• Elastomers and Composites
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• v.57 no.1
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• pp.13-19
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• 2022

Polycarbonate diol-based waterborne polyurethane (WPU) was prepared by prepolymer mixing process. The prepolymer mixture contained the polycarbonate diol, isophorone diisocyanate (IPDI), dimethylol propionic acid, triethylamine, and ethylenediamine (EDA). The NCO/OH ratio in the prepolymer was adjusted by controlling the molar ratio of IPDI, and its effects on the properties of WPU were studied. The structure of WPU was characterized by fourier transform infrared spectroscopy. The average particle size increased and viscosity decreased with increasing NCO/OH ratio and EDA content in WPU. The reduced phase separation between soft and hard segments increased glass transition temperature. The reduction in the thermal decomposition temperature could be attributed to the low bond energy of urethane and urea groups, which constituted the hard segment. Additionally, the polyurethane chain mobility was restricted, elongation decreased, and tensile strength increased. The hydrogen bond between the hard segments formed a dense structure that hindered water absorption.

• Journal of Agricultural Extension & Community Development
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• v.16 no.2
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• pp.363-384
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• 2009

This study aimed at finding directions for Korean agriculture to establish a new paradigm of sustainable development. Various problematic issues and concerns in the environment necessitate the transformation of Korea's development paradigm from unconditional growth to "Green Growth" through new policies on green value and review of various advanced researches. In this research, the environment-friendly agriculture's problems, particularly in agribusiness were analyzed. Drawing from Michael Porter's Value Chain Analysis, this research developed a value chain model in agriculture that reflects the environment and the present situations. Future directions in the agriculture sector were also discussed. Korea realized food self-sufficiency through the green revolution in the early 1970s. However, a lot of problems have also occurred, including ground and water pollution and the destruction of ecosystems as a result of the overuse of pesticides and chemical fertilizers. In the late 1970s, the growing interest on environment-friendly agriculture led to the introduction of sustainable methods and techniques. Unfortunately however, these were not innovative enough to foster environment-friendly agriculture. Thereafter, the consumers' distrust on agricultural products has worsened and concerns about health have increased. In view of this, the Ministry of Food, Agriculture, Forestry and Fisheries introduced in December 1993 a system of Quality-Certified Products for organic and pesticide-free agri-foods. Although a fundamental step toward the sustainability of the global environment, this system was not enough to promote environment-friendly agriculture. In 2008, Korea's vision is for "Low Carbon Green Growth" to move forward while also coping with climate change. But primary sectors in a typical value chain do not consider the green value of their operations nor look at production from an environmental perspective. In order to attain sustainable development, there is a need to use less resources and energy than what is presently used in Korean agricultural and value production. The typical value chain should be transformed into a "closed-loop" such that the beginning and the end of the chain are linked together. Such structure allows the flow of materials, products and even wastes among participants in the chain in a sustained cycle. This may result in a zero-waste sustainable production without destroying the ecosystem.

• Bulletin of the Korean Mathematical Society
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• v.41 no.4
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• pp.779-783
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• 2004

A group G is said to satisfy the minimal condition on normal subgroups of infinite index if there does not exist an infinite properly descending chain $G_1$ > $G_2$ > ... of normal subgroups of infinite index in G. We characterize the structure of locally nilpotent groups satisfying this chain condition.

• Korea-Australia Rheology Journal
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• v.18 no.2
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• pp.99-102
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• 2006

Primitive chain network model for block copolymers is used here to simulate molecular dynamics in the entangled state with acceptable computational cost. It was found that i) the hooking procedure rearranging the topology of the entangled network is critical for the equilibrium structure of the system, and ii) simulations accounting for the different chemistry, i.e., with a biased hooking probability based on interaction parameter ${\chi}$ for selection of the hooked partner, generates a reasonable phase diagram.

• IE interfaces
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• v.13 no.3
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• pp.396-404
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• 2000

For most order-based production, it is important to meet urgent orders from important customers while maintaining high on-time delivery rate for successful supply chain management. In this paper, we propose an approach and a structure of planning system to implement Capable-To-Promise which promises the delivery time to the received order. We suggest and compare a few alternative order receiving policies for CTP.

• Bulletin of the Korean Mathematical Society
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• v.41 no.3
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• pp.465-472
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• 2004

A group G is said to satisfy the maximal condition on infinite normal subgroups if there does not exist an infinite properly ascending chain of infinite normal subgroups. We characterize the structure of locally nilpotent groups satisfying this chain condition. We then show how to construct locally nilpotent groups with the maximal condition on infinite normal subgroups, but not the maximal condition on subgroups.

• Proceedings of the Korean Fiber Society Conference
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• 1998.04a
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• pp.5-8
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• 1998

Polyurethane elastomers are segmented cocoplymer with an [HS]n-type structure. Typically, these materials are two-phase systems, prepared from relatively polar and stiff component called the hard segment(H) and relatively flexible component known as the soft segment(S). Diisocyanate and chain extender together form the hard segment, which is dispersed within a matrix of the soft segment, composed of the macrodiolos.(omitted)

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.600-603
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• 2003

VA-LCDs is widely used for recent LCD productions owing to wide viewing angle characteristics with an unusually high contrast ratio. To apply for VA-LCDs, the novel homeotropic alignment materials were synthesized, which have the liquid crystal molecule as a side chain at aromatic diamine in a polyimide structure. These polyimides generated a high pretilt angle $90^{\circ}C$. In this paper, the synthesis and alignment properties of new homeotropic alignment materials will be discussed..

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.129-130
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• 2000

The emission color stability of poly(fluorene) derivatives upon thermal annealing or passage of current in an electroluminescent device is affected by the structure of the main chain polymer unit and particularly by the polymer chain end substituents. Proper attention to these features leads to colorfast blue emission in both photo- and electoluminescence. Furthermore, the spectral emission characteristics can be tuned by the incorporation of various comonomers. Preliminary single layer device studies validate the potential utility of poly(fluorene) homo and copolymers for OLED applications.

• Journal of KIISE:Information Networking
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• v.32 no.4
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• pp.462-470
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• 2005

A hash chain is highly efficient and attractive structure to use in electronic cash. Previous systems using hash chain are used extensively in various cryptography applications such as one-time passwords, server-supported signatures and microments. However, The most hash chain based systems using fro-paid method provide anonymity but have the problem to increase payment cost. Therefore, in this paper, we propose a new hash chain based microment system which improves efficiency using session key and guarantees user anonymity through blind signature in the withdrawal process of the root value without disclosing privacy Information.