Miroljub Kljajić

A sequential heuristic procedure for one-dimensional cutting

The article examines the Sequential Heuristic Procedure (SHP) for optimising one-dimensional stock cutting when all stock lengths are different. In order to solve a bicriterial multidimensional knapsack problem with side constraints a lexicographic approach is applied. An item-oriented solution was found through a combination of approximations and heuristics that minimize the influence of ending conditions leading to almost optimal solutions. The computer program CUT was developed, based on the proposed algorithm. Two sample problems are presented and solved. A statistical analysis of parameters that affect material utilisation was also made.

Simulation Approach to Decision Assessment in Enterprises

The methodology of an integrated simulation system application for decision-making support in enterprises is described in this article. The use of visual interac tive modelling and animation can help users better understand simulation results, especially those who are not experts. Decision-makers are motivated by the aniniation while seeking better solutions for pro duction problems. The method was tested in a medium- sized company in order to improve operational plan ning and re-engineering. The real process was recorded on video, digitized, and implemented on a PC. Anima tion of the simulated process, synchronized with video of the real process, was projected in a room to achieve model validation and participant confidence. Opera tional production plans were simulated using current demands as the basis. Application of discrete event simulation in reengineering is also presented. The article shows how to develop a model, prepare sce narios and evaluate alternatives. Two criteria were evaluated for the alternative: the expected value and the value of multiple criteria evaluation, which was examined with the AHP method. Model validation and its use for alternative selection is also discussed.

Evaluation of algorithms for one-dimensional cutting

The paper deals with the problem of evaluating and comparing different one-dimensional stock cutting algorithms regarding trim loss. Different types of problems are identified. An evaluation method is developed which enables a comparison of solutions of all types of problems. A practical example of this methods implementation is presented.

Application of a programmable dual-channel adaptive electrical stimulation system for the control and analysis of gait.

A dual-channel electrical stimulation system with a stimulator and a programmer/stride analyzer was designed for clinical rehabilitation of gait and for subsequent daily use as an orthotic aid. The stimulator, with controls to adjust amplitude only (50 mA), adapts chosen stimulation sequences to the walking rate of a patient. Pulse duration (50-500 microseconds), frequency (5-120 Hz), shape (symmetrical biphasic, monophasic), stimulation sequences (16 stride segments) and their cycle (2-12 sec), and right/left foot-switch choices are selected for each patient and programmed into a separate unit. The programming unit also statistically processes the foot-switch data collected by the stimulator. The device was evaluated with regard to the programmable parameters, effectiveness during gait, and feasibility in clinical use. It was applied to 11 stroke patients and 10 brain injury patients during gait, stimulating 22 combinations of peroneal nerve and hamstring, quadriceps, triceps brachii, and gluteus maximus muscles. Forces on both feet, equinovarus, knee extension and hyperextension, elbow flexion, and hip extension were corrected. Selection of the stimulation sequences, their adaptation, range of pulse duration, and valid statistics were verified. Improved forces and joint angles were recorded together with significant changes in the stride time, length, and velocity by the stimulation.

Systems approach to complex systems modelling with special regards to tourism

Purpose – The importance of context dependent modelling of complex systems, depending on the observers point of view will be discussed. Thus, context is synonymous for the content of a problem in a frame of the goals, starting points and ways to achieve these aims. In this light, difficulties of model validation and a general method how to overcome them was discussed. The relations among subject – object – model in the light of a systems approach; Charles Sanders Peirces triad principle and the semiotic principle of communication was presented.Design/methodology/approach – The appropriateness of a system dynamics methodology, which is due to its transparency and clarity an excellent tool for modelling of complex systems.Findings – In the paper the equivalence of different methodologies was shown, whose differences and similarities can be judged only in context of a problem and the aims of researches. For illustration, the methodology is applied to a tourism system, which possesses the typical properties...

