Science.gov

Sample records for accepted models surface

  1. A Distributive Model of Treatment Acceptability

    ERIC Educational Resources Information Center

    Carter, Stacy L.

    2008-01-01

    A model of treatment acceptability is proposed that distributes overall treatment acceptability into three separate categories of influence. The categories are comprised of societal influences, consultant influences, and influences associated with consumers of treatments. Each of these categories are defined and their inter-relationships within…

  2. Integrated Model for E-Learning Acceptance

    NASA Astrophysics Data System (ADS)

    Ramadiani; Rodziah, A.; Hasan, S. M.; Rusli, A.; Noraini, C.

    2016-01-01

    E-learning is not going to work if the system is not used in accordance with user needs. User Interface is very important to encourage using the application. Many theories had discuss about user interface usability evaluation and technology acceptance separately, actually why we do not make it correlation between interface usability evaluation and user acceptance to enhance e-learning process. Therefore, the evaluation model for e-learning interface acceptance is considered important to investigate. The aim of this study is to propose the integrated e-learning user interface acceptance evaluation model. This model was combined some theories of e-learning interface measurement such as, user learning style, usability evaluation, and the user benefit. We formulated in constructive questionnaires which were shared at 125 English Language School (ELS) students. This research statistics used Structural Equation Model using LISREL v8.80 and MANOVA analysis.

  3. Model of aircraft passenger acceptance

    NASA Technical Reports Server (NTRS)

    Jacobson, I. D.

    1978-01-01

    A technique developed to evaluate the passenger response to a transportation system environment is described. Reactions to motion, noise, temperature, seating, ventilation, sudden jolts and descents are modeled. Statistics are presented for the age, sex, occupation, and income distributions of the candidates analyzed. Values are noted for the relative importance of system variables such as time savings, on-time arrival, convenience, comfort, safety, the ability to read and write, and onboard services.

  4. 16 CFR 1505.7 - Maximum acceptable surface temperatures.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Maximum acceptable surface temperatures. 1505.7 Section 1505.7 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FEDERAL HAZARDOUS SUBSTANCES ACT REGULATIONS REQUIREMENTS FOR ELECTRICALLY OPERATED TOYS OR OTHER ELECTRICALLY OPERATED ARTICLES INTENDED FOR USE BY CHILDREN Regulations...

  5. Measuring Technology Acceptance Level of Turkish Pre-Service English Teachers by Using Technology Acceptance Model

    ERIC Educational Resources Information Center

    Kirmizi, Özkan

    2014-01-01

    The aim of this study is to investigate technology acceptance of prospective English teachers by using Technology Acceptance Model (TAM) in Turkish context. The study is based on Structural Equation Model (SEM). The participants of the study from English Language Teaching Departments of Hacettepe, Gazi and Baskent Universities. The participants…

  6. Surface moisture measurement system hardware acceptance test report

    SciTech Connect

    Ritter, G.A., Westinghouse Hanford

    1996-05-28

    This document summarizes the results of the hardware acceptance test for the Surface Moisture Measurement System (SMMS). This test verified that the mechanical and electrical features of the SMMS functioned as designed and that the unit is ready for field service. The bulk of hardware testing was performed at the 306E Facility in the 300 Area and the Fuels and Materials Examination Facility in the 400 Area. The SMMS was developed primarily in support of Tank Waste Remediation System (TWRS) Safety Programs for moisture measurement in organic and ferrocyanide watch list tanks.

  7. 49 CFR 41.120 - Acceptable model codes.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 1 2014-10-01 2014-10-01 false Acceptable model codes. 41.120 Section 41.120 Transportation Office of the Secretary of Transportation SEISMIC SAFETY § 41.120 Acceptable model codes. (a) This... of this part. (b)(1) The following are model codes which have been found to provide a level...

  8. 49 CFR 41.120 - Acceptable model codes.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false Acceptable model codes. 41.120 Section 41.120 Transportation Office of the Secretary of Transportation SEISMIC SAFETY § 41.120 Acceptable model codes. (a) This... of this part. (b)(1) The following are model codes which have been found to provide a level...

  9. Technological Diffusion within Educational Institutions: Applying the Technology Acceptance Model.

    ERIC Educational Resources Information Center

    Wolski, Stacy; Jackson, Sally

    Expectancy models of behavior such as the Theory of Reasoned Action (TRA) and the Technology Acceptance Model (TAM) offer guidelines that aid efforts to facilitate use of new technology. These models remind us that both acceptance of and resistance to technology use are grounded in beliefs and norms regarding the technology. Although TAM is widely…

  10. Evaluation of the Acceptance of Audience Response System by Corporations Using the Technology Acceptance Model

    NASA Astrophysics Data System (ADS)

    Chu, Hsing-Hui; Lu, Ta-Jung; Wann, Jong-Wen

    The purpose of this research is to explore enterprises' acceptance of Audience Response System (ARS) using Technology Acceptance Model (TAM). The findings show that (1) IT characteristics and facilitating conditions could be external variables of TAM. (2) The degree of E-business has positive significant correlation with behavioral intention of employees. (3) TAM is a good model to predict and explain IT acceptance. (4) Demographic variables, industry and firm characteristics have no significant correlation with ARS acceptance. The results provide useful information to managers and ARS providers that (1) ARS providers should focus more on creating different usages to enhance interactivity and employees' using intention. (2) Managers should pay attention to build sound internal facilitating conditions for introducing IT. (3) According to the degree of E-business, managers should set up strategic stages of introducing IT. (4) Providers should increase product promotion and also leverage academic and government to promote ARS.

  11. User Acceptance of Long-Term Evolution (LTE) Services: An Application of Extended Technology Acceptance Model

    ERIC Educational Resources Information Center

    Park, Eunil; Kim, Ki Joon

    2013-01-01

    Purpose: The aim of this paper is to propose an integrated path model in order to explore user acceptance of long-term evolution (LTE) services by examining potential causal relationships between key psychological factors and user intention to use the services. Design/methodology/approach: Online survey data collected from 1,344 users are analysed…

  12. Examining Engineering & Technology Students' Acceptance of Network Virtualization Technology Using the Technology Acceptance Model

    ERIC Educational Resources Information Center

    Yousif, Wael K.

    2010-01-01

    This causal and correlational study was designed to extend the Technology Acceptance Model (TAM) and to test its applicability to Valencia Community College (VCC) Engineering and Technology students as the target user group when investigating the factors influencing their decision to adopt and to utilize VMware as the target technology. In…

  13. User Acceptance of YouTube for Procedural Learning: An Extension of the Technology Acceptance Model

    ERIC Educational Resources Information Center

    Lee, Doo Young; Lehto, Mark R.

    2013-01-01

    The present study was framed using the Technology Acceptance Model (TAM) to identify determinants affecting behavioral intention to use YouTube. Most importantly, this research emphasizes the motives for using YouTube, which is notable given its extrinsic task goal of being used for procedural learning tasks. Our conceptual framework included two…

  14. Predicting User Acceptance of Collaborative Technologies: An Extension of the Technology Acceptance Model for E-Learning

    ERIC Educational Resources Information Center

    Cheung, Ronnie; Vogel, Doug

    2013-01-01

    Collaborative technologies support group work in project-based environments. In this study, we enhance the technology acceptance model to explain the factors that influence the acceptance of Google Applications for collaborative learning. The enhanced model was empirically evaluated using survey data collected from 136 students enrolled in a…

  15. Acceptance of health information technology in health professionals: an application of the revised technology acceptance model.

    PubMed

    Ketikidis, Panayiotis; Dimitrovski, Tomislav; Lazuras, Lambros; Bath, Peter A

    2012-06-01

    The response of health professionals to the use of health information technology (HIT) is an important research topic that can partly explain the success or failure of any HIT application. The present study applied a modified version of the revised technology acceptance model (TAM) to assess the relevant beliefs and acceptance of HIT systems in a sample of health professionals (n = 133). Structured anonymous questionnaires were used and a cross-sectional design was employed. The main outcome measure was the intention to use HIT systems. ANOVA was employed to examine differences in TAM-related variables between nurses and medical doctors, and no significant differences were found. Multiple linear regression analysis was used to assess the predictors of HIT usage intentions. The findings showed that perceived ease of use, but not usefulness, relevance and subjective norms directly predicted HIT usage intentions. The present findings suggest that a modification of the original TAM approach is needed to better understand health professionals' support and endorsement of HIT. Perceived ease of use, relevance of HIT to the medical and nursing professions, as well as social influences, should be tapped by information campaigns aiming to enhance support for HIT in healthcare settings. PMID:22733680

  16. Modeling of the charge acceptance of lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Thele, M.; Schiffer, J.; Karden, E.; Surewaard, E.; Sauer, D. U.

    This paper presents a model for flooded and VRLA batteries that is parameterized by impedance spectroscopy and includes the overcharging effects to allow charge-acceptance simulations (e.g. for regenerative-braking drive-cycle profiles). The full dynamic behavior and the short-term charge/discharge history is taken into account. This is achieved by a detailed modeling of the sulfate crystal growth and modeling of the internal gas recombination cycle. The model is applicable in the full realistic temperature and current range of automotive applications. For model validation, several load profiles (covering the dynamics and the current range appearing in electrically assisted or hybrid cars) are examined and the charge-acceptance limiting effects are elaborately discussed. The validation measurements have been performed for different types of lead-acid batteries (flooded and VRLA). The model is therefore an important tool for the development of automotive power nets, but it also allows to analyze different charging strategies and energy gains which can be achieved during regenerative-braking.

  17. Factors Influencing the Acceptance of Web-Based Training in Malaysia: Applying the Technology Acceptance Model

    ERIC Educational Resources Information Center

    Hashim, Junaidah

    2008-01-01

    Companies in Malaysia are beginning to use web-based training to reduce the cost of training and to provide employees with greater access to instruction. However, some people are uncomfortable with technology and prefer person-to-person methods of training. This study examines the acceptance of web-based training among a convenience sample of 261…

  18. Surface complexation modeling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Adsorption-desorption reactions are important processes that affect the transport of contaminants in the environment. Surface complexation models are chemical models that can account for the effects of variable chemical conditions, such as pH, on adsorption reactions. These models define specific ...

  19. The History of UTAUT Model and Its Impact on ICT Acceptance and Usage by Academicians

    ERIC Educational Resources Information Center

    Oye, N. D.; Iahad, N. A.; Rahim, N. Ab.

    2014-01-01

    This paper started with the review of the history of technology acceptance model from TRA to UTAUT. The expected contribution is to bring to lime light the current development stage of the technology acceptance model. Based on this, the paper examined the impact of UTAUT model on ICT acceptance and usage in HEIs. The UTAUT model theory was…

  20. Influence of Gender and Computer Teaching Efficacy on Computer Acceptance among Malaysian Student Teachers: An Extended Technology Acceptance Model

    ERIC Educational Resources Information Center

    Wong, Kung-Teck; Teo, Timothy; Russo, Sharon

    2012-01-01

    The purpose of this study is to validate the technology acceptance model (TAM) in an educational context and explore the role of gender and computer teaching efficacy as external variables. From the literature, it appeared that only limited studies had developed models to explain statistically the chain of influence of computer teaching efficacy…

  1. Modeling Computer Usage Intentions of Tertiary Students in a Developing Country through the Technology Acceptance Model

    ERIC Educational Resources Information Center

    Afari-Kumah, Eben; Achampong, Akwasi Kyere

    2010-01-01

    This study aims to examine the computer usage intentions of Ghanaian Tertiary Students. The Technology Acceptance Model was adopted as the theoretical framework to ascertain whether it could help explain behavioral intentions of individuals to accept and use technology. Factor analysis was used to assess the construct validity of the initial…

  2. Modeling eBook acceptance: A study on mathematics teachers

    NASA Astrophysics Data System (ADS)

    Jalal, Azlin Abd; Ayub, Ahmad Fauzi Mohd; Tarmizi, Rohani Ahmad

    2014-12-01

    The integration and effectiveness of eBook utilization in Mathematics teaching and learning greatly relied upon the teachers, hence the need to understand their perceptions and beliefs. The eBook, an individual laptop completed with digitized textbook sofwares, were provided for each students in line with the concept of 1 student:1 laptop. This study focuses on predicting a model on the acceptance of the eBook among Mathematics teachers. Data was collected from 304 mathematics teachers in selected schools using a survey questionnaire. The selection were based on the proportionate stratified sampling. Structural Equation Modeling (SEM) were employed where the model was tested and evaluated and was found to have a good fit. The variance explained for the teachers' attitude towards eBook is approximately 69.1% where perceived usefulness appeared to be a stronger determinant compared to perceived ease of use. This study concluded that the attitude of mathematics teachers towards eBook depends largely on the perception of how useful the eBook is on improving their teaching performance, implying that teachers should be kept updated with the latest mathematical application and sofwares to use with the eBook to ensure positive attitude towards using it in class.

  3. User Acceptance of Information Technology: Theories and Models.

    ERIC Educational Resources Information Center

    Dillon, Andrew; Morris, Michael G.

    1996-01-01

    Reviews literature in user acceptance and resistance to information technology design and implementation. Examines innovation diffusion, technology design and implementation, human-computer interaction, and information systems. Concentrates on the determinants of user acceptance and resistance and emphasizes how researchers and developers can…

  4. Do I Have to Learn Something New? Mental Models and the Acceptance of Replacement Technologies

    ERIC Educational Resources Information Center

    Zhang, Wei; Xu, Peng

    2011-01-01

    Few studies in technology acceptance have explicitly addressed the acceptance of replacement technologies, technologies that replace legacy ones that have been in use. This article explores this issue through the theoretical lens of mental models. We contend that accepting replacement technologies entails both mental model maintenance and mental…

  5. PCB contaminated dust on indoor surfaces--health risks and acceptable surface concentrations in residential and occupational settings.

    PubMed

    Kuusisto, Sari; Lindroos, Outi; Rantio, Tiina; Priha, Eero; Tuhkanen, Tuula

    2007-04-01

    Polychlorinated biphenyls (PCBs) have been used in diverse purposes such as indoor paints. Removal of these paints with dust creating techniques, like sandblasting, will result in contamination of building surfaces with PCB-containing dust. Objectives of this study was to analyze the PCB concentrations on surfaces after sandblasting with silica using wipe samples and estimate the resulting health risks and further calculate the risk based acceptable PCB surface concentrations that do not cause incremental lifetime cancer risk higher that 10(-5) or does not cause immunosupression effects in residential use or in occupational settings. Both deterministic and probabilistic approaches were used. The total PCB concentrations on surfaces ranged from 10 to 1100 microg/m(2). Estimated cancer risk was 1.2 x 10(-4) for childhood exposure, 1.3 x 10(-5) for adult residents and 1.5 x 10(-5) for occupational exposure. Probabilistic risk assessment revealed that point estimates were quite reasonable and located between 45th and 79th percentiles on probabilistic distribution of risk. The noncancer risks were calculated as hazard quotients (HQ) which ranged from 3.3 to 35 depending on the exposure scenario. Acceptable surface concentrations based on noncancer effects that are protective for 95% of exposed population were 7 microg/m(2) for residential use, 65 microg/m(2) for residential use if only adults will be exposed and 140 microg/m(2) for occupational use. Preliminary cleanup experiment revealed that when contaminated dust was carefully removed with industrial vacuum cleaner and further washed with terpene containing liquid the surface concentration dropped below the acceptable levels calculated in this study. PMID:17166563

  6. The Adult Roles Models Program: Feasibility, Acceptability, and Initial Outcomes

    PubMed Central

    Silver, Ellen Johnson; Dean, Randa; Perez, Amanda; Rivera, Angelic

    2014-01-01

    We present the feasibility and acceptability of a parent sexuality education program led by peer educators in community settings. We also report the results of an outcome evaluation with 71 parents who were randomized to the intervention or a control group, and surveyed one month prior to and six months after the 4-week intervention. The program was highly feasible and acceptable to participants, and the curriculum was implemented with a high level of fidelity and facilitator quality. Pilot data show promising outcomes for increasing parental knowledge, communication, and monitoring of their adolescent children. PMID:24883051

  7. Hybrid E-Learning Acceptance Model: Learner Perceptions

    ERIC Educational Resources Information Center

    Ahmed, Hassan M. Selim

    2010-01-01

    E-learning tools and technologies have been used to supplement conventional courses in higher education institutions creating a "hybrid" e-learning module that aims to enhance the learning experiences of students. Few studies have addressed the acceptance of hybrid e-learning by learners and the factors affecting the learners'…

  8. Modeling pinnacle reefs and their associated surfaces

    SciTech Connect

    Hamilton, D.E.; Henize, S.

    1989-03-01

    Although computer mapping programs are becoming widely available, simple to use, and powerful, the blind application of these programs often produces poor results. By considering the environment of deposition, postdepositional events, and scale of map when computer mapping, a better result can be achieved. To demonstrate the importance of these issues, data from Antrim and Kalkaska Counties, Michigan, were used to model pinnacle reefs in the Northern trend of the Michigan basin. The data consisted of 640 wells containing tops, facies, and show information for six units: Niagaran Gray, Niagaran Brown, Salina A1 evaporite, Salina A1 carbonate, Salina A2 evaporite, and Salina A2 carbonate. Building grids and contour maps of the Niagaran Brown (pinnacle) surface, using standard algorithms, produced a surface that either projected below or above the interreef surface. By using a mix of standard algorithms, the pinnacles and interreef surface were acceptably modeled. The Salina evaporites and carbonates are usually modeled using an isochore gridding approach. However, using this approach did not produce surfaces that reflected the geologist's interpretation. Simple modifications of the isochore approach allowed more accurate representation of the geologic interpretation. The evaporite surface models were built assuming they paralleled a paleowater surface. The carbonate surface models were built assuming they draped the surface existing at the time of deposition. Large- and small-scale maps were built for these data. Facies and show information were also mapped. Combined maps of several variables were constructed and evaluated for potential pinnacle locations.

  9. Surface Temperature Assimilation in Land Surface Models

    NASA Technical Reports Server (NTRS)

    Lakshmi, Venkataraman

    1999-01-01

    This paper examines the utilization of surface temperature as a variable to be assimilated in offline land surface hydrological models. Comparisons between the model computed and satellite observed surface temperatures have been carried out. The assimilation of surface temperature is carried out twice a day (corresponding to the AM and PM overpass of the NOAA10) over the Red-Arkansas basin in the Southwestern United States (31 degs 50 sec N - 36 degrees N, 94 degrees 30 seconds W - 104 degrees 3 seconds W) for a period of one year (August 1987 to July 1988). The effect of assimilation is to reduce the difference between the surface soil moisture computed for the precipitation and/or shortwave radiation perturbed case and the unperturbed case compared to no assimilation.

  10. Surface Temperature Assimilation in Land Surface Models

    NASA Technical Reports Server (NTRS)

    Lakshmi, Venkataraman

    1997-01-01

    This paper examines the utilization of surface temperature as a variable to be assimilated in offline land surface hydrological models. Comparisons between the model computed and satellite observed surface temperatures have been carried out. The assimilation of surface temperature is carried out twice a day (corresponding to the AM and PM overpass of the NOAA10) over the Red- Arkansas basin in the Southwestern United States (31 deg 50 min N - 36 deg N, 94 deg 30 min W - 104 deg 30 min W) for a period of one year (August 1987 to July 1988). The effect of assimilation is to reduce the difference between the surface soil moisture computed for the precipitation and/or shortwave radiation perturbed case and the unperturbed case compared to no assimilation.

  11. Acceptance and Commitment Therapy as a Unified Model of Behavior Change

    ERIC Educational Resources Information Center

    Hayes, Steven C.; Pistorello, Jacqueline; Levin, Michael E.

    2012-01-01

    The present article summarizes the assumptions, model, techniques, evidence, and diversity/social justice commitments of Acceptance and Commitment Therapy (ACT). ACT focused on six processes (acceptance, defusion, self, now, values, and action) that bear on a single overall target (psychological flexibility). The ACT model of behavior change has…

  12. Expectancies Underlying the Acceptability of Handicaps: The Pervasiveness of the Medical Model

    ERIC Educational Resources Information Center

    Abroms, Kippy; Kodera, Thomas L.

    1978-01-01

    Two groups of undergraduate students with diverse backgrounds ranked the acceptability of 15 handicapping conditions of which some were medical disorders and others were sociopsychological or functional impairments. Students adhered to the medical model, basing their judgments of acceptability on the amenability of a given handicap to medical…

  13. Uncertainties in Surface Layer Modeling

    NASA Astrophysics Data System (ADS)

    Pendergrass, W.

    2015-12-01

    A central problem for micrometeorologists has been the relationship of air-surface exchange rates of momentum and heat to quantities that can be predicted with confidence. The flux-gradient profile developed through Monin-Obukhov Similarity Theory (MOST) provides an integration of the dimensionless wind shear expression where is an empirically derived expression for stable and unstable atmospheric conditions. Empirically derived expressions are far from universally accepted (Garratt, 1992, Table A5). Regardless of what form of these relationships might be used, their significance over any short period of time is questionable since all of these relationships between fluxes and gradients apply to averages that might rarely occur. It is well accepted that the assumption of stationarity and homogeneity do not reflect the true chaotic nature of the processes that control the variables considered in these relationships, with the net consequence that the levels of predictability theoretically attainable might never be realized in practice. This matter is of direct relevance to modern prognostic models which construct forecasts by assuming the universal applicability of relationships among averages for the lower atmosphere, which rarely maintains an average state. Under a Cooperative research and Development Agreement between NOAA and Duke Energy Generation, NOAA/ATDD conducted atmospheric boundary layer (ABL) research using Duke renewable energy sites as research testbeds. One aspect of this research has been the evaluation of legacy flux-gradient formulations (the ϕ functions, see Monin and Obukhov, 1954) for the exchange of heat and momentum. At the Duke Energy Ocotillo site, NOAA/ATDD installed sonic anemometers reporting wind and temperature fluctuations at 10Hz at eight elevations. From these observations, ϕM and ϕH were derived from a two-year database of mean and turbulent wind and temperature observations. From this extensive measurement database, using a

  14. Modelling acceptance of sunlight in high and low photovoltaic concentration

    SciTech Connect

    Leutz, Ralf

    2014-09-26

    A simple model incorporating linear radiation characteristics, along with the optical trains and geometrical concentration ratios of solar concentrators is presented with performance examples for optical trains of HCPV, LCPV and benchmark flat-plate PV.

  15. Family support and acceptance, gay male identity formation, and psychological adjustment: a path model.

    PubMed

    Elizur, Y; Ziv, M

    2001-01-01

    While heterosexist family undermining has been demonstrated to be a developmental risk factor in the life of persons with same-gender orientation, the issue of protective family factors is both controversial and relatively neglected. In this study of Israeli gay males (N = 114), we focused on the interrelations of family support, family acceptance and family knowledge of gay orientation, and gay male identity formation, and their effects on mental health and self-esteem. A path model was proposed based on the hypotheses that family support, family acceptance, family knowledge, and gay identity formation have an impact on psychological adjustment, and that family support has an effect on gay identity formation that is mediated by family acceptance. The assessment of gay identity formation was based on an established stage model that was streamlined for cross-cultural practice by defining three basic processes of same-gender identity formation: self-definition, self-acceptance, and disclosure (Elizur & Mintzer, 2001). The testing of our conceptual path model demonstrated an excellent fit with the data. An alternative model that hypothesized effects of gay male identity on family acceptance and family knowledge did not fit the data. Interpreting these results, we propose that the main effect of family support/acceptance on gay identity is related to the process of disclosure, and that both general family support and family acceptance of same-gender orientation play a significant role in the psychological adjustment of gay men. PMID:11444052

  16. Adolescents' unconditional acceptance by parents and teachers and educational outcomes: A structural model of gender differences.

    PubMed

    Makri-Botsari, Evi

    2015-08-01

    The purpose of this study was to detect gender specific patterns in the network of relations between unconditionality of parental and teacher acceptance in the form of unconditional positive regard and a range of educational outcomes, as indexed by academic self-perception, academic intrinsic motivation, and academic achievement. To test the role of gender as a moderator, a multi-group analysis was employed within the framework of structural equation modelling with increasing restrictions placed on the structural paths across genders. The results on a sample of 427 adolescents in grades 7-9 showed that conditionality of acceptance undermined level of perceived acceptance for both social agents. Moreover, unconditionality of teacher acceptance exerted stronger influences on students' educational outcomes than unconditionality of parental acceptance, with effect sizes being larger for girls than for boys. PMID:26057875

  17. A proposed model of factors influencing hydrogen fuel cell vehicle acceptance

    NASA Astrophysics Data System (ADS)

    Imanina, N. H. Noor; Kwe Lu, Tan; Fadhilah, A. R.

    2016-03-01

    Issues such as environmental problem and energy insecurity keep worsening as a result of energy use from household to huge industries including automotive industry. Recently, a new type of zero emission vehicle, hydrogen fuel cell vehicle (HFCV) has received attention. Although there are argues on the feasibility of hydrogen as the future fuel, there is another important issue, which is the acceptance of HFCV. The study of technology acceptance in the early stage is a vital key for a successful introduction and penetration of a technology. This paper proposes a model of factors influencing green vehicle acceptance, specifically HFCV. This model is built base on two technology acceptance theories and other empirical studies of vehicle acceptance. It aims to provide a base for finding the key factors influencing new sustainable energy fuelled vehicle, HFCV acceptance which is achieved by explaining intention to accept HFCV. Intention is influenced by attitude, subjective norm and perceived behavioural control from Theory of Planned Behaviour and personal norm from Norm Activation Theory. In the framework, attitude is influenced by perceptions of benefits and risks, and social trust. Perceived behavioural control is influenced by government interventions. Personal norm is influenced by outcome efficacy and problem awareness.

  18. A Multivariate Model for the Study of Parental Acceptance-Rejection and Child Abuse.

    ERIC Educational Resources Information Center

    Rohner, Ronald P.; Rohner, Evelyn C.

    This paper proposes a multivariate strategy for the study of parental acceptance-rejection and child abuse and describes a research study on parental rejection and child abuse which illustrates the advantages of using a multivariate, (rather than a simple-model) approach. The multivariate model is a combination of three simple models used to study…

  19. Utilizing the health belief model to assess vaccine acceptance of patients on hemodialysis.

    PubMed

    Adams, Angela; Hall, Mellisa; Fulghum, Janis

    2014-01-01

    Vaccine rates in patients on hemodialysis are substantially lower than the Healthy People 2020 targets. The purpose of this study is to utilize the perceptions and cues for action constructs of the Health Belief Model (HBM) to assess the attitudes of patients receiving outpatient hemodialysis regarding acceptance of the seasonal influenza, pneumococcal, and hepatitis B virus vaccines. Vaccine acceptance is defined as receiving the vaccine. Study findings suggest age, perceived susceptibility, and perceived severity increase the odds of getting some vaccines. Findings have implications for the development of patient education materials, interdisciplinary team assessments, and plan of care strategies to increase vaccine acceptance. PMID:25244894

  20. Surface Water Response Modeling

    EPA Science Inventory

    During response to spills, or for facility planning, the vulnerability of downstream water resources is a major concern. How long and at what concentration do spilled contaminants reach downstream receptors? Models have the potential to answer these questions, but only if they ...

  1. THE TECHNOLOGY ACCEPTANCE MODEL: ITS PAST AND ITS FUTURE IN HEALTH CARE

    PubMed Central

    HOLDEN, RICHARD J.; KARSH, BEN-TZION

    2009-01-01

    Increasing interest in end users’ reactions to health information technology (IT) has elevated the importance of theories that predict and explain health IT acceptance and use. This paper reviews the application of one such theory, the Technology Acceptance Model (TAM), to health care. We reviewed 16 data sets analyzed in over 20 studies of clinicians using health IT for patient care. Studies differed greatly in samples and settings, health ITs studied, research models, relationships tested, and construct operationalization. Certain TAM relationships were consistently found to be significant, whereas others were inconsistent. Several key relationships were infrequently assessed. Findings show that TAM predicts a substantial portion of the use or acceptance of health IT, but that the theory may benefit from several additions and modifications. Aside from improved study quality, standardization, and theoretically motivated additions to the model, an important future direction for TAM is to adapt the model specifically to the health care context, using beliefs elicitation methods. PMID:19615467

  2. Modeling the acceptance of clinical information systems among hospital medical staff: an extended TAM model.

    PubMed

    Melas, Christos D; Zampetakis, Leonidas A; Dimopoulou, Anastasia; Moustakis, Vassilis

    2011-08-01

    Recent empirical research has utilized the Technology Acceptance Model (TAM) to advance the understanding of doctors' and nurses' technology acceptance in the workplace. However, the majority of the reported studies are either qualitative in nature or use small convenience samples of medical staff. Additionally, in very few studies moderators are either used or assessed despite their importance in TAM based research. The present study focuses on the application of TAM in order to explain the intention to use clinical information systems, in a random sample of 604 medical staff (534 physicians) working in 14 hospitals in Greece. We introduce physicians' specialty as a moderator in TAM and test medical staff's information and communication technology (ICT) knowledge and ICT feature demands, as external variables. The results show that TAM predicts a substantial proportion of the intention to use clinical information systems. Findings make a contribution to the literature by replicating, explaining and advancing the TAM, whereas theory is benefited by the addition of external variables and medical specialty as a moderator. Recommendations for further research are discussed. PMID:21292029

  3. Extending the Technology Acceptance Model to Explore the Intention to Use Second Life for Enhancing Healthcare Education

    ERIC Educational Resources Information Center

    Chow, Meyrick; Herold, David Kurt; Choo, Tat-Ming; Chan, Kitty

    2012-01-01

    Learners need to have good reasons to engage and accept e-learning. They need to understand that unless they do, the outcomes will be less favourable. The technology acceptance model (TAM) is the most widely recognized model addressing why users accept or reject technology. This study describes the development and evaluation of a virtual…

  4. Testing a developmental cascade model of emotional and social competence and early peer acceptance

    PubMed Central

    Blandon, Alysia Y.; Calkins, Susan D.; Grimm, Kevin J.; Keane, Susan P.; O’Brien, Marion

    2011-01-01

    A developmental cascade model of early emotional and social competence predicting later peer acceptance was examined in a community sample of 440 children across the ages of 2 to 7. Children’s externalizing behavior, emotion regulation, social skills within the classroom and peer acceptance were examined utilizing a multitrait-multimethod approach. A series of longitudinal cross-lag models that controlled for shared rater variance were fit using structural equation modeling. Results indicated there was considerable stability in children’s externalizing behavior problems and classroom social skills over time. Contrary to expectations, there were no reciprocal influences between externalizing behavior problems and emotion regulation, though higher levels of emotion regulation were associated with decreases in subsequent levels of externalizing behaviors. Finally, children’s early social skills also predicted later peer acceptance. Results underscore the complex associations among emotional and social functioning across early childhood. PMID:20883578

  5. Stochastic optimization model for order acceptance with multiple demand classes and uncertain demand/supply

    NASA Astrophysics Data System (ADS)

    Yang, Wen; Fung, Richard Y. K.

    2014-06-01

    This article considers an order acceptance problem in a make-to-stock manufacturing system with multiple demand classes in a finite time horizon. Demands in different periods are random variables and are independent of one another, and replenishments of inventory deviate from the scheduled quantities. The objective of this work is to maximize the expected net profit over the planning horizon by deciding the fraction of the demand that is going to be fulfilled. This article presents a stochastic order acceptance optimization model and analyses the existence of the optimal promising policies. An example of a discrete problem is used to illustrate the policies by applying the dynamic programming method. In order to solve the continuous problems, a heuristic algorithm based on stochastic approximation (HASA) is developed. Finally, the computational results of a case example illustrate the effectiveness and efficiency of the HASA approach, and make the application of the proposed model readily acceptable.

  6. Surface models of Mars, 1975

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Data derived from Mariners 6, 7, and 9, Russian Mars probes, and photographic and radar observations conducted from earth are used to develop engineering models of Martian surface properties. These models are used in mission planning and in the design of landing and exploration vehicles. Optical models needed in the design of camera systems, dielectric properties needed in the design of radar systems, and thermal properties needed in the design of the spacecraft thermal control system are included.

  7. Dynamic pushing on three frictional surfaces: maximum acceptable forces, cardiopulmonary and calf muscle metabolic responses in healthy men.

    PubMed

    Maikala, Rammohan V; Dempsey, Patrick G; Ciriello, Vincent M; O'Brien, Niall V

    2009-06-01

    Pushing is an important materials handling activity in many occupations; however, pushing-related physiological investigations are still in infancy. The purpose was to evaluate maximum acceptable forces and physiological responses while pushing on: treadmill (TREAD); plywood floor (PLY); and Teflon floor (TEF). Acceptable forces, cardiopulmonary and calf muscle oxygenation and blood volume responses were collected simultaneously while 12 men (age 39 +/- 13 years; height 178 +/- 6 cm; and body mass 91.5 +/- 16 kg) pushed for 2 h on each surface at their psychophysical workload. Participants selected higher forces on the PLY, resulting in higher pulmonary oxygen uptake compared to that of TEF (by approximately 9%) and TREAD (by approximately 18%). Pushing on the TEF demonstrated 50-56% lower blood volume changes and 1.5-1.8 times more oxygenation-force ratio than that for other surfaces. It is concluded that, to avoid a potential slip, participants were conservative in selecting acceptable forces to push on the slippery TEF. Part of this compensatory strategy on the TEF resulted in less muscle activity and, therefore, less demand for oxygen delivery to the calf muscle than for other surfaces. The present findings of significant force- and physiological-related differences in treadmill vs. high inertia pushcart clearly demonstrate that pushing experiments are essential to evaluate functional abilities of the workers. PMID:19431004

  8. 24 CFR 200.926c - Model code provisions for use in partially accepted code jurisdictions.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 24 Housing and Urban Development 2 2012-04-01 2012-04-01 false Model code provisions for use in partially accepted code jurisdictions. 200.926c Section 200.926c Housing and Urban Development Regulations Relating to Housing and Urban Development (Continued) OFFICE OF ASSISTANT SECRETARY FOR...

  9. Perceived Convenience in an Extended Technology Acceptance Model: Mobile Technology and English Learning for College Students

    ERIC Educational Resources Information Center

    Chang, Chi-Cheng; Yan, Chi-Fang; Tseng, Ju-Shih

    2012-01-01

    Since convenience is one of the features for mobile learning, does it affect attitude and intention of using mobile technology? The technology acceptance model (TAM), proposed by David (1989), was extended with perceived convenience in the present study. With regard to English language mobile learning, the variables in the extended TAM and its…

  10. Extended TAM Model: Impacts of Convenience on Acceptance and Use of Moodle

    ERIC Educational Resources Information Center

    Hsu, Hsiao-hui; Chang, Yu-ying

    2013-01-01

    The increasing online access to courses, programs, and information has shifted the control and responsibility of learning process from instructors to learners. Learners' perceptions of and attitudes toward e-learning constitute a critical factor to the success of such system. The purpose of this study is to take TAM (technology acceptance model)…

  11. Examining the Factors That Contribute to Successful Database Application Implementation Using the Technology Acceptance Model

    ERIC Educational Resources Information Center

    Nworji, Alexander O.

    2013-01-01

    Most organizations spend millions of dollars due to the impact of improperly implemented database application systems as evidenced by poor data quality problems. The purpose of this quantitative study was to use, and extend, the technology acceptance model (TAM) to assess the impact of information quality and technical quality factors on database…

  12. 24 CFR 200.926c - Model code provisions for use in partially accepted code jurisdictions.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 24 Housing and Urban Development 2 2010-04-01 2010-04-01 false Model code provisions for use in partially accepted code jurisdictions. 200.926c Section 200.926c Housing and Urban Development Regulations Relating to Housing and Urban Development (Continued) OFFICE OF ASSISTANT SECRETARY FOR HOUSING-FEDERAL HOUSING COMMISSIONER, DEPARTMENT...

  13. An Investigation of the Integrated Model of User Technology Acceptance: Internet User Samples in Four Countries

    ERIC Educational Resources Information Center

    Fusilier, Marcelline; Durlabhji, Subhash; Cucchi, Alain

    2008-01-01

    National background of users may influence the process of technology acceptance. The present study explored this issue with the new, integrated technology use model proposed by Sun and Zhang (2006). Data were collected from samples of college students in India, Mauritius, Reunion Island, and United States. Questionnaire methodology and…

  14. 24 CFR 200.926c - Model code provisions for use in partially accepted code jurisdictions.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 24 Housing and Urban Development 2 2011-04-01 2011-04-01 false Model code provisions for use in partially accepted code jurisdictions. 200.926c Section 200.926c Housing and Urban Development Regulations Relating to Housing and Urban Development (Continued) OFFICE OF ASSISTANT SECRETARY FOR HOUSING-FEDERAL HOUSING COMMISSIONER, DEPARTMENT...

  15. Understanding Student Teachers' Behavioural Intention to Use Technology: Technology Acceptance Model (TAM) Validation and Testing

    ERIC Educational Resources Information Center

    Wong, Kung-Teck; Osman, Rosma bt; Goh, Pauline Swee Choo; Rahmat, Mohd Khairezan

    2013-01-01

    This study sets out to validate and test the Technology Acceptance Model (TAM) in the context of Malaysian student teachers' integration of their technology in teaching and learning. To establish factorial validity, data collected from 302 respondents were tested against the TAM using confirmatory factor analysis (CFA), and structural equation…

  16. Modeling of a Parabolic Trough Solar Field for Acceptance Testing: A Case Study

    SciTech Connect

    Wagner, M. J.; Mehos, M. S.; Kearney, D. W.; McMahan, A. C.

    2011-01-01

    As deployment of parabolic trough concentrating solar power (CSP) systems ramps up, the need for reliable and robust performance acceptance test guidelines for the solar field is also amplified. Project owners and/or EPC contractors often require extensive solar field performance testing as part of the plant commissioning process in order to ensure that actual solar field performance satisfies both technical specifications and performance guaranties between the involved parties. Performance test code work is currently underway at the National Renewable Energy Laboratory (NREL) in collaboration with the SolarPACES Task-I activity, and within the ASME PTC-52 committee. One important aspect of acceptance testing is the selection of a robust technology performance model. NREL1 has developed a detailed parabolic trough performance model within the SAM software tool. This model is capable of predicting solar field, sub-system, and component performance. It has further been modified for this work to support calculation at subhourly time steps. This paper presents the methodology and results of a case study comparing actual performance data for a parabolic trough solar field to the predicted results using the modified SAM trough model. Due to data limitations, the methodology is applied to a single collector loop, though it applies to larger subfields and entire solar fields. Special consideration is provided for the model formulation, improvements to the model formulation based on comparison with the collected data, and uncertainty associated with the measured data. Additionally, this paper identifies modeling considerations that are of particular importance in the solar field acceptance testing process and uses the model to provide preliminary recommendations regarding acceptable steady-state testing conditions at the single-loop level.

  17. Improved Criteria for Acceptable Yield Point Elongation in Surface Critical Steels

    SciTech Connect

    Dr. David Matlock; Dr. John Speer

    2007-05-30

    Yield point elongation (YPE) is considered undesirable in surface critical applications where steel is formed since "strain lines" or Luders bands are created during forming. This project will examine in detail the formation of luders bands in industrially relevant strain states including the influence of substrate properties and coatings on Luders appearance. Mechanical testing and surface profilometry were the primary methods of investigation.

  18. Understanding Intention to Use Electronic Information Resources: A Theoretical Extension of the Technology Acceptance Model (TAM)

    PubMed Central

    Tao, Donghua

    2008-01-01

    This study extended the Technology Acceptance Model (TAM) by examining the roles of two aspects of e-resource characteristics, namely, information quality and system quality, in predicting public health students’ intention to use e-resources for completing research paper assignments. Both focus groups and a questionnaire were used to collect data. Descriptive analysis, data screening, and Structural Equation Modeling (SEM) techniques were used for data analysis. The study found that perceived usefulness played a major role in determining students’ intention to use e-resources. Perceived usefulness and perceived ease of use fully mediated the impact that information quality and system quality had on behavior intention. The research model enriches the existing technology acceptance literature by extending TAM. Representing two aspects of e-resource characteristics provides greater explanatory information for diagnosing problems of system design, development, and implementation. PMID:18999300

  19. Social trust, risk perceptions and public acceptance of recycled water: testing a social-psychological model.

    PubMed

    Ross, Victoria L; Fielding, Kelly S; Louis, Winnifred R

    2014-05-01

    Faced with a severe drought, the residents of the regional city of Toowoomba, in South East Queensland, Australia were asked to consider a potable wastewater reuse scheme to supplement drinking water supplies. As public risk perceptions and trust have been shown to be key factors in acceptance of potable reuse projects, this research developed and tested a social-psychological model of trust, risk perceptions and acceptance. Participants (N = 380) were surveyed a few weeks before a referendum was held in which residents voted against the controversial scheme. Analysis using structural equation modelling showed that the more community members perceived that the water authority used fair procedures (e.g., consulting with the community and providing accurate information), the greater their sense of shared identity with the water authority. Shared social identity in turn influenced trust via increased source credibility, that is, perceptions that the water authority is competent and has the community's interest at heart. The findings also support past research showing that higher levels of trust in the water authority were associated with lower perceptions of risk, which in turn were associated with higher levels of acceptance, and vice versa. The findings have a practical application for improving public acceptance of potable recycled water schemes. PMID:24603028

  20. The acceptance of in silico models for REACH: Requirements, barriers, and perspectives

    PubMed Central

    2011-01-01

    In silico models have prompted considerable interest and debate because of their potential value in predicting the properties of chemical substances for regulatory purposes. The European REACH legislation promotes innovation and encourages the use of alternative methods, but in practice the use of in silico models is still very limited. There are many stakeholders influencing the regulatory trajectory of quantitative structure-activity relationships (QSAR) models, including regulators, industry, model developers and consultants. Here we outline some of the issues and challenges involved in the acceptance of these methods for regulatory purposes. PMID:21982269

  1. Adding Innovation Diffusion Theory to the Technology Acceptance Model: Supporting Employees' Intentions to Use E-Learning Systems

    ERIC Educational Resources Information Center

    Lee, Yi-Hsuan; Hsieh, Yi-Chuan; Hsu, Chia-Ning

    2011-01-01

    This study intends to investigate factors affecting business employees' behavioral intentions to use the e-learning system. Combining the innovation diffusion theory (IDT) with the technology acceptance model (TAM), the present study proposes an extended technology acceptance model. The proposed model was tested with data collected from 552…

  2. The Effects of a Modified Treatment Package with and without Feeder Modeling on One Child's Acceptance of Novel Foods

    ERIC Educational Resources Information Center

    Seiverling, Laura; Harclerode, Whitney; Williams, Keith

    2014-01-01

    The purpose of this study was to examine if sequential presentation with feeder modeling would lead to an increase in bites accepted of new foods compared to sequential presentation without feeder modeling in a typically developing 4-year-old boy with food selectivity. The participant's acceptance of novel foods increased both in the modeling and…

  3. Plausible surface models for Titan

    NASA Technical Reports Server (NTRS)

    Lunine, Jonathan I.

    1992-01-01

    Current understanding of the nature of Titan's surface and some new ideas for explaining the curious radar returns from Saturn's largest satellite are reviewed. Pre-Voyager models of the surface, based largely on cosmochemistry and the discovery of atmospheric methane, allowed for a range of possibilities, including pure methane oceans. The Voyager 1 flyby ruled out this last possibility, replacing it with compelling observational arguments in favor of a mixed light hydrocarbon and nitrogen ocean. Ground based radar observations indicated a surprisingly reflective surface which is inconsistent with a hydrocarbon ocean and more reminiscent of the Galilean Satellites. Nonetheless, passive radiometric measurements of the surface do not support the notion that Titan's surface is like that of the Galilean satellites. One of the arguments against hydrocarbon oceans reflecting radar energy is that most solid, complex hydrocarbon and nitriles will be denser than the liquid and sink. Nonetheless, many of the aerosol species will coagulate in highly nonspherical patterns, and some species probably polymerize in long chains. Such chains will have very low sedimendation velocities in the ocean and may remain near the surface through ocean mixing process. The prospect of an oceanic 'soup' of polar polymers acting as volume reflectors at radio wevelengths suggests that the interpretation of radar observations needs evaluation.

  4. Integrating Health Belief Model and Technology Acceptance Model: An Investigation of Health-Related Internet Use

    PubMed Central

    2015-01-01

    Background Today, people use the Internet to satisfy health-related information and communication needs. In Malaysia, Internet use for health management has become increasingly significant due to the increase in the incidence of chronic diseases, in particular among urban women and their desire to stay healthy. Past studies adopted the Technology Acceptance Model (TAM) and Health Belief Model (HBM) independently to explain Internet use for health-related purposes. Although both the TAM and HBM have their own merits, independently they lack the ability to explain the cognition and the related mechanism in which individuals use the Internet for health purposes. Objective This study aimed to examine the influence of perceived health risk and health consciousness on health-related Internet use based on the HBM. Drawing on the TAM, it also tested the mediating effects of perceived usefulness of the Internet for health information and attitude toward Internet use for health purposes for the relationship between health-related factors, namely perceived health risk and health consciousness on health-related Internet use. Methods Data obtained for the current study were collected using purposive sampling; the sample consisted of women in Malaysia who had Internet access. The partial least squares structural equation modeling method was used to test the research hypotheses developed. Results Perceived health risk (β=.135, t 1999=2.676) and health consciousness (β=.447, t 1999=9.168) had a positive influence on health-related Internet use. Moreover, perceived usefulness of the Internet and attitude toward Internet use for health-related purposes partially mediated the influence of health consciousness on health-related Internet use (β=.025, t 1999=3.234), whereas the effect of perceived health risk on health-related Internet use was fully mediated by perceived usefulness of the Internet and attitude (β=.029, t 1999=3.609). These results suggest the central role of

  5. An Empirical Assessment of a Technology Acceptance Model for Apps in Medical Education.

    PubMed

    Briz-Ponce, Laura; García-Peñalvo, Francisco José

    2015-11-01

    The evolution and the growth of mobile applications ("apps") in our society is a reality. This general trend is still upward and the app use has also penetrated the medical education community. However, there is a lot of unawareness of the students' and professionals' point of view about introducing "apps" within Medical School curriculum. The aim of this research is to design, implement and verify that the Technology Acceptance Model (TAM) can be employed to measure and explain the acceptance of mobile technology and "apps" within Medical Education. The methodology was based on a survey distributed to students and medical professionals from University of Salamanca. This model explains 46.7% of behavioral intention to use mobile devise or "apps" for learning and will help us to justify and understand the current situation of introducing "apps" into the Medical School curriculum. PMID:26411928

  6. Optimizing surface quality of stainless alloys and using a modified ASTM G 48B procedure for acceptance testing

    SciTech Connect

    Maurer, J.R.

    1999-01-01

    The formation of high-temperature oxide scales and Cr-depleted zones on stainless alloys, such as 6% Mo superaustenitic steels, can significantly reduce their corrosion resistance. Effective methods to remove these layers and restore the surface to an optimized condition are detailed. Also, an acceptance test using a modified ASTM G 48B method at 35 C (95 F) for 72 h with a specimen having a crevice, and special corrosion criteria for failure, are described. Comparison of this test method with one using an uncreviced specimen at lower temperatures and for less time is discussed.

  7. Results of an emergency response atmospheric dispersion model comparison using a state accepted statistical protocol

    SciTech Connect

    Ciolek, J.T. Jr.

    1993-10-01

    The Rocky Flats Plant, located approximately 26 km northwest of downtown Denver, Colorado, has developed an emergency response atmospheric dispersion model for complex terrain applications. Plant personnel would use the model, known as the Terrain-Responsive Atmospheric Code (TRAC) (Hodgin 1985) to project plume impacts and provide off-site protective action recommendations to the State of Colorado should a hazardous material release occur from the facility. The Colorado Department of Health (CDH) entered into an interagency agreement with the Rocky Flats Plant prime contractor, EG&G Rocky Flats, and the US Department of Energy to evaluate TRAC as an acceptable emergency response tool. After exhaustive research of similar evaluation processes from other emergency response and regulatory organizations, the interagency committee devised a formal acceptance process. The process contains an evaluation protocol (Hodgin and Smith 1992), descriptions of responsibilities, an identified experimental data set to use in the evaluation, and judgment criteria for model acceptance. The evaluation protocol is general enough to allow for different implementations. This paper explains one implementation, shows protocol results for a test case, and presents results of a comparison between versions of TRAC with different wind Field codes: a two dimensional mass consistent code called WINDS (Fosberg et al. 1976) that has been extended to three dimensions, and a fully 3 dimensional mass conserving code called NUATMOS (Ross and Smith 1987, Ross et al. 1988).

  8. Integration of Heterogenous Digital Surface Models

    NASA Astrophysics Data System (ADS)

    Boesch, R.; Ginzler, C.

    2011-08-01

    The application of extended digital surface models often reveals, that despite an acceptable global accuracy for a given dataset, the local accuracy of the model can vary in a wide range. For high resolution applications which cover the spatial extent of a whole country, this can be a major drawback. Within the Swiss National Forest Inventory (NFI), two digital surface models are available, one derived from LiDAR point data and the other from aerial images. Automatic photogrammetric image matching with ADS80 aerial infrared images with 25cm and 50cm resolution is used to generate a surface model (ADS-DSM) with 1m resolution covering whole switzerland (approx. 41000 km2). The spatially corresponding LiDAR dataset has a global point density of 0.5 points per m2 and is mainly used in applications as interpolated grid with 2m resolution (LiDAR-DSM). Although both surface models seem to offer a comparable accuracy from a global view, local analysis shows significant differences. Both datasets have been acquired over several years. Concerning LiDAR-DSM, different flight patterns and inconsistent quality control result in a significantly varying point density. The image acquisition of the ADS-DSM is also stretched over several years and the model generation is hampered by clouds, varying illumination and shadow effects. Nevertheless many classification and feature extraction applications requiring high resolution data depend on the local accuracy of the used surface model, therefore precise knowledge of the local data quality is essential. The commercial photogrammetric software NGATE (part of SOCET SET) generates the image based surface model (ADS-DSM) and delivers also a map with figures of merit (FOM) of the matching process for each calculated height pixel. The FOM-map contains matching codes like high slope, excessive shift or low correlation. For the generation of the LiDAR-DSM only first- and last-pulse data was available. Therefore only the point distribution can

  9. Applying the Extended Technology Acceptance Model to the Use of Clickers in Student Learning: Some Evidence from Macroeconomics Classes

    ERIC Educational Resources Information Center

    Wu, Xiaoyu; Gao, Yuan

    2011-01-01

    This paper applies the extended technology acceptance model (exTAM) in information systems research to the use of clickers in student learning. The technology acceptance model (TAM) posits that perceived ease of use and perceived usefulness of technology influence users' attitudes toward using and intention to use technology. Research subsequent…

  10. The Acceptance Model of Intuitive Eating: A Comparison of Women in Emerging Adulthood, Early Adulthood, and Middle Adulthood

    ERIC Educational Resources Information Center

    Augustus-Horvath, Casey L.; Tylka, Tracy L.

    2011-01-01

    The acceptance model of intuitive eating (Avalos & Tylka, 2006) posits that body acceptance by others helps women appreciate their body and resist adopting an observer's perspective of their body, which contribute to their eating intuitively/adaptively. We extended this model by integrating body mass index (BMI) into its structure and…

  11. Theory development in nursing and healthcare informatics: a model explaining and predicting information and communication technology acceptance by healthcare consumers.

    PubMed

    An, Ji-Young; Hayman, Laura L; Panniers, Teresa; Carty, Barbara

    2007-01-01

    About 110 million American adults are looking for health information and services on the Internet. Identification of the factors influencing healthcare consumers' technology acceptance is requisite to understanding their acceptance and usage behavior of online health information and related services. The purpose of this article is to describe the development of the Information and Communication Technology Acceptance Model (ICTAM). From the literature reviewed, ICTAM was developed with emphasis on integrating multidisciplinary perspectives from divergent frameworks and empirical findings into a unified model with regard to healthcare consumers' acceptance and usage behavior of information and services on the Internet. PMID:17703115

  12. Lunar surface vehicle model competition

    NASA Technical Reports Server (NTRS)

    1990-01-01

    During Fall and Winter quarters, Georgia Tech's School of Mechanical Engineering students designed machines and devices related to Lunar Base construction tasks. These include joint projects with Textile Engineering students. Topics studied included lunar environment simulator via drop tower technology, lunar rated fasteners, lunar habitat shelter, design of a lunar surface trenching machine, lunar support system, lunar worksite illumination (daytime), lunar regolith bagging system, sunlight diffusing tent for lunar worksite, service apparatus for lunar launch vehicles, lunar communication/power cables and teleoperated deployment machine, lunar regolith bag collection and emplacement device, soil stabilization mat for lunar launch/landing site, lunar rated fastening systems for robotic implementation, lunar surface cable/conduit and automated deployment system, lunar regolith bagging system, and lunar rated fasteners and fastening systems. A special topics team of five Spring quarter students designed and constructed a remotely controlled crane implement for the SKITTER model.

  13. Measuring the Moderating Effect of Gender and Age on E-Learning Acceptance in England: A Structural Equation Modeling Approach for an Extended Technology Acceptance Model

    ERIC Educational Resources Information Center

    Tarhini, Ali; Hone, Kate; Liu, Xiaohui

    2014-01-01

    The success of an e-learning intervention depends to a considerable extent on student acceptance and use of the technology. Therefore, it has become imperative for practitioners and policymakers to understand the factors affecting the user acceptance of e-learning systems in order to enhance the students' learning experience. Based on an extended…

  14. Axelrod's model with surface tension

    NASA Astrophysics Data System (ADS)

    Pace, Bruno; Prado, Carmen P. C.

    2014-06-01

    In this work we propose a subtle change in Axelrod's model for the dissemination of culture. The mechanism consists of excluding from the set of potentially interacting neighbors those that would never possibly exchange. Although the alteration proposed does not alter the state space topologically, it yields significant qualitative changes, specifically the emergence of surface tension, driving the system in some cases to metastable states. The transient behavior is considerably richer, and cultural regions become stable leading to the formation of different spatiotemporal patterns. A metastable "glassy" phase emerges between the globalized phase and the disordered, multicultural phase.

  15. Development of a prediction model on the acceptance of electronic laboratory notebooks in academic environments.

    PubMed

    Kloeckner, Frederik; Farkas, Robert; Franken, Tobias; Schmitz-Rode, Thomas

    2014-04-01

    Documentation of research data plays a key role in the biomedical engineering innovation processes. It makes an important contribution to the protection of intellectual property, the traceability of results and fulfilling the regulatory requirement. Because of the increasing digitalization in laboratories, an electronic alternative to the commonly-used paper-bound notebooks could contribute to the production of sophisticated documentation. However, compared to in an industrial environment, the use of electronic laboratory notebooks is not widespread in academic laboratories. Little is known about the acceptance of an electronic documentation system and the underlying reasons for this. Thus, this paper aims to establish a prediction model on the potential preference and acceptance of scientists either for paper-based or electronic documentation. The underlying data for the analysis originate from an online survey of 101 scientists in industrial, academic and clinical environments. Various parameters were analyzed to identify crucial factors for the system preference using binary logistic regression. The analysis showed significant dependency between the documentation system preference and the supposed workload associated with the documentation system (p<0.006; odds ratio=58.543) and an additional personal component. Because of the dependency of system choice on specific parameters it is possible to predict the acceptance of an electronic laboratory notebook before implementation. PMID:24225123

  16. Computational model of collective nest selection by ants with heterogeneous acceptance thresholds

    PubMed Central

    Masuda, Naoki; O'shea-Wheller, Thomas A.; Doran, Carolina; Franks, Nigel R.

    2015-01-01

    Collective decision-making is a characteristic of societies ranging from ants to humans. The ant Temnothorax albipennis is known to use quorum sensing to collectively decide on a new home; emigration to a new nest site occurs when the number of ants favouring the new site becomes quorate. There are several possible mechanisms by which ant colonies can select the best nest site among alternatives based on a quorum mechanism. In this study, we use computational models to examine the implications of heterogeneous acceptance thresholds across individual ants in collective nest choice behaviour. We take a minimalist approach to develop a differential equation model and a corresponding non-spatial agent-based model. We show, consistent with existing empirical evidence, that heterogeneity in acceptance thresholds is a viable mechanism for efficient nest choice behaviour. In particular, we show that the proposed models show speed–accuracy trade-offs and speed–cohesion trade-offs when we vary the number of scouts or the quorum threshold. PMID:26543578

  17. Computational model of collective nest selection by ants with heterogeneous acceptance thresholds.

    PubMed

    Masuda, Naoki; O'shea-Wheller, Thomas A; Doran, Carolina; Franks, Nigel R

    2015-06-01

    Collective decision-making is a characteristic of societies ranging from ants to humans. The ant Temnothorax albipennis is known to use quorum sensing to collectively decide on a new home; emigration to a new nest site occurs when the number of ants favouring the new site becomes quorate. There are several possible mechanisms by which ant colonies can select the best nest site among alternatives based on a quorum mechanism. In this study, we use computational models to examine the implications of heterogeneous acceptance thresholds across individual ants in collective nest choice behaviour. We take a minimalist approach to develop a differential equation model and a corresponding non-spatial agent-based model. We show, consistent with existing empirical evidence, that heterogeneity in acceptance thresholds is a viable mechanism for efficient nest choice behaviour. In particular, we show that the proposed models show speed-accuracy trade-offs and speed-cohesion trade-offs when we vary the number of scouts or the quorum threshold. PMID:26543578

  18. Comparison of eggshell surface sanitization technologies and impacts on consumer acceptability.

    PubMed

    Al-Ajeeli, Morouj N; Taylor, T Matthew; Alvarado, Christine Z; Coufal, Craig D

    2016-05-01

    Shell eggs can be contaminated with many types of microorganisms, including bacterial pathogens, and thus present a risk for the transmission of foodborne disease to consumers. Currently, most United States egg processors utilize egg washing and sanitization systems to decontaminate surfaces of shell eggs prior to packaging. However, previous research has indicated that current shell egg sanitization technologies employed in the commercial egg industry may not completely eliminate bacteria from the surface of eggshells, and thus alternative egg sanitization technologies with the potential for increased microbial reductions on eggshells should be investigated. The objectives of this study were to compare the antimicrobial efficacy and consumer sensory attributes of industry-available eggshell sanitization methods (chlorine and quaternary ammonium compounds (QAC) applied via spray) to various alternative egg sanitization technologies. Eggs (White Leghorn hens; n=195) were obtained for evaluation of sanitizer-induced reduction in mesophilic aerobic bacteria (n=90) or inoculated Salmonella Enteritidis (SE) reduction (n=105). Sanitizing treatments evaluated in this experiment were: chlorine spray (100 ppm available chlorine), QAC spray (200 ppm), peracetic acid spray (PAA; 135 ppm) alone or in combination with ultraviolet light (UV; 254 nm), and hydrogen peroxide (H2O2; 3.5% solution) spray in combination with UV (H2O2+UV). For enumeration of aerobic bacteria, eggs were sampled at 0, 7, and 14 days of storage at 4°C; surviving SE cells from inoculated eggs were enumerated by differential plating. Sensory trials were conducted to determine consumer liking of scrambled eggs made from eggs sanitized with chlorine, QAC, H2O2+UV, or no treatment (control). The H2O2 and UV treatment resulted in the greatest reductions in eggshell aerobic plate counts compared to other treatments throughout egg storage (P<0.05). All treatments utilized reduced SE below the limit of

  19. An Investigation of Employees' Use of E-Learning Systems: Applying the Technology Acceptance Model

    ERIC Educational Resources Information Center

    Lee, Yi-Hsuan; Hsieh, Yi-Chuan; Chen, Yen-Hsun

    2013-01-01

    The purpose of this study is to apply the technology acceptance model to examine the employees' attitudes and acceptance of electronic learning (e-learning) systems in organisations. This study examines four factors (organisational support, computer self-efficacy, prior experience and task equivocality) that are believed to influence…

  20. An Elaboration Likelihood Model Based Longitudinal Analysis of Attitude Change during the Process of IT Acceptance via Education Program

    ERIC Educational Resources Information Center

    Lee, Woong-Kyu

    2012-01-01

    The principal objective of this study was to gain insight into attitude changes occurring during IT acceptance from the perspective of elaboration likelihood model (ELM). In particular, the primary target of this study was the process of IT acceptance through an education program. Although the Internet and computers are now quite ubiquitous, and…

  1. An Exploration of Student Internet Use in India: The Technology Acceptance Model and the Theory of Planned Behaviour

    ERIC Educational Resources Information Center

    Fusilier, Marcelline; Durlabhji, Subhash

    2005-01-01

    Purpose: The purpose of this paper is to explore behavioral processes involved in internet technology acceptance and use with a sample in India, a developing country that can potentially benefit from greater participation in the web economy. Design/methodology/approach - User experience was incorporated into the technology acceptance model (TAM)…

  2. Testing the Electronic Personal Health Record Acceptance Model by Nurses for Managing Their Own Health

    PubMed Central

    Trinkoff, A.M.; Storr, C.L.; Wilson, M.L.; Gurses, A.P.

    2015-01-01

    Summary Background To our knowledge, no evidence is available on health care professionals’ use of electronic personal health records (ePHRs) for their health management. We therefore focused on nurses’ personal use of ePHRs using a modified technology acceptance model. Objectives To examine (1) the psychometric properties of the ePHR acceptance model, (2) the associations of perceived usefulness, ease of use, data privacy and security protection, and perception of self as health-promoting role models to nurses’ own ePHR use, and (3) the moderating influences of age, chronic illness and medication use, and providers’ use of electronic health record (EHRs) on the associations between the ePHR acceptance constructs and ePHR use. Methods A convenience sample of registered nurses, those working in one of 12 hospitals in the Maryland and Washington, DC areas and members of the nursing informatics community (AMIA and HIMSS), were invited to respond to an anonymous online survey; 847 responded. Multiple logistic regression identified associations between the model constructs and ePHR use, and the moderating effect. Results Overall, ePHRs were used by 47%. Sufficient reliability for all scales was found. Three constructs were significantly related to nurses’ own ePHR use after adjusting for covariates: usefulness, data privacy and security protection, and health-promoting role model. Nurses with providers that used EHRs who perceived a higher level of data privacy and security protection had greater odds of ePHR use than those whose providers did not use EHRs. Older nurses with a higher self-perception as health-promoting role models had greater odds of ePHR use than younger nurses. Conclusions Nurses who use ePHRs for their personal health might promote adoption by the general public by serving as health-promoting role models. They can contribute to improvements in patient education and ePHR design, and serve as crucial resources when working with their

  3. Surface Contact Model for Comets and Asteroids

    NASA Technical Reports Server (NTRS)

    Blackmore, Lars James C.; Trease, Brian P.; Acikmese, Behcet; Mandic, Milan; Carson, John M.

    2011-01-01

    A contact force model was developed for use in touch and go (TAG) surface sampling simulations on small celestial bodies such as comets and asteroids. In TAG scenarios, a spacecraft descending toward the surface of a small body comes into contact with the surface for a short duration of time, collects material samples with a sampler device, and then ascends to leave the surface. The surface contact required 6-DOF (degrees of freedom) dynamics models due to coupling of the attitude and translation dynamics during the contact. The model described here is for contact scenarios that utilize a rotating brush wheel sampler (BWS) to collect surface material. The model includes stiffness and damping of the surface material during BWS vertical motion, lateral friction from the BWS dragging across the surface, and lateral shear from the rotating BWS scooping the surface material. This model is useful for any mission to asteroids or comets that incorporates surface sampling operations.

