Profiling users by online shopping behaviors

Online shopping has been prevalent in our daily life. Profiling users and understanding their browsing behaviors are critical for enhancing shopping experience and maximizing sales revenue. In this paper, based on a one-month dataset recording 2 million users’ 67 million online shopping and browsing logs, we seek to understand how users browse and shop products, and how distinct these behaviors are. We find that there exist dedicate groups of users that prefer certain product categories corresponding to similar demands. Moreover, distinct differences of behaviors exist in categories, where repetitive and targeted browsing are two major prevalent patterns.     

生物打印技术在组织与器官修复中的应用进展

三维打印是一门快速发展的增材制造技术,能精确控制三维支架的外形及内部微结构,从而实 现个性化医疗,在组织修复或再生领域拥有巨大的应用潜力。近年来,基于三维打印技术发展而成的三维生物打印(Three-Dimensional Bioprinting,Bio-3DP)受到越来越多研究者的关注,该技术突破了传统组织工程技术生物功能设计的局限性,可精确控制细胞在支架材料中的定点分布,微观上构建具有适合细胞生存的微环境,为细胞提供了真正的三维均衡生长环境,使得复杂器官具有匹配构建和个性化再生的可能。该文主要综述 Bio-3DP 技术和用于 Bio-3DP 的生物墨水的最新研究进展,由此展望 Bio-3DP 在组织与器官修复中的应用潜力。     

直接甲醇燃料电池技术及应用

本文回顾了直接甲醇燃料电池（ＤＭＦＣ）的研究开发历史,系统阐述了ＤＭＦＣ系统中电催化剂选择与设计基本原则、电解质膜材料与甲醇渗透的关系。分析了电池工作温度、工作压力和甲醇进料方式对ＤＭＦＣ电化学性能的影响。     

微波共沉淀法制备锂离子电池正极材料LiNi0.8Co0.2O2

采用微波共沉淀法合成了制备LiNi0.8Co0.2O2的前驱体球形α-Ni0.8Co0.2(OH)2,将其与LiOH·H2O混合,在氧气氛围下,用不同的烧结温度分别烧结10小时获得LiNi0.8Co0.2O2正极材料。用XRD、SEM对所制备的正极材料进行结构和形貌分析,用恒流充放电测试材料的电化学性能。结果表明,烧结温度对材料结构和电化学性能影响较大,所合成材料均具有α-NaFeO2的层状结构,烧结温度越高材料结晶越完善。900℃烧结的LiNi0.8Co0.2O2材料初级颗粒结晶最完善而且其二次团聚粒子的平均粒径最小,其表现出的电化学性能也最好,首次放电容量为189.1mA·h·g-1,首次循环放电效率达到92.5%。30循环后放电容量保持在148 mA·h·g-1,显示出较好的循环稳定性。     

可变负载防坠安全器试验台的研制

齿轮齿条型施工升降机防坠安全器试验台,利用安全器制停高速惯性飞轮来模拟实际吊笼制停过程,同时检测制动过程中制动力矩和制停距离来判定安全器的制动能力是否合格。推导了安全器试验台惯性飞轮负载计算方法,结合实际坠落试验统计数据,计算了各种规格的安全器在确定减速比的试验台上对应飞轮所需惯量值,并根据计算结果研制了一台可变负载的防坠安全器试验台。     

Analysis on collapse strength of casing wear

Carrying capacity of the casing will reduce after the casing is worn, which seriously affects the subsequent well drilling, well completion, oil extraction and well repair. A lot of researches on calculation of casing wear collapse strength have been done, but few of them focus on collapsing failure mechanism, and influencing factors and law of collapse strength. So, significant difference between estimated value and actual value of collapse strength comes into being. By theoretical analysis, numerical simulation and actual test, the collapsing failure mechanism of casing wear as well as the influencing factors and laws of collapse strength are investigated, and the investigation results show that collapse of crescent casing wear belongs to "three hinged" instability. The severely-worn position on the casing is yielded into the plastic zone first then deformed greatly, which causes the plastic instability of the whole structure. The casing wear collapse strength presents changes of exponent, power function and linear trend with the residual casing wall thickness, wear radius and axial load, respectively. When the flexibility is less than 10°/30 m, the borehole bending has less impact on casing collapse strength. Thus, the computation model for the casing wear collapsing strength is established by introducing wear radius coefficient and casing equivalent yield strength, at the same time, the model is tested. The test results show that the relative error for the computation model is less than 5%. The research results provide a basis for design of the casing string strength and evaluation of down-hole safety.     

矿体二次圈定在国外大型露天矿山的实践应用

刚果(金)SICOMINES铜钴矿是一个铜金属量达千万吨的特大型铜钴矿床,如何保证矿产资源的充分利用是影响矿山经济效益和可持续发展的重要课题。文章阐述了矿体二次圈定在该矿山生产中的应用情况,并结合矿体产状较平缓、上下层矿体厚度变化不均匀的特点,采用了分段取样方法,对矿体二次圈定进行优化,有效提高了矿体圈定的精度,降低了矿石损失贫化率,也取得了显著经济效益。     

Design and performance study of a gas-Cherenkov detector with an off-axis parabolic reflector for inertial confinement fusion experiments

In this work, the gas-Cherenkov detector with an off-axis parabolic reflector(Opr GCD) is designed using the Geant4 Monte Carlo simulation toolkit, which is helpful to improve the collection efficiency of Cherenkov photons. The method to study the performance of Opr GCD based on femtosecond laser-wakefield-accelerated electron beams is presented. Cherenkov signals with high signal-to-noise ratio were obtained, and the measured Cherenkov signals changing with the CO2 pressure were consistent well with the simulation results. The design and study of this Opr GCD system lay the foundation for the application of fusion gamma diagnostics system in large laser facilities of China.     

Study of General Incomplete Star Interconnection Networks

IIntroduct1OllThe star graph【1]proposed as a particular case ofC叫ley graphs[ZJ Is vertex－and edge－symmetric．strongly hlerarchlcal,maximally tault－tolerant,strongly resilient and has diameter and node degreethat are superior to those of a slmll。－slied hypercube(which Is also a Cnyley graph)IOr parallelcomputers[3]．MNor references can be found In studying the star graph regarding its propertiesllJ,e毗edding cwabllity[4],communication c叩劝ility[5－71,andfanfaut－toierm尬 cap劝ility…