• 한국전산유체공학회:학술대회논문집
• /
• 2006.10a
• /
• pp.110-119
• /
• 2006

An accurate and cost efficient method PSE is used for the stability analysis of 2D or 3D compressible boundary layers. A highly accurate finite difference PSE code has been developed at a general curvilinear coordinate system using an implicit marching procedure to deal with a broad range of transition predictions problems. Evolution of disturbances in compressible flat plate boundary layers are studied for free-stream Mach numbers ranging from 0 to 1.5. The effect of mean-flow nonparallelism is found to be weak on two dimensional waves and strong on three dimensional waves. The maximum amplification rate increases monotonically with Mach number. The present PSE solutions are compared with previous numerical investigations and experimental results and are found to be in good agreement.

• Journal of The Korean Digital Architecture Interior Association
• /
• v.7 no.2
• /
• pp.67-72
• /
• 2007

Water plays significant roles in constructing architectural structures. This is because a comfortable human life is impossible without proper distribution of water. Here the notion of water space is introduced in the field of the modern architecture. This study examines the typological variations of water space in the outdoor space of architectural structures and concludes the contents discussed. Unlike the traditional architecture, the modern architecture takes the types of water into account. And in the modern architecture the multiple considerations of water space are being made for the public, not for the specific customers.

• Proceedings of the KIEE Conference
• /
• 1998.11b
• /
• pp.713-716
• /
• 1998

To examine the influence of unsteady wake on the flow and heat transfer characteristics, an experiment has been conducted in a four-vane linear cascade. Flow and heat transfer measurements are made for the inlet Reynolds number of 66000(based on chord length and free-stream velocity). Turbulent intensity and stress were measured using hot wire anemometer, and to measure the convective heat transfer coefficients on the blade surfaces liquid crystal/gold film Intrex technique was used. The disturbance by the unsteady wake is characterized by the unresolved unsteadiness. The unsteady wake enhances the turbulent motion of flow in the cascade passage. It also promotes the boundary layer development and transition. The results show that heat transfer coefficients on the suction surface increase with increasing unresolved unsteadiness.

• Journal of Plant Biology
• /
• v.26 no.4
• /
• pp.197-206
• /
• 1983

Flora and distribution of vascular hygro- and hydrophytes were investigated from April to June, 1983 on the seven sampling sites along the estuary of Nagdong River. As the result, total 60 kinds of vascular plants are investigated, among them 13 kinds are aquatics; Rotala indica var. uliginosa, Myriophyllum spicatum, Allisma canalicultum, Vallisneria asiatica, Hydrilla verticillata, Potamogeton berchtoldii, P. crispus, Ruppia maritima, Phyllospadix iwatensis, Zostera marina, Juncus effusus, Phragmites communis, and Scirpus triqueter. Present hydrophytes are largely confined to the main-stream zone. The transition zone is poorly habitated by hydrophytes and considered for the distributconfined to the estuary and coastal zone. However, long-term conditions of salinity gradient appear to be primarily responsible for the present flora and distribution.

• Proceedings of the KIEE Conference
• /
• 1998.11a
• /
• pp.393-396
• /
• 1998

To examine the influence of unsteady wake on the flow and heat transfer characteristics, an experiment has been conducted in a four-vane linear cascade. Flow and heat transfer measurements are made for the inlet Reynolds number of 66000(based on chord length and free-stream velocity). Turbulent intensity and stress were measured using hot wire anemometer, and to measure the convective heat transfer coefficients on the blade surfaces liquid crystal/gold film Intrex technique was used. The disturbance by the unsteady wake is characterized by the unresolved unsteadiness. The unsteady wake enhances the turbulent motion of flow in the cascade passage. It also promotes the boundary layer development and transition. The results show that heat transfer coefficients on the suction surface increase with increasing unresolved unsteadiness.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.13 no.2
• /
• pp.88-95
• /
• 2001

Transition to chaotic convection is investigated for natural convection of a fluid with Pr=0.1 in a wide-gap horizontal annuls. The unsteady two-dimensional stream-function-vorticity equation is solved with finite difference method. As the Rayleigh number is increased, the steady 'downward flow' bifurcates to a time-periodic flow with a fundamental frequency, and afterwards a period-doubling bifurcation occurs. As the Rayleigh number is increased further, the chaotic flow regime is reached after a sequence of successive Hopf bifurcation to quasi-periodic and chaotic flow regimes. The route to chaos shows the Ruelle-Takens-Newhouse scenario. The flow of chaotic regime displays complex coalescence and separation of eddies in the side and lower region of the annulus.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.15 no.2
• /
• pp.142-149
• /
• 2012

This study deals with the investigation of the scale effect for the vertical-axis tidal stream turbine by evaluating the hydrodynamic efficiency of turbine rotors of different diameters at different flow conditions. Numerical analyses are made for the turbine rotors with a same shape, but different sizes obtained using the diameter evaluation equation suggested in this paper. It is shown that the performance of turbine is clearly dependent upon the rotor size and inflow velocity, i.e. Reynolds number dependency of different-scaled turbines showing better efficiency with increasing Reynolds number. The sudden decrease of efficiency is also noticed around the transition region of Reynolds number. The hydrodynamic capacity evaluation method needed at initial stage of turbine design is suggested and exercised with some test cases. It is recommended that the method is expected to be useful for turbines with demanding powers between 10 kW and 300 kW.

