• 한국자기학회지
• /
• 제5권5호
• /
• pp.672-678
• /
• 1995

The magnetic separation of Nd-Fe-B powders prepared by melt-spun and HDDR processes was investigated. The experiments show that the ununiform melt-spun powders can be separated into various standards by means of magnetic separation method. The magnetic powders with higher properties were obtained by the use of suitable separating field. For example, the properties of ununiform melt-spun powders are Br=7.95 kG, iHc=9.93 kOe and (BH)max=10.2 MGOe before separating. Through separating in different magnetic fields, the powders obtained with a separating field of 780 Oe has the optimum properties of Br=7.7 kG, iHc=11.0 kOe and (BH)max=15.3 MGOe. The magnetic properties of the HDDR magnetic powder are hardly separated by the magnetic separation method.

• Composites Research
• /
• 제34권2호
• /
• pp.82-87
• /
• 2021

The mechanical properties of carbon fiber-reinforced epoxy composites (CFRPs) are greatly dependent on the interfacial adhesion between the carbon fibers and the epoxy matrix. Introducing nanomaterial reinforcements into the interface is an effective approach to enhance the interfacial adhesion of CFRPs. The main purpose of this work was to introduce graphitic nanofiber (GNFs) between an epoxy matrix and carbon fibers to enhance interfacial properties. The composites were reinforced with various concentrations of GNFs. For all of the fabricated composites, the optimum GNF content was found to be 0.6 wt%, which enhanced the interlaminar shear strength (ILSS) and fracture toughness (KIC) by 101.9% and 33.2%, respectively, compared with those of neat composites. In particular, we observed a direct linear relationship between ILSS and KIC through surface free energy. The related reinforcing mechanisms were also analyzed and the enhancements in mechanical properties are mainly attributed to the interfacial interlocking effect. Such an effort could accelerate the conversion of composites into high performance materials and provide fundamental understanding toward realizing the theoretical limits of interfacial adhesion and mechanical properties.

• 한국포장학회지
• /
• 제15권3호
• /
• pp.99-104
• /
• 2009

Soy protein isolate (SPI)-based nanocomposite films with three different types of nanoclays, such as Cloisite $Na^+$, Cloisite 20A, and Cloisite 30B, were prepared using a solution casting method, and their optical, tensile, and water vapor barrier properties were determined to investigate the effect of nano-clay type on film properties. Among the tested nanoclays, Cloisite $Na^+$, a hydrophilic montmorillonite (MMT), exhibited the highest transparency with least opaqueness, the highest tensile strength, and the highest water vapor barrier properties, indicating Cloisite $Na^+$ is the most compatible with SPI polymer matrix to form nanocomposite films. The film properties of SPI/Cloisite $Na^+$ nanocomposite films were strongly dependent on the concentration of the clay. Film properties such as optical, tensile, and water vapor barrier properties improved significantly (p<0.05) as the concentration of clay increased. However, the effectiveness of addition of the clay reduced above a certain level (i.e., 5wt%), indicating that there is an optimum amount of clay addition to exploit the full advantage of nanocmposite films.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.3080-3085
• /
• 2007

Shape optimization of the 3-dimensional WIG airfoil with 3.0-aspect ratio has been performed by using the multi-objective genetic algorithm. The WIG ship effectively floating above the surface by the ram effect and the virtual additional aspect ratio by a ground is one of next-generation and cost-effective transportations. Unlike the airplane flying out of the ground effect, a WIG ship has possibility to capsize because of unsatisfying the static stability. The WIG ship should satisfy aerodynamic properties as well as a static stability. They tend to strong contradict and it is difficult to satisfy aerodynamic properties and static stability simultaneously. It is inevitable that lift force has to scarify to obtain a static stability. Multi-objective optimization technique that the individual objectives are considered separately instead of weighting can overcome the conflict. Due to handling individual objectives, the optimum cannot be unique but a set of nondominated potential solutions: pareto optimum. There are three objectives; lift coefficient, lift-to-drag ratio and static stability. After a few evolutions, the non-dominated pareto individuals can be obtained. Pareto sets are all the set of possible and excellent solution across the design space. At any selections of the pareto set, these are no better solutions in all design space

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2003년도 추계학술대회논문집
• /
• pp.229-232
• /
• 2003

In the roll forming process, a sheet or strip of metal is continuously and progressively formed into a desired cross-sectional profile by feeding it through a series of forming roll. Accordingly, it is important to maintain the material properties of the initial sheet and deform uniformly during the roll forming. The roll forming process was estimated in consideration of some factors such as material properties, strip thickness, roll diameter, roll velocity, and the deformation of the material that influence the forming length. The hydroforming technology has been recognized as a new technique in manufacturing industry, especially in automotive industry. The formed pipe in used in hydroforming process is manufactured by the roll forming. The formability during hydroforming is very sensitive to the state of pipes which are made by roll forming. Particularly the amount of hardening during roll forming affects the formability. Therefore, it is necessary to design the optimum roll flower to reduce the local hardening. In this paper, optimum roll flower which has uniform strain distribution through sheet width was obtained by comparing strain distribution in various roll flower. Finite element analysis(FEA) is performed to estimate the strain distribution related to hardening by roll forming. A numerical analysis is carried out by SHAPE-RF.

