• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.22 no.6
• /
• pp.374-386
• /
• 2010

Recently, the theoretical and experimental research is being made actively in control character of waves of perforated-wall caisson breakwater like the slit caisson. This study showed that the character of reflection coefficient and the wave pressure acting on the front and inner of slit caisson were estimated in two and three dimensional numerical wave flume and compared each other. The numerical experiment was set and conducted by various cases as to a variety of wave steepness under 7 sec, 9 sec, 11sec and 13 sec period condition. In this study using a 2 and 3 dimensional numerical wave flume, it applied the Model for the immiscible two-phase flow based on the Naveir-Stokes Equations. This technique can easily reproduce a complicated physical phenomenon more than others and organize the program simply. According to the results of the experiment, the reflection coefficient was estimated high in short-period waves. However, 2-dimensional numerical experiment and 3-dimensional numerical experiment were the same in case of the long-period waves and high wave steepness. And to conclude in case of short-period waves the pressures were a relatively small difference between the two, but there was a big gap in longperiod waves and high wave steepness.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.1
• /
• pp.159-167
• /
• 2000

In recent years, combined and separated sewer overflows (CSOs, SSOs) have been recognized as a significant pollution problem. To solve this problem a series of experiments were performed in a small scale Rapid Floc Settler (RFS) device to determine its ability in removing micro particles and dissolved materials from polluted waters. The RFS device is a compact physico-chemical wasterwater treatment system. Polyacrylamide (PAM) is used as a coagulant for treating stormwater in the RFS. The results of Jar test showed that PAM could be an excellent coagulant as compared with aluminum sulfate. and ferric chloride. In several experimental conditions, the influence of different variation parameters was tested to measure the efficiency of the RFS. Tests have been carried out with typical CSOs concentrations (50~1.000mg SS/L). The treatment efficiency with regard to SS and COD, which can be obtained at an overflow rate of $130m^3/m^2/day$, are 90% and 80%, respectively. Comparing other sedimentation technologies with RFS, the overflows rate of RFS is ten times faster. The distribution of particle size and number were analyzed. The RFS is suitable for the treatment of CSOs and also the removal of settleable and dissolved materials in urban stormwater runoff.

• Journal of Astronomy and Space Sciences
• /
• v.19 no.4
• /
• pp.305-318
• /
• 2002

We have constructed two flight models of airglow photometer system (AGP) to be onboard Korea Sounding Rocket-III (KSR-III) for detection of MUV dayglow above the Korean peninsular. The AGP system is designed to detect dayglow emissions of OI 2972${\AA}$, $N_2$ VK(0,6) 2780${\AA}$, $N_2$ 2PG 3150${\AA}$ and background 3070${\AA}$ toward the horizon at altitudes between 100 km and 300 km. The AGP system consists of a photometer body, a baffle an electronic control unit and a battery unit. The MUV dayglow emissions enter through a narrow band interference filter and focusing lens of the photometer, which contains an ultraviolet sensitive photomultiplier tube. The photometer is equipped with an in-flight calibration light source on a circular plane that will rotate at the rocket's apogee. A bane tube is installed at the entry of the photometer in order to block strong scattering lights from the lower atmosphere. We have carried out laboratory measurements of sensitivity and in-flight calibration light source for the AGP flight models. Although absolute sensitivities of the AGP flight models could not be determined in the country, relative sensitivities among channels are well measured so that observation data during rocket flight in the future can be analyzed with confidence.

• Journal of the Society of Disaster Information
• /
• v.15 no.4
• /
• pp.524-530
• /
• 2019

Purpose: In this paper, we construct a detailed three-dimensional interface element using a three-dimensional analysis program, and evaluate the composite behavior stability of the connector by applying physical properties such as the characteristics of general members and those of reinforced members Method: The analytical model uses solid elements, including non-linear material behavior, to complete the modeling of beam structures, circular flanges, bolting systems, etc. to the same dimensions as the design drawing, with each member assembled into one composite behavior linkage. In order to more effectively control the uniformity and mesh generation of other element type contact surfaces, the partitioning was performed. Modeled with 50 carbon steel materials. Results: It shows the displacement, deformation, and stress state of each load stage by the contact adjoining part, load loading part, fixed end part, and vulnerable anticipated part by member, and after displacement, deformation, The effect of the stress distribution was verified and the validity of the design was verified. Conclusion: Therefore, if the design support of the micro pile is determined based on this result, it is possible to identify the Vulnerable Parts of the composite behavior connector and the degree of reinforcement.

