• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.555-558
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• 1997

A new approach to silent MR imaging using a rotating DC gradient has been explored and experimentally studied. As is known, acoustic or sound noise has been one of the major problems in handling patients, mainly due to the fast gradient pulsings in interaction with the main magnetic field. The sound noise is also proportionally louder as the magnetic field strength becomes larger. In this article, we have described a new imaging technique using a mechanically rotating DC gradient coil as an approach toward silent MR imaging, i.e., a mechanically rotated DC gradient effectively replaces both the phase encoding as well as the readout gradient pulsings and data obtained in this manner provides a set of project ion data which later can be used or the projection reconstructionorwithsomeinterpolation techniques one can also perform conventional 2-D FFT (Fast Fourier Transform) image reconstruction. We found, with this new technique, that the sound noise intensity compared with the conventional imaging technique, such as spin echo sequence, is reduced down to -20.7 dB or about 117.5 times. The experimental pulse sequence and its principle are described and images obtained by the new silent MR imaging technique are reported.

• ETRI Journal
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• 제38권6호
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• pp.1145-1152
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• 2016

Because the nodes in a wireless sensor network (WSN) are mobile and the network is highly dynamic, monitoring every node at all times is impractical. As a result, an intruder can attack the network easily, thus impairing the system. Hence, detecting anomalies in the network is very essential for handling efficient and safe communication. To overcome these issues, in this paper, we propose a rule-based anomaly detection technique using roaming honeypots. Initially, the honeypots are deployed in such a way that all nodes in the network are covered by at least one honeypot. Honeypots check every new connection by letting the centralized administrator collect the information regarding the new connection by slowing down the communication with the new node. Certain predefined rules are applied on the new node to make a decision regarding the anomality of the node. When the timer value of each honeypot expires, other sensor nodes are appointed as honeypots. Owing to this honeypot rotation, the intruder will not be able to track a honeypot to impair the network. Simulation results show that this technique can efficiently handle the anomaly detection in a WSN.

• 한국HCI학회논문지
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• 제9권2호
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• pp.33-40
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• 2014

신제품/서비스를 설계함에 있어 해당 제품 혹은 서비스가 제공하여야 할 기능을 선정하는 것(feature selection)은 디자이너의 매우 어려운 의사결정 문제이지만, 기존 방법론들은 특정 제품-서비스에 대한 사용자의 니즈를 효과적으로 파악하기에는 한계점이 있다. 특히 기존의 선호도 서베이를 통한 방법은 사용자의 멘탈모델에 대한 분석에 기반하지 않기에 기능과부화(feature creep) 현상의 한 원인으로 지적되고 있다. 본 연구는 사용자에게 새로운 기능을 제공할 경우(혹은 제공된 기능을 제거해야 할 경우), 그 기능으로부터 추론되는 제품-서비스의 멘탈모델을 탐지하는 새로운 기법인 'False belief technique'을 제안하고, 이를 통해 디자이너의 기능 선정(feature selection) 의사결정에 활용될 수 있도록 하고자 한다.

• 대한화학회지
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• 제7권1호
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• pp.58-64
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• 1963

Authors propose a new technique using polyethylene film instead of sodium chloride window as a cell material. Nujol mulls, liquids and aqueous solutions are sandwitched between two pieces of polyethylene film which are held between cardboards. Ordinary lead or stainless steel spacers could be used if exact cell thickness is desired. A more elaborate cell can be assembled by injecting samples between two pieces of polyethylene film which are placed between sodium chloride windows of ordinary demountable liquid cell. The absorption bands due to polyethylene and Nujol are compensated by placing the polyethylene film of suitable thickness in the reference beam. The absorption bands due to solvents such as water can also be compensated by the polyethylene film cell sandwitched solvent of suitable thickness in the reference beam. This method would be a simple new technique. Especially this technique may offer a new helpful way for the investigation of the state of substances in aqueous system. Using this technique, authors have observed the appearance of an absorption bands at 3.2 micron, in the spectrum of phenol in aqueous solution, that is absent in the spectrum of phenol in benzene solution. The same absorption band also has been observed in the spectra of aqueous formaldehyde solution and aqueous polyvinyl alcohol solution, where the absorption bands due to polyethylene and water are compensated. Although it may be regarded that this absorption band is related to the intermolecular interaction between water and the solute having OH group, that is hydrogen bonding. The exact assignment of this absorption band is out of this work.

