ELASTIC AND INELASTIC RESPONSE OF TUNNELS UNDER LONGITUDINAL EARTHQUAKE EXCITATION

This paper addresses the problem of the behaviour of underground tunnels subjected to longitudinal earthquake excitation. State-of-the-art solutions, which are relative to infinite length tunnels in the stationary case, with linear models for both the ground and the structure, are first recalled. These models are either static or dynamic; results generally indicate large strains, often incompatible with reinforced concrete structures, and small crack widths.

For finite length tunnels, in this study the dynamic solution for the linear case is developed and it is shown that maximum strain is an increasing function of the tunnel length so that, in many situations, the behavior of the lining is satisfactory also under the aspect of crack formation. When the nonlinear behaviors of the tunnel and soil are taken into account, segments of reinforced concrete tunnels, after cracking, may undergo considerable relative displacement, undesired both for serviceability and ultimate limit states. After review of the constitutive relationship for the ground, a parametric study on the crack openings for an example tunnel is presented. It is shown that crack widths computed with linear static analyses underestimate the real value for tunnels embedded in stiff grounds and that the lining longitudinal reinforcement can reduce crack width so as to cope with serviceability and ultimate limit states.     

Population–Employment Models: Stationarity, Cointegration, and Dynamic Adjustment

Abstract.  Population and employment in the 50 United States are found to be non‐stationary and cointegrated. Vector error correction (VEC) models exhibit dynamics with adjustment to shocks essentially completed in 30–35 years . This contrasts with adjustment periods between one and two centuries for non‐stationary models specified in levels. These dynamic adjustment patterns support the hypothesis that relatively long adjustment periods and slow dynamics are probably the spurious results of using non‐stationary levels of population and employment outside of a VEC model framework. Recommendations for modeling the population–employment relationship are offered based on the findings reported.     

Land Absorption in U.S. Metropolitan Areas: Estimates and Projections from Regional Adjustment Models

This article adapts a regional adjustment model to estimate and project the spatial outcome of population and employment growth in U.S. metropolitan areas. The three-equation multiplicative model of population change, employment change, and land absorption is estimated using three-stage least squares to account for endogeneity among the dependent variables and contemporaneous correlation across the system of equations. In addition to the core model, alternative specifications are estimated, imposing the initial conditions of size, land availability, and economic structure. The stability of the solutions is then examined using reduced-form equations estimated via the seemingly unrelated regression equations approach. The results reveal substantive evidence that population and employment growth are jointly determined, of how the two affect the outcome of land development, and, perhaps most importantly, stable and fractionally reasonable estimates at projected equilibrium points. Lastly, the adapted model controlling for the initial condition of land availability is used to project patterns of land consumption at equilibrium in 50 rapid-growth metropolitan areas.     

Locke on representation in politics

This article contextualises Hegel's writings on international order, especially those concerning war and imperialism. The recurring theme is the tragic nature of the struggles for recognition which are instantiated by these phenomena. Section one examines Hegel's analysis of the Holy Roman Empire in the context of French incursions into German territories, as that analysis was developed in his early essay on ‘The German Constitution’ (1798–1802). The significance of his distinction between the political and civil spheres is explored, with particular attention being paid to its implications for Hegel's theory of nationalism. The second section examines Hegel's development of the latter theory in The Phenomenology of Spirit (1807), stressing the tragic interpenetration of ‘culture’ and intersubjective recognition. A recurring theme here is the influence of this theory on Hegel's interpretation of Napoleon's World-Historic mission, as that was revealed in his contemporaneous letters. Section three traces the tragic dynamic underlying the discussion of war between civilised states in The Philosophy of Right (1821). Section four examines three other types of imperial action in Hegel's mature writings, particularly The Philosophy of History (1832). These are relations between civilised states and culturally developed yet politically immature societies; colonial expansion motivated by capitalist under-consumption; and conflict between civilised states and barbarous peoples. It is concluded that it is misleading to claim that Hegel glorified conflict and war, and that he did not see domination by ‘civilised states’ as the ‘final stage’ of World History.     