  4. Development of a Health Information Technology Acceptance Model Using Consumers’ Health Behavior Intention

    PubMed Central

    2012-01-01

    Background For effective health promotion using health information technology (HIT), it is mandatory that health consumers have the behavioral intention to measure, store, and manage their own health data. Understanding health consumers’ intention and behavior is needed to develop and implement effective and efficient strategies. Objective To develop and verify the extended Technology Acceptance Model (TAM) in health care by describing health consumers’ behavioral intention of using HIT. Methods This study used a cross-sectional descriptive correlational design. We extended TAM by adding more antecedents and mediating variables to enhance the model’s explanatory power and to make it more applicable to health consumers’ behavioral intention. Additional antecedents and mediating variables were added to the hypothetical model, based on their theoretical relevance, from the Health Belief Model and theory of planned behavior, along with the TAM. We undertook structural equation analysis to examine the specific nature of the relationship involved in understanding consumers’ use of HIT. Study participants were 728 members recruited from three Internet health portals in Korea. Data were collected by a Web-based survey using a structured self-administered questionnaire. Results The overall fitness indices for the model developed in this study indicated an acceptable fit of the model. All path coefficients were statistically significant. This study showed that perceived threat, perceived usefulness, and perceived ease of use significantly affected health consumers’ attitude and behavioral intention. Health consumers’ health status, health belief and concerns, subjective norm, HIT characteristics, and HIT self-efficacy had a strong indirect impact on attitude and behavioral intention through the mediators of perceived threat, perceived usefulness, and perceived ease of use. Conclusions An extended TAM in the HIT arena was found to be valid to describe health

  5. Electronic Health Record Patient Portal Adoption by Health Care Consumers: An Acceptance Model and Survey

    PubMed Central

    2016-01-01

    Background The future of health care delivery is becoming more citizen centered, as today’s user is more active, better informed, and more demanding. Worldwide governments are promoting online health services, such as electronic health record (EHR) patient portals and, as a result, the deployment and use of these services. Overall, this makes the adoption of patient-accessible EHR portals an important field to study and understand. Objective The aim of this study is to understand the factors that drive individuals to adopt EHR portals. Methods We applied a new adoption model using, as a starting point, Ventkatesh's Unified Theory of Acceptance and Use of Technology in a consumer context (UTAUT2) by integrating a new construct specific to health care, a new moderator, and new relationships. To test the research model, we used the partial least squares (PLS) causal modelling approach. An online questionnaire was administrated. We collected 360 valid responses. Results The statistically significant drivers of behavioral intention are performance expectancy (beta=.200; t=3.619), effort expectancy (beta=.185; t=2.907), habit (beta=.388; t=7.320), and self-perception (beta=.098; t=2.285). The predictors of use behavior are habit (beta=0.206; t=2.752) and behavioral intention (beta=0.258; t=4.036). The model explained 49.7% of the variance in behavioral intention and 26.8% of the variance in use behavior. Conclusions Our research helps to understand the desired technology characteristics of EHR portals. By testing an information technology acceptance model, we are able to determine what is more valued by patients when it comes to deciding whether to adopt EHR portals or not. The inclusion of specific constructs and relationships related to the health care consumer area also had a significant impact on understanding the adoption of EHR portals. PMID:26935646

  6. Modelling dose distribution in tubing and cable using CYLTRAN and ACCEPT Monte Carlo simulation code

    SciTech Connect

    Weiss, D.E.; Kensek, R.P.

    1993-12-31

    One of the difficulties in the irradiation of non-slab geometries, such as a tube, is the uneven penetration of the electrons. A simple model of the distribution of dose in a tube or cable in relationship to voltage, composition, wall thickness and diameter can be mapped using the cylinder geometry provided for in the ITS/CYLTRAN code, complete with automatic subzoning. The reality of more complex 3D geometry to include effects of window foil, backscattering fixtures and beam scanning angles can be more completely accounted for by using the ITS/ACCEPT code with a line source update and a system of intersecting wedges to define input zones for mapping dose distributions in a tube. Thus, all of the variables that affect dose distribution can be modelled without the need to run time consuming and costly factory experiments. The effects of composition changes on dose distribution can also be anticipated.

  7. Modelling of biogas extraction at an Italian landfill accepting mechanically and biologically treated municipal solid waste.

    PubMed

    Calabrò, Paolo S; Orsi, Sirio; Gentili, Emiliano; Carlo, Meoni

    2011-12-01

    This paper presents the results of the modelling of the biogas extraction in a full-scale Italian landfill by the USEPA LandGEM model and the Andreottola-Cossu approach. The landfill chosen for this research ('Il Fossetto' plant, Monsummano Terme, Italy) had accepted mixed municipal raw waste for about 15 years. In the year 2003 a mechanical biological treatment (MBT) was implemented and starting from the end of the year 2006, the recirculation in the landfill of the concentrated leachate coming from the internal membrane leachate treatment plant was put into practice. The USEPA LandGEM model and the Andreottola-Cossu approach were chosen since they require only input data routinely acquired during landfill management (waste amount and composition) and allow a simplified calibration, therefore they are potentially useful for practical purposes such as landfill gas management. The results given by the models are compared with measured data and analysed in order to verify the impact of MBT on biogas production; moreover, the possible effects of the recirculation of the concentrated leachate are discussed. The results clearly show how both models can adequately fit measured data even after MBT implementation. Model performance was significantly reduced for the period after the beginning of recirculation of concentrated leachate when the probable inhibition of methane production, due to the competition between methanogens and sulfate-reducing bacteria, significantly influenced the biogas production and composition. PMID:21930528

  8. Comparing Cognitive, Metacognitive, and Acceptance and Commitment Therapy Models of Depression: a Longitudinal Study Survey.

    PubMed

    Ruiz, Francisco J; Odriozola-González, Paula

    2015-01-01

    This study analyzed the interrelationships between key constructs of cognitive therapy (CT; depressogenic schemas), metacognitive therapy (MCT; dysfunctional metacognitive beliefs), and acceptance and commitment therapy (ACT; psychological inflexibility) in the prediction of depressive symptoms. With a lapse of nine months, 106 nonclinical participants responded twice to an anonymous online survey containing the following questionnaires: the Depression subscale of the Depression Anxiety and Stress Scales (DASS), the Dysfunctional Attitude Scale Revised (DAS-R), the Positive beliefs, Negative beliefs and Need to control subscales of the Metacognitions Questionnaire-30 (MCQ-30), and the Acceptance and Action Questionnaire - II (AAQ-II). Results showed that when controlling for baseline levels of depressive symptoms and demographic variables, psychological inflexibility longitudinally mediated the effect of depressogenic schemas (path ab = .023, SE = .010; 95% BC CI [.008, .048]) and dysfunctional metacognitive beliefs on depressive symptoms (positive metacognitive beliefs: path ab = .052, SE = .031; 95% BC CI [.005, .134]; negative metacognitive beliefs: path ab = .087, SE = .049; 95% BC CI [.016, .214]; need to control: path ab = .087, SE = .051; 95% BC CI [.013, .220]). Results are discussed emphasizing the role of psychological inflexibility in the CT and MCT models of depression. PMID:26076977

  9. Consumer acceptance and stability of spray dried betanin in model juices.

    PubMed

    Kaimainen, Mika; Laaksonen, Oskar; Järvenpää, Eila; Sandell, Mari; Huopalahti, Rainer

    2015-11-15

    Spray dried beetroot powder was used to colour model juices, and the consumer acceptance of the juices and stability of the colour during storage at 60 °C, 20 °C, 4 °C, and -20 °C were studied. The majority of the consumers preferred the model juices coloured with anthocyanins or beetroot extract over model juices coloured with spray dried beetroot powder. The consumers preferred more intensely coloured samples over lighter samples. Spray dried betanin samples were described as 'unnatural' and 'artificial' whereas the colour of beetroot extract was described more 'natural' and 'real juice'. No beetroot-derived off-odours or off-flavours were perceived in the model juices coloured with beetroot powder. Colour stability in model juices was greatly dependent on storage temperature with better stability at lower temperatures. Colour stability in the spray dried powder was very good at 20 °C. Betacyanins from beetroot could be a potential colourant for food products that are stored cold. PMID:25977043

  10. Assimilation of Surface Temperature in Land Surface Models

    NASA Technical Reports Server (NTRS)

    Lakshmi, Venkataraman

    1998-01-01

    Hydrological models have been calibrated and validated using catchment streamflows. However, using a point measurement does not guarantee correct spatial distribution of model computed heat fluxes, soil moisture and surface temperatures. With the advent of satellites in the late 70s, surface temperature is being measured two to four times a day from various satellite sensors and different platforms. The purpose of this paper is to demonstrate use of satellite surface temperature in (a) validation of model computed surface temperatures and (b) assimilation of satellite surface temperatures into a hydrological model in order to improve the prediction accuracy of soil moistures and heat fluxes. The assimilation is carried out by comparing the satellite and the model produced surface temperatures and setting the "true"temperature midway between the two values. Based on this "true" surface temperature, the physical relationships of water and energy balance are used to reset the other variables. This is a case of nudging the water and energy balance variables so that they are consistent with each other and the true" surface temperature. The potential of this assimilation scheme is demonstrated in the form of various experiments that highlight the various aspects. This study is carried over the Red-Arkansas basin in the southern United States (a 5 deg X 10 deg area) over a time period of a year (August 1987 - July 1988). The land surface hydrological model is run on an hourly time step. The results show that satellite surface temperature assimilation improves the accuracy of the computed surface soil moisture remarkably.

  11. Where there's smoke: Cigarette use, social acceptability, and spatial approaches to multilevel modeling.

    PubMed

    O'Connell, Heather A

    2015-09-01

    I contribute to understandings of how context is related to individual outcomes by assessing the added value of combining multilevel and spatial modeling techniques. This methodological approach leads to substantive contributions to the smoking literature, including improved clarity on the central contextual factors and the examination of one manifestation of the social acceptability hypothesis. For this analysis I use restricted-use natality data from the Vital Statistics, and county-level data from the 2005-9 ACS. Critically, the results suggest that spatial considerations are still relevant in a multilevel framework. In addition, I argue that spatial processes help explain the relationships linking racial/ethnic minority concentration to lower overall odds of smoking. PMID:26188587

  12. WHERE THERE’S SMOKE: CIGARETTE USE, SOCIAL ACCEPTABILITY, AND SPATIAL APPROACHES TO MULTILEVEL MODELING

    PubMed Central

    O’Connell, Heather A.

    2015-01-01

    I contribute to understandings of how context is related to individual outcomes by assessing the added value of combining multilevel and spatial modeling techniques. This methodological approach leads to substantive contributions to the smoking literature, including improved clarity on the central contextual factors and the examination of one manifestation of the social acceptability hypothesis. For this analysis I use restricted-use natality data from the Vital Statistics, and county-level data from the 2005–9 ACS. Critically, the results suggest that spatial considerations are still relevant in a multilevel framework. In addition, I argue that spatial processes help explain the relationships linking racial/ethnic minority concentration to lower overall odds of smoking. PMID:26188587

  13. Surface modeling of soil antibiotics.

    PubMed

    Shi, Wen-jiao; Yue, Tian-xiang; Du, Zheng-ping; Wang, Zong; Li, Xue-wen

    2016-02-01

    Large numbers of livestock and poultry feces are continuously applied into soils in intensive vegetable cultivation areas, and then some veterinary antibiotics are persistent existed in soils and cause health risk. For the spatial heterogeneity of antibiotic residues, developing a suitable technique to interpolate soil antibiotic residues is still a challenge. In this study, we developed an effective interpolator, high accuracy surface modeling (HASM) combined vegetable types, to predict the spatial patterns of soil antibiotics, using 100 surface soil samples collected from an intensive vegetable cultivation area located in east of China, and the fluoroquinolones (FQs), including ciprofloxacin (CFX), enrofloxacin (EFX) and norfloxacin (NFX), were analyzed as the target antibiotics. The results show that vegetable type is an effective factor to be combined to improve the interpolator performance. HASM achieves less mean absolute errors (MAEs) and root mean square errors (RMSEs) for total FQs (NFX+CFX+EFX), NFX, CFX and EFX than kriging with external drift (KED), stratified kriging (StK), ordinary kriging (OK) and inverse distance weighting (IDW). The MAE of HASM for FQs is 55.1 μg/kg, and the MAEs of KED, StK, OK and IDW are 99.0 μg/kg, 102.8 μg/kg, 106.3 μg/kg and 108.7 μg/kg, respectively. Further, RMSE simulated by HASM for FQs (CFX, EFX and NFX) are 106.2 μg/kg (88.6 μg/kg, 20.4 μg/kg and 39.2 μg/kg), and less 30% (27%, 22% and 36%), 33% (27%, 27% and 43%), 38% (34%, 23% and 41%) and 42% (32%, 35% and 51%) than the ones by KED, StK, OK and IDW, respectively. HASM also provides better maps with more details and more consistent maximum and minimum values of soil antibiotics compared with the measured data. The better performance can be concluded that HASM takes the vegetable type information as global approximate information, and takes local sampling data as its optimum control constraints. PMID:26613514

  14. Coarse-grained modelling of surface nanobubbles

    NASA Astrophysics Data System (ADS)

    Grosfils, Patrick

    2013-05-01

    Surface nanobubbles are nanoscale gaseous objects that form on hydrophobic surfaces in contact with water. Understanding nanobubble formation and stability remains challenging due to the lack of appropriate theoretical framework and adequate modelling. Here we present a non-equilibrium coarse-grained model for nanobubbles at hydrophobic surfaces. The model is based on a lattice-gas model that has been proposed to understand the hydrophobic effect to which dynamical properties are added. The results presented demonstrate the ability of the model to reproduce the basic features of stable surface nanobubbles, which, thereby, supports the dynamical origin of these objects.

  15. The development of a model for predicting passenger acceptance of short-haul air transportation systems

    NASA Technical Reports Server (NTRS)

    Kuhlthau, A. R.; Jacobson, I. D.

    1977-01-01

    Meaningful criteria and methodology for assessing, particularly in the area of ride quality, the potential acceptability to the traveling public of present and future transportation systems were investigated. Ride quality was found to be one of the important variables affecting the decision of users of air transportation, and to be influenced by several environmental factors, especially motion, noise, pressure, temperature, and seating. Models were developed to quantify the relationship of subjective comfort to all of these parameters and then were exercised for a variety of situations. Passenger satisfaction was found to be strongly related to ride quality and was so modeled. A computer program was developed to assess the comfort and satisfaction levels of passengers on aircraft subjected to arbitrary flight profiles over arbitrary terrain. A model was deduced of the manner in which passengers integrate isolated segments of a flight to obtain an overall trip comfort rating. A method was established for assessing the influence of other links (e.g., access, terminal conditions) in the overall passenger trip.

  16. Dynamical Modeling of Surface Tension

    NASA Technical Reports Server (NTRS)

    Brackbill, Jeremiah U.; Kothe, Douglas B.

    1996-01-01

    In a recent review it is said that free-surface flows 'represent some of the difficult remaining challenges in computational fluid dynamics'. There has been progress with the development of new approaches to treating interfaces, such as the level-set method and the improvement of older methods such as the VOF method. A common theme of many of the new developments has been the regularization of discontinuities at the interface. One example of this approach is the continuum surface force (CSF) formulation for surface tension, which replaces the surface stress given by Laplace's equation by an equivalent volume force. Here, we describe how CSF formulation might be made more useful. Specifically, we consider a derivation of the CSF equations from a minimization of surface energy as outlined by Jacqmin (1996). This reformulation suggests that if one eliminates the computation of curvature in terms of a unit normal vector, parasitic currents may be eliminated. For this reformulation to work, it is necessary that transition region thickness be controlled. Various means for this, in addition to the one discussed by Jacqmin (1996), are discussed.

  17. Preservice Teachers' Acceptance of ICT Integration in the Classroom: Applying the UTAUT Model

    ERIC Educational Resources Information Center

    Birch, A.; Irvine, V.

    2009-01-01

    In this study, the researchers explore the factors that influence preservice teachers' acceptance of information and communication technology (ICT) integration in the classroom. The Unified Theory of Acceptance and Use of Technology (UTAUT) was developed by Venkatesh et al. ["MIS Quarterly, 27"(3), 425-478] in 2003 and shown to outperform eight…

  18. Determinants of Intention to Use eLearning Based on the Technology Acceptance Model

    ERIC Educational Resources Information Center

    Punnoose, Alfie Chacko

    2012-01-01

    The purpose of this study was to find some of the predominant factors that determine the intention of students to use eLearning in the future. Since eLearning is not just a technology acceptance decision but also involves cognition, this study extended its search beyond the normal technology acceptance variables into variables that could affect…

  19. A Quantitative Examination of User Experience as an Antecedent to Student Perception in Technology Acceptance Modeling

    ERIC Educational Resources Information Center

    Butler, Rory

    2013-01-01

    Internet-enabled mobile devices have increased the accessibility of learning content for students. Given the ubiquitous nature of mobile computing technology, a thorough understanding of the acceptance factors that impact a learner's intention to use mobile technology as an augment to their studies is warranted. Student acceptance of mobile…

  20. Empirical Testing of a Theoretical Extension of the Technology Acceptance Model: An Exploratory Study of Educational Wikis

    ERIC Educational Resources Information Center

    Liu, Xun

    2010-01-01

    This study extended the technology acceptance model and empirically tested the new model with wikis, a new type of educational technology. Based on social cognitive theory and the theory of planned behavior, three new variables, wiki self-efficacy, online posting anxiety, and perceived behavioral control, were added to the original technology…

  1. Learning with Interactive Whiteboards: Determining the Factors on Promoting Interactive Whiteboards to Students by Technology Acceptance Model

    ERIC Educational Resources Information Center

    Kilic, Eylem; Güler, Çetin; Çelik, H. Eray; Tatli, Cemal

    2015-01-01

    Purpose: The purpose of this study is to investigate the factors which might affect the intention to use interactive whiteboards (IWBs) by university students, using Technology Acceptance Model by the structural equation modeling approach. The following hypothesis guided the current study: H1. There is a positive relationship between IWB…

  2. Physician Acceptance of a Physician-Pharmacist Collaborative Treatment Model for Hypertension Management in Primary Care.

    PubMed

    Smith, Steven M; Hasan, Michaela; Huebschmann, Amy G; Penaloza, Richard; Schorr-Ratzlaff, Wagner; Sieja, Amber; Roscoe, Nicholai; Trinkley, Katy E

    2015-09-01

    Physician-pharmacist collaborative care (PPCC) is effective in improving blood pressure (BP) control, but primary care provider (PCP) engagement in such models has not been well-studied. The authors analyzed data from PPCC referrals to 108 PCPs, for patients with uncontrolled hypertension, assessing the proportion of referral requests approved, disapproved, and not responded to, and reasons for disapproval. Of 2232 persons with uncontrolled hypertension, PPCC referral requests were sent for 1516 (67.9%): 950 (62.7%) were approved, 406 (26.8%) were disapproved, and 160 (10.6%) received no response. Approval rates differed widely by PCP with a median approval rate of 75% (interquartile range, 41%-100%). The most common reasons for disapproval were: PCP prefers to manage hypertension (19%), and BP controlled per PCP (18%); 8% of cases were considered too complex for PPCC. Provider acceptance of a PPCC hypertension clinic was generally high and sustained but varied widely among PCPs. No single reason for disapproval predominated. PMID:26032586

  3. Low surface pressure models for Titan's atmosphere

    NASA Technical Reports Server (NTRS)

    Caldwell, J.

    1978-01-01

    The inversion model for the atmosphere of Titan is reviewed. The basic features of the model are: a cold surface (80 K), a warm stratosphere (160 K) and a low surface pressure (20 mbar). The model is consistent with all existing thermal infrared spectrophotometry, but it cannot preclude the existence of an opaque, cloud, thick atmosphere. The model excludes other gases than methane as bulk constituents. Radio wavelengths observations, including recent data from the very large array, are discussed. These long wavelength observations may be the only direct means of sampling the surface environment before an entry probe or flyby.

  4. Integrating Social Capital Theory, Social Cognitive Theory, and the Technology Acceptance Model to Explore a Behavioral Model of Telehealth Systems

    PubMed Central

    Tsai, Chung-Hung

    2014-01-01

    Telehealth has become an increasingly applied solution to delivering health care to rural and underserved areas by remote health care professionals. This study integrated social capital theory, social cognitive theory, and the technology acceptance model (TAM) to develop a comprehensive behavioral model for analyzing the relationships among social capital factors (social capital theory), technological factors (TAM), and system self-efficacy (social cognitive theory) in telehealth. The proposed framework was validated with 365 respondents from Nantou County, located in Central Taiwan. Structural equation modeling (SEM) was used to assess the causal relationships that were hypothesized in the proposed model. The finding indicates that elderly residents generally reported positive perceptions toward the telehealth system. Generally, the findings show that social capital factors (social trust, institutional trust, and social participation) significantly positively affect the technological factors (perceived ease of use and perceived usefulness respectively), which influenced usage intention. This study also confirmed that system self-efficacy was the salient antecedent of perceived ease of use. In addition, regarding the samples, the proposed model fitted considerably well. The proposed integrative psychosocial-technological model may serve as a theoretical basis for future research and can also offer empirical foresight to practitioners and researchers in the health departments of governments, hospitals, and rural communities. PMID:24810577

  5. Quantitative and qualitative variation of fat in model vanilla custard desserts: effects on sensory properties and consumer acceptance.

    PubMed

    Tomaschunas, Maja; Köhn, Ehrhard; Bennwitz, Petra; Hinrichs, Jörg; Busch-Stockfisch, Mechthild

    2013-06-01

    The effects of variation in fat content (0.1% to 15.8%) and type of fat, using different types of milk, dairy cream, or vegetable fat cream, on sensory characteristics and consumer acceptance of starch-based vanilla model custards were studied. Descriptive analysis with trained panelists and consumer testing with untrained assessors were applied. Descriptive data were related to hedonic data using principal component analysis to determine drivers of liking and disliking. Results demonstrated an increasing effect of fat concerning visual and oral thickness, creamy flavor, and fat-related texture properties, as well as a decreasing effect concerning yellow color and surface shine. A lack of fat caused moderate intensities in pudding-like flavor attributes and an intensive jelly texture. Adding a vegetable fat cream led to lower intensities in attributes yellow color, cooked flavor, thick, and jelly texture, whereas intensities in vegetable fat flavor and fat-related texture properties increased. All consumers favored custards with medium fat contents, being high in pudding-like and vegetable fat flavor as well as in fat-related texture attributes. Nonfat custards were rejected due to jelly texture and moderate intensities in pudding-flavor attributes. High-fat samples were liked by some consumers, but their high intensities in thickness, white color, and creamy flavor also drove disliking for others. PMID:23772708

  6. Response Surface Modeling Using Multivariate Orthogonal Functions

    NASA Technical Reports Server (NTRS)

    Morelli, Eugene A.; DeLoach, Richard

    2001-01-01

    A nonlinear modeling technique was used to characterize response surfaces for non-dimensional longitudinal aerodynamic force and moment coefficients, based on wind tunnel data from a commercial jet transport model. Data were collected using two experimental procedures - one based on modem design of experiments (MDOE), and one using a classical one factor at a time (OFAT) approach. The nonlinear modeling technique used multivariate orthogonal functions generated from the independent variable data as modeling functions in a least squares context to characterize the response surfaces. Model terms were selected automatically using a prediction error metric. Prediction error bounds computed from the modeling data alone were found to be- a good measure of actual prediction error for prediction points within the inference space. Root-mean-square model fit error and prediction error were less than 4 percent of the mean response value in all cases. Efficacy and prediction performance of the response surface models identified from both MDOE and OFAT experiments were investigated.

  7. Experience With Bayesian Image Based Surface Modeling

    NASA Technical Reports Server (NTRS)

    Stutz, John C.

    2005-01-01

    Bayesian surface modeling from images requires modeling both the surface and the image generation process, in order to optimize the models by comparing actual and generated images. Thus it differs greatly, both conceptually and in computational difficulty, from conventional stereo surface recovery techniques. But it offers the possibility of using any number of images, taken under quite different conditions, and by different instruments that provide independent and often complementary information, to generate a single surface model that fuses all available information. I describe an implemented system, with a brief introduction to the underlying mathematical models and the compromises made for computational efficiency. I describe successes and failures achieved on actual imagery, where we went wrong and what we did right, and how our approach could be improved. Lastly I discuss how the same approach can be extended to distinct types of instruments, to achieve true sensor fusion.

  8. Coupled land surface/hydrologic/atmospheric models

    NASA Technical Reports Server (NTRS)

    Pielke, Roger; Steyaert, Lou; Arritt, Ray; Lahtakia, Mercedes; Smith, Chris; Ziegler, Conrad; Soong, Su Tzai; Avissar, Roni; Wetzel, Peter; Sellers, Piers

    1993-01-01

    The topics covered include the following: prototype land cover characteristics data base for the conterminous United States; surface evapotranspiration effects on cumulus convection and implications for mesoscale models; the use of complex treatment of surface hydrology and thermodynamics within a mesoscale model and some related issues; initialization of soil-water content for regional-scale atmospheric prediction models; impact of surface properties on dryline and MCS evolution; a numerical simulation of heavy precipitation over the complex topography of California; representing mesoscale fluxes induced by landscape discontinuities in global climate models; emphasizing the role of subgrid-scale heterogeneity in surface-air interaction; and problems with modeling and measuring biosphere-atmosphere exchanges of energy, water, and carbon on large scales.

  9. Implicitly modelled stratigraphic surfaces using generalized interpolation

    NASA Astrophysics Data System (ADS)

    Hillier, Michael; de Kemp, Eric; Schetselaar, Ernst

    2016-06-01

    Stratigraphic surfaces implicitly modelled using a generalized interpolation approach in various geological settings is presented to demonstrate its modelling capabilities and limitations. The generalized interpolation approach provides a useful mathematical framework in modelling continuous surfaces from scattered data consisting of the following geological constraints: contact locations and planar orientations. Examples are presented to show the effectiveness of the method in generating plausible representations of geological structures in sparse data environments. One of the major advantages of implicit surface modelling has long been claimed as its ability to model geometries with arbitrary topology. It is, however, demonstrated that this is in fact a disadvantage in robustly generating geologically realistic surfaces in structurally complex domains with a known topology.

  10. The Theory of Planned Behavior (TPB) and Pre-Service Teachers' Technology Acceptance: A Validation Study Using Structural Equation Modeling

    ERIC Educational Resources Information Center

    Teo, Timothy; Tan, Lynde

    2012-01-01

    This study applies the theory of planned behavior (TPB), a theory that is commonly used in commercial settings, to the educational context to explain pre-service teachers' technology acceptance. It is also interested in examining its validity when used for this purpose. It has found evidence that the TPB is a valid model to explain pre-service…

  11. Factors of Online Learning Adoption: A Comparative Juxtaposition of the Theory of Planned Behaviour and the Technology Acceptance Model

    ERIC Educational Resources Information Center

    Ndubisi, Nelson

    2006-01-01

    Organisational investments in information technologies have increased significantly in the past few decades. All around the globe and in Malaysia particularly, a number of educational institutions are experimenting with e-learning. Adopting the theory of planned behaviour (TPB) and the technology acceptance model (TAM) this article tries to…

  12. Generalized Models for Rock Joint Surface Shapes

    PubMed Central

    Du, Shigui; Hu, Yunjin; Hu, Xiaofei

    2014-01-01

    Generalized models of joint surface shapes are the foundation for mechanism studies on the mechanical effects of rock joint surface shapes. Based on extensive field investigations of rock joint surface shapes, generalized models for three level shapes named macroscopic outline, surface undulating shape, and microcosmic roughness were established through statistical analyses of 20,078 rock joint surface profiles. The relative amplitude of profile curves was used as a borderline for the division of different level shapes. The study results show that the macroscopic outline has three basic features such as planar, arc-shaped, and stepped; the surface undulating shape has three basic features such as planar, undulating, and stepped; and the microcosmic roughness has two basic features such as smooth and rough. PMID:25152901

  13. An Improved MUSIC Model for Gibbsite Surfaces

    SciTech Connect

    Mitchell, Scott C.; Bickmore, Barry R.; Tadanier, Christopher J.; Rosso, Kevin M.

    2004-06-01

    Here we use gibbsite as a model system with which to test a recently published, bond-valence method for predicting intrinsic pKa values for surface functional groups on oxides. At issue is whether the method is adequate when valence parameters for the functional groups are derived from ab initio structure optimization of surfaces terminated by vacuum. If not, ab initio molecular dynamics (AIMD) simulations of solvated surfaces (which are much more computationally expensive) will have to be used. To do this, we had to evaluate extant gibbsite potentiometric titration data that where some estimate of edge and basal surface area was available. Applying BET and recently developed atomic force microscopy methods, we found that most of these data sets were flawed, in that their surface area estimates were probably wrong. Similarly, there may have been problems with many of the titration procedures. However, one data set was adequate on both counts, and we applied our method of surface pKa int prediction to fitting a MUSIC model to this data with considerable success—several features of the titration data were predicted well. However, the model fit was certainly not perfect, and we experienced some difficulties optimizing highly charged, vacuum-terminated surfaces. Therefore, we conclude that we probably need to do AIMD simulations of solvated surfaces to adequately predict intrinsic pKa values for surface functional groups.

  14. Modeling nurses' acceptance of bar coded medication administration technology at a pediatric hospital

    PubMed Central

    Brown, Roger L; Scanlon, Matthew C; Karsh, Ben-Tzion

    2012-01-01

    Objective To identify predictors of nurses' acceptance of bar coded medication administration (BCMA). Design Cross-sectional survey of registered nurses (N=83) at an academic pediatric hospital that recently implemented BCMA. Methods Surveys assessed seven BCMA-related perceptions: ease of use; usefulness for the job; social influence from non-specific others to use BCMA; training; technical support; usefulness for patient care; and social influence from patients/families. An all possible subset regression procedure with five goodness-of-fit indicators was used to identify which set of perceptions best predicted BCMA acceptance (intention to use, satisfaction). Results Nurses reported a moderate perceived ease of use and low perceived usefulness of BCMA. Nurses perceived moderate-or-higher social influence to use BCMA and had moderately positive perceptions of BCMA-related training and technical support. Behavioral intention to use BCMA was high, but satisfaction was low. Behavioral intention to use was best predicted by perceived ease of use, perceived social influence from non-specific others, and perceived usefulness for patient care (56% of variance explained). Satisfaction was best predicted by perceived ease of use, perceived usefulness for patient care, and perceived social influence from patients/families (76% of variance explained). Discussion Variation in and low scores on ease of use and usefulness are concerning, especially as these variables often correlate with acceptance, as found in this study. Predicting acceptance benefited from using a broad set of perceptions and adapting variables to the healthcare context. Conclusion Success with BCMA and other technologies can benefit from assessing end-user acceptance and elucidating the factors promoting acceptance and use. PMID:22661559

  15. Investigating IT Faculty Resistance to Learning Management System Adoption Using Latent Variables in an Acceptance Technology Model

    PubMed Central

    Bousbahi, Fatiha; Alrazgan, Muna Saleh

    2015-01-01

    To enhance instruction in higher education, many universities in the Middle East have chosen to introduce learning management systems (LMS) to their institutions. However, this new educational technology is not being used at its full potential and faces resistance from faculty members. To investigate this phenomenon, we conducted an empirical research study to uncover factors influencing faculty members' acceptance of LMS. Thus, in the Fall semester of 2014, Information Technology faculty members were surveyed to better understand their perceptions of the incorporation of LMS into their courses. The results showed that personal factors such as motivation, load anxiety, and organizational support play important roles in the perception of the usefulness of LMS among IT faculty members. These findings suggest adding these constructs in order to extend the Technology acceptance model (TAM) for LMS acceptance, which can help stakeholders of the university to implement the use of this system. This may assist in planning and evaluating the use of e-learning. PMID:26491712

  16. Investigating IT Faculty Resistance to Learning Management System Adoption Using Latent Variables in an Acceptance Technology Model.

    PubMed

    Bousbahi, Fatiha; Alrazgan, Muna Saleh

    2015-01-01

    To enhance instruction in higher education, many universities in the Middle East have chosen to introduce learning management systems (LMS) to their institutions. However, this new educational technology is not being used at its full potential and faces resistance from faculty members. To investigate this phenomenon, we conducted an empirical research study to uncover factors influencing faculty members' acceptance of LMS. Thus, in the Fall semester of 2014, Information Technology faculty members were surveyed to better understand their perceptions of the incorporation of LMS into their courses. The results showed that personal factors such as motivation, load anxiety, and organizational support play important roles in the perception of the usefulness of LMS among IT faculty members. These findings suggest adding these constructs in order to extend the Technology acceptance model (TAM) for LMS acceptance, which can help stakeholders of the university to implement the use of this system. This may assist in planning and evaluating the use of e-learning. PMID:26491712

  17. Minimal model for spoof acoustoelastic surface states

    SciTech Connect

    Christensen, J. Willatzen, M.; Liang, Z.

    2014-12-15

    Similar to textured perfect electric conductors for electromagnetic waves sustaining artificial or spoof surface plasmons we present an equivalent phenomena for the case of sound. Aided by a minimal model that is able to capture the complex wave interaction of elastic cavity modes and airborne sound radiation in perfect rigid panels, we construct designer acoustoelastic surface waves that are entirely controlled by the geometrical environment. Comparisons to results obtained by full-wave simulations confirm the feasibility of the model and we demonstrate illustrative examples such as resonant transmissions and waveguiding to show a few examples of many where spoof elastic surface waves are useful.

  18. Integrating Telemedicine for Disaster Response: Testing the Emergency Telemedicine Technology Acceptance Model

    ERIC Educational Resources Information Center

    Davis, Theresa M.

    2013-01-01

    Background: There is little evidence that technology acceptance is well understood in healthcare. The hospital environment is complex and dynamic creating a challenge when new technology is introduced because it impacts current processes and workflows which can significantly affect patient care delivery and outcomes. This study tested the effect…

  19. Using the UTAUT Model to Examine the Acceptance Behavior of Synchronous Collaboration to Support Peer Translation

    ERIC Educational Resources Information Center

    Liu, Yi Chun; Huang, Yong-Ming

    2015-01-01

    The teaching of translation has received considerable attention in recent years. Research on translation in collaborative learning contexts, however, has been less studied. In this study, we use a tool of synchronous collaboration to assist students in experiencing a peer translation process. Afterward, the unified theory of acceptance and use of…

  20. WebCT--The Quasimoderating Effect of Perceived Affective Quality on an Extending Technology Acceptance Model

    ERIC Educational Resources Information Center

    Sanchez-Franco, Manuel J.

    2010-01-01

    Perceived affective quality is an attractive area of research in Information System. Specifically, understanding the intrinsic and extrinsic individual factors and interaction effects that influence Information and Communications Technology (ICT) acceptance and adoption--in higher education--continues to be a focal interest in learning research.…

  1. Perceived Playfulness, Gender Differences and Technology Acceptance Model in a Blended Learning Scenario

    ERIC Educational Resources Information Center

    Padilla-Melendez, Antonio; del Aguila-Obra, Ana Rosa; Garrido-Moreno, Aurora

    2013-01-01

    The importance of technology for education is increasing year-by-year at all educational levels and particularly for Universities. This paper reexamines one important determinant of technology acceptance and use, such as perceived playfulness in the context of a blended learning setting and reveals existing gender differences. After a literature…

  2. An Investigation of University Student Readiness Towards M-Learning Using Technology Acceptance Model

    ERIC Educational Resources Information Center

    Iqbal, Shakeel; Bhatti, Zeeshan Ahmed

    2015-01-01

    M-learning is learning delivered via mobile devices and mobile technology. The research indicates that this medium of learning has potential to enhance formal as well as informal learning. However, acceptance of m-learning greatly depends upon the personal attitude of students towards this medium; therefore this study focuses only on the…

  3. Exploring Students' Intention to Use LINE for Academic Purposes Based on Technology Acceptance Model

    ERIC Educational Resources Information Center

    Van De Bogart, Willard; Wichadee, Saovapa

    2015-01-01

    The LINE application is often conceived as purely social space; however, the authors of this paper wanted to determine if it could be used for academic purposes. In this study, we examined how undergraduate students accepted LINE in terms of using it for classroom-related activities (e.g., submit homework, follow up course information queries,…

  4. Adult Role Models: Feasibility, Acceptability, and Initial Outcomes for Sex Education

    ERIC Educational Resources Information Center

    Colarossi, Lisa; Silver, Ellen Johnson; Dean, Randa; Perez, Amanda; Rivera, Angelic

    2014-01-01

    The authors present the feasibility and acceptability of a parent sexuality education program led by peer educators in community settings. They also report the results of an outcome evaluation with 71 parents who were randomized to the intervention or a control group and surveyed one month prior to and six months after the four-week intervention.…

  5. Uncertainty and Sensitivity in Surface Dynamics Modeling

    NASA Astrophysics Data System (ADS)

    Kettner, Albert J.; Syvitski, James P. M.

    2016-05-01

    Papers for this special issue on 'Uncertainty and Sensitivity in Surface Dynamics Modeling' heralds from papers submitted after the 2014 annual meeting of the Community Surface Dynamics Modeling System or CSDMS. CSDMS facilitates a diverse community of experts (now in 68 countries) that collectively investigate the Earth's surface-the dynamic interface between lithosphere, hydrosphere, cryosphere, and atmosphere, by promoting, developing, supporting and disseminating integrated open source software modules. By organizing more than 1500 researchers, CSDMS has the privilege of identifying community strengths and weaknesses in the practice of software development. We recognize, for example, that progress has been slow on identifying and quantifying uncertainty and sensitivity in numerical modeling of earth's surface dynamics. This special issue is meant to raise awareness for these important subjects and highlight state-of-the-art progress.

  6. Preventing repetition of attempted suicide--I. Feasibility (acceptability, adherence, and effectiveness) of a Baerum-model like aftercare.

    PubMed

    Hvid, Marianne; Wang, August G

    2009-01-01

    Repetition after attempted suicide is high with only limited research been put into effect studies. The Baerum-model from Norway offers a practical and affordable intervention. Our aim was to study the acceptability and effectiveness of a Baerum-model like intervention after attempted suicide using a quasi-experimental design. During a period in 2004, attempted suicide patients were offered follow-up care by a rapid-response outreach programme, an intervention lasting 6 months; a control group was established prospectively from a similar period in 2002. The design was an intent-to-treat analysis. The outcome was measured by: 1) participation by acceptance and adherence, 2) repetition of suicide attempt and suicide, and 3) including the number of repetitive acts in 1 year after the attempted suicide episode. Follow-up period was 1 year. Participation was 70%. There was a significant lower repetition rate in the intervention group, where the proportion of repetitive patients fell from 34% to 14%. There were also fewer suicidal acts, in total 37 acts in 58 patients in the control group and 22 acts in 93 patients for the intervention group. We have concluded that the outreach programme has a good feasibility because of high acceptability and adherence, and has an acceptable effectiveness in the follow up period of 1 year. We have therefore initiated a similar study using a randomization design in order to study efficacy. PMID:19016074

  7. Stress exposure and generation: A conjoint longitudinal model of body dysmorphic symptoms, peer acceptance, popularity, and victimization.

    PubMed

    Webb, Haley J; Zimmer-Gembeck, Melanie J; Mastro, Shawna

    2016-09-01

    This study examined the bidirectional (conjoint) longitudinal pathways linking adolescents' body dysmorphic disorder (BDD) symptoms with self- and peer-reported social functioning. Participants were 367 Australian students (45.5% boys, mean age=12.01 years) who participated in two waves of a longitudinal study with a 12-month lag between assessments. Participants self-reported their symptoms characteristic of BDD, and perception of peer acceptance. Classmates reported who was popular and victimized in their grade, and rated their liking (acceptance) of their classmates. In support of both stress exposure and stress generation models, T1 victimization was significantly associated with more symptoms characteristic of BDD at T2 relative to T1, and higher symptom level at T1 was associated with lower perceptions of peer acceptance at T2 relative to T1. These results support the hypothesized bidirectional model, whereby adverse social experiences negatively impact symptoms characteristic of BDD over time, and symptoms also exacerbate low perceptions of peer-acceptance. PMID:27236472

  8. Surface Adsorption in Nonpolarizable Atomic Models.

    PubMed

    Whitmer, Jonathan K; Joshi, Abhijeet A; Carlton, Rebecca J; Abbott, Nicholas L; de Pablo, Juan J

    2014-12-01

    Many ionic solutions exhibit species-dependent properties, including surface tension and the salting-out of proteins. These effects may be loosely quantified in terms of the Hofmeister series, first identified in the context of protein solubility. Here, our interest is to develop atomistic models capable of capturing Hofmeister effects rigorously. Importantly, we aim to capture this dependence in computationally cheap "hard" ionic models, which do not exhibit dynamic polarization. To do this, we have performed an investigation detailing the effects of the water model on these properties. Though incredibly important, the role of water models in simulation of ionic solutions and biological systems is essentially unexplored. We quantify this via the ion-dependent surface attraction of the halide series (Cl, Br, I) and, in so doing, determine the relative importance of various hypothesized contributions to ionic surface free energies. Importantly, we demonstrate surface adsorption can result in hard ionic models combined with a thermodynamically accurate representation of the water molecule (TIP4Q). The effect observed in simulations of iodide is commensurate with previous calculations of the surface potential of mean force in rigid molecular dynamics and polarizable density-functional models. Our calculations are direct simulation evidence of the subtle but sensitive role of water thermodynamics in atomistic simulations. PMID:26583244

  9. An analytic model for the Phobos surface

    NASA Technical Reports Server (NTRS)

    Duxbury, Thomas C.

    1991-01-01

    Analytic expressions are derived to model the surface topography and the normal to the surface of Phobos. The analytic expressions are comprised of a spherical harmonic expansion for the global figure of Phobos, augmented by addition terms for the large crater Stickney and other craters. Over 300 craters were measured in more than 100 Viking Orbiter images to produce the model. In general, the largest craters were measured since they have a significant effect on topography. The topographic model derived has a global spatial and topographic accuracy ranging from about 100 m in areas having the highest resolution and convergent, stereo coverage, up to 500 m in the poorest areas.

  10. Laser Induced Aluminum Surface Breakdown Model

    NASA Technical Reports Server (NTRS)

    Chen, Yen-Sen; Liu, Jiwen; Zhang, Sijun; Wang, Ten-See (Technical Monitor)

    2002-01-01

    Laser powered propulsion systems involve complex fluid dynamics, thermodynamics and radiative transfer processes. Based on an unstructured grid, pressure-based computational aerothermodynamics; platform, several sub-models describing such underlying physics as laser ray tracing and focusing, thermal non-equilibrium, plasma radiation and air spark ignition have been developed. This proposed work shall extend the numerical platform and existing sub-models to include the aluminum wall surface Inverse Bremsstrahlung (IB) effect from which surface ablation and free-electron generation can be initiated without relying on the air spark ignition sub-model. The following tasks will be performed to accomplish the research objectives.

  11. Lakes representation in a land surface model

    NASA Astrophysics Data System (ADS)

    Dutra, E.; Stepanenko, V. M.; Balsamo, G.; Viterbo, P.; Miranda, P. M. A.; Mironov, D.

    2009-04-01

    Lakes and other inland water bodies can, in certain areas, compose a large fraction of the land surface. Inland waters have an important role in determining local and regional climates, primarily because of large differences in albedo, heat capacity, roughness, and energy exchange compared to vegetated land surfaces. Despite the radically different physical characteristics of inland waters when compared to their surrounding, most land surface models put more emphasis on the comparatively weaker differences within continental surface types (such as various types of vegetation and bare soil). Thus so far sub-grid lakes have been largely neglected. The present work describes the incorporation of the lake model FLAKE (Mironov 2008, http://lakemodel.net) into the ECMWF land surface scheme HTESSEL (Balsamo 2008). Results from global offline simulations are presented in order to (i) evaluate the model's performance in different climates and (ii) assess the impact of lakes representation in the surface energy balance. The model was forced by new ECMWF reanalysis product ERA-INTERIM (1989-present) near surface meteorology and surface fluxes (radiation and precipitation) for the entire globe. Model validation includes lake surface temperatures (global) and lake ice duration (Northern Hemisphere). Lake surface temperatures, derived from the TERRA-MODIS satellite (http://oceancolor.gsfc.nasa.gov/), are compared against simulations for the period 2001-2008, while lake ice duration is validated using data from the Global Lake and River Ice Phenology (Benson and Magnunson, 2007). The impact of the snow insulator effect on lake ice cover duration is also discussed and compared with frozen soil duration in neighbouring areas. The sensitivity of the present analysis to the lake depth, which is important and often unknown lake parameter, is also addressed. In addition, the implementation of the lake model within the land surface model allows for sub-grid cover variability. The impact

  12. Free surface modeling in OWC chamber with parabolic side walls using 3D BEM

    SciTech Connect

    Hasanabad, Madjid Ghodsi

    2015-03-10

    In this paper, BEM was used for free surface modeling in OWC chamber and out of it. Linear kinematic and dynamic boundary conditions were used for free surface out of OWC chamber and nonlinear forms were used for free surface in the chamber. These boundary conditions were discretized by finite differences method. Also, some thermodynamics relations were applied for trapped air behavior modeling in OWC chamber. Wave specifications in Chabahar region were used in modeling because these waves have an acceptable power for electricity generation. The results show a good agreement with results of other researches.

  13. A continuum method for modeling surface tension

    NASA Technical Reports Server (NTRS)

    Brackbill, J. U.; Kothe, D. B.; Zemach, C.

    1992-01-01

    In the novel method presented for modeling the effects of surface tension on fluid motion, the interfaces between fluids with different, color-represented properties are finite-thickness transition regions across which the color varies continuously. A force density proportional to the surface curvature of constant color is defined at each point in the transition region; this force-density is normalized in such a way that the conventional description of surface tension on an interface is recovered when the ratio of local transition-reion thickness to local curvature radius approaches zero. The properties of the method are illustrated by computational results for 2D flows.

  14. Modelling the appearance of heritage metallic surfaces

    NASA Astrophysics Data System (ADS)

    MacDonald, L.; Hindmarch, J.; Robson, S.; Terras, M.

    2014-06-01

    Polished metallic surfaces exhibit a high degree of specularity, which makes them difficult to reproduce accurately. We have applied two different techniques for modelling a heritage object known as the Islamic handbag. Photogrammetric multi-view stereo enabled a dense point cloud to be extracted from a set of photographs with calibration targets, and a geometrically accurate 3D model produced. A new method based on photometric stereo from a set of images taken in an illumination dome enabled surface normals to be generated for each face of the object and its appearance to be rendered, to a high degree of visual realism, when illuminated by one or more light sources from any angles. The specularity of the reflection from the metal surface was modelled by a modified Lorentzian function.

  15. Atomistic Method Applied to Computational Modeling of Surface Alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo H.; Abel, Phillip B.

    2000-01-01

    The formation of surface alloys is a growing research field that, in terms of the surface structure of multicomponent systems, defines the frontier both for experimental and theoretical techniques. Because of the impact that the formation of surface alloys has on surface properties, researchers need reliable methods to predict new surface alloys and to help interpret unknown structures. The structure of surface alloys and when, and even if, they form are largely unpredictable from the known properties of the participating elements. No unified theory or model to date can infer surface alloy structures from the constituents properties or their bulk alloy characteristics. In spite of these severe limitations, a growing catalogue of such systems has been developed during the last decade, and only recently are global theories being advanced to fully understand the phenomenon. None of the methods used in other areas of surface science can properly model even the already known cases. Aware of these limitations, the Computational Materials Group at the NASA Glenn Research Center at Lewis Field has developed a useful, computationally economical, and physically sound methodology to enable the systematic study of surface alloy formation in metals. This tool has been tested successfully on several known systems for which hard experimental evidence exists and has been used to predict ternary surface alloy formation (results to be published: Garces, J.E.; Bozzolo, G.; and Mosca, H.: Atomistic Modeling of Pd/Cu(100) Surface Alloy Formation. Surf. Sci., 2000 (in press); Mosca, H.; Garces J.E.; and Bozzolo, G.: Surface Ternary Alloys of (Cu,Au)/Ni(110). (Accepted for publication in Surf. Sci., 2000.); and Garces, J.E.; Bozzolo, G.; Mosca, H.; and Abel, P.: A New Approach for Atomistic Modeling of Pd/Cu(110) Surface Alloy Formation. (Submitted to Appl. Surf. Sci.)). Ternary alloy formation is a field yet to be fully explored experimentally. The computational tool, which is based on

  16. Laser Induced Aluminum Surface Breakdown Model

    NASA Technical Reports Server (NTRS)

    Chen, Yen-Sen; Liu, Jiwen; Zhang, Sijun; Wnag, Ten-See (Technical Monitor)

    2001-01-01

    Laser powered propulsion systems involve complex fluid dynamics, thermodynamics and radiative transfer processes. Based on an unstructured grid., pressure-based computational aerothermodynamics, platform, several sub-nio"'dels describing such underlying physics as laser ray tracing and focusing, thermal non-equilibrium, plasma radiation and air spark ignition have been developed. This proposed work shall extend the numerical platform and existing sub-models to include the aluminum wall surface Inverse Bremsstrahlung (113) effect from which surface ablation and free-electron generation can be initiated without relying on the air spark ignition sub-model. The following tasks will be performed to accomplish the research objectives.

  17. Stellar Surface Differential Rotation from Dynamo Models

    NASA Astrophysics Data System (ADS)

    Korhonen, H.; Elstner, D.

    2006-08-01

    We have previously published dynamo models that can reproduce the flip-flop phenomenon. In this phenomenon the main part of the stellar activity changes longitude by 180 degrees. Here we use these dynamo models for studying the stellar surface differential rotation. We use standard cross-correlation methods to study the changes in the magnetic pressure maps obtained from the dynamo calculations. As these maps can be treated the same way as the temperature maps, e.g., ones obtained with the Doppler imaging, we can use the same techniques as for real observations to analyse the maps produced by the dynamo calculations. Our investigation reveals that the input rotation used in the dynamo calculations is not always obtained with the analysis. In some cases even the sign of the surface differential rotation changes from the solar type input surface rotation to anti-solar surface rotation obtained from the analysis. This means that the spot motion is not determined by the differential rotation, but mainly by the underlying magnetic field structure. There is also some indication that in some cases the strength of the surface differential rotation varies with the activity cycle. These results could have important implications for observational studies of the stellar surface differential rotation.

  18. Functional Risk Modeling for Lunar Surface Systems

    NASA Technical Reports Server (NTRS)

    Thomson, Fraser; Mathias, Donovan; Go, Susie; Nejad, Hamed

    2010-01-01

    We introduce an approach to risk modeling that we call functional modeling , which we have developed to estimate the capabilities of a lunar base. The functional model tracks the availability of functions provided by systems, in addition to the operational state of those systems constituent strings. By tracking functions, we are able to identify cases where identical functions are provided by elements (rovers, habitats, etc.) that are connected together on the lunar surface. We credit functional diversity in those cases, and in doing so compute more realistic estimates of operational mode availabilities. The functional modeling approach yields more realistic estimates of the availability of the various operational modes provided to astronauts by the ensemble of surface elements included in a lunar base architecture. By tracking functional availability the effects of diverse backup, which often exists when two or more independent elements are connected together, is properly accounted for.

  19. Quantitative Modeling of Earth Surface Processes

    NASA Astrophysics Data System (ADS)

    Pelletier, Jon D.

    This textbook describes some of the most effective and straightforward quantitative techniques for modeling Earth surface processes. By emphasizing a core set of equations and solution techniques, the book presents state-of-the-art models currently employed in Earth surface process research, as well as a set of simple but practical research tools. Detailed case studies demonstrate application of the methods to a wide variety of processes including hillslope, fluvial, aeolian, glacial, tectonic, and climatic systems. Exercises at the end of each chapter begin with simple calculations and then progress to more sophisticated problems that require computer programming. All the necessary computer codes are available online at www.cambridge.org/9780521855976. Assuming some knowledge of calculus and basic programming experience, this quantitative textbook is designed for advanced geomorphology courses and as a reference book for professional researchers in Earth and planetary science looking for a quantitative approach to Earth surface processes.

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  21. Modeling surface roughness scattering in metallic nanowires

    SciTech Connect

    Moors, Kristof; Sorée, Bart; Magnus, Wim

    2015-09-28

    Ando's model provides a rigorous quantum-mechanical framework for electron-surface roughness scattering, based on the detailed roughness structure. We apply this method to metallic nanowires and improve the model introducing surface roughness distribution functions on a finite domain with analytical expressions for the average surface roughness matrix elements. This approach is valid for any roughness size and extends beyond the commonly used Prange-Nee approximation. The resistivity scaling is obtained from the self-consistent relaxation time solution of the Boltzmann transport equation and is compared to Prange-Nee's approach and other known methods. The results show that a substantial drop in resistivity can be obtained for certain diameters by achieving a large momentum gap between Fermi level states with positive and negative momentum in the transport direction.

  1. Global modelling of Cryptosporidium in surface water

    NASA Astrophysics Data System (ADS)

    Vermeulen, Lucie; Hofstra, Nynke

    2016-04-01

    Introduction Waterborne pathogens that cause diarrhoea, such as Cryptosporidium, pose a health risk all over the world. In many regions quantitative information on pathogens in surface water is unavailable. Our main objective is to model Cryptosporidium concentrations in surface waters worldwide. We present the GloWPa-Crypto model and use the model in a scenario analysis. A first exploration of global Cryptosporidium emissions to surface waters has been published by Hofstra et al. (2013). Further work has focused on modelling emissions of Cryptosporidium and Rotavirus to surface waters from human sources (Vermeulen et al 2015, Kiulia et al 2015). A global waterborne pathogen model can provide valuable insights by (1) providing quantitative information on pathogen levels in data-sparse regions, (2) identifying pathogen hotspots, (3) enabling future projections under global change scenarios and (4) supporting decision making. Material and Methods GloWPa-Crypto runs on a monthly time step and represents conditions for approximately the year 2010. The spatial resolution is a 0.5 x 0.5 degree latitude x longitude grid for the world. We use livestock maps (http://livestock.geo-wiki.org/) combined with literature estimates to calculate spatially explicit livestock Cryptosporidium emissions. For human Cryptosporidium emissions, we use UN population estimates, the WHO/UNICEF JMP sanitation country data and literature estimates of wastewater treatment. We combine our emissions model with a river routing model and data from the VIC hydrological model (http://vic.readthedocs.org/en/master/) to calculate concentrations in surface water. Cryptosporidium survival during transport depends on UV radiation and water temperature. We explore pathogen emissions and concentrations in 2050 with the new Shared Socio-economic Pathways (SSPs) 1 and 3. These scenarios describe plausible future trends in demographics, economic development and the degree of global integration. Results and

  2. Cleaning level acceptance criteria and a high pressure liquid chromatography procedure for the assay of Meclizine Hydrochloride residue in swabs collected from pharmaceutical manufacturing equipment surfaces.

    PubMed

    Mirza, T; Lunn, M J; Keeley, F J; George, R C; Bodenmiller, J R

    1999-04-01

    A method using pharmacologically based and visual limit of detection criteria to determine the acceptable residue level for Meclizine Hydrochloride (MH) on pharmaceutical manufacturing equipment surfaces after cleaning is described. A formula was used in order to determine the pharmacologically safe cleaning level for MH. This level was termed as specific residual cleaning Level (SRCL) and calculated to be 50 microg 100 cm(-2). The visual limit of detection (VLOD) was determined by spiking different levels of MH on stainless steel plates and having the plates examined by a group of observers. The lowest level that could be visually detected by the majority of the observers, 62.5 microg 100 cm(-2), was considered as the VLOD for MH. The lower of the SRCL and VLOD values, i.e. 50 microg 100 cm(-2), was therefore chosen as the cleaning acceptance criterion. A sensitive reversed-phase HPLC method was developed and validated for the assay of MH in swabs used to test equipment surfaces. Using this method, the mean recoveries of MH from spiked swabs and '180-Grit' stainless steel plates were 87.0 and 89.5% with relative standard deviations (RSD) of +/- 3.3 and +/- 2.4%, respectively. The method was successfully applied to the assay of actual swab samples collected from the equipment surfaces. The stability of MH on stainless steel plates, on cleaning swabs and in the extraction solution was investigated. PMID:10698538

  3. Modeling aspects of the surface reconstruction problem

    NASA Astrophysics Data System (ADS)

    Toth, Charles K.; Melykuti, Gabor

    1994-08-01

    The ultimate goal of digital photogrammetry is to automatically produce digital maps which may in turn form the basis of GIS. Virtually all work in surface reconstruction deals with various kinds of approximations and constraints that are applied. In this paper we extend these concepts in various ways. For one, matching is performed in object space. Thus, matching and densification (modeling) is performed in the same reference system. Another extension concerns the solution of the second sub-problem. Rather than simply densifying (interpolating) the surface, we propose to model it. This combined top-down and bottom-up approach is performed in scale space, whereby the model is refined until compatibility between the data and expectations is reached. The paper focuses on the modeling aspects of the surface reconstruction problem. Obviously, the top-down and bottom-up model descriptions ought to be in a form which allows the generation and verification of hypotheses. Another crucial question is the degree of a priori scene knowledge necessary to constrain the solution space.

  4. Work Functions for Models of Scandate Surfaces

    NASA Technical Reports Server (NTRS)

    Mueller, Wolfgang

    1997-01-01

    The electronic structure, surface dipole properties, and work functions of scandate surfaces have been investigated using the fully relativistic scattered-wave cluster approach. Three different types of model surfaces are considered: (1) a monolayer of Ba-Sc-O on W(100), (2) Ba or BaO adsorbed on Sc2O3 + W, and (3) BaO on SC2O3 + WO3. Changes in the work function due to Ba or BaO adsorption on the different surfaces are calculated by employing the depolarization model of interacting surface dipoles. The largest work function change and the lowest work function of 1.54 eV are obtained for Ba adsorbed on the Sc-O monolayer on W(100). The adsorption of Ba on Sc2O3 + W does not lead to a low work function, but the adsorption of BaO results in a work function of about 1.6-1.9 eV. BaO adsorbed on Sc2O3 + WO3, or scandium tungstates, may also lead to low work functions.

  5. RF models for plasma-surface interactions

    NASA Astrophysics Data System (ADS)

    Jenkins, Thomas; Smithe, David; Lin, Ming-Chieh; Kruger, Scott; Stoltz, Peter

    2013-09-01

    Computational models for DC and oscillatory (RF-driven) sheath potentials, arising at metal or dielectric-coated surfaces in contact with plasma, are developed within the VSim code and applied in parameter regimes characteristic of fusion plasma experiments and plasma processing scenarios. Results from initial studies quantifying the effects of various dielectric wall coating materials and thicknesses on these sheath potentials, as well as on the ensuing flux of plasma particles to the wall, are presented. As well, the developed models are used to model plasma-facing ICRF antenna structures in the ITER device; we present initial assessments of the efficacy of dielectric-coated antenna surfaces in reducing sputtering-induced high-Z impurity contamination of the fusion reaction. Funded by U.S. DoE via a Phase I SBIR grant, award DE-SC0009501.

  6. Time series modelling of surface pressure data

    NASA Astrophysics Data System (ADS)

    Al-Awadhi, Shafeeqah; Jolliffe, Ian

    1998-03-01

    In this paper we examine time series modelling of surface pressure data, as measured by a barograph, at Herne Bay, England, during the years 1981-1989. Autoregressive moving average (ARMA) models have been popular in many fields over the past 20 years, although applications in climatology have been rather less widespread than in some disciplines. Some recent examples are Milionis and Davies (Int. J. Climatol., 14, 569-579) and Seleshi et al. (Int. J. Climatol., 14, 911-923). We fit standard ARMA models to the pressure data separately for each of six 2-month natural seasons. Differences between the best fitting models for different seasons are discussed. Barograph data are recorded continuously, whereas ARMA models are fitted to discretely recorded data. The effect of different spacings between the fitted data on the models chosen is discussed briefly.Often, ARMA models can give a parsimonious and interpretable representation of a time series, but for many series the assumptions underlying such models are not fully satisfied, and more complex models may be considered. A specific feature of surface pressure data in the UK is that its behaviour is different at high and at low pressures: day-to-day changes are typically larger at low pressure levels than at higher levels. This means that standard assumptions used in fitting ARMA models are not valid, and two ways of overcoming this problem are investigated. Transformation of the data to better satisfy the usual assumptions is considered, as is the use of non-linear, specifically threshold autoregressive (TAR), models.

  7. Discrete Modal Decomposition for surface appearance modelling and rendering

    NASA Astrophysics Data System (ADS)

    Pitard, Gilles; Le Goïc, Gaëtan; Favrelière, Hugues; Samper, Serge; Desage, Simon-Frédéric; Pillet, Maurice

    2015-05-01

    Controlling surface appearance has become essential in the supplier/customer relationship. In this context, many industries have implemented new methods to improve the sensory inspection, particularly in terms of variability. A trend is to develop both hardware and methods for moving towards the automation of appearance inspection and analysis. If devices inspired from dimensional control solutions generally allow to identify defects far apart the expected quality of products, it do not allow to quantify finely appearance anomalies, and decide on their acceptance. To address this issue, new methods devoted to appearance modelling and rendering have been implemented, such as the Reflectance Transformation Imaging (RTI) technique. By varying the illumination positions, the RTI technique aims at enriching the classical information conveyed by images. Thus each pixel is described by a set of values rather than one value classically; each value corresponding to a specific illumination position. This set of values could be interpolated or approximated by a continuous model (function), associated to the reflectance of the pixel, generally based on a second order polynomial (namely, Polynomial Texture Mapping Technique). This paper presents a new approach to evaluate this information from RTI acquisitions. A modal projection based on dynamics (Discrete Modal Decomposition) is used to estimate surface reflectance on each measurement point. After presenting the acquisition device, an application on an industrial surface is proposed in order to validate the approach, and compare it to the more classical polynomial transformation. Results show that the proposed projection basis not only provides closer assessment of surface reflectance (modelling) but also yields to a more realistic rendering.

  8. Global modeling of fresh surface water temperature

    NASA Astrophysics Data System (ADS)

    Bierkens, M. F.; Eikelboom, T.; van Vliet, M. T.; Van Beek, L. P.

    2011-12-01

    Temperature determines a range of water physical properties, the solubility of oxygen and other gases and acts as a strong control on fresh water biogeochemistry, influencing chemical reaction rates, phytoplankton and zooplankton composition and the presence or absence of pathogens. Thus, in freshwater ecosystems the thermal regime affects the geographical distribution of aquatic species through their growth and metabolism, tolerance to parasites, diseases and pollution and life history. Compared to statistical approaches, physically-based models of surface water temperature have the advantage that they are robust in light of changes in flow regime, river morphology, radiation balance and upstream hydrology. Such models are therefore better suited for projecting the effects of global change on water temperature. Till now, physically-based models have only been applied to well-defined fresh water bodies of limited size (e.g., lakes or stream segments), where the numerous parameters can be measured or otherwise established, whereas attempts to model water temperature over larger scales has thus far been limited to regression type of models. Here, we present a first attempt to apply a physically-based model of global fresh surface water temperature. The model adds a surface water energy balance to river discharge modelled by the global hydrological model PCR-GLOBWB. In addition to advection of energy from direct precipitation, runoff and lateral exchange along the drainage network, energy is exchanged between the water body and the atmosphere by short and long-wave radiation and sensible and latent heat fluxes. Also included are ice-formation and its effect on heat storage and river hydraulics. We used the coupled surface water and energy balance model to simulate global fresh surface water temperature at daily time steps on a 0.5x0.5 degree grid for the period 1970-2000. Meteorological forcing was obtained from the CRU data set, downscaled to daily values with ECMWF

  9. Renormalization of stochastic lattice models: epitaxial surfaces.

    PubMed

    Haselwandter, Christoph A; Vvedensky, Dimitri D

    2008-06-01

    We present the application of a method [C. A. Haselwandter and D. D. Vvedensky, Phys. Rev. E 76, 041115 (2007)] for deriving stochastic partial differential equations from atomistic processes to the morphological evolution of epitaxial surfaces driven by the deposition of new material. Although formally identical to the one-dimensional (1D) systems considered previously, our methodology presents substantial additional technical issues when applied to two-dimensional (2D) surfaces. Once these are addressed, subsequent coarse-graining is accomplished as before by calculating renormalization-group (RG) trajectories from initial conditions determined by the regularized atomistic models. Our applications are to the Edwards-Wilkinson (EW) model [S. F. Edwards and D. R. Wilkinson, Proc. R. Soc. London, Ser. A 381, 17 (1982)], the Wolf-Villain (WV) model [D. E. Wolf and J. Villain, Europhys. Lett. 13, 389 (1990)], and a model with concurrent random deposition and surface diffusion. With our rules for the EW model no appreciable crossover is obtained for either 1D or 2D substrates. For the 1D WV model, discussed previously, our analysis reproduces the crossover sequence known from kinetic Monte Carlo (KMC) simulations, but for the 2D WV model, we find a transition from smooth to unstable growth under repeated coarse-graining. Concurrent surface diffusion does not change this behavior, but can lead to extended transient regimes with kinetic roughening. This provides an explanation of recent experiments on Ge(001) with the intriguing conclusion that the same relaxation mechanism responsible for ordered structures during the early stages of growth also produces an instability at longer times that leads to epitaxial breakdown. The RG trajectories calculated for concurrent random deposition and surface diffusion reproduce the crossover sequences observed with KMC simulations for all values of the model parameters, and asymptotically always approach the fixed point corresponding

  10. Renormalization of stochastic lattice models: Epitaxial surfaces

    NASA Astrophysics Data System (ADS)

    Haselwandter, Christoph A.; Vvedensky, Dimitri D.

    2008-06-01

    We present the application of a method [C. A. Haselwandter and D. D. Vvedensky, Phys. Rev. E 76, 041115 (2007)] for deriving stochastic partial differential equations from atomistic processes to the morphological evolution of epitaxial surfaces driven by the deposition of new material. Although formally identical to the one-dimensional (1D) systems considered previously, our methodology presents substantial additional technical issues when applied to two-dimensional (2D) surfaces. Once these are addressed, subsequent coarse-graining is accomplished as before by calculating renormalization-group (RG) trajectories from initial conditions determined by the regularized atomistic models. Our applications are to the Edwards-Wilkinson (EW) model [S. F. Edwards and D. R. Wilkinson, Proc. R. Soc. London, Ser. A 381, 17 (1982)], the Wolf-Villain (WV) model [D. E. Wolf and J. Villain, Europhys. Lett. 13, 389 (1990)], and a model with concurrent random deposition and surface diffusion. With our rules for the EW model no appreciable crossover is obtained for either 1D or 2D substrates. For the 1D WV model, discussed previously, our analysis reproduces the crossover sequence known from kinetic Monte Carlo (KMC) simulations, but for the 2D WV model, we find a transition from smooth to unstable growth under repeated coarse-graining. Concurrent surface diffusion does not change this behavior, but can lead to extended transient regimes with kinetic roughening. This provides an explanation of recent experiments on Ge(001) with the intriguing conclusion that the same relaxation mechanism responsible for ordered structures during the early stages of growth also produces an instability at longer times that leads to epitaxial breakdown. The RG trajectories calculated for concurrent random deposition and surface diffusion reproduce the crossover sequences observed with KMC simulations for all values of the model parameters, and asymptotically always approach the fixed point corresponding

  11. Modelling Ocean Surface Waves in Polar Regions

    NASA Astrophysics Data System (ADS)

    Hosekova, Lucia; Aksenov, Yevgeny; Coward, Andrew; Bertino, Laurent; Williams, Timothy; Nurser, George A. J.

