Molecular Modeling for Rational Design of Polymer Dielectrics

The state-of-the-art in high voltage and high energy density capacitors is dominated by biaxially oriented polypropylene (BOPP), a linear dielectric with electronic polarizability but low dielectric constant (2.2). BOPP provides an energy density of 5 J/cm3 at the breakdown, which occurs at 720 MV/m for films 10 micrometer thick. While there are many approaches to increase the energy, they either offer solutions to specific applications or suffer from fundamental limitations. The principal focus of the dissertation will be centered on rational design for the development of such materials. We study all three verticals of dielectric properties, namely: dielectric permittivity; dielectric loss; and breakdown strength. We then use the information obtained to design a copolymer with enhanced dielectric properties. We start by using simulations and experiments to delineate the mechanism by which the addition of a small number of polar --OH groups to a nonpolar polymer increases the static relative permittivity (or dielectric constant) by a factor of 2. However, the dielectric loss in the frequency regime of interest to power electronics is less than 1%. We observe that a small amount of adsorbed water plays a critical role in this attenuated loss. Further, we study the effect of other polar pendant groups on dielectric properties of polyethylene. By systematically comparing the static relative permittivity of crystalline and semi-crystalline samples we find amorphous phase as the dominant player in these types of material. The constraints provided by the surrounding chains significantly impede dipolar relaxations in the crystalline regions, whereas amorphous chains must sample all configurations to attain their fully isotropic spatial distributions. We also explore the use of the time--temperature superposition (tTS) principle for calculating the dielectric loss of the dielectric materials. This approach helps us explore time scales in simulations which were previously inaccessible using classical MD. We find that the tTS method performed well in determining dielectric losses in the system as long as unrelaxed components are not included in the calculation. This methodology, which provides us with a significantly faster and reliable pathway for calculation of dielectric loss, allows us to identify the role of polar sidegroups on the dielectric loss of common non-polar polymeric dielectrics. Further, we explore the dielectric breakdown mechanism in polymer dielectrics by introducing external electric fields in the materials. Conventionally the prediction of dielectric strength has focused on ground state energy calculation, thus restricting the analysis of the breakdown process to purely electronic in nature. While this provides reasonable predictions for low-temperature systems, we observe that electromechanical breakdown plays a crucial role in the high-temperature regimes. Our simulation results suggest that fracture mechanics drive electromechanical breakdown, which dominates over electronic breakdown at relevant operating temperatures.  Finally, we utilized these fundamental insights into dielectric properties for designing copolymer with enhanced dielectric properties

A Cost Estimating Method for Agile Software Development

In every software development project, the software effort estimating procedure is an important process in software engineering and always critical. The consistency of effort and timeline estimation, along with several factors, determines whether a project succeeds or fails. Both academics and professionals worked on the estimation approaches in software engineering. But, all these approaches have many problems that need to be addressed. One of the most difficult aspects of software engineering is estimating effort in agile development. This study aims to provide an effort estimation method for agile software development projects. Because in software engineering, the agile method is widely used for the development of software applications. The development and usage of the agile method are described in depth in this study. The framework is configured with empirical data gathered by projects from the software industry. The test findings reveal that the estimation method has great estimation accuracy in respect of mean magnitude of relative error (MMRE) and Prediction of Error PRED (n). The suggested approach achieves more accuracy for effort estimation as compare to others

ExplainEx: An Explainable Artificial Intelligence Framework for Interpreting Predictive Models

Artificial Intelligence (AI) systems are increasingly dependent on machine learning models which lack interpretability and algorithmic transparency, and hence may not be trusted by its users. The fear of failure in these systems is driving many governments to demand more explanation and accountability. Take, for example, the “Right of Explanation” rule proposed in the European Union in 2019, which gives citizens the right to demand an explanation from AI-based predictions. Explainable Artificial Intelligence (XAI) is an attempt to open up the “black box” and create more explainable systems which create predictive models whose results are easily understandable to humans. This paper describes an explanation model called ExplainEx which automatically generates natural language explanation for predictive models by consuming REST API provided by ExpliClas open-source web service. The classification model consists of four main decision tree algorithms including J48, Random Tree, RepTree and FURIA. The user interface was designed based on Microsoft.Net Framework programming platform. At the background is a software engine automating a seamless interaction between Expliclas API and the trained datasets, to provide natural language explanation to users. Unlike other studies, our proposed model is both a stand-alone and client-server based system capable of providing global explanations for any decision tree classifier. It supports multiple concurrent users in a client-server environment and can apply all four algorithms concurrently on a single dataset, returning both precision score and explanation. It is a ready tool for researchers who have datasets and classifiers prepared for explanation. This work bridges the gap between prediction and explanation, thereby allowing researchers to concentrate on data analysis and building state-of-the-art predictive models

<span style="font-size:14.0pt;line-height: 115%;font-family:"Times New Roman";mso-fareast-font-family:"Times New Roman"; color:black;mso-ansi-language:EN-IN;mso-fareast-language:EN-IN;mso-bidi-language: HI" lang="EN-IN">Liposomes of terbutaline sulphate: <i>In vitro </i>and <i>in vivo </i>studies</span>

881-887In vitro studies were conducted to understand the comparative drug diffusion pattern, across artificial membrane, of the drug and of the prepared liposomes of different liposomal membrane composition. In vivo studies were carried out to determine the extent and time-course of pulmonary tissue uptake of administered liposomes containing terbutaline sulphate(TER) on rat lungs. In vitro studies revealed that the drug released from the prepared liposomes obeys Higuchi's diffusion controlled model. Different loading doses and release patterns of drug from the liposomes can be obtained by altering the PC:CHOL ratio and incorporation of cholesterol was found to reduce permeability of the membrane. Similarly drug absorption in vivo in rat's lung following intratracheal instillation, prolonged over 12 hr by liposomal entrapment of TER. The findings of present investigation indicated that liposomally encapsulated TER can be used for pulmonary delivery for maximizing the therapeutic efficacy and reducing undesirable side effects

