• Korean Journal of Materials Research
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• v.32 no.6
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• pp.301-306
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• 2022

This study explored the possibility of forming a coating layer containing alginic acid on the surface of a magnesium alloy to be used as a biomaterial. We formed a coating layer on the surface of a magnesium alloy using a plasma electrolytic oxidation process in an electrolytic solution with different amounts of alginic acid (0 g/L ~ 8 g/L). The surface morphology of all samples was observed, and craters and nodules typical of the PEO process were formed. The cross-sectional shape of the samples confirmed that the thickness of the coating layer became thicker as the alginic acid concentration increased. It was confirmed that the thickness and hardness of the sample significantly increase with increasing alginic acid concentration. The porosity of the surface and cross section tended to decrease as the alginic acid concentration increased. The XRD patterns of all samples revealed the formation of MgO, Mg₂SiO₄, and MgF₂ complex phases. Polarization tests were conducted in a Stimulate Body Fluid solution similar to the body's plasma. We found that a high amount of alginic acid concentration in the electrolyte improved the degree of corrosion resistance of the coating layer.

• Journal of Korea Multimedia Society
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• v.19 no.12
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• pp.1992-1999
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• 2016

In layered communication architecture, each layer is designed to service its own functions to higher layer while getting serviced by lower layer. Usually layered architectures are not optimized in a total view of whole services and functions. So cross layer design pursues performance enhancements by optimizing in various ways. In LTE, MAC layer uses HARQ mechanism and RLC layer uses ARQ mechanism for retransmission. According to the 3GPP 36.331 specification, two layers' cooperation may not happen in an optimized way. This paper suggests an adaptive MAC layer approach which RLC layer's function might be initiated in MAC layer in advance to utilize MAC layer's idling wasting time for RLC layer's next decision. This adaptive ARQ method in MAC layer speeds up the next retransmission and reduces the overall transmission time. Emulation shows the improved performance in total retransmission time and retransmission success ratio. In wireless shadow area, the retransmission occurs frequently. Our approach has strong points in this poor wireless condition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.1
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• pp.161-169
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• 2009

Multicast-based data communication is an efficient communication scheme in wireless networks where the Media Access Control (MAC) layer is based on one-hop broadcast from one source to multiple receivers. Compared with unicast, multicast over wireless channel should handle varying channel conditions of multiple users and user mobility to achieve good quality for all users. However, IEEE 802.11 does not support reliable multicast due to its inability to exchange RTS/CTS and ACK with multiple recipients. Thus, several MAC layer protocols have been proposed to provide reliable multicast. For the reliable multicast, an additional overhead is introduced and it degrades the system performance. In this paper, we propose a cross-layer design to reduce the control overhead for reliable multicast in OFDMA systems. We present an analytical formulation of the system throughput associated with the overhead.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1070_1071
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• 2009

Recently, small hydropower attracts attention because of its clean, renewable and abundant energy resources to develop. Therefore, a cross-flow hydraulic turbine is proposed for small hydropower development in this study. The turbine‘s simple structure and high possibility of applying to the sites of relatively low effective head and large flow rate can be advantages for the introduction of the small hydropower development. The purpose of this study is not only to investigate the effects of air layer in the turbine chamber on the performance and internal flow of the cross-flow turbine, but also to suggest a newly developed air supply method. CFD analysis for the performance and internal flow of the turbine is conducted by an unsteady state calculation using a two-phase flow model in order to embody the air layer effect on the turbine performance effectively. The result shows that air layer effect on the performance of the turbine is considerable. The air layer located in the turbine runner passage plays the role of preventing a shock loss in the runner axis and suppressing a recirculation flow in the runner. The location of air suction hole on the chamber wall is very important factor for the performance improvement. Moreover, the ratio between air from suction pipe and water from turbine inlet is also significant factor of the turbine performance.

