• Journal of Magnetics
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• 제10권2호
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• pp.41-43
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• 2005

We have investigated an optical waveguide isolator with a multimode interference section by wafer direct bonding, operating at a wavelength $1.55\;{\mu}m$. In order to fabricate the device for monolithic integration, the wafer direct bonding between a magnetic garnet material as a cladding layer and a semiconductor guiding layer has been achieved. We found that wafer direct bonding between InP and GGG $(Gd_3Ga_5O_{12})$ is effective for the integration of a waveguide optical isolator. The isolation ratio was obtained to be 2.9 dB in the device.

• 보존과학연구
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• 통권23호
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• pp.113-129
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• 2002

This study is to disclose the gilding technique and distinctive features of using surface improvement technique in ancient gilt. There are many kinds of the ancient gilding technique so this thesis mainly focused on mercury amalgam gilding. Gilding technique can be largely divided into two branches – the cladding and amalgam method - in ancient periods. The researches have been carried out on two parts; the first is to find the making progress of amalgam on all sort of the gilding materials and the second is to show features of the gilded layer among basic metals. As a result of this experiment, to achieve good quality of amalgam, suitable particle size of the gilding material should be needed and the heating, a primary factor, has an effect on amalgam to be formed. Aspecial features of amalgam gilding, according to changing the basicmetal, would be influenced by chemical attraction for the mercury, condition of the surface and some other factors. A platers abilities and the making progress of amalgam would be influenced by a uniform and good gilding layer. In conclusion, it should be profoundly studied and investigated on the ancient gilding techniques and gold-gilt relics.

• Current Optics and Photonics
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• 제3권6호
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• pp.583-589
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• 2019

We report experimental results on 940-nm 350-mW AlGaAs/InGaAs transverse single-mode laser diodes (LDs) adopting graded-index separate confinement heterostructures (GRIN-SCH) and p,n-clad asymmetric structures, with improved temperature and small-divergence beam characteristics under high-output-power operation, for a three-dimensional (3D) motion-recognition sensor. The GRIN-SCH design provides good carrier confinement and prevents current leakage by adding a grading layer between cladding and waveguide layers. The asymmetric design, which differs in refractive-index distribution of p-n cladding layers, reduces the divergence angle at high-power operation and widens the transverse mode distribution to decrease the power density around emission facets. At an optical power of 350 mW under continuous-wave (CW) operation, Gaussian narrow far-field patterns (FFP) are measured with the full width at half maximum vertical divergence angle to be 18 degrees. A threshold current (I_th) of 65 mA, slope efficiency (SE) of 0.98 mW/mA, and operating current (I_op) of 400 mA are obtained at room temperature. Also, we could achieve catastrophic optical damage (COD) of 850 mW and long-term reliability of 60℃ with a TO-56 package.

• Steel and Composite Structures
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• 제34권2호
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• pp.189-213
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• 2020

Stainless-clad (SC) bimetallic steels that are manufactured by metallurgically bonding stainless steels as cladding metal and conventional mild steels as substrate metal, are kind of advanced steel plate products. Such advanced composite steels are gaining increasingly widespread usage in a range of engineering structures and have great potential to be used extensively for large civil and building infrastructures. Unfortunately, research work on the SC bimetallic steels from material level to structural design level for the applications in structural engineering field is very limited. Therefore, the aim of this paper is to investigate the material behaviour of the SC bimetallic steels under the cyclic loading which structural steels usually could encounter in seismic scenario. A number of SC bimetallic steel coupon specimens are tested under monotonic and cyclic loadings. The experimental monotonic and cyclic stress-strain curves of the SC bimetallic steels are obtained and analysed. The effects of the clad ratio that is defined as the ratio of the thickness of cladding layer to the total thickness of SC bimetallic steel plate on the monotonic and cyclic behaviour of the SC bimetallic steels are studied. Based on the experimental observations, a cyclic constitutive model with combined hardening criterion is recommended for numerical simulation of the cyclic behaviour of the SC bimetallic steels. The parameters of the constitutive model for the SC bimetallic steels with various clad ratios are calibrated. The research outcome presented in this paper may provide essential reference for further seismic analysis of structures fabricated from the SC bimetallic steels.

• 대한금속재료학회지
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• 제49권7호
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• pp.549-556
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• 2011

This study aimed to evaluate the performance of diffusion barriers in order to prevent fuel-cladding chemical interaction (FCCI) between the metallic fuels and the cladding materials, a potential hazard for nuclear fuel in sodium-cooled fast reactors. In order to prevent FCCI, Zr or V metal is deposited on the ferritic-martensitic stainless steel surface by physical vapor deposition with a thickness up to $5{\mu}m$. The diffusion couple tests using uranium alloy (U-10Zr) and a rare earth metal such as Ce-La alloy and Nd were performed at temperatures between 660~800$^{\circ}C$. Microstructural analysis using SEM was carried out over the coupled specimen. The results show that significant interdiffusion and an associated eutectic reaction ocurred in the specimen without a diffusion barrier. However, with the exception of the local dissolution of the Zr layer in the Ce-La alloy, the specimens deposited with Zr and V exhibited superior eutectic resistance to the uranium alloy and rare earth metal.

