• Journal of the Microelectronics and Packaging Society
• /
• v.18 no.1
• /
• pp.35-39
• /
• 2011

Shearing characteristics of Sn-3.0wt%Ag-0.5wt%Cu ball for standardization of high speed shear test were investigated. The solder ball of 450 ${\mu}m$ in diameter was reflowed at $245^{\circ}C$ on FR4 PCB (Printed Circuit Board) to prepare a sample for the high-speed shear test. The metal pads on the PCB were OSP (Organic Solderability Preservative, Cu pad) and ENIG (Electroless Nickel/Immersion Gold, i.e CulNi/Au). Shearing speed was varied from 0.5 to 3.0 m/s, and tip height from 10 to 135 ${\mu}m$. As experimental results, for the OSP pad, a ductile fracture increased with tip height, and it decreased with shearing speed. In the case of ENIG pad, the ductile fracture increased with the tip height. The tip height of 10 ${\mu}m$ (2% of solder ball diameter) was unsuitable since the fracture mode was mostly pad lift. Shear energy increased with increasing shearing tip height from 10 to 135 ${\mu}m$ for both of OSP and ENIG pads.

• The Journal of Korean Academy of Prosthodontics
• /
• v.58 no.1
• /
• pp.23-29
• /
• 2020

Purpose: The purpose of this retrospective study was to evaluate the method using the S-reamer and gel-type graft material by the success rate and survival rate. Materials and methods: Implantation period was from 2008 to 2014, Follow check up year is 2019. There were 59 patients and 117 implants. All implants were placed in the posterior maxilla with the sinus lift. The patients population consisted of 34 men and 25 women, ranging from 19 to 75 years. The residual bone heights were from 1 mm to 6 mm. Sinus was perforated with S-reamer without membrane tearing and gel type bone graft material was used for membrane lifting and filling the space. all implants were placed simultaneously. Panoramic X-ray was taken. After 5 - 6 months healing period, final prostheses were restored. After more 5-years implant surgery, Panoramic X-ray was obtained and X-ray analysis and clinical examination were performed. Success criteria was referred to a Buser's success critera. All implants were classified to success implant, survival implant, failed implant. A success implant was satisfying success criteria, a survival implant was a implant that was acute infection with suppuration and bone loss, a failed implant was a implant that was mobile, removed. Results: Five implants were removed, and 4 implants had infected with bone loss. Survival rate was 95.7% and success rate was 92.3%. Conclusion: This retrospective study presented that this method with S-reamer and gel-type graft material was a successful treatment without membrane tear in the condition of 1-6 mm residual bone height.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.10
• /
• pp.1458-1464
• /
• 2002

$CO_2$ is well known greenhouse gas which is the major source of global warming. Reducing $CO_2$ emission in combustion process can be achieved by increasing combustion efficiency, oxygen enriched combustion and recirculation of the emitted $CO_2$ gas. Stability of non-premixed flame in oxygen enriched environment will be affected by the amount of oxygen, kind of diluents and fuel exit velocity. The effects of these parameters on flame liftoff and blowout are studied experimentally oxidizer coflowing burner. Experiments were divided into three cases according as where $CO_2$gas was supplied. - 1) to coflowing air, 2) to fuel with 0$_2$-$N_2$ coflow, 3) to coflowing oxygen. Flame in air coflowing case was lifted in turbulent region. Flame lift and blowout in laminar region with the increase in $CO_2$ volume fraction in $CO_2$-Air mixture makes flame lift and blowout in laminar region. Increase in oxygen volume fraction makes flame stable-i.e. flame liftoff and blowout occur at higher fuel flowrates. Liftoff height was non-linear function of nozzle exit velocity and affected by the $O_2$ volume fraction. It was found that the flame in $O_2$-$N_2$ coflow case was more stable than $O_2$-$CO_2$ case, Liftoff heights vs (nozzle exit velocity/laminar burning velocity)$^{3.8}$ has a good correlation in $O_2$-$CO_2$ oxidizer case.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.30 no.4
• /
• pp.563-575
• /
• 2003

