• Journal of the Korean Geotechnical Society
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• v.33 no.11
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• pp.5-19
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• 2017

This study has been conducted to improve the conventional compaction management method by measuring the water content and dry unit weight of soil using the Time Domain Reflectometry (TDR) method. In order to verify the measured value of the developed flat TDR system, laboratory tests were conducted on six soils. Also, based on laboratory experiments, field tests were conducted to evaluate the applicability of the developed flat TDR system. Also, a comparison experiment was conducted with the Purdue TDR system. In addition, FE analysis was done to confirm the influence range of the Flat probe. As a result, it was confirmed that the influence range was about 10 cm. As a result of laboratory experiment, the water content ratio showed an error of about 0.4% on the average, and in the case of dry unit weight, it showed an error of about 1.6%. For the field test, the water content ratio and unit weight showed an error of 0.8% and 2.5%, respectively. Through the experimental results, it was confirmed that the measured value of the Flat TDR system is more accurate than that of the conventional TDR system.

• The Journal of the Acoustical Society of Korea
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• v.38 no.4
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• pp.371-377
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• 2019

In this paper, we present the sea trial results of long distance underwater acoustic communication in the East Sea, October 2018. One transmitter and sixteen vertical array receivers were used to collect underwater acoustic communication signals, and the maximum distance between the transmitter and the receiver was 90 km. Information was transmitted by BFSK (Binary Frequency Shift Keying) and BCSK (Binary Chirp Shift Keying) method, which are typical digital frequency modulation techniques. Experimental results show that there is no error in all cases at the transmission distance of 60 km, and BFSK and BCSK have average uncoded bit error rate of 0.0197 and 0.0007 respectively without channel coding at 90 km transmission distance.

• Composite Materials and Engineering
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• v.3 no.3
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• pp.201-220
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• 2021

In this study, potential of three machine learning techniques i.e., M5P, Support vector machines and Gaussian processes were evaluated to find the best algorithm for the prediction of flexural strength of concrete mix with steel fibre. The study comprises the comparison of results obtained from above-said techniques for given dataset. The dataset consists of 124 observations from past research studies and this dataset is randomly divided into two subsets namely training and testing datasets with (70-30)% proportion by weight. Cement, fine aggregates, coarse aggregates, water, super plasticizer/ high-range water reducer, steel fibre, fibre length and curing days were taken as input parameters whereas flexural strength of the concrete mix was taken as the output parameter. Performance of the techniques was checked by statistic evaluation parameters. Results show that the Gaussian process technique works better than other techniques with its minimum error bandwidth. Statistical analysis shows that the Gaussian process predicts better results with higher coefficient of correlation value (0.9138) and minimum mean absolute error (1.2954) and Root mean square error value (1.9672). Sensitivity analysis proves that steel fibre is the significant parameter among other parameters to predict the flexural strength of concrete mix. According to the shape of the fibre, the mixed type performs better for this data than the hooked shape of the steel fibre, which has a higher CC of 0.9649, which shows that the shape of fibers do effect the flexural strength of the concrete. However, the intricacy of the mixed fibres needs further investigations. For future mixes, the most favorable range for the increase in flexural strength of concrete mix found to be (1-3)%.

• The Korean Journal of Food And Nutrition
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• v.35 no.6
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• pp.537-542
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• 2022

This study was conducted to provide basic data on the amount of sodium and the setting of permissible error range of actual measurement, which is a problem for cabbage kimchi nutrients subject to labeling. The sample targeted was baechu (Kimchi cabbage) kimchi, which might have a large variation in sodium content by part of kimchi. Kimchi samples were collected twice from eight companies by season (spring, summer, fall, and winter). The average sodium content in kimchi samples was 619±87 mg/100 g (range, 534±63 mg/100 g to 783±40 mg/100 g). The error in average annual sodium content of abandonment kimchi (maximum value difference compared to the minimum value) was 26.8 to 64.3%. Sodium contents in kimchi produced in spring and summer were relatively low. However, deviation between individuals was large. It was found that cases exceeding the permissible error (120%) standard varied depending on the criteria for setting the amount of sodium. In addition, due to seasonal differences, sodium content in kimchi exceeded 120% of the labeling value. Thus, it is necessary to set standards suitable for characteristics of kimchi to prevent unintentional violations of labeling standards by raw materials and manufacturing processes.

• Journal of Sensor Science and Technology
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• v.31 no.3
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• pp.163-167
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• 2022

In this study, we investigated a carbon nanotube (CNT) film sensor to detect hazardous and noxious substances distributed in seawater. The response change of the sensor was studied according to environmental temperature, and its temperature coefficient of resistance (TCR, α) was measured. The temperature of the CNT film (~50 ㎛) was in the range of 20-50 ℃, and αCNT was calculated to be -0.0011 %/ ℃. We experimentally confirmed that the CNT film had a smaller TCR value than that of the conventional sensor. Therefore, we investigated the response change of the CNT sensor according to temperature. The CNT sensor showed a relatively small error of approximately 2.3 % up to 30 ℃, which is within the temperature range of the seawater of the Korean Peninsula. However, when the temperature exceeded 40 ℃, the error in the CNT sensor increased by more than 5.2 %. We fabricated a metal oxide (ITO, indium-tin-oxide) film and compared its performance with that of the CNT sensor. The ITO sensor showed an error of >12.5 % at 30 ℃, indicating that in terms of the stability of the sensor to temperature, the CNT film sensor has superior performance.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.451-462
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• 2024

