• 대한수학회보
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• 제49권3호
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• pp.635-645
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• 2012

In this study, we investigate the curvature functions of ruled surface with lightlike ruling for a null curve with Cartan frame in Minkowski 3-space. Also, we give relations between the curvature functions of this ruled surface and curvature functions of central normal surface. Finally, we use the curvature theory of the ruled surface for determine differential properties of a robot end-effector motion.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.768-771
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• 2002

A method to derive the constitutive relations of a piezoelectric bender actuator is developed here. The constitutive relations are derived from the geometry, material properties of the actuator. The very complicated constitutive relations can be easily calculated by use of symbolic function in Mathematica. The developed program can calculate the constitutive relations for the unimorph bender made by attaching a short piezoelectric beam on a longer metal beam. The program can also calculate the constitutive relations of a piezoelectric bender with spring at its end.

• 한국육종학회지
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• 제42권1호
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• pp.75-86
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• 2010

국산밀 주요 26개 품종의 가공적성평가를 통하여 국내산 밀의 품질향상과 향후 소비자 요구에 맞는 용도별 고품질 밀 품종육성을 위한 기초자료로 이용하고자 용도별 수입원맥 6종과 시중에서 유통되고 있는 밀가루 5종을 비교 평가하였다. 제면적성평가에서 제면용으로 수입되는 ASW와 시중밀가루의 가수량과 유사한 품종은 안백밀, 은파밀, 고분밀, 한백밀, 적중밀, 조농밀, 남해밀과 수강밀이었다. 면대두께에서 국산밀 품종은 그 범위가 적었으며, 수입밀에서는 제과용 밀가루가 가장 적고 제빵용 밀가루가 가장 두꺼웠으며 제면용 밀가루가 그 사이의 값을 나타냈다. 면대밝기에서 국산밀 품종 밀가루는 시중밀가루와 비교하여 비교적 어두웠으며 밀성밀이 가장 밝았다. 국수면대 밝기는 밀가루 입자크기, 회분, 손상전분, 단백질함량과 부의 상관을 보였다. 삶은 국수의 식미검정 결과 단백질함량은 삶은 국수의 경도와 고도의 정의 상관을 보였다. 삶은 국수의 경도에서 생면용과 비슷한 국산밀 품종은 알찬밀, 다홍밀, 적중밀과 수강밀 등이었으며, 자장면용과 비슷한 국산밀 품종은 고분밀, 조경밀, 조농밀, 금강밀과 남해밀 등이었다. 제빵적성 결과에서 빵용 밀가루와 비슷한 빵 부피를 보인 품종은 알찬밀, 조경밀, 금강밀과 남해밀이었으나, 빵 속질의 경도는 모두 DNS와 시중 빵용 밀가루 보다 높았다. 또한 침전가가 높고, 믹소그래프의 반죽시간이 길고, 빵 반죽시 발효되어 증가되는 반죽의 높이가 높을수록 빵 부피는 컸으며, 빵 속질 경도가 부드러울수록 빵 부피가 컸다. 과자직경은 밀가루 입자 크기가 작고, 손상전분 함량이 적고, 단백질함량이 적을수록 컸으며, 과자직경이 클수록 균열등급은 높았다. 국산밀 품종 중 다홍밀, 그루밀, 올그루밀, 탑동밀과 우리밀은 시중 제과용 밀가루보다 과자직경이 컸지만, 균열정도는 제과용 밀가루보다 작았다.

• 소음진동
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• 제1권2호
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• pp.121-128
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• 1991

In order to use viscoelastic materials efficiently for noise and vibration control, or th qualify newly developed materials, knowledge of the Young' s modulus and loss factor is essemtial. These material properties, the so-called complex Young' s modulus, are frequently treated as dynamic charicteristics because of their dependence upon the frequency. Many techniques have been developed and verified for measuring complex Young' s modulus of viscoelastic materials. Among them, the impedance method is preferable in order to obtain the frequency information in detail. In this method, a cylindrical or prismatic specimen is excited into longitudinal harmonic vibration at one end, the other being fixed, and the resulting force is measured at the driving or fixed end. The amplitude ratio of the two signals and phase angle between them are then used to compute the material properties using various mathematical models. In this paper, the impedance method is investigated theoretically and experimentally. A way to determine the specimen geometry which is most appropriate for the identification of complex Young' s modulus using the lumped mass model is presented and discussed. Then experimental results supporting the theoretical predictions are presented.

• Carbon letters
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• 제9권4호
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• pp.324-339
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• 2008

The principal aims of the review paper are (1) to establish broad overview information, both qualitative and quantitative, relating to the world market for polyacrylonitrile (PAN) or pitch-based carbon fibers; and (2) to generate an effective analysis and break down of consumption by process route and eventual end-use. The review paper also designed specifically to provide subscribers with an accurate, independent, and realistic assessment of the current status and future perspective of the market for carbon fibers in the world. The world market for carbon fibers continues to grow rapidly, fuelled by new industrial end uses, such as sport and leisure goods, aerospace, automotive applications, civil engineering and infrastructure repair, and immerging applications in energy generation. Demands for properties of carbon fibers used in those applications include many things such as strength, toughness, fatigue property, corrosion resistance, heat resistance, etc., and these become to be higher level. On the other hand, demands for manufacturing technologies of carbon fibers become to be difficult with these demands for properties, and these are wide variety such as high efficiencies, high qualities, many functions, labor saving, and low cost. In this review paper, thus, the recent carbon fibers corresponded to these needs, and its latest manufacturing technologies as well as market prospects are described.

