• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권7호
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• pp.1868-1887
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• 2024

Recommendation systems research is a subfield of information retrieval, as these systems recommend appropriate items to users during their visits. Appropriate recommendation results will help users save time searching while increasing productivity at work, travel, or shopping. The problem becomes more difficult when the items are geographical locations on the ground, as they are associated with a wealth of contextual information, such as geographical location, opening time, and sequence of related locations. Furthermore, on social networking platforms that allow users to check in or express interest when visiting a specific location, their friends receive this signal by spreading the word on that online social network. Consideration should be given to relationship data extracted from online social networking platforms, as well as their impact on the geolocation recommendation process. In this study, we compare the similarity of geographic locations based on their distance on the ground and their correlation with users who have checked in at those locations. When calculating feature embeddings for users and locations, social relationships are also considered as attention signals. The similarity value between location and correlation between users will be exploited in the overall architecture of the recommendation model, which will employ graph convolution networks to generate recommendations with high precision and recall. The proposed model is implemented and executed on popular datasets, then compared to baseline models to assess its overall effectiveness.

• 복식문화연구
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• 제26권5호
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• pp.754-763
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• 2018

This study examined the color reproducibility and color fastness of digital textile printing for nylon sublimation transfer. After measuring the temperature and time suited to nylon sublimation transfer, the researchers conducted various tests for comparison and analysis including polyester transfer paper on polyester fabric to check dyeing characteristics, color change, sharpness, and the rubbing fastness of the dyeing samples for nylon sublimation transfer. These tests produced the following results. At $185^{\circ}C$ and $187^{\circ}C$, the sublimation transfer dyeing characteristics of nylon were similar to those of polyester and the researchers even observed superior color development in some colors; at a low temperature of $180^{\circ}C$, the sample that was worked on had the lowest level of color development. The examination of color difference (${\Delta}E$), which compared $L^*a^*b^*$ values, showed that the ${\Delta}E$ value of magenta was 10.34, that of yellow was 24.70, and that of black was 15.28. These results highlight the important role of heat treatment temperature and time on color development in nylon sublimation transfer. Concerning sharpness, the samples subjected to higher temperature heat treatment exhibited fewer color spreading phenomena around lines. Thus, dyeing properties and fastness can be enhanced by elongating time at low temperatures and shortening time at high temperatures; however, considering production time constraints as well as the need to produce industrially marketable quantities, the findings of this study suggest that the heat treatment temperature most suitable for nylon sublimation transfer is $187^{\circ}C$ for a duration of 50 seconds.

• 한국재료학회지
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• 제12권3호
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• pp.200-204
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• 2002

We fabricated TMR devices which have double oxidized tunnel barrier using plasma oxidation method to form homogeneously oxidized AlO tunnel barrier. We sputtered 10 $\AA$-bottom Al layer and oxidized it by varying oxidation time for 5, 10, 20 sec. Subsequent sputtering of 13 $\AA$ - Al was performed and the matallic layer was oxidized for 120 sec. The electrical resistance changed from 700$\Omega$ to 2700$\Omega$ with increase of oxidation time, while variation of MR ratio was little spreading 27~31% which is larger than that of TMR device of ordinary single tunnel barrier. We calculated effective barrier height and width by measuring I-V curves, from which we found the barrier height was 1.3~1.5 eV, sufficient for tunnel barrier, and the barrier width(<16.2 $\AA$) was smaller than that of directly measured value by the tunneling electron microscopy. Our results may be caused by insufficient oxidation of Al precursor into $Al_2O_3$. However, double oxidized tunnel barriers were superior to conventional single tunnel barrier in uniformity and density. We found that the external magnetic field to switch spin direction of ferromagnetic layer of pinned layer breaking ferro-antiferro exchange coupling was increased as bottom layer oxidation time increased. Our results imply that we were able to improve MR ratio and tune switching field by employing double oxidized tunnel barrier process.

