Simulation on Reliability Enhancement Testing Technology of Ramming System

Ramming system is the key device to guarantee the firing speed of self-propelled gun. Based on traditional reliability enhancement testing method, a new kind of reliability enhancement testing simulation method of ramming system is put forward firstly. In CAD software Pro/E and dynamic simulation software ADAMS, the virtual prototype of ramming system is established. In EASY5 software, the corresponding hydraulic system and control system models are built. The reliability enhancement testing virtual environment of ramming system is developed using the mechanical-electrical-hydraulic co-simulation technology. Based on the load spectra provided by virtual prototype, and the stress distribution provided by finite element analysis and material's S-N curve(S is fatigue strength, N is fatigue life), a model of fatigue enhancement coefficient is established through the failure mechanism analysis. The simulation processes and simulation results show the feasibility of reliability enhancement testing based on virtual prototype, and provide sufficient theory reference for structure improvement and optimization of ramming system.

地铁车站空调水系统可靠性及安全性指标研究

RAMS工作是提升系统可靠性、安全性最直接有效的方式。但在地铁工程中该技术并未普及,同时也缺少具体的指标数据。本研究分析了空调水系统主要故障,建立了空调水系统串并联结构逻辑框图,同时引入机械系统已有的安全性指标概念,确定了适用于地铁空调水系统可靠性及安全性指标计算方法,解析得到了以平均故障间隔时间MTBF、失效率、可靠度R(t)、平均无危害性失效时间MTBF(H)为主的可靠性及安全性指标。

基于CPLD和Embedded System的LED点阵显示系统的实现

采用自顶向下的设计思想,综合运用EDA技术、CPLD技术和共享式双口RAM,解决了大屏幕LED点阵显示屏无闪烁显示的技术难题。给出了系统设计方法及实际电路。

Characterization of combined blast-and fragments-induced synergetic damage in polyurea coated liquid-filled container

Liquid-filled containers(LFC)are widely used to store and transport petroleum,chemical reagents,and other resources.As an important target of military strikes and terrorist bombings,LFC are vulnerable to blast waves and fragments.To explore the protective effect of polyurea elastomer on LFC,the damage characteristics of polyurea coated liquid-filled container(PLFC)under the combined loading of blast shock wave and fragments were studied experimentally.The microstructure of the polyurea layer was observed by scanning electron microscopy,and the fracture and self-healing phenomena were analyzed.The simulation approach was used to explain the combined blast-and fragments-induced on the PLFC in detail.Finally,the effects of shock wave and fragment alone and in combination on the damage of PLFC were comprehensively compared.Results showed that the polyurea reduces the perforation rate of the fragment to the LFC,and the self-healing phenomenon could also reduce the liquid loss rate inside the container.The polyurea reduces the degree of depression in the center of the LFC,resulting in a decrease in the distance between adjacent fragments penetrating the LFC,and an increase in the probability of transfixion and fracture between holes.Under the close-in blast,the detonation shock wave reached the LFC before the fragment.Polyurea does not all have an enhanced effect on the protection of LFC.The presence of internal water enhances the anti-blast performance of the container,and the hydrodynamic ram(HRAM)formed by the fragment impacting the water aggravated the plastic deformation of the container.The combined action has an enhancement effect on the deformation of the LFC.The depth of the container depression was 27%higher than that of the blast shock wave alone;thus,it cannot be simply summarized as linear superposition.

Charge Structure of a Summer Thunderstorm in North China:Simulation Using a Regional Atmospheric Model System

Electrification and simple discharge schemes are coupled into a 3D Regional Atmospheric Model System （RAMS） as microphysical parameterizations, in accordance with electrical experiment results. The dynamics, microphysics, and electrifi- cation components are fully integrated into the RAMS model, and the inductive and non-inductive electrification mechanisms are considered in the charging process. The results indicate that the thunderstorm mainly had a normal tripole charge structure. The simulated charge structure and lightning frequency are basically consistent with observations of the lightning radiation source distribution. The non-inductive charging mechanism contributed to the electrification during the whole lifetime of the thunderstorm, while the inductive electrification mechanism played a significant role in the development period and the mature stage when the electric field reached a large value. The charge structure in the convective region and the rearward region are analyzed, showing that the charge density in the convective region was double that in the rearward region.

