• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1577-1579
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• 2003

AlN thin films are prepared on Si (111) substrate by RF magnetron sputtering. Two-step deposition method is proposed to obtain AlN thin films with high c-axis (002)-TC value and low surface roughnesses. For all the deposited AlN films, the c-axis (002)-orientation, surface mophology, and roughness are characterized in terms of deposition conditions FEAR devices with Al/AlN/Mo/Si(111) configuration are also fabricated. From the frequency response characteristics, the return loss and electromechanical coupling contant($k_t{^2}$) are estimated.

• Journal of Ecology and Environment
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• 제32권2호
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• pp.123-127
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• 2009

Weight loss and nutrient dynamics of Quercus mongolica leaf litter during decomposition were investigated from December 2005 through August 2008 in Mt. Worak National Park as a part of National Long-Term Ecological Research Program in Korea. The decay constant (k) of Q. mongolica litter was 0.26. After 33 months decomposition, remaining weight of Q. mongolica litter was 49.3$\pm$4.4%. Initial C/N and C/P ratios of Q. mongolica litter were 43.3 and 2,032, respectively. C/N ratio in decomposing litter decreased rapidly from the beginning to nine months decomposition, and then showed more or less constant. C/P ratio increased to 2,407 after three months decomposition, and then decreased steadily thereafter. N and P concentration increased significantly during decomposition. N immobilization occurred from the beginning through 18 months decomposition, and mineralization occurred afterwards in decomposing litter. P immobilized significantly from fifteen months during decomposition. K concentration decreased rapidly from the beginning to six months decomposition. However it showed an increasing pattern during later stage of decomposition. Remaining K decreased rapidly during early stage of decomposition. There was no net K immobilization. Ca concentration increased from the beginning to twelve months decomposition, and then decreased rapidly till twenty one months elapsed. However, it increased again thereafter. Ca mineralization occurred from fifteen months. Mg concentration increased during decomposition. There was no Mg immobilization during litter decomposition. After 33 months decomposition, remaining N, P, K, Ca and Mg in Q. mongolica litter were 79.2, 110.9, 36.2, 52.7 and 74.4%, respectively.

• The Korean Journal of Ecology
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• 제25권1호
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• pp.41-44
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• 2002

Weight loss, N and P dynamics during decomposition of fine roots (<2mm) of alder(Alnus japonica), oak (Quercus acutissima) and pitch pine(Pinus rigida) were studied for 33 months in Kongju, Korea. After 33 months, remaining weight of fine roots of alder, oak and pitch pine was 29.2%, 47.7% and 53.4% of the initial weight, respectively. The decomposition rate constant (k) for alder, oak and pitch pine was 0.448 $yr^1$, 0.269 $yr^1$, 0.228 $yr^1$, respectively. Initial concentration of N and P in fine roots was 10.32mg/g and 0.69mg/g for alder, 6.20mg/g and 0.37mg/g for oak and 7.26mg/g and 0.44mg/g for pitch pine, respectively. Initial concentration of N and P in alder were higher than those in oak and pitch pine. After 33 months, remaining N and P in fine roots was 39.5$\%$ and 31.8$\%$ for alder, 59.4$\%$ and 57.8$\%$ for oak, 63.0$\%$ and 83.4$\%$ for pitch pine, respectively. Decomposition rate and the rate of N released from decomposing fine roots was positively correlated with the initial N concentration of the fine roots.

• Archives of Reconstructive Microsurgery
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• 제22권1호
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• pp.33-37
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• 2013

Purpose: The concept and development of perforator free flaps have led to significant advances in microsurgery. Ongoing developments in perforator free flap surgery are aimed at reducing complications and improving surgical outcomes. The aim of this study was to evaluate the effectiveness and application of supermicrosurgery in free flap surgery. Materials and Methods: A total of 267 patients with soft tissue defects of the lower extremity due to various etiologies from January, 2007 to January, 2013. The patients received either an anterolateral thigh free flap (n=83), a superficial circumflex iliac artery free flap (n=152), an upper medial thigh free flap (n=19), or a superior gluteal artery perforator free flap (n=13). Microanastomosis was performed using a perforator-to-perforator technique, either end-to-end or end-to-side. Results: The mean postoperative follow up period was eight months (range: one to 16 months) and flap loss occurred in 11 cases out of 267. All cases of flap loss occurred within two weeks of surgery due to either arterial insufficiency (n=5) or venous congestion (n=6). Conclusion: Supermicrosurgery enables the selection of the most efficient perforator for microanastomosis at the defect site. It also reduces the time required for dissection of recipient vessels, and reduces the possibility of injury to major vessels. Microsurgery using a vessel of less than 1 mm has been reported to increase the risk of flap failure; however, using the most advanced surgical tools and developing experience in the technique can produce success rates similar to those found in the literature.

• The Plant Pathology Journal
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• 제23권2호
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• pp.90-96
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• 2007

To overcome the problem of the yield reduction due to the viral satellite mediated protection, a culture mix of three nitrogen-fixing bacteria species of the genus Azospirillum (A. brasilienses N040, A. brasilienses SP7, and A. lipoferum MRB16), and one strain of cyanobacteria (Anabena oryzae Fritsch) were utilized as biofertilizer mixture in both greenhouse and field experiments. When protected plants were treated with biofertilizer mixtures, the fruit yield of biofertilized plants increased by 48% and 40% in a greenhouse and field experiment, respectively, compared to untreated plants inoculated with the protective viral strain alone. Polyacrylamide gel electrophoresis (PAGE) analysis of total nucleic acid (TNA) extracts revealed that biofertilization did not affect the accumulation of the viral satellite RNA (CARNA 5) that is required for plant protection against other destructive viral strains of CMV. The yield increment was a good compensation for the yield loss caused by the use of the protective viral strain associated with CARNA 5.