• 한국정보통신학회논문지
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• 제18권8호
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• pp.1818-1826
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• 2014

해면 상태의 변화는 수중 음향 통신 수신 신호에 전방 산란 및 도플러 확산을 야기하여 수신 신호의 진폭, 주파수 및 위상은 시간적으로 변화한다. 따라서 통신채널의 일관성 대역폭과 페이딩 변화에 의해 고속 동기식 디지털 통신 성능은 장애를 받게 된다. 본 논문에서는 2가지의 해면 상태에서 QPSK의 성능을 평가하였다. 해면 산란이 성능에 미치는 영향은 LFM 신호를 이용하여 구한 채널의 임펄스 응답과 시간 일관성을 기반으로 해석하였다. 잔잔한 해면보다 거친 해면 상태의 임펄스 응답은 불안정하고 일관성 시간은 짧다. 이러한 결과와 수신 신호의 포락선, 진폭 및 위상과의 관계를 해석하여 QPSK의 비트 오류율이 해면 상태와 직접적으로 관계되는 것을 확인하였다.

• 산업경영시스템학회지
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• 제44권4호
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• pp.154-168
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• 2021

COVID-19 has been spreading all around the world, and threatening global health. In this situation, identifying and isolating infected individuals rapidly has been one of the most important measures to contain the epidemic. However, the standard diagnosis procedure with RT-PCR (Reverse Transcriptase Polymerase Chain Reaction) is costly and time-consuming. For this reason, pooled testing for COVID-19 has been proposed from the early stage of the COVID-19 pandemic to reduce the cost and time of identifying the COVID-19 infection. For pooled testing, how many samples are tested in group is the most significant factor to the performance of the test system. When the arrivals of test requirements and the test time are stochastic, batch-service queueing models have been utilized for the analysis of pooled-testing systems. However, most of them do not consider the false-negative test results of pooled testing in their performance analysis. For the COVID-19 RT-PCR test, there is a small but certain possibility of false-negative test results, and the group-test size affects not only the time and cost of pooled testing, but also the false-negative rate of pooled testing, which is a significant concern to public health authorities. In this study, we analyze the performance of COVID-19 pooled-testing systems with false-negative test results. To do this, we first formulate the COVID-19 pooled-testing systems with false negatives as a batch-service queuing model, and then obtain the performance measures such as the expected number of test requirements in the system, the expected number of RP-PCR tests for a test sample, the false-negative group-test rate, and the total cost per unit time, using the queueing analysis. We also present a numerical example to demonstrate the applicability of our analysis, and draw a couple of implications for COVID-19 pooled testing.

• Journal of Biosystems Engineering
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• 제3권2호
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• pp.22-33
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• 1978