• 한국가구학회지
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• 제22권4호
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• pp.270-277
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• 2011

This study aims to find new solutions to the problem of utilization of materials and techniques represented in the development of modern lighting design. LED is an important component in modern lighting design and pine tree is one of the most popular domestic wood in furniture design in Korea. In this study, design is developed into various types of furniture such as a table, a chest, and a lighting, by researching manufacturing process and examining the use of slicing pine tree. The technique of slicing pine tree is a simple linear arrangement that was traditionally used in wooden furniture in Lee dynasty, with an emphasis on repetitive rhythm. The slicing technology is used to expand the usage of domestic pine tree. The beauty of natural wood is expressed with the transmission of light by applying this technique to the lighting design. It also brings new communication in between artificial lighting and natural wood combining this traditional technique and LED lighting in design. Finally, this study suggests particular value through the convergence of analog and digital by using the traditional wooden technique that keeps natural wood prints and new digital technology by using LED lighting. More discussions and research about this subject are expected continuously through this study.

• Steel and Composite Structures
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• 제34권2호
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• pp.227-239
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• 2020

The aim of this study is to obtain the nonlinear and post-buckling responses of relatively thick functionally graded plates with oblique elliptical cutouts using a new semi-analytical approach. To model the oblique elliptical hole in a FGM plate, six plate-elements are used and the connection between these elements is provided by the well-known Penalty method. Therefore, the semi-analytical technique used in this paper is known as the plate assembly technique. In order to take into account for functionality of the material in a perforated plate, the volume fraction of the material constituents follows a simple power law distribution. Since the FGM perforated plates are relatively thick in this research, the structural model is assumed to be the first order shear deformation theory and Von-Karman's assumptions are used to incorporate geometric nonlinearity. The equilibrium equations for FGM plates containing elliptical holes are obtained by the principle of minimum of total potential energy. The obtained nonlinear equilibrium equations are solved numerically using the quadratic extrapolation technique. Various sets of boundary conditions for FGM plates and different cutout sizes and orientations are assumed here and their effects on nonlinear response of plates under compressive loads are examined.

• Advances in nano research
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• 제7권5호
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• pp.311-324
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• 2019

The present study aims to evaluate the nonlinear and post-buckling behaviors of orthotropic graphene sheets exposed to end-shortening strain by implementing a semi-Galerkin technique, as a new approach. The nano-sheets are regarded to be on elastic foundations and different out-of-plane boundary conditions are considered for graphene sheets. In addition, nonlocal elasticity theory is employed to achieve the post-buckling behavior related to the nano-sheets. In the present study, first, out-of-plane deflection function is considered as the only displacement field in the proposed technique, which is hypothesized by an appropriate deflected form. Then, the exact nonlocal stress function is calculated through a complete solution of the von-Karman compatibility equation. In the next step, Galerkin's method is used to solve the unknown parameters considered in the proposed technique. In addition, three different scenarios, which are significantly different with respect to concept, are used to satisfy the natural in-plane boundary conditions and completely attain the stress function. Finally, the post-buckling behavior of thin graphene sheets are evaluated for all three different scenarios, and the impacts of boundary conditions, polymer substrate, and nonlocal parameter are examined in each scenario.

• 한국음향학회지
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• 제4권2호
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• pp.3-12
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• 1985

The surface intensity method is a relatively new tool which can identify the noise source or path and measure the radiation power. One microphone and one accelerometer are used in this new technique. In this study, this new technique has been used to measure the field transmission loss trough doors. The results of the experiment indicate that the surface intensity method produces reliable data and can be applied to the transmission loss measurement.

• 한국음향학회지
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• 제4권2호
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• pp.3.1-3.1
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• 1985

The surface intensity method is a relatively new tool which can identify the noise source or path and measure the radiation power. One microphone and one accelerometer are used in this new technique. In this study, this new technique has been used to measure the field transmission loss trough doors. The results of the experiment indicate that the surface intensity method produces reliable data and can be applied to the transmission loss measurement.

• Journal of Chest Surgery
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• 제26권5호
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• pp.422-426
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• 1993

We report three cases of children who underwent definitive conversion to the Fontan circulation using a new surgical technique, Extracardiac Epicardial Lateral Tunnel. This new procedure allows the operation to be performed as a totally extracardiac operation [especially in ventricular dysfunction] and allows it to be performed in a very small atrium and in cases with unsuitable pulmonary venous drainage.Our data suggest that this procedure may achieve satisfactory hemodynamics of the total cavopulmonary connection.