The environment effect on fish assemblage structure in waters adjacent to the Changjiang (Yangtze) River estuary (1998-2001)

We collected fish abundance data in the Changjiang (Yangtze River) estuary and adjacent waters in November 1998, May 1999, November 2000, and May 2001. Using the data, we evaluated the characteristics of the fish assemblages at each site and investigated the effect of several environmental factors. We used a multivariate analysis, including community ordination methods such as detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA), and two-way indicator species analysis (TWINSPAN). We analyzed the biological community structure and environmental factors to determine their spatial distributions, temporal dynamics, and seasonal variations. Among the fish species, five exceeded 5% of the total abundance: Harpodon nehereus (42.82%), Benthosema pterotum (13.85%), Setipinna taty (11.64%), Thryssa kammalensis (9.17%) and Apogonichthys lineatus (6.49%). These were separated into four ecological assemblages: hypsithermal-saline, hypsithermal-brackish, hypothermal-brackish, and hypothermal-saline. We evaluated the degree of influence of environmental factors on the fish community. Our analyses suggested that environmental factors including water depth, salinity, turbidity, transparency, nutrient, and suspended matter formed a synthetic spatial gradient between the coastal and pelagic areas. Ecological and environmental factors changed temporally from 1998 to 2001, and drove the fish community succession. The environmental factors driving the fish community structure included bottom temperature, water depth, bottom and surface pH, surface total phosphorous, and bottom dissolved oxygen. This investigation was completed before completion of the Three Gorges Dam; therefore the results of this study provide an important foundation for evaluating the influence of the human activities.

偏动式双程SMA驱动器工作机理与能量转换研究

研究了偏动式双程ＳＭＡ驱动器的工作机理，建立了驱动器输出力、输出位移、负载与驱动元件弹性刚度和预变形之间的变量关系。基于热力学基本定律，给出了双程ＳＭＡ驱动器工作过程中能量的周期性流动、转移和转化模型，指出双程ＳＭＡ驱动器双程做功的能量都来源于ＳＭＡ元件的相变弹性势能，能量的一部分用于来程做功，一部分在来程转移给偏置元件，用于回程时做工，还有一部分被释放掉。

总线桥:概念、方法和实现

在基于不同总线标准的个人计算机、工程工作站以及一些工业控制机间建立高速的并行通信通道,将它们构成多机系统,能够以较小的代价获得增强的系统特性.本文引入了一种在系统总线间提供并行数据通道的异种总线互连底板——总线桥的概念,讨论了它的结构和工作原理,提出了其实现方案,并着重描述了为总线桥定义的双向并行通讯协议 BBP(Bus Bridge Prtocol)

