电磁超声检测钢板厚度实验的参数优化

为提高电磁超声检测信号的信噪比,研究激励信号频率、脉宽及换能器提离距离对厚度测量结果的影响,搭建了电磁超声实验系统。该系统利用RITEC-SNAP 5000产生高能正弦波激励电磁超声换能器EMAT ( Electromagnetic Acoustic Trans-ducer),通过调节激励信号的频率、脉宽,改变提离距离来观测超声回波幅度的变化。实验结果表明：当激励频率和EMAT固有频率相同时其换能效率最高,采用6个周期的脉冲串时前后波包之间分界明显,为获得较大的回波幅度应尽可能减小提离距离。     

以临界屈曲应变为判断依据的非开挖内衬修复设计改进方法

《城镇排水管道非开挖修复更新工程技术规程》(CJJ/T 210-2014)选取管道的长期弹性模量EL进行内衬修复设计,并规定EL为短期弹性模量Es的0.5倍,但是对于这一做法的理论依据仍然存在较多质疑,也导致设计过于保守。据此考虑引入临界屈曲应变理论,提出以内衬的临界屈曲应变εr为破坏判据,并选取管道短期弹性模量Es进行设计的改进方法。研究表明,改进后的设计方法能够保证内衬设计在理论上的正确性,满足内衬的长期强度要求,减小大约21%的内衬设计壁厚,能够有效降低工程成本。     

Figure of merit for environmental SEM and its implications

A recently introduced figure of merit for environmental and low vacuum scanning electron microscopes has now been computed in the full operational pressure range for one commercial instrument. The direct simulation Monte Carlo method has been used in lieu of experimental measurements. The theory of this figure of merit is further consolidated. It is shown that a thin pressure limiting aperture can indeed be used as an optimum reference system for all instruments employing differential pumping in the transfer of an electron beam from high vacuum to high pressure. The implications of the results obtained are discussed both in relation to existing commercial instruments and associated literature to pave the way for future progress in the field.     

Ketamine effects on the urogenital system--changes in the urinary bladder and sperm motility

Different doses of ketamine (10 mg/kg, 20 mg/kg, 30 mg/kg, 40 mg/kg, 50 mg/kg, and 60 mg/kg) were injected i.p. (I.P.), respectively, to male ICR mice to determine the optimal dosage for chronic administration. At and above 40 mg/kg I.P. injection, mice had almost no hindlimb movement during swimming test. Subsequently, 30 mg/kg was used as the dose for the study in the toxicity of long-term ketamine administration on urinary bladder and sperm motility. The treatment group were subdivided into two (n = 10 each group); one received daily ketamine treatment i.p. for 3 months and another group for 6 months. Corresponding number of mice in control groups (n = 5 each group) received saline injection instead of ketamine. Terminal dUTP nick and labeling (TUNEL) study and Sirius red staining were carried out on the sectioned slides of the urinary bladders to study the degree of apoptosis in both epithelium and muscular layers of the urinary bladder and the relative thickness of the muscular layers in this organ was also computed. Apoptosis in the bladder epithelium was observed initially in the 3-month ketamine treated mice and the number of apoptotic cells was significantly different (P < 0.05) between the 3-month and 6-month ketamine treated mice and the control. The relative thickness of muscular layers in the bladder wall also decreased significantly (P < 0.05) when the 6-month treated mice and the control were compared. Sirius red staining revealed increase of collagen in the urinary bladder of the treated mice, most evidently 6 months after ketamine treatment. In addition, the sperm motility was studied and there was a statistically significant difference between the control and ketamine treated groups in the percentages of sperms which were motile (P < 0.05). This suggested that the chronic administration of ketamine affected the genital system as well.     

