Problems of the Dual in Soqotri

Problems of the Dual in Soqotripublished or submitted for publicationis peer reviewe

Calling the lp_solve Linear Program Software from R, S-PLUS and Excel

We present a link that allows R, S-PLUS and Excel to call the functions in the lp_solve system. lp_solve is free software (licensed under the GNU Lesser GPL) that solves linear and mixed integer linear programs of moderate size (on the order of 10,000 variables and 50,000 constraints). R does not include this ability (though two add-on packages offer linear programs without integer variables), while S-PLUS users need to pay extra for the NuOPT library in order to solve these problems. Our link manages the interface between these statistical packages and lp_solve. Excel has a built-in add-in named Solver that is capable of solving mixed integer programs, but only with fewer than 200 variables. This link allows Excel users to handle substantially larger problems at no extra cost. While our primary concern has been the Windows operating system, the package has been tested on some Unix-type systems as well.

An Excel Add-In for Statistical Process Control Charts

Statistical process control (SPC) descibes a widely-used set of approaches used to detect shifts in processes in, for example, manufacturing. Among these are "control charts". Control charts and other SPC techniques have been in use since at least the'50s, and, because they are comparatively unsophisticated, are often used by management or operations personnel without formal statistical training. These personnel will often have experience with the popular spreadsheet program Excel, but may have less training on a mainstream statistical package. Base Excel does not provide the ability to draw control charts directly, although add-ins for that purpose are available for purchase. We present a free add-in for Excel that draws the most common sorts of control charts. It follows the development of the textbook of Montgomery (2005), so it may be well-suited for instructional purposes.

The Speech Styles of a Pastor in a Public Anda Youth Service

This researched focused on the observation about the speech styles used by a Pastor in delivering the sermon in a Public Service and a Youth Service. In order to know the characteristics of speech styles used by the Pastor, this writer chooses the main theory of formal and informal Bahasa Indonesia as proposed by Tampubolon (1978) which are supported by the theory of lexical and grammatical characteristics for standard Bahasa Indonesia by Kridalaksana (1989). As results, this research shows that the Pastor mostly used informal style in both services because she wanted to more get closer with the Public and Youth Service congregation. However, the Pastor tended to use more formal style to the Public Service congregation than to the Youth Service congregation because she knew exactly that the Youth Service was supposed to be given more attention and clearer explanation about the message given

Spacetime approach to force-free magnetospheres

Force-Free Electrodynamics (FFE) describes magnetically dominated relativistic plasma via non-linear equations for the electromagnetic field alone. Such plasma is thought to play a key role in the physics of pulsars and active black holes. Despite its simple covariant formulation, FFE has primarily been studied in 3+1 frameworks, where spacetime is split into space and time. In this article we systematically develop the theory of force-free magnetospheres taking a spacetime perspective. Using a suite of spacetime tools and techniques (notably exterior calculus) we cover 1) the basics of the theory, 2) exact solutions that demonstrate the extraction and transport of the rotational energy of a compact object (in the case of a black hole, the Blandford-Znajek mechanism), 3) the behavior of current sheets, 4) the general theory of stationary, axisymmetric magnetospheres and 5) general properties of pulsar and black hole magnetospheres. We thereby synthesize, clarify and generalize known aspects of the physics of force-free magnetospheres, while also introducing several new results.Comment: v2: numerous improvements; v3: further improvements, matches published versio