• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.3
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• pp.275-281
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• 2014

Recently, the need for various underwater application systems targeting efficient resource exploration and aquatic ecosystem monitoring is rapidly increasing in littoral sea and inland waters. In this paper, we focus on the research and development of digital module of acoustic micro modem which can be used for underwater mobile communication systems and underwater sensor network systems. Specifically, a digital module of acoustic modem embedding digital signal processor is designed and implemented. On top of the developed hardware platform, physical layer frame generation and recovery and channel coding algorithms are mounted and tested in a water tank and a pond to verify its functionality and performance. According to experimental results, less than 1 percent of total computational power is consumed in the processing of frame control and convolutional code with the data rate of 1 kbps. Thus, the performance of micro modem could be improved by loading efficient baseband algorithms into the processor while maintaining the implemented hardware.

• Journal of radiological science and technology
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• v.45 no.2
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• pp.127-134
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• 2022

In order to overcome the image quality limitations of the conventional C-arm, a flat panel detector (FPD) is used to enhance spatial resolution, detective quantum efficiency, frame rate, and dynamic range. Three-dimensional (3D) visualized information can be obtained from C-arm computed tomography (CT) equipped with an FPD, which can reduce patient discomfort and provide various medical information to health care providers by conducting procedures in the interventional procedure room without moving the patient to the CT scan room. Unlike a conventional C-arm device, a C-arm CT requires different basic safety and essential performance evaluation criteria; therefore, in this study, basic safety and essential performance evaluation criteria to protect patients, medical staff, and radiologists were derived based on International Electrotechnical Commission (IEC) standards, the Ministry of Food and Drug Safety (MFDS) standards in Korea, and the rules on the installation and operation of special medical equipment in Korea. As a result of the study, six basic safety evaluation criteria related to electrical and mechanical radiation safety (leakage current, collision protection, emergency stopping device, overheating, recovery management, and ingress of water or particulate matter into medical electrical (ME) equipment and ME systems: footswitches) and 14 essential performance evaluation criteria (accuracy of tube voltage, accuracy of tube current, accuracy of loading time, accuracy of current time product, reproducibility of radiation output, linearity and consistency in radiography, half layer value in X-ray equipment, focal size and collimator, relationship between X-ray field and image reception area, consistency of light irradiation versus X-ray irradiation, performance of the mechanical device, focal spot to skin distance accuracy, image quality evaluation, and technical characteristic of cone-beam computed tomography) were selected for a total of 20 criteria.

• Membrane Journal
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• v.6 no.3
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• pp.173-181
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• 1996

Common volatile organic compounds(VOCs) such as toluene and methanol were removed successfully from N$_{2}$ using a novel silicone-coated hollow fiber membrane module. This novel membrane is a thin film composite(TFC) and was highly efficient in removing VOCs selectively from a N$_{2}$ stream. This membrane had some innate advantages over other silicone-based membrane in that the selective barrier was ultrathin(~1 $\mu$m) and the porosity of the polypropylene substrate was high which leads to a low permeation resistance. The substram was very strongly bonded to the coating layer by plasma polymerization and can withstand a very high pressure. A small hollow fiber module having a length of 25cm and 50 fibers could remove 96~99% of toluene as well as methanol vapors when the feed flow rate was up to 60cc/min. The percent removal of VOCs were even higher when the feed inlet concentration was higher. This process is especially suitable for treating streams having a low flow rate and high VOCs concentration. The permeances of VOCs through this membrane was in the range of $4~30 \times 10^{-9}gmol/sec \cdot cm^{2}\cdot cmHg$ for both toluene and methanol, and nitrogen permeance was between $3~9 \times 10^{-10}gmol/sec \cdot cm^{2} \cdot cmHg$. High separation factor between 10~55 for toluene/N$_{2}$ and 15~125 for methanol/N$_{2}$ were obtained depending on the feed flow rate ranges and feed VOCs concentration levels.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.3
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• pp.49-55
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• 2017

In this study, gas turbine engine inlet duct was designed to satisfy uniform flow at aerodynamic interface plane (AIP). Haack-series was selected as nose cone profile and duct outer radius($r_o$) was designed to satisfy to match with area change rate between the nose cone and outer duct wall by the 1-D sizing. The design object of the inlet duct wall profile which has the gradual area change rate was uniform Mach number in the core flow region and minimum boundary later thickness at the both inner nose wall and outer duct wall. The flow characteristics inside the inlet duct was evaluated using CFD. The static pressure distribution at the AIP showed uniform pattern within 0.16%. Based on Mach number profile, the boundary layer thickness was 2% of channel height. Kiel temperature rake location was decided less than 100 mm in front of nose cone where the Mach number is less than 0.1 in order to maximize the temperature probe recovery rate.

