落锤冲击气囊施加均布动荷载的试验方法

在结构构件上施加均布冲击(爆炸)荷载一直是动力试验领域的难题。提出了一种落锤冲击气囊施加均布动荷载的试验装置,和一个双自由度弹簧阻尼冲击加载简化分析模型;给出了该模型的基本力学方程、边界条件和求解方法,并进行了有限元验证;建立了所提出冲击加载试验装置的精细化有限元模型,分析了构件上各受荷区域的荷载均布情况,验证了所提出装置的可行性。基于所建立的简化分析模型,讨论了刚度、荷载作用时间和阻尼比等关键参数,对构件上动荷载的影响,并给出了基本规律。计算结果表明,在选定合适的参数后,落锤冲击气囊试验装置能够较好地模拟构件上的均布动荷载,为实验室中进行爆炸冲击试验提供了一种可能。     

芋头冻结规律与速冻工艺的试验研究

对芋头的冻结规律与速冻工艺进行了研究。结果表明,芋头冻结时过冷点为-2．8℃,冰点为-1．7℃,最大冰晶生成区范围在-1.7-15℃之间。速冻芋头的最佳热烫工艺为100℃／6min。采用液氮间接冻结工艺进行速冻芋头的生产效果最佳。     

黄连木种子小蜂的发生规律及防治试验

黄连木种子小蜂严重影响黄连木种子的产量和质量。掌握其发生规律和筛选防治的有效药剂是控制危害的关键。试验结果证明，在成虫羽化期，用20％乙酰甲胺磷乳油500～800倍液进行地面封闭和树冠喷雾，防效显著。     

农村市场开拓的广告传播分析

“农村市场”己不是地域的意义,而代表了一种消费能力和层次。农村市场消费需求的市场化、商品化程度提高;农民消费升级较快,消费亮点不断涌现,具有和城市消费不同的特点.企业在开拓农村市场时总体上采用“全面进攻+重点突破”的广告策略,具体地,做好五结合,即中央媒体与地方媒体相结合,商业广告与公益广告相结合,媒体广告与口碑营销相结合,固定媒体与移动媒体相结合,空中广告与地面推广相结合。     

关于家兔毛色遗传规律的探讨分析

文章归纳完善了控制家兔毛色不同座位基因的作用,对不同位点基因互作关系进行了分析,指出家兔毛色是由多个位点基因共同作用的结果;认为影响家兔毛色的基因至少涉及10个位点,野鼠色家兔毛色基因型是家兔毛色的基本基因型,其它家兔毛色来源于野鼠色家兔基因突变以及突变基因重组;提出了特征基因和特征基因型概念,制定了26种毛色兔的毛色与“完整基因型”对照表。     

不同频率下超声波水处理对苹果内传热传质影响规律的试验研究

为探究超声波处理对果蔬加工过程中热质传递的影响规律,以苹果为研究对象,结合不同频率（40、68、80 kHz）超声波处理技术,分别进行超声波辅助低温水浴试验和超声波水预冷处理辅助苹果片真空冷冻干燥试验。结果表明：超声波辅助低温水浴可有效强化苹果与冷水间的热量交换,频率为80 kHz时,苹果果肉中部和近果核处的冷却系数与对照组相比分别增加了35.3%和28.6%;超声波水预冷处理后,真空冷冻干燥过程有效水分扩散系数比对照组分别增加了51.6%（超声波频率40 kHz）、55.9%（超声波频率68 kHz）、58.7%（超声波频率80 kHz）。     

灌浆压力测量误差的正交试验分析

灌浆规范中的灌浆压力是作用在灌浆岩体上的孔内灌浆压力。由于工艺的约束,现行灌浆监控过程常用孔口压力表示孔内灌浆压力,造成了灌浆压力的测量误差。针对非循环灌浆工艺,通过建立流体管道流动模型开展数值计算,采用多因素多水平正交法探究灌浆压力误差受浆液配比、浆液流速、灌浆孔深的相对影响,并采用统计法来分析不同工况下的显著影响因素。研究结果表明：灌浆压力较小时,灌浆压力误差普遍较大;若此时灌浆孔深且流速较大时,灌浆压力的测量误差则会超过灌浆压力仪表0.5%的精度要求,须进行误差补偿。其次,极差分析结果表明灌浆孔深是造成测量误差的主要因素,灌浆流速是第二个主要因素。而综合所有试验结果,浆液流速和灌浆孔深接近时,浆液配比越小,绝对偏差越大。结合上述正交试验和数值模型获取了不同工况下孔内灌浆压力值。     

