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Anisotropic emission of gravitational waves during the merger of black holes induces a recoil velocity on the centre of mass of the binary and the final merger product can then be ejected from its host galaxy. We consider ejected black holes which stay on bound orbits around their host haloes. A recoiled black hole which moves on an almost radial orbit outside the virial radius of its central galaxy, in the cold dark matter background, reaches its apapsis in a finite time. Due to small dark matter velocity dispersion at high redshifts and also the small black hole velocity near the apapsis passage a high-density wake forms around these black hole. Gamma-ray emission can result from the enhancement of dark matter annihilation in these wakes. The diffuse high-energy gamma-ray background from the ensemble of such black holes in the Hubble volume is also evaluated. 相似文献
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大歧口凹陷位于渤海湾盆地黄骅坳陷中北部,是中新生代叠合盆地中新生界沉积最厚的凹陷。本文基于大量二维、三维地震剖面和钻井资料,从凹陷主控断裂活动性、沉积沉降中心分布和构造格架等方面,侧重对大歧口凹陷新生代构造演化过程和原型盆地类型进行研究。认为:1)大歧口凹陷构造单元有4级,凹陷具有"东西分带、南北分块"的平面构造格局和北断南超箕状断陷的剖面结构。2)凹陷内断裂有4级,主要断裂的规模、活动期次和断裂活动具有演化的阶段性和空间的迁移性,典型构造带活动性具有由北往南迁移的特点。3)新生代期间整个大歧口凹陷的沉积沉降中心均在东部海域的歧口主凹内,但整体具有往南迁移的趋势。4)凹陷经历了拓展裂谷、拉分断陷、箕状断陷和碟状坳陷4个构造演化阶段,断陷阶段在整个构造演化时期意义重大,且具有走滑拉分特点。故认为大歧口凹陷原型盆地是一种"板内拉分盆地"。 相似文献
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It is expected that episodic tremors and slips (ETS) as a type of slow earthquakes with periodic property will be detected using harmonic estimation techniques. The principal goal of this paper is the detection of these kinds of earthquakes using least squares harmonic estimation (LSHE). To accomplish this, the raw time series of 38 permanent GPS stations of the Pacific Northwest Geodetic Array have been analyzed. Previously, some independent techniques could confirm the occurrences of the aforementioned quakes at these stations. However, the current research intends to evaluate the spectrum of each of the de-trended time series using the LS-HE method. In each station, the period of the detected harmonic with the maximum power spectrum is equivalent to the average period previously reported for these events. According to the obtained results, the recurrence interval of these events ranges from 9 months to 3 years. In sum, the study confirms this method being efficient for investigating the occurrences of ETSs when the length of the GPS time series is sufficiently large. 相似文献
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This paper presents probabilistic seismic hazard analysis (PSHA) of Tehran, Iran, accounting the effect of nonlinear soil response. It is well-known that soil nonlinearity and its accurate prediction could play important role in seismic hazard study. For this purpose, two different approaches have been carried out for predicting the hazard curves by (1) applying site modifications to the ground motion prediction equation based on generic site classes and use of constant coefficients (2) using a close-form solution that modifies the hazard results at the rock level. Also, efficiency of the Monte Carlo method in modeling of amplification function for the six selected sites in the study area was examined. Results showed important effect of nonlinear soil response mainly for frequencies lower than 8?Hz, which should be considered properly in hazard estimation. As an interesting subject, influence of soil plasticity index (PI) on hazard estimation of clayey sites including the nonlinear soil response was evaluated. 相似文献
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Y. Brenier U. Frisch M. Hénon G. Loeper S. Matarrese R. Mohayaee A. Sobolevski 《Monthly notices of the Royal Astronomical Society》2003,346(2):501-524
We show that the deterministic past history of the Universe can be uniquely reconstructed from knowledge of the present mass density field, the latter being inferred from the three-dimensional distribution of luminous matter, assumed to be tracing the distribution of dark matter up to a known bias. Reconstruction ceases to be unique below those scales – a few Mpc – where multistreaming becomes significant. Above 6 h −1 Mpc we propose and implement an effective Monge–Ampère–Kantorovich method of unique reconstruction. At such scales the Zel'dovich approximation is well satisfied and reconstruction becomes an instance of optimal mass transportation, a problem which goes back to Monge. After discretization into N point masses one obtains an assignment problem that can be handled by effective algorithms with not more than O ( N 3 ) time complexity and reasonable CPU time requirements. Testing against N -body cosmological simulations gives over 60 per cent of exactly reconstructed points.
We apply several interrelated tools from optimization theory that were not used in cosmological reconstruction before, such as the Monge–Ampère equation, its relation to the mass transportation problem, the Kantorovich duality and the auction algorithm for optimal assignment. A self-contained discussion of relevant notions and techniques is provided. 相似文献
We apply several interrelated tools from optimization theory that were not used in cosmological reconstruction before, such as the Monge–Ampère equation, its relation to the mass transportation problem, the Kantorovich duality and the auction algorithm for optimal assignment. A self-contained discussion of relevant notions and techniques is provided. 相似文献
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Seismic demand evaluation of medium ductility RC moment frames using nonlinear procedures 总被引：1，自引：1，他引：0
Performance-based earthquake engineering is a recent focus of research that has resulted in widely developed design methodologies due to its ability to realistically simulate structural response characteristics.Precise prediction of seismic demands is a key component of performance-based design methodologies.This paper presents a seismic demand evaluation of reinforced concrete moment frames with medium ductility.The accuracy of utilizing simplified nonlinear static analysis is assessed by comparison against the results of time history analysis on a number of frames.Displacement profiles,drift demand and maximum plastic rotation were computed to assess seismic demands.Estimated seismic demands were compared to acceptance criteria in FEMA 356.The results indicate that these frames have sufficient capacity to resist interstory drifts that are greater than the limit value. 相似文献
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Roya Narimani Mahdi Erfanian Habib Nazarnejad Ahmad Mahmodzadeh 《Environmental Earth Sciences》2017,76(9):353
This study was undertaken to evaluate land use change impact and management scenarios on annual average surface runoff (SR) and sediment yield (SY) using the GeoWEPP tool in the Lighvanchai watershed (located in northwestern Iran). Following a sensitivity analysis, the WEPP model was calibrated (2005–2007) and validated (2008–2010) against monthly observed SY and SR. The coefficient of determination (R 2), Nash–Sutcliffe efficiency (NSE), mean bias error (MBE), and root-mean-square error (RMSE) were applied to quantitatively evaluate the WEPP model. The results indicate a satisfactory model performance with R 2 > 0.80 and NSE > 0.60. Therefore, the model for current land use (scenario 1) was run for a 30-year time period (1982–2011). The annual average of SR and sediment load were predicted as 93,584 m3/year and 4340 ton/year, respectively. To reduce the annual average surface runoff and sediment yield at the watershed scale, the second scenario (alfalfa cultivation with suitable tillage) and the third scenario (grassland development) as two management scenarios of land use changes were defined by identifying the critical hillslopes. The rate of SR and sediment load in the second scenario were 42,096 m3/year and 429 ton/year, respectively. For the third scenario, the model predictions were 30,239 m3/year and 226 ton/year, respectively. Compared to the first scenario, the reduction rates in annual average of sediment load were about 90 and 94%, respectively. Moreover, for the second and third management scenarios, the reduction rates in annual average of SR were about 55 and 67%, respectively. 相似文献