Mg-1.3Mn-xCe-xZn镁合金显微组织和力学性能的研究

以Mg-1.3Mn合金为基合金,添加质量分数为1.0%或者2.0%的Ce以及质量分数为2.0%~6.0%的Zn,进行多元合金化,研究Ce,Zn对Mg-1.3Mn合金显微组织和力学性能的影响.实验结果表明：在Mg-1.3Mn合金中,一定量Ce,Zn的加入不但能明显地细化晶粒,而且能提高实验合金的抗拉强度和硬度.Mg-1.3Mn-1.0Ce-xZn合金的室温拉伸断裂机理随着Zn含量的增加也将发生改变.     

A Mesoscopic Simulation Analysis of Interface Transition Zone Characteristics Effect on Mechanical Properties of Concrete

The concrete was equivalent to a three-ingredient compound material, which was composed by aggregate, mortar and interface transition zone (ITZ). The random aggregate model was established using the Monte Carlo method. The relation between linear stress and crack was analyzed, which was used to describe the mechanics of concrete ingredients. The extended finite element method was used to simulate the failure response to various ITZ characteristics of concrete under uniaxial tension. With the tensile strength of ITZ increasing, the tensile strength, fracture energy and ductility of concrete are enhanced. The fractured modes are altered. The concrete’s elastic modulus increases with the elastic modulus of ITZ. With the thickness of ITZ decreasing, the tensile strength, elastic modulus and fracture energy of concrete increase. The interface thickness effect on concrete is reduced.     

Energy analysis of concrete’s fracture expanding elements

Assume the material of concrete structure with crack is viscoelastic material, the relative displacement of crack side increases under load. If stress intensity factor is calculated by displacement direct method, the stress intensity factor will increase and may be even bigger than the concrete’s fracture toughness. The fracture problem of viscoelastic material is studied based on Entropy theory. It is showed that if the structure is viscoelastic material, there is no energy dissipation and release during the rheological process; the entropy is a constant and the crack remains stable, which means the displacement direct method is not feasible to rheological fracture problem. The blunt crack band model is preliminarily studied as well. It is believed that when fracture expanding element cracks, the structure energy will release, which is equal to the energy difference value between external work external work and total elastic energy and also approximately equal to the difference value between the total elastic energies of fracture expanding elements before and after cracking. As to linear elastic fracture problem, the stress intensity factor can be obtained by simply transforming the ratio of the energy difference value and virtual expanding length (plane problem) or virtual expanding area (spatial problem). It is also indicated by the analysis that blunt crack band model is independent of mesh size partly and its mesh can be obtained easier comparing with discrete crack model.     

Recognition and prediction of fracture by using antcolony algorithm analysis in carbonate reservoir

A fracture-developed carbonate oil field in the east has a complicate oil and gas distribution in facture network at late development stage, which leads to multiplicity of favorable reservoir estimation. In view of problems above, ant colony algorithm is adapted to recognition and predict facture in this field. The ant parameters are optimized on the basis of core and image log data, and the spatial distribution feature of fracture is described, as a reticulate structure with three dominant clusters of fracture (NW, NNE & NE). Drilling leakage, production data and image log are then used for reliability analysis of fracture predict, which presents that ant colony algorithm is a practicable methodology to recognition fracture and provides a support for remaining oil distribution analysis. As a booming bionic algorithm, ant colony algorithm has great potential for quantitative fracture predict with seismic materials.     

针叶材在超细粉碎过程中细胞壁断裂的理论计算

将针叶材的超微结构破坏分为细胞壁间分离和细胞壁断裂两种形式。在制备其超细木粉过程中,涉及到针叶材细胞的破壁力计算时,提出以细胞壁中存在大量的原生细观缺陷作为已存在的裂纹,将单一细胞壁看作是带有裂纹体受拉应力的平板,利用弹塑性断裂力学中J积分与积分路径无关这一常数的性质,避开裂纹尖端的弹塑性区域进行理论计算,应用J积分与应力强度因子在平面应力下的关系,计算出针叶材细胞壁断裂韧性的大小,并将不同针叶树种的木材细胞断裂韧性数值与其相应的细胞壁抗拉强度实验结果相比较,得出以此理论计算木材细胞断裂韧性值较为合理,表明利用J积分计算木材细胞壁断裂韧性这一方法是可行的。     

黄淮海夏玉米新品种抗病性和抗倒性评价

为了筛选出适宜黄淮海区种植的玉米优良品种,对22个玉米新品种的田间抗逆性进行了调查分析。结果表明,22个品种对瘤黑粉病和小斑病的整体抗性较好,而部分品种对青枯病和倒伏的抗性较差。相关分析表明,抗倒能力较强的品种主要得益于穗位低和重心低、第三节间直径和总维管束横截面积较大,以及抗折力较高。对2个密度组的分析发现,以60 000株/hm2组综合表现较好,67 500株/hm2组的抗病和抗倒性整体劣于60 000株/hm2组的。可见,耐密品种选育在注重耐密性和丰产性的同时,还应重视其抗逆性和稳产性。     

