• Journal of Korean Association for Spatial Structures
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• v.7 no.2 s.24
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• pp.105-114
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• 2007

Large span spaces have been widely used for various purposes including sports events in other countries. Due to increasing demands on multi-purpose use of such spaces, recently built large span sport facilities such dome stadiums have been required to accommodate sport events as well as performing events. Also, retractable ceilings and/or walls were generally adopted in those spaces for providing various event conditions. It seems obvious that the openings between diffuse fields and free field may cause difficulties in the acoustic design of such spaces In the present work, the acoustic characteristics of non-diffuse field has been investigated using 1/10 acoustic scale models. It was found that RTs at low- and mid-frequencies decayed faster than those at high-frequencies as the percentage of opening area increased. The decay rate of RTs at high frequencies were not influenced by increasing the area of an opening. Also high dependence of EDT on the percentage of opening area was observed at all frequency range. D50 was not improved by increasing the area of an opening up to 12.5% and then sharply increased. The application of Schroeder integration to evaluate the reverberation charateristics of coupled spaces may not be proper, since non-exponential decay process with double or triple decays of those spaces can not be properly defined. EDT seems more appropriate to predict reverberation at the early acoustic design stage of acoustically coupled spaces.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.522-525
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• 2018

In this paper, we design a UWB / WAS microstrip antenna for wireless local high - speed communication. The substrate of the proposed antenna is FR-4 (er = 4.3) and its size is $30[mm]{\times}30[mm]$. It is designed to have characteristics that can be used in the frequency bands of 3.5 [GHz] and 5.2 [GHz], which are UWB / WAS frequency bands. The simulation was performed using CST Microwave Studio 2014. Simulation results show that the gain is 1.592 [dBi] at 3.5 [GHz] and 2.210 [dBi] at 5.2 [GHz]. The S-parameter also showed a result of less than -10 [dB] (WSWR 2: 1) in the desired frequency band. Microstrip antennas have been miniaturized, high performance, and light weight, and excellent and low cost systems are continuously being developed. In addition, many people use wireless local area network systems used in homes, companies, and public facilities. Since the UWB / WAS technology is proposed according to the development of the system and the demand increase, the antenna that satisfies the above conditions will be designed and the technology applicable to the system will be used more conveniently.

• Journal of the Korean GEO-environmental Society
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• v.14 no.10
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• pp.39-47
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• 2013

Recently, there have been various domestic construction activities related to the reclamation of the dredged soils to expand the land use. However, the reclaimed grounds made of the dredged soils cause various problems due to highly compressible and low shear strength nature. Particularly, this nature induces huge problems in case of the harbor facilities and road construction on the reclaimed sites. Furthermore, in the reclamation activities, the marine dredged soils are often used instead of the well sorted sand, which induces problems of compressibilities. Therefore, in this study, the mechanical characteristics of artificial soil mixture of kaolinite representing the marine dredged soils and the pond ash. A large consolidometer is designed and manufactured to produce the artificial soil mixture. To represent various mixing ratio between the fly ash and bottom ash in the pond ash, six samples with the same stress history are made with different mixing ratio among kaolinite, bottom ash and fly ash. Isotropically consolidated and undrained compression tests are performed to investigate the shear characteristics of soil mixtures. Based on the experimental results, as the components of mixed ash increase, the friction angle increase and the cohesion values decrease. Also, the porepressure parameters at failure, Af increase with the mixing components of the pond ash. The portion of bottom ash has more impact on the shear behavior than that of fly ash.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.34 no.3
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• pp.67-77
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• 2016

This study was initiated from question raised on existing study achievement that purpose for Wolji construction simply was to build gardens. In this research, after raising a question on existing theory about the Wolji construction, another purpose of Wolji construction is investigated. Study result is as follows. First, two questions raised on Wolji construction are "Was Wolji constructed as a garden from the beginning?" and "Was Wolji region available land as now at time of creation?" However, it was verified that the purpose of Wolji construction was to use not as a garden but as a detention pond, and the land of such region was unserviceable at time of Wolji construction. Second, in terms of locations and Topography, it was confirmed that Wolji has a favorable condition for undercurrent function as it is positioned at the end point of flow path formed by gushout water spurting from the water flooded from Bukcheon, or low and wetland. Third, from hydraulic point of view, Bukcheon always has a possibility of flooding occurrence before completing river bank build up, and such flooding damage was curved at Guhwangdongwonji, and at Wolji once again in order to prevent the damage spread into the center of Wanggyeong. Fourth, from urban planning point of view, it was confirmed that urban functions were not established in Wolji region before Wolji construction, and urban planning was completed through the opening of roads and others, after Wolji construction. Fifth, it was confirmed that inflow and outflow device of Wolji, and vertical stone platform at western side of Wolji were the facilities to provide sufficient functions as detention ponds.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.731-732
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• 2007

