SELECTING CLUSTER MODEL IN Sn - BASED SOLDER ALLOY DESIGN WITH DV - X_α CALCULATION METHOD

Applying calculation method in alloy design should be an important tendency due to its characters of inexpensive cost, high efficiency and prediction. DOS calculations of AuSn, AsSn and SbSn Sn- based alloys have been investigated by employing DV - Xa method, in which different cluster models were adopted to calculate electron structure.It is proved that some regulations must be taken into ac- count in order to carry out alloy design calculation successfully,which are described in this paper in detail.

Shell and shrinking core kinetics model of Mg-based hydrogen storage alloys

The kinetics equation of the Mg-based hydrogen storage alloys (Mg-Ni-MO) was established by the shell and shrinking core model. The total coefficients of the kinetics equation of the hydrogen absorption and desorption process with shell diffusion as the controlling step were determined by semi-empirical and semi-theoretical methods, and the apparent activation energy of the hydrogen absorption process was obtained. The calculation results can well accord with the experimental data, and can well forecast the hydrogen storage capacity and absorption rate at different times. By using the kinetics equation, the effects of temperature and pressure on the hydrogen storage process can also be well understood. The kinetics equation is helpful for the design of the hydrogen storage container.

Pricing Bermudan Option with Variable Transaction Costs under the Information-Based Model

The Bermudan option pricing problem with variable transaction costs is considered for a risky asset whose price process is derived under the information-based model. The price is formulated as the value function of an optimal stopping problem, which is the value function of a stochastic control problem given by a non-linear second order partial differential equation. The theory of viscosity solutions is applied to solve the stochastic control problem such that the value function is also the solution of the corresponding Bellman equation. Under some regularity assumptions, the existence and uniqueness of the solution of the pricing equation are derived by the application of the Perron method and Banach Fixed Point theorem.

Fuzzy Modeling on L - R Fuzzy Number and Its Application

A new fuzzy modeling method, which based on L - R fuzzy number, is discussed in this paper. First, the fuzzy state equation model is constructed based on fuzzy state variable,fuzzy Input variable and fuzzy output variable whkh are represented by L - R fuzzy number. And then, identification of time - varying parameter in this model is discussed further. At the end, a simulated application is given to Indicate the effectiveness of this fuzzy modeling method.

Equation of State of Nuclear Matter in Chiral σ-ω Model

The equation of state of nuclear matter is studied in the 1-loop approximation of chiral linear σ-ω model.By introducing the density-dependent coupling constants, the problem of tachyon pole in the chiral σ-ω model is resolved.The 1-loop contributions ofσ and π mesons to the nucleon's binding energy are included, while the empirical properties of nuclear matter such as saturation density, binding energy, and incompressibility are well reproduced.

Direct modeling for computational fluid dynamics

All fluid dynamic equations are valid under their modeling scales, such as the particle mean free path and mean collision time scale of the Boltzmann equation and the hydrodynamic scale of the Navier-Stokes （NS） equations. The current computational fluid dynamics （CFD） focuses on the numerical solution of partial differential equations （PDEs）, and its aim is to get the accurate solution of these governing equations. Under such a CFD practice, it is hard to develop a unified scheme that covers flow physics from kinetic to hydrodynamic scales continuously because there is no such governing equation which could make a smooth transition from the Boltzmann to the NS modeling. The study of fluid dynamics needs to go beyond the traditional numer- ical partial differential equations. The emerging engineering applications, such as air-vehicle design for near-space flight and flow and heat transfer in micro-devices, do require fur- ther expansion of the concept of gas dynamics to a larger domain of physical reality, rather than the traditional dis- tinguishable governing equations. At the current stage, the non-equilibrium flow physics has not yet been well explored or clearly understood due to the lack of appropriate tools. Unfortunately, under the current numerical PDE approach, it is hard to develop such a meaningful tool due to the absence of valid PDEs. In order to construct multiscale and multiphysics simulation methods similar to the modeling process of con- structing the Boltzmann or the NS governing equations, the development of a numerical algorithm should be based on the first principle of physical modeling. In this paper, instead of following the traditional numerical PDE path, we introduce direct modeling as a principle for CFD algorithm develop- ment. Since all computations are conducted in a discretized space with limited cell resolution, the flow physics to be mod- eled has to be done in the mesh size and time step scales. Here, the CFD is more or less a direct construction of dis- crete numerical evolution equations, where the mesh size and time step will play dynamic roles in the modeling process. With the variation of the ratio between mesh size and local particle mean free path, the scheme will capture flow physics from the kinetic particle transport and collision to the hydro- dynamic wave propagation. Based on the direct modeling, a continuous dynamics of flow motion will be captured in the unified gas-kinetic scheme. This scheme can be faithfully used to study the unexplored non-equilibrium flow physics in the transition regime.

