• The Journal of Advanced Prosthodontics
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• v.7 no.2
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• pp.115-121
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• 2015

PURPOSE. This study aimed to evaluate the effect of implant thread depth on primary stability in low density bone. MATERIALS AND METHODS. The insertion torque was measured by inserting Ti implants with different thread depths into solid rigid polyurethane blocks (Sawbones) with three different bone densities ($0.16g/cm^3$, $0.24g/cm^3$, and $0.32g/cm^3$). The insertion torque value was evaluated with a surgical engine. The static compressive strength was measured with a universal testing machine (UTM) and the Ti implants were aligned at $30^{\circ}$ against the loading direction of the UTM. After the static compressive strength test, the Ti implants were analyzed with a Measurescope. RESULTS. The Ti implants with deeper thread depth showed statistically higher mean insertion torque values (P<.001). Groups A and group B had similar maximum static compressive strengths, as did groups C and D (P>.05). After the static compressive strength, the thread shape of the Ti implants with deeper thread depth did not show any breakage but did show deformation of the implant body and abutment. CONCLUSION. The implants with deeper thread depth had higher mean insertion torque values but not lower compressive strength. The deep threads had a mechanical stability. Implants with deeper thread depth may increase the primary stability in areas of poor quality bone without decreasing mechanical strength.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.3
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• pp.55-63
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• 2000

Studies for tube spin forming have been implemented restrictively compared to spinning process, because of the complex of deformation mechanism. Especially there were not many studies by using FEM(Finite Element Method) for overcoming restriction of upper bound method. In this paper, the tube spinning process is analyzed to produce cylindrical body made by titanium alloy. In analysis, processing parameters was obtained by using upper bound method to consider material properties of titanium alloy and finite element analysis was implemented to investigate the flatness and the elongation of the titanium alloy workpiece by using ABAQUS code. The independent variables are ; material properties of workpiece, angles of roller, reduction of diameter. Three variables, two angles of roller and reduction of diameter are optimized by using the upper bound method. In this method, we can estimate the workable power, working force and reduction of diameter, and also the flatness and the elongation of workpiece by the finite elements analysis using ABAQUS/standard. The results indicates that these variables play a critical factors of spinning process for the titanium alloy and the optimum values of these variables.

• Journal of the Korea Convergence Society
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• v.6 no.2
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• pp.19-24
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• 2015

Nowadays, the number of people who do not move actively or are treated for rehabilitation is increasing because of the disorder or the paralysis of their own lower body by the industrial disaster. In this study, the walker for the people whose bodies are not convenient or the old is investigated. The walkers due to the height of walker are designed and the structural simulation analysis is carried out. The study models of walker are modelled with CATIA program and analyzed with ANSYS program. As the analysis result, the models of 1, 2 and 3 have the maximum stresses extremely below the yield stress of this model and the elastic deformations at these models occurs. Among these models, As the maximum deformation of model 3 has the least value among these models, models 3 is thought to have the best durability. The safety of walker model can be estimated by the basis of the result of this study. The damage can be prevented and the durability is examined by applying this result into the design of walker. And it is possible to be grafted onto the convergence technique at design and show the esthetic sense.

• Journal of Chest Surgery
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• v.25 no.7
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• pp.693-701
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• 1992

