Thermoviscoelastic Properties of Phenolic Resin/Polymeric Isocyanate Binder Systems

Thermoviscoelastic properties of phenolic resin/polymeric isocyanate binder systems (i.e., ISOCURE Parts I and II) are reported. The effects of blend composition and the reaction between the binders on these properties of the systems are also considered. The viscous properties of binders and their blends were measured using computer-controlled rotational viscometers (Brookfield HBDV-II+ viscometer and HAAKE Rotovisco 12 rheometer in the cone-and-plate mode). The elastic properties of the phenolic urethane polymer (the blend composition) were measured by means of a modified jet thrust technique based on measuring the thrust of a liquid jet. Although both binders are Newtonian liquids, their blends exhibit viscoelastic non-Newtonian fluid flow behavior. The viscosity of the blends increases both with time and with an increasing Part I content and may reach comparatively high values at high values of either parameter. This behavior is explained as a result of the rubbery nature of the phenolic urethane polymer, which was produced as a product of reaction between Part I and Part II. The use of the jet thrust method allowed determination of the relaxation time of various blends at different shear rates.     

不同温度下硒化镉(CdSe)量子点的生长及荧光性研究

研究了以氧化镉（CdO）和硒（Se）粉为前驱体,在三辛基膦（TOP）和油酸中合成无机半导体量子点（quantum dots, QDs）CdSe.研究了在不同的反应温度下粒子的生长,通过紫外吸收光谱（UV-Vis）、荧光发射光谱（PL）、透射电子显微镜（TEM）等手段跟踪反应过程并对样品性能进行了表征.实验结果表明,反应温度和反应时间对量子点的生长和荧光性能有很大的影响.     

Resilience and the temporal dimension – the chimera of timely response

This paper presents a framework for reasoning about ‘timely response’, and control versus the temporal organisation of a controlling system. By three empirical examples, we show how a controlling system can be described in terms of perception points, decision points and action points. Our conclusions are that (1) temporal expectancies shape our ability to exercise control at least as much our ability to understand relations and causality, but temporality is rarely part of approaches to modelling human or system performance, (2) temporal organisation of activities shape our ability to exercise control, (3) by utilising the temporal control framework, we can describe important properties of the temporal organisation of a socio-technical system, and (4) the capacity of modelling is limited to what can be known or imagined. Therefore, models describing resilience or stability should include temporality and be based on frameworks generic enough to be applied to a wide variety of situations.     

A model/solution-adaptive explicit-implicit time-marching technique for wave propagation analysis

In this work, an explicit-implicit time-marching procedure with model/ solution-adaptive time integration parameters is proposed for the analysis of hyperbolic models. The two time integrators of the methodology are locally evaluated, enabling their different spatial and temporal distributions. The first parameter defines the explicit/implicit subdomains of the model, and it is defined in a way that stability is always ensured, as well as period elongation errors are reduced; the second parameter controls the dissipative properties of the methodology, allowing spurious high-frequency modes to be properly eliminated, rendering reduced amplitude decay errors. In addition, the proposed explicit-implicit approach allows contracted systems of equations to be obtained, reducing the computational effort of the analysis. The main features of the novel methodology can be summarized as follows: (i) it is simple; (ii) it is locally defined; (iii) it has guaranteed stability; (iv) it is an efficient noniterative single-step procedure; (v) it provides enhanced accuracy; (vi) it enables advanced controllable algorithmic dissipation in the higher modes; (vii) it considers a link between the temporal and the spatial discretization; (viii) it stands as a single-solve framework based on reduced systems of equations; (ix) it is truly self-starting; and (x) it is entirely automatic.     

Exploring the influential factors in incident clearance time: Disentangling causation from self-selection bias

Understanding the relationships between influential factors and incident clearance time is crucial to make effective countermeasures for incident management agencies. Although there have been a certain number of achievements on incident clearance time modeling, limited effort is made to investigate the relative role of incident response time and its self-selection in influencing the clearance time. To fill this gap, this study uses the endogenous switching model to explore the influential factors in incident clearance time, and aims to disentangle causation from self-selection bias caused by response process. Under the joint two-stage model framework, the binary probit model and switching regression model are formulated for both incident response time and clearance time, respectively. Based on the freeway incident data collected in Washington State, full information maximum likelihood (FIML) method is utilized to estimate the endogenous switching model parameters. Significant factors affecting incident response time and clearance time can be identified, including incident, temporal, geographical, environmental, traffic and operational attributes. The estimate results reveal the influential effects of incident, temporal, geographical, environmental, traffic and operational factors on incident response time and clearance time. In addition, the causality of incident response time itself and its self-selection correction on incident clearance time are found to be indispensable. These findings suggest that the causal effect of response time on incident clearance time will be overestimated if the self-selection bias is not considered.     

