• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.5
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• pp.827-834
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• 2022

Recently, marine surveys using unmanned ships are attracting attention, and research on small unmanned ships using sails is on the rise. Sail drones can be used for marine surveys, monitoring, and pollution management. Therefore, in this study, using the method of estimating the ship speed for twin sail drones, the optimal conditions for sailing are checked, and the performance to be considered in the initial design stage, such as the motion performance and resistance of the sail drone. Consequently, the twin sail drone had a speed lower than 2.0 m/s, and the stability satisfied the rule by DNV. In addition, the maximum speed at an angle of attack of 20° at TWA 100° was 1.69 m/s and that at an angle of attack of 25° at TWA 100° was 1.74 m/s.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.3
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• pp.161-167
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• 1992

We consider the preparation of long finite amplitude nondispersive waves over a step bottom between two regions of finite different depths. Two dimensional motion is assumed. with the wave crests parallel to the step, and irrotational flow in the inviscid fluid is considered. To describe the transformation of finite amplitude waves we use the finite-amplitude shallow-water equations, the conditions of mass flow conservation and pressure continuity at the cut above the step in Riemann's variables. The equations define four families of curves-characteristics on which the values of the Riemann's invariants remain constant and a system of two nonlinear equations that relates the amplitudes of incident reflected and transmitted waves. The system obtained is difficult to analyze in common form. Thus we consider some special cases having practical usage for tsunami waves. The results obtained are compared with the long wave theory and significant nonlinear effects are found even for quite small amplitude waves.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.1
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• pp.37-47
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• 2023

A new clamped mechanical splice system was proposed to develop structural performance and constructability for precast concrete connections. The proposed mechanical splice resists external loading immediately after the engagement. The mechanical splices applicable for both large-scale rebars for plants and small-scale rebars for buildings were developed with the same design concept. Quasi-static lateral cyclic loading tests were conducted with reinforced and precast concrete members to verify the seismic performance. Also, shaking table tests with three types of seismic wave excitation, 1) random wave with white noise, 2) the 2016 Gyeongju earthquake, and 3) the 1999 Chi-Chi earthquake, were conducted to confirm the dynamic performance. All tests were performed with real-scale concrete specimens. Sensors measured the lateral load, acceleration, displacement, crack pattern, and secant system stiffness, and energy dissipation was determined by lateral load-displacement relation. As a result, the precast specimen provided the emulative performance with RC. In the shaking table tests, PC frames' maximum acceleration and displacement response were amplified 1.57 - 2.85 and 2.20 - 2.92 times compared to the ground motions. The precast specimens utilizing clamped mechanical splice showed ductile behavior with energy dissipation capacity against strong motion earthquakes.

• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.63-71
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• 2023

In the present study, the effect of pitch amplitude on the unsteady aerodynamics of a NACA 0012 airfoil is numerically investigated. When the frequency ratio is equal to 1.0, airfoil pitching with 20 and 30 degrees of pitch amplitude shows almost small lift generation, but the lift is significantly increased in case of 10-degree pitch amplitude. When the frequency is 0.5, the lift coefficients have large values, and the lift increases with a decrease in pitch amplitude. When the frequency ratio is 1.0, the airfoil generates large thrust. The thrust decreases as the pitch amplitude decreases. When the frequency ratio is 0.5, drag is generated for the 30-degree pitch amplitude, but the thrust is generated for 10-degree pitch amplitude. In future, the effect of heave amplitude on the unsteady aerodynamics of the airfoil will be studied.

• Journal of Veterinary Science
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• v.25 no.1
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• pp.2.1-2.14
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• 2024

Background: Sufficient surgical resection is necessary for effective tumor control, but is usually limited for vertebral tumors, especially in the cervical spine in small animal neurosurgery. Objective: To evaluate the primary stability and safety of customized three-dimensional (3D)-printed implants for cervical spine reconstruction after total vertebrectomy. Methods: Customized guides and implants were designed based on computed tomography (CT) imaging of five beagle cadavers and were 3D-printed. They were used to reconstruct C5 after total vertebrectomy. Postoperative CT images were obtained to evaluate the safety and accuracy of screw positioning. After harvesting 10 vertebral specimens (C3-C7) from intact (group A) and implanted spines (group B), implant stability was analyzed using a 4-point bending test comparing with groups A and C (reconstituted with plate and pins/polymethylmethacrylate after testing in Group A). Results: All customized implants were applied without gross neurovascular damage. In addition, 90% of the screws were in a safe area, with 7.5% in grade 1 (< 1.3 mm) and 2.5% in grade 2 (> 1.3 mm). The mean entry point and angular deviations were 0.81 ± 0.43 mm and 6.50 ± 5.11°, respectively. Groups B and C significantly decreased the range of motion (ROM) in C3-C7 compared with intact spines (p = 0.033, and 0.018). Both groups reduced overall ROM and neutral zone in C4-C6, but only group B showed significance (p = 0.005, and 0.027). Conclusion: Customized 3D-printed implants could safely and accurately replace a cervical vertebra in dog cadavers while providing primary stability.

