• Journal of the Korean Geotechnical Society
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• v.21 no.2
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• pp.113-120
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• 2005

An understanding of soil-structure interaction is the key to rational and economical design for laterally loaded drilled shafts. It is very difficult to formulate the ultimate lateral capacity into a general equation because of the inherent soil nonlincarity, nonhomogeneity, and complexity enhanced by the three dimensional and asymmetric nature of the problem though extensive research works on the behavior of deep foundations subjected to lateral loads have been conducted for several decades. This study reviews the four most well known methods (i.e., Reese, Broms, Hansen, and Davidson) among many design methods according to the specific site conditions, the drilled shaft geometric characteristics (D/B ratios), and the loading conditions. And the hyperbolic lateral capacities (H$_h$) interpreted by the hyperbolic transformation of the load-displacement curves obtained from model tests carried out as a part of this research have been compared with the ultimate lateral capacities (Hu) predicted by the four methods. The H$_u$ / H$_h$ ratios from Reese's and Hansen's methods are 0.966 and 1.015, respectively, which shows both the two methods yield results very close to the test results. Whereas the H$_u$ predicted by Davidson's method is larger than H$_h$ by about $30\%$, the C.0.V. of the predicted lateral capacities by Davidson is the smallest among the four. Broms' method, the simplest among the few methods, gives H$_u$ / H$_h$ : 0.896, which estimates the ultimate lateral capacity smaller than the others because some other resisting sources against lateral loading are neglected in this method. But it results in one of the most reliable methods with the smallest S.D. in predicting the ultimate lateral capacity. Conclusively, none of the four can be superior to the others in a sense of the accuracy of predicting the ultimate lateral capacity. Also, regardless of how sophisticated or complicated the calculating procedures are, the reliability in the lateral capacity predictions seems to be a different issue.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.4
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• pp.375-390
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• 2009

Statement of problem: Implant supported overdenture is accepted widely as a way to restore edentulous ridge providing better retention and support of dentures. Various types of attachment for overdenture have been developed. Purpose: The purpose of this study was to investigate the influence of attachment type in implant overdentures on the biomechanical stress distribution in the surrounding bone, prosthesis and interface between implant and bone. Material and methods: Finite element analysis method was used. Average CT image of mandibular body(Digital $Korea^{(R)}$, KISTI, Korea) was used to produce a mandibular model. Overdentures were placed instead of mandibular teeth and 2mm of mucosa was inserted between the overdenture and mandible. Two implants($USII^{(R)}$, Osstem, Korea) were placed at both cuspid area and 4 types of overdenture were fabricated ; ball and socket, Locator, magnet and bar type. Load was applied on the from second premolar to second molar tooth area. 6 times of finite element analyses were performed according to the direction of the force $90^{\circ}$, $45^{\circ}$, $0^{\circ}$ and unilateral or bilateral force applied. The stress at interface between implants and bone, and prosthesis and the bone around implants ware compared using von Mises stress. The results were explained with color coded graphs based on the equivalent stress to distinguish the force distribution pattern and the site of maximum stress concentration. Results: Unilateral loading showed that connection area between implant fixture and bar generated maximum stress in bar type overdentures. Bar type produced 100 Mpa which means the most among 4 types of attachments. Bilateral loading, however, showed that bar type was more stable than other implants(magnet, ball and socket). 26 Mpa of bar type was about a half of other types on overdenture under $90^{\circ}$ bilateral loading. Conclusions: In any directions of stress, bar type was proved to be the most vulnerable type in both implants and overdentures. Interface stress did not show any significant difference in stress distribution pattern.