An Application of the RAMS/FLUENT System on the Multi-Scale Numerical Simulation of the Urban Surface Layer—A Preliminary Study

The Regional Atmospheric Modeling System （RAMS） and the computational fluid dynamics （CFD） codes known as FLUENT are combinatorially applied in a multi-scale numerical simulation of the urban surface layer （USL）. RAMS and FLUENT are combined as a multi-scale numerical modeling system, in which the RAMS simulated data are delivered to the computational model for FLUENT simulation in an offline way. Numerical simulations are performed to present and preliminarily validate the capability of the multi-scale modeling system, and the results show that the modeling system can reasonably provide information on the meteorological elements in an urban area from the urban scale to the city-block scale, especially the details of the turbulent flows within the USL.

Sintering Behaviour of Al_2O_3-SiC-C Ramming Mix

Silicon fines, boron acid solid powders and microfine SiO 2 as sintering agents were incorporated into Al 2O 3-SiC-C ramming mix in order to investigated their effects on the microstructure, mechanical properties and sintering behavior of the ramming mix. Results show that all the three agents could improved both densification and mehanical properties markedly, compared to that of non-agent specimens and the effect of the composite of boron acid solid powders and microfine SiO 2 is the best. The oxidation resistance increased with the addition of agents, which is supported by densification. Microstructures showed that agent powders could fill pores or produce liquid phases at high temperature, therefore, improve the sintering of the ramming mix.

Environmental-friendly Ramming Materials for Mud Package and Taphole of Large-scaled Blast Furnaces

The compositions, structures and properties of envi- ronmental-friendly ramming materials for mud package and taphole of large-scaled blast furnaces were studied. The results show that the formation of silica fibers makes structure of ramming materials dense. During the process of extruding mud and ramming materials, SiC is partly oxidized ; CaO , F% 03 and carbon penetrate towards the outer wall. The improvement of ramming materials can inhibit the penetration of molten slag, iron and carbon. The bulk density of environmental-friendly ramming ma- terials dried at 200 ℃ is 2.90 g · cm-3, the cold com- pressive strength of this kind of ramming materials dried at 200 ℃ is about 17. 0 MPa and fired at I 450 ℃ is about 39. 2 MPa.

High Speed Network Intrusion Detection System(NIDS)Using Low Power Precomputation Based Content Addressable Memory

NIDS(Network Intrusion Detection Systems)plays a vital role in security threats to computers and networks.With the onset of gigabit networks,hardware-based Intrusion Detection System gains popularity because of its high performance when compared to the software-based NIDS.The software-based system limits parallel execution,which in turn confines the performance of a modern network.This paper presents a signature-based lookup technique using reconfigurable hardware.Content Addressable Memory(CAM)is used as a lookup table architecture to improve the speed instead of search algorithms.To minimize the power and to increase the speed,pre-computation based CAM(PBCAM)can be used,as this technique avoids repeated search comparisons.PBCAM employs the two-stage comparison with a parameter memory in the first stage and data memory in the second stage.Only the matched data in the parameter memory are compared in the data memory.This reduces the number of comparisons,thereby increasing the speed of the system.In this work dual-port RAM-based PBCAM(DP-PBCAM)is used to design a signature-based intrusion detection system.A low power parameter extractor is used with a minimum number of gates for precomputation.The hardware implementation is done using Xilinx Spartan 3E FPGA.The proposed DP-PBCAM lookups support a gigabit-speed of 7.42 Gbps.

