88,548 research outputs found

    On the Weak Localization Principle of the Eigenfunction Expansions of the Laplace-Beltrami Operator by Riesz Method

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    In this paper we deal with the problems of the weak localization of the eigenfunction expansions related to Laplace-Beltrami operator on unit sphere. The conditions for weak localization of Fourier-Laplace series are investigated by comparing the Riesz and Cesaro methods of summation for eigenfunction expansions of the Laplace-Beltrami operator. It is shown that the weak localization principle for the integrable functions f(x) at the point x depends not only on behavior of the function around x but on the behavior of the function around diametrically opposite point \overline{x}

    Dynamic safety assessment of a nonlinear pumped-storage generating system in a transient process

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    This paper focuses on a pumped-storage generating system with a reversible Francis turbine and presents an innovative framework for safety assessment in an attempt to overcome their limitations. Thus the aim is to analyze the dynamic safety process and risk probability of the above nonlinear generating system. This study is carried out based on an existing pumped-storage power station. In this paper we show the dynamic safety evaluation process and risk probability of the nonlinear generating system using Fisher discriminant method. A comparison analysis for the safety assessment is performed between two different closing laws, namely the separate mode only to include a guide vane and the linkage mode that includes a guide vane and a ball valve. We find that the most unfavorable condition of the generating system occurs in the final stage of the load rejection transient process. It is also demonstrated that there is no risk to the generating system with the linkage mode but the risk probability of the separate mode is 6 percent. The results obtained are in good agreement with the actual operation of hydropower stations. The developed framework may not only be adopted for the applications of the pumped-storage generating system with a reversible Francis turbine but serves as the basis for the safety assessment of various engineering applications.National Natural Science Foundation of ChinaFundamental Research Funds for the Central UniversitiesScientific research funds of Northwest A&F UniversityScience Fund for Excellent Young Scholars from Northwest A&F University and Shaanxi Nova progra

    Return to education in Malaysia

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    The aim of this paper is to present a picture of return to education in Malaysia over the period from 1984 to 1997 based on earning equations model. The paper employed a set of data comprising micro-level data from the Household Income Survey (HIS) for several years during the period 1984 to 1997. The main finding of this paper is the changes in the wage differentials favouring the middle level of education (secondary level of education) workers. In general, the results show that the return for each level of qualification declined between 1984 and 1997,especially at the higher levels (diploma and degree). Interestingly, the return to education for females at low levels of education is higher than the return by males. However, at higher levels of qualification, especially for those with secondary and high school qualifications, males traditionally have a higher return compared to females workers. The results also indicated a significant gender differential, however the differences has fallen over time

    Frequency shifting approach towards textual transcription of heartbeat sounds

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    Auscultation is an approach for diagnosing many cardiovascular problems. Automatic analysis of heartbeat sounds and extraction of its audio features can assist physicians towards diagnosing diseases. Textual transcription allows recording a continuous heart sound stream using a text format which can be stored in very small memory in comparison with other audio formats. In addition, a text-based data allows applying indexing and searching techniques to access to the critical events. Hence, the transcribed heartbeat sounds provides useful information to monitor the behavior of a patient for the long duration of time. This paper proposes a frequency shifting method in order to improve the performance of the transcription. The main objective of this study is to transfer the heartbeat sounds to the music domain. The proposed technique is tested with 100 samples which were recorded from different heart diseases categories. The observed results show that, the proposed shifting method significantly improves the performance of the transcription

    The mazEF toxin-antitoxin system as a novel antibacterial target in Acinetobacter baumannii

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    Although analysis of toxin-antitoxin (TA) systems can be instructive, to date, there is no information on the prevalence and identity of TA systems based on a large panel of Acinetobacter baumannii clinical isolates. The aim of the current study was to screen for functional TA systems among clinical isolates of A. baumannii and to identify the systems' locations. For this purpose, we screened 85 A. baumannii isolates collected from different clinical sources for the presence of the mazEF, relBE and higBA TA genes. The results revealed that the genes coding for the mazEF TA system were commonly present in all clinical isolates of A. baumannii. Reverse transcriptase-polymerase chain reaction analysis showed that transcripts were produced in the clinical isolates. Our findings showed that TA genes are prevalent, harboured by chromosomes and transcribed within A. baumannii. Hence, activation of the toxin proteins in the mazEF TA system should be investigated further as an effective antibacterial strategy against this bacterium

    Ayer Hitam Forest (AHFR) from space using satellite remote sensing

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    There is a high demand to map and monitor the land use and assess their condition for ecological and economic reasons. Information on existing land and cover and their spatial distribution is a pre-requisite for any planning, development and management programme. In this study, Landsat TM data of 1998 were acquired over the AHFR and it's vicinity which covers an area more than 1, 300 ha. The objective of this paper is to map AHFR and assess the land cover of AHFR in 1998 as well as its surrounding area using remote sensing technology. Digital data processing and analysis were carried out using PCI/EASI PACE software, version 6.2 available in Faculty of Forestry, UPM. A false Colour Composite (FCC) of Landsat TM band 4-5-3 (R-G-B) was used in supervised classification using Maximum Likelihood Classifier (MLC). From a visual interpretation, several features of AHFR could be identified such as federal road, forest road, cleared land, built-up area, oil palm, water bodies and rubber plantation etc. Meanwhile, digital classification showed that seven land use types surrounding AHFR such as forest, secondary forest/shrubs, oil palm, rubber, built-up area, cleared land and water bodies could a easily be mapped out. The mean overall classification accuracy obtained is 86.08 percent with an average accuracy o] 85.64 percent. Satellite map of AHFR is found to be useful for the macro planning and management purposes especially on the Environmental Impact Assessment (EIA) if further development on the area is to be politicized

