Registration of longitudinal data by means of musical notation: some applications

Graphic representation of complicated courses is often necessary to detect patterns that may be worth analysing. Examples are given to show how musical notation or modifications of musical notation may be used to register courses (or cross-sectional data) with more variables than usual. One can register courses with known duration of components (and then also simultaneities); the time scale may be defined according to data. One can also register sequences without known duration of components. Finally the method can be modified so as to suit cross-sectional data. The method can be used to register a single case but also a group of cases that are thus rendered comparable. It is a method of registration, not of analysis but one that may help prepare a refined analysis.     

Registration of longitudinal data by means of musical notation

There is a lack of good registration methods for complex longitudinal data. Cumulating longitudinal data into cross-sections, even repeated ones, in order to allow for statistical analysis means considerable distortion of data; if they interact with each other, this is not possible to observe directly and the time factor is not taken into account to its full value, if at all. In this context, music may be defined as a complicated development in the course of time. Music is usually represented by musical notation which, if not ideal, means that we already possess a high precision registration method for complicated temporal developments. Musical notation used for registration of other longitudinal variables than musical ones allows for a multitude of qualitative variables being taken into account simultaneously and a high precision regarding the time factor. It should be no more difficult to analyse statistically a longitudinal pattern than a surface pattern.     

High precision registration of complicated longitudinal and cross-sectional data

In the article are given examples showing how, by using musical notation in registering (complicated) developments, considerably more qualitative variables may be taken into account than we were used to; furthermore, the temporal element may be represented with a degree of precision that corresponds to our needs. In case of cross-sectional data modifications of musical notation may be used. However, we have to recognize that there are also variables, maybe important ones, that — for several reasons — cannot be registered with a very high precision. Other complications are hinted at. The method described is rather a working method by means of which to improve the basis for a further quantitative analysis than a method suitable for showing final research results.     

Formulating Hypotheses Graphically in Social Research

This article explores the proposition that the appropriate use of suitable forms of graphic communication can improve the formulation and presentation of hypotheses in quantitative social science research. The creative nature of scientific diagrams is discussed and the technological advances in computer graphic media are seen as part of a visual revolution which is markedly changing not only the way we see things but also the way we think and do things today. Brief historical views on the use of hypotheses and diagrammatic languages in science are given. The restricted use of graphic communication tools in social research academic documents is discussed and the importance of using well-designed data graphics in the production and transmission of scientific knowledge is highlighted. Hypotheses are conceptualised and their importance within social research is emphasised. A methodological approach for formulating hypotheses graphically is proposed based on the use of three types of language: notation, statement (ordinary language) and diagram. Some criteria are suggested for the selection of diagram type dependent on the related variables. Several examples are given covering the different models proposed.     

FTP服务器的分级管理在机房中的应用

现代网络教学是以学生为中心的教学结构、互动式的学习环境、图文声像并茂的多媒体课件应用,这使得教育变得更加直观、生动,更有助于发挥学生的主动性和积极性。所有高校为了满足教学需要,各院系都有自己的计算机机房,随着计算机课程的不断开设,计算机数量的不断增多,机房规模的不断扩大给机房的维护带来了很大的不便。而学生在学习应用的过程中有很多的信息需要存储,但是在机房里又不能给我们提供这样的条件。我们在实际的教学实践中怎样来解决这些矛盾呢?这就是我们在这里所要探讨的问题。     

Social representations and social marketing: Effectiveness of awareness campaigns on the representation of public policies?

The research fits into the theory of the central core within the social representations theory. The approach argues the existence of two components: the core and the periphery. Each one has its own characteristics and a role to play. Within this framework, transformation of social representations can be the consequence of practices modification. However, in this study, we are interested in the effect of communication. We focus on the social representation of the public policy of the 30 kmh speed limit developed in Europe since the 1990's. And we test the impact of two awareness campaigns: the first one aims at reinforcing one aspect of the central core of the representation, the second one aims at contradicting one aspect of the core. Three groups of participants answer a questionnaire of representation related to the 30 kmh speed limit: two experimental groups (each one receiving a campaign) and one control group. Results confirm the relevance of using communication and social marketing methods in order to transform social representations. According to the type information, results are different. Discussion highlights the interest of using social representations in order to build social marketing campaigns.     

A study on the mean past lifetime of the components of (n − k + 1)-out-of-n system at the system level

In the present paper, we consider a (n − k + 1)-out-of-n system with identical components where it is assumed that the lifetimes of the components are independent and have a common distribution function F. We assume that the system fails at time t or sometime before t, t > 0. Under these conditions, we are interested in the study of the mean time elapsed since the failure of the components. We call this as the mean past lifetime (MPL) of the components at the system level. Several properties of the MPL are studied. It is proved that the relation between the proposed MPL and the underlying distribution is one-to-one. We have shown that when the components of the system have decreasing reversed hazard then the MPL of the system is increasing with respect to time. Some examples are also provided.     

