• Title, Summary, Keyword: Gap Theory

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Study of supersonic flame acceleration within AN-based high explosive containing various gap materials (AN계열 화약의 다양한 Gap 실험을 통한 초음속 화염 전파 특성 연구)

  • Lee, Jin-Wook;Yoh, Jai-Ick
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.342-349
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    • 2012
  • We study the gap effect on detonating high explosives using the characteristic acoustic impedance theory and numerical simulation. A block of charge embedded with multiple gap inserts is detonated at one end to understand the ensuing flame propagation through multiple gap materials. The present high-order multimaterial simulation provides meaningful validation of complex interface tracking algorithm as it is implemented in the SNU-Hydropack code.

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Advances and current problems in process control - a review

  • Lee, Won-Kyoo
    • 제어로봇시스템학회:학술대회논문집
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    • pp.29-29
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    • 1992
  • Interest in process control has rebounded from an all-time low in the mid-1970s, with a new focus on bridging the gap between academic theory and industrial practice. Since then, much progress has been made in the new generation of process control theory to bridge this gap. This review summarizes the recent advances and cur-rent problems in process control on a qualitative level.

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Characterization of Segmented Block Copolyurethane Network Based on Glycidyl Azide Polymer and Polycaprolactone

  • Min, Byoung-Sun;Ko, Seung-Won
    • Macromolecular Research
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    • v.15 no.3
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    • pp.225-233
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    • 2007
  • To improve the poor mechanical and low-temperature properties of glycidyl azide polymer (GAP)-based propellants, the addition of binders was investigated using GAP and flexible polymer backbone-structural polycaprolactone (PCP) at various weight(wt) ratios, and varying the ratio of Desmodur N-100 pluriisocyanate (N-100) to isophorone diisocyanate (IPDI). Using Gee's theory, the solubility parameter of the PCP network was determined, in order to elucidate the physical and chemical interaction between GAP and PCP. The structure of the binder networks was characterized by measuring the cross-link densities and molecular weights between cross-links ($M_c$) obtained by a swelling experiment using Flory-Rhener theory. The thermal and mechanical properties of the segmented block copolyurethane (GAP-b-PCP) binders prepared by the incorporation of PCP into the binder recipes were investigated, along with the effect of the different curatives ratios.

A theoretical study on Determinants of National Competitive Advantage (산업의 국제경쟁력 결정요인에 관한 이론적 관찰)

  • 이학헌;민성규
    • Journal of the Korean Institute of Navigation
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    • v.19 no.1
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    • pp.49-69
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    • 1995
  • What is the national competitive power\ulcorner What are the determinants of national competitive advantage\ulcorner In order to find these problems, this study was initiated theoretically through the international trade theory and international managerial strategic theory. The flow of studies, in connection with these competitive advantage, come into industries competitive advantage from national competitive advantage. It is understood that the flow of studies is based on the change of paradigm about the international industry environment. Today, the international industry environment has been changed into vigorous situation with the new trade system such as globalization, UR negotiation, WTO system instead of GATT. Among these environments, all enterprises in any industries should try to enhance their benefit, income profits and develop their management strategy, because it is essential for them to keep and make a profit in order to be competitive against all other rivaling enterprises. According to researchers and the ages of history, the concept and determinants of competitive advantage have been dissimiliar as followings. 1) Theory of absolute advantage : Absolute Product Cost. 2) Theory of comparative advantage : Comparative Product Cost. 3) Theory of reciprocal demand : the Reciprocal Demand Structure. 4) Theory of Hechsher-Ohlin : Factor Endowment. 5) Paradox of Leontief : the Quality of Factor Endowment. 6) Theory of technological gap : R & D. 7) Technological gap model : The Technological Gap. 8) Theory of the product life cycle : Product Life Cycle. 9) Christensen's study : Firm's character & manager's character. 10) Monopolistic Advantage Theories : Monopolistic Advantage 11) Electic theory : Ownership, location and internalization specific advantages. 12) Theory of value chain : Cost advantage, Differentiation, Focus. However all these theories have the limit of illustration regarding today's competitive situation, the Porter's theory shows well the determinants of competitive advantage with competitive strategy. Therefore, the analysis of the competitive advantage for maritime industry should be studied by the determinants of competitive advantage of nations

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The Role of Stem Cells and Gap Junctional Intercellular Communication in Carcinogenesis

  • Trosko, James E.
    • BMB Reports
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    • v.36 no.1
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    • pp.43-48
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    • 2003
  • Understanding the process of carcinogenesis will involve both the accumulation of many scientific facts derived from molecular, biochemical, cellular, physiological, whole animal experiments and epidemiological studies, as well as from conceptual understanding as to how to order and integrate those facts. From decades of cancer research, a number of the "hallmarks of cancer" have been identified, as well as their attendant concepts, including oncogenes, tumor suppressor genes, cell cycle biochemistry, hypotheses of metastasis, angiogenesis, etc. While all these "hallmarks" are well known, two important concepts, with their associated scientific observations, have been generally ignored by many in the cancer research field. The objective of the short review is to highlight the concept of the role of human adult pluri-potent stem cells as "target cells" for the carcinogenic process and the concept of the role of gap junctional intercellular communication in the multi-stage, multi-mechanism process of carcinogenesis. With these two concepts, an attempt has been made to integrate the other well-known concepts, such as the multi-stage, multi-mechanisn or the "initiation/promotion/progression" hypothesis; the stem cell theory of carcinogenesis; the oncogene/tumor suppression theory and the mutation/epigenetic theories of carcinogenesis. This new "integrative" theory tries to explain the well-known "hallmarks" of cancers, including the observation that cancer cells lack either heterologous or homologous gap junctional intercellular communication whereas normal human adult stem cells do not have expressed or functional gap junctional intercellular communication. On the other hand, their normal differentiated, non-stem cell derivatives do express connexins and express gap junctional intercellular communication during their differentiation. Examination of the roles of chemical tumor promoters, oncogenes, connexin knock-out mice and roles of genetically-engineered tumor and normal cells with connexin and anti-sense connexin genes, respectively, seems to provide evidence which is consistent with the roles of both stem cells and gap junctional communication playing a major role in carcinogenesis. The integrative hypothesis provides new strategies for chemoprevention and chemotherapy which focuses on modulating connexin gene expression or gap junctional intercellular communication in the premalignant and malignant cells, respectively.

