• The Journal of the Acoustical Society of Korea
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• v.42 no.4
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• pp.329-344
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• 2023

In this study, we comprehensively analyze the generalization performance of various deep learning-based active sonar target classifiers when applied to small and imbalanced active sonar datasets. To generate the active sonar datasets, we use data from two different oceanic experiments conducted at different times and ocean. Each sample in the active sonar datasets is a time-frequency domain image, which is extracted from audio signal of contact after the detection process. For the comprehensive analysis, we utilize 22 Convolutional Neural Networks (CNN) models. Two datasets are used as train/validation datasets and test datasets, alternatively. To calculate the variance in the output of the target classifiers, the train/validation/test datasets are repeated 10 times. Hyperparameters for training are optimized using Bayesian optimization. The results demonstrate that shallow CNN models show superior robustness and generalization performance compared to most of deep CNN models. The results from this paper can serve as a valuable reference for future research directions in deep learning-based active sonar target classification.

• Journal of the Korean Regional Science Association
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• v.40 no.3
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• pp.95-108
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• 2024

This study analyzes the location determinants of newly established and relocated manufacturing firms in South Korea using the National Business Survey data from 2016 to 2019. Both new establishments and relocations are concentrated in the Seoul metropolitan area, Chungcheong, Yeongnam, and Daegyeong regions, with relocated firms showing a higher degree of spatial concentration. Employing a negative binomial regression model, we find that manufacturing concentration, population density, industrial diversity, and lower wage levels positively influence both new establishments and relocations. The proportion of highly educated workers, accessibility to producer services, and average land prices only positively affect the frequency of new establishments, suggesting that firms in the early stages of their life cycle, which are more dependent on human capital and producer services, demonstrate a higher willingness to pay for land use. Conversely, increased travel time to Seoul and improved transportation accessibility enhance the probability of attracting relocated firms. This implies that cost reduction incentives associated with distance from Seoul may outweigh the benefits of proximity to the capital in relocation decisions. Our findings suggest that strengthening agglomeration economies and improving transportation infrastructure efficiency could increase the likelihood of attracting relocated manufacturing firms to non-capital regions.

• Journal of Food Hygiene and Safety
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• v.31 no.4
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• pp.250-257
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• 2016

This study was conducted to extract the factors affecting the microbial safety of leaf and stem vegetables in the high school foodservice and to provide information for supplying the safe foodservice menu. The lunch and dinner menu (1,945 data) of the total 6 high schools at the Central and the South Region in March, June, September, and December were collected. The frequency analysis and the multiple correspondence analysis (MCA) based on the 3 factors (potentially hazardous food (PHF), leafy and stem vegetables in the menu, the cooking methods) were conducted. The most frequent PHF was the menu of blanched vegetables, salads, seaweeds and fried chicken. The most frequent consumed leaf and stem vegetables were spinach, chive, lettuce, Western cabbage, perilla leaf, iceberg lettuce, chicory, leek and broccoli. MCA based on the leaf and stem vegetables, the region, and the cooking method (cooked/non-cooked) showed that garlic stem and spinach were more used in the Central Region, while water drop-wort were more used in the South Region. Iceberg lettuce, Bok choy and leek were included frequently in the PHF menu. Plant products frequently used in PHF menu requires the food safety system such as Good Agricultural Practice (GAP) to reduce the microbial risk. The menu database according to raw materials based on cooking methods (heating or mixing) as well as the development and verification of menu based on the microbial safety will be contributed to provide the safer foodservice menu.

• KIPS Transactions on Software and Data Engineering
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• v.2 no.6
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• pp.423-432
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• 2013

Smart phones have been technologically advanced in many ways from basic cellular phones. However, most of all smart phone users in Korea still have been using the traditional Korean character keypads used in the basic cellular phones. It would be required to develop new keypads on smart phones with touch screen. In this paper, we extended the three standard Korean character keypads - Cheonjiin, Naragul, and SKY-Hangul - by adding dragging function on touch screen, then we compared writing speeds of the keypads based on the number of touching buttons and moving distance of the finger while writing a sentence. In addition, we proposed two new Korean keypads - 's-Gana' and 's-Bada', which are more suitable on smart phones. s-Gana assigned 7 representative consonants and 5 representative vowels in order on the 4x3 keypad, and s-Bada assigned consonants and vowels by considering their frequency of use. s-Gana and s-Bada keypads showed 3~19% and 9~24% of performance improvement, respectively, compared with the standard Korean keypads. Finally, we set up 5 requisites of SELF-T in order to evaluate the usability of Korean character keypads in smart phones, then we compared the keypads using the requisites.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.1
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• pp.126-130
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• 2005

Manufacturing method and ingredient ratio for young radish kimchi (yulmoo kimchi) and young radish watery kimchi (yulmoo mool-kimchi) were standardized from literatures. Ingredients having frequency of use greater than 50% were only used in the standardization process. Green onion, red pepper, red pepper powder, garlic, ginger, and anchovy juice were included in young radish kimchi. Green pepper, red pepper, garlic, ginger, and starch were included in young radish watery kimchi. The standardized ingredients ratio of young radish kimchi (yulmoo kimchi) on young radish 100 g was as follows: green onion 8.0$\pm$3.8, crushed garlic 2.9$\pm$1.3, crushed ginger 1.6$\pm$0.7, red pepper 7.0$\pm$1.7, red pepper powder 4.2$\pm$1.2, and anchovy juice 3.7$\pm$0.5. The standardized ingredients ratio of young radish watery kimchi (yulmoo mool-kimchi) on added water 100 mL was as follows: young radish 50.6:$\pm$10.8, crushed garlic 3.0$\pm$0.7, crushed ginger $1.5\pm$0, green onion 3.3$\pm$1.3, green pepper 3.3$\pm$1.9, red pepper 2.4$\pm$1.3, and starch $1.5\pm$0.6.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.8 s.350
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• pp.35-46
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• 2006

