Characterization of a new chiral antiferroelectric liquid crystal with a lateral bromo substituent

In this paper we present the characterization of a new chiral mesogen with a lateral bromo substituent. The identification of the various smectic phases is achieved by texture observation, miscibility studies and DSC. The optic and electro-optic properties are also investigated. The real part of the complex dielectric permittivity as a function of the temperature was also measured in the planar geometry for thin samples. The dielectric behaviour will be qualitatively discussed on the simple assumption of different anchorings. These results point out the importance of anchoring conditions in relation to the macroscopic properties observed in very thin cells of antiferroelectric liquid crystals.     

How parabolic free boundaries approximate hyperbolic fronts

A rather complete study of the existence and qualitative behaviour of the boundaries of the support of solutions of the Cauchy problem for nonlinear first-order and second-order scalar conservation laws is presented. Among other properties, it is shown that, under appropriate assumptions, parabolic interfaces converge to hyperbolic ones in the vanishing viscosity limit.

     

Hydrophobically modified polyelectrolytes I. Dilute solution properties of fluorocarbon-containing poly (acrylic acid)

Dilute solution viscosity of fluorocarbon‐containing hydrophobically modified poly (acrylic add) was measured in aqueous solutions of various NaCl concentrations. The intrinsic viscosity ([η]) and Huggins coefficient (k_H) were evaluated using Huggins equations. It is found that, at low Nacl concentration, the modified polymers exhibit values of intrinsic viscosity ([η]) and Huggins coefficient (k_H) similar to those of unmodified polymers. For both of the modified and unmodified polymers, the intrinsic viscosity decreases with increase of NaCl concentration, while the Huggins coefficient increases upon addition of NaCl. But the variation of [η] and k_H is more significant for the modified polymers, which reflects the enhanced intra‐ and intermolecular hydrophobic association at higher Nacl concentration.     

Procrustes rotation as a diagnostic tool for projection pursuit analysis

Projection pursuit (PP) is an effective exploratory data analysis tool because it optimizes the projection of high dimensional data using distributional characteristics rather than variance or distance metrics. The recent development of fast and simple PP algorithms based on minimization of kurtosis for clustering data has made this powerful tool more accessible, but under conditions where the sample-to-variable ratio is small, PP fails due to opportunistic overfitting of random correlations to limiting distributional targets. Therefore, some kind of variable compression or data regularization is required in these cases. However, this introduces an additional parameter whose optimization is manually time consuming and subject to bias. The present work describes the use of Procrustes analysis as diagnostic tool that can be used to evaluate the results of PP analysis in an efficient manner. Through Procrustes rotation, the similarity of different PP projections can be examined in an automated fashion with “Procrustes maps” to establish regions of stable projections as a function of the parameter to be optimized. The application of this diagnostic is demonstrated using principal components analysis to compress FTIR spectra from ink samples of ten different brands of pen, and also in conjunction with regularized PP for soybean disease classification.     

Valuation of variable annuities with guaranteed minimum withdrawal and death benefits via stochastic control optimization

In this paper we present a numerical valuation of variable annuities with combined Guaranteed Minimum Withdrawal Benefit (GMWB) and Guaranteed Minimum Death Benefit (GMDB) under optimal policyholder behavior solved as an optimal stochastic control problem. This product simultaneously deals with financial risk, mortality risk and human behavior. We assume that market is complete in financial risk and mortality risk is completely diversified by selling enough policies and thus the annuity price can be expressed as appropriate expectation. The computing engine employed to solve the optimal stochastic control problem is based on a robust and efficient Gauss–Hermite quadrature method with cubic spline. We present results for three different types of death benefit and show that, under the optimal policyholder behavior, adding the premium for the death benefit on top of the GMWB can be problematic for contracts with long maturities if the continuous fee structure is kept, which is ordinarily assumed for a GMWB contract. In fact for some long maturities it can be shown that the fee cannot be charged as any proportion of the account value — there is no solution to match the initial premium with the fair annuity price. On the other hand, the extra fee due to adding the death benefit can be charged upfront or in periodic installment of fixed amount, and it is cheaper than buying a separate life insurance.     

Ultrasound-assisted nanofluid flooding to enhance heavy oil recovery in a simulated porous media

Herein thermally treated empty fruit bunch SiO₂ nanoparticles (EFBSNP) was produced by ultrasound-assisted wet-milling and their effectiveness in enhancing cavitation effect of ultrasound to improve heavy oil recovery was evaluated. Empty fruit bunch ash (EFBA) was thermally treated to enhance its SiO₂ content. Surface properties and size distribution of EFBSNP were studied using transmission electron microscopy and dynamic light scattering. X-ray diffractometer identified the crystal phase, the active group was ascertain using Fourier-transform infrared spectroscopy and thermal stability was established by differential scanning calorimetry. Moreover, the surface chemical composition was determined by X-ray photoelectron spectroscopy. The ability of empty fruit bunch SiO₂ nanofluid (EFBSNF) to absorb ultrasound in heavy oil and the impact of ultrasound assisted EFBSNF flooding to enhance oil recovery of heavy oil was assessed. The microstructure analysis revealed EFBSNP of size ranges 17.78–115.38 nm with a purity of 94%. EFBSNF assisted ultrasound decreased interfacial tension to 0.2 mN/m, thus mobilizing the trapped oil droplet in the pores effectively. Ultrasound assisted EFBSNF flooding increased oil recovery by 44.33% compared to 26.33% without ultrasound.     

Bistable Periodic Traveling Wave Solutions to Lattice Competitive Systems北大核心CSCD

该文研究了一类格竞争系统的双稳周期行波解的存在性.首先,将两种群竞争系统转化为合作系统;其次,构造合作系统的上下解,并建立比较原理,得到当初始函数满足一定条件时,解在无穷远处是收敛的;最后,利用黏性消去法证明系统连接两个稳定周期平衡点的行波解的存在性.     

Blow-up for the Timoshenko-type equation with variable exponents

The finite time blow-up of solutions to a nonlinear Timoshenko-type equation with variable exponents is studied. More concretely, we prove that the solutions blow up in finite time with positive initial energy. Also, the existence of finite time blow-up solutions with arbitrarily high initial energy is established. Meanwhile, the upper and lower bounds of the blow-up time are derived. These results deepen and generalize the ones obtained in [Nonlinear Anal. Real World Appl., 61: Paper No. 103341, 2021].     

Global weak solutions to the Novikov equation by viscous approximation

We study global weak solutions to the Novikov equation by vanishing viscosity method. We prove that global weak solutions can be obtained as weak limits of viscous approximations for a class of initial data. The proof relies on a space–time higher integrability estimate and the method of renormalization. In addition, we analyze the interaction of peakon and antipeakon and prove that wave breaking leads to energy concentration. By different continuations beyond the wave breaking, we obtain conservative solutions and dissipative solutions respectively.     

Hybrid viscosity approach for hierarchical fixed-point problems

Abstract

In this paper, we propose hybrid implicit and explicit viscosity iterative algorithms for solving general hierarchical fixed-point problems for a countable family of non-expansive mappings in uniformly smooth Banach spaces. These hybrid viscosity algorithms are based on the well-known viscosity approximation method and hybrid steepest-descent method. We obtain some strong convergence theorems under suitable conditions. Our results extend, improve, supplement and develop the recent results in the literature.