• 한국재료학회지
• /
• 제21권6호
• /
• pp.334-340
• /
• 2011

Saw wires have been widely used in industries to slice silicon (Si) ingots into thin wafers for semiconductor fabrication. This study investigated the microstructural and mechanical properties, such as abrasive wear and tensile properties, of a saw wire sample of 0.84 wt.% carbon steel with a 120 ${\mu}M$ diameter. The samples were subjected to heat treatment at different linear velocities of the wire during the patenting process and two different wear tests were performed, 2-body abrasive wear (grinding) and 3-body abrasive wear (rolling wear) tests. With an increasing linear velocity of the wire, the tensile strength and microhardness of the samples increased, whereas the interlamellar spacing in a pearlite structure decreased. The wear properties from the grinding and rolling wear tests exhibited an opposite tendency. The weight loss resulting from grinding was mainly affected by the tensile strength and microhardness, while the diameter loss obtained from rolling wear was affected by elongation or ductility of the samples. This result demonstrates that the wear mechanism in the 3-body wear test is much different from that for the 2-body abrasive wear test. The ultra-high tensile strength of the saw wire produced by the drawing process was attributed to the pearlite microstructure with very small interlamellar spacing as well as the high density of dislocation.

• 한국식품영양과학회지
• /
• 제38권6호
• /
• pp.750-756
• /
• 2009

기능성 소재로서의 버찌분말의 이용가능성을 알아보기 위해 버찌분말을 0, 3, 5, 7 및 10% 첨가한 머핀을 제조하여 품질특성을 조사하였다. 머핀의 물성은 버찌분말의 첨가에 따라 경도(hardness)는 증가하였고 검성(gumminess) 및 씹힘성(chewiness)은 감소하였다. 색도는 첨가량이 증가할수록 빵껍질(crust)과 빵속(crumb)에서 명도와 황색도가 감소하고 적색도는 증가하였다. 또한 버찌 분말의 농도가 증가함에 따라 항산화 활성이 증가하였다. 관능검사 결과 버찌분말첨가 머핀에서 색, 향, 맛, 부드러움, 촉촉함, 전체적인 기호도면에서 무첨가구에 비해 전반적으로 높게 평가되었으며, 전체적인 기호도는 5% 첨가구에서 가장 높은 점수를 나타내었다. 이러한 결과로 볼 때 머핀의 품질 및 관능 특성, 기능성을 고려한 버찌분말 첨가량은 5% 첨가구가 최적 조건일것으로 판단되었다.

• 한국통신학회논문지
• /
• 제33권5B호
• /
• pp.344-355
• /
• 2008

본 논문에서는 차등서비스 망의 성능 평가 문제를 다룬다. 성공적인 성능 평가를 위하여 적절한 트래픽 모델에 의하여 네트워크상의 실제 트래픽을 정확히 나타낼 수 있는 능력이 필수 요소이다. 실제 트래픽 측정의 성질에 대한 많은 연구 결과는 웹과 텔넷, P2P 트래픽을 포함하여 인터넷 트래픽에 대한 장기간-의존성을 증명하였다. 장기간 의존성은 자기유사성에 의하여 효과적으로 표현될 수 있다. 본 논문에서는 중첩된 On-Off 소스 모델, FFT-FGN 모델과 RMD 모델에 대한 특성 분석을 기반으로, 중첩된 On-Off 소스 모델을 이용하여 자기유사트래픽 발생기를 설계하고 구현한다. 생성된 트래픽의 자기유사성은 TCPdump 데이터의 패킷 도착 간격을 조사하여 확인하였다. 또한 구현된 트래픽 발생기를 차등서비스 망의 성능평가에 적용하여 On/Off 모델의 $\alpha$ 값에 대한 성능이 영향과, CBQ(Class-Based Queueing)에 의한 EF(Expedited Forwarding)/BE(Best Effort) 클래스 트래픽의 성능을 관찰한다.

• Nuclear Engineering and Technology
• /
• 제50권3호
• /
• pp.470-477
• /
• 2018

With a highly functional methyl vinyl silicone rubber (VMQ) matrix and filler materials of $B_4C$, PbO, and benzophenone (BP) and through powder surface modification, silicone rubber mixing, and vulcanized molding, a flexible radiation shielding and resistant composite was prepared in the study. The dispersion property of the powder in the matrix filler was improved by powder surface modification. BP was added into the matrix to enhance the radiation resistance performance of the composites. After irradiation, the tensile strength, elongation, and tear strength of the composites decreased, while the Shore hardness of the composites and the crosslinking density of the VMQ matrix increased. Moreover, the composites with BP showed better mechanical properties and smaller crosslinking density than those without BP after irradiation. The initial degradation temperatures of the composites containing BP before and after irradiation were $323.6^{\circ}C$ and $335.3^{\circ}C$, respectively. The transmission of neutrons for a 2-mm thick sample was only 0.12 for an Am-Be neutron source. The transmission of ${\gamma}$-rays with energies of 0.662, 1.173, and 1.332 MeV for 2-cm thick samples were 0.7, 0.782, and 0.795, respectively.