Adaptive backward Euler time stepping with truncation error control for numerical modelling of unsaturated fluid flow

An automatic time stepping scheme with embedded error control is developed and applied to the moisture‐based Richards equation. The algorithm is based on the first‐order backward Euler scheme, and uses a numerical estimate of the local truncation error and an efficient time step selector to control the temporal accuracy of the integration. Local extrapolation, equivalent to the use of an unconditionally stable Thomas–Gladwell algorithm, achieves second‐order temporal accuracy at minimal additional costs. The time stepping algorithm also provides accurate initial estimates for the iterative non‐linear solver. Numerical tests confirm the ability of the scheme to automatically optimize the time step size to match a user prescribed temporal error tolerance. An important merit of the proposed method is its conceptual and computational simplicity. It can be directly incorporated into existing or new software based on the backward Euler scheme (currently prevalent in subsurface hydrologic modelling), and markedly improves their performance compared with simple fixed or heuristic time step selection. The generality of the approach also makes possible its use for solving PDEs in other engineering applications, where strong non‐linearity, stability or implementation considerations favour a simple and robust low‐order method, or where there is a legacy of backward Euler codes in current use. Copyright © 2001 John Wiley & Sons, Ltd.     

A NEW TECHNIQUE FOR BEHAVIOR AND TEMPORAL ANALYSIS OF TIMED PETRI NETS

ABSTRACT

The Firing Sequence Graph (FSG) technique is proposed as a new technique to do behavior analysis and temporal verification of a system modeled by the real-time Petrinet model. It employs simple mechanical procedures to do analysis to reduce the involvement of human beings during firing sequence derivation. It derives firing sequences from local configurations by local sequence accumulation to alleviate the state-space explosion problem. It contains more transition sequencing information in a firing sequence. It allows the efficient derivation of temporal propagation expressions to do various temporal verification, including triggering, deadline, response, and period time constraints check against what the user specifies. All these features make the technique work better in system evaluation than traditional Petri-net languages, reachability tree analysis, incidence matrix technique, marking transition, or state graph technique.     

苯乙烯/异戊二烯渐变嵌段共聚物的负离子法合成和性能

一次加料延时加入极性结构调节剂四氢呋喃(THF)、以正丁基锂(n-BuLi)为引发剂、环己烷为溶剂,用活性负离子聚合技术合成了具有渐变嵌段结构的苯乙烯(St)/异戊二烯(Ip)共聚物(S/I)。使用核磁共振氢谱(¹H-NMR)和动态粘弹谱(DMA)等仪器表征共聚物的微观结构并测定共聚物的动态力学性能,研究了THF的加入时间和St含量对S/I共聚物微观结构和性能的影响。结果表明,加入THF的时间显著影响共聚物的微观结构、力学和动态力学性能。控制THF的加入时间能调控St和Ip单体的共聚合活性从而调控共聚物的微观结构和共聚物的组成及其分布,生成具有渐变嵌段结构的S/I共聚物,拓宽共聚物的玻璃化转变温度(T_g)区间。对S/I共聚物的结构和性能的变化过程也进行了理论分析。     

Microelectrode array microscopy: investigation of dynamic behavior of localized corrosion at type 304 stainless steel surfaces

Scanning electrochemical microscopy (SECM) and a recently developed microelectrode array microscope have been used to study localized corrosion and electron-transfer characteristics of native oxide layers of type 304 stainless steels. The I-/I3- redox couple was employed as a mediator and allowed sensitive detection of oxide breakdown events. In solutions containing I-, a signal at the microelectrode was observed on type 304 stainless steel surfaces at active pitting corrosion sites. Under conditions where pitting corrosion occurs, SECM was used to track the temporal characteristics of the reaction in a spatial manner. However, because of the time required to create an image, much of the temporal information was not obtained. To improve the temporal resolution of the measurement, microelectrode array microscopy (MEAM) was developed as a parallel method of performing SECM. The demonstration shown reveals the potential of MEAM for analysis of surface chemistry on temporal and spatial domains.     

Efficient finite element formulation for geothermal heating systems. Part II: transient

This paper presents an extension to the work presented in Part I of this series of two articles to the transient case. Emphasis is placed on the development of a new model for heat flow in a double U‐shape vertical borehole heat exchanger and its thermodynamic interactions with surrounding soil mass. The discretization of the spatial‐temporal domain of the heat pipe model is done by the use of the space–time finite element technique in conjunction with the Petrov–Galerkin method and the finite difference method. The paper shows that the proposed model and the choice of the discretization technique, in addition to the utilization of a sequential numerical algorithm for solving the resulting system of non‐linear equations, have contributed in reducing significantly the required number of finite elements necessary for describing geothermal heating systems. Details of the mathematical derivations and comparison to experimental data are presented. Copyright © 2006 John Wiley & Sons, Ltd.     

