• Advances in aircraft and spacecraft science
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• v.4 no.1
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• pp.81-91
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• 2017

The performances of lifting surfaces are particularly critical in specific flight conditions like takeoff and landing. Different systems can be used to increase the lift and drag coefficients in such conditions like slat, flap or ailerons. Nevertheless they increase the losses and make difficult the mechanical design of wing structures. Morphing surfaces are a compromise between a right increase in lift and a reduction of parts movements involved in the actuation. Furthermore these systems are suitable for more than one flight condition with low inertia problems. So, flap and slats can be easily substituted by the corresponding morphing shapes. This paper deals with a genetic optimization of an airfoil with morphing flap with an already optimized nose. Indeed, two different codes are used to solve the equations, a finite volume code suitable for structured grids named ZEN and the EulerBoundary Layer Drela's code MSES. First a number of different preliminary design tests were done considering a specific set of design variables in order to restrict the design region. Then a RANS optimization with a single design point related to the take-off flight condition has been carried out in order to refine the previous design. Results are shown using the characteristic curves of the best and of the baseline reported to outline the computed performances enhancements. They reveal how the contemporary use of a morphing acting on the nose of the main component and the trailing edge of the flap drive towards a total not negligible increment in lift.

• Journal of the Korean Society of Combustion
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• v.2 no.1
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• pp.1-8
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• 1997

Premixed combustion within porous ceramic media is numerically studied to understand burning characteristics and to find best configurations for burner implementations. Among many parameters, critical to burner performance, flame location and extinction coefficient are selected as major parameters for this study. The flame structure and burner performance with respect to these two parameters are observed. In the study, it is found that the location of flame is the most important in porous burner operation since it affects the rate of heat transfer and flame structure. Stability of the flame within the porous ceramic burner is discussed with respect to the flame location. It is found that to obtain high radiative output, the flame should be located downstream section of the burner. But the flame is to be unstable at most of downstream section except near the exit plane. To overcome this problem, new porous ceramic burner, using different ceramic properties in one burner instead of single property ceramic, is made and tested. With a combination of ceramics of high extinction coefficient at upstream and another material of low extinction coefficient at downstream of the burner, the flame can be stabilized at wider region of the burner with higher radiative output compared to the original burner configuration.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.85.1-85.1
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• 2012

Energetic outflow from active galactic nuclei (AGNs) may play a critical role in galaxy evolution. We present a velocity diagnostics for detecting gas outflow in the narrow-line region of Type-2 AGNs using line-of-sight velocity offset of the [O III]${\lambda}5007$ and $H{\alpha}$ emission lines with respect to the systemic velocity of stars in host galaxies. We apply the diagnostics to nearby galaxies at 0.02 < z < 0.05: 3775 AGN-host and 907 star-forming galaxies as a comparison sample, which are selected from the Sloan Digital Sky Survey DR7. After obtaining a best-fit stellar population model for the continuum and a systemic velocity based on stellar lines, we subtract stellar component to measure velocity offsets of each emission line. We find a sample of 169 AGN-host galaxies with outflow signatures, displaying a larger velocity shift of [O III] than that of $H{\alpha}$, as expected in a decelerating outflow model. We find that the offset velocity of [O III] increases with Eddington ratio, suggesting that gas outflow depends on the energetics of AGN.

• Journal of Communications and Networks
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• v.11 no.3
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• pp.287-296
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• 2009

Although asymptotic bounds of wireless network capacity have been heavily pursued, the answers to the following questions are still critical for network planning, protocol and architecture design: Given a three-dimensional (3D) network space with the number of active users randomly located in the space and using the wireless communication technology, what are the expected per-flow throughput, network capacity, and network transport capacity? In addition, how can the protocol parameters be tuned to enhance network performance? In this paper, we focus on the ultra wideband (UWB) based wireless personal area networks (WPANs) and provide answers to these questions, considering the salient features of UWB communications, i.e., low transmission/interference power level, accurate ranging capability, etc. Specifically, we demonstrate how to explore the spatial multiplexing gain of UWB networks by allowing appropriate concurrent transmissions. Given 3D space and the number of active users, we derive the expected number of concurrent transmissions, network capacity and transport capacity of the UWB network. The results reveal the main factors affecting network (transport) capacity, and how to determine the best protocol parameters, e.g., exclusive region size, in order to maximize the capacity. Extensive simulation results are given to validate the analytical results.

• Nuclear Engineering and Technology
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• v.53 no.6
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• pp.1924-1930
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• 2021

By using miniature SENB specimens, the fracture properties of the materials in the region of welded metal, 321 stainless steel heat affected zone, 690 alloy heat affected zone of 321/690 dissimilar metal girth welded joints were tested. Both the J-resistance curves and critical fracture toughness of the three different materials are affected by the crack size because of the effect of crack tip constraint. Groups of constraint corrected J-resistance curves of the three materials are obtained according to J-Q-M approach. The welded metals exhibit the best fracture resistance but the worst fracture resistance is observed in the material of 690 alloy heat affected zone.

