• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4B
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• pp.365-371
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• 2002

In this paper, the fabricated power PHEMT devices for millimeter-wave that is below a gate-length of 0.2 $\mu\textrm{m}$ using electronic beam lithography technologies, and the DC and frequency characteristics and an output power characteristics were Measured at the various bias conditions. The unit process that is used in PHEMT's manufacture used that low-resistance ohmic contact, air-bridge and back-side lapping process technologies, and so on. The fabricated power PHEMT have an S521 gain of 4 dB and a maximum transconductance(gm) of 317 mS/mm, an unilateral current gain(fT) of 62 GHz, a maximum oscillation frequency(fmax) of 120 GHz at 35 GHz, and a maximum power output(Pmax) of 16 dBm, a power gain(GP) of 4 dB and a drain efficiency(DE) of 35.5 %.

• Journal of Environmental Science International
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• v.23 no.3
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• pp.359-368
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• 2014

The aim of our research was to apply experimental design methodology in the optimization of N, N-Dimethyl-4-nitrosoaniline (RNO, which is indictor of OH radical formation) degradation using gas mixing-circulation plasma process. The reaction was mathematically described as a function of four independent variables [voltage ($X_1$), gas flow rate ($X_2$), liquid flow rate ($X_3$) and time ($X_4$)] being modeled by the use of the central composite design (CCD). RNO removal efficiency was evaluated using a second-order polynomial multiple regression model. Analysis of variance (ANOVA) showed a high coefficient of determination ($R^2$) value of 0.9111, thus ensuring a satisfactory adjustment of the second-order polynomial multiple regression model with the experimental data. The application of response surface methodology (RSM) yielded the following regression equation, which is an empirical relationship between the RNO removal efficiency and independent variables in a coded unit: RNO removal efficiency (%) = $77.71+10.04X_1+10.72X_2+1.78X_3+17.66X_4+5.91X_1X_2+3.64X_2X_3-8.72X_2X_4-7.80X{_1}^2-6.49X{_2}^2-5.67X{_4}^2$. Maximum RNO removal efficiency was predicted and experimentally validated. The optimum voltage, air flow rate, liquid flow rate and time were obtained for the highest desirability at 117.99 V, 4.88 L/min, 6.27 L/min and 24.65 min, respectively. Under optimal value of process parameters, high removal(> 97 %) was obtained for RNO.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.40-48
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• 2019

New concept of fine dust measurement method is suggested based on ultrasonic scattering. These days, fine dust has been social problem in Korea, and many researches has been conducted including the area structural maintenance. Conventional measurement system such as optical scattering and semiconductor has a limit from environmental factors like relative humidity. However, ultrasound is based on mechanical waves, which perturb mechanical properties of medium such as density and elastic constants. Using the advantage, the algorithm for fine dust measurement is derived and evaluated using 2-D finite difference method. The numerical analysis simulates ultrasonic wave propagation inside multiple scattering medium like fine dust in air. Signal processing scheme is also suggested and the results show that the error of the algorithm is around minimum of 0.7 and maximum of 24.9 in the number density unit. It is shown that cross-section of fine dust is a key parameter to improve the accuracy of algorithm.

• Environmental and Resource Economics Review
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• v.26 no.2
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• pp.205-227
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• 2017

Today, the global environment has so many serious problems such as global warming, ecological destruction and air pollution. Now China is the second largest carbon emissions country in the world. In this paper, we estimated the ratio of GDP per unit of carbon emissions for each of 30 provinces in China, and then also estimated the carbon emission efficiency of 30 provinces and analyzed the factors that affecting them. There are differences in carbon emission efficiency among different provinces, and carbon emission efficiency is relatively high in Hainan Province, Beijing, and Tianjin. In the regression results of the factors affecting the carbon emission efficiency, when the proportion of service industries is higher, the efficiency is higher. Also, when the higher the proportion of heavy industry and the higher the proportion of coal consumption are estimated to be worse.

• Journal of Dental Anesthesia and Pain Medicine
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• v.15 no.1
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• pp.31-34
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• 2015

Vascular injury caused by a central venous catheter (CVC) has been reported to be a rare complication, especially delayed vascular injury due to CVC has a few cases and it can be fatal because of delayed recognition and more serious complications. A 59-year-old woman with no available medical history was admitted for treatment of ovarian cancer. For the surgery, a triple-lumen CVC was placed through the left subclavian vein. Parenteral nutrition through the CVC was used for postoperative nutritional management in the first postoperative day. On the sixth postoperative day (POD), the patient suddenly complained of dyspnea. The CT revealed bilateral pleural effusion and irregular soft tissue density and air bubble in anterior mediastinum suggesting migration of the distal portion of the CVC into the anterior mediastium. In the intensive care unit (ICU) bilateral thoracentesis and percutaneous drainage were performed. She was discharged from the ICU in 3 days later and transferred to the general ward. This case emphasizes the possibility of the delayed vascular injury related to CVC and some strategies for prevention of vascular injury.

