• Journal of Periodontal and Implant Science
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• v.29 no.1
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• pp.233-249
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• 1999

Primary fixation is one of the most important factor in establishing adequate osseointegration between implant and bone. To evaluate the initial healing response of bone around implants without primary bone contact, this study was designed to create considerable space between implant and bone in 5 mongrel dogs, about 1-year old. After 3 holes of 6.0mm in diameter were prepared at the femur neck of the dogs, commercially pure titanium thread type implants(STERI-$OSS^{(R)}$), 8mm in length and 3.8mm, 5.0mm and 6.0mm in diameter, were inserted. Implants were supported by only nonresorbable membrane($Teflon^{(R)}$), and the penetration of upper soft tissue into the gap was inhibited by it. The each implant was positioned in the center of the drilled hole. 9 implants with different diameters were inserted in 3 dogs for histologic observation, and 12 were inserted in 2 dogs for mobility test and removal torque test.Fluorescent dyes were injected in order of Doxycycline, Alizarin Red S, and Calcein at intervals of 2 weeks. At 4-, 8-, and 12-week after placement, 3 dogs were sacrificed for histologic observation, and at 8- and 12-week after placement, 2 dogs were sacrificed for mobility test using $Periotest^{(R)}$ (Simens AG, Bensheim, Germany) and torque test using Autograph AGS-1000D $series^{(R)}$(Japan). The result were as follows: 1. The wider the gap between bone and implant was, the less bone maturity was, and the later osseointegration was occurred. Trabecular direction of new bone around implant was changed from parallel to perpendicular to the implant, and the gap was filled with new bone, over time. 2. There was a decreasing tendency over time in the mobility of all implants, but the wider gap between bone and implant was, the smaller decrease of the mobility was. 3. There was a increasing tendency over time in the removal torque gauge of all implants, and the wider gap was, the smaller increase of the removal torque gauge was. The results suggest that osseointegration in case of implant without primary bone contact may be obtained by guided bone regeneration technique with prolonged healing period, but the time of second surgery should be considered carefully.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.3
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• pp.383-394
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• 1999

The indirect technique for making cast restoration requires that dies be as accurate and durable as possible. Currently, stone is the most commonly used material for die. However, it has some problems such as the weakness in its strength and low abrasion resistance. Recently, epoxy resin die systems have become available. The purpose of this study was to examine two commercially available resin die systems and evaluate some characteristics for their clinical performance. This study evaluated the dimensional accuracy of epoxy resins and their wettability with impression materials. In this study, the first experiment was about dimensional accuracy of different die materials. The master model was made of stainless steel. 10 models were made of two epoxy resins (Die-epoxy, Tri-epoxy) and a die stone (Fujirock) each. Occlusal diameter (Dimension I), occluso-gingival height (Dimension II), and interabutment distance (Dimension III) were measured in each model. Next, the contact angles of die materials with impression materials were observed. The blocks were made of polyether, hydrophilic additional silicone, polysulfide impression materials. By drop-ping the same amount (0.05ml) of Tri-epoxy, Die-epoxy, and die stone on the blocks, 10 samples of each die material were made. After setting of materials, the contact angles were measured. The results of this study were as follows. 1. The expansion of stone die and the shrinkage of resin dies in occlusal diameter were observed, and stone and Tri-epoxy were expanded and Die-epoxy was shrinked in occluso-gingival height. There was little change among materials in interabutment distance (p<0.05). 2. In comparison with the master model Tri-epoxy had the least variation in measurement of the three die systems examined. Die-epoxy was next, and die stone showed the greatest variation. 3. The compatibility of die stone for polyether, hydrophilic additional silicone, polysulfide decreased in order, wherease epoxy materials had the decreased compatibility for polyether and polysulnde, hydrophilic additional silicone in order. It was not statistically different between polyether and polysulfide (p<0.05). 4. The contact angles of Tri-epoxy, Die-epoxy, die stone were getting bigger in order.