When an RFID reader attempts to read the tags, interference might occur if the neighboring readers also attempt to communicate with the same tag at the same time or the neighboring readers use the same frequency simultaneously. These interferences cause the RFID reader collision. When the RFID reader collision occurs, either the command from the reader cannot be transmitted to the tags or the response of the tags cannot receive to the reader correctly, Therefore, the international standard for RFID and some papers proposed the methods to reduce the reader collision. Among those, Colorwave and Enhanced Colorwave is the reader anti-collision algorithm using the frame slotted ALOHA based a TDM(Time Division Multiplex) and are able to reduce the reader collision because theses change the frame size according to a collision probability. However, these can generate the reader collisions or interrupt the tag reading of other readers because the reader that collides with another reader randomly chooses a new slot in the frame. In this paper, we propose a new RFID reader anti-collision algorithm that each reader monitors the slots in the frame and chooses the slot having the minimum occupation probability when the reader collision occurs. Then we analyze the performance of the proposed algorithm using simulation tool.

• Journal of the Korea Society of Computer and Information
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• v.16 no.12
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• pp.227-234
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• 2011

Many technologies for wireless internet are increasing as more and more laptop computers, net books, smart phone and other terminals, which provide wireless network, are created. IEEE 802.11 is computer wireless network technology that used in small area, called wireless LAN or Wi-Fi. IEEE 802.11 is a set of standards for implementing wireless local area network (WLAN) computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee (IEEE 802). AP (Access Point) is installed at cafes and public places providing wireless environment. It is more convenient to use wireless internet, however, It can be seen easily around us and possible to communicate with AP. IEEE 802.11 has many vulnerability, such as packet manipulation and information disclosure, so we should pay more attention when using IEEE 802.11. Therefore this paper developing monitoring system which can find out AP and Stations that connect with it, and capturing AP's information to find out vulnerability. This paper suggests monitoring system which traffic analysis in wireless environment.

• Journal of the Korean Society for information Management
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• v.29 no.1
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• pp.253-277
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• 2012

The purpose of this study is to clarify the spatial characteristics of the children's library and user's behavioral characteristics and to empirically analyze the difference in preference of the spatial characteristics based on the using behaviors. For doing this, this study selected 16 children's libraries in the country as a sampling institute and collected and analyzed 661 questionnaires targeting infants, and the lower and upper graders. The results of analysis are as follows. First, while there was a difference in the relation between the spatial characteristics and the user's characteristics according to ages and sexes, there was no difference in the developing stage. Second, there was a difference in the relation between the spatial characteristics and the using behaviors. Detailed results are as follows. While users who visit the library for reading prefer amenity and peacefulness, those who visit the library for other reasons prefer communication and territoriality. Children prefer diversity, peacefulness and communication when they visit in group rather than to visit individually. In terms of behavioral patterns, users who act quietly prefer diversity than those who act actively. Reading use frequency, as the number of times to visit increased, preference on esthetic sense, dynamics, flexibility, leisure, communication and territoriality increased, but preference on safety decreased. As the length of visit became longer, preference on diversity, self-esteem, peacefulness, dynamics and flexibility increased.

• Journal of the Korean earth science society
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• v.24 no.3
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• pp.190-204
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• 2003

The PM (particulate matter) concentration data sets exceeding the Daily Air Quality Guidance Levels (i.e., established by the Korean Ministry of Environment) were selected from 31 air qality monitoring stations in Seoul from 1990 to 2000. (For reference, the 24hr environmental standard values of PM$_{10}$ and TSP are 150 and 300${\mu}$g/m$^{3}$, respectively.) When the data sets were compared between land use types, both PM fractions were exceeded most frequently in residential areas. However, the highest TSP concentration was measured at industrial areas (351.0${\pm}$35.9${\mu}$g m$^{3}$), while the highest PM$_{10}$ concentration was measured in residential areas (182.9${\pm}$42.4${\mu}$g m$^{3}$). When the temporal distribution patterns of the exceedance data sets were compared to those measured routinely (without any discrimination based on exceedance criteria), large differences were present. It was demonstrated that the occurrences of exceedance data sets increased rather significantly in recent years.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.796-804
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• 2010

It is important to use the comb type pilot allocation for the continuous channel and efficient processing. And DFT-spreading OFDM is used a lot to solve high PAPR problem of OFDM system. However, PAPR is increased again when comb type pilot is used to estimate channel characteristics. So, in this paper, we employ a new SLM method to DFT-spreading OFDM system to reduce increased high PAPR. And we suggest an effective method to transmit side information without additional bandwidth. Pilot and side information must be preserved from jamming or intentional interferences since those are very important in DFT spread OFDM system using SLM. So, in this paper, we like to analyze and simulate the performance of DFT spread OFDM system based on SLM against jamming signal. To remedy the vulnerable shortcomings of DFT spread OFDM about jamming or intentional interferences, we employ FH(Frequency Hopping) method and analyze system performance under the several jamming conditions such as MTJ(Multi Tone Jamming) and PBJ(Partial Band Jamming).