摘要：As one of the key characteristics in cognitive wireless networks(CWNs),network environment awareness techniques have received much attention *** of traditional spectrum sensing technology that suffers from problems of miss detection,false alarm,hidden node,and inefficiency,cognitive pilot channel(CPC) technology has been proposed as one of the candidate solutions for an efficient and accurate network information delivery scheme to user equipment(UE).The aim of the CPC technology is to provide the necessary information for the reconfiguration of the UE using the public signaling *** ensure the efficient information delivery,the whole geographical area covered by the CPC is divided into square meshes of the same ***,two typical network information transmission modes for CPC deployment are also proposed:broadcast CPC mode and on-demand CPC *** further improve the efficiency of network information delivery,an efficient dynamic mesh grouping scheme has been designed which is based on the fractal theory for the broadcast CPC mode,where adaptive rectangular sized meshes are used to approximately cover the whole *** to the traditional fixed size mesh division strategy,results show that the proposed dynamic mesh grouping scheme significantly reduces the number of meshes by grouping similar meshes together,and the average delay of receiving CPC information on the UE side is therefore reduced.

摘要：论文在房地产税纳税意愿理论模型的基础上,建构纳税意愿的测量指标,再使用《中国家庭追踪调查》的数据,根据区域、住房类型、拥有套数、购房贷款和社会经济地位等因素,对不同地区和收入的居民的房地产税纳税意愿进行多维度比较,发现:一、不同地区和收入的家庭的房地产税纳税意愿存在较大差异,说明房地产税的地方税特征和差异化设计的必要性。二、在不同减免方案下,房地产税的财政效应明显不同。三、没有证据表明减免额度越大纳税意愿越高。研究结果表明,简单地提高减免额未必能减少开征房地产税的阻力。论文认为:以人均价值减免为基础,综合考量房地产税的税收潜能和居民纳税意愿,理论上的最优减免额度不宜超过当地人均三分之一建筑面积的当年市场价值。

摘要：2018年1月21日,中国城市科学研究会景观学与美丽中国建设专业委员会座谈会于北京大学建筑与景观设计学院举办。来自景观、生态、水利、规划等领域的30余位学者、设计师、教育者及其他从业人士参加了会议,并围绕美丽中国建设、生态文明建设、景观设计学科建设、行业融合等议题展开讨论。座谈会最终达成共识,提出了跨界生态实践的迫切性和必要性,同时探讨了在教育和实践层面跨界的难点与问题——不同行业的优势、职责以及在"跨界"中的作用尚不明确,学科教育也未能很好地构建并明晰自身的核心竞争力——呼吁应积极促进学科与行业融合,使其适应当代需求。

摘要：The aim of ＂green chemistry＂ and ＂atom economy＂ is to utilize carbon dioxide and replace harmful reactants such as CO and phosgene for the production of cyclic carbonates. In this paper, metal-free catalysts including organic bases, ionic liquids, supported catalysts, organic copolymers and carbon materials for the synthesis of cyclic carbonates by the cycloaddition of carbon dioxide to epoxides are reviewed. Recent advances in the design of the catalysts and the understanding of the reaction mechanism are summarized and discussed. The synergistic effects of organic bases and hydrogen bond donors, organic bases and nucleophilic anions, hydrogen bond donors and nucleophilic anions and active components and supports are highlighted. The challenge is to develop metal-free catalysts suitable for carbon dioxide capture and fixation. The ultimate goal is to synthesize cyclic carbonates in a flow reactor directly using carbon dioxide from industrial flue gas at ambient temperature and atmospheric pressure. By using synergetic effects, a multi-functional approach can meet the design strategy of metal-free catalysts for carbon dioxide adsorption and activation as well as epoxide ring opening.

