• Restorative Dentistry and Endodontics
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• 제42권4호
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• pp.316-323
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• 2017

Objectives: This study compared the amount of apically extruded bacteria during the glide-path preparation by using multi-file and single-file glide-path establishing nickel-titanium (NiTi) rotary systems. Materials and Methods: Sixty mandibular first molar teeth were used to prepare the test apparatus. They were decoronated, blocked into glass vials, sterilized in ethylene oxide gas, infected with a pure culture of Enterococcus faecalis, randomly assigned to 5 experimental groups, and then prepared using manual stainless-steel files (group KF) and glide-path establishing NiTi rotary files (group PF with PathFiles, group GF with G-Files, group PG with ProGlider, and group OG with One G). At the end of canal preparation, 0.01 mL NaCl solution was taken from the experimental vials. The suspension was plated on brain heart infusion agar and colonies of bacteria were counted, and the results were given as number of colony-forming units (CFU). Results: The manual instrumentation technique tested in group KF extruded the highest number of bacteria compared to the other 4 groups (p < 0.05). The 4 groups using rotary glide-path establishing instruments extruded similar amounts of bacteria. Conclusions: All glide-path establishment instrument systems tested caused a measurable apical extrusion of bacteria. The manual glide-path preparation showed the highest number of bacteria extruded compared to the other NiTi glide-path establishing instruments.

• 천문학회보
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• 제42권1호
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• pp.49.2-49.2
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• 2017

Star forming dwarf galaxies in various environments are attractive objects for investigating the environmental effects on chemical evolution of dwarf galaxies. Using SDSS DR7 spectroscopic data and GALEX ultraviolet (UV) imaging data, we study the chemical properties of star forming dwarf galaxies in various environments of the Virgo cluster, Ursa Major group, and field. We derived gas-phase abundance, galaxy mass, and UV specific star formation rate (sSFR) of subsample, early-type (ETD) and late-type star forming dwarf (LTD) galaxies, which are divided by visually classified galaxy morphology. We found no O/H enhancement of LTDs in cluster and group environments compared to the field, implying no environmental dependence of the mass-metallicity relation for LTDs. LTDs in the Virgo cluster and Ursa Major group have similar sSFR at a given galaxy mass, but they exhibit systematically lower sSFR than those in isolated field environment. We suggest that LTDs in the Virgo cluster are an infalling population that was recently accreted from the outside of the cluster. We found that ETDs in the Virgo cluster and Ursa Major group exhibit enhanced O/H compared to those in the field. However, no distinct difference of N/O of galaxies between different environments. The chemically evolved ETDs in the Virgo cluster and Ursa Major group also show similar mass-sSFR relation, but systematically lower sSFR at a fixed galaxy mass compared to the field counterparts. We suggest that ETDs in the Virgo cluster and Ursa Major group have evolved under the similar local environments. We also discuss the evolutionary path of ETDs and LTDs with respect to the environmental effects of ram pressure stripping and galaxy interaction/merging.

• 디지털융복합연구
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• 제13권11호
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• pp.509-515
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• 2015

본 연구는 융복합시대 청소년기의 다양한 경제관련 경험이 경제관 형성에 미치는 효과를 검증하였다. 2015년 9월 1일부터 11일까지 충남 아산시 거주자와 온라인 홈페이지 방문자를 대상으로 설문조사를 실시하여 최종 116부를 분석하였다. 경제 관심도가 청소년기 경제 경험과 경제관 형성 간의 관계에 미치는 조절효과를 파악하고, 경제지식 습득경로에 따른 차이를 분석하였다. 청소년기의 다양한 경제 경험이 경제 이해도(${\beta}=.485$), 합리적 소비태도(.458) 및 창업의지(.293)에 유의한 정(+)의 영향을 미쳤으며 경제 관심도의 조절효과가 검증되었다. 또한 인구학적 특성과 경제지식 습득경로에 따른 경제관의 집단별 차이가 나타났다. 본 연구결과를 통해 청소년기의 다양한 경제경험이 경제관 형성에 미치는 영향을 종합적으로 검증함으로써 체험형 청소년 경제교육이 경제관 형성에 효과적임을 밝혔다는 데 그 의의가 있다.

