Off-campus but hands-on: Mail out practicals with synchronous online activities during COVID-19

This paper discusses alternatives to on-campus teaching laboratories, to allow for hands-on learning for remote students. Wholly online practical equivalents have become increasingly popular post-COVID (online simulations or processing experimental data only) which can offer lower overheads and easy scale-up, but often miss hands-on learning outcomes. This paper reviews opportunities for mail-out practicals, where the equipment is delivered to students’ homes, combined with live synchronous learning activities via video streaming or online software. The combination of mail-out experimental kits plus synchronous interactive learning activities creates a host of new opportunities for teaching to remote students. Complimentary online teaching activities could include direct interaction with teaching staff or other students, but it can also be real-time simulations of their experiment. The paper presents a specific case study for a 2nd year undergraduate chemical engineering heat exchanger practical, that facilitated hands-on practical learning with synchronous online activities during COVID-19 campus closure. The paper uses a mixed methods approach in a 2 year study to assess student learning outcomes.     

挤压力对晶体生长速度及枝晶间距的影响

研究了挤压铸造时挤压力对宏观晶体生长速度的影响，给出了晶体生长速度表达式。结果表明：挤压力对合金宏观晶体生长速度的影响除与合金成分有关外，在某些挤压条件下，当形核率的增加幅度超过长大速度时，则挤压力可使宏观晶粒细化；反之，会使宏观晶粒变粗。随着挤压力的提高，合金凝固速度加快，一次枝晶间距和二次枝晶间距都随之减小，从而细化了树枝晶。     

一对有孔距要求的异型孔加工

介绍了加工有孔距的两异型孔的工艺,通过冲压加工,圆满地解决了加工、装配过程中出现的种种问题,达到了使用要求。     

LMD及马氏距离敏感阈值的滚动轴承故障诊断

针对滚动轴承非平稳性的振动信号,提出了基于局部均值分解(Local Mean Decomposition,LMD)及马氏距离敏感阈值的滚动轴承故障诊断方法。首先,对振动信号进行LMD分解,获得一系列乘积函数(Production Function,PF),有的PF分量包含的故障信息多,有的包含的少,为此采用K-L散度法提取出主要PF分量;计算主要PF分量的时域参数指标,将其组合成特征向量,根据马氏距离提出马氏距离敏感阈值来表征不同的故障状态,取多组正常信号的特征向量均值作为标准特征向量,计算未知特征向量与标准特征向量的马氏距离敏感阈值,从而对其故障状态进行识别。试验结果表明,在不同转速下,该方法能够有效的对滚动轴承故障进行识别,且效果较EMD方法好。     

一种新型四自由度混联机器人的设计与分析

通过对机器人串并联结构的分析,设计了一种新型的四自由度混联机器人,克服了同类机器人腕部俯仰电机不容易被安放在机架上的困难。将控制电机都设计在机架上,大小臂电机不同轴,腕部俯仰电机与大臂电机同轴,通过一种双平行四边形机构实现腕部俯仰动作,结构简单、俯仰角容易控制,俯仰运动不受大小臂运动的影响而发生牵连运动。腕部俯仰驱动的传动件为连杆,与大小臂以并联的形式进行连接,对机器人模型进行静力学分析,分析结果表明这种腕部俯仰机构能够提高机械臂的抗弯刚度。     

柱塞斜槽工作棱边展开图的应用与试验验证

利用CAD设计将柱塞斜槽工作棱边逼真展开,再结合计算确定柱塞斜槽上各工况的供油位置,进而验证柱塞设计、喷油泵供停油的可靠性以及拉杆位移及调速器相关结构参数的正确性,将原来复杂的理论计算过程变得直观、简便又精确。通过解决问题的实例分析了柱塞斜槽工作棱边展开图的应用,并试验验证了柱塞斜槽展开图的实用性与准确性。     

Application of distance sampling techniques for diving ducks on Lake St. Clair and western Lake Erie

Lake St. Clair and western Lake Erie are important migration staging areas for diving ducks including canvasbacks (Aythya valisineria), redheads (Aythya americana), and lesser and greater scaup (Aythya affinis and Aythya marila). Starting in 1983, the Michigan Department of Natural Resources (MDNR) attempted to census diving ducks on the United States portion of Lake St. Clair throughout autumn migration; however, in 2010 the MDNR expanded the traditionally surveyed area to include all of Lake St. Clair and a portion of western Lake Erie. The idea of achieving a census over the expanded study area was unrealistic, and instead distance sampling techniques were adopted in an effort to generate statistically valid estimates of detection probabilities and abundances for diving ducks during spring and autumn migration. We found distance sampling techniques to be a viable option for estimating diving duck abundance as long as flock size is accounted for as a covariate affecting the detection function. Diving ducks were generally more abundant on our study area during autumn migration with a mean of 306,327 ducks/survey (SE = 40,729) compared to an average spring abundance of 91,053 ducks/survey (SE = 19,175). Peak abundance occurred on 20 November 2012 with an estimated 596,335 diving ducks on Lake St. Clair and western Lake Erie. Ultimately, our methodology could be used to establish long-term, standardized data collection techniques and applied to conservation planning for waterfowl in the Great Lakes region.     

Line transect distance sampling in aerial surveys for double-crested cormorants in coastal regions of Lake Huron

Line transect distance sampling was employed in aerial surveys of double-crested cormorants (Phalacrocorax auritus) along the coasts of Georgian Bay and the North Channel, Lake Huron. A double-observer method was used to estimate detection probability near the transect line (g(0) = 0.724). Detection of cormorants was not consistent but varied based on group size, location (water, land, flying), and season. Probability of detection in the area covered by the survey was often below 0.5. Incorporating both lack of detection on the flight line along with lack of detection over the covered area inherent in distance sampling provided defensible density estimates of free-ranging double-crested cormorants. Most cormorants were detected loafing on shore (land) among the many islands defining this area of the Lake Huron coast. Land detections exceeded the combined detections of birds on the water and flying. Density in 2004 ranged from a peak of 2.30 cormorants per km² (95% CI = 1.72–3.03) in late July to 1.21 cormorants per km² (95% CI = 0.78–1.70) in late August in the sampled areas extending from shore to approximately 20 km offshore. Aerial surveys employing distance sampling can be useful tools in monitoring the distribution and abundance of free-ranging double-crested cormorants and other waterbirds in the Laurentian Great Lakes.     

Vehicle tests of a longitudinal control law for application to stop-and-go cruise control

This paper presents the implementation and vehicle tests of a vehicle longitudinal control scheme for Stop and Go cruise control. The control scheme consists of a vehicle-to-vehicle distance control algorithm and throttle/brake control algorithm for acceleration tracking. The desired acceleration of a vehicle for vehicle-to-vehicle distance control has been designed using Linear Quadratic optimal control theory. Performance of the control algorithm has been investigated via vehicle tests. A millimeter wave radar sensor has been used for distance measurement. A stepper motor and an electronic vacuum booster have been used for throttle/ brake actuators, respectively. It has been shown that the proposed control algorithm can provide satisfactory performance.     

远程教学网格门户的设计

远程教学网格是网格计算技术在远程教育中的应用。文章从需求分析、体系结构、功能、用户界面、开发工具的选用等多个方面，阐述了远程教学网格门户的设计思想。