一种最小机械比能计算参数优化的方法

机械比能是衡量钻井效率的重要因素之一,它用来衡量钻头破碎单位体积岩石耗能大小[1]。传统的比能计算模型通过多个参数进行计算来求得比能值,较为复杂。文章通过利用比能计算模型中参数之间的关系,假设并通过Matlab拟合验证参数之间关系的函数方程,将原有的模型化简为只拥有钻压一个计算参量的新计算模型。通过求解新模型一阶导数的零点,求得最优钻压值,并以此求得最小机械比能,最终确定最佳钻井参数。     

A portable high-density absolute-measure NIRS imager for detecting prefrontal lobe activity under fatigue driving

Driving fatigue is one of the primary causes of traffic accidents nowadays. It is thus imperative to develop a technique to monitor levels of driving fatigue. The emergent near-infrared spectroscopy (NIRS) is now capable of measuring functional cerebral activities noninvasively and sensitively in terms of hemodynamic responses, shedding light on the possibility to detect signals regarding fatigue-specified cerebral activities. This work innovatively developed a NIRS device aimed at fatigue detection of drivers, and the device was designed to be portable so that it can be easily operated during driving. Moreover, the device is absolute-measure so that the data can be compared among drivers. The probe is high-density and we can visualize brain functional responses after imaging. The high sensitivity, stability, and reliabilities of our device were fully tested in the order of ink experiment, cuff experiment, and on-human test. For the in-situation on-human test, we recruited 3 taxi drivers and collected data by our device during 8 h' driving. It's found that the hemodynamics-represented cerebral activation decreased with driving duration, which indicated our device's strong potential in monitoring fatigue.     

Gradient based adaptive thresholding

For images with poor and non-uniform illumination, adaptive thresholding is required to separate the objects of interest from the background. In this paper a new approach to create an adaptive threshold surface is proposed to segment an image. The technique is inspired by the Yanowitz’s method and is improved upon by the introduction of a simpler and more accurate threshold surface. The method is tested on several images of different patterns with varying illumination and the results are compared to the ones produced by a number of adaptive thresholding algorithms. In order to demonstrate the effectiveness, the proposed method had been implemented in medical and document images. The proposed method compares favorably against those using watershed and morphology in medical image and favorably against variable threshold and adaptive Otsu’s N-thresholding for document image.     

Task-oriented design method and research on force compliant experiment of six-axis wrist force sensor

This paper analyzes the task-oriented design method of six-axis force sensor and proposes the task model of the sensor. The task mathematical model of the sensor is established based on the idea of task ellipsoid. The models of force ellipsoid and moment ellipsoid are also established. The relational expression between the task model and ellipsoid model of sensor is obtained. Then, a fully pre-stressed dual-layer parallel six-axis wrist force sensor is proposed, whose static mathematical model is also established. The sensor task model for assembly work is proposed and the analytical expression between the sensor structure parameters and task model is deduced. According to the assembly work, the sensor structure is designed specifically, and the specific structure sizes of the sensor are obtained. Then the new sensor prototype manufactured for peg-in-hole assembly is processed. The calibration experiment and peg-in-hole assembly experiment on the prototype are completed and each performance index is well examined by the experiment results. The experiment results also lay the foundation for the practical application of six-axis force sensor.     

Realizing improved performance of down-conversion white organic light-emitting diodes by localized surface plasmon resonance effect of Ag nanoparticles

Down-conversion structure white organic light-emitting diodes (WOLEDs), in which white light is generated by a blue emission organic light-emitting diodes (OLEDs) in combination with a color conversion layer (CCL) outside the substrate, has attracted extensive interest due to its significant advantages in low cost and stabilized white-light emissions. However, low color-conversion efficiency of CCL is still a bottleneck for the performance improvement of down-conversion WOLEDs. Here, we demonstrate an approach to enhance the color-conversion efficiency of CCL-WOLEDs by localized surface plasmon resonance (LSPR) effect. In this approach, a blend of Ag nanoparticles and polyvinyl alcohol (PVA) is solution-deposited between the blue organic light emitting diodes and color-conversion layer. Based on the LSPR effect of this modified structure, the color conversion efficiency has improved 32%, from 45.4% to 60%, resulting a 14.4% enhancement of the current efficiency, from 9.73 cd/A to 11.14 cd/A. Our work provides a simple and low-cost way to enhance the performance of down-conversion WOLEDs, which highlights its potential in illumination applications.     

