A new discretization method and its application to solve incompressible Navier–Stokes equations

 A new numerical method is presented in this paper. This method directly solves partial differential equations in the Cartesian coordinate system. It can be easily applied to solve irregular domain problems without introducing the coordinate transformation technique. The concept of the present method is different from the conventional discretization methods. Unlike the conventional numerical methods where the discrete form of the differential equation only involves mesh points inside the solution domain, the new discretization method reduces the differential equation into a discrete form which may involve some points outside the solution domain. The functional values at these points are computed by the approximate form of the solution along a vertical or horizontal line. This process is called extrapolation. The form of the solution along a line can be approximated by Lagrange interpolated polynomial using all the points on the line or by low order polynomial using 3 local points. In this paper, the proposed new discretization method is first validated by its application to solve sample linear and nonlinear differential equations. It is demonstrated that the present method can easily treat different solution domains without any additional programming work. Then the method is applied to simulate incompressible flows in a smooth expansion channel by solving Navier–Stokes equations. The numerical results obtained by the new discretization method agree very well with available data in the literature. All the numerical examples showed that the present method is very efficient, which is suitable for solving irregular domain problems. Received 19 July 2000     

The “LED-version” of the electron gun

We report on our progress to develop and optimize electron sources for practical applications. A simple fabrication process is introduced based on a wafer dicing saw and a wet chemical etch step without the need for a clean room. Due to the formation of crystal facets the samples show a homogeneous geometry throughout the array. Characterization techniques are developed to systematically compare various arrays. A very defined measurement procedure based on current controlled IV-sweeps as well as lifetime measurements at various currents is proposed. To investigate the current distribution in the array a commercial CMOS detector is used and shows the potential for in depth analysis of the arrays. Finally, a compact hermetically sealed housing is presented enabling electron generation in atmospheric pressure environments.     

The impact of a paper’s new combinations and new components on its citation

Scientometrics - A paper’s novelty enhances its impact and citation. In this paper, we examine two dimensions of a paper’s novelty: new combinations and new components. We define new...     

William Goffman's “Mathematical approach to the prediction of scientific discovery” and its application to logic, revisited

Based on the observation of regular “epidemic” recurrence of activity in the history of symbolic logic, a new wave of logic activity was predicted byGoffman in 1971 for the coming years. This prediction is examined and confirmed to some extent. It is shown, however, that the whole mathematics came in a wave-like fashion in the last 200 years, that the main fluctuations of logic were isochronic with the main fluctuations of mathematics, and, in addition, that fundamental logic contributions appeared on the top of the waves. After considering some problems of time-series analysis, relationships to business cycles of the Kondratiev, Kuznets, and Juglar types are discussed.     

The analysis of a solar‐assisted desiccant evaporative cooling system and its application

Abstract

The direct application of an evaporative cooling system is impractical in Taiwan due to local hot and humid weather conditions. In this study, a hybrid cooling system utilizing an evaporative cooler coupled with a chemical dehumidifier is investigated. The solid desiccant, or silica gel, which could be regenerated by solar energy, dehumidifies the incoming air while the evaporative cooler effectively cools it down to the indoor comfort condition. An optimal design approach including a sensitivity study was performed during the computer simulation process. A systematic result was obtained providing design information, such as the desiccant consumption rate and solar collector area needed for indoor comfort air‐conditioning.     

XPS and NEXAFS studies of VUV/O₃-treated aromatic polyurea and its application to microchip electrophoresis

In this study, the authors performed X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) studies of vacuum ultraviolet (VUV)/O?-treated aromatic polyurea films to investigate their treatment effects. XPS and NEXAFS spectra indicate that the benzene ring was cleaved after treatment and that carboxyl, hydroxyl, ketone and aldehyde groups were formed at the cleaved sites. The VUV/O?-treated polyurea film was applied to a polymethylmethacrylate (PMMA) microchip for microchip electrophoresis (MCE) of bovine serum albumin (BSA). Fast electro-osmotic mobility of 4.6×10(-4)?cm2/V/s as well as reduction of the BSA adhesion was achieved. This functional surface is useful for high-speed MCE analysis.     

Photoconductive properties of TiO2 films prepared by the sol–gel method and its application

The Photoconductive characteristics of TiO2 films prepared by the sol-gel method, and the photovoltaic characteristics fabricated with the resulting TiO2 film and phthalocyanine nickel (NiPc) are investigated. For a TiO2 film with hydroxypropyl cellulose (Hpc) heat treated at 500°C for 10 min, the relative sensitivity is about ten times higher than that without Hpc. A space-charge-limited current is observed in the dark current–voltage characteristic of the TiO2 film with Hpc. It is found that the TiO2 film with Hpc has a photosensitizing effect. The photovoltaic characteristics of TiO2(Hpc)/NiPc are as follows: the short-circuit current density, Jsc is 5.6×10-7 A cm-2, the open-circuit voltage, Voc is 0.24 V, the fill factor (F.F) is 0.64 and the power conversion efficiency, is 0.73. Furthermore, the carrier transport mechanisms of the TiO2(Hpc)/NiPc photovoltaic cell are discussed.     

