• 한국강구조학회 논문집
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• 제17권3호통권76호
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• pp.365-373
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• 2005

건축물이 고층이 될 수록 고강도 강재의 사용요구가 증대된다. 그러나 고강도 강재는 일반 강재와는 전혀 다른 기계적 특성을 갖고 있다. 고강도 강재를 건축구조물에 적용하기 위해서는 비탄성 영역에서의 거동이 일반 강재와 동등한가를 확인해야 한다. 본 연구에서는 최근 국내에서 개발된 SM570TMC 강재를 건축구조용으로 사용하기 위해서 기계적 성질 및 용접부 특성을 평가하였다. 연속항복현상을 보이는 SM570TMC 강재는 판두께가 증대되어도 강도저감이 발생되지 않았으며, 최소 항복강도가 440MPa로 나타났다. 또한 판두께 방향으로 균일한 경도분포를 보였다. -5oC에서의 Charpy 충격값도 충분한 인성을 보였다. 용접성과 관련있는 탄소당량은 기존 건축구조용 강재보다 훨씬 낮았으며, 용접부 특성도 우수하였다.

• 한국재료학회지
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• 제7권4호
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• pp.310-316
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• 1997

The effects of carbide and matrix structures on the abrasion wear resistance of multi-component white cast irons with 3.0 mass%C have been studied in this paper. Four different heats were poured in order to obtain the specimens with different combinations of the carbide structures: a basic iron(3.0 mass%C-5.0 mass%Cr-5.0 mass%V-5.0 mass% Mo-12.5mass%W)for M$_{6}$C and M$_{7}$C$_{3}$ carbides, and a Cr free iron(3.0 mass%C-5.0 mass%V-2.5mass%Mo-12.5 mass%W) for MC and M6C carbides. A conventional high Cr free free iron(3.0 mass%C-5.0 mass%V-2.5 mass%Mo-12.5 mass%W) for MC and M6C carbides. A conventional high Cr white cast iron was also poured to compare its wear resistance with those of the multi-component white cast irons. In the as-cast condition, the range of abrasive wear rate(Rw=mg/min) was from 4.15 to 5.98 . The lowest Rw, which means the highest wear resistance, was obtained in the basic iron with nodular MC, lamellar M$_{2}$C and cellular M$_{7}$C$_{3}$ carbides. On the other hand, the Rw of the high Cr white cast iron ranked between the basic iron and the Mo and W free iron. In each alloy, the Rw of air hardened or tempered specimen was lower than that of the as-cast one because of the change of matrix structures by the heat treatments. The Rw of the hear treated speci-mens increased in the order Mo and W free iron, basic iron, Cr free iron, high Cr iron, and V free iron.n.n.n.

• 한국분말재료학회지
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• 제21권4호
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• pp.277-285
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• 2014

The effects of processing parameters on the flow behavior and microstructures were investigated in hot compression of powder metallurgy (P/M) Ti-6Al-4V alloy. The alloy was fabricated by a blended elemental (B/E) approach and it exhibited lamellar ${\alpha}+{\beta}$ microstructure. The hot compression tests were performed in the range of temperature $800-1000^{\circ}C$ with $50^{\circ}C$ intervals, strain rate $10^{-4}-10s^{-1}$, and strain up to 0.5. At $800-950^{\circ}C$, continuous flow softening after a peak stress was observed with strain rates lower than $0.1s^{-1}$. At strain rates higher than $1s^{-1}$, rapid drop in flow stress with strain hardening or broad oscillations was recorded. The processing map of P/M Ti-6Al-4V was designed based on the compression test and revealed the peak efficiency at $850^{\circ}C$ and $0.001s^{-1}$. As the processing temperature increased, the volume fraction of ${\beta}$ phase was increased. In addition, below $950^{\circ}C$, the globularization of phase at the slower strain rate and kinking microstructures were found. Based on these data, the preferred working condition of the alloy may be in the range of $850-950^{\circ}C$ and strain rate of $0.001-0.01s^{-1}$.

