The canadian traveller problem and its competitive analysis

From the online point of view, we study the Canadian Traveller Problem (CTP), in which the traveller knows in advance the structure of the graph and the costs of all edges. However, some edges may fail and the traveller only observes that upon reaching an adjacent vertex of the blocked edge. The goal is to find the least-cost route from the source O to the destination D, more precisely, to find an adaptive strategy minimizing the competitive ratio, which compares the performance of this strategy with that of a hypothetical offline algorithm that knows the entire topology in advance. In this paper, we present two adaptive strategies—a greedy or myopic strategy and a comparison strategy combining the greedy strategy and the reposition strategy in which the traveller backtracks to the source every time when he/she sees a failed edge. We prove tight competitive ratios of 2 ^k+1−1 and 2k+1 respectively for the two strategies, where k is the number of failed edges in the graph. Finally, we propose an explanation of why the greedy strategy and the comparison strategy are usually preferred by drivers in an urban traffic environment, based on an argument related to the length of the second-shortest path in a grid graph. We would like to acknowledge the support from NSF of China (No. 70525004, No. 70121001 and No. 60736027), and the support from K.C. Wong Education Foundation, Hong Kong.     

广义不确定性下广义博弈中NS均衡的存在性

把不确定性引入广义博弈的研究之中,在此博弈中,局中人策略之间存在相互影响,局中人的策略可以改变不确定参数的变化范围,而且局中人的支付函数和策略可行反应映射都受到不确定参数的作用,此类型博弈定义为广义不确定性下的广义博弈问题。进一步定义出此类型博弈中的NS均衡,并且凭借Fan-Glicksberg不动点定理,证明此均衡点的存在性。最后给出算例验证其可行性。     

Availability of Canadian government information

In summary, great improvements have been made, in recent years in the distribution procedures for Canadian Federal Government publications. These, and Bill C-43 have significantly raised the level of availability of the Federal Government information to residents of Canada. Beyond the borders, and specifically in the United States, this information can certainly not be described as readily available to the average citizen. In fairness, it seems likely that U.S. librarians have not been moved to acquire this information because there is no perceived demand for it.Canada's Prime Minister, Pierre Trudeau, has described the effect upon Canada of sharing 3,000 miles of border with the U.S. as akin to “sleeping with an elephant.” Mass media and commerce keep Canadians vividly aware of every aspect of American life. Perhaps it is time Canada attempted to raise its image in the U.S. Active promotion of Canadian Government Information would be a viable beginning.     

Generalized Instrumental Variable Models

This paper develops characterizations of identified sets of structures and structural features for complete and incomplete models involving continuous or discrete variables. Multiple values of unobserved variables can be associated with particular combinations of observed variables. This can arise when there are multiple sources of heterogeneity, censored or discrete endogenous variables, or inequality restrictions on functions of observed and unobserved variables. The models generalize the class of incomplete instrumental variable (IV) models in which unobserved variables are single‐valued functions of observed variables. Thus the models are referred to as generalized IV (GIV) models, but there are important cases in which instrumental variable restrictions play no significant role. Building on a definition of observational equivalence for incomplete models the development uses results from random set theory that guarantee that the characterizations deliver sharp bounds, thereby dispensing with the need for case‐by‐case proofs of sharpness. The use of random sets defined on the space of unobserved variables allows identification analysis under mean and quantile independence restrictions on the distributions of unobserved variables conditional on exogenous variables as well as under a full independence restriction. The results are used to develop sharp bounds on the distribution of valuations in an incomplete model of English auctions, improving on the pointwise bounds available until now. Application of many of the results of the paper requires no familiarity with random set theory.     

Canadian collections in the United States

The purpose of this article is to identify the libraries in the United States with collections of Canadian materials, the extent of the collections and some of the problems encountered in collecting Canadian publications. Questionnaires were sent to 49 selective and full depositories of Canadian federal documents and 306 depositories of United States federal documents, drawn from theList of Depository Libraries by random sample. It was found that those libraries not already designated as Canadian federal depositories in the United States for the most part either do not collect Canadian materials at all or have very limited collections. A directory of the Canadian depository libraries is included.In selecting Canadian publications, one person usually handles the federal documents while other publications are primarily selected by subject area. Thus it is understandable that upon receiving Canadian publications libraries primarily class some documents by catalogue number and integrate others into the library's main collection.Bibliographic control has improved greatly since 1927 with many changes in the public printing law and concerted attempts by concerned librarians and the Canadian Library Association.     

