Through scanning electron microscope and optical microscope, a compara- tive study on morphological features and anatomical characters of the leaves of some pear cultivars （strains） was carried out. The results show...Through scanning electron microscope and optical microscope, a compara- tive study on morphological features and anatomical characters of the leaves of some pear cultivars （strains） was carried out. The results showed that the size and shapes of leaf epidermal cells were different, stomatal apparatuses were distributed in the hypodermis, the shapes of stornas were mainly oval, and these of ＇Jinxiang- shui＇ were long oval; the stomatal type was irregular, the cultivar with the maximum density of leaf stomas was ＇Jinxiangshui＇, and the minimum was ＇Aishanli＇. The thickness of palisade tissues and spongy tissues of different pear cultivars （strains） was different, the maximum thickness of palisade tissues of ＇Aishanli＇ was 105.5 iJm, and the maximum thickness of spongy tissues of ＇Jinxiangshui＇ was 98.4 IJm. The ratios of palisade tissues to spongy tissues from high to low were ＇Qiuyueli＇, ＇Zaoxiangshui＇, ＇Aishanli＇, ＇Hongjinqiu＇ and ＇8404＇. The differences on these mi- cromorphological characters among different pear cultivars （strains） had important significance to the identification of the cultivars and the early choice of breeding.展开更多
With the growing energetic need present in the world, it is increasingly necessary for the researches and facilities to seek a better use of renewable natural resources. This paper is applied in the study of the perfo...With the growing energetic need present in the world, it is increasingly necessary for the researches and facilities to seek a better use of renewable natural resources. This paper is applied in the study of the performance of the aeration system of the Francis turbines present in Itaipu Hydroelectric Power Plant. When a Francis turbine operates off its optimal conditions, a vortex is formed inside the draft tube that, besides produces cavitation and pressure fluctuations, can pulse at frequencies with risk of resonance with hydraulic system, producing efforts and vibrations that may cause structural failures in the turbines, generators and civil parts of the power house. These damaging effects can be reduced using atmospheric aeration of the turbines. Because of this, the availability and effectively of the aeration system is fundamental to smooth the behavior of the turbines, helping preserve the health of the power plant. An analysis of the performance of the aeration system will be done using maintenance records and disturbances analysis reports （RAP）, allowing verification of the operating conditions of the turbine and fatality of water inlet in air pipes. Through the improvements detected, it is possible to reduce machine stoppages by tripping, thus increasing the availability of the turbines.展开更多
This paper analyzes and values an American barrier option with continuous payment plan written on a dividend paying asset under the classical Black-Scholes model.The integral representation of the initial premium alon...This paper analyzes and values an American barrier option with continuous payment plan written on a dividend paying asset under the classical Black-Scholes model.The integral representation of the initial premium along with the delta hedge parameter for an American continuous-installment down-and-out call option are obtained by using the decomposition technique.This offers a system of nonlinear integral equations for determining the optimal exercise and stopping boundaries,which can be utilized to approximate the option price and delta hedge parameter.The implementation is based on discretizing the quadrature formula in the system of equations and using the Newton-Raphson method to compute the two optimal boundaries at each time points.Numerical results are provided to illustrate the computational accuracy and the effects on the initial premium and optimal boundaries with respect to barrier.展开更多
文摘Through scanning electron microscope and optical microscope, a compara- tive study on morphological features and anatomical characters of the leaves of some pear cultivars （strains） was carried out. The results showed that the size and shapes of leaf epidermal cells were different, stomatal apparatuses were distributed in the hypodermis, the shapes of stornas were mainly oval, and these of ＇Jinxiang- shui＇ were long oval; the stomatal type was irregular, the cultivar with the maximum density of leaf stomas was ＇Jinxiangshui＇, and the minimum was ＇Aishanli＇. The thickness of palisade tissues and spongy tissues of different pear cultivars （strains） was different, the maximum thickness of palisade tissues of ＇Aishanli＇ was 105.5 iJm, and the maximum thickness of spongy tissues of ＇Jinxiangshui＇ was 98.4 IJm. The ratios of palisade tissues to spongy tissues from high to low were ＇Qiuyueli＇, ＇Zaoxiangshui＇, ＇Aishanli＇, ＇Hongjinqiu＇ and ＇8404＇. The differences on these mi- cromorphological characters among different pear cultivars （strains） had important significance to the identification of the cultivars and the early choice of breeding.
文摘With the growing energetic need present in the world, it is increasingly necessary for the researches and facilities to seek a better use of renewable natural resources. This paper is applied in the study of the performance of the aeration system of the Francis turbines present in Itaipu Hydroelectric Power Plant. When a Francis turbine operates off its optimal conditions, a vortex is formed inside the draft tube that, besides produces cavitation and pressure fluctuations, can pulse at frequencies with risk of resonance with hydraulic system, producing efforts and vibrations that may cause structural failures in the turbines, generators and civil parts of the power house. These damaging effects can be reduced using atmospheric aeration of the turbines. Because of this, the availability and effectively of the aeration system is fundamental to smooth the behavior of the turbines, helping preserve the health of the power plant. An analysis of the performance of the aeration system will be done using maintenance records and disturbances analysis reports （RAP）, allowing verification of the operating conditions of the turbine and fatality of water inlet in air pipes. Through the improvements detected, it is possible to reduce machine stoppages by tripping, thus increasing the availability of the turbines.
基金supported by the National Natural Science Foundation of China under Grant No.40675023Guangxi Natural Science Foundation under Grant No.0991091
文摘This paper analyzes and values an American barrier option with continuous payment plan written on a dividend paying asset under the classical Black-Scholes model.The integral representation of the initial premium along with the delta hedge parameter for an American continuous-installment down-and-out call option are obtained by using the decomposition technique.This offers a system of nonlinear integral equations for determining the optimal exercise and stopping boundaries,which can be utilized to approximate the option price and delta hedge parameter.The implementation is based on discretizing the quadrature formula in the system of equations and using the Newton-Raphson method to compute the two optimal boundaries at each time points.Numerical results are provided to illustrate the computational accuracy and the effects on the initial premium and optimal boundaries with respect to barrier.
