Non‐parametric estimation for time-dependent AUC

The area under the receiver operating characteristic (ROC) curve (AUC) is one of the commonly used measure to evaluate or compare the predictive ability of markers to the disease status. Motivated by an angiographic coronary artery disease (CAD) study, our objective is mainly to evaluate and compare the performance of several baseline plasma levels in the prediction of CAD-related vital status over time. Based on censored survival data, the non-parametric estimators are proposed for the time-dependent AUC. The limiting Gaussian processes of the estimators and the estimated asymptotic variance–covariance functions enable us to further construct confidence bands and develop testing procedures. Applications and finite sample properties of the proposed estimation methods and inference procedures are demonstrated through the CAD-related death data from the British Columbia Vital Statistics Agency and Monte Carlo simulations.     

On the Hardness of Approximating the Min-Hack Problem

We show several hardness results for the Minimum Hacking problem, which roughly can be described as the problem of finding the best way to compromise a target node given a few initial compromised nodes in a network. We give several reductions to show that Minimum Hacking is not approximable to within where δ = 1− ^c n, for any c < 1/2. We also analyze some heuristics on this problem.     

Children's ideas about the bank and shop profit: Developmental stages and the influence of cognitive contrasts and conflict

Ninety-six Hong Kong boys, aged 6 to 13, were given a questionnaire dealing with the operation of the bank and shop transactions. The developmental progression in the understanding of the bank, though more complex in the Hong Kong sample, was essentially similar to that of a Scottish sample reported by Jahoda (1981). A full understanding of the bank emerged at age 10, while that of shop profit emerged at age 6, both showing a precocity over the Scottish sample. The study also considered the roles of cognitive differentiation and conflict, and experimentally tested for any new understanding that might result from the experience of cognitive contrasts and conflict. The experience was found to produce a significant improvement in the understanding of the bank among 10 to 13 year old boys, and of shop profit among 8 to 10 year old boys.     

The Quality of Life of Hong Kong’s Poor Households in the 1990s: Levels of Expenditure,Income Security and Poverty

This paper examines the changes in the quality of life of poor households in Hong Kong in the late 1990s by analyzing their levels of expenditure, income security and poverty before and after 1997. Though there have been significant increases in the levels of expenditure among CSSA recipients, the expenditure among these poorest households in Hong Kong is still below that of non-CSSA recipients. Increasing poverty in Hong Kong is the result of increasing housing costs borne by these low expenditure households, who have to squeeze their expenditure on food and other items in order to meet the rising cost of housing. De-industrialisation and mass unemployment have given capital and the state unchecked authority to restructure the economy and to deregulate the labour market. Many low-income households have been hit hard as they faced redundancy, unemployment and wage-cuts after the 1997 Asian financial crisis. What jobs have been created are mostly part-time, temporary and contract jobs, and there has thus been an erosion in both job and income security. The quality of life of poor households is devastating not only in the sense that their living standards are low, but also that they are socially excluded from the mainstream of society.     

Management performance: An empirical study of the manufacturing companies in Taiwan

This paper proposes a methodology to measure the management performance of the firms of an industry. The idea is to break down the very complicated concept of management into subjects such that the performance of each subject can be measured. The performances of all subjects are then aggregated to form an overall performance of management. The weights associated with the subjects which play a decisive role in aggregation are determined from a two-stage method. This method takes into account both the experience of the experts and the reality reflected by the data collected from the firms. Therefore, the weights generated are more acceptable to the firms. An example of the manufacturing firms in Taiwan illustrates how management is broken down into subjects and how their performances are aggregated. A regression analysis shows that management, in addition to capital and labor, makes a significant contribution to organizational performance. Although the discussion of this paper is confined to the manufacturing industry in Taiwan, the methodology can be applied to other industries and other countries.     

Assessing the Exacerbations Risk of Influenza‐Associated Chronic Occupational Asthma

The purpose of this article was to conduct a risk‐based study based on a linkage of experimental human influenza infections and fluctuation analysis of airway function to assess whether influenza viral infection was risk factor for exacerbations of chronic occupational asthma. Here we provided a comprehensive probabilistic analysis aimed at quantifying influenza‐associated exacerbations risk for occupational asthmatics, based on a combination of published distributions of viral shedding and symptoms scores and lung respiratory system properties characterized by long‐range peak expiratory flow (PEF) dynamics. Using a coupled detrended fluctuation analysis‐experimental human influenza approach, we estimated the conditional probability of moderate or severe lung airway obstruction and hence the exacerbations risk of influenza‐associated occupational asthma in individuals. The long‐range correlation exponent (α) was used as a predictor of future exacerbations risk of influenza‐associated asthma. For our illustrative distribution of PEF fluctuations and influenza‐induced asthma exacerbations risk relations, we found that the probability of exacerbations risk can be limited to below 50% by keeping α to below 0.53. This study also found that limiting wheeze scores to 0.56 yields a 75% probability of influenza‐associated asthma exacerbations risk and a limit of 0.34 yields a 50% probability that may give a representative estimate of the distribution of chronic respiratory system properties. This study implicates that influenza viral infection is an important risk factor for exacerbations of chronic occupational asthma.     

An Industrial Ocean-Cargo Shipping Problem

This paper reports the modeling and solution of an industrial ocean-cargo shipping problem. The problem involves the delivery of bulk products from an overseas port to transshipment ports on the Atlantic Coast, and then over land to customers. The decisions made include the number and the size of ships to charter in each time period during the planning horizon, the number and location of transshipment ports to use, and transportation from ports to customers. The complexity of this problem is compounded by the cost structure, which includes fixed charges in both ship charters and port operations. Such a large scale, dynamic, and stochastic problem is reduced to a solvable stationary, deterministic, and cyclical model. The process of modeling the problem and the solution of the resultant mixed integer program are described in detail. Recommendations from this study have been implemented.