• Nuclear Engineering and Technology
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• 제50권2호
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• pp.218-222
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• 2018

An oxide-dispersion-strengthened (ODS) layer was formed on Zircaloy-4 tubes by a laser beam scanning process to increase mechanical strength. Laser beam was used to scan the yttrium oxide ($Y_2O_3$)-coated Zircaloy-4 tube to induce the penetration of $Y_2O_3$ particles into Zircaloy-4. Laser surface treatment resulted in the formation of an ODS layer as well as microstructural phase transformation at the surface of the tube. The mechanical strength of Zircaloy-4 increased with the formation of the ODS layer. The ring-tensile strength of Zircaloy-4 increased from 790 to 870 MPa at room temperature, from 500 to 575 MPa at $380^{\circ}C$, and from 385 to 470 MPa at $500^{\circ}C$. Strengthening became more effective as the test temperature increased. It was noted that brittle fracture occurred at room temperature, which was not observed at elevated temperatures. Resistance to dynamic high-temperature bursting improved. The burst temperature increased from 760 to $830^{\circ}C$ at a heating rate of $5^{\circ}C/s$ and internal pressure of 8.3 MPa. The burst opening was also smaller than those in fresh Zircaloy-4 tubes. This method is expected to enhance the safety of Zr fuel cladding tubes owing to the improvement of their mechanical properties.

• 한국재료학회지
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• 제29권4호
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• pp.271-276
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• 2019

Oxide-dispersion-strengthened (ODS) alloy has been developed to increase the mechanical strength of metallic materials; such an improvement can be realized by distributing fine oxide particles within the material matrix. In this study, the ODS layer was formed in the surface region of Zr-based alloy tubes by laser beam treatment. Two kinds of Zr-based alloys with different alloying elements and microstructures were used: KNF-M (recrystallized) and HANA-6 (partial recrystallized). To form the ODS layer, $Y_2O_3$-coated tubes were scanned by a laser beam, which induced penetration of $Y_2O_3$ particles into the substrates. The thickness of the ODS layer varied from 20 to $55{\mu}m$ depending on the laser beam conditions. A heat affected zone developed below the ODS layer; its thickness was larger in the KNF-M alloy than in the HANA-6 alloy. The ring tensile strengths of the KNF-M and HANA-6 alloy samples increased more than two times and 20-50%, respectively. This procedure was effective to increase the strength while maintaining the ductility in the case of the HANA-6 alloy samples; however, an abrupt brittle facture was observed in the KNF-M alloy samples. It is considered that the initial microstructure of the materials affects the formation of ODS and the mechanical behavior.

• ETRI Journal
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• 제31권6호
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• pp.778-783
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• 2009

To fabricate uniform and reliable thin gold stripes that provide low-loss optical waveguides, we developed a novel liftoff process placing an additional $SiN_x$ layer under conventional photoresists. By patterning a photoresist and over-etching the $SiN_x$, the photoresist patterns become free-standing structures on a lower-cladding. This leads to uniform metal stripes with good reproducibility and effectively removes parasitic structures on the edge of the metal stripe in the image reversal photolithography process. By applying the newly developed process to polymer-based gold stripe waveguide fabrication, we improved the propagation losses about two times compared with that incurred by the conventional image-reversal process.

• Wind and Structures
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• 제4권4호
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• pp.279-298
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• 2001

The greatest suction on the cladding of flat roof low-rise buildings is known to occur beneath the conical vortices that form along the roof edges for cornering winds. In a companion paper, a model of the vortex flow mechanism has been developed which can be used to connect the surface pressure beneath the vortex to adjacent flow conditions. The flow model is experimentally validated in this paper using simultaneous velocity and surface pressure measurement on a 1 : 50 model of the Texas Tech University experimental building in a wind tunnel simulated atmospheric boundary layer. Flow visualization gives further insight into the nature of peak suction events. The flow model is shown to account for the increase in suction towards the roof corner as well as the presence of the highest suction at wind angles of $60^{\circ}$. It includes a parameter describing vortex suction strength, which is shown to be related to the nature of the reattachment, and also suggests how different components of upstream turbulence could influence the surface pressure.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 하계학술발표회
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• pp.34-35
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• 2000

A Y-branch phase modulator made of an electro-optic(EO) polymer has been designed and fabricated. An EO polymer, PMMA-DR1, is used for the core layer, and UV-curable polymers, UV-15 and UV-15 LV, for the cladding layers. The rib type polymeric waveguides are fabricated by the reactive ion etching method and their EO effects are obtained by the poling process. The optical properties of the fabricated phase modulator are as follows: the halfwave voltage, $V_{\pi}$, is 25 V, the insertion loss of TM mode is 13.8 dB, and the intensity modulation is 0.17 % (V).