• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.5669-5675
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• 2012

To reduce the cost and the time of transport in Eurasian railroad networks such as TKR(Trans-Korea Railway), TCR(Trans-China Railway) and TSR(Trans-Siberia Railway) owing to the problem of different track gauges (narrow/standard/broad gauge), it is important to develop the gauge-adjustable wheelset(GAW) system to adapt easily to these gauges. The Korean GAW system is developing and will be adapting to the brand new freight trains' to improve the conventional overseas GAW system. In this study, structural and durability analyses are performed from the viewpoint of the safe-life design. The core parts of the system might be safe in range of $1{\times}10^7$ cycles from the result of durability analysis. Moreover, to examine the safety of the system while running on a track, rig fatigue test was performed according to UIC code. The safety of the Korean GAW system is demonstrated through testing that all safety-relevant conditions are satisfied.

• Journal of Microbiology and Biotechnology
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• v.21 no.8
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• pp.777-790
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• 2011

To elucidate the biodiversity of plant growth-promoting rhizobacteria (PGPR) in Korea, 7,638 bacteria isolated from the rhizosphere of plant species growing in many different regions were screened. A large number of PGPR were identified by testing the ability of each isolate to promote the growth of cucumber seedlings. After redundant rhizobacteria were removed via amplified rDNA restriction analysis, 90 strains were finally selected as PGPR. On the basis of 16S ribosomal RNA sequences, 68 Gram-positive (76%) and 22 Gram-negative (24%) isolates were assigned to 21 genera and 47 species. Of these genera, Bacillus (32 species) made up the largest complement, followed by Paenibacillus (19) and Pseudomonas (11). Phylogenetic analysis showed that most of the Grampositive PGPR fell into two categories: low- and high- G+C (Actinobacteria) strains. The Gram-negative PGPR were distributed in three categories: ${\alpha}$-proteobacteria, ${\beta}$- proteobacteria, and ${\gamma}$-proteobacteria. To our knowledge, this is the largest screening study designed to isolate diverse PGPR. The enlarged understanding of PGPR genetic diversity provided herein will expand the knowledge base regarding beneficial plant-microbe interactions. The outcome of this research may have a practical effect on crop production methodologies.

• Journal of Microbiology and Biotechnology
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• v.30 no.7
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• pp.1060-1066
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• 2020

This study was focused on developing and obtaining a kimchi starter for use in commercial kimchi production. Kimchi varieties made with selected starters are of high quality, have high levels of mannitol, and extended shelf life. The starters were screened for properties such as mannitol production, low gas/acid production, and acid resistance. Finally, kimchi fermentation testing was performed using selected LAB starters. Kimchi samples were prepared with lactic acid bacteria (LAB) starters, including Leuconostoc mesenteroides PBio03 and Leuconostoc mesenteroides PBio104. The LAB starters are isolated from kimchi and can grow under pH 3.0 and low temperature conditions of 5℃. Four kimchi samples were fermented and stored for 28 days at 5℃. The kimchi samples made with starters (PBio03 and PBio104) had better quality (production of mannitol and maintenance of heterofermentative LAB dominance) than the non-starter kimchi samples. In the starter kimchi, Leu. mesenteroides was the dominant LAB, comprising 80% and 70% of total LAB counts at 7 and 21 days, respectively. Mannitol content of the kimchi with Leu. mesenteroides PBio03 was 1,423 ± 19.1 mg/100 g at 28 days, which was higher than that of the non-starter kimchi sample (1,027 ± 12.2 mg/100 g). These results show the possibility of producing kimchi with improved qualities using Leu. mesenteroides PBio03 and PBio104 as starters.

• Journal of Advanced Navigation Technology
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• v.21 no.1
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• pp.50-57
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• 2017

Recently, safety-critical aviation system development programs promoted domestically have been terminated in the middle stage or they have not been put to practical use at the final stage. The program failure may be caused by various factors, but this study focused on imperfect test and evaluation(T&E) procedures. In general, T&E process of a safety-critical system must be distributed throughout the entire life-cycle of the system, have a continuity in phases, and can be implemented in a variety of ways depending on the maturity of the system development and acquisition strategy. This paper aims to present a new strategy by analyzing the domestic and overseas T&E processes to reduce the risk of domestic safety-critical CNS/ATM system development program and increase the success rate of program. First, we discuss the verification and validation techniques for safety-critical systems, analyze the T&E procedures of advanced institutes and the domestic situation, and then compare the domestic and overseas T&E processes to complement the imperfect testing procedure.

• 연구논문집
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• s.23
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• pp.127-140
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• 1993

The drive pulley, which is employed for loading and unloading raw materials in a steel mill, is usually manufactured by use of various welding processes. In this study the weldment in the pulley, in which TIG and $CO_2$ welding processes are used, has been analyzed from view point of fracture mechanics. Fracture toughness tests have been performed according to ASTM E813. A servo-hydraulic testing machine (10kN) has been employed. Also the crack propagation tests (Mode I) have been performed with compact tension specimen in compliance with ASTM E647. To predict the critical crack size in the weldment, finite element stress analysis for the drive pulley under real operating conditions have been performed. In addition, the residual stresses at the weldment and in heat-affected zone have been obtained by hole drilling method. The planar critical crack size have been predicted for the drive pulley by considering the stress analysis results and the residual stresses due to welding process. For the drive pulley considered in this study, it has been concluded that the most important factor in determining the critical crack size is the welding residual stress in the transverse direction. Also the effect of stress concentration at the root of the weldment have been noticeable. For the planar crack, the fatigue crack growth life from an initial crack size of 2mm to the critical crack size obtained as in the above have been predicted. The predicted lives were between 55, 900 and 72, 000 cycles depending on the shape of the elliptical crack. The predicted lives were in fairly good agreement for the drive pulley considered in this study.

