比较地

In this paper, the change of back electromotive force current with the different PWM modes are analyzed in detail on the base of BLDCM model. According to theory and experiment ,ON-PWM type restrains the peak value of back electromotive force current and brings the lest effect to the motor control system.

基于无刷直流电动机的数学模型，分析比较了不同PWM调制方式下反电势电流的变化规律，并通过理论推导和仿真实验证明了当电机系统采用ON-PWM调制方式时，能有效地抑制反电势电流的峰值且对电机控制系统造成的影响最小。

The paper are consisted of four chapters as follows: In the first chapter, the background and significance of the task from the practical and theoretical viewpoints were discussed. Through comparing and referring the related works.

本文的工作主要按照以下四个章节来展开：第一章从理论和实际应用的角度论述了课题研究的背景和意义，对等离子体脱硝理论和应用的研究和发展动态进行了系统地综述，在比较和借鉴相关领域的研究工作的基础上，提出了本文的研究内容。

Through simulation,the new algorithm has better performance than classical method in balancing nodes' energy costs as well as extending the lifetime of the network.

通过与传统分簇算法的仿真比较证明新算法有效地均衡了网络中节点的能耗，延长了网络生命周期。

Effect of Cu, Mo and Si fertilizers on balsam pear yield and quality were studied in two different textural soils.

通过田间试验，比较研究了在细砂土和粉壤土两种质地的土壤上，Cu、Mo、Si营养对苦瓜产量和品质的影响。

The characteristic, difference and relation of the normal and inverse design are compared detailedly. The formula of the first and second class eigen sensitivity are given. For the horizotal vibration system of building structure, the sensitivity method and perturbation method are adopted to modify the dynamic characteristics. The inverse eigenvalue problem of Jacobi matrix and the positive, symmetry, band matrix are studied. The method of Evolutionany Computation is first used in the inverse design of building structure, the principal problems are studied. The features of aseismatic inverse design of building are analysed.

本文较详细地比较了正、逆设计的特点；给出了特征值和特征向量的一阶和二阶灵敏度分析公式；对于建筑结构水平振动系统，提出了结构动态特征的修改方法；对Jacobi矩阵及实对称带状矩阵的逆特征值问题进行了分析研究，首次将其引入建筑结构抗震逆设计中；首次将进化计算方法应用于建筑结构抗震逆设计中，对主要问题作了探讨；对建筑结构抗震逆设计的特点进行了分析，提出未来的发展方向和前景。

The Barbour＇s mathematical model can be used to roughly predict and evaluate the effects of schistosomiasis control measures.

借助Barbour 血吸虫病传播数学模型能够粗略地评价和比较控制措施的效应。

Further more,at present,there are tess systemic professional references about intercepted and captured bark beetle during quarantine in China,so it\'s time to establish a database of morphologic characteristics of bark beetle for quarantine in order to help quarantine inspection officer correctly identify them.Together with DNA bar-coding technique,the database will greatly promote the ability in identifying intercepted and captured bark beetle during quarantine.

此外，由于小蠹科昆虫种类繁多，目前对检疫截获小蠹虫的鉴定工作存在较大困难，且比较系统地反映我国进口货物中截获小蠹虫的专业资料较少，因此，急需建立针对我国进口木材中小蠹虫检疫用的形态图谱以加强检疫人员对其的识别；并通过分子生物学分类技术的研究，辅以DNA条形码技术以提高对其的鉴定水平。

In order to understand the seismic performance of the large complex structure with basement, the structure-pile-soil finite element model of two typical cross sections of the Tianjin Transportation Junction were established by using the ANSYS software. The elasto-plastic time history analysis was made, and the seismic responses of the whole system under the horizontal seismic load were got. Comparing the results of the seismic response with the rigid foundation model, some reasonable conclusions are drawn.

为弄清楚带有地下室大型复杂结构的抗震性能，本文针对天津站交通枢纽工程，分别取结构典型的横向及纵向剖面，应用大型通用有限元分析软件ANSYS，建立了结构－桩－土体系相互作用的有限元模型，采用动力时程分析方法，研究体系在水平地震作用下的弹塑性动力反应规律，分析结构在地震动作用下的位移和内力的分布；并与假定刚性基础周边土简化为弹簧的结构模型的计算结果进行比较，通过两种模型的地震反应的对比分析，得到了一些有益的结论。

First, commonly used methods of flight segment volume forecasting are systematically elaborated, Then theory basis of support vector machine and its principle are introduced, support vector machine model is inferred, the support vector machines algorithm is studied.

首先，系统地介绍了航空运量预测中常用的预测方法，并对几种常用方法的特点进行了分析比较。

This paper aims to research the idea historia which is the central conception in the artistic theory of Leon Battista Alberti. To demonstrate the original meaning of historia in different period of time, which ranged from antique Greek to Renaissance, is the first chapter of this paper.

本文以文艺复兴时期伟大的人文主义者里昂·巴蒂斯塔·阿尔贝蒂艺术理论中的historia观念为主要关注点，将该词本体含义、在阿尔贝蒂理论中的应用并结合对已有研究成果的分析比较进行较为客观地考释研究。

According to the clear water experiment, aeration performance of the new equipment is good with high total oxygen transfer coefficient and oxygen utilization ratio.

曝气设备的动力效率在叶轮转速为120rpm～150rpm时取得最大值，此时氧利用率和充氧能力也具有较高值。

The environmental stability of that world - including its crushing pressures and icy darkness - means that some of its most famous inhabitants have survived for eons as evolutionary throwbacks, their bodies undergoing little change.

稳定的海底环境─包括能把人压扁的压力和冰冷的黑暗─意谓海底某些最知名的栖居生物已以演化返祖的样态活了万世，形体几无变化。