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Hubble Tension Explanation from This Cosmological Model AΛΩ (Slow Bang Model, SB)
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作者 Jean Perron 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第1期106-125,共20页
In this article we present a model of Hubble-Lemaître law using the notions of a transmitter (galaxy) and a receiver (MW) coupled to a model of the universe (Slow Bang Model, SB), based on a quantum approach of t... In this article we present a model of Hubble-Lemaître law using the notions of a transmitter (galaxy) and a receiver (MW) coupled to a model of the universe (Slow Bang Model, SB), based on a quantum approach of the evolution of space-time as well as an equation of state that retains all the infinitesimal terms. We find an explanation of the Hubble tension H<sub>0</sub>. Indeed, we have seen that this constant depends on the transceiver pair which can vary from the lowest observable value, from photons of the CMB (theoretical [km/s/Mpc]) to increasingly higher values depending on the earlier origin of the formation of the observed galaxy or cluster (ETG ~0.3 [Gy], ~74 [km/s/Mpc]). We have produced a theoretical table of the values of the constant according to the possible pairs of transmitter/receiver in the case where these galaxies follow the Hubble flow without large disturbance. The calculated theoretical values of the constant are in the order of magnitude of all values mentioned in past studies. Subsequently, we applied the models to 9 galaxies and COMA cluster and found that the models predict acceptable values of their distances and Hubble constant since these galaxies mainly follow the Hubble flow rather than the effects of a galaxy cluster or a group of clusters. In conclusion, we affirm that this Hubble tension does not really exist and it is rather the understanding of the meaning of this constant that is questioned. 展开更多
关键词 Model of the Universe Cosmological Constant hubble Constant hubble’s Tension hubble-Lemaître Law hubble’s flow
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Analysis of debris flow control effect and hazard assessment in Xinqiao Gully,Wenchuan M_(s)8.0 earthquake area based on numerical simulation
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作者 Chang Yang Yong-bo Tie +3 位作者 Xian-zheng Zhang Yan-feng Zhang Zhi-jie Ning Zong-liang Li 《China Geology》 CAS CSCD 2024年第2期248-263,共16页
Xinqiao Gully is located in the area of the 2008 Wenchuan M_(s)8.0 earthquake in Sichuan province,China.Based on the investigation of the 2023"6-26"Xinqiao Gully debris flow event,this study assessed the eff... Xinqiao Gully is located in the area of the 2008 Wenchuan M_(s)8.0 earthquake in Sichuan province,China.Based on the investigation of the 2023"6-26"Xinqiao Gully debris flow event,this study assessed the effectiveness of the debris flow control project and evaluated the debris flow hazards.Through field investigation and numerical simulation methods,the indicators of flow intensity reduction rate and storage capacity fullness were proposed to quantify the effectiveness of the engineering measures in the debris flow event.The simulation results show that the debris flow control project reduced the flow intensity by41.05%to 64.61%.The storage capacity of the dam decreases gradually from upstream to the mouth of the gully,thus effectively intercepting and controlling the debris flow.By evaluating the debris flow of different recurrence intervals,further measures are recommended for managing debris flow events. 展开更多
关键词 Landslide Debris flow Hazard assessment Numerical simulation OpenLIsEM Prevention and control project Wenchuan M_(s)8.0 earthquake Xinqiao Gully sichuan province Geological hazards survey engineering