Hegel, war and the tragedy of imperialism

This article contextualises Hegel's writings on international order, especially those concerning war and imperialism. The recurring theme is the tragic nature of the struggles for recognition which are instantiated by these phenomena. Section one examines Hegel's analysis of the Holy Roman Empire in the context of French incursions into German territories, as that analysis was developed in his early essay on ‘The German Constitution’ (1798–1802). The significance of his distinction between the political and civil spheres is explored, with particular attention being paid to its implications for Hegel's theory of nationalism. The second section examines Hegel's development of the latter theory in The Phenomenology of Spirit (1807), stressing the tragic interpenetration of ‘culture’ and intersubjective recognition. A recurring theme here is the influence of this theory on Hegel's interpretation of Napoleon's World-Historic mission, as that was revealed in his contemporaneous letters. Section three traces the tragic dynamic underlying the discussion of war between civilised states in The Philosophy of Right (1821). Section four examines three other types of imperial action in Hegel's mature writings, particularly The Philosophy of History (1832). These are relations between civilised states and culturally developed yet politically immature societies; colonial expansion motivated by capitalist under-consumption; and conflict between civilised states and barbarous peoples. It is concluded that it is misleading to claim that Hegel glorified conflict and war, and that he did not see domination by ‘civilised states’ as the ‘final stage’ of World History.     

A REGIONAL ECONOMY,LAND USE,AND TRANSPORTATION MODEL (RELU‐TRAN©): FORMULATION,ALGORITHM DESIGN,AND TESTING*

ABSTRACT RELU is a dynamic general equilibrium model of a metropolitan economy and its land use, derived by unifying in a theoretically valid way, models developed by one of the authors [ Anas (1982) , Anas–Arnott (1991, 1997) , Anas–Kim (1996) , Anas–Xu (1999) ]. RELU equilibrates floor space, land and labor markets, and the market for the products of industries, treating development (construction and demolition), spatial interindustry linkages, commuting, and discretionary travel. Mode choices and equilibrium congestion on the highway network are treated by unifying RELU with the TRAN algorithm of stochastic user equilibrium [ Anas–Kim (1990) ]. The RELU‐TRAN algorithm's performance for a stationary state is demonstrated for a prototype consisting of 4‐building, 4‐industry, 4‐labor‐type, 15‐land‐use‐zone, 68‐link‐highway‐network version of the Chicago MSA. The algorithm solves 656 equations in a special block‐recursive convergent procedure by iterations nested within loops and loops within cycles. Runs show excellent and smooth convergence from different starting points, so that the number of loops within successive cycles continually decreases. The tests also imply a numerically ascertained unique stationary equilibrium solution of the unified model for the calibrated parameters.     

Establishment of a Time-Varying Modified Kanai-Tajimi Non Stationary Stochastic Model of Seismic Records Based on the S-transform

This article investigates the time-varying characteristics of seismic records. Time-varying amplitude and energy spectrums are defined to reflect the time-frequency dependence, and a general formulation of the S-transform is introduced. The S-transform is tested with various window functions to analyse the Kobe seismic records. The results indicate that using a complex window function with properly adjusted parameters gives favorable outcomes. Analyses of three soil sites show that sites with hard soil feature seismic records with shorter stationary durations, higher frequency centers, and broader frequency bands than other soil sites. The average time-varying spectrums of the seismic records are simulated using a uniform non stationary stochastic model and a time-varying modified non stationary Kanai-Tajimi stochastic model. Empirical formulas are established for the time-varying spectrums of the earthquake records from these sites by nonlinearly fitting stochastic models to the record data. The values of the time-varying spectrum factors for different earthquake intensities and sites agreeing with the Chinese Seismic Code are obtained. Based on these analyses and observations, we propose using the solutions to the stochastic models to simulate non stationary ground motions.     

Poverty Alleviation Programmes In Rural India: An Assessment

ABSTRACT The Planning Commission estimated a sharp reduction of poverty during the early 1980s, which it attributed largely to the poverty alleviation strategy followed during the Sixth Plan. Specifically, it was claimed that the Integrated Rural Development Programme (IRDP) was responsible for a substantial reduction in rural poverty. This claim is critically evaluated here. Drawing upon the results of an applied general equilibrium model, selected anti-poverty interventions are compared from a macro perspective. Noting the incentive and information-related problems, some key issues in designing anti-poverty interventions are addressed. Section I reviews changes in rural poverty at the all-India level. Section II explores the relationship between rural poverty, agricultural production and (consumer) prices. Distinguishing between transitory and persistent poverty, alternative measures of persistent poverty are presented in Section III. A case is then made for an interventionist anti-poverty strategy, followed by a brief review (Section IV) of salient features and selected performance indicators of poverty alleviation programmes launched/implemented during the Sixth Plan period. Section V investigates whether these programmes — especially the IRDP — played a significant role in alleviating poverty. Section VI discusses selected anti-poverty interventions and possible design-related reforms; concluding observations are offered in the final section.     

Acheulean variation and selection: does handaxe symmetry fit neutral expectations?