• Toxicological Research
• /
• 제33권4호
• /
• pp.343-350
• /
• 2017

Lamivudine belongs to the set of antiviral agents effective against hepatitis B virus infection. Given case reports on liver injuries after certain antiviral agent treatments, this study examined the effects of lamivudine on alanine aminotransferase (ALT) and total bilirubin (TB) using a medical system database. A total of 1,321 patients taking lamivudine alone or with others were evaluated using laboratory hits in an electronic medical system at Seoul National University Hospital from 2005 through 2011. The patients were grouped according to prior ALT results: G#1, ALT < 40 IU/L; G#2, 40 IU/L ${\leq}$ ALT < 120 IU/L; G#3, 120 IU/L ${\leq}$ ALT < 240 IU/L; and G#4, ALT ${\geq}$ 240 IU/L. In G#1 and G#2 patients, lamivudine or adefovir treatment decreased ALT and TB compared to prior values. In G#3 and G#4 patients with three times the upper limit of normal (ULN) ${\leq}$ ALT < 15 times the ULN, both ALT and TB were decreased after treatment with lamivudine alone, or adefovir following lamivudine therapy, indicating that lamivudine therapy ameliorated liver functions. However, in G#4 patients who experienced severely advanced hepatitis (ALT ${\geq}$ 15 times the ULN, or ${\geq}$ 600 IU/L), lamivudine augmented TBmax ($6.3{\rightarrow}13.3mg/dL$) despite a slight improvement in ALT ($839{\rightarrow}783IU/L$), indicative of exacerbation of bilirubinemia. Patients who used adefovir after lamivudine also showed a high incidence of hyperbilirubinemia when they experienced severely advanced hepatitis. Treatment with adefovir alone did not show the effect. In conclusion, lamivudine may increase the risk of hyperbilirubinemia in patients with severely advanced hepatitis, implying that caution should be exercised when using lamivudine therapy in certain patient populations.

• 자동차안전학회지
• /
• 제13권2호
• /
• pp.30-34
• /
• 2021

Electrical failures and reliability problems of electronic components by ionic migration between adjacent device terminals have become an issue in automotive electronics. Especially unlike galvanic corrosion, ionic migration is occurred at high temperature and high humidity under applied electric field condition. Until now, although extensive studies of the ionic migrations dealing with PCBs, electrodes, and solders were reported, there is no study on the effect of insulation polymers and metallic fillers for ionic migration. In this research, therefore, ionic migration induced by the types and contents of polymers and metallic fillers, and variety conditions of temperature, humidity, and applied voltage was studied in detail. Ester and amide types of liquid crystal polymer (LCP) and poly (phthalamide) (PPA) were used as base polymers, respectively and compounded with the metallic fillers of Copper iodide (CuI), Zinc stearate (Zn-st), or Calcium stearate (Ca-st) in various compositions. The compounding polymers were fabricated in IPC-B-24 of SIR test coupon according to ISO 9455-17 with Cu electrodes for ionic migration test. While there is no change in LCP-based samples, ionic migration in PPA compounding sample with a high water absorption property was accelerated in the presence of 0.25 wt% or above of CuI at the environmental conditions of 85℃, 85% RH and 48V. The dendritic short-circuit growth of Cu caused by ionic migration between the electrodes on the surface of compounded polymers was systematically observed and analyzed by using optical microscopy and SEM (EDX).

• 대한한방소아과학회지
• /
• 제35권1호
• /
• pp.76-103
• /
• 2021

Objectives This study was designed to examine the effect of Gleditsiae Fructus n-hexane (GSF_Hx) on two different groups (on the LPS-induced activation of Raw264.7 cells in vitro, and on the DNCB-induced activation of atopic dermatitis NC/Nga Tnd mice in vivo) to find index components and active components of Gleditsiae Fructus. Methods GSF_Hx was analyzed by HPLC profiling and confirmed echinocystic acid (EA), oleanolic acid (OA) as index components of Gleditsiae Fructus. Using GSF_Hx, EA, OA, we investigated IL-6, TNF-α, NO production by ELISA analysis and evaluated manifestations of MAPKs transcription factors and NF-κB p65 translocation by western blotting. During In vivo study, atopic dermatitis was induced on NC/Nga Tnd mice by DNCB and administered GSF_Hx, EA, OA orally, and checked skin lesions and measured skin clinical score. Serum IgE level, Th1 and Th2 cytokines secretion and modulating molecular mediators and immune cells in the spleenocyte culture supernatant, PBMCs, ALN and dorsal skin were also measured by real-time PCR. Then, skin rash was evaluated and mast cell distribution was verified by H&E and toluidine blue staining on dorsal skin. Results It is possible that GSF_Hx, EA and OA reduce inflammation and allergic response of atopic dermatitis by suppressing Th1 and Th2 cytokines secretion and modulating molecular mediators and immune cells. They also had moisturizing effect by raising vitality of ceramide in dorsal skin of atopic dermatitis NC/Nga Tnd mice. However, EA particularly had better overall activity data than OA, that EA could be a more effective active component of Gleditsiae Fructus than OA. Conclusions Based on the inflammatory reduction property with moisturizing effect, GSF_Hx may play a role in effective treatment for atopic dermatitis.

