Siren(旋笛式)激励系统设计及输出特性研究

设计了用于研究燃烧不稳定性、测量火焰传递函数(FTF)的Siren(旋笛式)激励实验系统。采用实验和数值的方法,研究了测量段进出口压差、脉动气路流量、脉动频率对系统输出特性的影响,并分析了系统的共振模态。结果表明,系统输出平均速度由测量段进出口压差决定,脉动速度u′主要受脉动气路流量m′的影响,且流量越大,脉动速度/平均速度百分比(u′/uˉ)也越大,实验中u′/uˉ最大超过了4%。脉动频率则通过影响旋笛出口压力脉动的分布进而影响速度脉动,而系统共振会导致输出u′/uˉ明显增大,系统共振频率在270Hz附近,此时旋笛出口压力脉动达到最大。

基于Siren函数改进的循环神经网络机器阅读理解

由于现有的循环神经网络存在着梯度消失与梯度爆炸的问题,会影响模型精度。为提升机器阅读理解模型的效率,采用了一种新型正弦激活函数Siren函数,结合注意力机制对循环神经网络进行改进。使用循环神经网络对文本数据进行特征提取,同时引入注意力机制,可以进一步抓住文本中的重点信息。经由Siren激活函数层对神经网络的输出进行处理后,传递至Softmax层与全连接层返回问题所需答案。采用该网络所实现的机器阅读理解模型,相较于原有的模型在精准度上有大幅度提升。实验数据采用SQuAD英文问答数据集,在对比实验中,相较于仅使用注意力机制的RNN版DrQA模型,EM指数提升了6.1,F1指数提升了5.9,同时Siren函数也在与其他激活函数的对比实验中均取得了较好的效果。

SIRENE——欧洲铁路通讯上层服务系统

欧洲的铁路运输业拥有悠久的光荣传统,它以多年一贯的准时安全的服务为欧洲近百年来的繁荣作出了很大的贡献。但是近三十年来它的陆上运输霸主的地位受到了来自航空业及公路运输业的挑战。为保住霸主地位,适应新的形势发展及变化。

Synergy between CSST galaxy survey and gravitational-wave observation: Inferring the Hubble constant from dark standard sirens

Gravitational waves(GWs) from compact binary coalescences encode the absolute luminosity distances of GW sources. Once the redshifts of GW sources are known, one can use the distance-redshift relation to constrain cosmological parameters. One way to obtain the redshifts is to localize GW sources by GW observations and then use galaxy catalogs to determine redshifts from a statistical analysis of redshift information of the potential host galaxies, commonly referred to as the dark siren method. The third-generation(3G) GW detectors are planned to work in the 2030s and will observe numerous compact binary coalescences.Using these GW events as dark sirens requires high-quality galaxy catalogs from future sky survey projects. The China Space Station Telescope(CSST) will be launched in 2024 and will observe billions of galaxies within a 17500 deg^(2) survey area with redshift up to z ~ 4, providing photometric and spectroscopic galaxy catalogs. In this work, we simulate the CSST galaxy catalogs and the 5-year GW data from the 3G GW detectors and combine them to infer the Hubble constant(H_(0)). Our results show that the measurement precision of H0could reach the sub-percent level, meeting the standard of precision cosmology. We conclude that the synergy between CSST and the 3G GW detectors is of great significance in measuring the Hubble constant.

Taiji-TianQin-LISA network:Precisely measuring the Hubble constant using both bright and dark sirens

In the coming decades,the space-based gravitational-wave(GW)detectors such as Taiji,TianQin,and LISA are expected to form a network capable of detecting millihertz GWs emitted by the mergers of massive black hole binaries(MBHBs).In this work,we investigate the potential of GW standard sirens from the Taiji-TianQin-LISA network in constraining cosmological parameters.For the optimistic scenario in which electromagnetic(EM)counterparts can be detected,we predict the number of detectable bright sirens based on three different MBHB population models,i.e.,popⅢ,Q3d,and Q3nod.Our results show that the TaijiTianQin-LISA network alone could achieve a constraint precision of 0.9%for the Hubble constant,meeting the standard of precision cosmology.Moreover,the Taiji-TianQin-LISA network could effectively break the cosmological parameter degeneracies generated by the CMB data,particularly in the dynamical dark energy models.When combined with the CMB data,the joint CMB+Taiji-TianQin-LISA data offerσ(w)=0.036 in the wCDM model,which is close to the latest constraint result obtained from the CMB+SN data.We also consider a conservative scenario in which EM counterparts are not available.Due to the precise sky localizations of MBHBs by the Taiji-TianQin-LISA network,the constraint precision of the Hubble constant is expected to reach 1.2%.In conclusion,the GW standard sirens from the Taiji-TianQin-LISA network will play a critical role in helping solve the Hubble tension and shedding light on the nature of dark energy.

