最优最小开关损耗SVPWM地板水暖变频调速系统

为了提高地板水暖系统的整体性能,除了考虑管道系统的设计和水泵本身机械特性,还要考虑水泵电机变频调速系统的效率。针对提高电机变频调速系统效率的问题,在分析电压源逆变器多解性的基础上,分析几种最小开关损耗电压空间矢量脉冲宽度调制策略,提出一种最优化的解决方案,并应用于永磁同步电机-变频调速地板水暖系统,给出相应的开关损耗计算公式,采用Matlab/SIMULINK进行仿真分析,并基于TMS320F2401设计和实验整个变频调速地板水暖系统。实验结果表明,永磁同步电机-变频调速地板水暖系统中采用最小开关损耗电压空间矢量脉冲宽度调制策略是可行的,降低了有效开关次数的1/3。对于额定功率50 W负荷而言,相比非最优电压空间矢量脉冲宽度调制策略,开关损耗降低2 W左右,电压源逆变器变换效率提升4%左右,改善了工况。

地板水暖矢量控制调速系统转子位置滑模观测器的研究

地板水暖是一种新型的房间采暖技术,为了提高地板水暖系统的整体性能、改善调速性能、节能降耗、降低成本和节约空间,水泵电机采用无速度传感器永磁同步电机(PMSM)矢量控制系统。在理论分析PMSM滑模观测器矢量控制原理的基础上,设计和实现了地板热水供暖的变频调速传动系统,描述了该系统的设计过程,给出了有关MATLAB/Simulink仿真波形和基于TMS320F2401控制器的实测波形,整个系统效率高达35%。

耐水木塑复合地板弯曲性能的测试方法

为配合有关标准的制定,对6种异型结构的耐水木塑地板进行了弯曲性能测试公式的推导,并按照实际常用的跨距进行了测试。结果表明:300 mm和400 mm两种跨距的弯曲挠度均加大,但后者最大承载能力较前者小;这两种跨距对抗弯强度测试值影响不大,但弹性模量测试值变化较大。在使用中还需结合最大承载力和弯曲挠度,来确定合适的跨距。

木地板蜡水护理剂的配方研究及性能测试

木地板蜡水护理剂是以金属交联丙烯酸系聚合物作为主成膜剂,配合碱溶性树脂、蜡乳液、成膜助剂、润湿剂、增塑剂等配制而成。通过对木地板蜡水护理剂的配方研究及性能测试,结果表明:金属交联丙烯酸系聚合物、碱溶性树脂、蜡这三种原料的干料比对地板蜡水的光泽值有一定的影响,经过优选得出的木地板蜡水护理剂配方有较好的稳定性、光泽度、防水性、抗洗涤性、抗磨蚀性和流平性。

演马庄矿二_1煤层底板突水原因及防治措施

根据演马庄矿的水文地质条件及历年的突水资料,阐述了二1煤层底板突水的原因,提出了底板含水层突水的防治措施。

我国木地板再图辉煌的出路在于加大出口

改革开放以来，我国经济发展迅速，人民生生活水平不断得到提高 ，国家城市化推进加快，旅游业及居民住宅建设呈现欣欣向荣的局面，特别是加入WTO以后，诸多因素的合力，构成了对我国装饰装修建材市场的巨大需求。而在连续几年高热不下的装修大潮中，

低温地板辐射采暖的设计体会

介绍了低温地板辐射采暖的优越性 ,并对低温地板辐射采暖工程设计中遇到的若干实质性问题进行剖析 ,提出了问题 。

浓妆淡抹总相宜

仿佛一个"好色之徒",设计师"色胆包天"的运用了好多色彩。无论书房安静的黑、还是厨房眩目的红以及儿童房里明快的黄,都被他运用得游刃有余,恰到好处。整套居室采用了现代而简约的设计手法,在柔美的灯光轻盈地照射下,一种含蓄而持久的空间气氛被营造地淋漓尽致。

Determining areas in an inclined coal seam floor prone to water-inrush by micro-seismic monitoring

The failure depth of the coal seam floor is one important consideration that must be kept in mind when mining is carried out above a confined aquifer.Determining the floor failure depth is the essential precondition for predicting the water-resisting ability of the floor.We have used a high-precision microseismic monitoring technique to overcome the limited amount of data available from field measurements. The failure depth of a coal seam floor,especially an inclined coal seam floor,may be more accurately estimated by monitoring the continuous,dynamic failure of the floor.The monitoring results indicate the failure depth of the coal seam floor near the workface conveyance roadway（the lower crossheading） is deeper and that the failure range is wider here compared to the coal seam floor near the return airway（the upper crossheading）.The results of micro-seismic monitoring show that the dangerous area for water-inrush from the coal seam floor may be identified.This provides an important field measurement that helps ensure safe and highly efficient mining of the inclined coal seam above the confined aquifer at the Taoyuan Coal Mine.

