海船稳性调整质疑及改正意见

对《船舶货运》、《货运技术》等教科书关于“船舶稳性调整”这一内容中存在的问题作了系统分析,提出了一些不同看法及修正意见,为船舶驾驶员在调整船舶稳性时提供了正确的方法,准确的计算公式及判别式,修正了在船舶稳性调整方面长期来存在的欠缺,对保障船舶的安全航行具有积极意义。     

Analysis of Passive Limited Supporting Force of Curved Shield Tunnel Excavation FaceEI北大核心

Research purposes: In the construction process of curved shield tunnels, the force of excavation face is extremely complex and the stability is difficult to control, so it is very likely that the thrust of the jack will cause uplift of the soil in front because of passive failure. Taking the sand strata as an example, this paper established a combination model of "inverted ladder-wedge prism" to reveal that the soil in front of the excavation face of curved shield tunnels uplifts up because of passive failure based on the silo theory and limit equilibrium method, and deduced the calculation method of passive limited supporting force for curved tunnels. Then, we confirmed the accuracy and reliability of this model and calculation method through programing and simulating. Research conclusions:(1) The passive limited supporting force increases with the increase of buried depth and internal friction angle, and the growth rate gradually increases. (2) When the radius of the line is less than 200 m and the internal friction angle is more than 25 degrees, the passive limited supporting force is very sensitive to the curvature radius, and when the radius is more than 800 m, the passive limited supporting force is almost no difference with straight tunnels. (3) The numerical results indicate that the numerical solution is consistent with the theoretical solution and the difference is quite small. (4) The research results can provide theoretical basis for determining the passive limited supporting force in the constructions of similar curved shield tunnels especially small turn radius shield tunnels. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

Research on the Cause and Influential Factors of Tunnel Lining Cracking of Side Wall in Seasonally-frozen RegionsEI北大核心

Research purposes: In recent years, tunnel diseases like lining cracking and water leaking during spring thawing period, caused by frost heaving of surrounding rock, have occasionally occurred in high-latitude seasonally-frozen regions of northwest China and northeast China, which has seriously affected the tunnel structure and operation safety. Taking several railway tunnels in northwest China as an example, this paper investigates the cause and main influencing factors of longitudinal cracking of side wall in winter in seasonal frozen soil area by means of field test, laboratory experiment and numerical simulation. Research conclusions:(1) When the water content of surrounding rock of tunnel built in strongly-weathered sandstone is 12.3% and the frozen depth of surrounding rock is up to 60 cm, the maximum tensile stress of side walls is 2.28 MPa, which is larger than the ultimate tensile strength of C30 concrete, then the horizontal lining cracking will appear on side walls under the effect of continuous negative temperature in winter. If the lining bears part of the surrounding rock load, the longitudinal cracking degree of the side wall will increase. (2) Under the effect of frost heaving loads, the cracking of tunnel lining has its own characteristics of symmetry, seasonality and accumulation, etc. The cracks appear in winter and distribute in the middle of side walls. As the temperature is rising, the crack begins to shrink. (3) The frozen circle thickness and water content of surrounding rock should be used as main indicators during the process of calculation of frost heaving loads of surrounding rock in seasonally-frozen regions. (4) The research results can be used for reference in tunnel design, operation and maintenance in seasonal frozen soil area. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

螺杆式空气压缩机试验方法的探讨

主要研究机车、动车组用螺杆式空气压缩机启停机交替运转试验的试验方法,以及润滑油消耗量的测定。对比TB/T2711—2005《机车、动车用空气压缩机试验方法》,结合实验室试验经验,提出合理可行的方案。建议在标准中增加电气绝缘性能测试。     

采用“一刀成型法”加工直齿圆锥齿轮时切削角的误差分析与修正

在铁路柴油机检修非标设备制造中,在铣床上试验成功了直齿圆锥齿轮"一刀成型法"的加工工艺,可满足精度要求,并提高了生产效率。根据收集的多组加工数据,利用工程数学方法,分析切削角产生误差的原因,推导出修正经验公式,进一步提高了加工精度。     

基于回溯算法的轻轨排班问题的研究

根据目前地铁(轻轨)行业中工作轮班的情况,每天有m个人工作,n个人休息.在保证工作和休息合理交替的前提下,要求m+n个司乘人员在m+n天内分别轮完m+n个不同的任务,以达到相对公平的目的.本文通过建立数学模型,结合回溯算法和深度搜索,完成任务序列的求解.最后考虑最坏情况下的近似解,并计算回溯算法的时间复杂度.     

西北地区

陕西省 位于西北地区东部,黄河中游. 春秋战国时为秦国地.汉属司隶和并、益州.唐属关内、山南等道.宋初置陕西道.元设陕西行省.清为陕西省.现全省面积19万多平方千米,人口3 611万.     

平溃散治疗胃溃疡的作用机制研究

目的　探讨平溃散对胃溃疡的治疗作用和机制。方法　分别用组胺、乙醇及消炎痛诱发急性胃溃疡模型 ,观察平溃散对胃粘液 -碳酸氢盐屏障功能、胃液 pH值和胃跨膜电位的影响。结果　 2～ 4 g·kg-1的平溃散作用组溃疡指数下降 ,胃液 pH值和粘液含量增加 ,与对照组比较差异有显著性意义 (P <0 .0 5 ,P <0 .0 1,P <0 .0 1)。平溃散对乙醇引起的胃跨膜电位降低的抑制作用和模型组比较无显著性差异 (P >0 .0 5 )。结论　平溃散对胃溃疡具有良好的治疗作用 ,主要通过保护胃粘膜、抑制胃酸发挥作用     

大鼠骨髓间充质干细胞骨向分化及体外诱导实验

目的建立骨髓间充质干细胞(MSCs)体外分离培养体系,进行骨向分化诱导,并将诱导的成骨细胞复合钛网体外成骨,为MSCs进一步的临床应用研究提供实验依据。方法用密度梯度离心法分离大鼠骨髓MSCs,并对其形态学特征进行观察。用诱导剂对MSCs向成骨细胞进行诱导分化,并进行形态学观察和免疫细胞化学检测。用扫描电镜观察骨向诱导后细胞复合钛网的情况。结果用密度梯度离心法成功分离获得了高纯度的骨髓MSCs。经骨向诱导后,ALP和矿化结节染色阳性。扫描电镜可观察到骨向诱导后细胞复合在钛网表面有矿化的基质沉积。结论成功建立了大鼠骨髓MSCs体外分离和培养体系,MSCs能够向成骨细胞分化,骨向诱导后细胞复合钛网体外有矿化的基质。     

甲状腺激素抵抗综合征一家系临床表型分析

目的对一甲状腺激素抵抗综合征患者及其家系成员进行调查分析。方法对患者及其14名家系成员详细询问病史,并行TT3、TT4、FT3、FT4、uTSH、TGAB及TMAB检查。结果家系中5名患者血清甲状腺激素水平升高,促甲状腺激素水平(TSH)也高于正常;他们的临床表现各异,有的表现为甲减,有的表现为甲亢,有的无任何临床症状。结论甲状腺激素抵抗综合征是一种临床表现复杂多变、极易漏诊、误诊的遗传性疾病。