井下微地震监测技术在公003-H16井水力压裂中的应用

井下微地震监测技术是目前国际上公认的最先进的裂缝监测技术,利用该技术对公003-H16井水力压裂裂缝形态进行了监测。井下微地震监测结果与压裂施工曲线进行紧密结合后,对及时优化压裂参数、实时调整施工方案提供了重要依据。井下检波器监测到的最远微地震事件信号距离检波器达到950m,监测结果清晰地反映了压裂井地层地应力方向与大小,地层非均质性,水力压裂产生的裂缝方位、缝长、缝高、缝宽等参数,为该区块以后油井的部署与储层改造提供了重要参考。     

A high-capacity performance-preserving blind technique for reversible information hiding via MIDI files using delta times

A new high-capacity information hiding method for embedding secret messages into MIDI files is proposed. The method can preserve the original musical performance of the cover MIDI file. The property of the variable-length quantity, which expresses the magnitude of the delta time before every event in a MIDI file, is utilized for secret bit embedding. The embedding is accomplished by padding the delta times with different numbers of leading constant bytes of 80₁₆ to represent the secret bits. The method is both reversible and blind because the original cover MIDI file can be restored completely from the stego-MIDI file by extracting the embedded data out from the resulting stego-MIDI file without referencing the original cover MIDI file. A capability of hiding a large amount of secret information is achieved since the delta time is a basic parameter that appears before every event in the MIDI file. Good experimental results yielded by the proposed method as well as a comparison of the method with five existing performance-preserving methods from the viewpoints of stego-file quality, payload capacity, and data security show the superiority and feasibility of the proposed method.

     

Embedding of any type of data in images based on a human visual model and multiple-based number conversion

A novel approach to embedding any type of digital data into a cover image is proposed, which utilizes a human visual model to guarantee that the modification of the cover image is imperceptible. A quantized contrast function based on the model is constructed first. The gray values of each 3×3 sub-image of the cover image are used to compute, using the function, a range of gray levels with the same contrast as that of the central pixel of the sub-image. The embedding process proceeds by replacing the gray value of the central pixel by one of the values in the range. This guarantees that the changes be imperceptible. The data to be embedded is treated as a binary stream and is partitioned into a number of sub-streams. A multiple-base number conversion mechanism is used to convert each sub-stream of data into values which are then embedded in the central pixels of sub-images. The embedded data can be extracted out from the resulting stego-image without referencing the original image. Experimental results show that the proposed method is feasible.     

小剂量丙泊酚联合曲马多治疗椎管内麻醉后寒战

目的: 探讨亚麻醉（催眠）剂量丙泊酚联合曲马多静注对椎管内麻醉后患者寒战的止颤效果及恶心呕吐的发生率以及安全性。方法: 120例ASAⅠ级或Ⅱ级椎管内麻醉后发生术中或术后早期寒战的下腹部或下肢手术患者,随机分成3组。分别为曲马多联合丙泊酚0.5 mg/kg组（A组）及联合丙泊酚0.25 mg/kg组（B组）、曲马多组（C组）。患者发生寒战时,均给予曲马多1 mg/kg,其中A组与B组再同时分别静推丙泊酚0.5 mg/kg或0.25 mg/kg。观察并记录三组患者用药前寒战分级、用药后寒战缓解程度、恶心呕吐发生率、镇静情况及其它不良反应。监测患者给药前后平均动脉压(MAP)、心率(HR)、脉搏血氧饱和度(SpO₂)。结果: 用药后组内比较三组寒战分级均显著降低（P＜0.01）,其中A、B和C组寒战完全停止的病人比例分别为100%、95%和92.5%,组间疗效比较无统计学差异。三组患者MAP、HR、SpO2组内比较均无统计学差异（P＞0.05）,均未发生镇静过度或呼吸抑制。与C组比较（30%）,A组（2.5%）和B组（15%）呕吐发生率明显较低（P＜0.05）。结论: 小剂量丙泊酚（0.5 mg/kg）联合曲马多1 mg/kg治疗椎管内麻醉后患者寒战安全有效,并能显著降低恶心呕吐的发生。     

