AN ALGORITHM FOR THE SPATIAL PRICE EQUILIBRIUM PROBLEM ON A GENERAL NETWORK IN THE SPACE OF THE PATH FLOWS*

ABSTRACT. The spatial price equilibrium on a general network may be formulated as a nonlinear-cost mathematical programming problem with simple constraints, when the decision variables are the path flows. The solution of this problem is difficult due to the very large number of variables (paths) and the impracticality of generating all the paths from all the origins to all the destinations. In this paper, we develop a Gauss-Seidel-Newton Projection algorithm and combine it with a restriction strategy. That makes it unnecessary to generate a priori all the paths. This algorithm may be further improved by exploiting the equivalence between the spatial price equilibrium on a general network and the network equilibrium. Computational results that we present in this paper demonstrate the efficiency of the proposed solution algorithms.     

AN ALGORITHM FOR COMPUTING ISODUCTILE RESPONSE SPECTRA

The computation of constant ductility (or isoductile) response spectra for single-degree-of-freedom systems can require numerous individual response history analyses. Recognising that the same ductility response may be obtained for different strength oscillators of a given period, greater computational effort is required to reduce the possibility that a desired solution is not overlooked. Even a single solution may not exist if a local discontinuity in the strength-ductility relationship coincides with the desired value of ductility. This paper describes a two-phase algorithm to identify the highest strength solution for which the corresponding ductility equals (or does not exceed) the desired ductility. The first phase adopts a “check-reject” approach to reject intervals of strength where the possibility of unidentified higher-strength solutions is considered to be remote, thereby narrowing the strength interval in which the solution will be found. The second phase identifies a solution within this interval as rapidly as possible using a bisection approach. The algorithm is implemented in the USEE software program. The efficiency and accuracy of the algorithm are demonstrated by comparison to results obtained with other software programs.     

关于建设我国北方集装箱枢纽港问题的思考

集装箱运输是世界交通运输发展的趋势,在这一进程中,集装箱枢纽港与支线港的形成与分化日益明显,它是集装箱运输规模效益发展的必然结果。随着我国集装箱运量的增加,合量布局我国集装箱枢纽港和支线港的问题日益突出,目前,香港和上海作为我国南方和中部集装箱枢纽港的地位已确立,而北方形成了大连、青岛、天津三足鼎立格局,合理布局北方集装箱枢纽港是我国北方各省区社会经济发展的客观要求。文章深入分析了北方主要集装箱港口的现状和潜力,并提出了我国北方集装箱枢纽港未来的发展战略。     

AN ECONOMIC INTERPRETATION OF KUHN'S DUAL FOR THE STEINER-WEBER PROBLEM A NOTE*

In this paper, we given an economic interpretation of Kuhn's dual of the Steiner-Weber problem. It depends essentially on the notion that different transportation systems arerelevant for the primal and the dual. Moreover, the Euclidean metric underlies the interpretation of the primal, the block one that of the dual.     

CENTER POINTS, EQUILIBRIUM POSITIONS, AND THE OBNOXIOUS LOCATION PROBLEM

ABSTRACT. Real variable analysis has een used to great benefit in a variety of classical problems in location theory. In this paper we explore basic complex variable techniques in one formulation of the obnoxious location problem. A general definition of center points is first given and used to formulate several alternate versions of the obnoxious location problem. A logarithmic transformation is then used to demonstrate some equivalences between these families of distinct location problems (defined via center points). A prototype logarithmic potential function which results from this formulation is then investigated, and it is demonstrated that the extremal solutions with this objective reside on the boundary of its domain of definition. An application using zero- and one-dimensional centers is discussed, and a generalization to the spatial obnoxious problem is also briefly examined. We define a zero-dimensional center as a critical point of the logarithmic potential function, and it is shown that these centers are equivalent to the solutions of the Complex Moment Problem.     

AN EFFICIENT APPROACH FOR PUSHOVER ANALYSIS OF UNREINFORCED MASONRY (URM) STRUCTURES

This article presents a new method for the calculation of the moment-rotation (M-θ) curves of URM elements using an analytical phenomenogical closed form solution for flexure, combined with a hybrid analytical-statistical model for shear. These are used to define the constitutive law of nonlinear springs located at the areas of lumped inelasticity of an equivalent frame model. The method constitutes an analytical design/assessment tool, to be used by the practicing engineer, for the pushover analysis of URM buildings. The proposed procedure is implemented as a pre-processor to a commercial nonlinear software codes capable of static pushover analysis using the point hinge approach.     

MARKET CAPTURE BY TWO COMPETITORS: THE PREEMPTIVE LOCATION PROBLEM*

ABSTRACT. We consider a location and allocation game for two competitor firms, A and B, that each seek to locate p facilities in a network. A market is captured by a particular firm if that market's closest facility belongs to that firm rather than a competitor. The question is as follows: Firm A wants to locate its p facilities so that B, which enters also with p facilities after Firm A has located its facilities, will capture the minimum market value possible. That is, Firm A wishes to preempt Firm B in its bid to capture market share to the maximum extent possible. A model is presented that addresses this issue, together with solution methods and computing times.     

南极旅游开发与设想

本文提出,随着我国南极长城站和中山站的建立、以及"极地号"和"雪龙号"破冰船的购置,更由于人民生活水平的逐步提高,我国开发南极旅游的时机已经到来。本文认为与低层次的物质享受相比,南极旅游更有助于促进国民素质提高和全国主义、国际主义精神的培养。本文对南极旅游资源作了评价.划分出南极半岛等4个旅游区。本文构思了我国未来南极旅游组织实施的规划和设想,提出可先开辟南极半岛旅游区和环南极旅行两条旅游线路,沿途可开展海外观光、远洋考察和远洋捕捞业,以促进我国旅游业、南大洋考察和远洋捕捞运输业的全面发展。