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An Improved Coupled Level Set and Continuous Moment-of-Fluid Method for Simulating Multiphase Flows with Phase Change
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作者 Zhouteng Ye Cody Estebe +8 位作者 Yang Liu Mehdi Vahab Zeyu Huang Mark Sussman Alireza Moradikazerouni Kourosh Shoele Yongsheng Lian Mitsuhiro Ohta M.Yousuff Hussaini 《Communications on Applied Mathematics and Computation》 EI 2024年第2期1034-1069,共36页
An improved algorithm for computing multiphase flows is presented in which the multimaterial Moment-of-Fluid(MOF)algorithm for multiphase flows,initially described by Li et al.(2015),is enhanced addressing existing MO... An improved algorithm for computing multiphase flows is presented in which the multimaterial Moment-of-Fluid(MOF)algorithm for multiphase flows,initially described by Li et al.(2015),is enhanced addressing existing MOF difficulties in computing solutions to problems in which surface tension forces are crucial for understanding salient flow mechanisms.The Continuous MOF(CMOF)method is motivated in this article.The CMOF reconstruction method inherently removes the"checkerboard instability"that persists when using the MOF method on surface tension driven multiphase(multimaterial)flows.The CMOF reconstruction algorithm is accelerated by coupling the CMOF method to the level set method and coupling the CMOF method to a decision tree machine learning(ML)algorithm.Multiphase flow examples are shown in the two-dimensional(2D),three-dimensional(3D)axisymmetric"RZ",and 3D coordinate systems.Examples include two material and three material multiphase flows:bubble formation,the impingement of a liquid jet on a gas bubble in a cryogenic fuel tank,freezing,and liquid lens dynamics. 展开更多
关键词 Moment-of-Fluid(MOF) surface tension Two phase flow Phase change Deforming boundaries with change(s)in topology Two-dimensional(2D) Three-dimensional(3D)axisymmetric 3D
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Non-Darcy Flow in Molding Sands
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作者 Miguel A. Barron-Meza Joan Reyes-Miranda Daniel Flores-Sanchez 《Open Journal of Applied Sciences》 2024年第4期976-982,共7页
Darcy’s law is widely used to describe the flow in porous media in which there is a linear relationship between fluid velocity and pressure gradient. However, it has been found that for high numbers of Reynolds this ... Darcy’s law is widely used to describe the flow in porous media in which there is a linear relationship between fluid velocity and pressure gradient. However, it has been found that for high numbers of Reynolds this law ceases to be valid. In this work, the Ergun equation is employed to consider the non-linearity of air velocity with the pressure gradient in casting sands. The contribution of non-linearity to the total flow in terms of a variable defined as a non-Darcy flow fraction is numerically quantified. In addition, the influence of the shape factor of the sand grains on the non-linear flow fraction is analyzed. It is found that for values of the Reynolds number less or equal than 1, the contribution of non-linearity for spherical particles is around 1.15%. 展开更多
关键词 Darcy’s Law Molding sands Non-Darcy flow Reynolds Number shape Factor
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甘肃积石山 M_(s)6.2级地震的震害特征与启示 被引量:5
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作者 王丽丽 王兰民 +5 位作者 卢育霞 许世阳 夏晓雨 盖海龙 池佩红 郭梅 《世界地震工程》 北大核心 2024年第1期58-71,共14页
2023年12月18日,甘肃省临夏回族自治州积石山保安族东乡族撒拉族自治县(35.70°N,102.79°E)发生了6.2级地震,震中烈度为VIII度。地震发生后,通过实地烈度评估与科学考察,对震区VI~VIII度区不同建(构)筑物与生命线工程的震害特... 2023年12月18日,甘肃省临夏回族自治州积石山保安族东乡族撒拉族自治县(35.70°N,102.79°E)发生了6.2级地震,震中烈度为VIII度。地震发生后,通过实地烈度评估与科学考察,对震区VI~VIII度区不同建(构)筑物与生命线工程的震害特点进行了统计分析;从抗震设计与施工管理、场地放大效应与地震次生灾害对建筑结构抗震性能的影响等角度,提出了此次地震的震害启示。结果表明:1)严重破坏和毁坏的建筑结构主要集中在老旧的土木结构、砖木结构和无设防或设防不规范的砖混结构。2)造成建筑结构破坏的主要原因是少量自建房抗震设计和施工的不规范、场地放大效应和地震次生灾害。3)优化和改良生土砌筑材料,改进纵横墙间的拉结措施,强化结构整体性是提高土木结构抗震的有效方法;普及“上下圈梁与构造柱”等基本抗震设防措施,规范水泥砂浆强度,提升农村工匠的施工水平,可有效提高砌体结构的整体性,避免房屋出现整体性垮塌;室内洗手间的墙体应该与房顶、纵横墙间建立有效联接,提高结构的抗震性能。4)孤突斜坡、河流高阶地与岸边为抗震不利地带。当建造用地极为匮乏,不得不选址在这些场地之上时,应该综合考虑场地的地形地貌特征、岩土体物理力学特性、水文地质条件、抗震设防目标、建筑结构类型等影响因素,做好地震灾害风险评估,根据评估结果进行科学设防。灾后重建过程中,应由政府统一规划选址、统一设计,规范施工。 展开更多
