关于中国数字声音广播的讨论

随着数字化技术的深入发展及音频广播业的不断扩大,音频广播数字化的发展获得了强劲的推动力.目前国际上主流的数字声音广播技术有数字音频广播(DAB)、数字调幅广播(DRM)、数字高清广播(HD-Radio)等,这些技术各有其优势特点,但也各有适用性.探讨了中国数字化声音广播的发展方向,介绍了一种全新的带内高清数字广播技术系...     

伺服运动系统控制参数在线调节算法研究

针对传统伺服运动系统跟踪性能容易受到外界干扰、速度变化、非线性等因素影响的缺陷,提出根据速度变化实时切换控制参数的在线调节算法,并基于PMAC控制器实现其算法,通过实验证明了算法对改善伺服运动系统跟踪性能的有效性。     

不锈钢超精抛光蜡的研制

目前,国产不锈钢超精抛光蜡不能满足市场需求,对其配方研制报道较少。为此,对不锈钢粗抛光后,采用超精抛光蜡进行精抛光,对其组分进行了筛选：以仪型氧化铝粉为抛光磨料;以混合硬脂酸作抛光内脂;利用油酸的润滑作用降低不锈钢表面的抛光温度,利用三乙醇胺与有机酸的皂化反应生成物润滑和清洁不锈钢表面;利用松香和石油磺酸钡提高不锈钢表...     

Influence of hot working on microstructure and mechanical behavior of high nitrogen stainless steel

The relationship between microstructures and mechanical properties of a high nitrogen stainless (HNS) steel (0.65N–1.8Ni, wt%) manufactured by argon oxygen decarburization and continuous casting was investigated in this article. The plates with different thicknesses were obtained by thermo-mechanical control process. The results revealed that the plates prepared by hot rolled and solution treated possessed good balanced mechanical properties, i.e., satisfactory strength and higher toughness. Compared with hot-rolled and solution-treated plates, the hot-rolled plate had much higher tensile strength, but its impact toughness was extremely low. Furthermore, with the increase of deformation strain, the plate with finer grains, more precipitates and higher strength was achieved, but its plasticity decreased obviously. The worm-like carbides formed along the grain boundary during the finish rollings at 850 °C, which are detrimental to the toughness of hot-rolled plates. In addition, small amount of ferrite precipitated in the steel due to the non-equilibrium solidification during continuous casting, and to ensure full austenitic structure, composition design method was recommended.     

Study on two operating conditions of a full-scale oxidation ditch for optimization of energy consumption and effluent quality by using CFD model

The operating condition of an oxidation ditch (OD) has significant impact on energy consumption and effluent quality of wastewater treatment plants (WWTPs). An experimentally validated numerical tool, based on computational fluid dynamics (CFD) model, was proposed to optimize the operating condition by considering two important factors: flow field and dissolved oxygen (DO) concentration profiles. The model is capable of predicting flow pattern and oxygen mass transfer characteristics in ODs equipped with surface aerators and submerged impellers. Performance demonstration and comparison of two operating conditions (existing and improved) were carried out in two full-scale Carrousel ODs at the Ping Dingshan WWTP in Henan, China. A moving wall model and a fan model were designed to simulate surface aerators and submerged impellers, respectively. Oxygen mass transfer in the ditch was predicted by using a unit analysis method. In aeration zones, the mass inlets representing the surface aerators were set as one source of DO. In the whole straight channel, the oxygen consumption was modeled by using modified BOD-DO model. The following results were obtained: (1) the CFD model characterized flow pattern and DO concentration profiles in the full-scale OD. The predicted flow field values were within 1.98 ± 4.28% difference from the actual measured values while the predicted DO concentration values were within −4.71 ± 4.15% of the measured ones, (2) a surface aerator should be relocated to around 15 m from the curve bend entrance to reduce energy loss caused by fierce collisions at the wall of the curve bend, and (3) DO concentration gradients in the OD under the improved operating condition were more favorable for occurrence of simultaneous nitrification and denitrification (SND).     

某工程大跨简支缺口梁开裂事故的检测鉴定及加固处理

深圳某8层建筑大跨简支缺口梁简支端在主体结构竣工后出现较为严重的开裂.通过对受损结构进行裂缝普查以裂缝深度超声检测,发现裂缝可分为多种类型;裂缝形式复杂,且裂缝深度较深,大部分为贯通裂缝,严重影响构件承载力.在分析裂缝开展原因及对结构安全性影响程度的基础上,综合分析采取支座处理、加大截面、粘钢等多种加固方式对该结构进行...     

焊线机超声波闭环控制

超声波是焊线机焊接过程中的重要参与元素,超声波控制效果决定着焊接的品质和速度。在分析超声换能器频率特性和电流响应的基础上,给出了频率自动跟踪和电流受控输出的闭环控制方案,提高了超声波效率,缩短了响应时间,增强了超声波输出的稳定性。实验结果表明,此方法实现了受控的上升时间和较小的超调     

自适应THP模运算因子选取方法

以下行多用户多输入单输出(MU-MISO)系统为例,分析了在发送端采用汤姆林森-哈拉希玛预编码(THP)时,模运算因子的选取对系统性能的影响。通过考察每一步与该因子相关的数据处理过程,说明了在低信噪比(SNR)区域,为了获得较好的系统性能,应当在保证星座图不重叠的基础上,使模运算因子尽可能地小。而后通过固定SNR下的梯度调整,寻找出最佳的模运算因子。通过仿真可以看出,理论分析结果与蒙特卡洛仿真结果相吻合,随着SNR的增加,系统的最佳模运算因子趋于某个固定值,该值与经典论文在对应调制方式下的推荐值相接近。为了优化低SNR区域的系统性能,该文进一步提出了一种自适应的模运算因子选取方法。     

一种区分服务模型及其在三层交换机的实现

服务质量（QoS）是用来定义网络给不同形式的流量提供不同级别的服务保障的能力.当前服务质量的体系结构和模型有多种,本文参照RFC2474、RFC2475 标准,提出了一种新的服务质量-区分服务（Diffserv）应用模型,该模型包括：流量的分类器、计量器、标记（或重标记）器、丢弃器和调度器等模块, 其中对于核心模块-调度器, 提出基于最大延迟的加权轮转调度（WRR-MBD）算法,同时给出区分服务模型在3 层以太网交换机的实现方法.通过网络测试分析仪对3 层交换机QoS 性能进行测试,得出在WRR 调度策略下,不同优先级数据包的丢失率基本按所设置的权重比例进行分配,从而避免了严格优先级（SP）调度存在的低优先级队列“饥饿”的现象.     

长庆油田油藏动态模拟模型资源管控系统设计与实现

随着勘探开发的不断深入,精细油藏描述过程中产生了大量的历史油藏模拟模型,因缺乏模型资源处理与管控技术,导致无法应用其进行油藏动态模拟计算,为此开展了油藏模型资源管控系统研究。针对长庆油田工作人员在油藏动态模拟计算过程中模型资源的采集、管控、标准化处理、可视化输出与动态计算等方面需求,利用B/S与C/S相结合的系统架构模式,开发了用于油藏动态模拟计算的资源管控系统,有效提升了油藏动态模拟过程数据的采集与应用效率,提高了模型资源再利用率;对油藏模型资源管控系统建设思路、开发工具、架构设计、实现方法以及应用功能等方面进行了探讨与总结,开发了中文版界面的应用系统,为油田的精细描述成果再应用与智能化建设提供了有效的技术支撑。