    2015-04-01

    In the Polar Oceans, the surface ocean waves break up sea ice cover and create the Marginal Ice Zone (MIZ), an area between the sea-ice free ocean and pack ice characterized by highly fragmented ice. This band of sea ice cover is undergoing dramatic changes due to sea ice retreat, with up to a 39% widening in the Arctic Ocean reported over the last three decades and projections predicting a continuing increase. The surface waves, sea ice and ocean interact in the MIZ through multiple complex feedbacks and processes which are not accounted for in any of the present-day climate models. To address this issue, we present a model development which implements surface ocean wave effects in the global Ocean General Circulation Model NEMO, coupled to the CICE sea ice model. Our implementation takes into account a number of physical processes specific to the MIZ dynamics. Incoming surface waves are attenuated due to reflection and energy dissipation induced by the presence of ice cover, which is in turn fragmented in response to external stresses. This process generates a distribution of floe sizes and impacts the dynamics of sea ice by the means of combined rheology that takes into account floe collisions and allows for a more realistic representation of the MIZ. We present results from the NEMO OGCM at 1 degree resolution with a wave-ice interaction module described above. The module introduces two new diagnostics previously unavailable in GCM's: surface wave spectra in sea ice covered areas, and floe size distribution due to wave-induced fragmentation. We discuss the impact of these processes on the ocean and sea ice state, including ocean circulation, mixing, stratification and the role of the MIZ in the ocean variability. The model predictions for the floe sizes in the summer Arctic Ocean range from 60 m in the inner MIZ to a few tens of meters near the open ocean, which agrees with estimates from the satellites. The extent of the MIZ throughout the year is also in

  12. Can the KTP laser change the cementum surface of healthy and diseased teeth providing an acceptable root surface for fibroblast attachment?

    NASA Astrophysics Data System (ADS)

    Mailhot, Jason M.; Garnick, Jerry J.

    1996-04-01

    The purpose of our research is to determine the effects of KTP laser on root cementum and fibroblast attachment. Initial work has been completed in testing the effect of different energy levels on root surfaces. From these studies optimal energy levels were determined. In subsequent studies the working distance and exposure time required to obtain significant fibroblast attachment to healthy cementum surfaces were investigated. Results showed that lased cemental surfaces exhibited changes in surface topography which ranged from a melted surface to an apparent slight fusion of the surface of the covering smear layer. When the optimal energy level was used, fibroblasts demonstrate attachment on the specimens, resulting in the presence of a monolayer of cells on the control surfaces as well as on the surfaces lased with this energy level. The present study investigates the treatment of pathological root surfaces and calculus with a KTP laser utilizing these optimal parameters determine previously. Thirty single rooted teeth with advanced periodontal disease and ten healthy teeth were obtained, crowns were sectioned and roots split longitudinally. Forty test specimens were assigned into 1 of 4 groups; pathologic root--not lased, pathologic root--lased, root planed root and health root planed root. Human gingival fibroblasts were seeded on specimens and cultured for 24 hours. Specimens were processed for SEM. The findings suggest that with the KTP laser using a predetermined energy level applied to pathological root surfaces, the lased surfaces provided an unacceptable surface for fibroblast attachment. However, the procedural control using healthy root planed surfaces did demonstrate fibroblast attachment.

  13. Critical Surface of the Hexagonal Polygon Model

    NASA Astrophysics Data System (ADS)

    Grimmett, Geoffrey R.; Li, Zhongyang

    2016-05-01

    The hexagonal polygon model arises in a natural way via a transformation of the 1-2 model on the hexagonal lattice, and it is related to the high temperature expansion of the Ising model. There are three types of edge, and three corresponding parameters α ,β ,γ >0. By studying the long-range order of a certain two-edge correlation function, it is shown that the parameter space (0,∞)^3 may be divided into subcritical and supercritical regions, separated by critical surfaces satisfying an explicitly known formula. This result complements earlier work on the Ising model and the 1-2 model. The proof uses the Pfaffian representation of Fisher, Kasteleyn, and Temperley for the counts of dimers on planar graphs.

  14. Specific surface area model for foam permeability.

    PubMed

    Pitois, O; Lorenceau, E; Louvet, N; Rouyer, F

    2009-01-01

    Liquid foams were recognized early to be porous materials, as liquid flowed between the gas bubbles. Drainage theories have been established, and foam permeability has been modeled from the microscopic description of the equivalent pores geometry, emphasizing similarities with their solid counterparts. But to what extent can the theoretical work devoted to the permeability of solid porous materials be useful to liquid foams? In this article, the applicability of the Carman-Kozeny model on foam is investigated. We performed measurements of the permeability of foams with nonmobile surfactants, and we show that, in introducing an equivalent specific surface area for the foam, the model accurately describes the experimental data over two orders of magnitude for the foam liquid fraction, without any additional parameters. Finally, it is shown that this model includes the previous permeability models derived for foams in the dry foams limit. PMID:19032030

  15. An Empirical Analysis of Citizens' Acceptance Decisions of Electronic-Government Services: A Modification of the Unified Theory of Acceptance and Use of Technology (UTAUT) Model to Include Trust as a Basis for Investigation

    ERIC Educational Resources Information Center

    Awuah, Lawrence J.

    2012-01-01

    Understanding citizens' adoption of electronic-government (e-government) is an important topic, as the use of e-government has become an integral part of governance. Success of such initiatives depends largely on the efficient use of e-government services. The unified theory of acceptance and use of technology (UTAUT) model has provided a…

  16. Acceptability of the Nestorone®/Ethinyl Estradiol Contraceptive Vaginal Ring: Development of a Model; Implications for Introduction

    PubMed Central

    Merkatz, Ruth B.; Plagianos, Marlena; Hoskin, Elena; Cooney, Michael; Hewett, Paul C; Mensch, Barbara S.

    2015-01-01

    Objectives Develop and test a theoretical acceptability model for the Nestorone®/ethinyl estradiol (NES/EE) contraceptive vaginal ring (CVR); explore whether domains of use within the model predict satisfaction, method adherence and CVR continuation. Study Design Four domains of use were considered relative to outcome markers of acceptability, i.e. method satisfaction, adherence, and continuation. A questionnaire to evaluate subjects’ experiences relative to the domains, their satisfaction (Likert scale), and adherence to instructions for use was developed and administered to 1036 women enrolled in a 13-cycle Phase 3 trial. Method continuation was documented from the trial database. Stepwise logistic regression (LR) analysis was conducted and odds ratios calculated to assess associations of satisfaction with questions from the 4 domains. Fisher’s exact test was used to determine the association of satisfaction with outcome measures. Results A final acceptability model was developed based on the following determinants of CVR satisfaction: ease of use, side effects, expulsions/feeling the CVR, and sexual activity including physical effects during intercourse. Satisfaction was high (89%) and related to higher method adherence [OR 2.6(1.3,5.2)] and continuation [OR5.5(3.5, 8.4)]. According to the LR analysis, attributes of CVR use representing items from the 4 domains — finding it easy to remove, not complaining of side effects, not feeling the CVR while wearing it, and experiencing no change or an increase in sexual pleasure and/or frequency — were associated with higher odds of satisfaction. Conclusion Hypothesized domains of CVR use were related to satisfaction, which was associated with adherence and continuation. Results provide a scientific basis for introduction and future research. PMID:24993487

  17. Soil erosion and surface runoff model SMODERP

    NASA Astrophysics Data System (ADS)

    Kavka, P.; Vrana, K.; Dostal, T.

    2012-04-01

    This contribution presents a software tool for calculation and prediction of soil erosion and surface runoff from agricultural lands. There is no universal tool to properly describe the origin and the processes related to the surface runoff and sediment transport in different scales. For a design of any technical erosion control measures, that are used to interrupt the surface runoff, it is necessary to identify basic outflow characteristics (discharge, flow volume). Numerical model SMODERP was developed for determination of these characteristics. The model is being developed at the Department of Irrigation, Drainage and Landscape Engineering , Civil Engineering Faculty, CTU in Prague. SMODERP is physically based one-dimensional episodic model that includes the processes of infiltration, surface retention, surface roughness and vegetation impact on runoff. The model has been substantially upgraded and tested in last few years. Especially runoff parameters, time and spatial discretisation were recalibrated and validated. Runoff parameters were recalibrated on the set of forty measurements performed on the laboratory rainfall simulator on five soil types. The parameters were designed for five soil types categories according to content of particles with size up to 0.01 mm (Novak soil classification). The precipitation episodes can be chosen from the attached catalogue or can be designed by a user. We also present how the input data can be obtained based on available resources (soil maps and data, land use, terrain models, field research, etc.) and how can be used in the assessment erosion risk and in designing of erosion control measures. The model is meant to be used not only for the research purposes, but mainly for the engineering practice. We present the new version of the model that includes a new user friendly graphical interface. The research has been supported by the research grants SGS SGS11/148/OHK1/3T/11 "Experimental Research on Rainfall-runoff and Erosion

  18. Stochastic models for surface diffusion of molecules

    SciTech Connect

    Shea, Patrick Kreuzer, Hans Jürgen

    2014-07-28

    We derive a stochastic model for the surface diffusion of molecules, starting from the classical equations of motion for an N-atom molecule on a surface. The equation of motion becomes a generalized Langevin equation for the center of mass of the molecule, with a non-Markovian friction kernel. In the Markov approximation, a standard Langevin equation is recovered, and the effect of the molecular vibrations on the diffusion is seen to lead to an increase in the friction for center of mass motion. This effective friction has a simple form that depends on the curvature of the lowest energy diffusion path in the 3N-dimensional coordinate space. We also find that so long as the intramolecular forces are sufficiently strong, memory effects are usually not significant and the Markov approximation can be employed, resulting in a simple one-dimensional model that can account for the effect of the dynamics of the molecular vibrations on the diffusive motion.

  19. Simulation of model swimmers near ciliated surfaces

    NASA Astrophysics Data System (ADS)

    Shum, Henry; Tripathi, Anurag; Yeomans, Julia; Balazs, Anna

    2013-03-01

    Biofouling by micro-organisms is problematic on scales from microfluidic devices to the largest ships in the ocean. One solution found in nature for clearing undesired material from surfaces is to employ active cilia, for example, in the respiratory tract. It is feasible to fabricate surfaces covered with artificial cilia actuated by an externally imposed field. Using numerical simulation, we investigate the interactions between these artificial cilia and self-propelled model swimmers. One of the key aims is to explore the possibility of steering swimmers to influence their trajectories through the flow field produced by the cilia. In our simulations, the fluid dynamics is solved using the lattice Boltzmann method while the cilia and model swimmers are governed by elastic internal mechanics. We implement an immersed boundary approach to couple the solid and fluid dynamics.

  20. Modeling superhydrophobic surfaces comprised of random roughness

    NASA Astrophysics Data System (ADS)

    Samaha, M. A.; Vahedi Tafreshi, H.; Gad-El-Hak, M.

    2011-11-01

    We model the performance of superhydrophobic surfaces comprised of randomly distributed roughness that resembles natural surfaces, or those produced via random deposition of hydrophobic particles. Such a fabrication method is far less expensive than ordered-microstructured fabrication. The present numerical simulations are aimed at improving our understanding of the drag reduction effect and the stability of the air-water interface in terms of the microstructure parameters. For comparison and validation, we have also simulated the flow over superhydrophobic surfaces made up of aligned or staggered microposts for channel flows as well as streamwise or spanwise ridge configurations for pipe flows. The present results are compared with other theoretical and experimental studies. The numerical simulations indicate that the random distribution of surface roughness has a favorable effect on drag reduction, as long as the gas fraction is kept the same. The stability of the meniscus, however, is strongly influenced by the average spacing between the roughness peaks, which needs to be carefully examined before a surface can be recommended for fabrication. Financial support from DARPA, contract number W91CRB-10-1-0003, is acknowledged.

  1. Modeling of ESD events from polymeric surfaces

    SciTech Connect

    Pfeifer, Kent Bryant

    2014-03-01

    Transient electrostatic discharge (ESD) events are studied to assemble a predictive model of discharge from polymer surfaces. An analog circuit simulation is produced and its response is compared to various literature sources to explore its capabilities and limitations. Results suggest that polymer ESD events can be predicted to within an order of magnitude. These results compare well to empirical findings from other sources having similar reproducibility.

  2. Diurnal ocean surface layer model validation

    NASA Technical Reports Server (NTRS)

    Hawkins, Jeffrey D.; May, Douglas A.; Abell, Fred, Jr.

    1990-01-01

    The diurnal ocean surface layer (DOSL) model at the Fleet Numerical Oceanography Center forecasts the 24-hour change in a global sea surface temperatures (SST). Validating the DOSL model is a difficult task due to the huge areas involved and the lack of in situ measurements. Therefore, this report details the use of satellite infrared multichannel SST imagery to provide day and night SSTs that can be directly compared to DOSL products. This water-vapor-corrected imagery has the advantages of high thermal sensitivity (0.12 C), large synoptic coverage (nearly 3000 km across), and high spatial resolution that enables diurnal heating events to be readily located and mapped. Several case studies in the subtropical North Atlantic readily show that DOSL results during extreme heating periods agree very well with satellite-imagery-derived values in terms of the pattern of diurnal warming. The low wind and cloud-free conditions necessary for these events to occur lend themselves well to observation via infrared imagery. Thus, the normally cloud-limited aspects of satellite imagery do not come into play for these particular environmental conditions. The fact that the DOSL model does well in extreme events is beneficial from the standpoint that these cases can be associated with the destruction of the surface acoustic duct. This so-called afternoon effect happens as the afternoon warming of the mixed layer disrupts the sound channel and the propagation of acoustic energy.

  3. Improvements in Modeling Thruster Plume Erosion Damage to Spacecraft Surfaces

    NASA Technical Reports Server (NTRS)

    Soares, Carlos; Olsen, Randy; Steagall, Courtney; Huang, Alvin; Mikatarian, Ron; Myers, Brandon; Koontz, Steven; Worthy, Erica

    2015-01-01

    Spacecraft bipropellant thrusters impact spacecraft surfaces with high speed droplets of unburned and partially burned propellant. These impacts can produce erosion damage to optically sensitive hardware and systems (e.g., windows, camera lenses, solar cells and protective coatings). On the International Space Station (ISS), operational constraints are levied on the position and orientation of the solar arrays to mitigate erosion effects during thruster operations. In 2007, the ISS Program requested evaluation of erosion constraint relief to alleviate operational impacts due to an impaired Solar Alpha Rotary Joint (SARJ). Boeing Space Environments initiated an activity to identify and remove sources of conservatism in the plume induced erosion model to support an expanded range of acceptable solar array positions ? The original plume erosion model over-predicted plume erosion and was adjusted to better correlate with flight experiment results. This paper discusses findings from flight experiments and the methodology employed in modifying the original plume erosion model for better correlation of predictions with flight experiment data. The updated model has been successful employed in reducing conservatism and allowing for enhanced flexibility in ISS solar array operations.

  4. Modeling of surface flashover on spacecraft

    NASA Technical Reports Server (NTRS)

    Kushner, Mark J.

    1991-01-01

    A model for predicting the onset of surface flashover discharges (SFDs) in the context of high voltage pulse power modulators was developed and used to investigate mechanisms leading to the onset of SFDs. We demonstrated that it is possible to analyze surface discharges in a manner similar to gas phase discharges using transport coefficients such as the first Townsend coefficient. Our parameterization of various methods to prevent, or at least delay, the onset of SFDs was not particularly successful in that many of the strategies that we investigated do not yield significantly improved performance. The only safe strategy to reduce the occurrence of SFDs is to prevent the dielectric from being charged in the first place. This leads one to consider passive or active schemes which employ the low pressure of attaching gases which flood the surface prior or coincident to pulsing the high voltage apparatus. Our calculations indicate that only small amounts gas (10s Torr effective pressure at substrate) would be sufficient for many of the anticipated applications. If the surface is flooded only when high voltage is applied across the dielectric, the gas consumption would be nominal.

  5. Surface Segregation in Multicomponent Systems: Modeling of Surface Alloys and Alloy Surfaces

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John; Noebe, Ronald D.; Good, Brian; Honecy, Frank S.; Abel, Phillip

    1999-01-01

    The study of surface segregation, although of great technological importance, has been largely restricted to experimental work due to limitations associated with theoretical methods. However, recent improvements in both first-particle and semi-empirical methods are opening, the doors to an array of new possibilities for surface scientists. We apply one of these techniques, the Bozzolo, Ferrante and Smith (BFS) method for alloys, which is particularly suitable for complex systems, to several aspects of the computational modeling of surfaces and segregation, including alloy surface segregation, structure and composition of alloy surfaces, and the formation of surface alloys. We conclude with the study of complex NiAl-based binary, ternary and quaternary thin films (with Ti, Cr and Cu additions to NiAl). Differences and similarities between bulk and surface compositions are discussed, illustrated by the results of Monte Carlo simulations. For some binary and ternary cases, the theoretical predictions are compared to experimental results, highlighting the accuracy and value of this developing theoretical tool.

  6. The surface of Io - A new model

    NASA Technical Reports Server (NTRS)

    Hapke, Bruce

    1989-01-01

    The role of elemental sulfur on Io is evaluated in light of duplications of its spectral properties by combinations of basalt and condensates of SO2 and its S2O and polysulfur oxide (PSO) dissociation products. Elemental sulfur is not seen to be present in spectrally significant amounts. It is instead suggested that Io's exposed surface consists of mafic silicates which have been partially covered by thin deposits of SO2, PSO, and S2O. A model in which most of the spectrally active frost occurs in the form of thin and ephemeral partial coatings on the topmost regolith particles is seen as most consistent with observations. Attention is drawn to similarities with the surface of Europa.

  7. Atmospheric radiation model for water surfaces

    NASA Technical Reports Server (NTRS)

    Turner, R. E.; Gaskill, D. W.; Lierzer, J. R.

    1982-01-01

    An atmospheric correction model was extended to account for various atmospheric radiation components in remotely sensed data. Components such as the atmospheric path radiance which results from singly scattered sky radiation specularly reflected by the water surface are considered. A component which is referred to as the virtual Sun path radiance, i.e. the singly scattered path radiance which results from the solar radiation which is specularly reflected by the water surface is also considered. These atmospheric radiation components are coded into a computer program for the analysis of multispectral remote sensor data over the Great Lakes of the United States. The user must know certain parameters, such as the visibility or spectral optical thickness of the atmosphere and the geometry of the sensor with respect to the Sun and the target elements under investigation.

  8. Improving Technology Acceptance Modeling for Disadvantaged Communities Using a Systems Engineering Approach

    ERIC Educational Resources Information Center

    Fletcher, Jordan L.

    2013-01-01

    Developing nations are poised to spend billions on information and communication technology (ICT) innovation in 2020. A study of the historical adoption of ICT in developing nations has indicated that their adoption patterns do not follow typical technology innovation adoption models. This study addressed the weaknesses found in existing…

  9. Acceptance of the bodypainting as supportive method to learn the surface locomotor apparatus anatomy of the horse.

    PubMed

    Senos, R; Ribeiro, M S; Martins, K de Souza; Pereira, L V; Mattos, M F; Kfoury Júnior, J R; Rodrigues, M R

    2015-01-01

    Although bodypainting has been reported as a great resource for teaching surface anatomy of humans, its use in veterinary anatomy has not been scientifically reported. In the present study, bodypainting was performed on 4 horses for anatomy teaching purposes of the equine locomotor apparatus. We aimed to use the bodypainting method as an additional tool to classic teaching and to test the relevance of our purpose. Twenty one Brazilian veterinary students were given a 90-min session, which included a presentation of painted horses, with opportunities for the students to ask questions and to palpate anatomic locations on the horses. Based on a questionnaire, there was unanimous student satisfaction with this technique. Furthermore, student scores on practical tests to evaluate the attention retain given immediately before and 1 h after the session were 33.9 ± 19.8% and 69.0 ± 18.4%, respectively (p < 0.001). We concluded that bodypainting has great potential for support the classic lectures of the equine locomotor apparatus. PMID:26620513

  10. Parental modelling and prompting effects on acceptance of a novel fruit in 2-4-year-old children are dependent on children's food responsiveness.

    PubMed

    Blissett, Jackie; Bennett, Carmel; Fogel, Anna; Harris, Gillian; Higgs, Suzanne

    2016-02-14

    Few children consume the recommended portions of fruit or vegetables. This study examined the effects of parental physical prompting and parental modelling in children's acceptance of a novel fruit (NF) and examined the role of children's food-approach and food-avoidance traits on NF engagement and consumption. A total of 120 caregiver-child dyads (fifty-four girls, sixty-six boys) participated in this study. Dyads were allocated to one of the following three conditions: physical prompting but no modelling, physical prompting and modelling or a modelling only control condition. Dyads ate a standardised meal containing a portion of a fruit new to the child. Parents completed measures of children's food approach and avoidance. Willingness to try the NF was observed, and the amount of the NF consumed was measured. Physical prompting but no modelling resulted in greater physical refusal of the NF. There were main effects of enjoyment of food and food fussiness on acceptance. Food responsiveness interacted with condition such that children who were more food responsive had greater NF acceptance in the prompting and modelling conditions in comparison with the modelling only condition. In contrast, children with low food responsiveness had greater acceptance in the modelling control condition than in the prompting but no modelling condition. Physical prompting in the absence of modelling is likely to be detrimental to NF acceptance. Parental use of physical prompting strategies, in combination with modelling of NF intake, may facilitate acceptance of NF, but only in food-responsive children. Modelling consumption best promotes acceptance in children with low food responsiveness. PMID:26603382

  11. A Stochastic Cratering Model for Asteroid Surfaces

    NASA Technical Reports Server (NTRS)

    Richardson, J. E.; Melosh, H. J.; Greenberg, R. J.

    2005-01-01

    The observed cratering records on asteroid surfaces (four so far: Gaspra, Ida, Mathilde, and Eros [1-4]) provide us with important clues to their past bombardment histories. Previous efforts toward interpreting these records have led to two basic modeling styles for reproducing the statistics of the observed crater populations. The first, and most direct, method is to use Monte Carlo techniques [5] to stochastically populate a matrix-model test surface with craters as a function of time [6,7]. The second method is to use a more general, parameterized approach to duplicate the statistics of the observed crater population [8,9]. In both methods, several factors must be included beyond the simple superposing of circular features: (1) crater erosion by subsequent impacts, (2) infilling of craters by impact ejecta, and (3) crater degradation and era- sure due to the seismic effects of subsequent impacts. Here we present an updated Monte Carlo (stochastic) modeling approach, designed specifically with small- to medium-sized asteroids in mind.

  12. Modeling of surface myoelectric signals--Part I: Model implementation.

    PubMed

    Merletti, R; Lo Conte, L; Avignone, E; Guglielminotti, P

    1999-07-01

    The relationships between the parameters of active motor units (MU's) and the features of surface electromyography (EMG) signals have been investigated using a mathematical model that represents the surface EMG as a summation of contributions from the single muscle fibers. Each MU has parallel fibers uniformly scattered within a cylindrical volume of specified radius embedded in an anisotropic medium. Two action potentials, each modeled as a current tripole, are generated at the neuromuscular junction, propagate in opposite directions and extinguish at the fiber-tendon endings. The neuromuscular junctions and fiber-tendon endings are uniformly scattered within regions of specified width. Muscle fiber conduction velocity and average fiber length to the right and left of the center of the innervation zone are also specified. The signal produced by MU's with different geometries and conduction velocities are superimposed. Monopolar, single differential and double differential signals are computed from electrodes placed in equally spaced locations on the surface of the muscle and are displayed as functions of any of the model's parameters. Spectral and amplitude variables and conduction velocity are estimated from the surface signals and displayed as functions of any of the model's parameters. The influence of fiber-end effects, electrode misalignment, tissue anisotropy, MU's location and geometry are discussed. Part II of this paper will focus on the simulation and interpretation of experimental signals. PMID:10396899

  13. Regulatory acceptance and use of 3R models for pharmaceuticals and chemicals: expert opinions on the state of affairs and the way forward.

    PubMed

    Schiffelers, Marie-Jeanne W A; Blaauboer, Bas J; Bakker, Wieger E; Beken, Sonja; Hendriksen, Coenraad F M; Koëter, Herman B W M; Krul, Cyrille

    2014-06-01

    Pharmaceuticals and chemicals are subjected to regulatory safety testing accounting for approximately 25% of laboratory animal use in Europe. This testing meets various objections and has led to the development of a range of 3R models to Replace, Reduce or Refine the animal models. However, these models must overcome many barriers before being accepted for regulatory risk management purposes. This paper describes the barriers and drivers and options to optimize this acceptance process as identified by two expert panels, one on pharmaceuticals and one on chemicals. To untangle the complex acceptance process, the multilevel perspective on technology transitions is applied. This perspective defines influences at the micro-, meso- and macro level which need alignment to induce regulatory acceptance of a 3R model. This paper displays that there are many similar mechanisms within both sectors that prevent 3R models from becoming accepted for regulatory risk assessment and management. Shared barriers include the uncertainty about the value of the new 3R models (micro level), the lack of harmonization of regulatory requirements and acceptance criteria (meso level) and the high levels of risk aversion (macro level). In optimizing the process commitment, communication, cooperation and coordination are identified as critical drivers. PMID:24534000

  14. Precise orbit computation and sea surface modeling

    NASA Technical Reports Server (NTRS)

    Wakker, Karel F.; Ambrosius, B. A. C.; Rummel, R.; Vermaat, E.; Deruijter, W. P. M.; Vandermade, J. W.; Zimmerman, J. T. F.

    1991-01-01

    The research project described below is part of a long-term program at Delft University of Technology aiming at the application of European Remote Sensing satellite (ERS-1) and TOPEX/POSEIDON altimeter measurements for geophysical purposes. This program started in 1980 with the processing of Seasat laser range and altimeter height measurements and concentrates today on the analysis of Geosat altimeter data. The objectives of the TOPEX/POSEIDON research project are the tracking of the satellite by the Dutch mobile laser tracking system MTLRS-2, the computation of precise TOPEX/POSEIDON orbits, the analysis of the spatial and temporal distribution of the orbit errors, the improvement of ERS-1 orbits through the information obtained from the altimeter crossover difference residuals for crossing ERS-1 and TOPEX/POSEIDON tracks, the combination of ERS-1 and TOPEX/POSEIDON altimeter data into a single high-precision data set, and the application of this data set to model the sea surface. The latter application will focus on the determination of detailed regional mean sea surfaces, sea surface variability, ocean topography, and ocean currents in the North Atlantic, the North Sea, the seas around Indonesia, the West Pacific, and the oceans around South Africa.

  15. Exercise motives and positive body image in physically active college women and men: Exploring an expanded acceptance model of intuitive eating.

    PubMed

    Tylka, Tracy L; Homan, Kristin J

    2015-09-01

    The acceptance model of intuitive eating posits that body acceptance by others facilitates body appreciation and internal body orientation, which contribute to intuitive eating. Two domains of exercise motives (functional and appearance) may also be linked to these variables, and thus were integrated into the model. The model fit the data well for 406 physically active U.S. college students, although some pathways were stronger for women. Body acceptance by others directly contributed to higher functional exercise motives and indirectly contributed to lower appearance exercise motives through higher internal body orientation. Functional exercise motives positively, and appearance exercise motives inversely, contributed to body appreciation. Whereas body appreciation positively, and appearance exercise motives inversely, contributed to intuitive eating for women, only the latter association was evident for men. To benefit positive body image and intuitive eating, efforts should encourage body acceptance by others and emphasize functional and de-emphasize appearance exercise motives. PMID:26281958

  16. Mycorrhizal fungi and global land surface models?

    NASA Astrophysics Data System (ADS)

    Brzostek, E. R.; Fisher, J. B.; Shi, M.; Phillips, R.

    2013-12-01

    In the current generation of Land Surface Models (LSMs), the representation of coupled carbon (C) and nutrient cycles does not account for allocation of C by plants to mycorrhizal fungi in exchange for limiting nutrients. Given that the amount of C transferred to mycorrhizae can exceed 20% of net primary production (NPP), mycorrhizae can supply over half of the nitrogen (N) needed to support NPP, and that large majority of plants form associations with mycorrhizae; integrating these mechanisms into LSMs may significantly alter our understanding of the role of the terrestrial biosphere in mitigating climate change. Here, we present results from the integration of a mycorrhizal framework into a cutting-edge global plant nitrogen model -- Fixation & Uptake of Nitrogen (FUN; Fisher et al., 2010) -- that can be coupled into existing LSMs. In this mycorrhizal framework, the C cost of N acquisition varies as a function of mycorrhizal type with: (1) plants that support arbuscular mycorrhizae (AM) benefiting when N is plentiful and (2) plants that support ectomycorrhizae (ECM) benefiting when N is limiting. At the plot scale (15 x 15m), the My-FUN model improved predictions of retranslocation, N uptake, and the amount of C transferred into the soil relative to the base model across 45 plots that vary in mycorrhizal type in Indiana, USA. At the ecosystem scale, when we coupled this new framework into the Community Land Model (CLM-CN), the model estimated lower C uptake than the base model and more accurately predicted C uptake at the Morgan Monroe State Forest AmeriFlux site. These results suggest that the inclusion of a mycorrhizal framework into LSMs will enhance our ability to predict feedbacks between global change and the terrestrial biosphere.

  17. Bioadhesion to model thermally responsive surfaces

    NASA Astrophysics Data System (ADS)

    Andrzejewski, Brett Paul

    This dissertation focuses on the characterization of two surfaces: mixed self-assembled monolayers (SAMs) of hexa(ethylene glycol) and alkyl thiolates (mixed SAM) and poly(N-isopropylacrylamide) (PNIPAAm). The synthesis of hexa(ethylene gylcol) alkyl thiol (C11EG 6OH) is presented along with the mass spectrometry and nuclear magnetic resonance results. The gold substrates were imaged prior to SAM formation with atomic force micrscopy (AFM). Average surface roughness of the gold substrate was 0.44 nm, 0.67 nm, 1.65 nm for 15, 25 and 60 nm gold thickness, respectively. The height of the mixed SAM was measured by ellipsometry and varied from 13 to 28°A depending on surface mole fraction of C11EG6OH. The surface mole fraction of C11EG6OH for the mixed SAM was determined by X-ray photoelectron spectroscopy (XPS) with optimal thermal responsive behavior in the range of 0.4 to 0.6. The mixed SAM surface was confirmed to be thermally responsive by contact angle goniometry, 35° at 28°C and ˜55° at 40°C. In addition, the mixed SAM surfaces were confirmed to be thermally responsive for various aqueous mediums by tensiometry. Factors such as oxygen, age, and surface mole fraction and how they affect the thermal responsive of the mixed SAM are discussed. Lastly, rat fibroblasts were grown on the mixed SAM and imaged by phase contrast microscopy to show inhibition of attachment at temperatures below the molecular transition. Qualitative and quantitative measurements of the fibroblast adhesion data are provided that support the hypothesis of the mixed SAM exhibits a dominantly non-fouling molecular conformation at 25°C whereas it exhibits a dominantly fouling molecular conformation at 40°C. The adhesion of six model proteins: bovine serum albumin, collagen, pyruvate kinase, cholera toxin subunit B, ribonuclease, and lysozyme to the model thermally responsive mixed SAM were examined using AFM. All six proteins possessed adhesion to the pure component alkyl thiol, in

  18. 3D-manufactured patient-specific models of congenital heart defects for communication in clinical practice: feasibility and acceptability

    PubMed Central

    Biglino, Giovanni; Capelli, Claudio; Wray, Jo; Schievano, Silvia; Leaver, Lindsay-Kay; Khambadkone, Sachin; Giardini, Alessandro; Derrick, Graham; Jones, Alexander; Taylor, Andrew M

    2015-01-01

    Objectives To assess the communication potential of three-dimensional (3D) patient-specific models of congenital heart defects and their acceptability in clinical practice for cardiology consultations. Design This was a questionnaire-based study in which participants were randomised into two groups: the ‘model group’ received a 3D model of the cardiac lesion(s) being discussed during their appointment, while the ‘control group’ had a routine visit. Setting Outpatient clinic, cardiology follow-up visits. Participants 103 parents of children with congenital heart disease were recruited (parental age: 43±8 years; patient age: 12±6 years). In order to have a 3D model made, patients needed to have a recent cardiac MRI examination; this was the crucial inclusion criterion. Interventions Questionnaires were administered to the participants before and after the visits and an additional questionnaire was administered to the attending cardiologist. Main outcome measures Rating (1–10) for the liking of the 3D model, its usefulness and the clarity of the explanation received were recorded, as well as rating (1–10) of the parental understanding and their engagement according to the cardiologist. Furthermore, parental knowledge was assessed by asking them to mark diagrams, tick keywords and provide free text answers. The duration of consultations was recorded and parent feedback collected. Results Parents and cardiologists both found the models to be very useful and helpful in engaging the parents in discussing congenital heart defects. Parental knowledge was not associated with their level of education (p=0.2) and did not improve following their visit. Consultations involving 3D models lasted on average 5 min longer (p=0.02). Conclusions Patient-specific models can enhance engagement with parents and improve communication between cardiologists and parents, potentially impacting on parent and patient psychological adjustment following treatment. However, in

  19. A new MRI land surface model HAL

    NASA Astrophysics Data System (ADS)

    Hosaka, M.

    2011-12-01

    A land surface model HAL is newly developed for MRI-ESM1. It is used for the CMIP simulations. HAL consists of three submodels: SiByl (vegetation), SNOWA (snow) and SOILA (soil) in the current version. It also contains a land coupler LCUP which connects some submodels and an atmospheric model. The vegetation submodel SiByl has surface vegetation processes similar to JMA/SiB (Sato et al. 1987, Hirai et al. 2007). SiByl has 2 vegetation layers (canopy and grass) and calculates heat, moisture, and momentum fluxes between the land surface and the atmosphere. The snow submodel SNOWA can have any number of snow layers and the maximum value is set to 8 for the CMIP5 experiments. Temperature, SWE, density, grain size and the aerosol deposition contents of each layer are predicted. The snow properties including the grain size are predicted due to snow metamorphism processes (Niwano et al., 2011), and the snow albedo is diagnosed from the aerosol mixing ratio, the snow properties and the temperature (Aoki et al., 2011). The soil submodel SOILA can also have any number of soil layers, and is composed of 14 soil layers in the CMIP5 experiments. The temperature of each layer is predicted by solving heat conduction equations. The soil moisture is predicted by solving the Darcy equation, in which hydraulic conductivity depends on the soil moisture. The land coupler LCUP is designed to enable the complicated constructions of the submidels. HAL can include some competing submodels (precise and detailed ones, and simpler ones), and they can run at the same simulations. LCUP enables a 2-step model validation, in which we compare the results of the detailed submodels with the in-situ observation directly at the 1st step, and follows the comparison between them and those of the simpler ones at the 2nd step. When the performances of the detailed ones are good, we can improve the simpler ones by using the detailed ones as reference models.

  20. Merging Digital Surface Models Implementing Bayesian Approaches

    NASA Astrophysics Data System (ADS)

    Sadeq, H.; Drummond, J.; Li, Z.

    2016-06-01

    In this research different DSMs from different sources have been merged. The merging is based on a probabilistic model using a Bayesian Approach. The implemented data have been sourced from very high resolution satellite imagery sensors (e.g. WorldView-1 and Pleiades). It is deemed preferable to use a Bayesian Approach when the data obtained from the sensors are limited and it is difficult to obtain many measurements or it would be very costly, thus the problem of the lack of data can be solved by introducing a priori estimations of data. To infer the prior data, it is assumed that the roofs of the buildings are specified as smooth, and for that purpose local entropy has been implemented. In addition to the a priori estimations, GNSS RTK measurements have been collected in the field which are used as check points to assess the quality of the DSMs and to validate the merging result. The model has been applied in the West-End of Glasgow containing different kinds of buildings, such as flat roofed and hipped roofed buildings. Both quantitative and qualitative methods have been employed to validate the merged DSM. The validation results have shown that the model was successfully able to improve the quality of the DSMs and improving some characteristics such as the roof surfaces, which consequently led to better representations. In addition to that, the developed model has been compared with the well established Maximum Likelihood model and showed similar quantitative statistical results and better qualitative results. Although the proposed model has been applied on DSMs that were derived from satellite imagery, it can be applied to any other sourced DSMs.

  1. Regulatory acceptance of animal models of disease to support clinical trials of medicines and advanced therapy medicinal products.

    PubMed

    Cavagnaro, Joy; Silva Lima, Beatriz

    2015-07-15

    The utility of animal models of disease for assessing the safety of novel therapeutic modalities has become an increasingly important topic of discussion as research and development efforts focus on improving the predictive value of animal studies to support accelerated clinical development. Medicines are approved for marketing based upon a determination that their benefits outweigh foreseeable risks in specific indications, specific populations, and at specific dosages and regimens. No medicine is 100% safe. A medicine is less safe if the actual risks are greater than the predicted risks. The purpose of preclinical safety assessment is to understand the potential risks to aid clinical decision-making. Ideally preclinical studies should identify potential adverse effects and design clinical studies that will minimize their occurrence. Most regulatory documents delineate the utilization of conventional "normal" animal species to evaluate the safety risk of new medicines (i.e., new chemical entities and new biological entities). Animal models of human disease are commonly utilized to gain insight into the pathogenesis of disease and to evaluate efficacy but less frequently utilized in preclinical safety assessment. An understanding of the limitations of the animal disease models together with a better understanding of the disease and how toxicity may be impacted by the disease condition should allow for a better prediction of risk in the intended patient population. Importantly, regulatory authorities are becoming more willing to accept and even recommend data from experimental animal disease models that combine efficacy and safety to support clinical development. PMID:25814257

  2. Acceptance, values, and probability.

    PubMed

    Steel, Daniel

    2015-10-01

    This essay makes a case for regarding personal probabilities used in Bayesian analyses of confirmation as objects of acceptance and rejection. That in turn entails that personal probabilities are subject to the argument from inductive risk, which aims to show non-epistemic values can legitimately influence scientific decisions about which hypotheses to accept. In a Bayesian context, the argument from inductive risk suggests that value judgments can influence decisions about which probability models to accept for likelihoods and priors. As a consequence, if the argument from inductive risk is sound, then non-epistemic values can affect not only the level of evidence deemed necessary to accept a hypothesis but also degrees of confirmation themselves. PMID:26386533

  3. Examining the Intention to Use Technology among Pre-Service Teachers: An Integration of the Technology Acceptance Model and Theory of Planned Behavior

    ERIC Educational Resources Information Center

    Teo, Timothy

    2012-01-01

    This study examined pre-service teachers' self-reported intention to use technology. One hundred fifty-seven participants completed a survey questionnaire measuring their responses to six constructs from a research model that integrated the Technology Acceptance Model (TAM) and Theory of Planned Behavior (TPB). Structural equation modeling was…

  4. APPLICATION OF SURFACE COMPLEXATION MODELS TO SOIL SYSTEMS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chemical surface complexation models were developed to describe potentiometric titration and ion adsorption data on oxide minerals. These models provide molecular descriptions of adsorption using an equilibrium approach that defines surface species, chemical reactions, mass and charge balances and ...

  5. Factors That Influence the Acceptance of Telemetry by Emergency Medical Technicians in Ambulances: An Application of the Extended Technology Acceptance Model

    PubMed Central

    Hwang, Ji Young; Kim, Ki Young

    2014-01-01

    Abstract Objective: The aim of the study was to verify the effects of patient factors perceived by emergency medical technicians (EMTs) as well as their social and organizational factors on prehospital telemetry use intention based on the technology use intention and elaboration likelihood models. Materials and Methods: This is a retrospective empirical study. Questionnaires were developed on the basis of clinical factors of 72,907 patients assessed by prehospital telemetry from January 1, 2009 to April 30, 2012 by reviewing their prehospital medical care records and in-hospital medical records. Questionnaires regarding the social and organizational factors of EMTs were created on the basis of a literature review. To verify which factors affect the utilization of telemetry, we developed a partial least-squares route model on the basis of each characteristic. In total, 136 EMTs who had experience in using prehospital telemetry were surveyed from April 1 to April 7, 2013. Reliability, validity, hypotheses, and the model goodness of fit of the study tools were tested. Results: The clinical factors of the patients (path coefficient=−0.12; t=2.38), subjective norm (path coefficient=0.18; t=2.63), and job fit (path coefficient=0.45; t=5.29) positively affected the perceived usefulness (p<0.010). Meanwhile, the clinical factors of the patients (path coefficients=−0.19; t=4.46), subjective norm (path coefficient=0.08; t=1.97), loyalty incentives (path coefficient=−0.17; t=3.83), job fit (path coefficient=−0.32; t=7.06), organizational facilitations (path coefficient=0.08; t=1.99), and technical factors (i.e., usefulness and ease of use) positively affected attitudes (path coefficient=0.10, 0.58; t=2.62, 5.81; p<0.010). Attitudes and perceived usefulness significantly positively affected use intention. Conclusions: Factors that influence the use of telemetry by EMTs in ambulances included patients' clinical factors, as well as complex organizational and

  6. Coupled inverse and forward modelling to assess the range of acceptable thermal histories, a case study from SE Brazil

    NASA Astrophysics Data System (ADS)

    Cogné, N.; Gallagher, K.; Cobbold, P. R.

    2012-04-01

    We performed a new thermochronological study (fission track analysis and (U-Th)/He dating on apatite) in SE Brazil and integrate those data with inverse and forward modelling via QTQt software (Gallagher, 2012) to obtain thermal histories. The inversion results were used to characterize the general thermal histories and the associated uncertainties. For most of the samples we had a first phase of cooling during Late Cretaceous or Early Tertiary with subsequent reheating followed by Neogene cooling. The inverse modelling does not provide a unique solution and the associated uncertainties can be quite significant. Moreover the Tertiary parts of thermal histories were usually near the accepted resolution of the thermochronometric methods (~50-40°C). Therefore we performed deterministic forward modelling within the range of uncertainties to assess which solution is the most consistent with the data and independent geological information. These results are always conditional on the assumed kinetics for fission track annealing and diffusion of He, so we do not test the validity of that aspect. However, we can look at the range of predictions for the different forward models tested. This apporach implies that the reheating is required only for the samples around onshore Tertiary basins. For other samples we cannot conclude but geological information are against this hypothesis. However the Neogene cooling is required for all the samples.The combination of forward and inverse modelling allows us to better constrain the thermal histories for each sample in exploring the range of uncertainties and to reconcile a range of possible thermal histories with independent geological information. It also provides new information on the contrasting thermal evolution between different regions of the onshore SE Brazilian margin. Gallagher, K. 2012, Transdimensional Inverse thermal history modeling for quantitative thermochronology, Journal of Geophysical Research, in press.

  7. A surface hydrology model for regional vector borne disease models

    NASA Astrophysics Data System (ADS)

    Tompkins, Adrian; Asare, Ernest; Bomblies, Arne; Amekudzi, Leonard

    2016-04-01

    Small, sun-lit temporary pools that form during the rainy season are important breeding sites for many key mosquito vectors responsible for the transmission of malaria and other diseases. The representation of this surface hydrology in mathematical disease models is challenging, due to their small-scale, dependence on the terrain and the difficulty of setting soil parameters. Here we introduce a model that represents the temporal evolution of the aggregate statistics of breeding sites in a single pond fractional coverage parameter. The model is based on a simple, geometrical assumption concerning the terrain, and accounts for the processes of surface runoff, pond overflow, infiltration and evaporation. Soil moisture, soil properties and large-scale terrain slope are accounted for using a calibration parameter that sets the equivalent catchment fraction. The model is calibrated and then evaluated using in situ pond measurements in Ghana and ultra-high (10m) resolution explicit simulations for a village in Niger. Despite the model's simplicity, it is shown to reproduce the variability and mean of the pond aggregate water coverage well for both locations and validation techniques. Example malaria simulations for Uganda will be shown using this new scheme with a generic calibration setting, evaluated using district malaria case data. Possible methods for implementing regional calibration will be briefly discussed.

  8. Some aerodynamic considerations related to wind tunnel model surface definition

    NASA Technical Reports Server (NTRS)

    Gloss, B. B.

    1980-01-01

    The aerodynamic considerations related to model surface definition are examined with particular emphasis in areas of fabrication tolerances, model surface finish, and orifice induced pressure errors. The effect of model surface roughness texture on skin friction is also discussed. It is shown that at a given Reynolds number, any roughness will produce no skin friction penalty.

  9. Particle-Surface Interaction Model and Method of Determining Particle-Surface Interactions

    NASA Technical Reports Server (NTRS)

    Hughes, David W. (Inventor)

    2012-01-01

    A method and model of predicting particle-surface interactions with a surface, such as the surface of a spacecraft. The method includes the steps of: determining a trajectory path of a plurality of moving particles; predicting whether any of the moving particles will intersect a surface; predicting whether any of the particles will be captured by the surface and/or; predicting a reflected trajectory and velocity of particles reflected from the surface.

  10. Acceptance speech.

    PubMed

    Carpenter, M

    1994-01-01

    In Bangladesh, the assistant administrator of USAID gave an acceptance speech at an awards ceremony on the occasion of the 25th anniversary of oral rehydration solution (ORS). The ceremony celebrated the key role of the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) in the discovery of ORS. Its research activities over the last 25 years have brought ORS to every village in the world, preventing more than a million deaths each year. ORS is the most important medical advance of the 20th century. It is affordable and client-oriented, a true appropriate technology. USAID has provided more than US$ 40 million to ICDDR,B for diarrheal disease and measles research, urban and rural applied family planning and maternal and child health research, and vaccine development. ICDDR,B began as the relatively small Cholera Research Laboratory and has grown into an acclaimed international center for health, family planning, and population research. It leads the world in diarrheal disease research. ICDDR,B is the leading center for applied health research in South Asia. It trains public health specialists from around the world. The government of Bangladesh and the international donor community have actively joined in support of ICDDR,B. The government applies the results of ICDDR,B research to its programs to improve the health and well-being of Bangladeshis. ICDDR,B now also studies acute respiratory diseases and measles. Population and health comprise 1 of USAID's 4 strategic priorities, the others being economic growth, environment, and democracy, USAID promotes people's participation in these 4 areas and in the design and implementation of development projects. USAID is committed to the use and improvement of ORS and to complementary strategies that further reduce diarrhea-related deaths. Continued collaboration with a strong user perspective and integrated services will lead to sustainable development. PMID:12345470

  11. Acceptance speech.

    PubMed

    Yusuf, C K

    1994-01-01

    I am proud and honored to accept this award on behalf of the Government of Bangladesh, and the millions of Bangladeshi children saved by oral rehydration solution. The Government of Bangladesh is grateful for this recognition of its commitment to international health and population research and cost-effective health care for all. The Government of Bangladesh has already made remarkable strides forward in the health and population sector, and this was recognized in UNICEF's 1993 "State of the World's Children". The national contraceptive prevalence rate, at 40%, is higher than that of many developed countries. It is appropriate that Bangladesh, where ORS was discovered, has the largest ORS production capacity in the world. It was remarkable that after the devastating cyclone in 1991, the country was able to produce enough ORS to meet the needs and remain self-sufficient. Similarly, Bangladesh has one of the most effective, flexible and efficient control of diarrheal disease and epidemic response program in the world. Through the country, doctors have been trained in diarrheal disease management, and stores of ORS are maintained ready for any outbreak. Despite grim predictions after the 1991 cyclone and the 1993 floods, relatively few people died from diarrheal disease. This is indicative of the strength of the national program. I want to take this opportunity to acknowledge the contribution of ICDDR, B and the important role it plays in supporting the Government's efforts in the health and population sector. The partnership between the Government of Bangladesh and ICDDR, B has already borne great fruit, and I hope and believe that it will continue to do so for many years in the future. Thank you. PMID:12345479

  12. Health research access to personal confidential data in England and Wales: assessing any gap in public attitude between preferable and acceptable models of consent.

    PubMed

    Taylor, Mark J; Taylor, Natasha

    2014-12-01

    England and Wales are moving toward a model of 'opt out' for use of personal confidential data in health research. Existing research does not make clear how acceptable this move is to the public. While people are typically supportive of health research, when asked to describe the ideal level of control there is a marked lack of consensus over the preferred model of consent (e.g. explicit consent, opt out etc.). This study sought to investigate a relatively unexplored difference between the consent model that people prefer and that which they are willing to accept. It also sought to explore any reasons for such acceptance.A mixed methods approach was used to gather data, incorporating a structured questionnaire and in-depth focus group discussions led by an external facilitator. The sampling strategy was designed to recruit people with different involvement in the NHS but typically with experience of NHS services. Three separate focus groups were carried out over three consecutive days.The central finding is that people are typically willing to accept models of consent other than that which they would prefer. Such acceptance is typically conditional upon a number of factors, including: security and confidentiality, no inappropriate commercialisation or detrimental use, transparency, independent overview, the ability to object to any processing considered to be inappropriate or particularly sensitive.This study suggests that most people would find research use without the possibility of objection to be unacceptable. However, the study also suggests that people who would prefer to be asked explicitly before data were used for purposes beyond direct care may be willing to accept an opt out model of consent if the reasons for not seeking explicit consent are accessible to them and they trust that data is only going to be used under conditions, and with safeguards, that they would consider to be acceptable even if not preferable. PMID:26085451

  13. Inverse modeling of hydrologic parameters using surface flux and runoff observations in the Community Land Model

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Hou, Z.; Huang, M.; Tian, F.; Leung, L. R.

    2013-04-01

    This study demonstrates the possibility of inverting hydrologic parameters using surface flux and runoff observations in version 4 of the Community Land Model (CLM4). Previous studies showed that surface flux and runoff calculations are sensitive to major hydrologic parameters in CLM4 over different watersheds, and illustrated the necessity and possibility of parameter calibration. Two inversion strategies, the deterministic least-square fitting and stochastic Markov-Chain Monte-Carlo (MCMC) Bayesian inversion approaches, are evaluated by applying them to CLM4 at selected sites. The unknowns to be estimated include surface and subsurface runoff generation parameters and vadose zone soil water parameters. We find that using model parameters calibrated by the least-square fitting provides little improvements in the model simulations but the sampling-based stochastic inversion approaches are consistent - as more information comes in, the predictive intervals of the calibrated parameters become narrower and the misfits between the calculated and observed responses decrease. In general, parameters that are identified to be significant through sensitivity analyses and statistical tests are better calibrated than those with weak or nonlinear impacts on flux or runoff observations. Temporal resolution of observations has larger impacts on the results of inverse modeling using heat flux data than runoff data. Soil and vegetation cover have important impacts on parameter sensitivities, leading to different patterns of posterior distributions of parameters at different sites. Overall, the MCMC-Bayesian inversion approach effectively and reliably improves the simulation of CLM under different climates and environmental conditions. Bayesian model averaging of the posterior estimates with different reference acceptance probabilities can smooth the posterior distribution and provide more reliable parameter estimates, but at the expense of wider uncertainty bounds.

  14. Inverse Modeling of Hydrologic Parameters Using Surface Flux and Runoff Observations in the Community Land Model

    SciTech Connect

    Sun, Yu; Hou, Zhangshuan; Huang, Maoyi; Tian, Fuqiang; Leung, Lai-Yung R.

    2013-12-10

    This study demonstrates the possibility of inverting hydrologic parameters using surface flux and runoff observations in version 4 of the Community Land Model (CLM4). Previous studies showed that surface flux and runoff calculations are sensitive to major hydrologic parameters in CLM4 over different watersheds, and illustrated the necessity and possibility of parameter calibration. Two inversion strategies, the deterministic least-square fitting and stochastic Markov-Chain Monte-Carlo (MCMC) - Bayesian inversion approaches, are evaluated by applying them to CLM4 at selected sites. The unknowns to be estimated include surface and subsurface runoff generation parameters and vadose zone soil water parameters. We find that using model parameters calibrated by the least-square fitting provides little improvements in the model simulations but the sampling-based stochastic inversion approaches are consistent - as more information comes in, the predictive intervals of the calibrated parameters become narrower and the misfits between the calculated and observed responses decrease. In general, parameters that are identified to be significant through sensitivity analyses and statistical tests are better calibrated than those with weak or nonlinear impacts on flux or runoff observations. Temporal resolution of observations has larger impacts on the results of inverse modeling using heat flux data than runoff data. Soil and vegetation cover have important impacts on parameter sensitivities, leading to the different patterns of posterior distributions of parameters at different sites. Overall, the MCMC-Bayesian inversion approach effectively and reliably improves the simulation of CLM under different climates and environmental conditions. Bayesian model averaging of the posterior estimates with different reference acceptance probabilities can smooth the posterior distribution and provide more reliable parameter estimates, but at the expense of wider uncertainty bounds.

  15. Testing a model for parental acceptance of human papillomavirus vaccine in 9- to 18-year-old girls: a theory-guided study.

    PubMed

    Reynolds, Diane; O'Connell, Kathleen A

    2012-12-01

    Gardasil is the first vaccine developed to prevent cervical cancer and other diseases caused by certain types of genital human papillomavirus in females, but little is known about parental acceptance of this vaccine. The purpose of this study was to test a model that predicts intention to vaccinate that includes constructs from the health belief model and the theory of reasoned action. PMID:22020360

  16. A NEW LAND-SURFACE MODEL IN MM5

    EPA Science Inventory

    There has recently been a general realization that more sophisticated modeling of land-surface processes can be important for mesoscale meteorology models. Land-surface models (LSMs) have long been important components in global-scale climate models because of their more compl...

  17. RIPPLE - A new model for incompressible flows with free surfaces

    NASA Technical Reports Server (NTRS)

    Kothe, D. B.; Mjolsness, R. C.

    1991-01-01

    A new free surface flow model, RIPPLE, is summarized. RIPPLE obtains finite difference solutions for incompressible flow problems having strong surface tension forces at free surfaces of arbitrarily complex topology. The key innovation is the continuum surface force model which represents surface tension as a (strongly) localized volume force. Other features include a higher-order momentum advection model, a volume-of-fluid free surface treatment, and an efficient two-step projection solution method. RIPPLE's unique capabilities are illustrated with two example problems: low-gravity jet-induced tank flow, and the collision and coalescence of two cylindrical rods.

  18. A Patient Survey Assessing the Awareness and Acceptability of the Emergency Care Summary and Its Consent Model in Scotland

    PubMed Central

    Johnstone, Chris; McCartney, Gerry

    2010-01-01

    Background The Emergency Care Summary (ECS) was introduced in 2006 to allow aspects of the general practitioner (GP; family doctor, equivalent to primary care physician) medical record to be viewed in hospitals and out-of-hours centers in Scotland. Records were automatically uploaded unless patients actively opted out. This study investigated patient awareness and acceptance of this process. Methods This was a questionnaire survey of patients in a GP surgery (office) in Paisley, Scotland. Results Survey results indicated that 42 percent of patients were aware of the ECS, and 16 percent said that they recognized the leaflet posted to households. Of those who recognized the leaflet, 92 percent said they were happy for their record to be part of the system, while the others did not realize their record was to be included. Having read the leaflet, 97 percent said that they were happy for their record to be included in the ECS. Conclusions This study shows that most patients were not aware of the Emergency Care Summary or did not remember seeing the leaflet posted to households. Having read the leaflet, the vast majority of patients were happy for their records to be included in the system. The low awareness of the ECS calls into question the validity of an implied consent model using an information leaflet distributed by post. PMID:20697469

  19. Acceptance and Commitment Therapy and Contextual Behavioral Science: Examining the Progress of a Distinctive Model of Behavioral and Cognitive Therapy

    PubMed Central

    Hayes, Steven C.; Levin, Michael E.; Plumb-Vilardaga, Jennifer; Villatte, Jennifer L.; Pistorello, Jacqueline

    2012-01-01

    A number of recent authors have compared acceptance and commitment therapy (ACT) and traditional cognitive behavior therapy (CBT). The present article describes ACT as a distinct and unified model of behavior change, linked to a specific strategy of scientific development, which we term “contextual behavioral science.” We outline the empirical progress of ACT and describe its distinctive development strategy. A contextual behavioral science approach is an inductive attempt to build more adequate psychological systems based on philosophical clarity; the development of basic principles and theories; the development of applied theories linked to basic ones; techniques and components linked to these processes and principles; measurement of theoretically key processes; an emphasis on mediation and moderation in the analysis of applied impact; an interest in effectiveness, dissemination, and training; empirical testing of the research program across a broad range of areas and levels of analysis; and the creation of a more effective scientific and clinical community. We argue that this is a reasonable approach, focused on long-term progress, and that in broad terms it seems to be working. ACT is not hostile to traditional CBT, and is not directly buoyed by whatever weaknesses traditional CBT may have. ACT should be measured at least in part against its own goals as specified by its own developmental strategy. PMID:23611068

  20. A Model of Surface Energy Budget over Water, Snow and Ice Surfaces

    NASA Astrophysics Data System (ADS)

    Wang, J.; Bras, R. L.

    2012-12-01

    The recently developed maximum entropy production (MEP) model of turbulent and conductive heat fluxes over land surfaces is generalized to water/snow/ice surfaces. Analogous to the case of land surfaces, an analytical solution of latent, sensible and surface water/snow/ice heat flux is derived as a function of surface temperature (e.g. sea surface temperature) and surface net short- and long wave radiation. Compared to the classical bulk transfer equations based models, the MEP model does not need wind speed, near-surface air temperature and roughness lengths as input. The model is parameter parsimonious. A test of the MEP model against observations from several field experiments has suggested its usefulness and potential for predicting conductive and turbulent fluxes over water/snow/ice surfaces. The model is a suitable tool for remote sensing of the surface energy balance over oceans, snow covered Antarctica and sea ice. The model can also be incorporated into regional and global atmospheric models as an alternative algorithm for surface energy/water balance.

  1. GLDAS Land Surface Models based Aridity Indices

    NASA Astrophysics Data System (ADS)

    Pande, S.; Ghazanfari, S.

    2011-12-01

    Identification of dryland areas is crucial to guide policy aimed at intervening in water stressed areas and addressing its perennial livelihood or food insecurity. Aridity indices based on spatially relative soil moisture conditions such as NCEP aridity index allow cross comparison of dry conditions between sites. NCEP aridity index is based on the ratio of annual precipitation (supply) to annual potential evaporation (demand). Such an index ignores subannual scale competition between evaporation and drainage functions well as rainfall and temperature regimes. This determines partitioning of annual supply of precipitation into two competing (but met) evaporation and runoff demands. We here introduce aridity indices based on these additional considerations by using soil moisture time series for the past 3 decades from three Land Surface Models (LSM) models and compare it with NCEP index. We analyze global monthly soil moisture time series (385 months) at 1 x 1 degree spatial resolution as modeled by three GLDAS LSMs - VIC, MOSAIC and NOAH. The first eigen vector from Empirical Orthogonal Function (EOF) analysis, as it is the most dominant spatial template of global soil moisture conditions, is extracted. Frequency of nonexceedences of this dominant soil moisture mode for a location by other locations is calculated and is used as our proposed aridity index. An area is indexed drier (relative to other areas in the world) if its frequency of nonexceedence is lower. The EOF analysis reveals that their first eigen vector explains approximately 32%, 43% and 47% of variance explained by first 385 eigen vectors for VIC, MOSAIC and NOAH respectively. The temporal coefficients associated with it for all three LSMS show seasonality with a jump in trend around the year 1999 for NOAH and MOSAIC. The VIC aridity index displays a pattern most closely resembling that of NCEP though all LSM based indices isolate dominant dryland areas. However, all three LSMs identify some parts of

  2. Multiwalled Carbon Nanotube Deposition on Model Environmental Surfaces

    EPA Science Inventory

    Deposition of multiwalled carbon nanotubes (MWNTs) on model environmental surfaces was investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D). Deposition behaviors of MWNTs on positively and negatively charged surfaces were in good agreement with Der...

  3. Perceptions of a Specific Family Communication Application among Grandparents and Grandchildren: An Extension of the Technology Acceptance Model

    PubMed Central

    Tsai, Tsai-Hsuan; Chang, Hsien-Tsung; Ho, Yi-Lun

    2016-01-01

    Many studies have noted that the use of social networks sites (SNSs) can enhance social interaction among the elderly and that the motivation for the elderly to use SNSs is to keep in contact with remote friends and family or the younger generation. Memotree is designed to promote intergenerational family communication. The system incorporates the Family Tree design concept and provides family communication mechanisms based on the Family Communication Scale. In addition, the system optimizes hardware and interface use to conform to the specific needs of older and substantially younger individuals. Regarding the impact of variables on SNS with respect to the interaction of usability variables in the construction of a cross-generational communication platform, we adopted the TAM model and Chung et al.’s suggestions to promote user acceptance of the proposed Memotree system. A total of 39 grandchildren and 39 grandparents met the criteria and were included in the study. The elderly and young respondents revealed substantial willingness to use and/or satisfaction with using the Memotree system. Empirical results indicate that technology affordances and perceived ease of use have a positive impact on perceived usefulness, while perceived ease of use is affected by technology affordances. Internet self-efficacy and perceived usefulness have a positive impact on the user’s behavioral intention toward the system. In addition, this study investigated age as a moderating variable in the model. The results indicate that grandchildren have a larger significant effect on the path between perceived usefulness and behavioral intention than grandparents. This study proposes a more complete framework for investigating the user’s behavioral intention and provides a more appropriate explanation of related services for cross-generational interaction with SNS services. PMID:27270915

  4. Perceptions of a Specific Family Communication Application among Grandparents and Grandchildren: An Extension of the Technology Acceptance Model.

    PubMed

    Tsai, Tsai-Hsuan; Chang, Hsien-Tsung; Ho, Yi-Lun

    2016-01-01

    Many studies have noted that the use of social networks sites (SNSs) can enhance social interaction among the elderly and that the motivation for the elderly to use SNSs is to keep in contact with remote friends and family or the younger generation. Memotree is designed to promote intergenerational family communication. The system incorporates the Family Tree design concept and provides family communication mechanisms based on the Family Communication Scale. In addition, the system optimizes hardware and interface use to conform to the specific needs of older and substantially younger individuals. Regarding the impact of variables on SNS with respect to the interaction of usability variables in the construction of a cross-generational communication platform, we adopted the TAM model and Chung et al.'s suggestions to promote user acceptance of the proposed Memotree system. A total of 39 grandchildren and 39 grandparents met the criteria and were included in the study. The elderly and young respondents revealed substantial willingness to use and/or satisfaction with using the Memotree system. Empirical results indicate that technology affordances and perceived ease of use have a positive impact on perceived usefulness, while perceived ease of use is affected by technology affordances. Internet self-efficacy and perceived usefulness have a positive impact on the user's behavioral intention toward the system. In addition, this study investigated age as a moderating variable in the model. The results indicate that grandchildren have a larger significant effect on the path between perceived usefulness and behavioral intention than grandparents. This study proposes a more complete framework for investigating the user's behavioral intention and provides a more appropriate explanation of related services for cross-generational interaction with SNS services. PMID:27270915

  5. An interval model updating strategy using interval response surface models

    NASA Astrophysics Data System (ADS)

    Fang, Sheng-En; Zhang, Qiu-Hu; Ren, Wei-Xin

    2015-08-01

    Stochastic model updating provides an effective way of handling uncertainties existing in real-world structures. In general, probabilistic theories, fuzzy mathematics or interval analyses are involved in the solution of inverse problems. However in practice, probability distributions or membership functions of structural parameters are often unavailable due to insufficient information of a structure. At this moment an interval model updating procedure shows its superiority in the aspect of problem simplification since only the upper and lower bounds of parameters and responses are sought. To this end, this study develops a new concept of interval response surface models for the purpose of efficiently implementing the interval model updating procedure. The frequent interval overestimation due to the use of interval arithmetic can be maximally avoided leading to accurate estimation of parameter intervals. Meanwhile, the establishment of an interval inverse problem is highly simplified, accompanied by a saving of computational costs. By this means a relatively simple and cost-efficient interval updating process can be achieved. Lastly, the feasibility and reliability of the developed method have been verified against a numerical mass-spring system and also against a set of experimentally tested steel plates.

