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针对当前国内外生产使用的一般卧式辗扩机的工作特性,提出了使辗扩机辗压力与制件变形工艺力相平衡,避免产生滑块倾翻力矩的原则设计卧式辗扩机结构的理论,设计制造出结构新颖的卧式辗扩机——φ500齿轮毛坯辗扩机,将它与一般卧式辗扩机作了对比分析,指出了新结构的诸多优点,这些优点已在生产使用中得到验证。 相似文献
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研究了径向辗环的力能参数的计算方法。认为径向辗环是一种特殊的压力轧制,用上限理论导出了径向辗压力的计算公式;根据塑性变形中移位体积所消耗的能量导出了辗环扭矩的计算公式;用摩擦圆代换法导出了型槽侧面摩擦力矩的计算公式;以环件变形扩大产生塑性铰链的理论,导出了压力辊(抱辊)力矩;在综合分析各项力矩的基础上,给出了径向辗环电机功率的计算方法,并进行了实例计算,和实测值进行了比较。 相似文献
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研究了冷摆辗环形法兰的工艺过程、尺寸关系,应力应变状态。提出了冷摆辗环形法兰时的有关公式和辗具轴线对毛坯轴线的倾角推荐值。 相似文献
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介绍了摆动辗压成形技术在美国、英国、波兰、前苏联、瑞士、日本和德国等工业发达国家的研制和生产概况。综述了我国科技工作者在摆动辗压机的机身设计计算与制造、摆头的设计计算、摆动辗压的运动轨迹以及摆动辗压成形过程中坯料与摆头之间的接触情况等;在摆动辗压成形过程中的应力、应变分布的实验研究与数值模拟分析,缺陷形成机理分析,以及摆辗变形力的工程计算等;热摆动辗压成形工艺、温摆辗成形工艺和冷摆辗成形工艺在汽车、摩托车、五金工具和兵器工业等加工制造业的工程应用等方面所作的成形机理、数值模拟、设备和工艺研究情况。 相似文献
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此文介绍了利用数字计算机进行矩形截面环轧制的优化规程设计方法,优化是基于轧制过程的物理模型,考虑了各种轧制约束条件,结果符合实际生产情况,并且可使轧机容量得到充分利用,大大缩短轧制所需时间,节约材料与能源消耗。 相似文献
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摆动辗压过程中锥形摆头与坯料接触面积是一个十分重要的参数,此文从辗压过程中坯料螺旋式送进的事实出发,首次给出了环形坯料,接触区域轮廓坐标的数值求解过程,为正确计算接触面积提供了精确的计算方法。 相似文献
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A ring chromosome 19 was found in 14 of 20 metaphases (67 per cent) derived from amniotic fluid cell cultures following amniocentesis because of increased maternal age. Elective termination of the pregnancy revealed a hypotrophic female fetus with mild dysmorphic signs, but no congenital malformations. The case is discussed in relation to three reports in the literature of ring chromosome 19 mosaicism in a phenotypically normal girl, a mentally retarded man, and a boy with normal psychomotor development and minor dysmorphic features. 相似文献
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本文对海南东环铁路海口城区的南海大道附近的敏感点列车开通的近期(2020年)和远期(2030年)的噪声进行预测:根据噪声暴露声级与等效声级的关系公式,对列车加密后南海大道距离轨道30m处的噪声进行预测,发现当小时列车数达到14车次时,其昼问等效声级将超过70dBA的标准,为城区段控制小时列车次数提供参考。 相似文献
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B. Eiben M. Unger G. Stoltenberg G. Rutt R. Goebel A. Meyer U. Gamerdinger W. Hammans S. Hansen H. Hauss M. Vogel G. Schwanitz 《黑龙江环境通报》1992,12(11):945-950
The case of monosomy 18/ring chromosome 18 mosaicism which was detected prenatally by amniocentesis is presented. The pregnancy was terminated in week 18. Autopsy showed complex malformation of the fetus consisting of cebocephaly, hypotelorism, microphthalmia, severe defects of brain development, and arrest of placental maturation. 相似文献
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P. A. Benn Ph.D. D. Warburton J. M. Byrne R. Rudelli A. Shonhaut K. Yeboa H. Mootabar L. Y. F. Hsu 《黑龙江环境通报》1983,3(4):297-302
A fetus was identified by prenatal cytogenetic diagnosis as having a karyotype 46,XY,r(13) (p11q13). Termination of the pregnancy yielded a severely malformed fetus. Fetal abnormalities included anencephaly, imperforate anus and urethral meatus, severe talipes, syndactyly, cardiac defects and other anomalies. Confirmatory studies on cultured placental villi cells indicated a second cell line, 46,XY, −13,+ 13qter→cen::13ql3→qter. This cell line was not detectable in cells derived from the fetus despite extensive studies. It seems likely that the two cell lines arose simultaneously with selection favouring the 46,XY,r(13) line. How the chromosome rearrangements may have arisen is discussed. We are unaware of other cases where a cell line identifiable by a chromosome abnormality appeared to be confined to placental tissue. However, studies on placental tissue may be helpful in understanding the origin of other unbalanced de novo rearrangements. 相似文献
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应急监测中便携式顶空/GC-MS法测定水中VOCs的初步研究 总被引:1,自引:0,他引:1
通过对实验室加标水样和实际水样的测定,研究了便携式顶空/气相色谱-质谱法(GC-MS)与吹扫捕集/GC-MS法测定水中VOCs的性能比较,探讨了利用Loop环测定水中高浓度VOCs的准确度. 结果表明:便携式顶空/GC-MS测定水中54种低浓度VOCs的检出限略高于吹扫捕集/GC-MS系统,准确度和精密度分别为67.4%~136%和9.08%~19.80%,均满足环境应急监测分析的要求;利用Loop环,便携式顶空/GC-MS可对水中高浓度级(mg/L)VOCs进行较为准确地测定,回收率为100%~149%;复杂的实际样品基本不干扰便携式顶空/GC-MS的测定,与吹扫捕集/GC-MS法相比,二者对实际水样的测定结果相对偏差小于20%;便携式顶空/GC-MS在水污染事故现场可得到基本准确的结果,可为事故后续处理提供有效的数据支持. 相似文献
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Tao Wang Zhonghuan Xi Minmin Wu Qianqian Zhang Shiqi Sun Jing Yin Yanchi Zhou Hao Yang 《环境科学学报(英文版)》2017,29(5):118-128
