• 한국가시화정보학회지
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• 제19권3호
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• pp.99-105
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• 2021

In this study, the thermal stratification in solar seasonal thermal storage tanks was numerically simulated. The effects of the aspect ratio (AR) and inlet velocity on the thermal stratification in the diffuser type heat storage tank were investigated. The temperature distributions inside the tank were similar with velocity fields. Jet flows from opposite diffusers encountered each other at the tank center region. Thereafter, the downward flows occurred, and this flows strongly affected the thermal stratification. When AR was smaller than 2, these downward flows influenced a further distance and enhanced mixing inside the tank. Thermal stratification was evaluated by thermocline thickness and degree of stratification, and AR of 3 had the highest degree of stratification. The inlet velocity effect was expressed with the ratio (Re/Ri) of Reynolds and Richardson numbers. The second-order approximation was found for the relationship between the thermocline thickness and log Re/Ri.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1604-1615
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• 2023

In an open-pool type research reactor with a downward forced flow in the core, pipes can be under sub-atmospheric pressure because of the large pressure drop at the reactor core in the atmospheric pool. Sub-atmospheric pressure can result in air inflow into the pipe from the pressure difference between the atmosphere and the inside of the pipe, which in a postulated pipe break scenario can lead to the breakdown of the cooling pump. In this study, a plant-scale experiment was conducted to study air inflow in large piping systems by considering the actual operational conditions of an advanced research reactor. The air inflow rate was measured, and the entrained air was visualized to investigate the behavior of air inflow and flow regime depending on the pipe break size. In addition, the developed drift-flux model for a large vertical pipe with a diameter of 600 mm was compared with other correlations. The flow regime transition in a large vertical pipe under downward flow was also studied using the newly developed drift-flux model. Consequently, the characteristics of two-phase flow in a large vertical pipe were found to differ from those in small vertical pipes where liquid recirculation was not dominant.

• 대한전기학회논문지
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• 제35권2호
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• pp.62-66
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• 1986

Ion beam etching of silicon with N2 and Ar gas has been found to cause the band edge to bend downward near the surface in p-type silicon. Rectifying, rather than ohmic contacts are obtained on the structures formed by evaporation of gold and titanium onto ion-bean-etched p-type silicon. The 1/C2 versus V relationship measured at 1MHz is found to be nonlinear for small voltages indicating alteration of the effective doping colse to the silicon surface.

• Journal of Chest Surgery
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• 제18권3호
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• pp.391-397
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• 1985

Ebstein`s anomaly is a rare congenital cardiac malformation and characterized by downward displacement of an abnormal tricuspid valve cusps. But until now, the ideal surgical correction is still controversial. We present a case of Ebstein`s anomaly experienced lately. The patient was 13 year old girl with the complaints of dyspnea on exertion, fatigability and cyanosis. Echocardiography revealed downward displacement of septal leaflet of tricuspid valve and atrialized right ventricle. Cardiac catheterization and cineangiography revealed ASD and large right atrium. During operation, the atrialized right ventricle was plicated and tricuspid annuloplasty was done. And the two secundum type ASD`s were closed by direct suture closure. The patient`s postoperative course was uneventful and discharged on the 24th postoperative days.

• 한국정밀공학회지
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• 제14권3호
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• pp.57-65
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• 1997

In this study, a cutting force in the Ball-end milling process is calculated using Z-map. Z-map can describe any type of cutting area resulting from the previous cutting geometry and cutting condition. Cutting edge of a ball-end mill is divided into infinitesimal cutting edge elements and the position of the ele- ment is projected to the cutter plane normal to the Z axis. Also the cutting area in the cutter plane is obtained by using the Z-map. Comparing this projected position with cutting area, it can be determined whether it engages in the cutting. The cutting force can be calculated by numerical integration of cutting force acting on the engaged cutting edge elements. A series of experiments such as contouring and upward/downward ramp cutting was performed to verify the calculated cutting force.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 추계 학술논문 발표대회
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• pp.43-47
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• 2008

CWSII method was developed to overcome the problems of frequent occurrence in the application of existing downward construction methods, especially in the case of using slurry wall instead of SCW or CIP as a retaining wall. By the improvements in connecting steel beams with the wall, CWSII method is able to ensure the settlement of a steel beam and the diaphragm effect of a slab while reducing the degree of difficulty and the term of works and the cost of construction. As the desired results, CWS method can be applied as a practical downward construction method regardless of the type of retaining wall. In this paper, besides the concept and features of CWSII method, it can be seen that the method can provide reliable and economical performances by comparing with existing methods.

• 대한치과보철학회지
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• 제28권2호
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• pp.199-215
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• 1990

This study was to analyze the stress distribution of implant and supporting tissue in $Br{\aa}nemark$ osseointegration implant. The analysis has been conducted by using the axisymmetric finite element method and type of model according to crown material. Tests have been performed at 1 kg load on central fossa of crown portion. Each type of model was designed differently according to crown material. 1) Porcelain fused to metal crown(Model A) 2) Composite resin veneered crown(Model B) 3) Acrylic resin veneered crown(Model C) 4) Type III gold crown(Model D) The displacements and stresses of implant and supporting structures were analyzed to investigate the influence of the type of crown material. The results were obtained as follows : 1. Displacement of implant was shown uniformly downward displacement in all models and abutments were observed distally downward displacement. 2. In supporting tissues, stress was concentrated on the crest of compact bone and the spongy bone below implant. 3. The PFM and the type III gold crown showed the largest concentration of stress at the crest of compact bone and the spongy bone below implant, respectively. Acrylic resin artificial teeth and composite resin veneered crown indicated almost the same distribution of stress. 4. The gold screw, the abutment screw and the top of abutment showed the concentration of stress in implants of every model.

