This paper considers the optimal replacement problem of a repairable system consisting of one component and a single repairman, assume that the system after repair is not 'as good as new', by using the geometr...This paper considers the optimal replacement problem of a repairable system consisting of one component and a single repairman, assume that the system after repair is not 'as good as new', by using the geometric process, we consider a placement policy T based on the age of the system. The problem is to determine the optimal replacement policy T * such that the long_run expected benefit per unit time is maximized. Also, the explicit expression of the long_run expected benefit per unit time can be found. In some conditions, the existence and uniqueness of the optimal policy T * can be proved, finally, we prove that the policy T * is better than the policy T * in .展开更多
REE （rare earth element） analysis of bioapatite has recently been used to determine fossil provenience, taphonomy, stratigraphic correlation and paleoenvironmental conditions. This research has determined that REE s...REE （rare earth element） analysis of bioapatite has recently been used to determine fossil provenience, taphonomy, stratigraphic correlation and paleoenvironmental conditions. This research has determined that REE signatures are independent of diet, species, phylogeny and osteological material. Therefore, REE signatures are solely dependent on the depositional environment. Timing of emplacement could limit the resolution of REE analysis so it is vital to understand the length of time for REE signatures incorporation into bioapatite. A fossiliferous Pleistocene sites in Fossil Lake, Oregon has the potential to address this variable. A fossilized rabbit was found in its burrow and was contained in the uppermost unit that also is host to a semi-articulated fossilized salmon. The rabbit burrowed into this unit after the lake was subaerially exposed and is not contemporaneous with the salmon. REE signatures were found to be equivalent. The timing of emplacement of the REE signatures has to be less than the difference between the age of the salmon and the rabbit. Since the uppermost units of Fossil Lake are younger than 45,000 BP the remains can be dated with carbon-14. Therefore, this research aids in further quantifying the timing of emplacement of REE signature in bioapatite.展开更多
A model to describe the hysteresis damper character of rubber material is presented in this paper. It consists of a parallel spring and damper, whose coefficients change with vibration frequencies. In order to acquire...A model to describe the hysteresis damper character of rubber material is presented in this paper. It consists of a parallel spring and damper, whose coefficients change with vibration frequencies. In order to acquire these relations, the force decomposition is carried out according to some sine vibration measurement data about nonlinear forces changing with deformations of the rubber material. The nonlinear force is decomposed into a spring force and a damper force, which are represented by a frcquency-dependent spring and damper coefficient, respectively. Repeating this step for different measurements will give different coefficients corresponding to different frequencies. Then, application of a parameter identification method will provide the requested functions over frequency. Using those formulae, as an example, the dynamic character of a hollow shaft system supported by rubber rings is analyzed and the acceleration response curve in the centroid position is calculated. Comparisons with sine vibration experiments of the real system show a maximal inaccuracy of 8. 8 %. Application of this model and procedure can simplify the modeling and analysis of mechanical systems including rubber materials.展开更多
We study the entropy of the Gibbons-Maeda-Garfinkle-Horowitz-Strominger （GMGHS） charged black hole, originated from the effective action that emerges in the low-energy of string theory, beyond semiclassical approxi-...We study the entropy of the Gibbons-Maeda-Garfinkle-Horowitz-Strominger （GMGHS） charged black hole, originated from the effective action that emerges in the low-energy of string theory, beyond semiclassical approxi- mations. Applying the properties of exact differentials for three variables to the first law thermodynamics we derive the quantum corrections to the entropy of the black hole. The leading （logarithmic） and non leading corrections to the area law are obtained.展开更多
In N = 2 super Yang-Mills theory, the Matone＇s relation relates instanton corrections of the prepotential to instanton corrections of scMar field condensation （Trφ2）. This relation has been proved to hold for Omeg...In N = 2 super Yang-Mills theory, the Matone＇s relation relates instanton corrections of the prepotential to instanton corrections of scMar field condensation （Trφ2）. This relation has been proved to hold for Omega deformed theories too, using localization method. In this paper, we first give a case study supporting the relation, which does not rely on the localization technique. Especially, we show that the magnetic expansion also satisfies a relation of Matone＇s type. Then we discuss implication of the relation for proposed Nekrasov-Shatashvili scheme. the spectrum of periodic Toda chain, in the context of recentlyproposed Nekrasov-Shatashvili scheme.展开更多
The use of AVL （automatic vehicle locator） systems has increased considerably. By using an AVL system, it is possible to know vehicle positions at the dispatch center, which allows the use of several applications, s...The use of AVL （automatic vehicle locator） systems has increased considerably. By using an AVL system, it is possible to know vehicle positions at the dispatch center, which allows the use of several applications, such as safety and security, logistics, and emergency response. High communication and data storage costs, however, lead to a low position update rate with the AVL products available, causing poor track representation, and making the route determined by the vehicle in urban areas almost illegible. This paper proposes a new approach by using intelligent techniques to choose the best position update moment to improve track representations. The principle underlying these techniques is based on vehicle status analysis （speed, direction and timing）, which tries to determine when a position update is required, in order to better represent the path that a vehicle has traced, thus avoiding excessive communication and data storage. Therefore, the better the correspondence between the traced track and the real track followed by the vehicle, the greater the added value offered by system applications. This enhancement to the representation of the track allows the creation of new applications in the realm of AVL systems, particularly for situations where accuracy plays an important role.展开更多
