• Journal of architectural history
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• v.5 no.1 s.9
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• pp.50-72
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• 1996

The typical Japanese house has the characteristics of open dwellings to make them cool in the hot and humid summer. And then the traditional town house 'Machiya', being built very closely to each other and walled up both sides, it has taken the open-oriented characteristics in itself. The purpose of this study is to clarify that the open-oriented of traditional 'Machiya' has been succeeded to the new 'Machiya' in the latest. The new 'Machiya' shows the open-oriented, taking the ventilative 'Huki-nuke' space of traditional 'Machiya' as the new spatial formal elements, in the changes such as scale material space organization. The characteristics of 'Huki-nuke' space are represented as follows ; 1. The facade of the traditional 'Machiya', which has taken on a semitransparent qualty, has been generally changed to the closing qualty except for the open parts of shop and garage. This facade of the new 'Machiya' has been taken to be in keeping with the existing town as much as possible. 2. A series of three rooms, composed of shop/living dining kitchen/room from the road, have been dispersed to every floors in a building with a very extensive scale. But this serial and linear type remains as the loosefit space, and the long dwellings of the upper stories are divided by type each dwelling unit. 3. 'Tori-niwa', which is a consecutive and penetrating space, connects the road with the rooms of dwelling and functions as the circulation of man thing energy, The new 'Machiya' changed to the multi-story, the corridor and the stair have been fumed up as the elements in the place of 'Tori-niwa' The 'Huki-nuke' space was locted in the hall, stairwell, living dining kitchen room, and so on. 4. The small court yard 'Tsubo-niwa' and back yard 'Ura-niwa' at the both ends of living spaces would be made a hole in a series of rooms and enclosed by the neighboring 'Machiya'. On the contrary the new 'Machiya' at present takes in the private and closing organization enclosing the innercourt. 5. The open-oriented ${\ulcorner}$In${\lrcorner}$ or ${\ulcorner}$Out${\lrcorner}$ is not brought out because of the delicate spatial formal configuration in the traditional 'Machiya'. But the open-oriented ${\ulcorner}$In${\lrcorner}$, all sides being closed by walls, is well brought out in the new 'Machiya'.

• Nuclear Engineering and Technology
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• v.18 no.2
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• pp.97-106
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• 1986

System thermal-hydraulic parameters and simulated, using the best-estimate system code(RELAPS/MODl/NSC), based upon the sequence of events for the KNU1 (Korea Nuclear Unit 1) loss of offsite power transient at 77.5% power which occurred on June 9,1981. The results are compared with the actual plant transient data and show good agreements. After the flow coastdown following the trips of both reactor coolant pumps, the establishment of natural circulation by the temperature difference between the hot and the cold legs is confirmed. The calculated reactor coolant flowrate closely approximates the plant data indicating the validity of relevant thermal-hydraulic models in the RELAP5/MOD1/NSC. Results also show that the sufficient heat removal capability is secured by the appropriate supply of the auxiliary feedwater without the operation of S/G PORVs. In addition, a scenario accident at full power, based upon the same sequence of events described above, is also analysed and the results confirmed that the safety of KNU1 is secured by the appropriate operation of the S/G PORVs coupled with the supply of auxiliary feedwater which ensures sufficient heat removal capability. The characteristics of the non-safety related components such as the turbine stop valve closing time, S/G PORV settings etc. are recognized to be important in the transient analyses on a bestestimate basis.

• Tunnel and Underground Space
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• v.31 no.1
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• pp.41-51
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• 2021

