• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.5
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• pp.795-801
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• 2001

A method of miniaturizing branch line coupler is presented. The method utilizes the microstrip line with overlay(or superstrate). The frequency dependent characteristics, dispersion and characteristic impedance, of this line are obtained by Immitance method in spectral domain and Method of Line. The relevant spectral domain Green's function is given and used to obtain numerical results. The branch line couplers with overlays are designed and fabricated at 2 GHz. The experimental results show that the size of coupler with overlay(${epsilon}_r$=10.2) is 31.4 precent smaller than conventional coupler. This minimized coupler is suitable for Butler Matrix as feeder for mobile communication beam forming antenna.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.279-280
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• 1998

A new algorithm is developed that can reduce the metal artifact on CT caused by pedicle screws. Metal artifact has been recognized as a major problem in precise reading of CT images. In particular, spine surgeons have been bothered with the artifact appearing on CT taken after pedicle screw insertion. To reduce the artifact, our new algorithm first finds the center line from CT images, and then overlays an exact size screw image on the CT. The exact screw is obtained from an actual design specifications of screw, and the CT images are processed to maximize bone margins while minimizing screw images through adjusting the window width and level. 실험 결과 단순한 Window W/L 조절로는 해결되지 않는군요. This algorithm provides spine surgeons with more accurate CT images and thus better interpretation of CT to ascertain the success or failure of pedicle screw insertion.

• Journal of the Korean Wood Science and Technology
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• v.26 no.1
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• pp.87-96
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• 1998

The bending performances were evaluated at the radiata pine plywood through veneer compositions encompassing veneer quality, ply-numbers and overlays of the high density- or medium density-phenol resin impregnated sheets (hereafter abbreviated as resin sheets) on the raw plywood. In addition, a prediction on the bending MOE of veneers and plywoods was carried out by the nondestructive testing with stresswave timer. The summarized results were as follows: I. Bending strength and bending MOE of resin sheets-overlaid plywoods in parallel surface grain direction through 5 and 7ply were increased by 13 to 45% and 17 to 34%, respectively. Resin sheets-overlay occurred an increasing effect of the strength efficiency i.e. strength perpendicular-to-grain direction versus that parallel-to-grain direction, showing the phenomenon that the plywood strength becomes greater at the perpendicular-to-grain direction of 7ply than at that of 5ply. Displacement at bending failure had a greater trend at 7ply than at 5ply, and was decreased by resin sheets-overlay. 2. After the nondestructive bending MOEs were measured for individual veneers, these veneers were rearranged in plywood-manufacture. In these plywoods, including resin sheets-overlay, the actual MOE was predictable with feasibility of $R^2$=0.53, and also the nondestructively-evaluated MOE was lower by 20% in raw plywood, and higher 20% in LVL than actual bending MOEs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.4
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• pp.1768-1789
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• 2016

In contemporary video streaming systems based on HTTP protocol, video players at the client side are responsible for adjusting video quality to network conditions and user expectations. However, when multiple video clips are streamed simultaneously, an intricate application logic implemented in the video players overlays the TCP mechanism which is responsible for a balanced access to a shared network link. As a result, some video players may not obtain a fair share of network throughput and may be vulnerable to an unstable video bit-rate. Therefore, we propose to simplify the algorithms implemented in the video players, which are responsible for the adjustment of video quality and constrain their functionality only to sending feedback to a server about a state of the player buffer. The main logic of the system is shifted to the server, which is now responsible for bit-rate selection and prioritisation of the video streams transmitted to multiple clients. To verify our proposition, we performed several experiments in a laboratory environment which show that when the server cooperates with the clients, the video players experience fewer quality switches and the system achieves better fairness when allocating network throughput among the video players. However, this comes at the cost of worse utilisation of network bandwidth.

• Journal of Communications and Networks
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• v.9 no.4
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• pp.428-437
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• 2007

Along with the development of network, more and more functions and services are required by users, while traditional network fails to support all of them. Although overlay is a good solution to some demands, using them in an efficient, scalable way is still a problem. This paper puts forward a framework on how to construct an efficient, scalable overlay mesh in real network. Main differences between other overlays and ours are that our overlay mesh processes some nice features including class-of-service(CoS) and traffic engineering(TE). It embeds the end-to-end optimal traffic control law which can distribute traffic in an optimal way. Then, an example is given for better understanding the framework. Particularly, besides good scalability, and failure recovery, it possesses other characteristics such as routing simplicity, self-organization, etc. In such an overlay mesh, an applicable source routing scheme called hierarchical source routing is used to transmit data packet based on UDP protocol. Finally, a guideline derived from a number of simulations is proposed on how to set various parameters in this overlay mesh, which makes the overlay more efficient.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.4
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• pp.185-195
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• 2001