To maintain the self-sufficiency of food production , it is required to improved the productivity and increase the effective utilization of land in the double cropping areas using improved cultivation technology. The following reasons encourage this cours of action because the overlapping rice harvest and barely seeding seasons complete for labour, the lower price of barley makes it financially less attractive to grow and these two facts together are responsible for a decrease in barley being planted in certain more seasonably marginal double cropping areas. Fro these reasons, it is desirable to carry out tests to improve the current cultivation techniques . In this interest , the following studies were carried out in the experimental field located at Banweol-myeon, Whasung-jkun, Gyeonggi-do from October 1977 to July 1978 in order to establish the mechanical method of barley cultivation using the power tiller. The summarized results are as follows. 1. The work performance in the seeding operation using the rotary barley seeder was 68 minutes per 10 ares which compares favourably with 408 min/10a using the conventional method. This is only one sixth of the time required by th conventional method. The operating costs using the rotary barley seeder was 1, 463 won per 10 areas as against 3, 486 Won per 10 ares for the conventional method, showing a saving of about 50% in comparison with the conventional method. 2. In the manure spreading operation, the work performance was 25 min/10a for the manure spreading machine , compared to 1089 min/10a for the manual operations. This is about one fourth of the time required by the conventional method, The operating costs were 810 Won/10a for the machine and 857 Won/10a for the manual labour. This cost shows little advantage by the machine over the manual labor costs. The conventional method of manure spreading will continue pending decision which will develope and improve the machine.3. Work performance in the rolling operation using the barley rolIer was 30 min/lOa which compares favourably with 135 min/10a using conventional method. This was one fourth of the time required by the conventional method. The operating costs were 514 Won/103. for the machine and 1, 003 Won/lOa for manual labour. In the weed control operation, the work performance and operating costs were 45min/lOa, 1, 399won/10a for the herbcide application using the power sprayer, 1, 149min/10a 8, 541won/lOa for the conventional method respectively. This is 26 times higher efficiency in comparison to the conventional method. 4. In the harvesting operation using the reaper binder and tiller attachment, the work performance was 60min/lOa and represents a cost of 2, 039won/10a. The con\ulcornerventional method took 640min/10a at a cost of 4, 757won/lOa. The reaper binder showns a saving of one tenth over the conventional method. The automatic thresher is already recommended for the current situations, and is now being used. 5. From a comparison of the results of the above trials, the serial cultivation system using the attachment for the power tiller such as the rotary barley seeder is now to be recommended for the current barley cultivation system. It is also recommend from these results that the mechanized technology now available must be used to improve and maintain the increase in barley production. It is seen th1t this is the only course now avaihble to solve the peak seasonal requirements of labour needed for l11rvesting and seeding between rice and barley cultivation.

• Journal of the Korean Wood Science and Technology
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• 제16권4호
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• pp.48-53
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• 1988

본(本) 연구(硏究)는 리기다소나무판재(板材)를 이용(利用)하여 집성재(集成材)를 제조(製造)할 경우(境遇), 압체시간(壓締時間) 및 접착제도포량(接着劑塗布量), 목재(木材)의 함수율(含水率), Butt-joint의 틈새간격(間隔) 및 접착제(接着劑)의 종류(種類) 등(等)이 접착강도(接着强度)에 미치는 영향(影響)을 알아보기 위해 수행(遂行)되었다. 1. 리기다소나무집성재(集成材)의 제조(製造)에 수성(水性)비닐우레탄접착제(接着劑)를 사용(使用)한 결과(結果), 접착제도포량(接着劑塗布量) 200g/$m^2$, 압체압력(壓締壓力) 10kg/$cm^2$에서 12시간(時間) 압체(壓締)하면 기준강도(基準强度)(50kg/$cm^2$)이상(以上)에 달(達)하였다. 2. 판재(板材)의 함수율(含水率)의 접착력(接着力)을 크게 감소(減少)시켰으나, 고함수시(高含水時) 접착(接着)한 후(後) 기건(氣乾)하여 접착력(接着力)을 측정(測定)한 결과(結果), 100kg/$cm^2$)이상(以上)의 블록전단강도(剪斷强度)를 나타내었다. 3. 판재(板材)의 Butt joint 부분(部分)의 틈새간격(間隔)이 0.5mm이하(以下)인 경우(境遇), 강도(强度)값은 영향(影響)하지 않았고, 하중방향(荷重方向)이 접착력(接着力)과 수치(垂値)일 때가 수평(水平)일 때보다 강도성태(强度性能)이 양호(良好)하였다. 4. 시험(試驗)에 사용(使用)된 5종(種)의 접착제(接着劑) 중(中) 수성(水性)비닐우레탄수지접착제(樹脂接着劑)가 상태(常態) 및 내수접착력면(耐水接着力面)에서 가장 양호(良好)하였다.