关键词 积石山6.2级地震 震害调查 场地放大效应 黄土液化流滑 震害特征
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Temporal change of plankton size structure preserved by Lugol's solution:a FlowCAM study
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作者 Zijia LIU Yuan DONG +3 位作者 Qian P.LI Zhengchao WU Zaiming GE Mengzhen MA 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2023年第1期290-299,共10页
Plankton size structure is crucial for understanding marine ecosystem dynamics and the associated biogeochemical processes.A fixation step by acid Lugol’s solution has been commonly employed to preserve plankton samp... Plankton size structure is crucial for understanding marine ecosystem dynamics and the associated biogeochemical processes.A fixation step by acid Lugol’s solution has been commonly employed to preserve plankton samples in the field.However,the acid Lugol’s solution can bias the estimation of size structure and the preserved plankton size structure can vary with time.Here,we explore the impact of sample storage time on the size-structure of the plankton community preserved by Lugol’s solution.Two short-term experiments and one long-term experiment were conducted to explore the change of plankton community size structure with the storage time:covering from a week to a month,and to nearly seven months based on particle-size data obtained by continuous Flow Cytometer and Microscope(FlowCAM)measurements.We found a linear change of plankton size with the storage time in short-term periods(less than 3 months)with a decrease of the slope but an increase of the intercept for the normalized biomass size spectrum(NBS S).However,there were opposite trends for NBSS with increasing slope but decreasing intercept after3 months.The potential causes of the distinct patterns of the NBSS parameters are addressed in terms of the interplay between particle aggregation and fragmentation.We found large changes in plankton biovolume and abundance among different size classes,which may indicate a distinct effect of acid Lugol’s solution on various plankton size classes.The mechanism driving temporal change in the size-structure of the Lugolfixed plankton community was further discussed in terms of particle aggregation and fragmentation.Finally,we emphasize that the effect of storage time should be taken into account when interpreting or comparing data of plankton community acquired from samples with various storage durations. 展开更多
关键词 Lugol’s PLANKTON size structure flow Cytometer and Microscope(flowCAM)
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Extended Hubble Diagram on the Basis of Gamma Ray Bursts Including the High Redshift Range of z = 0.0331 - 8.1 被引量:2
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作者 Laszlo A. Marosi 《International Journal of Astronomy and Astrophysics》 2019年第1期1-11,共11页
It is generally accepted that the history of the expansion of the universe can be exactly described by the concordance model, which makes specific predictions about the shape of the Hubble diagram. The redshift-magnit... It is generally accepted that the history of the expansion of the universe can be exactly described by the concordance model, which makes specific predictions about the shape of the Hubble diagram. The redshift-magnitude Hubble diagram in the redshift range z = 0.0104 - 1 seems to confirm this expectation, and it is believed that this conformity is also valid in the high redshift range. However, this belief