Analysis of a multimode transmission line model of the shielding effectiveness of enclosures with apertures

The equivalent transmission line method is extended to multi-transverse electric modes of cavity which are introduced by aperture coupling, and it is used to analyze the shielding effectiveness of rectangular enclosures with apertures. The multimode transmission line method is verified by HFSS(High Frequency Structure Simulator). The results show that higher-order mode is essential to obtain an accurate shielding effectiveness of rectangular enclosure on wide frequency domain. Below the frequency of 1 GHz, nearer to the slot, the impact of higher-order mode on the shielding effectiveness is greater in the place mear the slot. Higher-order mode leads to a better shielding effectiveness.     

Spatio-temporal channel assignment in multi-radio wireless mesh networks

A method of spatio-temporal channel assignment based on graph decomposition was proposed to solve the ripple effect and link failure problem in multi-radio wireless mesh networks. Network topology was decomposed into subgraphs in several time slots to extend channel assignment from spatial domain to time domain. Then, graph coloring algorithm was used to optimize the channel assignment on the basis of the subgraph in each time slot. Each subgraph obtained channel resource dynamically according to the network constraints to improve the channel assignment efficiency. Simulation results show that, compared to static channel assignment scheme, the impact of negative factors, such as the ripple effect and link failure caused by channel switching, are effectively confined with this strategy. The network throughput is increased at least by 30% while satisfying the constraints on the number of radios and the number of network channels.     

Lightning Shielding Simulation Model of Transmission Line

Transmission lines are easily hit by lightning, and lightning shielding failure is an important reason of lightning accidents of transmission line. So researches on lightning shielding of transmission line should be strengthened. On the basis of the abundant understand to known lightning shielding models of transmission line, a new lightning shielding simulation model of transmission line is presented in the paper. In this model, the effect of attracting lightning of upward leader is considered reasonably, and the method of variable descending step is adopted to simulate the descending process of lightning leader. The simulation calculating results show that the model is in good agreement with field experience of transmission line. It can guide lightning shielding design of transmission line and estimate the performance of lightning shielding of transmission line.     

A Thermal Simulation of the Enclosure in Physical Model of Atria under Fire

This article elaborates the significance of the thermal simulation of the enclosure in physical model of atria under fire and presents an idea to conduct the thermal simulation. A series of one-dimensional thermal transfer equations of the enclosure are found for the atria with a round section under fire. The series of equations can be solved by the method of numerical analysis and based on the result, the analysis and comparison are carried out.     

Biomass of Natural Grassland under Different Enclosure Conditions

Taking natural grassland on the northern slope of the Qilian Mountain for example, this paper investigated and compared aboveground and belowground biomass of grassland in multi-year enclosure(20 years), one-year enclosure, control areas(natural grazing areas). The results showed that coverage and height of the enclosure sample plots were significantly higher than that of natural grazing area(P <0.05); mean aboveground biomass of grassland: multi-year enclosure(316.58 g/m~2) > one-year enclosure area(299.07 g/m~2) > multi-year enclosure control area(254.39 g/m~2) > one-year enclosure control area(187.37 g/m~2); belowground biomass: multi-year enclosure(2,906.90 g/m~2) > one-year enclosure area(2,587.26 g/m~2) > multi-year enclosure control area(2,378.93 g/m~2) > one-year enclosure control area(2,029.17 g/m~2); mean aboveground biomass of natural grassland was 263.60 g/m~2, mean belowground biomass 2,225.56 g/m~2; ratio of belowground biomass to aboveground biomass varied between 6.79 and 12.90, distribution of belowground biomass and aboveground biomass in each plot showed significant differences(P <0.05). Enclosure was favorable for improving the coverage and biomass of natural grassland plant communities in the Qilian Mountains.     