SPAD array module for multi-dimensional photon timing applications

Multi-dimensional time correlated single-photon counting has reached a prominent position among analytical techniques employed in the medical and biological fields. The development of instruments able to perform temporal and spectral fluorescence analysis (sFLIM) at the same time is limited by the performance of single-photon detectors, since currently available arrays cannot simultaneously satisfy all the requirements. To face this rising quest, a fully-parallel eight-channel module, based on a monolithic single-photon avalanche diode (SPAD) array with great temporal resolution, high photon detection efficiency and low dark count rate, has been designed and fabricated. The system relies on a novel architecture of the single pixel, based on the integration of the timing pick-up circuit next to the photodetector, making the negative effects of electrical and optical crosstalk on photon timing performance negligible. To this end, the custom technological process used to fabricate the SPAD has been modified, allowing the integration of MOS transistors without impairing the structure and the performance of the detector. The single channel is complemented by an external active quenching circuit, fabricated in a standard CMOS technology, that ensures high maximum counting rate (>5?MHz) and low after-pulsing (<2%). Finally, the output timing signals are read and conditioned by proper CMOS electronics. The complete system shows a very good temporal resolution of about 45?ps (FWHM).     

瞬态高速光子多普勒测速技术研究现状及展望

面对短时间、高速度等极端测量条件的挑战,光子多普勒测速系统朝向更大测速范围、更高时间分辨力、更高灵敏度和多点测量能力四个方面快速发展.首先文章详细介绍了光子多普勒系统测速原理和背景;其次对测量速度在100 m/s以上、记录时间为纳秒级的瞬态高速光子多普勒测速系统的经典改进方法和发展现状进行了分类和总结;然后着重介绍时域...     

A dynamic scheduling algorithm for singe-arm two-cluster tools with flexible processing times

This article presents a dynamic algorithm for job scheduling in two-cluster tools producing multi-type wafers with flexible processing times. Flexible processing times mean that the actual times for processing wafers should be within given time intervals. The objective of the work is to minimize the completion time of the newly inserted wafer. To deal with this issue, a two-cluster tool is decomposed into three reduced single-cluster tools (RCTs) in a series based on a decomposition approach proposed in this article. For each single-cluster tool, a dynamic scheduling algorithm based on temporal constraints is developed to schedule the newly inserted wafer. Three experiments have been carried out to test the dynamic scheduling algorithm proposed, comparing with the results the ‘earliest starting time’ heuristic (EST) adopted in previous literature. The results show that the dynamic algorithm proposed in this article is effective and practical.     

Application of dynamic phase shifting with wavelet analysis to electronic speckle contouring

Dynamic phase shifting is a temporal phase unwrapping method, i.e., a method in which a sequence of speckle patterns is analyzed along the time axis. Each pixel can thus be considered as an independent detector, which is of particular interest for the study of complex surfaces. I report the application of this technique, which is based on a wavelet analysis, to contouring measurements with a dual-beam illumination electronic speckle pattern interferometry setup. I present a new, more general geometric model of the setup. I also investigate the possibility of enhancing the accuracy by using the intermediate phase values. Tests are performed on a simply described object and compared with coordinate measuring machine measurements.     

含有机胶凝剂的Al_2O_3-SiO_2系泡沫料浆的流变性能与固化特性

采用泡沫法结合凝胶注模工艺制备莫来石多孔轻质材料,通过在Al_2O_3-SiO_2系泡沫料浆中分别引入三醋酸甘油酯、聚酰亚胺、羟丙基纤维素作为胶凝剂,研究胶凝剂的种类对泡沫料浆流变性能的影响及其与固化时间的关系规律。结果表明:3种胶凝剂对泡沫料浆的流变性能影响程度不同。流变性能直接影响泡沫料浆的固化时间,提高泡沫料浆的触变性、黏度增长速率以及扩大线性黏弹性区间是缩短泡沫料浆固化时间的有效途径。3种胶凝剂中,三醋酸甘油酯固化效果最佳,以其作为胶凝剂的泡沫料浆初凝时间和固化时间均最短。     

Development of an accident duration prediction model on the Korean Freeway Systems