is not undisputed. Recent work in the high redshift range of up to z = 8.1 has shown that the shape of the Hubble diagram deviates considerably from the predictions made by the Lambda cold dark matter model. These analyses, however, were based on mixed SN1a and gamma ray burst data, and some astronomers argue that this may have biased the results. In this paper, 109 cosmology-independent, calibrated gamma ray burst z/&mu;data points are used to calculate the Hubble diagram in the range z = 0.034 to z = 8.1. The outcome of this analysis confirms prior results: contrary to expectations, the shape of the Hubble diagram turns out to be exponential, and this is difficult to explain within the framework of the standard model. The cosmological implications of this unexpected result are discussed. 展开更多
关键词 REDsHIFT Gamma Ray BURsTs hubble DIAGRAM EXPONENTIAL slope hubble’s Law ΛCDM Model
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S弯收扩喷管过膨胀状态下流动分离特性研究
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作者 王明新 周莉 +2 位作者 史经纬 张诣 王占学 《推进技术》 EI CAS CSCD 北大核心 2024年第9期71-82,共12页
为了研究S弯收扩喷管过膨胀状态下的流动分离特性,数值模拟了不同落压比(NPR)下S弯收扩喷管内的流动特征。结果表明:在落压比为2.0时,喷管内发生非对称分离,出现非对称的双“λ”激波结构,喷流整体向上偏转,上侧出现限制性流动分离RSS,... 为了研究S弯收扩喷管过膨胀状态下的流动分离特性,数值模拟了不同落压比(NPR)下S弯收扩喷管内的流动特征。结果表明:在落压比为2.0时,喷管内发生非对称分离,出现非对称的双“λ”激波结构,喷流整体向上偏转,上侧出现限制性流动分离RSS,下侧出现自由性流动分离FSS,并产生三维分离涡,喷流出现明显的三维效应。随着落压比从高度过膨胀状态下开始增加,喷管下侧保持FSS不变,喷管上侧RSS逐渐向后移动,直至与外界大气相连,转变为FSS,之后随着落压比增加,上下侧分离结构逐渐对称。推力矢量角随着落压比的增加先增加,后在极小的落压比变化范围内快速降低,直至变为0°,之后保持0°不变。 展开更多
关键词 s弯收扩喷管 过膨胀状态 流动分离 落压比 推力矢量角
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S型皮托管对向和非对向测量方法准确度实验研究
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作者 张乐垚 张亮 +3 位作者 郭素娜 郭虎林 鲁贵祥 孔令彩 《计量学报》 CSCD 北大核心 2024年第6期864-872,共9页
S型皮托管的对向和非对向测量方法准确度在不同工况下有较大差异。通过风洞实流实验对风速、流速攻角和结构参数对S型皮托管对向和非对向测量方法准确度的影响进行了研究。结果表明:风速由5 m/s变化至30 m/s时,在不同流速攻角下S型皮托... S型皮托管的对向和非对向测量方法准确度在不同工况下有较大差异。通过风洞实流实验对风速、流速攻角和结构参数对S型皮托管对向和非对向测量方法准确度的影响进行了研究。结果表明:风速由5 m/s变化至30 m/s时,在不同流速攻角下S型皮托管对向和非对向测量准确度最大差异超过10%;对向和非对向测量中静压孔的压力变化是皮托管在较大流速攻角下造成测量误差的主因;外径较小、总静压孔距较大、测量端弯曲角度在15°至30°间、取压孔内径更小的S型皮托管在对向和非对向测量中都有更高的测量准确度;俯仰角取正值时对向测量准确度全面优于非对向测量,在俯仰角和偏航角同为45°时测量准确度差异达到最大值,大于70%。 展开更多
关键词 流量测量 s型皮托管 烟道流量 对向测量 非对向测量 测量准确度
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基于Hansbo渗流的平面应变固结分析
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作者 马跃 刘忠玉 刘朝凡 《河北工业科技》 CAS 2024年第5期345-350,共6页
为了考察非Darcy渗流对二维地基固结过程的影响,引入Hansbo渗流方程描述饱和黏性土中的渗流规律,修正了Terzaghi-Rendulic平面应变固结方程,并给出了有限体积法数值求解格式;采用不同的Hansbo渗流参数,分析了条形荷载作用下有限深度地... 为了考察非Darcy渗流对二维地基固结过程的影响,引入Hansbo渗流方程描述饱和黏性土中的渗流规律,修正了Terzaghi-Rendulic平面应变固结方程,并给出了有限体积法数值求解格式;采用不同的Hansbo渗流参数,分析了条形荷载作用下有限深度地基的固结特性。结果表明:Hansbo渗流延缓了平面应变固结的过程,并且随着Hansbo渗流参数的增大,超静孔压的消散变得更为缓慢,因此,按Darcy渗流对二维地基进行的常规固结分析将会高估其固结速率;与Biot固结理论相比,在Terzaghi固结理论框架内,条形荷载下固结初期地基中局部的孔压增大现象并不明显。研究成果可为探寻更为准确的饱和黏性土地基沉降预测方法提供理论基础。 展开更多
关键词 地基基础工程 平面应变固结 饱和黏性土 Hansbo渗流 有限体积法
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“Λ”型凸台对低隔道亚声速S弯进气道的流场控制研究
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作者 唐小松 金志光 《机械制造与自动化》 2024年第4期259-263,共5页
针对某无人机进气系统低隔道亚声速S弯进气道出口流场畸变较大的问题,研究一种利用隔道内置“Λ”型凸台生成反向涡抑制出口畸变的流场控制手段。通过数值仿真分析“Λ”型凸台结构对抑制流场畸变的作用机制,给出不同来流条件下凸台结... 针对某无人机进气系统低隔道亚声速S弯进气道出口流场畸变较大的问题,研究一种利用隔道内置“Λ”型凸台生成反向涡抑制出口畸变的流场控制手段。通过数值仿真分析“Λ”型凸台结构对抑制流场畸变的作用机制,给出不同来流条件下凸台结构参数对进气道出口总压恢复系数和流场畸变的影响规律。研究表明:畸变控制效果与凸台几何尺寸密切相关,合理设计的凸台对出口畸变抑制效果明显。 展开更多
关键词 无人机 亚声速进气道 s弯进气道 流场畸变 流场控制 数值仿真
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Effects of reservoir fluids on sand packs consolidated by furan and epoxy resins:Static and dynamic states
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作者 Mohammad Nabi Tabbakhzadeh Feridun Esmaeilzadeh +1 位作者 Dariush Mowla Reza Zabihi 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第11期4504-4514,共11页