• Journal of Periodontal and Implant Science
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• v.29 no.2
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• pp.415-433
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• 1999

Implant stability is the key to long-term successful outcome for osseointegrated implants. To evaluate the initial healing response of bone around HA-coated implants without primary bone contact. 21 HA-coated thread type implants(STERI-OSS?) were placed in the femurs of 5 mongrel dogs, about 1-year old. Implants, 8 mm in length and 3.8mm(experimental 1group), 5.0mm(experimental 2group) and 6.0mm(control group) in diameter, were inserted after 3 holes of 6.0mm in diameter and 10mm in depth were prepared in the surgical sites each dog. Implants were supported by only nonresorbable membrane($Teflon^{(R)}$), in order to prevent the ingrowth of upper soft tissue into the gap between bone and implant, and to maintain each implant to be positioned in the center of the drilled hole. 9 implants with different diameters were inserted in 3 dogs for histologic observation, and 12 implants were inserted in 2 dogs for mobility test and removal torque test. Fluorescent dyes were injected for the observation of new bone formation in order of $Terramycin^{(R)}$, Arizarin $Red^{(R)}$, and $Calcein^{(R)}$ at an interval of 2 weeks. 3 dogs were sacrificed for histologic observation at 4, 8, and 12-week after placement. Light microscopy and confocal laser scanning microscopy were used to qualitatively characterize the bone around HA-coated implant. 2 dogs were sacrificed for mobility test($Periotest^{(R)}$, Simens AG, Bensheim, Germany) and removal torque test($Autograph^{(R)}$ AGS-1000D series, Japan) at 8 and 12-week after placement The results were as follows: 1. Histologic observation showed that osseointegration occurred to both control and experimental groups as time lapse, but delayed bone healing was revealed in 3.8mm group (experimental 1group), compared to contrtol group and 5.0mm group (experimental 2group). 2. The mobility test showed that the experimental groups had no distinguishable movement during experimental periods of 8 and 12-week, and there was no difference in mobility depending on the gap between bone and implant, and time lapse. 3. The removal torque forces were increased depended on the gaps decreasing between bone and implant, and time lapse. The results suggest that HA-coated implant without primary bone contact, based on guided bone regeneration could obtain its stability in all experimental groups as time lapse, but bone healing was delayed in experimental group of 3.8mm. And the results suggested that studies on correlationship between mobility test and removal torque test for implant stability would be necessary.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.2
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• pp.74-80
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• 2005

A new dimension measuring method for the measurement of diameter of an object has been developed using laser triangulation. The 3D data of an object was calculated from the 2 dimensional image information obtained by the laser stripe using the laser triangulation. The system that use existing theory can measure the diameter of hole not only in a normal plane but also ill an incline plane. However, in the existing theory, since the lens with fixed feral length was used, the area of measurement was fixed. The simplest way to solve this problem is to change distance between a CCD camera and object. Other way is to use a zoom lens having variable focal length. In this paper, the zoom lens with variable focal length was used. Therefore, we ran experiment with magnification that is optimized according to size of object using zoom lens with variable focal length.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.4
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• pp.418-429
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• 1992

Recently, many researchers make a great effort to develop high efficient marine diesel engines using low grade heavy oil, and also study substitution fuel oil for engines and boilers. In case of Fisheries Vessels, we need to know that fish oil can be substituted for fuel oil. Therefore, it is studied that evaporation, ignition and combustion phenomena of the single droplet of fish oils (i.e., Sardine fish oil, File fish oil and Alaska pollac oil) on heated plane surface to evaluate appropriateness as substitution oil. Methanol and light oil are tested simultaneously to help the evaluation on these Fish oils. The results are summarized as follows: 1. The type of evaporation and combustion is spherical evaporation in case of methanol and light oil. And fish oil blended with light oil was finished after spherical evaporation happen when high temperature. 2. Ignition of Pure fish oil was shorter than that of fish oil blended with light oil. 3. Heat transferred to droplet could make qualitative comparison by contact diameter of droplet with hot surface as time changes. Life time of droplet according to the change of heated surface temperature was greatly influenced by droplet contact condition on the heated surface. 4. As far as combustion phenomena was concerned, apparent diameter of the fish oil droplet increased after ignition and decreased suddenly by internal boiling of droplet. 5. Three fish oils had similar phenomena on the evaporation, ignition and combustion. 6. Evaporation and combustion feature of fish oil could not be shown by coefficient of evaporation velocity of droplet and coefficient of combustion velocity of droplet.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.9
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• pp.615-622
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• 2017

A normal shock wave is initially formed in the shock tube that migrates towards the closed end of the tube, which, in turn, leads to the reflection of shock. Due to the interaction of the reflected shock with the boundary layer, bifurcation of the shock wave takes place. A shock train will be generated after the bifurcated shock wave approaches the contact surface. Until now, only a few studies have been conducted to investigate this shock train phenomenon inside the shock tube. For the present study, a CFD analysis has been performed on a two dimensional axisymmetric model of a shock tube using unsteady, compressible Navier-Stokes equations. In order to investigate the detailed characteristics of the shock train phenomenon, quantitative studies have been performed by varying shock tube length, diameter under fixed diaphragm, and pressure ratio inside a shock tube.

