Based on theory of mechanical dynamics, meshing characteristic as well as thedynamic model of double circular arc helical gearing, an analysis approach and a computer programhave been developed for studying the state ...Based on theory of mechanical dynamics, meshing characteristic as well as thedynamic model of double circular arc helical gearing, an analysis approach and a computer programhave been developed for studying the state of dynamic load and factor of dynamic load of thegearing, the changing situation of dynamic load and dynamic load factor vs some affecting factorssuch as gear width, helix angle and accuracy grade etc are investigated. A series of conclusions areobtained: ①With the increasing in the values of gear width, the dynamic load factor appears slowdecreasing tendency in most region of gear width. ②When the accuracy grades of the gearing areimproved, the values of dynamic load factor decrease. ③The value of dynamic load factor appears adecreasing tendency with the increasing of value of helix angle at the same ratio of criticalrotational speed.展开更多
目的探讨外周血红细胞分布宽度(red blood cell distribution width,RDW)、系统免疫炎症指数(systemic immune-inflammation index,SⅡ)与重性抑郁障碍(major depressive disorder,MDD)的相关性。方法回顾性分析2020-2022年于我院临床...目的探讨外周血红细胞分布宽度(red blood cell distribution width,RDW)、系统免疫炎症指数(systemic immune-inflammation index,SⅡ)与重性抑郁障碍(major depressive disorder,MDD)的相关性。方法回顾性分析2020-2022年于我院临床心理科住院的176例MDD患者和常规体检的209例非MDD对照者的临床资料。从血液分析结果中,得到RDW、SⅡ、红细胞分布宽度与血小板计数比值(RDW to platelet ratio,RPR)。绘制受试者操作特征(receiver operator characteristic,ROC)曲线以确定RDW区分患者与对照的最佳临界值及曲线下面积(area under the curve,AUC)。结果MDD组患者的RDW[中位数及四分位数:13.20(12.70,13.98)vs.12.80(12.40,13.35)]、SⅡ水平[中位数及四分位数:510.87(350.95,878.12)vs.405.33(313.74,539.92)]高于非MDD组对照者,差异有统计学意义(P<0.05),两组间RPR差异无统计学意义(P>0.05)。多因素logistic回归分析结果显示,调整混杂因素后,RDW与MDD呈正关联(OR=3.086,95%CI:1.926~4.944)。ROC曲线结果显示,RDW区分MDD与非MDD的最佳临界值为12.85,AUC为0.647(95%CI:0.592~0.702;P<0.001)。结论高RDW可能是MDD发生的危险因素,是对MDD诊断有价值的重要参数。展开更多
目的研究慢性心力衰竭(chronic heart failure,CHF)与红细胞分布宽度/白蛋白比(red blood cell distribution width to albumin ratio,RAR)的关系。方法美国的国家健康与营养检查调查数据库(National Health and Nutrition Examination ...目的研究慢性心力衰竭(chronic heart failure,CHF)与红细胞分布宽度/白蛋白比(red blood cell distribution width to albumin ratio,RAR)的关系。方法美国的国家健康与营养检查调查数据库(National Health and Nutrition Examination Survey Database,NHANES)提供了1999-2020间CHF的流行病学和随访数据,静海区医院(Jinghai District Hospital,JHDH)提供了2021-2022年的CHF流行病学数据。两个队列根据是否患有CHF,分为了CHF组和Con组。逐步特征消除被用来筛选协变量,广义线性模型被用来统计患病率的比值比(odds ratio,OR),使用4种模型观察CHF与RAR的关系。Cox回归模型对NHANES的CHF生存数据进行统计,分析RAR对CHF的远期预后价值。通过RAR的四分位分段(RARQ)观察RAR与CHF患病率之间的关系。限制性三次样条(restricted cubic spline,RCS)被用来寻找RAR预后的最佳分界值,Kaplan-Meier曲线用来分析RAR对CHF的远期预后。结果NHANES队列包括Con组(n=58687)和CHF组(n=2067)。JHDH队列包括Con组(n=12760)和CHF(n=2342)。RARQ中Q1~Q4的CHF患病率在NHANES中是0.69%,1.52%,2.80%,6.00%;在JHDH中是4.75%,9.04%,17.42%,50.17%。Q4的CHF患病率是Q1的8.70倍(NHANES)和10.56倍(JHDH)。两个队列RAR在Model4校正后的OR分别是2.27(95 CI%:1.5~3.42)和1.85(95 CI%:1.7~2.01)。分析NHANES队列存活(n=784)和死亡(n=958)的CHF患者,校正后的RAR的危险比(HF)为2.28(95 CI%:1.55~3.36)。RCS提示RAR对CHF远期预后的最佳分界值是3.4 dL/g。生存曲线显示高RAR组(>3.4 dL/g)的远期预后差于低RAR组(≤3.4 dL/g)。RAR的预测价值远远高于传统的红细胞分布宽度(RDW)。结论RAR是CHF患病率和远期预后的危险因素。RAR对CHF的预测价值优于传统的红细胞分布宽度和血清白蛋白。RAR预测CHF远期预后的最佳分界值是3.4 dL/g。展开更多
A quasicrystal has a structure intermediate between crystals and compound glasses. The disorder in glass makes its diffraction diffuse, so it is surprising that quasicrystals diffract more sharply than crystals. The g...A quasicrystal has a structure intermediate between crystals and compound glasses. The disorder in glass makes its diffraction diffuse, so it is surprising that quasicrystals diffract more sharply than crystals. The greater sharpness is computed to be due to the hierarchic structure with unit cell alignment in 3-dimensional space. Electron microscope phase contrast images map