• Journal of Computing Science and Engineering
• /
• v.2 no.3
• /
• pp.274-300
• /
• 2008

Software testing cost can be reduced if the process of testing is automated. However, the test data generation task is still performed mostly by hand although numerous theoretical works have been proposed to automate the process of generating test data and even commercial test data generators appeared on the market. Despite prolific research reports, few attempts have been made to evaluate and characterize those techniques. Therefore, a lot of works have been proposed to automate the process of generating test data. However, there is no overall evaluation and comparison of these techniques. Evaluation and comparison of existing techniques are useful for choosing appropriate approaches for particular applications, and also provide insights into the strengths and weaknesses of current methods. This paper conducts experiments on four representative test data generation techniques and discusses the experimental results. The results of the experiments show that the genetic algorithm (GA)-based test data generation performs the best. However, there are still some weaknesses in the GA-based method. Therefore, we modify the standard GA-based method to cope with these weaknesses. The experiments are carried out to compare the standard GA-based method and two modified versions of the GA-based method.

• Journal of the Korean Vacuum Society
• /
• v.6 no.2
• /
• pp.109-113
• /
• 1997

PR spectra of MBE grown AlGaAs/GaAs MQW have been measured at room temperature using the He-Ne laser and the Ar laser as the pump source. We have observed various subband transition peaks and PR spectra were fitted to standard analytic line shape. Above that results, obtained us transition energy from n=1 conduction band to heavy hole(C1-H1) and to light hole(C1-L1) subband. Photoluminescence(PL) at room temperature showed main peak with a shoulder. Good agreement between PL and PR measured n=1 intersubband transition energies was confirmed that PL main peak with a shoulder is associated with the C1-H1, C1-L1 transition. Additionally, we have calculated the C1-H1 and C1-L1 intersubband energy within envelope function approximation(EFA).

• Journal of Sensor Science and Technology
• /
• v.18 no.1
• /
• pp.86-94
• /
• 2009

Temperature measurement capability was inter-compared using the transfer standard platinum resistance thermometers(SPRT) among four laboratories of KRISS. The transfer SPRTs were primarily calibrated at the triple point of water and Ga melting point, then used at inter-comparison experiment. Temperature difference of calibration value between temperature laboratory and length laboratory at $20^{\circ}C$ was -0.7 mK and +2.4 mK at density laboratory. Temperature measured near $20^{\circ}C$, $25^{\circ}C$ and $30^{\circ}C$ at fluid flow laboratory was deviated by $34.2{\sim}80.4\;mK$ from the calibration values of the transfer SPRT. Ga melting points was inter-compared among three laboratories, and the difference of Ga melting points against the standard Ga melting point of temperature laboratory were $0.03{\sim}0.54\;mK$ at length laboratory and 0.02 mK at density laboratory.

• Journal of Ubiquitous Convergence Technology
• /
• v.2 no.1
• /
• pp.40-50
• /
• 2008

The problem of assigning customers to satellite channels is a difficult combinatorial optimization problem and is NP-complete. For this combinatorial optimization problem, standard optimization methods take a large computation time and so genetic algorithms (GA) and ant colony optimization (ACO) can be used to obtain the best and/or optimal assignment of customers to satellite channels. In this paper, we present a comparative study of GA and ACO to this problem. Various issues related to genetic algorithms approach to this problem, such as solution representation, selection methods, genetic operators and repair of invalid solutions are presented. We also discuss an ACO for this problem. In ACO methodology, three strategies, ACO with only ranking, ACO with only max-min ant system (MMAS), and ACO with both ranking and MMAS, are considered. A comparison of these two approaches (i,e., GA and ACO) with the standard optimization method is presented to show the advantages of these approaches in terms of computation time.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.1
• /
• pp.68-72
• /
• 2008

