• 제목/요약/키워드: Regime change

검색결과 353건 처리시간 0.024초

온도구배가 Taylor-Couette유동의 불안정성에 주는 영향에 관한 연구 (Study of Different Radial Temperature Gradient Effect on Taylor-Couette Flow Instability)

  • 차재은;류동;도흔승;김형범
    • 한국가시화정보학회지
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    • 제8권3호
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    • pp.35-40
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    • 2010
  • We have investigated different radial temperature gradient effect on the stability of Taylor-Couette flow. The radius ratio and aspect ratio of the model was 0.825 and 48, respectively. Two heating exchangers were used for generating different temperature gradient along the radial direction. The change of flow regime in the Taylor-Couette flow was studied by increasing the Reynolds number. The results showed that: as Gr is increased in helical vortex flow regime, the vortices with the same direction of convection flow increased in size, and the vortex moving velocity also increased. It is also shown that the presence of temperature gradient obviously increased the flow instability when the Richardson number is larger than 0.0045.

현대 공간디자인에서의 현상학적 특징과 가능성 - 메를로퐁티의 지각의 현상학을 중심으로 - (Phenomenological characteristics and possibilities in the contemporary spatial design - From the Viewpoint of Phenomenology of Perception of M. Merleau-Ponty -)

  • 이미경
    • 한국실내디자인학회논문집
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    • 제20권2호
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    • pp.10-19
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    • 2011
  • This study is to predict the possibilities of phenomenological spatial design, by recognizing that a phenomenological spatial design brings about a change in the type, regime, role and materials of a spatiality due to the effect of contemporary digital technology and by analyzing their characteristics. Therefore, the study is based on the phenomenology of perception of Morris Merleau Ponty, which has the same concept to contemporary out-of-material and out-of-hierarchical paradigm. The case study has been carried out by selecting some of all works since 1980s, which were influenced by Merleau-Ponty. The analyses were performed by substituting the cases into the spatiality of Situation, spatiality of participation and creation, spatiality of retrospect and prospect, and the spatiality of unpredictability, which were the concept of phenomenological space of Merleau-Ponty for the analyses of features of type, regime, role and material of a spatial design. This article has a great significance in expecting the possibilities of changes of phenomenological spatial design by examining the characteristics of phenomenological spatial design.

Effects of thermal boundary conditions and microgravity environments on physical vapor transport of $Hg_2Cl_2-Xe$ system

  • Kim, Geug-Tae;Kwon, Moo-Hyun;Lee, Kyong-Hwan
    • 한국결정성장학회지
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    • 제19권4호
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    • pp.172-183
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    • 2009
  • For the effects of the nonlinear temperature profiles and reduced-gravity conditions we conduct a two-dimensional numerical modeling and simulations on the physical vapor transport processes of $Hg_2Cl_2-Xe$ system in the horizontal orientation position. Our results reveal that: (1) A decrease in aspect ratio from 5 to 2 leads to an increasingly nonuniform interfacial distribution and enhances the growth rate by one-order magnitude for normal gravity and linear wall temperature conditions. (2) Increasing the molecular weight of component B, Xenon results in a reduction in the effect of solutal convection. (3) The effect of aspect ratio affects the interfacial growth rates significantly under normal gravity condition rather than under reduced gravitational environments. (4) The transition from the convection-dominated regime to the diffusion-dominated regime ranges arises near at 0.1g$_0$ for operation conditions under consideration in this study.

