排序方式： 共有10条查询结果，搜索用时 15 毫秒
1
1.
In astronomical photometry, the sensitivity of observations is limited by the dark counts of the photomultiplier tube. In the present work, the effect of dark count noise in photon counting systems is investigated by theory and experimental measurements. Dark counts are considered to be originating from two sources, namely: dc fluctuations and random pulses.Experimental measurements were carried out to determine noise effects in different operating regions of noise dominance. The results provide strong evidence that: in normal operating mode, where the effect of random pulses is dominant, dark counts do not follow Poisson statistics. The observed noise shows strong (1/f) power spectrum, where the observed noise power is found to increase with time of observation.The results are important in photon counting systems operating under dark count limited mode. The conclusions drawn can be useful in obtaining more accurate error estimates and in assessing astronomical photometric observations and data reduction techniques. 相似文献
2.
Increased traffic volume has made it necessary to increase highway capacities by widening embankments and pavements. Adding a new embankment to an existing embankment induces additional stresses and deformations beneath the widened and existing portions of the embankment. Differential settlement may develop between and within the new and existing portions of the embankment, especially over soft soils. This differential settlement often causes pavement distress, such as longitudinal cracks or the drop-off (or sinking) of pavement sections. Different techniques have been adopted to remedy these problems, including the use of foundation columns, such as deep mixed columns, vibro-concrete columns, stone columns, and aggregate piers. However, design procedures for foundation columns constructed for this purpose are not well developed. The analyses of eight cases of column-supported widened embankments and two untreated foundations are presented in this paper. The factors considered include the consolidation of foundation soils under existing embankments and the spacing, region, and modulus of foundation columns. Two-dimensional finite difference software was used after the calibration of the model against a field case study and numerical analyses were conducted to investigate stresses and deformations of the widened embankments over soft soil with or without the remediation of foundation columns. The results presented in this paper include the vertical and the horizontal displacements, the maximum settlements, the transverse gradient change, and the distribution of the additional stresses induced by the widening. Recommendations are made for the design of foundation columns to remedy roadway pavement failure due to widening of embankments. 相似文献
3.
Millen Maxim Viana da Fonseca Antonio Quintero Julieth Ferreira Cristiana Oztoprak Sadik Oser Cihan Bozbey Ilknur Aysal Namik Kosič Mirko Logar Janko 《Bulletin of Earthquake Engineering》2021,19(10):3987-4012
The seismic behaviour of a building on a liquefiable deposit is a complex interaction which involves quantifying both shaking induced damage and permanent ground deformation-related damage. In this paper the key parameters that influence both surface shaking and foundation settlements have been identified as the depth, thickness and liquefaction resistance of an equivalent liquefiable layer. These parameters can be used to develop an ‘equivalent soil profile’ that is analogous to the equivalent single degree-of-freedom that reduces the complexity of the dynamic response of a building into comparable and easily understood quantities. The equivalent soil profile is quantified independent of the seismic hazard, making it compatible with performance based design and assessment frameworks such that the building and soil profile can be directly assessed at different levels of seismic hazard. Several numerical studies are presented that demonstrate the influence of these key parameters on the ground surface shaking and foundation settlement. A set of criteria are proposed for classifying soil profiles into 22 different soil classes for regional loss assessment. An algorithm was developed for automatically fitting the equivalent soil profile to a cone penetration test trace and issues with the fitting are discussed. Field reconnaissance was undertaken to collect additional data to support existing datasets on the performance of buildings in Adapazari, during the 1999 Kocaeli, Turkey, earthquake (Mw = 7.4). The field case history data was used to investigate the correlation between the depth, thickness and liquefaction resistance of an equivalent liquefiable layer, on the extent of foundation permanent deformation. The case history data showed that in general a shallow, thick and weak liquefiable layer near the surface results in significant settlement but a lack of data for buildings on non-liquefiable deposits and the additional complexities involved with real buildings and soil deposits, meant that the trends observed in the idealised numerical models could not identified in the field case history data set.
相似文献4.
Jian-Feng Chen Jie Han Sadik Oztoprak Xiao-Ming Yang 《Computers and Geotechnics》2009,36(7):1191-1199
A three-dimensional numerical method was used to simulate cavity expansion during installation and an in situ load test conducted on a single rammed aggregate pier (RAP). Verification of the numerical model was carried out by comparing the computed settlements at top and tip of the pier with the measured values. An un-rammed aggregate pier (UAP) of the same diameter and length was also simulated using the numerical method to demonstrate the effect of installation. Interpretations of the numerical results were focused on the load–settlement behavior, the bulging of the pier, the axial load distributions along the pier, and the stress paths of the soil around the pier. A parametric study was conducted to investigate the influence of the pier length/diameter ratio and the soil properties on the behavior of rammed and un-rammed aggregate piers. 相似文献
5.
Khan Nafis Sadik Roy Sujit Kumar Mazumder Md. Touhidur Rahman Talukdar Swapan Mallick Javed 《Natural Hazards》2022,114(1):883-906
Natural Hazards - The confluence of the Ganges, Jamuna, and Padma rivers is one of the most dynamic in the world, an internationally important research area because of the confluence of two of the... 相似文献
6.
