微纳力值计量标准的研究和溯源体系的建立

微牛、纳牛范围力值计量研究是目前国际计量领域的重要研究发展方向。总结了美国标准技术研究院、英国国家物理实验室、德国物理技术研究院、韩国标准和科学研究院等研究机构近年来研制的可溯源到SI的微纳力值标准装置、微纳力值传感器、参考悬臂梁以及微纳力值溯源方法。提出了微纳力值溯源体系的框架,为新材料、生物、微电子等各应用领域微纳力学特性计量量值溯源提供了技术保证。     

砖烟囱爆破拆除不同切口形状的数值模拟

针对烟囱爆破拆除时爆破切口形状的确定往往按经验确定,没有重视烟囱倒塌过程中一些问题很难通过理论预见的情况,利用ANSYS/LS-DYNA软件数值模拟了常见的长方形切口、正梯形切口、倒梯形切口这3种爆破切口形状对烟囱倒塌拆除过程并进行了对比和分析,研究结果表明:首先从爆破切口闭合时间看到,倒梯形切口闭合时间最长,正梯形切口闭合时间次之,长方形切口闭合时间最短。其次从烟囱顶端着地时间分析,正梯形切口烟囱顶端着地时间最长,而其它两种切口方案次之,并且这两种方案对烟囱倒塌时间差不多相等。再从模拟烟囱倒塌的过程分析,正梯形切口及长方形切口烟囱倒塌过程出现"后座"现象。最后从烟囱倒塌顶端速度变化曲线中看出正梯形切口烟囱倒塌方案对地面的冲击力最小,引起地面的振动强度最小。     

传递对准中主惯导数据延时的LCKF算法研究

瞄准吊舱进行传递对准时,主惯导数据到达吊舱惯导系统存在延时,影响滤波收敛速度和估计精度。文中提出了一种基于延时卡尔曼滤波的主惯导数据延时补偿算法(LCKF算法),将时间基准统一到主惯导数据时刻进行卡尔曼滤波,修正子惯导姿态信息,再利用子惯导的实时IMU数据进行捷联更新,获得子惯导当前时刻的姿态信息。基于比力积分匹配传递对准,对LCKF算法进行仿真,结果表明该方法明显提高了传递对准收敛速度和估计精度。     

四柱式力传感器固有频率提升研究

为研制高动态性能的四柱式力传感器,基于机理分析法,建立了四柱式传感器固有频率模型,得到了通过改进四柱式传感器结构参数来提高四柱式传感器固有频率的方法,并通过Solidworks仿真与标准锤击法实验验证了该方法的正确性。研究结果表明：四柱式传感器的固有频率主要由其四立柱的结构参数决定,增大四立柱横截面长度或宽度,降低柱体高度,有利于提高其固有频率。研究结果也指出,除改进四柱式传感器结构外,增大材料弹性模量,降低材料密度,也能进一步提高其固有频率。     

Effect of Surface Forces on Subcritical Crack Growth in Glass

Data on the growth of cracks tested in aqueous solutions were interpreted in terms of surface force theory. For applied stress intensity factors greater than 0.25 MPa · m½, the position and the slope of the curves and their dependence on pH and ion concentration can be explained in terms of surface force theory, provided these forces are of a magnitude and range that are representative of those involved in the cohensive bonding of solids. Weaker forces, such as structural, double-layer, or dispersion forces, have little effect on crack growth in silica glass for K _I > 0.25 MPa · m½.     

CHARACTERISTICS OF MICROCUTTING FORCE VARIATION IN ULTRAPRECISION DIAMOND TURNING

An investigation of the characteristics of microcutting forces in diamond turning of crystalline materials is presented. The characteristics of the cutting forces were extracted and analyzed using statistical and spectrum analysis methods. A series of cutting experiments were done on a copper alloy and copper single crystals with different crystallographic orientations. Experimental results indicate that there exists a dominant frequency component and a periodicity of fluctuation of the cutting forces per workpiece revolution in the diamond turning of a single crystal material. The periodicity is closely related to the crystallographic orientation of the material being cut. As the depth of cut increases, the influence of crystallographic orientation of the single-crystal materials on microcutting forces is found to be more pronounced. Moreover, the cutting force ratio between the mean thrust force and the mean cutting force is found to vary with the depth of cut, and a large ratio was observed at a small depth of cut. These findings help to explain quantitatively the periodic fluctuations of microcutting forces (and hence the materials-induced vibration) in ultraprecision diamond turning, which are not encountered in conventional machining.     

