• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.2
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• pp.529-539
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• 1996

Fracture resistance(J-R) curves, which are used for elastic-plastic fracture mechanics analyses, are known to be dependent on the specimen geometry. The objective of this paper is to investigate the effect of crack tip constraint an the J-R curves in CT specimens. Fracture toughness tests on CT specimens with varying planform size were performed and test results showed that the J-R curves were increased with an increase in the planform size. Finite element analysis were also performed and the numerical results showed that this experimental phenomenon was probably due to the relaxation of crack tip constraint resulting from the stress triaxiality.

• Tribology and Lubricants
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• v.14 no.4
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• pp.79-87
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• 1998

Morphological analysis of wear particles in the lubricating oil is a very effective and versatile means of lubricant analysis for machine condition monitoring and fault diagnosis. The prospects for determining quantitative information about wear particle morphology have been considerably enhanced by recent developments reported in the application of image processing and analysis techniques. This study was undertaken to investigate the influence of oiliness agent and extreme pressure agent on the shape of wear particles. The wear test was performed under different experimental conditions with stearic acid, dibenzyl disulfide(DBDS) and tricresol phosphate(TCP) in paraffinic base oil. Wear particles characteristics were described using four shape parameters, namely 50% volumetric diameter, aspect, roundness and reflectivity. The results showed that the four shape parameters of wear particles depend on a kind of the additives. This analysis of wear debris with computer image processing techniques is sufficient to distinguish some types of wear debris. The wear volume of three kinds of the specimens are affected by the additives with boundary films.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.04a
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• pp.131-135
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• 1997

최근 자동차에 요구되는 주요한 기술과제 중에서 최우선으로 해결해야 될 문제는 환경규제와 관련된 대응방안을 강구하는 것이다. 또한 지속적으로 강화되고 있는 환경규제를 만족하면서 소비자가 요구하는 자동차의 주행성, 안전성, 연비, 메인터난스 등과 관련된 고성능화가 추구되고 있다. 엔진유 측면에서는 배기규제, 연비향상, 장수명화 및 고성능화와 관련이 되는 성능 개선이 요구되고 있다. 특히 배기 규제와 관련해서는 오일 소모량의 감소와 배기 정화 장치에의 피독작용 감소등의 측면에서 물성이 규제되고 있는데 Noack증발 감량 및 함유량 규제가 대표적인 예이다. 본 보고에서는 제1보의 실험에 추가하여 윤활유의 혼입이 휘발유의 연소및 배기에 주는 영향에 관하여 연구하였다.

• Journal of Korean Society on Water Environment
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• v.25 no.2
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• pp.329-334
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• 2009

Bacterial numbers, such as endospore-formers, and treatment efficiencies were investigated for Rotating Activated Bacillus Contactors (RABC) and other advanced wastewater treatment processes including anaerobic-anoxic-oxic (A2O), sequencing batch reactor (SBR) and biological aerated filter (BAF). Endospore-forming bacterial numbers in the RABC showed 129-fold higher levels than those of the existing advanced systems. RABC process demonstrated the highest bacterial numbers in its bioreactors (paired t-test, p<0.01). RBC biofilms and aeration tanks of the RABC system showed 131- and 476-fold higher than other existing advanced processes, respectively. Mean treatment efficiencies of the existing systems were 83.5% for chemical oxygen demand (COD), 59.1% for total nitrogen (TN) and 76.8% for total phosphorus (TP). However, RABC process removed 96.9% for COD, 96.9% for TN and 91.9% for TP for highly concentrated food wastewater (COD>1,500 mg/L, TN>150 mg/L, TP>50 mg/L). Treatment efficiency was significantly reduced when the numbers of Bacillus genus in the bioreactors decreased below $10^6CFU/mL$. The automated RABC (A-RABC), in which dissolved oxygen concentrations are automatically controlled, showed higher treatment efficiencies compared to the RABC process. The RABC system maintained sufficient bacterial numbers for the effective treatment of highly concentrated food wastewater. Moreover, final effluent was in agreement to water quality standards.

• Journal of Advanced Navigation Technology
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• v.24 no.3
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• pp.184-191
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• 2020

Avionics System Integration Laboratory is the integrated test environment for integration and verification of avionics systems. When real equipment can not be used in the laboratory for various reasons, software models should be needed. Because there hasn't been any standardized method for the models so that it is difficult to reuse the developed models, the need for a framework to develop the avionics software models was emerged. We adopted DEVS(discrete event system specification) formalism as the standardized modeling method for the avionics software models. Due to DEVS formalism is based on event-driven algorithm, it doesn't accord a legacy system which has sequential and periodic algorithms. In this paper, we propose real-time event-driven modeling and simulation method for SIL to overcome these restrictions and to maximize reusability of avionics models through the analysis of the characteristics and the limitations of avionics models.

