Effect of interactions of two holes on tensile behavior of patch repaired carbon/epoxy woven laminates

The conventional case of patch repair involves bonding a patch over single damage/hole in the laminate.This work investigates the effect of interaction of two holes on the tensile behavior patch repaired carbon epoxy woven laminates. The specimens of [0°/45°/45°/0°] laminates were repaired with adhesively bonded two-ply [45°]2external patches. Three different cases of drilled specimens were produced with different hole arrangements viz. specimens with single central hole(SH), with two holes alig...     

含能共晶的分子间作用力、性质规律及设计方法

为了给含能共晶的设计和制备提供参考,按照共晶前驱体的类别,分别综述了形成含能共晶的分子间作用力,感度和爆轰性能等性质.总结了含能共晶前驱体的结构特点、性质规律以及指导含能共晶设计的理论方法.得出结论:氢键是含能共晶形成的主要驱动力,共晶前驱体分子中应当同时具有作为氢键的给体和受体官能团.π-π作用以及极性-π作用也是非...     

小时候父亲这样教我

当我还坐在婴儿椅上的时候,父亲有一天带回家一堆小瓷片,就是那种装修浴室用的各种颜色的玩艺儿。我父亲把它叠垒起来,弄成像多米诺骨牌似的,然后我推动一边,它们就全倒了。过一会儿,我又帮着把小瓷片重新堆起来。 这次父亲让我变出些复杂点儿的花样：两白一蓝,两白一蓝 ......我母亲忍不住说：“唉,你让小家伙随便玩不就是了？他爱在哪儿加个蓝,就让他加好了。” 可我父亲回答道,“这不行,我正教他什么是序列,并告诉他这是多么有趣呢！这是数学的第一步。”我家有一套《大英百科全书》,父亲常让我坐在他的膝上,给我读里边的…     

寻求新生的墨西哥海军

墨西哥位于北美洲南部,濒临太平洋和墨西哥湾,领土面积约190万平方公里,海岸线长达9300公里。墨西哥本应成为该地区重要的军事强国,但是它依赖美国抵御外来侵略,自己的武装部队仅充当维护内部安全的角色。无论从人员上还是从可用舰船数量上来讲,墨西哥海军一直与此不相称。墨西哥海军实质上只是一支海岸警备队,军事潜力非常有限。舰队虽然也拥有少数新式舰艇,但多数舰艇均是在20世纪40年代末期甚至更早服役的。整个舰队就像是20世纪海军技术博物馆。     

High-Velocity Projectile Impact Behaviour of Friction Stir Welded AA7075 Thick Plates

In this study, high velocity impact behaviour of friction stir welded AA7075-T651 25 mm thick plates were investigated using a 7.62 mm × 51 mm lead core and 7.62 mm × 39 mm steel core projectiles. Prior to ballistic trails, mechanical and metallurgical properties of friction stir welded AA 7075-T651 25 mm thick plates were studied. Microstructural and hardness studies revealed that friction stir welds constituted three distinct regions namely Weld Nugget(WN), Thermo-Mechanically Affected Zone(TM...     

Aerial multi-spectral AI-based detection system for unexploded ordnance

Unexploded ordnance(UXO) poses a threat to soldiers operating in mission areas, but current UXO detection systems do not necessarily provide the required safety and efficiency to protect soldiers from this hazard. Recent technological advancements in artificial intelligence(AI) and small unmanned aerial systems(sUAS) present an opportunity to explore a novel concept for UXO detection. The new UXO detection system proposed in this study takes advantage of employing an AI-trained multi-spectral(MS...     

Burning rate analysis of laser controlled 5-aminotetrazole propellant

As an innovative propulsion technique, laser augmented chemical propulsion(LACP) seems superior to the traditional ones. However, the corresponding combustion theories have still to be ascertained for LACP. Burning rate of 5-aminotetrazole(5-ATZ) propellant has been studied by testing pressed samples under different combustor pressures and laser powers. Based on micro computed tomography(Micro CT),an advanced thickness-over-time(TOT) method to characterize the regression of the produced nonplana...     

Microwave absorption properties of carbonyl iron-based paint coatings for military applications

The paper explores the possibilities of using carbonyl iron in the form of a powder for the manufacture of radar-absorbing paints-reducing the radar signature of the objects that they cover. The attenuation values in the range of 4-18 GHz for various coating thicknesses, ranging from 0.5 to 2.00 mm with 0.5 mm increment, and for different absorber content-75% and 80%, as well as the use of two different binders in the form of epoxy resins with hardeners, were investigated. For the frequency of 1...     

追猎“佩刀”

关于朝鲜战争空战一直是个颇有争议的话题。根据美方材料,美军飞行员取得了“1:10”的惊人战绩。美军认为这是因为西方飞行员的技战术普遍过人一筹。近年来,随着众多历史文件的解密,苏联空军参加朝鲜战争这个史实已不再是秘密。颇为有趣的是,苏联空军对朝鲜战争有着截然不同的看法。苏方统计共击落美制战机1106架。其中F-86“佩刀”式650架,战损比为1:3.31。换言之,美军要想击落一架米格机至少损失两架“佩刀”。对于所谓美国飞行员素质高超的说法,苏联更是不屑一顾。美军击落5架以上敌机的“王牌”飞行员有40人,而苏联空军有此战绩者为51人。更说明问题的是,美方承认非战斗损失战机945架,而苏军仅10架。