copper using transient grating spectroscopy

DOE PAGES

Dennett, C. A.; So, K. P.; Kushima, A.; ...

2017-12-20

Irradiation-induced void swelling remains a major challenge to nuclear reactor operation. Swelling may take years to initiate and often results in rapid material property degradation once started. Alloy development for advanced nuclear systems will require rapid characterization of the swelling breakaway dose in new alloys, yet this capability does not yet exist. In this paper, we demonstrate that transient grating spectroscopy (TGS) can detect void swelling in single crystal copper via changes in surface acoustic wave (SAW) velocity. Scanning transmission electron microscopy (STEM) links the TGS-observed changes with void swelling-induced microstructural evolution. Finally, these results are considered in the contextmore » of previous work to suggest that in situ TGS will be able to rapidly determine when new bulk materials begin void swelling, shortening alloy development and testing times.« less

Module assemblage technology for floating systems: in vitro flotation and in vivo gastro-retention.

PubMed

Strusi, Orazio Luca; Sonvico, Fabio; Bettini, Ruggero; Santi, Patrizia; Colombo, Gaia; Barata, Pedro; Oliveira, Ana; Santos, Delfim; Colombo, Paolo

2008-07-14

The aim of this research was to study, in vitro by resultant-weight measurement and in vivo by gamma-scintigraphy experiments in humans, the floatation behavior of systems obtained by modules assembled in void configuration. The assembled system technology allowed the manufacturing of a system characterized by the presence of an internal void space that provided an apparent density lower than water. The gastro-retention times of floating assembled systems were determined in comparison with non-floating systems having the same mass and composition. In vitro the floatation of the system started immediately after immersion in water and lasted for more than 5 h. The in vivo studies confirmed that the in vitro floating ability of void configuration was maintained also in the human stomach where the system stayed for periods of time ranging from 2.5 to 5.0 h, depending on the food regimen and the sex of the subject. Reiterate eating and drinking further prolonged the stomach residence time.

Finite-difference numerical simulations of underground explosion cavity decoupling

NASA Astrophysics Data System (ADS)

Aldridge, D. F.; Preston, L. A.; Jensen, R. P.

2012-12-01

Earth models containing a significant portion of ideal fluid (e.g., air and/or water) are of increasing interest in seismic wave propagation simulations. Examples include a marine model with a thick water layer, and a land model with air overlying a rugged topographic surface. The atmospheric infrasound community is currently interested in coupled seismic-acoustic propagation of low-frequency signals over long ranges (~tens to ~hundreds of kilometers). Also, accurate and efficient numerical treatment of models containing underground air-filled voids (caves, caverns, tunnels, subterranean man-made facilities) is essential. In support of the Source Physics Experiment (SPE) conducted at the Nevada National Security Site (NNSS), we are developing a numerical algorithm for simulating coupled seismic and acoustic wave propagation in mixed solid/fluid media. Solution methodology involves explicit, time-domain, finite-differencing of the elastodynamic velocity-stress partial differential system on a three-dimensional staggered spatial grid. Conditional logic is used to avoid shear stress updating within the fluid zones; this approach leads to computational efficiency gains for models containing a significant proportion of ideal fluid. Numerical stability and accuracy are maintained at air/rock interfaces (where the contrast in mass density is on the order of 1 to 2000) via a finite-difference operator "order switching" formalism. The fourth-order spatial FD operator used throughout the bulk of the earth model is reduced to second-order in the immediate vicinity of a high-contrast interface. Current modeling efforts are oriented toward quantifying the amount of atmospheric infrasound energy generated by various underground seismic sources (explosions and earthquakes). Source depth and orientation, and surface topography play obvious roles. The cavity decoupling problem, where an explosion is detonated within an air-filled void, is of special interest. A point explosion source located at the center of a spherical cavity generates only diverging compressional waves. However, we find that shear waves are generated by an off-center source, or by a non-spherical cavity (e.g. a tunnel). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Two-phase flow research using the DC-9/KC-135 apparatus

NASA Technical Reports Server (NTRS)

McQuillen, John B.; Neumann, Eric S.; Shoemaker, J. Michael

1996-01-01

Low-gravity gas-liquid flow research can be conducted aboard the NASA Lewis Research Center DC-9 or the Johnson Space Center KC-135. Air and water solutions serve as the test liquids in cylindrical test sections with constant or variable inner diameters of approximately 2.54 cm and lengths of up to 3.0 m. Superficial velocities range from 0.1 to 1.1 m/sec for liquids and from 0.1 to 25 m/sec for air. Flow rate, differential pressure, void fraction, film thickness, wall shear stress, and acceleration data are measured and recorded at data rates of up to 1000 Hz throughout the 20-sec duration of the experiment. Flow is visualized with a high-speed video system. In addition, the apparatus has a heat-transfer capability whereby sensible heat is transferred between the test-section wall and a subcooled liquid phase so that the heat-transfer characteristics of gas-liquid two-phase flows can be determined.

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

May, C.A.; Breitigam, W.; Bauer, R.S.

The laminates that are used to prepare advanced composite parts generally require curing at high temperature and pressure, and their raw material shelf lives are limited. The epoxy resin systems that the authors describe here offer the potential of extended shelf life while curing at relatively low temperatures with a method the authors call rapid thermoset processing (RTP). A laminate is formed by stacking the prepreg in a pre-determined manner as required by the end product configuration. The prepreg is then bagged by placing it in a sealed envelope of a heat-resistant film, which is subsequently bonded to a metalmore » surface (the tool) with a heat-resistant vacuum bag putty. The bag has an access hole through which vacuum can be applied to the prepreg stack, facilitating removal of air and other volatiles. This assembly is then heated under vacuum and pressure in an autoclave, the resin melts, and any excess air or volatile matter bleeds from the configuration, resulting in the required dense, void-free laminate.« less

Oxy-fuel combustion with integrated pollution control

DOEpatents

Patrick, Brian R [Chicago, IL; Ochs, Thomas Lilburn [Albany, OR; Summers, Cathy Ann [Albany, OR; Oryshchyn, Danylo B [Philomath, OR; Turner, Paul Chandler [Independence, OR

2012-01-03

An oxygen fueled integrated pollutant removal and combustion system includes a combustion system and an integrated pollutant removal system. The combustion system includes a furnace having at least one burner that is configured to substantially prevent the introduction of air. An oxygen supply supplies oxygen at a predetermine purity greater than 21 percent and a carbon based fuel supply supplies a carbon based fuel. Oxygen and fuel are fed into the furnace in controlled proportion to each other and combustion is controlled to produce a flame temperature in excess of 3000 degrees F. and a flue gas stream containing CO2 and other gases. The flue gas stream is substantially void of non-fuel borne nitrogen containing combustion produced gaseous compounds. The integrated pollutant removal system includes at least one direct contact heat exchanger for bringing the flue gas into intimated contact with a cooling liquid to produce a pollutant-laden liquid stream and a stripped flue gas stream and at least one compressor for receiving and compressing the stripped flue gas stream.

48 CFR 803.703 - Authority.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Authority. 803.703 Section... BUSINESS PRACTICES AND PERSONAL CONFLICTS OF INTEREST Voiding and Rescinding Contracts 803.703 Authority. The authority to make determinations under FAR Subpart 3.7, Voiding and Rescinding Contracts, is...

Analysis of Dislocation Emission during Microvoid Growth in Ductile Metals

NASA Astrophysics Data System (ADS)

Belak, James; Rudd, Robert E.

2001-03-01

Fracture in ductile metals occurs through the nucleation and growth of microscopic voids. This talk focuses on the initial stage when dislocations are first emitted from the void surface. The model system consists of a spherical void in an otherwise perfect crystal under triaxial tension. The stress field is calculated using continuum techniques, both finite element and analytic forms due to Eshelby, and compared with large-scale molecular dynamics (MD) simulation. The stress field is used to derive a criterion for dislocation nucleation on the glide planes intersecting the void surface. The critical resolved shear stress and the unstable stacking fault energy for the strain at the surface are used to compare to the critical stress for void growth in the MD simulations. Acknowledgement: This work was performed under the auspices of the US Dept. of Energy at the University of California/Lawrence Livermore National Laboratory under contract no. W-7405-Eng-48. [1] J. Belak, "On the nucleation and growth of voids at high strain-rates," J. Comp.-Aided Mater. Design 5, 193 (1998).

Year-Round Use Of Thermography In House Doctoring

NASA Astrophysics Data System (ADS)

Gadsby, Kenneth J.; Harrje, David T.; Dutt, Gautam S.

1983-03-01

There have been many presentations of thermographic residential building analyses at the past ThermosInse conferences. A number of these papers have dealt with evaluation of insulation voids and more recently a few have described air leakage detection 2,3 during the colder winter months. This paper will focus on the thermographic application in the House Doctor instrumented energy analysis approach as developed by Princeton University. The central theme will be the application to a year-round research or commercial activity. Some of the conditions that could create thermographic problems, as well as techniques that may be used to lessen these difficulties, thereby extending the thermographic "season" is discussed. Our experiences in summer thermography with and without the use of a building pressurization system is also covered.

Observations of Gas-Liquid Flows Through Contractions in Microgravity

NASA Technical Reports Server (NTRS)

McQuillen, John

1996-01-01

Tests were conducted for an air-water flow through two sudden contractions aboard the NASA DC-9 low gravity aircraft. Flow rate, residual accelerations, void fraction, film thickness, and pressure drop data were recorded and flow visualization at 250 images per second were recorded. Some preliminary results based on the flow visualization data are presented for bubbly, slug and annular flow.

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

White, D.B.

This paper reports on experiments to examine gas migration rates in drilling muds that were performed in a 15-m-long, 200-mm-ID inclinable flow loop where air injection simulates gas entry during a kick. These tests were conducted using a xanthum gum (a common polymer used in drilling fluids) solution to simulate drilling muds as the liquid phase and air as the gas phase. This work represents a significant extension of existing correlations for gas/liquid flows in large pipe diameters with non- Newtonian fluids. Bubbles rise faster in drilling muds than in water despite the increased viscosity. This surprising result is causedmore » by the change in the flow regime, with large slug-type bubbles forming at lower void fractions. The gas velocity is independent of void fraction, thus simplifying flow modeling. Results show that a gas influx will rise faster in a well than previously believed. This has major implications for kick simulation, with gas arriving at the surface earlier than would be expected and the gas outflow rate being higher than would have been predicted. A model of the two-phase gas flow in drilling mud, including the results of this work, has been incorporated into the joint Schlumberger Cambridge Research (SCR)/BP Intl. kick model.« less

Venturi flow meter and Electrical Capacitance Probe in a horizontal two-phase flow

NASA Astrophysics Data System (ADS)

Monni, G.; Caramello, M.; De Salve, M.; Panella, B.

2015-11-01

The paper presents the results obtained with a spool piece (SP) made of a Venturi flow meter (VMF) and an Electrical Capacitance Probe (ECP) in stratified two-phase flow. The objective is to determine the relationship between the test measurements and the physical characteristics of the flow such as superficial velocities, density and void fraction. The outputs of the ECP are electrical signals proportional to the void fraction between the electrodes; the parameters measured by the VFM are the total and the irreversible pressure losses of the two- phase mixture. The fluids are air and demineralized water at ambient conditions. The flow rates are in the range of 0,065-0,099 kg/s for air and 0- 0,039 kg/s (0-140 l/h) for water. The flow patterns recognized during the experiments are stratified, dispersed and annular flow. The presence of the VFM plays an important role on the alteration of the flow pattern due to wall flow detachment phenomena. The signals of differential pressure of the VFM in horizontal configuration are strongly dependent on the superficial velocities and on the flow pattern because of a lower symmetry of the flow with respect to the vertical configuration.

Cave air and hydrological controls on prior calcite precipitation and stalagmite growth rates: Implications for palaeoclimate reconstructions using speleothems

NASA Astrophysics Data System (ADS)

Sherwin, Catherine M.; Baldini, James U. L.

2011-07-01

Hourly resolved cave air P and cave drip water hydrochemical data illustrate that calcite deposition on stalagmites can be modulated by prior calcite precipitation (PCP) on extremely short timescales. A very clear second-order covariation between cave air P and drip water Ca 2+ concentrations during the winter months demonstrates the effects of degassing-induced PCP on drip water chemistry. Estimating the strength of the cave air P control on PCP is possible because the PCP signal is so clear; at our drip site a one ppm shift in Ca 2+ concentrations requires a P shift of between 333 and 667 ppm. This value will undoubtedly vary from site to site, depending on drip water flow rate, residence time, drip water-cave air P differential, and availability of low P void spaces in the vadose zone above the cave. High-resolution cave environmental measurements were used to model calcite deposition on one stalagmite in Crag Cave, SW Ireland, and modelled growth over the study period (222 μm over 171 days) is extremely similar to the amount of actual calcite growth (240 μm) over the same time interval, strongly suggesting that equations used to estimate stalagmite growth rates are valid. Although cave air P appears to control drip water hydrochemistry in the winter, drip water dilution caused by rain events may have played a larger role during the summer, as evidenced by a series of sudden drops in Ca 2+ concentrations (dilution) followed by much more gradual increases in drip water Ca 2+ concentrations (slow addition of diffuse water). This research demonstrates that PCP on stalactites, cave ceilings, and void spaces within the karst above the cave partially controls drip water chemistry, and that thorough characterisation of this process at individual caves is necessary to most accurately interpret climate records from those sites.

The Aeroflex: A Bicycle for Mobile Air Quality Measurements

PubMed Central

Elen, Bart; Peters, Jan; Van Poppel, Martine; Bleux, Nico; Theunis, Jan; Reggente, Matteo; Standaert, Arnout

2013-01-01

Fixed air quality stations have limitations when used to assess people's real life exposure to air pollutants. Their spatial coverage is too limited to capture the spatial variability in, e.g., an urban or industrial environment. Complementary mobile air quality measurements can be used as an additional tool to fill this void. In this publication we present the Aeroflex, a bicycle for mobile air quality monitoring. The Aeroflex is equipped with compact air quality measurement devices to monitor ultrafine particle number counts, particulate mass and black carbon concentrations at a high resolution (up to 1 second). Each measurement is automatically linked to its geographical location and time of acquisition using GPS and Internet time. Furthermore, the Aeroflex is equipped with automated data transmission, data pre-processing and data visualization. The Aeroflex is designed with adaptability, reliability and user friendliness in mind. Over the past years, the Aeroflex has been successfully used for high resolution air quality mapping, exposure assessment and hot spot identification. PMID:23262484

The Aeroflex: a bicycle for mobile air quality measurements.

PubMed

Elen, Bart; Peters, Jan; Poppel, Martine Van; Bleux, Nico; Theunis, Jan; Reggente, Matteo; Standaert, Arnout

2012-12-24

Fixed air quality stations have limitations when used to assess people's real life exposure to air pollutants. Their spatial coverage is too limited to capture the spatial variability in, e.g., an urban or industrial environment. Complementary mobile air quality measurements can be used as an additional tool to fill this void. In this publication we present the Aeroflex, a bicycle for mobile air quality monitoring. The Aeroflex is equipped with compact air quality measurement devices to monitor ultrafine particle number counts, particulate mass and black carbon concentrations at a high resolution (up to 1 second). Each measurement is automatically linked to its geographical location and time of acquisition using GPS and Internet time. Furthermore, the Aeroflex is equipped with automated data transmission, data pre-processing and data visualization. The Aeroflex is designed with adaptability, reliability and user friendliness in mind. Over the past years, the Aeroflex has been successfully used for high resolution air quality mapping, exposure assessment and hot spot identification. 

Numerical study of the influence of geometrical characteristics of a vertical helical coil on a bubbly flow

NASA Astrophysics Data System (ADS)

Saffari, H.; Moosavi, R.

2014-11-01

In this article, turbulent single-phase and two-phase (air-water) bubbly fluid flows in a vertical helical coil are analyzed by using computational fluid dynamics (CFD). The effects of the pipe diameter, coil diameter, coil pitch, Reynolds number, and void fraction on the pressure loss, friction coefficient, and flow characteristics are investigated. The Eulerian-Eulerian model is used in this work to simulate the two-phase fluid flow. Three-dimensional governing equations of continuity, momentum, and energy are solved by using the finite volume method. The k- ɛ turbulence model is used to calculate turbulence fluctuations. The SIMPLE algorithm is employed to solve the velocity and pressure fields. Due to the effect of a secondary force in helical pipes, the friction coefficient is found to be higher in helical pipes than in straight pipes. The friction coefficient increases with an increase in the curvature, pipe diameter, and coil pitch and decreases with an increase in the coil diameter and void fraction. The close correlation between the numerical results obtained in this study and the numerical and empirical results of other researchers confirm the accuracy of the applied method. For void fractions up to 0.1, the numerical results indicate that the friction coefficient increases with increasing the pipe diameter and keeping the coil pitch and diameter constant and decreases with increasing the coil diameter. Finally, with an increase in the Reynolds number, the friction coefficient decreases, while the void fraction increases.

The Unicorn Cave, Southern Harz Mountains, Germany: From known passages to unknown extensions with the help of geophysical surveys

NASA Astrophysics Data System (ADS)

Kaufmann, Georg; Nielbock, Ralf; Romanov, Douchko

2015-12-01

In soluble rocks (limestone, dolomite, anhydrite, gypsum, …), fissures and bedding partings can be enlarged with time by both physical and chemical dissolution of the host rock. With time, larger cavities evolve, and a network of cave passages can evolve. If the enlarged cave voids are not too deep under the surface, geophysical measurements can be used to detect, identify and trace these karst structures, e.g.: (i) gravity revealing air- and sediment-filled cave voids through negative Bouguer anomalies, (ii) electrical resistivity imaging (ERI) mapping different infillings of cavities either as high resistivities from air-filled voids or dry soft sediments, or low resistivities from saturated sediments, and (iii) groundwater flow through electrical potential differences (SP) arising from dislocated ionic charges from the walls of the underground flow paths. We have used gravity, ERI, and SP methods both in and above the Unicorn Cave located in the southern Harz Mountains in Germany. The Unicorn Cave is a show cave developed in the Werra dolomite formation of the Permian Zechstein sequence, characterised by large trunk passages interrupted by larger rooms. The overburden of the cave is only around 15 m, and passages are filled with sediments reaching infill thicknesses up to 40 m. We present results from our geophysical surveys above the known cave and its northern and southern extension, and from the cave interior. We identify the cave geometry and its infill from gravity and ERI measurements, predict previously unknown parts of the cave, and subsequently confirm the existence of these new passages through drilling. From the wealth of geophysical data acquired we derive a three-dimensional structural model of the Unicorn Cave and its surrounding, especially the cave infill.

Thermographic Analysis of Composite Cobonds on the X-33

NASA Technical Reports Server (NTRS)

Russell, S. S.; Walker, J. L.; Lansing, M. D.

2001-01-01

During the manufacture of the X-33 liquid hydrogen (LH2) Tank 2, a total of 36 reinforcing caps were inspected thermographically. The cured reinforcing sheets of graphite/epoxy were bonded to the tank using a wet cobond process with vacuum bagging and low temperature curing. A foam filler material wedge separated the reinforcing caps from the outer skin of the tank. Manufacturing difficulties caused by a combination of the size of the reinforcing caps and their complex geometry lead to a potential for trapping air in the bond line. An inspection process was desired to ensure that the bond line was free of voids before it had cured so that measures could be taken to rub out the entrapped air or remove the cap and perform additional surface matching. Infrared thermography was used to perform the procure 'wet bond' inspection as well a to document the final 'cured' condition of the caps. The thermal map of the bond line was acquired by heating the cap with either a flash lamp or a set of high intensity quartz lamps and then viewing it during cool down. The inspections were performed through the vacuum bag and voids were characterized by localized hot spots. In order to ensure that the cap had bonded to the tank properly, a post cure 'flash heating' thermographic investigation was performed with the vacuum bag removed. Any regions that had opened up after the preliminary inspection or that were hidden during the bagging operation were marked and filled by drilling small holes in the cap and injecting resin. This process was repeated until all critical sized voids were filled.

Thermographic Analysis of Composite Cobonds on the X-33

NASA Technical Reports Server (NTRS)

Russell, Samuel S.; Walker, James L.; Lansing, Matthew D.; Whitaker, Ann F. (Technical Monitor)

2000-01-01

During the manufacture of the X-33 liquid hydrogen (LH2) Tank 2, a total of thirty-six reinforcing caps were inspected thermographically. The cured reinforcing sheets of graphite/epoxy were bonded to the tank using a wet cobond process with vacuum bagging and low temperature curing. A foam filler material wedge separated the reinforcing caps from the outer skin of the tank. Manufacturing difficulties caused by a combination of the size of the reinforcing caps and their complex geometry lead to a potential for trapping air in the bond line. An inspection process was desired to ensure that the bond line was free of voids before it had cured so that measures could be taken to rub out the entrapped air or remove the cap and perform additional surface matching. Infrared thermography was used to perform the precure "wet bond" inspection as well as to document the final "cured" condition of the caps. The thermal map of the bond line was acquired by heating the cap with either a flash lamp or a set of high intensity quartz lamps and then viewing it during cool down. The inspections were performed through the vacuum bag and voids were characterized by localized hot spots. In order to ensure that the cap had bonded to the tank properly, a post cure "flash heating" thermographic investigation was performed with the vacuum bag removed. Any regions that had opened up after the preliminary inspection or that were hidden during the bagging operation were marked and filled by drilling small holes in the cap and injecting resin. This process was repeated until all critical sized voids were filled.

An Experimental Study of Plunging Liquid Jet Induced Air Carryunder and Dispersion

DTIC Science & Technology

1991-12-24

the ’ greenhouse ’ effect (ie, the absorption of CO2 by the oceans), and a number of other important maritime-related applications. In particular, the air entrainment process due to the breaking bow waves of surface ships may cause long (ie, up to 5 km in length) wakes. Naturally easily detectable wakes are undesirable for naval warships. In the present study plunging liquid jet experiments were performed and detailed Laser Doppler Anemometer (LDA) data were taken of the phasic velocity field and the void fraction distribution in the induced two-phase

Thermal analysis of heat storage canisters for a solar dynamic, space power system

NASA Technical Reports Server (NTRS)

Wichner, R. P.; Solomon, A. D.; Drake, J. B.; Williams, P. T.

1988-01-01

A thermal analysis was performed of a thermal energy storage canister of a type suggested for use in a solar receiver for an orbiting Brayton cycle power system. Energy storage for the eclipse portion of the cycle is provided by the latent heat of a eutectic mixture of LiF and CaF2 contained in the canister. The chief motivation for the study is the prediction of vapor void effects on temperature profiles and the identification of possible differences between ground test data and projected behavior in microgravity. The first phase of this study is based on a two-dimensional, cylindrical coordinates model using an interim procedure for describing void behavor in 1-g and microgravity. The thermal analysis includes the effects of solidification front behavior, conduction in liquid/solid salt and canister materials, void growth and shrinkage, radiant heat transfer across the void, and convection in the melt due to Marangoni-induced flow and, in 1-g, flow due to density gradients. A number of significant differences between 1-g and o-g behavior were found. This resulted from differences in void location relative to the maximum heat flux and a significantly smaller effective conductance in 0-g due to the absence of gravity-induced convection.

Dimensionality effects in void-induced explosive sensitivity

DOE PAGES

Herring, Stuart Davis; Germann, Timothy Clark; Gronbech-Jensen, Niels

2016-09-02

Here, the dimensionality of defects in high explosives controls their heat generation and the expansion of deflagrations from them. We compare the behaviour of spherical voids in three dimensions to that of circular voids in two dimensions. The behaviour is qualitatively similar, but the additional focusing along the extra transverse dimension significantly reduces the piston velocity needed to initiate reactions. However, the reactions do not grow as well in three dimensions, so detonations require larger piston velocities. Pressure exponents are seen to be similar to those for the two-dimensional system.

Diffusional creep and creep degradation in the dispersion-strengthened alloy TD-NiCr

NASA Technical Reports Server (NTRS)

Whittenberger, J. D.

1972-01-01

Dispersoid-free regions were observed in TD-NiCr (Ni-20Cr-2ThO2) after slow strain rate testing in air from 1145 to 1590 K. Formation of the dispersoid-free regions appears to be the result of diffusional creep. The net effect of this creep is the degradation of TD-NiCr to a duplex microstructure. Degradation is further enhanced by the formation of voids and integranular oxidation in the thoria-free regions. These regions apparently provided sites for void formation and oxide growth since the strength and oxidation resistance of Ni-20Cr is much less than Ni-20Cr-2ThO2. This localized oxidation does not appear to reduce the static load bearing capacity of TD-NiCr since long stress rupture lives were observed even with heavily oxidized microstructures. But this oxidation does significantly reduce the ductility and impact resistance of the material. Dispersoid-free bands and voids were also observed for two other dispersion strengthened alloys, TD-NiCrAl and IN-853. Thus, it appears that diffusional creep is charactertistic of dispersion-strengthened alloys and can play a major role in the creep degradation of these materials.

46 CFR 151.50-55 - Sulfur (molten).

Code of Federal Regulations, 2013 CFR

2013-10-01

... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-55 Sulfur (molten). (a... below one-half of its lower explosive limit throughout the cargo tank vapor space for all conditions of... depositing of sulfur within the system. (b) Void spaces: (1) Openings to void spaces adjacent to cargo tanks...

46 CFR 151.50-55 - Sulfur (molten).

Code of Federal Regulations, 2014 CFR

2014-10-01

... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-55 Sulfur (molten). (a... below one-half of its lower explosive limit throughout the cargo tank vapor space for all conditions of... depositing of sulfur within the system. (b) Void spaces: (1) Openings to void spaces adjacent to cargo tanks...

46 CFR 151.50-55 - Sulfur (molten).

Code of Federal Regulations, 2012 CFR

2012-10-01

... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-55 Sulfur (molten). (a... below one-half of its lower explosive limit throughout the cargo tank vapor space for all conditions of... depositing of sulfur within the system. (b) Void spaces: (1) Openings to void spaces adjacent to cargo tanks...

46 CFR 151.50-55 - Sulfur (molten).

Code of Federal Regulations, 2011 CFR

2011-10-01

... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-55 Sulfur (molten). (a... below one-half of its lower explosive limit throughout the cargo tank vapor space for all conditions of... depositing of sulfur within the system. (b) Void spaces: (1) Openings to void spaces adjacent to cargo tanks...

46 CFR 151.50-55 - Sulfur (molten).

Code of Federal Regulations, 2010 CFR

2010-10-01

... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-55 Sulfur (molten). (a... below one-half of its lower explosive limit throughout the cargo tank vapor space for all conditions of... depositing of sulfur within the system. (b) Void spaces: (1) Openings to void spaces adjacent to cargo tanks...

Nanobonding: A key technology for emerging applications in health and environmental sciences

NASA Astrophysics Data System (ADS)

Howlader, Matiar M. R.; Deen, M. Jamal; Suga, Tadatomo

2015-03-01

In this paper, surface-activation-based nanobonding technology and its applications are described. This bonding technology allows for the integration of electronic, photonic, fluidic and mechanical components into small form-factor systems for emerging sensing and imaging applications in health and environmental sciences. Here, we describe four different nanobonding techniques that have been used for the integration of various substrates — silicon, gallium arsenide, glass, and gold. We use these substrates to create electronic (silicon), photonic (silicon and gallium arsenide), microelectromechanical (glass and silicon), and fluidic (silicon and glass) components for biosensing and bioimaging systems being developed. Our nanobonding technologies provide void-free, strong, and nanometer scale bonding at room temperature or at low temperatures (<200 °C), and do not require chemicals, adhesives, or high external pressure. The interfaces of the nanobonded materials in ultra-high vacuum and in air correspond to covalent bonds, and hydrogen or hydroxyl bonds, respectively.

Attenuation of low-frequency underwater sound using an array of air-filled balloons and comparison to effective medium theory.

PubMed

Lee, Kevin M; Wilson, Preston S; Wochner, Mark S

2017-12-01

The ultimate goal of this work is to accurately predict the attenuation through a collection of large (on the order of 10-cm-radius) tethered encapsulated bubbles used in underwater noise abatement systems. Measurements of underwater sound attenuation were performed during a set of lake experiments, where a low-frequency compact electromechanical sound source was surrounded by different arrays of encapsulated bubbles with various individual bubbles sizes and void fractions. The measurements were compared with an existing predictive model [Church, J. Acoust. Soc. Am. 97, 1510-1521 (1995)] of the dispersion relation for linear propagation in liquid containing encapsulated bubbles. Although the model was originally intended to describe ultrasound contrast agents, it is evaluated here for large bubbles, and hence low frequencies, as a design tool for future underwater noise abatement systems, and there is good quantitative agreement between the observations and the model.

Simulation of void formation in interconnect lines

NASA Astrophysics Data System (ADS)

Sheikholeslami, Alireza; Heitzinger, Clemens; Puchner, Helmut; Badrieh, Fuad; Selberherr, Siegfried

2003-04-01

The predictive simulation of the formation of voids in interconnect lines is important for improving capacitance and timing in current memory cells. The cells considered are used in wireless applications such as cell phones, pagers, radios, handheld games, and GPS systems. In backend processes for memory cells, ILD (interlayer dielectric) materials and processes result in void formation during gap fill. This approach lowers the overall k-value of a given metal layer and is economically advantageous. The effect of the voids on the overall capacitive load is tremendous. In order to simulate the shape and positions of the voids and thus the overall capacitance, the topography simulator ELSA (Enhanced Level Set Applications) has been developed which consists of three modules, a level set module, a radiosity module, and a surface reaction module. The deposition process considered is deposition of silicon nitride. Test structures of interconnect lines of memory cells were fabricated and several SEM images thereof were used to validate the corresponding simulations.

Detection of atomic scale changes in the free volume void size of three-dimensional colorectal cancer cell culture using positron annihilation lifetime spectroscopy.

PubMed

Axpe, Eneko; Lopez-Euba, Tamara; Castellanos-Rubio, Ainara; Merida, David; Garcia, Jose Angel; Plaza-Izurieta, Leticia; Fernandez-Jimenez, Nora; Plazaola, Fernando; Bilbao, Jose Ramon

2014-01-01

Positron annihilation lifetime spectroscopy (PALS) provides a direct measurement of the free volume void sizes in polymers and biological systems. This free volume is critical in explaining and understanding physical and mechanical properties of polymers. Moreover, PALS has been recently proposed as a potential tool in detecting cancer at early stages, probing the differences in the subnanometer scale free volume voids between cancerous/healthy skin samples of the same patient. Despite several investigations on free volume in complex cancerous tissues, no positron annihilation studies of living cancer cell cultures have been reported. We demonstrate that PALS can be applied to the study in human living 3D cell cultures. The technique is also capable to detect atomic scale changes in the size of the free volume voids due to the biological responses to TGF-β. PALS may be developed to characterize the effect of different culture conditions in the free volume voids of cells grown in vitro.

Detection of Atomic Scale Changes in the Free Volume Void Size of Three-Dimensional Colorectal Cancer Cell Culture Using Positron Annihilation Lifetime Spectroscopy

PubMed Central

Castellanos-Rubio, Ainara; Merida, David; Garcia, Jose Angel; Plaza-Izurieta, Leticia; Fernandez-Jimenez, Nora; Plazaola, Fernando; Bilbao, Jose Ramon

2014-01-01

Positron annihilation lifetime spectroscopy (PALS) provides a direct measurement of the free volume void sizes in polymers and biological systems. This free volume is critical in explaining and understanding physical and mechanical properties of polymers. Moreover, PALS has been recently proposed as a potential tool in detecting cancer at early stages, probing the differences in the subnanometer scale free volume voids between cancerous/healthy skin samples of the same patient. Despite several investigations on free volume in complex cancerous tissues, no positron annihilation studies of living cancer cell cultures have been reported. We demonstrate that PALS can be applied to the study in human living 3D cell cultures. The technique is also capable to detect atomic scale changes in the size of the free volume voids due to the biological responses to TGF-β. PALS may be developed to characterize the effect of different culture conditions in the free volume voids of cells grown in vitro. PMID:24392097

Rice Starch Particle Interactions at Air/Aqueous Interfaces—Effect of Particle Hydrophobicity and Solution Ionic Strength

PubMed Central

McNamee, Cathy E.; Sato, Yu; Wiege, Berthold; Furikado, Ippei; Marefati, Ali; Nylander, Tommy; Kappl, Michael; Rayner, Marilyn

2018-01-01

Starch particles modified by esterification with dicarboxylic acids to give octenyl succinic anhydride (OSA) starch is an approved food additive that can be used to stabilize oil in water emulsions used in foods and drinks. However, the effects of the OSA modification of the starch particle on the interfacial interactions are not fully understood. Here, we directly measured the packing of films of rice starch granules, i.e., the natural particle found inside the plant, at air/aqueous interfaces, and the interaction forces in that system as a function of the particle hydrophobicity and ionic strength, in order to gain insight on how starch particles can stabilize emulsions. This was achieved by using a combined Langmuir trough and optical microscope system, and the Monolayer Interaction Particle Apparatus. Native rice starch particles were seen to form large aggregates at air/water interfaces, causing films with large voids to be formed at the interface. The OSA modification of the rice starches particles decreased this aggregation. Increasing the degree of modification improved the particle packing within the film of particles at the air/water interface, due to the introduction of inter-particle electrostatic interactions within the film. The introduction of salt to the water phase caused the particles to aggregate and form holes within the film, due to the screening of the charged groups on the starch particles by the salt. The presence of these holes in the film decreased the stiffness of the films. The effect of the OSA modification was concluded to decrease the aggregation of the particles at an air/water interface. The presence of salts, however, caused the particles to aggregate, thereby reducing the strength of the interfacial film. PMID:29868551

Rice Starch Particle Interactions at Air/Aqueous Interfaces-Effect of Particle Hydrophobicity and Solution Ionic Strength.

PubMed

McNamee, Cathy E; Sato, Yu; Wiege, Berthold; Furikado, Ippei; Marefati, Ali; Nylander, Tommy; Kappl, Michael; Rayner, Marilyn

2018-01-01

Starch particles modified by esterification with dicarboxylic acids to give octenyl succinic anhydride (OSA) starch is an approved food additive that can be used to stabilize oil in water emulsions used in foods and drinks. However, the effects of the OSA modification of the starch particle on the interfacial interactions are not fully understood. Here, we directly measured the packing of films of rice starch granules, i.e., the natural particle found inside the plant, at air/aqueous interfaces, and the interaction forces in that system as a function of the particle hydrophobicity and ionic strength, in order to gain insight on how starch particles can stabilize emulsions. This was achieved by using a combined Langmuir trough and optical microscope system, and the Monolayer Interaction Particle Apparatus. Native rice starch particles were seen to form large aggregates at air/water interfaces, causing films with large voids to be formed at the interface. The OSA modification of the rice starches particles decreased this aggregation. Increasing the degree of modification improved the particle packing within the film of particles at the air/water interface, due to the introduction of inter-particle electrostatic interactions within the film. The introduction of salt to the water phase caused the particles to aggregate and form holes within the film, due to the screening of the charged groups on the starch particles by the salt. The presence of these holes in the film decreased the stiffness of the films. The effect of the OSA modification was concluded to decrease the aggregation of the particles at an air/water interface. The presence of salts, however, caused the particles to aggregate, thereby reducing the strength of the interfacial film.

Rice starch particle interactions at air/aqueous interfaces– effect of particle hydrophobicity and solution ionic strength

NASA Astrophysics Data System (ADS)

McNamee, Cathy E.; Sato, Yu; Wiege, Berthold; Furikado, Ippei; Marefati, Ali; Nylander, Tommy; Kappl, Michael; Rayner, Marilyn

2018-05-01

Starch particles modified by esterification with dicarboxylic acids to give octenyl succinic anhydride (OSA) starch is an approved food additive that can be used to stabilize oil in water emulsions used in foods and drinks. However, the effects of the OSA modification of the starch particle on the interfacial interactions are not fully understood. Here, we directly measured the packing of films of rice starch granules, i.e. the natural particle found inside the plant, at air/aqueous interfaces and the interaction forces in that system as a function of the particle hydrophobicity and ionic strength, in order to gain insight on how starch particles can stabilize emulsions. This was achieved by using a combined Langmuir trough and optical microscope system, and the Monolayer Interaction Particle Apparatus. Native rice starch particles were seen to form large aggregates at air/water interfaces, causing films with large voids to be formed at the interface. The OSA modification of the rice starches particles decreased this aggregation. Increasing the degree of modification improved the particle packing within the film of particles at the air/water interface, due to the introduction of inter-particle electrostatic interactions within the film. The introduction of salt to the water phase caused the particles to aggregate and form holes within the film, due to the screening of the charged groups on the starch particles by the salt. The presence of these holes in the film decreased the stiffness of the films. The effect of the OSA modification was concluded to decrease the aggregation of the particles at an air/water interface. The presence of salts, however, caused the particles to aggregate, thereby reducing the strength of the interfacial film.

The Metallicity of Void Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Kreckel, K.; Croxall, K.; Groves, B.; van de Weygaert, R.; Pogge, R. W.

2015-01-01

The current ΛCDM cosmological model predicts that galaxy evolution proceeds more slowly in lower density environments, suggesting that voids are a prime location to search for relatively pristine galaxies that are representative of the building blocks of early massive galaxies. To test the assumption that void galaxies are more pristine, we compare the evolutionary properties of a sample of dwarf galaxies selected specifically to lie in voids with a sample of similar isolated dwarf galaxies in average density environments. We measure gas-phase oxygen abundances and gas fractions for eight dwarf galaxies (Mr > -16.2), carefully selected to reside within the lowest density environments of seven voids, and apply the same calibrations to existing samples of isolated dwarf galaxies. We find no significant difference between these void dwarf galaxies and the isolated dwarf galaxies, suggesting that dwarf galaxy chemical evolution proceeds independent of the large-scale environment. While this sample is too small to draw strong conclusions, it suggests that external gas accretion is playing a limited role in the chemical evolution of these systems, and that this evolution is instead dominated mainly by the internal secular processes that are linking the simultaneous growth and enrichment of these galaxies.

Evaluation of the Air Void Analyzer

DTIC Science & Technology

2013-07-01

lack of measurement would help explain the difference in values shown. Brief descriptions of other unpublished testing (Wang et al. 2008)  CTL Group...structure measurements taken from the controlled laboratory mixtures. A three-phase approach was used to evaluate the machine. First, a global ...method. Hypothesis testing using t-statistics was performed to increase understanding of the data collected globally in terms of the processes used for

Reducing ingress of organic vapours into homes situated on contaminated land.

PubMed

Crump, D; Brown, V; Rowley, J; Squire, R

2004-04-01

The efficacy of current landfill gas and radon mitigation measures for the prevention of ingress of organic vapours was investigated by the study of four houses situated on contaminated land in North West England. The chemical present in the ground of greatest concern for health due to exposure to vapour in the indoor air was hexachlorobutadiene (HCBD) and the concentration of this compound was used to assess the effectiveness of the remedial measures. A two stage remediation was undertaken. For a house with a solid floor the top surface of the floor was sealed and then for the second stage a fan was used to pressurise the soil gas beneath the house. In a house with a suspended timber floor, extra air bricks were installed to increase ventilation of the floor void and then a fan to further increase air exchange in the void. HCBD in air was monitored by both pumped and diffusive sampling methods. Control houses were also monitored that were not subject to remediation. It is concluded that the remedial measures used for radon protection of a suspended floor have the potential to reduce indoor HCBD concentrations by about 80%, at least in downstairs rooms (where initial levels were highest). The two techniques used for properties with solid floors do not appear to be as effective, and no benefit at all was seen without making allowances for changes in concentration that occurred in the control house over the same period. Further work is required to test the efficacy of the techniques over a longer period and under different circumstances of type of contamination and building characteristics.

Apparatus for observing a hostile environment

DOEpatents

Nance, Thomas A.; Boylston, Micah L.; Robinson, Casandra W.; Sexton, William C.; Heckendorn, Frank M.

2000-01-01

An apparatus is provided for observing a hostile environment, comprising a housing and a camera capable of insertion within the housing. The housing is a double wall assembly with an inner and outer wall with an hermetically sealed chamber therebetween. A housing for an optical system used to observe a hostile environment is provided, comprising a transparent, double wall assembly. The double wall assembly has an inner wall and an outer wall with an hermetically sealed chamber therebetween. The double wall assembly has an opening and a void area in communication with the opening. The void area of the housing is adapted to accommodate the optical system within said void area. An apparatus for protecting an optical system used to observe a hostile environment is provided comprising a housing; a tube positioned within the housing; and a base for supporting the housing and the tube. The housing comprises a double wall assembly having an inner wall and an outerwall with an hermetically sealed chamber therebetween. The tube is adapted to house the optical system therein.

CAD/CAM-designed 3D-printed electroanalytical cell for the evaluation of nanostructured gas-diffusion electrodes

NASA Astrophysics Data System (ADS)

Chervin, Christopher N.; Parker, Joseph F.; Nelson, Eric S.; Rolison, Debra R.; Long, Jeffrey W.

2016-04-01

The ability to effectively screen and validate gas-diffusion electrodes is critical to the development of next-generation metal-air batteries and regenerative fuel cells. The limiting electrode in a classic two-terminal device such as a battery or fuel cell is difficult to discern without an internal reference electrode, but the flooded electrolyte characteristic of three-electrode electroanalytical cells negates the prime function of an air electrode—a void volume freely accessible to gases. The nanostructured catalysts that drive the energy-conversion reactions (e.g., oxygen reduction and evolution in the air electrode of metal-air batteries) are best evaluated in the electrode structure as-used in the practical device. We have designed, 3D-printed, and characterized an air-breathing, thermodynamically referenced electroanalytical cell that allows us to mimic the Janus arrangement of the gas-diffusion electrode in a metal-air cell: one face freely exposed to gases, the other wetted by electrolyte.

CAD/CAM-designed 3D-printed electroanalytical cell for the evaluation of nanostructured gas-diffusion electrodes.

PubMed

Chervin, Christopher N; Parker, Joseph F; Nelson, Eric S; Rolison, Debra R; Long, Jeffrey W

2016-04-29

The ability to effectively screen and validate gas-diffusion electrodes is critical to the development of next-generation metal-air batteries and regenerative fuel cells. The limiting electrode in a classic two-terminal device such as a battery or fuel cell is difficult to discern without an internal reference electrode, but the flooded electrolyte characteristic of three-electrode electroanalytical cells negates the prime function of an air electrode-a void volume freely accessible to gases. The nanostructured catalysts that drive the energy-conversion reactions (e.g., oxygen reduction and evolution in the air electrode of metal-air batteries) are best evaluated in the electrode structure as-used in the practical device. We have designed, 3D-printed, and characterized an air-breathing, thermodynamically referenced electroanalytical cell that allows us to mimic the Janus arrangement of the gas-diffusion electrode in a metal-air cell: one face freely exposed to gases, the other wetted by electrolyte.

