A Brane World in an Arbitrary Number of Dimensions without Z_2 Symmetry

We consider a brane world in an arbitrary number of dimensions without Z_2 symmetry and derive the effective Einstein equation on the brane, where its right-hand side is given by the matter on the brane and the curvature in the bulk. This is achieved by first deriving the junction conditions for a non-Z_2 symmetric brane and second solving the Gauss equation, which relates the mean extrinsic curvature of the brane to the curvature in the bulk, with respect to the mean extrinsic curvature. The latter corresponds to formulating an explicit junction condition on the mean of the extrinsic curvature, analogue to the Israel junction condition for the jump of the extrinsic curvature. We find that there appears a new type of an effective anisotropic fluid on the right-hand side of the effective Einstein equation due to the fact that there is no Z_2 symmetry. The derived equation is a basic equation for the study of Kaluza-Klein brane worlds in which some dimensions on the brane are compactified or for a regularization scheme for a higher codimension brane world, where the Kaluza-Klein compactification on the brane is regarded as a means to regularize the uncontrollable spacetime singularity caused by the higher codimension brane.Comment: 12 pages, no figure, PTPtex. Typos corrected and references updated. The title has been slightly modified. Final version to be published in Prog. Theor. Phy

Hamiltonian formulation of f(Riemann) theories of gravity

We present a canonical formulation of gravity theories whose Lagrangian is an arbitrary function of the Riemann tensor. Our approach allows a unified treatment of various subcases and an easy identification of the degrees of freedom of the theory.Comment: 12 pages, REVTeX

Visualization of Global Trade-Offs in Aerodynamic Problems by ARMOGAs

Trade-offs is one of important elements for engineering design problems characterized by multiple conflicting design objectives to be simultaneously improved. In many design problems such as aerodynamic design, due to computational reasons, only a limited number of evaluations can be allowed for industrial use. Efficient MOEAs, Adaptive Range Multi-Objective Genetic Algorithms (ARMOGAs), to identify trade-offs using a small number of function evaluations have been developed. In this study, ARMOGAs are applied to aerodynamic designs problems to identify trade-offs efficiently. In addition to identify trade-offs, trade-off analysis is also important to obtain useful knowledge about the design problem. To analyze the high-dimensional data of aerodynamic optimization problem, Self-Organizing Maps are applied to understand the trade-offs

Risk Management in an Electricity Transmission Project between Iceland and the UK

In recent years, energy is transmitted in the form of electricity in some parts of the world. Furthermore, all member states of the European Union (EU) have a legal obligation to ensure that 20% of their community energy consumption comes from renewable sources by 2020. Therefore, there is a great demand for electricity derived from renewable sources while at the same time there are non-negligible risks in electricity transmission between nations. Addressing these risks is thus of great importance. Under such circumstances, the national power company in Iceland is investigating the possibility of installing a series of 800–1,200 MW high-voltage direct current (HVDC) submarine power cables of over a span of 1,000 km in an effort to deliver more than 5 TWh of renewable electricity to the UK each year. In order to accelerate this project, the company must employ measures of risk prevention and/or mitigation. This study aims at revealing the potential risks of this project (called IceLink) using qualitative analysis. Thus far, there seems to be very few similar studies concerning the project, yet the results are significant from the viewpoint of risk management. Based on the results of interviews and a survey of the literature, we identify three major potential risks of the project: regulatory risk, political risk, and financial risk. In this regard, we classify risk in the same manner as a previous research. Subsequently, we suggest ways to manage these risks and as a result, we find that many of these measures can be introduced even under the present circumstances

Application of artificial pneumatic rubber muscles to a human friendly robot

When robots work together with a human or contact with a human body directly in such as a medical welfare field, in order to avoid an accident from crash and so on, a flexibility is required for the robot. The purpose of this study is to realize a safe mechanism for a human-friendly robot. In this paper, the structure and the fundamental characteristics of a pneumatic rubber muscle and soft mechanism are described, and then the structure and the fundamental operation of the developed soft hand are shown. Finally, the shaking hands is discussed as an example of force communication tasks between a robot and a human. </p