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Sample records for artificial intelligence-based atomistic

  1. Artificial Intelligence based technique for BTS placement

    Science.gov (United States)

    Alenoghena, C. O.; Emagbetere, J. O.; Aibinu, A. M.

    2013-12-01

    The increase of the base transceiver station (BTS) in most urban areas can be traced to the drive by network providers to meet demand for coverage and capacity. In traditional network planning, the final decision of BTS placement is taken by a team of radio planners, this decision is not fool proof against regulatory requirements. In this paper, an intelligent based algorithm for optimal BTS site placement has been proposed. The proposed technique takes into consideration neighbour and regulation considerations objectively while determining cell site. The application will lead to a quantitatively unbiased evaluated decision making process in BTS placement. An experimental data of a 2km by 3km territory was simulated for testing the new algorithm, results obtained show a 100% performance of the neighbour constrained algorithm in BTS placement optimization. Results on the application of GA with neighbourhood constraint indicate that the choices of location can be unbiased and optimization of facility placement for network design can be carried out.

  2. An Artificial Intelligence-Based Distance Education System: Artimat

    Science.gov (United States)

    Nabiyev, Vasif; Karal, Hasan; Arslan, Selahattin; Erumit, Ali Kursat; Cebi, Ayca

    2013-01-01

    The purpose of this study is to evaluate the artificial intelligence-based distance education system called ARTIMAT, which has been prepared in order to improve mathematical problem solving skills of the students, in terms of conceptual proficiency and ease of use with the opinions of teachers and students. The implementation has been performed…

  3. Evaluation of Artificial Intelligence Based Models for Chemical Biodegradability Prediction

    Directory of Open Access Journals (Sweden)

    Aleksandar Sabljic

    2004-12-01

    Full Text Available This study presents a review of biodegradability modeling efforts including a detailed assessment of two models developed using an artificial intelligence based methodology. Validation results for these models using an independent, quality reviewed database, demonstrate that the models perform well when compared to another commonly used biodegradability model, against the same data. The ability of models induced by an artificial intelligence methodology to accommodate complex interactions in detailed systems, and the demonstrated reliability of the approach evaluated by this study, indicate that the methodology may have application in broadening the scope of biodegradability models. Given adequate data for biodegradability of chemicals under environmental conditions, this may allow for the development of future models that include such things as surface interface impacts on biodegradability for example.

  4. Artificial organic networks artificial intelligence based on carbon networks

    CERN Document Server

    Ponce-Espinosa, Hiram; Molina, Arturo

    2014-01-01

    This monograph describes the synthesis and use of biologically-inspired artificial hydrocarbon networks (AHNs) for approximation models associated with machine learning and a novel computational algorithm with which to exploit them. The reader is first introduced to various kinds of algorithms designed to deal with approximation problems and then, via some conventional ideas of organic chemistry, to the creation and characterization of artificial organic networks and AHNs in particular. The advantages of using organic networks are discussed with the rules to be followed to adapt the network to its objectives. Graph theory is used as the basis of the necessary formalism. Simulated and experimental examples of the use of fuzzy logic and genetic algorithms with organic neural networks are presented and a number of modeling problems suitable for treatment by AHNs are described: ·        approximation; ·        inference; ·        clustering; ·        control; ·        class...

  5. Predicting chick body mass by artificial intelligence-based models

    Directory of Open Access Journals (Sweden)

    Patricia Ferreira Ponciano Ferraz

    2014-07-01

    Full Text Available The objective of this work was to develop, validate, and compare 190 artificial intelligence-based models for predicting the body mass of chicks from 2 to 21 days of age subjected to different duration and intensities of thermal challenge. The experiment was conducted inside four climate-controlled wind tunnels using 210 chicks. A database containing 840 datasets (from 2 to 21-day-old chicks - with the variables dry-bulb air temperature, duration of thermal stress (days, chick age (days, and the daily body mass of chicks - was used for network training, validation, and tests of models based on artificial neural networks (ANNs and neuro-fuzzy networks (NFNs. The ANNs were most accurate in predicting the body mass of chicks from 2 to 21 days of age after they were subjected to the input variables, and they showed an R² of 0.9993 and a standard error of 4.62 g. The ANNs enable the simulation of different scenarios, which can assist in managerial decision-making, and they can be embedded in the heating control systems.

  6. AN ARTIFICIAL INTELLIGENCE-BASED DISTANCE EDUCATION SYSTEM: Artimat

    Directory of Open Access Journals (Sweden)

    Vasif NABIYEV

    2013-04-01

    Full Text Available The purpose of this study is to evaluate the artificial intelligence-based distance education system called as ARTIMAT, which has been prepared in order to improve mathematical problem solving skills of the students, in terms of conceptual proficiency and ease of use with the opinions of teachers and students. The implementation has been performed with 4 teachers and 59 students in 10th grade in an Anatolian High School in Trabzon. Many institutions and organizations in the world approach seriously to distance education besides traditional education. It is inevitable to use the distance education in teaching the problem solving skills in this different dimension of the education. In the studies in Turkey and abroad in the field of mathematics teaching, problem solving skills are generally stated not to be at the desired level and often expressed to have difficulty in teaching. For this reason, difficulties of the students in problem solving have initially been evaluated and the system has been prepared utilizing artificial intelligence algorithms according to the obtained results. In the evaluation of the findings obtained from the application, it has been concluded that the system is responsive to the needs of the students and is successful in general, but that conceptual changes should be made in order that students adapt to the system quickly.

  7. Artificial Intelligence Based Three-Phase Unified Power Quality Conditioner

    Directory of Open Access Journals (Sweden)

    Moleykutty George

    2007-01-01

    Full Text Available Power quality is an important measure of the performance of an electrical power system. This paper discusses the topology, control strategies using artificial intelligent (AI based controllers and the performance of a unified power quality conditioner (UPQC for power quality improvement. UPQC is an integration of shunt and series compensation to limit the harmonic contamination within 5 %, the limit imposed by IEEE-519 standard. The novelty of this paper lies in the application of neural network control (NNC algorithms such as model reference control (MRC, and nonlinear autoregressive-moving average (NARMA–L2 control to generate switching signals for the series compensator of the UPQC system. The entire system has been modeled using MATLAB 7.0 toolbox. Simulation results demonstrate the applicability of MRC and NARMA-L2 controllers for the control of UPQC.

  8. Adaptive Artificial Intelligence Based Model Base Controller: Applied to Surgical Endoscopy Telemanipulator

    Directory of Open Access Journals (Sweden)

    Farzin Piltan

    2013-08-01

    Full Text Available This research involved developing a surgical robot assistant using an articulated PUMA robot running on a linear or nonlinear axis. The research concentrated on studying the artificial intelligence based switching computed torque controller to localization of an endoscopic tool. Results show that the switching artificial nonlinear control algorithm is capable to design a stable controller. For this system, error was used as the performance metric. Positioning of the endoscopic manipulator relative to the world coordinate frame was possible to within 0.05 inch. Error in maintaining a constant point in space is evident during repositioning however this was caused by limitations in the robot arm.

  9. A comparative study of artificial intelligent-based maximum power point tracking for photovoltaic systems

    Science.gov (United States)

    Hussain Mutlag, Ammar; Mohamed, Azah; Shareef, Hussain

    2016-03-01

    Maximum power point tracking (MPPT) is normally required to improve the performance of photovoltaic (PV) systems. This paper presents artificial intelligent-based maximum power point tracking (AI-MPPT) by considering three artificial intelligent techniques, namely, artificial neural network (ANN), adaptive neuro fuzzy inference system with seven triangular fuzzy sets (7-tri), and adaptive neuro fuzzy inference system with seven gbell fuzzy sets. The AI-MPPT is designed for the 25 SolarTIFSTF-120P6 PV panels, with the capacity of 3 kW peak. A complete PV system is modelled using 300,000 data samples and simulated in the MATLAB/SIMULINK. The AI-MPPT has been tested under real environmental conditions for two days from 8 am to 18 pm. The results showed that the ANN based MPPT gives the most accurate performance and then followed by the 7-tri-based MPPT.

  10. Artificial Intelligence Based Selection of Optimal Cutting Tool and Process Parameters for Effective Turning and Milling Operations

    Science.gov (United States)

    Saranya, Kunaparaju; John Rozario Jegaraj, J.; Ramesh Kumar, Katta; Venkateshwara Rao, Ghanta

    2016-06-01

    With the increased trend in automation of modern manufacturing industry, the human intervention in routine, repetitive and data specific activities of manufacturing is greatly reduced. In this paper, an attempt has been made to reduce the human intervention in selection of optimal cutting tool and process parameters for metal cutting applications, using Artificial Intelligence techniques. Generally, the selection of appropriate cutting tool and parameters in metal cutting is carried out by experienced technician/cutting tool expert based on his knowledge base or extensive search from huge cutting tool database. The present proposed approach replaces the existing practice of physical search for tools from the databooks/tool catalogues with intelligent knowledge-based selection system. This system employs artificial intelligence based techniques such as artificial neural networks, fuzzy logic and genetic algorithm for decision making and optimization. This intelligence based optimal tool selection strategy is developed using Mathworks Matlab Version 7.11.0 and implemented. The cutting tool database was obtained from the tool catalogues of different tool manufacturers. This paper discusses in detail, the methodology and strategies employed for selection of appropriate cutting tool and optimization of process parameters based on multi-objective optimization criteria considering material removal rate, tool life and tool cost.

  11. Artificial intelligence based approach to forecast PM2.5 during haze episodes: A case study of Delhi, India

    Science.gov (United States)

    Mishra, Dhirendra; Goyal, P.; Upadhyay, Abhishek

    2015-02-01

    Delhi has been listed as the worst performer across the world with respect to the presence of alarmingly high level of haze episodes, exposing the residents here to a host of diseases including respiratory disease, chronic obstructive pulmonary disorder and lung cancer. This study aimed to analyze the haze episodes in a year and to develop the forecasting methodologies for it. The air pollutants, e.g., CO, O3, NO2, SO2, PM2.5 as well as meteorological parameters (pressure, temperature, wind speed, wind direction index, relative humidity, visibility, dew point temperature, etc.) have been used in the present study to analyze the haze episodes in Delhi urban area. The nature of these episodes, their possible causes, and their major features are discussed in terms of fine particulate matter (PM2.5) and relative humidity. The correlation matrix shows that temperature, pressure, wind speed, O3, and dew point temperature are the dominating variables for PM2.5 concentrations in Delhi. The hour-by-hour analysis of past data pattern at different monitoring stations suggest that the haze hours were occurred approximately 48% of the total observed hours in the year, 2012 over Delhi urban area. The haze hour forecasting models in terms of PM2.5 concentrations (more than 50 μg/m3) and relative humidity (less than 90%) have been developed through artificial intelligence based Neuro-Fuzzy (NF) techniques and compared with the other modeling techniques e.g., multiple linear regression (MLR), and artificial neural network (ANN). The haze hour's data for nine months, i.e. from January to September have been chosen for training and remaining three months, i.e., October to December in the year 2012 are chosen for validation of the developed models. The forecasted results are compared with the observed values with different statistical measures, e.g., correlation coefficients (R), normalized mean square error (NMSE), fractional bias (FB) and index of agreement (IOA). The performed

  12. Artificial Intelligence Based Control Power Optimization on Tailless Aircraft. [ARMD Seedling Fund Phase I

    Science.gov (United States)

    Gern, Frank; Vicroy, Dan D.; Mulani, Sameer B.; Chhabra, Rupanshi; Kapania, Rakesh K.; Schetz, Joseph A.; Brown, Derrell; Princen, Norman H.

    2014-01-01

    Traditional methods of control allocation optimization have shown difficulties in exploiting the full potential of controlling large arrays of control devices on innovative air vehicles. Artificial neutral networks are inspired by biological nervous systems and neurocomputing has successfully been applied to a variety of complex optimization problems. This project investigates the potential of applying neurocomputing to the control allocation optimization problem of Hybrid Wing Body (HWB) aircraft concepts to minimize control power, hinge moments, and actuator forces, while keeping system weights within acceptable limits. The main objective of this project is to develop a proof-of-concept process suitable to demonstrate the potential of using neurocomputing for optimizing actuation power for aircraft featuring multiple independently actuated control surfaces. A Nastran aeroservoelastic finite element model is used to generate a learning database of hinge moment and actuation power characteristics for an array of flight conditions and control surface deflections. An artificial neural network incorporating a genetic algorithm then uses this training data to perform control allocation optimization for the investigated aircraft configuration. The phase I project showed that optimization results for the sum of required hinge moments are improved by more than 12% over the best Nastran solution by using the neural network optimization process.

  13. Prodiag--a hybrid artificial intelligence based reactor diagnostic system for process faults

    Energy Technology Data Exchange (ETDEWEB)

    Reifman, J.; Wei, T.Y.C.; Vitela, J.E. [Argonne National Lab., IL (United States); Applequist, C. A. [Commonwealth Research Corp., Chicago, IL (United States); Chasensky, T.M. [Commonwealth Edison Co., Chicago, IL (United States)

    1996-03-01

    Commonwealth Research Corporation (CRC) and Argonne National Laboratory (ANL) are collaborating on a DOE-sponsored Cooperative Research and Development Agreement (CRADA), project to perform feasibility studies on a novel approach to Artificial Intelligence (Al) based diagnostics for component faults in nuclear power plants. Investigations are being performed in the construction of a first-principles physics-based plant level process diagnostic expert system (ES) and the identification of component-level fault patterns through operating component characteristics using artificial neural networks (ANNs). The purpose of the proof-of-concept project is to develop a computer-based system using this Al approach to assist process plant operators during off-normal plant conditions. The proposed computer-based system will use thermal hydraulic (T-H) signals complemented by other non-T-H signals available in the data stream to provide the process operator with the component which most likely caused the observed process disturbance.To demonstrate the scale-up feasibility of the proposed diagnostic system it is being developed for use with the Chemical Volume Control System (CVCS) of a nuclear power plant. A full-scope operator training simulator representing the Commonwealth Edison Braidwood nuclear power plant is being used both as the source of development data and as the means to evaluate the advantages of the proposed diagnostic system. This is an ongoing multi-year project and this paper presents the results to date of the CRADA phase.

  14. On the Idea of a New Artificial Intelligence Based Optimization Algorithm Inspired From the Nature of Vortex

    Directory of Open Access Journals (Sweden)

    Utku Kose

    2015-07-01

    Full Text Available In this paper, the idea of a new artificial intelligence based optimization algorithm, which is inspired from the nature of vortex, has been provided briefly. As also a bio-inspired computation algorithm, the idea is generally focused on a typical vortex flow / behavior in nature and inspires from some dynamics that are occurred in the sense of vortex nature. Briefly, the algorithm is also a swarm-oriented evolutional problem solution approach; because it includes many methods related to elimination of weak swarm members and trying to improve the solution process by supporting the solution space via new swarm members. In order have better idea about success of the algorithm; it has been tested via some benchmark functions. At this point, the obtained results show that the algorithm can be an alternative to the literature in terms of single-objective optimizationsolution ways. Vortex Optimization Algorithm (VOA is the name suggestion by the authors; for this new idea of intelligent optimization approach.

  15. The Use of Artificial-Intelligence-Based Ensembles for Intrusion Detection: A Review

    Directory of Open Access Journals (Sweden)

    Gulshan Kumar

    2012-01-01

    Full Text Available In supervised learning-based classification, ensembles have been successfully employed to different application domains. In the literature, many researchers have proposed different ensembles by considering different combination methods, training datasets, base classifiers, and many other factors. Artificial-intelligence-(AI- based techniques play prominent role in development of ensemble for intrusion detection (ID and have many benefits over other techniques. However, there is no comprehensive review of ensembles in general and AI-based ensembles for ID to examine and understand their current research status to solve the ID problem. Here, an updated review of ensembles and their taxonomies has been presented in general. The paper also presents the updated review of various AI-based ensembles for ID (in particular during last decade. The related studies of AI-based ensembles are compared by set of evaluation metrics driven from (1 architecture & approach followed; (2 different methods utilized in different phases of ensemble learning; (3 other measures used to evaluate classification performance of the ensembles. The paper also provides the future directions of the research in this area. The paper will help the better understanding of different directions in which research of ensembles has been done in general and specifically: field of intrusion detection systems (IDSs.

  16. Artificial intelligence based models for stream-flow forecasting: 2000-2015

    Science.gov (United States)

    Yaseen, Zaher Mundher; El-shafie, Ahmed; Jaafar, Othman; Afan, Haitham Abdulmohsin; Sayl, Khamis Naba

    2015-11-01

    The use of Artificial Intelligence (AI) has increased since the middle of the 20th century as seen in its application in a wide range of engineering and science problems. The last two decades, for example, has seen a dramatic increase in the development and application of various types of AI approaches for stream-flow forecasting. Generally speaking, AI has exhibited significant progress in forecasting and modeling non-linear hydrological applications and in capturing the noise complexity in the dataset. This paper explores the state-of-the-art application of AI in stream-flow forecasting, focusing on defining the data-driven of AI, the advantages of complementary models, as well as the literature and their possible future application in modeling and forecasting stream-flow. The review also identifies the major challenges and opportunities for prospective research, including, a new scheme for modeling the inflow, a novel method for preprocessing time series frequency based on Fast Orthogonal Search (FOS) techniques, and Swarm Intelligence (SI) as an optimization approach.

  17. Towards sustainability: artificial intelligent based approach for soil stabilization using various pozzolans

    KAUST Repository

    Ouf, M. S.

    2012-07-03

    Due to the gradual depletion in the conventional resources, searching for a more rational road construction approach aimed at reducing the dependence on imported materials while improving the quality and durability of the roads is necessary. A previous study carried out on a sample of Egyptian soil aimed at reducing the road construction cost, protect the environment and achieving sustainability. RoadCem, ground granulated blast furnace slag (GGBS), lime and ordinary Portland cement (OPC) were employed to stabilise the Egyptian clayey soil. The results revealed that the unconfined compressive strength (UCS) of the test soil increased while the free swelling percent (FSP) decreased with an increase in the total stabiliser and the curing period. This paper discusses attempts to reach optimum stabilization through: (1) Recognizing the relationship between the UCS/FSP of stabilized soil and the stabilization parameters using artificial neural network (ANN); and (2) Performing a backward optimization on the developed (ANN) model using general algorithm (GA) to meet practical design preferences. © 2012 WIT Press.

  18. Quality Model and Artificial Intelligence Base Fuel Ratio Management with Applications to Automotive Engine

    Directory of Open Access Journals (Sweden)

    Mojdeh Piran

    2014-01-01

    Full Text Available In this research, manage the Internal Combustion (IC engine modeling and a multi-input-multi-output artificial intelligence baseline chattering free sliding mode methodology scheme is developed with guaranteed stability to simultaneously control fuel ratios to desired levels under various air flow disturbances by regulating the mass flow rates of engine PFI and DI injection systems. Modeling of an entire IC engine is a very important and complicated process because engines are nonlinear, multi inputs-multi outputs and time variant. One purpose of accurate modeling is to save development costs of real engines and minimizing the risks of damaging an engine when validating controller designs. Nevertheless, developing a small model, for specific controller design purposes, can be done and then validated on a larger, more complicated model. Analytical dynamic nonlinear modeling of internal combustion engine is carried out using elegant Euler-Lagrange method compromising accuracy and complexity. A baseline estimator with varying parameter gain is designed with guaranteed stability to allow implementation of the proposed state feedback sliding mode methodology into a MATLAB simulation environment, where the sliding mode strategy is implemented into a model engine control module (“software”. To estimate the dynamic model of IC engine fuzzy inference engine is applied to baseline sliding mode methodology. The fuzzy inference baseline sliding methodology performance was compared with a well-tuned baseline multi-loop PID controller through MATLAB simulations and showed improvements, where MATLAB simulations were conducted to validate the feasibility of utilizing the developed controller and state estimator for automotive engines. The proposed tracking method is designed to optimally track the desired FR by minimizing the error between the trapped in-cylinder mass and the product of the desired FR and fuel mass over a given time interval.

  19. Artificial Intelligence based Solver for Governing Model of Radioactivity Cooling, Self-gravitating Clouds and Clusters of Galaxies

    Directory of Open Access Journals (Sweden)

    Junaid Ali Khan

    2013-06-01

    Full Text Available In this study, a reliable alternate platform is developed based on artificial neural network optimized with soft computing technique for a non-linear singular system that can model complex physical phenomenas of the nature like radioactivity cooling, self-gravitating clouds and clusters of galaxies. The trial solution is mathematically represented by feed-forward neural network. A cost function is defined in an unsupervised manner that is optimized by a probabilistic meta-heuristic global search technique based on annealing in metallurgy. The results of the designed scheme are evaluated by comparing with the desired response of the system. The applicability, stability and reliability of the proposed method is validated by Monte Carlo simulations.

  20. Multi-modal low cost mobile indoor surveillance system on the Robust Artificial Intelligence-based Defense Electro Robot (RAIDER)

    Science.gov (United States)

    Nair, Binu M.; Diskin, Yakov; Asari, Vijayan K.

    2012-10-01

    We present an autonomous system capable of performing security check routines. The surveillance machine, the Clearpath Husky robotic platform, is equipped with three IP cameras with different orientations for the surveillance tasks of face recognition, human activity recognition, autonomous navigation and 3D reconstruction of its environment. Combining the computer vision algorithms onto a robotic machine has given birth to the Robust Artificial Intelligencebased Defense Electro-Robot (RAIDER). The end purpose of the RAIDER is to conduct a patrolling routine on a single floor of a building several times a day. As the RAIDER travels down the corridors off-line algorithms use two of the RAIDER's side mounted cameras to perform a 3D reconstruction from monocular vision technique that updates a 3D model to the most current state of the indoor environment. Using frames from the front mounted camera, positioned at the human eye level, the system performs face recognition with real time training of unknown subjects. Human activity recognition algorithm will also be implemented in which each detected person is assigned to a set of action classes picked to classify ordinary and harmful student activities in a hallway setting.The system is designed to detect changes and irregularities within an environment as well as familiarize with regular faces and actions to distinguish potentially dangerous behavior. In this paper, we present the various algorithms and their modifications which when implemented on the RAIDER serves the purpose of indoor surveillance.

  1. Artificial intelligence based model for optimization of COD removal efficiency of an up-flow anaerobic sludge blanket reactor in the saline wastewater treatment.

    Science.gov (United States)

    Picos-Benítez, Alain R; López-Hincapié, Juan D; Chávez-Ramírez, Abraham U; Rodríguez-García, Adrián

    2017-03-01

    The complex non-linear behavior presented in the biological treatment of wastewater requires an accurate model to predict the system performance. This study evaluates the effectiveness of an artificial intelligence (AI) model, based on the combination of artificial neural networks (ANNs) and genetic algorithms (GAs), to find the optimum performance of an up-flow anaerobic sludge blanket reactor (UASB) for saline wastewater treatment. Chemical oxygen demand (COD) removal was predicted using conductivity, organic loading rate (OLR) and temperature as input variables. The ANN model was built from experimental data and performance was assessed through the maximum mean absolute percentage error (= 9.226%) computed from the measured and model predicted values of the COD. Accordingly, the ANN model was used as a fitness function in a GA to find the best operational condition. In the worst case scenario (low energy requirements, high OLR usage and high salinity) this model guaranteed COD removal efficiency values above 70%. This result is consistent and was validated experimentally, confirming that this ANN-GA model can be used as a tool to achieve the best performance of a UASB reactor with the minimum requirement of energy for saline wastewater treatment.

  2. Artificial intelligence-based rural road maintenance management assessment system%基于AI的农村公路养护管理评价方法研究

    Institute of Scientific and Technical Information of China (English)

    李月光; 吴小萍; 吕安涛; 聂敏

    2013-01-01

    An analytical hierarchy process (AHP)-based three-level assessment system (including target,criterion,and index) was established to cover all elements relevant to rural road maintenance management.This paper applies the artificial intelligence (AI)-based fuzzy neural network approach to the rural road maintenance management evaluation to handle problems related to knowledge acquirement and accumulation that is essential to comprehensive evaluation.Modular design,coupled with fuzzy theory and the neural network approach,was employed to tentatively develop a rural road maintenance management assessment model with built-in expert knowledge.Indexes in this model are initially fuzzified according to fuzzy theory,then analyzed in the multi-layer neural network,and conversely defuzzified to produce data that support and finalize the rural road maintenance management assessment.An example was given to illustrate the working mechanism of this assessment system,and to prove the feasibility and validity of the fuzzy neural network-based assessment model.%综合考虑影响农村公路养护管理的各要素,采用层次分析方法,建立了包含目标层、准则层、指标层的农村公路养护管理评价三级指标体系.针对综合评价中知识学习积累问题,研究了基于人工智能的模糊神经网络方法在农村公路养护管理评价中的应用.结合模糊理论和神经网络方法,采用模块化设计思想初步建立了农村公路养护管理评价的结构模型,在评估系统中嵌入专家知识,采用模糊理论对评价指标进行模糊化处理,再利用多层神经网络进行数值分析,最后将结果反模糊化,实现对农村公路养护管理系统的综合评价.同时通过实例说明了系统学习、系统评价的过程,实例验证了所建模糊神经网络模型的可行性与有效性.

  3. Intelligence-based systems engineering

    CERN Document Server

    Tolk, Andreas

    2011-01-01

    The International Council on Systems Engineering (INCOSE) defines Systems Engineering as an interdisciplinary approach and means to enable the realization of successful systems. Researchers are using intelligence-based techniques to support the practices of systems engineering in an innovative way. This research volume includes a selection of contributions by subject experts to design better systems.

  4. Artificial intelligence based algorithm for using spectrum to adaptively eliminate exceptional data and automatically classify%基于人工智能的异常地物光谱自适应剔除及分类算法研究

    Institute of Scientific and Technical Information of China (English)

    郝建明; 李宗南; 谢静

    2014-01-01

    针对传统光谱数据预处理与分析的现状,提出一种基于人工智能的光谱异常数据自适应剔除及自动分类算法,通过遗传算法的优化搜索确定马氏距离的阈值,实现异常光谱的自适应剔除,并提出可量化光谱剔除效果的异常一致性指数(ACI)。在此基础上,借助自组织神经网络方法,以各类观测对象的特征光谱作为输入对象,对剔除后的光谱进行自动分类。经过实验验证,算法取得了较好的剔除效果(ACI 达到86%以上)和分类效果(总体分类精度达到94%),较好地实现了异常光谱剔除和光谱分类的自动化处理。%The spectral data measured from spectral measurements are easily affected by human,en-vironmental,equipment and other factors leading to the abnormal spectral characteristics and impacting analyses especially in spectral measurements in the fields.According to the situations of traditional spec-tral data in preprocessing and analysis,a novel algorithm used for abnormal data excluding adaptively and spectral data classifying automatically based on artificial intelligence was established.The Mahalano-bis distance threshold by genetic algorithm searching was determined to exclude abnormal spectral data adaptively and to quantify the effect of excluding abnormal spectral consistency index (ACI).With the self-organizing neural network,spectral characteristics of various types of observing objects were used as input and classified automatically after removing the abnormal.The results showed that the algorithm a-chieved good excluding (ACI more than 86%)and classification (overall classification accuracy of 94%).It can be used to well automate the handling of excluding spectrum and spectral classification.

  5. Bearing capacity of thin-walled shallow foundations:an experimental and artificial intelligence-based study%基于人工智能的薄壁浅地基的承重能力研究

    Institute of Scientific and Technical Information of China (English)

    Hossein REZAEI; Ramli NAZIR; Ehsan MOMENI

    2016-01-01

    Thin-walled spread foundations are used in coastal projects where the soil strength is relatively low. Developing a predictive model of bearing capacity for this kind of foundation is of interest due to the fact that the famous bearing capacity equations are proposed for conventional footings. Many studies underlined the applicability of artificial neural networks (ANNs) in predicting the bearing capacity of foundations. However, the majority of these models are built using conventional ANNs, which suffer from slow rate of learning as well as getting trapped in local minima. Moreover, they are mainly developed for conventional footings. The prime objective of this study is to propose an improved ANN-based predictive model of bearing capacity for thin-walled shallow foundations. In this regard, a relatively large dataset comprising 145 recorded cases of related footing load tests was compiled from the literature. The dataset includes bearing capacity (Qu), friction angle, unit weight of sand, footing width, and thin-wall length to footing width ratio (Lw/B). Apart fromQu, other parameters were set as model inputs. To enhance the diversity of the data, four more related laboratory footing load tests were conducted on the Johor Bahru sand, and results were added to the dataset. Experimental findings suggest an almost 0.5 times increase in the bearing capacity in loose and dense sands whenLw/B is increased from 0.5 to 1.12. Overall, findings show the feasibility of the ANN-based predictive model improved with particle swarm optimization (PSO). The correlation coefficient was 0.98 for testing data, suggesting that the model serves as a reliable tool in predicting the bearing capacity.%目的:薄壁扩展式地基已被广泛应用于土壤强度相对较低的沿海工程。目前,已有很多学者对其进行了人工神经网络的适用性研究,希望用此对地基的承重能力进行预测。但是这些研究多数是基于传统的人工神经网络,

  6. Artificial intelligence based decision support for trumpeter swan management

    Science.gov (United States)

    Sojda, Richard S.

    2002-01-01

    The number of trumpeter swans (Cygnus buccinator) breeding in the Tri-State area where Montana, Idaho, and Wyoming come together has declined to just a few hundred pairs. However, these birds are part of the Rocky Mountain Population which additionally has over 3,500 birds breeding in Alberta, British Columbia, Northwest Territories, and Yukon Territory. To a large degree, these birds seem to have abandoned traditional migratory pathways in the flyway. Waterfowl managers have been interested in decision support tools that would help them explore simulated management scenarios in their quest towards reaching population recovery and the reestablishment of traditional migratory pathways. I have developed a decision support system to assist biologists with such management, especially related to wetland ecology. Decision support systems use a combination of models, analytical techniques, and information retrieval to help develop and evaluate appropriate alternatives. Swan management is a domain that is ecologically complex, and this complexity is compounded by spatial and temporal issues. As such, swan management is an inherently distributed problem. Therefore, the ecological context for modeling swan movements in response to management actions was built as a multiagent system of interacting intelligent agents that implements a queuing model representing swan migration. These agents accessed ecological knowledge about swans, their habitats, and flyway management principles from three independent expert systems. The agents were autonomous, had some sensory capability, and could respond to changing conditions. A key problem when developing ecological decision support systems is empirically determining that the recommendations provided are valid. Because Rocky Mountain trumpeter swans have been surveyed for a long period of time, I was able to compare simulated distributions provided by the system with actual field observations across 20 areas for the period 1988-2000. Applying the Matched Pairs Multivariate Permutation Test as a statistical tool was a new approach for comparing flyway distributions of waterfowl over time that seemed to work well. Based on this approach, the empirical evidence that I gathered led me to conclude that the base queuing model does accurately simulate swan distributions in the flyway. The system was insensitive to almost all model parameters tested. That remains perplexing, but might result from the base queuing model, itself, being particularly effective at representing the actual ecological diversity in the world of Rocky Mountain trumpeter swans, both spatial and temporally.

  7. Artificial intelligence based event detection in wireless sensor networks

    NARCIS (Netherlands)

    Bahrepour, Majid

    2013-01-01

    Wireless sensor networks (WSNs) are composed of large number of small, inexpensive devices, called sensor nodes, which are equipped with sensing, processing, and communication capabilities. While traditional applications of wireless sensor networks focused on periodic monitoring, the focus of more r

  8. Atomistic simulations of nanoindentation

    Directory of Open Access Journals (Sweden)

    Izabela Szlufarska

    2006-05-01

    Full Text Available Our understanding of mechanics is pushed to its limit when the functionality of devices is controlled at the nanometer scale. A fundamental understanding of nanomechanics is needed to design materials with optimum properties. Atomistic simulations can bring an important insight into nanostructure-property relations and, when combined with experiments, they become a powerful tool to move nanomechanics from basic science to the application area. Nanoindentation is a well-established technique for studying mechanical response. We review recent advances in modeling (atomistic and beyond of nanoindentation and discuss how they have contributed to our current state of knowledge.

  9. Parallel Atomistic Simulations

    Energy Technology Data Exchange (ETDEWEB)

    HEFFELFINGER,GRANT S.

    2000-01-18

    Algorithms developed to enable the use of atomistic molecular simulation methods with parallel computers are reviewed. Methods appropriate for bonded as well as non-bonded (and charged) interactions are included. While strategies for obtaining parallel molecular simulations have been developed for the full variety of atomistic simulation methods, molecular dynamics and Monte Carlo have received the most attention. Three main types of parallel molecular dynamics simulations have been developed, the replicated data decomposition, the spatial decomposition, and the force decomposition. For Monte Carlo simulations, parallel algorithms have been developed which can be divided into two categories, those which require a modified Markov chain and those which do not. Parallel algorithms developed for other simulation methods such as Gibbs ensemble Monte Carlo, grand canonical molecular dynamics, and Monte Carlo methods for protein structure determination are also reviewed and issues such as how to measure parallel efficiency, especially in the case of parallel Monte Carlo algorithms with modified Markov chains are discussed.

  10. Atomistic simulations of fracture

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, D. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering

    1997-12-31

    Embedded atom interaction potentials are used to simulate the atomistic aspects of the fracture process. Simulations are presented for the behavior of cracks in pure metals and intermetallics, near the Griffith condition. The materials considered include Fe, Cu, Ni as well as Fe, Ni, Co, and Ti aluminides. The work focuses on the comparative study of fracture behavior in the different materials. The role of the atomic relaxation at the crack tip and of lattice trapping phenomena is analyzed.

  11. Atomistic Properties of Solids

    CERN Document Server

    Sirdeshmukh, Dinker B; Subhadra, K G

    2011-01-01

    The book deals with atomistic properties of solids which are determined by the crystal structure, interatomic forces and atomic displacements influenced by the effects of temperature, stress and electric fields. The book gives equal importance to experimental details and theory. There are full chapters dedicated to the tensor nature of physical properties, mechanical properties, lattice vibrations, crystal structure determination and ferroelectricity. The other crystalline states like nano-, poly-, liquid- and quasi crystals are discussed. Several new topics like nonlinear optics and the Rietveld method are presented in the book. The book lays emphasis on the role of symmetry in crystal properties. Comprehensiveness is the strength of the book; this allows users at different levels a choice of chapters according to their requirements.

  12. New development thoughts on the bio-inspired intelligence based control for unmanned combat aerial vehicle

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Bio-inspired intelligence is in the spotlight in the field of international artificial intelligence,and unmanned combat aerial vehicle(UCAV),owing to its potential to perform dangerous,repetitive tasks in remote and hazardous,is very promising for the technological leadership of the nation and essential for improving the security of society.On the basis of introduction of bioinspired intelligence and UCAV,a series of new development thoughts on UCAV control are proposed,including artificial brain based high-level autonomous control for UCAV,swarm intelligence based cooperative control for multiple UCAVs,hy-brid swarm intelligence and Bayesian network based situation assessment under complicated combating environments, bio-inspired hardware based high-level autonomous control for UCAV,and meta-heuristic intelligence based heterogeneous cooperative control for multiple UCAVs and unmanned combat ground vehicles(UCGVs).The exact realization of the proposed new development thoughts can enhance the effectiveness of combat,while provide a series of novel breakthroughs for the intelligence,integration and advancement of future UCAV systems.

  13. Terahertz Nanoscience of Multifunctional Materials: Atomistic Exploration

    Science.gov (United States)

    2014-03-28

    Approved for Public Release; Distribution Unlimited Final report on the project "Terahertz Nanoscience of Multifunctional Materials: Atomistic...non peer-reviewed journals: Final report on the project "Terahertz Nanoscience of Multifunctional Materials: Atomistic Exploration" Report Title In... nanoscience of multifunctional materials: atomistic exploration” PI:Inna Ponomareva We have accomplished the following. 1. We have developed a set of

  14. Nano sculpt: A methodology for generating complex realistic configurations for atomistic simulations.

    Science.gov (United States)

    Prakash, A; Hummel, M; Schmauder, S; Bitzek, E

    2016-01-01

    Atomistic simulations have now become commonplace in the study of the deformation and failure of materials. Increase in computing power in recent years has made large-scale simulations with billions, or even trillions, of atoms a possibility. Most simulations to-date, however, are still performed with quasi-2D geometries or rather simplistic 3D setups. Although controlled studies on such well-defined structures are often required to obtain quantitative information from atomistic simulations, for qualitative studies focusing on e.g. the identification of mechanisms, researchers would greatly benefit from a methodology that helps realize more realistic configurations. The ideal scenario would be a one-on-one reconstruction of experimentally observed structures. To this end, we propose a new method and software tool called nano sculpt with the following features:•The method allows for easy sample generation for atomistic simulations from any arbitrarily shaped 3D enclosed volume.•The tool can be used to build atomistic samples from artificial geometries, including CAD geometries and structures obtained from simulation methods other than atomistic simulations.•The tool enables the generation of experimentally informed atomistic samples, by e.g. digitization of micrographs or usage of tomography data.

  15. Atomistic Simulations of Bicelle Mixtures

    OpenAIRE

    Jiang, Yong; Wang, Hao; Kindt, James T.

    2010-01-01

    Mixtures of long- and short-tail phosphatidylcholine lipids are known to self-assemble into a variety of aggregates combining flat bilayerlike and curved micellelike features, commonly called bicelles. Atomistic simulations of bilayer ribbons and perforated bilayers containing dimyristoylphosphatidylcholine (DMPC, di-C14 tails) and dihexanoylphosphatidylcholine (DHPC, di-C6 tails) have been carried out to investigate the partitioning of these components between flat and curved microenvironmen...

  16. Atomistic Simulations of Nanotube Fracture

    CERN Document Server

    Belytschko, T; Schatz, G; Ruoff, R S

    2002-01-01

    The fracture of carbon nanotubes is studied by atomistic simulations. The fracture behavior is found to be almost independent of the separation energy and to depend primarily on the inflection point in the interatomic potential. The rangle of fracture strians compares well with experimental results, but predicted range of fracture stresses is marketly higher than observed. Various plausible small-scale defects do not suffice to bring the failure stresses into agreement with available experimental results. As in the experiments, the fracture of carbon nanotubes is predicted to be brittle. The results show moderate dependence of fracture strength on chirality.

  17. Artificial intelligence in nanotechnology.

    Science.gov (United States)

    Sacha, G M; Varona, P

    2013-11-15

    During the last decade there has been increasing use of artificial intelligence tools in nanotechnology research. In this paper we review some of these efforts in the context of interpreting scanning probe microscopy, the study of biological nanosystems, the classification of material properties at the nanoscale, theoretical approaches and simulations in nanoscience, and generally in the design of nanodevices. Current trends and future perspectives in the development of nanocomputing hardware that can boost artificial-intelligence-based applications are also discussed. Convergence between artificial intelligence and nanotechnology can shape the path for many technological developments in the field of information sciences that will rely on new computer architectures and data representations, hybrid technologies that use biological entities and nanotechnological devices, bioengineering, neuroscience and a large variety of related disciplines.

  18. Artificial intelligence in nanotechnology

    Science.gov (United States)

    Sacha, G. M.; Varona, P.

    2013-11-01

    During the last decade there has been increasing use of artificial intelligence tools in nanotechnology research. In this paper we review some of these efforts in the context of interpreting scanning probe microscopy, the study of biological nanosystems, the classification of material properties at the nanoscale, theoretical approaches and simulations in nanoscience, and generally in the design of nanodevices. Current trends and future perspectives in the development of nanocomputing hardware that can boost artificial-intelligence-based applications are also discussed. Convergence between artificial intelligence and nanotechnology can shape the path for many technological developments in the field of information sciences that will rely on new computer architectures and data representations, hybrid technologies that use biological entities and nanotechnological devices, bioengineering, neuroscience and a large variety of related disciplines.

  19. Atomistic properties of γ uranium.

    Science.gov (United States)

    Beeler, Benjamin; Deo, Chaitanya; Baskes, Michael; Okuniewski, Maria

    2012-02-22

    The properties of the body-centered cubic γ phase of uranium (U) are calculated using atomistic simulations. First, a modified embedded-atom method interatomic potential is developed for the high temperature body-centered cubic (γ) phase of U. This phase is stable only at high temperatures and is thus relatively inaccessible to first principles calculations and room temperature experiments. Using this potential, equilibrium volume and elastic constants are calculated at 0 K and found to be in close agreement with previous first principles calculations. Further, the melting point, heat capacity, enthalpy of fusion, thermal expansion and volume change upon melting are calculated and found to be in reasonable agreement with experiment. The low temperature mechanical instability of γ U is correctly predicted and investigated as a function of pressure. The mechanical instability is suppressed at pressures greater than 17.2 GPa. The vacancy formation energy is analyzed as a function of pressure and shows a linear trend, allowing for the calculation of the extrapolated zero pressure vacancy formation energy. Finally, the self-defect formation energy is analyzed as a function of temperature. This is the first atomistic calculation of γ U properties above 0 K with interatomic potentials.

  20. Soft computing in artificial intelligence

    CERN Document Server

    Matson, Eric

    2014-01-01

    This book explores the concept of artificial intelligence based on knowledge-based algorithms. Given the current hardware and software technologies and artificial intelligence theories, we can think of how efficient to provide a solution, how best to implement a model and how successful to achieve it. This edition provides readers with the most recent progress and novel solutions in artificial intelligence. This book aims at presenting the research results and solutions of applications in relevance with artificial intelligence technologies. We propose to researchers and practitioners some methods to advance the intelligent systems and apply artificial intelligence to specific or general purpose. This book consists of 13 contributions that feature fuzzy (r, s)-minimal pre- and β-open sets, handling big coocurrence matrices, Xie-Beni-type fuzzy cluster validation, fuzzy c-regression models, combination of genetic algorithm and ant colony optimization, building expert system, fuzzy logic and neural network, ind...

  1. Atomistic stimulation of defective oxides

    CERN Document Server

    Minervini, L

    2000-01-01

    defect processes. The predominant intrinsic disorder reaction and the mechanism by which excess oxygen is accommodated are established. Furthermore, the most favourable migration mechanism and pathway for oxygen ions is predicted. Chapters 7 and 8 investigate pyrochlore oxides. These materials are candidates for solid oxide fuel cell components and as actinide host phases. Such applications require a detailed understanding of the defect processes. The defect energies, displayed as contour maps, are able to account for structure stability and, given an appropriate partial charge potential model, to accurately determine the oxygen positional parameter. In particular, the dependence of the positional parameter on intrinsic disorder is predicted. It is demonstrated, by radiation damage experiments, that these results are able to predict the radiation performance of pyrochlore oxides. Atomistic simulation calculations based on energy minimization techniques and classical pair potentials are used to study several i...

  2. A Swarm Intelligence Based Model for Mobile Cloud Computing

    Directory of Open Access Journals (Sweden)

    Ahmed S. Salama

    2015-01-01

    Full Text Available Mobile Computing (MC provides multi services and a lot of advantages for millions of users across the world over the internet. Millions of business customers have leveraged cloud computing services through mobile devices to get what is called Mobile Cloud Computing (MCC. MCC aims at using cloud computing techniques for storage and processing of data on mobile devices, thereby reducing their limitations. This paper proposes architecture for a Swarm Intelligence Based Mobile Cloud Computing Model (SIBMCCM. A model that uses a proposed Parallel Particle Swarm Optimization (PPSO algorithm to enhance the access time for the mobile cloud computing services which support different E Commerce models and to better secure the communication through the mobile cloud and the mobile commerce transactions.

  3. Towards an intelligence based conceptual framework for e-maintenance

    CERN Document Server

    Mouzoune, Abdessamad

    2012-01-01

    Since the time when concept of e-maintenance was introduced, most of the works insisted on the relevance of the underlying Information and Communication Technologies infrastructure. Through a review of current e-maintenance conceptual approaches and realizations, this paper aims to reconsider the predominance of ICT within e-maintenance projects and literature. The review brings to light the importance of intelligence as a fundamental dimension of e-maintenance that is to be led in a holistic predefined manner rather than isolated efforts within ICT driven approaches. As a contribution towards an intelligence based e-maintenance conceptual framework, a proposal is outlined in this paper to model e-maintenance system as an intelligent system. The proposed frame is based on CogAff architecture for intelligent agents. Within the proposed frame, more importance was reserved to the environment that the system is to be continuously aware of: Plant Environment, Internal and External Enterprise Environment and Human ...

  4. Design New Intelligent-Base Chattering Free Nonlinear Control of Spherical Motor

    Directory of Open Access Journals (Sweden)

    Mohammad Ali Tayebi

    2014-09-01

    Full Text Available The main four objectives to design controllers are: stability, robust, minimum error and reliability. Linear PID controller is model-free controller and this controller is not reliable. One of the robust nonlinear controller to control of nonlinear systems is sliding mode controller (SMC. Sliding mode controller (SMC is robust conventional nonlinear controller in a partly uncertain dynamic system’s parameters. Sliding mode controller is divided into two main sub parts: discontinues controller〖(τ〗_dis and equivalent controller〖(τ〗_eq. Discontinues controller is used to design suitable tracking performance based on very fast switching. Fast switching or discontinuous part have essential role to achieve to good trajectory following, but it is caused system instability and chattering phenomenon. Chattering phenomenon is one of the main challenges in conventional sliding mode controller and it can causes some important mechanical problems such as saturation and heats the mechanical parts of robot manipulators or drivers. To reduce or eliminate the chattering two methods are used in many researches which these methods are: boundary layer saturation method and artificial intelligence based method. In this research fuzzy switching methodology is used to eliminate the chattering in presence of uncertainty to increase the robust of this controller with application to three dimensions of spherical motor.

  5. Atomistic simulations of dislocation processes in copper

    DEFF Research Database (Denmark)

    Vegge, T.; Jacobsen, K.W.

    2002-01-01

    We discuss atomistic simulations of dislocation processes in copper based on effective medium theory interatomic potentials. Results on screw dislocation structures and processes are reviewed with particular focus on point defect mobilities and processes involving cross slip. For example, the sta......We discuss atomistic simulations of dislocation processes in copper based on effective medium theory interatomic potentials. Results on screw dislocation structures and processes are reviewed with particular focus on point defect mobilities and processes involving cross slip. For example...

  6. Artificial Intelligence in Civil Engineering

    Directory of Open Access Journals (Sweden)

    Pengzhen Lu

    2012-01-01

    Full Text Available Artificial intelligence is a branch of computer science, involved in the research, design, and application of intelligent computer. Traditional methods for modeling and optimizing complex structure systems require huge amounts of computing resources, and artificial-intelligence-based solutions can often provide valuable alternatives for efficiently solving problems in the civil engineering. This paper summarizes recently developed methods and theories in the developing direction for applications of artificial intelligence in civil engineering, including evolutionary computation, neural networks, fuzzy systems, expert system, reasoning, classification, and learning, as well as others like chaos theory, cuckoo search, firefly algorithm, knowledge-based engineering, and simulated annealing. The main research trends are also pointed out in the end. The paper provides an overview of the advances of artificial intelligence applied in civil engineering.

  7. Atomistic simulations of bicelle mixtures.

    Science.gov (United States)

    Jiang, Yong; Wang, Hao; Kindt, James T

    2010-06-16

    Mixtures of long- and short-tail phosphatidylcholine lipids are known to self-assemble into a variety of aggregates combining flat bilayerlike and curved micellelike features, commonly called bicelles. Atomistic simulations of bilayer ribbons and perforated bilayers containing dimyristoylphosphatidylcholine (DMPC, di-C(14) tails) and dihexanoylphosphatidylcholine (DHPC, di-C(6) tails) have been carried out to investigate the partitioning of these components between flat and curved microenvironments and the stabilization of the bilayer edge by DHPC. To approach equilibrium partitioning of lipids on an achievable simulation timescale, configuration-bias Monte Carlo mutation moves were used to allow individual lipids to change tail length within a semigrand-canonical ensemble. Since acceptance probabilities for direct transitions between DMPC and DHPC were negligible, a third component with intermediate tail length (didecanoylphosphatidylcholine, di-C(10) tails) was included at a low concentration to serve as an intermediate for transitions between DMPC and DHPC. Strong enrichment of DHPC is seen at ribbon and pore edges, with an excess linear density of approximately 3 nm(-1). The simulation model yields estimates for the onset of edge stability with increasing bilayer DHPC content between 5% and 15% DHPC at 300 K and between 7% and 17% DHPC at 323 K, higher than experimental estimates. Local structure and composition at points of close contact between pores suggest a possible mechanism for effective attractions between pores, providing a rationalization for the tendency of bicelle mixtures to aggregate into perforated vesicles and perforated sheets.

  8. An artificial intelligence-based structural health monitoring system for aging aircraft

    Science.gov (United States)

    Grady, Joseph E.; Tang, Stanley S.; Chen, K. L.

    1993-01-01

    To reduce operating expenses, airlines are now using the existing fleets of commercial aircraft well beyond their originally anticipated service lives. The repair and maintenance of these 'aging aircraft' has therefore become a critical safety issue, both to the airlines and the Federal Aviation Administration. This paper presents the results of an innovative research program to develop a structural monitoring system that will be used to evaluate the integrity of in-service aerospace structural components. Currently in the final phase of its development, this monitoring system will indicate when repair or maintenance of a damaged structural component is necessary.

  9. ARTIFICIAL INTELLIGENCE-BASED ESTIMATION OF MERCURY SPECIATION IN COMBUSTION FLUE GASES. (R827649)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  10. Advances in Intelligent Modelling and Simulation Artificial Intelligence-Based Models and Techniques in Scalable Computing

    CERN Document Server

    Khan, Samee; Burczy´nski, Tadeusz

    2012-01-01

    One of the most challenging issues in today’s large-scale computational modeling and design is to effectively manage the complex distributed environments, such as computational clouds, grids, ad hoc, and P2P networks operating under  various  types of users with evolving relationships fraught with  uncertainties. In this context, the IT resources and services usually belong to different owners (institutions, enterprises, or individuals) and are managed by different administrators. Moreover, uncertainties are presented to the system at hand in various forms of information that are incomplete, imprecise, fragmentary, or overloading, which hinders in the full and precise resolve of the evaluation criteria, subsequencing and selection, and the assignment scores. Intelligent scalable systems enable the flexible routing and charging, advanced user interactions and the aggregation and sharing of geographically-distributed resources in modern large-scale systems.   This book presents new ideas, theories, models...

  11. Design Novel Model Reference Artificial Intelligence Based Methodology to Optimized Fuel Ratio in IC Engine

    Directory of Open Access Journals (Sweden)

    FarzinPiltan

    2013-08-01

    Full Text Available In this research, model reference fuzzy based control is presented as robust controls for IC engine. The objective of the study is to design controls for IC engines without the knowledge of the boundary of uncertainties and dynamic information by using fuzzy model reference PD plus mass of air while improve the robustness of the PD plus mass of air control. A PD plus mass of air provides for eliminate the mass of air and ultimate accuracy in the presence of the bounded disturbance/uncertainties, although this methods also causes some oscillation. The fuzzy PD plus mass of air is proposed as a solution to the problems crated by unstability. This method has a good performance in presence of uncertainty.

  12. An Artificial Intelligence-Based Approach for Arbitration in Food Chains

    OpenAIRE

    Thomopoulos, Rallou; Bourguet, Jean-Rémi; Abécassis, Joël

    2011-01-01

    International audience; Food chain analysis is a highly complex procedure since it relies on numerous criteria of various types: environmental, economical, functional, sanitary, etc. Quality objectives imply different stakeholders, technicians, managers, professional organizations, end-users, public collectivities, etc. Since the goals of the implied stakeholders may be divergent, decision-making raises arbitration issues. Arbitration can be done through a compromise - a solution that satisfi...

  13. Use of Hypermedia as a User Interface for an Artificial Intelligence- Based Problem Solver

    Science.gov (United States)

    1989-12-01

    these editors can be linked together to form a hypermedia network [ Beeman and others, 1987:7 1]. Note(ards. This application was developed at Xerox... Beeman , William 0. and others. Hypertext and Pluralism: From Lineal to Non-lineal Thinking. Hypertext 󈨛, Department of Computer Science, University of...34 Final Report, 30 Nov 1982. AD-A133103 Teknowledge, Inc. S.1 Reference Manual. September 1987. Thomas, Donald L. and Jeffrey D. Clay. "Computer

  14. Felicity Conditions for Human Skill Acquisition: Validating an AI (Artificial Intelligence)-Based Theory.

    Science.gov (United States)

    1983-11-01

    bugs have the same cause? Most importantly, how is the educaional process involved in the development of bugs? This research was launched partly in...arithmetic. Philadelphia, PA : John C. Winston, "* .1930. lunderson, C.V. Cognitive bugs and arithmetic skills: Their diagnosis and remediation (interim tech...Psychology of Learning and Motivation, Vol. 16, New York: Academic Press, in press. Currently available as Tech. Rep. ONR-6, Pittsburgh, PA : Carnegie

  15. Atomistic modeling of dropwise condensation

    Science.gov (United States)

    Sikarwar, B. S.; Singh, P. L.; Muralidhar, K.; Khandekar, S.

    2016-05-01

    The basic aim of the atomistic modeling of condensation of water is to determine the size of the stable cluster and connect phenomena occurring at atomic scale to the macroscale. In this paper, a population balance model is described in terms of the rate equations to obtain the number density distribution of the resulting clusters. The residence time is taken to be large enough so that sufficient time is available for all the adatoms existing in vapor-phase to loose their latent heat and get condensed. The simulation assumes clusters of a given size to be formed from clusters of smaller sizes, but not by the disintegration of the larger clusters. The largest stable cluster size in the number density distribution is taken to be representative of the minimum drop radius formed in a dropwise condensation process. A numerical confirmation of this result against predictions based on a thermodynamic model has been obtained. Results show that the number density distribution is sensitive to the surface diffusion coefficient and the rate of vapor flux impinging on the substrate. The minimum drop radius increases with the diffusion coefficient and the impinging vapor flux; however, the dependence is weak. The minimum drop radius predicted from thermodynamic considerations matches the prediction of the cluster model, though the former does not take into account the effect of the surface properties on the nucleation phenomena. For a chemically passive surface, the diffusion coefficient and the residence time are dependent on the surface texture via the coefficient of friction. Thus, physical texturing provides a means of changing, within limits, the minimum drop radius. The study reveals that surface texturing at the scale of the minimum drop radius does not provide controllability of the macro-scale dropwise condensation at large timescales when a dynamic steady-state is reached.

  16. Atomistic computer simulations a practical guide

    CERN Document Server

    Brazdova, Veronika

    2013-01-01

    Many books explain the theory of atomistic computer simulations; this book teaches you how to run them This introductory ""how to"" title enables readers to understand, plan, run, and analyze their own independent atomistic simulations, and decide which method to use and which questions to ask in their research project. It is written in a clear and precise language, focusing on a thorough understanding of the concepts behind the equations and how these are used in the simulations. As a result, readers will learn how to design the computational model and which parameters o

  17. Atomistic Processes of Catalyst Degradation

    Energy Technology Data Exchange (ETDEWEB)

    None

    2004-11-27

    The purpose of this cooperative research and development agreement (CRADA) between Sasol North America, Inc., and the oak Ridge National Laboratory (ORNL) was to improve the stability of alumina-based industrial catalysts through the combination of aberration-corrected scanning transmission electron microscopy (STEM) at ORNL and innovative sample preparation techniques at Sasol. Outstanding progress has been made in task 1, 'Atomistic processes of La stabilization'. STEM investigations provided structural information with single-atom precision, showing the lattice location of La dopant atoms, thus enabling first-principles calculations of binding energies, which were performed in collaboration with Vanderbilt University. The stabilization mechanism turns out to be entirely due to a particularly strong binding energy of the La tom to the {gamma}-alumina surface. The large size of the La atom precludes incorporation of La into the bulk alumina and also strains the surface, thus preventing any clustering of La atoms. Thus highly disperse distribution is achieved and confirmed by STEM images. la also affects relative stability of the exposed surfaces of {gamma}-alumina, making the 100 surface more stable for the doped case, unlike the 110 surface for pure {gamma}-alumina. From the first-principles calculations, they can estimate the increase in transition temperature for the 3% loading of La used commercially, and it is in excellent agreement with experiment. This task was further pursued aiming to generate useable recommendations for the optimization of the preparation techniques for La-doped aluminas. The effort was primarily concentrated on the connection between the boehmitre-{gamma}-Al{sub 2}O{sub 3} phase transition (i.e. catalyst preparation) and the resulting dispersion of La on the {gamma}-Al{sub 2}O{sub 3} surface. It was determined that the La distribution on boehmite was non-uniform and different from that on the {gamma}-Al{sub 2}O{sub 3} and thus

  18. A Novel Robot System Integrating Biological and Mechanical Intelligence Based on Dissociated Neural Network-Controlled Closed-Loop Environment

    Science.gov (United States)

    Wang, Yuechao; Li, Hongyi; Zheng, Xiongfei

    2016-01-01

    We propose the architecture of a novel robot system merging biological and artificial intelligence based on a neural controller connected to an external agent. We initially built a framework that connected the dissociated neural network to a mobile robot system to implement a realistic vehicle. The mobile robot system characterized by a camera and two-wheeled robot was designed to execute the target-searching task. We modified a software architecture and developed a home-made stimulation generator to build a bi-directional connection between the biological and the artificial components via simple binomial coding/decoding schemes. In this paper, we utilized a specific hierarchical dissociated neural network for the first time as the neural controller. Based on our work, neural cultures were successfully employed to control an artificial agent resulting in high performance. Surprisingly, under the tetanus stimulus training, the robot performed better and better with the increasement of training cycle because of the short-term plasticity of neural network (a kind of reinforced learning). Comparing to the work previously reported, we adopted an effective experimental proposal (i.e. increasing the training cycle) to make sure of the occurrence of the short-term plasticity, and preliminarily demonstrated that the improvement of the robot’s performance could be caused independently by the plasticity development of dissociated neural network. This new framework may provide some possible solutions for the learning abilities of intelligent robots by the engineering application of the plasticity processing of neural networks, also for the development of theoretical inspiration for the next generation neuro-prostheses on the basis of the bi-directional exchange of information within the hierarchical neural networks. PMID:27806074

  19. Intelligence-based anti-doping from an equine biological passport.

    Science.gov (United States)

    Cawley, Adam T; Keledjian, John

    2017-03-07

    The move towards personalised medicine derived from individually-focused clinical chemistry measurements has been translated by the human anti-doping movement over the past decade into developing the athlete biological passport (ABP). There is considerable potential for animal sports to adapt this model to facilitate an intelligence-based anti-doping system.

  20. Effectiveness of Multiple Intelligence Based Teaching (MIBT) in Teaching Mathematics for Primary School Students

    Science.gov (United States)

    Xavier, P.; Annaraja, P.

    2007-01-01

    Multiple Intelligence Based Teaching (MIBT) applies the multiple intelligence theory in the process of teaching and learning. MIBT explores and develops the intelligence of the students. Also, it teaches the content in a multiple way to the students. The objective of the present study is to find out the effectiveness of multiple intelligence based…

  1. Atomistic deformation mechanisms in twinned copper nanospheres.

    Science.gov (United States)

    Bian, Jianjun; Niu, Xinrui; Zhang, Hao; Wang, Gangfeng

    2014-01-01

    In the present study, we perform molecular dynamic simulations to investigate the compression response and atomistic deformation mechanisms of twinned nanospheres. The relationship between load and compression depth is calculated for various twin spacing and loading directions. Then, the overall elastic properties and the underlying plastic deformation mechanisms are illuminated. Twin boundaries (TBs) act as obstacles to dislocation motion and lead to strengthening. As the loading direction varies, the plastic deformation transfers from dislocations intersecting with TBs, slipping parallel to TBs, and then to being restrained by TBs. The strengthening of TBs depends strongly on the twin spacing.

  2. Atomistic Mechanisms of Fatigue in Nanocrystalline Metals

    Science.gov (United States)

    Farkas, D.; Willemann, M.; Hyde, B.

    2005-04-01

    We investigate the mechanisms of fatigue behavior in nanocrystalline metals at the atomic scale using empirical force laws and molecular level simulations. A combination of molecular statics and molecular dynamics was used to deal with the time scale limitations of molecular dynamics. We show that the main atomistic mechanism of fatigue crack propagation in these materials is the formation of nanovoids ahead of the main crack. The results obtained for crack advance as a function of stress intensity amplitude are consistent with experimental studies and a Paris law exponent of about 2.

  3. Bridging Atomistic/Continuum Scales in Solids with Moving Dislocations

    Institute of Scientific and Technical Information of China (English)

    TANG Shao-Qiang; LIU Wing K.; KARPOV Eduard G.; HOU Thomas Y.

    2007-01-01

    @@ We propose a multiscale method for simulating solids with moving dislocations. Away from atomistic subdomains where the atomistic dynamics are fully resolved, a dislocation is represented by a localized jump profile, superposed on a defect-free field. We assign a thin relay zone around an atomistic subdomain to detect the dislocation profile and its propagation speed at a selected relay time. The detection technique utilizes a lattice time history integral treatment. After the relay, an atomistic computation is performed only for the defect-free field. The method allows one to effectively absorb the fine scale fluctuations and the dynamic dislocations at the interface between the atomistic and continuum domains. In the surrounding region, a coarse grid computation is adequate.

