• Bangmulgwan gwa yeongu (The National Museum of Korea Journal)
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• v.1
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• pp.278-305
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• 2024

Gelatin dry plate photographs dating to the Japanese colonial era and the official documents from the Japanese Government-General of Korea Museum in the collection of the National Museum of Korea are significant materials documenting cultural heritage in North Korea before it was severely damaged in 1950 during the Korean War. There has been an increase in recent years in studies of Buddhist sculptures in North Korea based on these photographs and documents. This paper presents some new comments on the Buddhist sculptures at Seongbulsa Temple in Hwangju, one of the most famous temples in Hwanghae-do Province, based on the related existing research outcomes. This paper aims to facilitate a more comprehensive understanding of the Buddhist sculptures at Seongbulsa Temple by chronicling its history based on historical records, examining its current status, and exploring in detail the production dates and backgrounds of the Buddhist sculptures featured on gelatin dry plates. Prior to Korea's liberation from Japan in 1945, Seongbulsa housed at least seven sculptural items: two Bodhisattva statues, four Buddha statues, and a triad. Two items are from the early Goryeo period, one is from the late Goryeo period, three are from the early Joseon period, and one is from the late Joseon period. Among them, two surviving items are noteworthy. One is the early Goryeo-era Stone Seated Bhaishajyaguru Buddha photographed in Eungjinjeon Hall at Seongbulsa Temple. A close examination of a schematic drawing of the sculpture's pedestal made at the time it was photographed reveals that its material accords with the materials used for the headless Stone Seated Bhaishajyaguru Buddha and pedestal currently found in the old Sangwonam Hermitage site in the Inner Geumgang Valley of Jeongbangsan Mountain. This accordance could mean that the statue is a new significant example of early Goryeo Buddhist sculpture in North Korea. The other notable sculpture is the Gilt-bronze Seated Amitabha Buddha Triad created in 1454 (the second year of the reign of King Danjong) and discovered in Geungnakjeon Hall at Seongbulsa. This statue is currently in the collection of the Sariwon History Museum in Hwanghae-do Province. It is an important example of a dated small gilt-bronze Buddhist statue from the early Joseon period found in North Korea. This paper is a case study of Buddhist sculptures in North Korea, focusing on Seongbulsa Temple. Further utilization of the National Museum of Korea's gelatin dry plates will contribute to developing the study of the history of Korean Buddhist sculpture.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.157.1-157.1
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• 2016

In this work, we experimentally investigated the solar absorption performance of Cu-based scalable nanostructured surfaces and compared their performance with the conventional TiNOX. We fabricated Cu-based nanostructured surfaces with a controlled chemical oxidation process applicable to a large area or complex geometry. We optimized the process parameters including the chemical compounds, dipping time and process temperature. We conducted both lab-scale and outdoor experiments to characterize the conversion efficiency of each absorber surfaces with single and double glazing setup. Lab-scale experiment was conducted with $50mm{\times}50mm$ absorber sample with 1-sun condition (1kW/m2) using a solar simulator (PEC-L01) with measuring the temperature at the absorber plate, cover glass, air gap and ambient. From the lab-scale experiment, we obtained ${\sim}91^{\circ}C$ and $94^{\circ}C$ for CuO and TiNOX surfaces after 1 hr of solar illumination at single glazing, respectively. To measure the absorber performance at actual operating condition, outdoor experiment was also conducted using $110mm{\times}110mm$ absorber sample. We measured the solar flux with thermopile detector (919P-040-50). From outdoor experiment, we observed ${\sim}123^{\circ}C$ and $131^{\circ}C$ for CuO and TiNOX with 0.6 kW/m2 insolation at double glazing, respectively. We showed that the suggested nanostructured CuO solar absorber has near-equivalent collection efficiency compared with the state-of-the-art TiNOX surfaces even with much simpler manufacturing process that does not require an expensive equipment.