• 한국해양생명과학회지
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• 제7권1호
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• pp.29-36
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• 2022

돌기해삼 Apostichopus japonicus는 주요 양식 대상 무척추동물로서 우리나라 연안 해역에 서식하고 있다. 본 연구는 방류 방법에 따른 단기간의 생리학적 스트레스 정도를 평가하기 위하여 heat shock protein 90 (HSP90) 유전자의 발현 변화를 실시간 정량적 중합효소연쇄반응법으로 조사하였다. 어린 돌기해삼을 비닐봉지에 산소 포장하여 30분간 수송하거나 방류 해역의 간조기에 1시간 공기 중에 노출된 실험군의 HSP90 유전자 발현은 대조군의 HSP90 유전자 발현에 비하여 통계학적으로 유의미하게 증가하였다(수송 후 실험군 p=0.001; 간조기 실험군 p=0.032). 어린 돌기해삼을 방류 후 6시간까지 분석한 결과, 선상에서 씨뿌림 방식으로 방류된 6시간째의 개체 및 호스를 통과하여 수중으로 방류된 2~6시간째의 HSP90 유전자 발현율은 대조군에 비하여 약간 감소하는 경향을 보였다(씨뿌림 실험군 p=0.069; 호스 방류군 p=0.093). 한편, 잠수부에 의해 수중에서 방류된 어린 돌기해삼은 방류 후 시간이 경과할수록 HSP90 유전자 발현율은 증가하는 패턴이 관찰되었다(p=0.061). 이상의 결과는 방류된 어린 돌기해삼의 단기간 스트레스 반응 연구와 효과적인 방류 방법의 개발에 HSP90 유전자 발현이 유용하게 사용될 수 있음을 시사한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권10호
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• pp.3475-3489
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• 2014

Here we present a simple flame detection method for an infrared (IR) thermal camera based real-time fire surveillance digital signal processor (DSP) system. Infrared thermal cameras are especially advantageous for unattended fire surveillance. All-weather monitoring is possible, regardless of illumination and climate conditions, and the data quantity to be processed is one-third that of color videos. Conventional IR camera-based fire detection methods used mainly pixel-based temporal correlation functions. In the temporal correlation function-based methods, temporal changes in pixel intensity generated by the irregular motion and spreading of the flame pixels are measured using correlation functions. The correlation values of non-flame regions are uniform, but the flame regions have irregular temporal correlation values. To satisfy the requirement of early detection, all fire detection techniques should be practically applied within a very short period of time. The conventional pixel-based correlation function is computationally intensive. In this paper, we propose an IR camera-based simple flame detection algorithm optimized with a compact embedded DSP system to achieve early detection. To reduce the computational load, block-based calculations are used to select the candidate flame region and measure the temporal motion of flames. These functions are used together to obtain the early flame detection algorithm. The proposed simple algorithm was tested to verify the required function and performance in real-time using IR test videos and a real-time DSP system. The findings indicated that the system detected the flames within 5 to 20 seconds, and had a correct flame detection ratio of 100% with an acceptable false detection ratio in video sequence level.

• 한국항행학회논문지
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• 제6권2호
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• pp.130-137
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• 2002

본 논문은 STTC(Space-Time Trellis Codes)의 디버시티 이득과 부호화 이득을 그대로 유지하면서, 다중 경로 페이딩 채널 환경에서의 성능 열화에 대한 면역성을 가진 STTC CDMA시스템을 제안하였다. 제안된 시스템은 STTC시스템에 PN(Pseudo Noise) 부호의 확산, 역확산 과정을 추가하여 구성할 수 있다. 다중 경로 페이딩 채널 환경에서 제안된 시스템은 다중 경로 신호를 검출한 후, PRC(Principal Ratio Combining)를 하고 복호하는 방식을 사용하고 있다. 컴바이닝과 복호 방식에 따라 모든 신호들을 ML 복호하는 최적의 복호 방식, 각각의 수신 안테나 별로 다중 경로 신호를 단순히 합하여 복호하는 방식, 각각의 수신 안테나 별로 다중 경로 신호를 PRC한 후 복호하는 방식, 그리고, 모든 수신 신호들을 PRC한 후 복호하는 방식이 있다. 이 방식들은 복잡도에 비례하여 좋은 성능을 보이며 4가지 방식들 모두 다중 경로 페이딩 채널 환경에서 발생하는 정정할 수 없는 오류율(irreducible error rate)을 제거함을 알 수 있다.