• Journal of KIISE
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• v.44 no.11
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• pp.1130-1137
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• 2017

The multi-leveling technique that stores multiple bits in a single memory cell has significantly improved the density of NAND flash memory along with shrinking processes. However, because of the side effects of the multi-leveling technique, the average write performance of MLC NAND flash memory is degraded more than twice that of SLC NAND flash memory. In this paper, we introduce existing cross-layer optimization techniques proposed to improve the performance of MLC NAND flash-based storages, and propose a new integration technique that overcomes the limitations of existing techniques by exploiting their complementarity. By fully exploiting the performance asymmetry in MLC NAND flash devices at the flash translation layer, the proposed technique can handle many write requests with the performance of SLC NAND flash devices, thus significantly improving the performance of NAND flash-based storages. Experimental results show that the proposed technique improves performance 39% on average over individual techniques.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.2
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• pp.21-25
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• 2009

The organic-inorganic thin film transistors (OITFTs) with ZnO channel layer and the cross-linked PVP (Poly-4-vinylphenol) gate insulator were fabricated on the patterned ITO gate/glass substrate. ZnO channel layer was deposited by using atomic layer deposition (ALD). In order to improve the electrical properties, $O_2$ plasma treatment onto PVP film was introduced and investigated the effect of the plasma treatments on the electrical properties of the OITFTs. The field effect mobility and sub-threshold slope (SS) values of the OITFT decreased slightly from 0.24 to 0.16 $cm^2/V{\cdot}s$ and from 9.7 to 9.2 V/dec, respectively with increasing RF power from 30 to 50 Watt. The $I_{on/off}$ ratio was about $10^3$ for all samples with $O_2$ plasma treatment.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.12
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• pp.545-552
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• 2003

When a Si PIN diode is exposed to fast neutrons, it results in displacement damage to the Si lattice structure of the diode. Defects induced from structural dislocation become effective recombination centers for carriers which pass through the base of a PIN diode. Hence, increasing the resistivity of the diode decreases the current for the applied forward voltage. This paper involves the development of a neutron sensor based on the phenomena of the displacement effect damaged by neutron exposure. The neutron effect on the semiconductor was analyzed. Several PIN diode arrays with various thickness and cross-section area of the intrinsic layer(I layer) were fabricated. Under irradiation tests with a neutron beam, the manufactured diodes have a good linearity to neutron dose and show that the increase of thickness of I layer and the decrease of cross-section of PIN diodes improve the sensitivity. Newly developed PIN diodes with thicker I layer and various cross section, were retested and then showed the best neutron sensitivity at the condition that the I layer thickness was similar to a side length. On the basis of two test results, final discrete PIN diodes with a rectangular shape were manufactured and the characteristics as neutron detectors were analyzed through the neutron beam test using on-line electronic dosimetry system. Developed PIN diode shows a good linearity as dosimetry in the range of 0 to 1,000cGy(Tissue) and its neutron sensitivity is 13mV/cGy at constant current of 5mA, that is three times higher than that of commercially available neutron detectors. And the device shows little dependency on the orientation of the neutron beam and a considerable stability in annealing test for a long period.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.5
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• pp.430-437
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• 2021

In this paper, we propose a robust face recognition method against soft errors with a deep convolutional generative adversarial network(DCGAN) based compensation method by a cross-layer approach. When soft-errors occur in block data of JPEG files, these blocks can be decoded inappropriately. In previous results, these blocks have been replaced using a mean face, thereby improving recognition ratio to a certain degree. This paper uses a DCGAN-based compensation approach to extend the previous results. When soft errors are detected in an embedded system layer using parity bit checkers, they are compensated in the application layer using compensated block data by a DCGAN-based compensation method. Regarding soft errors and block data loss in facial images, a DCGAN architecture is redesigned to compensate for the block data loss. Simulation results show that the proposed method effectively compensates for performance degradation due to soft errors.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.2
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• pp.62-73
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• 1998

The aim of this work was to investigate the effects of pigment composition on the calendering response and structure of the coated paper. Calendering response of the coated paper was determined from the gloss values of the uncalendered and calendered coated papers, and the relationship between gloss and coating structure was discussed. The surface and cross section of the coating layer was observed using a scanning electron microscope to examine the coating structure. Coating layers were hardened in epoxy resin and polished with carbimet paper disc for preparing SEM samples. Maximum calendering response was obtained for the coated paper prepared from 80pph of clay and 20pph of ground calcium carbonate (GCC) as pigments. Photomicrographs of the surface and cross section of the coating layer show that clay tends to form dense coating structure, while GCC tends to form bulky coating layer.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.445-448
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• 2006

Bias stress effect in pentacene organic thin-flim transistors with cross-linked PVA gate dielectric is analyzed. For negative gate bias stress, positive threshold voltage shift is observed. The injected charges from the gate electrode to the defect states of gate dielectric are regarded as the main origin of $V_T$ shift. The reduced bias stress effect using $SiO_2$ blocking layer confirms the assumed mechanism. It is also demonstrated that the inverter with $SiO_2$ blocking layer shows the negligible hysteresis owing to the reduced bias stress effect.