The hydraulic fracturing developed to improve permeability of tight reservoir is one of key stimulation technologies for developing unconventional resources such as shale gas and deep geothermal energy. The experimental study was conducted to improve disadvantage of hydraulic fracturing which has simple fracture pattern and poor fracturing efficiency. The fracturing experiments was conducted for tight rock using various fracturing fluids, water, N2, and CO2 and the created fracture pattern and fracturing efficiency was analyzed depending on fracturing fluids. The borehole pressure increased rapidly and then made fractures for hydraulic fracturing with constant injection rate, however, gas fracturing shows slowly increased pressure and less fracture pressure. The 3D tomography technic was used to generate images of induced fracture using hydraulic and gas fracturing. The stimulated reservoir volume (SRV) was estimated increment of 5.71% (water), 12.72% (N2), and 43.82% (CO2) respectively compared to initial pore volume. In addition, permeability measurement was carried out before and after fracturing experiments and the enhanced permeability by gas fracturing showed higher than hydraulic fracturing. The fracture conductivity was measured by increasing confining stress to consider newly creating fracture and closing induced fracture right after fracturing. When the confining stress was increased from 2MPa to 10MPa, the initial permeability was decreased by 89% (N2) and 50% (CO2) respectively. This study shows that the gas fracturing makes more permeability enhancement and less reduction of induced fracture conductivity than hydraulic fracturing.

• Environmental and Resource Economics Review
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• v.27 no.2
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• pp.261-286
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• 2018

This paper evaluated the economic feasibility of the life extension of Kori unit 1 and Wolsong unit 1 according to the types of the nuclear power plants (NPPs) and the life extension period comparing to the levelized costs of energy (LCOE) of the new NPPs, coal-fired plants (CFPs), and combined cycle gas turbine (CCGTs) which proposed in the $7^{th}$ Basic Plan for Electricity Supply and Demand. The economic feasibility of the life extension of NPPs using LCOE method is affected by the types of NPPs, lifetime extension periods, discount rate, and capacity factor. According to the analysis results, the pressurized light water reactor (PWR) is more economical than the pressurized heavy water reactor (PHWR). Comparing the economical efficiency between the life extension of NPPs and other alternatives, the operation of the PWR for 20 years is more economical than the one of new NPPs and CFPs. However, 20 years of life extension of PHWR is more economical than the CCGTs, but less economical than new NPPs and CFPs. In summary, the 20 years of life extension of the NPPs seems to be more, especially for the PWR, which is more cost effective than other generation alternatives. Therefore, the government policy of the life extension of NPPs need to be a selective approach that simultaneously considers both safety and economics rather than closing all NPPs.

• Nuclear Engineering and Technology
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• v.52 no.7
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• pp.1396-1408
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• 2020

Filtered containment venting system (FCVS) is one of the severe accident mitigation systems designed to release containment pressurization to maintain its integrity. The thermal-hydraulic behaviors in FCVSs are important since they affect the operation characteristics of the FCVS. In this study, a representative FCVS was modeled by RELAP5/Mod3.3 code, and the Station BlackOut (SBO) was chosen as an accident scenario. The thermal-hydraulic behaviors of an FCVS during long-term operation with two venting strategies (open-and-close strategy, open-and-non-close strategy) and the sensitivity analysis of important parameters were investigated. The results show that the FCVS can operate up to 250 h with a periodic open-and-close strategy during an SBO. Under the combined effects of steam condensation and water evaporation, the solution inventory in the FCVS increases during the venting phase and decreases during the intermission phase, showing a periodic pattern. Under this condition, the appropriate initial water level is 3-4 m; however, it should be adjusted according to the environment temperature. The FCVS can accommodate a decay heat power of 150-260 kW and may need to feed water for a higher decay heat power or drain water for a lower decay heat power during the late phase. The FCVS can function within an opening pressure range from 450 kPa to 500 kPa and a closing pressure range between 250 kPa and 350 kPa. When the open-and-non-close strategy is adopted, the solution inventory increases quickly in the early venting phase due to steam condensation and then decreases gradually due to the evaporation of water; drying-up may occur in the late venting phase. Decreasing the venting pipe diameter and increasing the initial water level can mitigate the evaporation of the scrubbing solution. These results are expected to provide useful references for the design and engineering application of FCVSs.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.4
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• pp.224-232
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• 2004