• The KIPS Transactions:PartC
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• v.13C no.7 s.110
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• pp.803-812
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• 2006

This paper analytically evaluates the FEC(Forward Error Correction) symbol size's effect on the performance and energy consumption of 802.11 protocol with the block FEC algorithm over WSN(Wireless Sensor Network). Since the basic recovery unit of block FEC algorithms is symbols not bits, the FEC symbol size affects the packet correction rate even with the same amount of FEC check bits over a given WSN channel. Precisely, when the same amount of FEC check bits are allocated, the small-size symbols are effective over channels with frequent short bursts of propagation errors while the large ones are good at remedying the long rare bursts. To estimate the effect of the FEC symbol site, the paper at first models the WSN channel with Gilbert model based on real packet traces collected over TIP50CM sensor nodes and measures the energy consumed for encoding and decoding the RS (Reed-Solomon) code with various symbol sizes. Based on the WSN channel model and each RS code's energy expenditure, it analytically calculates the transmission efficiency and power consumption of 802.11 equipped with RS code. The computational analysis combined with real experimental data shows that the RS symbol size makes a difference of up to 4.2% in the transmission efficiency and 35% in energy consumption even with the same amount of FEC check bits.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.22 no.5
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• pp.266-280
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• 1989

Gonadal maturation of the Korean pomfrets, Pampus echinogaster (Basilewsky) and Pampus argenteus (Euphrasen) were histologically investigated based on the samples captured in the East China Sea from January 1987 to December 1988. Gonadosomatic index (GSI) of P. echinogaster began to increase from March, and reached maximum between May and July. It began to decrease from July and reached mini-mum between August and February. P. argenteus had a similar cycle, however, P. argenteus has higher values in April than P. echinogaster. Hepatosomatic index (HSI) were positively related to GSI. HIS of P. echinogaster and P. argenteus reached maximum in $April\~July$ and $April\~August$, respectively, Fatness coefficient of two Pampus species were low in the summer, and high in the winter. Ovary is of saccular structure, and testis is of lobular structure. From February, the early oocyte (ca. $100\mu$ in diameter grows) rapidly at the germinal epithelium of ovarian sacs. From March to April the oocytes grew up to cu $400\~500\mu$ in diameter. At this stage, the yolk globules are accumulated rapidly in the cytoplasmic layer. From May, the oocytes roached ca. $650\~850\mu$ in diameter, and they are spawned in $May\~July$. After spawning the residual follicles and remained ripe eggs degenerate. From February, spermatogonia grows into spermatocyte on the epithelium of the testicular lobuli. From May, spermatozoa appeared and spawning occurs. After spawning, the epithelium is thickened and the remained spermatozoa degenerate. Annual reproductive cycle of two Pampus species could be divided into four successive stages: Growing stage ($March\~April$), Mature stage ($April\~May$), Ripe and spent stage ($June\~July$) and Recovery and resting stage ($August\~January$). Absolute fecundity of P. echinogaster was $9,441\~135,294$, and that of P. argenteus was $50,678\~221,894$. Absolute fecundity of two Pampus species were positively related to body length and total weight. Relative fecundity was positively related to body length, while it was reversely related to total weight. The increasing rate of absolute fecundity of P. echinogaster was lower than P. argenteus. In P. echinogaster half of female and male reached first maturity at body length of $15.0\~$17.9cm and $12.0\~14.9cm$, respectively. All of females and males reached first maturity at body length of $18.0\~20.9cm$ and $21.0\~23.9cm, respectively. In P. argenteus all of females and males reached first maturity at body length of 18.6cm and 16.7cm$, respectively.