• The Korean Journal of Ecology
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• v.28 no.4
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• pp.231-235
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• 2005

Comparative water relations of Quercus acuta and Castanopsis cuspidata var, sieboldii were analyzed to assess their resistance to drought and low temperature stresses from early November to early December, As air temperature decreased both species showed an increased content of osmotically active solute concentration per unit of dry weight (NS/DW), leading to lower osmotic potential of both species at both full turgid state $(OP_{sat})$ and turgor loss point $(OP_{tlp})$ in December than November. No major difference in the ability to adjust osmotically was noticed between the two. This finding suggests that both species must respond adaptively under water and low temperature stresses to maintain turgor pressure in winter season. In addition to osmotic adjustment, a low bulk modulus of elasticity $(E_{max})$ shown in Castanopsis cuspidata var. sieboldii must also play an important role in turgor maintenance during winter season being apt to happen water and low temperature stresses in plants.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.5
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• pp.409-416
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• 2006

Operating Characteristics of LLC Series resonant converter with a LLT(Inductor-Inductor-Transformer) transformer is presented. LLT transformer used to combine the inductor and transformer into one unit has the increased leakage inductance in the primary and secondary due to the winging method and the use of the gaped core. The increased leakage inductance in the primary and secondary of LLT transformer can be impacted on the DC voltage gain characteristics of LLC series resonant converter. In the paper, DC gain characteristics and the experimental results of the LLC series resonant converter with a LLT transformer are verified on the simulation based on the theoretical analysis and the 400W experimental prototype.

• Journal of the Korea Concrete Institute
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• v.12 no.2
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• pp.99-107
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• 2000

This research investigates experimentally an effect on the properties of the high flowing concrete to be poured in the under-ground slurry wall of Inchon LNG receiving terminal(#213,214-TK) according to variations of concrete materials. Variables for sensitivity test were selected items as followings. 1) Concrete temperature (3cases), 2) Unit water (5cases), 3) Fineness modulus of fine aggregate (5cases), 4) Particle size of lime stone powder (3cases), 5) Replacement ratio of blast-furnace slag (4cases) and 6) Addition ratio of high range water reducing agent (5cases). And fresh conditions of the super flowing concrete should be satisfied with required range including slump flow(65$\pm$5cm), 50cm reaching time of flow(4~10sec), V-lot flowing time(10~ 20sec), U-box height(min. 300mm) and air content(4$\pm$1%). As results for sensitivity test, considered flow-ability, self-compaction and segregation resistance of the high flowing concrete, material variations and conditions of fresh concrete should be satisfied with the range as follwings. 1) Concrete temperature are 10~2$0^{\circ}C$(below 3$0^{\circ}C$), 2) Surface moisture of fine aggregate is within $\pm$ 0.6%, 3) Fineness modulus of fine aggregate is 2.6$\pm$0.2, 4)Replacement ratio of blast-furnace slag is 45~50% and 5) Addition ratio of high range water reducing agent is within 1%. Based on the specification for quality control, we successfully finished concrete pouring on the under-ground slurry wall having 75,000㎥(#213,214-TK) and accumulated real date in site.

• Journal of Environmental Science International
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• v.18 no.8
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• pp.885-897
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• 2009

In order to make sure the impact of spatial resolution of wind energy map on the estimation of wind power density in the Korean Peninsula, the comparison studies on the characteristics of wind energy map with three different spatial resolutions were carried out. Numerical model used in the establishment of wind map is MM5 (5th generation Mesoscale Model) with RBAPS (Regional Data Assimilation and Prediction System) as initial and boundary data. Analyzed Period are four months (March, August, October, and December), which are representative of four seasons. Since high spatial resolution of wind map make the undulation of topography be clear, wind pattern in high resolution wind map is correspond well with topography pattern and maximum value of wind speed is also increase. Indication of island and mountains in wind energy map depends on the its spatial resolution, so wind patterns in Heuksan island and Jiri mountains are clearly different in high and low resolutions. And area averaged power density can be changed by estimation method of wind speed for unit area in the numerical model and by treatment of air density. Therefore the studiable resolution for the topography should be evaluated and set before the estimation of wind resources in the Korean Peninsula.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.5
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• pp.521-526
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• 2020

Airfield pavements, such as runways and taxiways, are essential for smooth take-off and landing of fixed-wing aircraft and are the most important installation for the military to carry out air operations during wartime. Therefore, in wartime, it is necessary to reduce the damage to these installations and repair them in the shortest possible time. Recently, the pattern of attack is changing from the use of conventional high explosive which is to create large craters to the use of multiple warheads weapon system which is to effectively attack enemy's airfields but unrelated to accuracy. Hence in this study, through identifying the specification and composition of multiple warheads weapon system, we checked the protection performance and damage patterns of the pavement when explosion occurred on the installed military runway and taxiway by the multiple warheads weapon system. And The multiple warheads weapon systems is able to cause extensive damage but the destructive power of each warhead is not as great, so I would like to propose an airfield pavement design plan for minimal protection against such attacks.