• 한국통신학회논문지
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• 제41권11호
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• pp.1566-1573
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• 2016

본 논문은 무인기(UAV) 기반 공중 네트워크 시스템을 위한 polyphase In-phase/Quadrature-phase(I/Q) 네트워크 기반 빔-포밍 수신부를 제안한다. 제안하는 polyphase I/Q 네트워크는 낮은 Q-factor와 높은 임피던스를 갖기 때문에 작은 손실로 벡터 변조기를 구동할 수 있다. 벡터 변조기는 가변 이득 증폭기(VGA)로 구성되며, In-phase 및 Quadrature-phase 위상 신호의 진폭 제어 및 벡터 합을 통해 위상을 가변한다. 제안하는 빔-포밍 수신부는 TSMC $0.18{\mu}m$ CMOS 공정을 통해 구현하였다. 프로토타입은 5-6GHz 주파수 대역(-40dB 입력)에서 검증하였다. 6bit 벡터 변조기 제어를 통해 $5.6^{\circ}$ LSB (least significant bit)로 $360^{\circ}$ 위상 가변이 가능하다. 위상 오차는 평균 $1.6^{\circ}$이며, 진폭 오차는 평균 0.3dB이다.

• 한국정보통신학회논문지
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• 제4권2호
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• pp.397-406
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• 2000

유전자 알고리즘은 탐색, 최적화 및 기계 학습의 도구로 많이 사용되고 있는데, 구조는 단순하지만, 다양한 분야에서 적용되고 있다. 그리고 변화하는 환경에서 유연하게 대처 할 수 있는 자율운송장치의 능동적이고 효과적인 제어기에 관한 연구와 스스로 진화하여 학습할 수 있도록 하는 행동 기반 시스템에 관한 연구 또한 활발히 진행되고 있다. 퍼지 제어기 설계를 위한 소속 함수와 제어규칙의 구성 시 전문가의 경험적인 지식에 전적으로 의존하는 문제점을 가지고 있다. 본 논문에서는 자기 조직이 가능한 자율 운송 장치를 구성하기 위해서, 유전자 알고리즘을 이용하여 최적에 가깝도록 멤버십 함수를 조정했으며 제어규칙의 자기수정과 생성에 의해 제어 성능을 향상시켰다.

• Journal of Hydrospace Technology
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• 제2권1호
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• pp.41-54
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• 1996

Sculptured surface structures such as ship hulls are traditionally formed up to the required double curved shape by line heating method. The nature of the line heating process is a transient thermal process, followed by a thermo-elastic-plastic stress field. The permanant shape is dependent on many factors involved in the process, Among them are torch speed and path, supplied heat type and amount , and plate size. Thus, the work is essentially leaded by experts with lots of experiences. However, in order to effectively improve productivity through automation, each factor should be clearly examined how much it affects the final shape. This can not be done only by experiments, but can be achieved by a mechanics-based approach. In this paper, we propose a conceptual configuration for plate forming system, and then present simulations of the line heating process with numerical data in practices and suggest a computerized process of the line heating for practical applications. The modeling of heating torch, water cooling, and the plate to be formed is proposed for the finite element analysis after the mechanics of line heating is studied. Parametric studies are given and discussed for the effects of plate thickness, torch speed and initial curvature in forming a saddle typed surface.

• 대한조선학회논문집
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• 제45권4호
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• pp.417-425
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• 2008

In the line heating process, only angular distortion whose direction is perpendicular to that of a heating path is expected. However, it is observed that a deformation is induced in the direction of the heating line. Because of this, during forming a saddle type plate we experience unfavorable deformations in the unintended direction. In this paper we discuss the unwanted distortion in the manufacturing process by analyzing intermediate plates of saddle type during fabrication. For this analysis we consider the longitudinal and transversal directions separately and use the bending strain for the analysis.

