有初始缺陷板件超屈曲强度的半分析法研究

本文应用大挠度理论分析了初始缺陷对板件超屈曲强度的影响,并为板件后屈曲分析提出了一个样条函数半分析计算法.该法对各种载荷及位移边界条件板件均可进行计算,与有限元法等相比较,具有计算量少,精度高等显著特点.数值计算结果为冷弯型钢结构设计提供了较完善的理论依据.     

卷边板件屈曲分析的半能量法

A semi-energy method to analyse the buckling behaviour of edge-stiffened plates under combined compression and bending is presented in this paper, One unloaded edge of the plate is restrained elastically against rotation and the other is stiffened by a st     

两端不等弯矩作用下薄壁梁柱的弯扭屈曲

本文采用Ｒａｙｌｅｉｇｈ－Ｒｉｔｚ法求解两端不等弯矩作用下单轴对称开口薄壁截面梁柱弯扭屈曲临界荷载，分析中考虑了三种常见的边界条件以及屈曲前变形的影响，将本文弯扭屈由临界荷载理论值与试验值比较，吻合较好。     

开口薄壁结构弯扭屈曲能量原理的有限变形理论分析

The formulas of the total potential energy of arbitrary thin- walled open cross section member counting in the geometric non-linear factors is deduced. The deductions are based on the most general finite deformation theory and the two assumptions that"the     

Peaks of brainstem auditory evoked potentials in dogs

The effects of electrode configuration and click polarity on brainstem auditory evoked potentials (BAEP) in dogs were investigated to clarify the inconsistent nomenclature for each peak. Four positive peaks (waves 1, 2, 3 and 4) before a deep negative trough and a fifth positive peak (wave 5) following the trough were the basic components of BAEP in dogs, which were easily identified regardless of recording conditions such as electrode configuration and click polarity. Additional peaks tended to be present when a noncephalic reference electrode and/or single-polarity (rarefaction or condensation) click stimuli were used. The Roman nomenclature for the individual positive peaks of BAEP in dogs is confused owing to variations in the observed waveforms among researchers, but click polarity and/or reference electrode position can explain all the previously reported variations in BAEP waveforms in dogs. When the criteria concerning wave V in the guidelines of BAEP in human beings are applied to avoid further confusion of Roman nomenclature in dogs, it is recommended that the basic five positive peaks (waves 1, 2, 3, 4 and 5 as identified easily with Ai-Vertex configuration and alternating clicks) are designated as waves I, II, III, V and VI, respectively. Wave IV (wave 3b) occurs occasionally before wave V in dogs.Abbreviations BAEP brainstem auditory evoked potentials - dBHL dB hearing level - IPL interpeak latency - Ai the caudodorsal end of the zygomatic arch ipsilateral to the stimulated ear - Nape the neck over the spinous process of the fourth cervical vertebra     

湖南省长沙市羊布鲁氏菌病基线调查

为了解湖南省长沙市布鲁氏菌病流行现状,对奶羊养殖场(户)和种羊场采用普查策略,对其他羊养殖场(户)采用两阶抽样策略,选择羊群并选定群体中个体,采集血样进行布鲁氏菌抗体检测。同时,通过问卷调查和查阅资料等方式,分析布鲁氏菌病感染和传播风险。结果显示:全市羊布鲁氏菌病表观场群流行率为1.54%(95%CI:0.42%~3.91%),表观个体流行率为0.60%(95%CI:0.43%~0.80%);4个阳性群集中分布于长沙县和宁乡县;和以往监测数据相比,长沙市的羊群布鲁氏菌病流行率和人间发病率均呈下降趋势,说明前期的防治策略取得积极成效。总体来说,长沙市布鲁氏菌病流行率较低,疫情处于稳定控制状态,因而可以分区域逐步实现全市布鲁氏菌病净化。     

Dietary mannitol increased the absorption of calcium and magnesium in rats

The effect of mannitol on bone‐related mineral absorption and retention and the mechanism was investigated in this study. Fourteen 8‐week‐old male Wistar rats in experiment 1 and same number and age cecectomized Wistar male rats in experiment 2 were divided into two subgroups of seven animals, respectively, fed diets containing 0 or 4% mannitol for 28 days. Mineral balance tests were determined twice during days 8–12 and days 22–26, and the rats were slaughtered on day 28 both in experiment 1 and experiment 2. The whole caecum and colon were collected with the content to analyse tissue weight, content weight, content's pH and moisture, organic acids' concentration and mineral levels. In experiment 1, Ca absorption and retention and Mg absorption were significantly increased by mannitol feeding during days 8–12. Caecal total weight, tissue weight and content weight were increased, the pH of caecum and colon was reduced, and the concentrations of caecal short‐chain fatty acids (SCFAs) were modified by mannitol feeding. In experiment 2, during days 8–12 and days 22–26, Ca absorption and retention were significantly lowered by mannitol feeding in cecectomized rats; however, mannitol feeding decreased Mg absorption during days 8–12, but did not impact Mg retention. Colonic total weight, tissue weight and content weight were significantly increased, and colonic pH was reduced by mannitol feeding. In conclusion, dietary mannitol increased the absorption of Ca and Mg and the caecum markedly contributed to this promoting effect of mannitol.     

