• Journal of Drive and Control
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• v.17 no.1
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• pp.21-26
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• 2020

The load characteristics of a piston pump holder due to the squeeze effect are influenced by the surface shape and gap thickness of the holder (cradle). Therefore, the pressure distribution and the load capacity of the piston pump holder due to the squeeze effect are studied by using the CFD software and the surface shape and gap thickness of the piston pump holder are considered. In order to verify the accuracy of numerical results, the load capacities of a circular plate holder are numerically studied, and the accuracy of numerical results is verified by comparing with the theoretical results. Also, the pressure distribution and load capacity of the rectangular plate holder of a piston pump are obtained by using the CFD software. The results show that the load capacity of the square plate holder with grooves is slightly higher at a low gap thickness, but the effects of the number and arrangement of grooves on the load capacity of the holder are weak. We conclude that the load capacity and the maximum pressure are slightly affected due to the existence of grooves on the holder surface, and the fluid storing effect of the holder surface grooves during the operation is likely to prevent the dry-sticking phenomenon.

• Journal of Drive and Control
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• v.17 no.1
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• pp.27-36
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• 2020

The aim of this study is to design a simulation model for an electric All-Wheel-Drive (AWD) tractor to evaluate the performance of the selected component and agricultural work ability. The electric AWD tractor consists of four motors independently for each drive wheel, and each motor is combined with an engine generator, a battery pack, and reducers. The torque data of a 78 kW-class tractor was measured during plow tillage and driving operation to develop a workload cycle. A simulation model was developed by using commercial software, Simulation X, and it used the workload as the simulation condition. As a result of simulation analysis, the drive system, including an electric motor and reducers, was able to cope with high load during plow tillage. The SOC (State of Charge) level was influenced by the output power of the motor, and it was maintained in the range of 50~80%. The fuel consumed by the engine was about 18.23 L during working on a total of 8 fields. The electric AWD tractor was able to perform agricultural work for about 7 hours. In the future study, the electric AWD tractor will be developed reflecting the simulation condition. Research on the comparison between the simulation model and the electric AWD tractor should be performed.

• Journal of the Korea Concrete Institute
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• v.11 no.6
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• pp.3-12
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• 1999

The larger, loftier and more highly strengthened the recent structures become, the greater attention is paid to the problem of thermal crack occurrence associate with hydration heat. As one of methods to solve the problem, a care has been taken to the improvement of construction such as the application of pre-cooling or pipe-cooling, adjustment of concrete block size, concrete placement timing, joint arrangement and so on. But it is expected that a proper selection of cement shall additionally contribute to the control of thermal cracks. In this study, thus, we selected 4 types of cements such as Type V for anti-sulphate, blast furnace cements (slag content of 45% and 65% respectively)and ternary blended low heat cement, and carried out mock-up tests. In every assigned time, temperatures and thermal stresses were measured and calculated from raw data. As a result of measurement, it was found that the magnitude of hydration heat is in order of blast furnace slag cement. Type V and ternary blended low heat cement. Results of thermal stresses were same as the order of temperature. In addition, thermal stresses calculated from the data of strain gauges showed almost similar to those measured from effective stress gauges only when strain values were adjusted properly in accordance with initial time of stress appearance. Theoretical results agreed well with the measured values comparatively, but showed slight differences. It is inferred that these differences shall be reduced if more tests capable of evaluating thermal characteristics of concrete are carried out.

• The korean journal of orthodontics
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• v.33 no.1 s.96
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• pp.21-29
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• 2003

Recent developments in software technology have made it possible to create a virtual three-dimensional model of the dental arches from digitally scanned casts of a patient's dentition. This modelmay then be manipulated with software to produce stages of tooth movement from the initial malocclusion to the final desired occlusion. A sterolithograghic model is made for each stage of tooth movement which is the basis for construction of a series of clear and thin overlay appliances. These appliances are worn full time by the patient to move the teeth according to the programmed stages of movement. Malocclusions involving mild to moderate crowding and space closure have been proven to be successfully treated with this appliance. Experience with this appliance has demonstrated excellent patient compliance with less discomfort, improved esthetics and oral hygiene control, when compared with fixed orthodontic appliances. Orthodontic treatment with this appliance is a potentially useful alternative approach to fixed appliances for treatment of a variety of malocclusions in patients with fully erupted permanent teeth.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.2
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• pp.168-174
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• 2008

Diagnosis on setteability based on human operator's experimental knowledge, which could be established by long term operation, is a limit factor to construction of automation control system in wastewater treatment plant. On-line SVI(Sludge Volume Index) analyzer was developed which can measure SV30 automatically by image capture and image analysis method. In this paper, information got by settling process was studied using On-line SVI analyzer for better operation & management of WWTPs. First, SV30 detection algorithm was developed using image capture and image analysis for settling test and it showed that automatic detection is feasible even if deflocculation and bulking was occurred. Second, turbidity assessment model was developed using image analysis.

