• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2000년도 추계학술발표강연 및 논문개요집
• /
• pp.103-103
• /
• 2000

• 펄프종이기술
• /
• 제30권1호
• /
• pp.59-70
• /
• 1998

A steady-state molecular diffusion experiment was conducted to evaluate the water vapor proof properties of paper Handsheets prepared from unbleached Itraft pulps(UKP) and old newspapers(ONP) and four different types of polymer-laminated white duplex board were tested under appropriate standard conditions. The diffusivity was determined on the basis of the Fickean first law. Results obtained from this study can be summarized as follows ; 1. The diffusivity data for handsheets showed about $10^{-5}cm^2/min$. whereas polymer-laminated paperboards had remarkably improved water-vapor resistance with about $10^3 to 10^4$ times lower diffusivity : 2. Sheet basis weight, wet-swelling and sizing degree had little influence on the diffusivity of paper; 3 Linear relationship existed between sheet density and diffusivity, and, 4. Highly sfgnificant linear relationship could be observed between diffusivity and Darcy s gas permeability. Results indicate that diffusivity, an intrinsic property of paper, can provide a valuable information for precise evaluation and improved quality control of water-vapor proof properties of paper.

• Carbon letters
• /
• 제12권4호
• /
• pp.185-193
• /
• 2011

Carbon nanotubes (CNTs) have developed into one of the most competitively researched nano-materials of this decade because of their structural uniqueness and excellent physical properties such as nanoscale one dimensionality, high aspect ratio, high mechanical strength, thermal conductivity and excellent electrical conductivity. Mass production and structure control of CNTs are key factors for a feasible CNT industry. Water and ethanol vapor enhance the catalytic activity for massive growth of vertically aligned CNTs. A shower system for gas flow improves the growth of vertically aligned single walled CNTs (SWCNTs) by controlling the gas flow direction. Delivery of gases from the top of the nanotubes enables direct and precise supply of carbon source and water vapor to the catalysts. High quality vertically aligned SWCNTs synthesized using plasma enhance the chemical vapor deposition technique on substrate with suitable metal catalyst particles. This review provides an introduction to the concept of the growth of vertically aligned SWCNTs and covers advanced topics on the controlled synthesis of vertically aligned SWCNTs.

• 동력기계공학회지
• /
• 제18권5호
• /
• pp.88-93
• /
• 2014

In this paper, the performance analysis of condensation and evaporation capacity, turbine work and efficiency of the OTEC power system using vapor-liquid Ejector is presented to offer the basic design data for the operating parameters of the system. The working fluid used in this system is $CO_2$. The operating parameters considered in this study include the vapor quality at heat exchanger outlet, pressure ratio of ejector and inlet pressure of low turbine, mass flow ratio of separator at condenser outlet. The main results were summarized as follows. The efficiency of the OTEC power cycle has an enormous effect on the mass flow ratio of separator at condenser outlet. With a thorough grasp of these effects, it is possible to design the OTEC power cycle proposed in this study.

• 대한기계학회논문집
• /
• 제16권12호
• /
• pp.2340-2348
• /
• 1992

본 연구에서는 드릴(SKH9종)에 스퍼터링법으로 Ti 중간층을 약 0.2$\mu\textrm{m}$의 두께 로 코팅한후, 그 위에 플라즈마 화학증착법으로 TiN박막을 코팅한 드릴로 드릴링 시험 을 행하여 수명을 평가하였으며, 드릴의 내마멸성 및 드릴링한 구멍 내면의 조도를 코 팅하지 않은 드릴 및 TiN 코팅한 드릴과 비교하므로서 Ti/TiN코팅처리에 의한 공구성 능 및 수명향상 효과를 평가하고자 하였다.

• 한국측량학회지
• /
• 제20권2호
• /
• pp.215-222
• /
• 2002

As the GPS signals propagate from the GPS satellites to the receivers on the ground, they are delayed by the atmosphere. The tropospheric delay consists of two components. The hydrostatic (or "dry") component that is dependent on the dry air gasses in the atmosphere and accounts for approximately 90% of the delay. And the "wet" component that depends on the moisture content of the atmosphere and accounts for the remaining effect of the delay. The Zenith Hydrostatic Delay (ZHD) can be calculated from the local surface pressure. The Total Zenith Delay (TZD) will be estimated and the wet component extracted later. Integrated water Vapor (IWV) gives the total amount of water vapor that a signal from the zenith direction would encounter. Precipitable Water Vapor (PWV) is the IWV scaled by the density of water. The quality of this PWV has been verified by comparison with radiosonde data(at Osan). We processed data for JULY 2 and JULY 14, 1999 from four stations(Cheju, Kwangju, Suwon, Daegu). We found the coincidence between PWV of the estimations using GPS and PWV of pressing the radiosonde data. The average of the difference between PWV using GPS and PWV using radiosonde was 3.77 mm(Std. ＝ $\pm$0.013 mm) and 2.70 mm(Std. = $\pm$0.0011 mm) at Suwon & Kwangju.

