高速艇自由变深水动力试验研究

通过模型试验，研究了高速艇从压栽半潜状态自由变深到高速滑行状态的水动力现象．结果表明，当客积傅氏数大于1.25时，与舷外相通的水能完全自动排出．高速艇自由变深主要有以下5个原因：惯性作用、压栽水逐渐排出导致的艇体上抬作用、艇艉由于负压形成的空穴对压戢水的吸附作用、艇体动升力导致的艇体上抬作用、有利的艉倾作用．其中对具有较快加速运动的情形，惯性作用起重要地位，艇体动升力在排出流道水方面所发挥的作用相对较小，但在保持流道水排空方面发挥主导作用．     

Dynamic flow‐based particle splitting in smoothed particle hydrodynamics

In this work, a dynamic procedure for local particle refinement to be used in smoothed particle hydrodynamics (SPH) is presented. The algorithm is able to consistently produce successive levels of particle splitting in accordance to a flow‐based criterion. It has been applied together with accurate and robust formulations for variable spatial resolution in the framework of a semi‐implicit, truly incompressible scheme for SPH. Different test cases have been considered to assess the capabilities and advantages of the proposed procedure, namely, the laminar flow around circular and square obstacles in a plane channel for various regimes. Such flow cases entail the simulation of attached and separated shear layers, recirculating flow, vortex shedding and surface discontinuities. The results obtained for two levels of particle splitting have demonstrated that significant improvements may be obtained with respect to uniform particle spacing solutions in a variety of situations, thus presenting an excellent trade‐off between accuracy and computational cost. Copyright © 2015 John Wiley & Sons, Ltd.     

APP动效设计中的用户专注沉浸度模型研究

目的基于MaterialDesign的交互动效理论,通过拓展TAM的三个维度研究用户对APP使用的专注沉浸度,并对比研究不同的交互动画在不同的应用中对用户专注沉浸度的影响,从而得出动效设计中用户专注沉浸度的理论假设模型,以补充TAM模型理论在交互设计方面的扩展研究。方法分析运用TAM和专注沉浸度模型的相关理论,综合扩展APP中交互动画研究测度,构建出新的假设理论模型,再通过两类典型交互动画对其动效做专注沉浸度实验,实验主要利用SPSS对由用户研究和体验测度组成的调查问卷进行数据统计和分析,最终检验本文的假设理论模型。结论实验结果表明H1-H7呈正相关,理论假设模型成立。验证了在一定条件下,运用本文构建的假设理论模型设计的交互动画在APP设计实践中能够更加有效地提高用户的专注沉浸度,能给用户带来更好的体验。     

An Efficient Approximate Markov Chain Method in Dynamic Fault Tree Analysis

Approximate Markov chain method for dynamic fault tree analysis is suggested for both reparable and non‐reparable systems. The approximation is based on truncation, aggregation and elimination of Markov chain states during the process of dynamic fault tree transformation to corresponding Markov chain. The method is valid for small probabilities. For reparable systems, it is true if mean time to repair is much less than mean time to failure. Several examples are studied. Additional simplification is considered in case the system is in a steady state. Copyright © 2015 John Wiley & Sons, Ltd.     

高速轧辊磨床微进给机构动力学分析

以高速轧辊磨床微进给机构为研究对象,利用HYPERMESH建立各零部件的有限元模型,并在ANSYS中采用弹簧阻尼器单元COMBIN14建立各结合部的动力学模型,从而建立微进给机构整体有限元模型,进行了模态分析和谐响应分析,得到微进给机构前10阶模态,识别了微进给机构的薄弱环节,从而为微进给机构的设计改进提供依据。     

Approximate prediction intervals in the original units when fitting models using data transformations

In this paper, we consider prediction interval estimation in the original units of observation after fitting a linear model to an appropriately transformed response variable. We assume that the residuals obtained from fitting the linear model in the transformed space are iid zero‐mean normal random variables, at least approximately. We discuss the bias in the retransformed mean and derive a reduced‐bias estimator for the k^th moment of the original response, given settings of the design variables. This is then used to compute reduced‐bias estimates for the mean and variance of the untransformed response at various locations in design space. We then exploit a well‐known probability inequality, along with our proposed moment estimator, to construct an approximate 100(1?α)% prediction interval on the original response, given settings of the design factors. We used Monte Carlo simulation to evaluate the performance of the proposed prediction interval estimator relative to 2 commonly used alternatives. Our results suggest the proposed method is often the better alternative when the sample size is small and/or when the underlying model is misspecified. We illustrate the application of our new method by applying it to a real experimental data set obtained from the literature, where machine tool life was studied as a function of various machining parameters.     