Risk of groundwater inrush in subterranean gypsum quarries: the case study of Moncalvo near Asti (North Italy)

NASA Astrophysics Data System (ADS)

Banzato, Cinzia; Fiorucci, Adriano; Gianotti, Alberto; de Waele, Jo; Vigna, Bartolomeo

2010-05-01

During the realisation of underground excavations in gypsum bedrock there is a possibility of intercepting large karst voids that can be completely filled with water under a considerable hydraulic pressure. The casual breaching of such voids can cause sudden and abundant water inrushes with consequences concerning safety of the excavation area and flooding of the tunnels. The presence of air-filled caves of great dimensions can also cause problems related to collapse of walls, ceilings and floors. In the subterranean quarry of Moncalvo d'Asti (Central Piedmont, Italy) in January 2005 an important inrush (60,000 m3 overnight) occurred causing damage to machinery and the flooding of several kilometres of underground tunnels. This inrush was caused by the breaching of a thin diaphragm of rock that separated the quarry from a large water-filled cave with water pressure of around 300 kPa along the front of the excavation. The rapid emptying of this void has caused a partial collapse of the roof of one of the largest cave chambers with the formation at the surface of a 20 metre wide sinkhole. To prevent similar phenomena to happen in the future a hydrogeological study concerning the entire gypsum mass was carried out. These investigations included monitoring of water levels intercepted by a series of boreholes, measurements of flow rates of water veins encountered by the excavations and chemical analysis of the different types of water coming from several points. This study has evidenced the presence of different drainage networks and the existence of a main karst circuit fed by diffused infiltration and recharge from the overlying marly-silty deposits and from adjacent minor less karstified systems in particularly fractured sectors of the gypsum. The waters coming from the main karst circuit are chemically very different from the waters deriving from deeper pathways. To be able to continue the excavation of gypsum in safe conditions the water levels were lowered for a couple of metres through the realisation of a series of boreholes located at lower elevations. These boreholes have intercepted the most conductive aquifer developed along a marly limestone level located at the base of the Messinian evaporite sequence. Some near-horizontal drill holes carried out along the front of the excavations have also been realised and have intercepted a second karst system with water under pressure (> 300 kPa), independent from the main one. A controlled drainage is now being carried out (30 l/s) to slowly lower the hydraulic head so to avoid future collapse of these new karst voids. Some geophysical surveys have also been carried out to discover other karst voids of great dimensions, but these did not give positive results. The performed investigations have shown the importance of hydrogeological studies and speleological surveys in understanding better the development of the karst systems and in the realisation of the excavation activities in conditions of safety, allowing to avoid expensive interruptions of the mining operations.

Shrinkage void formation and its effect on freeze and thaw processes of lithium and lithium-fluoride for space applications

NASA Astrophysics Data System (ADS)

Yang, Jae-Young; El-Genk, M. S.

1991-07-01

The effects of shrinkage void forming during freezing of lithium and lithium-fluoride on subsequent thaw processes are investigated using a numerical scheme that is based on a single (solid/liquid) cell approach. Results show that a void forming at the wall appreciably reduces the solid-liquid interface velocity, during both freeze and thaw, and causes a substantial rise in the wall temperature during thaw. However, in the case of Li, the maximum wall temperature was much lower than the melting temperature of PWC-11, which is used as the structure material in the SP-100 system. Hence, it is concluded that a formation of hot spots is unlikely during the startup or restart of the SP-100 system.

Shrinkage void formation and its effect on freeze and thaw processes of lithium and lithium-fluoride for space applications

NASA Technical Reports Server (NTRS)

Yang, Jae Y.; El-Genk, Mohamed S.

1991-01-01

The effects of shrinkage void forming during freezing of lithium and lithium fluoride on subsequent thaw processes are investigated using a numerical scheme that is based on a single (solid/liquid) cell approach. Results show that a void forming at the wall appreciably reduces the solid-liquid interface velocity, during both freeze and thaw, and causes a substantial rise in the wall temperature during thaw. However, in the case of Li, the maximum wall temperature was much lower than the melting temperature of PWC-11, which is used as the structure material in the SP-100 system. Hence, it is concluded that a formation of hot spots is unlikely during the startup or restart of the SP-100 system.

Investigating Deformation and Mesoscale Void Creation in HMX Based Composites using Tomography Based Grain Scale Finite Element Modeling

NASA Astrophysics Data System (ADS)

Walters, David J.; Luscher, Darby J.; Manner, Virginia; Yeager, John D.; Patterson, Brian M.

2017-06-01

The microstructure of plastic bonded explosives (PBXs) significantly affects their macroscale mechanical characteristics. Imaging and modeling of the mesoscale constituents allows for a detailed examination of the deformation of mechanically loaded PBXs. In this study, explosive composites, formulated with HMX crystals and various HTPB based polymer binders have been imaged using micro Computed Tomography (μCT). Cohesive parameters for simulation of the crystal/binder interface are determined by comparing numerical and experimental results of the delamination of a polymer bound bi-crystal system. Similarly, polycrystalline samples are discretized into a finite element mesh using the mesoscale geometry captured by in-situ μCT imaging. Experimentally, increasing the stiffness of the HTPB binder in the polycrystalline system resulted in a transition from ductile flow with little crystal/binder delamination to brittle behavior with increased void creation along the interfaces. Simulating the macroscale compression of these samples demonstrates the effects that the mesoscale geometry, cohesive properties, and binder stiffness have on the creation and distribution of interfacial voids. Understanding void nucleation is critical for modeling damage in these complex materials.

The sparkling Universe: clustering of voids and void clumps

NASA Astrophysics Data System (ADS)

Lares, Marcelo; Ruiz, Andrés N.; Luparello, Heliana E.; Ceccarelli, Laura; Garcia Lambas, Diego; Paz, Dante J.

2017-07-01

We analyse the clustering of cosmic voids using a numerical simulation and the main galaxy sample from the Sloan Digital Sky Survey. We take into account the classification of voids into two types that resemble different evolutionary modes: those with a rising integrated density profile (void-in-void mode or R-type) and voids with shells (void-in-cloud mode or S-type). The results show that voids of the same type have stronger clustering than the full sample. We use the correlation analysis to define void clumps, associations with at least two voids separated by a distance of at most the mean void separation. In order to study the spatial configuration of void clumps, we compute the minimal spanning tree and analyse their multiplicity, maximum length and elongation parameter. We further study the dynamics of the smaller sphere that enclose all the voids in each clump. Although the global densities of void clumps are different according to their member-void types, the bulk motions of these spheres are remarkably lower than those of randomly placed spheres with the same radius distribution. In addition, the coherence of pairwise void motions does not strongly depend on whether voids belong to the same clump. Void clumps are useful to analyse the large-scale flows around voids, since voids embedded in large underdense regions are mostly in the void-in-void regime, where the expansion of the larger region produces the separation of voids. Similarly, voids around overdense regions form clumps that are in collapse, as reflected in the relative velocities of voids that are mostly approaching.

TMI-2 (Three Mile Island Unit 2) core region defueling

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

Rodabaugh, J.M.; Cowser, D.K.

1988-01-01

In July of 1982, a video camera was inserted into the Three Mile Island Unit 2 reactor vessel providing the first visual evidence of core damage. This inspection, and numerous subsequent data acquisition tasks, revealed a central void /approx/1.5 m (5 ft) deep. This void region was surrounded by partial length fuel assemblies and ringed on the periphery by /approx/40 full-length, but partial cross-section, fuel assemblies. All of the original 177 fuel assemblies exhibited signs of damage. The bottom of the void cavity was covered with a bed of granular rubble, fuel assembly upper end fittings, control rod spiders, fuelmore » rod fragments, and fuel pellets. It was obvious that the normal plant refueling system not suitable for removing the damaged core. A new system of defueling tools and equipment was necessary to perform this task. Design of the new system was started immediately, followed by >1 yr of fabrication. Delivery and checkout of the defueling system occurred in mid-1985. Actual defueling was initiated in late 1985 with removal of the debris bed at the bottom of the core void. Obstructions to the debris, such as end fittings and fuel rod fragments ere removed first; then /approx/23,000 kg (50,000lb) of granular debris was quickly loaded into canisters. Core region defueling was completed in late 1987, /approx/2 yr after it was initiated.« less

Fabrication of Nanovoid-Imbedded Bismuth Telluride with Low Dimensional System

NASA Technical Reports Server (NTRS)

Chu, Sang-Hyon (Inventor); Choi, Sang H. (Inventor); Kim, Jae-Woo (Inventor); Park, Yeonjoon (Inventor); Elliott, James R. (Inventor); King, Glen C. (Inventor); Stoakley, Diane M. (Inventor)

2013-01-01

A new fabrication method for nanovoids-imbedded bismuth telluride (Bi--Te) material with low dimensional (quantum-dots, quantum-wires, or quantum-wells) structure was conceived during the development of advanced thermoelectric (TE) materials. Bismuth telluride is currently the best-known candidate material for solid-state TE cooling devices because it possesses the highest TE figure of merit at room temperature. The innovative process described here allows nanometer-scale voids to be incorporated in Bi--Te material. The final nanovoid structure such as void size, size distribution, void location, etc. can be also controlled under various process conditions.

Fabrication and structural studies of opal-III nitride nanocomposites

NASA Astrophysics Data System (ADS)

Davydov, V. Yu; Golubev, V. G.; Kartenko, N. F.; Kurdyukov, D. A.; Pevtsov, A. B.; Sharenkova, N. V.; Brogueira, P.; Schwarz, R.

2000-12-01

In this paper, regular three-dimensional systems of GaN, InN and InGaN nanoclusters have been fabricated for the first time in a void sublattice of artificial opal. The opal consisted of 220 nm diameter close packed amorphous silica spheres and had a regular sublattice of voids accessible to filling by other substances. GaN, InN and InGaN were synthesized directly in the opal voids from precursors such as metal salts and nitrogen hydrides. The composites' structures have been characterized using x-ray diffraction, Raman spectroscopy, atomic force microscopy and optical measurements.

NDE Imaging of Time Differential Terahertz Waves

NASA Technical Reports Server (NTRS)

Trinh, Long B.

2008-01-01

Natural voids are present in the vicinity of a conathane interface that bonds two different foam materials. These voids are out of focus with the terahertz imaging system and multiple optical reflections also make it difficult to determine their depths. However, waves passing through the top foam article at normal incidence are partially reflected at the denser conathane layer prior to total reflection at the tank s wall. Reflections embedded in the oscillating noise segment prior to the main signals can be extracted with dual applications of filtering and time derivative. Void's depth is computed from direct path's time of flight.

Pick-off annihilation of positronium in matter using full correlation single particle potentials: solid He.

PubMed

Zubiaga, A; Tuomisto, F; Puska, M J

2015-01-29

We investigate the modeling of positronium (Ps) states and their pick-off annihilation trapped at open volumes pockets in condensed molecular matter. Our starting point is the interacting many-body system of Ps and a He atom because it is the smallest entity that can mimic the energy gap between the highest occupied and lowest unoccupied molecular orbitals of molecules, and yet the many-body structure of the HePs system can be calculated accurately enough. The exact-diagonalization solution of the HePs system enables us to construct a pairwise full-correlation single-particle potential for the Ps-He interaction, and the total potential in solids is obtained as a superposition of the pairwise potentials. We study in detail Ps states and their pick-off annihilation rates in voids inside solid He and analyze experimental results for Ps-induced voids in liquid He obtaining the radii of the voids. More importantly, we generalize our conclusions by testing the validity of the Tao-Eldrup model, widely used to analyze ortho-Ps annihilation measurements for voids in molecular matter, against our theoretical results for the solid He. Moreover, we discuss the influence of the partial charges of polar molecules and the strength of the van der Waals interaction on the pick-off annihilation rate.

GeoBioScience: Red Wood Ants as Bioindicators for Active Tectonic Fault Systems in the West Eifel (Germany)

PubMed Central

Berberich, Gabriele; Schreiber, Ulrich

2013-01-01

Simple Summary In a 1.140 km² study area of the volcanic West Eifel, approx. 3,000 Red Wood Ant (RWA; Formica rufa-group) mounds had been identified and correlated with tectonically active gas-permeable faults, mostly strike-slip faults. Linear alignment of RWA mounds and soil gas anomalies distinctly indicate the course of these faults, while clusters of mounds indicate crosscut zones of fault systems, which can be correlated with voids caused by crustal block rotation. This demonstrates that RWA are bioindicators for identifying active fault systems and useful where information on the active regime is incomplete or the resolution by technical means is insufficient. Abstract In a 1.140 km² study area of the volcanic West Eifel, a comprehensive investigation established the correlation between red wood ant mound (RWA; Formica rufa-group) sites and active tectonic faults. The current stress field with a NW-SE-trending main stress direction opens pathways for geogenic gases and potential magmas following the same orientation. At the same time, Variscan and Mesozoic fault zones are reactivated. The results showed linear alignments and clusters of approx. 3,000 RWA mounds. While linear mound distribution correlate with strike-slip fault systems documented by quartz and ore veins and fault planes with slickensides, the clusters represent crosscut zones of dominant fault systems. Latter can be correlated with voids caused by crustal block rotation. Gas analyses from soil air, mineral springs and mofettes (CO2, Helium, Radon and H2S) reveal limiting concentrations for the spatial distribution of mounds and colonization. Striking is further the almost complete absence of RWA mounds in the core area of the Quaternary volcanic field. A possible cause can be found in occasionally occurring H2S in the fault systems, which is toxic at miniscule concentrations to the ants. Viewed overall, there is a strong relationship between RWA mounds and active tectonics in the West Eifel. PMID:26487413

The nondestructive evaluation of high temperature conditioned concrete in conjunction with acoustic emission and x-ray computed tomography

NASA Astrophysics Data System (ADS)

Su, Yu-Min; Hou, Tsung-Chin; Lin, Li-Chiang; Chen, Gwan-Ying; Pan, Huang-Hsing

2016-04-01

Portland Cement Concrete plays a vital part of protecting structural rebars or steels when high-temperature fire incidents occur, that induces loss of evaporate water, dehydration of CH, and deconstruction of C-S-H. The objective of the study was to assess fire-damaged concrete in conjunction with nondestructive evaluation methods of acoustic emission, visual inspections, and X-ray computed tomography. The experimental program was to mix an Ordinary Portland Cement concrete firstly. Concrete cylinders with twenty-day moisture cure were treated in a furnace with 400 and 600°C for one hour. After temperature is cooled down, the concrete cylinders were brought to air or moisture re-curing for ten days. Due to the incident of the furnace, acoustic emission associated with splitting tensile strength test was not able to continue. Future efforts are planned to resume this unfinished task. However, two proposed tasks were executed and completed, namely visual inspections and voids analysis on segments obtained from X-ray CT facility. Results of visual inspections on cross-sectional and cylindrical length of specimens showed that both aggregates and cement pastes turned to pink or red at 600°C. More surface cracks were generated at 600°C than that at 400°C. On the other hand, voids analysis indicated that not many cracks were generated and voids were remedied at 400°C. However, a clear tendency was found that remedy by moisture curing may heal up to 2% voids of the concrete cylinder that was previously subject to 600°C of high temperature conditioning.

Cross-stacked carbon nanotubes assisted self-separation of free-standing GaN substrates by hydride vapor phase epitaxy

NASA Astrophysics Data System (ADS)

Wei, Tongbo; Yang, Jiankun; Wei, Yang; Huo, Ziqiang; Ji, Xiaoli; Zhang, Yun; Wang, Junxi; Li, Jinmin; Fan, Shoushan

2016-06-01

We report a novel method to fabricate high quality 2-inch freestanding GaN substrate grown on cross-stacked carbon nanotubes (CSCNTs) coated sapphire by hydride vapor phase epitaxy (HVPE). As nanoscale masks, these CSCNTs can help weaken the interface connection and release the compressive stress by forming voids during fast coalescence and also block the propagation of threading dislocations (TDs). During the cool-down process, thermal stress-induced cracks are initiated at the CSCNTs interface with the help of air voids and propagated all over the films which leads to full self-separation of FS-GaN substrate. Raman and photoluminescence spectra further reveal the stress relief and crystalline improvement of GaN with CSCNTs. It is expected that the efficient, low cost and mass-producible technique may enable new applications for CNTs in nitride optoelectronic fields.

Recognition and measurement gas-liquid two-phase flow in a vertical concentric annulus at high pressures

NASA Astrophysics Data System (ADS)

Li, Hao; Sun, Baojiang; Guo, Yanli; Gao, Yonghai; Zhao, Xinxin

2018-02-01

The air-water flow characteristics under pressure in the range of 1-6 MPa in a vertical annulus were evaluated in this report. Time-resolved bubble rising velocity and void fraction were also measured using an electrical void fraction meter. The results showed that the pressure has remarkable effect on the density, bubble size and rise velocity of the gas. Four flow patterns (bubble, cap-bubble, cap-slug, and churn) were also observed instead of Taylor bubble at high pressure. Additionally, the transition process from bubble to cap-bubble was investigated at atmospheric and high pressures, respectively. The results revealed that the flow regime transition criteria for atmospheric pressure do not work at high pressure, hence a new flow regime transition model for annular flow channel geometry was developed to predict the flow regime transition, which thereafter exhibited high accuracy at high pressure condition.

Cross-stacked carbon nanotubes assisted self-separation of free-standing GaN substrates by hydride vapor phase epitaxy.

PubMed

Wei, Tongbo; Yang, Jiankun; Wei, Yang; Huo, Ziqiang; Ji, Xiaoli; Zhang, Yun; Wang, Junxi; Li, Jinmin; Fan, Shoushan

2016-06-24

We report a novel method to fabricate high quality 2-inch freestanding GaN substrate grown on cross-stacked carbon nanotubes (CSCNTs) coated sapphire by hydride vapor phase epitaxy (HVPE). As nanoscale masks, these CSCNTs can help weaken the interface connection and release the compressive stress by forming voids during fast coalescence and also block the propagation of threading dislocations (TDs). During the cool-down process, thermal stress-induced cracks are initiated at the CSCNTs interface with the help of air voids and propagated all over the films which leads to full self-separation of FS-GaN substrate. Raman and photoluminescence spectra further reveal the stress relief and crystalline improvement of GaN with CSCNTs. It is expected that the efficient, low cost and mass-producible technique may enable new applications for CNTs in nitride optoelectronic fields.

Cross-stacked carbon nanotubes assisted self-separation of free-standing GaN substrates by hydride vapor phase epitaxy

PubMed Central

Wei, Tongbo; Yang, Jiankun; Wei, Yang; Huo, Ziqiang; Ji, Xiaoli; Zhang, Yun; Wang, Junxi; Li, Jinmin; Fan, Shoushan

2016-01-01

We report a novel method to fabricate high quality 2-inch freestanding GaN substrate grown on cross-stacked carbon nanotubes (CSCNTs) coated sapphire by hydride vapor phase epitaxy (HVPE). As nanoscale masks, these CSCNTs can help weaken the interface connection and release the compressive stress by forming voids during fast coalescence and also block the propagation of threading dislocations (TDs). During the cool-down process, thermal stress-induced cracks are initiated at the CSCNTs interface with the help of air voids and propagated all over the films which leads to full self-separation of FS-GaN substrate. Raman and photoluminescence spectra further reveal the stress relief and crystalline improvement of GaN with CSCNTs. It is expected that the efficient, low cost and mass-producible technique may enable new applications for CNTs in nitride optoelectronic fields. PMID:27340030

Detecting voids in a 0.6 m coal seam, 7 m deep, using seismic reflection

USGS Publications Warehouse

Miller, R.D.; Steeples, D.W.

1991-01-01

Surface collapse over abandoned subsurface coal mines is a problem in many parts of the world. High-resolution P-wave reflection seismology was successfully used to evaluate the risk of an active sinkhole to a main north-south railroad line in an undermined area of southeastern Kansas, USA. Water-filled cavities responsible for sinkholes in this area are in a 0.6 m thick coal seam, 7 m deep. Dominant reflection frequencies in excess of 200 Hz enabled reflections from the coal seam to be discerned from the direct wave, refractions, air wave, and ground roll on unprocessed field files. Repetitive void sequences within competent coal on three seismic profiles are consistent with the "room and pillar" mining technique practiced in this area near the turn of the century. The seismic survey showed that the apparent active sinkhole was not the result of reactivated subsidence but probably erosion. ?? 1991.

Rigid and Flexible Pavement Aircraft Tie-Downs

DTIC Science & Technology

2010-05-01

Concrete Pier, Prior to PCC Placement Neenah anchors are equipped with two ½-in-diameter cored holes to allow insertion of a section of rebar through...facilitate this process, a Hilti drill was utilized to perform the concrete drilling process. The drill bit diameter exceeded the rebar diameter by...aggregate particles not become lodged against the rebar sections inside the dowel sleeves, impeding the flow of concrete and possibly creating air voids

Intact urothelial barrier function in a mouse model of ketamine-induced voiding dysfunction

PubMed Central

Rajandram, Retnagowri; Ong, Teng Aik; Razack, Azad H. A.; MacIver, Bryce; Zeidel, Mark

2016-01-01

Ketamine is a popular choice for young drug abusers. Ketamine abuse causes lower urinary tract symptoms, with the underlying pathophysiology poorly understood. Disruption of urothelial barrier function has been hypothesized to be a major mechanism for ketamine cystitis, yet the direct evidence of impaired urothelial barrier function is still lacking. To address this question, 8-wk-old female C57BL/6J mice were injected intraperitoneally with 30 mg·kg−1·day−1 ketamine for 12 wk to induce ketamine cystitis. A spontaneous voiding spot assay showed that ketamine-treated mice had increased primary voiding spot numbers and smaller primary voiding spot sizes than control mice (P < 0.05), indicating a contracted bladder and bladder overactivity. Consistently, significantly increased voiding frequency was observed in ketamine-treated mice on cystometrograms. These functional experiments indicate that ketamine induces voiding dysfunction in mice. Surprisingly, urothelial permeability in ketamine-treated mice was not changed when measured using an Ussing chamber system with isotopic urea and water. Mouse urothelial structure was also not altered, and intact umbrella cell structure was observed by both transmission and scanning electron microscopy. Furthermore, immunostaining and confocal microscopy confirmed the presence of a well-defined distribution of zonula occuldens-1 in tight junctions and uroplakin in umbrella cells. In conclusion, these data indicate that ketamine injection induces voiding dysfunction in mice but does not necessarily disrupt mouse bladder barrier function. Disruption of urothelial barrier function may not be the major mechanism in ketamine cystitis. PMID:26911853

Local random configuration-tree theory for string repetition and facilitated dynamics of glass

NASA Astrophysics Data System (ADS)

Lam, Chi-Hang

2018-02-01

We derive a microscopic theory of glassy dynamics based on the transport of voids by micro-string motions, each of which involves particles arranged in a line hopping simultaneously displacing one another. Disorder is modeled by a random energy landscape quenched in the configuration space of distinguishable particles, but transient in the physical space as expected for glassy fluids. We study the evolution of local regions with m coupled voids. At a low temperature, energetically accessible local particle configurations can be organized into a random tree with nodes and edges denoting configurations and micro-string propagations respectively. Such trees defined in the configuration space naturally describe systems defined in two- or three-dimensional physical space. A micro-string propagation initiated by a void can facilitate similar motions by other voids via perturbing the random energy landscape, realizing path interactions between voids or equivalently string interactions. We obtain explicit expressions of the particle diffusion coefficient and a particle return probability. Under our approximation, as temperature decreases, random trees of energetically accessible configurations exhibit a sequence of percolation transitions in the configuration space, with local regions containing fewer coupled voids entering the non-percolating immobile phase first. Dynamics is dominated by coupled voids of an optimal group size, which increases as temperature decreases. Comparison with a distinguishable-particle lattice model (DPLM) of glass shows very good quantitative agreements using only two adjustable parameters related to typical energy fluctuations and the interaction range of the micro-strings.

RF-plasma vapor deposition of siloxane on paper. Part 1: Physical evolution of paper surface

NASA Astrophysics Data System (ADS)

Sahin, Halil Turgut

2013-01-01

An alternative, new approach to improve the hydrophobicity and barrier properties of paper was evaluated by radio-frequency (RF) plasma octamethylcyclotetrasiloxane (OMCTSO) vapor treatment. The interaction between OMCTSO and paper, causing the increased hydophobicity, is likely through covalent bonding. The deposited thin silicone-like polymeric layer from OMCTSO plasma treatment possessed desirable hydrophobic properties. The SEM micrographs showed uniformly distributed grainy particles with various shapes on the paper surface. Deposition of the silicone polymer-like layer with the plasma treatment affects the distribution of voids in the network structure and increases the barrier against water intake and air. The water absorptivity was reduced by 44% for the OMCTSO plasma treated sheet. The highest resistance to air flow was an approximately 41% lower air permeability than virgin paper.

Discrimination of chemical vapor and temperature using an in-line modal interferometer based on an exterior hole-assisted polarization-maintaining photonic crystal fiber

NASA Astrophysics Data System (ADS)

Yoon, Min-Seok; Jun, Naram; Lee, Sang Bae; Han, Young-Geun

2014-05-01

A reflective in-line modal interferometer based on a polarization-maintaining photonic crystal fiber (PM-PCF) with two exterior air holes is proposed for simultaneous measurement of chemical vapor and temperature. After fusion-splicing the PM-PCF with a standard single-mode fiber, we collapse all of air holes in the PM-PCF resulting in two types of interference patterns between the core and the cladding modes in the PM-PCF depending on two polarization states. Since two large air holes at the facet of the proposed modal interferometer are left open, a chemical vapor can be infiltrated into the voids. Different sensitivities corresponding to input polarization states are utilized for discrimination between chemical vapor and temperature sensitivities.

Use of fly-ash slurry in backfill grouting in coal mines.

PubMed

Jiang, Ning; Zhao, Jinhai; Sun, Xizhen; Bai, Liyang; Wang, Changxiang

2017-11-01

Cave backfill grouting implies grouting of the caving rock mass prior to it being compacted. The filling materials strengthen the caving rock and support the overlying strata to achieve the purpose of slowing down the surface subsidence. The broken roof will fail and collapse during mining operations performed without appropriate supporting measures being taken. It is difficult to perform continuous backfill mining on the working face of such roofs using the existing mining technology. In order to solve the above problems, fly ash and mine water are considered as filling materials, and flow characteristics of fly-ash slurry are investigated through laboratory experiments and theoretical analyses. Laws governing the diffusion of fly-ash slurry in the void of caving rock masses and in the void between a caving rock mass and a basic roof are obtained and verified. Based on the results obtained from the above analyses and actual conditions at the Zhaoguan coal mine, Shandong Province, China, a cave backfill grouting system of the hauling pipeline is developed and successfully tested at the 1703 working face in the Zhaoguan coal mine. The results demonstrate that a filling rate of 43.46% is achieved, and the surface subsidence coefficient of the grouting process is found to be 0.475. Compared to the total caving method, the proposed system is found to achieve a reduction rate of 40.63%. This effectively helps in lowering the value of the surface subsidence coefficient. Fly ash and mine water, considered as primary materials in this study, also play a significant role in improving the air quality and water environment.

Void Management in MEPHISTO and Other Space Experiments

NASA Technical Reports Server (NTRS)

deGroh, Henry C., III; Johnston, J. Christopher; Wei, Bingbo

1998-01-01

The second flight of NASA's Shuttle Flight experiment program known as MEPHISTO suffered from a void in the liquid portion of the sample, even though a piston arrangement was in place to keep the ampoule filled. In preparations for the next flight of the MEPHISTO furnace an animated computer program, called MEPHISTO Volume Visualizer (MVV), was written to help avoid the formation of unwanted voids. A piston system on MEPHISTO has the ability to move approximately 5 mm in compression, to accommodate expansion of the solid during heating; then from the completely compressed position, the piston can move up to 25 mm in towards the sample, effectively making the ampoule smaller and hopefully eliminating any voids. Due to the nature of the piston design and ampoule and sample arrangement, the piston has gotten stuck during normal directional solidification; this creates the risk of a void. To eliminate such a void, the liquid in the hot zones of the furnace can be heated, thereby expanding the liquid and consuming any void. The problem with this approach is that if the liquid is heated too much an overpressure could result, breaking the ampoule and ending the experiment catastrophically. The MVV has been found to be a useful tool in the assessment of the risks associated with the formation of a void and the additional heating of the liquid in the hot zone of this Bridgman type furnace. The MVV software will be discussed and copies available; it is written in the Delphi 2 programming language and runs under Windows 95 and NT. The strategies used in other flight experiments, such as the Isothermal Dendritic Growth Experiment, will also be presented.

Probabilistic immortality of Cu damascene interconnects

NASA Astrophysics Data System (ADS)

Hau-Riege, Stefan P.

2002-02-01

We have studied electromigration short-line effects in Cu damascene interconnects through experiments on lines of various lengths L, stressed at a variety of current densities j, and embedded in different dielectric materials. We observed two modes of resistance evolution: Either the resistance of the lines remains constant for the duration of the test, so that the lines are considered immortal, or the lines fail due to abrupt open-circuit failure. The resistance was not observed to gradually increase and then saturate, as commonly observed in Al-based interconnects, because the barrier is too thin and resistive to serve as a redundant current path should voiding occur. The critical stress for void nucleation was found to be smaller than 41 MPa, since voiding occurred even under the mildest test conditions of j=2 MA/cm2 and L=10.5 μm at 300 °C. A small fraction of short Cu lines failed even at low current densities, which deems necessary a concept of probabilistic immortality rather than deterministic immortality. Experiments and modeling suggest that the probability of immortality is described by (jL2/B), where B is the effective elastic modulus of the metallization scheme. By contrast, the immortality of Al-based interconnects with shunt layers is described by (jL) if no voids nucleate, and (jL/B) if voids do nucleate. Even though the phenomenology of short-line effects differs for Al- and Cu-based interconnects, the immortality of interconnects of either materials system can be explained by the phenomena of nucleation barriers for void formation and void-growth saturation. The differences are due solely to the absence of a shunt layer and the low critical stress for void nucleation in the case of Cu.

The wire-mesh sensor as a two-phase flow meter

NASA Astrophysics Data System (ADS)

Shaban, H.; Tavoularis, S.

2015-01-01

A novel gas and liquid flow rate measurement method is proposed for use in vertical upward and downward gas-liquid pipe flows. This method is based on the analysis of the time history of area-averaged void fraction that is measured using a conductivity wire-mesh sensor (WMS). WMS measurements were collected in vertical upward and downward air-water flows in a pipe with an internal diameter of 32.5 mm at nearly atmospheric pressure. The relative frequencies and the power spectral density of area-averaged void fraction were calculated and used as representative properties. Independent features, extracted from these properties using Principal Component Analysis and Independent Component Analysis, were used as inputs to artificial neural networks, which were trained to give the gas and liquid flow rates as outputs. The present method was shown to be accurate for all four encountered flow regimes and for a wide range of flow conditions. Besides providing accurate predictions for steady flows, the method was also tested successfully in three flows with transient liquid flow rates. The method was augmented by the use of the cross-correlation function of area-averaged void fraction determined from the output of a dual WMS unit as an additional representative property, which was found to improve the accuracy of flow rate prediction.

Utilization of polyethylene terephthalate (PET) in bituminous mixture for improved performance of roads

NASA Astrophysics Data System (ADS)

Ahmad, A. F.; Razali, A. R.; Razelan, I. S. M.; Jalil, S. S. A.; Noh, M. S. M.; Idris, A. A.

2017-05-01

Plastic bottle for recycling can be found from the household waste stream, and most of them are made from Polyethylene Terephthalate. In this research, PET is utilized to explore the potential prospects to upgrade asphalt mixture properties. The objectives include deciding the best measure of PET to be used. For experimental, Marshall mix design was utilized to determine the ideal bitumen binder content and to test the modified mixture properties. The samples were created per the requirement for aggregate course wearing (ACW14) using the Standard Specification of Road Work (SSRW) in Malaysia. 20 samples were utilized to determine the binder content, and 30 samples were used to research the impact of modifying asphalt mixtures. 2%, 5%, 10%, 15% and 20% of PET by weight of the optimum binder content (4.8%) were tested. Optimum PET content is 10%, and the result shows a good stability with 16.824kN, 2.32g/cm3 bulk density, void filled with bitumen (VFB) with 71.35%, flow with 3.2248mm, air void (AV) with 4.53%, and void of mineral aggregate (VMA) with 15.15%. The outcomes showed that PET modifier gives better engineering properties. Therefore, 10% of PET by the weight of binder content was suggested as the best amount of the modifier.

Demonstrating the Operational Value of Atmospheric Infrared Sounder (AIRS) Retrieved Profiles in the Pre-Convective Environment

NASA Technical Reports Server (NTRS)

Kozlowski, Danielle M.; Zavodsky, T.; Jedloved, Gary J.

2011-01-01

The Short-term Prediction Research and Transition Center (SPoRT) is a collaborative partnership between NASA and operational forecasting partners, including a number of National Weather Service offices. SPoRT provides real-time NASA products and capabilities to its partners to address specific operational forecast challenges. One operational forecast challenge is forecasting convective weather in data-void regions such as large bodies of water (e.g. Gulf of Mexico). To address this forecast challenge, SPoRT produces a twice-daily three-dimensional analysis that blends a model first-guess from the Advanced Research Weather Research and Forecasting (WRF-ARW) model with retrieved profiles from the Atmospheric Infrared Sounder (AIRS) -- a hyperspectral sounding instrument aboard NASA's Aqua satellite that provides temperature and moisture profiles of the atmosphere. AIRS profiles are unique in that they give a three dimensional view of the atmosphere that is not available through the current rawinsonde network. AIRS has two overpass swaths across North America each day, one valid in the 0700-0900 UTC timeframe and the other in the 1900-2100 UTC timeframe. This is helpful because the rawinsonde network only has data from 0000 UTC and 1200 UTC at specific land-based locations. Comparing the AIRS analysis product with control analyses that include no AIRS data demonstrates the value of the retrieved profiles to situational awareness for the pre-convective (and convective) environment. In an attempt to verify that the AIRS analysis was a good representation of the vertical structure of the atmosphere, both the AIRS and control analyses are compared to a Rapid Update Cycle (RUC) analysis used by operational forecasters. Using guidance from operational forecasters, convective available potential energy (CAPE) was determined to be a vital variable in making convective forecasts and is used herein to demonstrate the utility of the AIRS profiles in changing the vertical thermodynamic structure of the atmosphere in the pre-convective and convective environment. CAPE is an important metric because of it is a quantitative measure of atmospheric stability, which is necessary information when forecasting for convective weather. Case studies from the summer of 2010 were examined, and most impact from the AIRS retrieved profiles occurred over the data-void Gulf of Mexico with fields of convective potential closer to the RUC than the CNTL. Mixed results were found when AIRS retrieved profiles were used over land, so more cases need to be examined to determine whether AIRS would be an effective tool over land. Additional analyses of problematic convective forecasts over the Gulf Coast will be needed to determine the operational impact of AIRS. SPoRT eventually plans to transition the AIRS product to select Weather Forecast Office (WFO) partners, pending the outcome of these additional analyses.

Field joint protection system rain qualification test report

NASA Technical Reports Server (NTRS)

Cook, M.

1989-01-01

This report documents the procedures, performance, and results obtained from the Field Joint Protection System (FJPS) rain test. This test was performed to validate that the flight configuration FJPS prevents the accumulation of moisture in the redesigned solid rocket motor (RSRM) field joints when subjected to simulated prelaunch natural rain environments. The FJPS test article was exposed to rain simulation for approximately 50 minutes. During the test, water entered through the open upper end of the systems tunnel and was funneled down between the tunnel and case. A sealant void at the moisture seal butt splice allowed this water to flow underneath the FJPS. The most likely cause of voids was improper bondline preparation, particularly on the moisture seal surface. In total, water penetrated underneath approximately 60 percent of the FJPS circumference. Because the test article was substantially different from flight configuration (no systems tunnel closeout), results of this test will not affect current flight motors. Due to the omission of systems tunnel covers and systems tunnel floor plate closeout, the test assembly was not representative of flight hardware and resulted in a gross overtest. It is therefore recommended that the test be declared void. It is also recommended that the test be repeated with a complete closeout of the systems tunnel, sealed systems tunnel ends, and improved adhesive bondline preparation.

An approach for maximizing the smallest eigenfrequency of structure vibration based on piecewise constant level set method

NASA Astrophysics Data System (ADS)

Zhang, Zhengfang; Chen, Weifeng

2018-05-01

Maximization of the smallest eigenfrequency of the linearized elasticity system with area constraint is investigated. The elasticity system is extended into a large background domain, but the void is vacuum and not filled with ersatz material. The piecewise constant level set (PCLS) method is applied to present two regions, the original material region and the void region. A quadratic PCLS function is proposed to represent the characteristic function. Consequently, the functional derivative of the smallest eigenfrequency with respect to PCLS function takes nonzero value in the original material region and zero in the void region. A penalty gradient algorithm is proposed, which initializes the whole background domain with the original material and decreases the area of original material region till the area constraint is satisfied. 2D and 3D numerical examples are presented, illustrating the validity of the proposed algorithm.

Structural Investigations of Fibers and Films of Poly(p-phenylene benzobisthiazole). Volume 1

DTIC Science & Technology

1982-05-01

differential scanning calorimetry, is unrelated to the diffuse scattered intensity [45]. Cellulose acetate which is known to be noncrystalline exhibits a high...Weidinger [45] found the diffuse scattered intensity increased with decreasing density and therefore, increasing void fraction, in air swollen cellulose ... Cellulose , and Poly(y-Benzyl-L-Glutamate)." J. Polym. Sci., Polym. Phys. Ed., 18, 663-682 (1980). 39. C.H. Kao and J.M. Ottino, personal communication

Inverse opal with an ultraviolet photonic gap

NASA Astrophysics Data System (ADS)

Ni, Peigen; Cheng, Bingying; Zhang, Daozhong

2002-03-01

Photonic crystals composed of TiO2 and air voids fabricated by the template method exhibit an ultraviolet photonic stop band (˜380 nm) in the Γ-L direction. Scanning electron microscopy images show that the inverse opal possesses face-centered-cubic symmetry with a lattice constant of 240 nm. The transmission spectra show that the change in transmittance is one order of magnitude in the gap, which is in accord with the reflection spectrum.

Effect of different mixing and placement methods on the quality of MTA apical plug in simulated apexification model.

PubMed

Ghasemi, Negin; Janani, Maryam; Razi, Tahmineh; Atharmoghaddam, Faezeh

2017-03-01

It is necessary apical plug material to exhibit proper adaptation with the root canal walls. Presence of voids at the interface between the root canal wall and this material result in micro leakage, which might have a relationship with post treatment disease. The aim of the present study was to evaluate the effect of different mixing (manual and ultrasonic) and placement (manual and manual in association with indirect ultrasonic) method of Mineral Trioxide Aggregate (MTA) on the void count and dimension in the apical plug in natural teeth with simulated open apices. Eighty human maxillary central incisors were selected. After simulation of the open apex model, the teeth were assigned to 4 groups based on the mixing and placement techniques of MTA: group 1, manual mixing and manual placement; group 2, manual mixing and manual placement in association with indirect ultrasonic; group 3, ultrasonic mixing and and manual placement; and group 4, ultrasonic mixing and manual placement in association with indirect ultrasonic. The prepared samples were placed within gypsum sockets in which the periodontal ligament was reconstructed with polyether impression material. In group 1, after mixing, the material was condensed with a hand plugger. In group 2, after mixing, the ultrasonic tip was contacted with the hand plugger for 2 seconds. In groups 3 and 4, mixing was carried out with the ultrasonic tip for 5 seconds and in groups 3 and 4, similar to groups 1 and 2, respectively, the materials were placed as apical plugs, measuring 3 mm in length. A wet cotton pellet was placed at canal orifices and dressed with Cavit. After one week, the cone beam computed tomography (CBCT) technique was used to count the number of voids between the material and root canal walls. The void dimensions were determined using the following scoring system: score 1, absence of voids; score 2, the void size less than half of the dimensions of the evaluated cross-section; score 3, the void size larger than half of the dimensions of the evaluated cross-section. Chi-squared and Fisher's exact tests were used for statistical analyses. Statistical significance was set at P <0.05. The maximum (13) and minimum (3) number of voids were detected in groups 2 and 3, respectively. There were no significant differences between groups 1 and 3 in the number of voids ( p >0.05). Evaluation of void dimensions showed no score 3 in any of the study groups and the dimensions of all the voids conformed to score 2. Under the limitations of the present study, use of ultrasonic mixing and manual placement techniques resulted in a decrease in the number of voids in the apical plug. Key words: Apical plug, MTA, ultrasonic, void.

Annular Air Leaks in a liquid hydrogen storage tank

NASA Astrophysics Data System (ADS)

Krenn, AG; Youngquist, RC; Starr, SO

2017-12-01

Large liquid hydrogen (LH2) storage tanks are vital infrastructure for NASA, the DOD, and industrial users. Over time, air may leak into the evacuated, perlite filled annular region of these tanks. Once inside, the extremely low temperatures will cause most of the air to freeze. If a significant mass of air is allowed to accumulate, severe damage can result from nominal draining operations. Collection of liquid air on the outer shell may chill it below its ductility range, resulting in fracture. Testing and analysis to quantify the thermal conductivity of perlite that has nitrogen frozen into its interstitial spaces and to determine the void fraction of frozen nitrogen within a perlite/frozen nitrogen mixture is presented. General equations to evaluate methods for removing frozen air, while avoiding fracture, are developed. A hypothetical leak is imposed on an existing tank geometry and a full analysis of that leak is detailed. This analysis includes a thermal model of the tank and a time-to-failure calculation. Approaches to safely remove the frozen air are analyzed, leading to the conclusion that the most feasible approach is to allow the frozen air to melt and to use a water stream to prevent the outer shell from chilling.

