Testing for a Unit Root in ARIMA Processes

A unit root has important long-run implications for many time series in economics and finance. This paper develops a unit-root test of an ARIMA(p-1, 1, q) with drift null process against a trend-stationary ARMA(p, q) alternative process, where the order of the time series is assumed known through previous statistical testing or relevant theory. This test uses a point-optimal test statistic, but it estimates the null and alternative variance-covariance matrices that are used in the test statistic. Consequently, this test approximates a point-optimal test. Simulations show that its small-sample size is close to the nominal test level for a variety of unit-root processes, that it has a robust power curve against a variety of stationary alternatives, that its combined small-sample size and power properties are highly competitive with previous unit-root tests, and that it is robust to conditional heteroskedasticity. An application to post-Second World War real per capita gross domestic product is provided.     

论郭店楚简《太一生水》本体生成系统

“太一生水”的“太一”是郭店《老子》的“自然”之“状”,又与北极星有关,是主客体相融的“自然”。与“道”也 有区别。“太一生水”可以在先秦和汉代的文献中找到旁证。“太一生水”的逻辑生成系统是是本体论生成,与《易》学 象数、方向、五行生成系统不同。但可在象数系统上投射而加深理解。     

我国财政赤字与国债规模的现实性思考

改革开放以来 ,国家实施赤字预算使国债发行成为弥补赤字的主要方法。随着经济的持续稳定增长 ,赤字和国债的规模都呈不断扩大的趋势 ,尤其是近几年来 ,为扩大内需而实施的积极财政政策使国债累积余额以超过 30 %的年增长率上升 ,因此如果不考虑对国债适度规模的控制 ,就有引发国家财政风险的可能。     

A flexibly structured lot sizing heuristic for a static remanufacturing system

An effective planning of lot sizes is a key strategy to efficiently manage a combined manufacturing/remanufacturing system in the presence of substantial setup costs. Due to its complex interdependencies, optimal policies and solutions have not been identified so far, but several heuristic approaches have been analyzed in recent contributions. The main heuristic shortcuts are forcing equally sized lot sizes over the planning horizon as well as imposing a specific cycle structure, i.e., a sequence of manufacturing batches is followed by a sequence of remanufacturing batches. We are instead proposing a flexibly structured heuristic that allows for differently sized remanufacturing batches. We show in a comprehensive numerical study that our approach outperforms other existing approaches in more than half of all instances by up to 17%.     

The resource recovery level decision for end-of-life products

Resource recovery from end-of-life (EOL) products is becoming increasingly engaged in by companies as a response to customer, consumer, government and social pressures, the electronics industry cites competitor pressures as being the main driver of EOL product take-back and recovery. Recovery can occur at three levels; i.e. product, part and material. Each of these options has economic and environmental advantages and disadvantages depending on the product type and a host of other influencing factors. The work described in this paper supports the decision as to the most favourable route from a cost and value perspective, a software model that provides such support is also described.     

Modelling end-of-life product recovery chains - a case study

European Union legislation, and existing national legislation of many European countries, mandates that manufacturers take back and recover their electronic and electrical equipment. If manufacturers are to comply with legislation, models need to be developed for these activities. Whilst infrastructural and technological deficits exist and must be addressed, so too must the organization of recovery, from a business perspective. In this paper, models of resource recovery are presented and a case study described.     

Production seat booking system for the combination of make-to-order and make-to-stock products

This study deals with the problem of the production seat booking system. Like an airline or train booking system, customers' orders are assigned a production seat. Using the production seat booking system, inquiries about the delivery for individual orders can be answered quickly. The key issues in the production seat booking system are: (1) In which manufacturing environments are the production seat booking system appropriate and efficient? (2) How should the production seat be set? (3) How should orders be assigned a production seat? A production planning model is formulated for a production seat booking system with a combination of make-to-order and maketo-stock as production environment. Two kinds of variables are set as policy in the model: one is a variable for setting production capacity and the other a variable for assigning orders a production seat. By focusing on the characteristics of market demand, this paper clarifies the following points: (1) How do these policy variables affect the manufactuiring performance? (2) How does the buffer inventory for make-to-stock product affect the degree of the delivery date satisfaction for make-toorder products? (3) Within what range should the two policy variables be set in order to maintain the unfilled-rate of maketo-stock product under the specified level and the degree of delivery date satisfaction for make-to-order products over the specified level? This paper presents a basis for designing for a production seat booking system through a series of numerical experiments.     

Stein’s method and the distribution of the product of zero mean correlated normal random variables

Abstract

Over the last 80?years there has been much interest in the problem of finding an explicit formula for the probability density function of two zero mean correlated normal random variables. Motivated by this historical interest, we use a recent technique from the Stein’s method literature to obtain a simple new proof, which also serves as an exposition of a general method that may be useful in related problems.     

产品造型中技术含量与美术含量

从形式服从功能这一观点入手,举例论述了产品造型中技术与形式美学法则的关系,及在不同的产品造型中它的重要性。     

Technology‐Based New Product Development Partnerships*

Hypotheses were developed to capture the dynamic capabilities that result from interfirm partnerships during the joint new product development (NPD) process—the ability to build, integrate, and reconfigure existing resources to adapt to rapidly changing environments. These capabilities, in turn, were proposed to have a positive impact on NPD performance outcomes: (a) proportion of new product success and (b) superior new product commercialization. In contexts where the locus of innovation is rapidly changing, the impact of interfirm NPD dynamic capabilities was hypothesized to be diminished in high‐technology contexts, especially for buyers (original equipment manufacturers) and to a lesser extent for suppliers. Still, technology‐based interfirm NPD partnerships were predicted to ultimately outperform low‐technology ones in both NPD performance outcomes. Finally, information technology (IT) support for NPD was hypothesized to influence the interfirm NPD partnership's dynamic capabilities. Using survey data from 72 auto company managers and their suppliers, the proposed model in which IT support for NPD influences the success of interfirm NPD partnerships through the mediating role of interfirm NPD partnership dynamic capabilities in high‐ and low‐technology contexts was generally supported. The results shed light on the nature of technology‐based interfirm NPD partnerships and have implications for their success. Theoretical and managerial implications are discussed.