• Korean Journal of Optics and Photonics
• /
• v.14 no.3
• /
• pp.331-337
• /
• 2003

This paper represents 50 ㎓ narrow band pass filters for fiber optical communication fabricated by dual ion beam sputtering method. We have analyzed the characteristics of the TA$_2$ $O_{5}$ and $SiO_2$ single layers in order to optimize the process conditions for the 50 ㎓ narrow band pass filters, and controlled the film thickness uniformity to less than 0.1 nm deviation by dual peak spike filter pre-deposition. We designed and fabricated 50 ㎓ narrow band pass filters that consist of 216 layers including 4 cavities based on quarter wave optical thickness. Class substrates with high thermal expansion coefficients were used to reduce the film stress. Anti-reflection coating at the rear side of the substrate was also needed to reduce the optical thickness errors of the Optical Monitoring System caused by multiple beam interference between the front side and the rear side of substrate. The optical characteristics of this 50 ㎓ narrow band pass filters are insertion loss of 0.40 ㏈, pass band ripple of 0.20 ㏈, and pass bandwidth at -0.5 ㏈ of 0.20 nm. and isolation bandwidth at -25 ㏈ of 0.6 nm, which satisfy specifications of dense WDM system in fiber optical communications.tions.

• Journal of the Korean Society of Radiology
• /
• v.14 no.7
• /
• pp.1003-1011
• /
• 2020

This study aims to compare and evaluate the image differences between single and dual sources in applying a technique to reduce metal artifacts using dual energy CT. Discovery CT 256 (GE, USA) as a single source device and Somatom Definition Flash (Siemens Health Care, Forchheim, Germany) as a dual source device. The self-made phantom (pigs with medical titanium screws inserted) was quantitative and qualitatively evaluated under the same conditions by varying the dose under the same conditions using a dual energy CT. The evaluation method was compared by measuring SNR for metal artifacts (scattering, stripe) generated by metal inserts, divided around bones and around tissues. There was a difference in images in the method of reducing metal artifacts between single-source and dual-source devices. In a single source device, the linearized prosthesis by metal implantation showed a greater decrease than the image obtained from a double source device, and the surrounding tissue was well observed without interference from the artifact. In dual-source devices, scattering and stripe artifacts caused by metal inserts decreased more than on a single source device, and signals from adjacent tissues surrounding the metal implant were well observed without diminishing. If the examination is conducted separately between single source and dual source devices depending on whether the area to which the patient is intended to be viewed during the examination is adjacent to the metal insert or the total tissue surrounding the metal insert, it is believed that diagnostic helpful images can be obtained.

• Journal of the Microelectronics and Packaging Society
• /
• v.28 no.1
• /
• pp.1-12
• /
• 2021

Here, we introduce a laser-induced graphene synthesis technology and its applications for the electric/electronic device manufacturing process. Recently, the micro/nanopatterning technique of graphene has received great attention for the utilization of these new graphene structures, which shows progress developments at present with a variety of uses in electronic devices. Some examples of practical applications suggested a great potential for the tunable graphene synthetic manners through the control of the laser set-up, such as a selection of the wavelength, power adjustment, and optical techniques. This emerging technology has expandability to electric/electronic devices combined together with existed micro-packaging technology and can be integrated with the new processing steps to be applied for the operation in the fields of biosensors, supercapacitors, electrochemical sensors, etc. We believe that the laser-induced graphene technology introduced in this paper can be easily applied to portable small electronic devices and wearable electronics in the near future.

• Journal of Korean Society of Disaster and Security
• /
• v.16 no.3
• /
• pp.17-26
• /
• 2023

Prestressed Concrete (PSC) girders are divided into pre- and post-tension types as prestressing method, and I- and U-type as cross-sectional shape. There are both advantages and disadvantages depending on each prestressing method and cross-sectional shape, and each method is applied to bridge construction sites. In this study, a new girder design was attempted to develop that overcomes its shortcomings by using the pretension method and U-type cross sectional shape. Its structural performance was verified in this study. Pretension type girders are mainly manufactured in factories because they require a reaction arm and related facilities, and have the disadvantage of being limited in weight and span length for road transportation. In addition, in the case of the U-type cross-section, structural stability is very reliable during construction against overturning, but its own weight is relatively large comparing to I-type, and the post-tension method is mainly applied after on-site production. In this study, a PSC girder manufacturing method using the field pretension was proposed and a span length of 40 m real-scale test specimen was manufactured and verified its structural performance.

