Experimental and numerical analyses of the effect of fibre content on the close-in blast performance of a UHPFRC beam

Limited research has been conducted on the influences of fiber content on close-in blasting characteristics for ultrahigh-performance fiber-reinforced concrete(UHPFRC)beams.This paper aims to address this knowledge gap through experimental and mesoscale numerical methods.Experiments were conducted on ten UHPFRC beams built with varying steel fiber volumetric fractions subjected to close-in explosive conditions.Additionally,this study considered other parameters,such as the longitudinal reinforcement type and ratio.In the case of UHPFRC beams featuring normal-strength longitudinal reinforcement of diametersΦ12,Φ16,andΦ20,a reduction in maximum displacement by magnitudes of19.6%,19.5%,and 17.4%was observed,respectively,as the volumetric fractions of fiber increased from1.0%to 2.5%.In addition,increasing the longitudinal reinforcement ratio and using high-strength steel longitudinal reinforcement both significantly reduced the deformation characteristics and increase the blasting resistances of UHPFRC beams.However,the effects on the local crushing and spalling damage were not significant.A mesoscale finite element model,which considers the impacts of fiber parameters on UHPFRC beam behaviors,was also established and well correlated with the test findings.Nevertheless,parametric analyses were further conducted to examine the impacts of the steel fiber content and length and the hybrid effects of various types of microfibers and steel fibers on the blasting performance of UHPFRC beams.

Experimental investigation of p-section concrete beams under contact explosion and close-in explosion conditions

This paper presents the results of an experimental investigation on explosive breaching of p-section concrete beams. Twenty three p-section concrete beams with a 100 cm length were tested. TNT charges were placed at three positions: contact detonation in the center, contact detonation above the web and close-in detonation in the center. The external and internal breach parameters of the panels were evaluated by measuring the diameter of the ejection crater, spalling crater and breach hole created by the charge detonation. The experimental results were compared to predict values obtained by the analytical models proposed by McVay, Morishita and Remennikov. A modified breach with crater limit line and breach without crater limit line were put forward based on the experimental results. The maximum cross-sectional destruction area ratio(MCDAR) values were used to evaluate the damage degree. The maximum value of MCDAR reached 0.331 corresponding to the C5 experimental condition, of which explosion occurred above the web.

Dynamic responses of reinforced concrete beams under double-endinitiated close-in explosion

The reinforced concrete(RC) structural component might suffer a great damage under close-in explosion.Different from distant explosions, blast loads generated by the close-in explosion are non-uniformly distributed on the structural component and may cause both local and structural failure. In this study,an experimental study was conducted to investigate the dynamic responses of RC beams under doubleend-initiated close-in explosions. The experimental results show that the distribution of blast loads generated by the double-end-initiated explosion is much more non-uniform than those generated by single-point detonation, which is caused by the self-Mach-reflection effects. A 3 D finite element model was developed and validated in LS-DYNA by employing the modified K&C model. Intensive numerical calculations were conducted to study the influences of the initiation way, scaled distance and longitudinal reinforcement ratio on the dynamic responses and failure modes of RC beams. Numerical results show that the RC beam suffers greater damage as the cylindrical explosive is detonated at its double ends than the scenario in which the cylindrical explosive is detonated at its central point. RC beams mainly suffer flexural failure and flexure-shear failure under the double-end close-in explosion, and the failure modes of RC beams change from the flexural damage to flexure-shear damage as the scaled distance or the longitudinal reinforcement ratio decreases. The direct shear failure mode is not usually observed in the double-end-initiated explosion, since the intense blast loads is basically concentrated in the midspan of RC beam, which is due to self-Mach-reflection enhancement.

Close-in weapon system planning based on multi-living agent theory

The close-in weapon system(CIWS)is a combat system that faces a complex environment full of dynamic and unknown challenges,whose construction and planning require a systematic design method.Multiliving agent(MLA)theory is a methodology for the combat system design,which uses the livelihood degree to evaluate the multi-dimensional long-term operational effectiveness of the system;whereas,there is still no uniform quantization framework for the livelihood degree,and the adjustment methods of livelihood degree need to be further improved.In this paper,we propose the uniform quantization framework for the livelihood degree and detailed discuss the methods of livelihood adjustment.Based on the MLA theory,the multi-dimensional operational effectiveness of the missile-gun integrated weapon system(MGIWS)is analyzed,and the long-term combat effectiveness against the saturation attack is assessed.Furthermore,the planning problem of the equipment deployment and configuration is investigated.Two objectives,including the overall livelihood degree and cost-effectiveness(CE),are proposed,and the optimization method based on genetic algorithm(GA)is studied for the planning problem.