• Nuclear Engineering and Technology
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• v.38 no.3
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• pp.293-300
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• 2006

A liquid metal reactor (LMR) operated at high temperatures is subjected to both cyclic mechanical loading and thermal loading; thus, creep-fatigue is a major concern to be addressed with regard to maintaining structural integrity. The Korea Advanced Liquid Metal Reactor (KALIMER), which has a normal operating temperature of $545^{\circ}C$ and a total service life time of 60 years, is composed of various cylindrical structures, such as the reactor vessel and the reactor baffle. This study focuses on the creepfatigue crack initiation for a cylindrical Y-junction structure made of 316 stainless steel (SS), which is subjected to cyclic axial tensile loading and thermal loading at a high-temperature hold time of $545^{\circ}C$. The evaluation of the considered creep-fatigue crack initiation was carried out utilizing the ${\sigma}_d$ approach of the RCC-MR A16 guide, which is the high-temperature defect assessment procedure. This procedure is based on the total accumulated strain during the service time. To confirm the evaluated result, a high-temperature creep-fatigue structural test was performed. The test model had a circumferential through wall defect at the center of the model. The defect front of the test model was investigated after the $100^{th}$ cycle of the testing by utilizing a metallurgical inspection technique with an optical microscope, after which the test result was compared with the evaluation result. This study shows how creep-fatigue crack initiation for a high-temperature structure can be predicted with conservatism per the RCC-MR A16 guide.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.2
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• pp.172-182
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• 2006

Telematics is a kind of the convergence of industries such as an automobile, communication, contents, and so on. Jeju-Do has been selected as a model city for telematics and has carried out the telematics service project. Jeju Telematics contains six service areas including navigation, traffic information, emergency assistance, leisure information, tour destination information, and cultural life information. Jeju telematics project has been planned to be dealt with the aspects of technological skills and content development. In fact, because of the nature of model project for testing information technologies, Jeju telematics has been strongly approached by technical aspects. However, telematics is composed of services for users. Then, the success or fail of telematics project can be dependent upon the demand of users, and, in general, users are influenced by the contents of services. Thus, the contents of services should be also dealt as a major concern in the telematics project. In this sense, the purpose of this study is to examine the degree of recognition and preference of contents by users about telematics service. Examination is proceeded by a survey method. Based on the result of the survey, this paper proposes the alternatives for the future directions of Jeju Telematics project regarding contents.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.2
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• pp.210-220
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• 2013

Recently, as we move toward a society with an increasingly aged population, wearable U-health devices in various shapes with smart wear have been developed in order to conveniently measure health variables without using hands in daily life or at home. However, the problem is that only supply of the wearable U-health devices is focused and its applicable devices are studied and developed, which has resulted in lack of awareness of importance of performance evaluation. In this study, two electrodes were fabricated using conductive fabric which can be used as electrode if attached to wearable U-health devices or smart wear in order to measure ECG signal. Two electrodes those were fabricated using conductive fabric were compared the correlation, impedance and CMRR with patch typed Ag-AgCl electrode-normally used for measurement of ECG signal, so that the study would find out if the fabricated electrode can be used with the wearable U-health devices by testing and evaluating performances.

• Journal of Forest and Environmental Science
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• v.17 no.1
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• pp.62-73
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• 2001

This study was conducted to predict the tractive resistance for tree length logs being skidded by ground based logging machine. The mathematical models for predicting the tractive resistance of tree length log have been developed. The tractive resistance is expressed as a function of log weight, skidding coefficient, and ground gradient. The skidding coefficients for four species of Korean pine, Japanese larch, mongolian oak, and cork oak were determined under laboratory condition using universal testing machine and small soil bin, Three different tractive resistance models were applied to four species and compared with each other. The ratios (T/Wt) of skidding-line tensions to the skidding log weight increased linearly with increment in ground gradient. Semi-ground skidding generally required smaller tensions than ground skidding under given condition. Results of this study can be utilized as basic information for logging machine selection and power requirement of skidding winch.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.28-31
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• 2001

Recently, in order to satisfy the consumer's demand the life cycle and the lead-time of a product is to be shortened. It is thus important to reduce the time and cost in manufacturing trial products. Several techniques have been developed and successfully commercialized in the market RPM(Rapid Prototyping and Manufacturing). However, most commercial systems currently use resins or waxes as the raw materials. So, the limited mechanical strength for functional testing is regarded as an obstacle towards broader application of rapid prototyping techniques. To overcome this problems, high-speed machining technology is being investigated worldwide for rapid manufacturing and even for direct rapid tooling application. In this paper, some fundamental experiments and analyses are carried out to obtain the filling time, materials, method, and process parameters for HisRP process. HisRP is a combination process using high-speed machining technology with automatic filling. In filling process, Bi58-Sn alloy is chosen because of the properties of los-melting point, low coefficient of thermal expansion and enviromental friendship. Also the use of filling wire is of advantage in term of simple and flexible mechanism. Then the rapid manufacturing product, for example a skull, is machined for aluminum material by HisRP process with an automatic set-up device of 4-faces machining.