• Particle and aerosol research
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• v.14 no.4
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• pp.121-133
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• 2018

In this study, we developed a flat-plate type wet electrostatic precipitator that generates stable corona discharge compared to wire type discharge electrode. In order to compare the particle removal efficiency according to the shape of the discharge electrode such as the variation of the horizontal and vertical distance between spiked edges, and the variation of the height of discharge pin support were tested. As a result, when the horizontal distance between spiked edges was increased up to 36 mm, the vertical distance between spiked edges was increased up to 54 mm, and the height of the discharge pin support was increased up to 76 mm, the removal efficiency of PM10 was maintained at approximate 60.0%. Furthermore, the removal efficiency of particles over $5{\mu}m$ was about 80% or more. When the flow rate was 4 m/s, the gap between collection plates was 60 mm, and -14 kV was applied to the discharge electrode. The particle removal efficiency of the flat-plate type electrostatic precipitator was maintained when the horizontal and vertical distance between spiked edges, and the height of the discharge pin support was below a certain level. Those variables may be the important design factors for the shape of the discharge electrode. Therefore, when designing the electrostatic precipitator with multiple channels, the horizontal and vertical distance between spiked edges, and the height of discharge pin support must be selected in consideration of the weight of the discharge electrode and the processing cost.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.82-96
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• 2019

A semi-submersible structure has been widely used for offshore drilling and production of oil and gas. The small water plane area makes the structure very sensitive to weight increase in terms of payload and stability. Therefore, it is necessary to lighten the substructure from the early design stage. This study aims at an optimization of hull structure based on a sophisticated yield and buckling strength in accordance with classification rules. An in-house strength assessment system is developed to automate the procedure such as a generation of buckling panels, a collection of required panel information, automatic buckling and yield check and so on. The developed system enables an automatic yield and buckling strength check of all panels composing the hull structure at each iteration of the optimization. Design variables are plate thickness and stiffener section profiles. In order to overcome the difficulty of large number of design variables and the computational burden of FE analysis, various methods are proposed. The steepest descent method is selected as the optimization algorithm for an efficient search. For a reduction of the number of design variables and a direct application to practical design, the stiffener section variable is determined by selecting one from a pre-defined standard library. Plate thickness is also discretized at 0.5t interval. The number of FE analysis is reduced by using equations to analytically estimating the stress changes in gradient calculation and line search steps. As an endeavor to robust optimization, the number of design variables to be simultaneously optimized is divided by grouping the scantling variables by the plane. A sequential optimization is performed group by group. As a verification example, a central column of a semi-submersible structure is optimized and compared with a conventional optimization of all design variables at once.

• Particle and aerosol research
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• v.19 no.3
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• pp.53-62
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• 2023

This study compared the collection efficiency of a two-stage electrostatic precipitator (ESP) with a lightweight PET film-coated carbon electrode collector plate, depending on the relative humidity of the exhaust gas and the applied voltage to the pre-charger. It was confirmed that the onset voltage at which corona discharge occurs decreases and the discharge current decreases at the same voltage as the relative humidity increases. On the other hand, even though there was almost no change in the diameter of the particles generated depending on the relative humidity, the efficiency was higher at the same voltage as the relative humidity increased. In addition, by applying a two-stage ESP structure, the collection efficiency was higher than that of a single-stage electrostatic precipitator under the same conditions. The ESP using the carbon electrode coated with PET film used in this study is expected to be effective in various aspects such as weight and in the current situation where environmental regulations are rapidly tightening.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.349-358
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• 2004

A low pressure impactor is an impaction device to separate airborne particles into aerodynamic size classes at low pressure condition. We designed a two-stage low-pressure impactor to classify submicron sized environmental aerosols. Performance evaluation was carried out for stages 1 and 2 by using an electrical method. Monodisperse liquid dioctyl sebacate (DOS) particles were generated using evaporation-condensation process followed by electrostatic classification using a DMA (differential mobility analyzer). The test particles were in the range of 0.08∼0.8$\mu\textrm{m}$. For the evaluation of the impactor we used two electrometers; one was connected to the impaction plate of the impactor and the other was to the Faraday cage used as a backup filter. The effect of polydispersity of test aerosols on the performance was investigated. The results showed that the experimental 50-% cutoff diameters at each impactor's operation pressure were 0.53 and 0.187$\mu\textrm{m}$ for stages 1 and stage 2, respectively. The effects of operation pressure on the cutoff diameter and the steepness of collection efficiency curves were also investigated.