A Model for the Mass-Growth of Wild-Caught Fish

The paper searched for raw data about wild-caught fish, where a sigmoidal growth function described the mass growth significantly better than non-sigmoidal functions. Specifically, von Bertalanffy’s sigmoidal growth function (metabolic exponent-pair a = 2/3, b = 1) was compared with unbounded linear growth and with bounded exponential growth using the Akaike information criterion. Thereby the maximum likelihood fits were compared, assuming a lognormal distribution of mass (i.e. a higher variance for heavier animals). Starting from 70+ size-at-age data, the paper focused on 15 data coming from large datasets. Of them, six data with 400 - 20,000 data-points were suitable for sigmoidal growth modeling. For these, a custom-made optimization tool identified the best fitting growth function from the general von Bertalanffy-Pütter class of models. This class generalizes the well-known models of Verhulst (logistic growth), Gompertz and von Bertalanffy. Whereas the best-fitting models varied widely, their exponent-pairs displayed a remarkable pattern, as their difference was close to 1/3 (example: von Bertalanffy exponent-pair). This defined a new class of models, for which the paper provided a biological motivation that relates growth to food consumption.

Bi-variable damage model for fatigue life prediction of metal components

Based on the theory of continuum damage mechanics,a bi-variable damage mechanics model is developed,which,according to thermodynamics,is accessible to derivation of damage driving force,damage evolution equation and damage evolution criteria. Furthermore,damage evolution equations of time rate are established by the generalized Drucker＇s postulate. The damage evolution equation of cycle rate is obtained by integrating the time damage evolution equations,and the fatigue life prediction method for smooth specimens under repeated loading with constant strain amplitude is constructed. Likewise,for notched specimens under the repeated loading with constant strain amplitude,the fatigue life prediction method is obtained on the ground of the theory of conservative integral in damage mechanics. Thus,the material parameters in the damage evolution equation can be obtained by reference to the fatigue test results of standard specimens with stress concentration factor equal to 1,2 and 3.

Green fuel from coal via Fischer-Tropsch process： scenario of optimal condition of process and modelling

Extracting, transportation and the using from fossil fuels can damage to the hydrosphere, the biosphere and the Earth＇s atmosphere. But humans always need to this valuable substance. The production of oil derivatives by means of forest waste and coal through the Fischer-Tropsch process is an appropriate solution for the cleanliness of all parts of the environment. For the production of favorite products by the synthesis of Fischer-Tropsch, the performance of the catalyst under different operating conditions should be predictable. For this reason, in this paper, eight mathematical models were determined for the selectivity of five products of methane, light hydrocarbons, gasoline, diesel and wax based on three factors of reduction temperature, time on stream, and He/CO ratio inlet gas on iron-based catalyst. The results showed that the reduction temperature factor had the most effective on the selectivity of hydrocarbon products, exception diesel, so that the increase of the reduction temperature led to increase of the selectivity of methane, light hydrocarbons, gasoline and reduce of the degree of selectivity of the wax and vice versa. For the diesel selectivity, factor of the He/CO ratio inlet gas was the most effective than other factors.