Since duration prediction is one of the most important steps in an accident management process, there have been several approaches developed for modeling accident duration. This paper presents a model for the purpose of accident duration prediction based on accurately recorded and large accident dataset from the Korean Freeway Systems. To develop the duration prediction model, this study utilizes the log-logistic accelerated failure time (AFT) metric model and a 2-year accident duration dataset from 2006 to 2007. Specifically, the 2006 dataset is utilized to develop the prediction model and then, the 2007 dataset was employed to test the temporal transferability of the 2006 model. Although the duration prediction model has limitations such as large prediction error due to the individual differences of the accident treatment teams in terms of clearing similar accidents, the results from the 2006 model yielded a reasonable prediction based on the mean absolute percentage error (MAPE) scale. Additionally, the results of the statistical test for temporal transferability indicated that the estimated parameters in the duration prediction model are stable over time. Thus, this temporal stability suggests that the model may have potential to be used as a basis for making rational diversion and dispatching decisions in the event of an accident. Ultimately, such information will beneficially help in mitigating traffic congestion due to accidents.     

Impulse response of an S-cone pathway in the aging visual system

Age-related changes in the temporal properties of an S-cone pathway were characterized by the psychophysical impulse-response function (IRF). Participants included 49 color-normal observers ranging in age from 16.8 to 86.3 years. A double-pulse method was used to measure the IRF with S-cone modulation at constant luminance. Stimuli were presented as a Gaussian patch (+/-1SD = 2.3 degrees ) in one of four quadrants around a central fixation cross on a CRT screen. The test stimulus was modulated from the equal-energy white of the background toward the short-wave spectrum locus. Each of the two pulses (6.67 ms) was separated by an interstimulus interval (ISI) from 20 to 720 ms. Chromatic detection thresholds were determined by a four-alternative forced-choice method with staircases for each ISI in one session. IRFs were calculated from the threshold data using a model with four parameters of an exponentially damped sine wave. S-cone IRFs have only an excitatory phase and a much longer time course compared with IRFs for luminance modulation measured with the same apparatus. The results demonstrated significant age-related losses in IRF amplitude, but the latency (time to peak) of the IRF was stable with age.     

Evolution of the characteristics of a field-electron emitter based on nitrocellulose-carbon nanotube composite

Characteristics of a field-electron emitter based on a nitrocelulose-multiwalled carbon nanotube composite have been studied. A new method of the recording and online processing of current-voltage (I–U) characteristics of multipoint field-electron emitters has been developed for monitoring the evolution of their properties. Using this method, we have (i) determined the dependences of the field enhancement factor and number of emission centers on the interelectrode distance, (ii) discovered hysteresis of the I–V curve related to variation of the amplitude of applied voltage pulses, and (iii) revealed the influence of the initial emission current level on the temporal evolution of emitter properties.     

煮制时间对绿豆中淀粉性质的影响及相关性分析

目的 探究绿豆煮制过程中淀粉含量及理化性质的变化规律,从而根据不同目的 选用最优煮制时间,且为绿豆煮制加工提供科学数据.方法 以明绿豆为主要原料,采用传统煮制方法,以10 min为间隔时间采样,进行淀粉含量和淀粉性质测定及相关性分析.结果 随着煮制时间的延长,绿豆中总淀粉含量和直/支链淀粉含量均呈下降趋势.溶解度在煮制30 min后呈上升趋势,在60 min时达最大;膨胀力呈下降趋势,煮制50 min后趋于稳定;糊透明度在煮制40 min后明显增大,在60 min时达最大;凝沉稳定性在煮制40 min后逐渐增强.由相关性分析结果可知,煮制时间与溶解度呈极显著正相关,与绿豆中总淀粉含量和膨胀力呈极显著负相关,与透光率呈显著正相关,与直/支链淀粉含量和凝沉体积呈显著负相关.结论 煮制时间是影响绿豆中淀粉含量和性质的主要因素,而淀粉含量则可以直接影响绿豆的膨胀力、透明度等理化性质.在绿豆食品加工过程中,可根据加工目的 选择不同的煮制时间.     

Design of Gamma Charts Based on Average Time to Signal

Gamma charts for time between events are very useful in the high‐quality processes, which monitor the time until the rth event. The average time to signal (ATS) is adopted to evaluate the performance of Gamma charts, because it reflects both the number and the sampling interval of samples inspected until an out‐of‐control signal occurs. An ATS‐unbiased design for Gamma charts with known parameters is proposed based on the hypothesis test of the scale parameter. For the phase I monitoring, a new ATS‐unbiased design with unknown parameters is developed, and a sequential sampling scheme is adopted to start process monitoring as soon as possible. Some specific guidelines to stop updating the control limits are suggested from the convergence of the width between control limits with different phase I sample sizes. Finally, a real example is illustrated to demonstrate the implementation of the proposed approach. Copyright © 2015 John Wiley & Sons, Ltd.