Experimental and computational correlation of fracture parameters KIc, JIc, and GIc for unimodular and bimodular graphite components

NASA Astrophysics Data System (ADS)

Bhushan, Awani; Panda, S. K.

2018-05-01

The influence of bimodularity (different stress ∼ strain behaviour in tension and compression) on fracture behaviour of graphite specimens has been studied with fracture toughness (KIc), critical J-integral (JIc) and critical strain energy release rate (GIc) as the characterizing parameter. Bimodularity index (ratio of tensile Young's modulus to compression Young's modulus) of graphite specimens has been obtained from the normalized test data of tensile and compression experimentation. Single edge notch bend (SENB) testing of pre-cracked specimens from the same lot have been carried out as per ASTM standard D7779-11 to determine the peak load and critical fracture parameters KIc, GIc and JIc using digital image correlation technology of crack opening displacements. Weibull weakest link theory has been used to evaluate the mean peak load, Weibull modulus and goodness of fit employing two parameter least square method (LIN2), biased (MLE2-B) and unbiased (MLE2-U) maximum likelihood estimator. The stress dependent elasticity problem of three-dimensional crack progression behaviour for the bimodular graphite components has been solved as an iterative finite element procedure. The crack characterizing parameters critical stress intensity factor and critical strain energy release rate have been estimated with the help of Weibull distribution plot between peak loads versus cumulative probability of failure. Experimental and Computational fracture parameters have been compared qualitatively to describe the significance of bimodularity. The bimodular influence on fracture behaviour of SENB graphite has been reflected on the experimental evaluation of GIc values only, which has been found to be different from the calculated JIc values. Numerical evaluation of bimodular 3D J-integral value is found to be close to the GIc value whereas the unimodular 3D J-value is nearer to the JIc value. The significant difference between the unimodular JIc and bimodular GIc indicates that GIc should be considered as the standard fracture parameter for bimodular brittle specimens.

Critical laboratory values in hemostasis: toward consensus.

PubMed

Lippi, Giuseppe; Adcock, Dorothy; Simundic, Ana-Maria; Tripodi, Armando; Favaloro, Emmanuel J

2017-09-01

The term "critical values" can be defined to entail laboratory test results that significantly lie outside the normal (reference) range and necessitate immediate reporting to safeguard patient health, as well as those displaying a highly and clinically significant variation compared to previous data. The identification and effective communication of "highly pathological" values has engaged the minds of many clinicians, health care and laboratory professionals for decades, since these activities are vital to good laboratory practice. This is especially true in hemostasis, where a timely and efficient communication of critical values strongly impacts patient management. Due to the heterogeneity of available data, this paper is hence aimed to analyze the state of the art and provide an expert opinion about the parameters, measurement units and alert limits pertaining to critical values in hemostasis, thus providing a basic document for future consultation that assists laboratory professionals and clinicians alike. KEY MESSAGES Critical values are laboratory test results significantly lying outside the normal (reference) range and necessitating immediate reporting to safeguard patient health. A broad heterogeneity exists about critical values in hemostasis worldwide. We provide here an expert opinion about the parameters, measurement units and alert limits pertaining to critical values in hemostasis.

Workflow for Criticality Assessment Applied in Biopharmaceutical Process Validation Stage 1.

PubMed

Zahel, Thomas; Marschall, Lukas; Abad, Sandra; Vasilieva, Elena; Maurer, Daniel; Mueller, Eric M; Murphy, Patrick; Natschläger, Thomas; Brocard, Cécile; Reinisch, Daniela; Sagmeister, Patrick; Herwig, Christoph

2017-10-12

Identification of critical process parameters that impact product quality is a central task during regulatory requested process validation. Commonly, this is done via design of experiments and identification of parameters significantly impacting product quality (rejection of the null hypothesis that the effect equals 0). However, parameters which show a large uncertainty and might result in an undesirable product quality limit critical to the product, may be missed. This might occur during the evaluation of experiments since residual/un-modelled variance in the experiments is larger than expected a priori. Estimation of such a risk is the task of the presented novel retrospective power analysis permutation test. This is evaluated using a data set for two unit operations established during characterization of a biopharmaceutical process in industry. The results show that, for one unit operation, the observed variance in the experiments is much larger than expected a priori, resulting in low power levels for all non-significant parameters. Moreover, we present a workflow of how to mitigate the risk associated with overlooked parameter effects. This enables a statistically sound identification of critical process parameters. The developed workflow will substantially support industry in delivering constant product quality, reduce process variance and increase patient safety.

Improving the quality of parameter estimates obtained from slug tests

USGS Publications Warehouse

Butler, J.J.; McElwee, C.D.; Liu, W.

1996-01-01

The slug test is one of the most commonly used field methods for obtaining in situ estimates of hydraulic conductivity. Despite its prevalence, this method has received criticism from many quarters in the ground-water community. This criticism emphasizes the poor quality of the estimated parameters, a condition that is primarily a product of the somewhat casual approach that is often employed in slug tests. Recently, the Kansas Geological Survey (KGS) has pursued research directed it improving methods for the performance and analysis of slug tests. Based on extensive theoretical and field research, a series of guidelines have been proposed that should enable the quality of parameter estimates to be improved. The most significant of these guidelines are: (1) three or more slug tests should be performed at each well during a given test period; (2) two or more different initial displacements (Ho) should be used at each well during a test period; (3) the method used to initiate a test should enable the slug to be introduced in a near-instantaneous manner and should allow a good estimate of Ho to be obtained; (4) data-acquisition equipment that enables a large quantity of high quality data to be collected should be employed; (5) if an estimate of the storage parameter is needed, an observation well other than the test well should be employed; (6) the method chosen for analysis of the slug-test data should be appropriate for site conditions; (7) use of pre- and post-analysis plots should be an integral component of the analysis procedure, and (8) appropriate well construction parameters should be employed. Data from slug tests performed at a number of KGS field sites demonstrate the importance of these guidelines.

Stress-Dilatancy of Cambria Sand for Triaxial Tests at High Pressures

NASA Astrophysics Data System (ADS)

Szypcio, Zenon

2017-12-01

In this paper, the stress-dilatancy relationship of Cambria sand for drained triaxial compression and extension tests at high stress level is investigated. The stress dilatancy relationship is obtained by use of frictional state theory and experimental tests data published in literature. It is shown that stress-dilatancy relationship is bilinear, described by three parameters of frictional state theory: critical frictional angle and two other parameters. It is accepted that critical friction angle is independent of confining pressure. The two additional parameters are strongly dependent on confining pressure and different for initial and advanced stages. The point at which the values of these parameters change is termed as Transformation Shear Point. This point is not simply visible either in stress ratio-strain or the volume strain-shear strain relationship which are traditionally shown in soil mechanics papers. Transformation Shear Point is very characteristic in stress ratio-plastic dilatancy plane. Thus, stress ratio- plastic dilatancy is very important for describing stress-strain behaviour of soils. The relationship shown in the paper can be used in soil modelling in the future.

Quality-by-design (QbD): effects of testing parameters and formulation variables on the segregation tendency of pharmaceutical powder measured by the ASTM D 6940-04 segregation tester.

PubMed

Xie, Lin; Wu, Huiquan; Shen, Meiyu; Augsburger, Larry L; Lyon, Robbe C; Khan, Mansoor A; Hussain, Ajaz S; Hoag, Stephen W

2008-10-01

The objective of this study was to examine the effects of testing parameters and formulation variables on the segregation tendency of pharmaceutical powders measured by the ASTM D 6940-04 segregation tester using design of experiments (DOE) approaches. The test blends consisted of 4% aspirin (ASP) and 96% microcrystalline cellulose (MCC) with and without magnesium stearate (MgS). The segregation tendency of a blend was determined by measuring the last/first (L/F) ratio, the ratio of aspirin concentrations between the first and last samples discharged from the tester. A 2(2) factorial design was used to determine the effects of measurement parameters [amount of material loaded (W), number of segregation cycles] with number of replicates 6. ANOVA showed that W was a critical parameter for segregation testing. The L/F value deviated further from 1 (greater segregation tendency) with increasing W. A 2(3) full factorial design was used to assess the effects of formulation variables: grade of ASP (unmilled, milled), grade of MCC, and amount of lubricant, MgS. MLR and ANOVA showed that the grade of ASP was the main effect contributing to segregation tendency. Principal Component Regression Analysis established a correlation between L/F and the physical properties of the blend related to ASP and MCC, the ASP/MCC particle size ratio (PSR) and powder cohesion. The physical properties of the blend related to density and flow were not influenced by the grade of ASP and were not related to the segregation tendency of the blend. The direct relationship between L/F and PSR was determined by univariate analysis. Segregation tendency increased as the ASP to MCC particle size increased. This study highlighted critical test parameters for segregation testing and identified critical physical properties of the blends that influence segregation tendency. (c) 2008 Wiley-Liss, Inc. and the American Pharmacists Association

An effective combined environment test facility

NASA Technical Reports Server (NTRS)

Deitch, A.

1980-01-01

A critical missile component required operational verification while subjected to combined environments within and beyond flight parameters. The testing schedule necessitated the design and fabrication of a test facility in order to provide the specified temperatures combined with humidity, altitude and vibration.

Determination of fiber-matrix interface failure parameters from off-axis tests

NASA Technical Reports Server (NTRS)

Naik, Rajiv A.; Crews, John H., Jr.

1993-01-01

Critical fiber-matrix (FM) interface strength parameters were determined using a micromechanics-based approach together with failure data from off-axis tension (OAT) tests. The ply stresses at failure for a range of off-axis angles were used as input to a micromechanics analysis that was performed using the personal computer-based MICSTRAN code. FM interface stresses at the failure loads were calculated for both the square and the diamond array models. A simple procedure was developed to determine which array had the more severe FM interface stresses and the location of these critical stresses on the interface. For the cases analyzed, critical FM interface stresses were found to occur with the square array model and were located at a point where adjacent fibers were closest together. The critical FM interface stresses were used together with the Tsai-Wu failure theory to determine a failure criterion for the FM interface. This criterion was then used to predict the onset of ply cracking in angle-ply laminates for a range of laminate angles. Predictions for the onset of ply cracking in angle-ply laminates agreed with the test data trends.

Acoustic emission monitoring and critical failure identification of bridge cable damage

NASA Astrophysics Data System (ADS)

Li, Dongsheng; Ou, Jinping

2008-03-01

Acoustic emission (AE) characteristic parameters of bridge cable damage were obtained on tensile test. The testing results show that the AE parameter analysis method based on correlation figure of count, energy, duration time, amplitude and time can express the whole damage course, and can correctly judge the signal difference of broken wire and unbroken wire. It found the bridge cable AE characteristics aren't apparent before yield deformation, however they are increasing after yield deformation, at the time of breaking, and they reach to maximum. At last, the bridge cable damage evolution law is studied applying the AE characteristic parameter time series fractal theory. In the initial and middle stage of loading, the AE fractal value of bridge cable is unsteady. The fractal value reaches to the minimum at the critical point of failure. According to this changing law, it is approached how to make dynamic assessment and estimation of damage degrees.

Benchmark Testing of a New 56Fe Evaluation for Criticality Safety Applications

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

Leal, Luiz C; Ivanov, E.

2015-01-01

The SAMMY code was used to evaluate resonance parameters of the 56Fe cross section in the resolved resonance energy range of 0–2 MeV using transmission data, capture, elastic, inelastic, and double differential elastic cross sections. The resonance analysis was performed with the code SAMMY that fits R-matrix resonance parameters using the generalized least-squares technique (Bayes’ theory). The evaluation yielded a set of resonance parameters that reproduced the experimental data very well, along with a resonance parameter covariance matrix for data uncertainty calculations. Benchmark tests were conducted to assess the evaluation performance in benchmark calculations.

Hot-crack test for aluminium alloys welds using TIG process

NASA Astrophysics Data System (ADS)

Niel, A.; Deschaux-Beaume, F.; Bordreuil, C.; Fras, G.

2010-06-01

Hot cracking is a critical defect frequently observed during welding of aluminium alloys. In order to better understand the interaction between cracking phenomenon, process parameters, mechanical factors and microstructures resulting from solidification after welding, an original hot-cracking test during welding is developed. According to in-situ observations and post mortem analyses, hot cracking mechanisms are investigated, taking into account the interaction between microstructural parameters, depending on the thermal cycles, and mechanical parameters, depending on geometry and clamping conditions of the samples and on the thermal field on the sample. Finally, a process map indicating the limit between cracking and non-cracking zones according to welding parameters is presented.

Using discharge data to reduce structural deficits in a hydrological model with a Bayesian inference approach and the implications for the prediction of critical source areas

NASA Astrophysics Data System (ADS)

Frey, M. P.; Stamm, C.; Schneider, M. K.; Reichert, P.

2011-12-01

A distributed hydrological model was used to simulate the distribution of fast runoff formation as a proxy for critical source areas for herbicide pollution in a small agricultural catchment in Switzerland. We tested to what degree predictions based on prior knowledge without local measurements could be improved upon relying on observed discharge. This learning process consisted of five steps: For the prior prediction (step 1), knowledge of the model parameters was coarse and predictions were fairly uncertain. In the second step, discharge data were used to update the prior parameter distribution. Effects of uncertainty in input data and model structure were accounted for by an autoregressive error model. This step decreased the width of the marginal distributions of parameters describing the lower boundary (percolation rates) but hardly affected soil hydraulic parameters. Residual analysis (step 3) revealed model structure deficits. We modified the model, and in the subsequent Bayesian updating (step 4) the widths of the posterior marginal distributions were reduced for most parameters compared to those of the prior. This incremental procedure led to a strong reduction in the uncertainty of the spatial prediction. Thus, despite only using spatially integrated data (discharge), the spatially distributed effect of the improved model structure can be expected to improve the spatially distributed predictions also. The fifth step consisted of a test with independent spatial data on herbicide losses and revealed ambiguous results. The comparison depended critically on the ratio of event to preevent water that was discharged. This ratio cannot be estimated from hydrological data only. The results demonstrate that the value of local data is strongly dependent on a correct model structure. An iterative procedure of Bayesian updating, model testing, and model modification is suggested.

Structural dynamic analysis of the Space Shuttle Main Engine

NASA Technical Reports Server (NTRS)

Scott, L. P.; Jamison, G. T.; Mccutcheon, W. A.; Price, J. M.

1981-01-01

This structural dynamic analysis supports development of the SSME by evaluating components subjected to critical dynamic loads, identifying significant parameters, and evaluating solution methods. Engine operating parameters at both rated and full power levels are considered. Detailed structural dynamic analyses of operationally critical and life limited components support the assessment of engine design modifications and environmental changes. Engine system test results are utilized to verify analytic model simulations. The SSME main chamber injector assembly is an assembly of 600 injector elements which are called LOX posts. The overall LOX post analysis procedure is shown.

A Modified Cramer-von Mises and Anderson-Darling Test for the Weibull Distribution with Unknown Location and Scale Parameters.

DTIC Science & Technology

1981-12-01

preventing the generation of 16 6 negative location estimators. Because of the invariant pro- perty of the EDF statistics, this transformation will...likelihood. If the parameter estimation method developed by Harter and Moore is used, care must be taken to prevent the location estimators from being...vs A 2 Critical Values, Level-.Ol, n-30 128 , 0 6N m m • w - APPENDIX E Computer Prgrams 129 Program to Calculate the Cramer-von Mises Critical Values

Using Scatterplots to Teach the Critical Power Concept

ERIC Educational Resources Information Center

Pettitt, Robert W.

2012-01-01

The critical power (CP) concept has received renewed attention and excitement in the academic community. The CP concept was originally conceived as a model derived from a series of exhaustive, constant-load, exercise bouts. All-out exercise testing has made quantification of the parameters for the two-component model easier to arrive at, which may…

Boiling Visualization and Critical Heat Flux Phenomena In Narrow Rectangular Gap

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

J. J. Kim; Y. H. Kim; S. J. Kim

2004-12-01

An experimental study was performed to investifate the pool boling critical hear flux (CHF) on one-dimensional inclined rectangular channels with narrow gaps by changing the orientation of a copper test heater assembly. In a pool of saturated water at atmospheric pressure, the test parameters include the gap sizes of 1,2,5, and 10 mm, andthe surface orientation angles from the downward facing position (180 degrees) to the vertical position (90 degress) respectively.

7 CFR 90.103 - [Reserved

Code of Federal Regulations, 2010 CFR

2010-01-01

... most recent years: (a) Prepared solution standardizations; (b) Recovery studies by known analyte... check sample testing or collaborative studies; (g) Daily critical parameter checks of equipment, such as...

7 CFR 90.103 - [Reserved

Code of Federal Regulations, 2011 CFR

2011-01-01

... most recent years: (a) Prepared solution standardizations; (b) Recovery studies by known analyte... check sample testing or collaborative studies; (g) Daily critical parameter checks of equipment, such as...

The fundamentals of biotribology and its application to spine arthroplasty

PubMed Central

Harper, Megan L.; Dooris, Andrew; Paré, Philippe E.

2009-01-01

The biological effect of wear of articulating surfaces is a continued concern with large joint replacements and, likewise, of interest for total disc replacements. There are a number of important biotribological testing parameters that can greatly affect the outcome of a wear study in addition to the implant design and material selection. The current ASTM and ISO wear testing standards/guides for spine arthroplasty leave many choices as testing parameters. These factors include but are not limited to the sequence of kinematics and load, phasing, type of lubricant, and specimen preparation (sterilization and artificial aging). The spinal community should critically assess wear studies and be cognizant of the influence of the selected parameters on the test results. PMID:25802638

Total dose bias dependency and ELDRS effects in bipolar linear devices

NASA Technical Reports Server (NTRS)

Yui, C. C.; McClure, S. S.; Rex, B. G.; Lehman, J. M.; Minto, T. D.; Wiedeman, M.

2002-01-01

Total dose tests of several bipolar linear devices show sensitivity to both dose rate and bias during exposure. All devices exhibited Enhanced Low Dose Rate Sensitivity (ELDRS). An accelerated ELDRS test method for three different devices demonstrate results similar to tests at low dose rate. Behavior and critical parameters from these tests are compared and discussed.

Technical and investigative support for high density digital satellite recording systems

NASA Technical Reports Server (NTRS)

Schultz, R. A.

1983-01-01

Recent results of dropout measurements and defect analysis conducted on one reel of Ampex 721 which was submitted for evaluation by the manufacturer are described. The results or status of other tape evaluation activities are also reviewed. Several changes in test interpretations and applications are recommended. In some cases, deficiencies in test methods or equipment became apparent during continued work on this project and other IITRI tape evaluation projects. Techniques and equipment for future tasks such as tape qualification are also recommended and discussed. Project effort and expenditures were kept at a relatively low level. This rate provided added development time and experience with the IITRI Dropout Measurement System, which is approaching its potential as a computer based dropout analysis tool. Another benefit is the expanded data base on critical parameters that can be achieved from tests on different tape types and lots as they become available. More consideration and effort was directed toward identification of critical parameters, development of meaningful repeatable test procedures, and tape procurement strategy.

Critical Science Instrument Alignment of the James Webb Space Telescope (JWST) Integrated Science Instrument Module (ISIM)

NASA Technical Reports Server (NTRS)

Rohrbach, Scott O.; Kubalak, David A.; Gracey, Renee M.; Sabatke, Derek S.; Howard, Joseph M.; Telfer, Randal C.; Zielinski, Thomas P.

2016-01-01

This paper describes the critical instrument alignment terms associated with the six-degree of freedom alignment of each the Science Instrument (SI) in the James Webb Space Telescope (JWST), including focus, pupil shear, pupil clocking, and boresight. We present the test methods used during cryogenic-vacuum tests to directly measure the performance of each parameter, the requirements levied on each, and the impact of any violations of these requirements at the instrument and Observatory level.

Space Qualification Test of a-Silicon Solar Cell Modules

NASA Technical Reports Server (NTRS)

Kim, Q.; Lawton, R. A.; Manion, S. J.; Okuno, J. O.; Ruiz, R. P.; Vu, D. T.; Vu, D. T.; Kayali, S. A.; Jeffrey, F. R.

2004-01-01

The basic requirements of solar cell modules for space applications are generally described in MIL-S-83576 for the specific needs of the USAF. However, the specifications of solar cells intended for use on space terrestrial applications are not well defined. Therefore, this qualifications test effort was concentrated on critical areas specific to the microseismometer probe which is intended to be included in the Mars microprobe programs. Parameters that were evaluated included performance dependence on: illuminating angles, terrestrial temperatures, lifetime, as well as impact landing conditions. Our qualification efforts were limited to these most critical areas of concern. Most of the tested solar cell modules have met the requirements of the program except the impact tests. Surprisingly, one of the two single PIN 2 x 1 amorphous solar cell modules continued to function even after the 80000G impact tests. The output power parameters, Pout, FF, Isc and Voc, of the single PIN amorphous solar cell module were found to be 3.14 mW, 0.40, 9.98 mA and 0.78 V, respectively. These parameters are good enough to consider the solar module as a possible power source for the microprobe seismometer. Some recommendations were made to improve the usefulness of the amorphous silicon solar cell modules in space terrestrial applications, based on the results obtained from the intensive short term lab test effort.

European tests on materials outgassing

NASA Technical Reports Server (NTRS)

Zwaal, A.

1977-01-01

With a view to international coordination of spacecraft materials, a number of European firms and institutes performed outgassing tests on identical materials at 125 C in high vacuum. The outgassing data obtained with the different types of equipment is presented and both the results and the critical parameters are discussed.

40 CFR 85.2120 - Maintenance and submittal of records.

Code of Federal Regulations, 2010 CFR

2010-07-01

... testing program, including all production part sampling techniques used to verify compliance of the... subsequent analyses of that data; (7) A description of all the methodology, analysis, testing and/or sampling techniques used to ascertain the emission critical parameter specifications of the originial equipment part...

[Team approaches to critical bleeding (massive bleeding and transfusion) - chairmen's introductory remarks. Questionnaire survey on current status of hospital clinical laboratories evaluating critical hemorrhage].

PubMed

Kino, Shuichi; Suwabe, Akira

2014-12-01

In 2007, "the Guidelines for Actions against Intraoperative Critical Hemorrhage" were established by the Japanese Society of Anaesthesiologists and the Japanese Society of Blood transfusion and Cell Therapy. The documentation of in-hospital procedures for critical hemorrhage, especially about how to select RBC units, has widely standardized hospital practice. Patients with intraoperative critical hemorrhage sometimes suffer from massive blood loss. In this situation, some patients develop coagulopathy. To treat them, we need to evaluate their coagulation status based on laboratory test results. So, we performed a nationwide questionnaire survey on the current status of hospital clinical laboratories evaluating critical hemorrhage. From the results of this survey, it was recommended that central hospital laboratories should try to reduce the turn-around time required to test for coagulation parameters as much as possible for appropriate substitution therapy. (Review).

An Examination of Two Procedures for Identifying Consequential Item Parameter Drift

ERIC Educational Resources Information Center

Wells, Craig S.; Hambleton, Ronald K.; Kirkpatrick, Robert; Meng, Yu

2014-01-01

The purpose of the present study was to develop and evaluate two procedures flagging consequential item parameter drift (IPD) in an operational testing program. The first procedure was based on flagging items that exhibit a meaningful magnitude of IPD using a critical value that was defined to represent barely tolerable IPD. The second procedure…

Utility of transthoracic echocardiography (TTE) in assessing fluid responsiveness in critically ill patients - a challenge for the bedside sonographer.

PubMed

Mielnicki, Wojciech; Dyla, Agnieszka; Zawada, Tomasz

2016-12-05

Transthoracic echocardiography (TTE) has become one of the most important diagnostic tools in the treatment of critically ill patients. It allows clinicians to recognise potentially reversible life-threatening situations and is also very effective in the monitoring of the fluid status of patients, slowly substituting invasive methods in the intensive care unit. Hemodynamic assessment is based on a few static and dynamic parameters. Dynamic parameters change during the respiratory cycle in mechanical ventilation and the level of this change directly corresponds to fluid responsiveness. Most of the parameters cannot be used in spontaneously breathing patients. For these patients the most important test is passive leg raising, which is a good substitute for fluid bolus. Although TTE is very useful in the critical care setting, we should not forget the important limitations, not only technical ones but also caused by the critical illness itself. Unfortunately, this method does not allow continuous monitoring and every change in the patient's condition requires repeated examination.

40 CFR 53.62 - Test procedure: Full wind tunnel test.

Code of Federal Regulations, 2010 CFR

2010-07-01

... distributions to provide six estimates of measured mass concentration. Critical parameters for these idealized... (expressed as a percentage) of the mass concentration of particles of a specific size reaching the sampler filter or filters to the mass concentration of particles of the same size approaching the sampler. (c...

Systematic parameter estimation and sensitivity analysis using a multidimensional PEMFC model coupled with DAKOTA.

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

Wang, Chao Yang; Luo, Gang; Jiang, Fangming

2010-05-01

Current computational models for proton exchange membrane fuel cells (PEMFCs) include a large number of parameters such as boundary conditions, material properties, and numerous parameters used in sub-models for membrane transport, two-phase flow and electrochemistry. In order to successfully use a computational PEMFC model in design and optimization, it is important to identify critical parameters under a wide variety of operating conditions, such as relative humidity, current load, temperature, etc. Moreover, when experimental data is available in the form of polarization curves or local distribution of current and reactant/product species (e.g., O2, H2O concentrations), critical parameters can be estimated inmore » order to enable the model to better fit the data. Sensitivity analysis and parameter estimation are typically performed using manual adjustment of parameters, which is also common in parameter studies. We present work to demonstrate a systematic approach based on using a widely available toolkit developed at Sandia called DAKOTA that supports many kinds of design studies, such as sensitivity analysis as well as optimization and uncertainty quantification. In the present work, we couple a multidimensional PEMFC model (which is being developed, tested and later validated in a joint effort by a team from Penn State Univ. and Sandia National Laboratories) with DAKOTA through the mapping of model parameters to system responses. Using this interface, we demonstrate the efficiency of performing simple parameter studies as well as identifying critical parameters using sensitivity analysis. Finally, we show examples of optimization and parameter estimation using the automated capability in DAKOTA.« less

A Study of Cavitation Erosion

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

Hiromu Isaka; Masatsugu Tsutsumi; Tadashi Shiraishi

2002-07-01

The authors performed experimental study for the purpose of the following two items from a viewpoint of cavitation erosion of a cylindrical orifice in view of a problem at the letdown orifice in PWR (Pressurized Water Reactor). 1. To get the critical cavitation parameter of the cylindrical orifice to establish the design criteria for prevention of cavitation erosion, and 2. to ascertain the erosion rate in such an eventuality that the cavitation erosion occurs with the orifice made of stainless steel with precipitation hardening (17-4-Cu hardening type stainless steel), so that we confirm the appropriateness of the design criteria. Regardingmore » the 1. item, we carried out the cavitation tests to get the critical cavitation parameters inside and downstream of the orifice. The test results showed that the cavitation parameter at inception is independent of the length or the diameter of the orifice. Moreover, the design criteria of cavitation erosion of cylindrical orifices have been established. Regarding the 2. item, we tested the erosion rate under high-pressure conditions. The cavitation erosion actually occurred in the cylindrical orifice at the tests that was strongly resemble to the erosion occurred at the plant. It will be seldom to reproduce resemble cavitation erosion in a cylindrical orifice with the hard material used at plants. We could establish the criteria for preventing the cavitation erosion from the test results. (authors)« less

Influence of structural parameters on the tendency of VVER-1000 reactor pressure vessel steel to temper embrittlement

NASA Astrophysics Data System (ADS)

Gurovich, B.; Kuleshova, E.; Zabusov, O.; Fedotova, S.; Frolov, A.; Saltykov, M.; Maltsev, D.

2013-04-01

In this paper the influence of structural parameters on the tendency of steels to reversible temper embrittlement was studied for assessment of performance properties of reactor pressure vessel steels with extended service life. It is shown that the growth of prior austenite grain size leads to an increase of the critical embrittlement temperature in the initial state. An embrittlement heat treatment at the temperature of maximum manifestation of temper embrittlement (480 °C) shifts critical embrittlement temperature to higher values due to the increase of the phosphorus concentration on grain boundaries. There is a correlation between phosphorus concentration on boundaries of primary austenite grains and the share of brittle intergranular fracture (that, in turn, depends on impact test temperature) in the fracture surfaces of the tested Charpy specimens.

Physical characterization and modeling of chitosan/peg blends for injectable scaffolds.

PubMed

Lima, Daniel B; Almeida, Renata D; Pasquali, Matheus; Borges, Sílvia P; Fook, Marcus L; Lisboa, Hugo M

2018-06-01

Injectable scaffolds find many applications on the biomedical field due to several advantages on preformed scaffolds such as being able to fill any defect can be used in minimal invasion surgeries and are ready to use products. The most critical parameter for an injectable scaffold usage is its injectability, which can be related with rheological properties. Therefore, the objective of the present work was to increase knowledge about the critical parameters influencing injectability of biopolymers used for injectable scaffolds. Rheological and mechanical properties of a biopolymer blend in combination with injectability tests for a given design space controlled by the concentrations of both polymers and temperatures was made. Then those results were modeled to better understand the impact of parameters on injectability. The biopolymer blend chosen was Chitosan physically blended with Poly(ethylene glycol) where variations of both polymer concentrations and molecular weights were tested. Rheological and mechanical properties of all samples were determined, together with the injection force using a compression test at different injection conditions. All solutions were clear and transparent suggesting perfect miscibility. Rheological results were modeled using Ostwald-Waelle law and revealed a shear thinning pseudo-plastic solution at any composition and temperature, being chitosan concentration the most influencing variable. Compression tests results revealed mean injection forces ranging from 9.9 ± 0.06N to 29.9 ± 0.65N and it was possible to accurately estimate those results. Simulations revealed draw speed as the most influencing parameter. Cell viability tests revealed a non-cytotoxic biopolymer blend. Copyright © 2018 Elsevier Ltd. All rights reserved.

Benchmark Calibration Tests Completed for Stirling Convertor Heater Head Life Assessment

NASA Technical Reports Server (NTRS)

Krause, David L.; Halford, Gary R.; Bowman, Randy R.

2005-01-01

A major phase of benchmark testing has been completed at the NASA Glenn Research Center (http://www.nasa.gov/glenn/), where a critical component of the Stirling Radioisotope Generator (SRG) is undergoing extensive experimentation to aid the development of an analytical life-prediction methodology. Two special-purpose test rigs subjected SRG heater-head pressure-vessel test articles to accelerated creep conditions, using the standard design temperatures to stay within the wall material s operating creep-response regime, but increasing wall stresses up to 7 times over the design point. This resulted in well-controlled "ballooning" of the heater-head hot end. The test plan was developed to provide critical input to analytical parameters in a reasonable period of time.

Multiaxial Fatigue Life Prediction Based on Nonlinear Continuum Damage Mechanics and Critical Plane Method

NASA Astrophysics Data System (ADS)

Wu, Z. R.; Li, X.; Fang, L.; Song, Y. D.

2018-04-01

A new multiaxial fatigue life prediction model has been proposed in this paper. The concepts of nonlinear continuum damage mechanics and critical plane criteria were incorporated in the proposed model. The shear strain-based damage control parameter was chosen to account for multiaxial fatigue damage under constant amplitude loading. Fatigue tests were conducted on nickel-based superalloy GH4169 tubular specimens at the temperature of 400 °C under proportional and nonproportional loading. The proposed method was checked against the multiaxial fatigue test data of GH4169. Most of prediction results are within a factor of two scatter band of the test results.

Goodness-of-Fit Tests for Generalized Normal Distribution for Use in Hydrological Frequency Analysis

NASA Astrophysics Data System (ADS)

Das, Samiran

2018-04-01

The use of three-parameter generalized normal (GNO) as a hydrological frequency distribution is well recognized, but its application is limited due to unavailability of popular goodness-of-fit (GOF) test statistics. This study develops popular empirical distribution function (EDF)-based test statistics to investigate the goodness-of-fit of the GNO distribution. The focus is on the case most relevant to the hydrologist, namely, that in which the parameter values are unidentified and estimated from a sample using the method of L-moments. The widely used EDF tests such as Kolmogorov-Smirnov, Cramer von Mises, and Anderson-Darling (AD) are considered in this study. A modified version of AD, namely, the Modified Anderson-Darling (MAD) test, is also considered and its performance is assessed against other EDF tests using a power study that incorporates six specific Wakeby distributions (WA-1, WA-2, WA-3, WA-4, WA-5, and WA-6) as the alternative distributions. The critical values of the proposed test statistics are approximated using Monte Carlo techniques and are summarized in chart and regression equation form to show the dependence of shape parameter and sample size. The performance results obtained from the power study suggest that the AD and a variant of the MAD (MAD-L) are the most powerful tests. Finally, the study performs case studies involving annual maximum flow data of selected gauged sites from Irish and US catchments to show the application of the derived critical values and recommends further assessments to be carried out on flow data sets of rivers with various hydrological regimes.

A Review of the Effects on IRT Item Parameter Estimates with a Focus on Misbehaving Common Items in Test Equating

PubMed Central

Michaelides, Michalis P.

2010-01-01

Many studies have investigated the topic of change or drift in item parameter estimates in the context of item response theory (IRT). Content effects, such as instructional variation and curricular emphasis, as well as context effects, such as the wording, position, or exposure of an item have been found to impact item parameter estimates. The issue becomes more critical when items with estimates exhibiting differential behavior across test administrations are used as common for deriving equating transformations. This paper reviews the types of effects on IRT item parameter estimates and focuses on the impact of misbehaving or aberrant common items on equating transformations. Implications relating to test validity and the judgmental nature of the decision to keep or discard aberrant common items are discussed, with recommendations for future research into more informed and formal ways of dealing with misbehaving common items. PMID:21833230

A Review of the Effects on IRT Item Parameter Estimates with a Focus on Misbehaving Common Items in Test Equating.

PubMed

Michaelides, Michalis P

2010-01-01

Many studies have investigated the topic of change or drift in item parameter estimates in the context of item response theory (IRT). Content effects, such as instructional variation and curricular emphasis, as well as context effects, such as the wording, position, or exposure of an item have been found to impact item parameter estimates. The issue becomes more critical when items with estimates exhibiting differential behavior across test administrations are used as common for deriving equating transformations. This paper reviews the types of effects on IRT item parameter estimates and focuses on the impact of misbehaving or aberrant common items on equating transformations. Implications relating to test validity and the judgmental nature of the decision to keep or discard aberrant common items are discussed, with recommendations for future research into more informed and formal ways of dealing with misbehaving common items.

Strain Modal Analysis of Small and Light Pipes Using Distributed Fibre Bragg Grating Sensors

PubMed Central

Huang, Jun; Zhou, Zude; Zhang, Lin; Chen, Juntao; Ji, Chunqian; Pham, Duc Truong

2016-01-01

Vibration fatigue failure is a critical problem of hydraulic pipes under severe working conditions. Strain modal testing of small and light pipes is a good option for dynamic characteristic evaluation, structural health monitoring and damage identification. Unique features such as small size, light weight, and high multiplexing capability enable Fibre Bragg Grating (FBG) sensors to measure structural dynamic responses where sensor size and placement are critical. In this paper, experimental strain modal analysis of pipes using distributed FBG sensors ispresented. Strain modal analysis and parameter identification methods are introduced. Experimental strain modal testing and finite element analysis for a cantilever pipe have been carried out. The analysis results indicate that the natural frequencies and strain mode shapes of the tested pipe acquired by FBG sensors are in good agreement with the results obtained by a reference accelerometer and simulation outputs. The strain modal parameters of a hydraulic pipe were obtained by the proposed strain modal testing method. FBG sensors have been shown to be useful in the experimental strain modal analysis of small and light pipes in mechanical, aeronautic and aerospace applications. PMID:27681728

Critical phenomena at the threshold of immediate merger in binary black hole systems: The extreme mass ratio case

NASA Astrophysics Data System (ADS)

Gundlach, Carsten; Akcay, Sarp; Barack, Leor; Nagar, Alessandro

2012-10-01

In numerical simulations of black hole binaries, Pretorius and Khurana [Classical Quantum Gravity 24, S83 (2007)CQGRDG0264-938110.1088/0264-9381/24/12/S07] have observed critical behavior at the threshold between scattering and immediate merger. The number of orbits scales as n≃-γln⁡|p-p*| along any one-parameter family of initial data such that the threshold is at p=p*. Hence, they conjecture that in ultrarelativistic collisions almost all the kinetic energy can be converted into gravitational waves if the impact parameter is fine-tuned to the threshold. As a toy model for the binary, they consider the geodesic motion of a test particle in a Kerr black hole spacetime, where the unstable circular geodesics play the role of critical solutions, and calculate the critical exponent γ. Here, we incorporate radiation reaction into this model using the self-force approximation. The critical solution now evolves adiabatically along a sequence of unstable circular geodesic orbits under the effect of the self-force. We confirm that almost all the initial energy and angular momentum are radiated on the critical solution. Our calculation suggests that, even for infinite initial energy, this happens over a finite number of orbits given by n∞≃0.41/η, where η is the (small) mass ratio. We derive expressions for the time spent on the critical solution, number of orbits and radiated energy as functions of the initial energy and impact parameter.

Effect of Common Cryoprotectants on Critical Warming Rates and Ice Formation in Aqueous Solutions

PubMed Central

Hopkins, Jesse B.; Badeau, Ryan; Warkentin, Matthew; Thorne, Robert E.

2012-01-01

Ice formation on warming is of comparable or greater importance to ice formation on cooling in determining survival of cryopreserved samples. Critical warming rates required for ice-free warming of vitrified aqueous solutions of glycerol, dimethyl sulfoxide, ethylene glycol, polyethylene glycol 200 and sucrose have been measured for warming rates of order 10 to 104 K/s. Critical warming rates are typically one to three orders of magnitude larger than critical cooling rates. Warming rates vary strongly with cooling rates, perhaps due to the presence of small ice fractions in nominally vitrified samples. Critical warming and cooling rate data spanning orders of magnitude in rates provide rigorous tests of ice nucleation and growth models and their assumed input parameters. Current models with current best estimates for input parameters provide a reasonable account of critical warming rates for glycerol solutions at high concentrations/low rates, but overestimate both critical warming and cooling rates by orders of magnitude at lower concentrations and larger rates. In vitrification protocols, minimizing concentrations of potentially damaging cryoprotectants while minimizing ice formation will require ultrafast warming rates, as well as fast cooling rates to minimize the required warming rates. PMID:22728046

Hierarchical multistage MCMC follow-up of continuous gravitational wave candidates

NASA Astrophysics Data System (ADS)

Ashton, G.; Prix, R.

2018-05-01

Leveraging Markov chain Monte Carlo optimization of the F statistic, we introduce a method for the hierarchical follow-up of continuous gravitational wave candidates identified by wide-parameter space semicoherent searches. We demonstrate parameter estimation for continuous wave sources and develop a framework and tools to understand and control the effective size of the parameter space, critical to the success of the method. Monte Carlo tests of simulated signals in noise demonstrate that this method is close to the theoretical optimal performance.

Statistical Validation of Surrogate Endpoints: Another Look at the Prentice Criterion and Other Criteria.

PubMed

Saraf, Sanatan; Mathew, Thomas; Roy, Anindya

2015-01-01

For the statistical validation of surrogate endpoints, an alternative formulation is proposed for testing Prentice's fourth criterion, under a bivariate normal model. In such a setup, the criterion involves inference concerning an appropriate regression parameter, and the criterion holds if the regression parameter is zero. Testing such a null hypothesis has been criticized in the literature since it can only be used to reject a poor surrogate, and not to validate a good surrogate. In order to circumvent this, an equivalence hypothesis is formulated for the regression parameter, namely the hypothesis that the parameter is equivalent to zero. Such an equivalence hypothesis is formulated as an alternative hypothesis, so that the surrogate endpoint is statistically validated when the null hypothesis is rejected. Confidence intervals for the regression parameter and tests for the equivalence hypothesis are proposed using bootstrap methods and small sample asymptotics, and their performances are numerically evaluated and recommendations are made. The choice of the equivalence margin is a regulatory issue that needs to be addressed. The proposed equivalence testing formulation is also adopted for other parameters that have been proposed in the literature on surrogate endpoint validation, namely, the relative effect and proportion explained.

Quality by control: Towards model predictive control of mammalian cell culture bioprocesses.

PubMed

Sommeregger, Wolfgang; Sissolak, Bernhard; Kandra, Kulwant; von Stosch, Moritz; Mayer, Martin; Striedner, Gerald

2017-07-01

The industrial production of complex biopharmaceuticals using recombinant mammalian cell lines is still mainly built on a quality by testing approach, which is represented by fixed process conditions and extensive testing of the end-product. In 2004 the FDA launched the process analytical technology initiative, aiming to guide the industry towards advanced process monitoring and better understanding of how critical process parameters affect the critical quality attributes. Implementation of process analytical technology into the bio-production process enables moving from the quality by testing to a more flexible quality by design approach. The application of advanced sensor systems in combination with mathematical modelling techniques offers enhanced process understanding, allows on-line prediction of critical quality attributes and subsequently real-time product quality control. In this review opportunities and unsolved issues on the road to a successful quality by design and dynamic control implementation are discussed. A major focus is directed on the preconditions for the application of model predictive control for mammalian cell culture bioprocesses. Design of experiments providing information about the process dynamics upon parameter change, dynamic process models, on-line process state predictions and powerful software environments seem to be a prerequisite for quality by control realization. © 2017 The Authors. Biotechnology Journal published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Developing a quality by design approach to model tablet dissolution testing: an industrial case study.

PubMed

Yekpe, Ketsia; Abatzoglou, Nicolas; Bataille, Bernard; Gosselin, Ryan; Sharkawi, Tahmer; Simard, Jean-Sébastien; Cournoyer, Antoine

2018-07-01

This study applied the concept of Quality by Design (QbD) to tablet dissolution. Its goal was to propose a quality control strategy to model dissolution testing of solid oral dose products according to International Conference on Harmonization guidelines. The methodology involved the following three steps: (1) a risk analysis to identify the material- and process-related parameters impacting the critical quality attributes of dissolution testing, (2) an experimental design to evaluate the influence of design factors (attributes and parameters selected by risk analysis) on dissolution testing, and (3) an investigation of the relationship between design factors and dissolution profiles. Results show that (a) in the case studied, the two parameters impacting dissolution kinetics are active pharmaceutical ingredient particle size distributions and tablet hardness and (b) these two parameters could be monitored with PAT tools to predict dissolution profiles. Moreover, based on the results obtained, modeling dissolution is possible. The practicality and effectiveness of the QbD approach were demonstrated through this industrial case study. Implementing such an approach systematically in industrial pharmaceutical production would reduce the need for tablet dissolution testing.

Assessing the performance of community-available global MHD models using key system parameters and empirical relationships

NASA Astrophysics Data System (ADS)

Gordeev, E.; Sergeev, V.; Honkonen, I.; Kuznetsova, M.; Rastätter, L.; Palmroth, M.; Janhunen, P.; Tóth, G.; Lyon, J.; Wiltberger, M.

2015-12-01

Global magnetohydrodynamic (MHD) modeling is a powerful tool in space weather research and predictions. There are several advanced and still developing global MHD (GMHD) models that are publicly available via Community Coordinated Modeling Center's (CCMC) Run on Request system, which allows the users to simulate the magnetospheric response to different solar wind conditions including extraordinary events, like geomagnetic storms. Systematic validation of GMHD models against observations still continues to be a challenge, as well as comparative benchmarking of different models against each other. In this paper we describe and test a new approach in which (i) a set of critical large-scale system parameters is explored/tested, which are produced by (ii) specially designed set of computer runs to simulate realistic statistical distributions of critical solar wind parameters and are compared to (iii) observation-based empirical relationships for these parameters. Being tested in approximately similar conditions (similar inputs, comparable grid resolution, etc.), the four models publicly available at the CCMC predict rather well the absolute values and variations of those key parameters (magnetospheric size, magnetic field, and pressure) which are directly related to the large-scale magnetospheric equilibrium in the outer magnetosphere, for which the MHD is supposed to be a valid approach. At the same time, the models have systematic differences in other parameters, being especially different in predicting the global convection rate, total field-aligned current, and magnetic flux loading into the magnetotail after the north-south interplanetary magnetic field turning. According to validation results, none of the models emerges as an absolute leader. The new approach suggested for the evaluation of the models performance against reality may be used by model users while planning their investigations, as well as by model developers and those interesting to quantitatively evaluate progress in magnetospheric modeling.

Impedance learning for robotic contact tasks using natural actor-critic algorithm.

PubMed

Kim, Byungchan; Park, Jooyoung; Park, Shinsuk; Kang, Sungchul

2010-04-01

Compared with their robotic counterparts, humans excel at various tasks by using their ability to adaptively modulate arm impedance parameters. This ability allows us to successfully perform contact tasks even in uncertain environments. This paper considers a learning strategy of motor skill for robotic contact tasks based on a human motor control theory and machine learning schemes. Our robot learning method employs impedance control based on the equilibrium point control theory and reinforcement learning to determine the impedance parameters for contact tasks. A recursive least-square filter-based episodic natural actor-critic algorithm is used to find the optimal impedance parameters. The effectiveness of the proposed method was tested through dynamic simulations of various contact tasks. The simulation results demonstrated that the proposed method optimizes the performance of the contact tasks in uncertain conditions of the environment.

Energy Absorption in Chopped Carbon Fiber Compression Molded Composites

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

Starbuck, J.M.

2001-07-20

In passenger vehicles the ability to absorb energy due to impact and be survivable for the occupant is called the ''crashworthiness'' of the structure. To identify and quantify the energy absorbing mechanisms in candidate automotive composite materials, test methodologies were developed for conducting progressive crush tests on composite plate specimens. The test method development and experimental set-up focused on isolating the damage modes associated with the frond formation that occurs in dynamic testing of composite tubes. Quasi-static progressive crush tests were performed on composite plates manufactured from chopped carbon fiber with an epoxy resin system using compression molding techniques. Themore » carbon fiber was Toray T700 and the epoxy resin was YLA RS-35. The effect of various material and test parameters on energy absorption was evaluated by varying the following parameters during testing: fiber volume fraction, fiber length, fiber tow size, specimen width, profile radius, and profile constraint condition. It was demonstrated during testing that the use of a roller constraint directed the crushing process and the load deflection curves were similar to progressive crushing of tubes. Of all the parameters evaluated, the fiber length appeared to be the most critical material parameter, with shorter fibers having a higher specific energy absorption than longer fibers. The combination of material parameters that yielded the highest energy absorbing material was identified.« less

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

Urbic, Tomaz, E-mail: tomaz.urbic@fkkt.uni-lj.si; Dias, Cristiano L.

The thermodynamic and structural properties of the planar soft-sites dumbbell fluid are examined by Monte Carlo simulations and integral equation theory. The dimers are built of two Lennard-Jones segments. Site-site integral equation theory in two dimensions is used to calculate the site-site radial distribution functions for a range of elongations and densities and the results are compared with Monte Carlo simulations. The critical parameters for selected types of dimers were also estimated. We analyze the influence of the bond length on critical point as well as tested correctness of site-site integral equation theory with different closures. The integral equations canmore » be used to predict the phase diagram of dimers whose molecular parameters are known.« less

Analysis of screeching in a cold flow jet experiment

NASA Technical Reports Server (NTRS)

Wang, M. E.; Slone, R. M., Jr.; Robertson, J. E.; Keefe, L.

1975-01-01

The screech phenomenon observed in a one-sixtieth scale model space shuttle test of the solid rocket booster exhaust flow noise has been investigated. A critical review is given of the cold flow test data representative of Space Shuttle launch configurations to define those parameters which contribute to screech generation. An acoustic feedback mechanism is found to be responsible for the generation of screech. A simple equation which permits prediction of screech frequency in terms of basic testing parameters such as the jet exhaust Mach number and the separating distance from nozzle exit to the surface of model launch pad is presented and is found in good agreement with the test data. Finally, techniques are recommended to eliminate or reduce the screech.

Visual motor response of crewmen during a simulated 90 day space mission as measured by the critical task battery

NASA Technical Reports Server (NTRS)

Allen, R. W.; Jex, H. R.

1972-01-01

In order to test various components of a regenerative life support system and to obtain data on the physiological and psychological effects of long-duration exposure to confinement in a space station atmosphere, four carefully screened young men were sealed in space station simulator for 90 days. A tracking test battery was administered during the above experiment. The battery included a clinical test (critical instability task) related to the subject's dynamic time delay, and a conventional steady tracking task, during which dynamic response (describing functions) and performance measures were obtained. Good correlation was noted between the clinical critical instability scores and more detailed tracking parameters such as dynamic time delay and gain-crossover frequency. The comprehensive data base on human operator tracking behavior obtained in this study demonstrate that sophisticated visual-motor response properties can be efficiently and reliably measured over extended periods of time.

Validation of a New Small-Volume Sodium Citrate Collection Tube for Coagulation Testing in Critically Ill Patients with Coagulopathy.

PubMed

Adam, Elisabeth H; Zacharowski, Kai; Hintereder, Gudrun; Raimann, Florian; Meybohm, Patrick

2018-06-01

Blood loss due to phlebotomy leads to hospital-acquired anemia and more frequent blood transfusions that may be associated with increased risk of morbidity and mortality in critically ill patients. Multiple blood conservation strategies have been proposed in the context of patient blood management to minimize blood loss. Here, we evaluated a new small-volume sodium citrate collection tube for coagulation testing in critically ill patients. In 46 critically adult ill patients admitted to an interdisciplinary intensive care unit, we prospectively compared small-volume (1.8 mL) sodium citrate tubes with the conventional (3 mL) sodium citrate tubes. The main inclusion criterium was a proven coagulopathy (Quick < 60% and/or aPTT > 40 second) due to anticoagulation therapy or perioperative coagulopathy. In total, 92 coagulation analyses were obtained. Linear correlation analysis detected a positive relationship for 7 coagulation parameters (Prothrombin Time, r = 0.987; INR, r = 0.985; activated Partial Thromboplastin Time, r = 0.967; Thrombin Clotting Time, r = 0.969; Fibrinogen, r = 0.986; Antithrombin, r = 0.988; DDimer, r = 0.969). Bland-Altman analyses revealed an absolute mean of differences of almost zero. Ninety-five percent of data were within two standard deviations of the mean difference suggesting interchangeability. As systematic deviations between measured parameters of the two tubes were very unlikely, test results of small-volume (1.8 mL) sodium citrate tubes were equal to conventional (3 mL) sodium citrate tubes and can be considered interchangeable. Small-volume sodium citrate tubes reduced unnecessary diagnostic-related blood loss by about 40% and, therefore, should be the new standard of care for routine coagulation analysis in critically ill patients.

Microfissuring of Inconel 718

NASA Technical Reports Server (NTRS)

Nunes, A. C., Jr.

1983-01-01

A tentative mathematical computer model of the microfissuring process during electron beam welding of Inconel 718 has been constructed. Predictions of the model are compatible with microfissuring tests on eight 0.25-in. thick test plates. The model takes into account weld power and speed, weld loss (efficiency), parameters and material characteristics. Besides the usual material characteristics (thermal and strength properties), a temperature and grain size dependent critical fracture strain is required by the model. The model is based upon fundamental physical theory (i.e., it is not a mere data interpolation system), and can be extended to other metals by suitable parameter changes.

Testing and Performance Analysis of the Multichannel Error Correction Code Decoder

NASA Technical Reports Server (NTRS)

Soni, Nitin J.

1996-01-01

This report provides the test results and performance analysis of the multichannel error correction code decoder (MED) system for a regenerative satellite with asynchronous, frequency-division multiple access (FDMA) uplink channels. It discusses the system performance relative to various critical parameters: the coding length, data pattern, unique word value, unique word threshold, and adjacent-channel interference. Testing was performed under laboratory conditions and used a computer control interface with specifically developed control software to vary these parameters. Needed technologies - the high-speed Bose Chaudhuri-Hocquenghem (BCH) codec from Harris Corporation and the TRW multichannel demultiplexer/demodulator (MCDD) - were fully integrated into the mesh very small aperture terminal (VSAT) onboard processing architecture and were demonstrated.

Critical issues with the in vivo comet assay: A report of the comet assay working group in the 6th International Workshop on Genotoxicity Testing (IWGT).

PubMed

Speit, Günter; Kojima, Hajime; Burlinson, Brian; Collins, Andrew R; Kasper, Peter; Plappert-Helbig, Ulla; Uno, Yoshifumi; Vasquez, Marie; Beevers, Carol; De Boeck, Marlies; Escobar, Patricia A; Kitamoto, Sachiko; Pant, Kamala; Pfuhler, Stefan; Tanaka, Jin; Levy, Dan D

2015-05-01

As a part of the 6th IWGT, an expert working group on the comet assay evaluated critical topics related to the use of the in vivo comet assay in regulatory genotoxicity testing. The areas covered were: identification of the domain of applicability and regulatory acceptance, identification of critical parameters of the protocol and attempts to standardize the assay, experience with combination and integration with other in vivo studies, demonstration of laboratory proficiency, sensitivity and power of the protocol used, use of different tissues, freezing of samples, and choice of appropriate measures of cytotoxicity. The standard protocol detects various types of DNA lesions but it does not detect all types of DNA damage. Modifications of the standard protocol may be used to detect additional types of specific DNA damage (e.g., cross-links, bulky adducts, oxidized bases). In addition, the working group identified critical parameters that should be carefully controlled and described in detail in every published study protocol. In vivo comet assay results are more reliable if they were obtained in laboratories that have demonstrated proficiency. This includes demonstration of adequate response to vehicle controls and an adequate response to a positive control for each tissue being examined. There was a general agreement that freezing of samples is an option but more data are needed in order to establish generally accepted protocols. With regard to tissue toxicity, the working group concluded that cytotoxicity could be a confounder of comet results. It is recommended to look at multiple parameters such as histopathological observations, organ-specific clinical chemistry as well as indicators of tissue inflammation to decide whether compound-specific toxicity might influence the result. The expert working group concluded that the alkaline in vivo comet assay is a mature test for the evaluation of genotoxicity and can be recommended to regulatory agencies for use. Copyright © 2014 Elsevier B.V. All rights reserved.

Uncertainty analysis on simple mass balance model to calculate critical loads for soil acidity.

PubMed

Li, Harbin; McNulty, Steven G

2007-10-01

Simple mass balance equations (SMBE) of critical acid loads (CAL) in forest soil were developed to assess potential risks of air pollutants to ecosystems. However, to apply SMBE reliably at large scales, SMBE must be tested for adequacy and uncertainty. Our goal was to provide a detailed analysis of uncertainty in SMBE so that sound strategies for scaling up CAL estimates to the national scale could be developed. Specifically, we wanted to quantify CAL uncertainty under natural variability in 17 model parameters, and determine their relative contributions in predicting CAL. Results indicated that uncertainty in CAL came primarily from components of base cation weathering (BC(w); 49%) and acid neutralizing capacity (46%), whereas the most critical parameters were BC(w) base rate (62%), soil depth (20%), and soil temperature (11%). Thus, improvements in estimates of these factors are crucial to reducing uncertainty and successfully scaling up SMBE for national assessments of CAL.

A drilling tool design and in situ identification of planetary regolith mechanical parameters

NASA Astrophysics Data System (ADS)

Zhang, Weiwei; Jiang, Shengyuan; Ji, Jie; Tang, Dewei

2018-05-01

The physical and mechanical properties as well as the heat flux of regolith are critical evidence in the study of planetary origin and evolution. Moreover, the mechanical properties of planetary regolith have great value for guiding future human planetary activities. For planetary subsurface exploration, an inchworm boring robot (IBR) has been proposed to penetrate the regolith, and the mechanical properties of the regolith are expected to be simultaneously investigated during the penetration process using the drilling tool on the IBR. This paper provides a preliminary study of an in situ method for measuring planetary regolith mechanical parameters using a drilling tool on a test bed. A conical-screw drilling tool was designed, and its drilling load characteristics were experimentally analyzed. Based on the drilling tool-regolith interaction model, two identification methods for determining the planetary regolith bearing and shearing parameters are proposed. The bearing and shearing parameters of lunar regolith simulant were successfully determined according to the pressure-sinkage tests and shear tests conducted on the test bed. The effects of the operating parameters on the identification results were also analyzed. The results indicate a feasible scheme for future planetary subsurface exploration.

Lead-acid batteries in micro-hybrid applications. Part II. Test proposal

NASA Astrophysics Data System (ADS)

Schaeck, S.; Stoermer, A. O.; Albers, J.; Weirather-Koestner, D.; Kabza, H.

In the first part of this work [1] selected key parameters for applying lead-acid (LA) batteries in micro-hybrid power systems (MHPS) were investigated. Main results are integrated in an accelerated, comprehensive test proposal presented here. The test proposal aims at a realistic representation of the pSoC operation regime, which is described in Refs. [1,6]. The test is designed to be sensitive with respect to dynamic charge acceptance (DCA) at partially discharged state (critical for regenerative braking) and the internal resistance at high-rate discharge (critical for idling stop applications). First results are presented for up-to-date valve-regulated LA batteries with absorbent glass mat (AGM) separators. The batteries are close to the limits of the first proposal of pass/fail-criteria. Also flooded batteries were tested; the first out of ten units failed already.

Use of Subjective Global Assessment, Patient-Generated Subjective Global Assessment and Nutritional Risk Screening 2002 to evaluate the nutritional status of non-critically ill patients on parenteral nutrition.

PubMed

Badia-Tahull, M B; Cobo-Sacristán, S; Leiva-Badosa, E; Miquel-Zurita, M E; Méndez-Cabalerio, N; Jódar-Masanés, R; Llop-Talaverón, J

2014-02-01

To evaluate the nutritional status of non-critically ill digestive surgery patients at the moment of parenteral nutrition initiation using three different nutritional test tools and to study their correlation. To study the association between the tests and the clinical and laboratory parameters used in the follow-up of PN treatment. Prospective study over 4 months. Anthropometric and clinical variables were recorded. Results of Subjective Global Assessment; Patient-Generated Subjective Global Assessment; and Nutritional Risk Screening 2002 were compared applying kappa test. Relationship between the clinical and laboratory parameters with Subjective Global Assessment was studied by multinominal regression and with the other two tests by multiple linear regression models. Age and sex were included as adjustment variables. Malnutrition in 45 studied patients varied from 51% to 57%. Subjective Global Assessment correlated well with Patient-Generated Subjective Global Assessment and Nutritional Risk Screening 2002 (κ = 0531 p = 0.000). The test with the greatest correlation with the clinical and analytical variables was the Nutritional Risk Screening 2002. Worse nutritional state in this test was associated with worse results in albumin (B = -0.087; CI = -0.169/-0.005], prealbumin (B = -0.005; CI = [-0.011/-0.001]), C-reactive protein (B = 0.006;CI = [0.001/ 0.011]) and leukocytes (B = 0.134; CI = [0.031/0.237]) at the en of parenteral nutrition treatment. Half of the digestive surgery patients were at malnutritional risk at the moment of initiating parenteral nutrition. Nutritional Risk Screening 2002 was the test with best association with the parameters used in the clinical follow-up of parenteral nutrition treated patients. Copyright AULA MEDICA EDICIONES 2014. Published by AULA MEDICA. All rights reserved.

Study of Critical Heat Flux and Two-Phase Pressure Drop Under Reduced Gravity

NASA Technical Reports Server (NTRS)

Abdollahian, Davood; Quintal, Joseph; Barez, Fred; Zahm, Jennifer; Lohr, Victor

1996-01-01

The design of the two-phase flow systems which are anticipated to be utilized in future spacecraft thermal management systems requires a knowledge of two-phase flow and heat transfer phenomena in reduced gravities. This program was funded by NASA headquarters in response to NRA-91-OSSA-17 and was managed by Lewis Research Center. The main objective of this program was to design and construct a two-phase test loop, and perform a series of normal gravity and aircraft trajectory experiments to study the effect of gravity on the Critical Heat Flux (CHF) and onset of instability. The test loop was packaged on two aircraft racks and was also instrumented to generate data for two-phase pressure drop. The normal gravity tests were performed with vertical up and downflow configurations to bound the effect of gravity on the test parameters. One set of aircraft trajectory tests was performed aboard the NASA DC-9 aircraft. These tests were mainly intended to evaluate the test loop and its operational performance under actual reduced gravity conditions, and to produce preliminary data for the test parameters. The test results were used to demonstrate the applicability of the normal gravity models for prediction of the two-phase friction pressure drop. It was shown that the two-phase friction multipliers for vertical upflow and reduced gravity conditions can be successfully predicted by the appropriate normal gravity models. Limited critical heat flux data showed that the measured CHF under reduced gravities are of the same order of magnitude as the test results with vertical upflow configuration. A simplified correlation was only successful in predicting the measured CHF for low flow rates. Instability tests with vertical upflow showed that flow becomes unstable and critical heat flux occurs at smaller powers when a parallel flow path exists. However, downflow tests and a single reduced gravity instability experiment indicated that the system actually became more stable with a parallel single-phase flow path. Several design modifications have been identified which will improve the system performance for generating reduced gravity data. The modified test loop can provide two-phase flow data for a range of operating conditions and can serve as a test bed for component evaluation.

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

Bamberger, Judith A.; Piepel, Gregory F.; Enderlin, Carl W.

Understanding how uncertainty manifests itself in complex experiments is important for developing the testing protocol and interpreting the experimental results. This paper describes experimental and measurement uncertainties, and how they can depend on the order of performing experimental tests. Experiments with pulse-jet mixers in tanks at three scales were conducted to characterize the performance of transient-developing periodic flows in Newtonian slurries. Other test parameters included the simulant, solids concentration, and nozzle exit velocity. Critical suspension velocity and cloud height were the metrics used to characterize Newtonian slurry flow associated with mobilization and mixing. During testing, near-replicate and near-repeat tests weremore » conducted. The experimental results were used to quantify the combined experimental and measurement uncertainties using standard deviations and percent relative standard deviations (%RSD) The uncertainties in critical suspension velocity and cloud height tend to increase with the values of these responses. Hence, the %RSD values are the more appropriate summary measure of near-replicate testing and measurement uncertainty.« less

VizieR Online Data Catalog: Statistical test on binary stars non-coevality (Valle+, 2016)

NASA Astrophysics Data System (ADS)

Valle, G.; Dell'Omodarme, M.; Valle, G.; Prada Moroni, P. G.; Degl'Innocenti, S.

2016-01-01

The table contains the W0.95 critical values, for the 1087 binary systems considered in the paper. Tha table also lists the parameters of the beta distributions approximating the empirical W distributions. (1 data file).

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

Costa, David A.; Cournoyer, Michael E.; Merhege, James F.

Criticality is the state of a nuclear chain reacting medium when the chain reaction is just self-sustaining (or critical). Criticality is dependent on nine interrelated parameters. Moreover, we design criticality safety controls in order to constrain these parameters to minimize fissions and maximize neutron leakage and absorption in other materials, which makes criticality more difficult or impossible to achieve. We present the consequences of criticality accidents are discussed, the nine interrelated parameters that combine to affect criticality are described, and criticality safety controls used to minimize the likelihood of a criticality accident are presented.

Verifying Data Integrity of Electronically Scanned Pressure Systems at the NASA Glenn Research Center

NASA Technical Reports Server (NTRS)

Panek, Joseph W.

2001-01-01

The proper operation of the Electronically Scanned Pressure (ESP) System critical to accomplish the following goals: acquisition of highly accurate pressure data for the development of aerospace and commercial aviation systems and continuous confirmation of data quality to avoid costly, unplanned, repeat wind tunnel or turbine testing. Standard automated setup and checkout routines are necessary to accomplish these goals. Data verification and integrity checks occur at three distinct stages, pretest pressure tubing and system checkouts, daily system validation and in-test confirmation of critical system parameters. This paper will give an overview of the existing hardware, software and methods used to validate data integrity.

Generalization of the photo process window and its application to OPC test pattern design

NASA Astrophysics Data System (ADS)

Eisenmann, Hans; Peter, Kai; Strojwas, Andrzej J.

2003-07-01

From the early development phase up to the production phase, test pattern play a key role for microlithography. The requirement for test pattern is to represent the design well and to cover the space of all process conditions, e.g. to investigate the full process window and all other process parameters. This paper shows that the current state-of-the-art test pattern do not address these requirements sufficiently and makes suggestions for a better selection of test pattern. We present a new methodology to analyze an existing layout (e.g. logic library, test pattern or full chip) for critical layout situations which does not need precise process data. We call this method "process space decomposition", because it is aimed at decomposing the process impact to a layout feature into a sum of single independent contributions, the dimensions of the process space. This is a generalization of the classical process window, which examines defocus and exposure dependency of given test pattern, e.g. CD value of dense and isolated lines. In our process space we additionally define the dimensions resist effects, etch effects, mask error and misalignment, which describe the deviation of the printed silicon pattern from its target. We further extend it by the pattern space using a product based layout (library, full chip or synthetic test pattern). The criticality of pattern is defined by their deviation due to aerial image, their sensitivity to the respective dimension or several combinations of these. By exploring the process space for a given design, the method allows to find the most critical patterns independent of specific process parameters. The paper provides examples for different applications of the method: (1) selection of design oriented test pattern for lithography development (2) test pattern reduction in process characterization (3) verification/optimization of printability and performance of post processing procedures (like OPC) (4) creation of a sensitive process monitor.

A primer on criticality safety

DOE PAGES

Costa, David A.; Cournoyer, Michael E.; Merhege, James F.; ...

2017-05-01

Criticality is the state of a nuclear chain reacting medium when the chain reaction is just self-sustaining (or critical). Criticality is dependent on nine interrelated parameters. Moreover, we design criticality safety controls in order to constrain these parameters to minimize fissions and maximize neutron leakage and absorption in other materials, which makes criticality more difficult or impossible to achieve. We present the consequences of criticality accidents are discussed, the nine interrelated parameters that combine to affect criticality are described, and criticality safety controls used to minimize the likelihood of a criticality accident are presented.

Fabrication, test and demonstration of critical environment monitoring system

NASA Technical Reports Server (NTRS)

Heimendinger, K. W.

1972-01-01

Design and performance of an analytical system for the evaluation of certain environmental constituents in critical environmental areas of the Quality Reliability and Assurance Laboratory are reported. Developed was a self-contained, integrated, minimum sized unit that detects, interrogates, and records those parameters of the environment dictated for control in large storage facilities, clean rooms, temporarily curtained enclosures, and special working benches. The system analyzes humidity, temperature, hydrocarbons particle size, and particle count within prescribed clean areas.

Diamond turning of glass

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

Blackley, W.S.; Scattergood, R.O.

A new research initiative will be undertaken to investigate the critical cutting depth concepts for single point diamond turning of brittle, amorphous materials. Inorganic glasses and a brittle, thermoset polymer (organic glass) are the principal candidate materials. Interrupted cutting tests similar to those done in earlier research are Ge and Si crystals will be made to obtain critical depth values as a function of machining parameters. The results will provide systematic data with which to assess machining performance on glasses and amorphous materials

Analytical Verifications in Cryogenic Testing of NGST Advanced Mirror System Demonstrators

NASA Technical Reports Server (NTRS)

Cummings, Ramona; Levine, Marie; VanBuren, Dave; Kegley, Jeff; Green, Joseph; Hadaway, James; Presson, Joan; Cline, Todd; Stahl, H. Philip (Technical Monitor)

2002-01-01

Ground based testing is a critical and costly part of component, assembly, and system verifications of large space telescopes. At such tests, however, with integral teamwork by planners, analysts, and test personnel, segments can be included to validate specific analytical parameters and algorithms at relatively low additional cost. This paper opens with strategy of analytical verification segments added to vacuum cryogenic testing of Advanced Mirror System Demonstrator (AMSD) assemblies. These AMSD assemblies incorporate material and architecture concepts being considered in the Next Generation Space Telescope (NGST) design. The test segments for workmanship testing, cold survivability, and cold operation optical throughput are supplemented by segments for analytical verifications of specific structural, thermal, and optical parameters. Utilizing integrated modeling and separate materials testing, the paper continues with support plan for analyses, data, and observation requirements during the AMSD testing, currently slated for late calendar year 2002 to mid calendar year 2003. The paper includes anomaly resolution as gleaned by authors from similar analytical verification support of a previous large space telescope, then closes with draft of plans for parameter extrapolations, to form a well-verified portion of the integrated modeling being done for NGST performance predictions.