Effects of sodium bicarbonate containing traces of citric acid in combination with sodium chloride on yield and some properties of white shrimp (Penaeus vannamei) frozen by shelf freezing, air-blast and cryogenic freezing

Effects of sodium bicarbonate with traces of citric acid in combination with sodium chloride on yield, freezing time, freezing rate, freezing loss and cutting force of white shrimp frozen by shelf, air-blast and cryogenic freezing with/without precooking were investigated. Shelf freezing was done at −40 °C ± 2 °C while air-blast freezing was carried out at −35 °C ± 2 °C, and cryogenic freezing was done at −35 °C, −40 °C and −60 °C. The freezing loss in the non-treated samples was 8.25, 4.6-5.84 and 1.92-3.48 g/100 g fresh shrimp for peeled samples frozen without precooking and increased to 21.85, 17.54-26.97, 17.92-20.31 g/100 g fresh shrimp in the precooked samples frozen by shelf, air-blast and cryogenic freezing, respectively. The treatment of sodium bicarbonate containing traces of citric acid at 4 g/100 ml with sodium chloride at 3 g/100 ml lead to the increase of yield thus reduced the freezing loss by about 6.83-10.28 and 6.41-12.4 g/100 g fresh shrimp for the frozen-thawed samples frozen as uncooked and cooked products, respectively. The toughening of shrimp was observed while sodium bicarbonate containing traces of citric acid treatment with sodium chloride could reduce the texture change occurred during the freezing.     

Cu-Sn-Ti体系边际二元系界面反应的研究

Cu-Sn-Ti三元系及其相关的3个二元系均具有重要的实用价值.实验制备了Ti/Sn和Cu/Sn固-液扩散偶及Cu/Ti二元固相扩散偶,经电子显微和探针观测发现: Ti/Sn固-液扩散偶在873K下退火30～160min,只生成1个Sn3Ti2中间相; Cu/Sn固-液扩散偶在808K下退火10min时也只生成1个Cu3Sn中间相,但退火时间延长至30min时在Cu与Cu3Sn界面上生成Cu41Sn11,退火60min后在Cu与Cu41Sn11之间又生成了bcc-a2; Cu/Ti二元固相扩散偶在1023K下退火1000h后,在其界面处生成了CuTi2、CuTi、Cu4Ti3、Cu4Ti 4个化合物,而Cu3Ti2相并未在扩散偶中出现.还采用最大驱动力模型对上述3个二元系的界面反应过程进行了计算并成功解释了相应的实验现象.     

基于定向移动的水下传感器网络覆盖算法

覆盖率是衡量无线传感器网络服务质量的重要指标。为提高网络覆盖率,针对水下三维传感器网络模型,提出一种基于定向移动的虚拟力算法。将虚拟力简化为节点只受邻居节点的斥力作用,定义当2个邻居节点的感知圆球相切时,其位置为相对理想位置。节点所受虚拟力大小与节点移动到相对该邻居的理想位置所需移动的距离成正比,而节点移动的距离与节点所受到的虚拟力的合力相关。实验结果表明,该算法能有效地对水下传感器网络的布局进行优化,提高网络覆盖率。     

海底瞬变电磁探测技术的装置参数研究及实验

可控源时间域电磁法应用在海底探测,需要确定装置参数,通过实验和理论计算确定了发射频率的最大值;分析了发射线圈的电性对发射电流后沿的影响,确定了作为发射线圈的导线的时间常数应尽量小;对接收线圈的参数及过渡过程进行了理论分析和室内模型实验,理论计算了接收线圈电路模型在发射电流斜阶跃下降和关断后在欠阻尼、临界阻尼和过阻尼状态的一次感应电动势解的情况,确定了采用并联匹配电阻消除振荡的方法,并依据所分析的装置参数设计实施了海上实验,探测出海底低阻体的准确位置.