干湿交替下膨胀土裂隙演化与强度衰减规律试验研究

为揭示干湿循环效应下膨胀土胀缩裂隙的演化特征及土体结构强度的劣化规律,对合肥弱膨胀土试样开展不同循环幅度下的干湿循环试验,利用图像处理技术从试样表面裂隙图像中提取出裂隙参数,并进行低应力下的抗剪强度试验。试验结果表明:1)裂隙开展分为裂隙酝酿期、裂隙快速传播期和裂隙平稳发展期3个阶段,裂隙指标的增长主要集中在裂隙快速传播期,且循环幅度的增大会使土体的开裂程度加剧;2)在干湿循环作用下,膨胀土的内摩擦角变化幅度小于2.2°,其受干湿循环次数的影响很小,土体的强度衰减主要源于粘聚力的大幅降低。膨胀土的粘聚力呈现出先快后缓的衰减趋势,其中前4次干湿循环期间粘聚力的衰减率达到50.97%～66.92%,且衰减率也与干湿循环幅度的大小密切相关;3)通过灰色关联度分析发现,粘聚力的衰减与裂隙面积率、裂隙总长度、裂隙平均宽度的变化趋势具有明显的关联性,其中裂隙面积率的关联度最大,其与粘聚力衰减率间的关联度为0.785～0.832,相应的权重达到0.461～0.472,且裂隙面积率与粘聚力衰减率间具有较好的线性关系,而裂隙平均宽度的关联度最小,其与粘聚力衰减率间的关联度为0.392～0.414,对应的权重仅为0.228～0.240。研究成果可为进一步揭示剧烈温湿变化诱发的膨胀土边坡灾变机理提供重要依据。     

发酵床垫料翻耙结合网床养殖改善鸭舍空气质量与鸭生产性能

为解决规模化肉鸭生产中粪污影响鸭健康和污染环境的问题,研发了一种发酵床结合网床架养新技术及其配套的可移动式网床下发酵床垫料翻耙系统,并研究了该模式在控制舍内气载微生物数量和提高鸭生产性能中的优势。结果显示:1)可移动式发酵床垫料翻耙系统实现不同发酵床体共用一台翻耙机。2)与发酵床平养相比,鸭26日龄之前未翻耙垫料时,发酵床网养舍内需氧菌总数(1.531×105 CFU/m3)和大肠杆菌数量(1.298×104 CFU/m3)显著升高(P0.05);鸭27~34日龄时每4 d翻耙垫料,发酵床网养舍内需氧菌总数(2.304×105 CFU/m3)和金黄色葡萄球菌数量(1.353×105 CFU/m3)显著降低(P0.05);鸭35~39日龄时每天翻耙垫料,发酵床网养舍内需氧菌总数(1.255×105 CFU/m3)和"沙门+志贺"氏菌数量(14.13 CFU/m3)显著降低(P0.05)。3)在发酵床平养舍内,与每4 d翻耙1次垫料相比,每天翻耙1次垫料舍内需氧菌总数(2.688×105 CFU/m3)、大肠杆菌(2.038×104 CFU/m3)、金黄色葡萄球菌(8.90×104 CFU/m3)和"沙门+志贺"氏菌(47.11 CFU/m3)数量显著(P0.05)降低,而在发酵床网养舍内,每天翻耙1次垫料舍内需氧菌总数(1.255×105 CFU/m3)和"沙门+志贺"氏菌(14.13 CFU/m3)数量显著降低(P0.05)。4)与发酵床平养相比,发酵床网养增加鸭体质量(P0.05),降低死亡率和上市淘汰率(P0.05)。结果表明研发的肉鸭养殖新模式能更好地减少舍内空气中病原菌浓度,改善鸭舍内空气环境,提高鸭生产性能。该研究为发酵床结合网床架养新模式在规模企业中推广应用提供技术支持。     

The changes in proximate compositions and glycogen contents in the dorsal ordinary muscles of the full-cycle cultured Pacific bluefin tuna Thunnus orientalis occurring with growth

ABSTRACT:   Using full-cycle cultured (FC) Pacific bluefin tuna (body length [BL], 42.6–66.4 cm; body weight [BW], 1.66–7.40 kg, n  = 15), the changes in chemical compositions and histological structure of the cephalal parts of the dorsal ordinary muscles (DOM) occurring with growth were investigated. A positive correlation ( r  = 0.9644, P  < 0.05) was observed between BL and BW with growth. The protein, lipid and ash contents of DOM and condition factor did not change with growth. However, the glycogen content of DOM increased ( P  < 0.05) from approximately 55 cm (BL) in this study. Using optical microscopic photographs, the various shapes of muscle fibers were observed and it was noted that the muscle fiber diameter increased ( P  < 0.05) with growth. Using transmission electron microscopic observation, many glycogen granules were observed in muscle fibers (especially, side of connective tissue) of DOM throughout the growth stage in this study. These results indicate that the glycogen content of DOM of FC Pacific bluefin tuna increases before the lipid with growth.