The Local Ly(alpha) Forest: Association of Clouds with Superclusters and Voids

NASA Technical Reports Server (NTRS)

Stocke, John T.; Shull, J. Michael; Penton, Steve; Donahue, Megan; Carilli, Chris

1995-01-01

The Goddard High Resolution Spectrograph aboard the Hubble Space Telescope was used with the G160M grating to obtain high-resolution (6.2 A) spectra of three very bright active galactic nuclei located behind voids in the nearby distribution of bright galaxies (i.e., CfA and Arecibo redshift survey regions). A total of eight definite (greater than or equal to 4 sigma) Ly(alpha) absorption lines were discovered ranging in equivalent width from 26 to 240 mA at Galactocentric velocities 1740-7740 km/s. Of these eight systems, we locate seven in supercluster structures and one, in the sight line of Mrk 501 at 7740 km/s, in a void. In addition, one of two tentative (3-4 sigma) Ly(alpha) absorption lines are found in voids. Thus, the voids are not entirely devoid of matter, and not all Ly(alpha) clouds are associated with galaxies. Also, since the path lengths through voids and superclusters probed by our observations thus far are nearly equal, there is some statistical evidence that the Ly(alpha) clouds avoid the voids. The nearest galaxy neighbors to these absorbing clouds are 0.45-5.9 Mpc away, too far to be physically associated by most models. The lower equivalent width absorption lines (W(sub lambda) less than or equal to 100 mA) are consistent with random locations with respect to galaxies and may be truly intergalactic, similar to the bulk of the Ly(alpha) forest seen at high z. These results on local Ly(alpha) clouds are in full agreement with those found by Morris et al. (1993) for the 3C 273 sight line but are different from the results for higher equivalent width systems where closer cloud-galaxy associations were found by Lanzetta et al. (1994). Pencil-beam optical and 21 cm radio line observations of the area of sky surrounding Mrk 501 fail to find faint galaxies near the velocities of the Ly(alpha) clouds in that sight line. Specifically, for the 'void absorption' system at 7740 km/s, we find no galaxy at comparable redshift to the absorber within 100 h(sub 75)(sup -1) kpc (H(sub 0) = 75 h(sub 75) km/s Mpc(sup -1)) with an absolute magnitude of B less than or equal to - 16 and no object with H I mass greater than or equal to 7 x 10(exp 8) h(sub 75)(sup -2) M(solar) within 500 h(sub 75)(sup -1) kpc. Thus, neither a faint optical galaxy nor a gas-rich, optically dim or low surface brightness galaxy is present close to this absorber.

Mathematical Model of Two Phase Flow in Natural Draft Wet-Cooling Tower Including Flue Gas Injection

NASA Astrophysics Data System (ADS)

Hyhlík, Tomáš

2016-03-01

The previously developed model of natural draft wet-cooling tower flow, heat and mass transfer is extended to be able to take into account the flow of supersaturated moist air. The two phase flow model is based on void fraction of gas phase which is included in the governing equations. Homogeneous equilibrium model, where the two phases are well mixed and have the same velocity, is used. The effect of flue gas injection is included into the developed mathematical model by using source terms in governing equations and by using momentum flux coefficient and kinetic energy flux coefficient. Heat and mass transfer in the fill zone is described by the system of ordinary differential equations, where the mass transfer is represented by measured fill Merkel number and heat transfer is calculated using prescribed Lewis factor.

Lower urinary tract dysfunction in children after intravesical ureteric reimplantation surgery under one year of age.

PubMed

Ooi, S M; Kane, N; Khosa, J; Barker, A; Samnakay, N

2014-12-01

To report the results of a study conducted on voiding function in children who have undergone intravesical trans-trigonal Cohen ureteric reimplantation surgery before the age of one year. Twenty-eight children (18 males, 10 females) had surgery at a mean age of 4.9 months (range 8-352 days). Bladder function was assessed at a mean age of 7.3 years using questionnaires, the dysfunctional voiding scoring system, PinQ quality of life tool, uroflowmetry and post-void residuals. Of the total children, 72% had normal lower urinary tract (LUT) function. Eight children (28%) had evidence of LUT dysfunction, two had urge incontinence, two had giggle incontinence, two had voiding postponement, one had dysfunctional elimination syndrome and one had evidence of dysfunctional voiding. Five of the eight children were managed with continence physiotherapy (urotherapy) and one required ongoing anticholinergic therapy. When compared to the published rates of LUT dysfunction in the general paediatric community, no evidence was found to suggest an increased incidence of bladder dysfunction in children undergoing intravesical Cohen ureteric reimplantation surgery under one year of age. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

The evolution of voids in the adhesion approximation

NASA Astrophysics Data System (ADS)

Sahni, Varun; Sathyaprakah, B. S.; Shandarin, Sergei F.

1994-08-01

We apply the adhesion approximation to study the formation and evolution of voids in the universe. Our simulations-carried out using 1283 particles in a cubical box with side 128 Mpc-indicate that the void spectrum evolves with time and that the mean void size in the standard Cosmic Background Explorer Satellite (COBE)-normalized cold dark matter (CDM) model with H50 = 1 scals approximately as bar D(z) = bar Dzero/(1+2)1/2, where bar Dzero approximately = 10.5 Mpc. Interestingly, we find a strong correlation between the sizes of voids and the value of the primordial gravitational potential at void centers. This observation could in principle, pave the way toward reconstructing the form of the primordial potential from a knowledge of the observed void spectrum. Studying the void spectrum at different cosmological epochs, for spectra with a built in k-space cutoff we find that the number of voids in a representative volume evolves with time. The mean number of voids first increases until a maximum value is reached (indicating that the formation of cellular structure is complete), and then begins to decrease as clumps and filaments erge leading to hierarchical clustering and the subsequent elimination of small voids. The cosmological epoch characterizing the completion of cellular structure occurs when the length scale going nonlinear approaches the mean distance between peaks of the gravitaional potential. A central result of this paper is that voids can be populated by substructure such as mini-sheets and filaments, which run through voids. The number of such mini-pancakes that pass through a given void can be measured by the genus characteristic of an individual void which is an indicator of the topology of a given void in intial (Lagrangian) space. Large voids have on an average a larger measure than smaller voids indicating more substructure within larger voids relative to smaller ones. We find that the topology of individual voids is strongly epoch dependent, with void topologies generally simplifying with time. This means that as voids grow older they become progressively more empty and have less structure within them. We evaluate the genus measure both for individual voids as well as for the entire ensemble of voids predicted by CDM model. As a result we find that the topology of voids when taken together with the void spectrum is a very useful statistical indicator of the evolution of the structure of the universe on large scales.

The evolution of voids in the adhesion approximation

NASA Technical Reports Server (NTRS)

Sahni, Varun; Sathyaprakah, B. S.; Shandarin, Sergei F.

1994-01-01

We apply the adhesion approximation to study the formation and evolution of voids in the universe. Our simulations-carried out using 128(exp 3) particles in a cubical box with side 128 Mpc-indicate that the void spectrum evolves with time and that the mean void size in the standard Cosmic Background Explorer Satellite (COBE)-normalized cold dark matter (CDM) model with H(sub 50) = 1 scals approximately as bar D(z) = bar D(sub zero)/(1+2)(exp 1/2), where bar D(sub zero) approximately = 10.5 Mpc. Interestingly, we find a strong correlation between the sizes of voids and the value of the primordial gravitational potential at void centers. This observation could in principle, pave the way toward reconstructing the form of the primordialpotential from a knowledge of the observed void spectrum. Studying the void spectrum at different cosmological epochs, for spectra with a built in k-space cutoff we find that the number of voids in a representative volume evolves with time. The mean number of voids first increases until a maximum value is reached (indicating that the formation of cellular structure is complete), and then begins to decrease as clumps and filaments erge leading to hierarchical clustering and the subsequent elimination of small voids. The cosmological epoch characterizing the completion of cellular structure occurs when the length scale going nonlinear approaches the mean distance between peaks of the gravitaional potential. A central result of this paper is that voids can be populated by substructure such as mini-sheets and filaments, which run through voids. The number of such mini-pancakes that pass through a given void can be measured by the genus characteristic of an individual void which is an indicator of the topology of a given void in intial (Lagrangian) space. Large voids have on an average a larger measure than smaller voids indicating more substructure within larger voids relative to smaller ones. We find that the topology of individual voids is strongly epoch dependent, with void topologies generally simplifying with time. This means that as voids grow older they become progressively more empty and have less structure within them. We evaluate the genus measure both for individual voids as well as for the entire ensemble of voids predicted by CDM model. As a result we find that the topology of voids when taken together with the void spectrum is a very useful statistical indicator of the evolution of the structure of the universe on large scales.

Synthesis of porous graphene powder through improved Hummers' method

NASA Astrophysics Data System (ADS)

Gupta, Siddhant; Bonageri, Shrilakshmi; Achar, Siddarth Krishnaraja; Menon, Atul; Basavaraja R., J.

2018-05-01

Graphene due to its high specific surface area is considered to be a potential adsorbent for air and water purification systems. In this study, graphene was synthesized using the recently developed Improved Hummers' method to achieve a high oxidation rate and thermal treatment of the synthesized graphene was done to increase its pore size and make it more capable for applications in purification systems. Graphite flakes were oxidized to obtain graphene oxide which was then reduced to obtain graphene. The synthesized graphene was then thermally treated at 200 °C for two hours in a muffle furnace to improve its surface properties. The characterization results of graphene oxide and graphene show the presence of many impurities which is inferred to be the result of contaminated water used in the experimentation. The analysis of the characterization results also shows that the thermally treated graphene has more spacing and voids when compared to graphene which makes it a better suit for adsorption of gases such as carbon dioxide.

The 371 deg C mechanical properties of graphite/polyimide composites

NASA Technical Reports Server (NTRS)

Delvigs, P.

1985-01-01

A series of condensation polyimides based on pyromellitic dianhydride is synthesized and evaluated for potential application at 371 C. Several three-and four-ring benzenoid diamine systems containing oxygen bridging groups are investigated. Thermomechanical analysis of neat resin specimens indicate that the polyimide prepared from the dimethyl ester of pyrometallitic acid (PMDE) and 2,2-bis4-(4'-aminophenoxy) phenyl]-1,1,1,3,3,3- hexafluoropropane (BDAF) is the only resin system which has a glass transition temperature (Tg) above 371 C. The Tg of the PMDE/BDAF polyimide is found to be 390 C after a postcure air at 371 C for 24 hr. Unidirectional composites are fabricated from the PMDE/BDAF system and unsized Celion 6000 graphite fibers. Final cure temperatures in the range of 371 to 427 C with an applied pressure of 10.34 to 13.78 MPa are investigated. The void content of the composites ranges from 4.6 to 8.6 percent. Composites cured at 399 C under a pressure of 10.34 MPa and postcured in air at 371 C for 24 hr exhibit the highest 371 C interlaminar shear strength (ILSS, 40.7 MPa) and flexural strength (758 MPa). The thermo-oxidative stability of the composites is determined by subjecting specimens to isothermal exposure at 371 C in air at atmospheric pressure, as well as a pressure of 0.52 MPa. Specimens exposed at atmospheric pressure exhibit a weight loss of 12 percent after 200 hr of exposure and 88 percent retention of its original 371 C ILSS. In contrast, the specimens exposed at 0.52 MPa pressure exhibit a comparable weight loss after only 72 hr, and a 71 percent retention of its original 371 C ILSS.

Integrated Field Scale, Lab Scale, and Modeling Studies for Improving Our Ability to Assess the Groundwater to Indoor Air Pathway at Chlorinated Solvent Impacted Groundwater Sites

DTIC Science & Technology

2016-01-07

clays . The Emean/Estatic values were greater for loam than the other two types of soil – indicating greater amplification of emissions relative to a...ɸT): 0.35 m3-voids/m3- soil Soil permeability to soil gas flow (Kg): 1E-7 cm2 Soil gas phase dynamic viscosity : 1.8E-4 g/cm/s Soil domain

Software Design Document for the AirNET Aeromodel and Weapons Model Conversion. Volume 1. Version 0.0,

DTIC Science & Technology

1993-01-22

AUGLPITCHROLLCONTROLa ttitude .-ontrol_roll_command, MAX..STABAUG3_PITCH-.ROLL..CONTROL); return ( attitude -.control-roll-commuand); static REAL set...pitch...if any). V V RETURNS: TRUE if successful, FALSE if not. V * PURPOSE: This routine performs the functions V V specifically related to the firing of a...specifically related to the flying a ADAT * missile. * void missile _adaLfly (aptr, sightiocation, locqsightto.world, tube, veh_list) ADATMISSILE

Anderson localized modes in a disordered glass optical fiber

NASA Astrophysics Data System (ADS)

Karbasi, Salman; Hosseini, Seyedrasoul; Koch, Karl W.; Hawkins, Thomas; Ballato, John; Mafi, Arash

2014-02-01

A beam of light can propagate in a time-invariant transversely disordered waveguide because of transverse Anderson localization. We developed a disordered glass optical ber from a porous artisan glass (satin quartz). The refractive index pro le of the disordered glass optical ber is composed of a non-uniform distribution of air voids which can be approximated as longitudinally invariant. The ll-fraction of air voids is higher at the regions closer to the boundary compared with the central regions. The experimental results show that the beam radius of a localized beam is smaller at the regions closer to the boundary than the one at the central regions. In order to understand the reason behind these observations, the fully vectorial modes of the disordered glass ber are calculated using the actual scanning electron microscope image of the ber tip. The numerical calculations show that the modes at regions closer to the boundary of the ber are more localized compared with the modes at the central regions. Coupling of an input beam to the less-localized modes with large tails at the central regions of the ber results in a large beam radius. In comparison, a beam of light launched at the regions close to the boundary couples to the highly compact modes of the ber and results in a small localized beam radius.

ONLY THE LONELY: H I IMAGING OF VOID GALAXIES

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

Kreckel, K.; Van Gorkom, J. H.; Platen, E.

2011-01-15

Void galaxies, residing within the deepest underdensities of the Cosmic Web, present an ideal population for the study of galaxy formation and evolution in an environment undisturbed by the complex processes modifying galaxies in clusters and groups, as well as provide an observational test for theories of cosmological structure formation. We have completed a pilot survey for the H I imaging aspects of a new Void Galaxy Survey (VGS), imaging 15 void galaxies in H I in local (d < 100 Mpc) voids. H I masses range from 3.5 x 10{sup 8} to 3.8 x 10{sup 9} M{sub sun}, withmore » one nondetection with an upper limit of 2.1 x 10{sup 8} M{sub sun}. Our galaxies were selected using a structural and geometric technique to produce a sample that is purely environmentally selected and uniformly represents the void galaxy population. In addition, we use a powerful new backend of the Westerbork Synthesis Radio Telescope that allows us to probe a large volume around each targeted galaxy, simultaneously providing an environmentally constrained sample of fore- and background control samples of galaxies while still resolving individual galaxy kinematics and detecting faint companions in H I. This small sample makes up a surprisingly interesting collection of perturbed and interacting galaxies, all with small stellar disks. Four galaxies have significantly perturbed H I disks, five have previously unidentified companions at distances ranging from 50 to 200 kpc, two are in interacting systems, and one was found to have a polar H I disk. Our initial findings suggest void galaxies are a gas-rich, dynamic population which present evidence of ongoing gas accretion, major and minor interactions, and filamentary alignment despite the surrounding underdense environment.« less

Nebular Metallicities in Two Isolated Local Void Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Nicholls, David C.; Jerjen, Helmut; Dopita, Michael A.; Basurah, Hassan

2014-01-01

Isolated dwarf galaxies, especially those situated in voids, may provide insight into primordial conditions in the universe and the physical processes that govern star formation in undisturbed stellar systems. The metallicity of H II regions in such galaxies is key to investigating this possibility. From the SIGRID sample of isolated dwarf galaxies, we have identified two exceptionally isolated objects, the Local Void galaxy [KK98]246 (ESO 461-G036) and another somewhat larger dwarf irregular on the edge of the Local Void, MCG-01-41-006 (HIPASS J1609-04). We report our measurements of the nebular metallicities in these objects. The first object has a single low luminosity H II region, while the second is in a more vigorous star forming phase with several bright H II regions. We find that the metallicities in both galaxies are typical for galaxies of this size, and do not indicate the presence of any primordial gas, despite (for [KK98]246) the known surrounding large reservoir of neutral hydrogen.

Asymmetric bubble collapse

NASA Astrophysics Data System (ADS)

Lai, Lipeng; Turitsyn, Konstantin S.; Zhang, Wendy W.

2008-11-01

Recent studies reveal that an inertial implosion, analogous to the collapse of a large cavity in water, governs how a submerged air bubble disconnects from a nozzle. For the bubble, slight asymmetries in the initial neck shape give rise to vibrations that grow pronounced over time. These results motivate our study of the final stage of asymmetric cavity collapse. We are particularly interested in the generic situation where the initial condition is sufficiently well-focused that a cavity can implode inwards energetically. Yet, because the initial condition is not perfectly symmetric, the implosion fails to condense all the energy. We consider cavity shapes in the slender-body limit, for which the collapse dynamics is quasi two-dimensional. In this limit, each cross-section of the cavity evolves as if it were a distorted void immersed in an inviscid and irrotational fluid. Simulations of a circular void distorted by an elongation-compression vibrational mode reveal that a variety of outcomes are possible in the 2D problem. Opposing sides of the void surface can curve inwards and contact smoothly in a finite amount of time. Depending on the phase of the vibration excited, the contact can be either north-south or east-west. Phase values that lie in the transition zone from one orientation to the other give rise to final shapes with large lengthscale separation. We show also that the final outcome varies non-monotonically with the initial amplitude of the vibrational mode.

Voids and superstructures: correlations and induced large-scale velocity flows

NASA Astrophysics Data System (ADS)

Lares, Marcelo; Luparello, Heliana E.; Maldonado, Victoria; Ruiz, Andrés N.; Paz, Dante J.; Ceccarelli, Laura; Garcia Lambas, Diego

2017-09-01

The expanding complex pattern of filaments, walls and voids build the evolving cosmic web with material flowing from underdense on to high density regions. Here, we explore the dynamical behaviour of voids and galaxies in void shells relative to neighbouring overdense superstructures, using the Millenium simulation and the main galaxy catalogue in Sloan Digital Sky Survey data. We define a correlation measure to estimate the tendency of voids to be located at a given distance from a superstructure. We find voids-in-clouds (S-types) preferentially located closer to superstructures than voids-in-voids (R-types) although we obtain that voids within ˜40 h-1 Mpc of superstructures are infalling in a similar fashion independently of void type. Galaxies residing in void shells show infall towards the closest superstructure, along with the void global motion, with a differential velocity component depending on their relative position in the shell with respect to the direction to the superstructure. This effect is produced by void expansion and therefore is stronger for R-types. We also find that galaxies in void shells facing the superstructure flow towards the overdensities faster than galaxies elsewhere at the same relative distance to the superstructure. The results obtained for the simulation are also reproduced for the Sky Survey Data Release data with a linearized velocity field implementation.

Intravesical PAC1 Receptor Antagonist, PACAP(6–38), Reduces Urinary Bladder Frequency and Pelvic Sensitivity in NGF-OE Mice

PubMed Central

Girard, Beatrice M.; Malley, Susan E.; Mathews, Morgan M.; May, Victor

2017-01-01

Chronic NGF overexpression (OE) in the urothelium, achieved through the use of a highly urothelium-specific uroplakin II promoter, stimulates neuronal sprouting in the urinary bladder, produces increased voiding frequency and non-voiding contractions, and referred somatic sensitivity. Additional NGF-mediated pleiotropic changes might contribute to increased voiding frequency and pelvic hypersensitivity in NGF-OE mice such as neuropeptide/receptor systems including PACAP(Adcyap1) and PAC1 receptor (Adcyap1r1). Given the presence of PAC1-immunoreactive fibers and the expression of PAC1 receptor expression in bladder tissues, and PACAP-facilitated detrusor contraction, whether PACAP/receptor signaling contributes to increased voiding frequency and somatic sensitivity was evaluated in NGF-OE mice. Intravesical administration of the PAC1 receptor antagonist, PACAP(6–38) (300 nM), significantly (p ≤ 0.01) increased intercontraction interval (2.0-fold) and void volume (2.5-fold) in NGF-OE mice. Intravesical instillation of PACAP(6–38) also decreased baseline bladder pressure in NGF-OE mice. PACAP(6–38) had no effects on bladder function in WT mice. Intravesical administration of PACAP(6–38) (300 nM) significantly (p ≤ 0.01) reduced pelvic sensitivity in NGF-OE mice but was without effect in WT mice. PACAP/receptor signaling contributes to the increased voiding frequency and pelvic sensitivity observed in NGF-OE mice. PMID:27146136

Evaluation of a mobile voiding diary for pediatric patients with voiding dysfunction: a prospective comparative study.

PubMed

Johnson, Emilie K; Estrada, Carlos R; Johnson, Kathryn L; Nguyen, Hiep T; Rosoklija, Ilina; Nelson, Caleb P

2014-09-01

One potential strategy for improving voiding diary completion rates and data quality is use of a mobile electronic format. We evaluated the acceptability and feasibility of mobile voiding diaries for patients with nonneurogenic lower urinary tract dysfunction, and compared mobile and paper voiding diaries. We prospectively enrolled children presenting with daytime symptoms of lower urinary tract dysfunction between July 2012 and April 2013. We enrolled an initial cohort of patients who were provided a paper voiding diary and a subsequent cohort who were provided a mobile voiding diary. We conducted in person interviews and assessed completion rates and quality, comparing paper and mobile voiding diary groups. We enrolled 45 patients who received a paper voiding diary and 38 who received a mobile voiding diary. Completion rates were 78% for paper voiding diaries and 61% for mobile voiding diaries (p = 0.10). Data quality measures for patients completing paper vs mobile voiding diaries revealed a larger proportion (63% vs 52%) providing a full 5 days of data and a smaller proportion (20% vs 65%) with data gaps. However, the paper voiding diary also demonstrated a lower proportion (80% vs 100%) that was completely legible and a lower proportion (40% vs 65%) with completely prospective data entry. The use of a mobile voiding diary was acceptable and feasible for our patients with lower urinary tract dysfunction, although completion rates were somewhat lower compared to paper voiding diaries. Data quality was not clearly better for either version. The mobile voiding diary format may offer data quality advantages for select groups but it did not display significant superiority when provided universally. Copyright © 2014 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Phase-field study on geometry-dependent migration behavior of voids under temperature gradient in UO2 crystal matrix

NASA Astrophysics Data System (ADS)

Chen, Weijin; Peng, Yuyi; Li, Xu'an; Chen, Kelang; Ma, Jun; Wei, Lingfeng; Wang, Biao; Zheng, Yue

2017-10-01

In this work, a phase-field model is established to capture the void migration behavior under a temperature gradient within a crystal matrix, with an appropriate consideration of the surface diffusion mechanism and the vapor transport mechanism. The interfacial energy and the coupling between the vacancy concentration field and the crystal order parameter field are carefully modeled. Simulations are performed on UO2. The result shows that for small voids (with an area ≤ πμm2), the well-known characteristics of void migration, in consistence with the analytical model, can be recovered. The migration is manifested by a constant velocity and a minor change of the void shape. In contrast, for large voids (with an area of ˜10 μm2) initially in circular shapes, significant deformation of the void from a circular to cashew-like shape is observed. After long-time migration, the deformed void would split into smaller voids. The size-dependent behavior of void migration is due to the combined effect of the interfacial energy (which tends to keep the void in circular shape) and the surface diffusion flow (which tends to deform the void due to the nonuniform diffusion along the surface). Moreover, the initial shape of the void modifies the migration velocity and the time point when splitting occurs (for large voids) at the beginning of migration due to the shape relaxation of the void. However, it has a minor effect on the long-time migration. Our work reveals novel void migration behaviors in conditions where the surface-diffusion mechanism is dominant over the vapor transport mechanism; meanwhile, the size of the void lies at a mediate size range.

Corrosion resistance of inconel 690 to borax, boric acid, and boron nitride at 1100{degrees}C

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

Imrich, K.J.

1996-12-12

Significant general and localized corrosion was observed on Inconel 690 coupons following exposure to borax, boric acid and boron nitride at 1100{degrees}C. Severe localized attack at and below the melt line was observed on coupons exposed to borax. An intergranular attack at and below the melt line was observed on coupons exposed to borax. An intergranular attack (IGA) of the Inconel 690 was also observed. Severe internal void formation and IGA (30 mils penetration after 3 days) was observed in the coupon exposed to boric acid. Both borax and boric acid remove the protective chromium oxide; however, this layer canmore » be reestablished by heating the Inconel 690 to 975 {degrees}C in air for several hours. Inconel 690 in direct contact with boron nitride resulted in the formation of a thick chromium borate layer, a general corrosion rate of 50 to 90 mils per year, and internal void formation of 1 mil per day.« less

Evolution of the Florida Launch Site Architecture: Embracing Multiple Customers, Enhancing Launch Opportunities

NASA Technical Reports Server (NTRS)

Colloredo, Scott; Gray, James A.

2011-01-01

The impending conclusion of the Space Shuttle Program and the Constellation Program cancellation unveiled in the FY2011 President's budget created a large void for human spaceflight capability and specifically launch activity from the Florida launch Site (FlS). This void created an opportunity to re-architect the launch site to be more accommodating to the future NASA heavy lift and commercial space industry. The goal is to evolve the heritage capabilities into a more affordable and flexible launch complex. This case study will discuss the FlS architecture evolution from the trade studies to select primary launch site locations for future customers, to improving infrastructure; promoting environmental remediation/compliance; improving offline processing, manufacturing, & recovery; developing range interface and control services with the US Air Force, and developing modernization efforts for the launch Pad, Vehicle Assembly Building, Mobile launcher, and supporting infrastructure. The architecture studies will steer how to best invest limited modernization funding from initiatives like the 21 st elSe and other potential funding.

Time-resolved flowmetering of gas-liquid two-phase pipe flow by ultrasound pulse Doppler method

NASA Astrophysics Data System (ADS)

Murai, Yuichi; Tasaka, Yuji; Takeda, Yasushi

2012-03-01

Ultrasound pulse Doppler method is applied for componential volumetric flow rate measurement in multiphase pipe flow consisted of gas and liquid phases. The flowmetering is realized with integration of measured velocity profile over the cross section of the pipe within liquid phase. Spatio-temporal position of interface is detected also with the same ultrasound pulse, which further gives cross sectional void fraction. A series of experimental demonstration was shown by applying this principle of measurement to air-water two-phase flow in a horizontal tube of 40 mm in diameter, of which void fraction ranges from 0 to 90% at superficial velocity from 0 to 15 m/s. The measurement accuracy is verified with a volumetric type flowmeter. We also analyze the accuracy of area integration of liquid velocity distribution for many different patterns of ultrasound measurement lines assigned on the cross section of the tube. The present method is also identified to be pulsation sensor of flow rate that fluctuates with complex gas-liquid interface behavior.

Redshift-space distortions around voids

NASA Astrophysics Data System (ADS)

Cai, Yan-Chuan; Taylor, Andy; Peacock, John A.; Padilla, Nelson

2016-11-01

We have derived estimators for the linear growth rate of density fluctuations using the cross-correlation function (CCF) of voids and haloes in redshift space. In linear theory, this CCF contains only monopole and quadrupole terms. At scales greater than the void radius, linear theory is a good match to voids traced out by haloes; small-scale random velocities are unimportant at these radii, only tending to cause small and often negligible elongation of the CCF near its origin. By extracting the monopole and quadrupole from the CCF, we measure the linear growth rate without prior knowledge of the void profile or velocity dispersion. We recover the linear growth parameter β to 9 per cent precision from an effective volume of 3( h-1Gpc)3 using voids with radius >25 h-1Mpc. Smaller voids are predominantly sub-voids, which may be more sensitive to the random velocity dispersion; they introduce noise and do not help to improve measurements. Adding velocity dispersion as a free parameter allows us to use information at radii as small as half of the void radius. The precision on β is reduced to 5 per cent. Voids show diverse shapes in redshift space, and can appear either elongated or flattened along the line of sight. This can be explained by the competing amplitudes of the local density contrast, plus the radial velocity profile and its gradient. The distortion pattern is therefore determined solely by the void profile and is different for void-in-cloud and void-in-void. This diversity of redshift-space void morphology complicates measurements of the Alcock-Paczynski effect using voids.

The effectiveness of transcutaneous electrical neural stimulation therapy in patients with urinary incontinence resistant to initial medical treatment or biofeedback.

PubMed

Tugtepe, H; Thomas, D T; Ergun, R; Kalyoncu, A; Kaynak, A; Kastarli, C; Dagli, T E

2015-06-01

While there are many options for children with treatment refractory urinary incontinence, there is no single accepted method. This study's aim was to prospectively evaluate the effect of transcutaneous electrical nerve stimulation in children with urinary incontinence resistant to standard medical, urological therapy and/or biofeedback. This study was performed at a university hospital. For inclusion, patients >5 years of age first underwent evaluation with urinary ultrasonography, uroflow-electromyogram and voiding diaries. Treatment with biofeedback, alpha adrenergic blockers, anticholinergics and/or urotherapy was commenced according to uroflow-EMG and voiding diary findings. Patients with partial or no response to this standard therapy were then included in this study, performed between April 2012 and February 2014. Patients with anatomical or neurological causes for urinary incontinence were excluded. TENS was performed on S3 dermatome, every day for 3 months. Each session lasted 20 min with a frequency of 10 Hz and generated pulse of 350 μs. Intensity was determined by the child's sensitivity threshold. Medical treatment and urological therapy was continued during TENS. Uroflow parameters (voiding volume as percentage of expected bladder capacity, Qmax, Qave, flow and voiding time, postvoiding residual urine) and urinary system symptoms (presence of urinary tract infection, frequency, urge incontinence, fractionated voiding and constipation) were compared immediately before commencement and immediately after the completion of 3 months of TENS. Twenty-seven patients were included in this study (4 males, 23 females). Patients' average age was 7.2 years, 11 had overactive bladder and 16 had dysfunctional voiding. Comparison of urinary system symptoms and uroflow parameters before and after TENS are shown in Table. After 3 months of TENS; a statistically significant decrease was observed in the number of patients with frequency, urge incontinence, urinary tract infections and constipation. There was a decrease in the number of patients with fractionated voiding, although this change was not statistically significant. Similarly, for uroflow-EMG parameters; bladder capacity, Qmax, Qave and flow time increased while voiding time and PVR decreased. Changes seen in bladder capacity, Qmax and PVR were statically significant, while other changes were not. Patients' response rates after 3 months of TENS were; complete response in 70.4%, partial response in 22.2% and no response in 7.4%. This study has shown that transcutaneous electrical nerve stimulation is a promising treatment option for standard-treatment refractory children with urinary incontinence. Copyright © 2015 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.

Spatial organization and correlation properties quantify structural changes on mesoscale of parenchymatous plant tissue

NASA Astrophysics Data System (ADS)

Valous, N. A.; Delgado, A.; Drakakis, K.; Sun, D.-W.

2014-02-01

The study of plant tissue parenchyma's intercellular air spaces contributes to the understanding of anatomy and physiology. This is challenging due to difficulty in making direct measurements of the pore space and the complex mosaic of parenchymatous tissue. The architectural complexity of pore space has shown that single geometrical measurements are not sufficient for characterization. The inhomogeneity of distribution depends not only on the percentage content of phase, but also on how the phase fills the space. The lacunarity morphometric, as multiscale measure, provides information about the distribution of gaps that correspond to degree of spatial organization in parenchyma. Additionally, modern theories have suggested strategies, where the focus has shifted from the study of averages and histograms to the study of patterns in data fluctuations. Detrended fluctuation analysis provides information on the correlation properties of the parenchyma at different spatial scales. The aim is to quantify (with the aid of the aforementioned metrics), the mesostructural changes—that occur from one cycle of freezing and thawing—in the void phase of pome fruit parenchymatous tissue, acquired with X-ray microcomputed tomography. Complex systems methods provide numerical indices and detailed insights regarding the freezing-induced modifications upon the arrangement of cells and voids. These structural changes have the potential to lead to physiological disorders. The work can further stimulate interest for the analysis of internal plant tissue structures coupled with other physico-chemical processes or phenomena.

Model validation using CFD-grade experimental database for NGNP Reactor Cavity Cooling Systems with water and air

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

Manera, Annalisa; Corradini, Michael; Petrov, Victor

This project has been focused on the experimental and numerical investigations of the water-cooled and air-cooled Reactor Cavity Cooling System (RCCS) designs. At this aim, we have leveraged an existing experimental facility at the University of Wisconsin-Madison (UW), and we have designed and built a separate effect test facility at the University of Michigan. The experimental facility at UW has underwent several upgrades, including the installation of advanced instrumentation (i.e. wire-mesh sensors) built at the University of Michigan. These provides highresolution time-resolved measurements of the void-fraction distribution in the risers of the water-cooled RCCS facility. A phenomenological model has beenmore » developed to assess the water cooled RCCS system stability and determine the root cause behind the oscillatory behavior that occurs under normal two-phase operation. Testing under various perturbations to the water-cooled RCCS facility have resulted in changes in the stability of the integral system. In particular, the effects on stability of inlet orifices, water tank volume have and system pressure been investigated. MELCOR was used as a predictive tool when performing inlet orificing tests and was able to capture the Density Wave Oscillations (DWOs) that occurred upon reaching saturation in the risers. The experimental and numerical results have then been used to provide RCCS design recommendations. The experimental facility built at the University of Michigan was aimed at the investigation of mixing in the upper plenum of the air-cooled RCCS design. The facility has been equipped with state-of-theart high-resolution instrumentation to achieve so-called CFD grade experiments, that can be used for the validation of Computational Fluid Dynanmics (CFD) models, both RANS (Reynold-Averaged) and LES (Large Eddy Simulations). The effect of risers penetration in the upper plenum has been investigated as well.« less

Cause Analysis on the Void under Slabs of Cement Concrete Pavement

NASA Astrophysics Data System (ADS)

Wen, Li; Zhu, Guo Xin; Baozhu

2017-06-01

This paper made a systematic analysis on the influence of the construction, environment, water and loads on the void beneath road slabs, and also introduced the formation process of structural void and pumping void, and summarizes the deep reasons for the bottom of the cement concrete pavement. Based on the analysis above, this paper has found out the evolution law of the void under slabs which claimed that the void usually appeared in the slab corners and then the cross joint, resulting void in the four sides with the void area under the front slab larger than the rear one.

The Effect of CO2 Pressure on Chromia Scale Microstructure at 750°C

NASA Astrophysics Data System (ADS)

Pint, B. A.; Unocic, K. A.

2018-06-01

To understand and model performance in supercritical CO2 (sCO2) for high-efficiency, concentrating solar power (CSP) and fossil energy power cycles, reaction rates are compared at 750°C in 0.1 MPa CO2 and 30 MPa sCO2 as well as laboratory air as a baseline on structural materials such as Ni-based alloy 625. Due to the thin reaction products formed even after 5000 h, scanning transmission electron microscopy was used to study the Cr-rich surface oxide scale. The scales formed in CO2 and sCO2 had a much finer grain size with more voids observed in CO2. However, the observations on alloy 625 were complicated by Mo and Nb-rich precipitates in the adjacent substrate and Al internal oxidation. To simplify the system, a binary Ni-22Cr alloy was exposed for 1000 h in similar environments. After exposure in sCO2, there was an indication of carbon segregation detected on the Cr2O3 grain boundaries. After exposure in air, metallic Ni precipitates were observed in the scale that were not observed in the scale formed on alloy 625. The scale formed in air on a second Ni-22Cr model alloy with Mn and Si additions did not contain Ni precipitates, suggesting caution when drawing conclusions from model alloys.

Relationship between water status in dentin and interfacial morphology in all-in-one adhesives.

PubMed

Yoshida, Eiji; Uno, Sigeru; Nodasaka, Yoshinobu; Kaga, Msayuki; Hirano, Susumu

2007-05-01

All-in-one adhesive systems have been recently developed to simplify bonding procedures. The adhesives containing acidic resin monomers generate a relatively thin bonding zone between dentin and composite. This zone may be left acidic and permeable when polymerization is poor. In this study, the effect of water contained in dentin on the quality of the bonding interface was morphologically investigated for all-in-one adhesives. Intact coronal dentin (hydrated dentin), desiccated coronal dentin (dehydrated dentin), caries-affected dentin (CAD) and resin composites were used for adherends to assess the effects of water contained in dentin on the ultra-structures of bonding interfaces created with two all-in-one adhesives and a resin composite. The bonding interfaces were observed under TEM without demineralization. Voids of various sizes were found at the bottom of the adhesive resin layers along the bonding interface of hydrated dentin, while dehydrated dentin, CAD and resin composites did not generate voids. The results showed that the voids were possibly formed by water that had penetrated from the underlying dentin. When the adherend contains little water, the formation of voids will not occur. It was verified that a phenomenon of void formation would not occur in a clinical situation in which caries-affected dentin is mainly subjected to adhesive practices.

Extracting and identifying concrete structural defects in GPR images

NASA Astrophysics Data System (ADS)

Ye, Qiling; Jiao, Liangbao; Liu, Chuanxin; Cao, Xuehong; Huston, Dryver; Xia, Tian

2018-03-01

Traditionally most GPR data interpretations are performed manually. With the advancement of computing technologies, how to automate GPR data interpretation to achieve high efficiency and accuracy has become an active research subject. In this paper, analytical characterizations of major defects in concrete structures, including delamination, air void and moisture in GPR images, are performed. In the study, the image features of different defects are compared. Algorithms are developed for defect feature extraction and identification. For validations, both simulation results and field test data are utilized.

Environmental Assessment Supplement for C-17Southwest Landing Zone Articulated Concrete Block Shoulders Travis Air Force Base, Fairfield, California

DTIC Science & Technology

2012-03-01

shoulders in place of soil shoulders adjacent to the runway shoulder. The EA Supplement evaluates the potential impacts that could result from...potential impacts that could result from constructing and operating ACB in place of soil shoulders. Resources with the potential to be affected by...excavated and graded prior to installing ACB mats. Soil from grading activities will be used to fill the voids in the ACB, with any remaining soil being

Evolution of the plasma-sprayed microstructure in 7 wt% yttria-stabilized zirconia thermal barrier coatings during uniaxial stress relaxation and the concomitant changes in material properties

NASA Astrophysics Data System (ADS)

Petorak, Christopher

The understanding of failure mechanisms in plasma sprayed 7 wt% yttria stabilized zirconia (YSZ) is a key step toward optimizing thermal barrier coating (TBC) usage, design, and life prediction. The purpose of the present work is to characterize and understand the stress relaxation behavior occurring in plasma-sprayed YSZ coatings, so that the correlating magnitude of unfavorable tensile stress, which coatings experienced upon cooling, may be reduced through microstructural design. The microstructure and properties of as-sprayed coatings changes immensely during service at high temperature, and therefore the effects of long heat-treatment times, and the concomitant change within the microstructure, on the time-dependent mechanical behavior of stand-alone YSZ coatings was studied in parallel with the as-sprayed coating condition. Aside from influencing the mechanical properties, stress relaxation also affects the insulating efficiency of plasma-sprayed 7wt% YSZ coatings. Directionally dependent changes in microstructure due to stress relaxation of a uniaxially applied stress at 1200°C were observed in plasma-sprayed coatings. Small angle neutron scattering (SANS) investigation of coatings after stress relaxation displayed a 46% reduction in the specific surface area connected to the load-orientation dependent closure of void surface area perpendicular to the applied load when compared to coatings sintered in air, i.e. no applied load. These anisotropic microstructural changes were linked to the thermal properties of the coating. For example, a coating stress relaxed from 60 MPa for 5-min at 1200°C exhibited a thermal conductivity of 2.1 W/m-K. A coating that was only heat-treated for 5-min at 1200°C (i.e. no stress applied) exhibited a thermal conductivity of 1.7 W/m·K. In the current study, uniaxial stress relaxation in plasma-sprayed 7wt% YSZ coatings was determined the result of: (1) A more uniform distribution of the applied load with time, (2) A reduction in the SSA associated with void systems due to sintering, specifically the closing and healing of intralamellar cracks perpendicular to the applied stress, and (3) A compaction and closure of void systems under the applied load. These anisotropic changes in microstructure result in distinguishable changes in thermo-mechanical properties, with very minute changes to the overall bulk density.

Hyperuniformity, quasi-long-range correlations, and void-space constraints in maximally random jammed particle packings. I. Polydisperse spheres.

PubMed

Zachary, Chase E; Jiao, Yang; Torquato, Salvatore

2011-05-01

Hyperuniform many-particle distributions possess a local number variance that grows more slowly than the volume of an observation window, implying that the local density is effectively homogeneous beyond a few characteristic length scales. Previous work on maximally random strictly jammed sphere packings in three dimensions has shown that these systems are hyperuniform and possess unusual quasi-long-range pair correlations decaying as r(-4), resulting in anomalous logarithmic growth in the number variance. However, recent work on maximally random jammed sphere packings with a size distribution has suggested that such quasi-long-range correlations and hyperuniformity are not universal among jammed hard-particle systems. In this paper, we show that such systems are indeed hyperuniform with signature quasi-long-range correlations by characterizing the more general local-volume-fraction fluctuations. We argue that the regularity of the void space induced by the constraints of saturation and strict jamming overcomes the local inhomogeneity of the disk centers to induce hyperuniformity in the medium with a linear small-wave-number nonanalytic behavior in the spectral density, resulting in quasi-long-range spatial correlations scaling with r(-(d+1)) in d Euclidean space dimensions. A numerical and analytical analysis of the pore-size distribution for a binary maximally random jammed system in addition to a local characterization of the n-particle loops governing the void space surrounding the inclusions is presented in support of our argument. This paper is the first part of a series of two papers considering the relationships among hyperuniformity, jamming, and regularity of the void space in hard-particle packings.

Extended Burnup Credit for BWR Spent Nuclear Fuel in Storage and Transportation Systems

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

Ade, Brian J; Bowman, Stephen M; Gauld, Ian C

2015-01-01

[Full Text] Oak Ridge National Laboratory and the United States Nuclear Regulatory Commission have initiated a multiyear project to investigate the application of burnup credit (BUC) for boiling-water reactor (BWR) fuel in storage and transportation casks. This project includes two phases. The first phase investigates the applicability of peak reactivity methods currently used for spent fuel pools to spent fuel storage and transportation casks and the validation of reactivity (k eff) calculations and depleted fuel compositions. The second phase focuses on extending BUC beyond peak reactivity. This paper documents work performed to date, investigating some aspects of extended BUC, andmore » it also describes the plan to complete the evaluations. The technical basis for application of peak reactivity methods to BWR fuel in storage and transportation systems is presented in a companion paper. Two reactor operating parameters are being evaluated to establish an adequate basis for extended BWR BUC, including investigation of the axial void profile effect and the effect of control blade utilization during operation. A detailed analysis of core simulator data for one cycle of an operating BWR plant was performed to determine the range of void profiles and the variability of the profile experienced during irradiation. While a single cycle does not provide complete data, the data obtained are sufficient to use to determine the primary effects and identify conservative modeling approaches. Using data resulting from a single cycle, the axial void profile is studied by first determining the temporal fidelity necessary in depletion modeling, and then using multiple void profiles to examine the effect of the void profile on cask reactivity. The results of these studies are being used to develop recommendations for conservatively modeling the void profile effects for BWR depletion calculations. The second operational parameter studied is control blade exposure. Control blades are inserted in various locations and at varying degrees during BWR operation based on the reload design. The presence of control blades during depletion hardens the neutron spectrum locally due to both moderator displacement and introduction of a thermal neutron absorber. The reactivity impact of control blade presence is investigated herein, as well as the effect of multiple (continuous and intermittent) exposure periods. The coupled effects of control blade presence on power density, void profile, or burnup profile have not been considered to date but will be addressed in future work.« less

Magnetic particles as liquid carriers in the microfluidic lab-in-tube approach to detect phase change.