• 전자공학회논문지D
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• 제34D권12호
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• pp.14-21
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• 1997

This study was conducte dto fabricate 2GHz circulator using Ca,Sn substituted UIG(yttrium iron garnet)ceramics. When the electric, magnetic and microwave properties were measured in Ca, Sn substituted YIG, the measured perimittivity and perfmeability in microwave frequencies were 16.25, 0.8964. For $Y_{2.4}$C $a_{0.3}$A $n_{0.3}$F $e_{3.5}$A $l_{1.5}$ $O_{12}$ garnet ceramics sintered at 1400.deg. C, the ferrimagnetic resonance line width (.DELTA.H) at 10GHz was 53 Oe and saturation magnetization was 375G. The strip-line circulator was simulated with 3-D FEM (finite element method) software and designed at the center frequency of 2GHz. The fabricated strip-line junction circulator using above YIG ceramics had insertion loss of 1.271dB, return loss of 23.843dB, isolation of 21.751dB at the center frequency 1.855GHz.z.z.z.z.z.z.

• Smart Structures and Systems
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• 제5권2호
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• pp.119-137
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• 2009

Smart sensors densely distributed over structures can use their computational and wireless communication capabilities to provide rich information for structural health monitoring (SHM). Though smart sensor technology has seen substantial advances during recent years, implementation of smart sensors on full-scale structures has been limited. Hardware resources available on smart sensors restrict data acquisition capabilities; intrinsic to these wireless systems are packet loss, data synchronization errors, and relatively slow communication speeds. This paper addresses these issues under the hardware limitation by developing corresponding middleware services. The reliable communication service requires only a few acknowledgement packets to compensate for packet loss. The synchronized sensing service employs a resampling approach leaving the need for strict control of sensing timing. The data aggregation service makes use of application specific knowledge and distributed computing to suppress data transfer requirements. These middleware services are implemented on the Imote2 smart sensor platform, and their efficacy demonstrated experimentally.

• ETRI Journal
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• 제26권5호
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• pp.375-383
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• 2004

This paper proposes a common interleaving method associated with independent channel-encoding among transmitter antenna branches in orthogonal frequency and code division multiplexing based on multiple-input multiple-output (MIMO) multiplexing to achieve an extremely high throughput such as 1 Gbps using a 100 MHz bandwidth. This paper also investigates the average packet error rate performance as a function of the average received signal energy per bit-to-background noise power spectrum density ratio $(E_b/N_0)$. We found that the loss in the required average received $E_b/N_0$ of the proposed method is only within approximately 0.3 dB in up to a 12-path Rayleigh fading channel, using 16QAM and Turbo coding with a coding rate of 5/6. We also clarify that even for a large fading correlation among antenna branches, 1 Gbps is still possible by increasing the transmission power. Therefore, the proposed method reduces the processing rate to 1/4 in the turbo decoder with only a slight loss in the required average received $E_b/N_0$.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.327-334
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• 2004

Spectroscopic and electrostatic probe measurements were made to examine plasma characteristics with or without a metal plate for a 10-㎾-class direct-current arcjet Heat fluxes into the plate from the plasma were also evaluated with a Nickel slug and thermocouple arrangement. Ammonia and mixtures of nitrogen and hydrogen were used. The NH$_3$ and $N_2$+3H$_2$ plasmas in the nozzle and in the downstream plume without a plate were in thermodynamical nonequilibrium states. As a result, the H-atom electronic excitation temperature and the $N_2$ molecule-rotational excitation temperature intensively decreased downstream in the nozzle although the NH molecule-rotational excitation temperature did not show an axial decrease. Each temperature was kept in a small range in the plume without a plate except for the NH rotational temperature for NH$_3$ gas. On the other hand, as approaching the plate, the thermodynamical nonequilibrium plasma came to be a temperature-equilibrium one because the plasma flow tended to stagnate in front of the plate. The electron temperature had a small radial variation near the plate. Both the electron number density and the heat flux decreased radially outward, and an increase in H$_2$ mole fraction raised them at a constant radial position. In cases with NH$_3$ and $N_2$+3H$_2$ a large number of NH radical with a radially wide distribution was considered to cause a large amount of energy loss, i.e., frozen flow loss, for arcjet thrusters.

• The Korean Journal of Ecology
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• 제23권2호
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• pp.157-161
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• 2000

Mass loss and changes of mineral nutrients during decomposition of Phragmites communis for 13 months from November 1998 to December 1999, were investigated at the fringe of stream at Boryeong, Chungnam Province in Korea. Plant materials, which were collected in November 1998. were divided into leaves, culms and rhizomes. Litterbags, 15${\times}$15 cm, were made of nylon mesh with 2-mm$^2$ holes. At 13 months after installation, remaining mass of leaves, culms and rhizomes was 29.0%, 57.4%, 20.6%, respectively. Mass loss rate of the culms was significantly lower than those of the leaves and rhizomes. The decay rate of leaves, culms and rhizomes was 1.21. 0.42 and 1.48 per year, respectively. Initial concentration of N, P, K, Ca and Mg of leaves. culms and rhizomes was 22.5, 9.0, 15.5 mg/g for N, 0.34. 0.10, 0.33 mg/g for P, 15.0, 12.5. 12.3 mg/g for K, 2.84. 0.80, 0.03 mg/g for Ca. 1.94. 0.97, 0.40 mg/g for Mg, respectively. Concentrations of nutrients were higher in leaves than in culms and rhizomes. Except for N and Mg in rhizomes, there was no immobilization period during the decomposition. In the case of remaining K and Ca, most are lost during the first 3 months. Without any suitable method for removal of dead part, eutrophication of freshwater may be accelerated by dead macrophytes.