  4. Atomistic simulations of nanoscale electrokinetic transport

    Science.gov (United States)

    Liu, Jin; Wang, Moran; Chen, Shiyi; Robbins, Mark

    2011-11-01

    An efficient and accurate algorithm for atomistic simulations of nanoscale electrokinetic transport will be described. The long-range interactions between charged molecules are treated using the Particle-Particle Particle-Mesh method and the Poisson equation for the electric potential is solved using an efficient multi-grid method in physical space. Using this method, we investigate two important applications in electrokinetic transport: electroosmotic flow in rough channels and electowetting on dielectric (EWOD). Simulations of electroosmotic and pressure driven flow in exactly the same geometries show that surface roughness has a much more pronounced effect on electroosmotic flow. Analysis of local quantities shows that this is because the driving force in electroosmotic flow is localized near the wall where the charge density is high. In atomistic simulations of EWOD, we find the contact angle follows the continuum theory at low voltages and always saturates at high voltages. Based on our results, a new mechanism for saturation is identified and possible techniques for controlling saturation are proposed. This work is supported by the National Science Foundation under Grant No. CMMI 0709187.

  5. Atomistic Monte Carlo Simulation of Lipid Membranes

    Directory of Open Access Journals (Sweden)

    Daniel Wüstner

    2014-01-01

    Full Text Available Biological membranes are complex assemblies of many different molecules of which analysis demands a variety of experimental and computational approaches. In this article, we explain challenges and advantages of atomistic Monte Carlo (MC simulation of lipid membranes. We provide an introduction into the various move sets that are implemented in current MC methods for efficient conformational sampling of lipids and other molecules. In the second part, we demonstrate for a concrete example, how an atomistic local-move set can be implemented for MC simulations of phospholipid monomers and bilayer patches. We use our recently devised chain breakage/closure (CBC local move set in the bond-/torsion angle space with the constant-bond-length approximation (CBLA for the phospholipid dipalmitoylphosphatidylcholine (DPPC. We demonstrate rapid conformational equilibration for a single DPPC molecule, as assessed by calculation of molecular energies and entropies. We also show transition from a crystalline-like to a fluid DPPC bilayer by the CBC local-move MC method, as indicated by the electron density profile, head group orientation, area per lipid, and whole-lipid displacements. We discuss the potential of local-move MC methods in combination with molecular dynamics simulations, for example, for studying multi-component lipid membranes containing cholesterol.

  6. Artificial intelligence

    CERN Document Server

    Hunt, Earl B

    1975-01-01

    Artificial Intelligence provides information pertinent to the fundamental aspects of artificial intelligence. This book presents the basic mathematical and computational approaches to problems in the artificial intelligence field.Organized into four parts encompassing 16 chapters, this book begins with an overview of the various fields of artificial intelligence. This text then attempts to connect artificial intelligence problems to some of the notions of computability and abstract computing devices. Other chapters consider the general notion of computability, with focus on the interaction bet

  7. Scalable Atomistic Simulation Algorithms for Materials Research

    Directory of Open Access Journals (Sweden)

    Aiichiro Nakano

    2002-01-01

    Full Text Available A suite of scalable atomistic simulation programs has been developed for materials research based on space-time multiresolution algorithms. Design and analysis of parallel algorithms are presented for molecular dynamics (MD simulations and quantum-mechanical (QM calculations based on the density functional theory. Performance tests have been carried out on 1,088-processor Cray T3E and 1,280-processor IBM SP3 computers. The linear-scaling algorithms have enabled 6.44-billion-atom MD and 111,000-atom QM calculations on 1,024 SP3 processors with parallel efficiency well over 90%. production-quality programs also feature wavelet-based computational-space decomposition for adaptive load balancing, spacefilling-curve-based adaptive data compression with user-defined error bound for scalable I/O, and octree-based fast visibility culling for immersive and interactive visualization of massive simulation data.

  8. Atomistic Monte Carlo simulation of lipid membranes

    DEFF Research Database (Denmark)

    Wüstner, Daniel; Sklenar, Heinz

    2014-01-01

    Biological membranes are complex assemblies of many different molecules of which analysis demands a variety of experimental and computational approaches. In this article, we explain challenges and advantages of atomistic Monte Carlo (MC) simulation of lipid membranes. We provide an introduction......, as assessed by calculation of molecular energies and entropies. We also show transition from a crystalline-like to a fluid DPPC bilayer by the CBC local-move MC method, as indicated by the electron density profile, head group orientation, area per lipid, and whole-lipid displacements. We discuss the potential...... of local-move MC methods in combination with molecular dynamics simulations, for example, for studying multi-component lipid membranes containing cholesterol....

  9. Tunnel-coupled quantum dots: Atomistic Theory of Quantum Dot Molecules and Arrays

    Science.gov (United States)

    Bryant, Garnett W.; Aizpurua, J.; Jaskolski, W.; Zielinski, Michal

    2003-03-01

    Quantum dots are studied as artificial atoms for building novel artificial solids, as nanodevices in nanoelectronics, and as bio/nanohybrids. We present an atomistic tight-binding theory of coupled CdS nanocrystals and vertically and laterally coupled InAs self-assembled dots. Electron states of coupled dots follow the analogy of coupled dots as artificial molecules. Symmetric/antisymmetric pairs are formed with strongest coupling between states with high density at interdot interfaces. Complex coupling of hole states, with significant departures from the artificial molecule analogy, occurs because the coupling is determined by the hole envelope function and the hole atomic state. Some hole states couple to form symmetric/antisymmetric pairs. Other hole states couple through additional intermediate states to form two strongly split symmetric states and an antisymmetric state insensitive to coupling. These coupling effects lead to level reordering, changes in state symmetry, conversion of dark states to bright states and vice versa, and tailored polarization dependence.

  10. Artificial Intelligence.

    Science.gov (United States)

    Waltz, David L.

    1982-01-01

    Describes kinds of results achieved by computer programs in artificial intelligence. Topics discussed include heuristic searches, artificial intelligence/psychology, planning program, backward chaining, learning (focusing on Winograd's blocks to explore learning strategies), concept learning, constraint propagation, language understanding…

  11. Health Data Entanglement and artificial intelligence-based analysis: a brand new methodology to improve the effectiveness of healthcare services.

    Science.gov (United States)

    Capone, A; Cicchetti, A; Mennini, F S; Marcellusi, A; Baio, G; Favato, G

    2016-01-01

    Healthcare expenses will be the most relevant policy issue for most governments in the EU and in the USA. This expenditure can be associated with two major key categories: demographic and economic drivers. Factors driving healthcare expenditure were rarely recognised, measured and comprehended. An improvement of health data generation and analysis is mandatory, and in order to tackle healthcare spending growth, it may be useful to design and implement an effective, advanced system to generate and analyse these data. A methodological approach relied upon the Health Data Entanglement (HDE) can be a suitable option. By definition, in the HDE a large amount of data sets having several sources are functionally interconnected and computed through learning machines that generate patterns of highly probable future health conditions of a population. Entanglement concept is borrowed from quantum physics and means that multiple particles (information) are linked together in a way such that the measurement of one particle's quantum state (individual health conditions and related economic requirements) determines the possible quantum states of other particles (population health forecasts to predict their impact). The value created by the HDE is based on the combined evaluation of clinical, economic and social effects generated by health interventions. To predict the future health conditions of a population, analyses of data are performed using self-learning AI, in which sequential decisions are based on Bayesian algorithmic probabilities. HDE and AI-based analysis can be adopted to improve the effectiveness of the health governance system in ways that also lead to better quality of care.

  12. Atomistic Mechanisms for Viscoelastic Damping in Inorganic Solids

    Science.gov (United States)

    Ranganathan, Raghavan

    Viscoelasticity, a ubiquitous material property, can be tuned to engineer a wide range of fascinating applications such as mechanical dampers, artificial tissues, functional foams and optoelectronics, among others. Traditionally, soft matter such as polymers and polymer composites have been used extensively for viscoelastic damping applications, owing to the inherent viscous nature of interactions between polymer chains. Although this leads to good damping characteristics, the stiffness in these materials is low, which in turn leads to limitations. In this context, hard inorganic materials and composites are promising candidates for enhanced damping, owing to their large stiffness and, in some cases large loss modulus. Viscoelasticity in these materials has been relatively unexplored and atomistic mechanisms responsible for damping are not apparent. Therefore, the overarching goal of this work is to understand mechanisms for viscoelastic damping in various classes of inorganic composites and alloys at an atomistic level from molecular dynamics simulations. We show that oscillatory shear deformation serves as a powerful probe to explain mechanisms for exceptional damping in hitherto unexplored systems. The first class of inorganic materials consists of crystalline phases of a stiff inclusion in a soft matrix. The two crystals within the composite, namely the soft and a stiff phase, individually show a highly elastic behavior and a very small loss modulus. On the other hand, a composite with the two phases is seen to exhibit damping that is about 20 times larger than predicted theoretical bounds. The primary reason for the damping is due to large anharmonicity in phonon-phonon coupling, resulting from the composite microstructure. A concomitant effect is the distribution of shear strain, which is observed to be highly inhomogeneous and mostly concentrated in the soft phase. Interestingly, the shear frequency at which the damping is greatest is observed to scale with

  13. NiTi superelasticity via atomistic simulations

    Science.gov (United States)

    Chowdhury, Piyas; Ren, Guowu; Sehitoglu, Huseyin

    2015-12-01

    The NiTi shape memory alloys (SMAs) are promising candidates for the next-generation multifunctional materials. These materials are superelastic i.e. they can fully recover their original shape even after fairly large inelastic deformations once the mechanical forces are removed. The superelasticity reportedly stems from atomic scale crystal transformations. However, very few computer simulations have emerged, elucidating the transformation mechanisms at the discrete lattice level, which underlie the extraordinary strain recoverability. Here, we conduct breakthrough molecular dynamics modelling on the superelastic behaviour of the NiTi single crystals, and unravel the atomistic genesis thereof. The deformation recovery is clearly traced to the reversible transformation between austenite and martensite crystals through simulations. We examine the mechanistic origin of the tension-compression asymmetries and the effects of pressure/temperature/strain rate variation isolatedly. Hence, this work essentially brings a new dimension to probing the NiTi performance based on the mesoscale physics under more complicated thermo-mechanical loading scenarios.

  14. Strain Functionals for Characterizing Atomistic Geometries

    Science.gov (United States)

    Kober, Edward; Rudin, Sven

    The development of a set of strain tensor functionals that are capable of characterizing arbitrarily ordered atomistic structures is described. This approach defines a Gaussian-weighted neighborhood around each atom and characterizes that local geometry in terms of n-th order strain tensors, which are equivalent to the moments of the neighborhood. Fourth order expansions can distinguish the cubic structures (and deformations thereof), but sixth order expansions are required to fully characterize hexagonal structures. Other methods used to characterize atomic structures, such as the Steinhardt parameters or the centrosymmetry metric, can be derived from this more general approach. These functions are continuous and smooth and much less sensitive to thermal fluctuations than other descriptors based on discrete neighborhoods. They allow material phases, deformations, and a large number of defect structures to be readily identified and classified. Applications to the analysis of shock-loaded samples of Cu, Ta and Ti will be presented. This strain functional basis can also then be used for developing interatomic potential functions, and an initial application to Cu will be presented.

  15. Stress in titania nanoparticles: An atomistic study

    Energy Technology Data Exchange (ETDEWEB)

    Darkins, Robert; Sushko, Maria L.; Liu, Jun; Duffy, Dorothy M.

    2014-04-24

    Stress engineering is becoming an increasingly important method for controlling electronic, optical, and magnetic properties of nanostructures, although the concept of stress is poorly defined at the nanoscale. We outline a methodology for computing bulk and surface stress in nanoparticles using atomistic simulation. The method is applicable to ionic and non- ionic materials alike and may be extended to other nanostructures. We apply it to spherical anatase nanoparticles ranging from 2 to 6 nm in diameter and obtain a surface stress of 0.89 N/m, in agreement with experimental measurements. Based on the extent that stress inhomogeneities at the surface are transmitted into the bulk, two characteristic length-scales are identified: below 3 nm bulk and surface regions cannot be defined and the available analytic theories for stress are not applicable, and above about 5 nm the stress becomes well-described by the theoretical Young-Laplace equation. The effect of a net surface charge on the bulk stress is also investigated. It is found that moderate surface charges can induce significant bulk stresses, on the order of 100 MPa, in nanoparticles within this size range.

  16. Atomistic simulation of Voronoi-based coated nanoporous metals

    Science.gov (United States)

    Onur Yildiz, Yunus; Kirca, Mesut

    2017-02-01

    In this study, a new method developed for the generation of periodic atomistic models of coated and uncoated nanoporous metals (NPMs) is presented by examining the thermodynamic stability of coated nanoporous structures. The proposed method is mainly based on the Voronoi tessellation technique, which provides the ability to control cross-sectional dimension and slenderness of ligaments as well as the thickness of coating. By the utilization of the method, molecular dynamic (MD) simulations of randomly structured NPMs with coating can be performed efficiently in order to investigate their physical characteristics. In this context, for the purpose of demonstrating the functionality of the method, sample atomistic models of Au/Pt NPMs are generated and the effects of coating and porosity on the thermodynamic stability are investigated by using MD simulations. In addition to that, uniaxial tensile loading simulations are performed via MD technique to validate the nanoporous models by comparing the effective Young’s modulus values with the results from literature. Based on the results, while it is demonstrated that coating the nanoporous structures slightly decreases the structural stability causing atomistic configurational changes, it is also shown that the stability of the atomistic models is higher at lower porosities. Furthermore, adaptive common neighbour analysis is also performed to identify the stabilized atomistic structure after the coating process, which provides direct foresights for the mechanical behaviour of coated nanoporous structures.

  17. A robust, coupled approach for atomistic-continuum simulation.

    Energy Technology Data Exchange (ETDEWEB)

    Aubry, Sylvie; Webb, Edmund Blackburn, III (Sandia National Laboratories, Albuquerque, NM); Wagner, Gregory John; Klein, Patrick A.; Jones, Reese E.; Zimmerman, Jonathan A.; Bammann, Douglas J.; Hoyt, Jeffrey John (Sandia National Laboratories, Albuquerque, NM); Kimmer, Christopher J.

    2004-09-01

    This report is a collection of documents written by the group members of the Engineering Sciences Research Foundation (ESRF), Laboratory Directed Research and Development (LDRD) project titled 'A Robust, Coupled Approach to Atomistic-Continuum Simulation'. Presented in this document is the development of a formulation for performing quasistatic, coupled, atomistic-continuum simulation that includes cross terms in the equilibrium equations that arise due to kinematic coupling and corrections used for the calculation of system potential energy to account for continuum elements that overlap regions containing atomic bonds, evaluations of thermo-mechanical continuum quantities calculated within atomistic simulations including measures of stress, temperature and heat flux, calculation used to determine the appropriate spatial and time averaging necessary to enable these atomistically-defined expressions to have the same physical meaning as their continuum counterparts, and a formulation to quantify a continuum 'temperature field', the first step towards constructing a coupled atomistic-continuum approach capable of finite temperature and dynamic analyses.

  18. Hybrid continuum-atomistic approach to model electrokinetics in nanofluidics

    Energy Technology Data Exchange (ETDEWEB)

    Amani, Ehsan, E-mail: eamani@aut.ac.ir; Movahed, Saeid, E-mail: smovahed@aut.ac.ir

    2016-06-07

    In this study, for the first time, a hybrid continuum-atomistic based model is proposed for electrokinetics, electroosmosis and electrophoresis, through nanochannels. Although continuum based methods are accurate enough to model fluid flow and electric potential in nanofluidics (in dimensions larger than 4 nm), ionic concentration is too low in nanochannels for the continuum assumption to be valid. On the other hand, the non-continuum based approaches are too time-consuming and therefore is limited to simple geometries, in practice. Here, to propose an efficient hybrid continuum-atomistic method of modelling the electrokinetics in nanochannels; the fluid flow and electric potential are computed based on continuum hypothesis coupled with an atomistic Lagrangian approach for the ionic transport. The results of the model are compared to and validated by the results of the molecular dynamics technique for a couple of case studies. Then, the influences of bulk ionic concentration, external electric field, size of nanochannel, and surface electric charge on the electrokinetic flow and ionic mass transfer are investigated, carefully. The hybrid continuum-atomistic method is a promising approach to model more complicated geometries and investigate more details of the electrokinetics in nanofluidics. - Highlights: • A hybrid continuum-atomistic model is proposed for electrokinetics in nanochannels. • The model is validated by molecular dynamics. • This is a promising approach to model more complicated geometries and physics.

  19. Atomistic Modelling of Si Nanoparticles Synthesis

    Directory of Open Access Journals (Sweden)

    Giovanni Barcaro

    2017-02-01

    Full Text Available Silicon remains the most important material for electronic technology. Presently, some efforts are focused on the use of Si nanoparticles—not only for saving material, but also for improving the efficiency of optical and electronic devices, for instance, in the case of solar cells coated with a film of Si nanoparticles. The synthesis by a bottom-up approach based on condensation from low temperature plasma is a promising technique for the massive production of such nanoparticles, but the knowledge of the basic processes occurring at the atomistic level is still very limited. In this perspective, numerical simulations can provide fundamental information of the nucleation and growth mechanisms ruling the bottom-up formation of Si nanoclusters. We propose to model the low temperature plasma by classical molecular dynamics by using the reactive force field (ReaxFF proposed by van Duin, which can properly describe bond forming and breaking. In our approach, first-principles quantum calculations are used on a set of small Si clusters in order to collect all the necessary energetic and structural information to optimize the parameters of the reactive force-field for the present application. We describe in detail the procedure used for the determination of the force field and the following molecular dynamics simulations of model systems of Si gas at temperatures in the range 2000–3000 K. The results of the dynamics provide valuable information on nucleation rate, nanoparticle size distribution, and growth rate that are the basic quantities for developing a following mesoscale model.

  20. An object oriented Python interface for atomistic simulations

    Science.gov (United States)

    Hynninen, T.; Himanen, L.; Parkkinen, V.; Musso, T.; Corander, J.; Foster, A. S.

    2016-01-01

    Programmable simulation environments allow one to monitor and control calculations efficiently and automatically before, during, and after runtime. Environments directly accessible in a programming environment can be interfaced with powerful external analysis tools and extensions to enhance the functionality of the core program, and by incorporating a flexible object based structure, the environments make building and analysing computational setups intuitive. In this work, we present a classical atomistic force field with an interface written in Python language. The program is an extension for an existing object based atomistic simulation environment.

  1. Artificial blood

    Directory of Open Access Journals (Sweden)

    Sarkar Suman

    2008-01-01

    Full Text Available Artificial blood is a product made to act as a substitute for red blood cells. While true blood serves many different functions, artificial blood is designed for the sole purpose of transporting oxygen and carbon dioxide throughout the body. Depending on the type of artificial blood, it can be produced in different ways using synthetic production, chemical isolation, or recombinant biochemical technology. Development of the first blood substitutes dates back to the early 1600s, and the search for the ideal blood substitute continues. Various manufacturers have products in clinical trials; however, no truly safe and effective artificial blood product is currently marketed. It is anticipated that when an artificial blood product is available, it will have annual sales of over $7.6 billion in the United States alone.

  2. Artificial blood.

    Science.gov (United States)

    Sarkar, Suman

    2008-07-01

    Artificial blood is a product made to act as a substitute for red blood cells. While true blood serves many different functions, artificial blood is designed for the sole purpose of transporting oxygen and carbon dioxide throughout the body. Depending on the type of artificial blood, it can be produced in different ways using synthetic production, chemical isolation, or recombinant biochemical technology. Development of the first blood substitutes dates back to the early 1600s, and the search for the ideal blood substitute continues. Various manufacturers have products in clinical trials; however, no truly safe and effective artificial blood product is currently marketed. It is anticipated that when an artificial blood product is available, it will have annual sales of over $7.6 billion in the United States alone.

  3. A swarm intelligence based memetic algorithm for task allocation in distributed systems

    Science.gov (United States)

    Sarvizadeh, Raheleh; Haghi Kashani, Mostafa

    2012-01-01

    This paper proposes a Swarm Intelligence based Memetic algorithm for Task Allocation and scheduling in distributed systems. The tasks scheduling in distributed systems is known as an NP-complete problem. Hence, many genetic algorithms have been proposed for searching optimal solutions from entire solution space. However, these existing approaches are going to scan the entire solution space without considering the techniques that can reduce the complexity of the optimization. Spending too much time for doing scheduling is considered the main shortcoming of these approaches. Therefore, in this paper memetic algorithm has been used to cope with this shortcoming. With regard to load balancing efficiently, Bee Colony Optimization (BCO) has been applied as local search in the proposed memetic algorithm. Extended experimental results demonstrated that the proposed method outperformed the existing GA-based method in terms of CPU utilization.

  4. SWARM INTELLIGENCE BASED DYNAMIC REAL-TIME SCHEDULING APPROACH FOR SEMICONDUCTOR WAFER FAB

    Institute of Scientific and Technical Information of China (English)

    Li Li; Fei Qiao; Wu Qidi

    2005-01-01

    Based on the analysis of collective activities of ant colonies, the typical example of swarm intelligence, a new approach to construct swarm intelligence based multi-agent-system (SMAS) for dynamic real-time scheduling for semiconductor wafer fab is proposed. The relevant algorithm,pheromone-based dynamic real-time scheduling algorithm (PBDR), is given. MIMAC test bed data set mini-fab is used to compare PBDR with FIFO (first in first out), SRPT(shortest remaining processing time) and CR(critical ratio) under three different release rules, i.e. deterministic rule, Poisson rule and CONWIP (constant WIP). It is shown that PBDR is prior to FIFO, SRPT and CR with better performance of cycle time, throughput, and on-time delivery, especially for on-time delivery performance.

  5. The Effect of Using a Multiple Intelligences-Based Training Programme on Developing English Majors' Oral Communication Skills

    Science.gov (United States)

    Abdallah, Mahmoud Mohammad Sayed

    2005-01-01

    The main purpose of the present study is to investigate the effect of using a Multiple Intelligences-Based Training Programme on developing first-year English majors' oral communication skills. Based on literature review and related studies, a list of 20 oral communication skills was prepared and displayed over a panel of jury members to select…

  6. The Impact of Multiple Intelligences-Based Instruction on Developing Speaking Skills of the Pre-Service Teachers of English

    Science.gov (United States)

    Salem, Ashraf Atta M. S.

    2013-01-01

    The current study investigates the impact of multiple intelligences-based Instruction on developing speaking skills of the pre-service teachers of English. Therefore, the problem of the current study can be stated in the lack of speaking skills of the pre-service teachers of English in Hurgada faculty of Education, South Valley University. To…

  7. Artificial intelligence

    CERN Document Server

    Ennals, J R

    1987-01-01

    Artificial Intelligence: State of the Art Report is a two-part report consisting of the invited papers and the analysis. The editor first gives an introduction to the invited papers before presenting each paper and the analysis, and then concludes with the list of references related to the study. The invited papers explore the various aspects of artificial intelligence. The analysis part assesses the major advances in artificial intelligence and provides a balanced analysis of the state of the art in this field. The Bibliography compiles the most important published material on the subject of

  8. Artificial urushi.

    Science.gov (United States)

    Kobayashi, S; Uyama, H; Ikeda, R

    2001-11-19

    A new concept for the design and laccase-catalyzed preparation of "artificial urushi" from new urushiol analogues is described. The curing proceeded under mild reaction conditions to produce the very hard cross-linked film (artificial urushi) with a high gloss surface. A new cross-linkable polyphenol was synthesized by oxidative polymerization of cardanol, a phenol derivative from cashew-nut-shell liquid, by enzyme-related catalysts. The polyphenol was readily cured to produce the film (also artificial urushi) showing excellent dynamic viscoelasticity.

  9. Definition and detection of contact in atomistic simulations

    NARCIS (Netherlands)

    Solhjoo, Soheil; Vakis, Antonis I.

    2015-01-01

    In atomistic simulations, contact depends on the accurate detection of contacting atoms as well as their contact area. While it is common to define contact between atoms based on the so-called ‘contact distance’ where the interatomic potential energy reaches its minimum, this discounts, for example,

  10. Adaptive resolution simulation of an atomistic protein in MARTINI water

    NARCIS (Netherlands)

    Zavadlav, Julija; Melo, Manuel Nuno; Marrink, Siewert J.; Praprotnik, Matej

    2014-01-01

    We present an adaptive resolution simulation of protein G in multiscale water. We couple atomistic water around the protein with mesoscopic water, where four water molecules are represented with one coarse-grained bead, farther away. We circumvent the difficulties that arise from coupling to the coa

  11. Atomistic Determination of Cross-Slip Pathway and Energetics

    DEFF Research Database (Denmark)

    Rasmussen, Torben; Jacobsen, Karsten Wedel; Leffers, Torben;

    1997-01-01

    The mechanism for cross slip of a screw dislocation in Cu is determined by atomistic simulations that only presume the initial and final states of the process. The dissociated dislocation constricts in the primary plane and redissociates into the cross-slip plane while still partly in the primary...

  12. Atomistic simulations of jog migration on extended screw dislocations

    DEFF Research Database (Denmark)

    Vegge, T.; Leffers, T.; Pedersen, O.B.;

    2001-01-01

    We have performed large-scale atomistic simulations of the migration of elementary jogs on dissociated screw dislocations in Cu. The local crystalline configurations, transition paths. effective masses. and migration barriers for the jogs are determined using an interatomic potential based on the...

  13. Application of Intelligence Based Genetic Algorithm for Job Sequencing Problem on Parallel Mixed-Model Assembly Line

    Directory of Open Access Journals (Sweden)

    A. Norozi

    2010-01-01

    Full Text Available Problem statement: In the area of globalization the degree of competition in the market increased and many companies attempted to manufacture the products efficiently to overcome the challenges faced. Approach: Mixed model assembly line was able to provide continuous flow of material and flexibility with regard to model change. The problem under study attempted to describe the mathematical programming limitation for minimizing the overall make-span and balancing objective for set of parallel lines. Results: A proposed mixed-integer model only able to find the best job sequence in each line to meet the problem objectives for the given number of job allotted to each line. Hence using the proposed mathematical model for large size problem was time consuming and inefficient as so many job allocation values should be checked. This study presented an intelligence based genetic algorithm approach to optimize the considered problem objectives through reducing the problem complexity. A heuristic algorithm was introduced to generate the initial population for intelligence based genetic algorithm. Then, it started to find the best sequence of jobs for each line based on the generated population by heuristic algorithm. By this means, intelligence based genetic algorithm only concentrated on those initial populations that produce better solutions instead of probing the entire search space. Conclusion/Recommendations: The results obtained from intelligence based genetic algorithm were used as an initial point for fine-tuning by simulated annealing to increase the quality of solution. In order to check the capability of proposed algorithm, several experimentations on the set of problems were done. As the total objective values in most of problems could not be improved by simulated algorithm, it proved the well performing of proposed intelligence based genetic algorithm in reaching the near optimal solutions.

  14. Artificial Reefs

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — An artificial reef is a human-made underwater structure, typically built to promote marine life in areas with a generally featureless bottom, control erosion, block...

  15. Artificial Limbs

    Science.gov (United States)

    ... diabetes. They may cause you to need an amputation. Traumatic injuries, including from traffic accidents and military combat Cancer Birth defects If you are missing an arm or leg, an artificial limb can sometimes replace it. The device, which is ...

  16. Natural - synthetic - artificial!

    DEFF Research Database (Denmark)

    Nielsen, Peter E

    2010-01-01

    The terms "natural," "synthetic" and "artificial" are discussed in relation to synthetic and artificial chromosomes and genomes, synthetic and artificial cells and artificial life.......The terms "natural," "synthetic" and "artificial" are discussed in relation to synthetic and artificial chromosomes and genomes, synthetic and artificial cells and artificial life....

  17. Artificial Intelligence as a Business Forecasting and Error Handling Tool

    Directory of Open Access Journals (Sweden)

    Md. Tabrez Quasim

    2015-10-01

    Full Text Available  Any business enterprise must rely a lot on how well it can predict the future happenings. To cope up with the modern global customer demand, technological challenges, market competitions etc., any organization is compelled to foresee the future having maximum impact and least chances of errors. The traditional forecasting approaches have some limitations. That is why the business world is adopting the modern Artificial Intelligence based forecasting techniques. This paper has tried to present different types of forecasting and AI techniques that are useful in business forecasting. At the later stage we have also discussed the forecasting errors and the steps involved in planning the AI support system.

  18. Artificial Intelligence for Controlling Robotic Aircraft

    Science.gov (United States)

    Krishnakumar, Kalmanje

    2005-01-01

    A document consisting mostly of lecture slides presents overviews of artificial-intelligence-based control methods now under development for application to robotic aircraft [called Unmanned Aerial Vehicles (UAVs) in the paper] and spacecraft and to the next generation of flight controllers for piloted aircraft. Following brief introductory remarks, the paper presents background information on intelligent control, including basic characteristics defining intelligent systems and intelligent control and the concept of levels of intelligent control. Next, the paper addresses several concepts in intelligent flight control. The document ends with some concluding remarks, including statements to the effect that (1) intelligent control architectures can guarantee stability of inner control loops and (2) for UAVs, intelligent control provides a robust way to accommodate an outer-loop control architecture for planning and/or related purposes.

  19. Artificial Intelligence

    CERN Document Server

    Warwick, Kevin

    2011-01-01

    if AI is outside your field, or you know something of the subject and would like to know more then Artificial Intelligence: The Basics is a brilliant primer.' - Nick Smith, Engineering and Technology Magazine November 2011 Artificial Intelligence: The Basics is a concise and cutting-edge introduction to the fast moving world of AI. The author Kevin Warwick, a pioneer in the field, examines issues of what it means to be man or machine and looks at advances in robotics which have blurred the boundaries. Topics covered include: how intelligence can be defined whether machines can 'think' sensory

  20. Artificial sweeteners

    DEFF Research Database (Denmark)

    Raben, Anne Birgitte; Richelsen, Bjørn

    2012-01-01

    Artificial sweeteners can be a helpful tool to reduce energy intake and body weight and thereby risk for diabetes and cardiovascular diseases (CVD). Considering the prevailing diabesity (obesity and diabetes) epidemic, this can, therefore, be an important alternative to natural, calorie-containin......Artificial sweeteners can be a helpful tool to reduce energy intake and body weight and thereby risk for diabetes and cardiovascular diseases (CVD). Considering the prevailing diabesity (obesity and diabetes) epidemic, this can, therefore, be an important alternative to natural, calorie...

  1. Adhesive contact:from atomistic model to continuum model

    Institute of Scientific and Technical Information of China (English)

    Fan Kang-Qi; Jia Jian-Yuan; Zhu Ying-Min; Zhang Xiu-Yan

    2011-01-01

    Two types of Lennard-Jones potential are widely used in modeling adhesive contacts. However, the relationships between the parameters of the two types of Lennard-Jones potential are not well defined. This paper employs a selfconsistent method to derive the Lennard-Jones surface force law from the interatomic Lennard-Jones potential with emphasis on the relationships between the parameters. The effect of using correct parameters in the adhesion models is demonstrated in single sphere-flat contact via continuum models and an atomistic model. Furthermore, the adhesion hysteresis behaviour is investigated, and the S-shaped force-distance relation is revealed by the atomistic model. It shows that the adhesion hysteresis loop is generated by the jump-to-contact and jump-off-contact, which are illustrated by the S-shaped force-distance curve.

  2. Atomistic aspects of crack propagation along high angle grain boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, D. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering

    1997-12-31

    The author presents atomistic simulations of the crack tip configuration near a high angle {Sigma} = 5 [001](210) symmetrical tilt grain boundary in NiAl. The simulations were carried out using molecular statics and embedded atom (EAM) potentials. The cracks are stabilized near a Griffith condition involving the cohesive energy of the grain boundary. The atomistic configurations of the tip region are different in the presence of the high angle grain boundary than in the bulk. Three different configurations of the grain boundary were studied corresponding to different local compositions. It was found that in ordered NiAl, cracks along symmetrical tilt boundaries show a more brittle behavior for Al rich boundaries than for Ni-rich boundaries. Lattice trapping effects in grain boundary fracture were found to be more significant than in the bulk.

  3. The notion of a plastic material spin in atomistic simulations

    Science.gov (United States)

    Dickel, D.; Tenev, T. G.; Gullett, P.; Horstemeyer, M. F.

    2016-12-01

    A kinematic algorithm is proposed to extend existing constructions of strain tensors from atomistic data to decouple elastic and plastic contributions to the strain. Elastic and plastic deformation and ultimately the plastic spin, useful quantities in continuum mechanics and finite element simulations, are computed from the full, discrete deformation gradient and an algorithm for the local elastic deformation gradient. This elastic deformation gradient algorithm identifies a crystal type using bond angle analysis (Ackland and Jones 2006 Phys. Rev. B 73 054104) and further exploits the relationship between bond angles to determine the local deformation from an ideal crystal lattice. Full definitions of plastic deformation follow directly using a multiplicative decomposition of the deformation gradient. The results of molecular dynamics simulations of copper in simple shear and torsion are presented to demonstrate the ability of these new discrete measures to describe plastic material spin in atomistic simulation and to compare them with continuum theory.

  4. Atomistic modeling of carbon Cottrell atmospheres in bcc iron

    Science.gov (United States)

    Veiga, R. G. A.; Perez, M.; Becquart, C. S.; Domain, C.

    2013-01-01

    Atomistic simulations with an EAM interatomic potential were used to evaluate carbon-dislocation binding energies in bcc iron. These binding energies were then used to calculate the occupation probability of interstitial sites in the vicinity of an edge and a screw dislocation. The saturation concentration due to carbon-carbon interactions was also estimated by atomistic simulations in the dislocation core and taken as an upper limit for carbon concentration in a Cottrell atmosphere. We obtained a maximum concentration of 10 ± 1 at.% C at T = 0 K within a radius of 1 nm from the dislocation lines. The spatial carbon distributions around the line defects revealed that the Cottrell atmosphere associated with an edge dislocation is denser than that around a screw dislocation, in contrast with the predictions of the classical model of Cochardt and colleagues. Moreover, the present Cottrell atmosphere model is in reasonable quantitative accord with the three-dimensional atom probe data available in the literature.

  5. Predicting dislocation climb: Classical modeling versus atomistic simulations

    OpenAIRE

    Clouet, Emmanuel

    2011-01-01

    International audience; The classical modeling of dislocation climb based on a continuous description of vacancy diffusion is compared to recent atomistic simulations of dislocation climb in body-centered cubic iron under vacancy supersaturation [Phys. Rev. Lett. 105 095501 (2010)]. A quantitative agreement is obtained, showing the ability of the classical approach to describe dislocation climb. The analytical model is then used to extrapolate dislocation climb velocities to lower dislocation...

  6. Redox reactions with empirical potentials: Atomistic battery discharge simulations

    OpenAIRE

    Dapp, Wolf B.; Müser, Martin H.

    2013-01-01

    Batteries are pivotal components in overcoming some of today's greatest technological challenges. Yet to date there is no self-consistent atomistic description of a complete battery. We take first steps toward modeling of a battery as a whole microscopically. Our focus lies on phenomena occurring at the electrode-electrolyte interface which are not easily studied with other methods. We use the redox split-charge equilibration (redoxSQE) method that assigns a discrete ionization state to each ...

  7. The atomistic representation of first strain-gradient elastic tensors

    Science.gov (United States)

    Admal, Nikhil Chandra; Marian, Jaime; Po, Giacomo

    2017-02-01

    We derive the atomistic representations of the elastic tensors appearing in the linearized theory of first strain-gradient elasticity for an arbitrary multi-lattice. In addition to the classical (2nd-Piola) stress and elastic moduli tensors, these include the rank-three double-stress tensor, the rank-five tensor of mixed elastic moduli, and the rank-six tensor of strain-gradient elastic moduli. The atomistic representations are closed-form analytical expressions in terms of the first and second derivatives of the interatomic potential with respect to interatomic distances, and dyadic products of relative atomic positions. Moreover, all expressions are local, in the sense that they depend only on the atomic neighborhood of a lattice site. Our results emanate from the condition of energetic equivalence between continuum and atomistic representations of a crystal, when the kinematics of the latter is governed by the Cauchy-Born rule. Using the derived expressions, we prove that the odd-order tensors vanish if the lattice basis admits central-symmetry. The analytical expressions are implemented as a KIM compliant algorithm to compute the strain gradient elastic tensors for various materials. Numerical results are presented to compare representative interatomic potentials used in the literature for cubic crystals, including simple lattices and multi-lattices. We observe that central potentials exhibit generalized Cauchy relations for the rank-six tensor of strain-gradient elastic moduli. In addition, this tensor is found to be indefinite for many potentials. We discuss the relationship between indefiniteness and material stability. Finally, the atomistic representations are specialized to central potentials in simple lattices. These expressions are used with analytical potentials to study the sensitivity of the elastic tensors to the choice of the cutoff radius.

  8. A dynamic atomistic-continuum method for the simulation of crystalline materials

    CERN Document Server

    Huang Zhon Gy

    2002-01-01

    We present a coupled atomistic-continuum method for the modeling of defects and interface dynamics in crystalline materials. The method uses atomistic models such as molecular dynamics near defects and interfaces, and continuum models away from defects and interfaces. We propose a new class of matching conditions between the atomistic and the continuum regions. These conditions ensure the accurate passage of large-scale information between the atomistic and the continuum regions and at the same time minimize the reflection of phonons at the atomistic-continuum interface. They can be made adaptive by choosing appropriate weight functions. We present applications to dislocation dynamics, friction between two-dimensional crystal surfaces, and fracture dynamics. We compare results of the coupled method and of the detailed atomistic model.

  9. Artificial ribonucleases.

    Science.gov (United States)

    Morrow, J R

    1994-01-01

    Many inorganic and organic compounds promote the reactions catalyzed by RNase A. Both the transesterification step, where a 2',3'-cyclic phosphate is formed with concomitant cleavage of RNA, and the hydrolysis step, where the 2',3'-cyclic phosphate is converted to a phosphate monoester, may be mimicked with compounds that are readily synthesized in the laboratory. Electrophilic activation of the phosphate ester and charge neutralization are generally important means by which artificial RNases promote phosphate diester displacement reactions. Several artificial RNases operate by a bifunctional general acid/general base mechanism, as does RNase A. Provision of an intramolecular nucleophile appears to be an important pathway for metal complex promoted phosphate diester hydrolysis. In contrast to the successful design of compounds that promote the reactions catalyzed by RNase A, there are no artificial nucleases to date that will cleave the 3' P-O bond of RNA or hydrolyze an oligonucleotide of DNA. Artificial RNases based on both metal complexes and organic compounds have been described. Metal complexes may be particularly effective catalysts for both transesterification and hydrolysis reactions of phosphate diesters. Under physiological conditions (37 degrees C and neutral pH), several metal complexes catalyze the transesterification of RNA. Future work should involve the development of metal complexes which are inert to metal ion release but which maintain open coordination sites for catalytic activity. The design of compounds containing multiple amine or imidazole groups that may demonstrate bifunctional catalysis is a promising route to new artificial RNases. Further design of these compounds and careful placement of catalytic groups may yield new RNase mimics that operate under physiological conditions. The attachment of artificial RNases to recognition agents such as oligodeoxynucleotides to create new sequence-specific endoribonucleases is an exciting field of

  10. Artificial Intelligence.

    Science.gov (United States)

    Lawrence, David R; Palacios-González, César; Harris, John

    2016-04-01

    It seems natural to think that the same prudential and ethical reasons for mutual respect and tolerance that one has vis-à-vis other human persons would hold toward newly encountered paradigmatic but nonhuman biological persons. One also tends to think that they would have similar reasons for treating we humans as creatures that count morally in our own right. This line of thought transcends biological boundaries-namely, with regard to artificially (super)intelligent persons-but is this a safe assumption? The issue concerns ultimate moral significance: the significance possessed by human persons, persons from other planets, and hypothetical nonorganic persons in the form of artificial intelligence (AI). This article investigates why our possible relations to AI persons could be more complicated than they first might appear, given that they might possess a radically different nature to us, to the point that civilized or peaceful coexistence in a determinate geographical space could be impossible to achieve.

  11. Artificial blood.

    OpenAIRE

    1983-01-01

    #Blood substitutes have been developed for almost a century. The various type of artificial blood was continuously available on the market. The theme of this report is to identify the best substitute in emergency situation for some patients and science students. The definition of best is given; thus, as the vital part of the report, the comparison between them is described and discussed. Modified hemoglobin, bovine-based hemoglobin and PFCs are three basic types. In terms of the perfor...

  12. Artificial vision.

    Science.gov (United States)

    Zarbin, M; Montemagno, C; Leary, J; Ritch, R

    2011-09-01

    A number treatment options are emerging for patients with retinal degenerative disease, including gene therapy, trophic factor therapy, visual cycle inhibitors (e.g., for patients with Stargardt disease and allied conditions), and cell transplantation. A radically different approach, which will augment but not replace these options, is termed neural prosthetics ("artificial vision"). Although rewiring of inner retinal circuits and inner retinal neuronal degeneration occur in association with photoreceptor degeneration in retinitis pigmentosa (RP), it is possible to create visually useful percepts by stimulating retinal ganglion cells electrically. This fact has lead to the development of techniques to induce photosensitivity in cells that are not light sensitive normally as well as to the development of the bionic retina. Advances in artificial vision continue at a robust pace. These advances are based on the use of molecular engineering and nanotechnology to render cells light-sensitive, to target ion channels to the appropriate cell type (e.g., bipolar cell) and/or cell region (e.g., dendritic tree vs. soma), and on sophisticated image processing algorithms that take advantage of our knowledge of signal processing in the retina. Combined with advances in gene therapy, pathway-based therapy, and cell-based therapy, "artificial vision" technologies create a powerful armamentarium with which ophthalmologists will be able to treat blindness in patients who have a variety of degenerative retinal diseases.

  13. Atomistic simulation of the structural and elastic properties of magnesite

    Indian Academy of Sciences (India)

    ZI-JIANG LIU; XIAO-WEI SUN; TING SONG; YUAN GUO; CAI-RONG ZHANG; ZHENG-RONG ZHANG

    2016-09-01

    Atomistic simulation was carried out to study the structural and elastic properties of MgCO$_3$ magnesite within the pressure range of the Earth’s mantle based on a novel force field. The lattice parameters and elasticconstants as a function of pressure up to 150 GPa are calculated. The results are in good agreement with the available experimental data and previous theoretical results, showing no phase transition over the pressure range of interest. We also found that magnesite exhibits a strong anisotropy throughout the lower mantle and that the nature of the anisotropy changes significantly with depth.

  14. Predicting dislocation climb and creep from explicit atomistic details.

    Science.gov (United States)

    Kabir, Mukul; Lau, Timothy T; Rodney, David; Yip, Sidney; Van Vliet, Krystyn J

    2010-08-27

    Here we report kinetic Monte Carlo simulations of dislocation climb in heavily deformed, body-centered cubic iron comprising a supersaturation of vacancies. This approach explicitly incorporates the effect of nonlinear vacancy-dislocation interaction on vacancy migration barriers as determined from atomistic calculations, and enables observations of diffusivity and climb over time scales and temperatures relevant to power-law creep. By capturing the underlying microscopic physics, the calculated stress exponents for steady-state creep rates agree quantitatively with the experimentally measured range, and qualitatively with the stress dependence of creep activation energies.

  15. Atomistic Molecular Dynamics Simulations of Mitochondrial DNA Polymerase γ

    DEFF Research Database (Denmark)

    Euro, Liliya; Haapanen, Outi; Róg, Tomasz

    2017-01-01

    DNA polymerase γ (Pol γ) is a key component of the mitochondrial DNA replisome and an important cause of neurological diseases. Despite the availability of its crystal structures, the molecular mechanism of DNA replication, the switch between polymerase and exonuclease activities, the site...... of replisomal interactions, and functional effects of patient mutations that do not affect direct catalysis have remained elusive. Here we report the first atomistic classical molecular dynamics simulations of the human Pol γ replicative complex. Our simulation data show that DNA binding triggers remarkable...

  16. Interfacial Phenomena: Linking Atomistic and Molecular Level Processes

    Energy Technology Data Exchange (ETDEWEB)

    Jay A Brandes

    2009-09-23

    This was a grant to support travel for scientists to present data and interact with others in their field. Specifically, speakers presented their data in a session entitled “Interfacial Phenomena: Linking Atomistic and Macroscopic Properties: Theoretical and Experimental Studies of the Structure and Reactivity of Mineral Surfaces”. The session ran across three ½ day periods, March 30-31 2004. The session’s organizers were David J. Wesolowski andGordon E. Brown Jr. There were a total of 30 talks presented.

  17. Control of density fluctuations in atomistic-continuum simulations of dense liquids

    DEFF Research Database (Denmark)

    Kotsalis, E.M.; Walther, Jens Honore; Koumoutsakos, P.

    2007-01-01

    We present a control algorithm to eliminate spurious density fluctuations associated with the coupling of atomistic and continuum descriptions for dense liquids. A Schwartz domain decomposition algorithm is employed to couple molecular dynamics for the simulation of the atomistic system with a co...

  18. Going Backward : A Flexible Geometric Approach to Reverse Transformation from Coarse Grained to Atomistic Models

    NARCIS (Netherlands)

    Wassenaar, Tsjerk A.; Pluhackova, Kristyna; Böckmann, Rainer A.; Marrink, Siewert J.; Tieleman, D. Peter

    2014-01-01

    The conversion of coarse-grained to atomistic models is an important step in obtaining insight about atomistic scale processes from coarse-grained simulations. For this process, called backmapping or reverse transformation, several tools are available, but these commonly require libraries of molecul

  19. The Effect of Multiple Intelligence-Based Instruction on Critical Thinking of Full Day Islamic Elementary Schools Students

    Directory of Open Access Journals (Sweden)

    Alhamuddin Alhamuddin

    2016-09-01

    Full Text Available Lack of critical thinking skills of elementary schools’ students was influenced by teachers’ domination in instructional activities; meanwhile students did not play independently as the learners. Theoretically, multiple intelligences based instruction is an appropriate solution. For that reason, this research aims to know the impact of multiple intelligences based instruction on students' critical thinking skills. The research was conducted at Al-Amanah and Buahati Islamic Elementary Schools by using a quantitative approach with case study method. Data collected through critical thinking tests was analyzed by using independent sample t-test to examine the impact of instruction on students' critical thinking skills. The results showed that the implementation of multiple intelligences based intruction had significant effect on students’ critical thinking skills. From the finding, some recommendations are given as follows: 1 The teacher’s role is not only for transferring knowledge based on his/her competencies but also students’ characteristics reflecting their instruction styles; and 2 for further researcher, it is suggested to investigate this issues more specifically and comprehensively.   Kurangnya keterampilan berpikir kritis dari siswa sekolah dasar dipengaruhi oleh dominasi guru dalam kegiatan pembelajaran; Sementara itu siswa tidak bermain secara independen sebagai peserta didik. Secara teoritis, pendekatan berbasis kecerdasan ganda merupakan solusi yang tepat. Untuk itu, penelitian ini bertujuan untuk mengetahui dampak pendekatan berbasis kecerdasan ganda pada keterampilan berpikir kritis siswa. Penelitian ini dilakukan di Sekolah Dasar Islam Al-Amanah dan Buahati dengan menggunakan pendekatan kuantitatif dengan metode studi kasus. Data dikumpulkan melalui tes berpikir kritis dianalisis dengan menggunakan sampel independent t-test untuk menguji dampak dari pendekatan pada keterampilan berpikir kritis siswa. Hasil penelitian

  20. Coupling Length Scales for Multiscale Atomistics-Continuum Simulations: Atomistically Induced Stress Distributions in Si/Si{sub 3}N

    Energy Technology Data Exchange (ETDEWEB)

    Lidorikis, Elefterios; Bachlechner, Martina E.; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya; Voyiadjis, George Z.

    2001-08-20

    A hybrid molecular-dynamics (MD) and finite-element simulation approach is used to study stress distributions in silicon/silicon-nitride nanopixels. The hybrid approach provides atomistic description near the interface and continuum description deep into the substrate, increasing the accessible length scales and greatly reducing the computational cost. The results of the hybrid simulation are in good agreement with full multimillion-atom MD simulations: atomic structures at the lattice-mismatched interface between amorphous silicon nitride and silicon induce inhomogeneous stress patterns in the substrate that cannot be reproduced by a continuum approach alone.

  1. Quantum transport in RTD and atomistic modeling of nanostructures

    Science.gov (United States)

    Jiang, Zhengping

    As devices are scaled down to nanometer scale, new materials and device structures are introduced to extend Moore's law beyond Si devices. In this length scale, carrier transport moves from classical transport to quantum transport; material granularity has more and more impacts on performance. Computer Aided Design (CAD) becomes essential for both industrial and educational purposes. First part focuses on physical models and numerical issues in nano-scale devices modeling. Resonance Tunneling Diode (RTD) is simulated and used to illustrate phenomena in carrier transport. Non-Equilibrium Green's Function (NEGF) formulism is employed in quantum transport simulation. Inhomogeneous energy grid is used in energy integration, which is critical to capture essential physics in RTD simulation. All simulation results could be reproduced by developed simulators RTDNEGF and NEMO5. In nanostructures, device length becomes comparable to material granularity; it is not proper to consider materials as continuous in many situations. Second part of this work resolves this problem by introducing atomistic modeling method. Valley degeneracy in Si (110) QW is investigated. Inconsistency of experimental observations is resolved by introducing miscut in surface. Impacts of strain and electric field on electronic bandstructure are studied. Research of SiGe barrier disorder effects on valley splitting in Si (100) QW is then conducted. Behaviors of valley splitting in different well widths under electric field are predicted by atomistic simulation. Nearest neighbor empirical tight-binding method is used in electronic calculation and VFF Keating model is used in strain relaxation.

  2. Atomistic interpretation of solid solution hardening from spectral analysis.

    Science.gov (United States)

    Plendl, J N

    1971-05-01

    From analysis of a series of vibrational spectra of ir energy absorption and laser Raman, an attempt is made to interpret solid solution hardening from an atomistic point of view for the system CaF(2)/SrF(2). It is shown to be caused by the combined action of three atomic characteristics, i.e., their changes as a function of composition. They are deformation of the atomic coordination polyhedrons, overlap of the outer electron shells of the atom pairs, and the ratio of the ionic to covalent share of binding. A striking nonlinear behavior of the three characteristics, as a function of composition, gives maximum atomic bond strength to the 55/45 position of the system CaF(2)/SrF(2), in agreement with the measured data of the solid solution hardening. The curve for atomic bond strength, derived from the three characteristics, is almost identical to the curve for measured microhardness data. This result suggests that the atomistic interpretation, put forward in this paper, is correct.

  3. Void Coalescence Processes Quantified Through Atomistic and Multiscale Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Rudd, R E; Seppala, E T; Dupuy, L M; Belak, J

    2007-01-12

    Simulation of ductile fracture at the atomic scale reveals many aspects of the fracture process including specific mechanisms associated with void nucleation and growth as a precursor to fracture and the plastic deformation of the material surrounding the voids and cracks. Recently we have studied void coalescence in ductile metals using large-scale atomistic and continuum simulations. Here we review that work and present some related investigations. The atomistic simulations involve three-dimensional strain-controlled multi-million atom molecular dynamics simulations of copper. The correlated growth of two voids during the coalescence process leading to fracture is investigated, both in terms of its onset and the ensuing dynamical interactions. Void interactions are quantified through the rate of reduction of the distance between the voids, through the correlated directional growth of the voids, and through correlated shape evolution of the voids. The critical inter-void ligament distance marking the onset of coalescence is shown to be approximately one void radius based on the quantification measurements used, independent of the initial separation distance between the voids and the strain-rate of the expansion of the system. No pronounced shear flow is found in the coalescence process. We also discuss a technique for optimizing the calculation of fine-scale information on the fly for use in a coarse-scale simulation, and discuss the specific case of a fine-scale model that calculates void growth explicitly feeding into a coarse-scale mechanics model to study damage localization.

  4. Void Coalescence Processes Quantified through Atomistic and Multiscale Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Rudd, R E; Seppala, E T; Dupuy, L M; Belak, J

    2005-12-31

    Simulation of ductile fracture at the atomic scale reveals many aspects of the fracture process including specific mechanisms associated with void nucleation and growth as a precursor to fracture and the plastic deformation of the material surrounding the voids and cracks. Recently we have studied void coalescence in ductile metals using large-scale atomistic and continuum simulations. Here we review that work and present some related investigations. The atomistic simulations involve three-dimensional strain-controlled multi-million atom molecular dynamics simulations of copper. The correlated growth of two voids during the coalescence process leading to fracture is investigated, both in terms of its onset and the ensuing dynamical interactions. Void interactions are quantified through the rate of reduction of the distance between the voids, through the correlated directional growth of the voids, and through correlated shape evolution of the voids. The critical inter-void ligament distance marking the onset of coalescence is shown to be approximately one void radius based on the quantification measurements used, independent of the initial separation distance between the voids and the strain-rate of the expansion of the system. No pronounced shear flow is found in the coalescence process.

  5. Adaptive resolution simulation of an atomistic protein in MARTINI water

    Science.gov (United States)

    Zavadlav, Julija; Melo, Manuel Nuno; Marrink, Siewert J.; Praprotnik, Matej

    2014-02-01

    We present an adaptive resolution simulation of protein G in multiscale water. We couple atomistic water around the protein with mesoscopic water, where four water molecules are represented with one coarse-grained bead, farther away. We circumvent the difficulties that arise from coupling to the coarse-grained model via a 4-to-1 molecule coarse-grain mapping by using bundled water models, i.e., we restrict the relative movement of water molecules that are mapped to the same coarse-grained bead employing harmonic springs. The water molecules change their resolution from four molecules to one coarse-grained particle and vice versa adaptively on-the-fly. Having performed 15 ns long molecular dynamics simulations, we observe within our error bars no differences between structural (e.g., root-mean-squared deviation and fluctuations of backbone atoms, radius of gyration, the stability of native contacts and secondary structure, and the solvent accessible surface area) and dynamical properties of the protein in the adaptive resolution approach compared to the fully atomistically solvated model. Our multiscale model is compatible with the widely used MARTINI force field and will therefore significantly enhance the scope of biomolecular simulations.

  6. 3d visualization of atomistic simulations on every desktop

    Science.gov (United States)

    Peled, Dan; Silverman, Amihai; Adler, Joan

    2013-08-01

    Once upon a time, after making simulations, one had to go to a visualization center with fancy SGI machines to run a GL visualization and make a movie. More recently, OpenGL and its mesa clone have let us create 3D on simple desktops (or laptops), whether or not a Z-buffer card is present. Today, 3D a la Avatar is a commodity technique, presented in cinemas and sold for home TV. However, only a few special research centers have systems large enough for entire classes to view 3D, or special immersive facilities like visualization CAVEs or walls, and not everyone finds 3D immersion easy to view. For maximum physics with minimum effort a 3D system must come to each researcher and student. So how do we create 3D visualization cheaply on every desktop for atomistic simulations? After several months of attempts to select commodity equipment for a whole room system, we selected an approach that goes back a long time, even predating GL. The old concept of anaglyphic stereo relies on two images, slightly displaced, and viewed through colored glasses, or two squares of cellophane from a regular screen/projector or poster. We have added this capability to our AViz atomistic visualization code in its new, 6.1 version, which is RedHat, CentOS and Ubuntu compatible. Examples using data from our own research and that of other groups will be given.

  7. Amp: A modular approach to machine learning in atomistic simulations

    Science.gov (United States)

    Khorshidi, Alireza; Peterson, Andrew A.

    2016-10-01

    Electronic structure calculations, such as those employing Kohn-Sham density functional theory or ab initio wavefunction theories, have allowed for atomistic-level understandings of a wide variety of phenomena and properties of matter at small scales. However, the computational cost of electronic structure methods drastically increases with length and time scales, which makes these methods difficult for long time-scale molecular dynamics simulations or large-sized systems. Machine-learning techniques can provide accurate potentials that can match the quality of electronic structure calculations, provided sufficient training data. These potentials can then be used to rapidly simulate large and long time-scale phenomena at similar quality to the parent electronic structure approach. Machine-learning potentials usually take a bias-free mathematical form and can be readily developed for a wide variety of systems. Electronic structure calculations have favorable properties-namely that they are noiseless and targeted training data can be produced on-demand-that make them particularly well-suited for machine learning. This paper discusses our modular approach to atomistic machine learning through the development of the open-source Atomistic Machine-learning Package (Amp), which allows for representations of both the total and atom-centered potential energy surface, in both periodic and non-periodic systems. Potentials developed through the atom-centered approach are simultaneously applicable for systems with various sizes. Interpolation can be enhanced by introducing custom descriptors of the local environment. We demonstrate this in the current work for Gaussian-type, bispectrum, and Zernike-type descriptors. Amp has an intuitive and modular structure with an interface through the python scripting language yet has parallelizable fortran components for demanding tasks; it is designed to integrate closely with the widely used Atomic Simulation Environment (ASE), which

  8. Material fields in atomistics as pull-backs of spatial distributions

    Science.gov (United States)

    Chandra Admal, Nikhil; Tadmor, Ellad B.

    2016-04-01

    The various fields defined in continuum mechanics have both a material and a spatial description that are related through the deformation mapping. In contrast, continuum fields defined for atomistic systems using the Irving-Kirkwood or Murdoch-Hardy procedures correspond to a spatial description. It is uncommon to define atomistic fields in the reference configuration due to the lack of a unique definition for the deformation mapping in atomistic systems. In this paper, we construct referential atomistic distributions as pull-backs of the spatial distributions obtained in the Murdoch-Hardy procedure with respect to a postulated deformation mapping that tracks particles. We then show that some of these referential distributions are independent of the choice of the deformation mapping and only depend on the reference and current configuration of particles. Therefore, the fields obtained from these distributions can be calculated without explicitly constructing a deformation map, and by construction they satisfy the balance equations. In particular, we obtain definitions for the first and second atomistic Piola-Kirchhoff stress tensors. We demonstrate the validity of these definitions through a numerical example involving finite deformation of a slab containing a notch under tension. An interesting feature of the atomistic first Piola-Kirchhoff stress tensor is the absence of a kinetic part, which in the atomistic Cauchy stress tensor accounts for thermal fluctuations. We show that this effect is implicitly included in the atomistic first Piola-Kirchhoff stress tensor through the motion of the particles. An open source program to compute the atomistic Cauchy and first Piola-Kirchhoff stress fields called MDStressLab is available online at

  9. Atomistic simulation of static magnetic properties of bit patterned media

    Science.gov (United States)

    Arbeláez-Echeverri, O. D.; Agudelo-Giraldo, J. D.; Restrepo-Parra, E.

    2016-09-01

    In this work we present a new design of Co based bit pattern media with out-of-plane uni-axial anisotropy induced by interface effects. Our model features the inclusion of magnetic impurities in the non-magnetic matrix. After the material model was refined during three iterations using Monte Carlo simulations, further simulations were performed using an atomistic integrator of Landau-Lifshitz-Gilbert equation with Langevin dynamics to study the behavior of the system paying special attention to the super-paramagnetic limit. Our model system exhibits three magnetic phase transitions, one due to the magnetically doped matrix material and the weak magnetic interaction between the nano-structures in the system. The different magnetic phases of the system as well as the features of its phase diagram are explained.

  10. Atomistic Hydrodynamics and the Dynamical Hydrophobic Effect in Porous Graphene.

    Science.gov (United States)

    Strong, Steven E; Eaves, Joel D

    2016-05-19

    Mirroring their role in electrical and optical physics, two-dimensional crystals are emerging as novel platforms for fluid separations and water desalination, which are hydrodynamic processes that occur in nanoscale environments. For numerical simulation to play a predictive and descriptive role, one must have theoretically sound methods that span orders of magnitude in physical scales, from the atomistic motions of particles inside the channels to the large-scale hydrodynamic gradients that drive transport. Here, we use constraint dynamics to derive a nonequilibrium molecular dynamics method for simulating steady-state mass flow of a fluid moving through the nanoscopic spaces of a porous solid. After validating our method on a model system, we use it to study the hydrophobic effect of water moving through pores of electrically doped single-layer graphene. The trend in permeability that we calculate does not follow the hydrophobicity of the membrane but is instead governed by a crossover between two competing molecular transport mechanisms.

  11. Quantum-based Atomistic Simulation of Transition Metals

    Energy Technology Data Exchange (ETDEWEB)

    Moriarty, J A; Benedict, L X; Glosli, J N; Hood, R Q; Orlikowski, D A; Patel, M V; Soderlind, P; Streitz, F H; Tang, M; Yang, L H

    2005-08-29

    First-principles generalized pseudopotential theory (GPT) provides a fundamental basis for transferable multi-ion interatomic potentials in d-electron transition metals within density-functional quantum mechanics. In mid-period bcc metals, where multi-ion angular forces are important to structural properties, simplified model GPT or MGPT potentials have been developed based on canonical d bands to allow analytic forms and large-scale atomistic simulations. Robust, advanced-generation MGPT potentials have now been obtained for Ta and Mo and successfully applied to a wide range of structural, thermodynamic, defect and mechanical properties at both ambient and extreme conditions of pressure and temperature. Recent algorithm improvements have also led to a more general matrix representation of MGPT beyond canonical bands allowing increased accuracy and extension to f-electron actinide metals, an order of magnitude increase in computational speed, and the current development of temperature-dependent potentials.