• Journal of Genetic Medicine
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• 제16권2호
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• pp.62-66
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• 2019

Harlequin ichthyosis (HI, OMIM #242500) is one of the most severe skin diseases among the autosomal recessive congenital ichthyoses, with high morbidity and mortality, particularly in newborns. Clinically, it is characterized by a typical appearance of generalized, thick, yellowish, hyperkeratotic plates with deep erythematous fissures on the skin. Herein, we present the case of a newborn girl with HI that was genetically confirmed by targeted gene panel analysis. The premature baby was encased in an opaque white membrane with erosion covering the skin of the entire body except the lips, with her hands and feet restricted by the membrane. Humidification, emollient, and retinoic acid treatment were started; the thick ichthyosis gradually peeled off and the underlying skin was only covered with thin scales. Targeted gene panel analysis using next-generation sequencing and validation with Sanger sequencing and quantitative polymerase chain reaction analyses confirmed compound heterozygous mutations of the ABCA12 gene (p.N1380S and a partial gene deletion encompassing exon 9). The parents were carriers for each of the identified mutations. Early recognition of the genetic etiology of congenital ichthyosis can, thus, facilitate genetic counseling for patients and their families.

• Applied Microscopy
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• 제47권3호
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• pp.131-147
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• 2017

In this work further optical and electrical investigations of pure and Zr doped $Mn_3O_4$ (from 0 up to 20 at.%) thin films as a function of frequency. First, the refractive index, the extinction coefficient and the dielectric constants in terms of Zr content are reached from transmittance and reflectance data. The dispersion of the refractive index is discussed by means of Cauchy model and Wemple and DiDomenico single oscillator models. By exploiting these results, it was possible to estimate the plasma pulse ${\omega}_p$, the relaxation time ${\tau}$ and the dielectric constant ${\varepsilon}_{\infty}$. Second, we have performed original ac and dc conductivity studies inspired from Jonscher model and Arrhenius law. These studies helped establishing significant correlation between temperature, activation energy and Zr content. From the spectroscopy impedance analysis, we investigated the frequency relaxation phenomenon and hopping mechanisms of such thin films. Moreover, a special emphasis has been putted on the effect of the oxidation in air of hausmannite thin films to form $Mn_2O_3$ ones at $350^{\circ}C$. This intrigue phenomenon which occurred at such temperature is discussed along with this electrical study. Finally, all results have been discussed in terms of the thermal activation energies which were determined with two methods for both undoped and Zr doped $Mn_3O_4$ thin films in two temperature ranges.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제33권3호
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• pp.281-285
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• 2011

Sinus floor elevation is a predictable and standard procedure for the treatment of the posterior maxilla before insertion of dental implants. Although overall complication rates are low, complications can occur including sinus membrane perforation, infection of sinus, swelling and hemorrhage. The most common complication is membrane perforation. Recently, various techniques and materials for repair of perforation to the sinus membrane have been proposed. The purpose of this article is to report on various techniques and materials that can be used for repair of perforations to the sinus membrane. The search protocol used was the following electronic database: Pubmed, with a time limit from 1998 to 2009. The key words such as 'sinus lift', 'sinus augmentation', 'sinus floor elevation', 'sinus graft', 'sinus perforation', 'repair of sinus perforation' and 'repair of sinus membrane' were used, alone and in combination, when searching the database. Various techniques have been proposed to manage of perforation of sinus membranes. These include that the use of collagen membranes, demineralized freeze-dried human lamellar bone sheets, processed human allografts, lamella bone, buccal fat pads and suturing. Implant success rate ranges from 69.9% to 98.9%.

• 대한치과의사협회지
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• 제50권9호
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• pp.574-585
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• 2012

Purpose : This study was performed to evaluate the healing response around the root perforation restorative material. Materials and Methods : Four beagle dogs were used for experimental study. Endodontic treatment was performed at four maxillary premolars and artificial perforation was formed at furcation area of pulp chamber. Canal was filled with gutta percha cone and the perforation was sealed with MTA at group 1. At group 2, canal was filled and the perforation was sealed with dentin paste. Tooth paste was fabricated using extracted human teeth. Histologic examination of furcation area was performed 2, 4, 8 and 12 weeks after experiment. Results : New trabecular bone formation was observed around the MTA and tooth paste. Lamellar bone was observed as time is over. There were no inflammatory reaction in both groups. Conclusion : There is a possibility which endodontic filling material can be developed using extracted teeth.