豌豆植潜蝇在河南中牟大蒜田的幼虫为害规律与防治试验

田间调查表明,河南中牟大蒜田豌豆植潜蝇幼虫数量消长呈典型的3个高峰期,即9月下旬至10月上旬、10月下旬至11月上中旬、5月上中旬。药剂防治试验结果证明0.5％甲氨基阿维菌素苯甲酸盐乳油2000倍、40.7％乐斯本乳油1000倍对豌豆植潜蝇防治效果较好。回归分析表明,5d后相对防效与产量损失率呈显著负相关。     

生态气候因子对黄土高原中部冬小麦粒重的影响规律分析

为了掌握黄土高原中部地区旱作冬小麦粒重受生态气候因素的影响规律,科学开发利用气候资源,提高冬小麦生产效益,使用1995—2009年位于黄土高原中部旱作农业区的甘肃西峰试验田资料和当地平行气象观测资料,应用统计学原理和分析方法,较系统地分析了冬小麦千粒重与灌浆速率及灌浆时间之间的增长规律,探讨了生态气候综合因子对千粒重的影响特征。结果表明：灌浆速率对千粒重的贡献比率为69%,是灌浆时间贡献比率的2.23倍;千粒重和灌浆速率逐年变化为线性增加趋势,反映出生态气候因子对冬小麦生长表征为适宜有利限度内,单位面积产量仍有增加潜能;千粒重与生态气候因子的逐步回归分析表明,灌浆期降水量每增加10 mm千粒重增加2.15 g,≥20℃的活动积温每增加100℃千粒重减少2.7 g,空气相对湿度每增大1%千粒重减少1.0 g。     

青稞品种的比较试验及分析评价

2012年海南州农科所从青海省农林科学院和青海省种子管理站引进2个青稞品种,种植在海南州农科所院内,以当地主要种植的青稞品种为对照,进行品种间比较试验,通过对生育期、抗性、植株农艺性状、产量等性状调查和分析,结果表明,对照12QKS-3表现优良,12QKS-1、12QKS-2表现较好,可以作为搭配和后备品种。     

Protection Performance of the Various Structures with Cylindrical Shells under Plane Impact Loadings

Aiming at the design for distribution layer in defense works, attenuation mechanism and evolution law of stress waves in distribution layer with cylindrical shells were focused on. It was found that dispersion and diffraction effect of stress waves were occurred in the concrete medium on the basis of theoretical analysis and numerical simulations, which significantly weakened the strength of stress waves behind the shells. The position、interlayer spacing and the arrangement forms of the shells had great influence on the protection performance of the structures. The results show: in the structures with single-layer cylindrical shells, the smaller the space between the shells and the protected area is, the better the protection performance is; in the structure with two-layer cylindrical shells, the smaller the interlayer spacing is, the better the protection performance is, and the protection performance of the stagger structure is better than that of the aligned structure.     

Numerical analysis of the spherical surface piezoelectricity ceramics extracorporeal shock wave lithotripsy launch

We calculate a few numerical solutions of the focusing question related to different flare angle spherical surface piezoelectric ceramics ESWL shock waves. To do so, we first calculate the actual dynamic focus of spherical surface shock waves near the center of a sphere launched by the spherical surface piezoelectricity ceramics (ESWL) by using a discrete form of the Chisnell Chester Whitham(CCW) beam method. The numerical results show a focusing characteristic of the shock waves near the spherical surface piezoelectricity ceramics EWSL's geometric center, namely near the center of a sphere. The actual dynamic focus is not the center of the sphere but was somewhat offset. The focusing energy and the pressure ratio in the axis increase as the angles increase.     

Characteristics of Blast Wave Propagation in Saturated Soil with High Degree of Saturation

The test simulating contact explosion in saturated soil was completed in the φ2.5×5m pothole. Through the experiment, the data of the free field in the saturated soil was obtained. The formulas of pressure, momentum and rise time with distance were fitted out based on a large number of test data. According to analysis of the test data, the spreading law of the wave in free field of saturated soil was obtained. Theoretical analysis showed that saturated soil had the nature of liquid dynamic area appearing and shock wave forming when the stress wave spread in the saturated soil. The bilinear progressively increasing harding constitutive relation in saturated soil was established. Dividing pressure was determined and that was the value from shock wave to elastic wave. Moreover, the diving pressure related to media character was different in various soils. Because shock wave was formed easily, the structures in saturated soils had much higher risk of failure under the same explosive conditions.     

