抗结核药固定剂量复合剂分析方法研究进展

综述了抗结核固定剂量复合剂分析方法的研究进展。根据已报道的抗结核固定剂量复合剂的分析方法的相关文献,分析检测方法的优缺点。通过分析检测方法,提出建议,为抗结核固定剂量复合剂的分析方法的开发提供参考依据。     

Stochastic predictions of bulk properties of amorphous polyethylene based on molecular dynamics simulations

The effect of the chain length, the temperature and the strain rate on the yield stress and the elastic modulus of glassy polyethylene is systematically studied using united-atom molecular dynamics (MD) simulations. Based on our MD results, a sensitivity analysis (SA) is carried out in order to quantify the influence of the uncertain input parameters on the predicted yield stress and elastic modulus. The SA is based on response surface (RS) models (polynomial regression and moving least squares). We use partial derivatives (local SA) and variance-based methods (global SA) where we compute first-order and total sensitivity indices. In addition, we use the elementary effects method on the mechanical model. All stochastic methods predict that the key parameter influencing the yield stress and elastic modulus is the temperature, followed by the strain rate.     

Using an Experimental Design to Identify and Quantify the Effects of Environment Related Test Parameters on the In Vitro Mucoadhesivity Testing of a Propanolol Buccal Tablet

ABSTRACT

This study sought to identify and quantify the effects of environmental test parameters on the mucoadhesivity of a propranolol tablet. Their effects on Maximum Detachment Force (MDF) measurements were evaluated using a Box-Behnken design matrix. Prehydration time (PT) had a statistically significant negative main effect while contact force (CF) had no significant effect on in vitro MDF measurements. While contact time (CT) had no significant main or quadratic effects, it had a positive interaction effect with PT. The mathematical model was statistically validated and a PT of 3.5 min and a CT of 5 min was proposed for mucoadhesion testing by the tensile method during formulation optimization.     

Applying artificial optimization methods for transformer model reduction of lumped parameter models

Detailed R-C-L-M models of power transformers, which are based on lumped parameters, are used extensively not only for transient analysis of power transformers to determine electrical stresses in windings, but also for studying transients in power systems. Models with few elements are generally more practicable for power system studies but at the expense of accuracy. The use of artificial methods to reduce an R-C-L-M model is the main contribution of this paper. Advantages of the suggested method include: (1) a reduced loss of accuracy compared with the original model and (2) the flexibility to choose the number of model elements to achieve the desired model depending on size and accuracy. The ability of three different artificial methods, genetic algorithm, particle swarm optimization, and bacterial foraging algorithm, to model reduction is evaluated using measurements on an actual 400 kV test object and the results are compared with those obtained by common analytical formulae.     

环形分布器内变质量流动的CFD模拟研究

环形分布器是实现导热介质在列管式固定床反应器壳程均匀流动的关键部件,文中采用计算流体力学方法(CFD)对环形分布器内的变质量流动进行了模拟研究。首先计算了环形通道内的速度和静压力分布,在此基础上研究了穿孔阻力系数随开孔几何结构以及入口流体流速的变化规律。模拟结果表明:环形通道内存在较明显的速度梯度和压力梯度;随着流体不断分流,在流道内的流动速度不断减小,静压力逐渐增大。因此,需要沿流动方向将开孔直径逐渐减小,以增大穿孔阻力,从而实现流体的均布。对穿孔阻力系数变化规律的研究结果表明:穿孔阻力系数ξ与出口和主流道的流速比ui/u、厚径比δ/di和入口雷诺数Re0有关。在模拟范围内,ξ先随ui/u的增大而减小,到达一个临界值后,ξ不再随ui/u的增大而变化;δ/di对ξ影响不太明显;当Re0属于湍流范围时,ξ随Re0的变化不太明显,但是总体随Re0的增大而减小。     

Limit requirements simulation of sundial solar tracking machine

Sundial solar tracking machines are machines that tracking the sun,and can promote sunshine receiving efficiency of solar panels.Their operations are strongly influenced by wind load.Previous studies w...     

Structural and mechanical stability of the nano-crystalline Ni–Ti (50.9 at.% Ni) shape memory alloy during short-term heat treatments

In this study, the nano-crystalline Nitinol (50.9 at.% Ni) was prepared by 40% cold deformation. Subsequently it was subjected to 15-min-heat treatments at 300–550 °C. Changes of the structure and mechanical properties were studied by transmission electron microscopy, micro X-ray diffraction, differential scanning calorimetry, Vickers hardness measurements, tensile and bend-type fatigue testing. It was shown that the cold drawn material contains textured nano-crystalline B2 grains of 50 nm in thickness and a high concentration of lattice defects. Its tensile strength, hardness and fatigue life were 1521 MPa, 421 HV0.05 and 2435 bending cycles to fracture, respectively. After heat-treatment up to 450 °C/15 min the material underwent Ni₄Ti₃ precipitation and partial recovery processes. Heat-treatments at above 450 °C induced recrystallization, grain and precipitate growth. Hardness and fatigue lives showed maxima of 692 HV0.05 and 5883 cycles, respectively, after heat-treatments at 450 °C/15 min. In contrast, both tensile strength and B2 → B19′ transformation stress decreased with increasing heat-treatment temperature, but a decrease of the tensile strength after heat-treatments at 300–450 °C was slow (tensile strength after heat-treatment at 450 °C/15 min was 1486 MPa). The observed variations of mechanical characteristics were discussed in relation to structural changes observed.     

An energy approach to account for crack initiation in nanocrystalline materials

An energy balance method to calculate the initiation of crack at triple junctions in nanocrystalline materials with the finest grains is developed. In the steady state of crack initiation, work done by an applied stress is considered to be dissipated as heat by specific rotational deformation, grain boundary sliding and diffusion. The stress field at crack tips, the energies of rotational deformation, grain boundary sliding and grain boundary diffusion are calculated. The analysis demonstrates that the existence of finest grains will lead to enhanced local fracture toughness.     

A direct method for assessing distance-protection behavior during power swings

The aim of this work is to include the distance-protection behavior in direct methods for transient stability assessments. In this way the direct methods assess an electric-power system’s behavior more realistically and hence more reliably. In order to consider the delayed tripping zones of distance-protection relays, the time component was added to the Lyapunov energy function. The main innovation is that the dwell time of the post-fault impedance trajectory inside various tripping zones is calculated based on the speed of the transformation between the kinetic and the potential energy parts of the Lyapunov function. It enables the identification of unwanted trips during power swings. The tripping-zone settings can be revised accordingly. The method was verified by a comparison between the direct method and the well-known, time-domain, numerical-simulation method on a single-machine, infinite-bus test system where the results have to be identical. The application of the proposed method on a multi-machine power system gives good results.     

Lyapunov-based switched extremum seeking for photovoltaic power maximization

This paper presents a practical variation of extremum seeking (ES) that guarantees asymptotic convergence through a Lyapunov-based switching scheme (Lyap-ES). Traditional ES methods enter a limit cycle around the optimum. Lyap-ES converges to the optimum by exponentially decaying the perturbation signal once the system enters a neighborhood around the extremum. As a case study, we consider maximum power point tracking (MPPT) for photovoltaics. Simulation results demonstrate how Lyap-ES is self-optimizing in the presence of varying environmental conditions and produces greater energy conversion efficiencies than traditional MPPT methods. Experimentally measured environmental data is applied to investigate performance under realistic operating scenarios.