• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집B
• /
• pp.541-547
• /
• 2000

Experiments were done for the comparison of performance and flow characteristics between a two stage axial flow fan and a counter-rotating axial flow fm. The fan performance curves were obtained by the Korean Standard Testing Methods for Turbo Fans and Blowers (KS B 6311). The fan flow characteristics were measured using a five-hole probe by the non-nulling method. Each stage of the two stage axial flow fan used for the present study has an eight bladed rotor and thirteen stator blades. The front and the rear rotor of the counter-rotating axial flow fan have eight blades each and are driven by coaxial counter rotating shafts through a gear box located between the rear rotor and the electric motor. Both of the two axial fan configurations use identical rotor blades and the same operating conditions for the one-to-one comparison of the two. Performance characteristics of the two configurations were obtained and compared by varying the blade setting angles and axial gaps between the blade rows. The passage flow fields between the hub and tip of the fans were measured and analyzed for the particular operating conditions of peak efficiency, minimum and maximum pressure coefficients.

• 자원ㆍ환경경제연구
• /
• 제15권1호
• /
• pp.51-69
• /
• 2006

국내석유제품의 가격은 정부에 의해 최고가격 고시제에서 1997년 1월 국내 정유산업의 경쟁체제 도입을 위하여 유가자유화를 실시하였다. 이에 본 연구는 유가자유화 이후 국내정유산업의 경쟁도를 분석하였다. 분석방법은 구조적 모형인 Bresnahan (1982)과 Lau (1982)의 방법론(B-L 모형)과 비구조적 모형인 Panzar and Rosse (1987)의 방법론(P-R 모형)을 이용하였으며 분석 자료는 1994년 1월부터 2005년 6월까지 휘발유, 등유, 경유의 세전 소비자가격을 사용하여 유가자유화 이전과 이후를 나누어 비교하였다. 분석 결과, B-L 모형은 유가연동제 기간에 시장지배력이 존재하였으나 유가자유화의 도입으로 인해 균형가격이 감소하였음을 보였고, P-R 모형은 두 기간 모두 독점적 경쟁을 이루고 있음을 보였다. 그러나 두 모형에서 동일하게 유가자유화의 도입으로 인해 경쟁도가 증가하였음을 확인하였다.

• Composites Research
• /
• 제24권3호
• /
• pp.25-30
• /
• 2011

복합재료의 비파괴 검사 방법에 관한 연구는 복합재료의 신뢰성 및 안전성을 개선시키는데 매우 중요하다. AE기법은 소성변형, 섬유파손, 모재균열 또는 박리에 의해 생성되는 탄성파에서 감지되는 변형 에너지를 감지하여 결함을 평가하는 기법이다. 본 논문에서는 외부 수압을 받는 필라멘트 와인딩 복합재 원통과 샌드위치 원통의 수압시험이 수행되었고, PVDF센서로부터 측정된 AE 신호특성을 분석하였다. 또한, L-C 동조회로와 Band-pass filter 회로를 가진 AE 신호분석기를 설계, 제작 하였으며, 필라멘트 와인딩 원통과 샌드위치 원통에 대한 수압실험에서 제작된 AE 신호분석기의 균열 검출 능력을 평가하였다.

• The Journal of Asian Finance, Economics and Business
• /
• 제7권5호
• /
• pp.195-204
• /
• 2020

This research examines four specific objectives: (1) identifying factors that affect Vietnamese consumer attitudes towards smartphone advertising, (2) measuring the level of impact of the factors, (3) testing the difference of attitudes among groups of consumers with different characteristics in terms of gender, age, income, and academic level, and (4) proposing some managerial implications to have better Vietnamese consumer attitudes towards smartphone advertising. The study uses the online survey form via e-mail and Facebook in a convenience sampling method; the subjects surveyed are between the ages of 18 and 35, and all are in urban areas in Vietnam, and are using smartphones and accessing the internet and other phone applications. A sample of 490 respondents were valid and used for processing. The study employs a combination of qualitative and quantitative methods to analyze exploratory factors and linear multiple regression. The results reveal that there are five main factors affecting Vietnamese consumer attitudes towards smartphone advertising positively, arranged by reduced importance: entertainment, informativeness, credibility, non-irritation, permission and control. From that, the study offers some managerial suggestions for smartphone advertisers to improve their strategies and tatics to enhance their customer service, so that the smartphone advertising can attract people and help Vietnamese consumer in their buying behavior.

• 품질경영학회지
• /
• 제43권3호
• /
• pp.373-382
• /
• 2015

Purpose: In this paper, we developed a reliability index (RI) to efficiently compare reliability of products based on the design, development and production information such as reliability tests, quality, product life-cycle management. RI also can be applied to reliability prediction of a novel product as well as comparison evaluation among existing products. Methods: For evaluating RI, we proposed evaluation process which is composed of five steps. Target modules are selected based on warranty data and correlation analysis. Scores of selected target modules are calculated by scoring function. Finally, weights of RI model are determined by optimization method. Results: This paper presented an empirical analysis based on failure data of mobile devices. In this case study, we demonstrated that there is a direct correlation between evaluated RI and field failure probability of each product. Conclusion: We proposed the index for comprehensive and effective assessment of product reliability level. From the procedure of this study, we expected to be applied for reliability estimation of novel products and deduction of field failure-related factors.