Modification of SDOF model for reinforced concrete beams under close-in explosion

In this paper,a modified single-degree-of-freedom(SDOF)model of reinforced concrete(RC)beams under close-in explosion is proposed by developing the specific impulse equivalent method and flexural resistance calculation method.The equivalent uniform specific impulse was obtained based on the local conservation of momentum and global conservation of kinetic energy.Additionally,the influence of load uniformity,boundary condition and complex material behaviors(e.g.strain rate effect,hardening/softening and hoop-confined effect)was considered in the resistance calculation process by establishing a novel relationship between external force,bending moment,curvature and deflection successively.The accuracy of the proposed model was verified by carrying out field explosion tests on four RC beams with the scaled distances of 0.5 m/kg~(1/3)and 0.75 m/kg~(1/3).The test data in other literatures were also used for validation.As a result,the equivalent load implies that the blast load near the mid-span of beams would contribute more to the maximum displacement,which was also observed in the tests.Moreover,both the resistance model and test results declare that when the blast load becomes more concentrated,the ultimate resistance would become lower,and the compressive concrete would be more prone to softening and crushing.Finally,based on the modified SDOF model,the calculated maximum displacements agreed well with the test data in this paper and other literatures.This work fully proves the rationality of the modified SDOF method,which will contribute to a more accurate damage assessment of RC structures under close-in explosion.

Leonardo da Vinci’s The Last Supper: Reconstruction of the Room Using Reverse Geometric Perspective Processes

This article presents a geometric exploration of the reconstruction of a model of the three-dimensional space that Leonardo da Vinci had before him or imagined when he created The Last Supper. The purpose is to reveal the geometrical principles inherent in this work of art, as well as to propose an invert geometrical method, from 2D to 3D space reconstruction.

Argon supper-cryosurgery for patients with middle and late stage liver cancer

OBJECTIVE: To assess the value of argon supper-cryosurgery for 42 patients with middle and late stage liver cancer. METHODS: Forty-two patients who had received argon supper-cryosurgery were analyzed retrospectively in terms of their clinical characteristics as well as the performance of argon supper-cryosurgery. RESULTS: All patients were ameliorated in symptoms shortly after the operation, including pain alleviation, psyche straightening up, alpha-fetoprotein descending or recovery. Jaundice occurred in 1 patient and intraabdominal hemorrhage in 2. The levels of aspartate transaminase and alanine transaminase in all patients were elevated 1 month after the operation, and normalized after protective therapy of the liver. No operative death was noted. CONCLUSIONS: Cold and heat reversed therapy of argon supper-cryosurgery can drastically destroy tumor tissue, especially the tumors which are too large to resect or close to the large vessels. It is applicable to increase the operative rate, decrease the operative death rate, and enlarge the therapeutic scope.

Giorgio Vasari＇s Last Supper： A Thanksgiving Celebration

Among the numerous themes on the suppers cited in the Bible, the Last Supper of Christ with His twelve apostles is the most poignant and rewarding for Christianity. Florentine Renaissance depictions of the theme are numerous and varied, traditionally represented as a predella （step） panel and as an altarpiece in dining halls or sacristies of churches and convents. Vasari＇s Last Supper for the Refectory ofLe Murate （The Walled） in Florence is an unusual depiction of Christ＇s thanksgiving. This imposing religious structure was painted for a poor Benedictine nunnery＇s cenacolo （refectory） in Florence. Vasari completed two drawings for the commission in 1546. The drawings and painting reveal how Vasari drew upon the work of his predecessors to create an innovative expression of thanksgiving, betrayal, and departure. This large masterpiece was severely damaged, almost irreparably, by several mishaps and floods in 1583 and 1718 and, more recently, by the major Florentine alluvione （flood） of 1966. In commemoration of the 50th year anniversary of this last catastrophic event, Vasari＇s Le Mutate Last Supper was carefully and magically restored by a group of masterful technicians, artists, and scientists. Their collaboration and support from the private sector demonstrate the successful bond among art, technology, science, and patronage.

Supper

Aunt Hattie, putting on herhat after a Sunday afternoon visitto one of her married nephews,said to eight-year-old Tony, "Boy,would you like to walk with me tothe bus stop?"

