环状压电超声电机的多频率驱动分析与实验

针对压电超声电机的多频率驱动问题进行研究,设计并制作了利用定子内圆周面驱动的环状压电超声电机,明确了利用行波驱动电机转子的机理。通过有限元计算给出了电机定子所用弯曲模态的振型与位移云图。以计算结果为基础,分析了电机所用的压电陶瓷片的极化分区与定子弯曲模态激发之间的关系,得出了所用的压电陶瓷片能够实现电机多频率转动的结论。完成了所研制的超声电机的多频率驱动实验。实验结果表明,电机能够实现在多频率点的转动。依据本文分析思路,可以对其他结构形式的超声电机的多频率驱动问题进行研究。     

直线电机抽油泵流场数值研究

将直线电机置于井下,直接驱动柱塞泵举升原油,有利于提高系统效率和节能。根据直线电机抽油泵结构,结合柱塞和阀球运动模型,运用动网格技术和自编程UDF模块对Fluent进行二次开发,实现了柱塞和阀球运动与流场的耦合求解。可以确定泵筒内任意计算时刻流场状态,揭示了柱塞往复运动过程中泵筒内部流场演化、阀球运动和流场特性。计算结果与实验结果吻合较好,为研究新型抽油泵提供了参考和依据。     

电机精密同步控制技术的研究与应用

提出一种新型的步进电机控制算法,该算法不采用传统的速度加位置的双闭环,而使用在速度比例微分(PD)的基础上再进行位置补偿控制。给出了算法设计的原理和公式,并且最终在ORMON的CP1H-XA40DT-D的可编程控制器(PLC)上实现。同时,通过对ORMON的NT5Z型触摸屏的编程,为操作人员提供了一个友好的人机界面,实现了复杂绕线工艺参数的方便修改,提高了劳动生产率,成为真正适用的可批量生产的产品。实践证明,在对步进电机的控制系统中,该方法使步进电机不会出现速度振荡现象,运行更平稳,控制精度也更高。     

水工混凝土裂缝的检测与处理

介绍浙江省新昌门溪水库水工混凝土裂缝的检测及处理方法.     

复合伺服液压系统在压力机的应用

针对传统压力机液压系统能耗较高等不足,采用二伺服泵及开关型电动阀通过PID控制器进行控制的复合伺服 液压系统,设计了新型压力机( press servo hybrid,PSH);进行了液压系统主要部件设计计算和选型;利用AMESim软件对 新系统与传统液压系统进行建模和仿真比较,结果表明新系统同样能满足按VOITH公司技术要求,能耗有非常显著的 降低。     

Shedding Some (More) Light in Bourdieu's Habitus and Doxa: A Socio-Phenomenological Approach

In this paper, I attempt to shed more light in Bourdieu's habitus and doxa, by drawing on phenomenological and Bourdieusian-based literature, social theory and some findings from sociological research. Despite the fact that there is a vast work concerning the examination of these two concepts, there are still some misunderstandings about them. For that reason, I have tried to draw a clearer picture of habitus, by linking it with phenomenological “being-in-the-world” and describing its elements. As for doxa, I discuss its conceptual relation with habitus and phenomenology's natural attitude. Also, attention is given to some aspects of both habitus and doxa, which have not addressed in detailed fashion yet, but they are nevertheless theoretically useful for empirical qualitative research.     

变极调速异步电动机

变极调速异步电动机是在电源频率保持不变时，利用改变定子绕组的接法，在一套统组中获得两种或两种以上的转速，这些转速既可以是倍极比，也可以是非倍极比．本文利用极幅调制与槽电势星形矢量的原理，设计出性能优良，结构简单的单绕组多速异步电动机．     

新型压力控制阀的研究

本文针对现有压力伺服阀的不足之处 ,利用毛细阻尼管的调压原理和滑阀阀芯的双自由度运动设计制造了一种新型差压式液压控制阀。该阀具有结构简单、抗污染能力强、成本低等特点 ,并能实现数字控制     

The Effect of Geographic Proximity to Unconventional Oil and Gas Development on Public Support for Hydraulic Fracturing

With the rapid growth of unconventional oil and natural gas development transforming the U.S. economic and physical landscape, social scientists have increasingly explored the spatial dynamics of public support for this issue—that is, whether people closer to unconventional oil and gas development are more supportive or more opposed. While theoretical frameworks like construal‐level theory and the “Not in My Backyard” (or NIMBY) moniker provide insight into these spatial dynamics, case studies in specific locations experiencing energy development reveal substantial variation in community responses. Larger‐scale studies exploring the link between proximity and support have been hampered by data quality and availability. We draw on a unique data set that includes geo‐coded data from national surveys (nine waves; n  = 19,098) and high‐resolution well location data to explore the relationship between proximity and both familiarity with and support for hydraulic fracturing. We use two different measures of proximity—respondent distance to the nearest well and the density of wells within a certain radius of the respondent's location. We find that both types of proximity to new development are linked to more familiarity with hydraulic fracturing, even after controlling for various individual and contextual factors, but only distance‐based proximity is linked to more support for the practice. When significant, these relationships are similar to or exceed the effects of race, income, gender, and age. We discuss the implications of these findings for effective risk communication as well as the importance of incorporating spatial analysis into public opinion research on perceptions of energy development.     

Safety Impacts of SUVs, Vans, and Pickup Trucks in Two-Vehicle Crashes

Policy makers, vehicle manufacturers, and consumers have shown growing concern about the relative safety of sport utility vehicles (SUVs), vans, pickups, and cars. Empirical analysis of real-world crashes is complicated by the possibility that apparent relationships between vehicle type and safety may be confounded by other factors, such as driver behavior and crash circumstances. This study compares different vehicle types with respect to their crashworthiness (self-protection) and aggressivity (risk to others) in crashes between two passenger vehicles. The U.S. Crashworthiness Data System is used to analyze detailed information on 6,481 drivers involved in crashes during 1993-1999. Logistic regression analysis is used to model the risk of serious injury or death to a driver, conditional on a crash occurring. Covariates include the body type of each vehicle in the crash; the driver's age, gender, and restraint use; and the configuration of the crash. A unique feature of this study is the use of "delta-v" to represent the joint effects of vehicle mass and crash severity. While estimated effects are somewhat sensitive to the injury severity level used as the outcome variable, SUVs, vans, and pickups appear to be more aggressive and may be more crashworthy than cars. Effects of pickups are most pronounced. Drivers in pickups face less risk of serious injury than car drivers (odds ratio [OR], 0.35; 95% confidence interval [CI], 0.20-0.60), and drivers who collide with pickups experience more than twice the risk than those who collide with a car (OR, 2.18; 95% CI, 1.03-4.62). While vehicle mass and crash severity contribute to the apparent crashworthiness and aggressivity of passenger vehicles, other vehicle characteristics associated with body type (e.g., the stiffness and height of the underlying structure of the vehicle) also influence safety risks.