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11.
Credit scoring using support vector machines with direct search for parameters selection 总被引:1,自引:1,他引:0
Ligang Zhou Kin Keung Lai Lean Yu 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2009,13(2):149-155
Support vector machines (SVM) is an effective tool for building good credit scoring models. However, the performance of the
model depends on its parameters’ setting. In this study, we use direct search method to optimize the SVM-based credit scoring
model and compare it with other three parameters optimization methods, such as grid search, method based on design of experiment
(DOE) and genetic algorithm (GA). Two real-world credit datasets are selected to demonstrate the effectiveness and feasibility
of the method. The results show that the direct search method can find the effective model with high classification accuracy
and good robustness and keep less dependency on the initial search space or point setting. 相似文献
12.
Zhifeng Jiang Zhiquan Zhang Jianli Liang Min Zhou Daobin Liu Danjun Mao Qun Zhang Wei Zhang Huaming Li Li Song Taicheng An Po Keung Wong Chun-Sing Lee 《Advanced functional materials》2023,33(29):2301785
Solar-driven CO2 reduction reaction (CO2RR) with water into carbon-neutral fuels is of great significance but remains challenging due to thermodynamic stability and kinetic inertness of CO2. Biomass-derived nitrogen-doped carbon (N-Cb) have been considered as promising earth-abundant photocatalysts for CO2RR, although their activities are not ideal and the reaction mechanism is still unclear. Herein, an efficient catalyst is developed for CO2-to-CO conversion realized on diverse N-Cb materials with hierarchical pore structures. It is demonstrated that the CO2-to-CO conversion preferentially takes place on positively charged carbon atoms next to pyridinic-N using two representatives treated pollens with the largest difference in pyridinic-N density and N content as model photocatalysts. Systematic experimental results indicate that surface local electric field originating from charge separation can be boosted by hierarchical pore structures, doped N, as well as pyridinic-N. Mechanistic studies reveal that positively charged carbon atoms next to pyridinic-N serve as active sites for CO2RR, reduce the energy barrier on the formation of CO*, and facilitate the CO2RR performance. All these benefits cooperatively contribute to treated chrysanthemum pollen catalyst exhibiting excellent CO formation rate of 203.2 µmol h−1 g−1 with 97.2% selectivity in pure water vapor. These results provide a new perspective into CO2RR on N-Cb, which shall guide the design of nature-based photocatalysts for high-performance solar-fuel generation. 相似文献
13.
Feifeng Zheng Yinfeng Xu Chung Keung Poon E. Zhang Xiaoping Wu 《Computers & Industrial Engineering》2011
This paper presents a study of the problem of online deadline scheduling under the preemption penalty model of Zheng, Xu, and Zhang (2007). In that model, each preemption incurs a penalty of ρ times the weight of the preempted job, where ρ ? 0 is the preemption penalty parameter. The objective is to maximise the total weight of jobs completed on time minus the total penalty. 相似文献
14.
We study the communication primitives of broadcasting (one-to-all communication) and gossiping (all-to-all communication)
in known topology radio networks, i.e., where for each primitive the schedule of transmissions is precomputed based on full
knowledge about the size and the topology of the network. We show that gossiping can be completed in
time units in any radio network of size n, diameter D, and maximum degree Δ=Ω(log n). This is an almost optimal schedule in the sense that there exists a radio network topology, specifically a Δ-regular tree, in which the radio gossiping cannot be completed in less than
units of time. Moreover, we show a
schedule for the broadcast task. Both our transmission schemes significantly improve upon the currently best known schedules
by Gąsieniec, Peleg, and Xin (Proceedings of the 24th Annual ACM SIGACT-SIGOPS PODC, pp. 129–137, 2005), i.e., a O(D+Δlog n) time schedule for gossiping and a D+O(log 3
n) time schedule for broadcast. Our broadcasting schedule also improves, for large D, a very recent O(D+log 2
n) time broadcasting schedule by Kowalski and Pelc.
A preliminary version of this paper appeared in the proceedings of ISAAC’06.
