聚能破甲战斗部头螺凹槽结构

针对现有聚能破甲战斗部在打击装甲目标过程中,金属射流所经过的弹体头螺内腔狭窄,射流损伤较大的问题,提出了聚能破甲战斗部头螺凹槽结构。该结构利用破甲过程中凹槽的形变扩大头螺内腔口部尺寸,从而改善射流通道的通透性,使得高速射流能够稳定地通过头螺内腔。仿真与试验验证表明,该结构能够有效增加聚能战斗部的动破甲威力,使得战斗部穿透厚180mm的钢靶后,后效靶的平均穿透数由3层提高到6.2层,并且具备打击220mm厚钢靶的能力。

某头螺开舱性能与成形工艺研究

针对某头螺生产率低的主要问题,在保证头螺开舱性能良好的前提下,通过对头螺开舱机理的研究,建立了裂纹扩展方向与材料微观组织参数之间的关系模型,且指导制订了收口法和整体挤压法两套工艺方案,经计算机模拟,初步预测了新工艺成形产品微观组织变化符合开舱裂纹扩展要求,研制得到合格的头螺产品,并且其开舱性能测试合格。综合实验结果,应优先选用收口法成形头螺,比原工艺节约材料约4.8kg。

子母弹头螺开舱裂纹扩展机理研究

根据断裂力学基本原理,尝试建立了裂纹扩展方向与材料微观组织参数之间的关系模型,旨在指导头螺新成形工艺的制定,在满足头螺开舱性能的前提下,大幅度提高材料利用率.对现行头螺及其破片进行了宏微观分析,发现开舱是一个裂纹动态扩展过程,主扩展方向与材料流线一致.通过考虑裂纹尖端的塑性区以及对扩展模型进行等效处理,建立了头螺壳体裂纹扩展模型及理论判据,认为当裂纹尖端纵向位移小于流线间距离时,裂纹能够沿某一流线方向进行稳定贯穿.模型计算结果与静爆实验结果相吻合表明,建立的裂纹扩展模型基本合理,可用于指导头螺新成形工艺的制定.

某弹体头螺内孔缺陷原因分析

某弹体头螺在生产过程中发现缺陷,通过故障树分析、宏观观察、化学成分分析、金相检验等方法对弹体头螺缺陷原因进行了分析。结果表明:弹体头螺工件在冲拔收口过程中,进给不均匀及锤打数量偏少,造成金属流动不合理导致头螺发生缺陷失效。

DTT式100mm头螺毛坯产品工艺改进

DTT式100mm头螺毛坯产品的原生产工艺是经二次中频加热，整体冲压拉伸收口、后续需机加切断，并由整体分成分体，其产品的壁偏差过大，为6～8mm，因此需在热处理前进行二次粗加工，以保证产品的壁偏差达到设计要求。对工艺进行研究和优化设计，改进的生产工艺为经一次加热、三工位一次挤压完成，其产品的壁偏差小于0．8mm，达到了设计要求，并取消了产品热处理前的粗加工和半精加工。同时降低了材料消耗定额，提高了产品合格率，缩短了生产周期，提高了生产效率。

高速破甲弹破甲稳定性数值模拟与实验研究

文中采用数值模拟方法,对高速破甲弹生成的金属射流在头螺内运动过程进行了分析。在试验研究及其结果分析的基础上,通过改进头螺内腔结构,改善了射流的品质,提高了破甲稳定性,解决了高速破甲弹破甲稳定性技术问题。

Detection of small hepatocellular carcinoma:Comparison of dynamic enhancement magnetic resonance imaging and multiphase multirow-detector helical CT scanning

AIM: To compare the gadolinium-enhanced multiphase dynamic magnetic resonance imaging (MRI) and multiphase multirow-detector helical CT (MDCT) scanning for detection of small hepatocellular carcinoma (HCC). METHODS: MDCT scanning and baseline MRI with SE T1-WI and T2-WI sequence combined with FMPSPGR sequence were performed in 37 patients with 43 small HCCs. Receiver operating characteristic (ROC) curves were plotted to analyze the results for modality. RESULTS: The areas below ROC curve (Az) were calculated. There was no statistical difference in dynamic enhancement MDCT and MRI. The detection rate of small HCC was 97.5%-97.6% on multiphase MDCT scanning and 90.7%-94.7% on MRI, respectively. The sensitivity of detection for small HCC on MDCT scanning was higher than that on dynamic enhancement MRI. The sensitivity of detection for minute HCC (tumor diameter ≤ 1 cm) was 90.0%-95.0% on MDCT scanning and 70.0%-85.0% on MRI, respectively. CONCLUSION: MDCT scanning should be performed for early detection and effective treatment of small HCC in patients with chronic hepatitis and cirrhosis during follow-up.