Application of Fracture Mechanics in Explosion of Large Iron and Steel Wastes

The ex plosio n process a n d paramete rs in the blast of large iron a nd steel wastesare analysed by using the theory of fracture mechanice.A three-dimensional model is established us-ing pressurised cylinder with multiple semi-elliptical surface cracks.Reasons are given for the expla-nation that the dynamic fracture toughness for iron and steel is generally lower than the correspond-ing static value during the blast.The importance is emphasized of the critical duration time of the dy-namic stress intensity factor for crack extension.     

Study on the qualitative analysis and application of radio wave tunnel perspective

In order to accurately survey the situation of geologic anomalous body on the coal working surface, the influence situation of different anomalous bodies on the radio wave instrument is simulated and discussed, and the research results are used to instruct coal survey. In practical application, it can divide disaster unusual area more accurately, instruct the design and plan of coal mine disaster prevention and control reasonably, provide experience for similar coal mine of geological disaster prevention and control.     

Numerical Simulation for Dynamic Response of Large Space Cylindrical Reticulated Shell under Internal Explosion by Ritz POD Method

A numerical simulation test of the internal explosive loading on large space structure was carried out by employing algorithm ANSYS/LS DYNA.An appropriate model was established for calculating the dynamic responses of the large space cylindrical reticulated shell under inner blast loading based on the proof of correctness and reliability of the model and parameters selection.Combining the Ritz vibration mode superposition method with the Proper Orthogonal Decomposition (POD) method, the problems of spatiotemporal asynchrony of shock waveforms and pressure distributions on large space structure surface were solved and the calculation for dynamic response of large space structure was reduced and simplified.Furthermore, the numerical simulation of dynamic responses was carried out.And the influence of the ratio of rise to span and the explosive position on the dynamic responses of the structure was studied.It was found that the calculation model was suitable for the dynamic response analysis of the large space cylindrical reticulated shell under internal explosion and the cylindrical reticulated shells with bigger ratios of rise to span were stronger in the capacity of anti explosion.In general, the damages to the large space structure caused by eccentric blast shock waves were more serious than that caused by central explosion.And it was the most disadvantageous to the edge components of the structure.The more attention should be paid to the anti explosion capacity of the support areas and the edge components while designing the shells.     

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 ℃.     

A charge balance control algorithm of dual-transistors forward converter

An algorithm is proposed for dual-transistors forward converter (DTFC) by using the principle of charge balance control during a transient process to improve their dynamic performance. Combined with response curve,the theoretical analysis and some key equations are presented to improve the dynamic performance of the DTFC by minimizing the over/under shoot and the recovery time. In order to avoid the magnetic saturation of the transformer,an approximate method is introduced in the calculation of the optimal switching time,which can also be applied to other isolated converters when the maximum duty cycle is limited. Finally,the simulation results and the experimental results of the prototype show that,compared with the traditional voltage mode control,the proposed algorithm can significantly improve the dynamic performance of DTFCs.     

铝板材电磁超声兰姆波换能器的有限元分析及优化设计

电磁超声兰姆波换能器由于其激发的兰姆波具有多模式、频散性和信号较弱的特点,在一定程度上限制了其发展及应用。针对增强电磁超声兰姆波信号强度问题,提出了一种优化设计方法。通过在永磁铁和线圈之间加入超微晶叠片来减小永磁铁表面的涡流,增加试件中的涡流,同时改善静磁场的分布,从而增强铝板中的信号强度。重点研究了超微晶对电磁超声信号的影响,采用有限元软件进行仿真分析,并进行了实验验证。实验结果表明,该优化方法能够有效增强兰姆波信号强度。     

Clipping Performance of Advanced Structure under Explosion of Mass Ammunition

An advanced structure containing cavities is adopted in distribution layers. A series of large-scale similarity-simulation tests are carried out on defense effect of the four structures for mass ammunition, and numerical simulations are developed by LS-DYNA software. The results indicate that the stress peak is distinctively decayed behind the cavities, and the defense effect of circular-section cavity is more effective than that of rectangle-section cavity. But because the transmission coefficient of stress waves of the structure increases, the defense effect is weakened when a thin steel plate is laid above the cavities.