Tensile fracture properties of seven tropical grasses at different phenological stages

The intake of forage grasses by grazing ruminants is closely related to the mechanical fracture properties of grasses. The relationship between the tensile fracture properties of grasses and foraging behaviour is of particular importance in tropical reproductive swards composed of both stems and leaves. This study (i) quantified and compared the tensile fracture properties of stems and leaves of seven tropical grass species and (ii) provided insight into the underlying plant traits that explain differences in fracture properties between species. Fracture force, tensile strength, fracture energy and toughness of stems (in various phenological stages) and leaves were measured and compared among five introduced tropical grasses (Cenchrus ciliaris, Chloris gayana, Digitaria milanjiana, Megathyrsus maximus (syn. Panicum maximum), Setaria sphacelata) and two native tropical grasses (Setaria surgens and Dichanthium sericeum). Species differed significantly in fracture force and fracture energy, with stems and leaves of C. ciliaris and S. surgens requiring less force and energy to fracture and stems and leaves of M. maximus and S. sphacelata requiring more force and energy to fracture in comparison with the other species. Differences in tensile strength and toughness were less pronounced. The differences among species in fracture force and energy mainly resulted from differences in cross‐sectional area of plant parts rather than from differences in tensile strength and toughness.     

巴楚隆起西段色力布亚断裂在含油气系统下的封堵性能

分析了巴楚隆起西段色力布亚断裂构造及演化特征,并将色力布亚断裂置于含油气系统之内进行了研究,以对该断裂的封堵性以及其对成藏的控制作用有更清楚的认识。研究结果表明,色力布亚断裂构造带处于巴楚断隆西南缘,“古高新高”均是多期油气运移的有利指向,且断裂南段下盘构造带为勘探优选目标。     

水曲柳木材裂纹尖端应力强度因子研究( 英文)

该文研究了水曲柳 (FraxinusmandshuricaRupr .)木材发生Ⅰ型断裂时裂纹尖端的应力场应力强度因子的情况 .借助美国大型通用有限元分析软件NASTRAN计算出裂纹尖端附近的应力 ,并通过GRAFTOOL软件对数据进行后期处理 ,画出裂纹尖端附近的应力强度因子分布图     

Conservative management of comminuted central tarsal bone fracture and joint instability in a horse

A comminuted fracture of the central tarsal bone, fragmentation of the fourth tarsal bone and associated joint instability was diagnosed in a 14‐year‐old Sport Horse mare who presented for investigation of acute nonweightbearing hindlimb lameness. The mare responded well to conservative management and, unlike previously reported cases of similar injuries, returned to a similar level of athletic activity.     

Catastrophic biaxial proximal sesamoid bone fractures in UK Thoroughbred races (1999–2004): Horse characteristics and racing history

Reason for performing study: Catastrophic biaxial proximal sesamoid bone fractures (PSBF) have not yet been described in detail in the UK racing population. Objectives: To determine the incidence and relative risk (RR) of PSBF in different types of racing in the UK; and to describe horse‐level characteristics and racing histories of horses sustaining these injuries. Methods: Distal limbs were collected from all racehorses suffering catastrophic fractures during racing at all 59 racecourses in the UK, in a prospective study from February 1999 to December 2004. Post mortem investigation identified the anatomical location and type of fracture. Horse, racing history, race and racecourse details were obtained. Characteristics of the horses that sustained PSBF were described. The incidence and RR of PSBF in the different types of racing in the UK were calculated. Results: Thirty‐one horses suffered PSBF during the study period. The incidence of PSBF in all types of race was 0.63 per 10,000 starts (31/494,744). The incidence was highest in flat races on all weather surfaces (1.63 per 10,000 starts: 12/73,467; RR = 4.4 when compared to turf flat racing). Affected horses had an average age of 5.6 years and had started a mean of 28 races at the time of fracture. Conclusion and potential relevance: There is a strong association between type of racing surface and PSBF. Horses competing in flat races on all weather surfaces have an increased risk of PSBF. These fractures appear to happen in experienced horses with several starts, with few fractures occurring within the first season of racing. Further research should focus on identification of underlying pathology of these fractures. Epidemiological studies aimed at the identification of risk factors for PSBF in the UK racing population would require a large number of cases acquired over many years given the relatively low incidence of PSBF.     

