• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.4
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• pp.1-10
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• 2008

Shear wave velocity($V_S$), which can be obtained using various seismic tests, has been emphasized as representative geotechnical dynamic characteristic mainly for seismic design and seismic performance evaluation in the engineering field. For the application of conventional geotechnical site investigation techniques to geotechnical earthquake engineering, standard penetration tests(SPT) and piezocone penetration tests(CPTu) together with a variety of borehole seismic tests were performed at many sites in Korea. Through statistical modeling of the in-situ testing data, in this study, the correlations between $V_S$ and geotechnical in-situ penetrating data such as blow counts(N value) from SPT and piezocone penetrating data such as tip resistance ($q_t$), sleevefriction($f_s$), and pore pressure ratio($B_q$) were deduced and were suggested as an empirical method to determine $V_S$. Despite the incompatible strain levels of the conventional geotechnical penetration tests and the borehole seismic tests, it is shown that the suggested correlations in this study are applicable to the preliminary estimation of $V_S$ for Korean soil layers.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.119-119
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• 2009

인버터 DC 저항용접의 적용성 증대 : 인버터 DC 저항용접 공법이 SPOT, PROJECTON, SEAM, BUTT 등의 공정에 다양하게 적용되어 저항용접 현장에서 고효율, 친환경적 용접 환경을 만드는데 일조 하고 있다. 특히 자동차의 경량화, 충돌내성 증대, 진동 및 내구성 증대, 공간활용 극대화, 새로운 Design 개념 적용 등의 산업전반에 걸쳐 나타나는 신 Trends로 고 장력 철재의 적용 범위가 확대되고 HSS(High Strength Steel), EHSS(Extra High Strength Steel), UHSS (Ultra High strength Steel ; Hot - Formed Steel )등 다양한 철판의 SPOT 저항용접이 필요하게 되었다. 기존의 AC 단상용접의 전력 특성 상 통전 중 무 통전 시간 과 높은 PEAK 전력, 단상 대 전력 소모로 인한 전력 DROP 등의 문제로 인하여 신소재의 용접 시 매우 많은 Spatter가 발생하고, 높은 용접품질의 확보가 어려워 지므로 이를 대체하기 위한 공법으로 MFDC ( 인버터 DC 저항용접공법 )이 적용되고 있다. 인버터 DC 저항용접의 적응제어 : MFDC라는 높은 효율의 용접 전력원이 확보 됨에도 불구하고 용접현장에서는 원 자재, 도금 등의 품질 산포, 프레스 물의 가공산포, 공기압 산포, 전극 과열 및 마모 등의 요인에 의하여 저항용접 산포가 발생하고 있다. 이는 인위적인 조작이 어렵고 불규칙적이며, 어디서나 산재하고 있는 문제이다. 이를 용접전력 제어 법으로 개선하여 일정한 용접성을 확보하기 위한 노력이 적응제어 기법이다. 정 전류, 정 전력 제어는 정량 제어로 용접 물을 비롯한 용접부의 변화와는 관계없이 설정된 일정량의 전력을 공급하기만 하는데 반하여 적응제어는 적절한 용접 작업 시의 용접 물의 상태, 전극의 가압, 표면 상태 등에 따른 변화 페턴을 기억하고 이후 진행되는 용접에 대하여 정상 페턴과의 차이를 감지 이를 보상하므로 고품질의 용접성을 보장하는 제어기법이다. 따라서 다양한 용접 산포 유발 요인에 의해 용접부의 변화가 발생한다 하여도 그 변화를 감지 하고 적절한 용접전력을 공급한다면 고품질의 용접성을 확보하는데 유용한 공법이 될 수 있다. 인버터 DC 저항용접의 SPC 관리 : SPOT 용접 시 획득할 수 있는 다양한 파라메터에 대하여 모니터링 하고 이 자료를 data 화 하여 품질 관리에 응용하게 되면 양산라인에서 반복적으로 발생되는 문제점을 확인 할 수 있고 이를 통계적 방법으로 추적 개선해 나간다면 용접 불량 감소 및 생산성 향상에 도움이 되며 작업자의 공정 능력 향상 및 기업의 기술축적에도 높은 기여를 할 수 있을 것이다. 용접 적응제어와 다양한 파라메터 모니터링이 한 system에서 이루어 질 때 높은 용접성 확보와 불량률 감소, 원가절감, 생산성 향상 등의 효과가 극대화 될 것이다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.7
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• pp.1227-1234
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• 2008