Numerical sensitivity analysis of a variational data assimilation procedure for cardiac conductivities

NASA Astrophysics Data System (ADS)

Barone, Alessandro; Fenton, Flavio; Veneziani, Alessandro

2017-09-01

An accurate estimation of cardiac conductivities is critical in computational electro-cardiology, yet experimental results in the literature significantly disagree on the values and ratios between longitudinal and tangential coefficients. These are known to have a strong impact on the propagation of potential particularly during defibrillation shocks. Data assimilation is a procedure for merging experimental data and numerical simulations in a rigorous way. In particular, variational data assimilation relies on the least-square minimization of the misfit between simulations and experiments, constrained by the underlying mathematical model, which in this study is represented by the classical Bidomain system, or its common simplification given by the Monodomain problem. Operating on the conductivity tensors as control variables of the minimization, we obtain a parameter estimation procedure. As the theory of this approach currently provides only an existence proof and it is not informative for practical experiments, we present here an extensive numerical simulation campaign to assess practical critical issues such as the size and the location of the measurement sites needed for in silico test cases of potential experimental and realistic settings. This will be finalized with a real validation of the variational data assimilation procedure. Results indicate the presence of lower and upper bounds for the number of sites which guarantee an accurate and minimally redundant parameter estimation, the location of sites being generally non critical for properly designed experiments. An effective combination of parameter estimation based on the Monodomain and Bidomain models is tested for the sake of computational efficiency. Parameter estimation based on the Monodomain equation potentially leads to the accurate computation of the transmembrane potential in real settings.

Optimization of Equation of State and Burn Model Parameters for Explosives

NASA Astrophysics Data System (ADS)

Bergh, Magnus; Wedberg, Rasmus; Lundgren, Jonas

2017-06-01

A reactive burn model implemented in a multi-dimensional hydrocode can be a powerful tool for predicting non-ideal effects as well as initiation phenomena in explosives. Calibration against experiment is, however, critical and non-trivial. Here, a procedure is presented for calibrating the Ignition and Growth Model utilizing hydrocode simulation in conjunction with the optimization program LS-OPT. The model is applied to the explosive PBXN-109. First, a cylinder expansion test is presented together with a new automatic routine for product equation of state calibration. Secondly, rate stick tests and instrumented gap tests are presented. Data from these experiments are used to calibrate burn model parameters. Finally, we discuss the applicability and development of this optimization routine.

Precision diamond grinding of ceramics and glass

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

Smith, S.; Paul, H.; Scattergood, R.O.

A new research initiative will be undertaken to investigate the effect of machine parameters and material properties on precision diamond grinding of ceramics and glass. The critical grinding depth to initiate the plastic flow-to-brittle fracture regime will be directly measured using plunge-grind tests. This information will be correlated with machine parameters such as wheel bonding and diamond grain size. Multiaxis grinding tests will then be made to provide data more closely coupled with production technology. One important aspect of the material property studies involves measuring fracture toughness at the very short crack sizes commensurate with grinding damage. Short crack toughnessmore » value`s can be much less than the long-crack toughness values measured in conventional fracture tests.« less

Design, fabrication, and operation of a test rig for high-speed tapered-roller bearings

NASA Technical Reports Server (NTRS)

Signer, H. R.

1974-01-01

A tapered-roller bearing test machine was designed, fabricated and successfully operated at speeds to 20,000 rpm. Infinitely variable radial loads to 26,690 N (6,000 lbs.) and thrust loads to 53,380 N (12,000 lbs.) can be applied to test bearings. The machine instrumentation proved to have the accuracy and reliability required for parametric bearing performance testing and has the capability of monitoring all programmed test parameters at continuous operation during life testing. This system automatically shuts down a test if any important test parameter deviates from the programmed conditions, or if a bearing failure occurs. A lubrication system was developed as an integral part of the machine, capable of lubricating test bearings by external jets and by means of passages feeding through the spindle and bearing rings into the critical internal bearing surfaces. In addition, provisions were made for controlled oil cooling of inner and outer rings to effect the type of bearing thermal management that is required when testing at high speeds.

Disturbed State constitutive modeling of two Pleistocene tills

NASA Astrophysics Data System (ADS)

Sane, S. M.; Desai, C. S.; Jenson, J. W.; Contractor, D. N.; Carlson, A. E.; Clark, P. U.

2008-02-01

The Disturbed State Concept (DSC) provides a general approach for constitutive modeling of deforming materials. Here, we briefly explain the DSC and present the results of laboratory tests on two regionally significant North American tills, along with the results of a numerical simulation to predict the behavior of one of the tills in an idealized physical system. Laboratory shear tests showed that plastic strain starts almost from the beginning of loading, and that failure and resulting motion begin at a critical disturbance, when about 85% of the mass has reached the fully adjusted or critical state. Specimens of both tills exhibited distributed strain, deforming into barrel shapes without visible shear planes. DSC parameters obtained from shear and creep tests were validated by comparing model predictions against test data used to find the parameters, as well as against data from independent tests. The DSC parameters from one of the tills were applied in a finite-element simulation to predict gravity-induced motion for a 5000-m long, 100-m thick slab of ice coupled to an underlying 1.5-m thick layer of till set on a 4° incline, with pore-water pressure in the till at 90% of the load. The simulation predicted that in the middle segment of the till layer (i.e., from x=2000 to 3000 m) the induced (computed) shear stress, strain, and disturbance increase gradually with the applied shear stress. Induced shear stress peaks at ˜60 kPa. The critical disturbance, at which failure occurs, is observed after the peak shear stress, at an induced shear stress of ˜23 kPa and shear strain of ˜0.75 in the till. Calculated horizontal displacement over the height of the entire till section at the applied shear stress of 65 kPa is ˜4.5 m. We note that the numerical prediction of critical disturbance, when the displacement shows a sharp change in rate, compares very well with the occurrence of critical disturbance observed in the laboratory triaxial tests, when a sharp change in the rate of strain occurs. This implies that the failure and concomitant initiation of motion occur near the residual state, at large strains. In contrast to the Mohr-Coulomb model, which predicts failure and motion at very small (elastic) strain, the DSC thus predicts failure and initiation of motion after the till has undergone considerable (plastic) strain. These results suggest that subglacial till may be able to sustain stress in the vicinity of 20 kPa even after the motion begins. They also demonstrate the potential of the DSC to model not only local behavior, including potential "sticky spot" mechanisms, but also global behavior for soft-bedded ice.

A device for automatically measuring and supervising the critical care patient's urine output.

PubMed

Otero, Abraham; Palacios, Francisco; Akinfiev, Teodor; Fernández, Roemi

2010-01-01

Critical care units are equipped with commercial monitoring devices capable of sensing patients' physiological parameters and supervising the achievement of the established therapeutic goals. This avoids human errors in this task and considerably decreases the workload of the healthcare staff. However, at present there still is a very relevant physiological parameter that is measured and supervised manually by the critical care units' healthcare staff: urine output. This paper presents a patent-pending device capable of automatically recording and supervising the urine output of a critical care patient. A high precision scale is used to measure the weight of a commercial urine meter. On the scale's pan there is a support frame made up of Bosch profiles that isolates the scale from force transmission from the patient's bed, and guarantees that the urine flows properly through the urine meter input tube. The scale's readings are sent to a PC via Bluetooth where an application supervises the achievement of the therapeutic goals. The device is currently undergoing tests at a research unit associated with the University Hospital of Getafe in Spain.

Critical level setting of continuous air monitor.

PubMed

Li, Huibin; Jia, Mingyan; Wang, Kailiang

2013-01-01

Algorithms used to compensate the radon and thoron progeny's interference are one of the key technologies for continuous air monitors (CAMs). In this study, a CAM that can automatically change filter was manufactured, and equations used to calculate the transuranic aerosol concentration and the corresponding critical level were derived. The parameters used in calculation were acquired by continuous measurement in a high radon environment. At last, validation of the calculation was tested in a cave where the radon concentration fluctuated frequently, and the results were analysed.

Drop-on-Demand System for Manufacturing of Melt-based Solid Oral Dosage: Effect of Critical Process Parameters on Product Quality.

PubMed

Içten, Elçin; Giridhar, Arun; Nagy, Zoltan K; Reklaitis, Gintaras V

2016-04-01

The features of a drop-on-demand-based system developed for the manufacture of melt-based pharmaceuticals have been previously reported. In this paper, a supervisory control system, which is designed to ensure reproducible production of high quality of melt-based solid oral dosages, is presented. This control system enables the production of individual dosage forms with the desired critical quality attributes: amount of active ingredient and drug morphology by monitoring and controlling critical process parameters, such as drop size and product and process temperatures. The effects of these process parameters on the final product quality are investigated, and the properties of the produced dosage forms characterized using various techniques, such as Raman spectroscopy, optical microscopy, and dissolution testing. A crystallization temperature control strategy, including controlled temperature cycles, is presented to tailor the crystallization behavior of drug deposits and to achieve consistent drug morphology. This control strategy can be used to achieve the desired bioavailability of the drug by mitigating variations in the dissolution profiles. The supervisor control strategy enables the application of the drop-on-demand system to the production of individualized dosage required for personalized drug regimens.

Friction angle measurements on a naturally formed gravel streambed: Implications for critical boundary shear stress

Treesearch

John M. Buffington; William E. Dietrich; James W. Kirchner

1992-01-01

We report the first measurements of friction angles for a naturally formed gravel streambed. For a given test grain size placed on a bed surface, friction angles varied from 10º to over 100º; friction angle distributions can be expressed as a function of test grain size, median bed grain size, and bed sorting parameter. Friction angles decrease with increasing grain...

High-Pressure Oxygen Test Evaluations

NASA Technical Reports Server (NTRS)

Schwinghamer, R. J.; Key, C. F.

1974-01-01

The relevance of impact sensitivity testing to the development of the space shuttle main engine is discussed in the light of the special requirements for the engine. The background and history of the evolution of liquid and gaseous oxygen testing techniques and philosophy is discussed also. The parameters critical to reliable testing are treated in considerable detail, and test apparatus and procedures are described and discussed. Materials threshold sensitivity determination procedures are considered and a decision logic diagram for sensitivity threshold determination was plotted. Finally, high-pressure materials sensitivity test data are given for selected metallic and nonmetallic materials.

Fragmentation modeling of a resin bonded sand

NASA Astrophysics Data System (ADS)

Hilth, William; Ryckelynck, David

2017-06-01

Cemented sands exhibit a complex mechanical behavior that can lead to sophisticated models, with numerous parameters without real physical meaning. However, using a rather simple generalized critical state bonded soil model has proven to be a relevant compromise between an easy calibration and good results. The constitutive model formulation considers a non-associated elasto-plastic formulation within the critical state framework. The calibration procedure, using standard laboratory tests, is complemented by the study of an uniaxial compression test observed by tomography. Using finite elements simulations, this test is simulated considering a non-homogeneous 3D media. The tomography of compression sample gives access to 3D displacement fields by using image correlation techniques. Unfortunately these fields have missing experimental data because of the low resolution of correlations for low displacement magnitudes. We propose a recovery method that reconstructs 3D full displacement fields and 2D boundary displacement fields. These fields are mandatory for the calibration of the constitutive parameters by using 3D finite element simulations. The proposed recovery technique is based on a singular value decomposition of available experimental data. This calibration protocol enables an accurate prediction of the fragmentation of the specimen.

Parametric Analysis of a Hover Test Vehicle using Advanced Test Generation and Data Analysis

NASA Technical Reports Server (NTRS)

Gundy-Burlet, Karen; Schumann, Johann; Menzies, Tim; Barrett, Tony

2009-01-01

Large complex aerospace systems are generally validated in regions local to anticipated operating points rather than through characterization of the entire feasible operational envelope of the system. This is due to the large parameter space, and complex, highly coupled nonlinear nature of the different systems that contribute to the performance of the aerospace system. We have addressed the factors deterring such an analysis by applying a combination of technologies to the area of flight envelop assessment. We utilize n-factor (2,3) combinatorial parameter variations to limit the number of cases, but still explore important interactions in the parameter space in a systematic fashion. The data generated is automatically analyzed through a combination of unsupervised learning using a Bayesian multivariate clustering technique (AutoBayes) and supervised learning of critical parameter ranges using the machine-learning tool TAR3, a treatment learner. Covariance analysis with scatter plots and likelihood contours are used to visualize correlations between simulation parameters and simulation results, a task that requires tool support, especially for large and complex models. We present results of simulation experiments for a cold-gas-powered hover test vehicle.

Electromigration kinetics and critical current of Pb-free interconnects

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

Lu, Minhua; Rosenberg, Robert

2014-04-07

Electromigration kinetics of Pb-free solder bump interconnects have been studied using a single bump parameter sweep technique. By removing bump to bump variations in structure, texture, and composition, the single bump sweep technique has provided both activation energy and power exponents that reflect atomic migration and interface reactions with fewer samples, shorter stress time, and better statistics than standard failure testing procedures. Contact metallurgies based on Cu and Ni have been studied. Critical current, which corresponds to the Blech limit, was found to exist in the Ni metallurgy, but not in the Cu metallurgy. A temperature dependence of critical currentmore » was also observed.« less

Ambient mass density effects on the International Space Station (ISS) microgravity experiments

NASA Technical Reports Server (NTRS)

Smith, O. E.; Adelfang, S. I.; Smith, R. E.

1996-01-01

The Marshall engineering thermosphere model was specified by NASA to be used in the design, development and testing phases of the International Space Station (ISS). The mass density is the atmospheric parameter which most affects the ISS. Under simplifying assumptions, the critical ambient neutral density required to produce one micro-g on the ISS is estimated using an atmospheric drag acceleration equation. Examples are presented for the critical density versus altitude, and for the critical density that is exceeded at least once a month and once per orbit during periods of low and high solar activity. An analysis of the ISS orbital decay is presented.

Can Creatinine Height Index Predict Weaning and Survival Outcomes in Patients on Prolonged Mechanical Ventilation After Critical Illness?

PubMed

Datta, Debapriya; Foley, Raymond; Wu, Rong; Grady, James; Scalise, Paul

2018-02-01

Malnutrition is common in chronic critically ill patients on prolonged mechanical ventilation (PMV) and may affect weaning. The creatinine height index (CHI), which reflects lean muscle mass, is regarded as the most accurate indicator of malnutrition. The objective of this study was to determine the impact of CHI in comparison with other traditional nutritional indices on successful weaning and survival in patients on PMV after critical illness. Records of 167 patients on PMV following critical illness, admitted for weaning, were reviewed. Parameters studied included age, gender, body mass index (BMI), percentage ideal body weight (%IBW), total protein, albumin, prealbumin, hemoglobin (Hb), and cause of respiratory failure. Number successfully weaned and number discharged alive and time to wean and time to discharge alive were determined from records. The CHI was calculated from 24-hour urine creatinine using a standard formula. Unpaired 2-sample t test was performed to determine the association between the studied nutritional parameters and outcomes. Predictive value of studied parameters for successful weaning and survival was determined by multivariate logistic regression analysis to model dichotomous outcome of successful weaning and survival. Mean age was 68 ± 14 years, 49% were males, 64% were successfully weaned, and 65.8% survived. Total protein, Hb, and CHI had a significant impact on successful weaning. Weight, %IBW, BMI, and CHI had a significant effect on survival. Of all parameters, CHI was most strongly predictive of successful weaning and survival. The CHI is a strong predictor of successful weaning and survival in patients on PMV.

Clinical Validation of Therapeutic Drug Monitoring of Imipenem in Spent Effluent in Critically Ill Patients Receiving Continuous Renal Replacement Therapy: A Pilot Study.

PubMed

Wen, Aiping; Li, Zhe; Yu, Junxian; Li, Ren; Cheng, Sheng; Duan, Meili; Bai, Jing

2016-01-01

The primary objective of this pilot study was to investigate whether the therapeutic drug monitoring of imipenem could be performed with spent effluent instead of blood sampling collected from critically ill patients under continuous renal replacement therapy. A prospective open-label study was conducted in a real clinical setting. Both blood and effluent samples were collected pairwise before imipenem administration and 0.5, 1, 1.5, 2, 3, 4, 6, and 8 h after imipenem administration. Plasma and effluent imipenem concentrations were determined by reversed-phase high-performance liquid chromatography with ultraviolet detection. Pharmacokinetic and pharmacodynamic parameters of blood and effluent samples were calculated. Eighty-three paired plasma and effluent samples were obtained from 10 patients. The Pearson correlation coefficient of the imipenem concentrations in plasma and effluent was 0.950 (P<0.0001). The average plasma-to-effluent imipenem concentration ratio was 1.044 (95% confidence interval, 0.975 to 1.114) with Bland-Altman analysis. No statistically significant difference was found in the pharmacokinetic and pharmacodynamic parameters tested in paired plasma and effluent samples with Wilcoxon test. Spent effluent of continuous renal replacement therapy could be used for therapeutic drug monitoring of imipenem instead of blood sampling in critically ill patients.

Predicting Critical Power in Elite Cyclists: Questioning the Validity of the 3-Minute All-Out Test.

PubMed

Bartram, Jason C; Thewlis, Dominic; Martin, David T; Norton, Kevin I

2017-07-01

New applications of the critical-power concept, such as the modeling of intermittent-work capabilities, are exciting prospects for elite cycling. However, accurate calculation of the required parameters is traditionally time invasive and somewhat impractical. An alternative single-test protocol (3-min all-out) has recently been proposed, but validation in an elite population is lacking. The traditional approach for parameter establishment, but with fewer tests, could also prove an acceptable compromise. Six senior Australian endurance track-cycling representatives completed 6 efforts to exhaustion on 2 separate days over a 3-wk period. These included 1-, 4-, 6-, 8-, and 10-min self-paced efforts, plus the 3-min all-out protocol. Traditional work-vs-time calculations of CP and anaerobic energy contribution (W') using the 5 self-paced efforts were compared with calculations from the 3-min all-out protocol. The impact of using just 2 or 3 self-paced efforts for traditional CP and W' estimation was also explored using thresholds of agreement (8 W, 2.0 kJ, respectively). CP estimated from the 3-min all-out approach was significantly higher than from the traditional approach (402 ± 33, 351 ± 27 W, P < .001), while W' was lower (15.5 ± 3.0, 24.3 ± 4.0 kJ, P = .02). Five different combinations of 2 or 3 self-paced efforts led to CP estimates within the threshold of agreement, with only 1 combination deemed accurate for W'. In elite cyclists the 3-min all-out approach is not suitable to estimate CP when compared with the traditional method. However, reducing the number of tests used in the traditional method lessens testing burden while maintaining appropriate parameter accuracy.

Data error and highly parameterized groundwater models

USGS Publications Warehouse

Hill, M.C.

2008-01-01

Strengths and weaknesses of highly parameterized models, in which the number of parameters exceeds the number of observations, are demonstrated using a synthetic test case. Results suggest that the approach can yield close matches to observations but also serious errors in system representation. It is proposed that avoiding the difficulties of highly parameterized models requires close evaluation of: (1) model fit, (2) performance of the regression, and (3) estimated parameter distributions. Comparisons to hydrogeologic information are expected to be critical to obtaining credible models. Copyright ?? 2008 IAHS Press.

Distributed Evaluation of Local Sensitivity Analysis (DELSA), with application to hydrologic models

USGS Publications Warehouse

Rakovec, O.; Hill, Mary C.; Clark, M.P.; Weerts, A. H.; Teuling, A. J.; Uijlenhoet, R.

2014-01-01

This paper presents a hybrid local-global sensitivity analysis method termed the Distributed Evaluation of Local Sensitivity Analysis (DELSA), which is used here to identify important and unimportant parameters and evaluate how model parameter importance changes as parameter values change. DELSA uses derivative-based “local” methods to obtain the distribution of parameter sensitivity across the parameter space, which promotes consideration of sensitivity analysis results in the context of simulated dynamics. This work presents DELSA, discusses how it relates to existing methods, and uses two hydrologic test cases to compare its performance with the popular global, variance-based Sobol' method. The first test case is a simple nonlinear reservoir model with two parameters. The second test case involves five alternative “bucket-style” hydrologic models with up to 14 parameters applied to a medium-sized catchment (200 km2) in the Belgian Ardennes. Results show that in both examples, Sobol' and DELSA identify similar important and unimportant parameters, with DELSA enabling more detailed insight at much lower computational cost. For example, in the real-world problem the time delay in runoff is the most important parameter in all models, but DELSA shows that for about 20% of parameter sets it is not important at all and alternative mechanisms and parameters dominate. Moreover, the time delay was identified as important in regions producing poor model fits, whereas other parameters were identified as more important in regions of the parameter space producing better model fits. The ability to understand how parameter importance varies through parameter space is critical to inform decisions about, for example, additional data collection and model development. The ability to perform such analyses with modest computational requirements provides exciting opportunities to evaluate complicated models as well as many alternative models.

Testing critical point universality along the λ-line

NASA Astrophysics Data System (ADS)

Nissen, J. A.; Swanson, D. R.; Geng, Z. K.; Dohm, V.; Israelsson, U. E.; DiPirro, M. J.; Lipa, J. A.

1998-02-01

We are currently building a prototype for a new test of critical-point universality at the lambda transition in 4He, which is to be performed in microgravity conditions. The flight experiment will measure the second-sound velocity as a function of temperature at pressures from 1 to 30 bars in the region close to the lambda line. The critical exponents and other parameters characterizing the behavior of the superfluid density will be determined from the measurements. The microgravity measurements will be quite extensive, probably taking 30 days to complete. In addition to the superfluid density, some measurements of the specific heat will be made using the low-g simulator at the Jet Propulsion Laboratory. The results of the superfluid density and specific heat measurements will be used to compare the asymptotic exponents and other universal aspects of the superfluid density with the theoretical predictions currently established by renormalization group techniques.

Effect of microgravity on several visual functions during STS shuttle missions

NASA Technical Reports Server (NTRS)

Oneal, Melvin R.; Task, H. Lee; Genco, Louis V.

1992-01-01

Changes in the acuity of astronaut vision during flight are discussed. Parameters such as critical flicker vision, stereopsis to 10 seconds of arc, visual acuity in small steps to 20/7.7, cyclophoria, lateral and vertical phoria and retinal rivalry were tested using a visual function tester. Twenty-three Space Transportation System (STS) astronauts participated in the experiments. Their vision was assessed twice before launch and after landing, and three to four times while on-orbit and landing. No significant differences during space flight were observed for any of the visual parameters tested. In some cases, slight changes in acuity and stereopsis were observed with a subsequent return to normal vision after flight.

Standards and guidelines for biopolymers in tissue-engineered medical products: ASTM alginate and chitosan standard guides. American Society for Testing and Materials.

PubMed

Dornish, M; Kaplan, D; Skaugrud, O

2001-11-01

The American Society for Testing and Materials (ASTM) is making a concerted effort to establish standards and guidelines for the entire field of tissue-engineered medical products (TEMPS). Safety, consistency, and functionality of biomaterials used as matrices, scaffolds, and immobilizing agents in TEMPS are a concern. Therefore, the ASTM has established a number of task groups to produce standards and guidelines for such biomaterials. Alginate is a naturally occurring biomaterial used for immobilizing living cells to form an artificial organ, such as encapsulated pancreatic islets. In order to aid in successful clinical applications and to help expedite regulatory approval, the alginate used must be fully documented. The ASTM alginate guide gives information on selection of testing methodologies and safety criteria. Critical parameters such as monomer content, molecular weight, and viscosity, in addition to more general parameters, such as dry matter content, heavy metal content, bioburden, and endotoxin content are described in the ASTM document. In a like manner, the characterization parameters for chitosan, a bioadhesive polycationic polysaccharide, are described in a separate guide. For chitosan, the degree of deacetylation is of critical importance. Control of protein content and, hence, potential for hypersensitivity, endotoxin content, and total bioburden are important in chitosan preparations for TEMPS. Together these two guides represent part of the effort on behalf of the ASTM and other interested parties to ensure quality and standardization in TEMPS.

The assessment of body sway and the choice of the stability parameter(s).

PubMed

Raymakers, J A; Samson, M M; Verhaar, H J J

2005-01-01

This methodological study aims at comparison of the practical usefulness of several parameters of body sway derived from recordings of the center of pressure (CoP) with the aid of a static force platform as proposed in the literature. These included: mean displacement velocity, maximal range of movement along x- and y-co-ordinates, movement area, planar deviation, phase plane parameter of Riley and the parameters of the diffusion stabilogram according to Collins. They were compared in over 850 experiments in a group of young healthy subjects (n = 10, age 21-45 years), a group of elderly healthy (n = 38, age 61-78 years) and two groups of elderly subjects (n = 10 and n = 21, age 65-89 years) with stability problems under different conditions known to interfere with stability as compared to standing with open eyes fixing a visual anchoring point: closing the eyes, standing on plastic foam in stead of a firm surface and performing a cognitive task: the modified stroop test. A force platform (Kistler) was used and co-ordinates of the body's center of pressure were recorded during 60 s of quiet barefoot standing with a sampling frequency of 10 Hz. In general, the results show important overlapping among groups and test conditions. Mean displacement velocity shows the most consistent differences between test situations, health conditions and age ranges, but is not affected by an extra cognitive task in healthy old people. Mean maximal sideways sway range is different among groups and test conditions except for the cognitive task in young and elderly subjects. Standardised displacement parameters such as standard deviations of displacements and planar deviation discriminate less well than the actual range of motion or the velocity. The critical time interval derived from the diffusion stabilogram according to Collins et al. seems to add a specific type of information since it shows significant influence from addition of a cognitive task in old subjects standing on a firm surface but not when standing on plastic foam. The critical time interval shows no consistent relation to any other parameter. The influence of cognitive activity on balance merits further exploration. A new parameter, sum of maximal deviation time (SDT) was proposed showing complete discrimination between frail elderly and other old subjects when obtained while visual input was suppressed. It was concluded that mean displacement velocity seems to be the most informative parameter in most situations.

A method for identifying EMI critical circuits during development of a large C3

NASA Astrophysics Data System (ADS)

Barr, Douglas H.

The circuit analysis methods and process Boeing Aerospace used on a large, ground-based military command, control, and communications (C3) system are described. This analysis was designed to help identify electromagnetic interference (EMI) critical circuits. The methodology used the MIL-E-6051 equipment criticality categories as the basis for defining critical circuits, relational database technology to help sort through and account for all of the approximately 5000 system signal cables, and Macintosh Plus personal computers to predict critical circuits based on safety margin analysis. The EMI circuit analysis process systematically examined all system circuits to identify which ones were likely to be EMI critical. The process used two separate, sequential safety margin analyses to identify critical circuits (conservative safety margin analysis, and detailed safety margin analysis). These analyses used field-to-wire and wire-to-wire coupling models using both worst-case and detailed circuit parameters (physical and electrical) to predict circuit safety margins. This process identified the predicted critical circuits that could then be verified by test.

Roughness characterization of the galling of metals

NASA Astrophysics Data System (ADS)

Hubert, C.; Marteau, J.; Deltombe, R.; Chen, Y. M.; Bigerelle, M.

2014-09-01

Several kinds of tests exist to characterize the galling of metals, such as that specified in ASTM Standard G98. While the testing procedure is accurate and robust, the analysis of the specimen's surfaces (area=1.2 cm) for the determination of the critical pressure of galling remains subject to operator judgment. Based on the surface's topography analyses, we propose a methodology to express the probability of galling according to the macroscopic pressure load. After performing galling tests on 304L stainless steel, a two-step segmentation of the S q parameter (root mean square of surface amplitude) computed from local roughness maps (100 μ m× 100 μ m) enables us to distinguish two tribological processes. The first step represents the abrasive wear (erosion) and the second one the adhesive wear (galling). The total areas of both regions are highly relevant to quantify galling and erosion processes. Then, a one-parameter phenomenological model is proposed to objectively determine the evolution of non-galled relative area A e versus the pressure load P, with high accuracy ({{A}e}=100/(1+a{{P}2}) with a={{0.54}+/- 0.07}× {{10}-3} M P{{a}-2} and with {{R}2}=0.98). From this model, the critical pressure of galling is found to be equal to 43MPa. The {{S}5 V} roughness parameter (the five deepest valleys in the galled region's surface) is the most relevant roughness parameter for the quantification of damages in the ‘galling region’. The significant valleys’ depths increase from 10 μm-250 μm when the pressure increases from 11-350 MPa, according to a power law ({{S}5 V}=4.2{{P}0.75}, with {{R}2}=0.93).

Full Geant4 and FLUKA simulations of an e-LINAC for its use in particle detectors performance tests

NASA Astrophysics Data System (ADS)

Alpat, B.; Pilicer, E.; Servoli, L.; Menichelli, M.; Tucceri, P.; Italiani, M.; Buono, E.; Di Capua, F.

2012-03-01

In this work we present the results of full Geant4 and FLUKA simulations and comparison with dosimetry data of an electron LINAC of St. Maria Hospital located in Terni, Italy. The facility is being used primarily for radiotherapy and the goal of the present study is the detailed investigation of electron beam parameters to evaluate the possibility to use the e-LINAC (during time slots when it is not used for radiotherapy) to test the performance of detector systems, in particular those designed to operate in space. The critical beam parameters are electron energy, profile and flux available at the surface of device to be tested. The present work aims to extract these parameters from dosimetry calibration data available at the e-LINAC. The electron energy ranges from 4 MeV to 20 MeV. The dose measurements have been performed by using an Advanced Markus Chamber which has a small sensitive volume.

Critical behavior of phase interfaces in porous media: Analysis of scaling properties with the use of noncoherent and coherent light

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

Zimnyakov, D. A., E-mail: zimnykov@sgu.ru; Sadovoi, A. V.; Vilenskii, M. A.

2009-02-15

Image sequences of the surface of disordered layers of porous medium (paper) obtained under noncoherent and coherent illumination during capillary rise of a liquid are analyzed. As a result, principles that govern the critical behavior of the interface between liquid and gaseous phases during its pinning are established. By a cumulant analysis of speckle-modulated images of the surface and by the statistical analysis of binarized difference images of the surface under noncoherent illumination, it is shown that the macroscopic dynamics of the interface at the stage of pinning is mainly controlled by the power law dependence of the appearance ratemore » of local instabilities (avalanches) of the interface on the critical parameter, whereas the growth dynamics of the local instabilities is controlled by the diffusion of a liquid in a layer and weakly depends on the critical parameter. A phenomenological model is proposed for the macroscopic dynamics of the phase interface for interpreting experimental data. The values of critical indices are determined that characterize the samples under test within this model. These values are compared with the results of numerical simulation for discrete models of directed percolation corresponding to the Kardar-Parisi-Zhang equation.« less

Impact force as a scaling parameter

NASA Technical Reports Server (NTRS)

Poe, Clarence C., Jr.; Jackson, Wade C.

1994-01-01

The Federal Aviation Administration (FAR PART 25) requires that a structure carry ultimate load with nonvisible impact damage and carry 70 percent of limit flight loads with discrete damage. The Air Force has similar criteria (MIL-STD-1530A). Both civilian and military structures are designed by a building block approach. First, critical areas of the structure are determined, and potential failure modes are identified. Then, a series of representative specimens are tested that will fail in those modes. The series begins with tests of simple coupons, progresses through larger and more complex subcomponents, and ends with a test on a full-scale component, hence the term 'building block.' In order to minimize testing, analytical models are needed to scale impact damage and residual strength from the simple coupons to the full-scale component. Using experiments and analysis, the present paper illustrates that impact damage can be better understood and scaled using impact force than just kinetic energy. The plate parameters considered are size and thickness, boundary conditions, and material, and the impact parameters are mass, shape, and velocity.

The Generalized Higher Criticism for Testing SNP-Set Effects in Genetic Association Studies

PubMed Central

Barnett, Ian; Mukherjee, Rajarshi; Lin, Xihong

2017-01-01

It is of substantial interest to study the effects of genes, genetic pathways, and networks on the risk of complex diseases. These genetic constructs each contain multiple SNPs, which are often correlated and function jointly, and might be large in number. However, only a sparse subset of SNPs in a genetic construct is generally associated with the disease of interest. In this article, we propose the generalized higher criticism (GHC) to test for the association between an SNP set and a disease outcome. The higher criticism is a test traditionally used in high-dimensional signal detection settings when marginal test statistics are independent and the number of parameters is very large. However, these assumptions do not always hold in genetic association studies, due to linkage disequilibrium among SNPs and the finite number of SNPs in an SNP set in each genetic construct. The proposed GHC overcomes the limitations of the higher criticism by allowing for arbitrary correlation structures among the SNPs in an SNP-set, while performing accurate analytic p-value calculations for any finite number of SNPs in the SNP-set. We obtain the detection boundary of the GHC test. We compared empirically using simulations the power of the GHC method with existing SNP-set tests over a range of genetic regions with varied correlation structures and signal sparsity. We apply the proposed methods to analyze the CGEM breast cancer genome-wide association study. Supplementary materials for this article are available online. PMID:28736464

Looking at Gestalt Group Impact: An Experiment.

ERIC Educational Resources Information Center

Serok, Shraga; Bar, Ruth

1984-01-01

Tested the impact of gestalt group therapy on aspects of self-concept in graduate students (N=33). Results showed a significant rise in decisiveness, general adaptation and self-criticism in the gestalt group as compared to the control groups and showed no significant changes in the self-identification and self-acceptance parameters. (LLL)

A Three-Parameter Model for Predicting Fatigue Life of Ductile Metals Under Constant Amplitude Multiaxial Loading

NASA Astrophysics Data System (ADS)

Liu, Jia; Li, Jing; Zhang, Zhong-ping

2013-04-01

In this article, a fatigue damage parameter is proposed to assess the multiaxial fatigue lives of ductile metals based on the critical plane concept: Fatigue crack initiation is controlled by the maximum shear strain, and the other important effect in the fatigue damage process is the normal strain and stress. This fatigue damage parameter introduces a stress-correlated factor, which describes the degree of the non-proportional cyclic hardening. Besides, a three-parameter multiaxial fatigue criterion is used to correlate the fatigue lifetime of metallic materials with the proposed damage parameter. Under the uniaxial loading, this three-parameter model reduces to the recently developed Zhang's model for predicting the uniaxial fatigue crack initiation life. The accuracy and reliability of this three-parameter model are checked against the experimental data found in literature through testing six different ductile metals under various strain paths with zero/non-zero mean stress.

Accumulator and random-walk models of psychophysical discrimination: a counter-evaluation.

PubMed

Vickers, D; Smith, P

1985-01-01

In a recent assessment of models of psychophysical discrimination, Heath criticises the accumulator model for its reliance on computer simulation and qualitative evidence, and contrasts it unfavourably with a modified random-walk model, which yields exact predictions, is susceptible to critical test, and is provided with simple parameter-estimation techniques. A counter-evaluation is presented, in which the approximations employed in the modified random-walk analysis are demonstrated to be seriously inaccurate, the resulting parameter estimates to be artefactually determined, and the proposed test not critical. It is pointed out that Heath's specific application of the model is not legitimate, his data treatment inappropriate, and his hypothesis concerning confidence inconsistent with experimental results. Evidence from adaptive performance changes is presented which shows that the necessary assumptions for quantitative analysis in terms of the modified random-walk model are not satisfied, and that the model can be reconciled with data at the qualitative level only by making it virtually indistinguishable from an accumulator process. A procedure for deriving exact predictions for an accumulator process is outlined.

[Optimize dropping process of Ginkgo biloba dropping pills by using design space approach].

PubMed

Shen, Ji-Chen; Wang, Qing-Qing; Chen, An; Pan, Fang-Lai; Gong, Xing-Chu; Qu, Hai-Bin

2017-07-01

In this paper, a design space approach was applied to optimize the dropping process of Ginkgo biloba dropping pills. Firstly, potential critical process parameters and potential process critical quality attributes were determined through literature research and pre-experiments. Secondly, experiments were carried out according to Box-Behnken design. Then the critical process parameters and critical quality attributes were determined based on the experimental results. Thirdly, second-order polynomial models were used to describe the quantitative relationships between critical process parameters and critical quality attributes. Finally, a probability-based design space was calculated and verified. The verification results showed that efficient production of Ginkgo biloba dropping pills can be guaranteed by operating within the design space parameters. The recommended operation ranges for the critical dropping process parameters of Ginkgo biloba dropping pills were as follows: dropping distance of 5.5-6.7 cm, and dropping speed of 59-60 drops per minute, providing a reference for industrial production of Ginkgo biloba dropping pills. Copyright© by the Chinese Pharmaceutical Association.

Retrospective comparison of thromboelastography results to postmortem evidence of thrombosis in critically ill dogs: 39 cases (2005-2010).

PubMed

Thawley, Vincent J; Sánchez, Melissa D; Drobatz, Kenneth J; King, Lesley G

2016-05-01

To determine whether there is an association between thromboelastography (TEG) data and necropsy evidence of thrombosis in a cohort of critically ill dogs. Retrospective study (2005-2010). University teaching hospital. Thirty-nine client-owned critically ill dogs for which TEG was performed within 7 days of complete necropsy. None. Thrombi were found in 26 (67%) dogs. Spayed females (n = 20) were significantly more likely to have thrombosis (P = 0.0127). No significant association was found between presence of thrombosis and any TEG parameter, the calculated coagulation index, results of coagulation testing, type of vascular access, or clinical diagnosis. D-dimers were significantly higher in dogs with thrombosis (P = 0.0207) and a weak positive correlation was found between D-dimer value and number of sites of thrombosis (ρ = 0.18, P = 0.0045). Dogs with WBC > 16 × 10(3) /μL were more likely to have thrombosis compared to others (odds ratio 5.56, 95% confidence interval 1.2-25.7, P = 0.025). This study found no association between any TEG parameter and the presence of thrombosis on postmortem examination. © Veterinary Emergency and Critical Care Society 2016.

Critical behavior near the ferromagnetic phase transition in double perovskite Nd2NiMnO6

NASA Astrophysics Data System (ADS)

Ali, Anzar; Sharma, G.; Singh, Yogesh

2018-05-01

The knowledge of critical exponents plays a crucial role in trying to understand the interaction mechanism near a phase transition. In this report, we present a detailed study of the critical behaviour near the ferromagnetic (FM) transition (TC ˜ 193 K) in Nd2NiMnO6 using the temperature and magnetic field dependent isothermal magnetisation measurements. We used various analysis methods such as Arrott plot, modified Arrott plot, and Kouvel-Fisher plot to estimate the critical parameters. The magnetic critical parameters β = 0.49±0.02, γ = 1.05±0.04 and critical isothermal parameter δ = 3.05±0.02 are in excellent agreement with Widom scaling. The critical parameters analysis emphasizes that mean field interaction is the mechanism driving the FM transition in Nd2NiMnO6.

Critical parameters in the production of ceramic pot filters for household water treatment in developing countries.

PubMed

Soppe, A I A; Heijman, S G J; Gensburger, I; Shantz, A; van Halem, D; Kroesbergen, J; Wubbels, G H; Smeets, P W M H

2015-06-01

The need to improve the access to safe water is generally recognized for the benefit of public health in developing countries. This study's objective was to identify critical parameters which are essential for improving the performance of ceramic pot filters (CPFs) as a point-of-use water treatment system. Defining critical production parameters was also relevant to confirm that CPFs with high-flow rates may have the same disinfection capacity as pots with normal flow rates. A pilot unit was built in Cambodia to produce CPFs under controlled and constant conditions. Pots were manufactured from a mixture of clay, laterite and rice husk in a small-scale, gas-fired, temperature-controlled kiln and tested for flow rate, removal efficiency of bacteria and material strength. Flow rate can be increased by increasing pore sizes and by increasing porosity. Pore sizes were increased by using larger rice husk particles and porosity was increased with larger proportions of rice husk in the clay mixture. The main conclusions: larger pore size decreases the removal efficiency of bacteria; higher porosity does not affect the removal efficiency of bacteria, but does influence the strength of pots; flow rates of CPFs can be raised to 10-20 L/hour without a significant decrease in bacterial removal efficiency.

AST Combustion Workshop: Diagnostics Working Group Report

NASA Technical Reports Server (NTRS)

Locke, Randy J.; Hicks, Yolanda R.; Hanson, Ronald K.

1996-01-01

A workshop was convened under NASA's Advanced Subsonics Technologies (AST) Program. Many of the principal combustion diagnosticians from industry, academia, and government laboratories were assembled in the Diagnostics/Testing Subsection of this workshop to discuss the requirements and obstacles to the successful implementation of advanced diagnostic techniques to the test environment of the proposed AST combustor. The participants, who represented the major relevant areas of advanced diagnostic methods currently applied to combustion and related fields, first established the anticipated AST combustor flowfield conditions. Critical flow parameters were then examined and prioritized as to their importance to combustor/fuel injector design and manufacture, environmental concerns, and computational interests. Diagnostic techniques were then evaluated in terms of current status, merits and obstacles for each flow parameter. All evaluations are presented in tabular form and recommendations are made on the best-suited diagnostic method to implement for each flow parameter in order of applicability and intrinsic value.

Several Modified Goodness-Of-Fit Tests for the Cauchy Distribution with Unknown Scale and Location Parameters

DTIC Science & Technology

1994-03-01

labels of a, which is called significance levels. The hypothesis tests are done based on the a levels . The maximum probabilities of making type II error...critical values at specific a levels . This procedure is done for each of the 50,000 samples. The number of the samples passing each test at those specific... a levels is counted. The ratio of the number of accepted samples to 50,000 gives the percentage point. Then, subtracting that value from one would

28,000 Hour Xenon Hollow Cathode LifeTest Results

NASA Technical Reports Server (NTRS)

Sarver-Verhey, Timothy R.

1997-01-01

The International Space Station Plasma Contactor System requires a hollow cathode assembly (HCA) with a lifetime of at least 18,000 hours. Critical components of the HCA include the hollow cathode and electron emitter. A series of hollow cathode wear tests was performed which included a life test operated at the maximum current of the HCA. This test sought to verify the hollow cathode design and contamination control protocols. The life test accumulated 27,800 hours of operation before failing to ignite. The hollow cathode exhibited relatively small changes in operating parameters over the course of the test. This life test is the longest duration test of a high current xenon hollow cathode reported to date.

In-phase and out-of-phase axial-torsional fatigue behavior of Haynes 188 at 760 C

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Bonacuse, Peter J.

1991-01-01

Isothermal, in-phase and out-of-phase axial-torsional fatigue experiments have been conducted at 760 C on uniform gage section, thin-walled tubular specimens of a wrought cobalt-base superalloy, Haynes 188. Test-control and data acquisition were accomplished with a minicomputer. Fatigue lives of the in- and out-of-phase axial-torsional fatigue tests have been estimated with four different multiaxial fatigue life prediction models that were developed primarly for predicting axial-torsional fatigue lives at room temperature. The models investigated were: (1) the von Mises equivalent strain range; (2) the Modified Multiaxiality Factor Approach; (3) the Modified Smith-Watson-Topper Parameter; and (4) the critical shear plane method of Fatemi, Socie, and Kurath. In general, life predictions by the von Mises equivalent strain range model were within a factor of 2 for a majority of the tests and the predictions by the Modified Multiaxiality Factor Approach were within a factor of 2, while predictions of the Modified Smith-Watson-Topper Parameter and of the critical shear plane method of Fatemi, Socie, and Kurath were unconservative and conservative, respectively, by up to factors of 4. In some of the specimens tested under combined axial-torsional loading conditions, fatigue cracks initiated near extensometer indentations. Two design modifications have been proposed to the thin-walled tubular specimen to overcome this problem.

Analysis of Subcritical Crack Growth in Dental Ceramics Using Fracture Mechanics and Fractography

PubMed Central

Taskonak, Burak; Griggs, Jason A.; Mecholsky, John J.; Yan, Jia-Hau

2008-01-01

Objectives The aim of this study was to test the hypothesis that the flexural strengths and critical flaw sizes of dental ceramic specimens will be affected by the testing environment and stressing rate even though their fracture toughness values will remain the same. Methods Ceramic specimens were prepared from an aluminous porcelain (Vitadur Alpha; VITA Zahnfabrik, Bad Säckingen, Germany) and an alumina-zirconia-glass composite (In-Ceram® Zirconia; VITA Zahnfabrik). Three hundred uniaxial flexure specimens (150 of each material) were fabricated to dimensions of 25 mm × 4 mm × 1.2 mm according to the ISO 6872 standard. Each group of 30 specimens was fractured in water using one of four different target stressing rates ranging on a logarithmic scale from 0.1 to 100 MPa/s for Vitadur Alpha and from 0.01 to 10 MPa/s for In-Ceram® Zirconia. The fifth group was tested in inert environment (oil) with a target stressing rate of 100 MPa/s for Vitadur Alpha and 1000 MPa/s for In-Ceram® Zirconia. The effects of stressing rate and environment on flexural strength, critical flaw size, and fracture toughness were analyzed statistically by Kruskal-Wallis one-way ANOVA on ranks followed by post-hoc comparisons using Dunn’s test (α=0.05). In addition, 20 Vitadur Alpha specimens were fabricated with controlled flaws to simplify fractography. Half of these specimens were fracture tested in water and half in oil at a target stressing rate of 100 MPa/s, and the results were compared using Mann-Whitney rank sum tests (α=0.05). A logarithmic regression model was used to determine the fatigue parameters for each material. Results For each ceramic composition, specimens tested in oil had significantly higher strength (P≤0.05) and smaller critical flaw size (significant for Vitadur Alpha, P≤0.05) than those tested in water but did not have significantly different fracture toughness (P>0.05). Specimens tested at faster stressing rates had significantly higher strength (P≤0.05) but did not have significantly different fracture toughness (P>0.05). Regarding critical flaw size, stressing rate had a significant effect for In-Ceram® Zirconia specimens (P≤0.05) but not for Vitadur Alpha specimens (P>0.05). Fatigue parameters, n and ln B, were 38.4 and −12.7 for Vitadur Alpha and were 13.1 and 10.4 for In-Ceram® Zirconia. Significance Moisture assisted subcritical crack growth had a more deleterious effect on In-Ceram® Zirconia core ceramic than on Vitadur Alpha porcelain. Fracture surface analysis identified fracture surface features that can potentially mislead investigators into misidentifying the critical flaw. PMID:17845817

Analysis of subcritical crack growth in dental ceramics using fracture mechanics and fractography.

PubMed

Taskonak, Burak; Griggs, Jason A; Mecholsky, John J; Yan, Jia-Hau

2008-05-01

The aim of this study was to test the hypothesis that the flexural strengths and critical flaw sizes of dental ceramic specimens will be affected by the testing environment and stressing rate even though their fracture toughness values will remain the same. Ceramic specimens were prepared from an aluminous porcelain (Vitadur Alpha; VITA Zahnfabrik, Bad Säckingen, Germany) and an alumina-zirconia-glass composite (In-Ceram Zirconia; VITA Zahnfabrik). Three hundred uniaxial flexure specimens (150 of each material) were fabricated to dimensions of 25 mmx4 mmx1.2 mm according to the ISO 6872 standard. Each group of 30 specimens was fractured in water using one of four different target stressing rates ranging on a logarithmic scale from 0.1 to 100 MPa/s for Vitadur Alpha and from 0.01 to 10 MPa/s for In-Ceram Zirconia. The fifth group was tested in inert environment (oil) with a target stressing rate of 100 MPa/s for Vitadur Alpha and 1000 MPa/s for In-Ceram Zirconia. The effects of stressing rate and environment on flexural strength, critical flaw size, and fracture toughness were analyzed statistically by Kruskal-Wallis one-way ANOVA on ranks followed by post hoc comparisons using Dunn's test (alpha=0.05). In addition, 20 Vitadur Alpha specimens were fabricated with controlled flaws to simplify fractography. Half of these specimens were fracture tested in water and half in oil at a target stressing rate of 100 MPa/s, and the results were compared using Mann-Whitney rank sum tests (alpha=0.05). A logarithmic regression model was used to determine the fatigue parameters for each material. For each ceramic composition, specimens tested in oil had significantly higher strength (P0.05). Specimens tested at faster stressing rates had significantly higher strength (P0.05). Regarding critical flaw size, stressing rate had a significant effect for In-Ceram Zirconia specimens (P0.05). Fatigue parameters, n and lnB, were 38.4 and -12.7 for Vitadur Alpha and were 13.1 and 10.4 for In-Ceram Zirconia. Moisture assisted subcritical crack growth had a more deleterious effect on In-Ceram Zirconia core ceramic than on Vitadur Alpha porcelain. Fracture surface analysis identified fracture surface features that can potentially mislead investigators into misidentifying the critical flaw.

Critical attributes of transdermal drug delivery system (TDDS)--a generic product development review.

PubMed

Ruby, P K; Pathak, Shriram M; Aggarwal, Deepika

2014-11-01

Bioequivalence testing of transdermal drug delivery systems (TDDS) has always been a subject of high concern for generic companies due to the formulation complexity and the fact that they are subtle to even minor manufacturing differences and hence should be clearly qualified in terms of quality, safety and efficacy. In recent times bioequivalence testing of transdermal patches has gained a global attention and many regulatory authorities worldwide have issued recommendations to set specific framework for demonstrating equivalence between two products. These current regulatory procedures demand a complete characterization of the generic formulation in terms of its physicochemical sameness, pharmacokinetics disposition, residual content and/or skin irritation/sensitization testing with respect to the reference formulation. This paper intends to highlight critical in vitro tests in assessing the therapeutic equivalence of products and also outlines their valuable applications in generic product success. Understanding these critical in vitro parameters can probably help to decode the complex bioequivalence outcomes, directing the generic companies to optimize the formulation design in reduced time intervals. It is difficult to summarize a common platform which covers all possible transdermal products; hence few case studies based on this approach has been presented in this review.

Effect of Deformation Parameters on Microstructure and Properties During DIFT of X70HD Pipeline Steel

NASA Astrophysics Data System (ADS)

Wang, Jian; Zhu, Wei; Xiao, Hong; Zhang, Liang-liang; Qin, Hao; Yu, Yue

2018-02-01

Grain refinement is a critical approach to improve the strength of materials without damaging the toughness. The grains of deformation-induced ferrite are considerably smaller than those of proeutectoid ferrite. Grain refinement is crucial to the application of deformation-induced ferrite. The composition of ferrite and bainite or martensite is important in controlling the performance of X70HD pipeline steel, and cooling significantly influences the control of their ratio and grain size. By analyzing the static and dynamic phase-transition points using Gleeble-3800 thermal simulator, thermal simulations were performed through two-stage deformations in the austenite zone. Ferrite transformation rules were studied with thermal simulation tests under different deformation and cooling parameters based on the actual production of cumulative deformation. The influence of deformation parameters on the microstructure transformation was analyzed. Numerous fine-grain deformation-induced ferrites were obtained by regulating various parameters, including deformation temperature, strain rate, cooling rate, final cooling temperature and other parameters. Results of metallographic observation and microtensile testing revealed that the selection of appropriate parameters can refine the grains and improve the performance of the X70HD pipeline steel.

Investigation of two and three parameter equations of state for cryogenic fluids

NASA Technical Reports Server (NTRS)

Jenkins, Susan L.; Majumdar, Alok K.; Hendricks, Robert C.

1990-01-01

Two-phase flows are a common occurrence in cryogenic engines and an accurate evaluation of the heat-transfer coefficient in two-phase flow is of significant importance in their analysis and design. The thermodynamic equation of state plays a key role in calculating the heat transfer coefficient which is a function of thermodynamic and thermophysical properties. An investigation has been performed to study the performance of two- and three-parameter equations of state to calculate the compressibility factor of cryogenic fluids along the saturation loci. The two-parameter equations considered here are van der Waals and Redlich-Kwong equations of state. The three-parameter equation represented here is the generalized Benedict-Webb-Rubin (BWR) equation of Lee and Kesler. Results have been compared with the modified BWR equation of Bender and the extended BWR equations of Stewart. Seven cryogenic fluids have been tested; oxygen, hydrogen, helium, nitrogen, argon, neon, and air. The performance of the generalized BWR equation is poor for hydrogen and helium. The van der Waals equation is found to be inaccurate for air near the critical point. For helium, all three equations of state become inaccurate near the critical point.

Colloidal Fouling of Nanofiltration Membranes: Development of a Standard Operating Procedure

PubMed Central

Al Mamun, Md Abdullaha; Bhattacharjee, Subir; Pernitsky, David; Sadrzadeh, Mohtada

2017-01-01

Fouling of nanofiltration (NF) membranes is the most significant obstacle to the development of a sustainable and energy-efficient NF process. Colloidal fouling and performance decline in NF processes is complex due to the combination of cake formation and salt concentration polarization effects, which are influenced by the properties of the colloids and the membrane, the operating conditions of the test, and the solution chemistry. Although numerous studies have been conducted to investigate the influence of these parameters on the performance of the NF process, the importance of membrane preconditioning (e.g., compaction and equilibrating with salt water), as well as the determination of key parameters (e.g., critical flux and trans-membrane osmotic pressure) before the fouling experiment have not been reported in detail. The aim of this paper is to present a standard experimental and data analysis protocol for NF colloidal fouling experiments. The developed methodology covers preparation and characterization of water samples and colloidal particles, pre-test membrane compaction and critical flux determination, measurement of experimental data during the fouling test, and the analysis of that data to determine the relative importance of various fouling mechanisms. The standard protocol is illustrated with data from a series of flat sheet, bench-scale experiments. PMID:28106775

Guidelines for Proof Test Analysis

NASA Technical Reports Server (NTRS)

Chell, G. G.; McClung, R. C.; Kuhlman, C. J.; Russell, D. A.; Garr, K.; Donnelly, B.

1999-01-01

These guidelines integrate state-of-the-art elastic-plastic fracture mechanics (EPFM) and proof test implementation issues into a comprehensive proof test analysis procedure in the form of a road map which identifies the types of data, fracture mechanics based parameters, and calculations needed to perform flaw screening and minimum proof load analyses of fracture critical components. Worked examples are presented to illustrate the application of the road map to proof test analysis. The state-of-the art fracture technology employed in these guidelines is based on the EPFM parameter, J, and a pictorial representation of a J fracture analysis, called the failure assessment diagram (FAD) approach. The recommended fracture technology is validated using finite element J results, and laboratory and hardware fracture test results on the nickel-based superalloy Inconel 718, the aluminum alloy 2024-T3511, and ferritic pressure vessel steels. In all cases the laboratory specimens and hardware failed by ductile mechanisms. Advanced proof test analyses involving probability analysis and multiple-cycle proof testing (MCPT) are addressed. Finally, recommendations are provided on how to account for the effects of the proof test overload on subsequent service fatigue and fracture behaviors.

Investigation of aeroelastic stability phenomena of a helicopter by in-flight shake test

NASA Technical Reports Server (NTRS)

Miao, W. L.; Edwards, T.; Brandt, D. E.

1976-01-01

The analytical capability of the helicopter stability program is discussed. The parameters which are found to be critical to the air resonance characteristics of the soft in-plane hingeless rotor systems are detailed. A summary of two model test programs, a 1/13.8 Froude-scaled BO-105 model and a 1.67 meter (5.5 foot) diameter Froude-scaled YUH-61A model, are presented with emphasis on the selection of the final parameters which were incorporated in the full scale YUH-61A helicopter. Model test data for this configuration are shown. The actual test results of the YUH-61A air resonance in-flight shake test stability are presented. Included are a concise description of the test setup, which employs the Grumman Automated Telemetry System (ATS), the test technique for recording in-flight stability, and the test procedure used to demonstrate favorable stability characteristics with no in-plane damping augmentation (lag damper removed). The data illustrating the stability trend of air resonance with forward speed and the stability trend of ground resonance for percent airborne are presented.

Modelling aspects regarding the control in 13C isotope separation column

NASA Astrophysics Data System (ADS)

Boca, M. L.

2016-08-01

Carbon represents the fourth most abundant chemical element in the world, having two stable and one radioactive isotope. The 13Carbon isotopes, with a natural abundance of 1.1%, plays an important role in numerous applications, such as the study of human metabolism changes, molecular structure studies, non-invasive respiratory tests, Alzheimer tests, air pollution and global warming effects on plants [9] A manufacturing control system manages the internal logistics in a production system and determines the routings of product instances, the assignment of workers and components, the starting of the processes on not-yet-finished product instances. Manufacturing control does not control the manufacturing processes themselves, but has to cope with the consequences of the processing results (e.g. the routing of products to a repair station). In this research it was fulfilled some UML (Unified Modelling Language) diagrams for modelling the C13 Isotope Separation column, implement in STARUML program. Being a critical process and needing a good control and supervising, the critical parameters in the column, temperature and pressure was control using some PLC (Programmable logic controller) and it was made some graphic analyze for this to observe some critical situation than can affect the separation process. The main parameters that need to be control are: -The liquid nitrogen (N2) level in the condenser. -The electrical power supplied to the boiler. -The vacuum pressure.

Clinical Validation of Therapeutic Drug Monitoring of Imipenem in Spent Effluent in Critically Ill Patients Receiving Continuous Renal Replacement Therapy: A Pilot Study

PubMed Central

Wen, Aiping; Li, Zhe; Yu, Junxian; Li, Ren; Cheng, Sheng; Duan, Meili; Bai, Jing

2016-01-01

Objectives The primary objective of this pilot study was to investigate whether the therapeutic drug monitoring of imipenem could be performed with spent effluent instead of blood sampling collected from critically ill patients under continuous renal replacement therapy. Methods A prospective open-label study was conducted in a real clinical setting. Both blood and effluent samples were collected pairwise before imipenem administration and 0.5, 1, 1.5, 2, 3, 4, 6, and 8 h after imipenem administration. Plasma and effluent imipenem concentrations were determined by reversed-phase high-performance liquid chromatography with ultraviolet detection. Pharmacokinetic and pharmacodynamic parameters of blood and effluent samples were calculated. Results Eighty-three paired plasma and effluent samples were obtained from 10 patients. The Pearson correlation coefficient of the imipenem concentrations in plasma and effluent was 0.950 (P<0.0001). The average plasma-to-effluent imipenem concentration ratio was 1.044 (95% confidence interval, 0.975 to 1.114) with Bland-Altman analysis. No statistically significant difference was found in the pharmacokinetic and pharmacodynamic parameters tested in paired plasma and effluent samples with Wilcoxon test. Conclusion Spent effluent of continuous renal replacement therapy could be used for therapeutic drug monitoring of imipenem instead of blood sampling in critically ill patients. PMID:27093294

Design and technology parameters influence on durability for heat exchangers tube to tubesheet joints

NASA Astrophysics Data System (ADS)

Ripeanu, R. G.

2017-02-01

The main failures of heat exchangers are: corrosion of tubes and jacket, tubes blockage and failures of tube to tubesheet joints also by corrosion. The most critical zone is tube to tubesheet joints. Depending on types of tube to tubesheet joints, in order to better respect conditions of tension and compression, this paper analyses the tubesheet holes shapes, smooth and with a grove, on corrosion behavior. In the case of welding tubes with tubesheet, welding parameters modify corrosion behavior. Were realized welded joints by three welding regimes and tested at corrosion in two media, tap water and industrial water. Were tested also samples made of smooth tubes, finned tubes and tubes coated with a passive product as applied by a heat exchanger manufacturer. For all samples, the roughness parameters were measured, before and after the corrosion tests. The obtained corrosion rates show that stress values and their distribution along the joint modify the corrosion behavior. The optimum welding parameters were established in order to increase the joint durability. The paper has shown that passive product used is not proper chosen and the technology of obtaining rolled thread pipes diminishes tubes’ durability by increasing the corrosion rate.

An LTE effective temperature scale for red supergiants in the Magellanic clouds

NASA Astrophysics Data System (ADS)

Tabernero, H. M.; Dorda, R.; Negueruela, I.; González-Fernández, C.

2018-05-01

We present a self-consistent study of cool supergiants (CSGs) belonging to the Magellanic clouds. We calculated stellar atmospheric parameters using LTE KURUCZ and MARCS atmospheric models for more than 400 individual targets by fitting a careful selection of weak metallic lines. We explore the existence of a Teff scale and its implications in two different metallicity environments (each Magellanic cloud). Critical and in-depth tests have been performed to assess the reliability of our stellar parameters (i.e. internal error budget, NLTE systematics). In addition, several Monte Carlo tests have been carried out to infer the significance of the Teff scale found. Our findings point towards a unique Teff scale that seems to be independent of the environment.

[Non-animal toxicology in the safety testing of chemicals].

PubMed

Heinonen, Tuula; Tähti, Hanna

2013-01-01

There is an urgent need to develop predictive test methods better than animal experiments for assessing the safety of chemical substances to man. According to today's vision this is achieved by using human cell based tissue and organ models. In the new testing strategy the toxic effects are assessed by the changes in the critical parameters of the cellular biochemical routes (AOP, adverse toxic outcome pathway-principle) in the target tissues. In vitro-tests are rapid and effective, and with them automation can be applied. The change in the testing paradigm is supported by all stakeholders: scientists, regulators and people concerned on animal welfare.

In-flight friction and wear mechanism

NASA Technical Reports Server (NTRS)

Devine, E. J.; Evans, H. E.

1975-01-01

A unique mechanism developed for conducting friction and wear experiments in orbit is described. The device is capable of testing twelve material samples simultaneously. Parameters considered critical include: power, weight, volume, mounting, cleanliness, and thermal designs. The device performed flawlessly in orbit over an eighteen month period and demonstrated the usefulness of this design for future unmanned spacecraft or shuttle applications.

Development of Drop/Shock Test in Microelectronics and Impact Dynamic Analysis for Uniform Board Response

NASA Astrophysics Data System (ADS)

Kallolimath, Sharan Chandrashekar

For the past several years, many researchers are constantly developing and improving board level drop test procedures and specifications to quantify the solder joint reliability performance of consumer electronics products. Predictive finite element analysis (FEA) by utilizing simulation software has become widely acceptable verification method which can reduce time and cost of the real-time test process. However, due to testing and metrological limitations it is difficult not only to simulate exact drop condition and capture critical measurement data but also tedious to calibrate the system to improve test methods. Moreover, some of the important ever changing factors such as board flexural rigidity, damping, drop height, and drop orientation results in non-uniform stress/strain distribution throughout the test board. In addition, one of the most challenging tasks is to quantify uniform stress and strain distribution throughout the test board and identify critical failure factors. The major contributions of this work are in the four aspects of the drop test in electronics as following. First of all, an analytical FEA model was developed to study the board natural frequencies and responses of the system with the consideration of dynamic stiffness, damping behavior of the material and effect of impact loading condition. An approach to find the key parameters that affect stress and strain distributions under predominate mode responses was proposed and verified with theoretical solutions. Input-G method was adopted to study board response behavior and cut boundary interpolation methods was used to analyze local model solder joint stresses with the development of global/local FEA model in ANSYS software. Second, no ring phenomenon during the drop test was identified theoretically when the test board was modeled as both discrete system and continuous system. Numerical analysis was then conducted by FEA method for detailed geometry of attached chips with solder-joints. No ring test conditions was proposed and verified for the current widely used JEDEC standard. The significance of impact loading parameters such as pulse magnitude, pulse duration, pulse shapes and board dynamic parameter such as linear hysteretic damping and dynamic stiffness were discussed. Third, Kirchhoff's plate theory by principle of minimum potential energy was adopted to develop the FEA formulation to consider the effect of material hysteretic damping for the currently used JEDEC board test and proposed no-ring response test condition. Fourth, a hexagonal symmetrical board model was proposed to address the uniform stress and strain distribution throughout the test board and identify the critical failure factors. Dynamic stress and strain of the hexagonal board model were then compared with standard JEDEC board for both standard and proposed no-ring test conditions. In general, this line of research demonstrates that advanced techniques of FEA analysis can provide useful insights concerning the optimal design of drop test in microelectronics.

Critical Void Volume Fraction fc at Void Coalescence for S235JR Steel at Low Initial Stress Triaxiality

NASA Astrophysics Data System (ADS)

Grzegorz Kossakowski, Paweł; Wciślik, Wiktor

2017-10-01

The paper is concerned with the nucleation, growth and coalescence of microdefects in the form of voids in S235JR steel. The material is known to be one of the basic steel grades commonly used in the construction industry. The theory and methods of damage mechanics were applied to determine and describe the failure mechanisms that occur when the material undergoes deformation. Until now, engineers have generally employed the Gurson-Tvergaard- Needleman model. This material model based on damage mechanics is well suited to define and analyze failure processes taking place in the microstructure of S235JR steel. It is particularly important to determine the critical void volume fraction fc , which is one of the basic parameters of the Gurson-Tvergaard-Needleman material model. As the critical void volume fraction fc refers to the failure stage, it is determined from the data collected for the void coalescence phase. A case of multi-axial stresses is considered taking into account the effects of spatial stress state. In this study, the parameter of stress triaxiality η was used to describe the failure phenomena. Cylindrical tensile specimens with a circumferential notch were analysed to obtain low values of initial stress triaxiality (η = 0.556 of the range) in order to determine the critical void volume fraction fc . It is essential to emphasize how unique the method applied is and how different it is from the other more common methods involving parameter calibration, i.e. curve-fitting methods. The critical void volume fraction fc at void coalescence was established through digital image analysis of surfaces of S235JR steel, which involved studying real, physical results obtained directly from the material tested.

Implementation of quality by design approach in manufacturing process optimization of dry granulated, immediate release, coated tablets - a case study.

PubMed

Teżyk, Michał; Jakubowska, Emilia; Milanowski, Bartłomiej; Lulek, Janina

2017-10-01

The aim of this study was to optimize the process of tablets compression and identification of film-coating critical process parameters (CPPs) affecting critical quality attributes (CQAs) using quality by design (QbD) approach. Design of experiment (DOE) and regression methods were employed to investigate hardness, disintegration time, and thickness of uncoated tablets depending on slugging and tableting compression force (CPPs). Plackett-Burman experimental design was applied to identify critical coating process parameters among selected ones that is: drying and preheating time, atomization air pressure, spray rate, air volume, inlet air temperature, and drum pressure that may influence the hardness and disintegration time of coated tablets. As a result of the research, design space was established to facilitate an in-depth understanding of existing relationship between CPPs and CQAs of intermediate product (uncoated tablets). Screening revealed that spray rate and inlet air temperature are two most important factors that affect the hardness of coated tablets. Simultaneously, none of the tested coating factors have influence on disintegration time. The observation was confirmed by conducting film coating of pilot size batches.

Evaluation of variability and quality control procedures for a receptor-binding assay for paralytic shellfish poisoning toxins.

PubMed

Ruberu, S R; Langlois, G W; Masuda, M; Perera, S Kusum

2012-01-01

The receptor-binding assay (RBA) method for determining saxatoxin (STX) and its numerous analogues, which cause paralytic shellfish poisoning (PSP) in humans, was evaluated in a single laboratory study. Each step of the assay preparation procedure including the performance of the multi-detector TopCount® instrument was evaluated for its contribution to method variability. The overall inherent RBA variability was determined to be 17%. Variability within the 12 detectors was observed; however, there was no reproducible pattern in detector performance. This observed variability among detectors could be attributed to other factors, such as pipetting errors. In an attempt to reduce the number of plates rejected due to excessive variability in the method's quality control parameters, a statistical approach was evaluated using either Grubbs' test or the Student's t-test for rejecting outliers in the measurement of triplicate wells. This approach improved the ratio of accepted versus rejected plates, saving cost and time for rerunning the assay. However, the potential reduction in accuracy and the lack of improvement in precision suggests caution when using this approach. The current study has recommended an alternate quality control procedure for accepting or rejecting plates in place of the criteria currently used in the published assay, or the alternative of outlier testing. The recommended procedure involves the development of control charts to monitor the critical parameters identified in the published method (QC sample, EC₅₀, slope of calibration curve), with the addition of a fourth critical parameter which is the top value (100% binding) of the calibration curve.

Evaluation of an artificial intelligence guided inverse planning system: clinical case study.

PubMed

Yan, Hui; Yin, Fang-Fang; Willett, Christopher

2007-04-01

An artificial intelligence (AI) guided method for parameter adjustment of inverse planning was implemented on a commercial inverse treatment planning system. For evaluation purpose, four typical clinical cases were tested and the results from both plans achieved by automated and manual methods were compared. The procedure of parameter adjustment mainly consists of three major loops. Each loop is in charge of modifying parameters of one category, which is carried out by a specially customized fuzzy inference system. A physician prescribed multiple constraints for a selected volume were adopted to account for the tradeoff between prescription dose to the PTV and dose-volume constraints for critical organs. The searching process for an optimal parameter combination began with the first constraint, and proceeds to the next until a plan with acceptable dose was achieved. The initial setup of the plan parameters was the same for each case and was adjusted independently by both manual and automated methods. After the parameters of one category were updated, the intensity maps of all fields were re-optimized and the plan dose was subsequently re-calculated. When final plan arrived, the dose statistics were calculated from both plans and compared. For planned target volume (PTV), the dose for 95% volume is up to 10% higher in plans using the automated method than those using the manual method. For critical organs, an average decrease of the plan dose was achieved. However, the automated method cannot improve the plan dose for some critical organs due to limitations of the inference rules currently employed. For normal tissue, there was no significant difference between plan doses achieved by either automated or manual method. With the application of AI-guided method, the basic parameter adjustment task can be accomplished automatically and a comparable plan dose was achieved in comparison with that achieved by the manual method. Future improvements to incorporate case-specific inference rules are essential to fully automate the inverse planning process.

