Collaborating freight forwarding enterprises

The paper presents a model for the collaboration among independent freight forwarding entities. In the modern highly competitive transportation branch freight forwarders reduce their fulfillment costs by exploiting different execution modes (self-fulfillment and subcontraction). For self-fulfillment they use their own vehicles to execute the requests and for subcontracting they forward the orders to external freight carriers. Further enhancement of competitiveness can be achieved if the freight forwarders cooperate in coalitions in order to balance their request portfolios. Participation in such a coalition gains additional profit for the entire coalition and for each participant, therefore reinforcing the market position of the partners. The integrated operational transport problem as well as existing collaboration approaches are introduced. The presented model for collaboration is based on theoretical foundations in the field of combinatorial auctions and operational research game theory. It is applicable for coalitions of freight forwarders, especially for the collaboration of Profit Centres within large freight forwarding companies. The proposed theoretical approach and the presented collaboration model are suitable for a coalition of freight forwarding companies with nearly similar potential on the market.     

An analytical model to determine the ultimate load on masonry arch bridges.

This paper proposes an analytical elasto–plastic model to describe the behavior of arches. The modeling is carried out using the equations of (i) horizontal equilibrium, (ii) vertical equilibrium and (iii) equilibrium of moments. The latter equations of equilibrium are ordinary differential equations which can easily be solved by adding boundary conditions, imposing restrictions on the horizontal and vertical movement and on the rotation in the abutments of the arch. For masonry arches, including material properties allowing the occurrence of cracks and the subsequent formation of hinges is required. The latter theory has been implemented in a computer program (Matlab), offering numerical simulations. The software was used to illustrate two case-studies, i.e., the assessment of an arch loaded with a vertical point load and one with a horizontal point load.     

A structural model of science achievement and attitude: An extension to high school.

A previous structural model of Walberg's theory of educational productivity (A. J. Reynolds and H. J. Walberg, 1991) was tested with a national probability sample of 2,535 10th graders for science achievement and attitude. Using data from the Longitudinal Study of American Youth, a 3-wave design incorporated information from students, teachers, and parents. Results indicate that a revised mediated-effects model fit the data best and accounted for substantial variance in Grade 11 science achievement (56%) and attitude (44%). The variables prior achievement, home environment, exposure to mass media through reading, and instructional time had the greatest total effects on science achievement. Prior attitude, home environment, motivation, and prior achievement made the greatest total contributions to science attitude. Although there were different weightings of the factors between the present study and Reynolds and Walberg (1991), both studies support a mediated-effects model of educational productivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rethinking the validity of psychological assessment.

Comments on S. Messick's (see record 1996-10004-001) paper on the validity of psychological assessment. The author discusses the indeterminacy of construct validity, the overzealous scuttling of criterion-relevant validity, the drift away from measure-centered validity, and the need for reestablishing multiple forms of validity. The comments are aimed at combating an air of complacency fostered by the introduction and mounting elaboration of the concept of construct validation. The author concludes that the intractability of psychological measurement needs to be confronted more directly. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Policy Analysis, Peer Reviewed: Evaluation of Bioaccumulation Factors in Regulating Metals

Regulations.     

The computer — a new tool for visual art

The article points out some new possibilities for using computers as an instrument for visual art, especially stressing the mathematical method of picture synthesis. It is illustrated with results of recent computer art by Herbert W. Franke and Horst Helbig.