PubMed

Blumenschein, Nicholas A; Han, Daewoo; Caggioni, Marco; Steckl, Andrew J

2014-06-11

Magnetic beads (MBs) with ∼1.9 μm average diameter were used to transport specific microliter-scale volumes of liquids between adjacent reservoirs within a closed tube under the influence of a magnetic field. The tube's inner surface is coated with a hydrophobic layer, enabling the formation of a surface tension valve by inserting an air gap between reservoirs. This transfer process was implemented by keeping the MBs stationary with a fixed external magnet while the liquid reservoirs were translated by a computer-controlled syringe pump system. The magnet induces the aggregation of MBs in a loosely packed cluster (void volume ∼90-95%) against the tube's inner wall. The liquid trapped in the MB cluster is transported across the air gap between reservoirs. Fluorescence intensity from a dye placed in one reservoir is used to measure the volume of liquid transferred between reservoirs. The carry-over liquid volume is controlled by the mass of the MBs within the device. The typical volume of liquid carried by the MB cluster is ∼2 to 3 μL/mg of beads, allowing the use of small samples. This technique can be used to study the effect of small compositional variation on the properties of fluid mixtures. The feasibility of this "lab-in-tube" approach for binary phase diagram determination in a water-surfactant (C12E5) system was demonstrated.

Closure behavior of spherical void in slab during hot rolling process

NASA Astrophysics Data System (ADS)

Cheng, Rong; Zhang, Jiongming; Wang, Bo

2018-04-01

The mechanical properties of steels are heavily deteriorated by voids. The influence of voids on the product quality should be eliminated through rolling processes. The study on the void closure during hot rolling processes is necessary. In present work, the closure behavior of voids at the center of a slab at 800 °C during hot rolling processes has been simulated with a 3D finite element model. The shape of the void and the plastic strain distribution of the slab are obtained by this model. The void decreases along the slab thickness direction and spreads along the rolling direction but hardly changes along the strip width direction. The relationship between closure behavior of voids and the plastic strain at the center of the slab is analyzed. The effects of rolling reduction, slab thickness and roller diameter on the closure behavior of voids are discussed. The larger reduction, thinner slab and larger roller diameter all improve the closure of voids during hot rolling processes. Experimental results of the closure behavior of a void in the slab during hot rolling process mostly agree with the simulation results..

Voiding diary might serve as a useful tool to understand differences between bladder pain syndrome/interstitial cystitis and overactive bladder.

PubMed

Kim, Sung Han; Oh, Shin Ah; Oh, Seung-June

2014-02-01

To identify the voiding characteristics of bladder pain syndrome/interstitial cystitis and overactive bladder. Between September 2005 and June 2010, 3-day voiding diaries of 49 consecutive bladder pain syndrome/interstitial cystitis patients and 301 overactive bladder patients were prospectively collected at an outpatient clinic and retrospectively analyzed. The characteristics of the two groups were not significantly different. However, all voiding variables including volume and frequency were significantly different except for the total voided volume: patients with bladder pain syndrome/interstitial cystitis showed significantly higher voiding frequencies, smaller maximal and mean voided volume, and more constant and narrower ranges of voided volume compared with overactive bladder patients (P < 0.005). Furthermore, mean intervals between voiding in bladder pain syndrome/interstitial cystitis were shorter and more consistent during the day and night (P < 0.001), although mean night-time variances were greater than daytime variances. Logistic regression analysis showed that total night-time frequency, maximal night-time voided volume and mean variance of daytime voiding intervals most significantly differentiated the two groups. Some voiding characteristics of bladder pain syndrome/interstitial cystitis and overactive bladder patients differ significantly according to 3-day voiding diary records. These findings provide additional information regarding the differences between these two diseases in the outpatient clinical setting. © 2013 The Japanese Urological Association.

3D Simulations of Void collapse in Energetic Materials

NASA Astrophysics Data System (ADS)

Rai, Nirmal Kumar; Udaykumar, H. S.

2017-06-01

Voids present in the microstructure of heterogeneous energetic materials effect the sensitivity towards ignition. It is established that the morphology of voids can play a significant role in sensitivity enhancement of energetic materials. Depending on the void shape, sensitivity can be either increased or decreased under given loading conditions. In the past, effects of different void shapes i.e. triangular, ellipse, cylindrical etc. on the sensitivity of energetic materials have been analyzed. However, most of these studies are performed in 2D and are limited under the plain strain assumption. Axisymmetric studies have also been performed in the past to incorporate the 3D effects, however axisymmetric modeling is limited to only certain geometries i.e. sphere. This work analyzes the effects of various void shapes in three dimensions on the ignition behavior of HMX. Various void shapes are analyzed including spherical, prolate and oblate speheroid oriented at different orientations, etc. Three dimensional void collapse simulations are performed on a single void to quantify the effects void morphology on initiation. A Cartesian grid based Eulerian solver SCIMITAR3D is used to perform the void collapse simulations. Various aspects of void morphology i.e. size, thickness of voids, elongation, orientation etc. are considered to obtain a comprehensive analysis. Also, 2D plane strain calculations are compared with the three dimensional analysis to evaluate the salient differences between 2D and 3D modeling.

Stabilizing Lithium-Sulfur Batteries through Control of Sulfur Aggregation and Polysulfide Dissolution.

PubMed

Liu, Qian; Zhang, Jianhua; He, Shu-Ang; Zou, Rujia; Xu, Chaoting; Cui, Zhe; Huang, Xiaojuan; Guan, Guoqiang; Zhang, Wenlong; Xu, Kaibing; Hu, Junqing

2018-04-17

Lithium-sulfur (Li-S) batteries are investigated intensively as a promising large-scale energy storage system owing to their high theoretical energy density. However, the application of Li-S batteries is prevented by a series of primary problems, including low electronic conductivity, volumetric fluctuation, poor loading of sulfur, and shuttle effect caused by soluble lithium polysulfides. Here, a novel composite structure of sulfur nanoparticles attached to porous-carbon nanotube (p-CNT) encapsulated by hollow MnO 2 nanoflakes film to form p-CNT@Void@MnO 2 /S composite structures is reported. Benefiting from p-CNTs and sponge-like MnO 2 nanoflake film, p-CNT@Void@MnO 2 /S provides highly efficient pathways for the fast electron/ion transfer, fixes sulfur and Li 2 S aggregation efficiently, and prevents polysulfide dissolution during cycling. Besides, the additional void inside p-CNT@Void@MnO 2 /S composite structure provides sufficient free space for the expansion of encapsulated sulfur nanoparticles. The special material composition and structural design of p-CNT@Void@MnO 2 /S composite structure with a high sulfur content endow the composite high capacity, high Coulombic efficiency, and an excellent cycling stability. The capacity of p-CNT@Void@MnO 2 /S electrode is ≈599.1 mA h g -1 for the fourth cycle and ≈526.1 mA h g -1 after 100 cycles, corresponding to a capacity retention of ≈87.8% at a high current density of 1.0 C. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Instabilities of Damage and Surface Degradation Mechanisms in Brittle Material Structural Systems

DTIC Science & Technology

1992-03-15

I INTRODUCTION AND SCOPE 1.1 General Brittle materials such as rock and concrete contain a multitude of defects in the form of micro-voids and/or...micro-cracks even before any external load is applied. The term "structure" is associated with such defects . During a loading- unloading process, these...voids/cracks may undergo irreversible growth and new ones may nucleate. The ultimate coalescence of such defects may result in macro- crack initiation

Collapse of elongated voids in porous energetic materials: Effects of void orientation and aspect ratio on initiation

NASA Astrophysics Data System (ADS)

Rai, Nirmal Kumar; Schmidt, Martin J.; Udaykumar, H. S.

2017-04-01

The sensitivity of porous energetic materials depends on mesostructural heterogeneities such as voids, defects, cracks, and grain boundaries. The mesostructure of pressed explosives contains voids of arbitrary shapes including elongated voids of various orientations and aspect ratios. Mesoscale simulations to date have analyzed the effect of void morphology on the sensitivity of energetic materials for idealized shapes such as cylindrical, conical, and elliptical. This work analyzes the sensitivity behavior of elongated voids in an HMX matrix subject to shock loading. Simulations show that sensitivity of elongated voids depends strongly on orientation as well as aspect ratio. Ranges of orientations and aspects ratios are identified that enhance or inhibit initiation. Insights obtained from single elongated void analyses are used to identify sensitive locations in an imaged mesostructure of a pressed explosive sample.

Friction stir welding process to repair voids in aluminum alloys

NASA Technical Reports Server (NTRS)

Rosen, Charles D. (Inventor); Litwinski, Edward (Inventor); Valdez, Juan M. (Inventor)

1999-01-01

The present invention provides an in-process method to repair voids in an aluminum alloy, particularly a friction stir weld in an aluminum alloy. For repairing a circular void or an in-process exit hole in a weld, the method includes the steps of fabricating filler material of the same composition or compatible with the parent material into a plug form to be fitted into the void, positioning the plug in the void, and friction stir welding over and through the plug. For repairing a longitudinal void (30), the method includes machining the void area to provide a trough (34) that subsumes the void, fabricating filler metal into a strip form (36) to be fitted into the trough, positioning the strip in the trough, and rewelding the void area by traversing a friction stir welding tool longitudinally through the strip. The method is also applicable for repairing welds made by a fusing welding process or voids in aluminum alloy workpieces themselves.

Morphological Segregation in the Surroundings of Cosmic Voids

NASA Astrophysics Data System (ADS)

Ricciardelli, Elena; Cava, Antonio; Varela, Jesus; Tamone, Amelie

2017-09-01

We explore the morphology of galaxies living in the proximity of cosmic voids, using a sample of voids identified in the Sloan Digital Sky Survey Data Release 7. At all stellar masses, void galaxies exhibit morphologies of a later type than galaxies in a control sample, which represent galaxies in an average density environment. We interpret this trend as a pure environmental effect, independent of the mass bias, due to a slower galaxy build-up in the rarefied regions of voids. We confirm previous findings about a clear segregation in galaxy morphology, with galaxies of a later type being found at smaller void-centric distances with respect to the early-type galaxies. We also show, for the first time, that the radius of the void has an impact on the evolutionary history of the galaxies that live within it or in its surroundings. In fact, an enhanced fraction of late-type galaxies is found in the proximity of voids larger than the median void radius. Likewise, an excess of early-type galaxies is observed within or around voids of a smaller size. A significant difference in galaxy properties in voids of different sizes is observed up to 2 R void, which we define as the region of influence of voids. The significance of this difference is greater than 3σ for all the volume-complete samples considered here. The fraction of star-forming galaxies shows the same behavior as the late-type galaxies, but no significant difference in stellar mass is observed in the proximity of voids of different sizes.

Cosmic voids and void lensing in the Dark Energy Survey science verification data

DOE PAGES

Sánchez, C.; Clampitt, J.; Kovacs, A.; ...

2016-10-26

Galaxies and their dark matter halos populate a complicated filamentary network around large, nearly empty regions known as cosmic voids. Cosmic voids are usually identified in spectroscopic galaxy surveys, where 3D information about the large-scale structure of the Universe is available. Although an increasing amount of photometric data is being produced, its potential for void studies is limited since photometric redshifts induce line-of-sight position errors of ~50 Mpc/h or more that can render many voids undetectable. In this paper we present a new void finder designed for photometric surveys, validate it using simulations, and apply it to the high-quality photo-zmore » redMaGiC galaxy sample of the Dark Energy Survey Science Verification (DES-SV) data. The algorithm works by projecting galaxies into 2D slices and finding voids in the smoothed 2D galaxy density field of the slice. Fixing the line-of-sight size of the slices to be at least twice the photo- z scatter, the number of voids found in these projected slices of simulated spectroscopic and photometric galaxy catalogs is within 20% for all transverse void sizes, and indistinguishable for the largest voids of radius ~70 Mpc/h and larger. The positions, radii, and projected galaxy profiles of photometric voids also accurately match the spectroscopic void sample. Applying the algorithm to the DES-SV data in the redshift range 0.2 < z < 0.8 , we identify 87 voids with comoving radii spanning the range 18-120 Mpc/h, and carry out a stacked weak lensing measurement. With a significance of 4.4σ, the lensing measurement confirms the voids are truly underdense in the matter field and hence not a product of Poisson noise, tracer density effects or systematics in the data. In conclusion, it also demonstrates, for the first time in real data, the viability of void lensing studies in photometric surveys.« less

Turning the undesired voids in silicon into a tool: In-situ fabrication of free-standing 3C-SiC membranes

NASA Astrophysics Data System (ADS)

Khazaka, Rami; Michaud, Jean François; Vennéguès, Philippe; Alquier, Daniel; Portail, Marc

2017-02-01

In this contribution, we present a method to form free-standing cubic silicon carbide (3C-SiC) membranes in-situ during the growth stage. To do so, we exploit the presence of voids in the silicon (Si) epilayer underneath the 3C-SiC membrane, in stark contrast to the conventional view of voids as defects. The shape and the size of the 3C-SiC membranes can be controlled by a preceding patterning step of the Si epilayer. Afterwards, by controlling the expansion of voids in Si, the structured sacrificial layer is consumed during the 3C-SiC growth step. Consequently, the membranes are grown and released simultaneously in a single step process. This straightforward technique is expected to markedly simplify the fabrication process of membranes by reducing the fabrication duration and cost. Furthermore, it helps to overcome several technical issues and presents the cornerstone for micro and nano-electromechanical systems applications, profiting from the outstanding properties of cubic silicon carbide.

Morphological transformation of soot: investigation of microphysical processes during the condensation of sulphuric acid and limonene ozonolysis products vapours

NASA Astrophysics Data System (ADS)

Pathak, R. K. P.; Pei, X.; Hallquist, M.; Pagels, J. H.

2017-12-01

Morphological transformation of soot particle by condensation of low volatility materials on it is a dominant atmospheric process with serious implications for its optical and hygroscopic properties, and atmospheric lifetime. In this study, the morphological transformation of soot agglomerate under the influence of condensation of vapours of sulphuric acid, and/or limonene ozonolysis products were investigated systematically using a Differential Mobility Analyser-Aerosol Particle Mass Analyser (DMA-APM) and the Tandem DMA techniques integrated with a laminar flow-tube system. We discovered that the morphology transformation of soot in general was a sequence of two-step process, i.e. (i) filling of void space within soot agglomerate; (ii) growth of particle diameter. These two steps followed and complimented each other. In the very beginning the filling was the dominant process followed by growth until it led to the accumulation of enough material that in turn exerted surface forces that eventually facilitated the further filling. The filling of void space was constrained by the initial morphology of fresh soot and the nature and amount of the material condensed. This process continued in several sequential steps until all void space within the soot agglomerate was filled completely and then growth of a spherical particle continued as long as mass was condensed on it. In this study, we developed a framework to quantify the microphysical transformation of soot upon the condensation of various materials. The framework utilized experimental data and hypothesis of ideal sphere growth and filling of voids to quantify the distribution of condensed materials in these two processes complimenting each other. Using this framework, we have quantified the percentage of material that went into processes of particle growth and void filling at each step. Using the same framework, we further estimated the fraction of internal voids and open voids and used this information to derive the volume equivalent diameter of soot agglomerate containing internal voids and calculated in-situ dynamic shape factor. Our study is the first study that tracks in situ microphysical changes in soot morphology quantitatively, providing the detailed status of both fresh and coated soot particles.

Fuel Breeding and Core Behavior Analyses on In Core Fuel Management of Water Cooled Thorium Reactors

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

Permana, Sidik; Department of Physics, Bandung Institute of Technology, Gedung Fisika, Jl. Ganesha 10, Bandung 40132; Sekimoto, Hiroshi

2010-12-23

Thorium fuel cycle with recycled U-233 has been widely recognized having some contributions to improve the water-cooled breeder reactor program which has been shown by a feasible area of breeding and negative void reactivity which confirms that fissile of 233U contributes to better fuel breeding and effective for obtaining negative void reactivity coefficient as the main fissile material. The present study has the objective to estimate the effect of whole core configuration as well as burnup effects to the reactor core profile by adopting two dimensional model of fuel core management. About more than 40 months of cycle period hasmore » been employed for one cycle fuel irradiation of three batches fuel system for large water cooled thorium reactors. All position of fuel arrangement contributes to the total core conversion ratio which gives conversion ratio less than unity of at the BOC and it contributes to higher than unity (1.01) at the EOC after some irradiation process. Inner part and central part give the important part of breeding contribution with increasing burnup process, while criticality is reduced with increasing the irradiation time. Feasibility of breeding capability of water-cooled thorium reactors for whole core fuel arrangement has confirmed from the obtained conversion ratio which shows higher than unity. Whole core analysis on evaluating reactivity change which is caused by the change of voided condition has been employed for conservative assumption that 100% coolant and moderator are voided. It obtained always a negative void reactivity coefficient during reactor operation which shows relatively more negative void coefficient at BOC (fresh fuel composition), and it becomes less negative void coefficient with increasing the operation time. Negative value of void reactivity coefficient shows the reactor has good safety properties in relation to the reactivity profile which is the main parameter in term of criticality safety analysis. Therefore, this evaluation has confirmed that breeding condition and negative coefficient can be obtained simultaneously for water-cooled thorium reactor obtains based on the whole core fuel arrangement.« less

On the abundance of extreme voids II: a survey of void mass functions

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

Chongchitnan, Siri; Hunt, Matthew, E-mail: s.chongchitnan@hull.ac.uk, E-mail: m.d.hunt@2012.hull.ac.uk

2017-03-01

The abundance of cosmic voids can be described by an analogue of halo mass functions for galaxy clusters. In this work, we explore a number of void mass functions: from those based on excursion-set theory to new mass functions obtained by modifying halo mass functions. We show how different void mass functions vary in their predictions for the largest void expected in an observational volume, and compare those predictions to observational data. Our extreme-value formalism is shown to be a new practical tool for testing void theories against simulation and observation.

Atomistic modeling of shock-induced void collapse in copper

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

Davila, L P; Erhart, P; Bringa, E M

2005-03-09

Nonequilibrium molecular dynamics (MD) simulations show that shock-induced void collapse in copper occurs by emission of shear loops. These loops carry away the vacancies which comprise the void. The growth of the loops continues even after they collide and form sessile junctions, creating a hardened region around the collapsing void. The scenario seen in our simulations differs from current models that assume that prismatic loop emission is responsible for void collapse. We propose a new dislocation-based model that gives excellent agreement with the stress threshold found in the MD simulations for void collapse as a function of void radius.

Nanovoid growth in BCC α-Fe: influences of initial void geometry

NASA Astrophysics Data System (ADS)

Xu, Shuozhi; Su, Yanqing

2016-12-01

The growth of voids has a great impact on the mechanical properties of ductile materials by altering their microstructures. Exploring the process of void growth at the nanoscale helps in understanding the dynamic fracture of metals. While some very recent studies looked into the effects of the initial geometry of an elliptic void on the plastic deformation of face-centered cubic metals, a systematic study of the initial void ellipticity and orientation angle in body-centered cubic (BCC) metals is still lacking. In this paper, large scale molecular dynamics simulations with millions of atoms are conducted, investigating the void growth process during tensile loading of metallic thin films in BCC α-Fe. Our simulations elucidate the intertwined influences on void growth of the initial ellipticity and initial orientation angle of the void. It is shown that these two geometric parameters play an important role in the stress-strain response, the nucleation and evolution of defects, as well as the void size/outline evolution in α-Fe thin films. Results suggest that, together with void size, different initial void geometries should be taken into account if a continuum model is to be applied to nanoscale damage progression.

Comparison of sensation-related voiding patterns between continent and incontinent women: a study with a 3-day sensation-related bladder diary (SR-BD).

PubMed

Naoemova, Irina; De Wachter, Stefan; Wyndaele, Jean-Jacques

2008-01-01

To describe and compare voiding patterns on a 3-day sensation-related bladder diary (SR-BD) in women with urinary incontinence (UI) and healthy volunteers. A total of 251 women (224 incontinent patients and 27 healthy volunteers) who recorded a 3-day SR-BD and underwent standard cystometry participated in the study. Parameters from the 3-day SR-BD were compared between incontinent patients and healthy volunteers. Compared to continent women, all groups of incontinent women noted a significantly higher 24 hr voiding frequency, a greater voiding frequency per liter diuresis, a smaller mean voided volume for different degrees of bladder sensation with more voids made with higher intensity of desire to void. The smallest mean voided volumes for different degrees of desire to void and the highest voiding frequency per liter diuresis were observed in the urge incontinence group. There were different sensation-related voiding patterns on the 3-day SR-BD from incontinent women and healthy volunteers. All incontinence groups had increased bladder sensation compared to healthy volunteers. The most severe increase of bladder sensation was observed in the patients with urgency incontinence. (c) 2007 Wiley-Liss, Inc.

The dark matter of galaxy voids

NASA Astrophysics Data System (ADS)

Sutter, P. M.; Lavaux, Guilhem; Wandelt, Benjamin D.; Weinberg, David H.; Warren, Michael S.

2014-03-01

How do observed voids relate to the underlying dark matter distribution? To examine the spatial distribution of dark matter contained within voids identified in galaxy surveys, we apply Halo Occupation Distribution models representing sparsely and densely sampled galaxy surveys to a high-resolution N-body simulation. We compare these galaxy voids to voids found in the halo distribution, low-resolution dark matter and high-resolution dark matter. We find that voids at all scales in densely sampled surveys - and medium- to large-scale voids in sparse surveys - trace the same underdensities as dark matter, but they are larger in radius by ˜20 per cent, they have somewhat shallower density profiles and they have centres offset by ˜ 0.4Rv rms. However, in void-to-void comparison we find that shape estimators are less robust to sampling, and the largest voids in sparsely sampled surveys suffer fragmentation at their edges. We find that voids in galaxy surveys always correspond to underdensities in the dark matter, though the centres may be offset. When this offset is taken into account, we recover almost identical radial density profiles between galaxies and dark matter. All mock catalogues used in this work are available at http://www.cosmicvoids.net.

Prevalence and characteristics of voiding difficulties in women: are subjective symptoms substantiated by objective urodynamic data?

PubMed

Groutz, A; Gordon, D; Lessing, J B; Wolman, I; Jaffa, A; David, M P

1999-08-01

To examine the prevalence and characteristics of voiding difficulties in women. Two hundred six consecutive female patients who attended a urogynecology clinic were recruited. Patients were interviewed regarding the presence and severity of symptoms that would suggest voiding difficulties (ie, hesitancy, straining to void, weak or prolonged stream, intermittent stream, double voiding, incomplete emptying, reduction, and positional changes to start or complete voiding). Urodynamic evidence of voiding difficulty was considered as a peak flow rate less than 12 mL/s (voided volume greater than 100 mL), or residual urine volume greater than 150 mL, on two or more readings. Residual urinary volume, flow patterns, and pressure-flow parameters were analyzed and compared between symptomatic and asymptomatic patients who had urodynamic parameters of voiding difficulties. One hundred twenty-seven (61.7%) women reported having voiding difficulty symptoms; 79 others (38.3%) were free of such symptoms. Urodynamic diagnosis of voiding difficulty was made in 40 women (19.4% of the study population): 27 in the symptomatic group and 13 in the asymptomatic group (21.2% and 16.5%, respectively). Only 1 patient had voiding difficulty due to bladder outlet obstruction. All other cases of low flow rate were due to impaired detrusor contractility. Objective evidence of voiding difficulty may be found in both symptomatic and asymptomatic patients and is usually due to impaired detrusor contractility. The clinical significance of the abnormal flow parameters in asymptomatic patients is unclear.

Intergalactic Hydrogen Clouds at Low Redshift: Connections to Voids and Dwarf Galaxies

NASA Technical Reports Server (NTRS)

Shull, J. Michael; Stocke, John T.; Penton, Steve

1996-01-01

We provide new post-COSTAR data on one sightline (Mrk 421) and updated data from another (I Zw 1) from our Hubble Space Telescope (HST) survey of intergalactic Ly(alpha) clouds located along sightlines to four bright quasars passing through well-mapped galaxy voids (16000 km/s pathlength) and superclusters (18000 km/s). We report two more definite detections of low-redshift Ly(alpha) clouds in voids: one at 3047 km/s (heliocentric) toward Mrk 421 and a second just beyond the Local Supercluster at 2861 km/s toward I Zw 1, confirming our earlier discovery of Ly(alpha) absorption clouds in voids (Stocke et al., ApJ, 451, 24). We have now identified ten definite and one probable low-redshift neutral hydrogen absorption clouds toward four targets, a frequency of approximately one absorber every 3400 km/s above 10(exp 12.7/sq cm column density. Of these ten absorption systems, three lie within voids; the probable absorber also lies in a void. Thus, the tendency of Ly(alpha) absorbers to 'avoid the voids' is not as clear as we found previously. If the Ly(alpha) clouds are approximated as homogeneous spheres of 100 kpc radius, their masses are approximately 10(exp 9)solar mass (about 0.01 times that of bright L* galaxies) and they are 40 times more numerous, comparable to the density of dwarf galaxies and of low-mass halos in numerical CDM simulations. The Ly(alpha) clouds contribute a fraction Omega(sub cl)approximately equals 0.003/h(sub 75) to the closure density of the universe, comparable to that of luminous matter. These clouds probably require a substantial amount of nonbaryonic dark matter for gravitational binding. They may represent extended haloes of low-mass protogalaxies which have not experienced significant star formation or low-mass dwarf galaxies whose star formation ceased long ago, but blew out significant gaseous material.

Immortality of Cu damascene interconnects

NASA Astrophysics Data System (ADS)

Hau-Riege, Stefan P.

2002-04-01

We have studied short-line effects in fully-integrated Cu damascene interconnects through electromigration experiments on lines of various lengths and embedded in different dielectric materials. We compare these results with results from analogous experiments on subtractively-etched Al-based interconnects. It is known that Al-based interconnects exhibit three different behaviors, depending on the magnitude of the product of current density, j, and line length, L: For small values of (jL), no void nucleation occurs, and the line is immortal. For intermediate values, voids nucleate, but the line does not fail because the current can flow through the higher-resistivity refractory-metal-based shunt layers. Here, the resistance of the line increases but eventually saturates, and the relative resistance increase is proportional to (jL/B), where B is the effective elastic modulus of the metallization system. For large values of (jL/B), voiding leads to an unacceptably high resistance increase, and the line is considered failed. By contrast, we observed only two regimes for Cu-based interconnects: Either the resistance of the line stays constant during the duration of the experiment, and the line is considered immortal, or the line fails due to an abrupt open-circuit failure. The absence of an intermediate regime in which the resistance saturates is due to the absence of a shunt layer that is able to support a large amount of current once voiding occurs. Since voids nucleate much more easily in Cu- than in Al-based interconnects, a small fraction of short Cu lines fails even at low current densities. It is therefore more appropriate to consider the probability of immortality in the case of Cu rather than assuming a sharp boundary between mortality and immortality. The probability of immortality decreases with increasing amount of material depleted from the cathode, which is proportional to (jL2/B) at steady state. By contrast, the immortality of Al-based interconnects is described by (jL) if no voids nucleate, and (jL/B) if voids nucleate.

Comparison between wire mesh sensor and gamma densitometry void measurements in two-phase flows

NASA Astrophysics Data System (ADS)

Sharaf, S.; Da Silva, M.; Hampel, U.; Zippe, C.; Beyer, M.; Azzopardi, B.

2011-10-01

Wire mesh sensors (WMS) are fast imaging instruments that are used for gas-liquid and liquid-liquid two-phase flow measurements and experimental investigations. Experimental tests were conducted at Helmholtz-Zentrum Dresden-Rossendorf to test both the capacitance and conductance WMS against a gamma densitometer (GD). A small gas-liquid test facility was utilized. This consisted of a vertical round pipe approximately 1 m in length, and 50 mm internal diameter. A 16 × 16 WMS was used with high spatial and temporal resolutions. Air-deionized water was the two-phase mixture. The gas superficial velocity was varied between 0.05 m s-1 and 1.4 m s-1 at two liquid velocities of 0.2 and 0.7 m s-1. The GD consisted of a collimated source and a collimated detector. The GD was placed on a moving platform close to the plane of wires of the sensor, in order to align it accurately using a counter mechanism, with each of the wires of the WMS, and the platform could scan the full section of the pipe. The WMS was operated as a conductivity WMS for a half-plane with eight wires and as a capacitance WMS for the other half. For the cross-sectional void (time and space averaged), along each wire, there was good agreement between WMS and the GD chordal void fraction near the centre of the pipe.

Development of Electrical Capacitance Sensors for Accident Tolerant Fuel (ATF) Testing at the Transient Reactor Test (TREAT) Facility

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

Liu, Maolong; Ryals, Matthew; Ali, Amir

2016-08-01

A variety of instruments are being developed and qualified to support the Accident Tolerant Fuels (ATF) program and future transient irradiations at the Transient Reactor Test (TREAT) facility at Idaho National Laboratory (INL). The University of New Mexico (UNM) is working with INL to develop capacitance-based void sensors for determining the timing of critical boiling phenomena in static capsule fuel testing and the volume-averaged void fraction in flow-boiling in-pile water loop fuel testing. The static capsule sensor developed at INL is a plate-type configuration, while UNM is utilizing a ring-type capacitance sensor. Each sensor design has been theoretically and experimentallymore » investigated at INL and UNM. Experiments are being performed at INL in an autoclave to investigate the performance of these sensors under representative Pressurized Water Reactor (PWR) conditions in a static capsule. Experiments have been performed at UNM using air-water two-phase flow to determine the sensitivity and time response of the capacitance sensor under a flow boiling configuration. Initial measurements from the capacitance sensor have demonstrated the validity of the concept to enable real-time measurement of void fraction. The next steps include designing the cabling interface with the flow loop at UNM for Reactivity Initiated Accident (RIA) ATF testing at TREAT and further characterization of the measurement response for each sensor under varying conditions by experiments and modeling.« less

Molecular dynamics simulations of void defects in the energetic material HMX.

PubMed

Duan, Xiao Hui; Li, Wen Peng; Pei, Chong Hua; Zhou, Xiao Qing

2013-09-01

A molecular dynamics (MD) simulation was carried out to characterize the dynamic evolution of void defects in crystalline octahydro-1, 3, 5, 7-tetranitro-1, 3, 5, 7-tetrazocine (HMX). Different models were constructed with the same concentration of vacancies (10 %) to discuss the size effects of void. Energetic ground state properties were determined by annealing simulations. The void formation energy per molecule removed was found to be 55-63 kcal/mol(-1), and the average binding energy per molecule was between 32 and 34 kcal/mol(-1) according to the change in void size. Voids with larger size had lower formation energy. Local binding energies for molecules directly on the void surface decreased greatly compared to those in defect-free lattice, and then gradually increased until the distance away from the void surface was around 10 Å. Analysis of 1 ns MD simulations revealed that the larger the void size, the easier is void collapse. Mean square displacements (MSDs) showed that HMX molecules that had collapsed into void present liquid structure characteristics. Four unique low-energy conformers were found for HMX molecules in void: two whose conformational geometries corresponded closely to those found in HMX polymorphs and two, additional, lower energy conformers that were not seen in the crystalline phases. The ratio of different conformers changed with the simulated temperature, in that the ratio of α conformer increased with the increase in temperature.

Determination of Significant Composite Processing Factors by Designed Experiment (MSFC Center Director's Discretionary Fund)

NASA Technical Reports Server (NTRS)

Finckenor, J. L.

2003-01-01

To determie composite material properties' effects from porcessing variables, a 3 factorial designed experiment with two replicates was conducted. The factors were cure method (oven versus autoclave), layup (hand versus tape-laying machine), and thickness (8 versus 52 ply). Four material systems were tested: AS4/3501-6, IM7/8551-7, IM7/F655 bismaleimide (BMI), and shear tests on IM7/F584. Material properties were G(sub 12), v(sub 12), E(sub 1c) and E(sub 2c). Since the samples were necessarily nonstandard, strengths, though recorded, cannot be considered valid. Void content was also compared. Autoclave curing helped material properties for the low modulus fiber material but showed little benefit for higher stiffness fibers. The number of plies was very important for epoxy composites but not for the BMI. E(sub 1) was generally unaffected by any factor. Particularly high void content did correlate to reduced properties. Autoclave curing reduced void content over oven curiing but a moderate amount of voids, less than 1 percent void content, didnot correlate with material properties. Oven cures and hand layups can produce high-quality parts. Part thickness of epoxy composites is important, though cure optimization may improve performance. Significant variations can be caused by processing and it is important that test coupons always reflect the layup and processes of the final part.

Computational and experimental studies of microvascular void features for passive-adaptation of structural panel dynamic properties

NASA Astrophysics Data System (ADS)

Sears, Nicholas C.; Harne, Ryan L.

2018-01-01

The performance, integrity, and safety of built-up structural systems are critical to their effective employment in diverse engineering applications. In conflict with these goals, harmonic or random excitations of structural panels may promote large amplitude oscillations that are particularly harmful when excitation energies are concentrated around natural frequencies. This contributes to fatigue concerns, performance degradation, and failure. While studies have considered active or passive damping treatments that adapt material characteristics and configurations for structural control, it remains to be understood how vibration properties of structural panels may be tailored via internal material transitions. Motivated to fill this knowledge gap, this research explores an idea of adapting the static and dynamic material distribution of panels through embedded microvascular channels and strategically placed voids that permit the internal movement of fluids within the panels for structural dynamic control. Finite element model and experimental investigations probe how redistributing material in the form of microscale voids influences the global vibration modes and natural frequencies of structural panels. Through parameter studies, the relationships among void shape, number, size, and location are quantified towards their contribution to the changing structural dynamics. For the panel composition and boundary conditions considered in this report, the findings reveal that transferring material between strategically placed voids may result in eigenfrequency changes as great as 10.0, 5.0, and 7.4% for the first, second, and third modes, respectively.

21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Resorbable calcium salt bone void filler device... salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device is... entitled “Class II Special Controls Guidance: Resorbable Calcium Salt Bone Void Filler Device; Guidance for...

21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Resorbable calcium salt bone void filler device... salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device is... entitled “Class II Special Controls Guidance: Resorbable Calcium Salt Bone Void Filler Device; Guidance for...

21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Resorbable calcium salt bone void filler device... salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device is... entitled “Class II Special Controls Guidance: Resorbable Calcium Salt Bone Void Filler Device; Guidance for...

21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Resorbable calcium salt bone void filler device... salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device is... entitled “Class II Special Controls Guidance: Resorbable Calcium Salt Bone Void Filler Device; Guidance for...

21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Resorbable calcium salt bone void filler device... salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device is... entitled “Class II Special Controls Guidance: Resorbable Calcium Salt Bone Void Filler Device; Guidance for...

21 CFR 1305.28 - Canceling and voiding electronic orders.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 9 2014-04-01 2014-04-01 false Canceling and voiding electronic orders. 1305.28... I AND II CONTROLLED SUBSTANCES Electronic Orders § 1305.28 Canceling and voiding electronic orders. (a) A supplier may void all or part of an electronic order by notifying the purchaser of the voiding...

21 CFR 1305.28 - Canceling and voiding electronic orders.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Canceling and voiding electronic orders. 1305.28... I AND II CONTROLLED SUBSTANCES Electronic Orders § 1305.28 Canceling and voiding electronic orders. (a) A supplier may void all or part of an electronic order by notifying the purchaser of the voiding...

38 CFR 3.207 - Void or annulled marriage.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Void or annulled marriage... Void or annulled marriage. Proof that a marriage was void or has been annulled should consist of: (a... marriage void, together with such other evidence as may be required for a determination. (b) Annulled. A...

Molecular dynamics modeling and simulation of void growth in two dimensions

NASA Astrophysics Data System (ADS)

Chang, H.-J.; Segurado, J.; Rodríguez de la Fuente, O.; Pabón, B. M.; LLorca, J.

2013-10-01

The mechanisms of growth of a circular void by plastic deformation were studied by means of molecular dynamics in two dimensions (2D). While previous molecular dynamics (MD) simulations in three dimensions (3D) have been limited to small voids (up to ≈10 nm in radius), this strategy allows us to study the behavior of voids of up to 100 nm in radius. MD simulations showed that plastic deformation was triggered by the nucleation of dislocations at the atomic steps of the void surface in the whole range of void sizes studied. The yield stress, defined as stress necessary to nucleate stable dislocations, decreased with temperature, but the void growth rate was not very sensitive to this parameter. Simulations under uniaxial tension, uniaxial deformation and biaxial deformation showed that the void growth rate increased very rapidly with multiaxiality but it did not depend on the initial void radius. These results were compared with previous 3D MD and 2D dislocation dynamics simulations to establish a map of mechanisms and size effects for plastic void growth in crystalline solids.

Fuzzy Reasoning to More Accurately Determine Void Areas on Optical Micrographs of Composite Structures

NASA Technical Reports Server (NTRS)

Dominquez, Jesus A.; Tate, Lanetra C.; Wright, M. Clara; Caraccio, Anne

2013-01-01

Accomplishing the best-performing composite matrix (resin) requires that not only the processing method but also the cure cycle generate low-void-content structures. If voids are present, the performance of the composite matrix will be significantly reduced. This is usually noticed by significant reductions in matrix-dominated properties, such as compression and shear strength. Voids in composite materials are areas that are absent of the composite components: matrix and fibers. The characteristics of the voids and their accurate estimation are critical to determine for high performance composite structures. One widely used method of performing void analysis on a composite structure sample is acquiring optical micrographs or Scanning Electron Microscope (SEM) images of lateral sides of the sample and retrieving the void areas within the micrographs/images using an image analysis technique. Segmentation for the retrieval and subsequent computation of void areas within the micrographs/images is challenging as the gray-scaled values of the void areas are close to the gray-scaled values of the matrix leading to the need of manually performing the segmentation based on the histogram of the micrographs/images to retrieve the void areas. The use of an algorithm developed by NASA and based on Fuzzy Reasoning (FR) proved to overcome the difficulty of suitably differentiate void and matrix image areas with similar gray-scaled values leading not only to a more accurate estimation of void areas on composite matrix micrographs but also to a faster void analysis process as the algorithm is fully autonomous.

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

Ricciardelli, Elena; Tamone, Amelie; Cava, Antonio

We explore the morphology of galaxies living in the proximity of cosmic voids, using a sample of voids identified in the Sloan Digital Sky Survey Data Release 7. At all stellar masses, void galaxies exhibit morphologies of a later type than galaxies in a control sample, which represent galaxies in an average density environment. We interpret this trend as a pure environmental effect, independent of the mass bias, due to a slower galaxy build-up in the rarefied regions of voids. We confirm previous findings about a clear segregation in galaxy morphology, with galaxies of a later type being found atmore » smaller void-centric distances with respect to the early-type galaxies. We also show, for the first time, that the radius of the void has an impact on the evolutionary history of the galaxies that live within it or in its surroundings. In fact, an enhanced fraction of late-type galaxies is found in the proximity of voids larger than the median void radius. Likewise, an excess of early-type galaxies is observed within or around voids of a smaller size. A significant difference in galaxy properties in voids of different sizes is observed up to 2 R {sub void}, which we define as the region of influence of voids. The significance of this difference is greater than 3 σ for all the volume-complete samples considered here. The fraction of star-forming galaxies shows the same behavior as the late-type galaxies, but no significant difference in stellar mass is observed in the proximity of voids of different sizes.« less

Voids in cosmological simulations over cosmic time

NASA Astrophysics Data System (ADS)

Wojtak, Radosław; Powell, Devon; Abel, Tom

2016-06-01

We study evolution of voids in cosmological simulations using a new method for tracing voids over cosmic time. The method is based on tracking watershed basins (contiguous regions around density minima) of well-developed voids at low redshift, on a regular grid of density field. It enables us to construct a robust and continuous mapping between voids at different redshifts, from initial conditions to the present time. We discuss how the new approach eliminates strong spurious effects of numerical origin when voids' evolution is traced by matching voids between successive snapshots (by analogy to halo merger trees). We apply the new method to a cosmological simulation of a standard Λ-cold-dark-matter cosmological model and study evolution of basic properties of typical voids (with effective radii 6 h-1 Mpc < Rv < 20 h-1 Mpc at redshift z = 0) such as volumes, shapes, matter density distributions and relative alignments. The final voids at low redshifts appear to retain a significant part of the configuration acquired in initial conditions. Shapes of voids evolve in a collective way which barely modifies the overall distribution of the axial ratios. The evolution appears to have a weak impact on mutual alignments of voids implying that the present state is in large part set up by the primordial density field. We present evolution of dark matter density profiles computed on isodensity surfaces which comply with the actual shapes of voids. Unlike spherical density profiles, this approach enables us to demonstrate development of theoretically predicted bucket-like shape of the final density profiles indicating a wide flat core and a sharp transition to high-density void walls.

Effect of voids on Arrhenius relationship between H-solubility and temperature in nickel

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

Wu, Q.Y.; Sun, X.K.; Hu, Z.Q.

1997-01-15

Many investigations about the states of hydrogen in voids within metals have been carried out over the past years. These probable states of hydrogen in the voids are directly relevant to hydrogen embrittlement mechanisms. Therefore, a knowledge of the states of hydrogen in the voids is important to an understanding of hydrogen-related degradation of material properties. Some results show that hydrogen exists as a molecule in the voids, while others suggest it is in the chemisorbed state on the internal surface of the voids. The results of Sung-Man lee et al. suggested that hydrogen in the voids in nickel existsmore » both in the gaseous and chemisorbed stats, and most of the hydrogen trapped in the voids seems to be present as a chemisorbed state in 1 atm. hydrogen pressure in the temperature range of 350--582 C. But there is no quantitative description concerning the effects of the voids on the solubility of hydrogen in materials. The purpose of this work is to describe quantitatively the effects of the voids on hydrogen solubility in nickel, considering hydrogen exists as gaseous and chemisorbed states in the voids, and the very weak physical adsorption above room temperature is neglected.« less

Three-dimensional simulations of void collapse in energetic materials

NASA Astrophysics Data System (ADS)

Rai, Nirmal Kumar; Udaykumar, H. S.