Factors influencing user adoption of location based service:From the expanded TAM perspective

Purpose:This study intends to examine the factors influencing user adoption of location based service(LBS).Design/methodology/approach:This paper develops the research model for user adoption of LBS with the technology acceptance model(TAM) as the theoretical foundation.Using a questionnaire and sampling method,empirical data was collected from 386 participants.Structured equation modeling was used to test the validity of the proposed model.Findings:The results show that I) perceived ease of use.perceived usefulness and perceived playfulness were direct determinants of behavioral intention,and perceived ease of use has the greatest impact of the three;2) emergency,ubiquity,technology maturity and social trust all have positive and significant impacts on perceived ease of use;3) emergency and social trust significantly influence perceived usefulness positively:4) individualization and social impact significantly affect perceived playfulness positively.Research limitations:Subjects were from China’s mainland,which limits the generalizability of the research findings.The interaction effects of age,gender and user experience were not included.Practical implications:This study offers LBS operators,marketers and application developers insights into the way to attract more users by increasing perceived usefulness,ease of use and playfulness of LBS.Originality/value:Location based service is still a relatively new concept and there were few theoretical and empirical studies that examine user adoption of the serv ice.This study contributes to existing LBS adoption studies by modifying and extending TAM and meanwhile the empirical study will help the research community gain a deeper understanding of the factors affecting user adoption of LBS.

分网接入方式下LCC-HVDC系统运动方程模型及交互振荡模式的阻尼特征(一):扰动传递路径分解

与常规直流相比,永富直流逆变站存在功率全送和功率分送运行方式,而其处于分网接入方式时电网换相换流器高压直流输电(line commutated converter based high voltage directcurrent,LCC-HVDC)系统的交互振荡模式及特征尚不明确。针对这一特殊运行方式,采用模块化建模的思路建立可以反映系统电气/控制回路间交互耦合路径的运动方程模型。在此基础上,依据系统整流侧-逆变侧、正极-负极间的交互耦合路径分解得到影响系统主导模式稳定性的3条扰动传递路径,即整流侧内部自稳性路径、逆变侧内部自稳性路径、双极交互作用致稳性路径。最后,设置不同工况下的案例,量化评估不同作用路径提供的阻尼大小,并通过仿真验证运动方程模型及扰动传递路径分析结果的正确性,为后续研究分网接入方式下LCC-HVDC系统交互振荡模式的阻尼特征提供模型基础。

家庭成员活动-出行选择行为的相互影响

基于活动的方法对研究家庭成员活动-出行选择之间的相互影响关系提供了新的思路。针对已有研究多围绕发达国家展开的现状,以国内某直辖市2005年居民出行调查数据为来源,从基于活动方法的协作性限制出发,研究了主要家庭成员活动-出行选择之间的相互影响模式,利用结构方程模型,分析了活动和出行需求在家庭成员之间的分配情况,讨论了存在于同一成员和不同成员各次活动和出行中的替代、补充、陪同等影响关系对个体活动-出行选择行为的影响。研究得到了在行为学上具有较强解释力并达到各项统计学评价指标的模型,对出行行为分析有重要意义。

基于结构方程模型的既有住区适老化改造研究--以湖北省宜昌市为例

我国社会人口老龄化形势日趋严峻,未来居家养老在我国养老发展格局中仍将占据主导,现有的老旧小区将成为居家养老生活的重要载体。以宜昌市地区为例,构建适用于既有住区适老化现状及需求评价的社区适老化程度指标体系。并在此基础上选取宜昌市7个典型社区中老年居民开展问卷调研和上门走访,结合调研数据通过因子分析法确定研究变量的权重,构建适合宜昌本地的既有社区适老化改造评估的结构方程模型。最后根据各项指标排序,选取室内空间、无障碍改造和健康管理等权重排名靠前、对居家养老幸福感效应最显著的因素,对宜昌既有社区提出了建筑改造、信息化方面的适宜性改造技术策略。