Extracorporeal cardiopulmonary bypass[CPB] has been associated with a wide variety of hematologic derangements, including a transient deformation and hemolysis of red blood cells[RBCs], which is supposed to be due to mechanical trauma and/or metabolic alterations. Since membrane integrity is, in part, maintained by energy requiring process, inadequate function of erythrocyte glycolytic pathway, which is inevitalble during CPB, may cause depletion of high energy phosphate pool and result in hemolysis. The authors performed an investigation to assess whether administration of Fructose-l, 6-diphsphate [FDP], which has been known to enhance intracellular glycolytic activities, could counteract erythrocyte hemolytic events caused by CPB. Sixty pateints with cyanotic congenital heart diseases, who underwent open heart surgery under CPB longer than 60 minutes, were randomly divided into two groups depending on whether use of FDP[Group FDP] or not[Group Control]. The age, sex, CPB time, preoperative hemoglobin level, disease entities were all similar[Table 1], and membrane type oxygenators were used in all patients. In Group, FDP, a dose of 250mg/kg body weight of FDP was administered by intravenous dripping every 12 hours from the morning of the operation to postoperative 48 hours, To demonstrate the degree and pattern of hemolysis of erythrocyte, reticulocyte count, indirect /direct bilirubin, haptoglobin, plasma hemoglobin, lactate dehydrogenase were measured every 12 hours from the time of cessation of CPB to 48 hours and RBC morphologic study, osmotic fragility test were done every 24 hours. All parameters revealed less hemolytic in group FDP [Fig. 1~5], though the differences between two groups were not significant, except plasma hemoglobin, lactate dehydrogenase changes. A pattern of sequential changes of plasma hemoglobin, lactate deh-ydrogenase showed the highest level at the time of CPB stop and abrupt decrease in following 24 hours in both groups, and statistically significant differences were demonstrated in group FDP at least for the first 12 hours postoperatively[p<0.05]. The authors conclude that they can expect the benificial effect of FDP on the maintenance of membrane stability of RBC probably by energy enhancement during the shock status of CPB, but FDP could not completely prevent the damaging effect on RBC by cardiopulmonary bypass

• Economic and Environmental Geology
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• v.21 no.3
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• pp.235-255
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• 1988

Talc deposit of pipe-like form occurrs in the lower part of the Hyangsanri Dolomite with a strike of N40 -50 E and a dip of 40 -50 NW which is one formation of the Ogcheon Super Croup. The pipi-like ore body plunge at about $40^{\circ}$ to the west and are parallel to the lineation developed in the area. Structural formulae of tales occurred in this deposit are close to the ieal composition $Mg_6Si_8O_{20}(OH)_4$ showing limited deviation from ideal one. Substitution of Al for Si in tetrahedral site is of little or nothing ranging 0-0.04 and octahedral occupancy is close to six ranging 5.88-5.98 atoms per unit cell. Predominant octahedaral cation is Mg and proportion of divalent cations is generally over 97percent. Calcite -dolomite thermometry is obtained by determining the mol % $MgCO_3$using of EPMA and XRD methods. The peak metamorphic temperature can be estimated at $470{\pm}30^{\circ}C$ in the area whereas carbonates occurred at near talc ore show lower temperature than $400^{\circ}C$ that the calcite solvus limit is not well established. It indicates that the talc deposit was formed at the lower temperature that the metamorphic temperature. Cosequently, the formation of talc by metamorphism is questionable and the alteratin zone developed around the talc ore is very limited. The occurrence of talc ore in the dolomite as well as mineralogy, calcite-dolomite geothermometry, chlorite geothermometry, field and microscopic evidence suggest that siliceous ascending hydrothermal solution along the fracture is responsible for the formation of talc. It was considered that the slight fracturing of dolomite was formed by deformation prior to the mineralization.

• Journal of the Korea Convergence Society
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• v.10 no.7
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• pp.149-154
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• 2019

This paper is to study the durability through structural analysis on the front undercover of SUV car for offroad. It was investigated which model became structurally best by analyzing three kinds of models which are similar to the configuration of undercover for the protection of the part under car body which has been used really. The models of undercover were designed through CATIA program and analyzed by using ANSYS program as three kinds of models A, B and C. Through the analysis results, model B was expressed to have the best durability as model B has the least equivalent stress and the longest fatigue life among three models. As the design data with the durability of undercover obtained on the basis of this study result are utilized, the esthetic sense can be shown by being grafted onto the machine or structure at real life.

• Geomechanics and Engineering
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• v.17 no.2
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• pp.119-131
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• 2019