  6. Modeling the relationship between land use and surface water quality.

    PubMed

    Tong, Susanna T Y; Chen, Wenli

    2002-12-01

    It is widely known that watershed hydrology is dependent on many factors, including land use, climate, and soil conditions. But the relative impacts of different types of land use on the surface water are yet to be ascertained and quantified. This research attempted to use a comprehensive approach to examine the hydrologic effects of land use at both a regional and a local scale. Statistical and spatial analyses were employed to examine the statistical and spatial relationships of land use and the flow and water quality in receiving waters on a regional scale in the State of Ohio. Besides, a widely accepted watershed-based water quality assessment tool, the Better Assessment Science Integrating Point and Nonpoint Sources (BASINS), was adopted to model the plausible effects of land use on water quality in a local watershed in the East Fork Little Miami River Basin. The results from the statistical analyses revealed that there was a significant relationship between land use and in-stream water quality, especially for nitrogen, phosphorus and Fecal coliform. The geographic information systems (GIS) spatial analyses identified the watersheds that have high levels of contaminants and percentages of agricultural and urban lands. Furthermore, the hydrologic and water quality modeling showed that agricultural and impervious urban lands produced a much higher level of nitrogen and phosphorus than other land surfaces. From this research, it seems that the approach adopted in this study is comprehensive, covering both the regional and local scales. It also reveals that BASINS is a very useful and reliable tool, capable of characterizing the flow and water quality conditions for the study area under different watershed scales. With little modification, these models should be able to adapt to other watersheds or to simulate other contaminants. They also can be used to study the plausible impacts of global environmental change. In addition, the information on the hydrologic

  7. Eigenstress model for electrochemistry of solid surfaces.

    PubMed

    Ma, Hongxin; Xiong, Xilin; Gao, Panpan; Li, Xi; Yan, Yu; Volinsky, Alex A; Su, Yanjing

    2016-01-01

    Thermodynamic analysis and molecular dynamics simulations were conducted to systematically study the size-dependent electrochemical response of solids. By combining the generalized Young-Laplace equation with the popular Butler-Volmer formulation, the direct influence of surface stress on solid film electrochemical reactions was isolated. A series of thermodynamic formulas were developed to describe the size-dependent electrochemical properties of the solid surface. These formulas include intrinsic surface elastic parameters, such as surface eigenstress and surface elastic modulus. Metallic films of Au, Pt, Ni, Cu and Fe were studied as examples. The anodic current density of the metal film increased, while the equilibrium potential decreased with increasing solid film thickness. PMID:27256492

  8. Eigenstress model for electrochemistry of solid surfaces

    PubMed Central

    Ma, Hongxin; Xiong, Xilin; Gao, Panpan; Li, Xi; Yan, Yu; Volinsky, Alex A.; Su, Yanjing

    2016-01-01

    Thermodynamic analysis and molecular dynamics simulations were conducted to systematically study the size-dependent electrochemical response of solids. By combining the generalized Young-Laplace equation with the popular Butler-Volmer formulation, the direct influence of surface stress on solid film electrochemical reactions was isolated. A series of thermodynamic formulas were developed to describe the size-dependent electrochemical properties of the solid surface. These formulas include intrinsic surface elastic parameters, such as surface eigenstress and surface elastic modulus. Metallic films of Au, Pt, Ni, Cu and Fe were studied as examples. The anodic current density of the metal film increased, while the equilibrium potential decreased with increasing solid film thickness. PMID:27256492

  9. A study on solid modelling with surface trimming method

    NASA Astrophysics Data System (ADS)

    Hung, Ching-Yun; Chang, San-Cheng

    1993-07-01

    This paper proposes a Surface Trimming Method based on the intersection curves between free-form surfaces so that a complex solid model with several primitive surfaces can be constructed. These solid models will not only be used by the mechanical engineering industry to design and analyze conventional mechanical parts, but will also be used by the civil engineers to design and analyze structures of irregular shape. The scope of solid modelling application is thus enhanced.

  10. Modeling the Interrelationships among Pre-Service Science Teachers' Understanding and Acceptance of Evolution, Their Views on Nature of Science and Self-Efficacy Beliefs regarding Teaching Evolution

    ERIC Educational Resources Information Center

    Akyol, Gulsum; Tekkaya, Ceren; Sungur, Semra; Traynor, Anne

    2012-01-01

    This study proposed a path model of relationships among understanding and acceptance of evolution, views on nature of science, and self-efficacy beliefs regarding teaching evolution. A total of 415 pre-service science teachers completed a series of self-report instruments for the specified purpose. After the estimation of scale scores using…

  11. Assessing the Intention to Use Technology among Pre-Service Teachers in Singapore and Malaysia: A Multigroup Invariance Analysis of the Technology Acceptance Model (TAM)

    ERIC Educational Resources Information Center

    Teo, Timothy; Lee, Chwee Beng; Chai, Ching Sing; Wong, Su Luan

    2009-01-01

    This study assesses the pre-service teachers' self-reported future intentions to use technology in Singapore and Malaysia. A survey was employed to validate items from past research. Using the Technology Acceptance Model (TAM) as a research framework, 495 pre-service teachers from Singapore and Malaysia responded to an 11-item questionnaires…

  12. Analysis of Utility and Use of a Web-Based Tool for Digital Signal Processing Teaching by Means of a Technological Acceptance Model

    ERIC Educational Resources Information Center

    Toral, S. L.; Barrero, F.; Martinez-Torres, M. R.

    2007-01-01

    This paper presents an exploratory study about the development of a structural and measurement model for the technological acceptance (TAM) of a web-based educational tool. The aim consists of measuring not only the use of this tool, but also the external variables with a significant influence in its use for planning future improvements. The tool,…

  13. Re-examining the role of attitude in information system acceptance: a model from the satisfaction-dissatisfaction perspective

    NASA Astrophysics Data System (ADS)

    Guo, Bin; Zhou, Shasha

    2016-05-01

    This study attempts to re-examine the role of attitude in voluntary information system (IS) acceptance and usage, which has often been discounted in the previous technology acceptance research. We extend the unidimensional view of attitude into a bidimensional one, because of the simultaneous existence of both positive and negative evaluation towards IS in technology acceptance behaviour. In doing so, attitude construct is divided into two components: satisfaction as the positive attitudinal component and dissatisfaction as the negative attitudinal component. We argue that satisfaction and dissatisfaction will interactively affect technology usage intention. Besides, we explore the predictors of satisfaction and dissatisfaction based on the disconfirmation theory. Empirical results from a longitudinal study on bulletin board system (BBS) usage confirm the interaction effect of satisfaction and dissatisfaction on usage intention. Moreover, perceived task-related value has a significant effect on satisfaction, while perceived personal value has a significant effect on dissatisfaction. We also discuss the theoretical and managerial implications of our findings.

  14. Direct adhesive measurements between wood biopolymer model surfaces.

    PubMed

    Gustafsson, Emil; Johansson, Erik; Wågberg, Lars; Pettersson, Torbjörn

    2012-10-01

    For the first time the dry adhesion was measured for an all-wood biopolymer system using Johnson-Kendall-Roberts (JKR) contact mechanics. The polydimethylsiloxane hemisphere was successfully surface-modified with a Cellulose I model surface using layer-by-layer assembly of nanofibrillated cellulose and polyethyleneimine. Flat surfaces of cellulose were equally prepared on silicon dioxide substrates, and model surfaces of glucomannan and lignin were prepared on silicon dioxide using spin-coating. The measured work of adhesion on loading and the adhesion hysteresis was found to be very similar between cellulose and all three wood polymers, suggesting that the interaction between these biopolymers do not differ greatly. Surface energy calculations from contact angle measurements indicated similar dispersive surface energy components for the model surfaces. The dispersive component was dominating the surface energy for all surfaces. The JKR work of adhesion was lower than that calculated from contact angle measurements, which partially can be ascribed to surface roughness of the model surfaces and overestimation of the surface energies from contact angle determinations. PMID:22924973

  15. Modelling catalyst surfaces using DFT cluster calculations.

    PubMed

    Czekaj, Izabela; Wambach, Jörg; Kröcher, Oliver

    2009-10-01

    We review our recent theoretical DFT cluster studies of a variety of industrially relevant catalysts such as TiO(2), gamma-Al(2)O(3), V(2)O(5)-WO(3)-TiO(2) and Ni/Al(2)O(3). Aspects of the metal oxide surface structure and the stability and structure of metal clusters on the support are discussed as well as the reactivity of surfaces, including their behaviour upon poisoning. It is exemplarily demonstrated how such theoretical considerations can be combined with DRIFT and XPS results from experimental studies. PMID:20057947

  16. Modelling Catalyst Surfaces Using DFT Cluster Calculations

    PubMed Central

    Czekaj, Izabela; Wambach, Jörg; Kröcher, Oliver

    2009-01-01

    We review our recent theoretical DFT cluster studies of a variety of industrially relevant catalysts such as TiO2, γ-Al2O3, V2O5-WO3-TiO2 and Ni/Al2O3. Aspects of the metal oxide surface structure and the stability and structure of metal clusters on the support are discussed as well as the reactivity of surfaces, including their behaviour upon poisoning. It is exemplarily demonstrated how such theoretical considerations can be combined with DRIFT and XPS results from experimental studies. PMID:20057947

  17. A model of Martian surface chemistry

    NASA Technical Reports Server (NTRS)

    Oyama, V. I.; Berdahl, B. J.

    1979-01-01

    Alkaline earth and alkali metal superoxides and peroxides, gamma-Fe2O3 and carbon suboxide polymer, are proposed to be constituents of the Martian surface material. These reactive substances explain the water modified reactions and thermal behaviors of the Martian samples demonstrated by all of the Viking Biology Experiments. It is also proposed that the syntheses of these substances result mainly from electrical discharges between wind-mobilized particles at Martian pressures; plasmas are initiated and maintained by these discharges. Active species in the plasma either combine to form or react with inorganic surfaces to create the reactive constituents.

  18. Estimating long-term surface hydrological components by coupling remote sensing observation with surface flux model.

    SciTech Connect

    Song, J.; Wesely, M. L.

    2002-05-02

    A model framework for parameterized subgrid-scale surface fluxes (PASS) has been applied to use satellite data, models, and routine surface observations to infer root-zone available moisture content and evapotranspiration rate with moderate spatial resolution within Walnut River Watershed in Kansas. Biweekly composite normalized difference vegetative index (NDVI) data are derived from observations by National Oceanic and Atmospheric Administration (NOAA) satellites. Local surface observations provide data on downwelling solar irradiance, air temperature, relative humidity, and wind speed. Surface parameters including roughness length, albedo, surface water conductance, and the ratio of soil heat flux to net radiation are estimated; pixel-specific near-surface meteorological conditions such as air temperature, vapor pressure, and wind speed are adjusted according to local surface forcing. The PASS modeling system makes effective use of satellite data and can be run for large areas for which flux data do not exist and surface meteorological data are available from only a limited number of ground stations. The long-term surface hydrological budget is evaluated using radar-derived precipitation estimates, surface meteorological observations, and satellite data. The modeled hydrological components in the Walnut River Watershed compare well with stream gauge data and observed surface fluxes during 1999.

  19. Land Surface Emission Modeling to Support Physical Precipitation Retrievals

    NASA Technical Reports Server (NTRS)

    Peters-Lidard, Christina D.; Harrison, Kenneth; Kumar, Sujay; Ferraro, Ralph; Skofronick-Jackson, Gail

    2010-01-01

    Land surface modeling and data assimilation can provide dynamic land surface state variables necessary to support physical precipitation retrieval algorithms over land. It is well-known that surface emission, particularly over the range of frequencies to be included in the Global Precipitation Measurement Mission (GPM), is sensitive to land surface states, including soil properties, vegetation type and greenness, soil moisture, surface temperature, and snow cover, density, and grain size. In order to investigate the robustness of both the land surface model states and the microwave emissivity and forward radiative transfer models, we have undertaken a multi-site investigation as part of the NASA Precipitation Measurement Missions (PMM) Land Surface Characterization. Working Group.

  20. Mathematical Modeling of Surface Roughness of Castings Produced Using ZCast Direct Metal Casting

    NASA Astrophysics Data System (ADS)

    Chhabra, M.; Singh, R.

    2015-04-01

    Aim of this investigation is to develop a mathematical model for predicting surface roughness of castings produced using ZCast process by employing Buckingham's π-theorem. A relationship has been proposed between surface roughness of castings and shell wall thickness of the shell moulds fabricated using 3D printer. Based on model, experiments were performed to obtain the surface roughness of aluminium, brass and copper castings produced using ZCast process based on 3D printing technique. Based on experimental data, three best fitted third-degree polynomial equations have been established for predicting the surface roughness of castings. The predicted surface roughness values were then calculated using established best fitted equations. An error analysis was performed to compare the experimental and predicted data. The average prediction errors obtained for aluminium, brass and copper castings are 10.6, 2.43 and 3.12 % respectively. The obtained average surface roughness (experimental and predicted) values of castings produced are acceptable with the sand cast surface roughness values range (6.25-25 µm).

  1. Towards a Revised Monte Carlo Neutral Particle Surface Interaction Model

    SciTech Connect

    D.P. Stotler

    2005-06-09

    The components of the neutral- and plasma-surface interaction model used in the Monte Carlo neutral transport code DEGAS 2 are reviewed. The idealized surfaces and processes handled by that model are inadequate for accurately simulating neutral transport behavior in present day and future fusion devices. We identify some of the physical processes missing from the model, such as mixed materials and implanted hydrogen, and make some suggestions for improving the model.

  2. Digital Elevation Models of the Lunar Surface

    NASA Astrophysics Data System (ADS)

    Cook, A. C.; Robinson, M. S.

    1999-01-01

    Several digital elevation models (DEMs) have been produced at a scale of 1km/pixel and covering approximately one-fifth of the lunar surface. These were produced mostly by semiautomatically matching the stereo available between Clementine UV/VIS images, although some localized DEMs have been produced by applying this technique to Apollo Metric stereo pairs, or by digitizing an existing Apollo Metric contour map. The DEMS that result from Clementine UV/VIS images, although Of Poorer height accuracy (1300-600 in for a single matched point) than the Clementine laser altimeter point measurements (<+/-100 m), do provide considerably higher spatial resolution (e.g., every kilometer vs. every tens of kilometers) and allow topography in the polar regions to be determined. Nadir-pointing Clementine UV-VIS stereo pairs are automatically stereo matched using a patch-based matcher and fed through A stereo intersection camera model to yield a digital terrain model (DTM) of longitude, latitude, and height points. The DTM for each stereo pair is then replotted and interpolated to form map-projected DEM tiles. The DEM files can then be fitted to absolute height laser altimeter points, or iteratively to each other, to form a DEM mosaic. Uncertainties in UV-VIS camera pointing and the need to accumulate a sufficiently good topographic S/N ratio necessitates the use of 1 km pixels for the UV-VIS derived DEMs. For Apollo Metric stereo, an internal camera geometry correction and a full photogrammetric block adjustment must be performed using ground- control points to derive a DEM. The image scale of Apollo Metric, as well as the stereo angle, allow for a DEM with 100 m pixels and a height accuracy of +/- 25m. Apollo Metric imagery had previously been used to derive contour maps for much of the lunar equatorial regions; however, to recover this information in digital form these maps must be digitized. Most of the mare areas mapped contain noticeable topographic noise. This results from

  3. UGV acceptance testing

    NASA Astrophysics Data System (ADS)

    Kramer, Jeffrey A.; Murphy, Robin R.

    2006-05-01

    With over 100 models of unmanned vehicles now available for military and civilian safety, security or rescue applications, it is important to for agencies to establish acceptance testing. However, there appears to be no general guidelines for what constitutes a reasonable acceptance test. This paper describes i) a preliminary method for acceptance testing by a customer of the mechanical and electrical components of an unmanned ground vehicle system, ii) how it has been applied to a man-packable micro-robot, and iii) discusses the value of testing both to ensure that the customer has a workable system and to improve design. The test method automated the operation of the robot to repeatedly exercise all aspects and combinations of components on the robot for 6 hours. The acceptance testing process uncovered many failures consistent with those shown to occur in the field, showing that testing by the user does predict failures. The process also demonstrated that the testing by the manufacturer can provide important design data that can be used to identify, diagnose, and prevent long-term problems. Also, the structured testing environment showed that sensor systems can be used to predict errors and changes in performance, as well as uncovering unmodeled behavior in subsystems.

  4. A Revised Force Restore Model for Land Surface Modeling.

    NASA Astrophysics Data System (ADS)

    Ren, Diandong; Xue, Ming

    2004-11-01

    To clarify the definition of the equation for the temperature toward which the soil skin temperature is restored, the prediction equations in the commonly used force restore model for soil temperature are rederived from the heat conduction equation. The derivation led to a deep-layer temperature, commonly denoted T2, that is defined as the soil temperature at depth πd plus a transient term, where d is the e-folding damping depth of soil temperature diurnal oscillations. The corresponding prediction equation for T2 has the same form as the commonly used one except for an additional term involving the lapse rate of the “seasonal mean” soil temperature and the damping depth d. A term involving the same also appears in the skin temperature prediction equation, which also includes a transient term. In the literature, T2 was initially defined as the short-term (over several days) mean of the skin temperature, but in practice it is often used as the deep-layer temperature. Such inconsistent use can lead to drift in T2 prediction over a several-day period, as is documented in this paper. When T2 is properly defined and initialized, large drift in T2 prediction is avoided and the surface temperature prediction is usually improved. This is confirmed by four sets of experiments, each for a period during each season of 2000, that are initialized using and verified against measurements of the Oklahoma Atmospheric Surface-Layer Instrumentation System (OASIS) project.


  5. Surface aerodynamic temperature modeling over rainfed cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evapotranspiration (ET) or latent heat flux (LE) can be spatially estimated as an energy balance (EB) residual for land surfaces using remote sensing inputs. The EB equation requires the estimation of net radiation (Rn), soil heat flux (G), and sensible heat flux (H). Rn and G can be estimated with ...

  6. Surface Flux Modeling for Air Quality Applications

    EPA Science Inventory

    For many gasses and aerosols, dry deposition is an important sink of atmospheric mass. Dry deposition fluxes are also important sources of pollutants to terrestrial and aquatic ecosystems. The surface fluxes of some gases, such as ammonia, mercury, and certain volatile organic c...

  7. THEORETICAL MODEL OF SOILING OF SURFACES BY AIRBORNE PARTICLES

    EPA Science Inventory

    A model is developed which can be used to predict the change in reflectance from a surface as a function of time. Reflectance change is a measure of soiling caused by the deposition of particles on a surface. The major inputs to the model are the parameters to a bimodal distribut...

  8. COMPARISON OF SURFACE ENERGY BALANCE MODELS USING ASTER DATA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The knowledge of surface fluxes is of prime interest in agronomy, meteorology and hydrology. Several models have been developed recently to estimate surface fluxes using remote sensing data. A possible way to distinguish these models is the decoupling or not of soil and vegetation components, which ...

  9. Wetland methane modelling over the Scandinavian Arctic: Performance of current land-surface models

    NASA Astrophysics Data System (ADS)

    Hayman, Garry; Quiquet, Aurélien; Gedney, Nicola; Clark, Douglas; Friend, Andrew; George, Charles; Prigent, Catherine

    2014-05-01

    Wetlands are generally accepted as being the largest, but least well quantified, single natural source of CH4, with global emission estimates ranging from 100-231 Tg yr-1 [1] and for which the Boreal and Arctic regions make a significant contribution [2, 3]. The recent review by Melton et al. [4] has provided a summary of the current state of knowledge on the modelling of wetlands and the outcome of the WETCHIMP model intercomparison exercise. Melton et al. found a large variation in the wetland areas and associated methane emissions from the participating models and varying responses to climate change. In this paper, we report results from offline runs of two land surface models over Scandinavia (JULES, the Joint UK Land Environment Simulator [5, 6] and HYBRID8 [7]), using the same driving meteorological dataset (CRU-NCEP) for the period from January 1980 to December 2010. Although the two land surface models are very different, both models have used a TOPMODEL approach to derive the wetland area and have similar parameterisations of the methane wetland emissions. We find that both models give broadly similar results. They underestimate the wetland areas over Northern Scandinavia, compared to remote sensing and map-based datasets of wetlands [8]. This leads to lower predicted methane emissions compared to those observed on the ground and from aircraft [9]. We will present these findings and identify possible reasons for the underprediction. We will show the sensitivity to using the observed wetland areas to improve the methane emission estimates. References [1] Denman, K., et al.,: Couplings Between Changes in the Climate System and Biogeochemistry, In Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, United Kingdom, 2007; [2] Smith, L. C., et al.: Siberian peatlands a net carbon sink and global methane source since the early

  10. Wind tunnel model surface gauge for measuring roughness

    NASA Technical Reports Server (NTRS)

    Vorburger, T. V.; Gilsinn, D. E.; Teague, E. C.; Giauque, C. H. W.; Scire, F. E.; Cao, L. X.

    1987-01-01

    The optical inspection of surface roughness research has proceeded along two different lines. First, research into a quantitative understanding of light scattering from metal surfaces and into the appropriate models to describe the surfaces themselves. Second, the development of a practical instrument for the measurement of rms roughness of high performance wind tunnel models with smooth finishes. The research is summarized, with emphasis on the second avenue of research.

  11. A Model of Acceptance of Web 2.0 in Learning in Higher Education: A Case Study of Two Cultures

    ERIC Educational Resources Information Center

    Usoro, Abel; Echeng, Razep; Majewski, Grzegorz

    2014-01-01

    Though a few empirical studies on acceptance of Web 2.0 as a social networking tool in teaching and learning exist, apparently none consider students' and faculties' views from different cultures, which is the focus of this study. This article reports on a pilot study that begins to fill this gap by investigating the perceptions,…

  12. Personal Learning Environments Acceptance Model: The Role of Need for Cognition, e-Learning Satisfaction and Students' Perceptions

    ERIC Educational Resources Information Center

    del Barrio-García, Salvador; Arquero, José L.; Romero-Frías, Esteban

    2015-01-01

    As long as students use Web 2.0 tools extensively for social purposes, there is an opportunity to improve students' engagement in Higher Education by using these tools for academic purposes under a Personal Learning Environment approach (PLE 2.0). The success of these attempts depends upon the reactions and acceptance of users towards e-learning…

  13. Learner Differences in Perceived Satisfaction of an Online Learning: An Extension to the Technology Acceptance Model in an Arabic Sample

    ERIC Educational Resources Information Center

    Al-Azawei, Ahmed; Lundqvist, Karsten

    2015-01-01

    Online learning constitutes the most popular distance-learning method, with flexibility, accessibility, visibility, manageability and availability as its core features. However, current research indicates that its efficacy is not consistent across all learners. This study aimed to modify and extend the factors of the Technology Acceptance Model…

  14. E-Learning and the University of Huelva: A Study of WebCT and the Technological Acceptance Model

    ERIC Educational Resources Information Center

    Sanchez, R. Arteaga; Hueros, A. Duarte; Ordaz, M. Garcia

    2013-01-01

    Purpose: The purpose of this paper is to investigate the factors that determine the acceptance of the WebCT learning system among students of the faculties of Business and Education Sciences at the University of Huelva, and to verify the direct and indirect effects of these factors. Design/methodology/approach: A total of 226 students at the…

  15. Microcavity-array superhydrophobic surfaces: Limits of the model

    NASA Astrophysics Data System (ADS)

    Salvadori, M. C.; Oliveira, M. R. S.; Spirin, R.; Teixeira, F. S.; Cattani, M.; Brown, I. G.

    2013-11-01

    Superhydrophobic surfaces formed of microcavities can be designed with specific desired advancing and receding contact angles using a new model described by us in prior work. Here, we discuss the limits of validity of the model, and explore the application of the model to surfaces fabricated with small cavities of radius 250 nm and with large cavities of radius 40 μm. The Wenzel model is discussed and used to calculate the advancing and receding contact angles for samples for which our model cannot be applied. We also consider the case of immersion of a sample containing microcavities in pressurized water. A consideration that then arises is that the air inside the cavities can be dissolved in the water, leading to complete water invasion into the cavities and compromising the superhydrophobic character of the surface. Here, we show that this effect does not destroy the surface hydrophobia when the surface is subsequently removed from the water.

  16. Predictive model for ice formation on superhydrophobic surfaces.

    PubMed

    Bahadur, Vaibhav; Mishchenko, Lidiya; Hatton, Benjamin; Taylor, J Ashley; Aizenberg, Joanna; Krupenkin, Tom

    2011-12-01

    The prevention and control of ice accumulation has important applications in aviation, building construction, and energy conversion devices. One area of active research concerns the use of superhydrophobic surfaces for preventing ice formation. The present work develops a physics-based modeling framework to predict ice formation on cooled superhydrophobic surfaces resulting from the impact of supercooled water droplets. This modeling approach analyzes the multiple phenomena influencing ice formation on superhydrophobic surfaces through the development of submodels describing droplet impact dynamics, heat transfer, and heterogeneous ice nucleation. These models are then integrated together to achieve a comprehensive understanding of ice formation upon impact of liquid droplets at freezing conditions. The accuracy of this model is validated by its successful prediction of the experimental findings that demonstrate that superhydrophobic surfaces can fully prevent the freezing of impacting water droplets down to surface temperatures of as low as -20 to -25 °C. The model can be used to study the influence of surface morphology, surface chemistry, and fluid and thermal properties on dynamic ice formation and identify parameters critical to achieving icephobic surfaces. The framework of the present work is the first detailed modeling tool developed for the design and analysis of surfaces for various ice prevention/reduction strategies. PMID:21899285

  17. SSM - SOLID SURFACE MODELER, VERSION 6.0

    NASA Technical Reports Server (NTRS)

    Goza, S. P.

    1994-01-01

    The Solid Surface Modeler (SSM) is an interactive graphics software application for solid-shaded and wireframe three- dimensional geometric modeling. It enables the user to construct models of real-world objects as simple as boxes or as complex as Space Station Freedom. The program has a versatile user interface that, in many cases, allows mouse input for intuitive operation or keyboard input when accuracy is critical. SSM can be used as a stand-alone model generation and display program and offers high-fidelity still image rendering. Models created in SSM can also be loaded into other software for animation or engineering simulation. (See the information below for the availability of SSM with the Object Orientation Manipulator program, OOM, a graphics software application for three-dimensional rendering and animation.) Models are constructed within SSM using functions of the Create Menu to create, combine, and manipulate basic geometric building blocks called primitives. Among the simpler primitives are boxes, spheres, ellipsoids, cylinders, and plates; among the more complex primitives are tubes, skinned-surface models and surfaces of revolution. SSM also provides several methods for duplicating models. Constructive Solid Geometry (CSG) is one of the most powerful model manipulation tools provided by SSM. The CSG operations implemented in SSM are union, subtraction and intersection. SSM allows the user to transform primitives with respect to each axis, transform the camera (the user's viewpoint) about its origin, apply texture maps and bump maps to model surfaces, and define color properties; to select and combine surface-fill attributes, including wireframe, constant, and smooth; and to specify models' points of origin (the positions about which they rotate). SSM uses Euler angle transformations for calculating the results of translation and rotation operations. The user has complete control over the modeling environment from within the system. A variety of file

  18. Digital Elevation Models of the Lunar Surface

    NASA Astrophysics Data System (ADS)

    Cook, A. C.; Robinson, M. S.

    1999-01-01

    Several digital elevation models (DEMs) have been produced at a scale of 1km/pixel and covering approximately one-fifth of the lunar surface. These were produced mostly by semiautomatically matching the stereo available between Clementine UV/VIS images, although some localized DEMs have been produced by applying this technique to Apollo Metric stereo pairs, or by digitizing an existing Apollo Metric contour map. The DEMS that result from Clementine UV/VIS images, although Of Poorer height accuracy (1300-600 in for a single matched point) than the Clementine laser altimeter point measurements (<+/-100 m), do provide considerably higher spatial resolution (e.g., every kilometer vs. every tens of kilometers) and allow topography in the polar regions to be determined. Nadir-pointing Clementine UV-VIS stereo pairs are automatically stereo matched using a patch-based matcher and fed through A stereo intersection camera model to yield a digital terrain model (DTM) of longitude, latitude, and height points. The DTM for each stereo pair is then replotted and interpolated to form map-projected DEM tiles. The DEM files can then be fitted to absolute height laser altimeter points, or iteratively to each other, to form a DEM mosaic. Uncertainties in UV-VIS camera pointing and the need to accumulate a sufficiently good topographic S/N ratio necessitates the use of 1 km pixels for the UV-VIS derived DEMs. For Apollo Metric stereo, an internal camera geometry correction and a full photogrammetric block adjustment must be performed using ground- control points to derive a DEM. The image scale of Apollo Metric, as well as the stereo angle, allow for a DEM with 100 m pixels and a height accuracy of +/- 25m. Apollo Metric imagery had previously been used to derive contour maps for much of the lunar equatorial regions; however, to recover this information in digital form these maps must be digitized. Most of the mare areas mapped contain noticeable topographic noise. This results from

  19. Estimates of surface methane emissions over Europe using observed surface concentrations and the FLEXPART trajectory model

    NASA Astrophysics Data System (ADS)

    Weaver, C. J.; Kiemle, C.; Kawa, S. R.; Aalto, T.; Necki, J.; Steinbacher, M.; Arduini, J.; Apadula, F.; Berkhout, H.; Hatakka, J.; O'Doherty, S.

    2013-12-01

    We use surface methane observations from nine European ground stations, and the FLEXPART Lagrangian transport model to obtain surface methane emissions for 2010. Our inversion shows the strongest emissions from the Netherlands and the coal mines in Upper Silesia Poland. This is qualitatively consistent with the EDGAR surface flux inventory. We also report significant surface fluxes from wetlands in southern Finland during July and August and reduced wetland fluxes later in the year. Our simulated methane surface concentration captures at least half of the daily variability in the observations, suggesting that the transport model is correctly simulating the regional transport pathways over Europe. We also use our trajectory model to determine whether future space-based remote sensing instruments (MERLIN) will be able to detect both natural and anthropogenic changes in the surface flux strengths.

  20. Assimilation of land surface temperature into the land surface model JULES with an ensemble Kalman filter

    NASA Astrophysics Data System (ADS)

    Ghent, D.; Kaduk, J.; Remedios, J.; Ardö, J.; Balzter, H.

    2010-10-01

    Land surface models have uncertainties due to their approximation of physical processes and the heterogeneity of the land surface. These can be compounded when key variables are inadequately represented. Land surface temperature (LST) is critical as it forms an integral component in the surface energy budget, water stress evaluation, fuel moisture derivation, and soil moisture-climate feedbacks. A reduction in the uncertainty of surface energy fluxes, and moisture quantification, is assumed to be achievable by constraining simulations of LST with observation data. This technique is known as data assimilation and involves the adjustment of the model state at observation times with measurements of a predictable uncertainty. In this paper, the validity of LST simulations in a regionalized parameterization of the land surface model Joint UK Land Environment Simulator (JULES) for Africa is assessed by way of a multitemporal intercomparison study with the Moderate Resolution Imaging Spectroradiometer (MODIS), the Advanced Along Track Scanning Radiometer (AATSR), and the Spinning Enhanced Visible and Infrared Imager (SEVIRI) thermal products, with a two-thirds reduction in model bias found when soil properties are reparameterized. A data assimilation experiment of SEVIRI LST into the JULES model via an ensemble Kalman filter shows an improvement in the modeled LST, soil moisture, and latent and sensible heat fluxes. This paper presents the first investigation into reducing the uncertainty in modeling energy and water fluxes with the United Kingdom's most important land surface model, JULES, by means of data assimilation of LST.

  1. Tunnel surface recombination in optoelectronic device modeling

    NASA Astrophysics Data System (ADS)

    Ptashchenko, Alexander A.; Ptashchenko, Fedor A.

    1997-08-01

    The rate of tunnel surface recombination (TSR) in a p-n structure has been calculated as a function of the excitation level and temperature in a semiclassical approximation under the assumption that the excess energy of a recombining electron is transferred to phonons or to a photon. The approximating analytical expressions obtained are applied in calculations of the effect of TSR on the characteristics of photodiodes, solar cells, light-emitting diodes and diode lasers.

  2. A statistical model for landfill surface emissions.

    PubMed

    Héroux, Martin; Guy, Christophe; Millette, Denis

    2010-02-01

    Landfill operators require a rapid, simple, low-cost, and accurate method for estimation of landfill methane surface emissions over time. Several methods have been developed to obtain instantaneous field measurements of landfill methane surface emissions. This paper provides a methodology for interpolating instantaneous measurements over time, taking variations in meteorological conditions into account. The goal of this study was to determine the effects of three factors on landfill methane surface emissions: air temperature, pressure gradient between waste and atmosphere, and soil moisture content of the cover material. On the basis of a statistical three-factor and two-level full factorial design, field measurements of methane emissions were conducted at the City of Montreal landfill site during the summer of 2004. Three areas were measured: test area 1 (4800 m2), test area 2 (1400 m2), and test area 3 (1000 m2). Analyses of variance were performed on the data. They showed a significant statistical effect of the three factors and the interaction between temperature and soil moisture content on methane emissions. Analysis also led to the development of a multifactor correlation, which can be explained by the underlying processes of diffusive and advective flow and biological oxidation. This correlation was used to estimate total emissions of the three test areas for July and August 2004. The approach was validated using a second dataset for another area adjacent to the landfill. PMID:20222535

  3. Application of a simple cerebellar model to geologic surface mapping

    USGS Publications Warehouse

    Hagens, A.; Doveton, J.H.

    1991-01-01

    Neurophysiological research into the structure and function of the cerebellum has inspired computational models that simulate information processing associated with coordination and motor movement. The cerebellar model arithmetic computer (CMAC) has a design structure which makes it readily applicable as an automated mapping device that "senses" a surface, based on a sample of discrete observations of surface elevation. The model operates as an iterative learning process, where cell weights are continuously modified by feedback to improve surface representation. The storage requirements are substantially less than those of a conventional memory allocation, and the model is extended easily to mapping in multidimensional space, where the memory savings are even greater. ?? 1991.

  4. Surface tension driven flow in glass melts and model fluids

    NASA Technical Reports Server (NTRS)

    Mcneil, T. J.; Cole, R.; Subramanian, R. S.

    1982-01-01

    Surface tension driven flow has been investigated analytically and experimentally using an apparatus where a free column of molten glass or model fluids was supported at its top and bottom faces by solid surfaces. The glass used in the experiments was sodium diborate, and the model fluids were silicone oils. In both the model fluid and glass melt experiments, conclusive evidence was obtained to prove that the observed flow was driven primarily by surface tension forces. The experimental observations are in qualitative agreement with predictions from the theoretical model.

  5. Modeling and inversion of volcanic surface deformation based on Mogi model and McTigue model

    NASA Astrophysics Data System (ADS)

    Srigutomo, Wahyu; Trimadona, Martakusumah, Rocky; Anwar, Hairil

    2015-04-01

    Surface deformation occurred in a volcano is related strongly to the magmatic deformation beneath it. In this work we calculate the surface vertical and horizontal displacements due to hydrostatic pressure change of magma cavity based on point pressure source (Mogi) model and finite spherical source (McTigue) model. We apply the Levenberg-Marquardt inversion scheme to estimate the physical parameters contributing to the deformation.

  6. Modeling of surface microtopography and its impacts on hydrologic processes

    NASA Astrophysics Data System (ADS)

    Habtezion, Noah Lebassi

    Understanding the impacts of surface microtopography on hydrologic processes is critical. The objectives of this thesis research are: (1) to evaluate the effects of DEM resolution on microtopographic characteristics, hydrologic connectivity, and modeling of hydrologic processes; and (2) to assess the influences of multiple rainfall events on surface and subsurface hydrologic processes with the use of a puddle-to-puddle (P2P) modeling system. The change in DEM resolution has a significant effect on how surface microtopography is depicted, which in turn alters the hydrologic response of a topographic surface. The smoothing of reduced DEM resolution tends to enhance hydrologic connectivity, reduce the depression storage and infiltration, and increase surface runoff. Temporal rainfall distribution results in spatio-temporal variations in soil water dynamics, depression storage, infiltration, hydrologic connectivity, and surface runoff. The reduction in ponding time and infiltration, and the enhancement of hydrologic connectivity further caused earlier and greater surface runoff generation.

  7. Accuracy of functional surfaces on comparatively modeled protein structures

    PubMed Central

    Zhao, Jieling; Dundas, Joe; Kachalo, Sema; Ouyang, Zheng; Liang, Jie

    2012-01-01

    Identification and characterization of protein functional surfaces are important for predicting protein function, understanding enzyme mechanism, and docking small compounds to proteins. As the rapid speed of accumulation of protein sequence information far exceeds that of structures, constructing accurate models of protein functional surfaces and identify their key elements become increasingly important. A promising approach is to build comparative models from sequences using known structural templates such as those obtained from structural genome projects. Here we assess how well this approach works in modeling binding surfaces. By systematically building three-dimensional comparative models of proteins using Modeller, we determine how well functional surfaces can be accurately reproduced. We use an alpha shape based pocket algorithm to compute all pockets on the modeled structures, and conduct a large-scale computation of similarity measurements (pocket RMSD and fraction of functional atoms captured) for 26,590 modeled enzyme protein structures. Overall, we find that when the sequence fragment of the binding surfaces has more than 45% identity to that of the tempalte protein, the modeled surfaces have on average an RMSD of 0.5 Å, and contain 48% or more of the binding surface atoms, with nearly all of the important atoms in the signatures of binding pockets captured. PMID:21541664

  8. On comparison of modeled surface flux variations to aircraft observations.

    SciTech Connect

    Song, J.; Wesely, M. L.; Environmental Research; Northern Illinois Univ.

    2003-07-30

    Evaluation of models of air-surface exchange is facilitated by an accurate match of areas simulated with those seen by micrometeorological flux measurements. Here, spatial variations in fluxes estimated with the parameterized subgrid-scale surface (PASS) flux model were compared to flux variations seen aboard aircraft above the Walnut River Watershed (WRW) in Kansas. Despite interference by atmospheric eddies, the areas where the modeled sensible and latent heat fluxes were most highly correlated with the aircraft flux estimates were upwind of the flight segments. To assess whether applying a footprint function to the surface values would improve the model evaluation, a two-dimensional correlation distribution was used to identify the locations and relative importance of contributing modeled surface pixels upwind of each segment of the flight path. The agreement between modeled surface fluxes and aircraft measurements was improved when upwind fluxes were weighted with an optimized footprint parameter {var_phi}, which can be estimated from wind profiler data and surface eddy covariance. Variations of the flight-observed flux were consistently greater than those modeled at the surface, perhaps because of the smoothing effect of using 1 km pixels in the model. In addition, limited flight legs prevented sufficient filtering of the effects of atmospheric convection, possibly accounting for some of the more prominent changes in fluxes measured along the flight paths.

  9. DEVELOPMENT OF A LAND-SURFACE MODEL PART I: APPLICATION IN A MESOSCALE METEOROLOGY MODEL

    EPA Science Inventory

    Parameterization of land-surface processes and consideration of surface inhomogeneities are very important to mesoscale meteorological modeling applications, especially those that provide information for air quality modeling. To provide crucial, reliable information on the diurn...

  10. Generalized model for photoinduced surface structure in amorphous thin films.

    PubMed

    Lu, Chao; Recht, Daniel; Arnold, Craig

    2013-09-01

    We present a generalized model to explain the spatial and temporal evolution of photoinduced surface structure in photosensitive amorphous thin films. The model describes these films as an incompressible viscous fluid driven by a photoinduced pressure originating from dipole rearrangement. This derivation requires only the polarizability, viscosity and surface tension of the system. Using values of these physical parameters, we check the validity of the model by fitting to experimental data of As2S3 and demonstrating good agreement. PMID:25166680

  11. Software Surface Modeling and Grid Generation Steering Committee

    NASA Technical Reports Server (NTRS)

    Smith, Robert E. (Editor)

    1992-01-01

    It is a NASA objective to promote improvements in the capability and efficiency of computational fluid dynamics. Grid generation, the creation of a discrete representation of the solution domain, is an essential part of computational fluid dynamics. However, grid generation about complex boundaries requires sophisticated surface-model descriptions of the boundaries. The surface modeling and the associated computation of surface grids consume an extremely large percentage of the total time required for volume grid generation. Efficient and user friendly software systems for surface modeling and grid generation are critical for computational fluid dynamics to reach its potential. The papers presented here represent the state-of-the-art in software systems for surface modeling and grid generation. Several papers describe improved techniques for grid generation.

  12. Digital terrain modelling and industrial surface metrology - Converging crafts

    USGS Publications Warehouse

    Pike, R.J.

    2001-01-01

    Quantitative characterisation of surface form, increasingly from digital 3-D height data, is cross-disciplinary and can be applied at any scale. Thus, separation of industrial-surface metrology from its Earth-science counterpart, (digital) terrain modelling, is artificial. Their growing convergence presents an opportunity to develop in surface morphometry a unified approach to surface representation. This paper introduces terrain modelling and compares it with metrology, noting their differences and similarities. Examples of potential redundancy among parameters illustrate one of the many issues common to both disciplines. ?? 2001 Elsevier Science Ltd. All rights reserved.

  13. Testing the Technology Acceptance Model: HIV Case Managers' Intention to Use a Continuity of Care Record with Context-specific Links

    PubMed Central

    Bakken, Suzanne

    2014-01-01

    Objective The goal of this study was to examine the applicability of the Technology Acceptance Model (TAM) in explaining Human Immunodeficiency Virus (HIV) case managers’ acceptance of a prototype Continuity of Care Record (CCR) with context-specific links designed to meet their information needs. Design An online survey, based on the constructs of the Technology Acceptance Model (TAM), of 94 case managers who provide care to persons living with HIV (PLWH). To assess the consistency, reliability and fit of the model factors, three methods were used: principal components factor analysis, Cronbach’s alpha, and regression analysis. Results Principal components factor analysis resulted in three factors (Perceived Ease of Use, Perceived Usefulness, and Barriers to Use) that explained 84.88% of the variance. Internal consistency reliability estimates ranged from .69–.91. In a linear regression model, Perceived Ease of Use, Perceived Usefulness, and Barriers to Use scores explained 43.6% (p <.001) of the variance in Behavioral Intention to use a CCR with context-specific links. Conclusion Our study validated the use of the TAM in health information technology.Results from our study demonstrated that Perceived Ease of Use, Perceived Usefulness, and Barriers to Use are predictors of Behavioral Intention to use a CCR with context-specific links to web-based information resources. PMID:21848452

  14. Digital terrain modeling and industrial surface metrology: Converging realms

    USGS Publications Warehouse

    Pike, R.J.

    2001-01-01

    Digital terrain modeling has a micro-and nanoscale counterpart in surface metrology, the numerical characterization of industrial surfaces. Instrumentation in semiconductor manufacturing and other high-technology fields can now contour surface irregularities down to the atomic scale. Surface metrology has been revolutionized by its ability to manipulate square-grid height matrices that are analogous to the digital elevation models (DEMs) used in physical geography. Because the shaping of industrial surfaces is a spatial process, the same concepts of analytical cartography that represent ground-surface form in geography evolved independently in metrology: The surface topography of manufactured components, exemplified here by automobile-engine cylinders, is routinely modeled by variogram analysis, relief shading, and most other techniques of parameterization and visualization familiar to geography. This article introduces industrial surface-metrology, examines the field in the context of terrain modeling and geomorphology and notes their similarities and differences, and raises theoretical issues to be addressed in progressing toward a unified practice of surface morphometry.

  15. Modeling equine race surface vertical mechanical behaviors in a musculoskeletal modeling environment.

    PubMed

    Symons, Jennifer E; Fyhrie, David P; Hawkins, David A; Upadhyaya, Shrinivasa K; Stover, Susan M

    2015-02-26

    Race surfaces have been associated with the incidence of racehorse musculoskeletal injury, the leading cause of racehorse attrition. Optimal race surface mechanical behaviors that minimize injury risk are unknown. Computational models are an economical method to determine optimal mechanical behaviors. Previously developed equine musculoskeletal models utilized ground reaction floor models designed to simulate a stiff, smooth floor appropriate for a human gait laboratory. Our objective was to develop a computational race surface model (two force-displacement functions, one linear and one nonlinear) that reproduced experimental race surface mechanical behaviors for incorporation in equine musculoskeletal models. Soil impact tests were simulated in a musculoskeletal modeling environment and compared to experimental force and displacement data collected during initial and repeat impacts at two racetracks with differing race surfaces - (i) dirt and (ii) synthetic. Best-fit model coefficients (7 total) were compared between surface types and initial and repeat impacts using a mixed model ANCOVA. Model simulation results closely matched empirical force, displacement and velocity data (Mean R(2)=0.930-0.997). Many model coefficients were statistically different between surface types and impacts. Principal component analysis of model coefficients showed systematic differences based on surface type and impact. In the future, the race surface model may be used in conjunction with previously developed the equine musculoskeletal models to understand the effects of race surface mechanical behaviors on limb dynamics, and determine race surface mechanical behaviors that reduce the incidence of racehorse musculoskeletal injury through modulation of limb dynamics. PMID:25634662

  16. Land Surface Microwave Emissivity Dynamics: Observations, Analysis and Modeling

    NASA Technical Reports Server (NTRS)

    Tian, Yudong; Peters-Lidard, Christa D.; Harrison, Kenneth W.; Kumar, Sujay; Ringerud, Sarah

    2014-01-01

    Land surface microwave emissivity affects remote sensing of both the atmosphere and the land surface. The dynamical behavior of microwave emissivity over a very diverse sample of land surface types is studied. With seven years of satellite measurements from AMSR-E, we identified various dynamical regimes of the land surface emission. In addition, we used two radiative transfer models (RTMs), the Community Radiative Transfer Model (CRTM) and the Community Microwave Emission Modeling Platform (CMEM), to simulate land surface emissivity dynamics. With both CRTM and CMEM coupled to NASA's Land Information System, global-scale land surface microwave emissivities were simulated for five years, and evaluated against AMSR-E observations. It is found that both models have successes and failures over various types of land surfaces. Among them, the desert shows the most consistent underestimates (by approx. 70-80%), due to limitations of the physical models used, and requires a revision in both systems. Other snow-free surface types exhibit various degrees of success and it is expected that parameter tuning can improve their performances.

  17. Using combined hydrological variables for extracting functional signatures of catchments to better assess the acceptability of model structures in conceptual catchment modelling

    NASA Astrophysics Data System (ADS)

    Fovet, O.; Hrachowitz, M.; RUIZ, L.; Gascuel-odoux, C.; Savenije, H.

    2013-12-01

    While most hydrological models reproduce the general flow dynamics of a system, they frequently fail to adequately mimic system internal processes. This is likely to make them inadequate to simulate solutes transport. For example, the hysteresis between storage and discharge, which is often observed in shallow hard-rock aquifers, is rarely well reproduced by models. One main reason is that this hysteresis has little weight in the calibration because objective functions are based on time series of individual variables. This reduces the ability of classical calibration/validation procedures to assess the relevance of the conceptual hypothesis associated with hydrological models. Calibrating models on variables derived from the combination of different individual variables (like stream discharge and groundwater levels) is a way to insure that models will be accepted based on their consistency. Here we therefore test the value of this more systems-like approach to test different hypothesis on the behaviour of a small experimental low-land catchment in French Brittany (ORE AgrHys) where a high hysteresis is observed on the stream flow vs. shallow groundwater level relationship. Several conceptual models were applied to this site, and calibrated using objective functions based on metrics of this hysteresis. The tested model structures differed with respect to the storage function in each reservoir, the storage-discharge function in each reservoir, the deep loss expressions (as constant or variable fraction), the number of reservoirs (from 1 to 4) and their organization (parallel, series). The observed hysteretic groundwater level-discharge relationship was not satisfactorily reproduced by most of the tested models except for the most complex ones. Those were thus more consistent, their underlying hypotheses are probably more realistic even though their performance for simulating observed stream flow was decreased. Selecting models based on such systems-like approach is

  18. Real Time Land-Surface Hydrologic Modeling Over Continental US

    NASA Technical Reports Server (NTRS)

    Houser, Paul R.

    1998-01-01

    The land surface component of the hydrological cycle is fundamental to the overall functioning of the atmospheric and climate processes. Spatially and temporally variable rainfall and available energy, combined with land surface heterogeneity cause complex variations in all processes related to surface hydrology. The characterization of the spatial and temporal variability of water and energy cycles are critical to improve our understanding of land surface-atmosphere interaction and the impact of land surface processes on climate extremes. Because the accurate knowledge of these processes and their variability is important for climate predictions, most Numerical Weather Prediction (NWP) centers have incorporated land surface schemes in their models. However, errors in the NWP forcing accumulate in the surface and energy stores, leading to incorrect surface water and energy partitioning and related processes. This has motivated the NWP to impose ad hoc corrections to the land surface states to prevent this drift. A proposed methodology is to develop Land Data Assimilation schemes (LDAS), which are uncoupled models forced with observations, and not affected by NWP forcing biases. The proposed research is being implemented as a real time operation using an existing Surface Vegetation Atmosphere Transfer Scheme (SVATS) model at a 40 km degree resolution across the United States to evaluate these critical science questions. The model will be forced with real time output from numerical prediction models, satellite data, and radar precipitation measurements. Model parameters will be derived from the existing GIS vegetation and soil coverages. The model results will be aggregated to various scales to assess water and energy balances and these will be validated with various in-situ observations.

  19. Improved simulation of groundwater - surface water interaction in catchment models

    NASA Astrophysics Data System (ADS)

    teklesadik, aklilu; van Griensven, Ann; Anibas, Christian; Huysmans, Marijke

    2016-04-01

    Groundwater storage can have a significant contribution to stream flow, therefore a thorough understanding of the groundwater surface water interaction is of prime important when doing catchment modeling. The aim of this study is to improve the simulation of groundwater - surface water interaction in a catchment model of the upper Zenne River basin located in Belgium. To achieve this objective we used the "Groundwater-Surface water Flow" (GSFLOW) modeling software, which is an integration of the surface water modeling tool "Precipitation and Runoff Modeling system" (PRMS) and the groundwater modeling tool MODFLOW. For this case study, the PRMS model and MODFLOW model were built and calibrated independently. The PRMS upper Zenne River basin model is divided into 84 hydrological response units (HRUs) and is calibrated with flow data at the Tubize gauging station. The spatial discretization of the MODFLOW upper Zenne groundwater flow model consists of 100m grids. Natural groundwater divides and the Brussels-Charleroi canal are used as boundary conditions for the MODFLOW model. The model is calibrated using piezometric data. The GSFLOW results were evaluated against a SWAT model application and field observations of groundwater-surface water interactions along a cross section of the Zenne River and riparian zone. The field observations confirm that there is no exchange of groundwater beyond the Brussel-Charleroi canal and that the interaction at the river bed is relatively low. The results show that there is a significant difference in the groundwater simulations when using GSFLOW versus SWAT. This indicates that the groundwater component representation in the SWAT model could be improved and that a more realistic implementation of the interactions between groundwater and surface water is advisable. This could be achieved by integrating SWAT and MODFLOW.

  20. Photopolarimetry of scattering surfaces and their interpretation by computer model

    NASA Technical Reports Server (NTRS)

    Wolff, M.

    1979-01-01

    Wolff's computer model of a rough planetary surface was simplified and revised. Close adherence to the actual geometry of a pitted surface and the inclusion of a function for diffuse light resulted in a quantitative model comparable to observations by planetary satellites and asteroids. A function is also derived to describe diffuse light emitted from a particulate surface. The function is in terms of the indices of refraction of the surface material, particle size, and viewing angles. Computer-generated plots describe the observable and theoretical light components for the Moon, Mercury, Mars and a spectrum of asteroids. Other plots describe the effects of changing surface material properties. Mathematical results are generated to relate the parameters of the negative polarization branch to the properties of surface pitting. An explanation is offered for the polarization of the rings of Saturn, and the average diameter of ring objects is found to be 30 to 40 centimeters.

  1. Modeling of surface roughness effects on glaze ice accretion

    NASA Technical Reports Server (NTRS)

    Hansman, R. John, Jr.; Yamaguchi, Keiko; Berkowitz, Brian; Potapczuk, M.

    1989-01-01

    The cause and effects of roughness on accreting glaze ice surfaces were studied with microvideo observations. Distinct zones of surface water behavior were observed, including a smooth wet zone in the stagnation region with a uniform water film, a rough zone where surface tension effects caused coalescence of surface water into stationary beads, and a zone where roughness elements grow into horn shapes. In addition, a zone where surface water ran back as rivulets and a dry zone where rime feathers formed were observed. The locations and behaviors of these zones are discussed. A simple multizone modification to the glaze ice accretion model is proposed to include spatial variability in surface roughness. Two test cases using the multizone model showed significant improvements for the prediction of glaze ice shapes.

  2. Community Surface Dynamics Modeling System and its CSDMS Modeling Tool to couple models and data (Invited)

    NASA Astrophysics Data System (ADS)

    Syvitski, J. P.; Csdms Scientific; Software Team

    2010-12-01

    CSDMS is the virtual home for a diverse community who foster and promote the modeling of earth surface processes, with emphasis on the movement of fluids, sediment and solutes through landscapes, seascapes and through their sedimentary basins. CSDMS develops, integrates, disseminates & archives software (> 150 models and 3million+ lines of code) that reflects and predicts earth surface processes over a broad range of time and space scales. CSDMS deals with the Earth's surface—the ever-changing, dynamic interface between lithosphere, hydrosphere, cryosphere, and atmosphere. CSDMS employs state-of-the-art architectures, interface standards and frameworks that make it possible to convert stand-alone models into flexible, "plug-and-play" components that can be assembled into larger applications. The CSDMS model-coupling environment offers language interoperability, structured and unstructured grids, and serves as a migration pathway for surface dynamics modelers towards High-Performance Computing (HPC). The CSDMS Modeling Tool is a key product of the overall project, as it allows earth scientists with relatively modest computer coding experience to use the CSDMS modules for earth surface dynamics research and education. The CMT Tool is platform independent. CMT can easily couple models that have followed the CSDMS protocols for model contribution: 1) Open-source license; 2) Available; 3) Vetted; 4) Open-source language; 5) Refactored for componentization; 6) Metadata & test files; 7) Clean and documented using keywords.

  3. MODELING THE INTERACTION OF AGROCHEMICALS WITH ENVIRONMENTAL SURFACES: PESTICIDES ON RUTILE AND ORGANO-RUTILE SURFACES

    EPA Science Inventory

    Non-bonded interactions between model pesticides and organo-mineral surfaces have been studied using molecular mechanical conformational calculations and molecular dynamics simulations. The minimum energy conformations and relative binding energies for the interaction of atrazine...

  4. Rough surface scattering based on facet model

    NASA Technical Reports Server (NTRS)

    Khamsi, H. R.; Fung, A. K.; Ulaby, F. T.

    1974-01-01

    A model for the radar return from bare ground was developed to calculate the radar cross section of bare ground and the effect of the frequency averaging on the reduction of the variance of the return. It is shown that, by assuming that the distribution of the slope to be Gaussian and that the distribution of the length of the facet to be in the form of the positive side of a Gaussian distribution, the results are in good agreement with experimental data collected by an 8- to 18-GHz radar spectrometer system. It is also shown that information on the exact correlation length of the small structure on the ground is not necessary; an effective correlation length may be calculated based on the facet model and the wavelength of the incident wave.

  5. Integrating Surface Modeling into the Engineering Design Graphics Curriculum

    ERIC Educational Resources Information Center

    Hartman, Nathan W.

    2006-01-01

    It has been suggested there is a knowledge base that surrounds the use of 3D modeling within the engineering design process and correspondingly within engineering design graphics education. While solid modeling receives a great deal of attention and discussion relative to curriculum efforts, and rightly so, surface modeling is an equally viable 3D…

  6. Assimilation of Satellite Remote Sensing Retrievals into Land Surface Models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For at least two decades, remote sensing observations have been used to define static model parameters and/or forcing inputs for a range of land surface models. However, recent advances in remote sensing theory have also enabled the satellite-based retrieval of dynamic land model states (e.g. leaf ...

  7. Fabrication, surface properties, and origin of superoleophobicity for a model textured surface.

    PubMed

    Zhao, Hong; Law, Kock-Yee; Sambhy, Varun

    2011-05-17

    Inspired by the superhydrophobic effect displayed in nature, we set out to mimic the interplay between the chemistry and physics in the lotus leaf to see if the same design principle can be applied to control wetting and adhesion between toners and inks on various printing surfaces. Since toners and inks are organic materials, superoleophobicity has become our design target. In this work, we report the design and fabrication of a model superoleophobic surface on silicon wafer. The model surface was created by photolithography, consisting of texture made of arrays of ∼3 μm diameter pillars, ∼7 μm in height with a center-to-center spacing of 6 μm. The surface was then made oleophobic with a fluorosilane coating, FOTS, synthesized by the molecular vapor deposition technique with tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane. Contact angle measurement shows that the surface exhibits super repellency toward water and oil (hexadecane) with a water and hexadecane contact angles at 156° and 158°, respectively. Since the sliding angles for both liquids are also very small (∼10°), we conclude that the model surface is both superhydrophobic and superoleophobic. By comparing with the contact angle data of the bare silicon surfaces (both smooth and textured), we also conclude that the superoleophobicity is a result of both surface texturing and fluorination. Results from investigations of the effects of surface modification and pillar geometry indicate that both surface oleophobicity and pillar geometry are contributors to the superoleophobicity. More specifically, we found that superoleophobicity can only be attained on our model textured surface when the flat surface coating has a relatively high oleophobicity (i.e., with a hexadecane contact angle of >73°). SEM examination of the pillars with higher magnification reveals that the side wall in each pillar is not smooth; rather it consists of a ∼300 nm wavy structure (due to the Bosch etching process

  8. Hydration dynamics near a model protein surface

    SciTech Connect

    Russo, Daniela; Hura, Greg; Head-Gordon, Teresa

    2003-09-01

    The evolution of water dynamics from dilute to very high concentration solutions of a prototypical hydrophobic amino acid with its polar backbone, N-acetyl-leucine-methylamide (NALMA), is studied by quasi-elastic neutron scattering and molecular dynamics simulation for both the completely deuterated and completely hydrogenated leucine monomer. We observe several unexpected features in the dynamics of these biological solutions under ambient conditions. The NALMA dynamics shows evidence of de Gennes narrowing, an indication of coherent long timescale structural relaxation dynamics. The translational water dynamics are analyzed in a first approximation with a jump diffusion model. At the highest solute concentrations, the hydration water dynamics is significantly suppressed and characterized by a long residential time and a slow diffusion coefficient. The analysis of the more dilute concentration solutions takes into account the results of the 2.0M solution as a model of the first hydration shell. Subtracting the first hydration layer based on the 2.0M spectra, the translational diffusion dynamics is still suppressed, although the rotational relaxation time and residential time are converged to bulk-water values. Molecular dynamics analysis shows spatially heterogeneous dynamics at high concentration that becomes homogeneous at more dilute concentrations. We discuss the hydration dynamics results of this model protein system in the context of glassy systems, protein function, and protein-protein interfaces.

  9. Modelling surface roughness and rocks in LRO Diviner observations

    NASA Astrophysics Data System (ADS)

    Williams, J.-P.; Hayne, P. O.; Paige, D. A.

    2012-09-01

    The Diviner Lunar Radiometer Experiment on NASA's Lunar Reconnaissance Orbiter (LRO) observes radiance in 7 infrared spectral channels from which brightness temperatures of the lunar surface are derived. In general, Diviner's surface footprint contains small scale variations in temperature. This anisothermality results in different observed brightness temperatures in Diviner's individual channels. A three-dimensional heat diffusion model is used to explore anisothermality in Diviner observations resulting from surface roughness and rocks at multiple length-scales and illumination conditions.

  10. Casimir energy in a spherical surface within surface impedance approach: The Drude model

    NASA Astrophysics Data System (ADS)

    Rosa, Luigi; Trozzo, Lucia

    2016-09-01

    The Casimir Energy of a spherical cavity whose surface is characterized by means of its surface impedance is calculated. The material properties of the boundary are described by means of the Drude model, so that a generalization of a previous result, based on plasma model, is obtained. The limits of the proposed approach are analyzed and a possible solution is suggested. The possibility of modulating the sign of the Casimir force from positive (repulsion) to negative (attraction) is studied.

  11. Mathematical and computer modeling of component surface shaping

    NASA Astrophysics Data System (ADS)

    Lyashkov, A.

    2016-04-01

    The process of shaping technical surfaces is an interaction of a tool (a shape element) and a component (a formable element or a workpiece) in their relative movements. It was established that the main objects of formation are: 1) a discriminant of a surfaces family, formed by the movement of the shape element relatively the workpiece; 2) an enveloping model of the real component surface obtained after machining, including transition curves and undercut lines; 3) The model of cut-off layers obtained in the process of shaping. When modeling shaping objects there are a lot of insufficiently solved or unsolved issues that make up a single scientific problem - a problem of qualitative shaping of the surface of the tool and then the component surface produced by this tool. The improvement of known metal-cutting tools, intensive development of systems of their computer-aided design requires further improvement of the methods of shaping the mating surfaces. In this regard, an important role is played by the study of the processes of shaping of technical surfaces with the use of the positive aspects of analytical and numerical mathematical methods and techniques associated with the use of mathematical and computer modeling. The author of the paper has posed and has solved the problem of development of mathematical, geometric and algorithmic support of computer-aided design of cutting tools based on computer simulation of the shaping process of surfaces.

  12. The SRFR 5 modeling system for surface irrigation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The SRFR program is a modeling system for surface irrigation. It is a central component of WinSRFR, a software package for the hydraulic analysis of surface irrigation systems. SRFR solves simplified versions of the equations of unsteady open channel flow coupled to a user selected infiltration mod...

  13. Advanced microwave forward model for the land surface data assimilation

    NASA Astrophysics Data System (ADS)

    Park, Chang-Hwan; Pause, Marion; Gayler, Sebastian; Wollschlaeger, Ute; Jackson, Thomas J.; LeDrew, Ellsworth; Behrendt, Andreas; Wulfmeyer, Volker

    2015-04-01

    From local to global scales, microwave remote-sensing techniques can provide temporally and spatially highly resolved observations of land surface properties including soil moisture and temperature as well as the state of vegetation. These variables are critical for agricultural productivity and water resource management. Furthermore, having accurate information of these variables allows us to improve the performances of numerical weather forecasts and climate prediction models. However, it is challenging to translate a measured brightness temperature into the multiple land surface properties because of the inherent inversion problem. In this study, we introduce a novel forward model for microwave remote sensing to resolve this inversion problem and to close the gap between land surface modeling and observations. It is composed of the Noah-MP land surface model as well as new models for the dielectric mixing and the radiative transfer. For developing a realistic forward operator, the land surface model must simulate soil and vegetation processes properly. The Noah-MP land surface model provides an excellent starting point because it contains already a sophisticated soil texture and land cover data set. Soil moisture transport is derived using the Richards equation in combination with a set of soil hydraulic parameters. Vegetation properties are considered using several photosynthesis models with different complexity. The energy balance is closed for the top soil and the vegetation layers. The energy flux becomes more realistic due to including not only the volumetric ratio of land surface properties but also their surface fraction as sub-grid scale information (semitile approach). Dielectric constant is the fundamental link to quantify the land surface properties. Our physical based new dielectric-mixing model is superior to previous calibration and semi-empirical approaches. Furthermore, owing to the consideration of the oversaturated surface dielectric behaviour

  14. Land Surface Verification Toolkit (LVT) - A Generalized Framework for Land Surface Model Evaluation

    NASA Technical Reports Server (NTRS)

    Kumar, Sujay V.; Peters-Lidard, Christa D.; Santanello, Joseph; Harrison, Ken; Liu, Yuqiong; Shaw, Michael

    2011-01-01

    Model evaluation and verification are key in improving the usage and applicability of simulation models for real-world applications. In this article, the development and capabilities of a formal system for land surface model evaluation called the Land surface Verification Toolkit (LVT) is described. LVT is designed to provide an integrated environment for systematic land model evaluation and facilitates a range of verification approaches and analysis capabilities. LVT operates across multiple temporal and spatial scales and employs a large suite of in-situ, remotely sensed and other model and reanalysis datasets in their native formats. In addition to the traditional accuracy-based measures, LVT also includes uncertainty and ensemble diagnostics, information theory measures, spatial similarity metrics and scale decomposition techniques that provide novel ways for performing diagnostic model evaluations. Though LVT was originally designed to support the land surface modeling and data assimilation framework known as the Land Information System (LIS), it also supports hydrological data products from other, non-LIS environments. In addition, the analysis of diagnostics from various computational subsystems of LIS including data assimilation, optimization and uncertainty estimation are supported within LVT. Together, LIS and LVT provide a robust end-to-end environment for enabling the concepts of model data fusion for hydrological applications. The evolving capabilities of LVT framework are expected to facilitate rapid model evaluation efforts and aid the definition and refinement of formal evaluation procedures for the land surface modeling community.

  15. Analysis and Modelling of Sea-Surface Doppler Spectra

    NASA Astrophysics Data System (ADS)

    Fois, F.; Hoogeboom, P.; Le Chevalier, F.; Stoffelen, A.