• Korean Journal of Optics and Photonics
• /
• v.35 no.1
• /
• pp.9-17
• /
• 2024

A plenoptic optical system for microscopy comprises an objective lens, tube lens, microlens array (MLA), and an image sensor. Numerical aperture (NA) matching between the tube lens and MLA is used for optimal performance. This paper extends performance predictions from NA matching to unmatching cases and introduces a computational technique for plenoptic configurations using optical analysis software. Validation by fabricating and experimenting with two sample systems at 10× and 20× magnifications resulted in predicted spatial resolutions of 12.5 ㎛ and 6.2 ㎛ and depth of field (DOF) values of 530 ㎛ and 88 ㎛, respectively. The simulation showed resolutions of 11.5 ㎛ and 5.8 ㎛, with DOF values of 510 ㎛ and 70 ㎛, while experiments confirmed predictions with resolutions of 11.1 ㎛ and 5.8 ㎛ and DOF values of 470 ㎛ and 70 ㎛. Both formula-based prediction and simulations yielded similar results to experiments that were suitable for system design. However, regarding DOF values, simulations were closer to experimental values in accuracy, recommending reliance on simulation-based predictions before fabrication.

• Korean Journal of Optics and Photonics
• /
• v.35 no.3
• /
• pp.115-120
• /
• 2024

Magneto-optical (MO) materials have attracted much attention, since they can be utilized for various optical applications, such as magnetic field sensors, optical current sensors, optical isolators, and optical circulators. In this study, alumino-borosilicate (ABS) glasses with high concentrations of Dy³⁺ ions were fabricated by a conventional melt-quenching technique, and the dependence of their thermal, optical, and magneto-optical properties on Dy³⁺ ion concentration was investigated. The MO property of the glasses was investigated by measurement of Faraday rotation at 1550 nm. The Faraday rotation angle increased linearly with the increase of Dy³⁺ ion concentration in the glasses. A very high Verdet constant of -6.86 rad/(T·m) was obtained for glass with a Dy³⁺ ion concentration of 30 mol%. In addition, the ABS-Dy glasses showed good thermal stability of greater than 128 ℃ against crystallization, and high optical transmission of 70% in the visible to near-infrared windows of 480-720, 1390-1560, and 1800-2400 nm. Due to the high Verdet constant and good thermal stability, the ABS-Dy glasses in this study could be candidate optical materials for MO device applications at 1550 nm.

• 보존과학연구
• /
• s.32
• /
• pp.5-24
• /
• 2011

Neunghwaji(Embossed patterned paper) is a unique paper used for a traditional book cover in Korea. The research was carried out to investigate Neunghwaji's features. Physical property was studied through a test of tensile strength and folding endurance. Also, comparative analysis of virus resistance and waterproof ability was undertaken on Neunghwaji. 1. Folding endurance test showed that strength of non-embossed CB and HB decreased during deteriorating duration. Embossed CN and HN showed the strength increasing at early stage and decreasing from the 27th day of the deteriorating duration. Tensile strength was decreasing in both cases as deterioration progressed. 2. Growth of Arthrinium sp. fungus on embossed paper was 10% less than plain paper while Cladosporium sp. showed 20~30% less growth. Amur cork dyeing(H) showed 10~30% lower fungi growth than Gardenia seed dyeing(C). The result indicated that embossed paper has better virus resistance than Hanji, and Amur cork dyeing has better virus resistance than Gardenia seed dyeing. 3. Average contact angle of CN, CB, HN, and HB was $85{\sim}92^{\circ}$ and NON-N and NON-B was $59{\sim}63^{\circ}$. In detail, CN's contact angle was $1{\sim}7^{\circ}$ higher than CB's; HN was $1{\sim}6^{\circ}$ higher than HB. Therefore, it was found that embossed paper has higher contact angle than Hanji thus the former has better waterproof ability. The research suggested production technique of Neunghwaji and studied its features related to the technique. Neunghwaji was confirmed to have superior quality to Hanji though further study regarding above test result is needed to complement the research.

• Journal of Veterinary Clinics
• /
• v.28 no.5
• /
• pp.486-496
• /
• 2011

A special mesenchymal tissue layer called perichondrium has a chondrogenic capacity and is a candidate tissue for engineering of cartilage. To overcome limited potential for chondrocyte proliferation and re-absorption, we studied a method of cartilage tissue engineering comprising chondrocyte-hydrogel pluronic complex (CPC) and cultured perichondrial cell sheet (cPCs) which entirely cover CPC. For effective cartilage regeneration, cell-sheet engineering technique of high-density culture was used for fabrication of cPCs. Hydrogel pluronic as a biomimetic cell carrier used for stable and maintains the chondrocytes. The human cPCs was cultured as a single layer and entirely covered CPC. The tissue engineered constructs were implanted into the dorsal subcutaneous tissue pocket on nude mice (n = 6). CPC without cPCs were used as a controls (N = 6). Engineered cartilage specimens were harvested at 12 weeks after implantation and evaluated with gross morphology and histological examination. Biological analysis was also performed for glycosaminoglycan (GAG) and type II collagen. Indeed, we performed additional in vivo studies of cartilage regeneration using canine large fullthickness chondrial defect model. The dogs were allocated to the experimental groups as treated chondrocyte sheets with perichondrial cell sheet group (n = 4), and chondrocyte sheets only group (n = 4). The histological and biochemical studies performed 12 weeks later as same manners as nude mouse but additional immunofluorescence study. Grossly, the size of cartilage specimen of cPCs covered group was larger than that of the control. On histological examination, the specimen of cPCs covered group showed typical characteristics of cartilage tissue. The contents of GAG and type II collagen were higher in cPCs covered group than that of the control. These studies demonstrated the potential of such CPC/cPCs constructs to support chondrogenesis in vivo. In conclusion, the method of cartilage tissue engineering using cPCs supposed to be an effective method with higher cartilage tissue gain. We suggest a new method of cartilage tissue engineering using cultured perichondrial cell sheet as a promising strategy for cartilage tissue reconstruction.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.25 no.3
• /
• pp.225-235
• /
• 2009

