Short-term observation of wind energy potentiality in the Wol-Ryong wind site

Accurate analysis of the atmospheric wind profiles and climate characteristics in a certain area is a prerequisite for providing reliable information on a wind energy site. Two 2-D ultrasonic anemometers and one cup anemometer, arranged perpendicularly to the prevailing wind direction, were used to measure the atmospheric wind environment at a height of 4.5 m in the coastal region of Wol-Ryong, Jeju, South Korea. This study aims to estimate future wind resources with various estimation methods. The wind energy is theoretically estimated at 75 m, the hub height of 800 kW and 1500-kW-class wind turbines, at the Wol-Ryong site. Methods using three equations, a logarithmic profile, a modified logarithmic profile, and a power law, are applied for accurate prediction of the atmospheric wind profile. In addition, yearly wind power can be calculated by using the probability distribution from Weibull and Rayleigh profiles. It is found that the predicted wind speed is strongly affected by surface atmospheric conditions such as the friction velocity, atmospheric stability, and averaged roughness length. The Rayleigh profile gives more power generation than the Weibull distribution, especially under low-windspeed conditions. The logarithmic profile method seems to be the proper method for estimating the energy production at the Wol-Ryong site for neutral atmospheric conditions. On the other hand, the other two methods — the modified logarithmic profile method and the power law method — seem to be improper for neutral conditions.     

Friction of rubber on ice: A new machine,influence of rubber properties and sliding parameters

Friction of rubber on ice and snow is important for performance of vehicle tyres in winter. We introduce a new linear tribometer that was designed for measuring the friction of rubber on ice. We present a systematic study of rubber sliding on ice, investigating speed, load, temperature and rubber properties. The friction was linked to behaviour at the interface, particularly melt–water formation and real area of contact. Friction tends to decrease with conditions that promote melt–water formation, and tends to increase as real area of contact increases. We observe stick-slip behaviour with high real area of contact and high load.     

智能割草机的区域全覆盖算法设计与仿真

为解决无导航功能的智能割草机割草区域最佳覆盖的问题,提出了"单元分解目标区域,并逐一覆盖"的区域全覆盖算法。首先介绍了区域全覆盖的总体策略,接着基于特定割草机硬件,采用了单元分解法作为全区域覆盖算法的整体策略,对每个子区域则选择往复式行走方式进行逐一覆盖。然后具体提出了无障碍物区域和两障碍物区域的离线全覆盖算法,并对有障碍区域的算法加以了改进和推广。随后基于Matlab软件,对有两圆形障碍物的圆形区域进行了全区域覆盖算法的仿真实验。实验结果表明,所提出的区域全覆盖算法可以实现割草区域的最优覆盖。     

圆柱锂电池端面凹坑缺陷检测方法研究

端面凹坑是圆柱锂电池缺陷检测的重要指标之一。因为明暗对比度小的浅凹坑极易受金属表面上随机出现的亮点暗斑等强噪声的干扰,造成浅凹坑自动检测十分困难。为此,提出了一种解决方案：首先针对在单一光源角度下难以获取清晰的浅凹坑图像问题,采集6张凹坑在不同光源角度下的图像;其次采用时域平均和剔除异常值方法对6张图像进行融合得到基准面图像,并采用基于滑动窗口和奈奎斯特采样定理的空间滤波方法,减弱了信息强度较强的干扰噪声,再根据误差分析理论,提取灰度分布曲线的平均偏差;然后根据凹坑在灰度分布曲线中的形态,提取凹凸曲线段峰谷差和宽度比;最后采用BP神经网络方法建立检测模型来实现凹坑检测。对现场采集到的样本进行了测试,算法的正确检测率为100%。     

Stress Concentration in the Vicinity of a Hole Defect Under Conditions of Hertzian Contact

Two-dimensional photoelastic stress analyses were conducted for epoxy resin models containing a hole defect under the conditions of Hertzian contact. Stress concentrations around the defect were determined as a function of several parameters. These were hole diameter, its vertical distance from the contact surface, and the horizontal distance from the Hertzian contact area. Also determined was the effect of tangential traction (generated by a friction coefficient of 0.1) on the stress concentration.

Sharp stress concentrations occur in the vicinity of both the left and the right side of the hole. The stress concentration becomes more distinct the larger the hole diameter and the smaller the distance between the hole and the contact surface.

The stress concentration is greatest when the disk imposing a normal load is located at the contact surface directly over the hole. The magnitude and the location of stress concentration varies with the distance between the Hertzian contact area and the hole. Taking into account the stress amplitude, the area which can be involved in a process of rolling contact fatigue seems to be confined to a shallow region at both sides of the hole. The effect of tangential traction is comparatively small on the stress concentration around tile hole.     