    2012-12-01

    The modelling of the Doppler spectrum of a time-varying ocean surface has gained considerable attention in the last decades. Knowledge of how the evolution of the ocean surface wave spectrum affects the scattered electromagnetic field is essential for a quantitative understanding of the properties of the measured microwave Doppler spectra. Complicated hydrodynamics, influencing the motion of the ocean surface waves, make this understanding significantly difficult. Non linear hydrodynamics couple the motion of the large and small waves and, consequently, change statistical characteristics and shapes of the surface-wave components. These hydrodynamic surface interactions are not included in the simplest linear sea-surface model, which assumes that each surface harmonic propagates according to the dispersion relation typical of water waves. In the past decades, Bass [1968] and Barrick [1972] used a surface perturbation theory to predict the Doppler spectra; Valenzuela and Laing [1970], instead, obtained similar results by using a composite surface model. Later, Doppler spectra were studied by Thompson [1989], who computed the spectra using a time-dependent composite model. Zavorotny and Voronovich [1998] made use of an approximate "two-scale" surface model based on a directional wave spectrum. However, currently available analytical scattering models are unreliable at high incidence angles and do not provide a full-polarimetric information. Exact numerical simulations of microwave scattering from time-varying ocean-like surfaces are highly recommended to eliminate concerns on the applicability of approximate models and to provide a validation tool for approximate scattering theories. A more realistic model, that accounts for hydrodynamic surface interactions, is the non-linear model for surface waves by Creamer et ali [1989]. Rino et ali [ 1991] were the first to use the Creamer model to simulate the Doppler spectra from dynamically evolving surface realizations

  16. Including Finite Surface Span Effects in Empirical Jet-Surface Interaction Noise Models

    NASA Technical Reports Server (NTRS)

    Brown, Clifford A.

    2016-01-01

    The effect of finite span on the jet-surface interaction noise source and the jet mixing noise shielding and reflection effects is considered using recently acquired experimental data. First, the experimental setup and resulting data are presented with particular attention to the role of surface span on far-field noise. These effects are then included in existing empirical models that have previously assumed that all surfaces are semi-infinite. This extended abstract briefly describes the experimental setup and data leaving the empirical modeling aspects for the final paper.

  17. Emissivity and reflection model for calculating unpolarized isotropic water surface-leaving radiance in the infrared. I: Theoretical development and calculations.

    PubMed

    Nalli, Nicholas R; Minnett, Peter J; van Delst, Paul

    2008-07-20

    Although published sea surface infrared (IR) emissivity models have gained widespread acceptance for remote sensing applications, discrepancies have been identified against field observations obtained from IR Fourier transform spectrometers at view angles approximately > 40 degrees. We therefore propose, in this two-part paper, an alternative approach for calculating surface-leaving IR radiance that treats both emissivity and atmospheric reflection in a systematic yet practical manner. This first part presents the theoretical basis, development, and computations of the proposed model. PMID:18641735

  18. Microwave Remote Sensing Modeling of Ocean Surface Salinity and Winds Using an Empirical Sea Surface Spectrum

    NASA Technical Reports Server (NTRS)

    Yueh, Simon H.

    2004-01-01

    Active and passive microwave remote sensing techniques have been investigated for the remote sensing of ocean surface wind and salinity. We revised an ocean surface spectrum using the CMOD-5 geophysical model function (GMF) for the European Remote Sensing (ERS) C-band scatterometer and the Ku-band GMF for the NASA SeaWinds scatterometer. The predictions of microwave brightness temperatures from this model agree well with satellite, aircraft and tower-based microwave radiometer data. This suggests that the impact of surface roughness on microwave brightness temperatures and radar scattering coefficients of sea surfaces can be consistently characterized by a roughness spectrum, providing physical basis for using combined active and passive remote sensing techniques for ocean surface wind and salinity remote sensing.

  19. Sulfur passivation of GaAs surfaces: A model for reduced surface recombination without band flattening

    NASA Astrophysics Data System (ADS)

    Spindt, C. J.; Spicer, W. E.

    1989-10-01

    It has been shown by several workers that the passivation of GaAs surfaces using sulfides results in a large reduction in the surface recombination velocity accompanied by an increase in the band bending on n-type samples. This apparently contradictory pair of results leads to the suggestion that the responsible electronic states are a midgap donor compensated by an acceptor near the valence-band maximum. We explore the consequences of such a model, particularly when the midgap state is assumed to be a double donor. In the double donor case, simple qualitative arguments indicate that the surface recombination velocity can be reduced by a factor much greater than the reduction in surface-state density. The model is consistent with observations made using a variety of experimental techniques. A correlation between the electronic states and surface chemistry is made, and the As and Ga antisite defects are discussed as candidates for the donor and acceptor states.

  20. "It's all about acceptance": A qualitative study exploring a model of positive body image for people with spinal cord injury.

    PubMed

    Bailey, K Alysse; Gammage, Kimberley L; van Ingen, Cathy; Ditor, David S

    2015-09-01

    Using modified constructivist grounded theory, the purpose of the present study was to explore positive body image experiences in people with spinal cord injury. Nine participants (five women, four men) varying in age (21-63 years), type of injury (C3-T7; complete and incomplete), and years post-injury (4-36 years) were recruited. The following main categories were found: body acceptance, body appreciation and gratitude, social support, functional gains, independence, media literacy, broadly conceptualizing beauty, inner positivity influencing outer demeanour, finding others who have a positive body image, unconditional acceptance from others, religion/spirituality, listening to and taking care of the body, managing secondary complications, minimizing pain, and respect. Interestingly, there was consistency in positive body image characteristics reported in this study with those found in previous research, demonstrating universality of positive body image. However, unique characteristics (e.g., resilience, functional gains, independence) were also reported demonstrating the importance of exploring positive body image in diverse groups. PMID:26002149

  1. Developing an Empirical Model for Jet-Surface Interaction Noise

    NASA Technical Reports Server (NTRS)

    Brown, Clif

    2014-01-01

    The process of developing an empirical model for jet-surface interaction noise is described and the resulting model evaluated. Jet-surface interaction noise is generated when the high-speed engine exhaust from modern tightly integrated or conventional high-bypass ratio engine aircraft strikes or flows over the airframe surfaces. An empirical model based on an existing experimental database is developed for use in preliminary design system level studies where computation speed and range of configurations is valued over absolute accuracy to select the most promising (or eliminate the worst) possible designs. The model developed assumes that the jet-surface interaction noise spectra can be separated from the jet mixing noise and described as a parabolic function with three coefficients: peak amplitude, spectral width, and peak frequency. These coefficients are t to functions of surface length and distance from the jet lipline to form a characteristic spectra which is then adjusted for changes in jet velocity and/or observer angle using scaling laws from published theoretical and experimental work. The resulting model is then evaluated for its ability to reproduce the characteristic spectra and then for reproducing spectra measured at other jet velocities and observer angles; successes and limitations are discussed considering the complexity of the jet-surface interaction noise versus the desire for a model that is simple to implement and quick to execute.

  2. Developing an Empirical Model for Jet-Surface Interaction Noise

    NASA Technical Reports Server (NTRS)

    Brown, Clifford A.

    2014-01-01

    The process of developing an empirical model for jet-surface interaction noise is described and the resulting model evaluated. Jet-surface interaction noise is generated when the high-speed engine exhaust from modern tightly integrated or conventional high-bypass ratio engine aircraft strikes or flows over the airframe surfaces. An empirical model based on an existing experimental database is developed for use in preliminary design system level studies where computation speed and range of configurations is valued over absolute accuracy to select the most promising (or eliminate the worst) possible designs. The model developed assumes that the jet-surface interaction noise spectra can be separated from the jet mixing noise and described as a parabolic function with three coefficients: peak amplitude, spectral width, and peak frequency. These coefficients are fit to functions of surface length and distance from the jet lipline to form a characteristic spectra which is then adjusted for changes in jet velocity and/or observer angle using scaling laws from published theoretical and experimental work. The resulting model is then evaluated for its ability to reproduce the characteristic spectra and then for reproducing spectra measured at other jet velocities and observer angles; successes and limitations are discussed considering the complexity of the jet-surface interaction noise versus the desire for a model that is simple to implement and quick to execute.

  3. Volume conduction in an anatomically based surface EMG model.

    PubMed

    Lowery, Madeleine M; Stoykov, Nikolay S; Dewald, Julius P A; Kuiken, Todd A

    2004-12-01

    A finite-element model to simulate surface electromyography (EMG) in a realistic human upper arm is presented. The model is used to explore the effect of limb geometry on surface-detected muscle fiber action potentials. The model was based on magnetic resonance images of the subject's upper arm and includes both resistive and capacitive material properties. To validate the model geometry, experimental and simulated potentials were compared at different electrode sites during the application of a subthreshold sinusoidal current source to the skin surface. Of the material properties examined, the closest approximation to the experimental data yielded a mean root-mean-square (rms) error of the normalized surface potential of 18% or 27%, depending on the site of the applied source. Surface-detected action potentials simulated using the realistic volume conductor model and an idealized cylindrical model based on the same limb geometry were then compared. Variation in the simulated limb geometry had a considerable effect on action potential shape. However, the rate of decay of the action potential amplitude with increasing distance from the fiber was similar in both models. Inclusion of capacitive material properties resulted in temporal low-pass filtering of the surface action potentials. This effect was most pronounced in the end-effect components of action potentials detected at locations far from the active fiber. It is concluded that accurate modeling of the limb geometry, asymmetry, tissue capacitance and fiber curvature is important when the specific action potential shapes are of interest. However, if the objective is to examine more qualitative features of the surface EMG signal, then an idealized volume conductor model with appropriate tissue thicknesses provides a close approximation. PMID:15605861

  4. Analytical and numerical modeling of surface morphologies in thin films

    SciTech Connect

    Genin, F.Y.

    1995-05-01

    Experimental studies have show that strains due to thermal expansion mismatch between a film and its substrate can produce very large stresses in the film that can lead to the formation of holes and hillocks. Based on a phenomenological description of the evolution of a solid surface under both capillary and stress driving forces and for surface and grain boundary self-diffusion, this article provides analytical and numerical solutions for surface profiles of model geometries in polycrystalline thin films. Results can explain a variety of surface morphologies commonly observed experimentally and are discussed to give some practical insights on how to control the growth of holes and hillocks in thin films.

  5. Modeling of turbulent transport in the surface layer

    NASA Technical Reports Server (NTRS)

    Smith, G. L.

    1973-01-01

    The turbulence equations as written by Donaldson using the method of invariant modeling have been applied to the following limiting cases of the surface or constant flux layer of the planetary boundary layer: (1) Neutrally stable; (2) stable (above influence of surface roughness); (3) nearly neutrally stable; and (4) very unstable (free convection). For the neutrally stable case, the equations are shown to admit as a solution the familiar logarithmic profile. By use of this result, boundary conditions suitable for the surface layer are defined and are simple to apply to rough surfaces.

  6. Gulf Stream model. [which considers surface elevation deviations

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Surface elevation deviations in the Gulf Stream region off the eastern coast of the United States between Wallops Island, Virginia and Miami, Florida were investigated. The main causes of surface elevation deviations are geoid perturbations due to the continental shelf and the geostrophic adjustment of the density field due to the Gulf Stream. Quantitative surface elevation profiles were calculated based on geophysical measurements of gravity anomalies and hydrographic data. The results are presented graphically along with contemporaneous weather data. Comparisons are made between the profiles based on hydrographic data and a mean theoretical model. The theory of geostrophic flows including some classical Gulf Stream models is also presented briefly.

  7. Hybrid Surface Mesh Adaptation for Climate Modeling

    SciTech Connect

    Khamayseh, Ahmed K; de Almeida, Valmor F; Hansen, Glen

    2008-01-01

    Solution-driven mesh adaptation is becoming quite popular for spatial error control in the numerical simulation of complex computational physics applications, such as climate modeling. Typically, spatial adaptation is achieved by element subdivision (h adaptation) with a primary goal of resolving the local length scales of interest. A second, less-popular method of spatial adaptivity is called "mesh motion" (r adaptation); the smooth repositioning of mesh node points aimed at resizing existing elements to capture the local length scales. This paper proposes an adaptation method based on a combination of both element subdivision and node point repositioning (rh adaptation). By combining these two methods using the notion of a mobility function, the proposed approach seeks to increase the flexibility and extensibility of mesh motion algorithms while providing a somewhat smoother transition between refined regions than is produced by element subdivision alone. Further, in an attempt to support the requirements of a very general class of climate simulation applications, the proposed method is designed to accommodate unstructured, polygonal mesh topologies in addition to the most popular mesh types.

  8. Hybrid Surface Mesh Adaptation for Climate Modeling

    SciTech Connect

    Ahmed Khamayseh; Valmor de Almeida; Glen Hansen

    2008-10-01

    Solution-driven mesh adaptation is becoming quite popular for spatial error control in the numerical simulation of complex computational physics applications, such as climate modeling. Typically, spatial adaptation is achieved by element subdivision (h adaptation) with a primary goal of resolving the local length scales of interest. A second, less-popular method of spatial adaptivity is called “mesh motion” (r adaptation); the smooth repositioning of mesh node points aimed at resizing existing elements to capture the local length scales. This paper proposes an adaptation method based on a combination of both element subdivision and node point repositioning (rh adaptation). By combining these two methods using the notion of a mobility function, the proposed approach seeks to increase the flexibility and extensibility of mesh motion algorithms while providing a somewhat smoother transition between refined regions than is produced by element subdivision alone. Further, in an attempt to support the requirements of a very general class of climate simulation applications, the proposed method is designed to accommodate unstructured, polygonal mesh topologies in addition to the most popular mesh types.

  9. Grid generation and surface modeling for CFD

    NASA Technical Reports Server (NTRS)

    Connell, Stuart D.; Sober, Janet S.; Lamson, Scott H.

    1995-01-01

    When computing the flow around complex three dimensional configurations, the generation of the mesh is the most time consuming part of any calculation. With some meshing technologies this can take of the order of a man month or more. The requirement for a number of design iterations coupled with ever decreasing time allocated for design leads to the need for a significant acceleration of this process. Of the two competing approaches, block-structured and unstructured, only the unstructured approach will allow fully automatic mesh generation directly from a CAD model. Using this approach coupled with the techniques described in this paper, it is possible to reduce the mesh generation time from man months to a few hours on a workstation. The desire to closely couple a CFD code with a design or optimization algorithm requires that the changes to the geometry be performed quickly and in a smooth manner. This need for smoothness necessitates the use of Bezier polynomials in place of the more usual NURBS or cubic splines. A two dimensional Bezier polynomial based design system is described.

  10. Modeling apple surface temperature dynamics based on weather data.

    PubMed

    Li, Lei; Peters, Troy; Zhang, Qin; Zhang, Jingjin; Huang, Danfeng

    2014-01-01

    The exposure of fruit surfaces to direct sunlight during the summer months can result in sunburn damage. Losses due to sunburn damage are a major economic problem when marketing fresh apples. The objective of this study was to develop and validate a model for simulating fruit surface temperature (FST) dynamics based on energy balance and measured weather data. A series of weather data (air temperature, humidity, solar radiation, and wind speed) was recorded for seven hours between 11:00-18:00 for two months at fifteen minute intervals. To validate the model, the FSTs of "Fuji" apples were monitored using an infrared camera in a natural orchard environment. The FST dynamics were measured using a series of thermal images. For the apples that were completely exposed to the sun, the RMSE of the model for estimating FST was less than 2.0 °C. A sensitivity analysis of the emissivity of the apple surface and the conductance of the fruit surface to water vapour showed that accurate estimations of the apple surface emissivity were important for the model. The validation results showed that the model was capable of accurately describing the thermal performances of apples under different solar radiation intensities. Thus, this model could be used to more accurately estimate the FST relative to estimates that only consider the air temperature. In addition, this model provides useful information for sunburn protection management. PMID:25350507

  11. Modeling Apple Surface Temperature Dynamics Based on Weather Data

    PubMed Central

    Li, Lei; Peters, Troy; Zhang, Qin; Zhang, Jingjin; Huang, Danfeng

    2014-01-01

    The exposure of fruit surfaces to direct sunlight during the summer months can result in sunburn damage. Losses due to sunburn damage are a major economic problem when marketing fresh apples. The objective of this study was to develop and validate a model for simulating fruit surface temperature (FST) dynamics based on energy balance and measured weather data. A series of weather data (air temperature, humidity, solar radiation, and wind speed) was recorded for seven hours between 11:00–18:00 for two months at fifteen minute intervals. To validate the model, the FSTs of “Fuji” apples were monitored using an infrared camera in a natural orchard environment. The FST dynamics were measured using a series of thermal images. For the apples that were completely exposed to the sun, the RMSE of the model for estimating FST was less than 2.0 °C. A sensitivity analysis of the emissivity of the apple surface and the conductance of the fruit surface to water vapour showed that accurate estimations of the apple surface emissivity were important for the model. The validation results showed that the model was capable of accurately describing the thermal performances of apples under different solar radiation intensities. Thus, this model could be used to more accurately estimate the FST relative to estimates that only consider the air temperature. In addition, this model provides useful information for sunburn protection management. PMID:25350507

  12. The Blake-Zisserman model for digital surface models segmentation

    NASA Astrophysics Data System (ADS)

    Zanetti, M.; Vitti, A.

    2013-10-01

    The Blake-Zisserman functional is a second-order variational model for data segmentation. The model is build up of several terms, the nature and the interaction of them allow to obtain a smooth approximation of the data that preserves the constant-gradient areas morphology, which are explicitly detected by partitioning the data with the graph of two special functions: the edge-detector function, which detects discontinuities of the datum, and the edge/crease-detector function, which also detects discontinuities of the gradient. First, the main features of the model are presented to justify the sense of the application of the model to DSMs. It is stressed the fact that the model can yield an almost piecewise-linear approximation of the data. This result is certainly of some interest for the specific application of the model to urban DSMs. Then, an example of its application is presented and the results are discussed to highlight how the features of the model affect the model outputs. The smooth approximation of the data produced by the model is thought to be a better candidate for further processing. In this sense, the application of the Blake-Zisserman model can be seen as a useful preprocessing step in the chain of DSMs processing. Eventually, some perspectives are presented to show some promising applications and developments of the Blake-Zisserman model.

  13. A physically based model of global freshwater surface temperature

    NASA Astrophysics Data System (ADS)

    van Beek, Ludovicus P. H.; Eikelboom, Tessa; van Vliet, Michelle T. H.; Bierkens, Marc F. P.

    2012-09-01

    Temperature determines a range of physical properties of water and exerts a strong control on surface water biogeochemistry. Thus, in freshwater ecosystems the thermal regime directly affects the geographical distribution of aquatic species through their growth and metabolism and indirectly through their tolerance to parasites and diseases. Models used to predict surface water temperature range between physically based deterministic models and statistical approaches. Here we present the initial results of a physically based deterministic model of global freshwater surface temperature. The model adds a surface water energy balance to river discharge modeled by the global hydrological model PCR-GLOBWB. In addition to advection of energy from direct precipitation, runoff, and lateral exchange along the drainage network, energy is exchanged between the water body and the atmosphere by shortwave and longwave radiation and sensible and latent heat fluxes. Also included are ice formation and its effect on heat storage and river hydraulics. We use the coupled surface water and energy balance model to simulate global freshwater surface temperature at daily time steps with a spatial resolution of 0.5° on a regular grid for the period 1976-2000. We opt to parameterize the model with globally available data and apply it without calibration in order to preserve its physical basis with the outlook of evaluating the effects of atmospheric warming on freshwater surface temperature. We validate our simulation results with daily temperature data from rivers and lakes (U.S. Geological Survey (USGS), limited to the USA) and compare mean monthly temperatures with those recorded in the Global Environment Monitoring System (GEMS) data set. Results show that the model is able to capture the mean monthly surface temperature for the majority of the GEMS stations, while the interannual variability as derived from the USGS and NOAA data was captured reasonably well. Results are poorest for

  14. Adhesion of perfume-filled microcapsules to model fabric surfaces.

    PubMed

    He, Yanping; Bowen, James; Andrews, James W; Liu, Min; Smets, Johan; Zhang, Zhibing

    2014-01-01

    The retention and adhesion of melamine formaldehyde (MF) microcapsules on a model fabric surface in aqueous solution were investigated using a customised flow chamber technique and atomic force microscopy (AFM). A cellulose film was employed as a model fabric surface. Modification of the cellulose with chitosan was found to increase the retention and adhesion of microcapsules on the model fabric surface. The AFM force-displacement data reveal that bridging forces resulting from the extension of cellulose chains dominate the adhesion between the microcapsule and the unmodified cellulose film, whereas electrostatic attraction helps the microcapsules adhere to the chitosan-modified cellulose film. The correlation between results obtained using these two complementary techniques suggests that the flow chamber device can be potentially used for rapid screening of the effect of chemical modification on the adhesion of microparticles to surfaces, reducing the time required to achieve an optimal formulation. PMID:24697187

  15. Influence of surface tension on fractal contact model

    NASA Astrophysics Data System (ADS)

    Long, J. M.; Wang, G. F.; Feng, X. Q.; Yu, S. W.

    2014-03-01

    Almost all solid surfaces have roughness on different length scales, from macro, micro to nano. In the conventional fractal contact model, the macroscopic Hertzian contact theory is employed to predict the contact load-area relation for all sizes of contact spots. However, when the contact radius of an asperity shrinks to nanometers, surface tension may greatly alter the contact behavior. In the present paper, we address surface effects on the contact between a rigid sphere and an elastic half space, and we demonstrate that the contact load-area relation is size-dependent, especially for nanosized asperities. Then, the refined contact relation is incorporated into the Majumdar-Bhushan fractal contact model. It is found that the presence of surface tension requires higher load than the conventional fractal contact model to generate the same real contact area.

  16. Comparison of Transmission Line Methods for Surface Acoustic Wave Modeling

    NASA Technical Reports Server (NTRS)

    Wilson, William; Atkinson, Gary

    2009-01-01

    Surface Acoustic Wave (SAW) technology is low cost, rugged, lightweight, extremely low power and can be used to develop passive wireless sensors. For these reasons, NASA is investigating the use of SAW technology for Integrated Vehicle Health Monitoring (IVHM) of aerospace structures. To facilitate rapid prototyping of passive SAW sensors for aerospace applications, SAW models have been developed. This paper reports on the comparison of three methods of modeling SAWs. The three models are the Impulse Response Method (a first order model), and two second order matrix methods; the conventional matrix approach, and a modified matrix approach that is extended to include internal finger reflections. The second order models are based upon matrices that were originally developed for analyzing microwave circuits using transmission line theory. Results from the models are presented with measured data from devices. Keywords: Surface Acoustic Wave, SAW, transmission line models, Impulse Response Method.

  17. Evaluation of air-soil temperature relationships simulated by land surface models during winter across the permafrost region

    NASA Astrophysics Data System (ADS)

    Wang, Wenli; Rinke, Annette; Moore, John C.; Ji, Duoying; Cui, Xuefeng; Peng, Shushi; Lawrence, David M.; McGuire, A. David; Burke, Eleanor J.; Chen, Xiaodong; Decharme, Bertrand; Koven, Charles; MacDougall, Andrew; Saito, Kazuyuki; Zhang, Wenxin; Alkama, Ramdane; Bohn, Theodore J.; Ciais, Philippe; Delire, Christine; Gouttevin, Isabelle; Hajima, Tomohiro; Krinner, Gerhard; Lettenmaier, Dennis P.; Miller, Paul A.; Smith, Benjamin; Sueyoshi, Tetsuo; Sherstiukov, Artem B.

    2016-08-01

    A realistic simulation of snow cover and its thermal properties are important for accurate modelling of permafrost. We analyse simulated relationships between air and near-surface (20 cm) soil temperatures in the Northern Hemisphere permafrost region during winter, with a particular focus on snow insulation effects in nine land surface models, and compare them with observations from 268 Russian stations. There are large cross-model differences in the simulated differences between near-surface soil and air temperatures (ΔT; 3 to 14 °C), in the sensitivity of soil-to-air temperature (0.13 to 0.96 °C °C-1), and in the relationship between ΔT and snow depth. The observed relationship between ΔT and snow depth can be used as a metric to evaluate the effects of each model's representation of snow insulation, hence guide improvements to the model's conceptual structure and process parameterisations. Models with better performance apply multilayer snow schemes and consider complex snow processes. Some models show poor performance in representing snow insulation due to underestimation of snow depth and/or overestimation of snow conductivity. Generally, models identified as most acceptable with respect to snow insulation simulate reasonable areas of near-surface permafrost (13.19 to 15.77 million km2). However, there is not a simple relationship between the sophistication of the snow insulation in the acceptable models and the simulated area of Northern Hemisphere near-surface permafrost, because several other factors, such as soil depth used in the models, the treatment of soil organic matter content, hydrology and vegetation cover, also affect the simulated permafrost distribution.

  18. The determination of the surface stress in an atmospheric model

    SciTech Connect

    Janseen, P.A.E.M. ); Beljaars, A.C.M.; Simmons, A.; Viterbo, P. )

    1992-12-01

    By forcing a third-generation wave-prediction model with surface stresses from the European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric model, it was discovered that lower wave heights were generated than by forcing with the ECMWF surface winds. The apparent inconsistency between surface stresses and surface winds in the atmospheric model turns out to be time-step dependent. A similar conclusion may be inferred from results of the WAMDI group. Apparently, a number of atmospheric models have inaccuracies in the boundary-layer scheme near the surface. In this paper it is argued that the reason for the inaccuracies is related to the numerical integration scheme that is used in these models. It is shown that a numerical scheme that treats physics and dynamics separately has an equilibrium that is time-step dependent. An alternative scheme-namely, simultaneous, implicit treatment of both physics and dynamics-removes this deficiency. Possible consequences for atmospheric-, wave-, and ocean-circulation models are briefly discussed.

  19. Validating regional-scale surface energy balance models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    One of the major challenges in developing reliable regional surface flux models is the relative paucity of scale-appropriate validation data. Direct comparisons between coarse-resolution model flux estimates and flux tower data can often be dominated by sub-pixel heterogeneity effects, making it di...

  20. Assessing the ability of mechanistic volatilization models to simulate soil surface conditions: a study with the Volt'Air model.

    PubMed

    Garcia, L; Bedos, C; Génermont, S; Braud, I; Cellier, P

    2011-09-01

    Ammonia and pesticide volatilization in the field is a surface phenomenon involving physical and chemical processes that depend on the soil surface temperature and water content. The water transfer, heat transfer and energy budget sub models of volatilization models are adapted from the most commonly accepted formalisms and parameterizations. They are less detailed than the dedicated models describing water and heat transfers and surface status. The aim of this work was to assess the ability of one of the available mechanistic volatilization models, Volt'Air, to accurately describe the pedo-climatic conditions of a soil surface at the required time and space resolution. The assessment involves: (i) a sensitivity analysis, (ii) an evaluation of Volt'Air outputs in the light of outputs from a reference Soil-Vegetation-Atmosphere Transfer model (SiSPAT) and three experimental datasets, and (iii) the study of three tests based on modifications of SiSPAT to establish the potential impact of the simplifying assumptions used in Volt'Air. The analysis confirmed that a 5 mm surface layer was well suited, and that Volt'Air surface temperature correlated well with the experimental measurements as well as with SiSPAT outputs. In terms of liquid water transfers, Volt'Air was overall consistent with SiSPAT, with discrepancies only during major rainfall events and dry weather conditions. The tests enabled us to identify the main source of the discrepancies between Volt'Air and SiSPAT: the lack of gaseous water transfer description in Volt'Air. They also helped to explain why neither Volt'Air nor SiSPAT was able to represent lower values of surface water content: current classical water retention and hydraulic conductivity models are not yet adapted to cases of very dry conditions. Given the outcomes of this study, we discuss to what extent the volatilization models can be improved and the questions they pose for current research in water transfer modeling and parameterization

  1. Alloy Design Workbench-Surface Modeling Package Developed

    NASA Technical Reports Server (NTRS)

    Abel, Phillip B.; Noebe, Ronald D.; Bozzolo, Guillermo H.; Good, Brian S.; Daugherty, Elaine S.

    2003-01-01

    NASA Glenn Research Center's Computational Materials Group has integrated a graphical user interface with in-house-developed surface modeling capabilities, with the goal of using computationally efficient atomistic simulations to aid the development of advanced aerospace materials, through the modeling of alloy surfaces, surface alloys, and segregation. The software is also ideal for modeling nanomaterials, since surface and interfacial effects can dominate material behavior and properties at this level. Through the combination of an accurate atomistic surface modeling methodology and an efficient computational engine, it is now possible to directly model these types of surface phenomenon and metallic nanostructures without a supercomputer. Fulfilling a High Operating Temperature Propulsion Components (HOTPC) project level-I milestone, a graphical user interface was created for a suite of quantum approximate atomistic materials modeling Fortran programs developed at Glenn. The resulting "Alloy Design Workbench-Surface Modeling Package" (ADW-SMP) is the combination of proven quantum approximate Bozzolo-Ferrante-Smith (BFS) algorithms (refs. 1 and 2) with a productivity-enhancing graphical front end. Written in the portable, platform independent Java programming language, the graphical user interface calls on extensively tested Fortran programs running in the background for the detailed computational tasks. Designed to run on desktop computers, the package has been deployed on PC, Mac, and SGI computer systems. The graphical user interface integrates two modes of computational materials exploration. One mode uses Monte Carlo simulations to determine lowest energy equilibrium configurations. The second approach is an interactive "what if" comparison of atomic configuration energies, designed to provide real-time insight into the underlying drivers of alloying processes.

  2. A theoretical model for lunar surface material thermal conductivity.

    NASA Technical Reports Server (NTRS)

    Khader, M. S.; Vachon, R. I.

    1973-01-01

    This paper presents a theoretical thermal conductivity model for the uppermost layer of lunar surface material under the lunar vacuum environment. The model assumes that the lunar soil can be simulated by spherical particles in contact with each other and that the effective thermal conductivity is a function of depth, temperature, porosity, particle dimension, and mechanical-thermal properties of the solid particles. Two modes of heat transport are considered, conduction and radiation - with emphasis on the contact resistance between particles. The model gives effective conductivity values that compare favorably with the experimental data from lunar surface samples obtained on Apollo 11 and 12 missions.

  3. Modeling surface segregation phenomena in the (111) surface of ordered Pt3Ti crystal

    NASA Astrophysics Data System (ADS)

    Duan, Zhiyao; Zhong, Jun; Wang, Guofeng

    2010-09-01

    We investigated the surface segregation phenomena in the (111) surface of ordered Pt3Ti crystal using density functional theory (DFT) calculation (with no configuration sampling) and Monte Carlo (MC) simulation method (employing modified embedded atom method potentials and with extensive configuration sampling). Our DFT study suggested that the off-stoichiometric effect (specifically, a Pt concentration higher than 75 at. %) accounted for the experimentally observed Pt segregation to the outermost layer of the Pt3Ti (111). Our MC simulations predicted that in a Pt3Ti (111) sample with a Pt concentration slightly above 75 at. %, Pt atoms would segregate to the surface to form a pure Pt outermost layer, while the ordered Pt3Ti crystal structure would be maintained in the second layer and below. Moreover, our DFT calculations revealed that the d-band center of the Pt-segregated Pt3Ti (111) surface would downshift by 0.21 eV as compared to that of a pure Pt (111) surface. As a result, O adsorption energy on the Pt-segregated Pt3Ti (111) surface was found to be at least 0.16 eV weaker than that on the pure Pt (111) surface. Thus, we theoretically modeled the geometric and electronic structures of the Pt-segregated Pt3Ti (111) surface and further suggested that the Pt surface segregation could lead to enhanced catalytic activity for oxygen reduction reactions on Pt3Ti alloy catalysts.

  4. Wetting dynamics of alkyl ketene dimer on cellulosic model surfaces

    SciTech Connect

    Garnier, G.; Bertin, M.; Smrckova, M.

    1999-10-26

    The dynamic wetting of a commercial alkyl ketene dimer (AKD) wax was measured on model cellulosic surfaces. The variables investigated were temperature and the surface composition. The model surfaces consisted of cellulose and cellulose acetate films as well as glass. These surfaces are smooth by industrial standards but not on a molecular level. The objective of the study was to predict the extent of AKD wetting during the time frame of papermaking. For smooth surfaces, AKD particles wet but do not spread on the hydrophilic surfaces investigated. AKD wetting proceeds from the balance of the interfacial forces with the viscous dissipation. The effect of gravity can be neglected for papermaking conditions. The Hoffman-Tanner equation modified for partial wetting provided a very good fit of the dynamic wetting. The slope of the graph is a function of temperature but not of the solid surface composition. Maslyiah's model also fits the experimental results well, but with a physically unrealistic value of the fitting parameter. For partial wetting, the complex but rigorous Cox equation is recommended to estimate the slip length over macroscopic wetting dimensions.

  5. Superhydrophobic surfaces: A model approach to predict contact angle and surface energy of soil particles

    NASA Astrophysics Data System (ADS)

    Shirtcliffe, Neil; Hamlett, Christopher; McHale, Glen; Newton, Michael; Bachmann, Joerg; Woche, S.

    2010-05-01

    C. Hamlett(a), G. McHALE(a), N. Shirtcliffe(a), M. Newton(a), S.K. Woche(b), and J. BACHMANN(b) aSchool of Science & Technology, Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, UK and bInstitute of Soil Science, Leibniz University Hannover, Herrenhaeuser Str.2, 30419, Hannover, Germany. Summary Wettability of soil affects a wide variety of processes including infiltration, preferential flow and surface runoff. The problem of determining contact angles and surface energy of powders, such as soil particles, remains unsolved. So far, several theories and approaches have been proposed, but formulation of surface and interfacial free energy, as regards its components, is still a very debatable issue. In the present study, the general problem of the interpretation of contact angles and surface free energy on chemically heterogeneous and rough soil particle surfaces are evaluated by a reformulation of the Cassie-Baxter equation assuming that the particles are attached on to a plane and rigid surface. Compared with common approaches, our model considers a roughness factor which depends on the Young's Law contact angle determined by the surface chemistry. Results of the model are discussed and compared with independent contact angle measurements using the Sessile Drop and the Wilhelmy Plate methods. Based on contact angle data, the critical surface tension of the grains were determined by the method proposed by Zisman. Experiments were made with glass beads and three soil materials ranging from sand to clay. Soil particles were coated with different loadings of dichlorodimethylsilane (DCDMS) to vary the wettability. Varying the solid surface tension using DCDMS treatments provided pure water wetting behaviours ranging from wettable to extremely hydrophobic with contact angles >150°. Results showed that the critical surface energy measured on grains with the highest DCDMS loadings was similar to the surface energy measured independently on ideal DCDMS

  6. Analysis of Surface Heterogeneity Effects with Mesoscale Terrestrial Modeling Platforms

    NASA Astrophysics Data System (ADS)

    Simmer, C.

    2015-12-01

    An improved understanding of the full variability in the weather and climate system is crucial for reducing the uncertainty in weather forecasting and climate prediction, and to aid policy makers to develop adaptation and mitigation strategies. A yet unknown part of uncertainty in the predictions from the numerical models is caused by the negligence of non-resolved land surface heterogeneity and the sub-surface dynamics and their potential impact on the state of the atmosphere. At the same time, mesoscale numerical models using finer horizontal grid resolution [O(1)km] can suffer from inconsistencies and neglected scale-dependencies in ABL parameterizations and non-resolved effects of integrated surface-subsurface lateral flow at this scale. Our present knowledge suggests large-eddy-simulation (LES) as an eventual solution to overcome the inadequacy of the physical parameterizations in the atmosphere in this transition scale, yet we are constrained by the computational resources, memory management, big-data, when using LES for regional domains. For the present, there is a need for scale-aware parameterizations not only in the atmosphere but also in the land surface and subsurface model components. In this study, we use the recently developed Terrestrial Systems Modeling Platform (TerrSysMP) as a numerical tool to analyze the uncertainty in the simulation of surface exchange fluxes and boundary layer circulations at grid resolutions of the order of 1km, and explore the sensitivity of the atmospheric boundary layer evolution and convective rainfall processes on land surface heterogeneity.

  7. Using water isotopes in the evaluation of land surface models

    NASA Astrophysics Data System (ADS)

    Guglielmo, Francesca; Risi, Camille; Ottlé, Catherine; Bastrikov, Vladislav; Valdayskikh, Victor; Cattani, Olivier; Jouzel, Jean; Gribanov, Konstantin; Nekrasova, Olga; Zacharov, Vyacheslav; Ogée, Jérôme; Wingate, Lisa; Raz-Yaseef, Naama

    2013-04-01

    Several studies show that uncertainties in the representation of land surface processes contribute significantly to the spread in projections for the hydrological cycle. Improvements in the evaluation of land surface models would therefore translate into more reliable predictions of future changes. The isotopic composition of water is affected by phase transitions and, for this reason, is a good tracer for the hydrological cycle. Particularly relevant for the assessment of land surface processes is the fact that bare soil evaporation and transpiration bear different isotopic signatures. Water isotopic measurement could thus be employed in the evaluation of the land surface hydrological budget. With this objective, isotopes have been implemented in the most recent version of the land surface model ORCHIDEE. This model has undergone considerable development in the past few years. In particular, a newly discretised (11 layers) hydrology aims at a more realistic representation of the soil water budget. In addition, biogeophysical processes, as, for instance, the dynamics of permafrost and of its interaction with snow and vegetation, have been included. This model version will allow us to better resolve vertical profiles of soil water isotopic composition and to more realistically simulate the land surface hydrological and isotopic budget in a broader range of climate zones. Model results have been evaluated against temperature profiles and isotopes measurements in soil and stem water at sites located in semi-arid (Yatir), temperate (Le Bray) and boreal (Labytnangi) regions. Seasonal cycles are reasonably well reproduced. Furthermore, a sensitivity analysis investigates to what extent water isotopic measurements in soil water can help constrain the representation of land surface processes, with a focus on the partitioning between evaporation and transpiration. In turn, improvements in the description of this partitioning may help reduce the uncertainties in the land

  8. Comparison between Utsu's and Vere-Jones' aftershocks model by means of a computer simulation based on the acceptance-rejection sampling of von Neumann

    NASA Astrophysics Data System (ADS)

    Reyes, J.; Morales-Esteban, A.; González, E.; Martínez-Álvarez, F.

    2016-07-01

    In this research, a new algorithm for generating a stochastic earthquake catalog is presented. The algorithm is based on the acceptance-rejection sampling of von Neumann. The result is a computer simulation of earthquakes based on the calculated statistical properties of each zone. Vere-Jones states that an earthquake sequence can be modeled as a series of random events. This is the model used in the proposed simulation. Contrariwise, Utsu indicates that the mainshocks are special geophysical events. The algorithm has been applied to zones of Chile, China, Spain, Japan, and the USA. This allows classifying the zones according to Vere-Jones' or Utsu's model. The results have been quantified relating the mainshock with the largest aftershock within the next 5 days (which has been named as Bath event). The results show that some zones fit Utsu's model and others Vere-Jones'. Finally, the fraction of seismic events that satisfy certain properties of magnitude and occurrence is analyzed.

  9. Coopersmith Self-Esteem: Two Different Hypothesized Factor Models--Both Acceptable for the Same Data Structure.

    ERIC Educational Resources Information Center

    Hofmann, Rich; Sherman, Larry

    Using data from 135 sixth-, seventh-, and eighth-graders between 11 and 15 years old attending a middle school in a suburban Southwest Ohio school district, two hypothesized models of the factor structures for the Coopersmith Self-Esteem Inventory were tested. One model represents the original Coopersmith factor structure, and the other model is…

  10. SSM - SOLID SURFACE MODELER, VERSION 6.0

    NASA Technical Reports Server (NTRS)

    Goza, S. P.

    1994-01-01

    The Solid Surface Modeler (SSM) is an interactive graphics software application for solid-shaded and wireframe three- dimensional geometric modeling. It enables the user to construct models of real-world objects as simple as boxes or as complex as Space Station Freedom. The program has a versatile user interface that, in many cases, allows mouse input for intuitive operation or keyboard input when accuracy is critical. SSM can be used as a stand-alone model generation and display program and offers high-fidelity still image rendering. Models created in SSM can also be loaded into other software for animation or engineering simulation. (See the information below for the availability of SSM with the Object Orientation Manipulator program, OOM, a graphics software application for three-dimensional rendering and animation.) Models are constructed within SSM using functions of the Create Menu to create, combine, and manipulate basic geometric building blocks called primitives. Among the simpler primitives are boxes, spheres, ellipsoids, cylinders, and plates; among the more complex primitives are tubes, skinned-surface models and surfaces of revolution. SSM also provides several methods for duplicating models. Constructive Solid Geometry (CSG) is one of the most powerful model manipulation tools provided by SSM. The CSG operations implemented in SSM are union, subtraction and intersection. SSM allows the user to transform primitives with respect to each axis, transform the camera (the user's viewpoint) about its origin, apply texture maps and bump maps to model surfaces, and define color properties; to select and combine surface-fill attributes, including wireframe, constant, and smooth; and to specify models' points of origin (the positions about which they rotate). SSM uses Euler angle transformations for calculating the results of translation and rotation operations. The user has complete control over the modeling environment from within the system. A variety of file

  11. Assessment of Response Surface Models using Independent Confirmation Point Analysis

    NASA Technical Reports Server (NTRS)

    DeLoach, Richard

    2010-01-01

    This paper highlights various advantages that confirmation-point residuals have over conventional model design-point residuals in assessing the adequacy of a response surface model fitted by regression techniques to a sample of experimental data. Particular advantages are highlighted for the case of design matrices that may be ill-conditioned for a given sample of data. The impact of both aleatory and epistemological uncertainty in response model adequacy assessments is considered.

  12. Uniform surface complexation approaches to radionuclide sorption modeling

    SciTech Connect

    Turner, D.R.; Pabalan, R.T.; Muller, P.; Bertetti, F.P.

    1995-12-01

    Simplified surface complexation models, based on a uniform set of model parameters have been developed to address complex radionuclide sorption behavior. Existing data have been examined, and interpreted using numerical nonlinear least-squares optimization techniques to determine the necessary binding constants. Simplified modeling approaches have generally proven successful at simulating and predicting radionuclide sorption on (hydr)oxides and aluminosilicates over a wide range of physical and chemical conditions.

  13. A surface plasmon model for laser ablation of Ag sup + ions from a roughened Ag surface

    SciTech Connect

    Ritchie, R.H. Tennessee Univ., Knoxville, TN . Dept. of Physics); Manson, J.R. . Dept. of Physics); Echenique, P.M. . Faculdad de Quimica)

    1991-01-01

    Experimental work by Shea and Compton suggests that Ag{sup +} ions emitted from a roughened Ag surface irradiated by a nanosecond or picosecond laser beam may absorb the full energy of the Ag surface plasmon. We have modeled this process under the assumption that it proceeds through an inverse bremsstrahlung-type absorption of the SP quantum by Ag{sup +} ion which also undergoes a small-impact parameter collision with another ion or atom in the vicinity of the surface. We give a quantitative estimate of the absorption probability and find reasonable agreement with the Shea-Compton results. 8 refs., 2 figs.

  14. Improved representation of surface-groundwater interactions in land surface models

    NASA Astrophysics Data System (ADS)

    Ganji, Arman; Sushama, Laxmi

    2016-04-01

    Surface-groundwater interactions are important and determine the evolution of hydrologic variables such as soil moisture, evapotranspiration and surface runoff. Despite its importance, groundwater is not explicitly represented in many land surface schemes, used in climate models. In this study, the Canadian Land Surface Scheme (CLASS), which is used in the Canadian regional and global climate models, is modified to include groundwater dynamics. The impact of these modifications on the regional hydrology is assessed by comparing three simulations, performed with the original and modified versions of CLASS, driven by atmospheric forcing data from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-Interim), for the 1980-2011 period, over a northeast Canadian domain. The modified and original versions of CLASS differ in the underlying boundary condition for soil layer hydrology, with one version being based on gravitational drainage from an original version of CLASS and the other one is newly proposed unconfined groundwater at the depth of bedrock layer. Results suggest statistically significant increases in soil moisture, during the spring and summer seasons, for the simulation with the new groundwater scheme, compared to the original version of CLASS, which is also reflected in the increased summer surface runoff and streamflows in this simulation with modified CLASS, over most of the study domain. The streamflows in this simulation is in better agreement to those observed. This study thus demonstrates the importance of groundwater scheme in land surface models for realistic simulation of hydrological processes.

  15. Fractal prediction model of thermal contact conductance of rough surfaces

    NASA Astrophysics Data System (ADS)

    Ji, Cuicui; Zhu, Hua; Jiang, Wei

    2013-01-01

    The thermal contact conductance problem is an important issue in studying the heat transfer of engineering surfaces, which has been widely studied since last few decades, and for predicting which many theoretical models have been established. However, the models which have been existed are lack of objectivity due to that they are mostly studied based on the statistical methodology characterization for rough surfaces and simple partition for the deformation formats of contact asperity. In this paper, a fractal prediction model is developed for the thermal contact conductance between two rough surfaces based on the rough surface being described by three-dimensional Weierstrass and Mandelbrot fractal function and assuming that there are three kinds of asperity deformation modes: elastic, elastoplastic and fully plastic. Influences of contact load and contact area as well as fractal parameters and material properties on the thermal contact conductance are investigated by using the presented model. The investigation results show that the thermal contact conductance increases with the increasing of the contact load and contact area. The larger the fractal dimension, or the smaller the fractal roughness, the larger the thermal contact conductance is. The thermal contact conductance increases with decreasing the ratio of Young's elastic modulus to the microhardness. The results obtained indicate that the proposed model can effectively predict the thermal contact conductance at the interface, which provide certain reference to the further study on the issue of heat transfer between contact surfaces.

  16. Modelling cell motility and chemotaxis with evolving surface finite elements

    PubMed Central

    Elliott, Charles M.; Stinner, Björn; Venkataraman, Chandrasekhar

    2012-01-01

    We present a mathematical and a computational framework for the modelling of cell motility. The cell membrane is represented by an evolving surface, with the movement of the cell determined by the interaction of various forces that act normal to the surface. We consider external forces such as those that may arise owing to inhomogeneities in the medium and a pressure that constrains the enclosed volume, as well as internal forces that arise from the reaction of the cells' surface to stretching and bending. We also consider a protrusive force associated with a reaction–diffusion system (RDS) posed on the cell membrane, with cell polarization modelled by this surface RDS. The computational method is based on an evolving surface finite-element method. The general method can account for the large deformations that arise in cell motility and allows the simulation of cell migration in three dimensions. We illustrate applications of the proposed modelling framework and numerical method by reporting on numerical simulations of a model for eukaryotic chemotaxis and a model for the persistent movement of keratocytes in two and three space dimensions. Movies of the simulated cells can be obtained from http://homepages.warwick.ac.uk/∼maskae/CV_Warwick/Chemotaxis.html. PMID:22675164

  17. Surface differentiation by parametric modeling of infrared intensity scans

    NASA Astrophysics Data System (ADS)

    Aytac, Tayfun; Barshan, Billur

    2005-06-01

    We differentiate surfaces with different properties with simple low-cost IR emitters and detectors in a location-invariant manner. The intensity readings obtained with such sensors are highly dependent on the location and properties of the surface, which complicates the differentiation and localization process. Our approach, which models IR intensity scans parametrically, can distinguish different surfaces independent of their positions. Once the surface type is identified, its position (r,θ) can also be estimated. The method is verified experimentally with wood; Styrofoam packaging material; white painted matte wall; white and black cloth; and white, brown, and violet paper. A correct differentiation rate of 100% is achieved for six surfaces, and the surfaces are localized within absolute range and azimuth errors of 0.2 cm and 1.1 deg, respectively. The differentiation rate decreases to 86% for seven surfaces and to 73% for eight surfaces. The method demonstrated shows that simple IR sensors, when coupled with appropriate signal processing, can be used to recognize different types of surfaces in a location-invariant manner.

  18. Scale-adaptive surface modeling of vascular structures

    PubMed Central

    2010-01-01

    Background The effective geometric modeling of vascular structures is crucial for diagnosis, therapy planning and medical education. These applications require good balance with respect to surface smoothness, surface accuracy, triangle quality and surface size. Methods Our method first extracts the vascular boundary voxels from the segmentation result, and utilizes these voxels to build a three-dimensional (3D) point cloud whose normal vectors are estimated via covariance analysis. Then a 3D implicit indicator function is computed from the oriented 3D point cloud by solving a Poisson equation. Finally the vessel surface is generated by a proposed adaptive polygonization algorithm for explicit 3D visualization. Results Experiments carried out on several typical vascular structures demonstrate that the presented method yields both a smooth morphologically correct and a topologically preserved two-manifold surface, which is scale-adaptive to the local curvature of the surface. Furthermore, the presented method produces fewer and better-shaped triangles with satisfactory surface quality and accuracy. Conclusions Compared to other state-of-the-art approaches, our method reaches good balance in terms of smoothness, accuracy, triangle quality and surface size. The vessel surfaces produced by our method are suitable for applications such as computational fluid dynamics simulations and real-time virtual interventional surgery. PMID:21087525

  19. Internal Physical Features of a Land Surface Model Employing a Tangent Linear Model

    NASA Technical Reports Server (NTRS)

    Yang, Runhua; Cohn, Stephen E.; daSilva, Arlindo; Joiner, Joanna; Houser, Paul R.

    1997-01-01

    The Earth's land surface, including its biomass, is an integral part of the Earth's weather and climate system. Land surface heterogeneity, such as the type and amount of vegetative covering., has a profound effect on local weather variability and therefore on regional variations of the global climate. Surface conditions affect local weather and climate through a number of mechanisms. First, they determine the re-distribution of the net radiative energy received at the surface, through the atmosphere, from the sun. A certain fraction of this energy increases the surface ground temperature, another warms the near-surface atmosphere, and the rest evaporates surface water, which in turn creates clouds and causes precipitation. Second, they determine how much rainfall and snowmelt can be stored in the soil and how much instead runs off into waterways. Finally, surface conditions influence the near-surface concentration and distribution of greenhouse gases such as carbon dioxide. The processes through which these mechanisms interact with the atmosphere can be modeled mathematically, to within some degree of uncertainty, on the basis of underlying physical principles. Such a land surface model provides predictive capability for surface variables including ground temperature, surface humidity, and soil moisture and temperature. This information is important for agriculture and industry, as well as for addressing fundamental scientific questions concerning global and local climate change. In this study we apply a methodology known as tangent linear modeling to help us understand more deeply, the behavior of the Mosaic land surface model, a model that has been developed over the past several years at NASA/GSFC. This methodology allows us to examine, directly and quantitatively, the dependence of prediction errors in land surface variables upon different vegetation conditions. The work also highlights the importance of accurate soil moisture information. Although surface

  20. Application of the PTT model to axisymmetric free surface flows

    NASA Astrophysics Data System (ADS)

    Merejolli, R.; Paulo, G. S.; Tomé, M. F.

    2013-10-01

    This work is concerned with numerical simulation of axisymmetric viscoelastic free surface flows using the Phan-Thien-Tanner (PTT) constitutive equation. A finite difference technique for solving the governing equations for unsteady incompressible flows written in Cylindrical coordinates on a staggered grid is described. The fluid is modelled by a Marker-and-Cell type method and an accurate representation of the fluid surface is employed. The full free surface stress conditions are applied. The numerical method is verified by comparing numerical predictions of fully developed flow in a pipe with the corresponding analytic solutions. To demonstrate that the numerical method can simulate axisymmetric free surface flows governed by the PTT model, numerical results of the flow evolution of a drop impacting on a rigid dry plate are presented. In these simulations, the rheological effects of the parameters ɛ and ξ are investigated.

  1. Left Ventricle Segmentation Using Model Fitting and Active Surfaces

    PubMed Central

    Tay, Peter C.; Li, Bing; Garson, Chris D.; Acton, Scott T.; Hossack, John A.

    2010-01-01

    A method to perform 4D (3D over time) segmentation of the left ventricle of a mouse heart using a set of B mode cine slices acquired in vivo from a series of short axis scans is described. We incorporate previously suggested methods such as temporal propagation, the gradient vector flow active surface, superquadric models, etc. into our proposed 4D segmentation of the left ventricle. The contributions of this paper are incorporation of a novel despeckling method and the use of locally fitted superellipsoid models to provide a better initialization for the active surface segmentation algorithm. Average distances of the improved surface segmentation to a manually segmented surface throughout the entire cardiac cycle and cross-sectional contours are provided to demonstrate the improvements produced by the proposed 4D segmentation. PMID:20300558

  2. A surface mass balance model for the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Bougamont, Marion; Bamber, Jonathan L.; Greuell, Wouter

    2005-12-01

    A surface mass balance model aimed at being coupled to a Global Circulation Model (GCM) for future climate prediction is described and tested for the Greenland Ice Sheet. The model builds on previous modeling designed to be forced by automatic weather station data, and includes surface energy balance as well as processes occurring near the surface such as water percolation and refreezing. Surface albedo is calculated with a new scheme that differentiates the timescale for aging of wet and dry snow and incorporates the effect of a thin layer of water and/or fresh snow at the surface. The model was driven with automatic weather station data from two sites located in the ablation zone in the Kangerlussuaq area (West Greenland), and calculated reasonable annual mass balance values (within 10% in seven out of eight cases) for four individual and consecutive years (1998-2001), using both measured and calculated albedo. This implies that the albedo parameterization is adequate and climate feedbacks affecting the mass balance are well captured. The model was then applied to a distributed 20-km-resolution grid covering the whole ice sheet, and forced with 10 years of the European Centre for Medium-range Weather Forecast (ECMWF) reanalysis (ERA-40) data. With the aim of coupling the model to a GCM, this study focuses on the ability to model the interannual variability in mass balance rather than to assess the present state of balance of the ice sheet. Modeled spatial and temporal wet zone extent compares well with information derived from passive microwave satellite data.

  3. Land Surface Temperature Variational Assimilation within the ORCHIDEE Continental Surface model

    NASA Astrophysics Data System (ADS)

    Benavides-Pinjosovsky, H. S.; Ottle, C.; Thiria, S.; Badran, F.; Crepon, M. R.; Maugis, P.; Brajard, J.

    2013-12-01

    Variational data assimilation is applied to the energy and water budgets modules of the ORCHIDEE land surface model. This part of the model called SECHIBA, describes the exchanges of water and energy between the surface and the atmosphere. The adjoint semi-generator software called YAO is used as a framework to implement 4D-Var assimilation. First, sensitivity analysis was performed in order to validate the adjoint and to identify the most influential parameters. Following, the results of twin experiments using synthetic observations, are shown in order to demonstrate the robustness of the assimilation. In addition, assimilation were made using observational meteorology dataset from the Surface Monitoring Of Soil Reservoir EXperiment (SMOSREX). The results obtained when controlling the most sensitive parameters and the initial soil water content, show the flexibility of the assimilation scheme and the potential of land surface temperature variational data assimilation to improve model calibration and reduce prediction errors. Keywords: Sensibility Analysis, Data Assimilation, Model Calibration, Land Surface Temperature

  4. Modeling of gun barrel surface erosion: Historic perspective

    SciTech Connect

    Buckingham, A.C.

    1996-08-01

    Results and interpretations of numerical simulations of some dominant processes influencing gun barrel propellant combustion and flow-induced erosion are presented. Results include modeled influences of erosion reduction techniques such as solid additives, vapor phase chemical modifications, and alteration of surface solid composition through use of thin coatings. Precedents and historical perspective are provided with predictions from traditional interior ballistics compared to computer simulations. Accelerating reactive combustion flow, multiphase and multicomponent transport, flow-to-surface thermal/momentum/phase change/gas-surface chemical exchanges, surface and micro-depth subsurface heating/stress/composition evolution and their roles in inducing surface cracking, spall, ablation, melting, and vaporization are considered. Recognition is given to cyclic effects of previous firing history on material preconditioning. Current perspective and outlook for future are based on results of a US Army-LLNL erosion research program covering 7 y in late 1970s. This is supplemented by more recent research on hypervelocity electromagnetic projectile launchers.

  5. Modeling surface backgrounds from radon progeny plate-out

    SciTech Connect

    Perumpilly, G.; Guiseppe, V. E.; Snyder, N.

    2013-08-08

    The next generation low-background detectors operating deep underground aim for unprecedented low levels of radioactive backgrounds. The surface deposition and subsequent implantation of radon progeny in detector materials will be a source of energetic background events. We investigate Monte Carlo and model-based simulations to understand the surface implantation profile of radon progeny. Depending on the material and region of interest of a rare event search, these partial energy depositions can be problematic. Motivated by the use of Ge crystals for the detection of neutrinoless double-beta decay, we wish to understand the detector response of surface backgrounds from radon progeny. We look at the simulation of surface decays using a validated implantation distribution based on nuclear recoils and a realistic surface texture. Results of the simulations and measured α spectra are presented.

  6. Modelling of frost formation and growth on microstuctured surface

    NASA Astrophysics Data System (ADS)

    Muntaha, Md. Ali; Haider, Md. Mushfique; Rahman, Md. Ashiqur

    2016-07-01

    Frost formation on heat exchangers is an undesirable phenomenon often encountered in different applications where the cold surface with a temperature below freezing point of water is exposed to humid air. The formation of frost on the heat transfer surface results in an increase in pressure drop and reduction in heat transfer, resulting in a reduction of the system efficiency. Many factors, including the temperature and moisture content of air, cold plate temperature, surface wettability etc., are known to affect frost formation and growth. In our present study, a model for frost growth on rectangular, periodic microgroove surfaces for a range of microgroove dimension (ten to hundreds of micron) is presented. The mathematical model is developed analytically by solving the governing heat and mass transfer equations with appropriate boundary conditions using the EES (Engineering Equation Solver) software. For temperature, a convective boundary condition at frost-air interface and a fixed cold plate surface temperature is used. Instead of considering the saturation or super-saturation models, density gradient at the surface is obtained by considering experimentally-found specified heat flux. The effect of surface wettability is incorporated by considering the distribution of condensed water droplets at the early stage of frost formation. Thickness, density and thermal conductivity of frost layer on the micro-grooved surfaces are found to vary with the dimension of the grooves. The variation of density and thickness of the frost layer on these micro-grooved surfaces under natural convection is numerally determined for a range of plate temperature and air temperature conditions and is compared with experimental results found in the open literature.

  7. Laboratories for the 21st Century: Best Practices; Modeling Exhaust Dispersion for Specifying Acceptable Exhaust/Intake Design (Brochure)

    SciTech Connect

    Not Available

    2011-09-01

    This guide provides general information on specifying acceptable exhaust and intake designs. It also provides various quantitative approaches that can be used to determine expected concentration levels resulting from exhaust system emissions. In addition, the guide describes methodologies that can be employed to operate laboratory exhaust systems in a safe and energy efficient manner by using variable air volume (VAV) technology. The guide, one in a series on best practices for laboratories, was produced by Laboratories for the 21st Century (Labs21), a joint program of the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Energy (DOE). Geared toward architects, engineers, and facility managers, the guides contain information about technologies and practices to use in designing, constructing, and operating safe, sustainable, high-performance laboratories. Studies show a direct relationship between indoor air quality and the health and productivity of building occupants. Historically, the study and protection of indoor air quality focused on emission sources emanating from within the building. For example, to ensure that the worker is not exposed to toxic chemicals, 'as manufactured' and 'as installed' containment specifications are required for fume hoods. However, emissions from external sources, which may be re-ingested into the building through closed circuiting between the building's exhaust stacks and air intakes, are an often overlooked aspect of indoor air quality.

  8. Modeling GPR data from lidar soil surface profile

    NASA Astrophysics Data System (ADS)

    Burns, Brian; Clark, William W.; McMichael, Ian

    2012-06-01

    Ground Penetrating Radar (GPR) has been applied for several years to the problem of detecting both anti-personnel and anti-tank landmines. One major challenge for reliable mine detection using GPR is removing the response from the ground. When the ground is flat this is a straightforward process. For the NIITEK GPR, the flat ground will show up as one of the largest responses and will be consistent across all the channels, making the surface simple to detect and remove. Typically, the largest responses from each channel, assumed to be the surface, are aligned in range and then zeroed out. When the ground is not flat, the response from the ground becomes more complicated making it no longer possible to just assume the largest response is from the ground. Also, certain soil surface features can create responses that look very similar to those of mines. To further complicate the ground removal process, the motion of the GPR antenna is not measured, making it impossible to determine if the ground or antenna is moving from just the GPR data. To address surface clutter issues arising from uneven ground, NVESD investigated profiling the soil surface with a LIDAR. The motion of both the LIDAR and GPR was tracked so the relative locations could be determined. Using the LIDAR soil surface profile, GPR data was modeled using a simplified version of the Physical Optics model. This modeled data could then be subtracted from the measured GPR data, leaving the response without the soil surface. In this paper we present a description and results from an experiment conducted with a NIITEK GPR and LIDAR over surface features and buried landmines. A description of the model used to generate the GPR response from the soil and the algorithm that was used to subtract the two provided. Mine detection performances using both GPR only and GPR with LIDAR algorithms are compared.

  9. Geometry of surfaces associated to Grassmannian sigma models

    NASA Astrophysics Data System (ADS)

    Delisle, L.; Hussin, V.; Zakrzewski, W. J.

    2015-04-01

    We investigate the geometric characteristics of constant Gaussian curvature surfaces obtained from solutions of the G(m, n) sigma model. Most of these solutions are related to the Veronese sequence. We show that we can distinguish surfaces with the same Gaussian curvature using additional quantities like the topological charge and the mean curvature. The cases of G(1,n) = CPn-1 and G(2,n) are used to illustrate these characteristics.

  10. Modeling of reservoir compaction and surface subsidence at South Belridge

    SciTech Connect

    Hansen, K.S.; Chan, C.K.; Prats, M.

    1995-08-01

    Finite-element models of depletion-induced reservoir compaction and surface subsidence have been calibrated with observed subsidence, locations of surface fissures, and regions of subsurface casing damage at South Belridge and used predictively for the evaluation of alternative reservoir-development plans. Pressure maintenance through diatomite waterflooding appears to be a beneficial means of minimizing additional subsidence and fissuring as well as reducing axial-compressive-type casing damage.

  11. Modeling the Surface Temperature of Earth-like Planets

    NASA Astrophysics Data System (ADS)

    Vladilo, Giovanni; Silva, Laura; Murante, Giuseppe; Filippi, Luca; Provenzale, Antonello

    2015-05-01

    We introduce a novel Earth-like planet surface temperature model (ESTM) for habitability studies based on the spatial-temporal distribution of planetary surface temperatures. The ESTM adopts a surface energy balance model (EBM) complemented by: radiative-convective atmospheric column calculations, a set of physically based parameterizations of meridional transport, and descriptions of surface and cloud properties more refined than in standard EBMs. The parameterization is valid for rotating terrestrial planets with shallow atmospheres and moderate values of axis obliquity (ɛ ≲ 45{}^\\circ ). Comparison with a 3D model of atmospheric dynamics from the literature shows that the equator-to-pole temperature differences predicted by the two models agree within ≈ 5 K when the rotation rate, insolation, surface pressure and planet radius are varied in the intervals 0.5≲ {Ω }/{{{Ω }}\\oplus }≲ 2, 0.75≲ S/{{S}\\circ }≲ 1.25, 0.3≲ p/(1 bar)≲ 10, and 0.5≲ R/{{R}\\oplus }≲ 2, respectively. The ESTM has an extremely low computational cost and can be used when the planetary parameters are scarcely known (as for most exoplanets) and/or whenever many runs for different parameter configurations are needed. Model simulations of a test-case exoplanet (Kepler-62e) indicate that an uncertainty in surface pressure within the range expected for terrestrial planets may impact the mean temperature by ˜ 60 K. Within the limits of validity of the ESTM, the impact of surface pressure is larger than that predicted by uncertainties in rotation rate, axis obliquity, and ocean fractions. We discuss the possibility of performing a statistical ranking of planetary habitability taking advantage of the flexibility of the ESTM.

  12. Regional scale hydrology with a new land surface processes model

    NASA Technical Reports Server (NTRS)

    Laymon, Charles; Crosson, William

    1995-01-01

    Through the CaPE Hydrometeorology Project, we have developed an understanding of some of the unique data quality issues involved in assimilating data of disparate types for regional-scale hydrologic modeling within a GIS framework. Among others, the issues addressed here include the development of adequate validation of the surface water budget, implementation of the STATSGO soil data set, and implementation of a remote sensing-derived landcover data set to account for surface heterogeneity. A model of land surface processes has been developed and used in studies of the sensitivity of surface fluxes and runoff to soil and landcover characterization. Results of these experiments have raised many questions about how to treat the scale-dependence of land surface-atmosphere interactions on spatial and temporal variability. In light of these questions, additional modifications are being considered for the Marshall Land Surface Processes Model. It is anticipated that these techniques can be tested and applied in conjunction with GCIP activities over regional scales.

  13. A model of the diurnal variation in lake surface temperature

    NASA Astrophysics Data System (ADS)

    Hodges, Jonathan L.

    Satellite measurements of water surface temperature can benefit several environmental applications such as predictions of lake evaporation, meteorological forecasts, and predictions of lake overturning events, among others. However, limitations on the temporal resolution of satellite measurements restrict these improvements. A model of the diurnal variation in lake surface temperature could potentially increase the effective temporal resolution of satellite measurements of surface temperature, thereby enhancing the utility of these measurements in the above applications. Herein, a one-dimensional transient thermal model of a lake is used in combination with surface temperature measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard the Aqua and Terra satellites, along with ambient atmospheric conditions from local weather stations, and bulk temperature measurements to calculate the diurnal surface temperature variation for the five major lakes in the Savannah River Basin in South Carolina: Lakes Jocassee, Keowee, Hartwell, Russell, and Thurmond. The calculated solutions are used to obtain a functional form for the diurnal surface temperature variation of these lakes. Differences in diurnal variation in surface temperature between each of these lakes are identified and potential explanations for these differences are presented.

