Journal of Mechanical Engineering 54 (2008)9

Cover plate

FlowFigure represents vector velocity distribution around the sitting human body and respiration area during the exhalation in a space with displacement ventilation. Exhaled air flow of the normal breathing cycle is strong enough to penetrate through the thermal plume around the body. Courtesy of the Laboratory for Heating, sanitary and Solar Technique, Faculty of Mechanical Engineering, University of Ljubljana.

 

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Relative Decrease of Tracer Gas Concentration as a Measure of the Ventilation Effectiveness

Corresponding author - Simon Muhič

Authors - Mitja Mazej - Vincenc Butala

Abstract

An analysis of the ventilation effectiveness measured on a prototype system for local air-conditioning named PERMICS (Personal Microclimate System) was made based on simultaneous measurements of velocity field and of tracer gas concentration using the decay method. A new parameter based on a relative decrease of tracer gas concentration in the first minute of system operation dC(1) was introduced. The newly defined parameter has been verified by simulation results from commercial computational fluid dynamics (CFD) software. The usefulness of the parameter is the possibility to make quick measurements of the local efficiency of personalized ventilation systems.  

Keywords - air distribution, air conditioning, ventilation, efficiency

Paper's information

Strojniški vestnik - Journal of Mechanical Engineering 54(2008)9, 579-587
UDC 697

 Relative Decrease of Tracer Gas Concentration as a Measure of the Ventilation Effectiveness (pdf)

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Project Management of Product Development

Corresponding author - Janez Kušar

Authors - Lidija Bradeško - Jože Duhovnik - Marko Starbek

Abstract

The market requires that companies continuously reduce their product and process development time and costs, in order not to lose their competitive advantage on the global market. Short product and process development time in combination with low costs and achievement of required quality can be obtained only by integrating project management methods with concurrent engineering elements. Project management of orders combined with concurrent engineering elements allows for considerable reduction of development time, reduction of costs, and provides for a higher quality of order/product [1]. Order planning phase is very important in integrated product/process development. In the traditional product/process development, on average only 3% of total order development time is used for planning, while at the concurrent concept this time increases to about 20% [2].
The company which has decided for the integrated product/process development as a mode of its operation, first has to carry out organization and information redesign of its business process, as well as to make system and operation project management guidelines.
The paper presents an example of project management implementation in a company, the emphasis being on the development of planning procedure and project management of orders, as well as design of a project dossier. 

Keywords - project management, orders management, project management office, dossier, cuncurrent engineering

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 54(2008)9, 588-606
UDC 658.5

 Project Management of Product Development (pdf)

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Assembly Initiated Production as a Prerequisite for Mass Customization and Effective Manufacturing

Corresponding author - Zoran Anišić
Authors - Cvijan Krsmanović

 

Abstract

The paper deals with a review of a complex IPS-DFA methodology with a purpose of rating and improving design characteristics regarding the aspect of the assembly process. The approach has to be applied at the level of the product assortment, basic product structure and at the component level, aiming to achieve two primary goals: rationalization of the part count and the optimization of handling and fitting parts, through the developed tools for assembly suitability enhancement. Comprehensiveness of the methodology, especially at the product assortment level, simultaneously enables increasing suitability for mass customization. The paper provides an insight into the results of circular pumps product family application with a special emphasis on the consequences concerning mass customization.

Keywords - product design, design for assembly, mass customization, concurrent engineering

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 54(2008)9, 607-618 
UDC 658.5

 Assembly Initiated Production as a Prerequisite for Mass Customization and Effective Manufacturing (pdf)

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Uncalibrated Visual Servo Control with Neural Network

Corresponding author - Rok Klobučar

Authors - Jure Čas - Riko Šafarič - Miran Brezočnik

Abstract

Research into robotics visual servo systems is an important content in the robotics field. This paper describes a control approach for a robotics manipulator. In this paper, a multilayer feedforward network is applied to a robot visual servo control problem. The model uses new neural network architecture and a new algorithm for modifying neural connection strength. No a-prior knowledge is required of robot kinematics and camera calibration. The network is trained using an end-effector position. After training, performance is measured by having the network generate joint-angles for arbitrary end effector trajectories. A 2-degrees-of-freedom (DOF) parallel manipulator was used for the study. It was discovered that neural networks provide a simple and effective way of controlling robotic tasks. This paper explores the application of a neural network for approximating nonlinear transformation relating to the robot’s tip-position, from the image coordinates to its joint coordinates. Real experimental examples are given to illustrate the significance of this method. Experimental results are compared with a similar method called the Broyden method, for uncalibrated visual servo-control.

Keywords - robots, neural networks, visual servoing, parallel manipulator

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 54(2008)9, 619-628 
UDC 681.5:007.52

 Uncalibrated Visual Servo Control with Neural Network (pdf)

 

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A Device for Simulating the Thermoregulatory Responses of the Foot: Estimation of Footwear Insulation and Evaporative Resistance

Corresponding author - Mitja Babič

Authors - Jadran Lenarčič, Leon Žlajpah, Nigel A. S. Taylor, Igor B. Mekjavić

Abstract

A sweating thermal foot manikin was developed for evaluating the thermal and evaporative resistance of footwear. The sweating thermal foot manikin can be programmed to simulate physiological patterns of conductive, convective and evaporative heat loss. The manikin can simulate the initiation and magnitude of human non-evaporative and evaporative heat loss based on core and skin temperatures.  The system comprises a computer controlled system for regulating the heaters in each of the 16 segments of the foot, as well as the sweating function provided by peristaltic pumps. Each of the 16 segments is autonomous: its heating and sweating responses are controlled independently, thus the calculation of the heat exchange can also be determined for each segment separately.  Results of the footwear evaluation were compared to the results obtained for identical footwear with foot manikins from other laboratories.

Keywords - human foot, thermal manikin, sweating, foot wear, physiological simulation system

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 54(2008)9, 628-638 
UDC 658.34.17

 A Device for Simulating the Thermoregulatory Responses of the Foot: Estimation of Footwear Insulation and Evaporative Resistance (pdf)

 

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Results Research of Energetics Characteristics of Convection Drying

Corresponding author - Slavica Prvulović

Authors - Dragiša Tolmać - Ljiljana Radovanović

Abstract

Experimental and theoretic researches are presented in this paper and they are implemented on the real industrial equipment of convection dryer with pneumatic transport of material. The numeric values are given for optimum parameters of drying, energetic characteristics and balances as well as the coefficient of the heat transfer. The heat transfer in these systems is accomplished based on the principle of direct contact of dryed material and warm air. Then, an intensive transfer of heat and mass is accomplished.
This paper presents the results of researches which can be useful in designing and construction of such dryers in the food and agri industry. It refers to the technological technical characteristics of the dryer, energetic balances and coefficient of heat transfer.

Keywords - energy balance, drying , numeric data, heat transfer

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 54(2008)9, 639-644 
UDC 66.047

 Results Research of Energetics Characteristics of Convection Drying (pdf)

 

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