A corrected likelihood method for the proportional hazards model with covariates subject to measurement error

There has been extensive interest in discussing inference methods for survival data when some covariates are subject to measurement error. It is known that standard inferential procedures produce biased estimation if measurement error is not taken into account. With the Cox proportional hazards model a number of methods have been proposed to correct bias induced by measurement error, where the attention centers on utilizing the partial likelihood function. It is also of interest to understand the impact on estimation of the baseline hazard function in settings with mismeasured covariates. In this paper we employ a weakly parametric form for the baseline hazard function and propose simple unbiased estimating functions for estimation of parameters. The proposed method is easy to implement and it reveals the connection between the naive method ignoring measurement error and the corrected method with measurement error accounted for. Simulation studies are carried out to evaluate the performance of the estimators as well as the impact of ignoring measurement error in covariates. As an illustration we apply the proposed methods to analyze a data set arising from the Busselton Health Study [Knuiman, M.W., Cullent, K.J., Bulsara, M.K., Welborn, T.A., Hobbs, M.S.T., 1994. Mortality trends, 1965 to 1989, in Busselton, the site of repeated health surveys and interventions. Austral. J. Public Health 18, 129–135].     

高职教育综合实验教学的研究与探讨

高等职业教育的目标是培养应用型、技能型人才。综合实验能激发学生的学习兴趣,调动学生的积极性,有助于培养学生的动手能力和独立工作能力,确实是一条实验教学改革的好路子。     

Online interval scheduling: randomized and multiprocessor cases

We consider the problem of scheduling a set of equal-length intervals arriving online, where each interval is associated with a weight and the objective is to maximize the total weight of completed intervals. An optimal 4-competitive algorithm has long been known in the deterministic case, but the randomized case remains open. We give the first randomized algorithm for this problem, achieving a competitive ratio of 3.5822. We also prove a randomized lower bound of 4/3, which is an improvement over the previous 5/4 result. Then we show that the techniques can be carried to the deterministic multiprocessor case, giving a 3.5822-competitive 2-processor algorithm, and a 4/3 lower bound for any number of processors. We also give a lower bound of 2 for the case of two processors. A preliminary version of this paper appeared in the Proceedings of COCOON 2007, LNCS, vol. 4598, pp. 176–186. The work described in this paper was fully supported by a grant from City University of Hong Kong (SRG 7001969), and NSFC Grant No. 70525004 and 70702030.     

Initiating Sexual Experiences: How Do Young Adolescents Make Decisions Regarding Early Sexual Activity?

Understanding how young adolescents make decisions to engage in early sexual activities is vital for intervention efforts aimed at fostering positive youth development and reducing the negative outcomes of adolescent sexual behavior. In‐depth interviews with 42 suburban, mostly White, ninth‐grade adolescents (52% females, mean age=14.1, SD=.45) elicited accounts of their early sexual decisions. We adapted grounded theory methodology to build a model of sexual decision making from the adolescents' narratives. Six dominant categories emerged: contextual factors (relationship and personal characteristics), consideration of risks and benefits, boundary setting, boundary communication, the sexual experience, and evaluation. Our model of early sexual decision‐making processes, developed from the perspectives of young adolescents, highlights active consideration of health and social risks and benefits, as well as the generation of options regarding sexual activity. The model also shows that young adolescents set clear boundaries of sexual limits and evaluate sexual experiences, suggesting a dynamic process of decision making.     

Online bin packing of fragile objects with application in cellular networks

We study a specific bin packing problem which arises from the channel assignment problems in cellular networks. In cellular communications, frequency channels are some limited resource which may need to share by various users. However, in order to avoid signal interference among users, a user needs to specify to share the channel with at most how many other users, depending on the user’s application. Under this setting, the problem of minimizing the total channels used to support all users can be modeled as a specific bin packing problem as follows: Given a set of items, each with two attributes, weight and fragility. We need to pack the items into bins such that, for each bin, the sum of weight in the bin must be at most the smallest fragility of all the items packed into the bin. The goal is to minimize the total number of bins (i.e., the channels in the cellular network) used. We consider the on-line version of this problem, where items arrive one by one. The next item arrives only after the current item has been packed, and the decision cannot be changed. We show that the asymptotic competitive ratio is at least 2. We also consider the case where the ratio of maximum fragility and minimum fragility is bounded by a constant. In this case, we present a class of online algorithms with asymptotic competitive ratio at most of 1/4+3r/2, for any r>1. A preliminary version of this paper appeared in Proc. of Workshop on Internet and Network Economics (WINE’05, pp. 564–573). The research of W.-T.C. was supported in part by Hong Kong RGC grant HKU5172/03E. The research of F.Y.-L.C. was supported in part by Hong Kong RGC Grant HKU7142/03E. The research of D.Y. was supported by NSFC (10601048). The research of G.Z. was supported in part by NSFC (60573020).     