  14. Photosynthesis sensitivity to climate change in land surface models

    NASA Astrophysics Data System (ADS)

    Manrique-Sunen, Andrea; Black, Emily; Verhoef, Anne; Balsamo, Gianpaolo

    2016-04-01

    Accurate representation of vegetation processes within land surface models is key to reproducing surface carbon, water and energy fluxes. Photosynthesis determines the amount of CO2 fixated by plants as well as the water lost in transpiration through the stomata. Photosynthesis is calculated in land surface models using empirical equations based on plant physiological research. It is assumed that CO2 assimilation is either CO2 -limited, radiation -limited ; and in some models export-limited (the speed at which the products of photosynthesis are used by the plant) . Increased levels of atmospheric CO2 concentration tend to enhance photosynthetic activity, but the effectiveness of this fertilization effect is regulated by environmental conditions and the limiting factor in the photosynthesis reaction. The photosynthesis schemes at the 'leaf level' used by land surface models JULES and CTESSEL have been evaluated against field photosynthesis observations. Also, the response of photosynthesis to radiation, atmospheric CO2 and temperature has been analysed for each model, as this is key to understanding the vegetation response that climate models using these schemes are able to reproduce. Particular emphasis is put on the limiting factor as conditions vary. It is found that while at present day CO2 concentrations export-limitation is only relevant at low temperatures, as CO2 levels rise it becomes an increasingly important restriction on photosynthesis.

  15. Modeling studies of geothermal systems with a free water surface

    SciTech Connect

    Bodvarsson, G.S.; Pruess, K.

    1983-12-01

    A numerical simulator was developed for the modeling of air-steam-water systems. The simulator was applied to various problems involving injection into or production from a geothermal reservoir in hydraulic communication with a shallow free-surface aquifer. First, a one-dimensional column problem is considered and the water level movement during exploitation is studied using different capillary pressure functions. Second, a two-dimensional radial model is used to study and compare reservoir depletion for cases with and without a free-surface aquifer. Finally, the contamination of a shallow free-surface aquifer due to cold water injection is investigated. The primary aim of these studies is to obtain an understanding of the response of a reservoir in hydraulic communication with a unconfined aquifer during exploitation or injection and to determine under which circumstances conventional modeling techniques (fully saturated systems) can be applied to such systems.

  16. Surface photovoltage measurements and finite element modeling of SAW devices.

    SciTech Connect

    Donnelly, Christine

    2012-03-01

    Over the course of a Summer 2011 internship with the MEMS department of Sandia National Laboratories, work was completed on two major projects. The first and main project of the summer involved taking surface photovoltage measurements for silicon samples, and using these measurements to determine surface recombination velocities and minority carrier diffusion lengths of the materials. The SPV method was used to fill gaps in the knowledge of material parameters that had not been determined successfully by other characterization methods. The second project involved creating a 2D finite element model of a surface acoustic wave device. A basic form of the model with the expected impedance response curve was completed, and the model is ready to be further developed for analysis of MEMS photonic resonator devices.

  17. Atomistic modelling of residual stress at UO2 surfaces.

    PubMed

    Arayro, Jack; Tréglia, Guy; Ribeiro, Fabienne

    2016-01-13

    Modelling oxide surface behaviour is of both technological and fundamental interest. In particular, in the case of the UO2 system, which is of major importance in the nuclear industry, it is essential to account for the link between microstructure and macroscopic mechanical properties. Indeed micromechanical models at the mesoscale need to be supplied by the energetic and stress data calculated at the nanoscale. In this framework, we present a theoretical study, coupling an analytical model and thermostatistical simulation to investigate the modifications induced by the presence of a surface regarding atomic relaxation and energetic and stress profiles. In particular, we show that the surface effective thickness as well as the stress profile, which are required by micromechanical approaches, are strongly anisotropic. PMID:26648246

  18. Novel Surface Reaction Model in Dry-Etching Process Simulator

    NASA Astrophysics Data System (ADS)

    Misaka, Akio; Harafuji, Kenji; Kubota, Masafumi; Nomura, Noboru

    1992-12-01

    A new surface reaction model has been presented to simulate topological evolutions by taking into account the existence of adsorbed radicals on the substrate surface. The model treats the etching rate as a function of the coverage ratio by adsorbed radicals on the surface. Based on the model, a two-dimensional topography simulator has been developed. The simulator is applied to silicon-dioxide trench etchings made by hydrofluorocarbon gases. First, micro-loading effects in an important ion-assisted etching process are studied. It is confirmed that the micro-loading effect is due to the shortage of supplied active radicals inside the trench structure. Secondly, the competitive process between etching and deposition is examined. The side-wall protection phenomena resulting from the process are well simulated.

  19. An Algebraic Spline Model of Molecular Surfaces for Energetic Computations

    PubMed Central

    Zhao, Wenqi; Bajaj, Chandrajit; Xu, Guoliang

    2009-01-01

    In this paper, we describe a new method to generate a smooth algebraic spline (AS) approximation of the molecular surface (MS) based on an initial coarse triangulation derived from the atomic coordinate information of the biomolecule, resident in the PDB (Protein data bank). Our method first constructs a triangular prism scaffold covering the PDB structure, and then generates a piecewise polynomial F on the Bernstein-Bezier (BB) basis within the scaffold. An ASMS model of the molecular surface is extracted as the zero contours of F which is nearly C1 and has dual implicit and parametric representations. The dual representations allow us easily do the point sampling on the ASMS model and apply it to the accurate estimation of the integrals involved in the electrostatic solvation energy computations. Meanwhile comparing with the trivial piecewise linear surface model, fewer number of sampling points are needed for the ASMS, which effectively reduces the complexity of the energy estimation. PMID:21519111

  20. Gender and Acceptance of E-Learning: A Multi-Group Analysis Based on a Structural Equation Model among College Students in Chile and Spain

    PubMed Central

    2015-01-01

    The scope of this study was to evaluate whether the adoption of e-learning in two universities, and in particular, the relationship between the perception of external control and perceived ease of use, is different because of gender differences. The study was carried out with participating students in two different universities, one in Chile and one in Spain. The Technology Acceptance Model was used as a theoretical framework for the study. A multi-group analysis method in partial least squares was employed to relate differences between groups. The four main conclusions of the study are: (1) a version of the Technology Acceptance Model has been successfully used to explain the process of adoption of e-learning at an undergraduate level of study; (2) the finding of a strong and significant relationship between perception of external control and perception of ease of use of the e-learning platform; (3) a significant relationship between perceived enjoyment and perceived ease of use and between results demonstrability and perceived usefulness is found; (4) the study indicates a few statistically significant differences between males and females when adopting an e-learning platform, according to the tested model. PMID:26465895

  1. Gender and Acceptance of E-Learning: A Multi-Group Analysis Based on a Structural Equation Model among College Students in Chile and Spain.

    PubMed

    Ramírez-Correa, Patricio E; Arenas-Gaitán, Jorge; Rondán-Cataluña, F Javier

    2015-01-01

    The scope of this study was to evaluate whether the adoption of e-learning in two universities, and in particular, the relationship between the perception of external control and perceived ease of use, is different because of gender differences. The study was carried out with participating students in two different universities, one in Chile and one in Spain. The Technology Acceptance Model was used as a theoretical framework for the study. A multi-group analysis method in partial least squares was employed to relate differences between groups. The four main conclusions of the study are: (1) a version of the Technology Acceptance Model has been successfully used to explain the process of adoption of e-learning at an undergraduate level of study; (2) the finding of a strong and significant relationship between perception of external control and perception of ease of use of the e-learning platform; (3) a significant relationship between perceived enjoyment and perceived ease of use and between results demonstrability and perceived usefulness is found; (4) the study indicates a few statistically significant differences between males and females when adopting an e-learning platform, according to the tested model. PMID:26465895

  2. Two-scale modeling of adsorption processes at structured surfaces

    NASA Astrophysics Data System (ADS)

    Kundin, Julia; de Cuba, Maria Radke; Gemming, Sibylle; Emmerich, Heike

    2009-01-01

    We present an algorithm for the simulation of vicinal surface growth. It combines a lattice gas anisotropic Ising model with a phase-field model. The molecular behavior of individual adatoms is described by the lattice gas model. The microstructure dynamics on the vicinal surface are calculated using the phase-field method. In this way, adsorption processes on two different length scales can be described: nucleation processes on the terraces (lattice gas model) and step-flow growth (phase field model). The hybrid algorithm that is proposed here, is therefore able to describe an epitaxial layer-by-layer growth controlled by temperature and by deposition rate. This method is faster than kinetic Monte Carlo simulations and can take into account the stochastic processes in a comparable way.

  3. Evaluating soil moisture constraints on surface fluxes in land surface models globally

    NASA Astrophysics Data System (ADS)

    Harris, Phil; Gallego-Elvira, Belen; Taylor, Christopher; Folwell, Sonja; Ghent, Darren; Veal, Karen; Hagemann, Stefan

    2016-04-01

    Soil moisture availability exerts a strong control over land evaporation in many regions. However, global climate models (GCMs) disagree on when and where evaporation is limited by soil moisture. Evaluation of the relevant modelled processes has suffered from a lack of reliable, global observations of land evaporation at the GCM grid box scale. Satellite observations of land surface temperature (LST) offer spatially extensive but indirect information about the surface energy partition and, under certain conditions, about soil moisture availability on evaporation. Specifically, as soil moisture decreases during rain-free dry spells, evaporation may become limited leading to increases in LST and sensible heat flux. We use MODIS Terra and Aqua observations of LST at 1 km from 2000 to 2012 to assess changes in the surface energy partition during dry spells lasting 10 days or longer. The clear-sky LST data are aggregated to a global 0.5° grid before being composited as a function dry spell day across many events in a particular region and season. These composites are then used to calculate a Relative Warming Rate (RWR) between the land surface and near-surface air. This RWR can diagnose the typical strength of short term changes in surface heat fluxes and, by extension, changes in soil moisture limitation on evaporation. Offline land surface model (LSM) simulations offer a relatively inexpensive way to evaluate the surface processes of GCMs. They have the benefits that multiple models, and versions of models, can be compared on a common grid and using unbiased forcing. Here, we use the RWR diagnostic to assess global, offline simulations of several LSMs (e.g., JULES and JSBACH) driven by the WATCH Forcing Data-ERA Interim. Both the observed RWR and the LSMs use the same 0.5° grid, which allows the observed clear-sky sampling inherent in the underlying MODIS LST to be applied to the model outputs directly. This approach avoids some of the difficulties in analysing free

  4. Coupled surface-water and ground-water model

    USGS Publications Warehouse

    Swain, Eric D.; Wexler, Eliezer J.

    1991-01-01

    In areas with dynamic and hydraulically well connected ground-water and surface-water systems, it is desirable that stream-aquifer interaction be simulated with models of equal sophistication and accuracy. Accordingly, a new, coupled ground-water and surface-water model was developed by combining the U.S. Geological Survey models MODFLOW and BRANCH. MODFLOW is the widely used modular three-dimensional, finite-difference, ground-water model and BRANCH is a one-dimensional numerical model commonly used to simulate flow in open-channel networks. Because time steps used in ground-water modeling commonly are much longer than those used in surface-water simulations, provision has been made for handling multiple BRANCH time steps within one MODFLOW time step. Verification testing of the coupled model was done using data from previous studies and by comparing results with output from a simpler four-point implicit open-channel flow model linked with MODFLOW.

  5. Enhancing the Representation of Subgrid Land Surface Characteristics in Land Surface Models

    SciTech Connect

    Ke, Yinghai; Leung, Lai-Yung R.; Huang, Maoyi; Li, Hongyi

    2013-09-27

    Land surface heterogeneity has long been recognized and increasingly incorporated in the land surface modelling. In most existing land surface models, the spatial variability of surface cover is represented as subgrid composition of multiple surface cover types. In this study, we developed a new subgrid classification method (SGC) that accounts for the topographic variability of the vegetation cover. Each model grid cell was represented with a number of elevation classes and each elevation class was further described by a number of vegetation types. The numbers of elevation classes and vegetation types were variable and optimized for each model grid so that the spatial variability of both elevation and vegetation can be reasonably explained given a pre-determined total number of classes. The subgrid structure of the Community Land Model (CLM) was used as an example to illustrate the newly developed method in this study. With similar computational burden as the current subgrid vegetation representation in CLM, the new method is able to explain at least 80% of the total subgrid PFTs and greatly reduced the variations of elevation within each subgrid class compared to the baseline method where a single elevation class is assigned to each subgrid PFT. The new method was also evaluated against two other subgrid methods (SGC1 and SGC2) that assigned fixed numbers of elevation and vegetation classes for each model grid with different perspectives of surface cover classification. Implemented at five model resolutions (0.1°, 0.25°, 0.5°, 1.0° and 2.0°) with three maximum-allowed total number of classes N_class of 24, 18 and 12 representing different computational burdens over the North America (NA) continent, the new method showed variable performances compared to the SGC1 and SGC2 methods. However, the advantage of the SGC method over the other two methods clearly emerged at coarser model resolutions and with moderate computational intensity (N_class = 18) as it

  6. Modeling the Asteroseismic Surface Term across the HR Diagram

    NASA Astrophysics Data System (ADS)

    Schmitt, Joseph R.; Basu, Sarbani

    2015-08-01

    Asteroseismology is a powerful tool that can precisely characterize the mass, radius, and other properties of field stars. However, our inability to properly model the near-surface layers of stars creates a frequency-dependent frequency difference between the observed and the modeled frequencies, usually referred to as the “surface term.” This surface term can add significant errors to the derived stellar properties unless removed properly. In this paper, we simulate surface terms across a significant portion of the HR diagram, exploring four different masses (M=0.8,1.0,1.2, and 1.5 {M}⊙ ) at five metallicities ([{Fe}/{{H}}]=0.5,0.0,-0.5,-1.0, and -1.5) from the main sequence to red giants for stars with {T}{eff}\\lt 6500 K and explore how well the most common ways of fitting and removing the surface term actually perform. We find that the two-term model proposed by Ball & Gizon works much better than other models across a large portion of the HR diagram, including the red giants, leading us to recommend its use for future asteroseismic analyses.

  7. Modeling electron emission and surface effects from diamond cathodes

    SciTech Connect

    Dimitrov, D. A.; Smithe, D.; Cary, J. R.; Ben-Zvi, I.; Rao, T.; Smedley, J.; Wang, E.

    2015-02-07

    We developed modeling capabilities, within the Vorpal particle-in-cell code, for three-dimensional simulations of surface effects and electron emission from semiconductor photocathodes. They include calculation of emission probabilities using general, piece-wise continuous, space-time dependent surface potentials, effective mass, and band bending field effects. We applied these models, in combination with previously implemented capabilities for modeling charge generation and transport in diamond, to investigate the emission dependence on applied electric field in the range from approximately 2 MV/m to 17 MV/m along the [100] direction. The simulation results were compared to experimental data. For the considered parameter regime, conservation of transverse electron momentum (in the plane of the emission surface) allows direct emission from only two (parallel to [100]) of the six equivalent lowest conduction band valleys. When the electron affinity χ is the only parameter varied in the simulations, the value χ = 0.31 eV leads to overall qualitative agreement with the probability of emission deduced from experiments. Including band bending in the simulations improves the agreement with the experimental data, particularly at low applied fields, but not significantly. Using surface potentials with different profiles further allows us to investigate the emission as a function of potential barrier height, width, and vacuum level position. However, adding surface patches with different levels of hydrogenation, modeled with position-dependent electron affinity, leads to the closest agreement with the experimental data.

  8. Modeling electron emission and surface effects from diamond cathodes

    SciTech Connect

    Dimitrov, D. A.; Smithe, D.; Cary, J. R.; Ben-Zvi, I.; Rao, T.; Smedley, J.; Wang, E.

    2015-02-05

    We developed modeling capabilities, within the Vorpal particle-in-cell code, for three-dimensional (3D) simulations of surface effects and electron emission from semiconductor photocathodes. They include calculation of emission probabilities using general, piece-wise continuous, space-time dependent surface potentials, effective mass and band bending field effects. We applied these models, in combination with previously implemented capabilities for modeling charge generation and transport in diamond, to investigate the emission dependence on applied electric field in the range from approximately 2 MV/m to 17 MV/m along the [100] direction. The simulation results were compared to experimental data. For the considered parameter regime, conservation of transverse electron momentum (in the plane of the emission surface) allows direct emission from only two (parallel to [100]) of the six equivalent lowest conduction band valleys. When the electron affinity χ is the only parameter varied in the simulations, the value χ = 0.31 eV leads to overall qualitative agreement with the probability of emission deduced from experiments. Including band bending in the simulations improves the agreement with the experimental data, particularly at low applied fields, but not significantly. In this study, using surface potentials with different profiles further allows us to investigate the emission as a function of potential barrier height, width, and vacuum level position. However, adding surface patches with different levels of hydrogenation, modeled with position-dependent electron affinity, leads to the closest agreement with the experimental data.

  9. Surface complexation modeling of americium sorption onto volcanic tuff.

    PubMed

    Ding, M; Kelkar, S; Meijer, A

    2014-10-01

    Results of a surface complexation model (SCM) for americium sorption on volcanic rocks (devitrified and zeolitic tuff) are presented. The model was developed using PHREEQC and based on laboratory data for americium sorption on quartz. Available data for sorption of americium on quartz as a function of pH in dilute groundwater can be modeled with two surface reactions involving an americium sulfate and an americium carbonate complex. It was assumed in applying the model to volcanic rocks from Yucca Mountain, that the surface properties of volcanic rocks can be represented by a quartz surface. Using groundwaters compositionally representative of Yucca Mountain, americium sorption distribution coefficient (Kd, L/Kg) values were calculated as function of pH. These Kd values are close to the experimentally determined Kd values for americium sorption on volcanic rocks, decreasing with increasing pH in the pH range from 7 to 9. The surface complexation constants, derived in this study, allow prediction of sorption of americium in a natural complex system, taking into account the inherent uncertainty associated with geochemical conditions that occur along transport pathways. PMID:24963803

  10. Modeling electron emission and surface effects from diamond cathodes

    DOE PAGESBeta

    Dimitrov, D. A.; Smithe, D.; Cary, J. R.; Ben-Zvi, I.; Rao, T.; Smedley, J.; Wang, E.

    2015-02-05

    We developed modeling capabilities, within the Vorpal particle-in-cell code, for three-dimensional (3D) simulations of surface effects and electron emission from semiconductor photocathodes. They include calculation of emission probabilities using general, piece-wise continuous, space-time dependent surface potentials, effective mass and band bending field effects. We applied these models, in combination with previously implemented capabilities for modeling charge generation and transport in diamond, to investigate the emission dependence on applied electric field in the range from approximately 2 MV/m to 17 MV/m along the [100] direction. The simulation results were compared to experimental data. For the considered parameter regime, conservation of transversemore » electron momentum (in the plane of the emission surface) allows direct emission from only two (parallel to [100]) of the six equivalent lowest conduction band valleys. When the electron affinity χ is the only parameter varied in the simulations, the value χ = 0.31 eV leads to overall qualitative agreement with the probability of emission deduced from experiments. Including band bending in the simulations improves the agreement with the experimental data, particularly at low applied fields, but not significantly. In this study, using surface potentials with different profiles further allows us to investigate the emission as a function of potential barrier height, width, and vacuum level position. However, adding surface patches with different levels of hydrogenation, modeled with position-dependent electron affinity, leads to the closest agreement with the experimental data.« less

  11. Incorporating groundwater-surface water interaction into river management models.

    PubMed

    Valerio, Allison; Rajaram, Harihar; Zagona, Edith

    2010-01-01

    Accurate representation of groundwater-surface water interactions is critical to modeling low river flows in the semi-arid southwestern United States. Although a number of groundwater-surface water models exist, they are seldom integrated with river operation/management models. A link between the object-oriented river and reservoir operations model, RiverWare, and the groundwater model, MODFLOW, was developed to incorporate groundwater-surface water interaction processes, such as river seepage/gains, riparian evapotranspiration, and irrigation return flows, into a rule-based water allocations model. An explicit approach is used in which the two models run in tandem, exchanging data once in each computational time step. Because the MODFLOW grid is typically at a finer resolution than RiverWare objects, the linked model employs spatial interpolation and summation for compatible communication of exchanged variables. The performance of the linked model is illustrated through two applications in the Middle Rio Grande Basin in New Mexico where overappropriation impacts endangered species habitats. In one application, the linked model results are compared with historical data; the other illustrates use of the linked model for determining management strategies needed to attain an in-stream flow target. The flows predicted by the linked model at gauge locations are reasonably accurate except during a few very low flow periods when discrepancies may be attributable to stream gaging uncertainties or inaccurate documentation of diversions. The linked model accounted for complex diversions, releases, groundwater pumpage, irrigation return flows, and seepage between the groundwater system and canals/drains to achieve a schedule of releases that satisfied the in-stream target flow. PMID:20412319

  12. Modeling of surface roughness effects on glaze ice accretion

    NASA Technical Reports Server (NTRS)

    Hansman, R. John, Jr.; Yamaguchi, Keiko; Berkowitz, Brian M.; Potapczuk, Mark

    1990-01-01

    A series of experimental investigations focused on studying the cause and effect of roughness on accreting glaze ice surfaces were conducted. Detailed microvideo observations were made of glaze ice accretions on 1 to 4 inch diameter cylinders in three icing wind tunnels (the Data Products of New England six inch test facility, the NASA Lewis Icing Research Tunnel, and the B. F. Goodrich Ice Protection Research Facility). Infrared thermal video recordings were made of accreting ice surfaces in the Goodrich facility. Distinct zones of surface water behavior were observed; a smooth wet zone in the stagnation region with a uniform water film; a rough zone where surface tension effects caused coalescence of surface water into stationary beads; a horn zone where roughness elements grow into horn shapes; a runback zone where surface water ran back as rivulets; and a dry zone where rime feathers formed. The location of the transition from the smooth to the rough zone was found to migrate with time towards the stagnation point. The behavior of the transition appeared to be controlled by boundary layer transition and bead formation mechanisms at the interface between the smooth and rough zones. Regions of wet ice growth and enhanced heat transfer were clearly visible in the infrared video recordings of glaze ice surfaces. A simple multi-zone modification to the current glaze ice accretion model was proposed to include spatial variability in surface roughness.

  13. Model approach to estimate the probability of accepting a lot of heterogeneously contaminated powdered food using different sampling strategies.

    PubMed

    Valero, Antonio; Pasquali, Frédérique; De Cesare, Alessandra; Manfreda, Gerardo

    2014-08-01

    Current sampling plans assume a random distribution of microorganisms in food. However, food-borne pathogens are estimated to be heterogeneously distributed in powdered foods. This spatial distribution together with very low level of contaminations raises concern of the efficiency of current sampling plans for the detection of food-borne pathogens like Cronobacter and Salmonella in powdered foods such as powdered infant formula or powdered eggs. An alternative approach based on a Poisson distribution of the contaminated part of the lot (Habraken approach) was used in order to evaluate the probability of falsely accepting a contaminated lot of powdered food when different sampling strategies were simulated considering variables such as lot size, sample size, microbial concentration in the contaminated part of the lot and proportion of contaminated lot. The simulated results suggest that a sample size of 100g or more corresponds to the lower number of samples to be tested in comparison with sample sizes of 10 or 1g. Moreover, the number of samples to be tested greatly decrease if the microbial concentration is 1CFU/g instead of 0.1CFU/g or if the proportion of contamination is 0.05 instead of 0.01. Mean contaminations higher than 1CFU/g or proportions higher than 0.05 did not impact on the number of samples. The Habraken approach represents a useful tool for risk management in order to design a fit-for-purpose sampling plan for the detection of low levels of food-borne pathogens in heterogeneously contaminated powdered food. However, it must be outlined that although effective in detecting pathogens, these sampling plans are difficult to be applied since the huge number of samples that needs to be tested. Sampling does not seem an effective measure to control pathogens in powdered food. PMID:24462218

  14. A simple iterative method for estimating evapotranspiration with integrated surface/subsurface flow models

    NASA Astrophysics Data System (ADS)

    Hwang, H.-T.; Park, Y.-J.; Frey, S. K.; Berg, S. J.; Sudicky, E. A.

    2015-12-01

    This work presents an iterative, water balance based approach to estimate actual evapotranspiration (ET) with integrated surface/subsurface flow models. Traditionally, groundwater level fluctuation methods have been widely accepted and used for estimating ET and net groundwater recharge; however, in watersheds where interactions between surface and subsurface flow regimes are highly dynamic, the traditional method may be overly simplistic. Here, an innovative methodology is derived and demonstrated for using the water balance equation in conjunction with a fully-integrated surface and subsurface hydrologic model (HydroGeoSphere) in order to estimate ET at watershed and sub-watershed scales. The method invokes a simple and robust iterative numerical solution. For the proof of concept demonstrations, the method is used to estimate ET for a simple synthetic watershed and then for a real, highly-characterized 7000 km2 watershed in Southern Ontario, Canada (Grand River Watershed). The results for the Grand River Watershed show that with three to five iterations, the solution converges to a result where there is less than 1% relative error in stream flow calibration at 16 stream gauging stations. The spatially-averaged ET estimated using the iterative method shows a high level of agreement (R2 = 0.99) with that from a benchmark case simulated with an ET model embedded directly in HydroGeoSphere. The new approach presented here is applicable to any watershed that is suited for integrated surface water/groundwater flow modelling and where spatially-averaged ET estimates are useful for calibrating modelled stream discharge.

  15. Practical applications of Zernike phase surfaces in optical system modeling

    NASA Astrophysics Data System (ADS)

    Vogel, Steven H.

    2010-04-01

    There are times when it would be helpful to share performance information about an optical system without disclosing proprietary information between multiple parties. A combination of Zernike phase surfaces and paraxial surfaces can be used to model an optical system and provide a method to safely transfer the required information without disclosing the specifics of the design such as details about the optical materials or the specific element geometry. This paper deals with some of the practical aspects of this approach such as aperture stop location, the affects of windows which may change thickness on the construction of the model, and the need for multiple field positions and wavelengths.

  16. A Coupled Surface/Subsurface Model for Hydrological Drought Investigations

    NASA Astrophysics Data System (ADS)

    Musuuza, J. L.; Kumar, R.; Samaniego, L. E.; Fischer, T.; Kolditz, O.; Attinger, S.

    2013-12-01

    Hydrological droughts occur when storage in the ground and surface-water bodies falls below statistical average. Due to the inclusion of regional groundwater, hydrological droughts evolve relatively slowly. The atmospheric and surface components of the hydrological cycle have been widely studied, are well understood, and their prognoses are fairly accurate. In large-scale land surface models on the other hand, subsurface (groundwater) flow processes are usually assumed unidirectional and limited to the vertically-downward percolation and the horizontal runoffs. The vertical feedback from groundwater to the unsaturated zone as well as the groundwater recharge from surface waters are usually misrepresented, resulting in poor model performance during low-flow periods. The feedback is important during meteorological droughts because it replenishes soil moisture from ground- and surface water, thereby delaying the onset of agricultural droughts. If sustained for long periods however, the depletion can significantly reduce surface and subsurface storage and lead to severe hydrological droughts. We hypothesise that an explicit incorporation of the groundwater component into an existing land surface model would lead to better representation of low flows, which is critical for drought analyses. It would also improve the model performance during low-flow periods. For this purpose, we coupled the process-based mHM surface model (Samaniego et al. 2010) with MODFLOW (Harbaugh 2005) to analyse droughts in the Unstrut catchment, one of the tributaries of the Elbe. The catchment is located in one of the most drought-prone areas of Germany. We present results for stand-alone and coupled mHM simulations for the period 1970-2000. References Arlen W. Harbaugh. MODFLOW-2005, The U.S. Geological Survey Modular Ground-water Model-the Ground-water Flow Process, chapter Modelling techniques, sec. A. Ground water, pages 1:1-9:62. USGS, 2005. Luis Samaniego, Rohini Kumar, and Sabine Attinger

  17. Model of evolution of surface grain structure under ion bombardment

    SciTech Connect

    Knyazeva, Anna G.; Kryukova, Olga N.

    2014-11-14

    Diffusion and chemical reactions in multicomponent systems play an important role in numerous technology applications. For example, surface treatment of materials and coatings by particle beam leads to chemical composition and grain structure change. To investigate the thermal-diffusion and chemical processes affecting the evolution of surface structure, the mathematical modeling is efficient addition to experiment. In this paper two-dimensional model is discussed to describe the evolution of titanium nitride coating on the iron substrate under implantation of boron and carbon. The equation for diffusion fluxes and reaction rate are obtained using Gibbs energy expansion into series with respect to concentration and their gradients.

  18. An operator calculus for surface and volume modeling

    NASA Technical Reports Server (NTRS)

    Gordon, W. J.

    1984-01-01

    The mathematical techniques which form the foundation for most of the surface and volume modeling techniques used in practice are briefly described. An outline of what may be termed an operator calculus for the approximation and interpolation of functions of more than one independent variable is presented. By considering the linear operators associated with bivariate and multivariate interpolation/approximation schemes, it is shown how they can be compounded by operator multiplication and Boolean addition to obtain a distributive lattice of approximation operators. It is then demonstrated via specific examples how this operator calculus leads to practical techniques for sculptured surface and volume modeling.

  19. Multi-site evaluation of the JULES land surface model using global and local data

    NASA Astrophysics Data System (ADS)

    Slevin, D.; Tett, S. F. B.; Williams, M.

    2014-08-01

    Changes in atmospheric carbon dioxide and water vapour change the energy balance of the atmosphere and thus climate. One important influence on these greenhouse gases is the land surface. Land Surface Models (LSMs) represent the interaction between the atmosphere and terrestrial biosphere in Global Climate Models (GCMs). As LSMs become more advanced, there is a need to test their accuracy. Uncertainty from LSMs contributes towards uncertainty in carbon cycle simulations and thus uncertainty in future climate change. In this study, we evaluate the ability of the JULES LSM to simulate photosynthesis using local and global datasets at 12 FLUXNET sites. Model parameters include site-specific (local) values for each flux tower site and the default parameters used in the Hadley Centre Global Environmental Model (HadGEM) climate model. Firstly, we compare Gross Primary Productivity (GPP) estimates from driving JULES with data derived from local site measurements with driving JULES with data derived from global parameter and atmospheric reanalysis (on scales of 100 km or so). We find that when using local data, a negative bias is introduced into model simulations with yearly GPP underestimated by 16% on average compared to observations while when using global data, model performance decreases further with yearly GPP underestimated by 30% on average. Secondly, we drive the model using global meteorological data and local parameters and find that global data can be used in place of FLUXNET data with only a 7% reduction in total annual simulated GPP. Thirdly, we compare the global meteorological datasets, WFDEI and PRINCETON, to local data and find that the WATCH dataset more closely matches the local meteorological measurements (FLUXNET). Finally, we compare the results from forcing JULES with the remote sensing product MODIS Leaf Area Index (LAI). JULES was modified to accept MODIS LAI at daily timesteps. We show that forcing the model with daily satellite LAI results in

  20. Modelling and updating of large surface-to-surface joints in the AWE-MACE structure

    NASA Astrophysics Data System (ADS)

    Ahmadian, Hamid; Mottershead, John E.; James, Simon; Friswell, Michael I.; Reece, Carole A.

    2006-05-01

    Model updating of joints in the AWE-MACE system is carried out using a sensitivity method. The joints are characterised by large surface-to-surface contact regions and are excited in vibration tests within the linear range. The joints are modelled using a layer of special interface elements having material properties that may be adjusted to improve the prediction of the complete model. A series of three updating exercises are described and it is shown that by using only six parameters based upon the circumferential-wave and bending modes that the prediction of the axial and torsional modes is improved sufficiently to be of practical usefulness for many applications. Fewer numbers of updating parameters are found to be sufficient to correct different subsets of vibration modes. Linear equivalent models identified by this approach are found to be valid within the usual range of vibration tests.

  1. Exposing earth surface process model simulations to a large audience

    NASA Astrophysics Data System (ADS)

    Overeem, I.; Kettner, A. J.; Borkowski, L.; Russell, E. L.; Peddicord, H.

    2015-12-01

    The Community Surface Dynamics Modeling System (CSDMS) represents a diverse group of >1300 scientists who develop and apply numerical models to better understand the Earth's surface. CSDMS has a mandate to make the public more aware of model capabilities and therefore started sharing state-of-the-art surface process modeling results with large audiences. One platform to reach audiences outside the science community is through museum displays on 'Science on a Sphere' (SOS). Developed by NOAA, SOS is a giant globe, linked with computers and multiple projectors and can display data and animations on a sphere. CSDMS has developed and contributed model simulation datasets for the SOS system since 2014, including hydrological processes, coastal processes, and human interactions with the environment. Model simulations of a hydrological and sediment transport model (WBM-SED) illustrate global river discharge patterns. WAVEWATCH III simulations have been specifically processed to show the impacts of hurricanes on ocean waves, with focus on hurricane Katrina and super storm Sandy. A large world dataset of dams built over the last two centuries gives an impression of the profound influence of humans on water management. Given the exposure of SOS, CSDMS aims to contribute at least 2 model datasets a year, and will soon provide displays of global river sediment fluxes and changes of the sea ice free season along the Arctic coast. Over 100 facilities worldwide show these numerical model displays to an estimated 33 million people every year. Datasets storyboards, and teacher follow-up materials associated with the simulations, are developed to address common core science K-12 standards. CSDMS dataset documentation aims to make people aware of the fact that they look at numerical model results, that underlying models have inherent assumptions and simplifications, and that limitations are known. CSDMS contributions aim to familiarize large audiences with the use of numerical

  2. Satellite Derived Land Surface Temperature for Model Assimilation

    NASA Technical Reports Server (NTRS)

    Suggs, Ronnie J.; Jedlovec, Gary J.; Lapenta, William

    1999-01-01

    Studies have shown that land surface temperature (LST) tendencies are sensitive to the surface moisture availability which is a function of soil moisture and vegetation. The assimilation of satellite derived LST tendencies into the surface energy budget of mesoscale models has shown promise in improving the representation of the complex effects of both soil moisture and vegetation within the models for short term simulations. LST derived from geostationary satellites has the potential of providing the temporal and spatial resolution needed for an LST assimilation process. This paper presents an analysis comparing the LST derived from GOES-8 infrared measurements with LST calculated by the MM5 numerical model. The satellite derived LSTs are calculated using a physical split window approach using channels 4 and 5 of GOES-8. The differences in the LST data sets, especially the tendencies, are presented and examined. Quantifying the differences between the data sets provide insight of possible weaknesses in the model parameterizations affecting the surface energy budget calculations and an indication of the potential effectiveness o f assimilating LST into the models.

  3. A finite difference model for free surface gravity drainage

    SciTech Connect

    Couri, F.R.; Ramey, H.J. Jr.

    1993-09-01

    The unconfined gravity flow of liquid with a free surface into a well is a classical well test problem which has not been well understood by either hydrologists or petroleum engineers. Paradigms have led many authors to treat an incompressible flow as compressible flow to justify the delayed yield behavior of a time-drawdown test. A finite-difference model has been developed to simulate the free surface gravity flow of an unconfined single phase, infinitely large reservoir into a well. The model was verified with experimental results in sandbox models in the literature and with classical methods applied to observation wells in the Groundwater literature. The simulator response was also compared with analytical Theis (1935) and Ramey et al. (1989) approaches for wellbore pressure at late producing times. The seepage face in the sandface and the delayed yield behavior were reproduced by the model considering a small liquid compressibility and incompressible porous medium. The potential buildup (recovery) simulated by the model evidenced a different- phenomenon from the drawdown, contrary to statements found in the Groundwater literature. Graphs of buildup potential vs time, buildup seepage face length vs time, and free surface head and sand bottom head radial profiles evidenced that the liquid refills the desaturating cone as a flat moving surface. The late time pseudo radial behavior was only approached after exaggerated long times.

  4. Modeling of a Surface Acoustic Wave Strain Sensor

    NASA Technical Reports Server (NTRS)

    Wilson, W. C.; Atkinson, Gary M.

    2010-01-01

    NASA Langley Research Center is investigating Surface Acoustic Wave (SAW) sensor technology for harsh environments aimed at aerospace applications. To aid in development of sensors a model of a SAW strain sensor has been developed. The new model extends the modified matrix method to include the response of Orthogonal Frequency Coded (OFC) reflectors and the response of SAW devices to strain. These results show that the model accurately captures the strain response of a SAW sensor on a Langasite substrate. The results of the model of a SAW Strain Sensor on Langasite are presented

  5. Simultaneous application of dissolution/precipitation and surface complexation/surface precipitation modeling to contaminant leaching.

    PubMed

    Apul, Defne S; Gardner, Kevin H; Eighmy, T Taylor; Fällman, Ann-Marie; Comans, Rob N J

    2005-08-01

    This paper discusses the modeling of anion and cation leaching from complex matrixes such as weathered steel slag. The novelty of the method is its simultaneous application of the theoretical models for solubility, competitive sorption, and surface precipitation phenomena to a complex system. Selective chemical extractions, pH dependent leaching experiments, and geochemical modeling were used to investigate the thermodynamic equilibrium of 12 ions (As, Ca, Cr, Ba, SO4, Mg, Cd, Cu, Mo, Pb, V, and Zn) with aqueous complexes, soluble solids, and sorptive surfaces in the presence of 12 background analytes (Al, Cl, Co, Fe, K, Mn, Na, Ni, Hg, NO3, CO3, and Ba). Modeling results show that surface complexation and surface precipitation reactions limit the aqueous concentrations of Cd, Zn, and Pb in an environment where Ca, Mg, Si, and CO3 dissolve from soluble solids and compete for sorption sites. The leaching of SO4, Cr, As, Si, Ca, and Mg appears to be controlled by corresponding soluble solids. PMID:16124310

  6. Land Surface Temperature Variational Assimilation within the ORCHIDEE Continental Surface model

    NASA Astrophysics Data System (ADS)

    Benavides, Hector Simon; Ottlé, Catherine; Thiria, Sylvie; Brajard, Julien; Bradan, Fouad; Maugis, Pascal

    2014-05-01

    Variational data assimilation of FLUXNET soil surface temperature is applied to the energy and water budgets modules of the ORCHIDEE land surface model. This part of the model, called SECHIBA, describes the exchanges of water and energy between the surface and the atmosphere. The adjoint semi-generator software YAO is used as a framework to implement 4D-VAR assimilation. First, sensitivity analysis was performed in order to validate the adjoint and to identify the most influential parameters. Following, the results of twin experiments using synthetic observations demonstrate the robustness, consistency and flexibility of the process. Rendundant combinations of parameters and insensitive ones can then be detected, thus allowing to document the most efficient set of parameters to calibrate. However, optimal sets of parameter vary with time of day, season, site and initial state, thus suggesting a calibration strategy based on different time windows and sites to help constrain a larger set of parameter than on a single space-time window. Doing so on two FLUXNET sites and including initial soil water content as a parameter improves the model output. Although it proved difficult to characterize at the same time state variables and fluxes, this study puts forward the potential of land surface temperature variational data assimilation in model calibration and prediction errors reduction.

  7. Model of a small surface wave discharge at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Ivanov, A.; Kiss'ovski, Zh

    2016-05-01

    Self-consistent model of a small microwave plasma source based on a surface wave sustained discharge at 2.45 GHz is presented in this study. The model includes dispersion relation of azimuthally symmetric surface waves, sustaining the discharge in a high permittivity ceramic tube (εd = 9.3) and the radial distribution of the field components at curtain values of the electron density are obtained. The electron Boltzmann equation under the local approximation is solved together with the heavy particle balance equations. A detailed collisional-radiative model for argon discharge at atmospheric pressure is implemented in the model. The changes in the EEDF shape and the mean electron energy with the value of the electron density are investigated. Results show that the EEDF is close to Maxwellian at our experimental conditions for the plasma density above 2.1020 (m-3).

  8. Lithospheric Thickness Modeled From Long Period Surface Wave Dispersion

    NASA Astrophysics Data System (ADS)

    Pasyanos, M. E.

    2007-12-01

    The behavior of surface waves at long periods is indicative of subcrustal velocity structure. Using recently published dispersion models, we invert surface wave group velocities for lithospheric structure, including lid velocity and lithospheric thickness, over much of the Eastern Hemisphere, encompassing Eurasia, Africa, and the Indian Ocean. Thicker lithosphere keels and faster upper mantle velocities under Precambrian shields and platforms are clearly observed, not only under the large cratons (West African Craton, Congo Craton, Baltic Shield, Russian Platform, Siberian Platform, Indian Shield, Kalahari Craton), but also under smaller blocks like the Tarim Basin and Yangtze Craton. There are also interesting variations within cratons like the Congo Craton. As expected, the thinnest lithospheric thickness is found under oceanic and continental rifts, and also along convergence zones. We compare our results to thermal lithospheric models of the continents, lithospheric cooling models of oceanic lithosphere, lithosphere-asthenosphere boundary (LAB) estimates from S-wave receiver functions, and velocity variations of global tomography models.

  9. Observational & modeling analysis of surface heat and moisture fluxes

    SciTech Connect

    Smith, E.

    1995-09-01

    An observational and modeling study was conducted to help assess how well current GCMs are predicting surface fluxes under the highly variable cloudiness and flow conditions characteristic of the real atmosphere. The observational data base for the study was obtained from a network of surface flux stations operated during the First ISLSCP Field Experiment (FIFE). The study included examination of a surface-driven secondary circulation in the boundary layer resulting from a persistent cross-site gradient in soil moisture, to demonstrate the sensitivity of boundary layer dynamics to heterogeneous surface fluxes, The performance of a biosphere model in reproducing the measured surface fluxes was evaluated with and without the use of satellite retrieval of three key canopy variables with RMS uncertainties commensurate with those of the measurements themselves. Four sensible heat flux closure schemes currently being used in GCMs were then evaluated against the FIFE observations. Results indicate that the methods by which closure models are calibrated lead to exceedingly large errors when the schemes are applied to variable boundary layer conditions. 4 refs., 2 figs.

  10. Subgrid-scale Modeling in the Atmospheric Surface Layer^1

    NASA Astrophysics Data System (ADS)

    Khanna, S.; Wyngaard, J. C.; Brasseur, J. G.

    1996-11-01

    Subgrid-scale (SGS) modeling is crucial in the surface layer of wall-bounded flows where the vertical velocity fluctuations cannot be well resolved. We focus on the distinct characteristics of the surface layer of the atmospheric boundary layer (ABL), and analyze, from a highly resolved surface-layer field of a moderately convective ABL, the extent to which Smagorinsky-based SGS models predict these characteristics. The fields were generated using a nested-mesh large-eddy simulation (LES) with the finest mesh having an effective grid resolution of 512^3 covering 1/16^th of the boundary-layer depth. At a height where the fine mesh resolves 90 % of the total fluxes and variances, the resolved fields were treated as surrogate fully resolved fields that were filtered onto a coarser mesh to get ``resolvable'' and ``subgrid'' fields. Preliminary results show that Smagorinsky-based models fail to capture many of the distinctive characteristics of the ABL surface layer. For example, they do not capture the anisotropic distribution of subgrid-scale energy among the horizontal and the vertical components, and they grossly underestimate the SGS horizontal temperature flux. Currently we are focusing on more suitable closures for the atmospheric surface layer. A DNS-based study is also underway and will be used to supplement this analysis. ^1 supported by ARO (# DAAL03-92-G-0117) and ONR (# N00014-92-J-1688)

  11. Incorporating floating surface objects into a fully dispersive surface wave model

    NASA Astrophysics Data System (ADS)

    Orzech, Mark D.; Shi, Fengyan; Veeramony, Jayaram; Bateman, Samuel; Calantoni, Joseph; Kirby, James T.

    2016-06-01

    The shock-capturing, non-hydrostatic, three-dimensional (3D) finite-volume model NHWAVE was originally developed to simulate wave propagation and landslide-generated tsunamis in finite water depth (Ma, G., Shi, F., Kirby, J. T., 2012. Ocean Model. 43-44, 22-35). The model is based on the incompressible Navier-Stokes equations, in which the z-axis is transformed to a σ-coordinate that tracks the bed and surface. As part of an ongoing effort to simulate waves in polar marginal ice zones (MIZs), the model has now been adapted to allow objects of arbitrary shape and roughness to float on or near its water surface. The shape of the underside of each floating object is mapped onto an upper σ-level slightly below the surface. In areas without floating objects, this σ-level continues to track the surface and bed as before. Along the sides of each floating object, an immersed boundary method is used to interpolate the effects of the object onto the neighboring fluid volume. Provided with the object's shape, location, and velocity over time, NHWAVE determines the fluid fluxes and pressure variations from the corresponding accelerations at neighboring cell boundaries. The system was validated by comparison with analytical solutions and a VOF model for a 2D floating box and with laboratory measurements of wave generation by a vertically oscillating sphere. A steep wave simulation illustrated the high efficiency of NHWAVE relative to a VOF model. In a more realistic MIZ simulation, the adapted model produced qualitatively reasonable results for wave attenuation, diffraction, and scattering.

  12. Development of land surface reflectance models based on multiscale simulation

    NASA Astrophysics Data System (ADS)

    Goodenough, Adam A.; Brown, Scott D.

    2015-05-01

    Modeling and simulation of Earth imaging sensors with large spatial coverage necessitates an understanding of how photons interact with individual land surface processes at an aggregate level. For example, the leaf angle distribution of a deciduous forest canopy has a significant impact on the path of a single photon as it is scattered among the leaves and, consequently, a significant impact on the observed bidirectional reflectance distribution function (BRDF) of the canopy as a whole. In particular, simulation of imagery of heterogeneous scenes for many multispectral/hyperspectral applications requires detailed modeling of regions of the spectrum where many orders of scattering are required due to both high reflectance and transmittance. Radiative transfer modeling based on ray tracing, hybrid Monte Carlo techniques and detailed geometric and optical models of land cover means that it is possible to build effective, aggregate optical models with parameters such as species, spatial distribution, and underlying terrain variation. This paper examines the capability of the Digital Image and Remote Sensing Image Generation (DIRSIG) model to generate BRDF data representing land surfaces at large scale from modeling at a much smaller scale. We describe robust methods for generating optical property models effectively in DIRSIG and present new tools for facilitating the process. The methods and results for forest canopies are described relative to the RAdiation transfer Model Intercomparison (RAMI) benchmark scenes, which also forms the basis for an evaluation of the approach. Additional applications and examples are presented, representing different types of land cover.

  13. Kinetic measurements of hydrocarbon conversion reactions on model metal surfaces.

    PubMed

    Wilson, Jarod; Guo, Hansheng; Morales, Ricardo; Podgornov, Egor; Lee, Ilkeun; Zaera, Francisco

    2007-08-01

    Examples from recent studies in our laboratory are presented to illustrate the main tools available to surface scientists for the determination of the kinetics of surface reactions. Emphasis is given here to hydrocarbon conversions and studies that rely on the use of model systems, typically single crystals and controlled (ultrahigh vacuum) environments. A detailed discussion is provided on the use of temperature-programmed desorption for the determination of activation energies as well as for product identification and yield estimations. Isothermal kinetic measurements are addressed next by focusing on studies under vacuum using molecular beams and surface-sensitive spectroscopies. That is followed by a review of the usefulness of high-pressure cells and other reactor designs for the emulation of realistic catalytic conditions. Finally, an analysis of the power of isotope labeling and chemical substitutions in mechanistic research on surface reactions is presented. PMID:17637975

  14. Mathematical model of the metal mould surface temperature optimization

    SciTech Connect

    Mlynek, Jaroslav Knobloch, Roman; Srb, Radek

    2015-11-30

    The article is focused on the problem of generating a uniform temperature field on the inner surface of shell metal moulds. Such moulds are used e.g. in the automotive industry for artificial leather production. To produce artificial leather with uniform surface structure and colour shade the temperature on the inner surface of the mould has to be as homogeneous as possible. The heating of the mould is realized by infrared heaters located above the outer mould surface. The conceived mathematical model allows us to optimize the locations of infrared heaters over the mould, so that approximately uniform heat radiation intensity is generated. A version of differential evolution algorithm programmed in Matlab development environment was created by the authors for the optimization process. For temperate calculations software system ANSYS was used. A practical example of optimization of heaters locations and calculation of the temperature of the mould is included at the end of the article.

  15. Mathematical model of the metal mould surface temperature optimization

    NASA Astrophysics Data System (ADS)

    Mlynek, Jaroslav; Knobloch, Roman; Srb, Radek

    2015-11-01

    The article is focused on the problem of generating a uniform temperature field on the inner surface of shell metal moulds. Such moulds are used e.g. in the automotive industry for artificial leather production. To produce artificial leather with uniform surface structure and colour shade the temperature on the inner surface of the mould has to be as homogeneous as possible. The heating of the mould is realized by infrared heaters located above the outer mould surface. The conceived mathematical model allows us to optimize the locations of infrared heaters over the mould, so that approximately uniform heat radiation intensity is generated. A version of differential evolution algorithm programmed in Matlab development environment was created by the authors for the optimization process. For temperate calculations software system ANSYS was used. A practical example of optimization of heaters locations and calculation of the temperature of the mould is included at the end of the article.

  16. A rough-surface thermophysical model for airless planets

    SciTech Connect

    Spencer, J.R. )

    1990-01-01

    A model for determining diurnal temperatures in spherical-section depressions and which encompasses both subsurface heat-flow and direct and scattered sunlight effects is presently applied to the disk-integrated thermal emission of a rough planetary surface with nonzero thermal inertia. Attention is given to the variation with roughness and thermal inertia of the beaming parameter eta, which characterizes zero-phase thermal emission by comparison with a smooth, nonrotating body and is almost independent of albedo for a given surface roughness. The thermal phase curve of Ceres is noted to be well matched by the model features of (1) prograde rotation, (2) 44-deg rms surface slope, and (3) a thermal inertia that is 30 percent of the lunar value. 23 refs.

  17. Session on coupled land surface/hydrological/atmospheric models

    NASA Technical Reports Server (NTRS)

    Pielke, Roger

    1993-01-01

    The current model capabilities in the context of land surface interactions with the atmosphere include only one-dimensional characteristics of vegetation and soil surface heat, moisture, momentum, and selected other trace gas fluxes (e.g., CO2). The influence of spatially coherent fluxes that result from landscape heterogeneity were not included. Valuable representations of several aspects of the landscape pattern currently exist. These include digital elevation data and measures of the leaf area index (i.e., Normalized Difference Vegetation Index (NDVI) from Advanced Very High Resolution Radiometer (AVHRR) data). A major deficiency, however, is the lack of an ability to sample spatially representative shallow and (especially) deep soil moisture. Numerous mesoscale modeling and observed studies demonstrated the sensitivity of planetary boundary layer structure and deep convection to the magnitude of the surface moisture flux.

  18. Wetting and free surface flow modeling for potting and encapsulation.

    SciTech Connect

    Brooks, Carlton, F.; Brooks, Michael J. (Los Alamos National Laboratory, Los Alamos, NM); Graham, Alan Lyman; Noble, David F. ); Notz, Patrick K.; Hopkins, Matthew Morgan; Castaneda, Jaime N.; Mahoney, Leo James; Baer, Thomas A.; Berchtold, Kathryn (Los Alamos National Laboratory, Los Alamos, NM); Adolf, Douglas Brian; Wilkes, Edward Dean; Rao, Rekha Ranjana; Givler, Richard C.; Sun, Amy Cha-Tien; Cote, Raymond O.; Mondy, Lisa Ann; Grillet, Anne Mary; Kraynik, Andrew Michael

    2007-06-01

    As part of an effort to reduce costs and improve quality control in encapsulation and potting processes the Technology Initiative Project ''Defect Free Manufacturing and Assembly'' has completed a computational modeling study of flows representative of those seen in these processes. Flow solutions are obtained using a coupled, finite-element-based, numerical method based on the GOMA/ARIA suite of Sandia flow solvers. The evolution of the free surface is solved with an advanced level set algorithm. This approach incorporates novel methods for representing surface tension and wetting forces that affect the evolution of the free surface. In addition, two commercially available codes, ProCAST and MOLDFLOW, are also used on geometries representing encapsulation processes at the Kansas City Plant. Visual observations of the flow in several geometries are recorded in the laboratory and compared to the models. Wetting properties for the materials in these experiments are measured using a unique flowthrough goniometer.

  19. A rough-surface thermophysical model for airless planets

    NASA Technical Reports Server (NTRS)

    Spencer, John R.

    1990-01-01

    A model for determining diurnal temperatures in spherical-section depressions and which encompasses both subsurface heat-flow and direct and scattered sunlight effects is presently applied to the disk-integrated thermal emission of a rough planetary surface with nonzero thermal inertia. Attention is given to the variation with roughness and thermal inertia of the beaming parameter eta, which characterizes zero-phase thermal emission by comparison with a smooth, nonrotating body and is almost independent of albedo for a given surface roughness. The thermal phase curve of Ceres is noted to be well matched by the model features of (1) prograde rotation, (2) 44-deg rms surface slope, and (3) a thermal inertia that is 30 percent of the lunar value.

  20. Advances in Thermal Infrared Remote Sensing for Land Surface Modeling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Over 10 years ago, John Norman and co-authors proposed a thermal-based land surface modeling strategy that treated the energy exchange and kinetic temperatures of the soil and vegetated components in a unique “Two-Source Model” (TSM) approach. The TSM formulation addresses key factors affecting the...

  1. Surface tension and viscosity of nuclei in liquid drop model

    NASA Astrophysics Data System (ADS)

    Khokonov, A. Kh

    2015-11-01

    An analytical solution for the capillary oscillations of the charged drop in dielectric medium obtained with taking into account the damping due to viscosity. The model has been applied for the estimation of even-even spherical nuclei surface tension and nuclei viscosity. Attenuation factor to nuclear capillary oscillation frequency ratio has been found.

  2. A Metacognitive-Motivational Model of Surface Approach to Studying

    ERIC Educational Resources Information Center

    Spada, Marcantonio M.; Moneta, Giovanni B.

    2012-01-01

    In this study, we put forward and tested a model of how surface approach to studying during examination preparation is influenced by the trait variables of motivation and metacognition and the state variables of avoidance coping and evaluation anxiety. A sample of 528 university students completed, one week before examinations, the following…

  3. Student Attitudes towards and Use of ICT in Course Study, Work and Social Activity: A Technology Acceptance Model Approach

    ERIC Educational Resources Information Center

    Edmunds, Rob; Thorpe, Mary; Conole, Grainne

    2012-01-01

    The increasing use of information and communication technology (ICT) in higher education has been explored largely in relation to student experience of coursework and university life. Students' lives and experience beyond the university have been largely unexplored. Research into student experience of ICT used a validated model--the technology…

  4. The Adoption of Blended E-Learning Technology in Vietnam Using a Revision of the Technology Acceptance Model

    ERIC Educational Resources Information Center

    Tran, Khanh Ngo Nhu

    2016-01-01

    This study examines factors that determine the attitudes of learners toward a blended e-learning system (BELS) using data collected by questionnaire from a sample of 396 students involved in a BELS environment in Vietnam. A theoretical model is derived from previous studies and is analyzed and developed using structural equation modeling…

  5. Predicting the Use of Paired Programming: Applying the Attitudes of Application Development Managers through the Technology Acceptance Model

    ERIC Educational Resources Information Center

    Zecca, Mark S.

    2010-01-01

    Business managers who look for ways to cut costs face difficult questions about the efficiency and effectiveness of software engineering practices that are used to complete projects on time, on specification, and within budget (Johnson, 1995; Lindstrom & Jeffries, 2004). Theoretical models such as the Theory of Reasoned Action (TRA) have linked…

  6. Surface science studies of catalyzed methanol synthesis on model copper and Cu-Zn-O surfaces

    SciTech Connect

    Fu, Sabrina Su-Bin . Dept. of Chemistry Lawrence Berkeley Lab., CA )

    1991-06-01

    Cu-Zn-O surfaces that are catalysts for methanol synthesis from CO, CO{sub 2}, and H{sub 2} modeled using zinc oxide overlayers on copper single crystals. These studies were performed in ultra-high vacuum (UHV) utilizing Temperature Programmed Desorption, Auger Electron Spectroscopy, and Low Energy Electron Diffraction techniques. The chemisorption of O{sub 2}, CO, CO{sub 2}, and D{sub 2} were compared on a stepped on Cu(311), and a flat Cu(110). At low pressures ({approximately}10{sup {minus}6} Torr), Cu(311) was found to be much more reactive than Cu(110) for the dissociative adsorption of CO{sub 2} and D{sub 2}, and the formation of CO{sub 2} from surface oxygen and CO. Since these reactions are important in methanol synthesis, these results suggest that methanol synthesis over copper may be a structure sensitive reaction. The interaction of copper, zinc, and oxygen were examined by the deposition of submonolayers to multilayers of zinc and oxygen in UHV on Cu(110). The interaction of methanol with these model Cu-Zn-O surfaces was also studied. Oxygen was adsorbed onto these exposed copper part of the surface to form ZnO{sub x}/y ML O/Cu(110) surfaces. The roles of ZnO{sub x} islands and chemisorbed oxygen on copper were investigated by monitoring methanol decomposition, into surface formate and methoxy species, on these ZnO{sub x}/y ML O/Cu(11) surfaces.

  7. Comparison of spectral surface albedos and their impact on the general circulation model simulated surface climate

    NASA Astrophysics Data System (ADS)

    Roesch, A.; Wild, M.; Pinker, R.; Ohmura, A.

    2002-07-01

    This study investigates the impact of spectrally resolved surface albedo on the total surface albedo. The neglect of albedo variation within the shortwave spectrum may lead to substantial errors as the atmospheric water greatly influences the spectral distribution of the incoming radiation. It is shown that ignoring the spectral dependence of the surface albedo will affect the predicted climate. The study reveals substantial changes in the climate over northern Africa when modifying the surface albedo of the Sahara deserts. Detailed information is given how the European Center/Hamburg General Circulation Model (ECHAM4) can be extended to include surface boundary conditions for both the visible and near-infrared incoming radiation. This comprises global climatologies for both the visible and near-infrared albedo for snow-free conditions, as well as the corresponding albedo values over snow, land-/sea ice and over snow covered forests. Comparisons between several available surface albedo climatologies and a newly compiled albedo data set show substantial scatter in estimated albedos. The largest albedo differences are found in snow covered forest regions as well as in arid and semi-arid terrains.

  8. Acceptability of GM foods among Pakistani consumers.

    PubMed

    Ali, Akhter; Rahut, Dil Bahadur; Imtiaz, Muhammad

    2016-04-01

    In Pakistan majority of the consumers do not have information about genetically modified (GM) foods. In developing countries particularly in Pakistan few studies have focused on consumers' acceptability about GM foods. Using comprehensive primary dataset collected from 320 consumers in 2013 from Pakistan, this study analyzes the determinants of consumers' acceptability of GM foods. The data was analyzed by employing the bivariate probit model and censored least absolute deviation (CLAD) models. The empirical results indicated that urban consumers are more aware of GM foods compared to rural consumers. The acceptance of GM foods was more among females' consumers as compared to male consumers. In addition, the older consumers were more willing to accept GM food compared to young consumers. The acceptability of GM foods was also higher among wealthier households. Low price is the key factor leading to the acceptability of GM foods. The acceptability of the GM foods also reduces the risks among Pakistani consumers. PMID:27494790

  9. Surface accuracy measurement sensor test on a 50-meter antenna surface model

    NASA Technical Reports Server (NTRS)

    Spiers, R. B.; Burcher, E. E.; Stump, C. W.; Saunders, C. G.; Brooks, G. F.

    1984-01-01

    The Surface Accuracy Measurement Sensor (SAMS) is a telescope with a focal plane photo electric detector that senses the lateral position of light source targets in its field of view. After extensive laboratory testing the engineering breadboard sensor system was installed and tested on a 30 degree segment of a 50-meter diameter, mesh surface, antenna model. Test results correlated well with the laboratory tests and indicated accuracies of approximately 0.59 arc seconds at 21 meters range. Test results are presented and recommendations given for sensor improvements.

  10. A Comparison of Surface Acoustic Wave Modeling Methods

    NASA Technical Reports Server (NTRS)

    Wilson, W. c.; Atkinson, G. M.

    2009-01-01

    Surface Acoustic Wave (SAW) technology is low cost, rugged, lightweight, extremely low power and can be used to develop passive wireless sensors. For these reasons, NASA is investigating the use of SAW technology for Integrated Vehicle Health Monitoring (IVHM) of aerospace structures. To facilitate rapid prototyping of passive SAW sensors for aerospace applications, SAW models have been developed. This paper reports on the comparison of three methods of modeling SAWs. The three models are the Impulse Response Method a first order model, and two second order matrix methods; the conventional matrix approach, and a modified matrix approach that is extended to include internal finger reflections. The second order models are based upon matrices that were originally developed for analyzing microwave circuits using transmission line theory. Results from the models are presented with measured data from devices.

  11. Evaluation of surface composition of surface active water-alcohol type mixtures: a comparison of semiempirical models.

    PubMed

    Salonen, Martta; Malila, Jussi; Napari, Ismo; Laaksonen, Ari

    2005-03-01

    We study adsorption at planar liquid-vapor interface of surface active binary mixtures and test three well-known models for the composition of surface phase. The models were originally presented by Guggenheim. These are compared to results for model fluids from density functional theory (DFT). The model of Laaksonen and Kulmala is in best agreement with DFT calculations. Surface mole fraction of the solute component from the Guggenheim model exceeds one for a mixture with high surface activity. The failure of the Guggenheim model is also evident in our calculations for water-methanol, water-ethanol, and water-n-propanol mixtures. PMID:16851381

  12. Comparison of Contamination Model Predictions to LDEF Surface Measurements

    NASA Technical Reports Server (NTRS)

    Gordon, Tim; Rantanen, Ray; Pippin, Gary; Finckenor, Miria

    1998-01-01

    Contaminant deposition measurements have been made on species content and depth profiles on three experiments trays from the Long Duration Exposure Facility (LDEF), Auger, Argon sputtering, Electron Spectroscopy for Chemical Analysis (ESCA) and Scanning Electron Microscopy (SEM) analysis. The integrated spacecraft environment model (ISEM) was used to predict the deposition levels of the contaminants measured on the three trays. The details of the modeling and assumptions used are presented along with the predictions for the deposition on select surfaces on the trays. These are compared to the measured results. The trays represent surfaces that have a high atomic oxygen flux, and intermediate oxygen flux, and no oxygen flux. All surfaces received significant solar Ultraviolet flux. It appears that the atomic oxygen was the primary agent that caused significant deposition to occur. Surfaces that saw significant contaminant flux solar UV and no atomic oxygen did not show any appreciable levels of observable deposition. The implications of the atom ic oxygen interaction with contaminant deposits containing silicon contaminant sources is discussed. The primary contaminant sources are DC61104 adhesive and Z306 paint. The results and interpretation of the findings have a potential significant impact on spacecraft surfaces that are exposed to solar UV and atomic oxygen in low Earth orbit.

  13. Modeling propellant combustion interacting with an eroding solid surface

    SciTech Connect

    Buckingham, A.C.

    1980-05-06

    A computatonal model of turbulent combustion flow acting on and influenced by an eroding wall surface is introduced. The combustion flow field is particle laden. Significant particulate mass loading occurs in the immediate neighborhood of the wall as a result of erosion products issuing from the deteriorating solid surface. In addition, cases are considered in which a substantial particle mass loading develops near the wall as a result of finely divided (sub micron diameter) particulates such as TiO/sub 2/ and talcum powder which are added to suppress erosion. In addition to statistical turbulent field particle flow interaction, the model includes multi-component molecular diffusion processes, and gas phase, gas/surface and or solid surface chemical reactions. Results indicate that despite the unsteady flow conditions, a limiting erosion rate is approached. This occurs as a result of the effective blowing off of the issing vapor phase products. The blowing reduces the gradients driving the incident combustion heat and mass transfer. An analogy is drawn to unsteady, ablative, heat transfer and thermal/material response in hypersonic aerodynamics. Surfaces investigated, at present, include bare steel and refractory metal coated steel walls.

