7,419 research outputs found

    Power coupling

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    Power coupling is the subject of a huge amount of literature and material since for each particular RF structure it is necessary to design a coupler that satisfies some requirements, and several approaches are in principle possible. The choice of one coupler with respect to another depends on the particular RF design expertise. Nevertheless some 'design criteria' can be adopted and the scope of this paper is to give an overview of the basic concepts in power coupler design and techniques. We illustrate both the cases of normal-conducting and superconducting structures as well as the cases of standing-wave and travelling-wave structures. Problems related to field distortion induced by couplers, pulsed heating, and multipacting are also addressed. Finally a couple of design techniques using electromagnetic codes are illustrated. The paper brings together pictures, data, and information from several works reported in the references and I would like to thank all the authors of the papers.Comment: 23 pages, contribution to the CAS - CERN Accelerator School: Specialised Course on RF for Accelerators; 8 - 17 Jun 2010, Ebeltoft, Denmar

    Pembangunan dan penganalisisan aplikasi permohonan peruntukkan penyelenggaraan bangunan sekolah berasaskan proses pengurusan dalam kejuruteraan awam

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    Penyelenggaraan adalah aktiviti yang dilakukan secara berterusan bagi memastikan fungsi bangunan dapat dilaksanakan sebagaimana fungsinya secara normal. Penyelenggaraan bangunan sekolah adalah aktiviti rutin yang harus dijalankan memandangkan sekolah adalah lokasi pertama dalam pengembangan minda kanak�kanak. Namun begitu, kajian literatur menunjukkan terdapat beberapa masalah dalam pengurusan penyelenggaraan yang lazimnya diselia oleh ahli jawatankuasa penyelenggaraan sekolah. Antaranya ialah kegagalan mereka mematuhi Pekeliling Am Bil.2 Tahun 1995 dalam proses permohonan penyelenggaraan. Disebabkan permasalahan tersebut, tesis ini diwujudkan bagi membantu mereka dalam menyelesaikan sebahagian masalah yang dihadapi dengan cara membangunkan satu aplikasi permohonan penyelenggaraan sekolah berkomputer. Pembangunan aplikasi adalah menggunakan Microsoft Access. Aplikasi pertama yang dibangunkan adalah CoRTMaS di mana ia hanya tertumpu kepada penyelenggaraan bumbung dan tandas berdasarkan kepada kajian literatur yang mengatakan 2 komponen ini paling kerap mengalami kerosakan. Hasil soal selidik diuji menggunakan SPSS dan mendapati kadar ketepatan hasil kajian adalah α = 0.893. Walaupun hasil kajian CoRTMaS amat memuaskan, aplikasi SiPBaS dibangunkan bagi menambah baik fungsi aplikasi dalam CoRTMaS. Kesimpulannya, pembangunan aplikasi dapat menyumbang kepada kelancaran proses permohonan penyelenggaraan sekolah namun terdapat beberapa cadangan lanjutan yang dicadangkan bagi memantapkan aplikasi SiPBaS iaitu menjadikan aplikasi ini berfungsi secara atas talian, mewujudkan ruangan bagi memuat turun gambar kerosakan serta mewujudkan kod keselamatan untuk kontraktor terlibat

    Hubungan di antara status Sosio Ekonomi (SSE) keluarga dengan pencapaian akademk : satu kajian ke at as pelajar aliran teknikal di Sekolah Menengah Teknik Negeri Sembilan