• Steel and Composite Structures
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• v.50 no.2
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• pp.201-216
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• 2024

This paper is motivated by the lack of studies relating to vibration and nonlinear resonance of fluid-conveying cantilever porous GPLR pipes with fractional viscoelastic model resting on nonlinear foundations. A dynamical model of cantilever porous Graphene Platelet Reinforced (GPLR) pipes conveying fluid and resting on nonlinear foundation is proposed, and the vibration, natural frequencies and primary resonant of such system are explored. The pipe body is considered to be composed of GPLR viscoelastic polymeric pipe with porosity in which Halpin-Tsai scheme in conjunction with fractional viscoelastic model is used to govern the construction relation of the nanocomposite pipe. Three different porosity distributions through the pipe thickness are introduced. The harmonic concentrated force is also applied on pipe and excitation frequency is close to the first natural frequency. The governing equation for transverse motion of the pipe is derived by the Hamilton principle and then discretized by the Galerkin procedure. In order to obtain the frequency-response equation, the differential equation is solved with the assumption of small displacement, damping coefficient, and excitation amplitude by the multiple scale method. A parametric sensitivity analysis is carried out to reveal the influence of different parameters, such as nanocomposite pipe properties, fluid velocity and nonlinear viscoelastic foundation coefficients, on the primary resonance and linear natural frequency. Results indicate that the GPLs weight fraction porosity coefficient, fractional derivative order and the retardation time have substantial influences on the dynamic response of the system.

• Geomechanics and Engineering
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• v.36 no.2
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• pp.167-181
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• 2024

The soil-structure relative stiffness is a key factor affecting the seismic response of underground structures. It is of great significance to study the soil-structure relative stiffness for the soil-structure interaction and the seismic disaster reduction of subway stations. In this paper, the dynamic shear modulus ratio and damping ratio of an inhomogeneous soft soil site under different buried depths which were obtained by a one-dimensional equivalent linearization site response analysis were used as the input parameters in a 2D finite element model. A visco-elasto-plastic constitutive model based on the Mohr-Coulomb shear failure criterion combined with stiffness degradation was used to describe the plastic behavior of soil. The damage plasticity model was used to simulate the plastic behavior of concrete. The horizontal and vertical relative stiffness ratios of soil and structure were defined to study the influence of relative stiffness on the seismic response of subway stations in inhomogeneous soft soil. It is found that the compression damage to the middle columns of a subway station with a higher relative stiffness ratio is more serious while the tensile damage is slighter under the same earthquake motion. The relative stiffness has a significant influence on ground surface deformation, ground acceleration, and station structure deformation. However, the effect of the relative stiffness on the deformation of the bottom slab of the subway station is small. The research results can provide a reference for seismic fortification of subway stations in the soft soil area.

• Clinics in Shoulder and Elbow
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• v.26 no.3
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• pp.287-295
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• 2023

Background: Posterolateral rotatory instability (PLRI) is a common mechanism of recurrent elbow instability. While the essential lesion is a deficiency in the lateral ulnar collateral ligament (LUCL), there are often associated concomitant bony lesions, such as an Osborne-Cotterill lesions (posterior capitellar fractures) and marginal radial head fractures, that compromise stability. Currently, there is no standard treatment for posterior capitellar deficiency associated with recurrent PLRI. Methods: We conducted a retrospective review of five patients with recurrent PLRI of the elbow associated with a posterior capitellar impaction fracture engaging with the radial head during normal range of motion. The patients were treated surgically with LUCL reconstruction or repair and off-label reconstruction of the capitellar joint surface using a small metal prosthesis designed for metatarsal head resurfacing (HemiCAP toe classic). Results: Five patients (three adolescent males, two adult females) were treated between 2007 and 2018. At a median follow-up of 5 years, all patients had complete relief of their symptomatic instability. No patients had pain at rest, but two patients had mild pain (visual analog scale 1-3) during physical activity. Three patients rated their elbow as normal, one as almost normal, and one as greatly improved. On short-term radiographic follow-up there were no signs of implant loosening. None of the patients needed reoperation. Conclusions: Recurrent PLRI of the elbow associated with an engaging posterior capitellar lesion can be treated successfully by LUCL reconstruction and repair and filling of the capitellar defect with a metal prosthesis. This treatment option has excellent clinical results in the short-medium term. Level of evidence: IV.