This paper presents the final configuration of test field and test items for the application of IEC 60364-4-44 in Korea. IEC 60364-4-44 provides rules for the protection against the effects of conducted and radiated disturbances on electrical installations. Especially this standard deals with the protection of low voltage facility against the ground fault in the high voltage side of power distribution system. Many countries define the regulations on the use of electrical facilities based on their own power system and technical references which are considered to be suitable for them. The background of circuit of IEC 60364-4-44 is based on the ungrounded system as most of European countries. However, domestic electric power distribution system is based on multi-grounding system different from European system. Therefore, it is necessary to evaluate or prove the effect of the IEC 60364-4-44 for introducing and applying it to the domestic grounding system as a national standard. The authors with KEA(Korea Electric Association) carried out a project on the application of IEC 60364-4-44 to Korean electrical installations of buildings sponsored by Korean ministry of commerce, industry and energy for three years(2004.4.1$\sim$2007.3.31). The test field is established in K.E.R.I.(Korea Electrotechnology Research Institute), which is the purpose of evaluating the formula to calculate touch voltage and stress voltage in the IEC standards. This paper presents some considerations and final configuration of test field to evaluate and introduce the IEC 60364-4-44 applicable to domestic rule for the protection against ground fault.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2001.06a
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• pp.51-64
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• 2001

The qualities including taste of sweetpotato stored during the winter which can display in the spring market in Korea are affected by availability of storage for the roots. In order to make high storage availability of sweetpotato, the postharvest handlings should be done thoroughly from the moment of harvest until shipping them to the market. A lot of procedures that must be handled carefully for improving postharvest management are as follows; digging, trimming, gathering, putting in storage containers, carrying them from field to house, curing, storing, washing, drying, selecting marketable roots, packing and shipping to the market, etc.. Sweetpotatoes have a high moisture content, and a relatively thin and delicate skin, and are sensitive to chilling, so careless postharvest handling can lead to both quantitative and qualitative losses which may be extremely high in some circumstances. From now on research has concentrated on the improvement of postharvest conditions to increase yield and lower disease rates. Storage, which makes sweetpotatoes available through out the year, benefits both the producer and the consumer. Seven very important points must be needed in order to get the best quality marketable roots in the storing of sweetpotatos : $\circled1$The storage house must be clean and sanitary, $\circled2$The crop must be harvested before the first frost to avoid low-temperature injury, $\circled3$Particular care must be taken to avoid cutting, bruising, or other injuries of the sweetpotatoes during digging, picking up, grading, placing in containers, and moving to the storage house, $\circled4$Select sound, disease-free roots for storage $\circled5$Sweetpotatoes should be stored in properly stacked containers $\circled6$Cure immediately after harvest, preferably at 32∼33$^{\circ}C$ and 90 to 95 percent relative humidity for 4 to 7 days, After curing the temperature should be reduced to 13$^{\circ}C$ to 16$^{\circ}C$ by ventilating the storage with outside air. $\circled7$Store at 12$^{\circ}C$ to 14$^{\circ}C$ and a relative humidity of 80 to 85 percent. Storage houses should be located on suitable sites and should be tightly constructed and insulated so that temperature and humidity will be uniform. Sweetpotatoes are usually not washed and graded, and lately sometimes washed, graded, waxed, before being shipped to market. Consumer packaging of sweetpotatoes in paper boxes(10-15kg) or film bags is done mainly to aid marketing. The shelf life of washed roots in consumer packs in only 1 to 2 weeks. Weight loss of roots during marketing is much less in perforated film bags than in mesh and paper bags. Perforation of 0.8 to 1kg polyethylene bags with about six 6mm holes is essential ; to lower the internal relative humidity and avoid excessive sprouting, rooting, and dampness. Development and use of better postharvest handling with good storage facilities or marketing methods can minimize sweetpotate losses and has an effect of indirectly increasing productivity and farmer’s income.

• Ecology and Resilient Infrastructure
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• v.8 no.4
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• pp.273-280
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• 2021

In the past, the government made a total of 357 hydrophilic districts into parks to create rest areas in the national river with the four major river projects. According to the results of the survey, 60 water-friendly districts with low utilization were lifted in January 2017, and 297 water-friendly districts are currently being managed. Local governments are in charge of the maintenance costs necessary to maintain these hydrophilic districts, which require considerable costs, so it is necessary to accurately grasp the characteristics and needs of local residents at the operation stage after designation. In this study, the characteristics of local residents in the hydrophilic district were analyzed by correlating social factors with river users, crawling social network data to analyze visit patterns, and derived related Keywords, and analyzed the characteristics of the hydrophilic district. The study target areas are Samrak and Daejeo Ecological Park, located downstream of the Nakdonggang River. Social factors analyzed real estate transaction price data, economic activity income, households, stress perception rate, and pet breeding status through public data provided by Statistics Korea, and analyzed user visit patterns and image keywords on weekends.

