排序方式: 共有36条查询结果,搜索用时 15 毫秒
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为提高承受内部爆炸载荷钢筒的抗爆性能,研究了泡沫铝内衬对钢筒变形的影响。首先通过对比实验,发现在本文的实验条件下,泡沫铝内衬导致钢筒变形增大,甚至发生了严重的破坏;进而建立有限元模型,研究了钢筒变形随爆炸当量、泡沫铝内衬厚度的变化机理和规律。结果表明,添加足够厚度的泡沫铝内衬能够减小钢筒变形,但泡沫铝厚度不足时,则可能起到相反的效果。对于固定尺寸的含泡沫铝内衬钢筒,随着爆炸当量增加,泡沫铝内衬对钢筒塑性变形的影响主要包含3种模式。模式1,泡沫铝可通过塑性变形吸收爆炸载荷,从而减小钢筒变形。模式2,泡沫铝内衬导致钢筒承受的载荷强度增大,钢筒塑性变形增大。模式3,泡沫铝对载荷强度的影响可忽略,泡沫铝通过增大结构质量减小钢筒塑性变形。 相似文献
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In this paper we carried out experiments using two-stage light gas gun with Gram-grade cylindrical tungsten alloy projectiles, impacting concrete targets at velocity from 1.82 km/s to 3.66 km/s ton investigate the cratering mechanism of concrete targets in hypervelocity impact conditions. We obtained the penetration depth and residual length of the projectiles using computerized tomography (CT) and used the numerical simulation results conducted by Euler algorithm to further examine the mechanism of hypervelocity impact, and achieved the following results: (1) The craters were structured by spalling areas and bullet holes; (2) The penetration depth increases at first and then decreases with the increase of the impact velocities, and the maximum penetration depth was 8.5 times that of the projectile length, which showed no significant advantage over low velocity penetration; (3) According to the pressure of the interface of the projectiles and targets, the penetration processes were divided into four stages, of which the quasi-steady stage and the third stage were crucial in determining the total penetration depth; (4) When the projectiles were completely eroded with the increase of the impact velocities, the penetration depth of the quasi-steady stages almost remained the same and the penetration depth of the third stage decreased so that the total penetration depth was observed to increase at first and then decrease. 相似文献
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采用原位聚合法,制备了聚氨酯(PU)/聚甲基丙烯酸甲酯(PMMA)/层状双金属氢氧化物(LDH)纳米复合体系(PU/PMMA/LDH).通过广角X射线衍射(WXRD)、透射电子显微镜(TEM)对其结构和形貌进行了表征,并通过热失重(TGA)、动态力学分析(DMA)和宽频介电谱(BDRS)研究了LDH含量(φ)对PU/PMMA体系热稳定性和弛豫行为的影响.结果表明,当φ<1 wt%时,LDH在聚合物基体中以剥离结构为主,PU/PMMA/LDH体系的玻璃化温度(Tg)降低,最大损耗因子(tanδmax)增大;而当φ>1 wt%时,LDH在聚合物基体中以插层结构为主,插层结构对聚合物分子链的限制使复合体系的Tg升高、tanδmax降低.LDH表面与PU硬段间的氢键作用,使复合体系的α介电弛豫转变随φ增加而向高温方向移动,弛豫过程激活参数增大. 相似文献
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自蒿属植物万年蒿(Artemisia sacrorrum ledeb.)地上部份首次分得三个贝壳杉烷型(Kaurane Type)二萜类化合物,经理化常数测定,元素分析,光谱分析(红外光谱、1~H核磁共振光谱、(13)~C核磁共振光谱),鉴定其结构分别为:3α,16α,17-三羟基贝壳杉烷 (3,16,17-trihydroxykaurane I),3α,16α-二羟基贝壳杉烷-17-O-β-D-葡萄糖甙(3,16,-dihydroxykaurane-17-O--d-glucoside 相似文献
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中国富硒食品的生产现状及趋势 总被引:2,自引:0,他引:2
对硒的生物学作用和目前已经开发的富硒食品(富硒西瓜、富硒灵芝、富硒茶叶、富硒牛奶、富硒猪肉和富硒鸡蛋等)进行了概述。当前富硒食品的技术含量大多偏低,技术水平有待提高;价廉物美的富硒食品受市场欢迎,科学论证富硒食品的转化机制是今后科研的一个方向。 相似文献
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为了探讨爆炸载荷下飞机典型加筋结构的响应规律,开展了爆炸实验,获得了飞机典型结构表面的反射超压历程,加筋结构的应变、位移等结构响应数据。并结合实验结果建立了高置信度的有限元模型,研究了所选结构的变形分布规律和塑性毁伤特性。结果表明,对于本文中选取的飞机加筋结构,塑性变形除了会开始于常见的加强筋中点外,还会开始于加强筋与加强筋联结处、加强筋与外框联结处。这主要是受加筋板的双向拉伸变形和应力集中的影响。进一步总结了随冲击波正压时间增长,能够引发加筋结构塑性变形的有效冲量和反射超压峰值阈值。研究结果对飞机气动外形、抗爆能力设计具有重要意义。 相似文献
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一个新倍半萜内酯的分离与结构研究 总被引:1,自引:0,他引:1
张德志 《广东微量元素科学》2006,13(5):59-63
自蒿属植物万年蒿(Artemisia sacrorumLedeb)地上部分分离得三个倍半萜内酯类化合物,经理化常数测定,化学相关及光谱(红外光谱1、H-核磁共振光谱1、3C-核磁共振光谱、质谱)分析,鉴定其结构分别为万年蒿氯内酯chlorosacroratin(Ⅰ),去乙酰氧母菊内酯deacetoxymatricarin(Ⅱ)和ridentin(Ⅲ)。其中,万年蒿氯内酯为一未见报道的新化合物。 相似文献
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Oscillatory integral such as ∫_(B~2) e~((itf)(x))g(x)dx is studied and asymptotic behavior of theoscillatory integral is obtained.The phase f(x)is analytic and has only isolated criticalpoint in B~2,while g(x)is smooth and compactly supported in B~2. 相似文献