Mathematical Model for Tempering Time Effect on Quenched Steel Based on Hollomon Parameter

Through the differentiating and integrating process, a mathematical model for tempering time effect on quenched steel was derived based on the attribute of state function and the general equation of Hollomon parameter, which correlates the tempering hardness with the tempering time at different tempering temperature. Using the established model, the linear relationship between the tempering hardness and the tempering time in logarithm was proved theoretically, and the tempering hardness for various tempering time was reduced to the measurement and calculation of a hardness experiment tempered for 1 h at different tempering temperatures. Moreover, the hardness of steel 42CrMo and T8Mn tempered for various times at 200-600℃ was calculated using this method. The predicted results are in good agreement with those of the available experiments.

Modeling of Fluid Turbulence Modification Using Two-time-scale Dissipation Models and Accounting for the Particle Wake Effect

Presently developed two-phase turbulence models under-predict the gas turbulent fluctuation, because their turbulence modification models cannot fully reflect the effect of particles. In this paper, a two-time-scale dis- sipation model of turbulence modification, developed for the two-phase velocity correlation and for the dissipation rate of gas turbulent kinetic energy, is proposed and used to simulate sudden-expansion and swirling gas-particle flows. The proposed two-time scale model gives better results than the single-time scale model. Besides, a gas tur- bulence augmentation model accounting for the finite-size particle wake effect in the gas Reynolds stress equation is proposed. The proposed turbulence modification models are used to simulate two-phase pipe flows. It can prop- erly predict both turbulence reduction and turbulence enhancement for a certain size of particles observed in ex- periments.

Monitoring models for base flow effect and daily variation of dam seepage elements considering time lag effect

Affected by external environmental factors and evolution of dam performance, dam seepage behavior shows nonlinear time-varying characteristics. In this study, to predict and evaluate the long-term development trend and short-term fluctuation of the dam seepage behavior, two monitoring models were developed, one for the base flow effect and one for daily variation of dam seepage elements. In the first model, to avoid the influence of the time lag effect on the evaluation of seepage variation with the time effect component of seepage elements, the base values of the seepage element and the reservoir water level were extracted using the wavelet multi-resolution analysis method, and the time effect component was separated by the established base flow effect monitoring model. For the development of the daily variation monitoring model for dam seepage elements, all the previous factors, of which the measured time series prior to the dam seepage element monitoring time may have certain influence on the monitored results, were considered. Those factors that were positively correlated with the analyzed seepage element were initially considered to be the support vector machine(SVM) model input factors, and then the SVM kernel function-based sensitivity analysis was performed to optimize the input factor set and establish the optimized daily variation SVM model. The efficiency and rationality of the two models were verified by case studies of the water level of two piezometric tubes buried under the slope of a concrete gravity dam.Sensitivity analysis of the optimized SVM model shows that the influences of the daily variation of the upstream reservoir water level and rainfall on the daily variation of piezometric tube water level are processes subject to normal distribution.

Research for time-temperature equivalence effect of rock(Ⅱ):Experimental research

With the creep test data of granite taken from Three Gorges,the existence of time-temperature equivalence effect(TTEE) of granite is investigated.Based on the creep test data at different temperatures,which are 20 ℃,60 ℃,80 ℃,100 ℃,200 ℃,300 ℃,four-component viscoelastic Burgers model is presented to characterize the creep curves.The parameters of elasticity modulus and viscosity coefficient in the constitutive model at different temperatures and their functional dependences on temperature are obtained.Then,according to the basic theory of TTEE presented in research(I),the TTEE of granite is investigated through modifying the compliance curves with vertical shift function and checking the coincidence of the modified curves with horizontal shift functions.It is concluded that:① Burgers model could appropriately characterize the creep property of granite in a short time scale.② Both elastic modulus and viscosity coefficient in the Burgers model decay exponentially with temperature.③ The coincidence of the curves at different temperatures after vertical shift modification and horizontal shift is fine,which indicates the existence of TTEE of granite.④The master curves which reflect the long time scale test data at temperatures 20 ℃,100 ℃,200 ℃ are obtained.