Latex Modified Concrete(LMC) has been widely used for the pavement of highway bridges over the past 35years around the world since it is more resistant to the intrusion of chloride ions, has higher tensile, compressive, and flexural strength, and has greater freeze-thaw resistance. However, in Korea, it has not been introduced to fields due to higher initial construction cost for its overlay compared with that of conventional pavement materials. Due to durable characteristics, it should be noted that the LMC may be more cost-effective than conventional pavements such as asphalt pavement, when life-cycle cost(LCC) concept is considered. The objective of this study is intended to suggest a practical LCC analysis model for pavement projects and to demonstrate relative cost-effectiveness of the LMC overlays in comparison with conventional pavement techniques. It may be stated that the procedure proposed in this study may be utilized for making optimal decision on cost-effective pavement design.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.8
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• pp.4160-4173
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• 2019

Borescopes facilitate the inspection of areas inside machines and systems that are not directly accessible for visual inspection. They offer real-time, up-close access to confined and hard-to-access spaces without having to dismantle or destructure the object under inspection. Borescopes are ideal instruments for routine maintenance, quality inspection and monitoring of systems and structures. The main application being fault or defect detection, it is useful to have measuring capability to quantify object dimensions in a target area. High-end borescopes use multi-optic solutions to provide measurement information of viewed objects. Multi-optic solutions can provide accurate measurements at the expense of structural complexity and cost increase. Measuring functionality is often unavailable in low-end, single camera borescopes. In this paper, a single camera measurement solution that enables the size estimation of viewed objects is proposed. The proposed solution computes and overlays a scaled grid of known spacing value over the screen view, enabling the human inspector to estimate the size of the objects in view. The proposed method provides a simple means of measurement that is applicable to low-end borescopes with no built-in measurement capability.

• Current Optics and Photonics
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• v.5 no.3
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• pp.243-249
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• 2021

In this paper, the sensing characteristics of a double cladding fiber (DCF) long-period fiber grating (LPFG) to the surrounding refractive index (SRI) are studied. The outer cladding of the DCF plays the role of the overlay, thus, the mode transition (MT) phenomenon of DCF can be induced by etching the outer cladding radius instead of coating overlays. The response characteristics of the effective refractive index (ERI) of the cladding mode to the outer cladding radius are analyzed. It is found that in the MT range, the change rate of ERIs of cladding modes is relatively larger than that for other ranges. Further, based on the features of the mode transition region (MTR), the phase-matching curve of the 11^th cladding mode is investigated, and the response of the DCF-LPFG to the SRI is characterized by the change of wavelength intervals between the dual peaks under different outer cladding radii. The numerical simulation results show that the SRI sensitivity is greatly improved, which is available to 3484.0 nm/RIU with the fitting degree 0.998 in the SRI range of 1.33-1.37. The proposed DCF-LPFG can provide new theoretical support for designing the DCF-LPFG refractive index sensor with excellent performances of sensitivity, linearity and structure.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.39-44
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• 2008

This paper proposes a real-time geometric correction system based on a projector to project digital images onto deformable surface. Markers use to trace lots of corresponding points would spoil the projected image when the projector projects a digital image onto the surface because they leave marks on the surface. In addition, it is difficult to build a real-time geometric correction system since bottlenecks occur through the process of the geometric correction for projecting images. In this paper, we use invisible infrared markers and a vertex shader of GPU using Cg TookKit of NVIDIA in order to eliminate disadvantage and bottlenecks in the process of markers recognition so that it is possible to project natural correction images in real-time. As a result, this system overlays an interactive virtual texture onto the real paper by using the geometric transformation. Therefore, it is possible to develop variation of AR(Augmented Reality) based on digital contents systems.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.1
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• pp.11-19
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• 2007

There are have been reports that the distribution of electromyographical(EMG) activity is determined in a predictable manner by both the location and number of occlusal contacts. However, these reports placed an emphasis on whole dentition. Inclined plane contacts in the frontal plane are classified as A-, B- or C-types. Objectives: The aim of this study was to evaluate the relation between occlusal tooth contact patterns and EMG activity of masseter muscle during maximum voluntary clenching. Methods: Fifteen healthy human subjects(Mean age; 25.3 years) volunteered to participate in this study. Acrylic resin overlays were fabricated for upper 2nd premolars and 1st molars bilaterally, and offered 3 types(A-, B- and AB- type contact). EMG activity of the masseter muscles was recorded bilaterally during maximum voluntary clenching. Statistical analysis was performed using the one-way ANOVA. Results: The group with a A-type contact showed a statistically lower EMG activity of masseter muscle than that of natural group(p<0.05) and that of B- and AB- type groups(p<0.01) on both upper 2nd premolars and upper 1st molars. Conclusions: These results suggest that occlusal tooth contact patterns have an influence on EMG activity of masseter muscle during maximum voluntary clenching.