• Journal of the Korean Institute of Navigation
• /
• v.22 no.4
• /
• pp.51-57
• /
• 1998

According to the rapid development of the electric industry, the demand of the frequency allocation and the usage of electromagnetic wave are increased due to automation of modem society. Electromagnetic wave absorbers for anechoic chamber are needed to broaden the effective frequency bandwidth, reduce the thickness, and decrease the weight. There are various absorbers proposed for the above conditions, but they could not decisively solve the above requirements. The Electromagnetic wave absorber made by a conventional ferrite tile has, for example, broadened the effective frequency bandwidth by the way of forming air layer(practically in urethane foam, etc.) on the ferrite tile. Therefore, an air layer is formed between a reflection plate and a sintered Ni-Zn ferrite tile of 7 mm in thickness, which has reflectivity less than -20 dB from 30 MHz to 400 MHz in bandwidth. In this paper, a broadband electromagnetic wave absorber are designed, which has the reflection characteristics less than -20 dB from 30 MHz to 8,000 MHz in the bandwidth. A super broadband electromagnetic wave absorber is achieved by inserting square Ferrite Cylinders Type with the thickness less than 23.5 mm and with the frequency band from 30 MHz to 8,000 MHz under the above tolerance limits. The purpose of this research is on the development of a universal anechoic chamber for measuring radiated electromagnetic wave or immunity of electronic equipments, GTEM-cell and also a wall material for preventing TV ghost, etc.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.3 no.1
• /
• pp.43-50
• /
• 1999

Electromagnetic wave absorbers for anechoic chamber are needed to broaden the useful frequency bandwidth, reduce the thickness, and decrease the weight. There are various absorbers proposed for the above conditions, but they could not decisively solve the above requirements. The Electromagnetic wave absorber made by a conventional ferrite tile has, for example, broadened the useful frequency bandwidth by the way of forming air layer. Therefore, an air layer is formed absorber between a reflection plate and a sintered Ni-Zn ferrite tile of 7 mm in thickness, which has reflectivity less than -20 dB from 30 MHz to 450 MHz in frequency band, far narrower than the aimed bandwidth. The purpose of this paper is on the development of a universal anechoic chamber for measuring radiated electromagnetic wave or immunity of electronic equipments, GTEM-cell, wall material for prevention of TV ghost, etc. Accordingly, in this paper, a broadened electromagnetic wave absorber is designed, which has the reflection characteristics less than -20 dB from 30 MHz to 5,430 or 8,000 MHz in the bandwidth. Then we will design a super broadband electromagnetic wave absorber by inserting square Ferrite Cylinders Type with the thickness less than 23.5 m in three-layed type and with the frequency band from 30 MHz to 5,430-8,000 MHz under the above tolerance limits.

• Applied Biological Chemistry
• /
• v.39 no.5
• /
• pp.379-383
• /
• 1996

The ultrastructure of the compound starch granules and the protein bodies of Odaebyeo rice of early matured variety were examined by light microscope and electron microscope. The endosperm cell appealed rectangular or octangular shape on the cross section. The thickness of cell wall containing of membraneous materials was about $0.5\;{\mu}m$ in diameter. The starch cell was filled compactly with globular or oval shaped compound starch granules with the size of $20{\sim}25\;{\mu}m$ in diameter. The compound starch granules were consisted of central core starch granule and concentrical $2{\sim}3$ layers of starch granules. The average thickness of the starch granules were about $5\;{\mu}m$. Most protein bodies were found in the aleurone layer The globular protin bodies were scattered near the compound starch granules and $2.5{\sim}3\;{\mu}m$ in diameter. The protein bodies composed of central electron dense materials and peripheral electron loose materials in limiting membrane.

• Applied Microscopy
• /
• v.21 no.1
• /
• pp.86-107
• /
• 1991

An experimental study was performed to observe the early effects of monocrotaline on pulmonary vascular system by means of light microscopy and scanning electron microscopy, attempting to expore the mechanism behind the process of pulmonary hypertension. Experimental animal(Sprague-Dawley male rats ; 150-200g B. W.) were intra-peritoneal administered with 100mg/kg B. W. monocrotaline. Authors observed light microscopically various gradational increase of wall thickness in pulmonary muscular and non-muscular arteries in duration from 2 weeks to 5 weeks after monocrotaline administration and the changes were more sever in the latter than the former. The scanning electron microscopy shows severe and diffuse endothelical cell swelling, microvilli and microbleb formation since 1 hour after monocrotaline administration and during the course, after 5 hours the severity of endothelial cell damage was prominent with presence of fibrin, webs, platelet thrombi and white cell adherence. It was concluded that the monocrotaline primarily induced severe and diffuse endothelial cell damage of pulmonary arteries and laterly added the participation of platelets, which attributed to the pathogenesis of monocrotaline induced pulmonary vascular lesions in relation to pulmonary hypertension.