• 한국산업융합학회 논문집
• /
• 제26권4_2호
• /
• pp.577-584
• /
• 2023

In this study, among the parts of oil vapor collectors that are already being produced, weaving wire brush automatic transplanters for oil vapor collectors for machine tools of the weaving fixing method, which are not automated due to the specificity of the process and are being produced manually, are developed and reliability is secured through performance evaluation. did Oil vapor collectors play an important role in removing air pollutants and improving air quality, and the coagulation effect of the collection technology is mostly due to brushes. In the experiment, an automatic transplanter was developed to automatically manufacture and produce the wire brush of the oil vapor collector, which is manufactured and used manually. For the experiment of the developed wire brush, an experimental chamber was built, and performance and durability were evaluated through the dust collection efficiency evaluation using the electrostatic precipitator method of contaminants (oil mist). Through this study, we intend to reduce the production time and unit cost of collectors and improve the environment at industrial sites.

• Current Optics and Photonics
• /
• 제7권2호
• /
• pp.207-212
• /
• 2023

In this paper, we introduce our system for manufacturing a Rb vapor cell and describe its fabrication process in a sequence of removing impurities, cold trapping, and sealing off. Saturated absorption spectroscopy was performed to verify the quality of our cell by comparing it to that of a commercial one. By using the lab-fabricated Rb vapor cell, we observed electromagnetically induced transparency in a ladder-type system corresponding to the 5S_1/2-5P_3/2-28D_5/2 transition of the ⁸⁵Rb atom. A highly excited Rydberg atomic system was prepared using two counter-propagating external cavity diode lasers with wavelengths of 780 nm and 480 nm. We also observed the Autler-Townes splitting signal while a radio-frequency source around 100 GHz incidents into the Rydberg atomic medium.

• Journal of Advanced Marine Engineering and Technology
• /
• 제39권7호
• /
• pp.702-708
• /
• 2015

본 연구에서는 FC-72를 작동 유체로 사용하여 이상 유동 비등에 관한 실험을 수행하였다. 마이크로 채널은 깊이 0.2mm, 폭 0.45mm, 길이 60mm 그리고 채널의 개수는 15개로 구성되었다. 실험은 질량유속과 열유속 각각 $200-400kg/m^2s$, $5.6-49.0kW/m^2$ 범위와 증기 건도 0.02-0.93 범위에서 수행되었다. 실험 결과에 따르면 낮은 건도(x<0.2)영역에서는 핵비등에 의한 열전달이 지배적으로 작용하며, 그 이상의 증기 건도 영역에서는 핵비등과 강제 대류 비등의 영향이 복합적으로 작용하는 것으로 나타났다. 핵비등과 강제 대류 비등은 각각 비등수와 대류수에 관한 함수로 표현할 수 있으며, 실험에서 얻어진 열전달 계수는 기존의 상관식에 의한 열전달 계수와 비교하였다.

• Nuclear Engineering and Technology
• /
• 제51권8호
• /
• pp.1897-1904
• /
• 2019

Three-layer back propagation network (BPN) and genetic neural network (GNN) were developed in this study to predict the flow boiling heat transfer coefficient (HTC) in conventional and small-diameter channels. The GNN has higher precision than BPN (with root mean square errors of 17.16% and 20.50%, respectively) and other correlations. The inputs include vapor quality x, mass flux G, heat flux q, diameter D and physical parameter φ, and the predicted flow boiling HTC is set as the outputs. Influences of input parameters on the flow boiling HTC are discussed based on the trained GNN: nucleate boiling promoted by a larger saturated pressure, a larger heat flux and a smaller diameter is dominant in small channels; convective boiling improved by a larger mass flux and a larger vapor quality is more significant in conventional channels. The HTC increases with pressure both in conventional and small channels. The HTC in conventional channels rises when mass flux increases but remains almost unaffected in small channels. A larger heat flux leads to the HTC growth in small channels and an increase of HTC was observed in conventional channels at a higher vapor quality. HTC increases inversely with diameter before dry out.