It has been shown that non-rotating black holes Recently study showed that thermal fluctuations would give in three or four dimensions possess a canonical entropy. rise to logarithmic corrections to Bekenstein Hawking...It has been shown that non-rotating black holes Recently study showed that thermal fluctuations would give in three or four dimensions possess a canonical entropy. rise to logarithmic corrections to Bekenstein Hawking entropy in area with a model-dependent uncertain coefficient. In this paper, the thermal fluctuations on Bekenstein-Hawking entropy in three-dimensional AdS black holes, Schwarzschild-de Sitter space and Kerr-de Sitter （KdS） spacetime with J = 0 will be considered based on a uniformly spaced area spectrum approach. Our conclusion shows that there is the same correction form in all cases we considered.展开更多
A cogeneration plant can run at off-design due to change of load demand or ambient conditions. The cogeneration considered for this study is gas turbine based engine consists of variable stator vanes （VSVs） compress...A cogeneration plant can run at off-design due to change of load demand or ambient conditions. The cogeneration considered for this study is gas turbine based engine consists of variable stator vanes （VSVs） compressor that are re-staggered for loads greater than 50% to maintain the gas turbine exhaust gas temperature at the set value. In order to evaluate the exergetic performance of the cogeneration, exergy model of each cogeneration component is formulated. A 4.2 MW gas turbine based cogeneration plant is analysed for a wide range of part load operations including the effect of VSVs modulation. For loads less than 50%, the major exergy destruction contributors are the combustor and the loss with the stack gas. At full load, the exergy destructions in the combustor, turbine, heat recovery, compressor and the exergy loss with stack gas are 63.7, 14.1, 11.5, 5.7, and 4.9%, respectively. The corresponding first and second law cogeneration efficiencies are 78.5 and 45%, respectively. For comparison purpose both the first and second law efticiencies of each component are represented together. This analysis would help to identify the equipment where the potential for performance improvement is high, and trends which may aid in the design of future plants.展开更多
Qash Qooly valley runs parallel to Pera Magroon, Sara and Surdash anticlines, almost in SE-NW trend, and merges with the Lesser Zab River 9 km southeast to Dokan town. Before its development, it was a large basin with...Qash Qooly valley runs parallel to Pera Magroon, Sara and Surdash anticlines, almost in SE-NW trend, and merges with the Lesser Zab River 9 km southeast to Dokan town. Before its development, it was a large basin with width ranges between 2-3 km, which was filled during Pleistocene or may be Late Pliocene by different types of sediments. The presence of the calcrete on the top indicates a wet period that has lasted for a long time as indicated from the thickness of the calcrete and alluvial fan sediments. The age of Qash Qooly valley was estimated using the exposure age determination method. The type of the sediments, their thicknesses, and erosion intensity and sediments＇ dens dissection by rills were the main features used. This study concluded that the age of the basin is Pliocene--Late Pleistocene, whereas the valley started to be developed during uppermost Late Pleistocene and is still active in shifting its course.展开更多
Aims Our objective was to quantify the contributions of the seed bank and the established vegetation to the species composition,functional composition and diversity,and discuss the implications of these differences in...Aims Our objective was to quantify the contributions of the seed bank and the established vegetation to the species composition,functional composition and diversity,and discuss the implications of these differences in regeneration and persistence of floodplain plant communities.Methods We sampled all ground cover vegetation up to 1.5 m height and seed bank in 25 plots(10 m×1 m)distributed across five sites in dry and rainy seasons in a periodically flooded savanna in the Pantanal wetland,Brazil.We evaluated the soil seed bank by seedling emergence method.Important Findings The seed bank species had traits that conferred regeneration to the communities,while persistence traits characterized the vegetation.The seed bank had higher functional richness and lower functional evenness than the vegetation.The existence of different plant traits between seed bank and vegetation allowed the coexistence of species with functionally contrasting persistence and regeneration traits,which may help maintain functional diversity.It may allow the community to be more resilient when dealing with different environmental filters such as drought,fire and flood.展开更多
文摘This paper considers the optimal replacement problem of a repairable system consisting of one component and a single repairman, assume that the system after repair is not 'as good as new', by using the geometric process, we consider a placement policy T based on the age of the system. The problem is to determine the optimal replacement policy T * such that the long_run expected benefit per unit time is maximized. Also, the explicit expression of the long_run expected benefit per unit time can be found. In some conditions, the existence and uniqueness of the optimal policy T * can be proved, finally, we prove that the policy T * is better than the policy T * in .