• Applied Microscopy
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• 제28권3호
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• pp.307-314
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• 1998

The author has undertaken this study for demonstrating the relationship between keratinization and proliferation as well as remodeling of epidermis. Healthy ICR strain male mice, weighing about $20\sim25gm$, were used as experimental animals. Under the general anesthesia with ether the skins of experimental animals were subjected to a dorsal, transverse, full-thickness incision with 0.5cm in length, and removed them on 3rd day, 7th day and 2nd week after operation Specimens were prepared for electron microscopic study. The results obtained were as follows: The epidermis of 3rd day group is made up of $7\sim8$ keratinocytes. The new epidermal cells are grown beneath the necrotic tissue. Keratohyaline granules (KHGs) are visible in some granular cells. Various sited-KHGs are seen in granular layer cell, and in spinous cell ribosomes, tonofilaments and lamellar granules are seen. The epidermis of 7th day group is made up of $7\sim8$ keratinocytes. Numerous KHGs are seen in granular layer cells. KHGs are located in granular layer cells as well as spinous layer cells. The epidermis of End week group is composed of one-layered basal cell and $1\sim2$ layered superficial cells. Various sized-KHGs are observed in granular layer cells. The results of the present study suggest that as the epidermis should be keratinized during proliferation and remodeling process, so keratinization of the epidermis would play a major role of wound healing process.

• 한국어병학회지
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• 제20권3호
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• pp.291-297
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• 2007

양식 뱀장어(Anguilla japonica)의 사육 중 발생하는 아질산중독에 대한 aspirin(ASA)의 효과를 알아보기 위하여 인위적으로 메트헤모글로빈혈증을 유발시킨 다음 ASA, 식염, 식염과 ASA 및 1/2 환수시키고 24시간 동안 사육하였다. 각 처리군의 뱀장어에서 동맥구에서 말초혈액을 채취하여 헤마토크리트치, 혈구의 형태 변화, 혈장 중의 아질산의 농도 및 메트헤모글로빈의 농도와 아가미의 병리조직학적 변화를 조사하였다. ASA약욕군이 헤마토크리트치가 높고, 혈장중의 아질산 농도와 메트헤모글로빈의 농도가 낮을 뿐만 아니라 적혈구의 형태도 정상어와 유사하였다. 또한 아가미의 병리조직변화도 다른 처리군에서는 상피세포의 증생과 유착 및 모세혈관의 충혈 등이 확인되었지만, ASA처리군에서는 발견할 수 없었다. 이러한 결과로부터 ASA의 약욕이 뱀장어의 아질산의 독성저하에 효과적일 것으로 판단되었다.

• Macromolecular Research
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• 제12권2호
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• pp.172-177
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• 2004

We have studied the lamella-level morphology of poly(ethylene terephthalate) (PET)/polycarbonate (PC) blends using small-angle X-ray scattering (SAXS). Measurements were made as a function of the holding time in the melt. We determined the morphological parameters at the lamellar level by correlation function analysis of the SAXS data. An increased amorphous layer thickness was identified in the blend, indicating that some PC was incorporated into the interlamellar regions of PET during crystallization. The blend also exhibits a larger lamella crystalline thickness (l$\sub$c/) than that of pure PET. A possible reason for the increase in l$\sub$c/ is that the inclusion of the PC molecules in the interlamellar regions causes an increase in the surface free energy of folding. At the early stage of isothermal crystallization, we observed a rapid drop in the value of l$\sub$c/ in the blend; this finding indicates that a relatively large fraction of secondary crystals form during the primary crystallization. In contrast, the value of l$\sub$c/ for the sample that underwent a prolonged holding time increased with time in the secondary crystallization-dominant regime; this observation suggests that the disruption of chain periodicity, which results from transesterification between the two polymers, favors the development of fringed micellar crystals that have larger values of l$\sub$c/ rather than the development of normal chain-folded crystals.