• Smart Structures and Systems
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• 제24권3호
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• pp.403-414
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• 2019

Offshore drilling has become a key process for obtaining oil. Offshore platforms have many applications, including oil exploration and production, navigation, ship loading and unloading, and bridge and causeway support. However, vibration problems caused by severe environmental loads, such as ice, wave, wind, and seismic loads, threaten the functionality of platform facilities and the comfort of workers. These concerns may result in piping failures, unsatisfactory equipment reliability, and safety concerns. Therefore, the vibration control of offshore platforms is essential for assuring structural safety, equipment functionality, and human comfort. In this study, an optimal multiple tuned mass damper (MTMD) system was proposed to mitigate the excessive vibration of a three-dimensional offshore platform under ice and earthquake loadings. The MTMD system was designed to control the first few dominant coupled modes. The optimal placement and system parameters of the MTMD are determined based on controlled modal properties. Numerical simulation results show that the proposed MTMD system can effectively reduce the displacement and acceleration responses of the offshore platform, thus improving safety and serviceability. Moreover, this study proposes an optimal design procedure for the MTMD system to determine the optimal location, moving direction, and system parameters of each unit of the tuned mass damper.

• Annals of Clinical Neurophysiology
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• 제11권2호
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• pp.41-47
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• 2009

Background: Discogenic pain can develop into chronic low back pain that is very difficult to treat effectively, because the pathogenesis of the disease still remains controversial. To clarify the pathogenesis, numerous animal models of intervertebral disc degeneration have been proposed in the literature, each with attendant advantages and disadvantages. The aim of this study was to determine the most efficacious method and dose of complete Freund's adjuvant (CFA) injection into intervertebral disc to develop a discogenic pain in a rat. Methods: CFA was injected into the L5-L6 or L4-L5 disc of male Sprague-Dawley rats in various conditions including a dose of CFA (10, 20, or 50 uL), drilling, injection site sealing using cyanoacrylate, and injection velocity. Sham animals were subjected to the same procedure, except for the CFA injection. Mechanical and heat allodynia were serially measured at both hindpaws until 8 weeks post-operatively. Serial MRI analyses were performed to observe degenerative changes of the discs. In addition, CGRP & Substance P-immunoreactivities (ir) in the superficial dorsal horn were evaluated at 4 weeks using immunohistochemistry. Results: Each condition provoked various problems such as development of hindpaw paralysis, CFA leakage, and no pain development. Mid-sagittal T2 MRI revealed no significant degenerative changes in the CFA injected disc. The CGRP-ir of the bilateral superficial dorsal horns at the level of L5-L6 was significantly increased in the CFA group. Conclusions: A total of 10 uL CFA injection into L5-L6 disc for a period of 10 minutes using a 26-gauge needle without drilling was the most efficacious way to develop discogenic pain animal model.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.245-248
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• 1997

Operative interventions for the management of osteonecrosis of the femoral head (ONFH) include core drilling, with or without vascularized fibular bone grafting. Nevertheless, their clinical results have not been consistently satisfactory. Recently, a new surgical procedure that incorporates cementation with polymethylmethacrylate (PMMA) after core drilling has been tried clinically. In this study, a biomechanical analysis using a finite element method(FEM) was undertaken to evaluate surgical methods and their underlying surgical parameter. Our finite element models included five types. They were (1) normal model (Type I), (2) necrotic model (Type II), (3) core decompressed model (Type III). (4) fibular bone grafted model (Type IV), and (5) cemented with PMMA model (Type V). The geometric dimensions of the femur were based on digitized CT-scan data of a normal person. Various physiological loading conditions and surgical penetration depths by the core were used as mechanical variables to study their biomechanical contributions in stress transfer within the femoral head region. In addition. the peak von Mises stress(PVMS) within the necrotic cancellous bone of the femoral head was obtained. The fibular bone grafted method and cementation method provided optimal stress transfer behaviors. Here. substantial increase in the low stress level was observed when the penetration depth was extended to 0mm and 5mm from the subchondral region. Moreover, significant decrease in PVMS due to surgery was observed in the fibular bone grafted method and the cementation method when the penetration depths were extended up to 0 and 5mm from the subchondral region. The drop in PVMS was greater during toe-off than during heel-strike (57% vs. 28% in Type IV and 49% vs. 22% in Type V). Both the vascularized fibular bone grafting method (Type IV) and the new PMMA technique (Type V) appear to be very effective in providing good stress transfer and reducing the peak Von-Mises stress within the necrotic region. Overall results show that fibular bone grafting and cementation methods are quite similar. In light of above results, the new cementation method appears to be a promising surgical alternative or the treatment of ONFH. The use of PMMA for the core can be less prone to surgical complication as opposed to preparation of fibular bone graft and can achieve more immediate fixation between the core and the surrounding region.

