阳离子表面活性剂三甲基溴化铵与硝酸铵相互作用的表面和热力学研究

本文系统研究了阳离子表面活性剂三甲基溴化铵和硝酸铵盐的表面现象和自聚集行为. 采用电导法和表面张力法研究在不同温度下阳离子表面活性剂三甲基溴化铵的表面性质和热力学性质. 通过表面张力测定得到临界胶束浓度、吸附自由能、胶束化的自由能、最小分子面积和表面过量浓度. 该研究表明,胶束化过程是自发放热反应. 电导测定结果确定了临界胶束浓度、电离程度和反离子结合度. 加入硝酸铵盐至表面活性剂溶液后,临界胶束浓度降低,电离程度和反离子结合度增加,更加有利于胶束化过程的自发. 该研究对进一步理解电解质和表面活性剂之间相互作用具有重要意义.     

Electron acoustic solitary waves in unmagnetized nonthermal plasmas

Electron acoustic(EA) solitary waves(SWs) are studied in an unmagnetized plasma consisting of hot electrons(following Cairns-Tsalli distribution), inertial cold electrons, and stationary ions.By employing a reductive perturbation technique(RPT), the nonlinear Korteweg–de Vries(KdV) equation is derived and its SW solution is analyzed. Here, the effects of plasma parameters such as the nonextensivity parameter(q), the nonthermality of electrons(α), and the cold-to-hot electron density ratio(β) are investigated.     

Spectral Analysis and Generation Results for Streaming Operators with Multiplying Boundary Conditions

This paper deals with the spectral theory of streaming equations for smooth or partly smooth boundary operators. Generation results for muliplying boundary operators in L₁-spaces are also given.     

Nonlinear propagation of fast and slow magnetosonic waves in collisional plasmas

Low-frequency fast and slow magnetosonic waves propagating in electron ion plasmas with damping effects through ions and neutral atoms collisions are investigated. Linear wave analysis is performed to obtain dispersion relation. The reductive perturbation method is applied and it is shown that fast and slow modes of nonlinear magnetosonic wave are governed by damped Korteweg-de Vries (DKdV) equation in the presence of ion neutral collisions in plasmas. The analytical solution of DKdV soliton is presented under the assumption of weak collisional effects and numerical solutions of DKdV equation are also obtained using two-level finite difference scheme with the help of Runge–Kutta method at different plasma parameters. The damping of nonlinear fast and slow magnetosonic wave structures at different times are discussed in the context of space plasma situations where ions and neutral atoms collisions exist.     

Polarization insensitive, broadband terahertz metamaterial absorber

We present the simulation, implementation, and measurement of a polarization insensitive broadband resonant terahertz metamaterial absorber. By stacking metal-insulator layers with differing structural dimensions, three closely positioned resonant peaks are merged into one broadband absorption spectrum. Greater than 60% absorption is obtained across a frequency range of 1.86?THz where the central resonance frequency is 5?THz. The FWHM of the device is 48%, which is two and half times greater than the FWHM of a single layer structure. Such metamaterials are promising candidates as absorbing elements for bolometric terahertz imaging.     

Interval Scheduling on identical machines

Interval Scheduling problems (IS) address the situation where jobs with fixed start and fixed end times are to be processed on parallel identical machines. The optimization criteria of interest are the maximization of the number of jobs completed and, in case weights are associated with jobs, the subset of jobs with maximal total weight. We present polynomial solutions to several IS problems and study computational complexity issues in the situation where bounds are imposed on the total operating time of the machines. With this constraint, we show that tractability is achieved again when job preemption is allowed.     

Use of Average Mutual Information and Derived Measures to Find Coding Regions

One of the important steps in the annotation of genomes is the identification of regions in the genome which code for proteins. One of the tools used by most annotation approaches is the use of signals extracted from genomic regions that can be used to identify whether the region is a protein coding region. Motivated by the fact that these regions are information bearing structures we propose signals based on measures motivated by the average mutual information for use in this task. We show that these signals can be used to identify coding and noncoding sequences with high accuracy. We also show that these signals are robust across species, phyla, and kingdom and can, therefore, be used in species agnostic genome annotation algorithms for identifying protein coding regions. These in turn could be used for gene identification.     

Optimizing Few-Shot Learning Based on Variational Autoencoders

Despite the importance of few-shot learning, the lack of labeled training data in the real world makes it extremely challenging for existing machine learning methods because this limited dataset does not well represent the data variance. In this research, we suggest employing a generative approach using variational autoencoders (VAEs), which can be used specifically to optimize few-shot learning tasks by generating new samples with more intra-class variations on the Labeled Faces in the Wild (LFW) dataset. The purpose of our research is to increase the size of the training dataset using various methods to improve the accuracy and robustness of the few-shot face recognition. Specifically, we employ the VAE generator to increase the size of the training dataset, including the basic and the novel sets while utilizing transfer learning as the backend. Based on extensive experimental research, we analyze various data augmentation methods to observe how each method affects the accuracy of face recognition. The face generation method based on VAEs with perceptual loss can effectively improve the recognition accuracy rate to 96.47% using both the base and the novel sets.     

Phase Transitions in a Driven Lattice Gas with Anisotropic Interactions

The Ising lattice gas, with its well known equilibrium properties, displays a number of surprising phenomena when driven into nonequilibrium steady states. We study such a model with anisotropic interparticle interactions (J _||J ), using both Monte Carlo simulations and high temperature series techniques. Under saturation drive, the shift in the transition temperature can be both positive and negative, depending on the ratio J _||/J ! For finite drives, both first- and second-order transitions are observed. Some aspects of the phase diagram can be predicted by investigating the two-point correlation function at the first nontrivial order of a high-temperature series expansion.     

Parametric Studies on the Grafting of Poly(Methyl Methacrylate) onto Organophilic Montmorillonite Using Silylated Clay Platelets

Poly(methyl methacrylate) (PMMA)/organophilic montmorillonite (Cloisite 30B) nanocomposites were synthesized by the chemical grafting of PMMA onto Cloisite 30B via solution polymerization of methyl methacrylate (MMA) with vinyl-modified organoclay. The effects of different parameters such as clay weight percent (CWP), solvent per monomer volume ratio, and dispersion time on the properties of the PMMA grafted Cloisite 30B were investigated using the Taguchi experimental design method. This method gives a much-reduced variance for the experiments with optimum setting of control parameters and provides a set of minimum experiments compared to the conventional methods. Qualitative evidence for the chemical grafting of the PMMA onto Cloisite 30B was confirmed by Fourier transform infrared spectroscopy (FT-IR). X-ray diffraction (XRD) was used to investigate interlayer changes of the clay in the grafted nanoplatelets. The exfoliated/intercalated morphology of the nanocomposites was confirmed by XRD. Furthermore, thermal properties were measured by thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). Statistical analysis of results revealed that clay weight percent and solvent per monomer ratio had significant effects on the properties of final products. The percent of grafted PMMA and storage modulus of PMMA/30B nanocomposites decreased with increasing clay content due to better dispersion of the clay at lower loadings. On the other hand, because of a tendency to formation of homopolymer and oligomers at higher solvent loadings; the percent of grafted PMMA, storage modulus and glass transition temperature of PMMA/30B nanocomposites decreased with an increase in solvent per monomer volume ratio. However, the obtained PMMA/30B nanocomposites at the optimum conditions, was exhibited a higher glass transition temperature, higher storage modulus and better thermal stability than the pure PMMA.