• Structural Engineering and Mechanics
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• v.85 no.4
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• pp.433-443
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• 2023

The current paper discusses the dynamic and stability responses of cross-ply composite laminated plates by employing a refined quasi-3D trigonometric shear deformation theory. The proposed theory takes into consideration shear deformation and thickness stretching by a trigonometric variation of in-plane and transverse displacements through the plate thickness and assures the vanished shear stresses conditions on the upper and lower surfaces of the plate. The strong point of the new formulation is that the displacements field contains only 4 unknowns, which is less than the other shear deformation theories. In addition, the present model considers the thickness extension effects (ε_z≠0). The presence of the Winkler-Pasternak elastic base is included in the mathematical formulation. The Hamilton's principle is utilized in order to derive the four differentials' equations of motion, which are solved via Navier's technique of simply supported structures. The accuracy of the present 3-D theory is demonstrated by comparing fundamental frequencies and critical buckling loads numerical results with those provided using other models available in the open literature.

• Advances in nano research
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• v.15 no.5
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• pp.401-410
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• 2023

Vibration investigation of fluid-filled three layered cylindrical shells is studied here. A cylindrical shell is immersed in a fluid which is a non-viscous one. Shell motion equations are framed first order shell theory due to Love. These equations are partial differential equations which are usually solved by approximate technique. Robust and efficient techniques are favored to get precise results. Employment of the wave propagation approach procedure gives birth to the shell frequency equation. Use of acoustic wave equation is done to incorporate the sound pressure produced in a fluid. Hankel's functions of second kind designate the fluid influence. Mathematically the integral form of the Lagrange energy functional is converted into a set of three partial differential equations. It is also exhibited that the effect of frequencies is investigated by varying the different layers with constituent material. The coupled frequencies changes with these layers according to the material formation of fluid-filled FG-CSs. Throughout the computation, it is observed that the frequency behavior for the boundary conditions follow as; clamped-clamped (C-C), simply supported-simply supported (SS-SS) frequency curves are higher than that of clamped-simply (C-S) curves. Expressions for modal displacement functions, the three unknown functions are supposed in such way that the axial, circumferential and time variables are separated by the product method. Computer software MATLAB codes are used to solve the frequency equation for extracting vibrations of fluid-filled.

• Steel and Composite Structures
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• v.49 no.5
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• pp.487-502
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• 2023

In the realm of nanotechnology, the nonlocal strain gradient theory takes center stage as it scrutinizes the behavior of spinning cantilever nanobeams and nanotubes, pivotal components supporting various mechanical movements in sport structures. The dynamics of these structures have sparked debates within the scientific community, with some contending that nonlocal cantilever models fail to predict dynamic softening, while others propose that they can indeed exhibit stiffness softening characteristics. To address these disparities, this paper investigates the dynamic response of a nonlocal cantilever cylindrical beam under the influence of external discontinuous dynamic loads. The study employs four distinct models: the Euler-Bernoulli beam model, Timoshenko beam model, higher-order beam model, and a novel higher-order tube model. These models account for the effects of functionally graded materials (FGMs) in the radial tube direction, giving rise to nanotubes with varying properties. The Hamilton principle is employed to formulate the governing differential equations and precise boundary conditions. These equations are subsequently solved using the generalized differential quadrature element technique (GDQEM). This research not only advances our understanding of the dynamic behavior of nanotubes but also reveals the intriguing phenomena of both hardening and softening in the nonlocal parameter within cantilever nanostructures. Moreover, the findings hold promise for practical applications, including drug delivery, where the controlled vibrations of nanotubes can enhance the precision and efficiency of medication transport within the human body. By exploring the multifaceted characteristics of nanotubes, this study not only contributes to the design and manufacturing of rotating nanostructures but also offers insights into their potential role in revolutionizing drug delivery systems.

• KIPS Transactions on Software and Data Engineering
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• v.13 no.1
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• pp.17-27
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• 2024

Video frame interpolation is an important technique used in the field of video and media, as it increases the continuity of motion and enables smooth playback of videos. In the study of video frame interpolation using deep learning, Kernel Based Method captures local changes well, but has limitations in handling global changes. In this paper, we propose a new U-Net structure that applies feature map differentiation and two directions to focus on capturing major changes to generate intermediate frames more accurately while reducing the number of parameters. Experimental results show that the proposed structure outperforms the existing model by up to 0.3 in PSNR with about 61% fewer parameters on common datasets such as Vimeo, Middle-burry, and a new YouTube dataset. Code is available at https://github.com/Go-MinSeong/SF-AdaCoF.