• The Journal of Advanced Prosthodontics
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• 제1권1호
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• pp.19-25
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• 2009

STATEMENT OF PROBLEM. Primary stability at the time of implant placement is related to the level of primary bone contact. The level of bone contact with implant is affected by thread design, surgical procedure and bone quality, etc. PURPOSE. The aim of this study was to compare the initial stability of the various taper implants according to the thread designs, half of which were engaged to inferior cortical wall of type IV bone(Group 1) and the rest of which were not engaged to inferior cortical wall(Group 2) by measuring the implant stability quotient(ISQ) and the removal torque value(RTV). MATERIAL AND METHODS. In this study, 6 different implant fixtures with 10 mm length were installed. In order to simulate the sinus inferior wall of type IV bone, one side cortical bone of swine rib was removed. 6 different implants were installed in the same bone block following manufacturer s recommended procedures. Total 10 bone blocks were made for each group. The height of Group 1 bone block was 10 mm for engagement and that of group 2 was 13 mm. The initial stability was measured with ISQ value using Osstell $mentor^{(R)}$ and with removal torque using MGT50 torque gauge. RESULTS. In this study, we found the following results. 1. In Group 1 with fixtures engaged to the inferior cortical wall, there was no significant difference in RTV and ISQ value among the 6 types of implants. 2. In Group 2 with fixtures not engaged to the inferior cortical wall, there was significant difference in RTV and ISQ value among the 6 types of implants(P < .05). 3. There was significant difference in RTV and ISQ value according to whether fixtures were engaged to the inferior cortical wall or not(P < .05). 4. Under-drilling made RTV and ISQ value increase significantly in the NT implants which had lower RTV and ISQ value in Group 2(P < .05). CONCLUSIONS. Without being engaged to the inferior cortical wall fixtures had initial stability affected by implant types. Also in poor quality bone, under-drilling improved initial stability.

• Journal of Korean Neurosurgical Society
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• 제49권4호
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• pp.212-216
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• 2011

Objective : It is well known that plate-to-disc distance (POD) is closely related to adjacent-level ossification following anterior cervical plate placement. The study was undertaken to compare the outcomes of two different anterior cervical plating methods for degenerative cervical condition. Specifically, the new method involves making holes for plate screws first with an air drill and then choosing a plate size. The other method was standard, that is, decide on the plate size first, locate the plate on the anterior vertebral body, and then drilling the screw holes. Our hypothesis was that the new technical tip may increase POD as compared with the standard anterior cervical plating procedure. Methods : We retrospectively reviewed 49 patients who had a solid fusion after anterior cervical arthrodesis with a plate for the treatment of cervical disc degeneration. Twenty-three patients underwent the new anterior cervical plating technique (Group A) and 26 patients underwent the standard technique (Group B). POD and ratios between POD to anterior body heights (ABH) were measured using postoperative lateral radiographs. In addition, operating times and clinical results were reviewed in all cases. Results : The mean durations of follow-up were $16.42{\pm}5.99$ (Group A) and $19.83{\pm}6.71$ (Group B) months, range 12 to 35 months. Of these parameters mentioned above, cephalad POD (5.43 versus 3.46 mm, p=0.005) and cephalad POD/ABH (0.36 versus 0.23, p=0.004) were significantly greater in the Group A, whereas operation time for two segment arthrodesis (141.9 versus 170.6 minutes, p=0.047) was significantly lower in the Group A. There were no significant difference between the two groups in caudal POD (5.92 versus 5.06 mm), caudal POO/ABH (0.37 versus 0.32) and clinical results. Conclusion : The new anterior cervical plating method represents an improvement over the standard method in terms of cephalad plate-to-disc distance and operating time.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제16권3호
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• pp.499-507
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• 1994

The aim of this experiment is to compare the healing process of extraction sockets after immediate implant placement with those using autogenous bone grafts and guided tissue regeneration with Gore-Tex. The first lower premolars and the second premolars of six experimental dogs were extracted and Stryker fin type implants were placed into the extraction sockets immediately after extraction. In the control group, any graft materials were'not used and the dead space around implants was left in itself and covered with only periosteum. In the experimental group A, implants were covered with Gore tex without any bone grafts, and in the experimental group B, the dead space around implants was filled with the bone chips gained from drilling procedure. Each experimental dogs were sacrificed at the 1st, 2nd, 3rd, 6th, and 8th week and the specimens were observed by gross examination, radiological examination, and light microscopic examination. The following results were obtained. 1. Well healed soft tissue and no mobility of the implants were observed in control and two experimental groups. 2. In the radiogical examination, radiopacity around implants had been increased gradually. 3. In the microscopic examination, there were good healing process and active new bone formation in both in the experimental groups, Especially the more amount of new bone formation occurred in the experimental group B using bone chips. 4. Bone chip grafts and guided tissue regeneration (GTR) using Gore-Tex may be one of the successful methods in the immediate implantation.