It has been suggested that the property of symmetry observed in Acheulean handaxes was selected for functional, adaptive or social and aesthetic reasons. However, selectionist accounts of variation may be contrasted with the approach taken by population geneticists to molecular variation. Population geneticists always first assume a neutral pattern of variation for molecular data, and only look to non-neutral (e.g., selective) scenarios for pattern and variation in the face of strong evidence against this null model of neutral expectation. Here, using a combination of cultural transmission theory, morphometrics, and the principles of population genetics, (null) neutral expectations for Acheulean handaxe symmetry are tested. The results of the analyses are inconsistent with a null hypothesis of neutral expectation for patterns of handaxe symmetry variation. Rather, the results imply that the property of symmetry in Acheulean handaxes was subject to selection for functional, adaptive or social reasons.     

An Explicit Integration Scheme for Solving Dynamic Problems of Solid and Porous Media

In this article, an explicit integration scheme for dynamic finite element analysis is developed and the formulations for linear elastic solid and two-phase porous media are derived. The accuracy and stability characteristics analyses show this scheme is second-order accurate, which is the same as the Central Difference Method (CDM), and possesses a broader scope of stability within the range of normal damping ratios of media. Comparing with the CDM, this explicit scheme requires no matrix factorization even if a non diagonal damping matrix is included. Therefore, the dynamic finite element equations can be integrated economically provided that the mass matrix is diagonal. To demonstrate the validity of the present scheme, three examples are provided. First, taking a single-degree-of-freedom system as an example, the results obtained by the proposed scheme are compared with the exact solutions. Second, the dynamic responses of half-space saturated porous media, subjected to a concentrated load pulse at the surface, are analyzed. Both examples show that the results obtained by the proposed scheme agree well with the analytical solutions. Finally, the dynamic responses of a plane strain plate due to a load pulse are analyzed, respectively, by the proposed procedure and the commercial code ABAQUS (both implicit module and explicit module), and the CPU costs are compared.     

ANALYSIS OF A DYNAMIC RESIDENTIAL LOCATION CHOICE MODEL WITH TRANSACTION COSTS*

ABSTRACT. This paper incorporates transaction costs in a residential location choice model. An individual's choice is assumed to be an outcome of a two-stage process: a decision to change, or to undertake a transaction and, conditional on a change occurring, a choice of a new alternative. The dynamic choice model is aggregated to yield a Markovian model of residential location patterns. It is shown that recent contributions to dynamical urban modeling correspond to special cases of the deterministic version of this model. The Markovian model is used in a theoretical analysis of the influence of transaction costs on the properties of the stationary state. The effects of residential mobility rates and of interdependencies among individuals, caused by supply-side and density-related interactions, are also analyzed. It is shown how these dynamical factors modify the stationary state, thereby demonstrating the type of errors which may occur with static models that omit them.     

The direction of migration: a dynamic general equilibrium model

A two-sector dynamic general equilibrium model is developed "to investigate the direction of migration in response to differing demographic and consumption demand behavior, as well as variations in production conditions." The model, which involves a rural sector and an urban sector, incorporates "returns to scale and the natural rate of sectoral population growth as important determinants of the direction of migration, in addition to price and income elasticities, and the sectoral technical change rate with which...previous studies dealt."     

人口的区位过程与城市的分形形态——关于城市生长的一个理论探讨

基于中心地假设,从城市人口分布的Sherratt模型和Naroll Bertalanffy的城乡人口异速生长关系出发导出关于人口分布空间动力学和城市扩展时空过程的数学模型,然后借助Batty等关于城市生长的DLA -DBM模拟结果证明人口的区位选择过程与城市的分形形态存在着内在关系。文章提出了关于区域人口运动和城市形态演化的三个基本原理:信息火商增原理、异速生长原理和Logistic发展原理。     

A Model to Relate the Size of the Central Business District to the Population of a City

A set of dynamic models of CBD growth are developed. They hypothesize that growth rates depend upon the population growth rate together with the increasing unwillingness of people to travel to the city center as city size increases. A prediction of the model is that absolute decreases in CBD size can occur associated simply with population growth rather than technological change as is usually postulated. The models are tested using retail sales data for the United States. Good predictions are generally found, especially when the unique CBD of New York City is removed from the data set. However, the model which has the greatest theoretical validity relative to central place theory does not have the best fit to the data. Implications of this are discussed, along with those of utilizing transformations in regression models.     