• Archives of Plastic Surgery
• /
• v.38 no.5
• /
• pp.691-694
• /
• 2011

Purpose: With an increase in the population of immunocompromised patients, the incidence of maxillary sinus aspergillus infection has also escalated. Maxillary sinus aspergillosis is generally extended to the sinus antrum, base or thin orbital wall and ethmoid air cell region. We experienced a case of maxillary sinus aspergillosis which was extended directly to the soft tissue of the cheek. Methods: A 46-year-old man with acute myelogenous leukemia was consulted for the defect of the anterior wall of the maxillary sinus, and cheek. Radiologic and histologic findings were consistent with invasive maxillary sinus aspergillosis. The otolaryngology department performed debridement via endoscopic sinus surgery first. Coverage of the resulting defect in the anterior wall of the maxillary sinus and its inner layer was undergone by the plastic and reconstructive surgery department, using a pedicled superficial temporal fascia flap and a split thickness skin graft. The remaining skin defect of the cheek was covered with a local skin flap. Results: The patient went through an uneventful recovery. There was no recurrence during 6 months of follow-up. Conclusion: Maxillary sinus aspergillosis usually involves the orbit or the gingiva but in some cases it may directly invade soft tissues of the cheek. Such an atypical infection extending into the cheek may lead to a large soft tissue defect requiring coverage. Thus, any undiagnosed soft tissue defect involving the cheek or maxillofacial area, especially in immunocompromised patients, should be evaluated for aspergillosis. We present this rare case, with a review of the related literature.

• Proceedings of the KIEE Conference
• /
• 1998.07e
• /
• pp.1788-1790
• /
• 1998

The dielectric layers in AC plasma display panel(AC PDP) are essential to the discharge cell structure, because they protect metal electrodes from sputtering by positive ion bombarding in discharge plasma and form a sheath of wall charges which are essential to memory function of AC PDP. This layer should have high dielectric strength and also be transparent because the luminance of PDP is strongly correlated this layer. In this paper, we discussed the dielectric strength and transparency of the dielectric layer under various conditions. As a result, on the $15{\mu}m$ thickness, the minimum dielectric strength was $29V/{\mu}m$ and the transmittance coefficient was about 80% after $570^{\circ}C$ firing process. It can be proposed that the resonable dielectric thickness in AC PDP is $15{\mu}m$ because it has about 80V margin on the maximum applied voltage.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.48 no.1
• /
• pp.39-44
• /
• 1999

The dielectric layers in AC plasma display panel(PDP) are essential to the discharge cell structure, because they protect metal electrodes from sputtering by positive ion bombarding in discharge plasma and form a sheath of wall charges which are essential to memory function of AC PDP. This layer should have high dielectric breakdown voltage, and also be transparent because the luminance of PDP is strongly correlated this layer. In this paper, we discussed the dielectric breakdown voltage and transparency of the dielectric layer under various conditions. As a result, on the $15\mum$ thickness, the minimum dielectric breakdown voltage was 435V and the transmission coefficient was about 80% after $570^{\circ}C$ firing process. It can be proposed that the resonable dielectric thickness in AC PDP is $15\mum$ because it has about 75V margin on the maximum applied voltage.

• Korean Chemical Engineering Research
• /
• v.54 no.2
• /
• pp.268-273
• /
• 2016

To improve mechanical strength of carbon foams, the carbon black (CB) added carbon foams were fabricated by impregnating different contents of carbon black (CB) and mesophase pitch using polyvinyl alcohol (PVA) solution into polyurethane foam and being followed by heat treatment. The cell wall-thicknesses of carbon foams were controlled by adding amounts of CB, and it was confirmed that the compressive strength of carbon foams was increased as increasing cell wall-thickness. The compressive strength had the highest value of $0.22{\pm}0.05MPa$ with the highest bulk density of $0.44g/cm^3$ when adding 5 wt% CB in carbon foam. However, the thermal conductivity was decreased by adding CB in carbon foam. The results indicated that the thermal conductivities of carbon foams were reduced by increased interlayer spacing ($d_{002}$) with the addition of CB in carbon foams.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.2238-2243
• /
• 2007

A new microcombustor configuration for a micro fuel-cell reformer integrated with a micro evaporator was studied experimentally and computationally. The present microcombustor is simply cylindrical to be easily fabricated but two-staged, expending downstream, to feasibly control ignition and stable burning. Results show that the aspect ratio of the first stage and the wall thickness of the microcombustors substantially affect ignition and thermal characteristics. For the optimized design conditions, a premixed microflame was easily ignited in the expanded second stage combustor, moved into the smaller first stage combustor, and finally stabilized therein. The measured and predicted temperature distributions across the microcombustor walls indicated that heat generated in the microcombustor is well transferred. Thus, the present microcombustor configuration could be applied to the practical micro reformers integrated with a micro evaporator for use of fuel cells.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.31 no.3
• /
• pp.96-104
• /
• 1999

Anatomical and chemical properties of three mulberry species (Morus spp) were analyzed as an alternative row material for the paper mulberry (Broussonetia kazinoki) . The pulping and papermaing characteristics of bast fiber and whole stalks by three different pulping processes, conventional alkali, alkali-hydrogen peroxide, and sulfomethylated, for the Hanji were investigated. The fiber dimension of M.bombycis was the biggest of the species. The fiber length of upper part and the fiber width and cell wall thickness of lower part were bigger than the others. The extractives and ash contents of bast fiber were higher than those of whole stalk , and holocellulose and lignin contents of whole stalk were higher than those of bast fiber. The pulp yields of M.alba bast fiber, M.bombycis whole stalk, and sufomethylated pulping were higher than the others.