• Journal of Information Management
• /
• v.42 no.1
• /
• pp.113-135
• /
• 2011

The final report of the Functional Requirement of Subject Authority Data(FRSAD), the 3rd report of the FRBR family model, is announced by IFLA in June, 2010. This model represents the international trends of subject authority control and suggests a direction to the future subject authority record suitable for the FRBR system. Therefore aims of this study are to analysis the FRSAD model in context of the FRBR family and apply the model to the subject headings and bibliographic records of Korean National Library. For these aims, we analyse the model focused on the entities, attributes, and relationships between entities. From this analysis, we have found the openness of the FRSAD, which does not force a certain entity types and has focus on the conceptual aspects of the entity not only the form of the headings. Moreover, we suggest examples by applying the FRSAD frame and facets of the FAST to the Headings of the NLSH and related KORMARC fields. The scope of this study is the additional entities of the FRBR groups, so personal names, corporate names, family names and titles are not included. As a result, it is necessary to determine the criteria for the types of thema and to apply the types consistently in bibliographic records. A follow up research will be needed to suggest more detailed examples.

• The KIPS Transactions:PartA
• /
• v.15A no.4
• /
• pp.227-238
• /
• 2008

Recently, as network environment has broadened, the demands on VOD have been increased. The VOD services can be categorized into two types, RVOD and NVOD. Practical VOD services adopt one of them exclusively. Since a method using only one of RVOD and NVOD is not able to deal with frequently variable demand of clients, it leads to a result of overload on a server and a waste of server bandwidth. The efficiency of the network resource usage becomes lower. Hence this paper presents a study on the protocol for efficient VOD services. We propose a new protocol appliable for the existing VOD service algorithm, analyze its performance through simulation, and developed server/client systems applying the new protocol. We propose a mode switching protocol combined with protocols used in RVOD and NVOD. The proposed protocol is not able only to control both RVOD and NVOD but also to change the mode between RVOD and NVOD. As a result of using the proposed protocol to meet frequently variable demand, server bandwidth can be used efficiently. Especially, it can be applied to the existing VOD service algorithms. Therefore, we expect that the proposed protocol in this paper will be widely used in emerging VOD markets.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.257-257
• /
• 2007

고밀도 FeRAM (Ferroe!ectric Random Access Memory) 소자를 개발하기 위해서는 강유전체 물질을 이용한 안정적인 스텍형의 커패시터 개발이 필수적이다. 특히 $(Bi,La)_4Ti_3O_{12}$ (BLT) 강유전체 물질을 이용하는 경우에는 낮은 열처리 온도에서도 균질하고 높은 값의 잔류 분극 값을 확보하는 것이 가장 중요한 과제 중의 하나이다. 불행히도, BLT 물질은 a-축으로는 약 $50\;{\mu}C/cm^2$ 정도의 높은 잔류 분극 값을 갖지만, c-축 방향으로는 $4\;{\mu}C/cm^2$ 정도의 낮은 잔류 분극 값을 나타내는 동의 강한 비등방성 특성을 보인다. 따라서 BLT 박막에서 각각 입자들의 크기 및 결정 방향성을 세밀하게 제어하는 것은 무엇보다 중요하다. 본 연구에서는 16 Mb의 1T/1C (1-transistor/1-capacitor) 형의 FeRAM 소자를 BLT 박막을 적용하여 제작하였다. 솔-젤 (sol-gel) 용액을 이용하여 스핀코팅법으로 BLT 박막을 증착하고, 후속 열처리 공정을 RTP (rapid thermal process) 공정을 이용하여 수행하였다. 커패시터의 하부 전극 및 상부 전극은 각각 Pt/IrOx/lr 및 Pt을 적용하였다. 반응성 이온 에칭 (RIE: reactive ion etching) 공정을 이용하여 커패시터를 형성시킨 후, 32k-array (unit capacitor: $0.68\;{\mu}m$) 패턴에서 측정한 스위칭 분극 (dP=P*-P^) 값은 약 $16\;{\mu}C/cm^2$ 정도이고, 웨이퍼 내에서의 균일도도 2.8% 정도로 매우 우수한 특성을 보였다. 그러나 단위 셀들의 특성을 평가하기 위하여 bit-line의 전압을 측정한 결과, 약 10% 정도의 커패시터에서 불량이 발생하였다. 그리고 이러한 불량 젤들은 매우 불규칙적으로 분포함을 확인할 수 있었다. 이러한 불량 원인을 파악하기 위하여 양호한 젤과 불량이 발생한 셀에서의 BLT 박막의 미세구조를 분석하였다. 양호한 셀의 BLT 박막 입자들은 불량한 셀에 비하여 작고 비교적 균일한 크기를 갖고 있었다. 이에 비하여 불량한 셀에서의 BLT 박막에는 과대 성장한 입자들이 존재하고 이에 따라서 입자 크기가 매우 불균질한 것으로 확인되었다. 또 이러한 과대 성장한 입자들은 거의 모두 c-축 배향성을 나타내었다. 이상의 실험 결과들로부터, BLT 박막을 이용하여 제작한 FeRAM 소자에서 발생하는 불규칙한 셀 불량의 주된 원인은 c-축 배향성을 갖는 과대 성장한 입자의 생성임을 알 수 있었다. 즉 BLT 박막을 이용하여 FeRAM 소자를 제작하는 경우, 균일한 크기의 입자 및 c-축 배향성의 입자 억제가 매우 중요한 기술적 요소임을 알 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.39-39
• /
• 2007