• 한국미생물·생명공학회지
• /
• 제18권5호
• /
• pp.484-489
• /
• 1990

Bacillus subtilis의 세포내 이눌라아제가 부분정제되고 그의 작용 모드와 일반적 특성이 조사되었다. 이 효소는 gel filtration에 의하여 분자량을 추정하였을 때 49,000이었고, 등진점은 5.2 이었다. 기질에 대한 친화성의 지표인 Km값은 설탕에 대해서는 10mM, 라피노오스에 대해서는 18mM 이었다. 이 효소는 산성쪽에서는 불안정한 단백질로서 pH6.6에서 최대 활성을 보였으며 최적온도는 10분간 반응시켰을 때 50'C였다. 이 효소의 작용모든는 이눌린같은 구조를 가지는 과당 중합체를 과당 끝부분으로부터 하나씩 잘라가는 exo-cleavage 형이었다.

• 콘크리트학회지
• /
• 제11권2호
• /
• pp.115-125
• /
• 1999

콘크리트의 품질확보와 문제점 해결방안으로서 20세기 전반까지는 주로 시멘트의 종류를 달리하는 경우가 많았으나, 그 후반기부터는 각종 혼화재료를 사용하여 콘크리트의 결점을 보완하고 각종 요구성능에 부응하는 다양한 품질의 콘크리트를 제조하고 있다. 따라서 이같은 다양한 요구에 부응키 위해서는 혼화재료의 사용이 필수적이므로 본 연구에서는 강도증진 및 수화열 저감목적으로 많이 사용되고 있는 실리카흄, 플라이애쉬, 고로슬래그 미분말 및 농업부산물인 왕겨재의 특성을 규명키 위하여 이들을 혼입한 콘크리트에 대해서 단위결합재량별(300~600kg/$m^3$)로 이들 각각의 혼입률에 따라서 시공성 및 강도특성을 분석한 후 각 혼화재의 성능을 발휘할 수 있는 최소 결합재량과 시공성 및 강도특성이 가장 우수한 최적 혼입률 등을 도출하였다.

• 한국식품과학회지
• /
• 제12권1호
• /
• pp.1-5
• /
• 1980

고려 인삼(Panax ginseng C. A. Meyer)중의 invertase를 연구하기 위하여 조(租) 인삼 invertase를 분리 조제하여 그 성질을 조사해 본 결과 다음과 같았다. 1. 조 인삼 invertase는 ammonium sulfate $0.8{\sim}1.0$포화 분획에 의하여 효과적으로 조제되었다. 2. 조 인삼 invertase는 pH $5{\sim}9\;35^{\circ}C$이하의 조건에서 안정성을 나타내었다. 3. 조 인삼 invertase는 최적 pH 5.0, 최적온도 $50^{\circ}C$를 나타내었다. 4. 조 인삼 invertase는 $Ag^{+}\;Mn^{+}\;Hg^{+}\;Zn^{+}\;Rb^{+}$등의 금속 이온에 의하여 저해되었으나 그 저해 정도는 크지 못하였다. 한편 $Ca^{+}\;Cu^{+}\;Fe^{3+}$등에 의한 효소 활성 증대 효과는 특이적이었다.

• 한국염색가공학회지
• /
• 제20권2호
• /
• pp.9-18
• /
• 2008

Wool has excellent properties, such as heat retention, absorbency, and elasticity, but it has a disadvantage in washability because the fabric will felt and shrink greatly. Felting causes the interlocking of the fiber surface scales with one another. Therefore, the studies on wool finishing have been focused on shrink proofing. Precedent researches on wool shrink proofing are mostly on eco-friendly method. using enzyme. The purpose of this study is to examine the effect of L-cysteine, EDTA in papain treatment of wool fabrics. The specific contents of study are as follows. Depending on pH, temperature, treatment time, enzyme concentration and L-cysteine, EDTA concentration, weight loss, tensile strength, whiteness, SEM were examined. Each papain treatment conditions depending on L-cysteine, EDTA were optimized from these properties. Papain had very low activation without activators. The optimum conditions of papain treatment were pH 7.5, temperature $75^{\circ}C$, time 30minutes(L-cysteine), 180minutes(EDTA) and papain concentration 5%(o.w.f.). In the use of papain 5%(o.w.f.), the activators optimum concentration was L-cysteine 2%(o.w.f.), EDTA 7%(o.w.f.)

• 한국식품조리과학회지
• /
• 제23권4호통권100호
• /
• pp.481-491
• /
• 2007

This study was conducted to develop pizza crust with additions of Chungkukjang and onion. The stickiness of the pizza dough containing fresh Chungkukjang (C), heated Chungkukjang (HC), and fresh Chungkukjang with added dough-improver (CI), was measured to evaluate the dough properties. The optimum conditions for pizza crust preparation relating to the processing suitability and sensory quality were established using response surface methodology (RSM). When HC and CI were used in dough making, dough stickiness was reduced to 37% and 51%, respectively. Therefore, the dough-improver(2%) offered the pizza dough better rheological properties when C was used without heat treatment. On the other hand, processing suitability such as the spreadability and overall acceptability, which included the smell and taste of the pizza, were impaired as the amount of CI increased. However, the use of fresh ground onion in the pizza dough compensated for these impairments. The optimum conditions for pizza crust making as determined by RSM were 25.1% onion, 7.1% Chungkukjang, and 52.3 min of fermentation time.