New geometric design consistency model based on operating speed profiles for road safety evaluation

To assist in the on-going effort to reduce road fatalities as much as possible, this paper presents a new methodology to evaluate road safety in both the design and redesign stages of two-lane rural highways. This methodology is based on the analysis of road geometric design consistency, a value which will be a surrogate measure of the safety level of the two-lane rural road segment. The consistency model presented in this paper is based on the consideration of continuous operating speed profiles. The models used for their construction were obtained by using an innovative GPS-data collection method that is based on continuous operating speed profiles recorded from individual drivers. This new methodology allowed the researchers to observe the actual behavior of drivers and to develop more accurate operating speed models than was previously possible with spot-speed data collection, thereby enabling a more accurate approximation to the real phenomenon and thus a better consistency measurement.     

Investigation of a model of a physical experiment to estimate the retardation of gravitational potential

A model of a physical experiment to estimate the speed of gravitational interaction from observations of the geocentric orbits of an artificial satellite in the framework of the consistent Lagrange formalism of the retarded-potential hypothesis is considered. It is shown that it is mathematically correct to postulate the corresponding inverse problem, and results are presented of its numerical investigation, including local estimates of the accuracy of the solution. __________ Translated from Izmeritel’naya Tekhnika, No. 8, pp. 3–5, August, 2007.     

齿轮拍击系统的动力响应

在考虑不平衡质量，主动轴转速波动及齿侧间隙的情况下，建立了单级齿轮传动系统的拍击振动模型，通过数值仿真，得到了系统的时间响应，根据时间响应及其相图可知，在拍击过程中，齿面碰撞，齿背碰撞及齿轮正常啮合现象交替出现，在某一转速下，拍击周期等于激励周期，在一个激励周期中，拍击过程中只出现一次，在另一转速下，出现二周期的拍击特性，在一个激励周期中，出现更多的拍击过程。在不同转速下，拍击振动的幅值有很大差异，当拍击次数增加，或出现齿背碰撞时，系统的动力学特性变得较复杂。     

头戴式耳机跌落冲击的仿真分析与实验

目的对跌落测试中的破坏风险进行预测和改进,从而提升设计效率。方法基于Abaqus,对头戴式耳机进行整机跌落仿真分析,对其在规定高度下撞击地面的整机结构耐冲击性进行研究,考虑到材料的非线性和应变率效应,采用质量缩放、应力包络图等技术来提升仿真效率,并将高速摄影下的实际跌落过程与仿真结果进行对比。结果数值仿真预测了产品在跌落过程中的破坏风险,并对优化后的设计进行了验证,与实验结果高度吻合。结论在头戴式耳机一类消费电子产品的设计中,合理利用数值仿真,可有效缩短产品研发周期,降低研发成本,提升产品质量,从而提高产品的市场竞争力。     

Studying the effect of different operation parameters on the grinding energy efficiency in laboratory stirred mill

In this study, considering different operational parameters for stirred media mill, change in specific energy was compared to the change in R_x values, i.e. the cumulative weight of the material undersized to a specific sieve. R values, namely R₃₈, R₇₅, R₁₀₆, were measured before and after grinding in stirred mill. The change in R_x (ΔR_x, %) values were calculated and they were used to evaluate the certain unit of effectual energy (Ecb). This abovementioned calculation is performed by proportioning the Specific Energy (SE) to ΔR_x values. The effectual part of SE is considered to be the ratio of the energy needed only for size reduction in grinding and it should be related to the ΔR_x. The relative Ecb ratios of different grinding conditions give the relative specific energy efficiency ratio (SEe). The relative specific energy efficiency ratio is inversely proportional to specific grinding parameters and ground product particle sizes. The relative specific energy efficiency can be considered as the relative amount of energy for various grinding conditions. The variation between relative energy amount and the previously specified particle size provides a realistic comparison of different grinding parameters. The abovementioned variation could be employed to understand the resistance particle size which is a new concept to describe the particle size at which the maximum effectual SE is directly used. In the context of this study, it was aimed to figure out the interrelation between specific energy efficiency and PSD variation along with the resistance particle size.     