A legal regime to govern the exploitation of the natural resources of the Moon and other celestial bodies

  • Tronchetti, Fabio
    • 한국항공우주법학회:학술대회논문집
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    • 한국항공우주법학회 2008년도 제40회 국제학술발표대회
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    • pp.185-215
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    • 2008
  • The exploitation of the natural resources of the Moon and other celestial bodies represents one of the most exiting future developments in the field of space law as well as a unique occasion for the economic and social growth of mankind as a whole. The large number of benefits that are expected to be generated from the exploitation of these resources, indeed, not only will contribute to the betterment of conditions of people on Earth but also will allow mankind to face and likely solve one of the biggest problems currently affecting our planet, namely the exhaustion of the stocks of raw materials and other source of energy, such as fossil fuels. The exploitation of the natural resources of the Moon and other celestial bodies, however, has been prevented so far by the absence of dedicated space law rules allowing its orderly and peaceful development and clarifying the rights and duties of the parties involved in it. Due to the uncertainty generated by the absence of these rules, indeed, States as well as private operators have refrained from investing in the exploitation of space resources so far. The time to change this situation and to allow the exploitation of extraterrestrial resources to begin has finally come. This paper aims at fulfilling this purpose by proposing a legal regime containing specific and detailed rules to regulate the exploitation of the natural resources of the Moon and other celestial bodies.

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A Study on the Modernization of Japanese costume

  • Jeon, Hyun-Sil;Kang, Soon-Che
    • International Journal of Costume and Fashion
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    • 제8권1호
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    • pp.1-17
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    • 2008
  • This research analyzes the patterns in modernization of costume that reflects the attitude of accepting the Western culture and the differences in perception, during modernization period (1850-early 1910) in Japan. The Japanese attitude toward the Western costume can be roughly classified into three periods: impetuous acceptance in the early Restoration of Imperial Regime(1867-1883), aggressive acceptance in Rokumeikan period(1883-1887), and the coexistence of traditional and modern costumes after Meiji 20(1887-1910). A Western costume symbolizes wealth and power until Rokumeikan period, however, as it becomes more common, it is considered as an ordinary dress rather than a ceremonial dress. The exact opposite phenomenon occurs to traditional costume. Although Japanese modernization is initially forced by western ideology of power, positive reactions to western culture and changes in perception toward China leads to more active importation of western culture. This reflects the governmental effort such as the Foreigners Employment Policy in the early Meiji period, and the public also became receptive toward change. However, acceptance of the Western culture is only limited to academic and technological areas, while the traditional Japanese ethos(the Emperor system, Shintoism, patriarchism) is obstinately protected. Therefore, it can be inferred that such extreme polarization of modernization and traditional inheritance enabled both perspectives to retain their own characteristics.

The Study on ensuring Effectiveness of IMO Instrument regarding GHG emission from Ships - focusing on MARPOL73/78 Annex VI

  • Doo, Hyun-Wook;Lee, Yun-Cheol
    • 한국항해항만학회지
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    • 제37권5호
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    • pp.511-517
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    • 2013
  • UNFCCC was adopted in 1992 in order to prevent global warming. However, as a lack of concrete reduction goal and implementation plan, UNFCCC could not have effectiveness. In 1997, Kyoto Protocol to UNFCCC was adopted and UNFCCC regime started practically binding on the parties. Global warming takes the leading role in changing marine environment such as the rising of water level and sea water temperature. Also, Ocean plays the vital role in storing carbon to prevent global warming. Meanwhile ships which get the propulsion generated by consuming the fossil fuel are identified as GHG source and the discussions regarding the control of GHG emitted from ships are still in progress in IMO. IMO instrument has some legal conflicts with UNFCCC in principle. Therefore, this paper reviews the present UNFCCC regime and UNCLOS. Also, it surveys activities of IMO and analyze the Amendment to MARPOL73/78 Annex VI which entered into force on January 1, 2013. Finally, conclusions suggest the improvements in order to ensure effectiveness the new Amendment to MARPOL73/78 practically.

금속의 펨토초 어블레이션의 수치해석 (Numerical analysis of fs laser ablation of metals)

  • 오부국;김동식;김재구;이제훈
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2006년도 춘계학술대회 논문집
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    • pp.657-658
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    • 2006
  • Although there are many numerical models to simulate fs laser ablation of metals, no model can analyze the ablation phenomena over a wide range of fluence. In this work, a numerical code for simulating the fs laser ablation phenomena of metals has been developed. The two temperature model is employed to predict the ablation rate and the crater shape of metals using phase explosion mechanism in the relatively high fluence regime. Also, the ultrashort thermoelastic model is used for the low fluence regime to account for spallation of the sample by high strain rate. It has been demonstrated that the thermoelastic stress generated within the sample can exceed the yield stress of the material even near the threshold fluence. Numerical computation results are compared with the experiment for Cu and Ni and show good agreement. Discussions are made on the hydrodynamic model considering phase change and hydrodynamic flow.

