超细石墨粉体高温高压合成金刚石研究

为研究超细石墨粉体合成金刚石的可能性,以5000目的超细石墨粉和Fe70Ni30触媒为原料,用静态高压技术合成出金刚石。研究结果表明：以超细石墨粉为碳源材料合成金刚石是完全可行的,但在合成晶体里发现有大量缺陷存在;合成金刚石单产接近120ct,明显要高于相同合成腔体和工艺条件下合成普通金刚石的单产;晶体粒度平均为270μm左右,小于相同条件下以200目人造石墨粉为原料合成晶体的粒度。以超细石墨粉体为碳源材料合成金刚石的生产工艺等各方面影响因素有待深入研究。     

海洋二维双船拖缆与宽频带地震采集实验

双船拖缆地震采集可以布设灵活的观测系统,如形成大炮检距、增加覆盖次数、中间激发提供两个方向照明等,进而改善复杂构造的地震成像效果。同时,宽频地震技术日益受到重视,通过大容量宽频震源激发,变深度拖缆接收,并进行数据去鬼波处理,达到拓宽频带的效果。综合双船拖缆与宽频采集的优势所开展的实验表明,成像剖面的浅层分辨率得到提高,中深目标层揭示效果有了改善,该技术在构造成像难点区值得尝试。     

苹果醋发酵过程中L-苯丙氨酸促进乙酸-2-苯乙酯的合成

为了初步研究食品添加剂L-苯丙氨酸对苹果醋发酵过程中的特征性香气成分乙酸-2-苯乙酯的合成途径及关键酶活的影响,采用HS-SPME-GC-MS和ELISA,检测各合成相关基质生成量和关键酶活性的变化。结果表明,不同添加量的L-苯丙氨酸有明显促进乙酸-2-苯乙酯及其相关合成基质生成量积累的作用,并且对ADH、AAT的酶活性也有一定的促进作用,而对Esterase酶活性有抑制作用。其中当L-苯丙氨酸添加量为8 g/L时,乙酸-2-苯乙酯生成量显著提高了43.76%～86.59%。因此,本试验初步将8 g/L作为L-苯丙氨酸的最佳添加量,初步推测L-苯丙氨酸通过醇酰基转移酶途径促进乙酸-2-苯乙酯的合成及其相关基质和关键酶活的生成量,赋予苹果醋产品更多独特的香气和风味,为生产工艺提供一定的参考依据。     

The influence of hand hole on the ultimate strength and crack pattern of shield tunnel segment joints by scaled model test

With the shield tunnel going deeper and deeper, the circumferential axial force becomes the governing factor rather than the bending moment. The hand hole acts as a weak point and initial damage in the segment joint especially when the circumferential axial force is extremely high. Despite the wide application of steel fiber or synthetic fiber in the tunneling, limited researches focus on the structural responses of segment joint with macro structural synthetic fiber (MSSF). In this paper, a 1:2 reduced-scale experiment was conducted to study the structural performance of the segment joint with different types of hand holes under ultra-high axial force. Special attention is paid to failure mode and structural performance (bearing capacity, deformation, cracking, and toughness). Moreover, segment joints with MSSF are also tested to evaluate the effects of MSSF on the failure mode and structural performance of the segment joints. The experiment results show that the hand hole becomes the weakest point of the segment joint under ultra-high axial force. A \ /-type crack pattern is always observed before the final failure of the segment joints. Different types and sizes of the hand hole have different degree of influences on the structural behavior of segment joints. The segment joint with MSSF shows higher ultimate bearing capacity and toughness compared to segment joint with common concrete. Besides, the MSSF improves the initial cracking load and anti-spallling resistance of the segment joint.     

基于图像深度学习与三维电场仿真的电力用复合绝缘子缺陷挖掘分析

鉴于复合绝缘子运行环境差异较大、表面电场分布特征各异,亟需合理评估现役运行复合绝缘子运行状态。为此,首先应用紫外、红外成像技术对典型复合绝缘子进行观测形成电-热影像图谱数据库;然后应用小波成像技术对原始图像进行去噪处理,并基于聚类算法对复合绝缘子进行图像区域分割,联合视觉深度学习实现了复合绝缘子类型自适应识别和外轮廓匹配。同时应用三维建模技术对典型复合绝缘子电场分布规律进行仿真模拟,实现复合绝缘子高场强区域电场分布可视化;最终联合深度学习图像后处理结果和电场分布特征形成现役复合绝缘子运行状态评估策略。研究结果对于电力系统用复合绝缘子运行维护具有较好指导意义。     

Wind tunnel quantification of dynamic stall on an S817 airfoil and its control using synthetic jet actuators

