• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1305-1310
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• 2014

MR(Magneto-Rheological) damper generates the magnetic shear force due to the cohesiveness of MR fluid influenced by a magnetic field. MR fluid consists of magnetic particles and a base liquid. In the present study, the damping forces of MR damper were investigated for density 1.3, 1.5 and $1.7g/cm^3$, and viscosity 1000 and 10000cp, and for the change of orifice shapes. It was found that the increase in the density and viscosity of MR fluid could change the damping force of MR damper due to the magnetic effects. Also, the damping forces on orifice shapes increased as the orifice gap and length decreased. These results showed that the properties of MR fluid and orifice shapes were important for the optimum design of MR damper.

• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.676-680
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• 2002

The specific gravity meter is the instrument used to measure the density of fluids under the reference conditions and it can be widely used in industrial areas, especially in massive flow rate natural gas industry. This study has been carried out in an attempt to improve measurement accuracy of natural gas flow rate calculation, providing the adequate installation and proper operation conditions of specific gravity meter. The test results are 1) the density measurement errors in case of using methane and standard gas as calibration gases are smaller than using methane and nitrogen gas, 2) the periodical calibration to maintain accurate density measurements is essential, and 3) the specific gravity meter is sensitive to changes of environmental conditions, especially environmental temperature surrounding the specific gravity meter.

• Journal of the Korean Magnetics Society
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• v.4 no.4
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• pp.326-334
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• 1994

This paper describes the fabrication of the hydrophilic magnetic fluid with high viscosity and its application to oil seal apparatus used with the Nd-permanent magnet. The results are as follows. 1) The ultrafine magnetite particles under the size of $100\;{\AA}$ are first coated by the oleic acid ion and again adsorbed by the hydrophilic D. B. S. ion, and there by hydrophilic magnetic fluid with high viscosity could be made by dispersing them into the ethylene glycol. 2) In development of the oil seal apparatus using magnetic fluid and Nd-permanent magnet, the viscosity and magnetic susceptibility show high when the $Fe_{3}O_{4}$ content is over 50%(g/cc) in the fluid, so that such properties could improve highly the capability of oil seal. 3) The maximum of the resisting pressure of the oil seal using the ethylene glycol base magnetic fluid and the Nd-permanent magnet, is about $50\;g/\textrm{cm}^2$, under the condition of this experiment. Therefore the oil seal may not be suitable for the ship engine and the driving part of the automobile, and thus it needs a lot further complementary reserch. However, it is quite favourable for such an oil seal apparatus as speed reducer under the condition of atmospheric pressure.

• The Journal of the Korea Contents Association
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• v.5 no.3
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• pp.29-35
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• 2005

The task for chromosome analysis and diagnosis by experienced cytogenetists are being concerned as repetitive, time consuming job and expensive. For that reason, intelligent agent based on chromosome knowledge base using web has been developed to be able to analyze chromosomes and obtain necessary advises from the knowledge base instead of human experts. That is to say, the knowledge base of IF THEN production rule was implemented to a knowledge domain with normal and abnormal chromosomes, and then the inference results by the knowledge base could enter the inference data into the database. Experimental data were composed of normal chromosomes of 2,736 cases and abnormal chromosomes of 259 cases that have been obtained from GTG-banding metaphase peripheral blood and amniotic fluid samples. The completed intelligent agent for the chromosome knowledge base provides variously morphological information by analysis of normal or abnormal chromosomes also has the advantage of being able to consult with the user on the chromosome analysis and diagnosis.

• Archives of Plastic Surgery
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• v.49 no.2
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• pp.174-183
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• 2022

Management of traumatic skull base fractures and associated complications pose a unique reconstructive challenge. The goals of skull base reconstruction include structural support for the brain and orbit, separation of the central nervous system from the aerodigestive tract, volume to decrease dead space, and restoration of the three-dimensional appearance of the face and cranium with bone and soft tissues. An open bicoronal approach is the most commonly used technique for craniofacial disassembly of the bifrontal region, with evacuation of intracranial hemorrhage and dural repair performed prior to reconstruction. Depending on the defect size and underlying patient and operative factors, reconstruction may involve bony reconstruction using autografts, allografts, or prosthetics in addition to soft tissue reconstruction using vascularized local or distant tissues. The vast majority of traumatic anterior cranial fossa (ACF) injuries resulting in smaller defects of the cranial base itself can be successfully reconstructed using local pedicled pericranial or galeal flaps. Compared with historical nonvascularized ACF reconstructive options, vascularized reconstruction using pericranial and/or galeal flaps has decreased the rate of cerebrospinal fluid (CSF) leak from 25 to 6.5%. We review the existing literature on this uncommon entity and present our case series of n = 6 patients undergoing traumatic reconstruction of the ACF at an urban Level 1 trauma center from 2016 to 2018. There were no postoperative CSF leaks, mucoceles, episodes of meningitis, or deaths during the study follow-up period. In conclusion, use of pericranial, galeal, and free flaps, as indicated, can provide reliable and durable reconstruction of a wide variety of injuries.