One of the most effective methods for sand control is the chemical consolidation of sandstone structures.In this paper,the impacts of crude oil and brine in the static state and the impact of the flow rates of the flu... One of the most effective methods for sand control is the chemical consolidation of sandstone structures.In this paper,the impacts of crude oil and brine in the static state and the impact of the flow rates of the fluids in the dynamic state have been assessed at the reservoir conditions.The analyses in this research were Young’s modulus,compressive strength,porosity,and permeability which were done on core samples after and before fluid contact.Samples made with two different resins showed good resistance to crude oil in both states.No considerable change was seen in the analyses even at high crude oil injection rates in the dynamic state.Conversely,brine caused a noticeable change in the analyses in both states.In the presence of brine at the static state,Young’s modulus and compressive strength respectively decreased by 37.5%and 34.5%for epoxy cores,whereas these parameters respectively reduced by 30%and 41%for furan cores.In brine presence at the dynamic state,compressive strength reduction was 10.28 MPa for furan and 6.28 MPa for epoxy samples and their compressive strength reached 16.75 MPa and 26.54 MPa respectively which are higher than the critical point to be known as weak sandstone core.Moreover,Young’s modulus decrease values for furan and epoxy samples were respectively 0.37 GPa and 0.44 GPa.Therefore,brine had a more destructive effect on the mechanical characteristics of samples in the static state than the dynamic one for two resins.In addition,brine injection increased permeability by about 13.6%for furan and 34.8%for epoxy.Also,porosity raised by about 21.8%for furan,and 19%for epoxy by brine injection.The results showed that the chemical sand consolidation weakens in the face of brine production along with crude oil which can lead to increasing cost of oil production and treating wellbore again. 展开更多
关键词 Chemical sand consolidation Brine flow rate static and dynamic states Crude oil Compressive strength Permeability Young’s modulus
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Heuristic Estimation of the Vacuum Energy Density of the Universe: Part II-Analysis Based on Frequency Domain Electromagnetic Radiation
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作者 Vernon Cooray Gerald Cooray +1 位作者 Marcos Rubinstein Farhad Rachidi 《Journal of Electromagnetic Analysis and Applications》 2024年第1期1-9,共9页
In Part I of this paper, an inequality satisfied by the vacuum energy density of the universe was derived using an indirect and heuristic procedure. The derivation is based on a proposed thought experiment, according ... In Part I of this paper, an inequality satisfied by the vacuum energy density of the universe was derived using an indirect and heuristic procedure. The derivation is based on a proposed thought experiment, according to which an electron is accelerated to a constant and relativistic speed at a distance L from a perfectly conducting plane. The charge of the electron was represented by a spherical charge distribution located within the Compton wavelength of the electron. Subsequently, the electron is incident on the perfect conductor giving rise to transition radiation. The energy associated with the transition radiation depends on the parameter L. It was shown that an inequality satisfied by the vacuum energy density will emerge when the length L is pushed to cosmological dimensions and the product of the radiated energy, and the time duration of emission is constrained by Heisenberg’s uncertainty principle. In this paper, a similar analysis is conducted with a chain of electrons oscillating sinusoidally and located above a conducting plane. In the thought experiment presented in this