977 research outputs found

    Effects of Length and Diameter of Open-Ended Coaxial Sensor on its Reflection Coefficient

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    This paper presents a calibration technique for a coaxial sensor using a transmission signal approach. The sensor was fabricated from commercially available RG402/U and RG405/U semi-rigid coaxial cable. The length of the coaxial sensor was correlated with the attenuation and standing wave inside the coaxial line. The functions of multiple reflection amplitude and tolerance length with respect to the actual length of coaxial line were empirically formulated using regression analysis. The tolerances and the undesired standing wave which occurs along the coaxial line were analyzed in detai

    In situ imaging of microstructure formation in electronic interconnections

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    The development of microstructure during melting, reactive wetting and solidification of solder pastes on Cu-plated printed circuit boards has been studied by synchrotron radiography. Using Sn-3.0Ag-0.5Cu/Cu and Sn-0.7Cu/Cu as examples, we show that the interfacial Cu6Sn5 layer is present within 0.05 s of wetting, and explore the kinetics of flux void formation at the interface between the liquid and the Cu6Sn5 layer. Quantification of the nucleation locations and anisotropic growth kinetics of primary Cu6Sn5 crystals reveals a competition between the nucleation of Cu6Sn5 in the liquid versus growth of Cu6Sn5 from the existing Cu6Sn5 layer. Direct imaging confirms that the β-Sn nucleates at/near the Cu6Sn5 layer in Sn-3.0Ag-0.5Cu/Cu joints

    A new multistage lattice vector quantization with adaptive subband thresholding for image compression

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    Lattice vector quantization (LVQ) reduces coding complexity and computation due to its regular structure. A new multistage LVQ (MLVQ) using an adaptive subband thresholding technique is presented and applied to image compression. The technique concentrates on reducing the quantization error of the quantized vectors by "blowing out" the residual quantization errors with an LVQ scale factor. The significant coefficients of each subband are identified using an optimum adaptive thresholding scheme for each subband. A variable length coding procedure using Golomb codes is used to compress the codebook index which produces a very efficient and fast technique for entropy coding. Experimental results using the MLVQ are shown to be significantly better than JPEG 2000 and the recent VQ techniques for various test images

    The effects of Mg addition on the microstructure and mechanical properties of thixoformed Al–5%Si–Cu alloys

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    AbstractIn this study, the effects of different amounts of magnesium (Mg) on the microstructures and tensile properties of thixoformed Al–5%Si–Cu alloys were investigated. Three different alloys containing various amounts of Mg (0.5, 0.8 and 1.2wt%) were prepared through the cooling slope casting technique, before they were thixoformed using a compression press. Several of the thixoformed samples were then treated with a T6 heat treatment, that is, solution treatment at 525°C for 8h, quenching in warm water at 60°C, followed by aging at 155°C for 4h. All of the samples were then characterised by optical microscopy (OM), scanning electron microscopy (SEM) energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as by tensile tests. The results revealed that magnesium was able to refine the size of α-Al globules and the eutectic silicon in the samples. It was also observed that a compact π-Al9FeMg3Si5 phase was formed when the magnesium content was 0.8wt% and 1.2wt%. The mechanical properties of the thixoformed alloys improved significantly after the T6 heat treatment. The highest attainment was recorded by the latter alloy (i.e. with 1.2wt%Mg) with its ultimate tensile strength (UTS) as high as 306MPa, yield strength (YS), 264MPa, and elongation to fracture of 1.8%. The fracture of thixoformed alloy with a low Mg content (0.5wt%) showed a combination of dimple and cleavage fracture, whereas in the alloy that contained the highest Mg content (1.2wt%), cleavage fracture was observed

    Non-Predictive Multistage Lattice Vector Quantization Video Coding

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    Supplementary feeding increases nestling feather corticosterone early in the breeding season in house sparrows

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    Several studies on birds have proposed that a lack of invertebrate prey in urbanized areas could be the main cause for generally lower levels of breeding success compared to rural habitats. Previous work on house sparrows Passer domesticus found that supplemental feeding in urbanized areas increased breeding success but did not contribute to population growth. Here, we hypothesize that supplementary feeding allows house sparrows to achieve higher breeding success but at the cost of lower nestling quality. As abundant food supplies may permit both high-and low-quality nestlings to survive, we also predict that within-brood variation in proxies of nestling quality would be larger for supplemental food broods than for unfed broods. As proxies of nestling quality, we considered feather corticosterone (CORTf), body condition (scaled mass index, SMI), and tarsus-based fluctuating asymmetry (FA). Our hypothesis was only partially supported as we did not find an overall effect of food supplementation on FA or SMI. Rather, food supplementation affected nestling phenotype only early in the breeding season in terms of elevated CORTf levels and a tendency for more variable within-brood CORTf and FA. Early food supplemented nests therefore seemed to include at least some nestlings that faced increased stressors during development, possibly due to harsher environmental (e.g., related to food and temperature) conditions early in the breeding season that would increase sibling competition, especially in larger broods. The fact that CORTf was positively, rather than inversely, related to nestling SMI further suggests that factors influencing CORTf and SMI are likely operating over different periods or, alternatively, that nestlings in good nutritional condition also invest in high-quality feathers