水轮发电机转子系统磁悬浮装置 结构优化设计

针对水轮发电机混合磁悬浮承重系统中电磁悬浮装置局部磁饱和问题,进行了结构优化设计,提出了适当增加推力盘及电磁铁顶部厚度的方法,有效地减轻了电磁悬浮装置局部磁饱和现象,同时也使总的磁浮力有所增加。从承载力与漏磁角度考虑,得出了推力盘及电磁铁顶部厚度的最佳设计值。     

基于二维金属亚波长孔阵列结构的MEMS红外辐射源特性研究

以MEMS红外气敏传感器为应用目标,采用MEMS技术设计和制作一种二维金属亚波长孔阵列结构红外辐射源。探讨了不同厚度SU-8膜对金属/电介质/金属(M/D/M)二维金属亚波长孔阵列结构在中远红外波段透射特性的影响。设计并制作了Au/SU-8/Au的M/D/M结构,测试采用傅里叶变换红外光谱仪器。同时对M/D/M结构不同电介质层情况下的中远红外波段透射特性进行了模拟。实验结果表明,SU-8厚度在小于1μm时,透射强度远大于厚度1μm以上的结构,且有透射强度最大值出现(SU-8厚度为360nm),同时,随着SU-8厚度的增加,透射谱峰值呈现规律性红移。     

Vegetation water content during SMEX04 from ground data and Landsat 5 Thematic Mapper imagery

Vegetation water content is an important parameter for retrieval of soil moisture from microwave data and for other remote sensing applications. Because liquid water absorbs in the shortwave infrared, the normalized difference infrared index (NDII), calculated from Landsat 5 Thematic Mapper band 4 (0.76-0.90 μm wavelength) and band 5 (1.55-1.65 μm wavelength), can be used to determine canopy equivalent water thickness (EWT), which is defined as the water volume per leaf area times the leaf area index (LAI). Alternatively, average canopy EWT can be determined using a landcover classification, because different vegetation types have different average LAI at the peak of the growing season. The primary contribution of this study for the Soil Moisture Experiment 2004 was to sample vegetation for the Arizona and Sonora study areas. Vegetation was sampled to achieve a range of canopy EWT; LAI was measured using a plant canopy analyzer and digital hemispherical (fisheye) photographs. NDII was linearly related to measured canopy EWT with an R² of 0.601. Landcover of the Arizona, USA, and Sonora, Mexico, study areas were classified with an overall accuracy of 70% using a rule-based decision tree using three dates of Landsat 5 Thematic Mapper imagery and digital elevation data. There was a large range of NDII per landcover class at the peak of the growing season, indicating that canopy EWT should be estimated directly using NDII or other shortwave-infrared vegetation indices. However, landcover classifications will still be necessary to obtain total vegetation water content from canopy EWT and other data, because considerable liquid water is contained in the non-foliar components of vegetation.     

水泥生产线篦冷机料层厚度新型控制技术

新型干法水泥窑第三代篦冷机熟料料层厚度控制是保证水泥成品质量的重要环节。使用安装在篦冷机本体上的料层测厚仪,直接测量出篦冷机熟料的料层厚度,通过自动控制系统对篦冷机的料层厚度进行直接控制,以保证篦冷机内部热工参数的稳定,提高和稳定水泥产品的质量和产量。     

Uniform strength for large deflections of cantilever beams under end point load

Analysis is conducted for slender beams with a varying cross-section under large non-linear elastic deformation. A thickness variation function is derived to achieve optimal - constant maximum bending stress distribution along the beam for inclined end load of arbitrary direction. Closed form solutions are derived for the large deflections that correspond to the various loading conditions. The analysis is repeated for a beam with optimally varying width (for arbitrary end force) and the width variation function is also determined.     

太赫兹时域光谱技术在涂层检测中的研究进展

涂层结构具有美观、隔热和耐腐蚀等优点,被广泛应用于航空航天、汽车船舶制造和制药等领域。但在涂层制备和服役过程中会不可避免地出现气泡和裂纹等缺陷,且涂层厚度和均匀性会直接影响涂层寿命,因此对涂层结构的检测显得十分重要。与常规无损检测技术相比,太赫兹时域光谱(THz-TDS)技术非接触性好、抗干扰性强,适用于涂层结构快速无损检测。首先,简要地介绍了太赫兹波、太赫兹时域光谱技术和典型的太赫兹时域光谱系统;然后,详细地阐述了太赫兹时域光谱技术在光学参量、厚度和微结构检测方面的国内外研究进展,特别是太赫兹波在汽车船舶、航空航天和生物制药方向的厚度检测与成像;最后,分析了涂层结构无损检测的现状,对现有的太赫兹波检测涂层存在的问题进行了总结,并对其未来的发展进行了讨论和展望。