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    Kajian ini bertujuan untuk melihat hubungan di antara status sosio ekonomi (SSE) keluarga dengan pencapaian akademik di kalangan pelajar aliran teknikal. Kajian ini dijalankan ke atas pelajar tingkatan empat aliran teknikal di lima buah Sekolah Menengah Teknik di Negeri Sembilan iaitu Sekolah Menengah Teknik Tuanku Jaafar, Sekolah Menengah Teknik Juasseh, Sekolah Menengah Teknik Pertanian Rembau, Sekolah Menengah Teknik Ampangan dan Sekolah Menengah Teknik Port Dicksoa Seramai 350 orang pelajar terlibat dalam kajian ini dan dipilih secara rawak mudah. Analisis regresi mudah dan regresi berbilang digunakan untuk melihat hubungan di antara pembolehubah yang dikaji. Keseluruhan data kajian telah dianahsis menggunakan perisian Statistical Packages for the Social Sciences (SPSS) versi 11.5 dengan membuat pengiraan peratusan dan regresi. Dapatan kajian menunjukkan secara majoritinya, SSE mempunyai hubungan yang signifikan dengan tahap pencapaian akademik pelajar. Dengan itu dapat dirumuskan bahawa SSE mempengaruhi tahap pencapaian akademik pelajar aliran teknikal. Beberapa cadangan dikemukakan untuk panduan kajian selanjutnya

    A theoretical analysis of the electromagnetic environment of the AS330 super Puma helicopter external and internal coupling

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    Numerical techniques such as Finite Difference Time Domain (FDTD) computer programs, which were first developed to analyze the external electromagnetic environment of an aircraft during a wave illumination, a lightning event, or any kind of current injection, are now very powerful investigative tools. The program called GORFF-VE, was extended to compute the inner electromagnetic fields that are generated by the penetration of the outer fields through large apertures made in the all metallic body. Then, the internal fields can drive the electrical response of a cable network. The coupling between the inside and the outside of the helicopter is implemented using Huygen's principle. Moreover, the spectacular increase of computer resources, as calculations speed and memory capacity, allows the modellization structures as complex as these of helicopters with accuracy. This numerical model was exploited, first, to analyze the electromagnetic environment of an in-flight helicopter for several injection configurations, and second, to design a coaxial return path to simulate the lightning aircraft interaction with a strong current injection. The E field and current mappings are the result of these calculations

    Circularly-polarised cavity-backed wearable antenna in SIW technology

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    This study presents a circularly-polarised substrate-integrated waveguide (SIW) antenna implemented using a textile substrate and operating at 2.45GHz, in the industrial, scientific, and medical frequency band. The antenna topology is based on a folded cavity with an annular ring as a radiating element, and it permits to obtain compact size and low sensitivity to the environment, without deteriorating the radiating performance. These characteristics, together with the choice of adopting a textile substrate, make the SIW antenna suitable for the integration in wearable systems for body-centric applications. The electromagnetic performance of the proposed antenna achieved in simulations was verified through the measurement of the device in an anechoic chamber. The circularly-polarised antenna exhibits a maximum gain of 6.5dBi, a radiation efficiency of 73% and a very high front-to-back ratio

    Near-Field Microwave Microscopy of Materials Properties

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    Near-field microwave microscopy has created the opportunity for a new class of electrodynamics experiments of materials. Freed from the constraints of traditional microwave optics, experiments can be carried out at high spatial resolution over a broad frequency range. In addition, the measurements can be done quantitatively so that images of microwave materials properties can be created. We review the five major types of near-field microwave microscopes and discuss our own form of microscopy in detail. Quantitative images of microwave sheet resistance, dielectric constant, and dielectric tunability are presented and discussed. Future prospects for near-field measurements of microwave electrodynamic properties are also presented.Comment: 31 pages, 9 figures, lecture given at the 1999 NATO ASI on Microwave Superconductivity Changes suggested by editor, including full reference

    Superconducting elliptical cavities

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    We give a brief overview of the history, state of the art, and future for elliptical superconducting cavities. Principles of the cell shape optimization, criteria for multi-cell structures design, HOM damping schemes and other features are discussed along with examples of superconducting structures for various applications.Comment: 25 pages, contribution to the CAS - CERN Accelerator School: Specialised Course on RF for Accelerators; 8 - 17 Jun 2010, Ebeltoft, Denmar
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