Slovenian national excellence award and total quality management deployment in Slovenian companies

This paper aims to study the deployment and use of total quality management (TQM) approaches and tools for the systematic implementation of TQM, especially within companies that have been applicants for the National Quality Award – Slovenian Business Excellence Prize (SBEP), and its relation to tools and approaches regarding people involvement, external recognition, benchmarking and financial results. The survey was based on the analysis of a sample of companies composed of the three subgroups: ‘top companies’ (based on their financial performance), a randomly chosen control group, and a group consisting of SBEP applicants. The questionnaire was distributed to 500 companies. The research was done on the basis of 110 respondents. Factor analysis was used to narrow the initial number of items, ANOVA to obtain statistically significant differences between the three group means and discriminant analysis to classify the sample according their use of TQM tools and approaches. The results showed that the main differences between the three groups of companies in favour of the SBEP group were related to the importance of benchmarking, peer assessment, collaborating in national quality awards (NQA) and partly in financial results. Based on the findings of this research, it can be concluded that the companies that took part in the NQA have higher mean scores of observed variables as compared to the other two groups of companies.

The anticipative concept in warehouse optimization using simulation in an uncertain environment

The modern business environment is highly unpredictable. An anticipation approach in a real case study is presented to cope with such instability and minimize the total inventory cost without stock-outs occurring and inventory capacity being exceeded. The anticipation concept is performed using simulation models supported by inventory control algorithms on a selected sample of representative items. The inventory control algorithms include Silver-Meal, Part period balancing, Least-unit cost, and Fuzzy inventory control algorithm based on fuzzy stock-outs, highest inventory level and total cost. Transportation cost is explicitly defined as a discrete function of shipment size. The algorithms are tested on historic data. Simulation results are presented and the risk of accepting them as reliable is discussed. The process of simulation model implementation is briefly discussed to further validate the model and train order managers to use the simulation model in their order placement process.

The Role of Systems Engineering in the Development of Information Systems

In this article, the inter-relationship between information systems (IS), systems engineering (SE), and information system development (ISD) is discussed from past, present, and future perspectives. While SE is relatively a well-established discipline based upon an interdisciplinary approach to enable the realization of successful systems, ISD has evolved to a variant of SE applied mainly for the development of IS. Given the growth in complexity and cost and schedule over-runs associated with software centric systems, well-established methodologies are needed for the development of good IS. Similarities and differences of methodology as well as their evolution and perspectives are also presented herein. We found a positive trend in the evolution of research methodology in SE and its use in IS towards a system’s approach as a holistic methodology.

The System Dynamics Model for Development of Organic Agriculture

Organic agriculture is the highest environmentally valuable agricultural system, and has strategic importance at national level that goes beyond the interests of agricultural sector. In this paper we address development of organic farming simulation model based on a system dynamics methodology (SD). The system incorporates relevant variables, which affect the development of the organic farming. The group decision support system (GDSS) was used in order to identify most relevant variables for construction of causal loop diagram and further model development. The model seeks answers to strategic questions related to the level of organically utilized area, levels of production and crop selection in a long term dynamic context and will be used for simulation of different policy scenarios for organic farming and their impact on economic and environmental parameters of organic production at an aggregate level.

Determination of recruitment and transition strategies

Purpose – This paper aims to describe the development and application of a manpower planning system for the Slovenian armed forces using a system approach, system dynamics (SD) and numerical optimization.Design/methodology/approach – The model of the hierarchical manpower system was developed by SD methodology and formulated in discrete time space. The problem of tracking the goal trajectories in the eight topmost ranks at the prescribed boundaries was solved by application of the quadratic performance index and finite automata (FA) which was used for classification of acceptable strategies. Genetic algorithms (GA) as well as pattern search were compared at the numeric optimization.Findings – Employing SD and a system approach increases the understanding of the system control. The definition of an optimum strategy, which would consider only target values for ranks within prescribed parameter boundaries, could provide an undesired oscillatory solution. Inclusion of rules by FA to determine acceptable strat...