Sedimentation changes related with bottom shear stress attenuation at JangHang channel in the Keum River Estuary, where several huge coastal constructions including an estuarine dam have been conducted for last 2 decades, were evaluated for 7 cases to figure out passage hindrance through the channel by a hydrodynamic model using hind-casting technique from 1988 to 2000 at every 2 years interval. Due to the construction of Keum River Estuary Dam, the maximum bottom shear stress rapidly lessened to $0.2-0.6N/m^2$ compared to$1-2N/m^2$ in natural status. Especially it marks below the critical shear stress of $0.4N/m^2$ resulting in severe siltation in the channel just after the closing of dam gates in 1994. It is concluded that the dam may block the tidal energy propagation to upstream and directly results in sedimentation environment in front of dam site. It is also revealed that at least 20% of passage hindrance of small fishing boats through the channel could be counted due to sedimentation by analysis of predicted mean spring tides.

• The Journal of the Acoustical Society of Korea
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• v.30 no.7
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• pp.390-395
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• 2011

This paper covers the studies on common voice parameters through the voice analysis of female main news anchors on weekday evening by the station, and differences of relative voices and sounds among stations. To examine voice characteristics, 6 voice parameters were analyzed and it showed anchors of each station had distinctive characteristics of voices and phonations over all fields except the speech rate, and there were also differences in sound systems. As major analysis parameters, basic pitch, tone of the 1st formant and pitch ratio, level of closeness by pitch bandwidth, type of sentence closing through average pitch position within pitch bandwidth, average speech rate, and acoustic tone analysis by energy distribution by frequency band were used. Analyzed values and results could be referred to and utilized in the criteria of phonation characteristics for domestic female news anchors.

• Tunnel and Underground Space
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• v.22 no.6
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• pp.373-382
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• 2012

Cessation of dewatering usually results in groundwater rebound after closing an underground coal mine because the mine voids and surrounding strata flood up to the levels of decant points such as shafts and drifts. Several numerical models have been developed to predict the timing, magnitude and location of discharges resulting from groundwater rebound. This study reviews the numerical models such as VSS-NET, GRAM and MODFLOW, and compares their scopes of assessment at different spatial and time scales. In particular, the GRAM model was reviewed in details to implement it. This paper describes the implementation of GRAM model and its application to the Dongwon coal mine in Korea. The application showed that the groundwater level modeled at the shaft of Dongwon coal mine using the GRAM model is similar to the observed one in the field.

• Journal of the Korean Institute of Gas
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• v.17 no.3
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• pp.14-19
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• 2013

This paper presents an experimental study on the safety of a valve for a special gas cylinder. The test valves that were randomly dismantled from the special gas cylinder were experimented on the gas leakage and operation safeties. The crack, wear and deformation of the valve body, screw thread, safety disk, vent hole, stem and handle components that may affect to the gas leakage safety of a used valve were not found in this experimental study. A painted handle of a valve was partly stripped from the coated surface, and the surface of PT screw of a used valve body was rusted. But, these paint and rust problems do not affected to the gas leakage safety of used valves. And there was no gas leakage in the dismantled valve, and the permanent deformation and partial scars of a valve stem and O-rings were observed on the rubbing surfaces. Thus, the valve seat and O-rings are recommended to be replaced for a gas leakage safety of a dismantled valve. And it is necessary to repair and inspect handle fastening forces for a safe opening and closing operations of a valve.

• Journal of the Korean Institute of Gas
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• v.12 no.2
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• pp.57-62
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• 2008

Difference of failure modes was studied by finite element analysis for elbows with local wall thinning area particularly at inner surface of intrados of the elbow. Longitudinal wall thinning length, minimum thickness were kept constant but circumferential wall thinning width was varied to get $90^{\circ}$, $180^{\circ}$ and $360^{\circ}$ thinning width. Elastic-plastic analysis were carried out under the combined loading conditions of internal pressure and in-plane bending moment closing the elbow. Von Mises stress were obtained from the outer surface central surface location in intrados, extrados and crown parts in elbow. The results showed that the plastic deformation and failure started from the crown location when the thinning width small ($90{\sim}180^{\circ}$). However, plastic collapse started from the intrados location when the thinning width is approaching $360^{\circ}C$. This should be reflected to assess structural integrity of elbows after wall thinning measurement is made.