• Safety and Health at Work
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• v.10 no.4
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• pp.452-460
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• 2019

Background: Monitoring and control of PM_2.5 are being recognized as key to address health issues attributed to PM_2.5. Availability of low-cost PM_2.5 sensors made it possible to introduce a number of portable PM_2.5 monitors based on light scattering to the consumer market at an affordable price. Accuracy of light scatteringe-based PM_2.5 monitors significantly depends on the method of calibration. Static calibration curve is used as the most popular calibration method for low-cost PM_2.5 sensors particularly because of ease of application. Drawback in this approach is, however, the lack of accuracy. Methods: This study discussed the calibration of a low-cost PM_2.5-monitoring device (PMD) to improve the accuracy and reliability for practical use. The proposed method is based on construction of the PM_2.5 sensor network using Message Queuing Telemetry Transport (MQTT) protocol and web query of reference measurement data available at government-authorized PM monitoring station (GAMS) in the republic of Korea. Four machine learning (ML) algorithms such as support vector machine, k-nearest neighbors, random forest, and extreme gradient boosting were used as regression models to calibrate the PMD measurements of PM_2.5. Performance of each ML algorithm was evaluated using stratified K-fold cross-validation, and a linear regression model was used as a reference. Results: Based on the performance of ML algorithms used, regression of the output of the PMD to PM_2.5 concentrations data available from the GAMS through web query was effective. The extreme gradient boosting algorithm showed the best performance with a mean coefficient of determination (R²) of 0.78 and standard error of 5.0 ㎍/㎥, corresponding to 8% increase in R² and 12% decrease in root mean square error in comparison with the linear regression model. Minimum 100 hours of calibration period was found required to calibrate the PMD to its full capacity. Calibration method proposed poses a limitation on the location of the PMD being in the vicinity of the GAMS. As the number of the PMD participating in the sensor network increases, however, calibrated PMDs can be used as reference devices to nearby PMDs that require calibration, forming a calibration chain through MQTT protocol. Conclusions: Calibration of a low-cost PMD, which is based on construction of PM_2.5 sensor network using MQTT protocol and web query of reference measurement data available at a GAMS, significantly improves the accuracy and reliability of a PMD, thereby making practical use of the low-cost PMD possible.

• KIEAE Journal
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• v.17 no.3
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• pp.83-90
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• 2017

Purpose: With the increase in the energy consumption in the building sector, many studies have recently been conducted to address this issue. Due to its efficiency, diverse studies on a light-shelf, which is a natural lighting system, are in progress. However, there has been no research on the external illumination that determines the performance of a light-shelf. Therefore, the present study aimed to prepare the external illumination standard for securing the lighting performance of a light-shelf through the light-shelf performance evaluation based on a 1:1 scale testbed, and to suggest a height-adjustable light-shelf based on an open and closed concept for the case in which the lighting performance of the light-shelf significantly deteriorates, by collecting the external illumination. Method: In this study, a 1:1 scale testbed was established for performance evaluation, and the external illumination standard for securing the performance of the light-shelf was prepared by comparing the lighting performance of the light-shelf depending on the open and closed condition of the light-shelf and the external illumination. Result: 1) In this study, a light-shelf that can be opened or closed depending on the external illumination was suggested. As a result, the prospect right can be secured by creating the condition where there is no light-shelf installation by moving the light-shelf to the top of the window when the lighting performance is not secured. 2) In the summer solstice, the external illuminations appropriate for lighting energy reduction were more than 75,000 lx and 60,000 lx for the light-shelf width of 0.3 m and 0.6 m, respectively. 3) In the intermediate period, the external illumination appropriate for lighting energy reduction was 60,000 lx. In the winter solstice, making the condition where there is no light-shelf installation by closing the light-shelf would be appropriate. 4) Based on the aforementioned results, the external illumination standard for the opening and closing of the height-adjustable light-shelf based on an open and closed concept suggested in this study was 60,000 lx, and the light-shelf with a width of 0.6 m would be advantageous for lighting energy reduction.

• Journal of Distribution Science
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• v.14 no.6
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• pp.89-98
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• 2016