  12. Shock Hugoniot behavior of single crystal titanium using atomistic simulations

    Science.gov (United States)

    Mackenchery, Karoon; Dongare, Avinash

    2017-01-01

    Atomistic shock simulations are performed for single crystal titanium using four different interatomic potentials at impact velocities ranging from 0.5 km/s to 2.0 km/s. These potentials comprise of three parameterizations in the formulation of the embedded atom method and one formulation of the modified embedded atom method. The capability of the potentials to model the shock deformation and failure behavior is investigated by computing the shock hugoniot response of titanium and comparing to existing experimental data. In addition, the capability to reproduce the shock induced alpha (α) to omega (ω) phase transformation seen in Ti is investigated. The shock wave structure is discussed and the velocities for the elastic, plastic and the α-ω phase transformation waves are calculated for all the interatomic potentials considered.

  13. Effective Transparency: A Test of Atomistic Laser-Cluster Models

    CERN Document Server

    Pandit, Rishi; Teague, Thomas; Hartwick, Zachary; Bigaouette, Nicolas; Ramunno, Lora; Ackad, Edward

    2016-01-01

    The effective transparency of rare-gas clusters, post-interaction with an extreme ultraviolet (XUV) pump pulse, is studied by using an atomistic hybrid quantum-classical molecular dynamics model. We find there is an intensity range in which an XUV probe pulse has no lasting effect on the average charge state of a cluster after being saturated by an XUV pump pulse: the cluster is effectively transparent to the probe pulse. The range of this phenomena increases with the size of the cluster and thus provides an excellent candidate for an experimental test of the effective transparency effect. We present predictions for the clusters at the peak of the laser pulse as well as the experimental time-of-flight signal expected along with trends which can be compared with. Significant deviations from these predictions would provide evidence for enhanced photoionization mechanism(s).

  14. Artificial Economy

    Directory of Open Access Journals (Sweden)

    Alexandru JIVAN

    2011-08-01

    Full Text Available This paper proposes to eliminate, a routine in the economic thinking, claimed to be responsible for the negative essence of economic developments, from the point of view, of the ecological implications (employment in the planetary ecosystem. The methodological foundations start from the natural origins of the functionality of the human economic society according to the originary physiocrat liberalism, and from specific natural characteristics of the humankind. This paper begins with a comment-analysis of the difference between natural and artificial within the economy, and then explains some of the most serious diversions from the natural essence of economic liberalism. It shall be explained the original (heterodox interpretation of the Classical political economy (economics, by making calls to the Romanian economic thinking from aggravating past century. Highlighting the destructive impact of the economy - which, under the invoked doctrines, we call unnatural - allows an intuitive presentation of a logical extension of Marshall's market price, based on previous research. Besides the doctrinal arguments presented, the economic realities inventoried along the way (major deficiencies and effects, determined demonstrate the validity of the hypothesis of the unnatural character and therefore necessarily to be corrected, of the concept and of the mechanisms of the current economy.The results of this paper consist of original heterodox methodspresented, intuitive or developed that can be found conclusively within the key proposals for education and regulation.

  15. Effects of Atomistic Domain Size on Hybrid Lattice Boltzmann-Molecular Dynamics Simulations of Dense Fluids

    Science.gov (United States)

    Dupuis, A.; Koumoutsakos, P.

    We present a convergence study for a hybrid Lattice Boltzmann-Molecular Dynamics model for the simulation of dense liquids. Time and length scales are decoupled by using an iterative Schwarz domain decomposition algorithm. The velocity field from the atomistic domain is introduced as forcing terms to the Lattice Boltzmann model of the continuum while the mean field of the continuum imposes mean field conditions for the atomistic domain. In the present paper we investigate the effect of varying the size of the atomistic subdomain in simulations of two dimensional flows of liquid argon past carbon nanotubes and assess the efficiency of the method.

  16. Control of density fluctuations in atomistic-continuum simulations of dense liquids

    Science.gov (United States)

    Kotsalis, E. M.; Walther, J. H.; Koumoutsakos, P.

    2007-07-01

    We present a control algorithm to eliminate spurious density fluctuations associated with the coupling of atomistic and continuum descriptions for dense liquids. A Schwartz domain decomposition algorithm is employed to couple molecular dynamics for the simulation of the atomistic system with a continuum solver for the simulation of the Navier-Stokes equations. The lack of periodic boundary conditions in the molecular dynamics simulations hinders the proper accounting for the virial pressure leading to spurious density fluctuations at the continuum-atomistic interface. An ad hoc boundary force is usually employed to remedy this situation. We propose the calculation of this boundary force using a control algorithm that explicitly cancels the density fluctuations. The results demonstrate that the present approach outperforms state-of-the-art algorithms. The conceptual and algorithmic simplicity of the method makes it suitable for any type of coupling between atomistic and continuum descriptions of dense fluids.

  17. Hybrid simulations: combining atomistic and coarse-grained force fields using virtual sites.

    Science.gov (United States)

    Rzepiela, Andrzej J; Louhivuori, Martti; Peter, Christine; Marrink, Siewert J

    2011-06-14

    Hybrid simulations, in which part of the system is represented at atomic resolution and the remaining part at a reduced, coarse-grained, level offer a powerful way to combine the accuracy associated with the atomistic force fields to the sampling speed obtained with coarse-grained (CG) potentials. In this work we introduce a straightforward scheme to perform hybrid simulations, making use of virtual sites to couple the two levels of resolution. With the help of these virtual sites interactions between molecules at different levels of resolution, i.e. between CG and atomistic molecules, are treated the same way as the pure CG-CG interactions. To test our method, we combine the Gromos atomistic force field with a number of coarse-grained potentials, obtained through several approaches that are designed to obtain CG potentials based on an existing atomistic model, namely iterative Boltzmann inversion, force matching, and a potential of mean force subtraction procedure (SB). We also explore the use of the MARTINI force field for the CG potential. A simple system, consisting of atomistic butane molecules dissolved in CG butane, is used to study the performance of our hybrid scheme. Based on the potentials of mean force for atomistic butane in CG solvent, and the properties of 1:1 mixtures of atomistic and CG butane which should exhibit ideal mixing behavior, we conclude that the MARTINI and SB potentials are particularly suited to be combined with the atomistic force field. The MARTINI potential is subsequently used to perform hybrid simulations of atomistic dialanine peptides in both CG butane and water. Compared to a fully atomistic description of the system, the hybrid description gives similar results provided that the dielectric screening of water is accounted for. Within the field of biomolecules, our method appears ideally suited to study e.g. protein-ligand binding, where the active site and ligand are modeled in atomistic detail and the rest of the protein

  18. Atomistic study of crack propagation and dislocation emission in Cu-Ni multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Clinedinst, J.; Farkas, D. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering

    1997-09-01

    The authors present atomistic simulations of the crack tip configuration in multilayered Cu-Ni materials. The simulations were carried out using molecular statics and EAM potentials. The atomistic structure of the interface was studied first for a totally coherent structure. Cracks were simulated near a Griffith condition in different possible configurations of the crack plane and front with respect to the axis of the layers. Results show that interface effects predominantly control the mechanical behavior of the system studied.

  19. Three-dimensional Hybrid Continuum-Atomistic Simulations for Multiscale Hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Wijesinghe, S; Hornung, R; Garcia, A; Hadjiconstantinou, N

    2004-04-15

    We present an adaptive mesh and algorithmic refinement (AMAR) scheme for modeling multi-scale hydrodynamics. The AMAR approach extends standard conservative adaptive mesh refinement (AMR) algorithms by providing a robust flux-based method for coupling an atomistic fluid representation to a continuum model. The atomistic model is applied locally in regions where the continuum description is invalid or inaccurate, such as near strong flow gradients and at fluid interfaces, or when the continuum grid is refined to the molecular scale. The need for such ''hybrid'' methods arises from the fact that hydrodynamics modeled by continuum representations are often under-resolved or inaccurate while solutions generated using molecular resolution globally are not feasible. In the implementation described herein, Direct Simulation Monte Carlo (DSMC) provides an atomistic description of the flow and the compressible two-fluid Euler equations serve as our continuum-scale model. The AMR methodology provides local grid refinement while the algorithm refinement feature allows the transition to DSMC where needed. The continuum and atomistic representations are coupled by matching fluxes at the continuum-atomistic interfaces and by proper averaging and interpolation of data between scales. Our AMAR application code is implemented in C++ and is built upon the SAMRAI (Structured Adaptive Mesh Refinement Application Infrastructure) framework developed at Lawrence Livermore National Laboratory. SAMRAI provides the parallel adaptive gridding algorithm and enables the coupling between the continuum and atomistic methods.

  20. Physically representative atomistic modeling of atomic-scale friction

    Science.gov (United States)

    Dong, Yalin

    Nanotribology is a research field to study friction, adhesion, wear and lubrication occurred between two sliding interfaces at nano scale. This study is motivated by the demanding need of miniaturization mechanical components in Micro Electro Mechanical Systems (MEMS), improvement of durability in magnetic storage system, and other industrial applications. Overcoming tribological failure and finding ways to control friction at small scale have become keys to commercialize MEMS with sliding components as well as to stimulate the technological innovation associated with the development of MEMS. In addition to the industrial applications, such research is also scientifically fascinating because it opens a door to understand macroscopic friction from the most bottom atomic level, and therefore serves as a bridge between science and engineering. This thesis focuses on solid/solid atomic friction and its associated energy dissipation through theoretical analysis, atomistic simulation, transition state theory, and close collaboration with experimentalists. Reduced-order models have many advantages for its simplification and capacity to simulating long-time event. We will apply Prandtl-Tomlinson models and their extensions to interpret dry atomic-scale friction. We begin with the fundamental equations and build on them step-by-step from the simple quasistatic one-spring, one-mass model for predicting transitions between friction regimes to the two-dimensional and multi-atom models for describing the effect of contact area. Theoretical analysis, numerical implementation, and predicted physical phenomena are all discussed. In the process, we demonstrate the significant potential for this approach to yield new fundamental understanding of atomic-scale friction. Atomistic modeling can never be overemphasized in the investigation of atomic friction, in which each single atom could play a significant role, but is hard to be captured experimentally. In atomic friction, the

  1. Artificial Intelligence-based control for torque ripple minimization in switched reluctance motor drives - doi: 10.4025/actascitechnol.v36i1.18097

    Directory of Open Access Journals (Sweden)

    Kalaivani Lakshmanan

    2014-01-01

    Full Text Available In this paper, various intelligent controllers such as Fuzzy Logic Controller (FLC and Adaptive Neuro Fuzzy Inference System (ANFIS-based current compensating techniques are employed for minimizing the torque ripples in switched reluctance motor. FLC and ANFIS controllers are tuned using MATLAB Toolbox. For the purpose of comparison, the performance of conventional Proportional-Integral (PI controller is also considered. The statistical parameters like minimum, maximum, mean, standard deviation of total torque, torque ripple coefficient and the settling time of speed response for various controllers are reported. From the simulation results, it is found that both FLC and ANFIS controllers gives better performance than PI controller. Among the intelligent controllers, ANFIS gives outer performance than FLC due to its good learning and generalization capabilities thereby improves the dynamic performance of SRM drives.

  2. Atomistic modeling of electronic structure and transport in disordered nanostructures

    Science.gov (United States)

    Kharche, Neerav

    As the Si-CMOS technology approaches the end of the International Technology Roadmap for Semiconductors (ITRS), the semiconductor industry faces a formidable challenge to continue the transistor scaling according to Moore's law. To continue the scaling of classical devices, alternative channel materials such as SiGe, carbon nanotubes, nanowires, and III-V based materials are being investigated along with novel 3D device geometries. Researchers are also investigating radically new quantum computing devices, which are expected to perform calculations faster than the existing classical Si-CMOS based structures. Atomic scale disorders such as interface roughness, alloy randomness, non-uniform strain, and dopant fluctuations are routinely present in the experimental realization of such devices. These disorders now play an increasingly important role in determining the electronic structure and transport properties as device sizes enter the nanometer regime. This work employs the atomistic tight-binding technique, which is ideally suited for modeling systems with local disorders on an atomic scale. High-precision multi-million atom electronic structure calculations of (111) Si surface quantum wells and (100) SiGe/Si/SiGe heterostructure quantum wells are performed to investigate the modulation of valley splitting induced by atomic scale disorders. The calculations presented here resolve the existing discrepancies between theoretically predicted and experimentally measured valley splitting, which is an important design parameter in quantum computing devices. Supercell calculations and the zone-unfolding method are used to compute the bandstructures of inhomogeneous nanowires made of AlGaAs and SiGe and their connection with the transmission coefficients computed using non-equilibrium Green's function method is established. A unified picture of alloy nanowires emerges, in which the nanodevice (transmission) and nanomaterials (bandstructure) viewpoints complement each other

  3. Application of Artificial Intelligence for Bridge Deterioration Model.

    Science.gov (United States)

    Chen, Zhang; Wu, Yangyang; Li, Li; Sun, Lijun

    2015-01-01

    The deterministic bridge deterioration model updating problem is well established in bridge management, while the traditional methods and approaches for this problem require manual intervention. An artificial-intelligence-based approach was presented to self-updated parameters of the bridge deterioration model in this paper. When new information and data are collected, a posterior distribution was constructed to describe the integrated result of historical information and the new gained information according to Bayesian theorem, which was used to update model parameters. This AI-based approach is applied to the case of updating parameters of bridge deterioration model, which is the data collected from bridges of 12 districts in Shanghai from 2004 to 2013, and the results showed that it is an accurate, effective, and satisfactory approach to deal with the problem of the parameter updating without manual intervention.

  4. Application of Artificial Intelligence for Bridge Deterioration Model

    Directory of Open Access Journals (Sweden)

    Zhang Chen

    2015-01-01

    Full Text Available The deterministic bridge deterioration model updating problem is well established in bridge management, while the traditional methods and approaches for this problem require manual intervention. An artificial-intelligence-based approach was presented to self-updated parameters of the bridge deterioration model in this paper. When new information and data are collected, a posterior distribution was constructed to describe the integrated result of historical information and the new gained information according to Bayesian theorem, which was used to update model parameters. This AI-based approach is applied to the case of updating parameters of bridge deterioration model, which is the data collected from bridges of 12 districts in Shanghai from 2004 to 2013, and the results showed that it is an accurate, effective, and satisfactory approach to deal with the problem of the parameter updating without manual intervention.

  5. Optimization Algorithms in Optimal Predictions of Atomistic Properties by Kriging.

    Science.gov (United States)

    Di Pasquale, Nicodemo; Davie, Stuart J; Popelier, Paul L A

    2016-04-12

    The machine learning method kriging is an attractive tool to construct next-generation force fields. Kriging can accurately predict atomistic properties, which involves optimization of the so-called concentrated log-likelihood function (i.e., fitness function). The difficulty of this optimization problem quickly escalates in response to an increase in either the number of dimensions of the system considered or the size of the training set. In this article, we demonstrate and compare the use of two search algorithms, namely, particle swarm optimization (PSO) and differential evolution (DE), to rapidly obtain the maximum of this fitness function. The ability of these two algorithms to find a stationary point is assessed by using the first derivative of the fitness function. Finally, the converged position obtained by PSO and DE is refined through the limited-memory Broyden-Fletcher-Goldfarb-Shanno bounded (L-BFGS-B) algorithm, which belongs to the class of quasi-Newton algorithms. We show that both PSO and DE are able to come close to the stationary point, even in high-dimensional problems. They do so in a reasonable amount of time, compared to that with the Newton and quasi-Newton algorithms, regardless of the starting position in the search space of kriging hyperparameters. The refinement through L-BFGS-B is able to give the position of the maximum with whichever precision is desired.

  6. Dislocation climb models from atomistic scheme to dislocation dynamics

    Science.gov (United States)

    Niu, Xiaohua; Luo, Tao; Lu, Jianfeng; Xiang, Yang

    2017-02-01

    We develop a mesoscopic dislocation dynamics model for vacancy-assisted dislocation climb by upscalings from a stochastic model on the atomistic scale. Our models incorporate microscopic mechanisms of (i) bulk diffusion of vacancies, (ii) vacancy exchange dynamics between bulk and dislocation core, (iii) vacancy pipe diffusion along the dislocation core, and (iv) vacancy attachment-detachment kinetics at jogs leading to the motion of jogs. Our mesoscopic model consists of the vacancy bulk diffusion equation and a dislocation climb velocity formula. The effects of these microscopic mechanisms are incorporated by a Robin boundary condition near the dislocations for the bulk diffusion equation and a new contribution in the dislocation climb velocity due to vacancy pipe diffusion driven by the stress variation along the dislocation. Our climb formulation is able to quantitatively describe the translation of prismatic loops at low temperatures when the bulk diffusion is negligible. Using this new formulation, we derive analytical formulas for the climb velocity of a straight edge dislocation and a prismatic circular loop. Our dislocation climb formulation can be implemented in dislocation dynamics simulations to incorporate all the above four microscopic mechanisms of dislocation climb.

  7. Transistor roadmap projection using predictive full-band atomistic modeling

    Energy Technology Data Exchange (ETDEWEB)

    Salmani-Jelodar, M., E-mail: m.salmani@gmail.com; Klimeck, G. [Network for Computational Nanotechnology and School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Kim, S. [Intel Corporation, 2501 Northwest 229th Avenue, Hillsboro, Oregon 97124 (United States); Ng, K. [Semiconductor Research Corporation (SRC), 1101 Slater Rd, Durham, North Carolina 27703 (United States)

    2014-08-25

    In this letter, a full band atomistic quantum transport tool is used to predict the performance of double gate metal-oxide-semiconductor field-effect transistors (MOSFETs) over the next 15 years for International Technology Roadmap for Semiconductors (ITRS). As MOSFET channel lengths scale below 20 nm, the number of atoms in the device cross-sections becomes finite. At this scale, quantum mechanical effects play an important role in determining the device characteristics. These quantum effects can be captured with the quantum transport tool. Critical results show the ON-current degradation as a result of geometry scaling, which is in contrast to previous ITRS compact model calculations. Geometric scaling has significant effects on the ON-current by increasing source-to-drain (S/D) tunneling and altering the electronic band structure. By shortening the device gate length from 20 nm to 5.1 nm, the ratio of S/D tunneling current to the overall subthreshold OFF-current increases from 18% to 98%. Despite this ON-current degradation by scaling, the intrinsic device speed is projected to increase at a rate of at least 8% per year as a result of the reduction of the quantum capacitance.

  8. Scoring multipole electrostatics in condensed-phase atomistic simulations.

    Science.gov (United States)

    Bereau, Tristan; Kramer, Christian; Monnard, Fabien W; Nogueira, Elisa S; Ward, Thomas R; Meuwly, Markus

    2013-05-09

    Permanent multipoles (MTPs) embody a natural extension to common point-charge (PC) representations in atomistic simulations. In this work, we propose an alternative to the computationally expensive MTP molecular dynamics simulations by running a simple PC simulation and later reevaluate-"score''-all energies using the more detailed MTP force field. The method, which relies on the assumption that the PC and MTP force fields generate closely related phase spaces, is accomplished by enforcing identical sets of monopoles between the two force fields-effectively highlighting the higher MTP terms as a correction to the PC approximation. We first detail our consistent parametrization of the electrostatics and van der Waals interactions for the two force fields. We then validate the method by comparing the accuracy of protein-ligand binding free energies from both PC and MTP-scored representations with experimentally determined binding constants obtained by us. Specifically, we study the binding of several arylsulfonamide ligands to human carbonic anhydrase II. We find that both representations yield an accuracy of 1 kcal/mol with respect to experiment. Finally, we apply the method to rank the energetic contributions of individual atomic MTP coefficients for molecules solvated in water. All in all, MTP scoring is a computationally appealing method that can provide insight into the multipolar electrostatic interactions of condensed-phase systems.

  9. Atomistic Simulations of Uranium Incorporation into Iron (Hydr)Oxides

    Energy Technology Data Exchange (ETDEWEB)

    Kerisit, Sebastien N.; Felmy, Andrew R.; Ilton, Eugene S.

    2011-04-29

    Atomistic simulations were carried out to characterize the coordination environments of U incorporated in three Fe-(hydr)oxide minerals: goethite, magnetite, and hematite. The simulations provided information on U-O and U-Fe distances, coordination numbers, and lattice distortion for U incorporated in different sites (e.g., unoccupied versus occupied sites, octahedral versus tetrahedral) as a function of the oxidation state of U and charge compensation mechanisms (i.e., deprotonation, vacancy formation, or reduction of Fe(III) to Fe(II)). For goethite, deprotonation of first shell hydroxyls enables substitution of U for Fe(III) with a minimal amount of lattice distortion, whereas substitution in unoccupied octahedral sites induced appreciable distortion to 7-fold coordination regardless of U oxidation states and charge compensation mechanisms. Importantly, U-Fe distances of ~3.6 Å were associated with structural incorporation of U and cannot be considered diagnostic of simple adsorption to goethite surfaces. For magnetite, the octahedral site accommodates U(V) or U(VI) with little lattice distortion. U substituted for Fe(III) in hematite maintained octahedral coordination in most cases. In general, comparison of the simulations with available experimental data provides further evidence for the structural incorporation of U in iron (hydr)oxide minerals.

  10. Atomistic modeling at experimental strain rates and timescales

    Science.gov (United States)

    Yan, Xin; Cao, Penghui; Tao, Weiwei; Sharma, Pradeep; Park, Harold S.

    2016-12-01

    Modeling physical phenomena with atomistic fidelity and at laboratory timescales is one of the holy grails of computational materials science. Conventional molecular dynamics (MD) simulations enable the elucidation of an astonishing array of phenomena inherent in the mechanical and chemical behavior of materials. However, conventional MD, with our current computational modalities, is incapable of resolving timescales longer than microseconds (at best). In this short review article, we briefly review a recently proposed approach—the so-called autonomous basin climbing (ABC) method—that in certain instances can provide valuable information on slow timescale processes. We provide a general summary of the principles underlying the ABC approach, with emphasis on recent methodological developments enabling the study of mechanically-driven processes at slow (experimental) strain rates and timescales. Specifically, we show that by combining a strong physical understanding of the underlying phenomena, kinetic Monte Carlo, transition state theory and minimum energy pathway methods, the ABC method has been found to be useful in a variety of mechanically-driven problems ranging from the prediction of creep-behavior in metals, constitutive laws for grain boundary sliding, void nucleation rates, diffusion in amorphous materials to protein unfolding. Aside from reviewing the basic ideas underlying this approach, we emphasize some of the key challenges encountered in our own personal research work and suggest future research avenues for exploration.

  11. Atomistic modeling of H absorption in Pd nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ruda, M., E-mail: ruda@cab.cnea.gov.a [Centro Atomico Bariloche, 8400 Bariloche (Argentina); Centro Regional Universitario Bariloche, U.N. Comahue (Argentina); Crespo, E.A., E-mail: crespo@uncoma.edu.a [Depto. de Fisica, Fac. de Ingenieria, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquen (Argentina); Debiaggi, S. Ramos de, E-mail: ramos@uncoma.edu.a [Depto. de Fisica, Fac. de Ingenieria, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquen (Argentina); CONICET (Argentina)

    2010-04-16

    Size affects the properties of absorption of H in Palladium nanoparticles. Because of their higher proportion of surface atoms compared to the bulk, the pressure-composition (P-C) isotherms of the nanoparticles are modified. We performed atomistic simulations for different-sized Pd nanoparticles and for the bulk at different H concentrations using the Monte Carlo technique in the TP{mu}N ensemble to calculate the P-C isotherms. The Pd-H interatomic potentials are of the Embedded Atom (EAM) type and have been recently developed by Zhou et al. . From the related van't Hoff equation we obtained |{Delta}H{sup o}| = (28 {+-} 7) kJ/0.5 mol of H{sub 2} and |{Delta}S{sup o}| = (71 {+-} 19) J/0.5 mol of H{sub 2}.K for the PdH formation in the bulk. For Pd nanoparticles previous simulations results based on a different set of EAM potentials showed that H was absorbed primarily in the surface before diffusing into the inside of small Pd clusters . Considering the better performance of Zhou's potentials for the bulk, in this work we analyzed the evolution of the equilibrium microstructure of Pd nanoparticles as a function of their size and H concentration. Our simulations predict enhanced hydrogen solubilities and vanishing plateaux when compared to the bulk and that H is absorbed in the subsurface of the nanoparticles.

  12. Atomistic modeling of phonon transport in turbostratic graphitic structures

    Science.gov (United States)

    Mao, Rui; Chen, Yifeng; Kim, Ki Wook

    2016-05-01

    Thermal transport in turbostratic graphitic systems is investigated by using an atomistic analytical model based on the 4th-nearest-neighbor force constant approximation and a registry-dependent interlayer potential. The developed model is shown to produce an excellent agreement with the experimental data and ab initio results in the calculation of bulk properties. Subsequent analysis of phonon transport in combination with the Green's function method illustrates the significant dependence of key characteristics on the misorientation angle, clearly indicating the importance of this degree of freedom in multi-stacked structures. Selecting three angles with the smallest commensurate unit cells, the thermal resistance is evaluated at the twisted interface between two AB stacked graphite. The resulting values in the range of 35 × 10-10 K m2/W to 116 × 10-10 K m2/W are as large as those between two dissimilar material systems such as a metal and graphene. The strong rotational effect on the cross-plane thermal transport may offer an effective means of phonon engineering for applications such as thermoelectric materials.

  13. Atomistic simulation of hydrogen dynamics near dislocations in vanadium hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, Hiroshi, E-mail: h.ogawa@aist.go.jp

    2015-10-05

    Highlights: • Hydrogen–dislocation interaction was simulated by molecular dynamics method. • Different distribution of H atoms were observed at edge and screw dislocation. • Planner distribution of hydrogen may be caused by partialized edge dislocation. • Hydrogen diffusivity was reduced in both edge and screw dislocation models. • Pipe diffusion was observed for edge dislocation but not for screw dislocation. - Abstract: Kinetics of interstitial hydrogen atoms near dislocation cores were analyzed by atomistic simulation. Classical molecular dynamics method was applied to model structures of edge and screw dislocations in α-phase vanadium hydride. Simulation showed that hydrogen atoms aggregate near dislocation cores. The spatial distribution of hydrogen has a planner shape at edge dislocation due to dislocation partialization, and a cylindrical shape at screw dislocation. Simulated self-diffusion coefficients of hydrogen atoms in dislocation models were a half- to one-order lower than that of dislocation-free model. Arrhenius plot of self-diffusivity showed slightly different activation energies for edge and screw dislocations. Directional dependency of hydrogen diffusion near dislocation showed high and low diffusivity along edge and screw dislocation lines, respectively, hence so called ‘pipe diffusion’ possibly occur at edge dislocation but does not at screw dislocation.

  14. Atomistic Molecular Dynamics Simulations of Shock Compressed Quartz

    CERN Document Server

    Farrow, Matthew R

    2011-01-01

    Atomistic non-equilibrium molecular dynamics (NEMD) simulations of shock wave compression of quartz have been performed using the so-called BKS semi-empirical potential of van Beest, Kramer and van Santen to construct the Hugoniot of quartz. Our scheme mimics the real world experimental set up by using a flyer-plate impactor to initiate the shock wave and is the first shock wave simulation that uses a geom- etry optimised system of a polar slab in a 3-dimensional system employing periodic boundary conditions. Our scheme also includes the relaxation of the surface dipole in the polar quartz slab which is an essential pre-requisite to a stable simulation. The original BKS potential is unsuited to shock wave calculations and so we propose a simple modification. With this modification, we find that our calculated Hugoniot is in good agreement with experimental shock wave data up to 25 GPa, but significantly diverges beyond this point. We conclude that our modified BKS potential is suitable for quartz under repres...

  15. Trends in Artificial Intelligence.

    Science.gov (United States)

    Hayes, Patrick

    1978-01-01

    Discusses the foundations of artificial intelligence as a science and the types of answers that may be given to the question, "What is intelligence?" The paradigms of artificial intelligence and general systems theory are compared. (Author/VT)

  16. Artificiality in Social Sciences

    OpenAIRE

    Rennard, Jean-Philippe

    2007-01-01

    This text provides with an introduction to the modern approach of artificiality and simulation in social sciences. It presents the relationship between complexity and artificiality, before introducing the field of artificial societies which greatly benefited from the computer power fast increase, gifting social sciences with formalization and experimentation tools previously owned by "hard" sciences alone. It shows that as "a new way of doing social sciences", artificial societies should undo...

  17. Artificial life and Piaget.

    Science.gov (United States)

    Mueller, Ulrich; Grobman, K H.

    2003-04-01

    Artificial life provides important theoretical and methodological tools for the investigation of Piaget's developmental theory. This new method uses artificial neural networks to simulate living phenomena in a computer. A recent study by Parisi and Schlesinger suggests that artificial life might reinvigorate the Piagetian framework. We contrast artificial life with traditional cognitivist approaches, discuss the role of innateness in development, and examine the relation between physiological and psychological explanations of intelligent behaviour.

  18. Peridynamics as a rigorous coarse-graining of atomistics for multiscale materials design.

    Energy Technology Data Exchange (ETDEWEB)

    Lehoucq, Richard B.; Aidun, John Bahram; Silling, Stewart Andrew; Sears, Mark P.; Kamm, James R.; Parks, Michael L.

    2010-09-01

    This report summarizes activities undertaken during FY08-FY10 for the LDRD Peridynamics as a Rigorous Coarse-Graining of Atomistics for Multiscale Materials Design. The goal of our project was to develop a coarse-graining of finite temperature molecular dynamics (MD) that successfully transitions from statistical mechanics to continuum mechanics. The goal of our project is to develop a coarse-graining of finite temperature molecular dynamics (MD) that successfully transitions from statistical mechanics to continuum mechanics. Our coarse-graining overcomes the intrinsic limitation of coupling atomistics with classical continuum mechanics via the FEM (finite element method), SPH (smoothed particle hydrodynamics), or MPM (material point method); namely, that classical continuum mechanics assumes a local force interaction that is incompatible with the nonlocal force model of atomistic methods. Therefore FEM, SPH, and MPM inherit this limitation. This seemingly innocuous dichotomy has far reaching consequences; for example, classical continuum mechanics cannot resolve the short wavelength behavior associated with atomistics. Other consequences include spurious forces, invalid phonon dispersion relationships, and irreconcilable descriptions/treatments of temperature. We propose a statistically based coarse-graining of atomistics via peridynamics and so develop a first of a kind mesoscopic capability to enable consistent, thermodynamically sound, atomistic-to-continuum (AtC) multiscale material simulation. Peridynamics (PD) is a microcontinuum theory that assumes nonlocal forces for describing long-range material interaction. The force interactions occurring at finite distances are naturally accounted for in PD. Moreover, PDs nonlocal force model is entirely consistent with those used by atomistics methods, in stark contrast to classical continuum mechanics. Hence, PD can be employed for mesoscopic phenomena that are beyond the realms of classical continuum mechanics and

  19. Computational intelligence-based polymerase chain reaction primer selection based on a novel teaching-learning-based optimisation.

    Science.gov (United States)

    Cheng, Yu-Huei

    2014-12-01

    Specific primers play an important role in polymerase chain reaction (PCR) experiments, and therefore it is essential to find specific primers of outstanding quality. Unfortunately, many PCR constraints must be simultaneously inspected which makes specific primer selection difficult and time-consuming. This paper introduces a novel computational intelligence-based method, Teaching-Learning-Based Optimisation, to select the specific and feasible primers. The specified PCR product lengths of 150-300 bp and 500-800 bp with three melting temperature formulae of Wallace's formula, Bolton and McCarthy's formula and SantaLucia's formula were performed. The authors calculate optimal frequency to estimate the quality of primer selection based on a total of 500 runs for 50 random nucleotide sequences of 'Homo species' retrieved from the National Center for Biotechnology Information. The method was then fairly compared with the genetic algorithm (GA) and memetic algorithm (MA) for primer selection in the literature. The results show that the method easily found suitable primers corresponding with the setting primer constraints and had preferable performance than the GA and the MA. Furthermore, the method was also compared with the common method Primer3 according to their method type, primers presentation, parameters setting, speed and memory usage. In conclusion, it is an interesting primer selection method and a valuable tool for automatic high-throughput analysis. In the future, the usage of the primers in the wet lab needs to be validated carefully to increase the reliability of the method.

  20. Atomistic study of the buckling of gold nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Olsson, Paer A.T., E-mail: par.olsson@mek.lth.se [Division of Mechanics, Lund University, PO Box 118, SE-221 00 Lund (Sweden); Park, Harold S., E-mail: parkhs@bu.edu [Department of Mechanical Engineering, Boston University, Boston, MA 02215 (United States)

    2011-06-15

    In this work, we present results from atomistic simulations of gold nanowires under axial compression, with a focus on examining the effects of both axial and surface orientation effects on the buckling behavior. This was accomplished by using molecular statics simulations while considering three different crystallographic systems: <1 0 0>/{l_brace}1 0 0{r_brace}, <1 0 0>/{l_brace}1 1 0{r_brace} and <1 1 0>/{l_brace}1 1 0{r_brace}{l_brace}1 0 0{r_brace}, with aspect ratios spanning from 20 to 50 and cross-sectional dimensions ranging from 2.45 to 5.91 nm. The simulations indicate that there is a deviation from the inverse square length dependence of critical forces predicted from traditional linear elastic Bernoulli-Euler and Timoshenko beam theories, where the nature of the deviation from the perfect inverse square length behavior differs for different crystallographic systems. This variation is found to be strongly correlated to either stiffening or increased compliance of the tangential stiffness due to the influence of nonlinear elasticity, which leads to normalized critical forces that decrease with decreasing aspect ratio for the <1 0 0>/{l_brace}1 0 0{r_brace} and <1 0 0>/{l_brace}1 1 0{r_brace} systems, but increase with decreasing aspect ratio for the <1 1 0>/{l_brace}1 1 0{r_brace}{l_brace}1 0 0{r_brace} system. In contrast, it was found that the critical strains are all lower than their bulk counterparts, and that the critical strains decrease with decreasing cross-sectional dimensions; the lower strains may be an effect emanating from the presence of the surfaces, which are all more elastically compliant than the bulk and thus give rise to a more compliant flexural rigidity.

  1. Linking Atomistic and Mesoscale Simulations of Water Soluble Polymers

    Science.gov (United States)

    Jones, J. L.

    2003-03-01

    There exist a range of techniques for studying surfactants and polymers in the mesoscale regime. One of the challenges is to link mesoscale theories and simulations to other calculation methods which address different length scales of the system. We introduce some mesoscale methods of calculation for polymers and surfactants and then present a case study of where mesoscale modelling is used for mechanistic understanding, by linking the method to high throughput in-silico screening methods. We look at the adsorption onto silica of ethylene oxide (EO)/ propylene oxide (PO) block copolymers (lutrols) which have been modified by end-grafting of short, cationic dimethylamino ethyl methacrylate (DMAEMA)chains. Given that the silica surface is negatively charged, it is remarkable that in some circumstances, polymers with longercationic chains have a lower adsorption. The effect is attributed to a competition between strong adsorption of the cationic DMAEMA groups driven by electrostatics, and weaker adsorption of the more numerous EO groups. This then raises the question of how we produce the values for the mesoscale parameters in these models and in the second part of the talk we describe a calculation method for doing this for water soluble polymers. The most promising route, but notoriously costly, is based on free energy calculations at the atomistic level. Free energy calculations are computationally intensive in general, but in an aqueous system one is also faced with the additional problem of using complex continuum models and/or accurate interaction potentials for water. Here we show how potential of mean force (PMF)calculations offer a practical alternative which avoids these drawbacks, though one is still faced with extremely long simulations.

  2. Megasonic cleaning, cavitation, and substrate damage: an atomistic approach

    Science.gov (United States)

    Kapila, Vivek; Deymier, Pierre A.; Shende, Hrishikesh; Pandit, Viraj; Raghavan, Srini; Eschbach, Florence O.

    2006-05-01

    Megasonic cleaning has been a traditional approach for the cleaning of photomasks. Its feasibility as a damage free approach to sub 50 nm particulate removal is under investigation for the cleaning of optical and EUV photomasks. Two major mechanisms are active in a megasonic system, namely, acoustic streaming and acoustic cavitation. Acoustic streaming is instrumental in contaminant removal via application of drag force and rolling of particles, while cavitation may dislodge particles by the release of large energy during cavity implosion or by acting as a secondary source of microstreaming. Often times, the structures (substrates with or without patterns) subjected to megasonic cleaning show evidence of damage. This is one of the impediments in the implementation of megasonic technology for 45 nm and future technology nodes. Prior work suggests that acoustic streaming does not lead to sufficiently strong forces to cause damage to the substrates or patterns. However, current knowledge of the effects of cavitation on cleaning and damage can be described, at best, as speculative. Recent experiments suggest existence of a cavity size and energy distributions in megasonic systems that may be responsible for cleaning and damage. In the current work, we develop a two-dimensional atomistic model to study such multibubble cavitation phenomena. The model consists of a Lennard-Jones liquid which is subjected to sinusoidal pressure changes leading to the formation of cavitation bubbles. The current work reports on the effects of pressure amplitude (megasonic power) and frequency on cavity size distributions in vaporous and gaseous cavitation. The findings of the work highlight the role of multibubble cavitation as cleaning and damage mechanism in megasonic cleaning.

  3. A fully atomistic model of the Cx32 connexon.

    Directory of Open Access Journals (Sweden)

    Sergio Pantano

    Full Text Available Connexins are plasma membrane proteins that associate in hexameric complexes to form channels named connexons. Two connexons in neighboring cells may dock to form a "gap junction" channel, i.e. an intercellular conduit that permits the direct exchange of solutes between the cytoplasm of adjacent cells and thus mediate cell-cell ion and metabolic signaling. The lack of high resolution data for connexon structures has hampered so far the study of the structure-function relationships that link molecular effects of disease-causing mutations with their observed phenotypes. Here we present a combination of modeling techniques and molecular dynamics (MD to infer side chain positions starting from low resolution structures containing only C alpha atoms. We validated this procedure on the structure of the KcsA potassium channel, which is solved at atomic resolution. We then produced a fully atomistic model of a homotypic Cx32 connexon starting from a published model of the C alpha carbons arrangement for the connexin transmembrane helices, to which we added extracellular and cytoplasmic loops. To achieve structural relaxation within a realistic environment, we used MD simulations inserted in an explicit solvent-membrane context and we subsequently checked predictions of putative side chain positions and interactions in the Cx32 connexon against a vast body of experimental reports. Our results provide new mechanistic insights into the effects of numerous spontaneous mutations and their implication in connexin-related pathologies. This model constitutes a step forward towards a structurally detailed description of the gap junction architecture and provides a structural platform to plan new biochemical and biophysical experiments aimed at elucidating the structure of connexin channels and hemichannels.

  4. Mechanics of low-dimensional carbon nanostructures: Atomistic, continuum, and multi-scale approaches

    Science.gov (United States)

    Mahdavi, Arash

    A new multiscale modeling technique called the Consistent Atomic-scale Finite Element (CAFE) method is introduced. Unlike traditional approaches for linking the atomic structure to its equivalent continuum, this method directly connects the atomic degrees of freedom to a reduced set of finite element degrees of freedom without passing through an intermediate homogenized continuum. As a result, there is no need to introduce stress and strain measures at the atomic level. The Tersoff-Brenner interatomic potential is used to calculate the consistent tangent stiffness matrix of the structure. In this finite element formulation, all local and non-local interactions between carbon atoms are taken into account using overlapping finite elements. In addition, a consistent hierarchical finite element modeling technique is developed for adaptively coarsening and refining the mesh over different parts of the model. This process is consistent with the underlying atomic structure and, by refining the mesh to the scale of atomic spacing, molecular dynamic results can be recovered. This method is valid across the scales and can be used to concurrently model atomistic and continuum phenomena so, in contrast with most other multi-scale methods, there is no need to introduce artificial boundaries for coupling atomistic and continuum regions. Effect of the length scale of the nanostructure is also included in the model by building the hierarchy of elements from bottom up using a finite size atom cluster as the building block. To be consistent with the bravais multi-lattice structure of sp2-bonded carbon, two independent displacement fields are used for reducing the order of the model. Sparse structure of the stiffness matrix of these nanostructures is exploited to reduce the memory requirement and to speed up the formation of the system matrices and solution of the equilibrium equations. Applicability of the method is shown with several examples of the nonlinear mechanics of carbon

  5. Nonadiabatic Dynamics in Atomistic Environments: Harnessing Quantum-Classical Theory with Generalized Quantum Master Equations.

    Science.gov (United States)

    Pfalzgraff, William C; Kelly, Aaron; Markland, Thomas E

    2015-12-03

    The development of methods that can efficiently and accurately treat nonadiabatic dynamics in quantum systems coupled to arbitrary atomistic environments remains a significant challenge in problems ranging from exciton transport in photovoltaic materials to electron and proton transfer in catalysis. Here we show that our recently introduced MF-GQME approach, which combines Ehrenfest mean field theory with the generalized quantum master equation framework, is able to yield quantitative accuracy over a wide range of charge-transfer regimes in fully atomistic environments. This is accompanied by computational speed-ups of up to 3 orders of magnitude over a direct application of Ehrenfest theory. This development offers the opportunity to efficiently investigate the atomistic details of nonadiabatic quantum relaxation processes in regimes where obtaining accurate results has previously been elusive.

  6. Accelerating a hybrid continuum-atomistic fluidic model with on-the-fly machine learning

    CERN Document Server

    Stephenson, David; Lockerby, Duncan A

    2016-01-01

    We present a hybrid continuum-atomistic scheme which combines molecular dynamics (MD) simulations with on-the-fly machine learning techniques for the accurate and efficient prediction of multiscale fluidic systems. By using a Gaussian process as a surrogate model for the computationally expensive MD simulations, we use Bayesian inference to predict the system behaviour at the atomistic scale, purely by consideration of the macroscopic inputs and outputs. Whenever the uncertainty of this prediction is greater than a predetermined acceptable threshold, a new MD simulation is performed to continually augment the database, which is never required to be complete. This provides a substantial enhancement to the current generation of hybrid methods, which often require many similar atomistic simulations to be performed, discarding information after it is used once. We apply our hybrid scheme to nano-confined unsteady flow through a high-aspect-ratio converging-diverging channel, and make comparisons between the new s...

  7. Local stress and heat flux in atomistic systems involving three-body forces.

    Science.gov (United States)

    Chen, Youping

    2006-02-01

    Local densities of fundamental physical quantities, including stress and heat flux fields, are formulated for atomistic systems involving three-body forces. The obtained formulas are calculable within an atomistic simulation, in consistent with the conservation equations of thermodynamics of continuum, and can be applied to systems with general two- and three-body interaction forces. It is hoped that this work may correct some misuse of inappropriate formulas of stress and heat flux in the literature, may clarify the definition of site energy of many-body potentials, and may serve as an analytical link between an atomistic model and a continuum theory. Physical meanings of the obtained formulas, their relation with virial theorem and heat theorem, and the applicability are discussed.

  8. An atomistic modelling of the porosity impact on UO{sub 2} matrix macroscopic properties

    Energy Technology Data Exchange (ETDEWEB)

    Jelea, A., E-mail: andrei.jelea@irsn.fr [Institut de Radioprotection et de Surete Nucleaire (IRSN), DPAM, SEMCA, LEC, Cadarache (France); Centre Interdisciplinaire des Nanosciences de Marseille, CNRS, Campus de Luminy, Marseille 13288 (France); Institute of Physical Chemistry Ilie Murgulescu, Romanian Academy, 202 Spl Independentei St., 060021 Bucharest-12 (Romania); Colbert, M. [Institut de Radioprotection et de Surete Nucleaire (IRSN), DPAM, SEMCA, LEC, Cadarache (France); Centre Interdisciplinaire des Nanosciences de Marseille, CNRS, Campus de Luminy, Marseille 13288 (France); Ribeiro, F. [Institut de Radioprotection et de Surete Nucleaire (IRSN), DPAM, SEMCA, LEC, Cadarache (France); Treglia, G. [Centre Interdisciplinaire des Nanosciences de Marseille, CNRS, Campus de Luminy, Marseille 13288 (France); Pellenq, R.J.-M. [Centre Interdisciplinaire des Nanosciences de Marseille, CNRS, Campus de Luminy, Marseille 13288 (France); Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

    2011-08-15

    Highlights: > The porosity impact on the UO{sub 2} matrix thermomechanical properties was investigated. > Atomistic simulation techniques were used in this study. > The UO{sub 2} thermal expansion coefficient is modified due to the pore surface effects. > The elastic moduli at 0 K and at finite temperature decrease linearly with porosity. - Abstract: The porosity impact on the UO{sub 2} matrix thermomechanical properties was investigated using atomistic simulation techniques. The porosity modifies the thermal expansion coefficient and this is attributed to pore surface effects. The elastic moduli at 0 K and at finite temperature decrease with porosity, this variation being well approximated using affine functions. These results agree with other mesoscale model predictions and experimental data, showing the ability of the semiempirical potential atomistic simulations to give an overall good description of the porous UO{sub 2}. However, the surface effects are incompletely described.

  9. Atomistic simulation of nanoporous layered double hydroxide materials and their properties. I. Structural modeling

    Science.gov (United States)

    Kim, Nayong; Kim, Yongman; Tsotsis, Theodore T.; Sahimi, Muhammad

    2005-06-01

    An atomistic model of layered double hydroxides, an important class of nanoporous materials, is presented. These materials have wide applications, ranging from adsorbents for gases and liquid ions to nanoporous membranes and catalysts. They consist of two types of metallic cations that are accommodated by a close-packed configuration of OH- and other anions in a positively charged brucitelike layer. Water and various anions are distributed in the interlayer space for charge compensation. A modified form of the consistent-valence force field, together with energy minimization and molecular dynamics simulations, is utilized for developing an atomistic model of the materials. To test the accuracy of the model, we compare the vibrational frequencies, x-ray diffraction patterns, and the basal spacing of the material, computed using the atomistic model, with our experimental data over a wide range of temperature. Good agreement is found between the computed and measured quantities.

  10. Origin of unrealistic blunting during atomistic fracture simulations based on MEAM potentials

    Science.gov (United States)

    Ko, Won-Seok; Lee, Byeong-Joo

    2014-06-01

    Atomistic simulations based on interatomic potentials have frequently failed to correctly reproduce the brittle fracture of materials, showing an unrealistic blunting. We analyse the origin of the unrealistic blunting during atomistic simulations by modified embedded-atom method (MEAM) potentials for experimentally well-known brittle materials such as bcc tungsten and diamond silicon. The radial cut-off which has been thought to give no influence on MEAM calculations is found to have a decisive effect on the crack propagation behaviour. Extending both cut-off distance and truncation range can prevent the unrealistic blunting, reproducing many well-known fracture behaviour which have been difficult to reproduce. The result provides a guideline for future atomistic simulations that focus on various fracture-related phenomena including the failure of metallic-covalent bonding material systems using MEAM potentials.

  11. Reducing Energy Waste in Post-secondary Educational Institutions using Artificial Intelligence

    Science.gov (United States)

    Motta Cabrera, David Francisco

    This thesis focuses on computer-related and lighting energy consumption in post-secondary educational institutions. In this respect, artificial intelligence and data association mining are proposed as tools to identify and reduce energy waste. First, an artificial intelligence-based method for forecasting computer usage is proposed. Based on the models' forecast, workstations can be turned on and off, in order to strike a balance between energy savings and user comfort. The models are evaluated on different datasets and their results compared to commercially available alternatives. Second, a data association mining-based approach is proposed to uncover possible relationships between occupancy patterns and lighting-related energy waste in classrooms. A wireless data collection system is used to log data from both lighting consumption and occupancy states during a year. Next, energy savings results of using the proposed approach are compared to those of an occupancy-activated lighting control system for classrooms.

  12. Analysis of Twisting of Cellulose Nanofibrils in Atomistic Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Paavilainen, S.; Rog, T.; Vattulainen, I.

    2011-01-01

    We use atomistic molecular dynamics simulations to study the crystal structure of cellulose nanofibrils, whose sizes are comparable with the crystalline parts in commercial nanocellulose. The simulations show twisting, whose rate of relaxation is strongly temperature dependent. Meanwhile, no sign......We use atomistic molecular dynamics simulations to study the crystal structure of cellulose nanofibrils, whose sizes are comparable with the crystalline parts in commercial nanocellulose. The simulations show twisting, whose rate of relaxation is strongly temperature dependent. Meanwhile......, no significant bending or stretching of nanocellulose is discovered. Considerations of atomic-scale interaction patterns bring about that the twisting arises from hydrogen bonding within and between the chains in a fibril....

  13. Hypercrosslinked polystyrene networks: An atomistic molecular dynamics simulation combined with a mapping/reverse mapping procedure

    Energy Technology Data Exchange (ETDEWEB)

    Lazutin, A. A.; Glagolev, M. K.; Vasilevskaya, V. V.; Khokhlov, A. R. [A. N. Nesmeyanov Institute of Organoelement Compounds RAS, Vavilova Str. 28, 119991 Moscow (Russian Federation)

    2014-04-07

    An algorithm involving classical molecular dynamics simulations with mapping and reverse mapping procedure is here suggested to simulate the crosslinking of the polystyrene dissolved in dichloroethane by monochlorodimethyl ether. The algorithm comprises consecutive stages: molecular dynamics atomistic simulation of a polystyrene solution, the mapping of atomistic structure onto coarse-grained model, the crosslink formation, the reverse mapping, and finally relaxation of the structure dissolved in dichloroethane and in dry state. The calculated values of the specific volume and the elastic modulus are in reasonable quantitative correspondence with experimental data.

  14. Scalable and portable visualization of large atomistic datasets

    Science.gov (United States)

    Sharma, Ashish; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

    2004-10-01

    A scalable and portable code named Atomsviewer has been developed to interactively visualize a large atomistic dataset consisting of up to a billion atoms. The code uses a hierarchical view frustum-culling algorithm based on the octree data structure to efficiently remove atoms outside of the user's field-of-view. Probabilistic and depth-based occlusion-culling algorithms then select atoms, which have a high probability of being visible. Finally a multiresolution algorithm is used to render the selected subset of visible atoms at varying levels of detail. Atomsviewer is written in C++ and OpenGL, and it has been tested on a number of architectures including Windows, Macintosh, and SGI. Atomsviewer has been used to visualize tens of millions of atoms on a standard desktop computer and, in its parallel version, up to a billion atoms. Program summaryTitle of program: Atomsviewer Catalogue identifier: ADUM Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUM Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer for which the program is designed and others on which it has been tested: 2.4 GHz Pentium 4/Xeon processor, professional graphics card; Apple G4 (867 MHz)/G5, professional graphics card Operating systems under which the program has been tested: Windows 2000/XP, Mac OS 10.2/10.3, SGI IRIX 6.5 Programming languages used: C++, C and OpenGL Memory required to execute with typical data: 1 gigabyte of RAM High speed storage required: 60 gigabytes No. of lines in the distributed program including test data, etc.: 550 241 No. of bytes in the distributed program including test data, etc.: 6 258 245 Number of bits in a word: Arbitrary Number of processors used: 1 Has the code been vectorized or parallelized: No Distribution format: tar gzip file Nature of physical problem: Scientific visualization of atomic systems Method of solution: Rendering of atoms using computer graphic techniques, culling algorithms for data

  15. Atomistic Simulation of Non-Equilibrium Phenomena in Hypersonic Flows

    Science.gov (United States)

    Norman, Paul Erik

    The goal of this work is to model the heterogeneous recombination of atomic oxygen on silica surfaces, which is of interest for accurately predicting the heating on vehicles traveling at hypersonic speeds. This is accomplished by creating a finite rate catalytic model, which describes recombination with a set of elementary gas-surface reactions. Fundamental to a description of surface catalytic reactions are the in situ chemical structures on the surface where recombination can occur. Using molecular dynamics simulations with the Reax GSISiO potential, we find that the chemical sites active in direct gas-phase reactions on silica surfaces consist of a small number of specific structures (or defects). The existence of these defects on real silica surfaces is supported by experimental results and the structure and energetics of these defects have been verified with quantum chemical calculations. The reactions in the finite rate catalytic model are based on the interaction of molecular and atomic oxygen with these defects. Trajectory calculations are used to find the parameters in the forward rate equations, while a combination of detailed balance and transition state theory are used to find the parameters in the reverse rate equations. The rate model predicts that the oxygen recombination coefficient is relatively constant at T (300-1000 K), in agreement with experimental results. At T > 1000 K the rate model predicts a drop off in the oxygen recombination coefficient, in disagreement with experimental results, which predict that the oxygen recombination coefficient increases with temperature. A discussion of the possible reasons for this disagreement, including non-adiabatic collision dynamics, variable surface site concentrations, and additional recombination mechanisms is presented. This thesis also describes atomistic simulations with Classical Trajectory Calculation Direction Simulation Monte Carlo (CTC-DSMC), a particle based method for modeling non

  16. Atomistic Method Applied to Computational Modeling of Surface Alloys

    Science.gov (United States)

    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

  17. Artificial cognition architectures

    CERN Document Server

    Crowder, James A; Friess, Shelli A

    2013-01-01

    The goal of this book is to establish the foundation, principles, theory, and concepts that are the backbone of real, autonomous Artificial Intelligence. Presented here are some basic human intelligence concepts framed for Artificial Intelligence systems. These include concepts like Metacognition and Metamemory, along with architectural constructs for Artificial Intelligence versions of human brain functions like the prefrontal cortex. Also presented are possible hardware and software architectures that lend themselves to learning, reasoning, and self-evolution

  18. Atomistic simulation of laser ablation of gold : Effect of pressure relaxation

    NARCIS (Netherlands)

    Norman, G. E.; Starikov, S. V.; Stegailov, V. V.

    2012-01-01

    The process of ablation of a gold target by femto- and picosecond laser radiation pulses has been studied by numerical simulations using an atomistic model with allowance for the electron subsystem and the dependence of the ion-ion interaction potential on the electron temperature. Using this potent

  19. Software News and Update Reconstruction of Atomistic Details from Coarse-Grained Structures

    NARCIS (Netherlands)

    Rzepiela, Andrzej J.; Schafer, Lars V.; Goga, Nicolae; Risselada, H. Jelger; De Vries, Alex H.; Marrink, Siewert J.

    2010-01-01

    We present an algorithm to reconstruct atomistic structures from their corresponding coarse-grained (CG) representations and its implementation into the freely available molecular dynamics (MD) program package GROMACS. The central part of the algorithm is a simulated annealing MD simulation in which

  20. A Mathematical Analysis of Atomistic-to-Continuum (AtC) Multiscale Coupling Methods

    Energy Technology Data Exchange (ETDEWEB)

    Gunzburger, Max

    2013-11-13

    We have worked on several projects aimed at improving the efficiency and understanding of multiscale methods, especially those applicable to problems involving atomistic-to-continuum coupling. Activities include blending methods for AtC coupling and efficient quasi-continuum methods for problems with long-range interactions.

  1. Atomistic study on the FCC/BCC interface structure with {112}KS orientation

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Keonwook [Los Alamos National Laboratory; Beyerlein, Irene [Los Alamos National Laboratory

    2011-09-23

    In this study, atomistic simulation is used to explore the atomic interface structure, the intrinsic defect network, and mechanism of twin formation from the {112}KS Cu-Nb interface. The interface structure of different material systems AI-Fe and AI-Nb are also compared with Cu-Nb interface.

  2. Hybrid simulations : combining atomistic and coarse-grained force fields using virtual sites

    NARCIS (Netherlands)

    Rzepiela, Andrzej J.; Louhivuori, Martti; Peter, Christine; Marrink, Siewert J.

    2011-01-01

    Hybrid simulations, in which part of the system is represented at atomic resolution and the remaining part at a reduced, coarse-grained, level offer a powerful way to combine the accuracy associated with the atomistic force fields to the sampling speed obtained with coarse-grained (CG) potentials. I

  3. Artificial life and life artificialization in Tron

    Directory of Open Access Journals (Sweden)

    Carolina Dantas Figueiredo

    2012-12-01

    Full Text Available Cinema constantly shows the struggle between the men and artificial intelligences. Fiction, and more specifically fiction films, lends itself to explore possibilities asking “what if?”. “What if”, in this case, is related to the eventual rebellion of artificial intelligences, theme explored in the movies Tron (1982 and Tron Legacy (2010 trat portray the conflict between programs and users. The present paper examines these films, observing particularly the possibility programs empowering. Finally, is briefly mentioned the concept of cyborg as a possibility of response to human concerns.

  4. Analysis of Boundary Conditions for Crystal Defect Atomistic Simulations

    Science.gov (United States)

    Ehrlacher, V.; Ortner, C.; Shapeev, A. V.

    2016-12-01

    Numerical simulations of crystal defects are necessarily restricted to finite computational domains, supplying artificial boundary conditions that emulate the effect of embedding the defect in an effectively infinite crystalline environment. This work develops a rigorous framework within which the accuracy of different types of boundary conditions can be precisely assessed. We formulate the equilibration of crystal defects as variational problems in a discrete energy space and establish qualitatively sharp regularity estimates for minimisers. Using this foundation we then present rigorous error estimates for (i) a truncation method (Dirichlet boundary conditions), (ii) periodic boundary conditions, (iii) boundary conditions from linear elasticity, and (iv) boundary conditions from nonlinear elasticity. Numerical results confirm the sharpness of the analysis.

  5. Onion artificial muscles

    Science.gov (United States)

    Chen, Chien-Chun; Shih, Wen-Pin; Chang, Pei-Zen; Lai, Hsi-Mei; Chang, Shing-Yun; Huang, Pin-Chun; Jeng, Huai-An

    2015-05-01

    Artificial muscles are soft actuators with the capability of either bending or contraction/elongation subjected to external stimulation. However, there are currently no artificial muscles that can accomplish these actions simultaneously. We found that the single layered, latticed microstructure of onion epidermal cells after acid treatment became elastic and could simultaneously stretch and bend when an electric field was applied. By modulating the magnitude of the voltage, the artificial muscle made of onion epidermal cells would deflect in opposing directions while either contracting or elongating. At voltages of 0-50 V, the artificial muscle elongated and had a maximum deflection of -30 μm; at voltages of 50-1000 V, the artificial muscle contracted and deflected 1.0 mm. The maximum force response is 20 μN at 1000 V.

  6. Understanding materials behavior from atomistic simulations: Case study of al-containing high entropy alloys and thermally grown aluminum oxide

    Science.gov (United States)

    Yinkai Lei

    Atomistic simulation refers to a set of simulation methods that model the materials on the atomistic scale. These simulation methods are faster and cheaper alternative approaches to investigate thermodynamics and kinetics of materials compared to experiments. In this dissertation, atomistic simulation methods have been used to study the thermodynamic and kinetic properties of two material systems, i.e. the entropy of Al-containing high entropy alloys (HEAs) and the vacancy migration energy of thermally grown aluminum oxide. (Abstract shortened by ProQuest.).

  7. Artificial intelligence in medicine.

    Science.gov (United States)

    Ramesh, A. N.; Kambhampati, C.; Monson, J. R. T.; Drew, P. J.

    2004-01-01

    INTRODUCTION: Artificial intelligence is a branch of computer science capable of analysing complex medical data. Their potential to exploit meaningful relationship with in a data set can be used in the diagnosis, treatment and predicting outcome in many clinical scenarios. METHODS: Medline and internet searches were carried out using the keywords 'artificial intelligence' and 'neural networks (computer)'. Further references were obtained by cross-referencing from key articles. An overview of different artificial intelligent techniques is presented in this paper along with the review of important clinical applications. RESULTS: The proficiency of artificial intelligent techniques has been explored in almost every field of medicine. Artificial neural network was the most commonly used analytical tool whilst other artificial intelligent techniques such as fuzzy expert systems, evolutionary computation and hybrid intelligent systems have all been used in different clinical settings. DISCUSSION: Artificial intelligence techniques have the potential to be applied in almost every field of medicine. There is need for further clinical trials which are appropriately designed before these emergent techniques find application in the real clinical setting. PMID:15333167

  8. Coupling-of-length-scale approach for multiscale atomistic-continuum simulations: Atomistically-induced stress distributions in Si/Si_3N4 nanopixels

    Science.gov (United States)

    Lidorikis, Elefterios; Bachlechner, Martina E.; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya; Voyiadjis, George; Madhukar, Anupam

    2001-03-01

    A hybrid molecular-dynamics and finite-element simulation approach has been used to investigate stress distributions in Si(111) nanopixels covered with both crystalline and amorphous Si_3N4 thin films. Surfaces, lattice-mismatched interfaces, edges, and corners create stress fields on the order of 1 GPa inside the Si substrate with patterns that cannot be reproduced by a continuum approach alone. For these atomistically-induced inhomogeneouse stresses, the hybrid simulation approach provides an excellent agreement with the standard molecular dynamics, with considerably less computational costs.

  9. Coupling Length Scales for Multiscale Atomistics-Continuum Simulations: Atomistically Induced Stress Distributions in Si/Si3N4 Nanopixels

    Science.gov (United States)

    Lidorikis, Elefterios; Bachlechner, Martina E.; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya; Voyiadjis, George Z.

