一种减少电压互感器的模块化多电平换流器分组控制策略

针对模块化多电平换流器(MMC)需要配置大量电压互感器的问题,提出一种减少电压互感器的分组控制策略。该控制策略将每个桥臂的2N个子模块按照2~0,2~1,2~2,…,2^(N-1),2~0分成N+1个子模块组。将每组的子模块作为一个整体,开关状态保持一致,并且配备一个电压互感器,用于测量每组的电容电压。根据这种结构设计相应的电容电压平衡控制方法、均压控制方法和调制方法。电容电压平衡控制采用PI调节器稳定各组子模块的电容电压;均压控制用来保持组间子模块电压平均值均衡;调制方法用来确定各个模块组的通断状态。该分组方法极大地减少了电压互感器的数量,降低MMC系统的造价。最后通过在Matlab/Simulink平台上搭建三十三电平的三相MMC仿真模型进行证明,并搭建九电平单相MMC实验平台,进行实验验证,结果表明了该分组控制策略的有效性。

Magnetic Resonance Imaging and Biological Markers in Pituitary Adenomas with Invasion of the Cavernous Sinus Space

Objective: To investigate the predictability of MRI and the possiblebiological markers of cavernous sinus invasion of pituitary adenomas associated with fourphenomenas: angiogenesis, cell proliferation, apoptosis and matrix metalloproteinase. Methods: Weevaluated 45 patients with pituitary adenoma according to the MRI, surgical findings and theimmunohistochemistry staining of tumor tissues. Results: The results have shown that the sensitivityof MRI for predicting cavernous sinus invasion in this prospective study was 60%, its specificity85%, its positive predictive value 83.33%, negative predictive value 62.96%. 45 specimens ofpituitary adenomas were analyzed for expression of F8, VEGF, Ki-67, c-myc, Bcl-2, nm23 and MMP-9immunoreactivity using immunoperoxidase staining. MVD was assessed using F8-related antigen. Theresults have shown that MVD of invasive pituitary adenomas was significantly higher than that ofnoninvasive (P 【 0.001). There was an association between the invasion of pituitary adenomas andKi-67 LI (P = 0.039) or the expression of VEGF (P 【 0.001) and MMP-9 (P 【 0.001). But c-myc LI andBcl-2 expression have no association with invasiveness of pituitary adenomas (P = 0.061 versus P =0.201). On the other hand, there is an inverse relationship between nm23 expression and tumorinvasion (P 【 0.001). Conclusion: Parasellar extension of pituitary adenomas through the medial wallof the cavernous sinus is diagnosed at surgery, and with sensitive gadolinium-enhanced MRI, itsextent can be partly determined by radiology. Although our study has shown that MVD and theexpression of VEGF, Ki-67, nm23 and MMP-9 have associations with invasiveness of pituitary adenomas,they are lack of specificity. These markers can only provide some useful information.

基于DRGs的高值耗材监控预警体系的构建及应用

目的基于疾病诊断相关分类DRGs绩效评价系统(以下简称DRGs系统)构建高值耗材监控预警体系。方法利用DRGs系统中某三甲妇产专科医院妇科肿瘤科高值耗材使用数据,从监控类高值耗材占比和监控类高值耗材标化均值两个维度对监控类高值耗材使用的合理性进行预警。结果通过监控类高值耗材占比和监控类高值耗材标化均值的协同预警,将不合理用耗的风险范围定位缩小至不同手术级别的各诊疗组。结论基于DRGs系统构建高值耗材监控预警体系,对高值耗材使用的精细化管理及医疗服务质量的提升具有一定的参考价值。

Circadian Rhythm of Root＇s Apical Meristem Mitosis Cells of Soybean

The circadian rhythms of apical meristem mitosis cells of the two types of soybean were investigated： wild soybeans - Glycine max （L.） Merr. （G. hispida Max.）, G. soja Sieb., and Zucc （G, ussuriensis Reg. and Maack）; and the hybrids of their homozygous forms （F6）. Representatives of the initial kinds and interspecific hybrids for reproduction were grown up in comparable conditions. Seeds of a soybean were grown up at 24℃ in Petri cups in thermostat in darkness during winter. For research of mitotic meristem cages activity the tips of roots were fixed temporal by acetoalcohol （fractional fixing） from 1 p.m. till 12 a.m., further up to 12 p.m. each 60 minutes. Acetokarmin was used for preparing the coloring. For researching of mitotic indexes, there have been analyzed from 6 up to 10 thousand cells at each stage （during each moment of time： 01 hour, 02, 03 06 ... 12, 13 ... 18 hours and further）. Within a day （day ＋ night） in cells of root apical meristem, three mitosis ＂waves＂ in each of the investigated forms with an absolute starting point of rest at 12 p.m., with precisely expressed further periodicity were found out. Each of the investigated forms misses in character of wave processes, on a degree of increase and recession of mitosis waves, on the level of mitotic indexes. Maximal mitotic activity at all the investigated forms is noted at 6 and 12 a.m. and 6 p.m.

