248 research outputs found

    Simulation, Measurement, and Emulation of Photovoltaic Modules Using High Frequency and High Power Density Power Electronic Circuits

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    The number of solar photovoltaic (PV) installations is growing exponentially, and to improve the energy yield and the efficiency of PV systems, it is necessary to have correct methods for simulation, measurement, and emulation. PV systems can be simulated using PV models for different configurations and technologies of PV modules. Additionally, different environmental conditions of solar irradiance, temperature, and partial shading can be incorporated in the model to accurately simulate PV systems for any given condition. The electrical measurement of PV systems both prior to and after making electrical connections is important for attaining high efficiency and reliability. Measuring PV modules using a current-voltage (I-V) curve tracer allows the installer to know whether the PV modules are 100% operational. The installed modules can be properly matched to maximize performance. Once installed, the whole system needs to be characterized similarly to detect mismatches, partial shading, or installation damage before energizing the system. This will prevent any reliability issues from the onset and ensure the system efficiency will remain high. A capacitive load is implemented in making I-V curve measurements with the goal of minimizing the curve tracer volume and cost. Additionally, the increase of measurement resolution and accuracy is possible via the use of accurate voltage and current measurement methods and accurate PV models to translate the curves to standard testing conditions. A move from mechanical relays to solid-state MOSFETs improved system reliability while significantly reducing device volume and costs. Finally, emulating PV modules is necessary for testing electrical components of a PV system. PV emulation simplifies and standardizes the tests allowing for different irradiance, temperature and partial shading levels to be easily tested. Proper emulation of PV modules requires an accurate and mathematically simple PV model that incorporates all known system variables so that any PV module can be emulated as the design requires. A non-synchronous buck converter is proposed for the emulation of a single, high-power PV module using traditional silicon devices. With the proof-of-concept working and improvements in efficiency, power density and steady-state errors made, dynamic tests were performed using an inverter connected to the PV emulator. In order to improve the dynamic characteristics, a synchronous buck converter topology is proposed along with the use of advanced GaNFET devices which resulted in very high power efficiency and improved dynamic response characteristics when emulating PV modules

    Dimensions of Principals’ Characteristics for Improving Efficiency of Schools

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    The quality of education could be improved by promoting the internal efficiency of secondary schools, which largely depends on leadership skills of the principals. Principals today function as instructional leaders, who continuously struggle for promoting learning outcomes of pupils, understand curriculum content and instructional skills and motivate teachers to improve these skills by providing them professional and instructional support. Their instructional leaderships could be improved by knowledge of curriculum content and modern teaching methodologies, which promote the internal efficiency of schools. The principals benefit from each other in professional matters and promote collegiality among them. They interact with their colleagues to share knowledge and skills. The experienced principals are good mediators and conflict resolvers. They collaborate with parents and community for improving learning outcomes of students. Administrative competence is important in determining the performance of the best and worst schools. But it is hard to measure it directly. Years of administrative skills and planning are also relevant to competence, but are less likely to be available on any consistent basis and affect the internal efficiency of school. The education level of the principal must ensure that he is an excellent evaluator of the classroom and school objectives. He checks students’ work and gives feedback to teachers after classroom observations. Professional development of principals has an impact on the knowledge, skills and their dispositions. The professional development need of principal is somewhat different from those of teachers and is reflective of the four major categories of development: leadership skills, curriculum related (Instructional, supervision and evaluation) skills, human and financial resource management skills, and knowledge in using departmental rules and regulations. Effective supervision and good governance is affected by number of teachers in a school. Small number of teachers in school ensures close contact between principal and teachers, which makes monitoring and financial accountability more effective, resultantly promotes its efficiency

    The army and democracy: military politics in Pakistan

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    Strategy and Model of Socialization of Draft E-Government Law to Citizens (G2C)

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    The United Nations ranks e-government and e-participation in various countries to measure the success of democratization. The wave of global spatial participation demands a social response in building a responsive legal order. Socialization of the Draft Law with the Website was annulled as a strategy to open a mouthpiece for accountable and responsive public aspirations. Resistance in the community becomes unavoidable because there is an inappropriate gap between the drafting of the bill and the aspirations of the people. This paper has succeeded in revealing the process of absorbing the aspirations of the people in the socialization of the draft law. Then explore strategies and models of participatory socialization of the current e-Government to Citizens-based Draft Law in Indonesia using the Netnographic method accompanied by testing through the Nvivo application. The findings of the absorption of people's aspirations based on e-government have been running but are not effective. This is evidenced by the fact that there are still bills that have not absorbed the aspirations of using e-participation. These deficiencies were answered by redesigning the formulation of the PUU Simas and “My Participation” so that the harmonization and simplification of the bill could be integrated

    Pakistan: Teetering on the Brink of Islamic Revolution?

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    Tingkat Kebisingan dan Suhu pada USAha Stone Crusher PT. X, Kabupaten Pasaman Barat, Provinsi Sumatera Barat

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    PT. X adalah salah satu Perusahaan swasta yang bergerak disektor pertambangan, yaitu pengolahan pemurnian Stone crusher di Jorong Bandua Balai, Nagari Kinali, Kecamatan Kinali, Kabupaten Pasaman Barat Propinsi Sumatera Barat. Kegiatan pertambangan merupakan kegiatan yang padat akan aktivitas peralatan mesin yang dapat menimbulkan gangguan pada lingkungan kerja. Efek tekanan lingkungan kerja pada pekerja dapat berupa penurunan kualitas fisik dan nonfisik (psikologi) dan juga akan menjadi pemicu munculnya berbagai konflik lingkungan yang ada. Salah satu bentuk tekanan lingkungan adalah kebisingan dan suhu di tempat kerja. Pengukuran kebisingan di PT. X bertujuan untuk mengetahui apakah tingkat kebisingan di lokasi kegiatan Stone crusher memenuhi persyaratan menurut standar baku tingkat kebisingan berdasarkan Nilai Ambang Batas (NAB) yang telah ditetapkan oleh Keputusan Menteri Tenaga Kerja Nomor KEP-51/MENAKER/1999 untuk lokasi kerja. Dari hasil penelitian ini berdasarkan ruang lingkup kerja bahwa di lokasi penelitian pada jarak 3 m dari stone crusher untuk operatornya sebesar 97,31 dB, dan di daerah perlintasan pekerja pada jarak 6m adalah sebesar 95,47 dB sementara di lokasi bengkel yang berjarak 12 m dari stone crusher sebesar 89,14 dB. Berdasarkan KEP-51/MENAKER/1999 untuk semua lokasi pengukuran tersebut sudah melebihi Nilai Ambang Batas (NAB) yang diizinkan untuk pekerja yang terperjan kebisingan selama 8 jam/hari. Untuk hasil pengukuran suhu/tekanan panas lokasi operator dan lokasi bengkel rata-rata adalah 27,40C dan 26,80C. Bila dirujuk kepada KEP-51/MENAKER/1999 untuk berkerja selama 6 jam/hari (75% kerja) dengan status beban kerja sedang dengan Nilai Ambang Batasnya (NAB) 280C berarti masih dibawah NAB. Tetapi bila bekerja penuh 8 jam/hari (100%) kedua lokasi tersebut telah melebihi NAB yaitu 26,70C
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