大功率APFC开关电源中的并联均流技术

本文在对APFC大功率高频开关电源研究的过程中,着重对开关管的并联均流技术进行了深入研究,并对一种新的并联均流技术进行了理论分析、模拟仿真,结合中功率(3KW)ZVT-APFC模块电路实验,探讨了这种并联均流技术应用在APFC电路中的设计方法.     

Human Interaction with Motion Planning Algorithm

This paper presents an interactive motion planning system to compute free collision motion in a numerical model. The system is based on interaction between a user and a motion planning algorithm. On one hand the user moves the object with an interactive device and on the other hand a motion planning algorithm searches a solution in the configuration space. The interaction aims at improving the guidance of an operator during a robot motion task in a virtual environment with the help of an automatic path planning algorithm. Existing works use a two-step decomposition which limits the interaction between the user and the ongoing process. We propose a modification of a classic motion planning method, the Rapidly-exploring Random Tree to build an Interactive-RRT. This method is based on exchanging pseudo-forces between the algorithm and the user, and on data gathering (labels) from the virtual scene. Examples are shown to illustrate the Interactive motion planning system with different interactive devices (space mouse and haptic arm). We analyze the influence of the user’s dexterity to find a solution depending on various parameters of the algorithm and we show how we can adapt these parameters to a user.     

更冷、更省、更安静——散热新技术前瞻

随着CPU频率的提高，核心的增加，其性能也在成倍的提升，然而，在享受产品强劲性能的同时，你是否也发现为了适应CPU日益增长的功率所带来的高发热量，散热器似乎不可避免地要变得庞大，发出更大的噪音、消耗更多的电能。有没有解决方法？目蓟比较困难，不过当本文介绍的散热新技术能全面应用的那一天，这些问题或许就迎刃而解了。     

薄壁圆筒谐振式液体密度传感器的设计

在对圆筒谐振子的数学模型计算和有限元分析的基础上,设计了一种新型的谐振式液体密度传感器.该传感器由双端固定的圆筒谐振子、自动增益和相位调节的测量控制电路、C8051F020单片机的信号处理系统组成,具有对压力变化不敏感和智能温度补偿的功能.实验结果表明,20℃时传感器系数为K0=-129.5668 kg/m3,K1=-0.253 5×106(kg/m3)/s,K2=0.623 9×1010 (kg/m3)/s2,在700～900 kg/m3的测量范围内,综合测量精度为0.1%.     

嵌入式光纤光栅传感器应力传递规律研究

从力学的观点,将被测对象混凝土构件和埋入其中的光纤光栅传感器看成是一种复合材料或复合体,首次将剪滞法理论(shear lag theory)应用于分析光栅传感器埋入混凝土构件时的应力传递规律,得到了光栅传感器的应力传递公式和应力传递系数.利用得到的光栅传感器的应力传递公式,计算了混凝土实验构件的应力变化情况,实验证明,理论计算结果和实测数据基本吻合.     

基于NEMS技术的硅基纳机电探针阵列器件研究

进行一种用于高密度存储的硅基纳机电探针阵列器件研究.并采用理论计算和有限元模拟相结合方法对器件进行了设计;使用先进的微纳加工工艺技术将压阻敏感器和电阻加热器集成到超薄悬臂梁-针尖结构纳机电探针阵列器件上,实现器件制作;随后,进行器件电热特性及其敏感特性测试,测试结果与模拟结果相吻合;借助于原子力学显微镜在聚合物有机薄膜上实现了数据写入,优化写入条件后,数据记录面密度达31.6 GB/in2.     

Hydrosonography as an alternative or supplement to endosonography in stomach carcinoma

This study examined the effect of mothers' exposure to the 1957 A2/Singapore influenza virus in the first, second, and third trimesters of pregnancy on the electrodermal activity of their 15-year-old offspring. The epidemic occurred during cold months of the year. The results show that maternal viral (and cold) exposure during all trimesters of pregnancy produced a lower frequency of nonspecific electrodermal responses and diminished responsivity to 75-db and 90-db tones as compared with the offspring of mothers who were not exposed. However, there was a critical effect of second trimester exposure as indicated by an increase in frequency of nonresponses to orienting tones. The findings are compared with those from an earlier study from Mauritius involving 3-year-old children in which the effects of exposure to the 1968 A2/Hong Kong virus were examined and in which the effect of could exposure could be examined separately because viral exposure occurred during the hot months.     

Differences in eicosanoid and cytokine production between injury/hemorrhage and bacteremic shock in the pig

The effect of melatonin on the gonadotropin-releasing-hormone (GnRH)-induced oscillatory rises in intracellular calcium concentration, [Ca2+]i, was studied in cultured cells from the anterior pituitary gland of 6- to 8-day-old rats. GnRH-induced [Ca2+]i oscillations were recorded indirectly by monitoring the activity of apamin-sensitive Ca(2+)-activated K+ channels using the perforated patch-clamp technique and fast microperfusion system. Melatonin (1 nM) inhibited the initiation or attenuated the amplitude of oscillatory current responses induced by 10 nM GnRH in 72% of GnRH-sensitive cells. Analysis of the melatonin dose-inhibition relationship showed that melatonin inhibited the initiation of [Ca2+]i oscillations with IC50 = 0.35 nM. In partially inhibited cells, melatonin reduced the GnRH-induced current amplitude by 55% on the average, prolonged the delay in onset of response to GnRH and decreased the frequency of oscillations. Once initiated by GnRH, the amplitude and frequency of oscillatory currents was inhibited by melatonin after a latency of 10-30 s. These effects of melatonin were fully reversible. After pretreatment of neonatal gonadotropes with pertussis toxin, no inhibition by melatonin was observed. The inhibitory effect of melatonin on initiation, amplitude and frequency of GnRH-induced oscillatory current persisted in the absence of external Ca2+. Melatonin alone did not induce any transmembrane current or membrane potential changes. These observations suggest that melatonin reduces GnRH-induced calcium mobilization from intracellular stores.     

Myocardial ischemia and reperfusion are associated with an increased stiffness of remote nonischemic myocardium

During and after an ischemic injury, maintenance and recovery of cardiac function may critically depend on remote nonischemic myocardium. Graded myocardial ischemia is associated with an approximately 50% increase in stiffness of nonischemic myocardium. We determined whether this increase in stiffness is unique to the ischemic period or persists during reperfusion. Ten anesthetized (isoflurane 1.0% vol/vol) open-chest dogs were instrumented to measure left ventricular pressure and dimensions (sonomicrometry) in ischemic and nonischemic myocardium. Regional chamber stiffness and myocardial stiffness were assessed using the end-diastolic pressure-length relationship which was modified by stepwise infusion and withdrawal of 200 mL of the animals' own blood during baseline, 45 min low flow ischemia (systolic bulge), and 60 min after the onset of reperfusion. In remote nonischemic myocardium, regional myocardial ischemia was associated with a significant (P < 0.05) increase in chamber stiffness (+44%) and myocardial stiffness (+48%). Sixty minutes after the onset of reperfusion, chamber stiffness (+54%, P < 0.05 versus baseline) and myocardial stiffness (+55%, P < 0.05 versus baseline) remained increased. Thus, the ischemia-induced increase in stiffness of remote nonischemic myocardium persists for at least 60 min after reperfusion.