Experimental study on vibration and structure noise of marine gear box with heavy load

The performance requirements of marine gear box are much higher than that of other gear boxes due to its special working conditions. The structure and transmission principle of a high-power marine gearbox are analyzed, and the experimental test is carried out for the analysis and calculation of its vibration characteristics and intensity. Measured by FFT analysis of vibration signals, the main peak is caused by its octave and the engagement frequency of input stage and middle-class transmission. The vibration severity of high-power marine gearbox reached 4.47 mm/s. In addition, the calculated structure noise of the measuring points is at the 1/3 octaves, and the largest structure noise is 131.27 dB which occurred in the frequency of 329 Hz.     

Gear-bearing coupling dynamics characteristics of wind turbine planetary gear transmission system under variable load

Considering that the transmission system of wind turbine works in complex and changing load environment caused by stochastic wind speed,this paper uses sparse least squares support vector machine(SL-SVM) to simulate wind speed of true wind field,and obtains time-varying wind load caused by stochastic wind speed. The lumped-parameter method is used to develop a dynamic model of planetary gear transmission system of wind turbine coupled with bearing. The model includes the varying wind load,time-vary mesh stiffness of gear pair and time-vary stiffness of rolling element bearing. The numerical method is used to simulate the dynamic performance of planetary gear system of Multibrid Technology Wind Turbine with 1.5 MW rated power. The vibration displacement responses of the transmission system are obtained as well as dynamic meshing force each pair of gear and nonlinear bearing forces. The research can provide a foundation for optimizing dynamic performance and reliable design of gear transmission system of wind generator.     

Experimental analysis of the evolution law of the coal seam gas permeability under long-term load

Gas-filled coal permeability evolution tests are carried out before and after the long-term load with temperature and effective stress changing by using the triaxial permeability equipment. Based on the experiments,temperature sensitivity coefficient and effective stress sensitivity coefficient of the permeability of the coal sample are analyzed before and after the long-term load. The experimental results are shown as follows：1)Before and after the long-term load,with the increase of effective stress,the permeability and effective stress sensitivity coefficient both decrease when the temperature keeps constant. At the same time,with the increase of temperature,the permeability and temperature sensitivity coefficient also decrease when the effective stress keeps constant;2)The difference of the permeability between before and after long-term load is different with temperature and effective stress changing,and it reflects thermal-fluid-solid coupling effect;3) Before and after the long-term load,the difference of temperature sensitivity coefficient first increases and then decreases with effective stress increasing,and it becomes negative when the effective stress is about 4.3 MPa. What’s more,the difference of effective stress sensitivity coefficient will decrease with the temperature increasing,and become negative after 26 ℃.     

玄武岩纤维喷射混凝土在热害环境下的性能试验研究

以隧道热害问题为背景,通过模型试验、近似模拟湿喷技术、定量分析及微观测试相结合的方法研究不同掺量玄武岩纤维喷射混凝土劈裂强度和粘结强度等力学性能的影响,横向对比标准养护和干热养护下的不同体积掺量的玄武岩纤维混凝土的力学性能,同时也加入硅灰以及钢钎维作为参照,以便从机理程度上提出更有效的解决热害措施。试验研究表明：在混凝土中加入玄武岩纤维,对混凝土起到了增强和阻裂的作用,改善了混凝土的脆性易裂的破坏状况。干热环境下,加入少量的玄武岩纤维能够提高混凝土的力学性能。当玄武岩掺量为0.1%玄+5%硅灰时,喷射混凝土的力学性能最好,加入0.2%玄武岩纤维掺量,也有一定程度的改善。实际隧道施工中,可通过加入适量的玄武岩纤维和适量的硅灰,可降低混凝土在热害环境下的危害。     

Seventh supplementary list of wheat varieties classified according to their genotype for hybrid necrosis and geographical distribution of Ne-genes

Summary The seventh supplement of the genotype hybrid necrosis in Triticum is presented. This list contains 414 Ne ₁-, 179 Ne ₂- and 662 non-carriers. The total number of varieties tested is 4629 viz. 1298 (28.0%) Ne-, 1031 (22.3%) Ne ₂- and 2300 (49.7%) non-carriers.The various aspects reported in literature and those studied by me are discussed.The geographical distribution of Ne-genes and their alleles indicates two Ne ₁ ^w -areas, one Ne ₁ ^m -area, probably two Ne ₂ ^ms.s -areas and four non-carrier-areas.     