晚餐时光乐队Supper Moment 唱着梦想之歌

在今年美国音乐盛事格莱美颁奖典礼上,泰勒·斯威夫特(Taylor Swift)的一段致谢辞触动人心,大致意思是:"也许过程中有人会攻击你、嫉妒你的成功,但只要你专注于做好自己,有朝一日你会发现身边有一群人支持你,这种感觉是最美好的。"成立10年的晚餐时光乐队(Supper Moment),他们从不是娱乐版的宠儿,没有绯闻等炒作,但近年却在多个颁奖台上获得肯定。人生有多少个10年?抓紧自己的梦想,人生梦一场革命至苍老。

17m超高坐地式玻璃肋幕墙系统结构性能和试验研究

文章以泰康大厦工程为背景,针对超高坐地式玻璃肋幕墙系统进行了大风压作用下的结构性能和位移能力试验研究,通过有限元、试验、理论三者进行对比分析。研究表明,该幕墙系统不仅满足1.75kPa风压作用下的结构性能要求和2.63kPa大风压下结构的安全性能要求,而且满足三个方向位移能力的要求。充分说明17m超高坐地式玻璃肋幕墙系统的设计方案安全可行,设计方案和试验结果可为今后超高坐地式玻璃肋幕墙系统的设计提供支持。

中国物流业全要素碳排放效率测算及影响因素研究

“双碳”目标下,国家高度重视物流业的节能降碳.基于2007—2021年中国30个省份物流业的样本数据,采用超效率SBM模型测算全要素碳排放效率,进一步构建空间杜宾模型分析其影响因素.研究发现:①中国物流业全要素碳排放效率整体水平不高,省份、区域间差距较大,相邻省份空间正相关性显著;②选取经济发展水平、节能技术水平、产业结构、要素禀赋和城镇化水平为碳排放效率的主要影响因素,采用双固定空间杜宾模型分析其影响程度;③效应结果显示,经济发展水平、节能技术水平和要素禀赋对邻近地区的碳排放效率具有负向溢出效应,其他因素的影响具有正向溢出效应.最后,提出了提高我国物流业碳排放效率的对策建议.

中非新元古代造山带钴超常富集研究进展与展望

钴被誉为“低碳能源金属”,是我国乃至全球急缺的关键金属矿产。中非新元古代铜钴矿带内的沉积岩容矿型铜钴矿床每年为全球提供了60%以上的钴金属产量,是研究钴超常富集的最佳区域。前人对该矿带的研究主要聚焦于铜的成矿作用,然而该矿带内的铜矿床并非都伴生钴,目前对伴生钴的来源-富集过程及其与沉积、成岩、造山作用的成因联系仍缺乏系统研究。本文综述了中非铜钴矿带内沉积岩容矿型铜钴矿床主要研究进展及存在问题,认为超大陆裂解过程改变了中非铜钴矿带的沉积盆地环境,使得钴在沉积地层中发生初始预富集,此外古气候条件,包括增氧事件和冰川事件,也可能对该矿带内的大规模钴的聚集产生了积极作用。新元古代造山作用重新活化沉积地层呈分散分布的钴元素,导致钴的进一步富集。因此,中非铜钴矿带中的钴超常富集是大气-地球-水圈-生物圈之间长期相互作用而形成的成矿效应。在矿床尺度,深入理解沉积岩容矿型铜钴矿床的形成过程,有助于在中非铜钴矿带,甚至在全球其他有利沉积盆地内,勘探更多的钴资源。

超高层总部办公建筑外围护系统创新设计

城市化进程的快速推进带动了超高层办公建筑的发展。以中国中化大厦为例,从外围护系统的优化设计、光伏玻璃的应用、低碳技术的整合及绿色建筑标准的融入等方面,探讨超高层建筑在满足安全性、舒适性和经济性的基础上,通过综合应用创新材料、智能化技术和绿色建筑标准,完成建筑外围护系统创新设计,践行绿色可持续的发展理念。

大型加工中心超长床身灰铁件的铸造工艺设计

介绍了大型超长床身铸件的结构及技术要求,从模具材料选取、分型面选择、浇注系统设计及造型工艺等方面阐述了该铸件的生产工艺,经实际生产验证,铸件未发现错箱现象,床身变形量控制到5 mm以内,铸件也没有出现裂纹、气孔及夹砂等问题,铸件硬度符合技术要求。最后指出:对于大型超长床身铸件,选择先封闭后开放式浇注系统,在不用过滤网的情况下,也能达到浇注系统挡渣和减小内浇道流速的作用;模型分两段制作有利于大型超长床身挠度的控制。

水稻超高产栽培模式及系统理论的研究进展

围绕着超高产,回顾了水稻超高产栽培模式的发展,并重点介绍了其中几种水稻超高产栽培模式,进而分析了水稻超高产形成的系统理论和途径,探讨了水稻超高产栽培在大面积推广和生产中存在的问题并提出了解决途径,最后展望了水稻超高产栽培模式的未来发展。

