• 대한조선학회논문집
• /
• 제51권4호
• /
• pp.311-320
• /
• 2014

Test uncertainty of a towed underwater Stereoscopic Particle Image Velocimetry (SPIV) system was assessed in a towing tank. To estimate the systematic error and random error of mean velocity and turbulence properties measurement, velocity field of uniform flow was measured. Total uncertainty of the axial component of mean velocity was 1.45% of the uniform flow speed and total uncertainty of turbulence properties was 3.03%. Besides, variation of particle displacement was applied to identify the change of error distribution. In results for variation of particle displacement, the error rapidly increases with particle movement under one pixel. In addition, a nominal wake of a model ship was measured and compared with existing experimental data by five-hole Pitot tubes, Pitot-static tube, and hot wire anemometer. For mean velocity, small local vortex was identified with high spatial resolution of SPIV, but has serious disagreement in local maxima of turbulence properties due to limited sampling rate.

• 한국재료학회지
• /
• 제30권4호
• /
• pp.169-175
• /
• 2020

Silicon nitride thin films are deposited by RF (13.57 MHz) magnetron sputtering process using a Si (99.999 %) target and with different ratios of Ar/N₂ sputtering gas mixture. Corning G type glass is used as substrate. The vacuum atmosphere, RF source power, deposit time and temperature of substrate of the sputtering process are maintained consistently at 2 ~ 3 × 10^-3 torr, 30 sccm, 100 watt, 20 min. and room temperature, respectively. Cross sectional views and surface morphology of the deposited thin films are observed by field emission scanning electron microscope, atomic force microscope and X-ray photoelectron spectroscopy. The hardness values are determined by nano-indentation measurement. The thickness of the deposited films is approximately within the range of 88 nm ~ 200 nm. As the amount of N₂ gas in the Ar:N₂ gas mixture increases, the thickness of the films decreases. AFM observation reveals that film deposited at high Ar:N₂ gas ratio and large amount of N₂ gas has a very irregular surface morphology, even though it has a low RMS value. The hardness value of the deposited films made with ratio of Ar:N₂=9:1 display the highest value. The XPS spectrum indicates that the deposited film is assigned to non-stoichiometric silicon nitride and the transmittance of the glass with deposited SiO₂-Si_xN_y thin film is satisfactory at 97 %.

• 디지털콘텐츠학회 논문지
• /
• 제16권2호
• /
• pp.275-282
• /
• 2015

2001년 지상파 디지털방송 시작 이후, 디지털방송의 장점 중 하나인 다채널방송 서비스 도입에 대한 논의가 계속되던 중, 2013년 10월 정부기관, 방송사, 가전사가 참여하는 지상파 다채널 실험방송 추진반이 구성되어 2014년 1월부터 4월 사이에 지상파 다채널 실험방송이 실시되었다. 이 실험방송 결과를 바탕으로 EBS에서는 2015년 2월 11일 국내 최초로 2HD MMS 시험방송을 시작하였다. 본 연구는 압축 기술의 발전으로 기존 6MHz 대역에 2개의 HD 채널을 MPEG-2 코덱기반으로 운영하기 위하여 실시하였다. 1080i 와 720p 주사방식에 따른 변화 및 효율적 데이터 사용을 위한 가변 비트율(Variable Bit Rate) 적용 실험을 통하여 화질 최적화 연구를 실시하고 2HD MMS 시험방송에 적용하였다.