Purpose - This article tackles risk communication issues and aims to address the characteristics of MERS risk information distribution in South Korea, and secondly to examine the communicative behavior of the public health authority in terms of the quality of communication strategies. Thirdly, the study attempts to figure out the risk communication to cope with MERS through the applications of SMCRE model in chronological order. We employ the social amplification of risk framework for analyzing the emergent public response as one of the main approaches. Research Design, Data and Methodology - The main framework of this study is theoretically based on the social amplification of risk, which describes signals about risk transmitted and processed by individuals and social groups. The model also reflects the interactions between social groups and institutes about disaster-related risk issues, which are potential amplifiers or attenuators of communication signals. S-M-C-R-E Model is methodologically employed to examine the social amplification for MERS risk information in each period, which we defined operationally. The proposed methodology allows the assessment of effectiveness and ineffectiveness on risk communication to be conceptualized as a countermeasure against disasters. The paper focuses on exploring how social risk amplification can be applied and organized in each stage. Results - The SMCRE model describes the exchange of risk information and is also applied to all forms of communication between stakeholders including public health authority, local government and media. Each factor of risk communication includes source, message, channel, receiver and effect. The results support that the effective risk communication involves not only the improved reliability of public health authority as a key factor of risk communication, but also a close cooperation and good collaboration with local governments. It does not seem to be possible that the government-initiated risk communication based on controllability and management cope effectively with infectious disease in early stage. The results of this study imply that the shared risks between local, regional and national authorities can enhance risk communication system. Conclusions - The study supports that the disparities in how disaster-related risk information is interpreted and coded, have made effective risk communication and public sense-making impeded. Our findings support a more communicative discussion about the role of risk information sharing between governments for the improvement of emergency management and underline the importance of social elements in the risk communication, such as relationship and trust building. Findings suggest that trust building between stakeholders could be added to help explain the processes of social amplification and attenuation of risk. It would be recommended that the continuous risk communication with all the involved stakeholders will be able to help national health promotion policy to be improved regarding emergency management. Furthermore, risk communication has to be a scientific approach for the communication pertaining to potentially sensitive or controversial situations with public concerns and low public trust.

• Journal of Korean Society for Geospatial Information Science
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• v.19 no.3
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• pp.57-66
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• 2011

The purpose of this study is to research into a method of selecting the subject parcel with a change in the category of land given surveying the land alteration state focusing on the present state of road in the government-owned and public land by using the fuzzy membership function and GIS spatial analysis. It selected the old town center of Incheon Jung-gu, and the new downtown & the forest land of Gyeyang-gu as the research subject region, and carried out GIS spatial analysis on a serial cadastral map, urban planning road layer of Korea Land Information System, practical width of road layer of Road Name Address Management System & cadastral data base, and then calculated the suitable index for the subject parcel with a change in the category of land by using the fuzzy membership function with having the critical value as the area ratio of each parcel on a serial cadastral map that was incorporated into road layer or practical width of road layer. It finally selected the parcel, which is different in land category from the real land usage, as the final subject parcel for altering land category, by using the screen of visualizing the suitable index and the aerial ortho photograph. As a result of the final selection, the fuzzy GIS spatial analysis method, which was suggested in this study, is judged to be efficient in the selection period and the methodology compared to the existing manual method. It could be confirmed to be more suitable method for downtown than forest land and for the new downtown than the old town center.

• Journal of Convergence for Information Technology
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• v.10 no.11
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• pp.47-54
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• 2020

This study proposes an NFC-based payment system that considers user convenience while expanding the existing payment method for RFID-based individual food and logistics waste equipment. In line with this trend, I proposed to apply NFC to the existing RFID-based food meter to release the food in the meantime and to address the problem of re-carrying due to card loss, card not possessed, and non-filling, and the question that could not be identified by various cumbersome procedures. NFC's function alone has been certified for its convenience, which led to its introduction and research in the period of time. Of course, we need to negotiate fees with the transportation card company, but if we see a market share related to transportation card soon, we think smooth negotiations will take place. NFC method will be expanded to all phones with iPhone NFC opening. Therefore, in the next study, we intend to apply the payment system in NFC by linking with local currency, mobile vouchers, and card companies, which are being paid as respective payment means according to the recent emergency support system for COVID-19.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.209-220
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• 2013

Handover is the technology to minimize data lose of mobile devices and make continuous communication possible even if the device could be moved from one digital cell site to another one. That is, it is a function that enables the mobile user to avoid the disconnection of phone conversations when moving from a specific mobile communication area to another. Today, there are a lot of ongoing researches for fast and efficient hand-over, in order to address phone call's delay and disconnection which are believed to be the mobile network's biggest problems, and these should essentially be resolved in all mobile networks. Thanks to recent technology development in mobile network, the LTE network has been commercialized today and it has finally opened a new era that makes it possible for mobile phones to process data at high speed. In LTE network environment, however, a new authentication key must be generated for the hand-over. In this case, there can be a problem that the authentication process conducted by the hand-over incurs its authentication cost and delay time. This essay suggests an efficient key caching hand-over method which simplifies the authentication process: when UE makes hand-over from oMME to nMME, the oMME keeps the authentication key for a period of time, and if it returns to the previous MME within the key's lifetime, the saved key can be re-used.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.3
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• pp.64-69
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• 2007

Motion control of the system is a position control of motor. Motion control of an uncertain robot system is considered as one of the most important and fundamental research directions in the robotics. Some distinguished works using linear control, adaptive control, robust control strategies based on computed torque methodology have been reported. However, it is generally recognized within the control community that these strategies suffer from the following problems : the exact robot dynamics are needed and hard to implement, the adaptive control cannot guarantee the performance during the transient period for adaptation under the variation, the robust control algorithms such as the sliding mode control need information on the bounds of the possible uncertainty and disturbance. And it produces a large control input as well. In this dissertation, a motion control for the unmanned intelligent robot system using disturbance observer is studied. This system is affected with an impact vibration disturbance. This paper describes a stable motion control of the system with the consideration of external disturbance. To obtain the stable motion independently against the external disturbance, the disturbance rejection is strongly required. To address the above issue, this paper presents a Disturbance OBserver(DOB) control algorithm. The validity of the suggested DOB robust control scheme is confirmed by several computer simulation results. And the experiments with a motor system is performed to give the validity of applicability in the industrial field. This results make the easier implementation of the controller possible in the field.