炭包覆LiFePO4纳米片的制备及电化学性能研究

为改善磷酸铁锂正极材料的倍率性能, 以乙二醇为溶剂, 采用一步溶剂热法制备磷酸铁锂纳米片。再以葡萄糖为碳前驱体, 对磷酸铁锂纳米片进行炭包覆。通过X射线衍射, N₂吸脱附曲线、扫描电子显微镜、透射电子显微镜和循环伏安法等测试方法考察了炭包覆量对磷酸铁锂纳米片结构与电化学性能的影响。结果表明, 制备的磷酸铁锂为具有较短b轴的纳米片状结构, 尺寸约为150 nm×100 nm×60 nm。磷酸铁锂纳米片的倍率性能随炭包覆量的增加而增强, 当炭包覆量为6.4wt%时具有最佳的倍率性能, 在0.2C和10C的电流密度下放电容量分别为157.3和132.6 mAh/g。同时循环稳定性良好, 在5C电流密度下循环500次后容量保持率达到了80.2%。     

安徽地级市承接外商直接投资竞争力实证分析

外商对中西部地区直接投资的影响因素主要表现为人力资源、劳动力工资水平、产业结构水平、基础设施等方面.安徽16个地级市在承接外商直接投资竞争力方面存在一定差距,要切实提高工业化水平,增强承接外商直接投资的能力;找出自身制约根源,抓住工业化主旋律不放.     

A novel 3D mesh compression using mesh segmentation with multiple principal plane analysis

This paper proposes a novel scheme for 3D model compression based on mesh segmentation using multiple principal plane analysis. This algorithm first performs a mesh segmentation scheme, based on fusion of the well-known k-means clustering and the proposed principal plane analysis to separate the input 3D mesh into a set of disjointed polygonal regions. The boundary indexing scheme for the whole object is created by assembling local regions. Finally, the current work proposes a triangle traversal scheme to encode the connectivity and geometry information simultaneously for every patch under the guidance of the boundary indexing scheme. Simulation results demonstrate that the proposed algorithm obtains good performance in terms of compression rate and reconstruction quality.     

Impact of Impeller Stagger Angles on Pressure Fluctuation for a Double-Suction Centrifugal Pump

Pressure fluctuation may cause high amplitude of vibration of double-suction centrifugal pumps, but the impact of impeller stagger angles is still not well understood. In this paper, pressure fluctuation experiments are carried out for five impeller configurations with different stagger angles by using the same test rig system. Results show that the stagger angles exert negligible effects on the characteristics of head and efficiency. The distributions of pressure fluctuations are relatively uniform along the suction chamber wall, and the maximum pressure fluctuation amplitude is reached near the suction inlet tongue region. The pressure fluctuation characteristics are affected largely by impeller rotation, whose dominant frequencies include impeller rotation frequency and its harmonic frequencies, and half blade passage frequency. The stagger angle exerts a small effect on the pressure fluctuations in the suction chamber while a great effect on the pressure fluctuation in volute casing, especially on the aspect of decreasing the amplitude on blade passage frequency. Among the tested cases, the distribution of pressure fluctuations in the volute becomes more uniform than the other impeller configurations and the level of pressure fluctuation may be reduced by up to 50% when the impeller stagger angle is close to 24° or 360°.The impeller structure pattern needs to be taken into consideration during the design period, and the halfway staggered impeller is strongly recommended.     

面向区域侦察的实拍实传卫星规划推演系统

为支持多颗实拍实传卫星区域侦察任务,研制规划推演系统.设计了规划推演系统的总体结构和信息流程,并研究了系统研制所需关键技术,分别提出了面向区域侦察的数传任务规划算法、基于网格的卫星区域覆盖分析算法、基于OSGEarth的目标区域和侦察范围组合可视化方法.研制的规划推演系统已成功应用于某任务中,进行数传任务规划、能力分析和过程推演.