超高产冬小麦对氮素的吸收、积累和分配

为明确超高产（9000 kg/hm2左右）栽培条件下冬小麦的氮素营养特点，于2004~2005年、2005~2006年2个小麦生长季主要生育时期，取样分析小麦各器官氮的含量，总结出超高产冬小麦氮素的吸收、积累和分配特点。结果表明， 小麦全生育期各器官的氮含量为0.22%~3.55%（干重）。生育前期叶片中氮的含量和积累量最高，生育后期籽粒中氮的含量和积累量最高。小麦生育期间氮的总积累量为232.48~285.18 kg/hm2，每生产100 kg籽粒吸收氮2.63~3.13 kg。小麦吸收的氮孕穗期前主要分配在叶片中，一般都在50%以上， 成熟期氮在籽粒中的分配率最高，各品种均在80%以上。成熟期籽粒中积累的氮68.02%~73.31% 来自营养器官中氮的再分配。出苗到起身期、拔节到孕穗期、开花到成熟期都是小麦氮素吸收的重要阶段。根据小麦的氮素吸收积累特点，河北平原冬小麦实现9000 kg/hm2的超高产，需要土壤全氮不低于0.75 g/kg，秸秆全量还田后施N 260 kg/hm2左右。

金属材料激光快速成形的研究进展

激光快速成形技术以其特有的技术优势,已经成为金属材料快速成形的研究热点。叙述了金属材料激光快速成形在国内外的发展概况,表明在国外激光快速成形金属材料在理论、工艺及制造方面已经取得了非常显著的成果,其制造的结构件已经在航空航天领域取得了重要应用,而该技术在国内仍处于理论研究和试制阶段;介绍了激光快速成形钛合金和高温合金的研究现状,表明国内对钛合金的激光快速成形已进行了较为系统的研究,取得了一些重要成果,制作了典型结构件,对高温合金,裂纹是其激光成形技术的关键问题;对激光快速成形的发展进行了展望。

地力与施氮量对超级稻产量、品质及氮素利用率的影响

以中熟中粳超级稻徐稻3号为供试材料,研究麦茬田高、中、低3种地力水平下施氮肥（0、148.5、223.5、297.0、372.0、445.5kghm-2）对超级稻产量及其构成因素、氮素利用率、稻米品质的影响。结果表明：（1）徐稻3号的产量在不同施氮水平下均表现高地力〉中地力〉低地力的趋势;高、中、低地力上出现的最高产量对应的最适施氮量分别为260.8、290.5和345.5kghm-2。（2）氮肥表观利用率与施氮量之间存在显著或极显著的二次相关关系,高、中、低3种地力土壤条件下氮肥最高利用率对应的施氮量分别为268.6、293.4和335.2kghm-2。（3）培肥地力有利于稻米营养品质、加工品质、蒸煮食味品质的提高,不同地力土壤要施适量氮肥才可以改善稻米的外观品质,优化稻米的营养品质。综合高产、优质、高效目标,建议该区超级稻施氮范围为高地力田240.0~270.0kghm-2,中地力田285.0~315.0kghm-2,低地力田330.0~360.0kghm-2。

双季稻超高产栽培条件下根系特性的研究

试验在大田条件下进行，以国家水稻工程醴陵基地应用的旺壮重栽培法作超高产栽培途径，与当地习惯栽培法比较研究了超高产双季稻根系生长及生理特性，结果表明：根系生长量以生长中期最大，其次为前期，生长后期新根发生和老根衰亡同时进行，因此根量增加很少甚至呈负增长。超高产栽培条件下早稻 Ｖ４０２ 和晚稻 Ｖ１９８ 全生育根系生长总量为 １８４４３ 和１７１０４ｋｇ·ｈｍ － ２，比对照分别提高 ２０６４％ 和 ２５０５％ ，并且这种根量优势主要在水稻生长的前、中期形成；根系总吸收表面积和活跃表面积也表现出相同的趋势，同时，早稻中期、晚稻中后期根系 α－ 萘胺氧化力比对照增加；根系对３２ Ｐ吸收活力以前期和中期较高，抽穗后明显降低；超高产水稻各生育期单蔸根系吸收的３２ Ｐ 总量明显高于对照，其增加的幅度为 ３８６％ ～３７７７％ ，并且前、中期提高的幅度大于后期，超高产栽培条件下这种根系生长和根系活力的优势最终转化为产量优势，１９９７ 和 １９９８ 年实际产量分别为 １７６５２ 和 １７７７２ｋｇ·ｈｍ － ２，比习惯栽培法提高 ２１２８％ 和 １５５７％ 。