Influence of Raw Material on the Properties of MgO-Al_2O_3-Cr_2O_3 Ramming Mixes

Mg0-Al2O3-Cr2O3 ramming mixes made of different raw materials have different mineral structure and different physical properties though with the identical particle size distribution, the same amount of binder and chemical composition . The residual carbon content of the fused magnesia-chrome material made in reducing atmosphere is very high, if this material is used in the MgO-Al203-Cr2O3 ramming mix , it would cause spalling of the furnace lining during drying-out.

Effect of Magnesia-Chrome Synthetic Materials on Magnesia-Alumina-Chrome Ramming Mixes

Magnesia-alumina-chrome ramming mixes with same chemical compositions were prepared by using different raw materials such as fused magnesia-chrome synthetic materials and sintered one, wasted bricks and magnesia-alumina spinels. Their physical properties were tested and microstructures were analyzed. The results show that the ramming mixes made of different raw materials bring about different microstructures and properties although the mixes have the same chemical composition, binder content and aggregate size composition.

Advanced Ramming Mix Based on Fused Zirconia Stabilized by Com-bined Additives of CaO and MgO for Lining of Carbon Black Production Reactor

Fused materials from ZrO2 stabilized by CaO or MgO, or the combined additive consisting of CaO and MgO are made. With using chemical, petrographic, X-ray phase and electron microscopic researches the main characteristics of these materials are determined. It is shown that, the materials of all compositions have low water absorption; they are characterized by equal struc-ture. The materials stabilized by the combined additive consisting of CaO and MgO are presented by generally the cubic phase and a small amount of tetragonal and monoclinic ZrO2 phases. Depending on CaO： MgO ratio in the materials the tetragonal ZrO2 phase settles down in a cubic matrix in the form of separate grains, and sites of net like structure in the form of a ＂woven＂ interlacing （2.9% of CaO and 2. 6% of MgO ）. An influence of the above mentioned fused stabilized ZrO2 materials and quantity of monoclinic zirconia, on the forming of zirconia mix on a phosphate bond and properties of＂ .fired samples is studied. The samples from mix based on ZrO2 stabilized by the combined additive consisting of 2.9% CaO and 2.6% MgO with 20% of monoclinic Zr02 are characterized by the highest properties： after .firing at 1 580 ~C open porosity of 14. 3% - 14. 8%, apparent density of 4. 67 -4. 69 g · cm^-5, cold crushing strength of 62 - 68 MPa, thermal shock resistance （ 1 300℃←→air） of 15 thermal cycles, linear growth of 0. 2%. The manufacturing technology of powders mix-ture for ramming mix based on the new fused material .from ZrO2 stabilized by the combined additive is developed and its production is mastered. From this mixture the large-size, shaped products on the phosphate bond are made at one carbon black production plant, which are installed in the combustion chamber of the carbon black production reactor.

Research on Direct Torque Control System Based on Induction Motor

The mathematic model of direct torque control (DTC) was deduced. Two simulating models based on the MATLAB & SIMULINK were established. The emphasis is focused on study of the performance difference of the DTC system with stator flux hexagon and circle trajectories. The simulation waveforms of flux, torque and current characters with two flux trajectories were given. Experiments were carried out in an AC drive system based on induction motor and two-level inverter. A dual-CPU structure was used and the communication with two CPUs was obtained by a dual-port RAM in this system.

Effect of Al Addition on Properties of Al_2O_3-SiC-C Dry Ramming Mixes for BF Trough

Aluminium powders were introduced to Al2O3-SiC-C dry ramming mixes in order to improve sintering properties and oxidation resistance according to their service conditions and installation methods. Properties such as bulk density, porosity, modulus of rupture, crushing strength and hot modulus of rupture as a function of aluminium addition were investigated in the present work. The microstructure and thermodynamics for the heat treated specimens were also analyzed. The results show that as aluminium addition increasing, the bulk density of the specimen treated at 220℃ tends to decrease and the apparent porosity increases, the strength of the specimens treated at 1100℃ and 1450℃ increases markedly, the bulk density tends to increase, apparent porosity and linear shrinkage decrease. The HMOR at 1400℃ is enhanced from 1.0 MPa to 3.5 MPa with 3% aluminium. Aluminium is served as sintering agent and anti-oxidant and it will react with CO and CO2 forming Al2O3 , which is helpful to enhance the strength, densify the structure and improve the overall properties.