Time dependent creep settlements are one of the most important causes of material deteriorations for the huge water structures such as concrete faced rockfill dams (CFRDs). For this reason, performing creep analyses of CFRDs is vital important for monitoring and evaluating of the future and safety of such dams. In this study, it is observed how changes viscoplastic behaviour of a CFR dam depending the time. Ilısu dam that is the longest concrete faced rockfill dam (1775 m) in the world is selected for the three dimensional (3D) analyses. 3D finite difference model of Ilısu dam is modelled using FLAC3D software based on the finite difference method. Two different special creep material models are considered in the numerical analyses. Wipp-creep viscoplastic material model and burger-creep viscoplastic material model were rarely used for the creep analyses of CFRDs in the last are taken into account for the concrete slab and rockfill materials-foundation, respectively. Moreover, interface elements are defined between the concrete slab-rockfill materials and rockfill materials-foundation to provide interaction condition for 3D model. Firstly, dam and foundation are collapsed under its self-weight and static behaviour of the dam is evaluated for the empty reservoir conditions. Then, reservoir water is modelled considering maximum water level of the dam and time-dependent creep analyses are performed for maximum reservoir condition. In this paper, maximum principal stresses, vertical-horizontal displacements and pore pressures that may occur on the dam body surface during 30 years (from 2017 to 2047) are evaluated in detail. According to numerical analyses, empty and maximum reservoir conditions of Ilısu dam are compared with each other in detail. 4 various nodal points are selected under the concrete slab to better seen viscoplastic behaviour changes of the dam and viscoplastic behaviour differences of these points during 30 years are graphically presented. It is clearly seen that horizontal-vertical displacements and principal stresses for maximum reservoir condition are more than the empty reservoir condition of the dam and significant pore pressures are observed during 30 years for maximum reservoir condition. In addition, horizontal-vertical displacements, principal stresses and pore pressures for 4 nodal points obviously increased until a certain time and changes decreased after this time.

• Geomechanics and Engineering
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• v.28 no.3
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• pp.265-281
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• 2022

A set of slurry shield test system capable of cutter cutting and slurry automatic circulation is used to investigate the deformation characteristics, the evolution characteristics of support resistance and the distribution and evolution process of earth pressure during excavating and collapsing of slurry shield tunneling in circular-gravel layer. The influence of cover-span ratio on surface subsidence, support resistance and failure mode of excavation face is also discussed. Three-dimensional numerical calculations are performed to verify the reliability of the test results. The results show that, with the decrease of the supporting force of the excavation face, the surface subsidence goes through four stages: insensitivity, slow growth, rapid growth and stability. The influence of shield excavation on the axial earth pressure of the front soil is greater than that of the vertical earth pressure. When the support resistance of the excavation face decreases to the critical value, the soil in front of the excavation face collapses. The shape of the collapse is similar to that of a bucket. The ultimate support resistance increase with the increase of the cover-span ratio, however, the angle between the bottom of the collapsed body and the direction of the tunnel excavation axis when the excavation face is damaged increase first and then becomes stable. The surface settlement value and the range of settlement trough decrease with the increase of cover-span ratio. The numerical results are basically consistent with the model test results.

• Smart Media Journal
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• v.11 no.1
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• pp.46-57
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• 2022

In this paper, multi-region based Radial Graph Convolutional Network (MRGCN) algorithm which can perform end-to-end action recognition using the optical flow and gradient of input image is described. Because this method does not use information of skeleton that is difficult to acquire and complicated to estimate, it can be used in general CCTV environment in which only video camera is used. The novelty of MRGCN is that it expresses the optical flow and gradient of the input image as directional histograms and then converts it into six feature vectors to reduce the amount of computational load and uses a newly developed radial type network model to hierarchically propagate the deformation and shape change of the human body in spatio-temporal space. Another important feature is that the data input areas are arranged being overlapped each other, so that information is not spatially disconnected among input nodes. As a result of performing MRGCN's action recognition performance evaluation experiment for 30 actions, it was possible to obtain Top-1 accuracy of 84.78%, which is superior to the existing GCN-based action recognition method using skeleton data as an input.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.369-372
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• 2021

These days, people spend more time sitting at a desk for studies or work. Also, because people continue to use computers, smartphones, and tablet PCs often during break times, their posture is getting worse. Maintaining a position of bad posture for an extended period of time causes problems with the musculoskeletal system related to the neck, shoulders, and spine. Additionally, problems such as physical fatigue and posture deformation are predicted to expand to a wide range of age groups. Therefore, the core function of the system we are developing is to ensure correct sitting posture and to receive alert notifications via the created mobile application. To create the system, a flex sensor, pressure sensor, and tilt sensor are attached to a chair and utilized. The flex sensor detects and compares the amount of bending in the chair's posture and transmits this value to an Arduino Uno R3 board. Additionally, information such as body balance and incline angle are collected to determine whether or not the current sitting posture is correct. When the posture is incorrect, a notification is sent through the mobile application to indicate to the user and the monitoring app that their posture is not correct. The system proposed in this study is expected to be of great help in future posture-related research.