• Journal of Broadcast Engineering
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• v.25 no.5
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• pp.672-684
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• 2020

Restoring a low resolution and motion blurred light field has become essential due to the growing works on parallax-based image processing. These tasks are known as light-field enhancement process. Unfortunately, only a few state-of-the-art methods are introduced to solve the multiple problems jointly. In this work, we design a framework that jointly solves light field spatial super-resolution and motion deblurring tasks. Particularly, we generate a straight-forward neural network that is trained under low-resolution and 6-degree-of-freedom (6-DOF) motion-blurred light field dataset. Furthermore, we propose the strategy of local region optimization on the adversarial network to boost the performance. We evaluate our method through both quantitative and qualitative measurements and exhibit superior performance compared to the state-of-the-art methods.

• Journal of the Semiconductor & Display Technology
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• v.14 no.3
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• pp.1-5
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• 2015

In photolithography process, resolution enhancement techniques such as optical proximity correction (OPC) and phase shift mask (PSM) have been applied to improve resolution. Especially, sub-resolution assist feature (SRAF) is one of the most important OPC to enhance image quality including depth of focus (DOF). However, imaging performance of the mask could be varied with the diffraction order amplitude changed by inserting SRAF. Therefore, in this study, we investigated the imaging properties and process margin of attenuated PSM with SRAF. Reflectivities of attenuated PSMs at 13.5 nm were 3, 6, 9% and simulation was performed by $PROLITH^{TM}$. As a result, aerial image properties and DOF as well as diffraction efficiency were improved by increasing the reflectivity of attenuated PSM. Additionally, printed critical dimension variations depending on SRAF width and space error were also reduced for attenuated PSM with high reflectivity. However, SRAF could be printed when reflectivity of attenuated PSM is high enough. In conclusion, optimization of reflectivity of attenuated PSM and SRAF to prevent side-lobe from being printed is needed to be considered.

• Wind and Structures
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• v.10 no.5
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• pp.463-479
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• 2007

A series of wind tunnel sectional model dynamic tests of a twin-deck bridge were conducted at the CLP Power Wind/Wave Tunnel Facility (WWTF) of The Hong Kong University of Science and Technology (HKUST) to investigate the effects of gap-width on the self-excited vibrations and the dynamic and aerodynamic characteristics of the bridge. Five 2.9 m long models with different gap-widths were fabricated and suspended in the wind tunnel to simulate a two-degrees-of-freedom (2DOF) bridge dynamic system, free to vibrate in both vertical and torsional directions. The mass, vertical frequency, and the torsional-to-vertical frequency ratio of the 2DOF systems were fixed to emphasize the effects of gap-width. A free-vibration test methodology was employed and the Eigensystem Realization Algorithm (ERA) was utilized to extract the eight flutter derivatives and the modal parameters from the coupled free-decay responses. The results of the zero gap-width configuration were in reasonable agreement with the theoretical values for an ideal thin flat plate in smooth flow and the published results of models with similar cross-sections, thus validating the experimental and analytical techniques utilized in this study. The methodology was further verified by the comparison between the measured and predicted free-decay responses. A comparison of results for different gap-widths revealed that variations of the gap-width mainly affect the torsional damping property, and that the configurations with greater gap-widths show a higher torsional damping ratio and hence stronger aerodynamic stability of the bridge.

• Journal of the Korean Society for Railway
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• v.17 no.5
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• pp.342-348
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• 2014

Contact between wheel and rail leads to the creep phenomenon. Linear creep theory, assuming linear increase in the creep force vs creep, results in a critical speed at which the vibration of a railway vehicle goes to infinity. However, the actual creep force converges to a limited value, so that the vibration of a railway vehicle cannot increase indefinitely. In this study, the dynamics of a railway vehicle is investigated with a 6 DOF bogie model includingthe nonlinear creep curves of Vermeulen, Polach, and a newly calculated creep curve with strip theory. Strip theory considers the profiles of the wheel and rail. The results show that the vibration of a railway vehicle results in a limit-cycle over a specific running speed, and this limit-cycle becomes smaller as the slope of the creep-curve steepens. Moreover, a hunting phenomenon is caused due to flange contact, which restricts the magnitude of the limit-cycle.

• Journal of Gastric Cancer
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• v.21 no.1
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• pp.38-48
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• 2021

Purpose: As the number of gastric cancer survivors is increasing and their quality of life after surgery is being emphasized, single-port surgery is emerging as an alternative to conventional gastrectomy. A novel multi-degree-of-freedom (DOF) articulating device, the ArtiSential® device (LivsMed, Seongnam, Korea), was designed to allow more intuitive and meticulous control for surgeons facing ergonomic difficulties with conventional tools. In this study, we evaluated the feasibility of this new device during single-port laparoscopic distal gastrectomy (SP-LDG) for early gastric cancer (EGC) patients. Materials and Methods: Consecutive patients diagnosed with EGC who underwent SP-LDG with ArtiSential® (LivsMed) graspers between April 2018 and August 2020 were enrolled in the study. The clinical outcomes were compared with those of a control group, in which prebent graspers (Olympus Medical Systems Corp) were used for the same procedures. Results: Seventeen patients were enrolled in the ArtiSential® group. There was no significant difference in operative time (205.4±6.0 vs. 218.1±9.9 minutes, P= 0.270) or the quality of surgery, in terms of the number of retrieved lymph nodes (49.5±3.5 vs. 45.9±4.0, P=0.473), length of hospital stay (15.4±2.0 vs. 12.4±1.3 days, P=0.588), and postoperative complications (40.0% vs. 41.2%, P=0.595), between the ArtiSential® group and the control group. Conclusions: The new multi-DOF articulating grasper is feasible and can be used as an alternative for prebent graspers during SP-LDG.