Estimating non-simultaneous changes in the mean of vectors

A sequence of independent vectors with correlated components is considered. It is supposed that there is one change point in the mean of each component and changes need not occur simultaneously. The asymptotic distribution of the change point estimators is studied. If the true change points are well separated, the explicit asymptotic distribution of the change point estimators is presented. In the case the true change points coincide, it is shown that the limit distribution of properly standardized change points estimates exists. It depends not only on the underlying time series dependence structure, but also on the ratio of the sizes of the changes. The asymptotic distribution function is not known, but due to the invariance principle it can be obtained by simulations.     

A study on the conditional inactivity time of coherent systems

The study on the inactivity times is useful in evaluating the aging and reliability properties of coherent systems in reliability engineering. In the present paper, we investigate the inactivity time of a coherent system consisting of n i.i.d. components. We drive some mixture representations for the reliability function of conditional inactivity times of coherent systems under two specific conditions on the status of the system components. Some ageing and stochastic properties of the proposed conditional inactivity times are also explored.     

New unit root asymptotics in the presence of deterministic trends

Recent work by Phillips (Econometrica 66 (1998) 1299) has shown that stochastic trends can be validly represented in empirical regressions in terms of deterministic functions of time. These representations offer an alternative mechanism for modelling stochastic trends. It is shown here that the alternate representations affect the asymptotics of all commonly used unit root tests in the presence of trends. In particular, the critical values of unit root tests diverge when the number of deterministic regressors K→∞ as the sample size n→∞. When they are appropriately recentered and standardized, unit root limit distributions are shown to be normal as K→∞.     

Matrix balancing with unknown total costs: preserving economic relationships in the electric power sector

Many preferred matrix balancing methods suffer limitations when total costs (i.e. column sums) are unknown or uncertain. If the total cost (column) constraint is relaxed, economic relationships both between inputs to and/or amongst the sub-sectors may not be preserved (i.e. cost structure and row share, respectively). These relationships are significant in modeling, where production behavior depends on relative costs. This paper presents a share preserving cross-entropy (SPCE) approach which targets economic relationships directly and allows the column constraint to be relaxed. Further, the SPCE solution is identical to the RAS solution when the column constraint is imposed. This cross-entropy formulation complements an existing sum squared error-type approach. The two matrix balancing methods are demonstrated with a disaggregation of the electric power industry where only unit input costs are known with greater certainty. There is a clear trade-off between preserving economic relationships versus the column totals when compared to their column-constrained counterparts.     

Trend/cycle decomposition of regime-switching processes

We present a new approach to trend/cycle decomposition of time series that follow regime-switching processes. The proposed approach, which we label the “regime-dependent steady-state” (RDSS) decomposition, is motivated as the appropriate generalization of the Beveridge and Nelson decomposition [Beveridge, S., Nelson, C.R., 1981. A new approach to decomposition of economic time series into permanent and transitory components with particular attention to measurement of the business cycle. Journal of Monetary Economics 7, 151–174] to the setting where the reduced-form dynamics of a given series can be captured by a regime-switching forecasting model. For processes in which the underlying trend component follows a random walk with possibly regime-switching drift, the RDSS decomposition is optimal in a minimum mean-squared-error sense and is more broadly applicable than directly employing an Unobserved Components model.     

Robust min–max portfolio strategies for rival forecast and risk scenarios

We consider an extension of the Markowitz mean–variance optimization framework to multiple return and risk scenarios. It is well known that asset return forecasts and risk estimates are inherently inaccurate. The method proposed provides a means for considering rival representations of the future. The optimal portfolio is computed, simultaneously with the worst case, to take account of all rival scenarios. This is a min-max strategy which is essentially equivalent to a robust pooling of the scenarios. Robustness is ensured by the noninferiority of min–max. For example, a basic worst-case optimal return is guaranteed in view of multiple return scenarios. If robustness happens to have too high a cost, guided by the min–max pooling, it is also possible to explore other pooling alternatives. A min–max algorithm is used to solve the problem and illustrate the robust character of min–max with return and risk scenarios. We study the properties of the min–max risk–return frontier and compare with the potentially suboptimal worst-case where the investment strategy and the worst case are computed separately.     

