• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.382-382
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• 2010

$TaO_2$ thin films as gate dielectrics have been proposed to overcome the problems of tunneling current and degradation mobility in achieving a thin equivalent oxide thickness. An extremely thin $SiO_2$ layer is used in order to separate the carrier in MOSFETchannel from the dielectric field fluctuation caused by phonons in the dielectric which decreases the carrier mobility. The electronic and optical properties influenced the device performance to a great extent. The atomic structure of amorphous and crystalline Tantalum oxide ($TaO_2$) gate dielectrics thin film on Si (100) were grown by utilizing atomic layer deposition method was examined using Ta-K edge x-ray absorption spectroscopy. By using X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy (REELS) the electronic and optical properties was obtained. In this study, the band gap (3.400.1 eV) and the optical properties of $TaO_2$ thin films were obtained from the experimental inelastic scattering cross section of reflection electron energy loss spectroscopy (REELS) spectra. EXAFS spectra show that the ordered bonding of Ta-Ta for c-$TaO_2$ which is not for c-$TaO_2$ thin film. The optical properties' e.g., index refractive (n), extinction coefficient (k) and dielectric function ($\varepsilon$) were obtained from REELS spectra by using QUEELS-$\varepsilon$(k, $\omega$)-REELS software shows good agreement with other results. The energy-dependent behaviors of reflection, absorption or transparency in $TaO_2$ thin films also have been determined from the optical properties.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.381-381
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• 2010

$(ZrO_2)_{0.66}(HfO_2)_{0.34}$ thin films as gate dielectrics have been proposed to overcome the problems of tunneling current and degradation mobility inachieving a thin equivalent oxide thickness. An extremely thin $SiO_2$ layer is used in order to separate the carrier in MOSFET channel from the dielectric field fluctuation caused by phonons in the dielectric which decreases the carrier mobility. The electronic and optical properties influenced the device performance to a great extent. $(ZrO_2)_{0.66}(HfO_2)_{0.34}$ dielectric films on p-Si (100) were grown by atomic layer deposition method, for which the conduction band offsets, valence band offsets and band gapswere obtained by using X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy. The band gap, valence and conduction band offset values for $(ZrO_2)_{0.66}(HfO_2)_{0.34}$ dielectric thin film, grown on Si substrate were about 5.34, 2.35 and 1.87 eV respectively. This band alignment was similar to that of $ZrO_2$. In addition, The dielectric function (k, $\omega$), index of refraction n and the extinction coefficient k for the $(ZrO_2)_{0.66}(HfO_2)_{0.34}$ thin films were obtained from a quantitative analysis of REELS data by comparison to detailed dielectric response model calculations using the QUEELS-$\varepsilon$(k, $\omega$)-REELS software package. These optical properties are similar with $ZrO_2$ dielectric thin films.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.114-114
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• 2010

