• Journal of the Korean Society of Radiology
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• v.16 no.6
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• pp.703-708
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• 2022

A detector module measuring the depth of interaction(DOI) was designed to improve the spatial resolution of positron emission tomography(PET). The scintillation pixel array consists of two layers, and a light guide is inserted between the layers to make the light generated through the gamma-ray event different for each layer. There are four light guides, and one light guide is designed to be coupled to a 2 × 2 array of scintillation pixels. The light generated from the top layer is moved to the photosensor with a wider distribution through the light guide, and the light generated from the bottom layer is incident on the photosensor with a narrower distribution than the top layer. When a flood image is reconstructed based on the signals obtained from the photosensor by different distributions, scintillation pixels are imaged at different positions for each layer. To verify this, a DETECT2000 simulation tool that simulates the behavior of light in a scintillator was used. By designing a scintillation pixel array, a detector consisting of a light guide and a photosensor, a gamma ray event was generated in all scintillation pixels to obtain a flood imgae. As a result, it was confirmed that the top and bottom layers were imaged at different positions and completely separated. When this detector is applied to PET, it is considered that image quality can be improved through imporved spatial resolution.

• Journal of the Korean Society of Marine Environment & Safety
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• v.1 no.2
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• pp.53-60
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• 1995

We measured lagrangian currents in the coastal regions off east coast of Korea. The experiment sites are the Ulijin region where Polar Front of the East Sea is formed and the Ulgi region where coastal upwelling occurs frequently in summer. Each drifters are equipped with GPS receiver, and their trajectories are montiored by receiving the data transmitted from drifters through radio signal. The experiment with 'transmitting' GPS is very useful in monitering flows in coastal regions. Trajectories of drifters in the Uljin Polar Front region in October 1994 showed counterclockwise flow pattern. The flow pattern agrees with the SST distributions obtained from NOAA-11 AVHRR image for the same period. The lagrangian trajectories of drifters at 5m and 15m depths in the Ulgi region for normal period of April 1995 showed that the currents at the top 15m layer are almost uniform and their magnitude is 29cm/s. However, the currents, measured by KORDI, during the upwelling period of June 1994 showed that the currents at 5m depth were 1.2 times stronger than those at 15m depth. The current pattern in the Ulgi upwelling region agrees with the horizontal and vertical distributions of seawater temperature measured by NFRDA at the same period.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.5
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• pp.728-733
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• 2018

Deep learning has been actively studied for predicting protein secondary structure based only on the sequence information of the amino acids constituting the protein. In this paper, we compared the performances of the convolutional neural networks of various structures to predict the protein secondary structure. To investigate the optimal depth of the layer of neural network for the prediction of protein secondary structure, the performance according to the number of layers was investigated. We also applied the structure of GoogLeNet and ResNet which constitute building blocks of many image classification methods. These methods extract various features from input data, and smooth the gradient transmission in the learning process even using the deep layer. These architectures of convolutional neural networks were modified to suit the characteristics of protein data to improve performance.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.61-64
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• 2007

Subsurface Internal Waves (IWs) can be detected in satellite images as periodic alternating brighter/darker stripes. It is known that there are two types of IWs - depression type and elevation type - depending on the water depth in stratified oceans. In this study, we have quantitatively verified the process of converting polarity from depression waves to elevation waves using ERS-2 SAR images acquired over the northern South China Sea. We simulated the evolution of IWs near a turning point with a numerical model for internal wave propagation. The simulation results near the turning point clearly showed us not only a conversion process of IWs from depression to elevation waves, but also a similar wave pattern with the observed SAR image. We also simulated SAR intensity variation near the turning point. The upper layer currents were computed at regular intervals using the numerical model, as the IWs were passing through the turning point. Then, an integrated hydrodynamic-electromagnetic model was used for simulating SAR intensity profiles from the upper layer currents at each position. The simulated SAR intensity profiles at each position were compared with the observed SAR intensities.

• Journal of Korean Vacuum Science & Technology
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• v.6 no.3
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• pp.133-138
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• 2002

The growth of Au films grown on a Si(100)-2x1 surface and Si films on a Ge(100)-2x1 substrate is studied using Positron-annihilation induced Auger Electron Spectroscopy(PAES), Electron induced Auger Electron Spectroscopy(EAES), and Low Energy Electron Diffraction(LEED). Previous work has shown that PAES is almost exclusively sensitive to the top-most atomic layer due to the trapping of positrons in an image potential well just outside the surface before annihilation. This surface specificity is exploited to profile the surface atomic concentrations during the growth of Au on Si(100) and Si on Ge(100) and EAES provides concentrations averaged over the top 3-10 atomic layers simultaneously. The difference in the probe-depth makes us possible to use PAES and EAES in a complementary fashion to estimate the surface and near surface concentration profiles. The results show that (i) the intermixing of Au and Si atoms occurs during the room temperature deposition, (ii) the segregated Ge layer is observed onto the Si layers deposited at 300k. In addition, the prior adsorption of hydrogen prevents the segregation of Ge on top of the deposited Si and that the hydrogen adsorption is useful in growing a thermally stable structure.