Fourier有限差分法深度偏移与正演模拟

With the development of seismic exploration, the target becomes more and more complex, which leads to a higher demand for the accuracy and efficiency in 3D exploration. Fourier finite-difference (FFD) method is one of the most valuable methods in complex structure exploration, which keeps the ability of finite-differenc method in dealing with laterally varing media and inherits the predominance of the phase-screen method in stablility and efficiency. In this thesis, the accuracy of the FFD operator is highly improved by using simulated annealing algorithm. This method takes the extrapolation step and band width into account, which is more suitable to various band width and discrete scale than the commonely-used optimized method based on velocity contrast alone. In this thesis, the FFD method is extended to viscoacoustic modeling. Based on one-way wave equation, the presented method is implemented in frequency domain; thus, it is more efficient than two-way methods, and is more convenient than time domain methods in handling attenuation and dispersion effects. The proposed method can handle large velocity contrast and has a high efficiency, which is helpful to further research on earth absorption and seismic resolution. Starting from the frequency dispersion of the acoustic VTI wave equation, this thesis extends the FFD migration method to the acoustic VTI media. Compared with the convetional FFD method, the presented method has a similar computational efficiency, and keeps the abilities of dealing with large velocity contrasts and steep dips. The numerical experiments based on the SEG salt model show that the presented method is a practical migration method for complex acoustical VTI media, because it can handle both large velocity contrasts and large anisotropy variations, and its accuracy is relatively high even in strong anisotropic media. In 3D case, the two-way splitting technique of FFD operator causes artificial azimuthal anisotropy. These artifacts become apparent with increasing dip angles and velocity contrasts, which prevent the application of the FFD method in 3D complex media. The current methods proposed to reduce the azimuthal anisotropy significantly increase the computational cost. In this thesis, the alternating-direction-implicit plus interpolation scheme is incorporated into the 3D FFD method to reduce the azimuthal anisotropy. By subtly utilizing the Fourier based scheme of the FFD method, the improved fast algorithm takes approximately no extra computation time. The resulting operator keeps both the accuracy and the efficiency of the FFD method, which is helpful to the inhancements of both the accuracy and the efficiency for prestack depth migration. The general comparison is presented between the FFD operator and the generalized-screen operator, which is valuable to choose the suitable method in practice. The percentage relative error curves and migration impulse responses show that the generalized-screen operator is much sensiutive to the velocity contrasts than the FFD operator. The FFD operator can handle various velocity contrasts, while the generalized-screen operator can only handle some range of the velocity contrasts. Both in large and weak velocity contrasts, the higher order term of the generalized-screen operator has little effect on improving accuracy. The FFD operator is more suitable to large velocity contrasts, while the generalized-screen operator is more suitable to middle velocity contrasts. Both the one-way implicit finite-difference migration and the two-way explicit finite-differenc modeling have been implemented, and then they are compared with the corresponding FFD methods respectively. This work gives a reference to the choosen of proper method. The FFD migration is illustrated to be more attractive in accuracy, efficiency and frequency dispertion than the widely-used implicit finite-difference migration. The FFD modeling can handle relatively coarse grids than the commonly-used explicit finite-differenc modeling, thus it is much faster in 3D modeling, especially for large-scale complex media.

风险偏好为什么是不稳定的？——后悔调节风险偏好的理论探索

Emotion is one of the most popular spots in recent decision making research, while regret is always being considered as the most relevant emotion with decision making. Current article firstly reviewed the literature of regret theory to date to profile the relation between regret and decision making under uncertainty through three mainlines: experienced regret, anticipated regret and regret orientation, respectively. And then, based on the theory of regret regulation raised by Zeelenberg recently, we came up with a theory of risk preference regulated by regret. Then three studies were conducted under the current framework, by using experiment, survey, and quasi experiment design. The major findings were below: In study 1, when playing ultimatum game, risk preference in decision making can be determined by experienced regret and anticipated regret of risk aversion, which made individual risk taking; In study 2, survey showed that risk orientation was negatively related with risk taking (health/safety, recreational and social); In study 3, when asked the Asian Disease Problem, risk preference can be determined by the coherence of the risk preference between the past decision and the current alternative. Individuals much more like alternative with the same risk preference of the past decision. A two way interaction was found, regret orientation, as a personality, was found as a moderator. Individuals with high regret orientation were more sensitive to the coherence of the risk preference than those with low regret orientation. Three studies provide fruitful evidences for the theory of risk preference regulated by regret in different prospective, show us the function of regret in decision making.

网上协同工作中的等待时距知觉研究

A newly developed experimental model called simulation of real mission was used to explore law of time perception and user endurance for feedback delay under Network-Supported Co-operative Work. Some non-technological factors influencing time perception and user endurance (mission type、difficulty level、feedback method、partner type、gender and A type behavior pattern) were also examined. Results of the study showed that: (1) Under condition of waiting without feedback, mission type and difficulty level demonstrated significant main effects on judgment of waiting duration. People will wait more time to receive partner's feedback if he or she perceives that partner's task is difficult, and the longest waiting duration (LWD) in the mission of computation is longer than the LWD in the mission of proof searching. (2) Under condition of waiting with feedback, experimental data perfectly supported Vierordt's Law: short duration is underestimated, long duration is overestimated, only proper duration (2-6 second) can be estimated correctly. The proper duration will vary with the changing of difficulty levels of mission. More long the waiting duration is, more estimation error will be occurred. The type difference of partner has no significant effect on the law of time perception. (3) Under condition of waiting with feedback, non-technology factors can significantly effect user's endurance. When subjects were told their partner was human, mission type and difficulty level of mission could significantly effect user's endurance. When subjects were told their partner was computer, A type behavior pattern and difficulty level of mission could significantly effect user's endurance. The two-way interaction effect between A type behavior pattern and gender was detected.