Role stress among Canadian white-collar workers

The incidence of various stressors at work and outside work was examined in a group of public service workers with a large Canadian federal government department. Workers were either in clerical, technical and supervisory ('officers'), or management positions. Measures of work stress included role stressors (load, insufficiency, conflict ambiguity and responsibility), as well as stress due to the physical environment. Both life events and daily hassles were included as measures of non-work stress. The consequences of stress were considered in terms of vocational, psychological, interpersonal, and physical strain, as well as in terms of job satisfaction and organizational commitment. Potential moderators of stress included social support and self-esteem. Among work stressors conflict, ambiguity and insufficiency were the more closely associated with vocational outcomes. MANCOVA followed by discriminant function analysis showed that clerical workers were distinguished by higher levels of insufficiency, officers by higher levels of conflict and the lowest levels of job satisfaction and organizational commitment, and managers by higher levels of perceived responsibility for others. The results are discussed in terms of social role theory.     

Generalized perfect domination in graphs

Let k be a positive integer and G=(V,E) be a graph. A vertex subset D of a graph G is called a perfect k-dominating set of G, if every vertex v of G, not in D, is adjacent to exactly k vertices of D. The minimum cardinality of a perfect k-dominating set of G is the perfect k-domination number γ _kp (G). In this paper, we give characterizations of graphs for which γ _kp (G)=γ(G)+k?2 and prove that the perfect k-domination problem is NP-complete even when restricted to bipartite graphs and chordal graphs. Also, by using dynamic programming techniques, we obtain an algorithm to determine the perfect k-domination number of trees.     

Generalized median graphs and applications

We study the so-called Generalized Median graph problem where the task is to construct a prototype (i.e., a ‘model’) from an input set of graphs. While our primary motivation comes from an important biological imaging application, the problem effectively captures many vision (e.g., object recognition) and learning problems, where graphs are increasingly being adopted as a powerful representation tool. Existing techniques for his problem are evolutionary search based; in this paper, we propose a polynomial time algorithm based on a linear programming formulation. We propose an additional algorithm based on a bi-level method to obtain solutions arbitrarily close to the optimal in (worst case) non-polynomial time. Within this new framework, one can optimize edit distance functions that capture similarity by considering vertex labels as well as he graph structure simultaneously. We first discuss experimental evaluations in context of molecular image analysis problems—he methods will provide the basis for building a topological map of all 23 pairs of the human chromosome. Later, we include (a) applications to other biomedical problems and (b) evaluations on a public pattern recognition graph database. This work was supported by NSF grants CCF-0546509, IIS-0713489, and NIH grant GM 072131-23. The second author was also supported in part by the Department of Biostatistics and Medical Informatics, UW-Madison and UW ICTR, funded through an NIH Clinical and Translational Science Award (CTSA), grant number 1 UL1 RR025011.     

广义关键路线法的初步探索

利用关键路线法(简称CPM)网络计划技术对项目进度的分析完成后,由于某种原因,网络计划中一些工序需要对自己的开始和结束时间进行重新预计,事必对原有进度计划产生影响.针对该类问题,本文以关键路线法的基本方法为基础,提出关键路线法的拓展方法一和二,并综合这两个方面,给出了广义关键路线法,进而量化并分析了当任意多个工序需要重新预计各自开始和结束时间时,网络计划图中各节点和工序的时间参数以及总工期受影响的程度.算例验证了其正确性和可行性.     

广义判断矩阵研究的若干新进展

介绍了近年AHP理论研究中提出的计算广义判断矩阵排序向量的四种不同的特征向量法,并给予评价.     

An insider's view of the Canadian system

There is much to be learned from examination of health care delivery systems of other countries. But the task must be approached with caution. No other system is likely to lend itself to wholescale reproduction in this country, and all are certain to have their own flaws. In this article, based on a presentation at the 1991 ACPE National Conference in Toronto, Ontario, Canada, a Canadian describes his country's system, warts and all, and how it might be made better.     

Generalized Steiner Problems and Other Variants

In this paper, we examine combinatorial optimization problems by considering the case where the set N (the ground set of elements) is expressed as a union of a finite number of m nonempty distinct subsets N ₁,...,N _m. The term we use is the generalized Steiner problems coined after the Generalized Traveling Salesman Problem. We have collected a short list of classical combinatorial optimization problems and we have recast each of these problems in this broader framework in an attempt to identify a linkage between these “generalized” problems. In the literature one finds generalized problems such as the Generalized Minimum Spanning Tree (GMST), Generalized Traveling Salesman Problem (GTSP) and Subset Bin-packing (SBP). Casting these problems into the new problem setting has important implications in terms of the time effort required to compute an optimal solution or a “good” solution to a problem. We examine questions like “is the GTSP “harder” than the TSP?” for a number of paradigmatic problems starting with “easy” problems such as the Minimal Spanning Tree, Assignment Problem, Chinese Postman, Two-machine Flow Shop, and followed by “hard” problems such as the Bin-packing, and the TSP.     

