首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   20篇
  免费   1篇
  2015年   1篇
  2014年   5篇
  2013年   10篇
  2011年   1篇
  2009年   1篇
  2002年   2篇
  1979年   1篇
排序方式: 共有21条查询结果,搜索用时 15 毫秒
1.
It is still a serious challenge for structural engineers to effectively reduce the seismic responses of tall and super tall buildings to further improve these structural safeties. In order to solve this problem, in this article a new kind of structural configuration, named passive mega-sub controlled structure (PMSCS), is presented, which is constructed by applying the structural control principle into structural configuration itself, to form a new structure with obvious response self-control ability, instead of employing the conventional method. In the analysis of PMSCS the equations of motion of the seismically excited system are developed, based on a realistic analytical model of the complete mega-structural system. Expressions of the displacement and acceleration response of the structure, resulting from simulated earthquake ground motions represented by stationary and nonstationary random processes, are derived. These responses are then determined for both the PMSCS and its conventional mega-sub structure (MSS) counterpart, whose configuration was modeled after the traditional mega-frame that was used in the construction of the Tokyo City Hall. A parametric study of the structural characteristics that influence the response control effectiveness of the PMSCS is presented and discussed. The region over which these structural characteristics yield the optimum seismic response control of the PMSCS is identified and serves as a very useful design tool for practitioners. The study illustrates that the proposed PMSCS offers an effective means of controlling the seismic displacement and acceleration response of tall/super-tall mega-systems. It also overcomes shortcomings exhibited in earlier proposed mega-sub controlled structural configurations.  相似文献   
2.
Despite repeated announcements of its death or uselessness, the ‘linear model’ of science–technology relations persists, the notion that fundamental scientific research precedes applied studies that in time generate technological advances. This article undertakes first to revisit investigations and critiques of the model, and to remind historians of technology that intriguing alternatives to it have been developed. Second, using the case study of Cold War military jet propulsion, it argues that innovative, complex technologies have been created without reliable understanding of scientific fundamentals. These were messy, non‐linear, and failure‐filled processes, to be sure, yet they may well prove to have been more the rule than the exception, once scholars pursue richly textured studies of technical practice in experimental development. Ultimately, project needs to overcome engineering obstacles in technological innovation may provide the platforms and the funding to support basic scientific research as well, reversing the linear model’s expected flows.  相似文献   
3.
A recurrent problem for scholars who investigate traditional and historical clothing is the measuring of items of clothing and subsequent pattern construction. The challenge is to produce exact data without damaging the item. The main focus of this paper is to present a new procedure for establishing a three‐dimensional model and the corresponding two‐dimensional pattern for items of skin clothing that are not flat. The new method is non‐destructive, and also accurate and fast. Furthermore, this paper presents an overview of the more traditional methods of pattern documentation and measurement. Their weaknesses and strengths are also assessed.  相似文献   
4.
An investigation of pollen and non-pollen palynomorphs in the organic material in bronze objects found in Vani provides evidence that, in the first half of the first century BC, the climate of the area was cooler and much more humid than nowadays. The local population was engaged in cattle-breeding and agriculture, and both viticulture and horticulture were also well developed. The analysis of the contents of an oil lamp showed that the lamp was in use for a long time and was filled with flax oil. Large pieces of beeswax found in the hoard provide evidence of the existence of local bronze-casting industry. The palynological studies of the recent and fossil soil of Vani have shown that only in soil spectra large quantities of spores of various fungi were found, which distinguishes them from the domestic dust spectra. On the basis of this argument it was established that most part of the studied fossil material is not contaminated by the soil where the hoard of bronze objects was buried.  相似文献   
5.
This study investigates the effectiveness of the modal analysis using three-degree-of freedom (3DOF) modal equations of motion to deal with the seismic analysis of two-way asymmetric elastic systems with supplemental damping. The 3DOF modal equations of motion possessing the non proportional damping property enable the two modal translations and one modal rotation to be non proportional in an elastic state. The simple approximation method is to use the single degree-of-freedom (SDOF) modal equations of motion, which are obtained by neglecting the off-diagonal elements of the transformed damping matrix. One, one-story and one, three-story non proportionally damped two-way asymmetric buildings under the excitation of bi-directional seismic ground motions are analyzed. The analytical results are obtained by using the proposed method, noted simple approximation method, and direct integration of the equation of motion. It is seen that the proposed method can significantly improve the accuracy of the analytical results compared with those obtained by using the simple approximation method. Moreover, the proposed method does not substantially increase the computational efforts.  相似文献   
6.
Relative displacement floor spectra represent a powerful tool to evaluate the seismic displacement requirements of non-structural elements relative to their attachment points and can be used for displacement-based design of ductile components.