Blood Culture Testing via a Mobile App That Uses a Mobile Phone Camera: A Feasibility Study

PubMed Central

Chong, Yong Pil; Jang, Seongsoo; Kim, Mi Na; Kim, Jeong Hoon; Kim, Woo Sung

2016-01-01

Background To evaluate patients with fever of unknown origin or those with suspected bacteremia, the precision of blood culture tests is critical. An inappropriate step in the test process or error in a parameter could lead to a false-positive result, which could then affect the direction of treatment in critical conditions. Mobile health apps can be used to resolve problems with blood culture tests, and such apps can hence ensure that point-of-care guidelines are followed and processes are monitored for blood culture tests. Objective In this pilot project, we aimed to investigate the feasibility of using a mobile blood culture app to manage blood culture test quality. We implemented the app at a university hospital in South Korea to assess the potential for its utilization in a clinical environment by reviewing the usage data among a small group of users and by assessing their feedback and the data related to blood culture sampling. Methods We used an iOS-based blood culture app that uses an embedded camera to scan the patient identification and sample number bar codes. A total of 4 medical interns working at 2 medical intensive care units (MICUs) participated in this project, which spanned 3 weeks. App usage and blood culture sampling parameters (including sampler, sampling site, sampling time, and sample volume) were analyzed. The compliance of sampling parameter entry was also measured. In addition, the participants’ opinions regarding patient safety, timeliness, efficiency, and usability were recorded. Results In total, 356/644 (55.3%) of all blood culture samples obtained at the MICUs were examined using the app, including 254/356 (71.3%) with blood collection volumes of 5-7 mL and 256/356 (71.9%) with blood collection from the peripheral veins. The sampling volume differed among the participants. Sampling parameters were completely entered in 354/356 cases (99.4%). All the participants agreed that the app ensured good patient safety, disagreed on its timeliness, and did not believe that it was efficient. Although the bar code scanning speed was acceptable, the Wi-Fi environment required improvement. Moreover, the participants requested feedback regarding their sampling quality. Conclusions Although this app could be used in the clinical setting, improvements in the app functions, environment network, and internal policy of blood culture testing are needed to ensure hospital-wide use. PMID:27784649

Blood Culture Testing via a Mobile App That Uses a Mobile Phone Camera: A Feasibility Study.

PubMed

Lee, Guna; Lee, Yura; Chong, Yong Pil; Jang, Seongsoo; Kim, Mi Na; Kim, Jeong Hoon; Kim, Woo Sung; Lee, Jae-Ho

2016-10-26

To evaluate patients with fever of unknown origin or those with suspected bacteremia, the precision of blood culture tests is critical. An inappropriate step in the test process or error in a parameter could lead to a false-positive result, which could then affect the direction of treatment in critical conditions. Mobile health apps can be used to resolve problems with blood culture tests, and such apps can hence ensure that point-of-care guidelines are followed and processes are monitored for blood culture tests. In this pilot project, we aimed to investigate the feasibility of using a mobile blood culture app to manage blood culture test quality. We implemented the app at a university hospital in South Korea to assess the potential for its utilization in a clinical environment by reviewing the usage data among a small group of users and by assessing their feedback and the data related to blood culture sampling. We used an iOS-based blood culture app that uses an embedded camera to scan the patient identification and sample number bar codes. A total of 4 medical interns working at 2 medical intensive care units (MICUs) participated in this project, which spanned 3 weeks. App usage and blood culture sampling parameters (including sampler, sampling site, sampling time, and sample volume) were analyzed. The compliance of sampling parameter entry was also measured. In addition, the participants' opinions regarding patient safety, timeliness, efficiency, and usability were recorded. In total, 356/644 (55.3%) of all blood culture samples obtained at the MICUs were examined using the app, including 254/356 (71.3%) with blood collection volumes of 5-7 mL and 256/356 (71.9%) with blood collection from the peripheral veins. The sampling volume differed among the participants. Sampling parameters were completely entered in 354/356 cases (99.4%). All the participants agreed that the app ensured good patient safety, disagreed on its timeliness, and did not believe that it was efficient. Although the bar code scanning speed was acceptable, the Wi-Fi environment required improvement. Moreover, the participants requested feedback regarding their sampling quality. Although this app could be used in the clinical setting, improvements in the app functions, environment network, and internal policy of blood culture testing are needed to ensure hospital-wide use.

White Dwarf Critical Tests for Modified Gravity.

PubMed

Jain, Rajeev Kumar; Kouvaris, Chris; Nielsen, Niklas Grønlund

2016-04-15

Scalar-tensor theories of gravity can lead to modifications of the gravitational force inside astrophysical objects. We exhibit that compact stars such as white dwarfs provide a unique setup to test beyond Horndeski theories of G^{3} type. We obtain stringent and independent constraints on the parameter ϒ characterizing the deviations from Newtonian gravity using the mass-radius relation, the Chandrasekhar mass limit, and the maximal rotational frequency of white dwarfs. We find that white dwarfs impose stronger constraints on ϒ than red and brown dwarfs.

Development of a new test for the easy characterization of the adhesion at the interface of bilayer tablets: proof-of-concept study by experimental design.

PubMed

Busignies, Virginie; Mazel, Vincent; Diarra, Harona; Tchoreloff, Pierre

2014-12-30

Although, adhesion at the interface of bilayer tablets is critical for their design it is difficult to characterize this adhesion between layers. In view of this, a new test with an easy implementation was proposed for the characterization of the interface of bilayer tablets. This work is presented as a proof-of-concept study to investigate the reliability of this new test with regard to the effects of some critical process parameters (e.g., compaction pressure applied on each layer) and material attributes (e.g., elasticity of the layered materials) on the interfacial adhesion of bilayer tablets. This was investigated using a design of experiment approach and the results obtained were in good accordance with those obtained with other tests and thus, confirms the potential of such a method for the measurement of the interfacial adhesion of bilayer tablets. Copyright © 2014 Elsevier B.V. All rights reserved.

Crosswinds Effect on the Thermal Performance of Wet Cooling Towers Under Variable Operating Conditions

NASA Astrophysics Data System (ADS)

Chen, You Liang; Shi, Yong Feng; Hao, Jian Gang; Chang, Hao; Sun, Feng Zhong

2018-01-01

In order to quantitatively analyze the influence of the variable operating parameters on the cooling performance of natural draft wet cooling towers (NDWCTs), a hot model test system was set up with adjustable ambient temperature and humidity, circulating water flowrate and temperature. In order to apply the hot model test results to the real tower, the crosswind Froude number is defined. The results show that the crosswind has a negative effect on the thermal performance of the cooling tower, and there is a critical crosswind velocity corresponding to the lowest cooling efficiency. According to the crosswind Froude number similarity, when the ambient temperature decreases, or the circulating water flowrate and temperature increase, the cooling tower draft force will increase, and the critical crosswind velocity will increase correspondingly.

Variability metrics in Josephson Junction fabrication for Quantum Computing circuits

NASA Astrophysics Data System (ADS)

Rosenblatt, Sami; Hertzberg, Jared; Brink, Markus; Chow, Jerry; Gambetta, Jay; Leng, Zhaoqi; Houck, Andrew; Nelson, J. J.; Plourde, Britton; Wu, Xian; Lake, Russell; Shainline, Jeff; Pappas, David; Patel, Umeshkumar; McDermott, Robert

Multi-qubit gates depend on the relative frequencies of the qubits. To reliably build multi-qubit devices therefore requires careful fabrication of Josephson junctions in order to precisely set their critical currents. The Ambegaokar-Baratoff relation between tunnel conductance and critical current implies a correlation between qubit frequency spread and tunnel junction resistance spread. Here we discuss measurement of large numbers of tunnel junctions to assess these resistance spreads, which can exceed 5% of mean resistance. With the goal of minimizing these spreads, we investigate process parameters such as lithographic junction area, evaporation and masking scheme, oxidation conditions, and substrate choice, as well as test environment, design and setup. In addition, trends of junction resistance with temperature are compared with theoretical models for further insights into process and test variability.

Design and landing dynamic analysis of reusable landing leg for a near-space manned capsule

NASA Astrophysics Data System (ADS)

Yue, Shuai; Nie, Hong; Zhang, Ming; Wei, Xiaohui; Gan, Shengyong

2018-06-01

To improve the landing performance of a near-space manned capsule under various landing conditions, a novel landing system is designed that employs double chamber and single chamber dampers in the primary and auxiliary struts, respectively. A dynamic model of the landing system is established, and the damper parameters are determined by employing the design method. A single-leg drop test with different initial pitch angles is then conducted to compare and validate the simulation model. Based on the validated simulation model, seven critical landing conditions regarding nine crucial landing responses are found by combining the radial basis function (RBF) surrogate model and adaptive simulated annealing (ASA) optimization method. Subsequently, the adaptability of the landing system under critical landing conditions is analyzed. The results show that the simulation effectively results match the test results, which validates the accuracy of the dynamic model. In addition, all of the crucial responses under their corresponding critical landing conditions satisfy the design specifications, demonstrating the feasibility of the landing system.

Measurement of the Rheological Properties of High Performance Concrete: State of the Art Report

PubMed Central

Ferraris, Chiara F.

1999-01-01

The rheological or flow properties of concrete in general and of high performance concrete (HPC) in particular, are important because many factors such as ease of placement, consolidation, durability, and strength depend on the flow properties. Concrete that is not properly consolidated may have defects, such as honeycombs, air voids, and aggregate segregation. Such an important performance attribute has triggered the design of numerous test methods. Generally, the flow behavior of concrete approximates that of a Bingham fluid. Therefore, at least two parameters, yield stress and viscosity, are necessary to characterize the flow. Nevertheless, most methods measure only one parameter. Predictions of the flow properties of concrete from its composition or from the properties of its components are not easy. No general model exists, although some attempts have been made. This paper gives an overview of the flow properties of a fluid or a suspension, followed by a critical review of the most commonly used concrete rheology tests. Particular attention is given to tests that could be used for HPC. Tentative definitions of terms such as workability, consistency, and rheological parameters are provided. An overview of the most promising tests and models for cement paste is given.

Buckling of thermally fluctuating spherical shells: Parameter renormalization and thermally activated barrier crossing

NASA Astrophysics Data System (ADS)

Baumgarten, Lorenz; Kierfeld, Jan

2018-05-01

We study the influence of thermal fluctuations on the buckling behavior of thin elastic capsules with spherical rest shape. Above a critical uniform pressure, an elastic capsule becomes mechanically unstable and spontaneously buckles into a shape with an axisymmetric dimple. Thermal fluctuations affect the buckling instability by two mechanisms. On the one hand, thermal fluctuations can renormalize the capsule's elastic properties and its pressure because of anharmonic couplings between normal displacement modes of different wavelengths. This effectively lowers its critical buckling pressure [Košmrlj and Nelson, Phys. Rev. X 7, 011002 (2017), 10.1103/PhysRevX.7.011002]. On the other hand, buckled shapes are energetically favorable already at pressures below the classical buckling pressure. At these pressures, however, buckling requires to overcome an energy barrier, which only vanishes at the critical buckling pressure. In the presence of thermal fluctuations, the capsule can spontaneously overcome an energy barrier of the order of the thermal energy by thermal activation already at pressures below the critical buckling pressure. We revisit parameter renormalization by thermal fluctuations and formulate a buckling criterion based on scale-dependent renormalized parameters to obtain a temperature-dependent critical buckling pressure. Then we quantify the pressure-dependent energy barrier for buckling below the critical buckling pressure using numerical energy minimization and analytical arguments. This allows us to obtain the temperature-dependent critical pressure for buckling by thermal activation over this energy barrier. Remarkably, both parameter renormalization and thermal activation lead to the same parameter dependence of the critical buckling pressure on temperature, capsule radius and thickness, and Young's modulus. Finally, we study the combined effect of parameter renormalization and thermal activation by using renormalized parameters for the energy barrier in thermal activation to obtain our final result for the temperature-dependent critical pressure, which is significantly below the results if only parameter renormalization or only thermal activation is considered.

A criticality result for polycycles in a family of quadratic reversible centers

NASA Astrophysics Data System (ADS)

Rojas, D.; Villadelprat, J.

2018-06-01

We consider the family of dehomogenized Loud's centers Xμ = y (x - 1)∂x + (x + Dx2 + Fy2)∂y, where μ = (D , F) ∈R2, and we study the number of critical periodic orbits that emerge or disappear from the polycycle at the boundary of the period annulus. This number is defined exactly the same way as the well-known notion of cyclicity of a limit periodic set and we call it criticality. The previous results on the issue for the family {Xμ , μ ∈R2 } distinguish between parameters with criticality equal to zero (regular parameters) and those with criticality greater than zero (bifurcation parameters). A challenging problem not tackled so far is the computation of the criticality of the bifurcation parameters, which form a set ΓB of codimension 1 in R2. In the present paper we succeed in proving that a subset of ΓB has criticality equal to one.

Product Module Rig Test

NASA Technical Reports Server (NTRS)

Holdeman, James D. (Technical Monitor); Chiappetta, Louis, Jr.; Hautman, Donald J.; Ols, John T.; Padget, Frederick C., IV; Peschke, William O. T.; Shirley, John A.; Siskind, Kenneth S.

2004-01-01

The low emissions potential of a Rich-Quench-Lean (RQL) combustor for use in the High Speed Civil Transport (HSCT) application was evaluated as part of Work Breakdown Structure (WBS) 1.0.2.7 of the NASA Critical Propulsion Components (CPC) Program under Contract NAS3-27235. Combustion testing was conducted in cell 1E of the Jet Burner Test Stand at United Technologies Research Center. Specifically, a Rich-Quench-Lean combustor, utilizing reduced scale quench technology implemented in a quench vane concept in a product-like configuration (Product Module Rig), demonstrated the capability of achieving an emissions index of nitrogen oxides (NOx EI) of 8.5 gm/Kg fuel at the supersonic flight condition (relative to the program goal of 5 gm/Kg fuel). Developmental parametric testing of various quench vane configurations in the more fundamental flametube, Single Module Rig Configuration, demonstrated NOx EI as low as 5.2. All configurations in both the Product Module Rig configuration and the Single Module Rig configuration demonstrated exceptional efficiencies, greater than 99.95 percent, relative to the program goal of 99.9 percent efficiency at supersonic cruise conditions. Sensitivity of emissions to quench orifice design parameters were determined during the parametric quench vane test series in support of the design of the Product Module Rig configuration. For the rectangular quench orifices investigated, an aspect ratio (length/width) of approximately 2 was found to be near optimum. An optimum for orifice spacing was found to exist at approximately 0.167 inches, resulting in 24 orifices per side of a quench vane, for the 0.435 inch quench zone channel height investigated in the Single Module Rig. Smaller quench zone channel heights appeared to be beneficial in reducing emissions. Measurements were also obtained in the Single Module Rig configuration on the sensitivity of emissions to the critical combustor parameters of fuel/air ratio, pressure drop, and residence time. Minimal sensitivity was observed for all of these parameters.

TESTING OF TMR SAND MANTIS FINAL REPORT

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

Krementz, D; William Daugherty, W

2007-06-12

Screening tests of Sand Mantis candidate materials selected for erosion resistance have been completed. The results of this testing identified that over a relatively short period of operation (<1 hour), measurable erosion will occur in each of the candidate zoom tube materials given equal operating exposure. Additionally, this testing has shown that erosion of the rubber discharge hose directly downstream of the vehicle could be expected to limit the service life of the discharge hose. On the basis of these test results, SRNL recommends the following; {lg_bullet} redesign of critical system components (e.g., zoom tube, discharge hose) should be conductedmore » to improve system characteristics relative to erosion and capitalize on the results of this testing, {lg_bullet} continued efforts to deploy the Sand Mantis should include testing to better define and optimize operating parameters, and gain an understanding of system dynamics, {lg_bullet} discontinue wear testing with the selected materials pending redesign of critical system components (1st recommendation) and inclusion of other candidate materials. The final selection of additional candidate materials should be made following design changes, but might include a Stellite alloy or zirconia.« less

Original electric-vertex formulation of the symmetric eight-vertex model on the square lattice is fully nonuniversal

NASA Astrophysics Data System (ADS)

Krčmár, Roman; Šamaj, Ladislav

2018-01-01

The partition function of the symmetric (zero electric field) eight-vertex model on a square lattice can be formulated either in the original "electric" vertex format or in an equivalent "magnetic" Ising-spin format. In this paper, both electric and magnetic versions of the model are studied numerically by using the corner transfer matrix renormalization-group method which provides reliable data. The emphasis is put on the calculation of four specific critical exponents, related by two scaling relations, and of the central charge. The numerical method is first tested in the magnetic format, the obtained dependencies of critical exponents on the model's parameters agree with Baxter's exact solution, and weak universality is confirmed within the accuracy of the method due to the finite size of the system. In particular, the critical exponents η and δ are constant as required by weak universality. On the other hand, in the electric format, analytic formulas based on the scaling relations are derived for the critical exponents ηe and δe which agree with our numerical data. These exponents depend on the model's parameters which is evidence for the full nonuniversality of the symmetric eight-vertex model in the original electric formulation.

Critical parameters for sterilization of oil palm fruit by microwave irradiation

NASA Astrophysics Data System (ADS)

Sarah, Maya; Taib, M. R.

2017-08-01

Study to evaluate critical parameters for microwave irradiation to sterilize oil palm fruit was carried out at power density of 560 to 1120 W/kg. Critical parameters are important to ensure moisture loss during sterilization exceed the critical moisture (Mc) but less than maximum moisture (Mmax). Critical moisture in this study was determined according to dielectric loss factor of heated oil palm fruits at 2450 MHz. It was obtained from slope characterization of dielectric loss factor-vs-moisture loss curve. The Mc was used to indicate critical temperature (Tc) and critical time (tc) for microwave sterilization. To ensure moisture loss above critical value but not exceed maximum value, the combinations of time-temperature for sterilization of oil palm fruits by microwave irradiation were 6 min and 75°C to 17 min and 82°C respectively.

Standard methods for filled hole tension testing of textile composites

NASA Technical Reports Server (NTRS)

Portanova, M. A.; Masters, J. E.

1995-01-01

The effects of two test specimen geometry parameters, the specimen width and W/D ratio, on filled-hole tensile strength were determined for textile composite materials. Test data generated by Boeing and Lockheed on 2-D and 3-D braids, and 3-D weaves were used to make these evaluations. The investigation indicated that filled-hole tensile-strength showed little sensitivity to either parameter. Test specimen configurations used in open-hole tension tests, such as those suggested by ASTM D5766 - Standard Test Method for Open Hole Tensile Strength of Polymer Matrix Composite Laminates or those proposed by MIL-HDBK-17-lD should provide adequate results for material comparisons studies. Comparisons of the materials' open-hole and filled-hole tensile strengths indicated that the latter were generally lower than the former. The 3-D braids were the exception; their filled-hole strengths were unexpected larger than their open-hole strengths. However, these increases were small compared to the scatter in the data. Thus, filled hole tension may be a critical design consideration for textile composite materials.

Aspirated High Pressure Compressor

DTIC Science & Technology

2006-08-01

nature of blowdown experiments dictate that these parameters vary throughout the duration of the test. Previous work, by many investigators, has shown...Figure 3.5. Important aspects of the design of the forward section are the pressure screen, the cantilevered nature of the housing for the 32...flywheel, and choosing tolerances of critical interfaces so that the appropriate parts were concentric about an axis. fl - .crt Flowpath

Residual Stress Measurement and Calibration for A7N01 Aluminum Alloy Welded Joints by Using Longitudinal Critically Refracted ( LCR) Wave Transmission Method

NASA Astrophysics Data System (ADS)

Zhu, Qimeng; Chen, Jia; Gou, Guoqing; Chen, Hui; Li, Peng; Gao, W.

2016-10-01

Residual stress measurement and control are highly important for the safety of structures of high-speed trains, which is critical for the structure design. The longitudinal critically refracted wave technology is the most widely used method in measuring residual stress with ultrasonic method, but its accuracy is strongly related to the test parameters, namely the flight time at the free-stress condition ( t 0), stress coefficient ( K), and initial stress (σ0) of the measured materials. The difference of microstructure in the weld zone, heat affected zone, and base metal (BM) results in the divergence of experimental parameters. However, the majority of researchers use the BM parameters to determine the residual stress in other zones and ignore the initial stress (σ0) in calibration samples. Therefore, the measured residual stress in different zones is often high in errors and may result in the miscalculation of the safe design of important structures. A serious problem in the ultrasonic estimation of residual stresses requires separation between the microstructure and the acoustoelastic effects. In this paper, the effects of initial stress and microstructure on stress coefficient K and flight time t 0 at free-stress conditions have been studied. The residual stress with or without different corrections was investigated. The results indicated that the residual stresses obtained with correction are more accurate for structure design.

Ultrasonic fatigue of a high strength steel

NASA Astrophysics Data System (ADS)

Koster, M.; Wagner, G.; Eifler, D.

2010-07-01

At the Institute of Materials Science and Engineering at the University of Kaiserslautern an ultrasonic testing system for the fatigue assessment of metallic materials in the very high cycle fatigue (VHCF) regime was developed. The ultrasonic testing system allows to control the test and to measure detailed fatigue data. The achieved results can be used to describe the cyclic deformation behaviour of wheel steels at ultrasonic frequencies. In load increase tests (LIT), the critical stress amplitude can be determined, which leads to a defined change of process parameters like generator power, dissipated energy and specimen temperature. With SEM investigations it was proved that the change of the process parameters correlates with irreversible changes in the microstructure. It can be shown that the stress amplitude, leading to first irreversible changes in the microstructure, strongly depends on the depth position within the original wheel rim. New and basic results on the fatigue mechanisms of high strength steels in the VHCF-regime can be achieved.

1 MVA HTS-2G Generator for Wind Turbines

NASA Astrophysics Data System (ADS)

Kovalev, K. L.; Poltavets, V. N.; Ilyasov, R. I.; Verzhbitsky, L. G.; Kozub, S. S.

2017-10-01

The calculation, design simulations and design performance of 1 MVA HTS-2G (second-generation high-temperature superconductor) Generator for Wind Turbines were done in 2013-2014 [1]. The results of manufacturing and testing of 1 MVA generator are presented in the article. HTS-2G field coils for the rotor were redesigned, fabricated and tested. The tests have shown critical current of the coils, 41-45 A (self field within the ferromagnetic core, T = 77 K), which corresponds to the current of short samples at self field. Application of the copper inner frame on the pole has improved internal cooling conditions of HTS coil windings and reduced the magnetic field in the area, thereby increased the critical current value. The original construction of the rotor with a rotating cryostat was developed, which decreases the thermal in-flow to the rotor. The stator of 1 MW HTS-2G generator has been manufactured. In order to improve the specific weight of the generator, the wave (harmonic drive) multiplier was used, which provides increasing RPM from 15 RPM up to 600 RPM. The total mass of the multiplier and generator is significantly smaller compared to traditional direct-drive wind turbines generators [2-7]. Parameters of the multiplier and generator were chosen based on the actual parameters of wind turbines, namely: 15 RPM, power is 1 MVA. The final test of the assembled synchronous generator with HTS-2G field coils for Wind Turbines with output power 1 MVA was completed during 2015.

Testing General Relativity with the Radio Science Experiment of the BepiColombo mission to Mercury

NASA Astrophysics Data System (ADS)

Schettino, Giulia; Tommei, Giacomo

2016-09-01

The relativity experiment is part of the Mercury Orbiter Radio science Experiment (MORE) on-board the ESA/JAXA BepiColombo mission to Mercury. Thanks to very precise radio tracking from the Earth and accelerometer, it will be possible to perform an accurate test of General Relativity, by constraining a number of post-Newtonian and related parameters with an unprecedented level of accuracy. The Celestial Mechanics Group of the University of Pisa developed a new dedicated software, ORBIT14, to perform the simulations and to determine simultaneously all the parameters of interest within a global least squares fit. After highlighting some critical issues, we report on the results of a full set of simulations, carried out in the most up-to-date mission scenario. For each parameter we discuss the achievable accuracy, in terms of a formal analysis through the covariance matrix and, furthermore, by the introduction of an alternative, more representative, estimation of the errors. We show that, for example, an accuracy of some parts in 10^-6 for the Eddington parameter β and of 10^-5 for the Nordtvedt parameter η can be attained, while accuracies at the level of 5×10^-7 and 1×10^-7 can be achieved for the preferred frames parameters α1 and α2, respectively.

Critical parameters of hard-core Yukawa fluids within the structural theory

NASA Astrophysics Data System (ADS)

Bahaa Khedr, M.; Osman, S. M.

2012-10-01

A purely statistical mechanical approach is proposed to account for the liquid-vapor critical point based on the mean density approximation (MDA) of the direct correlation function. The application to hard-core Yukawa (HCY) fluids facilitates the use of the series mean spherical approximation (SMSA). The location of the critical parameters for HCY fluid with variable intermolecular range is accurately calculated. Good agreement is observed with computer simulation results and with the inverse temperature expansion (ITE) predictions. The influence of the potential range on the critical parameters is demonstrated and the universality of the critical compressibility ratio is discussed. The behavior of the isochoric and isobaric heat capacities along the equilibrium line and the near vicinity of the critical point is discussed in details.

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

Khomkin, A. L., E-mail: alhomkin@mail.ru; Shumikhin, A. S.

The conductivity of metal vapors at the critical point and near it has been considered. The liquid-metal conductivity originates in this region. The thermodynamic parameters of the critical point, the density of conduction electrons, and the conductivities of various metal vapors have been calculated within the unified approach. It has been proposed to consider the conductivity at the critical point—critical conductivity—as the fourth critical parameter in addition to the density, temperature, and pressure.

Unscented Kalman filter with parameter identifiability analysis for the estimation of multiple parameters in kinetic models

PubMed Central

2011-01-01

In systems biology, experimentally measured parameters are not always available, necessitating the use of computationally based parameter estimation. In order to rely on estimated parameters, it is critical to first determine which parameters can be estimated for a given model and measurement set. This is done with parameter identifiability analysis. A kinetic model of the sucrose accumulation in the sugar cane culm tissue developed by Rohwer et al. was taken as a test case model. What differentiates this approach is the integration of an orthogonal-based local identifiability method into the unscented Kalman filter (UKF), rather than using the more common observability-based method which has inherent limitations. It also introduces a variable step size based on the system uncertainty of the UKF during the sensitivity calculation. This method identified 10 out of 12 parameters as identifiable. These ten parameters were estimated using the UKF, which was run 97 times. Throughout the repetitions the UKF proved to be more consistent than the estimation algorithms used for comparison. PMID:21989173

Critical physiological factors influencing the outcome of antimicrobial testing according to ISO 22196 / JIS Z 2801.

PubMed

Wiegand, Cornelia; Völpel, Andrea; Ewald, Andrea; Remesch, Markko; Kuever, Jan; Bauer, Janine; Griesheim, Stefanie; Hauser, Carolin; Thielmann, Julian; Tonndorf-Martini, Silke; Sigusch, Bernd W; Weisser, Jürgen; Wyrwa, Ralf; Elsner, Peter; Hipler, Uta-Christina; Roth, Martin; Dewald, Carolin; Lüdecke-Beyer, Claudia; Bossert, Jörg

2018-01-01

Bactericidal materials gained interest in the health care sector as they are capable of preventing material surfaces from microbial colonization and subsequent spread of infections. However, commercialization of antimicrobial materials requires proof of their efficacy, which is usually done using in vitro methods. The ISO 22196 standard (Japanese test method JIS Z 2801) is a method for measuring the antibacterial activity of daily goods. As it was found reliable for testing the biocidal activity of antimicrobially active materials and surface coatings most of the laboratories participating in this study used this protocol. Therefore, a round robin test for evaluating antimicrobially active biomaterials had to be established. To our knowledge, this is the first report on inaugurating a round robin test for the ISO 22196 / JIS Z 2801. The first round of testing showed that analyses in the different laboratories yielded different results, especially for materials with intermediate antibacterial effects distinctly different efficacies were noted. Scrutinizing the protocols used by the different participants and identifying the factors influencing the test outcomes the approach was unified. Four critical factors influencing the outcome of antibacterial testing were identified in a series of experiments: (1) incubation time, (2) bacteria starting concentration, (3) physiological state of bacteria (stationary or exponential phase of growth), and (4) nutrient concentration. To our knowledge, this is the first time these parameters have been analyzed for their effect on the outcome of testing according to ISO 22196 / JIS Z 2801. In conclusion, to enable assessment of the results obtained it is necessary to evaluate these single parameters in the test protocol carefully. Furthermore, uniform and robust definitions of the terms antibacterial efficacy / activity, bacteriostatic effects, and bactericidal action need to be agreed upon to simplify communication of results and also regulate expectations regarding antimicrobial tests, outcomes, and materials.

Critical physiological factors influencing the outcome of antimicrobial testing according to ISO 22196 / JIS Z 2801

PubMed Central

Völpel, Andrea; Ewald, Andrea; Remesch, Markko; Kuever, Jan; Bauer, Janine; Griesheim, Stefanie; Hauser, Carolin; Thielmann, Julian; Tonndorf-Martini, Silke; Sigusch, Bernd W.; Weisser, Jürgen; Wyrwa, Ralf; Elsner, Peter; Hipler, Uta-Christina; Roth, Martin; Dewald, Carolin; Lüdecke-Beyer, Claudia; Bossert, Jörg

2018-01-01

Bactericidal materials gained interest in the health care sector as they are capable of preventing material surfaces from microbial colonization and subsequent spread of infections. However, commercialization of antimicrobial materials requires proof of their efficacy, which is usually done using in vitro methods. The ISO 22196 standard (Japanese test method JIS Z 2801) is a method for measuring the antibacterial activity of daily goods. As it was found reliable for testing the biocidal activity of antimicrobially active materials and surface coatings most of the laboratories participating in this study used this protocol. Therefore, a round robin test for evaluating antimicrobially active biomaterials had to be established. To our knowledge, this is the first report on inaugurating a round robin test for the ISO 22196 / JIS Z 2801. The first round of testing showed that analyses in the different laboratories yielded different results, especially for materials with intermediate antibacterial effects distinctly different efficacies were noted. Scrutinizing the protocols used by the different participants and identifying the factors influencing the test outcomes the approach was unified. Four critical factors influencing the outcome of antibacterial testing were identified in a series of experiments: (1) incubation time, (2) bacteria starting concentration, (3) physiological state of bacteria (stationary or exponential phase of growth), and (4) nutrient concentration. To our knowledge, this is the first time these parameters have been analyzed for their effect on the outcome of testing according to ISO 22196 / JIS Z 2801. In conclusion, to enable assessment of the results obtained it is necessary to evaluate these single parameters in the test protocol carefully. Furthermore, uniform and robust definitions of the terms antibacterial efficacy / activity, bacteriostatic effects, and bactericidal action need to be agreed upon to simplify communication of results and also regulate expectations regarding antimicrobial tests, outcomes, and materials. PMID:29558480

Mean curvature model for a quasi-static advancing meniscus: a drop tower test

NASA Astrophysics Data System (ADS)

Chen, Yongkang; Tavan, Noel; Weislogel, Mark

A critical geometric wetting condition resulting in a significant shift of a capillary fluid from one region of a container to another was recently demonstrated during experiments performed aboard the International Space Station (the Capillary Flow Experiments, Vane Gap test units, bulk shift phenomena). Such phenomena are of interest for advanced methods of control for large quantities of liquids aboard spacecraft. The dynamics of the flows are well understood, but analytical models remain qualitative without the correct capillary pressure driving force for the shifting bulk fluid—where one large interface (meniscus) advances while another recedes. To determine this pressure an investigation of the mean curvature of the advancing meniscus is presented which is inspired by earlier studies of receding bulk menisci in non-circular cylindrical containers. The approach is permissible only in the quasi-static limit. It will be shown that the mean curvature of the advancing bulk meniscus is related to that of the receding bulk meniscus, both of which are highly sensitive to container geometry and wetting conditions. The two meniscus curvatures are identical for any control parameter at the critical value identified by the Concus-Finn analysis. However, they differ when the control parameter is below its critical value. Experiments along these lines are well suited for drop towers and comparisons with the analytical predictions implementing the mean curvature model are presented. The validation opens a pathway to the analysis of such flows in containers of great geometric complexity.

Hall Thruster Thermal Modeling and Test Data Correlation

NASA Technical Reports Server (NTRS)

Myers, James; Kamhawi, Hani; Yim, John; Clayman, Lauren

2016-01-01

The life of Hall Effect thrusters are primarily limited by plasma erosion and thermal related failures. NASA Glenn Research Center (GRC) in cooperation with the Jet Propulsion Laboratory (JPL) have recently completed development of a Hall thruster with specific emphasis to mitigate these limitations. Extending the operational life of Hall thursters makes them more suitable for some of NASA's longer duration interplanetary missions. This paper documents the thermal model development, refinement and correlation of results with thruster test data. Correlation was achieved by minimizing uncertainties in model input and recognizing the relevant parameters for effective model tuning. Throughout the thruster design phase the model was used to evaluate design options and systematically reduce component temperatures. Hall thrusters are inherently complex assemblies of high temperature components relying on internal conduction and external radiation for heat dispersion and rejection. System solutions are necessary in most cases to fully assess the benefits and/or consequences of any potential design change. Thermal model correlation is critical since thruster operational parameters can push some components/materials beyond their temperature limits. This thruster incorporates a state-of-the-art magnetic shielding system to reduce plasma erosion and to a lesser extend power/heat deposition. Additionally a comprehensive thermal design strategy was employed to reduce temperatures of critical thruster components (primarily the magnet coils and the discharge channel). Long term wear testing is currently underway to assess the effectiveness of these systems and consequently thruster longevity.

NASA Contractor Report: Guidelines for Proof Test Analysis

NASA Technical Reports Server (NTRS)

Chell, G. G.; McClung, R. C.; Kuhlman, C. J.; Russell, D. A.; Garr, K.; Donnelly, B.

1997-01-01

These Guidelines integrate state-of-the-art Elastic-Plastic Fracture Mechanics (EPFM) and proof test implementation issues into a comprehensive proof test analysis procedure in the form of a Road Map which identifies the types of data, fracture mechanics based parameters, and calculations needed to perform flaw screening and minimum proof load analyses of fracture critical components. Worked examples are presented to illustrate the application of the Road Map to proof test analysis. The state-of-the-art fracture technology employed in these Guidelines is based on the EPFM parameter, J, and a pictorial representation of a J fracture analysis, called the Failure Assessment Diagram (FAD) approach. The recommended fracture technology is validated using finite element J results, and laboratory and hardware fracture test results on the nickel-based superalloy IN-718, the aluminum alloy 2024-T351 1, and ferritic pressure vessel steels. In all cases the laboratory specimens and hardware failed by ductile mechanisms. Advanced proof test analyses involving probability analysis and Multiple Cycle Proof Testing (MCPT) are addressed. Finally, recommendations are provided on to how to account for the effects of the proof test overload on subsequent service fatigue and fracture behaviors.

Highly adaptive tests for group differences in brain functional connectivity.

PubMed

Kim, Junghi; Pan, Wei

2015-01-01

Resting-state functional magnetic resonance imaging (rs-fMRI) and other technologies have been offering evidence and insights showing that altered brain functional networks are associated with neurological illnesses such as Alzheimer's disease. Exploring brain networks of clinical populations compared to those of controls would be a key inquiry to reveal underlying neurological processes related to such illnesses. For such a purpose, group-level inference is a necessary first step in order to establish whether there are any genuinely disrupted brain subnetworks. Such an analysis is also challenging due to the high dimensionality of the parameters in a network model and high noise levels in neuroimaging data. We are still in the early stage of method development as highlighted by Varoquaux and Craddock (2013) that "there is currently no unique solution, but a spectrum of related methods and analytical strategies" to learn and compare brain connectivity. In practice the important issue of how to choose several critical parameters in estimating a network, such as what association measure to use and what is the sparsity of the estimated network, has not been carefully addressed, largely because the answers are unknown yet. For example, even though the choice of tuning parameters in model estimation has been extensively discussed in the literature, as to be shown here, an optimal choice of a parameter for network estimation may not be optimal in the current context of hypothesis testing. Arbitrarily choosing or mis-specifying such parameters may lead to extremely low-powered tests. Here we develop highly adaptive tests to detect group differences in brain connectivity while accounting for unknown optimal choices of some tuning parameters. The proposed tests combine statistical evidence against a null hypothesis from multiple sources across a range of plausible tuning parameter values reflecting uncertainty with the unknown truth. These highly adaptive tests are not only easy to use, but also high-powered robustly across various scenarios. The usage and advantages of these novel tests are demonstrated on an Alzheimer's disease dataset and simulated data.

Techniques and Protocols for Dispersing Nanoparticle Powders in Aqueous Media-Is there a Rationale for Harmonization?

PubMed

Hartmann, Nanna B; Jensen, Keld Alstrup; Baun, Anders; Rasmussen, Kirsten; Rauscher, Hubert; Tantra, Ratna; Cupi, Denisa; Gilliland, Douglas; Pianella, Francesca; Riego Sintes, Juan M

2015-01-01

Selecting appropriate ways of bringing engineered nanoparticles (ENP) into aqueous dispersion is a main obstacle for testing, and thus for understanding and evaluating, their potential adverse effects to the environment and human health. Using different methods to prepare (stock) dispersions of the same ENP may be a source of variation in the toxicity measured. Harmonization and standardization of dispersion methods applied in mammalian and ecotoxicity testing are needed to ensure a comparable data quality and to minimize test artifacts produced by modifications of ENP during the dispersion preparation process. Such harmonization and standardization will also enhance comparability among tests, labs, and studies on different types of ENP. The scope of this review was to critically discuss the essential parameters in dispersion protocols for ENP. The parameters are identified from individual scientific studies and from consensus reached in larger scale research projects and international organizations. A step-wise approach is proposed to develop tailored dispersion protocols for ecotoxicological and mammalian toxicological testing of ENP. The recommendations of this analysis may serve as a guide to researchers, companies, and regulators when selecting, developing, and evaluating the appropriateness of dispersion methods applied in mammalian and ecotoxicity testing. However, additional experimentation is needed to further document the protocol parameters and investigate to what extent different stock dispersion methods affect ecotoxicological and mammalian toxicological responses of ENP.

Uncertainty quantification and propagation of errors of the Lennard-Jones 12-6 parameters for n-alkanes

PubMed Central

Knotts, Thomas A.

2017-01-01

Molecular simulation has the ability to predict various physical properties that are difficult to obtain experimentally. For example, we implement molecular simulation to predict the critical constants (i.e., critical temperature, critical density, critical pressure, and critical compressibility factor) for large n-alkanes that thermally decompose experimentally (as large as C48). Historically, molecular simulation has been viewed as a tool that is limited to providing qualitative insight. One key reason for this perceived weakness in molecular simulation is the difficulty to quantify the uncertainty in the results. This is because molecular simulations have many sources of uncertainty that propagate and are difficult to quantify. We investigate one of the most important sources of uncertainty, namely, the intermolecular force field parameters. Specifically, we quantify the uncertainty in the Lennard-Jones (LJ) 12-6 parameters for the CH4, CH3, and CH2 united-atom interaction sites. We then demonstrate how the uncertainties in the parameters lead to uncertainties in the saturated liquid density and critical constant values obtained from Gibbs Ensemble Monte Carlo simulation. Our results suggest that the uncertainties attributed to the LJ 12-6 parameters are small enough that quantitatively useful estimates of the saturated liquid density and the critical constants can be obtained from molecular simulation. PMID:28527455

Effect of Stress Corrosion and Cyclic Fatigue on Fluorapatite Glass-Ceramic

NASA Astrophysics Data System (ADS)

Joshi, Gaurav V.

2011-12-01

Objective: The objective of this study was to test the following hypotheses: 1. Both cyclic degradation and stress corrosion mechanisms result in subcritical crack growth in a fluorapatite glass-ceramic. 2. There is an interactive effect of stress corrosion and cyclic fatigue to cause subcritical crack growth (SCG) for this material. 3. The material that exhibits rising toughness curve (R-curve) behavior also exhibits a cyclic degradation mechanism. Materials and Methods: The material tested was a fluorapatite glass-ceramic (IPS e.max ZirPress, Ivoclar-Vivadent). Rectangular beam specimens with dimensions of 25 mm x 4 mm x 1.2 mm were fabricated using the press-on technique. Two groups of specimens (N=30) with polished (15 mum) or air abraded surface were tested under rapid monotonic loading. Additional polished specimens were subjected to cyclic loading at two frequencies, 2 Hz (N=44) and 10 Hz (N=36), and at different stress amplitudes. All tests were performed using a fully articulating four-point flexure fixture in deionized water at 37°C. The SCG parameters were determined by using a statistical approach by Munz and Fett (1999). The fatigue lifetime data were fit to a general log-linear model in ALTA PRO software (Reliasoft). Fractographic techniques were used to determine the critical flaw sizes to estimate fracture toughness. To determine the presence of R-curve behavior, non-linear regression was used. Results: Increasing the frequency of cycling did not cause a significant decrease in lifetime. The parameters of the general log-linear model showed that only stress corrosion has a significant effect on lifetime. The parameters are presented in the following table.* SCG parameters (n=19--21) were similar for both frequencies. The regression model showed that the fracture toughness was significantly dependent (p<0.05) on critical flaw size. Conclusions: 1. Cyclic fatigue does not have a significant effect on the SCG in the fluorapatite glass-ceramic IPS e.max ZirPress. 2. There was no interactive effect between cyclic degradation and stress corrosion for this material. 3. The material exhibited a low level of R-curve behavior. It did not exhibit cyclic degradation. *Please refer to dissertation for table.

Volume-energy parameters for heat transfer to supercritical fluids

NASA Technical Reports Server (NTRS)

Kumakawa, A.; Niino, M.; Hendricks, R. C.; Giarratano, P. J.; Arp, V. D.

1986-01-01

Reduced Nusselt numbers of supercritical fluids from different sources were grouped by several volume-energy parameters. A modified bulk expansion parameter was introduced based on a comparative analysis of data scatter. Heat transfer experiments on liquefied methane were conducted under near-critical conditions in order to confirm the usefulness of the parameters. It was experimentally revealed that heat transfer characteristics of near-critical methane are similar to those of hydrogen. It was shown that the modified bulk expansion parameter and the Gibbs-energy parameter grouped the heat transfer data of hydrogen, oxygen and methane including the present data on near-critical methane. It was also indicated that the effects of surface roughness on heat transfer were very important in grouping the data of high Reynolds numbers.

Photon orbits and thermodynamic phase transition of d -dimensional charged AdS black holes

NASA Astrophysics Data System (ADS)

Wei, Shao-Wen; Liu, Yu-Xiao

2018-05-01

We study the relationship between the null geodesics and thermodynamic phase transition for the charged AdS black hole. In the reduced parameter space, we find that there exist nonmonotonic behaviors of the photon sphere radius and the minimum impact parameter for the pressure below its critical value. The study also shows that the changes of the photon sphere radius and the minimum impact parameter can serve as order parameters for the small-large black hole phase transition. In particular, these changes have an universal exponent of 1/2 near the critical point for any dimension d of spacetime. These results imply that there may exist universal critical behavior of gravity near the thermodynamic critical point of the black hole system.

Electrokinetic remediation prefield test methods

NASA Technical Reports Server (NTRS)

Hodko, Dalibor (Inventor)

2000-01-01

Methods for determining the parameters critical in designing an electrokinetic soil remediation process including electrode well spacing, operating current/voltage, electroosmotic flow rate, electrode well wall design, and amount of buffering or neutralizing solution needed in the electrode wells at operating conditions are disclosed These methods are preferably performed prior to initiating a full scale electrokinetic remediation process in order to obtain efficient remediation of the contaminants.

Water Vapour Effects in Mass Measurement

NASA Astrophysics Data System (ADS)

Khélifa, N.

2008-01-01

Water vapour density inside the mass comparator enclosure is a critical parameter whose fluctuations during mass weighing can lead to errors in the determination of an unknown mass. To monitor them, a method using DFB laser diode in the near infrared has been proposed and tested. Preliminary results of our observation of water vapour sorption and de-sorption processes from the walls and the mass standard are reported.

A multipurpose model of Hermes-Columbus docking mechanism

NASA Technical Reports Server (NTRS)

Gonzalez-Vallejo, J. J.; Fehse, W.; Tobias, A.

1992-01-01

One of the foreseen missions of the HERMES spacevehicle is the servicing to the Columbus Free Flying Laboratory (MTFF). Docking between the two spacecraft is a critical operation in which the Docking Mechanism (DM) has a major role. In order to analyze and assess robustness of initially selected concepts and to identify suitable implementation solutions, through the investigation of main parameters involved in the docking functions, a multipurpose model of DM was developed and tested. This paper describes the main design features as well as the process of calibrating and testing.

An Improved Method to Control the Critical Parameters of a Multivariable Control System

NASA Astrophysics Data System (ADS)

Subha Hency Jims, P.; Dharmalingam, S.; Wessley, G. Jims John

2017-10-01

The role of control systems is to cope with the process deficiencies and the undesirable effect of the external disturbances. Most of the multivariable processes are highly iterative and complex in nature. Aircraft systems, Modern Power Plants, Refineries, Robotic systems are few such complex systems that involve numerous critical parameters that need to be monitored and controlled. Control of these important parameters is not only tedious and cumbersome but also is crucial from environmental, safety and quality perspective. In this paper, one such multivariable system, namely, a utility boiler has been considered. A modern power plant is a complex arrangement of pipework and machineries with numerous interacting control loops and support systems. In this paper, the calculation of controller parameters based on classical tuning concepts has been presented. The controller parameters thus obtained and employed has controlled the critical parameters of a boiler during fuel switching disturbances. The proposed method can be applied to control the critical parameters like elevator, aileron, rudder, elevator trim rudder and aileron trim, flap control systems of aircraft systems.

Chemometrics-based process analytical technology (PAT) tools: applications and adaptation in pharmaceutical and biopharmaceutical industries.

PubMed

Challa, Shruthi; Potumarthi, Ravichandra

2013-01-01

Process analytical technology (PAT) is used to monitor and control critical process parameters in raw materials and in-process products to maintain the critical quality attributes and build quality into the product. Process analytical technology can be successfully implemented in pharmaceutical and biopharmaceutical industries not only to impart quality into the products but also to prevent out-of-specifications and improve the productivity. PAT implementation eliminates the drawbacks of traditional methods which involves excessive sampling and facilitates rapid testing through direct sampling without any destruction of sample. However, to successfully adapt PAT tools into pharmaceutical and biopharmaceutical environment, thorough understanding of the process is needed along with mathematical and statistical tools to analyze large multidimensional spectral data generated by PAT tools. Chemometrics is a chemical discipline which incorporates both statistical and mathematical methods to obtain and analyze relevant information from PAT spectral tools. Applications of commonly used PAT tools in combination with appropriate chemometric method along with their advantages and working principle are discussed. Finally, systematic application of PAT tools in biopharmaceutical environment to control critical process parameters for achieving product quality is diagrammatically represented.

A means to estimate thermal and kinetic parameters of coal dust layer from hot surface ignition tests.

PubMed

Park, Haejun; Rangwala, Ali S; Dembsey, Nicholas A

2009-08-30

A method to estimate thermal and kinetic parameters of Pittsburgh seam coal subject to thermal runaway is presented using the standard ASTM E 2021 hot surface ignition test apparatus. Parameters include thermal conductivity (k), activation energy (E), coupled term (QA) of heat of reaction (Q) and pre-exponential factor (A) which are required, but rarely known input values to determine the thermal runaway propensity of a dust material. Four different dust layer thicknesses: 6.4, 12.7, 19.1 and 25.4mm, are tested, and among them, a single steady state dust layer temperature profile of 12.7 mm thick dust layer is used to estimate k, E and QA. k is calculated by equating heat flux from the hot surface layer and heat loss rate on the boundary assuming negligible heat generation in the coal dust layer at a low hot surface temperature. E and QA are calculated by optimizing a numerically estimated steady state dust layer temperature distribution to the experimentally obtained temperature profile of a 12.7 mm thick dust layer. Two unknowns, E and QA, are reduced to one from the correlation of E and QA obtained at criticality of thermal runaway. The estimated k is 0.1 W/mK matching the previously reported value. E ranges from 61.7 to 83.1 kJ/mol, and the corresponding QA ranges from 1.7 x 10(9) to 4.8 x 10(11)J/kg s. The mean values of E (72.4 kJ/mol) and QA (2.8 x 10(10)J/kg s) are used to predict the critical hot surface temperatures for other thicknesses, and good agreement is observed between measured and experimental values. Also, the estimated E and QA ranges match the corresponding ranges calculated from the multiple tests method and values reported in previous research.

Fracture strength of flawed cylindrical pressure vessels under cryogenic temperatures

NASA Astrophysics Data System (ADS)

Christopher, T.; Sankarnarayanasamy, K.; Nageswara Rao, B.

2002-11-01

Damage tolerant and fail-safe approaches have been employed increasingly in the design of critical engineering components. In these approaches, one has to assess the residual strength of a component with an assumed pre-existing crack. In other cases, cracks may be detected during service. Then, there is a need to evaluate the residual strength of the cracked components in order to decide whether they can be continued safely or repair and replacement are imperative. A three-parameter fracture criterion is applied to correlate the fracture data on aluminium, titanium and steel materials from test results on cylindrical tanks/pressure vessels at cryogenic temperatures. Fracture parameters to generate the failure assessment diagram are determined for the materials considered in the present study. Failure pressure estimates were found to be in good agreement with test results.

Response Time Analysis and Test of Protection System Instrument Channels for APR1400 and OPR1000

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

Lee, Chang Jae; Han, Seung; Yun, Jae Hee

2015-07-01

Safety limits are required to maintain the integrity of physical barriers designed to prevent the uncontrolled release of radioactive materials in nuclear power plants. The safety analysis establishes two critical constraints that include an analytical limit in terms of a measured or calculated variable, and a specific time after the analytical limit is reached to begin protective action. Keeping with the nuclear regulations and industry standards, satisfying these two requirements will ensure that the safety limit will not be exceeded during the design basis event, either an anticipated operational occurrence or a postulated accident. Various studies on the setpoint determinationmore » methodology for the safety-related instrumentation have been actively performed to ensure that the requirement of the analytical limit is satisfied. In particular, the protection setpoint methodology for the advanced power reactor 1400 (APP1400) and the optimized power reactor 1000 (OPR1000) has been recently developed to cover both the design basis event and the beyond design basis event. The developed setpoint methodology has also been quantitatively validated using specific computer programs and setpoint calculations. However, the safety of nuclear power plants cannot be fully guaranteed by satisfying the requirement of the analytical limit. In spite of the response time verification requirements of nuclear regulations and industry standards, it is hard to find the studies on the systematically integrated methodology regarding the response time evaluation. In cases of APR1400 and OPR1000, the response time analysis for the plant protection system is partially included in the setpoint calculation and the response time test is separately performed via the specific plant procedure. The test technique has a drawback which is the difficulty to demonstrate completeness of timing test. The analysis technique has also a demerit of resulting in extreme times that not actually possible. Thus, the establishment of the systematic response time evaluation methodology is needed to justify the conformance to the response time requirement used in the safety analysis. This paper proposes the response time evaluation methodology for APR1400 and OPR1000 using the combined analysis and test technique to confirm that the plant protection system can meet the analytical response time assumed in the safety analysis. In addition, the results of the quantitative evaluation performed for APR1400 and OPR1000 are presented in this paper. The proposed response time analysis technique consists of defining the response time requirement, determining the critical signal path for the trip parameter, allocating individual response time to each component on the signal path, and analyzing the total response time for the trip parameter, and demonstrates that the total analyzed response time does not exceed the response time requirement. The proposed response time test technique is composed of defining the response time requirement, determining the critical signal path for the trip parameter, determining the test method for each component on the signal path, performing the response time test, and demonstrates that the total test result does not exceed the response time requirement. The total response time should be tested in a single test that covers from the sensor to the final actuation device on the instrument channel. When the total channel is not tested in a single test, separate tests on groups of components or single components including the total instrument channel shall be combined to verify the total channel response. For APR1400 and OPR1000, the ramp test technique is used for the pressure and differential pressure transmitters and the step function testing technique is applied to the signal processing equipment and final actuation device. As a result, it can be demonstrated that the response time requirement is satisfied by the combined analysis and test technique. Therefore, the proposed methodology in this paper plays a crucial role in guaranteeing the safety of the nuclear power plants systematically satisfying one of two critical requirements from the safety analysis. (authors)« less

Competence training in evidence-based medicine for patients, patient counsellors, consumer representatives and health care professionals in Austria: a feasibility study.

PubMed

Berger, Bettina; Gerlach, Anja; Groth, Sylvia; Sladek, Ulla; Ebner, Katharina; Mühlhauser, Ingrid; Steckelberg, Anke

2013-01-01

Informed and shared decision-making require competences for both partners - healthcare professionals and patients. There is a lack of training courses in evidence-based medicine for patients and counsellors. We investigated feasibility, acceptability and the potential effects of a 2 x 2.5 days training course on critical health competences in patients, patient counsellors, consumer representatives and healthcare professionals in Austria. We adapted a previously developed curriculum for patient and consumer representatives. The adaptation comprised the specific needs of our target group in Austria and was founded on Carl Rogers' theory of person-centred education. For the formative evaluation a questionnaire was applied to address the domains: 1) organisational conditions (time and duration of the course, location, and information given in advance, registration); 2) assistance outside the courses; 3) teaching methods (performance of lecturers, teaching materials, structure of modules and blocks) and 4) satisfaction; 5) subjective assessment of competences. Participants evaluated the course, using a 5-point Likert scale. Long-term implementation was assessed using semi-structured interviews three to six months after the course. To estimate the increase in critical health competences we used the validated Critical Health Competence Test (CHC test). Eleven training courses were conducted including 142 participants: patients (n=21); self-help group representatives (n=17); professional counsellors (n=29); healthcare professionals (n=10); psychologists (n=8); teachers (n=10) and others (n=29). 97 out of 142 (68 %) participants returned the questionnaire. On average, participants strongly agreed or agreed to 1) organisational conditions: 71 % / 23 %; 2) assistance outside the courses: 96 % / 10 %; 3) teaching methods: 60 % / 28 %; and 4) satisfaction: 78 % / 20 %, respectively. Interviews showed that the training course raised awareness, activated and empowered participants. Participants passed the CHC test with mean person parameters of 463±111 (pre-test, n=120) and 547±135 (post-test, n=91). For participants who returned both tests (n=71) person parameters were comparable: pre-test 466±121 versus post-test 574±100, p<0,001. Training in evidence-based medicine for patients, patient counsellors, consumer representatives and healthcare professionals is feasible. For a broad implementation, train-the trainer courses and further research are needed. Copyright © 2012. Published by Elsevier GmbH.

Virtual Shaker Testing: Simulation Technology Improves Vibration Test Performance

NASA Technical Reports Server (NTRS)

Ricci, Stefano; Peeters, Bart; Fetter, Rebecca; Boland, Doug; Debille, Jan

2008-01-01

In the field of vibration testing, the interaction between the structure being tested and the instrumentation hardware used to perform the test is a critical issue. This is particularly true when testing massive structures (e.g. satellites), because due to physical design and manufacturing limits, the dynamics of the testing facility often couples with the test specimen one in the frequency range of interest. A further issue in this field is the standard use of a closed loop real-time vibration control scheme, which could potentially shift poles and change damping of the aforementioned coupled system. Virtual shaker testing is a novel approach to deal with these issues. It means performing a simulation which closely represents the real vibration test on the specific facility by taking into account all parameters which might impact the dynamic behavior of the specimen. In this paper, such a virtual shaker testing approach is developed. It consists of the following components: (1) Either a physical-based or an equation-based coupled electro-mechanical lumped parameter shaker model is created. The model parameters are obtained from manufacturer's specifications or by carrying out some dedicated experiments; (2) Existing real-time vibration control algorithm are ported to the virtual simulation environment; and (3) A structural model of the test object is created and after defining proper interface conditions structural modes are computed by means of the well-established Craig-Bampton CMS technique. At this stage, a virtual shaker test has been run, by coupling the three described models (shaker, control loop, structure) in a co-simulation routine. Numerical results have eventually been correlated with experimental ones in order to assess the robustness of the proposed methodology.

A test-retest dataset for assessing long-term reliability of brain morphology and resting-state brain activity.

PubMed

Huang, Lijie; Huang, Taicheng; Zhen, Zonglei; Liu, Jia

2016-03-15

We present a test-retest dataset for evaluation of long-term reliability of measures from structural and resting-state functional magnetic resonance imaging (sMRI and rfMRI) scans. The repeated scan dataset was collected from 61 healthy adults in two sessions using highly similar imaging parameters at an interval of 103-189 days. However, as the imaging parameters were not completely identical, the reliability estimated from this dataset shall reflect the lower bounds of the true reliability of sMRI/rfMRI measures. Furthermore, in conjunction with other test-retest datasets, our dataset may help explore the impact of different imaging parameters on reliability of sMRI/rfMRI measures, which is especially critical for assessing datasets collected from multiple centers. In addition, intelligence quotient (IQ) was measured for each participant using Raven's Advanced Progressive Matrices. The data can thus be used for purposes other than assessing reliability of sMRI/rfMRI alone. For example, data from each single session could be used to associate structural and functional measures of the brain with the IQ metrics to explore brain-IQ association.

A Computational Approach for Model Update of an LS-DYNA Energy Absorbing Cell

NASA Technical Reports Server (NTRS)

Horta, Lucas G.; Jackson, Karen E.; Kellas, Sotiris

2008-01-01

NASA and its contractors are working on structural concepts for absorbing impact energy of aerospace vehicles. Recently, concepts in the form of multi-cell honeycomb-like structures designed to crush under load have been investigated for both space and aeronautics applications. Efforts to understand these concepts are progressing from tests of individual cells to tests of systems with hundreds of cells. Because of fabrication irregularities, geometry irregularities, and material properties uncertainties, the problem of reconciling analytical models, in particular LS-DYNA models, with experimental data is a challenge. A first look at the correlation results between single cell load/deflection data with LS-DYNA predictions showed problems which prompted additional work in this area. This paper describes a computational approach that uses analysis of variance, deterministic sampling techniques, response surface modeling, and genetic optimization to reconcile test with analysis results. Analysis of variance provides a screening technique for selection of critical parameters used when reconciling test with analysis. In this study, complete ignorance of the parameter distribution is assumed and, therefore, the value of any parameter within the range that is computed using the optimization procedure is considered to be equally likely. Mean values from tests are matched against LS-DYNA solutions by minimizing the square error using a genetic optimization. The paper presents the computational methodology along with results obtained using this approach.

Properties of the two-dimensional heterogeneous Lennard-Jones dimers: An integral equation study

PubMed Central

Urbic, Tomaz

2016-01-01

Structural and thermodynamic properties of a planar heterogeneous soft dumbbell fluid are examined using Monte Carlo simulations and integral equation theory. Lennard-Jones particles of different sizes are the building blocks of the dimers. The site-site integral equation theory in two dimensions is used to calculate the site-site radial distribution functions and the thermodynamic properties. Obtained results are compared to Monte Carlo simulation data. The critical parameters for selected types of dimers were also estimated and the influence of the Lennard-Jones parameters was studied. We have also tested the correctness of the site-site integral equation theory using different closures. PMID:27875894

Additive-manufactured sandwich lattice structures: A numerical and experimental investigation

NASA Astrophysics Data System (ADS)

Fergani, Omar; Tronvoll, Sigmund; Brøtan, Vegard; Welo, Torgeir; Sørby, Knut

2017-10-01

The utilization of additive-manufactured lattice structures in engineered products is becoming more and more common as the competitiveness of AM as a production technology has increased during the past several years. Lattice structures may enable important weight reductions as well as open opportunities to build products with customized functional properties, thanks to the flexibility of AM for producing complex geometrical configurations. One of the most critical aspects related to taking AM into new application areas—such as safety critical products—is currently the limited understanding of the mechanical behavior of sandwich-based lattice structure mechanical under static and dynamic loading. In this study, we evaluate manufacturability of lattice structures and the impact of AM processing parameters on the structural behavior of this type of sandwich structures. For this purpose, we conducted static compression testing for a variety of geometry and manufacturing parameters. Further, the study discusses a numerical model capable of predicting the behavior of different lattice structure. A reasonably good correlation between the experimental and numerical results was observed.

Critical Analysis of Dual-Probe Heat-Pulse Technique Applied to Measuring Thermal Diffusivity

NASA Astrophysics Data System (ADS)

Bovesecchi, G.; Coppa, P.; Corasaniti, S.; Potenza, M.

2018-07-01

The paper presents an analysis of the experimental parameters involved in application of the dual-probe heat pulse technique, followed by a critical review of methods for processing thermal response data (e.g., maximum detection and nonlinear least square regression) and the consequent obtainable uncertainty. Glycerol was selected as testing liquid, and its thermal diffusivity was evaluated over the temperature range from - 20 °C to 60 °C. In addition, Monte Carlo simulation was used to assess the uncertainty propagation for maximum detection. It was concluded that maximum detection approach to process thermal response data gives the closest results to the reference data inasmuch nonlinear regression results are affected by major uncertainties due to partial correlation between the evaluated parameters. Besides, the interpolation of temperature data with a polynomial to find the maximum leads to a systematic difference between measured and reference data, as put into evidence by the Monte Carlo simulations; through its correction, this systematic error can be reduced to a negligible value, about 0.8 %.

Atherosclerosis and Liver Function Tests in Coronary Angiography Patients.

PubMed

Doganer, Y C; Rohrer, J E; Aydogan, U; Agerter, D C; Cayci, T; Barcin, C

2015-09-01

Elevated aminotransferase levels indicating liver function, even in the normal range, have attracted great concern as potential novel markers of cardiovascular risk assessment. We hypothesized the possibility that liver function test variations in the normal range might be meaningfully associated to coronary artery disease (CAD). Eighty-eight patients were randomly selected from those who underwent coronary angiography from June 2010 to June 2011 after applying to the outpatient cardiology clinic in Gulhane Military Medical Academy. According to the results of angiographies, patients were classified into three groups as normal, non-critical (< 50% involvement in coronaries), and critical (≥ 50% involvement in coronaries). In addition to angiographic intervention, measurements of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) concentrations, albumin and the other serum parameters were performed in all patients. The patient groups of CAD were balanced (28 critical cases, 30 non-critical cases and 30 normal cases). Mean age was 51.93 ± 9.3 (range 32-65) years and 19.3 per cent (n = 17) were females. Multiple linear regression analysis of all three liver function tests explained a significant portion of the variance, but adjusted r-squares were small (AST = 0.174, ALT = 0.242, albumin = 0.124). Albumin was significantly higher for patients with critical CAD than for patients with no CAD (beta = 3.205, p = 0.002). Non-critical CAD was not significantly different from no CAD for any of the dependent variables. Mean AST was significantly higher for patients taking aspirin (beta = 0.218, p = 0.049), as was mean ALT (beta = 0.264, p = 0.015). Alanine aminotransferase and AST may not be associated with angiographically determined coronary atherosclerosis. Albumin may be more sensitive to demonstrate the burden of atherosclerosis. These results indicate that the association between the liver function tests and coronary atherosclerosis may be more complex than generally appreciated.

Crack Instability Predictions Using a Multi-Term Approach

NASA Technical Reports Server (NTRS)

Zanganeh, Mohammad; Forman, Royce G.

2015-01-01

Present crack instability analysis for fracture critical flight hardware is normally performed using a single parameter, K(sub C), fracture toughness value obtained from standard ASTM 2D geometry test specimens made from the appropriate material. These specimens do not sufficiently match the boundary conditions and the elastic-plastic constraint characteristics of the hardware component, and also, the crack instability of most commonly used aircraft and aerospace structural materials have some amount of stable crack growth before fracture which makes the normal use of a K(sub C) single parameter toughness value highly approximate. In the past, extensive studies have been conducted to improve the single parameter (K or J controlled) approaches by introducing parameters accounting for the geometry or in-plane constraint effects. Using 'J-integral' and 'A' parameter as a measure of constraint is one of the most accurate elastic-plastic crack solutions currently available. In this work the feasibility of the J-A approach for prediction of the crack instability was investigated first by ignoring the effects of stable crack growth i.e. using a critical J and A and second by considering the effects of stable crack growth using the corrected J-delta a using the 'A' parameter. A broad range of initial crack lengths and a wide range of specimen geometries including C(T), M(T), ESE(T), SE(T), Double Edge Crack (DEC), Three-Hole-Tension (THT) and NC (crack from a notch) manufactured from Al7075 were studied. Improvements in crack instability predictions were observed compared to the other methods available in the literature.

Phase Transformation and Lattice Parameter Changes of Non-trivalent Rare Earth-Doped YSZ as a Function of Temperature

NASA Astrophysics Data System (ADS)

Jiang, Shengli; Huang, Xiao; He, Zhang; Buyers, Andrew

2018-01-01

To examine the effect of doping/co-doping on high-temperature phase compositions of YSZ, stand-alone YSZ and CeO2 and Nb2O5 co-doped YSZ samples were prepared using mechanical alloy and high-temperature sintering. XRD analysis was performed on these samples from room temperature to 1100 °C. The results show that the structure for the co-doped samples tends to be thermally stable when the test temperature is higher than a critical value. Monoclinic phase was dominant in Nb2O5 co-doped YSZ at temperatures lower than 600 °C, while for the YSZ and CeO2 co-doped YSZ, cubic/tetragonal phase was dominant in the whole test temperature range. The lattice parameters for all the samples increase with increasing test temperature generally. The lattice parameters for the two non-trivalent rare earth oxides co-doped YSZ show that the lattice parameter a for the cubic phase of the Ce4+ co-doped YSZ is consistently greater than that of 7YSZ which is related to the presence of larger radius of Ce4+ in the matrix. The lattice parameters a, b, c for the monoclinic phase of Ce4+ co-doped YSZ are much closer to each other than that of the Nb5+ co-doped YSZ, indicating the former has better tendency to form cubic/tetragonal phase, which is desired for vast engineering applications.

Phase Transformation and Lattice Parameter Changes of Non-trivalent Rare Earth-Doped YSZ as a Function of Temperature

NASA Astrophysics Data System (ADS)

Jiang, Shengli; Huang, Xiao; He, Zhang; Buyers, Andrew

2018-05-01

To examine the effect of doping/co-doping on high-temperature phase compositions of YSZ, stand-alone YSZ and CeO2 and Nb2O5 co-doped YSZ samples were prepared using mechanical alloy and high-temperature sintering. XRD analysis was performed on these samples from room temperature to 1100 °C. The results show that the structure for the co-doped samples tends to be thermally stable when the test temperature is higher than a critical value. Monoclinic phase was dominant in Nb2O5 co-doped YSZ at temperatures lower than 600 °C, while for the YSZ and CeO2 co-doped YSZ, cubic/tetragonal phase was dominant in the whole test temperature range. The lattice parameters for all the samples increase with increasing test temperature generally. The lattice parameters for the two non-trivalent rare earth oxides co-doped YSZ show that the lattice parameter a for the cubic phase of the Ce4+ co-doped YSZ is consistently greater than that of 7YSZ which is related to the presence of larger radius of Ce4+ in the matrix. The lattice parameters a, b, c for the monoclinic phase of Ce4+ co-doped YSZ are much closer to each other than that of the Nb5+ co-doped YSZ, indicating the former has better tendency to form cubic/tetragonal phase, which is desired for vast engineering applications.

A fuzzy rumor spreading model based on transmission capacity

NASA Astrophysics Data System (ADS)

Zhang, Yi; Xu, Jiuping; Wu, Yue

This paper proposes a rumor spreading model that considers three main factors: the event importance, event ambiguity, and the publics critical sense, each of which are defined by decision makers using linguistic descriptions and then transformed into triangular fuzzy numbers. To calculate the resultant force of these three factors, the transmission capacity and a new parameter category with fuzzy variables are determined. A rumor spreading model is then proposed which has fuzzy parameters rather than the fixed parameters in traditional models. As the proposed model considers the comprehensive factors affecting rumors from three aspects rather than examining special factors from a particular aspect. The proposed rumor spreading model is tested using different parameters for several different conditions on BA networks and three special cases are simulated. The simulation results for all three cases suggested that events of low importance, those that are only clarifying facts, and those that are strongly critical do not result in rumors. Therefore, the model assessment results were proven to be in agreement with reality. Parameters for the model were then determined and applied to an analysis of the 7.23 Yong-Wen line major transportation accident (YWMTA). When the simulated data were compared with the real data from this accident, the results demonstrated that the interval for the rumor spreading key point in the model was accurate, and that the key point for the YWMTA rumor spread fell into the range estimated by the model.

Aerodynamic Reconstruction Applied to Parachute Test Vehicle Flight Data Analysis

NASA Technical Reports Server (NTRS)

Cassady, Leonard D.; Ray, Eric S.; Truong, Tuan H.

