• Proceedings of the Materials Research Society of Korea Conference
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• 2005.05a
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• pp.293-293
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• 2005

• Journal of the Korean Chemical Society
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• v.62 no.5
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• pp.341-343
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• 2018

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.184-184
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• 2012

Recently, InGaN/GaN multi-quantum well grown on GaN pyramid structures have attracted much attention due to their hybrid characteristics of quantum well, quantum wire, and quantum dot. This gives us broad band emission which will be useful for phosphor-free white light emitting diode. On the other hand, by using quantum dot emission on top of the pyramid, site selective single photon source could be realized. However, these structures still have several limitations for the single photon source. For instance, the quantum efficiency of quantum dot emission should be improved further. As detection systems have limited numerical aperture, collection efficiency is also important issue. It has been known that micro-cavities can be utilized to modify the radiative decay rate and to control the radiation pattern of quantum dot. Researchers have also been interested in nano-cavities using localized surface plasmon. Although the plasmonic cavities have small quality factor due to high loss of metal, it could have small mode volume because plasmonic wavelength is much smaller than the wavelength in the dielectric cavities. In this work, we used localized surface plasmon to improve efficiency of InGaN qunatum dot as a single photon emitter. We could easily get the localized surface plasmon mode after deposit the metal thin film because lnGaN/GaN multi quantum well has the pyramidal geometry. With numerical simulation (i.e., Finite Difference Time Domain method), we observed highly enhanced decay rate and modified radiation pattern. To confirm these localized surface plasmon effect experimentally, we deposited metal thin films on InGaN/GaN pyramid structures using e-beam deposition. Then, photoluminescence and time-resolved photoluminescence were carried out to measure the improvement of radiative decay rate (Purcell factor). By carrying out cathodoluminescence (CL) experiments, spatial-resolved CL images could also be obtained. As we mentioned before, collection efficiency is also important issue to make an efficient single photon emitter. To confirm the radiation pattern of quantum dot, Fourier optics system was used to capture the angular property of emission. We believe that highly focused localized surface plasmon around site-selective InGaN quantum dot could be a feasible single photon emitter.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.11-16
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• 2012

Opportunistic transmit cooperative relaying (OTR) system has been interested for its ability to mitigate the fading in wireless channel without multiple antennas in a small terminal. In OTR system, only the relays that the received Signal-to-noise ratio (SNR) from a source is greater than the threshold transmit to the destination. However, the receiving branches of a destination in a realistic system is fixed, the excess number of signals from the transmit relays does not improve the system performance and consequently increases power consumption. In this paper, we adopt Double Opportunistic Transmit (DOT) cooperative diversity system which controls the average number of transmit relays. Although the average number of the transmit relays can be controlled by adjusting the two thresholds in DOT system, the instantaneous number of transmit relays is varying in fading channel. Thus we propose Maximal Ratio Combining (MRC) or Generalized Selection Combining (GSC) according to the number of the signals from relays at the destination. The outage probability of the proposed system is derived in closed form. The analytical results show that the system performance is improved with the number of the branches. Also it is noticed that when the number of the branches is fixed, the outage probability decreases with the increase of the average SNR of S-R path and R-D path.

• Journal of Korea Spatial Information System Society
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• v.8 no.2 s.17
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• pp.13-38
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• 2006

Range query is one of the most important operations for spatial objects, it retrieves all spatial objects that overlap a given query region in multi-dimensional space. The DOT(DOuble Transformation) is known as an efficient indexing methods, it transforms the MBR of a spatial object into a single numeric value using a space filling curve, and stores the value in a $B^+$-tree. The DOT index is possible to be employed as a primary index for spatial objects. However, the range query processing based on the DOT index requires much overhead for spatial transformations to get the query region in the final space. Also, the detailed range query processing method for 2-dimensional spatial objects has not been studied yet in this paper, we propose an efficient multi-dimensional range query processing technique based on the DOT index. The proposed technique exploits the regularities in the moving patterns of space filling curves to divide a query region into a set of maximal sub-legions within which space filling curves traverse without interruption. Such division reduces the number of spatial transformations required to perform the range query and thus improves the performance of range query processing. A visual simulator is developed to show the evaluation method and the performance of our technique.