• 한국정밀공학회지
• /
• 제32권7호
• /
• pp.619-625
• /
• 2015

There is a large interest to find reliable and automatic methods for crack detection and quantification in the railway bogie frame. The non-destructive inspection of railway bogie frame has been performed by ultrasonic and magnetic particle testing in general inspection. The magnetic particle method has been utilized in the defect inspection of the bogie frame but the grinding process is required before inspection and the dust is developed resulting from the processing. The objective of this paper is to apply the inspection method of bogie frame using infra-red thermography. The infra-red thermography system using the excitation of eddy current was performed for the defect evaluation of weld specimen inserted artificial defects. The result shows that the infra-red thermography method can detect the surface and inner defects in weld specimen for bogie frame.

• 대한임상검사과학회지
• /
• 제46권4호
• /
• pp.136-139
• /
• 2014

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the severe nosocomial infectious agents. The traditional diagnostic methods including biochemical test, antibiotic susceptibility test and PCR amplification are time consuming and require much work. The Surface enhanced Raman spectroscopy (SERS) biosensor is a rapid and powerful tool for analyzing the chemical composition within a single living cell. To identify the biochemical and genetic characterization of clinical MRSA, all isolates from patients were performed with VITEK2 gram positive (GP) bacterial identification and Antibiotic Susceptibility Testing (AST). Virulence genes of MRSA also were identified by DNA based PCR using specific primers. All isolates, which were placed on a gold coated nanochip, were analyzed by a confocal Raman microscopy system. All isolates were identified as S. aureus by biochemical tests. MRSA, which exhibited antibiotic resistance, demonstrated to be positive gene expression of both femA and mecA. Furthermore, Raman shift of S. aureus and MRSA (n=20) was perfectly distinguished by a confocal Raman microscopy system. This novel technique explained that a SERS based confocal Raman microscopy system can selectively isolate MRSA from non-MRSA. The study recommends the SERS technique as a rapid and sensitive method to detect antibiotic resistant S. aureus in a single cell level.

• Korean Journal of Acupuncture
• /
• 제25권3호
• /
• pp.15-27
• /
• 2008

Objectives : The objective of the current study is to optimize an acupoint electrical property measurement system by using the procedures and strengths of the Taguchi method. Methods : Taguchi method was applied in the optimization of the acupoint electrical property measurement system, as in the following steps: (1) determine evaluation index; (2) execute the 1st gage R&R; (3) identify controllable and uncontrollable factors; (4) design Taguchi crossed array layout; (5) execute experiments according to trial conditions; (6) analyze testing results; (7) determine optimum run; (8) execute the 2nd gage R&R; (9) confirm optimum run. Results : The results showed that electrodes with larger diameter and efferent electric current, with music played, can produce the larger different electrical conductivity between the acupoints and the non-acupoints under various conditions. Taguchi process optimization improved repeatability and reproducibility of the acupoint electrical property measurement system. Conclusions : In the optimized condition, repeatability and reproducibility of the acupoint electrical property measurement system was acceptable.

• 대한치과기공학회지
• /
• 제35권2호
• /
• pp.97-103
• /
• 2013

Purpose: The purpose of this study was to investigate the effect of addition of fiber glass on the physical properties of silanized fiber mesh and non silanized mesh of denture base resins. Methods: The denture base resins were used in this study heat curing acrylic resins(Vertex Rs, Lucitone 199, $20{\times}80mm$) and fiber glass(SES, Green B&D co., Ltd, $20{\times}80mm$) were used as reinforcement. The specimens were stored in distilled water at $37{\pm}2^{\circ}C$ for 72 hours before test. Bending strength and tensile strength were measured by an universal testing machine(Instron 4301, Instron Corp.). Penetration distribution on fiber was observed by scanning electron microscopy(JSM 840A, Jeol Ltd). Results: The bending strength and modulus were increased by 30% after adding fiber glass on denture base resins. Tensile strength showed significant increasing by adding fiber glass on denture base resins. Conclusion: In this study, Addition of silanized fiber in denture base resins were improved physical properties. we confirmed the fiber glass possibility of the replacement about conventional materials.

• Journal of Magnetics
• /
• 제21권1호
• /
• pp.57-60
• /
• 2016

Non Destructive Testing (NDT) methods that are capable of detecting the wall thinning and defects through insulation and cladding sheets are necessary. In this study we developed a Pulsed Eddy Current (PEC) system to detect wall thinning of ferro magnetic steel pipes covered with 95 mm thick fiber glass thermal insulator and shielded with aluminum plate of thickness 0.4 mm. In order to confirm the thickness change due to wall thinning, two different sensors, a hall sensor and a search coil sensor were used as a detecting element. In both the cases, the experimental data indicates a considerable change in the detected pulse corresponding to the change in sample thickness. The thickness of the tube was made to change such as 2.5 mm, 5 mm and 8 mm from the inner surface to simulate wall thinning. Fast Fourier Transform (FFT) was calculated using window approach and the results were summarized which shows a clear identification of thickness change in the test specimen by comparing the magnitude spectra.