The determination of the permeability of concrete to oxygen by the Cembureau method—a recommendation

A committee was set up in 1981 by the Cembureau Working Party on the Quality of Concrete with the following aims and objectives:

From product documentation to a ‘method prototype’ and standard times: a new technique for complex manual assembly

This paper suggests a new technique to facilitate consistent transition between planning and production stages of small lots of complex products (in quantities that do not justify full automation). Despite the usage of modern approaches such as design for assembly and design for manufacturing the typical product planning ends up before production planning begins, instead of having a unified seamless planning process. This paper presents a new three stage technique to fill the gap between product planning and production. The paper shows how to generate a rigorous production plan by: (1) extending the Bill-of-Materials to include additional required information, (2) constructing an assembly ‘method prototype’ and (3) using the ‘method prototype’ to calculate time standards for executing the assembly. A case study illustrates the proposed technique.     

The application software of the CERN PS accelerator controls system — analysis of its cost and resources

The CERN PS accelerators have evolved into one of the world's most sophisticated high energy physics facility. The variety of beams and their high repetition rate means that a most sophisticated controls system is required. This reflects on the application software. At the time of the completion of the new control system, nearly 1000 programs, amounting to around 450 000 lines of code, have been developed at the cost of approximately 120 man-years. The span of this software ranges from real-time application programs to special purpose development and management tools.This paper documents the cost, resources and production of this software project. These are analyzed in terms of the structure of the application software. Rules-of-thumb are suggested for estimating the required effort at various phases of the project and to define the implementation strategy.     

A new method for measuring the shape and size of the plastic zones around slit ends — the direct showing method

The direct showing method is a new method for measuring the plastic zones by using photoelastic coating technique. An experimental study for the plastic zones of four kinds of metal thin plate tensile specimens containing slits has been made by the method. Some typical experimental results and primary knowledge have been given in this paper. Non-symmetrical isochromatic fringe patterns and plastic zones were observed in annealed B3 thin steel plate specimens. This non-symmetrical phenomenon is well worth further research.     

Calorimetric and X-ray diffraction studies of mechanically activated α-PbF2 in relation to its conversion intoβ-PbF2

Calorimetric measurements and X-ray diffraction line-broadening analysis on-PbF₂ reveal that significant amounts of energy and microstrains can be introduced in the solid as a result of grinding. The stored energy is closely related to microstrains. Thermal annealing in the temperature range from 25 to 280° C relieves some of the strains and energy stored and leads to a sample characterized by residual microstrains and an energy stored whose amount depends on the initial mechanical treatment. The remaining stored energy at 295° C is the actual parameter acting on the transformation and is entirely liberated during this conversion. The initial temperature and heat of this transformation are very sensitive to the microstructure and they are 328° C and 1630 J mol^–1 for a strain-free material.     

A new method for measuring the neutron-induced background in BGO Compton-suppressed Ge detectors applied to in-beam γ-ray studies

A method for measuring the response of intrinsic Ge detectors equipped with bismuth germanate (BGO) anti-Compton shields to evaporation neutrons is presented.     

A new method for DEM simulation of dust-bearing granular flow – Modeling the effect of dust on the change in granule friction coefficient

The simulation of dust-bearing granular accumulation flow in the theoretical and practical aspects of the engineering field poses a significant challenge due to the massive computational requirements associated with cross-scale simulations. In this study, a novel approach is proposed to address this issue by developing a model that accounts for the impact of dust on granular flow through changes in the granule friction coefficient. Initially, the theoretical analysis was conducted to examine the effects of dust on granular flow. Subsequently, a method was developed to measure the equivalent friction coefficient of granules by combining theoretical analysis and experimental work. The proposed method was then employed to simulate the stability of a spherical granule pile in a drum influenced by dust content and compared against experimental results. The simulation results demonstrate agreement with the experimental results, indicating the feasibility of modeling the effect of dust on dust-bearing granular flow through the granule equivalent friction coefficient. The dust effect can be considered equivalent to a change in the granule friction coefficient, which facilitates the reduction of the computational load generated by the Discrete Element Method (DEM) method and enables cross-scale simulations.     

On the application of the “rule of mixture” to microhardness of complex polymer systems containing a soft component and/or phase

The main goal of this work is to find a reasonable explanation for the frequently reported drastic deviations from the “rule of mixture” applied for calculation of the overall microhardness, H, of complex polymer systems comprising a soft, (with a glass transition, T _g, or melting, T _m, temperatures below room temperature) component and/or phase. According to the common practice, the contribution to H of the soft component and/or phase, H ^s, is considered as H ^s = 0, which results in extremely large differences between the measured and calculated H values for systems comprising more than 20–25 wt% soft component and/or phase. For such systems a different deformation mechanism during indentation process is postulated, namely “floating” of the solid particles in the soft component and/or phase, in addition to their plastic deformation. The contribution of the “floating effect” to the overall H is accounted for by the empirically derived relationship H = 1.97 T _g−571. Using the reported data on H and T _g for homopolymers, blockcopolymers and blends, the H values are recalculated and a good agreement with the experimentally measured values is found. A modified additivity law is suggested, which contains a term accounting for the contribution of the soft component and/or phase to the overall microhardness via the relationship between H and T _g; its application results in much smaller differences between the measured and calculated H values. On leave from Laboratory on Polymers, University of Sofia, 1126 Sofia, Bulgaria.