• Ocean and Polar Research
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• v.42 no.4
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• pp.293-301
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• 2020

Blades of tidal stream turbines have to sustain many different loads during operation in the underwater environment, so securing their structural safety is a key issue. In this study, we focused on periodic loads due to wave orbital motion and propose a load reduction method with a blade design. The flap of an airplane wing is a well-known structure designed to increase lift, and it can also change the load distribution on the wing through deflection. For this reason, we adopted a passive flap structure for the load reduction and investigated its effectiveness by an analytical method based on the blade element moment theory. Flap torsional stiffness required for the design of the passive flap can be obtained by calculating the flap moment based on the analytic method. Comparison between a flapped and a fixed blade showed the effect of the flap on load reduction in a high amplitude wave condition.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.1
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• pp.46-57
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• 2013

Flutter stability and buffeting response have been the topics of most concern in the design state of long-span suspension bridges. Among approaches towards the aerodynamic stability, the aerodynamic-based control method which uses control surfaces to generate forces counteracting the unstable excitations has shown to be promising. This study focused on the mechanically controlled system using flaps; two flaps were attached on both sides of a bridge deck and were driven by the motions of the bridge deck. When the flaps moved, the overall cross section of the bridge deck containing these flaps was continuously changing. As a consequence, the aerodynamic forces also changed. The efficiency of the control was studied through the numerical simulation and experimental investigations. The values of quasi-steady forces, together with the experimental aerodynamic force coefficients, were proposed in the simulation. The results showed that the passive flap control can, with appropriate motion of the flaps, solve the aerodynamic instability. The efficiency of the flap control on the full span of a simple suspension bridge was also carried out. The mode-by-mode technique was applied for the investigation. The results revealed that the efficiency of the flap control relates to the mode number, the installed location of the flap, and the flap length.

• Archives of Plastic Surgery
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• v.36 no.4
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• pp.450-457
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• 2009

Purpose: The second toe PIP joint free flap is a method of reconstruction used for abnormalities of the PIP joint of the finger. We report the results of the additional tenolysis in patients with a difference between passive ROM and active ROM after second toe PIP joint free flap. Methods: From March 2001 to July 2008, tenolysis was performed in patients with a difference in their active and passive ROM after second toe PIP joint free transfer, performed on 14 fingers. We performed a retrospective analysis of the medical records, noting the clinical and radiological findings. In addition, we measured the preoperative and postoperative range of motion of the PIP joint. Results: The average active ROM was $22.5^{\circ}$ at the three months after the joint transfer surgery, and was $38^{\circ}$ after additional tenolysis between five months and twelve months after the joint transfer. Conclusions: Additional tenolysis, after the second toe PIP joint free flap, might be a good option for improved results in patients with difference in active and passive ROM of a transferred PIP joint.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.1
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• pp.11-19
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• 2005

In order to improve dynamic stall characteristics of an oscillating airfoil, optimal design has been performed for fixed nose droop and Gurney flap. Fixed nose droop is known to be very effective to improve pitching moment characteristics but may cause degeneration of aerodynamic lift at the same time. On the other hand, Gurney flap has the opposite characteristics. For fixed nose droop, location and angle are chosen as design variables, while length is defined as design variable for Gurney flap. Higher order response surface methodology and sensitivity based optimal design method are employed to handle highly nonlinear problem such as dynamic stall. Optimal design has been performed so that lift and pitching moment are simultaneously improved. The design results show that aerodynamic characteristics can be remarkably improved through present design approach and the present passive control method is as good as active control method which combines variable nose droop and Gurney flap.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.5
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• pp.10-17
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• 2004

To achieve the advanced forward flight performance of helicopter, the passive control methods for enhancement of the dynamic stall characteristics of rotor blades are studied. To enhance the dynamic stall characteristics of the rotor blades, it is essential to improve the lift performance and the pitching moment performance simultaneously with the control of the separation on the rotor blades. For this point of view, both the fixed droop leading edge and the Gurney flap which are simply realized are used for control of the dynamic stall in severe dynamic stall conditions. From this study, the combination of both passive control methods showed dramatic enhancement of lift and pitching moment performance in dynamic stall than previous research results.