paper, the behavior of the energy radiated by the chain of oscillating electrons is studied in the frequency domain as a function of the length L of the chain. It is shown that when the length L is pushed to cosmological dimensions and the energy radiated within a single burst of duration of half a period of oscillation is constrained by the fact that electromagnetic energy consists of photons, an inequality satisfied by the vacuum energy density emerges as a result. The derived inequality is given by where is the vacuum energy density. This result is consistent with the measured value of the vacuum energy density, which is 5.38 × 10<sup>-10</sup> J/m. The result obtained here is in better agreement with experimental data than the one obtained in Part I of this paper with time domain radiation. 展开更多
关键词 Classical Electrodynamics Electromagnetic Radiation Action Radiated Energy PHOTON Heisenberg’s Uncertainty Principle Dark Energy Vacuum Energy Cosmological Constant hubble Radius
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Proof of Hubble’s Law and the Truth about the Expansion of the Universe as Well as Dark Matter and Dark Energy
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作者 ZHONG Cuixiang CHEN Jiansheng 《Journal of Physical Science and Application》 2018年第1期13-22,共10页
In 1929,American astronomer Hubble first discovered that the recessional velocity of a galaxy increases with its distance from the earth,and therefore put forward Hubble’s law.It is considered the first observational... In 1929,American astronomer Hubble first discovered that the recessional velocity of a galaxy increases with its distance from the earth,and therefore put forward Hubble’s law.It is considered the first observational basis for the expansion of the universe and today serves as one of the pieces of evidence most often cited in support of the Big Bang model.Since then the astrophysics community has believed that the universe is in a constant rate of expansion until Saul Permutter,Brian Paul Schmit and Adam Guy Riees discovered the accelerating expansion of the universe through observation of several dozen distant supernovas in 1998,who then won the Nobel Prize in Physics 2011.But human still cannot completely explain the phenomenon that the universe is expanding at an ever-accelerating rate.Thus the author of this paper studied the origin and evolution of galaxies again,and revealed the structure of galaxy and proved Hubble’s law,then revealed the truth about the expansion of the universe as well as dark matter and dark energy. 展开更多
关键词 Galaxies structure hubble’s LAW universe’s expansion DARK matter DARK energy
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An Extended Version of Hubble’s Law
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作者 G. Alagar Ramanujam Keith Fitzcharles S. Muralidharan 《Journal of Modern Physics》 2017年第7期1067-1071,共5页
Friedmann-like cosmological equations were derived by us in a recent paper by using axioms proposed by us for the so called empty Space. By using one of our cosmological equations we have derived in this paper a relat... Friedmann-like cosmological equations were derived by us in a recent paper by using axioms proposed by us for the so called empty Space. By using one of our cosmological equations we have derived in this paper a relation between the expansion velocity of the universe and the radius of the universe. This relation may be considered as an extended version of Hubbles’ Law. According to our relation derived here, the Hubble factor H goes on decreasing as the radius increases. 展开更多
关键词 COsMOLOGICAL EQUATIONs Expansion of the UNIVERsE hubble’s CONsTANT DARK Energy
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Hubble’s Constant and Flat Rotation Curves of Stars: Are Dark Matter and Energy Needed?
