• The Journal of Korean Academy of Prosthodontics
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• v.48 no.4
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• pp.294-300
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• 2010

Purpose: The template-guided implant surgery offers several advantages over the traditional approach. The purpose of this study was to evaluate the accuracy of coordinate synchronization procedure with 5-axis milling machine for surgical template fabrication by means of reverse engineering through universal CAD software. Materials and methods: The study was performed on ten edentulous models with imbedded gutta percha stoppings which were hidden under silicon gingival form. The platform for synchordination was formed on the bottom side of models and these casts were imaged in Cone beam CT. Vectors of stoppings were extracted and transferred to those of planned implant on virtual planning software. Depth of milling process was set to the level of one half of stoppings and the coordinate of the data was synchronized to the model image. Synchronization of milling coordinate was done by the conversion process for the platform for the synchordination located on the bottom of the model. The models were fixed on the synchordination plate of 5-axis milling machine and drilling was done as the planned vector and depth based on the synchronized data with twist drill of the same diameter as GP stopping. For the 3D rendering and image merging, the impression tray was set on the conbeam CT and pre- and post- CT acquiring was done with the model fixed on the impression body. The accuracy analysis was done with Solidworks (Dassault systems, Concord, USA) by measuring vector of stopping’s top and bottom centers of experimental model through merging and reverse engineering the planned and post-drilling CT image. Correlations among the parameters were tested by means of Pearson correlation coefficient and calculated with SPSS (release 14.0, SPSS Inc. Chicago, USA) ($\alpha$ = 0.05). Results: Due to the declination, GP remnant on upper half of stoppings was observed for every drilled bores. The deviation between planned image and drilled bore that was reverse engineered was 0.31 (0.15 - 0.42) mm at the entrance, 0.36 (0.24 - 0.51) mm at the apex, and angular deviation was 1.62 (0.54 - 2.27)$^{\circ}$. There was positive correlation between the deviation at the entrance and that at the apex (Pearson Correlation Coefficient = 0.904, P = .013). Conclusion: The coordinate synchronization 5-axis milling procedure has adequate accuracy for the production of the guided surgical template.

• The Korean Society of Law and Medicine
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• v.17 no.1
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• pp.281-297
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• 2016

In order to make a treatment plan and outcome prediction, it is important to evaluate accurately and objectively osseous tissues of the implant area. The evaluation of osseous tissues is the most objective method for the decision of production time of upper structure of alveolar bone. However, the evaluation of osseous tissues contains contradiction because it is made by subjective opinions of dental surgeons. Many dentists also point out the problem of subjective evaluation of osseous tissues. Therefore, it is necessary to create accurate and objective standards. Previously, the evaluation of bone density depends on dentist's subjective sensation during drilling procedure of implant. However, the HU(Hounsfield unit) figure of CT(computed tomography) scan allows of objective and precise categorization of bone density now. Misch and Kircos divided the bone density levels from D1 to D5 with subjective separation of bone density. Their method also depended on not objective and quantification data but subjective separation by sensation. Thus, we need the evaluation of implant area through comparative analysis of more objective and quantification data. Implant treatment comprises the highest frequency of medical disputes of dental clinic. If we bring objective checkup and reasonable treatment method in the implant treatment, we can deduce more reasonable results, and the failure late of implant treatment also can decrease. The ultimate objective of this study is the minimization of dental disputes between dental patients and dentists by creating new legal standards on the basis of objective and quantification data.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.2
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• pp.151-160
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• 2017

Growing demand and rapid development of the synthetic fiber rope in mooring system have taken place since it has been used in deep water platform lately. Unlike a chain mooring, synthetic fiber rope composed of lightweight materials such as Polyester(polyethylene terephthalate), HMPE(high modulus polyethylene) and Aramid(aromatic polyamide). Non-linear stiffness and another failure mode are distinct characteristics of synthetic fiber rope when compared to mooring chain. When these ropes are exposed to environmental load for a long time, the length of rope will be increased permanently. This is called 'the creep phenomenon'. Due to the phenomenon, The initial characteristics of mooring systems would be changed because the length and stiffness of the rope have been changed as time goes on. The changed characteristics of fiber rope cause different mooring tension and vessel offset compared to the initial design condition. Commercial mooring analysis software that widely used in industries is unable to take into account this phenomenon automatically. Even though the American Petroleum Institute (API) or other classification rules present some standard or criteria with respect to length and stiffness of a mooring line, simulation guide considers the mechanical properties that is not mentioned in such rules. In this paper, the effect of creep phenomenon in the fiber rope mooring system under specific environment condition is investigated. Desiged mooring system for a Mobile Offshore Drilling Unit(MODU) with HMPE rope which has the highest creep is analyzed in a time domain in order to investigate the effects creep phenomenon to vessel offset and mooring tension. We have developed a new procedure to an analysis of mooring system reflecting the creep phenomenon and it is validated through a time domain simulation using non-linear mooring analysis software, OrcaFlex. The result shows that the creep phenomenon should be considered in analysis procedure because it affects the length and stiffness of synthetic fiber rope in case of high water temperature and permanent mooring system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.1
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• pp.67-75
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• 2023

In this study, the dynamic characteristics of an offshore platform being installed and physical phenomena are analyzed from the perspective of interaction between operation and maneuvering simulation using a real-time Maneuvering & Operation simulator of Shipbuilding & Marine Simulation Center at Tongmyong University. It was simulated to install the semi-submersible drilling rig moored by 8 mooring lines according to a scenario that is similar to it on the real sea, and 4 tug boats for position keeping of the rig and an offshore support vessel for hook-up of the mooring lines were operated. During the simulation, the motion, trajectory, tension of the objects were output in real time, and they were analyzed at each work procedure. This study about the simultaneous simulation of operation and maneuvering showed the detailed motion of the offshore platform and ships on the operation procedure and the interaction between operation and maneuvering in specific environment condition. Also, it confirmed that the simulation can be utilized to determine the possibility of offshore platform installation in specific situations.