• Wind and Structures
• /
• 제30권6호
• /
• pp.617-631
• /
• 2020

Wake-induced aerodynamics of yawed circular cylinders with smooth and grooved surfaces in a tandem arrangement was studied. This pair of cylinders represent sections of stay-cables with smooth surfaces and high-voltage power conductors with grooved surfaces that are vulnerable to flow-induced structural failure. The study provides some insight for a better understanding of wake-induced loads and galloping problem of bundled cables. All experiments in this study were conducted using a pair of stationary section models of circular cylinders in a wind tunnel subjected to uniform and smooth flow. The aerodynamic force coefficients and vortex-shedding frequency of the downstream model were extracted from the surface pressure distribution. For measurement, polished aluminum tubes were used as smooth cables; and hollow tubes with a helically grooved surface were used as power conductors. The aerodynamic properties of the downstream model were captured at wind speeds of about 6-23 m/s (Reynolds number of 5×10⁴ to 2.67×10⁵ for smooth cable and 2×10⁴ to 1.01×10⁵ for grooved cable) and yaw angles ranging from 0° to 45° while the upstream model was fixed at the various spacing between the two model cylinders. The results showed that the Strouhal number of yawed cable is less than the non-yawed case at a given Reynolds number, and its value is smaller than the Strouhal number of a single cable. Additionally, compared to the single smooth cable, it was observed that there was a reduction of drag coefficient of the downstream model, but no change in a drag coefficient of the downstream grooved case in the range of Reynolds number in this study.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
• /
• pp.521-532
• /
• 2008

Supporting system design and construction management for the soft and hard rock layers with fractured zones are very important theme for the safety of temporary retaining wall, surrounding ground and structures in the urban deep excavation for the construction of subway, railway, building etc. The prevailing design method of supporting system for the soft and hard rock layers in the deep excavation is mostly carrying out by simplification without proper consideration for the characteristic of rock discontinuities. Therefore the behaviors of rock discontinuities and fractured zones dominate the whole safety of excavation work in the real construction stage, serious disaster due to the failure of temporary retaining wall can be induced in the case of developing large deformations in the ground and large axial forces in the supporting system. This paper introduces examples of deep excavation where the soft and hard rock layers with fractured zones were designed to be supported by shotcrete and rock bolt, deformations of corresponding ground and supporting systems in the construction period and increments of axial force in the upper earth anchors and strut due to the these deformations were investigated through detailed analysis of measurement data, the results were so used for the management of consecutive construction that led to the safe and economical completion of excavation work. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

• Journal of Oral Medicine and Pain
• /
• 제19권2호
• /
• pp.153-168
• /
• 1994

The aim of the present study was to investigate a relation between occlusal wear area and occlusal contact patterns. For the purpose, occlusal wear area were measured in 58 dental students and in 129 patients with temporomandibular disorders(TMDs) from dental casts. Teeth used in this study were from canine to second molar on both sides in upper arch, totally ten. Occlusal wear area on casts was marked by pencil and photocopies, and then, the area was measured with planimeter. Occlusal relation was clinically examined with regard to Angle's classification, chewing side preference, lateral guidance pattern and bruxing and/or clenching habit. T-Scan, electronic occlusal contact analyzer, was used to record occlusal contact number, contact force, contact time and occlusal balance that is TLR(total left-right statistics) during tooth contact. All measurement were repeated 3 times and the average value was used for data processing. The obtained results were as follows : 1. Mean value of occlusal wear area did not differ significantly between dental students and patients. 2. There ws not significant difference in wear area between chewing side and non-chewing side in both groups. 3. Occlusal wear area was significantly increased with age in both groups. 4. Three subgroups divided by Angle's classification did not show any difference in occlusal wear area among them, but three subgroups divided by lateral guidance pattern showed slightly significant difference between canine guide subgroup and group function subgroup in patients. Occlusal wear ares\a in group function subgroup wear larger than canine guide subgroup. 5. Mean value of wear area in patients with bruxing and/or clenching habit did not differ from those in patients without such habit. 6. Correlationship among items related to occlusal contact pattern were highly consistent and significant in dental students and only one item significantly correlated with occlusal wear area was tooth contact time.