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作者 Alexandre Chaloum Elbeze 《Journal of Modern Physics》 2017年第1期24-34,共11页
Although dark energy and dark matter have not yet been detected, they are believed to comprise the majority of the universe. Observations of the flat rotation curve of galaxies may be explained by dark matter and dark... Although dark energy and dark matter have not yet been detected, they are believed to comprise the majority of the universe. Observations of the flat rotation curve of galaxies may be explained by dark matter and dark energy. This article, using Newton’s laws and Einstein’s theory of gravitation, shows that it is possible to define a new term, called E0, variable in time and space, of which one of its limits is the Hubble constant H0. I show that E0?is strongly linked to an explanation of the flat rotation curve of galaxies. This strong correlation between Hubble’s constant H0?and E0 enables us to solve the mystery of the surplus of gravity that is stabilizing the universe. 展开更多
关键词 hubble’s Law General RELATIVITY COsMOLOGICAL CONsTANT EXPANDING UNIVERsE Dark ENERGY
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基于流体振荡器阵列的S型流道主动控制实验研究
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作者 王士奇 邵冬 +3 位作者 罗斌 贾志刚 陆华伟 孔晓治 《推进技术》 EI CAS CSCD 北大核心 2024年第9期60-70,共11页
本文针对一个典型的大折转角、大尺度S弯流道,设计并制造了一个由16个流体振荡器组成的大型阵列,并对S弯内部流动进行了主动控制实验研究。首先采用高频响热线风速仪、高精度质量流量计等手段测量了流体振荡器的频率、速度、流量等随进... 本文针对一个典型的大折转角、大尺度S弯流道,设计并制造了一个由16个流体振荡器组成的大型阵列,并对S弯内部流动进行了主动控制实验研究。首先采用高频响热线风速仪、高精度质量流量计等手段测量了流体振荡器的频率、速度、流量等随进口压力的响应变化规律及其在大型阵列中的工作特性一致性。其次采用壁面压力采集、五孔探针等手段测量了不同激励条件下,S弯流道的壁面压力分布以及出口截面的总压分布情况。结果表明,所设计的脉冲型流体振荡器能够产生1 kHz以上,峰值速度高于300 m/s的高频高速振荡射流,且阵列中多个振荡器的流量、频率、振荡速度范围等工作特性保持了较好的一致性。流体振荡器阵列在S弯流道上壁面一弯前缘形成了一排开孔率仅为10%的脉冲射流孔,在与主流成45°射流角度、进口马赫数Ma=0.15,激励速度比uR=4.31条件下,仅使用激励质量流量比Cm=0.39%的激励质量流量,就使S弯流道的出口平均总压损失改善了10.6%。本研究验证了流体振荡器阵列控制大尺寸分离流动的高效能力。 展开更多
关键词 s型流道 流体振荡器阵列 脉冲射流 主动流动控制 非定常激励器