Experimental investigation of the failure mechanism of Cu–Sn intermetallic compounds in SAC solder joints

A detailed experimental study on the fracture mechanism of Cu–Sn intermetallic compounds (IMCs) in the Pb-free solder was presented in this paper. The growth behaviors of the Cu₆Sn₅ and Cu₃Sn IMCs were inspected and the respective evolution pattern of their microstructures was investigated. Then, a detailed fractographic analysis on brittle fractured solder joints was conducted after the high speed ball pull test. The fracture locations in the Cu–Sn IMC layers during different periods of aging process were identified. The fracture modes of Cu₆Sn₅ and Cu₃Sn were determined as well. Afterwards, the fracture energies of different Cu–Sn IMC materials were directly compared using the Charpy impact test with a specially designed specimen. It was found that the grain boundary of Cu₃Sn is the weakest link in the Cu–Sn IMC system. Finally, based on these three parts of study, a mechanism to explain the thermal degradation of Cu–Sn IMCs was proposed.     

基于地磁与角速度传感器的弹体姿态测量方法研究

为了获取炮射弹体最优的姿态解算方法,使其能满足弹体的实际应用要求,文中阐述了目前用于弹体姿态测量的主要方法及缺点,提出了一种运用地磁传感器进行姿态测量的方案,并建立了坐标系完成参量解算。当地磁传感器测量方法不可靠时,可以使用角速度传感器完成姿态解算。使用两种信息融合方法进行姿态解算,可在全弹道上可靠的进行姿态测量。     

着靶角对PELE横向效应的影响

PELE是一种基于新型作用机理的弹药,能使目标产生明显的横向效应,对靶后目标形成有效的杀伤。为研究着靶角对PELE横向效应的影响,对不同着靶角下PELE侵彻靶板的过程进行了数值分析。结果表明:着角对PELE横向效应影响显著。当着角在0～60°,随着着角的增大,破片最大径向速度增大,散布面积增大,破片数量增多,横向效应增强;当着角大于60°,随着着角的增大,PELE横向效应逐渐丧失;当着角在30～60°,PELE横向效应和后效毁伤性能最佳。     

爆炸网络在聚能装药战斗部上的应用技术研究

针对目前聚能装药破甲弹大多采用隔板法提高破甲威力中存在的问题,提出了采用爆炸网络技术作为聚能破甲战斗部的起爆方式。以某破甲战斗部为背景,根据药型罩和主药柱等装药结构参数,设计了同步爆炸网络样机。通过性能对比试验可知,采用爆炸网络替代隔板和副药柱,不仅起爆可靠,可以精确控制并获得理想的爆轰波形,而且破甲威力及破甲稳定性得到了大幅度的提高。试验结果表明,采用爆炸网络技术是提高破甲性能非常有效的方法之一。研究结果为该技术在聚能装药战斗部上的工程应用奠定了基础。     

高g值高频响微机械加速度计研究

针对侵彻武器测试过程中冲击过载大和频率范围宽的特点,提出了一种微机械电容式加速度计结构,结构中采用分布在整个芯片上的小电容阵列来代替位于中间的单个大电容器.利用ANSYS对加速度计进行了仿真分析,得出加速度计的固有频率超过600 kHz,抗过载能力超过200 000 g,且电容变化量大,灵敏度高.文中还给出了加速度计芯片的加工工艺流程和接口电路.