F. Cicalese supported by the Sofja Kovalevskaja Award 2004 of the Alexander von Humboldt Stiftung. F. Manne and Q. Xin supported
by the Research Council of Norway through the SPECTRUM project. 相似文献
15.
Bingo Wing‐Kuen Ling Charlotte Yuk‐Fan Ho Raymond Shing‐Keung Leung Peter Kwong‐Shun Tam 《International Journal of Circuit Theory and Applications》2004,32(2):57-64
This letter explains the oscillatory behaviours exhibited in a second‐order digital filter with saturation‐type non‐linearity via the Hopf bifurcation theorem. It is shown that depending on the bifurcation parameter, the state variables may converge to zero even when the eigenvalues of the system matrix are outside the unit circle. Copyright © 2004 John Wiley & Sons, Ltd. abstract 相似文献
16.
In this study, we develop a system for interactive snow simulation and rendering. Snow is modeled as a hybrid structure that handles movable snow and static snow separately. We develop a simple approach to convert between these two types of snow. Movable snow is represented by a set of particles, whereas static snow is modeled as grid cells. For a piece of movable snow (e.g., snowflake), the particles are connected using springs. Thus, we can model snow as a type of brittle material, such as a snow pile split into chunks of smaller snow pieces after a collision. To render the snow, we adopt a shell structure that has a series of concentric, semitransparent, textured shells. We applied our system to several examples, with the rendered snow appearing similar to real snow. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
17.
Chee Keung Chow 《Fuel》1981,60(12):1153-1158
The liquefaction behaviour of a Kentucky coal was studied in batch autoclave experiments at 410 °C under either a H2 or a N2 atmosphere (≈ 13.8 MPa) for reaction times of up to 2 h. To understand the catalytic roles of FeSO4 and a Co&z.sbnd;Mo catalyst in coal liquefaction and to assess the feasibility of using FeSO4 as a model for coal pyrites, effects of impregnation of the coal with FeSO4 and direct charges of a Co&z.sbnd;Mo catalyst on coal liquefaction and tetralin dehydrogenation were examined. Both catalysts increase the conversion to benzene-soluble material by 7–10%, and improve the selectivity values for conversion to oil and gas. In addition they are also active in the dehydrogenation of tetralin. The dehydrogenation activities of these catalysts correlate with their catalytic activities during coal liquefaction. Analyses of the mean chemical structures and the product distributions of the coal-derived liquid from liquefaction in H2 and in N2 atmospheres indicate that:
- 1. (1) H-transfer from tetralin is the only major mechanism of coal liquefaction; and
- 2. (2) both pyrrhotite, generated in-situ from FeSO4, and Co&z.sbnd; Mo catalyst can provide a major liquefaction mechanism by catalysing the H-transfer from the donor solvent to the coal or the coal-derived liquid.
18.
Kit Nam Francis Leung Yuan Lin ZhangKin Keung Lai 《Reliability Engineering & System Safety》2011,96(11):1542-1551
In this paper, a cold standby repairable system consisting of two dissimilar components and one repairman is studied. Assume that working time distributions and repair time distributions of the two components are both exponential, and Component 1 has repair priority when both components are broken down. After repair, Component 1 follows a geometric process repair while Component 2 obeys a perfect repair. Under these assumptions, using the perfect repair model, the geometric process repair model and the supplementary variable technique, we not only study some important reliability indices, but also consider a replacement policy T, under which the system is replaced when the working age of Component 1 reaches T. Our problem is to determine an optimal policy T? such that the long-run average loss per unit time (i.e. average loss rate) of the system is minimized. The explicit expression for the average loss rate of the system is derived, and the corresponding optimal replacement policy T? can be found numerically. Finally, a numerical example for replacement policy T is given to illustrate some theoretical results and the model's applicability. 相似文献
19.
20.
The Job Scheduling with Cancellation problem is a variation of classical scheduling problems in which jobs can be cancelled while waiting for execution. In this paper we prove a tight lower bound of 5 for the competitive ratio of any deterministic online algorithm for this problem, for the case where all jobs have the same processing time. 相似文献