• The Journal of Korean Academy of Prosthodontics
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• v.23 no.1
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• pp.39-59
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• 1985

The purpose of this study was to investigate how gap distances of 0.13mm, 0.15mm, 0.20mm, and 0.30mm affects solder joint strength from gold alloys and nickel-chromium base alloys and to examine the composition of solder gold, the solder joint of gold alloys and nickel-chromium base alloys. The tensile test specimens were prepared in the split stainless steel mold with a half dumbbell shape 2.5mm in diameter and l2mm in length. 6 pairs of specimens of each gap distance group of gold alloys and nickel-chromium base alloys were made and 48 pairs of all specimens were soldered with solder gold of 666 fineness. All soldered specimens were machined to a uniform diameter and then a tensile load was applied at a cross-head speed of 0.10mm/min using Instron Universal Testing Machine, Model 1115. The fractured specimens at solder gold of solder joint fracture with each gap distance of 0.13mm, 0.15mm, 0.20mm, and 0.30mm were examined under the Scanning Electron Microscope, JSM-35c and the composition of solder gold, the solder joint of gold alloys and nickel-chromium base alloys was analyzed by Electron Probe Micro Analyzer. The results of this study were obtained as follows: 1. In case of soldering of gold alloys, the tensile strength between gold alloys showed $37.33{\pm}2.52kg/mm^2$ at 0.13, $39.14{\pm}3.35kg/mm^2$ at 0.15mm, $43.76{\pm}2.97kg/mm^2$ at 0.20mm, and $49.18{\pm}4.60kg/mm^2$ at 0.30mm. There was statistically significant difference at each gap distance, and so the greater increase of gap distance showed the greater tensile strength. 2. In case of soldering of nickel-chromium base alloys, the tensile strength between nickel-chromium base alloys showed $34.84{\pm}4.26kg/mm^2$ at 0.13mm, $37.25{\pm}2.49kg/mm^2$ at 0.15mm, $42.91{\pm}4.32kg/mm^2$ at 0.20mm, and $46.93{\pm}4.21kg/mm^2$ at 0.30mm. There was not statistically significant difference only between 0.13mm and 0.15mm and bet ween 0.20 mm and 0.30mm, but generally the greater increase of gap distance showed the greater tensile strength. 3. The greater increase of gap distance shoed less porosities in solder gold at solder joint fracture. 4. In solder gold Au, Cu, Ag, Zn, and Sn were composed and Au and Cu were mostly distributed uniformly. 5. In solder joints of solder gold and gold alloys Au, Cu, Ag, Zn, and Sn were composed in solder gold and Au, Cu, Ag, Pt, and Pd were composed in gold alloys. Au and Cu of solder gold and gold alloys were mostly distributed uniformly and the diffusion of other elements except Pt and Pd around the solder joint was not almost found. In solder joints of solder gold and nickel-chromium base alloys Au, Cu, Ag, Zn, and Sn were composed in solder gold and Ni, Cr, and Al were composed in nickel-chromium base alloys. Au and Cu of solder gold and Ni and Cr of nickel-chromium base alloys were mostly distributed uniformly and the diffusion of other elements except Cr around the solder joint was not almost found.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.12
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• pp.605-619
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• 2014

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.6
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• pp.346-361
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• 2013

