共查询到20条相似文献，搜索用时 234 毫秒
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通过FEM/BEM方法,建立了行星减速器箱体振动及声辐射分析模型,对其振动以及声辐射特性进行分析研究.首先,在ABAQUS里建立有限元分析模型,通过模态分析,找出影响其动态特性的主要因素,分析了主要结构参数对传递特性的影响.其次,在振动特性分析的基础上,通过VA-one建立其声辐射边界元模型,计算箱体表面及声场的声压分布云图、噪声谱及箱体辐射噪声板面贡献度和模态贡献度,并分析主要结构参数对辐射噪声特性的影响规律.研究结果表明:箱体结构前后端板相对箱体周向刚度较弱,但由于箱体内部轴系等因素影响,对端部局部厚度进行加强并不能有效改善箱体的动态特性.最后,对结构进行声学防护,通过声学防护,发现改变其结构损耗因子可以有效对箱体进行降噪设计,为行星减速器箱体的结构设计提供技术支撑. 相似文献
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研究了低速冲击作用下复合材料结构破坏行为与冲击速度及材料属性间的关系.采用碰撞力分段模型和一阶剪切理论分析了给定初始速度的铁球与四边夹支的叠层复合材料板中心发生碰撞的动力学行为,包括碰撞力及表面沉陷随时间的变化规律;然后根据忽略厚度的界面模型假设及简化的Tsai-Wu张量破坏准则对叠层复合材料板的解层破坏进行了计算和分析.结果表明最大碰撞力与初始碰撞速度成正比,夹支矩形叠层复合材料板的解层破坏区域最先出现在应力幅值较大的中轴线及边界附近,并随初始碰撞速度的增大而扩展并改变几何形状. 相似文献
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研制了可转动的叶片式吸热板集热器,该集热器与传统的太阳能集热器不同,集热器的叶片吸热板可转动,实现了吸热板跟踪太阳能运行,最大限度吸收太阳辐射.吸热板背面涂以热反射涂层,夏季叶片翻转180°,反射红外辐射隔热降温.分析了影响太阳空气集热器瞬时集热效率的各种因素,并对其热性能进行了试验.结果表明,叶片式吸热板集热器在强迫对流循环试验条件下最佳风机风量为120 m3·h-1. 相似文献
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为了合理处理高速铁路板式轨道结构动力学分析中板壳与梁-杆、叠加板、梁轴与弹簧、板与弹簧、板与实体等连接问题,基于Timoshenko板壳理论和直接引入法建立了多点约束方程,构造了板式轨道组合结构计算模型.该模型将组合结构中相关节点对之间位移关系,通过偏心关系和板壳理论的直线假设,建立了多点约束方程,并把该约束方程引入到Galerkin法的弱积分形式中,解决了各种不同类型单元因偏移连接而对组合结构总体刚度矩阵修正.数值分析结果与变形测试试验结果表明,基于Timoshenko板壳理论和直接引入法所建立的高速铁路板式轨道结构层有限元模型具有合理性,实现了板式轨道不同结构层的良好连接和位移协调,消除了常规方法产生的不合理附加应力,从理论上完善了有限元分析中的不同构件连接问题. 相似文献
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阐述了微生物生长动力学模型、热动力学模型在细菌生长中的应用及微生物热动力学研究现状,并展望了生物热动力学研究的发展趋势. 相似文献
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本文采用机械系统动力学自动分析软件ADAMS和有限元分析软件ANSYS建立电磁振动排种器排种盘子系统的仿真模型,并用 ADAMS/Vibration模块对仿真模型进行模态分析,求出系统的固有频率,并验证了仿真模型的正确性,为后续的排种盘子系统的结构参数优化设计奠定了基础. 相似文献
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用光声光谱仪检测结果表明，暗适应叶在光诱导期间出现非常复杂的光声瞬态放氧，产生了一种称为氧峰(oxygengush)的现象.该文利用自制的光声仪对暗适应菠菜叶在光诱导期间出现的光声瞬态放氧与暗适应时间关系，远红光、饱和光预处理以及高浓度CO2对光声瞬态放氧的影响，光声热信号与光声放氧信号之间的关系作了初步研究.推测由两个组分组成的氧峰与其动力学可能反映光系统Ⅱ的状态. 相似文献
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研究了不同强度的普通混凝土及橡胶混凝土在静态弯曲加载条件下的抗弯性能及其破坏过程的声发射性能.力学性能测试结果表明，橡胶混凝土的抗折强度高于同等抗压强度的普通混凝土.采用声发射系统对加载全程进行了信号采集.结果表明，随着普通混凝土强度的提高，弯曲过程中的声发射信号的活度减小，而信号的强度增大.橡胶混凝土的声发射信号的活度和强度均小于普通混凝土.对声发射信号的强度和活度的分析表明，在相同加载条件下，橡胶混凝土的损伤程度比相同抗压强度的普通混凝土小，这与两种混凝土反映出的宏观性能的差异是一致的.应用声发射信号定位研究了混凝土的损伤区域，定位分析结果与实际观察结果一致. 相似文献
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建立了弹性板-壳-声腔耦合模型,研究弹性板(壳)结构振动与声场耦合的特性,基于板壳振动微分方程,利用模态叠加法求解位移响应,分析结构与声场耦合之后,弹性板-壳-声腔结构的振动产生的声辐射,分别推导弹性板以及圆柱壳受到外载荷作用情况下振动产生声辐射指定外场点的声压级公式;然后根据点源组合原理,探讨有源力噪声控制,并给出算例予以验证。 相似文献
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Wise SW 《Science (New York, N.Y.)》1970,167(3924):1486-1488
The microarchitecture of gastropod nacre reveals deposition of aragonite in the form of crystal stacks and differs markedly from the characteristic microstructure of pelecypod nacre. The structure permits direct observation of both organic and mineral phases of deposition on a growth surface topography that is ideal for the study of processes of mollusk shell calcification. The stack mode of deposition is functionally useful to the animal because it increases the number of crystals which can form and develop on the growth surface at one time. 相似文献
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Ole Green Esmaeil S. Nadimi Victoria Blanes-Vidal Rasmus N. Jrgensen Ida M.L. Drejer Storm Claus G. Srensen 《Computers and Electronics in Agriculture》2009,69(2):149-157
By monitoring silage temperature at different locations inside silage stacks, it is possible to detect any significant increases in temperature occurring during silage decomposition. The objectives of this study were: (1) to develop novel noninvasive wireless sensor nodes for measuring the temperature inside silage stacks; (2) to design a suitable sensor protection housing that prevents physical and chemical damage to the sensor; and (3) to mathematically model temperature variations inside a silage stack, using system identification techniques. The designed wireless nodes were used to monitor temperatures in a full-sized silage stack over 53 days. Results showed that the wireless sensor nodes accurately monitored the temperature inside the silage stack at depths of 25 and 50 cm and reliably transmitted the measured data through the network; between 98.9% and 99.4% of the packets disseminated from the sensor nodes were successfully delivered to the gateway. The reliable