俄罗斯西伯利亚人口状况及其地理分析

西伯利亚人口问题一直非常尖锐,20世纪90年代以来更有不断恶化趋势。基于1989年和2002年俄罗斯人口普查资料,对西伯利亚人口状况及其动态变化进行了分析,得出了一些重要结论:1989-2002年间西伯利亚人口减少了95.9万,减少幅度达3.7%,远高于全俄1.5%的平均减幅;出生率降低、死亡率提高和人口大量迁移导致多数城市和区域人口持续减少,劳动力短缺问题日趋严重,制约了地区经济的发展;实现人口自然增长、调节人口迁移、引进合法移民乃西伯利亚人口和经济社会发展的当务之急。     

Explaining Gun Deaths: Gun Control,Mental Illness,and Policymaking in the American States

Seeking to test two commonly proposed solutions to gun deaths in the United States, we examine the extent to which (1) tougher gun control laws, (2) greater access to mental health services, and (3) a combination of both approaches affect the rate of gun deaths in American states. We find that tougher gun control laws, as well as a combination of both approaches, are associated with a lower overall rate of gun deaths, and with a lower rate of nonsuicide gun deaths, while only tougher gun control laws are significantly associated with a reduction in the rate of gun-related suicides. Our findings serve as an initial guide to policymakers seeking to reduce the rate of gun deaths in their states.     

On the Implications of a Stationary Urban Population For the Size Distribution of Cities

The paper analyzes the limiting case for a modified Yule-Simon model of city growth. The aim of the paper is primarily to reintroduce geographers to the notion of a closed system of cities, i.e., a system of cities where the aggregate population is stationary in size. The Yule-Simon model, while successful in dealing with the observed properties of open systems, is seen to break down for closed systems. Moreover, incorporating Simon's assumptions regarding intercity migration into the model produces implausible results. Also, the traditional approach of employing entropy-maximizing procedures assumes a certain pattern of intercity migration. This pattern, while not inherently implausible, does present features which are questionable. The authors conclude that an adequate theory for closed systems has yet to be developed.     

World Justice,Global Politics and Nation States: Three Ethico-Political Problems

This paper identifies three sets of problems of a specific ethico-political type, generated by the interrelationship between ethics and politics in the areas of world justice and global politics. One instance in which this interrelationship is tested is that of the conflict of duties and values as it appears in the particular domain of the relations amongst sovereign nation states as well as between them and other social groups. Following the general Introduction, the main body of the paper contains the following three sections. (1) Without elaborating on the detailed mechanics of Kant's theory of perpetual peace, Section II discusses criticisms against the Kantian version of world peace in the context of which the first problem is encountered. The problem identified here is the ambiguity as to whether the establishment of a federated kind of peaceful co-existence between sovereign nations depends on the moral improvement of mankind or whether it is the other way round--i.e. whether ethical progress is a necessary presupposition or, rather, a consequence of political peace. That is, what is here identified as worrying is that the direction of dependence is not clear in such a proposal. Furthermore, such an approach, when applied to certain cases of inter-state differences, yields a rather alarming result as to the de-politicization of national states (Section II.2). (2) Yet such a type of international federalism requires a certain, peculiar, kind of legal enforcement of order without recourse to a supra state. So a re-examination of the notion of a legal order in general is needed. Given these requirements, Section III moves on to discuss moral conflict from the standpoint of relativism as it appears in the ethical and in the legal spheres. The second of our problems, identified in this section, is that, before discussing world justice we must first acknowledge the special relation and asymmetry between ethical standards and legal rules required by such a world order. (3) Finally, Section IV asks whether, given the above two problems, it is possible to envisage theoretically the logical possibility of moral conflict-resolution by postulating unchanging and encompassing super-norms of conduct. These special norms, if possible, would be able to direct action unequivocally when confronted with ethical or other dilemmas of duties (involving equally valid but conflicting demands among sovereign nations). This is the third problem. The Conclusion offers an evaluation of the whole discussion. These three ethico-political problems are shown to be interrelated. The overall thrust of the discussion is that it points to a number of philosophical difficulties in understanding the changing role of national states in a globalized political, economic and cultural environment. Accordingly, such difficulties have repercussions for any moral criticism of issues of world justice and global politics. I must make clear at the outset, though, that the discussion does not concern international relations theories per se.     

Symmetry and symmetry breaking in nature

Abstract

According to Hermann Weyl and in the words of Richard P. Feynman, an object is symmetric if one can subject it to a certain operation and it appears exactly the same after the operation. This paper generalises this definition of symmetry of objects in space to symmetries of the laws of nature. Consequences of the laws of physics that follow from their symmetries are derived and compared with the experimental evidence. It is pointed out that unobservability is at the root of all symmetries in the natural sciences. Symmetries of the laws of physics can be hidden by asymmetries of realisable states that follow from a lack of symmetry in the ground state of the system. If that is the case, transitions from states that share the symmetries of the laws, to states in the neighbourhood of the ground state that do not, involve symmetry breaking through self-organisation.