基于DEFORM-3D和SPSS的镍基高温合金Inconel 718车削力模型分析

为找到影响镍基高温合金Inconel718车削的主要可控因素,选择CNC编程中常用的切削用量设计正交试验,并模拟车削时三个方向的车削力对其进行极差与方差分析,建立了车削力模型预测的回归方程。对影响车削力的主要因素进行了F统计,分析出各因素的显著性影响因子与极差和方差的分析基本一致,证实了车削力模型的真实性。

THREE-DIMENSIONAL SIMULATION OF MEANDERING RIVER BASED ON 3-D RNG k-ε TURBULENCE MODEL

A 3-D numerical model for calculating flow in non-curvilinear coordinates was established in this article. The flow was simulated by solving the full Reynolds-averaged Navier-Stokes equations with the RNG κ-ε turbulence model. In the horizontal x-y-plane, a boundary-fitted curvilinear co-ordinate system was adopted, while in the vertical direction, a σ co-ordinate transformation was used to represent the free surface and bed topography. The water level was determined by solving the 2-D Poisson equation derived from 2-D depth averaged momentum equations. The finite-volume method was used to discretize the equations and the SIMPLEC algorithm was applied to acquire the coupling of velocity and pressure. This model was applied to simulate the meandering channels and natural rivers, and the water levels and the velocities for all sections were given. By contrasting and analyzing, the agreement with measurements is generally good. The feasibility studies of simulating flow of the natural fiver have been conducted to demonstrate its applicability to hydraulic engineering research.

Culm characteristics and volume-weight relationship of a forest bamboo(Melocanna baccifera(Roxb.) Kurz) from northeast India

Culm characteristics of Melocanna baccifera, locally ＇muli＇, culms at five different culm ages of 11 girth classes （5-6 to 15-16 cm） were studied from Cachar Dis- trict of southern Assam, northeast India. We recorded internode length, internode diameter, number of internodes per culm, total culm height, total culm green weight and total culm volume of all five culm age classes. Data were gathered on 165 culms, each culm age class containing 33 culms with 3 culms per girth class. Culm height ranged from 3.2 to 15.3 m with highest mean of 9.15 m （in threeyear old culms） and maximum culm height was recorded in four-year old culms. Highest mean and maximum internode length （27.45 and 54.2 cm, respectively）, internode diameter （3.12 and 4.75 cm, respectively） and total culm green weight （5.42 and 12.87 kg/culm, respectively） were recorded in three-year old culms and lowest in current-year culms. Best fitted regression models for all parameters were developed. Significant linear relationships between culm green weight and culm solid volume were documented for all five culm age classes. Their corresponding best-fit regression models were also developed.

Dynamic prediction of building subsidence deformation with data-based mechanistic self-memory model

This paper describes a building subsidence deformation prediction model with the self-memorization principle.According to the non-linear specificity and monotonic growth characteristics of the time series of building subsidence deformation,a data-based mechanistic self-memory model considering randomness and dynamic features of building subsidence deformation is established based on the dynamic data retrieved method and the self-memorization equation.This model first deduces the differential equation of the building subsidence deformation system using the dynamic retrieved method,which treats the monitored time series data as particular solutions of the nonlinear dynamic system.Then,the differential equation is evolved into a difference-integral equation by the self-memory function to establish the self-memory model of dynamic system for predicting nonlinear building subsidence deformation.As the memory coefficients of the proposed model are calculated with historical data,which contain useful information for the prediction and overcome the shortcomings of the average prediction,the model can predict extreme values of a system and provide higher fitting precision and prediction accuracy than deterministic or random statistical prediction methods.The model was applied to subsidence deformation prediction of a building in Xi'an.It was shown that the model is valid and feasible in predicting building subsidence deformation with good accuracy.