Sixth supplementary list of wheat varieties classified according to their genotype for hybrid necrosis and geographical distribution of Ne-genes

Summary During 1971 and 1972 further progress in the identification of the Ne-genotype of wheat varieties has been made. Many data have been published in literature. Especially Russian workers identified many varieties. The picture formerly given for the distribution of Ne-genes remained unaltered.The sixth supplement consists of 287 Ne-carriers, 198 Ne ₂-carriers and 376 non-carriers, together 861 varieties etc. The total number of varieties is 3374 being 884 (26.2%) Ne _1-, 852 (25.2%) Ne ₂-and 1638 (48.5%) non-carriers.     

Fifth supplementary list of wheat varieties classified according to their genotype for hybrid necrosis and geographical distribution of Ne-genes

Summary An account is given about the progress in the work of the last two years. Further work is being done on the geographical distribution of both the Ne-genes.The fifth supplement consists of 144 Ne ₁-carriers, 208 Ne ₂-carriers and 326 noncarriers, together 678 varieties. The total number of varieties is 2513 being 597 Ne ₁-(23.8%), 654 Ne ₂-(26.0%) and 1262 (50.2%) non-carriers.     

约束再生混凝土足尺试件受压应力应变全曲线试验研究

为研究箍筋约束再生混凝土的单轴受压应力应变全曲线,对9个直径为500 mm、高度为1 500 mm的再生混凝土圆形柱进行试验,采用20 000 kN伺服液压试验机进行位移控制加载。试验参数主要为纵筋率、箍筋间距与直径、加载应变速率。试验结果表明,箍筋间距、配箍率对试件延性影响较大。当加载应变速率由0.000 003/s增大到0.003 3/s时,试件的峰值应力增大1.14倍。分析表明,再生混凝土应力应变全曲线与普通混凝土类似,但下降段较普通混凝土陡峭,脆性更为明显。     

种子企业在市场经济下如何实施良

随着《种子法》的实施和 WTO来临 ,国有种子企业将面临更加严峻地挑战 ,一些观念陈旧、体制老化、缺乏活力的种子企业将从历史舞台上消失。笔者根据近十年来在种子营销领域的探索和经验 ,认为在市场经济下 ,种子企业提高竞争力的最重要举措就是如何成功实施良种营销 ,具体说来应全力抓好以下 7项措施 :1　加强科技开发 ,培育或引进增产潜力大的农作物新品种科技是第一生产力。种子企业要想在当今立于不败之地 ,必须依靠科技 ,培育、引进或买断适合市场需求的拳头品种。根据对枣阳及周边地区用种农户的随机调查得知 ,农民对种子期望值最高…     

Detecting a fault line under a single phase to ground of distribution network based on analysis of multi frequency bands

Addressing the problem of choosing a fault line under single phase to ground of distribution network, we presented a new criterion based on analysis of the development of fault line selection and a method using wavelet packets. The feature frequency band, or the combined feature frequency bands of each line, in which the transient capacity current was concentrated was chosen for maximum energy. Based on the principle that the transient capacity current's energy of the fault line was larger than the that of normal lines, fault line selection can be carried out adaptively by contrasting the energy of the transient capacity currents of all lines in each chosen frequency band. The simulation results and spot testing data shows the proposed method can detect the fault line in distribution networks precisely and reliably.     

公司+农户种子生产合同初探

自我国实行土地联产承包责任制以来,种子公司进行种子生产时,基本上是以"公司 农户"的形式运作,即种子公司选择适宜生产区,与农户共同建立种子生产基地,由种子公司向农户供应必要的生产资料,提供技术服务;农户负责生产管理,所产种子由种子公司收购,价格按合同规定的方式确定,生产经营风险按合同规定分配.这种种子生产形式是公司与农户在经营层面上的联结,其表现形式为合同关系.