摘要：为了探究具有不同认知卷入程度的分心活动对儿童延迟等待时间的影响,本研究使用自我延迟满足范式,选取一所普通幼儿园120名3~4岁幼儿作为被试,随机分配到认知卷入度逐步提高的静等组、想象组和绘画组,结果表明静等组幼儿平均等待时间最短,只有1.26分钟;想象组幼儿等待时间有所延长,平均6.09分钟;绘画组幼儿等待时间最长,平均11.83分钟。另外,随着年龄的增长,无论是静等组、想象组还是绘画组,4岁儿童的延迟等待时间均显著长于3岁儿童。这证明增加认知卷入度的分心活动(如想象与绘画)可以帮助儿童更好地把奖励物的热表征转换为冷表征,从而促进延迟等待时间的增加。当儿童面对诱惑物时,成人可以让其进行想象等认知转化或艺术创作活动,能够有效地减弱儿童的冲动,提高其自我延迟满足的能力。

摘要：The anchoring property of the substrate surface of liquid crystal cells plays an important role in display and nondisplay fields. This property directly affects the deformation of liquid crystal molecules to change the phase difference through liquid crystal cells. In this paper, a test method based on the alternating-current bridge is proposed to determine the capacitance of liquid crystal cells and thus measure the anchoring energy of the substrate surface. The anchoring energy can be obtained by comparing the capacitance-voltage curves of twisted nematic liquid crystal cells with different anchoring properties in experimental and theoretical results simulated on the basis of Frank elastic theory. Compared with the other methods to determine the anchoring energy, our proposed method requires a simple treatment of liquid crystal cells and allows easy and high-accuracy measurements, thereby expanding the test ideas on the performance parameters of liquid crystal devices.

摘要：This article investigates transmitter design in Rayleigh fading multiple input multiple output （MIMO） channels with spatial correlation when there are channel uncertainties caused by a combined effect of channel estimation error and limited feedback. To overcome the high computational complexity of the optimal transmit power allocation, a simple and suboptimal allocation is proposed by exploiting the transmission constraint and differentiating a bound based on Jensen inequality on the channel capacity. The simulation results show that the mutual information corresponding to the proposed power allocation closely approaches the channel capacity corresponding to the optimal one and meanwhile the computational complexity is greatly reduced.

摘要：档案文化创造性转化和创新性发展对满足人民精神文化需求、繁荣发展文化事业和文化产业、增进全社会文化认同意义重大。档案领域应把握历史思维、坚持全局观念、回应时代呼声、正视社会需要,通过坚持党的领导、担当时代使命,加强顶层设计、激活战略自觉,强化数智赋能、襄助质效提升,深化服务利用、激发深层潜能,聚力才智培育、筑牢智力根基,探索档案文化“双创”的实践进路,为中国式现代化贡献档案文化力量。

摘要：本文从移动通信演进规律和泛在性出发,研究第六代移动通信系统(sixth generation, 6G).在前期引入代表智慧或意识的"灵"的基础上,提出6G信息交换中枢Ubiquitous-X网络,使人–机–物–灵的新通信对象全面协作和融合于现有网络,以构建未来的6G网络.针对Ubiquitous-X网络构架面临的信息密度非均匀增长导致的传播非线性、信息维度增加导致的信息空间高维性、承载服务差异化导致的信息处理复杂性3大挑战,借鉴复杂系统耗散理论和信息负熵促进有序的思想,给出设计与优化Ubiquitous-X网络的演进范式和核心技术,为6G研究提供参考.

摘要：随着地下矿山开采向深部逐渐延伸,断层滑移引起的岩爆事件日益增多且破坏性极大,已经成为威胁矿山安全的重要因素。通过建立三维离散元模型,基于平面应变问题,开展了三维模型平面应变等效计算与二维离散元模型对比分析,结果表明该研究模型在三维空间模拟地震波的传播是可行的。通过研究辐射特征对应力波传播的影响,揭示了P/S波传播过程的方向性并进行了验证,计算结果符合断层滑移的双力偶模型。在此基础上,通过与Kaiser等提出的设计尺度率公式进行对比,发现已有的设计尺度率公式并不能完全满足工程实际要求,利用三维离散元程序开展数值计算分析能够进一步优化支护参数,以此更好地服务矿山支护系统设计,确保地下矿山安全高效开采。