Modeling drivers’ speed selection as a trade-off behavior

This paper proposes a new model of driver-preferred speeds derived from the assumption that drivers trade-off a portion of their safety for a time gain. The risk of receiving a ticket for speeding is also considered. A trip disutility concept is selected to combine the three components of speed choice (safety, time, and enforcement). The perceived crash risk and speed enforcement are considered as speed deterrents while the perceived value of a time gain is considered as a speed enticement. According to this concept, speeds that minimize the perceived trip disutility are preferred by drivers. The modeled trade-off behavior does not have to be fully rational since it is affected by drivers’ preferences and their ability to perceive the risk. As such, the proposed framework follows the concept of bound rationality.The attractiveness of the model lies in its parameters being estimable with the observed preferred speeds and then interpretable as the factors of risk perception, the subjective value of time, and the perceived risk of speed enforcement. The proposed method may successfully supplement behavioral studies based on a driver survey.The study focuses on four-lane rural and suburban roads in Indiana, USA. The behavior of two types of drivers (trucks and cars) is modeled. The selection of test sites was such that the roads and other local characteristics varied across the studied sites while the population of drivers could be assumed as the same. The density of intersections, land development along the road, and the presence of sidewalks were the identified prominent risk perception factors. Another interesting finding is that the speed limit seems to encourage slow drivers to drive faster and fast drivers to drive slower.     

Simulation of strength difference in elasto‐plasticity for adhesive materials

Experimental evidence of certain adhesive materials reveals elastic strains, plastic strains and hardening. Furthermore, a pronounced strength difference effect between tension, torsion or combined loading is observed. For simulation of these phenomena, a yield function dependent on the first and second basic invariants of the related stress tensor in the framework of elasto‐plasticity is used in this work. A plastic potential with the same mathematical structure is introduced to formulate the evolution equation for the inelastic strains. Furthermore, thermodynamic consistency of the model equations is considered, thus rendering some restrictions on the material parameters. For evolution of the strain like internal variable, two cases are considered, and the consequences on the thermodynamic consistency and the numerical implementation are extensively discussed. The resulting evolution equations are integrated with an implicit Euler scheme. In particular, the reduction of the resulting local problem is performed, and for the finite‐element equilibrium iteration, the algorithmic tangent operator is derived. Two examples are presented. The first example demonstrates the capability of the model equations to simulate the yield strength difference between tension and torsion for the adhesive material Betamate 1496. A second example investigates the deformation evolution of a compact tension specimen with an adhesive zone. Copyright © 2005 John Wiley & Sons, Ltd.     

A broadband analog-to-digital converter of sinusoidal voltages

A block diagram and an algorithm of the operation of a broadband analog-to-digital converter of sinusoidal voltages are presented. The choice of the parameters is considered. Estimates of the speed of response are obtained. __________ Translated from Izmeritel’naya Tekhnika, No. 3, pp. 37–40, March, 2008.     

非参数自回归函数的有限元估计及其收敛速度

针对局部方法不能给出所拟合模型的简单的显式表达式,而且拟合和预报的计算量较大,本文考虑一种估计非参数自回归函数的全局有限元方法。该方法不但能克服上述局部方法之不足,而且在一定情形下优于多项式样条方法。在α-混合条件下得出了非参数自回归函数有限元估计的收敛速度,同时给出了利用AIC准则自动选择结点个数的数据追赶法,模拟算例说明了有限元估计方法的可行性。     

裂纹非线性呼吸行为对转子临界转速的影响

为了研究复杂涡动引起的裂纹非线性呼吸行为对转子临界转速的影响,构建了带横向裂纹Jeffcott转子的通用运动方程,利用新建运动方程对临界转速附近裂纹转子的稳态响应进行了数值研究。发现裂纹的非线性呼吸行为对转子不但具有增强稳定性的作用(与开裂纹转子相比),而且在一定条件下具有降低振动响应的作用(与无裂纹转子相比)。与无裂纹转子相似,稳定的裂纹转子的临界转速等于响应振幅最大且重心转向约90°对应的转速。裂纹转子的临界转速值随不平衡量方位角在开裂纹和闭裂纹转子固有频率之间变化。在转子实验台上进行了裂纹转子通过临界转速的实验验证,观察数据支持理论研究结果。     

瓦楞纸横切机控制系统建模

通过对计算机控制系统和机械传动系统的分析,指出对于小负载的传动系统,其飞轮转矩可以忽略负载的影响;可以把变频调速器和异步交流电机认为是一个比例积分环节;在电机的转差率较小的某个转速下,电机转矩与电源频率成正比.在此基础上提出了瓦楞纸横切机控制系统的数学模型,并验证了这类系统采用PI控制算法可以得到较好的控制效果.     

Driving simulator for speed research on two-lane rural roads

The paper reports on a validation study of the interactive fixed-base driving simulator of Inter-University Research Center for Road Safety (CRISS) that was effectuated in order to verify the CRISS driving simulator's usefulness at a tool for speed research on two-lane rural roads. Speeds were recorded at eleven measurement sites with different alignment configurations on a two-lane rural road near Rome. The real world was reproduced in the CRISS driving simulator. Forty drivers drove the simulator. The results of the comparative and statistical analysis established the relative validity and also revealed that absolute validity was obtained in nine measurements sites. Only in two non-demanding configurations, were the speeds in simulator significantly higher than those recorded in the field. In these sites the mean speed in simulator was equal to or greater than 94 km/h. For these configurations, the higher speeds recorded in simulator appeared to stem from the different risk perception on the simulated road as opposed to that on the real road. The study's results should be considered for driving speed behavior research, in which simulator equipment with similar features of the CRISS driving simulator is used.     