최근 고용량의 디커플링 캐패시터를 기판에 내장하여 고주파 발생의 원인인 배선길이와 실장 면적을 획기적으로 줄이는 임베디드 디커플링 캐패시터에 대한 연구가 활발히 진행되고 있다. 하지만 기존의 공정들은 높은 공정온도와 같은 공정상의 한계를 가지고 있어 상온 저 진공 분위기에서 세라믹 분말을 기판에 고속 분사시켜 기공과 균열이 거의 없는 치밀한 나노구조의 세라믹 제작이 가능한 후막코팅기술인 Aerosol Deposition Method (ADM)에 착목하였으며, 이 ADM을 박막공정으로 응용하여 $BaTiO_3$ 박막을 제작하고 고용량의 디커플링 캐패시터 제작을 실현하고자 한다. 하지만, Cu 기판 상에 성막 된 $0.5\;{\mu}m$이하의 $BaTiO_3$ 박막에서는 $BaTiO_3$ 분말 내에 존재하는 평균입자 보다 큰 입자와 응집분말로 인해 발생하는 pore, crater, not-fully-crushed particles와 같은 거시적인 결함들에서의 전류 통전과 울퉁불퉁한 $BaTiO_3$ 박막과 기판 사이의 계면에서의 전계의 집중에 의한 전류의 증가로 인하여 큰 누설전류 발생하는 문제에 봉착하였다. 이러한 문제를 해결하기 위하여 제시된 효과적인 방법으로 Stainless steel 기판과 같이 표면경도가 높은 기판을 사용하는 것이며, 이를 통해 $0.2\;{\mu}m$의 두께까지 유전 $BaTiO_3$ 박막을 성막 할 수 있었으며, 치밀한 표면 미세구조와 줄어든 $BaTiO_3$ 박막과 기판 사이의 계면의 거칠기를 확인하였다. 하지만, $BaTiO_3$ 박막 내에 발생하는 누설전류의 근본원인을 확인하기 위해서는 누설전류에 대한 미시적인 접근이 더욱 요구된다. 이에 본 연구에서는 누설전류 발생원인의 미시적 접근을 위해 두께에 따른 $BaTiO_3$ 박막의 누설전류 전도기구에 대한 조사하였으며, 이를 통해 $BaTiO_3$ 박막내 발생하는 누설전류의 원인은 $BaTiO_3$막 내에서 donor로서 역할을 하는 oxygen vacancy와 불균일한 전계의 집중으로 인한 전자의 tunneling 현상임을 확인할 수 있었다. 또한, Nano-indenter와 Conductive atomic force microscopic를 이용한 정밀 측정을 통해 표면경도의 중요성을 재확인하였으며 $BaTiO_3$ 박막의 두께가 $0.2\;{\mu}m$이하로 더욱 얇아지게 되면 입자간 결합 문제 또한 ADM을 박막화 하는데 있어 중요한 요소임을 확인하였다.

• Journal of Korea Multimedia Society
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• v.10 no.2
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• pp.226-235
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• 2007

Recently, the lETF NEMO working group on network mobility is standardizing a basic support for moving networks. We need a handover scheme for achieving the performance of transparency during the movement of mobile routers in nested mobile networks. But existing handover schemes for a mobile host are not suitable for network mobility because the packet transmission delay and traffic increase during mobile router's handover in nested mobile networks. Therefore, we propose a new seamless handover scheme using the bi-casting based on Mobile IPv6 for nested mobile networks in this paper. Compared with the handover schemes using bi-directional edge tunneling for host mobility support on simulation. And, the results show that the proposed handover scheme reduces the packet delay during a mobile router changes the point of attachment in nested mobile networks.

• The KIPS Transactions:PartC
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• v.18C no.6
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• pp.423-432
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• 2011

Recently, OpenFlow has been paid attention to as a fundamental technology which provides a function of virtualization and programmability in network. In Korea, deployment of OpenFlow networks in campuses and the interconnection between them through tunneling in layer 3 has been performed. However, the performance of the interconnected networks is decreased due to delay in IP layer. In this paper, we design and deploy nation-wide, not local, OpenFlow networks in a pure layer 2 environment over KREONET. After that, we do end-to-end Round-trip Time measurements and TCP/UDP performance tests in OpenFlow and normal networks, and do comparison and analysis on the test results. The results show that the nation-wide OpenFlow networks provide equal performance to normal networks except for the initial packet loss for UDP streaming. In regards to the performance decrease due to early UDP packet loss, we can mitigate it by implementing exceptional procedures in a controller which deal with the same continuous "Packet_in" events.

• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.3
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• pp.31-43
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• 2001

In this study, we carried out investigation and analysis on damages in tunnels on order to provide the basic information for the safety assessment of tunnels and to minimize the potential damage of the same kind as investigated. The frequencies of occurrence in terms of 4 items, i.e., service life interval, type of the damage, cause of the damage, and geological condition, were examined and summarized based on 44 foreign and domestic cases of tunnel damages. Also, we carried out a survey research of which the content included 28 questions on the tunnel safety assessment. The answers collected from domestic experts in tunneling suggested that the most probable cause of the tunnel damages was cracking in tunnels at 42~58%. They also suggested that the poor constrution work strongly caused the damages. Therefore, to ensure tunnel safety, high quality of constrution should be maintained as examined. The types of damage and their extent of influence on the overall tunnel safety are of practical importance to be used in the artficial intelligent system for tunnel safety assessment.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.2
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• pp.141-157
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• 2012

For the application TBM tunneling method, Both tunnel design standard and case study designed & constructed in domestic and foreign have been conducted. According to the study, the number of lane and inner shape (single or duplex) vary depending on the volume of traffic. Also extra space located in the top and bottom of tunnel is used for a multipurpose such as ventilation, disaster prevention, maintenance and administration. To find area ratio according to the components of road TBM tunnel, a standard section was considered as a two-lane road. Then, the analysis of area ratio of this section which consists of components for clearance, extra space in upper and lower tunnel was carried on two widths of shoulder. In addition, after a structural analysis, a thickness requirement of lower slab which is essential for road tunnel was derived on a few supporting types. Through correlation analysis, the ranges of available cross-sectional area between slab thickness and lower extra space of the tunnel was presented.

• Journal of Magnetics
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• v.18 no.1
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• pp.43-49
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• 2013

A pulsed ferrite magnetic field generator (FMFG) was designed for the use in the 1000 m long through-the-earth (TTE) communication system for mining disaster situations. To miniaturize the TTE system, a ferrite core having 10,000 of permeability was used for the FMFG. Attenuation of the magnetic field intensity from the FMFG (200-turn and 0.18 m diameter) was calculated to be 89.95 dB at 1000 m depth soil having 0.1 S/m of conductivity. This attenuation was lower than 151.13 dB attenuation of 1 kHz electromagnetic wave at the same conditions. Therefore, the magnetic-field was found to be desirable as a signal carrier source for TTE communications as compared to the electromagnetic wave. The designed FMFG generates the magnetic field intensity of $1{\times}10^{-10}$ Tesla at 1000 m depth. This magnetic field is detectable by compact magnetic sensors such as flux gate or magnetic tunneling junction sensor. Therefore, the miniature FMFG TTE communication system can replace the conventional electromagnetic wave carrier type TTE system and allow reliable signal transmission between rescuer and trapped miners.

• Journal of the Korea Convergence Society
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• v.10 no.8
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• pp.217-226
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• 2019

This study examines the effect of the wedge between voting rights and cash flow rights of controlling shareholders on the implied cost of equity. Prior studies posit that controlling shareholder's voting rights exceeding cash flow rights causes expropriating minority shareholders. Using date from 793 group-affiliated Korean firms for 10 years from 2005 to 2016, the result shows that there is a positive and significant relationship between controlling shareholders' wedge and implied cost of equity. This result implies that investors regard the controlling shareholders' wedge as potential agency cost in which they require additional risk premium because controlling shareholders have a strong incentive to pursue their private interests trough tunneling practices.

• Tunnel and Underground Space
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• v.29 no.3
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• pp.148-156
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• 2019

In urban area, the use of mechanical excavators (e.g., TBM and roadheader) has been increasing in construction of tunnelling and underground space. The undercutting technology, which is modified from the conventional rock-cutting concept, has been developed by advanced countries. Therefore, research on the latest technology of mechanical excavation is required, and keeping carrying out research on conventional mechanical tunneling methods at the same time. In this study, as a fundamental study of the undercutting technique, the principle and concept of the undercutting were introduced, as well as the current status of the research of advanced countries. The undercutting is applicable as a full-face excavation method for the tunnels and underground spaces, as well as an auxiliary(partial-face excavation) method for extension of the existing tunnels.