2018-03-01

The collapse of voids in porous energetic materials leads to hot-spot formation and reaction initiation. This work advances the current knowledge of the dynamics of void collapse and hot-spot formation using 3D reactive void collapse simulations in HMX. Four different void shapes, i.e., sphere, cylinder, plate, and ellipsoid, are studied. For all four shapes, collapse generates complex three-dimensional (3D) baroclinic vortical structures. The hot spots are collocated with regions of intense vorticity. The differences in the vortical structures for the different void shapes are shown to significantly impact the relative sensitivity of the voids. Voids of high surface area generate hot spots of greater intensity; intricate, highly contorted vortical structures lead to hot spots of corresponding tortuosity and therefore enhanced growth rates of reaction fronts. In addition, all 3D voids are shown to be more sensitive than their two-dimensional (2D) counterparts. The results provide physical insights into hot-spot formation and growth and point to the limitations of 2D analyses of hot-spot formation.

Underground barrier construction apparatus with soil-retaining shield

DOEpatents

Gardner, Bradley M.; Smith, Ann Marie; Hanson, Richard W.; Hodges, Richard T.

1998-01-01

An apparatus for building a horizontal underground barrier by cutting through soil and depositing a slurry, preferably one which cures into a hardened material. The apparatus includes a digging means for cutting and removing soil to create a void under the surface of the ground, a shield means for maintaining the void, and injection means for inserting barrier-forming material into the void. In one embodiment, the digging means is a continuous cutting chain. Mounted on the continuous cutting chain are cutter teeth for cutting through soil and discharge paddles for removing the loosened soil. This invention includes a barrier placement machine, a method for building an underground horizontal containment barrier using the barrier placement machine, and the underground containment system. Preferably the underground containment barrier goes underneath and around the site to be contained in a bathtub-type containment.

Methods of predicting aggregate voids.

DOT National Transportation Integrated Search

2013-03-01

Percent voids in combined aggregates vary significantly. Simplified methods of predicting aggregate : voids were studied to determine the feasibility of a range of gradations using aggregates available in Kansas. : The 0.45 Power Curve Void Predictio...

Direct evidence of void passivation in Cu(InGa)(SSe){sub 2} absorber layers

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

Lee, Dongho; Kim, Young-Su; Mo, Chan B.

We have investigated the charge collection condition around voids in copper indium gallium sulfur selenide (CIGSSe) solar cells fabricated by sputter and a sequential process of selenization/sulfurization. In this study, we found direct evidence of void passivation by using the junction electron beam induced current method, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The high sulfur concentration at the void surface plays an important role in the performance enhancement of the device. The recombination around voids is effectively suppressed by field-assisted void passivation. Hence, the generated carriers are easily collected by the electrodes. Therefore, when the S/(S + Se)more » ratio at the void surface is over 8% at room temperature, the device performance degradation caused by the recombination at the voids is negligible at the CIGSSe layer.« less

Log-Normal Distribution of Cosmic Voids in Simulations and Mocks

NASA Astrophysics Data System (ADS)

Russell, E.; Pycke, J.-R.

2017-01-01

Following up on previous studies, we complete here a full analysis of the void size distributions of the Cosmic Void Catalog based on three different simulation and mock catalogs: dark matter (DM), haloes, and galaxies. Based on this analysis, we attempt to answer two questions: Is a three-parameter log-normal distribution a good candidate to satisfy the void size distributions obtained from different types of environments? Is there a direct relation between the shape parameters of the void size distribution and the environmental effects? In an attempt to answer these questions, we find here that all void size distributions of these data samples satisfy the three-parameter log-normal distribution whether the environment is dominated by DM, haloes, or galaxies. In addition, the shape parameters of the three-parameter log-normal void size distribution seem highly affected by environment, particularly existing substructures. Therefore, we show two quantitative relations given by linear equations between the skewness and the maximum tree depth, and between the variance of the void size distribution and the maximum tree depth, directly from the simulated data. In addition to this, we find that the percentage of voids with nonzero central density in the data sets has a critical importance. If the number of voids with nonzero central density reaches ≥3.84% in a simulation/mock sample, then a second population is observed in the void size distributions. This second population emerges as a second peak in the log-normal void size distribution at larger radius.

Theory of Dust Voids in Plasmas

NASA Technical Reports Server (NTRS)

Goree, J.; Morfill, G. E.; Tsytovich, V. N.; Vladimirov, S. V.

1999-01-01

Dusty plasmas in a gas discharge often feature a stable void, i.e., a dust-free region inside the dust cloud. This occurs under conditions relevant to both plasma processing discharges and plasma crystal experiments. The void results from a balance of the electrostatic and ion drag forces on a dust particle. The ion drag force is driven by a flow of ions outward from an ionization source and toward the surrounding dust cloud, which has a negative space charge. In equilibrium the force balance for dust particles requires that the boundary with the dust cloud be sharp, provided that the particles are cold and monodispersive. Numerical solutions of the one-dimensional nonlinear fluid equations are carried out including dust charging and dust-neutral collisions, but not ion-neutral collisions. The regions of parameter space that allow stable void equilibria are identified. There is a minimum ionization rate that can sustain a void. Spatial profiles of plasma parameters in the void are reported. In the absence of ion-neutral collisions, the ion flow enters the dust cloud's edge at Mach number M = 1. Phase diagrams for expanding or contracting voids reveal a stationary point corresponding to a single stable equilibrium void size, provided the ionization rate is constant. Large voids contract and small voids expand until they attain this stationary void size. On the other hand, if the ionization rate is not constant, the void size can oscillate. Results are compared to recent laboratory and microgravity experiments.

VizieR Online Data Catalog: A cosmic void catalog of SDSS DR12 BOSS galaxies (Mao+, 2017)

NASA Astrophysics Data System (ADS)

Mao, Q.; Berlind, A. A.; Scherrer, R. J.; Neyrinck, M. C.; Scoccimarro, R.; Tinker, J. L.; McBride, C. K.; Schneider, D. P.; Pan, K.; Bizyaev, D.; Malanushenko, E.; Malanushenko, V.

2017-08-01

We present a cosmic void catalog using the large-scale structure galaxy catalog from the Baryon Oscillation Spectroscopic Survey (BOSS). This galaxy catalog is part of the Sloan Digital Sky Survey (SDSS) Data Release 12 and is the final catalog of SDSS-III. We take into account the survey boundaries, masks, and angular and radial selection functions, and apply the ZOBOV (Neyrinck 2008MNRAS.386.2101N) void finding algorithm to the Galaxy catalog. We identify a total of 10643 voids. After making quality cuts to ensure that the voids represent real underdense regions, we obtain 1228 voids with effective radii spanning the range 20-100h-1Mpc and with central densities that are, on average, 30% of the mean sample density. We release versions of the catalogs both with and without quality cuts. We discuss the basic statistics of voids, such as their size and redshift distributions, and measure the radial density profile of the voids via a stacking technique. In addition, we construct mock void catalogs from 1000 mock galaxy catalogs, and find that the properties of BOSS voids are in good agreement with those in the mock catalogs. We compare the stellar mass distribution of galaxies living inside and outside of the voids, and find no large difference. These BOSS and mock void catalogs are useful for a number of cosmological and galaxy environment studies. (1 data file).

Cosmic voids detection without density measurements

NASA Astrophysics Data System (ADS)

Elyiv, Andrii; Marulli, Federico; Pollina, Giorgia; Baldi, Marco; Branchini, Enzo; Cimatti, Andrea; Moscardini, Lauro

2015-03-01

Cosmic voids are effective cosmological probes to discriminate among competing world models. Their identification is generally based on density or geometry criteria that, because of their very nature, are prone to shot noise. We propose two void finders that are based on dynamical criterion to select voids in Lagrangian coordinates and minimize the impact of sparse sampling. The first approach exploits the Zel'dovich approximation to trace back in time the orbits of galaxies located in voids and their surroundings; the second uses the observed galaxy-galaxy correlation function to relax the objects' spatial distribution to homogeneity and isotropy. In both cases voids are defined as regions of the negative velocity divergence, which can be regarded as sinks of the back-in-time streamlines of the mass tracers. To assess the performance of our methods we used a dark matter halo mock catalogue CODECS, and compared the results with those obtained with the ZOBOV void finder. We find that the void divergence profiles are less scattered than the density ones and, therefore, their stacking constitutes a more accurate cosmological probe. The significance of the divergence signal in the central part of voids obtained from both our finders is 60 per cent higher than for overdensity profiles in the ZOBOV case. The ellipticity of the stacked void measured in the divergence field is closer to unity, as expected, than what is found when using halo positions. Therefore, our void finders are complementary to the existing methods, which should contribute to improve the accuracy of void-based cosmological tests.

Performance of a combined three-hole conductivity probe for void fraction and velocity measurement in air-water flows

NASA Astrophysics Data System (ADS)

Borges, João Eduardo; Pereira, Nuno H. C.; Matos, Jorge; Frizell, Kathleen H.

2010-01-01

The development of a three-hole pressure probe with back-flushing combined with a conductivity probe, used for measuring simultaneously the magnitude and direction of the velocity vector in complex air-water flows, is described in this paper. The air-water flows envisaged in the current work are typically those occurring around the rotors of impulse hydraulic turbines (like the Pelton and Cross-Flow turbines), where the flow direction is not known prior to the data acquisition. The calibration of both the conductivity and three-hole pressure components of the combined probe in a rig built for the purpose, where the probe was placed in a position similar to that adopted for the flow measurements, will be reported. After concluding the calibration procedure, the probe was utilized in the outside region of a Cross-Flow turbine rotor. The experimental results obtained in the present study illustrate the satisfactory performance of the combined probe, and are encouraging toward its use for characterizing the velocity field of other complex air-water flows.

Sensitivity of Short-Term Weather Forecasts to Assimilated AIRS Data: Implications for NPOESS Applications

NASA Technical Reports Server (NTRS)

Zavodsky, Bradley; McCarty, Will; Chou, Shih-Hung; Jedlovec, Gary

2009-01-01

The Atmospheric Infrared Sounder (AIRS) is acting as a heritage and risk reduction instrument for the Cross-track lnfrared Sounder (CrIS) to be flown aboard the NPP and NPOESS satellites. The hyperspectral nature of AIRS and CrIS provides high-quality soundings that, along with their asynoptic observation time over North America, make them attractive sources to fill the spatial and temporal data voids in upper air temperature and moisture measurements for use in data assimilation and numerical weather prediction. Observations from AlRS can be assimilated either as direct radiances or retrieved thermodynamic profiles, and the Short-Term Prediction Research and Transition (SPORT) Center at NASA's Marshall Space Flight Center has used both data types to improve short-term (0-48h), regional forecasts. The purpose of this paper is to share SPORT'S experiences using AlRS radiances and retrieved profiles in regional data assimilation activities by showing that proper handling of issues-including cloud contamination and land emissivity characterization-are necessary to produce optimal analyses and forecasts.

Cavitation transition in the energy landscape: Distinct tensile yielding behavior in strongly and weakly attractive systems.

PubMed

Altabet, Y Elia; Fenley, Andreia L; Stillinger, Frank H; Debenedetti, Pablo G

2018-03-21

Particles with cohesive interactions display a tensile instability in the energy landscape at the Sastry density ρ S . The signature of this tensile limit is a minimum in the landscape equation of state, the pressure-density relationship of inherent structures sampled along a liquid isotherm. Our previous work [Y. E. Altabet, F. H. Stillinger, and P. G. Debenedetti, J. Chem. Phys. 145, 211905 (2016)] revisited the phenomenology of Sastry behavior and found that the evolution of the landscape equation of state with system size for particles with interactions typical of molecular liquids indicates the presence of an athermal first-order phase transition between homogeneous and fractured inherent structures, the latter containing several large voids. Here, we study how this tensile limit manifests itself for different interparticle cohesive strengths and identify two distinct regimes. Particles with sufficiently strong cohesion display an athermal first-order phase transition, consistent with our prior characterization. Weak cohesion also displays a tensile instability. However, the landscape equation of state for this regime is independent of system size, suggesting the absence of a first-order phase transition. An analysis of the voids suggests that yielding in the energy landscape of weakly cohesive systems is associated with the emergence of a highly interconnected network of small voids. While strongly cohesive systems transition from exclusively homogeneous to exclusively fractured configurations at ρ S in the thermodynamic limit, this interconnected network develops gradually, starting at ρ S , even at infinite system size.

Cavitation transition in the energy landscape: Distinct tensile yielding behavior in strongly and weakly attractive systems

NASA Astrophysics Data System (ADS)

Altabet, Y. Elia; Fenley, Andreia L.; Stillinger, Frank H.; Debenedetti, Pablo G.

2018-03-01

Particles with cohesive interactions display a tensile instability in the energy landscape at the Sastry density ρS. The signature of this tensile limit is a minimum in the landscape equation of state, the pressure-density relationship of inherent structures sampled along a liquid isotherm. Our previous work [Y. E. Altabet, F. H. Stillinger, and P. G. Debenedetti, J. Chem. Phys. 145, 211905 (2016)] revisited the phenomenology of Sastry behavior and found that the evolution of the landscape equation of state with system size for particles with interactions typical of molecular liquids indicates the presence of an athermal first-order phase transition between homogeneous and fractured inherent structures, the latter containing several large voids. Here, we study how this tensile limit manifests itself for different interparticle cohesive strengths and identify two distinct regimes. Particles with sufficiently strong cohesion display an athermal first-order phase transition, consistent with our prior characterization. Weak cohesion also displays a tensile instability. However, the landscape equation of state for this regime is independent of system size, suggesting the absence of a first-order phase transition. An analysis of the voids suggests that yielding in the energy landscape of weakly cohesive systems is associated with the emergence of a highly interconnected network of small voids. While strongly cohesive systems transition from exclusively homogeneous to exclusively fractured configurations at ρS in the thermodynamic limit, this interconnected network develops gradually, starting at ρS, even at infinite system size.

Electromigration Mechanism of Failure in Flip-Chip Solder Joints Based on Discrete Void Formation.

PubMed

Chang, Yuan-Wei; Cheng, Yin; Helfen, Lukas; Xu, Feng; Tian, Tian; Scheel, Mario; Di Michiel, Marco; Chen, Chih; Tu, King-Ning; Baumbach, Tilo

2017-12-20

In this investigation, SnAgCu and SN100C solders were electromigration (EM) tested, and the 3D laminography imaging technique was employed for in-situ observation of the microstructure evolution during testing. We found that discrete voids nucleate, grow and coalesce along the intermetallic compound/solder interface during EM testing. A systematic analysis yields quantitative information on the number, volume, and growth rate of voids, and the EM parameter of DZ*. We observe that fast intrinsic diffusion in SnAgCu solder causes void growth and coalescence, while in the SN100C solder this coalescence was not significant. To deduce the current density distribution, finite-element models were constructed on the basis of the laminography images. The discrete voids do not change the global current density distribution, but they induce the local current crowding around the voids: this local current crowding enhances the lateral void growth and coalescence. The correlation between the current density and the probability of void formation indicates that a threshold current density exists for the activation of void formation. There is a significant increase in the probability of void formation when the current density exceeds half of the maximum value.

Morphology of the supercluster-void network in ΛCDM cosmology

NASA Astrophysics Data System (ADS)

Shandarin, Sergei F.; Sheth, Jatush V.; Sahni, Varun

2004-09-01

We report here the first systematic study of the supercluster-void network in the ΛCDM concordance cosmology in which voids and superclusters are treated on an equal footing. We study the dark matter density field in real space smoothed on a scale of 5 h-1 Mpc. Superclusters are defined as individual members of an overdense excursion set, and voids are defined as individual members of a complementary underdense excursion set at the same density threshold. We determine the geometric, topological and morphological properties of the cosmic web at a large set of density levels by computing Minkowski functionals for every supercluster and void using SURFGEN (described recently by Sheth et al.). The properties of the largest (percolating) supercluster and the complementary void are found to be very different from those of the individual superclusters and voids. In total, the individual superclusters occupy no more than about 5 per cent of the volume and contain no more than 20 per cent of the mass if the largest supercluster is excluded. Likewise, in total, individual voids occupy no more than 14 per cent of the volume and contain no more than 4 per cent of the mass if the largest void is excluded. Although superclusters are more massive and voids are more voluminous, the difference in maximum volumes is no greater than an order of magnitude. The genus value of individual superclusters can be ~5, while the genus of individual voids can reach ~50, implying a significant amount of substructure in superclusters and especially in voids. One of our main results is that large voids, as defined through the dark matter density field in real space, are distinctly non-spherical.

Methods of predicting aggregate voids : [technical summary].

DOT National Transportation Integrated Search

2013-03-01

Percent voids in combined aggregates vary significantly. Simplified methods of predicting aggregate voids were studied to determine the feasibility of a range of gradations using aggregates available in Kansas. : The 0.45 Power Curve Void Prediction ...

Gas Bubble Dynamics under Mechanical Vibrations

NASA Astrophysics Data System (ADS)

Mohagheghian, Shahrouz; Elbing, Brian

2017-11-01

The scientific community has a limited understanding of the bubble dynamics under mechanical oscillations due to over simplification of Navier-Stockes equation by neglecting the shear stress tensor and not accounting for body forces when calculating the acoustic radiation force. The current work experimental investigates bubble dynamics under mechanical vibration and resulting acoustic field by measuring the bubble size and velocity using high-speed imaging. The experimental setup consists of a custom-designed shaker table, cast acrylic bubble column, compressed air injection manifold and an optical imaging system. The mechanical vibrations resulted in accelerations between 0.25 to 10 times gravitational acceleration corresponding to frequency and amplitude range of 8 - 22Hz and 1 - 10mm respectively. Throughout testing the void fraction was limited to <5%. The bubble size is larger than resonance size and smaller than acoustic wavelength. The amplitude of acoustic pressure wave was estimated using the definition of Bjerknes force in combination with Rayleigh-Plesset equation. Physical behavior of the system was capture and classified. Bubble size, velocity as well as size and spatial distribution will be presented.

Effective Porosity Measurements by Wet- and Dry-type Vacuum Saturations using Process-Programmable Vacuum Saturation System

NASA Astrophysics Data System (ADS)

Lee, T. J.; Lee, K. S., , Dr; Lee, S. K.

2017-12-01

One of the most important factors in measuring effective porosity by vacuum saturation method is that the air in the pore space can be fully substituted by water during the vacuum saturation process. International Society of Rock Mechanics (ISRM) suggests vacuuming a rock sample submerged in the water, while American Society of Test and Materials (ASTM) vacuuming the sample and water separately and then pour the water to the sample. In this study, we call the former wet-type vacuum saturation (WVS) method and the latter dry-type vacuum saturation (DVS) method, and compare the effective porosity measured by the two different vacuum saturation processes. For that purpose, a vacuum saturation system has been developed, which can support both WVS and DVS by only changing the process by programming. Comparison of effective porosity has been made for a cement mortar and rock samples. As a result, DVS can substitute more void volume to water than WVS, which in turn insists that DVS can provide more exact value of effective porosity than WVS.

Neurotrophin/receptor expression in urinary bladder of mice with overexpression of NGF in urothelium.

PubMed

Girard, Beatrice M; Malley, Susan E; Vizzard, Margaret A

2011-02-01

Urothelium-specific overexpression of nerve growth factor (NGF) in the urinary bladder of transgenic mice stimulates neuronal sprouting in the urinary bladder, produces increased voiding frequency, and results in increased referred somatic hypersensitivity. Additional NGF-mediated pleiotropic changes might contribute to the increased voiding frequency and pelvic hypersensitivity observed in these transgenic mice, such as modulation of other growth factor/receptor systems. Chronic overexpression of NGF in the urothelium was achieved through the use of a highly urothelium-specific uroplakin II promoter. In the present study, we examined NGF, brain-derived neurotrophic factor (BDNF), and associated receptor [p75(NTR), tyrosine kinase (Trk)A, TrkB] transcript and protein expression in urothelium and detrusor smooth muscle of NGF-overexpressing (OE) and littermate wild-type mice, using real-time quantitative reverse transcription-polymerase chain reaction, ELISAs, and semiquantitation of immunohistochemistry. We focused on these growth factor/receptors given the established roles of NGF/TrkA, NGF/p75(NTR), and BDNF/TrkB systems in bladder function. Increased voiding frequency in NGF-OE mice was confirmed by examining urination patterns. BDNF, TrkA, and TrkB protein expression was significantly (P ≤ 0.01) reduced and p75(NTR) protein expression was significantly (P ≤ 0.01) increased in urinary bladder of NGF-OE mice. The NGF-OE-induced changes in neurotrophic factor/receptor expression in urinary bladder may represent compensatory changes to reduce voiding frequency in the NGF-OE mouse.

Effects of cement alkalinity, exposure conditions and steel-concrete interface on the time-to-corrosion and chloride threshold for reinforcing steel in concrete

NASA Astrophysics Data System (ADS)

Nam, Jingak

Effects of (1) cement alkalinity (low, normal and high), (2) exposure conditions (RH and temperature), (3) rebar surface condition (as-received versus cleaned) and (4) density and distribution of air voids at the steel-concrete interface on the chloride threshold and time-to-corrosion for reinforcing steel in concrete have been studied. Also, experiments were performed to evaluate effects of RH and temperature on the diffusion of chloride in concrete and develop a method for ex-situ pH measurement of concrete pore water. Once specimens were fabricated and exposed to a corrosive chloride solution, various experimental techniques were employed to determine time-to-corrosion, chloride threshold, diffusion coefficient and void density along the rebar trace as well as pore water pH. Based upon the resultant data, several findings related to the above parameters have been obtained as summarized below. First, time for the corrosion initiation was longest for G109 concrete specimens with high alkalinity cement (HA). Also, chloride threshold increased with increasing time-to-corrosion and cement alkalinity. Consequently, the HA specimens exhibited the highest chloride threshold compared to low and normal alkalinity ones. Second, high temperature and temperature variations reduced time-to-corrosion of reinforcing steel in concrete since chloride diffusion was accelerated at higher temperature and possibly by temperature variations. The lowest chloride threshold values were found for outdoor exposed specimens suggesting that variation of RH or temperature (or both) facilitated rapid chloride diffusion. Third, an elevated time-to-corrosion and chloride threshold values were found for the wire brushed steel specimens compared to as-received ones. The higher ratio of [OH-]/[Fe n+] on the wire brushed steel surface compared to that of as-received case can be the possible cause because the higher ratio of this parameter enables the formation of a more protective passive film on the rebar. Fourth, voids at the steel-concrete interface facilitated passive film breakdown and onset of localized corrosion. This tendency for corrosion initiation increased in proportion to void size irrespective of specimen type. Also, [Cl -]th decreased with increasing void diameter. In addition, new ex-situ leaching method for determining concrete pore water alkalinity was developed.

Impact of posterior urethral diameter/external urethral sphincter diameter as a new tool to predict detrusor pressure in the voiding phase.

PubMed

Kon, Masafumi; Mitsui, Takahiko; Kitta, Takeya; Moriya, Kimihiko; Shinohara, Nobuo; Takeda, Masayuki; Nonomura, Katsuya

2018-02-01

We measured posterior urethra diameter (PUD) and external urethral sphincter diameter (EUSD), which can also be measured by voiding cystourethrography (VCUG) and investigated the relationship between PUD/EUSD and detrusor pressure (Pdet) during voiding by videourodynamics (VUDS). Sixty-three children, who were 3 years old or less and underwent VUDS, were enrolled in the present study. We measured PUD and EUSD in addition to detrusor pressure at the time of the widest EUS during voiding (Pdet-voiding) by VUDS, and PUD/EUSD was investigated compared to Pdet-voiding. Seventy-eight VUDS were performed in 63 patients, and the median age at VUDS was 10.2 months. These studies revealed a significant correlation between PUD/EUSD and Pdet-voiding (r = 0.641, p < 0.001). However, a significant correlation was not observed between PUD/EUSD and age (r = 0.180). We defined Pdet-voiding of more than 80 cmH 2 O as a high voiding pressure, and a PUD/EUSD of 2.4 was a good predictor for the cutoff value for high voiding pressure. Pdet-voiding was significantly higher in children with a PUD/EUSD of ≥ 2.4 (p < 0.001). In 19 children who had neurological diseases, a significant correlation was found between PUD/EUSD and Pdet-voiding (r = 0.842, p < 0.001), and a PUD/EUSD of 2.4 was a useful cutoff value for high voiding pressure. PUD/EUSD is a valuable tool to predict high voiding pressure in pediatric patients. A PUD/EUSD of ≥ 2.4 in VCUG indicates the need to perform more invasive tests, such as VUDS, in pediatric patients aged 3 and under with neuropathic diseases.

Velocity field measurement in gas-liquid metal two-phase flow with use of PIV and neutron radiography techniques.

PubMed

Saito, Y; Mishima, K; Tobita, Y; Suzuki, T; Matsubayashi, M

2004-10-01

To establish reasonable safety concepts for the realization of commercial liquid-metal fast breeder reactors, it is indispensable to demonstrate that the release of excessive energy due to re-criticality of molten core could be prevented even if a severe core damage accident took place. Two-phase flow due to the boiling of fuel-steel mixture in the molten core pool has a larger liquid-to-gas density ratio and higher surface tension in comparison with those of ordinary two-phase flows such as air-water flow. In this study, to investigate the effect of the recirculation flow on the bubble behavior, visualization and measurement of nitrogen gas-molten lead bismuth in a rectangular tank was performed by using neutron radiography and particle image velocimetry techniques. Measured flow parameters include flow regime, two-dimensional void distribution, and liquid velocity field in the tank. The present technique is applicable to the measurement of velocity fields and void fraction, and the basic characteristics of gas-liquid metal two-phase mixture were clarified.

On the observability of coupled dark energy with cosmic voids

NASA Astrophysics Data System (ADS)

Sutter, P. M.; Carlesi, Edoardo; Wandelt, Benjamin D.; Knebe, Alexander

2015-01-01

Taking N-body simulations with volumes and particle densities tuned to match the sloan digital sky survey DR7 spectroscopic main sample, we assess the ability of current void catalogues to distinguish a model of coupled dark matter-dark energy from Λ cold dark matter cosmology using properties of cosmic voids. Identifying voids with the VIDE toolkit, we find no statistically significant differences in the ellipticities, but find that coupling produces a population of significantly larger voids, possibly explaining the recent result of Tavasoli et al. In addition, we use the universal density profile of Hamaus et al. to quantify the relationship between coupling and density profile shape, finding that the coupling produces broader, shallower, undercompensated profiles for large voids by thinning the walls between adjacent medium-scale voids. We find that these differences are potentially measurable with existing void catalogues once effects from survey geometries and peculiar velocities are taken into account.

Cave Buttes Dam Foundation Report. Gila River Basin: Phoenix, Arizona and Vicinity (Including New River).

DTIC Science & Technology

1983-08-01

bedrock. Reservoir deposits are rich in silt and clay as shown by the plastic nature of material behind Cave Creek Dam. Recent alluvium is directly...formation and the zone I, impervious material. Then rolling with the rubber tired equipment would fill voids and small cracks with the clayey, plastic ...Assoclates US " 2 t 64urvey air J.1y 1969. ___OSOWRS g.Aorizatnfa( conirol ji 45 on G1A - EEA fSI Alaon~ral ieodtc Survey Dafum. Yerftci 4 1 -5 AtE

Numerical simulation of asphalt mixtures fracture using continuum models

NASA Astrophysics Data System (ADS)

Szydłowski, Cezary; Górski, Jarosław; Stienss, Marcin; Smakosz, Łukasz

2018-01-01

The paper considers numerical models of fracture processes of semi-circular asphalt mixture specimens subjected to three-point bending. Parameter calibration of the asphalt mixture constitutive models requires advanced, complex experimental test procedures. The highly non-homogeneous material is numerically modelled by a quasi-continuum model. The computational parameters are averaged data of the components, i.e. asphalt, aggregate and the air voids composing the material. The model directly captures random nature of material parameters and aggregate distribution in specimens. Initial results of the analysis are presented here.

Void-Free Lid for Food Packaging

NASA Technical Reports Server (NTRS)

Watson, C. D.; Farris, W. P.

1986-01-01

Flexible cover eliminates air pockets in sealed container. Universal food-package lid formed from flexible plastic. Partially folded, lid unfolded by depressing center portion. Height of flat portion of lid above flange thereby reduced. Pressure of food against central oval depression pops it out, forming dome that provides finger grip for mixing contents with water or opening lid. Therefore food stays fresh, allows compact stacking of partially filled containers, and resists crushing. Originally developed for packaging dehydrated food for use in human consumption on Space Shuttle missions. Other uses include home canning and commercial food packaging.

Direct Contact Heat Exchange Interfacial Phenomena for Liquid Metal Reactors: Part II - Void Fraction

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

Abdulla, S.; Liu, X.; Anderson, M.H.

One concept being considered for steam generation in innovative nuclear reactor applications, involves water coming into direct contact with a circulating molten metal. The vigorous agitation of the two fluids, the direct liquid-liquid contact and the consequent large interfacial area can give rise to large heat transfer coefficients and rapid steam generation. For an optimum design of such direct contact heat exchange and vaporization systems, detailed knowledge is necessary of the various flow regimes, interfacial transport phenomena, heat transfer and operational stability. In order to investigate the interfacial transport phenomena, heat transfer and operational stability of direct liquid-liquid contact, amore » series of experiments are being performed in a 1-d test facility at Argonne National Laboratory and a 2-d experimental facility at UW-Madison. Each of the experimental facilities primarily consist of a liquid-metal melt chamber, heated test section (10 cm diameter tube for 1-d facility and 10 cm 50 cm rectangle for 2-d facility), water injection system and steam suppression tank. This paper is part II which, primarily addresses results and analysis of a set of preliminary experiments and void fraction measurements conducted in the 2-d facility at UW-Madison, part I deals with the heat transfer in the 1-d test facility at Argonne National Laboratory. A real-time high energy X-ray imaging system was developed and utilized to visualize the multiphase flow and measure line-average local void fractions, time-dependent void fraction distribution as well as estimates of the vapor bubble sizes and velocities. These measurements allowed us to determine the volumetric heat transfer coefficient and gain insight into the local heat transfer mechanisms. In this study, the images were captured at frame rates of 100 fps with spatial resolution of about 7 mm with a full-field view of a 15 cm square and five different positions along the test section height. The full-field average void fraction increases rapidly to about 15% in these preliminary tests, with the apparent boiling length of less than 20 cm. The volumetric heat transfer coefficient between the liquid metal and water are compared to the CRIEPI data, the only prior data for direct contact heat exchange for these liquid metal/water systems. (authors)« less

Smouldering Remediation (STAR) Technology: Field Pilot Tests and First Full Scale Application

NASA Astrophysics Data System (ADS)

Gerhard, J.; Kinsman, L.; Torero, J. L.

2015-12-01

STAR (Self-sustaining Treatment for Active Remediation) is an innovative remediation technology based on the principles of smoldering combustion where the contaminants are the fuel. The self-sustaining aspect means that a single, local ignition event can result in many days of contaminant destruction in situ. Presented research to date has focused on bench scale experiments, numerical modelling and process understanding. Presented here is the maturation of the in situ technology, including three field pilot tests and a full-scale implementation to treat coal tar-impacted soils. The first pilot determined a Radius of Influence (ROI) for a single ignition of approximately eight feet with an average propagation rate of the reaction of approximately one foot per day. TPH concentrations in soils were reduced from 10,000 milligrams per kilogram to a few hundred milligrams per kilogram. The second pilot was conducted in an area of significant void spaces created through the anthropogenic deposition of clay bricks and tiles. The void spaces led to pre-mature termination of the combustion reaction, limiting ROI and the effectiveness of the technology in this setting. The third case study involved the pilot testing, design, and full-scale implementation of STAR at a 37-acre former chemical manufacturing facility. Three phases of pilot testing were conducted within two hydrogeologic units at the site (i.e., surficial fill and deep alluvial sand units). Pilot testing within the fill demonstrated self-sustained coal tar destruction rates in excess of 800 kg/day supported through air injection at a single well. Deep sand unit testing (twenty-five feet below the water table) resulted in the treatment of a targeted six-foot layer of impacted fine sands to a radial distance of approximately twelve feet. These results (and additional parameters) were used to develop a full-scale STAR design consisting of approximately 1500 surficial fill ignition points and 500 deep sand ignition points and two treatment (air distribution and vapor collection / treatment) systems to remediate an approximately 14-acre footprint of contaminated soils within the project timelines (i.e., by mid-2016). Field activities began in 2014 and progress is currently on-schedule.

Micro-CT and nano-CT analysis of filling quality of three different endodontic sealers.

PubMed

Huang, Yan; Celikten, Berkan; de Faria Vasconcelos, Karla; Ferreira Pinheiro Nicolielo, Laura; Lippiatt, Nicholas; Buyuksungur, Arda; Jacobs, Reinhilde; Orhan, Kaan

2017-12-01

To investigate voids in different root canal sealers using micro-CT and nano-CT, and to explore the feasibility of using nano-CT for quantitative analysis of sealer filling quality. 30 extracted mandibular central incisors were randomly assigned into three groups according to the applied root canal sealers (Total BC Sealer, Sure Seal Root, AH Plus) by the single cone technique. Subsequently, micro-CT and nano-CT were performed to analyse the incidence rate of voids, void fraction, void volume and their distribution in each sample. Micro-CT evaluation showed no significant difference among sealers for the incidence rate of voids or void fraction in the whole filling materials (p > 0.05), whereas a significant difference was found between AH Plus and the other two sealers using nano-CT (p < 0.05). All three sealers presented less void volume in the apical third; however, higher void volumes were observed in the apical and coronal thirds in AH Plus using micro-CT (p < 0.05), while nano-CT results displayed higher void volume in AH Plus among all the sealers and regions (p < 0.05). Bioactive sealers showed higher root filling rate, lower incidence rate of voids, void fraction and void volume than AH Plus under nano-CT analysis, when round root canals were treated by the single cone technique. The disparate results suggest that the higher resolution of nano-CT have a greater ability of distinguishing internal porosity, and therefore suggesting the potential use of nano-CT in quantitative analysis of filling quality of sealers.

Rayleigh-wave diffractions due to a void in the layered half space

USGS Publications Warehouse

Xia, J.; Xu, Y.; Miller, R.D.; Nyquist, Jonathan E.

2006-01-01

Void detection is challenging due to the complexity of near-surface materials and the limited resolution of geophysical methods. Although multichannel, high-frequency, surface-wave techniques can provide reliable shear (S)-wave velocities in different geological settings, they are not suitable for detecting voids directly based on anomalies of the S-wave velocity because of limitations on the resolution of S-wave velocity profiles inverted from surface-wave phase velocities. Xia et al. (2006a) derived a Rayleigh-wave diffraction traveltime equation due to a void in the homogeneous half space. Encouraging results of directly detecting a void from Rayleigh-wave diffractions were presented (Xia et al., 2006a). In this paper we used four two-dimensional square voids in the layered half space to demonstrate the feasibility of detecting a void with Rayleigh-wave diffractions. Rayleigh-wave diffractions were recognizable for all these models after removing direct surface waves by F-K filtering. We evaluate the feasibility of applying the Rayleigh-wave diffraction traveltime equation to a void in the layered earth model. The phase velocity of diffracted Rayleigh waves is predominately determined by surrounding materials of a void. The modeling results demonstrate that the Rayleigh-wave diffraction traveltime equation due to a void in the homogeneous half space can be applied to the case of a void in the layered half space. In practice, only two diffraction times are necessary to define the depth to the top of a void and the average velocity of diffracted Rayleigh waves. ?? 2005 Society of Exploration Geophysicists.

LOG-NORMAL DISTRIBUTION OF COSMIC VOIDS IN SIMULATIONS AND MOCKS

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

Russell, E.; Pycke, J.-R., E-mail: er111@nyu.edu, E-mail: jrp15@nyu.edu

2017-01-20

Following up on previous studies, we complete here a full analysis of the void size distributions of the Cosmic Void Catalog based on three different simulation and mock catalogs: dark matter (DM), haloes, and galaxies. Based on this analysis, we attempt to answer two questions: Is a three-parameter log-normal distribution a good candidate to satisfy the void size distributions obtained from different types of environments? Is there a direct relation between the shape parameters of the void size distribution and the environmental effects? In an attempt to answer these questions, we find here that all void size distributions of thesemore » data samples satisfy the three-parameter log-normal distribution whether the environment is dominated by DM, haloes, or galaxies. In addition, the shape parameters of the three-parameter log-normal void size distribution seem highly affected by environment, particularly existing substructures. Therefore, we show two quantitative relations given by linear equations between the skewness and the maximum tree depth, and between the variance of the void size distribution and the maximum tree depth, directly from the simulated data. In addition to this, we find that the percentage of voids with nonzero central density in the data sets has a critical importance. If the number of voids with nonzero central density reaches ≥3.84% in a simulation/mock sample, then a second population is observed in the void size distributions. This second population emerges as a second peak in the log-normal void size distribution at larger radius.« less

Detection of coal mine workings using high-resolution earth resistivity techniques. Final technical report, September 1979-September 1980

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

Peters, W.R.; Campbell, T.M.; Sturdivant, V.R.

1980-09-26

Shallow underground voids resulting from early coal mining and other resource recovery activities over the past several decades are now being recognized as a significant cause of ground subsidence problems in developing urban areas. Uncertain knowledge of abandoned coal mines also imposes potential hazards in coal excavation operations since water inundation or the release of methane gas is a principal hazard when mine excavation operations break into an abandoned mine. US Army requirements for an effective method for detecting and mapping subversive abandoned tunnels have resulted in a surface-operated automatic earth resistivity survey system with a digital computer data processingmore » system. Field tests aimed at demonstrating the system performance resulted in successful detection of tunnels having depth-to-diameter ratios up to 15 to 1. Under the sponsorship of the Bureau of Mines, a similar system was designed and constructed for use in the detection of coal mine workings. This report discusses the hardware and software aspects of the system and the application of the high-resolution earth resistivity method to the survey and mapping of abandoned coal mine workings. In the field tests reported, the targets of interest were both air- and water-filled workings.« less

Using Aerogel-Based Insulation Material To Prevent Foam Loss on the Liquid-Hydrogen Intertank

NASA Technical Reports Server (NTRS)

2008-01-01

Uninsulated areas on cryogenic propellant tanks and feedlines cause moisture in the air to condense or ice to form. Flange joints, bracket supports, expansion bellows, and other cavities are uninsulated by design. These areas cannot be sealed because conventional thermal insulation materials would restrict mechanical articulations. Aerogel-based thermal insulation systems are able to seal critical locations such as the liquid-oxygen (LO2) feedline bellows. A new thermal insulation system was also necessary between the intertank wall, flange, and the liquid-hydrogen (LH2) tank dome, where there is a cavity (or crevice) with an exposed 20-K surface. When nitrogen gas is used for purging within the intertank volume, it condenses on this cold surface. Some solid nitrogen may also form on the colder side of the crevice. Voids or discontinuities within the foam can pressurize and cause areas of foam to weaken and break off, reducing thermal efficiency and creating potentially dangerous debris. To prevent this foam loss, we developed a thermal insulation system using bulk-fill aerogel material and demonstrated it with a one-tenth-scale model of the LH2 intertank flange area

Are the measurements of water-filled and air-charged catheters the same in urodynamics?

PubMed

Digesu, G Alessandro; Derpapas, Alexandros; Robshaw, Penny; Vijaya, Gopalan; Hendricken, Caroline; Khullar, Vik

2014-01-01

The aim of our study was to compare air-charged and water-filled catheters simultaneously in the measurement of the intravesical, abdominal and detrusor pressure during urodynamic investigations. Consecutive women with lower urinary tract symptoms, referred for urodynamics were prospectively studied. Readings of intravesical pressure (p(ves)), abdominal pressure (p(abd)) and detrusor pressure (p(det)), recorded by both the air-charged and water-filled catheters, were displayed simultaneously and compared at the end of filling, on standing, on sitting prior to voiding and at the maximum involuntary detrusor contraction. The signals (pressures) recorded by both types of catheter were compared using the Bland-Altman plot and paired samples t test. Twenty women with a mean age of 49 (range 36-72) were recruited. One patient with normal urodynamics was excluded in view of the poor quality trace. At each of the four comparison points, the air-charged catheters consistently produced higher mean pressures than the water-filled catheters. There were wide variations in the difference between the readings produced by the two types of catheter. Pressures measured using air-charged catheters are not comparable with water-filled catheters and are therefore not interchangeable. Caution must be used when comparing urodynamic parameters using air-charged and water-filled catheters.

Morphological statistics of the cosmic web

NASA Astrophysics Data System (ADS)

Shandarin, Sergei F.

2004-07-01

We report the first systematic study of the supercluster-void network in the ΛCDM concordance cosmology treating voids and superclusters on an equal footing. We study the dark matter density field in real space smoothed with the Ls = 5 h[minus sign]1Mpc Gaussian window. Superclusters and voids are defined as individual members of over-dense and under-dense excursion sets respectively. We determine the morphological properties of the cosmic web at a large number of dark matter density levels by computing Minkowski functionals for every supercluster and void. At the adopted smoothing scale individual superclusters totally occupy no more than about 5% of the total volume and contain no more than 20% of mass if the largest supercluster is excluded. Likewise, individual voids totally occupy no more than 14% of volume and contain no more than 4% of mass if the largest void is excluded. The genus of individual superclusters can be ˜ 5 while the genus of individual voids reaches ˜ 55, implying significant amount of substructure in superclusters and especially in voids. Large voids are typically distinctly non-spherical.

Fluid intake and voiding; habits and health knowledge in a young, healthy population

PubMed Central

Das, Rebekah N; Grimmer-Somers, Karen A

2012-01-01

Objectives Health professionals commonly advise patients with incontinence and other lower urinary tract symptoms about modifiable contributing factors such as drinking and voiding habits. Poor drinking and voiding habits may begin early in life, before symptoms emerge. However, little is known about the habits and knowledge young people have regarding healthy drinking and voiding behaviors. This research aimed to assess the habits and health knowledge of young people regarding fluid intake and voiding. Methods A questionnaire was used to assess the drinking and voiding behaviors of first year university students and their knowledge about healthy fluid intake and voiding. Results The average daily fluid intake was >2 L/day for both genders. Poor drinking and voiding habits (such as high consumption of caffeinated drinks and alcohol, or nocturia) were common. Widely reported myths about the benefits of a high fluid intake were commonly believed. Conclusion More informed public education regarding healthy fluid intake, and drinking and voiding habits, is required as part of the effort to reduce the development of lower urinary tract symptoms, including incontinence. PMID:24199175

Fluid intake and voiding; habits and health knowledge in a young, healthy population.

PubMed

Das, Rebekah N; Grimmer-Somers, Karen A

2012-01-01

Health professionals commonly advise patients with incontinence and other lower urinary tract symptoms about modifiable contributing factors such as drinking and voiding habits. Poor drinking and voiding habits may begin early in life, before symptoms emerge. However, little is known about the habits and knowledge young people have regarding healthy drinking and voiding behaviors. This research aimed to assess the habits and health knowledge of young people regarding fluid intake and voiding. A questionnaire was used to assess the drinking and voiding behaviors of first year university students and their knowledge about healthy fluid intake and voiding. The average daily fluid intake was >2 L/day for both genders. Poor drinking and voiding habits (such as high consumption of caffeinated drinks and alcohol, or nocturia) were common. Widely reported myths about the benefits of a high fluid intake were commonly believed. More informed public education regarding healthy fluid intake, and drinking and voiding habits, is required as part of the effort to reduce the development of lower urinary tract symptoms, including incontinence.