• 대한두개안면성형외과학회지
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• 제24권1호
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• pp.18-23
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• 2023

Background: When performing reduction of zygomatic arch fractures, locating the inward portion of the fracture can be difficult. Therefore, this study investigated the discrepancy between the locations of the depression on the soft tissue and bone and sought to identify how to determine the inward portion of the fracture on the patient's face. Methods: We conducted a retrospective review of chart with isolated zygomatic arch fractures of type V in the Nam and Jung classification from March 2013 to February 2022. For consistent measurements, a reference point (RP), at the intersection between a vertical line passing through the end point of the root of the ear helix in the patient's side-view photograph and a transverse line passing through the longest horizontal axis of the external meatus opening, was established. We then measured the distance between the RP and the soft tissue depression in a portrait and the bone depression on a computed tomography (CT) scan. The discrepancy between these distances was quantified. Results: Among the patients with isolated zygomatic arch fractures, only those with a fully visible ear on a side-view photograph were included. Twenty-four patients met the inclusion criteria. There were four types of discrepancies in the location of the soft tissue depression compared to the bone depression: type I, forward and upward discrepancy (7.45 and 3.28 mm), type II, backward and upward (4.29 and 4.21 mm), type III, forward and downward (10.06 and 5.15 mm), and type IV, backward and downward (2.61 and 3.27 mm). Conclusion: This study showed that discrepancy between the locations of the depressions on the soft tissue and bone exists in various directions. Therefore, applying the transverse and vertical distances measured from a bone image of the CT scan onto the patient's face at the indicated RP will be helpful for predicting the reduction location.

• 대한치과교정학회지
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• 제22권3호
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• pp.509-529
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• 1992

Skeletal Class III malocclusion is one of the most difficult type to treat and stabilize. For a child with developing skeletal Class III malocclusion, the treatment objective would be to stimulate maxillary growth, particulary one who has markedly deficient maxilla, and to restrain excessive mandibular growth. In order to stimulate the maxillary growth, maxillary protraction appliance is the one of the effective orthopedic appliances in skeletal Class III. The purposes of this study were as follows ; evaluation of the skeletal and dental changes of the maxillary protraction in children with Class III Maxillary deficiency , comparison of the clinical effects between the group with RPE and labiolingual intraoral appliances , comparison of the clinical effects and stability related to the ages of the patients : stability of the maxillary protraction about 1 year after retention. The subjects consisted of 60 children between the ages of 8 and 13.4 who were diagnosed as Class III with maxillary deficiency and were treated with Face Mask (Delaire Type) from the Dept. of Orthodontics Yong Dong Severance Hospital, Yonsei University. 48 children wore the RPE and 12 children wore Labiolingual Appliance. Lateral Cephalograms were taken for each patient at before and after correction of anterior cross-bite in 60 children, and after an observation period of 10 to 14 months in 19 children. X and Y coordinate of 10 landmarks were analyzed using a horizontal line through sella and rotated $6^{\circ}$ down anteriorly as the horizontal reference axis, and a perpendicular verticual line through sella as the vertical reference axis. Each of the 31 measurents (10 verticals, 10 horizontals, 2 angles and 9 others) was statistically analyzed using SPSS/PC statistics. The results are as follows; 1. After maxillary protraction the maxilla and maxillary teeth moved downward and forward, while the mandible and mandibular incisor rotated downward and backward. 2. Maxillary protraction with rapid palatal expansion appliance was more effective than with labiolingual appliance. 3. More downward movement of the posterior palatal plane obserbed with maxillary protraction doing the midpalatal suture opening than with protraction after finishing the palatal expansion 4. The clinical effects of protraction and changes of the retention periods were not statistically significant among the age groups. 5. During the retention period, maxilla and maxillary teeth, and mandible and mandibular teeth moved downward and forward, however the mandibular changes were larger than the maxillary changes.

• 상하수도학회지
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• 제16권6호
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• pp.717-725
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• 2002

A bench-scale submerged-type membrane filtration system (SMFS) was constructed to study a feasibility of membrane filtration for solid-liquid separation in water and wastewater treatment processes. In the case of applying the SMFS to a biological wastewater treatment process, so-called membrane bioreactor, aeration underneath membrane modules is usually employed in order to provide oxygen demand for microbial growth as well as to control membrane fouling. A study was investigated the effects of operation parameters by aeration intensity, feed concentration, foulant type and airlift pore size on critical flux. Critical flux tends to increase with aeration rate. Optimal aeration flow rate was found to be 10 L/min/module. Feed concentration and foulant type has a significant effect on membrane fouling and filtration performance. But downward position and pore size of airlift has no a significant effects on membrane fouling and filtration performance.