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2012. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. The conclusions are as follows : (1) The research works on thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and valves, fuel cells and power plants, ground-coupled heat pumps, and general heat and mass transfer systems. Research issues are mainly focused on new and renewable energy systems, such as fuel cells, ocean thermal energy conversion power plants, and ground-coupled heat pump systems. (2) Research works on the heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer, and industrial heat exchangers. Researches on heat transfer characteristics included the results for natural convection in a square enclosure with two hot circular cylinders, non-uniform grooved tube considering tube expansion, single-tube annular baffle system, broadcasting LED light with ion wind generator, mechanical property and microstructure of SA213 P92 boiler pipe steel, and flat plate using multiple tripping wires. In the area of pool boiling and condensing heat transfer, researches on the design of a micro-channel heat exchanger for a heat pump, numerical simulation of a heat pump evaporator considering the pressure drop in the distributor and capillary tubes, critical heat flux on a thermoexcel-E enhanced surface, and the performance of a fin-and-tube condenser with non-uniform air distribution and different tube types were actively carried out. In the area of industrial heat exchangers, researches on a plate heat exchanger type dehumidifier, fin-tube heat exchanger, an electric circuit transient analogy model in a vertical closed loop ground heat exchanger, heat transfer characteristics of a double skin window for plant factory, a regenerative heat exchanger depending on its porous structure, and various types of plate heat exchangers were performed. (3) In the field of refrigeration, various studies were executed to improve refrigeration system performance, and to evaluate the applicability of alternative refrigerants and new components. Various topics were presented in the area of refrigeration cycle. Research issues mainly focused on the enhancement of the system performance. In the alternative refrigerant area, studies on CO2, R32/R152a mixture, and R1234yf were performed. Studies on the design and performance analysis of various compressors and evaporator were executed. (4) In building mechanical system research fields, twenty-nine studies were conducted to achieve effective design of mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, renewable energy systems, and lighting systems in buildings. New designs and performance tests using numerical methods and experiments provide useful information and key data, which can improve the energy efficiency of buildings. (5) In the fields of the architectural environment, studies for various purposes, such as indoor environment, building energy, and renewable energy were performed. In particular, building energy-related researches and renewable energy systems have been mainly studied, reflecting interests in global climate change, and efforts to reduce building energy consumption by government and architectural specialists. In addition, many researches have been conducted regarding indoor environments.

• Korean Journal of Ecology and Environment
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• v.48 no.3
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• pp.147-152
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• 2015

Nitrogen (N) loading from domestic, agricultural and industrial sources can lead to excessive growth of macrophytes or phytoplankton in aquatic environment. Many studies have used nitrogen stable isotope ratios to identify anthropogenic nitrogen in aquatic systems as a useful method for studying nitrogen cycle. In this study to evaluate the precision and accuracy of Kjeldahl processes, two reference materials (IAEA-NO-3, N-1) were analyzed repeatedly. Measured the ${\delta}^{15}N-NO_3$ and ${\delta}^{15}N-NH_4$ values of IAEA-NO-3 and IAEA-N-1 were $4.7{\pm}0.2$‰ and $0.4{\pm}0.3$‰, respectively, which are within recommended values of analytical uncertainties. Also, we investigated spatial patterns of ${\delta}^{15}N-NO_3$ and ${\delta}^{15}N-NH_4$ in effluent plumes from a waste water treatment plant in Han River, Korea. ${\delta}^{15}N-NO_3$ and ${\delta}^{15}N-NH_4$ values are enriched at downstream areas of water treatment plant suggesting that dissolved nitrogen in effluent plumes should be one of the main N sources in those areas. The current study clarifies the reliability of Kjeldahl analytical method and the usefulness of stable isotopic techniques to trace the contamination source of dissolved nitrogen such as nitrate and ammonia.

• Restorative Dentistry and Endodontics
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• v.34 no.4
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• pp.324-332
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• 2009

The purpose of this study was to investigate the effect of rigidity of post core systems on stress distribution by the theoretical technique, finite element stress-analysis method. Three-dimensional finite element models simulating an endodontically treated maxillary central incisor restored with a zirconia ceramic crown were prepared and 1.5 mm ferrule height was provided. Each model contained cortical bone, trabecular bone, periodontal ligament, 4 mm apical root canal filling, and post-and-core. Six combinations of three parallel type post (zirconia ceramic, glass fiber, and stainless steel) and two core (Paracore and Tetric ceram) materials were evaluated, respectively. A 50 N static occlusal load was applied to the palatal surface of the crown with a $60^{\circ}$angle to the long axis of the tooth. The differences in stress transfer characteristics of the models were analyzed. von Mises stresses were chosen for presentation of results and maximum displacement and hydrostatic pressure were also calculated. An increase of the elastic modulus of the post material increased the stress, but shifted the maximum stress location from the dentin surface to the post material. Buccal side of cervical region (junction of core and crown) of the glass fiber post restored tooth was subjected to the highest stress concentration. Maximum von Mises stress in the remaining radicular tooth structure for low elastic modulus resin core (29.21 MPa) was slightly higher than that for high elastic modulus resin core (29.14 MPa) in case of glass fiber post. Maximum displacement of glass fiber post restored tooth was higher than that of zirconia ceramic or stainless steel post restored tooth.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.237-237
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• 2015