A continuum traffic flow model with the consideration of coupling effect for two-lane freeways

A new higher-order continuum model is proposed by considering the coupling and lane changing effects of the vehicles on two adjacent lanes. A stability analysis of the proposed model provides the conditions that ensure its linear stability. Issues related to lane changing, shock waves and rarefaction waves, local clustering and phase transition are also investigated with numerical experiments. The simulation results show that the proposed model is capable of providing explanations to some particular traffic phenomena commonly observable in real traffic flows.

RESIDENCE TIME DISTRIBUTION IN AN OPEN REACTOR:EFFECT OF BACKGROUND REACTANT ON TRACER DISPERSION

A new approach is presented for deriving the residence time distribution(RTD)in open-type reactors with exclusion of residence in the fore section.Inasmuch as failure to predict the con-version of chemical reactions has been evidenced in many occasions,numerical solution of tracerdispersion in the presence of background concentration gradient of reactant is given to demonstratethe strong effect of background reactant on the true RTD a reactant molecule experiences.Withinthe error of computation,the conversion of a first-order chemical reaction under steady state is shownto be equal in both closed and open reactors,despite difference in relevant

A Measure for Assessing Functions of Time-Varying Effects in Survival Analysis

A standard approach for analyses of survival data is the Cox proportional hazards model. It assumes that covariate effects are constant over time, i.e. that the hazards are proportional. With longer follow-up times, though, the effect of a variable often gets weaker and the proportional hazards (PH) assumption is violated. In the last years, several approaches have been proposed to detect and model such time-varying effects. However, comparison and evaluation of the various approaches is difficult. A suitable measure is needed that quantifies the difference between time-varying effects and enables judgement about which method is best, i.e. which estimate is closest to the true effect. In this paper we adapt a measure proposed for the area between smoothed curves of exposure to time-varying effects. This measure is based on the weighted area between curves of time-varying effects relative to the area under a reference function that represents the true effect. We introduce several weighting schemes and demonstrate the application and performance of this new measure in a real-life data set and a simulation study.

Western Pacific Warm Pool and ENSO Asymmetry in CMIP3 Models

Theoretical and empirical studies have suggested that an underestimate of the ENSO asymmetry may be accompanied by a climatologically smaller and warmer western Pacific warm pool. In light of this suggestion, simulations of the tropical Pacific climate by 19 Coupled Model Intercomparison Project Phase 3 （CMIP3） climate models that do not use flux adjustment were evaluated. Our evaluation revealed systematic biases in both the mean state and ENSO statistics. The mean state in most of the models had a smaller and warmer warm pool. This common bias in the mean state was accompanied by a common bias in the simulated ENSO statistics： a significantly weak asymmetry between the two phases of ENSO. Moreover, despite the generally weak ENSO asymmetry simulated by all models, a positive correlation between the magnitude of the bias in the simulated warm-pool size and the magnitude of the bias in the simulated ENSO asymmetry was found. These findings support the suggested link between ENSO asymmetry and the tropical mean state--the climatological size and temperature of the warm pool in particular. Together with previous studies, these findings light up a path to improve the simulation of the tropical Pacific mean state by climate models： enhancing the asymmetry of ENSO in the climate models.

Far-infrared conductivity of CuS nanoparticles measured by terahertz time-domain spectroscopy

This paper reports that terahertz time-domain spectroscopy is used to measure the optical properties of CuS nanoparticles in composite samples. The complex conductivity of pure CuS nanoparticles is extracted by applying the Bruggeman effective medium theory. The experimental data are consistent with the Drude-Smith model of conductivity in the range of 0.2 1.5 THz. The results demonstrate that carriers become localized with a backscattering behaviour in small-size nanostructures. In addition, the time constant for the carrier scattering is obtained and is only 64.3 fs due to increased electron interaction with interfaces and grain boundaries.