    2001-08-01

    A hybrid molecular-dynamics (MD) and finite-element simulation approach is used to study stress distributions in silicon/silicon-nitride nanopixels. The hybrid approach provides atomistic description near the interface and continuum description deep into the substrate, increasing the accessible length scales and greatly reducing the computational cost. The results of the hybrid simulation are in good agreement with full multimillion-atom MD simulations: atomic structures at the lattice-mismatched interface between amorphous silicon nitride and silicon induce inhomogeneous stress patterns in the substrate that cannot be reproduced by a continuum approach alone.

  10. Artificial Neural Networks

    OpenAIRE

    Chung-Ming Kuan

    2006-01-01

    Artificial neural networks (ANNs) constitute a class of flexible nonlinear models designed to mimic biological neural systems. In this entry, we introduce ANN using familiar econometric terminology and provide an overview of ANN modeling approach and its implementation methods.

  11. Introduction to artificial intelligence

    Science.gov (United States)

    Cheeseman, P.; Gevarter, W.

    1986-01-01

    This paper presents an introductory view of Artificial Intelligence (AI). In addition to defining AI, it discusses the foundations on which it rests, research in the field, and current and potential applications.

  12. Principles of artificial intelligence

    CERN Document Server

    Nilsson, Nils J

    1980-01-01

    A classic introduction to artificial intelligence intended to bridge the gap between theory and practice, Principles of Artificial Intelligence describes fundamental AI ideas that underlie applications such as natural language processing, automatic programming, robotics, machine vision, automatic theorem proving, and intelligent data retrieval. Rather than focusing on the subject matter of the applications, the book is organized around general computational concepts involving the kinds of data structures used, the types of operations performed on the data structures, and the properties of th

  13. Physics of Artificial Gravity

    Science.gov (United States)

    Bukley, Angie; Paloski, William; Clement, Gilles

    2006-01-01

    This chapter discusses potential technologies for achieving artificial gravity in a space vehicle. We begin with a series of definitions and a general description of the rotational dynamics behind the forces ultimately exerted on the human body during centrifugation, such as gravity level, gravity gradient, and Coriolis force. Human factors considerations and comfort limits associated with a rotating environment are then discussed. Finally, engineering options for designing space vehicles with artificial gravity are presented.

  14. Symmetry Breaking and Fine Structure Splitting in Zincblende Quantum Dots: Atomistic Simulations of Long-Range Strain and Piezoelectric Field

    Science.gov (United States)

    Ahmed, Shaikh; Usman, Muhammad; Heitzinger, Clemens; Rahman, Rajib; Schliwa, Andrei; Klimeck, Gerhard

    2007-04-01

    Electrons and holes captured in self-assembled quantum dots (QDs) are subject to symmetry breaking that cannot be represented in with continuum material representations. Atomistic calculations reveal symmetry lowering due to effects of strain and piezo-electric fields. These effects are fundamentally based on the crystal topology in the quantum dots. This work studies these two competing effects and demonstrates the fine structure splitting that has been demonstrated experimentally can be attributed to the underlying atomistic structure of the quantum dots.

  15. Heidegger and artificial intelligence

    Energy Technology Data Exchange (ETDEWEB)

    Diaz, G.

    1987-01-01

    The discipline of Artificial Intelligence, in its quest for machine intelligence, showed great promise as long as its areas of application were limited to problems of a scientific and situation neutral nature. The attempts to move beyond these problems to a full simulation of man's intelligence has faltered and slowed it progress, largely because of the inability of Artificial Intelligence to deal with human characteristic, such as feelings, goals, and desires. This dissertation takes the position that an impasse has resulted because Artificial Intelligence has never been properly defined as a science: its objects and methods have never been identified. The following study undertakes to provide such a definition, i.e., the required ground for Artificial Intelligence. The procedure and methods employed in this study are based on Heidegger's philosophy and techniques of analysis as developed in Being and Time. Results of this study show that both the discipline of Artificial Intelligence and the concerns of Heidegger in Being and Time have the same object; fundamental ontology. The application of Heidegger's conclusions concerning fundamental ontology unites the various aspects of Artificial Intelligence and provides the articulation which shows the parts of this discipline and how they are related.

  16. The Concept Mastery in the Perspective of Gender of Junior High School Students on Eclipse Theme in Multiple Intelligences-based of Integrated Earth and Space Science Learning

    Science.gov (United States)

    Liliawati, W.; Utama, J. A.; Mursydah, L. S.

    2017-03-01

    The purpose of this study is to identify gender-based concept mastery differences of junior high school students after the implementation of multiple intelligences-based integrated earth and space science learning. Pretest-posttest group design was employed to two different classes at one of junior high school on eclipse theme in Tasikmalaya West Java: one class for boys (14 students) and one class of girls (18 students). The two-class received same treatment. The instrument of concepts mastery used in this study was open-ended eight essay questions. Reliability test result of this instrument was 0.9 (category: high) while for validity test results were high and very high category. We used instruments of multiple intelligences identification and learning activity observation sheet for our analysis. The results showed that normalized N-gain of concept mastery for boys and girls were improved, respectively 0.39 and 0.65. Concept mastery for both classes differs significantly. The dominant multiple intelligences for boys were in kinesthetic while girls dominated in the rest of multiple intelligences. Therefor we concluded that the concept mastery was influenced by gender and student’s multiple intelligences. Based on this finding we suggested to considering the factor of gender and students’ multiple intelligences given in the learning activity.

  17. Nanoscale finite element models for vibrations of single-walled carbon nanotubes:atomistic versus continuum

    Institute of Scientific and Technical Information of China (English)

    R ANSARI; S ROUHI; M ARYAYI

    2013-01-01

    By the atomistic and continuum finite element models, the free vibration behavior of single-walled carbon nanotubes (SWCNTs) is studied. In the atomistic finite element model, the bonds and atoms are modeled by the beam and point mass elements, respectively. The molecular mechanics is linked to structural mechanics to determine the elastic properties of the mentioned beam elements. In the continuum finite element approach, by neglecting the discrete nature of the atomic structure of the nanotubes, they are modeled with shell elements. By both models, the natural frequencies of SWCNTs are computed, and the effects of the geometrical parameters, the atomic structure, and the boundary conditions are investigated. The accuracy of the utilized methods is verified in comparison with molecular dynamic simulations. The molecular structural model leads to more reliable results, especially for lower aspect ratios. The present analysis provides valuable information about application of continuum models in the investigation of the mechanical behaviors of nanotubes.

  18. Systematic study of grain boundary atomistic structures and related properties in cubic zirconia bicrystals

    Energy Technology Data Exchange (ETDEWEB)

    Shibata, N.; Ikuhara, Y. [Inst. of Engineering Innovation, Univ. of Tokyo, Tokyo (Japan); Oba, F. [Dept. of Materials Science and Engineering, Graduate School of Engineering, Kyoto Univ., Kyoto (Japan); Yamamoto, T. [Dept. of Advanced Materials Science, Graduate School of Frontier Science, Univ. of Tokyo, Kashiwa, Chiba (Japan)

    2005-02-01

    Systematic grain boundary study of cubic zirconia has been conducted by using bicrystals. It is clearly demonstrated that grain boundary atomistic structures dramatically change according to the misorientations and plane orientations of the boundaries, resulting in a dramatic change of excess energies and solute segregation behaviors. Combining with theoretical calculations, it is found that grain boundaries possess unique coordination-deficient cation sites at the cores, and their densities have a clear correlation with these properties in high-angle grain boundaries. This result indicates that grain boundary properties in ceramics are possibly determined by the accumulation of coordination-deficient sites. Thus, systematic grain boundary study using bicrystal offers fundamental understandings of the relationship between atomistic structures and properties in ceramic grain boundaries. (orig.)

  19. Atomistic electrodynamics simulations of bare and ligand-coated nanoparticles in the quantum size regime.

    Science.gov (United States)

    Chen, Xing; Moore, Justin E; Zekarias, Meserret; Jensen, Lasse

    2015-11-10

    The optical properties of metallic nanoparticles with nanometre dimensions exhibit features that cannot be described by classical electrodynamics. In this quantum size regime, the near-field properties are significantly modified and depend strongly on the geometric arrangements. However, simulating realistically sized systems while retaining the atomistic description remains computationally intractable for fully quantum mechanical approaches. Here we introduce an atomistic electrodynamics model where the traditional description of nanoparticles in terms of a macroscopic homogenous dielectric constant is replaced by an atomic representation with dielectric properties that depend on the local chemical environment. This model provides a unified description of bare and ligand-coated nanoparticles, as well as strongly interacting nanoparticle dimer systems. The non-local screening owing to an inhomogeneous ligand layer is shown to drastically modify the near-field properties. This will be important to consider in optimization of plasmonic nanostructures for near-field spectroscopy and sensing applications.

  20. Atomistic simulation of grain boundary structure in a series of B2 intermetallics

    Energy Technology Data Exchange (ETDEWEB)

    Mutasa, B. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Engineering; Farkas, D. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Engineering

    1996-08-01

    Using molecular statics and interatomic potentials of the embedded atom type, the relaxed atomistic grain boundary structures in B2 aluminides were investigated in order to study trends in a series of B2 compounds. The compounds studied: FeAl, NiAl and CoAl show increasing anti-phase boundary energies. The atomistic structure of the {Sigma}=5(310)[100] and {Sigma}=5(210)[100] symmetrical tilt grain boundaries in these compounds was studied considering possible variations of local chemical composition on grain boundary energetics. The structures obtained for the three alloys are very similar. A discussion of the trends in energetics across this series of compounds is entered into. (orig.)

  1. Multiscale Modeling of Carbon/Phenolic Composite Thermal Protection Materials: Atomistic to Effective Properties

    Science.gov (United States)

    Arnold, Steven M.; Murthy, Pappu L.; Bednarcyk, Brett A.; Lawson, John W.; Monk, Joshua D.; Bauschlicher, Charles W., Jr.

    2016-01-01

    Next generation ablative thermal protection systems are expected to consist of 3D woven composite architectures. It is well known that composites can be tailored to achieve desired mechanical and thermal properties in various directions and thus can be made fit-for-purpose if the proper combination of constituent materials and microstructures can be realized. In the present work, the first, multiscale, atomistically-informed, computational analysis of mechanical and thermal properties of a present day - Carbon/Phenolic composite Thermal Protection System (TPS) material is conducted. Model results are compared to measured in-plane and out-of-plane mechanical and thermal properties to validate the computational approach. Results indicate that given sufficient microstructural fidelity, along with lowerscale, constituent properties derived from molecular dynamics simulations, accurate composite level (effective) thermo-elastic properties can be obtained. This suggests that next generation TPS properties can be accurately estimated via atomistically informed multiscale analysis.

  2. A Novel Application of Artificial Neural Network for the Solution of Inverse Kinematics Controls of Robotic Manipulators

    Directory of Open Access Journals (Sweden)

    Santosh Kumar Nanda

    2012-08-01

    Full Text Available In robotic applications and research, inverse kinematics is one of the most important problems in terms of robot kinematics and control. Consequently, finding the solution of Inverse Kinematics in now days is considered as one of the most important problems in robot kinematics and control. As the intricacy of robot manipulator increases, obtaining the mathematical, statistical solutions of inverse kinematics are difficult and computationally expensive. For that reason, now soft-computing based highly intelligent based model applications should be adopted to getting appropriate solution for inverse kinematics. In this paper, a novel application of artificial neural network is used for controlling a robotic manipulator. The proposed methods are based on the establishments of the non-linear mapping between Cartesian and joint coordinates using multi layer perceptron and functional link artificial neural network.

  3. Atomistic-continuum modeling of ultrafast laser-induced melting of silicon targets

    OpenAIRE

    Lipp, Vladimir

    2015-01-01

    In this work, we present an atomistic-continuum model for simulations of ultrafast laser-induced melting processes in semiconductors on the example of silicon. The kinetics of transient non-equilibrium phase transition mechanisms is addressed with MD method on the atomic level, whereas the laser light absorption, strong generated electron-phonon nonequilibrium, fast heat conduction, and photo-excited free carrier diffusion are accounted for with a continuum TTM-like model (called nTTM). First...

  4. Atomistic Failure Mechanism of Single Wall Carbon Nanotubes with Small Diameters

    Institute of Scientific and Technical Information of China (English)

    JI Dong; GAO Xiang; KONG Xiang-Yang; LI Jia-Ming

    2007-01-01

    @@ Single wall carbon nanotubes with small diameters (< 5.0 (A)) subjected to bending deformation are simulated by orthogonal tight-binding molecular dynamics approach. Based on the calculations of C-C bond stretching and breaking in the bending nanotubes, we elucidate the atomistic failure mechanisms of nanotube with small diameters. In the folding zone of bending nanotube, a large elongation of C-C bonds occurs, accounting for the superelastic behaviour.

  5. Idealized vs. Realistic Microstructures: An Atomistic Simulation Case Study on γ/γ′ Microstructures

    Directory of Open Access Journals (Sweden)

    Aruna Prakash

    2017-01-01

    Full Text Available Single-crystal Ni-base superalloys, consisting of a two-phase γ/ γ ′ microstructure, retain high strengths at elevated temperatures and are key materials for high temperature applications, like, e.g., turbine blades of aircraft engines. The lattice misfit between the γ and γ ′ phases results in internal stresses, which significantly influence the deformation and creep behavior of the material. Large-scale atomistic simulations that are often used to enhance our understanding of the deformation mechanisms in such materials must accurately account for such misfit stresses. In this work, we compare the internal stresses in both idealized and experimentally-informed, i.e., more realistic, γ/ γ ′ microstructures. The idealized samples are generated by assuming, as is frequently done, a periodic arrangement of cube-shaped γ ′ particles with planar γ/ γ ′ interfaces. The experimentally-informed samples are generated from two different sources to produce three different samples—the scanning electron microscopy micrograph-informed quasi-2D atomistic sample and atom probe tomography-informed stoichiometric and non-stoichiometric atomistic samples. Additionally, we compare the stress state of an idealized embedded cube microstructure with finite element simulations incorporating 3D periodic boundary conditions. Subsequently, we study the influence of the resulting stress state on the evolution of dislocation loops in the different samples. The results show that the stresses in the atomistic and finite element simulations are almost identical. Furthermore, quasi-2D boundary conditions lead to a significantly different stress state and, consequently, different evolution of the dislocation loop, when compared to samples with fully 3D boundary conditions.

  6. Atomistic resolution structure and dynamics of lipid bilayers in simulations and experiments.

    Science.gov (United States)

    Ollila, O H Samuli; Pabst, Georg

    2016-10-01

    Accurate details on the sampled atomistic resolution structures of lipid bilayers can be experimentally obtained by measuring C-H bond order parameters, spin relaxation rates and scattering form factors. These parameters can be also directly calculated from the classical atomistic resolution molecular dynamics simulations (MD) and compared to the experimentally achieved results. This comparison measures the simulation model quality with respect to 'reality'. If agreement is sufficient, the simulation model gives an atomistic structural interpretation of the acquired experimental data. Significant advance of MD models is made by jointly interpreting different experiments using the same structural model. Here we focus on phosphatidylcholine lipid bilayers, which out of all model membranes have been studied mostly by experiments and simulations, leading to the largest available dataset. From the applied comparisons we conclude that the acyl chain region structure and rotational dynamics are generally well described in simulation models. Also changes with temperature, dehydration and cholesterol concentration are qualitatively correctly reproduced. However, the quality of the underlying atomistic resolution structural changes is uncertain. Even worse, when focusing on the lipid bilayer properties at the interfacial region, e.g. glycerol backbone and choline structures, and cation binding, many simulation models produce an inaccurate description of experimental data. Thus extreme care must be applied when simulations are applied to understand phenomena where the interfacial region plays a significant role. This work is done by the NMRlipids Open Collaboration project running at https://nmrlipids.blogspot.fi and https://github.com/NMRLipids. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg.

  7. Atomistic insight into the minimum wear depth of Cu(111) surface

    OpenAIRE

    2013-01-01

    In the present work, we investigate the minimum wear depth of single crystalline Cu(111) under single asperity friction by means of molecular dynamics simulations. The atomistic mechanisms governing the incipient plasticity are elucidated by characterizing specific defect structures and are correlated to the observed mechanical and frictional responses of the material. Furthermore, the effect of probe radius on the friction process is studied. Our simulations indicate that the formation of we...

  8. Phase field crystal modelling of the order-to-disordered atomistic structure transition of metallic glasses

    Science.gov (United States)

    Zhang, W.; Mi, J.

    2016-03-01

    Bulk metallic glass composites are a new class of metallic alloy systems that have very high tensile strength, ductility and fracture toughness. This unique combination of mechanical properties is largely determined by the presence of crystalline phases uniformly distributed within the glassy matrix. However, there have been very limited reports on how the crystalline phases are nucleated in the super-cooled liquid and their growth dynamics, especially lack of information on the order-to-disordered atomistic structure transition across the crystalline-amorphous interface. In this paper, we use phase field crystal (PFC) method to study the nucleation and growth of the crystalline phases and the glass formation of the super cooled liquid of a binary alloy. The study is focused on understanding the order-to-disordered transition of atomistic configuration across the interface between the crystalline phases and amorphous matrix of different chemical compositions at different thermal conditions. The capability of using PFC to simulate the order-to-disorder atomistic transition in the bulk material or across the interface is discussed in details.

  9. Markov-chain model of classified atomistic transition states for discrete kinetic Monte Carlo simulations.

    Science.gov (United States)

    Numazawa, Satoshi; Smith, Roger

    2011-10-01

    Classical harmonic transition state theory is considered and applied in discrete lattice cells with hierarchical transition levels. The scheme is then used to determine transitions that can be applied in a lattice-based kinetic Monte Carlo (KMC) atomistic simulation model. The model results in an effective reduction of KMC simulation steps by utilizing a classification scheme of transition levels for thermally activated atomistic diffusion processes. Thermally activated atomistic movements are considered as local transition events constrained in potential energy wells over certain local time periods. These processes are represented by Markov chains of multidimensional Boolean valued functions in three-dimensional lattice space. The events inhibited by the barriers under a certain level are regarded as thermal fluctuations of the canonical ensemble and accepted freely. Consequently, the fluctuating system evolution process is implemented as a Markov chain of equivalence class objects. It is shown that the process can be characterized by the acceptance of metastable local transitions. The method is applied to a problem of Au and Ag cluster growth on a rippled surface. The simulation predicts the existence of a morphology-dependent transition time limit from a local metastable to stable state for subsequent cluster growth by accretion. Excellent agreement with observed experimental results is obtained.

  10. State Representation Approach for Atomistic Time-Dependent Transport Calculations in Molecular Junctions.

    Science.gov (United States)

    Zelovich, Tamar; Kronik, Leeor; Hod, Oded

    2014-08-12

    We propose a new method for simulating electron dynamics in open quantum systems out of equilibrium, using a finite atomistic model. The proposed method is motivated by the intuitive and practical nature of the driven Liouville-von-Neumann equation approach of Sánchez et al. [J. Chem. Phys. 2006, 124, 214708] and Subotnik et al. [J. Chem. Phys. 2009, 130, 144105]. A key ingredient of our approach is a transformation of the Hamiltonian matrix from an atomistic to a state representation of the molecular junction. This allows us to uniquely define the bias voltage across the system while maintaining a proper thermal electronic distribution within the finite lead models. Furthermore, it allows us to investigate complex molecular junctions, including multilead configurations. A heuristic derivation of our working equation leads to explicit expressions for the damping and driving terms, which serve as appropriate electron sources and sinks that effectively "open" the finite model system. Although the method does not forbid it, in practice we find neither violation of Pauli's exclusion principles nor deviation from density matrix positivity throughout our numerical simulations of various tight-binding model systems. We believe that the new approach offers a practical and physically sound route for performing atomistic time-dependent transport calculations in realistic molecular junction models.

  11. A study of conditions for dislocation nucleation in coarser-than-atomistic scale models

    Science.gov (United States)

    Garg, Akanksha; Acharya, Amit; Maloney, Craig E.

    2015-02-01

    We perform atomistic simulations of dislocation nucleation in defect free crystals in 2 and 3 dimensions during indentation with circular (2D) or spherical (3D) indenters. The kinematic structure of the theory of Field Dislocation Mechanics (FDM) is shown to allow the identification of a local feature of the atomistic velocity field in these simulations as indicative of dislocation nucleation. It predicts the precise location of the incipient spatially distributed dislocation field, as shown for the cases of the Embedded Atom Method potential for Al and the Lennard-Jones pair potential. We demonstrate the accuracy of this analysis for two crystallographic orientations in 2D and one in 3D. Apart from the accuracy in predicting the location of dislocation nucleation, the FDM based analysis also demonstrates superior performance than existing nucleation criteria in not persisting in time beyond the nucleation event, as well as differentiating between phase boundary/shear band and dislocation nucleation. Our analysis is meant to facilitate the modeling of dislocation nucleation in coarser-than-atomistic scale models of the mechanics of materials.

  12. The injection of a screw dislocation into a crystal: Atomistics vs. continuum elastodynamics

    Science.gov (United States)

    Verschueren, J.; Gurrutxaga-Lerma, B.; Balint, D. S.; Dini, D.; Sutton, A. P.

    2017-01-01

    The injection (creation) process of a straight screw dislocation is compared atomistically with elastodynamic continuum theory. A method for injecting quiescent screw dislocations into a crystal of tungsten is simulated using non-equilibrium molecular dynamics. The resulting stress fields are compared to the those of elastodynamic solutions for the injection of a quiescent screw dislocation. A number of differences are found: a plane wave emission is observed to emanate from the whole surface of the cut used to create the dislocation, affecting the displacement field along the dislocation line (z), and introducing displacement field components perpendicular to the line (along x and y). It is argued that, in part, this emission is the result of the finite time required to inject the dislocation, whereby the atoms in the cut surface must temporarily be displaced to unstable positions in order to produce the required slip. By modelling this process in the continuum it is shown that the displacements components normal to the dislocation line arise from transient displacements of atoms in the cut surface parallel to x and y. It is shown that once these displacements are included in the elastodynamic continuum formulation the plane wave emission in uz is correctly captured. A detailed comparison between the atomistic and continuum models is then offered, showing that the main atomistic features can also be captured in the continuum.

  13. Ion beam processing of surfaces and interfaces. Modeling and atomistic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Liedke, Bartosz

    2011-03-24

    Self-organization of regular surface pattern under ion beam erosion was described in detail by Navez in 1962. Several years later in 1986 Bradley and Harper (BH) published the first self-consistent theory on this phenomenon based on the competition of surface roughening described by Sigmund's sputter theory and surface smoothing by Mullins-Herring diffusion. Many papers that followed BH theory introduced other processes responsible for the surface patterning e.g. viscous flow, redeposition, phase separation, preferential sputtering, etc. The present understanding is still not sufficient to specify the dominant driving forces responsible for self-organization. 3D atomistic simulations can improve the understanding by reproducing the pattern formation with the detailed microscopic description of the driving forces. 2D simulations published so far can contribute to this understanding only partially. A novel program package for 3D atomistic simulations called TRIDER (TRansport of Ions in matter with DEfect Relaxation), which unifies full collision cascade simulation with atomistic relaxation processes, has been developed. The collision cascades are provided by simulations based on the Binary Collision Approximation, and the relaxation processes are simulated with the 3D lattice kinetic Monte-Carlo method. This allows, without any phenomenological model, a full 3D atomistic description on experimental spatiotemporal scales. Recently discussed new mechanisms of surface patterning like ballistic mass drift or the dependence of the local morphology on sputtering yield are inherently included in our atomistic approach. The atomistic 3D simulations do not depend so much on experimental assumptions like reported 2D simulations or continuum theories. The 3D computer experiments can even be considered as 'cleanest' possible experiments for checking continuum theories. This work aims mainly at the methodology of a novel atomistic approach, showing that: (i) In

  14. Artificial vision workbench.

    Science.gov (United States)

    Frenger, P

    1997-01-01

    Machine vision is an important component of medical systems engineering. Inexpensive miniature solid state cameras are now available. This paper describes how these devices can be used as artificial retinas, to take snapshots and moving pictures in monochrome or color. Used in pairs, they produce a stereoscopic field of vision and enable depth perception. Macular and peripheral vision can be simulated electronically. This paper also presents the author's design of an artificial orbit for this synthetic eye. The orbit supports the eye, protects it, and provides attachment points for the ocular motion control system. Convergence and image fusion can be produced, and saccades simulated, along with the other ocular motions. The use of lenses, filters, irises and focusing mechanisms are also discussed. Typical camera-computer interfaces are described, including the use of "frame grabbers" and analog-to-digital image conversion. Software programs for eye positioning, image manipulation, feature extraction and object recognition are discussed, including the application of artificial neural networks.

  15. Artificial muscles on heat

    Science.gov (United States)

    McKay, Thomas G.; Shin, Dong Ki; Percy, Steven; Knight, Chris; McGarry, Scott; Anderson, Iain A.

    2014-03-01

    Many devices and processes produce low grade waste heat. Some of these include combustion engines, electrical circuits, biological processes and industrial processes. To harvest this heat energy thermoelectric devices, using the Seebeck effect, are commonly used. However, these devices have limitations in efficiency, and usable voltage. This paper investigates the viability of a Stirling engine coupled to an artificial muscle energy harvester to efficiently convert heat energy into electrical energy. The results present the testing of the prototype generator which produced 200 μW when operating at 75°C. Pathways for improved performance are discussed which include optimising the electronic control of the artificial muscle, adjusting the mechanical properties of the artificial muscle to work optimally with the remainder of the system, good sealing, and tuning the resonance of the displacer to minimise the power required to drive it.

  16. Artificial organ engineering

    CERN Document Server

    Annesini, Maria Cristina; Piemonte, Vincenzo; Turchetti, Luca

    2017-01-01

    Artificial organs may be considered as small-scale process plants, in which heat, mass and momentum transfer operations and, possibly, chemical transformations are carried out. This book proposes a novel analysis of artificial organs based on the typical bottom-up approach used in process engineering. Starting from a description of the fundamental physico-chemical phenomena involved in the process, the whole system is rebuilt as an interconnected ensemble of elemental unit operations. Each artificial organ is presented with a short introduction provided by expert clinicians. Devices commonly used in clinical practice are reviewed and their performance is assessed and compared by using a mathematical model based approach. Whilst mathematical modelling is a fundamental tool for quantitative descriptions of clinical devices, models are kept simple to remain focused on the essential features of each process. Postgraduate students and researchers in the field of chemical and biomedical engineering will find that t...

  17. Bayesian artificial intelligence

    CERN Document Server

    Korb, Kevin B

    2003-01-01

    As the power of Bayesian techniques has become more fully realized, the field of artificial intelligence has embraced Bayesian methodology and integrated it to the point where an introduction to Bayesian techniques is now a core course in many computer science programs. Unlike other books on the subject, Bayesian Artificial Intelligence keeps mathematical detail to a minimum and covers a broad range of topics. The authors integrate all of Bayesian net technology and learning Bayesian net technology and apply them both to knowledge engineering. They emphasize understanding and intuition but also provide the algorithms and technical background needed for applications. Software, exercises, and solutions are available on the authors' website.

  18. Artificial human vision.

    Science.gov (United States)

    Dowling, Jason

    2005-01-01

    Can vision be restored to the blind? As early as 1929 it was discovered that stimulating the visual cortex of an individual led to the perception of spots of light, known as phosphenes [1] . The aim of artificial human vision systems is to attempt to utilize the perception of phosphenes to provide a useful substitute for normal vision. Currently, four locations for electrical stimulation are being investigated; behind the retina (subretinal), in front of the retina (epiretinal), the optic nerve and the visual cortex (using intra- and surface electrodes). This review discusses artificial human vision technology and requirements, and reviews the current development projects.

  19. Spatially Resolved Artificial Chemistry

    DEFF Research Database (Denmark)

    Fellermann, Harold

    2009-01-01

    Although spatial structures can play a crucial role in chemical systems and can drastically alter the outcome of reactions, the traditional framework of artificial chemistry is a well-stirred tank reactor with no spatial representation in mind. Advanced method development in physical chemistry has...... made a class of models accessible to the realms of artificial chemistry that represent reacting molecules in a coarse-grained fashion in continuous space. This chapter introduces the mathematical models of Brownian dynamics (BD) and dissipative particle dynamics (DPD) for molecular motion and reaction...

  20. General artificial neuron

    Science.gov (United States)

    Degeratu, Vasile; Schiopu, Paul; Degeratu, Stefania

    2007-05-01

    In this paper the authors present a model of artificial neuron named the general artificial neuron. Depending on application this neuron can change self number of inputs, the type of inputs (from excitatory in inhibitory or vice versa), the synaptic weights, the threshold, the type of intensifying functions. It is achieved into optoelectronic technology. Also, into optoelectronic technology a model of general McCulloch-Pitts neuron is showed. The advantages of these neurons are very high because we have to solve different applications with the same neural network, achieved from these neurons, named general neural network.

  1. Micromachined Artificial Haircell

    Science.gov (United States)

    Liu, Chang (Inventor); Engel, Jonathan (Inventor); Chen, Nannan (Inventor); Chen, Jack (Inventor)

    2010-01-01

    A micromachined artificial sensor comprises a support coupled to and movable with respect to a substrate. A polymer, high-aspect ratio cilia-like structure is disposed on and extends out-of-plane from the support. A strain detector is disposed with respect to the support to detect movement of the support.

  2. Artificial Gravity Research Plan

    Science.gov (United States)

    Gilbert, Charlene

    2014-01-01

    This document describes the forward working plan to identify what countermeasure resources are needed for a vehicle with an artificial gravity module (intermittent centrifugation) and what Countermeasure Resources are needed for a rotating transit vehicle (continuous centrifugation) to minimize the effects of microgravity to Mars Exploration crewmembers.

  3. Artificial Left Ventricle

    CERN Document Server

    Ranjbar, Saeed; Meybodi, Mahmood Emami

    2014-01-01

    This Artificial left ventricle is based on a simple conic assumption shape for left ventricle where its motion is made by attached compressed elastic tubes to its walls which are regarded to electrical points at each nodal .This compressed tubes are playing the role of myofibers in the myocardium of the left ventricle. These elastic tubes have helical shapes and are transacting on these helical bands dynamically. At this invention we give an algorithm of this artificial left ventricle construction that of course the effect of the blood flow in LV is observed with making beneficiary used of sensors to obtain this effecting, something like to lifegates problem. The main problem is to evaluate powers that are interacted between elastic body (left ventricle) and fluid (blood). The main goal of this invention is to show that artificial heart is not just a pump, but mechanical modeling of LV wall and its interaction with blood in it (blood movement modeling) can introduce an artificial heart closed to natural heart...

  4. Artificial intelligence and psychiatry.

    Science.gov (United States)

    Servan-Schreiber, D

    1986-04-01

    This paper provides a brief historical introduction to the new field of artificial intelligence and describes some applications to psychiatry. It focuses on two successful programs: a model of paranoid processes and an expert system for the pharmacological management of depressive disorders. Finally, it reviews evidence in favor of computerized psychotherapy and offers speculations on the future development of research in this area.

  5. Observations of artificial satellites

    Directory of Open Access Journals (Sweden)

    A. MAMMANO

    1964-06-01

    Full Text Available The following publication gives the results of photographic
    observations of artificial satellites made at Asiago during the second
    and third year of this programme. The fixed camera technique and that
    with moving film (the latter still in its experimental stage have been used.

  6. Artificial intelligence within AFSC

    Science.gov (United States)

    Gersh, Mark A.

    1990-01-01

    Information on artificial intelligence research in the Air Force Systems Command is given in viewgraph form. Specific research that is being conducted at the Rome Air Development Center, the Space Technology Center, the Human Resources Laboratory, the Armstrong Aerospace Medical Research Laboratory, the Armamant Laboratory, and the Wright Research and Development Center is noted.

  7. Introduction to Artificial Neural Networks

    DEFF Research Database (Denmark)

    Larsen, Jan

    1999-01-01

    The note addresses introduction to signal analysis and classification based on artificial feed-forward neural networks.......The note addresses introduction to signal analysis and classification based on artificial feed-forward neural networks....

  8. Cholesterol-Induced Suppression of Membrane Elastic Fluctuations at the Atomistic Level

    Science.gov (United States)

    Molugu, Trivikram R.

    2017-01-01

    Applications of solid-state NMR spectroscopy for investigating the influences of lipid-cholesterol interactions on membrane fluctuations are reviewed in this paper. Emphasis is placed on understanding the energy landscapes and fluctuations at an emergent atomistic level. Solid-state 2H NMR spectroscopy directly measures residual quadrupolar couplings (RQCs) due to individual C–2H labeled segments of the lipid molecules. Moreover, residual dipolar couplings (RDCs) of 13C–1H bonds are obtained in separated local-field NMR spectroscopy. The distributions of RQC or RDC values give nearly complete profiles of the order parameters as a function of acyl segment position. Measured equilibrium properties of glycerophospholipids and sphingolipids including their binary and tertiary mixtures with cholesterol show unequal mixing associated with liquid-ordered domains. The entropic loss upon addition of cholesterol to sphingolipids is less than for glycerophospholipids and may drive the formation of lipid rafts. In addition relaxation time measurements enable one to study the molecular dynamics over a wide time-scale range. For 2H NMR the experimental spin-lattice (R1Z) relaxation rates follow a theoretical square-law dependence on segmental order parameters (SCD) due to collective slow dynamics over mesoscopic length scales. The functional dependence for the liquid-crystalline lipid membranes is indicative of viscoelastic properties as they emerge from atomistic-level interactions. A striking decrease in square-law slope upon addition of cholesterol denotes stiffening relative to the pure lipid bilayers that is diminished in the case of lanosterol. Measured equilibrium properties and relaxation rates infer opposite influences of cholesterol and detergents on collective dynamics and elasticity at an atomistic scale that potentially affects lipid raft formation in cellular membranes. PMID:27154600

  9. Cholesterol-induced suppression of membrane elastic fluctuations at the atomistic level.

    Science.gov (United States)

    Molugu, Trivikram R; Brown, Michael F

    2016-09-01

    Applications of solid-state NMR spectroscopy for investigating the influences of lipid-cholesterol interactions on membrane fluctuations are reviewed in this paper. Emphasis is placed on understanding the energy landscapes and fluctuations at an emergent atomistic level. Solid-state (2)H NMR spectroscopy directly measures residual quadrupolar couplings (RQCs) due to individual C-(2)H labeled segments of the lipid molecules. Moreover, residual dipolar couplings (RDCs) of (13)C-(1)H bonds are obtained in separated local-field NMR spectroscopy. The distributions of RQC or RDC values give nearly complete profiles of the order parameters as a function of acyl segment position. Measured equilibrium properties of glycerophospholipids and sphingolipids including their binary and tertiary mixtures with cholesterol show unequal mixing associated with liquid-ordered domains. The entropic loss upon addition of cholesterol to sphingolipids is less than for glycerophospholipids and may drive the formation of lipid rafts. In addition relaxation time measurements enable one to study the molecular dynamics over a wide time-scale range. For (2)H NMR the experimental spin-lattice (R1Z) relaxation rates follow a theoretical square-law dependence on segmental order parameters (SCD) due to collective slow dynamics over mesoscopic length scales. The functional dependence for the liquid-crystalline lipid membranes is indicative of viscoelastic properties as they emerge from atomistic-level interactions. A striking decrease in square-law slope upon addition of cholesterol denotes stiffening relative to the pure lipid bilayers that is diminished in the case of lanosterol. Measured equilibrium properties and relaxation rates infer opposite influences of cholesterol and detergents on collective dynamics and elasticity at an atomistic scale that potentially affects lipid raft formation in cellular membranes.

  10. Using a scalar parameter to trace dislocation evolution in atomistic modeling

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jinbo [ORNL; Zhang, Z F [Shenyang National Laboratory for Materials Science; Osetskiy, Yury N [ORNL; Stoller, Roger E [ORNL

    2015-01-01

    A scalar gamma-parameter is proposed from the Nye tensor. Its maximum value occurs along a dislocation line, either straight or curved, when the coordinate system is purposely chosen. This parameter can be easily obtained from the Nye tensor calculated at each atom in atomistic modeling. Using the gamma-parameter, a fully automated approach is developed to determine core atoms and the Burgers vectors of dislocations simultaneously. The approach is validated by revealing the smallest dislocation loop and by tracing the whole formation process of complicated dislocation networks on the fly.

  11. Electron and phonon transport in silicon nanowires: Atomistic approach to thermoelectric properties

    DEFF Research Database (Denmark)

    Markussen, Troels; Jauho, Antti-Pekka; Brandbyge, Mads

    2009-01-01

    We compute both electron and phonon transmissions in thin disordered silicon nanowires (SiNWs). Our atomistic approach is based on tight-binding and empirical potential descriptions of the electronic and phononic systems, respectively. Surface disorder is modeled by introducing surface silicon...... apply this averaging method to surface disordered SiNWs in the diameter range of 1–3 nm to compute the thermoelectric figure of merit ZT. It is found that the phonon transmission is affected more by the vacancies than the electronic transmission leading to an increased thermoelectric performance...

  12. Atomistic understanding of hydrogen loading phenomenon into palladium cathode: A simple nanocluster approach and electrochemical evidence

    Indian Academy of Sciences (India)

    Mohsen Lashgari; Davood Matloubi

    2015-03-01

    The inherent potency of palladium to sorb hydrogen atoms was examined empirically and theoretically through various electrochemical methods and high-level quantum chemical calculations (HSE06) based on cluster model (CM) and density functional theory (DFT). The CM-DFT approach using QZVP/cc-PV6Z basis sets revealed a strong attraction between Pd nanoclusters and H atoms that generates some charged entities. This atomistically justifies why the electrochemical impedance of the system becomes less by the loading phenomenon. It is concluded that hydrogen atoms enter the palladium subsurface through hollow and bridge sites by diffusing as proton-like species and get loaded predominantly in the octahedral voids.

  13. Methods for atomistic abrasion simulations of laterally periodic polycrystalline substrates with fractal surfaces

    Science.gov (United States)

    Eder, S. J.; Bianchi, D.; Cihak-Bayr, U.; Gkagkas, K.

    2017-03-01

    In this work we discuss a method to generate laterally periodic polycrystalline samples with fractal surfaces for use in molecular dynamics simulations of abrasion. We also describe a workflow that allows us to produce random lateral distributions of simple but realistically shaped hard abrasive particles with Gaussian size distribution and random particle orientations. We evaluate some on-the-fly analysis and visualization possibilities that may be applied during a molecular dynamics simulation to considerably reduce the post-processing effort. Finally, we elaborate on a parallelizable post-processing approach to evaluating and visualizing the surface topography, the grain structure and orientation, as well as the temperature distribution in large atomistic systems.

  14. Predicting growth of graphene nanostructures using high-fidelity atomistic simulations

    Energy Technology Data Exchange (ETDEWEB)

    McCarty, Keven F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Zhou, Xiaowang [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ward, Donald K. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Schultz, Peter A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Foster, Michael E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bartelt, Norman Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    In this project we developed t he atomistic models needed to predict how graphene grows when carbon is deposited on metal and semiconductor surfaces. We first calculated energies of many carbon configurations using first principles electronic structure calculations and then used these energies to construct an empirical bond order potentials that enable s comprehensive molecular dynamics simulation of growth. We validated our approach by comparing our predictions to experiments of graphene growth on Ir, Cu and Ge. The robustness of ou r understanding of graphene growth will enable high quality graphene to be grown on novel substrates which will expand the number of potential types of graphene electronic devices.

  15. Atomistic Simulation of Intrinsic Defects and Trivalent and Tetravalent Ion Doping in Hydroxyapatite

    Directory of Open Access Journals (Sweden)

    Ricardo D. S. Santos

    2014-01-01

    Full Text Available Atomistic simulation techniques have been employed in order to investigate key issues related to intrinsic defects and a variety of dopants from trivalent and tetravalent ions. The most favorable intrinsic defect is determined to be a scheme involving calcium and hydroxyl vacancies. It is found that trivalent ions have an energetic preference for the Ca site, while tetravalent ions can enter P sites. Charge compensation is predicted to occur basically via three schemes. In general, the charge compensation via the formation of calcium vacancies is more favorable. Trivalent dopant ions are more stable than tetravalent dopants.

  16. Rotational viscosity of a liquid crystal mixture:a fully atomistic molecular dynamics study

    Institute of Scientific and Technical Information of China (English)

    Zhang Ran; Peng Zeng-Hui; Liu Yong-Gang; Zheng Zhi-Gang; Xuan Li

    2009-01-01

    Fully atomistic molecular dynamics(MD)simulations at 293, 303 and 313 K have been performed for the four. component liquid crystal mixture, E7, using the software package Material Studio. Order parameters and orientational time correlation functions(TCFs)were calculated from MD trajectories. The rotational viscosity coefficients(RVCs)of the mixture were ca]culated using the Nemtsov-Zakharov and Fialkowski methods based on statistical-mechanical approaches. Temperature dependences of RVC and density were discussed in detall. Reasonable agreement between the simulated and experimental values was found.

  17. Dislocation pinning effects on fracture behavior: Atomistic and dislocation dynamics simulations

    Science.gov (United States)

    Noronha, S. J.; Farkas, D.

    2002-10-01

    We introduce an approach in which results from atomistic simulations are combined with discrete dislocation dynamics simulations of crack-tip plasticity. The method is used to study the effects of dislocation pinning due to grain boundaries or secondary particles on the fracture behavior of aluminum. We find that the fracture resistance is reduced with decreasing pinning distance. The results show that the pinning of the dislocations causes a net decrease in the shear stress projected on the slip plane, preventing further dislocation emission. Semibrittle cleavage occurs after a certain number of dislocations is emitted.

  18. Investigations on the mechanical behavior of nanowires with twin boundaries by atomistic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Xia, E-mail: tianxia@lsec.cc.ac.cn [College of Mechanics and Materials, HoHai University, Nanjing 210098 (China)

    2015-03-10

    Atomistic simulations are used to study the deformation behavior of twinned Cu nanowires with a <111> growth orientation under tension. Due to the existence of the twin boundaries, the strength of the twinned nanowires is higher than that of the twin-free nanowire and the yielding stress of twinned nanowires is inversely proportional to the spacings of the twin boundaries. Moreover, The ductility of the twin-free nanowire is the highest of all and it grows with the increasing spacings of the twin boundaries for twinned nanowires. Besides, we find that the twin boundaries can be served as dislocation sources as well as the free surfaces and grain boundaries.

  19. Multiscale Modeling of Grain-Boundary Fracture: Cohesive Zone Models Parameterized From Atomistic Simulations

    Science.gov (United States)

    Glaessgen, Edward H.; Saether, Erik; Phillips, Dawn R.; Yamakov, Vesselin

    2006-01-01

    A multiscale modeling strategy is developed to study grain boundary fracture in polycrystalline aluminum. Atomistic simulation is used to model fundamental nanoscale deformation and fracture mechanisms and to develop a constitutive relationship for separation along a grain boundary interface. The nanoscale constitutive relationship is then parameterized within a cohesive zone model to represent variations in grain boundary properties. These variations arise from the presence of vacancies, intersticies, and other defects in addition to deviations in grain boundary angle from the baseline configuration considered in the molecular dynamics simulation. The parameterized cohesive zone models are then used to model grain boundaries within finite element analyses of aluminum polycrystals.

  20. Elastic behavior of amorphous-crystalline silicon nanocomposite: An atomistic view

    Science.gov (United States)

    Das, Suvankar; Dutta, Amlan

    2017-01-01

    In the context of mechanical properties, nanocomposites with homogeneous chemical composition throughout the matrix and the dispersed phase are of particular interest. In this study, the elastic moduli of amorphous-crystalline silicon nanocomposite have been estimated using atomistic simulations. A comparison with the theoretical model reveals that the elastic behavior is significantly influenced by the crystal-amorphous interphase. On observing the effect of volume-fraction of the crystalline phase, an anomalous trend for the bulk modulus is obtained. This phenomenon is attributed to the relaxation displacements of the amorphous atoms.

  1. Atomistic spin dynamic method with both damping and moment of inertia effects included from first principles.

    Science.gov (United States)

    Bhattacharjee, Satadeep; Nordström, Lars; Fransson, Jonas

    2012-02-03

    We consider spin dynamics for implementation in an atomistic framework and we address the feasibility of capturing processes in the femtosecond regime by inclusion of moment of inertia. In the spirit of an s-d-like interaction between the magnetization and electron spin, we derive a generalized equation of motion for the magnetization dynamics in the semiclassical limit, which is nonlocal in both space and time. Using this result we retain a generalized Landau-Lifshitz-Gilbert equation, also including the moment of inertia, and demonstrate how the exchange interaction, damping, and moment of inertia, all can be calculated from first principles.

  2. Atomistic formulas for local properties in systems with many-body interactions

    Science.gov (United States)

    Hardy, Robert J.

    2016-11-01

    Atomistic formulas are derived for the local densities and fluxes used in the continuum description of energy and momentum transport. Two general methods for the distribution of potential energy among a system's constituent particles are presented and analyzed. The resulting formulas for the heat flux and stress tensor and the equations for energy and momentum transport are exact consequences of the definitions of the densities and the equations of classical mechanics. The formulas and equations obtained are valid for systems with very general types of many-body interactions.

  3. AGU Chapman Conference Hydrogeologic Processes: Building and Testing Atomistic- to Basin-Scale Models

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, B. [American Geophysical Union, Washington, DC (United States)

    1994-12-31

    This report presents details of the Chapman Conference given on June 6--9, 1994 in Lincoln, New Hampshire. This conference covered the scale of processes involved in coupled hydrogeologic mass transport and a concept of modeling and testing from the atomistic- to the basin- scale. Other topics include; the testing of fundamental atomic level parameterizations in the laboratory and field studies of fluid flow and mass transport and the next generation of hydrogeologic models. Individual papers from this conference are processed separately for the database.

  4. Cold melting of beryllium: Atomistic view on Z-machine experiments

    Science.gov (United States)

    Dremov, V. V.; Rykounov, A. A.; Sapozhnikov, F. A.; Karavaev, A. V.; Yakovlev, S. V.; Ionov, G. V.; Ryzhkov, M. V.

    2015-07-01

    Analysis of phase diagram of beryllium at high pressures and temperatures obtained as a result of ab initio calculations and large scale classical molecular dynamics simulations of beryllium shock loading have shown that the so called cold melting takes place when shock wave propagates through polycrystalline samples. Comparison of ab initio calculation results on sound speed along the Hugoniot with experimental data obtained on Z-machine also evidences for possible manifestation of the cold melting. The last may explain the discrepancy between atomistic simulations and experimental data on the onset of the melting on the Hugoniot.

  5. Consistent Energy-Based Atomistic/Continuum Coupling for Two-Body Potential: 1D and 2D Case

    CERN Document Server

    Shapeev, Alexander V

    2010-01-01

    This paper concerns the problem of consistent energy-based coupling of atomistic and continuum models of materials, limited to zero-temperature statics of simple crystalline materials. It has been widely recognized that the most practical coupled methods exhibit finite errors on the atomistic/continuum interface (which are often attributed to spurious forces called "ghost forces"). There are only few existing works that propose a coupling which is sufficiently accurate near the interface under certain limitations. In this paper a novel coupling that is free from "ghost forces" is proposed for a two-body interaction potential under the assumptions of either (i) one spatial dimension, or (ii) two spatial dimensions and piecewise affine finite elements for describing the continuum deformation. The computational efficiency of the proposed coupling is demonstrated with numerical experiments. The coupling strategy is based on judiciously defining the contributions of the atomistic bonds to the discrete and the cont...

  6. Artificial Enzymes, "Chemzymes"

    DEFF Research Database (Denmark)

    Bjerre, Jeannette; Rousseau, Cyril Andre Raphaël; Pedersen, Lavinia Georgeta M;

    2008-01-01

    Enzymes have fascinated scientists since their discovery and, over some decades, one aim in organic chemistry has been the creation of molecules that mimic the active sites of enzymes and promote catalysis. Nevertheless, even today, there are relatively few examples of enzyme models...... that successfully perform Michaelis-Menten catalysis under enzymatic conditions (i.e., aqueous medium, neutral pH, ambient temperature) and for those that do, very high rate accelerations are seldomly seen. This review will provide a brief summary of the recent developments in artificial enzymes, so called...... "Chemzymes", based on cyclodextrins and other molecules. Only the chemzymes that have shown enzyme-like activity that has been quantified by different methods will be mentioned. This review will summarize the work done in the field of artificial glycosidases, oxidases, epoxidases, and esterases, as well...

  7. Artificial neural network modelling

    CERN Document Server

    Samarasinghe, Sandhya

    2016-01-01

    This book covers theoretical aspects as well as recent innovative applications of Artificial Neural networks (ANNs) in natural, environmental, biological, social, industrial and automated systems. It presents recent results of ANNs in modelling small, large and complex systems under three categories, namely, 1) Networks, Structure Optimisation, Robustness and Stochasticity 2) Advances in Modelling Biological and Environmental Systems and 3) Advances in Modelling Social and Economic Systems. The book aims at serving undergraduates, postgraduates and researchers in ANN computational modelling. .

  8. Artificial Neural Network

    Directory of Open Access Journals (Sweden)

    Kapil Nahar

    2012-12-01

    Full Text Available An artificial neural network is an information-processing paradigm that is inspired by the way biological nervous systems, such as the brain, process information.The key element of this paradigm is the novel structure of the information processing system. It is composed of a large number of highly interconnected processing elements (neurons working in unison to solve specific problems.Ann’s, like people, learn by example.

  9. Essentials of artificial intelligence

    CERN Document Server

    Ginsberg, Matt

    1993-01-01

    Since its publication, Essentials of Artificial Intelligence has beenadopted at numerous universities and colleges offering introductory AIcourses at the graduate and undergraduate levels. Based on the author'scourse at Stanford University, the book is an integrated, cohesiveintroduction to the field. The author has a fresh, entertaining writingstyle that combines clear presentations with humor and AI anecdotes. At thesame time, as an active AI researcher, he presents the materialauthoritatively and with insight that reflects a contemporary, first hand

  10. Artificial Neural Network

    Directory of Open Access Journals (Sweden)

    Kapil Nahar

    2012-12-01

    Full Text Available An artificial neural network is an information-processing paradigm that is inspired by the way biological nervous systems, such as the brain, process information. The key element of this paradigm is the novel structure of the information processing system. It is composed of a large number of highly interconnected processing elements (neurons working in unison to solve specific problems. Ann’s, like people, learn by example.

  11. Artificial sweetener; Jinko kanmiryo

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-08-01

    The patents related to the artificial sweetener that it is introduced to the public in 3 years from 1996 until 1998 are 115 cases. The sugar quality which makes an oligosaccharide and sugar alcohol the subject is greatly over 28 cases of the non-sugar quality in the one by the kind as a general tendency of these patents at 73 cases in such cases as the Aspartame. The method of manufacture patent, which included new material around other peptides, the oligosaccharide and sugar alcohol isn`t inferior to 56 cases of the formation thing patent at 43 cases, and pays attention to the thing, which is many by the method of manufacture, formation. There is most improvement of the quality of sweetness with 31 cases in badness of the aftertaste which is characteristic of the artificial sweetener and so on, and much stability including the improvement in the flavor of food by the artificial sweetener, a long time and dissolution, fluid nature and productivity and improvement of the economy such as a cost are seen with effect on a purpose. (NEDO)

  12. ARTIFICIAL INSEMINATION IN BOVINE

    Directory of Open Access Journals (Sweden)

    A. L. M Marinho

    2016-02-01

    Full Text Available This literature review aims to show the main scientific advances achieved in the area of Artificial Insemination (AI within animal reproduction and how these can improve reproductive efficiency and productive of the Brazilian cattle herd. With knowledge of the mechanisms involved in the control of reproductive physiology, in levels endocrine, cellular and molecular, it was possible the development of reproductive biotechnologies, standing out the IA, It has been used on a large scale, by allow the multiplication of animals superior genetically , increase the birthrate and be particularly effective in adjusting the breeding season in cattle. Artificial insemination has an important role in animal genetic improvement; it is the main and more viable middle of spread of genes worldwide when compared to other methods how technologies of embryos and the natural breeding. There are several advantages in using artificial insemination in herd both of cutting as milkman, as herd genetic improvement in lesser time and at a low cost through the use of semen of demonstrably superior sires for production, well as in the control and decrease of diseases which entail reproductive losses and consequently productive, by allowing the creator The crossing of zebuine females with bulls of European breeds and vice-versa, through the use of semen, increasing the number of progeny of a reproducer superior

  13. New Developments in the Embedded Statistical Coupling Method: Atomistic/Continuum Crack Propagation

    Science.gov (United States)

    Saether, E.; Yamakov, V.; Glaessgen, E.

    2008-01-01

    A concurrent multiscale modeling methodology that embeds a molecular dynamics (MD) region within a finite element (FEM) domain has been enhanced. The concurrent MD-FEM coupling methodology uses statistical averaging of the deformation of the atomistic MD domain to provide interface displacement boundary conditions to the surrounding continuum FEM region, which, in turn, generates interface reaction forces that are applied as piecewise constant traction boundary conditions to the MD domain. The enhancement is based on the addition of molecular dynamics-based cohesive zone model (CZM) elements near the MD-FEM interface. The CZM elements are a continuum interpretation of the traction-displacement relationships taken from MD simulations using Cohesive Zone Volume Elements (CZVE). The addition of CZM elements to the concurrent MD-FEM analysis provides a consistent set of atomistically-based cohesive properties within the finite element region near the growing crack. Another set of CZVEs are then used to extract revised CZM relationships from the enhanced embedded statistical coupling method (ESCM) simulation of an edge crack under uniaxial loading.

  14. An atomistic model for cross-linked HNBR elastomers used in seals

    Science.gov (United States)

    Molinari, Nicola; Sutton, Adrian; Stevens, John; Mostofi, Arash

    2015-03-01

    Hydrogenated nitrile butadiene rubber (HNBR) is one of the most common elastomeric materials used for seals in the oil and gas industry. These seals sometimes suffer ``explosive decompression,'' a costly problem in which gases permeate a seal at the elevated temperatures and pressures pertaining in oil and gas wells, leading to rupture when the seal is brought back to the surface. The experimental evidence that HNBR and its unsaturated parent NBR have markedly different swelling properties suggests that cross-linking may occur during hydrogenation of NBR to produce HNBR. We have developed a code compatible with the LAMMPS molecular dynamics package to generate fully atomistic HNBR configurations by hydrogenating initial NBR structures. This can be done with any desired degree of cross-linking. The code uses a model of atomic interactions based on the OPLS-AA force-field. We present calculations of the dependence of a number of bulk properties on the degree of cross-linking. Using our atomistic representations of HNBR and NBR, we hope to develop a better molecular understanding of the mechanisms that result in explosive decompression.

  15. Integrating atomistic molecular dynamics simulations, experiments, and network analysis to study protein dynamics

    DEFF Research Database (Denmark)

    Papaleo, Elena

    2015-01-01

    In the last years, we have been observing remarkable improvements in the field of protein dynamics. Indeed, we can now study protein dynamics in atomistic details over several timescales with a rich portfolio of experimental and computational techniques. On one side, this provides us with the pos......In the last years, we have been observing remarkable improvements in the field of protein dynamics. Indeed, we can now study protein dynamics in atomistic details over several timescales with a rich portfolio of experimental and computational techniques. On one side, this provides us...... that we observe and the functional properties of these important cellular machines. To make progresses in this direction, we need to improve the physical models used to describe proteins and solvent in molecular dynamics, as well as to strengthen the integration of experiments and simulations to overcome...... simulations with attention to the effects that can be propagated over long distances and are often associated to important biological functions. In this context, approaches inspired by network analysis can make an important contribution to the analysis of molecular dynamics simulations....

  16. Atomistic protein folding simulations on the submillisecond time scale using worldwide distributed computing.

    Science.gov (United States)

    Pande, Vijay S; Baker, Ian; Chapman, Jarrod; Elmer, Sidney P; Khaliq, Siraj; Larson, Stefan M; Rhee, Young Min; Shirts, Michael R; Snow, Christopher D; Sorin, Eric J; Zagrovic, Bojan

    2003-01-01

    Atomistic simulations of protein folding have the potential to be a great complement to experimental studies, but have been severely limited by the time scales accessible with current computer hardware and algorithms. By employing a worldwide distributed computing network of tens of thousands of PCs and algorithms designed to efficiently utilize this new many-processor, highly heterogeneous, loosely coupled distributed computing paradigm, we have been able to simulate hundreds of microseconds of atomistic molecular dynamics. This has allowed us to directly simulate the folding mechanism and to accurately predict the folding rate of several fast-folding proteins and polymers, including a nonbiological helix, polypeptide alpha-helices, a beta-hairpin, and a three-helix bundle protein from the villin headpiece. Our results demonstrate that one can reach the time scales needed to simulate fast folding using distributed computing, and that potential sets used to describe interatomic interactions are sufficiently accurate to reach the folded state with experimentally validated rates, at least for small proteins.

  17. Quantum Thermodynamics: Non-equilibrium 3D Description of an Unbounded System at an Atomistic Level

    Directory of Open Access Journals (Sweden)

    Vittorio Verda

    2010-03-01

    Full Text Available Quantum thermodynamics (QT provides a general framework for the description of non-equilibrium phenomena at any level, particularly the atomistic one. This theory and its dynamical postulate are used here to extend the work reported in previous papers of modeling the storage of hydrogen in an isolated system, by extending the modeling to 3D. The system is prepared in a state with the hydrogen molecules initially far from stable equilibrium after which the system is allowed to relax (evolve to a state of stable equilibrium. The so-called energy eigenvalue problem, which entails a many-body problem that for dilute and moderately dense gases can be solved using virial expansion theory, is used to determine the energy eigenvalues and eigenstates of the system. This information is then used in the nonlinear Beretta equation of motion of QT to determine the evolution of the thermodynamic state of the system as well as the spatial distributions of the hydrogen molecules in time. The results of our simulations provide a quantification of the entropy generated due to irreversibilities at an atomistic level and show in detail the trajectory of the state of the system as the hydrogen molecules, which are initially arranged to be far from the carbon nanotube, spread out in the system and eventually become more concentrated near the carbon atoms which make up the nanotube.

  18. Fully atomistic molecular-mechanical model of liquid alkane oils: Computational validation.

    Science.gov (United States)

    Zahariev, Tsvetan K; Slavchov, Radomir I; Tadjer, Alia V; Ivanova, Anela N

    2014-04-15

    Fully atomistic molecular dynamics simulations were performed on liquid n-pentane, n-hexane, and n-heptane to derive an atomistic model for middle-chain-length alkanes. All simulations were based on existing molecular-mechanical parameters for alkanes. The computational protocol was optimized, for example, in terms of thermo- and barostat, to reproduce properly the properties of the liquids. The model was validated by comparison of thermal, structural, and dynamic properties of the normal alkane liquids to experimental data. Two different combinations of temperature and pressure coupling algorithms were tested. A simple differential approach was applied to evaluate fluctuation-related properties with sufficient accuracy. Analysis of the data reveals a satisfactory representation of the hydrophobic systems behavior. Thermodynamic parameters are close to the experimental values and exhibit correct temperature dependence. The observed intramolecular geometry corresponds to extended conformations domination, whereas the intermolecular structure demonstrates all characteristics of liquid systems. Cavity size distribution function was calculated from coordinates analysis and was applied to study the solubility of gases in hexane and heptane oils. This study provides a platform for further in-depth research on hydrophobic solutions and multicomponent systems.

  19. Fracture toughness from atomistic simulations: Brittleness induced by emission of sessile dislocations

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, D. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering

    1998-08-04

    Using atomistic simulations of crack response for intermetallic materials the author shows that when the emitted dislocations are sessile and stay in the immediate vicinity of the crack tip the emitted dislocations can actually lead to brittle failure. She present the results of an atomistic simulation study of the simultaneous dislocation emission and crack propagation process in this class of materials. She used a molecular statics technique with embedded atom (EAM) potentials developed for NiAl. The crystal structure of NiAl is the CsCl type (B2) with a lattice parameter of 0.287 nm, which is reproduced by the potential together with the cohesive energy and elastic constants. The compound stays ordered up to the melting point, indicating a strong tendency towards chemical ordering with a relatively high energy of the antiphase boundary (APB). As a result of this relatively large energy the dislocations of 1/2<111> type Burgers vectors imply a high energy and the deformation process occurs via the larger <100> type dislocations.

  20. Atomistic studies of dislocations in {alpha}-iron using bond-order potential

    Energy Technology Data Exchange (ETDEWEB)

    Mrovec, Matous; Elsaesser, Christian; Gumbsch, Peter [Fraunhofer-Institut fuer Werkstoffmechanik IWM, Freiburg (Germany); IZBS, Universitaet Karlsruhe, Karlsruhe (Germany)

    2010-07-01

    Macroscopic plastic behavior is closely linked to properties of dislocations at the nanometer scale. Direct experimental observations of the dislocation core region and of its changes during dislocation motion are unfortunately impossible and better understanding of these phenomena can be obtained only with the help of atomistic simulations. Recent atomistic studies of dislocations in iron have provided however very different outcomes, both in terms of atomic structures and energetics. The most likely reason of these large differences is a lack of reliable interatomic potentials, which would be able to describe adequately the atomic bonding and magnetic interactions in iron. In the present work we present studies of dislocations in {alpha}-iron using a bond-order potential, which is based on a tight-binding bond representation. The model is able to capture the directional character of bonds present in transition metals and includes a description of magnetic effects within the Stoner model of itinerant magnetism. We compare results of our simulations with available first-principles predictions as well as with predictions of other empirical interatomic potentials and discuss underlying causes of the differences.

