基于完备序列集的扩频码构造方法

为了改善传统扩频序列周期短、复杂度低的问题,提出一种基于完备序列集的扩频码构造方法。利用移位算法将二进制理想的二元自相关序列转换为长周期、高复杂度的完备序列集,随机地按行或列抽取完备序列集中的子序列,以其作为扩频码并用于扩频通信。利用传统伪随机序列和Logistic混沌序列分析该方法的有效性,并与现有方法相比得知,新方法可改善序列相关性,提高序列复杂度。仿真测试结果显示,完备序列具有较强的抗噪声干扰能力,并能获得较低的扩频误码率。     

面向交互应用的HEVC编码性能分析

结合现行的视频编码标准H.264/AVC,分析HEVC的具体编码技术,并对HEVC编码算法的编码效率和编码复杂度进行了对比研究。以交互应用视频序列为样本,对HEVC的具体性能进行测试,结果表明,在交互领域,和H.264/AVC相比,HEVC编码效率获得有大约50%的提升,编码复杂度也增加到了170%左右。     

近钻头旋扭冲击器结构设计与试验

PDC钻头在深井高硬度、研磨性较强的地层钻进时会出现蹩钻、跳钻现象,从而导致钻头机械钻速低、进尺少、经济效益差等问题。为提高钻头机械钻速,克服深井高硬地层普遍存在的粘滑现象,开展了近钻头旋扭冲击器设计研究工作。结合流体力学对工具进行结构优化设计,通过建立三维模型,运用模拟软件对工具结构流场进行有限元仿真分析,确定了工具结构参数。试制样机开展室内及现场的性能测试,样机各项功能正常,达到设计指标,满足现场应用要求。可为后期现场应用及工具的进一步优化改进提供借鉴。     

Effect of MgO sintering additive on mullite structures manufactured by fused deposition modeling (FDM) technology

An optimized recipe for 3D printing of Mullite-based structures was used to investigate the effect of MgO sintering additive on the processing stages and final ceramic properties. To achieve dense 3:2 mullite, ceramic filaments were prepared based on an alumina powder, a methyl silicone resin, EVA elastomeric binder and MgO powder. Using 1 wt% MgO and a dwell time of 5 h at 1600 °C, a dense mullite structure could be obtained from filaments with a diameter of 1.75 mm. Ceramic structures with and without sintering additive were printed in vertical and horizontal direction, to investigate the effect of printing direction on mechanical strength after sintering. Using four-point bending test, it was demonstrated that by using MgO, the printing orientation did not affect the mechanical strength significantly anymore. The low Weibull modulus could be explained by the closed porosity that emerge during the degassing of the preceramic polymer due to cross-linking.     

Failure modes of PDC cutters under different loads

The capability of several types of flat PDC cutters to withstand combined loads were tested and evaluated by the impact and cutting of single PDC cutter on granite in a linear impact-cutting table.The primary failure modes of PDC cutters withstanding different combined loads were investigated and analyzed.The suggestions of enhancing PDC cutters to be suitable for drilling very hard rock have been made.     

复合电镀新工艺金刚石钻头的研制与应用

本文采用复合电镀新工艺来研制和生产金刚石钻头。在研制过程中,往普通钻头镀液中加入10g/l金刚石微粉,得到镍—钻—金刚石微粉复合镀层,提高了钻头胎体的耐磨性。将两种品级、三种粒度金刚石按一定比例混合使用,扩大了钻头的适用范围,提高了钻头的自锐性。通过改变内、外径和底唇面镀层厚度的比例,做到镀层基本同步消耗完。一年多来的工地现场使用结果证明,这种钻头适用于坚硬、强研磨性地层的钻进,具有时效快、寿命长的优点。     

PDC钻头自动焊接技术

在对PDC钻头的焊接性进行分析的基础上，选择了火焰加热的钎焊方法，研制出了适用于PDC钻头火焰钎焊，并具有专利技术的复合片焊接温度测控系统和数控变位操作系统，实现了复合片与钻头基体焊接工艺参数的自动控制和复合片焊接位置的数控定位，在稳定PDC钻头的焊接质量、提高焊接效率、降低劳动强度方面迈出了重要的一步。     

An Experimental Study on Laser Cutting Mechanisms of Polycrystalline Diamond Compacts

The objective of this study is to experimentally investigate the cutting mechanisms of polycrystalline diamond compacts (PDC) using two different lasers: (a) a near infrared Nd:YAG laser (Neodymium-doped Yttrium Aluminum Garnet) of 1064 nm wavelength and 100 μs pulse width; and (b) a green light KTP (Potassium Titanyl Phosphate)/Nd:YAG laser of 532 nm wavelength and 120 ns pulse width. To realize the objective, the study applies polishing, lapping and etching processes to the cut-surfaces of the PDC samples. It further observes and analyzes the processed cut-surfaces with scanning electron microscopy (SEM) and Raman spectroscopy. A discussion is provided to reveal the underlying physics of the laser cutting mechanisms, and a conclusion is drawn based on the outcomes from the experimental investigation and the discussion.     

钻柄温挤成形及模具设计

介绍了钻柄温挤成形工艺及其模具设计。     

GPU-OSDDA: a bit-vector GPU-based deadlock detection algorithm for single-unit resource systems

This article presents a GPU-based single-unit deadlock detection methodology and its algorithm, GPU-OSDDA. Our GPU-based design utilizes parallel hardware of GPU to perform computations and thus is able to overcome the major limitation of prior hardware-based approaches by having the capability of handling thousands of processes and resources, whilst achieving real-world run-times. By utilizing a bit-vector technique for storing algorithm matrices and designing novel, efficient algorithmic methods, we not only reduce memory usage dramatically but also achieve two orders of magnitude speedup over CPU equivalents. Additionally, GPU-OSDDA acts as an interactive service to the CPU, because all of the aforementioned computations and matrix management techniques take place on the GPU, requiring minimal interaction with the CPU. GPU-OSDDA is implemented on three GPU cards: Tesla C2050, Tesla K20c, and Titan X. Our design shows overall speedups of 6-595X over CPU equivalents.