The purpose of this study was to investigate differences in craniofacial characteristics of professional sportsmen who have practiced since their prepubertal periods. From the standardized lateral and P-A cephalograms of 137 sportsmen, 7 angular, 19 linear, 4 ratio, and 2 index measurements were measured and evaluated by means of statistical methods. The samples were divided into three groups: Group 1; ice hockey(n=17), foot-ball(n=27), basketball(n=16) Group 2; baseball(n=16), gymnastics(n=13), and Group 3; judo(n=18), ssireum(n=10), weight lift(n=20). The results were as follows: It seemed obvious that the cephalic indices of the 3 groups exhibited brachycephalic headform (Group 1; $0.85{\pm}0.04$, Group 2; $0.84{\pm}0.04$, Group 3; $0.83{\pm}0.06$) and there was no statistical difference among the groups (p>0.05). The facial indices of the Group 1 ($0.93{\pm}0.05$) and Group 2 ($0.93{\pm}0.04$) exhibited definite leptoprosopic facial forms while the Group 3 ($0.90{\pm}0.04$) showed more or less euryprosopic facial form, and there appeared significant difference between the Group 1 and 3 (p<0.05), and also between the Group 2 and 3 (p<0.05). There appeared strong relationships between the facial indices and the facial axis angle, mandibular plane angle, total craniofacial height, total facial height, upper anterior dental height, lower anterior dental height, mandibular length, lower anterior facial height ratio, and especially with lower anterior facial height (p<0.001). It seemed that most of the vertical facial measurements of the Group 1 and 2 appeared to be larger than those of the Group 3.

• Journal of Advanced Marine Engineering and Technology
• /
• v.36 no.1
• /
• pp.94-100
• /
• 2012

The passive control by vertical splitter plate of fluid force acting on a square prism near a plane wall was studied by measuring of fluid force on the prism and by visualization of the flow field using PIV. The hight of the splitter plate was 10% of the square width. The experimental parameters were the attaching position of vertical splitter plate and the space ratios G/B to the prism height. Time variation of vorticity was most remarkable at 3.0B(B: prism height) position toward wake direction from the center of the prism. The point of inflection of average lift coefficient and Strouhal number on the prism were represented at the space ratio G/B=0.4~0.6 for the prism having vertical splitter plate. The drag of the prism was reduced average 5.0% with the space ratios by attaching the vertical splitter plate at the upper and rear corner on the prism. In this case, the size of the separated region on the upside of the prism was smaller than that of prism having no the splitter plate.

• Imaging Science in Dentistry
• /
• v.50 no.2
• /
• pp.93-98
• /
• 2020

Purpose: Little is known regarding the accuracy of clinical magnetic resonance imaging (MRI) protocols with acceptable scan times in sinus graft assessment. The aim of this study was to evaluate the correlations between MRI and cone-beam computed tomographic (CBCT) measurements of maxillary sinus grafts using 2 different clinical MRI imaging protocols. Materials and Methods: A total of 15 patients who underwent unilateral sinus lift surgery with biphasic calcium phosphate were included in this study. CBCT, T1-weighted MRI, and T2-weighted MRI scans were taken 6 months after sinus lift surgery. Linear measurements of the maximum height and buccolingual width in coronal images, as well as the maximum anteroposterior depth in sagittal images, were performed by 2 trained observers using CBCT and MRI Digital Imaging and Communication in Medicine files. Micro-computed tomography (micro-CT) was also performed to confirm the presence of bone tissue in the grafted area. Correlations between MRI and CBCT measurements were assessed with the Pearson test. Results: Significant correlations between CBCT and MRI were found for sinus graft height (T1-weighted, r=0.711 and P<0.05; T2-weighted, r=0.713 and P<0.05), buccolingual width (T1-weighted, r=0.892 and P<0.05; T2-weighted, r=0.956 and P<0.05), and anteroposterior depth (T1-weighted, r=0.731 and P<0.05; T2-weighted, r=0.873 and P<0.05). The presence of bone tissue in the grafted areas was confirmed via micro-CT. Conclusion: Both MRI pulse sequences tested can be used for sinus graft measurements, as strong correlations with CBCT were found. However, correlations between T2-weighted MRI and CBCT were slightly higher than those between T1-weighted MRI and CBCT.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.35 no.5
• /
• pp.346-352
• /
• 2009