원자층 증착(Atomic Layer Deposition: ALD) 방법은 반응물질들을 펄스형태로 챔버에 공급하여 기판표면에 반응물질의 표면 포화반응에 의한 화학적 흡착과 탈착을 이용한 박막증착기술이다. ALD법은 기존의 화학적 기상증착(Chemical Vapor Deposition: CVD)과 달리 자기 제한적 반응(self-limiting reaction) 에 의하여 반응가스가 기판 표면에서만 반응하고 가스와 가스 간에는 반응하지 않는다. 따라서 박막의 조성 정밀제어가 쉽고, 파티클 발생이 없으며, 대면적의 박막 증착시 균일성이 우수하고, 박막 두께의 정밀 조절이 용이한 장점이 있다. 이러한 ALD 방식으로 3차원의 반도체 장치 구조물에 산화막 등을 형성하는 공정에서 중요한 요소 중의 하나는 전구체의 충분한 공급이다. 따라서 증기압이 높은 전구체를 선호하는 경향이 있다. 그러나 증기압이 낮은 전구체를 사용할 경우, 공급량이 부족하여 단차 도포성(step coverage)이 떨어지는 문제가 있다. 원자층 증착 공정에서 전구체를 충분히 공급하기 위해전구체 온도를 증가시키거나 전구체의 공급시간을 늘리는 방법을 사용한다. 그러나 전구체 온도를 상승시키는 경우, 전구체의 변질이나 수명을 단축시키는 문제점을 발생시킬 수 있으며. 전구체를 충분히 공급하기 위하여 전구체의 공급시간을 늘이는 방법을 사용하면, 원하는 박막을 형성하기 위하여 소요되는 공정시간과 전구체 사용량이 증가된다. 본 논문에서는 이러한 문제점을 해결하기 위해 반응기 안에서 전구체 노출 시간을 조절하는 새로운 ALD 공정을 소개한다. 특히 이러한 기술을 적용하면 나노튜브를 성장시키는데 매우 유리하다. 본 연구에서 전구체 노출 시간을 조절하기 위하여 사용된 ALD 장비는 Lucida-D200-PL (NCD Technology사)이며 (TEMA)Zr와 H2O를 사용하여 ZrO2 나노튜브를 폴리카보네이트 위에 성장시켰다. 전구체의 노출 시간은 반응기의 Stop 밸브를 이용하여 조절하였으며, SEM, TEM 등을 이용하여 나노튜브의 균일성과 단차피복성 등의 특성을 관찰하였다. 그 결과 전구체 노출시간을 조절함으로써 높은 종횡비를 갖는 나노튜브를 성장 시킬 수 있음을 확인하였다. 또한 낮은 증기압을 가지는 전구체를 이용하여도 우수한 특성의 나노튜브를 균일하게 성장시킬 수 있었다.

• Polymer(Korea)
• /
• v.26 no.5
• /
• pp.644-652
• /
• 2002

This study aims at developing the conductive pastes consisting of room temperature vulcanizing (RTV) silicone and metal powder as matrix and filler, respectively. Electrical and rheological properties of metal - filled polymer composites are in general strongly affected by particle shape, side and dispersion state of the filler. In highly filled systems, particles tend to form very complex agglomerated structure which is easily changed when subjected to shear deformation. And the breakdown of agglomerated particles due to shear usually leads to the change of electrical conductivity of the composite. In this study, the effect of particle size and dispersion state of filler on the electrical conductivity of the composites are investigated to offer the selection criteria of conductive filler by measuring the rheological properties of uncured composites and the electrical conductivity of the cured composites. It was found that the type of metal filler systematically affected the rheological property, the susceptibility to shear and the degree of change of electrical conductivity of the composite. The effect of shear on the properties is more conspicuous in the composites containing large particle, indicating that both rheological and electrical properties can be improved by controlling the dispersion state at a given filler content.

• Journal of the Korean Vacuum Society
• /
• v.12 no.4
• /
• pp.263-268
• /
• 2003

Precise thickness control and excellent properties of silicon nitride thin films are essential for the next-generation semiconductor and display devices. In this study, silicon nitride thin films were deposited by batch-type atomic layer deposition (ALD) method using $SiC1_4$ and $NH_3$ as the precursors at temperatures ranging from 500 to $600^{\circ}C$. Thin film deposition using a batch-type ALD reactor was a layer-by-layer atomic growth by self-limiting surface reactions, and the thickness of the deposited film can be controlled by the number of deposition cycles. The silicon nitride thin films deposited by ALD method exhibited composition, refractive index and wet etch rate similar with those of the thin films deposited by low-pressure chemical vapor deposition method at $760^{\circ}C$. The addition of pyridine mixed with precursors increased deposition rate by 50%, however, the films deposited with pyridine was readily oxidized owing to its unstable structure, which is unsuitable for the application to semiconductor or display devices.