The evaluation of electrolytically polished surfaces

A new method for the evalution of the quality of electropolished suraces is presented. A theoretical analysis was carried out and the results were confirmed by experiment. The relevance of the slope of the surface profile to the evaluation of surface quality was determined. Electropolishing processes affect to a much greater extent the reduction of the standard deviation of the slope than the reduction of the standard deviation ordinates.     

The first metro line in Warsaw

Construction on the first metro line in Warsaw began in 1983. The total length of the line will be 23 km, with an average distance between stations of 1 km. According to plans, the first 12 km of the line will be in service in 1990, and the total line will be completed in 1994. The line will run at relatively shallow depths, with an average of 9 m between track and ground level. The metro facilities will be constructed in Quarternary soil formations, mainly by the cut-and-cover method. The paper describes the development of the plans and gives detailed information about the design.     

Passive dosimeters — an approach to atmospheric pollutants analysis

The paper presents a review of the passive methods of sampling of inorganic and organic atmospheric pollutants. The importance of these methods, enabling both evaluation of workplace personal exposure and area monitoring, has been discussed. Commercially available personal monitors, as well as devices under further laboratory investigation have been described. Fundamental theoretical equations describing the operation of both passive devices based on diffusion through an air gap to a layer of collective media and passive devices with permeable membranes have been put forward. Presented and discussed herein are papers dealing with the investigation of the applicability of these devices under laboratory and field conditions, as well as with the comparison of passive monitors with active devices (e.g., detector tubes).     

Effect of discontinuity size on the energy absorption of structural steel beam profiles

The effect of size discontinuities on the energy absorption performance of squared steel profiles is reported. Finite element simulations of the compression strength of profiles with discontinuities, placed at mid span of the steel profiles in two opposite walls, were carried out. Circular and elliptical forms of the discontinuities were evaluated. Energy absorption capabilities were increased up to 12.54% and the peak load value was decreased to 10.52% with respect to the same structure without discontinuities. A buckling effect is observed in structures with discontinuities, which contributes to reducing the peak value while the energy absorbing characteristics decrease.     

Mixed integer programming for scheduling surface mount technology lines

This paper presents new mixed integer programming formulations for blocking scheduling of SMT (Surface Mount Technology) lines for printed wiring board assembly. The SMT line consists of several processing stages in series, separated by finite intermediate buffers, where each stage has one or more identical parallel machines. A board that has completed processing on a machine may remain there and block the machine until a downstream machine becomes available for processing. The objective is to determine an assembly schedule for a mix of board types so as to complete the boards in a minimum time. Scheduling with continuous or with limited machine availability is considered. Numerical examples and some computational results are presented to illustrate applications of the models proposed.     

A high duty-cycle,multi-channel,power amplifier for high-resolution radiofrequency encoded magnetic resonance imaging

Magnetic Resonance Materials in Physics, Biology and Medicine - A radiofrequency (RF) power amplifier is an essential component of any magnetic resonance imaging (MRI) system. Unfortunately, no...     

Photoreactivity of Hair Melanin from Different Skin Phototypes—Contribution of Melanin Subunits to the Pigments Photoreactive Properties

Photoreactivity of melanin has become a major focus of research due to the postulated involvement of the pigment in UVA-induced melanoma. However, most of the hitherto studies were carried out using synthetic melanin models. Thus, photoreactivity of natural melanins is yet to be systematically analyzed. Here, we examined the photoreactive properties of natural melanins isolated from hair samples obtained from donors of different skin phototypes (I, II, III, and V). X-band and W-band electron paramagnetic resonance (EPR) spectroscopy was used to examine the paramagnetic properties of the pigments. Alkaline hydrogen peroxide degradation and hydroiodic acid hydrolysis were used to determine the chemical composition of the melanins. EPR oximetry and spin trapping were used to examine the oxygen photoconsumption and photo-induced formation of superoxide anion, and time-resolved near infrared phosphorescence was employed to determine the singlet oxygen photogeneration by the melanins. The efficiency of superoxide and singlet oxygen photogeneration was related to the chemical composition of the studied melanins. Melanins from blond and chestnut hair (phototypes II and III) exhibited highest photoreactivity of all examined pigments. Moreover, melanins of these phototypes showed highest quantum efficiency of singlet oxygen photogeneration at 332 nm and 365 nm supporting the postulate of the pigment contribution in UVA-induced melanoma.     

Influence of Induction Motor Design Data on Effects of Cage Asymmetry

The purpose of this paper is to analyze influence of design data on a component （1 - 2s）~ in stator currents of induction motors, mainly used for cage fault diagnosis. This paper shows that such an approach does not always lead to a correct outcome. The considerations are based on a ＂classical＂ model of induction motors extended to cage asymmetry by introducing cage asymmetry factors ko~ and ka. It has been found that in order to estimate the level of the component （1 - 2s）7~, it is enough to know the pole-pair number ＂p＂ and the number of rotor slots ＂N＂. The main objective of the paper is to provide engineers with simple qualitative prediction of effects due to cage faults for various motors when information on design data is very limited.     

A global coal production forecast with multi-Hubbert cycle analysis

Based on economic and policy considerations that appear to be unconstrained by geophysics, the Intergovernmental Panel on Climate Change (IPCC) generated forty carbon production and emissions scenarios. In this paper, we develop a base-case scenario for global coal production based on the physical multi-cycle Hubbert analysis of historical production data. Areas with large resources but little production history, such as Alaska and the Russian Far East, are treated as sensitivities on top of this base-case, producing an additional 125 Gt of coal. The value of this approach is that it provides a reality check on the magnitude of carbon emissions in a business-as-usual (BAU) scenario. The resulting base-case is significantly below 36 of the 40 carbon emission scenarios from the IPCC. The global peak of coal production from existing coalfields is predicted to occur close to the year 2011. The peak coal production rate is 160 EJ/y, and the peak carbon emissions from coal burning are 4.0 Gt C (15 Gt CO₂) per year. After 2011, the production rates of coal and CO₂ decline, reaching 1990 levels by the year 2037, and reaching 50% of the peak value in the year 2047. It is unlikely that future mines will reverse the trend predicted in this BAU scenario.     

Adapting the pinch point analysis to improve the ORC design process

Pinch point analysis can be adapted so as to assist in the early stages of designing the Organic Rankine Cycle (ORC) systems. Typically used in determining the working parameters of heat exchangers, it can be employed to improve the heat fitting between the source of heat and the working fluids of the ORC system. To attain the parametric match, an algorithm was built enabling quick estimation of the possible heat reception by the specific working fluid. In effect, it is now possible to attain quick estimation of the upper limits of the electrical power output and the overall conversion efficiency. This paper outlines the developed algorithm and the range of its possible applications and presents the results of sample calculations. Copyright © 2013 John Wiley & Sons, Ltd.