Physical property measurements for the mathematical modeling of fluid flow in solidification processes

Measurement methods are being developed to provide values for the density, viscosity, heat capacity, enthalpy, fraction solid, surface tension, and thermal diffusivity and conductivity of commercial alloys in the liquid and mushy states. These data are needed for the mathematical modeling of heat and fluid flow in solidification processes. This paper briefly describes the present state of development of apparatus for the measurement of density by the levitated drop and hydrostatic probe methods and viscosity by the oscillating viscometer in our laboratory. Paper presented at the Fourth Asian Thermophysical Properties Conference, September 5–8, 1995, Tokyo, Japan.     

Some mathematical models in ecotoxicology: Effects of toxicants on biological species

In this paper, some nonlinear mathematical models to study the effect of one or more toxicants on a single or two interacting biological species are described. A model governing a subclass of affected population, exhibiting severe symptoms such as deformity, lesion, blister etc., is proposed. Another model for allelopathy where a plant population produces toxicants that affect other competing species is also suggested. It has been noted that the continuous emission of one or more toxicants into the environment is detrimental to the growth and survival of the affected biological species.     

Numerical investigation of hydrodynamics in liquid-solid circulating fluidized beds under different operating conditions

A computational fluid dynamics (CFD) model was employed to investigate the hydrodynamics of the liquid–solid circulating fluidized bed (LSCFB). The numerical simulations of the flow in the LSCFB under different operating conditions, including different superficial liquid velocities, superficial solid velocities, particle densities and shapes, are carried out using the CFD model developed in the previous work. The numerical predictions show correct trends and good agreements with the experimental data. It is demonstrated that the radial non-uniformity and axial uniformity exist in the flow structures under different operating conditions. By increasing the superficial solid velocity, the average solids holdup and radial non-uniformity increase, while the opposite trends are observed by increasing the superficial liquid velocity. Besides, the solids holdup decreases with the decrease in the particle density. It is also observed that all the flow distributions in the radial and axial directions in LSCFBs are more uniform than those in GSCFBs.     

Setting safety stocks in multi-stage inventory systems under rolling horizon mathematical programming models

This paper considers the problem of determining safety stocks in multi-item multi-stage inventory systems that face demand uncertainties. Safety stocks are necessary to make the supply chain, which is driven by forecasts of customer orders, responsive to (demand) uncertainties and to achieve predefined target service levels. Although there exists a large body of literature on determining safety stock levels, this literature does not provide an effective methodology that can address complex multi-constrained supply chains. In this paper, the problem of determining safety stocks is addressed by a simulation based approach, where the simulation studies are based on solving the supply chain planning problem (formulated as a mathematical programming model) in a rolling horizon setting. To demonstrate the utility of the proposed approach, an application of the approach at Organon, a worldwide operating biopharmaceutical company, will be discussed.     

低温高速动静压轴承气液两相润滑氧介质物性参数获取

研究了高速涡轮泵动静压轴承的液氧润滑介质物性情况,获取了氧介质在单相及两相下的物性参数.研究结果表明:对于单相(液相或气相)氧介质,在一定的压力和温度下可建立其密度和粘度随压力和温度的变化关系或直接查表获得；对于两相氧介质,其物性参数的荻取可以采用两相均质混合模型方法进行计算.计算结果表明在液氧不断汽化并最终转变为气态...     

支撑液膜分离过程应用研究新进展

简要回顾液膜分离过程的发展史;介绍支撑液膜法的基本原理.在分析支撑液膜所存在问题的基础上重点论述近10年来支撑液膜的应用和发展.     

Dual Critical Points and Related Phenomena in Simple Fluids from the Perspective of (Approximate) Renormalization Theory

It is known that some single component fluids can have coexisting low-density and high-density liquid phases with two, separate, gas–liquid and liquid–liquid, critical points. Such behavior is found both by experiments and in recent molecular-dynamics simulations performed for certain simple isotropic attractive pair potentials with softened repulsive cores. In the present investigation, a global renormalization group theory that was employed previously to make predictions for simple Lennard–Jones and square-well fluids over wide ranges of density and temperature, including the critical point, in reasonably good agreement with molecular dynamics and Monte Carlo simulations, is applied to simple shoulder potentials and to square-well potentials with softened repulsive cores. Results using this renormalization approach are compared with some previously reported results for a shoulder potential and expectations regarding dual critical points for water.     