长汀强度水土流失区不同治理模式恢复效果的灰色关联分析

为了筛选出强度水土流失区理想的生物治理模式,为南方水土流失区治理提供植被恢复“范本”,通过对福建长汀强度水土流失区4种不同生物治理模式的群落调查、物种多样性和土壤理化性质测定,采用灰色关联分析方法进行不同治理模式恢复效果的评价。结果表明：不同生物治理模式恢复效果均比对照好,可改良土壤结构,增加土壤蓄水保肥功能,提高土壤有机质和养分含量,丰富植被物种种类和数量。不同模式恢复效果不同,灰色关联序为：乔灌草混交模式(0.934)＞经济林+封育模式(0.794)＞灌木+草本模式(0.487)＞灌木模式(0.484)＞对照(0.337),其中乔灌草混交模式、经济林+封育模式的改良土壤肥力作用显著,植被物种多样性高,治理恢复效果好,是南方强度水土流失区值得推广治理模式。     

南方建筑非透明围护结构热工与节能设计

如何兼顾冬夏两季建筑供暖空调负荷和能耗,保证室内热环境质量,确定最适宜的热工特性,是长期困扰中国南方建筑围护结构热工与节能设计的难点。通过对夏热冬冷和夏热冬暖地区建筑在采暖、空调与自然通风条件下动态热过程的分析,研究了这一地区围护结构热特性与能耗的制约关系,以及对室内热环境与建筑热稳定性的作用机理。在兼顾冬季保温与夏季隔热的情况下,将建筑全年能耗作为控制目标,从室内热环境质量、节能效果、围护结构的安全性、可靠性、经济性和实用性等角度评价目前所采用的围护结构节能技术存在的问题,提出一种适宜南方气候的建筑围护结构热特性指标及构造形式。     

Lightning Proof Performance of 500 kV Transmission Line in Chongqing Area

Considering the importance of 500 kV line and taking 500 kV transmission line in Chongqing as an example, the authors calculate lightning strike outage rate (including return stroke and lightning shielding failure) using regulation method, outage rate of return stroke using travelling wave method, and outage rate of lightning shielding failure using EGM. By comparing and analysing the calculating fesults, weakness of insulation and the area of easy to striking are found out, and corresponding improving measure is brought forward. The results show bigger gradient of lightning higher return stroke tripping, and in regulations result of accounting return stroke tripping is more closed to practical experience, accounting shielding failure rate exists obviously defect, and in EGM accounting shielding failure rate have take much factor, result is more close to practical experience.     

Bi Moment in Spacial Rod with Opening Thin Walled Section

The models,principle,deducing constitutive equation by means of variational method,and general solution are researched for bi moment in anisotropic spacial rod with opening thin walled seation.     

不同养殖模式对三角帆蚌体内氮磷和生长的影响

以三峡童庄河库湾不投饵养殖模式和湖北公安养殖池塘中肥水养殖模式下的三角帆蚌为对象,研究了不同放养模式对三角帆蚌生长及养殖产量的影响,同时测定不同养殖模式下三角帆蚌体内和水体中TN、TP,分析三角帆蚌组织中TN、TP与不同水质环境下TN、TP的关系。结果表明：水体中N、P的水平对三角帆蚌的生长具有一定的影响;不同TN、TP水质条件下,三角帆蚌组织中的TN、TP没有差异,表明三角帆蚌组织中的TN、TP与水环境中的TN、TP没有相关性;传统肥水养殖模式下三角帆蚌的生长和产量都优于三峡童庄河库湾不投饵养殖模式,不投饵养殖模式珍珠的产能接近池塘传统养殖模式的下线。研究同时表明在大水面水体采取低密度吊样三角帆蚌的放养模式,在增加经济效益的同时,还可以充分利用水体中的初级生产力。这为控制水体的富营养化提供新的思路。     

STUDY ON THE OPTIMUM DISTANCE BETWEEN CUTTING SLOTS FOR WEDGE PICKS

r The effect of the distance between cutting slots on the cutting specific energy consumption experimentally through cutting artificial coal samples with wedge picks is discussed in this paper. The optimum distances between cutting slots in different cut depths are presented, and the theoretical values are in good agreement with the experimental resurts.     

