Frictionally excited thermoelastic instability in disc brakes—Transient problem in the full contact regime

Exceeding the critical sliding velocity in disc brakes can cause unwanted forming of hot spots, non-uniform distribution of contact pressure, vibration, and also, in many cases, permanent damage of the disc. Consequently, in the last decade, a great deal of consideration has been given to modeling methods of thermoelastic instability (TEI), which leads to these effects. Models based on the finite element method are also being developed in addition to the analytical approach.The analytical model of TEI development described in the paper by Lee and Barber [Frictionally excited thermoelastic instability in automotive disk brakes. ASME Journal of Tribology 1993;115:607-14] has been expanded in the presented work. Specific attention was given to the modification of their model, to catch the fact that the arc length of pads is less than the circumference of the disc, and to the development of temperature perturbation amplitude in the early stage of breaking, when pads are in the full contact with the disc. A way is proposed how to take into account both of the initial non-flatness of the disc friction surface and change of the perturbation shape inside the disc in the course of braking.     

风景名胜区总体规划编制的新形势与变革趋向探讨

风景名胜区总体规划是管理的重要抓手,在当前自然保护地体系改革的新时期,风景名胜区面临新的形势要求,为进一步管理好风景名胜区,风景名胜区总体规划编制导向亟须明确。基于风景名胜区的突出特色、风景名胜区总体规划的核心要求,融合新时代发展形势,认为风景名胜区总体规划未来在延续综合性规划特点的基础上,应深化生态保护内容,强化历史文化保护传承,加强人为活动管控以促进人与自然和谐共生,重视其范围研究以解决历史遗留问题,精准空间落位以纳入“一张图”管理,精简实施性弱的内容并突出规划管理重点,捋顺重大建设工程项目与总体规划的关系以契合发展实际。以此期望今后风景名胜区总体规划编制能够守正创新,更加符合时代要求,更加适应实际需求。     

北京飞云瀑景点崩塌地质灾害分析及防治方法研究

近15年来,北京飞云瀑景点附近发生过2次大规模崩塌,崩塌堆积岩块体积累计达450 m3,崩塌岩块已滚落覆盖至景区小路。经勘查,确定了1处危岩体及1处危岩带,该危岩体及危岩带对本景点的正常观赏及过往游人构成极大威胁。本文对该景点的崩塌地质灾害地质特征进行了简要介绍;对地质灾害成因、自然发展趋势等进行了初步探讨;对危岩体(带)的稳定性进行了计算、分析及评价;对可能采用的治理方法进行了比选分析。为了最大程度地保护景观资源,最终选择了以避让为主的治理措施,并对选定的治理方案及计算进行了阐述。     

转型背景下的太湖风景名胜区经济发展引导研究

我国经济社会发展已经进入转型期,将对风景名胜区发展提出新的要求,研究长三角经济腹地由多个景区组成的太湖风景名胜区的经济转型路径更具有代表性与现实意义。首先论述了区域发展转型的新趋势及转型背景下太湖风景名胜区经济发展中资源保护与利用的思路;其次,针对区内经济发展存在的问题,研究各景区经济发展模式、经济结构优化与产业发展方向及产业空间布局引导等方面的内容;最后,提出促进太湖风景名胜区经济合理发展的措施建议。     

我国城市湖泊风景区发展状况及规划设想

通过规划设计,引导城市湖泊风景区与现代城市亲和,要使其功能满足城市居民的需要,避免城市化给风景区带来破坏,使城市湖泊风景区发挥其生态优势,促进城市和谐发展。     

双光斑重叠式PSD空间点位测量系统研究

针对空间点位测量的问题,设计了一种新型双光斑重叠式PSD空间点位测量系统。构建了测量系统的测量平台和运动控制平台,并将光电位敏传感器PSD作为测量系统测头上的靶标,形成了空间测量三角形,采用逐次逼近算法,使两个光斑在PSD上轮流交替跟踪,实现了测量系统的自动跟踪,并利用PSD对于光斑重心采集的原理,判断两光斑重合情况,进行了空间点位信息的采集测量。以某型航空发动机8级涡轮转子叶片为测量对象,用三坐标测量机和本测量系统分别对其进行了测量对比试验。研究结果表明,测量系统对距离测量系统1.5 m远处,对目标点的测量偏差为亚mm级,正向偏差维持在0.4 mm以内,负向偏差维持在-0.25 mm以内。     

人、佛、日的契合——福州琅岐旅游度假区白云山景区规划设计构想

根据白云山景区的地域特征和现状，在规划设计中以生态设计为基础，充分挖掘“可意象性”元素，突出场地文脉的继续和再生，以期取得较为理想的规划设计效果，即建设一个人、佛、日（自然）契合的特色游览胜地。     

异步触发CCD摄像机电子快门的预测方法和实现

用激光回波脉冲控制电子快门来操纵摄像机的曝光时间，是抑制背景噪声的一种有效方法。提出了异步触发摄像机电子快门的预测方法，并将它应用在激光光斑的捕捉和测量中，提高了光斑图像的信噪比。该方法适宜 和于测量经过编码后的远距离激光脉冲光斑，为应用电视摄像机捕捉有规律的瞬态存在的目标提供了一个途径。     

加热对竖置平板水边界层影响的实验研究

本文用流场显示，电视录像与测量局部摩擦阻力同时进行的方法，研究了加热对竖置平板水边界层流态及摩擦阻力的影响，实验发现在流场湍度１％的水洞中，模型前部壁面的加热有效地延迟了水边界层的转捩，延长了层流区长度，相应地斑生成频率下降，处于转捩区的测力板上的平均摩擦阻力明显下降，处于层流区测力板上的摩阻略有减小，而处于湍流区侧力板上的摩阻略有增大，实验中还观察了模型头部加热引起层流分离现象。     

Use of liquid-crystal thermography for defect location on semiconductor devices

Hot-spot detection, a thermographic technique with liquid crystals, marks hot regions on a surface. The use of this highly sensitive method in failure analysis of integrated devices allows the detection of points on a chip where electrical power is converted into heat. Points such as these are often indicative of a fault, e.g. a leakage path or an increase in transfer resistance. The technique is based on the birefringence of a liquid crystal (LC) in the anisotropic state below the clearing temperature (T_c). Above this temperature, in the isotropic state, the effect disappears. The device under test, covered with the LC, is observed below the clearing point in polarized light with a crossed polarizer and analyser. Owing to the optical rotation of the anisotropic LC the image is bright. At hot spots the LC changes to the isotropic state and a dark spot is produced. A decisive factor for the thermal resolution of the technique is the precise temperature adjustment of the tested device. With lateral resolution of some tenths of a μ-m it is still possible to detect current paths with dissipation of 50 to 500μW. The sensitivity can be increased further. Square-wave pulses of selectable voltage, frequency and duty cycle are used to drive the test item. Four examples from failure analysis demonstrate the possibilities of using hot-spot thermography, the main features of which are speed, uncomplicated handling and depth of information.