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排序方式: 共有2580条查询结果,搜索用时 21 毫秒
71.
72.
Sergio F. León-LuisAuthor VitaeUlises R. Rodríguez-MendozaAuthor Vitae Emmanuel LallaAuthor VitaeVíctor LavínAuthor Vitae 《Sensors and actuators. B, Chemical》2011,158(1):208-213
The temperature dependence of the green upconverted emission from the two thermally coupled 2H11/2 and 4S3/2 levels of the Er3+ ion in a fluorotellurite glass has been analyzed as a function of the optically active ion concentration in order to check its availability as a temperature sensor. The infrared-to-green upconverted emission have been observed by the naked eyes after a cw laser diode excitation at 800 nm. The fluorescence intensity ratio between the thermally coupled emitting levels as well as the temperature sensitivity has been experimentally obtained up to 540 K. A better behaviour as a temperature sensor has been obtained for the less Er3+ concentrated glass with a maximum sensitivity of 54 × 10−4 K−1 at 540 K, one of the highest found in rare-earth doped transparent materials. 相似文献
73.
Chvátal-Gomory cuts are among the most well-known classes of cutting planes for general integer linear programs (ILPs). In
case the constraint multipliers are either 0 or
mg src="/content/j47876m531149061/453_2008_9218_Article_IEq3.gif" alt="$\frac {1}{2}$" align="middle" border="0">
, such cuts are known as
mg src="/content/j47876m531149061/453_2008_9218_Article_IEq4.gif" alt="$\{0,\frac {1}{2}\}$" align="middle" border="0">
-cuts. It has been proven by Caprara and Fischetti (Math. Program. 74:221–235, 1996) that separation of
mg src="/content/j47876m531149061/453_2008_9218_Article_IEq5.gif" alt="$\{0,\frac {1}{2}\}$" align="middle" border="0">
-cuts is
mg src="/content/j47876m531149061/453_2008_9218_Article_IEq6.gif" alt="$\mathcal {NP}$" align="middle" border="0">
-hard.
In this paper, we study ways to separate
mg src="/content/j47876m531149061/453_2008_9218_Article_IEq7.gif" alt="$\{0,\frac {1}{2}\}$" align="middle" border="0">
-cuts effectively in practice. We propose a range of preprocessing rules to reduce the size of the separation problem. The
core of the preprocessing builds a Gaussian elimination-like procedure. To separate the most violated
mg src="/content/j47876m531149061/453_2008_9218_Article_IEq8.gif" alt="$\{0,\frac {1}{2}\}$" align="middle" border="0">
-cut, we formulate the (reduced) problem as integer linear program. Some simple heuristic separation routines complete the
algorithmic framework.
Computational experiments on benchmark instances show that the combination of preprocessing with exact and/or heuristic separation
is a very vital idea to generate strong generic cutting planes for integer linear programs and to reduce the overall computation
times of state-of-the-art ILP-solvers. 相似文献
74.
The paper is devoted to developing methods for control of ecological-economic systems consisting of three hierarchically subordinate subjects of control. In describing the dynamics of a system state, equations in partial derivatives that are solved numerically according to a semi-implicit scheme of the finite-difference method are used. To achieve its main goal (maintenance of an ecological subsystem in stable state), the subject of control of the upper level applies different control methods. Methods of hierarchical control (motivation, enforcement, and persuasion) that differ in the direction of action (on the objective function or domain of admissible controls) are proposed; examples of their use are represented and a comparative analysis of the obtained results is made. 相似文献
75.
We propose a visualization based approach for digital signature authentication. Using our method, the speed and pressure aspects of a digital signature process can be clearly and intuitively conveyed to the user for digital signature authentication. Our design takes into account both the expressiveness and aesthetics of the derived visual patterns. With the visual aid provided by our method, digital signatures can be authenticated with better accuracy than using existing methods—even novices can examine the authenticity of a digital signature in most situations using our method. To validate the effectiveness of our method, we conducted a comprehensive user study which confirms positively the advantages of our approach. Our method can be employed as a new security enhancement measure for a range of business and legal applications in reality which involve digital signature authorization and authentication. 相似文献
76.
77.
Dan Song Ruofeng Tong Jian Chang Xiaosong Yang Min Tang Jian Jun Zhang 《Computer Graphics Forum》2016,35(7):147-156
Estimation of 3D body shapes from dressed‐human photos is an important but challenging problem in virtual fitting. We propose a novel automatic framework to efficiently estimate 3D body shapes under clothes. We construct a database of 3D naked and dressed body pairs, based on which we learn how to predict 3D positions of body landmarks (which further constrain a parametric human body model) automatically according to dressed‐human silhouettes. Critical vertices are selected on 3D registered human bodies as landmarks to represent body shapes, so as to avoid the time‐consuming vertices correspondences finding process for parametric body reconstruction. Our method can estimate 3D body shapes from dressed‐human silhouettes within 4 seconds, while the fastest method reported previously need 1 minute. In addition, our estimation error is within the size tolerance for clothing industry. We dress 6042 naked bodies with 3 sets of common clothes by physically based cloth simulation technique. To the best of our knowledge, We are the first to construct such a database containing 3D naked and dressed body pairs and our database may contribute to the areas of human body shapes estimation and cloth simulation. 相似文献
78.
ATM论坛将基于速率的流量控制选定为ABR业务的流量控制方法。通过对基于速率的流量控制和基于凭证的流量控制方法的研究,提出了一种信元丢弃流量控制原则,该模型继承了基于凭证方法的记数机制,通过设定高低缓存门限和调节速率升降因数来控制源端速率,仿真结果表明,这种控制机制不仅能够保证缓存的充分利用,而且能够提高其在减少信元丢失等方面的性能。 相似文献
79.
80.
Attempts to carry out the hydroformylation of allyldiethylamine homogeneously catalyzed by rhodium complexes led to unexpected formation of N,N,Nmg src="/content/m475t57mx6066728/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">,Nmg src="/content/m475t57mx6066728/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-tetraethyl-1,4-diaminobutane and 4-(diethylamino)-1-butanole as final products. The role of the catalyst on the product formation and the reaction mechanism are briefly discussed. 相似文献