一种用于电子雷管的电点火头的研究?

针对电点火头发火一致性差而影响电子雷管精度的问题,设计了点火头发火电压、发火时间的测试电路系统,研究了LDNP(二硝基酚铅)系不同桥丝直径的点火头发火电压和发火时间的一致性。结果表明:在一定范围内,该点火头发火电压、发火时间及发火时间标准偏差随桥丝直径的减小而减小;当桥丝直径减小至16μm时,发火电压波动较大,出现瞎火;18μm桥丝直径的点火头,其发火电压一致性较好,其发火时间标准偏差较小,能满足电子雷管性能的要求。     

Performance increase in turbomolecular pumps with curved type blades

Mostly, flat-type blades are used in the turbomolecular pumps in both rotor and stator sections. In this study, performance characteristics of the turbomolecular pumps consist of one rotor or rotor-stator pair with flat-type blades is calculated in different flow regimes. Next, the same calculations are realized for the curved-type blades in dissimilar geometries. Following, these performance characteristics are compared to find out which combination is the most efficient in terms of maximum pumping speed and maximum compression ratio. In case of turbomolecular pump consists of only one rotor, flat blades give the best performance. However in rotor-stator pairs, the performance of the flat-type only blades is surpassed by a combination of rotor with flat-type blades and stator with curved-type blades. Consequently, it is concluded that curved-type blades should also be considered in stator sections in addition to the flat-type blades in order to increase the performance of the multi-stage turbomolecular pumps.     

组合热膜探头在气体流速测量中的应用

介绍了一种用于测量气体流速的组合热膜探头,并对组合热膜探头的温度特性以及温度补偿性能进行了实验研究.实验结果表明,组合热膜探头在微小流速测量中具有较高的灵敏度,可以弥补毕托管在低速情况下测量误差较大的缺陷,且具有较好的一致性。     

标准一致性程度研究

本文对标准"一致性"的定义、内涵进行深入分析,对标准一致性的模型构建、判定方法等主要问题进行研究.建议在我国推行标准一致性程度评估制度,促进我国标准的国际化,促进标准化工作发展.     

A Microwave–Ultrasonic Cell for Sound-Speed Measurements in Liquids

In this work preliminary results obtained in developing a prototype cylindrical ultrasonic cell designed to apply a microwave resonance technique to the determination of its internal dimensions are described. Since the apparatus is intended for speed-of-sound measurements in pressurized liquid-phase media, the cell design is such that a double reflector pulse-echo technique can be used for time-of-flight measurements. The main absorption and dispersion effects that influence the acoustic measurement in this interferometer-like configuration and the values of the corresponding corrections are considered and discussed. The performance of the experimental apparatus and method in terms of achievable precision and accuracy was tested by measuring the speed of sound in water on a single isotherm at 325 K between 0.1 and 90 MPa. Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A.     

A comparison of signal consistency of common ultrasonic couplants used in the inspection of composite structures

To conduct acousto-ultrasonic tests, the transducers should to be coupled to the structure under consideration with couplants that are generally recommended by the equipment manufacturers. Experiments with several ultrasonic couplants have revealed that one of the factors influencing the repeatability of the results is the type used and that for certain couplants a settling time is required. In this paper a comparison of the signal consistency of common ultrasonic couplants is detailed. The aim of this study was to select the couplant that produces the most repeatable results.     

考虑结构柔性的多级齿轮箱变速过程动态特性研究

为了满足齿轮箱在变速过程中的分析需求,在集中参数/有限元法基础上提出一种适合变速过程分析且考虑结构柔性的多级齿轮箱耦合动力学建模方法.为验证所提方法的有效性,以某型直升机主减速器为研究对象,构建其耦合动力学模型;模型中考虑了传动轴和箱体结构的柔性,并将齿轮时变啮合刚度和综合啮合误差表示为齿轮角位移的周期函数.研究了多级...     

燃气轮机转子系统典型振动特性试验研究

搭建气体轴承支撑的微型燃气轮机发电机试验装置,试验呈现微型燃气轮机发电机气体轴承-转子系统升速过程典型区域振动特征,并基于试验数据关联分析振动参数与燃气轮机运行参数、气体轴承的关键参数之间的耦合关系,结果表明:压气机出口压力波动对转子轴向振动影响较大;微型燃气轮机转子径向振动受点火压力波动、主燃料燃烧压力波动以及压气机...