• Journal of Korean society of Dental Hygiene
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• v.6 no.4
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• pp.325-337
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• 2006

The purpose of this study was to examine the oral health state of the elderly in an effort to pave the way for dental health project planning for the elderly for the city of Jeonju and to help promote the oral health of the elderly population to which health care services weren't accessible a lot. The subjects in this study were 300 elderly people who were in their 60s and up and used 10 different welfare establishments for the elderly in Jeonju. A survey was conducted from May 3 through 13, 2005, by interviewing them in person, and the collected data were analyzed. The findings of the study were as follows: 1. In terms of the period of oral health examination, 44.1 percent of the 66-70 age group, 48.1 percent of the elementary school graduates and 39.4 percent of the house owners had their teeth examined whenever they had a toothache. So their cycle of oral health examination was statistically significantly different according to age(p<.05), education(p<0.001) and form of residence(p<0.001). 2. Regarding the necessity of prosthesis, prosthesis was needed by 52.1 percent of the age group from 71 to 80, 44.3 percent of the women, 48.9 percent of the men, 60.0 percent of the community college graduates and 55.9 percent who rent a house on a deposit or monthly basis. But there was no statistically significant gap among the groups. 3. As for the necessity of oral health education, the necessity of it was absolutely supported by 89.7 percent of the 66-70 age group, 76.0 percent of the women, 87.2 percent of the men, 95.3 percent of the middle school graduates and 87.7 percent of the house owners. Their age(p<.0.01), gender(p<0.05) education(p<0.05) and form of residence(p<0.01) made a statistically significant difference to that. 4. Concerning oral health education experience, 79.3 percent of the high school graduates and 79.8 percent of the house owners had never received oral health education, and that experience statistically significantly varied with education(p<0.001) and form of residence (p<0.001). 5. As to the biggest reason for oral health care, 50.0 percent found it necessary to take care of their teeth to ensure their own perpetual oral health, and 33.7 percent felt the need for that because they had a toothache. The above-mentioned findings indicated that the elderly people were definitely in want of oral health education. Dental hygienists in public dental clinics should serve as dental health educators to address their needs, and regular oral health care programs should be prepared to spread awareness about the importance of oral health among elderly locals.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.10
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• pp.1808-1814
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• 2008

In addition to RBL function, which is used to applying for spam e-mail filtering, as an effective way to deal with the recently widespread spam types, this paper proposes how to extract URL that was comprised in the original e-mail, apply it to RBL, and expand it. The BotNet, which is used to using for sending spam mails these days, has a problem that it is not able to solve with the distributed addresses of sent mails in spam e-mails. In general, as these spam e-mails are sent from the infected Zombi PC of individual user, the sent address itself is not efficient and is meaningless to use in RBL. As an effective way to filter spam e-mail sent by BotNet, this paper analyzes URLs that contained in the original spam e-mail and proposes how to effectively improve filter rate, based on the distribution data of URL site tempting users. This paper proposes the sending mechanism of spam e-mails from BotNet and the methods to realize those types of spam e-mails. In order to gather analyzable spam e-mails, this paper also carries out an experiment by configuring trap system of spam e-mail. By analyzing spam e-mails, which have been received during the certain period of experiment, this paper shows that the expanded RBL method, using URLs that contained in spam e-mails, is effective way to improve the filter distribution of spam e-mail.

• 한국사회정책
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• v.25 no.4
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• pp.233-263
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• 2018

This study sought to identify gender-specific mechanisms of increased suicide rates during economic crises in South Korea. In order to address research aims, we focused on two international economic crises: IMF financial crisis in 1997, and international recession in 2008. This study provides three main findings. First, different mechanisms increased suicide rates during the two economic crises. Particularly, the high level of unemployment raised suicide rates during the 1997 IMF while the high level of working poor in the 2008 recession. Second, suicidal risk patterns for men and women differed at each period. The 1997 crisis which mostly affected full-time permanent workers had had relatively greater impacts on men suicide, whereas the 2008 crisis which affected precarious workers had done on women suicide. Finally, our finding indicated that these gender-specific risk patterns had been derived from the gendered labour market and male-friendly social policy. Placing women at the periphery of the labor market and using them as a buffer in times of crisis, governments failed to protect them from their economic difficulties. Suicide is fundamental and important public health and social problems. These findings suggest that the national suicide prevention strategy should pay attention to the social determinants of suicide through gendered as well as population health perspectives.