Conjugate Natural Convective Heat Transfer in an Enclosure with Discrete Protruded Heat Sources

The mathematic model on natural convection is proposed in a two-dimensional enclosure cavity with an isothermal heat sink at one vertical wall and five discrete protruded sources. Numerical study is performed to analyze the natural convection in the enclosure with a variety of aspect ratio, the range of which is from 3.0 to 12.22, Ra H is 10 7 and Pr is 30.The computed results show that the total heat transfer effect under the situation with discrete protruded heat sources is prior to that with flat wall heated. Moreover, when the aspect ratio is comparatively large, there is several secondary flow in the enclosure, which enhance the convective heat transfer. On the contrary, when the aspect ratio is small, the secondary flow weakened or disappeared, and the total convective heat transfer drop. Finally, the convective heat transfer criteria in the enclosure is obtained.     

基于生物量的油菜主茎叶片形态参数模拟研究

为了定量油菜主茎叶片形态参数与生物量间的关系,本研究基于2011—2012年和2012—2013年不同品种、移栽密度及施肥水平油菜田间试验,通过观测不同品种和处理油菜叶片长、最大叶宽和叶柄长等形态参数,并分析了上述参数与叶片生物量的关系,构建了基于生物量的油菜叶长、最大叶宽和叶柄长模型。结果表明,在全生育期,不同品种和处理下油菜主茎叶长和最大叶宽均与叶片生物量的平方根成正比,而叶柄长与叶长成正比。所建模型利用截距为0的线性函数描述叶长和最大叶宽随生物量平方根的变化,用直线式描述叶柄长随叶长的变化。经独立试验资料检验,除宁油16叶柄长模型误差较大外,所建模型对其余形态参数均具有较好预测性,为通过生物量将油菜生长模型与形态结构模型结合提供了机理性较强的方法,为建立油菜功能-结构模型奠定了基础。     

Soil properties behavior on grazed and ungrazed plots of a grassland sodic soil

Most of the alkaline soils of the Flooding Pampa (Argentina) are suffering severe structural deterioration, due to grazing on its natural vegetation. Because of the classical reclamation by chemical means has very restricted possibilities, soil improvement was studied by the exclusion of grazing. The study was performed in a Typic Natraqualf and conducted in a 3 years old enclosure, a 12 years old enclosure and the surrounding grazed area. Most of the studied soil parameters: total and water-soluble organic matter, structural stability, bulk density, hydraulic conductivity, infiltration rate, and the water easily dispersed fraction were not significantly different among the treatments. The soil of the enclosure did not accumulate soil organic matter and an important proportion of it was still water soluble. The absence of trampling, even after cattle exclusion for 12 years, did not improve the soil structural stability, clay dispersion and other properties. Sodium removal and flocculation would be a prerequisite for improvement of those sodic soils.     

短期封育对滇西北亚高山草甸土壤呼吸速率的影响

为了认识短期封育对滇西北亚高山草甸土壤呼吸速率、土壤温度、土壤水分等方面的影响,对香格里拉县小中甸镇和平村封育2年后的冬季牧场开展了研究。结果表明,与自然放牧的草甸相比,短期封育不但显著提高了春季和夏季的土壤呼吸速率,而且明显提高了亚高山草甸的植被盖度。封育对春季的土壤温度没有明显影响(P＞0.05),相反,显著地提高夏季的土壤温度(P<0.01)。另外,研究发现,在短期封育下,无论是春季还是夏季,亚高山草甸的土壤呼吸速率、土壤温度和土壤含水量两两之间的相关性不显著;而自然放牧状态下,春季的土壤温度和土壤含水量之间存在显著的负相关(P<0.05)。     

