铣制三元流叶轮时产生误差的原因分析及解决方法

对在五坐标数控加工中心上铣制三元流叶轮时出现的叶轮附面尺寸误差问题，进行了详细分析，并提出了问题的解决方法，有效地避免了加工中产生的超差。     

除尘系统纤尘集中回收的研讨

提出了除尘系统纤维粉尘集中回收的必要性和技术方案,介绍了结构原理研究和实验情况,探讨了对纤维粉尘集中回收和处理系统的形式、应用前景和价值.     

Computing aware scheduling in mobile edge computing system

Mobile edge computing (MEC) is an emerging technology recognized as an effective solution to guarantee the Quality of Service for computation-intensive and latency-critical traffics. In MEC system, the mobile computing, network control and storage functions are deployed by the servers at the network edges (e.g., base station and access points). One of the key issue in designing the MEC system is how to allocate finite computational resources to multi-users. In contrast with previous works, in this paper we solve this issue by combining the real-time traffic classification and CPU scheduling. Specifically, a support vector machine based multi-class classifier is adopted, the parameter tunning and cross-validation are designed in the first place. Since the traffic of same class has similar delay budget and characteristics (e.g. inter-arrival time, packet length), the CPU scheduler could efficiently scheduling the traffic based on the classification results. In the second place, with the consideration of both traffic delay budget and signal baseband processing cost, a preemptive earliest deadline first (EDF) algorithm is deployed for the CPU scheduling. Furthermore, an admission control algorithm that could get rid off the domino effect of the EDF is also given. The simulation results show that, by our proposed scheduling algorithm, the classification accuracy for specific traffic class could be over 82 percent, meanwhile the throughput is much higher than the existing scheduling algorithms.

     

HP40-Nb耐热合金在石化装置离心铸管上的应用

持续工作于650℃以上高温工况下的铸件被划归为耐热铸件。用于这类铸件的合金主要有铁-铬、铁-铬-镍、铁-镍-铬、镍基和钴基合金。在耐热合金的应用中,需要考虑以下三个问题:①高温下的耐腐蚀性能;②稳定性(耐扭曲、开裂或热疲劳性能);③     

High-resolution data acquisition technique in broadband seismic observation systems

The dynamic range of the currently most widely used 24-bit seismic data acquisition devices is 10–20 d B lower than that of broadband seismometers, and this can affect the completeness of seismic waveform recordings under certain conditions. However, this problem is not easy to solve because of the lack of analog to digital converter(ADC) chips with more than 24 bits in the market. In this paper, we propose a method in which an adder, an integrator, a digital to analog converter chip, a field-programmable gate array, and an existing low-resolution ADC chip are used to build a third-order 16-bit oversampling delta-sigma modulator. This modulator is equipped with a digital decimation filter, thus facilitating higher resolution and larger dynamic range seismic data acquisition. Experimental results show that, within the 0.1–40 Hz frequency range, the circuit board's dynamic range reaches 158.2 d B, its resolution reaches 25.99 bits, and its linearity error is below 2.5 ppm, which is better than what is achieved by the commercial 24-bit ADC chips ADS1281 and CS5371. This demonstrates that the proposed method may alleviate or even completely resolve the amplitude-limitation problem that so commonly occurs with broadband observation instruments during strong earthquakes.     

PCI Express总线PHY接口技术分析

从技术的角度分析了PCI Express总线PHY层的结构与原理,对该层的接口信号给出了详细描述.论述了其时钟容限补偿及实现的基本原理.     

基于高响应直线电机的非圆曲面加工技术研究

针对非圆车削加工技术的研究,提出一种直线驱动快速刀具进给机构,构建了非圆车削系统。重点研究了非圆截面零件的软靠模生成,并提出一种非类椭圆的建模方法。以中凸变椭圆活塞为例,利用快速刀具进给机构加工出最大椭圆度为6mm的中凸椭圆活塞试件,误差在15μm以内。实验结果表明,该设计方案能顺利完成非圆车削的任务。     

RoHS指令及我国对策

介绍了RoHS指令的适用范围、新修改内容、豁免条款和产品，以及我国针对RoHS指令所采取的一系列措施。     

我国东中西部典型城市居民PM2.5科普现状及需求探析——以北京、合肥、西安为例的研究

PM2.5污染已成突出的环境问题,对居民健康、交通安全及经济发展都存在较大危害。本文针对这一科学传播新热点,对PM2.5污染发生区PM2.5科普现状及需求进行典型研究,以了解我国公民PM2.5科普需求,基于受众视角寻求有效的科学传播路径及方式,为PM2.5科普工作改进提供依据。本研究选定我国东中西部三个典型城市进行PM2.5科普现状及需求问卷调查,通过分析得到我国东中西部典型城市公民PM2.5科普现状及科普需求要点,并为PM2.5科普工作提出政策建议。     

数控插铣二元叶轮的工艺方法

简要介绍了大直径、宽深流道二元流叶轮的一种高效数控加工方法——插铣法。指出该工艺的优缺点，阐述了刀具的选择、走刀及编程。