基于混杂系统DC-DC变换器的永磁风电并网系统直流母线电压稳定控制

为了提高基于固态变压器的永磁风电并网系统中直流母线电压的稳定性,在低压直流侧,通过双向DC-DC加入超级电容器。文章基于Boost电路建立混杂系统模型,引入类滑模控制策略,利用超级电容器的快速充放电特性,提高直流电压的稳定性。仿真研究表明,在风速改变和电网电压跌落两种工况下,直流侧电压波动、超级电容器充放电电压和充放电电流均变小。该方案可以快速准确地抑制直流母线电压波动,改善并网风力发电机组的电能质量和稳定性。     

Inpatient Diabetology

Tight glycemic control is now an imperative of outpatient diabetes care. The inpatient arena remains under the influence of an ineffective paradigm characterized by tolerance for hyperglycemia and a reluctance to use insulin intensively. This article is a call to action against the lip service paid to inpatient diabetes care. The compelling in vitro and in vivo evidence for the benefit of intensive insulin-mediated glycemic control is summarized. The linchpin of current inpatient care is a commonly used insulin sliding scale. This autopilot approach as the sole mode of treatment for inpatient hyperglycemia has been strongly condemned. Nevertheless, it continues to survive. The evidence supports the compelling argument that the adverse effect of hyperglycemia on hospital length of stay, morbidity, and mortality is substantial. Clinicians, nurses, administrators, and insurers ought to look critically at the prevailing paradigm and spearhead the much-needed revolution in inpatient diabetology. The issue of glycemic targets, the need for noninvasive blood glucose monitoring, and the role of nursing staff in this revolution are raised. We call for the banning of the insulin sliding scale use as the sole diabetes order. Also, the use of basal insulin via continuous intravenous insulin infusion or subcutaneous insulin analogs should be embraced. Educating nurses, house staff, and other frontline professionals in the adverse consequences of the current paradigm is essential. Inpatient glycemic control matters; clinical and financial outcomes are at stake. It behooves the health care system and the diabetic public to address the contemporary state of inpatient diabetology as soon as possible.     

滑动加压螺纹钉的力学研究及疗效评价

对滑动加压螺纹钉（Ｒｉｃｈａｒｄｓ钉）进行了力学测试，结果显示，滑动加压螺纹钉的力学性能较可靠。３１例临床资料分析发现，滑动加压螺纹钉的临床效果理想。作者认为，滑动加压螺纹钉有动力性和静力性加压作用，它结构牢固，固定效果可靠，病人可早期下地活动，是当今治疗股骨转子间骨折比较理想的内固定物。其不足之处是无有效的抗旋转作用。     

Pin-on-Disc Modelling with Mesh Deformation Using Discrete Element Method

The pin-on-disc test is a standard sliding wear test used to analyse sliding properties, including wear contour and wear volume. In this study, long-term laboratory test performance is compared with a short-term numerical model. A discrete element method (DEM) approach combined with an Archard wear model and a deformable geometry technique is used. The effect of mesh size on wear results is evaluated, and a scaling factor is defined to relate the number of revolutions between the experiment and the numerical model. The simulation results indicate that the mesh size of the disc has a significant effect on the wear contour. The wear depth and wear width follow a normal distribution after experiencing a run-in phase, while the wear volume has a quadratic relation with the number of revolutions. For the studied material combination, the calibration of the wear coefficient shows that the wear volume of the pin-on-disc test accurately matches the simulation results for a minimum of eight revolutions with a wear coefficient lower than 2 × 10⁻¹¹ Pa⁻¹.     