2013-01-01

The aerodynamics, both static and dynamic, of a test vehicle are critical to determining the performance of the parachute cluster in a drop test and for conducting a successful test. The Capsule Parachute Assembly System (CPAS) project is conducting tests of NASA's Orion Multi-Purpose Crew Vehicle (MPCV) parachutes at the Army Yuma Proving Ground utilizing the Parachute Test Vehicle (PTV). The PTV shape is based on the MPCV, but the height has been reduced in order to fit within the C-17 aircraft for extraction. Therefore, the aerodynamics of the PTV are similar, but not the same as, the MPCV. A small series of wind tunnel tests and computational fluid dynamics cases were run to modify the MPCV aerodynamic database for the PTV, but aerodynamic reconstruction of the flights has proven an effective source for further improvements to the database. The acceleration and rotational rates measured during free flight, before parachute inflation but during deployment, were used to con rm vehicle static aerodynamics. A multibody simulation is utilized to reconstruct the parachute portions of the flight. Aerodynamic or parachute parameters are adjusted in the simulation until the prediction reasonably matches the flight trajectory. Knowledge of the static aerodynamics is critical in the CPAS project because the parachute riser load measurements are scaled based on forebody drag. PTV dynamic damping is critical because the vehicle has no reaction control system to maintain attitude - the vehicle dynamics must be understood and modeled correctly before flight. It will be shown here that aerodynamic reconstruction has successfully contributed to the CPAS project.

Soft material adhesion characterization for in vivo locomotion of robotic capsule endoscopes: Experimental and modeling results.

PubMed

Kern, Madalyn D; Ortega Alcaide, Joan; Rentschler, Mark E

2014-11-01

The objective of this work is to validate an experimental method and nondimensional model for characterizing the normal adhesive response between a polyvinyl chloride based synthetic biological tissue substrate and a flat, cylindrical probe with a smooth polydimethylsiloxane (PDMS) surface. The adhesion response is a critical mobility design parameter of a Robotic Capsule Endoscope (RCE) using PDMS treads to provide mobility to travel through the gastrointestinal tract for diagnostic purposes. Three RCE design characteristics were chosen as input parameters for the normal adhesion testing: pre-load, dwell time and separation rate. These parameters relate to the RCE׳s cross sectional dimension, tread length, and tread speed, respectively. An inscribed central composite design (CCD) prescribed 34 different parameter configurations to be tested. The experimental adhesion response curves were nondimensionalized by the maximum stress and total displacement values for each test configuration and a mean nondimensional curve was defined with a maximum relative error of 5.6%. A mathematical model describing the adhesion behavior as a function of the maximum stress and total displacement was developed and verified. A nonlinear regression analysis was done on the maximum stress and total displacement parameters and equations were defined as a function of the RCE design parameters. The nondimensional adhesion model is able to predict the adhesion curve response of any test configuration with a mean R(2) value of 0.995. Eight additional CCD studies were performed to obtain a qualitative understanding of the impact of tread contact area and synthetic material substrate stiffness on the adhesion response. These results suggest that the nondimensionalization technique for analyzing the adhesion data is sufficient for all values of probe radius and substrate stiffness within the bounds tested. This method can now be used for RCE tread design optimization given a set of environmental conditions for device operation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Multi-Response Optimization of WEDM Process Parameters Using Taguchi Based Desirability Function Analysis

NASA Astrophysics Data System (ADS)

Majumder, Himadri; Maity, Kalipada

2018-03-01

Shape memory alloy has a unique capability to return to its original shape after physical deformation by applying heat or thermo-mechanical or magnetic load. In this experimental investigation, desirability function analysis (DFA), a multi-attribute decision making was utilized to find out the optimum input parameter setting during wire electrical discharge machining (WEDM) of Ni-Ti shape memory alloy. Four critical machining parameters, namely pulse on time (TON), pulse off time (TOFF), wire feed (WF) and wire tension (WT) were taken as machining inputs for the experiments to optimize three interconnected responses like cutting speed, kerf width, and surface roughness. Input parameter combination TON = 120 μs., TOFF = 55 μs., WF = 3 m/min. and WT = 8 kg-F were found to produce the optimum results. The optimum process parameters for each desired response were also attained using Taguchi’s signal-to-noise ratio. Confirmation test has been done to validate the optimum machining parameter combination which affirmed DFA was a competent approach to select optimum input parameters for the ideal response quality for WEDM of Ni-Ti shape memory alloy.

Study on Material Parameters Identification of Brain Tissue Considering Uncertainty of Friction Coefficient

NASA Astrophysics Data System (ADS)

Guan, Fengjiao; Zhang, Guanjun; Liu, Jie; Wang, Shujing; Luo, Xu; Zhu, Feng

2017-10-01

Accurate material parameters are critical to construct the high biofidelity finite element (FE) models. However, it is hard to obtain the brain tissue parameters accurately because of the effects of irregular geometry and uncertain boundary conditions. Considering the complexity of material test and the uncertainty of friction coefficient, a computational inverse method for viscoelastic material parameters identification of brain tissue is presented based on the interval analysis method. Firstly, the intervals are used to quantify the friction coefficient in the boundary condition. And then the inverse problem of material parameters identification under uncertain friction coefficient is transformed into two types of deterministic inverse problem. Finally the intelligent optimization algorithm is used to solve the two types of deterministic inverse problems quickly and accurately, and the range of material parameters can be easily acquired with no need of a variety of samples. The efficiency and convergence of this method are demonstrated by the material parameters identification of thalamus. The proposed method provides a potential effective tool for building high biofidelity human finite element model in the study of traffic accident injury.

Reporting of various methodological and statistical parameters in negative studies published in prominent Indian Medical Journals: a systematic review.

PubMed

Charan, J; Saxena, D

2014-01-01

Biased negative studies not only reflect poor research effort but also have an impact on 'patient care' as they prevent further research with similar objectives, leading to potential research areas remaining unexplored. Hence, published 'negative studies' should be methodologically strong. All parameters that may help a reader to judge validity of results and conclusions should be reported in published negative studies. There is a paucity of data on reporting of statistical and methodological parameters in negative studies published in Indian Medical Journals. The present systematic review was designed with an aim to critically evaluate negative studies published in prominent Indian Medical Journals for reporting of statistical and methodological parameters. Systematic review. All negative studies published in 15 Science Citation Indexed (SCI) medical journals published from India were included in present study. Investigators involved in the study evaluated all negative studies for the reporting of various parameters. Primary endpoints were reporting of "power" and "confidence interval." Power was reported in 11.8% studies. Confidence interval was reported in 15.7% studies. Majority of parameters like sample size calculation (13.2%), type of sampling method (50.8%), name of statistical tests (49.1%), adjustment of multiple endpoints (1%), post hoc power calculation (2.1%) were reported poorly. Frequency of reporting was more in clinical trials as compared to other study designs and in journals having impact factor more than 1 as compared to journals having impact factor less than 1. Negative studies published in prominent Indian medical journals do not report statistical and methodological parameters adequately and this may create problems in the critical appraisal of findings reported in these journals by its readers.

Hydrazine Gas Generator Program. [space shuttles

NASA Technical Reports Server (NTRS)

Kusak, L.; Marcy, R. D.

1975-01-01

The design and fabrication of a flight gas generator for the space shuttle were investigated. Critical performance parameters and stability criteria were evaluated as well as a scaling laws that could be applied in designing the flight gas generator. A test program to provide the necessary design information was included. A structural design, including thermal and stress analysis, and two gas generators were fabricated based on the results. Conclusions are presented.

The core mass-radius relation for giants - A new test of stellar evolution theory

NASA Technical Reports Server (NTRS)

Joss, P. C.; Rappaport, S.; Lewis, W.

1987-01-01

It is demonstrated here that the measurable properties of systems containing degenerate dwarfs can be used as a direct test of the core mass-radius relation for moderate-mass giants if the final stages of the loss of the envelope of the progenitor giant occurred via stable critical lobe overflow. This relation directly probes the internal structure of stars at a relatively advanced evolutionary state and is only modestly influenced by adjustable parameters. The measured properties of six binary systems, including such diverse systems as Sirius and Procyon and two millisecond pulsars, are utilized to derive constraints on the empirical core mass-radius relation, and the constraints are compared to the theoretical relation. The possibility that the final stages of envelope ejection of the giant progenitor of Sirius B occurred via critical lobe overflow in historical times is considered.

Injection of a Body into a Geodesic: Lessons Learnt from the LISA Pathfinder Case

NASA Technical Reports Server (NTRS)

Bortoluzzi, Daniele; Armano, M.; Audley, H.; Auger, G.; Baird, J.; Binetruy, P.; Born, M.; Bortoluzzi, D.; Brandt, N.; Bursi, A.;

Calibration of DEM parameters on shear test experiments using Kriging method

NASA Astrophysics Data System (ADS)

Bednarek, Xavier; Martin, Sylvain; Ndiaye, Abibatou; Peres, Véronique; Bonnefoy, Olivier

2017-06-01

Calibration of powder mixing simulation using Discrete-Element-Method is still an issue. Achieving good agreement with experimental results is difficult because time-efficient use of DEM involves strong assumptions. This work presents a methodology to calibrate DEM parameters using Efficient Global Optimization (EGO) algorithm based on Kriging interpolation method. Classical shear test experiments are used as calibration experiments. The calibration is made on two parameters - Young modulus and friction coefficient. The determination of the minimal number of grains that has to be used is a critical step. Simulations of a too small amount of grains would indeed not represent the realistic behavior of powder when using huge amout of grains will be strongly time consuming. The optimization goal is the minimization of the objective function which is the distance between simulated and measured behaviors. The EGO algorithm uses the maximization of the Expected Improvement criterion to find next point that has to be simulated. This stochastic criterion handles with the two interpolations made by the Kriging method : prediction of the objective function and estimation of the error made. It is thus able to quantify the improvement in the minimization that new simulations at specified DEM parameters would lead to.

A Statistical Representation of Pyrotechnic Igniter Output

NASA Astrophysics Data System (ADS)

Guo, Shuyue; Cooper, Marcia

2017-06-01

The output of simplified pyrotechnic igniters for research investigations is statistically characterized by monitoring the post-ignition external flow field with Schlieren imaging. Unique to this work is a detailed quantification of all measurable manufacturing parameters (e.g., bridgewire length, charge cavity dimensions, powder bed density) and associated shock-motion variability in the tested igniters. To demonstrate experimental precision of the recorded Schlieren images and developed image processing methodologies, commercial exploding bridgewires using wires of different parameters were tested. Finally, a statistically-significant population of manufactured igniters were tested within the Schlieren arrangement resulting in a characterization of the nominal output. Comparisons between the variances measured throughout the manufacturing processes and the calculated output variance provide insight into the critical device phenomena that dominate performance. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's NNSA under contract DE-AC04-94AL85000.

Validation study and routine control monitoring of moist heat sterilization procedures.

PubMed

Shintani, Hideharu

2012-06-01

The proposed approach to validation of steam sterilization in autoclaves follows the basic life cycle concepts applicable to all validation programs. Understand the function of sterilization process, develop and understand the cycles to carry out the process, and define a suitable test or series of tests to confirm that the function of the process is suitably ensured by the structure provided. Sterilization of product and components and parts that come in direct contact with sterilized product is the most critical of pharmaceutical processes. Consequently, this process requires a most rigorous and detailed approach to validation. An understanding of the process requires a basic understanding of microbial death, the parameters that facilitate that death, the accepted definition of sterility, and the relationship between the definition and sterilization parameters. Autoclaves and support systems need to be designed, installed, and qualified in a manner that ensures their continued reliability. Lastly, the test program must be complete and definitive. In this paper, in addition to validation study, documentation of IQ, OQ and PQ concretely were described.

Comparison of Critical Power and W' Derived From 2 or 3 Maximal Tests.

PubMed

Simpson, Len Parker; Kordi, Mehdi

2017-07-01

Typically, accessing the asymptote (critical power; CP) and curvature constant (W') parameters of the hyperbolic power-duration relationship requires multiple constant-power exhaustive-exercise trials spread over several visits. However, more recently single-visit protocols and personal power meters have been used. This study investigated the practicality of using a 2-trial, single-visit protocol in providing reliable CP and W' estimates. Eight trained cyclists underwent 3- and 12-min maximal-exercise trials in a single session to derive (2-trial) CP and W' estimates. On a separate occasion a 5-min trial was performed, providing a 3rd trial to calculate (3-trial) CP and W'. There were no differences in CP (283 ± 66 vs 282 ± 65 W) or W' (18.72 ± 6.21 vs 18.27 ± 6.29 kJ) obtained from either the 2-trial or 3-trial method, respectively. After 2 familiarization sessions (completing a 3- and a 12-min trial on both occasions), both CP and W' remained reliable over additional separate measurements. The current study demonstrates that after 2 familiarization sessions, reliable CP and W' parameters can be obtained from trained cyclists using only 2 maximal-exercise trials. These results offer practitioners a practical, time-efficient solution for incorporating power-duration testing into applied athlete support.

Evaluation of the priority heuristic as a descriptive model of risky decision making: comment on Brandstätter, Gigerenzer, and Hertwig (2006).

PubMed

Birnbaum, Michael H

2008-01-01

E. Brandstätter, G. Gigerenzer, and R. Hertwig (2006) contended that their priority heuristic, a type of lexicographic semiorder model, is more accurate than cumulative prospect theory (CPT) or transfer of attention exchange (TAX) models in describing risky decisions. However, there are 4 problems with their argument. First, their heuristic is not descriptive of certain data that they did not review. Second, their analysis relied on a global index of fit, percentage of correct predictions of the modal choice. Such analyses can lead to wrong conclusions when parameters are not properly estimated from the data. When parameters are estimated from the data, CPT and TAX fit the D. Kahneman and A. Tversky (1979) data perfectly. Reanalysis shows that TAX and CPT do as well as the priority heuristic for 2 of the data sets reviewed and outperform the priority heuristic for the other 3. Third, when 2 of these sets of data are reexamined, the priority heuristic is seen to make systematic violations. Fourth, new critical implications have been devised for testing the family of lexicographic semiorders including the priority heuristic; new results with these critical tests show systematic evidence against lexicographic semiorder models. (c) 2008 APA, all rights reserved

Beethoven recordings reviewed: a systematic method for mapping the content of music performance criticism

PubMed Central

Alessandri, Elena; Williamson, Victoria J.; Eiholzer, Hubert; Williamon, Aaron

2015-01-01

Critical reviews offer rich data that can be used to investigate how musical experiences are conceptualized by expert listeners. However, these data also present significant challenges in terms of organization, analysis, and interpretation. This study presents a new systematic method for examining written responses to music, tested on a substantial corpus of music criticism. One hundred critical reviews of Beethoven’s piano sonata recordings, published in the Gramophone between August 1934 and July 2010, were selected using in-depth data reduction (qualitative/quantitative approach). The texts were then examined using thematic analysis in order to generate a visual descriptive model of expert critical review. This model reveals how the concept of evaluation permeates critical review. It also distinguishes between two types of descriptors. The first characterizes the performance in terms of specific actions or features of the musical sound (musical parameters, technique, and energy); the second appeals to higher-order properties (artistic style, character and emotion, musical structure, communicativeness) or assumed performer qualities (understanding, intentionality, spontaneity, sensibility, control, and care). The new model provides a methodological guide and conceptual basis for future studies of critical review in any genre. PMID:25741295

Beethoven recordings reviewed: a systematic method for mapping the content of music performance criticism.

PubMed

Alessandri, Elena; Williamson, Victoria J; Eiholzer, Hubert; Williamon, Aaron

2015-01-01

Critical reviews offer rich data that can be used to investigate how musical experiences are conceptualized by expert listeners. However, these data also present significant challenges in terms of organization, analysis, and interpretation. This study presents a new systematic method for examining written responses to music, tested on a substantial corpus of music criticism. One hundred critical reviews of Beethoven's piano sonata recordings, published in the Gramophone between August 1934 and July 2010, were selected using in-depth data reduction (qualitative/quantitative approach). The texts were then examined using thematic analysis in order to generate a visual descriptive model of expert critical review. This model reveals how the concept of evaluation permeates critical review. It also distinguishes between two types of descriptors. The first characterizes the performance in terms of specific actions or features of the musical sound (musical parameters, technique, and energy); the second appeals to higher-order properties (artistic style, character and emotion, musical structure, communicativeness) or assumed performer qualities (understanding, intentionality, spontaneity, sensibility, control, and care). The new model provides a methodological guide and conceptual basis for future studies of critical review in any genre.

Control System Applicable Use Assessment of the Secure Computing Corporation - Secure Firewall (Sidewinder)

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

Hadley, Mark D.; Clements, Samuel L.

2009-01-01

Battelle’s National Security & Defense objective is, “applying unmatched expertise and unique facilities to deliver homeland security solutions. From detection and protection against weapons of mass destruction to emergency preparedness/response and protection of critical infrastructure, we are working with industry and government to integrate policy, operational, technological, and logistical parameters that will secure a safe future”. In an ongoing effort to meet this mission, engagements with industry that are intended to improve operational and technical attributes of commercial solutions that are related to national security initiatives are necessary. This necessity will ensure that capabilities for protecting critical infrastructure assets aremore » considered by commercial entities in their development, design, and deployment lifecycles thus addressing the alignment of identified deficiencies and improvements needed to support national cyber security initiatives. The Secure Firewall (Sidewinder) appliance by Secure Computing was assessed for applicable use in critical infrastructure control system environments, such as electric power, nuclear and other facilities containing critical systems that require augmented protection from cyber threat. The testing was performed in the Pacific Northwest National Laboratory’s (PNNL) Electric Infrastructure Operations Center (EIOC). The Secure Firewall was tested in a network configuration that emulates a typical control center network and then evaluated. A number of observations and recommendations are included in this report relating to features currently included in the Secure Firewall that support critical infrastructure security needs.« less

Optimizing Muscle Parameters in Musculoskeletal Modeling Using Monte Carlo Simulations

NASA Technical Reports Server (NTRS)

Hanson, Andrea; Reed, Erik; Cavanagh, Peter

2011-01-01

Astronauts assigned to long-duration missions experience bone and muscle atrophy in the lower limbs. The use of musculoskeletal simulation software has become a useful tool for modeling joint and muscle forces during human activity in reduced gravity as access to direct experimentation is limited. Knowledge of muscle and joint loads can better inform the design of exercise protocols and exercise countermeasure equipment. In this study, the LifeModeler(TM) (San Clemente, CA) biomechanics simulation software was used to model a squat exercise. The initial model using default parameters yielded physiologically reasonable hip-joint forces. However, no activation was predicted in some large muscles such as rectus femoris, which have been shown to be active in 1-g performance of the activity. Parametric testing was conducted using Monte Carlo methods and combinatorial reduction to find a muscle parameter set that more closely matched physiologically observed activation patterns during the squat exercise. Peak hip joint force using the default parameters was 2.96 times body weight (BW) and increased to 3.21 BW in an optimized, feature-selected test case. The rectus femoris was predicted to peak at 60.1% activation following muscle recruitment optimization, compared to 19.2% activation with default parameters. These results indicate the critical role that muscle parameters play in joint force estimation and the need for exploration of the solution space to achieve physiologically realistic muscle activation.

Mixed-order phase transition in a colloidal crystal.

PubMed

Alert, Ricard; Tierno, Pietro; Casademunt, Jaume

2017-12-05

Mixed-order phase transitions display a discontinuity in the order parameter like first-order transitions yet feature critical behavior like second-order transitions. Such transitions have been predicted for a broad range of equilibrium and nonequilibrium systems, but their experimental observation has remained elusive. Here, we analytically predict and experimentally realize a mixed-order equilibrium phase transition. Specifically, a discontinuous solid-solid transition in a 2D crystal of paramagnetic colloidal particles is induced by a magnetic field [Formula: see text] At the transition field [Formula: see text], the energy landscape of the system becomes completely flat, which causes diverging fluctuations and correlation length [Formula: see text] Mean-field critical exponents are predicted, since the upper critical dimension of the transition is [Formula: see text] Our colloidal system provides an experimental test bed to probe the unconventional properties of mixed-order phase transitions.

Mixed-order phase transition in a colloidal crystal

NASA Astrophysics Data System (ADS)

Alert, Ricard; Tierno, Pietro; Casademunt, Jaume

2017-12-01

Mixed-order phase transitions display a discontinuity in the order parameter like first-order transitions yet feature critical behavior like second-order transitions. Such transitions have been predicted for a broad range of equilibrium and nonequilibrium systems, but their experimental observation has remained elusive. Here, we analytically predict and experimentally realize a mixed-order equilibrium phase transition. Specifically, a discontinuous solid-solid transition in a 2D crystal of paramagnetic colloidal particles is induced by a magnetic field H. At the transition field Hs, the energy landscape of the system becomes completely flat, which causes diverging fluctuations and correlation length ξ∝|H2-Hs2|-1/2. Mean-field critical exponents are predicted, since the upper critical dimension of the transition is du=2. Our colloidal system provides an experimental test bed to probe the unconventional properties of mixed-order phase transitions.

PROTEIN NEEDS OF CRITICALLY ILL PATIENTS RECEIVING PARENTERAL NUTRITION.

PubMed

Germano Borges de Oliveira Nascimento Freitas, Renata; Negrão Nogueira, Roberto José; Hessel, Gabriel

2015-07-01

assess whether the current protein intake recommendations may improve the biochemical parameters of critical patients receiving parenteral nutrition. longitudinal study with three evaluations made (during the first 72 hours, on the 7th and the 14th days of PN). The following tests were applied: albumin, C-reactive protein, prealbumin, total cholesterol, HDL, triglycerides, lymphocytes, and glutathione peroxidase. The severity was determined by SOFA. The statistical analysis included the Spearman and Mann-Whitney tests, as well as ANOVA (analysis of variance). among the 53 patients evaluated, 20 (37.74%) died. The mean calorie was 24.68 ± 9.78 kcal/kg (beginning of PN), 26.49 ± 8.89 kcal/kg (3rd to 7th days of PN), and 30.9 ± 12.19 kcal/kg (7th to 14th days of PN). The mean protein was 1.19 ± 0.44 g/kcal/kg (first 72 hours of PN), 1.29 ± 0.44 g/kcal/kg (3rd to 7th days of PN) and 1.49 ± 0.69 g/kcal/kg (7th to 14th days of PN). Prealbumin, albumin, total cholesterol and HDL were below the reference values, while the CRP levels were high. Throughout the three evaluation times, there was no a significant improvement on the levels of laboratory examinations. A strong and negative correlation was found between SOFA and prealbumin (r = -0.64, p = 0.05). the protein offer, according to the traditional recommendations, was not enough to improve the biochemical parameters of critical patients undergoing parenteral nutrition. Copyright AULA MEDICA EDICIONES 2014. Published by AULA MEDICA. All rights reserved.

Criticality features in ULF magnetic fields prior to the 2011 Tohoku earthquake

PubMed Central

HAYAKAWA, Masashi; SCHEKOTOV, Alexander; POTIRAKIS, Stelios; EFTAXIAS, Kostas

2015-01-01

The criticality of ULF (Ultra-low-frequency) magnetic variations is investigated for the 2011 March 11 Tohoku earthquake (EQ) by natural time analysis. For this attempt, some ULF parameters were considered: (1) Fh (horizontal magnetic field), (2) Fz (vertical magnetic field), and (3) Dh (inverse of horizontal magnetic field). The first two parameters refer to the ULF radiation, while the last parameter refers to another ULF effect of ionospheric signature. Nighttime (L.T. = 3 am ± 2 hours) data at Kakioka (KAK) were used, and the power of each quantity at a particular frequency band of 0.03–0.05 Hz was averaged for nighttime hours. The analysis results indicate that Fh fulfilled all criticality conditions on March 3–5, 2011, and that the additional parameter, Dh reached also a criticality on March 6 or 7. In conclusion, criticality has reached in the pre-EQ fracture region a few days to one week before the main shock of the Tohoku EQ. PMID:25743063

Validation of a clinical critical thinking skills test in nursing.

PubMed

Shin, Sujin; Jung, Dukyoo; Kim, Sungeun

2015-01-27

The purpose of this study was to develop a revised version of the clinical critical thinking skills test (CCTS) and to subsequently validate its performance. This study is a secondary analysis of the CCTS. Data were obtained from a convenience sample of 284 college students in June 2011. Thirty items were analyzed using item response theory and test reliability was assessed. Test-retest reliability was measured using the results of 20 nursing college and graduate school students in July 2013. The content validity of the revised items was analyzed by calculating the degree of agreement between instrument developer intention in item development and the judgments of six experts. To analyze response process validity, qualitative data related to the response processes of nine nursing college students obtained through cognitive interviews were analyzed. Out of initial 30 items, 11 items were excluded after the analysis of difficulty and discrimination parameter. When the 19 items of the revised version of the CCTS were analyzed, levels of item difficulty were found to be relatively low and levels of discrimination were found to be appropriate or high. The degree of agreement between item developer intention and expert judgments equaled or exceeded 50%. From above results, evidence of the response process validity was demonstrated, indicating that subjects respondeds as intended by the test developer. The revised 19-item CCTS was found to have sufficient reliability and validity and will therefore represents a more convenient measurement of critical thinking ability.

Validation of a clinical critical thinking skills test in nursing

PubMed Central

2015-01-01

Purpose: The purpose of this study was to develop a revised version of the clinical critical thinking skills test (CCTS) and to subsequently validate its performance. Methods: This study is a secondary analysis of the CCTS. Data were obtained from a convenience sample of 284 college students in June 2011. Thirty items were analyzed using item response theory and test reliability was assessed. Test-retest reliability was measured using the results of 20 nursing college and graduate school students in July 2013. The content validity of the revised items was analyzed by calculating the degree of agreement between instrument developer intention in item development and the judgments of six experts. To analyze response process validity, qualitative data related to the response processes of nine nursing college students obtained through cognitive interviews were analyzed. Results: Out of initial 30 items, 11 items were excluded after the analysis of difficulty and discrimination parameter. When the 19 items of the revised version of the CCTS were analyzed, levels of item difficulty were found to be relatively low and levels of discrimination were found to be appropriate or high. The degree of agreement between item developer intention and expert judgments equaled or exceeded 50%. Conclusion: From above results, evidence of the response process validity was demonstrated, indicating that subjects respondeds as intended by the test developer. The revised 19-item CCTS was found to have sufficient reliability and validity and will therefore represents a more convenient measurement of critical thinking ability. PMID:25622716

Prediction of Long-Term Strength of Thermoplastic Composites Using Time-Temperature Superposition. Degree awarded by Texas A&M Univ., May 1998

NASA Technical Reports Server (NTRS)

Reeder, James R.

2002-01-01

Accelerated tests for composite failure were investigated. Constant ramp transverse strength tests on thermoplastic composite specimens were conducted at four temperatures from 300 F to 450 F and five duration times from 0.5 sec to 24 hrs. Up to 400 F, the time-temperature-superposition method produces a master curve allowing strength at longer times to be estimated from strength tests conducted over shorter times but at higher temperatures. The shift factors derived from compliance tests applied well to the strength data. To explain why strength behaved similar to compliance, a viscoelastic fracture model was investigated based on the hypothesis that the work of fracture for crack initiation at some critical flaw remains constant with time and temperature. The model, which used compliance as input, was found to fit the strength data only if the critical fracture energy was allowed to vary with stress rate. Fracture tests using double cantilever beam specimens were conducted from 300 F to 450 F over time scales similar to the strength study. The toughness data showed a significant change with loading rate, less variation with temperature, did not form a master curve, and could not be correlated with the fracture model. Since the fracture model did not fit the fracture data, an alternative explanation based on the dilatational strain energy density was proposed. However the usefulness of this model is severely limited because it relies on a critical parameter which varies with loading rate.

Critical levels as applied to ozone for North American forests

Treesearch

Robert C. Musselman

2006-01-01

The United States and Canada have used concentration-based parameters for air quality standards for ozone effects on forests in North America. The European critical levels method for air quality standards uses an exposure-based parameter, a cumulative ozone concentration index with a threshold cutoff value. The critical levels method has not been used in North America...

Corresponding-states laws for protein solutions.

PubMed

Katsonis, Panagiotis; Brandon, Simon; Vekilov, Peter G

2006-09-07

The solvent around protein molecules in solutions is structured and this structuring introduces a repulsion in the intermolecular interaction potential at intermediate separations. We use Monte Carlo simulations with isotropic, pair-additive systems interacting with such potentials. We test if the liquid-liquid and liquid-solid phase lines in model protein solutions can be predicted from universal curves and a pair of experimentally determined parameters, as done for atomic and colloid materials using several laws of corresponding states. As predictors, we test three properties at the critical point for liquid-liquid separation: temperature, as in the original van der Waals law, the second virial coefficient, and a modified second virial coefficient, all paired with the critical volume fraction. We find that the van der Waals law is best obeyed and appears more general than its original formulation: A single universal curve describes all tested nonconformal isotropic pair-additive systems. Published experimental data for the liquid-liquid equilibrium for several proteins at various conditions follow a single van der Waals curve. For the solid-liquid equilibrium, we find that no single system property serves as its predictor. We go beyond corresponding-states correlations and put forth semiempirical laws, which allow prediction of the critical temperature and volume fraction solely based on the range of attraction of the intermolecular interaction potential.

Quality index of radiological devices: results of one year of use.

PubMed

Tofani, Alessandro; Imbordino, Patrizia; Lecci, Antonio; Bonannini, Claudia; Del Corona, Alberto; Pizzi, Stefano

2003-01-01

The physical quality index (QI) of radiological devices summarises in a single numerical value between 0 and 1 the results of constancy tests. The aim of this paper is to illustrate the results of the use of such an index on all public radiological devices in the Livorno province over one year. The quality index was calculated for 82 radiological devices of a wide range of types by implementing its algorithm in a spreadsheet-based software for the automatic handling of quality control data. The distribution of quality index values was computed together with the associated statistical quantities. This distribution is strongly asymmetrical, with a sharp peak near the highest QI values. The mean quality index values for the different types of device show some inhomogeneity: in particular, mammography and panoramic dental radiography devices show far lower quality than other devices. In addition, our analysis has identified the parameters that most frequently do not pass the quality tests for each type of device. Finally, we sought some correlation between quality and age of the device, but this was poorly significant. The quality index proved to be a useful tool providing an overview of the physical conditions of radiological devices. By selecting adequate QI threshold values for, it also helps to decide whether a given device should be upgraded or replaced. The identification of critical parameters for each type of device may be used to improve the definition of the QI by attributing greater weights to critical parameters, so as to better address the maintenance of radiological devices.

Re-Tooling the Agency's Engineering Predictive Practices for Durability and Damage Tolerance

NASA Technical Reports Server (NTRS)

Piascik, Robert S.; Knight, Norman F., Jr.

2017-01-01

Over the past decade, the Agency has placed less emphasis on testing and has increasingly relied on computational methods to assess durability and damage tolerance (D&DT) behavior when evaluating design margins for fracture-critical components. With increased emphasis on computational D&DT methods as the standard practice, it is paramount that capabilities of these methods are understood, the methods are used within their technical limits, and validation by well-designed tests confirms understanding. The D&DT performance of a component is highly dependent on parameters in the neighborhood of the damage. This report discusses D&DT method vulnerabilities.

Quantum critical fluctuations in disordered d-wave superconductors.

PubMed

Meyer, Julia S; Gornyi, Igor V; Altland, Alexander

2003-03-14

To explain the strong quasiparticle damping in the cuprates, Sachdev and collaborators proposed to couple the system to a critically fluctuating id(xy)- or is-order parameter mode. Here we generalize the approach to the presence of static disorder. In the id case, the order parameter dynamics becomes diffusive, but otherwise much of the phenomenology of the clean case remains intact. In contrast, the interplay of disorder and is-order parameter fluctuations leads to a secondary superconductor transition, with a critical temperature exponentially sensitive to the impurity concentration.

Evaluation of the biological effects of police radar RAMER 7F

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

Rotkovska, D.; Kautska, J.; Bartonickova, A.

1993-06-01

This paper presents results of experiments on the effects of electromagnetic radiation in the millimeter range (frequency 34.0 [+-] 0.1 GHz, power density 20 [mu]W/cm[sup 2]) emitted by a police radar device. Considering the physical properties of the radiation in millimeter range (skin effects), the experiments were carried out on hairless mice. The main physiological parameters tested were body mass, body temperature, peripheral blood, and mass and cellularity of several important organs. Critical organs, the skin, and cornea were examined by electron microscopy. Differentiation ability of hematopoietic cells, progenitors of granulocytes and macrophages, and DNA synthesis in the cornea weremore » compared in irradiated and nonirradiated animals. None of the parameters tested was affected to an extent that would indicate the start of a pathological process or the risk of damage to genetic material.« less

Applications of terahertz-pulsed technology in the pharmaceutical industry

NASA Astrophysics Data System (ADS)

Taday, Philip F.

2010-02-01

Coatings are applied to pharmaceutical tablets (or pills) to for either cosmetic or release control reasons. Cosmetic coatings control the colour or to mask the taste of an active ingredient; the thickness of these coating is not critical to the performance of the product. On the other hand the thickness and uniformity of a controlled release coating has been found affect the release of the active ingredient. In this work we have obtained from a pharmacy single brand of pantoprazole tablet and mapped them using terahertz pulsed imaging (TPI) prior to additional dissolution testing. Three terahertz parameters were derived for univariate analysis for each layer: coating thickness, terahertz electric field peak strength and terahertz interface index. These parameters were then correlated dissolution tested. The best fit was found to be with combined coating layer thickness of the inert layer and enteric coating. The commercial tablets showed a large variation in coating thickness.

Critical processes and parameters in the development of accident tolerant fuels drop-in capsule irradiation tests

DOE PAGES

Barrett, K. E.; Ellis, K. D.; Glass, C. R.; ...

2015-12-01

The goal of the Accident Tolerant Fuel (ATF) program is to develop the next generation of Light Water Reactor (LWR) fuels with improved performance, reliability, and safety characteristics during normal operations and accident conditions and with reduced waste generation. An irradiation test series has been defined to assess the performance of proposed ATF concepts under normal LWR operating conditions. The Phase I ATF irradiation test series is planned to be performed as a series of drop-in capsule tests to be irradiated in the Advanced Test Reactor (ATR) operated by the Idaho National Laboratory (INL). Design, analysis, and fabrication processes formore » ATR drop-in capsule experiment preparation are presented in this paper to demonstrate the importance of special design considerations, parameter sensitivity analysis, and precise fabrication and inspection techniques for figure innovative materials used in ATF experiment assemblies. A Taylor Series Method sensitivity analysis approach was used to identify the most critical variables in cladding and rodlet stress, temperature, and pressure calculations for design analyses. The results showed that internal rodlet pressure calculations are most sensitive to the fission gas release rate uncertainty while temperature calculations are most sensitive to cladding I.D. and O.D. dimensional uncertainty. The analysis showed that stress calculations are most sensitive to rodlet internal pressure uncertainties, however the results also indicated that the inside radius, outside radius, and internal pressure were all magnified as they propagate through the stress equation. This study demonstrates the importance for ATF concept development teams to provide the fabricators as much information as possible about the material properties and behavior observed in prototype testing, mock-up fabrication and assembly, and chemical and mechanical testing of the materials that may have been performed in the concept development phase. Special handling, machining, welding, and inspection of materials, if known, should also be communicated to the experiment fabrication and inspection team.« less

Critical and post-critical behaviour of two-degree-of-freedom flutter-based generators

NASA Astrophysics Data System (ADS)

Pigolotti, Luca; Mannini, Claudio; Bartoli, Gianni; Thiele, Klaus

2017-09-01

Energy harvesting from flow-induced vibrations is a recent research field, which considers a diverse range of systems, among which two-degree-of-freedom flutter-based solutions were individuated as good candidates to obtain high energy performance. In the present work, numerical linear analyses and wind-tunnel tests were conducted on a flat-plate sectional model. The aim is to identify some design guidelines for generators exploiting the classical-flutter instability, through the investigation of the critical condition and the response during the post-critical regime. Many sets of governing parameters of interest from the energy-harvesting point of view were considered, including high levels of heaving damping to simulate the operation of a conversion apparatus. In particular, eccentricity of the elastic centre and small downstream mass unbalance can be introduced as solutions aiming at optimal operative ranges. The collected results suggest the high potentiality of flutter-based generators, and a significant enhancement of performance can be envisaged. Moreover, they contribute to improve the knowledge of the flutter excitation mechanism and to widen the dataset of measurements in the post-critical regime.

Surface property modification of silicon

NASA Technical Reports Server (NTRS)

Danyluk, S.

1984-01-01

The main emphasis of this work has been to determine the wear rate of silicon in fluid environments and the parameters that influence wear. Three tests were carried out on single crystal Czochralski silicon wafers: circular and linear multiple-scratch tests in fluids by a pyramidal diamond simulated fixed-particle abrasion; microhardness and three-point bend tests were used to determine the hardness and fracture toughness of abraded silicon and the extent of damage induced by abrasion. The wear rate of (100) and (111) n and p-type single crystal Cz silicon abraded by a pyramidal diamond in ethanol, methanol, acetone and de-ionized water was determined by measuring the cross-sectional areas of grooves of the circular and linear multiple-scratch tests. The wear rate depends on the loads on the diamond and is highest for ethanol and lowest for de-ionized water. The surface morphology of the grooves showed lateral and median cracks as well as a plastically deformed region. The hardness and fracture toughness are critical parameters that influence the wear rate. Microhardness tests were conducted to determine the hardness as influenced by fluids. Median cracks and the damage zone surrounding the indentations were also related to the fluid properties.

A gravitational puzzle.

PubMed

Caldwell, Robert R

2011-12-28

The challenge to understand the physical origin of the cosmic acceleration is framed as a problem of gravitation. Specifically, does the relationship between stress-energy and space-time curvature differ on large scales from the predictions of general relativity. In this article, we describe efforts to model and test a generalized relationship between the matter and the metric using cosmological observations. Late-time tracers of large-scale structure, including the cosmic microwave background, weak gravitational lensing, and clustering are shown to provide good tests of the proposed solution. Current data are very close to proving a critical test, leaving only a small window in parameter space in the case that the generalized relationship is scale free above galactic scales.

MECHANICAL STRENGTH RESPONSES OF POLED LEAD ZIRCONATE TITANATE UNDER EXTREME ELECTRIC FIELD AND VARIOUS TEMPERATURE CONDITIONS

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

Wang, Hong; Matsunaga, Tadashi; Zhang, Kewei

PZT (lead zirconate titanate), particularly PZT-5A, is used in a variety of critical actuation and sensing systems because of its high Curie temperature and large piezoelectric coefficients. However, PZT is susceptible to mechanical failure. The evaluation of the mechanical strength of the material under the target working conditions is very important. This study presents part of the recent experimental developments in mechanical testing and evaluation of PZT materials at Oak Ridge National Laboratory. Ball-on-ring and four-point bending testing setups were used, with modifications made to account for testing requirements from high-level electric field and elevated temperature. The poled PZT-5A ormore » equivalent material was tested under various specimen and testing conditions. The parameters of the distribution of strengths (characteristic strength and Weibull modulus) are discussed in relation to the testing conditions. Fractographic results based on scanning electron microscopy are also presented and discussed. The related data can serve as input for the design of piezoceramic devices, not only those used in energy systems like fuel injectors in heavy-duty diesel engines, but also those used in structural health monitoring, energy harvesting, and other critical systems in aerospace and civil engineering.« less

Relationship between simulated extravehicular activity tasks and measurements of physical performance.

PubMed

Ade, C J; Broxterman, R M; Craig, J C; Schlup, S J; Wilcox, S L; Barstow, T J

2014-11-01

The purpose was to evaluate the relationships between tests of fitness and two activities that simulate components of Lunar- and Martian-based extravehicular activities (EVA). Seventy-one subjects completed two field tests: a physical abilities test and a 10km Walkback test. The relationships between test times and the following parameters were determined: running V˙O2max, gas exchange threshold (GET), speed at V˙O2max (s-V˙O2max), highest sustainable rate of aerobic metabolism [critical speed (CS)], and the finite distance that could be covered above CS (D'): arm cranking V˙O2peak, GET, critical power (CP), and the finite work that can be performed above CP (W'). CS, running V˙O2max, s-V˙O2max, and arm cranking V˙O2peak had the highest correlations with the physical abilities field test (r=0.66-0.82, P<0.001). For the 10km Walkback, CS, s-V˙O2max, and running V˙O2max were significant predictors (r=0.64-0.85, P<0.001). CS and to a lesser extent V˙O2max are most strongly associated with tasks that simulate aspects of EVA performance, highlighting CS as a method for evaluating astronaut physical capacity. Copyright © 2014 Elsevier B.V. All rights reserved.

Live maternal speech and singing have beneficial effects on hospitalized preterm infants.

PubMed

Filippa, Manuela; Devouche, Emmanuel; Arioni, Cesare; Imberty, Michel; Gratier, Maya

2013-10-01

To study the effects of live maternal speaking and singing on physiological parameters of preterm infants in the NICU and to test the hypothesis that vocal stimulation can have differential effects on preterm infants at a behavioural level. Eighteen mothers spoke and sang to their medically stable preterm infants in their incubators over 6 days, between 1 and 2 pm. Heart rate (HR), oxygen saturation (OxSat), number of critical events (hypoxemia, bradycardia and apnoea) and change in behavioural state were measured. Comparisons of periods with and without maternal vocal stimulation revealed significantly greater oxygen saturation level and heart rate and significantly fewer negative critical events (p < 0.0001) when the mother was speaking and singing. Unexpected findings were the comparable effects of maternal talk and singing on infant physiological parameters and the differential ones on infant behavioural state. A renewed connection to the mother's voice can be an important and significant experience for preterm infants. Exposure to maternal speech and singing shows significant early beneficial effects on physiological state, such as oxygen saturation levels, number of critical events and prevalence of calm alert state. These findings have implications for NICU interventions, encouraging maternal interaction with their medically stable preterm infants. ©2013 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.

A model for gravity-wave spectra observed by Doppler sounding systems

NASA Technical Reports Server (NTRS)

Vanzandt, T. E.

1986-01-01

A model for Mesosphere - Stratosphere - Troposphere (MST) radar spectra is developed following the formalism presented by Pinkel (1981). Expressions for the one-dimensional spectra of radial velocity versus frequency and versus radial wave number are presented. Their dependence on the parameters of the gravity-wave spectrum and on the experimental parameters, radar zenith angle and averaging time are described and the conditions for critical tests of the gravity-wave hypothesis are discussed. The model spectra is compared with spectra observed in the Arctic summer mesosphere by the Poker Flat radar. This model applies to any monostatic Doppler sounding system, including MST radar, Doppler lidar and Doppler sonar in the atmosphere, and Doppler sonar in the ocean.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Removal of target odorous molecules on to activated carbon cloths.

PubMed

Le Leuch, L M; Subrenat, A; Le Cloirec, P

2004-01-01

Activated carbon materials are adsorbents whose physico-chemical properties are interesting for the treatment of odorous compounds like hydrogen sulfide. Indeed, their structural parameters (pore structure) and surface chemistry (presence of heteroatoms such as oxygen, hydrogen, nitrogen, sulfur, phosphorus) play an important role in H2S removal. The cloth texture of these adsorbents (activated carbon cloths) is particularly adapted for dealing with high flows, often found in the treatment of odor emissions. Thus, this paper first presents the influence of these parameters through adsorption isothermal curves performed on several materials. Secondly, tests in a dynamic system are described. They highlight the low critical thickness of the fabric compared to granular activated carbon.

Comparison of two blood sampling techniques for the determination of coagulation parameters in the horse: Jugular venipuncture and indwelling intravenous catheter.

PubMed

Mackenzie, C J; McGowan, C M; Pinchbeck, G; Carslake, H B

2018-05-01

Evaluation of coagulation status is an important component of critical care. Ongoing monitoring of coagulation status in hospitalised horses has previously been via serial venipuncture due to concerns that sampling directly from the intravenous catheter (IVC) may alter the accuracy of the results. Adverse effects such as patient anxiety and trauma to the sampled vessel could be avoided by the use of an indwelling IVC for repeat blood sampling. To compare coagulation parameters from blood obtained by jugular venipuncture with IVC sampling in critically ill horses. Prospective observational study. A single set of paired blood samples were obtained from horses (n = 55) admitted to an intensive care unit by direct jugular venipuncture and, following removal of a presample, via an indwelling IVC. The following coagulation parameters were measured on venipuncture and IVC samples: whole blood prothrombin time (PT), fresh plasma PT and activated partial thromboplastin time (aPTT) and stored plasma antithrombin activity (AT) and fibrinogen concentration. D-dimer concentration was also measured in some horses (n = 22). Comparison of venipuncture and IVC results was performed using Lin's concordance correlation coefficient. Agreement between paired results was assessed using Bland Altman analysis. Correlation was substantial and agreement was good between sample methods for all parameters except AT and D-dimers. Each coagulation parameter was tested using only one assay. Sampling was limited to a convenience sample and timing of sample collection was not standardised in relation to when the catheter was flushed with heparinised saline. With the exception of AT and D-dimers, coagulation parameters measured on blood samples obtained via an IVC have clinically equivalent values to those obtained by jugular venipuncture. © 2017 EVJ Ltd.

Mixed-order phase transition in a colloidal crystal

PubMed Central

Tierno, Pietro; Casademunt, Jaume

2017-01-01

Mixed-order phase transitions display a discontinuity in the order parameter like first-order transitions yet feature critical behavior like second-order transitions. Such transitions have been predicted for a broad range of equilibrium and nonequilibrium systems, but their experimental observation has remained elusive. Here, we analytically predict and experimentally realize a mixed-order equilibrium phase transition. Specifically, a discontinuous solid–solid transition in a 2D crystal of paramagnetic colloidal particles is induced by a magnetic field H. At the transition field Hs, the energy landscape of the system becomes completely flat, which causes diverging fluctuations and correlation length ξ∝|H2−Hs2|−1/2. Mean-field critical exponents are predicted, since the upper critical dimension of the transition is du=2. Our colloidal system provides an experimental test bed to probe the unconventional properties of mixed-order phase transitions. PMID:29158388

Molecular dynamics study of combustion reactions in supercritical environment. Part 1: Carbon dioxide and water force field parameters refitting and critical isotherms of binary mixtures

DOE PAGES

Masunov, Artem E.; Atlanov, Arseniy Alekseyevich; Vasu, Subith S.

2016-10-04

Oxy-fuel combustion process is expected to drastically increase the energy efficiency and enable easy carbon sequestration. In this technology the combustion products (carbon dioxide and water) are used to control the temperature and nitrogen is excluded from the combustion chamber, so that nitrogen oxide pollutants do not form. Therefore, in oxycombustion the carbon dioxide and water are present in large concentrations in their transcritical state, and may play an important role in kinetics. The computational chemistry methods may assist in understanding these effects, and Molecular Dynamics with ReaxFF force field seem to be a suitable tool for such a study.more » Here we investigate applicability of the ReaxFF to describe the critical phenomena in carbon dioxide and water and find that several nonbonding parameters need adjustment. We report the new parameter set, capable to reproduce the critical temperatures and pressures. Furthermore, the critical isotherms of CO 2/H 2O binary mixtures are computationally studied here for the first time and their critical parameters are reported.« less

Molecular dynamics study of combustion reactions in supercritical environment. Part 1: Carbon dioxide and water force field parameters refitting and critical isotherms of binary mixtures

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

Masunov, Artem E.; Atlanov, Arseniy Alekseyevich; Vasu, Subith S.

Oxy-fuel combustion process is expected to drastically increase the energy efficiency and enable easy carbon sequestration. In this technology the combustion products (carbon dioxide and water) are used to control the temperature and nitrogen is excluded from the combustion chamber, so that nitrogen oxide pollutants do not form. Therefore, in oxycombustion the carbon dioxide and water are present in large concentrations in their transcritical state, and may play an important role in kinetics. The computational chemistry methods may assist in understanding these effects, and Molecular Dynamics with ReaxFF force field seem to be a suitable tool for such a study.more » Here we investigate applicability of the ReaxFF to describe the critical phenomena in carbon dioxide and water and find that several nonbonding parameters need adjustment. We report the new parameter set, capable to reproduce the critical temperatures and pressures. Furthermore, the critical isotherms of CO 2/H 2O binary mixtures are computationally studied here for the first time and their critical parameters are reported.« less

[Application of quality by design in granulation process for Ginkgo leaf tablet (Ⅲ)： process control strategy based on design space].

PubMed

Cui, Xiang-Long; Xu, Bing; Sun, Fei; Dai, Sheng-Yun; Shi, Xin-Yuan; Qiao, Yan-Jiang

2017-03-01

In this paper, under the guidance of quality by design (QbD) concept, the control strategy of the high shear wet granulation process of the ginkgo leaf tablet based on the design space was established to improve the process controllability and product quality consistency. The median granule size (D50) and bulk density (Da) of granules were identified as critical quality attributes (CQAs) and potential critical process parameters (pCPPs) were determined by the failure modes and effect analysis (FMEA). The Plackeet-Burmann experimental design was used to screen pCPPs and the results demonstrated that the binder amount, the wet massing time and the wet mixing impeller speed were critical process parameters (CPPs). The design space of the high shear wet granulation process was developed within pCPPs range based on the Box-Behnken design and quadratic polynomial regression models. ANOVA analysis showed that the P-values of model were less than 0.05 and the values of lack of fit test were more than 0.1, indicating that the relationship between CQAs and CPPs could be well described by the mathematical models. D₅₀ could be controlled within 170 to 500 μm, and the bulk density could be controlled within 0.30 to 0.44 g•cm⁻³ by using any CPPs combination within the scope of design space. Besides, granules produced by process parameters within the design space region could also meet the requirement of tensile strength of the ginkgo leaf tablet.. Copyright© by the Chinese Pharmaceutical Association.

Model parameter learning using Kullback-Leibler divergence

NASA Astrophysics Data System (ADS)

Lin, Chungwei; Marks, Tim K.; Pajovic, Milutin; Watanabe, Shinji; Tung, Chih-kuan

2018-02-01

In this paper, we address the following problem: For a given set of spin configurations whose probability distribution is of the Boltzmann type, how do we determine the model coupling parameters? We demonstrate that directly minimizing the Kullback-Leibler divergence is an efficient method. We test this method against the Ising and XY models on the one-dimensional (1D) and two-dimensional (2D) lattices, and provide two estimators to quantify the model quality. We apply this method to two types of problems. First, we apply it to the real-space renormalization group (RG). We find that the obtained RG flow is sufficiently good for determining the phase boundary (within 1% of the exact result) and the critical point, but not accurate enough for critical exponents. The proposed method provides a simple way to numerically estimate amplitudes of the interactions typically truncated in the real-space RG procedure. Second, we apply this method to the dynamical system composed of self-propelled particles, where we extract the parameter of a statistical model (a generalized XY model) from a dynamical system described by the Viscek model. We are able to obtain reasonable coupling values corresponding to different noise strengths of the Viscek model. Our method is thus able to provide quantitative analysis of dynamical systems composed of self-propelled particles.

Pedestrians' vulnerability in floodwaters: sensitivity to gender and age

NASA Astrophysics Data System (ADS)

Arrighi, Chiara; Castelli, Fabio

2017-04-01

Among the causes of fatalities during floods, the loss of stability is an aspect which has been usually investigated with conceptual models and laboratory experiments. The human body geometry has been often simplified to derive mechanical equilibrium conditions for toppling and sliding due to weight and hydrodynamic actions. Experimental activity produced water depth versus velocity diagrams showing the critical conditions for people partly immersed in floodwaters, whose scatter reflects the large variability of tested subjects (i.e. children, men and women with different physical characteristics). Nevertheless, the proposed hazard criteria based on the product number HV are not capable of distinguishing between different subjects. A dimensionless approach with a limited number of parameters and 3D numerical simulations highlight the significance of subject height and quantify the drag forces different subjects are able to withstand. From the mechanical point of view, this approach significantly reduces the experimental scatter. Differences in subjects' height are already an evidence of gender differences; however, many other parameters such as age and skeletal muscle mass may play a significant role in individual responses to floodwater actions, which can be responsible of the residual unexplained variance. In this work, a sensitivity analysis of critical instability conditions with respect to gender/age-related parameters is carried out and results and implications for flood risk management are discussed.

Friction Stir Welding in Wrought and Cast Aluminum Alloys: Weld Quality Evaluation and Effects of Processing Parameters on Microstructure and Mechanical Properties

NASA Astrophysics Data System (ADS)

Pan, Yi; Lados, Diana A.

2017-04-01

Friction stir welding (FSW) is a solid-state process widely used for joining similar and dissimilar materials for critical applications in the transportation sector. Understanding the effects of the process on microstructure and mechanical properties is critical in design for structural integrity. In this study, four aluminum alloy systems (wrought 6061-T651 and cast A356, 319, and A390) were processed in both as-fabricated and pre-weld heat-treated (T6) conditions using various processing parameters. The effects of processing and heat treatment on the resulting microstructures, macro-/micro-hardness, and tensile properties were systematically investigated and mechanistically correlated to changes in grain size, characteristic phases, and strengthening precipitates. Tensile tests were performed at room temperature both along and across the welding zones. A new method able to evaluate weld quality (using a weld quality index) was developed based on the stress concentration calculated under tensile loading. Optimum processing parameter domains that provide both defect-free welds and good mechanical properties were determined for each alloy and associated with the thermal history of the process. These results were further related to characteristic microstructural features, which can be used for component design and materials/process optimization.

Critical point and phase behavior of the pure fluid and a Lennard-Jones mixture

NASA Astrophysics Data System (ADS)

Potoff, Jeffrey J.; Panagiotopoulos, Athanassios Z.

1998-12-01

Monte Carlo simulations in the grand canonical ensemble were used to obtain liquid-vapor coexistence curves and critical points of the pure fluid and a binary mixture of Lennard-Jones particles. Critical parameters were obtained from mixed-field finite-size scaling analysis and subcritical coexistence data from histogram reweighting methods. The critical parameters of the untruncated Lennard-Jones potential were obtained as Tc*=1.3120±0.0007, ρc*=0.316±0.001 and pc*=0.1279±0.0006. Our results for the critical temperature and pressure are not in agreement with the recent study of Caillol [J. Chem. Phys. 109, 4885 (1998)] on a four-dimensional hypersphere. Mixture parameters were ɛ1=2ɛ2 and σ1=σ2, with Lorentz-Berthelot combining rules for the unlike-pair interactions. We determined the critical point at T*=1.0 and pressure-composition diagrams at three temperatures. Our results have much smaller statistical uncertainties relative to comparable Gibbs ensemble simulations.

Optimal critic learning for robot control in time-varying environments.

PubMed

Wang, Chen; Li, Yanan; Ge, Shuzhi Sam; Lee, Tong Heng

2015-10-01

In this paper, optimal critic learning is developed for robot control in a time-varying environment. The unknown environment is described as a linear system with time-varying parameters, and impedance control is employed for the interaction control. Desired impedance parameters are obtained in the sense of an optimal realization of the composite of trajectory tracking and force regulation. Q -function-based critic learning is developed to determine the optimal impedance parameters without the knowledge of the system dynamics. The simulation results are presented and compared with existing methods, and the efficacy of the proposed method is verified.

Critical research and advanced technology (CRT) support project

NASA Technical Reports Server (NTRS)

Furman, E. R.; Anderson, D. N.; Hodge, P. E.; Lowell, C. E.; Nainiger, J. J.; Schultz, D. F.

1983-01-01

A critical technology base for utility and industrial gas turbines by planning the use of coal-derived fuels was studied. Development tasks were included in the following areas: (1) Combustion - investigate the combustion of coal-derived fuels and methods to minimize the conversion of fuel-bound nitrogen to NOx; (2) materials - understand and minimize hot corrosion; (3) system studies - integrate and focus the technological efforts. A literature survey of coal-derived fuels was completed and a NOx emissions model was developed. Flametube tests of a two-stage (rich-lean) combustor defined optimum equivalence ratios for minimizing NOx emissions. Sector combustor tests demonstrated variable air control to optimize equivalence ratios over a wide load range and steam cooling of the primary zone liner. The catalytic combustion of coal-derived fuels was demonstrated. The combustion of coal-derived gases is very promising. A hot-corrosion life prediction model was formulated and verified with laboratory testing of doped fuels. Fuel additives to control sulfur corrosion were studied. The intermittent application of barium proved effective. Advanced thermal barrier coatings were developed and tested. Coating failure modes were identified and new material formulations and fabrication parameters were specified. System studies in support of the thermal barrier coating development were accomplished.

An Innovative Software Tool Suite for Power Plant Model Validation and Parameter Calibration using PMU Measurements

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

Li, Yuanyuan; Diao, Ruisheng; Huang, Renke

Maintaining good quality of power plant stability models is of critical importance to ensure the secure and economic operation and planning of today’s power grid with its increasing stochastic and dynamic behavior. According to North American Electric Reliability (NERC) standards, all generators in North America with capacities larger than 10 MVA are required to validate their models every five years. Validation is quite costly and can significantly affect the revenue of generator owners, because the traditional staged testing requires generators to be taken offline. Over the past few years, validating and calibrating parameters using online measurements including phasor measurement unitsmore » (PMUs) and digital fault recorders (DFRs) has been proven to be a cost-effective approach. In this paper, an innovative open-source tool suite is presented for validating power plant models using PPMV tool, identifying bad parameters with trajectory sensitivity analysis, and finally calibrating parameters using an ensemble Kalman filter (EnKF) based algorithm. The architectural design and the detailed procedures to run the tool suite are presented, with results of test on a realistic hydro power plant using PMU measurements for 12 different events. The calibrated parameters of machine, exciter, governor and PSS models demonstrate much better performance than the original models for all the events and show the robustness of the proposed calibration algorithm.« less

[Symptomatic sinus dysfunction. A new use of electrophysiology].

PubMed

Graux, P; Jacquemart, T; Carlioz, R; Lemaire, N; Dutoit, A; Croccel, L

1993-06-01

The authors undertook a prospective electrophysiological study of 950 patients: 53 subjects considered to be "controls" since they were free of any history of syncope or faintness were identified, as well as 39 symptomatic subjects with a strong suspicion of sinus dysfunction, since no other detectable cause of fainting episodes was found by extracardiac investigation, 24 hour ECG nor electrophysiology. Following the creation of a computerised tool enabling not only the entry of indirect tests, processing, averaging of results, printing and memorization, but also assistance in interpretation, several electrophysiological parameters were used: heart rate and existence of sinus arrhythmia, Strauss tests with adjusted data or not, effective nodal refractory period, Guize, Narula and Mandel tests, and an atropine (0.03 mg/kg) test which was performed only in the symptomatic group. These tests were studied by single-variate and correlative analysis to define their normal ranges, their critical values and their dependence or independence. The performance of each test (i.e. its efficiency, and the specificity and sensitivity of each critical value) was measured. Tests found to be most useful (specificity and efficiency > 90%) were as follows: Mandel test = CSRT > or = 534 ms, Narula test = TECASA > or = 339 ms, heart rate < or = 55/min, type II, IIa and chaotic Strauss curve associated with a pathological Guize test. The combination of these tests in this algorithm resulted in an increase in sensitivity to 84%, at the price of a very moderate fall in specificity to 87%.(ABSTRACT TRUNCATED AT 250 WORDS)

Geometric parameter analysis to predetermine optimal radiosurgery technique for the treatment of arteriovenous malformation

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

Mestrovic, Ante; Clark, Brenda G.; Department of Medical Physics, British Columbia Cancer Agency, Vancouver, British Columbia

2005-11-01

Purpose: To develop a method of predicting the values of dose distribution parameters of different radiosurgery techniques for treatment of arteriovenous malformation (AVM) based on internal geometric parameters. Methods and Materials: For each of 18 previously treated AVM patients, four treatment plans were created: circular collimator arcs, dynamic conformal arcs, fixed conformal fields, and intensity-modulated radiosurgery. An algorithm was developed to characterize the target and critical structure shape complexity and the position of the critical structures with respect to the target. Multiple regression was employed to establish the correlation between the internal geometric parameters and the dose distribution for differentmore » treatment techniques. The results from the model were applied to predict the dosimetric outcomes of different radiosurgery techniques and select the optimal radiosurgery technique for a number of AVM patients. Results: Several internal geometric parameters showing statistically significant correlation (p < 0.05) with the treatment planning results for each technique were identified. The target volume and the average minimum distance between the target and the critical structures were the most effective predictors for normal tissue dose distribution. The structure overlap volume with the target and the mean distance between the target and the critical structure were the most effective predictors for critical structure dose distribution. The predicted values of dose distribution parameters of different radiosurgery techniques were in close agreement with the original data. Conclusions: A statistical model has been described that successfully predicts the values of dose distribution parameters of different radiosurgery techniques and may be used to predetermine the optimal technique on a patient-to-patient basis.« less

Application of a renormalization-group treatment to the statistical associating fluid theory for potentials of variable range (SAFT-VR).

PubMed

Forte, Esther; Llovell, Felix; Vega, Lourdes F; Trusler, J P Martin; Galindo, Amparo

2011-04-21

An accurate prediction of phase behavior at conditions far and close to criticality cannot be accomplished by mean-field based theories that do not incorporate long-range density fluctuations. A treatment based on renormalization-group (RG) theory as developed by White and co-workers has proven to be very successful in improving the predictions of the critical region with different equations of state. The basis of the method is an iterative procedure to account for contributions to the free energy of density fluctuations of increasing wavelengths. The RG method has been combined with a number of versions of the statistical associating fluid theory (SAFT), by implementing White's earliest ideas with the improvements of Prausnitz and co-workers. Typically, this treatment involves two adjustable parameters: a cutoff wavelength L for density fluctuations and an average gradient of the wavelet function Φ. In this work, the SAFT-VR (variable range) equation of state is extended with a similar crossover treatment which, however, follows closely the most recent improvements introduced by White. The interpretation of White's latter developments allows us to establish a straightforward method which enables Φ to be evaluated; only the cutoff wavelength L then needs to be adjusted. The approach used here begins with an initial free energy incorporating only contributions from short-wavelength fluctuations, which are treated locally. The contribution from long-wavelength fluctuations is incorporated through an iterative procedure based on attractive interactions which incorporate the structure of the fluid following the ideas of perturbation theories and using a mapping that allows integration of the radial distribution function. Good agreement close and far from the critical region is obtained using a unique fitted parameter L that can be easily related to the range of the potential. In this way the thermodynamic properties of a square-well (SW) fluid are given by the same number of independent intermolecular model parameters as in the classical equation. Far from the critical region the approach provides the correct limiting behavior reducing to the classical equation (SAFT-VR). In the critical region the β critical exponent is calculated and is found to take values close to the universal value. In SAFT-VR the free energy of an associating chain fluid is obtained following the thermodynamic perturbation theory of Wertheim from the knowledge of the free energy and radial distribution function of a reference monomer fluid. By determining L for SW fluids of varying well width a unique equation of state is obtained for chain and associating systems without further adjustment of critical parameters. We use computer simulation data of the phase behavior of chain and associating SW fluids to test the accuracy of the new equation.

Quantitative analysis of microstructure deformation in creep fenomena of ferritic SA-213 T22 and austenitic SA-213 TP304H material

NASA Astrophysics Data System (ADS)

Mulyana, Cukup; Taufik, Ahmad; Gunawan, Agus Yodi; Siregar, Rustam Efendi

2013-09-01

The failure of critical component of fossil fired power plant that operated in creep range (high stress, high temperature and in the long term) depends on its microstructure characteristics. Ferritic low carbon steel (2.25Cr-1Mo) and Austenitic stainless alloy (18Cr-8Ni) are used as a boiler tube in the secondary superheater outlet header to deliver steam before entering the turbin. The tube failure is occurred in a form of rupture, resulting trip that disrupts the continuity of the electrical generation. The research in quantification of the microstructure deformation has been done in predicting the remaining life of the tube through interrupted accelerated creep test. For Austenitic Stainless Alloy (18Cr-8Ni), creep test was done in 550°C with the stress 424.5 MPa and for Ferritic Low Carbon Steel (2.25Cr-1Mo) in 570°C with the stress 189 MPa. The interrupted accelerated creep test was done by stopping the observation in condition 60%, 70%, 80% and 90% of remaining life, the creep test fracture was done before. Then the micro hardness test, photo micro, SEM and EDS were obtained from those samples. Refer to ASTM E122, microstructure parameters were calculated. The results indicated that there are a consistency of decreasing their grain diameters, increasing their grain size numbers, micro hardness, and the length of crack or void number per unit area with the decreasing of remaining life. While morphology of grain (stated in parameter α=LV/LH) relatively constant for austenitic. However, for ferritic the change of morphology revealed significantly. Fracture mode propagation of ferritic material is growth with voids transgranular and intergranular crack, and for austenitic material the fracture growth with intergranular creep fracture void and wedge crack. In this research, it was proposed a formulation of mathematical model for creep behavior corresponding their curve fitting resulted for the primary, secondary and tertiary in accelerated creep test. In addition, it was also developed a new method for predicting the remaining life using quantification of microstructure and using expansion of parameter Larson Miller from Taylor series for critical component in high temperature in industry. It was found that the proposed method was easier to be applied in field with the results more accurate then Larson Miller Method.

Twenty Years of Research on the Alcator C-Mod Tokamak

NASA Astrophysics Data System (ADS)

Greenwald, Martin

2013-10-01

Alcator C-Mod is a compact, high-field tokamak, whose unique design and operating parameters have produced a wealth of new and important results since its start in 1993, contributing data that extended tests of critical physical models into new parameter ranges and into new regimes. Using only RF for heating and current drive with innovative launching structures, C-Mod operates routinely at very high power densities. Research highlights include direct experimental observation of ICRF mode-conversion, ICRF flow drive, demonstration of Lower-Hybrid current drive at ITER-like densities and fields and, using a set of powerful new diagnostics, extensive validation of advanced RF codes. C-Mod spearheaded the development of the vertical-target divertor and has always operated with high-Z metal plasma facing components--an approach adopted for ITER. C-Mod has made ground-breaking discoveries in divertor physics and plasma-material interactions at reactor-like power and particle fluxes and elucidated the critical role of cross-field transport in divertor operation, edge flows and the tokamak density limit. C-Mod developed the I-mode and EDA H-mode regimes which have high performance without large ELMs and with pedestal transport self-regulated by short-wavelength electromagnetic waves. C-Mod has carried out pioneering studies of intrinsic rotation and found that self-generated flow shear can be strong enough to significantly modify transport. C-Mod made the first quantitative link between pedestal temperature and H-mode performance, showing that the observed self-similar temperature profiles were consistent with critical-gradient-length theories and followed up with quantitative tests of nonlinear gyrokinetic models. Disruption studies on C-Mod provided the first observation of non-axisymmetric halo currents and non-axisymmetric radiation in mitigated disruptions. Work supported by U.S. DoE

Prediction of the wetting-induced collapse behaviour using the soil-water characteristic curve

NASA Astrophysics Data System (ADS)

Xie, Wan-Li; Li, Ping; Vanapalli, Sai K.; Wang, Jia-Ding

2018-01-01

Collapsible soils go through three distinct phases in response to matric suction decrease during wetting: pre-collapse phase, collapse phase and post-collapse phase. It is reasonable and conservative to consider a strain path that includes a pre-collapse phase in which constant volume is maintained and a collapse phase that extends to the final matric suction to be experienced by collapsible soils during wetting. Upon this assumption, a method is proposed for predicting the collapse behaviour due to wetting. To use the proposed method, two parameters, critical suction and collapse rate, are required. The former is the suction value below which significant collapse deformations take place in response to matric suction decease, and the later is the rate at which void ratio reduces with matric suction in the collapse phase. The value of critical suction can be estimated from the water-entry value taking account of both the microstructure characteristics and collapse mechanism of fine-grained collapsible soils; the wetting soil-water characteristic curve thus can be used as a tool. Five sets of data of wetting tests on both compacted and natural collapsible soils reported in the literature were used to validate the proposed method. The critical suction values were estimated from the water-entry value with parameter a that is suggested to vary between 0.10 and 0.25 for compacted soils and to be lower for natural collapsible soils. The results of a field permeation test in collapsible loess soils were also used to validate the proposed method. The relatively good agreement between the measured and estimated collapse deformations suggests that the proposed method can provide reasonable prediction of the collapse behaviour due to wetting.

Comparing performance on the MNREAD iPad application with the MNREAD acuity chart.

PubMed

Calabrèse, Aurélie; To, Long; He, Yingchen; Berkholtz, Elizabeth; Rafian, Paymon; Legge, Gordon E

2018-01-01

Our purpose was to compare reading performance measured with the MNREAD Acuity Chart and an iPad application (app) version of the same test for both normally sighted and low-vision participants. Our methods included 165 participants with normal vision and 43 participants with low vision tested on the standard printed MNREAD and on the iPad app version of the test. Maximum Reading Speed, Critical Print Size, Reading Acuity, and Reading Accessibility Index were compared using linear mixed-effects models to identify any potential differences in test performance between the printed chart and the iPad app. Our results showed the following: For normal vision, chart and iPad yield similar estimates of Critical Print Size and Reading Acuity. The iPad provides significantly slower estimates of Maximum Reading Speed than the chart, with a greater difference for faster readers. The difference was on average 3% at 100 words per minute (wpm), 6% at 150 wpm, 9% at 200 wpm, and 12% at 250 wpm. For low vision, Maximum Reading Speed, Reading Accessibility Index, and Critical Print Size are equivalent on the iPad and chart. Only the Reading Acuity is significantly smaller (I. E., better) when measured on the digital version of the test, but by only 0.03 logMAR (p = 0.013). Our conclusions were that, overall, MNREAD parameters measured with the printed chart and the iPad app are very similar. The difference found in Maximum Reading Speed for the normally sighted participants can be explained by differences in the method for timing the reading trials.

