• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5C
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• pp.479-486
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• 2010

In this paper, we propose a novel low-complexity Alamouti coded orthogonal frequency division multiplexing (OFDM) scheme for asynchronous cooperative communications. Exploiting the combination of OFDM symbols at the source node and simple operations including sign change and complex product at the relay node, the proposed scheme can achieve cooperative diversity gain without use of time-reversion and shifting operations that the conventional scheme proposed by Li and Xia needs. In addition, by using the cyclic prefix (CP) removal and insertion operations at the relay node, the proposed scheme does not suffer from a considerable degradation of bit-error-rate (BER) performance even though perfect timing synchronization is not achieved at the relay node. From the simulation results, it is demonstrated that the BER performance of the proposed scheme is much superior to that of the conventional scheme in the presence of timing synchronization error at the relay node. It is also shown that the proposed scheme obtains two times higher diversity gain compared with the conventional scheme at the cost of half reduction in transmission efficiency.

• Journal of Convergence for Information Technology
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• v.9 no.1
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• pp.92-98
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• 2019

Due to the development of hologram display technology, various studies are being conducted to provide realistic contents for augmented reality. In the case of the HMD for hologram, since augmented reality objects must be rendered by a small processor, it is necessary to use a low-capacity content. To solve this problem, there is a need for a technique of rendering resources by providing resources through a network. In the case of the existing augmented reality system, there is no problem of contents modulation because the resources are loaded and rendered in the internal storage space. However, when providing resources through the network, security problems such as content tampering and malicious code insertion should be considered. Therefore, in this paper, we propose a network rendering technique applying security techniques to provide augmented reality contents in a holographic HMD device.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.5
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• pp.497-503
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• 2014

Minimally invasive intramedullary nail insertion or plate osteosynthesis has shown good results for the treatment of long bone fractures. However, directly seeing the fracture site is impossible; surgeons can only confirm bone fragments through a fluoroscopic imaging system. The narrow field of view of the equipment causes malalignment of the fracture reduction, and radiation exposure to medical staff is inevitable. This paper suggests two methods to solve these problems: surgical navigation using 3D models reconstructed from computed tomography (CT) images to show the real positions of bone fragments and estimating the rotational angle of proximal bone fragments from 2D fluoroscopic images. The suggested methods were implemented using open-source code or software and evaluated using a model bone. The registration error was about 2 mm with surgical navigation, and the rotation estimation software could discern differences of $2.5^{\circ}$ within a range of $15^{\circ}$ through a comparison with the image of a normal bone.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.3
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• pp.493-501
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• 2020

For the obfuscation of Flow Analysis on the Android operating system, the size of the Flow Graph can be large enough to make analysis difficult. To this end, a library in the form of aar was implemented so that it could be inserted into the application in the form of an external library. The library is designed to have up to five child nodes from the entry point in the dummy code, and for each depth has 2n+1 numbers of methods from 100 to 900 for each node, so it consists of a total of 2,500 entry points. In addition, entry points consist of a total of 150 views in XML, each of which is connected via asynchronous interface. Thus, the process of creating a Inter-procedural Control Flow Graph has a maximum of 14,175E+11 additional cases. As a result of applying this to application, the Inter Procedure Control Flow Analysis too generates an average of 10,931 edges and 3,015 nodes with an average graph size increase of 36.64%. In addition, in the APK analyzing process showed that up to average 76.33MB of overhead, but only 0.88MB of execution overhead in the user's ART environment.

• The Korean Journal of Nuclear Medicine
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• v.34 no.1
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• pp.62-73
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• 2000

Purpose: Esophageal cancer patients have a difficulty in the intake of meals through the blocked esophageal lumen, which is caused by an ingrowth of cancer cells and largely influences on the prognosis. It is reported that esophageal cancer has a very low survival rate due to the lack of nourishment and immunity as the result of this. In this study a new radioactive stent, which prevents tumor ingrowth and restenosis by additional radiation treatment, has been developed. Materials and Methods: Using ${\ulcorner}HANARO{\lrcorner}$ research reactor, the radioactive stent assembly ($^{166}Ho$-SA) was prepared by covering the metallic stent with a radioactive sleeve by means of a post-irradiation and pre-irradiation methods. Results: Scanning electron microscopy and autoradiography exhibited that the distribution of $^{165/166}Ho\;(NO_3)$ compounds in polyurethane matrix was homogeneous. A geometrical model of the esophagus considering its structural properties, was developed for the computer simulation of energy deposition to the esophageal wall. The dose distributions of $^{166}Ho$-stent were calculated by means of the EGS4 code system. The sources are considered to be distributed uniformly on the surface in the form of a cylinder with a diameter of 20 mm and length of 40 mm. As an animal experiment, when radioactive stent developed in this study was inserted into the esophagus of a Mongrel dog, tissue destruction and widening of the esophageal lumen were observed. Conclusion: We have developed a new radioactive stent comprising of a radioactive tubular sleeve covering the metallic stent, which emits homogeneous radiation. If it is inserted into the blocked or narrowed lumen, it can lead to local destruction of the tumor due to irradiation effect with dilatation resulting from self-expansion of the metallic property. Accordingly, it is expected that restenosis esophageal lumen by the continuous ingrowth and infiltration of cancer after insertion of our radioactive stent will be decreased remarkably.