• Bulletin of the Society of Naval Architects of Korea
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• v.54 no.4
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• pp.39-46
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• 2017

Jack-up drilling rigs are widely used in offshore oil and gas exploration industry. It is originally designed for use in the shallow waters less than 60m of water depth; there is growing demand for their use in deeper water depth over 150m and harsher environmental conditions. In this study, global in-place analysis of jack-up rig leg for North-sea oil well is performed through numerical analysis. Firstly, environmental conditions and seabed characteristics at the North-sea are collected and investigated measurements from survey report. Based on these data, design specifications are established and the overall basic design is performed. Dynamic characteristics of the jack-up rig for North-sea are considered in the global in-place analysis both leg and hull and the basic stability against overturning moment is also analyzed. The structural integrity of the jack-up rig leg/hull is verified through the code checks and the adequate safety margin is observed. The uncertainty in jack-up behaviour is greatly influenced by the uncertainties in the soil characteristics that determine the resistance of the foundation to the forces imposed by the jack-up structure. Among the risks above mentioned, the punch-through during pre-loading is the most frequently encountered foundation problem for jack-up rigs. The objective of this paper is to clarify the detailed structure and installation engineering matters for prove the structural safety of jack-up rigs during operation. With this intention the following items are addressed; - Characteristics of structural behavior considering soil effect against environmental loads - Modes of failure and related pre-loading procedure and parameters - Typical results of structural engineering and verification by actual measurement.

• Archives of Hand and Microsurgery
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• v.23 no.4
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• pp.223-229
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• 2018

Purpose: A number of procedures were introduced to stabilize the 1st metacarpal bone after resection of the trapezium in the thumb carpometacarpal joint (CMCJ) arthroplasty. However, some surgical procedures may inevitably damage normal structures, such as harvesting tendons or drilling of a bone for tendon passage. Suture suspension arthroplasty is relatively less invasive and easier to perform than the previously described surgical methods. The purpose of this study was to report the therapeutic efficiency of the suture suspension arthroplasty. Methods: We retrospectively reviewed 12 patients who underwent suture suspension arthroplasty for the treatment of thumb CMCJ arthritis. Pain visual analogue scale (VAS), satisfaction about surgical outcomes, and the disabilities of the arm, shoulder and hand (DASH) scores were measured to evaluate the functional outcomes and the Trapezial Space Ratios were measured. Satisfaction was measured in the range of "very dissatisfied" (0) to "very satisfied" (10). Results: The mean follow-up period was 23 months. Pain VAS score improved significantly from 7.0 to 2.9 (p<0.05). And mean satisfaction scale was 6.9. However, there was no significant difference in DASH scores between before and after surgery (p=0.06). The mean trapezial space ratio was calculated to be 0.45 before surgery, 0.33 immediately after surgery, 0.23 at the last follow-up. Conclusion: Suture suspension arthroplasty is a satisfactory surgical procedure. And compared with other procedures, there is no significant difference in the reduction of the trapezial space. It may be useful in advanced thumb CMCJ arthritis.

• The Korean Journal of Nuclear Medicine
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• v.33 no.6
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• pp.484-492
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• 1999

Purpose: This study was to evaluate the clinical usefulness of $^{99m}Tc$-MDP bone scintigraphy for assessing vascular ingrowth into the ocular implants after enucleation or evisceration. Materials and Methods: Twenty-four patients (M:F=7:17, mean age: 36 years), who buried a coralline hydroxyapatite after uncomplicated enucleation or evisceration surgery were studied. Dynamic and static scintigraphy on the orbit fossa were obtained after injection of 740 MBq $^{99m}Tc$-MDP to evaluate the status of vascularization. The study was performed from the 3 to 33 weeks after surgery. According to the visual analysis, activity greater than nasal bridge was graded as 4, equal to the nasal bridge as 3, less than nasal bridge but greater than normal orbit as 2, greater than normal orbit but less than grade 2 as 1. Uptake ratio was also calculated by measuring the implants activity (H) and contralateral orbit activity (N). Grading score and uptake ratio were compared with clinical outcome of vascularization. Additionally, we also analyzed the vascularization status as time lapse between primary surgery and scintigraphic study and surgical methods. Results: Twenty-one patients who had bone scintigraphy at 11 weeks after surgery showed increased uptake above grade 2 and greater H/N ratio than 1.16. Of these, 19 patients who had drilling surgery for permanent peg application showed adequate bleeding during the procedure. The activity grade and uptake ratio were inversely correlated with vascular ingrowth. Higher than grade 2 or greater than 1.56 in H/N ratio seemed to be an indicator for better prognosis. Accomplishment of vascularization was not affected by the surgical way such as enucleation or evisceration. Conclusion: $^{99m}Tc$-MDP bone scintigraphy can be a useful method to evaluate the vascularized status of implants. Adequate time for $^{99m}Tc$-MDP bone scintigraphy may be 11-20 weeks after enucleation or evisceration.