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.3
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• pp.269-274
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• 2009

Recently, the construction of Liquefied Natural Gas Carriers(LNGC) is being promoted larger and larger depending on long voyage. In 1950 years, $5,000m^3$ class of LNGC had been changed to $71,500m^3$ class in 1973. and to $210,000-266,000m^3$ class in 2007. Especially, the system of main engines and cargo control, Re-liquefaction of natural gases have become possible in LNGC. This research deals with the LNG projects, world markets of energy and developing tendency of liquefied natural gas carriers.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.5
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• pp.1-8
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• 2009

Photobioreactor (PBR) that houses and cultivates microalgae providing a suitable environment for its growth, such as light, nutrients, CO2, heat, etc. is now getting more popular in the last decade. Among the many types of PBRs, the bubble column type is very attractive because of its simple construction and easy operation. However, despite the availability of these PBRs, only a few of them can be practically used for mass production. Many limitations still holdback their use especially during their scale-up. To enlarge the culture volume and productivity while supplying optimum environmental conditions, various PBR structures and process control are needed to be investigated. In this study, computational fluid dynamics (CFD) was economically used to design a bubble-column type PBR taking the place of field experiments. CFD is a promising technique which can simulate the growth and production of microalgae in the PBR. To study bubble column PBR with CFD, the most important factor is the possibility of realizing bubble. In this study, multi-phase models which are generally used to realize bubbles were compared by theoretical approaches and comparing in a 2D simulation. As a result, the VOF (volume of fluid) model was found to be the most effective model to realize the bubbles shape as well as the flow inside PBR which may be induced by bubble injection. Considering the accuracy and economical efficiency, 0.005 second time step size was chosen for 2.5 mm mesh size. These results will be used as criteria for scale-up in the PBR simulation.

• Environmental Mutagens and Carcinogens
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• v.22 no.3
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• pp.175-182
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• 2002

Endocrine disruptors (EDs) are the chemicals that affect endocrine systems through activation or inhibition of steroid hormone response. It is necessary to have a good system to evaluate rapidly and accurately endocrine-disrupting activities of suspected chemicals and their degradation products. The key targets of EDs are nuclear hormone receptors, which bind to steroid hormones and regulate their gene transcription. We constructed a co-expression system of Gal4p DNA binding domain (DBD)- ligand binding domain of human estrogen receptor $\alpha$ or $\beta$, and Gal4p transactivation domain (TAD)-co-activator AIB-1, SRC-1 or TIF-2 in Saccharomyces cerevisiae with a chromosome-integrated lacZ reporter gene under the control of CYC1 promoter and Gal4p binding site (GAL4 upstream activating sequence, GAL4$_{UAS}$). Expression of this reporter gene was dependent on the presence of estrogen or EDs in the culture medium. We found that the two-hybrid system with combination of the hER$\beta$ LBD and co-activator SRC-1 was most effective in the xenoestrogen-dependent induction of reporter activity. The extent of transcriptional activation by those chemicals correlated with their estrogenic activities measured by other assay systems, indicating that this assay system is efficient and reliable for measuring estrogenic activity. The data in this research demonstrated that the yeast detection system using steroid hormone receptor and co-activator is a useful tool for identifying chemicals that interact with steroid receptors.s.

• Journal of the Korean Institute of Landscape Architecture
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• v.34 no.4 s.117
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• pp.84-95
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• 2006

This study begins by examining the reason for the lack of urban planning that takes the water cycle into consideration. While there are institutions that support environmentally friendly development or smooth water circulation, these designs are not reflected in planning nor in the real world. After reviewing foreign case studies, policy suggestions and possible policy implications for Korea are derived. In Korea, there is not a sufficient level of relevant laws or institutions systematically established to make it possible to deal with rainwater in a decentralized way. Instead, facility standards or guidelines are considered separately for the control of water and for preventing natural disasters. And even though an environmentally friendly approach is stipulated in relevant laws in terms of spatial planning, there are no planning systems or implementation tools to actualize this kind of approach. The factors that make decentralized rainwater management possible in urban planning are analyzed based on the case study of Germany. Germany requires developers to plan in order to achieve ecological urban development. In addition, as a detailed implementation tool to promote conservation of the water cycle, the law provides for various kinds of measures such as restrictions on the proportion of impervious surface area according to the use of the land, required compensation measures for environmental degradation following development, introduction of a fee for rainwater runoff and the establishment of ecological landscape planning. The actual reason these measures can be implemented however is the provision of planning guidelines and design criteria for rainwater utilization, absorption and containment, and the construction of a database for various environmental information.

• Resources Recycling
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• v.16 no.2 s.76
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• pp.40-47
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• 2007

This paper described recycling of the bottom ash, sourced from the local incinerators as a fine sand for concrete. 10% bottom ash was substituted for the ordinary beach sand in the mortar(on a weigh basis), in conjunction with the pozzolznic diatomite. The specimens were tested according to KS L 5105 and analysed by TCLP(Toxic Chemical Leaching Procedure). The results showed that the hazardous heavy metals in the bottom ash are within the maximum permissible limit of TCLP. The compressive strength of the mortar with 10% bottom ash was highly improved, compared to the control mortar when the pozzolanic diatomite was used. It revealed that the hazardous heavy metals of the mortar with 10% bottom ash were leached within the maximum permissible limit of TCLP. It was concluded that the bottom ash can be reused as a fine sand for concrete when the pozzolanic diatomite was used as a stabilizer.