There have been reports of successful bone formation with sinus floor elevation by simply elevating the maxillary sinus membrane and filling the sinus cavity below the lifted sinus membrane with a blood clot. But, in a review of the current literature, we found no animal study that substantiated blood clot's ability in this respect. The aim of this study was to investigate the effect of the method of maxillary sinus floor augmentation using the patient's own venous blood in conjunction with a sinus membrane elevation procedure. An implant was placed bilaterally in the maxillary sinus of six adult mongrel dogs so that it protruded 8 mm into the maxillary sinus after sinus membrane elevation. On one side of the maxillary sinus, the resultant space between the membrane and the sinus floor was filled with autologous venous blood retrieved from the dog. On the opposite side, the maxillary sinus was left untreated as a control. The implants were left in place for six months. The mean height of the newly formed bone in the sinus was 3.7 mm on the side without venous blood and 3.5 mm on the side with venous blood (p>0.05). There was no difference between the two sides regarding new bone height in the sinus. Our results indicate that filling the space between the lifted sinus membrane and the sinus floor with venous blood has no effect on bone formation around implants placed in the maxillary sinus cavity.

• International Journal of Railway
• /
• v.3 no.2
• /
• pp.60-67
• /
• 2010

This paper deals with an experimental study on the wheel flange climbing of railway vehicles, which is a major factor leading to derailment. An experiment is carried out on a 1/5-scale model wheelset of a truck used on a standard-gauge track, which is placed on a roller rig. The lateral external force acting on the wheelset is ramped up until derailment occurs under the condition of a fixed attack angle and wheel-load unbalance ratio. Three parameters, the height of wheel lift, the lateral force, and the wheel load acting on the outer rail, are measured until derailment occurs. From these measurements, it is possible to observe the behavior of the wheelset and to elucidate how the attack angle, the wheel-load unbalance ratio and the lateral external force affect flange-climb derailment. Then, a numerical simulation is carried out using an analytical model based on a single wheelset. As a result, the flange-climb behavior observed in the experiment can be explained theoretically on the bases of the analytical results, although further improvement of the model is desired.

• Journal of computational fluids engineering
• /
• v.13 no.1
• /
• pp.57-62
• /
• 2008

Laminar flows over a cube and a cuboid (cube extended in the streamwise direction) are numerically investigated for the Reynolds numbers between 50 and 350. First, vortical structures behind a cube and lift characteristics are scrutinized in order to understand the variation in vortex shedding characteristics with respect to the Reynolds number. As the Reynolds number increases, the flow over a cube experiences the steady planar-symmetric, unsteady planar-symmetric, and unsteady asymmetric flows. Similar to the sphere wake, the planar-symmetric flow over a cube can be divided into two different regimes: single-frequency regime and multiple-frequency regime. The former has a single frequency due to regular shedding of vortices with the same strength in time, while the latter has multiple frequency components due to temporal variation in the strength of shed vortices. Second, the effect of the length-to-height ratio of the cuboid on the flow characteristics is investigated for the Reynolds number of 270, at which planar-symmetric vortex shedding takes place behind a cube. With the ratio smaller than one, the flow over the cuboid becomes unsteady asymmetric flow, whereas it becomes steady flow for the ratios greater than one. With increasing the ratio, the drag coefficient first decreases and then increases. This feature is related to the flow reattachment on the side faces of the cuboid.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.38 no.5
• /
• pp.627-634
• /
• 2018

In the study, computational fluid dynamics analysis was performed to estimate wind force coefficients for a box-type concrete girder bridge under the influence of wind. The drag, lift and pitching moment coefficients were obtained for the bridge section without noise barrier and compared with those of the bridge section with noise barriers of various heights. The shear stress transport $k-{\omega}$ turbulence model was employed to estimate the wind force coefficients, and the contribution of the friction drag force to the total drag force was investigated. It was found from the study that the drag force coefficients increased as the height of noise barrier increased when a wind blew horizontally, and that the contribution of the friction drag force was highest for the bridge section without noise barrier. It is concluded that the impact of the height of noise barriers should be considered in the design of bridges, and the friction force played an important role in evaluating wind forces on bridges.