• Journal of Korea Multimedia Society
• /
• v.6 no.2
• /
• pp.208-215
• /
• 2003

For playing a multimedia presentation in a Internet, the case that the presentation QoS(Quality of Services) at a destination nay be different from the QoS of multimedia data at the source occurs frequently. In this case, the process of trancoding the multimedia data at the source Into the multimedia data satisfying the QoS at the destination should be requited. In addition, even the presentation description having the homogeneous QoS at both sides may have different transcoding paths due to the limitation of display terminals or network bandwidth. That is, for a multimedia description, it is required to regenerate a proper transcoding path whenever the displaying terminals or the network environment gets decided. And the delay time required to go through the transcoding path may affect the playability of the give presentation. Therefore it should be checked whether the presentation requiring a transcoding process is able to be played in a real time. In this paper, the algorithm for generating all the possible transcoding paths for a given multimedia description under a fixed set of transcoders and the network environment is proposed. The algorithm adopts the concept of QoS transition diagram to Prevent from a trancoding Path being cycled by the repetition of a cyclic Path which generates the same QoS of multimedia data as its input QoS. By eliminating all the cyclic Paths, the algorithm can guarantee the termination of the process. And for the playability check, a method of computing the transcoding time and the delay lime between logical data units are proposed.Finally all the proposed methods were implemented in the stream engine, called TransCore and the presentation-authoring tool, called VIP, we had developed. And the test results with sample scenarios were presented at the last.

• Iberoamérica
• /
• v.13 no.1
• /
• pp.123-152
• /
• 2011

The long standing people's culture of Latin America based on social solidarity of the communities makes the political relations between the leader and the people very different from them of the european societies based on the representative democracy. At any rate, the main stream of the Populist Discourses sees the real populist political processes with the pejorative senses attributing the demagogue style of the leaders. In these sense, it is very important to re-consider the populism discourses of Ernesto Laclau who thinks that the populism is a way of interpreting the emergence of the people to establish the social demands in the context of populist real politics. According to Laclau, "the populism seeks for the radical reconfiguration of the revolt of the 'Status Quo' and new order". This work will confirm if this interpretation of Laclau can be applied to Peronist political regime. Meanwhile the first group of the orthodox line of the discourses on populism including Gino Germani shows that the populism is a political movement based on the manipulation and demagogue by the charismatic leader of the irrational mass during the period in transition after the crises of the traditional oligarchy in Latin America. And another line of the main stream of discourses on populism including Cardoso and O'Donnell says that the populism is a political phenomena in a period of transition towards the modernization and the national development by means of the industrialization through the substitution of the imports and the alliance between the classes after the 1930's. But these principal interpretations on populism disregards that in Argentina many urban poor working class people had lived under the racist, unequal painful social relations due to the underestimation and the discrimination by the upper and the middle class with many intellectuals. But Peronism had considered them as the new social subjects with human dignities. And so we have to rethink the clientelism also with another meanings. In this sense, the theories of Ernesto Laclau on populism is very helpful to illuminate the sensitive and ambiguous meanings of Peronism. Especially Peronism makes the urban working class maintain their life styles more tended to them of the traditional communities and go towards the anti-Status Quo. That is a key of success of Peronism not only that time but until these days. And so this study will show that it is the most important thing that Peronist regime had made the emergence of the 'people' in the meaning of advancing the democracy in Argentina.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.1
• /
• pp.31-39
• /
• 2013

A Quad Tilt Wing UAV is a new concept hybrid UAV having the advantages of both fixed-wing and rotary-wing aircraft. This paper presents longitudinal flight dynamic characteristics of a Quad Tilt Wing UAV. The designed Quad Tilt Wing UAV is a configuration of a tandem wing type aircraft with an actuating motor and propeller mounted at each wing. Momentum theory is used to calculate the thrust, and nonlinear modeling is performed considering lift and drag generated by slip stream effect of propellers. Also, Force and moment variation at each tilting angle is considered. Static trim on longitudinal axis is analyzed via numerical simulation. Componentwise force contribution was analyzed at each trim mode. Dynamic characteristics were evaluated through eigenvalue analysis for a linear model at each flight mode. It is verified that longitudinal dynamic characteristics are changing from unstable to stable state by continuous transition of dominant poles.