• Journal of Korean Neurosurgical Society
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• v.65 no.3
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• pp.457-468
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• 2022

Objective : The clinical management paradigm of skull base chordomas is still challenging. Surgical resection plays an important role of affecting the prognosis. Endonasal endoscopic approach (EEA) has gradually become the preferred surgical approach in most cases, but traditional transcranial surgery cannot be completely replaced. This study presents a comparison of the results of the two surgical strategies and a summary of the treatment algorithms for skull base chordomas. Methods : We retrospectively analyzed the surgical outcomes and follow-up data of 48 patients with skull base chordomas diagnosed pathologically who received transnasal midline approaches (TMA) and transcranial lateral approaches (TLA) from 2010 to 2020. Results : Among the 48 patients, 36 cases were adopted TMA and 12 cases were performed with TLA. In terms of gross total resection (GTR) rate, 27.8% in TMA and 16.7% in TLA and with EEA alone it was increased to 38.9%, while 29.7% in primary surgery. In TMA, the cerebrospinal fluid (CSF) leak remains the most common complication (13 cases, 36.1%), other main complications included death, cranial nerve palsy, hypopituitarism, all the comparisons were no statistical significance. The Karnofsky Performance Scale scores in TMA were all better than those in TLA at different time, and the overall survival (OS) and recurrence free survival/progression free survival was just the reverse. Conclusion : The EEA for skull base chordomas resection has improved the GTR rate, but transcranial approach is still an alternative approach. It is necessary to select an appropriate surgical approach based on the location and the pattern of tumor growth in order to obtain the best surgical outcomes.

• Geomechanics and Engineering
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• v.38 no.3
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• pp.215-229
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• 2024

Because of the various patterns of deep-water inrush and complicated mechanisms, accurately predicting mine water inflows is always a difficult problem for coal mine geologists. In study presented in this paper, the water inrush channels were divided into four basic water diversion structures: aquifer, rock fracture zone, fracture zone and goaf. The fluid flow characteristics in each water-conducting structure were investigated by laboratory tests, and multistructure and multisystem coupling flow analysis models of different water-conducting structures were established to describe the entire water inrush process. Based on the research of the water inrush flow paths, the analysis model of different water inrush space structures was established and applied to the prediction of mine water inrush inflow. The results prove that the conduction sequence of different water-conducting structures and the changing rule of permeability caused by stress changes before and after the peak have important influences on the characteristics of mine water-gushing. Influenced by the differences in geological structure and combined with rock mass RQD and fault conductivity characteristics and other mine exploration data, the prediction of mine water inflow can be realized accurately. Taking the water transmitting path in the multistructure as the research object of water inrush, breaking through the limitation of traditional stratigraphic structure division, the prediction of water inflow and the estimation of potentially flooded area was realized, and water bursting intensity was predicted. It is of great significance in making reasonable emergency plans.

• Transactions of The Korea Fluid Power Systems Society
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• v.3 no.3
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• pp.14-19
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• 2006

Recently, the cylinder of the excavator is applied in the various environment. So, we need the development of the simulator for the excavator. The simulator has the effects of the decrease of the cost and improvement of the cylinder's performance. In this paper, we design the simulator for the excavator and makes an analysis of the dynamics and structure. The simulator was applied to the excavator's models of 10ton, 20ton and 30ton because we built the data base of a real excavator's cylinder of information in the experiment. And we used the FEM analysis for the comparative study on the characteristics.

• The KSFM Journal of Fluid Machinery
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• v.15 no.3
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• pp.51-56
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• 2012

This study analyzed the influence of firing biogas on the performance and operation of a gas/steam turbine combined system. A reference gas/steam turbine combined system, designed with biogas fuel(57% volumetric methane) was set up and off-design simulation was made to investigate operating characteristics when a couple of operating schemes to mitigate turbine blade overheating were applied. Performance at base-load operation using each scheme was compared and part load operation using the variable inlet guide vane was analysed. Also, differences in operating characteristics and performance caused by changes in the methane content of biogas and ambient temperature were examined.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.303-309
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• 2009

In this study, the heat transfer and flow field of condenser used on Kim-chi refrigerator is analysed with numerical method. Main objective is to present the base data for designing new condenser model with improvement of heat transfer performance. For CFD analysis, a commercial code, STAR-CCM+ was used. The water was used for the inner working fluid and the air was used for the outer fluid. The condenser type used in this study is a flat plate fin-and-tube heat exchanger. As factors for performance analysis, the effect of condenser geometry and air velocity was investigated. As a result, it has been observed that there is a suitable fin pitch with which heat transfer performance of condenser is maximized.