740,898 research outputs found

    PENGARUH TEMPERATUR TUANG TERHADAP SIFAT MEKANIS DAN MIKROSTRUKTUR ALUMINIUM A356 MENGGUNAKAN PENGECORAN METODE COOLING SLOPE

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    Penggunaan aluminium yang begitu luas dalam bidang teknik dikarenakan memiliki massa jenis yang ringan dan ketahanan korosi yang baik tetapi aluminium memiliki sifat mekanis yang masih perlu ditingkatkan khususnya aluminium yang diproduksi dengan menggunakan metode pengecoran. Pada proses pengecoran sangat banyak variabel yang akan mempengaruhi kekuatan aluminium yang salah satunya adalah temperatur tuang. Penelitian ini bertujuan untuk melihat pengaruh temperatur tuang terhadap sifat mekanis aluminium A356 yang meliputi kekerasan,impak,tarik,aus, serta mikrostruktur dengan menggunakan metode pengecoran tipe cooling slope. Cooling slope digunakan untuk mengalirkan alumunium yang sudah mencair ke dalam cetakan. Cooling slope ini sendiri mempunyai 5 sudut kemiringan, yaitu 15˚, 30˚, 45˚, 60˚,dan 75˚. Penelitian ini dilakukan dengan memvariasikan temperatur tuang 620˚C, 650˚C, 680˚C, 710˚C, dan 740˚C serta sudut dari cooling slope adalah 15˚ menggunakan cetakan permanen. Kekerasan tertinggi diperoleh pada variasi temperatur tuang 680˚C sebesar 52,8 BHN. Nilai impak tertinggi di dapat pada variasi temperatur tuang 710˚C sebesar 0,18 J/mm². Nilai uji tarik tertinggi diperoleh pada variasi temperatur tuang 680˚C sebesar 106,72 Mpa. Pengujian keausan dilakukan dengan metode pin on disk dengan variasi putaran 150 Rpm, 180 Rpm, dan 210 Rpm. Hasil photo mikro terlihat pada temperatur 680˚C distribus silikon di dalam matrik alumunium lebih merata dibandingkan dengan temperatur yang lainnya

    Top Quark Mass Measurements at CDF

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    The mass of the top quark M_top is interesting both as a fundamental parameter of the standard model and as an important input to precision electroweak tests. The Collider Detector at Fermilab (CDF) has a robust program of top quark mass analyses, including the most precise single measurement, M_top = 173.4 +/- 2.8 GeV/c^2, using 680 pb^-1 of ppbar collision data. A combination of current results from CDF gives M_top = 172.0 +/- 2.7 GeV/c^2, surpassing the stated goal of 3 GeV/c^2 precision using 2 fb^-1 of data. Finally, a combination with current D0 results gives a world average top quark mass of 172.5 +/- 2.3 GeV/c^2.Comment: 8 pages, Contribution to Proceedings of the 41st Rencontres de Moriond: Electroweak Interactions and Unified Theories, La Thuile, Italy, 11-18 March 200

    Control of spontaneous emission from InP single quantum dots in GaInP photonic crystal nanocavities

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    We demonstrate semiconductor quantum dots coupled to photonic crystal cavity modes operating in the visible spectrum. We present the design, fabrication, and characterization of two dimensional photonic crystal cavities in GaInP and measure quality factors in excess of 7500 at 680 nm. We demonstrate full control over the spontaneous emission rate of InP quantum dots and by spectrally tuning the exciton emission energy into resonance with the fundamental cavity mode we observe a Purcell enhancement of similar to 8. (C) 2010 American Institute of Physics. [doi:10.1063/1.3510469

    Search for resonant ttbar production in ppbar collisions at sqrt{s}=1.96 TeV

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    We report on a search for narrow-width particles decaying to a top and antitop quark pair. The data set used in the analysis corresponds to an integrated luminosity of 680 pb^{-1} collected with the Collider Detector at Fermilab in Run II. We present 95% confidence level upper limits on the cross section times branching ratio. Assuming a specific topcolor-assisted technicolor production model, the leptophobic Z' with width \Gamma_{Z'}=0.012M_{Z'}, we exclude the mass range M_{Z'} < 725 GeV/c^2 at the 95% confidence level.Comment: 7 pages, 3 figures. submitted to Phys. Rev. Let

    Структура и свойства хромомолибденовой стали после смягчающей термической обработки

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    Целью работы является разработка режимов термической обработки сортового проката из легированной конструкционной хромомолибденовой стали, обеспечивающих снижение энергозатрат. Показано влияние температурно–временных параметров термической обработки на структурообразование и твердость хромомолибденовой стали. Установлено, что отжиг по сокращенному режиму (на 15–20%) с длительностью выдержки 3 часа при температурах 680–6500° C гарантированно обеспечит требуемые качественные показатели проката и экономию энергоресурсов.Метою роботи є розроблення режимів термічної обробки сортового прокату з легованої конструкційної хромомолібденової сталі, що забезпечують зниження енерговитрат. Показано вплив температурно–часових параметрів термічної обробки на структуроутворення та твердість хромомолібденової сталі. Встановлено, що відпал за скороченим режимом (на 15–20%) з тривалістю витримки 3 години при температурах 680–6500° C гарантовано забезпечить потрібні якісні показники прокату та економію енергоресурсів.The aim is to develop a heat treatment of rolled structural stainless chromium-molybdenum steel, providing lower energy costs. It is shown the influence of temperature and time parameters of heat treatment on structure and hardness of chrome-molybdenum steel. Found that annealing of the reduced mode (15-20%) with duration of exposure for 3 hours at temperatures of 680-6500° C is guaranteed to provide the required quality parameters and the rental cost of energy

    Physicochemical properties and leaching behavior of eight U.S. long-grain rice cultivars as related to rice texture

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    There are many long-grain rice cultivars produced commercially in the U.S.; however, little work has been done on correlating the structure and physicochemical properties of starch with their texture. The physicochemical properties, leaching behavior, and texture attributes of eight longgrain rice cultivars were studied. Differences were observed in the approximate composition of kernels, including crude protein (6.6-9.3%), crude lipid (0.18-0.51%), and apparent amylose content (25.5-30.9%). These cultivars also differed slightly in thermal properties, such as onset temperature (73.7° to 77.4°C) and peak temperature (78.8° to 81.9°C). Although they showed a similar pasting temperature, their peak viscosities ranged from 680 to 982 Brabender units. The amount and the molecular size distribution of the leached starch molecules varied greatly among the samples. The leached amylose, instead of the apparent amylose, was suggested to play an important role in cooked rice texture

    Growth, Characterisation, And Properties of Bi1.8Lu1.2Fe3.6Al1.4O12 Garnet Films Prepared Using Two Different Substrate Temperatures

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    We prepare highly Bismuth substituted iron garnet of composition type Bi1.8Lu1.2Fe3.6Al1.4O12 by using low and high substrate temperatures (250°C and 680°C) during the deposition process inside the vacuum chamber of RF magnetron sputtering system. The crystallisation process of this garnet type thin film materials are performed by means of optimised high temperature oven annealing process and conduct several characterisation techniques to obtain and evaluate their properties. All the optimally annealed samples possess very promising and attractive properties. Comparatively low coercive force (below 15 Oe) is achieved in garnet films prepared at high substrate temperature of 680°C, simultaneously with high MO quality and almost in-plane magnetisation direction, which are the properties desired in various MO sensing, switching and imaging applications
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