Estimation of coolant void reactivity for CANDU-NG lattice using DRAGON and validation using MCNP5 and TRIPOLI-4.3

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

Karthikeyan, R.; Tellier, R. L.; Hebert, A.

2006-07-01

The Coolant Void Reactivity (CVR) is an important safety parameter that needs to be estimated at the design stage of a nuclear reactor. It helps to have an a priori knowledge of the behavior of the system during a transient initiated by the loss of coolant. In the present paper, we have attempted to estimate the CVR for a CANDU New Generation (CANDU-NG) lattice, as proposed at an early stage of the Advanced CANDU Reactor (ACR) development. We have attempted to estimate the CVR with development version of the code DRAGON, using the method of characteristics. DRAGON has several advancedmore » self-shielding models incorporated in it, each of them compatible with the method of characteristics. This study will bring to focus the performance of these self-shielding models, especially when there is voiding of such a tight lattice. We have also performed assembly calculations in 2 x 2 pattern for the CANDU-NG fuel, with special emphasis on checkerboard voiding. The results obtained have been validated against Monte Carlo codes MCNP5 and TRIPOLI-4.3. (authors)« less

A Study of Wing Flutter

NASA Technical Reports Server (NTRS)

Zahm, A F; Bear, R M

1929-01-01

Part I describes vibration tests, in a wind tunnel, of simple airfoils and of the tail plane of an M0-1 airplane model; it also describes the air flow about this model. From these tests are drawn inferences as to the cause and cure of aerodynamic wing vibrations. Part II derives stability criteria for wing vibrations in pitch and roll, and gives design rules to obviate instability. Part III shows how to design spars to flex equally under a given wing loading and thereby economically minimize the twisting in pitch that permits cumulative flutter. Resonant flutter is not likely to ensue from turbulence of air flow along past wings and tail planes in usual flying conditions. To be flutterproof a wing must be void of reversible autorotation and not have its centroid far aft of its pitching axis, i. e., axis of pitching motion. Danger of flutter is minimized by so proportioning the wing's torsional resisting moment to the air pitching moment at high-speed angles that the torsional flexure is always small. (author)

Reliability of scanning laser acoustic microscopy for detecting internal voids in structural ceramics

NASA Technical Reports Server (NTRS)

Roth, D. J.; Baaklini, G. Y.

1986-01-01

The reliability of 100 MHz scanning laser acoustic microscopy (SLAM) for detecting internal voids in sintered specimens of silicon nitride and silicon carbide was evaluated. The specimens contained artificially implanted voids and were positioned at depths ranging up to 2 mm below the specimen surface. Detection probability of 0.90 at a 0.95 confidence level was determined as a function of material, void diameter, and void depth. The statistical results presented for void detectability indicate some of the strengths and limitations of SLAM as a nondestructive evaluation technique for structural ceramics.

Mechanisms for Ductile Rupture - FY16 ESC Progress Report

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

Boyce, Brad L.; Carroll, Jay D.; Noell, Phillip

2017-01-01

Ductile rupture in metals is generally a multi-step process of void nucleation, growth, and coalescence. Particle decohesion and particle fracture are generally invoked as the primary microstructural mechanisms for room-temperature void nucleation. However, because high-purity materials also fail by void nucleation and coalescence, other microstructural features must also act as sites for void nucleation. Early studies of void initiation in high-purity materials, which included post-mortem fracture surface characterization using scanning electron microscopy (SEM) and high-voltage electron microscopy (HVEM) and in-situ HVEM observations of fracture, established the presence of dislocation cell walls as void initiation sites in high-purity materials. Direct experimentalmore » evidence for this contention was obtained during in-situ HVEM tensile tests of Be single crystals. Voids between 0.2 and 1 μm long appeared suddenly along dislocation cell walls during tensile straining. However, subsequent attempts to replicate these results in other materials, particularly α -Fe single crystals, were unsuccessful because of the small size of the dislocation cells, and these remain the only published in-situ HVEM observations of void nucleation at dislocation cell walls in the absence of a growing macrocrack. Despite this challenge, other approaches to studying void nucleation in high-purity metals also indicate that dislocation cell walls are nucleation sites for voids.« less

Quantifying Effects of Voids in Woven Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Goldsmith, Marlana B.; Sankar, Bhavani V.; Haftka, Raphael T.; Goldberg, Robert K.

2013-01-01

Randomness in woven ceramic matrix composite architecture has been found to cause large variability in stiffness and strength. The inherent voids are an aspect of the architecture that may cause a significant portion of the variability. A study is undertaken to investigate the effects of many voids of random sizes and distributions. Response surface approximations were formulated based on void parameters such as area and length fractions to provide an estimate of the effective stiffness. Obtaining quantitative relationships between the properties of the voids and their effects on stiffness of ceramic matrix composites are of ultimate interest, but the exploratory study presented here starts by first modeling the effects of voids on an isotropic material. Several cases with varying void parameters were modeled which resulted in a large amount of variability of the transverse stiffness and out-of-plane shear stiffness. An investigation into a physical explanation for the stiffness degradation led to the observation that the voids need to be treated as an entity that reduces load bearing capabilities in a space larger than what the void directly occupies through a corrected length fraction or area fraction. This provides explanation as to why void volume fraction is not the only important factor to consider when computing loss of stiffness.

Regional dust storm modeling for health services: The case of valley fever

NASA Astrophysics Data System (ADS)

Sprigg, William A.; Nickovic, Slobodan; Galgiani, John N.; Pejanovic, Goran; Petkovic, Slavko; Vujadinovic, Mirjam; Vukovic, Ana; Dacic, Milan; DiBiase, Scott; Prasad, Anup; El-Askary, Hesham

2014-09-01

On 5 July 2011, a massive dust storm struck Phoenix, Arizona (USA), raising concerns for increased cases of valley fever (coccidioidomycosis, or, cocci). A quasi-operational experimental airborne dust forecast system predicted the event and provides model output for continuing analysis in collaboration with public health and air quality communities. An objective of this collaboration was to see if a signal in cases of valley fever in the region could be detected and traced to the storm - an American haboob. To better understand the atmospheric life cycle of cocci spores, the DREAM dust model (also herein, NMME-DREAM) was modified to simulate spore emission, transport and deposition. Inexact knowledge of where cocci-causing fungus grows, the low resolution of cocci surveillance and an overall active period for significant dust events complicate analysis of the effect of the 5 July 2011 storm. In the larger context of monthly to annual disease surveillance, valley fever statistics, when compared against PM10 observation networks and modeled airborne dust concentrations, may reveal a likely cause and effect. Details provided by models and satellites fill time and space voids in conventional approaches to air quality and disease surveillance, leading to land-atmosphere modeling and remote sensing that clearly mark a path to advance valley fever epidemiology, surveillance and risk avoidance.

Underground barrier construction apparatus with soil-retaining shield

DOEpatents

Gardner, B.M.; Smith, A.M.; Hanson, R.W.; Hodges, R.T.

1998-08-04

An apparatus is described for building a horizontal underground barrier by cutting through soil and depositing a slurry, preferably one which cures into a hardened material. The apparatus includes a digging means for cutting and removing soil to create a void under the surface of the ground, a shield means for maintaining the void, and injection means for inserting barrier-forming material into the void. In one embodiment, the digging means is a continuous cutting chain. Mounted on the continuous cutting chain are cutter teeth for cutting through soil and discharge paddles for removing the loosened soil. This invention includes a barrier placement machine, a method for building an underground horizontal containment barrier using the barrier placement machine, and the underground containment system. Preferably the underground containment barrier goes underneath and around the site to be contained in a bathtub-type containment. 17 figs.

Fabrication of Advanced Thermoelectric Materials by Hierarchical Nanovoid Generation

NASA Technical Reports Server (NTRS)

Park, Yeonjoon (Inventor); Elliott, James R. (Inventor); Stoakley, Diane M. (Inventor); Chu, Sang-Hyon (Inventor); King, Glen C. (Inventor); Kim, Jae-Woo (Inventor); Choi, Sang Hyouk (Inventor); Lillehei, Peter T. (Inventor)

2011-01-01

A novel method to prepare an advanced thermoelectric material has hierarchical structures embedded with nanometer-sized voids which are key to enhancement of the thermoelectric performance. Solution-based thin film deposition technique enables preparation of stable film of thermoelectric material and void generator (voigen). A subsequent thermal process creates hierarchical nanovoid structure inside the thermoelectric material. Potential application areas of this advanced thermoelectric material with nanovoid structure are commercial applications (electronics cooling), medical and scientific applications (biological analysis device, medical imaging systems), telecommunications, and defense and military applications (night vision equipments).

Joint Test Protocol for Validation of Alternative Low-Emission Surface Preparation/Depainting Technologies for Structural Steel

NASA Technical Reports Server (NTRS)

Lewis, Pattie

2005-01-01

Headquarters National Aeronautics and Space Administration (NASA) chartered the Acquisition Pollution Prevention (AP2) Office to coordinate agency activities affecting pollution prevention issues identified during system and component acquisition and sustainment processes. The primary objectives of the AP2 Office are to: (1) Reduce or eliminate the use of hazardous materials (HazMats) or hazardous processes at manufacturing, remanufacturing, and sustainment locations. (2) A void duplication of effort in actions required to reduce or eliminate HazMats through joint center cooperation and technology sharing. This project will identify, evaluate and approve alternative surface preparation technologies for use at NASA and Air Force Space Command (AFSPC) installations. Materials and processes will be evaluated with the goal of selecting those processes that will improve corrosion protection at critical systems, facilitate easier maintenance activity, extend maintenance cycles, eliminate flight hardware contamination and reduce the amount of hazardous waste generated. This Joint Test Protocol (JTP) contains the critical requirements and tests necessary to qualify alternative Low-Emission Surface Preparation/Depainting Technologies for Structural Steel Applications. These tests were derived from engineering, performance, and operational impact (supportability) requirements defined by a consensus of NASA and Air Force Space Command (AFSPC) participants. The Field Test Plan (FTP), entitled Joint Test Protocol for Validation of Alternative Low Emission Surface Preparation/Depainting Technologies for Structural Steel, prepared by ITB, defines the field evaluation and testing requirements for validating alternative surface preparation/depainting technologies and supplements the JTP.

Method of simulating spherical voids for use as a radiographic standard

DOEpatents

Foster, Billy E.

1977-01-01

A method of simulating small spherical voids in metal is provided. The method entails drilling or etching a hemispherical depression of the desired diameter in each of two sections of metal, the sections being flat plates or different diameter cylinders. A carbon bead is placed in one of the hemispherical voids and is used as a guide to align the second hemispherical void with that in the other plate. The plates are then bonded together with epoxy, tape or similar material and the two aligned hemispheres form a sphere within the material; thus a void of a known size has been created. This type of void can be used to simulate a pore in the development of radiographic techniques of actual voids (porosity) in welds and serve as a radiographic standard.

Terahertz Computed Tomography of NASA Thermal Protection System Materials

NASA Technical Reports Server (NTRS)

Roth, D. J.; Reyes-Rodriguez, S.; Zimdars, D. A.; Rauser, R. W.; Ussery, W. W.

2011-01-01

A terahertz axial computed tomography system has been developed that uses time domain measurements in order to form cross-sectional image slices and three-dimensional volume renderings of terahertz-transparent materials. The system can inspect samples as large as 0.0283 cubic meters (1 cubic foot) with no safety concerns as for x-ray computed tomography. In this study, the system is evaluated for its ability to detect and characterize flat bottom holes, drilled holes, and embedded voids in foam materials utilized as thermal protection on the external fuel tanks for the Space Shuttle. X-ray micro-computed tomography was also performed on the samples to compare against the terahertz computed tomography results and better define embedded voids. Limits of detectability based on depth and size for the samples used in this study are loosely defined. Image sharpness and morphology characterization ability for terahertz computed tomography are qualitatively described.

Voids characteristics of asphaltic concrete containing coconut shell

NASA Astrophysics Data System (ADS)

Ezree Abdullah, Mohd; Hannani Madzaili, Amirah; Putra Jaya, Ramadhansyah; Yaacob, Haryati; Hassan, Norhidayah Abdul; Nazri, Fadzli Mohamed

2017-07-01

Asphalt durability is often linked to the thickness of the asphalt coating on the aggregate particles. In order to have adequate film thickness in asphaltic concrete, there must be sufficient space between the aggregate particles in the compacted pavement. This void space is referred to as voids in total mix (VTM), voids with filled bitumen (VFB), and voids in mineral aggregate (VMA). Hence, this study investigates the performance of coconut shell (CS) as coarse aggregate replacement on voids characteristics of asphaltic concrete. Four CS were used as coarse aggregates replacement in asphalt mixture namely 0%, 10%, 20%, 30%, and 40% (by weight volume). The voids properties of asphalt mixture were determined based on Marshall Mix design test. Test results show that VTM and VMA values were decrease with the increasing bitumen content where VFB was increase with increasing bitumen content. Furthermore, increasing the percentage of coconut shell in asphalt mixture was found to increases the voids value up to a peak level and then decreases with further additions of CS.

Mass and heat transfer in crushed oil shale

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

Carley, J.F.; Straub, J.S.; Ott, L.L.

1984-04-01

Heat and mass transfer between gases and oil-shale particles are both important for all proposed retorting processes. Past studies of transfer in packed beds, which have disagreed substantially in their results, have nearly all been done with beds of regular particles of uniform size, whereas oil-shale retorting involves particles of diverse shapes and widely ranging sizes. To resolve these questions, we have made 349 runs in which we measured mass-transfer rates from naphthalene particles of diverse shapes buried in packed beds through which air was passed at room temperature. This technique permits calculation of the mass-transfer coefficient for each activemore » particle in the bed rather than, as in most past studies, for the bed as a whole. The data were analyzed in two ways: (1) by the traditional correlation of Colburn j/sub D/ vs Reynolds number and (2) by multiple regression of the mass-transfer coefficient on air rate, traditional correlation of Colburn j/sub D/ vs Reynolds number and (3) by multiple regression of the mass-transfer coefficient on air rate, sizes of active and inert particles, void fraction, and temperature. Principal findings are: (1) local Reynolds number should be based on active particle size rather than average size for the bed; (2) no appreciable differences were seen between shallow beds and deep ones; (3) mass transfer was 26% faster for spheres and lozenges buried in shale than for all-sphere beds; (4) orientation of lozenges in shale beds has little effect on mass-transfer rate; (5) a useful summarizing equation for either mass or heat transfer in shale beds is log j.epsilon = -.0747 - .6344 log Re + .0592 log/sup 2/Re where j = either j/sub D/ or j/sub H/, the Chilton-Colburn j-factors for mass and heat transfer, Re = the Reynolds number defined for packed beds, and epsilon = the void fraction in the bed. 12 references, 15 figures.« less

Systematic void fraction studies with RELAP5, FRANCESCA and HECHAN

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

Stosic, Z.; Preusche, G.

1996-08-01

In enhancing the scope of standard thermal-hydraulic codes applications beyond its capabilities, i.e. coupling with a one and/or three-dimensional kinetics core model, the void fraction, transferred from thermal-hydraulics to the core model, plays a determining role in normal operating range and high core flow, as the generated heat and axial power profiles are direct functions of void distribution in the core. Hence, it is very important to know if the void quality models in the programs which have to be coupled are compatible to allow the interactive exchange of data which are based on these constitutive void-quality relations. The presentedmore » void fraction study is performed in order to give the basis for the conclusion whether a transient core simulation using the RELAP5 void fractions can calculate the axial power shapes adequately. Because of that, the void fractions calculated with RELAP5 are compared with those calculated by BWR safety code for licensing--FRANCESCA and the best estimate model for pre- and post-dryout calculation in BWR heated channel--HECHAN. In addition, a comparison with standard experimental void-quality benchmark tube data is performed for the HECHAN code.« less

Fluid outlet at the bottom of an in situ oil shale retort

DOEpatents

Hutchins, Ned M.

1984-01-01

Formation is excavated from within the boundaries of a retort site in formation containing oil shale for forming at least one retort level void extending horizontally across the retort site, leaving at least one remaining zone of unfragmented formation within the retort site. A production level drift is excavated below the retort level void, leaving a lower zone of unfragmented formation between the retort level void and the production level drift. A plurality of raises are formed between the production level drift and the retort level void for providing product withdrawal passages distributed generally uniformly across the horizontal cross section of the retort level void. The product withdrawal passages are backfilled with a permeable mass of particles. Explosive placed within the remaining zone of unfragmented formation above the retort level void is detonated for explosively expanding formation within the retort site toward at least the retort level void for forming a fragmented permeable mass of formation particles containing oil shale within the boundaries of the retort site. During retorting operations products of retorting are conducted from the fragmented mass in the retort through the product withdrawal passages to the production level void. The products are withdrawn from the production level void.

Method for explosive expansion toward horizontal free faces for forming an in situ oil shale retort

DOEpatents

Ricketts, Thomas E.

1980-01-01

Formation is excavated from within a retort site in formation containing oil shale for forming a plurality of vertically spaced apart voids extending horizontally across different levels of the retort site, leaving a separate zone of unfragmented formation between each pair of adjacent voids. Explosive is placed in each zone, and such explosive is detonated in a single round for forming an in situ retort containing a fragmented permeable mass of formation particles containing oil shale. The same amount of formation is explosively expanded upwardly and downwardly toward each void. A horizontal void excavated at a production level has a smaller horizontal cross-sectional area than a void excavated at a lower level of the retort site immediately above the production level void. Explosive in a first group of vertical blast holes is detonated for explosively expanding formation downwardly toward the lower void, and explosive in a second group of vertical blast holes is detonated in the same round for explosively expanding formation upwardly toward the lower void and downwardly toward the production level void for forming a generally T-shaped bottom of the fragmented mass.

Cosmic void clumps

NASA Astrophysics Data System (ADS)

Lares, M.; Luparello, H. E.; Garcia Lambas, D.; Ruiz, A. N.; Ceccarelli, L.; Paz, D.

2017-10-01

Cosmic voids are of great interest given their relation to the large scale distribution of mass and the way they trace cosmic flows shaping the cosmic web. Here we show that the distribution of voids has, in consonance with the distribution of mass, a characteristic scale at which void pairs are preferentially located. We identify clumps of voids with similar environments and use them to define second order underdensities. Also, we characterize its properties and analyze its impact on the cosmic microwave background.

Gravitational Effects on Closed-Cellular-Foam Microstructure

NASA Technical Reports Server (NTRS)

Noever, David A.; Cronise, Raymond J.; Wessling, Francis C.; McMannus, Samuel P.; Mathews, John; Patel, Darayas

1996-01-01

Polyurethane foam has been produced in low gravity for the first time. The cause and distribution of different void or pore sizes are elucidated from direct comparison of unit-gravity and low-gravity samples. Low gravity is found to increase the pore roundness by 17% and reduce the void size by 50%. The standard deviation for pores becomes narrower (a more homogeneous foam is produced) in low gravity. Both a Gaussian and a Weibull model fail to describe the statistical distribution of void areas, and hence the governing dynamics do not combine small voids in either a uniform or a dependent fashion to make larger voids. Instead, the void areas follow an exponential law, which effectively randomizes the production of void sizes in a nondependent fashion consistent more with single nucleation than with multiple or combining events.

The Santiago-Harvard-Edinburgh-Durham void comparison - I. SHEDding light on chameleon gravity tests

NASA Astrophysics Data System (ADS)

Cautun, Marius; Paillas, Enrique; Cai, Yan-Chuan; Bose, Sownak; Armijo, Joaquin; Li, Baojiu; Padilla, Nelson

2018-05-01

We present a systematic comparison of several existing and new void-finding algorithms, focusing on their potential power to test a particular class of modified gravity models - chameleon f(R) gravity. These models deviate from standard general relativity (GR) more strongly in low-density regions and thus voids are a promising venue to test them. We use halo occupation distribution (HOD) prescriptions to populate haloes with galaxies, and tune the HOD parameters such that the galaxy two-point correlation functions are the same in both f(R) and GR models. We identify both three-dimensional (3D) voids and two-dimensional (2D) underdensities in the plane of the sky to find the same void abundance and void galaxy number density profiles across all models, which suggests that they do not contain much information beyond galaxy clustering. However, the underlying void dark matter density profiles are significantly different, with f(R) voids being more underdense than GR ones, which leads to f(R) voids having a larger tangential shear signal than their GR analogues. We investigate the potential of each void finder to test f(R) models with near-future lensing surveys such as EUCLID and LSST. The 2D voids have the largest power to probe f(R) gravity, with an LSST analysis of tunnel (which is a new type of 2D underdensity introduced here) lensing distinguishing at 80 and 11σ (statistical error) f(R) models with parameters, |fR0| = 10-5 and 10-6, from GR.

The Evolution of Nondestructive Evaluation Methods for the Space Shuttle External Tank Thermal Protection System

NASA Technical Reports Server (NTRS)

Walker, James L.; Richter, Joel D.

2006-01-01

Three nondestructive evaluation methods are being developed to identify defects in the foam thermal protection system (TPS) of the Space Shuttle External Tank (ET). Shearography is being developed to identify shallow delaminations, shallow voids and crush damage in the foam while terahertz imaging and backscatter radiography are being developed to identify voids and cracks in thick foam regions. The basic theory of operation along with factors affecting the results of these methods will be described. Also, the evolution of these methods from lab tools to implementation on the ET will be discussed. Results from both test panels and flight tank inspections will be provided to show the range in defect sizes and types that can be readily detected.

GeoBioScience: Red Wood Ants as Bioindicators for Active Tectonic Fault Systems in the West Eifel (Germany).

PubMed

Berberich, Gabriele; Schreiber, Ulrich

2013-05-17

In a 1.140 km² study area of the volcanic West Eifel, a comprehensive investigation established the correlation between red wood ant mound (RWA; Formica rufa-group) sites and active tectonic faults. The current stress field with a NW-SE-trending main stress direction opens pathways for geogenic gases and potential magmas following the same orientation. At the same time, Variscan and Mesozoic fault zones are reactivated. The results showed linear alignments and clusters of approx. 3,000 RWA mounds. While linear mound distribution correlate with strike-slip fault systems documented by quartz and ore veins and fault planes with slickensides, the clusters represent crosscut zones of dominant fault systems. Latter can be correlated with voids caused by crustal block rotation. Gas analyses from soil air, mineral springs and mofettes (CO₂, Helium, Radon and H₂S) reveal limiting concentrations for the spatial distribution of mounds and colonization. Striking is further the almost complete absence of RWA mounds in the core area of the Quaternary volcanic field. A possible cause can be found in occasionally occurring H₂S in the fault systems, which is toxic at miniscule concentrations to the ants. Viewed overall, there is a strong relationship between RWA mounds and active tectonics in the West Eifel.

Proposed Space Flight Experiment Hardware

NASA Technical Reports Server (NTRS)

2003-01-01

The primary thrust for this plan is to develop design tools and fundamental understanding that are timely and consistent with the goal of the various exploration initiatives. The plan will utilize ISS facilities, such as the Fluids Integrated Rack (FIR) and the Microgravity Science Glovebox (MSG). A preliminary flow schematic of Two-Phase Flow Facility (T(phi)FFy) which would utilize FIR is shown in Figure 3. MSG can be utilized to use the Boiling eXperiment Facility (BXF) and Contact Line Dynamics Experiment (CLiDE) Facility. The T(phi)FFy system would have multiple test sections whereby different configurations of heat exchangers could be used to study boiling and condensation phenomena. The test sections would be instrumented for pressure drop, void fraction, heat fluxes, temperatures, high-speed imaging and other diagnostics. Besides a high-speed data acquisition system with a large data storage capability, telemetry could be used to update control and test parameters and download limited amounts of data. In addition, there would be multiple accumulators that could be used to investigate system stability and fluid management issues. The system could accommodate adiabatic tests through either the space station nitrogen supply or have an experiment-specific compressor to pressurize a sufficient amount of air or other non-condensable gas for reuse as the supply bottle is depleted.

Hollow-Wall Heat Shield for Fuel Injector Component

NASA Technical Reports Server (NTRS)

Hanson, Russell B. (Inventor)

2018-01-01

A fuel injector component includes a body, an elongate void and a plurality of bores. The body has a first surface and a second surface. The elongate void is enclosed by the body and is integrally formed between portions of the body defining the first surface and the second surface. The plurality of bores extends into the second surface to intersect the elongate void. A process for making a fuel injector component includes building an injector component body having a void and a plurality of ports connected to the void using an additive manufacturing process that utilizes a powdered building material, and removing residual powdered building material from void through the plurality of ports.

Note: Void effects on eddy current distortion in two-phase liquid metal.

PubMed

Kumar, M; Tordjeman, Ph; Bergez, W; Cavaro, M

2015-10-01

A model based on the first order perturbation expansion of magnetic flux in a two-phase liquid metal flow has been developed for low magnetic Reynolds number Rem. This model takes into account the distortion of the induced eddy currents due to the presence of void in the conducting medium. Specific experiments with an eddy current flow meter have been realized for two periodic void distributions. The results have shown, in agreement with the model, that the effects of velocity and void on the emf modulation are decoupled. The magnitude of the void fraction and the void spatial frequency can be determined from the spectral density of the demodulated emf.

Quiet Cruise Efficient Short Take-off and Landing Subsonic Transport System

NASA Technical Reports Server (NTRS)

Kawai, Ron

2008-01-01

This NASA funded study conceived a revolutionary airplane concept to enable future traffic growth by using regional air space. This requires a very quiet airplane with STOL capability. Starting with a Blended Wing Body that is cruise efficient with inherent low noise characteristics from forward noise shielding and void of aft downward noise reflections, integration of embedded distributed propulsion enables incorporation of the revolutionary concept for jet noise shielding. Embedded distributed propulsion also enables incorporation of a fan bleed internally blown flap for quiet powered lift. The powered lift provides STOL capability for operation at regional airports with rapid take-off and descent to further reduce flyover noise. This study focused on configuring the total engine noise shielding STOL concept with a BWB airplane using the Boeing Phantom Works WingMOD multidisciplinary optimization code to define a planform that is pitch controllable. The configuration was then sized and mission data developed to enable NASA to assess the flyover and sideline noise. The foundational technologies needed are identified including military dual use benefits.

Microwave and Millimeter Wave Imaging of the Space Shuttle External Fuel Tank Spray on Foam Insulation (SOFI) using Synthetic Aperture Focusing Techniques (SAFT}

NASA Technical Reports Server (NTRS)

Case, J. T.; Robbins, J.; Kharkivskiy, S.; Hepburn, F.; Zoughi, R.

2005-01-01

The Space Shuttle Columbia s catastrophic failure is thought to have been caused by a dislodged piece of external tank spray on foam insulation (SOFI) striking the left wing of the orbiter causing significant damage to some of the reinforced carbodcarbon leading edge wing panels. Microwave and millimeter wave nondestructive evaluation methods have shown great potential for inspecting SOFI for the purpose of detecting anomalies such as small air voids that may cause separation of the SOFI from the external tank during a launch. These methods are capable of producing relatively high-resolution images of the interior of SOFI particularly when advanced imaging algorithms are incorporated into the overall system. To this end, synthetic aperture focusing techniques (SAFT) are being developed. This paper presents some of the preliminary results of this investigation using SAFT-based methods and microwave holography at relatively low frequencies illustrating their potential capabilities for operation at millimeter wave frequencies.

Cosmology with void-galaxy correlations.

PubMed

Hamaus, Nico; Wandelt, Benjamin D; Sutter, P M; Lavaux, Guilhem; Warren, Michael S

2014-01-31

Galaxy bias, the unknown relationship between the clustering of galaxies and the underlying dark matter density field is a major hurdle for cosmological inference from large-scale structure. While traditional analyses focus on the absolute clustering amplitude of high-density regions mapped out by galaxy surveys, we propose a relative measurement that compares those to the underdense regions, cosmic voids. On the basis of realistic mock catalogs we demonstrate that cross correlating galaxies and voids opens up the possibility to calibrate galaxy bias and to define a static ruler thanks to the observable geometric nature of voids. We illustrate how the clustering of voids is related to mass compensation and show that volume-exclusion significantly reduces the degree of stochasticity in their spatial distribution. Extracting the spherically averaged distribution of galaxies inside voids from their cross correlations reveals a remarkable concordance with the mass-density profile of voids.

Deformation of periodic nanovoid structures in Mg single crystals

NASA Astrophysics Data System (ADS)

Xu, Shuozhi; Su, Yanqing; Zare Chavoshi, Saeed

2018-01-01

Large scale molecular dynamics (MD) simulations in Mg single crystal containing periodic cylindrical voids subject to uniaxial tension along the z direction are carried out. Models with different initial void sizes and crystallographic orientations are explored using two interatomic potentials. It is found that (i) a larger initial void always leads to a lower yield stress, in agreement with an analytic prediction; (ii) in the model with x[\\bar{1}100]-y[0001]-z[11\\bar{2}0] orientations, the two potentials predict different types of tension twins and phase transformation; (iii) in the model with x[0001]-y[11\\bar{2}0]-z[\\bar{1}100] orientations, the two potentials identically predict the nucleation of edge dislocations on the prismatic plane, which then glide away from the void, resulting in extrusions at the void surface; in the case of the smallest initial void, these surface extrusions pinch the void into two voids. Besides bringing new physical understanding of the nanovoid structures, our work highlights the variability and uncertainty in MD simulations arising from the interatomic potential, an issue relatively lightly addressed in the literature to date.

Impact of cholesterol on voids in phospholipid membranes

NASA Astrophysics Data System (ADS)

Falck, Emma; Patra, Michael; Karttunen, Mikko; Hyvönen, Marja T.; Vattulainen, Ilpo

2004-12-01

Free volume pockets or voids are important to many biological processes in cell membranes. Free volume fluctuations are a prerequisite for diffusion of lipids and other macromolecules in lipid bilayers. Permeation of small solutes across a membrane, as well as diffusion of solutes in the membrane interior are further examples of phenomena where voids and their properties play a central role. Cholesterol has been suggested to change the structure and function of membranes by altering their free volume properties. We study the effect of cholesterol on the properties of voids in dipalmitoylphosphatidylcholine (DPPC) bilayers by means of atomistic molecular dynamics simulations. We find that an increasing cholesterol concentration reduces the total amount of free volume in a bilayer. The effect of cholesterol on individual voids is most prominent in the region where the steroid ring structures of cholesterol molecules are located. Here a growing cholesterol content reduces the number of voids, completely removing voids of the size of a cholesterol molecule. The voids also become more elongated. The broad orientational distribution of voids observed in pure DPPC is, with a 30% molar concentration of cholesterol, replaced by a distribution where orientation along the bilayer normal is favored. Our results suggest that instead of being uniformly distributed to the whole bilayer, these effects are localized to the close vicinity of cholesterol molecules.

Hot spot formation and chemical reaction initiation in shocked HMX crystals with nanovoids: a large-scale reactive molecular dynamics study.

PubMed

Zhou, Tingting; Lou, Jianfeng; Zhang, Yangeng; Song, Huajie; Huang, Fenglei

2016-07-14

We report million-atom reactive molecular dynamic simulations of shock initiation of β-cyclotetramethylene tetranitramine (β-HMX) single crystals containing nanometer-scale spherical voids. Shock induced void collapse and subsequent hot spot formation as well as chemical reaction initiation are observed which depend on the void size and impact strength. For an impact velocity of 1 km s(-1) and a void radius of 4 nm, the void collapse process includes three stages; the dominant mechanism is the convergence of upstream molecules toward the centerline and the downstream surface of the void forming flowing molecules. Hot spot formation also undergoes three stages, and the principal mechanism is kinetic energy transforming to thermal energy due to the collision of flowing molecules on the downstream surface. The high temperature of the hot spot initiates a local chemical reaction, and the breakage of the N-NO2 bond plays the key role in the initial reaction mechanism. The impact strength and void size have noticeable effects on the shock dynamical process, resulting in a variation of the predominant mechanisms leading to void collapse and hot spot formation. Larger voids or stronger shocks result in more intense hot spots and, thus, more violent chemical reactions, promoting more reaction channels and generating more reaction products in a shorter duration. The reaction products are mainly concentrated in the developed hot spot, indicating that the chemical reactivity of the hmx crystal is greatly enhanced by void collapse. The detailed information derived from this study can aid a thorough understanding of the role of void collapse in hot spot formation and the chemical reaction initiation of explosives.

Effect of Preoperative Low Maximal Flow Rate on Postoperative Voiding Trials after the Midurethral Sling Procedure in Women with Stress Urinary Incontinence.

PubMed

Chae, Ji Y; Bae, Jae H; Lee, Jeong G; Park, Hong S; Moon, Du G; Oh, Mi M

2017-06-02

To evaluate the effects of preoperative low maximal flow rate (Qmax) on voiding trials after the midurethral sling (MUS) procedure in women with stress urinary incontinence (SUI). One hundred and sixty-eight women who underwent MUS procedure were enrolled. Preoperative free uroflowmetry was performed and patients were divided by Qmax. Low Qmax was defined as a Qmax under 15 mL/sec with voided volume at least 150 mL. Surgical results, failure of voiding trial, and postoperative uroflowmetry parameters were compared between the groups. Failure of voiding trial was defined by a PVR more than 100 mL on postoperative uroflowmetry. At the discharge day, there were 42 cases showing failure of voiding trial and 33 cases requiring CIC, but only one patient showed failure of voiding trial at 12 months postoperatively. Overall, 48 patients had preoperative low Qmax. Low Qmax group showed lower Qmax in all of postoperative uroflowmetry, but there were no significant differences in the rate of postoperative voiding trial failure or CIC. The low Qmax group was then divided into two groups according to the preoperative detrusor pressure at Qmax over and under 20 cmH 2 O in pressure flow study. Comparing the two groups, no significant differences were observed in the cure rate, voiding trial failure or CIC. Our results suggest that women with preoperative low Qmax experienced no definite unfavorable voiding problem from the MUS procedure compared to those with normal voiding function. MUS procedure may be regarded as a safe and successful procedure in SUI women with low Qmax. © 2017 John Wiley & Sons Australia, Ltd.

Systematic reviews of bladder training and voiding programmes in adults: a synopsis of findings from data analysis and outcomes using metastudy techniques.

PubMed

Roe, Brenda; Ostaszkiewicz, Joan; Milne, Jill; Wallace, Sheila

2007-01-01

This paper reports a comparison of the data analysis and outcomes from four Cochrane systematic reviews on bladder training and voiding programmes for the management of urinary incontinence using metastudy descriptive techniques to inform clinical practice, generate new ideas and identify future research directions. Bladder training is used for cognitively and physically able adults to regain continence by increasing the time interval between voids. Prompted voiding, habit retraining and timed voiding, collectively known as voiding programmes, are generally used for people with cognitive and physical impairments in institutional settings. Bladder training and voiding programmes feature as common clinical practice for the management of urinary incontinence. A synopsis of four Cochrane systematic reviews that included randomized controlled trials on bladder training, prompted voiding, habit retraining and timed voiding was undertaken using metastudy techniques for the synthesis of qualitative research, and has provided a discursive comparison and contrast of the meta-data analysis and outcomes of these reviews. Frequency of incontinence was the most common and constant outcome measure of effectiveness in the reviews. Limited data were available on other health outcomes, change in dependency status, quality of life and cost-effectiveness. The systematic review on bladder training included different types of urinary incontinence, whereas those on voiding programmes did not differentiate the type of incontinence. There is evidence on the effectiveness of bladder training but long-term follow up studies are needed. Evidence on the effectiveness of voiding programmes is limited and not available for many outcomes. Future research needs to consider the theory underpinning interventions for bladder training and voiding programmes for urinary incontinence and should incorporate recognized 'quality' research designs, established outcomes and long-term follow up. It is unclear whether health outcomes for people with comorbidities, cognitive and physical impairments will improve if extensive diagnostic and assessment investigations are undertaken.

Voids in Gravitational Instability Scenarios - Part One - Global Density and Velocity Fields in an Einstein - De-Sitter Universe

NASA Astrophysics Data System (ADS)

van de Weygaert, R.; van Kampen, E.

1993-07-01

The first results of an extensive study of the structure and dynamics of underdense regions in gravitational instability scenarios are presented. Instead of adopting spherically symmetric voids with some idealized initial density and velocity profile, underdense regions of a given size and depth, embedded in an initial density fluctuation field, are generated. In order to accomplish this in a consistent way, these initial conditions are set up by means of Bertschinger's constrained random field code. The generated particle samples of 64^3^ particles in a box of side 100 Mpc are followed into the non-linear regime by Bertschinger's PM N- body code. In this way we address the dependence of the structure and kinematics of the void both on the initial depth of the void and on the fluctuation field in which it is embedded. In particular, this study provides some understanding of how far fluctuations on small scales modify the dynamics of the large-scale void, and especially of how far the properties of small structures inside the void are affected by the global properties of the void. One of the conspicuous features of the initial density fields inside protovoids appears to be the existence of a `void hierarchy', with small voids embedded in larger voids. The survival of this hierarchy during the riot evolution of the void depends critically on the initial depth as well as on the clustering scenario involved. As well as presenting a qualitative discussion of the structure of underdense regions in initial density fields in different scenarios, and the results of simulations of the ensuing non-linear evolution, we concentrate in particular on a comparison of the global density and velocity fields in voids with predictions from linear theory as well as from the spherical outflow model. The relation between the initial linear depth, the resulting non-linear depth and the excess expansion velocities in voids is addressed. In addition, we find that, while near its centre a void becomes more and more spherical, the shape of its boundary is influenced to a large extent by the structures surrounding the void and therefore is generally more irregular. In this first study we concentrate on single voids in Einstein-de Sitter universes. The underdense regions considered are linear 1 σ_0_, 2 σ_0_ and 3 σ_0_ dips in fields that are Gaussian-smoothed on a scale of R_G_ = 10 h^-1^ Mpc, approximately half the size of the Bootes void. These regions are studied in terms of the Cold Dark Matter and Hot Dark Matter scenarios as well as in terms of the scale-free scenarios P(k) is proportional to k^0^, k^-1^ and k^-2^. The Hubble constant is taken to be H_0_ = 100 h km s^-1^ Mpc^-1^.

Remote Infrared Thermal Sensing of Sewer Voids, Four-Year Update

NASA Astrophysics Data System (ADS)

Weil, Gary J.

1988-01-01

When a sewer caves in, it often takes the street, sidewalks, and surrounding buildings along for the ride. These collapses endanger public health and safety. Repairing a sewer before such a cave-in is obviously the preferred method. Emergency repairs cost far more than prevention measures - often millions of dollars more. Many combined sewers in the St. Louis area, as in many of America's cities, are more than 125 years old and are subject to structural failure. In 1981 alone, St. Louis had 4,000 sewer collapses and an astronomical repair bill. These and similar problems have been described as "a crisis of national proportions. The question addressed by this paper is how to detect unseen problem areas in sewer systems before they give way. At the present, progressive sewer administrations may use crawl crews to inspect sewers when problems are suspected. This can be extremely costly and dangerous, and a void around the outside of the sewer is often invisible from within. Thus, even a crawl crew can fail to detect most voids. Infrared Thermography has been found by sewer districts and independent evaluation engineering firms to be an extremely accurate method of finding sewer voids, before they can cause expensive and dangerous problems. This technique uses a non-contact, remote sensing method, with the potential for surveying large areas quickly and efficiently. This paper reviews our initial paper presented to The International Society for Optical Engineering in October of 1983 and presents an update of our experience, both successes and failures, in several large-scale void detection projects. Infrared Thermographic techniques of non-destructive testing will have major implications for cities and for the engineering profession because it promises to make the crisis of infrastructure repair and rehabilitation more manageable. Intelligent, systematic use of this relatively low cost void detection method, Infrared Thermography, may revolutionize the way sewer problems are handled in the future.

Effect of pelvic floor muscle exercise on pelvic floor muscle activity and voiding functions during pregnancy and the postpartum period.

PubMed

Kahyaoglu Sut, Hatice; Balkanli Kaplan, Petek

2016-03-01

The aim of this study was to investigate the effects of pelvic floor muscle exercise during pregnancy and the postpartum period on pelvic floor muscle activity and voiding functions. Pregnant women (n = 60) were randomly assigned into two groups (Training [n = 30] and Control [n = 30]) using a computer-based system. Pelvic floor muscle strength was measured using a perineometry device. Urinary symptoms were measured using the Urinary Distress Inventory (UDI-6), Incontinence Impact Questionnaire (IIQ-7), and the Overactive Bladder Questionnaire (OAB-q). Voiding functions were measured using uroflowmetry and 3-day voiding diaries. Measurements were obtained at week 28, weeks 36-38 of pregnancy, and postpartum weeks 6-8. Pelvic floor muscle strength significantly decreased during the pregnancy (P < 0.001). However, pelvic floor muscle strength improvement was significantly higher in the Training group compared to the Control group (P < 0.001). The UDI-6, IIQ-7, and OAB-q scores did not significantly change during weeks 36-38 of pregnancy in the Training group (P > 0.05). However, UDI-6, coping, concern, and total scores of OAB-q were significantly decreased during weeks 36-38 of pregnancy in the Control group (P < 0.05). The UDI-6 and OAB-q scores were significantly improved during postpartum weeks 6-8 (P < 0.05). Voiding functions were negatively affected in both groups, decreasing during weeks 36-38 of pregnancy and improving during the postpartum period. Pregnancy and delivery affect pelvic floor muscle strength, urinary symptoms, quality of life, and voiding functions. Pelvic floor muscle exercises applied during pregnancy and the postpartum period increase pelvic floor muscle strength and prevent deterioration of urinary symptoms and quality of life in pregnancy. © 2015 Wiley Periodicals, Inc.

48 CFR 603.704 - Policy.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 48 Federal Acquisition Regulations System 4 2011-10-01 2011-10-01 false Policy. 603.704 Section 603.704 Federal Acquisition Regulations System DEPARTMENT OF STATE GENERAL IMPROPER BUSINESS PRACTICES AND PERSONAL CONFLICTS OF INTEREST Voiding and Rescinding Contracts 603.704 Policy. The Procurement...

Mutations in HPSE2 cause urofacial syndrome.