AlGaInP high-brightness LEDs(HB-LEDs) have gained importance a variety of application operating in the red, orange, yellow and yellow-green wavelength. The light generated from inside LED chips should be emitted to the air through the surfaces of the chips. However, because of the differences between the semiconductor and air or epoxy's refractive index, some of the light was blocked so that caused lowering external quantum efficiency. In this study, nano-scale roughness on the top-GaP layer of AlGaInP epitaxial wafer was fabricated to improve' the brightness of AlGaInP LEDs. Nano-scale roughness was made by ICP dry etcher. Our AlGaInP LEDs with nano-scale roughness has higher brightness (about 28.5 %) than standard AlGaInP LEDs.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.52 no.6
• /
• pp.316-324
• /
• 2003

This paper applied Elite-based Simplex-GA hybrid approach combined with Muptipop-GA (ESGA) to determining the location, size and number of capacitors to improve voltage profile and minimize power losses in unbalanced distribution systems. One of the main obstacles in applying GA to complex problems has been the high computational cost due to their slow convergence rate. To alleviate this difficulty, ESGA approach was developed that combines Elite-based Simplex-GA hybrid approach with Muptipop-GA. The objective function formulated consists of two terms: cost for energy losses and cost related to capacitor purchase and capacitor installation. The cost function associated with capacitor placement is considered as a step function due to banks of standard discrete capacities. Its efficiency was proved through the application in IEEE 13 bus and 34 bus test systems and was compared with several methods using GA.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2005.05a
• /
• pp.245-245
• /
• 2005

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.47 no.6
• /
• pp.1-6
• /
• 2010

We present simulation results on DC characteristics of AlGaN/GaN HEMT having stair-type gate electrodes, in comparison with those of the conventional single gate AlGaN/GaN HEMTs and field-plate enhanced AlGaN/GaN HEMTs. In order to reduce the internal electric field near the gate electrode of conventional HEMT and thereby to increase their DC characteristics, we applied three-layered stacking electrode schemes to the standard AlGaN/GaN HEMT structure. As a result, we found that the internal electric field was decreased by 70% at the same drain bias condition and the transconductance (gm) was improved by 11.4% for the proposed stair-type gate AlGaN/GaN HEMT, compared with those of the conventional single gate and field-plate enhanced AlGaN/GaN HEMTs.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.46 no.4
• /
• pp.10-14
• /
• 2009

We propose a trapezoidal gate AlGaN/GaN high electron mobility transistor(HEMT) to improve the breakdown voltage characteristics and its feasibility is investigated by two-dimensional device simulations. The use of a trapezoidal gate structure appears to be quite effective in dispersing the electric fields concentrated near the gate edge on the drain side from the simulation result. We find that a peak value of the electric field along the 2-DEG channel is reduced by 30%, from 4.8 to 3.5 MV/cm and thereby, the breakdown voltage(Vbr) of the proposed AlGaN/GaN HEMT is increased by about 40%, from 49 to 69 V, compared to those of the standard AlGaN/GaN HEMT.

• Journal of the Korean Society of Food Culture
• /
• v.30 no.5
• /
• pp.502-544
• /
• 2015

This study researched a document regarding 'Pyeon (tteok)' on 25 Jong-ga ancestral ritual foods through "Jong-ga Ancestral ritual formalities and food", published during 2003~2008 by the National Research Institute of Cultural Heritage of Cultural Heritage Administration. A after about 10 years, the transmission process of the setting and recipe was compared and analyzed in 2015 by directly visiting 4 Jong-ga. This research classified regions into 7 Gyeonggi, 4 Chungcheong, 2 Honam, and 12 Yeongnam, and classified hakpa, Gyeonggi, Chungcheong, Honam region into 13 Gihohakpa, Yeongnam region into 12 Yeongnamhakpa. The important analysis standard of Jong-ga ancestral ritual food was the region and hakpa, which appeared to considerably influence 'Pyeon' setting style, which represents and symbolizes family and recipe. Gihohakpa Jong-ga, which is an academic tradition that pursues practical interests, seems to highly regard practicality to adapt to changes along with the period. On the contrary, Yeongnamhakpa Jong-ga, which highly regards self-sufficiency living base and moral justification, seems to be highly conservative. Increase in Jong-ga, which utilizes mill, is the result of adaptation to the period environment such as Jongbu aging and lack of labor, etc.