• 보건교육건강증진학회지
• /
• 제22권1호
• /
• pp.147-160
• /
• 2005

The purpose of this study is to identify the nature of the patient service quality of health center, and based on that, to examine the relationship of health center visitor's perceived quality and overall satisfaction. Data were collected on the basis of 'the 3rd Regional Health Care Planning' operated by Rural Health Care Service Technology Aid Task-force Team(RHCSTAT), Ministry of Health and Welfare. Basically, the Manual of 3rd Regional Health Care Planning is composed of structure, process, and outcome measurement indicators. Of these indicators, 21 patient satisfaction questions as outcome indicators are used in this study. The samples are 3,530 patients who visited 80 health centers all of the nation. First, the reliability and validity of patient service quality items was evaluated. Second, the descriptive statistics of health service quality are calculated. Third, through the T-test and ANOVA, the differences of patient satisfaction by responder's general characteristics are compared. In final, to explore the relationship of service quality and overall satisfaction, multiple regression analysis was used. This study shows firstly, the dimension of patient service quality was categorized into 3 dimensions, that is, facilities and environment, staff kindness, and access convenience. Secondly, the reliability and validity of patient service quality items was satisfied. Thirdly, the mean score of staff kindness factors are high in contrast to the facilities and environment. And in regard to the overall satisfaction, the mean score is more higher in Daegu region, County type health center, male group, and upper 65 age group than comparison groups. Lastly, as a result of multiple regression analysis, the effect of patient's perceived service quality, especially, appropriateness of billing time(Beta=0.190) and of reservation time(Beta=0.132) are statistically significant(P<0.01). In conclusion, to satisfy the health need of community people and improve the service quality of the health center, the efforts for the access convenience might be needed. Additionally, the enlargement on health center space and supply of new medical equipment is urgent for the patient satisfaction.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
• /
• pp.965-968
• /
• 2004

Effective transverse Piezoelectric Coefficients $(e_{31,f})$ of thick PZT $(Pb(Zr_{0.52}Ti{0.48}Ti_{0.48})O_3)$ films on $SiN_x/Si$ substrates were measured with PZT thicknesses and top electrode dimensions. $e_{31,f}$ is one of important Parameters characterizing Piezoelectricity of PZT films. Thick PZT films have been used as various sensors and actuators because of their high driving force and high breakdown voltage. Thick PZT films were fabricated on Pt/Ta/$SiN_x$/Si substrates using sol-gel method. Thicknesses of PZT films were $1{\mu}m$ and $1.8{\mu}m$. $|e_{31,f}|$ values of $1.8{\mu}m$-thick-PZT films were higher than those of $1{\mu}$-thick-PZT films. Maximum $|e_{31,f}|$ of $1.8{\mu}$-thick-PZT films was about $50^{\circ}C/m^2$.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
• /
• pp.938-941
• /
• 2003

It is well known that the state of existence of molecules on the surface of water changes during compression of the molecules. Electric methods, such as measurement of the surface potential or displacement current are also useful for investigating dynamic changes of molecular state on the water surface during compression and Transformation of molecular film occurs only usually in air-water interface, 2 dimensions domain's growth and crash are achieved. Organic thin film that consist of growth of domain can understand correct special quality of accumulation film supplying information about fine structure and properties of matter of device observing information and so on that is surface forward player and optic enemy using AFM one of SPM application by nano electronics. In this paper Langmuir (L) that is one of basis technology to manufacture of organic matter device using biology material PBDG that is kind of polypeptide that have biology adaptedness. The Experiment method used ${\pi}-A$ isotherm and BAM(Brewster Angle Microscopy), using the BAM, we can to the molecular orientation of monolayer on the water surface and directly see the morphology of the films on water subphase as well as that of the films.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
• /
• pp.424-424
• /
• 2008

Dye-sensitized Solar Cell (DSC) is a new type of solar cell by using photocatalytic properties of $TiO_2$. The electric potential distribution in DSCs has played a major role in the operation of such cells. Models based on a built-in electric field which sets the upper limit for the open circuit voltage(Voc) and/or the possibility of a Schottky barrier at the interface between the mesoporous wide band gap semiconductor and the transparent conducting substrate have been presented. $TiO_2$ thin films were deposited on the FTO substrate by Nd:YAG Pulsed Laser Deposition(PLD) at room temperature and post-deposition annealing at $500^{\circ}C$ in flowing $O_2$ atmosphere for 1 hour. The structural properties of $TiO_2$ thin films have investigated by X-ray diffraction(XRD) and atomic force microscope(AFM). Thickness of $TiO_2$ thin films were controlled deference deposition time and measurement by scanning electron microscope(SEM). Then we manufactured a DSC unit cells and I-V and efficiency were tested using solar simulator.