    Stock overreaction and financial bubbles: Evidence from Malaysia

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    This paper attempts to seek linkage between stock overreaction behaviour and financial bubbles in the Malaysian stock market. Monthly data over a period between January 1987 and December 2006 shows no clear evidence of stock overreaction behavior in the market. However, when the study split the analysis into two sub-periods, evidence of stock overreaction behaviour becomes significant in the pre-crisis sub-period, but there is no significant evidence of financial bubbles in the same sub-period. During the post crisis, evidence of stock overreaction seems to diminish, and evidence of financial bubbles however, is observed in the period. This study believes that evidence of bubbles observed in the Malaysian stock market in the post crisis period is due to stock overreaction that took place in the market prior to the crisis

    Photon signature analysis using template matching

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    We describe an approach to detect improvised explosive devices (IEDs) by using a template matching procedure. This approach relies on the signature due to backstreaming ? photons from various targets. In this work we have simulated cylindrical targets of aluminum, iron, copper, water and ammonium nitrate (nitrogen-rich fertilizer). We simulate 3.5 MeV source photons distributed on a plane inside a shielded area using Monte Carlo N-Particle (MCNP TM) code version 5 (V5). The 3.5 MeV source gamma rays yield 511 keV peaks due to pair production and scattered gamma rays. In this work, we simulate capture of those photons that backstream, after impinging on the target element, toward a NaI detector. The captured backstreamed photons are expected to produce a unique spectrum that will become part of a simple signal processing recognition system based on the template matching method. Different elements were simulated using different sets of random numbers in the Monte Carlo simulation. To date, the sum of absolute differences (SAD) method has been used to match the template. In the examples investigated, template matching was found to detect all elements correctly

    Water absorption and curing time performance of urea formaldehyde resin mixed with different amount phosphorous-based fire retardants.

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    The curing time and the properties of urea formaldehyde (UF) resin mixed with fire retardants, BP (mixture of boric acid, guanylurea phosphate and phosphoric acid), monoammonium phosphate (MAP) and diammonium phosphate (DAP) were studied. There were two amounts used, 8% w/w and 10% w/w. The curing time of the mixed resin was determined by using thermo oil at the temperature of 170ºC. Water absorption test and physical observations were done to evaluate the properties of the fire retardant-mixed resin. The non-fire retardant UF resin samples were used as controls. The solubility of MAP and DAP in the water at different weights also has been studied. The solubility test was done with and without the involvement of heat. The study showed that UF resin mixed with MAP and BP cured faster than DAP-mixed UF and control samples. The time taken for UF resin to mix with 10 % w/w and 8 % w/w MAP were 20 s and 28 s respectively. The time taken for UF resin mixed with 10 % and 8 % w/w DAP was slightly than the controls, which are 160 s and 150 s respectively. The time taken for UF resin mixed with 10 % w/w and 8 % w/w BP was 101 s and 92 s respectively.The curing time for control samples was 140 s respectively. MAP and DAP were shown to be highly soluble, as they took less than 1 minute to be dissolved in the water without heat, but BP took 30 minutes to be dissolved in the water without heat and less than 1 minute with heat. Water absorption test showed that the higher the amount of MAP, DAP and BP mixed into the resin, the higher would be the rate of water absorbed

    Linear-nonlinear stiffness responses of carbon fiber-reinforced polymer composite materials and structures: a numerical study

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    The stiffness response or load-deformation/displacement behavior is the most important mechanical behavior that frequently being utilized for validation of the mathematical-physical models representing the mechanical behavior of solid objects in numerical method, compared to actual experimental data. This numerical study aims to investigate the linear-nonlinear stiffness behavior of carbon fiber-reinforced polymer (CFRP) composites at material and structural levels, and its dependency to the sets of individual/group elastic and damage model parameters. In this regard, a validated constitutive damage model, elastic-damage properties as reference data, and simulation process, that account for elastic, yielding, and damage evolution, are considered in the finite element model development process. The linear-nonlinear stiffness responses of four cases are examined, including a unidirectional CFRP composite laminate (material level) under tensile load, and also three multidirectional composite structures under flexural loads. The result indicated a direct dependency of the stiffness response at the material level to the elastic properties. However, the stiffness behavior of the composite structures depends both on the structural configuration, geometry, lay-ups as well as the mechanical properties of the CFRP composite. The value of maximum reaction force and displacement of the composite structures, as well as the nonlinear response of the structures are highly dependent not only to the mechanical properties, but also to the geometry and the configuration of the structures
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