塔河油田盐体覆盖区奥陶系储层发育特征及主控因素研究 总被引：2，自引：0，他引：2
塔河盐下地区储层分布特征为奥陶系裂缝发育程度较高，溶蚀孔洞和半-未充填的高角度构造缝、溶蚀缝是本区最主要的储集空间类型．大型洞穴发育程度低于土体区，最主要的储集层类型为孔洞。裂缝型或裂缝-孔洞型储层．该区西部储层发育程度优于东部，本区有利储层多呈近NS条带状（或指状）展布；中下奥陶统上部储层发育程度高于下部；中下奥陶统储层发育程度高于上奥陶统良里塔格纽．控制盐下奥陶系储层发育与展布的主要因素是构造变形作用、加里东中期岩溶和沉积相． 相似文献
7.
Wolfgang Lutz Mahendra Shah Richard E. Bilsborrow John Bon-gaarts Partha DasGupta Barbara Entwisle Günther Fischer Brigida Garcia Daniel J. Hogan Arne Jernelöv Zhenghua Jiang Robert W. Kates Sanjaya Lall F. Landis MacKellar P.K. Makinwa-Adebusoye Anthony J. McMichael Vinod Mishra Norman Myers Nebojsa Nakicenovic Sten Nilsson Brian C. O'Neill Xizhe Peng Harriet B. Presser Nafis Sadik Warren C. Sanderson Gita Sen Barbara Torrey Dirk van de Kaa Hans J.A. van Ginkel Brenda Yeoh Huda Zurayk 《Global Change & Human Health》2002,3(1):33-35
The forthcoming World Summit on Sustainable Development (WSSD) in Johannesburg (August 26-September 4, 2002) has been set
by the United Nations to consider strategies toward sustainable development in all its dimensions. Hence, its mandate is broader
than that of the Rio 1992 United Nations Conference on Environment and Development (UNCED). Population issues have so far
been discussed in a separate series of World Population Conferences (Bucharest 1974, Mexico City 1984, Cairo 1994). With no
new World Population Conference scheduled for 2004 and Johannesburg having a mandate that is stated to explicitly include
social and economic aspects, population as a key component of sustainable development should figure prominently on the Johannesburg
agenda. Yet, after the third of four preparatory meetings for Johannesburg (which ended in New York on April 5th), consideration
of population is completely absent. The reasons for this are not entirely clear. We assume that they have to do with the fear
of entering into political controversies over abortion. We are concerned that, despite its broader mandate, in most countries
inputs to Johannesburg are being prepared mainly by environment ministries who have little experience in dealing with population
questions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
In the present work we have presented and analysedB andV light curves and the (B-V)-colour curve of the short period (RS CVn type) binary system UV Psc, and derived absolute information from the available data.x
2 minimization procedures were utilized to a large extent in fitting light and colour curves.The solutions show the binary to be at a distance of about 90 pc with two detached components which are close to the main sequence (G2 and K0). The inclination of the orbit is close to 90°Photometric irregularities present in the light curve are briefly considered in relation to current ideas on RS CVn systems, and the colour information indicates a locally hotter (rather than cooler) region is responsible for the irregularities. 相似文献
9.
S. Feyza Cinicioglu Ilknur Bozbey Sadik Oztoprak M. Kubilay Kelesoglu 《Engineering Geology》2007,94(3-4):145-165
This paper presents an integrated, earthquake-damage assessment that standardizes and quantifies methods of analysis. The proposed methodology evaluates all damage-causing phenomena, both individually and in combination. This approach inherently relates to soil-structure interactions by quantifying site-specific geotechnical and structural properties. Specifically considered is ground shaking, the primary damage-causing phenomenon. Also evaluated are the collateral effects of liquefaction, degradation of seismic-bearing capacity and slope failure (landslides). The methodology incorporates a literature-derived probabilistic assessment of damage-causation, and is interpreted and presented as single numbers deemed “Damage Grades.” These damage grades integrate the initial probabilistic evaluation with professional experience and judgment in order to determine potential damage to a particular structure at a particular location. This methodology was applied, with success, to two different locations in Istanbul, Turkey. It should be tested by engineering geologists and geotechnical engineers, for it may be applicable to earthquake-prone areas elsewhere. 相似文献
10.
Mohammadreza Moharrami Ioannis Koutromanos Marios Panagiotou Sadik Can Girgin 《地震工程与结构动力学》2015,44(5):677-694
This paper uses nonlinear truss models for the analysis of shear‐dominated reinforced concrete (RC) columns subjected to cyclic loading. A previously established method, aimed to the analysis of RC walls, is enhanced to allow simulations of column members. The concrete constitutive equations are modified to account for the contribution of the aggregate interlock to the shear resistance. Additionally, an equation is proposed to determine the inclination angle of the diagonal members in the truss models. The modeling approach is validated using the results of quasi‐static and dynamic tests on shear‐dominated RC columns. The combination of predictive capabilities and conceptual simplicity establishes truss‐based models as an attractive approach for the systematic analysis of shear‐dominated RC frame construction. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
1