This article examines the displacement floor spectra on single-degree of freedom systems subject to accelerograms of varying intensity. A new method is proposed to predict floor spectra on single degree of freedom supporting structures. The results of nonlinear time-history analyses of a series of case-study structures indicate that the new methodology provides good results.

Future research will aim to validate this approach for multi-degrees of freedom supporting structures.  相似文献   

7.
Gavin Brown  Helen Yaffe 《对极》2014,46(1):34-52
International solidarity is frequently presented as an asymmetrical flow of assistance travelling from one place to another. In contrast, we theorise the more complex, entangled and reciprocal flows of solidarity that serve to enact social change in more than one place simultaneously. The international campaign against apartheid was one of the most widespread, sustained social movements of the last century. This paper examines the spatial practices of the Non‐Stop Picket of the South African Embassy in London (1986–1990). Drawing on archival and interview material, we examine how the Picket produced solidarity with those resisting apartheid in South(ern) Africa. We argue that how the need for anti‐apartheid solidarity was framed politically cannot be understood in isolation from how it was performed in practice. The study of solidarity is enriched by paying attention to the micropolitics of the practices through which it is enacted and articulated through key sites.  相似文献   
8.
Isotopic analysis of human bone is becoming an increasingly important tool for the archaeologist in divining past life-ways. The isotopic ratios within bone are often assumed to be preserved as in life, but diagenetic change can alter the ratios, invalidating the results of isotopic analysis. Diagenesis can be evaluated in a number of ways, but most often spectroscopic techniques are utilised as the most efficient and easiest to understand methods for the archaeologist. Many isotopic studies do not report the possibility of diagenetic change, and if it is reported it has often been quantified using a single method of chemical analysis, FTIR spectroscopy. This study set out to test the value of FTIR analysis using human remains from the prehistoric site of Ban Non Wat, Northeast Thailand, and to compare the results with the non-destructive technique of FT-Raman spectroscopy. The study shows that FTIR spectroscopic analysis gives far less detail on the condition of bone than Raman spectroscopy, which does not merely indicate recrystallisation has occurred, but also shows clearly whether or not collagen is present, allows identification of ionic substitions which have occurred and identification of secondary minerals which have formed. Raman spectroscopy, combined with LA-ICP-MS analysis also revealed that soil composition and groundwater flow are the conditions which most affect diagenesis at Ban Non Wat.  相似文献   
9.
The dramatic growth of dietary isotope studies in archaeological literature attests to the significant potential this technique has for shedding light on past societies. Human diet reflects complex, inter-linked factors such as status, cultural preferences or environmental constraints on food production. In this study dietary isotope analysis is used to examine the human skeletal remains from Ban Non Wat, northeast Thailand. The study aims to use isotopic data to give insight into patterns of migration and subsistence strategy during prehistory. Ban Non Wat is the most comprehensively excavated site in the Upper Mun River Valley (UMRV), and understanding of prehistoric society in this area is crucial to answering questions of how social complexity arose in the region. Carbon isotope analysis has highlighted migrant individuals invisible to strontium isotope analysis and shown links between unusual burial practice and differences in diet. Results also indicate that diet changed substantially through time, with more reliance on rice in the Bronze Age, correlated with an increase in social differentiation. There is a move away from reliance on rice agriculture in the Iron Age, a time when oxygen isotopes show that environmental conditions were becoming drier, possibly resulting in rice agriculture becoming less viable.  相似文献   
10.
Beginning with a detailed presentation of the faunal spectra from Ban Chiang and related sites in Northeast Thailand, this essay reconstructs the palaeoenvironment during the period 3500 BC to the end of the prehistoric period. The evidence from the freshwater molluscs found in prehistoric layers suggests that the first occupants of Ban Chiang encountered a habitat with permanent lakes and clear, slow moving streams. Since the lakes contracted in the dry season, there were ideal conditions for practising wet swidden agriculture. From c. 1600 BC, the presence of water buffalo and associated changes in the faunal spectrum suggests the inception of wet rice cultivation. Such agricultural intensification, it is held, follows population pressure and accounts for subsequent settlement in the more arid plains of Thailand.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号