In order to optimize the operational safety and reliability of the upper launcher for the CFETR ECRH system, a design of the launcher based on the remote steering concept is currently being carried out for comparison with the front steering equivalent. This paper presents the remote steering system's conceptual design and simulation analysis. A Square Corrugated Waveguide (SCW) of 65 × 65 mm has been designed with an optimized length of 9.35 m. By changing the relative length of the waveguide, the transmission efficiency of the SCW is optimized within the range of steering angles ±12°. Different error factors are investigated in detail, and corresponding acceptable error ranges are provided. Considering these error factors and ignoring ohmic losses and thermal effects, the relative transmission efficiency of the SCW is estimated to be >98 % within the steering angle range. A matching steering unit for the SCW is designed, which consists of an ellipsoidal focusing mirror and a steerable flat mirror. The detailed design of the steerable mirror motion trajectory is presented. Also, the influence of the possible beam incident errors caused by the steering unit on the transmission efficiency is analyzed in detail.

• Journal of KIISE:Information Networking
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• v.35 no.4
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• pp.282-291
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• 2008

This paper focuses on message complexity performance analysis of MANET AAPs in reference to link errors generated by the mobile wireless nodes. To obtain the message complexity performance of AAPs in reference to the link error probability ($P_e$), an enhancement was made by proposing the retransmission limit (S) to be computed for error recovery (based on the link error probability), and then for each of the AAPs the control procedures for the retransmission limit have been properly included. The O-notation has been applied in analyzing the upper bound of the number of messages generated by a MANET group of N nodes. Based on a link error probability range of $P_e=0$ to 0.8, the AAPs investigated in this paper are Strong DAD, Weak DAD with proactive routing protocol (WDP), Weak DAD with on-demand routing protocol (WDO), and MANETconf. Based on the simulation results and analysis of the message complexity, for nominal situations, the message complexity of WDP was lowest, closely followed by WDO. The message complexity of MANETconf is higher than that of WDO, and Strong DAD results to be most complex among the four AAPs.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.103-103
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• 2014

Manufacturing of lens and mirror using Diamond Turning Machine (DTM) offers distinct advantages including short fabrication time and low cost as compared to grinding or polishing process. However, the DTM process can leave mid-frequency error in the optical surface which generates an undesirable diffraction effect and stray light. The mid-frequency error is expected to be eliminated by mechanical polishing after the DTM process, but polishing of soft surface of ductile aluminum is extremely difficult because the polishing process inevitably degrades the surface form accuracy. In order to increase its surface hardness, we performed electroless nickel plating on the surface of diamond-turned aluminum (Al-6061T6) off-axis mirrors, which was followed by the 6-hour-long baking process at $200^{\circ}C$ for improving its hardness. Then we polished the nickel plated off-axis mirrors to remove the mid-frequency error and measured polished mirror surfaces using the optical surface profilometer (NT 2000, Wyko Inc.). Finally, we ascertained that the mid-frequency error on the mirror surface was successfully removed. During the whole processes of nickel plating and polishing, we monitored the form accuracy using the ultra-high accurate 3-D profilometer (UA3P, Panasonic Corp.) to maintain it within the allowable tolerance range (< tens of nm). The polished off-axis mirror was optically tested using a visible laser source and a pinhole, and the airy pattern obtained from the polished mirror was compared with the unpolished case to check the influence of mid-frequency error on optical images.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5A
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• pp.504-512
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• 2010

The paper proposes the 6bit 800MS/s flash A/D converter that can be applied to wireless USB chip-set. The paper simplified the error correction circuit and synchronization block as one circuit which are used respectively, and furthermore reduced the burden on the hardware. Comparing to the conventional error correction circuit, the proposed error correction circuit in this paper reduced 5 MOS transistors, the area of each error correction circuit is reduced by 9%. The A/D converter is fabricated with 0.18um CMOS 1-poly 6-metal process, and power dissipation is 182mW at 0.8Vpp input range and 1.8V supply voltage. The measured result shows 4.0bit of ENOB at 800MS/s conversion rate and 128.1MHz input frequency.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.2
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• pp.133-139
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• 2017

The timing chain system, which is a typical power transmission technology applied to a vehicle, has been widely used by the automotive industry because it is normally designed to last a car's lifetime. However, the timing chain system may cause some problems due to the shape of the chains and the polygonal behavior on contact between the chain and the sprocket. In addition, noise and vibration caused by transmission error are the most typical problems encountered by major automotive manufacturers and they are considered as the main source of customer complaint. The initial tension of the chain-sprocket system is thought to be the main cause of transmission error, and it is regarded as the source of engine vibration and noise. The initial tension of the chain system should be controlled carefully since a low initial tension can cause twisting, which may lead to a system malfunction, while a high initial tension can reduce the service life due to a worn down contact surface. In this paper, the kinematic analysis model is generated with various initial tensions, which are controlled by changing the shape of the fixed guide with the largest contact surface with chain. The results showed that the transmission error was minimized on a particular range of initial tension, and the tendency showed that the error changed with a higher sensitivity at a lower initial tension.