FoxO4 is the main forkhead transcriptional factor localized in the gastrointestinal tracts of pigs

Forkhead box （Fox） proteins play critical roles in the regulation of differentiation, proliferation, immunity and aging of cells. Most studies on Fox proteins are limited to cultured cells and rodent. The aim of the current study is to detect by immunohistrochemistry whether FoxO1, FoxO3a and FoxO4 proteins are localized in the stomach and intestine of the pig. The results showed that FoxO4 exists in the mucosa in all parts of the stomach and intestine; FoxO3a exists mainly in the lamina propria and muscularis of some parts. However, FoxOl is not detectable in all parts of the stomach and intestine. Collectively, the results of the present study indicate that there exists a distinct expression pattern of Fox proteins, and that FoxO4 is a primary forkhead transcriptional factor localized in the gastrointestinal tracts of the pig.

Design methods of headed studs for composite decks of through steel bridges in high-speed railway

Aimed at two typical composite floor systems of through steel bridges in high speed railway,design methods of headed studs were put forward for different composite members through comparing and analyzing the structure,mechanical characteristics and transmission routes of deck loads.The simplified calculation models were brought out for the stud design of the longitudinal girders and transverse girders in the composite floor system of Nanjing Dashengguan Yangtze River Bridge (NDB).Studs were designed and arranged by taking the middle panel of 336 m main span for example.The results show that under deck loads,the longitudinal girders in the composite floor system of through steel bridges are in tension-bending state,longitudinal shear force on the interface is caused by both longitudinal force of "The first mechanical system" and vertical bending of "The second mechanical system",and studs can be arranged with equal space in terms of the shear force in range of 0.2d (where d is the panel length) on the top ends.Transverse girders in steel longitudinal and transverse girders-concrete slab composite deck are in compound-bending state,and out-of-plane bending has to be taken into account in the stud design.In orthotropic integral steel deck-concrete slab composite deck,out-of-plane bending of transverse girders is very small so that it can be neglected,and studs on the orthotropic integral steel deck can be arranged according to the structural requirements.The above design methods and simplified calculation models have been applied in the stud design of NDB.

Effects of spinneret structure on poly-ether-ether-ketone fibers by screw extrusion

According to the characters of poly-ether-ether-ketone (PEEK) plastic, the spinnerets with three kinds of different structure were designed. The effects of spinneret structure on the melt spinning conditions, melt flow instability of the screw extrusion, and the performance of PEEK fibers were studied. The results show that the appropriate screw extrusion temperature is 370 385℃. The PEEK fibers extruded using the spinnerets with L/D=6, 8holes and 0.5mm in diameter have better performances. The performances of PEEK fibers are related to the dia- meter of the spinneret hole. Increasing the L/D value of the spinnerets can not always improve the surface quality and the performances of PEEK fibers. The extrusion pressure is about 50% of that of the spinneret with 12holes and 0.3mm in diameter.

Seismic Behavior of Confined RC ColumnComposite Beam Joints

In order to evaluate the seismic behavior of confined RC column-composite beam joints, five interior joints were tested under low cyclic reversed load. The weakening extent of flanges, the number of studs, and whether to reinforce weakened flanges were used as parameters in designing these five joints. Failure characteristics, hysteretic curves, skeleton curves, ductility, energy dissipation, strength degradation, and stiffness degradation were analyzed. The test results revealed that the steel beam flanges in the joints were equivalent to the tie rod. Weakened flanges resulted in poor seismic behavior; however, the seismic behavior could be improved by increasing studs and reinforcing weakened flanges. The joint steel plate hoops, equivalent to stirrups, did not yield when the maximum load was reached, but yielded when the failure load was reached for the joints with shear failure. Increasing stud-type joints and reinforcing flange-type joints ensured good seismic behavior and met project requirements. Based on the experimental results, the failure mechanism of the joints was discussed, and the shear capacity equations of the joints was presented.

Optimization of ice cuttings transportation by cable-suspended core auger drills

Ice cores contain an abundance of information about the Earth＇s climate in the past, and recovered from shallow drilling down to 300-350 m give sufficient information for reconstructing of the last climatic changes and for monitoring of pollution from human being. Cable-suspended core auger drills use an armored cable with a winch to provide power to the down-hole motor system and to retrieve the down-hole unit. Because of their lightweight, convenient transportation and installation, high penetration rates and low power consumption, core auger drills are widely used for shallow drilling in ice. Nowadays at least 14 types of auger electromechani- cal drills were designed and tested in different foreign and national glaciological laboratories. However, auger options were usually determined by experience, and the main parameters （ helix angle of the fights and rotational speed） are varied in a wide range from drill to drill. If parameters of auger are not chosen properly, poorly en- gineered drills had troubles with low efficiency of cuttings transportation, jam of ice cuttings, repeated fragmen- tation, cutters icing and stop penetration, abnormal power consumption, high rotation torques, and so on. Thus, this paper presents the method of optimization of iee cuttings transportation of cable-suspended core auger drill on the base of the theory of rotary auger. As the result, the optimal helix angle was determined correspond- ing to the rotational speed from the transportation efficiency point of view.