The district of Marlborough has had more than its share of river management projects over the past 150 years, each one uniquely affecting the geomorphology and flood hazard of the Wairau Plains. A major early project was to block the Opawa distributary channel at Conders Bend. The Opawa distributary channel took a third and more of Wairau River floodwaters and was a major increasing threat to Blenheim. The blocking of the Opawa required the Wairau and Lower Wairau rivers to carry greater flood flows more often. Consequently the Lower Wairau River was breaking out of its stopbanks approximately every seven years. The idea of diverting flood waters at Tuamarina by providing a direct diversion to the sea through the beach ridges was conceptualised back around the 1920s however, limits on resources and machinery meant the mission of excavating this diversion didn't become feasible until the 1960s. In 1964 a 10 m wide pilot channel was cut from the sea to Tuamarina with an initial capacity of $700m^3/s$. It was expected that floods would eventually scour this 'Wairau Diversion' to its design channel width of 150 m. This did take many more years than initially thought but after approximately 50 years with a little mechanical assistance the Wairau Diversion reached an adequate capacity. Using the power of the river to erode the channel out to its design width and depth was a brilliant idea that saved many thousands of dollars in construction costs and it is somewhat ironic that it is that very same concept that is now being used to deal with the aggradation problem that the Wairau Diversion has caused. The introduction of the Wairau Diversion did provide some flood relief to the lower reaches of the river but unfortunately as the Diversion channel was eroding and enlarging the Lower Wairau River was aggrading and reducing in capacity due to its inability to pass its sediment load with reduced flood flows. It is estimated that approximately $2,000,000m^3$ of sediment was deposited on the bed of the Lower Wairau River in the time between the Diversion's introduction in 1964 and 2010, raising the Lower Wairau's bed upwards of 1.5m in some locations. A numerical morphological model (MIKE-11 ST) was used to assess a number of options which led to the decision and resource consent to construct an erodible (fuse plug) bank at the head of the Wairau Diversion to divert more frequent scouring-flows ($+400m^3/s$)down the Lower Wairau River. Full control gates were ruled out on the grounds of expense. The initial construction of the erodible bank followed in late 2009 with the bank's level at the fuse location set to overtop and begin washing out at a combined Wairau flow of $1,400m^3/s$ which avoids berm flooding in the Lower Wairau. In the three years since the erodible bank was first constructed the Wairau River has sustained 14 events with recorded flows at Tuamarina above $1,000m^3/s$ and three of events in excess of $2,500m^3/s$. These freshes and floods have resulted in washout and rebuild of the erodible bank eight times with a combined rebuild expenditure of $80,000. Marlborough District Council's Rivers & Drainage Department maintains a regular monitoring program for the bed of the Lower Wairau River, which consists of recurrently surveying a series of standard cross sections and estimating the mean bed level (MBL) at each section as well as an overall MBL change over time. A survey was carried out just prior to the installation of the erodible bank and another survey was carried out earlier this year. The results from this latest survey show for the first time since construction of the Wairau Diversion the Lower Wairau River is enlarging. It is estimated that the entire bed of the Lower Wairau has eroded down by an overall average of 60 mm since the introduction of the erodible bank which equates to a total volume of $260,000m^3$. At a cost of $$0.30/m^3$ this represents excellent value compared to mechanical dredging which would likely be in excess of $$10/m^3$. This confirms that the idea of using the river to enlarge the channel is again working for the Wairau River system and that in time nature's "excavator" will provide a channel capacity that will continue to meet design requirements.