PubMed

Daly, Sarah B; Urquhart, Jill E; Hilton, Emma; McKenzie, Edward A; Kammerer, Richard A; Lewis, Malcolm; Kerr, Bronwyn; Stuart, Helen; Donnai, Dian; Long, David A; Burgu, Berk; Aydogdu, Ozgu; Derbent, Murat; Garcia-Minaur, Sixto; Reardon, Willie; Gener, Blanca; Shalev, Stavit; Smith, Rupert; Woolf, Adrian S; Black, Graeme C; Newman, William G

2010-06-11

Urinary voiding dysfunction in childhood, manifesting as incontinence, dysuria, and urinary frequency, is a common condition. Urofacial syndrome (UFS) is a rare autosomal recessive disease characterized by facial grimacing when attempting to smile and failure of the urinary bladder to void completely despite a lack of anatomical bladder outflow obstruction or overt neurological damage. UFS individuals often have reflux of infected urine from the bladder to the upper renal tract, with a risk of kidney damage and renal failure. Whole-genome SNP mapping in one affected individual defined an autozygous region of 16 Mb on chromosome 10q23-q24, within which a 10 kb deletion encompassing exons 8 and 9 of HPSE2 was identified. Homozygous exonic deletions, nonsense mutations, and frameshift mutations in five further unrelated families confirmed HPSE2 as the causative gene for UFS. Mutations were not identified in four additional UFS patients, indicating genetic heterogeneity. We show that HPSE2 is expressed in the fetal and adult central nervous system, where it might be implicated in controlling facial expression and urinary voiding, and also in bladder smooth muscle, consistent with a role in renal tract morphology and function. Our findings have broader implications for understanding the genetic basis of lower renal tract malformations and voiding dysfunction.

Mutations in HPSE2 Cause Urofacial Syndrome

PubMed Central

Daly, Sarah B.; Urquhart, Jill E.; Hilton, Emma; McKenzie, Edward A.; Kammerer, Richard A.; Lewis, Malcolm; Kerr, Bronwyn; Stuart, Helen; Donnai, Dian; Long, David A.; Burgu, Berk; Aydogdu, Ozgu; Derbent, Murat; Garcia-Minaur, Sixto; Reardon, Willie; Gener, Blanca; Shalev, Stavit; Smith, Rupert; Woolf, Adrian S.; Black, Graeme C.; Newman, William G.

2010-01-01

Urinary voiding dysfunction in childhood, manifesting as incontinence, dysuria, and urinary frequency, is a common condition. Urofacial syndrome (UFS) is a rare autosomal recessive disease characterized by facial grimacing when attempting to smile and failure of the urinary bladder to void completely despite a lack of anatomical bladder outflow obstruction or overt neurological damage. UFS individuals often have reflux of infected urine from the bladder to the upper renal tract, with a risk of kidney damage and renal failure. Whole-genome SNP mapping in one affected individual defined an autozygous region of 16 Mb on chromosome 10q23-q24, within which a 10 kb deletion encompassing exons 8 and 9 of HPSE2 was identified. Homozygous exonic deletions, nonsense mutations, and frameshift mutations in five further unrelated families confirmed HPSE2 as the causative gene for UFS. Mutations were not identified in four additional UFS patients, indicating genetic heterogeneity. We show that HPSE2 is expressed in the fetal and adult central nervous system, where it might be implicated in controlling facial expression and urinary voiding, and also in bladder smooth muscle, consistent with a role in renal tract morphology and function. Our findings have broader implications for understanding the genetic basis of lower renal tract malformations and voiding dysfunction. PMID:20560210

A novel method for flow pattern identification in unstable operational conditions using gamma ray and radial basis function.

PubMed

Roshani, G H; Nazemi, E; Roshani, M M

2017-05-01

Changes of fluid properties (especially density) strongly affect the performance of radiation-based multiphase flow meter and could cause error in recognizing the flow pattern and determining void fraction. In this work, we proposed a methodology based on combination of multi-beam gamma ray attenuation and dual modality densitometry techniques using RBF neural network in order to recognize the flow regime and determine the void fraction in gas-liquid two phase flows independent of the liquid phase changes. The proposed system is consisted of one 137 Cs source, two transmission detectors and one scattering detector. The registered counts in two transmission detectors were used as the inputs of one primary Radial Basis Function (RBF) neural network for recognizing the flow regime independent of liquid phase density. Then, after flow regime identification, three RBF neural networks were utilized for determining the void fraction independent of liquid phase density. Registered count in scattering detector and first transmission detector were used as the inputs of these three RBF neural networks. Using this simple methodology, all the flow patterns were correctly recognized and the void fraction was predicted independent of liquid phase density with mean relative error (MRE) of less than 3.28%. Copyright © 2017 Elsevier Ltd. All rights reserved.

Thermal modeling using enthalpy methods to aid in the study of microstructural changes of multilayered phase change optical memories

NASA Astrophysics Data System (ADS)

Nagpal, Swati; Aurora, Aradhna

1999-11-01

In DOW type of phase change optical memories the focus has been mainly on gestate based systems due to their good overwriting capability and very high order cyclability. To avoid the material deterioration problems such as material flow, high melting point, high viscosity or high-density components such as CrTe, (which have the same refractive index) can be added to the active layer. This has led to an improved performance of overwrite cycles from 105 to 106. Material flow occurs due to void formation. Voids and sinks are formed due to porosity of the active layer because the active layer has a density lower than that of the bulk material. One of the reasons for the formation and coalescence of voids is the way in which the film is deposited viz. Sputtering which makes Ar atoms accumulate in the films during deposition. Also the mechanical strength of the protective layer effects the repeatability of the active layer. All the above mentioned processes occur during melting and re- solidification of the nano-sized spots which are laser irradiated. Since the structure of the protective layers is very important in controlling the void formation, it is very important to study the thermal modeling of the full layer structure.

42 CFR 457.216 - Treatment of uncashed or canceled (voided) CHIP checks.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 42 Public Health 4 2011-10-01 2011-10-01 false Treatment of uncashed or canceled (voided) CHIP... canceled (voided) CHIP checks. (a) Purpose. This section provides rules to ensure that States refund the... section— Canceled (voided) check means an CHIP check issued by a State or fiscal agent that prior to its...

42 CFR 457.216 - Treatment of uncashed or canceled (voided) CHIP checks.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 42 Public Health 4 2014-10-01 2014-10-01 false Treatment of uncashed or canceled (voided) CHIP... canceled (voided) CHIP checks. (a) Purpose. This section provides rules to ensure that States refund the... section— Canceled (voided) check means an CHIP check issued by a State or fiscal agent that prior to its...

42 CFR 457.216 - Treatment of uncashed or canceled (voided) CHIP checks.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 42 Public Health 4 2010-10-01 2010-10-01 false Treatment of uncashed or canceled (voided) CHIP... canceled (voided) CHIP checks. (a) Purpose. This section provides rules to ensure that States refund the... section— Canceled (voided) check means an CHIP check issued by a State or fiscal agent that prior to its...

42 CFR 457.216 - Treatment of uncashed or canceled (voided) CHIP checks.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 42 Public Health 4 2012-10-01 2012-10-01 false Treatment of uncashed or canceled (voided) CHIP... canceled (voided) CHIP checks. (a) Purpose. This section provides rules to ensure that States refund the... section— Canceled (voided) check means an CHIP check issued by a State or fiscal agent that prior to its...

42 CFR 457.216 - Treatment of uncashed or canceled (voided) CHIP checks.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 42 Public Health 4 2013-10-01 2013-10-01 false Treatment of uncashed or canceled (voided) CHIP... canceled (voided) CHIP checks. (a) Purpose. This section provides rules to ensure that States refund the... section— Canceled (voided) check means an CHIP check issued by a State or fiscal agent that prior to its...

Dynamics of voids and their shapes in redshift space

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

Maeda, Kei-ichi; Sakai, Nobuyuki; Triay, Roland, E-mail: maeda@waseda.jp, E-mail: nsakai@e.yamagata-u.ac.jp, E-mail: triay@cpt.univ-mrs.fr

2011-08-01

We investigate the dynamics of a single spherical void embedded in a Friedmann-Lemaitre universe, and analyze the void shape in the redshift space. We find that the void in the redshift space appears as an ellipse shape elongated along the line of sight (i.e., an opposite deformation to the Kaiser effect). Applying this result to observed void candidates at the redshift z ∼ 1-2, it may provide us with a new method to evaluate the cosmological parameters, in particular the value of a cosmological constant.

Pores and Void in Asclepiades’ Physical Theory

PubMed Central

Leith, David

2012-01-01

This paper examines a fundamental, though relatively understudied, aspect of the physical theory of the physician Asclepiades of Bithynia, namely his doctrine of pores. My principal thesis is that this doctrine is dependent on a conception of void taken directly from Epicurean physics. The paper falls into two parts: the first half addresses the evidence for the presence of void in Asclepiades’ theory, and concludes that his conception of void was basically that of Epicurus; the second half focuses on the precise nature of Asclepiadean pores, and seeks to show that they represent void interstices between the primary particles of matter which are the constituents of the human body, and are thus exactly analogous to the void interstices between atoms within solid objects in Epicurus’ theory. PMID:22984299

Multiphase flow calculation software

DOEpatents

Fincke, James R.

2003-04-15

Multiphase flow calculation software and computer-readable media carrying computer executable instructions for calculating liquid and gas phase mass flow rates of high void fraction multiphase flows. The multiphase flow calculation software employs various given, or experimentally determined, parameters in conjunction with a plurality of pressure differentials of a multiphase flow, preferably supplied by a differential pressure flowmeter or the like, to determine liquid and gas phase mass flow rates of the high void fraction multiphase flows. Embodiments of the multiphase flow calculation software are suitable for use in a variety of applications, including real-time management and control of an object system.

3D simulation of polyurethane foam injection and reacting mold flow in a complex geometry

NASA Astrophysics Data System (ADS)

Özdemir, İ. Bedii; Akar, Fırat

2018-05-01

The aim of the present work is to develop a flow model which can be used to determine the paths of the polyurethane foam in the mold filling process of a refrigerator cabinet so that improvements in the distribution and the size of the venting holes can be achieved without the expensive prototyping and experiments. For this purpose, the multi-component, two-phase chemically reacting flow is described by Navier Stokes and 12 scalar transport equations. The air and the multi-component foam zones are separated by an interface, which moves only with advection since the mass diffusion of species are set zero in the air zone. The inverse density, viscosity and other diffusion coefficients are calculated by a mass fraction weighted average of the corresponding temperature-dependent values of all species. Simulations are performed in a real refrigerator geometry, are able to reveal the problematical zones where air bubbles and voids trapped in the solidified foam are expected to occur. Furthermore, the approach proves itself as a reliable design tool to use in deciding the locations of air vents and sizing the channel dimensions.

Stress relaxation in quasi-two-dimensional self-assembled nanoparticle monolayers

NASA Astrophysics Data System (ADS)

Boucheron, Leandra S.; Stanley, Jacob T.; Dai, Yeling; You, Siheng Sean; Parzyck, Christopher T.; Narayanan, Suresh; Sandy, Alec R.; Jiang, Zhang; Meron, Mati; Lin, Binhua; Shpyrko, Oleg G.

2018-05-01

We experimentally probed the stress relaxation of a monolayer of iron oxide nanoparticles at the water-air interface. Upon drop-casting onto a water surface, the nanoparticles self-assembled into islands of two-dimensional hexagonally close packed crystalline domains surrounded by large voids. When compressed laterally, the voids gradually disappeared as the surface pressure increased. After the compression was stopped, the surface pressure (as measured by a Wilhelmy plate) evolved as a function of the film aging time with three distinct timescales. These aging dynamics were intrinsic to the stressed state built up during the non-equilibrium compression of the film. Utilizing x-ray photon correlation spectroscopy, we measured the characteristic relaxation time (τ ) of in-plane nanoparticle motion as a function of the aging time through both second-order and two-time autocorrelation analysis. Compressed and stretched exponential fitting of the intermediate scattering function yielded exponents (β ) indicating different relaxation mechanisms of the films under different compression stresses. For a monolayer compressed to a lower surface pressure (between 20 mN/m and 30 mN/m), the relaxation time (τ ) decreased continuously as a function of the aging time, as did the fitted exponent, which transitioned from being compressed (>1 ) to stretched (<1 ), indicating that the monolayer underwent a stress release through crystalline domain reorganization. However, for a monolayer compressed to a higher surface pressure (around 40 mN/m), the relaxation time increased continuously and the compressed exponent varied very little from a value of 1.6, suggesting that the system may have been highly stressed and jammed. Despite the interesting stress relaxation signatures seen in these samples, the structural ordering of the monolayer remained the same over the sample lifetime, as revealed by grazing incidence x-ray diffraction.

Modeling the effects of biomass accumulation on the performance of a biotrickling filter packed with PUF support for the alkaline biotreatment of dimethyl disulfide vapors in air.

PubMed

Arellano-García, Luis; Dorado, Antonio D; Morales-Guadarrama, Axayacatl; Sacristan, Emilio; Gamisans, Xavier; Revah, Sergio

2015-01-01

Excess biomass buildup in biotrickling filters leads to low performance. The effect of biomass accumulation in a biotrickling filter (BTF) packed with polyurethane foam (PUF) was assessed in terms of hydrodynamics and void space availability in a system treating dimethyl disulfide (DMDS) vapors with an alkaliphilic consortium. A sample of colonized support from a BTF having been operating for over a year was analyzed, and it was found that the BTF void bed fraction was reduced to almost half of that calculated initially without biomass. Liquid flow through the examined BTF yielded dispersion coefficient values of 0.30 and 0.72 m(2) h(-1), for clean or colonized PUF, respectively. 3D images of attached biomass obtained with magnetic resonance imaging allowed to calculate the superficial area and the biofilm volume percentage and depth as 650 m(2) m(-3), 35%, and 0.6 mm respectively. A simplified geometric approximation of the complex PUF structure was proposed using an orthogonal 3D mesh that predicted 600 m(2) m(-3) for the same biomass content. With this simplified model, it is suggested that the optimum biomass content would be around 20% of bed volume. The activity of the microorganisms was evaluated by respirometry and the kinetics represented with a Haldane equation type. Experimentally determined parameters were used in a mathematical model to simulate the DMDS elimination capacity (EC), and better description was found when the removal experimental data were matched with a model including liquid axial dispersion in contrast to an ideal plug flow model.

Causes and remedies for porosity in composite manufacturing

NASA Astrophysics Data System (ADS)

Fernlund, G.; Wells, J.; Fahrang, L.; Kay, J.; Poursartip, A.

2016-07-01

Porosity is a challenge in virtually all composite processes but in particular in low pressure processes such as out of autoclave processing of prepregs, where the maximum pressure is one atmosphere. This paper discusses the physics behind important transport phenomena that control porosity and how we can use our understanding of the underlying science to develop strategies to achieve low porosity for these materials and processes in an industrial setting. A three step approach is outlined that addresses and discusses: gas evacuation of trapped air, volatiles and off-gassing, and resin infiltration of evacuated void space.

Hydraulic, water-quality, and temperature performance of three types of permeable pavement under high sediment loading conditions

USGS Publications Warehouse

Selbig, William R.; Buer, Nicolas

2018-05-11

Three permeable pavement surfaces - asphalt (PA), concrete (PC), and interlocking pavers (PIP) - were evaluated side-by-side to measure changes to the infiltrative capacity and water quality of stormwater runoff originating from a conventional asphalt parking lot in Madison, Wisconsin. During the 24-month monitoring period (2014-16), all three permeable pavements resulted in statistically significant reductions in the cumulative load of solids (total suspended solids and suspended sediment), total phosphorus, Escherichia coli (E. coli), and Enterococci. Most of the removal occurred through capture and retention in the void spaces of each permeable surface and aggregate base. The largest reduction in total suspended solids was for PC at 80 percent, followed by PIP and PA at 69 and 65 percent, respectively. Reductions (generally less than 50 percent) in total phosphorus also were observed, which might have been tempered by increases in the dissolved fraction observed in PIP and PA. Conversely, PC results indicated a slight reduction in dissolved phosphorus but failed to meet statistical significance. E. coli and Enterococci were reduced by about 80 percent for PC, almost twice the amount observed for PIP and PA.Results for the PIP and PC surfaces initially indicated higher pollutant load reduction than results for the PA surface. The efficiency of PIP and PC surfaces capturing sediment, however, led to a decline in infiltration rates that resulted in more runoff flowing over, not through, the permeable surface. This result led to a decline in treatment until the permeable surface was partially restored through maintenance practices, to which PIP responded more dramatically than PC or PA. Conversely, the PA surface was capable of infiltrating most of the influent runoff volume during the monitoring period and, thus, continued to provide some level of treatment. The combined effect of underdrain and overflow drainage resulted in similar pollutant treatment for all three permeable surfaces.Temperatures below each permeable surface generally followed changes in air temperature with a more gradual response observed in deeper layers. Therefore, permeable pavement may do little to mitigate heated runoff during summer. During winter, deeper layers remained above freezing even when air temperature was below freezing. Although temperatures were not high enough to melt snow or ice accumulated on the surface, temperatures below each permeable pavement did allow void spaces to remain open, which promoted infiltration of melted ice and snow as air temperatures rose above freezing. These open void spaces could potentially reduce the need for application of deicing agents in winter because melted snow and ice would infiltrate, thereby preventing refreezing of pooled water in what is known as the “black ice” effect.

A proposed rationale and test methodology for establishment of acceptance criteria for vacuum integrity testing of pharmaceutical freeze dryers.

PubMed

Hardwick, Lisa M; Nail, Steven L; Jarman, James; Hasler, Kai; Hense, Thomas

2013-10-01

A scientific rationale is proposed for the establishment of acceptance criteria for leak rates in pharmaceutical freeze dryers. A method was developed to determine the quantity of air that could leak into any lyophilizer from the outside while still maintaining Class 100/Grade A microbial conditions. A lyophilizing product is assumed most vulnerable to microbial contamination during secondary drying, when mass transfer of water vapor from product to condenser is minimal. Using the void volume of the dryer, calculated from change in internal pressure when a known volume of air is introduced, and the potential maximum bioburden of the leaked air (based on measured values), calculations can determine the allowable leaked volume of air, the flow rate required to admit that volume in a given time frame, and the pressure rise that would result from the leak over a given testing period. For the dryers in this study, using worst-case air quality conditions, it was determined that a leak resulting in a pressure rise of 0.027 mbar over a 30 min period would allow the dryers to remain in secondary drying conditions for 62 h before the established action level of one colony forming unit for each cubic meter of air space would be reached. Copyright © 2013 Elsevier B.V. All rights reserved.

Three-dimensional gas exchange pathways in pome fruit characterized by synchrotron x-ray computed tomography.

PubMed

Verboven, Pieter; Kerckhofs, Greet; Mebatsion, Hibru Kelemu; Ho, Quang Tri; Temst, Kristiaan; Wevers, Martine; Cloetens, Peter; Nicolaï, Bart M

2008-06-01

Our understanding of the gas exchange mechanisms in plant organs critically depends on insights in the three-dimensional (3-D) structural arrangement of cells and voids. Using synchrotron radiation x-ray tomography, we obtained for the first time high-contrast 3-D absorption images of in vivo fruit tissues of high moisture content at 1.4-microm resolution and 3-D phase contrast images of cell assemblies at a resolution as low as 0.7 microm, enabling visualization of individual cell morphology, cell walls, and entire void networks that were previously unknown. Intercellular spaces were always clear of water. The apple (Malus domestica) cortex contains considerably larger parenchyma cells and voids than pear (Pyrus communis) parenchyma. Voids in apple often are larger than the surrounding cells and some cells are not connected to void spaces. The main voids in apple stretch hundreds of micrometers but are disconnected. Voids in pear cortex tissue are always smaller than parenchyma cells, but each cell is surrounded by a tight and continuous network of voids, except near brachyssclereid groups. Vascular and dermal tissues were also measured. The visualized network architecture was consistent over different picking dates and shelf life. The differences in void fraction (5.1% for pear cortex and 23.0% for apple cortex) and in gas network architecture helps explain the ability of tissues to facilitate or impede gas exchange. Structural changes and anisotropy of tissues may eventually lead to physiological disorders. A combined tomography and internal gas analysis during growth are needed to make progress on the understanding of void formation in fruit.

On-line consolidation of thermoplastic composites

NASA Astrophysics Data System (ADS)

Shih, Po-Jen

An on-line consolidation system, which includes a computer-controlled filament winding machine and a consolidation head assembly, has been designed and constructed to fabricate composite parts from thermoplastic towpregs. A statistical approach was used to determine the significant processing parameters and their effect on the mechanical and physical properties of composite cylinders fabricated by on-line consolidation. A central composite experimental design was used to select the processing conditions for manufacturing the composite cylinders. The thickness, density, void content, degree of crystallinity and interlaminar shear strength (ILSS) were measured for each composite cylinder. Micrographs showed that complete intimate contact and uniform fiber-matrix distribution were achieved. The degree of crystallinity of the cylinders was found to be in the range of 25-30%. Under optimum processing conditions, an ILSS of 58 MPa and a void content of <1% were achieved for APC-2 (PEEK/Carbon fiber) composite cylinders. An in-situ measurement system which uses a slip ring assembly and a computer data acquisition system was developed to obtain temperature data during winding. Composite cylinders were manufactured with eight K-type thermocouples installed in various locations inside the cylinder. The temperature distribution inside the composite cylinder during winding was measured for different processing conditions. ABAQUS finite element models of the different processes that occur during on-line consolidation were constructed. The first model was used to determine the convective heat transfer coefficient for the hot-air heat source. A convective heat transfer coefficient of 260 w/msp{2°}K was obtained by matching the calculated temperature history to the in-situ measurement data. To predict temperature distribution during winding an ABAQUS winding simulation model was developed. The winding speed was modeled by incrementally moving the convective boundary conditions around the outer surface of the composite cylinder. A towpreg heating model was constructed to predict the temperature distribution on the cross section of the incoming towpreg. For the process-induced thermal stresses analysis, a thermoelastic finite element model was constructed. Using the temperature history obtained from thermal analysis as the initial conditions, the thermal stresses during winding and cooling were investigated.

Determination of void volume in normal phase liquid chromatography.

PubMed

Jiang, Ping; Wu, Di; Lucy, Charles A

2014-01-10

Void volume is an important fundamental parameter in chromatography. Little prior discussion has focused on the determination of void volume in normal phase liquid chromatography (NPLC). Various methods to estimate the total void volume are compared: pycnometry; minor disturbance method based on injection of weak solvent; tracer pulse method; hold-up volume based on unretained compounds; and accessible volume based on Martin's rule and its descendants. These are applied to NPLC on silica, RingSep and DNAP columns. Pycnometry provides a theoretically maximum value for the total void volume and should be performed at least once for each new column. However, pycnometry does not reflect the volume of adsorbed strong solvent on the stationary phase, and so only yields an accurate void volume for weaker mobile phase conditions. 1,3,5-Tri-t-butyl benzene (TTBB) results in hold-up volumes that are convenient measures of the void volume for all eluent conditions on charge-transfer columns (RingSep and DNAP), but is weakly retained under weak eluent conditions on silica. Injection of the weak mobile phase component (hexane) may be used to determine void volume, but care must be exercised to select the appropriate disturbance feature. Accessible volumes, that are determined using a homologous series, are always biased low, and are not recommended as a measure of the void volume. Copyright © 2013 Elsevier B.V. All rights reserved.

40 CFR 1065.525 - Engine starting, restarting, shutdown, and optional repeating of void discrete modes.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., and optional repeating of void discrete modes. 1065.525 Section 1065.525 Protection of Environment... repeating of void discrete modes. (a) Start the engine using one of the following methods: (1) Start the... during one of the modes of a discrete-mode test, you may void the results only for that individual mode...

Stability limit of liquid water in metastable equilibrium with subsaturated vapors.

PubMed

Wheeler, Tobias D; Stroock, Abraham D

2009-07-07

A pure liquid can reach metastable equilibrium with its subsaturated vapor across an appropriate membrane. This situation is analogous to osmotic equilibrium: the reduced chemical potential of the dilute phase (the subsaturated vapor) is compensated by a difference in pressure between the phases. To equilibrate with subsaturated vapor, the liquid phase assumes a pressure that is lower than its standard vapor pressure, such that the liquid phase is metastable with respect to the vapor phase. For sufficiently subsaturated vapors, the liquid phase can even assume negative pressures. The appropriate membrane for this metastable equilibrium must provide the necessary mechanical support to sustain the difference in pressure between the two phases, limit nonhomogeneous mechanisms of cavitation, and resist the entry of the dilutant (gases) into the pure phase (liquid). In this article, we present a study of the limit of stability of liquid water--the degree of subsaturation at which the liquid cavitates--in this metastable state within microscale voids embedded in hydrogel membranes. We refer to these structures as vapor-coupled voids (VCVs). In these VCVs, we observed that liquid water cavitated when placed in equilibrium with vapors of activity aw,vapair

A sharp interface model for void growth in irradiated materials

NASA Astrophysics Data System (ADS)

Hochrainer, Thomas; El-Azab, Anter

2015-03-01

A thermodynamic formalism for the interaction of point defects with free surfaces in single-component solids has been developed and applied to the problem of void growth by absorption of point defects in irradiated metals. This formalism consists of two parts, a detailed description of the dynamics of defects within the non-equilibrium thermodynamic frame, and the application of the second law of thermodynamics to provide closure relations for all kinetic equations. Enforcing the principle of non-negative entropy production showed that the description of the problem of void evolution under irradiation must include a relationship between the normal fluxes of defects into the void surface and the driving thermodynamic forces for the void surface motion; these thermodynamic forces are identified for both vacancies and interstitials and the relationships between these forces and the normal point defect fluxes are established using the concepts of transition state theory. The latter theory implies that the defect accommodation into the surface is a thermally activated process. Numerical examples are given to illustrate void growth dynamics in this new formalism and to investigate the effect of the surface energy barriers on void growth. Consequences for phase field models of void growth are discussed.

Small-angle x-ray scattering in amorphous silicon: A computational study

NASA Astrophysics Data System (ADS)

Paudel, Durga; Atta-Fynn, Raymond; Drabold, David A.; Elliott, Stephen R.; Biswas, Parthapratim

2018-05-01

We present a computational study of small-angle x-ray scattering (SAXS) in amorphous silicon (a -Si) with particular emphasis on the morphology and microstructure of voids. The relationship between the scattering intensity in SAXS and the three-dimensional structure of nanoscale inhomogeneities or voids is addressed by generating large high-quality a -Si networks with 0.1%-0.3% volume concentration of voids, as observed in experiments using SAXS and positron annihilation spectroscopy. A systematic study of the variation of the scattering intensity in the small-angle scattering region with the size, shape, number density, and the spatial distribution of the voids in the networks is presented. Our results suggest that the scattering intensity in the small-angle region is particularly sensitive to the size and the total volume fraction of the voids, but the effect of the geometry or shape of the voids is less pronounced in the intensity profiles. A comparison of the average size of the voids obtained from the simulated values of the intensity, using the Guinier approximation and Kratky plots, with that of the same from the spatial distribution of the atoms in the vicinity of void surfaces is presented.

Neuropeptides in Lower Urinary Tract (LUT) Function

PubMed Central

Arms, Lauren; Vizzard, Margaret A.

2014-01-01

Numerous neuropeptide/receptor systems including vasoactive intestinal polypeptide, pituitary adenylate cyclase-activating polypeptide, calcitonin gene-related peptide, substance P, neurokinin A, bradykinin, and endothelin-1 are expressed in the lower urinary tract (LUT) in both neural and non-neural (e.g., urothelium) components. LUT neuropeptide immunoreactivity is present in afferent and autonomic efferent neurons innervating the bladder and urethra and in the urothelium of the urinary bladder. Neuropeptides have tissue-specific distributions and functions in the LUT and exhibit neuroplastic changes in expression and function with LUT dysfunction following neural injury, inflammation and disease. LUT dysfunction with abnormal voiding including urinary urgency, increased voiding frequency, nocturia, urinary incontinence and pain may reflect a change in the balance of neuropeptides in bladder reflex pathways. LUT neuropeptide/receptor systems may represent potential targets for therapeutic intervention. PMID:21290237

The void in the Sculptor group spiral galaxy NGC 247

NASA Astrophysics Data System (ADS)

Wagner-Kaiser, R.; De Maio, T.; Sarajedini, A.; Chakrabarti, S.

2014-10-01

The dwarf galaxy NGC 247, located in the Sculptor Filament, displays an apparent void on the north side of its spiral disc. The existence of the void in the disc of this dwarf galaxy has been known for some time, but the exact nature and cause of this strange feature has remained unclear. We investigate the properties of the void in the disc of NGC 247 using photometry of archival Hubble Space Telescope data to analyse the stars in and around this region. Based on a grid of isochrones from log(t) = 6.8 to 10.0, we assign ages using nearest-neighbour interpolation. Examination of the spatial variation of these ages across the galaxy reveals an age difference between stars located inside the void region and stars located outside this region. We speculate that the void in NGC 247 's stellar disc may be due to a recent interaction with a nearly dark subhalo that collided with the disc and could account for the long-lived nature of the void.

Modeling and Simulation of Voids in Composite Tape Winding Process Based on Domain Superposition Technique

NASA Astrophysics Data System (ADS)

Deng, Bo; Shi, Yaoyao

2017-11-01

The tape winding technology is an effective way to fabricate rotationally composite materials. Nevertheless, some inevitable defects will seriously influence the performance of winding products. One of the crucial ways to identify the quality of fiber-reinforced composite material products is examining its void content. Significant improvement in products' mechanical properties can be achieved by minimizing the void defect. Two methods were applied in this study, finite element analysis and experimental testing, respectively, to investigate the mechanism of how void forming in composite tape winding processing. Based on the theories of interlayer intimate contact and Domain Superposition Technique (DST), a three-dimensional model of prepreg tape void with SolidWorks has been modeled in this paper. Whereafter, ABAQUS simulation software was used to simulate the void content change with pressure and temperature. Finally, a series of experiments were performed to determine the accuracy of the model-based predictions. The results showed that the model is effective for predicting the void content in the composite tape winding process.

Predictors of early postoperative voiding dysfunction and other complications following a midurethral sling.

PubMed

Ripperda, Christopher M; Kowalski, Joseph T; Chaudhry, Zaid Q; Mahal, Aman S; Lanzer, Jennifer; Noor, Nabila; Good, Meadow M; Hynan, Linda S; Jeppson, Peter C; Rahn, David D

2016-11-01

The rates reported for postoperative urinary retention following midurethral sling procedures are highly variable. Determining which patients have a higher likelihood of failing a voiding trial will help with preoperative counseling prior to a midurethral sling. The objective of the study was to identify preoperative predictors for failed voiding trial following an isolated midurethral sling. A retrospective, multicenter, case-control study was performed by including all isolated midurethral sling procedures performed between Jan. 1, 2010 to June 30, 2015, at 6 academic centers. We collected demographics, medical and surgical histories, voiding symptoms, urodynamic evaluation, and intraoperative data from the medical record. We excluded patients not eligible for attempted voiding trial after surgery (eg, bladder perforation requiring catheterization). Cases failed a postoperative voiding trial and were discharged with an indwelling catheter or taught intermittent self-catheterization; controls passed a voiding trial. We also recorded any adverse events such as urinary tract infection or voiding dysfunction up to 6 weeks after surgery. Bivariate analyses were completed using Mann-Whitney and Pearson χ 2 tests as appropriate. Multivariable stepwise logistic regression was used to determine predictors of failing a voiding trial. A total of 464 patients had an isolated sling (70.9% retropubic, 28.4% transobturator, 0.6% single incision); 101 (21.8%) failed the initial voiding trial. At follow-up visits, 90.4% passed a second voiding trial, and 38.5% of the remainder passed on the third attempt. For the bivariate analyses, prior prolapse or incontinence surgery was similar in cases vs controls (31% vs 28%, P = .610) as were age, race, body mass index, and operative time. Significantly more of the cases (32%) than controls (22%) had a Charlson comorbidity index score of 1 or greater (P = .039). Overactive bladder symptoms of urgency, frequency, and urgency incontinence were similar in both groups as was detrusor overactivity in those with a urodynamic evaluation (29% vs 22%, P = .136), but nocturia was reported more in the cases (50% vs 38%, P = .046). Mean (SD) bladder capacity was similar in both groups (406 [148] mL vs 388 [122] mL, P = .542) as was maximum flow rate with uroflowmetry and pressure flow studies. Cases were significantly more likely to have a voiding type other than detrusor contraction: 37% vs 25%, P = .027, odds ratio, 1.79 (95% confidence interval, 1.07-3.00). There was no difference in voiding trial failures between retropubic and transobturator routes (23.1% vs 18.9%, P = .329). Within 6 weeks of surgery, the frequency of urinary tract infection in cases was greater than controls (20% vs 6%, P < .001; odds ratio, 3.51 [95% confidence interval, 1.82-6.75]). After passing a repeat voiding trial, cases were more likely to present with acute urinary retention (10% vs 3%, P = .003; odds ratio, 4.00 [95% confidence interval, 1.61-9.92]). For multivariable analyses, increasing Charlson comorbidity index increased the risk of a voiding trial failure; apart from this, we did not identify other demographic information among the patients who did not undergo urodynamic evaluation that reliably forecasted a voiding trial failure. The majority of women will pass a voiding trial on the first attempt after an isolated midurethral sling. Current medical comorbidities are predictive of a voiding trial failure, whereas other demographic/examination findings are not. Patients failing the initial voiding trial are at an increased risk of postoperative urinary tract infection or developing acute retention after passing a subsequent voiding trial. Copyright © 2016 Elsevier Inc. All rights reserved.

Flight experiment of thermal energy storage

NASA Technical Reports Server (NTRS)

Namkoong, David

1989-01-01

Thermal energy storage (TES) enables a solar dynamic system to deliver constant electric power through periods of sun and shade. Brayton and Stirling power systems under current considerations for missions in the near future require working fluid temperatures in the 1100 to 1300+ K range. TES materials that meet these requirements fall into the fluoride family of salts. These salts store energy as a heat of fusion, thereby transferring heat to the fluid at constant temperature during shade. The principal feature of fluorides that must be taken into account is the change in volume that occurs with melting and freezing. Salts shrink as they solidify, a change reaching 30 percent for some salts. The location of voids that form as result of the shrinkage is critical when the solar dynamic system reemerges into the sun. Hot spots can develop in the TES container or the container can become distorted if the melting salt cannot expand elsewhere. Analysis of the transient, two-phase phenomenon is being incorporated into a three-dimensional computer code. The code is capable of analysis under microgravity as well as 1 g. The objective of the flight program is to verify the predictions of the code, particularly of the void location and its effect on containment temperature. The four experimental packages comprising the program will be the first tests of melting and freezing conducted under microgravity. Each test package will be installed in a Getaway Special container to be carried by the shuttle. The package will be self-contained and independent of shuttle operations other than the initial opening of the container lid and the final closing of the lid. Upon the return of the test package from flight, the TES container will be radiographed and finally partitioned to examine the exact location and shape of the void. Visual inspection of the void and the temperature data during flight will constitute the bases for code verification.

An investigation of the plastic fracture of AISI 4340 and 18 nickel - 200 grade maraging steels

NASA Technical Reports Server (NTRS)

Cox, T. B.; Low, J. R., Jr.

1974-01-01

The mechanisms of plastic fracture (dimpled rupture) in high-purity and commercial 18 Ni, 200 grade maraging steels and quenched and tempered AISI 4340 steels have been studied. Plastic fracture takes place in the maraging alloys through void initiation by fracture of titanium carbo-nitride inclusions and the growth of these voids until impingement results in coalescence and final fracture. The fracture of AISI 4340 steel at a yield strength of 200 ksi occurs by nucleation and subsequent growth of voids formed by fracture of the interface between manganese sulfide inclusions and the matrix. The growth of these inclusion-nucleated voids is interrupted long before coalescence by impingement, by the formation of void sheets which connect neighboring sulfide-nucleated voids.

Delaunay based algorithm for finding polygonal voids in planar point sets

NASA Astrophysics Data System (ADS)

Alonso, R.; Ojeda, J.; Hitschfeld, N.; Hervías, C.; Campusano, L. E.

2018-01-01

This paper presents a new algorithm to find under-dense regions called voids inside a 2D point set. The algorithm starts from terminal-edges (local longest-edges) in a Delaunay triangulation and builds the largest possible low density terminal-edge regions around them. A terminal-edge region can represent either an entire void or part of a void (subvoid). Using artificial data sets, the case of voids that are detected as several adjacent subvoids is analyzed and four subvoid joining criteria are proposed and evaluated. Since this work is inspired on searches of a more robust, effective and efficient algorithm to find 3D cosmological voids the evaluation of the joining criteria considers this context. However, the design of the algorithm permits its adaption to the requirements of any similar application.

Influence of voids distribution on the deformation behavior of nanocrystalline palladium

NASA Astrophysics Data System (ADS)

Bachurin, D. V.

2018-07-01

Uniaxial deformation of three-dimensional nanocrystalline palladium containing porosity in the form of voids was investigated by means of molecular dynamics method. Simulations were performed at temperature of 300 K and at a constant strain rate of 108s-1. Two cases of voids distribution were considered: random and at triple or quadrupole junctions. It has been revealed that both the voids distribution and subsequent annealing at elevated temperature influence the deformation behavior of nanocrystalline palladium. In particular, the presence of voids at grain junctions results in a reduction of the Young's modulus and more pronounced softening effect during plastic deformation. The subsequent annealing evokes shrinkage of voids and strengthening effect. Contribution of grain boundary accommodation processes into both elastic and plastic deformation of nanocrystalline materials is discussed.

Constrained optimization framework for interface-aware sub-scale dynamics models for voids closure in Lagrangian hydrodynamics

DOE PAGES

Barlow, Andrew; Klima, Matej; Shashkov, Mikhail

2018-04-02

In hydrocodes, voids are used to represent vacuum and model free boundaries between vacuum and real materials. We give a systematic description of a new treatment of void closure in the framework of the multimaterial arbitrary Lagrangian–Eulerian (ALE) methods. This includes a new formulation of the interface-aware sub-scale-dynamics (IA-SSD) closure model for multimaterial cells with voids, which is used in the Lagrangian stage of our indirect ALE scheme. The results of the comprehensive testing of the new model are presented for one- and two-dimensional multimaterial calculations in the presence of voids. Finally, we also present a sneak peek of amore » realistic shaped charge calculation in the presence of voids and solids.« less

Voids and the Cosmic Web: cosmic depression & spatial complexity

NASA Astrophysics Data System (ADS)

van de Weygaert, Rien

2016-10-01

Voids form a prominent aspect of the Megaparsec distribution of galaxies and matter. Not only do theyrepresent a key constituent of the Cosmic Web, they also are one of the cleanest probesand measures of global cosmological parameters. The shape and evolution of voids are highly sensitive tothe nature of dark energy, while their substructure and galaxy population provides a direct key to thenature of dark matter. Also, the pristine environment of void interiors is an important testing groundfor our understanding of environmental influences on galaxy formation and evolution. In this paper, we reviewthe key aspects of the structure and dynamics ofvoids, with a particular focus on the hierarchical evolution of the void population. We demonstratehow the rich structural pattern of the Cosmic Web is related to the complex evolution and buildupof voids.

Constrained optimization framework for interface-aware sub-scale dynamics models for voids closure in Lagrangian hydrodynamics

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

Barlow, Andrew; Klima, Matej; Shashkov, Mikhail

In hydrocodes, voids are used to represent vacuum and model free boundaries between vacuum and real materials. We give a systematic description of a new treatment of void closure in the framework of the multimaterial arbitrary Lagrangian–Eulerian (ALE) methods. This includes a new formulation of the interface-aware sub-scale-dynamics (IA-SSD) closure model for multimaterial cells with voids, which is used in the Lagrangian stage of our indirect ALE scheme. The results of the comprehensive testing of the new model are presented for one- and two-dimensional multimaterial calculations in the presence of voids. Finally, we also present a sneak peek of amore » realistic shaped charge calculation in the presence of voids and solids.« less

Preparation and Optical Properties of Spherical Inverse Opals by Liquid Phase Deposition Using Spherical Colloidal Crystals

NASA Astrophysics Data System (ADS)

Aoi, Y.; Tominaga, T.

2013-03-01

Titanium dioxide (TiO2) inverse opals in spherical shape were prepared by liquid phase deposition (LPD) using spherical colloidal crystals as templates. Spherical colloidal crystals were produced by ink-jet drying technique. Aqueous emulsion droplets that contain polystyrene latex particles were ejected into air and dried. Closely packed colloidal crystals with spherical shape were obtained. The obtained spherical colloidal crystals were used as templates for the LPD. The templates were dispersed in the deposition solution of the LPD, i.e. a mixed solution of ammonium hexafluorotitanate and boric acid and reacted for 4 h at 30 °C. After the LPD process, the interstitial spaces of the spherical colloidal crystals were completely filled with titanium oxide. Subsequent heat treatment resulted in removal of templates and spherical titanium dioxide inverse opals. The spherical shape of the template was retained. SEM observations indicated that the periodic ordered voids were surrounded by titanium dioxide. The optical reflectance spectra indicated that the optical properties of the spherical titanium dioxide inverse opals were due to Bragg diffractions from the ordered structure. Filling in the voids of the inverse opals with different solvents caused remarkable changes in the reflectance peak.

Catalytically enhanced thermal decomposition of chemically grown silicon oxide layers on Si(001)

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

Leroy, F., E-mail: leroy@cinam.univ-mrs.fr; Passanante, T.; Cheynis, F.

2016-03-14

The thermal decomposition of Si dioxide layers formed by wet chemical treatment on Si(001) has been studied by low-energy electron microscopy. Independent nucleations of voids occur into the Si oxide layers that open by reaction at the void periphery. Depending on the voids, the reaction rates exhibit large differences via the occurrence of a nonlinear growth of the void radius. This non-steady state regime is attributed to the accumulation of defects and silicon hydroxyl species at the SiO{sub 2}/Si interface that enhances the silicon oxide decomposition at the void periphery.

Theory of void formation in dusty plasmas

NASA Astrophysics Data System (ADS)

Hu, Zuquan; Chen, Yinhua; Zheng, Xiang; Huang, Feng; Shi, Gei-fen; Yu, M. Y.

2009-06-01

A fluid theory of void formation in dusty plasmas taking into account ionization is proposed. It is shown that if the ionization rate is larger than a threshold, an initial steady-state dust-density distribution can evolve into a stable distribution containing a void. As the ionization rate is further increased, the time required for void formation decreases. The void size first increases, but then decreases. However, for still larger ionization rates, the dusty region of the plasma becomes ringlike, including the convection term in dust momentum equation. The results are in agreement with existing experiments and theories.

Demonstrating the Operational Value of Thermodynamic Hyperspectral Profiles in the Pre-Convective Environment

NASA Technical Reports Server (NTRS)

Kozlowski, Danielle; Zavodsky, Bradley T.; Jedlovec, Gary J.

