• Journal of Marine Life Science
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• v.5 no.2
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• pp.81-91
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• 2020

This study was conducted to find the faunal composition and distribution patterns of macrobenthos where the sand tidal flat around barrier island at Nakdong River estuary in May, 2016 and 2017. The number of species ranged from 31 to 39, and density was from 789 to 1,644 ind.m^-2 during the study period in the three tidal flats. The number of species and density were the highest in the tidal flat of Shinja-do and Jinwoo-do, respectively. The dominant species were Gammaridae unid. in amphipods of crustacea, Scoletoma heteropoda, Scoloplos armiger, Heteromastus filiformis, Prionospio japonica in polychaeta and Batillaria cumingii, Laternula marilina in mollusks from the three tidal flats. The proportion of carnivores such as crustacea and mollusks was higher in the upper part of the tidal flat, and polychaetes of deposit feeders, dominated in the middle and lower tidal flat. Overall, the intertidal macrobenthic communities in the study area showed a high proportion of carnivores. However, the sites where the mud content is high such as muddy sand sites, they showed a higher proportion of surface deposit feeders belonging to tube-builders which contribute to sediment stability. From this study, it seemed that the macrobenthic fauna of the sandy tidal flat at the Nakdong River estuary showed a similar fauna composition and zonal distribution patterns from those in other sandy tidal flats in Korea.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.28 no.4
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• pp.143-157
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• 2023

This study confirmed the characteristics of macrobenthic community due to anthropogenic environmental changes in the Boryeong Jugyo tidal flat, where the habitat of manila clam (Ruditapes philippinarum) and mud shrimp (Upogebia major) is separated. The total number of occurring species was 55 during the study period with an average habitat density of 338 ind./m² and a biomass of 212.2 gWWt/m². The number of occuring species increased from 27 species at the upper flat to 37 species at the lower flat, and the dominant species differed by tide levels (Upper: Leonnates persica, Middle: Heteromastus filiformis, Lower: R. philippinarum). The macro-benthic community sturctures of the top 10 species using cluster analysis and nMDS were divided into two groups, focusing on Manila clam culture farm of lower flats and middle flats with high habitat density, reflecting the influence of specific species. The sediment composition of the U. major habitat space fluctuated highly, but it was maintained annually, and the sorting coefficient was 2.1 𝜑, and the proportion of the same particle size was increased. In particular, because the middle flat has a dense anthropogenic impact, a dominant species, H. filiformis dominated and revealed a relationship with the density of burrow holes of U. major, which is considered to be a biological interaction between these two macrofauna in this tidal flat.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.927-930
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• 2004

We report on a new type of a flat and thin display with a secondary emission electron source. In this display device electrons are multiplied between two secondary emission plates under a high frequency electric field. This principle has a few important advantages over a field emission display: the emission comes from flat plates, which reduces the life-time problems of ion bombardment of field emitter tips. Furthermore, the electron emission is space charge limited which gives a uniform electron distribution. The electrons are extracted from the source and accelerated to a phosphor screen to generate light. Gray levels are made by pulse width modulation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2114-2120
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• 1997

This paper presents precision machining of sculptured surfaces with a flat end cutter as follows; tool path generation using partition machining method and elimination interference. These days many researchers are getting interested in flat end cutter having a good cutting performance as machine tool for machining sculptured surfaces. It can get low curvature surfaces and have a much better material removal rates and longer tool life. Partition machining method is the first submitted in this paper. It is a new method of tool path generation, which means the way to map surfaces under the normal vector and then to cut them partially.

• Journal of the Korean housing association
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• v.15 no.2
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• pp.97-105
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• 2004

This research is about Apartment Remodeling Upgrading Programme by Singapore Housing Development Board(HDB). For this study, we visited HDB and made field survey of the projects. There are basically three types of upgrading, namely, Precinct Upgrading, Apartment Block Upgrading and Flat Upgrading. Precint Upgrading refers the upgrading of services and facilities of the precinct. It involves the extention of open space, car-park, commercial space and additional covered linkways. These afford the residents greater convenience and comfort and generally enhance the environment of the community. Apartment Upgrading refers the upgrading of the block facade, improvements to the elevator, lift lobbies, letter boxes, trash chute and rain chute. The upgrading improves the quality of life of the residents. Flat Upgrading Involves the addition of space which may be in the form of a new Utility-room, replacement of old services, piping and equipment within an apartment unit. These provide the residents with a bigger and more comfortable living space.