performance of the network confirmed the correct choice of network characteristics (i.e., frequency range of 433 MHz, a handshaking communication protocol, and 10 mW transmission power). The designed sensor housings were capable of withstanding the high loads that occurred during ensiling, storage, and feed-out. Mathematical models estimating the relations between the silage temperatures (at depths of 25 and 50 cm) and air and soil temperatures were obtained. Black-box modeling using the prediction error method (PEM) was selected as the identification method. Among different black-box models such as ARX, ARMAX, output-error (OE), and Box–Jenkins (BJ), with different model orders, a third-order Box–Jenkins model structure gave the best performance in terms of prediction accuracy. The success rate of the models proposed for silage temperature prediction ranged between 90.0% and 94.3%. Furthermore, there was no significant autocorrelation remaining in the residuals. The results of this study indicate that the designed wireless sensor nodes could potentially be used for detecting silage decomposition processes and improving the efficacy of silage conservation systems. 相似文献
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《Computers and Electronics in Agriculture》2010,70(2):149-157
By monitoring silage temperature at different locations inside silage stacks, it is possible to detect any significant increases in temperature occurring during silage decomposition. The objectives of this study were: (1) to develop novel noninvasive wireless sensor nodes for measuring the temperature inside silage stacks; (2) to design a suitable sensor protection housing that prevents physical and chemical damage to the sensor; and (3) to mathematically model temperature variations inside a silage stack, using system identification techniques. The designed wireless nodes were used to monitor temperatures in a full-sized silage stack over 53 days. Results showed that the wireless sensor nodes accurately monitored the temperature inside the silage stack at depths of 25 and 50 cm and reliably transmitted the measured data through the network; between 98.9% and 99.4% of the packets disseminated from the sensor nodes were successfully delivered to the gateway. The reliable performance of the network confirmed the correct choice of network characteristics (i.e., frequency range of 433 MHz, a handshaking communication protocol, and 10 mW transmission power). The designed sensor housings were capable of withstanding the high loads that occurred during ensiling, storage, and feed-out. Mathematical models estimating the relations between the silage temperatures (at depths of 25 and 50 cm) and air and soil temperatures were obtained. Black-box modeling using the prediction error method (PEM) was selected as the identification method. Among different black-box models such as ARX, ARMAX, output-error (OE), and Box–Jenkins (BJ), with different model orders, a third-order Box–Jenkins model structure gave the best performance in terms of prediction accuracy. The success rate of the models proposed for silage temperature prediction ranged between 90.0% and 94.3%. Furthermore, there was no significant autocorrelation remaining in the residuals. The results of this study indicate that the designed wireless sensor nodes could potentially be used for detecting silage decomposition processes and improving the efficacy of silage conservation systems. 相似文献
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网络协议栈虚拟化的目标是在一台网络设备上虚拟出多个协议栈以实现网络设备的一虚多功能。由于Linux操作系统的网络协议栈本身是不支持这种网络协议栈虚拟化技术的，因此本文通过对Linux操作系统3.11.10版本IPV4网络协议栈进行改造以实现Linux网络协议栈的虚拟化，并在设备平台上验证了经过网络协议栈虚拟化改造后的以太网交换机对业务流的隔离功能。 相似文献
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陈红英 《农业图书情报学刊》2012,24(5):107-110
通过对中国传媒大学图书馆样本书库现状和管理存在的问题的分析,提出做好样本书库工作的对策及创新与发展的建议,并通过开架阅览和其他管理、服务措施的完善,推动样本书库更好地发挥为高校教学科研服务的功能,同时也为其他高校图书馆样本书库的发展提供借鉴。 相似文献
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复杂技术创新是发展中国家进行产业结构升级的一个重要努力方向，也是我国实施自主创新战略的重要方面。高度不确定性是复杂技术创新的主要特征，如何从创新模式及组织形式等方面减少创新过程的不确定性，成为复杂技术创新管理的关键所在。复杂技术创新过程中需要多种知识和技能并且需要创造新知识，创新主体对知识资源的获取成为复杂技术创新不确定性的主要来源。自组织网络能够有效降低这种不确定性，从而促进复杂技术创新。 相似文献
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建立包含三个层次54个指标的长沙市“十二五”时期发展指标体系，通过运用长沙市2006~2009年的数据对各指标的得分值进行分析发现，“十二五”时期的发展不能过多注重经济增长方面的指标，而应更多考虑社会民生和区域创新方面的指标，在具体运用时应尽量避免主观赋权。 相似文献