Canadian executives' perceptions of the U.S. and Canadian free-trade agreement and their potential effects on decision-making

This study analyzes executives' perceptions of free trade negotiations and the potential effects of these perceptions on strategy. Top executives in 300 major Canadian industrial firms were surveyed to test two propositions. They are: (1) Executives tend to perceive that free trade would lead to market expansion which, in turn, would increase trade, production, and investment efficiencies and (2) Decisions in business strategy formulation and implementation may be influenced by the perceptions of the trade policy.The propositions were tested with the following results. Support for proposition one is mixed. Support for proposition two, however, is for the most part predominant.     

Corporate governance and accounting irregularities: Canadian evidence

This study examines the extent to which corporate governance acts as an efficient means of protecting investors against accounting irregularities. It is grounded in the literatures on public enforcement of securities laws by market authorities, governance, and fraudulent financial statements. A unique feature of the Canadian tracking and enforcement system for reporting issuers in default is used to refine the definitions of accounting irregularities or fraudulent financial statements used in other studies. We test and find that the governance mechanisms of firms found in default of financial reporting regulations during the first 5 years of existence of the Canadian system are weak compared to a sample of no-default firms. For instance, they have fewer independent and financial expert directors on their boards and audit committees, are more prone to have recently changed auditor and to having their CEO as chair of the board. They also appear to fulfill their financing requirements through private rather than public funds, which is consistent with the fact that default firms are less likely to be in a position to return to the public market to fulfill their needs. This study offers evidence relevant to policy makers and others who are concerned with the potential role of market authorities and governance in protecting investors against accounting irregularities.     

Voluntary disclosure of sustainability reports by Canadian universities

In contrast to corporate firms, voluntary sustainability reporting by universities is still in its infancy. Against this background, we have investigated which Canadian universities report their sustainability performance and what specifically is reported. Our study applies content analyses as a methodological approach to determine the relative importance of disclosure topics by using a university-specific catalogue of indicators. This unique study completely covers all sustainability reports published between 2011 and 2015 by Canadian universities and as such provides evidence and analyses of voluntary sustainability reporting by universities, which has been the subject of very little research to date. The findings show that sustainability reporting by Canadian universities diverges considerably and the range of aspects included is relatively narrow. Overall, the results show a clear focus on the environmental dimension and very weak coverage of the social dimension. The environmental orientation of many Canadian universities seems to be a result of their participation in the STARS program.     

Changes and Trends in Canadian Corporate Ethics Programs

This article reports and analyzes the findings of comprehensive surveys on ethics programs in Canada's largest corporations in 2002 and 2006. A usable response rate of 25 percent was obtained in the 2002 and 21.8 percent in the 2006 survey of the country's 500 largest corporations as identified by the National Post Business Magazine, which annually ranks Canadian corporations according to revenue. It was found that ethics programs have taken root in Canada's largest organizations and are now of strategic importance to these organizations. In 2006, a statistically significant increase was observed in the proportion of boards of directors involved in the establishment of codes of ethics. In a reflection of technological developments, a significant increase in the use of electronic communication of these codes was also observed in 2006. Almost all (96 percent in 2002 and 98 percent in 2006) of the respondents indicated that there were consequences for breaching their codes. In other aspects of ethics programs, it was found that the proportion of corporations having standing ethics committees rose significantly as did the prevalence of ethics audits and support for whistleblowers and whistleblowing. These measures are having a positive effect as 83.5 percent of respondents in 2006, up from 68 percent in 2002 (P≤ 0.01), saw their firms’ ethics codes improving profit. Overall, 89.7 percent of respondents in 2002 and 91.9 percent in 2006 saw their codes as having a positive impact on organizational policies.     

Generalized Utilitarianism and Harsanyi's Impartial Observer Theorem

Harsanyi's impartial observer must consider two types of lotteries: imaginary identity lotteries (“accidents of birth”) that she faces as herself and the real outcome lotteries (“life chances”) to be faced by the individuals she imagines becoming. If we maintain a distinction between identity and outcome lotteries, then Harsanyi‐like axioms yield generalized utilitarianism, and allow us to accommodate concerns about different individuals' risk attitudes and concerns about fairness. Requiring an impartial observer to be indifferent as to which individual should face similar risks restricts her social welfare function, but still allows her to accommodate fairness. Requiring an impartial observer to be indifferent between identity and outcome lotteries, however, forces her to ignore both fairness and different risk attitudes, and yields a new axiomatization of Harsanyi's utilitarianism.     

Generalized Diameters and Rabin Numbers of Networks

Reliability and efficiency are important criteria in the design of interconnection networks. Recently, the w-wide diameter d_w(G), the (w – 1)-fault diameter D_w(G), and the w-Rabin number r_w(G) have been used to measure network reliability and efficiency. In this paper, we study d_w(G), D_w(G) and r_w(G) using the strong w-Rabin number r_w ^*(G) for 1 w k(G) and G is a circulant network G(d_n; {1, d,..., d^{n –1}}), a d-ary cube network C(d, n), a generalized hypercube GH(m_{n – 1},..., m0), a folded hypercube FH(n) or a WK-recursive network WK(d, t).