• Smart Structures and Systems
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• v.33 no.2
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• pp.165-175
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• 2024

Rotating beams play a crucial role in representing complex mechanical components that are prevalent in vital sectors like energy and transportation industries. These components are susceptible to the initiation and propagation of cracks, posing a substantial risk to their structural integrity. This study presents a two-stage methodology for detecting the location and estimating the size of an open-edge transverse crack in a rotating Euler-Bernoulli beam with a uniform cross-section. Understanding the dynamic behavior of beams is vital for the effective design and evaluation of their operational performance. In this regard, modal parameters such as natural frequencies and eigenmodes are frequently employed to detect and identify damages in mechanical components. In this instance, the Frobenius method has been employed to determine the first two natural frequencies and corresponding eigenmodes associated with flapwise bending vibration. These calculations have been performed by solving the governing differential equation that describes the motion of the beam. Various parameters have been considered, such as rotational speed, beam slenderness, hub radius, and crack size and location. The effect of the crack has been replaced by a rotational spring whose stiffness represents the increase in local flexibility as a result of the damage presence. In the initial phase of the proposed methodology, a damage index utilizing the slope of the beam's eigenmode has been employed to estimate the location of the crack. After detecting the presence of damage, the size of the crack is determined using a Genetic Algorithm optimization technique. The ultimate goal of the proposed methodology is to enable the development of more suitable and reliable maintenance plans.

• Hip & pelvis
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• v.34 no.4
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• pp.219-226
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• 2022

Purpose: The purpose of this study was to examine the clinical outcomes and efficacy of hip resurfacing arthroplasty (HRA) in patients with osteonecrosis of the femoral head after the failure of porous tantalum rod insertion without rod removal. Materials and Methods: Conversion to hip resurfacing arthroplasty was performed in 10 patients (11 hips) with a mean period of 14.9 months after the primary surgery. The mean follow-up period was 73.7 months. Analysis of pre and postoperative range of motion (ROM), University of California at Los Angeles (UCLA) activity score, modified Harris hip score, and visual analog scale (VAS) pain score was performed. Radiographic analysis of component loosening and osteolysis was performed. Results: The postoperative ROM showed significant improvement (P<0.05), excluding flexion contracture. The modified Harris hip score showed improvement from 65.82 to 96.18, the UCLA score showed improvement from 4.18 to 8.00, and the VAS pain score was reduced from 6.09 to 1.80. All scores showed statistically significant improvement (P<0.05). No component loosening or osteolysis was detected by radiographic analysis. Conclusion: Satisfactory results were obtained from conversion hip resurfacing arthroplasty after failure of porous tantalum rod insertion without rod removal. The findings of this study demonstrate the advantages of HRA, including no risk of trochanteric fracture and no bone loss around the tantalum rod. In addition, the remaining porous tantalum rod provided mechanical support, which reduced the potential risk of femoral neck fracture or loosening. This technique can be regarded as a favorable treatment option.

• Korean Journal of Applied Biomechanics
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• v.34 no.3
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• pp.133-144
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• 2024

Objective: Neuromuscular training may often result in an incomplete improvement of biomechanical risk factors associated with non-contact ACL injury. This study aimed to investigate the effects of reactive neuromuscular training (RNT) on dynamic postural control of the lower extremity during single-leg drop landing (SLDL) in comparison with conventional neuromuscular training (CNT). Method: Twenty-eight recreational female athletes were randomized to a CNT group (n=15) or a RNT group (n=13). All participants performed SLDL for three-dimensional motion analysis before and after CNT and RNT. The kinematic variable was calculated from before 50 milliseconds (ms) to after 100 ms initial contact: joint angle (degree). The kinetic variable was calculated from initial contact to after 100 ms: internal net joint moment (Nm/kg). Time series curve for normalized data was represented for group means and associated 95% confidence intervals. Effect sizes using Cohen's d was also calculated. Results: In within-group differences, the CNT group showed decreased knee flexion angle (0~100% of the task) and decreased knee valgus angle (0~50% of the task) after the intervention, whereas the RNT group showed increased hip flexion angle (0~14% of the task), decreased hip adduction angle (0~100% of the task), and decreased knee valgus angle (0~100% of the task) after the intervention. In between-group differences, the RNT group exhibited more hip flexion angle (0~49, 61~91% of the task), more knee flexion angle (0~100% of the task), and less knee valgus angle (0~55% of the task) than the CNT group. Conclusion: These findings suggest that both training intervention programs modified dynamic posture of the hip and knee during SLDL. Therefore, combining a neuromuscular training program with RNT technique would be more efficient for future injury prevention efforts.