• Journal of Distribution Science
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• v.15 no.8
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• pp.55-64
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• 2017

Purpose - PB products at convenience stores take up about 20% of all products, and strategies for differentiation from other companies and brand image building are very important. This study would investigate the strategy for differentiating PB products and successful brand building strategy, focusing on BGF Retail that is operating 'CU', the leader in the convenience store industry in Korea. Research design, data, and methodology - This study would attempt to make an exploratory approach to PB products limited to those in convenience stores. As a research subject, this study chose BGF Retail, the operator of CU, which is the leader in the convenience store industry in Korea and chose the case study method in order to examine the strategy for differentiating PB products in convenience stores more in depth. For this purpose, this study collected materials such as papers, newspaper articles and various reports on convenience store-related PB products and conducted an in-depth study including more practical contents through an interview with CU workers. Results - CU pursued the diversity of PB products and has had the diversity of products, more than 120 kinds. It founded a product research institute and has been in charge of the differentiation strategy from planning products to launching them. Changing the target layer of consumers to those in middle age of the 40s-50s, it succeeded in the strategy expanding the consumer class. In the long run, despite it changed the name of the company, it has built a successful image, and both revenue and operating profit have continuously grown up. Conclusions - In results, CU has reset the changing main target population, and the product research institute succeeded in the innovation of products, reflecting new trends the customers want. Through this study, the practical implications could be provided for competitors.

• Journal of IKEEE
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• v.23 no.1
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• pp.318-321
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• 2019

The apparent soil resistivity is used for estimating multilayer soil parameters, such as, layer's depth and soil resistivity. The apparent soil resistivity can be measured, and also can be calculated if soil parameters are given, becacuse the apparent soil resistivity is a function of these parameters. Therefore, any optimization algorithms can be used to find these parameters which make the calculated apparent soil resistivity close to the measured one. The equation for calculating the apparent soil resistivity is complicated and time consumed, because it is composed of an infinite integral which includes a zero order Bessel's function of the first kind. In this paper, a fast algorithm for calculating the apparent soil resistivity of horizontal multilayer earth structure has been presented using complex image method.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.732-736
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• 2009

In this paper we focus on EPI (Epipolar-Plane Image), the horizontal cross section of Ray-Space, and we propose a novel method that chooses objects we want and edits scenes by using multi-view images. On the EPI acquired by camera arrays uniformly distributed along a line, all the objects are represented as straight lines, and the slope of straight lines are decided by the distance between objects and camera plane. Detecting a straight line of a specific slope and removing it mean that an object in a specific depth has been detected and removed. So we propose a scheme to make a layer of a specific slope compete with other layers instead of extracting layers sequentially from front to back. This enables an effective removal of obstacles, object manipulation and a clearer 3D scene with what we want to see will be made.

• Geophysics and Geophysical Exploration
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• v.8 no.1
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• pp.26-33
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• 2005

Inversion of multi-mode surface-wave phase velocity for shallow engineering site investigation has received much attention in recent years. A sensitivity analysis and inversion of both synthetic and field data demonstrates the greater effectiveness of this method over employing the fundamental mode alone. Perturbation of thickness and shear-wave velocity parameters in multi-modal Rayleigh wave phase velocities revealed that the sensitivities of higher modes: (a) concentrate in different frequency bands, and (b) are greater than the fundamental mode for deeper parameters. These observations suggest that multi-mode phase velocity inversion can provide better parameter discrimination and imaging of deep structure, especially with a velocity reversal, than can inversion of fundamental mode data alone. An inversion of the theoretical phase velocities in a model with a low velocity layer at 20 m depth can only image the soft layer when the first higher mode is incorporated. This is especially important when the lowest measurable frequency is only 6 Hz. Field tests were conducted at sites surveyed by borehole and PS logging. At the first site, an array microtremor survey, often used for deep geological surveying in Japan, was used to survey the soil down to 35 m depth. At the second site, linear multichannel spreads with a sledgehammer source were recorded, for an investigation down to 12 m depth. The f-k power spectrum method was applied for dispersion analysis, and velocities up to the second higher mode were observed in each test. The multi-mode inversion results agree well with PS logs, but models estimated from the fundamental mode alone show f large underestimation of the depth to shallow soft layers below artificial fill.

• Journal of the Korean Vacuum Society
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• v.18 no.5
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• pp.346-351
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• 2009

Due to the decrease of line width and increase of the integration level of the device, it is expected that 'Bottom-up' method will replace currently used 'Top-down' method. Researches about 'Bottom-up' device production such as Nanowires and Nanobelts are widely held on. To utilize these technologies in devices, properties of matter should be exactly measured. Nano-indenters are used to measure the properties of nano-scale structures. Additionally, Nano-indenters provide AFM(Atomic Force Microscopy) function to get the image of the surface and get physical properties for exact position of nano-structure using this image. However, nano-indenter tips have relatively much bigger size than ordinary AFM probes, there occurs considerable error in surface image by Nano-Indenter. Accordingly, this research used 50nm Berkovich tip and 1um $90^{\circ}$ Conical tip, which are commonly used in Nano-Indenter. To find out the surface characteristics for each kind of tip, we indented the surface of thin layer by each tip and compared surface image and indentation depth. Then, we got image of 100nm-size structure by surface scanning using Nano-Indenter and compared it with surface image gained by current AFM technology. We calculated the errors between two images and compared it with theoretical error.