Low-field standing magnetic resonance imaging findings of the metacarpo/metatarsophalangeal joint of racing Thoroughbreds with lameness localised to the region: a retrospective study of 131 horses

Reasons for performing study: The metacarpo/metatarsophalangeal (MCP/MTP) joint is a common site of lameness in the Thoroughbred racehorse. Radiographs may fail to show pathology consistent with the degree of lameness. With a high incidence of stress fractures occurring in the distal third metacarpal/metatarsal (MC3/MT3) condyles and proximal phalanx, a definitive diagnosis as to the nature of the pathology is essential. Objective: To describe the low‐field magnetic resonance imaging (MRI) findings in Thoroughbred racehorses with MCP/MTP joint pain scanned under standing sedation. Methods: The MR images and clinical records of all Thoroughbred racehorses undergoing MRI of the MCP/MTP joint between October 2006 and August 2010 were reviewed. A total of 168 joints from 131 horses were selected for inclusion. The MRI finding considered most significant in the lame (or lamest) limb was noted. Results: Diagnostic quality images were obtainable in 97.8% of horses. The most common finding was palmar/plantar osteochondral disease in MC3/MT3 (54.9% of horses). Incomplete condylar fracture was diagnosed in 19.8% of horses, with the lateral condyle predominating. An incomplete sagittal fracure of P1 was diagnosed in 14.5% of horses and 11.4% were diagnosed with ‘dorsal joint disease’. Other findings included transverse MC3 stress fractures (1.5%), soft tissue injuries (12.2%) and proximal phalangeal ‘contusions’ (3.8%). No significant bone/soft tissue injury was detected in 5.4% of cases. Conclusions: Standing MRI can detect a spectrum of disease within the MCP/MTP joints of racehorses. The procedure is well tolerated and may lead to a definitive diagnosis where radiographic imaging is inconclusive. Potential relevance: A total of 35.8% of cases had MRI findings consistent with fracture pathology, which could not be confirmed radiographically at the time of the MRI examination. This has important therapeutic and prognostic implications and may help to prevent catastrophic injury.     

Magnetic resonance imaging‐detected adaptation and pathology in the distal condyles of the third metacarpus,associated with lateral condylar fracture in Thoroughbred racehorses

Reasons for performing the study: Lateral condylar (LC) fractures of the third metacarpus (McIII) are a common reason for euthanasia in racehorses, and may be the result of repetitive overloading or cumulative pathological change. Magnetic resonance imaging (MRI) allows monitoring of bone and cartilage to detect pathological and adaptive changes that may be precursors of fracture. Objectives: To describe bone and cartilage MRI features in the distal condyles of McIII of Thoroughbred racehorses, with and without condylar fracture. Hypotheses: 1) A greater degree of bone and cartilage adaptation or pathology will be seen in fractured McIIIs compared with their respective contralateral McIIIs. 2) Contralateral McIIIs will have a greater degree of bone and cartilage adaptation or pathology than McIIIs from control horses that did not sustain a LC fracture. Methods: The McIIIs from 96 horses subjected to euthanasia at racecourses were divided into 3 groups: Group 1: nonfractured bones from horses without LC fracture; Group 2: nonfractured bones from horses with unilateral LC fracture; and Group 3: fractured bones from horses with unilateral LC fracture. The MR images were examined and graded for bone and cartilage changes. Results: Nine percent of Group 1 (n = 9) and 11% of Group 2 bones (n = 5) had incomplete LC fractures. Focal palmar necrosis was most frequently detected in bones from Group 1 (12%) compared with Groups 2 (9%) and 3 (4%). The prevalence of bone and/or cartilage abnormalities tended to increase from Group 1 to Group 2 to Group 3. Conclusions: Magnetic resonance imaging is able to detect cartilage and bone changes that may be associated with LC fracture. There was no significant difference in bone/cartilage changes between bones from Groups 1 and 2, despite increased pathology in Group 2 bones. Potential relevance: Periodic monitoring of bone and/or cartilage changes in distal McIII of Thoroughbred racehorses may help to prevent catastrophic LC fractures.     

多发性骨折合并休克的临床处理(附28例分析)

本文分析28例多发性骨折并休克病人的治疗经过、措施及疗效。强调凡有休克的病人,应先积极抗休克,挽救生命,注重保留肢体,尽量恢复肢体功能的原则。对抗休克与骨折处理的关系、选择骨折处理方法、综合治疗及漏诊问题作了简要的讨论。     

纤维桥作用的探讨与验证

结合高含量钢纤维混凝土小梁的试验，采用界面理论讨论影响纤维桥作用的因素，提出验证纤维桥作用的断裂力学方法。