Joint constraints on cosmological parameters using future multi-band gravitational wave standard siren observations

Gravitational waves(GWs)from compact binary coalescences can be used as standard sirens to explore the cosmic expansion history.In the next decades,it is anticipated that we could obtain the multi-band GW standard siren data(from nanohertz to a few hundred hertz),which are expected to play an important role in cosmological parameter estimation.In this work,we provide,for the first time to the best of our knowledge,joint constraints on cosmological parameters using the future multi-band GW standard siren observations.We simulate the multi-band GW standard sirens based on the SKA-era pulsar timing array(PTA),Taiji observatory,and Cosmic Explorer(CE)to perform cosmological analysis.In theΛCDM model,we find that the joint PTA+Taiji+CE data could provide a tight constraint on the Hubble constant with a 0.5%precision.Moreover,PTA+Taiji+CE could break the cosmological parameter degeneracies generated by CMB,especially in the dynamical dark energy models.When combining the PTA+Taiji+CE data with the CMB data,the constraint precisions of?_(m)and H_(0)are 1.0%and 0.3%,respectively,meeting the standard of precision cosmology.The joint CMB+PTA+Taiji+CE data giveσ(_(w))=0.028 in the wCDM model andσ(w_(0))=0.11 andσ(w_(a))=0.32 in the w_(0)w_(a)CDM model,which are comparable with or close to the latest constraint results by CMB+BAO+SN.In conclusion,the future multi-band GW observations are expected to be used for exploring the nature of dark energy and measuring the Hubble constant.

Siren(旋笛式)激励系统的气动声学特性

基于siren(旋笛式)激励系统,理论推导了旋笛产生的非定常脉动速度和双传声器法获得的声质点振动速度之间的能量转换关系,并通过系统的气动声学特性实验考察了激励强度、频率、马赫数以及传感器间距对声质点振动速度的影响,验证了理论模型.结果表明:由旋笛产生的非定常脉动速度并不完全转换为声质点振动速度,这种转换关系主要与马赫数有关.且当流体为不可压缩气体,即马赫数小于0.3时,能量转换因子与马赫数的平方成正比,马赫数越大,能量转换因子越大,非定常流动转换为声能的效率越高.

Prospects for improving cosmological parameter estimation with gravitational-wave standard sirens from Taiji

Taiji,a space-based gravitational-wave observatory,consists of three satellites forming an equilateral triangle with arm length of 3×10^6 km,orbiting around the Sun.Taiji is able to observe the gravitationalwave standard siren events of massive black hole binary(MBHB)merger,which is helpful in probing the expansion of the universe.In this paper,we preliminarily forecast the capability of Taiji for improving cosmological parameter estimation with the gravitational-wave standard siren data.We simulate fiveyear standard siren data based on three fiducial cosmological models and three models of MBHB’s formation and growth.It is found that the standard siren data from Taiji can effectively break the cosmological parameter degeneracies generated by the cosmic microwave background(CMB)anisotropies data,especially for dynamical dark energy models.The constraints on cosmological parameters are significantly improved by the data combination CMB+Taiji,compared to the CMB data alone.Compared to the current optical cosmological observations,Taiji can still provide help in improving the cosmological parameter estimation to some extent.In addition,we consider an ideal scenario to investigate the potential of Taiji on constraining cosmological parameters.We conclude that the standard sirens of MBHB from Taiji will become a powerful cosmological probe in the future.

Forecast for cosmological parameter estimation with gravitational-wave standard sirens from the LISA-Taiji network

LISA and Taiji are expected to form a space-based gravitational-wave(GW)detection network in the future.In this work,we make a forecast for the cosmological parameter estimation with the standard siren observation from the LISA-Taiji network.We simulate the standard siren data based on a scenario with configuration angle of 40°between LISA and Taiji.Three models for the population of massive black hole binary(MBHB),i.e.,popⅢ,Q3d,and Q3nod,are considered to predict the events of MBHB mergers.We find that,based on the LISA-Taiji network,the number of electromagnetic(EM)counterparts detected is almost doubled compared with the case of single Taiji mission.Therefore,the LISA-Taiji network’s standard siren observation could provide much tighter constraints on cosmological parameters.For example,solely using the standard sirens from the LISA-Taiji network,the constraint precision of H;could reach 1.3%.Moreover,combined with the CMB data,the GW-EM observation based on the LISA-Taiji network could also tightly constrain the equation of state of dark energy,e.g.,the constraint precision of w reaches about 4%,which is comparable with the result of CMB+BAO+SN.It is concluded that the GW standard sirens from the LISA-Taiji network will become a useful cosmological probe in understanding the nature of dark energy in the future.