  14. Establishment and metabolic analysis of a model microbial community for understanding trophic and electron accepting interactions of subsurface anaerobic environments

    PubMed Central

    2010-01-01

    Background Communities of microorganisms control the rates of key biogeochemical cycles, and are important for biotechnology, bioremediation, and industrial microbiological processes. For this reason, we constructed a model microbial community comprised of three species dependent on trophic interactions. The three species microbial community was comprised of Clostridium cellulolyticum, Desulfovibrio vulgaris Hildenborough, and Geobacter sulfurreducens and was grown under continuous culture conditions. Cellobiose served as the carbon and energy source for C. cellulolyticum, whereas D. vulgaris and G. sulfurreducens derived carbon and energy from the metabolic products of cellobiose fermentation and were provided with sulfate and fumarate respectively as electron acceptors. Results qPCR monitoring of the culture revealed C. cellulolyticum to be dominant as expected and confirmed the presence of D. vulgaris and G. sulfurreducens. Proposed metabolic modeling of carbon and electron flow of the three-species community indicated that the growth of C. cellulolyticum and D. vulgaris were electron donor limited whereas G. sulfurreducens was electron acceptor limited. Conclusions The results demonstrate that C. cellulolyticum, D. vulgaris, and G. sulfurreducens can be grown in coculture in a continuous culture system in which D. vulgaris and G. sulfurreducens are dependent upon the metabolic byproducts of C. cellulolyticum for nutrients. This represents a step towards developing a tractable model ecosystem comprised of members representing the functional groups of a trophic network. PMID:20497531

  15. Models of the solvent-accessible surface of biopolymers

    SciTech Connect

    Smith, R.E.

    1996-09-01

    Many biopolymers such as proteins, DNA, and RNA have been studied because they have important biomedical roles and may be good targets for therapeutic action in treating diseases. This report describes how plastic models of the solvent-accessible surface of biopolymers were made. Computer files containing sets of triangles were calculated, then used on a stereolithography machine to make the models. Small (2 in.) models were made to test whether the computer calculations were done correctly. Also, files of the type (.stl) required by any ISO 9001 rapid prototyping machine were written onto a CD-ROM for distribution to American companies.

  16. MR image denoising method for brain surface 3D modeling

    NASA Astrophysics Data System (ADS)

    Zhao, De-xin; Liu, Peng-jie; Zhang, De-gan

    2014-11-01

    Three-dimensional (3D) modeling of medical images is a critical part of surgical simulation. In this paper, we focus on the magnetic resonance (MR) images denoising for brain modeling reconstruction, and exploit a practical solution. We attempt to remove the noise existing in the MR imaging signal and preserve the image characteristics. A wavelet-based adaptive curve shrinkage function is presented in spherical coordinates system. The comparative experiments show that the denoising method can preserve better image details and enhance the coefficients of contours. Using these denoised images, the brain 3D visualization is given through surface triangle mesh model, which demonstrates the effectiveness of the proposed method.

  17. Identifying and Addressing Land Surface Model Deficiencies with Data Assimilation

    NASA Technical Reports Server (NTRS)

    Rodell, Matthew; Li, Bailing; Beaudoing, Hiroko Kato; Houborg, Rasmus; Zaitchik, Ben; Reichle, Rolf; Kumar, Sujay

    2012-01-01

    Land surface models (LSMs) encapsulate our understanding of terrestrial water and energy cycle physics and provide estimates of land surface states and fluxes when and where measurement gaps exist. Gaps in our understanding of the physics are a different issue. Data assimilation can address that issue both directly, through updating of prognostic model variables, or indirectly, when the simulated world conflicts with observation, necessitating adjustment of the model. Here we will focus on the latter case and present several examples, including (1) depth to bedrock adjustment to accommodate assimilated GRACE terrestrial water storage data; (2) steps to prevent immediate melting of assimilated snow cover; (3) irrigation's contribution to evapotranspiration; (4) lessons learned from soil moisture data assimilation; (5) the potential impact of satellite based runoff observation

  18. Cyclic Evolution of Coronal Fields from a Coupled Dynamo Potential-Field Source-Surface Model

    NASA Astrophysics Data System (ADS)

    Dikpati, Mausumi; Suresh, Akshaya; Burkepile, Joan

    2016-02-01

    The structure of the Sun's corona varies with the solar-cycle phase, from a near spherical symmetry at solar maximum to an axial dipole at solar minimum. It is widely accepted that the large-scale coronal structure is governed by magnetic fields that are most likely generated by dynamo action in the solar interior. In order to understand the variation in coronal structure, we couple a potential-field source-surface model with a cyclic dynamo model. In this coupled model, the magnetic field inside the convection zone is governed by the dynamo equation; these dynamo-generated fields are extended from the photosphere to the corona using a potential-field source-surface model. Assuming axisymmetry, we take linear combinations of associated Legendre polynomials that match the more complex coronal structures. Choosing images of the global corona from the Mauna Loa Solar Observatory at each Carrington rotation over half a cycle (1986 - 1991), we compute the coefficients of the associated Legendre polynomials up to degree eight and compare with observations. We show that at minimum the dipole term dominates, but it fades as the cycle progresses; higher-order multipolar terms begin to dominate. The amplitudes of these terms are not exactly the same for the two limbs, indicating that there is a longitude dependence. While both the 1986 and the 1996 minimum coronas were dipolar, the minimum in 2008 was unusual, since there was a substantial departure from a dipole. We investigate the physical cause of this departure by including a North-South asymmetry in the surface source of the magnetic fields in our flux-transport dynamo model, and find that this asymmetry could be one of the reasons for departure from the dipole in the 2008 minimum.

  19. Probing model interstellar grain surfaces with small molecules

    NASA Astrophysics Data System (ADS)

    Collings, M. P.; Frankland, V. L.; Lasne, J.; Marchione, D.; Rosu-Finsen, A.; McCoustra, M. R. S.

    2015-05-01

    Temperature-programmed desorption and reflection-absorption infrared spectroscopy have been used to explore the interaction of oxygen (O2), nitrogen (N2), carbon monoxide (CO) and water (H2O) with an amorphous silica film as a demonstration of the detailed characterization of the silicate surfaces that might be present in the interstellar medium. The simple diatomic adsorbates are found to wet the silica surface and exhibit first-order desorption kinetics in the regime up to monolayer coverage. Beyond that, they exhibit zero-order kinetics as might be expected for sublimation of bulk solids. Water, in contrast, does not wet the silica surface and exhibits zero-order desorption kinetics at all coverages consistent with the formation of an islanded structure. Kinetic parameters for use in astrophysical modelling were obtained by inversion of the experimental data at sub-monolayer coverages and by comparison with models in the multilayer regime. Spectroscopic studies in the sub-monolayer regime show that the C-O stretching mode is at around 2137 cm-1 (5.43 μm), a position consistent with a linear surface-CO interaction, and is inhomogenously broadened as resulting from the heterogeneity of the surface. These studies also reveal, for the first time, direct evidence for the thermal activation of diffusion, and hence de-wetting, of H2O on the silica surface. Astrophysical implications of these findings could account for a part of the missing oxygen budget in dense interstellar clouds, and suggest that studies of the sub-monolayer adsorption of these simple molecules might be a useful probe of surface chemistry on more complex silicate materials.

  20. Modeling of surface cleaning by cavitation bubble dynamics and collapse.

    PubMed

    Chahine, Georges L; Kapahi, Anil; Choi, Jin-Keun; Hsiao, Chao-Tsung

    2016-03-01

    Surface cleaning using cavitation bubble dynamics is investigated numerically through modeling of bubble dynamics, dirt particle motion, and fluid material interaction. Three fluid dynamics models; a potential flow model, a viscous model, and a compressible model, are used to describe the flow field generated by the bubble all showing the strong effects bubble explosive growth and collapse have on a dirt particle and on a layer of material to remove. Bubble deformation and reentrant jet formation are seen to be responsible for generating concentrated pressures, shear, and lift forces on the dirt particle and high impulsive loads on a layer of material to remove. Bubble explosive growth is also an important mechanism for removal of dirt particles, since strong suction forces in addition to shear are generated around the explosively growing bubble and can exert strong forces lifting the particles from the surface to clean and sucking them toward the bubble. To model material failure and removal, a finite element structure code is used and enables simulation of full fluid-structure interaction and investigation of the effects of various parameters. High impulsive pressures are generated during bubble collapse due to the impact of the bubble reentrant jet on the material surface and the subsequent collapse of the resulting toroidal bubble. Pits and material removal develop on the material surface when the impulsive pressure is large enough to result in high equivalent stresses exceeding the material yield stress or its ultimate strain. Cleaning depends on parameters such as the relative size between the bubble at its maximum volume and the particle size, the bubble standoff distance from the particle and from the material wall, and the excitation pressure field driving the bubble dynamics. These effects are discussed in this contribution. PMID:25982895

  1. Surface matching for correlation of virtual models: Theory and application

    NASA Technical Reports Server (NTRS)

    Caracciolo, Roberto; Fanton, Francesco; Gasparetto, Alessandro

    1994-01-01

    Virtual reality can enable a robot user to off line generate and test in a virtual environment a sequence of operations to be executed by the robot in an assembly cell. Virtual models of objects are to be correlated to the real entities they represent by means of a suitable transformation. A solution to the correlation problem, which is basically a problem of 3-dimensional adjusting, has been found exploiting the surface matching theory. An iterative algorithm has been developed, which matches the geometric surface representing the shape of the virtual model of an object, with a set of points measured on the surface in the real world. A peculiar feature of the algorithm is to work also if there is no one-to-one correspondence between the measured points and those representing the surface model. Furthermore the problem of avoiding convergence to local minima is solved, by defining a starting point of states ensuring convergence to the global minimum. The developed algorithm has been tested by simulation. Finally, this paper proposes a specific application, i.e., correlating a robot cell, equipped for biomedical use with its virtual representation.

  2. 3D surface digitizing and modeling development at ITRI

    NASA Astrophysics Data System (ADS)

    Hsueh, Wen-Jean

    2000-06-01

    This paper gives an overview of the research and development activities in 3D surface digitizing and modeling conducted at the Industrial Technology Research Institute (ITRI) of Taiwan in the past decade. As a major technology and consulting service provider of the area, ITRI has developed 3D laser scanning digitizers ranging from low-cost compacts, industrial CAD/CAM digitizing, to large human body scanner, with in-house 3D surface modeling software to provide total solution in reverse engineering that requires processing capabilities of large number of 3D data. Based on both hardware and software technologies in scanning, merging, registration, surface fitting, reconstruction, and compression, ITRI is now exploring innovative methodologies that provide higher performances, including hardware-based correlation algorithms with advanced camera designs, animation surface model reconstruction, and optical tracking for motion capture. It is expected that the need for easy and fast high-quality 3D information in the near future will grow exponentially, at the same amazing rate as the internet and the human desire for realistic and natural images.

  3. A block-based landslide model using smooth surface reconstructions

    NASA Astrophysics Data System (ADS)

    Elsen, Katharina; Tinti, Stefano

    2014-05-01

    The present work is combining the block-based landslide-model developed by Tinti and Bertolucci (2000) with different smooth surface reconstruction methods. This enables us to directly solve the underlying ODE-system, that is describing the blocks motion, numerically. The numerical model is based on the idea that the sliding mass can be discretized by a certain number of quadrilateral blocks of finite volume, where the movement of the single blocks is described using a Lagrangian approach. Within this approach, the underlying equations of motion require for each time-step the computation of the acceleration of each of the blocks from their position on the sliding surface, where information on its curvature is needed in order to compute the centripetal component. To come up to this, different methods were used to interpolate smooth, two times differentiable, surface reconstructions from a given number of points that are describing the real sliding surface. The numerical solution of the model in time is obtained using higher-order explicit and implicit time-integration methods The results of the simulations are evaluated especially with respect to the arrival times and final velocities of the sliding mass and therefore a possible tsunamigenic impact.

  4. Contour-Based Surface Reconstruction using MPU Implicit Models.

    PubMed

    Braude, Ilya; Marker, Jeffrey; Museth, Ken; Nissanov, Jonathan; Breen, David

    2007-03-01

    This paper presents a technique for creating a smooth, closed surface from a set of 2D contours, which have been extracted from a 3D scan. The technique interprets the pixels that make up the contours as points in ℝ(3) and employs Multi-level Partition of Unity (MPU) implicit models to create a surface that approximately fits to the 3D points. Since MPU implicit models additionally require surface normal information at each point, an algorithm that estimates normals from the contour data is also described. Contour data frequently contains noise from the scanning and delineation process. MPU implicit models provide a superior approach to the problem of contour-based surface reconstruction, especially in the presence of noise, because they are based on adaptive implicit functions that locally approximate the points within a controllable error bound. We demonstrate the effectiveness of our technique with a number of example datasets, providing images and error statistics generated from our results. PMID:18496609

  5. Pain acceptance and personal control in pain relief in two maternity care models: a cross-national comparison of Belgium and the Netherlands

    PubMed Central

    2010-01-01

    Background A cross-national comparison of Belgian and Dutch childbearing women allows us to gain insight into the relative importance of pain acceptance and personal control in pain relief in 2 maternity care models. Although Belgium and the Netherlands are neighbouring countries sharing the same language, political system and geography, they are characterised by a different organisation of health care, particularly in maternity care. In Belgium the medical risks of childbirth are emphasised but neutralised by a strong belief in the merits of the medical model. Labour pain is perceived as a needless inconvenience easily resolved by means of pain medication. In the Netherlands the midwifery model of care defines childbirth as a normal physiological process and family event. Labour pain is perceived as an ally in the birth process. Methods Women were invited to participate in the study by independent midwives and obstetricians during antenatal visits in 2004-2005. Two questionnaires were filled out by 611 women, one at 30 weeks of pregnancy and one within the first 2 weeks after childbirth either at home or in a hospital. However, only women having a hospital birth without obstetric intervention (N = 327) were included in this analysis. A logistic regression analysis has been performed. Results Labour pain acceptance and personal control in pain relief render pain medication use during labour less likely, especially if they occur together. Apart from this general result, we also find large country differences. Dutch women with a normal hospital birth are six times less likely to use pain medication during labour, compared to their Belgian counterparts. This country difference cannot be explained by labour pain acceptance, since - in contrast to our working hypothesis - Dutch and Belgian women giving birth in a hospital setting are characterised by a similar labour pain acceptance. Our findings suggest that personal control in pain relief can partially explain the

  6. Interannual Variability of the Mosaic Land-Surface Model

    NASA Technical Reports Server (NTRS)

    Bosilovich, Michael G.; Houser, Paul R.; Schubert, Siegfried

    1999-01-01

    Recently, NASA Goddard Earth Observing System (GEOS-1) reanalysis data has been used to provide forcing for the Koster and Suarez Mosaic Land-surface Model (LSM). The LSM was integrated off-line at all global land points for the period of 1983 - 1995 by the Off-line Land- surface GEOS Assimilation system (OLGA). Here, we compare the interannual variability of OLGA, GEOS-1 and surface observing stations temperature and moisture. Particular attention is given to the United States because of the extreme seasons of 1988 and 1993. Furthermore, the comparison of OLGA is extended to include the analysis of data on the'tiles' (different surface types) in the Mosaic LSM. Results indicate that the GEOS-1 near-surface temperature and moisture reasonably represents the interannual variability in more normal years. However, OLGA also simulates the extreme drought and floods years well. The analysis of the tile information shows that the "Bare soil" surface type is most sensitive to the climate extremes. Off-line testing has provided valuable information on the performance of the Mosaic LSM prior to its incorporation into the new version of the GEOS Data Assimilation System and the integration of a new long reanalysis.

  7. Fusion of intraoperative force sensoring, surface reconstruction and biomechanical modeling

    NASA Astrophysics Data System (ADS)

    Röhl, S.; Bodenstedt, S.; Küderle, C.; Suwelack, S.; Kenngott, H.; Müller-Stich, B. P.; Dillmann, R.; Speidel, S.

    2012-02-01

    Minimally invasive surgery is medically complex and can heavily benefit from computer assistance. One way to help the surgeon is to integrate preoperative planning data into the surgical workflow. This information can be represented as a customized preoperative model of the surgical site. To use it intraoperatively, it has to be updated during the intervention due to the constantly changing environment. Hence, intraoperative sensor data has to be acquired and registered with the preoperative model. Haptic information which could complement the visual sensor data is still not established. In addition, biomechanical modeling of the surgical site can help in reflecting the changes which cannot be captured by intraoperative sensors. We present a setting where a force sensor is integrated into a laparoscopic instrument. In a test scenario using a silicone liver phantom, we register the measured forces with a reconstructed surface model from stereo endoscopic images and a finite element model. The endoscope, the instrument and the liver phantom are tracked with a Polaris optical tracking system. By fusing this information, we can transfer the deformation onto the finite element model. The purpose of this setting is to demonstrate the principles needed and the methods developed for intraoperative sensor data fusion. One emphasis lies on the calibration of the force sensor with the instrument and first experiments with soft tissue. We also present our solution and first results concerning the integration of the force sensor as well as accuracy to the fusion of force measurements, surface reconstruction and biomechanical modeling.

  8. Fourier method for large scale surface modeling and registration.

    PubMed

    Shen, Li; Kim, Sungeun; Saykin, Andrew J

    2009-06-01

    Spherical harmonic (SPHARM) description is a powerful Fourier shape modeling method for processing arbitrarily shaped but simply connected 3D objects. As a highly promising method, SPHARM has been widely used in several domains including medical imaging. However, its primary use has been focused on modeling small or moderately-sized surfaces that are relatively smooth, due to challenges related to its applicability, robustness and scalability. This paper presents an enhanced SPHARM framework that addresses these issues and show that the use of SPHARM can expand into broader areas. In particular, we present a simple and efficient Fourier expansion method on the sphere that enables large scale modeling, and propose a new SPHARM registration method that aims to preserve the important homological properties between 3D models. Although SPHARM is a global descriptor, our experimental results show that the proposed SPHARM framework can accurately describe complicated graphics models and highly convoluted 3D surfaces and the proposed registration method allows for effective alignment and registration of these 3D models for further processing or analysis. These methods greatly enable the potential of applying SPHARM to broader areas such as computer graphics, medical imaging, CAD/CAM, bioinformatics, and other related geometric modeling and processing fields. PMID:20161536

  9. ELECTRON AVALANCHE MODEL OF DIELECTRIC-VACUUM SURFACE BREAKDOWN

    SciTech Connect

    Lauer, E J

    2007-02-21

    The model assumes that an 'initiating event' results in positive ions on the surface near the anode and reverses the direction of the normal component of electric field so that electrons in vacuum are attracted to the dielectric locally. A sequence of surface electron avalanches progresses in steps from the anode to the cathode. For 200 kV across 1 cm, the spacing of avalanches is predicted to be about 13 microns. The time for avalanches to step from the anode to the cathode is predicted to be about a ns.

  10. Generation of digital textured surface models from hologram recordings

    NASA Astrophysics Data System (ADS)

    Frey, Susanne; Thelen, Andrea; Hirsch, Sven; Hering, Peter

    2007-04-01

    Digital sensors and fast digital image processing facilitate the use of pulsed holography for 3D surface measurement of moving objects. The real image of a hologram is reconstructed optically. A sequence of high-resolution projection images of the real image with a varying distance to the hologram is recorded digitally. Focus detection in this image sequence by digital image processing yields the shape of the recorded object. The image intensity serves as a precise pixel-matching texture. An application of this concept is the generation of a textured 3D computer model of a facial surface from a portrait hologram.

  11. Assimilation of GOES Land Surface Data into a Mesoscale Models

    NASA Technical Reports Server (NTRS)

    Lapenta, William M.; Suggs, Ron; McNider, Richard T.; Jedlovec, Gary; Dembek, Scott; Goodman, H. Michael (Technical Monitor)

    2001-01-01

    A technique has been developed for assimilating Geostationary Operational Environmental Satellite (GOES)-derived skin temperature tendencies and insolation into the surface energy budget equation of a mesoscale model so that the simulated rate of temperature change closely agrees with the satellite observations. A critical assumption of the technique is that the availability of moisture (either from the soil or vegetation) is the least known term in the model's surface energy budget. Therefore, the simulated latent heat flux, which is a function of surface moisture availability, is adjusted based upon differences between the modeled and satellite-observed skin temperature tendencies. An advantage of this technique is that satellite temperature tendencies are assimilated in an energetically consistent manner that avoids energy imbalances and surface stability problems that arise from direct assimilation of surface shelter temperatures. The fact that the rate of change of the satellite skin temperature is used rather than the absolute temperature means that sensor calibration is not as critical. The assimilation technique has been applied to the Oklahoma-Kansas region during the spring-summer 2000 time period when dynamic changes in vegetation cover occur. In April, central Oklahoma is characterized by large NDVI associated with winter wheat while surrounding areas are primarily rangeland with lower NDVI. In July the vegetation pattern reverses as the central wheat area changes to low NDVI due to harvesting and the surrounding rangeland is greener than it was in April. The goal of this study is to determine if assimilating satellite land surface data can improve simulation of the complex spatial distribution of surface energy and water fluxes across this region. The PSU/NCAR NM5 V3 system is used in this study. The grid configuration consists of a 36-km CONUS domain and a 12-km nest over the area of interest. Bulk verification statistics (BIAS and RMSE) of surface

  12. Surface complexation modeling of inositol hexaphosphate sorption onto gibbsite.

    PubMed

    Ruyter-Hooley, Maika; Larsson, Anna-Carin; Johnson, Bruce B; Antzutkin, Oleg N; Angove, Michael J

    2015-02-15

    The sorption of Inositol hexaphosphate (IP6) onto gibbsite was investigated using a combination of adsorption experiments, (31)P solid-state MAS NMR spectroscopy, and surface complexation modeling. Adsorption experiments conducted at four temperatures showed that IP6 sorption decreased with increasing pH. At pH 6, IP6 sorption increased with increasing temperature, while at pH 10 sorption decreased as the temperature was raised. (31)P MAS NMR measurements at pH 3, 6, 9 and 11 produced spectra with broad resonance lines that could be de-convoluted with up to five resonances (+5, 0, -6, -13 and -21ppm). The chemical shifts suggest the sorption process involves a combination of both outer- and inner-sphere complexation and surface precipitation. Relative intensities of the observed resonances indicate that outer-sphere complexation is important in the sorption process at higher pH, while inner-sphere complexation and surface precipitation are dominant at lower pH. Using the adsorption and (31)P MAS NMR data, IP6 sorption to gibbsite was modeled with an extended constant capacitance model (ECCM). The adsorption reactions that best described the sorption of IP6 to gibbsite included two inner-sphere surface complexes and one outer-sphere complex: ≡AlOH + IP₆¹²⁻ + 5H⁺ ↔ ≡Al(IP₆H₄)⁷⁻ + H₂O, ≡3AlOH + IP₆¹²⁻ + 6H⁺ ↔ ≡Al₃(IP₆H₃)⁶⁻ + 3H₂O, ≡2AlOH + IP₆¹²⁻ + 4H⁺ ↔ (≡AlOH₂)₂²⁺(IP₆H₂)¹⁰⁻. The inner-sphere complex involving three surface sites may be considered to be equivalent to a surface precipitate. Thermodynamic parameters were obtained from equilibrium constants derived from surface complexation modeling. Enthalpies for the formation of inner-sphere surface complexes were endothermic, while the enthalpy for the outer-sphere complex was exothermic. The entropies for the proposed sorption reactions were large and positive suggesting that changes in solvation of species play a major role in driving

  13. Comparison between two models of cooling surfaces using blowing.

    PubMed

    Mathelin, L; Bataille, F; Lallemand, A

    2001-05-01

    To protect surfaces against high temperatures, the blowing through a porous material is studied. The geometry is that of a circular cylinder in cross-flow and the effectiveness of the blowing for the thermal protection is numerically investigated. Two models are developed for the blowing simulation and comparisons are made with experimental data obtained in a heated wind-tunnel. It is shown that the blowing strongly affects the dynamical and thermal profiles over the surface, thickening the boundary layers and decreasing the external transfer coefficients. It results in a lower viscous drag and thermal stress. The wall temperature dramatically decreases with blowing and the heat flux is also affected. PMID:11460652

  14. Students Perception towards the Implementation of Computer Graphics Technology in Class via Unified Theory of Acceptance and Use of Technology (UTAUT) Model

    NASA Astrophysics Data System (ADS)

    Binti Shamsuddin, Norsila

    Technology advancement and development in a higher learning institution is a chance for students to be motivated to learn in depth in the information technology areas. Students should take hold of the opportunity to blend their skills towards these technologies as preparation for them when graduating. The curriculum itself can rise up the students' interest and persuade them to be directly involved in the evolvement of the technology. The aim of this study is to see how deep is the students' involvement as well as their acceptance towards the adoption of the technology used in Computer Graphics and Image Processing subjects. The study will be towards the Bachelor students in Faculty of Industrial Information Technology (FIIT), Universiti Industri Selangor (UNISEL); Bac. In Multimedia Industry, BSc. Computer Science and BSc. Computer Science (Software Engineering). This study utilizes the new Unified Theory of Acceptance and Use of Technology (UTAUT) to further validate the model and enhance our understanding of the adoption of Computer Graphics and Image Processing Technologies. Four (4) out of eight (8) independent factors in UTAUT will be studied towards the dependent factor.

  15. Quantifying near-surface water exchange to assess hydrometeorological models

    NASA Astrophysics Data System (ADS)

    Parent, Annie-Claude; Anctil, François; Morais, Anne

    2013-04-01

    Modelling water exchange from the lower atmosphere, crop and soil system using hydrometeorological models allows processing an actual evapotranspiration (ETa) which is a complex but critical value for numerous hydrological purposes e.g. hydrological modelling and crop irrigation. This poster presents a summary of the hydrometeorological research activity conducted by our research group. The first purpose of this research is to quantify ETa and drainage of a rainfed potato crop located in South-Eastern Canada. Then, the outputs of the hydrometeorological models under study are compared with the observed turbulent fluxes. Afterwards, the sensibility of the hydrometeorological models to different inputs is assessed for an environment under a changing climate. ETa was measured from micrometeorological instrumentation (CSAT3, Campbell SCI Inc.; Li7500, LiCor Inc.), and the eddy covariance techniques. Near surface soil heat flux and soil water content at different layers from 10 cm to 100 cm were also measured. Other parameters required by the hydrometeorological models were observed using meteorological standard instrumentation: shortwave and longwave solar radiation, wind speed, air temperature, atmospheric pressure and precipitation. The cumulative ETa during the growth season (123 days) was 331.5 mm, with a daily maximum of 6.5 mm at full coverage; precipitation was 350.6 mm which is rather small compared with the historical mean (563.3 mm). This experimentation allowed calculating crop coefficients that vary among the growth season for a rainfed potato crop. Land surface schemes as CLASS (Canadian Land Surface Scheme) and c-ISBA (a Canadian version of the model Interaction Sol-Biosphère-Atmosphère) are 1-D physical hydrometeorological models that produce turbulent fluxes (including ETa) for a given crop. The schemes performances were assessed for both energy and water balance, based on the resulting turbulent fluxes and the given observations. CLASS showed

  16. Establishment and metabolic analysis of a model microbial community for understanding trophic and electron accepting interactions of subsurface anaerobic environments

    SciTech Connect

    Miller, Lance D; Mosher, Jennifer J; Venkateswaran, Amudhan; Yang, Zamin Koo; Palumbo, Anthony Vito; Phelps, Tommy Joe; Podar, Mircea; Schadt, Christopher Warren; Keller, Martin

    2010-01-01

    Communities of microorganisms control the rates of key biogeochemical cycles, and are important for biotechnology, bioremediation, and industrial microbiological processes. For this reason, we constructed a model microbial community comprised of three species dependent on trophic interactions. The three species microbial community was comprised of Clostridium cellulolyticum, Desulfovibrio vulgaris Hildenborough, and Geobacter sulfurreducens and was grown under continuous culture conditions. Cellobiose served as the carbon and energy source for C. cellulolyticum, whereas D. vulgaris and G. sulfurreducens derived carbon and energy from the metabolic products of cellobiose fermentation and were provided with sulfate and fumarate respectively as electron acceptors.

  17. Supernova, baryon acoustic oscillations, and CMB surface distance constraints on f(G) higher order gravity models

    SciTech Connect

    Moldenhauer, Jacob; Ishak, Mustapha; Thompson, John; Easson, Damien A.

    2010-03-15

    We consider recently proposed higher-order gravity models where the action is built from the Einstein-Hilbert action plus a function f(G) of the Gauss-Bonnet invariant. The models were previously shown to pass physical acceptability conditions as well as solar system tests. In this paper, we compare the models to combined data sets of supernovae, baryon acoustic oscillations, and constraints from the CMB surface of last scattering. We find that the models provide fits to the data that are close to those of the lambda cold dark matter concordance model. The results provide a pool of higher-order gravity models that pass these tests and need to be compared to constraints from large scale structure and full CMB analysis.

  18. A simple hydrologically based model of land surface water and energy fluxes for general circulation models

    NASA Technical Reports Server (NTRS)

    Liang, XU; Lettenmaier, Dennis P.; Wood, Eric F.; Burges, Stephen J.

    1994-01-01

    A generalization of the single soil layer variable infiltration capacity (VIC) land surface hydrological model previously implemented in the Geophysical Fluid Dynamics Laboratory (GFDL) general circulation model (GCM) is described. The new model is comprised of a two-layer characterization of the soil column, and uses an aerodynamic representation of the latent and sensible heat fluxes at the land surface. The infiltration algorithm for the upper layer is essentially the same as for the single layer VIC model, while the lower layer drainage formulation is of the form previously implemented in the Max-Planck-Institut GCM. The model partitions the area of interest (e.g., grid cell) into multiple land surface cover types; for each land cover type the fraction of roots in the upper and lower zone is specified. Evapotranspiration consists of three components: canopy evaporation, evaporation from bare soils, and transpiration, which is represented using a canopy and architectural resistance formulation. Once the latent heat flux has been computed, the surface energy balance is iterated to solve for the land surface temperature at each time step. The model was tested using long-term hydrologic and climatological data for Kings Creek, Kansas to estimate and validate the hydrological parameters, and surface flux data from three First International Satellite Land Surface Climatology Project Field Experiment (FIFE) intensive field campaigns in the summer-fall of 1987 to validate the surface energy fluxes.

  19. Identification of response surface models using genetic programming

    NASA Astrophysics Data System (ADS)

    Lew, T. L.; Spencer, A. B.; Scarpa, F.; Worden, K.; Rutherford, A.; Hemez, F.

    2006-11-01

    There is a move in modern research in Structural Dynamics towards analysing the inherent uncertainty in a given problem. This may be quantifying or fusing uncertainty models, or can be propagation of uncertainty through a system or calculation. If the system of interest is represented by, e.g. a large Finite Element (FE) model the large number of computations involved can rule out many approaches due to the expense of carrying out many runs. One way of circumnavigating this problem is to replace the true system by an approximate surrogate/replacement model, which is fast-running compared to the original. In traditional approaches using response surfaces a simple least-squares multinomial model is often adopted. The objective of this paper is to extend the class of possible models considerably by carrying out a general symbolic regression using a Genetic Programming approach. The approach is demonstrated on both univariate and multivariate problems with both computational and experimental data.

  20. improved vegetation phenology in the JULES land-surface model

    NASA Astrophysics Data System (ADS)

    Los, S. O.

    2013-12-01

    Sietse Los, Steven Hancock, Peter North, Jose Gomez-Dans Introduction: Land-surface properties such as albedo, soil moisture and vegetation biophysical parameters affect water, energy and carbon fluxes from the land to the atmosphere an this can alter weather patterns. Here we use globally consistent satellite observations to improve modelling of the vegetation seasonal cycle in the JULES land-surface model (LSM) to better represent these fluxes. JULES model: The JULES LSM is the land surface component of the suite of UK MetOffice general circulation models. JULES is used both in operational weather forecasting and for simulations of future climate. Within JULES, seasonal changes in surface albedo are controlled by snow (not covered here) and vegetation dynamics (phenology). Vegetation phenology is controlled by temperature and water availability, with timings and rates set by a number of trigger thresholds and leaf growth/death rates. Satellite data: The ability of JULES to represent vegetation, in terms of its seasonal cycle as well as the interannual variation, was tested on normalised difference vegetation index (NDVI = (near-infrared - red) / (near-infrared + red)) data. JULES uses a 1D radiative transfer model to predict hemispheric surface albedo for a given leaf area whilst satellites measure reflectance from a single view direction and this may not match the hemispheric albedo. To test this, JULES predictions were compared to the FLIGHT (a 3D radiative transfer model) simulations for different view directions. This revealed that either NDVI profiles need to be normalised to allow a direct comparison (as done here) or else the JULES 1D model must be replaced by a full 3D radiative transfer model, which is computationally expensive. Experiments: The original phenology module in JULES was optimised against NDVI observations using a Monte-Carlo Markov chain method. This optimisation was unsuccessful; and we therefore concluded that the JULES phenology cannot

  1. Methods for the Update and Verification of Forest Surface Model

    NASA Astrophysics Data System (ADS)

    Rybansky, M.; Brenova, M.; Zerzan, P.; Simon, J.; Mikita, T.

    2016-06-01

    The digital terrain model (DTM) represents the bare ground earth's surface without any objects like vegetation and buildings. In contrast to a DTM, Digital surface model (DSM) represents the earth's surface including all objects on it. The DTM mostly does not change as frequently as the DSM. The most important changes of the DSM are in the forest areas due to the vegetation growth. Using the LIDAR technology the canopy height model (CHM) is obtained by subtracting the DTM and the corresponding DSM. The DSM is calculated from the first pulse echo and DTM from the last pulse echo data. The main problem of the DSM and CHM data using is the actuality of the airborne laser scanning. This paper describes the method of calculating the CHM and DSM data changes using the relations between the canopy height and age of trees. To get a present basic reference data model of the canopy height, the photogrammetric and trigonometric measurements of single trees were used. Comparing the heights of corresponding trees on the aerial photographs of various ages, the statistical sets of the tree growth rate were obtained. These statistical data and LIDAR data were compared with the growth curve of the spruce forest, which corresponds to a similar natural environment (soil quality, climate characteristics, geographic location, etc.) to get the updating characteristics.

  2. Modelling boundary layer flow over barnacle-fouled surfaces

    NASA Astrophysics Data System (ADS)

    Sadique, Jasim; Yang, Xiang; Meneveau, Charles; Mittal, Rajat

    2014-11-01

    Macro-biofouling is a critical concern for the marine industry. However, there is little data on flow and drag over such surfaces. Accurate modelling of such multi-scale flows remains a big challenge. Such simulations are vital in providing insights into the fundamental flow physics, and they can be used to estimate the timing, need and effectiveness of measures used to counteract bio-fouling. This talk focuses on the use of a sharp-interface immersed boundary method coupled with a wall model and large-eddy simulations to carry out accurate simulations of a turbulent boundary layer flow over macro-fouled surfaces. For the current study, high resolution scans of barnacles were used to create simple geometrical representations. Simulations were then carried out to test how well these simpler geometric models mimic the flow over actual barnacles. Simulations of array of modeled barnacles, with different barnacle densities have also been carried out and we present results on the effect distribution density on the flow physics and drag on the surfaces. This work is funded by ONR Grant N00014-12-1-0582.

  3. An Analytic Function of Lunar Surface Temperature for Exospheric Modeling

    NASA Technical Reports Server (NTRS)

    Hurley, Dana M.; Sarantos, Menelaos; Grava, Cesare; Williams, Jean-Pierre; Retherford, Kurt D.; Siegler, Matthew; Greenhagen, Benjamin; Paige, David

    2014-01-01

    We present an analytic expression to represent the lunar surface temperature as a function of Sun-state latitude and local time. The approximation represents neither topographical features nor compositional effects and therefore does not change as a function of selenographic latitude and longitude. The function reproduces the surface temperature measured by Diviner to within +/-10 K at 72% of grid points for dayside solar zenith angles of less than 80, and at 98% of grid points for nightside solar zenith angles greater than 100. The analytic function is least accurate at the terminator, where there is a strong gradient in the temperature, and the polar regions. Topographic features have a larger effect on the actual temperature near the terminator than at other solar zenith angles. For exospheric modeling the effects of topography on the thermal model can be approximated by using an effective longitude for determining the temperature. This effective longitude is randomly redistributed with 1 sigma of 4.5deg. The resulting ''roughened'' analytical model well represents the statistical dispersion in the Diviner data and is expected to be generally useful for future models of lunar surface temperature, especially those implemented within exospheric simulations that address questions of volatile transport.

  4. Global scale hydrology - Advances in land surface modeling

    SciTech Connect

    Wood, E.F. )

    1991-01-01

    Research into global scale hydrology is an expanding area that includes researchers from the meteorology, climatology, ecology and hydrology communities. This paper reviews research in this area carried out in the United States during the last IUGG quadrennial period of 1987-1990. The review covers the representation of land-surface hydrologic processes for general circulation models (GCMs), sensitivity analysis of these representations on global hydrologic fields like precipitation, regional studies of climate that have global hydrologic implications, recent field studies and experiments whose aims are the improved understanding of land surface-atmospheric interactions, and the use of remotely sensed data for the further understanding of the spatial variability of surface hydrologic processes that are important at regional and global climate scales. 76 refs.

  5. Cross comparisons of land surface process descriptions in land surface models using multiple sources of data

    NASA Astrophysics Data System (ADS)

    Park, Gi Hyeon

    2006-12-01

    Land surface-atmospheric interactions influence climate and weather varying spatial scales from local to mesoscale, and even to global. This dissertation deals with several topics: (1) evaluation of various sources of incoming solar radiations, (2) evaluation of land surface process descriptions in the land surface models in both basin-scale and point scale offline model simulations, and (3) inverse estimation of radiation components using net radiation and other meteorological variables. Incoming solar radiations from various sources were evaluated. This study identified the two sources of errors in the North American Data Assimilation system (NLDAS) solar radiation: One is related to bias inherited from the ETA Data Assimilation System (EDAS) during 2001 and 2003, and the other is software error at NESDIS operational system during 2002. Land surface processes are treated quite differently in the land surface models used in this study. Over the state of Oklahoma, Common Land Model 2.1 (CLM2.1) estimates more evaporation but less transpiration than the Variable Infiltration Capacity (VIC3L) model. This is due to the difference in the runoff algorithm, which results in more infiltration down to the soil layer and then providing more available water to plant roots in VIC3L. CLM2.1 overestimates ground heat flux in Point scale simulation. CoLM, which employs two stream radiative transfer scheme, shows better agreements to adjusted ground observations (using Bowen-ration closure method) in offline simulations than CLM2.1. CoLM, in addition, shows various model behaviors depending on vegetation cover types. Inverse radiation estimation methods were developed and evaluated at four AmeriFlux sites. Analysis of observed radiations showed a triangle shape relationship among net radiation, net solar radiation and cloud factor (defined in this study). Clear-sky downward longwave radiation is needed to be calibrated for each site. SCE-UA method was used to calibrate an

  6. Use of upscaled elevation and surface roughness data in two-dimensional surface water models

    USGS Publications Warehouse

    Hughes, J.D.; Decker, J.D.; Langevin, C.D.

    2011-01-01

    In this paper, we present an approach that uses a combination of cell-block- and cell-face-averaging of high-resolution cell elevation and roughness data to upscale hydraulic parameters and accurately simulate surface water flow in relatively low-resolution numerical models. The method developed allows channelized features that preferentially connect large-scale grid cells at cell interfaces to be represented in models where these features are significantly smaller than the selected grid size. The developed upscaling approach has been implemented in a two-dimensional finite difference model that solves a diffusive wave approximation of the depth-integrated shallow surface water equations using preconditioned Newton–Krylov methods. Computational results are presented to show the effectiveness of the mixed cell-block and cell-face averaging upscaling approach in maintaining model accuracy, reducing model run-times, and how decreased grid resolution affects errors. Application examples demonstrate that sub-grid roughness coefficient variations have a larger effect on simulated error than sub-grid elevation variations.

  7. Observations, models, and mechanisms of failure of surface rocks surrounding planetary surface loads

    NASA Technical Reports Server (NTRS)

    Schultz, R. A.; Zuber, M. T.

    1994-01-01

    Geophysical models of flexural stresses in an elastic lithosphere due to an axisymmetric surface load typically predict a transition with increased distance from the center of the load of radial thrust faults to strike-slip faults to concentric normal faults. These model predictions are in conflict with the absence of annular zones of strike-slip faults around prominent loads such as lunar maria, Martian volcanoes, and the Martian Tharsis rise. We suggest that this paradox arises from difficulties in relating failure criteria for brittle rocks to the stress models. Indications that model stresses are inappropriate for use in fault-type prediction include (1) tensile principal stresses larger than realistic values of rock tensile strength, and/or (2) stress differences significantly larger than those allowed by rock-strength criteria. Predictions of surface faulting that are consistent with observations can be obtained instead by using tensile and shear failure criteria, along with calculated stress differences and trajectories, with model stress states not greatly in excess of the maximum allowed by rock fracture criteria.

  8. Tangent linear analysis of the Mosaic land surface model

    NASA Astrophysics Data System (ADS)

    Yang, Runhua; Cohn, Stephen E.; da Silva, Arlindo; Joiner, Joanna; Houser, Paul R.

    2003-01-01

    In this study, a tangent linear eigenanalysis is applied to the Mosaic land surface model (LSM) [, 1992] to examine the impacts of the model internal dynamics and physics on the land surface state variability. The tangent linear model (TLM) of the Mosaic LSM is derived numerically for two sets of basic states and two tile types of land condition, grass and bare soil. An additional TLM, for the soil moisture subsystem of this LSM, is derived analytically for the same cases to obtain explicit expressions for the eigenvalues. An eigenvalue of the TLM determines a characteristic timescale, and the corresponding eigenvector, or mode, describes a particular coupling among the perturbed states. The results show that (1) errors in initial conditions tend to decay with e-folding times given by the characteristic timescales; (2) the LSM exhibits a wide range of internal variability, modes mainly representing surface temperature and surface moisture perturbations exhibit short timescales, whereas modes mainly representing deep soil temperature perturbations and moisture transfer throughout the entire soil column exhibit much longer timescales; (3) the modes of soil moisture tend to be weakly coupled with other perturbed variables, and the mode representing the deep soil temperature perturbation has a consistent e-folding time across the experiments; (4) the key parameters include soil moisture, soil layer depth, and soil hydraulic parameters. The results agree qualitatively with previous findings. However, tangent linear eigenanalysis provides a new approach to the quantitative substantiation of those findings. Also, it reveals the evolution and the coupling of the perturbed land states that are useful for the development of land surface data assimilation schemes. One must be careful when generalizing the quantitative results since they are obtained with respect to two specific basic states and two simple land conditions. Also, the methodology employed here does not apply

  9. Efficient modelling of droplet dynamics on complex surfaces.

    PubMed

    Karapetsas, George; Chamakos, Nikolaos T; Papathanasiou, Athanasios G

    2016-03-01

    This work investigates the dynamics of droplet interaction with smooth or structured solid surfaces using a novel sharp-interface scheme which allows the efficient modelling of multiple dynamic contact lines. The liquid-gas and liquid-solid interfaces are treated in a unified context and the dynamic contact angle emerges simply due to the combined action of the disjoining and capillary pressure, and viscous stresses without the need of an explicit boundary condition or any requirement for the predefinition of the number and position of the contact lines. The latter, as it is shown, renders the model able to handle interfacial flows with topological changes, e.g. in the case of an impinging droplet on a structured surface. Then it is possible to predict, depending on the impact velocity, whether the droplet will fully or partially impregnate the structures of the solid, or will result in a 'fakir', i.e. suspended, state. In the case of a droplet sliding on an inclined substrate, we also demonstrate the built-in capability of our model to provide a prediction for either static or dynamic contact angle hysteresis. We focus our study on hydrophobic surfaces and examine the effect of the geometrical characteristics of the solid surface. It is shown that the presence of air inclusions trapped in the micro-structure of a hydrophobic substrate (Cassie-Baxter state) result in the decrease of contact angle hysteresis and in the increase of the droplet migration velocity in agreement with experimental observations for super-hydrophobic surfaces. Moreover, we perform 3D simulations which are in line with the 2D ones regarding the droplet mobility and also indicate that the contact angle hysteresis may be significantly affected by the directionality of the structures with respect to the droplet motion. PMID:26828706

  10. Efficient modelling of droplet dynamics on complex surfaces

    NASA Astrophysics Data System (ADS)

    Karapetsas, George; Chamakos, Nikolaos T.; Papathanasiou, Athanasios G.

    2016-03-01

    This work investigates the dynamics of droplet interaction with smooth or structured solid surfaces using a novel sharp-interface scheme which allows the efficient modelling of multiple dynamic contact lines. The liquid-gas and liquid-solid interfaces are treated in a unified context and the dynamic contact angle emerges simply due to the combined action of the disjoining and capillary pressure, and viscous stresses without the need of an explicit boundary condition or any requirement for the predefinition of the number and position of the contact lines. The latter, as it is shown, renders the model able to handle interfacial flows with topological changes, e.g. in the case of an impinging droplet on a structured surface. Then it is possible to predict, depending on the impact velocity, whether the droplet will fully or partially impregnate the structures of the solid, or will result in a ‘fakir’, i.e. suspended, state. In the case of a droplet sliding on an inclined substrate, we also demonstrate the built-in capability of our model to provide a prediction for either static or dynamic contact angle hysteresis. We focus our study on hydrophobic surfaces and examine the effect of the geometrical characteristics of the solid surface. It is shown that the presence of air inclusions trapped in the micro-structure of a hydrophobic substrate (Cassie-Baxter state) result in the decrease of contact angle hysteresis and in the increase of the droplet migration velocity in agreement with experimental observations for super-hydrophobic surfaces. Moreover, we perform 3D simulations which are in line with the 2D ones regarding the droplet mobility and also indicate that the contact angle hysteresis may be significantly affected by the directionality of the structures with respect to the droplet motion.

  11. Surface and Flow Field Measurements on the FAITH Hill Model

    NASA Technical Reports Server (NTRS)

    Bell, James H.; Heineck, James T.; Zilliac, Gregory; Mehta, Rabindra D.; Long, Kurtis R.

    2012-01-01

    A series of experimental tests, using both qualitative and quantitative techniques, were conducted to characterize both surface and off-surface flow characteristics of an axisymmetric, modified-cosine-shaped, wall-mounted hill named "FAITH" (Fundamental Aero Investigates The Hill). Two separate models were employed: a 6" high, 18" base diameter machined aluminum model that was used for wind tunnel tests and a smaller scale (2" high, 6" base diameter) sintered nylon version that was used in the water channel facility. Wind tunnel and water channel tests were conducted at mean test section speeds of 165 fps (Reynolds Number based on height = 500,000) and 0.1 fps (Reynolds Number of 1000), respectively. The ratio of model height to boundary later height was approximately 3 for both tests. Qualitative techniques that were employed to characterize the complex flow included surface oil flow visualization for the wind tunnel tests, and dye injection for the water channel tests. Quantitative techniques that were employed to characterize the flow included Cobra Probe to determine point-wise steady and unsteady 3D velocities, Particle Image Velocimetry (PIV) to determine 3D velocities and turbulence statistics along specified planes, Pressure Sensitive Paint (PSP) to determine mean surface pressures, and Fringe Imaging Skin Friction (FISF) to determine surface skin friction (magnitude and direction). This initial report summarizes the experimental set-up, techniques used, data acquired and describes some details of the dataset that is being constructed for use by other researchers, especially the CFD community. Subsequent reports will discuss the data and their interpretation in more detail

  12. Interactive system for quick modeling of aircraft surfaces

    NASA Astrophysics Data System (ADS)

    Mudur, S. P.; Khandekar, Dilip R.

    1990-08-01

    The precise specification of surface geometry of an aircraft is one of the most important and major activities inits design. An initial design, defined by the fundamental requirements, is iteratively analysed and modified till a satisfactory configuration is obtained. Very often in the early stages the need to rapidly make modifications to the geometry for immediate analysis overrides the stringency of smoothness and correctness ofthe surfaces. This paper describes the design of an interactive system which enables the designer to quickly specify the surface geometry and to modify it easily and rapidly. In particular, the software engineering aspects are emphasized. The system uses B-splines for the representation of complex geometry. Surfaces of revolution, required to model certain parts ofthe aircraft, and other simple geometric primitives are also supported. Apart from the usual modeller facilities, features such as camber, twist and form constraints such as tangent or curvature control at a point, etc., are also provided. The system enables easy input and rapid editing of geomeiry through the use of a number of innovative concepts which aim at simplifying and speeding up the man-machine interaction. Multiple window display of entities, augmented by plots of curvature, cross sections etc. provide the visualization tool necessary to assist the designer in decision making.

  13. Modeling marine surface microplastic transport to assess optimal removal locations

    NASA Astrophysics Data System (ADS)

    Sherman, Peter; van Sebille, Erik

    2016-01-01

    Marine plastic pollution is an ever-increasing problem that demands immediate mitigation and reduction plans. Here, a model based on satellite-tracked buoy observations and scaled to a large data set of observations on microplastic from surface trawls was used to simulate the transport of plastics floating on the ocean surface from 2015 to 2025, with the goal to assess the optimal marine microplastic removal locations for two scenarios: removing the most surface microplastic and reducing the impact on ecosystems, using plankton growth as a proxy. The simulations show that the optimal removal locations are primarily located off the coast of China and in the Indonesian Archipelago for both scenarios. Our estimates show that 31% of the modeled microplastic mass can be removed by 2025 using 29 plastic collectors operating at a 45% capture efficiency from these locations, compared to only 17% when the 29 plastic collectors are moored in the North Pacific garbage patch, between Hawaii and California. The overlap of ocean surface microplastics and phytoplankton growth can be reduced by 46% at our proposed locations, while sinks in the North Pacific can only reduce the overlap by 14%. These results are an indication that oceanic plastic removal might be more effective in removing a greater microplastic mass and in reducing potential harm to marine life when closer to shore than inside the plastic accumulation zones in the centers of the gyres.

  14. Surface science studies of ethene containing model interstellar ices

    NASA Astrophysics Data System (ADS)

    Puletti, F.; Whelan, M.; Brown, W. A.

    2011-05-01

    The formation of saturated hydrocarbons in the interstellar medium (ISM) is difficult to explain only by taking into account gas phase reactions. This is mostly due to the fact that carbonium ions only react with H_2 to make unsaturated hydrocarbons, and hence no viable route to saturated hydrocarbons has been postulated to date. It is therefore likely that saturation processes occur via surface reactions that take place on interstellar dust grains. One of the species of interest in this family of reactions is C_2H_4 (ethene) which is an intermediate in several molecular formation routes (e.g. C_2H_2 → C_2H_6). To help to understand some of the surface processes involving ethene, a study of ethene deposited on a dust grain analogue surface (highly oriented pyrolytic graphite) held under ultra-high vacuum at 20 K has been performed. The adsorption and desorption of ethene has been studied both in water-free and water-dominated model interstellar ices. A combination of temperature programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS) have been used to identify the adsorbed and trapped species and to determine the kinetics of the desorption processes. In all cases, ethene is found to physisorb on the carbonaceous surface. As expected water has a very strong influence on the desorption of ethene, as previously observed for other model interstellar ice systems.

  15. Microfriction studies of model self-lubricating surfaces

    SciTech Connect

    Blau, P.J.; Yust, C.S.

    1993-05-06

    Self-lubricating composites consist of at least one structural (matrix) phase and at least one phase to provide lubrication. Modeling the behavior of such composites involves ascertaining the frictional contributions of each constituent phase under varying conditions of lubricating films coverage. The ORNL friction microprobe (FMP), a specialized microcontact tribometer, was used to investigate the frictional behavior of both matrix and lubricant phases to support the development of self-lubricating, surfaces. Polished CVD-silicon carbide deposits and silicon wafers were used as substrates. The wafers were intended to simulate the thin silica films present on SiC surfaces at elevated temperature. Molybdenum disulfide, in both sputtered and burnished forms, was used as the model lubricant. The effects of CVD-SiC substrate surface roughness and method of lubricant film deposition on the substrate were studied for single passes of a spherical silicon nitride slider (NBD 200 material). In contrast to the smooth sliding exhibit by burnished, films, sputtered MoS{sub 2} surfaces exhibited marked stick-slip behavior, indicating that the frictional behavior of solid lubricating coatings can be quite erratic on a microscale, especially when asperity contacts are elastically compliant.

  16. A scattering model for perfectly conducting random surfaces. I - Model development. II - Range of validity

    NASA Technical Reports Server (NTRS)

    Fung, A. K.; Pan, G. W.

    1987-01-01

    The surface current on a perfectly conducting randomly rough surface is estimated by solving iteratively a standard integral equation, and the estimate is then used to compute the far-zone scattered fields and the backscattering coefficients for vertical, horizontal and cross polarizations. The model developed here yields a simple backscattering coefficient expression in terms of the surface parameters. The expression reduces analytically to the Kirchhoff and the first-order small-perturbation model in the high- and low-frequency regions, respectively. The range of validity of the model is determined.

  17. Restraint of Liquid Jets by Surface Tension in Microgravity Modeled

    NASA Technical Reports Server (NTRS)

    Chato, David J.

    2001-01-01

    Tension in Microgravity Modeled Microgravity poses many challenges to the designer of spacecraft tanks. Chief among these are the lack of phase separation and the need to supply vapor-free liquid or liquidfree vapor to the spacecraft processes that require fluid. One of the principal problems of phase separation is the creation of liquid jets. A jet can be created by liquid filling, settling of the fluid to one end of the tank, or even closing a valve to stop the liquid flow. Anyone who has seen a fountain knows that jets occur in normal gravity also. However, in normal gravity, the gravity controls and restricts the jet flow. In microgravity, with gravity largely absent, jets must be contained by surface tension forces. Recent NASA experiments in microgravity (Tank Pressure Control Experiment, TPCE, and Vented Tank Pressure Experiment, VTRE) resulted in a wealth of data about jet behavior in microgravity. VTRE was surprising in that, although it contained a complex geometry of baffles and vanes, the limit on liquid inflow was the emergence of a liquid jet from the top of the vane structure. Clearly understanding the restraint of liquid jets by surface tension is key to managing fluids in low gravity. To model this phenomenon, we need a numerical method that can track the fluid motion and the surface tension forces. The fluid motion is modeled with the Navier-Stokes equation formulated for low-speed incompressible flows. The quantities of velocity and pressure are placed on a staggered grid, with velocity being tracked at cell faces and pressure at cell centers. The free surface is tracked via the introduction of a color function that tracks liquid as 1/2 and gas as -1/2. A phase model developed by Jacqmin is used. This model converts the discrete surface tension force into a barrier function that peaks at the free surface and decays rapidly. Previous attempts at this formulation have been criticized for smearing the interface. However, by sharpening the phase

  18. Modeling of electrohydrodynamic drying process using response surface methodology

    PubMed Central

    Dalvand, Mohammad Jafar; Mohtasebi, Seyed Saeid; Rafiee, Shahin

    2014-01-01

    Energy consumption index is one of the most important criteria for judging about new, and emerging drying technologies. One of such novel and promising alternative of drying process is called electrohydrodynamic (EHD) drying. In this work, a solar energy was used to maintain required energy of EHD drying process. Moreover, response surface methodology (RSM) was used to build a predictive model in order to investigate the combined effects of independent variables such as applied voltage, field strength, number of discharge electrode (needle), and air velocity on moisture ratio, energy efficiency, and energy consumption as responses of EHD drying process. Three-levels and four-factor Box–Behnken design was employed to evaluate the effects of independent variables on system responses. A stepwise approach was followed to build up a model that can map the entire response surface. The interior relationships between parameters were well defined by RSM. PMID:24936289

  19. Nanoimprint Lithography on curved surfaces prepared by fused deposition modelling

    NASA Astrophysics Data System (ADS)

    Köpplmayr, Thomas; Häusler, Lukas; Bergmair, Iris; Mühlberger, Michael

    2015-06-01

    Fused deposition modelling (FDM) is an additive manufacturing technology commonly used for modelling, prototyping and production applications. The achievable surface roughness is one of its most limiting aspects. It is however of great interest to create well-defined (nanosized) patterns on the surface for functional applications such as optical effects, electronics or bio-medical devices. We used UV-curable polymers of different viscosities and flexible stamps made of poly(dimethylsiloxane) (PDMS) to perform Nanoimprint Lithography (NIL) on FDM-printed curved parts. Substrates with different roughness and curvature were prepared using a commercially available 3D printer. The nanoimprint results were characterized by optical light microscopy, profilometry and atomic force microscopy (AFM). Our experiments show promising results in creating well-defined microstructures on the 3D-printed parts.

  20. Undergraduate technical skills training guided by student tutors – Analysis of tutors' attitudes, tutees' acceptance and learning progress in an innovative teaching model

    PubMed Central

    Weyrich, Peter; Schrauth, Markus; Kraus, Bernd; Habermehl, Daniel; Netzhammer, Nicolai; Zipfel, Stephan; Jünger, Jana; Riessen, Reimer; Nikendei, Christoph

    2008-01-01

    Background Skills labs provide a sheltered learning environment. As close supervision and individual feedback were proven to be important in ensuring effective skills training, we implemented a cross-year peer tutor system in our skills lab of internal medicine that allowed intense training sessions with small learning groups (3–4 students) taught by one student tutor. Methods The expectations, experiences and criticisms of peer tutors regarding the tutor system for undergraduate skills lab training were investigated in the context of a focus group. In addition, tutees' acceptance of this learning model and of their student tutors was evaluated by means of a pre/post web-based survey. Results 14 voluntary senior students were intensely prepared by consultants for their peer tutor activity. 127 students participated in the project, 66.9% of which responded to the web-based survey (23 topics with help of 6-point Likert scale + free comments). Acceptance was very high (5.69 ± 0.07, mean ± SEM), and self-confidence ratings increased significantly after the intervention for each of the trained skills (average 1.96 ± 0.08, all p < 0.002). Tutors received high global ratings (5.50 ± 0.07) and very positive anonymous individual feedback from participants. 82% of tutees considered the peer teaching model to be sufficient, and a mere 1% expressed the wish for skills training to be provided by faculty staff only. Focus group analyses with tutors revealed 18 different topics, including profit in personal knowledge and personal satisfaction through teaching activities. The ratio of 1:4 tutor/tutees was regarded to be very beneficial for effective feedback, and the personalized online evaluation by tutees to be a strong motivator and helpful for further improvements. The tutors ascribed great importance to the continuous availability of a contact doctor in case of uncertainties. Conclusion This study demonstrates that peer teaching in undergraduate technical clinical

  1. Theoretical model for the wetting of a rough surface.

    PubMed

    Hay, K M; Dragila, M I; Liburdy, J

    2008-09-15

    Many applications would benefit from an understanding of the physical mechanism behind fluid movement on rough surfaces, including the movement of water or contaminants within an unsaturated rock fracture. Presented is a theoretical investigation of the effect of surface roughness on fluid spreading. It is known that surface roughness enhances the effects of hydrophobic or hydrophilic behavior, as well as allowing for faster spreading of a hydrophilic fluid. A model is presented based on the classification of the regimes of spreading that occur when fluid encounters a rough surface: microscopic precursor film, mesoscopic invasion of roughness and macroscopic reaction to external forces. A theoretical relationship is developed for the physical mechanisms that drive mesoscopic invasion, which is used to guide a discussion of the implications of the theory on spreading conditions. Development of the analytical equation is based on a balance between capillary forces and frictional resistive forces. Chemical heterogeneity is ignored. The effect of various methods for estimating viscous dissipation is compared to available data from fluid rise on roughness experiments. Methods that account more accurately for roughness shape better explain the data as they account for more surface friction; the best fit was found for a hydraulic diameter approximation. The analytical solution implies the existence of a critical contact angle that is a function of roughness geometry, below which fluid will spread and above which fluid will resist spreading. The resulting equation predicts movement of a liquid invasion front with a square root of time dependence, mathematically resembling a diffusive process. PMID:18586259

  2. Axisymmetric model of drop spreading on a horizontal surface

    NASA Astrophysics Data System (ADS)

    Mistry, Aashutosh; Muralidhar, K.

    2015-09-01

    Spreading of an initially spherical liquid drop over a textured surface is analyzed by solving an integral form of the governing equations. The mathematical model extends Navier-Stokes equations by including surface tension at the gas-liquid boundary and a force distribution at the three phase contact line. While interfacial tension scales with drop curvature, the motion of the contact line depends on the departure of instantaneous contact angle from its equilibrium value. The numerical solution is obtained by discretizing the spreading drop into disk elements. The Bond number range considered is 0.01-1. Results obtained for sessile drops are in conformity with limiting cases reported in the literature [J. C. Bird et al., "Short-time dynamics of partial wetting," Phys. Rev. Lett. 100, 234501 (2008)]. They further reveal multiple time scales that are reported in experiments [K. G. Winkels et al., "Initial spreading of low-viscosity drops on partially wetting surfaces," Phys. Rev. E 85, 055301 (2012) and A. Eddi et al., "Short time dynamics of viscous drop spreading," Phys. Fluids 25, 013102 (2013)]. Spreading of water and glycerin drops over fully and partially wetting surfaces is studied in terms of excess pressure, wall shear stress, and the dimensions of the footprint. Contact line motion is seen to be correctly captured in the simulations. Water drops show oscillations during spreading while glycerin spreads uniformly over the surface.

  3. Model for outgassing of water from metal surfaces

    SciTech Connect

    Li, Minxu; Dylla, Fred

    1993-06-01

    Numerous measurements of outgassing from metal surfaces show that the outgassing obeys a power law of the form Q=Q{sub 10}t{sup -alpha}, where alpha is typically near unity. For unbaked systems, outgassing is dominated by water. This work demonstrates that alpha is a function of the water vapor exposure during venting of the system, and the physical properties of the passivation oxide layer on the surface. An analytic expression for the outgassing rate is derived based on the assumption that the rate of water diffusing through the passivation oxide layer to the surface governs the rate of its release into the vacuum. The source distribution function for the desorbing water is assumed to be a combination of a Gaussian distribution centered at the interior surface driven by atmospheric exposure, and a uniform concentration throughout the bulk. We have measured the outgassing rate from a clean stainless-steel (type 304) chamber as a function of water exposure to the chamber surface from <1 to 600 monolayers. The measured outgassing rate data show that alpha tends to 0.5 for low H{sub 2}O exposures and tends to 1.5 for high H{sub 2}O exposures as predicted by the model.

  4. Modeling the Interaction between AFM Tips and Pinned Surface Nanobubbles.

    PubMed

    Guo, Zhenjiang; Liu, Yawei; Xiao, Qianxiang; Schönherr, Holger; Zhang, Xianren

    2016-01-26

    Although the morphology of surface nanobubbles has been studied widely with different AFM modes, AFM images may not reflect the real shapes of the nanobubbles due to AFM tip-nanobubble interactions. In addition, the interplay between surface nanobubble deformation and induced capillary force has not been well understood in this context. In our work we used constraint lattice density functional theory to investigate the interaction between AFM tips and pinned surface nanobubbles systematically, especially concentrating on the effects of tip hydrophilicity and shape. For a hydrophilic tip contacting a nanobubble, its hydrophilic nature facilitates its departure from the bubble surface, displaying a weak and intermediate-range attraction. However, when the tip squeezes the nanobubble during the approach process, the nanobubble shows an elastic effect that prevents the tip from penetrating the bubble, leading to a strong nanobubble deformation and repulsive interactions. On the contrary, a hydrophobic tip can easily pierce the vapor-liquid interface of the nanobubble during the approach process, leading to the disappearance of the repulsive force. In the retraction process, however, the adhesion between the tip and the nanobubble leads to a much stronger lengthening effect on nanobubble deformation and a strong long-range attractive force. The trends of force evolution from our simulations agree qualitatively well with recent experimental AFM observations. This favorable agreement demonstrates that our model catches the main intergradient of tip-nanobubble interactions for pinned surface nanobubbles and may therefore provide important insight into how to design minimally invasive AFM experiments. PMID:26751634

  5. Modelling surface water flood risk using coupled numerical and physical modelling techniques

    NASA Astrophysics Data System (ADS)

    Green, D. L.; Pattison, I.; Yu, D.

    2015-12-01

    Surface water (pluvial) flooding occurs due to intense precipitation events where rainfall cannot infiltrate into the sub-surface or drain via storm water systems. The perceived risk appears to have increased in recent years with pluvial flood events seeming more severe and frequent within the UK. Surface water flood risk currently accounts for one third of all UK flood risk, with approximately two million people living in urban areas being at risk of a 1 in 200 year flood event. Surface water flooding research often focuses upon using 1D, 2D or 1D-2D coupled numerical modelling techniques to understand the extent, depth and severity of actual or hypothetical flood scenarios. Although much research has been conducted using numerical modelling, field data available for model calibration and validation is limited due to the complexities associated with data collection in surface water flood conditions. Ultimately, the data which numerical models are based upon is often erroneous and inconclusive. Physical models offer an alternative and innovative environment to collect data within. A controlled, closed system allows independent variables to be altered individually to investigate cause and effect relationships. Despite this, physical modelling approaches are seldom used in surface water flooding research. Scaled laboratory experiments using a 9m2, two-tiered physical model consisting of: (i) a mist nozzle type rainfall simulator able to simulate a range of rainfall intensities similar to those observed within the United Kingdom, and; (ii) a fully interchangeable, scaled plot surface have been conducted to investigate and quantify the influence of factors such as slope, impermeability, building density/configuration and storm dynamics on overland flow and rainfall-runoff patterns within a range of terrestrial surface conditions. Results obtained within the physical modelling environment will be compared with numerical modelling results using FloodMap (Yu & Lane, 2006

  6. Acceptance and commitment therapy (ACT): the foundation of the therapeutic model and an overview of its contribution to the treatment of patients with chronic physical diseases.

