循环水低温结垢的原因分析及处理

针对空分装置出现的循环水低温结垢的问题进行分析,并根据分析结果通过采用不同方法进行处理,寻找到一种经济、安全的方法。     

交叉耦合腔体滤波器的设计与实现

通过对广义Chebyshev滤波器设计方法的深入研究,改进了由技术指标提取滤波器阶数和传输零点的综合方法;基于提出的分析模型,用Ansoft HFSS建立同轴腔体滤波器,对谐振腔的本征频率、耦合系数、抽头位置进行仿真计算。通过960MHz交叉耦合滤波器实例设计验证了该综合方法的有效性。     

Electrospinning of hydroxyapatite fibrous mats

Polyvinyl alcohol (PVA) with an average molecular weight between 40,500 and 155,000 g/mol was electrospun with a calcium phosphate based sol. The sol was prepared by reacting triethyl phosphite and calcium nitrate and was directly added to an aqueous solution of PVA. This mixture was electrospun at a voltage of 20 kV. The results indicate that the sol was distributed uniformly in the PVA fibers, whose diameter was on the order of 2 μm. This electrospun structure was calcined at 600 °C for 6 h to obtain a residual inorganic, fibrous network, with fiber diameters between 200 and 800 nm. The fibrous structure consists predominantly of hydroxyapatite with an average crystal size of almost 10 to 30 nm. A variety of structures including non-woven mats of solid or micro-porous hydroxyapatite fibers and highly porous scaffolds could be obtained by varying the polymer molecular weight and the sol volume fraction. These structures can have many potential uses in the repair and treatment of bone defects, drug delivery and tissue engineering.     

Extending Loffeld's bistatic formula for the general bistatic SAR configuration

This study derives an accurate bistatic point target reference spectrum based on a zeroth-order polynomial model. The spectrum contains only two hyperbolic square root terms that are very analogous in form to the analytical monostatic spectrum. The new formulation can be considered as an improvement of the Loffeld?s bistatic formula (LBF) and allows it to handle a wider range of bistatic configurations. The original LBF works well only in the case where the contributions of transmitter and receiver to the total Doppler modulation are approximately equal. An earlier paper on the extended LBF (EBLF) uses time bandwidth product (TBP) to weight the azimuth phase modulation from each platform. However, this extension is valid only in the low squint bistatic geometry. Both LBF and ELBF are expanded up to the quadratic term to derive an approximate bistatic spectrum; however, they do not show a good focusing performance in the more complex bistatic geometry, for example, the high squint case. This is due to the inaccurate individual time- Doppler correspondences. In this study, a norm in Euclidean space is defined to derive the optimal individual time-Doppler correspondences. Using the accurate individual time-Doppler correspondences, a zeroth-order polynomial model can be used to readily derive a more accurate bistatic spectrum. Two simulation experiments in the high squint geometry are used to verify the accuracy of this new formulation. The first experiment uses a parallel-track spaceborne/spaceborne configuration, and the second experiment involves an orthogonal-track airborne/airborne case.     

Research and experimental analysis of drill string dynamics characteristics and stick-slip reduction mechanism

Stick-slip of the drill string, as one of the critical factors affecting drilling efficiency, has always been a hot topic for experts and scholars in related fields. Serious stick-slip vibration affects the well construction efficiency, drilling cost and even lead to a downhole accident. Therefore, based on the current research, this paper takes a new type of composite vibration tool as the research object, studies the working mechanism of the tool and analyzes the effect of stick-slip reduction. After establishing the multi-degree-of-freedom torsional dynamics model, we obtained the results of torsional vibration dynamics by cases analysis based on working conditions and related mechanical parameters. In addition, the results of the examples, compared with the field experimental data, verify that the vibration shock generated by the new composite tool can effectively reduce the torque fluctuation range of the system, avoid the occurrence of stick-slip phenomenon, improve the ROP (rate of penetration), and make drilling process more stable. This paper can provide reference for the optimization and development of stick-slip technology in drilling engineering, and the theoretical methods can also be developed to study the dynamics of drill string.     

基于SolidWorks和三坐标测量仪的螺杆转子精滚刀建模与检测方法

介绍了基于SolidWorks软件的螺杆转子精加工滚刀的一种精确建模方法和利用该模型对滚刀的关键工序进行模拟验证的方法,同时介绍了在三坐标测量仪上利用螺杆转子精滚刀模型和曲线功能对螺杆转子精滚刀齿形进行检测的方法。     

双叉式叶尖结构对风力发电机叶片固有频率影响的试验研究

在风洞实验室进行模态试验与风洞动频试验,研究双叉式叶尖结构对风力发电机叶片固有频率的影响。在研究中发现,双叉式叶尖结构叶片的固有频率在低阶时有减小的趋势,在高阶时有增大的趋势。振型图显示,双叉式叶尖结构可将未改型叶片的一部分扭转振型变为挥舞振型,并且明显改良了未改型叶片前缘出现的扭转振型。动频数据显示,双叉式叶尖结构可以调整风轮动频曲线的走势,使风轮进入共振区的时间缩短。通过研究确认,双叉式叶尖结构能够有效改良风力发电机叶片的固有频率等参数,为后续风力发电机叶片的减振研究奠定了基础。     

Biolak污水处理构筑物的结构设计

Biolak污水处理工艺近两年来在国内应用较广,由于其工艺流程的特点,部分构筑物可采用HDPE土工膜防渗漏的土池结构。这种复合结构同纯钢筋混凝土结构相比,造价低,维护方便,经济效果明显。本文介绍了该结构体系的设计原理及计算方法,提出了设计中存在的一些问题,对推广这种构筑物形式进行了有益的探讨。     

基于DSP的挖掘机工作装置轨迹控制系统

针对挖掘机工作装置具有多变量、强耦合的特点,以DSP芯片TMS320LF2407A作为核心电控单元,采用模糊自适应PID控制算法,实现了挖掘机工作装置轨迹控制,具有较高的稳定性和精确性。通过自动操纵,减轻了驾驶员的作业强度,加快了施工进度。