Comparing performance on the MNREAD iPad application with the MNREAD acuity chart

PubMed Central

Calabrèse, Aurélie; To, Long; He, Yingchen; Berkholtz, Elizabeth; Rafian, Paymon; Legge, Gordon E.

2018-01-01

Our purpose was to compare reading performance measured with the MNREAD Acuity Chart and an iPad application (app) version of the same test for both normally sighted and low-vision participants. Our methods included 165 participants with normal vision and 43 participants with low vision tested on the standard printed MNREAD and on the iPad app version of the test. Maximum Reading Speed, Critical Print Size, Reading Acuity, and Reading Accessibility Index were compared using linear mixed-effects models to identify any potential differences in test performance between the printed chart and the iPad app. Our results showed the following: For normal vision, chart and iPad yield similar estimates of Critical Print Size and Reading Acuity. The iPad provides significantly slower estimates of Maximum Reading Speed than the chart, with a greater difference for faster readers. The difference was on average 3% at 100 words per minute (wpm), 6% at 150 wpm, 9% at 200 wpm, and 12% at 250 wpm. For low vision, Maximum Reading Speed, Reading Accessibility Index, and Critical Print Size are equivalent on the iPad and chart. Only the Reading Acuity is significantly smaller (I. E., better) when measured on the digital version of the test, but by only 0.03 logMAR (p = 0.013). Our conclusions were that, overall, MNREAD parameters measured with the printed chart and the iPad app are very similar. The difference found in Maximum Reading Speed for the normally sighted participants can be explained by differences in the method for timing the reading trials. PMID:29351351

Analysis of Flow Behavior of an Nb-Ti Microalloyed Steel During Hot Deformation

NASA Astrophysics Data System (ADS)

Mohebbi, Mohammad Sadegh; Parsa, Mohammad Habibi; Rezayat, Mohammad; Orovčík, L'ubomír

2018-03-01

The hot flow behavior of an Nb-Ti microalloyed steel is investigated through hot compression test at various strain rates and temperatures. By the combination of dynamic recovery (DRV) and dynamic recrystallization (DRX) models, a phenomenological constitutive model is developed to derive the flow stress. The predefined activation energy of Q = 270 kJ/mol and the exponent of n = 5 are successfully set to derive critical stress at the onset of DRX and saturation stress of DRV as functions of the Zener-Hollomon parameter by the classical hyperbolic sine equation. The remaining parameters of the constitutive model are determined by fitting them to the experiments. Through substitution of a normalized strain in the DRV model and considering the interconnections between dependent parameters, a new model is developed. It is shown that, despite its fewer parameters, this model is in good agreement with the experiments. Accurate analyses of flow data along with microstructural analyses indicate that the dissolution of NbC precipitates and its consequent solid solution strengthening and retardation of DRX are responsible for the distinguished behaviors in the two temperature ranges between T < 1100 °C and T ≥ 1100 °C. Nevertheless, it is shown that a single constitutive equation can still be employed for the present steel in the whole tested temperature ranges.

Chromium released from leather – I: exposure conditions that govern the release of chromium(III) and chromium(VI)

PubMed Central

Hedberg, Yolanda S; Lidén, Carola; Odnevall Wallinder, Inger

2015-01-01

Background Approximately 1–3% of the adult population in Europe is allergic to chromium (Cr). A new restriction in REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) based on the ISO 17075 standard has recently been adopted in the EU to limit Cr(VI) in consumer and occupational leather products. Objectives The aim of this study was to critically assess key experimental parameters in this standard on the release of Cr(III) and Cr(VI) and their relevance for skin exposure. Material and methods Four differently tanned, unfinished, leather samples were systematically investigated for their release of Cr(III) and Cr(VI) in relation to surface area, key exposure parameters, temperature, ultraviolet irradiation, and time. Results Although the total release of Cr was largely unaffected by all investigated parameters, except exposure duration and temperature, the Cr oxidation state was highly dynamic, with reduced amounts of released Cr(VI) with time, owing to the simultaneous release of reducing agents from the leather. Significantly more Cr(III) than Cr(VI) was released from the Cr-tanned leather for all conditions tested, and it continued to be released in artificial sweat up to at least 1 week of exposure. Conclusions Several parameters were identified that influenced the outcome of the ISO 17075 test. PMID:25653094

Tool Support for Parametric Analysis of Large Software Simulation Systems

NASA Technical Reports Server (NTRS)

Schumann, Johann; Gundy-Burlet, Karen; Pasareanu, Corina; Menzies, Tim; Barrett, Tony

2008-01-01

The analysis of large and complex parameterized software systems, e.g., systems simulation in aerospace, is very complicated and time-consuming due to the large parameter space, and the complex, highly coupled nonlinear nature of the different system components. Thus, such systems are generally validated only in regions local to anticipated operating points rather than through characterization of the entire feasible operational envelope of the system. We have addressed the factors deterring such an analysis with a tool to support envelope assessment: we utilize a combination of advanced Monte Carlo generation with n-factor combinatorial parameter variations to limit the number of cases, but still explore important interactions in the parameter space in a systematic fashion. Additional test-cases, automatically generated from models (e.g., UML, Simulink, Stateflow) improve the coverage. The distributed test runs of the software system produce vast amounts of data, making manual analysis impossible. Our tool automatically analyzes the generated data through a combination of unsupervised Bayesian clustering techniques (AutoBayes) and supervised learning of critical parameter ranges using the treatment learner TAR3. The tool has been developed around the Trick simulation environment, which is widely used within NASA. We will present this tool with a GN&C (Guidance, Navigation and Control) simulation of a small satellite system.

Regional-scale integration of hydrological and geophysical data using Bayesian sequential simulation: application to field data

NASA Astrophysics Data System (ADS)

Ruggeri, Paolo; Irving, James; Gloaguen, Erwan; Holliger, Klaus

2013-04-01

Significant progress has been made with regard to the quantitative integration of geophysical and hydrological data at the local scale. However, extending corresponding approaches to the regional scale still represents a major challenge, yet is critically important for the development of groundwater flow and contaminant transport models. To address this issue, we have developed a regional-scale hydrogeophysical data integration technique based on a two-step Bayesian sequential simulation procedure. The objective is to simulate the regional-scale distribution of a hydraulic parameter based on spatially exhaustive, but poorly resolved, measurements of a pertinent geophysical parameter and locally highly resolved, but spatially sparse, measurements of the considered geophysical and hydraulic parameters. To this end, our approach first involves linking the low- and high-resolution geophysical data via a downscaling procedure before relating the downscaled regional-scale geophysical data to the high-resolution hydraulic parameter field. We present the application of this methodology to a pertinent field scenario, where we consider collocated high-resolution measurements of the electrical conductivity, measured using a cone penetrometer testing (CPT) system, and the hydraulic conductivity, estimated from EM flowmeter and slug test measurements, in combination with low-resolution exhaustive electrical conductivity estimates obtained from dipole-dipole ERT meausurements.

Antiwear Additive Mechanisms in Sliding Contacts

NASA Technical Reports Server (NTRS)

Baldwin, B. A.

1984-01-01

The possible mechanisms associated with wear in a sliding contact and how an oil and antiwear additive can mitigate wear or prevent catastropic seizure of the contacting parts was examined. The various load and temperature regimes are examined and the mechanisms which are predominant under these conditions are determined. The critical mechanism(s) depend on the test parameters, particularly load and temperature, although sliding speed is also a factor. Different ways to improve the efficiency of antiwear additives are suggested.

Application of stroboscopic and pulsed-laser electronic speckle pattern interferometry (ESPI) to modal analysis problems

NASA Astrophysics Data System (ADS)

Van der Auweraer, H.; Steinbichler, H.; Vanlanduit, S.; Haberstok, C.; Freymann, R.; Storer, D.; Linet, V.

2002-04-01

Accurate structural models are key to the optimization of the vibro-acoustic behaviour of panel-like structures. However, at the frequencies of relevance to the acoustic problem, the structural modes are very complex, requiring high-spatial-resolution measurements. The present paper discusses a vibration testing system based on pulsed-laser holographic electronic speckle pattern interferometry (ESPI) measurements. It is a characteristic of the method that time-triggered (and not time-averaged) vibration images are obtained. Its integration into a practicable modal testing and analysis procedure is reviewed. The accumulation of results at multiple excitation frequencies allows one to build up frequency response functions. A novel parameter extraction approach using spline-based data reduction and maximum-likelihood parameter estimation was developed. Specific extensions have been added in view of the industrial application of the approach. These include the integration of geometry and response information, the integration of multiple views into one single model, the integration with finite-element model data and the prior identification of the critical panels and critical modes. A global procedure was hence established. The approach has been applied to several industrial case studies, including car panels, the firewall of a monovolume car, a full vehicle, panels of a light truck and a household product. The research was conducted in the context of the EUREKA project HOLOMODAL and the Brite-Euram project SALOME.

Effect of process parameters on microstructure and mechanical properties of friction stir welded joints: A review

NASA Astrophysics Data System (ADS)

Wanare, S. P.; Kalyankar, V. D.

2018-04-01

Friction stir welding is emerging as a promising technique for joining of lighter metal alloys due to its several advantages over conventional fusion welding processes such as low thermal distortion, good mechanical properties, fine weld joint microstructure, etc. This review article mainly focuses on analysis of microstructure and mechanical properties of friction stir welded joints. Various microstructure characterization techniques used by previous researchers such as optical microscopes, x-ray diffraction, electron probe microscope, transmission electron microscope, scanning electron microscopes with electron back scattered diffraction, electron dispersive microscopy, etc. are thoroughly overviewed and their results are discussed. The effects of friction stir welding process parameters such as tool rotational speed, welding speed, tool plunge depth, axial force, tool shoulder diameter to tool pin diameter ratio, tool geometry etc. on microstructure and mechanical properties of welded joints are studied and critical observations are noted down. The microstructure examination carried out by previous researchers on various zones of welded joints such as weld zone, heat affected zone and base metal are studied and critical remarks have been presented. Mechanical performances of friction stir welded joints based on tensile test, micro-hardness test, etc. are discussed. This article includes exhaustive literature review of standard research articles which may become ready information for subsequent researchers to establish their line of action.

P-V criticality of conformal gravity holography in four dimensions

NASA Astrophysics Data System (ADS)

Pradhan, Parthapratim

2018-02-01

We examine the critical behavior, i.e. P-V criticality of conformal gravity (CG) in an extended phase space in which the cosmological constant should be interpreted as a thermodynamic pressure and the corresponding conjugate quantity as a thermodynamic volume. The main potential point of interest in CG is that there exists a nontrivial Rindler parameter (a) in the spacetime geometry. This geometric parameter has an important role to construct a model for gravity at large distances where the parameter “a” actually originates. We also investigate the effect of the said parameter on the black hole (BH) thermodynamic equation of state, critical constants, Reverse Isoperimetric Inequality, first law of thermodynamics, Hawking-Page phase transition and Gibbs free energy for this BH. We speculate that due to the presence of the said parameter, there has been a deformation in the shape of the isotherms in the P-V diagram in comparison with the charged-anti de Sitter (AdS) BH and the chargeless-AdS BH. Interestingly, we find that the critical ratio for this BH is ρc = Pcvc Tc = 3 2 32 ‑ 23, which is greater than the charged AdS BH and Schwarzschild-AdS BH, i.e. ρcCG : ρ cSch-AdS : ρ cRN-AdS = 0.67 : 0.50 : 0.37. The symbols are defined in the main work. Moreover, we observe that the critical ratio has a constant value and it is independent of the nontrivial Rindler parameter (a). Finally, we derive the reduced equation of state in terms of the reduced temperature, the reduced volume and the reduced pressure, respectively.

A critical number of workers in a honeybee colony triggers investment in reproduction

NASA Astrophysics Data System (ADS)

Smith, Michael L.; Ostwald, Madeleine M.; Loftus, J. Carter; Seeley, Thomas D.

2014-10-01

Social insect colonies, like individual organisms, must decide as they develop how to allocate optimally their resources among survival, growth, and reproduction. Only when colonies reach a certain state do they switch from investing purely in survival and growth to investing also in reproduction. But how do worker bees within a colony detect that their colony has reached the state where it is adaptive to begin investing in reproduction? Previous work has shown that larger honeybee colonies invest more in reproduction (i.e., the production of drones and queens), however, the term `larger' encompasses multiple colony parameters including number of adult workers, size of the nest, amount of brood, and size of the honey stores. These colony parameters were independently increased in this study to test which one(s) would increase a colony's investment in reproduction via males. This was assayed by measuring the construction of drone comb, the special type of comb in which drones are reared. Only an increase in the number of workers stimulated construction of drone comb. Colonies with over 4,000 workers began building drone comb, independent of the other colony parameters. These results show that attaining a critical number of workers is the key parameter for honeybee colonies to start to shift resources towards reproduction. These findings are relevant to other social systems in which a group's members must adjust their behavior as a function of the group's size.

Design, construction, and testing a purpose-built climate-controlled solvent vapor annealing chamber for guided self-assembly of block polymer thin films

NASA Astrophysics Data System (ADS)

Gnabasik, Ryan; Haase, Rustin; Baruth, Andrew

2014-03-01

Despite its efficacy to produce well-ordered, periodic nanostructures, the intricate role multiple parameters play in solvent vapor annealing has not been fully established. In solvent vapor annealing a thin polymer film is exposed to the vapors of a solvent(s) thus forming a swollen and mobile layer to direct the self-assembly process at the nanoscale. Recent developments in both theory and experiment have directly identified critical parameters, but controlling them in any systematic way has proven non-trivial. These identified parameters include vapor pressure, solvent concentration in the film, and, critically, the solvent evaporation rate. To explore their role, a purpose-built solvent vapor annealing chamber was designed and constructed. The all-metal chamber is inert to solvent exposure and pneumatically actuated valves allow for precision timing in the introduction and withdrawal of solvent vapor. Furthermore, the mass flow controlled inlet, chamber pressure gauges, in situ spectral reflectance-based thickness monitoring, and high precision micrometer relief valve, give real-time monitoring and control during the annealing and evaporation phases. Using atomic force microscopy to image the annealed films, we are able to map out the parameter space for a series of polystyrene- b-polylactide (Mn = 75 kg/mol and fPLA = 0.28) block polymer thin films with an intrinsic cylindrical morphology and identify their role in directed assembly. Funded by Creighton University Summer Research Grant.

Experimental and theoretical analysis of integrated circuit (IC) chips on flexible substrates subjected to bending

NASA Astrophysics Data System (ADS)

Chen, Ying; Yuan, Jianghong; Zhang, Yingchao; Huang, Yonggang; Feng, Xue

2017-10-01

The interfacial failure of integrated circuit (IC) chips integrated on flexible substrates under bending deformation has been studied theoretically and experimentally. A compressive buckling test is used to impose the bending deformation onto the interface between the IC chip and the flexible substrate quantitatively, after which the failed interface is investigated using scanning electron microscopy. A theoretical model is established based on the beam theory and a bi-layer interface model, from which an analytical expression of the critical curvature in relation to the interfacial failure is obtained. The relationships between the critical curvature, the material, and the geometric parameters of the device are discussed in detail, providing guidance for future optimization flexible circuits based on IC chips.

The Effect of Fin Pitch on Fluid Elastic Instability of Tube Arrays Subjected to Cross Flow of Water

NASA Astrophysics Data System (ADS)

Desai, Sandeep Rangrao; Pavitran, Sampat

2018-02-01

Failure of tubes in shell and tube exchangers is attributed to flow induced vibrations of such tubes. There are different excitations mechanisms due to which flow induced vibration occurs and among such mechanisms, fluid elastic instability is the most prominent one as it causes the most violent vibrations and may lead to rapid tube failures within short time. Fluid elastic instability is the fluid-structure interaction phenomenon which occurs when energy input by the fluid force exceeds energy expended in damping. This point is referred as instability threshold and corresponding velocity is referred as critical velocity. Once flow velocity exceeds critical flow velocity, the vibration amplitude increases very rapidly with flow velocity. An experimental program is carried out to determine the critical velocity at instability for plain and finned tube arrays subjected to cross flow of water. The tube array geometry is parallel triangular with cantilever end condition and pitch ratios considered are 2.6 and 2.1. The objective of research is to determine the effect of increase in pitch ratio on instability threshold for plain tube arrays and to assess the effect of addition of fins as well as increase in fin density on instability threshold for finned tube arrays. Plain tube array with two different pitch ratios; 2.1 and 2.6 and finned tube arrays with same pitch ratio; 2.6 but with two different fin pitches; such as fine (10 fpi) and coarse (4 fpi) are considered for the experimentation. Connors' equation that relates critical velocity at instability to different parameters, on which instability depends, has been used as the basis for analysis and the concept of effective diameter is used for the present investigation. The modal parameters are first suitably modified using natural frequency reduction setup that is already designed and developed to reduce natural frequency and hence to achieve experimental simulation of fluid elastic instability within the limited flow capacity of the pump. The tests are carried out first on plain tube arrays to establish the same as the datum case and results are compared to known results of plain tube arrays and hence the quality of the test rig is also assessed. The fluid elastic vibration tests are then carried out on finned tube arrays with coarse and fine fin pitches and effects of fins and fin pitch on instability threshold are shown. The vibration response of the tube is recorded for each gradually increasing flow rates of water till instability point is reached. The parameters at the instability are then presented in terms of dimensionless parameters to compare them with published results. It is concluded that, arrays with higher pitch ratios are unstable at comparatively higher flow velocities and instability threshold for finned tube arrays is delayed due to addition of the fins. Further, it is concluded that, instability threshold for finned tube arrays with fine fin pitch is delayed compared to coarse fin pitch and hence for increased fin density, instability threshold is delayed. The experimental results in terms of critical velocities obtained for different tube arrays subjected to water cross flow will serve as the base flow rates for air-water cross flow experiments to be conducted in the next phase.

Thermal stress analysis of ceramic gas-path seal components for aircraft turbines

NASA Technical Reports Server (NTRS)

Kennedy, F. E.; Bill, R. C.

1979-01-01

Stress and temperature distributions were evaluated numerically for a blade-tip seal system proposed for gas turbine applications. The seal consists of an abradable ceramic layer on metallic backing with intermediate layers between the ceramic layer and metal substrate. The most severe stresses in the seal, as far as failure is concerned, are tensile stresses at the top of the ceramic layer and shear and normal stresses at the layer interfaces. All these stresses reach their maximum values during the deceleration phase of a test engine cycle. A parametric study was carried out to evaluate the influence of various design parameters on these critical stress values. The influences of material properties and geometric parameters of the ceramic, intermediate, and backing layers were investigated. After the parametric study was completed, a seal system was designed which incorporated materials with beneficial elastic and thermal properties in each layer of the seal. An analysis of the proposed seal design shows an appreciable decrease in the magnitude of the maximum critical stresses over those obtained with earlier configurations.

Dose dependence of true stress parameters in irradiated bcc, fcc, and hcp metals

NASA Astrophysics Data System (ADS)

Byun, T. S.

2007-04-01

The dose dependence of true stress parameters has been investigated for nuclear structural materials: A533B pressure vessel steels, modified 9Cr-1Mo and 9Cr-2WVTa ferritic martensitic steels, 316 and 316LN stainless steels, and Zircaloy-4. After irradiation to significant doses, these alloys show radiation-induced strengthening and often experience prompt necking at yield followed by large necking deformation. In the present work, the critical true stresses for deformation and fracture events, such as yield stress (YS), plastic instability stress (PIS), and true fracture stress (FS), were obtained from uniaxial tensile tests or calculated using a linear strain-hardening model for necking deformation. At low dose levels where no significant embrittlement was detected, the true fracture stress was nearly independent of dose. The plastic instability stress was also independent of dose before the critical dose-to-prompt-necking at yield was reached. A few bcc alloys such as ferritic martensitic steels experienced significant embrittlement at doses above ∼1 dpa; and the true fracture stress decreased with dose. The materials fractured before yield at or above 10 dpa.

Modeling of Stone-impact Resistance of Monolithic Glass Ply Using Continuum Damage Mechanics

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

Sun, Xin; Khaleel, Mohammad A.; Davies, Richard W.

2005-04-01

We study the stone-impact resistance of a monolithic glass ply using a combined experimental and computational approach. Instrumented stone impact tests were first carried out in controlled environment. Explicit finite element analyses were then used to simulate the interactions of the indentor and the glass layer during the impact event, and a continuum damage mechanics (CDM) model was used to describe the constitutive behavior of glass. The experimentally measured strain histories for low velocity impact served as validation of the modeling procedures. Next, stair-stepping impact experiments were performed with two indentor sizes on two glass ply thickness, and the testmore » results were used to calibrate the critical stress parameters used in the CDM constitutive model. The purpose of this study is to establish the modeling procedures and the CDM critical stress parameters under impact loading conditions. The modeling procedures and the CDM model will be used in our future studies to predict through-thickness damage evolution patterns for different laminated windshield designs in automotive applications.« less

Accelerated Strength Testing of Thermoplastic Composites

NASA Technical Reports Server (NTRS)

Reeder, J. R.; Allen, D. H.; Bradley, W. L.

1998-01-01

Constant ramp strength tests on unidirectional thermoplastic composite specimens oriented in the 90 deg. direction were conducted at constant temperatures ranging from 149 C to 232 C. Ramp rates spanning 5 orders of magnitude were tested so that failures occurred in the range from 0.5 sec. to 24 hrs. (0.5 to 100,000 MPa/sec). Below 204 C, time-temperature superposition held allowing strength at longer times to be estimated from strength tests at shorter times but higher temperatures. The data indicated that a 50% drop in strength might be expected for this material when the test time is increased by 9 orders of magnitude. The shift factors derived from compliance data applied well to the strength results. To explain the link between compliance and strength, a viscoelastic fracture model was investigated. The model, which used compliance as input, was found to fit the strength data only if the critical fracture energy was allowed to vary with temperature reduced stress rate. This variation in the critical parameter severely limits its use in developing a robust time-dependent strength model. The significance of this research is therefore seen as providing both the indication that a more versatile acceleration method for strength can be developed and the evidence that such a method is needed.

A fluidized bed technique for estimating soil critical shear stress

USDA-ARS?s Scientific Manuscript database

Soil erosion models, depending on how they are formulated, always have erodibilitiy parameters in the erosion equations. For a process-based model like the Water Erosion Prediction Project (WEPP) model, the erodibility parameters include rill and interrill erodibility and critical shear stress. Thes...

Determination of Critical Parameters Based on the Intensity of Transmitted Light Around Gas-Liquid Interface: Critical Parameters of CO

NASA Astrophysics Data System (ADS)

Nakayama, Masaki; Katano, Hiroaki; Sato, Haruki

2014-05-01

A precise determination of the critical temperature and density for technically important fluids would be possible on the basis of the digital image for the visual observation of the phase boundary in the vicinity of the critical point since the sensitivity and resolution are higher than those of naked eyes. In addition, the digital image can avoid the personal uncertainty of an observer. A strong density gradient occurs in a sample cell at the critical point due to gravity. It was carefully assessed to determine the critical density, where the density profile in the sample cell can be observed from the luminance profile of a digital image. The density-gradient profile becomes symmetric at the critical point. One of the best fluids, whose thermodynamic properties have been measured with the highest reliability among technically important fluids, would be carbon dioxide. In order to confirm the reliability of the proposed method, the critical temperature and density of carbon dioxide were determined using the digital image. The critical temperature and density values of carbon dioxide are ( and ( kg m, respectively. The critical temperature and density values agree with the existing best values within estimated uncertainties. The reliability of the method was confirmed. The critical pressure, 7.3795 MPa, corresponding to the determined critical temperature of 304.143 K is also proposed. A new set of parameters for the vapor-pressure equation is also provided.

Multi-Dimensional Calibration of Impact Dynamic Models

NASA Technical Reports Server (NTRS)

Horta, Lucas G.; Reaves, Mercedes C.; Annett, Martin S.; Jackson, Karen E.

2011-01-01

NASA Langley, under the Subsonic Rotary Wing Program, recently completed two helicopter tests in support of an in-house effort to study crashworthiness. As part of this effort, work is on-going to investigate model calibration approaches and calibration metrics for impact dynamics models. Model calibration of impact dynamics problems has traditionally assessed model adequacy by comparing time histories from analytical predictions to test at only a few critical locations. Although this approach provides for a direct measure of the model predictive capability, overall system behavior is only qualitatively assessed using full vehicle animations. In order to understand the spatial and temporal relationships of impact loads as they migrate throughout the structure, a more quantitative approach is needed. In this work impact shapes derived from simulated time history data are used to recommend sensor placement and to assess model adequacy using time based metrics and orthogonality multi-dimensional metrics. An approach for model calibration is presented that includes metric definitions, uncertainty bounds, parameter sensitivity, and numerical optimization to estimate parameters to reconcile test with analysis. The process is illustrated using simulated experiment data.

Dynamics of Liquids in Edges and Corners (DYLCO): IML-2 Experiment for the BDPU

NASA Technical Reports Server (NTRS)

Langbein, D.; Weislogel, M.

1998-01-01

Knowledge of the behavior of fluids possessing free surfaces is important to many fluid systems, particularly in space, where the normally subtle effects of surface wettability play a more dramatic and often surprising role. DYLCO for the IML-2 mission was proposed as a simple experiment to probe the particular behavior of capillary surfaces in containers of irregular cross section. Temperature control was utilized to vary the fluid-solid contact angle, a questionable thermodynamic parameter of the system, small changes in which can dramatically influence the configuration, stability, and flow of a capillary surface. Container shapes, test fluid, and temperature ranges were selected for observing both local changes in interface curvature as well as a global change in fluid orientation due to a critical wetting phenomenon. The experiment hardware performed beyond what was expected and fluid interfaces could be readily digitized post flight to show the dependence of the interface curvature on temperature. For each of the containers tested surfaces were observed which did not satisfy the classic equations for the prediction of interface shape with constant contact angle boundary condition. This is explained by the presence of contact angle hysteresis arising from expansion and contraction of the liquid during the heating and cooling steps of the test procedure. More importantly, surfaces exceeding the critical surface curvature required for critical wetting were measured, yet no wetting was observed. These findings are indeed curious and pose key questions concerning the role of hysteresis for this critical wetting phenomena. The stability of such surfaces was determined numerically and it is shown that stability is enhance (reduced) when a surface is in its 'advancing' ('receding') state, The analysis shows complete instability as the critical wetting condition is reached. The case of ideal dynamic wetting is addressed analytically in detail with results of significant flow characteristics presented in closed form. The solutions indicate a square root of T dependence of the capillary 'rise' rate which is corroborated by drop tower tests. The analysis clearly shows that infinite time is necessary for surfaces to reorient at the critical wetting transition.

A comparison of the two approaches of the theory of critical distances based on linear-elastic and elasto-plastic analyses

NASA Astrophysics Data System (ADS)

Terekhina, A. I.; Plekhov, O. A.; Kostina, A. A.; Susmel, L.

2017-06-01

The problem of determining the strength of engineering structures, considering the effects of the non-local fracture in the area of stress concentrators is a great scientific and industrial interest. This work is aimed on modification of the classical theory of critical distance that is known as a method of failure prediction based on linear-elastic analysis in case of elasto-plastic material behaviour to improve the accuracy of estimation of lifetime of notched components. Accounting plasticity has been implemented with the use of the Simplified Johnson-Cook model. Mechanical tests were carried out using a 300 kN electromechanical testing machine Shimadzu AG-X Plus. The cylindrical un-notched specimens and specimens with stress concentrators of titanium alloy Grade2 were tested under tensile loading with different grippers travel speed, which ensured several orders of strain rate. The results of elasto-plastic analyses of stress distributions near a wide variety of notches are presented. The results showed that the use of the modification of the TCD based on elasto-plastic analysis gives us estimates falling within an error interval of ±5-10%, that more accurate predictions than the linear elastic TCD solution. The use of an improved description of the stress-strain state at the notch tip allows introducing the critical distances as a material parameter.

Quantitative Evaluation of 3 DBMS: ORACLE, SEED AND INGRES

NASA Technical Reports Server (NTRS)

Sylto, R.

1984-01-01

Characteristics required for NASA scientific data base management application are listed as well as performance testing objectives. Results obtained for the ORACLE, SEED, and INGRES packages are presented in charts. It is concluded that vendor packages can manage 130 megabytes of data at acceptable load and query rates. Performance tests varying data base designs and various data base management system parameters are valuable to applications for choosing packages and critical to designing effective data bases. An applications productivity increases with the use of data base management system because of enhanced capabilities such as a screen formatter, a reporter writer, and a data dictionary.

Threshold-Switchable Particles (TSP) to Control Internal Hemorrhage

DTIC Science & Technology

2013-12-01

and morphology and divided into three regimes: a 3-D gel, 2-D mat, and a 1-D thin film. They determined that the critical parameters determining...of critical physical parameters / dimensionless groups (through both simulation and experiment) such as pre-shear/mixing rate, the Weber and Ohnesorge...Capillary Pinch-Off Phase Diagram. This plot was constructed to aid in the identification of important physical parameters in blood plasma pinch-off

A New Energy-Critical Plane Damage Parameter for Multiaxial Fatigue Life Prediction of Turbine Blades.

PubMed

Yu, Zheng-Yong; Zhu, Shun-Peng; Liu, Qiang; Liu, Yunhan

2017-05-08

As one of fracture critical components of an aircraft engine, accurate life prediction of a turbine blade to disk attachment is significant for ensuring the engine structural integrity and reliability. Fatigue failure of a turbine blade is often caused under multiaxial cyclic loadings at high temperatures. In this paper, considering different failure types, a new energy-critical plane damage parameter is proposed for multiaxial fatigue life prediction, and no extra fitted material constants will be needed for practical applications. Moreover, three multiaxial models with maximum damage parameters on the critical plane are evaluated under tension-compression and tension-torsion loadings. Experimental data of GH4169 under proportional and non-proportional fatigue loadings and a case study of a turbine disk-blade contact system are introduced for model validation. Results show that model predictions by Wang-Brown (WB) and Fatemi-Socie (FS) models with maximum damage parameters are conservative and acceptable. For the turbine disk-blade contact system, both of the proposed damage parameters and Smith-Watson-Topper (SWT) model show reasonably acceptable correlations with its field number of flight cycles. However, life estimations of the turbine blade reveal that the definition of the maximum damage parameter is not reasonable for the WB model but effective for both the FS and SWT models.

A New Energy-Critical Plane Damage Parameter for Multiaxial Fatigue Life Prediction of Turbine Blades

PubMed Central

Yu, Zheng-Yong; Zhu, Shun-Peng; Liu, Qiang; Liu, Yunhan

2017-01-01

As one of fracture critical components of an aircraft engine, accurate life prediction of a turbine blade to disk attachment is significant for ensuring the engine structural integrity and reliability. Fatigue failure of a turbine blade is often caused under multiaxial cyclic loadings at high temperatures. In this paper, considering different failure types, a new energy-critical plane damage parameter is proposed for multiaxial fatigue life prediction, and no extra fitted material constants will be needed for practical applications. Moreover, three multiaxial models with maximum damage parameters on the critical plane are evaluated under tension-compression and tension-torsion loadings. Experimental data of GH4169 under proportional and non-proportional fatigue loadings and a case study of a turbine disk-blade contact system are introduced for model validation. Results show that model predictions by Wang-Brown (WB) and Fatemi-Socie (FS) models with maximum damage parameters are conservative and acceptable. For the turbine disk-blade contact system, both of the proposed damage parameters and Smith-Watson-Topper (SWT) model show reasonably acceptable correlations with its field number of flight cycles. However, life estimations of the turbine blade reveal that the definition of the maximum damage parameter is not reasonable for the WB model but effective for both the FS and SWT models. PMID:28772873

Modeling of the UAE Wind Turbine for Refinement of FAST{_}AD

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

Jonkman, J. M.

The Unsteady Aerodynamics Experiment (UAE) research wind turbine was modeled both aerodynamically and structurally in the FAST{_}AD wind turbine design code, and its response to wind inflows was simulated for a sample of test cases. A study was conducted to determine why wind turbine load magnitude discrepancies-inconsistencies in aerodynamic force coefficients, rotor shaft torque, and out-of-plane bending moments at the blade root across a range of operating conditions-exist between load predictions made by FAST{_}AD and other modeling tools and measured loads taken from the actual UAE wind turbine during the NASA-Ames wind tunnel tests. The acquired experimental test data representmore » the finest, most accurate set of wind turbine aerodynamic and induced flow field data available today. A sample of the FAST{_}AD model input parameters most critical to the aerodynamics computations was also systematically perturbed to determine their effect on load and performance predictions. Attention was focused on the simpler upwind rotor configuration, zero yaw error test cases. Inconsistencies in input file parameters, such as aerodynamic performance characteristics, explain a noteworthy fraction of the load prediction discrepancies of the various modeling tools.« less

Characterization of fine abrasive particles for optical fabrication

NASA Astrophysics Data System (ADS)

Funkenbusch, Paul D.; Zhou, Y. Y.; Takahashi, Toshio; Quesnel, David J.; Lambropoulos, John C.

1995-08-01

Material removal during fine grinding operations is accomplished primarily by the action of individual abrasive particles on the glass surface. The mechanical properties of the abrasive are therefore important. Unfortunately it is difficult to directly measure the mechanical response of abrasives once they reach the scale of approximately 10 microns. As a result mechanical properties of fine abrasives are sometimes characterized in terms of an empirical `friability', based on the response of the abrasive to crushing by a metal ball in a vial. In this paper we report on modeling/experiments designed to more precisely quantify the mechanical properties of fine abrasives and ultimately to relate them to the conditions experienced by bound particles during grinding. Experiments have been performed on various types and sizes of diamond abrasives. The response of the particles is a strong function of the loading conditions and can be tracked by changing the testing parameters. Diamond size is also found to play a critical role, with finer diamonds less susceptible to fracture. A micromechanical model from the literature is employed estimate the forces likely to be seen during testing. We are also developing dynamic models to better predict the forces experienced during `friability' testing as a function of the testing parameters.

Black hole complementarity in gravity's rainbow

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

Gim, Yongwan; Kim, Wontae, E-mail: yongwan89@sogang.ac.kr, E-mail: wtkim@sogang.ac.kr

2015-05-01

To see how the gravity's rainbow works for black hole complementary, we evaluate the required energy for duplication of information in the context of black hole complementarity by calculating the critical value of the rainbow parameter in the certain class of the rainbow Schwarzschild black hole. The resultant energy can be written as the well-defined limit for the vanishing rainbow parameter which characterizes the deformation of the relativistic dispersion relation in the freely falling frame. It shows that the duplication of information in quantum mechanics could not be allowed below a certain critical value of the rainbow parameter; however, itmore » might be possible above the critical value of the rainbow parameter, so that the consistent formulation in our model requires additional constraints or any other resolutions for the latter case.« less

Wireless remote monitoring of critical facilities

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

Tsai, Hanchung; Anderson, John T.; Liu, Yung Y.

A method, apparatus, and system are provided for monitoring environment parameters of critical facilities. A Remote Area Modular Monitoring (RAMM) apparatus is provided for monitoring environment parameters of critical facilities. The RAMM apparatus includes a battery power supply and a central processor. The RAMM apparatus includes a plurality of sensors monitoring the associated environment parameters and at least one communication module for transmitting one or more monitored environment parameters. The RAMM apparatus is powered by the battery power supply, controlled by the central processor operating a wireless sensor network (WSN) platform when the facility condition is disrupted. The RAMM apparatusmore » includes a housing prepositioned at a strategic location, for example, where a dangerous build-up of contamination and radiation may preclude subsequent manned entrance and surveillance.« less

Tape tracking and handling for magnetic tape recorders. [aboard spacecraft

NASA Technical Reports Server (NTRS)

Paroby, W.; Disilvestre, R.

1975-01-01

One of the critical performance and life limiting elements of a spacecraft tape recorder instrumentation system which has received little attention in technical literature is magnetic tape tracking and handling technology. This technology is required to understand how to gently transfer tape from one reel to another with proper alignment and a desirable uniform velocity at the read and write transducer heads. The increased demand for high data rate (i.e., multi-track spacecraft recording instrumentation systems), coupled with performance under extreme environmental conditions, requires a thorough knowledge of the various parameters which establish an optimum designed tape tracking and handling system. Stress analysis techniques are required to evaluate these parameters substantiated with test tape tracking data, to show the effect of each parameter on a tape recorder instrumentation tracking system. The technology is applicable to ground type tape recorders where the detrimental effects of edge guidance can be eliminated.

Whirling and stability of flywheel systems, part I: Derivation of combined and lumped parameter models

NASA Astrophysics Data System (ADS)

Ramanujam, G.; Bert, C. W.

1983-06-01

The objective of this paper is to provide a theoretical foundation to predict many aspects of dynamic behavior of flywheel systems when spin-tested with a quill shaft support and driven by an air turbine. Theoretical analyses for the following are presented: (1) determination of natural frequencies (or for brevity critical speeds of various orders), (2) Routh-type stability analysis to determine the stability limits (i.e., the speed range within which small perturbations attenuate rather than cause catastrophic failure), and (3) forced whirling analysis to estimate the response of major components of the system to flywheel mass eccentricity and initial tilt. For the first and third kinds of analyses, two different mathematical models of the generic system are investigated. One is a seven-degree-of-freedom lumped parameter analysis, while the other is a combined distributed and lumped parameter analysis.

Fault detection in heavy duty wheels by advanced vibration processing techniques and lumped parameter modeling

NASA Astrophysics Data System (ADS)

Malago`, M.; Mucchi, E.; Dalpiaz, G.

2016-03-01

Heavy duty wheels are used in applications such as automatic vehicles and are mainly composed of a polyurethane tread glued to a cast iron hub. In the manufacturing process, the adhesive application between tread and hub is a critical assembly phase, since it is completely made by an operator and a contamination of the bond area may happen. Furthermore, the presence of rust on the hub surface can contribute to worsen the adherence interface, reducing the operating life. In this scenario, a quality control procedure for fault detection to be used at the end of the manufacturing process has been developed. This procedure is based on vibration processing techniques and takes advantages of the results of a lumped parameter model. Indicators based on cyclostationarity can be considered as key parameters to be adopted in a monitoring test station at the end of the production line due to their not deterministic characteristics.

Thermal Analysis of Small Re-Entry Probe

NASA Technical Reports Server (NTRS)

Agrawal, Parul; Prabhu, Dinesh K.; Chen, Y. K.

2012-01-01

The Small Probe Reentry Investigation for TPS Engineering (SPRITE) concept was developed at NASA Ames Research Center to facilitate arc-jet testing of a fully instrumented prototype probe at flight scale. Besides demonstrating the feasibility of testing a flight-scale model and the capability of an on-board data acquisition system, another objective for this project was to investigate the capability of simulation tools to predict thermal environments of the probe/test article and its interior. This paper focuses on finite-element thermal analyses of the SPRITE probe during the arcjet tests. Several iterations were performed during the early design phase to provide critical design parameters and guidelines for testing. The thermal effects of ablation and pyrolysis were incorporated into the final higher-fidelity modeling approach by coupling the finite-element analyses with a two-dimensional thermal protection materials response code. Model predictions show good agreement with thermocouple data obtained during the arcjet test.

Three-dimensional simulation of helix traveling-wave tube cold-test characteristics using MAFIA

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

Kory, C.L.

1996-12-31

A critically important step in the traveling-wave tube (TWT) design process is the cold-testing of the slow-wave circuit for dispersion, beam interaction impedance and RF losses. Experimental cold-tests can be very time-consuming and expensive, thus limiting the freedom to examine numerous variations to the test circuit. This makes the need for computational methods crucial as they can lower cost, reduce tube development time and allow the freedom to introduce novel and improved designs. The cold-test parameters have been calculated for a C-Band Northrop-Grumman helix TWT slow-wave circuit using MAFIA, the three-dimensional electromagnetic finite-integration computer code. Measured and simulated cold-test datamore » for the Northrop-Grumman helix TWT including dispersion, impedance and attenuation will be presented. Close agreement between simulated and measured values of the dispersion, impedance and attenuation has been obtained.« less

Considerations In The Design And Specifications Of An Automatic Inspection System

NASA Astrophysics Data System (ADS)

Lee, David T.

1980-05-01

Considerable activities have been centered around the automation of manufacturing quality control and inspection functions. Several reasons can be cited for this development. The continuous pressure of direct and indirect labor cost increase is only one of the obvious motivations. With the drive for electronics miniaturization come more and more complex processes where control parameters are critical and the yield is highly susceptible to inadequate process monitor and inspection. With multi-step, multi-layer process for substrate fabrication, process defects that are not detected and corrected at certain critical points may render the entire subassembly useless. As a process becomes more complex, the time required to test the product increases significantly in the total build cycle. The urgency to reduce test time brings more pressure to improve in-process control and inspection. The advances and improvements of components, assemblies and systems such as micro-processors, micro-computers, programmable controllers, and other intelligent devices, have made the automation of quality control much more cost effective and justifiable.

Global and critical test of the perturbation density-functional theory based on extensive simulation of Lennard-Jones fluid near an interface and in confined systems.

PubMed

Zhou, Shiqi; Jamnik, Andrej

2005-09-22

The structure of a Lennard-Jones (LJ) fluid subjected to diverse external fields maintaining the equilibrium with the bulk LJ fluid is studied on the basis of the third-order+second-order perturbation density-functional approximation (DFA). The chosen density and potential parameters for the bulk fluid correspond to the conditions situated at "dangerous" regions of the phase diagram, i.e., near the critical temperature or close to the gas-liquid coexistence curve. The accuracy of DFA predictions is tested against the results of a grand canonical ensemble Monte Carlo simulation. It is found that the DFA theory presented in this work performs successfully for the nonuniform LJ fluid only on the condition of high accuracy of the required bulk second-order direct correlation function. The present report further indicates that the proposed perturbation DFA is efficient and suitable for both supercritical and subcritical temperatures.

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

McAdams, Brian J.; Pearson, Raymond A.

With the continuing trend of decreasing feature sizes in flip-chip assemblies, the reliability tolerance to interfacial flaws is also decreasing. Small-scale disbonds will become more of a concern, pointing to the need for a better understanding of the initiation stage of interfacial delamination. With most accepted adhesion metric methodologies tailored to predict failure under the prior existence of a disbond, the study of the initiation phenomenon is open to development and standardization of new testing procedures. Traditional fracture mechanics approaches are not suitable, as the mathematics assume failure to originate at a disbond or crack tip. Disbond initiation is believedmore » to first occur at free edges and corners, which act as high stress concentration sites and exhibit singular stresses similar to a crack tip, though less severe in intensity. As such, a 'fracture mechanics-like' approach may be employed which defines a material parameter--a critical stress intensity factor (K{sub c})--that can be used to predict when initiation of a disbond at an interface will occur. The factors affecting the adhesion of underfill/polyimide interfaces relevant to flip-chip assemblies were investigated in this study. The study consisted of two distinct parts: a comparison of the initiation and propagation phenomena and a comparison of the relationship between sub-critical and critical initiation of interfacial failure. The initiation of underfill interfacial failure was studied by characterizing failure at a free-edge with a critical stress intensity factor. In comparison with the interfacial fracture toughness testing, it was shown that a good correlation exists between the initiation and propagation of interfacial failures. Such a correlation justifies the continuing use of fracture mechanics to predict the reliability of flip-chip packages. The second aspect of the research involved fatigue testing of tensile butt joint specimens to determine lifetimes at sub-critical load levels. The results display an interfacial strength ranking similar to that observed during monotonic testing. The fatigue results indicate that monotonic fracture mechanics testing may be an adequate screening tool to help predict cyclic underfill failure; however lifetime data is required to predict reliability.« less

Quantum criticality of a spin-1 XY model with easy-plane single-ion anisotropy via a two-time Green function approach avoiding the Anderson-Callen decoupling

NASA Astrophysics Data System (ADS)

Mercaldo, M. T.; Rabuffo, I.; De Cesare, L.; Caramico D'Auria, A.

2016-04-01

In this work we study the quantum phase transition, the phase diagram and the quantum criticality induced by the easy-plane single-ion anisotropy in a d-dimensional quantum spin-1 XY model in absence of an external longitudinal magnetic field. We employ the two-time Green function method by avoiding the Anderson-Callen decoupling of spin operators at the same sites which is of doubtful accuracy. Following the original Devlin procedure we treat exactly the higher order single-site anisotropy Green functions and use Tyablikov-like decouplings for the exchange higher order ones. The related self-consistent equations appear suitable for an analysis of the thermodynamic properties at and around second order phase transition points. Remarkably, the equivalence between the microscopic spin model and the continuous O(2) -vector model with transverse-Ising model (TIM)-like dynamics, characterized by a dynamic critical exponent z=1, emerges at low temperatures close to the quantum critical point with the single-ion anisotropy parameter D as the non-thermal control parameter. The zero-temperature critic anisotropy parameter Dc is obtained for dimensionalities d > 1 as a function of the microscopic exchange coupling parameter and the related numerical data for different lattices are found to be in reasonable agreement with those obtained by means of alternative analytical and numerical methods. For d > 2, and in particular for d=3, we determine the finite-temperature critical line ending in the quantum critical point and the related TIM-like shift exponent, consistently with recent renormalization group predictions. The main crossover lines between different asymptotic regimes around the quantum critical point are also estimated providing a global phase diagram and a quantum criticality very similar to the conventional ones.

Continuous excitation chlorophyll fluorescence parameters: a review for practitioners.

PubMed

Banks, Jonathan M

2017-08-01

This review introduces, defines and critically reviews a number of chlorophyll fluorescence parameters with specific reference to those derived from continuous excitation chlorophyll fluorescence. A number of common issues and criticisms are addressed. The parameters fluorescence origin (F0) and the performance indices (PI) are discussed as examples. This review attempts to unify definitions for the wide range of parameters available for measuring plant vitality, facilitating their calculation and use. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Improving tablet coating robustness by selecting critical process parameters from retrospective data.

PubMed

Galí, A; García-Montoya, E; Ascaso, M; Pérez-Lozano, P; Ticó, J R; Miñarro, M; Suñé-Negre, J M

2016-09-01

Although tablet coating processes are widely used in the pharmaceutical industry, they often lack adequate robustness. Up-scaling can be challenging as minor changes in parameters can lead to varying quality results. To select critical process parameters (CPP) using retrospective data of a commercial product and to establish a design of experiments (DoE) that would improve the robustness of the coating process. A retrospective analysis of data from 36 commercial batches. Batches were selected based on the quality results generated during batch release, some of which revealed quality deviations concerning the appearance of the coated tablets. The product is already marketed and belongs to the portfolio of a multinational pharmaceutical company. The Statgraphics 5.1 software was used for data processing to determine critical process parameters in order to propose new working ranges. This study confirms that it is possible to determine the critical process parameters and create design spaces based on retrospective data of commercial batches. This type of analysis is thus converted into a tool to optimize the robustness of existing processes. Our results show that a design space can be established with minimum investment in experiments, since current commercial batch data are processed statistically.

Simulation verification techniques study

NASA Technical Reports Server (NTRS)

Schoonmaker, P. B.; Wenglinski, T. H.

1975-01-01

Results are summarized of the simulation verification techniques study which consisted of two tasks: to develop techniques for simulator hardware checkout and to develop techniques for simulation performance verification (validation). The hardware verification task involved definition of simulation hardware (hardware units and integrated simulator configurations), survey of current hardware self-test techniques, and definition of hardware and software techniques for checkout of simulator subsystems. The performance verification task included definition of simulation performance parameters (and critical performance parameters), definition of methods for establishing standards of performance (sources of reference data or validation), and definition of methods for validating performance. Both major tasks included definition of verification software and assessment of verification data base impact. An annotated bibliography of all documents generated during this study is provided.

MicroRNAs and Glucocorticoid-Induced Apoptosis in Lymphoid Malignancies

PubMed Central

Sionov, Ronit Vogt

2013-01-01

The initial response of lymphoid malignancies to glucocorticoids (GCs) is a critical parameter predicting successful treatment. Although being known as a strong inducer of apoptosis in lymphoid cells for almost a century, the signaling pathways regulating the susceptibility of the cells to GCs are only partly revealed. There is still a need to develop clinical tests that can predict the outcome of GC therapy. In this paper, I discuss important parameters modulating the pro-apoptotic effects of GCs, with a specific emphasis on the microRNA world comprised of small players with big impacts. The journey through the multifaceted complexity of GC-induced apoptosis brings forth explanations for the differential treatment response and raises potential strategies for overcoming drug resistance. PMID:23431463

Thermophilic treatment of acidified and partially acidified wastewater using an anaerobic submerged MBR: Factors affecting long-term operational flux.

PubMed

Jeison, D; van Lier, J B

2007-09-01

The long-term operation of two thermophilic anaerobic submerged membrane bioreactors (AnSMBRs) was studied using acidified and partially acidified synthetic wastewaters. In both reactors, cake formation was identified as the key factor governing critical flux. Even though cake formation was observed to be mostly reversible, particle deposition proceeds fast once the critical flux is exceeded. Very little irreversible fouling was observed during long-term operation, irrespective of the substrate. Critical flux values at the end of the reactors operation were 7 and 3L/m(2)h for the AnSMBRs fed with acidified and partially acidified wastewaters, respectively, at a gas superficial velocity of 70m/h. Small particle size was identified as the responsible parameter for the low observed critical flux values. The degree of wastewater acidification significantly affected the physical properties of the sludge, determining the attainable flux. Based on the fluxes observed in this research, the membrane costs would be in the range of 0.5euro/m(3) of treated wastewater. Gas sparging was ineffective in increasing the critical flux values. However, preliminary tests showed that cross-flow operation may be a feasible alternative to reduce particle deposition.

Labyrinth Seal Flutter Analysis and Test Validation in Support of Robust Rocket Engine Design

NASA Technical Reports Server (NTRS)

El-Aini, Yehia; Park, John; Frady, Greg; Nesman, Tom

2010-01-01

High energy-density turbomachines, like the SSME turbopumps, utilize labyrinth seals, also referred to as knife-edge seals, to control leakage flow. The pressure drop for such seals is order of magnitude higher than comparable jet engine seals. This is aggravated by the requirement of tight clearances resulting in possible unfavorable fluid-structure interaction of the seal system (seal flutter). To demonstrate these characteristics, a benchmark case of a High Pressure Oxygen Turbopump (HPOTP) outlet Labyrinth seal was studied in detail. First, an analytical assessment of the seal stability was conducted using a Pratt & Whitney legacy seal flutter code. Sensitivity parameters including pressure drop, rotor-to-stator running clearances and cavity volumes were examined and modeling strategies established. Second, a concurrent experimental investigation was undertaken to validate the stability of the seal at the equivalent operating conditions of the pump. Actual pump hardware was used to construct the test rig, also referred to as the (Flutter Rig). The flutter rig did not include rotational effects or temperature. However, the use of Hydrogen gas at high inlet pressure provided good representation of the critical parameters affecting flutter especially the speed of sound. The flutter code predictions showed consistent trends in good agreement with the experimental data. The rig test program produced a stability threshold empirical parameter that separated operation with and without flutter. This empirical parameter was used to establish the seal build clearances to avoid flutter while providing the required cooling flow metering. The calibrated flutter code along with the empirical flutter parameter was used to redesign the baseline seal resulting in a flutter-free robust configuration. Provisions for incorporation of mechanical damping devices were introduced in the redesigned seal to ensure added robustness

Order parameter fluctuations at a buried quantum critical point

PubMed Central

Feng, Yejun; Wang, Jiyang; Jaramillo, R.; van Wezel, Jasper; Haravifard, S.; Srajer, G.; Liu, Y.; Xu, Z.-A.; Littlewood, P. B.; Rosenbaum, T. F.

2012-01-01

Quantum criticality is a central concept in condensed matter physics, but the direct observation of quantum critical fluctuations has remained elusive. Here we present an X-ray diffraction study of the charge density wave (CDW) in 2H-NbSe2 at high pressure and low temperature, where we observe a broad regime of order parameter fluctuations that are controlled by proximity to a quantum critical point. X-rays can track the CDW despite the fact that the quantum critical regime is shrouded inside a superconducting phase; and in contrast to transport probes, allow direct measurement of the critical fluctuations of the charge order. Concurrent measurements of the crystal lattice point to a critical transition that is continuous in nature. Our results confirm the long-standing expectations of enhanced quantum fluctuations in low-dimensional systems, and may help to constrain theories of the quantum critical Fermi surface. PMID:22529348

High-speed microprocessor characterization. Final report/project accomplishments summary, CRADA Number KCP-94-1004

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

Brown, L.W.

The objective of the project was to characterize and document the critical operating parameters of an 0.8-micron, 350-MHz, 32-bit microprocessor prototype. The roles of FM and T and the participant company were: FM and T -- evaluation performance of the prototype 32-bit microprocessor using the IDS5000 and Tektronix S3260 Integrated Circuit Test System; Corda -- design and build the prototype microprocessor. This project was terminated with nearly all of the planned activities unaddressed.

Unconventional and conventional quantum criticalities in CeRh0.58Ir0.42In5

NASA Astrophysics Data System (ADS)

Luo, Yongkang; Lu, Xin; Dioguardi, Aadm P.; Rosa, Priscila F. S.; Bauer, Eric D.; Si, Qimiao; Thompson, Joe D.

2018-03-01

An appropriate description of the state of matter that appears as a second order phase transition is tuned toward zero temperature, viz. quantum-critical point (QCP), poses fundamental and still not fully answered questions. Experiments are needed both to test basic conclusions and to guide further refinement of theoretical models. Here, charge and entropy transport properties as well as AC specific heat of the heavy-fermion compound CeRh0.58Ir0.42In5, measured as a function of pressure, reveal two qualitatively different QCPs in a single material driven by a single non-symmetry-breaking tuning parameter. A discontinuous sign-change jump in thermopower suggests an unconventional QCP at pc1 accompanied by an abrupt Fermi-surface reconstruction that is followed by a conventional spin-density-wave critical point at pc2 across which the Fermi surface evolves smoothly to a heavy Fermi-liquid state. These experiments are consistent with some theoretical predictions, including the sequence of critical points and the temperature dependence of the thermopower in their vicinity.

Nonequilibrium critical dynamics of the two-dimensional Ashkin-Teller model at the Baxter line

NASA Astrophysics Data System (ADS)

Fernandes, H. A.; da Silva, R.; Caparica, A. A.; de Felício, J. R. Drugowich

2017-04-01

We investigate the short-time universal behavior of the two-dimensional Ashkin-Teller model at the Baxter line by performing time-dependent Monte Carlo simulations. First, as preparatory results, we obtain the critical parameters by searching the optimal power-law decay of the magnetization. Thus, the dynamic critical exponents θm and θp, related to the magnetic and electric order parameters, as well as the persistence exponent θg, are estimated using heat-bath Monte Carlo simulations. In addition, we estimate the dynamic exponent z and the static critical exponents β and ν for both order parameters. We propose a refined method to estimate the static exponents that considers two different averages: one that combines an internal average using several seeds with another, which is taken over temporal variations in the power laws. Moreover, we also performed the bootstrapping method for a complementary analysis. Our results show that the ratio β /ν exhibits universal behavior along the critical line corroborating the conjecture for both magnetization and polarization.

Application of Analytical Quality by Design concept for bilastine and its degradation impurities determination by hydrophilic interaction liquid chromatographic method.

PubMed

Terzić, Jelena; Popović, Igor; Stajić, Ana; Tumpa, Anja; Jančić-Stojanović, Biljana

2016-06-05

This paper deals with the development of hydrophilic interaction liquid chromatographic (HILIC) method for the analysis of bilastine and its degradation impurities following Analytical Quality by Design approach. It is the first time that the method for bilastine and its impurities is proposed. The main objective was to identify the conditions where an adequate separation in minimal analysis duration could be achieved within a robust region. Critical process parameters which have the most influence on method performance were defined as acetonitrile content in the mobile phase, pH of the aqueous phase and ammonium acetate concentration in the aqueous phase. Box-Behnken design was applied for establishing a relationship between critical process parameters and critical quality attributes. The defined mathematical models and Monte Carlo simulations were used to identify the design space. Fractional factorial design was applied for experimental robustness testing and the method is validated to verify the adequacy of selected optimal conditions: the analytical column Luna(®) HILIC (100mm×4.6mm, 5μm particle size); mobile phase consisted of acetonitrile-aqueous phase (50mM ammonium acetate, pH adjusted to 5.3 with glacial acetic acid) (90.5:9.5, v/v); column temperature 30°C, mobile phase flow rate 1mLmin(-1), wavelength of detection 275nm. Copyright © 2016 Elsevier B.V. All rights reserved.

Understanding controls of hydrologic processes across two monolithological catchments using model-data integration

NASA Astrophysics Data System (ADS)

Xiao, D.; Shi, Y.; Li, L.

2016-12-01

Field measurements are important to understand the fluxes of water, energy, sediment, and solute in the Critical Zone however are expensive in time, money, and labor. This study aims to assess the model predictability of hydrological processes in a watershed using information from another intensively-measured watershed. We compare two watersheds of different lithology using national datasets, field measurements, and physics-based model, Flux-PIHM. We focus on two monolithological, forested watersheds under the same climate in the Shale Hills Susquehanna CZO in central Pennsylvania: the Shale-based Shale Hills (SSH, 0.08 km2) and the sandstone-based Garner Run (GR, 1.34 km2). We firstly tested the transferability of calibration coefficients from SSH to GR. We found that without any calibration the model can successfully predict seasonal average soil moisture and discharge which shows the advantage of a physics-based model, however, cannot precisely capture some peaks or the runoff in summer. The model reproduces the GR field data better after calibrating the soil hydrology parameters. In particular, the percentage of sand turns out to be a critical parameter in reproducing data. With sandstone being the dominant lithology, GR has much higher sand percentage than SSH (48.02% vs. 29.01%), leading to higher hydraulic conductivity, lower overall water storage capacity, and in general lower soil moisture. This is consistent with area averaged soil moisture observations using the cosmic-ray soil moisture observing system (COSMOS) at the two sites. This work indicates that some parameters, including evapotranspiration parameters, are transferrable due to similar climatic and land cover conditions. However, the key parameters that control soil moisture, including the sand percentage, need to be recalibrated, reflecting the key role of soil hydrological properties.

Wetting properties and critical micellar concentration of benzalkonium chloride mixed in sodium hypochlorite.

PubMed

Bukiet, Frédéric; Couderc, Guillaume; Camps, Jean; Tassery, Hervé; Cuisinier, Frederic; About, Imad; Charrier, Anne; Candoni, Nadine

2012-11-01

The purposes of the present study were to (1) assess the effect of the addition of benzalkonium chloride to sodium hypochlorite on its wetting properties, contact angle, and surface energy; (2) determine the critical micellar concentration of benzalkonium chloride in sodium hypochlorite; and (3) investigate the influence of addition of benzalkonium chloride on the free chlorine level, cytotoxicity, and antiseptic properties of the mixture. Solutions of benzalkonium chloride, with concentrations ranging from 0%-1%, were mixed in 2.4% sodium hypochlorite and tested as follows. The wetting properties were investigated by measuring the contact angle of the solutions on a nondehydrated dentin surface by using the static sessile drop method. The pending drop technique was subsequently used to determine the surface energy of the solutions. The critical micellar concentration of benzalkonium chloride mixed in sodium hypochlorite was calculated from the data. When 2.4% NaOCl was mixed with benzalkonium chloride at the critical micellar concentration, 3 parameters were tested: free chloride content, cytotoxicity, and antibacterial effects against Enterococcus faecalis. The contact angle (P < .001) as well as the surface energy (P < .001) significantly decreased with increasing benzalkonium chloride concentrations. The critical micellar concentration of benzalkonium chloride in sodium hypochlorite was 0.008%. At this concentration, the addition of benzalkonium chloride had no effect on the free chlorine content, cytotoxicity, or antibacterial efficiency of the mixture. The addition of benzalkonium chloride to sodium hypochlorite at the critical micellar concentration reduced the contact angle by 51.2% and the surface energy by 53.4%, without affecting the free chloride content, cytotoxicity, or antibacterial properties of the mixture. Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Mice plan decision strategies based on previously learned time intervals, locations, and probabilities

PubMed Central

Tosun, Tuğçe; Gür, Ezgi; Balcı, Fuat

2016-01-01

Animals can shape their timed behaviors based on experienced probabilistic relations in a nearly optimal fashion. On the other hand, it is not clear if they adopt these timed decisions by making computations based on previously learnt task parameters (time intervals, locations, and probabilities) or if they gradually develop their decisions based on trial and error. To address this question, we tested mice in the timed-switching task, which required them to anticipate when (after a short or long delay) and at which of the two delay locations a reward would be presented. The probability of short trials differed between test groups in two experiments. Critically, we first trained mice on relevant task parameters by signaling the active trial with a discriminative stimulus and delivered the corresponding reward after the associated delay without any response requirement (without inducing switching behavior). During the test phase, both options were presented simultaneously to characterize the emergence and temporal characteristics of the switching behavior. Mice exhibited timed-switching behavior starting from the first few test trials, and their performance remained stable throughout testing in the majority of the conditions. Furthermore, as the probability of the short trial increased, mice waited longer before switching from the short to long location (experiment 1). These behavioral adjustments were in directions predicted by reward maximization. These results suggest that rather than gradually adjusting their time-dependent choice behavior, mice abruptly adopted temporal decision strategies by directly integrating their previous knowledge of task parameters into their timed behavior, supporting the model-based representational account of temporal risk assessment. PMID:26733674

A statistical analysis of elevated temperature gravimetric cyclic oxidation data of 36 Ni- and Co-base superalloys based on an oxidation attack parameter

NASA Technical Reports Server (NTRS)

Barrett, Charles A.

1992-01-01

A large body of high temperature cyclic oxidation data generated from tests at NASA Lewis Research Center involving gravimetric/time values for 36 Ni- and Co-base superalloys was reduced to a single attack parameter, K(sub a), for each run. This K(sub a) value was used to rank the cyclic oxidation resistance of each alloy at 1000, 1100, and 1150 C. These K(sub a) values were also used to derive an estimating equation using multiple linear regression involving log(sub 10)K(sub a) as a function of alloy chemistry and test temperature. This estimating equation has a high degree of fit and could be used to predict cyclic oxidation behavior for similar alloys and to design an optimum high strength Ni-base superalloy with maximum high temperature cyclic oxidation resistance. The critical alloy elements found to be beneficial were Al, Cr, and Ta.

Argon-oxygen atmospheric pressure plasma treatment on carbon fiber reinforced polymer for improved bonding

NASA Astrophysics Data System (ADS)

Chartosias, Marios

Acceptance of Carbon Fiber Reinforced Polymer (CFRP) structures requires a robust surface preparation method with improved process controls capable of ensuring high bond quality. Surface preparation in a production clean room environment prior to applying adhesive for bonding would minimize risk of contamination and reduce cost. Plasma treatment is a robust surface preparation process capable of being applied in a production clean room environment with process parameters that are easily controlled and documented. Repeatable and consistent processing is enabled through the development of a process parameter window utilizing techniques such as Design of Experiments (DOE) tailored to specific adhesive and substrate bonding applications. Insight from respective plasma treatment Original Equipment Manufacturers (OEMs) and screening tests determined critical process factors from non-factors and set the associated factor levels prior to execution of the DOE. Results from mode I Double Cantilever Beam (DCB) testing per ASTM D 5528 [1] standard and DOE statistical analysis software are used to produce a regression model and determine appropriate optimum settings for each factor.

Optimized design and research of secondary microprism for dense array concentrating photovoltaic module

NASA Astrophysics Data System (ADS)

Yang, Guanghui; Chen, Bingzhen; Liu, Youqiang; Guo, Limin; Yao, Shun; Wang, Zhiyong

2015-10-01

As the critical component of concentrating photovoltaic module, secondary concentrators can be effective in increasing the acceptance angle and incident light, as well as improving the energy uniformity of focal spots. This paper presents a design of transmission-type secondary microprism for dense array concentrating photovoltaic module. The 3-D model of this design is established by Solidworks and important parameters such as inclination angle and component height are optimized using Zemax. According to the design and simulation results, several secondary microprisms with different parameters are fabricated and tested in combination with Fresnel lens and multi-junction solar cell. The sun-simulator IV test results show that the combination has the highest output power when secondary microprism height is 5mm and top facet side length is 7mm. Compared with the case without secondary microprism, the output power can improve 11% after the employment of secondary microprisms, indicating the indispensability of secondary microprisms in concentrating photovoltaic module.

An Investigation of the Influence of Initial Roughness on the Friction and Wear Behavior of Ground Surfaces

PubMed Central

Liang, Guoxing; Schmauder, Siegfried; Lyu, Ming; Schneider, Yanling; Zhang, Cheng; Han, Yang

2018-01-01

Friction and wear tests were performed on AISI 1045 steel specimens with different initial roughness parameters, machined by a creep-feed dry grinding process, to study the friction and wear behavior on a pin-on-disc tester in dry sliding conditions. Average surface roughness (Ra), root mean square (Rq), skewness (Rsk) and kurtosis (Rku) were involved in order to analyse the influence of the friction and wear behavior. The observations reveal that a surface with initial roughness parameters of higher Ra, Rq and Rku will lead to a longer initial-steady transition period in the sliding tests. The plastic deformation mainly concentrates in the depth of 20–50 μm under the worn surface and the critical plastic deformation is generated on the rough surface. For surfaces with large Ra, Rq, low Rsk and high Rku values, it is easy to lose the C element in, the reciprocating extrusion. PMID:29401703

Anomalous solute transport in saturated porous media: Relating transport model parameters to electrical and nuclear magnetic resonance properties

USGS Publications Warehouse

Swanson, Ryan D; Binley, Andrew; Keating, Kristina; France, Samantha; Osterman, Gordon; Day-Lewis, Frederick D.; Singha, Kamini

2015-01-01

The advection-dispersion equation (ADE) fails to describe commonly observed non-Fickian solute transport in saturated porous media, necessitating the use of other models such as the dual-domain mass-transfer (DDMT) model. DDMT model parameters are commonly calibrated via curve fitting, providing little insight into the relation between effective parameters and physical properties of the medium. There is a clear need for material characterization techniques that can provide insight into the geometry and connectedness of pore spaces related to transport model parameters. Here, we consider proton nuclear magnetic resonance (NMR), direct-current (DC) resistivity, and complex conductivity (CC) measurements for this purpose, and assess these methods using glass beads as a control and two different samples of the zeolite clinoptilolite, a material that demonstrates non-Fickian transport due to intragranular porosity. We estimate DDMT parameters via calibration of a transport model to column-scale solute tracer tests, and compare NMR, DC resistivity, CC results, which reveal that grain size alone does not control transport properties and measured geophysical parameters; rather, volume and arrangement of the pore space play important roles. NMR cannot provide estimates of more-mobile and less-mobile pore volumes in the absence of tracer tests because these estimates depend critically on the selection of a material-dependent and flow-dependent cutoff time. Increased electrical connectedness from DC resistivity measurements are associated with greater mobile pore space determined from transport model calibration. CC was hypothesized to be related to length scales of mass transfer, but the CC response is unrelated to DDMT.

Dynamic response of NASA Rotor Test Apparatus and Sikorsky S-76 hub mounted in the 80- by 120-Foot Wind Tunnel

NASA Technical Reports Server (NTRS)

Peterson, Randall L.; Hoque, Muhammed S.

1994-01-01

A shake test was conducted in the 80- by 120-Foot Wind Tunnel at NASA Ames Research Center, using the NASA Ames Rotor Test Apparatus (RTA) and the Sikorsky S-76 rotor hub. The primary objective of this shake test was to determine the modal properties of the RTA, the S-76 rotor hub, and the model support system installed in the wind tunnel. Random excitation was applied at the rotor hub, and vibration responses were measured using accelerometers mounted at various critical locations on the model and the model support system. Transfer functions were computed using the load cell data and the accelerometer responses. The transfer function data were used to compute the system modal parameters with the aid of modal analysis software.

The development and use of a computer-interactive data acquisition and display system in a flight environment

NASA Technical Reports Server (NTRS)

Bever, G. A.

1981-01-01

The flight test data requirements at the NASA Dryden Flight Research Center increased in complexity, and more advanced instrumentation became necessary to accomplish mission goals. This paper describes the way in which an airborne computer was used to perform real-time calculations on critical flight test parameters during a flight test on a winglet-equipped KC-135A aircraft. With the computer, an airborne flight test engineer can select any sensor for airborne display in several formats, including engineering units. The computer is able to not only calculate values derived from the sensor outputs but also to interact with the data acquisition system. It can change the data cycle format and data rate, and even insert the derived values into the pulse code modulation (PCM) bit stream for recording.