时间效应下的健康信息说服机制研究--基于精细加工可能性模型的实证

通过健康信息传播和教育说服公众形成健康行为意愿是一个现实课题。本文以精细加工可能性模型(elabo‐ration likelihood model,ELM)为理论基础,将说服路径分为中心路径和外围路径,同时引入短期的时间纵向数据追踪。本文实施了10天左右持续使用健康信息的日记报告实验,基于30名大学生提交的377条健康信息日记数据,建立个体层面与信息线索、时间层面的多层线性回归模型(hierarchical linear modeling,HLM),探究健康信息对个体健康行为意愿的说服机制。研究结果表明,健康行为意愿的说服过程主要是信息质量和来源可信度的混合式说服路径;在7天周期内,健康信息说服效果逐渐增强,其中信息质量的说服效果更为稳定,来源可信度的说服效果则随着时间推移逐渐被抵消;健康信息说服路径随个体特征和接触时机而变;健康意识调节来源可信度和信息热度对说服效果的影响,且具有时间效应;卷入度调节信息质量和来源可信度对信息说服效果的影响,但不存在时间效应。本文的研究结果有助于深入理解健康信息对健康行为意愿改变的说服机制,为建立“以人为本”的个性化健康信息传播和健康教育方案提供了参考。

T=S Model to Simulate Regional Economic Development

This paper proposes a mechanism theory on regional development by using a modified Logistic model. It reveals regional evolution is an integration of fluctuation in temporal dimension and disparity in spatial dimension. T = S model is established by using Logistic model to simulate the growth of per capita GDP in China from 1990 to 1999. The result shows that T=S model accurately simulates the tracks of economic growth.

早龄期机制砂混凝土抗压强度与弹性模量时效关系及本构模型试验研究

为了研究早龄期机制砂混凝土在单轴受压状态下抗压强度与弹性模量的时效关系和本构模型,通过对8组不同龄期的C60机制砂混凝土试件进行立方体抗压强度试验、静力受压弹性模量试验和单轴受压应力-应变曲线试验,并参考多种已有研究模型,建立了早龄期机制砂混凝土在单轴受压状态下的抗压强度与弹性模量时效关系模型和分段式应力-应变本构模型。结果表明,采用的抗压强度与弹性模量时效关系模型和分段式应力-应变本构模型与试验数据吻合效果理想,能够较好地描述早龄期C60机制砂混凝土在单轴受压状态下的力学性能。

Constraining Forces Causing the Meissner Effect

As shown in former papers, the nonadiabatic Heisenberg model presents a novel mechanism of Cooper pair formation which is not the result of an attractive electron-electron interaction but can be described in terms of quantum mechanical constraining forces. This mechanism operates in narrow, roughly half-filled superconducting bands of special symmetry and is evidently responsible for the formation of Cooper pairs in all superconductors. Here we consider this new mechanism within an outer magnetic field. We show that in the magnetic field the constraining forces produce Cooper pairs of non-vanishing total momentum with the consequence that an electric current flows within the superconductor. This current satisfies the London equations and, consequently, leads to the Meissner effect. This theoretical result is confirmed by the experimental observation that all superconductors, whether conventional or unconventional, exhibit the Meissner effect.

Estimation of the Piecewise Exponential Model by Bayesian P-Splines via Gibbs Sampling: Robustness and Reliability of Posterior Estimates

In the investigation of disease dynamics, the effect of covariates on the hazard function is a major topic. Some recent smoothed estimation methods have been proposed, both frequentist and Bayesian, based on the relationship between penalized splines and mixed models theory. These approaches are also motivated by the possibility of using automatic procedures for determining the optimal amount of smoothing. However, estimation algorithms involve an analytically intractable hazard function, and thus require ad-hoc software routines. We propose a more user-friendly alternative, consisting in regularized estimation of piecewise exponential models by Bayesian P-splines. A further facilitation is that widespread Bayesian software, such as WinBUGS, can be used. The aim is assessing the robustness of this approach with respect to different prior functions and penalties. A large dataset from breast cancer patients, where results from validated clinical studies are available, is used as a benchmark to evaluate the reliability of the estimates. A second dataset from a small case series of sarcoma patients is used for evaluating the performances of the PE model as a tool for exploratory analysis. Concerning breast cancer data, the estimates are robust with respect to priors and penalties, and consistent with clinical knowledge. Concerning soft tissue sarcoma data, the estimates of the hazard function are sensitive with respect to the prior for the smoothing parameter, whereas the estimates of regression coefficients are robust. In conclusion, Gibbs sampling results an efficient computational strategy. The issue of the sensitivity with respect to the priors concerns only the estimates of the hazard function, and seems more likely to occur when non-large case series are investigated, calling for tailored solutions.