• Annual Conference of KIPS
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• 2007.05a
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• pp.333-336
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• 2007

We propose a simple method for tracking a nonparameterized subject contour in a single video stream with a moving camera and changing background. Then we present a method to eliminate the tracked contour object by replacing with the background scene we get from other frame. Our method consists of two parts: first we track the object using LOD (Level-of-Detail) canny edge maps, then we generate background of each image frame and replace the tracked object in a scene by a background image from other frame that is not occluded by the tracked object. Our tracking method is based on level-of-detail (LOD) modified Canny edge maps and graph-based routing operations on the LOD maps. To reduce side-effects because of irrelevant edges, we start our basic tracking by using strong Canny edges generated from large image intensity gradients of an input image. We get more edge pixels along LOD hierarchy. LOD Canny edge pixels become nodes in routing, and LOD values of adjacent edge pixels determine routing costs between the nodes. We find the best route to follow Canny edge pixels favoring stronger Canny edge pixels. Our accurate tracking is based on reducing effects from irrelevant edges by selecting the stronger edge pixels, thereby relying on the current frame edge pixel as much as possible. This approach is based on computing camera motion. Our experimental results show that our method works nice for moderate camera movement with small object shape changes.

• (The) Research of the performance art and culture
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• no.37
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• pp.5-31
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• 2018

The mask dance drama Goseong Ogwangdae's first act, Mundung Bukchum. The story is about a man who was born to the upper class but contracted leprosy, an incurable disease, due to his ancestors' accumulated sin. Although he is suffering, he is able to triumph over the disease through sinmyeong (catharsis) that is expressed through the wordless act of Mundung Bukchum. This thesis focuses on Goseong Ogwangdae's Mundung Bukchum, particularly the meaning, costume, accompanying music, and process of pedagogical transmission. The chronological characteristics of Goseong Ogwangdae's Mundung Bukchum are as follows. First, as time goes on, the number of dance motions in Mundung Bukchum has increased and the motions used have become reified. Second, I address the small barrel drum used in Mundung Bukchum and check how, through the drum, the changed expression of Mundung is shown.In a 1965 video introduced Mundung is grasping the drum and stick and the dance appears to be made up only of humorous motions. Also in a 1969 video, "Mundung Gwangdae," from the start Mundung is grasping the drum and stick. In 1988 in a video we can see the same scene as today, with the drum and stick sitting in the center of the stage at the start of the dance. We can also confirm that the same fourteen dance motions used today are present. Third, we can also confirm the changes in Goseong Ogwangdae's signature motion, baegimsae as time goes on. Observing the video from 1965, baegimsae does not appear in Mundung Bukchum. In 2000 we can clearly see the baegimsae performed once to the left and to the right while Mundung is squatting. Comparing 1969 to 1988, there is no symmetry in the motions, baegimsae is not done to both left and right, but only in one direction. Watching the record from 2000, the baegimsae motion is performed just as it is now, with the body thrown forward with a sharp push off the ground. Fourth I confirmed how the music used to accompany Goseong Ogwangdae's Mundung Bukchum has changed over time. In 1965 according to records of Mundung Bukchum's appearance, the dance was accompanied by the taryeong rhythmic pattern played on the usual four percussion instruments (barrel drum, hourglass drum, large gong, small gong). In the 1969 records of Mundung Bukchum the accompanying music is gutgeori rhythmic pattern performed on the usual four percussion instruments-an obvious difference. In 1988 the music with Mundung Bukchum is gutgeori rhythmic pattern transitioning into jajinmori rhythmic pattern. In 2000 the music with Mundung Bukchum includes the percussion instruments as well as taepyeongso (double reed oboe) playing gutgeori and jajinmori rhythmic patterns.