Nonlinear elastic behavior of sub-critically damaged body armor panel

NASA Astrophysics Data System (ADS)

Fisher, Jason T.; Chimenti, D. E.

2012-05-01

A simple go/no-go test for body armor panels using pressure-sensitive, dye-indicator film (PSF) has been shown to be statistically effective in revealing subcritical damage to body armor panels. Previous measurements have shown that static indicator levels are accurately reproduced in dynamic loading events. Further impact tests on armor worn by a human resuscitation dummy using instrumented masses with an attached accelerometer and embedded force transducer have been performed and analyzed. New impact tests have shown a reliable correlation between PSF indication (as digitized images) and impact force for a wide range of impactor energies and masses. Numerical evaluation of digital PSF images is presented and correlated with impact parameters. Relationships between impactor mass and energy, and corresponding measured force are shown. We will also report on comparisons between ballistic testing performed on panels damaged under various impact conditions and tests performed on undamaged panels.

The 4-parameter Compressible Packing Model (CPM) including a critical cavity size ratio

NASA Astrophysics Data System (ADS)

Roquier, Gerard

2017-06-01

The 4-parameter Compressible Packing Model (CPM) has been developed to predict the packing density of mixtures constituted by bidisperse spherical particles. The four parameters are: the wall effect and the loosening effect coefficients, the compaction index and a critical cavity size ratio. The two geometrical interactions have been studied theoretically on the basis of a spherical cell centered on a secondary class bead. For the loosening effect, a critical cavity size ratio, below which a fine particle can be inserted into a small cavity created by touching coarser particles, is introduced. This is the only parameter which requires adaptation to extend the model to other types of particles. The 4-parameter CPM demonstrates its efficiency on frictionless glass beads (300 values), spherical particles numerically simulated (20 values), round natural particles (125 values) and crushed particles (335 values) with correlation coefficients equal to respectively 99.0%, 98.7%, 97.8%, 96.4% and mean deviations equal to respectively 0.007, 0.006, 0.007, 0.010.

Development and evaluation of paclitaxel nanoparticles using a quality-by-design approach.

PubMed

Yerlikaya, Firat; Ozgen, Aysegul; Vural, Imran; Guven, Olgun; Karaagaoglu, Ergun; Khan, Mansoor A; Capan, Yilmaz

2013-10-01

The aims of this study were to develop and characterize paclitaxel nanoparticles, to identify and control critical sources of variability in the process, and to understand the impact of formulation and process parameters on the critical quality attributes (CQAs) using a quality-by-design (QbD) approach. For this, a risk assessment study was performed with various formulation and process parameters to determine their impact on CQAs of nanoparticles, which were determined to be average particle size, zeta potential, and encapsulation efficiency. Potential risk factors were identified using an Ishikawa diagram and screened by Plackett-Burman design and finally nanoparticles were optimized using Box-Behnken design. The optimized formulation was further characterized by Fourier transform infrared spectroscopy, X-ray diffractometry, differential scanning calorimetry, scanning electron microscopy, atomic force microscopy, and gas chromatography. It was observed that paclitaxel transformed from crystalline state to amorphous state while totally encapsulating into the nanoparticles. The nanoparticles were spherical, smooth, and homogenous with no dichloromethane residue. In vitro cytotoxicity test showed that the developed nanoparticles are more efficient than free paclitaxel in terms of antitumor activity (more than 25%). In conclusion, this study demonstrated that understanding formulation and process parameters with the philosophy of QbD is useful for the optimization of complex drug delivery systems. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.

Methods in hair research: how to objectively distinguish between anagen and catagen in human hair follicle organ culture.

PubMed

Kloepper, Jennifer Elisabeth; Sugawara, Koji; Al-Nuaimi, Yusur; Gáspár, Erzsébet; van Beek, Nina; Paus, Ralf

2010-03-01

The organ culture of human scalp hair follicles (HFs) is the best currently available assay for hair research in the human system. In order to determine the hair growth-modulatory effects of agents in this assay, one critical read-out parameter is the assessment of whether the test agent has prolonged anagen duration or induced catagen in vitro. However, objective criteria to distinguish between anagen VI HFs and early catagen in human HF organ culture, two hair cycle stages with a deceptively similar morphology, remain to be established. Here, we develop, document and test an objective classification system that allows to distinguish between anagen VI and early catagen in organ-cultured human HFs, using both qualitative and quantitative parameters that can be generated by light microscopy or immunofluorescence. Seven qualitative classification criteria are defined that are based on assessing the morphology of the hair matrix, the dermal papilla and the distribution of pigmentary markers (melanin, gp100). These are complemented by ten quantitative parameters. We have tested this classification system by employing the clinically used topical hair growth inhibitor, eflornithine, and show that eflornithine indeed produces the expected premature catagen induction, as identified by the novel classification criteria reported here. Therefore, this classification system offers a standardized, objective and reproducible new experimental method to reliably distinguish between human anagen VI and early catagen HFs in organ culture.

Centrifuge advances using HTS magnetic bearings

NASA Astrophysics Data System (ADS)

Werfel, F. N.; Flögel-Delor, U.; Rothfeld, R.; Wippich, D.; Riedel, T.

2001-05-01

Passive magnetic bearings are of increasing technical interest. We performed experiments with centrifugal rotors to analyze gyroscopic forces in terms imbalance, rotor elasticity and damping. Centrifuge rotors need to be operated soft and stable without whirling the sediments. In order to evaluate optimal parameters critical and resonance behaviors are investigated. Eccentricities up 2 mm are safely passed by accelerating test wheels. In a simple model we describe the effect of passing critical rotational speeds. Measurements of bearing properties and wheel performance are presented. We have constructed a first prototype centrifuge designed with a HTS double bearing which operates a titanium rotor safely up to 30 000 rpm. A 15 W Stirling cooler serves cryogenics of the YBCO stators. From the experiments design guidelines for centrifugal applications with HTS bearings are given.

Milestone 4: Test plan for Reusable Hydrogen Composite Tank System (RHCTS). Task 3: Composite tank materials

NASA Technical Reports Server (NTRS)

Greenberg, H. S.

1994-01-01

This document is the detailed test plan for the series of tests enumerated in the preceding section. The purpose of this plan is to present the test objectives, test parameters and procedures, expected performance and data analysis plans, criteria for success, test schedules, and related safety provisions and to describe the test articles, test instrumentation, and test facility requirements. Initial testing will be performed to screen four composite materials for suitability for SSTO LH2 tank loads and environmental conditions. The laminates for this testing will be fabricated by fiber placement, which is the manufacturing approach identified as baseline for the tank wall. Even though hand layup will be involved in fabricating many of the internal structural members of the tank, no hand-layup laminates will be evaluated in the screening or subsequent characterization testing. This decision is based on the understanding that mechanical properties measured for hand-layup material should be at least equivalent to properties measured for fiber-placed material, so that the latter should provide no less than a conservative approximation of the former. A single material will be downselected from these screening tests. This material will be subsequently characterized for impact-damage tolerance and durability under conditions of mechanical and thermal cycling, and to establish a preliminary design database to support ongoing analysis. Next, testing will be performed on critical structural elements fabricated from the selected material. Finally, the 8-foot diameter tank article, containing the critical structural features of the full-scale tank, will be fabricated by fiber placement and tested to verify its structural integrity and LH2 containment.

Adiabatic Coupling Constant of Nitrobenzene- n-Alkane Critical Mixtures. Evidence from Ultrasonic Spectra and Thermodynamic Data

NASA Astrophysics Data System (ADS)

Mirzaev, Sirojiddin Z.; Kaatze, Udo

2016-09-01

Ultrasonic spectra of mixtures of nitrobenzene with n-alkanes, from n-hexane to n-nonane, are analyzed. They feature up to two Debye-type relaxation terms with discrete relaxation times and, near the critical point, an additional relaxation term due to the fluctuations in the local concentration. The latter can be well represented by the dynamic scaling theory. Its amplitude parameter reveals the adiabatic coupling constant of the mixtures of critical composition. The dependence of this thermodynamic parameter upon the length of the n-alkanes corresponds to that of the slope in the pressure dependence of the critical temperature and is thus taken another confirmation of the dynamic scaling model. The change in the variation of the coupling constant and of several other mixture parameters with alkane length probably reflects a structural change in the nitrobenzene- n-alkane mixtures when the number of carbon atoms per alkane exceeds eight.

Prognostic value of severity by various visceral proteins in critically ill patients with SIRS during 7 days of stay.

PubMed

Bouharras-El Idrissi, Hicham; Molina-López, Jorge; Herrera-Quintana, Lourdes; Domínguez-García, Álvaro; Lobo-Támer, Gabriela; Pérez-Moreno, Irene; Pérez-de la Cruz, Antonio; Planells-Del Pozo, Elena

2016-11-29

Critically ill patients typically develop a catabolic stress state as a result of a systemic inflammatory response (SIRS) that alters clinical-nutritional biomarkers, increasing energy demands and nutritional requirements. To evaluate the status of albumin, prealbumin and transferrin in critically ill patients and the association between these clinical-nutritional parameters with the severity during a seven day stay in intensive care unit (ICU). Multicenter, prospective, observational and analytical follow-up study. A total of 115 subjects in critical condition were included in this study. Clinical and nutritional parameters and severity were monitored at admission and at the seventh day of the ICU stay. A significant decrease in APACHE II and SOFA (p < 0.05) throughout the evolution of critically ill patients in ICU. In general, patients showed an alteration of most of the parameters analyzed. The status of albumin, prealbumin and transferrin were below reference levels both at admission and the 7th day in ICU. A high percentage of patients presented an unbalanced status of albumin (71.3%), prealbumin (84.3%) and transferrin (69.0%). At admission, 27% to 47% of patients with altered protein parameters had APACHE II above 18. The number of patients with altered protein parameters and APACHE II below 18 were significantly higher than severe ones throughout the ICU stay (p < 0.01). Regarding the multivariate analysis, low prealbumin status was the best predictor of severity critical (p < 0.05) both at admission and 7th day of the ICU stay. The results of the present study support the idea of including low prealbumin status as a severity predictor in APACHE II scale, due to the association found between severity and poor status of prealbumin.

Chromium released from leather - I: exposure conditions that govern the release of chromium(III) and chromium(VI).

PubMed

Hedberg, Yolanda S; Lidén, Carola; Odnevall Wallinder, Inger

2015-04-01

Approximately 1-3% of the adult population in Europe is allergic to chromium (Cr). A new restriction in REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) based on the ISO 17075 standard has recently been adopted in the EU to limit Cr(VI) in consumer and occupational leather products. The aim of this study was to critically assess key experimental parameters in this standard on the release of Cr(III) and Cr(VI) and their relevance for skin exposure. Four differently tanned, unfinished, leather samples were systematically investigated for their release of Cr(III) and Cr(VI) in relation to surface area, key exposure parameters, temperature, ultraviolet irradiation, and time. Although the total release of Cr was largely unaffected by all investigated parameters, except exposure duration and temperature, the Cr oxidation state was highly dynamic, with reduced amounts of released Cr(VI) with time, owing to the simultaneous release of reducing agents from the leather. Significantly more Cr(III) than Cr(VI) was released from the Cr-tanned leather for all conditions tested, and it continued to be released in artificial sweat up to at least 1 week of exposure. Several parameters were identified that influenced the outcome of the ISO 17075 test. © 2015 The Authors. Contact Dermatitis published by John Wiley & Sons Ltd.

An assessment of spacecraft target mode selection methods

NASA Astrophysics Data System (ADS)

Mercer, J. F.; Aglietti, G. S.; Remedia, M.; Kiley, A.

2017-11-01

Coupled Loads Analyses (CLAs), using finite element models (FEMs) of the spacecraft and launch vehicle to simulate critical flight events, are performed in order to determine the dynamic loadings that will be experienced by spacecraft during launch. A validation process is carried out on the spacecraft FEM beforehand to ensure that the dynamics of the analytical model sufficiently represent the behavior of the physical hardware. One aspect of concern is the containment of the FEM correlation and update effort to focus on the vibration modes which are most likely to be excited under test and CLA conditions. This study therefore provides new insight into the prioritization of spacecraft FEM modes for correlation to base-shake vibration test data. The work involved example application to large, unique, scientific spacecraft, with modern FEMs comprising over a million degrees of freedom. This comprehensive investigation explores: the modes inherently important to the spacecraft structures, irrespective of excitation; the particular 'critical modes' which produce peak responses to CLA level excitation; an assessment of several traditional target mode selection methods in terms of ability to predict these 'critical modes'; and an indication of the level of correlation these FEM modes achieve compared to corresponding test data. Findings indicate that, although the traditional methods of target mode selection have merit and are able to identify many of the modes of significance to the spacecraft, there are 'critical modes' which may be missed by conventional application of these methods. The use of different thresholds to select potential target modes from these parameters would enable identification of many of these missed modes. Ultimately, some consideration of the expected excitations is required to predict all modes likely to contribute to the response of the spacecraft in operation.

The ENEA criticality accident dosimetry system: a contribution to the 2002 international intercomparison at the SILENE reactor.

PubMed

Gualdrini, G; Bedogni, R; Fantuzzi, E; Mariotti, F

2004-01-01

The present paper summarises the activity carried out at the ENEA Radiation Protection Institute for updating the methodologies employed for the evaluation of the neutron and photon dose to the exposed workers in case of a criticality accident, in the framework of the 'International Intercomparison of Criticality Accident Dosimetry Systems' (Silène reactor, IRSN-CEA-Valduc June 2002). The evaluation of the neutron spectra and the neutron dosimetric quantities relies on activation detectors and on unfolding algorithms. Thermoluminescent detectors are employed for the gamma dose measurement. The work is aimed at accurately characterising the measurement system and, at the same time, testing the algorithms. Useful spectral information were included, based on Monte Carlo simulations, to take into account the potential accident scenarios of practical interest. All along this exercise intercomparison a particular attention was devoted to the 'traceability' of all the experimental and computational parameters and therefore, aimed at an easy treatment by the user.

Verification of a SEU model for advanced 1-micron CMOS structures using heavy ions

NASA Technical Reports Server (NTRS)

Cable, J. S.; Carter, J. R.; Witteles, A. A.

1986-01-01

Modeling and test results are reported for 1 micron CMOS circuits. Analytical predictions are correlated with experimental data, and sensitivities to process and design variations are discussed. Unique features involved in predicting the SEU performance of these devices are described. The results show that the critical charge for upset exhibits a strong dependence on pulse width for very fast devices, and upset predictions must factor in the pulse shape. Acceptable SEU error rates can be achieved for a 1 micron bulk CMOS process. A thin retrograde well provides complete SEU immunity for N channel hits at normal incidence angle. Source interconnect resistance can be important parameter in determining upset rates, and Cf-252 testing can be a valuable tool for cost-effective SEU testing.

CRBRP modular steam generator tube-to-tubesheet and shell-closure welding

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

Viri, D.P.

1982-01-01

The original Modular Steam Generator (MSG), whiand inh was designed, built, and tested by the Energy Systems Group (ESG) of Rockwell International, was a departure from conventional boilers or heat exchangers. The design was a hockeystick concept - the upper section of the generator is curved 90/sup 0/. Factors affecting operating parameters were considered and incorporated in the original MSG design. The MSG was fully instrumented and functionally tested at the Energy Technology Engineering Center at Rockwell. The MSG steamed continuously for over 4000 h, and at the conclusion of the 9000-h test cycle, it was systematically dismantled and examinedmore » for wear to critical components. This paper explains the solutions to several manufacturing challenges presented by the unique design of the MSG.« less

Chemical and mineralogical characterization of highly and less reactive coal from Northern Natal and Venda-Pafuri coalfields in South Africa

NASA Astrophysics Data System (ADS)

Kataka, M. O.; Matiane, A. R.; Odhiambo, B. D. O.

2018-01-01

Spontaneous combustion of coal is a major hazard associated with the coal mining industry over centuries. It also a major cause of underground fires in South African collieries and in opencast operations, spoil heaps and stockpiles. Spontaneous combustion incidents are manifested in all major aspects of coal mining namely, underground mining, surface mining, including during sea-borne transportation, storage and waste disposal. Previous studies indicate that there are various factors (both intrinsic and extrinsic) that influence the spontaneous combustion of coals. This paper characterizes highly reactive coal from the Vryheid coalfields and less reactive coal from at Venda-Pafuri coalfield, to identify and delineate some intrinsic coal parameters that are considered to be most critical in terms of heat 'generation' and relationships between the two coals types by tracing their similarities and differences in their spontaneous combustion parameters. Various tests were carried out to characterize these coals in terms of their intrinsic properties, namely: ultimate, proximate, petrographic analysis and Glasser spontaneous tests. The ultimate and proximate analysis showed that spontaneous coal has high contents of carbon, oxygen, and volatile matter as compared to non-spontaneous coal, making it more susceptible to spontaneous combustion. Non-spontaneous coal has higher ash content than the spontaneous coal. Furthermore, the petrographic analysis showed that spontaneous coal has high total reactivity compared to the non-spontaneous coal. Results from Glasser spontaneous test indicate that spontaneous coal absorbs more oxygen than non-spontaneous coal, which explains why spontaneous coal is more susceptible to spontaneous combustion. High reactive coal has low values of critical self-heating temperature (CSHT), indicating that this coal has potential of spontaneous ignition.

Critical current degradation behaviour of GdBCO CC tapes in pure torsion and combined tension-torsion modes

NASA Astrophysics Data System (ADS)

Gorospe, Alking; Bautista, Zhierwinjay; Shin, Hyung-Seop

2016-10-01

Coated conductor (CC) tapes utilized in high-current-density superconducting cables are commonly subjected to different loading modes, primarily torsion and tension especially in the case of twisted stacked-tape cable. Torsion load can occur due to twisting along the length or when winding the CC tapes around a former, while tension load can occur due to pre-tension when coiled and as a hoop stress when the coil is energized. In this study, electromechanical properties of single CC tapes under torsion load were investigated using a new test apparatus. The results could provide basic information for cable designers to fully characterize stacked cables. Copper-electroplated and brass-laminated CC tapes fabricated with different deposition techniques were subjected to pure torsion and combined tension-torsion loading. The critical current, I c degradation behaviours of CC tapes under torsional deformation were examined. Also, the effect of further external lamination on the I c degradation behaviour of the CC tapes under such loading conditions was investigated. In the case of the combined tension-torsion test, short samples were subjected to twist pitches of 200 mm and 100 mm. Critical parameters including reversible axial stress and strain in such twist pitch conditions were also investigated.

Critical analysis of industrial electron accelerators

NASA Astrophysics Data System (ADS)

Korenev, S.

2004-09-01

The critical analysis of electron linacs for industrial applications (degradation of PTFE, curing of composites, modification of materials, sterlization and others) is considered in this report. Main physical requirements for industrial electron accelerators consist in the variations of beam parameters, such as kinetic energy and beam power. Questions for regulation of these beam parameters are considered. The level of absorbed dose in the irradiated product and throughput determines the main parameters of electron accelerator. The type of ideal electron linac for industrial applications is discussed.

Effects of commercial aircraft operating environment on composite materials

NASA Technical Reports Server (NTRS)

Chapman, A. J.; Hoffman, D. J.; Hodges, W. T.

1980-01-01

Long term effects of commercial aircraft operating environment on the properties and durability of composite materials are being systematically explored. Composite specimens configured for various mechanical property tests are exposed to environmental conditions on aircraft in scheduled airline service, on racks at major airports, and to controlled environmental conditions in the laboratory. Results of tests following these exposures will identify critical parameters affecting composite durability, and correlation of the data will aid in developing methods for predicting durability. Interim results of these studies show that mass change of composite specimens on commercial aircraft depends upon the regional climate and season, and that mass loss from composite surfaces due to ultraviolet radiation can be largely prevented by aircraft paint.

Rapid Reconstitution Packages (RRPs) implemented by integration of computational fluid dynamics (CFD) and 3D printed microfluidics.

PubMed

Chi, Albert; Curi, Sebastian; Clayton, Kevin; Luciano, David; Klauber, Kameron; Alexander-Katz, Alfredo; D'hers, Sebastian; Elman, Noel M

2014-08-01

Rapid Reconstitution Packages (RRPs) are portable platforms that integrate microfluidics for rapid reconstitution of lyophilized drugs. Rapid reconstitution of lyophilized drugs using standard vials and syringes is an error-prone process. RRPs were designed using computational fluid dynamics (CFD) techniques to optimize fluidic structures for rapid mixing and integrating physical properties of targeted drugs and diluents. Devices were manufactured using stereo lithography 3D printing for micrometer structural precision and rapid prototyping. Tissue plasminogen activator (tPA) was selected as the initial model drug to test the RRPs as it is unstable in solution. tPA is a thrombolytic drug, stored in lyophilized form, required in emergency settings for which rapid reconstitution is of critical importance. RRP performance and drug stability were evaluated by high-performance liquid chromatography (HPLC) to characterize release kinetics. In addition, enzyme-linked immunosorbent assays (ELISAs) were performed to test for drug activity after the RRPs were exposed to various controlled temperature conditions. Experimental results showed that RRPs provided effective reconstitution of tPA that strongly correlated with CFD results. Simulation and experimental results show that release kinetics can be adjusted by tuning the device structural dimensions and diluent drug physical parameters. The design of RRPs can be tailored for a number of applications by taking into account physical parameters of the active pharmaceutical ingredients (APIs), excipients, and diluents. RRPs are portable platforms that can be utilized for reconstitution of emergency drugs in time-critical therapies.

Simulations of potential future conditions in the cache critical groundwater area, Arkansas

USGS Publications Warehouse

Rashid, Haveen M.; Clark, Brian R.; Mahdi, Hanan H.; Rifai, Hanadi S.; Al-Shukri, Haydar J.

2015-01-01

A three-dimensional finite-difference model for part of the Mississippi River Valley alluvial aquifer in the Cache Critical Groundwater Area of eastern Arkansas was constructed to simulate potential future conditions of groundwater flow. The objectives of this study were to test different pilot point distributions to find reasonable estimates of aquifer properties for the alluvial aquifer, to simulate flux from rivers, and to demonstrate how changes in pumping rates for different scenarios affect areas of long-term water-level declines over time. The model was calibrated using the parameter estimation code. Additional calibration was achieved using pilot points with regularization and singular value decomposition. Pilot point parameter values were estimated at a number of discrete locations in the study area to obtain reasonable estimates of aquifer properties. Nine pumping scenarios for the years 2011 to 2020 were tested and compared to the simulated water-level heads from 2010. Hydraulic conductivity values from pilot point calibration ranged between 42 and 173 m/d. Specific yield values ranged between 0.19 and 0.337. Recharge rates ranged between 0.00009 and 0.0006 m/d. The model was calibrated using 2,322 hydraulic head measurements for the years 2000 to 2010 from 150 observation wells located in the study area. For all scenarios, the volume of water depleted ranged between 5.7 and 23.3 percent, except in Scenario 2 (minimum pumping rates), in which the volume increased by 2.5 percent.

Critical adsorption profiles around a sphere and a cylinder in a fluid at criticality: Local functional theory

NASA Astrophysics Data System (ADS)

Yabunaka, Shunsuke; Onuki, Akira

2017-09-01

We study universal critical adsorption on a solid sphere and a solid cylinder in a fluid at bulk criticality, where preferential adsorption occurs. We use a local functional theory proposed by Fisher et al. [M. E. Fisher and P. G. de Gennes, C. R. Acad. Sci. Paris Ser. B 287, 207 (1978); M. E. Fisher and H. Au-Yang, Physica A 101, 255 (1980), 10.1016/0378-4371(80)90112-0]. We calculate the mean order parameter profile ψ (r ) , where r is the distance from the sphere center and the cylinder axis, respectively. The resultant differential equation for ψ (r ) is solved exactly around a sphere and numerically around a cylinder. A strong adsorption regime is realized except for very small surface field h1, where the surface order parameter ψ (a ) is determined by h1 and is independent of the radius a . If r considerably exceeds a , ψ (r ) decays as r-(1 +η ) for a sphere and r-(1 +η )/2 for a cylinder in three dimensions, where η is the critical exponent in the order parameter correlation at bulk criticality.

Turbulent mixing of a critical fluid: The non-perturbative renormalization

NASA Astrophysics Data System (ADS)

Hnatič, M.; Kalagov, G.; Nalimov, M.

2018-01-01

Non-perturbative Renormalization Group (NPRG) technique is applied to a stochastical model of a non-conserved scalar order parameter near its critical point, subject to turbulent advection. The compressible advecting flow is modeled by a random Gaussian velocity field with zero mean and correlation function 〈υjυi 〉 ∼ (Pji⊥ + αPji∥) /k d + ζ. Depending on the relations between the parameters ζ, α and the space dimensionality d, the model reveals several types of scaling regimes. Some of them are well known (model A of equilibrium critical dynamics and linear passive scalar field advected by a random turbulent flow), but there is a new nonequilibrium regime (universality class) associated with new nontrivial fixed points of the renormalization group equations. We have obtained the phase diagram (d, ζ) of possible scaling regimes in the system. The physical point d = 3, ζ = 4 / 3 corresponding to three-dimensional fully developed Kolmogorov's turbulence, where critical fluctuations are irrelevant, is stable for α ≲ 2.26. Otherwise, in the case of "strong compressibility" α ≳ 2.26, the critical fluctuations of the order parameter become relevant for three-dimensional turbulence. Estimations of critical exponents for each scaling regime are presented.

The strength of plants: theory and experimental methods to measure the mechanical properties of stems.

PubMed

Shah, Darshil U; Reynolds, Thomas P S; Ramage, Michael H

2017-07-20

From the stems of agricultural crops to the structural trunks of trees, studying the mechanical behaviour of plant stems is critical for both commerce and science. Plant scientists are also increasingly relying on mechanical test data for plant phenotyping. Yet there are neither standardized methods nor systematic reviews of current methods for the testing of herbaceous stems. We discuss the architecture of plant stems and highlight important micro- and macrostructural parameters that need to be controlled and accounted for when designing test methodologies, or that need to be understood in order to explain observed mechanical behaviour. Then, we critically evaluate various methods to test structural properties of stems, including flexural bending (two-, three-, and four-point bending) and axial loading (tensile, compressive, and buckling) tests. Recommendations are made on best practices. This review is relevant to fundamental studies exploring plant biomechanics, mechanical phenotyping of plants, and the determinants of mechanical properties in cell walls, as well as to application-focused studies, such as in agro-breeding and forest management projects, aiming to understand deformation processes of stem structures. The methods explored here can also be extended to other elongated, rod-shaped organs (e.g. petioles, midribs, and even roots). © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Evaluation of a steady-state test of foam stability

NASA Astrophysics Data System (ADS)

Hutzler, Stefan; Lösch, Dörte; Carey, Enda; Weaire, Denis; Hloucha, Matthias; Stubenrauch, Cosima

2011-02-01

We have evaluated a steady-state test of foam stability, based on the steady-state height of a foam produced by a constant velocity of gas flow. This test is mentioned in the book by Bikerman [Foams, Springer, Berlin, 1973] and an elementary theory was developed for it by Verbist et al. [J. Phys. Condens. Matter 8 (1996) p. 3715]. For the study, we used an aqueous solution of the cationic surfactant dodecyl trimethylammonium bromide, C12TAB, at a concentration of two times the critical micelle concentration (2 cmc). During foam generation, bubbles collapse at the top of the column which, in turn, eventually counterbalances the rate of bubble production at the bottom. The resulting balance can be described mathematically by an appropriate solution of the foam drainage equation under specified boundary conditions. Our experimental findings are in agreement with the theoretical predictions of a diverging foam height at a critical gas velocity and a finite foam height in the limit of zero velocity. We identify a critical liquid fraction below which a foam is unstable as an important parameter for characterizing foam stability. Furthermore, we deduce an effective viscosity of the liquid which flows through the foam. Currently unexplained are two experimental observations, namely sudden changes of the steady-state foam height in experiments that run over several hours and a reduction in foam height once an overflow of the foam from the containing vessel has occurred.

Prediction of New-Onset and Recurrent Atrial Fibrillation by Complete Blood Count Tests: A Comprehensive Systematic Review with Meta-Analysis

PubMed Central

Weymann, Alexander; Ali-Hasan-Al-Saegh, Sadeq; Sabashnikov, Anton; Popov, Aron-Frederik; Mirhosseini, Seyed Jalil; Liu, Tong; Lotfaliani, Mohammadreza; de Oliveira Sá, Michel Pompeu Barros; Baker, William L.; Yavuz, Senol; Zeriouh, Mohamed; Jang, Jae-Sik; Dehghan, Hamidreza; Meng, Lei; Testa, Luca; D’Ascenzo, Fabrizio; Benedetto, Umberto; Tse, Gary; Nombela-Franco, Luis; Dohmen, Pascal M.; Deshmukh, Abhishek J.; Linde, Cecilia; Biondi-Zoccai, Giuseppe; Stone, Gregg W.; Calkins, Hugh

2017-01-01

Background Atrial fibrillation (AF) is one of the most critical and frequent arrhythmias precipitating morbidities and mortalities. The complete blood count (CBC) test is an important blood test in clinical practice and is routinely used in the workup of cardiovascular diseases. This systematic review with meta-analysis aimed to determine the strength of evidence for evaluating the association of hematological parameters in the CBC test with new-onset and recurrent AF. Material/Methods We conducted a meta-analysis of observational studies evaluating hematologic parameters in patients with new-onset AF and recurrent AF. A comprehensive subgroup analysis was performed to explore potential sources of heterogeneity. Results The literature search of all major databases retrieved 2150 studies. After screening, 70 studies were analyzed in the meta-analysis on new-onset AF and 23 studies on recurrent AF. Pooled analysis on new-onset AF showed platelet count (PC) (weighted mean difference (WMD)=WMD of −26.39×109/L and p<0.001), mean platelet volume (MPV) (WMD=0.42 FL and p<0.001), white blood cell (WBC) (WMD=−0.005×109/L and p=0.83), neutrophil to lymphocyte ratio (NLR) (WMD=0.89 and p<0.001), and red blood cell distribution width (RDW) (WMD=0.61% and p<0.001) as associated factors. Pooled analysis on recurrent AF revealed PC (WMD=−2.71×109/L and p=0.59), WBC (WMD=0.20×109/L (95% CI: 0.08 to 0.32; p=0.002), NLR (WMD=0.37 and p<0.001), and RDW (WMD=0.28% and p<0.001). Conclusions Hematological parameters have significant ability to predict occurrence and recurrence of AF. Therefore, emphasizing the potential predictive role of hematological parameters for new-onset and recurrent AF, we recommend adding the CBC test to the diagnostic modalities of AF in clinical practice. PMID:28496093

Prediction of New-Onset and Recurrent Atrial Fibrillation by Complete Blood Count Tests: A Comprehensive Systematic Review with Meta-Analysis.

PubMed

Weymann, Alexander; Ali-Hasan-Al-Saegh, Sadeq; Sabashnikov, Anton; Popov, Aron-Frederik; Mirhosseini, Seyed Jalil; Liu, Tong; Lotfaliani, Mohammadreza; Sá, Michel Pompeu Barros de Oliveira; Baker, William L L; Yavuz, Senol; Zeriouh, Mohamed; Jang, Jae-Sik; Dehghan, Hamidreza; Meng, Lei; Testa, Luca; D'Ascenzo, Fabrizio; Benedetto, Umberto; Tse, Gary; Nombela-Franco, Luis; Dohmen, Pascal M; Deshmukh, Abhishek J; Linde, Cecilia; Biondi-Zoccai, Giuseppe; Stone, Gregg W; Calkins, Hugh; Surgery And Cardiology-Group Imcsc-Group, Integrated Meta-Analysis Of Cardiac

2017-05-12

BACKGROUND Atrial fibrillation (AF) is one of the most critical and frequent arrhythmias precipitating morbidities and mortalities. The complete blood count (CBC) test is an important blood test in clinical practice and is routinely used in the workup of cardiovascular diseases. This systematic review with meta-analysis aimed to determine the strength of evidence for evaluating the association of hematological parameters in the CBC test with new-onset and recurrent AF. MATERIAL AND METHODS We conducted a meta-analysis of observational studies evaluating hematologic parameters in patients with new-onset AF and recurrent AF. A comprehensive subgroup analysis was performed to explore potential sources of heterogeneity. RESULTS The literature search of all major databases retrieved 2150 studies. After screening, 70 studies were analyzed in the meta-analysis on new-onset AF and 23 studies on recurrent AF. Pooled analysis on new-onset AF showed platelet count (PC) (weighted mean difference (WMD)=WMD of -26.39×10^9/L and p<0.001), mean platelet volume (MPV) (WMD=0.42 FL and p<0.001), white blood cell (WBC) (WMD=-0.005×10^9/L and p=0.83), neutrophil to lymphocyte ratio (NLR) (WMD=0.89 and p<0.001), and red blood cell distribution width (RDW) (WMD=0.61% and p<0.001) as associated factors. Pooled analysis on recurrent AF revealed PC (WMD=-2.71×109/L and p=0.59), WBC (WMD=0.20×10^9/L (95% CI: 0.08 to 0.32; p=0.002), NLR (WMD=0.37 and p<0.001), and RDW (WMD=0.28% and p<0.001). CONCLUSIONS Hematological parameters have significant ability to predict occurrence and recurrence of AF. Therefore, emphasizing the potential predictive role of hematological parameters for new-onset and recurrent AF, we recommend adding the CBC test to the diagnostic modalities of AF in clinical practice.

Topology versus Anderson localization: Nonperturbative solutions in one dimension

NASA Astrophysics Data System (ADS)

Altland, Alexander; Bagrets, Dmitry; Kamenev, Alex

2015-02-01

We present an analytic theory of quantum criticality in quasi-one-dimensional topological Anderson insulators. We describe these systems in terms of two parameters (g ,χ ) representing localization and topological properties, respectively. Certain critical values of χ (half-integer for Z classes, or zero for Z2 classes) define phase boundaries between distinct topological sectors. Upon increasing system size, the two parameters exhibit flow similar to the celebrated two-parameter flow of the integer quantum Hall insulator. However, unlike the quantum Hall system, an exact analytical description of the entire phase diagram can be given in terms of the transfer-matrix solution of corresponding supersymmetric nonlinear sigma models. In Z2 classes we uncover a hidden supersymmetry, present at the quantum critical point.

Error analysis in inverse scatterometry. I. Modeling.

PubMed

Al-Assaad, Rayan M; Byrne, Dale M

2007-02-01

Scatterometry is an optical technique that has been studied and tested in recent years in semiconductor fabrication metrology for critical dimensions. Previous work presented an iterative linearized method to retrieve surface-relief profile parameters from reflectance measurements upon diffraction. With the iterative linear solution model in this work, rigorous models are developed to represent the random and deterministic or offset errors in scatterometric measurements. The propagation of different types of error from the measurement data to the profile parameter estimates is then presented. The improvement in solution accuracies is then demonstrated with theoretical and experimental data by adjusting for the offset errors. In a companion paper (in process) an improved optimization method is presented to account for unknown offset errors in the measurements based on the offset error model.

Indocyanine green kinetics to assess liver function: Ready for a clinical dynamic assessment in major liver surgery?

PubMed Central

De Gasperi, Andrea; Mazza, Ernestina; Prosperi, Manlio

2016-01-01

Indocyanine green (ICG) kinetics (PDR/R15) used to quantitatively assess hepatic function in the perioperative period of major resective surgery and liver transplantation have been the object of an extensive, updated and critical review. New, non invasive bedside monitors (pulse dye densitometry technology) make this opportunity widely available in clinical practice. After having reviewed basic concepts of hepatic clearance, we analysed the most common indications ICG kinetic parameters have nowadays in clinical practice, focusing in particular on the diagnostic and prognostic role of PDR and R15 in the perioperative period of major liver surgery and liver transplantation. As recently pointed out, even if of extreme interest, ICG clearance parameters have still some limitations, to be considered when using these tests. PMID:26981173

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

Çataltepe, Ö. Aslan, E-mail: ozdenaslan@yahoo.com, E-mail: ozden.aslan@gedik.edu.tr; Özdemir, Z. Güven, E-mail: zguvenozdemir@yahoo.com; Onbaşlı, Ü., E-mail: phonon@doruk.net.tr

In this work, the effect of oxygen doping on the critical parameters of the mercury based superconducting sample such as critical transition temperature, T{sub c}, critical magnetic field, H{sub c}, critical current density, J{sub c}, has been investigated by the magnetic susceptibility versus temperature (χ-T) and magnetization versus applied magnetic field (M-H) measurements and, X-Ray Diffraction (XRD) patterns. It has been observed that regardless of the oxygen doping concentration, the mercury cuprate system possesses two intrinsic superconducting phases together, HgBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 8+x} and HgBa{sub 2}CaCu{sub 2}O{sub 6+x}. However, the highest T{sub c} has been determined for the optimummore » oxygen doped sample. Moreover, it has been revealed that superconducting properties, crystal lattice parameters, coherent lengths, ξ{sub ab}, ξ{sub c} and the anisotropy factor γ etc. are very sensitive to oxygen doping procedures. Hence, the results presented this work enables one to obtain the mercury based superconductor with the most desirable criticals and other parameters for theoretical and technological applications by arranging the oxygen doping concentration.« less

Evolution of mammographic image quality in the state of Rio de Janeiro*

PubMed Central

Villar, Vanessa Cristina Felippe Lopes; Seta, Marismary Horsth De; de Andrade, Carla Lourenço Tavares; Delamarque, Elizabete Vianna; de Azevedo, Ana Cecília Pedrosa

2015-01-01

Objective To evaluate the evolution of mammographic image quality in the state of Rio de Janeiro on the basis of parameters measured and analyzed during health surveillance inspections in the period from 2006 to 2011. Materials and Methods Descriptive study analyzing parameters connected with imaging quality of 52 mammography apparatuses inspected at least twice with a one-year interval. Results Amongst the 16 analyzed parameters, 7 presented more than 70% of conformity, namely: compression paddle pressure intensity (85.1%), films development (72.7%), film response (72.7%), low contrast fine detail (92.2%), tumor mass visualization (76.5%), absence of image artifacts (94.1%), mammography-specific developers availability (88.2%). On the other hand, relevant parameters were below 50% conformity, namely: monthly image quality control testing (28.8%) and high contrast details with respect to microcalcifications visualization (47.1%). Conclusion The analysis revealed critical situations in terms of compliance with the health surveillance standards. Priority should be given to those mammography apparatuses that remained non-compliant at the second inspection performed within the one-year interval. PMID:25987749

Investigation into the use of microwave sensors to monitor particulate manufacturing processes

NASA Astrophysics Data System (ADS)

Austin, John Samuel, III

Knowledge of a material's properties in-line during manufacture is of critical importance to many industries, including the pharmaceutical industry, and can be used for either process or quality control. Different microwave sensor configurations were tested to determine both the moisture content and the bulk density in pharmaceutical powders during processing on-line. Although these parameters can significantly affect a material's flowability, compressibility, and cohesivity, in the presence of blends, the picture is incomplete. Due to the ease with which particulate blends tend to segregate, blend uniformity and chemical composition are two critical parameters in nearly all solids manufacturing industries. The prevailing wisdom has been that microwave sensors are not capable of or sensitive enough to measure the relative concentrations of components in a blend. Consequently, it is common to turn to near infrared sensing to determine material composition on-line. In this study, a novel microwave sensor was designed and utilized to determine, separately, the concentrations of different components in a blend of pharmaceutical powders. This custom microwave sensor was shown to have comparable accuracy to the state-of-the-art for both chemical composition and moisture content determination.

Periodic flow hydrodynamic resistance parameters for woven screen matrices at cryogenic temperatures

NASA Astrophysics Data System (ADS)

Perrella, M. D.; Ghiaasiaan, S. M.

2017-12-01

The regenerator is a critical component in all Stirling and Pulse Tube cryocoolers. It generally consists of a microporous metallic or rare-earth filler material contained within a cylindrical shell. Accurate modelling of the hydrodynamic and thermal behaviour of different regenerator materials is crucial to the successful design of cryogenic systems. Previous investigations have used experimental measurements at steady and periodic flow conditions in conjunction with pore-level CFD analysis to determine the pertinent hydrodynamic parameters, namely the Darcy permeability and Forchheimer coefficients. Due to the difficulty associated with experimental measurement at cryogenic temperatures, past investigations were mostly performed at ambient conditions and their results are assumed to be appropriate for cryogenic temperatures. In this study, a regenerator filled with woven screen matrices such as 400 mesh T316 stainless steel were assembled and experimentally tested under periodic helium flow at cryogenic temperatures. The mass flow and pressure drop data were analysed using CFD to determine the dimensionless friction factor, Darcy Permeability and Forchheimer coefficients. These results are compared to previous investigations at ambient temperature conditions, and the relevance of room-temperature models and correlations to cryogenic temperatures is critically assessed.

Thermo-electric analysis of the interconnection of the LHC main superconducting bus bars

NASA Astrophysics Data System (ADS)

Granieri, P. P.; Breschi, M.; Casali, M.; Bottura, L.; Siemko, A.

2013-01-01

Spurred by the question of the maximum allowable energy for the operation of the Large Hadron Collider (LHC), we have progressed in the understanding of the thermo-electric behavior of the 13 kA superconducting bus bars interconnecting its main magnets. A deep insight of the underlying mechanisms is required to ensure the protection of the accelerator against undesired effects of resistive transitions. This is especially important in case of defective interconnections which can jeopardize the operation of the whole LHC. In this paper we present a numerical model of the interconnections between the main dipole and quadrupole magnets, validated against experimental tests of an interconnection sample with a purposely built-in defect. We consider defective interconnections featuring a lack of bonding among the superconducting cables and the copper stabilizer components, such as those that could be present in the machine. We evaluate the critical defect length limiting the maximum allowable current for powering the magnets. We determine the dependence of the critical defect length on different parameters as the heat transfer towards the cooling helium bath, the quality of manufacturing, the operating conditions and the protection system parameters, and discuss the relevant mechanisms.

A Simple Field Guides to Identify Fire Effects on Soils

NASA Astrophysics Data System (ADS)

Robichaud, Peter

2016-04-01

Following wildfires post fire assessment personnel or teams assess immediate post-fire watershed conditions. These assessment teams must determine threats from flooding, soil erosion, and instability in a relatively short time period. Various tools and guides have been developed to assist in that process. A soil burn severity map is often the first step in the rapid assessment process. It enables BAER teams to prioritize field reviews and locate burned areas that may pose a risk to critical values within or downstream of the burned area. Five field parameters are easily determined in the field 1) remaining ground cover and characteristic, 2) ash color and depth, 3) soil structure, 4) fine roots, and 5) soil water repellency. All parameters are visual identified except water repellency which can be determined by the Water Drop Penetration Time (WDPT) test or Mini-Disk Infiltrometer (MDI). Often times the MDI test takes less time, is less subjective, and provides a relative infiltration rate which the WDPT test does not. The MDI test results are often put into "degree of soil water repellency" categories (strong, weak, and none). These field procedures that indicate the fire effects on the soil conditions help assessment teams consistently interpret, field validate and map soil burn severity.

Thermal Shock Resistance of Si3N4/h -BN Composites Prepared via Catalytic Reaction-Bonding Route

NASA Astrophysics Data System (ADS)

Yang, Wanli; Peng, Zhigang; Dai, Lina; Shi, Zhongqi; Jin, Zhihao

2017-09-01

Si3N4/h-BN ceramic matrix composites were prepared via a catalytic reaction-bonding route by using ZrO2 as nitridation catalyst, and the water quenching (fast cooling) and molten aluminum quenching tests (fast heating) were carried out to evaluate the thermal shock resistance of the composites. The results showed that the thermal shock resistance was improved obviously with the increase in h-BN content, and the critical thermal shock temperature difference (Δ T c) reaches as high as 780 °C when the h-BN content was 30 wt.%. The improvement of thermal shock resistance of the composites was mainly due to the crack tending to quasi static propagating at weak bonding interface between Si3N4 and h-BN with the increase in h-BN content. For the molten aluminum quenching test, the residual strength showed no obvious decrease compared with water quenching test, which could be caused by the mild stress condition on the surface. In addition, a calculated parameter, volumetric crack density ( N f), was presented to quantitative evaluating the thermal shock resistance of the composites in contrast to the conventional R parameter.

[Decision analysis--a novel approach for calculating the cost-efficiency of medical tests].

PubMed

Becher, J

2008-09-01

Before issuing an insurance policy (e.g. life, disability, critical illness), insurers will usually carry out a medical risk assessment in order to prevent adverse selection. Often, the health questions in the application form will not be sufficient for this purpose since most applicants are not well-versed in medical science and terminology. If the insurer needs additional medical information such as a private medical attendant's report or current laboratory tests, however, costs will be incurred, which usually have to be paid by the insurer. What is the minimum sum insured which makes it worthwhile for the insurer to conduct certain screening tests, for example? Both the costs of medical screening and the associated savings are difficult to measure and involve a variety of different factors. Moreover, most parameters can only be estimated with limited accuracy. Therefore, we have developed a new calculation model using a decision-analysis approach. The new model makes it possible to analyse complex situations while taking into account the uncertainty of parameter estimation. Our findings show that in Germany, for instance, current sum thresholds for older applicants could in many cases be lowered and would still be cost-effective.

Liquid Nitrogen Removal of Critical Aerospace Materials

NASA Technical Reports Server (NTRS)

Noah, Donald E.; Merrick, Jason; Hayes, Paul W.

2005-01-01

Identification of innovative solutions to unique materials problems is an every-day quest for members of the aerospace community. Finding a technique that will minimize costs, maximize throughput, and generate quality results is always the target. United Space Alliance Materials Engineers recently conducted such a search in their drive to return the Space Shuttle fleet to operational status. The removal of high performance thermal coatings from solid rocket motors represents a formidable task during post flight disassembly on reusable expended hardware. The removal of these coatings from unfired motors increases the complexity and safety requirements while reducing the available facilities and approved processes. A temporary solution to this problem was identified, tested and approved during the Solid Rocket Booster (SRB) return to flight activities. Utilization of ultra high-pressure liquid nitrogen (LN2) to strip the protective coating from assembled space shuttle hardware marked the first such use of the technology in the aerospace industry. This process provides a configurable stream of liquid nitrogen (LN2) at pressures of up to 55,000 psig. The performance of a one-time certification for the removal of thermal ablatives from SRB hardware involved extensive testing to ensure adequate material removal without causing undesirable damage to the residual materials or aluminum substrates. Testing to establish appropriate process parameters such as flow, temperature and pressures of the liquid nitrogen stream provided an initial benchmark for process testing. Equipped with these initial parameters engineers were then able to establish more detailed test criteria that set the process limits. Quantifying the potential for aluminum hardware damage represented the greatest hurdle for satisfying engineers as to the safety of this process. Extensive testing for aluminum erosion, surface profiling, and substrate weight loss was performed. This successful project clearly demonstrated that the liquid nitrogen jet possesses unique strengths that align remarkably well with the unusual challenges that space hardware and missile manufacturers face on a regular basis. Performance of this task within the confines of a critical manufacturing facility marks a milestone in advanced processing.

The Finite-Size Scaling Relation for the Order-Parameter Probability Distribution of the Six-Dimensional Ising Model

NASA Astrophysics Data System (ADS)

Merdan, Ziya; Karakuş, Özlem

2016-11-01

The six dimensional Ising model with nearest-neighbor pair interactions has been simulated and verified numerically on the Creutz Cellular Automaton by using five bit demons near the infinite-lattice critical temperature with the linear dimensions L=4,6,8,10. The order parameter probability distribution for six dimensional Ising model has been calculated at the critical temperature. The constants of the analytical function have been estimated by fitting to probability function obtained numerically at the finite size critical point.

Zero-G experimental validation of a robotics-based inertia identification algorithm

NASA Astrophysics Data System (ADS)

Bruggemann, Jeremy J.; Ferrel, Ivann; Martinez, Gerardo; Xie, Pu; Ma, Ou

2010-04-01

The need to efficiently identify the changing inertial properties of on-orbit spacecraft is becoming more critical as satellite on-orbit services, such as refueling and repairing, become increasingly aggressive and complex. This need stems from the fact that a spacecraft's control system relies on the knowledge of the spacecraft's inertia parameters. However, the inertia parameters may change during flight for reasons such as fuel usage, payload deployment or retrieval, and docking/capturing operations. New Mexico State University's Dynamics, Controls, and Robotics Research Group has proposed a robotics-based method of identifying unknown spacecraft inertia properties1. Previous methods require firing known thrusts then measuring the thrust, and the velocity and acceleration changes. The new method utilizes the concept of momentum conservation, while employing a robotic device powered by renewable energy to excite the state of the satellite. Thus, it requires no fuel usage or force and acceleration measurements. The method has been well studied in theory and demonstrated by simulation. However its experimental validation is challenging because a 6- degree-of-freedom motion in a zero-gravity condition is required. This paper presents an on-going effort to test the inertia identification method onboard the NASA zero-G aircraft. The design and capability of the test unit will be discussed in addition to the flight data. This paper also introduces the design and development of an airbearing based test used to partially validate the method, in addition to the approach used to obtain reference value for the test system's inertia parameters that can be used for comparison with the algorithm results.

Phase diagram and universality of the Lennard-Jones gas-liquid system.

PubMed

Watanabe, Hiroshi; Ito, Nobuyasu; Hu, Chin-Kun

2012-05-28

The gas-liquid phase transition of the three-dimensional Lennard-Jones particles system is studied by molecular dynamics simulations. The gas and liquid densities in the coexisting state are determined with high accuracy. The critical point is determined by the block density analysis of the Binder parameter with the aid of the law of rectilinear diameter. From the critical behavior of the gas-liquid coexisting density, the critical exponent of the order parameter is estimated to be β = 0.3285(7). Surface tension is estimated from interface broadening behavior due to capillary waves. From the critical behavior of the surface tension, the critical exponent of the correlation length is estimated to be ν = 0.63(4). The obtained values of β and ν are consistent with those of the Ising universality class.

Odd-Parity Superconductivity near an Inversion Breaking Quantum Critical Point in One Dimension

DOE PAGES

Ruhman, Jonathan; Kozii, Vladyslav; Fu, Liang

2017-05-31

In this work, we study how an inversion-breaking quantum critical point affects the ground state of a one-dimensional electronic liquid with repulsive interaction and spin-orbit coupling. We find that regardless of the interaction strength, the critical fluctuations always lead to a gap in the electronic spin sector. The origin of the gap is a two-particle backscattering process, which becomes relevant due to renormalization of the Luttinger parameter near the critical point. The resulting spin-gapped state is topological and can be considered as a one-dimensional version of a spin-triplet superconductor. Interestingly, in the case of a ferromagnetic critical point, the Luttingermore » parameter is renormalized in the opposite manner, such that the system remains nonsuperconducting.« less

New Comment on Gibbs Density Surface of Fluid Argon: Revised Critical Parameters, L. V. Woodcock, Int. J. Thermophys. (2014) 35, 1770-1784

NASA Astrophysics Data System (ADS)

Umirzakov, I. H.

2018-01-01

The author comments on an article by Woodcock (Int J Thermophys 35:1770-1784, 2014), who investigates the idea of a critical line instead of a single critical point using the example of argon. In the introduction, Woodcock states that "The Van der Waals critical point does not comply with the Gibbs phase rule. Its existence is based upon a hypothesis rather than a thermodynamic definition". The present comment is a response to the statement by Woodcock. The comment mathematically demonstrates that a critical point is not only based on a hypothesis that is used to define values of two parameters of the Van der Waals equation of state. Instead, the author argues that a critical point is a direct consequence of the thermodynamic phase equilibrium conditions resulting in a single critical point. It is shown that the thermodynamic conditions result in the first and second partial derivatives of pressure with respect to volume at constant temperature at a critical point equal to zero which are usual conditions of an existence of a critical point.

Challenges in characterization of photonic crystal fibers

NASA Astrophysics Data System (ADS)

Borzycki, Krzysztof; Kobelke, Jens; Mergo, Pawel; Schuster, Kay

2011-05-01

We present experience with photonic crystal fiber (PCF) characterization during COST Action 299, focusing on phenomena causing errors and ways to mitigate them. PCFs developed at IPHT Jena (Germany; UMCS Lublin, Poland), designed for single mode operation were coupled to test instruments by fusion splicing to intermediate lengths of telecom single mode fibers (SMF). PCF samples were short (0.5-100 m), with 20-70 dB/km attenuation at 1310 nm and 1550 nm. Optical Time Domain Reflectometer (OTDR) was best for measuring loss as most PCFs produced strong backscattering, while variable splice losses and difficulties with PCF cleaving for optical power measurements made cutback and insertion loss measurements inaccurate. Experience with PCF handling and cleaving is also reviewed. Quality of splices to fiber under test was critical. Excitation of higher order modes produced strong "noise" during measurements of polarization parameters like PMD or PDL. Multimode propagation and vibration-induced interference precluded testing of fine dependence of PMD on temperature or strain, causing random variations comparable to true changes of PMD. OTDR measurements were not affected, but testing of short fiber sections with very different backscattering intensities puts special demands on instrument performance. Temperature testing of liquid-infiltrated PCF was time-consuming, as settling of parameters after temperature change took up to 40 minutes. PCFs were fragile, breaking below 2% linear expansion, sometimes in unusual way when twisted.

Hybrid phase transition into an absorbing state: Percolation and avalanches

NASA Astrophysics Data System (ADS)

Lee, Deokjae; Choi, S.; Stippinger, M.; Kertész, J.; Kahng, B.

2016-04-01

Interdependent networks are more fragile under random attacks than simplex networks, because interlayer dependencies lead to cascading failures and finally to a sudden collapse. This is a hybrid phase transition (HPT), meaning that at the transition point the order parameter has a jump but there are also critical phenomena related to it. Here we study these phenomena on the Erdős-Rényi and the two-dimensional interdependent networks and show that the hybrid percolation transition exhibits two kinds of critical behaviors: divergence of the fluctuations of the order parameter and power-law size distribution of finite avalanches at a transition point. At the transition point global or "infinite" avalanches occur, while the finite ones have a power law size distribution; thus the avalanche statistics also has the nature of a HPT. The exponent βm of the order parameter is 1 /2 under general conditions, while the value of the exponent γm characterizing the fluctuations of the order parameter depends on the system. The critical behavior of the finite avalanches can be described by another set of exponents, βa and γa. These two critical behaviors are coupled by a scaling law: 1 -βm=γa .

Polydisperse sphere packing in high dimensions, a search for an upper critical dimension

NASA Astrophysics Data System (ADS)

Morse, Peter; Clusel, Maxime; Corwin, Eric

2012-02-01

The recently introduced granocentric model for polydisperse sphere packings has been shown to be in good agreement with experimental and simulational data in two and three dimensions. This model relies on two effective parameters that have to be estimated from experimental/simulational results. The non-trivial values obtained allow the model to take into account the essential effects of correlations in the packing. Once these parameters are set, the model provides a full statistical description of a sphere packing for a given polydispersity. We investigate the evolution of these effective parameters with the spatial dimension to see if, in analogy with the upper critical dimension in critical phenomena, there exists a dimension above which correlations become irrelevant and the model parameters can be fixed a priori as a function of polydispersity. This would turn the model into a proper theory of polydisperse sphere packings at that upper critical dimension. We perform infinite temperature quench simulations of frictionless polydisperse sphere packings in dimensions 2-8 using a parallel algorithm implemented on a GPGPU. We analyze the resulting packings by implementing an algorithm to calculate the additively weighted Voronoi diagram in arbitrary dimension.

Gambling with Superconducting Fluctuations

NASA Astrophysics Data System (ADS)

Foltyn, Marek; Zgirski, Maciej

2015-08-01

Josephson junctions and superconducting nanowires, when biased close to superconducting critical current, can switch to a nonzero voltage state by thermal or quantum fluctuations. The process is understood as an escape of a Brownian particle from a metastable state. Since this effect is fully stochastic, we propose to use it for generating random numbers. We present protocol for obtaining random numbers and test the experimentally harvested data for their fidelity. Our work is prerequisite for using the Josephson junction as a tool for stochastic (probabilistic) determination of physical parameters such as magnetic flux, temperature, and current.

Fourier-transform and global contrast interferometer alignment methods

DOEpatents

Goldberg, Kenneth A.

2001-01-01

Interferometric methods are presented to facilitate alignment of image-plane components within an interferometer and for the magnified viewing of interferometer masks in situ. Fourier-transforms are performed on intensity patterns that are detected with the interferometer and are used to calculate pseudo-images of the electric field in the image plane of the test optic where the critical alignment of various components is being performed. Fine alignment is aided by the introduction and optimization of a global contrast parameter that is easily calculated from the Fourier-transform.

Boundary cooled rocket engines for space storable propellants

NASA Technical Reports Server (NTRS)

Kesselring, R. C.; Mcfarland, B. L.; Knight, R. M.; Gurnitz, R. N.

1972-01-01

An evaluation of an existing analytical heat transfer model was made to develop the technology of boundary film/conduction cooled rocket thrust chambers to the space storable propellant combination oxygen difluoride/diborane. Critical design parameters were identified and their importance determined. Test reduction methods were developed to enable data obtained from short duration hot firings with a thin walled (calorimeter) chamber to be used quantitatively evaluate the heat absorbing capability of the vapor film. The modification of the existing like-doublet injector was based on the results obtained from the calorimeter firings.

Weyl holographic superconductor in the Lifshitz black hole background

NASA Astrophysics Data System (ADS)

Mansoori, S. A. Hosseini; Mirza, B.; Mokhtari, A.; Dezaki, F. Lalehgani; Sherkatghanad, Z.

2016-07-01

We investigate analytically the properties of the Weyl holographic superconductor in the Lifshitz black hole background. We find that the critical temperature of the Weyl superconductor decreases with increasing Lifshitz dynamical exponent, z, indicating that condensation becomes difficult. In addition, it is found that the critical temperature and condensation operator could be affected by applying the Weyl coupling, γ. Moreover, we compute the critical magnetic field and investigate its dependence on the parameters γ and z. Finally, we show numerically that the Weyl coupling parameter γ and the Lifshitz dynamical exponent z together control the size and strength of the conductivity peak and the ratio of gap frequency over critical temperature ω g /T c .

Theory of Metastable State Relaxation for Non-Critical Binary Systems with Non-Conserved Order Parameter

NASA Technical Reports Server (NTRS)

Izmailov, Alexander; Myerson, Allan S.

1993-01-01

A new mathematical ansatz for a solution of the time-dependent Ginzburg-Landau non-linear partial differential equation is developed for non-critical systems such as non-critical binary solutions (solute + solvent) described by the non-conserved scalar order parameter. It is demonstrated that in such systems metastability initiates heterogeneous solute redistribution which results in formation of the non-equilibrium singly-periodic spatial solute structure. It is found how the time-dependent period of this structure evolves in time. In addition, the critical radius r(sub c) for solute embryo of the new solute rich phase together with the metastable state lifetime t(sub c) are determined analytically and analyzed.

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

Ruhman, Jonathan; Kozii, Vladyslav; Fu, Liang

In this work, we study how an inversion-breaking quantum critical point affects the ground state of a one-dimensional electronic liquid with repulsive interaction and spin-orbit coupling. We find that regardless of the interaction strength, the critical fluctuations always lead to a gap in the electronic spin sector. The origin of the gap is a two-particle backscattering process, which becomes relevant due to renormalization of the Luttinger parameter near the critical point. The resulting spin-gapped state is topological and can be considered as a one-dimensional version of a spin-triplet superconductor. Interestingly, in the case of a ferromagnetic critical point, the Luttingermore » parameter is renormalized in the opposite manner, such that the system remains nonsuperconducting.« less

Critical assessment of digital PCR for the detection and quantification of genetically modified organisms.

PubMed

Demeke, Tigst; Dobnik, David

2018-07-01

The number of genetically modified organisms (GMOs) on the market is steadily increasing. Because of regulation of cultivation and trade of GMOs in several countries, there is pressure for their accurate detection and quantification. Today, DNA-based approaches are more popular for this purpose than protein-based methods, and real-time quantitative PCR (qPCR) is still the gold standard in GMO analytics. However, digital PCR (dPCR) offers several advantages over qPCR, making this new technique appealing also for GMO analysis. This critical review focuses on the use of dPCR for the purpose of GMO quantification and addresses parameters which are important for achieving accurate and reliable results, such as the quality and purity of DNA and reaction optimization. Three critical factors are explored and discussed in more depth: correct classification of partitions as positive, correctly determined partition volume, and dilution factor. This review could serve as a guide for all laboratories implementing dPCR. Most of the parameters discussed are applicable to fields other than purely GMO testing. Graphical abstract There are generally three different options for absolute quantification of genetically modified organisms (GMOs) using digital PCR: droplet- or chamber-based and droplets in chambers. All have in common the distribution of reaction mixture into several partitions, which are all subjected to PCR and scored at the end-point as positive or negative. Based on these results GMO content can be calculated.

Estimation of Axial Fretting Fatigue Life at Elevated Temperatures Using Critical Distance Theory

NASA Astrophysics Data System (ADS)

Majzoobi, G. H.; Azhdarzadeh, P.

Fretting fatigue life is traditionally estimated by experiment. The objective of this work is to introduce a special approach for estimation of axial fretting fatigue life at elevated temperatures from plain fatigue test based on the critical distance theory. The method uses Fatemi-Socie parameter as a multiaxial criterion to compute the stress multiaxiality on focus path. This method considers only elastic behavior for materials, and two characteristic diagrams are obtained from plain fatigue tests on two U-shaped and V-shaped notched specimens. The results showed reasonable agreement between the predictions by the proposed method and the experiments for ambient temperature. For elevated temperatures, the results indicated that the predicted fretting fatigue life was considerably overestimated in the low cycle fatigue (LCF) regime and underestimated in the high cycle fatigue (HCF) region with respect to experimental measurements. The reason for such discrepancy is believed to be due to the complex behavior of AL 7075-T6, which exhibits at elevated temperatures because of the problems such as aging, oxidation and reduction of strength.

Acoustic emission analysis on tensile failure of steam-side oxide scales formed on T22 alloy superheater tubes

NASA Astrophysics Data System (ADS)

Huang, Jun-Lin; Zhou, Ke-Yi; Wang, Xin-Meng; Tu, Yi-You; Xu, Jian-Qun

2014-07-01

Failure of steam-side oxide scales on boiler tubes can seriously influence the safety of coal-fired power plants. Uniaxial tensile tests employing acoustic emission (AE) monitoring were performed, in this work, to investigate the failure behavior of steam-side oxide scales on T22 alloy boiler superheater tubes. The characteristic frequency spectra of the captured AE signals were obtained by performing fast Fourier transform. Three distinct peak frequency bands, 100-170, 175-250, and 280-390 kHz, encountered in different testing stages were identified in the frequency spectra, which were confirmed to, respectively, correspond to substrate plastic deformation, oxide vertical cracking, and oxide spalling with the aid of scanning electronic microscopy observations, and can thus be used for distinguishing different oxide failure mechanisms. Finally, the critical cracking strain of the oxide scale and the interfacial shear strength of the oxide/substrate interface were estimated, which are the critical parameters urgently desired for modeling the failure behavior of steam-side oxide scales on boiler tubes of coal-fired power plants.

Performance of the PEdiatric Logistic Organ Dysfunction-2 score in critically ill children requiring plasma transfusions.

PubMed

Karam, Oliver; Demaret, Pierre; Duhamel, Alain; Shefler, Alison; Spinella, Philip C; Stanworth, Simon J; Tucci, Marisa; Leteurtre, Stéphane

2016-12-01

Organ dysfunction scores, based on physiological parameters, have been created to describe organ failure. In a general pediatric intensive care unit (PICU) population, the PEdiatric Logistic Organ Dysfunction-2 score (PELOD-2) score had both a good discrimination and calibration, allowing to describe the clinical outcome of critically ill children throughout their stay. This score is increasingly used in clinical trials in specific subpopulation. Our objective was to assess the performance of the PELOD-2 score in a subpopulation of critically ill children requiring plasma transfusions. This was an ancillary study of a prospective observational study on plasma transfusions over a 6-week period, in 101 PICUs in 21 countries. All critically ill children who received at least one plasma transfusion during the observation period were included. PELOD-2 scores were measured on days 1, 2, 5, 8, and 12 after plasma transfusion. Performance of the score was assessed by the determination of the discrimination (area under the ROC curve: AUC) and the calibration (Hosmer-Lemeshow test). Four hundred and forty-three patients were enrolled in the study (median age and weight: 1 year and 9.1 kg, respectively). Observed mortality rate was 26.9 % (119/443). For PELOD-2 on day 1, the AUC was 0.76 (95 % CI 0.71-0.81) and the Hosmer-Lemeshow test was p = 0.76. The serial evaluation of the changes in the daily PELOD-2 scores from day 1 demonstrated a significant association with death, adjusted for the PELOD-2 score on day 1. In a subpopulation of critically ill children requiring plasma transfusion, the PELOD-2 score has a lower but acceptable discrimination than in an entire population. This score should therefore be used cautiously in this specific subpopulation.

Fem and Experimental Analysis of Thin-Walled Composite Elements Under Compression

NASA Astrophysics Data System (ADS)

Różyło, P.; Wysmulski, P.; Falkowicz, K.

2017-05-01

Thin-walled steel elements in the form of openwork columns with variable geometrical parameters of holes were studied. The samples of thin-walled composite columns were modelled numerically. They were subjected to axial compression to examine their behavior in the critical and post-critical state. The numerical models were articulately supported on the upper and lower edges of the cross-section of the profiles. The numerical analysis was conducted only with respect to the non-linear stability of the structure. The FEM analysis was performed until the material achieved its yield stress. This was done to force the loss of stability by the structures. The numerical analysis was performed using the ABAQUS® software. The numerical analysis was performed only for the elastic range to ensure the operating stability of the tested thin-walled structures.

Effect of notch depth of modified current collector on internal-short-circuit mitigation for lithium-ion battery

NASA Astrophysics Data System (ADS)

Wang, Meng; Noelle, Daniel J.; Shi, Yang; Le, Anh V.; Qiao, Yu

2018-01-01

Formation of internal short circuit (ISC) may result in catastrophic thermal runaway of lithium-ion battery (LIB). Among LIB cell components, direct contact between cathode and anode current collectors is most critical to the ISC behavior, yet is still relatively uninvestigated. In the current study, we analyze the effect of heterogeneity of current collector on the temperature increase of LIB cells subjected to mechanical abuse. The cathode current collector is modified by surface notches, so that it becomes effectively brittle and the ISC site can be isolated. Results from impact tests on LIB cells with modified current collectors suggest that their temperature increase can be negligible. The critical parameters include the failure strain and the failure work of modified current collector, both of which are related to the notch depth.

Bifurcation scenarios for bubbling transition.

PubMed

Zimin, Aleksey V; Hunt, Brian R; Ott, Edward

2003-01-01

Dynamical systems with chaos on an invariant submanifold can exhibit a type of behavior called bubbling, whereby a small random or fixed perturbation to the system induces intermittent bursting. The bifurcation to bubbling occurs when a periodic orbit embedded in the chaotic attractor in the invariant manifold becomes unstable to perturbations transverse to the invariant manifold. Generically the periodic orbit can become transversely unstable through a pitchfork, transcritical, period-doubling, or Hopf bifurcation. In this paper a unified treatment of the four types of bubbling bifurcation is presented. Conditions are obtained determining whether the transition to bubbling is soft or hard; that is, whether the maximum burst amplitude varies continuously or discontinuously with variation of the parameter through its critical value. For soft bubbling transitions, the scaling of the maximum burst amplitude with the parameter is derived. For both hard and soft transitions the scaling of the average interburst time with the bifurcation parameter is deduced. Both random (noise) and fixed (mismatch) perturbations are considered. Results of numerical experiments testing our theoretical predictions are presented.

Critically evaluating the theory and performance of Bayesian analysis of macroevolutionary mixtures

PubMed Central

Moore, Brian R.; Höhna, Sebastian; May, Michael R.; Rannala, Bruce; Huelsenbeck, John P.

2016-01-01

Bayesian analysis of macroevolutionary mixtures (BAMM) has recently taken the study of lineage diversification by storm. BAMM estimates the diversification-rate parameters (speciation and extinction) for every branch of a study phylogeny and infers the number and location of diversification-rate shifts across branches of a tree. Our evaluation of BAMM reveals two major theoretical errors: (i) the likelihood function (which estimates the model parameters from the data) is incorrect, and (ii) the compound Poisson process prior model (which describes the prior distribution of diversification-rate shifts across branches) is incoherent. Using simulation, we demonstrate that these theoretical issues cause statistical pathologies; posterior estimates of the number of diversification-rate shifts are strongly influenced by the assumed prior, and estimates of diversification-rate parameters are unreliable. Moreover, the inability to correctly compute the likelihood or to correctly specify the prior for rate-variable trees precludes the use of Bayesian approaches for testing hypotheses regarding the number and location of diversification-rate shifts using BAMM. PMID:27512038

Evaluating an Online Resourcefulness Training Intervention Pilot Test Using Six Critical Parameters.