EFFECT OF BACKGROUND REACTANT GRADIENT ON TRACER DISPERSION:A CASE STUDY OF IMPULSE INJECTION OF REACTANT INTO AN OPEN REACTOR

The paradox is well known that the residence time distribution(RTD)is not valid forthe estimation of the conversion of a first order reaction in an open tubular reactor.A casc ofδ injection of reactive species into an open flow system is investigated theoretically in this paper.The analytical solution with the Laplace transform demonstrated that the conversion of a first orderreaction is identical to that in a closed reactor under steady state.The effect of the backgroundreactant concentration gradient addressed by the authors in a previous paper was employed to thiscase.and the numerical solution of the tracer dispersion based on this novel argument gave rise to asimilar value of conversion.suggesting the validity of the concept and the significance of the subtledifference between RTDs determined with or without the presence of a background reactant in anopen flow system.

高质量的内部控制会提高企业回函效率吗?——基于证券交易所年报问询函的经验证据

年报问询函监管制度作为证券交易所监管市场的重要手段日益获得认可。为探索企业内部控制质量对年报问询函的影响,本文基于企业回函视角,运用stata15软件,采用固定效应模型进行检验及异质性分析。研究发现,高质量的企业内部控制能够提升回函效率。同时,由于产权性质和问询问题性质的不同,其回函效率亦有所差异。实证显示:非国有企业回函态度更积极,而如果问询问题性质越严重,则内部控制质量越高的企业回函效率越高。本文研究结论对于促进企业加强内部控制,提升会计信息披露质量,促进问询监管制度更好发挥效用具有积极意义。

金融冲击对劳动市场波动的时变效应——基于TVP-SV-VAR模型的实证研究

本文基于金融市场与劳动市场联动的视角,构建中国金融状况指数,并利用时变参数随机波动向量自回归模型(TVP-SV-VAR)研究金融冲击对劳动市场的影响及时变特征。结果表明,金融冲击显著引发劳动市场的供需失衡。金融状况恶化会提升失业率、降低工资水平并进一步引起宏观经济中的通货紧缩。机制分析表明,企业杠杆对金融冲击的负面影响有放大作用,金融条件紧缩经由企业杠杆的负向调整会进一步导致劳动需求萎缩与失业率上行。对跨境金融冲击和境内金融冲击效果的比较分析揭示,相较于传导渠道,冲击规模是金融冲击对我国劳动市场影响差异的主导因素。据此,本文建议在跨周期调节的同时注意防范化解金融风险,以提升金融支持“稳主体”和“稳就业”的政策效果。

“认房认贷”政策放松对房地产市场影响效应分析——基于住房交易挤出的视角

明晰需求端政策调控对二手房和新房市场的影响效应具有重要的现实意义。本文以“认房认贷”政策作为研究对象,运用时间断点回归模型,分析2022年部分二三线城市“认房认贷”政策放松对二手房和新房成交量价的影响以及两个子市场的联动规律,并进一步检验政策放松的空间挤出效应。研究发现,“认房认贷”政策放松显著增加了二手房的成交量,并减缓了二手房成交价格的下行趋势,但政策生效存在1~2个月的时滞。然而,二手房市场流动性增强挤出了新房市场的改善性住房需求,使得大户型新房成交量显著减少,并带来当期新房成交价格的下降。此外,高能级城市“认房认贷”政策的放松对周边低能级城市住房交易有较强的挤出效应,对小中大户型的新房交易均有持续显著的抑制效果。据此提出要因城施策引导刚性和改善性购房者分流。

数字化转型助力津门老字号企业品牌发展研究

数字经济改变着人们的生活与工作方式,历史底蕴和文化价值深厚的老字号品牌如何在数字经济时代传承创新、改革发展已成为研究热点。基于2011—2021年天津老字号企业面板数据,构建时间、个体双向固定效应模型和中介效应模型,探究企业数字化转型对品牌竞争力的影响及其作用机制。结果表明,老字号企业数字化转型能够显著提升品牌竞争力,企业创新水平对数字化转型提升品牌竞争力具有中介作用。基于此,对老字号企业转型发展提出相关对策建议,促进老字号企业利用数字化转型推动品牌发展,提升竞争力。