Using Time–Temperature Superposition for Determining Dielectric Loss in Functionalized Polyethylenes

Using Molecular Dynamics simulations, we probe the effect of various pendant polar groups on the dielectric loss of polyethylene copolymers. The dielectric loss was computed using the autocorrelation function of the total dipole moment of a completely relaxed PE–X sample. Since this calculation is computationally expensive (wall time ≥ 4200 h), we explore the use of the time–temperature superposition (tTS) principle to make it more tractable. An important point is that short time MD simulations do not allow the dipole autocorrelation function to decay completely to zero. However, we find that the tTS method performed well in determining dielectric losses in the system as long as these unrelaxed components are not included in the calculation. This methodology, which provides us with a significantly faster and reliable pathway for calculation of dielectric loss, allows us to identify the role of polar side groups on the behavior of nonpolar polymeric dielectrics

Optimization of operating parameters of earth air tunnel heat exchanger for space cooling: Taguchi method approach

Abstract In the present study, CFD-based parametric analysis is carried out to optimise the parameters affecting the temperature drop and heat transfer rate achieved from earth air tunnel heat exchanger (EATHE) system. ANSYS FLUENT 15.0 is used for CFD analysis, and k-ε model and energy equation were considered to define the turbulence and heat transfer phenomena. For a straight EATHE system configuration, four design and operating parameters, i.e., diameter of the pipe (A), length of pipe (B), inlet air velocity (C), and inlet air temperature (D), are considered at four different levels in Taguchi method. The Taguchi method is used to obtain maximum air temperature drop and heat transfer rate. The best combination of parameters for achieving a maximum drop in air temperature is A1B4C1D4 and that for obtaining maximum total heat transfer rate is A4B4C4D4. Statistical analysis reveals the percentage contribution of different factors for air temperature drop in the following order: inlet air temperature (57.80%), diameter of pipe (20.66%), length of pipe (12.03%), and air velocity (9.51%), while, for heat transfer rate, pipe diameter (53.28%), inlet air temperature (30.87%), air velocity (9.40%), and length of pipe (6.45%)

Mutualistic acacia ants exhibit reduced aggression and more frequent off-tree movements near termite mounds

In many ant-plant mutualisms, ants establish colonies in hollow thorns, leaf pouches, or other specialized structures on their host plants, which they then defend from herbivores. Resource heterogeneity could affect the maintenance of these mutualisms if it leads to one or both partners altering their investment in the interaction. Such a phenomenon may be especially pertinent to the Acacia-ant mutualism found in East African savannas, where termite mounds have a profound effect on the spatial structuring of resources used by both plants and ants. Here, we examined if the proximity to termite mounds of Acacia drepanolobium trees is associated with variation in the behavior of one of their ant associates, Crematogaster nigriceps. We found that ant colonies near termite mounds had decreased aggressive responses to simulated herbivory as well as increased off-tree movement. We hypothesize that these changes are the result of resident ant colonies near termite mounds shifting investment from defense of their host plant to foraging for nearby resources

Chromatin Modifications and the DNA Damage Response to Ionizing Radiation

In order to survive, cells have evolved highly effective repair mechanisms to deal with the potentially lethal DNA damage produced by exposure to endogenous as well as exogenous agents. Ionizing radiation exposure induces highly lethal DNA damage, especially DNA double strand breaks (DSBs), that is sensed by the cellular machinery and then subsequently repaired by either of two different DSB repair mechanisms: 1) non-homologous end-joining (NHEJ), which re-ligates the broken ends of the DNA and 2) homologous recombination (HR), that employs an undamaged identical DNA sequence as a template, to maintain the fidelity of DNA repair. Repair of DSBs must occur within the natural context of the cellular DNA which, along with specific proteins, is organized to form chromatin, the overall structure of which can impede DNA damage site access by repair proteins. The chromatin complex is a dynamic structure and is known to change as required for ongoing cellular processes such as gene transcription or DNA replication. Similarly, during the process of DNA damage sensing and repair, chromatin needs to undergo several changes in order to facilitate accessibility of the repair machinery. Cells utilize several factors to modify the chromatin in order to locally open up the structure to reveal the underlying DNA sequence but posttranslational modification (PTMs) of the histone components is one of the primary mechanisms. In this review, we will summarize chromatin modification by

Characterizing Moisture Uptake and Plasticization Effects of Water on Amorphous Amylose Starch Models Using Molecular Dynamics Methods

Dynamics and thermophysical properties of amorphous starch were explored using molecular dynamics (MD) simulations. Using the OPLS3e force field, simulations of short amylose chains in water were performed to determine force field accuracy. Using well-tempered metadynamics, a free energy map of the two glycosidic angles of an amylose molecule was constructed and compared with other modern force fields. Good agreement of torsional sampling for both solvated and amorphous amylose starch models was observed. Using combined grand canonical Monte Carlo (GCMC)/MD simulations, a moisture sorption isotherm curve is predicted along with temperature dependence. Concentration-dependent activation energies for water transport agree quantitatively with previous experiments. Finally, the plasticization effect of moisture content on amorphous starch was investigated. Predicted glass transition temperature (Tg) depression as a function of moisture content is in line with experimental trends. Further, our calculations provide a value for the dry Tg for amorphous starch, a value which no experimental value is available.</div