Gravitational wave standard sirens and cosmological parameter measurement

The first detection of gravitational waves (GWs) produced by the binary neutron star (BNS) merger in August 17, 2017[1] is fairly meaningful because it initiated the new era of multi-messenger astronomy. In this BNS merger event, we not only detected the gravitational waves.

Impacts of gravitational-wave standard siren observations from Einstein Telescope and Cosmic Explorer on weighing neutrinos in interacting dark energy models

Multi-messenger gravitational wave(GW)observation for binary neutron star merger events could provide a rather useful tool to explore the evolution of the Universe.In particular,for the third-generation GW detectors,i.e.the Einstein Telescope(ET)and the Cosmic Explorer(CE),proposed to be built in Europe and the U.S.,respectively,lots of GW standard sirens with known redshifts could be obtained,which would exert great impacts on the cosmological parameter estimation.The total neutrino mass could be measured by cosmological observations,but such a measurement is model-dependent and currently only gives an upper limit.In this work,we wish to investigate whether the GW standard sirens observed by ET and CE could help improve the constraint on the neutrino mass,in particular in the interacting dark energy(IDE)models.We find that the GW standard siren observations from ET and CE can only slightly improve the constraint on the neutrino mass in the IDE models,compared to the current limit.The improvements in the IDE models are weaker than those in the standard cosmological model.Although the limit on neutrino mass can only be slightly updated,the constraints on other cosmological parameters can be significantly improved by using the GW observations.

Constraining the Hubble constant to a precision of about 1% using multi-band dark standard siren detections

Gravitational wave signal from the inspiral of stellar-mass binary black hole can be used as standard sirens to perform cosmological inference.This inspiral covers a wide range of frequency bands,from the millihertz band to the audio-band,allowing for detections by both space-borne and ground-based gravitational wave detectors.In this work,we conduct a comprehensive study on the ability to constrain the Hubble constant using the dark standard sirens,or gravitational wave events that lack electromagnetic counterparts.To acquire the redshift information,we weight the galaxies within the localization error box with photometric information from several bands and use them as a proxy for the binary black hole redshift.We discover that Tian Qin is expected to constrain the Hubble constant to a precision of roughly 30%through detections of 10 gravitational wave events;in the most optimistic case,the Hubble constant can be constrained to a precision of<10%,assuming Tian Qin I+II.In the optimistic case,the multi-detector network of Tian Qin and LISA is capable of constraining the Hubble constant to within 5%precision.It is worth highlighting that the multi-band network of Tian Qin and Einstein Telescope is capable of constraining the Hubble constant to a precision of about 1%.We conclude that inferring the Hubble constant without bias from photo-z galaxy catalog is achievable,and we also demonstrate self-consistency using the P-P plot.On the other hand,high-quality spectroscopic redshift information is crucial for improving the estimation precision of Hubble constant.

四仁散贴敷涌泉穴在小儿外感发热中的应用

目的探讨四仁散贴敷涌泉穴在小儿外感发热中的应用。方法选取2022年5月至2023年1月广州中医药大学深圳医院(福田)收治的138例外感发热患儿作为研究对象,按照随机数字表法分为对照组和观察组,每组各69例。对照组予以常规对症处理,观察组在对照组基础上予以四仁散贴敷涌泉穴。比较两组体温下降幅度及退热效果。结果观察组不同时间点体温下降幅度均高于对照组(P<0.05)。观察组退热总有效率高于对照组(P<0.05)。结论四仁散贴敷涌泉穴在小儿外感发热中的应用可辅助患儿退热,值得临床推广。

Wife-Subduing Air Raid Siren Confiscated

德国的一对夫妇家中不和。为了让妻子屈服,73岁的Vladimir R.居然用 拉响警报的办法。妻子沉默了,而安装在屋顶上的警报却让四邻不安,最后警察 没收了此警报器。