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胎盘生长因子联合脐动脉S/D值对子痫前期的预测价值
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作者 戴红因 白砚耘 +4 位作者 脱鸣富 付蕊宁 陈蕾 石岩 多文博 《医学理论与实践》 2024年第6期921-924,920,共5页
目的:探讨胎盘生长因子(PLGF)联合脐血流S/D对子痫前期的预测价值。方法:采用病例对照研究,回顾性选取2020年4月—2021年4月就诊于我院产科并最终诊断为子痫前期的孕产妇52例作为研究组,并选取同期正常分娩的产妇122例作为对照组,将孕... 目的:探讨胎盘生长因子(PLGF)联合脐血流S/D对子痫前期的预测价值。方法:采用病例对照研究,回顾性选取2020年4月—2021年4月就诊于我院产科并最终诊断为子痫前期的孕产妇52例作为研究组,并选取同期正常分娩的产妇122例作为对照组,将孕期划分为三个阶段,孕早期(12~20周)、孕中期(20~34周)、孕晚期(34~42周),收集并分析两组孕妇早中晚期的胎盘生长因子(PLGF)、孕中晚期脐动脉收缩末期最大血流速度(S)与舒张末期最大血流速度(D)比值(S/D),评估PLGF、S/D值单独及联合预测子痫前期的效能。结果:研究组血清PLGF在妊娠各阶段平均值均明显低于对照组(P<0.05),研究组脐动脉S/D平均值高于对照组,孕中期两组间比较差异无统计学意义(P=0.21),孕晚期两组间比较差异有统计学意义(P=0.047),血清PLGF联合脐动脉S/D值在孕中期的特异度、灵敏度、AUC(ROC曲线下面积)分别为80.0%、63.6%、0.664,孕晚期的特异度、灵敏度、AUC分别为71.9%、81.8%、0.804。结论:研究组妊娠各个时期PLGF值均低于对照组,可以单独作为子痫前期患者的预测指标,S/D值单独预测价值与PLGF联合S/D值的预测价值在孕晚期优于孕中期,推测与纳入研究组患者的病情严重程度有关。 展开更多
关键词 子痫前期 PLGF 脐动脉s/D值 孕早期 孕中期 孕晚期
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Hubble’s Constant
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作者 Angel Fierros Palacios 《Journal of High Energy Physics, Gravitation and Cosmology》 2016年第3期293-297,共5页
An analytical method to calculate Hubble’s constant [1] is presented. The proposed procedure is an alternative scheme to the red shifts of spectral lines picture, to obtain the value of that constant [2].
关键词 hubble’s Constant
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S Zorb装置转剂线腐蚀风险评估与磨损特性分析
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作者 李松泰 《石油化工腐蚀与防护》 CAS 2024年第2期30-34,共5页
催化裂化汽油吸附脱硫技术(S Zorb)是一种清洁汽油生产的核心技术,近年来,S Zorb装置中出现的转剂线磨损和泄漏等问题已成为石油化工行业内的共性难点问题。某公司2号S Zorb装置自2013年投用以来,转剂线频繁出现磨损和泄漏问题,以该案... 催化裂化汽油吸附脱硫技术(S Zorb)是一种清洁汽油生产的核心技术,近年来,S Zorb装置中出现的转剂线磨损和泄漏等问题已成为石油化工行业内的共性难点问题。某公司2号S Zorb装置自2013年投用以来,转剂线频繁出现磨损和泄漏问题,以该案例为研究对象,对转剂线开展腐蚀风险评估以及气固两相流流态和磨损机理等综合特性分析,同时对弯管弯径比和气速对磨损的影响进行了讨论,为转剂线的设计优化以及运行可靠性的提升提供了参考。 展开更多
关键词 s Zorb装置 转剂线 腐蚀风险 气固两相流 磨损特性
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