V-BLAST-based demodulate-and-forward two-way relaying： protocol design and the detection

We propose a novel vertical Bell Laboratories layered space-time (V-BLAST) based two-way relaying protocol that comprises two user terminals and one multi-antenna demodulate-and-forward (DMF) relay station. We consider the situation when these two user terminals employ different modulation types and investigate its detection techniques. The key feature of the detection techniques is that we quantify decision reliability at the relay station by introducing a so-called normalized correlation coefficient (CORR), rather than having full confidence in demodulation at the relay station. With the assistance of the normalized correlation coefficient, we develop detection methods at both the relay station and user terminals. In particular, we propose a CORR-based ordering algorithm at the relay station which can be applied to detection for general V-BLAST architectures. Simulation results demonstrate the superiority of the CORR-based ordering algorithm over the conventional signal-to-noise based ordering algorithm. Finally, we demonstrate overall error-performance of the V-BLAST-based DMF two-way relaying protocol via simulations.     

Sleep behaviour: activity and sleep in dolphins

According to Lyamin and co-authors, neonate bottlenose dolphins (Tursiops truncatus) almost never sleep, unlike all other mammals that have been studied. Although we agree that young dolphins never stop and float at the surface, we find that they spend a considerable amount of time asleep while swimming. Our findings therefore call into question the conclusions of Lyamin et al..     

英语第三人称代词预指照应及其翻译模式

英语中第三人称代词的预指照应有着重要的语篇功能,正受到语言学界越来越多的关注。在理论层面就预指照应的理论定位及其在句子和语篇层面的功能进行探讨,有利于更通顺、精当地进行英汉翻译。     

英语第三人称代词预指照应及其翻译模式

英语中第三人称代词的预指照应有着重要的语篇功能,正受到语言学界越来越多的关注.在理论层面就预指照应的理论定位及其在句子和语篇层面的功能进行探讨,有利于更通顺、精当地进行英汉翻译.     

Microwave devices: carbon nanotubes as cold cathodes

To communicate, spacecraft and satellites rely on microwave devices, which at present are based on relatively inefficient thermionic electron sources that require heating and cannot be switched on instantaneously. Here we describe a microwave diode that uses a cold-cathode electron source consisting of carbon nanotubes and that operates at high frequency and at high current densities. Because it weighs little, responds instantaneously and has no need of heating, this miniaturized electron source should prove valuable for microwave devices used in telecommunications.     

Evolutionary biology: sex change and relative body size in animals

Organisms that change sex during their lifetime use a variety of strategies--they may be female first, male first or even repetitive sex changers. Natural selection should favour those individuals that change sex at a time when it increases their reproductive value. Allsop and West claim that the relative timing of sex change is invariant across all animals, with individuals changing sex at 72% of their maximum body size, and infer that natural selection for sex change must therefore be fundamentally similar across animals. Here we explain why we believe that Allsop and West's claims are not supported by their analysis or by their empirical data.     

债转股：运行风险及机制设计

债转股存在着国家、银行、资产管理公司以及企业的多方博弈，因而也就存在着多种运行风险，本从国家总体利益的角度出发，分析了各种运行风险存在的原因及表现，为了在最大程度上避免风险，进而对债转股的运行机制进行了设计。     

农民"养老"困境及对策浅析

农民“养老”已成为艰难的现实,农民要做到老有所养,需要认识农民养老困境,需要全社会与管理层的共识与救助。     

Seismology: dynamic triggering of earthquakes

After an earthquake, numerous smaller shocks are triggered over distances comparable to the dimensions of the mainshock fault rupture, although they are rare at larger distances. Here we analyse the scaling of dynamic deformations (the stresses and strains associated with seismic waves) with distance from, and magnitude of, their triggering earthquake, and show that they can cause further earthquakes at any distance if their amplitude exceeds several microstrain, regardless of their frequency content. These triggering requirements are remarkably similar to those measured in the laboratory for inducing dynamic elastic nonlinear behaviour, which suggests that the underlying physics is similar.     

永磁磁浮在心脏泵及其它应用中的稳定平衡

学术界一致公认无源磁浮是不稳定的，作者却找到两种实现稳定无源磁浮的方法，其一是引入非磁力，单独或者与永磁力一起，对浮体至少在一个自由度上产生作用；其二是利用浮体运动（旋转）的惯量，实现至少一个自由度上的稳定平衡，结合这两种方法，作者研制成两种不同设计的永磁磁浮心脏泵；并尝试将无源磁浮技术应用于高速列车和超静音螺旋桨。     

Second generation YBCO coated conductors： A review

The advance in first generation Bi-2223 HTS wire has enabled the demonstration of superconducting power cables, magnetic energy-storage devices, transformers,fault current limiters and motors. However, the low irreversibility field (H^*) prevents application of Bi-2223 at 77 Kin any significant field. Worldwide activities are therefore,focused on developing a second-generation HTS technology based on YBCO, for which H^* (77K)-7 T. In this paper, we discuss the status and commercial prospects of second generation HTS wire technologies. In addition, we review the recent results and discuss the prospects of future applications.     