  1. Comparison of atomistic and elasticity approaches for carbon diffusion near line defects in {alpha}-iron

    Energy Technology Data Exchange (ETDEWEB)

    Veiga, R.G.A., E-mail: rgaveiga@gmail.com [Universite de Lyon, INSA Lyon, Laboratoire MATEIS, UMR CNRS 5510, 25 Avenue Jean Capelle, F69621, Villeurbanne (France); Perez, M. [Universite de Lyon, INSA Lyon, Laboratoire MATEIS, UMR CNRS 5510, 25 Avenue Jean Capelle, F69621, Villeurbanne (France); Becquart, C.S. [Unite Materiaux et Transformations (UMET), Ecole Nationale Superieure de Chimie de Lille, UMR CNRS 8207, Bat. C6, F59655 Villeneuve d' Ascq Cedex (France); Laboratoire commun EDF-CNRS Etude et Modelisation des Microstructures pour le Vieillissement des Materiaux (EM2VM) (France); Clouet, E. [Service de Recherches de Metallurgie Physique, CEA/Saclay, 91191 Gif-sur-Yvette (France); Domain, C. [EDF, Recherche et Developpement, Materiaux et Mecanique des Composants, Les Renardieres, F77250 Moret sur Loing (France); Laboratoire commun EDF-CNRS Etude et Modelisation des Microstructures pour le Vieillissement des Materiaux (EM2VM) (France)

    2011-10-15

    Energy barriers for carbon migration in the neighborhood of line defects in body-centered cubic iron have been obtained by atomistic simulations. For this purpose, molecular statics with an Fe-C interatomic potential, based on the embedded atom method, has been employed. Results of these simulations have been compared to the predictions of anisotropic elasticity theory. The agreement is better for a carbon atom sitting on an octahedral site (energy minimum) than one on a tetrahedral site (saddle point). Absolute differences in the energy barriers obtained by the two methods are usually below 5 meV at distances larger than 1.5 nm from a screw dislocation and 2 nm (up to 4 nm in the glide plane) from the edge dislocation. Atomistic kinetic Monte Carlo simulations performed at T = 300 K and additional analysis based on the activation energies obtained by both methods show that they are in good qualitative agreement, despite some important quantitative discrepancies due to the large absolute errors found near the dislocation cores.

  2. 人工智能在教育中的应用研究%Application and Research of Artificial Intelligence in Education

    Institute of Scientific and Technical Information of China (English)

    傅莉

    2012-01-01

    文章从理论的角度介绍了人工智能的概念以及对现阶段人工智能研究领域的主要研究方向进行了阐述.文中利用BP神经网络算法建立高校教学评估体系的评估模型,并通过MATLAB仿真,得到了比较满意的评价结果,具有广泛的适用性.%This paper introduces the concept of the artificial intelligence based on the theory,and introduceds the major research directions of the artificial intelligence at the present stage. This paper establishes the evaluation model of university teaching quality based on BP neural networks,and runs in MATLAB,it gains more satisfied conclusion, and it has the widespread serviceability.

  3. Intelligence Based Fusion Control Strategy for Complex Vulcanizing Process%复杂硫化过程的智能融合控制策略

    Institute of Scientific and Technical Information of China (English)

    裴玉玲

    2013-01-01

    针对硫化过程中因模糊性与不确定性导致的塑胶产品成形过程难以控制、产品质量稳定性差的问题,提出了一种智能融合控制策略.总结了复杂硫化过程中的控制难点,探讨了硫化过程的控制论特性,研究了对不确定性复杂过程的控制策略,讨论了控制模型,提出了智能融合控制策略,基于仿人智能构造了基本控制算法.仿真结果显示该策略的鲁棒性强与控制精度高.研究结果表明:智能融合控制策略对不确定性复杂硫化过程实施控制是可行与有效的.%The vulcanization of plastic & rubber products is a typical complex control process with uncertainty.Aimed at the puzzle that the shaping process of plastic & rubber products is difficult to control resulted from fuzzification and uncertainty,and poor in stability of product quality in the process of vulcanization,the paper proposed a sort of intelligence based control strategy based on human simulated intelligent controller.In the paper,it summed up the control puzzles in the process of complex vulcanization,explored the cybernetics characteristic of vulcanizing process,researched on the control strategy of complex process with uncertainty,proposed a sort of intelligence based control strategy,discussed control model,and constructed the control algorithm based on human simulated intelligence.It made the simulation experiment,and the curve of algorithm response demonstrated that it could be stronger in robustness,and higher in control precision compared with PID controller.The research result shows that it is feasible and effective to the proposed control strategy based on human simulated intelligence in actualizing control for complex vulcanizing process with uncertainty.

  4. Study on the interaction of artificial and natural food colorants with human serum albumin: A computational point of view.

    Science.gov (United States)

    Masone, Diego; Chanforan, Céline

    2015-06-01

    Due to the high amount of artificial food colorants present in infants' diets, their adverse effects have been of major concern among the literature. Artificial food colorants have been suggested to affect children's behavior, being hyperactivity the most common disorder. In this study we compare binding affinities of a group of artificial colorants (sunset yellow, quinoline yellow, carmoisine, allura red and tartrazine) and their natural industrial equivalents (carminic acid, curcumin, peonidin-3-glucoside, cyanidin-3-glucoside) to human serum albumin (HSA) by a docking approach and further refinement through atomistic molecular dynamics simulations. Due to the protein-ligand conformational interface complexity, we used collective variable driven molecular dynamics to refine docking predictions and to score them according to a hydrogen-bond criterion. With this protocol, we were able to rank ligand affinities to HSA and to compare between the studied natural and artificial food additives. Our results show that the five artificial colorants studied bind better to HSA than their equivalent natural options, in terms of their H-bonding network, supporting the hypothesis of their potential risk to human health.

  5. Artificial intelligence in hematology.

    Science.gov (United States)

    Zini, Gina

    2005-10-01

    Artificial intelligence (AI) is a computer based science which aims to simulate human brain faculties using a computational system. A brief history of this new science goes from the creation of the first artificial neuron in 1943 to the first artificial neural network application to genetic algorithms. The potential for a similar technology in medicine has immediately been identified by scientists and researchers. The possibility to store and process all medical knowledge has made this technology very attractive to assist or even surpass clinicians in reaching a diagnosis. Applications of AI in medicine include devices applied to clinical diagnosis in neurology and cardiopulmonary diseases, as well as the use of expert or knowledge-based systems in routine clinical use for diagnosis, therapeutic management and for prognostic evaluation. Biological applications include genome sequencing or DNA gene expression microarrays, modeling gene networks, analysis and clustering of gene expression data, pattern recognition in DNA and proteins, protein structure prediction. In the field of hematology the first devices based on AI have been applied to the routine laboratory data management. New tools concern the differential diagnosis in specific diseases such as anemias, thalassemias and leukemias, based on neural networks trained with data from peripheral blood analysis. A revolution in cancer diagnosis, including the diagnosis of hematological malignancies, has been the introduction of the first microarray based and bioinformatic approach for molecular diagnosis: a systematic approach based on the monitoring of simultaneous expression of thousands of genes using DNA microarray, independently of previous biological knowledge, analysed using AI devices. Using gene profiling, the traditional diagnostic pathways move from clinical to molecular based diagnostic systems.

  6. Polymer artificial muscles

    Directory of Open Access Journals (Sweden)

    Tissaphern Mirfakhrai

    2007-04-01

    Full Text Available The various types of natural muscle are incredible material systems that enable the production of large deformations by repetitive molecular motions. Polymer artificial muscle technologies are being developed that produce similar strains and higher stresses using electrostatic forces, electrostriction, ion insertion, and molecular conformational changes. Materials used include elastomers, conducting polymers, ionically conducting polymers, and carbon nanotubes. The mechanisms, performance, and remaining challenges associated with these technologies are described. Initial applications are being developed, but further work by the materials community should help make these technologies applicable in a wide range of devices where muscle-like motion is desirable.

  7. Mechanism of artificial heart

    CERN Document Server

    Yamane, Takashi

    2016-01-01

    This book first describes medical devices in relation to regenerative medicine before turning to a more specific topic: artificial heart technologies. Not only the pump mechanisms but also the bearing, motor mechanisms, and materials are described, including expert information. Design methods are described to enhance hemocompatibility: main concerns are reduction of blood cell damage and protein break, as well as prevention of blood clotting. Regulatory science from R&D to clinical trials is also discussed to verify the safety and efficacy of the devices.

  8. Uncertainty in artificial intelligence

    CERN Document Server

    Kanal, LN

    1986-01-01

    How to deal with uncertainty is a subject of much controversy in Artificial Intelligence. This volume brings together a wide range of perspectives on uncertainty, many of the contributors being the principal proponents in the controversy.Some of the notable issues which emerge from these papers revolve around an interval-based calculus of uncertainty, the Dempster-Shafer Theory, and probability as the best numeric model for uncertainty. There remain strong dissenting opinions not only about probability but even about the utility of any numeric method in this context.

  9. Bayesian artificial intelligence

    CERN Document Server

    Korb, Kevin B

    2010-01-01

    Updated and expanded, Bayesian Artificial Intelligence, Second Edition provides a practical and accessible introduction to the main concepts, foundation, and applications of Bayesian networks. It focuses on both the causal discovery of networks and Bayesian inference procedures. Adopting a causal interpretation of Bayesian networks, the authors discuss the use of Bayesian networks for causal modeling. They also draw on their own applied research to illustrate various applications of the technology.New to the Second EditionNew chapter on Bayesian network classifiersNew section on object-oriente

  10. Atomistic simulation of the premelting of iron and aluminum : Implications for high-pressure melting-curve measurements

    NARCIS (Netherlands)

    Starikov, Sergey V.; Stegailov, Vladimir V.

    2009-01-01

    Using atomistic simulations we show the importance of the surface premelting phenomenon for the melting-curve measurements at high pressures. The model under consideration mimics the experimental conditions deployed for melting studies with diamond-anvil cells. The iron is considered in this work be

  11. Artificial Intelligence in Space Platforms.

    Science.gov (United States)

    1984-12-01

    computer algorithms, there still appears to be a need for Artificial Inteligence techniques in the navigation area. The reason is that navigaion, in...RD-RI32 679 ARTIFICIAL INTELLIGENCE IN SPACE PLRTFORNSMU AIR FORCE 1/𔃼 INST OF TECH WRIGHT-PRTTERSON AFB OH SCHOOL OF ENGINEERING M A WRIGHT DEC 94...i4 Preface The purpose of this study was to analyze the feasibility of implementing Artificial Intelligence techniques to increase autonomy for

  12. Trimaran Resistance Artificial Neural Network

    Science.gov (United States)

    2011-01-01

    11th International Conference on Fast Sea Transportation FAST 2011, Honolulu, Hawaii, USA, September 2011 Trimaran Resistance Artificial Neural Network Richard...Trimaran Resistance Artificial Neural Network 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e... Artificial Neural Network and is restricted to the center and side-hull configurations tested. The value in the parametric model is that it is able to

  13. Parallel artificial liquid membrane extraction

    DEFF Research Database (Denmark)

    Gjelstad, Astrid; Rasmussen, Knut Einar; Parmer, Marthe Petrine

    2013-01-01

    This paper reports development of a new approach towards analytical liquid-liquid-liquid membrane extraction termed parallel artificial liquid membrane extraction. A donor plate and acceptor plate create a sandwich, in which each sample (human plasma) and acceptor solution is separated by an arti...... by an artificial liquid membrane. Parallel artificial liquid membrane extraction is a modification of hollow-fiber liquid-phase microextraction, where the hollow fibers are replaced by flat membranes in a 96-well plate format....

  14. How to teach artificial organs.

    Science.gov (United States)

    Zapanta, Conrad M; Borovetz, Harvey S; Lysaght, Michael J; Manning, Keefe B

    2011-01-01

    Artificial organs education is often an overlooked field for many bioengineering and biomedical engineering students. The purpose of this article is to describe three different approaches to teaching artificial organs. This article can serve as a reference for those who wish to offer a similar course at their own institutions or incorporate these ideas into existing courses. Artificial organ classes typically fulfill several ABET (Accreditation Board for Engineering and Technology) criteria, including those specific to bioengineering and biomedical engineering programs.

  15. A hybrid atomistic electrodynamics-quantum mechanical approach for simulating surface-enhanced Raman scattering.

    Science.gov (United States)

    Payton, John L; Morton, Seth M; Moore, Justin E; Jensen, Lasse

    2014-01-21

    Surface-enhanced Raman scattering (SERS) is a technique that has broad implications for biological and chemical sensing applications by providing the ability to simultaneously detect and identify a single molecule. The Raman scattering of molecules adsorbed on metal nanoparticles can be enhanced by many orders of magnitude. These enhancements stem from a twofold mechanism: an electromagnetic mechanism (EM), which is due to the enhanced local field near the metal surface, and a chemical mechanism (CM), which is due to the adsorbate specific interactions between the metal surface and the molecules. The local field near the metal surface can be significantly enhanced due to the plasmon excitation, and therefore chemists generally accept that the EM provides the majority of the enhancements. While classical electrodynamics simulations can accurately simulate the local electric field around metal nanoparticles, they offer few insights into the spectral changes that occur in SERS. First-principles simulations can directly predict the Raman spectrum but are limited to small metal clusters and therefore are often used for understanding the CM. Thus, there is a need for developing new methods that bridge the electrodynamics simulations of the metal nanoparticle and the first-principles simulations of the molecule to facilitate direct simulations of SERS spectra. In this Account, we discuss our recent work on developing a hybrid atomistic electrodynamics-quantum mechanical approach to simulate SERS. This hybrid method is called the discrete interaction model/quantum mechanics (DIM/QM) method and consists of an atomistic electrodynamics model of the metal nanoparticle and a time-dependent density functional theory (TDDFT) description of the molecule. In contrast to most previous work, the DIM/QM method enables us to retain a detailed atomistic structure of the nanoparticle and provides a natural bridge between the electronic structure methods and the macroscopic

  16. Predictive atomistic simulations of electronic properties of realistic nanoscale devices: A multiscale modeling approach

    Science.gov (United States)

    Vedula, Ravi Pramod Kumar

    Scaling of CMOS towards its ultimate limits, where quantum effects and atomistic variability due to fabrication, along with recent emphasis on heterogeneous integration of non-digital devices for increasing the functional diversification presents us with fundamentally new challenges. A comprehensive understanding of design and operation of these nanoscale transistors, and other electronic devices like RF-MEMS, requires an insight into their electronic and mechanical properties that are strongly influenced by underlying atomic structure. Hence, continuum descriptions of materials and use of empirical models at these scales become questionable. This increase in complexity of electronic devices necessitates an understanding at a more fundamental level to accurately predict the performance and reliability of these devices. The objective of this thesis is to outline the application of multiscale predictive modeling methods, ranging from atoms to devices, for addressing these challenges. This capability is demonstrated using two examples: characterization of (i) dielectric charging in RF-MEMS, and (ii) transport properties of Ge-nanofins. For characterizing the dielectric charging phenomenon, a continuum dielectric charging model, augmented by first principles informed trap distributions, is used to predict current transient measurements across a broad range of voltages and temperatures. These simulations demonstrate using ab initio informed model not only reduces the empiricism (number of adjustable parameters) in the model but also leads to a more accurate model over a broad range of operating conditions, and enable the precise determination of additional material parameters. These atomistic calculations also provide detailed information about the nature of charge traps and their trapping mechanisms that are not accessible experimentally; such information could prove invaluable in defect engineering. The second problem addresses the effect of the in-homogeneous strain

  17. [Artificial neural networks in Neurosciences].

    Science.gov (United States)

    Porras Chavarino, Carmen; Salinas Martínez de Lecea, José María

    2011-11-01

    This article shows that artificial neural networks are used for confirming the relationships between physiological and cognitive changes. Specifically, we explore the influence of a decrease of neurotransmitters on the behaviour of old people in recognition tasks. This artificial neural network recognizes learned patterns. When we change the threshold of activation in some units, the artificial neural network simulates the experimental results of old people in recognition tasks. However, the main contributions of this paper are the design of an artificial neural network and its operation inspired by the nervous system and the way the inputs are coded and the process of orthogonalization of patterns.

  18. Development of artificial empathy.

    Science.gov (United States)

    Asada, Minoru

    2015-01-01

    We have been advocating cognitive developmental robotics to obtain new insight into the development of human cognitive functions by utilizing synthetic and constructive approaches. Among the different emotional functions, empathy is difficult to model, but essential for robots to be social agents in our society. In my previous review on artificial empathy (Asada, 2014b), I proposed a conceptual model for empathy development beginning with emotional contagion to envy/schadenfreude along with self/other differentiation. In this article, the focus is on two aspects of this developmental process, emotional contagion in relation to motor mimicry, and cognitive/affective aspects of the empathy. It begins with a summary of the previous review (Asada, 2014b) and an introduction to affective developmental robotics as a part of cognitive developmental robotics focusing on the affective aspects. This is followed by a review and discussion on several approaches for two focused aspects of affective developmental robotics. Finally, future issues involved in the development of a more authentic form of artificial empathy are discussed.

  19. Creating an Artificial Muscle

    Science.gov (United States)

    Bohon, Katherine; Krause, Sonja

    1997-03-01

    Striated skeletal muscle responds to a nerve impulse in less than 100 ms. In the past, polymeric gels and conducting polymers have been investigated for use as artificial muscle. However, the main problem with these materials is their relatively slow response (>3 seconds). On the other hand, electrorheological (ER) fluids are materials that change from a liquid to a solid upon application of an electric field. These fluids have a response on the order of a millisecond. A novel approach to artificial muscle utilizing the fast time response of ER fluids and the elasticity of polymeric gels has been investigated. A commercial sample of a two-part poly(dimethyl siloxane) (PDMS) dielectric gel was used. The PDMS was cured around two flexible electrodes 5 mm apart while a mixture of PDMS with solvent was cured between the electrodes. The solvents were either silicone oil or an ER fluid composed of crosslinked poly(ethylene oxide) (PEO) particles in silicone oil. The mixtures investigated were 90/10, 60/40, 50/50, 40/60, 10/90 PDMS/solvent. Upon application of a 6.2 kV/cm DC electric field the gel was reversibly compressed. The time response of the gel was actuator has been created using the 60/40 PDMS/ER fluid mixture.

  20. The total artificial heart.

    Science.gov (United States)

    Cook, Jason A; Shah, Keyur B; Quader, Mohammed A; Cooke, Richard H; Kasirajan, Vigneshwar; Rao, Kris K; Smallfield, Melissa C; Tchoukina, Inna; Tang, Daniel G

    2015-12-01

    The total artificial heart (TAH) is a form of mechanical circulatory support in which the patient's native ventricles and valves are explanted and replaced by a pneumatically powered artificial heart. Currently, the TAH is approved for use in end-stage biventricular heart failure as a bridge to heart transplantation. However, with an increasing global burden of cardiovascular disease and congestive heart failure, the number of patients with end-stage heart failure awaiting heart transplantation now far exceeds the number of available hearts. As a result, the use of mechanical circulatory support, including the TAH and left ventricular assist device (LVAD), is growing exponentially. The LVAD is already widely used as destination therapy, and destination therapy for the TAH is under investigation. While most patients requiring mechanical circulatory support are effectively treated with LVADs, there is a subset of patients with concurrent right ventricular failure or major structural barriers to LVAD placement in whom TAH may be more appropriate. The history, indications, surgical implantation, post device management, outcomes, complications, and future direction of the TAH are discussed in this review.

  1. Generative Artificial Intelligence : Philosophy and Theory of Artificial Intelligence

    NARCIS (Netherlands)

    van der Zant, Tijn; Kouw, Matthijs; Schomaker, Lambertus; Mueller, Vincent C.

    2013-01-01

    The closed systems of contemporary Artificial Intelligence do not seem to lead to intelligent machines in the near future. What is needed are open-ended systems with non-linear properties in order to create interesting properties for the scaffolding of an artificial mind. Using post-structuralistic

  2. Mechanism of the Cassie-Wenzel transition via the atomistic and continuum string methods

    Energy Technology Data Exchange (ETDEWEB)

    Giacomello, Alberto, E-mail: alberto.giacomello@uniroma1.it; Casciola, Carlo Massimo [Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma “La Sapienza,” 00184 Rome (Italy); Meloni, Simone, E-mail: simone.meloni@epfl.ch [Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Müller, Marcus [Institut für Theoretische Physik, Georg-August-Universität Göttingen, 37077 Göttingen (Germany)

    2015-03-14

    The string method is a general and flexible strategy to compute the most probable transition path for an activated process (rare event). We apply here the atomistic string method in the density field to the Cassie-Wenzel transition, a central problem in the field of superhydrophobicity. We discuss in detail the mechanism of wetting of a submerged hydrophobic cavity of nanometer size and its dependence on the geometry of the cavity. Furthermore, we analyze the algorithmic analogies between the continuum “interface” string method and CREaM [Giacomello et al., Phys. Rev. Lett. 109, 226102 (2012)], a method inspired by the string that allows for a faster and simpler computation of the mechanism and of the free-energy profiles of the wetting process.

  3. Atomistic and continuums modeling of cluster migration and coagulation in precipitation reactions.

    Science.gov (United States)

    Warczok, Piotr; Ženíšek, Jaroslav; Kozeschnik, Ernst

    2012-07-01

    The influence of vacancy preference towards one of the constituents in a binary system on the formation of precipitates was investigated by atomistic and continuums modeling techniques. In case of vacancy preference towards the solute atoms, we find that the mobility of individual clusters as well as entire atom clusters is significantly altered compared to the case of vacancy preference towards the solvent atoms. The increased cluster mobility leads to pronounced cluster collisions, providing a precipitate growth and coarsening mechanism competitive to that of pure solute evaporation and adsorption considered in conventional diffusional growth and Ostwald ripening. A modification of a numerical Kampmann-Wagner type continuum model for precipitate growth is proposed, which incorporates the influence of both mechanisms. The prognoses of the modified model are validated against the growth laws obtained with lattice Monte Carlo simulations and a growth simulation considering solely the coalescence mechanism.

  4. Atomistic Investigation of Cu-Induced Misfolding in the Onset of Parkinson's Disease

    Science.gov (United States)

    Rose, Francis; Hodak, Miroslav; Bernholc, Jerry

    2009-03-01

    A nucleation mechanism for the misfolding of α-synuclein, the protein implicated in Parkinson's Disease (PD), is investigated using computer simulations. Through a combination of ab initio and classical simulation techniques, the conformational evolution of copper-ion-initiated misfolding of α-synuclein is determined. Based on these investigations and available experimental evidence, an atomistic model detailing the nucleation-initiated pathogenesis of PD is proposed. Once misfolded, the proteins can assemble into fibrils, the primary structural components of the deleterious PD plaques. Our model identifies a process of structural modifications to an initially unfolded α-synuclein that results in a partially folded intermediate with a well defined nucleation site as a precursor to the fully misfolded protein. The identified pathway can enable studies of reversal mechanisms and inhibitory agents, potentially leading to the development of effective therapies.

  5. An atomistic vision of the Mass Action Law: Prediction of carbon/oxygen defects in silicon

    Energy Technology Data Exchange (ETDEWEB)

    Brenet, G.; Timerkaeva, D.; Caliste, D.; Pochet, P. [CEA, INAC-SP2M, Atomistic Simulation Laboratory, F-38000 Grenoble (France); Univ. Grenoble Alpes, INAC-SP2M, L-Sim, F-38000 Grenoble (France); Sgourou, E. N.; Londos, C. A. [University of Athens, Solid State Physics Section, Panepistimiopolis Zografos, Athens 157 84 (Greece)

    2015-09-28

    We introduce an atomistic description of the kinetic Mass Action Law to predict concentrations of defects and complexes. We demonstrate in this paper that this approach accurately predicts carbon/oxygen related defect concentrations in silicon upon annealing. The model requires binding and migration energies of the impurities and complexes, here obtained from density functional theory (DFT) calculations. Vacancy-oxygen complex kinetics are studied as a model system during both isochronal and isothermal annealing. Results are in good agreement with experimental data, confirming the success of the methodology. More importantly, it gives access to the sequence of chain reactions by which oxygen and carbon related complexes are created in silicon. Beside the case of silicon, the understanding of such intricate reactions is a key to develop point defect engineering strategies to control defects and thus semiconductors properties.

  6. Atomistic study of energy funneling in the light-harvesting complex of green sulfur bacteria

    CERN Document Server

    Huh, Joonsuk; Brookes, Jennifer C; Valleau, Stéphanie; Fujita, Takatoshi; Aspuru-Guzik, Alán

    2013-01-01

    Phototrophic organisms such as plants, photosynthetic bacteria and algae use microscopic complexes of pigment molecules to absorb sunlight. Within the light-harvesting complexes, which frequently have multiple functional and structural subunits, the energy is transferred in the form of molecular excitations with very high efficiency. Green sulfur bacteria are considered to be amongst the most efficient light-harvesting organisms. Despite multiple experimental and theoretical studies of these bacteria the physical origin of the efficient and robust energy transfer in their light-harvesting complexes is not well understood. To study excitation dynamics at the systems level we introduce an atomistic model that mimic a complete light-harvesting apparatus of green sulfur bacteria. The model contains about 4000 pigment molecules and comprises a double wall roll for the chlorosome, a baseplate and six Fenna-Matthews-Olson trimer complexes. We show that the fast relaxation within functional subunits combined with the...

  7. Atomistic Simulations of Functional Au-144(SR)(60) Gold Nanoparticles in Aqueous Environment

    DEFF Research Database (Denmark)

    Heikkila, E.; Gurtovenko, A. A.; Martinez-Seara, H.

    2012-01-01

    Charged monolayer-protected gold nanoparticles (AuNPs) have been studied in aqueous solution by performing atomistic molecular dynamics simulations at physiological temperature (310 K). Particular attention has been paid to electrostatic properties that modulate the formation of a complex comprised...... of the nanoparticle together with surrounding ions and water. We focus on Au-144 nanoparticles that comprise a nearly spherical Au core (diameter similar to 2 nm), a passivating Au-S interface, and functionalized alkanethiol chains. Cationic and anionic AuNPs have been modeled with amine and carboxyl terminal groups...... potential displays a minimum for AuNP- at 1.9 nm from the center of the nanoparticle, marking a preferable location for Na+, while the AuNP+ potential (affecting the distribution of Cl-) rises almost monotonically with a local maximum. Comparison to Debye-Huckel theory shows very good agreement for radial...

  8. Structures, nanomechanics, and disintegration of single-walled GaN nanotubes: atomistic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Jeong Won; Hwang, Ho Jung; Song, Ki Oh; Choi, Won Young; Byun, Ki Ryang [Chung-Ang University, Seoul (Korea, Republic of); Kwon, Oh Keun [Semyung University, Jecheon (Korea, Republic of); Lee, Jun Ha [Sangmyung University, Chonan (Korea, Republic of); Kim, Won Woo [Juseong College, Cheongwon (Korea, Republic of)

    2003-09-15

    We have investigated the structural, mechanical, and thermal properties of single-walled GaN nanotubes by using atomistic simulations and a Tersoff-type potential. The Tersoff potential for GaN effectively describes the properties of GaN nanotubes. The nanomechanics of GaN nanotubes under tensile and compressive loadings have also been investigated, and Young's modulus has been calculated. The caloric curves of single-walled GaN nanotubes can be divided into three regions corresponding to nanotubes, the disintegrating range, and vapor. Since the stability or the stiffness of a tube decreases with increasing curving sheet-to-tube strain energy, the disintegration temperatures of GaN nanotubes are closely related to the curving sheet-to-tube strain energy.

  9. A Spectral Multiscale Method for Wave Propagation Analysis: Atomistic-Continuum Coupled Simulation

    CERN Document Server

    Patra, Amit K; Ganguli, Ranjan

    2014-01-01

    In this paper, we present a new multiscale method which is capable of coupling atomistic and continuum domains for high frequency wave propagation analysis. The problem of non-physical wave reflection, which occurs due to the change in system description across the interface between two scales, can be satisfactorily overcome by the proposed method. We propose an efficient spectral domain decomposition of the total fine scale displacement along with a potent macroscale equation in the Laplace domain to eliminate the spurious interfacial reflection. We use Laplace transform based spectral finite element method to model the macroscale, which provides the optimum approximations for required dynamic responses of the outer atoms of the simulated microscale region very accurately. This new method shows excellent agreement between the proposed multiscale model and the full molecular dynamics (MD) results. Numerical experiments of wave propagation in a 1D harmonic lattice, a 1D lattice with Lennard-Jones potential, a ...

  10. Computer code for the atomistic simulation of lattice defects and dynamics. [COMENT code

    Energy Technology Data Exchange (ETDEWEB)

    Schiffgens, J.O.; Graves, N.J.; Oster, C.A.

    1980-04-01

    This document has been prepared to satisfy the need for a detailed, up-to-date description of a computer code that can be used to simulate phenomena on an atomistic level. COMENT was written in FORTRAN IV and COMPASS (CDC assembly language) to solve the classical equations of motion for a large number of atoms interacting according to a given force law, and to perform the desired ancillary analysis of the resulting data. COMENT is a dual-purpose intended to describe static defect configurations as well as the detailed motion of atoms in a crystal lattice. It can be used to simulate the effect of temperature, impurities, and pre-existing defects on radiation-induced defect production mechanisms, defect migration, and defect stability.

  11. Mapping between atomistic simulations and Eshelby inclusions in the shear deformation of an amorphous silicon model

    Science.gov (United States)

    Albaret, T.; Tanguy, A.; Boioli, F.; Rodney, D.

    2016-05-01

    In this paper we perform quasistatic shear simulations of model amorphous silicon bulk samples with Stillinger-Weber-type potentials. Local plastic rearrangements identified based on local energy variations are fitted through their displacement fields on collections of Eshelby spherical inclusions, allowing determination of their transformation strain tensors. The latter are then used to quantitatively reproduce atomistic stress-strain curves, in terms of both shear and pressure components. We demonstrate that our methodology is able to capture the plastic behavior predicted by different Stillinger-Weber potentials, in particular, their different shear tension coupling. These calculations justify the decomposition of plasticity into shear transformations used so far in mesoscale models and provide atomic-scale parameters that can be used to limit the empiricism needed in such models up to now.

  12. Thermochemistry of organic reactions in microporous oxides by atomistic simulations: benchmarking against periodic B3LYP.

    Science.gov (United States)

    Bleken, Francesca; Svelle, Stian; Lillerud, Karl Petter; Olsbye, Unni; Arstad, Bjørnar; Swang, Ole

    2010-07-15

    The methylation of ethene by methyl chloride and methanol in the microporous materials SAPO-34 and SSZ-13 has been studied using different periodic atomistic modeling approaches based on density functional theory. The RPBE functional, which earlier has been used successfully in studies of surface reactions on metals, fails to yield a qualitatively correct description of the transition states under study. Employing B3LYP as functional gives results in line with experimental data: (1) Methanol is adsorbed more strongly than methyl chloride to the acid site. (2) The activation energies for the methylation of ethene are slightly lower for SSZ-13. Furthermore, the B3LYP activation energies are lower for methyl chloride than for methanol.

  13. Atomistic Study on Size Effects in Thermally Induced Martensitic Phase Transformation of NiTi

    Directory of Open Access Journals (Sweden)

    Sourav Gur

    2016-01-01

    Full Text Available The atomistic study shows strong size effects in thermally induced martensitic phase transformation evolution kinetics of equiatomic NiTi shape memory alloys (SMAs. It is shown that size effects are closely related to the presence of free surfaces; thus, NiTi thin films and nanopillars are studied. Quasi-static molecular dynamics simulations for several cell sizes at various (constant temperatures are performed by employing well-established interatomic potentials for NiTi. The study shows that size plays a crucial role in the evolution of martensite phase fraction and, importantly, can significantly change the phase transformation temperatures, which can be used for the design of NiTi based sensors, actuators, or devices at nano- to microscales. Interestingly, it is found that, at the nanometer scale, Richard’s equation describes very well the martensite phase fraction evolution in NiTi thin films and nanopillars as a function of temperature.

  14. Atomistic simulations of surface coverage effects in anisotropic wet chemical etching of crystalline silicon

    Energy Technology Data Exchange (ETDEWEB)

    Gosalvez, M.A.; Foster, A.S.; Nieminen, R.M

    2002-12-30

    Atomistic simulations of anisotropic wet chemical etching of crystalline silicon have been performed in order to determine the dependence of the etch rates of different crystallographic orientations on surface coverage and clustering of OH radicals. We show that the etch rate is a non-monotonic function of OH coverage and that there always exists a coverage value at which the etch rate reaches a maximum. The dependence of the anisotropy of the etching process on coverage, including the dependence of the fastest-etched plane orientation, is implicitly contained in the model and predictions of convex corner under-etching structures are made. We show that the whole etching process is controlled by only a few surface configurations involving a particular type of next-nearest neighbours. The relative value of the removal probabilities of these confitions determines the balance in the occurrence of step propagation and etch pitting for all surface orientations.

  15. Atomistic-Continuum Hybrid Simulation of Heat Transfer between Argon Flow and Copper Plates

    CERN Document Server

    Mao, Yijin; Chen, C L

    2016-01-01

    A simulation work aiming to study heat transfer coefficient between argon fluid flow and copper plate is carried out based on atomistic-continuum hybrid method. Navier-Stokes equations for continuum domain are solved through the Pressure Implicit with Splitting of Operators (PISO) algorithm, and the atom evolution in molecular domain is solved through the Verlet algorithm. The solver is validated by solving Couette flow and heat conduction problems. With both momentum and energy coupling method applied, simulations on convection of argon flows between two parallel plates are performed. The top plate is kept as a constant velocity and has higher temperature, while the lower one, which is modeled with FCC copper lattices, is also fixed but has lower temperature. It is found that, heat transfer between argon fluid flow and copper plate in this situation is much higher than that at macroscopic when the flow is fully developed.

  16. Collective dynamics in atomistic models with coupled translational and spin degrees of freedom

    Science.gov (United States)

    Perera, Dilina; Nicholson, Don M.; Eisenbach, Markus; Stocks, G. Malcolm; Landau, David P.

    2017-01-01

    Using an atomistic model that simultaneously treats the dynamics of translational and spin degrees of freedom, we perform combined molecular and spin dynamics simulations to investigate the mutual influence of the phonons and magnons on their respective frequency spectra and lifetimes in ferromagnetic bcc iron. By calculating the Fourier transforms of the space- and time-displaced correlation functions, the characteristic frequencies and the linewidths of the vibrational and magnetic excitation modes were determined. Comparison of the results with that of the stand-alone molecular dynamics and spin dynamics simulations reveals that the dynamic interplay between the phonons and magnons leads to a shift in the respective frequency spectra and a decrease in the lifetimes. Moreover, in the presence of lattice vibrations, additional longitudinal magnetic excitations were observed with the same frequencies as the longitudinal phonons.

  17. Coupling Lattice Boltzmann with Atomistic Dynamics for the multiscale simulation of nano-biological flows

    CERN Document Server

    Fyta, Maria; Kaxiras, Efthimios; Succi, Sauro

    2007-01-01

    We describe a recent multiscale approach based on the concurrent coupling of constrained molecular dynamics for long biomolecules with a mesoscopic lattice Boltzmann treatment of solvent hydrodynamics. The multiscale approach is based on a simple scheme of exchange of space-time information between the atomistic and mesoscopic scales and is capable of describing self-consistent hydrodynamic effects on molecular motion at a computational cost which scales linearly with both solute size and solvent volume. For an application of our multiscale method, we consider the much studied problem of biopolymer translocation through nanopores: we find that the method reproduces with remarkable accuracy the statistical scaling behavior of the translocation process and provides valuable insight into the cooperative aspects of biopolymer and hydrodynamic motion.

  18. Identifying early stage precipitation in large-scale atomistic simulations of superalloys

    Science.gov (United States)

    Schmidt, Eric; Bristowe, Paul D.

    2017-04-01

    A method for identifying and classifying ordered phases in large chemically and thermally disordered atomistic models is presented. The method uses Steinhardt parameters to represent local atomic configurations and develops probability density functions to classify individual atoms using naïve Bayes. The method is applied to large molecular dynamics simulations of supersaturated Ni-20 at% Al solid solutions in order to identify the formation of embryonic γ‧-Ni3Al. The composition and temperatures are chosen to promote precipitation, which is observed in the form of ordering and is found to occur more likely in regions with above average Al concentration producing ‘clusters’ of increasing size. The results are interpreted in terms of a precipitation mechanism in which the solid solution is unstable with respect to ordering and potentially followed by either spinodal decomposition or nucleation and growth.

  19. Atomistic study of deposition process of Al thin film on Cu substrate

    Energy Technology Data Exchange (ETDEWEB)

    Cao Yongzhi, E-mail: yzcaohit@gmail.com [Center for Precision Engineering, Harbin Institute of Technology, Harbin (China); Zhang Junjie; Sun Tao; Yan Yongda; Yu Fuli [Center for Precision Engineering, Harbin Institute of Technology, Harbin (China)

    2010-08-01

    In this paper we report molecular dynamics based atomistic simulations of deposition process of Al atoms onto Cu substrate and following nanoindentation process on that nanostructured material. Effects of incident energy on the morphology of deposited thin film and mechanical property of this nanostructured material are emphasized. The results reveal that the morphology of growing film is layer-by-layer-like at incident energy of 0.1-10 eV. The epitaxy mode of film growth is observed at incident energy below 1 eV, but film-mixing mode commences when incident energy increase to 10 eV accompanying with increased disorder of film structure, which improves quality of deposited thin film. Following indentation studies indicate deposited thin films pose lower stiffness than single crystal Al due to considerable amount of defects existed in them, but Cu substrate is strengthened by the interface generated from lattice mismatch between deposited Al thin film and Cu substrate.

  20. Atomistic study of lipid membranes containing chloroform: looking for a lipid-mediated mechanism of anesthesia.

    Directory of Open Access Journals (Sweden)

    Ramon Reigada

    Full Text Available The molecular mechanism of general anesthesia is still a controversial issue. Direct effect by linking of anesthetics to proteins and indirect action on the lipid membrane properties are the two hypotheses in conflict. Atomistic simulations of different lipid membranes subjected to the effect of small volatile organohalogen compounds are used to explore plausible lipid-mediated mechanisms. Simulations of homogeneous membranes reveal that electrostatic potential and lateral pressure transversal profiles are affected differently by chloroform (anesthetic and carbon tetrachloride (non-anesthetic. Simulations of structured membranes that combine ordered and disordered regions show that chloroform molecules accumulate preferentially in highly disordered lipid domains, suggesting that the combination of both lateral and transversal partitioning of chloroform in the cell membrane could be responsible of its anesthetic action.

  1. Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations

    Science.gov (United States)

    Mazzaglia, Antonino; Ganazzoli, Fabio

    2015-01-01

    Summary Amphiphilically modified cyclodextrins may form various supramolecular aggregates. Here we report a theoretical study of the aggregation of a few amphiphilic cyclodextrins carrying hydrophobic thioalkyl groups and hydrophilic ethylene glycol moieties at opposite rims, focusing on the initial nucleation stage in an apolar solvent and in water. The study is based on atomistic molecular dynamics methods with a “bottom up” approach that can provide important information about the initial aggregates of few molecules. The focus is on the interaction pattern of amphiphilic cyclodextrin (aCD), which may interact by mutual inclusion of the substituent groups in the hydrophobic cavity of neighbouring molecules or by dispersion interactions at their lateral surface. We suggest that these aggregates can also form the nucleation stage of larger systems as well as the building blocks of micelles, vesicle, membranes, or generally nanoparticles thus opening new perspectives in the design of aggregates correlating their structures with the pharmaceutical properties. PMID:26734094

  2. NATO Advanced Study Institute on Surface Diffusion : Atomistic and Collective Processes

    CERN Document Server

    1997-01-01

    The interest in the problem of surface diffusion has been steadily growing over the last fifteen years. This is clearly evident from the increase in the number of papers dealing with the problem, the development of new experimental techniques, and the specialized sessions focusing on diffusion in national and international meetings. Part of the driving force behind this increasing activity is our recently acquired ability to observe and possibly control atomic scale phenomena. It is now possible to look selectively at individual atomistic processes and to determine their relative importance during growth and reactions at surfaces. The number of researchers interested in this problem also has been growing steadily which generates the need for a good reference source to farniliarize newcomers to the problem. While the recent emphasis is on the role of diffusion during growth, there is also continuing progress on the more traditional aspects of the problem describing mass transport in an ensemble of particles. S...

  3. Atomistic computer simulations of FePt nanoparticles. Thermodynamic and kinetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, M.

    2007-12-20

    In the present dissertation, a hierarchical multiscale approach for modeling FePt nanoparticles by atomistic computer simulations is developed. By describing the interatomic interactions on different levels of sophistication, various time and length scales can be accessed. Methods range from static quantum-mechanic total-energy calculations of small periodic systems to simulations of whole particles over an extended time by using simple lattice Hamiltonians. By employing these methods, the energetic and thermodynamic stability of non-crystalline multiply twinned FePt nanoparticles is investigated. Subsequently, the thermodynamics of the order-disorder transition in FePt nanoparticles is analyzed, including the influence of particle size, composition and modified surface energies by different chemical surroundings. In order to identify processes that reduce or enhance the rate of transformation from the disordered to the ordered state, the kinetics of the ordering transition in FePt nanoparticles is finally investigated by assessing the contributions of surface and volume diffusion. (orig.)

  4. Atomistic simulation study of linear alkylbenzene sulfonates at the water/air interface

    Science.gov (United States)

    He, Xibing; Guvench, Olgun; MacKerell, Alexander D.; Klein, Michael L.

    2010-01-01

    Molecular Dynamics simulations with the CHARMM atomistic force field have been used to study monolayers of a series of linear alkylbenzene sulfonates (LAS) at the water/air interface. Both the numbers of carbon atoms in the LAS alkyl tail (1 to 11), and the position of attachment of the benzene ring on the alkyl chain have been varied. Totally 36 LAS homologues and isomers have been investigated. The surface tensions of the systems and the average tilt angles of the LAS molecules are found to be related to both the length and the degree of branching of the alkyl tails, whereas the solubility and mobility are mostly determined by the tail length. PMID:20614916

  5. Long-time atomistic simulations with the Parallel Replica Dynamics method

    Science.gov (United States)

    Perez, Danny

    Molecular Dynamics (MD) -- the numerical integration of atomistic equations of motion -- is a workhorse of computational materials science. Indeed, MD can in principle be used to obtain any thermodynamic or kinetic quantity, without introducing any approximation or assumptions beyond the adequacy of the interaction potential. It is therefore an extremely powerful and flexible tool to study materials with atomistic spatio-temporal resolution. These enviable qualities however come at a steep computational price, hence limiting the system sizes and simulation times that can be achieved in practice. While the size limitation can be efficiently addressed with massively parallel implementations of MD based on spatial decomposition strategies, allowing for the simulation of trillions of atoms, the same approach usually cannot extend the timescales much beyond microseconds. In this article, we discuss an alternative parallel-in-time approach, the Parallel Replica Dynamics (ParRep) method, that aims at addressing the timescale limitation of MD for systems that evolve through rare state-to-state transitions. We review the formal underpinnings of the method and demonstrate that it can provide arbitrarily accurate results for any definition of the states. When an adequate definition of the states is available, ParRep can simulate trajectories with a parallel speedup approaching the number of replicas used. We demonstrate the usefulness of ParRep by presenting different examples of materials simulations where access to long timescales was essential to access the physical regime of interest and discuss practical considerations that must be addressed to carry out these simulations. Work supported by the United States Department of Energy (U.S. DOE), Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division.

  6. Atomic force microscope adhesion measurements and atomistic molecular dynamics simulations at different humidities

    Science.gov (United States)

    Seppä, Jeremias; Reischl, Bernhard; Sairanen, Hannu; Korpelainen, Virpi; Husu, Hannu; Heinonen, Martti; Raiteri, Paolo; Rohl, Andrew L.; Nordlund, Kai; Lassila, Antti

    2017-03-01

    Due to their operation principle atomic force microscopes (AFMs) are sensitive to all factors affecting the detected force between the probe and the sample. Relative humidity is an important and often neglected—both in experiments and simulations—factor in the interaction force between AFM probe and sample in air. This paper describes the humidity control system designed and built for the interferometrically traceable metrology AFM (IT-MAFM) at VTT MIKES. The humidity control is based on circulating the air of the AFM enclosure via dryer and humidifier paths with adjustable flow and mixing ratio of dry and humid air. The design humidity range of the system is 20–60 %rh. Force–distance adhesion studies at humidity levels between 25 %rh and 53 %rh are presented and compared to an atomistic molecular dynamics (MD) simulation. The uncertainty level of the thermal noise method implementation used for force constant calibration of the AFM cantilevers is 10 %, being the dominant component of the interaction force measurement uncertainty. Comparing the simulation and the experiment, the primary uncertainties are related to the nominally 7 nm radius and shape of measurement probe apex, possible wear and contamination, and the atomistic simulation technique details. The interaction forces are of the same order of magnitude in simulation and measurement (5 nN). An elongation of a few nanometres of the water meniscus between probe tip and sample, before its rupture, is seen in simulation upon retraction of the tip in higher humidity. This behaviour is also supported by the presented experimental measurement data but the data is insufficient to conclusively verify the quantitative meniscus elongation.

  7. Hybrid Artificial Bee Colony Algorithm and Particle Swarm Search for Global Optimization

    Directory of Open Access Journals (Sweden)

    Wang Chun-Feng

    2014-01-01

    Full Text Available Artificial bee colony (ABC algorithm is one of the most recent swarm intelligence based algorithms, which has been shown to be competitive to other population-based algorithms. However, there is still an insufficiency in ABC regarding its solution search equation, which is good at exploration but poor at exploitation. To overcome this problem, we propose a novel artificial bee colony algorithm based on particle swarm search mechanism. In this algorithm, for improving the convergence speed, the initial population is generated by using good point set theory rather than random selection firstly. Secondly, in order to enhance the exploitation ability, the employed bee, onlookers, and scouts utilize the mechanism of PSO to search new candidate solutions. Finally, for further improving the searching ability, the chaotic search operator is adopted in the best solution of the current iteration. Our algorithm is tested on some well-known benchmark functions and compared with other algorithms. Results show that our algorithm has good performance.

  8. Artificial Diets for Mosquitoes

    Directory of Open Access Journals (Sweden)

    Kristina K. Gonzales

    2016-12-01

    Full Text Available Mosquito-borne diseases are responsible for more than a million human deaths every year. Modern mosquito control strategies such as sterile insect technique (SIT, release of insects carrying a dominant lethal (RIDL, population replacement strategies (PR, and Wolbachia-based strategies require the rearing of large numbers of mosquitoes in culture for continuous release over an extended period of time. Anautogenous mosquitoes require essential nutrients for egg production, which they obtain through the acquisition and digestion of a protein-rich blood meal. Therefore, mosquito mass production in laboratories and other facilities relies on vertebrate blood from live animal hosts. However, vertebrate blood is expensive to acquire and hard to store for longer times especially under field conditions. This review discusses older and recent studies that were aimed at the development of artificial diets for mosquitoes in order to replace vertebrate blood.

  9. Artificial Immune Systems (2010)

    CERN Document Server

    Greensmith, Julie; Aickelin, Uwe

    2010-01-01

    The human immune system has numerous properties that make it ripe for exploitation in the computational domain, such as robustness and fault tolerance, and many different algorithms, collectively termed Artificial Immune Systems (AIS), have been inspired by it. Two generations of AIS are currently in use, with the first generation relying on simplified immune models and the second generation utilising interdisciplinary collaboration to develop a deeper understanding of the immune system and hence produce more complex models. Both generations of algorithms have been successfully applied to a variety of problems, including anomaly detection, pattern recognition, optimisation and robotics. In this chapter an overview of AIS is presented, its evolution is discussed, and it is shown that the diversification of the field is linked to the diversity of the immune system itself, leading to a number of algorithms as opposed to one archetypal system. Two case studies are also presented to help provide insight into the m...

  10. Sucrose compared with artificial sweeteners

    DEFF Research Database (Denmark)

    Sørensen, Lone Brinkmann; Vasilaras, Tatjana H; Astrup, Arne;

    2014-01-01

    There is a lack of appetite studies in free-living subjects supplying the habitual diet with either sucrose or artificially sweetened beverages and foods. Furthermore, the focus of artificial sweeteners has only been on the energy intake (EI) side of the energy-balance equation. The data are from...

  11. Instructional Applications of Artificial Intelligence.

    Science.gov (United States)

    Halff, Henry M.

    1986-01-01

    Surveys artificial intelligence and the development of computer-based tutors and speculates on the future of artificial intelligence in education. Includes discussion of the definitions of knowledge, expert systems (computer systems that solve tough technical problems), intelligent tutoring systems (ITS), and specific ITSs such as GUIDON, MYCIN,…

  12. A Primer on Artificial Intelligence.

    Science.gov (United States)

    Leal, Ralph A.

    A survey of literature on recent advances in the field of artificial intelligence provides a comprehensive introduction to this field for the non-technical reader. Important areas covered are: (1) definitions, (2) the brain and thinking, (3) heuristic search, and (4) programing languages used in the research of artificial intelligence. Some…

  13. Generalized Adaptive Artificial Neural Networks

    Science.gov (United States)

    Tawel, Raoul

    1993-01-01

    Mathematical model of supervised learning by artificial neural network provides for simultaneous adjustments of both temperatures of neurons and synaptic weights, and includes feedback as well as feedforward synaptic connections. Extension of mathematical model described in "Adaptive Neurons For Artificial Neural Networks" (NPO-17803). Dynamics of neural network represented in new model by less-restrictive continuous formalism.

  14. Artificial Ligaments: Promise or Panacea?

    Science.gov (United States)

    Lubell, Adele

    1987-01-01

    The Food and Drug Administration has approved a prosthetic ligament for limited use in persons with damaged anterior cruciate ligaments (ACL). This article addresses ligament repair, ACL tears, current treatment, development of the Gore-Tex artificial ligament, other artificial ligaments in process, and arguments for and against their use.…

  15. Beyond AI: Artificial Dreams Conference

    CERN Document Server

    Zackova, Eva; Kelemen, Jozef; Beyond Artificial Intelligence : The Disappearing Human-Machine Divide

    2015-01-01

    This book is an edited collection of chapters based on the papers presented at the conference “Beyond AI: Artificial Dreams” held in Pilsen in November 2012. The aim of the conference was to question deep-rooted ideas of artificial intelligence and cast critical reflection on methods standing at its foundations.  Artificial Dreams epitomize our controversial quest for non-biological intelligence, and therefore the contributors of this book tried to fully exploit such a controversy in their respective chapters, which resulted in an interdisciplinary dialogue between experts from engineering, natural sciences and humanities.   While pursuing the Artificial Dreams, it has become clear that it is still more and more difficult to draw a clear divide between human and machine. And therefore this book tries to portrait such an image of what lies beyond artificial intelligence: we can see the disappearing human-machine divide, a very important phenomenon of nowadays technological society, the phenomenon which i...

  16. What Is a Total Artificial Heart?

    Science.gov (United States)

    ... the NHLBI on Twitter. What Is a Total Artificial Heart? A total artificial heart (TAH) is a device ... outside power source. Normal Heart and CardioWest Total Artificial Heart Figure A shows the normal structure and location ...

  17. The artificial leaf.

    Science.gov (United States)

    Nocera, Daniel G

    2012-05-15

    To convert the energy of sunlight into chemical energy, the leaf splits water via the photosynthetic process to produce molecular oxygen and hydrogen, which is in a form of separated protons and electrons. The primary steps of natural photosynthesis involve the absorption of sunlight and its conversion into spatially separated electron-hole pairs. The holes of this wireless current are captured by the oxygen evolving complex (OEC) of photosystem II (PSII) to oxidize water to oxygen. The electrons and protons produced as a byproduct of the OEC reaction are captured by ferrodoxin of photosystem I. With the aid of ferrodoxin-NADP(+) reductase, they are used to produce hydrogen in the form of NADPH. For a synthetic material to realize the solar energy conversion function of the leaf, the light-absorbing material must capture a solar photon to generate a wireless current that is harnessed by catalysts, which drive the four electron/hole fuel-forming water-splitting reaction under benign conditions and under 1 sun (100 mW/cm(2)) illumination. This Account describes the construction of an artificial leaf comprising earth-abundant elements by interfacing a triple junction, amorphous silicon photovoltaic with hydrogen- and oxygen-evolving catalysts made from a ternary alloy (NiMoZn) and a cobalt-phosphate cluster (Co-OEC), respectively. The latter captures the structural and functional attributes of the PSII-OEC. Similar to the PSII-OEC, the Co-OEC self-assembles upon oxidation of an earth-abundant metal ion from 2+ to 3+, may operate in natural water at room temperature, and is self-healing. The Co-OEC also activates H(2)O by a proton-coupled electron transfer mechanism in which the Co-OEC is increased by four hole equivalents akin to the S-state pumping of the Kok cycle of PSII. X-ray absorption spectroscopy studies have established that the Co-OEC is a structural relative of Mn(3)CaO(4)-Mn cubane of the PSII-OEC, where Co replaces Mn and the cubane is extended in a

  18. [Research and development of artificial retina material].

    Science.gov (United States)

    Hu, Ning; Yang, Jun; Peng, Chenglin; Wang, Xing; Zhang, Sijie; Zhang, Ying; Zheng, Erxin

    2008-04-01

    The application of artificial retina was introduced. The principal characteristics of artificial retina material were reviewed in particular. Moreover, the recent research development and application prospect were discussed.

  19. natural or artificial diets

    Directory of Open Access Journals (Sweden)

    A. O. Meyer-Willerer

    2005-01-01

    Full Text Available Se probaron alimentos artificiales y naturales con larva de camarón (Litopenaeus vannamei cultivados en diferentes recipientes. Estos fueron ocho frascos cónicos con 15L, ocho acuarios con 50L y como grupo control, seis tanques de fibra de vidrio con 1500L; todos con agua marina fresca y filtrada. La densidad inicial en todos los recipientes fue de 70 nauplios/L. Aquellos en frascos y acuarios recibieron ya sea dieta natural o artificial. El grupo control fue cultivado con dieta natural en los tanques grandes que utilizan los laboratorios para la producción masiva de postlarvas. El principal producto de excreción de larva de camarón es el ión amonio, que es tóxico cuando está presente en concentraciones elevadas. Se determinó diariamente con el método colorimétrico del indofenol. Los resultados muestran diferencias en la concentración del ión amonio y en la sobrevivencia de larvas entre las diferentes dietas y también entre los diferentes recipientes. En aquellos con volúmenes pequeños comparados con los grandes, se presentó mayor concentración de amonio (500 a 750µg/L, en aquellos con dietas naturales, debido a que este ión sirve de fertilizante a las algas adicionadas, necesitando efectuar recambios diarios de agua posteriores al noveno día de cultivo para mantener este ión a una concentración subletal. Se obtuvo una baja cosecha de postlarvas (menor a 15% con el alimento artificial larvario, debido a la presencia de protozoarios, alimentándose con el producto comercial precipitado en el fondo de los frascos o acuarios. Los acuarios con larvas alimentadas con dieta natural también mostraron concentraciones subletales de amonio al noveno día; sin embargo, la sobrevivencia fue cuatro veces mayor que con dietas artificiales. Los tanques control con dietas naturales presentaron tasas de sobrevivencia (70 ± 5% similares a la reportada por otros laboratorios.

  20. 基于LOM的人工智能教学资源整合与个性化学习导航%Tutorial Material Integration and Learning Navigation for Artificial Intelligence Based on LOM

    Institute of Scientific and Technical Information of China (English)

    段琢华

    2010-01-01

    学习对象元数据(LOM,Learning Object Metadata)是IEEE采用的一种表示学习对象(教学资源)信息的规范,本文采用LOM规范管理网络教学资源,通过LOM中的"关系"元素表示教学资源之间的依赖关系,构造从LOM到扩展知识结构图的转换接口,从而利用基于扩展知识结构图的教学规划方法为学习者提供个性化学习导航.以人工智能教学资源整合和学习导航为例加以说明.

  1. Artificial Neural Network Analysis System

    Science.gov (United States)

    2007-11-02

    Contract No. DASG60-00-M-0201 Purchase request no.: Foot in the Door-01 Title Name: Artificial Neural Network Analysis System Company: Atlantic... Artificial Neural Network Analysis System 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Powell, Bruce C 5d. PROJECT NUMBER 5e. TASK NUMBER...34) 27-02-2001 Report Type N/A Dates Covered (from... to) ("DD MON YYYY") 28-10-2000 27-02-2001 Title and Subtitle Artificial Neural Network Analysis

  2. Bioengineering of Artificial Lymphoid Organs.

    Science.gov (United States)

    Nosenko, M A; Drutskaya, M S; Moisenovich, M M; Nedospasov, S A

    2016-01-01

    This review addresses the issue of bioengineering of artificial lymphoid organs.Progress in this field may help to better understand the nature of the structure-function relations that exist in immune organs. Artifical lymphoid organs may also be advantageous in the therapy or correction of immunodefficiencies, autoimmune diseases, and cancer. The structural organization, development, and function of lymphoid tissue are analyzed with a focus on the role of intercellular contacts and on the cytokine signaling pathways regulating these processes. We describe various polymeric materials, as scaffolds, for artificial tissue engineering. Finally, published studies in which artificial lymphoid organs were generated are reviewed and possible future directions in the field are discussed.

  3. Artificial intelligence in medicine.

    Science.gov (United States)

    Hamet, Pavel; Tremblay, Johanne

    2017-04-01

    Artificial Intelligence (AI) is a general term that implies the use of a computer to model intelligent behavior with minimal human intervention. AI is generally accepted as having started with the invention of robots. The term derives from the Czech word robota, meaning biosynthetic machines used as forced labor. In this field, Leonardo Da Vinci's lasting heritage is today's burgeoning use of robotic-assisted surgery, named after him, for complex urologic and gynecologic procedures. Da Vinci's sketchbooks of robots helped set the stage for this innovation. AI, described as the science and engineering of making intelligent machines, was officially born in 1956. The term is applicable to a broad range of items in medicine such as robotics, medical diagnosis, medical statistics, and human biology-up to and including today's "omics". AI in medicine, which is the focus of this review, has two main branches: virtual and physical. The virtual branch includes informatics approaches from deep learning information management to control of health management systems, including electronic health records, and active guidance of physicians in their treatment decisions. The physical branch is best represented by robots used to assist the elderly patient or the attending surgeon. Also embodied in this branch are targeted nanorobots, a unique new drug delivery system. The societal and ethical complexities of these applications require further reflection, proof of their medical utility, economic value, and development of interdisciplinary strategies for their wider application.

  4. Artificial Immune Systems Tutorial

    CERN Document Server

    Aickelin, Uwe

    2008-01-01

    The biological immune system is a robust, complex, adaptive system that defends the body from foreign pathogens. It is able to categorize all cells (or molecules) within the body as self-cells or non-self cells. It does this with the help of a distributed task force that has the intelligence to take action from a local and also a global perspective using its network of chemical messengers for communication. There are two major branches of the immune system. The innate immune system is an unchanging mechanism that detects and destroys certain invading organisms, whilst the adaptive immune system responds to previously unknown foreign cells and builds a response to them that can remain in the body over a long period of time. This remarkable information processing biological system has caught the attention of computer science in recent years. A novel computational intelligence technique, inspired by immunology, has emerged, called Artificial Immune Systems. Several concepts from the immune have been extracted an...

  5. Artificial Immune Systems

    CERN Document Server

    Aickelin, Uwe

    2009-01-01

    The biological immune system is a robust, complex, adaptive system that defends the body from foreign pathogens. It is able to categorize all cells (or molecules) within the body as self-cells or non-self cells. It does this with the help of a distributed task force that has the intelligence to take action from a local and also a global perspective using its network of chemical messengers for communication. There are two major branches of the immune system. The innate immune system is an unchanging mechanism that detects and destroys certain invading organisms, whilst the adaptive immune system responds to previously unknown foreign cells and builds a response to them that can remain in the body over a long period of time. This remarkable information processing biological system has caught the attention of computer science in recent years. A novel computational intelligence technique, inspired by immunology, has emerged, called Artificial Immune Systems. Several concepts from the immune have been extracted an...