Wind tunnel experiments were performed to quantify the aerodynamic characteristics of the S817 airfoil in dynamic stall conditions, and the subsequent application of active flow control to modify the manner by which dynamic stall incepts. Both quasi‐2D and cantilevered finite span configurations were tested. Surface pressure, six‐component force‐torque sensor, and stereoscopic particle image velocimetry (SPIV) were used to quantify the baseline flow and the benefits of actuating synthetic jets (installed at x/c = 0.35, angled 45° into the flow, and at a momentum coefficient C_μ = 0.012). The airfoil was pitched at reduced frequencies of k_f = 0.025 and 0.05 and at shallow and deep stall. Vortex induced lift from dynamic stall was observed and was eliminated by the use of synthetic jets for nearly all conditions; pitching moment deviation was also observed to be significant, and was eliminated at shallow stall and significantly reduced during deep dynamic stall when the synthetic jets were actuated. Moreover, the activation of synthetic jets resulted in significant reduction in the hysteresis (area within the pitching up and pitching down load history) of the lift and pitching moment through all experimental conditions, as much as 41% and 85%, respectively. SPIV flow fields in shallow dynamic stall demonstrated that actuation of synthetic jets confined the separated region to the trailing edge, in both the instantaneous and time averaged sense. To further reduce the lift and pitching moment hysteresis at high angles of attack, a pulse modulation technique was used and showed a marked increase in synthetic jet performance compared with the continuously actuated case and achieved this result with approximately 65% less power consumption.     

复合绝缘子局部微间隙对电场分布影响的有限元数值模拟及分析

由于高压复合绝缘子受模压、材料热胀冷缩特性、密封加工工艺等因素的影响,在金具、芯棒和伞裙护套之间容易产生局部微间隙,从而造成局部放电,导致复合绝缘子的耐老化性能降低。将复合绝缘子的静电场无界域问题等效为分层均匀媒质的多介质闭域电场问题,建立三维复合绝缘子模型,采用有限元方法对存在局部微间隙的复合绝缘子的电气性能进行分析,研究局部微间隙不同尺寸及位置对局部和整体电位、电场强度分布的影响规律。结果表明：局部微间隙邻近的3片伞裙的电场强度发生明显畸变,而对其余伞裙的影响可以忽略;局部微间隙尺寸增大将导致相应伞裙的电压承担率增加,球形微间隙表面的场强最大值也逐渐升高,导致微间隙内部区域放电几率增大。     

3种合成抗氧化剂在棕榈油煎炸过程中的损耗及其对煎炸油品质的影响

以棕榈油(熔点24℃)在180℃下间歇煎炸薯条60 h,研究合成抗氧化剂特丁基对苯二酚(TBHQ)、没食子酸丙酯(PG)和L-抗坏血酸棕榈酸酯(AP)的损耗情况及其对棕榈油中生育酚和生育三烯酚的保护效果;以酸价、极性组分含量、过氧化值、色泽和氧化诱导期评价这3种合成抗氧化剂对煎炸过程中棕榈油品质的影响。结果表明:3种合成抗氧化剂损耗速率的快慢顺序为TBHQPG AP,TBHQ和PG可以有效保护棕榈油中的生育酚和生育三烯酚,但是AP会促进生育酚和生育三烯酚损耗; PG和AP都可以显著抑制棕榈油酸价的升高,TBHQ无显著性影响; TBHQ和PG均可显著抑制煎炸过程中棕榈油极性组分含量的增加,AP无显著性影响;过氧化值与煎炸时间无线性关系; PG和AP可以抑制棕榈油煎炸过程中色泽的加深,TBHQ无显著性影响; TBHQ和PG可以延长棕榈油的氧化诱导期,而AP缩短了棕榈油的氧化诱导期。     

采用级数反转推导收发分置SAR二维点目标频谱的方法

概述:本文采用级数反转的方法,对任意收发分置合成孔径雷达的两维点目标频谱进行推导。通过采用级数反转法,可利用固定相位及傅立叶变换推导得出二维点目标的频谱。频谱的精度通过在两级数扩展中保留足够的项目数来进行控制。最后,文章对单点目标进行了仿真,证实了收发分置雷达的二维点目标频谱可通过将收发分置距离等式用指数级数的形式表示,并通过在方位频率函数中采用级数反转法来表达方位时间而获得。     

发电设备重要度的综合权重研究

为更准确地体现设备对系统的影响,提出了设备综合权重的概念.根据发电设备在系统中的固有结构和设备的基本功能,以及设备的实际运行指标参数计算得到的设备综合权重,既体现了设备在系统固有结构中的静态重要度,又考虑了设备实际运行状态对系统功能的动态影响,可以较全面地反映设备在系统中的实际重要度,对准确评估系统的运行风险、进行状态检修都具有重要的意义.通过给水泵综合权重计算实例验证了其有效性.