• Journal of Korean Society on Water Environment
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• v.20 no.2
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• pp.190-195
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• 2004

A new technology for advanced wastewater treatment was developed using a modified Rotating Biological Contactor (RBC) process, named as Rotating Activated Bacillus Contactor (RABC) process that utilizes Bacillus sp., the facultatively anaerobic or activated microaerophilic bacteria on multiple-stage reticular rotating carriers, as a predominant species. The RABC process for a municipal wastewater with relatively low concentrations of organics, nitrogen, and phosphorus showed stable and high removal efficiencies, less than $BOD_5$ 10 mg/L, T-N 15 mg/L, and T-P 1.5 mg/L in final effluent. The performance load of RABC process was shown to be $1.23kg{\cdot}BOD/m^2{\cdot}day$ for the first stage (average $0.31kg{\cdot}BOD/m^2{\cdot}day$ for the total stages) based on both removed BOD and converted disc area corresponding to the reticular one. The sludge produced in the RABC process is characterized by low generation rate (about $0.18kg{\cdot}MLSS/kg{\cdot}BOD$) and excellent settleability. The number ratio of Bacillus ($2.4{\times}10^6CFU/ml$) to heterotrophic bacteria ($3.6{\times}10^7CFU/ml$) inhabiting in the biofilms of the RABC process was 6.7 %, indicating that Bacillus sp. was a predominant species in the biofilms. The RABC process with reticular rotating carriers showed its excellent performance for the advanced wastewater treatment without any offensive odor problem due to organic overloading.

• Journal of Korean Society on Water Environment
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• v.21 no.1
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• pp.73-78
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• 2005

This study was performed to examine the disinfection capability of a Rotating Activated Bacillus Contactor (RABC) system, in which the predominant species, Bacillus sp. was expected to have a removal or inactivation effect of total coliforms. In a settling test with mixtures of E. coli and Bacillus sp., a high removal of E. coli was observed at $20{\sim}40^{\circ}C$, while insignificant removal at $10^{\circ}C$. In a batch test, a 4.5% addition of Bacillus sp. to activated sludge considerably enhanced the removal effect of total coliforms, indicating Bacillus sp. played an important role in improving the settlability of the sludge and coliforms. In a pilot scale RABC system, the concentration of total colifroms reduced remarkably in the settling tank, suggesting that total coliforms in the RABC process were eliminated through coagulation and precipitation, probably due to extracellular polymeric substance (EPS) of Bacillus sp. The fraction of Bacillus sp. in the total cell count in the RABC process was in the range of 4.5%~6.3%. The majority (75%) of the Bacillus sp. in the RABC process was Bacillus subtilis which is known to enhance coagulation and precipitation by producing EPS. Hence, an adoption of a RABC process might be able to eliminate the disinfection unit process from a wastewater treatment system.

• Journal of Advanced Navigation Technology
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• v.23 no.5
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• pp.361-366
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• 2019

In developing the avionics system, a system integration laboratory (SIL) is established to verify the function and interworking of individual components. In case of individual verification of SIL's components and system integration, a SIL model that simulates the function and interworking of each equipment is developed and used. A SIL model shall be pre-verified against all data defined in the interface control document (ICD) before interworking with the actual equipment and reverified even when the ICD changes or functions change. However, if the verification of the SIL model is performed manually, the verification of the individual SIL model takes considerable time. For this reason, selective regression tests are often performed to determine a impact of SIL models on ICD changes and some functional changes. In this paper, we designed SIL model verification automation method to perform regession test by reducing verification time of SIL model and verify the usefulness of verification automation design by developing SIL model verification automation tool.

• Journal of Advanced Navigation Technology
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• v.25 no.5
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• pp.336-343
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• 2021

Avionics corresponds to the brain, nerves and five senses of an aircraft, and consists of aircraft mounted electronic equipment of communication, identification, navigation, weapon, and display systems to perform flight and missions. It occupies about 50% of the aircraft system, and its importance is increasing as the technology based on the 4th industrial revolution is developed. As the development period of the aircraft is getting shorter, it is definitely necessary to develop a stable avionics SIL in a timely manner for the integration and verification of the avionics system. In this paper, we propose a method to replace the legacy SIL with the avionics simulation model framework based one and evaluate the framework based on the result of alternative application.

• Journal of Advanced Navigation Technology
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• v.27 no.5
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• pp.635-642
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• 2023

With the development of artificial intelligence technology, drones are evolving beyond simple remote control tools into intelligent drones that perform missions autonomously. The importance of drones is gradually gaining attention due to the use of drones in overseas military conflicts and the analysis of the future operational environment in Korea. AMAD is proposed for the rapid development of intelligent drones. In order to develop intelligent software based on AMAD, an integrated development environment (IDE) that supports users with functions such as debugging, performance evaluation, and monitoring is essential. In this paper, we define the concepts of the development environment required for intelligent software development and describe the results of reflecting them in the design of the IDE and AMAD's agents, SVI and MPD, which are interfaced with the IDE.