• Progress in Medical Physics
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• v.15 no.1
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• pp.9-16
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• 2004

The intensity modulated radiation therapy (IMRT) is believed to be on of the best treatment techniques for the goal of radiation therapy: to irradiate fatal dose to tumor region while minimizing dose to critical organs. It is essential to have comprehensive quality assurance program to assure the precision and the accuracy of the treatment due to the characteristic of the IMRT. The quality assurance technique for the Corvus treatment planning system was developed and its effectiveness was tested with the treatment planning of H&N region. Acrylic phantom, film and ionization chamber were used for this study, the discrepancy between the treatment planning and the film measurements showed 0.03 cm and 0.28 cm for the 90% of isodose line in each directions. Dose measurements showed 1% and 1.2% differences for ionization chamber and TLD, respectively. This concluded that the system can be used for clinic.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.3
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• pp.93-106
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• 2006

The purpose of this study was to find the method of spatial analysis using GIS that would best reflect the characteristics of study area. The purpose was successfully achieved. In order to carry out multicriteria decision analysis of the study results, the spatial analysis process reflecting the characteristics of study area was examined through stages of evaluation criteria standardization and evaluation indicator weighting decision. In the stage of evaluation criteria standardization, the characteristics of study area could be reflected through the adjustment of critical when converting a real value to a general value. In the stage of evaluation indicator weighting determination, the characteristics of the study area were reflected using the present condition of land use. The results of evaluating the grades of development-potential regions by reflecting characteristics of study area showed high correlativity between already developed region and new developing region. Such results show that, in spatial analysis, by combining expert questionnaire survey and literature survey, this method which reflects the characteristics of an area is very reasonable.

• Journal of the Korean Chemical Society
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• v.34 no.6
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• pp.663-672
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• 1990

The extraction of ginseng saponins with near critical or supercritical ammonia(SCF-NH$_3$) was carried out at 80$^{\circ}C$-160$^{\circ}C$ and ammonia densities of 339.8-525 $mg/cm^3$. In order to evaluate brownish color of white ginseng extracts, a spetrophotometric method was applied in ultraviolet and visible range. The extractibilities of ginseonoside $Rb_1$, -$Rb_2$, -Rc, -Rd, -Re, -Rf, $-Rg_1$, and $-Rg_2$ were determined by high performance liquid choromatography. The best extractability was 7.36% at 133$^{\circ}C$ and 403 $\pm$ 24.605 $mg/cm^3$. In the case of the high extraction temperature, it is thought that extraction times can be reduced and the selectivity of protopanaxatriol can be increased. The brownish color of extracts is affected by temperature and extractability. When extraction temperature is between 132$^{\circ}C$ and 140$^{\circ}C$, it is shown that the range is the retrograde region where extractablility decrease with increasing temperature.

• Smart Structures and Systems
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• v.31 no.4
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• pp.325-334
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• 2023

Computer vision-based damage detection enables non-contact, efficient and low-cost bridge health monitoring, which reduces the need for labor-intensive manual inspection or that for a large number of on-site sensing instruments. By leveraging recent semantic segmentation approaches, we can detect regions of critical structural components and identify damages at pixel level on images. However, existing methods perform poorly when detecting small and thin damages (e.g., cracks); the problem is exacerbated by imbalanced samples. To this end, we incorporate domain knowledge to introduce a hierarchical semantic segmentation framework that imposes a hierarchical semantic relationship between component categories and damage types. For instance, certain types of concrete cracks are only present on bridge columns, and therefore the noncolumn region may be masked out when detecting such damages. In this way, the damage detection model focuses on extracting features from relevant structural components and avoid those from irrelevant regions. We also utilize multi-scale augmentation to preserve contextual information of each image, without losing the ability to handle small and/or thin damages. In addition, our framework employs an importance sampling, where images with rare components are sampled more often, to address sample imbalance. We evaluated our framework on a public synthetic dataset that consists of 2,000 railway bridges. Our framework achieves a 0.836 mean intersection over union (IoU) for structural component segmentation and a 0.483 mean IoU for damage segmentation. Our results have in total 5% and 18% improvements for the structural component segmentation and damage segmentation tasks, respectively, compared to the best-performing baseline model.

• Journal of the Korean association of regional geographers
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• v.21 no.3
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• pp.489-502
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• 2015

Sometimes called the Silicon Fen, the Cambridge cluster is well known as the most innovative hi-tech cluster in the world. This paper attempts to explore the evolutionary dynamics of the Cambridge cluster, drawing upon the triple-helix approach. To understand the evolutionary dynamics of the Cambridge cluster, it is important to examine the role and impact of the University of Cambridge, which is conceived as one of the best higher educational institutions in the world. The Cambridge cluster has been evolved on the basis of a strong university-industry relationship. University spin-outs have a long tradition in Cambridge with the history of more than a century, and they have played a critical role in making the cluster more innovative. Business networks and social capital molded for a long time in the region become a foundation for active local spin-out activities. However, since 2000 the central government started steadily to require British universities to be an entrepreneurial university, with the purpose of the reduction of university subsidies. As a result of this, spin-out activities in the Cambridge cluster show a sharp decline, which is a factor of threatening the dynamic evolution of the cluster.