Graphene Grown by Chemical Vapour Deposition on Steel Substrates: Friction Behaviour

Graphene was grown by low-pressure chemical vapour deposition on polished steel samples using ethanol as a precursor at different pressures: 200 and 400 mTorr. The samples were characterized by Raman spectroscopy, and the Raman maps clearly show the formation of an inhomogeneous graphene coating with surface regions covered with single-layer, bilayer, and multilayer graphene, the last one covering most of the surface area of the sample when the sample was prepared at 400 mTorr. Scanning electron microscopy revealed the partial coverage of the sample surface when the graphene coating was prepared at a pressure of 200 mTorr. Friction measurements were taken using a micro-tribometer in a ball-on-flat contact geometry with a stainless steel ball as the counterbody. An important reduction in the coefficient of friction was verified even with partial coverage of the steel surface, and it was attributed to the formation of nanographitic structures in the wear track region and partially transferred to the counterbody.     

南通地区大型医用影像设备购置探讨

目的：解南通地区大型医用影像设备购置情况,根据南通地区大型医用影像设备的调研结果进行分析,探讨区域设备购置规划及卫生政策实施的合理性。资料与方法：对南通所属地区拥有DSA、CT、MR的55家医院进行现场调研,包括：南通各地大型医用影像设备的分布种类、台数、购机金额、二手机等,对其万人拥有CT台数、每台CT覆盖范围进行调研。结果：各类大型医用影像设备总台数为：DSA 10台、CT 60台、MR 11台;其中,二手CT机有7台均分布在一级医院;万人拥有CT台数平均为0.08台;每台CT机所覆盖的面积（km2）平均为141.60km2,覆盖面积最大的如东地区为每台覆盖267.42km2;不能满足诊疗需求。MR、DSA均分布在三级和二级医院;一家医院拥有多台CT机的均分布在三级和二级医院里。结论 ：要加大对南通部分地区大型医用影像设备购置的投入,制定规划时要充分考虑医院的等级、地区所在位置、人口、面积以及经济实力等重要影响因素。     

Quantitative analysis of the material flow in transitional region during isothermal local loading forming of Ti-alloy rib-web component

The material flow in transitional region plays an important role in the forming quality of transitional region in the isothermal local loading forming of titanium alloy large-scale rib-web component. To study the material flow in transitional region, the finite element (FE) model of transitional region was established based on DEFORM-2D software and validated by physical experiment. Then, a quick and easy method, which can measure the area of different local regions of forged part in DEFORM-2D via user subroutine, was proposed to achieve the quantitative analysis of material flow mechanism. This technique can also be used in the analysis of other forming process, such as the calculation of fill ratio in forging process. The material flow pattern of transitional region during local loading forming was analyzed step by step and compared with integral forming. The results show that the material flow of transitional region during local loading process can be divided into six stages according to the material flow pattern and load-time curve. Twice transverse material flow with opposite directions occurred in the first and second loading steps sequentially, which does not exist in the integral forming. Four characteristic values evaluating the transverse flow of material, which are associated with the formation of defects and their severities, are defined and quantitatively measured at various processing conditions. It is found that decreasing the spacer block thickness and increasing friction both can decrease the four characteristic values, thus weaken the transverse material flow, which are helpful to improve the forming quality in transitional region. However, the transverse flow of material is little affected by the loading speed.     

星形套闭塞模锻光塑性模拟研究

利用光塑性方法以聚碳酸脂为模拟材料研究轿车等速万向节星形套闭塞模锻成形过程，获得星形套闭塞模锻成形过程的三维光塑性应变分布，提出其应变分布特征，并对典型截面应变进行计算分析，研究结果可实际钢质星形套闭塞模锻工艺和模具设计起一定的指导作用。     

土压平衡盾构螺旋输送机配置选型研究

螺旋输送机是土压平衡盾构的排土装置,是土压平衡盾构的重要组成之一。它具有排渣、形成土塞保持土仓内土压稳定、通过控制排土速度实现动态土压平衡稳定开挖面三大功能。根据不同的施工水文地质条件,对螺旋输送机进行正确地配置选型,是盾构方案设计过程中的关键环节之一。若配置不当,将会造成喷涌、磨损、无法在掘进中途维修等严重后果,导致盾构施工无法正常进行。在介绍螺旋输送机工作原理、受力特征的基础上,结合不同的盾构施工水文地质条件对螺旋输送机配置选型进行分析研究,提出了土压平衡盾构螺旋输送机配置选型标准,并重点讨论针对复合地层的螺旋轴耐磨块结构设计。最后以成都为代表的砂卵石地层为例对该地区地铁隧道盾构施工的螺旋输送机进行配置选型。