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951.
S.M. KnupferA.M. Paradowska O. KirsteinA.J. Moore 《Journal of Materials Processing Technology》2012,212(1):90-99
In laser forming, thermally induced strains transverse to the laser scan line vary with depth in the material and contribute most significantly to the desired deformation. The through-thickness transverse residual strain distribution was measured by neutron diffraction in laser-formed low carbon steel and aluminium alloy specimens. The specimens were formed with a wide range of laser line energies covering the temperature gradient mechanism (TGM) and shortening or upsetting mechanism (SM), and for single and multi-pass forming (up to 3 laser passes). Below the saturation line energy where the TGM dominates, the gradient of the through-thickness strain distribution was found to increase with increasing line energy and number of laser passes; the gradient decreased again at line energies above the saturation line energy where the efficiency of the TGM decreases. Iterative laser forming can be applied to reduce weld-induced distortions. The peak longitudinal strain measured in the weld seam of a specimen that had been straightened by iterative laser forming was also significantly reduced. 相似文献
952.
Due to comfort, convenience, and flexibility, taxis have become increasingly more prevalent in China, especially in large cities. However, many violations and road crashes that occurred frequently were related to taxi drivers. This study aimed to investigate differences in driving performance between taxi drivers and non-professional drivers from the perspectives of red-light running violation and potential crash involvement based on a driving simulation experiment. Two typical scenarios were established in a driving simulator, which includes the red-light running violation scenario and the crash avoidance scenario. There were 49 participants, including 23 taxi drivers (14 males and 9 females) and 26 non-professional drivers (13 males and 13 females) recruited for this experiment. The driving simulation experiment results indicated that non-professional drivers paid more attention to red-light running violations in comparison to taxi drivers who had a higher probability of red-light running violation. Furthermore, it was found that taxi drivers were more inclined to turn the steering wheel in an attempt to avoid a potential collision and non-professional drivers had more abrupt deceleration behaviors when facing a potential crash. Moreover, the experiment results showed that taxi drivers had a smaller crash rate compared to non-professional drivers and had a better performance in terms of crash avoidance at the intersection. 相似文献
953.
NFPA 18 is used as a standard for the performance evaluation of wetting agents used in fire fighting. The performance evaluation of the wetting agent involves three tests: a wood crib fire test, a deep-seated fire test, and a wood fiberboard penetration test. In this study, a scale model experimental device, which can evaluate both extinguishing performance and penetration performance at once, was prepared to evaluate the performance of a wetting agent in various types of porous materials. Then, this result was compared with the results of an NFPA 18 test to validate the result of the novel test. Three types of commercial fire-fighting solutions and water were used as extinguishing agents in the experiment. The experimental materials used in this performance evaluation were wood crib which is used in the existing class A fire test and wood flour from New Zealand pine trees which has 75% of the domestic market share in wood cribs. The discrimination of the study result used in this study to determine penetration and extinguishing performances was found to be equivalent to the results of the NFPA18 test. Moreover, the study established the validity of the scale model that could check on both penetration and extinguishing performance, permitting a more economical and efficient performance evaluation of wetting agents. 相似文献
954.
955.
The objective of this work is to study the cryogenic sheet metal forming behaviour of precipitation hardening AW-6016-T4. In this regard, the flow curves and forming limit curves were obtained by tension and Nakazima experimental testing methods in the temperature ranges from ?196 to 25 °C. It was found that strength and elongation increase with decreasing temperature. Small but perceived differences between microstructure of the material deformed at the room and cryogenic temperatures respectively were identified by electron backscatter diffraction (EBSD) analysis. However, no significant difference in the precipitation kinetics during continuous heating in the DSC has been observed. This study has demonstrated the potential of cryogenic forming by manufacturing a B-pillar part with 8 mm depth of side design element as compared to 6 mm at room temperature. 相似文献
956.
《矿业科学技术学报(英文版)》2017,27(6):1057-1063
In the present investigation, an attempt is made to examine the interdependencies among the operating parameters and their interactional effect on the separation performance of a water-only cyclone for treating ferruginous chromite fines. Statistically designed experiments are carried out, and empirical models are developed for the critical response parameters, i,e., yield(%) to underflow, grade(%Cr_2O_3 and%SiO_2)and Cr:Fe ratio of the underflow stream. Further, using these empirical models, operating regime of the process parameters is optimized to obtain the peak performance of water-only cyclone. Also, efforts are made to validate the prediction models with the experimental results. 相似文献
957.
Talkachou Dzianis 《测试科学与仪器》2016,(3):272-278
防抱死制动系统(Antilock braking system,ABS)是通过车轮角加速度与阈限值的比较进行制动力控制.这种系统的优势是只需角速度传感器信号就足够了;缺点是工作时会出现制动压力连续的超调,使车轮从抱死模式到滚动模式来回转换,这样制动器不能产生在当前道路状况下最大可能的制动力矩值.增加制动效率的构思是制动压力增加的强度取决于当前道路状况,但面临的问题是制动器产生的制动力矩值、当前道路状况和牵引系数值是未知数.本文通过建立三层神经网络模型来识别和获取这些参数,并在设计的随机路面上进行仿真实验,验证了所设计控制器工作的准确性. 相似文献
958.
959.
《国际设备工程与管理》2012,(3):145-152
In this paper, the recent achievements in the advanced manufacturing technology are presented. The laser forming of sheet metals, rapid forming, precision casting, precision forging, inertia friction welding are developed for aviation and aerospace industries. The main topics including the advantages, principle of manufacturing, processing parameters and control, typical processing applied in practice and typical work-pieces for those advanced manufacturing technologies are summarized. 相似文献
960.
LinkedIn, with over 1.5 million Groups, has become a popular place for business employees to create private groups to exchange information and communicate. Recent research on social networking sites (SNSs) has widely explored the phenomenon and its positive effects on firms. However, social networking's negative effects on information security were not adequately addressed. Supported by the credibility, persuasion and motivation theories, we conducted 1) a field experiment, demonstrating how sensitive organizational data can be exploited, followed by 2) a qualitative study of employees engaged in SNSs activities; and 3) interviews with Chief Information Security Officers (CISOs). Our research has resulted in four main findings: 1) employees are easily deceived and susceptible to victimization on SNSs where contextual elements provide psychological triggers to attackers; 2) organizations lack mechanisms to control SNS online security threats, 3) companies need to strengthen their information security policies related to SNSs, where stronger employee identification and authentication is needed, and 4) SNSs have become important security holes where, with the use of social engineering techniques, malicious attacks are easily facilitated. 相似文献