This paper focused on the pollution characteristics,sources and lung cancer risk of atmospheric polycyclic aromatic hydrocarbons(PAHs) in a new urban district of Nanjing,China.Gaseous and aerosol PM_(2.5)(particulate matter with aerodynamic diameter smaller than2.5 urn) samples were collected in spring of 2015.Sixteen PAHs were extracted and analyzed after sampling.Firstly,arithmetic mean concentrations of PAHs and BaP_(eq)(benzo[a]pyrene equivalent) were calculated.The mean concentrations of PAHs were 29.26±14.13,18.14±5.37 and 48.47±16.03 ng/m~3 in gas phase,particle phase and both phases,respectively.The mean concentrations of BaP_(eq) were 0.87±0.51,2.71±2.17 and 4.06±2.31 ng/m~3 in gas phase,particle phase and both phases,respectively.Secondly,diagnostic ratios and principal component analysis were adopted to identify the sources of PAHs and the outcomes were the same:traffic exhaust was the predominant source followed by fuel combustion and industrial process.Finally,incremental lung cancer risk(ILCR) induced by whole year inhalation exposure to PAHs for population groups of different age and gender were estimated based on a Monte Carlo simulation.ILCR values caused by particle phase PAHs were greater than those caused by gas phase PAHs.ILCR values for adults were greater than those for other age groups.ILCR values caused by total(gas + particle) PAHs for diverse groups were all greater than the significant level(10~6),indicating high potential lung cancer risk.Sensitivity analysis results showed that cancer slope factor for BaP inhalation exposure and BaP_(eq) concentration had greater impact than body weight and inhalation rate on the ILCR. 相似文献
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Despite the widespread occurrence of phenols in anthropogenic and natural compounds, their fate in reactions with hypochlorous acid (HOCl), one of the most common water treatment disinfectants, remains incompletely understood. To close this knowledge gap, this study investigated the formation of disinfection by-products (DBPs) in the reaction of free chlorine with seven para-substituted phenols. Based on the chemical structures of the DBPs and the reaction mechanisms leading to their formation, the DBPs were categorized into four groups: chlorophenols, coupling products, substituent reaction products, and ring cleavage products. In contrast to previous studies that investigated the formation of early-stage chlorophenols, the primary focus of this study was on the elucidation of novel ring cleavage products, in particular α, β-unsaturated C4-dialdehydes, and C4-dicarboxylic acids, which, for the first time, were identified and quantified in this study. The molar yields of 2-butene-1,4-dial (BDA), one of the identified α, β-unsaturated C4-dialdehydes, varied among the different phenolic compounds, reaching a maximum value of 10.4% for bisphenol S. Molar yields of 2-chloromaleic acid (Cl-MA), one of the identified C4-dicarboxylic acids, reached a maximum value of 30.5% for 4-hydroxy-phenylacetic acid under given conditions. 2,4,6-trichlorophenol (TCP) was shown to be an important intermediate of the parent phenols and the C4-ring cleavage products. Based on the temporal trends of α, β-unsaturated C4-dialdehydes and C4-dicarboxylic acids, their formation is likely attributable to two separate ring cleavage pathways. Based on the obtained results, an overall transformation pathway for the reaction of para-substituted phenols with free chlorine leading to the formation of novel C4 ring cleavage products was proposed. 相似文献
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《环境科学学报(英文版)》2023,35(4):423-433
Decomposition of the polycation Al13O4(OH)24(H2O)127+ (Al13) promoted by ligand is a vital subject to advance our understanding of natural and artificial occurrence and evolution of aluminum ions, especially in the case of acidic condition that dissolved Al3+ species can be released from the Al-bearing substances. However, the microscopic pathway of synchronous proton-promoted and ligand-promoted decomposition process for Al13 is still in the status of ambiguity. Herein, we applied differential mass spectrometry method and DFT calculation to study the initial detailed process of Al13 decomposition under the presence of proton and salicylic acid (H2Sal). Mass results showed that the mononuclear Al3+-H2Sal complexes dominated the resulting Al species, whereas the monodentate complex Al13HSal6+ was not observed in the spectra. The difference of decomposition levels between the ligand/Al ratio 0.2 and 0.5 cases revealed that proton and ligand performed synergistic effect in initial Al13 decomposition process, and the proton transfer determined the ring closure efficiency. The ring closure reaction is the prerequisite for the collapse of Al13 structure and detachment of the mononuclear complex. DFT calculations reveal that hydrogen bond plays an important role in inducing the formation of chelated complex accompanying proton transfer. Attachment of protons at the bridging OH− can elongate and weaken the critical bond between targeted Al3+ and µ4-O2- resulting from delocalization of electron pairs in the oxygen atom. These results demonstrate the detailed mechanism of Al13 composition promoted by ligand and proton, and provide significant understanding for further application and control of Al13. 相似文献