  6. Programmable artificial phototactic microswimmer

    Science.gov (United States)

    Dai, Baohu; Wang, Jizhuang; Xiong, Ze; Zhan, Xiaojun; Dai, Wei; Li, Chien-Cheng; Feng, Shien-Ping; Tang, Jinyao

    2016-12-01

    Phototaxis is commonly observed in motile photosynthetic microorganisms. For example, green algae are capable of swimming towards a light source (positive phototaxis) to receive more energy for photosynthesis, or away from a light source (negative phototaxis) to avoid radiation damage or to hide from predators. Recently, with the aim of applying nanoscale machinery to biomedical applications, various inorganic nanomotors based on different propulsion mechanisms have been demonstrated. The only method to control the direction of motion of these self-propelled micro/nanomotors is to incorporate a ferromagnetic material into their structure and use an external magnetic field for steering. Here, we show an artificial microswimmer that can sense and orient to the illumination direction of an external light source. Our microswimmer is a Janus nanotree containing a nanostructured photocathode and photoanode at opposite ends that release cations and anions, respectively, propelling the microswimmer by self-electrophoresis. Using chemical modifications, we can control the zeta potential of the photoanode and program the microswimmer to exhibit either positive or negative phototaxis. Finally, we show that a school of microswimmers mimics the collective phototactic behaviour of green algae in solution.

  7. Towards Automated Benchmarking of Atomistic Forcefields: Neat Liquid Densities and Static Dielectric Constants from the ThermoML Data Archive

    CERN Document Server

    Beauchamp, Kyle A; Rustenburg, Ariën S; Bayly, Christopher I; Kroenlein, Kenneth; Chodera, John D

    2015-01-01

    Atomistic molecular simulations are a powerful way to make quantitative predictions, but the accuracy of these predictions depends entirely on the quality of the forcefield employed. While experimental measurements of fundamental physical properties offer a straightforward approach for evaluating forcefield quality, the bulk of this information has been tied up in formats that are not machine-readable. Compiling benchmark datasets of physical properties from non-machine-readable sources require substantial human effort and is prone to accumulation of human errors, hindering the development of reproducible benchmarks of forcefield accuracy. Here, we examine the feasibility of benchmarking atomistic forcefields against the NIST ThermoML data archive of physicochemical measurements, which aggregates thousands of experimental measurements in a portable, machine-readable, self-annotating format. As a proof of concept, we present a detailed benchmark of the generalized Amber small molecule forcefield (GAFF) using t...

  8. Continuum Plate Theory and Atomistic Modeling to Find the Flexural Rigidity of a Graphene Sheet Interacting with a Substrate

    Directory of Open Access Journals (Sweden)

    M. W. Roberts

    2010-01-01

    Full Text Available Using a combination of continuum modeling, atomistic simulations, and numerical optimization, we estimate the flexural rigidity of a graphene sheet. We consider a rectangular sheet that is initially parallel to a rigid substrate. The sheet interacts with the substrate by van der Waals forces and deflects in response to loading on a pair of opposite edges. To estimate the flexural rigidity, we model the graphene sheet as a continuum and numerically solve an appropriate differential equation for the transverse deflection. This solution depends on the flexural rigidity. We then use an optimization procedure to find the value of the flexural rigidity that minimizes the difference between the numerical solutions and the deflections predicted by atomistic simulations. This procedure predicts a flexural rigidity of 0.26 nN nm=1.62 eV.

  9. A Bayesian framework for adaptive selection, calibration, and validation of coarse-grained models of atomistic systems

    Energy Technology Data Exchange (ETDEWEB)

    Farrell, Kathryn, E-mail: kfarrell@ices.utexas.edu; Oden, J. Tinsley, E-mail: oden@ices.utexas.edu; Faghihi, Danial, E-mail: danial@ices.utexas.edu

    2015-08-15

    A general adaptive modeling algorithm for selection and validation of coarse-grained models of atomistic systems is presented. A Bayesian framework is developed to address uncertainties in parameters, data, and model selection. Algorithms for computing output sensitivities to parameter variances, model evidence and posterior model plausibilities for given data, and for computing what are referred to as Occam Categories in reference to a rough measure of model simplicity, make up components of the overall approach. Computational results are provided for representative applications.

  10. PF2fit: Polar Fast Fourier Matched Alignment of Atomistic Structures with 3D Electron Microscopy Maps.

    Directory of Open Access Journals (Sweden)

    Radhakrishna Bettadapura

    2015-10-01

    Full Text Available There continue to be increasing occurrences of both atomistic structure models in the PDB (possibly reconstructed from X-ray diffraction or NMR data, and 3D reconstructed cryo-electron microscopy (3D EM maps (albeit at coarser resolution of the same or homologous molecule or molecular assembly, deposited in the EMDB. To obtain the best possible structural model of the molecule at the best achievable resolution, and without any missing gaps, one typically aligns (match and fits the atomistic structure model with the 3D EM map. We discuss a new algorithm and generalized framework, named PF(2 fit (Polar Fast Fourier Fitting for the best possible structural alignment of atomistic structures with 3D EM. While PF(2 fit enables only a rigid, six dimensional (6D alignment method, it augments prior work on 6D X-ray structure and 3D EM alignment in multiple ways: Scoring. PF(2 fit includes a new scoring scheme that, in addition to rewarding overlaps between the volumes occupied by the atomistic structure and 3D EM map, rewards overlaps between the volumes complementary to them. We quantitatively demonstrate how this new complementary scoring scheme improves upon existing approaches. PF(2 fit also includes two scoring functions, the non-uniform exterior penalty and the skeleton-secondary structure score, and implements the scattering potential score as an alternative to traditional Gaussian blurring. Search. PF(2 fit utilizes a fast polar Fourier search scheme, whose main advantage is the ability to search over uniformly and adaptively sampled subsets of the space of rigid-body motions. PF(2 fit also implements a new reranking search and scoring methodology that considerably improves alignment metrics in results obtained from the initial search.

  11. Lattice Thermal Conductivity of Ultra High Temperature Ceramics ZrB2 and HfB2 from Atomistic Simulations

    Science.gov (United States)

    Lawson, John W.; Murray, Daw S.; Bauschlicher, Charles W., Jr.

    2011-01-01

    Atomistic Green-Kubo simulations are performed to evaluate the lattice thermal conductivity for single crystals of the ultra high temperature ceramics ZrB2 and HfB2 for a range of temperatures. Recently developed interatomic potentials are used for these simulations. Heat current correlation functions show rapid oscillations which can be identified with mixed metal-Boron optical phonon modes. Agreement with available experimental data is good.

  12. Atomistic study of hydrogen embrittlement of grain boundaries in nickel: I. Fracture

    Science.gov (United States)

    Tehranchi, A.; Curtin, W. A.

    Hydrogen ingress into a metal is a persistent source of embrittlement. Fracture surfaces are often intergranular, suggesting favorable cleave crack growth along grain boundaries (GBs) as one driver for embrittlement. Here, atomistic simulations are used to investigate the effects of segregated hydrogen on the behavior of cracks along various symmetric tilt grain boundaries in fcc Nickel. An atomistic potential for Ni-H is first recalibrated against new quantum level computations of the energy of H in specific sites within the NiΣ5(120)⟨100⟩ GB. The binding energy of H atoms to various atomic sites in the NiΣ3(111) (twin), NiΣ5(120)⟨100⟩, NiΣ99(557)⟨110⟩, and NiΣ9(221)⟨110⟩ GBs, and to various surfaces created by separating these GBs into two possible fracture surfaces, are computed and used to determine equilibrium H concentrations at bulk H concentrations typical of embrittlement in Ni. Mode I fracture behavior is then studied, examining the influence of H in altering the competition between dislocation emission (crack blunting; "ductile" behavior) and cleavage fracture ("brittle" behavior) for intergranular cracks. Simulation results are compared with theoretical predictions (Griffith theory for cleavage; Rice theory for emission) using the computed surface energies. The deformation behavior at the GBs is, however, generally complex and not as simple as cleavage or emission at a sharp crack tip, which is not unexpected due to the complexity of the GB structures. In cases predicted to emit dislocations from the crack tip, the presence of H atoms reduces the critical load for emission of the dislocations and no cleavage is found. In the cases predicted to cleave, the presence of H atoms reduces the cleavage stress intensity and makes cleavage easier, including NiΣ9(221)⟨110⟩ which emits dislocations in the absence of H. Aside from the one unusual NiΣ9(221)⟨110⟩ case, no tendency is found for H to cause a ductile

  13. Atomistic modeling of nanowires, small-scale fatigue damage in cast magnesium, and materials for MEMS

    Energy Technology Data Exchange (ETDEWEB)

    Dunn, Martin L. [Univ. of Colorado, Boulder, CO (United States); Talmage, Mellisa J. [Univ. of Colorado, Boulder, CO (United States); McDowell, David L. [Georgia Inst. of Technology, Atlanta, GA (United States); West, Neil [Univ. of Colorado, Boulder, CO (United States); Gullett, Philip Michael [Mississippi State Univ., Mississippi State, MS (United States); Miller, David C. [Univ. of Colorado, Boulder, CO (United States); Spark, Kevin [Univ. of Colorado, Boulder, CO (United States); Diao, Jiankuai [Univ. of Colorado, Boulder, CO (United States); Horstemeyer, Mark F. [Mississippi State Univ., Mississippi State, MS (United States); Zimmerman, Jonathan A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Gall, K. [Georgia Inst. of Technology, Atlanta, GA (United States)

    2006-10-01

    Lightweight and miniaturized weapon systems are driving the use of new materials in design such as microscale materials and ultra low-density metallic materials. Reliable design of future weapon components and systems demands a thorough understanding of the deformation modes in these materials that comprise the components and a robust methodology to predict their performance during service or storage. Traditional continuum models of material deformation and failure are not easily extended to these new materials unless microstructural characteristics are included in the formulation. For example, in LIGA Ni and Al-Si thin films, the physical size is on the order of microns, a scale approaching key microstructural features. For a new potential structural material, cast Mg offers a high stiffness-to-weight ratio, but the microstructural heterogeneity at various scales requires a structure-property continuum model. Processes occurring at the nanoscale and microscale develop certain structures that drive material behavior. The objective of the work presented in this report was to understand material characteristics in relation to mechanical properties at the nanoscale and microscale in these promising new material systems. Research was conducted primarily at the University of Colorado at Boulder to employ tightly coupled experimentation and simulation to study damage at various material size scales under monotonic and cyclic loading conditions. Experimental characterization of nano/micro damage will be accomplished by novel techniques such as in-situ environmental scanning electron microscopy (ESEM), 1 MeV transmission electron microscopy (TEM), and atomic force microscopy (AFM). New simulations to support experimental efforts will include modified embedded atom method (MEAM) atomistic simulations at the nanoscale and single crystal micromechanical finite element simulations. This report summarizes the major research and development accomplishments for the LDRD project

  14. Atomistic simulation of the structure and elastic properties of gold nanowires

    Science.gov (United States)

    Diao, Jiankuai; Gall, Ken; Dunn, Martin L.

    2004-09-01

    We performed atomistic simulations to study the effect of free surfaces on the structure and elastic properties of gold nanowires aligned in the and crystallographic directions. Computationally, we formed a nanowire by assembling gold atoms into a long wire with free sides by putting them in their bulk fcc lattice positions. We then performed a static relaxation on the assemblage. The tensile surface stresses on the sides of the wire cause the wire to contract along the length with respect to the original fcc lattice, and we characterize this deformation in terms of an equilibrium strain versus the cross-sectional area. While the surface stress causes wires of both orientations and all sizes to increasingly contract with decreasing cross-sectional area, when the cross-sectional area of a nanowire is less than 1.83 nm×1.83 nm, the wire undergoes a phase transformation from fcc to bct, and the equilibrium strain increases by an order of magnitude. We then applied a uniform uniaxial strain incrementally to 1.2% to the relaxed nanowires in a molecular statics framework. From the simulation results we computed the effective axial Young's modulus and Poisson's ratios of the nanowire as a function of cross-sectional area. We used two approaches to compute the effective elastic moduli, one based on a definition in terms of the strain derivative of the total energy and another in terms of the virial stress often used in atomistic simulations. Both give quantitatively similar results, showing an increase in Young's modulus with a decrease of cross-sectional area in the nanowires that do not undergo a phase transformation. Those that undergo a phase transformation experience an increase of about a factor of three of Young's modulus. The Poisson's ratio of the wires that do not undergo a phase transformation show little change with the cross-sectional area. Those wires that undergo a phase transformation experience an increase of about 10% in Poisson's ratio. The wires show

  15. Artificial intelligence: Deep neural reasoning

    Science.gov (United States)

    Jaeger, Herbert

    2016-10-01

    The human brain can solve highly abstract reasoning problems using a neural network that is entirely physical. The underlying mechanisms are only partially understood, but an artificial network provides valuable insight. See Article p.471

  16. Darwin, artificial selection, and poverty.

    Science.gov (United States)

    Sanchez, Luis

    2010-03-01

    This paper argues that the processes of evolutionary selection are becoming increasingly artificial, a trend that goes against the belief in a purely natural selection process claimed by Darwin's natural selection theory. Artificial selection is mentioned by Darwin, but it was ignored by Social Darwinists, and it is all but absent in neo-Darwinian thinking. This omission results in an underestimation of probable impacts of artificial selection upon assumed evolutionary processes, and has implications for the ideological uses of Darwin's language, particularly in relation to poverty and other social inequalities. The influence of artificial selection on genotypic and phenotypic adaptations arguably represents a substantial shift in the presumed path of evolution, a shift laden with both biological and political implications.

  17. Food analysis using artificial senses.

    Science.gov (United States)

    Śliwińska, Magdalena; Wiśniewska, Paulina; Dymerski, Tomasz; Namieśnik, Jacek; Wardencki, Waldemar

    2014-02-19

    Nowadays, consumers are paying great attention to the characteristics of food such as smell, taste, and appearance. This motivates scientists to imitate human senses using devices known as electronic senses. These include electronic noses, electronic tongues, and computer vision. Thanks to the utilization of various sensors and methods of signal analysis, artificial senses are widely applied in food analysis for process monitoring and determining the quality and authenticity of foods. This paper summarizes achievements in the field of artificial senses. It includes a brief history of these systems, descriptions of most commonly used sensors (conductometric, potentiometric, amperometic/voltammetric, impedimetric, colorimetric, piezoelectric), data analysis methods (for example, artificial neural network (ANN), principal component analysis (PCA), model CIE L*a*b*), and application of artificial senses to food analysis, in particular quality control, authenticity and falsification assessment, and monitoring of production processes.

  18. Protein Folding and Structure Prediction from the Ground Up: The Atomistic Associative Memory, Water Mediated, Structure and Energy Model.

    Science.gov (United States)

    Chen, Mingchen; Lin, Xingcheng; Zheng, Weihua; Onuchic, José N; Wolynes, Peter G

    2016-08-25

    The associative memory, water mediated, structure and energy model (AWSEM) is a coarse-grained force field with transferable tertiary interactions that incorporates local in sequence energetic biases using bioinformatically derived structural information about peptide fragments with locally similar sequences that we call memories. The memory information from the protein data bank (PDB) database guides proper protein folding. The structural information about available sequences in the database varies in quality and can sometimes lead to frustrated free energy landscapes locally. One way out of this difficulty is to construct the input fragment memory information from all-atom simulations of portions of the complete polypeptide chain. In this paper, we investigate this approach first put forward by Kwac and Wolynes in a more complete way by studying the structure prediction capabilities of this approach for six α-helical proteins. This scheme which we call the atomistic associative memory, water mediated, structure and energy model (AAWSEM) amounts to an ab initio protein structure prediction method that starts from the ground up without using bioinformatic input. The free energy profiles from AAWSEM show that atomistic fragment memories are sufficient to guide the correct folding when tertiary forces are included. AAWSEM combines the efficiency of coarse-grained simulations on the full protein level with the local structural accuracy achievable from all-atom simulations of only parts of a large protein. The results suggest that a hybrid use of atomistic fragment memory and database memory in structural predictions may well be optimal for many practical applications.

  19. Mechanical properties of artificial snow

    OpenAIRE

    Lintzén, Nina

    2013-01-01

    Mechanical properties of snow have been a subject of research since the mid-20th century. Theresearch done is based on natural snow. During the last decades the winter business industryhas been growing and also the interest for constructing buildings and artwork of snow. Suchconstructions are generally built using artificial snow, i.e. snow produced by snow guns. Up tothe present constructions of snow are designed based on knowledge by experience. Only minorscientific studies on artificial sn...

  20. What are artificial neural networks?

    DEFF Research Database (Denmark)

    Krogh, Anders

    2008-01-01

    Artificial neural networks have been applied to problems ranging from speech recognition to prediction of protein secondary structure, classification of cancers and gene prediction. How do they work and what might they be good for? Udgivelsesdato: 2008-Feb......Artificial neural networks have been applied to problems ranging from speech recognition to prediction of protein secondary structure, classification of cancers and gene prediction. How do they work and what might they be good for? Udgivelsesdato: 2008-Feb...

  1. The handbook of artificial intelligence

    CERN Document Server

    Barr, Avron

    1982-01-01

    The Handbook of Artificial Intelligence, Volume II focuses on the improvements in artificial intelligence (AI) and its increasing applications, including programming languages, intelligent CAI systems, and the employment of AI in medicine, science, and education. The book first elaborates on programming languages for AI research and applications-oriented AI research. Discussions cover scientific applications, teiresias, applications in chemistry, dependencies and assumptions, AI programming-language features, and LISP. The manuscript then examines applications-oriented AI research in medicine

  2. Medical applications of artificial intelligence

    CERN Document Server

    Agah, Arvin

    2013-01-01

    Enhanced, more reliable, and better understood than in the past, artificial intelligence (AI) systems can make providing healthcare more accurate, affordable, accessible, consistent, and efficient. However, AI technologies have not been as well integrated into medicine as predicted. In order to succeed, medical and computational scientists must develop hybrid systems that can effectively and efficiently integrate the experience of medical care professionals with capabilities of AI systems. After providing a general overview of artificial intelligence concepts, tools, and techniques, Medical Ap

  3. Artificial weathering of granite

    Directory of Open Access Journals (Sweden)

    Silva Hermo, B.

    2008-06-01

    Full Text Available This article summarizes a series of artificial weathering tests run on granite designed to: simulate the action of weathering agents on buildings and identify the underlying mechanisms, determine the salt resistance of different types of rock; evaluate consolidation and water-repellent treatment durability; and confirm hypotheses about the origin of salts such as gypsum that are often found in granite buildings. Salt crystallization tests were also conducted, using sodium chloride, sodium sulphate, calcium sulphate and seawater solutions. One of these tests was conducted in a chamber specifically designed to simulate salt spray weathering and another in an SO2 chamber to ascertain whether granite is subject to sulphation. The test results are analyzed and discussed, along with the shortcomings of each type of trial as a method for simulating the decay observed in monuments. The effect of factors such as wet-dry conditions, type of saline solution and the position of the planes of weakness on the type of decay is also addressed.En este trabajo se hace una síntesis de varios ensayos de alteración artificial realizados con rocas graníticas. Estos ensayos tenían distintos objetivos: reproducir las formas de alteración encontradas en los edificios para llegar a conocer los mecanismos que las generan, determinar la resistencia de las diferentes rocas a la acción de las sales, evaluar la durabilidad de tratamientos de consolidación e hidrofugación y constatar hipótesis acerca del origen de algunas sales, como el yeso, que aparecen frecuentemente en edificios graníticos. En los ensayos de cristalización de sales se utilizaron disoluciones de cloruro de sodio, sulfato de sodio, sulfato de calcio y agua de mar. Uno de estos ensayos se llevó a cabo en una cámara especialmente diseñada para reproducir la alteración por aerosol marino y otro se realizó en una cámara de SO2, con el objeto de comprobar si en rocas graníticas se puede producir

  4. Artificial Intelligence versus Statistical Modeling and Optimization of Cholesterol Oxidase Production by using Streptomyces Sp.

    Science.gov (United States)

    Pathak, Lakshmi; Singh, Vineeta; Niwas, Ram; Osama, Khwaja; Khan, Saif; Haque, Shafiul; Tripathi, C K M; Mishra, B N

    2015-01-01

    Cholesterol oxidase (COD) is a bi-functional FAD-containing oxidoreductase which catalyzes the oxidation of cholesterol into 4-cholesten-3-one. The wider biological functions and clinical applications of COD have urged the screening, isolation and characterization of newer microbes from diverse habitats as a source of COD and optimization and over-production of COD for various uses. The practicability of statistical/ artificial intelligence techniques, such as response surface methodology (RSM), artificial neural network (ANN) and genetic algorithm (GA) have been tested to optimize the medium composition for the production of COD from novel strain Streptomyces sp. NCIM 5500. All experiments were performed according to the five factor central composite design (CCD) and the generated data was analysed using RSM and ANN. GA was employed to optimize the models generated by RSM and ANN. Based upon the predicted COD concentration, the model developed with ANN was found to be superior to the model developed with RSM. The RSM-GA approach predicted maximum of 6.283 U/mL COD production, whereas the ANN-GA approach predicted a maximum of 9.93 U/mL COD concentration. The optimum concentrations of the medium variables predicted through ANN-GA approach were: 1.431 g/50 mL soybean, 1.389 g/50 mL maltose, 0.029 g/50 mL MgSO4, 0.45 g/50 mL NaCl and 2.235 ml/50 mL glycerol. The experimental COD concentration was concurrent with the GA predicted yield and led to 9.75 U/mL COD production, which was nearly two times higher than the yield (4.2 U/mL) obtained with the un-optimized medium. This is the very first time we are reporting the statistical versus artificial intelligence based modeling and optimization of COD production by Streptomyces sp. NCIM 5500.

  5. Artificial Intelligence versus Statistical Modeling and Optimization of Cholesterol Oxidase Production by using Streptomyces Sp.

    Science.gov (United States)

    Niwas, Ram; Osama, Khwaja; Khan, Saif; Haque, Shafiul; Tripathi, C. K. M.; Mishra, B. N.

    2015-01-01

    Cholesterol oxidase (COD) is a bi-functional FAD-containing oxidoreductase which catalyzes the oxidation of cholesterol into 4-cholesten-3-one. The wider biological functions and clinical applications of COD have urged the screening, isolation and characterization of newer microbes from diverse habitats as a source of COD and optimization and over-production of COD for various uses. The practicability of statistical/ artificial intelligence techniques, such as response surface methodology (RSM), artificial neural network (ANN) and genetic algorithm (GA) have been tested to optimize the medium composition for the production of COD from novel strain Streptomyces sp. NCIM 5500. All experiments were performed according to the five factor central composite design (CCD) and the generated data was analysed using RSM and ANN. GA was employed to optimize the models generated by RSM and ANN. Based upon the predicted COD concentration, the model developed with ANN was found to be superior to the model developed with RSM. The RSM-GA approach predicted maximum of 6.283 U/mL COD production, whereas the ANN-GA approach predicted a maximum of 9.93 U/mL COD concentration. The optimum concentrations of the medium variables predicted through ANN-GA approach were: 1.431 g/50 mL soybean, 1.389 g/50 mL maltose, 0.029 g/50 mL MgSO4, 0.45 g/50 mL NaCl and 2.235 ml/50 mL glycerol. The experimental COD concentration was concurrent with the GA predicted yield and led to 9.75 U/mL COD production, which was nearly two times higher than the yield (4.2 U/mL) obtained with the un-optimized medium. This is the very first time we are reporting the statistical versus artificial intelligence based modeling and optimization of COD production by Streptomyces sp. NCIM 5500. PMID:26368924

  6. First-principles calculations of thermoelectric properties of TiN/MgO superlattices: The route for an enhancement of thermoelectric effects in artificial nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Takaki, Hirokazu; Kobayashi, Kazuaki; Shimono, Masato [National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Kobayashi, Nobuhiko [Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Hirose, Kenji [Smart Energy Research Laboratories, NEC Corporation, 34 Miyukigaoka, Tsukuba, Ibaraki 305-8501 (Japan)

    2016-01-07

    We present the thermoelectric properties of TiN/MgO superlattices employing first-principles calculation techniques. The Seebeck coefficients, the electrical conductances, the thermal conductances, and the figure of merit are investigated employing electrical and thermal transport calculations based on density functional theory combined with the nonequilibrium Green's function and nonequilibrium molecular dynamics simulation methods. The TiN/MgO superlattices with a small lattice mismatch at the interfaces are ideal systems to study the way for an enhancement of thermoelectric properties in artificial nanostructures. We find that the interfacial scattering between the two materials in the metal/insulator superlattices causes the electrical conductance to change rapidly, which enhances the Seebeck coefficient significantly. We show that the figure of merit for the artificial superlattice nanostructures has a much larger value compared with that of the bulk material and changes drastically with the superlattice configurations at the atomistic level.

  7. Development of a totally implantable artificial larynx

    NARCIS (Netherlands)

    Verkerke, GJ; Veenstra, Aalze; de Vries, MP; Schutte, HK; Busscher, HJ; Herrmann, IF; Van der Mei, HC; Rakhorst, G; Clements, MP

    1996-01-01

    Background. The consequences of a life-saving laryngectomy are still very distressing. The Eureka project "Artificial Larynx" aims at realization of an implantable artificial larynx to eliminate all drawbacks. Methods. The artificial larynx will consist of artificial vocal folds of adjustable pitch

  8. Integrating atomistic molecular dynamics simulations, experiments, and network analysis to study protein dynamics: strength in unity.

    Science.gov (United States)

    Papaleo, Elena

    2015-01-01

    In the last years, we have been observing remarkable improvements in the field of protein dynamics. Indeed, we can now study protein dynamics in atomistic details over several timescales with a rich portfolio of experimental and computational techniques. On one side, this provides us with the possibility to validate simulation methods and physical models against a broad range of experimental observables. On the other side, it also allows a complementary and comprehensive view on protein structure and dynamics. What is needed now is a better understanding of the link between the dynamic properties that we observe and the functional properties of these important cellular machines. To make progresses in this direction, we need to improve the physical models used to describe proteins and solvent in molecular dynamics, as well as to strengthen the integration of experiments and simulations to overcome their own limitations. Moreover, now that we have the means to study protein dynamics in great details, we need new tools to understand the information embedded in the protein ensembles and in their dynamic signature. With this aim in mind, we should enrich the current tools for analysis of biomolecular simulations with attention to the effects that can be propagated over long distances and are often associated to important biological functions. In this context, approaches inspired by network analysis can make an important contribution to the analysis of molecular dynamics simulations.

  9. An Atomistic View of the Incipient Growth of Zinc Oxide Nanolayers

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Manh Hung; Tian, Liang; Chaker, Ahmad; Cantelli, Valentina; Ouled, Toufik; Boichot, Raphaël; Crisci, Alexandre; Lay, Sabine; Richard, Marie-Ingrid; Thomas, Olivier; Deschanvres, Jean-Luc; Renevier, Hubert; Fong, Dillon D.; Ciatto, Gianluca

    2016-09-07

    The growth of zinc oxide thin films by atomic layer deposition is believed to proceed through an embryonic step in which three-dimensional nanoislands form and then coalesce to trigger a layer-by-layer growth mode. This transient initial state is characterized by a poorly ordered atomic structure, which may be inaccessible by X-ray diffraction techniques. In this work, we apply X-ray absorption spectroscopy in situ to address the local structure of Zn after each atomic layer deposition cycle, using a custom-built reactor mounted at a synchrotron beamline, and we shed light on the atomistic mechanisms taking place during the first stages of the growth. We find that such mechanisms are surprisingly different for zinc oxide growth on amorphous (silica) and crystalline (sapphire) substrate. Ab initio simulations and quantitative data analysis allow the formulation of a comprehensive growth model, based on the different effects of surface atoms and grain boundaries in the nanoscale islands, and the consequent induced local disorder. From a comparison of these specttoscopy results with those from X-ray diffraction reported recently, we observe that the final structure of the zinc oxide nanolayers depends strongly on the mechanisms taking place during the initial stages of growth. The approach followed here for the case of zinc oxide will be of general interest for characterizing and optimizing the growth and properties of more complex nanostructures.

  10. Atomistic simulation of CO 2 solubility in poly(ethylene oxide) oligomers

    KAUST Repository

    Hong, Bingbing

    2013-10-02

    We have performed atomistic molecular dynamics simulations coupled with thermodynamic integration to obtain the excess chemical potential and pressure-composition phase diagrams for CO2 in poly(ethylene oxide) oligomers. Poly(ethylene oxide) dimethyl ether, CH3O(CH 2CH2O)nCH3 (PEO for short) is a widely applied physical solvent that forms the major organic constituent of a class of novel nanoparticle-based absorbents. Good predictions were obtained for pressure-composition-density relations for CO2 + PEO oligomers (2 ≤ n ≤ 12), using the Potoff force field for PEO [J. Chem. Phys. 136, 044514 (2012)] together with the TraPPE model for CO2 [AIChE J. 47, 1676 (2001)]. Water effects on Henrys constant of CO2 in PEO have also been investigated. Addition of modest amounts of water in PEO produces a relatively small increase in Henrys constant. Dependence of the calculated Henrys constant on the weight percentage of water falls on a temperature-dependent master curve, irrespective of PEO chain length. © 2013 Taylor & Francis.

  11. Features of structure and phase transitions in pure uranium and U-Mo alloys: atomistic simulation

    Science.gov (United States)

    Kolotova, L. N.; Kuksin, A. Yu; Smirnova, D. E.; Starikov, S. V.; Tseplyaev, V. I.

    2016-11-01

    We study structural properties of cubic and tetragonal phases of U-Mo alloys using atomistic simulations: molecular dynamics and density functional theory. For pure uranium and U-Mo alloys at low temperatures we observe body-centered tetragonal (bct) structure, which is similar to the metastable γ°-phase found in the experiments. At higher temperatures bct structure transforms to a quasi body-centered cubic (q-bcc) phase that exhibits cubic symmetry just on the scale of several interatomic spacings or when averaged over time. Instantaneous pair distribution function (PDF) differs from PDF for the time-averaged atomic coordinates corresponding to the bcc lattice. The local positions of uranium atoms in q-bcc lattice correspond to the bct structure, which is energetically favourable due to formation of short U-U bonds. Transition from bct to q-bcc could be considered as ferro-to paraelastic transition of order-disorder type. The temperature of transition depends on Mo concentration. For pure uranium it is equal to about 700 K, which is well below than the upper boundary of the stability region of the α-U phase. Due to this reason, bct phase is observed only in uranium alloys containing metals with low solubility in α-U.

  12. Atomistic Analysis of Room Temperature Quantum Coherence in Two-Dimensional CdSe Nanostructures.

    Science.gov (United States)

    Pal, Sougata; Nijjar, Parmeet; Frauenheim, Thomas; Prezhdo, Oleg V

    2017-03-02

    Recent experiments on CdSe nanoplatelets synthesized with precisely controlled thickness that eliminates ensemble disorder have allowed accurate measurement of quantum coherence at room temperature. Matching exactly the CdSe cores of the experimentally studied particles and considering several defects, we establish the atomistic origins of the loss of coherence between heavy and light hole excitations in two-dimensional CdSe and CdSe/CdZnS core/shell structures. The coherence times obtained using molecular dynamics based on tight-binding density functional theory are in excellent agreement with the measured values. We show that a long coherence time is a consequence of both small fluctuations in the energy gap between the excited state pair, which is much less than thermal energy, and a slow decay of correlation between the energies of the two states. Anionic defects at the core/shell interface have little effect on the coherence lifetime, while cationic defects strongly perturb the electronic structure, destroying the experimentally observed coherence. By coupling to the same phonon modes, the heavy and light holes synchronize their energy fluctuations, facilitating long-lived coherence. We further demonstrate that the electronic excitations are localized close to the surface of these narrow nanoscale systems, and therefore, they couple most strongly to surface acoustic phonons. The established features of electron-phonon coupling and the influence of defects, surfaces, and core/shell interfaces provide important insights into quantum coherence in nanoscale materials in general.

  13. Role of atomistic structure in the stochastic nature of conductivity in substoichiometric tantalum pentoxide

    Science.gov (United States)

    Bondi, Robert J.; Fox, Brian P.; Marinella, Matthew J.

    2016-03-01

    First-principles calculations of electrical conductivity (σo) are revisited to determine the atomistic origin of its stochasticity in a distribution generated from sampling 14 ab-initio molecular dynamics configurations from 10 independently quenched models (n = 140) of substoichiometric amorphous Ta2O5, where each structure contains a neutral O monovacancy (VO0). Structural analysis revealed a distinct minimum Ta-Ta separation (dimer/trimer) corresponding to each VO0 location. Bader charge decomposition using a commonality analysis approach based on the σo distribution extremes revealed nanostructural signatures indicating that both the magnitude and distribution of cationic charge on the Ta subnetwork have a profound influence on σo. Furthermore, visualization of local defect structures and their electron densities reinforces these conclusions and suggests σo in the amorphous oxide is best suppressed by a highly charged, compact Ta cation shell that effectively screens and minimizes localized VO0 interaction with the a-Ta2O5 network; conversely, delocalization of VO0 corresponds to metallic character and high σo. The random network of a-Ta2O5 provides countless variations of an ionic configuration scaffold in which small perturbations affect the electronic charge distribution and result in a fixed-stoichiometry distribution of σo; consequently, precisely controlled and highly repeatable oxide fabrication processes are likely paramount for advancement of resistive memory technologies.

  14. Molecular Simulations of Cyclic Loading Behavior of Carbon Nanotubes Using the Atomistic Finite Element Method

    Directory of Open Access Journals (Sweden)

    Jianfeng Wang

    2009-01-01

    Full Text Available The potential applications of carbon nanotubes (CNT in many engineered bionanomaterials and electromechanical devices have imposed an urgent need on the understanding of the fatigue behavior and mechanism of CNT under cyclic loading conditions. To date, however, very little work has been done in this field. This paper presents the results of a theoretical study on the behavior of CNT subject to cyclic tensile and compressive loads using quasi-static molecular simulations. The Atomistic Finite Element Method (AFEM has been applied in the study. It is shown that CNT exhibited extreme cyclic loading resistance with yielding strain and strength becoming constant within limited number of loading cycles. Viscoelastic behavior including nonlinear elasticity, hysteresis, preconditioning (stress softening, and large strain have been observed. Chiral symmetry was found to have appreciable effects on the cyclic loading behavior of CNT. Mechanisms of the observed behavior have been revealed by close examination of the intrinsic geometric and mechanical features of tube structure. It was shown that the accumulated residual defect-free morphological deformation was the primary mechanism responsible for the cyclic failure of CNT, while the bond rotating and stretching experienced during loading/unloading played a dominant role on the strength, strain and modulus behavior of CNT.

  15. Atomistic simulations of CO2 and N2 within cage-type silica zeolites.

    Science.gov (United States)

    Madison, Lindsey; Heitzer, Henry; Russell, Colin; Kohen, Daniela

    2011-03-01

    The behavior of CO(2) and N(2), both as single components and as binary mixtures, in two cage-type silica zeolites was studied using atomistic simulations. The zeolites considered, ITQ-3 and paradigm cage-type zeolite ZK4 (the all-silica analog of LTA), were chosen so that the principles illustrated can be generalized to other adsorbent/adsorbate systems with similar topology and types of interactions. N(2) was chosen both because of the potential uses of N(2)/CO(2) separations and because it differs from CO(2) most significantly in the magnitude of its Coulombic interactions with zeolites. Despite similarities between N(2) and CO(2) diffusion in other materials, we show here that the diffusion of CO(2) within cage-type zeolites is dominated by an energy barrier to diffusion located at the entrance to the narrow channels connecting larger cages. This barrier originates in Coulombic interactions between zeolites and CO(2)'s quadrupole and results in well-defined orientations for the diffusing molecules. Furthermore, CO(2)'s favorable electrostatic interactions with the zeolite framework result in preferential binding in the windows between cages. N(2)'s behavior, in contrast, is more consistent with that of molecules previously studied. Our analysis suggests that CO(2)'s behavior might be common for adsorbates with quadrupoles that interact strongly with a material that has narrow windows between cages.

  16. Atomistic insights into dislocation-based mechanisms of void growth and coalescence

    Science.gov (United States)

    Mi, Changwen; Buttry, Daniel A.; Sharma, Pradeep; Kouris, Demitris A.

    2011-09-01

    One of the low-temperature failure mechanisms in ductile metallic alloys is the growth of voids and their coalescence. In the present work we attempt to obtain atomistic insights into the mechanisms underpinning cavitation in a representative metal, namely Aluminum. Often the pre-existing voids in metallic alloys such as Al have complex shapes (e.g. corrosion pits) and the defromation/damage mechanisms exhibit a rich size-dependent behavior across various material length scales. We focus on these two issues in this paper through large-scale calculations on specimens of sizes ranging from 18 thousand to 1.08 million atoms. In addition to the elucidation of the dislocation propagation based void growth mechanism we highlight the observed length scale effect reflected in the effective stress-strain response, stress triaxiality and void fraction evolution. Furthermore, as expected, the conventionally used Gurson's model fails to capture the observed size-effects calling for a mechanistic modification that incorporates the mechanisms observed in our (and other researchers') simulation. Finally, in our multi-void simulations, we find that, the splitting of a big void into a distribution of small ones increases the load-carrying capacity of specimens. However, no obvious dependence of the void fraction evolution on void coalescence is observed.

  17. Atomistic modeling of structure II gas hydrate mechanics: Compressibility and equations of state

    Science.gov (United States)

    Vlasic, Thomas M.; Servio, Phillip; Rey, Alejandro D.

    2016-08-01

    This work uses density functional theory (DFT) to investigate the poorly characterized structure II gas hydrates, for various guests (empty, propane, butane, ethane-methane, propane-methane), at the atomistic scale to determine key structure and mechanical properties such as equilibrium lattice volume and bulk modulus. Several equations of state (EOS) for solids (Murnaghan, Birch-Murnaghan, Vinet, Liu) were fitted to energy-volume curves resulting from structure optimization simulations. These EOS, which can be used to characterize the compressional behaviour of gas hydrates, were evaluated in terms of their robustness. The three-parameter Vinet EOS was found to perform just as well if not better than the four-parameter Liu EOS, over the pressure range in this study. As expected, the Murnaghan EOS proved to be the least robust. Furthermore, the equilibrium lattice volumes were found to increase with guest size, with double-guest hydrates showing a larger increase than single-guest hydrates, which has significant implications for the widely used van der Waals and Platteeuw thermodynamic model for gas hydrates. Also, hydrogen bonds prove to be the most likely factor contributing to the resistance of gas hydrates to compression; bulk modulus was found to increase linearly with hydrogen bond density, resulting in a relationship that could be used predictively to determine the bulk modulus of various structure II gas hydrates. Taken together, these results fill a long existing gap in the material chemical physics of these important clathrates.

  18. Atomistic simulations of fracture in the B2 phase of the Nb-Ti-Al system

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, D. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Computer Simulation Lab.

    1998-06-30

    Atomistic simulations of the crack tip configuration in the B2 phase of Nb-rich alloys in the Nb-Ti-Al are presented. The alloy compositions studied are Nb-16Al-16Ti and Nb-16Al-33Ti. The simulations were carried out using molecular statics and empirical embedded atom method (EAM) potentials for the ternary system developed in previous work. The behavior of a semi-infinite crack was studied under mode I loading for different crack tip geometries. The crack was embedded in a simulation cell with periodic boundary conditions along the direction parallel to the crack front and fixed boundary conditions along the periphery of the simulation cell. The quasi-static simulations were carried out using a molecular statics relaxation technique to obtain the minimum energy configuration of the atoms starting from their initial elastic positions, under increasingly higher stress intensities. The competition between dislocation emission and cleavage was studied in these alloys as a function of Ti content. Cracks along {l_brace}110{r_brace}-type planes with crack fronts oriented along different directions were studied. The alloys showed increased ductility with increased Ti content. The simulations show more ductile behavior than other intermetallics, due to easier dislocation emission processes at the crack tip. (orig.) 30 refs.

  19. Atomistic structure of the coherent Ni/Ni[sub 3]Al interface

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, D. (Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering); Campos, M.F. de; Souze, R.M. de; Goldenstein, H. (Escola Politecnica USP, Sao Paulo (Brazil). Dept. de Metalurgia)

    1994-02-01

    Most Ni-based superalloys are strengthened by the presence of coherent precipitates of an ordered fcc bases phase, known as [gamma][prime]. This phase is basically Ni[sub 3]Al. The precipitates are coherent up to a certain size and they present a cubic shape with faces oriented in the (100) planes of both matrix and precipitate. The detailed atomistic structure of this interface has not been studied. Interest in the use of ordered intermetallic compounds as possible structural materials has resulted in a large amount of work in Ni[sub 3]Al and in particular, the development of interatomic potentials for the Ni-Al system using the embedded atom technique. These potentials have been employed in the simulation of a variety of defects in Ni[sub 3]Al, including dislocation cores, grain boundaries and free surfaces. However, there is no simulation of the Ni/Ni[sub 3]Al interface structure using the embedded atom method. The objective of the present work is to carry out such a simulation. Besides the practical importance of the interface in superalloys, it is the simplest type of interface that can be modeled and it is a good starting point for interface work using the embedded atom technique.

  20. Analytical potential for atomistic simulations of silicon, carbon, and silicon carbide

    Science.gov (United States)

    Erhart, Paul; Albe, Karsten

    2005-01-01

    We present an analytical bond-order potential for silicon, carbon, and silicon carbide that has been optimized by a systematic fitting scheme. The functional form is adopted from a preceding work [Phys. Rev. B 65, 195124 (2002)] and is built on three independently fitted potentials for SiSi , CC , and SiC interaction. For elemental silicon and carbon, the potential perfectly reproduces elastic properties and agrees very well with first-principles results for high-pressure phases. The formation enthalpies of point defects are reasonably reproduced. In the case of silicon stuctural features of the melt agree nicely with data taken from literature. For silicon carbide the dimer as well as the solid phases B1, B2, and B3 were considered. Again, elastic properties are very well reproduced including internal relaxations under shear. Comparison with first-principles data on point defect formation enthalpies shows fair agreement. The successful validation of the potentials for configurations ranging from the molecular to the bulk regime indicates the transferability of the potential model and makes it a good choice for atomistic simulations that sample a large configuration space.

  1. Atomistic simulation for deforming complex alloys with application toward TWIP steel and associated physical insights

    Science.gov (United States)

    Wang, Peng; Xu, Shaofeng; Liu, Jiabin; Li, Xiaoyan; Wei, Yujie; Wang, Hongtao; Gao, Huajian; Yang, Wei

    2017-01-01

    The interest in promoting deformation twinning for plasticity is mounting for advanced materials. In contrast to disordered grain boundaries, highly organized twin boundaries are beneficial to promoting strength-ductility combination. Twinning deformation typically involves the kinetics of stacking faults, its interplay with dislocations, as well as the interactions between dislocations and twin boundaries. While the latter has been intensively studied, the dynamics of stacking faults has been rarely touched upon. In this work, we report new physical insights on the stacking fault dynamics in twin induced plasticity (TWIP) steels. The atomistic simulation is made possible by a newly introduced approach: meta-atom molecular dynamics simulation. The simulation suggests that the stacking fault interactions are dominated by dislocation reactions that take place spontaneously, different from the existing mechanisms. Whether to generate a single stacking fault, or a twinning partial and a trailing partial dislocation, depends upon a unique parameter, namely the stacking fault energy. The latter in turn determines the deformation twinning characteristics. The complex twin-slip and twin-dislocation interactions demonstrate the dual role of deformation twins as both the dislocation barrier and dislocation storage. This duality contributes to the high strength and high ductility of TWIP steels.

  2. A Metascalable Computing Framework for Large Spatiotemporal-Scale Atomistic Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Nomura, K; Seymour, R; Wang, W; Kalia, R; Nakano, A; Vashishta, P; Shimojo, F; Yang, L H

    2009-02-17

    A metascalable (or 'design once, scale on new architectures') parallel computing framework has been developed for large spatiotemporal-scale atomistic simulations of materials based on spatiotemporal data locality principles, which is expected to scale on emerging multipetaflops architectures. The framework consists of: (1) an embedded divide-and-conquer (EDC) algorithmic framework based on spatial locality to design linear-scaling algorithms for high complexity problems; (2) a space-time-ensemble parallel (STEP) approach based on temporal locality to predict long-time dynamics, while introducing multiple parallelization axes; and (3) a tunable hierarchical cellular decomposition (HCD) parallelization framework to map these O(N) algorithms onto a multicore cluster based on hybrid implementation combining message passing and critical section-free multithreading. The EDC-STEP-HCD framework exposes maximal concurrency and data locality, thereby achieving: (1) inter-node parallel efficiency well over 0.95 for 218 billion-atom molecular-dynamics and 1.68 trillion electronic-degrees-of-freedom quantum-mechanical simulations on 212,992 IBM BlueGene/L processors (superscalability); (2) high intra-node, multithreading parallel efficiency (nanoscalability); and (3) nearly perfect time/ensemble parallel efficiency (eon-scalability). The spatiotemporal scale covered by MD simulation on a sustained petaflops computer per day (i.e. petaflops {center_dot} day of computing) is estimated as NT = 2.14 (e.g. N = 2.14 million atoms for T = 1 microseconds).

  3. Atomistic simulations of highly conductive molecular transport junctions under realistic conditions

    KAUST Repository

    French, William R.

    2013-01-01

    We report state-of-the-art atomistic simulations combined with high-fidelity conductance calculations to probe structure-conductance relationships in Au-benzenedithiolate (BDT)-Au junctions under elongation. Our results demonstrate that large increases in conductance are associated with the formation of monatomic chains (MACs) of Au atoms directly connected to BDT. An analysis of the electronic structure of the simulated junctions reveals that enhancement in the s-like states in Au MACs causes the increases in conductance. Other structures also result in increased conductance but are too short-lived to be detected in experiment, while MACs remain stable for long simulation times. Examinations of thermally evolved junctions with and without MACs show negligible overlap between conductance histograms, indicating that the increase in conductance is related to this unique structural change and not thermal fluctuation. These results, which provide an excellent explanation for a recently observed anomalous experimental result [Bruot et al., Nat. Nanotechnol., 2012, 7, 35-40], should aid in the development of mechanically responsive molecular electronic devices. © 2013 The Royal Society of Chemistry.

  4. Atomistic Studies of Cation Transport in Tetragonal ZrO2 During Zirconium Corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Xian-Ming Bai; Yongfeng Zhang; Michael R. Tonks

    2013-10-01

    Zirconium alloys are the major fuel cladding materials in current reactors. The water-side corrosion is one of the major degradation mechanisms of these alloys. During corrosion the transport of oxidizing species in zirconium dioxide (ZrO2) determines the corrosion kinetics. Previously it has been argued that the outward diffusion of cation ions is important for forming protective oxides. In this work, the migration of Zr defects in tetragonal ZrO2 is studied with temperature accelerated dynamics and molecular dynamics simulations. The results show that Zr interstitials have anisotropic diffusion and migrate preferentially along the [001] or c direction in tetragonal ZrO2. The compressive stresses can increase the Zr interstitial migration barrier significantly. The migration barriers of some defect clusters can be much lower than those of point defects. The migration of Zr interstitials at some special grain boundaries is much slower than in a bulk oxide. The implications of these atomistic simulation results in the Zr corrosion are discussed.

  5. Atomistic study of mixing at high Z / low Z interfaces at Warm Dense Matter Conditions

    Science.gov (United States)

    Haxhimali, Tomorr; Glosli, James; Rudd, Robert; Lawrence Livermore National Laboratory Team

    2016-10-01

    We use atomistic simulations to study different aspects of mixing occurring at an initially sharp interface of high Z and low Z plasmas in the Warm/Hot Dense Matter regime. We consider a system of Diamond (the low Z component) in contact with Ag (the high Z component), which undergoes rapid isochoric heating from room temperature up to 10 eV, rapidly changing the solids into warm dense matter at solid density. We simulate the motion of ions via the screened Coulomb potential. The electric field, the electron density and ionizations level are computed on the fly by solving Poisson equation. The spatially varying screening lengths computed from the electron cloud are included in this effective interaction; the electrons are not simulated explicitly. We compute the electric field generated at the Ag-C interface as well as the dynamics of the ions during the mixing process occurring at the plasma interface. Preliminary results indicate an anomalous transport of high Z ions (Ag) into the low Z component (C); a phenomenon that is partially related to the enhanced transport of ions due to the generated electric field. These results are in agreement with recent experimental observation on Au-diamond plasma interface. This work was performed under the auspices of the US Dept. of Energy by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344.

  6. Prediction of TF target sites based on atomistic models of protein-DNA complexes

    Directory of Open Access Journals (Sweden)

    Collado-Vides Julio

    2008-10-01

    Full Text Available Abstract Background The specific recognition of genomic cis-regulatory elements by transcription factors (TFs plays an essential role in the regulation of coordinated gene expression. Studying the mechanisms determining binding specificity in protein-DNA interactions is thus an important goal. Most current approaches for modeling TF specific recognition rely on the knowledge of large sets of cognate target sites and consider only the information contained in their primary sequence. Results Here we describe a structure-based methodology for predicting sequence motifs starting from the coordinates of a TF-DNA complex. Our algorithm combines information regarding the direct and indirect readout of DNA into an atomistic statistical model, which is used to estimate the interaction potential. We first measure the ability of our method to correctly estimate the binding specificities of eight prokaryotic and eukaryotic TFs that belong to different structural superfamilies. Secondly, the method is applied to two homology models, finding that sampling of interface side-chain rotamers remarkably improves the results. Thirdly, the algorithm is compared with a reference structural method based on contact counts, obtaining comparable predictions for the experimental complexes and more accurate sequence motifs for the homology models. Conclusion Our results demonstrate that atomic-detail structural information can be feasibly used to predict TF binding sites. The computational method presented here is universal and might be applied to other systems involving protein-DNA recognition.

  7. Atomistic Insights Into the Oriented Attachment of Tunnel-Based Oxide Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Yifei; Wood, Stephen M; He, Kun; Yao, Wentao; Tompsett, David; Lu, Jun; Nie, Anmin; Islam, M. Saiful; Shahbazian-Yassar, Reza

    2016-01-01

    Controlled synthesis of nanomaterials is one of the grand challenges facing materials scientists. In particular, how tunnel-based nanomaterials aggregate during synthesis while maintaining their well-aligned tunneled structure is not fully understood. Here, we describe the atomistic mechanism of oriented attachment (OA) during solution synthesis of tunneled α-MnO2 nanowires based on a combination of in situ liquid cell transmission electron microscopy (TEM), aberration-corrected scanning TEM with subangstrom spatial resolution, and first-principles calculations. It is found that primary tunnels (1 × 1 and 2 × 2) attach along their common {110} lateral surfaces to form interfaces corresponding to 2 × 3 tunnels that facilitate their short-range ordering. The OA growth of α-MnO2 nanowires is driven by the stability gained from elimination of {110} surfaces and saturation of Mn atoms at {110}-edges. During this process, extra [MnOx] radicals in solution link the two adjacent {110} surfaces and bond with the unsaturated Mn atoms from both surface edges to produce stable nanowire interfaces. Our results provide insights into the controlled synthesis and design of nanomaterials in which tunneled structures can be tailored for use in catalysis, ion exchange, and energy storage applications.

  8. Atomistic modelling and prediction of glass forming ability in bulk metallic glasses

    Science.gov (United States)

    Sedighi, Sina

    Atomistic modeling (via molecular dynamics with EAM interaction potentials) was conducted for the detailed investigation of kinetics, thermodynamics, structure, and bonding in Ni-Al and Cu-Zr metallic glasses. This work correlates GFA with the nature of atomic-level bonding and vibrational properties, with results potentially extensible to the Transition Metal -- Transition Metal and Transition Metal -- Metalloid alloy classes in general. As a first step in the development of a liquid-only GFA tuning approach, an automated tool has also been created for the broad compositional sampling of liquid and glassy phase properties in multicomponent (binary, ternary, quaternary) alloy systems. Its application to the Cu-Zr alloy system shows promising results, including the successful identification of the two highest GFA compositions, Cu50Zr50 and Cu64Zr 36. Combined, the findings of this work highlight the critical importance of incorporating more complex alloy-specific information regarding the nature of bonding and ordering at the atomic level into such an approach.

  9. Atomistic study of energy funneling in the light-harvesting complex of green sulfur bacteria.

    Science.gov (United States)

    Huh, Joonsuk; Saikin, Semion K; Brookes, Jennifer C; Valleau, Stéphanie; Fujita, Takatoshi; Aspuru-Guzik, Alán

    2014-02-05

    Phototrophic organisms such as plants, photosynthetic bacteria, and algae use microscopic complexes of pigment molecules to absorb sunlight. Within the light-harvesting complexes, which frequently have several functional and structural subunits, the energy is transferred in the form of molecular excitations with very high efficiency. Green sulfur bacteria are considered to be among the most efficient light-harvesting organisms. Despite multiple experimental and theoretical studies of these bacteria, the physical origin of the efficient and robust energy transfer in their light-harvesting complexes is not well understood. To study excitation dynamics at the systems level, we introduce an atomistic model that mimics a complete light-harvesting apparatus of green sulfur bacteria. The model contains approximately 4000 pigment molecules and comprises a double wall roll for the chlorosome, a baseplate, and six Fenna-Matthews-Olson trimer complexes. We show that the fast relaxation within functional subunits combined with the transfer between collective excited states of pigments can result in robust energy funneling to the initial excitation conditions and temperature changes. Moreover, the same mechanism describes the coexistence of multiple time scales of excitation dynamics frequently observed in ultrafast optical experiments. While our findings support the hypothesis of supertransfer, the model reveals energy transport through multiple channels on different length scales.

  10. Development and assessment of atomistic models for predicting static friction coefficients

    Science.gov (United States)

    Jahangiri, Soran; Heverly-Coulson, Gavin S.; Mosey, Nicholas J.

    2016-08-01

    The friction coefficient relates friction forces to normal loads and plays a key role in fundamental and applied areas of science and technology. Despite its importance, the relationship between the friction coefficient and the properties of the materials forming a sliding contact is poorly understood. We illustrate how simple relationships regarding the changes in energy that occur during slip can be used to develop a quantitative model relating the friction coefficient to atomic-level features of the contact. The slip event is considered as an activated process and the load dependence of the slip energy barrier is approximated with a Taylor series expansion of the corresponding energies with respect to load. The resulting expression for the load-dependent slip energy barrier is incorporated in the Prandtl-Tomlinson (PT) model and a shear-based model to obtain expressions for friction coefficient. The results indicate that the shear-based model reproduces the static friction coefficients μs obtained from first-principles molecular dynamics simulations more accurately than the PT model. The ability of the model to provide atomistic explanations for differences in μs amongst different contacts is also illustrated. As a whole, the model is able to account for fundamental atomic-level features of μs, explain the differences in μs for different materials based on their properties, and might be also used in guiding the development of contacts with desired values of μs.

  11. Lattice Thermal Conductivity from Atomistic Simulations: ZrB2 and HfB2

    Science.gov (United States)

    Lawson, John W.; Daw, Murray S.; Bauschlicher, Charles W.

    2012-01-01

    Ultra high temperature ceramics (UHTC) including ZrB2 and HfB2 have a number of properties that make them attractive for applications in extreme environments. One such property is their high thermal conductivity. Computational modeling of these materials will facilitate understanding of fundamental mechanisms, elucidate structure-property relationships, and ultimately accelerate the materials design cycle. Progress in computational modeling of UHTCs however has been limited in part due to the absence of suitable interatomic potentials. Recently, we developed Tersoff style parameterizations of such potentials for both ZrB2 and HfB2 appropriate for atomistic simulations. As an application, Green-Kubo molecular dynamics simulations were performed to evaluate the lattice thermal conductivity for single crystals of ZrB2 and HfB2. The atomic mass difference in these binary compounds leads to oscillations in the time correlation function of the heat current, in contrast to the more typical monotonic decay seen in monoatomic materials such as Silicon, for example. Results at room temperature and at elevated temperatures will be reported.

  12. Components for Atomistic-to-Continuum Multiscale Modeling of Flow in Micro- and Nanofluidic Systems

    Directory of Open Access Journals (Sweden)

    Helgi Adalsteinsson

    2008-01-01

    Full Text Available Micro- and nanofluidics pose a series of significant challenges for science-based modeling. Key among those are the wide separation of length- and timescales between interface phenomena and bulk flow and the spatially heterogeneous solution properties near solid-liquid interfaces. It is not uncommon for characteristic scales in these systems to span nine orders of magnitude from the atomic motions in particle dynamics up to evolution of mass transport at the macroscale level, making explicit particle models intractable for all but the simplest systems. Recently, atomistic-to-continuum (A2C multiscale simulations have gained a lot of interest as an approach to rigorously handle particle-level dynamics while also tracking evolution of large-scale macroscale behavior. While these methods are clearly not applicable to all classes of simulations, they are finding traction in systems in which tight-binding, and physically important, dynamics at system interfaces have complex effects on the slower-evolving large-scale evolution of the surrounding medium. These conditions allow decomposition of the simulation into discrete domains, either spatially or temporally. In this paper, we describe how features of domain decomposed simulation systems can be harnessed to yield flexible and efficient software for multiscale simulations of electric field-driven micro- and nanofluidics.

  13. Calculation of phonon dispersion in carbon nanotubes using a continuum-atomistic finite element approach

    Directory of Open Access Journals (Sweden)

    Michael J. Leamy

    2011-12-01

    Full Text Available Dispersion calculations are presented for cylindrical carbon nanotubes using a manifold-based continuum-atomistic finite element formulation combined with Bloch analysis. The formulated finite elements allow any (n,m chiral nanotube, or mixed tubes formed by periodically-repeating heterojunctions, to be examined quickly and accurately using only three input parameters (radius, chiral angle, and unit cell length and a trivial structured mesh, thus avoiding the tedious geometry generation and energy minimization tasks associated with ab initio and lattice dynamics-based techniques. A critical assessment of the technique is pursued to determine the validity range of the resulting dispersion calculations, and to identify any dispersion anomalies. Two small anomalies in the dispersion curves are documented, which can be easily identified and therefore rectified. They include difficulty in achieving a zero energy point for the acoustic twisting phonon, and a branch veering in nanotubes with nonzero chiral angle. The twisting mode quickly restores its correct group velocity as wavenumber increases, while the branch veering is associated with a rapid exchange of eigenvectors at the veering point, which also lessens its impact. By taking into account the two noted anomalies, accurate predictions of acoustic and low-frequency optical branches can be achieved out to the midpoint of the first Brillouin zone.

  14. Atomistic-Scale Simulations of Defect Formation in Graphene under Noble Gas Ion Irradiation.

    Science.gov (United States)

    Yoon, Kichul; Rahnamoun, Ali; Swett, Jacob L; Iberi, Vighter; Cullen, David A; Vlassiouk, Ivan V; Belianinov, Alex; Jesse, Stephen; Sang, Xiahan; Ovchinnikova, Olga S; Rondinone, Adam J; Unocic, Raymond R; van Duin, Adri C T

    2016-09-27

    Despite the frequent use of noble gas ion irradiation of graphene, the atomistic-scale details, including the effects of dose, energy, and ion bombardment species on defect formation, and the associated dynamic processes involved in the irradiations and subsequent relaxation have not yet been thoroughly studied. Here, we simulated the irradiation of graphene with noble gas ions and the subsequent effects of annealing. Lattice defects, including nanopores, were generated after the annealing of the irradiated graphene, which was the result of structural relaxation that allowed the vacancy-type defects to coalesce into a larger defect. Larger nanopores were generated by irradiation with a series of heavier noble gas ions, due to a larger collision cross section that led to more detrimental effects in the graphene, and by a higher ion dose that increased the chance of displacing the carbon atoms from graphene. Overall trends in the evolution of defects with respect to a dose, as well as the defect characteristics, were in good agreement with experimental results. Additionally, the statistics in the defect types generated by different irradiating ions suggested that the most frequently observed defect types were Stone-Thrower-Wales (STW) defects for He(+) irradiation and monovacancy (MV) defects for all other ion irradiations.

  15. Atomistic study of the long-lived quantum coherences in the Fenna-Matthews-Olson complex.

    Science.gov (United States)

    Shim, Sangwoo; Rebentrost, Patrick; Valleau, Stéphanie; Aspuru-Guzik, Alán

    2012-02-08

    A remarkable amount of theoretical research has been carried out to elucidate the physical origins of the recently observed long-lived quantum coherence in the electronic energy transfer process in biological photosynthetic systems. Although successful in many respects, several widely used descriptions only include an effective treatment of the protein-chromophore interactions. In this work, by combining an all-atom molecular dynamics simulation, time-dependent density functional theory, and open quantum system approaches, we successfully simulate the dynamics of the electronic energy transfer of the Fenna-Matthews-Olson pigment-protein complex. The resulting characteristic beating of populations and quantum coherences is in good agreement with the experimental results and the hierarchy equation of motion approach. The experimental absorption, linear, and circular dichroism spectra and dephasing rates are recovered at two different temperatures. In addition, we provide an extension of our method to include zero-point fluctuations of the vibrational environment. This work thus presents, to our knowledge, one of the first steps to explain the role of excitonic quantum coherence in photosynthetic light-harvesting complexes based on their atomistic and molecular description.