A common procedure of restoration of endodonticlly treated tooth with fiber-reinforced post is followed by core build-up after post cementation. However, this technique is complex and time-consuming. The aim of this study was to compare fracture strength of premolar, restored with various methods of core fabrications on fiber-reinforced posts and casting metal restoration. Forty five freshly extracted human mandibular premolars were obtained and devided into 5 groups acconding to the type of post and methods of core build-up. In Group A, D.T. $Light-post^{(R)}$ were cemented with $DUO-LINK^{TM}$ and then $LIGHT-CORE^{TM}$ was used for core restoration. In Group B, D.T. $Light-post^{(R)}$ and $DUO-LINK^{TM}$ were used for cementing in the postspace, and $DUO-LINK^{TM}$ was used again for core restoration. In Group C, $Light-post^{(R)}$ bonding and the core build-up were performed simultaneously by using $DUO-LINK^{TM}$. In Group D, $LuxaPost^{(R)}$ was bonded by using $LuxaCore^{(R)}-Dual$. Again, $LuxaCore^{(R)}-Dual$ was used for core restoration. In Group E, $LuxaPost^{(R)}$ bonding and the core build-up were performed simultaneously by using $LuxaCore^{(R)}-Dual$. Axial reduction was formed parallelly as possible and 45 degree bevel was made at buccal occlusal surface. Crowns were fabricated and cemented. Each tooth was embedded in self-curing acrylic resin to the level of 2mm below the CEJ. Specimens were fixed on universal testing machin such that the axis of the tooth was at 45 degree inclination to the horizontal plane, and compressive force was applied at a crosshead speed of 1mm/min until failure occurred. The mean fracture strength was the highest in group A followed by descending order in group B, D, E and C. However, there were no statistically significant differences between groups with regard to the fracture strength. The type of the post or build-up methods of the core does not seem to influence the fracture strength.

• Korean Journal of Optics and Photonics
• /
• v.14 no.1
• /
• pp.23-32
• /
• 2003

The spectroe-ellipsometric constant $\Delta$, Ψ and the ellipsometric growth curves at the wavelength of 632.8 nm are collected. These are critically examined to find out the optimum growth condition of phase change $Ge_2Sb_2Te_5(GST)$ thin films as an optical recording medium. GST films are prepared using DC magnetron sputtering technique, under the selected experimental conditions of Ar gas pressure (5 mTorr, 7 mTorr and 10 mTorr), DC power of sputtering gun (15 W, 30 W and 45 W), and substrate temperature (from room temperature to 18$0^{\circ}C$). Based on the three film model, the density distribution of deposited GST films are obtained versus Ar gas pressure and DC power by analyzing spectro-ellipsometric data. The calculated evolution curves at the wavelength of 632.8 nm, are fit into the in situ observed ones to get information about the evolution of density distribution during film growth. The density distribution showed different evolution curves depending on deposition conditions. The GST films fabricated at DC power of 30 W or 45 W, and at Ar gas pressure of 7 mTorr turned out to be the most homogeneous one out of those prepared at room temperature, even though the maximum density difference between the dense region and the dilute region of the GST film was still significant (~50%). Finally, in order to find the optimum growth condition of homogeneous GST thin films, the substrate temperature is varied while Ar gas pressure is fixed at 7 mTorr and DC power at 30 W and 45 W respectively. A monotonic decrease of void fraction except for a slight increase at 18$0^{\circ}C$ is observed as the substrate temperature increases. Decrease of void fraction indicates an increase of film density and hence an improvement of film homogeneity. The optimum condition of the most homogeneous GST film growth turned out to be 7 mTorr of Ar gas pressure, 15$0^{\circ}C$ of substrate temperature. and 45 W of DC power. The microscopic images obtained using scanning electron microscope, of the samples prepared at the optimum growth condition, confirmed this conclusion. It is believed that the fabrication of homogeneous GST films will be quite beneficial to provide a reliable optical recording medium compatible with repeated write/erase cycles.