Vector autoregression and causality: a theoretical overview and simulation study

This paper provides a theoretical overview of Wald tests for Granger causality in levels vector autoregressions (VAR's) and Johansen-type error correction models (ECM's). The theory is based on results in Toda and Phillips (1991a) and allows for stochastic and deterministic trends as well as arbitrary degrees of cointegration. We recommend some operational procedures for conducting Granger causality tests that are based on the Gaussian maximum likelihood estimation of ECM's. These procedures are applicable in the important practical case of testing the causal effects of one variable on another group of variables and vice versa. This paper also investigates the sampling properties of these testing procedures through simulation exercises. Three sequential causality tests in ECM's are compared with conventional causality tests in levels and differences VAR's.     

Use of Quality-Adjusted Life Year Weights with Dose-Response Models for Public Health Decisions: A Case Study of the Risks and Benefits of Fish Consumption

Risks associated with toxicants in food are often controlled by exposure reduction. When exposure recommendations are developed for foods with both harmful and beneficial qualities, however, they must balance the associated risks and benefits to maximize public health. Although quantitative methods are commonly used to evaluate health risks, such methods have not been generally applied to evaluating the health benefits associated with environmental exposures. A quantitative method for risk-benefit analysis is presented that allows for consideration of diverse health endpoints that differ in their impact (i.e., duration and severity) using dose-response modeling weighted by quality-adjusted life years saved. To demonstrate the usefulness of this method, the risks and benefits of fish consumption are evaluated using a single health risk and health benefit endpoint. Benefits are defined as the decrease in myocardial infarction mortality resulting from fish consumption, and risks are defined as the increase in neurodevelopmental delay (i.e., talking) resulting from prenatal methylmercury exposure. Fish consumption rates are based on information from Washington State. Using the proposed framework, the net health impact of eating fish is estimated in either a whole population or a population consisting of women of childbearing age and their children. It is demonstrated that across a range of fish methylmercury concentrations (0-1 ppm) and intake levels (0-25 g/day), individuals would have to weight the neurodevelopmental effects 6 times more (in the whole population) or 250 times less (among women of child-bearing age and their children) than the myocardial infarction benefits in order to be ambivalent about whether or not to consume fish. These methods can be generalized to evaluate the merits of other public health and risk management programs that involve trade-offs between risks and benefits.     

CEO humility,narcissism and firm innovation: A paradox perspective on CEO traits

We examine how two seemingly contradictory yet potentially complementary CEO traits—humility and narcissism—interact to affect firm innovation. We adopt a paradox perspective and propose that individuals can have paradoxical traits and that, in particular, humility and narcissism can coexist harmoniously, especially among the Chinese, whose philosophical tradition embraces paradoxical thinking and behaving. CEOs that are both humble and narcissistic are hypothesized to be more likely to have socialized charisma, to cultivate an innovative culture, and to deliver innovative performance. Two studies using multisource data involving 63 CEOs, 328 top managers, and 645 middle managers in Study 1 and 143 CEOs and 190 top managers in Study 2 support the hypotheses and point to new directions for studying CEO traits and their effects on firm outcomes.     

Organizational wisdom practices and firm product innovation

Review of Managerial Science - The manner in which organizational wisdom-related variables or practices (e.g., reasoning, intuition, virtue, prudence, and aesthetics) are related to firm product...     

基于组织忘记的企业动态能力成因机理研究

为了探索企业动态能力的成因和机理,对相关文献进行了梳理,提出了动态能力成因机制;运用复杂理论,从知识活动层面构建了NK模型,指出了组织忘记分别通过改变组织记忆系统和增强再学习能力而形成动态能力;最后进行了案例分析讨论.