文摘REE （rare earth element） analysis of bioapatite has recently been used to determine fossil provenience, taphonomy, stratigraphic correlation and paleoenvironmental conditions. This research has determined that REE signatures are independent of diet, species, phylogeny and osteological material. Therefore, REE signatures are solely dependent on the depositional environment. Timing of emplacement could limit the resolution of REE analysis so it is vital to understand the length of time for REE signatures incorporation into bioapatite. A fossiliferous Pleistocene sites in Fossil Lake, Oregon has the potential to address this variable. A fossilized rabbit was found in its burrow and was contained in the uppermost unit that also is host to a semi-articulated fossilized salmon. The rabbit burrowed into this unit after the lake was subaerially exposed and is not contemporaneous with the salmon. REE signatures were found to be equivalent. The timing of emplacement of the REE signatures has to be less than the difference between the age of the salmon and the rabbit. Since the uppermost units of Fossil Lake are younger than 45,000 BP the remains can be dated with carbon-14. Therefore, this research aids in further quantifying the timing of emplacement of REE signature in bioapatite.
文摘A model to describe the hysteresis damper character of rubber material is presented in this paper. It consists of a parallel spring and damper, whose coefficients change with vibration frequencies. In order to acquire these relations, the force decomposition is carried out according to some sine vibration measurement data about nonlinear forces changing with deformations of the rubber material. The nonlinear force is decomposed into a spring force and a damper force, which are represented by a frcquency-dependent spring and damper coefficient, respectively. Repeating this step for different measurements will give different coefficients corresponding to different frequencies. Then, application of a parameter identification method will provide the requested functions over frequency. Using those formulae, as an example, the dynamic character of a hollow shaft system supported by rubber rings is analyzed and the acceleration response curve in the centroid position is calculated. Comparisons with sine vibration experiments of the real system show a maximal inaccuracy of 8. 8 %. Application of this model and procedure can simplify the modeling and analysis of mechanical systems including rubber materials.
基金Supported by the Universidad Nacional de Colombia.Project Code 2010100
文摘We study the entropy of the Gibbons-Maeda-Garfinkle-Horowitz-Strominger （GMGHS） charged black hole, originated from the effective action that emerges in the low-energy of string theory, beyond semiclassical approxi- mations. Applying the properties of exact differentials for three variables to the first law thermodynamics we derive the quantum corrections to the entropy of the black hole. The leading （logarithmic） and non leading corrections to the area law are obtained.
基金Supported by the Natural Science Foundation of China under Grant No.11031005
文摘In N = 2 super Yang-Mills theory, the Matone＇s relation relates instanton corrections of the prepotential to instanton corrections of scMar field condensation （Trφ2）. This relation has been proved to hold for Omega deformed theories too, using localization method. In this paper, we first give a case study supporting the relation, which does not rely on the localization technique. Especially, we show that the magnetic expansion also satisfies a relation of Matone＇s type. Then we discuss implication of the relation for proposed Nekrasov-Shatashvili scheme. the spectrum of periodic Toda chain, in the context of recentlyproposed Nekrasov-Shatashvili scheme.