• 소성∙가공
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• 제24권3호
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• pp.176-180
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• 2015

The current study is concerned with the prediction of fracture strains for DP980 steel sheets over a wide range of loading paths. The use of DP980 steel is increasing significantly in automotive industries for enhanced safety and higher fuel efficiency. The material behavior of advanced high-strength steels (AHSSs) sheets sometimes show unpredictable and sudden fracture during sheet metal forming. A modified Lou-Huh ductile fracture criterion is utilized to predict the formability of AHSSs because the conventional forming limit diagram (FLD) constructed based on necking is unable to evaluate the formability of AHSSs sheets. Fracture loci were extracted from three dimensional fracture envelopes by assuming the plane-stress condition to evaluate equivalent plastic strains at the onset of fracture for a wide range of loading paths. Three different types of specimens -- pure shear, dog-bone and plane strain grooved -- were utilized for tensile testing to calibrate the fracture model of DP980 steel sheets. Fracture strains of each loading path were evaluated such that there shows little deviation between fracture strains predicted from the fracture model and the experimental measurements. From the comparison, it is clearly shown that the three dimensional fracture envelopes can accurately predict the onset of the fracture of DP980 steel sheets for complicated loading conditions from compressive loading to shear loading and to equibiaxial tensile loading.

• Asia Marketing Journal
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• 제13권4호
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• pp.29-54
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• 2012

본 연구는 영화 관람과정에서 이루어지는 관객의 정보처리 용이성과 선호도 유창성의 관계를 살펴보기 위한 것이다. 따라서 본 연구는 영화에 대한 정보처리의 유창성 정도가 영화의 선호도 결정 용이성에 영향을 주다고 가정하고, 선행연구를 토대로 영화의 처리 유창성을 물리적 특성의 식별 용이성인 영화의 지각적 유창성과 표적에 대한 의미 처리 용이성을 의미하는 개념적 유창성으로 구분하였다. 그리고 영화를 구성하는 표현 요소들을 지각적 유창성요인과 개념적 유창성요인으로 구분하여 이들의 영향 관계를 탐색하였다. 본 연구의 결과, 첫째, 영화의 개념적 유창성과 지각적 유창성은 모두 영화의 선호도 유창성에 영향을 주는 것으로 나타났다. 둘째, 소리 표현의 식별성과 배우의 역할 표현 식별성은 영화의 지각적 유창성에 영향을 주지만, 영상 표현의 식별성은 유의하지 않은 것으로 탐색되었다. 마지막으로, 대사 표현의 적합성과 스토리 구성력은 영화의 개념적 유창성에 영향을 주는 것으로 탐색되었다.

• 대한기계학회논문집A
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• 제32권3호
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• pp.240-249
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• 2008

This paper presents an electromagnetic design method for magneto-rheological (MR) valves. Since the apparent viscosity of MR fluids is adjusted by applying magnetic fields, the MR valves can control high-level fluid power without any mechanical moving parts. In order to improve the performances of the MR valve, it is important that the magnetic field is effectively supplied to the MR fluid. For the purpose, the magnetic circuit composed with the yoke for forming magnetic flux path, the electromagnetic coil and the MR fluid should be well designed. In order to improve the static characteristic of the MR valve, the length of the magnetic flux path is decreased by removing the unnecessary bulk of the yoke. Also, in order to improve its dynamic and hysteretic characteristics, the magnetic reluctance of the magnetic circuit should be increased by minimizing the cross-sectional area of the yoke through which the magnetic flux passes. After two MR valves, one is a conventional type valve and the other is the proposed one, are designed and fabricated, their performances are evaluated experimentally.