• 화약ㆍ발파
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• 제25권2호
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• pp.71-78
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• 2007

국내에서 실시하늘 수중발파의 경우 파리교각 건설을 위해 실시되는 우물통발파와 항만증심 준설 또는 가스관로 개설을 위한 굴착에 적용되고 있다. 우물통발파의 경우 작업과정은 수직구 발파작업과 동일하며 물을 채운 후 발과 하는 것이 다르다. 그러나 수중 증심 공사의 경우 바다위의 바지에서 천공 및 장약 준비작업, 결선작업이 이루어지고, 장약 및 전색작업은 전문 다이버에 의해 수중에서 이루어진다. 그러므로 수중발파작업은 같은 작업이라도 신중하고 치밀한 계획이 필요하다. 본 사례는 8,500TEU급 초대형 콘테이너 선박의 입항 가능성에 대비, 선박의 안전 운항을 위한 부산 신항 중심 공사에서 에멀젼폭약과 비전기뇌관을 사용하여 굴착 현장에 근접하여 위치한 무인등대에 대한 피해를 최소화 하면서 주변의 환경성 및 진동의 영향을 고려하여 수중발파를 실시하였다. 이 사례를 통하여 앞으로 에멀젼폭약과 비전기뇌관을 사용하여 수중발파를 하고자 하는 현장에 민은 도움이 될 것으로 예상된다.

• 한국지반공학회논문집
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• 제21권5호
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• pp.133-142
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• 2005

본 연구는 지난 5년간 개발해온 인홀 발진자를 터널 막장의 강성도 계측에 사용가능하도록 개선하는데 주력하였다. 프로브는 터널의 폭파를 위해 점보드릴로써 천공된 직경 45m의 홀에 맞추기 위하여 소형화되었다. 또한 트리거 시스템은 감속모터를 사용함으로서 편리하게 되었고, 에어 팩킹 시스템은 압축공기 없이 사용하기위한 플레이트 스프링으로 교체하였다. 이러한 개선은 프로브를 터널내부의 환경에 적합하게 만들고 추가되는 비용 없이 실험하기 위함이다. 프로브와 테스트 과정은 암반의 강성을 측정하기 위해 터널의 막장의 수평 홀에 성공적으로 적용되었다. 측정된 전단파 속도는 터널 해석을 위한 암반의 변형 특성을 측정하는 것에 사용될 수 있다.

• 대한관절경학회지
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• 제13권2호
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• pp.174-178
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• 2009

목적: 상완 골두 골괴사증에서의 관절경하 핵심 갑압술을 소개하고자 한다. 수술 술기: 후방 및 전방 삽입구를 이용하여 진단적 관절경을 시행하고 견봉 외측 연의 전방 1/3 부위의 3 cm 하방에 2cm의 천공술을 위한 삽입구를 만든 후, 유도핀 삽입시 주위 연부 조직 손상을 막기 위해 짧게 만든 회색 도관를 위치시킨다. C-형 투시 장치를 견관절의 전후방에 정확히 위치시키고, 관절경을 통해 상완 골두의 관절면을 관찰하면서 3~4개의 유도핀을 괴사 부위에 삽입한 후 7.0 mm 확공기를 이용하여 천공술을 시행한다. 결론: 본 술기는 기존의 삼각흉근 도달법을 이용한 개방적 핵심 감압술에 비해 합병증을 감소시킬 수 있으며, 견관절내 병변의 진단 및 치료를 동시에 할 수 있을 뿐 아니라 술후 통증 및 재활에 유리하여 초기 상완 골두 골괴사증의 치료로 활용할 수 있는 효과적인 술식으로 생각된다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.82-96
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• 2019

A semi-submersible structure has been widely used for offshore drilling and production of oil and gas. The small water plane area makes the structure very sensitive to weight increase in terms of payload and stability. Therefore, it is necessary to lighten the substructure from the early design stage. This study aims at an optimization of hull structure based on a sophisticated yield and buckling strength in accordance with classification rules. An in-house strength assessment system is developed to automate the procedure such as a generation of buckling panels, a collection of required panel information, automatic buckling and yield check and so on. The developed system enables an automatic yield and buckling strength check of all panels composing the hull structure at each iteration of the optimization. Design variables are plate thickness and stiffener section profiles. In order to overcome the difficulty of large number of design variables and the computational burden of FE analysis, various methods are proposed. The steepest descent method is selected as the optimization algorithm for an efficient search. For a reduction of the number of design variables and a direct application to practical design, the stiffener section variable is determined by selecting one from a pre-defined standard library. Plate thickness is also discretized at 0.5t interval. The number of FE analysis is reduced by using equations to analytically estimating the stress changes in gradient calculation and line search steps. As an endeavor to robust optimization, the number of design variables to be simultaneously optimized is divided by grouping the scantling variables by the plane. A sequential optimization is performed group by group. As a verification example, a central column of a semi-submersible structure is optimized and compared with a conventional optimization of all design variables at once.