中职学校中平面图像设计探索与研究

计算机平面广告设计是计算机相关专业的必修课之一。笔者结合自身对于平面图像设计探索与研究的实践经验,对中职学校中的平面图像设计做出了一些思考。     

Two heuristics for the deterministic,single operator,multiple machine,multiple run cyclic scheduling problem

The semiautomatic nature of machinery often makes it economical to assign more than one machine to a single operator. Multi-machine assignments are common in the textile, tooling and molding industries. They are also found where numerically controlled (NC) machinery are used and, more recently, where flexible manufacturing systems (FMS) are employed. Previous work on deterministic cyclic scheduling models has focused on determining the optimal number of usually identical machines with single runs to assign to an operator. In practice, the schedules are represented by man/machine charts.When, due to production requirements, we mix different types of runs with known times on non-identical machines, we have the deterministic, single operator, multiple machine, multiple run, cyclic scheduling problem. We present two heuristics for solving this more realistic generalization of earlier problems. For the nonidentical, multiple run case, the scheduling of the runs is crucial in minimizing the cycle time of the system. The integer programming formulation of small problems is large, and solving it directly could require excessive computation time on a large mainframe computer.Heuristic 1 selects the next machine run to schedule by minimizing the total immediate waiting cost of the operator and machines. The hourly machine costs reflect the relative merit of utilizing certain machines over others. Heuristic 2 first schedules the machine with the longest automatic processing time of run one. It then follows Heuristic 1 until the long processing time of the first run has ended. The next available run with the longest automatic processing time is then scheduled, and the process repeats. The underlying notion is that many short runs may be performed during the long automatic run of a machine.The heuristics are polynomially bounded, can be easily implemented on a mini- or micro-computer and in practice should be much faster than integer programming methods. In addition to the heuristics, we compute a lower bound on the cycle time. We use this bound as a measure of the effectiveness of a solution. If for a given schedule, the cycle time equals its lower bound, then the solution is optimal.Both heuristics were coded in FORTRAN on a CDC-6600 computer. An interactive version was also developed for a DEC PDP11/70. A detailed computational study is presented. In it, both heuristics solved 50 machine, 5 run problems in less than 10 CPU seconds on the CDC-6600. Computational experience indicates that the heuristics are efficient and often find schedules which have cycle times within 10% the lower bound.     

Attrition in longitudinal panel data and the empirical analysis of dynamic labour market behaviour

In the empirical analysis of unemployment durations and job durations, it is generally assumed that the stochastic processes underlying labour market behaviour and the behaviour concerning participation in a panel survey are independent. However, there are reasons to believe that the probability of dropping out of the panel is related to the rate at which a (different) job is found. If there is such a relation, and if it is ignored, then the estimator of the rate at which individuals become employed or change jobs will generally be inconsistent. In this paper we analyse the relation between the duration spent in a particular labour market state and the duration of panel survey participation, by explicitly modelling and estimating the joint distribution of both durations. The emphasis will be on models allowing for stochastically related unobserved determinants of both types of duration. We estimate models both for unemployment durations and for job durations.     

On the continuity of representations of effectivity functions

An effectivity function assigns to each coalition of individuals in a society a family of subsets of alternatives such that the coalition can force the outcome of society’s choice to be a member of each of the subsets separately. A representation of an effectivity function is a game form with the same power structure as that specified by the effectivity function. In the present paper we investigate the continuity properties of the outcome functions of such representation. It is shown that while it is not in general possible to find continuous representations, there are important subfamilies of effectivity functions for which continuous representations exist. Moreover, it is found that in the study of continuous representations one may practically restrict attention to effectivity functions on the Cantor set. Here it is found that general effectivity functions have representations with lower or upper semicontinuous outcome function.     

Tertiary student satisfaction with socialization: A statistical assessment

A careful evaluation of student satisfaction is central for tertiary education institutions because help them to pinpoint their strengths and identify areas for improvement. University student satisfaction is not directly measurable because it depends upon many different aspects. It may be studied through a composite indicator based on other variables (partial indicators) that are directly observed. In this paper we consider student socialization which is an important aspect of students’ educational experience even if it is not as widely considered as assessments of skills development and ratings of various aspects of courses and programs. More precisely we consider student relations with the other people that act within the university context: teachers, teacher assistants, non teaching staff, other students, citizens of the town that hosts the university. To grasp the complexity of university experience, it is not enough to know the degree to which students are satisfied, it is important to understand the factors that contribute to student satisfaction. To this end we propose a simple algorithm to find the most important partial aspects underlying the student satisfaction socialization issue. An application to students of the University of Padova is discussed. The method is compared to PCA, and it is shown that is much simpler to be used, requires milder assumptions and is always readily comprehended.