• Journal of the Korean Vacuum Society
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• v.18 no.5
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• pp.337-345
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• 2009

When the drill hole diameter for the package substrate is under $100{\mu}m$, the smear in the drill hole cannot be eliminated by wet desmear process only. We intended to change the substrate's hydrophobic characteristics to hydrophilic characteristics by adapting the atmospheric pressure plasma prior to the wet desmear process. Atmospheric pressure plasma process was made as the inline type equipment which is adequate for the package substrate's manufacturing process and remote DBD type electrodes were used for the equipment. As the result of atmospheric pressure plasma processing, the contact angle of the substrate was enhanced from 71 degree to 30 degree. Dielectric film thickness, drill hole diameter and surface roughness were measured to evaluated the characteristics of the wet desmear process in case of plasma processing and in case of none. By the measurement, it was analyzed that the process uniformity within the whole panel was largely enhanced. Also, it was verified that the smear in the drill hole was eliminated efficiently which was analyzed by the SEM image of the drill hole.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.2
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• pp.325-335
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• 1992

In this work, direct contact 4-stage fluidized bed heat exchanger is experimentally studied to develop a new type of heat exchanger which recovers the energy contained in the high temperature waste gas exhausted from the industrial furnaces. A sand is used as a heat transfer medium in this experiment. To determine the optimum operating condition, 11 different perforated plates which have a different free area ratio with different hole diameter are used in the experiment. From the room temperature experiment, the pressure drop which is caused by fluidized bed formation is observed. The high temperature experiment is carried out to seek the optimum operating condition of high heat efficiency at low heat exchanger operation cost. The results of experiment are as following. The pressure drop in the high temperature condition can be predicted from the results of the room temperature experiment. And Nusselt number becomes smaller due to the increased interference between sand particles as Reynolds number increases when the dilute phase fluidized beds are formed in nigh temperature condition. But heat transfer amount through the total sand surface area become larger due to the large resident amount of sand. Considering the heat transfer amount and the heat exchanger operation cost, perforated plates which have either a 30% or 35% of free area ratio with 15mm of hole diameter are best fitted for our goal of this work. The values of .phi. which is a dimensionless number representing the absorption heat amount per unit sand rate are in the range from 0.4 to 0.5, when Reynolds number of waste gas ranges from 25-30 with these perforated plates.

• Journal of Energy Engineering
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• v.8 no.2
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• pp.272-278
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• 1999

In the present study, measurements of thermal contact resistance (TCR) were conducted for joints of brass and aluminium cylinders of 30 mm in diameter, 45 mm in length, when their interfaces were; ⅰ) under vacuum, ⅱ) charged with a pure silicone grease and ⅲ) charged with a mixture of silicone grease and powder of aluminium (#325). Also the data were compared with analytical calculations using Fouche's model. The data of TCR for joints under vacuum state varied in the range of (2∼100)${\times}$10$\^$-5/(㎡$^{\circ}C$/W) depending on their surface roughness. When the contact surfaces were carefully ground, a reduction of 30∼50% in TCR was obtained. But the surface treatment with silicone grease gave rise to a reduction of about 5∼10 times more than that of vacuum state. The analytical prediction by Fouche's model showed a good agreement within 10~30%, for the case of contact surface charged with silicone grease.

• Journal of the Korean Society of Safety
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• v.32 no.2
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• pp.27-33
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• 2017

This study is intended to identify issues on the basis of investigating the actual state of laboratory environment and outlet circuit, and derive end states by expressing sequences from the initiating event of disaster to accident in leakage current, poor contact and overload through ETA(event tree analysis). To this end, this study investigated the actual state of electric equipment of laboratory at universities in all parts of country. And it is shown that most of them are failure in electric work and user negligence in the investigation of actual state. It is found that there is earth fault and defect in wire diameter in the failure of electric work and the problem of partial disconnection due to wire bundling and poor contact in user negligence. Outlet-related component, failure rate and initiating events are composed of a total of 41 initiating events, i.e., 30 internal initiating events and 11 external initiating events. And end states are composed of a total of 15 parts, i.e., 3 electric power parts and 12 safety parts. Earthing class 3 is the most important safety device against leakage current (initiating event). And in case of poor contact, it is necessary for manager to check thoroughly because there is no safety device. In case of overload/overcurrent, when high-capacity equipment is connected, a molded case circuit breaker, safety device, worked. However, in most cases, it is verified that this doesn't work. This study can be utilized as electric equipment safety guide for laboratory safety manager and managers.