• Composites Research
• /
• 제22권2호
• /
• pp.30-36
• /
• 2009

본 논문에서는 헬리콥터 착륙장치를 위한 복합재료 토크링크를 개발하기 위한 설계 기법을 제시하였다. 복합재 토크링크는 헬리콥터 착륙장치의 충격흡수부의 정렬을 위해 장착되는 장치로서 가벼우면서도 강성이 커서 외부하중에 대해 최소의 변형량을 가져야 한다. 또 가격적인 측면을 고려한 복합재 구조물 제조 공정(RTM: 수지충전공정)이 반영되어 대량생산이 가능한 구조 및 형태를 가져야 한다. 본 논문에서는 복합재 구조물 제조 공정과 동일한 공정으로 시편을 제작하여 설계에 필요한 기계적 특성을 얻었으며, 유한요소해석을 통하여 복합재 토크링크에 대한 최적 형상설계를 수행하였다. Lug 형태를 가지는 두꺼운 복합재료 구조물인 복합재료 토크링크의 설계를 위해서는 ABAQUS의 3D Layered Solid 요소로 구성된 유한요소모델을 활용하여 복합재료의 두께방향을 포함한 강도해석을 수행하였으며, Rigid-Deform 구속조건의 접촉문제를 고려한 비선형 정적 해석을 반복적으로 수행하여 주어진 정강도 요구조건을 만족시키는 복합재 토크링크를 설계하였다.

• 한국식생활문화학회지
• /
• 제21권2호
• /
• pp.171-178
• /
• 2006

Tarakjuk with different amylose content was made up using roasted rice flours that consisted of the highest enzyme-resistant starch (RS), while differential scanning calorimetry (DSC) was also utilized to measure the gelatinization temperature of these roasted rice flours in order to establish cooking temperature of tarakjuk. The following qualities of tarakjuk with different amylose content were studied: color, viscosity, spreadability, starch fractions involving total starch (TS), rapidly digestible starch (RDS), slowly digestible starch (SDS) and RS, in vitro starch digestibility (IVSD) and sensory properties. During experimentation, it was found that as the amylose content of the rice flour decreased, the L value of tarakjuk decreased, whereas a value increased significantly (p<0.05). Also, while viscosity showed to increase significantly (p<0.05), on the opposite end, the property of spreadability decreased. TS ranged from $15.95{\sim}17.31%$, RDS $9.36{\sim}10.16%$, SDS $5.46{\sim}6.91%$ and RS $0.33{\sim}1.07%$, on a dry basis. Although the amylose content of rice flours decreased, IVSD increased, however showing no significant difference. When testing the sensory properties of tarakjuk, color and viscosity increased, whereas clumpiness decreased. Ilpum tarakjuk showed the highest score for nutty taste and overall acceptance levels. In fact a high correlation was shown between nutty taste and overall acceptance level (p<0.01), which leads one to believe that nutty taste is a prime factor that greatly influences overall acceptance. Furthermore, viscosity was positively correlated with both a and b values, however negatively correlated with L value (p<0.05). Moreover, roasted nutty taste and overall acceptance were positively correlated with a value (p<0.05), respectively. In conclusion, the above results suggest that tarakjuk could be made by choosing the appropriate rice flour based on the nutritional or sensory purpose.

• Composites Research
• /
• 제37권2호
• /
• pp.132-138
• /
• 2024

본 연구에서는 분자동역학 전산모사를 통해 육방정계 단일벽 질화붕소 나노튜브(BNNT)의 반경 변화에 따른 압전탄성 변화를 규명하였다. 질화붕소의 거동을 비교적 잘 모사하는 Tersoff 포텐셜과 기계적 하중인가에 따른 질소 및 붕소원자의 상대변위로 인한 분극의 정량화를 위해 강체 이온 근사를 채택하였다. 선형 압전탄성 구성방정식을 기반으로 각각의 질화붕소에 변형률을 인가하고 이에 따른 전기적 변위와 응력을 산출하여 압전상수와 영률을 각각 예측하였다. 그 결과, BNNT의 압전상수는 반경이 증가함에 따라 점진적으로 감소하는 양상을 보였다. 반면 탄성계수의 경우 불연속적 구조를 가지는 질화붕소를 등가의 연속체 구조로 등가시키는 방법에 따라 증가 또는 감소하는 경향을 보였다. BNNT의 곡률변화에 따른 물성변화를 가상실험에 기반한 경험적 모델로 근사하기 위해 BNNT의 튜브반경-압전탄성물성 간 상관관계식을 제안하였다. 또한 BNNT의 반경변화에 따른 물성을 곡률의 관점에서 설명하기 위해, BNNT와 질화붕소 나노시트(BNNS)의 결합에너지와 탄성변형에 따른 원자간 결합길이 변화가 각각의 구조의 변형에너지 증가에 기여하는 정도를 상호 비교하였다.