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221.
222.
Joseph Shipman 《Mathematical Intelligencer》2007,29(4):9-14
Theorems 2 and 3 establish the minimum algebraic conditions necessary for a field to be algebraically closed, and they can
therefore be said to “optimize” the Fundamental Theorem of Algebra. But each specific“degree implication” is a first-order
consequence of the axioms for fields, and could have been discovered two centuries ago; the existence of these finitary relationships
appears to have been unsuspected by practically everyone, with one important exception. 相似文献
223.
Ling-yan Tang Song-he Song 《应用数学学报(英文版)》2007,23(2):303-310
In this paper,we use Daubechies scaling functions as test functions for the Galerkin method,and discuss Wavelet-Galerkin solutions for the Hamilton-Jacobi equations.It can be proved that the schemesare TVD schemes.Numerical tests indicate that the schemes are suitable for the Hamilton-Jacobi equations.Furthermore,they have high-order accuracy in smooth regions and good resolution of singularities. 相似文献
224.
Luca Lambertini Raimondello Orsini 《Central European Journal of Operations Research》2007,15(1):105-117
We reconsider the role of network externalities in a dynamic spatial monopoly where the firm must invest in order to accumulate
capacity, while consumers may have either linear or quadratic preferences. We (1) characterise saddle point equilibria, (2)
prove that the extent of market coverage is increasing in the network effect and (3) unlike the existing static literature
on the same problem, the monopolist may not make introductory price offers. Then, we briefly deal with the socially optimal
solution, showing that, in general, a planner would serve more consumers than a profit-seeking monopolist.
相似文献
225.
This paper reports positive results from an application of one type of group support system (GSS) to a training application. Reviews of the findings of other trials of GSS have been mixed, and inconclusive. We describe the results of a series of seven training sessions in a field-based application of group process support. The subjects were professionals working in various agencies concerned with the welfare of older people. A ‘low-profile’ type of group support system, based on wireless handsets, was used. This design enabled responses from each participant to be input and displayed anonymously. Each session was aimed at stimulating a dialogue focused on the reasons for differences of judgement, as displayed on a single projected feedback screen. Changes of individual judgements were recorded for subsequent analysis and comparison with already known ‘expert judgements’. Frequent changes of judgement were recorded. A significant proportion of these were related to an improvement, which could not be explained as simply the result of conforming behaviour. We propose that the mode of operation and design of a ‘low-profile’ GSS have the potential to create a learning environment by reducing personal anxieties while encouraging group-based learning with focussed conversation. We conclude that this type of GSS design is particularly suited to ‘selective’-type tasks in groups. 相似文献
226.
Hans Weber 《Order》2007,24(4):249-276
We study lattice theoretical properties of lattices of uniformities such as modularity, distributive laws and the existence
of (relative) complements. For this the concepts of permutable uniformities (see Definition 3.1) and independent uniformities
(see Definition 4.1) are important. Moreover, we show that e.g. the lattice of all lattice uniformities on a lattice L is a closed sublattice of the lattice of all uniformities on L. 相似文献
227.
The paper is concerned with a two-delay singular differential system with a twin parameter. Applying fixed-point index theory, we show the relationship between the asymptotic behaviors of nonlinearities (at zero and infinity) and the open regions (eigenvalue regions) of parameters, which are correlated with delays, such that the system has zero, one and two positive solution(s). 相似文献
228.
Bernardo Lafuerza-Guillén Donal O’regan Reza Saadati 《Proceedings Mathematical Sciences》2007,117(1):61-70
We introduce the concept of quotient in PN spaces and give some examples. We prove some theorems with regard to the completeness
of a quotient. 相似文献
229.
J Whittaker C Whitehead M Somers 《The Journal of the Operational Research Society》2007,58(7):911-921
A principled technique for monitoring the performance of a consumer credit scorecard through time is derived from Kalman filtering. Standard approaches sporadically compare certain characteristics of the new applicants with those predicted from the scorecard. The new approach systematically updates the scorecard combining new applicant information with the previous best estimate. The dynamically updated scorecard is tracked through time and compared to limits calculated by sequential simulation from the baseline scorecard. The observation equation of the Kalman filter is tailored to take the results of fitting local scorecards by logistic regression to batches of new clients that arrive in the current time interval. The states in the Kalman filter represent the true or underlying score for each attribute in the card: the parameters of the logistic regression. Their progress in time is modelled by a random walk and the filter provides the best estimate of the scores using past and present information. We illustrate the technique using a commercial mortgage portfolio and the results indicate significant emerging deficiencies in the baseline scorecard. 相似文献
230.
Fengfu Fu Liangjun Xu Wei Ye Yiquan Chen Mingyu Jiang Xueqin Xu 《中国颗粒学报》2006,4(6):323-326
Different-sized aerosols were collected by an Andersen air sampler to observe the detailed morphology of the black carbon (BC) aerosols which were separated chemically from the other accompanying aerosols, using a Scanning Electron Microscope equipped with an Energy Dispersive X-ray Spectrometer (SEM-EDX). The results indicate that most BC aerosols are spherical particles of about 50 nm in diameter and with a homogeneous surface. Results also show that these particles aggregate with other aerosols or with themselves to form larger agglomerates in the micrometer range. The shape of these 50-nm BC spherical particles was found to be very similar to that of BC particles released from petroleum-powered vehicular internal combustion engines. These spherical BC particles were shown to be different from the previously reported fullerenes found using Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF-MS). 相似文献