• Coupled systems mechanics
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• v.11 no.5
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• pp.439-458
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• 2022

Over-coating is one of the most popular engineering practices to strengthen Reinforced Concrete (RC) structures, due to the relative quickness and ease of construction. It consists of an external coat bonded to the outer surface of the structural RC element, either by the use of chemical adhesives, mechanical anchor bolts or simply mortar injection. In contrast to these constructive advantages, the numerical estimation of the bearing capacity of the strengthened reinforced concrete element is still complicated, not only for the complexity of modelling a flexible membrane or plate attached to a quasi-rigid solid, but also for the difficulties that raise of simulating any potential delamination between both materials. For these reasons, the standard engineering calculations used in the practice remain very approximated and clumsy. In this work, we propose the formulation of a new 2D solid-layer finite element capable to link a solid body with a flexible thin layer, as it were the "skin" of the body, allowing the potential delamination between both materials. In numerical terms, this "skin" element is intended to work as a transitional region between a solid body (modelled with a classical formulation of a standard quadrilateral four-nodes element) and a flexible coat layer (modelled with cubic beam element), dealing with the incompatibility of Degrees-Of-Freedom between them (two DOF for the solid and three DOF for the beam). The aim of the solid-layer element is to simplify the mesh construction of the strengthened RC element being aware of two aspects: a) to prevent the inappropriate use of very small solid elements to simulate the coat; b) to improve the numerical estimation of the real bearing capacity of the strengthened element when the coat is attached or detached from the solid body.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.5
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• pp.320-331
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• 2023

In this study, a model test was conducted using the soft-mooring technique to evaluate the added resistance of the ship in waves. The study also examined the specific factors that should be considered during the soft-mooring test. The main purpose of soft-mooring is to prevent drifting caused by waves by providing horizontal restoring forces. However, it can also create undesired restoring forces in the vertical direction. Therefore, we examined the restoring force of the ship's 6-DOF motion based on the arrangement of the soft-mooring and the height of the mooring connection point. We also checked the corresponding resonance period and drift distance. The soft-mooring test was conducted twice, once with self-propulsion and once without self-propulsion, allowing us to review the advantages and disadvantages of each test technique. The main parameters measured in these model tests were 6DOF motion and added resistance on the ship. We compared these measurements obtained from two different techniques (with and without self-propulsion). Additionally, we also compared the measurements based on the types of measuring sensors used (2D load cells on FP, AP, and 1D load cells on each mooring line) as well as the height of the mooring connection point.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.1
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• pp.5-10
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• 2001

A method is proposed to obtain the Jacobian matrix of the 5 -bar parallel manipulator by employing the orthogonality between position and velocity vectors of rotating rigid-body around a fixed point. The dynamics of the 5-bar parallel manipulator is analyzed and utilized to design the computed-torque controller by developing a transformation matrix of the passive joints with respect to the active ones. In experimental demonstration, it shows that high-speed and accuracy tasks are performed by the proposed computed-torque control.

• Structural Engineering and Mechanics
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• v.14 no.6
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• pp.699-712
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• 2002

In this paper, a new quadrilateral 5-node non-conforming membrane element with drilling degrees of freedom is presented. The main advantage of these elements is the relatively small number of integration points to evaluate a stiffness matrix comparing to the existing transition membrane elements (CLM elements). Moreover, the presented elements pass the patch test by virtue of the Direct Modification Method incorporated into the element formulation. The presented 5-node elements are proved to be very efficient when used in the local mesh refinement for the in-plane structures which have stress concentrations. And some numerical studies also show the good performance of the new element developed in this study.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.5
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• pp.445-455
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• 2023

Sea level rise due to global warming is accelerating. According to the IPCC survey, the expected sea level rise in 2100 was analyzed to be 47cm in the low-carbon scenario (SSP 1-2.6) and 82cm in the high-carbon scenario (SSP 5-8.5). Sea level rise can cause serious damage to port infrastructure and reduce the safety of ships docked inside ports. In this study, Mokpo Port, which frequently suffers from flooding during high tide, was selected and the sensitivity of mooring evaluation factors was analyzed for actual berthing ships according to sea level rise scenarios. From the analysis, we found that the tension of mooring line, the load of bollard, vertical angle of mooring line, and ship's motion of 6-DOF, which are evaluation factors, generally increased when the sea level increased. The most sensitive evaluation factor was sway motion of 6-DOF. Also, we analyzed that the value of mooring evaluation factors decreased when the crown height was raised. This was beneficial in improving ship and pier safety. The results of this study can be used as basic data to secure measures to improve port and ship safety according to sea level rise in Mokpo Port.