PubMed

Musil, Carol M; Zauszniewski, Jaclene A; Burant, Christopher J; Toly, Valerie B; Warner, Camille B

2015-12-01

Few resources are available to help grandmother caregivers to grandchildren manage their complex family situations that may have immediate and long-term consequences for themselves and their families. Resourcefulness training is an intervention designed to help grandmothers improve their ability to deal with these problems. The purpose of this pilot study was to evaluate the necessity, feasibility, acceptability, fidelity, safety, and effectiveness (i.e., effect sizes) of an online, computer-based resourcefulness training intervention that was adapted from a face-to-face intervention. Twelve grandmothers raising or living with grandchildren participated in the pilot intervention that included (a) watching an instructional video on resourcefulness, (b) completing two online questionnaires over a 6-week time period, and (c) writing in an online journal every day for 4 weeks. Data are evaluated within the context of the six parameters important to intervention development. Qualitative and quantitative results provide initial support for all six parameters. Recommendations to improve aspects of the intervention are discussed. © The Author(s) 2015.

Energy dissipation in polymer-polymer adhesion contacts

NASA Astrophysics Data System (ADS)

Garif, Yev Skip

This study focuses on self-adhesion in elastomers as a way of approaching a broader polymer adhesion problem. The model systems studied are cross-linked acrylic pressure-sensitive adhesives (PSA-LNs) synthesized to attain four surface types: neutral, acidic, basic, and polar. As the study progressed, it distinguished itself as the first of its kind to consistently report the effect of temperature on measurable intrinsic parameters of polymer adhesion. The main goal of the study was to understand why the magnitude of the practical adhesion energies of the four PSA-LN systems tested varies disproportionately greater than their respective surface energies. To achieve this goal, continuous sweeps of adhesion energy as a function of rate of interfacial separation were performed using three different adhesion-probing techniques--- peel, micro-scratch, and normal contact. The answer was found in the sub-micron-per-second limit of separation rates. In approaching this limit, the power law behavior of adhesion gradually transitioned into a linear region of markedly weaker sensitivity to rate. Referred to as the "intrinsic window", this linear region was characterized by three parameters: (1) the intrinsic adhesion energy at zero rate of separation; (2) the intrinsic rate sensitivity equal to the proportionality constant of the linear fit; and (3) the critical separation rate in the middle of the transition to the power law. All three were found to be thermally activated. Activation energies suggested that interfacial processes are attributed mainly to dispersive and electrostatic molecular interactions such as hydrogen bonding or van der Waals attraction. Comparative analysis of the intrinsic window of the four PSA-LNs tested showed that an increase in the intrinsic adhesion energy associated with higher surface energy is inherently coupled with an increase in the intrinsic rate sensitivity and reduction in the critical separation rate. When combined, the three parameters reshape the intrinsic window such that the entire power-law portion of the adhesion response is shifted to a level that appears disproportionately high based on the false assumption that there is only one intrinsic parameter contributing to the shift. Thus, the goal of explaining this disproportionality was achieved.

fissioncore: A desktop-computer simulation of a fission-bomb core

NASA Astrophysics Data System (ADS)

Cameron Reed, B.; Rohe, Klaus

2014-10-01

A computer program, fissioncore, has been developed to deterministically simulate the growth of the number of neutrons within an exploding fission-bomb core. The program allows users to explore the dependence of criticality conditions on parameters such as nuclear cross-sections, core radius, number of secondary neutrons liberated per fission, and the distance between nuclei. Simulations clearly illustrate the existence of a critical radius given a particular set of parameter values, as well as how the exponential growth of the neutron population (the condition that characterizes criticality) depends on these parameters. No understanding of neutron diffusion theory is necessary to appreciate the logic of the program or the results. The code is freely available in FORTRAN, C, and Java and is configured so that modifications to accommodate more refined physical conditions are possible.

Estimation of bipolar jets from accretion discs around Kerr black holes

NASA Astrophysics Data System (ADS)

Kumar, Rajiv; Chattopadhyay, Indranil

2017-08-01

We analyse flows around a rotating black hole and obtain self-consistent accretion-ejection solutions in full general relativistic prescription. Entire energy-angular momentum parameter space is investigated in the advective regime to obtain shocked and shock-free accretion solutions. Jet equations of motion are solved along the von Zeipel surfaces computed from the post-shock disc, simultaneously with the equations of accretion disc along the equatorial plane. For a given spin parameter, the mass outflow rate increases as the shock moves closer to the black hole, but eventually decreases, maximizing at some intermediate value of shock location. Interestingly, we obtain all types of possible jet solutions, for example, steady shock solution with multiple critical points, bound solution with two critical points and smooth solution with single critical point. Multiple critical points may exist in jet solution for spin parameter as ≥ 0.5. The jet terminal speed generally increases if the accretion shock forms closer to the horizon and is higher for corotating black hole than the counter-rotating and the non-rotating one. Quantitatively speaking, shocks in jet may form for spin parameter as > 0.6 and jet shocks range between 6rg and 130rg above the equatorial plane, while the jet terminal speed vj∞ > 0.35 c if Bernoulli parameter E≥1.01 for as > 0.99.

The Role of the Cooling Prescription for Disk Fragmentation: Numerical Convergence and Critical Cooling Parameter in Self-gravitating Disks

NASA Astrophysics Data System (ADS)

Baehr, Hans; Klahr, Hubert

2015-12-01

Protoplanetary disks fragment due to gravitational instability when there is enough mass for self-gravitation, described by the Toomre parameter, and when heat can be lost at a rate comparable to the local dynamical timescale, described by {t}{{c}}=β {{{Ω }}}-1. Simulations of self-gravitating disks show that the cooling parameter has a rough critical value at {β }{{crit}}=3. When below {β }{{crit}}, gas overdensities will contract under their own gravity and fragment into bound objects while otherwise maintaining a steady state of gravitoturbulence. However, previous studies of the critical cooling parameter have found dependences on simulation resolution, indicating that the simulation of self-gravitating protoplanetary disks is not so straightforward. In particular, the simplicity of the cooling timescale tc prevents fragments from being disrupted by pressure support as temperatures rise. We alter the cooling law so that the cooling timescale is dependent on local surface density fluctuations, which is a means of incorporating optical depth effects into the local cooling of an object. For lower resolution simulations, this results in a lower critical cooling parameter and a disk that is more stable to gravitational stresses, suggesting that the formation of large gas giants planets in large, cool disks is generally suppressed by more realistic cooling. At our highest resolution, however, the model becomes unstable to fragmentation for cooling timescales up to β =10.

Experimental Results of Site Calibration and Sensitivity Measurements in OTR for UWB Systems

NASA Astrophysics Data System (ADS)

Viswanadham, Chandana; Rao, P. Mallikrajuna

2017-06-01

System calibration and parameter accuracy measurement of electronic support measures (ESM) systems is a major activity, carried out by electronic warfare (EW) engineers. These activities are very critical and needs good understanding in the field of microwaves, antennas, wave propagation, digital and communication domains. EW systems are broad band, built with state-of-the art electronic hardware, installed on different varieties of military platforms to guard country's security from time to time. EW systems operate in wide frequency ranges, typically in the order of thousands of MHz, hence these are ultra wide band (UWB) systems. Few calibration activities are carried within the system and in the test sites, to meet the accuracies of final specifications. After calibration, parameters are measured for their accuracies either in feed mode by injecting the RF signals into the front end or in radiation mode by transmitting the RF signals on to system antenna. To carry out these activities in radiation mode, a calibrated open test range (OTR) is necessary in the frequency band of interest. Thus site calibration of OTR is necessary to be carried out before taking up system calibration and parameter measurements. This paper presents the experimental results of OTR site calibration and sensitivity measurements of UWB systems in radiation mode.

PFC2D simulation of thermally induced cracks in concrete specimens

NASA Astrophysics Data System (ADS)

Liu, Xinghong; Chang, Xiaolin; Zhou, Wei; Li, Shuirong

2013-06-01

The appearance of cracks exposed to severe environmental conditions can be critical for concrete structures. The research is to validate Particle Flow Code(PFC2D) method in the context of concrete thermally-induced cracking simulations. First, concrete was discreted as meso-level units of aggregate, cement mortar and the interfaces between them. Parallel bonded-particle model in PFC2D was adapted to describe the constitutive relation of the cementing material. Then, the concrete mechanics meso-parameters were obtained through several groups of biaxial tests, in order to make the numerical results comply with the law of the indoor test. The concrete thermal meso-parameters were determined by compared with the parameters in the empirical formula through the simulations imposing a constant heat flow to the left margin of concrete specimens. At last, a case of 1000mm×500mm concrete specimen model was analyzed. It simulated the formation and development process of the thermally-induced cracks under the cold waves of different durations and temperature decline. Good agreements in fracture morphology and process were observed between the simulations, previous studies and laboratory data. The temperature decline limits during cold waves were obtained when its tensile strength was given as 3MPa. And it showed the feasibility of using PFC2D to simulate concrete thermally-induced cracking.

Critical current measurements of high-temperature superconducting short samples at a wide range of temperatures and magnetic fields.

PubMed

Ma, Hongjun; Liu, Huajun; Liu, Fang; Zhang, Huahui; Ci, Lu; Shi, Yi; Lei, Lei

2018-01-01

High-Temperature Superconductors (HTS) are potential materials for high-field magnets, low-loss transmission cables, and Superconducting Magnetic Energy Storage (SMES) due to their high upper critical magnetic field (H c2 ) and critical temperature (T c ). The critical current (I c ) of HTS, which is one of the most important parameters for superconductor application, depends strongly on the magnetic fields and temperatures. A new I c measurement system that can carry out accurate I c measurement for HTS short samples with various temperatures (4.2-80 K), magnetic fields (0-14 T), and angles of the magnetic field (0°-90°) has been developed. The I c measurement system mainly consists of a measurement holder, temperature-control system, background magnet, test cryostat, data acquisition system, and DC power supply. The accuracy of temperature control is better than ±0.1 K over the 20-80 K range and ±0.05 K when measured below 20 K. The maximum current is over 1000 A with a measurement uncertainty of 1%. The system had been successfully used for YBa 2 Cu 3 O 7-x (YBCO) tapes I c determination with different temperatures and magnetic fields.

The relationship between critical flux and fibre movement induced by bubbling in a submerged hollow fibre system.

PubMed

Wicaksana, F; Fan, A G; Chen, V

2005-01-01

Bubbling has been used to enhance various processes. In this paper we deal with the effect of bubbling on submerged hollow fibre membranes, where bubbling is applied to prevent severe membrane fouling. Previous work with submerged hollow fibres has observed that significant fibre movement can be induced by bubbling and that there is a qualitative relationship between fibre movement and filtration performance. Therefore, the aim of the present research has been to analyse the link between bubbling, fibre movement and critical flux, identified as the flux at which the transmembrane pressure (TMP) starts to rise. Tests were performed on vertical isolated fibres with a model feed of yeast suspension. The fibres were subject to steady bubbling from below. The parameters of interest were the fibre characteristics, such as tightness, diameter and length, as well as feed concentration. The results confirmed that the critical fluxes are affected by the fibre characteristics and feed concentration. Higher critical flux values can be achieved by using loose fibres, smaller diameters and longer fibres. The enhancement is partially linked to fibre movement and this is confirmed by improved performance when fibres are subject to mechanical movement in the absence of bubbling.

Critical current measurements of high-temperature superconducting short samples at a wide range of temperatures and magnetic fields

NASA Astrophysics Data System (ADS)

Ma, Hongjun; Liu, Huajun; Liu, Fang; Zhang, Huahui; Ci, Lu; Shi, Yi; Lei, Lei

2018-01-01

High-Temperature Superconductors (HTS) are potential materials for high-field magnets, low-loss transmission cables, and Superconducting Magnetic Energy Storage (SMES) due to their high upper critical magnetic field (Hc2) and critical temperature (Tc). The critical current (Ic) of HTS, which is one of the most important parameters for superconductor application, depends strongly on the magnetic fields and temperatures. A new Ic measurement system that can carry out accurate Ic measurement for HTS short samples with various temperatures (4.2-80 K), magnetic fields (0-14 T), and angles of the magnetic field (0°-90°) has been developed. The Ic measurement system mainly consists of a measurement holder, temperature-control system, background magnet, test cryostat, data acquisition system, and DC power supply. The accuracy of temperature control is better than ±0.1 K over the 20-80 K range and ±0.05 K when measured below 20 K. The maximum current is over 1000 A with a measurement uncertainty of 1%. The system had been successfully used for YBa2Cu3O7-x(YBCO) tapes Ic determination with different temperatures and magnetic fields.

Dynamic behavior of the interaction between epidemics and cascades on heterogeneous networks

NASA Astrophysics Data System (ADS)

Jiang, Lurong; Jin, Xinyu; Xia, Yongxiang; Ouyang, Bo; Wu, Duanpo

2014-12-01

Epidemic spreading and cascading failure are two important dynamical processes on complex networks. They have been investigated separately for a long time. But in the real world, these two dynamics sometimes may interact with each other. In this paper, we explore a model combined with the SIR epidemic spreading model and a local load sharing cascading failure model. There exists a critical value of the tolerance parameter for which the epidemic with high infection probability can spread out and infect a fraction of the network in this model. When the tolerance parameter is smaller than the critical value, the cascading failure cuts off the abundance of paths and blocks the spreading of the epidemic locally. While the tolerance parameter is larger than the critical value, the epidemic spreads out and infects a fraction of the network. A method for estimating the critical value is proposed. In simulations, we verify the effectiveness of this method in the uncorrelated configuration model (UCM) scale-free networks.

Possibilities And Influencing Parameters For The Early Detection Of Sheet Metal Failure In Press Shop Operations

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

Gerlach, Joerg; Kessler, Lutz; Paul, Udo

2007-05-17

The concept of forming limit curves (FLC) is widely used in industrial practice. The required data should be delivered for typical material properties (measured on coils with properties in a range of +/- of the standard deviation from the mean production values) by the material suppliers. In particular it should be noted that its use for the validation of forming robustness providing forming limit curves for the variety of scattering in the mechanical properties is impossible. Therefore a forecast of the expected limit strains without expensive cost and time-consuming experiments is necessary. In the paper the quality of a regressionmore » analysis for determining forming limit curves based on tensile test results is presented and discussed.Owing to the specific definition of limit strains with FLCs following linear strain paths, the significance of this failure definition is limited. To consider nonlinear strain path effects, different methods are given in literature. One simple method is the concept of limit stresses. It should be noted that the determined value of the critical stress is dependent on the extrapolation of the tensile test curve. When the yield curve extrapolation is very similar to an exponential function, the definition of the critical stress value is very complicated due to the low slope of the hardening function at large strains.A new method to determine general failure behavior in sheet metal forming is the common use and interpretation of three criteria: onset on material instability (comparable with FLC concept), value of critical shear fracture and the value of ductile fracture. This method seems to be particularly successful for newly developed high strength steel grades in connection with more complex strain paths for some specific material elements. Nevertheless the identification of the different failure material parameters or functions will increase and the user has to learn with the interpretation of the numerical results.« less

Nonlinear Dynamic Characteristics of the Railway Vehicle

NASA Astrophysics Data System (ADS)

Uyulan, Çağlar; Gokasan, Metin

2017-06-01

The nonlinear dynamic characteristics of a railway vehicle are checked into thoroughly by applying two different wheel-rail contact model: a heuristic nonlinear friction creepage model derived by using Kalker 's theory and Polach model including dead-zone clearance. This two models are matched with the quasi-static form of the LuGre model to obtain more realistic wheel-rail contact model. LuGre model parameters are determined using nonlinear optimization method, which it's objective is to minimize the error between the output of the Polach and Kalker model and quasi-static LuGre model for specific operating conditions. The symmetric/asymmetric bifurcation attitude and stable/unstable motion of the railway vehicle in the presence of nonlinearities which are yaw damping forces in the longitudinal suspension system are analyzed in great detail by changing the vehicle speed. Phase portraits of the lateral displacement of the leading wheelset of the railway vehicle are drawn below and on the critical speeds, where sub-critical Hopf bifurcation take place, for two wheel-rail contact model. Asymmetric periodic motions have been observed during the simulation in the lateral displacement of the wheelset under different vehicle speed range. The coexistence of multiple steady states cause bounces in the amplitude of vibrations, resulting instability problems of the railway vehicle. By using Lyapunov's indirect method, the critical hunting speeds are calculated with respect to the radius of the curved track parameter changes. Hunting, which is defined as the oscillation of the lateral displacement of wheelset with a large domain, is described by a limit cycle-type oscillation nature. The evaluated accuracy of the LuGre model adopted from Kalker's model results for prediction of critical speed is higher than the results of the LuGre model adopted from Polach's model. From the results of the analysis, the critical hunting speed must be resolved by investigating the track tests under various kind of excitations.

A Systematic Approach of Employing Quality by Design Principles: Risk Assessment and Design of Experiments to Demonstrate Process Understanding and Identify the Critical Process Parameters for Coating of the Ethylcellulose Pseudolatex Dispersion Using Non-Conventional Fluid Bed Process.

PubMed

Kothari, Bhaveshkumar H; Fahmy, Raafat; Claycamp, H Gregg; Moore, Christine M V; Chatterjee, Sharmista; Hoag, Stephen W

2017-05-01

The goal of this study was to utilize risk assessment techniques and statistical design of experiments (DoE) to gain process understanding and to identify critical process parameters for the manufacture of controlled release multiparticulate beads using a novel disk-jet fluid bed technology. The material attributes and process parameters were systematically assessed using the Ishikawa fish bone diagram and failure mode and effect analysis (FMEA) risk assessment methods. The high risk attributes identified by the FMEA analysis were further explored using resolution V fractional factorial design. To gain an understanding of the processing parameters, a resolution V fractional factorial study was conducted. Using knowledge gained from the resolution V study, a resolution IV fractional factorial study was conducted; the purpose of this IV study was to identify the critical process parameters (CPP) that impact the critical quality attributes and understand the influence of these parameters on film formation. For both studies, the microclimate, atomization pressure, inlet air volume, product temperature (during spraying and curing), curing time, and percent solids in the coating solutions were studied. The responses evaluated were percent agglomeration, percent fines, percent yield, bead aspect ratio, median particle size diameter (d50), assay, and drug release rate. Pyrobuttons® were used to record real-time temperature and humidity changes in the fluid bed. The risk assessment methods and process analytical tools helped to understand the novel disk-jet technology and to systematically develop models of the coating process parameters like process efficiency and the extent of curing during the coating process.

Tack Measurements of Prepreg Tape at Variable Temperature and Humidity

NASA Technical Reports Server (NTRS)

Wohl, Christopher; Palmieri, Frank L.; Forghani, Alireza; Hickmott, Curtis; Bedayat, Houman; Coxon, Brian; Poursartip, Anoush; Grimsley, Brian

2017-01-01

NASA’s Advanced Composites Project has established the goal of achieving a 30 percent reduction in the timeline for certification of primary composite structures for application on commercial aircraft. Prepreg tack is one of several critical parameters affecting composite manufacturing by automated fiber placement (AFP). Tack plays a central role in the prevention of wrinkles and puckers that can occur during AFP, thus knowledge of tack variation arising from a myriad of manufacturing and environmental conditions is imperative for the prediction of defects during AFP. A full design of experiments was performed to experimentally characterize tack on 0.25-inch slit-tape tow IM7/8552-1 prepreg using probe tack testing. Several process parameters (contact force, contact time, retraction speed, and probe diameter) as well as environmental parameters (temperature and humidity) were varied such that the entire parameter space could be efficiently evaluated. Mid-point experimental conditions (i.e., parameters not at either extrema) were included to enable prediction of curvature in relationships and repeat measurements were performed to characterize experimental error. Collectively, these experiments enable determination of primary dependencies as well as multi-parameter relationships. Slit-tape tow samples were mounted to the bottom plate of a rheometer parallel plate fixture using a jig to prevent modification of the active area to be interrogated with the top plate, a polished stainless steel probe, during tack testing. The probe surface was slowly brought into contact with the pre-preg surface until a pre-determined normal force was achieved (2-30 newtons). After a specified dwell time (0.02-10 seconds), during which the probe substrate interaction was maintained under displacement control, the probe was retracted from the surface (0.1-50 millimeters per second). Initial results indicated a clear dependence of tack strength on several parameters, with a particularly strong dependence on temperature and humidity. Although an increase in either of these parameters reduces tack strength, a maximum in tack was predicted to occur under conditions of low temperature and moderate humidity.

Experimental Investigation of Compressed Thin-Walled Steel Members

NASA Astrophysics Data System (ADS)

Juhás, Pavol; Juhásová Šenitková, Ingrid

2017-10-01

The paper presents fundamental information about realized experimental-theoretical research to determinate the load-carrying capacities for thin-walled compressed steel members with quasi-homogenous and hybrid cross-sections. The webs of such members are stressed in the elastic-plastic region. This continuous research joins on previous research of the first author of the paper. The aim of this research is to investigate and analyse the elastic-plastic post-critical behaviour of thin web and its interaction with flanges. The experimental program, test members and their geometrical parameters and material properties are evident from table 1 and table 2 as well as from figure 1 and figure 2. The test arrangement and failures of the test members are illustrated on Figures 3, 4 and 5. Some partial results are presented in Table 3 of the paper, too.

Quality Assurance and T&E of Inertial Systems for RLV Mission

NASA Astrophysics Data System (ADS)

Sathiamurthi, S.; Thakur, Nayana; Hari, K.; Peter, Pilmy; Biju, V. S.; Mani, K. S.

2017-12-01

This work describes the quality assurance and Test and Evaluation (T&E) activities carried out for the inertial systems flown successfully in India's first reusable launch vehicle technology demonstrator hypersonic experiment mission. As part of reliability analysis, failure mode effect and criticality analysis and derating analysis were carried out in the initial design phase, findings presented to design review forums and the recommendations were implemented. T&E plan was meticulously worked out and presented to respective forums for review and implementation. Test data analysis, health parameter plotting and test report generation was automated and these automations significantly reduced the time required for these activities and helped to avoid manual errors. Further, T&E cycle is optimized without compromising on quality aspects. These specific measures helped to achieve zero defect delivery of inertial systems for RLV application.

Adapting Human Videofluoroscopic Swallow Study Methods to Detect and Characterize Dysphagia in Murine Disease Models

PubMed Central

Lever, Teresa E.; Braun, Sabrina M.; Brooks, Ryan T.; Harris, Rebecca A.; Littrell, Loren L.; Neff, Ryan M.; Hinkel, Cameron J.; Allen, Mitchell J.; Ulsas, Mollie A.

2015-01-01

This study adapted human videofluoroscopic swallowing study (VFSS) methods for use with murine disease models for the purpose of facilitating translational dysphagia research. Successful outcomes are dependent upon three critical components: test chambers that permit self-feeding while standing unrestrained in a confined space, recipes that mask the aversive taste/odor of commercially-available oral contrast agents, and a step-by-step test protocol that permits quantification of swallow physiology. Elimination of one or more of these components will have a detrimental impact on the study results. Moreover, the energy level capability of the fluoroscopy system will determine which swallow parameters can be investigated. Most research centers have high energy fluoroscopes designed for use with people and larger animals, which results in exceptionally poor image quality when testing mice and other small rodents. Despite this limitation, we have identified seven VFSS parameters that are consistently quantifiable in mice when using a high energy fluoroscope in combination with the new murine VFSS protocol. We recently obtained a low energy fluoroscopy system with exceptionally high imaging resolution and magnification capabilities that was designed for use with mice and other small rodents. Preliminary work using this new system, in combination with the new murine VFSS protocol, has identified 13 swallow parameters that are consistently quantifiable in mice, which is nearly double the number obtained using conventional (i.e., high energy) fluoroscopes. Identification of additional swallow parameters is expected as we optimize the capabilities of this new system. Results thus far demonstrate the utility of using a low energy fluoroscopy system to detect and quantify subtle changes in swallow physiology that may otherwise be overlooked when using high energy fluoroscopes to investigate murine disease models. PMID:25866882

Baryonic effects in cosmic shear tomography: PCA parametrization and importance of extreme baryonic models

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

Mohammed, Irshad; Gnedin, Nickolay Y.

Baryonic effects are amongst the most severe systematics to the tomographic analysis of weak lensing data which is the principal probe in many future generations of cosmological surveys like LSST, Euclid etc.. Modeling or parameterizing these effects is essential in order to extract valuable constraints on cosmological parameters. In a recent paper, Eifler et al. (2015) suggested a reduction technique for baryonic effects by conducting a principal component analysis (PCA) and removing the largest baryonic eigenmodes from the data. In this article, we conducted the investigation further and addressed two critical aspects. Firstly, we performed the analysis by separating the simulations into training and test sets, computing a minimal set of principle components from the training set and examining the fits on the test set. We found that using only four parameters, corresponding to the four largest eigenmodes of the training set, the test sets can be fitted thoroughly with an RMSmore » $$\\sim 0.0011$$. Secondly, we explored the significance of outliers, the most exotic/extreme baryonic scenarios, in this method. We found that excluding the outliers from the training set results in a relatively bad fit and degraded the RMS by nearly a factor of 3. Therefore, for a direct employment of this method to the tomographic analysis of the weak lensing data, the principle components should be derived from a training set that comprises adequately exotic but reasonable models such that the reality is included inside the parameter domain sampled by the training set. The baryonic effects can be parameterized as the coefficients of these principle components and should be marginalized over the cosmological parameter space.« less

Critical Thinking in Adulthood.

ERIC Educational Resources Information Center

Fulton, Rodney D.

Critical thinking is often defined as that which a particular instrument measures. The most prominent tests are the Watson-Glaser Critical Thinking Appraisal, the Ennis-Weir Critical Thinking Essay Test, and the Cornell Critical Thinking Tests. Watson and Glaser's (1980) view of critical thinking is "a composite of attitudes, knowledge, and…

Estimation of parameters of dose volume models and their confidence limits

NASA Astrophysics Data System (ADS)

van Luijk, P.; Delvigne, T. C.; Schilstra, C.; Schippers, J. M.

2003-07-01

Predictions of the normal-tissue complication probability (NTCP) for the ranking of treatment plans are based on fits of dose-volume models to clinical and/or experimental data. In the literature several different fit methods are used. In this work frequently used methods and techniques to fit NTCP models to dose response data for establishing dose-volume effects, are discussed. The techniques are tested for their usability with dose-volume data and NTCP models. Different methods to estimate the confidence intervals of the model parameters are part of this study. From a critical-volume (CV) model with biologically realistic parameters a primary dataset was generated, serving as the reference for this study and describable by the NTCP model. The CV model was fitted to this dataset. From the resulting parameters and the CV model, 1000 secondary datasets were generated by Monte Carlo simulation. All secondary datasets were fitted to obtain 1000 parameter sets of the CV model. Thus the 'real' spread in fit results due to statistical spreading in the data is obtained and has been compared with estimates of the confidence intervals obtained by different methods applied to the primary dataset. The confidence limits of the parameters of one dataset were estimated using the methods, employing the covariance matrix, the jackknife method and directly from the likelihood landscape. These results were compared with the spread of the parameters, obtained from the secondary parameter sets. For the estimation of confidence intervals on NTCP predictions, three methods were tested. Firstly, propagation of errors using the covariance matrix was used. Secondly, the meaning of the width of a bundle of curves that resulted from parameters that were within the one standard deviation region in the likelihood space was investigated. Thirdly, many parameter sets and their likelihood were used to create a likelihood-weighted probability distribution of the NTCP. It is concluded that for the type of dose response data used here, only a full likelihood analysis will produce reliable results. The often-used approximations, such as the usage of the covariance matrix, produce inconsistent confidence limits on both the parameter sets and the resulting NTCP values.

Local and nonlocal order parameters in the Kitaev chain

NASA Astrophysics Data System (ADS)

Chitov, Gennady Y.

2018-02-01

We have calculated order parameters for the phases of the Kitaev chain with interaction and dimerization at a special symmetric point applying the Jordan-Wigner and other duality transformations. We use string order parameters (SOPs) defined via the correlation functions of the Majorana string operators. The SOPs are mapped onto the local order parameters of some dual Hamiltonians and easily calculated. We have shown that the phase diagram of the interacting dimerized chain comprises the phases with the conventional local order as well as the phases with nonlocal SOPs. From the results for the critical indices, we infer the two-dimensional Ising universality class of criticality at the particular symmetry point where the model is exactly solvable.

Rossitsa River Basin: Flood Hazard and Risk Identification

NASA Astrophysics Data System (ADS)

Mavrova-Guirguinova, Maria; Pencheva, Denislava

2017-04-01

The process of Flood Risk Management Planning and adaptation of measures for flood risk reduction as the Early Warning provoke the necessity of surveys involving Identification aspects. This project presents risk identification combining two lines of analysis: (1) Creation a mathematical model of rainfall-runoff processes in a watershed based on limited number of observed input and output variables; (2) Procedures for determination of critical thresholds - discharges/water levels corresponding to certain consequences. The pilot region is Rossitsa river basin, Sevlievo, Bulgaria. The first line of analysis follows next steps: (a) Creation and calibration of Unit Hydrograph Models based on limited number of observed data for discharge and precipitation; The survey at the selected region has 22 observations for excess rainfall and discharge. (b) The relations of UHM coefficients from the input parameters have been determined statistically, excluding the ANN model of the run-off coefficient as a function of 3 parameters (amount of precipitation two days before, soil condition, intensity of the rainfall) where a feedforward neural network is used. (c) Additional simulations with UHM aiming at generation of synthetic data for rainfall-runoff events, which extend the range of observed data; (d) Training, validation and testing a generalized regional ANN Model for discharge forecasting with 4 input parameters, where the training data set consists of synthetic data, validation and testing data sets consists of observations. A function between consequences and discharges has been reached in the second line of analysis concerning critical hazard levels determination. Unsteady simulations with the hydraulic model using three typical hydrographs for determination of the existing time for reaction from one to upper critical threshold are made. Correction of the critical thresholds aiming at providing necessary time for reaction between the thresholds and probability analysis of the finally determined critical thresholds are made. The result of the described method is a Catalogue for off-line flood hazard and risk identification. It can be used as interactive computer system, based on simulations of the ANN "Catalogue". Flood risk identification of the future rainfall event is made in a multi-dimensional space for each kind of soil conditions (dry, average wet and wet condition) and observed amount of precipitation two days before. Rainfall-runoff scenarios in case of intensive rainfall or sustained rainfall (more than 6 hours) are taken into account. Critical thresholds and hazard zones needed of specific operative activities (rescue and recovery) corresponded to each of the regulated flood protection levels (unite, municipality, regional or national) are presented. The Catalogue gives the opportunity for flood hazard scenarios extraction. Regarding that, the Catalogue is useful on the prevention stage of flood protection planning (emergency operations, measures and resources for their implementation planning) and creation of scenarios for training the Emergency Plans. Concerning application for Early Warning, it gives approximate forecast for flood hazard. The Catalogue supplies the necessary time for reaction of about 24 hours. Thus, Early Warning is possible to the responsible authorities, all parts if the Unified Rescue System, members of suitable Headquarters for disaster protection (on municipality, region or national level).

Exact Critical Exponents for the Antiferromagnetic Quantum Critical Metal in Two Dimensions

NASA Astrophysics Data System (ADS)

Schlief, Andres; Lunts, Peter; Lee, Sung-Sik

2017-04-01

Unconventional metallic states which do not support well-defined single-particle excitations can arise near quantum phase transitions as strong quantum fluctuations of incipient order parameters prevent electrons from forming coherent quasiparticles. Although antiferromagnetic phase transitions occur commonly in correlated metals, understanding the nature of the strange metal realized at the critical point in layered systems has been hampered by a lack of reliable theoretical methods that take into account strong quantum fluctuations. We present a nonperturbative solution to the low-energy theory for the antiferromagnetic quantum critical metal in two spatial dimensions. Being a strongly coupled theory, it can still be solved reliably in the low-energy limit as quantum fluctuations are organized by a new control parameter that emerges dynamically. We predict the exact critical exponents that govern the universal scaling of physical observables at low temperatures.

[Application of the Salzburg reading desk in accommodation and presbyopic research].

PubMed

Dexl, A K

2011-08-01

The determination of reading acuity is still the most important clinical examination, whenever the potential benefits of "presbyopic surgery" are compared. Reading distance--the by far most critical parameter in testing reading acuity--seems to be quite variable for every patient tested, whenever patients are allowed to freely choose a subjectively convenient reading distance. Therefore, measuring reading acuity with a fixed reading distance does not allow conclusions to be drawn on the "every-day reading ability" of individual patients. Since 2004, the Eye Clinic of Salzburg University has been continuously working on the development of a standardised device that enables clinicians and researchers to systematically evaluate every patient's individual reading performance under standardised conditions. © Georg Thieme Verlag KG Stuttgart · New York.

Fast charging nickel-metal hydride traction batteries

NASA Astrophysics Data System (ADS)

Yang, Xiao Guang; Liaw, Bor Yann

This paper describes the fast charge ability, or "fast rechargeability", of nominal 85 Ah Ni-MH modules under various fast charge conditions, including constant current (CC); typically 1-3C, and constant power (CP) regimes. Our tests revealed that there is no apparent difference between CC and CP fast charge regimes with respect to charge efficiency and time. Following the USABC Electric Vehicle Battery Test Procedures Manual (Revision 2, 1996), we demonstrated that we were able to return 40% state of charge (SOC) from 60% depth of discharge (DOD) to 20% DOD within 15 min. Most importantly, we found that the internal pressure of the cell is the most critical parameter in the control of the fast charge process and the safe operation of the modules.

Development of a design basis tornado and structural design criteria for the Nevada Test Site, Nevada. Final report

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

McDonald, J.R.; Minor, J.E.; Mehta, K.C.

1975-06-01

In order to evaluate the ability of critical facilities at the Nevada Test Site to withstand the possible damaging effects of extreme winds and tornadoes, parameters for the effects of tornadoes and extreme winds and structural design criteria for the design and evaluation of structures were developed. The meteorological investigations conducted are summarized, and techniques used for developing the combined tornado and extreme wind risk model are discussed. The guidelines for structural design include methods for calculating pressure distributions on walls and roofs of structures and methods for accommodating impact loads from wind-driven missiles. Calculations for determining the design loadsmore » for an example structure are included. (LCL)« less

Grounding, bonding and shielding for safety and signal interference control

NASA Technical Reports Server (NTRS)

Forsyth, T. J.; Bautista, AL

1990-01-01

Aircraft models and other aerodynamic tests are conducted at the NASA Ames Research Center National Full Scale Aerodynamics Complex (NFAC). The models, tested in NFAC's wind tunnels, are sometimes heavily instrumented and are connected to a data acquisition system. Besides recording data for evaluation, certain critical information must be monitored to be sure the model is within operational limits. The signals for these parameters are for the most part low-level signals that require good instrumentation amplification. These amplifiers need to be grounded and shielded for common mode rejection and noise reduction. The instrumentation also needs to be grounded to prevent electrical shock hazards. The purpose of this paper is to present an understanding of the principles and purpose of grounding, bonding, and shielding.

Digital Beamforming Synthetic Aperture Radar (DBSAR): Performance Analysis During the Eco-3D 2011 and Summer 2012 Flight Campaigns

NASA Technical Reports Server (NTRS)

Rincon, Rafael F.; Fatoyinbo, Temilola; Carter, Lynn; Ranson, K. Jon; Vega, Manuel; Osmanoglu, Batuhan; Lee, SeungKuk; Sun, Guoqing

2014-01-01

The Digital Beamforming Synthetic Aperture radar (DBSAR) is a state-of-the-art airborne radar developed at NASA/Goddard for the implementation, and testing of digital beamforming techniques applicable to Earth and planetary sciences. The DBSAR measurements have been employed to study: The estimation of vegetation biomass and structure - critical parameters in the study of the carbon cycle; The measurement of geological features - to explore its applicability to planetary science by measuring planetary analogue targets. The instrument flew two test campaigns over the East coast of the United States in 2011, and 2012. During the campaigns the instrument operated in full polarimetric mode collecting data from vegetation and topography features.

Critical points of metal vapors

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

Khomkin, A. L., E-mail: alhomkin@mail.ru; Shumikhin, A. S.

2015-09-15

A new method is proposed for calculating the parameters of critical points and binodals for the vapor–liquid (insulator–metal) phase transition in vapors of metals with multielectron valence shells. The method is based on a model developed earlier for the vapors of alkali metals, atomic hydrogen, and exciton gas, proceeding from the assumption that the cohesion determining the basic characteristics of metals under normal conditions is also responsible for their properties in the vicinity of the critical point. It is proposed to calculate the cohesion of multielectron atoms using well-known scaling relations for the binding energy, which are constructed for mostmore » metals in the periodic table by processing the results of many numerical calculations. The adopted model allows the parameters of critical points and binodals for the vapor–liquid phase transition in metal vapors to be calculated using published data on the properties of metals under normal conditions. The parameters of critical points have been calculated for a large number of metals and show satisfactory agreement with experimental data for alkali metals and with available estimates for all other metals. Binodals of metals have been calculated for the first time.« less

Critical mass of public goods and its coevolution with cooperation

NASA Astrophysics Data System (ADS)

Shi, Dong-Mei; Wang, Bing-Hong

2017-07-01

In this study, the enhancing parameter represented the value of the public goods to the public in public goods game, and was rescaled to a Fermi-Dirac distribution function of critical mass. Public goods were divided into two categories, consumable and reusable public goods, and their coevolution with cooperative behavior was studied. We observed that for both types of public goods, cooperation was promoted as the enhancing parameter increased when the value of critical mass was not very large. An optimal value of critical mass which led to the best cooperation was identified. We also found that cooperations emerged earlier for reusable public goods, and defections became extinct earlier for the consumable public goods. Moreover, we observed that a moderate depreciation rate for public goods resulted in an optimal cooperation, and this range became wider as the enhancing parameter increased. The noise influence on cooperation was studied, and it was shown that cooperation density varied non-monotonically as noise amplitude increased for reusable public goods, whereas decreased monotonically for consumable public goods. Furthermore, existence of the optimal critical mass was also identified in other three regular networks. Finally, simulation results were utilized to analyze the provision of public goods in detail.

Buckling analysis of planar compression micro-springs

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

Zhang, Jing; Sui, Li; Shi, Gengchen

2015-04-15

Large compression deformation causes micro-springs buckling and loss of load capacity. We analyzed the impact of structural parameters and boundary conditions for planar micro-springs, and obtained the change rules for the two factors that affect buckling. A formula for critical buckling deformation of micro-springs under compressive load was derived based on elastic thin plate theory. Results from this formula were compared with finite element analysis results but these did not always correlate. Therefore, finite element analysis is necessary for micro-spring buckling analysis. We studied the variation of micro-spring critical buckling deformation caused by four structural parameters using ANSYS software undermore » two constraint conditions. The simulation results show that when an x-direction constraint is added, the critical buckling deformation increases by 32.3-297.9%. The critical buckling deformation decreases with increase in micro-spring arc radius or section width and increases with increase in micro-spring thickness or straight beam width. We conducted experiments to confirm the simulation results, and the experimental and simulation trends were found to agree. Buckling analysis of the micro-spring establishes a theoretical foundation for optimizing micro-spring structural parameters and constraint conditions to maximize the critical buckling load.« less

Bootstrap percolation on spatial networks

NASA Astrophysics Data System (ADS)

Gao, Jian; Zhou, Tao; Hu, Yanqing

2015-10-01

Bootstrap percolation is a general representation of some networked activation process, which has found applications in explaining many important social phenomena, such as the propagation of information. Inspired by some recent findings on spatial structure of online social networks, here we study bootstrap percolation on undirected spatial networks, with the probability density function of long-range links’ lengths being a power law with tunable exponent. Setting the size of the giant active component as the order parameter, we find a parameter-dependent critical value for the power-law exponent, above which there is a double phase transition, mixed of a second-order phase transition and a hybrid phase transition with two varying critical points, otherwise there is only a second-order phase transition. We further find a parameter-independent critical value around -1, about which the two critical points for the double phase transition are almost constant. To our surprise, this critical value -1 is just equal or very close to the values of many real online social networks, including LiveJournal, HP Labs email network, Belgian mobile phone network, etc. This work helps us in better understanding the self-organization of spatial structure of online social networks, in terms of the effective function for information spreading.

Statistics of the work done on a quantum critical system by quenching a control parameter.

PubMed

Silva, Alessandro

2008-09-19

We study the statistics of the work done on a quantum critical system by quenching a control parameter in the Hamiltonian. We elucidate the relation between the probability distribution of the work and the Loschmidt echo, a quantity emerging usually in the context of dephasing. Using this connection we characterize the statistics of the work done on a quantum Ising chain by quenching locally or globally the transverse field. We show that for local quenches starting at criticality the probability distribution of the work displays an interesting edge singularity.

Consensus statement with recommendations on active surveillance inclusion criteria and definition of progression in men with localized prostate cancer: the critical role of the pathologist.

PubMed

Montironi, Rodolfo; Hammond, Elizabeth H; Lin, Daniel W; Gore, John L; Srigley, John R; Samaratunga, Hema; Egevad, Lars; Rubin, Mark A; Nacey, John; Klotz, Laurence; Sandler, Howard; Zietman, Anthony L; Holden, Stuart; Humphrey, Peter A; Evans, Andrew J; Delahunt, Brett; McKenney, Jesse K; Berney, Daniel; Wheeler, Thomas M; Chinnaiyan, Arul; True, Lawrence; Knudsen, Beatrice; Epstein, Jonathan I; Amin, Mahul B

2014-12-01

Active surveillance (AS) is an important management option for men with low-risk, clinically localized prostate cancer. The clinical parameters for patient selection and definition of progression for AS protocols are evolving as data from several large cohorts matures. Vital to this process is the critical role pathologic parameters play in identifying appropriate candidates for AS. These findings need to be reproducible and consistently reported by surgical pathologists. This report highlights the importance of accurate pathology reporting as a critical component of these protocols.

Anticipatory Monitoring and Control of Complex Systems using a Fuzzy based Fusion of Support Vector Regressors

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

Miltiadis Alamaniotis; Vivek Agarwal

This paper places itself in the realm of anticipatory systems and envisions monitoring and control methods being capable of making predictions over system critical parameters. Anticipatory systems allow intelligent control of complex systems by predicting their future state. In the current work, an intelligent model aimed at implementing anticipatory monitoring and control in energy industry is presented and tested. More particularly, a set of support vector regressors (SVRs) are trained using both historical and observed data. The trained SVRs are used to predict the future value of the system based on current operational system parameter. The predicted values are thenmore » inputted to a fuzzy logic based module where the values are fused to obtain a single value, i.e., final system output prediction. The methodology is tested on real turbine degradation datasets. The outcome of the approach presented in this paper highlights the superiority over single support vector regressors. In addition, it is shown that appropriate selection of fuzzy sets and fuzzy rules plays an important role in improving system performance.« less

Pharmaceutical quality by design: product and process development, understanding, and control.

PubMed

Yu, Lawrence X

2008-04-01

The purpose of this paper is to discuss the pharmaceutical Quality by Design (QbD) and describe how it can be used to ensure pharmaceutical quality. The QbD was described and some of its elements identified. Process parameters and quality attributes were identified for each unit operation during manufacture of solid oral dosage forms. The use of QbD was contrasted with the evaluation of product quality by testing alone. The QbD is a systemic approach to pharmaceutical development. It means designing and developing formulations and manufacturing processes to ensure predefined product quality. Some of the QbD elements include: Defining target product quality profile; Designing product and manufacturing processes; Identifying critical quality attributes, process parameters, and sources of variability; Controlling manufacturing processes to produce consistent quality over time. Using QbD, pharmaceutical quality is assured by understanding and controlling formulation and manufacturing variables. Product testing confirms the product quality. Implementation of QbD will enable transformation of the chemistry, manufacturing, and controls (CMC) review of abbreviated new drug applications (ANDAs) into a science-based pharmaceutical quality assessment.

Direct fabrication of gas diffusion cathode by pulse electrodeposition for proton exchange membrane water electrolysis

NASA Astrophysics Data System (ADS)

Park, Hyanjoo; Choe, Seunghoe; Kim, Hoyoung; Kim, Dong-Kwon; Cho, GeonHee; Park, YoonSu; Jang, Jong Hyun; Ha, Don-Hyung; Ahn, Sang Hyun; Kim, Soo-Kil

2018-06-01

Pt catalysts for water electrolysis were prepared on carbon paper by using both direct current and pulse electrodeposition. Controlling the mass transfer of Pt precursor in the electrolyte by varying the deposition potential enables the formation of various Pt particle shapes such as flower-like and polyhedral particles. Further control of the deposition parameters for pulse electrodeposition resulted in changes to the particle size and density. In particular, the upper potential of pulse was found to be the critical parameter controlling the morphology of the particles and their catalytic activity. In addition to the typical electrochemical measurements, Pt samples deposited on carbon paper were used as cathodes for a proton exchange membrane water electrolyser. This single cell test revealed that our Pt particle samples have exceptional mass activity while being cost effective.

Correlation of nosetip boundary-layer transition data measured in ballistics-range experiments

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

Reda, D.C.

1980-01-01

Preablated nosetips of various carbonaceous materials were tested in a ballistics range. Surface-temperature contours, measured with image-converter cameras, were used to define boundary-layer transition-front contours. Measurements of surface roughness, surface temperature, average transition-front location, and freestream environment were combined with calculations of nosetip flowfields, and with calculations of laminar boundary-layer development in these flowfields, to transform all data into various dimensionless parameters. These parameters were defined by previous attempts to correlate existing wind-tunnel data for transition on rough/blunt bodies. Of the available correlating techniques, only one, based on the concept of a constant (critical) roughness Reynolds number for transition, wasmore » found to successfully describe both the wind-tunnel and ballistics-range data, thereby validating the extrapolation of this concept to actual reentry-vehicle materials and environments.« less

Sediment-transport experiments in zero-gravity

NASA Technical Reports Server (NTRS)

Iversen, James D.; Greeley, Ronald

1987-01-01

One of the important parameters in the analysis of sediment entrainment and transport is gravitational attraction. The availability of a laboratory in earth orbit would afford an opportunity to conduct experiments in zero and variable gravity environments. Elimination of gravitational attraction as a factor in such experiments would enable other critical parameters (such as particle cohesion and aerodynamic forces) to be evaluated much more accurately. A Carousel Wind Tunnel (CWT) is proposed for use in conducting experiments concerning sediment particle entrainment and transport in a space station. In order to test the concept of this wind tunnel design a one third scale model CWT was constructed and calibrated. Experiments were conducted in the prototype to determine the feasibility of studying various aeolian processes and the results were compared with various numerical analysis. Several types of experiments appear to be feasible utilizing the proposed apparatus.

Sediment-transport experiments in zero-gravity

NASA Technical Reports Server (NTRS)

Iversen, J. D.; Greeley, R.

1986-01-01

One of the important parameters in the analysis of sediment entrainment and transport is gravitational attraction. The availability of a laboratory in Earth orbit would afford an opportunity to conduct experiments in zero and variable gravity environments. Elimination of gravitational attraction as a factor in such experiments would enable other critical parameters (such as particle cohesion and aerodynamic forces) to be evaluated much more accurately. A Carousel Wind Tunnel (CWT) is proposed for use in conducting experiments concerning sediment particle entrainment and transport in a space station. In order to test the concept of this wind tunnel design a one third scale model CWT was constructed and calibrated. Experiments were conducted in the prototype to determine the feasibility of studying various aeolian processes and the results were compared with various numerical analysis. Several types of experiments appear to be feasible utilizing the proposed apparatus.

Calculation of the wetting parameter from a cluster model in the framework of nanothermodynamics.

PubMed

García-Morales, V; Cervera, J; Pellicer, J

2003-06-01

The critical wetting parameter omega(c) determines the strength of interfacial fluctuations in critical wetting transitions. In this Brief Report, we calculate omega(c) from considerations on critical liquid clusters inside a vapor phase. The starting point is a cluster model developed by Hill and Chamberlin in the framework of nanothermodynamics [Proc. Natl. Acad. Sci. USA 95, 12779 (1998)]. Our calculations yield results for omega(c) between 0.52 and 1.00, depending on the degrees of freedom considered. The findings are in agreement with previous experimental results and give an idea of the universal dynamical behavior of the clusters when approaching criticality. We suggest that this behavior is a combination of translation and vortex rotational motion (omega(c)=0.84).

Unified Scaling Law for flux pinning in practical superconductors: II. Parameter testing, scaling constants, and the Extrapolative Scaling Expression

NASA Astrophysics Data System (ADS)

Ekin, Jack W.; Cheggour, Najib; Goodrich, Loren; Splett, Jolene; Bordini, Bernardo; Richter, David

2016-12-01

A scaling study of several thousand Nb3Sn critical-current (I c) measurements is used to derive the Extrapolative Scaling Expression (ESE), a relation that can quickly and accurately extrapolate limited datasets to obtain full three-dimensional dependences of I c on magnetic field (B), temperature (T), and mechanical strain (ɛ). The relation has the advantage of being easy to implement, and offers significant savings in sample characterization time and a useful tool for magnet design. Thorough data-based analysis of the general parameterization of the Unified Scaling Law (USL) shows the existence of three universal scaling constants for practical Nb3Sn conductors. The study also identifies the scaling parameters that are conductor specific and need to be fitted to each conductor. This investigation includes two new, rare, and very large I c(B,T,ɛ) datasets (each with nearly a thousand I c measurements spanning magnetic fields from 1 to 16 T, temperatures from ˜2.26 to 14 K, and intrinsic strains from -1.1% to +0.3%). The results are summarized in terms of the general USL parameters given in table 3 of Part 1 (Ekin J W 2010 Supercond. Sci. Technol. 23 083001) of this series of articles. The scaling constants determined for practical Nb3Sn conductors are: the upper-critical-field temperature parameter v = 1.50 ± 0.04 the cross-link parameter w = 3.0 ± 0.3 and the strain curvature parameter u = 1.7 ± 0.1 (from equation (29) for b c2(ɛ) in Part 1). These constants and required fitting parameters result in the ESE relation, given by I c ( B , T , ɛ ) B = C [ b c 2 ( ɛ ) ] s ( 1 - t 1.5 ) η - μ ( 1 - t 2 ) μ b p ( 1 - b ) q with reduced magnetic field b ≡ B/B c2*(T,ɛ) and reduced temperature t ≡ T/T c*(ɛ), where: B c 2 * ( T , ɛ ) = B c 2 * ( 0 , 0 ) ( 1 - t 1.5 ) b c 2 ( ɛ ) T c * ( ɛ ) = T c * ( 0 ) [ b c 2 ( ɛ ) ] 1/3 and fitting parameters: C, B c2*(0,0), T c*(0), s, either η or μ (but not both), plus the parameters in the strain function b c2(ɛ). The pinning-force shape parameters p and q are also preferably fitted (simultaneously with the other parameters), but default values p = 0.5 and q = 2.0 also give high fitting accuracy when the range of relative magnetic fields is not extensive. Default values are also essential when the magnetic field data range is insufficient to determine p and q. The scaling constants are remarkably stable (changes less than ˜1%) with respect to different values of p and q, Nb3Sn conductor configurations, magnetic self-field corrections, and pinning-force trim values. The results demonstrate that the scaling of transport critical current holds down to the lowest temperatures measured ˜2.2 K, for both magnetic self-field corrected and uncorrected data. An initial comparison is also made between transport and magnetization scaling data in matched Nb3Sn samples and significant differences are found, especially for the upper critical field B c2*(T,ɛ), which may be a result of inhomogeneous shielding currents. In Part 3 of this topical review series (Ekin J W 2017 Supercond. Sci. Technol. at press), the smallest practical minimum dataset for extrapolating full I c(B,T,ɛ) datasets is derived. Application of the ESE relation is illustrated in several new areas, including full characterization of Nb3Sn conductors from as little as a single I c(B) curve when a few core parameters have been determined for similar conductors.

Study on design and cutting parameters of rotating needles for core biopsy.

PubMed

Giovannini, Marco; Ren, Huaqing; Cao, Jian; Ehmann, Kornel

2018-06-15

Core needle biopsies are widely adopted medical procedures that consist in the removal of biological tissue to better identify a lesion or an abnormality observed through a physical exam or a radiology scan. These procedures can provide significantly more information than most medical tests and they are usually performed on bone lesions, breast masses, lymph nodes and the prostate. The quality of the samples mainly depends on the forces exerted by the needle during the cutting process. The reduction of these forces is critical to extract high-quality tissue samples. The most critical factors that affect the cutting forces are the geometry of the needle tip and its motion while it is penetrating the tissue. However, optimal needle tip configurations and cutting parameters are not well established for rotating insertions. In this paper, the geometry and cutting forces of hollow needles are investigated. The fundamental goal of this study is to provide a series of guidelines for clinicians and surgeons to properly select the optimal tip geometries and speeds. Analytical models related to the cutting angles of several needle tip designs are presented and compared. Several needle tip geometries were manufactured from a 14-gauge cannula, commonly adopted during breast biopsies. The needles were then tested at different speeds and on different phantom tissues. According to these experimental measurements recommendations were formulated for rotating needle insertions. The findings of this study can be applied and extended to several biopsy procedures in which a cannula is used to extract tissue samples. Copyright © 2018 Elsevier Ltd. All rights reserved.

Meteorology and ethnicity as critical factors in HRIPT: Comparing responses between Chinese and Indian ethnicities.

PubMed

Yuan, Chao; Wang, Xue-Min; Galzote, Carlos; Tan, Yi-Mei; Bhagat, Kamlesh V; Yuan, Zhi-Kang; Du, Jian-Fei; Tan, Yuan

2013-06-01

Human repeated insult patch test (HRIPT) is regarded as one of the confirmatory test in determining the safety of skin sensitizers. A number of important factors should be considered when conducting and interpreting the results of the HRIPT. To investigate for probable critical factors that influence the results of HRIPT with the same protocol in Shanghai and Mumbai. Two HRIPTs were carried out in Shanghai and Mumbai in 2011. Six identical products and 1% sodium lauryl sulfate were tested. Two Chinese dermatologists performed the grading in the two cities. Climate conditions of Shanghai and Mumbai were also recorded. For four lower reaction ratio products, cumulative irritation scores in the induction phase were higher in individuals whose ethnicity was Indian rather than Chinese. Reaction ratio of the same four products was highly correlated to the climatic parameters. The other two higher reaction ratio products and the positive control had no difference between the two ethnicities. Greater attention ought to be paid to the impact of climate on the results of HRIPT, especially for the mild irritation cosmetics when giving the interpretation. Greater emphasis also needs to be placed on the ethnicity of the subjects. Crown Copyright © 2013. Published by Elsevier Inc. All rights reserved.

Mechanical behavior of a ceramic matrix composite material. M.S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Grosskopf, Paul P.; Duke, John C., Jr.

1991-01-01

Monolithic ceramic materials have been used in industry for hundreds of years. These materials have proven their usefulness in many applications, yet, their potential for critical structural applications is limited. The existence of an imperfection in a monolithic ceramic on the order of several microns in size may be critical, resulting in catastrophic failure. To overcome this extreme sensitivity to small material imperfections, reinforced ceramic materials were developed. A ceramic matrix which has been reinforced with continuous fibers is not only less sensitive to microscopic flaws, but is also able to sustain significant damage without suffering catastrophic failure. A borosilicate glass reinforced with several layers of plain weave silicon carbide cloth (Nicalon) was studied. The mechanical testing which was performed included both flexural and tensile loading configurations. This testing was done not only to determine the material properties, but also to initiate a controlled amount of damage within each specimen. Several nondestructive testing techniques, including acousto-ultrasonics (AU), were performed on the specimens periodically during testing. The AU signals were monitored through the use of an IBM compatible personal computer with a high speed data acquisition board. Software was written which manipulates the AU signals in both the time and frequency domains, resulting in quantitative measures of the mechanical response of the material. The measured AU parameters are compared to both the mechanical test results and data from other nondestructive methods including ultrasonic C-scans and penetrant enhanced x ray radiography.

Overcoming the sign problem at finite temperature: Quantum tensor network for the orbital eg model on an infinite square lattice

NASA Astrophysics Data System (ADS)

Czarnik, Piotr; Dziarmaga, Jacek; Oleś, Andrzej M.

2017-07-01

The variational tensor network renormalization approach to two-dimensional (2D) quantum systems at finite temperature is applied to a model suffering the notorious quantum Monte Carlo sign problem—the orbital eg model with spatially highly anisotropic orbital interactions. Coarse graining of the tensor network along the inverse temperature β yields a numerically tractable 2D tensor network representing the Gibbs state. Its bond dimension D —limiting the amount of entanglement—is a natural refinement parameter. Increasing D we obtain a converged order parameter and its linear susceptibility close to the critical point. They confirm the existence of finite order parameter below the critical temperature Tc, provide a numerically exact estimate of Tc, and give the critical exponents within 1 % of the 2D Ising universality class.

Motion in a modified Chermnykh's restricted three-body problem with oblateness

NASA Astrophysics Data System (ADS)

Singh, Jagadish; Leke, Oni

2014-03-01

In this paper, the restricted problem of three bodies is generalized to include a case when the passively gravitating test particle is an oblate spheroid under effect of small perturbations in the Coriolis and centrifugal forces when the first primary is a source of radiation and the second one an oblate spheroid, coupled with the influence of the gravitational potential from the belt. The equilibrium points are found and it is seen that, in addition to the usual three collinear equilibrium points, there appear two new ones due to the potential from the belt and the mass ratio. Two triangular equilibrium points exist. These equilibria are affected by radiation of the first primary, small perturbation in the centrifugal force, oblateness of both the test particle and second primary and the effect arising from the mass of the belt. The linear stability of the equilibrium points is explored and the stability outcome of the collinear equilibrium points remains unstable. In the case of the triangular points, motion is stable with respect to some conditions which depend on the critical mass parameter; influenced by the small perturbations, radiating effect of the first primary, oblateness of the test body and second primary and the gravitational potential from the belt. The effects of each of the imposed free parameters are analyzed. The potential from the belt and small perturbation in the Coriolis force are stabilizing parameters while radiation, small perturbation in the centrifugal force and oblateness reduce the stable regions. The overall effect is that the region of stable motion increases under the combine action of these parameters. We have also found the frequencies of the long and short periodic motion around stable triangular points. Illustrative numerical exploration is rendered in the Sun-Jupiter and Sun-Earth systems where we show that in reality, for some values of the system parameters, the additional equilibrium points do not in general exist even when there is a belt to interact with.

Study on viscosity of conventional and polymer modified asphalt binders in steady and dynamic shear domain

NASA Astrophysics Data System (ADS)

Saboo, Nikhil; Singh, Bhupendra; Kumar, Praveen; Vikram, Durgesh

2018-02-01

This study focuses on evaluating the flow behavior of conventional and polymer modified asphalt binders in steady- and dynamic-shear domain, for a temperature range of 20-70 °C, using a Dynamic Shear Rheometer (DSR). Steady-shear viscosity and frequency sweep tests were carried out on two conventional (VG 10 and VG 30) and two polymer (SBS and EVA) modified asphalt binders. Applicability of the Cox-Merz principle was evaluated and complex viscosity master curves were analyzed at five different reference temperatures. Cross model was used to simulate the complex viscosity master curves at different temperatures. It was found that asphalt binders exhibited shear-thinning behavior at all the test temperatures. The critical shear rate increased with increase in temperature and was found to be lowest for plastomeric modified asphalt binder. The Cox-Merz principle was found to be valid in the zero-shear viscosity (ZSV) domain and deviated at higher frequency/shear rate for all the binders. Results from the study indicated that the ratio of ZSV can be successfully used as shift factors for construction of master curves at different reference temperatures. Cross model was found to be suitable in simulating the complex viscosity master curves at all the test temperatures. Analysis of model parameters indicated that a strong relationship exists between ZSV and the critical shear rate. ZSV and critical shear rate varied exponentially with temperature. This relationship was used to propose a simple equation for assessing the shift factors for construction of master curves.

Experimental criticality specifications. An annotated bibliography through 1977

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

Paxton, H.C.

1978-05-01

The compilation of approximately 300 references gives sources of experimental criticality parameters of systems containing /sup 235/U, /sup 233/U, and /sup 239/Pu. The intent is to cover basic data for criticality safety applications. The references are arranged by subject.

Using noble gas tracers to estimate residual CO2 saturation in the field: results from the CO2CRC Otway residual saturation and dissolution test

NASA Astrophysics Data System (ADS)

LaForce, T.; Ennis-King, J.; Paterson, L.

2013-12-01

Residual CO2 saturation is a critically important parameter in CO2 storage as it can have a large impact on the available secure storage volume and post-injection CO2 migration. A suite of single-well tests to measure residual trapping was conducted at the Otway test site in Victoria, Australia during 2011. One or more of these tests could be conducted at a prospective CO2 storage site before large-scale injection. The test involved injection of 150 tonnes of pure carbon dioxide followed by 454 tonnes of CO2-saturated formation water to drive the carbon dioxide to residual saturation. This work presents a brief overview of the full test sequence, followed by the analysis and interpretation of the tests using noble gas tracers. Prior to CO2 injection krypton (Kr) and xenon (Xe) tracers were injected and back-produced to characterise the aquifer under single-phase conditions. After CO2 had been driven to residual the two tracers were injected and produced again. The noble gases act as non-partitioning aqueous-phase tracers in the undisturbed aquifer and as partitioning tracers in the presence of residual CO2. To estimate residual saturation from the tracer test data a one-dimensional radial model of the near-well region is used. In the model there are only two independent parameters: the apparent dispersivity of each tracer and the residual CO2 saturation. Independent analysis of the Kr and Xe tracer production curves gives the same estimate of residual saturation to within the accuracy of the method. Furthermore the residual from the noble gas tracer tests is consistent with other measurements in the sequence of tests.

Integration of Mahalanobis-Taguchi system and traditional cost accounting for remanufacturing crankshaft

NASA Astrophysics Data System (ADS)

Abu, M. Y.; Norizan, N. S.; Rahman, M. S. Abd

2018-04-01

Remanufacturing is a sustainability strategic planning which transforming the end of life product to as new performance with their warranty is same or better than the original product. In order to quantify the advantages of this strategy, all the processes must implement the optimization to reach the ultimate goal and reduce the waste generated. The aim of this work is to evaluate the criticality of parameters on the end of life crankshaft based on Taguchi’s orthogonal array. Then, estimate the cost using traditional cost accounting by considering the critical parameters. By implementing the optimization, the remanufacturer obviously produced lower cost and waste during production with higher potential to gain the profit. Mahalanobis-Taguchi System was proven as a powerful method of optimization that revealed the criticality of parameters. When subjected the method to the MAN engine model, there was 5 out of 6 crankpins were critical which need for grinding process while no changes happened to the Caterpillar engine model. Meanwhile, the cost per unit for MAN engine model was changed from MYR1401.29 to RM1251.29 while for Caterpillar engine model have no changes due to the no changes on criticality of parameters consideration. Therefore, by integrating the optimization and costing through remanufacturing process, a better decision can be achieved after observing the potential profit will be gained. The significant of output demonstrated through promoting sustainability by reducing re-melting process of damaged parts to ensure consistent benefit of return cores.

Control over dark current densities and cutoff wavelengths of GaAs/AlGaAs QWIP grown by multi-wafer MBE reactor

NASA Astrophysics Data System (ADS)

Roodenko, K.; Choi, K. K.; Clark, K. P.; Fraser, E. D.; Vargason, K. W.; Kuo, J.-M.; Kao, Y.-C.; Pinsukanjana, P. R.

2016-09-01

Performance of quantum well infrared photodetector (QWIP) device parameters such as detector cutoff wavelength and the dark current density depend strongly on the quality and the control of the epitaxy material growth. In this work, we report on a methodology to precisely control these critical material parameters for long wavelength infrared (LWIR) GaAs/AlGaAs QWIP epi wafers grown by multi-wafer production Molecular beam epitaxy (MBE). Critical growth parameters such as quantum well (QW) thickness, AlGaAs composition and QW doping level are discussed.

Desktop Systems for Manufacturing Carbon Nanotube Films by Chemical Vapor Deposition

DTIC Science & Technology

2007-06-01

existing low cost tube furnace designs limit the researcher’s ability to fully separate critical reaction parameters such as temperature and flow...Often heated using an external resistive heater coil, a typical configuration, shown in Figure 4, might place a tube made of a non- reactive ...researcher’s ability to fully separate critical parameters such as temperature and flow profiles. Additionally, the use of heating elements external to

Acoustically-Responsive Scaffolds: Control of Growth Factor Release for Tissue Regeneration Using Ultrasound

NASA Astrophysics Data System (ADS)

Moncion, Alexander

Administration of exogenous growth factors (GFs) is a proposed method of stimulating tissue regeneration. Conventional administration routes, such as at-site or systemic injections, have yielded problems with efficacy and/or safety, thus hindering the translation of GF-based regenerative techniques. Hydrogel scaffolds are commonly used as biocompatible delivery vehicles for GFs. Yet hydrogels do not afford spatial or temporal control of GF release - two critical parameters for tissue regeneration. Controlled delivery of GFs is critical for angiogenesis, which is a crucial process in tissue engineering that provides oxygen and nutrients to cells within an implanted hydrogel scaffold. Angiogenesis requires multiple GFs that are presented with distinct spatial and temporal profiles. Thus, controlled release of GFs with spatiotemporal modulation would significantly improve tissue regeneration by recapitulating endogenous GF presentation. In order to achieve this goal, we have developed acoustically-responsive scaffolds (ARSs), which are fibrin hydrogels doped with sonosensitive perfluorocarbon (PFC) emulsions capable of encapsulating various payloads. Focused, mega-Hertz range, ultrasound (US) can modulate the release of a payload non-invasively and in an on-demand manner from ARSs via physical mechanisms termed acoustic droplet vaporization (ADV) and inertial cavitation (IC). This work presents the relationship between the ADV/IC thresholds and various US and hydrogel parameters. These physical mechanisms were used for the controlled release of fluorescent dextran in vitro and in vivo to determine the ARS and US parameters that yielded optimal payload release. The optimal ARS and US parameters were used to demonstrate the controlled release of basic fibroblast growth factor from an in vivo subcutaneous implant model - leading to enhanced angiogenesis and perfusion. Additionally, different acoustic parameters and PFCs were tested and optimized to demonstrate the controlled release of two encapsulated payloads within an ARS. Overall, ARSs are a promising platform for GF delivery in tissue regeneration applications.

Modified Denavit-Hartenberg parameters for better location of joint axis systems in robot arms

NASA Technical Reports Server (NTRS)

Barker, L. K.

1986-01-01

The Denavit-Hartenberg parameters define the relative location of successive joint axis systems in a robot arm. A recent justifiable criticism is that one of these parameters becomes extremely large when two successive joints have near-parallel rotational axes. Geometrically, this parameter then locates a joint axis system at an excessive distance from the robot arm and, computationally, leads to an ill-conditioned transformation matrix. In this paper, a simple modification (which results from constraining a transverse vector between successive joint rotational axes to be normal to one of the rotational axes, instead of both) overcomes this criticism and favorably locates the joint axis system. An example is given for near-parallel rotational axes of the elbow and shoulder joints in a robot arm. The regular and modified parameters are extracted by an algebraic method with simulated measurement data. Unlike the modified parameters, extracted values of the regular parameters are very sensitive to measurement accuracy.

Critical Heat Flux Phenomena at HighPressure & Low Mass Fluxes: NEUP Final Report Part I: Experiments

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

Corradini, Michael; Wu, Qiao

2015-04-30

This report is a preliminary document presenting an overview of the Critical Heat Flux (CHF) phenomenon, the High Pressure Critical Heat Flux facility (HPCHF), preliminary CHF data acquired, and the future direction of the research. The HPCHF facility has been designed and built to study CHF at high pressure and low mass flux ranges in a rod bundle prototypical of conceptual Small Modular Reactor (SMR) designs. The rod bundle is comprised of four electrically heated rods in a 2x2 square rod bundle with a prototypic chopped-cosine axial power profile and equipped with thermocouples at various axial and circumferential positions embeddedmore » in each rod for CHF detection. Experimental test parameters for CHF detection range from pressures of ~80 – 160 bar, mass fluxes of ~400 – 1500 kg/m2s, and inlet water subcooling from ~30 – 70°C. The preliminary data base established will be further extended in the future along with comparisons to existing CHF correlations, models, etc. whose application ranges may be applicable to the conditions of SMRs.« less

Implications of Weak-Link Behavior on the Performance of Mo/Au Bilayer Transition-Edge Sensors

NASA Technical Reports Server (NTRS)

Smith, Stephen J.