• Land and Housing Review
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• v.12 no.2
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• pp.13-32
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• 2021

Rapid urbanization has resulted in the unprecedented growth of population in Metro Manila, the Philippines and has led to a 'dual' housing crisis - vacant/unoccupied socialized housing and a chronic housing shortage or delayed housing supply. By developing two GIS-based statistical models, this study is to examine socialized housing in comparison with private housing with respect to location patterns, integration, accessibility, social and economic aspects, and vulnerability to environmental hazards. Multiple regression analysis was integrated with the GIS to identify significant variables that influence the spatial distribution of socialized housing. The comparison between the two regression models has shown that socialized housing is located in areas with inappropriate land use and poor accessibility to transportation facilities and built urban resources. Moreover, both regression models have proven the statistical significance of the vulnerability of socialized housing to environmental hazards. The finding explains how the current housing policies do not address the country's housing crisis, especially for the marginalized and low-income households. Thus, the findings provide implications for urban planners and local decision-makers in reforming the current policy interventions.

• Journal of Korean Academy of Oral Health
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• v.42 no.4
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• pp.216-223
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• 2018

Objectives: The purpose of the study was to investigate factors affecting the assessment of objective and subjective masticatory ability in the elderly, and to evaluate masticatory ability assessment more accurately. Methods: A total of 112 participants were recruited after oral examination in senior citizen welfare facilities. The participants' masticatory ability was evaluated objectively (Mixing ability index; MAI), and subjectively (Key food intake ability; KFIA). Participants' general characteristics and oral health-related variables were also recorded. Based on masticatory ability assessment, participants were classified as either high or low. IBM SPSS Statistics Ver.23.0 was used for all analyses, including descriptive statistics, Chi-square test, Mann-Whitney U test, Spearman rank correlation, and Logistic regression analysis. Results: Higher masticatory ability was positively correlated with higher scores on MAI and KFIA. Additionally, there was a significant positive correlation between MAI and KFIA. When analyzing factors affecting objective and subjective masticatory ability assessments, Functional tooth units (FTUs) were revealed as a related factor. In subjective masticatory ability assessment, oral moisture, difficulty in chewing, and the Geriatric Oral Health Assessment Index (GOHAI) were also influential factors. Conclusions: In order to accurately assess masticatory ability, it is necessary to use both objective and subjective measures. Additionally, to improve the masticatory ability in the elderly, treatment should be provided to improve overall oral health and satisfaction.

• Safety and Health at Work
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• v.10 no.2
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• pp.229-236
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• 2019

Background: Emerging reports suggest the potential for adverse health effects from exposure to emissions from some additive manufacturing (AM) processes. There is a paucity of real-world data on emissions from AM machines in industrial workplaces and personal exposures among AM operators. Methods: Airborne particle and organic chemical emissions and personal exposures were characterized using real-time and time-integrated sampling techniques in four manufacturing facilities using industrial-scale material extrusion and material jetting AM processes. Results: Using a condensation nuclei counter, number-based particle emission rates (ERs) (number/min) from material extrusion AM machines ranged from $4.1{\times}10^{10}$ (Ultem filament) to $2.2{\times}10^{11}$ [acrylonitrile butadiene styrene and polycarbonate filaments). For these same machines, total volatile organic compound ERs (${\mu}g/min$) ranged from $1.9{\times}10^4$ (acrylonitrile butadiene styrene and polycarbonate) to $9.4{\times}10^4$ (Ultem). For the material jetting machines, the number-based particle ER was higher when the lid was open ($2.3{\times}10^{10}number/min$) than when the lid was closed ($1.5-5.5{\times}10^9number/min$); total volatile organic compound ERs were similar regardless of the lid position. Low levels of acetone, benzene, toluene, and m,p-xylene were common to both AM processes. Carbonyl compounds were detected; however, none were specifically attributed to the AM processes. Personal exposures to metals (aluminum and iron) and eight volatile organic compounds were all below National Institute for Occupational Safety and Health (NIOSH)-recommended exposure levels. Conclusion: Industrial-scale AM machines using thermoplastics and resins released particles and organic vapors into workplace air. More research is needed to understand factors influencing real-world industrial-scale AM process emissions and exposures.