the comparatively heavy Mn atoms in icosahedral Al<sub>6</sub>Mn, where the transition metal locates the centers of unit cells inside clusters and superclusters. Because the solid is aperiodic, each diffracted beam is a product of multiple interplanar spacings combined, and this contrasts with the unique relationship between spacing and incident angle in Bragg diffraction from crystals. Simulated quasi-structure factors add the relative phase shifts that are in geometric series from cell to cluster to superclusters of increasing order. The scattering becomes coherent in best fit, angular configuration between the aperiodic solid and a longitudinally periodic X-ray or electron probe. The quasi-structure factors express angular divergence in each diffracted beam from its corresponding Bragg condition, and the divergence provides a special metric, essential for atomic measurement in the geometric solids. The fit is reinforced at all levels from the unit cell to cluster to high order superclusters. The optics operates under a new quasi-Bragg law in a new geometric space. In this paper, we proceed to examine the effect of specimen size on line resolution in diffraction, first analytically and secondly in simulation. The line resolution follows a power law on the supercluster order, matching its atomic population.展开更多
The special case of a crack under mode Ⅲ conditions was treated, lying parallel to the edges of an infinite strip with finite width and with the shear modulus varying exponentially perpendicular to the edges. By usin...The special case of a crack under mode Ⅲ conditions was treated, lying parallel to the edges of an infinite strip with finite width and with the shear modulus varying exponentially perpendicular to the edges. By using Fourier transforms the problem was formulated in terms of a singular integral equation. It was numerically solved by representing the unknown dislocation density by a truncated series of Chebyshev polynomials leading to a linear system of equations. The stress intensity factor （SIF） results were discussed with respect to the influences of different geometric parameters and the strength of the non-homogeneity. It was indicated that the SIF increases with the increase of the crack length and decreases with the increase of the rigidity of the material in the vicinity of crack. The SIF of narrow strip is very sensitive to the change of the non-homogeneity parameter and its variation is complicated. With the increase of the non-homogeneity parameter, the stress intensity factor may increase, decrease or keep constant, which is mainly determined by the strip width and the relative crack location. If the crack is located at the midline of the strip or if the strip is wide, the stress intensity factor is not sensitive to the material non-homogeneity parameter.展开更多
基金This project is supported by Science and Technology Developing Foundation of Tianjin Higher Education (No.20030703).
文摘Based on theory of mechanical dynamics, meshing characteristic as well as thedynamic model of double circular arc helical gearing, an analysis approach and a computer programhave been developed for studying the state of dynamic load and factor of dynamic load of thegearing, the changing situation of dynamic load and dynamic load factor vs some affecting factorssuch as gear width, helix angle and accuracy grade etc are investigated. A series of conclusions areobtained: ①With the increasing in the values of gear width, the dynamic load factor appears slowdecreasing tendency in most region of gear width. ②When the accuracy grades of the gearing areimproved, the values of dynamic load factor decrease. ③The value of dynamic load factor appears adecreasing tendency with the increasing of value of helix angle at the same ratio of criticalrotational speed.