Modern Spontaneous Evolution and Research Value of Construction System of Tibetan Dwellings in Aba County: A Case Study of Tieqiong Village in Waerma Town

Based on the field survey of dwellings in Tieqiong Village of Waerma Town in Aba County, northwest Tibetan area of Sichuan Province, this paper firstly introduced main characteristics of the construction system in the structure, materials and structural system, and analyzed changes in construction practices of various dwellings from traditional to modern time. Finally, it summarized characteristics of spontaneous evolution and research value of the construction system of dwellings in the northwest Tibetan area of Sichuan Province, with rammed earth wooden dwellings in upper and middle Aba areas as representatives.

Carbon Ramming Materials for Blast Furnace Construction

1 Scope This standard specifies the definition, classifica- tion, technical requirements, test methods, quality ap- praisal procedure, packing, marking, transportation, stroage and quality certificate of carbon ramming mate- rials for blast furnace construction. This standard is applicable to carbon ramming materials for construction in leveling layer of blast furnace bottom, ramming layer upper or lower the cen- tral line of water cooling pipes, joints between carbon bricks, or joints between carbon bricks and cooling equipment.

A DYNAMIC ECG MONITORING AND RECORDING SYSTEM

This peper proposes a new type of dynamic ECG (Holier) monitoring andrecording system based on technology or computer controlling and high storage capacitydynamic RAM (DRAM). The system realizes the monitoring and recording ECG signalscontinuously up to 24 hours with the double error criterion ECG data compression algorithm or time error and amplitude error[1], adaptive algorithm for detecting andanalysing the oRS complexes[2] and the technology of high storage capacity DRAM. Itsadvantages are high storage Capacity (4MB), low power dissipation (less titan 30mA).

The Automatic Control System For High-speed Material Hoist

This paper introduces the principle, software and hardware structure of automatic control system for high-speed material hoist, and analysis feature of the

一种使用Flash阵列存储数据的方法研究

在航空航天领域,随着飞行器性能的提升,研制过程中试验所需的数据存储量和数据存储速度也在不断提高。该文基于高速大容量数据存储的目的,利用FPGA的强大数据处理能力,进行Flash存储阵列及流水线管理的设计,并针对Flash阵列坏块检测和突发坏块提出了对应处理方法。通过对不同组合方式的存储阵列速度及存储容量进行研究对比,得到了一种使用Flash阵列进行高速数据存储的设计方法。相较单片存储,设计的存储阵列数据存储容量和速度成倍增加,且存储阵列的有效块利用率在99%以上。

基于FPGA的LVDS转以太网接口的测试工装

在应用风洞试验对某结构模型进行动态测试时,需要用数据记录仪对多次试验过程的状态信息进行存储记录以及回读分析。数据记录仪的接口为LVDS接口,为了方便在地面阶段用上位机对记录仪进行指令下发以及回读测试,设计了一款LVDS转以太网的测试工装。此装置采用FPGA作为主控芯片,以8B/10B编解码的方式对LVDS线路的信号进行传输稳定性处理,通过以太网接口与上位机进行通信。记录仪的数据经LVDS传输至FPGA中的RAM,采用双RAM缓存提高传输效率,随后将RAM中的数据封装为以太网UDP/IP帧格式,在UDP协议的基础之上通过双RAM交替缓存实现指令-数据的“握手”操作,并使用CRC校验以及数据重传的方式降低传输过程中的误码率,最后通过物理层芯片发送至上位机。经验证,LVDS+FPGA+以太网的数据传输是可行的,具有良好的稳定性和可靠性,可应用于实际工程。