2011-01-01

Understanding the physical properties of the superconducting-to-normal transition is fundamental for optimizing the design and performance of transition-edge sensors (TESs). Recent critical current measurements of Mol Au bilayer test structures show that they act as weak superconducting links, exhibiting oscillatory, Fraunhofer-like behavior with applied magnetic field. In this paper we investigate the implications of this behavior for TES X-ray detectors, under operational bias conditions. These devices include normal metal features used for absorber attachment and unexplained noise suppression, which result in modifications to the previously reported critical current behavior. We present measurements of the logarithmic resistance sensitivity with temperature, a, and current, b, as a function of applied magnetic field and bias point within the resistive transition. Results show that these important device parameters exhibit similar oscillatory behavior with applied magnetic field, which in turn affects the signal responsivity and noise, and hence the energy resolution. These results show the significance of the critical current in determining the performance of TESs and hold promise to improve future.

Influence of dental occlusion on postural control and plantar pressure distribution.

PubMed

Scharnweber, Benjamin; Adjami, Frederic; Schuster, Gabriele; Kopp, Stefan; Natrup, Jörg; Erbe, Christina; Ohlendorf, Daniela

2017-11-01

The number of studies investigating correlations between the temporomandibular system and body posture, postural control or plantar pressure distribution is continuously increasing. If a connection can be found, it is often of minor influence or for only a single parameter. However, small subject groups are critical. This study was conducted to define correlations between dental parameters, postural control and plantar pressure distribution in healthy males. In this study, 87 male subjects with an average age of 25.23 ± 3.5 years (ranging from 18 to 35 years) were examined. Dental casts of the subjects were analyzed. Postural control and plantar pressure distribution were recorded by a force platform. Possible orthodontic and orthopedic factors of influence were determined by either an anamnesis or a questionnaire. All tests performed were randomized and repeated three times each for intercuspal position (ICP) and blocked occlusion (BO). For a statistical analysis of the results, non-parametric tests (Wilcoxon-Matched-Pairs-Test, Kruskall-Wallis-Test) were used. A revision of the results via Bonferroni-Holm correction was considered. ICP increases body sway in the frontal (p ≤ 0.01) and sagittal planes (p ≤ 0.03) compared to BO, whereas all other 29 correlations were independent of the occlusion position. For both of the ICP or BO cases, Angle-class, midline-displacement, crossbite, or orthodontic therapy were found to have no influence on postural control or plantar pressure distribution (p > 0.05). However, the contact time of the left foot decreased (p ≤ 0.001) while detecting the plantar pressure distribution in each position. Persistent dental parameters have no effect on postural sway. In addition, postural control and plantar pressure distribution have been found to be independent postural criteria.

A Comparison of Single-Cycle Versus Multiple-Cycle Proof Testing Strategies

NASA Technical Reports Server (NTRS)

McClung, R. C.; Chell, G. G.; Millwater, H. R.; Russell, D. A.; Millwater, H. R.

1999-01-01

Single-cycle and multiple-cycle proof testing (SCPT and MCPT) strategies for reusable aerospace propulsion system components are critically evaluated and compared from a rigorous elastic-plastic fracture mechanics perspective. Earlier MCPT studies are briefly reviewed. New J-integral estimation methods for semielliptical surface cracks and cracks at notches are derived and validated. Engineering methods are developed to characterize crack growth rates during elastic-plastic fatigue crack growth (FCG) and the tear-fatigue interaction near instability. Surface crack growth experiments are conducted with Inconel 718 to characterize tearing resistance, FCG under small-scale yielding and elastic-plastic conditions, and crack growth during simulated MCPT. Fractography and acoustic emission studies provide additional insight. The relative merits of SCPT and MCPT are directly compared using a probabilistic analysis linked with an elastic-plastic crack growth computer code. The conditional probability of failure in service is computed for a population of components that have survived a previous proof test, based on an assumed distribution of initial crack depths. Parameter studies investigate the influence of proof factor, tearing resistance, crack shape, initial crack depth distribution, and notches on the MCPT versus SCPT comparison. The parameter studies provide a rational basis to formulate conclusions about the relative advantages and disadvantages of SCPT and MCPT. Practical engineering guidelines are proposed to help select the optimum proof test protocol in a given application.

A Comparison of Single-Cycle Versus Multiple-Cycle Proof Testing Strategies

NASA Technical Reports Server (NTRS)

McClung, R. C.; Chell, G. G.; Millwater, H. R.; Russell, D. A.; Orient, G. E.

1996-01-01

Single-cycle and multiple-cycle proof testing (SCPT and MCPT) strategies for reusable aerospace propulsion system components are critically evaluated and compared from a rigorous elastic-plastic fracture mechanics perspective. Earlier MCPT studies are briefly reviewed. New J-integral estimation methods for semi-elliptical surface cracks and cracks at notches are derived and validated. Engineering methods are developed to characterize crack growth rates during elastic-plastic fatigue crack growth (FCG) and the tear-fatigue interaction near instability. Surface crack growth experiments are conducted with Inconel 718 to characterize tearing resistance, FCG under small-scale yielding and elastic-plastic conditions, and crack growth during simulated MCPT. Fractography and acoustic emission studies provide additional insight. The relative merits of SCPT and MCPT are directly compared using a probabilistic analysis linked with an elastic-plastic crack growth computer code. The conditional probability of failure in service is computed for a population of components that have survived a previous proof test, based on an assumed distribution of initial crack depths. Parameter studies investigate the influence of proof factor, tearing resistance, crack shape, initial crack depth distribution, and notches on the MCPT vs. SCPT comparison. The parameter studies provide a rational basis to formulate conclusions about the relative advantages and disadvantages of SCPT and MCPT. Practical engineering guidelines are proposed to help select the optimum proof test protocol in a given application.

Iterative Stable Alignment and Clustering of 2D Transmission Electron Microscope Images

PubMed Central

Yang, Zhengfan; Fang, Jia; Chittuluru, Johnathan; Asturias, Francisco J.; Penczek, Pawel A.

2012-01-01

SUMMARY Identification of homogeneous subsets of images in a macromolecular electron microscopy (EM) image data set is a critical step in single-particle analysis. The task is handled by iterative algorithms, whose performance is compromised by the compounded limitations of image alignment and K-means clustering. Here we describe an approach, iterative stable alignment and clustering (ISAC) that, relying on a new clustering method and on the concepts of stability and reproducibility, can extract validated, homogeneous subsets of images. ISAC requires only a small number of simple parameters and, with minimal human intervention, can eliminate bias from two-dimensional image clustering and maximize the quality of group averages that can be used for ab initio three-dimensional structural determination and analysis of macromolecular conformational variability. Repeated testing of the stability and reproducibility of a solution within ISAC eliminates heterogeneous or incorrect classes and introduces critical validation to the process of EM image clustering. PMID:22325773

Characterization of damage modes in dental ceramic bilayer structures.

PubMed

Deng, Yan; Lawn, Brian R; Lloyd, Isabel K

2002-01-01

Results of contact tests using spherical indenters on flat ceramic coating layers bonded to compliant substrates are reported for selected dental ceramics. Critical loads to produce various damage modes, cone cracking, and quasiplasticity at the top surfaces and radial cracking at the lower (inner) surfaces are measured as a function of ceramic-layer thickness. It is proposed that these damage modes, especially radial cracking, are directly relevant to the failure of all-ceramic dental crowns. The critical load data are analyzed with the use of explicit fracture-mechanics relations, expressible in terms of routinely measurable material parameters (elastic modulus, strength, toughness, hardness) and essential geometrical variables (layer thickness, contact radius). The utility of such analyses in the design of ceramic/substrate bilayer systems for optimal resistance to lifetime-threatening damage is discussed. Copyright 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 137--145, 2002; DOI 10.1002/jbm.10091

Corresponding states law for a generalized Lennard-Jones potential.

PubMed

Orea, P; Romero-Martínez, A; Basurto, E; Vargas, C A; Odriozola, G

2015-07-14

It was recently shown that vapor-liquid coexistence densities derived from Mie and Yukawa models collapse to define a single master curve when represented against the difference between the reduced second virial coefficient at the corresponding temperature and that at the critical point. In this work, we further test this proposal for another generalization of the Lennard-Jones pair potential. This is carried out for vapor-liquid coexistence densities, surface tension, and vapor pressure, along a temperature window set below the critical point. For this purpose, we perform molecular dynamics simulations by varying the potential softness parameter to produce from very short to intermediate attractive ranges. We observed all properties to collapse and yield master curves. Moreover, the vapor-liquid curve is found to share the exact shape of the Mie and attractive Yukawa. Furthermore, the surface tension and the logarithm of the vapor pressure are linear functions of this difference of reduced second virial coefficients.

Group additivity calculations of the thermodynamic properties of unfolded proteins in aqueous solution: a critical comparison of peptide-based and HKF models.

PubMed

Hakin, A W; Hedwig, G R

2001-02-15

A recent paper in this journal [Amend and Helgeson, Biophys. Chem. 84 (2000) 105] presented a new group additivity model to calculate various thermodynamic properties of unfolded proteins in aqueous solution. The parameters given for the revised Helgeson-Kirkham-Flowers (HKF) equations of state for all the constituent groups of unfolded proteins can be used, in principle, to calculate the partial molar heat capacity, C(o)p.2, and volume, V2(0), at infinite dilution of any polypeptide. Calculations of the values of C(o)p.2 and V2(0) for several polypeptides have been carried out to test the predictive utility of the HKF group additivity model. The results obtained are in very poor agreement with experimental data, and also with results calculated using a peptide-based group additivity model. A critical assessment of these two additivity models is presented.

Self-avoiding walk on a square lattice with correlated vacancies

NASA Astrophysics Data System (ADS)

Cheraghalizadeh, J.; Najafi, M. N.; Mohammadzadeh, H.; Saber, A.

2018-04-01

The self-avoiding walk on the square site-diluted correlated percolation lattice is considered. The Ising model is employed to realize the spatial correlations of the metric space. As a well-accepted result, the (generalized) Flory's mean-field relation is tested to measure the effect of correlation. After exploring a perturbative Fokker-Planck-like equation, we apply an enriched Rosenbluth Monte Carlo method to study the problem. To be more precise, the winding angle analysis is also performed from which the diffusivity parameter of Schramm-Loewner evolution theory (κ ) is extracted. We find that at the critical Ising (host) system, the exponents are in agreement with Flory's approximation. For the off-critical Ising system, we find also a behavior for the fractal dimension of the walker trace in terms of the correlation length of the Ising system ξ (T ) , i.e., DFSAW(T ) -DFSAW(Tc) ˜1/√{ξ (T ) } .

Pressure dependence of critical temperature of bulk FeSe from spin fluctuation theory

NASA Astrophysics Data System (ADS)

Hirschfeld, Peter; Kreisel, Andreas; Wang, Yan; Tomic, Milan; Jeschke, Harald; Jacko, Anthony; Valenti, Roser; Maier, Thomas; Scalapino, Douglas

2013-03-01

The critical temperature of the 8K superconductor FeSe is extremely sensitive to pressure, rising to a maximum of 40K at about 10GPa. We test the ability of the current generation of fluctuation exchange pairing theories to account for this effect, by downfolding the density functional theory electronic structure for each pressure to a tight binding model. The Fermi surface found in such a procedure is then used with fixed Hubbard parameters to determine the pairing strength using the random phase approximation for the spin singlet pairing vertex. We find that the evolution of the Fermi surface captured by such an approach is alone not sufficient to explain the observed pressure dependence, and discuss alternative approaches. PJH, YW, AK were supported by DOE DE-FG02-05ER46236, the financial support of MT, HJ, and RV from the DFG Schwerpunktprogramm 1458 is kindly acknowledged.

A remote sensing based vegetation classification logic for global land cover analysis

USGS Publications Warehouse

Running, Steven W.; Loveland, Thomas R.; Pierce, Lars L.; Nemani, R.R.; Hunt, E. Raymond

1995-01-01

This article proposes a simple new logic for classifying global vegetation. The critical features of this classification are that 1) it is based on simple, observable, unambiguous characteristics of vegetation structure that are important to ecosystem biogeochemistry and can be measured in the field for validation, 2) the structural characteristics are remotely sensible so that repeatable and efficient global reclassifications of existing vegetation will be possible, and 3) the defined vegetation classes directly translate into the biophysical parameters of interest by global climate and biogeochemical models. A first test of this logic for the continental United States is presented based on an existing 1 km AVHRR normalized difference vegetation index database. Procedures for solving critical remote sensing problems needed to implement the classification are discussed. Also, some inferences from this classification to advanced vegetation biophysical variables such as specific leaf area and photosynthetic capacity useful to global biogeochemical modeling are suggested.

Gas analysis system for the Eight Foot High Temperature Tunnel

NASA Technical Reports Server (NTRS)

Leighty, Bradley D.; Davis, Patricia P.; Upchurch, Billy T.; Puster, Richard L.

1992-01-01

This paper describes the development of a gas collection and analysis system that is to be installed in the Eight-Foot High Temperature Tunnel (8' HTT) at NASA's Langley Research Center. This system will be used to analyze the test gas medium that results after burning a methane-air mixture to achieve the proper tunnel test parameters. The system consists of a sampling rake, a gas sample storage array, and a gas chromatographic system. Gas samples will be analyzed after each run to assure that proper combustion takes place in the tunnel resulting in a correctly balanced composition of the test gas medium. The proper ratio of gas species is critically necessary in order for the proper operation and testing of scramjet engines in the tunnel. After a variety of methane-air burn conditions have been analyzed, additional oxygen will be introduced into the combusted gas and the enriched test gas medium analyzed. The pre/post enrichment sets of data will be compared to verify that the gas species of the test gas medium is correctly balanced for testing of air-breathing engines.

Phase transition with trivial quantum criticality in an anisotropic Weyl semimetal

NASA Astrophysics Data System (ADS)

Li, Xin; Wang, Jing-Rong; Liu, Guo-Zhu

2018-05-01

When a metal undergoes continuous quantum phase transition, the correlation length diverges at the critical point and the quantum fluctuation of order parameter behaves as a gapless bosonic mode. Generically, the coupling of this boson to fermions induces a variety of unusual quantum critical phenomena, such as non-Fermi liquid behavior and various emergent symmetries. Here, we perform a renormalization group analysis of the semimetal-superconductor quantum criticality in a three-dimensional anisotropic Weyl semimetal. Surprisingly, distinct from previously studied quantum critical systems, the anomalous dimension of anisotropic Weyl fermions flows to zero very quickly with decreasing energy, and the quasiparticle residue takes a nonzero value. These results indicate that the quantum fluctuation of superconducting order parameter is irrelevant at low energies, and a simple mean-field calculation suffices to capture the essential physics of the superconducting transition. We thus obtain a phase transition that exhibits trivial quantum criticality, which is unique comparing to other invariably nontrivial quantum critical systems. Our theoretical prediction can be experimentally verified by measuring the fermion spectral function and specific heat.

Estimability of geodetic parameters from space VLBI observables

NASA Technical Reports Server (NTRS)

Adam, Jozsef

1990-01-01

The feasibility of space very long base interferometry (VLBI) observables for geodesy and geodynamics is investigated. A brief review of space VLBI systems from the point of view of potential geodetic application is given. A selected notational convention is used to jointly treat the VLBI observables of different types of baselines within a combined ground/space VLBI network. The basic equations of the space VLBI observables appropriate for convariance analysis are derived and included. The corresponding equations for the ground-to-ground baseline VLBI observables are also given for a comparison. The simplified expression of the mathematical models for both space VLBI observables (time delay and delay rate) include the ground station coordinates, the satellite orbital elements, the earth rotation parameters, the radio source coordinates, and clock parameters. The observation equations with these parameters were examined in order to determine which of them are separable or nonseparable. Singularity problems arising from coordinate system definition and critical configuration are studied. Linear dependencies between partials are analytically derived. The mathematical models for ground-space baseline VLBI observables were tested with simulation data in the frame of some numerical experiments. Singularity due to datum defect is confirmed.

Airframe Icing Research Gaps: NASA Perspective

NASA Technical Reports Server (NTRS)

Potapczuk, Mark

2009-01-01

qCurrent Airframe Icing Technology Gaps: Development of a full 3D ice accretion simulation model. Development of an improved simulation model for SLD conditions. CFD modeling of stall behavior for ice-contaminated wings/tails. Computational methods for simulation of stability and control parameters. Analysis of thermal ice protection system performance. Quantification of 3D ice shape geometric characteristics Development of accurate ground-based simulation of SLD conditions. Development of scaling methods for SLD conditions. Development of advanced diagnostic techniques for assessment of tunnel cloud conditions. Identification of critical ice shapes for aerodynamic performance degradation. Aerodynamic scaling issues associated with testing scale model ice shape geometries. Development of altitude scaling methods for thermal ice protections systems. Development of accurate parameter identification methods. Measurement of stability and control parameters for an ice-contaminated swept wing aircraft. Creation of control law modifications to prevent loss of control during icing encounters. 3D ice shape geometries. Collection efficiency data for ice shape geometries. SLD ice shape data, in-flight and ground-based, for simulation verification. Aerodynamic performance data for 3D geometries and various icing conditions. Stability and control parameter data for iced aircraft configurations. Thermal ice protection system data for simulation validation.

Sobol' sensitivity analysis for stressor impacts on honeybee ...

EPA Pesticide Factsheets

We employ Monte Carlo simulation and nonlinear sensitivity analysis techniques to describe the dynamics of a bee exposure model, VarroaPop. Daily simulations are performed of hive population trajectories, taking into account queen strength, foraging success, mite impacts, weather, colony resources, population structure, and other important variables. This allows us to test the effects of defined pesticide exposure scenarios versus controlled simulations that lack pesticide exposure. The daily resolution of the model also allows us to conditionally identify sensitivity metrics. We use the variancebased global decomposition sensitivity analysis method, Sobol’, to assess firstand secondorder parameter sensitivities within VarroaPop, allowing us to determine how variance in the output is attributed to each of the input variables across different exposure scenarios. Simulations with VarroaPop indicate queen strength, forager life span and pesticide toxicity parameters are consistent, critical inputs for colony dynamics. Further analysis also reveals that the relative importance of these parameters fluctuates throughout the simulation period according to the status of other inputs. Our preliminary results show that model variability is conditional and can be attributed to different parameters depending on different timescales. By using sensitivity analysis to assess model output and variability, calibrations of simulation models can be better informed to yield more

Experimental investigation on hard turning of AISI 4340 steel using cemented coated carbide insert

NASA Astrophysics Data System (ADS)

Pradeep Kumar, J.; Kishore, K. P.; Ranjith Kumar, M.; Saran Karthick, K. R.; Vishnu Gowtham, S.

2018-02-01

Hard turning is a developing technology that offers many potential advantages compared to grinding, which remains the standard finishing process for critical hardened surfaces. In this work, an attempt has been made to experimentally investigate hard turning of AISI 4340 steel under wet and dry condition using cemented coated carbide insert. Hardness of the workpiece material is tested using Brinell and Rockwell hardness testers. CNC LATHE and cemented coated carbide inserts of designation CNMG 120408 are used for conducting experimental trials. Significant cutting parameters like cutting speed, feed rate and depth of cut are considered as controllable input parameters and surface roughness (Ra), tool wear are considered as output response parameters. Design of experiments is carried out with the help of Taguchi’s L9 orthogonal array. Results of response parameters like surface roughness and tool wear under wet and dry condition are analysed. It is found that surface roughness and tool wear are higher under dry machining condition when compared to wet machining condition. Feed rate significantly influences the surface roughness followed by cutting speed. Depth of cut significantly influences the tool wear followed by cutting speed.

Digital Radiography Using Digital Detector Arrays Fulfills Critical Applications for Offshore Pipelines

NASA Astrophysics Data System (ADS)

Moreira, EdsonVasques; Barbosa Rabello, JoséMaurício; Pereira, MarcelodosSantos; Lopes, RicardoTadeu; Zscherpel, Uwe

2010-12-01

Digital radiography in the inspection of welded pipes to be installed under deep water offshore gas and oil pipelines, like a presalt in Brazil, in the paper has been investigated. The aim is to use digital radiography for nondestructive testing of welds as it is already in use in the medical, aerospace, security, automotive, and petrochemical sectors. Among the current options, the DDA (Digital Detector Array) is considered as one of the best solutions to replace industrial films, as well as to increase the sensitivity to reduce the inspection cycle time. This paper shows the results of this new technique, comparing it to radiography with industrial films systems. In this paper, 20 test specimens of longitudinal welded pipe joints, specially prepared with artificial defects like cracks, lack of fusion, lack of penetration, and porosities and slag inclusions with varying dimensions and in 06 different base metal wall thicknesses, were tested and a comparison of the techniques was made. These experiments verified the purposed rules for parameter definitions and selections to control the required digital radiographic image quality as described in the draft international standard ISO/DIS 10893-7. This draft is first standard establishing the parameters for digital radiography on weld seam of welded steel pipes for pressure purposes to be used on gas and oil pipelines.

Generalized Fracture Toughness and Compressive Strength of Sustainable Concrete Including Low Calcium Fly Ash.

PubMed

Golewski, Grzegorz Ludwik

2017-12-06

The paper presents the results of tests on the effect of the low calcium fly ash (LCFA) addition, in the amounts of: 0% (LCFA-00), 20% (LCFA-20) and 30% (LCFA-30) by weight of cement, on fracture processes in structural concretes. In the course of the experiments, compressive strength of concrete and fracture toughness for: I (tensile), II (in-plane shear) and III (anti-plane shear) models of cracking were measured. The tests determined the effect of age of concretes modified with LCFA on the analyzed parameters. The experiments were carried out after: 3, 7, 28, 90, 180 and 365 days of curing. Fracture toughness of concretes was determined in terms of the critical stress intensity factors: K I c S , K I I c , K I I I c and then a generalized fracture toughness K c was specified. The obtained results are significant for the analysis of concrete structures subjected to complex loading. The properties of composites with the additive of LCFA depend on the age of the concrete tested. Mature concretes exhibit high fracture toughness at 20% additive of LCFA, while the additive of LCFA in the amount of 30% weight of cement has a beneficial effect on the parameters of concrete only after half a year of curing.

Predicting the Impact of Multiwalled Carbon Nanotubes on the Cement Hydration Products and Durability of Cementitious Matrix Using Artificial Neural Network Modeling Technique

PubMed Central

Fakhim, Babak; Hassani, Abolfazl; Rashidi, Alimorad; Ghodousi, Parviz

2013-01-01

In this study the feasibility of using the artificial neural networks modeling in predicting the effect of MWCNT on amount of cement hydration products and improving the quality of cement hydration products microstructures of cement paste was investigated. To determine the amount of cement hydration products thermogravimetric analysis was used. Two critical parameters of TGA test are PHPloss and CHloss. In order to model the TGA test results, the ANN modeling was performed on these parameters separately. In this study, 60% of data are used for model calibration and the remaining 40% are used for model verification. Based on the highest efficiency coefficient and the lowest root mean square error, the best ANN model was chosen. The results of TGA test implied that the cement hydration is enhanced in the presence of the optimum percentage (0.3 wt%) of MWCNT. Moreover, since the efficiency coefficient of the modeling results of CH and PHP loss in both the calibration and verification stages was more than 0.96, it was concluded that the ANN could be used as an accurate tool for modeling the TGA results. Another finding of this study was that the ANN prediction in higher ages was more precise. PMID:24489487

Generalized Fracture Toughness and Compressive Strength of Sustainable Concrete Including Low Calcium Fly Ash

PubMed Central

2017-01-01

The paper presents the results of tests on the effect of the low calcium fly ash (LCFA) addition, in the amounts of: 0% (LCFA-00), 20% (LCFA-20) and 30% (LCFA-30) by weight of cement, on fracture processes in structural concretes. In the course of the experiments, compressive strength of concrete and fracture toughness for: I (tensile), II (in-plane shear) and III (anti-plane shear) models of cracking were measured. The tests determined the effect of age of concretes modified with LCFA on the analyzed parameters. The experiments were carried out after: 3, 7, 28, 90, 180 and 365 days of curing. Fracture toughness of concretes was determined in terms of the critical stress intensity factors: KIcS, KIIc, KIIIc and then a generalized fracture toughness Kc was specified. The obtained results are significant for the analysis of concrete structures subjected to complex loading. The properties of composites with the additive of LCFA depend on the age of the concrete tested. Mature concretes exhibit high fracture toughness at 20% additive of LCFA, while the additive of LCFA in the amount of 30% weight of cement has a beneficial effect on the parameters of concrete only after half a year of curing. PMID:29211029

Computer Simulation of Microwave Devices

NASA Technical Reports Server (NTRS)

Kory, Carol L.

1997-01-01

The accurate simulation of cold-test results including dispersion, on-axis beam interaction impedance, and attenuation of a helix traveling-wave tube (TWT) slow-wave circuit using the three-dimensional code MAFIA (Maxwell's Equations Solved by the Finite Integration Algorithm) was demonstrated for the first time. Obtaining these results is a critical step in the design of TWT's. A well-established procedure to acquire these parameters is to actually build and test a model or a scale model of the circuit. However, this procedure is time-consuming and expensive, and it limits freedom to examine new variations to the basic circuit. These limitations make the need for computational methods crucial since they can lower costs, reduce tube development time, and lessen limitations on novel designs. Computer simulation has been used to accurately obtain cold-test parameters for several slow-wave circuits. Although the helix slow-wave circuit remains the mainstay of the TWT industry because of its exceptionally wide bandwidth, until recently it has been impossible to accurately analyze a helical TWT using its exact dimensions because of the complexity of its geometrical structure. A new computer modeling technique developed at the NASA Lewis Research Center overcomes these difficulties. The MAFIA three-dimensional mesh for a C-band helix slow-wave circuit is shown.

The critical crossover at the n-hexane-water interface

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

Tikhonov, A. M., E-mail: tikhonov@kapitza.ras.r

According to estimates of the parameters of the critical crossover in monolayers of long-chain alcohol molecules adsorbed at the n-hexane-water interface, all systems in which this phenomenon is observed are characterized by the same value of the critical exponent {nu} {approx} 1.8.

Correlation of Electric Field and Critical Design Parameters for Ferroelectric Tunable Microwave Filters

NASA Technical Reports Server (NTRS)

Subramanyam, Guru; VanKeuls, Fred W.; Miranda, Felix A.; Canedy, Chadwick L.; Aggarwal, Sanjeev; Venkatesan, Thirumalai; Ramesh, Ramamoorthy

2000-01-01

The correlation of electric field and critical design parameters such as the insertion loss, frequency ability return loss, and bandwidth of conductor/ferroelectric/dielectric microstrip tunable K-band microwave filters is discussed in this work. This work is based primarily on barium strontium titanate (BSTO) ferroelectric thin film based tunable microstrip filters for room temperature applications. Two new parameters which we believe will simplify the evaluation of ferroelectric thin films for tunable microwave filters, are defined. The first of these, called the sensitivity parameter, is defined as the incremental change in center frequency with incremental change in maximum applied electric field (EPEAK) in the filter. The other, the loss parameter, is defined as the incremental or decremental change in insertion loss of the filter with incremental change in maximum applied electric field. At room temperature, the Au/BSTO/LAO microstrip filters exhibited a sensitivity parameter value between 15 and 5 MHz/cm/kV. The loss parameter varied for different bias configurations used for electrically tuning the filter. The loss parameter varied from 0.05 to 0.01 dB/cm/kV at room temperature.

Revisiting the susceptibility testing of Mycobacterium tuberculosis to ethionamide in solid culture medium.

PubMed

Lakshmi, Rajagopalan; Ramachandran, Ranjani; Kumar, D Ravi; Sundar, A Syam; Radhika, G; Rahman, Fathima; Selvakumar, N; Kumar, Vanaja

2015-11-01

Increase in the isolation of drug resistant phenotypes of Mycobacterium tuberculosis necessitates accuracy in the testing methodology. Critical concentration defining resistance for ethionamide (ETO), needs re-evaluation in accordance with the current scenario. Thus, re-evaluation of conventional minimum inhibitory concentration (MIC) and proportion sensitivity testing (PST) methods for ETO was done to identify the ideal breakpoint concentration defining resistance. Isolates of M. tuberculosis (n=235) from new and treated patients were subjected to conventional MIC and PST methods for ETO following standard operating procedures. With breakpoint concentration set at 114 and 156 µg/ml, an increase in specificity was observed whereas sensitivity was high with 80 µg/ml as breakpoint concentration. Errors due to false resistant and susceptible isolates were least at 80 µg/ml concentration. Performance parameters at 80 µg/ml breakpoint concentration indicated significant association between PST and MIC methods.

A simplified model for equilibrium and transient swelling of thermo-responsive gels.

PubMed

Drozdov, A D; deClaville Christiansen, J

2017-11-01

A simplified model is developed for the elastic response of thermo-responsive gels subjected to swelling under an arbitrary deformation with finite strains. The constitutive equations involve five adjustable parameters that are determined by fitting observations in equilibrium water uptake tests and T-jump transient tests on thin gel disks. Two scenarios for water release under heating are revealed by means of numerical simulation. When the final temperature in a T-jump test is below the volume-phase transition temperature, deswelling is characterized by smooth distribution of water molecules and small tensile stresses. When the final temperature exceeds the critical temperature, a gel disk is split into three regions (central part with a high concentration of water molecules and two domains near the boundaries with low water content) separated by sharp interfaces, whose propagation is accompanied by development of large (comparable with the elastic modulus) tensile stresses. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Mach number of the cosmic flow - A critical test for current theories

NASA Technical Reports Server (NTRS)

Ostriker, Jeremiah P.; Suto, Yusushi

1990-01-01

A new cosmological, self-contained test using the ratio of mean velocity and the velocity dispersion in the mean flow frame of a group of test objects is presented. To allow comparison with linear theory, the velocity field must first be smoothed on a suitable scale. In the context of linear perturbation theory, the Mach number M(R) which measures the ratio of power on scales larger than to scales smaller than the patch size R, is independent of the perturbation amplitude and also of bias. An apparent inconsistency is found for standard values of power-law index n = 1 and cosmological density parameter Omega = 1, when comparing values of M(R) predicted by popular models with tentative available observations. Nonstandard models based on adiabatic perturbations with either negative n or small Omega value also fail, due to creation of unacceptably large microwave background fluctuations.

IC(B,T,STRAIN) Characterisation of a Nb3Sn Internal Tin Strand with Enhanced Specification for Use in Fusion Conductors

NASA Astrophysics Data System (ADS)

Pasztor, G.; Bruzzone, P.

2004-06-01

The dc performance of a recently produced internal tin route Nb3Sn strand with enhanced specification is studied extensively and compared with predecessor wires manufactured by the suppliers for the ITER Model Coils in 1996. The wire has been selected for use in a full size, developmental cable-in-conduit conductor sample, which is being tested in the SULTAN Test Facility. The critical current, Ic, and the index of the current/voltage characteristic, n, are measured over a broad range of field and temperature, using ITER standard sample holders, made of TiAlV grooved cylinders. The behavior of Ic versus applied tensile strain is also investigated at 4.2 K and 12 T, on straight specimens. Scaling law parameters are drawn from the fit of the experimental results. The implications of the test results to the design of the fusion conductors are discussed.

Development of a High Accuracy Angular Measurement System for Langley Research Center Hypersonic Wind Tunnel Facilities

NASA Technical Reports Server (NTRS)

Newman, Brett; Yu, Si-bok; Rhew, Ray D. (Technical Monitor)

2003-01-01

Modern experimental and test activities demand innovative and adaptable procedures to maximize data content and quality while working within severely constrained budgetary and facility resource environments. This report describes development of a high accuracy angular measurement capability for NASA Langley Research Center hypersonic wind tunnel facilities to overcome these deficiencies. Specifically, utilization of micro-electro-mechanical sensors including accelerometers and gyros, coupled with software driven data acquisition hardware, integrated within a prototype measurement system, is considered. Development methodology addresses basic design requirements formulated from wind tunnel facility constraints and current operating procedures, as well as engineering and scientific test objectives. Description of the analytical framework governing relationships between time dependent multi-axis acceleration and angular rate sensor data and the desired three dimensional Eulerian angular state of the test model is given. Calibration procedures for identifying and estimating critical parameters in the sensor hardware is also addressed.

Hardware Design of the Energy Efficient Fall Detection Device

NASA Astrophysics Data System (ADS)

Skorodumovs, A.; Avots, E.; Hofmanis, J.; Korāts, G.

2016-04-01

Health issues for elderly people may lead to different injuries obtained during simple activities of daily living. Potentially the most dangerous are unintentional falls that may be critical or even lethal to some patients due to the heavy injury risk. In the project "Wireless Sensor Systems in Telecare Application for Elderly People", we have developed a robust fall detection algorithm for a wearable wireless sensor. To optimise the algorithm for hardware performance and test it in field, we have designed an accelerometer based wireless fall detector. Our main considerations were: a) functionality - so that the algorithm can be applied to the chosen hardware, and b) power efficiency - so that it can run for a very long time. We have picked and tested the parts, built a prototype, optimised the firmware for lowest consumption, tested the performance and measured the consumption parameters. In this paper, we discuss our design choices and present the results of our work.

Sensitivity study of experimental measures for the nuclear liquid-gas phase transition in the statistical multifragmentation model

NASA Astrophysics Data System (ADS)

Lin, W.; Ren, P.; Zheng, H.; Liu, X.; Huang, M.; Wada, R.; Qu, G.

2018-05-01

The experimental measures of the multiplicity derivatives—the moment parameters, the bimodal parameter, the fluctuation of maximum fragment charge number (normalized variance of Zmax, or NVZ), the Fisher exponent (τ ), and the Zipf law parameter (ξ )—are examined to search for the liquid-gas phase transition in nuclear multifragmention processes within the framework of the statistical multifragmentation model (SMM). The sensitivities of these measures are studied. All these measures predict a critical signature at or near to the critical point both for the primary and secondary fragments. Among these measures, the total multiplicity derivative and the NVZ provide accurate measures for the critical point from the final cold fragments as well as the primary fragments. The present study will provide a guide for future experiments and analyses in the study of the nuclear liquid-gas phase transition.

Process analytical technologies (PAT) in freeze-drying of parenteral products.

PubMed

Patel, Sajal Manubhai; Pikal, Michael

2009-01-01

Quality by Design (QbD), aims at assuring quality by proper design and control, utilizing appropriate Process Analytical Technologies (PAT) to monitor critical process parameters during processing to ensure that the product meets the desired quality attributes. This review provides a comprehensive list of process monitoring devices that can be used to monitor critical process parameters and will focus on a critical review of the viability of the PAT schemes proposed. R&D needs in PAT for freeze-drying have also been addressed with particular emphasis on batch techniques that can be used on all the dryers independent of the dryer scale.

Estimated critical conditions for UO[sub 2]F[sub 2]--H[sub 2]O systems in fully water-reflected spherical geometry

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

Jordan, W.C.; Turner, J.C.

1992-12-01

The purpose of this report is to document reference calculations performed using the SCALE-4.0 code system to determine the critical parameters of UO[sub 2]F[sub 2]-H[sub 2]O spheres. The calculations are an extension of those documented in ORNL/CSD/TM-284. Specifically, the data for low-enriched UO[sub 2]F[sub 2]-H[sub 2]O spheres have been extended to highly enriched uranium. These calculations, together with those reported in ORNL/CSD/TM-284, provide a consistent set of critical parameters (k[sub [infinity

Self-organization in psychotherapy: testing the synergetic model of change processes

PubMed Central

Schiepek, Günter K.; Tominschek, Igor; Heinzel, Stephan

2014-01-01

In recent years, models have been developed that conceive psychotherapy as a self-organizing process of bio-psycho-social systems. These models originate from the theory of self-organization (Synergetics), from the theory of deterministic chaos, or from the approach of self-organized criticality. This process-outcome study examines several hypotheses mainly derived from Synergetics, including the assumption of discontinuous changes in psychotherapy (instead of linear incremental gains), the occurrence of critical instabilities in temporal proximity of pattern transitions, the hypothesis of necessary stable boundary conditions during destabilization processes, and of motivation to change playing the role of a control parameter for psychotherapeutic self-organization. Our study was realized at a day treatment center; 23 patients with obsessive compulsive disorder (OCD) were included. Client self-assessment was performed by an Internet-based process monitoring (referred to as the Synergetic Navigation System), whereby daily ratings were recorded through administering the Therapy Process Questionnaire (TPQ). The process measures of the study were extracted from the subscale dynamics (including the dynamic complexity of their time series) of the TPQ. The outcome criterion was measured by the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) which was completed pre-post and on a bi-weekly schedule by all patients. A second outcome criterion was based on the symptom severity subscale of the TPQ. Results supported the hypothesis of discontinuous changes (pattern transitions), the occurrence of critical instabilities preparing pattern transitions, and of stable boundary conditions as prerequisites for such transitions, but not the assumption of motivation to change as a control parameter. PMID:25324801

Quality risk management of top spray fluidized bed process for antihypertensive drug formulation with control strategy engendered by Box-behnken experimental design space.

PubMed

Mukharya, Amit; Patel, Paresh U; Shenoy, Dinesh; Chaudhary, Shivang

2013-01-01

Lacidipine (LCDP) is a very low soluble and highly biovariable calcium channel blocker used in the treatment of hypertension. To increase its apparent solubility and to reduce its biovariability, solid dispersion fluid bed processing technology was explored, as it produces highly dispersible granules with a characteristic porous structure that enhances dispersibility, wettability, blend uniformity (by dissolving and spraying a solution of actives), flow ability and compressibility of granules for tableting and reducing variability by uniform drug-binder solution distribution on carrier molecules. Main object of this quality risk management (QRM) study is to provide a sophisticated "robust and rugged" Fluidized Bed Process (FBP) for the preparation of LCDP tablets with desired quality (stability) and performance (dissolution) by quality by design (QbD) concept. THIS STUDY IS PRINCIPALLY FOCUSING ON THOROUGH MECHANISTIC UNDERSTANDING OF THE FBP BY WHICH IT IS DEVELOPED AND SCALED UP WITH A KNOWLEDGE OF THE CRITICAL RISKS INVOLVED IN MANUFACTURING PROCESS ANALYZED BY RISK ASSESSMENT TOOLS LIKE: Qualitative Initial Risk-based Matrix Analysis (IRMA) and Quantitative Failure Mode Effective Analysis (FMEA) to identify and rank parameters with potential to have an impact on In Process/Finished Product Critical Quality Attributes (IP/FP CQAs). These Critical Process Parameters (CPPs) were further refined by DoE and MVDA to develop design space with Real Time Release Testing (RTRT) that leads to implementation of a control strategy to achieve consistent finished product quality at lab scale itself to prevent possible product failure at larger manufacturing scale.

Quality risk management of top spray fluidized bed process for antihypertensive drug formulation with control strategy engendered by Box-behnken experimental design space

PubMed Central

Mukharya, Amit; Patel, Paresh U; Shenoy, Dinesh; Chaudhary, Shivang

2013-01-01

Introduction: Lacidipine (LCDP) is a very low soluble and highly biovariable calcium channel blocker used in the treatment of hypertension. To increase its apparent solubility and to reduce its biovariability, solid dispersion fluid bed processing technology was explored, as it produces highly dispersible granules with a characteristic porous structure that enhances dispersibility, wettability, blend uniformity (by dissolving and spraying a solution of actives), flow ability and compressibility of granules for tableting and reducing variability by uniform drug-binder solution distribution on carrier molecules. Materials and Methods: Main object of this quality risk management (QRM) study is to provide a sophisticated “robust and rugged” Fluidized Bed Process (FBP) for the preparation of LCDP tablets with desired quality (stability) and performance (dissolution) by quality by design (QbD) concept. Results and Conclusion: This study is principally focusing on thorough mechanistic understanding of the FBP by which it is developed and scaled up with a knowledge of the critical risks involved in manufacturing process analyzed by risk assessment tools like: Qualitative Initial Risk-based Matrix Analysis (IRMA) and Quantitative Failure Mode Effective Analysis (FMEA) to identify and rank parameters with potential to have an impact on In Process/Finished Product Critical Quality Attributes (IP/FP CQAs). These Critical Process Parameters (CPPs) were further refined by DoE and MVDA to develop design space with Real Time Release Testing (RTRT) that leads to implementation of a control strategy to achieve consistent finished product quality at lab scale itself to prevent possible product failure at larger manufacturing scale. PMID:23799202

Self-organization in psychotherapy: testing the synergetic model of change processes.

PubMed

Schiepek, Günter K; Tominschek, Igor; Heinzel, Stephan

2014-01-01

In recent years, models have been developed that conceive psychotherapy as a self-organizing process of bio-psycho-social systems. These models originate from the theory of self-organization (Synergetics), from the theory of deterministic chaos, or from the approach of self-organized criticality. This process-outcome study examines several hypotheses mainly derived from Synergetics, including the assumption of discontinuous changes in psychotherapy (instead of linear incremental gains), the occurrence of critical instabilities in temporal proximity of pattern transitions, the hypothesis of necessary stable boundary conditions during destabilization processes, and of motivation to change playing the role of a control parameter for psychotherapeutic self-organization. Our study was realized at a day treatment center; 23 patients with obsessive compulsive disorder (OCD) were included. Client self-assessment was performed by an Internet-based process monitoring (referred to as the Synergetic Navigation System), whereby daily ratings were recorded through administering the Therapy Process Questionnaire (TPQ). The process measures of the study were extracted from the subscale dynamics (including the dynamic complexity of their time series) of the TPQ. The outcome criterion was measured by the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) which was completed pre-post and on a bi-weekly schedule by all patients. A second outcome criterion was based on the symptom severity subscale of the TPQ. Results supported the hypothesis of discontinuous changes (pattern transitions), the occurrence of critical instabilities preparing pattern transitions, and of stable boundary conditions as prerequisites for such transitions, but not the assumption of motivation to change as a control parameter.

Analysis of SRB reentry acoustic environments. [aeroacoustic spectra determined from wind tunnel tests

NASA Technical Reports Server (NTRS)

Coffin, T.; Dandridge, R. E.; Haddock, U. W.

1979-01-01

Space shuttle solid rocket booster reentry aeroacoustic environments were estimated. Particular emphasis was given to the aft skirt/exit plane region for the Mach number regime 0.6 = or greater than M infinity = or less than 3.5. The analysis is based on the evaluation of wind tunnel model results in conjunction with Monte Carlo simulation of trajectory parameters. The experimental approach is described as well as the evaluation process utilized. Predicted environments are presented in terms of one-third octave band spectra representing space averaged values for critical regions on the solid rocket booster.

Space Station personal hygiene study

NASA Technical Reports Server (NTRS)

Prejean, Stephen E.; Booher, Cletis R.

1986-01-01

A personal hygiene system is currently under development for Space Station application that will provide capabilities equivalent to those found on earth. This paper addresses the study approach for specifying both primary and contingency personal hygiene systems and provisions for specified growth. Topics covered are system definition and subsystem descriptions. Subsystem interfaces are explored to determine which concurrent NASA study efforts must be monitored during future design phases to stay up-to-date on critical Space Station parameters. A design concept for a three (3) compartment personal hygiene facility is included as a baseline for planned test and verification activities.

Adapting the Critical Thinking Assessment Test for Palestinian Universities

ERIC Educational Resources Information Center

Basha, Sami; Drane, Denise; Light, Gregory

2016-01-01

Critical thinking is a key learning outcome for Palestinian students. However, there are no validated critical thinking tests in Arabic. Suitability of the US developed Critical Thinking Assessment Test (CAT) for use in Palestine was assessed. The test was piloted with university students in English (n = 30) and 4 questions were piloted in Arabic…

Vehicle response-based track geometry assessment using multi-body simulation

NASA Astrophysics Data System (ADS)

Kraft, Sönke; Causse, Julien; Coudert, Frédéric

2018-02-01

The assessment of the geometry of railway tracks is an indispensable requirement for safe rail traffic. Defects which represent a risk for the safety of the train have to be identified and the necessary measures taken. According to current standards, amplitude thresholds are applied to the track geometry parameters measured by recording cars. This geometry-based assessment has proved its value but suffers from the low correlation between the geometry parameters and the vehicle reactions. Experience shows that some defects leading to critical vehicle reactions are underestimated by this approach. The use of vehicle responses in the track geometry assessment process allows identifying critical defects and improving the maintenance operations. This work presents a vehicle response-based assessment method using multi-body simulation. The choice of the relevant operation conditions and the estimation of the simulation uncertainty are outlined. The defects are identified from exceedances of track geometry and vehicle response parameters. They are then classified using clustering methods and the correlation with vehicle response is analysed. The use of vehicle responses allows the detection of critical defects which are not identified from geometry parameters.

Deep soil compaction as a method of ground improvement and to stabilization of wastes and slopes with danger of liquefaction, determining the modulus of deformation and shear strength parameters of loose rock.

PubMed

Lersow, M

2001-01-01

For the stabilization of dumps with the construction of hidden dams and for building ground improvement, for instance for traffic lines over dumps, nearly all applied compaction methods have the aim to reduce the pore volume in the loose rock. With these methods, a homogenization of the compacted loose rock will be obtained too. The compaction methods of weight compaction by falling weight, compaction by vibration and compaction by blasting have been introduced, and their applications and efficiencies have been shown. For the estimation of the effective depth of the compaction and for a safe planning of the bearing layer, respectively, the necessary material parameters have to be determined for each deep compaction method. Proposals for the determination of these parameters have been made within this paper. In connection with the stabilization of flow-slide-prone dump slopes, as well as for the improvement of dump areas for the use as building ground, it is necessary to assess the deformation behavior and the bearing capacity. To assess the resulting building ground improvement, deformation indexes (assessment of the flow-prone layer) and strength indexes (assessment of the bearing capacity) have to be determined with soil mechanical tests. Förster and Lersow, [Patentschrift DE 197 17 988. Verfahren, auf der Grundlage last- und/oder weggesteuerter Plattendruckversuche auf der Bohrlochsohle, zur Ermittlung des Spannungs-Verformungs-Verhaltens und/oder von Deformationsmoduln und/oder von Festigkeitseigenschaften in verschiedenen Tiefen insbesondere von Lockergesteinen und von Deponiekörpern in situ; Förster W, Lersow M. Plattendruckversuch auf der Bohrlochsohle, Ermittlung des Spannungs-Verformungs-Verhaltens von Lockergestein und Deponiematerial Braunkohle--Surface Mining, 1998;50(4): 369-77; Lersow M. Verfahren zur Ermittlung von Scherfestigkeitsparametern von Lockergestein und Deponiematerial aus Plattendruckversuchen auf der Bohrlochsohle. Braunkohle--Surface Mining, 1995;51(1):39-47] improved a direct procedure, the so-called plate-loading test. With this improved procedure, it is possible to produce profiles of deformation parameters and shear-strength parameters of the loose rock. On this basis the settlement behavior and the bearing behavior of the ground can be described. The PDV-BS cone-penetration test and the pressiometer test are compared and the reliability of the soil mechanical indexes are assessed critically. The PDV-BS can be used as a calibration test for cone penetration tests as well as for the calibration of pressiometer tests. With the application of a PDV-BS and a pressiometer test in combination in a testing field, the anisotropy properties of the loose rock can be proved.

Loss of stability of a railway wheel-set, subcritical or supercritical

NASA Astrophysics Data System (ADS)

Zhang, Tingting; Dai, Huanyun

2017-11-01

Most researches on railway vehicle stability analysis are focused on the codimension 1 (for short, codim 1) bifurcations like subcritical and supercritical Hopf bifurcation. The analysis of codim 1 bifurcation can be completed based on one bifurcation parameter. However, two bifurcation parameters should be considered to give a general view of the motion of the system when it undergoes a degenerate Hopf bifurcation. This kind of bifurcation named the generalised Hopf bifurcation belongs to the codimension 2 (for short, codim 2) bifurcations where two bifurcation parameters need to be taken into consideration. In this paper, we give a numerical analysis of the codim 2 bifurcations of a nonlinear railway wheel-set with the QR algorithm to calculate the eigenvalues of the linearised system incorporating the Golden Cut method and the shooting method to calculate the limit cycles around the Hopf bifurcation points. Here, we found the existence of a generalised Hopf bifurcation where a subcritical Hopf bifurcation turns into a supercritical one with the increase of the bifurcation parameters, which belong to the codim 2 bifurcations, in a nonlinear railway wheel-set model. Only the nonlinear wheel/rail interactive relationship has been taken into consideration in the lateral model that is formulated in this paper. The motion of the wheel-set has been investigated when the bifurcation parameters are perturbed in the neighbourhood of their critical parameters, and the influences of different parameters on critical values of the bifurcation parameters are also given. From the results, it can be seen that the bifurcation types of the wheel-set will change with a variation of the bifurcation parameters in the neighbourhood of their critical values.

A Bayesian approach to the modelling of α Cen A

NASA Astrophysics Data System (ADS)

Bazot, M.; Bourguignon, S.; Christensen-Dalsgaard, J.

2012-12-01

Determining the physical characteristics of a star is an inverse problem consisting of estimating the parameters of models for the stellar structure and evolution, and knowing certain observable quantities. We use a Bayesian approach to solve this problem for α Cen A, which allows us to incorporate prior information on the parameters to be estimated, in order to better constrain the problem. Our strategy is based on the use of a Markov chain Monte Carlo (MCMC) algorithm to estimate the posterior probability densities of the stellar parameters: mass, age, initial chemical composition, etc. We use the stellar evolutionary code ASTEC to model the star. To constrain this model both seismic and non-seismic observations were considered. Several different strategies were tested to fit these values, using either two free parameters or five free parameters in ASTEC. We are thus able to show evidence that MCMC methods become efficient with respect to more classical grid-based strategies when the number of parameters increases. The results of our MCMC algorithm allow us to derive estimates for the stellar parameters and robust uncertainties thanks to the statistical analysis of the posterior probability densities. We are also able to compute odds for the presence of a convective core in α Cen A. When using core-sensitive seismic observational constraints, these can rise above ˜40 per cent. The comparison of results to previous studies also indicates that these seismic constraints are of critical importance for our knowledge of the structure of this star.

Characterization of the ITER CS conductor and projection to the ITER CS performance

DOE PAGES

Martovetsky, N.; Isono, T.; Bessette, D.; ...

2017-06-20

The ITER Central Solenoid (CS) is one of the critical elements of the machine. The CS conductor went through an intense optimization and qualification program, which included characterization of the strands, a conductor straight short sample testing in the SULTAN facility at the Swiss Plasma Center (SPC), Villigen, Switzerland, and a single-layer CS Insert coil recently tested in the Central Solenoid Model Coil (CSMC) facility in QST-Naka, Japan. In this paper, we obtained valuable data in a wide range of the parameters (current, magnetic field, temperature, and strain), which allowed a credible characterization of the CS conductor in different conditions.more » Finally, using this characterization, we will make a projection to the performance of the CS in the ITER reference scenario.« less

Characterization of the ITER CS conductor and projection to the ITER CS performance

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

Martovetsky, N.; Isono, T.; Bessette, D.

The ITER Central Solenoid (CS) is one of the critical elements of the machine. The CS conductor went through an intense optimization and qualification program, which included characterization of the strands, a conductor straight short sample testing in the SULTAN facility at the Swiss Plasma Center (SPC), Villigen, Switzerland, and a single-layer CS Insert coil recently tested in the Central Solenoid Model Coil (CSMC) facility in QST-Naka, Japan. In this paper, we obtained valuable data in a wide range of the parameters (current, magnetic field, temperature, and strain), which allowed a credible characterization of the CS conductor in different conditions.more » Finally, using this characterization, we will make a projection to the performance of the CS in the ITER reference scenario.« less

Using mechanobiological mimicry of red blood cells to extend circulation times of hydrogel microparticles

PubMed Central

Merkel, Timothy J.; Jones, Stephen W.; Herlihy, Kevin P.; Kersey, Farrell R.; Shields, Adam R.; Napier, Mary; Luft, J. Christopher; Wu, Huali; Zamboni, William C.; Wang, Andrew Z.; Bear, James E.; DeSimone, Joseph M.

2011-01-01

It has long been hypothesized that elastic modulus governs the biodistribution and circulation times of particles and cells in blood; however, this notion has never been rigorously tested. We synthesized hydrogel microparticles with tunable elasticity in the physiological range, which resemble red blood cells in size and shape, and tested their behavior in vivo. Decreasing the modulus of these particles altered their biodistribution properties, allowing them to bypass several organs, such as the lung, that entrapped their more rigid counterparts, resulting in increasingly longer circulation times well past those of conventional microparticles. An 8-fold decrease in hydrogel modulus correlated to a greater than 30-fold increase in the elimination phase half-life for these particles. These results demonstrate a critical design parameter for hydrogel microparticles. PMID:21220299

Sign reversal of transformation entropy change in Co{sub 2}Cr(Ga,Si) shape memory alloys

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

Xu, Xiao, E-mail: xu@material.tohoku.ac.jp; Omori, Toshihiro; Kainuma, Ryosuke

2015-11-02

In situ X-ray diffraction (XRD) measurements and compression tests were performed on Co{sub 2}Cr(Ga,Si) shape memory alloys. The reentrant martensitic transformation behavior was directly observed during the in situ XRD measurements. The high-temperature parent phase and low-temperature reentrant parent phase were found to have a continuous temperature dependence of lattice parameter, therefore suggesting that they are the same phase in nature. Moreover, compression tests were performed on a parent-phase single crystal sample; an evolution from normal to inverse temperature dependence of critical stress for martensitic transformation was directly observed. Based on the Clausius-Clapeyron analysis, a sign reversal of entropy changemore » can be expected on the same alloy.« less

Experimental evaluation of LPG tank explosion hazards.

PubMed

Stawczyk, Jan

2003-01-31

Liquefied-pressure gases (LPG) are transported and stored in the liquid phase in closed tanks under sufficiently high pressure. In the case of an accident, an abrupt tank unsealing may release enormous quantity of evaporating gas and energy that has a destructive effect on the tank and its surroundings. In this paper, experiments with explosions of small LPG tanks are described. The data acquisition equipment applied in the tests provided a chance to learn dynamics of the process and determine hazard factors. The tests enabled a determination of temperature and pressure at which tanks containing LPG disrupt. The results enable a reconstruction of consecutive phases of the explosion and identification of hazards resulting from damage of the tanks. An explanation of the tank unsealing process with fluid parameters above critical point is given.

Pressure-controlled injection of guar gum stabilized microscale zerovalent iron for groundwater remediation.

PubMed

Luna, M; Gastone, F; Tosco, T; Sethi, R; Velimirovic, M; Gemoets, J; Muyshondt, R; Sapion, H; Klaas, N; Bastiaens, L

2015-10-01

The paper reports a pilot injection test of microsized zerovalent iron (mZVI) dispersed in a guar gum shear thinning solution. The test was performed in the framework of the EU research project AQUAREHAB in a site in Belgium contaminated by chlorinated aliphatic hydrocarbons (CAHs). The field application was aimed to overcome those critical aspects which hinder mZVI field injection, mainly due to the colloidal instability of ZVI-based suspensions. The iron slurry properties (iron particles size and concentration, polymeric stabilizer type and concentration, slurry viscosity) were designed in the laboratory based on several tests (reactivity tests towards contaminants, sedimentation tests and rheological measurements). The particles were delivered into the aquifer through an injection well specifically designed for controlled-pressure delivery (approximately 10 bars). The well characteristics and the critical pressure of the aquifer (i.e. the injection pressure above which fracturing occurs) were assessed via two innovative injection step rate tests, one performed with water and the other one with guar gum. Based on laboratory and field preliminary tests, a flow regime at the threshold between permeation and preferential flow was selected for mZVI delivery, as a compromise between the desired homogeneous distribution of the mZVI around the injection point (ensured by permeation flow) and the fast and effective injection of the slurry (guaranteed by high discharge rates and injection pressure, resulting in the generation of preferential flow paths). A monitoring setup was designed and installed for the real-time monitoring of relevant parameters during injection, and for a fast determination of the spatial mZVI distribution after injection via non-invasive magnetic susceptibility measurements. Copyright © 2015 Elsevier B.V. All rights reserved.

CMC prediction for ionic surfactants in pure water and aqueous salt solutions based solely on tabulated molecular parameters.

PubMed

Karakashev, Stoyan I; Smoukov, Stoyan K

2017-09-01

The critical micelle concentration (CMC) of various surfactants is difficult to predict accurately, yet often necessary to do in both industry and science. Hence, quantum-chemical software packages for precise calculation of CMC were developed, but they are expensive and time consuming. We show here an easy method for calculating CMC with a reasonable accuracy. Firstly, CMC 0 (intrinsic CMC, absent added salt) was coupled with quantitative structure - property relationship (QSPR) with defined by us parameter "CMC predictor" f 1 . It can be easily calculated from a number of tabulated molecular parameters - the adsorption energy of surfactant's head, the adsorption energy of its methylene groups, its number of carbon atoms, the specific adsorption energy of its counter-ions, their valency and bare radius. We applied this method to determine CMC 0 to a test set of 11 ionic surfactants, yielding 7.5% accuracy. Furthermore, we calculated CMC in the presence of added salts using the advanced version of Corrin-Harkins equation, which accounts for both the intrinsic and the added counter-ions. Our salt-saturation multiplier, accounts for both the type and concentration of the added counter-ions. We applied our theory to a test set containing 11 anionic/cationic surfactant+salt systems, achieving 8% accuracy. Copyright © 2017 Elsevier Inc. All rights reserved.

Routine health monitoring in an aquatic species (Oryzias latipes) used in toxicological testing

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

Twerdok, L.E.; Beaman, J.R.; Curry, M.W.

1995-12-31

It is critical to establish baseline health endpoints in animal models used in toxicological studies. In mammalian models, procedures for monitoring the health status of test animals have been established and in use for many years; in many aquatic models, including medaka, much of this routine health screening has not been documented. Thus, the purpose of this study was to characterize routine health parameters in medaka and to identify parameters sensitive to changes in health status which could affect the suitability of animals for use in general toxicity and immunotoxicological studies. The endpoints assessed included histopathology (31 organs), identification ofmore » endogenous bacterial flora and, gross necropsy including body weight, length, hematocrit, leukocrit, and plasma immunoglobulin levels. Additional parameters included anterior kidney (the teleost bone marrow equivalent) weight and cell yields plus superoxide anion production. Histological findings included observation of age-related incidence of granulomatous lesions in a variety of organs. Multiple strains of Aeromonas and Pseudomonas were the predominant internal flora in healthy medaka. Hematocrit, leukocrit and plasma IgM levels were within the normal range for this species. Comparisons were made between healthy and handling-stressed fish. Evaluation of data collected to date suggest that leukocrit and superoxide anion production were the most sensitive indicators of the fish health status and suitability for use in general and/or immunotoxicological studies.« less

User's Guide for Monthly Vector Wind Profile Model

NASA Technical Reports Server (NTRS)

Adelfang, S. I.

1999-01-01

The background, theoretical concepts, and methodology for construction of vector wind profiles based on a statistical model are presented. The derived monthly vector wind profiles are to be applied by the launch vehicle design community for establishing realistic estimates of critical vehicle design parameter dispersions related to wind profile dispersions. During initial studies a number of months are used to establish the model profiles that produce the largest monthly dispersions of ascent vehicle aerodynamic load indicators. The largest monthly dispersions for wind, which occur during the winter high-wind months, are used for establishing the design reference dispersions for the aerodynamic load indicators. This document includes a description of the computational process for the vector wind model including specification of input data, parameter settings, and output data formats. Sample output data listings are provided to aid the user in the verification of test output.

Predictability and preparedness in influenza control.

PubMed

Smith, Derek J

2006-04-21

The threat of pandemic human influenza looms as we survey the ongoing avian influenza pandemic and wonder if and when it will jump species. What are the risks and how can we plan? The nub of the problem lies in the inherent variability of the virus, which makes prediction difficult. However, it is not impossible; mathematical models can help determine and quantify critical parameters and thresholds in the relationships of those parameters, even if the relationships are nonlinear and obscure to simple reasoning. Mathematical models can derive estimates for the levels of drug stockpiles needed to buy time, how and when to modify vaccines, whom to target with vaccines and drugs, and when to enforce quarantine measures. Regardless, the models used for pandemic planning must be tested, and for this we must continue to gather data, not just for exceptional scenarios but also for seasonal influenza.

AXIALLY ORIENTED SECTIONS OF NUMMULITIDS: A TOOL TO INTERPRET LARGER BENTHIC FORAMINIFERAL DEPOSITS

PubMed Central

Hohenegger, Johann; Briguglio, Antonino

2015-01-01

The “critical shear velocity” and “settling velocity” of foraminiferal shells are important parameters for determining hydrodynamic conditions during deposition of Nummulites banks. These can be estimated by determining the size, shape, and density of nummulitid shells examined in axial sections cut perpendicular to the bedding plane. Shell size and shape can be determined directly from the shell diameter and thickness, but density must be calculated indirectly from the thin section. Calculations using the half-tori method approximate shell densities by equalizing the chamber volume of each half whorl, based on the half whorl’s lumen area and its center of gravity. Results from this method yield the same lumen volumes produced empirically by micro-computed tomography. The derived hydrodynamic parameters help estimate the minimum flow velocities needed to entrain nummulitid tests and provide a potential tool to account for the nature of their accumulations. PMID:26166914

AXIALLY ORIENTED SECTIONS OF NUMMULITIDS: A TOOL TO INTERPRET LARGER BENTHIC FORAMINIFERAL DEPOSITS.

PubMed

Hohenegger, Johann; Briguglio, Antonino

2012-04-01

The "critical shear velocity" and "settling velocity" of foraminiferal shells are important parameters for determining hydrodynamic conditions during deposition of Nummulites banks. These can be estimated by determining the size, shape, and density of nummulitid shells examined in axial sections cut perpendicular to the bedding plane. Shell size and shape can be determined directly from the shell diameter and thickness, but density must be calculated indirectly from the thin section. Calculations using the half-tori method approximate shell densities by equalizing the chamber volume of each half whorl, based on the half whorl's lumen area and its center of gravity. Results from this method yield the same lumen volumes produced empirically by micro-computed tomography. The derived hydrodynamic parameters help estimate the minimum flow velocities needed to entrain nummulitid tests and provide a potential tool to account for the nature of their accumulations.

Application of solid/liquid extraction for the gravimetric determination of lipids in royal jelly.

PubMed

Antinelli, Jean-François; Davico, Renée; Rognone, Catherine; Faucon, Jean-Paul; Lizzani-Cuvelier, Louisette

2002-04-10

Gravimetric lipid determination is a major parameter for the characterization and the authentication of royal jelly quality. A solid/liquid extraction was compared to the reference method, which is based on liquid/liquid extraction. The amount of royal jelly and the time of the extraction were optimized in comparison to the reference method. Boiling/rinsing ratio and spread of royal jelly onto the extraction thimble were identified as critical parameters, resulting in good accuracy and precision for the alternative method. Comparison of reproducibility and repeatability of both methods associated with gas chromatographic analysis of the composition of the extracted lipids showed no differences between the two methods. As the intra-laboratory validation tests were comparable to the reference method, while offering rapidity and a decrease in amount of solvent used, it was concluded that the proposed method should be used with no modification of quality criteria and norms established for royal jelly characterization.

Prediction of multi performance characteristics of wire EDM process using grey ANFIS

NASA Astrophysics Data System (ADS)

Kumanan, Somasundaram; Nair, Anish

2017-09-01

Super alloys are used to fabricate components in ultra-supercritical power plants. These hard to machine materials are processed using non-traditional machining methods like Wire cut electrical discharge machining and needs attention. This paper details about multi performance optimization of wire EDM process using Grey ANFIS. Experiments are designed to establish the performance characteristics of wire EDM such as surface roughness, material removal rate, wire wear rate and geometric tolerances. The control parameters are pulse on time, pulse off time, current, voltage, flushing pressure, wire tension, table feed and wire speed. Grey relational analysis is employed to optimise the multi objectives. Analysis of variance of the grey grades is used to identify the critical parameters. A regression model is developed and used to generate datasets for the training of proposed adaptive neuro fuzzy inference system. The developed prediction model is tested for its prediction ability.

Interrelationship of Nondestructive Evaluation Methodologies Applied to Testing of Composite Overwrapped Pressure Vessels

NASA Technical Reports Server (NTRS)

Leifeste, Mark R.

2007-01-01

Composite Overwrapped Pressure Vessels (COPVs) are commonly used in spacecraft for containment of pressurized gases and fluids, incorporating strength and weight savings. The energy stored is capable of extensive spacecraft damage and personal injury in the event of sudden failure. These apparently simple structures, composed of a metallic media impermeable liner and fiber/resin composite overwrap are really complex structures with numerous material and structural phenomena interacting during pressurized use which requires multiple, interrelated monitoring methodologies to monitor and understand subtle changes critical to safe use. Testing of COPVs at NASA Johnson Space Center White Sands T est Facility (WSTF) has employed multiple in-situ, real-time nondestructive evaluation (NDE) methodologies as well as pre- and post-test comparative techniques to monitor changes in material and structural parameters during advanced pressurized testing. The use of NDE methodologies and their relationship to monitoring changes is discussed based on testing of real-world spacecraft COPVs. Lessons learned are used to present recommendations for use in testing, as well as a discussion of potential applications to vessel health monitoring in future applications.

Assessing value of innovative molecular diagnostic tests in the concept of predictive, preventive, and personalized medicine.

PubMed

Akhmetov, Ildar; Bubnov, Rostyslav V

2015-01-01

Molecular diagnostic tests drive the scientific and technological uplift in the field of predictive, preventive, and personalized medicine offering invaluable clinical and socioeconomic benefits to the key stakeholders. Although the results of diagnostic tests are immensely influential, molecular diagnostic tests (MDx) are still grudgingly reimbursed by payers and amount for less than 5 % of the overall healthcare costs. This paper aims at defining the value of molecular diagnostic test and outlining the most important components of "value" from miscellaneous assessment frameworks, which go beyond accuracy and feasibility and impact the clinical adoption, informing healthcare resource allocation decisions. The authors suggest that the industry should facilitate discussions with various stakeholders throughout the entire assessment process in order to arrive at a consensus about the depth of evidence required for positive marketing authorization or reimbursement decisions. In light of the evolving "value-based healthcare" delivery practices, it is also recommended to account for social and ethical parameters of value, since these are anticipated to become as critical for reimbursement decisions and test acceptance as economic and clinical criteria.

Towards a critical transition theory under different temporal scales and noise strengths

NASA Astrophysics Data System (ADS)

Shi, Jifan; Li, Tiejun; Chen, Luonan

2016-03-01

The mechanism of critical phenomena or critical transitions has been recently studied from various aspects, in particular considering slow parameter change and small noise. In this article, we systematically classify critical transitions into three types based on temporal scales and noise strengths of dynamical systems. Specifically, the classification is made by comparing three important time scales τλ, τtran, and τergo, where τλ is the time scale of parameter change (e.g., the change of environment), τtran is the time scale when a particle or state transits from a metastable state into another, and τergo is the time scale when the system becomes ergodic. According to the time scales, we classify the critical transition behaviors as three types, i.e., state transition, basin transition, and distribution transition. Moreover, for each type of transition, there are two cases, i.e., single-trajectory transition and multitrajectory ensemble transition, which correspond to the transition of individual behavior and population behavior, respectively. We also define the critical point for each type of critical transition, derive several properties, and further propose the indicators for predicting critical transitions with numerical simulations. In addition, we show that the noise-to-signal ratio is effective to make the classification of critical transitions for real systems.

Applicability of mode-coupling theory to polyisobutylene: a molecular dynamics simulation study.

PubMed

Khairy, Y; Alvarez, F; Arbe, A; Colmenero, J

2013-10-01

The applicability of Mode Coupling Theory (MCT) to the glass-forming polymer polyisobutylene (PIB) has been explored by using fully atomistic molecular dynamics simulations. MCT predictions for the so-called asymptotic regime have been successfully tested on the dynamic structure factor and the self-correlation function of PIB main-chain carbons calculated from the simulated cell. The factorization theorem and the time-temperature superposition principle are satisfied. A consistent fitting procedure of the simulation data to the MCT asymptotic power-laws predicted for the α-relaxation regime has delivered the dynamic exponents of the theory-in particular, the exponent parameter λ-the critical non-ergodicity parameters, and the critical temperature T(c). The obtained values of λ and T(c) agree, within the uncertainties involved in both studies, with those deduced from depolarized light scattering experiments [A. Kisliuk et al., J. Polym. Sci. Part B: Polym. Phys. 38, 2785 (2000)]. Both, λ and T(c)/T(g) values found for PIB are unusually large with respect to those commonly obtained in low molecular weight systems. Moreover, the high T(c)/T(g) value is compatible with a certain correlation of this parameter with the fragility in Angell's classification. Conversely, the value of λ is close to that reported for real polymers, simulated "realistic" polymers and simple polymer models with intramolecular barriers. In the framework of the MCT, such finding should be the signature of two different mechanisms for the glass-transition in real polymers: intermolecular packing and intramolecular barriers combined with chain connectivity.