A transient Eulerian-Eulerian simulation of bubbling regime hydrodynamics of coal ash particles in fluidized bed using different drag models

The transient multiphase model with the Eulerian-Eulerian approach based on the Two-Fluid Model (TFM) was executed to simulate the bubbling regime’s hydrodynamics of bed material in the fluidized bed using three different drag models. Coal ash particles having three different sizes were taken in bed for fluidization under cold conditions. The bubbling regime's superficial velocities were acquired from experimentations and used as inlet velocities during Computational Fluid Dynamics (CFD) simulation of a 2-Dimensional fluidized bed. The Syamlal-O'Brien, Gidaspow and Wen-Yu drag models were considered in this study, and their effects on the bed hydrodynamics were discussed. The study emphasized the suitability of drag models for the coal ash particles. The drag force was not adequate and showed a negligible effect on particles irrespective of the high inlet velocity displayed by the Gidaspow model. The other two drag models predicted sufficient drag, but there was more intensity in Syamlal-O'Brien than in the Wen-Yu model. The Syamlal-O'Brien model resembled more physical fluidization occurrences for smaller and larger sized coal ash particles. This study also supports the hydrodynamics of the Geldart-D type particles.     

Simulation of transient behaviour in refrigeration plant pressure vessels: mathematical models and experimental validation

Four dynamic models of different degrees of complexity were derived to represent a typical industrial refrigeration intercooler (pressure vessel). The models were validated against temperature and pressure data from two pilot plant calorimeters containing R-134a under a variety of transient operating conditions. The measured response rate was strongly influenced by sensible heat storage in the calorimeter shell and liquid refrigerant. Little difference in predictions by the four models was obtained in spite of major simplifying assumptions made to develop the less complex models. A model considering only the thermal capacity in the shell and liquid refrigerant predicted rates of temperature change within 10% of predictions by the other models, and also close to experimental data.     

动态液位的神经网络测量方法研究

利用BP神经网络高度的非线性函数逼近的能力,解决连续搅拌反应釜的动态液位测量的问题．介绍了BP的基本算法及其改进．并通过实验数据的学习建立了较为有效的动态液位测量网络模型．     

Impact of contact data resolution on the evaluation of interventions in mathematical models of infectious diseases

Computational models offer a unique setting to test strategies to mitigate the spread of infectious diseases, providing useful insights to applied public health. To be actionable, models need to be informed by data, which can be available at different levels of detail. While high-resolution data describing contacts between individuals are increasingly available, data gathering remains challenging, especially during a health emergency. Many models thus use synthetic data or coarse information to evaluate intervention protocols. Here, we evaluate how the representation of contact data might affect the impact of various strategies in models, in the realm of COVID-19 transmission in educational and work contexts. Starting from high-resolution contact data, we use detailed to coarse data representations to inform a model of SARS-CoV-2 transmission and simulate different mitigation strategies. We find that coarse data representations estimate a lower risk of superspreading events. However, the rankings of protocols according to their efficiency or cost remain coherent across representations, ensuring the consistency of model findings to inform public health advice. Caution should be taken, however, on the quantitative estimations of those benefits and costs triggering the adoption of protocols, as these may depend on data representation.     

Use of mathematical models for estimating the shelf‐life of cornflakes in flexible packaging

The objective of this work was to evaluate three different mathematical models (linear, middle point and logarithm interval) to predict the stability of commercial cornflakes in flexible packages. The limiting factor for cornflakes' shelf‐life was gain of moisture from the external environment, which caused loss of crispness and thus was unacceptable to the consumer. It was concluded that both middle point and logarithm interval methods are suitable for estimating the stability of cornflakes with a good approximation. The accuracy of these two methods depends on the precision of the experimental points of the sorption isotherms. The best fit to adjust the moisture isotherm was the GAB model. Knowledge of the mode of deterioration of the product and the sensory critical moisture content were fundamental to understanding and setting up the limits to confirm the models. Copyright © 2005 John Wiley & Sons, Ltd.     

An experimental design tool to optimize inference precision in data-driven mathematical models of bacterial infections in vivo

The management of bacterial diseases calls for a detailed knowledge about the dynamic changes in host–bacteria interactions. Biological insights are gained by integrating experimental data with mechanistic mathematical models to infer experimentally unobservable quantities. This inter-disciplinary field would benefit from experiments with maximal information content yielding high-precision inference. Here, we present a computationally efficient tool for optimizing experimental design in terms of parameter inference in studies using isogenic-tagged strains. We study the effect of three experimental design factors: number of biological replicates, sampling timepoint selection and number of copies per tagged strain. We conduct a simulation study to establish the relationship between our optimality criterion and the size of parameter estimate confidence intervals, and showcase its application in a range of biological scenarios reflecting different dynamics patterns observed in experimental infections. We show that in low-variance systems with low killing and replication rates, predicting high-precision experimental designs is consistently achieved; higher replicate sizes and strategic timepoint selection yield more precise estimates. Finally, we address the question of resource allocation under constraints; given a fixed number of host animals and a constraint on total inoculum size per host, infections with fewer strains at higher copies per strain lead to higher-precision inference.