Analysis of Leakage in Bolted-Flanged Joints Using Contact Finite Element Analvsis

The evolution of leakage is studied using detailed contact finite element analysis. The distribution of stress at the gasket is analyzed using a contact condition based on slide-line elements using ABAQUS, a commercial finite element code, Slide-line elements also take into account pressure penetration as contact that is lost between flange and gasket. Results are presented for a particular flange, a raised face flange sealed by a mild steel gasket. A comparison of the results from the gasket contact analysis and the contact conditions specified by the ASME Boiler and Pressure Vessel Code, Sections VIII, Division 1 shows that the conditions specified in the ASME Code predict leakage relatively accurately.

Phylogeny of forkhead genes in three spiralians and their expression in Pacific oyster Crassostrea gigas

The Fox genes encode a group of transcription factors that contain a forkhead domain, which forms a structure known as a winged helix. These transcription factors play a crucial role in several key biological processes, including development. High-degree identity in the canonical forkhead domain has been used to divide Fox proteins into 23 families （FoxA to FoxS）. We surveyed the genome of three spiralians, the oyster Crassostrea gigas, the limpet Lottia gigantea, and the annelid Capitella teleta. We identified 25 C. gigas fox genes, 21 L. gigantea fox genes, and 25 C. teleta fox genes. The C. gigas fox and L. giganteafox genes represented 19 of the 23 families, whereas FoxI, QI, R, and S were missing. The majority of the Fox families were observed within the C. teletafox genes, with the exception of FoxR and S. In addition, thefoxAB-like gene,foxY-like gene, andfoxH gene were also present in the three genomes. The conserved FoxC-FoxL 1 cluster, observed in mammals, was also found in C. gigas. The diversity of temporal expression patterns observed across the developmental process implies the C. gigasfox genes exert a wide range of functions. Further functional studies are required to gain insight into the evolution of Fox genes in bilaterians.

Dynamic hip screw with locking side plate： a viable treatment option for intertrochanteric fracture

Objective： Dynamic hip screw （DHS） is recommended for the fixation of stable intertrochanteric fractures. Its postoperative cut-out rate ranges from I% to 6%. In osteoporotic bone, normal screws in DHS blade provide less anchorage compared to locking screws. This study aims to compare DHS with locking side plate and conventional side plate. Methods： Fifty consecutive patients with intertrochanteric fractures were randomly allocated for fixation with a standard DHS （group A） and locking DHS （Combi plate, group B）. We compared the clinical and radiological outcomes for the conventional DHS and locking DHS in intertrochanteric fractures. Functional outcome was evaluated using the Parker mobility score. Results： Coxa valga was found more frequently in group A than in group B （12% vs. 0%, P=0.42）. Coxa vara showed the same trend （12% vs. 8%, P=0.81）. Rate of restoration of postoperative neck-shaft angle within 20° of sound side was higher in group B （8% cases） than in group A （4% cases, P=0.98）. The rate of anteversion angle restoration within 10° of sound side was also higher in group B （100% vs. 88%, P=0.85）. The average lag screw slippage in group A and group B was 3.2 mm and 4.2 mm, the average fracture union duration was 17.1 weeks and 16.4 weeks, and the mean Parker score was 5.6 and 5.8 respectively. Screw cut-out was seen in one patient in group A. No cut-out was seen in any of the patient in group B. No patient developed deep infection, avascular necrosis, deep vein thrombosis or any other significant complications. Conclusion： The present study demonstrated that treating intertrochanteric fracture with a locking DHS allows sound bone healing and is not associated with any major complications. Although this report is promising, it should be interpreted with caution because only a prospective study with a large sample size would allow definitive conclusion.

Prime waterfront real estate： Apple snails choose wild taro for oviposition sites

While difficult to prevent introductions, scientific research can help guide control efforts of exotic, invasive species. South American island apple snails Pomacea insularum have quickly spread across the United States Gulf Coast and few control measures exist to delay their spread. Usually occupying cryptic benthic habitats, female apple snails crawl out of the water to de-posit large, bright pink egg clutches on emergent objects. To help identify the most likely place to find and remove clutches, we conducted four lab experiments to investigate what specific object qualifies （i.e. material; shape and height; plant species; natural and artificial） attracted P. insularum females to lay clutches. In our fourth experiment, we specifically examined the relationship between female size and reproductive output. To further understand reproductive output, we quantified experimental clutch chara-cteristics （height above water, dimensions, mass, approximate volume, number of eggs, hatching efficiency）. Pomacea insu-larum females laid more clutches on plant material, chose round over flat surfaces and failed to differentiate between tall and short structures. In comparison to a common native plant in the eastern US, Pontederia cordata, snails clearly preferred to lay clutches on a widely distributed exotic, invasive plant （wild taro, Colocasia esculenta）. Unexpectedly, smaller snails showed higher overall total fecundity as well as more eggs per clutch than larger snails. Therefore, hand removal efforts of large fe-males may not be enough to slow down clutch production. Collectively, our results indicate that conservationists and managers should search emergent plants for P. insularum clutches carefully to guard against established populations [Current Zoology 57 （5）： 630-641, 2011].