文摘目的探讨外周血红细胞分布宽度(red blood cell distribution width,RDW)、系统免疫炎症指数(systemic immune-inflammation index,SⅡ)与重性抑郁障碍(major depressive disorder,MDD)的相关性。方法回顾性分析2020-2022年于我院临床心理科住院的176例MDD患者和常规体检的209例非MDD对照者的临床资料。从血液分析结果中,得到RDW、SⅡ、红细胞分布宽度与血小板计数比值(RDW to platelet ratio,RPR)。绘制受试者操作特征(receiver operator characteristic,ROC)曲线以确定RDW区分患者与对照的最佳临界值及曲线下面积(area under the curve,AUC)。结果MDD组患者的RDW[中位数及四分位数:13.20(12.70,13.98)vs.12.80(12.40,13.35)]、SⅡ水平[中位数及四分位数:510.87(350.95,878.12)vs.405.33(313.74,539.92)]高于非MDD组对照者,差异有统计学意义(P<0.05),两组间RPR差异无统计学意义(P>0.05)。多因素logistic回归分析结果显示,调整混杂因素后,RDW与MDD呈正关联(OR=3.086,95%CI:1.926~4.944)。ROC曲线结果显示,RDW区分MDD与非MDD的最佳临界值为12.85,AUC为0.647(95%CI:0.592~0.702;P<0.001)。结论高RDW可能是MDD发生的危险因素,是对MDD诊断有价值的重要参数。
文摘目的研究慢性心力衰竭(chronic heart failure,CHF)与红细胞分布宽度/白蛋白比(red blood cell distribution width to albumin ratio,RAR)的关系。方法美国的国家健康与营养检查调查数据库(National Health and Nutrition Examination Survey Database,NHANES)提供了1999-2020间CHF的流行病学和随访数据,静海区医院(Jinghai District Hospital,JHDH)提供了2021-2022年的CHF流行病学数据。两个队列根据是否患有CHF,分为了CHF组和Con组。逐步特征消除被用来筛选协变量,广义线性模型被用来统计患病率的比值比(odds ratio,OR),使用4种模型观察CHF与RAR的关系。Cox回归模型对NHANES的CHF生存数据进行统计,分析RAR对CHF的远期预后价值。通过RAR的四分位分段(RARQ)观察RAR与CHF患病率之间的关系。限制性三次样条(restricted cubic spline,RCS)被用来寻找RAR预后的最佳分界值,Kaplan-Meier曲线用来分析RAR对CHF的远期预后。结果NHANES队列包括Con组(n=58687)和CHF组(n=2067)。JHDH队列包括Con组(n=12760)和CHF(n=2342)。RARQ中Q1~Q4的CHF患病率在NHANES中是0.69%,1.52%,2.80%,6.00%;在JHDH中是4.75%,9.04%,17.42%,50.17%。Q4的CHF患病率是Q1的8.70倍(NHANES)和10.56倍(JHDH)。两个队列RAR在Model4校正后的OR分别是2.27(95 CI%:1.5~3.42)和1.85(95 CI%:1.7~2.01)。分析NHANES队列存活(n=784)和死亡(n=958)的CHF患者,校正后的RAR的危险比(HF)为2.28(95 CI%:1.55~3.36)。RCS提示RAR对CHF远期预后的最佳分界值是3.4 dL/g。生存曲线显示高RAR组(>3.4 dL/g)的远期预后差于低RAR组(≤3.4 dL/g)。RAR的预测价值远远高于传统的红细胞分布宽度(RDW)。结论RAR是CHF患病率和远期预后的危险因素。RAR对CHF的预测价值优于传统的红细胞分布宽度和血清白蛋白。RAR预测CHF远期预后的最佳分界值是3.4 dL/g。
文摘A quasicrystal has a structure intermediate between crystals and compound glasses. The disorder in glass makes its diffraction diffuse, so it is surprising that quasicrystals diffract more sharply than crystals. The greater sharpness is computed to be due to the hierarchic structure with unit cell alignment in 3-dimensional space. Electron microscope phase contrast images map the comparatively heavy Mn atoms in icosahedral Al<sub>6</sub>Mn, where the transition metal locates the centers of unit cells inside clusters and superclusters. Because the solid is aperiodic, each diffracted beam is a product of multiple interplanar spacings combined, and this contrasts with the unique relationship between spacing and incident angle in Bragg diffraction from crystals. Simulated quasi-structure factors add the relative phase shifts that are in geometric series from cell to cluster to superclusters of increasing order. The scattering becomes coherent in best fit, angular configuration between the aperiodic solid and a longitudinally periodic X-ray or electron probe. The quasi-structure factors express angular divergence in each diffracted beam from its corresponding Bragg condition, and the divergence provides a special metric, essential for atomic measurement in the geometric solids. The fit is reinforced at all levels from the unit cell to cluster to high order superclusters. The optics operates under a new quasi-Bragg law in a new geometric space. In this paper, we proceed to examine the effect of specimen size on line resolution in diffraction, first analytically and secondly in simulation. The line resolution follows a power law on the supercluster order, matching its atomic population.
基金Project supported by the National Natural Science Foundation of China (No.90305023)
文摘The special case of a crack under mode Ⅲ conditions was treated, lying parallel to the edges of an infinite strip with finite width and with the shear modulus varying exponentially perpendicular to the edges. By using Fourier transforms the problem was formulated in terms of a singular integral equation. It was numerically solved by representing the unknown dislocation density by a truncated series of Chebyshev polynomials leading to a linear system of equations. The stress intensity factor （SIF） results were discussed with respect to the influences of different geometric parameters and the strength of the non-homogeneity. It was indicated that the SIF increases with the increase of the crack length and decreases with the increase of the rigidity of the material in the vicinity of crack. The SIF of narrow strip is very sensitive to the change of the non-homogeneity parameter and its variation is complicated. With the increase of the non-homogeneity parameter, the stress intensity factor may increase, decrease or keep constant, which is mainly determined by the strip width and the relative crack location. If the crack is located at the midline of the strip or if the strip is wide, the stress intensity factor is not sensitive to the material non-homogeneity parameter.