文摘The use of AVL （automatic vehicle locator） systems has increased considerably. By using an AVL system, it is possible to know vehicle positions at the dispatch center, which allows the use of several applications, such as safety and security, logistics, and emergency response. High communication and data storage costs, however, lead to a low position update rate with the AVL products available, causing poor track representation, and making the route determined by the vehicle in urban areas almost illegible. This paper proposes a new approach by using intelligent techniques to choose the best position update moment to improve track representations. The principle underlying these techniques is based on vehicle status analysis （speed, direction and timing）, which tries to determine when a position update is required, in order to better represent the path that a vehicle has traced, thus avoiding excessive communication and data storage. Therefore, the better the correspondence between the traced track and the real track followed by the vehicle, the greater the added value offered by system applications. This enhancement to the representation of the track allows the creation of new applications in the realm of AVL systems, particularly for situations where accuracy plays an important role.
基金Supported by the National Natural Science Foundation of China under Grant No. 10573004
文摘It has been shown that non-rotating black holes Recently study showed that thermal fluctuations would give in three or four dimensions possess a canonical entropy. rise to logarithmic corrections to Bekenstein Hawking entropy in area with a model-dependent uncertain coefficient. In this paper, the thermal fluctuations on Bekenstein-Hawking entropy in three-dimensional AdS black holes, Schwarzschild-de Sitter space and Kerr-de Sitter （KdS） spacetime with J = 0 will be considered based on a uniformly spaced area spectrum approach. Our conclusion shows that there is the same correction form in all cases we considered.
文摘A cogeneration plant can run at off-design due to change of load demand or ambient conditions. The cogeneration considered for this study is gas turbine based engine consists of variable stator vanes （VSVs） compressor that are re-staggered for loads greater than 50% to maintain the gas turbine exhaust gas temperature at the set value. In order to evaluate the exergetic performance of the cogeneration, exergy model of each cogeneration component is formulated. A 4.2 MW gas turbine based cogeneration plant is analysed for a wide range of part load operations including the effect of VSVs modulation. For loads less than 50%, the major exergy destruction contributors are the combustor and the loss with the stack gas. At full load, the exergy destructions in the combustor, turbine, heat recovery, compressor and the exergy loss with stack gas are 63.7, 14.1, 11.5, 5.7, and 4.9%, respectively. The corresponding first and second law cogeneration efficiencies are 78.5 and 45%, respectively. For comparison purpose both the first and second law efticiencies of each component are represented together. This analysis would help to identify the equipment where the potential for performance improvement is high, and trends which may aid in the design of future plants.
文摘Qash Qooly valley runs parallel to Pera Magroon, Sara and Surdash anticlines, almost in SE-NW trend, and merges with the Lesser Zab River 9 km southeast to Dokan town. Before its development, it was a large basin with width ranges between 2-3 km, which was filled during Pleistocene or may be Late Pliocene by different types of sediments. The presence of the calcrete on the top indicates a wet period that has lasted for a long time as indicated from the thickness of the calcrete and alluvial fan sediments. The age of Qash Qooly valley was estimated using the exposure age determination method. The type of the sediments, their thicknesses, and erosion intensity and sediments＇ dens dissection by rills were the main features used. This study concluded that the age of the basin is Pliocene--Late Pleistocene, whereas the valley started to be developed during uppermost Late Pleistocene and is still active in shifting its course.
基金This work was supported by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior(CAPES)under grant PNADB-17/2009.
文摘Aims Our objective was to quantify the contributions of the seed bank and the established vegetation to the species composition,functional composition and diversity,and discuss the implications of these differences in regeneration and persistence of floodplain plant communities.Methods We sampled all ground cover vegetation up to 1.5 m height and seed bank in 25 plots(10 m×1 m)distributed across five sites in dry and rainy seasons in a periodically flooded savanna in the Pantanal wetland,Brazil.We evaluated the soil seed bank by seedling emergence method.Important Findings The seed bank species had traits that conferred regeneration to the communities,while persistence traits characterized the vegetation.The seed bank had higher functional richness and lower functional evenness than the vegetation.The existence of different plant traits between seed bank and vegetation allowed the coexistence of species with functionally contrasting persistence and regeneration traits,which may help maintain functional diversity.It may allow the community to be more resilient when dealing with different environmental filters such as drought,fire and flood.