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Hydrazine Doped Graphene and Its Stability

  • Song, MinHo;Shin, Somyeong;Kim, Taekwang;Du, Hyewon;Koo, Hyungjun;Kim, Nayoung;Lee, Eunkyu;Cho, Seungmin;Seo, Sunae
    • Applied Science and Convergence Technology
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    • 제23권4호
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    • pp.192-199
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    • 2014
  • The electronic property of graphene was investigated by hydrazine treatment. Hydrazine ($N_2H_4$) highly increases electron concentrations and up-shifts Fermi level of graphene based on significant shift of Dirac point to the negative gate voltage. We have observed contact resistance and channel length dependent mobility of graphene in the back-gated device after hydrazine monohydrate treatment and continuously monitored electrical characteristics under Nitrogen or air exposure. The contact resistance increases with hydrazine-treated and subsequent Nitrogen-exposed devices and reduces down in successive Air-exposed device to the similar level of pristine one. The channel conductance curve as a function of gate voltage in hole conduction regime keeps analogous value and shape even after Nitrogen/Air exposure specially whereas, in electron conduction regime change rate of conductance along with the level of conductance with gate voltage are decreased. Hydrazine could be utilized as the highly effective donor without degradation of mobility but the stability issue to be solved for future application.

환경변화에 따른 한국 연근해 삼치 (Scomberomorus niphonius) 어획량의 장기변동 (Long-term variation in catch of Spanish mackerel (Scomberomorus niphonius) related to environmental change in Korean waters)

  • 이승종;김병엽;장대수
    • 수산해양기술연구
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    • 제47권2호
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    • pp.99-107
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    • 2011
  • The relationships among long-term variation in catches of Spanish mackerel (Scomberomorus niphonius) and main food organism such as common mackerel (Scomber japonicus), anchovy (Engraulis japonicus), and oceanic condition in Korean waters were analyzed using 40 years of time-series data from 1971-2010. In the 1990s, oceanic conditions around the Korean peninsula shifted to a warmer regime with higher SST (sea surface temperature). The total catch of Spanish mackerel in Korean waters increased dramatically since the early 2000s, and main fishing ground form into South Sea in winter season from December to January. From the results of correlation analysis, we found a significant relationship between the Spanish mackerel catch and environmental factor such as SST, common mackerel and anchovy catch in Korean waters.

부상화염에서 예혼합화염과 삼지화염의 천이적 거동(II) (A Transitional Behavior of a Premixed Flame and a Triple Flame in a Lifted Flame(II))

  • 장준영;김태권
    • 대한기계학회논문집B
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    • 제29권3호
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    • pp.376-383
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    • 2005
  • In the paper we investigate characteristics of a transitional behavior from a premixed flame to a triple flame in a lifted flame according to the change of equivalence ratio. In previous study, we showed that the stabilized laminar lifted flame regime is categorized by regimes of premixed flame, triple flame and critical flame. A gas-chromatograph is used to measure concentration field, a smoke-wire system is used to measure streak line, and a PIV system is used to measure velocity field in lifted flame. In the visualization experiment of smoke wire, the flow divergence and redirection reappeared in premixed flame as well as triple flame. Thus we cannot express the flame front of lifted flame has a behavior of triple flame with only flow divergence and redirection. In PIV measurement, flow velocity for those three flames has minimum value at the tip of flame front. To differentiate triple flame and premixed flame, $\Phi$ value of partially premixed fraction is employed. The partially premixed fraction $\Phi$ was constant in premixed flame. In critical flame small gradient appears over the whole regime. In triple flame, typical diffusion flame shape is obtained as parabolic distribution type due to diffusion flame trailing.