On a Generalization of Some Restrictive Distribution Theorems

This paper is on a distribution question of Ⅰ type in the combinatorics (see: 'Ke Zhao, Wei WanDi, combinatorial theory, science press, 1981. '). Suppose n distrinct balls, m distinct boxes. The capacity set of every box is Now,place the n balls into the m boxes. Thenumber of distinct placed ways is expressed by , and simply by And it is called the distribution number.Main result is:Theorem The exponential generating function of sequence isThus .there is the recurrence relationhere (integer set).

Forecasting available parking space with largest Lyapunov exponents method

The techniques to forecast available parking space(APS) are indispensable components for parking guidance systems(PGS). According to the data collected in Newcastle upon Tyne, England, the changing characteristics of APS were studied. Thereafter, aiming to build up a multi-step APS forecasting model that provides richer information than a conventional one-step model, the largest Lyapunov exponents(largest LEs) method was introduced into PGS. By experimental tests conducted using the same dataset, its prediction performance was compared with traditional wavelet neural network(WNN) method in both one-step and multi-step processes. Based on the results, a new multi-step forecasting model called WNN-LE method was proposed, where WNN, which enjoys a more accurate performance along with a better learning ability in short-term forecasting, was applied in the early forecast steps while the Lyapunov exponent prediction method in the latter steps precisely reflect the chaotic feature in latter forecast period. The MSE of APS forecasting for one hour time period can be reduced from 83.1 to 27.1(in a parking building with 492 berths) by using largest LEs method instead of WNN and further reduced to 19.0 by conducted the new method.

The Impacts of the Interannual Variability of Vegetation on the Interannual Variability of Global Evapotranspiration: A Modeling Study

The impact of the interannual variability (IAV) of vegetation on the IAV of evapotranspiration is investigated with the Community Land Model (CLM3.0) and modified Dynamic Global Vegetation Model (DGVM). Two sets of 50-year off-line simulations are used in this study. The simulations begin with the same initial surface-water and heat states and are driven by the same atmospheric forcing data. The vegetation exhibits interannual variability in one simulation but not in the other simulation. However, the climatological means for the vegetation are the same. The IAV of the 50-year annual total evapotranspiration and its three partitions (ground evaporation, canopy evaporation, and transpiration) are analyzed. The global distribution of the evapotranspiration IAV and the statistics of evapotranspiration and its components in different ecosystems show that the IAV of ground evaporation is generally large in areas dominated by grass and deciduous trees, whereas the IAV of canopy evaporation and transpiration is large in areas dominated by bare soil and shrubs. For ground evaporation, canopy evaporation, and transpiration, the changes in IAV are larger than the mean state over most grasslands and shrublands. The study of two sites with the same IAV in the leaf area index (LAI) shows that the component with the smaller contribution to the total evapotranspiration is more sensitive to the IAV of vegetation. The IAV of the three components of evapotranspiration increases with the IAV of the fractional coverage (FC) and the LAI. The ground evaporation IAV shows the greatest increase, whereas the canopy evaporation shows the smallest increase.

公路路基材料的分类

本文系统介绍了现代美国州际公路交通协会(AASHTO)和美国材料试验协会(ASTM)路用土质材料的分类方法——以土的颗粒级配为基础和以界限含水量为核心的定量与定性分析试验法，并列举了工程实例，说明它是判定土质特性的首要准则。

Elliptic systems involving multiple critical nonlinearities and symmetric multi-polar potentials

In this paper,a system of elliptic equations is investigated,which involves multiple critical Sobolev exponents and symmetric multi-polar potentials.By variational methods and analytic techniques,the relevant best constants are studied and the existence of(Zk×SO(N.2))2-invariant solutions to the system is established.

PARAMETER ESTIMATION OF EXPONENTIAL DISTRIBUTION

Because of the importance of grouped data, many scholars have been devoted to the study of this kind of data. But, few documents have been concerned with the thresh-old parameter. In this paper, we assume that the threshold parameter is smaller than the first observing point. Then, on the basis of the two-parameter exponential distribution, the maximum likelihood estimations of both parameters are given, the sufficient and necessary conditions for their existence and uniqueness are argued, and the asymptotic properties of the estimations are also presented, according to which approximate confidence intervals of the parameters are derived. At the same time, the estimation of the parameters is generalized, and some methods are introduced to get explicit expressions of these generalized estimations. Also, a special case where the first failure time of the units is observed is considered.