Out-of-Plane Mechanical Properties of Masonry Wall with Homogenization

Based on the three-dimensional homogenization theory, the Characteristic 3D elementary pattern in the masonry was established. The homogenized masonry wall was considered as a vertical plate with four supports. The plate theory was used to research the out-of-plane mechanical properties of masonry panels. Homogenization models with theory of thin plates and theory of medium and heavy plates were given and the calculation formula of deflection of homogenization masonry wall were deduced as well. The mid span deflections of 120 mm, 180 mm, 240 mm and 370 mm masonry walls with both fixed and variable ratio of height to width were analyzed. The applicability of two kinds of plate theories on homogenization masonry walls of different sizes was obtained. This methodology was practical and the masonry theory was improved.     

三七须根粉碎物土壤添加的自毒效应研究

自毒作用是导致三七（Panax notoginseng（Burk.）F.H. Chen）连作障碍的重要原因。本文对三七须根粉碎物土壤添加的自毒效应进行了分析,结果发现：①三七须根粉碎物对其发芽指标呈“低浓度促进,高浓度抑制”的作用趋势,添加量≤10%时不会对发芽率和发芽指数产生显著抑制作用;②三七须根粉碎物对三七植株的出苗率、存苗率具有明显抑制作用;须根粉碎物添加使三七植株的株高、花苔高逐渐降低,茎粗变小,平均小叶数减少,中叶长、宽减小,同时主根的长、宽变小,须根长度变短;③随用量增加,三七植株的地上和地下鲜重、干重及总干重均呈明显下降趋势。三七须根粉碎物土壤添加具有明显的自毒作用。     

Angle factors between surfaces in a radiant air-conditioned room

Angle factors between enclosure structural surfaces, or between human body and enclosure structural surfaces are the basic parameters to calculate radiant heat transfer in a radiant air-conditioned room. At present, the angle factors between the human body, radiant panels, windows and doors are usually quite difficult to solve. Therefore, we derived the angle factor expressions of two rectangular surfaces in the positions both mutual perpendicular and mutual parallel by using curve integral formula of angle factor, instead of using conventional surface integral formula. Meanwhile, angle factors between human body and enclosure structural surfaces by simplifying a seated person as a rectangular solid were acquired. The results were shown to be efficient and practical, and were free from the limitation of envehpe sizes and relative positions.     

Axial Bearing Capacity Design Method of Cold-Formed Steel Quadruple-C Built-up Section Members

The finite element model involving geometric large deformation,materials and contact nonlinearity is established.Specimens of cold-formed steel quadruple-C built-up section members are simulated and the finite element models are proved to be valid.Then,numerical analysis on the behavior of specimens with different slenderness ratio and flange flakiness ratio are carried out,and then the axial bearing capacities of specimens are obtained.Based on effective width method and direct strength method (DSM) in related codes,two design methods of cold-formed steel quadruple-C built-up section members under axial compression are proposed:effective length method and correction factor method.It is shown that:the final failure characteristics of all specimens are local buckling and distortional buckling.In the case of not considering the reduction of effective length,the results calculated by each code are slightly lower than those of test and FEM when the slenderness ratio is less than 50,while the results are too conservative when the slenderness ratio is more than 50.     

Fatigue life finite element analysis of output gear pair of wind turbine speed-increase gearbox

Cracking monitoring provides an important way to evaluate structural safety. Cracking monitoring method based on distributed optical fiber sensor can effectively avoid undetected phenomenon existed in point-wise test method, and it can run automatically. A theoretical model of cracking monitoring based on obliquely intersected fibers and Brillouin Optical Time Domain Analysis (BOTDA) is introduced, and the numerical equation among fiber strain, crack width and crack angle is established by the calibration experiment. The experiments are also carried out to study the performance of different kinds of cracking sensors with different gauge length and pretension. The quantitative relationship between optical fiber measured strain and crack (including width and angle) is established for the 300 millimeter crack sensor. The cracking simulation test proved that this new method can effectively record the width and the angle of cracks during the whole cracking process.