• Korean Security Journal
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• no.19
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• pp.225-244
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• 2009

Electronic security system is composed mainly of electronic-information-communication device, so system technology, configuration and management of the electronic security system could be affected by the change of information-communication environment. This study is to propose the future prospect on the development of technique for electronic security system through the analysis of the trend and the actual condition on the development of technique. This study is based on literature study and interview with user and provider of electronic security system, also survey was carried out by system provider and members of security integration company to come up with more practical result. Hybrid DVR technology that has multi-function such as motion detection, target tracking and image identification is expected to be developed. And 'Embedded IP camera' technology that internet server and image identification software are built in. Those technologies could change the configuration and management of CCTV system. Fingerprint identification technology and face identification technology are continually developed to get more reliability, but continual development of surveillance and three-dimension identification technology for more efficient face identification system is needed. As radio identification and tracking function of RFID is appreciated as very useful for access control system, hardware and software of RFID technology is expected to be developed, but government's support for market revitalization is necessary. Behavior pattern identification sensor technology is expected to be developed and could replace passive infrared sensor that cause system error, giving security guard firm confidence for response. The principle of behavior pattern identification is similar to image identification, so those two technology could be integrated with tracking technology and radio identification technology of RFID for total monitoring system. For more efficient electronic security system, middle-ware's role is very important to integrate the technology of electronic security system, this could make possible of installing the integrated security system.

• Journal of the Korean Arthroscopy Society
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• v.17 no.1
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• pp.24-30
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• 2013

Purpose: To evaluate the outcome of arthroscopic posterior cruciate ligament (PCL) augmentation using an autogenous hamstring tendon graft and the posterior-posterior triangulation technique with preservation of ligament remnant or elongated ligament. Materials and Methods: From January 2002 to December 2009, we performed PCL augmentation using an autogenous hamstring tendon graft and the posterior-posterior triangulation technique in 32 patients. The mean age was 35.2 years. Twenty two cases were male and 10 cases were female. Average follow-up period was 5 years and 5 months (range: 2-7.9). Subjective and objective parameters were utilized in analyses, such as the mean range of motion, post. drawer test, Lysholm knee score, Tegner activity score, International Knee Documentation Cominittee (IKDC) grade, and second look arthroscopic examination. Results: At last follow up posterior displacement by the Telos stress test decreased from $10.8{\pm}5.1\;mm$ to $2.8{\pm}3.7\;mm$ (p<0.05). The final Lysholm knee score improved from $60.4{\pm}5.8$ to $84.6{\pm}4.8$. Tegner activity score improved from 3.2 to 4.8. The final IKDC grade was A in 18, B in 11, C in 3. Postoperative Lysholm knee score, IKDC grades, Tegner activity scale, and posterior displacement demonstrated statistically significant improvement compared to the preoperative state (p<0.05). Conclusion: Arthroscopic PCL reconstruction using an autogenous hamstring tendon with preservation of ligament remnant showed a good clinical results and posterior stability.

• Journal of the Korean Arthroscopy Society
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• v.8 no.2
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• pp.103-108
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• 2004

Purpose: This study reported the outcomes following the use of bioabsorbable knotless anchor in patients with anterior instability of shoulder. Methods: We studied fifteen cases with traumatic anterior shoulder instability underwent arthroscopic Bankart repair with bioabsorbable knotless suture anchor between January 2003 and June 2003. Among fifteen patients, fourteen were male and one was female, with a mean patient age of 24 years (range 16-42). The mean follow-up was 14 months (range 12-18 months). We compared with operation time of twenty cases of arthroscopic Bankart repair by the suture anchor technique between January 2002 and October 2002. Results: Neither recurrent dislocation nor subluxation was happened in postoperative follow-up. Mean score for functional evaluation by Rowe et al. was 89.4 and that for patient subjective satisfaction was 87,5. At last follow-up period, average shoulder range of motion for flexion and external rotation was 171$^{\circ}$ and 54$^{\circ}$ respectively. All patients were satisfied except three who had an apprehension at the follow up. During Bankart repair, it took an average of 25.5 minutes for one knot with the use of suture anchor technique whereas an average of 16.5 minutes for one knot with the use of bioabsorbable knotless anchor. Significantly, we saved operation time with the use of bioabsorbable knotless anchor (P<0.05).Conclusion: Repairing the Bankart lesion with the use of knotless anchor technique has the advantage of obtaining good capsular tensioning and saving operation time. And it is considered to be very successful in treating shoulder instability without recurrent dislocation or subluxation.