排序方式: 共有57条查询结果,搜索用时 15 毫秒
1.
为了对全国平均每百户居民私家车拥有量进行预测,建立了可分离变量微分方程的数学模型,采用最小二乘法,借助Excel作为计算工具,得到了微分方程近似解的参数值,并用微分方程的近似解估计了最大拥有量以及2010年以后某些年的拥有量. 相似文献
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Lanthanide p-toluene sulphonic acid (ptsa) complexes were prepared for La, Pr, Nd, Sm, Eu, Dy, Ho, Er and Yb, and found to exist as Ln(ptsa)3. Conductivity studies of La(ptsa)3 in DMSO and DMF suggest 1:2 and, possibly, 1:1 electrolyte behaviour in these solvents, respectively. NMR lanthanide-induced chemical shifts (LIS) for aromatic protons in (ptsa)? and methyl protons in DMSO, were measured for all complexes as a function of the [Ln3+[DMSO] in a medium consisting of CCl4, DMSO, and CH3CN. Analysis of the LIS data suggests a change in (ptsa)? coordination round Ln3+ across the lanthanide series. 相似文献
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This paper considers the problem of coordinating a single-vendor multi-buyer inventory system when there are privacy restrictions in the information required to solve the problem. The objective function and cost parameters of each facility are regarded as private information that no other facilities in the system have access to. Moreover, each facility is responsible to specify its own replenishment policy. The objective is to minimize the total average setup/ordering and inventory-related cost. Solution methodologies under private and global information are developed to find two types of nested power-of-two stationary policies. The first policy assumes all the buyers must replenish simultaneously. The second policy is a more general case where the common replenishment assumption is relaxed. A simple form of information exchange is uncovered that allows the solution methodologies for private and global information yield the same results. The experimental results suggest that the performance of the proposed heuristics is comparable or better than an existing method. 相似文献
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K R Brownstein 《Pramana》1983,21(6):401-402
Some errors in a recent article by Zadoo and Sofi are discussed. 相似文献
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The private car license plates issued in Shanghai are bestowed the title of “the most expensive sheet iron all over the world”, more expensive than gold. A citizen has to bid in a monthly auction to obtain a license plate for his new private car. We perform statistical analysis to investigate the influence of the minimal price Pmin of the bidding winners, the quota of private car license plates, the number of bidders, as well as two external shocks including the legality debate of the auction in 2004 and the auction regime reform in January 2008 on the average price of all bidding winners. It is found that the legality debate of the auction had marginal transient impact on the average price in a short time period. In contrast, the change of the auction rules has significant permanent influence on the average price, which reduces the price by about 3020 yuan Renminbi. It means that the average price exhibits nonlinear behaviors with a regime change. The evolution of the average price is independent of the number of bidders in both regimes. In the early regime before January 2008, the average price was influenced only by the minimal price Pmin in the preceding month with a positive correlation. In the current regime since January 2008, the average price is positively correlated with the minimal price and the quota in the preceding month and negatively correlated with the quota in the same month. We test the predictive power of the two models using 2-year and 3-year moving windows and find that the latter outperforms the former. It seems that the auction market becomes more efficient after the auction reform since the prediction error increases. 相似文献
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Laurens Cherchye Kristof De Witte Erwin Ooghe Ides Nicaise 《European Journal of Operational Research》2010
We present a nonparametric approach for (1) efficiency and (2) equity evaluation in education. Firstly, we use a nonparametric (Data Envelopment Analysis) model that is specially tailored to assess educational efficiency at the pupil level. The model accounts for the fact that typically minimal prior structure is available for the behavior (objectives and feasibility set) under evaluation. It allows for uncertainty in the data, while it corrects for exogenous ‘environmental’ characteristics that are specific to each pupil. Secondly, we propose two multidimensional stochastic dominance criteria as naturally complementary aggregation criteria for comparing the performance of different school types (private and public schools). While the first criterion only accounts for efficiency, the second criterion also takes equity into consideration. The model is applied for comparing private (but publicly funded) and public primary schools in Flanders. Our application finds that no school type robustly dominates another type when controlling for the school environment and taking equity into account. More generally, it demonstrates the usefulness of our nonparametric approach, which includes environmental and equity considerations, for obtaining ‘fair’ performance comparisons in the public sector context. 相似文献
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G. S. Khadekar Rupali Wanjari Cenap Ozel 《International Journal of Theoretical Physics》2009,48(9):2550-2557
In this study we have analyzed the Kaluza-Klein type Robertson Walker (RW) cosmological model by considering variable cosmological
constant term Λ of the form:
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and Λ∼ρ in the presence of strange quark matter with domain wall. The various physical aspects of the model are also discussed. 相似文献
10.
《Physics letters. A》2020,384(27):126730
Recently, there have been considerable progresses on the bounds of various quantum channel capacities for bosonic Gaussian channels. Especially, several upper bounds for the classical capacity and the quantum capacity on the bosonic Gaussian channels, via a technique known as quantum entropy power inequality, have been shed light on understanding the mysterious quantum-channel-capacity problems. However, upper bounds for the private capacity on quantum channels are still missing for the study on certain universal upper bounds. Here, we derive upper bounds on the private capacity for bosonic Gaussian channels involving a general Gaussian-noise case through the conditional quantum entropy power inequality. 相似文献