Current Issue : October - December Volume : 2012 Issue Number : 4 Articles : 5 Articles
The purpose of this study is to investigate dacites of different weathering grades from the Cakmakkaya and Damar open-pit\r\ncopper mines in northeastern Turkey based on their mineralogical, petrographical, and geomechanical characteristics. The dacites\r\nfor which surveys are carried out are mainly subjected to chemical weathering as well as physical disintegration and hydrothermal\r\nalteration. Discontinuities in this rock appear to be a major influence on the spatial distribution of weathering profiles, with the\r\nintensity of weathering increasing in the plagioclase phenocrystals and microlites as the weathering grade increases. The present\r\nresults show that the type and amount of clay minerals increase as the weathering grade increases. As the weathering increases, the\r\namount of mobile oxides, such as Na2O, MgO, and CaO, decreases while Fe2O3 and the loss on ignition (LOI) content increase\r\nfor most of the dacite samples. The microfracture frequency (qmf) may be a good indicator of fabric changes, and methylene blue\r\nadsorption (MBA) test and LOI may be good indicators of chemical weathering for the dacites. Geomechanical laboratory tests\r\nindicate that the strength of the samples is controlled by weathering. Field observations and mineralogical analyses show that the\r\neffects of weathering are critical for slope stability....
Unlike design basis accidents, some inherent uncertainties of the reliability of instrumentations are expected while subjected to\r\nharsh environments (e.g., high temperature and pressure, high humidity, and high radioactivity) occurring in severe nuclear\r\naccident conditions. Even under such conditions, an electrical signal should be within its expected range so that some mitigating\r\nactions can be taken based on the signal in the control room. For example, an industrial process control standard requires that\r\nthe normal signal level for pressure, flow, and resistance temperature detector sensors be in the range of 4~20mA for most\r\ninstruments.Whereas, in the case that an abnormal signal is expected from an instrument, such a signal should be refined through\r\na signal validation process so that the refined signal could be available in the control room. For some abnormal signals expected\r\nunder severe accident conditions, to date, diagnostics and response analysis have been evaluated with an equivalent circuit model\r\nof real instruments, which is regarded as the best method. The main objective of this paper is to introduce a program designed\r\nto implement a diagnostic and response analysis for equivalent circuit modeling. The program links signal analysis tool code to\r\nabnormal signal simulation engine code not only as a one body order system, but also as a part of functions of a PC-based ASSA\r\n(abnormal signal simulation analysis) module developed to obtain a varying range of the R-C circuit elements in high temperature\r\nconditions. As a result, a special function for abnormal pulse signal patterns can be obtained through the program, which in turn\r\nmakes it possible to analyze the abnormal output pulse signals through a response characteristic of a 4~20mA circuit model and\r\na range of the elements changing with temperature under an accident condition....
As a next-generation plant, a large-scale Japan sodium-cooled fast reactor (JSFR) adopts a number of innovative technologies in\r\norder to achieve economic competitiveness, enhanced reliability, and safety. This paper describes safety requirements for JSFR\r\nconformed to the defense-in-depth principle in IAEA. Specific design features of JSFR are a passive reactor shutdown system and\r\na recriticality-free concept against anticipated transients without scram (ATWS) in design extension conditions (DECs). A fully\r\npassive decay heat removal system with natural circulation is also introduced for design-basis events (DBEs) and DECs. In this\r\npaper, the safety design accommodation in JSFR was validated by safety analyses for representative DBEs: primary pump seizure\r\nand long-term loss-of-offsite power accidents. The safety analysis also showed the effectiveness of the passive shutdown system\r\nagainst a typical ATWS. Severe accident analysis supported by safety experiments and phenomenological consideration led to the\r\nfeasibility of in-vessel retention without energetic recriticality. Moreover, a probabilistic safety assessment indicated to satisfy the\r\nrisk target....
We have developed a simple process for sintering of soft magnetization materials using microwave sintering. The saturated\r\nmagnetization (Ms) of sintered magnetite was 85.6 emu/g, which was as high as 95% of magnetite before heating (90.4 emu/g).\r\nOn the other hand, the averaged remanence (Mr) and coercivity (Hc) of the magnetite after heating were 0.17 emu/g and 1.12 Oe\r\nunder measuring limit of SQUID, respectively. For the sintering process of soft magnetic materials, magnetic fields of microwave\r\nhave been performed in nitrogen atmosphere. Therefore, a microwave single-mode system operating at a frequency of 2.45 GHz\r\nand with a maximum power level of 1.5kW was used. We can sinter the good soft magnetic material in microwave magnetic\r\nfield. The sample shrank to 82% theoretical density (TD) from 45%TD of green body. The sintered sample was observed the\r\nmicrostructure by TEM and the crystal size was estimated the approximate average size is 10 nm....
Presently, there exist few numerical methods which treat the inverse problem for the determination of the geometry of wind turbine\r\nblades. In this work, authors intend to solve the inverse optimum project for horizontal axis wind turbine in which the selection\r\nof the circulation distribution is obtained by resolving two variational problems: the first consists in sorting the circulation distribution\r\non the lifting line, which, for a given power extracted by the wind turbine, minimizes the loses due to the induced velocity.\r\nIn the second, the optimal circulation distribution is selected such that the kinetic energy of the wind downstream of the rotor disc\r\nis minimum, when the energy extracted by the wind turbine for one rotating period is imposed. A code has been developed which\r\nincorporates the real pitch of the helicoidal vortex wake. Very promising results have been obtained: the circulation distribution\r\nfor a given extracted power and the chord lengths distribution law along the blade span....
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