Palaeoclimate: ocean tides and Heinrich events

Climate varied enormously over the most recent ice age--for example, large pulses of ice-rafted debris, originating mainly from the Labrador Sea, were deposited into the North Atlantic at roughly 7,000-year intervals, with global climatic implications. Here we show that ocean tides within the Labrador Sea were exceptionally large over the period spanning these huge, abrupt ice movements, which are known as Heinrich events. We propose that tides played a catalytic role in liberating iceberg armadas during that time.     

Laser technology: source of coherent kiloelectronvolt X-rays

Generating X-rays that have the properties of laser light has been a long-standing goal for experimental science. Here we describe the emission of highly collimated, spatially coherent X-rays, at a wavelength of about 1 nanometre and at photon energies extending to 1.3 kiloelectronvolts, from atoms that have been ionized by a 5-femtosecond laser pulse. This means that a laboratory source of laser-like, kiloelectronvolt X-rays, which will operate on timescales relevant to many chemical, biological and materials problems, is now within reach.     

语文教学,追求理想的教学生成

在新课程标准下,和谐统一的课堂教学预设与生成,正得以倡导,理想的教学生成,是语文课堂教学应有的追求,但伪生成也像泡沫一样浮泛:无预设、泛化课程资源、形式主义、脱离文本、鼓励误读。追求动态生成,应提供环境,留足空间掌握提问艺术。对语文教师的语文功底和德识才学水平提出了更高要求。     

Climate: large-scale warming is not urban

Controversy has persisted over the influence of urban warming on reported large-scale surface-air temperature trends. Urban heat islands occur mainly at night and are reduced in windy conditions. Here we show that, globally, temperatures over land have risen as much on windy nights as on calm nights, indicating that the observed overall warming is not a consequence of urban development.     

经济学视角下新闻保护调整模式析论

政府直接管制与基于市场的经济手段在新闻公共政策的调整领域都有其有利的地位,新闻政策的关键在于寻找市场调节与政府直接干预的均衡点,以达到新闻保护与经济发展协调的目的。从外部性、公共产品、信息不对称三个方面从"市场失灵"的角度分析新闻保护问题的法律调整模式,解决新闻领域的问题需要"看的见的手"和"看不见的手"兼而有之。     

Dynamical phenomena: walking and orbiting droplets

Small drops can bounce indefinitely on a bath of the same liquid if the container is oscillated vertically at a sufficiently high acceleration. Here we show that bouncing droplets can be made to 'walk' at constant horizontal velocity on the liquid surface by increasing this acceleration. This transition yields a new type of localized state with particle-wave duality: surface capillary waves emanate from a bouncing drop, which self-propels by interaction with its own wave and becomes a walker. When two walkers come close, they interact through their waves and this 'collision' may cause the two walkers to orbit around each other.     

基于深度学习的行为检测方法综述

行为检测在自动驾驶、视频监控等领域的广阔应用前景使其成为了视频分析的研究热点。近年来,基于深度学习的方法在行为检测领域取得了巨大的进展,引起了国内外研究者的关注,对这些方法进行了全面的梳理和总结,介绍了行为检测任务的详细定义和面临的主要挑战;从时序行为检测和时空行为检测2个方面对相关文献做了细致地分类,综合分析了每一类别中不同研究方法的思路和优缺点,并阐述了基于弱监督学习、图卷积神经网络、注意力机制等新兴研究话题的相关方法;介绍了行为检测领域常用的数据集以及性能评估指标,在这些数据集上比较了几种典型方法的性能;总结了当前行为检测方法需要解决的问题以及进一步发展的研究方向。     

Gene silencing: trans-histone regulatory pathway in chromatin

The fundamental unit of eukaryotic chromatin, the nucleosome, consists of genomic DNA wrapped around the conserved histone proteins H3, H2B, H2A and H4, all of which are variously modified at their amino- and carboxy-terminal tails to influence the dynamics of chromatin structure and function -- for example, conjugation of histone H2B with ubiquitin controls the outcome of methylation at a specific lysine residue (Lys 4) on histone H3, which regulates gene silencing in the yeast Saccharomyces cerevisiae. Here we show that ubiquitination of H2B is also necessary for the methylation of Lys 79 in H3, the only modification known to occur away from the histone tails, but that not all methylated lysines in H3 are regulated by this 'trans-histone' pathway because the methylation of Lys 36 in H3 is unaffected. Given that gene silencing is regulated by the methylation of Lys 4 and Lys 79 in histone H3, we suggest that H2B ubiquitination acts as a master switch that controls the site-selective histone methylation patterns responsible for this silencing.