• Journal of Periodontal and Implant Science
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• v.38 no.2
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• pp.247-252
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• 2008

Purpose: Passive eruption is characterized by the apical shift of the dentogingival junction. As this occurs, the length of the clinical crown increases as the epithelial attachment migrates apically. Altered passive eruption occurs when the margin of gingiva is malpositioned incisally on the anatomic crown in adulthood and results in excessive gingiva. The purpose of this article is to evaluate esthetic results of crown lengthening procedure in altered passive eruption.s. Materials and Methods: Three patients who complained "My front teeth look too short" were included. Bone sounding with periodontal probe revealed that alveolar bone crest was close to CEJ. Based on the diagnostic information, a diagnosis of altered passive eruption was made. They were performed apically positioned flap procedure with osseous resection. Results: Six months later, all patients achieved favorable esthetic results and gingival margins were healthy and stable. Conclusion: When the diagnostic procedures reveal alveolar bone crest levels approximating the CEJ, apically positioned flap procedure with osseous resection is indicated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.596-599
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• 1997

In this study, the flow control system with shape memory alloy in jet engine inlet was suggested to adjust the shock boundary layer interact~on for supersonic flight system. It consisted of the flap with shape memory alloy, spar with steel, and fixing device with aluminum alloy. The advantages of itself are a simple configuration, a passive air circulation by using the flap deflection due to pressure difference, and no need to be required the auxiliary devices. Finite element analysis was conducted to predict the thenno-mechanical behavlor of the flap system with shape memory alloy. The user-defined subroutine UMAT was implemented with ABAQUS to accon~modate the thermo-mechanical constitutive relation of shape memory alloy.

• Archives of Reconstructive Microsurgery
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• v.8 no.1
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• pp.56-63
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• 1999

We report two patients whose acute soft tissue and tendon defects in the hand were treated by the dorsalis pedis tendocutaneous delayed arterialized venous flap between 1994 and 1997. The surviving surface area was 100% in both patients. The flap size was $10{\times}10cm\;and\;6{\times}6cm$. At two weeks postoperatively, active flextion and passive extension commenced, and progressive resistance exercises were performed for an additional 5 weeks. Flaps showed a similar color match and skin texture compared with the normal skin of the hand. Advantages of the tendocutaneous delayed arterialized venous flap are developing a larger flap than can be obtained with pure venous flap or arterialized venous flap, increasing survival rate of the arterialized venous flap which permits using a composite flap, preservation of main artery of the donor site, taking thin non-bulky tissue and easy elevation without deep dissection. The disadvantages are the requirement of a two stage operation, donor site scarring and weak extension of the toe.

• The Journal of the Korean dental association
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• v.50 no.8
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• pp.474-481
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• 2012

The periodontal flap surgery is the most widely utilized surgical procedure to reduce the pocket depth and to access the subgingival root surfaces for scaling and root planing. The diagnosis of the periodontal lesion and the objective of the surgery will dictate the type of flap procedure which will be utilized to obtain the best result. The incisions, type of flap and the selection of suturing design must be planned and executed to fit the problem. Periodontal flaps are designed to preserve gingival integrity and to gain access to root surfaces for residual calculus removal and to thoroughly remove granulation tissue so bone defects can be visualized and treated. Gentle and efficient procedures result in optimum healing and minimal postoperative pain. When flaps need to be repositioned apically or less often, coronally, then the flaps must sit passively at the appropriate level before suturing. To ensure this, buccal and lingual flaps need to be elevated beyond the mucogingival junction so the elasticity of the mucosa allows for flap mobility. Sometimes it may be necessary to extend the flap elevation apically with a split incision approach to minimize the effect of the less elastic periosteum. Vertical incisions can aid in flap positioning by allow ing the clinician to suture the flap at a different level to the adjacent untreated gingiva. In osseous periodontal surgery, flaps are apically positioned to minimize postoperative pocket depth. In regenerative periodontal surgery including implant surgery, soft tissue cove rage of bony defects, graft materials, membranes, and bio logic agents is important so sulcular incisions and light suturing techniques are crucial.

• Structural Engineering and Mechanics
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• v.46 no.4
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• pp.549-569
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• 2013

A passive control using flaps will be an alternative solution for flutter stability and buffeting response of a long suspension bridge. This method not only enables a lightweight economic stiffening girder without an additional stiffness for aerodynamic stability but also avoid the problems from the malfunctions of control systems and energy supply system of an active control by winglets and flaps. A time domain approach for predicting the coupled flutter and buffeting response of bridge deck with flaps is investigated. First, the flutter derivatives of bridge deck and flaps are found by experiment. Next, the derivation of time domain model of self-excited forces and control forces of sectional model is reported by using the rational function approximation. Finally, the effectiveness of passive flap control is investigated by the numerical simulation. The results show that the passive control by using flaps can increase the flutter speed and decrease the buffeting response. The experiment results are matched with numerical ones.