微种植体支抗钉结合改良滑动杆近中移动 上颌前磨牙的临床应用

目的 探讨微种植体支抗钉结合改良滑动杆近中移动上颌前磨牙关闭缺牙间隙的可行性及有效性。方法 选取上颌侧切牙或尖牙缺失的患者5例（男2例,女3例）,年龄14~25岁。缺失侧磨牙关系均为安氏Ⅱ类。在上颌第二前磨牙及第一磨牙间植入微种植体支抗钉,结合改良滑动杆近中移动前磨牙。前磨牙移动到位后更换支抗钉位置,利用支抗钉拉磨牙近中移动,关闭剩余间隙。前磨牙移动疗程6~10个月。通过矫治前后石膏模型测量前磨牙近中移动有效性。结果 5例患者均得到有效治疗,上颌前磨牙及磨牙近中移动,缺牙间隙关闭,缺牙侧磨牙关系完全远中,治疗效果均令人满意。上颌前磨牙近中平均移动4.1 mm,平均移动速度0.96 mm/月。结论 对于上颌侧切牙或尖牙缺失的患者,微种植体支抗钉结合改良滑动杆可简单高效实现前磨牙近中移动,并最终关闭缺牙间隙,临床上可作为一种备选治疗方案。     

Evidence for centripetally shifting terminals on the tectum of postmetamorphic Rana pipiens

In larval frogs the retina and tectum grow in topologically dissimilar patterns: new cells are added as peripheral annuli in the retina and as caudal crescents in the tectum. Retinotopy is maintained by the continual caudalward shifting of the terminals of the optic axons. After metamorphosis the pattern of growth changes. The retina continues to add new ganglion cells peripherally, but there is no neurogenesis in the tectum. To maintain retinotopy in postmetamorphic frogs, the terminals of the optic axons must continually shift toward the central tectum. We tested the proposal of centripetally shifting axons by making punctate injections of horseradish peroxidase (HRP) in the tectum of adult Rana pipiens and observing the patterns of filled cells in the contralateral retina, as was done in the goldfish (Easter and Stuermer, '84). Punctate applications of HRP in the tectum should be taken up: 1) by fascicles, and label a partial anulus of cells, 2) by terminals, and label a cluster of cells in the corresponding retinotopic site, and 3) by the extrafascicular axonal segments, and label a band of cells connecting the partial annulus to the cluster. If the terminals have shifted centripetally, the band of cells labeled through their extrafascicular segments should have a spoke-like orientation, with the center of the retina as the hub. As the tectal site moves from rostral to caudal, this band of cells should move, pendulum-like, from temporal to nasal retina. In general, the patterns of HRP-filled retinal cells we observed were consistent with our predictions. In addition, HRP taken up by the oldest (rostral) tectal axons produced more complex patterns of filled cells that indicated that these axons had shifted both caudally before metamorphosis and centripetally after.     

基于双模态控制的交流异步电机直接转矩控制系统

针对PI控制和模糊滑模变结构控制在交流调试系统中的局限性,利用它们的各自优点,采用双模态控制方法对交流异步电动机系统进行控制,得到模糊滑模变结构设计过程以及采用PI控制和模糊滑模变结构控制相结合的双模态方法运行的结果。仿真结果表明：该方法不仅解决了模态抖动问题,而且改善了系统动态特性,证明了双模态控制在交流调速系统中的应用价值。     

两种滑动法关闭拔牙间隙的比较研究

目的：探讨直丝弓矫治器治疗安氏Ⅱ类1分类错[牙合]畸形过程中,采用主动结扎关闭间隙时,两种施力方式关闭拔牙间隙对牙齿移动的影响。方法：采用前瞻性配对设计,对30例拔除4个第一双尖牙的安氏Ⅱ类1分类病例进行配对,共配成15对,分为A、B两组,两组均采用主动结扎法关闭间隙,A组施力于弓丝上（弓丝法）,B组施力于牙上（牙列法）,对两组患者进行上颌牙齿移动的测量研究。结果：两种方法关闭间隙时,在所耗时间、前牙后移比率和消耗支抗方面无显著性差异（P〉0．05）,在垂直方向上,弓丝法压低前牙0．5mm,牙列法压低前牙0．25mm,差异有显著性（P〈0．05）。结论：主动结扎关闭拔牙间隙时,采用施力于牙列上或施力于弓丝上的方式都可以,两种方法都能有效的关闭间隙。