    Study: The Performance FFT and Wavelet Packet of OFDM Systems from through Demonstrated Numerical Examples

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    A major goal of the next-generation wireless communication systems is the development of a reliable highspeed wireless communication system that supports high user mobility. Multi-Carrier Modulation (MCM) technique is an attractive approach for high-speed digital radio communication systems in order to achieve a high spectral efficiency and to combat the frequency selectivity of the channel. Orthogonal frequency division multiplexing (OFDM) is a kind of MCM techniques. As proven by the success of OFDM, multicarrier modulation has been recognized as an efficient solution for wireless communications. Waveform bases other than sine functions could similarly be used for multicarrier systems in order to provide an alternative to OFDM. Wavelet Packet Modulation (WPM) was proposed as one of the multicarrier transmission methods like OFDM. Since it is a multicarrier transmission method. In this paper, we study the performance of FFT-OFDM and wavelet Packet (WP)- OFDM from through demonstrated numerical examples, and evaluation of FFT-OFDM and DWPT-OFDM in AWGN channel , Flat fading channel and Selective Fading Channel

    Students' Interest and Usefulness of Fieldwork Approaches to History

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    It is very exciting that history in the Integrated Cmriculum forSecondary School (ICSS) has been included as one of the core subjects inthe lower and upper secondary levels of Malaysian schools. These subjectsare officially included in the time table of the ordinary, religious, science,vocational and technical schools in the country. One of the most importantand effective methods introduced in the teaching and learning of historyis a fieldwork approaches, particularly a site visit. Since history is acompulsory subject, it is necessary to study and analyse the ICSS historycurriculum to see i f it really could achieve the objectives of the syllabus,successfully imparting knowledge and develop interest among studentsin the subject. The study involved about eight hundred students of selectedsecondary schools in the states of Perak and Terengganu. Instr\imentsused were questionnaire and interview which were conducted with theselected respondents. The analysis of the study were presented inpercentage by using six Likert scale responses. The study shows that historyfieldwork contain many usefulness such as to develop, spark/ stimulate,motivate, investigate, prove, gain social experience, social sldUs, buildteacher-student relation, teaching-learning method, and fulfil NationalCurriculum. Moreover, the effective used of history fieldwork can enhancestudent interest in developing the country towards the advancement of'first class mind' of human capital of Malaysian. It is hoped that the findingwill enlighten teachers and students in the learning of history in the ICSStowards achieving the stipulated aspiration, especially 1-Malaysia

    Regionalization and harmonization in TVET

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    A transversal skill is one of the skills needed in every type of workplace setting. There is limited information about the perceptions of which transferable skills are needed in the workplace. The objective of this study is to explore the transferable skills among students and lecturers in TVET higher learning institutions in Indonesia and Malaysia. In the present study, transferable skills consist of communication skills, collaboration skills, problem-solving skills, entrepreneurship, and learning to learn skills. A qualitative research was conducted using survey. The five Likert scale questionnaire was distributed to lecturers and students from selected Malaysian and Indonesian universities who have bachelor program in engineering. Based on the analysis outcomes, it is clearly shown that Malaysian university engineering students yielded significantly higher scores on the perceptions of transferable skill acquisition in all measured components compared to their counterparts in Indonesia. Similar patterns of data distribution have been observed in Malaysian and Indonesian engineering students. Based on the lecturers’ perception, Malaysian and Indonesian Engineering Lecturers have comparable perceptions in the aspects of problem solving skills and entrepreneurship skills. In contrast, Malaysian university engineering lecturers gained significantly higher scores on the perception of communication skill, collaboration skill, and learning to learn skill compared to the Indonesian lecturers. The results indicate the need to increase transferable skills of both lecturers and students

    Evidence base prioritisation of indoor comfort perceptions in Malaysian typical multi-storey hostels

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    This study focuses on assessing the effects of the indoor climate in typical multi-storey hostels in Malaysia on student occupants through objective, subjective and evidence based prioritisation measurements. The objective measurements consisted of operative temperature; daylight ratio; luminance and indoor noise level. The subjective measurements were sampled from the student occupants' thermal, visual, acoustics and overall indoor comfort votes. The prioritisation measurement using Multiple Linear Regression and Friedman Tests assessed the relationship between physical indoor thermal, visual and acoustics conditions and students' overall indoor comfort perception vote. Findings suggest that subjective sensor ratings were significantly more reliable than objective measurements at predicting overall indoor comfort. Moreover, students living in hostel rooms with projected balconies voted that they were more satisfied with their indoor condition than the ones living in rooms without projected balconies. The results of this study also provide evidence that student occupants were more concerned with their rooms' thermal condition then followed by acoustics and finally visual conditions
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