• ETRI Journal
• /
• 제29권5호
• /
• pp.673-675
• /
• 2007

We present the design and fabrication of a 60 GHz medium power amplifier monolithic microwave integrated circuit with excellent gain-flatness for a 60 GHz radio-over-fiber system. The circuit has a 4-stage structure using microstrip coupled lines instead of metal-insulator-metal capacitors for unconditional stability of the amplifier and yield enhancement. The gains of each stage of the amplifier are modified to provide broadband characteristics of input/output matching for the first and fourth stages and to achieve higher gains for the second and third stages to improve the gain-flatness of the amplifier for wideband.

• 전기학회논문지
• /
• 제60권4호
• /
• pp.823-828
• /
• 2011

We have systematically designed and experimentally demonstrated the opto-electrical predistortion optical transmitter using microwave circuit modelling for reducing the nonlinearity of the distributed-feedback laser diode (DFD-LD). The DFB-LD is analyzed using microwave circuits model based on rate equations. Through the system-level simulation for predistortion method, the optimized characteristics of the RF components in the system are confirmed. The simulated and experimental results show the reduced distortion products. These results are analyzed as the evaluation parameters for the miniaturization and optimization of the opto-electrical predistortion method in radio-over-fiber systems.

• Steel and Composite Structures
• /
• 제32권1호
• /
• pp.21-35
• /
• 2019

This study investigates the flexural behavior of steel-concrete composite beams strengthened with prestressed carbon fiber-reinforced polymer (CFRP) plates. An innovative mechanical anchorage system was developed. The components of the system can be easily assembled on site before applying a prestressing force, and removed from the structures after strengthening is completed. A total of seven steel-concrete composite specimens including four simply supported beams strengthened at the positive moment region and three continuous beams strengthened at the negative moment region were tested statically until failure. Experimental results showed that the use of prestressed CFRP plates enhanced the flexural capacity and reduced the mid-span deflection of the beams. Furthermore, by prestressing the CFRP laminates, the material was used more efficiently, and the crack resistance of the continuous composite specimens at the central support was significantly improved after strengthening. Overall, the anchorage system proved to be practical and feasible for the strengthening of steel-concrete composite beams. The theoretical analysis of ultimate bearing capacity is reported, and good agreement between analytical values and experimental results is achieved.

• Nuclear Engineering and Technology
• /
• 제52권12호
• /
• pp.2847-2851
• /
• 2020

A simple water level measurement method based on wavelength division multiplexing (WDM) is proposed and demonstrated. The measurement principle is based on the change of Fresnel reflection occurring at the end facet of the optical fiber tip (OFT). To increase the spatial resolution of water level sensing, a broadband light source (BLS) and an arrayed waveguide grating (AWG) are employed. The OFTs are multiplexed with the dedicated wavelength channels of AWG. By measuring all of the reflection powers reflected at the OFTs with a proposed on-site reflectometer, the water level can be monitored continuously for a fast emergency response. Moreover, it can be implemented easily with the commercially available optical components and devices with the simple configuration.

• Steel and Composite Structures
• /
• 제47권3호
• /
• pp.383-393
• /
• 2023

Conventional reinforced concrete design codes assume ideal strain evolution in semi-deep beams with externally bonded fiber-reinforced polymer (EB-FRP) web strips. However, there is a strain interaction between internal stirrups and web strips, leading to a notable difference between code-based and experimental shear strengths. Current study provides an experiment-verified detailed numerical framework to assess the potential strain interaction under quasi-static monotonic load. Based on the observations, steel stirrups are effective only for low EB-FRP amounts and the over-strengthening of semi-deep beams prevents the stirrups from yielding, reducing its shear strength contribution. A notable difference is detected between the code-based and the study-based EB-FRP strain values, which is a function of the normalized FRP stress parameter. Semi-analytical relations are proposed to estimate the effective strain and stress of the components considering the potential strain interaction. For the sake of simplification, a linearized correction factor is proposed for the EB-FRP web strip strain, assuming its restraining effect as constant for all steel stirrup amounts.

• Asia pacific journal of information systems
• /
• 제6권2호
• /
• pp.125-148
• /
• 1996

This paper is primarily focused on the function of model management systems such as higher level representations and buildings of optimization models using them, especially in the area of the telecommunication network models. This research attempts to provide the model builders an intuitive language-namely higher level representation-using five distinctivenesses : Objective, Node, Link, Topological Constraint including five components, and Decision. The paper elaborates all components included in each of distinctivenesses extracted from structural characteristics of typical telecommunication network models. Higher level representations represented with five distinctivenesses should be converted into base level representations which are employed for semantic representations of linear and integer programming problems in knowledge: assisted optimization modeling system(UNIK-OPT). Furthermore, for formulating the network model using higher level representations, the reasoning process is proposed. A system called UNIK-NET is developed to implement the approach proposed in this research, and the system is illustrated with an example of the network model.

• 한국식품영양과학회지
• /
• 제20권1호
• /
• pp.72-77
• /
• 1991

This study was designed to obseve the effect of defatted perilla as a dietary fiber on lipid components of serum feces and liver in rats. Serum cholesterol and triglyceride were signfican-ly decreased in defatty perilla added groups. total lipid cholesterol and triglyceride of feces were significantly increased in defatted perilla added groups. Liver phospholipid content was higher in the defatted perilla added groups. The other lipid components of the liver were not affected by the defatted perilla administration. These results suggest the possibitlity that defatted perilla have a reducing effect of serum cholesterol and triglyceride through the incre-ment of feacal excretion of lipid component and phospholipid in liver.

• Structural Engineering and Mechanics
• /
• 제24권5호
• /
• pp.561-584
• /
• 2006

The paper presents results of parametric studies, and an overall approach for the design of a modular bridge system which incorporates a steel-reinforcement free concrete slab cast on top of carbon FRP stiffened deck panels which act as both structural formwork and flexural reinforcement, spanning between hollow box type FRP girders. Results of the parametric studies are highlighted to elucidate important relationships between critical configurational parameters and empirical equations based on numerical studies are presented. Results are discussed at the level of the individual deck and girder components, and as a slab-on-girder bridge system. An overall design methodology for the components and bridge system including critical performance checks is also presented.

• Fibers and Polymers
• /
• 제5권1호
• /
• pp.25-30
• /
• 2004

The present paper reports the impact of thermal treatment on the characteristics of core-sheath type hybrid technical yarns. The core-sheath type hybrid yams are prepared using DREF-III technology. Polyester and glass multifilaments are used as core components whereas the cotton and polyester staple fibers are the sheath components wrapped around the core filament with different proportions to form a hybrid structure. The thermal treatment is carried out both in dry and in wet state under relaxed condition and the thermal shrinkage, sheath-slipping resistance and tensile and bending properties of hybrid yarns have been studied. Thermal treatment markedly increases the thermal shrinkage and sheath-slipping resistance of hybrid yarns with polyester multifilament in core, but insignificant effect for yarns with glass multifilament in core. Breaking elongation of hybrid yams with polyester multifilament in core increases with treatment temperature. The hybrid yarns with glass multifilament in core are least affected by thermal treatment.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1997년도 추계학술대회 논문집
• /
• pp.773-776
• /
• 1997

This paper presents an investigation of the energy absorption of composite laminates during ballistic impact. Three components are responsible for the absorption of energy-the tensile failure of fiber, the elastic deformation of the composite, the delamination of composite laminates. The ballistic limit, V/sub 0/, of the laminates is determined using a previous model implemented to determine the energy absorption of the three components listed above. The size of the deformed zone during impact was estimated by an approximate solution for impacts on plates. The carbon/epoxy plates were examined for this research.