• 한국농촌간호학회지
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• 제8권2호
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• pp.65-73
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• 2013

Purpose: The purpose of this study was to identify the relationship between intention to use advance directives and level of death anxiety in community-dwelling elders. Method: The participants were 200 older adults who were aged 60 or over and attended the community welfare centers. The level intention to use advance directive was measured by a questionnaire that was developed by the authors for the study. The measure by Kraus and Ellisond was administered to evaluate the level of death anxiety. Result: The average score for intention to use advance directives was $2.05{\pm}0.88$ and that of death anxiety was $6.2{\pm}2.28$. There were significant differences in the intention to use advance directives according to education levels and individual properties. Although there was no significant relationship between the intention to use advance directives and the level of death anxiety, they were negatively associated. Therefore, older adults who had lower death anxiety would tend to use advance directives. Conclusion: It would be necessary to screening the level of death anxiety to promote use of the advance directives. In addition, education programs for advance directives would be essential to consider about advance directives for their end-of-life especially for the community-dwelling elderly in Korea.

• Carbon letters
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• 제19권
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• pp.1-11
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• 2016

In efforts to characterize and understand the properties and processing of phenylethynyl-terminated imide (LaRC PETI-5, simply referred to as PETI-5) oligomers and polymers as a high-temperature sizing material for carbon fiber-reinforced polymer matrix composites, PETI-5 imidization and thermal curing behaviors have been extensively investigated based on the phenylethynyl end-group reaction. These studies are reviewed here. In addition, the use of PETI-5 to enhance interfacial adhesion between carbon fibers and a bismaleimide (BMI) matrix, as well as the dynamic mechanical properties of carbon/BMI composites, are discussed. Reports on the thermal expansion behavior of intercalated graphite flake, and the effects of exfoliated graphite nanoplatelets (xGnP) on the properties of PETI-5 matrix composites are also reviewed. The dynamic mechanical and thermal properties and the electrical resistivity of xGnP/PETI-5 composites are characterized. The effect of liquid rubber amine-terminated poly(butadiene-co-acrylonitrile) (ATBN)-coated xGnP particles incorporated into epoxy resin on the toughness of xGnP/epoxy composites is examined in terms of its impact on Izod strength. This paper provides an extensive overview from fundamental studies on PETI-5 and xGnP, as well as applied studies on relevant composite materials.

• 펄프종이기술
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• 제46권3호
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• pp.81-87
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• 2014

Conditions of paper manufacturing process should be changed depending on the end use and paper properties. Most of the case, mixed pulps with long softwood fibers and short hardwood fibers are used to achieve proper qualities of product with reasonable production cost. For specialty paper manufacture the wood pulp and cotton linter pulp are usually mixed together. The objectives of this study is to analyze physical, mechanical and fracture mechanical properties of paper depending on SwBKP, HwBKP and cotton linter pulp(CLP) mixing. When the mixing ratio of SwBKP was increased, strength properties, such as tensile, tear, and folding endurance, were also increased. When the mixing ratio of SwBKP and HwBKP was increased, stress concentration index was decreased and fracture toughness was increased.

• 마이크로전자및패키징학회지
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• 제22권3호
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• pp.1-7
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• 2015

In this study, properties of Pb-free solders for automotive electronics parts were discussed. Lead-free solders for electronics became important after RoHS (Restriction of the use of certain Hazardous Substances) to avoid environmental pollution. Also the growing electronic rate in automotive parts and ELV (End-of Life Vehicles) make Pb-free solder for automotive electronics to be inevitable trend. Definitely, Pb-free solder for automotive electronics should have good wettability, basic strength, but need more reliability than other solders, since it has harsh condition like high temperature, humidity and engine vibration. Thus, shear strength test, thermal shock, drop test and many others are needed to ensure the high reliability. This study describes the properties and requirements of Pb-free solders for automotive electronics.

• Food Science and Biotechnology
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• 제14권6호
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• pp.758-765
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• 2005

Instant powders that only require mixing with water prior to consumption can be produced by extrusion for use in products such as instant beverages. Both extrusion processing conditions and particle size of powder are important to end-product characteristics. In this study, a twin-screw extruder was used under various processing conditions (feed moisture, barrel temperature, and screw speed) to produce extrudates from soft wheat flour, which were ground to powders with particle size ranges of less than 93, 93-145, and $145-249\;{\mu}m$. Effects of adding soy lecithin to wheat flour before extrusion were also investigated. Water absorption, solubility, suspension viscosity, and dispersibility of wheat powders were related to specific. mechanical energy measured during extrusion. Powder particle size was important to instant properties, especially ease of dispersal in water and stability to sedimentation. Addition of lecithin significantly improved dispersibility of powders.