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1

Effects of potential level, rotation speed and electrode gap on food waste recovery using an electrostatic separator

Lai K., Lim S., Teh P., Yeap K.

Environment Protection Engineering

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2017

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Vol. 43, nr 2

81--92

EN

An environmentally friendly method to segregate FW from waste mixture has been presented. The potential level of the separator, the rotation speed and electrode gap are chosen as the independent experimental factors. Second-order quadratic equations have been elaborated to correlate the interactive relationship between the experimental factors and the separation efficiency. The results of the statistical analysis indicate that the electrode gap has immense influence on FW separation. The optimal conditions of segregation have been determined as follows: potential level of 30 kV, rotation speed of 60 rpm, electrode gap of 54 mm and a maximal separation efficiency of 84.0%.

2

Bringing Kano’s perspective to AHP: the 2D-AHP decision model

Jung U., Yim S., Lim S., Kim C.

Management and Production Engineering Review

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2016

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Vol. 7, No. 4

16--26

EN

AHP and the Kano model are such prevalent TQM tools that it may be surprising that a true hybrid decision-making model has so far eluded researchers. The quest for a hybrid approach is complicated by the differing output perspective of each model, namely discrete ranking (AHP) versus a multi-dimensional picture (Kano). This paper presents a hybrid model of AHP and Kano model, so called two-dimension AHP (2D-AHP). This paper first compares the two approaches and justifies a hybrid model based on a simple conceit drawn from the Kano perspective: given a decision hierarchy, child and parent elements can exhibit multi-dimension relationships under different circumstances. Based on this premise, the authors construct a hybrid two-dimension AHP model whereby a functionaldysfunctional question-pair technique is incorporated into a traditional AHP framework. Using the proposed hybrid model, this paper provides a practical test case of its implementation. The 2D-AHP approach revealed important evaluation variances obscured through AHP, while a survey study confirmed that the 2D-AHP approach is both feasible and preferred in some respects by respondents. Although there have been rich research efforts to combine AHP and Kano model, most of them is simply about a series of individual usage of each methodology. On the other hand, the type of hybridization between AHP and Kano model in this paper is quite unique in terms of the two dimensional perspective. The model provides a general approach with application possibilities far beyond the scope of the test case and its problem structure, and so calls for application and validation in new cases.

3

An Efficient Decoding of Goppa Codes for the McEliece Cryptosystem

Lim S., Lee H.-S., Choi M.

Fundamenta Informaticae

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2014

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Vol. 133, nr 4

387--397

EN

The McEliece cryptosystem is defined using a Goppa code, and decoding the Goppa code is a crucial step of its decryption. Patterson’s decoding algorithm is the best known algorithm for decoding Goppa codes. Currently, the most efficient implementation of Patterson’s algorithm uses a precomputation. In this paper, we modify Patterson’s decoding algorithm so that one can remove the precomputation part while sustaining the best efficiency. Precomputations yield additional storage requirement to store the precomputed value which increases as the security level increases in McEliece cryptosystem. In the original decoding algorithm of Patterson, computing square root in a quotient field of polynomial ring over a finite field is necessary. In our modification, the computations are involved only in the arithmetics of polynomial ring over a finite field, not in the quotient field. This achieves better efficiency because one can remove polynomial reductions in the computations of quotient field.

4

CNC extruder for varied section extrusion

Choi H. J, Lim S., Shin H. T., Choi S.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 29, nr 2

175-178

EN

Purpose: The work presented in this paper might be used for basic data in the design of a lot extruded aluminum products using the variable section extrusion process. Design/methodology/approach: The capacity of a CNC extruder was calculated and decided as analyzing the FEM results performed by commercial software DEFORM-2D. CNC extruder and die set for variable section extrusion was invented by field extrusion experts. Findings: CNC extruder had a key role in variable extrusion process. Furthermore there was few die sets with mold feeding parts for aluminum extrusion. To be capable of extruding aluminum products with variable cross section are CNC extruder and the die set. Research limitations/implications: For future research of developed CNC extruder, frame structures of the extruder would be analyzed and designed using FE analysis. In addition CNC extruder would be operated by the control program for variable section as a PC version. Practical implications: Aluminum parts with variable section would increase as utilizing the CNC extruder and cost price of the parts be down. Many industrial products using the variable section extrusion process would be used in diverse fields. Originality/value: Extruded aluminum part with variable section is rarely used since extruders don't be designed and developed for variable section extrusion. It is important that an extruder with CNC control, which could be easily handled and have accessible software to be operated by field user, are invented. As stated above, CNC extruder is needed for production of industrial products with variable section for today. Therefore design and development of CNC extruder having the die set for mold feeding parts was tackled in this paper as efficient approach using commercial FEM code.

5

Bead-on-plate weldability of Al 5052 alloy using a disk laser

Kim J., Lim S., Cho J. H., Kim C.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 28, nr 2

187-190

EN

Purpose: The paper presents the effect of the laser welding parameters of the laser focal position and beam angle on the weldability of an Al 5052 thick plate using a 4kW disk laser. Design/methodology/approach: Bead-on-plate welding was conducted on a 10mm-thick Al 5052 plate. Aspects of the bead, including the bead surface and cross sections, were evaluated with various laser welding parameters. The porosity formation was also examined in an X-ray transmission tests. Findings: Although the penetration depth decreased as the focal point moves away from the surface, the appearance of the bead improved and the porosity decreased. The weldability according to the inclination angle of the laser beam was also investigated. It was found that a forward inclination of the laser beam (when the inclination angle is an acute angle) could enhance the weldability compared with a backward inclination. Research limitations/implications: The results of the thick plate BOP welding experiments can be expanded to optimizing the Al alloy welding of thin sheets. Practical implications: It is applicable as a ground technique for the laser welding of aluminium alloy to increase the productivity and quality using the recently developed disk laser. Originality/value: The outcome of the research shows the influence of the welding parameters on weldability aspects in disk laser welding of an Al alloy.