    PubMed

    Prevedini, Anna Bianca; Presti, Giovambattista; Rabitti, Elisa; Miselli, Giovanni; Moderato, Paolo

    2011-01-01

    Nowadays, treatment of chronic illnesses, such as stroke, cancer, chronic heart and respiratory diseases, osteoarthritis, diabetes, and so forth, account for the largest part of expenses in western countries national health systems. Moreover, these diseases are by far the leading causes of mortality in the world, representing 60% of all deaths. Any treatment aimed at targeting them might engage an individual for a large portion of his/her life so that personal and environmental factors can play a crucial role in modulating the person's quality of life and functioning, on top of any medical cure. Anxiety, depression, and distress for examples are not rare in patients with chronic diseases. Therefore, Cognitive and Behavior Therapy research has largely contributed in the last decades in identifying and programming interventions on such aspects as real and perceived social and family support, coping abilities, locus of control, self-efficacy that might help patients living with their chronic disease. More recently, third generation Cognitive-Behavior-Therapies, such as Dialectical Behavioral Therapy (DBT), Mindfulness Based Cognitive Therapy (MBCT), Functional Analytic Psychotherapy (FAP) and Acceptance, and Commitment Therapy (ACT) focused their attention and research efforts on developing intervention models targeting the needs of patients with a chronic disease. This paper has three aims. First is to briefly introduce ACT epistemological (Functional Contextualism) and theoretical (Relational Frame Theory) foundations as a stand point for understanding the peculiarity of ACT as a modern form of Clinical Behavior Analysis. The second aim is to introduce ACT clinical model and its six core processes (acceptance, defusion, present moment, self as a context, values and committed action) as both accountable, in their continuum, for psychological flexibility and inflexibility. Third, to present a brief overview of studies and outcomes of ACT intervention protocols and

  7. ATLAS ACCEPTANCE TEST

    SciTech Connect

    J.C. COCHRANE; J.V. PARKER; ET AL

    2001-06-01

    The acceptance test program for Atlas, a 23 MJ pulsed power facility for use in the Los Alamos High Energy Density Hydrodynamics program, has been completed. Completion of this program officially releases Atlas from the construction phase and readies it for experiments. Details of the acceptance test program results and of machine capabilities for experiments will be presented.

  8. Modeling anomalous surface - wave propagation across the Southern Caspian basin

    SciTech Connect

    Priestly, K.F.; Patton, H.J.; Schultz, C.A.

    1998-01-09

    The crust of the south Caspian basin consists of 15-25 km of low velocity, highly attenuating sediment overlying high velocity crystalline crust. The Moho depth beneath the basin is about 30 km as compared to about 50 km in the surrounding region. Preliminary modeling of the phase velocity curves shows that this thick sediments of the south Caspian basin are also under-lain by a 30-35 km thick crystalline crust and not by typical oceanic crust. This analysis also suggest that if the effect of the over-pressuring of the sediments is to reduce Poissons` ratio, the over-pressured sediments observed to approximately 5 km do not persist to great depths. It has been shown since 1960`s that the south Caspian basin blocks the regional phase Lg. Intermediate frequency (0.02-0.04 Hz) fundamental mode Raleigh waves propagating across the basin are also severely attenuated, but the low frequency surface waves are largely unaffected. This attenuation is observed along the both east-to-west and west-to-east great circle paths across the basin, and therefore it cannot be related to a seismograph site effect. We have modeled the response of surface waves in an idealized rendition of the south Caspian basin model using a hybrid normal mode / 2-D finite difference approach. To gain insight into the features of the basin which cause the anomalous surface wave propagation, we have varied parameters of the basin model and computed synthetic record sections to compare with the observed seismograms. We varied the amount of mantel up-warp, the shape of the boundaries, the thickness and shear wave Q of the sediments and mantle, and the depth of the water layer. Of these parameters, the intermediate frequency surface waves are most severely affected by the sediments thickness and shear wave attenuation. fundamental mode Raleigh wave phase velocities measure for paths crossing the basin are extremely low.

  9. Program documentation: Surface heating rate of thin skin models (THNSKN)

    NASA Technical Reports Server (NTRS)

    Mcbryde, J. D.

    1975-01-01

    Program THNSKN computes the mean heating rate at a maximum of 100 locations on the surface of thin skin transient heating rate models. Output is printed in tabular form and consists of time history tabulation of temperatures, average temperatures, heat loss without conduction correction, mean heating rate, least squares heating rate, and the percent standard error of the least squares heating rates. The input tape used is produced by the program EHTS03.

  10. Modeling MOSFET surface capacitance behavior under non-equilibrium

    NASA Astrophysics Data System (ADS)

    Kapoor, Abhishek; Jindal, R. P.

    2005-06-01

    A normalized analytical solution for the capacitance associated with a MOSFET surface under non-equilibrium conditions is presented. It is shown that this model can be mapped into an equivalent equilibrium problem with 98% accuracy for near intrinsic samples (UB ≅ 2). The precision becomes even better for highly doped semiconductors. The physics behind this transformation is explained and nomograms generated to present data in a highly normalized form.

  11. Modeling the surface evapotranspiration over the southern Great Plains

    NASA Technical Reports Server (NTRS)

    Liljegren, J. C.; Doran, J. C.; Hubbe, J. M.; Shaw, W. J.; Zhong, S.; Collatz, G. J.; Cook, D. R.; Hart, R. L.

    1996-01-01

    We have developed a method to apply the Simple Biosphere Model of Sellers et al to calculate the surface fluxes of sensible heat and water vapor at high spatial resolution over the domain of the US DOE's Cloud and Radiation Testbed (CART) in Kansas and Oklahoma. The CART, which is within the GCIP area of interest for the Mississippi River Basin, is an extensively instrumented facility operated as part of the DOE's Atmospheric Radiation Measurement (ARM) program. Flux values calculated with our method will be used to provide lower boundary conditions for numerical models to study the atmosphere over the CART domain.

  12. Single-phase-field model of stepped surfaces

    NASA Astrophysics Data System (ADS)

    Castro, M.; Hernández-Machado, A.; Cuerno, R.

    2009-02-01

    We formulate a phase-field description of step dynamics on vicinal surfaces that makes use of a single dynamical field, at variance with previous analogous works in which two coupled fields are employed, namely, a phase-field proper plus the physical adatom concentration. Within an asymptotic sharp interface limit, our formulation is shown to retrieve the standard Burton-Cabrera-Frank model in the general case of asymmetric attachment coefficients (Ehrlich-Schwoebel effect). We confirm our analytical results by means of numerical simulations of our phase-field model. Our present formulation seems particularly well adapted to generalization when additional physical fields are required.

  13. Numerical modeling of runback water on ice protected aircraft surfaces

    NASA Technical Reports Server (NTRS)

    Al-Khalil, Kamel M.; Keith, Theo G., Jr.; Dewitt, Kenneth J.

    1992-01-01

    A numerical simulation for 'running wet' aircraft anti-icing systems is developed. The model includes breakup of the water film, which exists in regions of direct impingement, into individual rivulets. The wetness factor distribution resulting from the film breakup and the rivulet configuration on the surface are predicted in the numerical solution procedure. The solid wall is modeled as a multilayer structure and the anti-icing system used is of the thermal type utilizing hot air and/or electrical heating elements embedded with the layers. Details of the calculation procedure and the methods used are presented.

  14. Modeling the surface evapotranspiration over the southern Great Plains

    SciTech Connect

    Liljegren, J.C.; Doran, J.C.; Hubbe, J.M.; Shaw, W.J.; Zhong, S.; Collatz, G.J.; Cook, D.R.; Hart, R.L.

    1996-12-31

    We have developed a method to apply the Simple Biosphere Model of Sellers et al to calculate the surface fluxes of sensible heat and water vapor at high spatial resolution over the domain of the US DOE`s Cloud and Radiation Testbed (CART) in Kansas and Oklahoma. The CART, which is within the GCIP area of interest for the Mississippi River Basin, is an extensively instrumented facility operated as part of the DOE`s Atmospheric Radiation Measurement (ARM) program. Flux values calculated with our method will be used to provide lower boundary conditions for numerical models to study the atmosphere over the CART domain.

  15. Land and ocean surface temperature: data development and modeling

    NASA Astrophysics Data System (ADS)

    Zeng, X.; Wang, A.; Brunke, M.

    2014-12-01

    Surface temperature (ST) plays a critical role in land-atmosphere-ocean interactions, and is one of the fundamental variables for Earth system research. ST includes surface air temperature (SAT), surface skin temperature (Ts), and subsurface water or soil temperature at a given depth [T(z)]. In this presentation, we will review our recent work on land and ocean ST. Over land, we have developed the first global 0.5 deg hourly SAT datasets from 1948-2009 by merging in situ CRU data with reanalysis data. Using these datasets, over high latitudes in winter the monthly averaged diurnal temperature range is found to be much larger than the range of monthly averaged hourly temperature diurnal cycle. The former primarily reflects the movement of synoptic weather systems, while the latter is primarily affected by the diurnal radiative forcing. We have also compared Ts from satellite remote sensing (MODIS) and land modeling (CLM) with in situ measurements. For instance, we have identified five factors contributing to the Ts differences between the model and MODIS. Over ocean, we have developed a prognostic Ts parameterization for modeling and data analysis. For instance, the inclusion of the Ts diurnal cycle affects atmospheric processes at diurnal, intraseasonal, and longer time scales. Furthermore, our parameterization provides the relationship between water temperature T(z) at different depths and Ts, and hence helps to merge temperature data from satellite infrared and microwave sensors and in situ buoy and ship measurements.

  16. A simple model for surface charge on ion channel proteins.

    PubMed Central

    Naranjo, D; Latorre, R; Cherbavaz, D; McGill, P; Schumaker, M F

    1994-01-01

    We present a simple two-parameter model for surface charge directly associated with ion channels. A spherically symmetric "charged shell" models a distribution of surface charge arrayed about the channel entrance, with a corresponding set of image charges behind the plane of the membrane. The transition between a regime of buffered conductance and a regime of rapidly falling conductance at very low ionic strength is found to depend on the magnitude of the surface charge as well as the separation between the charge and the channel entrance. This resolves an apparent discrepancy between the experimental findings of Naranjo and Latorre (1993. Biophys. J. 64:1038-1050) and previous theoretical computations. The charged-shell model is used in a comparative study of the toad skeletal muscle conductance data of Naranjo and Latorre, the rat skeletal muscle conductances of Ravindran et al. (1992. Biophys. J. 61:494-508), and a second set of rat muscle conductances presented in this paper. PMID:7510530

  17. Evolution of Land Surface Modeling over the Last 30 Years

    NASA Astrophysics Data System (ADS)

    Wood, E. F.; Lettenmaier, D. P.

    2001-12-01

    John Schaake has been intimately involved in hydrological modeling and climate studies throughout his career, and initially proposed the Mississippi River basin as the first GEWEX continental scale basin. Land surface modeling has progressed to the point that coupled water-energy-vegetation macroscale models can run at high resolution at continental to global scales. This presentation will review this evolution of macroscale models and use recent results from the authors' Variable Infiltration Capacity (VIC) macroscale SVAT to revisit research quetions that John Schaake has investigated during his career. These results include a 17-year daily, 2-degree resolution global water balance simulation; a 50-year 3-hourly, 1/8-degree resolution U.S. LDAS-domain water-energy balance simulation; and real-time, hourly, 1/8-degree resolution U.S. LDAS-domain water-energy balance simulations.

  18. Model Study of Ozone Levels Over Snow-Covered Surfaces

    NASA Astrophysics Data System (ADS)

    Sandoval, A. E.; Jacobson, M. Z.

    2001-12-01

    A column gas-aerosol-radiative model is used to simulate chemistry and radiation in and above snowpack at mid-latitudes and over the Arctic. Fifty vertical layers are modeled, the lowest of which represent the upper 15 cm of the snowpack. Snow layers are treated as dense aerosol layers with the physical and optical properties of snow. Aqueous phase and heterogeneous reactions thought to occur in the snowpack are represented as reactions on the aerosol surface. Model simulations include analysis of (1) the spectral UV radiation extinction in the snowpack, (2) chemistry over the snowpack, including snowpack release of NOx and H2O2 and ozone reduction and its susceptibility to the presence of aldehydes and bromine, (3) and the effect of soot in snow on chemistry, UV extinction, and local energy balance. Model predictions are compared to measurements of UV fluxes and ozone over snow.

  19. Information-Theoretic Benchmarking of Land Surface Models

    NASA Astrophysics Data System (ADS)

    Nearing, Grey; Mocko, David; Kumar, Sujay; Peters-Lidard, Christa; Xia, Youlong

    2016-04-01

    Benchmarking is a type of model evaluation that compares model performance against a baseline metric that is derived, typically, from a different existing model. Statistical benchmarking was used to qualitatively show that land surface models do not fully utilize information in boundary conditions [1] several years before Gong et al [2] discovered the particular type of benchmark that makes it possible to *quantify* the amount of information lost by an incorrect or imperfect model structure. This theoretical development laid the foundation for a formal theory of model benchmarking [3]. We here extend that theory to separate uncertainty contributions from the three major components of dynamical systems models [4]: model structures, model parameters, and boundary conditions describe time-dependent details of each prediction scenario. The key to this new development is the use of large-sample [5] data sets that span multiple soil types, climates, and biomes, which allows us to segregate uncertainty due to parameters from the two other sources. The benefit of this approach for uncertainty quantification and segregation is that it does not rely on Bayesian priors (although it is strictly coherent with Bayes' theorem and with probability theory), and therefore the partitioning of uncertainty into different components is *not* dependent on any a priori assumptions. We apply this methodology to assess the information use efficiency of the four land surface models that comprise the North American Land Data Assimilation System (Noah, Mosaic, SAC-SMA, and VIC). Specifically, we looked at the ability of these models to estimate soil moisture and latent heat fluxes. We found that in the case of soil moisture, about 25% of net information loss was from boundary conditions, around 45% was from model parameters, and 30-40% was from the model structures. In the case of latent heat flux, boundary conditions contributed about 50% of net uncertainty, and model structures contributed

  20. Estimation of Arctic Land Surface Conditions and Fluxes via a Suite of Land Surface Models

    NASA Astrophysics Data System (ADS)

    Bohn, T. J.; Slater, A. G.; Lettenmaier, D. P.; Serreze, M. C.

    2004-12-01

    River runoff from the Arctic terrestrial drainage system is thought to exert a significant influence over global climate, contributing to the global thermohaline circulation via its effects on salinity, sea ice, and surface freshening in the North Atlantic. Changes in these freshwater fluxes, as well as other components of the Arctic terrestrial hydrologic cycle such as snow cover and albedo, have the potential to amplify the Arctic's response to global climate change. However, the extent to which the Arctic terrestrial hydrological cycle is changing or may contribute to change through feedback processes is still not well understood, in part due to the sparseness of observations of such variables as stream flow, soil moisture, soil temperature, snow water equivalent, and energy fluxes. The objective of this project is to assemble the best possible time series (covering a 20+ year period) of these and other prognostic variables for the Arctic terrestrial drainage basin. While these variables can be estimated with a single land surface model (LSM), the predictions are often subject to biases and errors in the input atmospheric forcings and limited by the accuracy of the model physics. To reduce these errors, we have implemented an ensemble of five LSMs: VIC, CLM, ECMWF, NOAH and CHASM, all of which have been used previously to simulate Arctic hydrology under the Project for Intercomparison of Land-surface Parameterization Schemes (PILPS) Experiment 2e. Model predictions of land surface state variables (snow water content, soil moisture, permafrost active layer depth) and fluxes (latent, sensible, and ground heat fluxes; runoff) are averaged both across the ensemble and over multiple runs, using the best available atmospheric forcing data with and without added random perturbations. Here we evaluate the multi-model ensemble averages in comparison with individual model simulations of variables including snow water equivalent, evaporation, total runoff, and soil thaw

  1. Modeling the surface photovoltage of silicon slabs with varying thickness.

    PubMed

    Vazhappilly, Tijo; Kilin, Dmitri S; Micha, David A

    2015-04-10

    The variation with thickness of the energy band gap and photovoltage at the surface of a thin semiconductor film are of great interest in connection with their surface electronic structure and optical properties. In this work, the change of a surface photovoltage (SPV) with the number of layers of a crystalline silicon slab is extracted from models based on their atomic structure. Electronic properties of photoexcited slabs are investigated using generalized gradient and hybrid density functionals, and plane wave basis sets. Si(1 1 1) surfaces have been terminated by hydrogen atoms to compensate for dangling bonds and have been described by large supercells with periodic boundary conditions. Calculations of the SPV of the Si slabs have been done in terms of the reduced density matrix of the photoactive electrons including dissipative effects due to their interaction with medium phonons and excitons. Surface photovoltages have been calculated for model Si slabs with 4-12, and 16 layers, to determine convergence trends versus slab thickness. Band gaps and the inverse of the SPVs have been found to scale nearly linearly with the inverse thickness of the slab, while the electronic density of states increases quadratically with thickness. Our calculations show the same trends as experimental values indicating band gap reduction and absorption enhancement for Si films of increasing thickness. Simple arguments on confined electronic structures have been used to explain the main effects of changes with slab thickness. A procedure involving shifted electron excitation energies is described to improve results from generalized gradient functionals so they can be in better agreement with the more accurate but also more computer intensive values from screened exchange hybrid functionals. PMID:25767101

  2. Modeling the surface photovoltage of silicon slabs with varying thickness

    NASA Astrophysics Data System (ADS)

    Vazhappilly, Tijo; Kilin, Dmitri S.; Micha, David A.

    2015-04-01

    The variation with thickness of the energy band gap and photovoltage at the surface of a thin semiconductor film are of great interest in connection with their surface electronic structure and optical properties. In this work, the change of a surface photovoltage (SPV) with the number of layers of a crystalline silicon slab is extracted from models based on their atomic structure. Electronic properties of photoexcited slabs are investigated using generalized gradient and hybrid density functionals, and plane wave basis sets. Si(1 1 1) surfaces have been terminated by hydrogen atoms to compensate for dangling bonds and have been described by large supercells with periodic boundary conditions. Calculations of the SPV of the Si slabs have been done in terms of the reduced density matrix of the photoactive electrons including dissipative effects due to their interaction with medium phonons and excitons. Surface photovoltages have been calculated for model Si slabs with 4-12, and 16 layers, to determine convergence trends versus slab thickness. Band gaps and the inverse of the SPVs have been found to scale nearly linearly with the inverse thickness of the slab, while the electronic density of states increases quadratically with thickness. Our calculations show the same trends as experimental values indicating band gap reduction and absorption enhancement for Si films of increasing thickness. Simple arguments on confined electronic structures have been used to explain the main effects of changes with slab thickness. A procedure involving shifted electron excitation energies is described to improve results from generalized gradient functionals so they can be in better agreement with the more accurate but also more computer intensive values from screened exchange hybrid functionals.

  3. Modelling Sea Ice and Surface Wave Interactions in Polar Regions

    NASA Astrophysics Data System (ADS)

    Hosekova, L.; Aksenov, Y.; Coward, A.; Williams, T.; Bertino, L.; Nurser, A. J. G.

    2015-12-01

    In the Polar Oceans, the surface ocean waves break up sea ice cover and create the Marginal Ice Zone (MIZ), an area between the sea-ice free ocean and pack ice characterized by highly fragmented ice. This band of sea ice cover is undergoing dramatic changes due to sea ice retreat, with a widening of up to 39% in the Arctic Ocean reported over the last three decades and projections predicting a continuing increase. The surface waves, sea ice and ocean interact in the MIZ through multiple complex feedbacks and processes which are not accounted for in any of the present-day climate models. To address this issue, we present a model development which implements surface ocean wave effects in the global Ocean General Circulation Model (OGCM) NEMO, coupled to the CICE sea ice model. Our implementation takes into account a number of physical processes specific to the MIZ dynamics. Incoming surface waves are attenuated due to scattering and energy dissipation induced by the presence of ice cover, which is in turn fragmented in response to flexural stresses. This fragmentation modifies the floe size distribution and impacts the sea ice thermodynamics by increasing lateral melting and thus affecting momentum and heat transfer between sea ice and the upper ocean. In addition, the dynamics of the sea ice is modified by a combined rheology that takes into account floe collisions and allows for a more realistic representation of the MIZ. We present results from the NEMO OGCM at 1 and 0.25 degree resolution with a wave-ice interaction module. The module introduces two new diagnostics previously unavailable in OGCM's: surface wave spectra in sea ice covered areas, and floe size distribution (FSD) due to wave-induced fragmentation. We evaluate the sea ice and wave simulations with available observational estimates, and analyze the impact of these MIZ processes on the ocean and sea ice state. We focus on ocean mixing, stratification, circulation and the role of the MIZ in ocean

  4. Modeling interactions between Antarctic Instability and Surface Mass Balance.

    NASA Astrophysics Data System (ADS)

    Ritz, Catherine; Agosta, Cecile; Peyaud, Vincent; Durand, Gael; Fettweis, Xavier; Favier, Vincent; Gallée, Hubert

    2015-04-01

    In the context of future global warming, Antarctic contribution to sea level rise (SLR) depends on several processes leading to opposite impacts. First, under a warming climate, precipitation is supposed to increase, inducing a plausible negative impact on SLR. Contrary to the Greenland ice sheet case, ablation should stay a marginal process at least on grounded ice. Second, oceanic warming and/or surface ponding on ice shelves may trigger a Marine Ice Sheet Instability by reducing the backforce they exert on outlet glaciers. Once engaged on such a self-entertained retreat a large positive contribution to SLR may be expected. This dynamic process is already going on in the Admundsen sea sector. Although these two processes (surface mass balance -- SMB -- and ice dynamics) have been modeled separately to infer sea level contribution, little work has been done to study their interactions. In this presentation we focus on how grounding line retreat can affect estimation of SMB in the future and the related contribution to sea level change. To evaluate the shift of precipitation pattern while the steep surface slope region migrates inward due to the grounding line retreat, we simulate surface mass balance on various surface topographies of the Antarctic ice sheet. Each ice sheet topography is obtained with an ice sheet model (GRISLI) in which grounding line retreat is parameterized according to glaciological considerations. Because we are looking at coastal changes, a high resolution is needed for the atmospheric model and here we use the regional circulation model MAR with a resolution of 40 km. The preliminary results show that the topographic change induces a shift in the precipitation pattern as high accumulation regions tend to follow the slope break at the ice sheet / shelf transition. This affects the calculation of total SMB on the grounded ice sheet (and sea level contribution) and its amplitude is related to the amplitude of the retreat. In our simulations

  5. Heterogeneous nucleation of ice on model carbon surfaces

    NASA Astrophysics Data System (ADS)

    Molinero, V.; Lupi, L.; Hudait, A.

    2014-12-01

    Carbonaceous particles account for 10% of the particulate matter in the atmosphere. The experimental investigation of heterogeneous freezing of water droplets by carbonaceous particles reveals widespread ice freezing temperatures. The origin of the soot and its oxidation and aging modulate its ice nucleation ability, however, it is not known which structural and chemical characteristics of soot account for the variability in ice nucleation efficiency. We find that atomically flat carbon surfaces promote heterogeneous nucleation of ice, while molecularly rough surfaces with the same hydrophobicity do not. We investigate a large set of graphitic surfaces of various dimensions and radii of curvature consistent with those of soot in experiments, and find that variations in nanostructures alone could account for the spread in the freezing temperatures of ice on soot in experiments. A characterization of the nanostructure of soot is needed to predict its ice nucleation efficiency. Atmospheric oxidation and aging of soot modulates its ice nucleation ability. It has been suggested that an increase in the ice nucleation ability of aged soot results from an increase in the hydrophilicity of the surfaces upon oxidation. Oxidation, however, also impacts the nanostructure of soot, making it difficult to assess the separate effects of soot nanostructure and hydrophilicity in experiments. We investigate the effect of changes in hydrophilicity of model graphitic surfaces on the freezing temperature of ice. Our results indicate that the hydrophilicity of the surface is not in general a good predictor of ice nucleation ability. We find a correlation between the ability of a surface to promote nucleation of ice and the layering of liquid water at the surface. The results of this work suggest that ordering of liquid water in contact with the surface plays an important role in the heterogeneous ice nucleation mechanism. References: L. Lupi, A. Hudait and V. Molinero, J. Am. Chem. Soc

  6. Evaluation of surface ozone simulated by the WRF/CMAQ online modelling system

    NASA Astrophysics Data System (ADS)

    Marougianni, Garyfalia; Katragkou, Eleni; Giannaros, Theodoros; Poupkou, Anastasia; Melas, Dimitris; Zanis, Prodromos; Feidas, Haralambos

    2013-04-01

    /CMAQ online model is successful in representing in an acceptable way a key atmospheric pollutant like ozone. Preliminary results indicate that WRF/CMAQ captures relatively well the spatial patterns of surface ozone over Europe. Its results are compared to the extensively tested offline modelling system WRF/CAMx, which runs with similar configuration in an identical domain over the same time slice. The aim is to assess the differences in surface ozone between the off-line and online model and try to find the mechanisms underlying these differences. Conclusively, this study aims in quantifying the differences in the results of the off-line WRF/CAMx and the online WRF/CMAQ modelling systems, in order to decide which can more adequately address the needs of emerging assessment for air quality-climate interactions and provide dynamically consistent predictions, ultimately justifying the choice of online versus off-line approaches.This work has been developed in the framework of the NSRF project: Development of a Geographical Information System for Climate information (Geoclima).

  7. Lithospheric Thickness Modeled from Long Period Surface Wave Dispersion

    SciTech Connect

    Pasyanos, M E

    2008-05-15

    The behavior of surface waves at long periods is indicative of subcrustal velocity structure. Using recently published dispersion models, we invert surface wave group velocities for lithospheric structure, including lithospheric thickness, over much of the Eastern Hemisphere, encompassing Eurasia, Africa, and the Indian Ocean. Thicker lithosphere under Precambrian shields and platforms are clearly observed, not only under the large cratons (West Africa, Congo, Baltic, Russia, Siberia, India), but also under smaller blocks like the Tarim Basin and Yangtze craton. In contrast, it is found that remobilized Precambrian structures like the Saharan Shield and Sino-Korean Paraplatform do not have well-established lithospheric keels. The thinnest lithospheric thickness is found under oceanic and continental rifts, as well as along convergence zones. We compare our results to thermal models of continental lithosphere, lithospheric cooling models of oceanic lithosphere, lithosphere-asthenosphere boundary (LAB) estimates from S-wave receiver functions, and velocity variations of global tomography models. In addition to comparing results for the broad region, we examine in detail the regions of Central Africa, Siberia, and Tibet. While there are clear differences in the various estimates, overall the results are generally consistent. Inconsistencies between the estimates may be due to a variety of reasons including lateral and depth resolution differences and the comparison of what may be different lithospheric features.

  8. A contoured continuum surface force model for particle methods

    NASA Astrophysics Data System (ADS)

    Duan, Guangtao; Koshizuka, Seiichi; Chen, Bin

    2015-10-01

    A surface tension model is essential to simulate multiphase flows with deformed interfaces. This study develops a contoured continuum surface force (CCSF) model for particle methods. A color function that varies sharply across the interface to mark different fluid phases is smoothed in the transition region, where the local contour curvature can be regarded as the interface curvature. The local contour passing through each reference particle in the transition region is extracted from the local profile of the smoothed color function. The local contour curvature is calculated based on the Taylor series expansion of the smoothed color function, whose derivatives are calculated accurately according to the definition of the smoothed color function. Two schemes are proposed to specify the smooth radius: fixed scheme, where 2 ×re (re = particle interaction radius) is assigned to all particles in the transition region; and varied scheme, where re and 2 ×re are assigned to the central and edged particles in the transition region respectively. Numerical examples, including curvature calculation for static circle and ellipse interfaces, deformation of square droplet to a circle (2D and 3D), droplet deformation in shear flow, and droplet coalescence, are simulated to verify the CCSF model and compare its performance with those of other methods. The CCSF model with the fixed scheme is proven to produce the most accurate curvature and lowest parasitic currents among the tested methods.

  9. Lithospheric thickness modeled from long-period surface wave dispersion

    NASA Astrophysics Data System (ADS)

    Pasyanos, Michael E.

    2010-01-01

    The behavior of surface waves at long periods is indicative of subcrustal velocity structure. Using recently published dispersion models, we invert surface wave group velocities for lithospheric structure, including lithospheric thickness, over much of the Eastern Hemisphere, encompassing Eurasia, Africa, and the Indian Ocean. Thicker lithospheres under Precambrian shields and platforms are clearly observed, not only under the large cratons (West Africa, Congo, Baltic, Russia, Siberia, India), but also under smaller blocks like the Tarim Basin and Yangtze craton. In contrast, it is found that remobilized Precambrian structures like the Saharan Shield and Sino-Korean Paraplatform do not have well-established lithospheric keels. The thinnest lithospheric thickness is found under oceanic and continental rifts, as well as along convergence zones. We compare our results to thermal models of continental lithosphere, lithospheric cooling models of oceanic lithosphere, lithosphere-asthenosphere boundary (LAB) estimates from S-wave receiver functions, and velocity variations of global tomography models. In addition to comparing results for the broad region, we examine in detail the regions of Central Africa, Siberia, and Tibet. While there are clear differences in the various estimates, overall the results are generally consistent. Inconsistencies between the estimates may be due to a variety of reasons including lateral and depth resolution differences and the comparison of what may be different lithospheric features.

  10. Parameter variability estimation using stochastic response surface model updating

    NASA Astrophysics Data System (ADS)

    Fang, Sheng-En; Zhang, Qiu-Hu; Ren, Wei-Xin

    2014-12-01

    From a practical point of view, uncertainties existing in structural parameters and measurements must be handled in order to provide reliable structural condition evaluations. At this moment, deterministic model updating loses its practicability and a stochastic updating procedure should be employed seeking for statistical properties of parameters and responses. Presently this topic has not been well investigated on account of its greater complexity in theoretical configuration and difficulty in inverse problem solutions after involving uncertainty analyses. Due to it, this paper attempts to develop a stochastic model updating method for parameter variability estimation. Uncertain parameters and responses are correlated through stochastic response surface models, which are actually explicit polynomial chaos expansions based on Hermite polynomials. Then by establishing a stochastic inverse problem, parameter means and standard deviations are updated in a separate and successive way. For the purposes of problem simplification and optimization efficiency, in each updating iteration stochastic response surface models are reconstructed to avoid the construction and analysis of sensitivity matrices. Meanwhile, in the interest of investigating the effects of parameter variability on responses, a parameter sensitivity analysis method has been developed based on the derivation of polynomial chaos expansions. Lastly the feasibility and reliability of the proposed methods have been validated using a numerical beam and then a set of nominally identical metal plates. After comparing with a perturbation method, it is found that the proposed method can estimate parameter variability with satisfactory accuracy and the complexity of the inverse problem can be highly reduced resulting in cost-efficient optimization.

  11. Modeling of surface roughness: application to physical properties of paper

    NASA Astrophysics Data System (ADS)

    Bloch, Jean-Francis; Butel, Marc

    2000-09-01

    Papermaking process consists in a succession of unit operations having for main objective the expression of water out of the wet paper pad. The three main stages are successively, the forming section, the press section and finally the drying section. Furthermore, another operation (calendering) may be used to improve the surface smoothness. Forming, pressing and drying are not on the scope of this paper, but the influence of formation and calendering on surface roughness is analyzed. The main objective is to characterize the materials and specially its superficial structure. The proposed model is described in order to analyze this topographical aspect. Some experimental results are presented in order to illustrate the interest of this method to better understand physical properties. This work is therefore dedicated to the description of the proposed model: the studied surface is measured at a microscopic scale using for example, a classical stylus profilometry method. Then the obtained surface is transformed using a conformal mapping that retains the surface orientations. Due to the anisotropy of the fiber distribution in the plane of the sheet, the resulting surface is often not isotropic. Hence, the micro facets that identify the interfaces between pores and solid (fibers in the studied case) at the micro level are transformed into a macroscopic equivalent structure. Furthermore, an ellipsoid may be fit to the experimental data in order to obtain a simple model. The ellipticities are proved to be linked for paper to both fiber orientation (through other optical methods) and roughness. These parameters (ellipticities) are shown to be very significant for different end-use properties. Indeed, they shown to be correlated to printing or optical properties, such as gloss for example. We present in a first part the method to obtain a macroscopic description from physical microscopic measurements. Then measurements carried on different paper samples, using a classical

  12. A surface-scattering model satisfying energy conservation and reciprocity

    NASA Astrophysics Data System (ADS)

    Sasihithlu, Karthik; Dahan, Nir; Hugonin, Jean-Paul; Greffet, Jean-Jacques

    2016-03-01

    Roughness scattering models based on Kirchhoff's approximation or perturbation theory give a good account of the angular distribution of the scattered intensity but do not satisfy energy conservation and reciprocity rigorously. For applications such as solar cells with rough interfaces producing a quasi isotropic intensity in the multiple scattering regime, an accurate model of the angular pattern is not required. Instead, energy conservation and reciprocity must be satisfied with great accuracy. Here we present a surface scattering model based on analysis of scattering from a layer of particles on top of a substrate in the dipole approximation which satisfies both energy conservation and reciprocity and is thus accurate in all frequency ranges. The model takes into account the absorption in the substrate induced by the particles but does not take into account the near-field interactions between the particles. In arriving at this model, we use the effective-medium approach to show how we can proceed from modeling the electromagnetic scattering from a single particle to modeling the scattering from a layer of particles positioned above a substrate, and finally relate this to the bidirectional scattering distribution function of the substrate.

  13. A spatially resolved surface kinetic model for forsterite dissolution

    NASA Astrophysics Data System (ADS)

    Maher, Kate; Johnson, Natalie C.; Jackson, Ariel; Lammers, Laura N.; Torchinsky, Abe B.; Weaver, Karrie L.; Bird, Dennis K.; Brown, Gordon E.

    2016-02-01

    The development of complex alteration layers on silicate mineral surfaces undergoing dissolution is a widely observed phenomenon. Given the complexity of these layers, most kinetic models used to predict rates of mineral-fluid interactions do not explicitly consider their formation. As a result, the relationship between the development of the altered layers and the final dissolution rate is poorly understood. To improve our understanding of the relationship between the alteration layer and the dissolution rate, we developed a spatially resolved surface kinetic model for olivine dissolution and applied it to a series of closed-system experiments consisting of three-phases (water (±NaCl), olivine, and supercritical CO2) at conditions relevant to in situ mineral carbonation (i.e. 60 °C, 100 bar CO2). We also measured the corresponding δ26/24Mg of the dissolved Mg during early stages of dissolution. Analysis of the solid reaction products indicates the formation of Mg-depleted layers on the olivine surface as quickly as 2 days after the experiment was started and before the bulk solution reached saturation with respect to amorphous silica. The δ26/24Mg of the dissolved Mg decreased by approximately 0.4‰ in the first stages of the experiment and then approached the value of the initial olivine (-0.35‰) as the steady-state dissolution rate was approached. We attribute the preferential release of 24Mg to a kinetic effect associated with the formation of a Mg-depleted layer that develops as protons exchange for Mg2+. We used experimental data to calibrate a surface kinetic model for olivine dissolution that includes crystalline olivine, a distinct "active layer" from which Mg can be preferentially removed, and secondary amorphous silica precipitation. By coupling the spatial arrangement of ions with the kinetics, this model is able to reproduce both the early and steady-state long-term dissolution rates, and the kinetic isotope fractionation. In the early stages of

  14. Forward model for the superconducting imaging-surface meg system

    SciTech Connect

    Kraus, Robert H., Jr.; Matlachov, A. N.; Espy, M. A.; Maharajh, K.; Volegov, P.

    2001-01-01

    We have recently completed a novel whole-head MEG system based on the Superconducting Imaging-Surface (SIS) concept originally proposed by van Hulsteyn, et al.[l]. The SIS concept is generally described as a source near a superconducting surface. The source field induces Meissner currents in the superconductor equivalent to a source image 'behind' the surface. A sensor (SQUIDS in our system) placed on the source-side of the SIS will measure the superposed fields from the real and image sources. A second consequence of the Meissner effect is to shield the SQUIDS sensors near the SIS from external or background fields. The shape of the SIS used in our MEG system is a hemisphere with two cut-outs at the nominal ear-locations. A brim is added around the entire periphery with a smooth 0.5 cm radius transition between brim and hemisphere. Benefits of the SIS concept over existing systems include significantly enhanced signal-to-noise as a consequence of the SIS shielding and inherently generating pseudo-first order gradient fields at the sensors. One of the most significant challenges in realizing this system has been to accurately describe how the SIS system impacts the forward physics of any source model. Two approaches have been examined. The first is a hybrid analytical and empirical model using the analytic formalism to describe the hemisphere [1] and a correction matrix derived from empirical measurements to correct for edge effects. This approach proved overly complex and difficult in practice to obtain sufficient empirical data to derive a well-conditioned correction matrix. The second approach, reported here, was to develop a boundary element model (BEM) description of the SIS using the exact as-built geometry. Each element is described by a uniform magnetization arising from a distribution of Meissner currents in the superconductor such that B{perpendicular} = 0 at the surface. B{sub i} at each element is a superposition of the source field and the fields

  15. Use of shape-preserving interpolation methods in surface modeling

    NASA Technical Reports Server (NTRS)

    Ftitsch, F. N.

    1984-01-01

    In many large-scale scientific computations, it is necessary to use surface models based on information provided at only a finite number of points (rather than determined everywhere via an analytic formula). As an example, an equation of state (EOS) table may provide values of pressure as a function of temperature and density for a particular material. These values, while known quite accurately, are typically known only on a rectangular (but generally quite nonuniform) mesh in (T,d)-space. Thus interpolation methods are necessary to completely determine the EOS surface. The most primitive EOS interpolation scheme is bilinear interpolation. This has the advantages of depending only on local information, so that changes in data remote from a mesh element have no effect on the surface over the element, and of preserving shape information, such as monotonicity. Most scientific calculations, however, require greater smoothness. Standard higher-order interpolation schemes, such as Coons patches or bicubic splines, while providing the requisite smoothness, tend to produce surfaces that are not physically reasonable. This means that the interpolant may have bumps or wiggles that are not supported by the data. The mathematical quantification of ideas such as physically reasonable and visually pleasing is examined.

  16. Surface Contaminants Inhibit Osseointegration in a Novel Murine Model

    PubMed Central

    Bonsignore, Lindsay A.; Colbrunn, Robb W.; Tatro, Joscelyn M.; Messerschmitt, Patrick J.; Hernandez, Christopher J.; Goldberg, Victor M.; Stewart, Matthew C.; Greenfield, Edward M.

    2011-01-01

    Surface contaminants, such as bacterial debris and manufacturing residues, may remain on orthopaedic implants after sterilization procedures and affect osseointegration. The goals of this study were to develop a murine model of osseointegration in order to determine whether removing surface contaminants enhances osseointegration. To develop the murine model, titanium alloy implants were implanted into a unicortical pilot hole in the mid-diaphysis of the femur and osseointegration was measured over a five week time course. Histology, backscatter scanning electron microscopy and x-ray energy dispersive spectroscopy showed areas of bone in intimate physical contact with the implant, confirming osseointegration. Histomorphometric quantification of bone-to-implant contact and peri-implant bone and biomechanical pullout quantification of ultimate force, stiffness and work to failure increased significantly over time, also demonstrating successful osseointegration. We also found that a rigorous cleaning procedure significantly enhances bone-to-implant contact and biomechanical pullout measures by two-fold compared with implants that were autoclaved, as recommended by the manufacturer. The most likely interpretation of these results is that surface contaminants inhibit osseointegration. The results of this study justify the need for the development of better detection and removal techniques for contaminants on orthopaedic implants and other medical devices. PMID:21801863

  17. Surface tension models for particle laden thin films

    NASA Astrophysics Data System (ADS)

    Wong, Jeffrey; Wang, Li; Bertozzi, Andrea

    We study viscous slurries on an incline, for which particles migrate in a fluid due to a combination of gravity-induced settling and shear-induced migration. The lubrication model for the bulk of the fluid is a hyperbolic system of conservation laws for the film height and particle concentration which exhibits in interesting behavior, including singular shock solutions corresponding to accumulation of particles at the front. The addition of surface tension to the model produces a a capillary ridge that is affected by the particle accumulation and in two dimensions leads to fingering instabilities. We compare this model to experimental results. This work is supported by NSF Grants DMS-1312543 and DMS-1045536.

  18. Modelling nanofluidic field amplified sample stacking with inhomogeneous surface charge

    NASA Astrophysics Data System (ADS)

    McCallum, Christopher; Pennathur, Sumita

    2015-11-01

    Nanofluidic technology has exceptional applications as a platform for biological sample preconcentration, which will allow for an effective electronic detection method of low concentration analytes. One such preconcentration method is field amplified sample stacking, a capillary electrophoresis technique that utilizes large concentration differences to generate high electric field gradients, causing the sample of interest to form a narrow, concentrated band. Field amplified sample stacking has been shown to work well at the microscale, with models and experiments confirming expected behavior. However, nanofluidics allows for further concentration enhancement due to focusing of the sample ions toward the channel center by the electric double layer. We have developed a two-dimensional model that can be used for both micro- and nanofluidics, fully accounting for the electric double layer. This model has been used to investigate even more complex physics such as the role of inhomogeneous surface charge.

  19. Computational modeling of in vitro biological responses on polymethacrylate surfaces

    PubMed Central

    Ghosh, Jayeeta; Lewitus, Dan Y; Chandra, Prafulla; Joy, Abraham; Bushman, Jared; Knight, Doyle; Kohn, Joachim

    2011-01-01

    The objective of this research was to examine the capabilities of QSPR (Quantitative Structure Property Relationship) modeling to predict specific biological responses (fibrinogen adsorption, cell attachment and cell proliferation index) on thin films of different polymethacrylates. Using 33 commercially available monomers it is theoretically possible to construct a library of over 40,000 distinct polymer compositions. A subset of these polymers were synthesized and solvent cast surfaces were prepared in 96 well plates for the measurement of fibrinogen adsorption. NIH 3T3 cell attachment and proliferation index were measured on spin coated thin films of these polymers. Based on the experimental results of these polymers, separate models were built for homo-, co-, and terpolymers in the library with good correlation between experiment and predicted values. The ability to predict biological responses by simple QSPR models for large numbers of polymers has important implications in designing biomaterials for specific biological or medical applications. PMID:21779132

  20. Surface-effect corrections for the solar model

    NASA Astrophysics Data System (ADS)

    Magic, Z.; Weiss, A.

    2016-07-01

    Context. Solar p-mode oscillations exhibit a systematic offset towards higher frequencies due to shortcomings in the 1D stellar structure models, in particular, the lack of turbulent pressure in the superadiabatic layers just below the optical surface, arising from the convective velocity field. Aims: We study the influence of the turbulent expansion, chemical composition, and magnetic fields on the stratification in the upper layers of the solar models in comparison with solar observations. Furthermore, we test alternative ⟨3D⟩ averages for improved results on the oscillation frequencies. Methods: We appended temporally and spatially averaged ⟨3D⟩ stratifications to 1D models to compute adiabatic oscillation frequencies that we then tested against solar observations. We also developed depth-dependent corrections for the solar 1D model, for which we expanded the geometrical depth to match the pressure stratification of the solar ⟨3D⟩ model, and we reduced the density that is caused by the turbulent pressure. Results: We obtain the same results with our ⟨3D⟩ models as have been reported previously. Our depth-dependent corrected 1D models match the observations to almost a similar extent as the ⟨3D⟩ model. We find that correcting for the expansion of the geometrical depth and the reducing of the density are both equally necessary. Interestingly, the influence of the adiabatic exponent Γ1 is less pronounced than anticipated. The turbulent elevation directly from the ⟨3D⟩ model does not match the observations properly. Considering different reference depth scales for the ⟨3D⟩ averaging leads to very similar frequencies. Solar models with high metal abundances in their initial chemical composition match the low-frequency part much better. We find a linear relation between the p-mode frequency shift and the vertical magnetic field strength with δvnl = 26.21Bz [μHz/kG], which is able to render the solar activity cycles correctly.

  1. A cellular automata approach for modeling surface water runoff

    NASA Astrophysics Data System (ADS)

    Jozefik, Zoltan; Nanu Frechen, Tobias; Hinz, Christoph; Schmidt, Heiko

    2015-04-01

    This abstract reports the development and application of a two-dimensional cellular automata based model, which couples the dynamics of overland flow, infiltration processes and surface evolution through sediment transport. The natural hill slopes are represented by their topographic elevation and spatially varying soil properties infiltration rates and surface roughness coefficients. This model allows modeling of Hortonian overland flow and infiltration during complex rainfall events. An advantage of the cellular automata approach over the kinematic wave equations is that wet/dry interfaces that often appear with rainfall overland flows can be accurately captured and are not a source of numerical instabilities. An adaptive explicit time stepping scheme allows for rainfall events to be adequately resolved in time, while large time steps are taken during dry periods to provide for simulation run time efficiency. The time step is constrained by the CFL condition and mass conservation considerations. The spatial discretization is shown to be first-order accurate. For validation purposes, hydrographs for non-infiltrating and infiltrating plates are compared to the kinematic wave analytic solutions and data taken from literature [1,2]. Results show that our cellular automata model quantitatively accurately reproduces hydrograph patterns. However, recent works have showed that even through the hydrograph is satisfyingly reproduced, the flow field within the plot might be inaccurate [3]. For a more stringent validation, we compare steady state velocity, water flux, and water depth fields to rainfall simulation experiments conducted in Thies, Senegal [3]. Comparisons show that our model is able to accurately capture these flow properties. Currently, a sediment transport and deposition module is being implemented and tested. [1] M. Rousseau, O. Cerdan, O. Delestre, F. Dupros, F. James, S. Cordier. Overland flow modeling with the Shallow Water Equation using a well balanced

  2. Transient Catalytic Combustor Model With Detailed Gas and Surface Chemistry

    NASA Technical Reports Server (NTRS)

    Struk, Peter M.; Dietrich, Daniel L.; Mellish, Benjamin P.; Miller, Fletcher J.; Tien, James S.

    2005-01-01

    In this work, we numerically investigate the transient combustion of a premixed gas mixture in a narrow, perfectly-insulated, catalytic channel which can represent an interior channel of a catalytic monolith. The model assumes a quasi-steady gas-phase and a transient, thermally thin solid phase. The gas phase is one-dimensional, but it does account for heat and mass transfer in a direction perpendicular to the flow via appropriate heat and mass transfer coefficients. The model neglects axial conduction in both the gas and in the solid. The model includes both detailed gas-phase reactions and catalytic surface reactions. The reactants modeled so far include lean mixtures of dry CO and CO/H2 mixtures, with pure oxygen as the oxidizer. The results include transient computations of light-off and system response to inlet condition variations. In some cases, the model predicts two different steady-state solutions depending on whether the channel is initially hot or cold. Additionally, the model suggests that the catalytic ignition of CO/O2 mixtures is extremely sensitive to small variations of inlet equivalence ratios and parts per million levels of H2.

  3. Newbery Medal Acceptance.

    ERIC Educational Resources Information Center

    Freedman, Russell

    1988-01-01

    Presents the Newbery Medal acceptance speech of Russell Freedman, writer of children's nonfiction. Discusses the place of nonfiction in the world of children's literature, the evolution of children's biographies, and the author's work on "Lincoln." (ARH)

  4. Newbery Medal Acceptance.

    ERIC Educational Resources Information Center

    Cleary, Beverly

    1984-01-01

    Reprints the text of Ms. Cleary's Newbery medal acceptance speech in which she gives personal history concerning her development as a writer and her response to the letters she receives from children. (CRH)

  5. Caldecott Medal Acceptance.

    ERIC Educational Resources Information Center

    Provensen, Alice; Provensen, Martin

    1984-01-01

    Reprints the text of the Provensens' Caldecott medal acceptance speech in which they describe their early interest in libraries and literature, the collaborative aspect of their work, and their current interest in aviation. (CRH)

  6. Assessing modeled Greenland surface mass balance in the GISS Model E2 and its sensitivity to surface albedo

    NASA Astrophysics Data System (ADS)

    Alexander, Patrick; LeGrande, Allegra N.; Koenig, Lora S.; Tedesco, Marco; Moustafa, Samiah E.; Ivanoff, Alvaro; Fischer, Robert P.; Fettweis, Xavier

    2016-04-01

    The surface mass balance (SMB) of the Greenland Ice Sheet (GrIS) plays an important role in global sea level change. Regional Climate Models (RCMs) such as the Modèle Atmosphérique Régionale (MAR) have been employed at high spatial resolution with relatively complex physics to simulate ice sheet SMB. Global climate models (GCMs) incorporate less sophisticated physical schemes and provide outputs at a lower spatial resolution, but have the advantage of modeling the interaction between different components of the earth's oceans, climate, and land surface at a global scale. Improving the ability of GCMs to represent ice sheet SMB is important for making predictions of future changes in global sea level. With the ultimate goal of improving SMB simulated by the Goddard Institute for Space Studies (GISS) Model E2 GCM, we compare simulated GrIS SMB against the outputs of the MAR model and radar-derived estimates of snow accumulation. In order to reproduce present-day climate variability in the Model E2 simulation, winds are constrained to match the reanalysis datasets used to force MAR at the lateral boundaries. We conduct a preliminary assessment of the sensitivity of the simulated Model E2 SMB to surface albedo, a parameter that is known to strongly influence SMB. Model E2 albedo is set to a fixed value of 0.8 over the entire ice sheet in the initial configuration of the model (control case). We adjust this fixed value in an ensemble of simulations over a range of 0.4 to 0.8 (roughly the range of observed summer GrIS albedo values) to examine the sensitivity of ice-sheet-wide SMB to albedo. We prescribe albedo from the Moderate Resolution Imaging Spectroradiometer (MODIS) MCD43A3 v6 to examine the impact of a more realistic spatial and temporal variations in albedo. An age-dependent snow albedo parameterization is applied, and its impact on SMB relative to observations and the RCM is assessed.

  7. An Integrated Snow Radiance and Snow Physics Modeling Framework for Cold Land Surface Modeling

    NASA Technical Reports Server (NTRS)

    Kim, Edward J.; Tedesco, Marco

    2006-01-01

    Recent developments in forward radiative transfer modeling and physical land surface modeling are converging to allow the assembly of an integrated snow/cold lands modeling framework for land surface modeling and data assimilation applications. The key elements of this framework include: a forward radiative transfer model (FRTM) for snow, a snowpack physical model, a land surface water/energy cycle model, and a data assimilation scheme. Together these form a flexible framework for self-consistent remote sensing and water/energy cycle studies. In this paper we will describe the elements and the integration plan. Each element of this framework is modular so the choice of element can be tailored to match the emphasis of a particular study. For example, within our framework, four choices of a FRTM are available to simulate the brightness temperature of snow: Two models are available to model the physical evolution of the snowpack and underlying soil, and two models are available to handle the water/energy balance at the land surface. Since the framework is modular, other models-physical or statistical--can be accommodated, too. All modules will operate within the framework of the Land Information System (LIS), a land surface modeling framework with data assimilation capabilities running on a parallel-node computing cluster at the NASA Goddard Space Flight Center. The advantages of such an integrated modular framework built on the LIS will be described through examples-e.g., studies to analyze snow field experiment observations, and simulations of future satellite missions for snow and cold land processes.

  8. Improvements to a Response Surface Thermal Model for Orion

    NASA Technical Reports Server (NTRS)

    Miller, Stephen W.; Walker, William Q.

    2011-01-01

    A study was performed to determine if a Design of Experiments (DOE)/Response Surface Methodology could be applied to on-orbit thermal analysis and produce a set of Response Surface Equations (RSE) that predict Orion vehicle temperatures within 10 F. The study used the Orion Outer Mold Line model. Five separate factors were identified for study: yaw, pitch, roll, beta angle, and the environmental parameters. Twenty-three external Orion components were selected and their minimum and maximum temperatures captured over a period of two orbits. Thus, there are 46 responses. A DOE case matrix of 145 runs was developed. The data from these cases were analyzed to produce a fifth order RSE for each of the temperature responses. For the 145 cases in the DOE matrix, the agreement between the engineering data and the RSE predictions was encouraging with 40 of the 46 RSEs predicting temperatures within the goal band. However, the verification cases showed most responses did not meet the 10 F goal. After reframing the focus of the study to better align the RSE development with the purposes of the model, a set of RSEs for both the minimum and maximum radiator temperatures was produced which predicted the engineering model output within +/-4 F. Therefore, with the correct application of the DOE/RSE methodology, RSEs can be developed that provide analysts a fast and easy way to screen large numbers of environments and assess proposed changes to the RSE factors.

  9. Application of a land surface model for simulating river streamflow in high latitudes

    NASA Astrophysics Data System (ADS)

    Gusev, Yeugeniy; Nasonova, Olga; Dzhogan, Larissa

    2010-05-01

    Nowadays modelling runoff from the pan-Arctic river basins, which represents nearly 50% of water flow to the Arctic Ocean, is of great interest among hydrological modelling community because these regions are very sensitive to natural and anthropogenic impacts. This motivates the necessity of increase of the accuracy of hydrological estimations, runoff predictions, and water resources assessments in high latitudes. However, in these regions, observations required for model simulations (to specify model parameters and forcing inputs) are very scarce or even absent (especially this concerns land surface parameters). At the same time river discharge measurements are usually available that makes it possible to estimate model parameters by their calibration against measured discharge. Such a situation is typical of most of the northern basins of Russia. The major goal of the work is to reveal whether a physically-based land surface model (LSM) Soil Water - Atmosphere - Plants (SWAP) is able to reproduce snowmelt and rain driven daily streamflow in high latitudes (using poor input information) with the accuracy acceptable for hydrologic applications. Three river basins, located on the north of the European part of Russia, were chosen for investigation. They are the Mezen River basin (area: area: 78 000 km2), the Pechora River basin (area: 312 000 km2) and the Severnaya Dvina River basin (area: 348 000 km2). For modeling purposes the basins were presented, respectively, by 10, 57 and 62 one-degree computational grid boxes connected by river network. A priori estimation of the land surface parameters for each grid box was based on the global one-degree datasets prepared within the framework of the International Satellite Land-Surface Climatology Project Initiative II (ISLSCP) / the Second Global Soil Wetness Project (GSWP-2). Three versions of atmospheric forcing data prepared for the basins were based on: (1) NCEP/DOE reanalysis dataset; (2) NCEP/DOE reanalysis product

  10. Modeling Tree Shade Effect on Urban Ground Surface Temperature.

    PubMed

    Napoli, Marco; Massetti, Luciano; Brandani, Giada; Petralli, Martina; Orlandini, Simone

    2016-01-01

    There is growing interest in the role that urban forests can play as urban microclimate modifiers. Tree shade and evapotranspiration affect energy fluxes and mitigate microclimate conditions, with beneficial effects on human health and outdoor comfort. The aim of this study was to investigate surface temperature () variability under the shade of different tree species and to test the capability in predicting of a proposed heat transfer model. Surface temperature data on asphalt and grass under different shading conditions were collected in the Cascine park, Florence, Italy, and were used to test the performance of a one-dimensional heat transfer model integrated with a routine for estimating the effect of plant canopies on surface heat transfer. Shading effects of 10 tree species commonly used in Italian urban settings were determined by considering the infrared radiation and the tree canopy leaf area index (LAI). The results indicate that, on asphalt, was negatively related to the LAI of trees ( reduction ranging from 13.8 to 22.8°C). On grass, this relationship was weaker probably because of the combined effect of shade and grass evapotranspiration on ( reduction ranged from 6.9 to 9.4°C). A sensitivity analysis confirmed that other factors linked to soil water content play an important role in reduction of grassed areas. Our findings suggest that the energy balance model can be effectively used to estimate of the urban pavement under different shading conditions and can be applied to the analysis of microclimate conditions of urban green spaces. PMID:26828170

  11. Radiolytic Model for Chemical Composition of Europa's Atmosphere and Surface

    NASA Technical Reports Server (NTRS)

    Cooper, John F.

    2004-01-01

    The overall objective of the present effort is to produce models for major and selected minor components of Europa s neutral atmosphere in 1-D versus altitude and in 2-D versus altitude and longitude or latitude. A 3-D model versus all three coordinates (alt, long, lat) will be studied but development on this is at present limited by computing facilities available to the investigation team. In this first year we have focused on 1-D modeling with Co-I Valery Shematovich s Direct Simulation Monte Carlo (DSMC) code for water group species (H2O, O2, O, OH) and on 2-D with Co-I Mau Wong's version of a similar code for O2, O, CO, CO2, and Na. Surface source rates of H2O and O2 from sputtering and radiolysis are used in the 1-D model, while observations for CO2 at the Europa surface and Na detected in a neutral cloud ejected from Europa are used, along with the O2 sputtering rate, to constrain source rates in the 2-D version. With these separate approaches we are investigating a range of processes important to eventual implementation of a comprehensive 3-D atmospheric model which could be used to understand present observations and develop science requirements for future observations, e.g. from Earth and in Europa orbit. Within the second year we expect to merge the full water group calculations into the 2-D version of the DSMC code which can then be extended to 3-D, pending availability of computing resources. Another important goal in the second year would be the inclusion of sulk and its more volatile oxides (SO, SO2).

  12. Tablet Personal Computer Integration in Higher Education: Applying the Unified Theory of Acceptance and Use Technology Model to Understand Supporting Factors

    ERIC Educational Resources Information Center

    Moran, Mark; Hawkes, Mark; El Gayar, Omar

    2010-01-01

    Many educational institutions have implemented ubiquitous or required laptop, notebook, or tablet personal computing programs for their students. Yet, limited evidence exists to validate integration and acceptance of the technology among student populations. This research examines student acceptance of mobile computing devices using a modification…

  13. The roughness of the Martian surface: A scale dependent model

    NASA Technical Reports Server (NTRS)

    Shepard, M. K.; Guinness, E. A.; Arvidson, R. E.

    1993-01-01

    In the coming decade, several lander missions to Mars are planned (e.g., MESUR Pathfinder, MESUR). One of the dangers facing planners of these missions is the rough topography observed at both Viking Lander sites. Both landing sites are ubiquitously covered with meter-scale boulders. Objects of this size pose obvious threats to soft landers, especially at Mars where the distance from Earth causes prohibitive time lags between the transmission of commands and feedback from the spacecraft. An obvious solution is to scout for a 'smooth' site prior to the landing. However, the best resolutions realizable on current and future missions (i.e., Mars Observer) are on the order of several meters. Even at this scale, boulders of 1-2 meters in size are unresolvable. Additionally, the amount of time and spacecraft resources required to search even a small area of the planet are unrealistic given other mission objectives. An alternative is to determine the 'roughness' of the surface at a subpixel scale using bidirectional reflectance observations. Much larger areas of the planet can be searched, and much of the search can easily be automated. The morphology of the martian plains observed by the Viking Landers is physically simple. The surface is covered with a layer (approximately flat lying) of aeolian sediment from which numerous outcrops of bedrock and boulders protrude. This morphology, while simple, will be difficult to characterize from orbit using traditional bidirectional reflectance models for two reasons. First, modeling the surface as facets with Gaussian or exponential slope distributions is not realistic given the morphology described above. Second, the roughness parameter is an 'average' of the roughness at scales ranging from the wavelength of light being scattered to the pixel size of the observation. Thus, there is no definite scale of roughness that can be extracted from the Hapke roughness parameter. Using the concepts of geometric and boolean models

  14. A Kinematic Model for Surface Irrigation: An Extension

    NASA Astrophysics Data System (ADS)

    Sherman, Bernard; Singh, Vijay P.

    1982-06-01

    The kinematic model for surface irrigation, reported previously by Sherman and Singh (1978), is extended. Depending upon the duration of irrigation and time variability of infiltration, three cases are distinguished. Explicit solutions are obtained when infiltration is constant. When infiltration is varying in time, a numerical procedure is developed which is stable and has fast convergence. A rigorous theoretical justification is developed for computation of the depth of water at and the time history of the front wall of water advancing down an infiltrating plane or channel. A derivation is given of the continuity and momentum equations when there is lateral inflow and infiltration into the channel bed.

  15. Models of Fate and Transport of Pollutants in Surface Waters

    NASA Astrophysics Data System (ADS)

    Okome, Gloria Eloho

    There is the need to answer very crucial questions of "what happens to pollutants in surface waters?" This question must be answered to determine the factors controlling fate and transport of chemicals and their evolutionary state in surface waters. Monitoring and experimental methods are used in establishing the environmental states. These measurements are used with the known scientific principles to identify processes and to estimate the future environmental conditions. Conceptual and computational models are needed to analyze environmental processes by applying the knowledge gained from experimentation and theory. Usually, a computational framework includes the mathematics and the physics of the phenomenon, and the measured characteristics to model pollutants interactions and transport in surface water. However, under certain conditions, the complexity of the situation in the actual environment precludes the utilization of these techniques. Pollutants in several forms: Nitrogen (Nitrate, Nitrite, Kjeldhal Nitrogen and Ammonia), Phosphorus (orthophosphate and total phosphorus), bacteria (E-coli and Fecal coliform), Salts (Chloride and Sulfate) are chosen to follow for this research. The objective of this research is to model the fate and transport of these pollutants in non-ideal conditions of surface water measurements and to develop computational methods to forecast their fate and transport. In an environment of extreme drought such as in the Brazos River basin, where small streams flow intermittently, there is added complexity due to the absence of regularly sampled data. The usual modeling techniques are no longer applicable because of sparse measurements in space and time. Still, there is a need to estimate the conditions of the environment from the information that is present. Alternative methods for this estimation must be devised and applied to this situation, which is the task of this dissertation. This research devices a forecasting technique that is

  16. Coastal Digital Surface Model on Low Contrast Images

    NASA Astrophysics Data System (ADS)

    Rosu, A.-M.; Assenbaum, M.; De la Torre, Y.; Pierrot-Deseilligny, M.

    2015-08-01

    Coastal sandy environments are extremely dynamic and require regular monitoring that can easily be achieved by using an unmanned aerial system (UAS) including a drone and a photo camera. The acquired images have low contrast and homogeneous texture. Using these images and with very few, if any, ground control points (GCPs), it is difficult to obtain a digital surface model (DSM) by classical correlation and automatic interest points determination approach. A possible response to this problem is to work with enhanced, contrast filtered images. To achieve this, we use and tune the free open-source software MicMac.

  17. Numerical modeling and simulation of flow through porous fabric surface

    NASA Astrophysics Data System (ADS)

    Gao, Zheng; Li, Xiaolin

    We designed a numerical scheme to model the permeability of the fabric surface in an incompressible fluid by coupling the projection method with the Ghost Fluid Method in the front tracking framework. The pressure jump condition is obtained by adding a source term to the Poisson's equation in the projection step without modifications on its coefficients. The numerical results suggest that this approach has the ability to reproduce the relationship between pressure drop and relative velocity observed in the experiments. We use this algorithm to study the effects of porosity on the drag force and stability of parachutes during its inflation and deceleration.

  18. Enhanced Surface Water and Energy Flux Calculation through the Integration of Thermal Remote Sensing Retrievals with Land Surface Models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The treatment of aerodynamic surface temperature in soil–vegetation–atmosphere transfer (SVAT) models can be used to classify approaches into two broad categories. The first category contains models utilizing remote sensing (RS) observations of surface radiometric temperature to estimate aerodynamic...

  19. Towards the development of an on-line model error identification system for land surface models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Due to the complexity of potential error sources in land surface models, the accurate specification of model error parameters has emerged as a major challenge in the development of effective land data assimilation systems for hydrologic and hydro-climatic applications. While several on-line procedur...

  20. Modeling and Prediction of Surface Plasmon Resonance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Guske, Joshua Travis

    Surface plasmon resonance (SPR) is a spectroscopy that measures the response of a surface wave at the interface of a conductor and a dielectric, called the surface plasmon polariton (SPP). In the Kretschmann configuration, a thin film of the conductor is illuminated under total internal reflection via a prism. At the appropriate angle and frequency, an absorption is seen in reflected p-polarized light. This excitation is highly sensitive to the properties of the dielectric medium, the conductor itself, and the substrate material. Theoretical modeling is valuable in SPR, because of the high sensitivity and the large number of experimental variables involved. As the technology advances, increasingly sophisticated modeling techniques become necessary. In addition, with the aid of theoretical modeling, SPR may be used as a materials characterization tool, to study the properties of the conductors themselves. In this dissertation, several plasmonic systems were studied. First, in chapters 2 and 3, films of silver sandwiched between two layers of non-conductive aluminum-doped zinc oxide (AZO) on glass were considered. The films were prepared by reactive pulsed DC magnetron sputtering, and the silver thickness was varied. The films' SPR response was measured in the near-IR in air. Theoretical modeling of Rp/Rs was performed by the multilayer transfer-matrix method, with the aid of a modified Nelder-Mead simplex optimization algorithm. The initial modeling results suggested that both the silver and AZO properties were significantly different from the bulk materials. In particular, the silver had a higher plasma frequency and high-frequency dielectric constant than bulk, and it was hypothesized that the AZO was contributing charge carriers into the silver layer. However, upon review it was determined that a miscalibration of the incident angles could also explain the results. Second, in chapter 4, films of silver sandwiched between two layers of AZO were deposited using