2011-01-01

The Short-term Prediction Research and Transition Center (SPoRT) is a collaborative partnership between NASA and operational forecasting partners, including a number of National Weather Service (NWS) Weather Forecasting Offices (WFO). As a part of the transition to operations process, SPoRT attempts to identify possible limitations in satellite observations and provide operational forecasters a product that will result in the most impact on their forecasts. One operational forecast challenge that some NWS offices face, is forecasting convection in data-void regions such as large bodies of water. The Atmospheric Infrared Sounder (AIRS) is a sounding instrument aboard NASA's Aqua satellite that provides temperature and moisture profiles of the atmosphere. This paper will demonstrate an approach to assimilate AIRS profile data into a regional configuration of the WRF model using its three-dimensional variational (3DVAR) assimilation component to be used as a proxy for the individual profiles.

Automatic correction of dental artifacts in PET/MRI

PubMed Central

Ladefoged, Claes N.; Andersen, Flemming L.; Keller, Sune. H.; Beyer, Thomas; Law, Ian; Højgaard, Liselotte; Darkner, Sune; Lauze, Francois

2015-01-01

Abstract. A challenge when using current magnetic resonance (MR)-based attenuation correction in positron emission tomography/MR imaging (PET/MRI) is that the MRIs can have a signal void around the dental fillings that is segmented as artificial air-regions in the attenuation map. For artifacts connected to the background, we propose an extension to an existing active contour algorithm to delineate the outer contour using the nonattenuation corrected PET image and the original attenuation map. We propose a combination of two different methods for differentiating the artifacts within the body from the anatomical air-regions by first using a template of artifact regions, and second, representing the artifact regions with a combination of active shape models and k-nearest-neighbors. The accuracy of the combined method has been evaluated using 25 F18-fluorodeoxyglucose PET/MR patients. Results showed that the approach was able to correct an average of 97±3% of the artifact areas. PMID:26158104

Enhancement of acoustical performance of hollow tube sound absorber

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

Putra, Azma, E-mail: azma.putra@utem.edu.my; Khair, Fazlin Abd, E-mail: fazlinabdkhair@student.utem.edu.my; Nor, Mohd Jailani Mohd, E-mail: jai@utem.edu.my

This paper presents acoustical performance of hollow structures utilizing the recycled lollipop sticks as acoustic absorbers. The hollow cross section of the structures is arranged facing the sound incidence. The effects of different length of the sticks and air gap on the acoustical performance are studied. The absorption coefficient was measured using impedance tube method. Here it is found that improvement on the sound absorption performance is achieved by introducing natural kapok fiber inserted into the void between the hollow structures. Results reveal that by inserting the kapok fibers, both the absorption bandwidth and the absorption coefficient increase. For testmore » sample backed by a rigid surface, best performance of sound absorption is obtained for fibers inserted at the front and back sides of the absorber. And for the case of test sample with air gap, this is achieved for fibers introduced only at the back side of the absorber.« less

Enhancement of acoustical performance of hollow tube sound absorber

NASA Astrophysics Data System (ADS)

Putra, Azma; Khair, Fazlin Abd; Nor, Mohd Jailani Mohd

2016-03-01

This paper presents acoustical performance of hollow structures utilizing the recycled lollipop sticks as acoustic absorbers. The hollow cross section of the structures is arranged facing the sound incidence. The effects of different length of the sticks and air gap on the acoustical performance are studied. The absorption coefficient was measured using impedance tube method. Here it is found that improvement on the sound absorption performance is achieved by introducing natural kapok fiber inserted into the void between the hollow structures. Results reveal that by inserting the kapok fibers, both the absorption bandwidth and the absorption coefficient increase. For test sample backed by a rigid surface, best performance of sound absorption is obtained for fibers inserted at the front and back sides of the absorber. And for the case of test sample with air gap, this is achieved for fibers introduced only at the back side of the absorber.

Rheological measurements in reduced gravity

NASA Astrophysics Data System (ADS)

Bakhtiyarov, Sayavur I.; Overfelt, Ruel A.

1999-01-01

Rheology of fluidized beds and settling suspensions were studied experimentally in a series of reduced gravity parabolic flights aboard NASA's KC-135 aircraft. Silica sands of two different size distributions were fluidized by air. The slurries were made using silica sand and Glycerol solution. The experimental set up incorporated instrumentation to measure the air flow rate, the pressure drop and the apparent viscosity of the fluidized sand and sand suspensions at a wide range of the shear rates. The fluidization chamber and container had transparent walls to allow visualization of the structure changes involved in fluidization and in Couette flow in reduced gravity. Experiments were performed over a broad range of gravitational accelerations including microgravity and double gravity conditions. The results of the flight and ground experiments reveal significant differences in overall void fraction and hence in the apparent viscosity of fluidized sand and sand suspensions under microgravity as compared to one-g conditions.

Advanced manufacturing development of a composite empennage component for L-1011 aircraft

NASA Technical Reports Server (NTRS)

1978-01-01

Work continued toward the development of tooling and processing concepts required for a cocured hat/skin cover assembly. A plan was developed and implemented to develop the process for using preimpregnated T300/5208 with a resin content of 34 + or - 2 percent by weight. Use of this material results in a simplified laminating process because removal by bleeding or prebleeding is no longer required. The approach to this task basically consists of fabricating and testing flat laminated panels and simulated structural panels to verify known processing techniques relative to end-laminate quality. The flat panels were used to determine air bleeding arrangement and required cure cycle. Single and multihat-stiffened panels were fabricated using the established air bleeding arrangement and cure cycle with the resulting cured parts yielding excellent correlation of ply thickness with all surfaces clear of porosity and voids.

Planetary Pits and Caves: Targets for Science Exploration

NASA Astrophysics Data System (ADS)

Whittaker, W. L.; Boston, P. J.; Cushing, G.; Titus, T. N.; Wagner, R. V.; Colaprete, A.; Haruyama, J.; Jones, H. L.; Blank, J. G.; Mueller, R. P.; Stopar, J. D.; Tabib, W.; Wong, U.

2017-02-01

Planetary pits, caves, and voids are compelling mission destinations for science, exploration, and habitation throughout the solar system. Questions of origins, geology, mineralogy, stratigraphy, gravimetry, aging, and astrobiology abound.

Laboratory and exterior decay of wood plastic composite boards: voids analysis and computed tomography

Treesearch

Grace Sun; Rebecca E. Ibach; Meghan Faillace; Marek Gnatowski; Jessie A. Glaeser; John Haight

2016-01-01

After exposure in the field and laboratory soil block culture testing, the void content of wood–plastic composite (WPC) decking boards was compared to unexposed samples. A void volume analysis was conducted based on calculations of sample density and from micro-computed tomography (microCT) data. It was found that reference WPC contains voids of different sizes from...

High-resolution electron microscope observation of voids in amorphous Ge.

NASA Technical Reports Server (NTRS)

Donovan, T. M.; Heinemann, K.

1971-01-01

Electron micrographs have been obtained which clearly show the existence of a void network in amorphous Ge films formed at substrate temperatures of 25 and 150 C, and the absence of a void network in films formed at higher substrate temperatures of 200 and 250 C. These results correlate quite well with density measurements and predictions of void densities by indirect methods.

Three-Dimensional Analysis of Voids in AM60B Magnesium Tensile Bars Using Computed Tomography Imagery

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

Waters, A M

2001-05-01

In an effort to increase automobile fuel efficiency as well as decrease the output of harmful greenhouse gases, the automotive industry has recently shown increased interest in cast light metals such as magnesium alloys in an effort to increase weight savings. Currently several magnesium alloys such as AZ91 and AM60B are being used in structural applications for automobiles. However, these magnesium alloys are not as well characterized as other commonly used structural metals such as aluminum. This dissertation presents a methodology to nondestructively quantify damage accumulation due to void behavior in three dimensions in die-cast magnesium AM60B tensile bars asmore » a function of mechanical load. Computed tomography data was acquired after tensile bars were loaded up to and including failure, and analyzed to characterize void behavior as it relates to damage accumulation. Signal and image processing techniques were used along with a cluster labeling routine to nondestructively quantify damage parameters in three dimensions. Void analyses were performed including void volume distribution characterization, nearest neighbor distance calculations, shape parameters, and volumetric renderings of voids in the alloy. The processed CT data was used to generate input files for use in finite element simulations, both two- and three-dimensional. The void analyses revealed that the overwhelming source of failure in each tensile bar was a ring of porosity within each bar, possibly due to a solidification front inherent to the casting process. The measured damage parameters related to void nucleation, growth, and coalescence were shown to contribute significantly to total damage accumulation. Void volume distributions were characterized using a Weibull function, and the spatial distributions of voids were shown to be clustered. Two-dimensional finite element analyses of the tensile bars were used to fine-tune material damage models and a three-dimensional mesh of an extracted portion of one tensile bar including voids was generated from CT data and used as input to a finite element analysis.« less

The effect of void creation prior to vertebroplasty on intravertebral pressure and cement distribution in cadaveric spines with simulated metastases.

PubMed

Li, Ka; Yan, Jun; Yang, Qiang; Li, Zhenfeng; Li, Jianmin

2015-01-28

For osteoporosis or spinal metastases, percutaneous vertebroplasty is effective in pain relief and improvement of mobility. However, the complication rate (cement extravasation and fat embolisms) is relatively higher in the treatment of spinal metastases. The presence of tumor tissue plays a significant role in intravertebral pressure and cement distribution and thereby affects the occurrence of complications. We investigated the effect of void creation prior to vertebroplasty on intravertebral pressure and cement distribution in spinal metastases. Eighteen vertebrae (T8-L4) from five cadaveric spines were randomly allocated for two groups (group with and without void) of nine vertebrae each. Defect was created by removing a central core of cancellous bone in the vertebral body and then filling it with 30% or 100% fresh muscle paste by volume to simulate void creation or no void creation, respectively. Then, 20% bone cement by volume of the vertebral body was injected into each specimen through a unipedicular approach at a rate of 3 mL/min. The gender of the donor, vertebral body size, bone density, cement volume, and intravertebral pressure were recorded. Then, computed tomography scans and cross sections were taken to evaluate the cement distribution in vertebral bodies. No significant difference was found between the two groups in terms of the gender of the donor, vertebral body size, bone density, or bone cement volume. The average maximum intravertebral pressure in the group with void creation was significantly lower than that in the group without void creation (1.20 versus 5.09 kPa, P = 0.001). Especially during the filling of void, the difference was more pronounced. Void creation prior to vertebroplasty allowed the bone cement to infiltrate into the lytic defect. In vertebroplasty for spinal metastases, void creation produced lower intravertebral pressure and facilitated cement filling. To reduce the occurrence of complication, it may be an alternative to eliminate the tumor tissue to create a void prior to cement injection.

Determination of Sinkholes with Different Geophysical Techniques; A Case Study in Yarımburgaz, Küçükçekmece Lake NW Istanbul, Turkey

NASA Astrophysics Data System (ADS)

Karabulut, Savas; Cengiz Cinku, Mualla; Tezel, Okan; Dedecan, Hasan; Oygo, Azat

2016-04-01

The Yarımburgaz cave which is located in the city of Istanbul, NW Turkey plays an important host to the first human culture and preserve significant archaeological and paleontological resources. The cave was formed as a result of a subterranean stream erosion on the limestones of the Eocene Kırklareli formation. It has been reported that a double cave with upper and lower entrance chambers exist, although no geophysical research was conducted to detect the cave's trunk passages and the extend of the sediment fill inside the cave. The aim of this study was to test the preferred order for detection the response to different geophysical methods applied on the cave. We therefore carried out an a series of geophysical study to determine the size, position, and depth of sinkholes inside the caves. Integrated methodological approaches including multichannel analysis of surface wave (MASW) 2- microtremor array method, 3-single station microtremor measurements, 4- electrical tomography (ET) measuruments and 5-microgravity imaging showed that the geophysical response was succesfully applied. Based upon the flow-chart we concluded that the microgravity survey should be applied as a first step to detect the air-filled void and the geometry of the cave. The electric tomography method was well applied showing high resistivity values across the voids. The surface wave method showed that the low-velocity zones are detected in various locations of the cave. In addition we the results of MASW and ReMi methods showed clearly the density variation in the lateral direction. Fundamental frequency value above void decraese according the properties of geological units in lateral directional, especially when they are engineering rock like limestone.

Experimental study on interfacial area transport in downward two-phase flow

NASA Astrophysics Data System (ADS)

Wang, Guanyi

In view of the importance of two group interfacial area transport equations and lack of corresponding accurate downward flow database that can reveal two group interfacial area transport, a systematic database for adiabatic, air-water, vertically downward two-phase flow in a round pipe with inner diameter of 25.4 mm was collected to gain an insight of interfacial structure and provide benchmarking data for two-group interfacial area transport models. A four-sensor conductivity probe was used to measure the local two phase flow parameters and data was collected with data sampling frequency much higher than conventional data sampling frequency to ensure the accuracy. Axial development of local flow parameter profiles including void fraction, interfacial area concentration, and Sauter mean diameter were presented. Drastic inter-group transfer of void fraction and interfacial area was observed at bubbly to slug transition flow. And the wall peaked interfacial area concentration profiles were observed in churn-turbulent flow. The importance of local data about these phenomenon on flow structure prediction and interfacial area transport equation benchmark was analyzed. Bedsides, in order to investigate the effect of inlet conditions, all experiments were repeated after installing the flow straightening facility, and the results were briefly analyzed. In order to check the accuracy of current data, the experiment results were cross-checked with rotameter measurement as well as drift-flux model prediction, the averaged error is less than 15%. Current models for two-group interfacial area transport equation were evaluated using these data. The results show that two-group interfacial area transport equations with current models can predict most flow conditions with error less than 20%, except some bubbly to slug transition flow conditions and some churn-turbulent flow conditions. The disagreement between models and experiments could result from underestimate of inter-group void transfer.

Eco-friendly porous concrete using bottom ash aggregate for marine ranch application.

PubMed

Lee, Byung Jae; Prabhu, G Ganesh; Lee, Bong Chun; Kim, Yun Yong

2016-03-01

This article presents the test results of an investigation carried out on the reuse of coal bottom ash aggregate as a substitute material for coarse aggregate in porous concrete production for marine ranch applications. The experimental parameters were the rate of bottom ash aggregate substitution (30%, 50% and 100%) and the target void ratio (15%, 20% and 25%). The cement-coated granular fertiliser was substituted into a bottom ash aggregate concrete mixture to improve marine ranch applications. The results of leaching tests revealed that the bottom ash aggregate has only a negligible amount of the ten deleterious substances specified in the Ministry of Environment - Enforcement Regulation of the Waste Management Act of Republic Korea. The large amount of bubbles/air gaps in the bottom ash aggregate increased the voids of the concrete mixtures in all target void ratios, and decreased the compressive strength of the porous concrete mixture; however, the mixture substituted with 30% and 10% of bottom ash aggregate and granular fertiliser, respectively, showed an equal strength to the control mixture. The sea water resistibility of the bottom ash aggregate substituted mixture was relatively equal to that of the control mixture, and also showed a great deal of improvement in the degree of marine organism adhesion compared with the control mixture. No fatality of fish was observed in the fish toxicity test, which suggested that bottom ash aggregate was a harmless material and that the combination of bottom ash aggregate and granular fertiliser with substitution rates of 30% and 10%, respectively, can be effectively used in porous concrete production for marine ranch application. © The Author(s) 2015.

PRECISION COSMOGRAPHY WITH STACKED VOIDS

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

Lavaux, Guilhem; Wandelt, Benjamin D.

2012-08-01

We present a purely geometrical method for probing the expansion history of the universe from the observation of the shape of stacked voids in spectroscopic redshift surveys. Our method is an Alcock-Paczynski (AP) test based on the average sphericity of voids posited on the local isotropy of the universe. It works by comparing the temporal extent of cosmic voids along the line of sight with their angular, spatial extent. We describe the algorithm that we use to detect and stack voids in redshift shells on the light cone and test it on mock light cones produced from N-body simulations. Wemore » establish a robust statistical model for estimating the average stretching of voids in redshift space and quantify the contamination by peculiar velocities. Finally, assuming that the void statistics that we derive from N-body simulations is preserved when considering galaxy surveys, we assess the capability of this approach to constrain dark energy parameters. We report this assessment in terms of the figure of merit (FoM) of the dark energy task force and in particular of the proposed Euclid mission which is particularly suited for this technique since it is a spectroscopic survey. The FoM due to stacked voids from the Euclid wide survey may double that of all other dark energy probes derived from Euclid data alone (combined with Planck priors). In particular, voids seem to outperform baryon acoustic oscillations by an order of magnitude. This result is consistent with simple estimates based on mode counting. The AP test based on stacked voids may be a significant addition to the portfolio of major dark energy probes and its potentialities must be studied in detail.« less

Serotonin (5-HT)2A/2C receptor agonist (2,5-dimethoxy-4-idophenyl)-2-aminopropane hydrochloride (DOI) improves voiding efficiency in the diabetic rat.

PubMed

Tu, Hongjian; Cao, Nailong; Gu, Baojun; Si, Jiemin; Chen, Zhong; Andersson, Karl-Erik

2015-07-01

To examine the effects of the serotonin (5-HT)2A/2C receptor agonist (2,5-dimethoxy-4-idophenyl)-2-aminopropane hydrochloride (DOI) on micturition in rats with diabetes mellitus (DM). Female Sprague-Dawley rats (n = 16) were divided into two groups: rats with Type 1 DM and age-matched control rats. DM was induced by i.p. injection of streptozotocin (65 mg/kg) and detailed cystometrogram (CMG) studies were performed 8 weeks post-injection in all rats under urethane anaesthesia. The selective 5-HT2A antagonist ketanserin was administered after each DOI dose-response curve was plotted. All drugs were administered i.v. Compared with controls, comprehensive urodynamic studies showed that DM rats had a higher bladder capacity and post-void residual urine volume (PVR), and a markedly lower voiding efficiency. In DM rats, DOI (0.01-0.3 mg/kg) induced significant dose-dependent increases in micturition volume and reductions in PVR, resulting in greater voiding efficiency. CMG measurements showed a dose-dependent increase in high-frequency oscillation (HFO) activity, evidenced by an increased duration of HFOs per voiding. This correlated with the improved voiding efficiency. Ketanserin (0.1 mg/kg) partially or completely reversed the DOI-induced changes. The HFOs observed in the present study seem to correlate with external urethral sphincter bursting activity during voiding. Bladder voiding efficiency was reduced in DM rats. The 5-HT2A receptor agonist can enhance HFO activity and improves voiding efficiency, and so may represent a new strategy to improve voiding efficiency after DM in experimental studies. © 2014 The Authors BJU International © 2014 BJU International Published by John Wiley & Sons Ltd.

Three-Dimensional Gas Exchange Pathways in Pome Fruit Characterized by Synchrotron X-Ray Computed Tomography1[C][W][OA

PubMed Central

Verboven, Pieter; Kerckhofs, Greet; Mebatsion, Hibru Kelemu; Ho, Quang Tri; Temst, Kristiaan; Wevers, Martine; Cloetens, Peter; Nicolaï, Bart M.

2008-01-01

Our understanding of the gas exchange mechanisms in plant organs critically depends on insights in the three-dimensional (3-D) structural arrangement of cells and voids. Using synchrotron radiation x-ray tomography, we obtained for the first time high-contrast 3-D absorption images of in vivo fruit tissues of high moisture content at 1.4-μm resolution and 3-D phase contrast images of cell assemblies at a resolution as low as 0.7 μm, enabling visualization of individual cell morphology, cell walls, and entire void networks that were previously unknown. Intercellular spaces were always clear of water. The apple (Malus domestica) cortex contains considerably larger parenchyma cells and voids than pear (Pyrus communis) parenchyma. Voids in apple often are larger than the surrounding cells and some cells are not connected to void spaces. The main voids in apple stretch hundreds of micrometers but are disconnected. Voids in pear cortex tissue are always smaller than parenchyma cells, but each cell is surrounded by a tight and continuous network of voids, except near brachyssclereid groups. Vascular and dermal tissues were also measured. The visualized network architecture was consistent over different picking dates and shelf life. The differences in void fraction (5.1% for pear cortex and 23.0% for apple cortex) and in gas network architecture helps explain the ability of tissues to facilitate or impede gas exchange. Structural changes and anisotropy of tissues may eventually lead to physiological disorders. A combined tomography and internal gas analysis during growth are needed to make progress on the understanding of void formation in fruit. PMID:18417636

Overview of the Epidemiology of Lower Urinary Tract Dysfunction in South Korea

PubMed Central

2016-01-01

This review assessed the epidemiology of voiding dysfunctions in South Korea. Comprehensive understanding of this epidemiology is crucial because the senior population and the social burden are increasing because of voiding dysfunctions is growing. We searched the medical records using several terms related to voiding dysfunction: benign prostatic hyperplasia, urinary incontinence, lower urinary tract symptoms, overactive bladder, and nocturia. We then estimated the prevalence of voiding dysfunctions in South Korea; our data were comparable with those from other countries, with slight differences. The ranges of incidences varied widely between studies, mostly because investigators defined disorders differently. Voiding dysfunction greatly affects healthcare costs and individual quality of life; therefore, more proper and valuable epidemiologic data are needed. In addition, efforts to unify the definitions of various voiding dysfunctions and progress in investigational methodologies using multimedia are warranted. PMID:27377940

Thermal analysis of void cavity for heat pipe receiver under microgravity

NASA Astrophysics Data System (ADS)

Gui, Xiaohong; Song, Xiange; Nie, Baisheng

2017-04-01

Based on theoretical analysis of PCM (Phase Change Material) solidification process, the model of improved void cavity distribution tending to high temperature region is established. Numerical results are compared with NASA (National Aeronautics and Space Administration) results. Analysis results show that the outer wall temperature, the melting ratio of PCM and the temperature gradient of PCM canister, have great difference in different void cavity distribution. The form of void distribution has a great effect on the process of phase change. Based on simulation results under the model of improved void cavity distribution, phase change heat transfer process in thermal storage container is analyzed. The main goal of the improved designing for PCM canister is to take measures in reducing the concentration distribution of void cavity by adding some foam metal into phase change material.

Reliability of void detection in structural ceramics using scanning laser acoustic microscopy

NASA Technical Reports Server (NTRS)

Roth, D. J.; Klima, S. J.; Kiser, J. D.; Baaklini, G. Y.

1985-01-01

The reliability of scanning laser acoustic microscopy (SLAM) for detecting surface voids in structural ceramic test specimens was statistically evaluated. Specimens of sintered silicon nitride and sintered silicon carbide, seeded with surface voids, were examined by SLAM at an ultrasonic frequency of 100 MHz in the as fired condition and after surface polishing. It was observed that polishing substantially increased void detectability. Voids as small as 100 micrometers in diameter were detected in polished specimens with 0.90 probability at a 0.95 confidence level. In addition, inspection times were reduced up to a factor of 10 after polishing. The applicability of the SLAM technique for detection of naturally occurring flaws of similar dimensions to the seeded voids is discussed. A FORTRAN program listing is given for calculating and plotting flaw detection statistics.

Force field inside the void in complex plasmas under microgravity conditions

NASA Astrophysics Data System (ADS)

Kretschmer, M.; Khrapak, S. A.; Zhdanov, S. K.; Thomas, H. M.; Morfill, G. E.; Fortov, V. E.; Lipaev, A. M.; Molotkov, V. I.; Ivanov, A. I.; Turin, M. V.

2005-05-01

Observations of complex plasmas under microgravity conditions onboard the International Space Station performed with the Plasma-Kristall experiment-Nefedov facility are reported. A weak instability of the boundary between the central void (region free of microparticles) and the microparticle cloud is observed at low gas pressures. The instability leads to periodic injections of a relatively small number of particles into the void region (by analogy this effect is called the “trampoline effect”). The trajectories of injected particles are analyzed providing information on the force field inside the void. The experimental results are compared with theory which assumes that the most important forces inside the void are the electric and the ion drag forces. Good agreement is found clearly indicating that under conditions investigated the void formation is caused by the ion drag force.

Murine social stress results in long lasting voiding dysfunction.

PubMed

Butler, Stephan; Luz, Sandra; McFadden, Kile; Fesi, Joanna; Long, Christopher; Spruce, Lynn; Seeholzer, Steven; Canning, Douglas; Valentino, Rita; Zderic, Stephen

2018-01-01

Repeated exposure to social stress shifts the voiding phenotype in male mice leading to bladder wall remodeling and is associated with increased expression of the stress neuropeptide, corticotropin-releasing factor (CRF) in Barrington's nucleus neurons. In these studies, we set out to determine if the voiding phenotype could recover upon removal from the stressor. Male mice were exposed for 1h daily to an aggressor and the voiding phenotype was assessed at one month followed by randomization to three groups. One group underwent immediate sacrifice. Two groups were allowed a one month recovery from the social stress exposure with or without the addition of fluoxetine (1.2mg/ml) in their drinking water and repeat voiding patterns were measured prior to sacrifice. Social stress significantly increased bladder mass, bladder mass corrected for body weight, voided volumes, and decreased urinary frequency. The abnormal voiding phenotype persisted after a 1month recovery with no effect from the addition of fluoxetine. CRF mRNA in Barrington's nucleus was increased by social stress and remained elevated following recovery with no effect from the addition of fluoxetine. The mRNA and protein expression for the alpha 1 chains of type 1 and type III collagen was unchanged across all groups suggesting that changes in the extracellular matrix of the bladder are not responsible for the voiding phenotype. This persisting voiding dysfunction correlates with the persistent elevation of CRF mRNA expression in Barrington's nucleus. Copyright © 2017. Published by Elsevier Inc.

Development of a prototype fluid volume measurement system. [for urine volume measurement on space missions

NASA Technical Reports Server (NTRS)

Poppendiek, H. F.; Sabin, C. M.; Meckel, P. T.

1974-01-01

The research is reported in applying the axial fluid temperature differential flowmeter to a urine volume measurement system for space missions. The fluid volume measurement system is described along with the prototype equipment package. Flowmeter calibration, electronic signal processing, and typical void volume measurements are also described.

Clinical Evaluation of Different Pre-impression Preparation Procedures of Dental Arch

PubMed Central

Arora, Nitin; Arora, Monika; Gupta, Naveen; Agarwal, Manisha; Verma, Rohit; Rathod, Pankaj

2015-01-01

Background: Bubbles and voids on the occlusal surface impede the actual intercuspation and pre-impression preparation aims to reduce the incidence of air bubbles and voids as well as influences the quality of occlusal reproduction and actual clinical intercuspation in the articulator. The study was undertaken to determine the influence of different pre-impression preparation procedures of antagonistic dental arch on the quality of the occlusal reproduction of the teeth in irreversible hydrocolloid impressions and to determine most reliable pre-impression preparation method to reduce the incidence of air bubbles. Materials and Methods: A total of 20 subjects were selected having full complement of mandibular teeth from second molar to second molar with well demarcated cusp height. 200 impressions were made with irreversible hydrocolloid material. The impressions were divided into five groups of 40 impressions each and each group had one specific type of pre-impression preparation. All the impressions were poured in die stone. A stereomicroscope with graduated eyepiece was used to count the number of bubbles on the occlusal surface of premolars and molars. The mean and standard deviations were calculated for each group. Mann–Whitney U-test was applied to find the significant difference between different groups. Results: Least bubbles were found in the group in which oral cavity was dried by saliva ejector and fluid hydrocolloid was finger painted onto the occlusal surfaces immediately before the placement of impression tray in the mouth. Conclusion: It was found that finger painting the tooth surfaces with fluid hydrocolloid immediately before the placement of loaded impression tray in the mouth was the most reliable method. The oral cavity can be cleared more easily of excess saliva by vacuum suction rather than by use of an astringent solution. PMID:26229376

Clinical Evaluation of Different Pre-impression Preparation Procedures of Dental Arch.

PubMed

Arora, Nitin; Arora, Monika; Gupta, Naveen; Agarwal, Manisha; Verma, Rohit; Rathod, Pankaj

2015-07-01

Bubbles and voids on the occlusal surface impede the actual intercuspation and pre-impression preparation aims to reduce the incidence of air bubbles and voids as well as influences the quality of occlusal reproduction and actual clinical intercuspation in the articulator. The study was undertaken to determine the influence of different pre-impression preparation procedures of antagonistic dental arch on the quality of the occlusal reproduction of the teeth in irreversible hydrocolloid impressions and to determine most reliable pre-impression preparation method to reduce the incidence of air bubbles. A total of 20 subjects were selected having full complement of mandibular teeth from second molar to second molar with well demarcated cusp height. 200 impressions were made with irreversible hydrocolloid material. The impressions were divided into five groups of 40 impressions each and each group had one specific type of pre-impression preparation. All the impressions were poured in die stone. A stereomicroscope with graduated eyepiece was used to count the number of bubbles on the occlusal surface of premolars and molars. The mean and standard deviations were calculated for each group. Mann-Whitney U-test was applied to find the significant difference between different groups. Least bubbles were found in the group in which oral cavity was dried by saliva ejector and fluid hydrocolloid was finger painted onto the occlusal surfaces immediately before the placement of impression tray in the mouth. It was found that finger painting the tooth surfaces with fluid hydrocolloid immediately before the placement of loaded impression tray in the mouth was the most reliable method. The oral cavity can be cleared more easily of excess saliva by vacuum suction rather than by use of an astringent solution.

Effect of mix parameters on longevity of bituminous mixtures

NASA Astrophysics Data System (ADS)

Reichle, Clayton Matthew

This study was performed to evaluate the effects of varying aggregate sources, aggregate gradations on the stripping and rutting potential of bituminous based plant mixes specified by the Missouri Department of Transportation. The different aggregate combinations included two different aggregate sources (Potosi Dolomite and Jefferson City Dolomite) including two variations for the Jefferson City Dolomite mix to simulate a marginally in-specification mix and an out-of-specification but in-field tolerance mix. The "field" mix simulated the marginal mix where field tolerance of high dust and low binder content were maximized. All three mixes were evaluated for stripping susceptibility using the Tensile Strength Ratio (TSR) test and the Hamburg Wheel Tracking Device (HWTD). The mix characteristics (unit weight, effective binder content, and air voids) were used for a Level 3 analysis in the Mechanistic-Empirical Pavement Design Guide (MEPDG) to determine long term pavement distress conditions such as fatigue cracking, rutting, and IRI (smoothness). The Potosi mix exhibited the best resistance to rutting and stripping during both the TSR testing as well as the Hamburg testing. The Jefferson City In-Spec and Out-of-Spec mixes showed less resistance to rutting and stripping in order, respectively. This was expected for the Jefferson City mixes where the aggregate was of lower quality (higher Los Angeles Abrasion, Micro Deval loss, absorption, and deleterious materials). Also, in the case of the Jefferson City Out-of-Spec mix, the binder content was lower. Upon evaluating the mixes using the MEPDG software, it was shown that mix characteristics such as air voids, VMA, and VFA influenced the fatigue cracking, rutting, and IRI predictions to a minor degree.

Cracking behavior and microstructure of austenitic stainless steels and alloy 690 irradiated in BOR-60 reactor, phase I.

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

Chen, Y.; Chopra, O. K.; Soppet, W. K.

2010-02-16

Cracking behavior of stainless steels specimens irradiated in the BOR-60 at about 320 C is studied. The primary objective of this research is to improve the mechanistic understanding of irradiation-assisted stress corrosion cracking (IASCC) of core internal components under conditions relevant to pressurized water reactors. The current report covers several baseline tests in air, a comparison study in high-dissolved-oxygen environment, and TEM characterization of irradiation defect structure. Slow strain rate tensile (SSRT) tests were conducted in air and in high-dissolved-oxygen (DO) water with selected 5- and 10-dpa specimens. The results in high-DO water were compared with those from earlier testsmore » with identical materials irradiated in the Halden reactor to a similar dose. The SSRT tests produced similar results among different materials irradiated in the Halden and BOR-60 reactors. However, the post-irradiation strength for the BOR-60 specimens was consistently lower than that of the corresponding Halden specimens. The elongation of the BOR-60 specimens was also greater than that of their Halden specimens. Intergranular cracking in high-DO water was consistent for most of the tested materials in the Halden and BOR-60 irradiations. Nonetheless, the BOR-60 irradiation was somewhat less effective in stimulating IG fracture among the tested materials. Microstructural characterization was also carried out using transmission electron microscopy on selected BOR-60 specimens irradiated to {approx}25 dpa. No voids were observed in irradiated austenitic stainless steels and cast stainless steels, while a few voids were found in base and grain-boundary-engineered Alloy 690. All the irradiated microstructures were dominated by a high density of Frank loops, which varied in mean size and density for different alloys.« less

Shock Initiation of Explosives - High Temperature Hot Spots Explained

NASA Astrophysics Data System (ADS)

Bassett, Will

2017-06-01

The pore-collapse mechanism for hot spot creation is currently one of the most intensely studied subjects in the initiation of energetic materials. In the present study, we use 1.5 - 3.5 km s-1 laser-driven flyer plates to impact microgram charges of both polymer-bound and pure pentaerythritol tetranitrate (PETN) while recording the temperature and spatially-averaged emissivity with a high-speed optical pyrometer. The 32-color pyrometer has nanosecond time resolution and a high dynamic range with sensitivity to temperatures from 7000 to 2000 K. Hot spot temperatures of 4000 K at impact are observed in the polymer-bound explosive charges where an elastomeric binder is used to fill void spaces. In pure PETN and more heterogeneous polymer-bound charges, in which significant void space is present, hot spot temperatures of 6000 K are observed, similar to previous reports with significant porosity. We attribute these high temperatures to gas-phase products formed in-situ being compressed under the driving shock. Experiments performed under various gas environments (air, butane, etc.) showed a strong influence on observed temperature upon impact. Control experiments where the PETN in the polymer-bound charges were replaced with sucrose and silica reinforce the result that hot spots are a result of in-situ gas formation from decomposition of organic molecules. US Air Force Office of Scientific Research awards FA9550-14-1-0142 and FA9550-16-1-0042; US Army Research Office award W911NF-13-1-0217; Defense Threat Reduction Agency award HDTRA1-12-1-0011. In collaboration with: Belinda Pacheco and Dana Dlott, University of Illinois at Urbana Champaign.

Comparison of different obturation techniques for primary molars by digital radiography.

PubMed

Memarpour, Mahtab; Shahidi, Shoaleh; Meshki, Razieh

2013-01-01

The purpose of this study was to compare six methods of root canal filling in primary mandibular second molars via digital radiography. A total of 239 canals were prepared and obturated with zinc-oxide eugenol paste. Obturation methods compared were: anesthetic syringe; NaviTip syringe; pressure syringe; tuberculin syringe; lentulo spiral; and packing with a plugger. The canals were evaluated in photostimulated phosphor radiographs for length of obturation, presence of voids, and number and sum of void sizes. The data were analyzed using chi-square, Kruskal-Wallis and Mann-Whitney tests. There were significant differences between all groups in the length of obturation (P>.01) and presence of voids (P<.001). The lentulo and tuberculin syringe groups, respectively, showed the best and worst results for length of obturation. Significant differences were also found in the number of voids (P<.001) and mean sum of void sizes in the coronal (P<.001) and middle third (P=.003). For the number and size of the voids, the NaviTip group showed the best results. Lentulo produced the best results in terms of length of obturation, while NaviTip syringe produced the best results in controlling paste extrusion from the apical foramen and having the smallest void size and lowest number of voids.

On localization and void coalescence as a precursor to ductile fracture.

PubMed

Tekoğlu, C; Hutchinson, J W; Pardoen, T

2015-03-28

Two modes of plastic flow localization commonly occur in the ductile fracture of structural metals undergoing damage and failure by the mechanism involving void nucleation, growth and coalescence. The first mode consists of a macroscopic localization, usually linked to the softening effect of void nucleation and growth, in either a normal band or a shear band where the thickness of the band is comparable to void spacing. The second mode is coalescence with plastic strain localizing to the ligaments between voids by an internal necking process. The ductility of a material is tied to the strain at macroscopic localization, as this marks the limit of uniform straining at the macroscopic scale. The question addressed is whether macroscopic localization occurs prior to void coalescence or whether the two occur simultaneously. The relation between these two modes of localization is studied quantitatively in this paper using a three-dimensional elastic-plastic computational model representing a doubly periodic array of voids within a band confined between two semi-infinite outer blocks of the same material but without voids. At sufficiently high stress triaxiality, a clear separation exists between the two modes of localization. At lower stress triaxialities, the model predicts that the onset of macroscopic localization and coalescence occur simultaneously. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Void collapse under distributed dynamic loading near material interfaces

NASA Astrophysics Data System (ADS)

Shpuntova, Galina; Austin, Joanna

2012-11-01

Collapsing voids cause significant damage in diverse applications from biomedicine to underwater propulsion to explosives. While shock-induced void collapse has been studied extensively, less attention has been devoted to stress wave loading, which will occur instead if there are mechanisms for wave attenuation or if the impact velocity is relatively low. A set of dynamic experiments was carried out in a model experimental setup to investigate the effect of acoustic heterogeneities in the surrounding medium on void collapse. Two tissue-surrogate polymer materials of varying acoustic properties were used to create flowfield geometries involving a boundary and a void. A stress wave, generated by projectile impact, triggered void collapse in the gelatinous polymer medium. When the length scales of features in the flow field were on the same order of magnitude as the stress wave length scale, the presence of the boundary was found to affect the void collapse process relative to collapse in the absence of a boundary. This effect was quantified for a range of geometries and impact conditions using a two-color, single-frame particle image velocimetry technique. Research supported by NSF Award #0954769, ``CAREER: Dynamics and damage of void collapse in biological materials under stress wave loading'' with Prof. Henning Winter as Program Manager.

Can recording only the day-time voided volumes predict bladder capacity?

PubMed

Cho, Won Yeol; Kim, Seong Cheol; Kim, Sun-Ouck; Park, Sungchan; Lee, Sang Don; Chung, Jae Min; Kim, Kyung Do; Moon, Du Geon; Kim, Young Sig; Kim, Jun Mo

2018-05-01

This study aimed to demonstrate a method to easily assess bladder capacity using knowledge of day-time voided volumes, which can be obtained even from patients with nocturnal enuresis where the first morning void cannot accurately predict the bladder capacity due to bladder emptying overnight. We evaluated 177 healthy children from 7 Korean medical centres entered the study between January 2008 and January 2009. Voided volumes measured for more than 48 hours were recorded in the frequency volume chart (FVC). Most voided volumes during day-time were showed between 30% and 80% of the maximal voided volume (MVV). The maximal voided volume during day-time (MVVDT) was significantly less than the MVV (179.5±71.1 mL vs. 227.0±79.2 mL, p<0.001). The correlation coefficients with the MVV were 0.801 for the estimated MVV using the MVVDT (MVVDT×1.25), which suggested a fairly strong relationship between the MVVDT×1.25 and the MVV. The MVV derived from the FVC excluding the FMV was less than if the FMV had been included. When an accurate first morning voided volume cannot be obtained, as in patients with nocturnal enuresis, calculating MVVDT×1.25 allows estimation of the bladder capacity in place of the MVV.

Thermal and ultrasonic evaluation of porosity in composite laminates

NASA Technical Reports Server (NTRS)

Johnston, Patrick H.; Winfree, William P.; Long, Edward R., Jr.; Kullerd, Susan M.; Nathan, N.; Partos, Richard D.

1992-01-01

The effects of porosity on damage incurred by low-velocity impact are investigated. Specimens of graphite/epoxy composite were fabricated with various volume fractions of voids. The void fraction was independently determined using optical examination and acid resin digestion methods. Thermal diffusivity and ultrasonic attenuation were measured, and these results were related to the void volume fraction. The relationship between diffusivity and fiber volume fraction was also considered. The slope of the ultrasonic attenuation coefficient was found to increase linearly with void content, and the diffusivity decreased linearly with void volume fraction, after compensation for an approximately linear dependence on the fiber volume fraction.

Characteristics of dust voids in a strongly coupled laboratory dusty plasma

NASA Astrophysics Data System (ADS)

Bailung, Yoshiko; Deka, T.; Boruah, A.; Sharma, S. K.; Pal, A. R.; Chutia, Joyanti; Bailung, H.

2018-05-01

A void is produced in a strongly coupled dusty plasma by inserting a cylindrical pin (˜0.1 mm diameter) into a radiofrequency discharge argon plasma. The pin is biased externally below the plasma potential to generate the dust void. The Debye sheath model is used to obtain the sheath potential profile and hence to estimate the electric field around the pin. The electric field force and the ion drag force on the dust particles are estimated and their balance accounts well for the maintenance of the size of the void. The effects of neutral density as well as dust density on the void size are studied.

Mechanical Stress Effects on Electromigration Voiding in a Meandering Test Stripe

NASA Technical Reports Server (NTRS)

Lowry, L. E.; Tai, B. H.; Mattila, J.; Walsh, L. H.

1993-01-01

Earlier experimental findings concluded that electromigratin voids in these meandering stripe test structures were not randomly distributed and that void nucleation frequenly occurred sub-surface at the metal/thermal oxide interface.

Using voids to unscreen modified gravity

NASA Astrophysics Data System (ADS)

Falck, Bridget; Koyama, Kazuya; Zhao, Gong-Bo; Cautun, Marius

2018-04-01

The Vainshtein mechanism, present in many models of gravity, is very effective at screening dark matter haloes such that the fifth force is negligible and general relativity is recovered within their Vainshtein radii. Vainshtein screening is independent of halo mass and environment, in contrast to e.g. chameleon screening, making it difficult to test. However, our previous studies have found that the dark matter particles in filaments, walls, and voids are not screened by the Vainshtein mechanism. We therefore investigate whether cosmic voids, identified as local density minima using a watershed technique, can be used to test models of gravity that exhibit Vainshtein screening. We measure density, velocity, and screening profiles of stacked voids in cosmological N-body simulations using both dark matter particles and dark matter haloes as tracers of the density field. We find that the voids are completely unscreened, and the tangential velocity and velocity dispersion profiles of stacked voids show a clear deviation from Λ cold dark matter at all radii. Voids have the potential to provide a powerful test of gravity on cosmological scales.

43 CFR 37.4 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... described in this part. (b) Cave means any naturally occurring void, cavity, recess, or system of interconnected passages beneath the surface of the earth or within a cliff or ledge, including any cave resource...

43 CFR 37.4 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... described in this part. (b) Cave means any naturally occurring void, cavity, recess, or system of interconnected passages beneath the surface of the earth or within a cliff or ledge, including any cave resource...

43 CFR 37.4 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... described in this part. (b) Cave means any naturally occurring void, cavity, recess, or system of interconnected passages beneath the surface of the earth or within a cliff or ledge, including any cave resource...

43 CFR 37.4 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-10-01

... described in this part. (b) Cave means any naturally occurring void, cavity, recess, or system of interconnected passages beneath the surface of the earth or within a cliff or ledge, including any cave resource...