Theoretical analysis on water-inrush mechanism of concealed collapse pillars in floor

In order to study the water-inrush mechanism of concealed collapse pillars from the mechanical view, a mechanical model for water-inrush of collapse pillars has been established based on thick plate theory of elastic mechanics in this paper.By solving this model the deformation of water-resistant rock strata under the action of water pressure and the expression of critical water pressure for collapse pillar waterinrush have been obtained The research results indicate that：the boundary conditions and strength of water-resistant strata play important roles in influencing water-inrush of collapse pillars.The critical water-inrush pressure is determined by both relative thickness and absolute thickness of water-resistant strata.

Fracture mechanics solution of confined water progressive intrusion height of mining fracture floor

In order to obtain the value of confined water progressive intrusion height of mining fracture floor, the analysis equation was deduced based on the fracture extension theory of the fracture mechanics. Further- more, the influence of some parameters （e.g., advancing distance of working face, water pressure, initial fracture length and its angle） on confined water progressive intrusion height were analyzed. The results indicate that tension-shearing fracture of floor is extended more easily than compression-shearing frac- ture under the same conditions. When floor fracture dip angle is less than 90% tension-shearing extension occurs more easily on the left edge of the goaf. If fracture dip angle is larger than 90% it occurs more easily on the right edge of the goal. The longer the advancing distance of working face is, the greater initial frac- ture length goes; or the larger water pressure is, the greater possibility of tension-shearing extension occurs. The confined water progressive intrusion height reaches the maximum on the edge of the goaf. Field in situ test is consistent with the theoretical analysis result.

Vertical drainage capacity of new electrical drainage board on improvement of super soft clayey ground

As an advanced polymer composites electro-kinetic geosynthetics, the electro-osmotic vertical drainage(EVD) board could drain water quickly and accelerate consolidation process. However, the drainage rate was mainly impacted by the vertical drainage capability. Therefore, vertical drainage capability at the top of EVD board was theoretically analyzed. Basic requirements for drainage at the top of the board were summed up, as well as the formula of anode pore pressure when losing the vertical drainage capability. Meanwhile, a contrast test on the top and bottom drainage capacities was conducted. In use of the advanced EVD board, the voltage potential and pore pressure of anode were measured. Moreover, the derived formulas were verified. The result shows that the decrease of electric force gradient had an observable impact on the drainage capability. There was nearly no difference between the energy consumption for the two drainage methods. Although a little less water was discharged, the top drainage method had more advantages, such as high initial drainage velocity, few soil cracks, low anode water content and high soil strength. All of these show that the super soft soil ground could be consolidated quickly in use of the advanced EVD board through the top drainage. The top drainage method could efficiently improve the drainage effect, decrease the energy consumption and speed up the project proceeding.

Safety thickness analysis of tunnel floor in karst region based on catastrophe theory

Based on the tunnel shape, span and depth, the previous elliptical plate model and clamped beam model were modified.The modified model was applied to different situations. For the elliptical plate model, the water effects were considered. For the clamped beam model, water and horizontal stress were considered. Corresponding potential functions and cusp catastrophe models of rock system were established based on the catastrophe theory. The expressions of critical safety thickness were derived with necessary and sufficient conditions. The method was applied to the practical engineering. Some parameters related to the stability were discussed. The results show that elastic modulus and thickness are advantageous to the floor stability, and that the load, span,horizontal stress and water are disadvantageous to the floor stability.

Reduced Ammonia Release by Frequently Removal of Manure below Draining Floors in a Floor Housing System for Laying Hens

The hygienic threshold limit values for ammonia （25 ppm） for animal welfare but also for occupational safety and health is often exceeded in floor housing systems for laying hens with long time storage of manure in bins below draining floors. The major reason for high ammonia concentrations is the large amounts of stored and exposed manure. The possibility to reduce ammonia release by reducing the amount of stored manure in bins in floor housing systems for laying hens has therefore been investigated. Investigations were carried out in a climate chamber equipped with a floor housing system with a manure removal system with two parallel motor driven conveyors placed below an elevated draining floor. The conditions when manure is stored in bins below draining floors were simulated by storing manure on the conveyors for several days at constant ventilation rates and temperatures. The investigations clearly showed that storage of manure in the bin caused a rapid increase in ammonia concentrations. After about 7 days storage of manure in the bin the ammonia concentration exceeded the hygienic threshold limit values. It can be concluded that long time storage of manure in storage bins below draining floors should not be recommended. It was possible to maintain the ammonia concentration below the hygienic threshold limit values when manure was removed frequently with conveyors. Floor housing systems for laying hens with elevated draining floors should therefore be equipped with manure removal systems that enable frequent removal of manure in the bins.

Characteristics of in situ stress field at Qingshui coal mine

In this study, the characteristics of geological structure at Qingshui coal mine were analyzed. And the hollow inclusion strain cell overcoring method was used to obtain the in situ stress. The effect of in situ stress on the stability of soft rock roadway was analyzed. The results show that the maximum principal stress is in the horizontal direction with a northeast orientation and has a value of about 1.2–1.9 times larger than gravity; the right side of roadway roof and floor is easily subject to serious deformation and failure, and the in situ stress is found to be a major factor. This paper presents important information for developing countermeasures against the large deformation of the soft rock roadway at Qingshui coal mine.