  16. Atomistic modeling of structure II gas hydrate mechanics: Compressibility and equations of state

    Directory of Open Access Journals (Sweden)

    Thomas M. Vlasic

    2016-08-01

    Full Text Available This work uses density functional theory (DFT to investigate the poorly characterized structure II gas hydrates, for various guests (empty, propane, butane, ethane-methane, propane-methane, at the atomistic scale to determine key structure and mechanical properties such as equilibrium lattice volume and bulk modulus. Several equations of state (EOS for solids (Murnaghan, Birch-Murnaghan, Vinet, Liu were fitted to energy-volume curves resulting from structure optimization simulations. These EOS, which can be used to characterize the compressional behaviour of gas hydrates, were evaluated in terms of their robustness. The three-parameter Vinet EOS was found to perform just as well if not better than the four-parameter Liu EOS, over the pressure range in this study. As expected, the Murnaghan EOS proved to be the least robust. Furthermore, the equilibrium lattice volumes were found to increase with guest size, with double-guest hydrates showing a larger increase than single-guest hydrates, which has significant implications for the widely used van der Waals and Platteeuw thermodynamic model for gas hydrates. Also, hydrogen bonds prove to be the most likely factor contributing to the resistance of gas hydrates to compression; bulk modulus was found to increase linearly with hydrogen bond density, resulting in a relationship that could be used predictively to determine the bulk modulus of various structure II gas hydrates. Taken together, these results fill a long existing gap in the material chemical physics of these important clathrates.

  17. Hierarchical Statistical 3D ' Atomistic' Simulation of Decanano MOSFETs: Drift-Diffusion, Hydrodynamic and Quantum Mechanical Approaches

    Science.gov (United States)

    Asenov, Asen; Brown, A. R.; Slavcheva, G.; Davies, J. H.

    2000-01-01

    When MOSFETs are scaled to deep submicron dimensions the discreteness and randomness of the dopant charges in the channel region introduces significant fluctuations in the device characteristics. This effect, predicted 20 year ago, has been confirmed experimentally and in simulation studies. The impact of the fluctuations on the functionality, yield, and reliability of the corresponding systems shifts the paradigm of the numerical device simulation. It becomes insufficient to simulate only one device representing one macroscopical design in a continuous charge approximation. An ensemble of macroscopically identical but microscopically different devices has to be characterized by simulation of statistically significant samples. The aims of the numerical simulations shift from predicting the characteristics of a single device with continuous doping towards estimating the mean values and the standard deviations of basic design parameters such as threshold voltage, subthreshold slope, transconductance, drive current, etc. for the whole ensemble of 'atomistically' different devices in the system. It has to be pointed out that even the mean values obtained from 'atomistic' simulations are not identical to the values obtained from continuous doping simulations. In this paper we present a hierarchical approach to the 'atomistic' simulation of aggressively scaled decanano MOSFETs. A full scale 3D drift-diffusion'atomostic' simulation approach is first described and used for verification of the more economical, but also more restricted, options. To reduce the processor time and memory requirements at high drain voltage we have developed a self-consistent option based on a thin slab solution of the current continuity equation only in the channel region. This is coupled to the Poisson's equation solution in the whole simulation domain in the Gummel iteration cycles. The accuracy of this approach is investigated in comparison with the full self-consistent solution. At low drain

  18. Computational aerodynamics and artificial intelligence

    Science.gov (United States)

    Mehta, U. B.; Kutler, P.

    1984-01-01

    The general principles of artificial intelligence are reviewed and speculations are made concerning how knowledge based systems can accelerate the process of acquiring new knowledge in aerodynamics, how computational fluid dynamics may use expert systems, and how expert systems may speed the design and development process. In addition, the anatomy of an idealized expert system called AERODYNAMICIST is discussed. Resource requirements for using artificial intelligence in computational fluid dynamics and aerodynamics are examined. Three main conclusions are presented. First, there are two related aspects of computational aerodynamics: reasoning and calculating. Second, a substantial portion of reasoning can be achieved with artificial intelligence. It offers the opportunity of using computers as reasoning machines to set the stage for efficient calculating. Third, expert systems are likely to be new assets of institutions involved in aeronautics for various tasks of computational aerodynamics.

  19. Knitting and weaving artificial muscles

    Science.gov (United States)

    Maziz, Ali; Concas, Alessandro; Khaldi, Alexandre; Stålhand, Jonas; Persson, Nils-Krister; Jager, Edwin W. H.

    2017-01-01

    A need exists for artificial muscles that are silent, soft, and compliant, with performance characteristics similar to those of skeletal muscle, enabling natural interaction of assistive devices with humans. By combining one of humankind’s oldest technologies, textile processing, with electroactive polymers, we demonstrate here the feasibility of wearable, soft artificial muscles made by weaving and knitting, with tunable force and strain. These textile actuators were produced from cellulose yarns assembled into fabrics and coated with conducting polymers using a metal-free deposition. To increase the output force, we assembled yarns in parallel by weaving. The force scaled linearly with the number of yarns in the woven fabric. To amplify the strain, we knitted a stretchable fabric, exhibiting a 53-fold increase in strain. In addition, the textile construction added mechanical stability to the actuators. Textile processing permits scalable and rational production of wearable artificial muscles, and enables novel ways to design assistive devices. PMID:28138542

  20. Artificial sweeteners: safe or unsafe?

    Science.gov (United States)

    Qurrat-ul-Ain; Khan, Sohaib Ahmed

    2015-02-01

    Artificial sweeteners or intense sweeteners are sugar substitutes that are used as an alternative to table sugar. They are many times sweeter than natural sugar and as they contain no calories, they may be used to control weight and obesity. Extensive scientific research has demonstrated the safety of the six low-calorie sweeteners currently approved for use in foods in the U.S. and Europe (stevia, acesulfame-K, aspartame, neotame, saccharin and sucralose), if taken in acceptable quantities daily. There is some ongoing debate over whether artificial sweetener usage poses a health threat .This review article aims to cover thehealth benefits, and risks, of consuming artificial sweeteners, and discusses natural sweeteners which can be used as alternatives.

  1. [Implantation of the artificial retina].

    Science.gov (United States)

    Yagi, T; Hayashida, Y

    1999-05-01

    In some degenerative retinal diseases, e.g., retinitis pigmentosa and age-related macular degeneration, the photoreceptors are destroyed to cause serious visual defects. Recent studies on blind human subjects revealed that a large number of ganglion cells remains intact and is capable of transmitting signals to the brain to evoke partial visual perception. This provided hope to compensate for the visual defects with retinal prostheses. The recent progress of microfabrication technique made it possible to implement the Vary Large Scale Integrated circuit, the artificial retina, which emulates a part of retinal function. The idea of implanting the artificial retina to the patients was proposed recently and experiments using animals have been put into practice. This article surveys the front line of the artificial retina implantation.

  2. Artificial heart for humanoid robot

    Science.gov (United States)

    Potnuru, Akshay; Wu, Lianjun; Tadesse, Yonas

    2014-03-01

    A soft robotic device inspired by the pumping action of a biological heart is presented in this study. Developing artificial heart to a humanoid robot enables us to make a better biomedical device for ultimate use in humans. As technology continues to become more advanced, the methods in which we implement high performance and biomimetic artificial organs is getting nearer each day. In this paper, we present the design and development of a soft artificial heart that can be used in a humanoid robot and simulate the functions of a human heart using shape memory alloy technology. The robotic heart is designed to pump a blood-like fluid to parts of the robot such as the face to simulate someone blushing or when someone is angry by the use of elastomeric substrates and certain features for the transport of fluids.

  3. Development and evaluation of an automatically adjusting coarse-grained force field for a β-O-4 type lignin from atomistic simulations

    Science.gov (United States)

    Li, Wenzhuo; Zhao, Yingying; Huang, Shuaiyu; Zhang, Song; Zhang, Lin

    2017-01-01

    This goal of this work was to develop a coarse-grained (CG) model of a β-O-4 type lignin polymer, because of the time consuming process required to achieve equilibrium for its atomistic model. The automatic adjustment method was used to develop the lignin CG model, which enables easy discrimination between chemically-varied polymers. In the process of building the lignin CG model, a sum of n Gaussian functions was obtained by an approximation of the corresponding atomistic potentials derived from a simple Boltzmann inversion of the distributions of the structural parameters. This allowed the establishment of the potential functions of the CG bond stretching and angular bending. To obtain the potential function of the CG dihedral angle, an algorithm similar to a Fourier progression form was employed together with a nonlinear curve-fitting method. The numerical potentials of the nonbonded portion of the lignin CG model were obtained using a potential inversion iterative method derived from the corresponding atomistic nonbonded distributions. The study results showed that the proposed CG model of lignin agreed well with its atomistic model in terms of the distributions of bond lengths, bending angles, dihedral angles and nonbonded distances between the CG beads. The lignin CG model also reproduced the static and dynamic properties of the atomistic model. The results of the comparative evaluation of the two models suggested that the designed lignin CG model was efficient and reliable.

  4. Thermodynamic and mechanical properties of copper precipitates in α-iron from atomistic simulations

    Science.gov (United States)

    Erhart, Paul; Marian, Jaime; Sadigh, Babak

    2013-07-01

    Precipitate hardening is commonly used in materials science to control strength by acting on the number density, size distribution, and shape of solute precipitates in the hardened matrix. The Fe-Cu system has attracted much attention over the last several decades due to its technological importance as a model alloy for Cu steels. In spite of these efforts several aspects of its phase diagram remain unexplained. Here we use atomistic simulations to characterize the polymorphic phase diagram of Cu precipitates in body-centered cubic (BCC) Fe and establish a consistent link between their thermodynamic and mechanical properties in terms of thermal stability, shape, and strength. The size at which Cu precipitates transform from BCC to a close-packed 9R structure is found to be strongly temperature dependent, ranging from approximately 4 nm in diameter (˜2700atoms) at 200 K to about 8 nm (˜22800atoms) at 700 K. These numbers are in very good agreement with the interpretation of experimental data given Monzen [Philos. Mag. APMAADG0141-861010.1080/01418610008212077 80, 711 (2000)]. The strong temperature dependence originates from the entropic stabilization of BCC Cu, which is mechanically unstable as a bulk phase. While at high temperatures the transition exhibits first-order characteristics, the hysteresis, and thus the nucleation barrier, vanish at temperatures below approximately 300 K. This behavior is explained in terms of the mutual cancellation of the energy differences between core and shell (wetting layer) regions of BCC and 9R nanoprecipitates, respectively. The proposed mechanism is not specific for the Fe-Cu system but could generally be observed in immiscible systems, whenever the minority component is unstable in the lattice structure of the host matrix. Finally, we also study the interaction of precipitates with screw dislocations as a function of both structure and orientation. The results provide a coherent picture of precipitate strength that unifies

  5. Atomistic kinetic Monte Carlo study of atomic layer deposition derived from density functional theory.

    Science.gov (United States)

    Shirazi, Mahdi; Elliott, Simon D

    2014-01-30

    To describe the atomic layer deposition (ALD) reactions of HfO2 from Hf(N(CH3)2)4 and H2O, a three-dimensional on-lattice kinetic Monte-Carlo model is developed. In this model, all atomistic reaction pathways in density functional theory (DFT) are implemented as reaction events on the lattice. This contains all steps, from the early stage of adsorption of each ALD precursor, kinetics of the surface protons, interaction between the remaining precursors (steric effect), influence of remaining fragments on adsorption sites (blocking), densification of each ALD precursor, migration of each ALD precursors, and cooperation between the remaining precursors to adsorb H2O (cooperative effect). The essential chemistry of the ALD reactions depends on the local environment at the surface. The coordination number and a neighbor list are used to implement the dependencies. The validity and necessity of the proposed reaction pathways are statistically established at the mesoscale. The formation of one monolayer of precursor fragments is shown at the end of the metal pulse. Adsorption and dissociation of the H2O precursor onto that layer is described, leading to the delivery of oxygen and protons to the surface during the H2O pulse. Through these processes, the remaining precursor fragments desorb from the surface, leaving the surface with bulk-like and OH-terminated HfO2, ready for the next cycle. The migration of the low coordinated remaining precursor fragments is also proposed. This process introduces a slow reordering motion (crawling) at the mesoscale, leading to the smooth and conformal thin film that is characteristic of ALD.

  6. Modeling micelle-templated mesoporous material SBA-15: atomistic model and gas adsorption studies.

    Science.gov (United States)

    Bhattacharya, Supriyo; Coasne, Benoit; Hung, Francisco R; Gubbins, Keith E

    2009-05-19

    We report the development of a realistic molecular model for mesoporous silica SBA-15, which includes both the large cylindrical mesopores and the smaller micropores in the pore walls. The methodology for modeling the SBA-15 structure involves molecular and mesoscale simulations combined with geometrical interpolation techniques. First, a mesoscale model is prepared by mimicking the synthesis process using lattice Monte Carlo simulations. The main physical features of this mesoscale pore model are then carved out of an atomistic silica block; both the mesopores and the micropores are incorporated from the mimetic simulations. The calculated pore size distribution, surface area, and simulated TEM images of the model structure are in good agreement with those obtained from experimental samples of SBA-15. We then investigate the adsorption of argon in this structure using Grand Canonical Monte Carlo (GCMC) simulations. The adsorption results for our SBA-15 model are compared with those for a similar model that does not include the micropores; we also compare with results obtained in a regular cylindrical pore. The simulated adsorption isotherm for the SBA-15 model shows semiquantitative agreement with the experimental isotherm for a SBA-15 sample having a similar pore size. We observe that the presence of the micropores leads to increased adsorption at low pressure compared to the case of a model without micropores in the pore walls. At higher pressures, for all models, the filling proceeds via the monolayer-multilayer adsorption on the mesopore surface followed by capillary condensation, which is mainly controlled by the mesopore diameter and is not influenced by the presence of the micropores.

  7. Are current atomistic force fields accurate enough to study proteins in crowded environments?

    Directory of Open Access Journals (Sweden)

    Drazen Petrov

    2014-05-01

    Full Text Available The high concentration of macromolecules in the crowded cellular interior influences different thermodynamic and kinetic properties of proteins, including their structural stabilities, intermolecular binding affinities and enzymatic rates. Moreover, various structural biology methods, such as NMR or different spectroscopies, typically involve samples with relatively high protein concentration. Due to large sampling requirements, however, the accuracy of classical molecular dynamics (MD simulations in capturing protein behavior at high concentration still remains largely untested. Here, we use explicit-solvent MD simulations and a total of 6.4 µs of simulated time to study wild-type (folded and oxidatively damaged (unfolded forms of villin headpiece at 6 mM and 9.2 mM protein concentration. We first perform an exhaustive set of simulations with multiple protein molecules in the simulation box using GROMOS 45a3 and 54a7 force fields together with different types of electrostatics treatment and solution ionic strengths. Surprisingly, the two villin headpiece variants exhibit similar aggregation behavior, despite the fact that their estimated aggregation propensities markedly differ. Importantly, regardless of the simulation protocol applied, wild-type villin headpiece consistently aggregates even under conditions at which it is experimentally known to be soluble. We demonstrate that aggregation is accompanied by a large decrease in the total potential energy, with not only hydrophobic, but also polar residues and backbone contributing substantially. The same effect is directly observed for two other major atomistic force fields (AMBER99SB-ILDN and CHARMM22-CMAP as well as indirectly shown for additional two (AMBER94, OPLS-AAL, and is possibly due to a general overestimation of the potential energy of protein-protein interactions at the expense of water-water and water-protein interactions. Overall, our results suggest that current MD force fields

  8. Role of Ionic Clusters in Dynamics of Ionomer Melts: From Atomistic to Coarse Grained Simulations

    Science.gov (United States)

    Agrawal, Anupriya

    Ionomers, polymers decorated with ionizable groups, have found application in numerous technologies where ionic transport is required. The ionic groups associate into random clusters resulting in substantial effect on structure, dynamics and transport of these materials. The effects of topology, size and dynamics of these aggregates however remain an open question. Here we probe cluster formation correlated with polymer dynamics through a model system of randomly sulfonated polystyrene (SPS) melts with molecular dynamics (MD) simulations over a broad time and length scales ranging from that within the ionic clusters through polymer segmental dynamics to the motion of the entire molecules. The cluster evolution was probed by fully atomistic studies. We find ladder-like aggregates that transform to globule-like with increasing the dielectric constant of media for sodium neutralized SPS. With increasing dielectric constant, the size of the aggregates decrease and their number increases. Concurrently, the mobility of the polymer increases. The counterion radius and valency affect both morphology and dynamics as is evident in the calculated static and dynamic structure factors. It is further manifested in the results of viscosity obtained through non-equilibrium molecular dynamics technique. Finally, to access larger length scales a three bead coarse-grained model to describe sulfonated styrene that we have developed will be discussed in view of the outstanding challenges in ionic polymers. Supported in part by DOE Grant No. DE-SC007908. This work was carried out in collaboration with Dvora Perahia and Gary Grest while I was a postdoc at Clemson University. I gratefully acknowledge both of them for their support and encouragement.

  9. Degenerate Ising model for atomistic simulation of crystal-melt interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Schebarchov, D., E-mail: Dmitri.Schebarchov@gmail.com [University Chemical Laboratories, Lensfield Road, Cambridge CB2 1EW (United Kingdom); Schulze, T. P., E-mail: schulze@math.utk.edu [Department of Mathematics, University of Tennessee, Knoxville, Tennessee 37996-1300 (United States); Hendy, S. C. [The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140 (New Zealand); Department of Physics, University of Auckland, Auckland 1010 (New Zealand)

    2014-02-21

    One of the simplest microscopic models for a thermally driven first-order phase transition is an Ising-type lattice system with nearest-neighbour interactions, an external field, and a degeneracy parameter. The underlying lattice and the interaction coupling constant control the anisotropic energy of the phase boundary, the field strength represents the bulk latent heat, and the degeneracy quantifies the difference in communal entropy between the two phases. We simulate the (stochastic) evolution of this minimal model by applying rejection-free canonical and microcanonical Monte Carlo algorithms, and we obtain caloric curves and heat capacity plots for square (2D) and face-centred cubic (3D) lattices with periodic boundary conditions. Since the model admits precise adjustment of bulk latent heat and communal entropy, neither of which affect the interface properties, we are able to tune the crystal nucleation barriers at a fixed degree of undercooling and verify a dimension-dependent scaling expected from classical nucleation theory. We also analyse the equilibrium crystal-melt coexistence in the microcanonical ensemble, where we detect negative heat capacities and find that this phenomenon is more pronounced when the interface is the dominant contributor to the total entropy. The negative branch of the heat capacity appears smooth only when the equilibrium interface-area-to-volume ratio is not constant but varies smoothly with the excitation energy. Finally, we simulate microcanonical crystal nucleation and subsequent relaxation to an equilibrium Wulff shape, demonstrating the model's utility in tracking crystal-melt interfaces at the atomistic level.

  10. Atomistic tensile deformation mechanisms of Fe with gradient nano-grained structure

    Directory of Open Access Journals (Sweden)

    Wenbin Li

    2015-08-01

    Full Text Available Large-scale molecular dynamics (MD simulations have been performed to investigate the tensile properties and the related atomistic deformation mechanisms of the gradient nano-grained (GNG structure of bcc Fe (gradient grains with d from 25 nm to 105 nm, and comparisons were made with the uniform nano-grained (NG structure of bcc Fe (grains with d = 25 nm. The grain size gradient in the nano-scale converts the applied uniaxial stress to multi-axial stresses and promotes the dislocation behaviors in the GNG structure, which results in extra hardening and flow strength. Thus, the GNG structure shows slightly higher flow stress at the early plastic deformation stage when compared to the uniform NG structure (even with smaller grain size. In the GNG structure, the dominant deformation mechanisms are closely related to the grain sizes. For grains with d = 25 nm, the deformation mechanisms are dominated by GB migration, grain rotation and grain coalescence although a few dislocations are observed. For grains with d = 54 nm, dislocation nucleation, propagation and formation of dislocation wall near GBs are observed. Moreover, formation of dislocation wall and dislocation pile-up near GBs are observed for grains with d = 105 nm, which is the first observation by MD simulations to our best knowledge. The strain compatibility among different layers with various grain sizes in the GNG structure should promote the dislocation behaviors and the flow stress of the whole structure, and the present results should provide insights to design the microstructures for developing strong-and-ductile metals.

  11. Atomistic simulation of nanoporous layered double hydroxide materials and their properties. II. Adsorption and diffusion

    Science.gov (United States)

    Kim, Nayong; Harale, Aadesh; Tsotsis, Theodore T.; Sahimi, Muhammad

    2007-12-01

    Nanoporous layered double hydroxide (LDH) materials have wide applications, ranging from being good adsorbents for gases (particularly CO2) and liquid ions to membranes and catalysts. They also have applications in medicine, environmental remediation, and electrochemistry. Their general chemical composition is [M1-xIIMxIII(OH-)2]x+[Xn/mm -•nH2O], where M represents a metallic cation (of valence II or III), and Xn/mm - is an m-valence inorganic, or heteropolyacid, or organic anion. We study diffusion and adsorption of CO2 in a particular LDH with MII=Mg, MIII=Al, and x ≃0.71, using an atomistic model developed based on energy minimization and molecular dynamics simulations, together with a modified form of the consistent-valence force field. The adsorption isotherms and self-diffusivity of CO2 in the material are computed over a range of temperature, using molecular simulations. The computed diffusivities are within one order of magnitude of the measured ones at lower temperatures, while agreeing well with the data at high temperatures. The measured and computed adsorption isotherms agree at low loadings, but differ by about 25% at high loadings. Possible reasons for the differences between the computed properties and the experimental data are discussed, and a model for improving the accuracy of the computed properties is suggested. Also studied are the material's hydration and swelling properties. As water molecules are added to the pore space, the LDH material swells to some extent, with the hydration energy exhibiting interesting variations with the number of the water molecules added. The implications of the results are discussed.

  12. An atomistically informed mesoscale model for growth and coarsening during discharge in lithium-oxygen batteries

    Energy Technology Data Exchange (ETDEWEB)

    Welland, Michael J.; Lau, Kah Chun; Redfern, Paul C.; Wolf, Dieter; Curtiss, Larry A., E-mail: curtiss@anl.gov [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Liang, Linyun [Mathematics and Computer Science, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Zhai, Denyun [Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2015-12-14

    An atomistically informed mesoscale model is developed for the deposition of a discharge product in a Li-O{sub 2} battery. This mescocale model includes particle growth and coarsening as well as a simplified nucleation model. The model involves LiO{sub 2} formation through reaction of O{sub 2}{sup −} and Li{sup +} in the electrolyte, which deposits on the cathode surface when the LiO{sub 2} concentration reaches supersaturation in the electrolyte. A reaction-diffusion (rate-equation) model is used to describe the processes occurring in the electrolyte and a phase-field model is used to capture microstructural evolution. This model predicts that coarsening, in which large particles grow and small ones disappear, has a substantial effect on the size distribution of the LiO{sub 2} particles during the discharge process. The size evolution during discharge is the result of the interplay between this coarsening process and particle growth. The growth through continued deposition of LiO{sub 2} has the effect of causing large particles to grow ever faster while delaying the dissolution of small particles. The predicted size evolution is consistent with experimental results for a previously reported cathode material based on activated carbon during discharge and when it is at rest, although kinetic factors need to be included. The approach described in this paper synergistically combines models on different length scales with experimental observations and should have applications in studying other related discharge processes, such as Li{sub 2}O{sub 2} deposition, in Li-O{sub 2} batteries and nucleation and growth in Li-S batteries.

  13. An atomistically informed mesoscale model for growth and coarsening during discharge in lithium-oxygen batteries

    Energy Technology Data Exchange (ETDEWEB)

    Welland, Michael J. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Lau, Kah Chun [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Redfern, Paul C. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Liang, Linyun [Mathematics and Computer Science, Argonne National Laboratory, Argonne, Illinois 60439, USA; Zhai, Denyun [Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Wolf, Dieter [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Curtiss, Larry A. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA

    2015-12-14

    An atomistically informed mesoscale model is developed for the deposition of a discharge product in a Li-O-2 battery. This mescocale model includes particle growth and coarsening as well as a simplified nucleation model. The model involves LiO2 formation through reaction of O-2(-) and Li+ in the electrolyte, which deposits on the cathode surface when the LiO2 concentration reaches supersaturation in the electrolyte. A reaction-diffusion (rate-equation) model is used to describe the processes occurring in the electrolyte and a phase-field model is used to capture microstructural evolution. This model predicts that coarsening, in which large particles grow and small ones disappear, has a substantial effect on the size distribution of the LiO2 particles during the discharge process. The size evolution during discharge is the result of the interplay between this coarsening process and particle growth. The growth through continued deposition of LiO2 has the effect of causing large particles to grow ever faster while delaying the dissolution of small particles. The predicted size evolution is consistent with experimental results for a previously reported cathode material based on activated carbon during discharge and when it is at rest, although kinetic factors need to be included. The approach described in this paper synergistically combines models on different length scales with experimental observations and should have applications in studying other related discharge processes, such as Li2O2 deposition, in Li-O-2 batteries and nucleation and growth in Li-S batteries.

  14. How anacetrapib inhibits the activity of the cholesteryl ester transfer protein? Perspective through atomistic simulations.

    Directory of Open Access Journals (Sweden)

    Tarja Äijänen

    2014-11-01

    Full Text Available Cholesteryl ester transfer protein (CETP mediates the reciprocal transfer of neutral lipids (cholesteryl esters, triglycerides and phospholipids between different lipoprotein fractions in human blood plasma. A novel molecular agent known as anacetrapib has been shown to inhibit CETP activity and thereby raise high density lipoprotein (HDL-cholesterol and decrease low density lipoprotein (LDL-cholesterol, thus rendering CETP inhibition an attractive target to prevent and treat the development of various cardiovascular diseases. Our objective in this work is to use atomistic molecular dynamics simulations to shed light on the inhibitory mechanism of anacetrapib and unlock the interactions between the drug and CETP. The results show an evident affinity of anacetrapib towards the concave surface of CETP, and especially towards the region of the N-terminal tunnel opening. The primary binding site of anacetrapib turns out to reside in the tunnel inside CETP, near the residues surrounding the N-terminal opening. Free energy calculations show that when anacetrapib resides in this area, it hinders the ability of cholesteryl ester to diffuse out from CETP. The simulations further bring out the ability of anacetrapib to regulate the structure-function relationships of phospholipids and helix X, the latter representing the structural region of CETP important to the process of neutral lipid exchange with lipoproteins. Altogether, the simulations propose CETP inhibition to be realized when anacetrapib is transferred into the lipid binding pocket. The novel insight gained in this study has potential use in the development of new molecular agents capable of preventing the progression of cardiovascular diseases.

  15. Shape evolution of nanostructures by thermal and ion beam processing. Modeling and atomistic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Roentzsch, L.

    2007-07-01

    Single-crystalline nanostructures often exhibit gradients of surface (and/or interface) curvature that emerge from fabrication and growth processes or from thermal fluctuations. Thus, the system-inherent capillary force can initiate morphological transformations during further processing steps or during operation at elevated temperature. Therefore and because of the ongoing miniaturization of functional structures which causes a general rise in surface-to-volume ratios, solid-state capillary phenomena will become increasingly important: On the one hand diffusion-mediated capillary processes can be of practical use in view of non-conventional nanostructure fabrication methods based on self-organization mechanisms, on the other hand they can destroy the integrity of nanostructures which can go along with the failure of functionality. Additionally, capillarity-induced shape transformations are effected and can thereby be controlled by applied fields and forces (guided or driven evolution). With these prospects and challenges at hand, formation and shape transformation of single-crystalline nanostructures due to the system-inherent capillary force in combination with external fields or forces are investigated in the frame of this dissertation by means of atomistic computer simulations. For the exploration (search, description, and prediction) of reaction pathways of nanostructure shape transformations, kinetic Monte Carlo (KMC) simulations are the method of choice. Since the employed KMC code is founded on a cellular automaton principle, the spatio-temporal development of lattice-based N-particle systems (N up to several million) can be followed for time spans of several orders of magnitude, while considering local phenomena due to atomic-scale effects like diffusion, nucleation, dissociation, or ballistic displacements. In this work, the main emphasis is put on nanostructures which have a cylindrical geometry, for example, nanowires (NWs), nanorods, nanotubes etc

  16. Bulk Heterojunction Morphologies with Atomistic Resolution from Coarse-Grain Solvent Evaporation Simulations

    Science.gov (United States)

    2017-01-01

    Control over the morphology of the active layer of bulk heterojunction (BHJ) organic solar cells is paramount to achieve high-efficiency devices. However, no method currently available can predict morphologies for a novel donor–acceptor blend. An approach which allows reaching relevant length scales, retaining chemical specificity, and mimicking experimental fabrication conditions, and which is suited for high-throughput schemes has been proven challenging to find. Here, we propose a method to generate atom-resolved morphologies of BHJs which conforms to these requirements. Coarse-grain (CG) molecular dynamics simulations are employed to simulate the large-scale morphological organization during solution-processing. The use of CG models which retain chemical specificity translates into a direct path to the rational design of donor and acceptor compounds which differ only slightly in chemical nature. Finally, the direct retrieval of fully atomistic detail is possible through backmapping, opening the way for improved quantum mechanical calculations addressing the charge separation mechanism. The method is illustrated for the poly(3-hexyl-thiophene) (P3HT)–phenyl-C61-butyric acid methyl ester (PCBM) mixture, and found to predict morphologies in agreement with experimental data. The effect of drying rate, P3HT molecular weight, and thermal annealing are investigated extensively, resulting in trends mimicking experimental findings. The proposed methodology can help reduce the parameter space which has to be explored before obtaining optimal morphologies not only for BHJ solar cells but also for any other solution-processed soft matter device. PMID:28209056

  17. Agent communication and artificial institutions

    OpenAIRE

    Fornara, Nicoletta; Viganò, Francesco; Colombetti, Marco

    2011-01-01

    In this paper we propose an application-independent model for the definition of artificial institutions that can be used to define open multi-agent systems. Such a model of institutional reality makes us able also to define an objective and external semantics of a commitment-based Agent Communication Language (ACL). In particular we propose to regard an ACL as a set of conventions to act on a fragment of institutional reality, defined in the context of an artificial institution. Another c...

  18. Training Applications of Artificial Intelligence.

    Science.gov (United States)

    1987-03-23

    nearifest tLer,sclvCs in ELO r operatii.L costs in the life C’VclE Of the ef’uijjteft. E F re\\ lously rcntione6 ey~ arrle of usingF the 1lirefineer...Ibid., p. 35. 4. Avron Barr and Edward Feigenbaum, The Handbook of Artificial Intelligence, Vol. 1, p. 2. 5. Wissam W. Ahmed, "Theories of Artificial...Barr, Avron and Geigenbaum, Edward A. ed. The Handbook of Arti- ficial Intelligence. Vol. 1. Stanford: heuristech Press. 1981. Gevartner, William B

  19. Rewritable artificial magnetic charge ice

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y. -L.; Xiao, Z. -L.; Snezhko, A.; Xu, J.; Ocola, L. E.; Divan, R.; Pearson, J. E.; Crabtree, G. W.; Kwok, W. -K.

    2016-05-19

    Artificial ices enable the study of geometrical frustration by design and through direct observation. However, it has proven difficult to achieve tailored long-range ordering of their diverse configurations, limiting both fundamental and applied research directions. We designed an artificial spin structure that produces a magnetic charge ice with tunable long-range ordering of eight different configurations. We also developed a technique to precisely manipulate the local magnetic charge states and demonstrate write-read-erase multifunctionality at room temperature. This globally reconfigurable and locally writable magnetic charge ice could provide a setting for designing magnetic monopole defects, tailoring magnonics, and controlling the properties of other two-dimensional materials.

  20. Fecundación artificial

    OpenAIRE

    2013-01-01

    Por Fecundación artificial se entiende, la fecundación de una hembra sin el servicio directo del macho, es decir la introducción al aparato genital femenino, del esperma que se ha recogido por medios artificiales. Esta fecundación, practicada en debidas condiciones, tiene el mismo efecto de la fecundación natural, con las ventajas que veremos más adelante. La fecundación artificial permite explotar un reproductor a su máximum de capacidad, ya que se considera, para no hacer cálculo...

  1. Artificial intelligence techniques in Prolog

    CERN Document Server

    Shoham, Yoav

    1993-01-01

    Artificial Intelligence Techniques in Prolog introduces the reader to the use of well-established algorithmic techniques in the field of artificial intelligence (AI), with Prolog as the implementation language. The techniques considered cover general areas such as search, rule-based systems, and truth maintenance, as well as constraint satisfaction and uncertainty management. Specific application domains such as temporal reasoning, machine learning, and natural language are also discussed.Comprised of 10 chapters, this book begins with an overview of Prolog, paying particular attention to Prol

  2. Atomistic modelling of scattering data in the Collaborative Computational Project for Small Angle Scattering (CCP-SAS).

    Science.gov (United States)

    Perkins, Stephen J; Wright, David W; Zhang, Hailiang; Brookes, Emre H; Chen, Jianhan; Irving, Thomas C; Krueger, Susan; Barlow, David J; Edler, Karen J; Scott, David J; Terrill, Nicholas J; King, Stephen M; Butler, Paul D; Curtis, Joseph E

    2016-12-01

    The capabilities of current computer simulations provide a unique opportunity to model small-angle scattering (SAS) data at the atomistic level, and to include other structural constraints ranging from molecular and atomistic energetics to crystallography, electron microscopy and NMR. This extends the capabilities of solution scattering and provides deeper insights into the physics and chemistry of the systems studied. Realizing this potential, however, requires integrating the experimental data with a new generation of modelling software. To achieve this, the CCP-SAS collaboration (http://www.ccpsas.org/) is developing open-source, high-throughput and user-friendly software for the atomistic and coarse-grained molecular modelling of scattering data. Robust state-of-the-art molecular simulation engines and molecular dynamics and Monte Carlo force fields provide constraints to the solution structure inferred from the small-angle scattering data, which incorporates the known physical chemistry of the system. The implementation of this software suite involves a tiered approach in which GenApp provides the deployment infrastructure for running applications on both standard and high-performance computing hardware, and SASSIE provides a workflow framework into which modules can be plugged to prepare structures, carry out simulations, calculate theoretical scattering data and compare results with experimental data. GenApp produces the accessible web-based front end termed SASSIE-web, and GenApp and SASSIE also make community SAS codes available. Applications are illustrated by case studies: (i) inter-domain flexibility in two- to six-domain proteins as exemplified by HIV-1 Gag, MASP and ubiquitin; (ii) the hinge conformation in human IgG2 and IgA1 antibodies; (iii) the complex formed between a hexameric protein Hfq and mRNA; and (iv) synthetic 'bottlebrush' polymers.

  3. Atomistic Simulations of Fluid Flow through Graphene Channels and Carbon Nanotubes

    DEFF Research Database (Denmark)

    Zambrano, Harvey A.; Walther, Jens Honore; Oyarzua, Elton E.;

    2015-01-01

    The transport of aqueous solutions in artificial nanopores is of both fundamental and technological interest. Recently, carbon nano-structured materials (fullerenes) have attracted a great deal of attention in nanotechnology. In fact, due to their large specific surface area, high thermal...... conductivity, extremely low surface friction and superior mechanical properties, graphene channels and carbon nanotubes (CNTs) are promising candidates to be implemented as fluid conduits in nanosystems. Performing Non-equilibrium Molecular Dynamics simulations, we study the transport of water...

  4. Atomistic studies of grain boundaries and heterophase interfaces in alloys and compounds. Final report, July 1987-August 1998

    Energy Technology Data Exchange (ETDEWEB)

    Vitek, Vaclav

    1998-08-01

    The overarching goal of the research supported by this grant was investigation of the structure and properties of interfaces in multicomponent systems by atomistic modeling. Initially, the research was devoted to studies of segregation to grain boundaries in binary disordered alloys. The next step was then studies of the structure and properties of grain boundaries in ordered compounds, specifically Ni3Al and NiAl, and grain boundary segregation in these compounds in the case of off-stoichiometry. Finally, the structure of Nb/sapphire interfaces, in particular the core configurations of the misfit dislocations, was studied.

  5. Atomistic Calculations of the Effect of Minor Actinides on Thermodynamic and Kinetic Properties of UO{sub 2{+-}x}

    Energy Technology Data Exchange (ETDEWEB)

    Deo, Chaitanya; Adnersson, Davis; Battaile, Corbett; uberuaga, Blas

    2012-10-30

    The team will examine how the incorporation of actinide species important for mixed oxide (MOX) and other advanced fuel designs impacts thermodynamic quantities of the host UO{sub 2} nuclear fuel and how Pu, Np, Cm and Am influence oxygen mobility. In many cases, the experimental data is either insufficient or missing. For example, in the case of pure NpO2, there is essentially no experimental data on the hyperstoichiometric form it is not even known if hyperstoichiometry NpO{sub 2{+-}x} is stable. The team will employ atomistic modeling tools to calculate these quantities

  6. Artificial Intelligence Assists Ultrasonic Inspection

    Science.gov (United States)

    Schaefer, Lloyd A.; Willenberg, James D.

    1992-01-01

    Subtle indications of flaws extracted from ultrasonic waveforms. Ultrasonic-inspection system uses artificial intelligence to help in identification of hidden flaws in electron-beam-welded castings. System involves application of flaw-classification logic to analysis of ultrasonic waveforms.

  7. Artificial neural networks in medicine

    Energy Technology Data Exchange (ETDEWEB)

    Keller, P.E.

    1994-07-01

    This Technology Brief provides an overview of artificial neural networks (ANN). A definition and explanation of an ANN is given and situations in which an ANN is used are described. ANN applications to medicine specifically are then explored and the areas in which it is currently being used are discussed. Included are medical diagnostic aides, biochemical analysis, medical image analysis and drug development.

  8. Thinking, Creativity, and Artificial Intelligence.

    Science.gov (United States)

    DeSiano, Michael; DeSiano, Salvatore

    This document provides an introduction to the relationship between the current knowledge of focused and creative thinking and artificial intelligence. A model for stages of focused and creative thinking gives: problem encounter/setting, preparation, concentration/incubation, clarification/generation and evaluation/judgment. While a computer can…

  9. Artificial penile nodules: case reports.

    OpenAIRE

    Lim, K B; Seow, C.S.; Tulip, T; Daniel, M.; Vijayasingham, S M

    1986-01-01

    An interesting cultural practice of implanting foreign bodies under the skin of the penis for enhancing sexual excitement in the man's sexual partner is described. Recognition of this is important to venereologists because of their primary concern with the genital area. The term artificial penile nodule has been suggested for the condition resulting from this practice.

  10. Artificial Video for Video Analysis

    Science.gov (United States)

    Gallis, Michael R.

    2010-01-01

    This paper discusses the use of video analysis software and computer-generated animations for student activities. The use of artificial video affords the opportunity for students to study phenomena for which a real video may not be easy or even possible to procure, using analysis software with which the students are already familiar. We will…

  11. Making Artificial Seawater More Natural

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    @@ Marine fish will die if placed in fresh water and they cannot live in simple salt water. Instead, they need water that contains a mixture of different ingredients, as found in natural seawater. Conventional methods of making artificial seawater have shortcomings, because the water so achieved is only composed of mineral elements and lacks organic components similar to those in natural seawater.

  12. Another Step Closer to Artificial Blood

    Science.gov (United States)

    ... news/fullstory_162357.html Another Step Closer to Artificial Blood Synthetic product could save lives on battlefield and ... 5, 2016 SATURDAY, Dec. 3, 2016 (HealthDay News) -- Artificial blood stored as a powder could one day revolutionize ...

  13. 21 CFR 886.3200 - Artificial eye.

    Science.gov (United States)

    2010-04-01

    ... OPHTHALMIC DEVICES Prosthetic Devices § 886.3200 Artificial eye. (a) Identification. An artificial eye is a... inserted in a patient's eye socket anterior to an orbital implant, or the eviscerated eyeball, for...

  14. Introduction to Concepts in Artificial Neural Networks

    Science.gov (United States)

    Niebur, Dagmar

    1995-01-01

    This introduction to artificial neural networks summarizes some basic concepts of computational neuroscience and the resulting models of artificial neurons. The terminology of biological and artificial neurons, biological and machine learning and neural processing is introduced. The concepts of supervised and unsupervised learning are explained with examples from the power system area. Finally, a taxonomy of different types of neurons and different classes of artificial neural networks is presented.

  15. Analysis of DoD inkjet printhead performance for printable electronics fabrication using dynamic lumped element modeling and swarm intelligence based optimal prediction

    Institute of Scientific and Technical Information of China (English)

    何茂伟; 孙丽玲; 胡琨元; 朱云龙; 陈瀚宁

    2015-01-01

    The major challenge in printable electronics fabrication is to effectively and accurately control a drop-on-demand (DoD) inkjet printhead for high printing quality. In this work, an optimal prediction model, constructed with the lumped element modeling (LEM) and the artificial bee colony (ABC) algorithm, was proposed to efficiently predict the combination of waveform parameters for obtaining the desired droplet properties. For acquiring higher simulation accuracy, a modified dynamic lumped element model (DLEM) was proposed with time-varying equivalent circuits, which can characterize the nonlinear behaviors of piezoelectric printhead. The proposed method was then applied to investigate the influences of various waveform parameters on droplet volume and velocity of nano-silver ink, and to predict the printing quality using nano-silver ink. Experimental results show that, compared with two-dimension manual search, the proposed optimal prediction model perform efficiently and accurately in searching the appropriate combination of waveform parameters for printable electronics fabrication.

  16. Topological Optimization of Artificial Microstructure Strategies

    Science.gov (United States)

    2015-04-02

    Topographic Optimization Through Artificial Microstructure Strategies During this project as part of DARPA MCMA we aimed to develop and demonstrate...Topographic Optimization Through Artificial Microstructure Strategies Report Title During this project as part of DARPA MCMA we aimed to develop and...Artificial Microstructure Strategies (Yale and Johns Hopkins) During DARPA MCMA we aimed to develop and demonstrate a 3D microstructural

  17. Artificial Intelligence and Its Importance in Education.

    Science.gov (United States)

    Tilmann, Martha J.

    Artificial intelligence, or the study of ideas that enable computers to be intelligent, is discussed in terms of what it is, what it has done, what it can do, and how it may affect the teaching of tomorrow. An extensive overview of artificial intelligence examines its goals and applications and types of artificial intelligence including (1) expert…

  18. Atomistic Simulations of Mass and Thermal Transport in Oxide Nuclear Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Anders D. [Los Alamos National Laboratory; Uberuaga, Blas P. [Los Alamos National Laboratory; Du, Shiyu [Los Alamos National Laboratory; Liu, Xiang-Yang [Los Alamos National Laboratory; Nerikar, Pankaj [IBM; Stanek, Christopher R. [Los Alamos National Laboratory; Tonks, Michael [Idaho National Laboratory; Millet, Paul [Idaho National Laboratory; Biner, Bulent [Idaho National Laboratory

    2012-06-04

    boundaries derived from separate atomistic calculations, we simulate Xe redistribution for a few simple microstructures using finite element methods (FEM), as implemented in the MOOSE framework from Idaho National Laboratory. Thermal transport together with the power distribution determines the temperature distribution in the fuel rod and it is thus one of the most influential properties on nuclear fuel performance. The fuel thermal conductivity changes as function of time due to microstructure evolution (e.g. fission gas redistribution) and compositional changes. Using molecular dynamics simulations we have studied the impact of different types of grain boundaries and fission gas bubbles on UO{sub 2} thermal conductivity.

  19. An atomistic approach to conduction between nanoelectrodes through a single molecule.

    Science.gov (United States)

    Reimers, Jeffrey R; Shapley, Warwick A; Lambropoulos, Nicholas; Hush, Noel S

    2002-04-01

    Capacitance and other properties of nanoelectrodes, finite-size metal clusters envisaged for use in complex molecular-electronic devices, are discussed. The applicability of classical electrostatics (Coulomb's and Gauss' law, Poisson's equation, etc.) to atomistic systems is investigated and the self-energy necessary to store a finite charge on an atom is found to be of central importance. In particular, the neglect of electron exchange is found to introduce severe limitations, with quantum calculations predicting fundamentally different electronic structures. Also, the well-known poor representation of the atomic self-energy inherent to modern DFT is discussed, along with its implications for molecular electronics calculations. An INDO/S method is introduced with new parameters for gold. This is the simplest approximate computational scheme that correctly includes quantum electrostatic, resonance, and spin effects, and is capable of describing arbitrary excited electronic states. Encouraging results are obtained for some trial problems. In particular, voltage differential between the electrodes in electrode-molecule-electrode conduction is obtained, not through an a priori prescription but rather by moving whole electrons between the electrodes and analyzing the response. The voltage drops across the molecule-electrode junctions and the central molecular region are then deduced. This alternative to the current Landauer-based 1-particle transmission equations for electrode-molecule-electrode conduction is discussed in terms of the use of the electronic states of the system. It provides a proper description not only of conduction via electrode-to-molecule charge or hole transfer but also of conduction via simultaneous charge and hole transfer via low-lying excited molecular electronic states, including the ability to account for electroluminescence and other chemical effects. In addition, various aspects of our research on the quantitative prediction of the I

  20. Automated Algorithms for Quantum-Level Accuracy in Atomistic Simulations: LDRD Final Report.

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Aidan Patrick; Schultz, Peter Andrew; Crozier, Paul; Moore, Stan Gerald; Swiler, Laura Painton; Stephens, John Adam; Trott, Christian Robert; Foiles, Stephen Martin; Tucker, Garritt J. (Drexel University)

    2014-09-01

    This report summarizes the result of LDRD project 12-0395, titled "Automated Algorithms for Quantum-level Accuracy in Atomistic Simulations." During the course of this LDRD, we have developed an interatomic potential for solids and liquids called Spectral Neighbor Analysis Poten- tial (SNAP). The SNAP potential has a very general form and uses machine-learning techniques to reproduce the energies, forces, and stress tensors of a large set of small configurations of atoms, which are obtained using high-accuracy quantum electronic structure (QM) calculations. The local environment of each atom is characterized by a set of bispectrum components of the local neighbor density projected on to a basis of hyperspherical harmonics in four dimensions. The SNAP coef- ficients are determined using weighted least-squares linear regression against the full QM training set. This allows the SNAP potential to be fit in a robust, automated manner to large QM data sets using many bispectrum components. The calculation of the bispectrum components and the SNAP potential are implemented in the LAMMPS parallel molecular dynamics code. Global optimization methods in the DAKOTA software package are used to seek out good choices of hyperparameters that define the overall structure of the SNAP potential. FitSnap.py, a Python-based software pack- age interfacing to both LAMMPS and DAKOTA is used to formulate the linear regression problem, solve it, and analyze the accuracy of the resultant SNAP potential. We describe a SNAP potential for tantalum that accurately reproduces a variety of solid and liquid properties. Most significantly, in contrast to existing tantalum potentials, SNAP correctly predicts the Peierls barrier for screw dislocation motion. We also present results from SNAP potentials generated for indium phosphide (InP) and silica (SiO 2 ). We describe efficient algorithms for calculating SNAP forces and energies in molecular dynamics simulations using massively parallel computers

  1. Atomistic simulation of laser-pulse surface modification: Predictions of models with various length and time scales

    Energy Technology Data Exchange (ETDEWEB)

    Starikov, Sergey V., E-mail: starikov@ihed.ras.ru; Pisarev, Vasily V. [Moscow Institute of Physics and Technology, Dolgoprudny 141700 (Russian Federation); Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow 125412 (Russian Federation)

    2015-04-07

    In this work, the femtosecond laser pulse modification of surface is studied for aluminium (Al) and gold (Au) by use of two-temperature atomistic simulation. The results are obtained for various atomistic models with different scales: from pseudo-one-dimensional to full-scale three-dimensional simulation. The surface modification after laser irradiation can be caused by ablation and melting. For low energy laser pulses, the nanoscale ripples may be induced on a surface by melting without laser ablation. In this case, nanoscale changes of the surface are due to a splash of molten metal under temperature gradient. Laser ablation occurs at a higher pulse energy when a crater is formed on the surface. There are essential differences between Al ablation and Au ablation. In the first step of shock-wave induced ablation, swelling and void formation occur for both metals. However, the simulation of ablation in gold shows an additional athermal type of ablation that is associated with electron pressure relaxation. This type of ablation takes place at the surface layer, at a depth of several nanometers, and does not induce swelling.

  2. Experimental approach and atomistic simulations to investigate the radiation tolerance of complex oxides: Application to the amorphization of pyrochlores

    Science.gov (United States)

    Sattonnay, G.; Thomé, L.; Sellami, N.; Monnet, I.; Grygiel, C.; Legros, C.; Tetot, R.

    2014-05-01

    Both experimental approach and atomistic simulations are performed in order to investigate the influence of the composition of pyrochlores on their radiation tolerance. Therefore, Gd2Ti2O7 and Gd2Zr2O7 were irradiated with 4 MeV Au and 92 MeV Xe ions in order to study the structural changes induced by low and high-energy irradiations. XRD results show that, for both irradiations, the structural modifications are strongly dependent on the sample composition: Gd2Ti2O7 is readily amorphized, whereas Gd2Zr2O7 is transformed into a radiation-resistant anion-deficient fluorite structure. Using atomistic simulations with new interatomic potentials derived from the SMTB-Q model, the lattice properties and the defect formation energies were calculated in Gd2Ti2O7 and Gd2Zr2O7. Calculations show that titanates have a more covalent character than zirconates. Moreover, in Gd2Ti2O7 the formation of cation antisite defects leads to strong local distortions around Ti-defects and to a decrease of the Ti coordination number, which are not observed in Gd2Zr2O7. Thus, the radiation resistance is related to the defect stability: the accumulation of structural distortions around Ti-defects could drive the Gd2Ti2O7 amorphization induced by irradiation.

  3. Evaluation of Alternative Atomistic Models for the Incipient Growth of ZnO by Atomic Layer Deposition

    Science.gov (United States)

    Chu, Manh-Hung; Tian, Liang; Chaker, Ahmad; Skopin, Evgenii; Cantelli, Valentina; Ouled, Toufik; Boichot, Raphaël; Crisci, Alexandre; Lay, Sabine; Richard, Marie-Ingrid; Thomas, Olivier; Deschanvres, Jean-Luc; Renevier, Hubert; Fong, Dillon; Ciatto, Gianluca

    2017-03-01

    ZnO thin films are interesting for applications in several technological fields, including optoelectronics and renewable energies. Nanodevice applications require controlled synthesis of ZnO structures at nanometer scale, which can be achieved via atomic layer deposition (ALD). However, the mechanisms governing the initial stages of ALD had not been addressed until very recently. Investigations into the initial nucleation and growth as well as the atomic structure of the heterointerface are crucial to optimize the ALD process and understand the structure-property relationships for ZnO. We have used a complementary suite of in situ synchrotron x-ray techniques to investigate both the structural and chemical evolution during ZnO growth by ALD on two different substrates, i.e., SiO2 and Al2O3, which led us to formulate an atomistic model of the incipient growth of ZnO. The model relies on the formation of nanoscale islands of different size and aspect ratio and consequent disorder induced in the Zn neighbors' distribution. However, endorsement of our model requires testing and discussion of possible alternative models which could account for the experimental results. In this work, we review, test, and rule out several alternative models; the results confirm our view of the atomistic mechanisms at play, which influence the overall microstructure and resulting properties of the final thin film.

  4. Atomistic Conversion Reaction Mechanism of WO 3 in Secondary Ion Batteries of Li, Na, and Ca

    Energy Technology Data Exchange (ETDEWEB)

    He, Yang [Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh PA 15261 USA; Gu, Meng [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99352 USA; Xiao, Haiyan [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 China; Luo, Langli [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99352 USA; Shao, Yuyan [Energy and Environmental Directorate, Pacific Northwest National Laboratory, Richland WA 99352 USA; Gao, Fei [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor MI 48109 USA; Du, Yingge [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99352 USA; Mao, Scott X. [Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh PA 15261 USA; Wang, Chongmin [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99352 USA

    2016-04-13

    Reversible insertion and extraction of ionic species into a host lattice governs the basic operating principle for both rechargeable battery (such as lithium batteries) and electrochromic devices (such as ANA Boeing 787-8 Dreamliner electrochromic window). Intercalation and/or conversion are two fundamental chemical processes for some materials in response to the ion insertion. The interplay between these two chemical processes has never been established. It is speculated that the conversion reaction is initiated by ion intercalation. However, experimental evidence of intercalation and subsequent conversion remains unexplored. Here, using in situ HRTEM and spectroscopy, we captured the atomistic conversion reaction processes during lithium, sodium and calcium ion insertion into tungsten trioxide (WO3) single crystal model electrodes. An intercalation step right prior to conversion is explicitly revealed at atomic scale for the first time for these three ion species. Combining nanoscale diffraction and ab initio molecular dynamics simulations, it is found that, beyond intercalation, the inserted ion-oxygen bonding formation destabilized the transition-metal framework which gradually shrunk, distorted and finally collapsed to a pseudo-amorphous structure. This study provides a full atomistic picture on the transition from intercalation to conversion, which is of essential for material applications in both secondary ion batteries and electrochromic devices.

  5. Atomistic modeling of two-dimensional electronic spectra and excited-state dynamics for a Light Harvesting 2 complex.

    Science.gov (United States)

    van der Vegte, C P; Prajapati, J D; Kleinekathöfer, U; Knoester, J; Jansen, T L C

    2015-01-29

    The Light Harvesting 2 (LH2) complex is a vital part of the photosystem of purple bacteria. It is responsible for the absorption of light and transport of the resulting excitations to the reaction center in a highly efficient manner. A general description of the chromophores and the interaction with their local environment is crucial to understand this highly efficient energy transport. Here we include this interaction in an atomistic way using mixed quantum-classical (molecular dynamics) simulations of spectra. In particular, we present the first atomistic simulation of nonlinear optical spectra for LH2 and use it to study the energy transport within the complex. We show that the frequency distributions of the pigments strongly depend on their positions with respect to the protein scaffold and dynamics of their local environment. Furthermore, we show that although the pigments are closely packed the transition frequencies of neighboring pigments are essentially uncorrelated. We present the simulated linear absorption spectra for the LH2 complex and provide a detailed explanation of the states responsible for the observed two-band structure. Finally, we discuss the energy transfer within the complex by analyzing population transfer calculations and 2D spectra for different waiting times. We conclude that the energy transfer from the B800 ring to the B850 ring is mediated by intermediate states that are delocalized over both rings, allowing for a stepwise downhill energy transport.

  6. Atomistic Modeling of the Negative Thermal Expansion in δ- Plutonium  Based on the Two-State Description

    Directory of Open Access Journals (Sweden)

    Steven M. Valone

    2012-06-01

    Full Text Available The δ phase  of plutonium with the fcc structure exhibits an unusual negative thermal expansion (NTE over its narrow  temperature range of stability, 593–736 K. An accurate description  of the anomalous high-temperature volume effect of plutonium  goes beyond the current capability  of electronic-structure  calculations.  We propose an atomistic scheme to model the thermodynamic properties of δ-Pu based on the two-state model of Weiss for the Invar alloys, inspired by the simple free-energy analysis previously conducted by Lawson et al. The two-state mechanism is incorporated into the atomistic description of a many-body  interacting  system.  Two modified  embedded atom method potentials are employed to represent the binding energies of two competing  electronic  states in δ-Pu. We demonstrate how the NTE takes place in δ-Pu by means of Monte Carlo simulations implemented with the two-state mechanism.

  7. Molecular and intermolecular effects in collagen fibril mechanics: a multiscale analytical model compared with atomistic and experimental studies.

    Science.gov (United States)

    Marino, Michele

    2016-02-01

    Both atomistic and experimental studies reveal the dependence of collagen fibril mechanics on biochemical and biophysical features such as, for instance, cross-link density, water content and protein sequence. In order to move toward a multiscale structural description of biological tissues, a novel analytical model for collagen fibril mechanics is herein presented. The model is based on a multiscale approach that incorporates and couples: thermal fluctuations in collagen molecules; the uncoiling of collagen triple helix; the stretching of molecular backbone; the straightening of the telopeptide in which covalent cross-links form; slip-pulse mechanisms due to the rupture of intermolecular weak bonds; molecular interstrand delamination due to the rupture of intramolecular weak bonds; the rupture of covalent bonds within molecular strands. The effectiveness of the proposed approach is verified by comparison with available atomistic results and experimental data, highlighting the importance of cross-link density in tuning collagen fibril mechanics. The typical three-region shape and hysteresis behavior of fibril constitutive response, as well as the transition from a yielding-like to a brittle-like behavior, are recovered with a special insight on the underlying nanoscale mechanisms. The model is based on parameters with a clear biophysical and biochemical meaning, resulting in a promising tool for analyzing the effect of pathological or pharmacological-induced histochemical alterations on the functional mechanical response of collagenous tissues.

  8. An Atomistic-Based Continuum Modeling for Evaluation of Effective Elastic Properties of Single-Walled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    M. S. M. Al-Kharusi

    2016-01-01

    Full Text Available The mechanical behavior of SWCNTs is characterized using an atomistic-based continuum method. At nanoscale, interatomic energy among carbon atoms and the corresponding force constants are defined. Subsequently, we used an atomistic finite element analysis to calculate the energy stored in the SWCNT model, which forms a basis for calculating effective elastic moduli. In the finite element model, the force interaction among carbon atoms in a SWCNT is modeled using load-carrying structural beams. At macroscale, the SWCNT is taken as cylindrical continuum solid with transversely isotropic mechanical properties. Equivalence of energies of both models establishes a framework to calculate effective elastic moduli of armchair and zigzag nanotubes. This is achieved by solving five boundary value problems under distinct essential-controlled boundary conditions, which generates a prescribed uniform strain field in both models. Elastic constants are extracted from the calculated elastic moduli. While results of Young’s modulus obtained in this study generally concur with the published theoretical and numerical predictions, values of Poisson’s ratio are on the high side.

  9. Economic reasoning and artificial intelligence.

    Science.gov (United States)

    Parkes, David C; Wellman, Michael P

    2015-07-17

    The field of artificial intelligence (AI) strives to build rational agents capable of perceiving the world around them and taking actions to advance specified goals. Put another way, AI researchers aim to construct a synthetic homo economicus, the mythical perfectly rational agent of neoclassical economics. We review progress toward creating this new species of machine, machina economicus, and discuss some challenges in designing AIs that can reason effectively in economic contexts. Supposing that AI succeeds in this quest, or at least comes close enough that it is useful to think about AIs in rationalistic terms, we ask how to design the rules of interaction in multi-agent systems that come to represent an economy of AIs. Theories of normative design from economics may prove more relevant for artificial agents than human agents, with AIs that better respect idealized assumptions of rationality than people, interacting through novel rules and incentive systems quite distinct from those tailored for people.

  10. Tadpole-like artificial micromotor

    Science.gov (United States)

    Liu, Limei; Liu, Mei; Su, Yajun; Dong, Yonggang; Zhou, Wei; Zhang, Lina; Zhang, Hui; Dong, Bin; Chi, Lifeng

    2015-01-01

    We describe a polymer-based artificial tadpole-like micromotor, which is fabricated through the electrospinning technique. By incorporating functional materials onto its surface or within its body, the resulting tadpole-like micromotor can not only move autonomously in an aqueous solution with a flexible tail, but also exhibit thermo- and magnetic responsive properties.We describe a polymer-based artificial tadpole-like micromotor, which is fabricated through the electrospinning technique. By incorporating functional materials onto its surface or within its body, the resulting tadpole-like micromotor can not only move autonomously in an aqueous solution with a flexible tail, but also exhibit thermo- and magnetic responsive properties. Electronic supplementary information (ESI) available: Experimental section, Fig. S1-S3 and Video S1-S4. See DOI: 10.1039/c4nr06621a

  11. Torsional Carbon Nanotube Artificial Muscles

    Science.gov (United States)

    Foroughi, Javad; Spinks, Geoffrey M.; Wallace, Gordon G.; Oh, Jiyoung; Kozlov, Mikhail E.; Fang, Shaoli; Mirfakhrai, Tissaphern; Madden, John D. W.; Shin, Min Kyoon; Kim, Seon Jeong; Baughman, Ray H.

    2011-10-01

    Rotary motors of conventional design can be rather complex and are therefore difficult to miniaturize; previous carbon nanotube artificial muscles provide contraction and bending, but not rotation. We show that an electrolyte-filled twist-spun carbon nanotube yarn, much thinner than a human hair, functions as a torsional artificial muscle in a simple three-electrode electrochemical system, providing a reversible 15,000° rotation and 590 revolutions per minute. A hydrostatic actuation mechanism, as seen in muscular hydrostats in nature, explains the simultaneous occurrence of lengthwise contraction and torsional rotation during the yarn volume increase caused by electrochemical double-layer charge injection. The use of a torsional yarn muscle as a mixer for a fluidic chip is demonstrated.

  12. Artificial intelligence and computer vision

    CERN Document Server

    Li, Yujie

    2017-01-01

    This edited book presents essential findings in the research fields of artificial intelligence and computer vision, with a primary focus on new research ideas and results for mathematical problems involved in computer vision systems. The book provides an international forum for researchers to summarize the most recent developments and ideas in the field, with a special emphasis on the technical and observational results obtained in the past few years.

  13. Artificial color perception using microwaves

    CERN Document Server

    Choudhury, Debesh

    2013-01-01

    We report the feasibility of artificial color perception under microwave illumination using a standard microwave source and an antenna. We have sensed transmitted microwave power through color objects and have distinguished the colors by analyzing the sensed transmitted power. Experiments are carried out using a Gunn diode as the microwave source, some colored liquids as the objects and a microwave diode as the detector. Results are presented which open up an unusual but new way of perceiving colors using microwaves.

  14. Automated Scheduling Via Artificial Intelligence

    Science.gov (United States)

    Biefeld, Eric W.; Cooper, Lynne P.

