Multi-stage production planning on the IBM PC — an application

Job shop scheduling is one of the most intriguing and potentially useful problems in Operations Research. It is also a very difficult problem to solve. In this article, we discuss a hybrid approach we have developed which automates the scheduling functions in a plant materials management department. The system performs multi-stage time phased materials planning calculations, while performing capacity checks and job sequencing. The scheduling algorithm performs a heuristic reduction of the n/m/Smin problem to a set of n/l/Smin problems which are solved optimally. The heuristic reduction and optimization algorithms are described. Design criteria which made implementation possible in a plant setting are also discussed.     

A statistical evaluation of aggregate monthly industrial demand for natural gas in the U.S.A.

We examine the temporal pattern and effect of heating degree days, price of natural gas, price of residual fuel oil, and industrial activity on industrial demand for natural gas between January 1980 and March 1984. Time plots are used to display these patterns. Regression analysis is used to estimate these effects. The results of the regression analysis are then evaluated, including an examination of the effect of measurement error on estimated coefficients. The evaluation indicates that the estimated coefficients are reliable.     

On the interaction between system and user characteristics

. The development of a representational framework, based on Moran's Command Language Grammar, for constructing adaptive computer systems is the main topic of this paper. A model of the user interface is developed of which two aspects are discussed: the mental model in the mind of the user and the perceptual model on the side of the machine. Cognitive style and personality factors are considered in their relation to the development of the mental model. The concept of metacommunication is analysed and discussed on all levels of Moran's CLG.     

Collaborating around vertical and horizontal large interactive displays: which way is best?

Large interactive displays are increasingly being placed in work and public settings. An assumption is that the shared surface they provide can facilitate collaboration among co-located groups. An exploratory study was carried out to investigate this claim, and, in particular, to examine the effects of the physical orientation of a display on group working. Two conditions were compared: vertical versus horizontal. A number of differences were found. In the horizontal condition group members switched more between roles, explored more ideas and had a greater awareness of what each other was doing. In the vertical condition groups found it more difficult to collaborate around the display. A follow-up study explored how participants, who had previous experience of using both displays, determined how to work together when provided with both kinds of display. The groups exhibited a more efficient and coordinated way of working but less collaboration in terms of the sharing and discussion of ideas.     

Tackling social inequality in development: beyond access to appropriation of ICTs for employability

ABSTRACT

This study was motivated to investigate social inequality in developed nations, by studying the impact of ICTs upon the vulnerable unemployed and under-employed in Singapore. First, drawing upon Amartya Sen’s capability approach, we operationalize the dependent variable as self-perceived employability, conceptualized as both a measure of well-being and a livelihood capability. Secondly, we used Neil Selwyn’s digital divide hierarchical impact assessment framework, to define and measure the ICT assets of access, usage, and appropriation. Primary data was gathered from 302 under-employed and unemployed workers in Singapore, a developed Asian economy. Regression analyses revealed that higher-order hierarchies of ICT usage and appropriation were associated with the dependent variable of employability, while access was not. We discuss the implications for development discourse in regions with ubiquitous access, advocating for policymakers to focus on ICT training. Further, we offer nuanced findings on vulnerability in developed economies as an enhancement to mainstream ICT4D scholarship, focused exclusively on poverty in developing countries.     

Modelling the dynamics of landscape transformations and population growth in the highlands of Ethiopia using remote-sensing data

This study models landscape transformations and settlement dynamics in a highland area of Ethiopia over a 56 year period (1957–2013). The analyses were performed using aerial photographs, satellite images, and field data. The remotely sensed images were geometrically and radiometrically corrected. Visual interpretation of aerial photographs and supervised classification of multispectral satellite images using the maximum likelihood algorithm were chosen for land-cover mapping. The population size was estimated by counting the houses on the aerial photographs and on the high-resolution images, and by direct census. The overall trend showed an increase of cropland and a decrease of other types of land cover. Landscape transformation rates recently slowed down due to ownership and policy restrictions. The average cropland holding size per family has decreased from 2.6 to 1.1 ha due to the exponential growth of the population. The relationship between settlement and cropland expansion is statistically significant. Models of logistic growth were fitted to the cropland area, and models of exponential and logistic growth to the population development to estimate the carrying capacity. The concomitant increase of population and the decrease of cropland per head resulted in a shortage of food and energy, highlighting the importance of policy decisions on land management.