生成扩散模型研究综述

扩散模型在生成模型领域具有高质量的样本生成能力,一经推出就不断地刷新图像生成评价指标FID分数的记录,成为了该领域的研究热点,而此类相关综述在国内还鲜有介绍。因此,文中对相关扩散生成模型的研究进行汇总与分析。首先,对去噪扩散概率模型、基于分数的扩散生成模型和随机微分方程的扩散生成模型这3类通用模型的特点和原理进行了论述,就每一类基本扩散模型中以优化模型内部算法、高效采样为改进目标的相关衍生模型进行分析。其次,对当下扩散模型在计算机视觉、自然语言处理、时间序列、多模态和跨学科领域等方面的应用进行总结。最后,基于上述论述,分别就目前扩散生成模型存在的采样步骤多、采样时间长等局限性提出了相关建议,并结合前述研究对未来扩散生成模型的发展方向进行了研判。

3D object retrieval based on histogram of local orientation using one-shot score support vector machine

In this paper, a content based descriptor is pro- posed to retrieve 3D models, which employs histogram of local orientation （HLO） as a geometric property of the shape. The proposed 3D model descriptor scheme consists of three steps. In the first step, Poisson equation is utilized to define a 3D model signature. Next, the local orientation is calculated for each voxel of the model using Hessian matrix. As the final step, a histogram-based 3D model descriptor is extracted by accumulating the values of the local orientation in bins. Due to efficiency of Poisson equation in describing the models with various structures, the proposed descriptor is capable of discriminating these models accurately. Since, the inner vox- els have a dominant contribution in the formation of the de- scriptor, sufficient robustness against noise can be achieved. This is because the noise mostly influences the boundary vox- els. Furthermore, we improve the retrieval performance us- ing support vector machine based one-shot score （SVM-OSS） similarity measure, which is more efficient than the conven- tional methods to compute the distance of feature vectors. The rotation normalization is performed employing the prin- cipal component analysis. To demonstrate the applicability of HLO, we implement experimental evaluations of precision- recall curve on ESB, PSB and WM-SHREC databases of 3D models. Experimental results validate the effectiveness of the proposed descriptor compared to some current methods.

基于结构方程模型的老年四肢骨折患者术后康复运动恐惧的影响因素分析

目的探讨基于结构方程模型的老年四肢骨折患者术后康复运动恐惧的影响因素,为促进患者进行康复运动提供参考。方法采用便利抽样法,选取2020年1月-2023年12月我院收治的老年四肢骨折患者200例为研究对象,采用一般资料调查表、恐动症评分表(TSK)、焦虑自评量表(SAS)、疼痛视觉模拟量表(VAS)、一般自我效能感量表(GSES)、家庭关怀度量表(APGAR)进行调查,采用AMOS软件构建老年四肢骨折患者术后康复运动恐惧影响因素的结构模型。结果老年四肢骨折患者术后TSK得分为(40.37±4.69)分,SAS为(51.87±7.84)分,VAS为(4.23±2.34)分,GSES为(21.21±4.40)分,APGAR为(5.46±0.90)分;不同个人月收入、有跌倒史的患者TSK得分比较差异有统计学意义(P<0.05)。康复运动恐惧与个人月收入、家庭关怀度、自我效能感呈负相关,与焦虑、疼痛、有跌倒史呈正相关。疼痛、跌倒史不仅对康复运动恐惧直接影响(直接效应值分别为0.586、0.081),也可通过焦虑中介效应影响康复运动恐惧(间接效应值分别为0.261、0.038);焦虑、家庭关怀度、自我效能感对康复运动恐惧产生直接效应,效应值为0.337、-0.139、-0.237;个人月收入对康复运动恐惧产生间接效应,效应值为-0.043。结论老年四肢骨折患者术后康复运动恐惧受多种因素影响,临床应针对影响因素,制定个性化护理方案,降低老年四肢骨折患者术后康复运动恐惧水平,促进患者康复。