• Korean Journal of Applied Biomechanics
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• v.15 no.1
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• pp.259-274
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• 2005

The purpose of this study was to compare the kinematic and kinetic parameters of lower extremity joints between novice and experienced sports aerobic dancers during two heights of depth jumps. Four male dancers were participated in this study and they performed 40cm and 60cm height depth jump three times, respectively. Four ProReflex MCU cameras (100frame/sec) and a Kistler force plate (1000Hz) were used for data collection. The results indicated that the duration of contact phase of experienced group was shorter than that of novice group regardless of jump height. For minimum angle of hip, knee, and ankle joints, the novice group had tendency to decrease the angle but the experienced group had increased the joint angle with jump height. There was no difference of total ground reaction force between the groups but the reaction force had tendency to increase with jump height. Thus, this study implied that repetition of jump and landing may induce joint related injury and further study such as. EMG analysis of lower extremity can be needed to verify the relationship between injury and ground reaction force.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1417-1422
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• 2003

An electrical cascade impactor is a multistage impaction device to separate airborne particles into aerodynamic size classes using electrical method. We designed a real-time three-stage electrical low-pressure impactor, which is proper to nanometer sized environmental aerosols. Performance evaluation was carried out for stage 1 and 2. The monodisperse liquid dioctyl sebacate (DOS) particles were generated using condensation-evaporation followed by electrostatic classification using DMA (differential mobility analizer) for particles with diameters in the range of $0.04{\sim}0.8{\mu}m$. The evaluation of the electrical impactor is based on the use of two electrometers, one connected to the impaction plate of the impactor, and the other to the faraday cage as backup filter. The results showed that the experimental 50% cutoff diameters in the operation pressure were 0.53 and $0.12{\mu}m$ for stage 1 and stage 2. The effect of operation pressure on the cutoff diameter and the steepness of collection effcieicy curves is investigated.

• Journal of Power System Engineering
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• v.13 no.5
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• pp.67-75
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• 2009

Recently, the higher capacity waste heat recovery PDC clean ventilation system has a tendency which is increasing due to the excellent energy reduction in factory, big building, and so on. This system was developed to complement the room environment which is deteriorated. However, the researches and technologies about this system were not well studied. Specially, the characteristic for heat exchanger element used to this system were not well known. Therefore, this study was carried out to evaluate the mechanical properties of the heat exchanger element as the core parts compose of this system. From results, tensile strength and elongation of the plate type heat exchanger element had about 10.11~14.32 kgf/$mm^2$ and 8.0~16.2%, respectively.

• Solar Energy
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• v.7 no.2
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• pp.37-53
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• 1987

This study has been prepared for the purpose of developing the system performance prediction method of natural circulation solar hot water system. The storage tank of the natural circulation solar hot water system equipped with flat-plate solar collector is located at higher elevation than the solar collectors. Therefor, the storage tank temperature distribution formed accordance with configuration of storage tank by flow rate of circulating fluid affect system collection efficiency. In this study measure the storage tank temperature distribution with various experimental system under real sun condition and present the theoretical prediction method of the storage tank temperature. Moreover measure the flow rate not only day-time but also night-time reverse flow rate with die injection visual flow meter. Main conclusion obtain from the present study is as follows; 1) The storage tank temperature distribution above the connecting pipe connection position is the same as that of the fully mixed tank and below the connection position is the same as that of stratified tank. 2) The system performance sensitive to the storage tank temperature distribution. Therefore detailed tank model is necessary. Average storage tank temperature can be calculate 3% and storage tank temperature profile can get less than 10% difference with this model system.