• Journal of the Korean Wood Science and Technology
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• v.42 no.6
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• pp.708-713
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• 2014

Trusses are widely used for wooden houses in the areas where wood construction in generalized for residential housings such as North America, Australian, New Zealand. In Korea, joist and rafter system is generally used because of the production cost, transportation cost and lack of experience required for truss manufacturing. In this study, roof trusses and flat trusses were manufactured by using oriented strand board (OSB) gusset plates for field assembly and tested under bending load to obtain the allowable loads. The allowable load and the actual load of 6m span roof trusses were 10.60 kN and 5.26 kN, respectively, which is regarded to be sufficient for use in construction. The allowable load and the actual load of 6m span floor flat trusses were 7.18 kN and 7.43 kN, respectively. For flat trusses, the allowable load is slightly lower than the actual load but the difference in very small, and it is thought that flat trusses can be used for construction by applying small change of structures and members.

• Journal of the Korean Wood Science and Technology
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• v.45 no.4
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• pp.382-398
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• 2017

This study was conducted to identify the potential of Quercus mongolica (QUM), Pinus densiflora (PID) and Pinus rigida (PIR) as a raw material for pellet production. Larix kaempferi (LAK), which has mostly been used for pellet production in Korea, was also used as a control. All specimens contained very minimal amounts of sulfur and chlorine. Ash content of LAK was the lowest, followed by PID, PIR and QUM. For the size distribution, the mass fraction between 0.42 mm and 0.25 mm was the highest in PIR. Most fuel characteristics of the produced wood pellets improved with the use of 12% moisture content (MC) particles and the increase of the ratio of length to diameter of a hole in flat-die (L/D ratio). When the MC, bulk density and durability of QUM, PID, PIR and LAK pellets was compared with the standards of the KFRI and ISO, the use of wood particles of 12% MC and flat-die with an L/D ratio of 5.00 for PID particles are suitable for high-quality pellets in the aspects of all fuel characteristics. For PIR and QUM, further work is needed to seek the optimum conditions for the production of high-quality and durable pellets.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.05a
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• pp.86-90
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• 2006

Discharge of the flat lamp lighting source research are requested very much. For improving brightness, life time, efficiency of flat lamp, plasma diagnosis of the f1at lamp lighting source to understand property of lighting source is very important. Distance of discharge electrode is 5.5mm and width is 16.5mm, we have measured electron temperature and electron density measured with single Langmuir probe in flat lamp. We have tested the discharge from 100 Torr to 300 Torr pressure. The pulse is rectangular pulse with frequency 20kHz and duty ratio 20%. In result, electron temperature decreases and electron density increase as increase the gas pressure and electron temperature decreases and electron density increase as increase the voltage.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.7
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• pp.98-104
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• 2022

Circular sawing and milling are general machining processes used for routing fiber-reinforced plastics (FRP). In this study, the productivity and cutting quality of a circular saw and flat endmill were compared. As a result, the productivity of the circular saw was approximately ten times higher than that of the endmill for the same tool life, and the burr size of the circular saw was 14 times smaller than that of the flat-end mill. The spectrogram analysis of the cutting sound also showed that the acoustic emission of the circular saw was more uniform than that of the flat end mill. Circular sawing is thus a more suitable process for the straight cutting of pultrusion FRP than a flat endmill.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.3
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• pp.109-121
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• 2020

Converting the agricultural land-use of rice field to upland has been increasingly conducted as farmers encourages themselves to grow higher value-added crops on rice fields under the policy support. Comparing to rice field, Upland shows different characteristic of discharge due to the slope, scale, and shape of field and characteristics of rainfall event. In this study, we designed the experiment fields reflecting flat-upland characteristics with different land scale, and tried to collect the discharge and load data. Soybeans and corn were selected as target crops considering the possibility of large-scale cultivation and crop demand. The cultivation was conducted during the growth period in 2019 with 3 different field scales. Hence, we have collected the discharge data from 17 rainfall events and the load data for 8 rainfall events. As a result, the magnitude of rainfall events and the discharge duration were found to have a strong positive correlation and field discharge occurred during the period by 55% to 83% of rainfall duration. Besides we found other relationships and characteristics of rainfall event, discharge, and pollutant load and also pointed out that continuous monitoring and more data are required to derive statistically significant results. Compared with slope-field monitoring data obtained from the precedent research, the runoff ratio of the flat-fields was significantly lower than slope-fields. Overall the discharge in the slop and flat-fields shows appreciably different characteristics so that the related researches need to be further conducted to reasonably assess environmental impact of agricultural activities at flat-field.