The Study on Diffraction of Waves About a Breakwater-Gap (방파제에서의 회절파에 관한 연구(제2보))

  • 강관원;송병하
    • Water for future
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    • v.9 no.1
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    • pp.70-80
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    • 1976
  • The efficient breakwater design requires a knowledge of the behaviour of the waves passing the breakwater. Wave Diffraction is an important factor and phenomeon in this behaviour. The diffraction ocean waves entering a gap in a breakwater normal to the incident wave direction in water of uniform depth has been investigated, applying a solution previously given in the author's paper, based on the theory of light diffraction by Sommerfeld. The wave profiles and heights on both the leeward side of the breakwater and the gap side have been studied and summarized in the form of diagrams with diffraction coefficients in range of x/L, y/L 0∼100, b/L=0.5∼12, with some extension of the diagrams made previously. The results of the theoretical approaches have not been experimentally verified. The theory ad computation methods with computer program in Fortran IV developed in this study make an efficient use for estimating the diffraction about a breakwater gap.

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A Calculation of C-V Characteristics for ${Hg}_{1-x}{Cd}_{x}$Te MIS Device (${Hg}_{1-x}{Cd}_{x}$Te MIS 소자의 C-V 특성 계산)

  • 이상돈;김봉흡;강형부
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.43 no.3
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    • pp.420-431
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    • 1994
  • The HgCdTe material, which is II-VI compound semiconductor, is important materials for the fabrication of the infrared detectros. To suggest the model of accurate MIS C-V calculation for narrow band gap semiconductors such as HgCdTe, non-parabolicity from k.p theory and degeneracy effect are considered. And partially ionized effect and compensation effect which are material's properties are also considerd. Especially, degenerated material C-V characteristics from Fermi-Dirac statistics and exact charge theory are presented to get more accurate analysis of the experimental results. Also the comparison with calculation results between the general MIS theory from Boltzmann appoximation method and this model which is considered the narrow band gap semiconductor properties, show that this model is more useful theory to determination of accurate low and high frequency C-V characteristics.

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Design Guideline Development for Managed Lane Access Spacing Using Gap Acceptance Theory (간격수락 이론을 이용한 다인승전용차로 진.출입을 위한 도로 디자인 지침정립)

  • Yang, Cheol-Su;Mattingly, Stephen P.;Kim, Hyeon-Ung;Gwon, Yong-Jang
    • Journal of Korean Society of Transportation
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    • v.28 no.4
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    • pp.177-186
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    • 2010
  • The principal objective of this paper is to develop road design guidelines, especially for managed lane access spacing between the expressway on-ramp (or off-ramp) and managed lane access point. Managed lanes are typically located in the expressway median and are accessed by weaving across the mainlines. The high level of lane-changing activity present in weaving areas affects capacity significantly. One promising tool for the analysis of lane-changing activity is "gap acceptance theory." This paper estimates the capacity of weaving areas based on the estimated degree of traffic turbulence using gap acceptance theory. The degree of traffic turbulence is represented by a function of the probability that lane-changing vehicles can complete their maneuvers successfully in a given weaving distance. In developing road design guidelines based on the developed gap acceptance model, the minimum managed lane access spacing is determined where the capacity with respect to the managed lane access spacing becomes stable.

Characteristics of Gap Flow of a 2-Dimensional Horn-Type Rudder Section (2차원 혼 타 단면의 간극유동 특성에 대한 연구)

  • Choi, Jung-Eun;Chung, Seok-Ho
    • Journal of the Society of Naval Architects of Korea
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    • v.44 no.2
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    • pp.101-110
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    • 2007
  • Recently, rudder erosion due to cavitation frequently has occurred at large high speed container carriers. Especially, in the case of a horn-type rudder, the rudder erosion is severe around a gap. The gap-flow characteristics are investigated through a computational method to understand the effects of a gap on the cavitation and rudder efficiency. A viscous flow theory utilizing a cavitation model is applied to calculate the flow around idealized 2-dimensional rudder sections in a full scale. The effects of gap clearance and flow-control projection are also investigated. From the computational results, the mass flow rate through a gap is found to be one of the important parameters to affect the cavitation and rudder efficiency.

The effect of strain on the electronic properties of MoS2 monolayers

  • Park, Soon-Dong;Kim, Sung Youb
    • Coupled systems mechanics
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    • v.5 no.4
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    • pp.305-314
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    • 2016
  • We utilize first-principles calculations within density-functional theory to investigate the possibility of strain engineering in the tuning of the band structure of two-dimensional $MoS_2$. We find that the band structure of $MoS_2$ monolayers transits from direct to indirect when mechanical strain is applied. In addition, we discuss the change in the band gap energy and the critical stains for the direct-to-indirect transition under various strains such as uniaxial, biaxial, and pure shear. Biaxial strain causes a larger change, and the pure shear stain causes a small change in the electronic band structure of the $MoS_2$ monolayer. We observe that the change in the interaction between molecular orbitals due to the mechanical strain alters the band gap type and energy.