In this paper is designed a 256-bit synchronous OTP(one-time programmable) memory required in application fields such as automobile appliance power ICs, display ICs, and CMOS image sensors. A 256-bit synchronous memory cell consists of NMOS capacitor as antifuse and access transistor without a high-voltage blocking transistor. A gate bias voltage circuit for the additional blocking transistor is removed since logic supply voltage VDD(=1.5V) and external program voltage VPPE(=5.5V) are used instead of conventional three supply voltages. And loading current of cell to be programmed increases according to RON(on resistance) of the antifuse and process variation in case of the voltage driving without current constraint in programming. Therefore, there is a problem that program voltage can be increased relatively due to resistive voltage drop on supply voltage VPP. And so loading current can be made to flow constantly by using the current driving method instead of the voltage driving counterpart in programming. Therefore, program voltage VPP can be lowered from 5.9V to 5.5V when measurement is done on the manufactured wafer. And the sens amplifier circuit is simplified by using the sens amplifier of clocked inverter type instead of the conventional current sent amplifier. The synchronous OTP of 256 bits is designed with Magnachip $0.13{\mu}m$ CMOS process. The layout area if $298.4{\times}314{\mu}m2$.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.12
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• pp.1923-1932
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• 2019

Objective: We investigated visual marbling level (VML) influence on pork loin physicochemical traits, consumer palatability responses, VML liking, purchase intent, and their relationships. Methods: For each of five slaughtering dates, at 24-h postmortem, nine paired Duroc castrated male boneless Longissimus dorsi (LD) muscles were categorized into low (LM, score 1 to 2, n = 3), medium (MM, score 3 to 4, n = 3), and high (HM, score 5 to 6, n = 3) VML. Meat physicochemical quality traits and consumer responses (n = 389) on palatability and VML liking, and purchase intent were evaluated. The experiment was in randomized complete block design. Analysis of variance, Duncan's multiple mean comparisons, and correlation coefficients were determined. Results: VML correspond to crude fat (r = 0.91, p<0.01), but both were reversely related to moisture content (r = -0.75 and -0.91, p<0.01, respectively). As VML increased, ash (p<0.05) and protein (p = 0.072) decreased, pH and $b^{\star}$ increased (p<0.05), but drip, cooking (p<0.05) and thawing (p = 0.088) losses decreased. Among treatments, muscle fiber diameter, sarcomere length, total and insoluble collagen contents, $L^{\star}$, and $a^{\star}$ did not differ (p>0.05). Compared to the others, HM had lower collagen solubility percentage (p<0.05), but similar (p>0.05) Warner-Bratzler shear force (WBSF). No differences (p>0.05) were found in juiciness, overall flavor, oiliness, and overall acceptability, but HM was more tender (p<0.05) than the others. Based on VML, consumers preferred MM to HM (p<0.05), while LM was similar to MM and HM (p>0.05). Corresponding to VML preference (r = 0.45, p<0.01), consumers (83%) would (p<0.01) definitely and probably buy MM, over LM (74%), and HM (68%), respectively. Conclusion: Increasing VML in pork LD altered its chemical composition, slightly increased pH, and improved water holding capacity, thereby improving its tenderness acceptability. Marbling might reduce chewing resistance, as lower collagen solubility in HM did not impact tenderness acceptability and WBSF. While HM was rated as most tender, consumers visually preferred and would purchase MM.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.4
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• pp.365-376
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• 2021

In general, domestic streams and rivers are composed of alluvial rivers consisting of sand and gravel beds. These rivers can cause erosion and riverbed changes due to sudden changes in flow rates, such as floods, torrential rains, and heavy rains. In particular, there are various types of erosion, such as contraction erosion caused by changes in river shape, or local erosion occurring around obstacles such as piers, abutments or embankments. In addition, river changes can occur in various forms, such as static or dynamic periods, due to limitations such as flow rate, velocity, and shear stress. This study focused on the erosions of embankments directly related to human casualties among various river structures, and evaluated limit velocities and critical shear stress in order to identify changes in strength of natural materials by identifying the characteristics of natural hoan materials and resistance to erosions. In particular, the limitations of materials according to the type of materials in the river, characteristics of particles, and size of particles were studied using Soil loss, which is a change in the volume of the revetment material, and it is intended to be used as basic data for river design and restoration.

• Composites Research
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• v.34 no.5
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• pp.290-295
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• 2021

The application of lightweight structural composites to automobiles as a solution in line with global fuel economy regulations to curb global warming is recognized as a megatrend. This study was conducted to provide a technical approach that can respond to the issue of replacing parts that require conductive properties to maximize the application of thermoplastic carbon fiber reinforced plastics (CFRPs), which are advantageous in terms of repair, disposal and recycling. By utilizing the properties of the low-viscosity polymerizable oligomer matrix, it was possible to prepare a thermoplastic CFRP exhibiting excellent impregnation properties while uniformly mixing the conductive filler. Various carbon-based conductive fillers such as carbon black, carbon nanotubes, graphene nanoplatelets, graphite, and pitch-based carbon fibers were filled up to the maximum content, and electrical and thermal conductive properties of the fabricated composites were compared and studied. It was confirmed that the maximum incorporation of filler was the most important factor to control the conductive properties of the composites rather than the type or shape of the conductive carbon filler. Experimental results were observed in which it might be advantageous to apply a one-dimensional conductive carbon filler to improve electrical conductivity, whereas it might be advantageous to apply a two-dimensional conductive carbon filler to improve thermal conductivity. The results of this study can provide potential insight into the optimization of structural design for controlling the conductive properties of thermoplastic CFRPs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.8-14
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• 2019