• Journal of radiological science and technology
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• v.39 no.4
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• pp.601-606
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• 2016

Because of non-coplanar therapy with couch rotation in respiratory gated radiation therapy, the recognition of marker movement due to the change in the distance between the infrared camera and the marker due to the rotation of the couch is called RPM (Real-time The purpose of this paper is to evaluate the accuracy of motion reflections (baseline changes) of 2D gating configuration (two dot marker block) and 3D gating configuration (six dot marker block). The motion was measured by varying the couch angle in the clockwise and counterclockwise directions by $10^{\circ}$ in the 2D gating configuration. In the 3D gating configuration, the couch angle was changed by $10^{\circ}$ in the clockwise direction and compared with the baseline at the reference $0^{\circ}$. The reference amplitude was 1.173 to 1.165, the couch angle at $20^{\circ}$ was 1.132, and the couch angle at $1.0^{\circ}$ was 1.083. At $350^{\circ}$ counterclockwise, the reference amplitude was 1.168 to 1.157, the couch angle at $340^{\circ}$ was 1.124, and the couch angle at $330^{\circ}$ was 1.079. In this study, the phantom is used to quantitatively evaluate the value of the amplitude according to couch change.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.347.2-347.2
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• 2016

Recently, in order to improve the performance of the colloidal quantum dot solar cells (CQDSCs), various efforts such as the modification of the cell architecture and surface treatment for quantum dot (QD) passivation have been made. Especially, the incorporation of halides into the QD matrix was reported to improve the performances significantly via passivating QD trap states that lower the life-time of the minority-carrier. In this work, we fabricated a lead sulfide (PbS) QD bilayer treated with different ligands and utilized it as a photoactive layer of the CQDSCs. The bottom and top PbS layer was treated using metal iodide ($MI_x$ and butanedithiol (BuDT), respectively. All the depositions and ligand treatments were carried out in air using layer-by-layer spin-coating process. The fabrication of the active layers as well as the n-type zinc oxide (ZnO) layer was successfully carried out on the bendable indium-tin-oxide (ITO)-coated polyethylene terephthalate (PET) substrate, which implies that this technique can be applied to the fabrication of flexible and/or wearable solar cells. The power conversion efficiency (PCE) of the CQDSCs with the architecture of $PET/ITO/ZnO/PbS-MI_x/PbS-BuDT/MoO_x/Ag$ reached 4.2 %, which is significantly larger than that of the cells with single QD (PbS-BuDT) layer.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.209-217
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• 1991

We have carried out a preliminary study to search for the new fracture mechanics parameter which can effectively estimate the fatigue life. In this study, the distribution of local fatigue strains near a fatigue crack tip was detailedly revealed using by fine dot grid strain measurement method. From these results, a single parameter (.DELTA.A), which characterize local fatigue strain field, was nearly proposed by the authors.

• Journal of Korea Multimedia Society
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• v.2 no.3
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• pp.308-319
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• 1999

In this paper we propose a new color inverse halftoning for color prints halftoned by clustered-dot. The proposed method divide channel image into blocks and then extract moire region according to its strength. To get more natural continuous tone image in human vision, the proposed method smooths the extracted moire region in proportion to moire strength. It can also preserve the significant edges well by considering edge information of color halftone image in the process of inverse halftoning. Experimental results show that the proposed method can make more improved inverse halftoning. Experimental results show that the proposed method can make more improved inverse halftoning image than the results of previous works. It could be applied to field of multimedia application, such as digital library construction, color print image compression and multimedia authoring.

• Journal of Advanced Navigation Technology
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• v.18 no.2
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• pp.178-184
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• 2014

CMOS technology based on PCA is very efficient at an implementation of memory or ALU. However, there has been a growing interest in quantum-dot cellular automata (QCA) because of the limitation of CMOS scaling. In this paper, we propose a design of PCA architecture based on QCA. In the proposed PCA design, we utilize D flip-flop and XOR logic gate without wire crossing technique, and design a input and rule control switches. In experiment, we perform the simulation of the proposed PCA architecture by QCADesigner. As the result, we confirm the efficiency the proposed architecture.