• Journal of Energy Engineering
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• v.28 no.3
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• pp.65-79
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• 2019

The study attempted to estimate the optimal facility capacity by combining renewable energy sources that can be connected with gas CHP in industrial complexes. In particular, we reviewed industrial complexes subject to energy use plan from 2013 to 2016. Although the regional designation was excluded, Sejong industrial complex, which has a fuel usage of 38 thousand TOE annually and a high heat density of $92.6Gcal/km^2{\cdot}h$, was selected for research. And we analyzed the optimal operation model of CHP Hybrid System linking fuel cell and photovoltaic power generation using HOMER Pro, a renewable energy hybrid system economic analysis program. In addition, in order to improve the reliability of the research by analyzing not only the heat demand but also the heat demand patterns for the dominant sectors in the thermal energy, the main supply energy source of CHP, the economic benefits were added to compare the relative benefits. As a result, the total indirect heat demand of Sejong industrial complex under construction was 378,282 Gcal per year, of which paper industry accounted for 77.7%, which is 293,754 Gcal per year. For the entire industrial complex indirect heat demand, a single CHP has an optimal capacity of 30,000 kW. In this case, CHP shares 275,707 Gcal and 72.8% of heat production, while peak load boiler PLB shares 103,240 Gcal and 27.2%. In the CHP, fuel cell, and photovoltaic combinations, the optimum capacity is 30,000 kW, 5,000 kW, and 1,980 kW, respectively. At this time, CHP shared 275,940 Gcal, 72.8%, fuel cell 12,390 Gcal, 3.3%, and PLB 90,620 Gcal, 23.9%. The CHP capacity was not reduced because an uneconomical alternative was found that required excessive operation of the PLB for insufficient heat production resulting from the CHP capacity reduction. On the other hand, in terms of indirect heat demand for the paper industry, which is the dominant industry, the optimal capacity of CHP, fuel cell, and photovoltaic combination is 25,000 kW, 5,000 kW, and 2,000 kW. The heat production was analyzed to be CHP 225,053 Gcal, 76.5%, fuel cell 11,215 Gcal, 3.8%, PLB 58,012 Gcal, 19.7%. However, the economic analysis results of the current electricity market and gas market confirm that the return on investment is impossible. However, we confirmed that the CHP Hybrid System, which combines CHP, fuel cell, and solar power, can improve management conditions of about KRW 9.3 billion annually for a single CHP system.

• Korean Journal of Agricultural and Forest Meteorology
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• v.24 no.1
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• pp.13-34
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• 2022

Soil moisture data have been collected at 11 agrometeorological stations operated by The Korea Meteorological Administration (KMA). This study aimed to verify the accuracy of soil moisture data of KMA and develop a correction formula to be applied to improve their quality. The soil of the observation field was sampled to analyze its physical properties that affect soil water content. Soil texture was classified to be sandy loam and loamy sand at most sites. The bulk density of the soil samples was about 1.5 g/cm³ on average. The content of silt and clay was also closely related to bulk density and water holding capacity. The EnviroSCAN model, which was used as a reference sensor, was calibrated using the self-manufactured "reference soil moisture observation system". Comparison between the calibrated reference sensor and the field sensor of KMA was conducted at least three times at each of the 11 sites. Overall, the trend of fluctuations over time in the measured values of the two sensors appeared similar. Still, there were sites where the latter had relatively lower soil moisture values than the former. A linear correction formula was derived for each site and depth using the range and average of the observed data for the given period. This correction formula resulted in an improvement in agreement between sensor values at the Suwon site. In addition, the detailed approach was developed to estimate the correction value for the period in which a correction formula was not calculated. In summary, the correction of soil moisture data at a regular time interval, e.g., twice a year, would be recommended for all observation sites to improve the quality of soil moisture observation data.