Bird-strike is one of the most important design factors for safety in the aviation industry. Bird-strikes have been the cause of significant damage to aircraft and rotorcraft structures and the loss of life. This study used DYTRAN software to simulate the transient response of an Euler-Lagrangian composite helicopter blade that has been impacted by a bird. The Arbitrary Lagrangian Eulerian (ALE) method and a suitable equation of state were applied to model the bird. ALE was applied to the bird-strike analysis due to the large difference between the properties of the blade and bird. The debris of the bird was assumed to be a fluid and applied as Euler elements after the collision. Through the analysis of bird impacts, the leading-edge of the rotor blade (50.8 mm) was used to identify a positive margin of 1.18 based on the TSAI-FILL criteria. The results are assessed to be sufficiently reliable and may be evaluated to replace tests with various analysis conditions. The structural stability of the rotor blade could be assessed by applying various load conditions and different modeling methods in the future.

• Journal of the Society of Naval Architects of Korea
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• v.56 no.1
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• pp.34-46
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• 2019

This paper provides the numerical results for the self-propulsion performance in waves of a car ferry vessel with damage in one of its twin-screw propulsion systems without flooding the engine room. The numerical simulations were carried out according to the Safe Return to Port (SRtP) regulation made by the Lloyd's register, where the regulation requires that damaged passenger ships should have an ability to return to port with a speed of 6 knots in a Beaufort 8 sea condition. For the validation of the present numerical analysis study, the resistance performance and the self-propulsion performance of the car ferry in intact and damaged conditions in calm water were calculated, which showed a satisfactory agreement with the model test results of Korea Research Institute of Ship and Ocean engineering (KRISO). Finally, the numerical simulation of self-propulsion performance in waves of the damaged car ferry ship was carried out for a normal sea state and for a Beaufort 8 sea state, respectively. The estimated average Brake Horse Power (BHP) for keeping the damaged car ferry ship advancing at a speed of 6 knots in a Beaufort 8 sea state reached about 47% of BHP at MCR condition or about 56% of BHP at NCR condition of the engine determined at the design state. In conclusion, it can be noted that the engine power of the damaged car ferry ship in single propulsion condition is sufficient to satisfy the SRtP requirement.

• Journal of Platform Technology
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• v.6 no.4
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• pp.59-68
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• 2018

The objective of this study is to develop an embedded antenna structure with NFC and WPC composite functions. By selecting stable materials, the optimal component ratio of the polymer sheet was determined. The low cost embedded winding method compared to the existing FPCB was devised. During the winding process, characterization and process technology were developed. We also fabricated a ferrite mold to process the WPC grooves and developed the process technology for optimizing the WPC antenna. The following conclusions were obtained. (1) Optimum composition ratio was derived as Fe 87.5%, Si 7%, Al 5.5% and selected as the final material. (2) Optimal sheet conditions were derived from the experimental evaluation method and the experimental design method through the combination test of the optimized sheet and the conventional mass production FPCB. (3) According to coil diameter and inner diameter, Q value fluctuation, resistance value and efficiency fluctuation are obtained. Therefore, the most suitable coil condition is selected and Rx matching is performed. (4) The EMV load modulation test and the cognitive distance test of the polymer sheet and the ferrite sheet showed that the recognition distance of the polymer sheet at 1k and 4K was 32-33 mm and the recognition distance of the ferrite sheet at the same condition was 30-31 mm.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.3
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• pp.180-190
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• 2019

Patients who have a moderate periodontitis with pathologic tooth migration of maxillary incisors, it is necessary not only periodontal treatment for reduce periodontal inflammation, but also orthodontic treatment to teeth repositioning. For orthodontic treatment, it is necessary to apply less force and careful considerations of the center of resistance of the tooth and optimal force of tooth movement. At this time, the segmental arch applied only to the target teeth, is more effective and predictable, because applied force and direction can be controlled. In addition, to design the orthodontic appliance that can prevent the unwanted tooth movement that used as an anchorage is important. In recent years, various types of skeletal anchorage system have been used for preventing loss of the anchorage. We reported the patient who had extruded maxillary central incisor due to pathologic tooth migration, treated by a successful periodontal-orthodontic multidisciplinary treatment using an orthodontic appliance designed to apply less traumatic force and reduce an anchorage loss.