从魔性的歌声到沉默的诱惑——论德语文学中塞壬神话的移变

女妖塞壬作为一种标准的世界文化图像为不同国家和民族的艺术、文学创作提供了一个理想的母本。几乎各个文学时期都有德语作家对此进行创新性的改编和重写。以侨易学中的“移变”现象为理论基础,追溯塞壬神话的根基源头,梳理这一形象在德语文学中的主要演变历程,解读这些移变发生的起因、背景,揭示背后所蕴藏的精神内涵,可以把握其作为一个“文化生命”所涉及到的个体、文明或概念之间互动共生的协调关系。

鸟类和爬行类离顶盖通路的电生理研究

用单位引导方法系统研究了鸽子、蛤蚧和石龙子的离顶盖通路单位反应特点 该通路视觉单位感受野较大 ;有照度和色觉两种光反应单位 ;在 3种动物的圆核和蛤蚧的前背侧室嵴总共找到 +B -Y ,+R -G ,+Y -B三种光谱拮抗单位 ;约半数视觉单位对运动物体反应良好 ,它们具有不同程度的方向选择性、朝向选择性以及运动物体大小选择性 ;2D运动单位中有一种覆盖缘反应单位 ,能区分在纹理背景上运动的纹理物体的前、后缘 ;3D单位只对在视轴方向运动的物体反应 ,其中一种对自远处飞近的物体产生强烈反应 ,此反应只发生在物体与眼即将‘碰撞’的瞬间 ,具有‘报警作用’ 在蛤蚧和鸟类的前背侧室嵴 (外纹体 )都发现既对运动物体反应 。

广东两次超强雷雨大风特征分析及服务探讨

通过对2011年4月17日和2005年3月22日前汛期造成广东严重灾情的这2次超强雷雨大风回波的演变进行对比分析,探讨这2次强对流天气的特征,并就目前广东在重大天气预警服务存在的问题作一些探讨。结果表明,造成严重灾害的强对流天气系统其天气背景、环流变化、雷达回波有明显特征;由于这种天气系统移动速度快且呈局部分布,当发现时灾害天气即将发生,预报时效非常短;通过被动的电视、气象电子显示屏、气象网站、天气微博传送预警信息无法覆盖所有公众,提出农村气象大喇叭预警系统的建立可以解决气象信息点对面的覆盖。

超声旋笛声波发生器在防蜡降粘方面的研究

作为一种特殊的流体动力式声波发生器,超声旋笛在电泵井防垢降粘方面有着显著的使用效果。文章介绍了超声旋笛的发声原理,开展了防垢降粘的实验研究。实验表明,超声旋笛能有效地降低原油粘度,减少油垢生成,为电泵井的正常生产提供了一种有效的措施。

塞壬的起源、形象与功能

塞壬是希腊神话中令人费解的角色,起源朦胧,争议颇多,其文学和艺术形象也并不协调。本文从文学、艺术和词源学角度追溯塞壬的起源,分析其形象和功能的演变,大致结论是:荷马讲述的塞壬故事可能源于希腊水手从海外获悉的民间传说,即海岛上的年轻女巫用魔歌诱惑水手致死的故事,后被诗人吸收到他的英雄史诗中。由于其歌声的不可抗拒性和致命性,塞壬的海仙女形象逐渐被妖魔化,与古希腊艺术中的鸟人怪物等同起来。塞壬的鸟女人形象可能源于埃及的灵魂鸟"巴",但其功能迥然有别,在希腊古风时代扮演着死亡天使和灵魂劫持者的可怕角色,类似于神话中的鸟形精灵克尔、哈尔皮和狮身人面有翼的斯芬克斯。从公元前5世纪起,塞壬的功能发生变化,逐渐从可怕的死亡精灵和辟邪怪物转变成温和的哀悼者、抚慰者和挽歌歌唱者。塞壬的女性特质源于其诱惑者的角色;其人禽混杂的特征源于其令人生畏的自然和社会属性;她们与天界缪斯的关联源于其有魔力的歌声和洞悉往事未来的能力;偶尔呈现的美人鱼形象(后成为中世纪的标准形象)则源自她们与海洋的固有联系。

方文《四壬子图》考论

清初著名遗民诗人方文,其诗歌创作主要取法东晋陶渊明和唐代的杜甫、白居易,并且四个人刚巧都是“壬子”年出生,因此他曾托人特地画了一幅《四壬子图》。而对方文诗歌,学术界一直重视不足,研究很少;现在结合《四壬子图》的考证,可以一并探讨方文的诗学渊源。