Fracture Energy and Strain Softening ofConcrete under Seawater Environment

Both Three Points Bending (TPB) test on notched beams and Wedge Splitting Test (WST) were carried out on concrete specimens under six different conditions, under which they were totally dry, partially dry, water immersed, seawater immersed, 5% and 23.4% NaCl solution immersed, respectively. The fracture energy of each type of concrete and their strain softening curves were calculated according to the force displacement diagrams and inverse analysis method. It was indicated that with water, seawater or salt solution penetrating into concrete, the surface tension of pore liquids in concrete increased, which resulted in the decrease of the surface energy and load bearing capacity of concrete. After water immersed, the maximum bearing loads of specimens’ were reduced by 19.6% (TPB) and 14.5% (WST) compared with those of totally dry concrete. And for those of seawater immersed, 28.9% and 21.7% were reduced respectively. Furthermore, fracture energy of concrete was decreased more than 24% and fracture toughness was reduced significantly as well for concrete with high concentration salt solution, which made crack formation in concrete easier. The adverse influence of seawater on concrete materials had been investigated in detail from the aspects of surface energy, fracture energy and strain softening.     

肱骨近端骨折术后中医骨折三期疗法的疗效分析

目的 探讨肱骨近端骨折术后采用中医三期疗法辅助治疗对患者骨折的疗效及肩关节功能恢复的影响。方法 选取本院骨科手术治疗的135例肱骨近端骨折后行锁定钢板固定治疗的患者采用信封法随机分为中医组68例和常规组67例,中医组术后采用中医三期疗法,常规组采用常规康复疗法,对比两组患者术后骨折恢复效果及肩关节功能。结果 中医组的平均愈合时间（6.4±1.5）周显著短于常规组的（7.1±1.5）周,差异具有统计学意义（P<0.05）。术后1周、术后2周中医组的VAS评分显著低于常规组（P<0.05）;中医组患者的肿胀程度优良率89.7%显著高于常规组患者的76.1%（P<0.05）;术后6个月中医组患者的肩关节后伸、外展上举、外旋程度、运动范围、功能及Neer总分均显著优于常规组（P<0.05）。结论 肱骨近端骨折术后采用中医三期疗法辅助治疗有助于骨折愈合,促进肩关节功能恢复。     

黄瓜子和生菜子提取物促进骨折愈合的试验研究

本试验主要研究黄瓜子和生菜子合用促进骨折愈合的作用及其初步机理。将蛋鸡60只,体重1.75～2.25 kg,造成右侧小腿中段横行闭合骨折模型,随机分为数目相等的高剂量组、中剂量组、低剂量组,阳性对照组和阴性对照组。试验组以不同比例的黄瓜子和生菜子提取物灌胃给药,阳性对照组以麝香接骨胶囊灌胃给药,阴性对照组以生理盐水灌胃,随后对各组进行动态观察、组织学观察、血清学观察和放射学观察。结果显示,黄瓜子和生菜子提取物中剂量组可促进全身代谢反应,提高血清碱性磷酸酶含量,加快血肿吸收机化,提高血钙、磷离子浓度,提高骨痂生成量和强度。结果表明黄瓜子和生菜子提取物可以通过提高钙、磷离子浓度,促进钙、磷向骨折断端转移而对骨折的愈合起到促进作用。     

木材损伤断裂过程的声发射特性与Felicity效应

以2种针叶材、2种阔叶材为试材,研究无缺陷试件和含横纹裂纹试件在弯曲破坏过程中材料内部微结构演化的声发射特性,并利用声发射特征参数对几种损伤类型进行辨识.结果表明:1)无缺陷试件在加载初期声发射事件发展较为缓慢,且出现的主要是一些低振幅的AE信号,而大量高振幅AE信号出现在峰值载荷附近及韧性断裂阶段;2)利用声发射监测含裂纹试件在三点弯曲载荷下的损伤并断裂全过程,可以明显地识别裂纹尖端启裂和扩展的不同阶段;3)声发射信号的特征与损伤模式有关,胞壁断裂对应的AE特征为高幅值、高能量及长持续时间,而胞壁界面损伤与层裂损伤和细胞屈服与压溃损伤对应的AE特征为低幅度、低能量及短持续时间;4)木试件在低载荷水平下呈现Kaiser效应,而在高载荷水平下呈现Felicity效应,应用Felicity比能够较好地反映木结构的损伤程度.     

锯链传动片疲劳试验失效分析

国产锯链在高速空载疲劳试验时出现早期损坏,其寿命比同型号的OREGON锯链短很多。通过化学成分、金相组织、表面硬度及零件制造精度的检测对比分析,认为这是由于国产锯链传动片、连接片和切齿片的制造精度不高,实际孔距尺寸偏大,使得锯链节距大于链轮分度圆节距。这时锯链与链轮的相互位置关系就无法保证,锯链与链轮的啮合状况变坏,传动过程中将产生冲击、滑移窜动、爬高、张力波动等现象,使锯链的负荷成倍增加,尤其是传动片清理齿齿尖部位承受长期反复的冲击载荷,从而导致早期疲劳断裂。提高零件制造精度后,锯链与链轮的啮合状况正常,高速空载疲劳试验寿命达到要求。