    1991-01-01

    Artificial-intelligence software that automates scheduling developed in Operations Mission Planner (OMP) research project. Software used in both generation of new schedules and modification of existing schedules in view of changes in tasks and/or available resources. Approach based on iterative refinement. Although project focused upon scheduling of operations of scientific instruments and other equipment aboard spacecraft, also applicable to such terrestrial problems as scheduling production in factory.

  15. Artificial color perception using microwaves

    OpenAIRE

    Choudhury, Debesh; Caulfield, H. John

    2013-01-01

    We report the feasibility of artificial color perception under microwave illumination using a standard microwave source and an antenna. We have sensed transmitted microwave power through color objects and have distinguished the colors by analyzing the sensed transmitted power. Experiments are carried out using a Gunn diode as the microwave source, some colored liquids as the objects and a microwave diode as the detector. Results are presented which open up an unusual but new way of perceiving...

  16. A Definition of Artificial Intelligence

    OpenAIRE

    2012-01-01

    In this paper we offer a formal definition of Artificial Intelligence and this directly gives us an algorithm for construction of this object. Really, this algorithm is useless due to the combinatory explosion. The main innovation in our definition is that it does not include the knowledge as a part of the intelligence. So according to our definition a newly born baby also is an Intellect. Here we differs with Turing's definition which suggests that an Intellect is a person with knowledge gai...

  17. Towards photovoltaic powered artificial retina

    OpenAIRE

    2011-01-01

    The aim of this article is to provide an overview of current and future concepts in the field of retinal prostheses, and is focused on the power supply based on solar energy conversion; we introduce the possibility of using PV minimodules as power supply for a new concept of retinal prostheses: Photovoltaic Powered Artificial Retina (PVAR). Main characteristics of these PV modules are presented showing its potential for this application. Peer Reviewed

  18. Artificial Sweeteners versus Natural Sweeteners

    OpenAIRE

    Neacsu, N.A.; Madar, A.

    2014-01-01

    Carbohydrates are an important dietary nutrient which is mostly used to supply energy to the body, as well as a carbon source for synthesis of other needed chemicals. In addition, mono- and disaccharides are craved because of their sweetness. We present different types of sweeteners, which are the basic contents of foods which we consume every day and are demonstrated the positive and negative effects of natural and artificial sweeteners.

  19. Artificial Sweeteners versus Natural Sweeteners

    Directory of Open Access Journals (Sweden)

    Neacsu, N.A.

    2014-06-01

    Full Text Available Carbohydrates are an important dietary nutrient which is mostly used to supply energy to the body, as well as a carbon source for synthesis of other needed chemicals. In addition, mono- and disaccharides are craved because of their sweetness. We present different types of sweeteners, which are the basic contents of foods which we consume every day and are demonstrated the positive and negative effects of natural and artificial sweeteners.

  20. Bioengineering of Artificial Lymphoid Organs

    OpenAIRE

    Nosenko, M. A.; Drutskaya, M. S; M. M. Moisenovich; Nedospasov, S A

    2016-01-01

    This review addresses the issue of bioengineering of artificial lymphoid organs.Progress in this field may help to better understand the nature of the structure-function relations that exist in immune organs. Artifical lymphoid organs may also be advantageous in the therapy or correction of immunodefficiencies, autoimmune diseases, and cancer. The structural organization, development, and function of lymphoid tissue are analyzed with a focus on the role of intercellular contacts and on the cy...

  1. Beller Lecture: Artificial Ferroic Systems

    Science.gov (United States)

    Heyderman, Laura

    In artificial ferroic systems, novel functionality is engineered through the combination of structured ferroic materials and the control of the interactions between the different components. I will present two classes of these systems, beginning with hybrid mesoscopic structures incorporating two different ferromagnetic layers whose static and dynamic behaviour result from the mutual imprint of the magnetic domain configurations. Here we have demonstrated a new vortex core reversal mechanism, which occurs when it is displaced across domain boundaries with a magnetic field. I will then describe our progress on artificial spin ice, consisting of arrays of dipolar-coupled nanomagnets arranged in frustrated geometries. We have employed photoemission electron microscopy to observe the behaviour of emergent magnetic monopoles in an array of nanomagnets placed on the kagome lattice. We have also created artificial spin ice with fluctuating magnetic moments and observed the evolution of magnetic configurations with time. This has provided a means to study relaxation processes with a controlled route to the lowest-energy state. Recently, we have demonstrated with muon spin relaxation that these magnetic metamaterials can support thermodynamic phase transitions, and future directions include the incorporation of novel magnetic materials such as ultrathin magnetic films, the investigation of 3D structures, as well as the implementation of x-ray resonant magnetic scattering to study magnetic correlations in smaller nanomagnets and at faster timescales

  2. Miniature curved artificial compound eyes.

    Science.gov (United States)

    Floreano, Dario; Pericet-Camara, Ramon; Viollet, Stéphane; Ruffier, Franck; Brückner, Andreas; Leitel, Robert; Buss, Wolfgang; Menouni, Mohsine; Expert, Fabien; Juston, Raphaël; Dobrzynski, Michal Karol; L'Eplattenier, Geraud; Recktenwald, Fabian; Mallot, Hanspeter A; Franceschini, Nicolas

    2013-06-04

    In most animal species, vision is mediated by compound eyes, which offer lower resolution than vertebrate single-lens eyes, but significantly larger fields of view with negligible distortion and spherical aberration, as well as high temporal resolution in a tiny package. Compound eyes are ideally suited for fast panoramic motion perception. Engineering a miniature artificial compound eye is challenging because it requires accurate alignment of photoreceptive and optical components on a curved surface. Here, we describe a unique design method for biomimetic compound eyes featuring a panoramic, undistorted field of view in a very thin package. The design consists of three planar layers of separately produced arrays, namely, a microlens array, a neuromorphic photodetector array, and a flexible printed circuit board that are stacked, cut, and curved to produce a mechanically flexible imager. Following this method, we have prototyped and characterized an artificial compound eye bearing a hemispherical field of view with embedded and programmable low-power signal processing, high temporal resolution, and local adaptation to illumination. The prototyped artificial compound eye possesses several characteristics similar to the eye of the fruit fly Drosophila and other arthropod species. This design method opens up additional vistas for a broad range of applications in which wide field motion detection is at a premium, such as collision-free navigation of terrestrial and aerospace vehicles, and for the experimental testing of insect vision theories.

  3. Artificial life: The coming evolution

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J.D. (Los Alamos National Lab., NM (USA) Santa Fe Inst., NM (USA)); Belin, A.d' A. (Shute, Mihaly, and Weinberger, Santa Fe, NM (USA))

    1990-01-01

    Within fifty to a hundred years a new class of organisms is likely to emerge. These organisms will be artificial in the sense that they will originally be designed by humans. However, they will reproduce, and will evolve into something other than their initial form; they will be alive'' under any reasonable definition of the word. These organisms will evolve in a fundamentally different manner than contemporary biological organisms, since their reproduction will be under at least partial conscious control, giving it a Lamarckian component. The pace of evolutionary change consequently will be extremely rapid. The advent of artificial life will be the most significant historical event since the emergence of human beings. The impact on humanity and the biosphere could be enormous, larger than the industrial revolution, nuclear weapons, or environmental pollution. We must take steps now to shape the emergence of artificial organisms; they have potential to be either the ugliest terrestrial disaster, or the most beautiful creation of humanity. 22 refs., 3 figs.

  4. Artificial insemination history: hurdles and milestones.

    Science.gov (United States)

    Ombelet, W; Van Robays, J

    2015-01-01

    Artificial insemination with homologous (AIH) or donor semen (AID) is nowadays a very popular treatment procedure used for many subfertile women worldwide. The rationale behind artificial insemination is to increase gamete density at the site of fertilisation. The sequence of events leading to today's common use of artificial insemination traces back to scientific studies and experimentation many centuries ago. Modern techniques used in human artificial insemination programmes are mostly adapted from the work on cattle by dairy farmers wishing to improve milk production by using artificial insemination with sperm of selected bulls with well chosen genetic traits. The main reason for the renewed interest in artificial insemination in human was associated with the refinement of techniques for the preparation of washed motile spermatozoa in the early years of IVF. The history of artificial insemination is reviewed with particular interest to the most important hurdles and milestones.

  5. Fecundación Artificial

    Directory of Open Access Journals (Sweden)

    Ochoa. Fidel

    1939-10-01

    Full Text Available Por Fecundación artificial se entiende, la fecundación de una hembra sin el servicio directo del macho, es decir la introducción al aparato genital femenino, del esperma que se ha recogido por medios artificiales. Esta fecundación, practicada en debidas condiciones, tiene el mismo efecto de la fecundación natural, con las ventajas que veremos más adelante. La fecundación artificial permite explotar un reproductor a su máximum de capacidad, ya que se considera, para no hacer cálculos alegres, que un servicio de un caballo puede servir, diluido, por lo menos para cuatro yeguas, según los autores americanos, y para 10 a 15, según otros autores. El toro y el carnero pueden dar esperma suficiente en un servicio para fecundar de 10 a 12 hembras, según,los americanos, y según otros autores, hasta para 40. Los investigadores rusos han podido fecundar hasta 60 vacas con un solo servicio y han logrado con reproductores valiosos, fecundar 10.263 vacas por toro, a pesar de que éstos sólo han servido, durante un periodo de monta de sólo dos meses. Estos mismos han logrado fecundar artificialmente 2.733 ovejas con un solo carnero, y 1.403 con otro Los investigadores americanos han contado 22 servicios a un carnero vigoroso en un periodo de ocho horas, y durante este tiempo produjo esperma suficiente para haber fecundado 200 ovejas artificialmente. La fecundación artificial sirve para evitar la trasmisión de enfermedades que se contagian por el coito, tales como la durina, enfermedad ésta producida por un tripanosoma que por fortuna no existe entre nosotros. A las estaciones de monta llevan con frecuencia hembras afectadas de enfermedades como la vaginitis granulosa de la vaca, que se contagia al toro y de éste a otras hembras. Como el control sanitario de toda hembra llevada al servicio de un reproductor de estas estaciones de monta no siempre puede efectuarse por dificultades de distinta índole, mediante la fecundación artificial

  6. 基于微博客的企业竞争情报搜集与分析%Collection and Analysis of Enterprise Competitive Intelligence Based on Micro-blogs

    Institute of Scientific and Technical Information of China (English)

    帕尔哈提·尼加提; 黄晓斌; 聂冰

    2012-01-01

    This paper describes the types of collecting enterprise competitive intelligence based on micro-blog,constructs the relevant collection framework,and discusses the main method of enterprise competitive intelligence analysis based on micro-blog.Finally,taking NOKIA intelligent mobile phone for example,the paper explains some applications of micro-blog in enterprise competitive intelligence work.%文章介绍了基于微博客的企业竞争情报收集方式,构建了相关的收集框架,探讨了通过微博客进行企业竞争情报分析的主要方法,并以诺基亚智能手机为例,说明微博客在企业竞争情报工作中的一些应用。

  7. An atomistic study on configuration, mechanics and growth of nanoscale filaments

    Science.gov (United States)

    Shahabi, Alireza

    conformations in these electronically active filaments open up the possibility of non-linear stretchable interconnects, and we study their reliability by extracting the elastic stiffness of the various conformations. We extract force-displacement curves of scrolls and plectonemes in the various systems. Our analysis sheds light on the relation between the shape of the nanostructures and the elastic stiffness of the nanofilaments. In overall, our study provides us with a novel route to engineer the nanofilaments and tune their mechanical properties using a combination of physical constraints and mechanical loading. In the next part of the dissertation, we perform a comprehensive atomistic study of the nanoscale crystal growth mechanisms of Au-catalyzed silicon nanowires grown via the vapor liquid solid method (VLS) during early stages of the droplet to nanowire transition. The transition sets the size of the nanowire, and the principles of diameter selection remain poorly understood. Our analysis reveals the role of the initial configuration of the nanodroplet and the effect of surface tension on the success of the VLS growth process. We observe lateral extension of liquid feet from the sides of nanodroplet during the VLS process. In addition to the nanodroplet diameter, the liquid feet plays a crucial role on determining the final geometry of the nanowire. We also observe an important correlation between the rate of deposition of Si atoms and presence of the twining in the nanowire structure, which significantly affects its properties. Higher deposition rates result in incorporation of metallic impurities in the nanowire structure, which consequently results in the formation of twining deformation. Our MD studies uncover a previously ignored interplay between solute trapping of catalyst particles in the nanowire, and twin formation, and we discuss this effect in the context of past experimental reports on twin formation in semiconducting nanowires, and the ability to

  8. The Soft Mode Driven Dynamics in Ferroelectric Perovskites at the Nanoscale: An Atomistic Study

    Science.gov (United States)

    McCash, Kevin

    The discovery of ferroelectricity at the nanoscale has incited a lot of interest in perovskite ferroelectrics not only for their potential in device application but also for their potential to expand fundamental understanding of complex phenomena at very small size scales. Unfortunately, not much is known about the dynamics of ferroelectrics at this scale. Many of the widely held theories for ferroelectric materials are based on bulk dynamics which break down when applied to smaller scales. In an effort to increase understanding of nanoscale ferroelectric materials we use atomistic resolution computational simulations to investigate the dynamics of polar perovskites. Within the framework of a well validated effective Hamiltonian model we are able to accurately predict many of the properties of ferroelectric materials at the nanoscale including the response of the soft mode to mechanical boundary conditions and the polarization reversal dynamics of ferroelectric nanowires. Given that the focus of our study is the dynamics of ferroelectric perovskites we begin by developing an effective Hamiltonian based model that could simultaneously describe both static and dynamic properties of such materials. Our study reveals that for ferroelectric perovskites that undergo a sequence of phase transitions, such as BaTiO3. for example, the minimal parameter effective Hamiltonian model is unable to reproduce both static and dynamical properties simultaneously. Nevertheless we developed two sets of parameters that accurately describes the static properties and dynamic properties of BaTiO3 independently. By creating a tool that accurately models the dynamical properties of perovskite ferroelectrics we are able to investigate the frequencies of the soft modes in the perovskite crystal. The lowest energy transverse optical soft modes in perovskite ferroelectrics are known to be cause of the ferroelectric phase transition in these materials and affect a number of electrical properties

  9. Atomistic Simulations of Chemical Reactivity of TATB Under Thermal and Shock Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Manaa, M R; Reed, E J; Fried, L E

    2009-09-23

    The study of chemical transformations that occur at the reactive shock front of energetic materials provides important information for the development of predictive models at the grain-and continuum scales. A major shortcoming of current high explosives models is the lack of chemical kinetics data of the reacting explosive in the high pressure and temperature regimes. In the absence of experimental data, long-time scale atomistic molecular dynamics simulations with reactive chemistry become a viable recourse to provide an insight into the decomposition mechanism of explosives, and to obtain effective reaction rate laws. These rates can then be incorporated into thermo-chemical-hydro codes (such as Cheetah linked to ALE3D) for accurate description of the grain and macro scales dynamics of reacting explosives. In this talk, I will present quantum simulations of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) crystals under thermal decomposition (high density and temperature) and shock compression conditions. This is the first time that condensed phase quantum methods have been used to study the chemistry of insensitive high explosives. We used the quantum-based, self-consistent charge density functional tight binding method (SCC{_}DFTB) to calculate the interatomic forces for reliable predictions of chemical reactions, and to examine electronic properties at detonation conditions for a relatively long time-scale on the order of several hundreds of picoseconds. For thermal decomposition of TATB, we conducted constant volume-temperature simulations, ranging from 0.35 to 2 nanoseconds, at {rho} = 2.87 g/cm{sup 3} at T = 3500, 3000, 2500, and 1500 K, and {rho} = 2.9 g/cm{sup 3} and 2.72 g/cm{sup 3}, at T = 3000 K. We also simulated crystal TATB's reactivity under steady overdriven shock compression using the multi-scale shock technique. We conducted shock simulations with specified shock speeds of 8, 9, and 10 km/s for up to 0.43 ns duration, enabling us to track the

  10. FPGA controlled artificial vascular system

    Directory of Open Access Journals (Sweden)

    Laqua D.

    2015-09-01

    Full Text Available Monitoring the oxygen saturation of an unborn child is an invasive procedure, so far. Transabdominal fetal pulse oximetry is a promising method under research, used to estimate the oxygen saturation of a fetus noninvasively. Due to the nature of the method, the fetal information needs to be extracted from a mixed signal. To properly evaluate signal processing algorithms, a phantom modeling fetal and maternal blood circuits and tissue layers is necessary. This paper presents an improved hardware concept for an artificial vascular system, utilizing an FPGA based CompactRIO System from National Instruments. The experimental model to simulate the maternal and fetal blood pressure curve consists of two identical hydraulic circuits. Each of these circuits consists of a pre-pressure system and an artificial vascular system. Pulse curves are generated by proportional valves, separating these two systems. The dilation of the fetal and maternal artificial vessels in tissue substitutes is measured by transmissive and reflective photoplethysmography. The measurement results from the pressure sensors and the transmissive optical sensors are visualized to show the functionality of the pulse generating systems. The trigger frequency for the maternal valve was set to 1 per second, the fetal valve was actuated at 0.7 per second for validation. The reflective curve, capturing pulsations of the fetal and maternal circuit, was obtained with a high power LED (905 nm as light source. The results show that the system generates pulse curves, similar to its physiological equivalent. Further, the acquired reflective optical signal is modulated by the alternating diameter of the tubes of both circuits, allowing for tests of signal processing algorithms.

  11. Formal Definition of Artificial Intelligence

    OpenAIRE

    Dobrev, Dimiter

    2005-01-01

    * This publication is partially supported by the KT-DigiCult-Bg project. A definition of Artificial Intelligence (AI) was proposed in [1] but this definition was not absolutely formal at least because the word "Human" was used. In this paper we will formalize the definition from [1]. The biggest problem in this definition was that the level of intelligence of AI is compared to the intelligence of a human being. In order to change this we will introduce some parameters to which AI ...

  12. Advanced Artificial Intelligence Technology Testbed

    Science.gov (United States)

    Anken, Craig S.

    1993-01-01

    The Advanced Artificial Intelligence Technology Testbed (AAITT) is a laboratory testbed for the design, analysis, integration, evaluation, and exercising of large-scale, complex, software systems, composed of both knowledge-based and conventional components. The AAITT assists its users in the following ways: configuring various problem-solving application suites; observing and measuring the behavior of these applications and the interactions between their constituent modules; gathering and analyzing statistics about the occurrence of key events; and flexibly and quickly altering the interaction of modules within the applications for further study.

  13. Epistasis analysis using artificial intelligence.

    Science.gov (United States)

    Moore, Jason H; Hill, Doug P

    2015-01-01

    Here we introduce artificial intelligence (AI) methodology for detecting and characterizing epistasis in genetic association studies. The ultimate goal of our AI strategy is to analyze genome-wide genetics data as a human would using sources of expert knowledge as a guide. The methodology presented here is based on computational evolution, which is a type of genetic programming. The ability to generate interesting solutions while at the same time learning how to solve the problem at hand distinguishes computational evolution from other genetic programming approaches. We provide a general overview of this approach and then present a few examples of its application to real data.

  14. Improving designer productivity. [artificial intelligence

    Science.gov (United States)

    Hill, Gary C.

    1992-01-01

    Designer and design team productivity improves with skill, experience, and the tools available. The design process involves numerous trials and errors, analyses, refinements, and addition of details. Computerized tools have greatly speeded the analysis, and now new theories and methods, emerging under the label Artificial Intelligence (AI), are being used to automate skill and experience. These tools improve designer productivity by capturing experience, emulating recognized skillful designers, and making the essence of complex programs easier to grasp. This paper outlines the aircraft design process in today's technology and business climate, presenting some of the challenges ahead and some of the promising AI methods for meeting these challenges.

  15. Artificial intelligence a beginner's guide

    CERN Document Server

    Whitby, Blay

    2012-01-01

    Tomorrow begins right here as we embark on an enthralling and jargon-free journey into the world of computers and the inner recesses of the human mind. Readers encounter everything from the nanotechnology used to make insect-like robots, to computers that perform surgery, in addition to discovering the biggest controversies to dog the field of AI. Blay Whitby is a Lecturer on Cognitive Science and Artificial Intelligence at the University of Sussex UK. He is the author of two books and numerous papers.

  16. Logical Foundations Of Artificial Intelligence

    Directory of Open Access Journals (Sweden)

    Angel Garrido

    2010-04-01

    Full Text Available The procedures of searching solutions to problems, in Artificial Intelligence, can be brought about, in many occasions, without knowledge of the Domain, and in other situations, with knowledge of it. This last procedure is usually called Heuristic Search. In such methods the matrix techniques reveal themselves as essential. Their introduction can give us an easy and precise way in the search of solution. Our paper explains how the matrix theory appears and fruitfully participates in A I, with feasible applications to Game Theory.

  17. Atomistic modeling of metal surfaces under electric fields: direct coupling of electric fields to a molecular dynamics algorithm

    CERN Document Server

    Djurabekova, Flyura; Pohjonen, Aarne; Nordlund, Kai

    2011-01-01

    The effect of electric fields on metal surfaces is fairly well studied, resulting in numerous analytical models developed to understand the mechanisms of ionization of surface atoms observed at very high electric fields, as well as the general behavior of a metal surface in this condition. However, the derivation of analytical models does not include explicitly the structural properties of metals, missing the link between the instantaneous effects owing to the applied field and the consequent response observed in the metal surface as a result of an extended application of an electric field. In the present work, we have developed a concurrent electrodynamic–molecular dynamic model for the dynamical simulation of an electric-field effect and subsequent modification of a metal surface in the framework of an atomistic molecular dynamics (MD) approach. The partial charge induced on the surface atoms by the electric field is assessed by applying the classical Gauss law. The electric forces acting on the partially...

  18. Can pyrene probes be used to measure lateral pressure profiles of lipid membranes? Perspective through atomistic simulations

    DEFF Research Database (Denmark)

    Franova, M. D.; Vattulainen, I.; Ollila, O. H. S.

    2014-01-01

    simulations, since established methods to measure the lateral pressure profile experimentally have not been available. The only experiments that have attempted to gauge the lateral pressure profile have been done by using di-pyrenyl-phosphatidylcholine (di-pyr-PC) probes. In these experiments, the excimer......The lateral pressure profile of lipid bilayers has gained a lot of attention, since changes in the pressure profile have been suggested to shift the membrane protein conformational equilibrium. This relation has been mostly studied with theoretical methods, especially with molecular dynamics....../monomer fluorescence ratio has been assumed to represent the lateral pressure in the location of the pyrene moieties. Here, we consider the validity of this assumption through atomistic molecular dynamics simulations in a DOPC (dioleoylphosphatidylcholine) membrane, which hosts di-pyr-PC probes with different acyl...

  19. General atomistic approach for modeling metal-semiconductor interfaces using density functional theory and nonequilibrium Green's function

    DEFF Research Database (Denmark)

    Stradi, Daniele; Martinez, Umberto; Blom, Anders

    2016-01-01

    an atomistic approach based on density functional theory and nonequilibrium Green's function, which includes all the relevant ingredients required to model realistic metal-semiconductor interfaces and allows for a direct comparison between theory and experiments via I-Vbias curve simulations. We apply......Metal-semiconductor contacts are a pillar of modern semiconductor technology. Historically, their microscopic understanding has been hampered by the inability of traditional analytical and numerical methods to fully capture the complex physics governing their operating principles. Here we introduce...... this method to characterize an Ag/Si interface relevant for photovoltaic applications and study the rectifying-to-Ohmic transition as a function of the semiconductor doping. We also demonstrate that the standard “activation energy” method for the analysis of I-Vbias data might be inaccurate for nonideal...

  20. Collaborative Simulation Grid: Multiscale Quantum-Mechanical/Classical Atomistic Simulations on Distributed PC Clusters in the US and Japan

    Science.gov (United States)

    Kikuchi, Hideaki; Kalia, Rajiv; Nakano, Aiichiro; Vashishta, Priya; Iyetomi, Hiroshi; Ogata, Shuji; Kouno, Takahisa; Shimojo, Fuyuki; Tsuruta, Kanji; Saini, Subhash; Biegel, Bryan (Technical Monitor)

    2002-01-01

    A multidisciplinary, collaborative simulation has been performed on a Grid of geographically distributed PC clusters. The multiscale simulation approach seamlessly combines i) atomistic simulation backed on the molecular dynamics (MD) method and ii) quantum mechanical (QM) calculation based on the density functional theory (DFT), so that accurate but less scalable computations are performed only where they are needed. The multiscale MD/QM simulation code has been Grid-enabled using i) a modular, additive hybridization scheme, ii) multiple QM clustering, and iii) computation/communication overlapping. The Gridified MD/QM simulation code has been used to study environmental effects of water molecules on fracture in silicon. A preliminary run of the code has achieved a parallel efficiency of 94% on 25 PCs distributed over 3 PC clusters in the US and Japan, and a larger test involving 154 processors on 5 distributed PC clusters is in progress.

  1. Multiscale atomistic simulation of metal-oxygen surface interactions: Methodological development, theoretical investigation, and correlation with experiment

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Judith C. [Univ. of Pittsburgh, Pittsburgh, PA (United States)

    2015-01-09

    The purpose of this grant is to develop the multi-scale theoretical methods to describe the nanoscale oxidation of metal thin films, as the PI (Yang) extensive previous experience in the experimental elucidation of the initial stages of Cu oxidation by primarily in situ transmission electron microscopy methods. Through the use and development of computational tools at varying length (and time) scales, from atomistic quantum mechanical calculation, force field mesoscale simulations, to large scale Kinetic Monte Carlo (KMC) modeling, the fundamental underpinings of the initial stages of Cu oxidation have been elucidated. The development of computational modeling tools allows for accelerated materials discovery. The theoretical tools developed from this program impact a wide range of technologies that depend on surface reactions, including corrosion, catalysis, and nanomaterials fabrication.

  2. Revised Atomistic Models of the Crystal Structure of C-S-H with high C/S Ratio

    Science.gov (United States)

    Kovačević, Goran; Nicoleau, Luc; Nonat, André; Veryazov, Valera

    2016-09-01

    The atomic structure of calcium-silicate-hydrate (C1.67-S-Hx) has been studied. Atomistic C-S-H models suggested in our previous study have been revised in order to perform a direct comparison of energetic stability of the different structures. An extensive set of periodic structures of C-S-H with variation of water content was created, and then optimized using molecular dynamics with reactive force field ReaxFF and quantum chemical semiempirical method PM6. All models show organization of water molecules inside the structure of C-S-H. The new geometries of C-S-H, reported in this paper, show lower relative energy with respect to the geometries from the original definition of C-S-H models. Model that corresponds to calcium enriched tobermorite structure has the lowest relative energy and the density closest to the experimental values.

  3. Atomistic insight into the catalytic mechanism of glycosyltransferases by combined quantum mechanics/molecular mechanics (QM/MM) methods.

    Science.gov (United States)

    Tvaroška, Igor

    2015-02-11

    Glycosyltransferases catalyze the formation of glycosidic bonds by assisting the transfer of a sugar residue from donors to specific acceptor molecules. Although structural and kinetic data have provided insight into mechanistic strategies employed by these enzymes, molecular modeling studies are essential for the understanding of glycosyltransferase catalyzed reactions at the atomistic level. For such modeling, combined quantum mechanics/molecular mechanics (QM/MM) methods have emerged as crucial. These methods allow the modeling of enzymatic reactions by using quantum mechanical methods for the calculation of the electronic structure of the active site models and treating the remaining enzyme environment by faster molecular mechanics methods. Herein, the application of QM/MM methods to glycosyltransferase catalyzed reactions is reviewed, and the insight from modeling of glycosyl transfer into the mechanisms and transition states structures of both inverting and retaining glycosyltransferases are discussed.

  4. An atomistic investigation on the mechanism of machining nanostructures when using single tip and multi-tip diamond tools

    Energy Technology Data Exchange (ETDEWEB)

    Tong, Zhen [Department of Design, Manufacture and Engineering Management, University of Strathclyde, Glasgow G1 1XQ (United Kingdom); Centre for Precision Technologies, University of Huddersfield, Huddersfield HD1 3DH (United Kingdom); Center for Precision Engineering, Harbin Institute of Technology, Harbin 150001 (China); Liang, Yingchun [Center for Precision Engineering, Harbin Institute of Technology, Harbin 150001 (China); Jiang, Xiangqian [Centre for Precision Technologies, University of Huddersfield, Huddersfield HD1 3DH (United Kingdom); Luo, Xichun, E-mail: xichun.luo@strath.ac.uk [Department of Design, Manufacture and Engineering Management, University of Strathclyde, Glasgow G1 1XQ (United Kingdom); Centre for Precision Technologies, University of Huddersfield, Huddersfield HD1 3DH (United Kingdom)

    2014-01-30

    In our previous work, a scale-up fabrication approach to cost effectively manufacturing nano-gratings over large area has been developed through diamond turning by using a multi-tip diamond tool fabricated by Focused Ion Beam. The objective of this study is to gain an in-depth understanding of the mechanism of machining nanostructures on single crystal copper through diamond turning when using a single tip and a multi-tip nanoscale diamond tool. For this purpose atomistic models of a single tip tool for multi-pass cutting and a multi-tip tool for single-pass cutting were built, respectively. The nature of the cutting chip formation, dislocation nucleation and propagation, cutting forces, and temperature distribution during nanometric cutting processes were studied through molecular dynamics (MD) simulations. Results show that nanostructure generation process at steady cutting stage was governed by a strong localization of the dislocation movement and the dynamic equilibrium of chip-tool contact area. Except the apparent improvement of machining efficiency that proportional to the tool tip numbers, the nano-grooves generated by multi-tip tool also have higher center symmetry than those machined by single tip tool. While the average tangential cutting force per tip were calculated all around 33.3 nN, a larger normal cutting force per tip being 54.1 nN was observed when using a multi-tip tool. A concept of atomistic equivalent temperature was proposed and used to analysis the important features of temperature distribution during the machining process. The advantage, disadvantage and applicability of diamond turning using multi-tip tool were discussed in comparison with those of using single-tip tool. The findings suggest that diamond turning using multi-tip tool might be more applicable than using single tip tool when apply to scale-up fabrication of periodic nanostructures.

  5. Large-scale atomistic and quantum-mechanical simulations of a Nafion membrane: Morphology, proton solvation and charge transport

    Directory of Open Access Journals (Sweden)

    Pavel V. Komarov

    2013-09-01

    Full Text Available Atomistic and first-principles molecular dynamics simulations are employed to investigate the structure formation in a hydrated Nafion membrane and the solvation and transport of protons in the water channel of the membrane. For the water/Nafion systems containing more than 4 million atoms, it is found that the observed microphase-segregated morphology can be classified as bicontinuous: both majority (hydrophobic and minority (hydrophilic subphases are 3D continuous and organized in an irregular ordered pattern, which is largely similar to that known for a bicontinuous double-diamond structure. The characteristic size of the connected hydrophilic channels is about 25–50 Å, depending on the water content. A thermodynamic decomposition of the potential of mean force and the calculated spectral densities of the hindered translational motions of cations reveal that ion association observed with decreasing temperature is largely an entropic effect related to the loss of low-frequency modes. Based on the results from the atomistic simulation of the morphology of Nafion, we developed a realistic model of ion-conducting hydrophilic channel within the Nafion membrane and studied it with quantum molecular dynamics. The extensive 120 ps-long density functional theory (DFT-based simulations of charge migration in the 1200-atom model of the nanochannel consisting of Nafion chains and water molecules allowed us to observe the bimodality of the van Hove autocorrelation function, which provides the direct evidence of the Grotthuss bond-exchange (hopping mechanism as a significant contributor to the proton conductivity.

  6. Large Scale 3-D Dislocation Dynamics and Atomistic Simulations of Flow and Strain-Hardening Behavior of Metallic Micropillars

    Science.gov (United States)

    Rao, Satish

    2015-03-01

    Experimental studies show strong strengthening effects for micrometer-scale FCC as well as two-phase superalloy crystals, even at high initial dislocation densities. This talk shows results from large-scale 3-D discrete dislocation simulations (DDS) used to explicitly model the deformation behavior of FCC Ni (flow stress and strain-hardening) as well as superalloy microcrystals for diameters ranging from 1 - 20 microns. The work shows that two size-sensitive athermal hardening processes, beyond forest and precipitation hardening, are sufficient to develop the dimensional scaling of the flow stress, stochastic stress variation, flow intermittency and, high initial strain-hardening rates, similar to experimental observations for various materials. In addition, 3D dislocation dynamics simulations are used to investigate strain-hardening characteristics and dislocation microstructure evolution with strain in large 20 micron size Ni microcrystals (bulk-like) under three different loading axes: 111, 001 and 110. Three different multi-slip loading axes, , and , are explored for shear strains of ~0.03 and final dislocation densities of ~1013/m2. The orientation dependence of initial strain hardening rates and dislocation microstructure evolution with strain are discussed. The simulated strain hardening results are compared with experimental data under similar loading conditions from bulk single-crystal Ni. Finally, atomistic simulation results on the operation of single arm sources in Ni bipillars with a large angle grain boundary is discussed. The atomistic simulation results are compared with experimental mechanical behavior data on Cu bipillars with a similar large angle grain boundary. This work was supported by AFOSR (Dr. David Stargel), and by a grant of computer time from the DOD High Performance Computing Modernization Program, at the Aeronautical Systems Center/Major Shared Resource Center.

  7. [Artificial crowns influence upon edge parodontium status].

    Science.gov (United States)

    Zhulev, E N; Serov, A B

    2010-01-01

    With the aim of prosthetic treatment efficacy increase study of edge parodontium tissue reaction upon different types of artificial crowns was done and methods of chronic localized parodontitis prevention were developed. Changes of the main gingival fluid characteristics (amount, acidity, interleukine-1beta concentration) and indicators of microcirculation in edge parodontium of the teeth under the artificial crowns influence were disclosed. There were developed methods of chronic localized parodontitis prevention produced by artificial crowns edge.

  8. Semantic Interpretation of An Artificial Neural Network

    Science.gov (United States)

    1995-12-01

    ARTIFICIAL NEURAL NETWORK .7,’ THESIS Stanley Dale Kinderknecht Captain, USAF 770 DEAT7ET77,’H IR O C 7... ARTIFICIAL NEURAL NETWORK THESIS Stanley Dale Kinderknecht Captain, USAF AFIT/GCS/ENG/95D-07 Approved for public release; distribution unlimited The views...Government. AFIT/GCS/ENG/95D-07 SEMANTIC INTERPRETATION OF AN ARTIFICIAL NEURAL NETWORK THESIS Presented to the Faculty of the School of Engineering of

  9. ARTIFICIAL LIVING SYSTEM AND ITS COMPLEXITY

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yongguang

    2001-01-01

    In this paper the author shows some artificial living systems, whose basic life characteristics are explored, especially the differentiation in evolution from single cellular to multi-cellular organism. In addition, the author discusses diversity and evolvability also.The author gives a modified entropy function to measure the diversity. Finally, the author drops an open problem about the structure of "gene" of artificial living systems, so that we can measure the evolutionary order between the artificial living systems.

  10. Meta-Learning Evolutionary Artificial Neural Networks

    OpenAIRE

    Abraham, Ajith

    2004-01-01

    In this paper, we present MLEANN (Meta-Learning Evolutionary Artificial Neural Network), an automatic computational framework for the adaptive optimization of artificial neural networks wherein the neural network architecture, activation function, connection weights; learning algorithm and its parameters are adapted according to the problem. We explored the performance of MLEANN and conventionally designed artificial neural networks for function approximation problems. To evaluate the compara...

  11. Operations and thermodynamics of an artificial rotary molecular motor in solution.

    Science.gov (United States)

    Moro, Lorenzo; di Giosia, Matteo; Calvaresi, Matteo; Bakalis, Evangelos; Zerbetto, Francesco

    2014-06-23

    A general framework is provided that makes possible the estimation of time-dependent properties of a stochastic system moving far from equilibrium. The process is investigated and discussed in general terms of nonequilibrium thermodynamics. The approach is simple and can be exploited to gain insight into the dynamics of any molecular-level machine. As a case study, the dynamics of an artificial molecular rotary motor, similar to the inversion of a helix, which drives the motor from a metastable state to equilibrium, are examined. The energy path that the motor walks was obtained from the results of atomistic calculations. The motor undergoes unidirectional rotation and its entropy, internal energy, free energy, and net exerted force are given as a function of time, starting from the solution of Smoluchowski's equation. The rather low value of the organization index, that is, the ratio of the work done by the particle against friction during the unidirectional motion per available free energy, reveals that the motion is mainly subject to randomness, and the amount of energy converted to heat due to the directional motion is very small.

  12. Artificial Intelligence versus Statistical Modeling and Optimization of Cholesterol Oxidase Production by using Streptomyces Sp.

    Directory of Open Access Journals (Sweden)

    Lakshmi Pathak

    Full Text Available Cholesterol oxidase (COD is a bi-functional FAD-containing oxidoreductase which catalyzes the oxidation of cholesterol into 4-cholesten-3-one. The wider biological functions and clinical applications of COD have urged the screening, isolation and characterization of newer microbes from diverse habitats as a source of COD and optimization and over-production of COD for various uses. The practicability of statistical/ artificial intelligence techniques, such as response surface methodology (RSM, artificial neural network (ANN and genetic algorithm (GA have been tested to optimize the medium composition for the production of COD from novel strain Streptomyces sp. NCIM 5500. All experiments were performed according to the five factor central composite design (CCD and the generated data was analysed using RSM and ANN. GA was employed to optimize the models generated by RSM and ANN. Based upon the predicted COD concentration, the model developed with ANN was found to be superior to the model developed with RSM. The RSM-GA approach predicted maximum of 6.283 U/mL COD production, whereas the ANN-GA approach predicted a maximum of 9.93 U/mL COD concentration. The optimum concentrations of the medium variables predicted through ANN-GA approach were: 1.431 g/50 mL soybean, 1.389 g/50 mL maltose, 0.029 g/50 mL MgSO4, 0.45 g/50 mL NaCl and 2.235 ml/50 mL glycerol. The experimental COD concentration was concurrent with the GA predicted yield and led to 9.75 U/mL COD production, which was nearly two times higher than the yield (4.2 U/mL obtained with the un-optimized medium. This is the very first time we are reporting the statistical versus artificial intelligence based modeling and optimization of COD production by Streptomyces sp. NCIM 5500.

  13. Progress and Challenge of Artificial Intelligence

    Institute of Scientific and Technical Information of China (English)

    Zhong-Zhi Shi; Nan-Ning Zheng

    2006-01-01

    Artificial Intelligence (AI) is generally considered to be a subfield of computer science, that is concerned to attempt simulation, extension and expansion of human intelligence. Artificial intelligence has enjoyed tremendous success over the last fifty years. In this paper we only focus on visual perception, granular computing, agent computing, semantic grid. Human-level intelligence is the long-term goal of artificial intelligence. We should do joint research on basic theory and technology of intelligence by brain science, cognitive science, artificial intelligence and others. A new cross discipline intelligence science is undergoing a rapid development. Future challenges are given in final section.

  14. Artificial senses for characterization of food quality

    Institute of Scientific and Technical Information of China (English)

    HUANG Yan-bo; LAN Yu-bin; R.E. Lacey

    2004-01-01

    Food quality is of primary concern in the food industry and to the consumer. Systems that mimic human senses have been developed and applied to the characterization of food quality. The five primary senses are: vision, hearing, smell, taste and touch.In the characterization of food quality, people assess the samples sensorially and differentiate "good" from "bad" on a continuum.However, the human sensory system is subjective, with mental and physical inconsistencies, and needs time to work. Artificial senses such as machine vision, the electronic ear, electronic nose, electronic tongue, artificial mouth and even artificial the head have been developed that mimic the human senses. These artificial senses are coordinated individually or collectively by a pattern recognition technique, typically artificial neural networks, which have been developed based on studies of the mechanism of the human brain. Such a structure has been used to formulate methods for rapid characterization of food quality. This research presents and discusses individual artificial sensing systems. With the concept of multi-sensor data fusion these sensor systems can work collectively in some way. Two such fused systems, artificial mouth and artificial head, are described and discussed. It indicates that each of the individual systems has their own artificially sensing ability to differentiate food samples. It further indicates that with a more complete mimic of human intelligence the fused systems are more powerful than the individual systems in differentiation of food samples.

  15. Artificial Promoters for Metabolic Optimization

    DEFF Research Database (Denmark)

    Jensen, Peter Ruhdal; Hammer, Karin

    1998-01-01

    In this article, we review some of the expression systems that are available for Metabolic Control Analysis and Metabolic Engineering, and examine their advantages and disadvantages in different contexts. In a recent approach, artificial promoters for modulating gene expression in micro-organisms......In this article, we review some of the expression systems that are available for Metabolic Control Analysis and Metabolic Engineering, and examine their advantages and disadvantages in different contexts. In a recent approach, artificial promoters for modulating gene expression in micro......-organisms were constructed using synthetic degenerated oligonucleotides. From this work, a promoter library was obtained for Lactococcus lactis, containing numerous individual promoters and covering a wide range of promoter activities. Importantly, the range of promoter activities was covered in small steps...... of activity change. Promoter libraries generated by this approach allow for optimization of gene expression and for experimental control analysis in a wide range of biological systems by choosing from the promoter library promoters giving, e.g., 25%, 50%, 200%, and 400% of the normal expression level...

  16. Artificial neural networks in neurosurgery.

    Science.gov (United States)

    Azimi, Parisa; Mohammadi, Hasan Reza; Benzel, Edward C; Shahzadi, Sohrab; Azhari, Shirzad; Montazeri, Ali

    2015-03-01

    Artificial neural networks (ANNs) effectively analyze non-linear data sets. The aimed was A review of the relevant published articles that focused on the application of ANNs as a tool for assisting clinical decision-making in neurosurgery. A literature review of all full publications in English biomedical journals (1993-2013) was undertaken. The strategy included a combination of key words 'artificial neural networks', 'prognostic', 'brain', 'tumor tracking', 'head', 'tumor', 'spine', 'classification' and 'back pain' in the title and abstract of the manuscripts using the PubMed search engine. The major findings are summarized, with a focus on the application of ANNs for diagnostic and prognostic purposes. Finally, the future of ANNs in neurosurgery is explored. A total of 1093 citations were identified and screened. In all, 57 citations were found to be relevant. Of these, 50 articles were eligible for inclusion in this review. The synthesis of the data showed several applications of ANN in neurosurgery, including: (1) diagnosis and assessment of disease progression in low back pain, brain tumours and primary epilepsy; (2) enhancing clinically relevant information extraction from radiographic images, intracranial pressure processing, low back pain and real-time tumour tracking; (3) outcome prediction in epilepsy, brain metastases, lumbar spinal stenosis, lumbar disc herniation, childhood hydrocephalus, trauma mortality, and the occurrence of symptomatic cerebral vasospasm in patients with aneurysmal subarachnoid haemorrhage; (4) the use in the biomechanical assessments of spinal disease. ANNs can be effectively employed for diagnosis, prognosis and outcome prediction in neurosurgery.

  17. Artificial Shortages and Strategic Pricing

    Directory of Open Access Journals (Sweden)

    Partha Gangopadhyay

    2012-01-01

    Full Text Available Problem statement: We consider a monopolist who manipulates the market by artificially creating shortages that result in an increase in current price that, in turn, boosts demand for the product in subsequent periods. The approach is to develop an intertemporal model of pricing strategy for a monopolist. Approach: The postulated pricing strategy creates an incentive for producers to reduce current supply and raise current prices and sacrifice current profits in order to increase future profits. The main problem is to explain the precise mathematical conditions under which the pricing strategy will be chosen by a monopolist. Results: We derive the optimal pricing strategy to argue that the monopolist has an incentive to adopt simple market manipulation that calls forth a close examination of issues concerning deregulation. Conclusion: The paper examines two possible strategies for a typical monopolist-strategic pricing vis-a-vis a myopic pricing. The intuition is that the monopolist can manipulate the market by artificially creating shortages that result in an increase in current price that, in turn, boosts demand for the product in subsequent periods.

  18. Artificial muscle: facts and fiction.

    Science.gov (United States)

    Schaub, Marcus C

    2011-12-19

    Mechanical devices are sought to support insufficient or paralysed striated muscles including the failing heart. Nickel-titanium alloys (nitinol) present the following two properties: (i) super-elasticity, and (ii) the potential to assume different crystal structures depending on temperature and/or stress. Starting from the martensite state nitinol is able to resume the austenite form (state of low potential energy and high entropy) even against an external resistance. This one-way shape change is deployed in self-expanding vascular stents. Heating induces the force generating transformation from martensite to the austenite state while cooling induces relaxation back to the martensite state. This two-way shape change oscillating between the two states may be used in cyclically contracting support devices of silicon-coated nitinol wires. Such a contractile device sutured to the right atrium has been tested in vitro in a bench model and in vivo in sheep. The contraction properties of natural muscles, specifically of the myocardium, and the tight correlation with ATP production by oxidative phosphorylation in the mitochondria is briefly outlined. Force development by the nitinol device cannot be smoothly regulated as in natural muscle. Its mechanical impact is forced onto the natural muscle regardless of the actual condition with regard to metabolism and Ca2+-homeostasis. The development of artificial muscle on the basis of nitinol wires is still in its infancy. The nitinol artificial muscle will have to prove its viability in the various clinical settings.

  19. A Pathway to Artificial Metalloenzymes

    KAUST Repository

    Fischer, Johannes

    2015-12-01

    The advancement of catalytic systems and the application thereof has proven to be the key to overcome traditional limitations of industrial-scale synthetic processes. Converging organometallic and biocatalytic principles lead to the development of Artificial Metalloenzymes (ArMs) that comprise a synthetic metal catalyst embedded in a protein scaffold, thereby combining the reactivity of the former with the versatility of the latter. This synergistic approach introduces rationally designed building blocks for the catalytic site and the host protein to assemble enzyme-like structures that follow regio-, chemo-, enantio- and substrate-selective principles. Yet, the identification of suitable protein scaffolds has thus far been challenging. Herein we report a rationally optimized fluorescent protein host, mTFP*, that was engineered to have no intrinsic metal binding capability and, owing to its robust nature, can act as scaffold for the design of novel ArMs. We demonstrate the potential of site-specific modifications within the protein host, use protein X-Ray analysis to validate the respective scaffolds and show how artificial mutant binding sites can be introduced. Transition metal Förster Resonance Energy transfer (tmFRET) methodologies help to evaluate micromolar dissociation constants and reveal structural rearrangements upon coordination of the metal centers. In conjunction with molecular insights from X-Ray crystallographic structure determination, dynamics of the binding pocket can be inferred. The versatile subset of different binding motifs paired with transition metal catalysts create artificial metalloenzymes that provide reactivities which otherwise do not exist in nature. As a proof of concept, Diels-Alder cycloadditions highlight the potential of the present mTFP* based catalysts by stereoselectively converting azachalcone and cyclopentadiene substrates. Screens indicate an enantiomeric excess of up to 60% and provide insights into the electronic and

  20. The Biological Relevance of Artificial Life: Lessons from Artificial Intelligence

    Science.gov (United States)

    Colombano, Silvano

    2000-01-01

    There is no fundamental reason why A-life couldn't simply be a branch of computer science that deals with algorithms that are inspired by, or emulate biological phenomena. However, if these are the limits we place on this field, we miss the opportunity to help advance Theoretical Biology and to contribute to a deeper understanding of the nature of life. The history of Artificial Intelligence provides a good example, in that early interest in the nature of cognition quickly was lost to the process of building tools, such as "expert systems" that, were certainly useful, but provided little insight in the nature of cognition. Based on this lesson, I will discuss criteria for increasing the biological relevance of A-life and the probability that this field may provide a theoretical foundation for Biology.

  1. Proyección, diseño y construcción de plataforma robótica para investigación en inteligencia artificial

    Directory of Open Access Journals (Sweden)

    Mariela Castiblanco Ortiz

    2010-12-01

    Full Text Available In order to consolidate research about artificial intelligence-based tools, the design and construc-tion of an autonomous robotic platform with simple mathematical model and high processing capacity is considered. The final prototype objective is to evaluate autonomous control strategies, artificial vision, route planning and collective intelligence. For this reason, the system was equipped with aFPGA as central control unit. In order to facilitate the development of a theoretical model, and provide the system with high mobility, the prototype was structured on a differential platform with two independent motors coupled with scroll wheels, and one third omni directional wheel of support. The mechanical structure was designed in acrylic (methacrylate, looking for mechanical strength, low weight, visualization of components and esthetic presentation. For primary space location, the prototype was equipped with encoded positionultrasonic sensors for wide range of vision. In addition, the system counts with ports to increase robot peripherals. The prototype was evaluated in laboratory, observing an excellent performance according to plan in design.

  2. A quality by design approach using artificial intelligence techniques to control the critical quality attributes of ramipril tablets manufactured by wet granulation.

    Science.gov (United States)

    Aksu, Buket; Paradkar, Anant; de Matas, Marcel; Özer, Özgen; Güneri, Tamer; York, Peter

    2013-02-01

    Quality by design (QbD) is an essential part of the modern approach to pharmaceutical quality. This study was conducted in the framework of a QbD project involving ramipril tablets. Preliminary work included identification of the critical quality attributes (CQAs) and critical process parameters (CPPs) based on the quality target product profiles (QTPPs) using the historical data and risk assessment method failure mode and effect analysis (FMEA). Compendial and in-house specifications were selected as QTPPs for ramipril tablets. CPPs that affected the product and process were used to establish an experimental design. The results thus obtained can be used to facilitate definition of the design space using tools such as design of experiments (DoE), the response surface method (RSM) and artificial neural networks (ANNs). The project was aimed at discovering hidden knowledge associated with the manufacture of ramipril tablets using a range of artificial intelligence-based software, with the intention of establishing a multi-dimensional design space that ensures consistent product quality. At the end of the study, a design space was developed based on the study data and specifications, and a new formulation was optimized. On the basis of this formulation, a new laboratory batch formulation was prepared and tested. It was confirmed that the explored formulation was within the design space.

  3. Text Classification using Artificial Intelligence

    CERN Document Server

    Kamruzzaman, S M

    2010-01-01

    Text classification is the process of classifying documents into predefined categories based on their content. It is the automated assignment of natural language texts to predefined categories. Text classification is the primary requirement of text retrieval systems, which retrieve texts in response to a user query, and text understanding systems, which transform text in some way such as producing summaries, answering questions or extracting data. Existing supervised learning algorithms for classifying text need sufficient documents to learn accurately. This paper presents a new algorithm for text classification using artificial intelligence technique that requires fewer documents for training. Instead of using words, word relation i.e. association rules from these words is used to derive feature set from pre-classified text documents. The concept of na\\"ive Bayes classifier is then used on derived features and finally only a single concept of genetic algorithm has been added for final classification. A syste...

  4. Artificial intelligence and science education

    Science.gov (United States)

    Good, Ron

    Artificial intelligence (AI) is defined and related to intelligent computer-assisted instruction (ICAI) and science education. Modeling the student, the teacher, and the natural environment are discussed as important parts of ICAI and the concept of microworlds as a powerful tool for science education is presented. Optimistic predictions about ICAI are tempered with the complex, persistent problems of: 1) teaching and learning as a soft or fuzzy knowledge base, 2) natural language processing, and 3) machine learning. The importance of accurate diagnosis of a student's learning state, including misconceptions and naive theories about nature, is stressed and related to the importance of accurate diagnosis by a physician. Based on the cognitive science/AI paradigm, a revised model of the well-known Karplus/Renner learning cycle is proposed.

  5. Innovative applications of artificial intelligence

    Science.gov (United States)

    Schorr, Herbert; Rappaport, Alain

    Papers concerning applications of artificial intelligence are presented, covering applications in aerospace technology, banking and finance, biotechnology, emergency services, law, media planning, music, the military, operations management, personnel management, retail packaging, and manufacturing assembly and design. Specific topics include Space Shuttle telemetry monitoring, an intelligent training system for Space Shuttle flight controllers, an expert system for the diagnostics of manufacturing equipment, a logistics management system, a cooling systems design assistant, and a knowledge-based integrated circuit design critic. Additional topics include a hydraulic circuit design assistant, the use of a connector assembly specification expert system to harness detailed assembly process knowledge, a mixed initiative approach to airlift planning, naval battle management decision aids, an inventory simulation tool, a peptide synthesis expert system, and a system for planning the discharging and loading of container ships.

  6. Apartes desde la inteligencia artificial

    Directory of Open Access Journals (Sweden)

    Luis Carlos Torres Soler

    2011-01-01

    Full Text Available El estudio y desarrollo de la inteligencia artificial no debe centrarse sólo en la creación de software o hardware que permita realizar procesos algorítmicos o heurísticos en el computador, de tal forma que produzcan soluciones óptimas y eficientes al resolver un problema complejo, ya sea de manejo de información o de toma de decisiones, o crear máquinas que tengan buena apariencia del ser humano; se debe, sobre todo, analizar la parte neurológica y sicológica que presenta el individuo al solucionar problemas. Además, es importante conocer la capacidad intelectual de la persona, de ahí la variedad de carreras profesionales que existen; no puede quedar por fuera de los sistemas inteligentes la concepción del amor o admiración.

  7. Artificial intelligence in medical diagnosis.

    Science.gov (United States)

    Szolovits, P; Patil, R S; Schwartz, W B

    1988-01-01

    In an attempt to overcome limitations inherent in conventional computer-aided diagnosis, investigators have created programs that simulate expert human reasoning. Hopes that such a strategy would lead to clinically useful programs have not been fulfilled, but many of the problems impeding creation of effective artificial intelligence programs have been solved. Strategies have been developed to limit the number of hypotheses that a program must consider and to incorporate pathophysiologic reasoning. The latter innovation permits a program to analyze cases in which one disorder influences the presentation of another. Prototypes embodying such reasoning can explain their conclusions in medical terms that can be reviewed by the user. Despite these advances, further major research and developmental efforts will be necessary before expert performance by the computer becomes a reality.

  8. Web Intelligence and Artificial Intelligence in Education

    Science.gov (United States)

    Devedzic, Vladan

    2004-01-01

    This paper surveys important aspects of Web Intelligence (WI) in the context of Artificial Intelligence in Education (AIED) research. WI explores the fundamental roles as well as practical impacts of Artificial Intelligence (AI) and advanced Information Technology (IT) on the next generation of Web-related products, systems, services, and…

  9. The artificial pancreas : From logic to life

    NARCIS (Netherlands)

    Kropff, J.

    2017-01-01

    In this thesis we investigated the efficacy of real-life use of an artificial pancreas starting with use of these systems in a hotel setting and finally 24/7 long-term use at home. We investigated the accuracy of continuous glucose monitoring (CGM) systems that act as input for the artificial pancre

  10. 50 CFR 27.73 - Artificial lights.

    Science.gov (United States)

    2010-10-01

    ... 50 Wildlife and Fisheries 6 2010-10-01 2010-10-01 false Artificial lights. 27.73 Section 27.73 Wildlife and Fisheries UNITED STATES FISH AND WILDLIFE SERVICE, DEPARTMENT OF THE INTERIOR (CONTINUED) THE... Artificial lights. No unauthorized person shall use or direct the rays of a spotlight or other...

  11. Creativity in design and artificial neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Neocleous, C.C.; Esat, I.I. [Brunel Univ. Uxbridge (United Kingdom); Schizas, C.N. [Univ. of Cyprus, Nicosia (Cyprus)

    1996-12-31

    The creativity phase is identified as an integral part of the design phase. The characteristics of creative persons which are relevant to designing artificial neural networks manifesting aspects of creativity, are identified. Based on these identifications, a general framework of artificial neural network characteristics to implement such a goal are proposed.

  12. Artificial Intelligence--Applications in Education.

    Science.gov (United States)

    Poirot, James L.; Norris, Cathleen A.

    1987-01-01

    This first in a projected series of five articles discusses artificial intelligence and its impact on education. Highlights include the history of artificial intelligence and the impact of microcomputers; learning processes; human factors and interfaces; computer assisted instruction and intelligent tutoring systems; logic programing; and expert…

  13. Isolated Speech Recognition Using Artificial Neural Networks

    Science.gov (United States)

    2007-11-02

    In this project Artificial Neural Networks are used as research tool to accomplish Automated Speech Recognition of normal speech. A small size...the first stage of this work are satisfactory and thus the application of artificial neural networks in conjunction with cepstral analysis in isolated word recognition holds promise.

  14. Artificial Neural Networks and Instructional Technology.

    Science.gov (United States)

    Carlson, Patricia A.

    1991-01-01

    Artificial neural networks (ANN), part of artificial intelligence, are discussed. Such networks are fed sample cases (training sets), learn how to recognize patterns in the sample data, and use this experience in handling new cases. Two cognitive roles for ANNs (intelligent filters and spreading, associative memories) are examined. Prototypes…

  15. Airway Complications of Total Artificial Heart.

    Science.gov (United States)

    Pathak, Vikas; Donovan, Colin; Malhotra, Rajiv

    2017-02-01

    The total artificial heart is the mechanical device which is used as a bridge to the heart transplant in patients with biventricular failure. Due to the mechanical nature of the device, patients receiving total artificial heart (TAH) require to be on anticoagulation therapy. Hemorrhage and coagulopathy are few of the known complications of TAH.

  16. Dynamic optimization of artificial lighting in greenhouses.

    NARCIS (Netherlands)

    Heuvelink, E.; Challa, H.

    1989-01-01

    A principle for dynamic optimization of artificial lighting in greenhouses is presented, where the optimization criterion is maximization of the term . To this purpose it is important to consider the break-even point for artificial lighting, which can be defined a

  17. Artificial Intelligence in Education: An Exploration.

    Science.gov (United States)

    Cumming, Geoff

    1998-01-01

    Gives a brief outline of the development of Artificial Intelligence in Education (AIED) which includes psychology, education, cognitive science, computer science, and artificial intelligence. Highlights include learning environments; learner modeling; a situated approach to learning; and current examples of AIED research. (LRW)

  18. Biofluid lubrication for artificial joints

    Science.gov (United States)

    Pendleton, Alice Mae

    This research investigated biofluid lubrication related to artificial joints using tribological and rheological approaches. Biofluids studied here represent two categories of fluids, base fluids and nanostructured biofluids. Base fluids were studied through comparison of synthetic fluids (simulated body fluid and hyaluronic acid) as well as natural biofluids (from dogs, horses, and humans) in terms of viscosity and fluid shear stress. The nano-structured biofluids were formed using molecules having well-defined shapes. Understanding nano-structured biofluids leads to new ways of design and synthesis of biofluids that are beneficial for artificial joint performance. Experimental approaches were utilized in the present research. This includes basic analysis of biofluids' property, such as viscosity, fluid shear stress, and shear rate using rheological experiments. Tribological investigation and surface characterization were conducted in order to understand effects of molecular and nanostructures on fluid lubrication. Workpiece surface structure and wear mechanisms were investigated using a scanning electron microscope and a transmission electron microscope. The surface topography was examined using a profilometer. The results demonstrated that with the adding of solid additives, such as crown ether or fullerene acted as rough as the other solids in the 3-body wear systems. In addition, the fullerene supplied low friction and low wear, which designates the lubrication purpose of this particular particle system. This dissertation is constructed of six chapters. The first chapter is an introduction to body fluids, as mentioned earlier. After Chapter II, it examines the motivation and approach of the present research, Chapter III discusses the experimental approaches, including materials, experimental setup, and conditions. In Chapter IV, lubrication properties of various fluids are discussed. The tribological properties and performance nanostructured biofluids are

  19. A DISTRIBUTED SMART HOME ARTIFICIAL INTELLIGENCE SYSTEM

    DEFF Research Database (Denmark)

    Lynggaard, Per

    2013-01-01

    A majority of the research performed today explore artificial intelligence in smart homes by using a centralized approach where a smart home server performs the necessary calculations. This approach has some disadvantages that can be overcome by shifting focus to a distributed approach where...... the artificial intelligence system is implemented as distributed as agents running parts of the artificial intelligence system. This paper presents a distributed smart home architecture that distributes artificial intelligence in smart homes and discusses the pros and cons of such a concept. The presented...... distributed model is a layered model. Each layer offers a different complexity level of the embedded distributed artificial intelligence. At the lowest layer smart objects exists, they are small cheap embedded microcontroller based smart devices that are powered by batteries. The next layer contains a more...

  20. Reinforcement Learning Based Artificial Immune Classifier

    Directory of Open Access Journals (Sweden)

    Mehmet Karakose

    2013-01-01

    Full Text Available One of the widely used methods for classification that is a decision-making process is artificial immune systems. Artificial immune systems based on natural immunity system can be successfully applied for classification, optimization, recognition, and learning in real-world problems. In this study, a reinforcement learning based artificial immune classifier is proposed as a new approach. This approach uses reinforcement learning to find better antibody with immune operators. The proposed new approach has many contributions according to other methods in the literature such as effectiveness, less memory cell, high accuracy, speed, and data adaptability. The performance of the proposed approach is demonstrated by simulation and experimental results using real data in Matlab and FPGA. Some benchmark data and remote image data are used for experimental results. The comparative results with supervised/unsupervised based artificial immune system, negative selection classifier, and resource limited artificial immune classifier are given to demonstrate the effectiveness of the proposed new method.