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101.
设计了一套用于制造汽车覆盖件模具原模的数控机床,该机床的主机可以实现三坐标平动和两个坐标转动,工作台采用液压传动装置,可实现工作台的抬起、回转180°和回落,完成对车身的测量、原模的加工和模具的喷涂等工序.该机床具有加工测量精度高、柔性好、结构简单等优点,满足汽车覆盖件模具原模的加工要求. 相似文献
102.
In the perspective of an announced prohibition to bring Salmonella-contaminated fresh poultry meat on the retail market as of December 2010, requirements are postulated for rapid methods for
detection of Salmonella in poultry meat. These rapid methods should deliver reliable results in time to make it possible to steer the finished products
in poultry slaughterhouses into the direction of the fresh poultry market or into the direction of industrial treatment. The
most important requirements are the detection limit (1 cfu/25 g), the time of analysis (within hours up to a maximum of 24 h),
the sensitivity and specificity, and the validation of the rapid detection method. To determine a requirement for the number
of samples to be analyzed per unit of time of the detection methods, a sampling plan for pooling of samples is suggested.
Information of commercially available detection methods from literature and data provided by the suppliers was compared to
the postulated requirements. The results showed that none of the commercially available detection methods meet all the suggested
requirements. For all available methods, the time of analysis is too long to steer the production process in time. This implicates
that faster methods should be developed before the announced prohibition can be sensibly introduced. Also, information about
sensitivity and specificity, which is essential for the reliability of the rapid test method, should be examined in a more
uniform way. 相似文献
103.
Haisheng Di Xin He Peng Zhang Zhi Wang Margaret S. Wooldridge Chung K. Law Cuiping Wang Shijin Shuai Jianxin Wang 《Combustion and Flame》2014
Experimental and numerical studies have been performed on the thermal and chemical effects of buffer gas composition on low temperature ignition of iso-octane and n-heptane. Experiments were conducted using a recently developed rapid compression machine in the temperature range of 600–850 K. Three buffer gases were studied including nitrogen (N2), argon (Ar), and a mixture of Ar and carbon dioxide (CO2) at a mole ratio of 65.1%/34.9%. Iso-octane was studied at 20 bar, ? = 1, and a dilution level of buffer gas to O2 of 3.76:1 (mole ratio). n-Heptane was studied at 9 bar, ? = 1, and a dilution level of buffer gas to O2 of 5.63:1 (mole ratio). For experiments where two-stage ignition was observed, the buffer gas composition had no impact on the first-stage ignition time but, as expected, it caused differences in the total heat release, pressure and temperature rise after the first-stage ignition. As a consequence, significant differences were observed for the total ignition delay time as a function of the buffer gas composition, with up to 40% and 42.5% faster total ignition time for iso-octane and n-heptane, respectively, by using Ar instead of N2. The chemical effects of the buffer gas composition were studied experimentally by comparing the results of the N2 and Ar/CO2 (65.1%/34.9%) mixtures, recognizing that while the Ar/CO2 mixture has the same heat capacity as N2, its predicted combined third-body collision efficiency is about 76% higher than N2. The experimental results showed negligible chemical effects on the first-stage and total ignition delay times. Numerical simulations were carried out over a wider range of temperatures for pure N2, Ar, and CO2 as buffer gases. Results showed that thermal effects are very pronounced and dominated at the negative temperature coefficient and two-stage ignition conditions, which is consistent with the experimental results and previous studies in the literature. However, the simulation results also showed at temperatures higher than 850 K, the chemical effects of CO2 became more important than the thermal effects. 相似文献
104.
Removing low ppb level perchlorate, RDX, and HMX from groundwater with cetyltrimethylammonium chloride (CTAC) pre-loaded activated carbon 总被引:4,自引:0,他引:4
Perchlorate contaminates vast amounts of groundwater throughout the United States which could potentially be used as potable water. Activated carbon pre-loaded with cetyltrimethylammonium chloride has been shown in this research to be an effective adsorbent for removing perchlorate from three low conductivity (50-66 microS/cm) groundwaters containing perchlorate (ClO(4)(-)) concentrations of 0.85, 1.0, and 5.6 parts per billion (ppb), respectively. In rapid small-scale column tests (RSSCTs), the virgin granular activated carbon (GAC) (used as a control) treated between 20,000 and 40,000 bed volumes (BV) of water. In contrast, the activated carbon that was pre-loaded with CTAC processed 170,000-270,000 BV before perchlorate was detected above 0.25 ppb in the effluent. Though this pre-loading significantly increased the capacity for perchlorate, it also diminished the GAC's capacity to remove organics. The groundwater containing 1 ppb ClO(4)(-) also contained the nitro-organics HMX (0.6 ppb) and RDX (5.5-6.6 ppb). RDX was detected in the effluent from the CTAC-pre-loaded bed after only 8000 BV had been processed whereas 308,000 BV could be processed through the virgin bed before RDX was detected. Likewise, HMX breakthrough was observed after 116,000 BV in the CTAC-pre-loaded bed while the virgin RSSCT exhibited no breakthrough of HMX during a test that was operated for 309,000 BV. However, by combining a CTAC-pre-loaded bed followed by a virgin GAC bed in series, both perchlorate and RDX could be removed for the same length of time. 相似文献
105.
Direct laser sintering of a copper-based alloy for creating three-dimensional metal parts 总被引:12,自引:0,他引:12
Y. Tang H.T. Loh Y.S. Wong J.Y.H. Fuh L. Lu X. Wang 《Journal of Materials Processing Technology》2003,140(1-3):368-372
Direct laser sintering of metal, as one of the important developments in rapid prototyping technologies, is discussed in this paper. A special copper-based alloy is used for this rapid prototyping process. Experiments on the sintering conditions of this material had been conducted in a self-developed high temperature metal sintering machine. The mechanism of laser sintering for this kind of material was disclosed by SEM analysis of microstructures of sintered parts. The density, surface roughness and mechanical properties of the laser sintering parts due to variation of process parameters were measured and analysed. The effect of process parameters to the accuracy of sintered parts was also investigated. Thus, optimum parameters were obtained for direct laser sintering of three-dimensional metal parts. 相似文献
106.
快速成型制造技术能将Pro/E软件设计的三维实体零件快速地制作成零件或者模具。采用STL转换格式进行Pro/E软件与快速成型软件数据对接,通过控制曲面到三角面片的弦高差来控制成型精度。 相似文献
107.
本文叙述了用快速成形技术制造玻璃模具电火花加工电极.对客户提供的玻璃器皿样品尺寸进行三坐标测量,并将样品的尺寸放大1 mm以补偿样品生产时的收缩.利用快速成形技术对样品进行三雏造型,并制得样品的树脂原型.利用熔模铸造技术和树脂原型来制作模具电火花加工的电极.用这种工艺可以快速得到铜电极,实现玻璃模具的快速加工. 相似文献
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