• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.2
• /
• pp.61.2-61.2
• /
• 2013

We present a study of optically emitting supernova remnants (SNRs) in M31 based on $H{\alpha}$ and [S II] images in the Local Group Survey. Using these images, we have selected objects that have [S II]:$H{\alpha}$ > 0.4 and morphology for typical SNRs. We find 76 new SNRs. We have also inspected 233 SNR candidates presented in previous studies, confirming that only 80 of them are SNRs. Combining these, we produce a master catalog of 156 SNRs in M31. We classify these SNRs according to two types of criteria: the SNR progenitor types (Type Ia and core-collapse (CC) SNRs) and the morphological types. Type Ia and CC SNRs are 23% and 77%, respectively, of the total sample. Most of CC SNRs are concentrated along the spiral arms, while Type Ia SNRs are rather spread over the entire galaxy including the inner region. CC SNRs are brighter in $H{\alpha}$ and [S II] than Type Ia SNRs. The cumulative size distribution of the SNRs with 15 < D < 50 pc is well fitted by a power law with an index, ${\alpha}=2.53{\pm}04$. It indicates that most SNRs in M31 are in Sedov-Taylor phase. Properties of these SNRs show little variation depending on the galactocentric distance. The $H{\alpha}$ and [S II] surface brightness shows a good correlation with X-ray luminosity for the SNRs that are center-bright.

• Journal of Astronomy and Space Sciences
• /
• v.16 no.2
• /
• pp.91-104
• /
• 1999

We use BV CCD images to investigate the reality of the color gradient within a King type globular cluster NGC 7089. Surface photometry shows that there is a strong radial color gradient in the central region of the cluster in the sense of bluer center with the amplitude of ~0.39 $\pm$ 0.07 mag/$arcsec^2$ in (B - V). In the outer region of the cluster, however, the radial color gradient shows a reverse case, i.e., redder toward the center. (B - V) color profile which was derived from resolved stars in VGC 7089 field also shows a significant color gradient in the central region of the clusters, indicating that lights from the combination of red giant stars and blue horizontal branch stars cause the radial color gradient. Color gradient of the outer region of NGC 7089 may be due to the unresolved background of the cluster. Similar color gradients in the central area of clusters have been previously observed exserved exclusively in highly concentrated systems classified as post core collapse clusters. We caution, however, to confirm the reality of the color gradient from resolved stars, we need more accurate imaging data of the cluster with exceptional seeing condition because the effect of completeness correlates with local density of stars.

• The Journal of Fisheries Business Administration
• /
• v.28 no.1
• /
• pp.51-70
• /
• 1997

The fishing industry of Korea is now i a critical transitional stage. That is, broadly speaking, there are two dominant factors that constrain the further development of Korea fishey and effective competition in the international fishing industry. First of all, the global fishing industry has experienced many significant changes due to the execution of U.N, maritime law, the establishment of EEZ(the Exclusive Economic Zones), the increased roles of WTO(the World Trade Organization) as well as Korea being a member of OECD(the Organization for Economic Co-operation and Development). Second, the fishing industry of Korea is faced with the following domestic troubles, such as the icreasing fishing expenses, insufficient labor supply, and the collapse of traditional local co-operative organizations of fishing villages, etc. However, the demand for aquatic products of home consumers not only continues to increase but also is shifting to select more valuable species, completely ignoring the above-mentioned serious pressures incurred by the Korean fishery. To solve these problems and keep developing steadily, it is necessary for the fishing industry of Korea to adopt a more active and flexible development pattern in order to reset up the regional economic base in fishing villages nation-wide and make the exploitation of fishing resources balance. The paper gives an reconsideration to the primary alternatives facing the Korean fishery and its prospective roles in a realistic and far-sighted attitude. It may serve as an endeavour in seeking an outlet for the fishing industry of korea to advance forwardly and lastingly.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.3
• /
• pp.877-887
• /
• 2015

Rapid development of cities with constant increasing load and deregulation in electricity market had forced the transmission lines to operate near their threshold capacity and can easily lead to voltage instability and caused system breakdown. To prevent such catastrophe from happening, accurate readings of voltage stability condition is required so that preventive equipment and operators can execute security procedures to restore system condition to normal. This paper introduced Enhanced Hybrid Particle Swarm Optimization algorithm to estimate the voltage stability condition which utilized Fast Voltage Stability Index (FVSI) to indicate how far or close is the power system network to the collapse point when the reactive load in the system increases because reactive load gives the highest impact to the stability of the system as it varies. Particle Swarm Optimization (PSO) had been combined with the ANN to form the Enhanced Hybrid PSO-ANN (EHPSO-ANN) algorithm that worked accurately as a prediction algorithm. The proposed algorithm reduced serious local minima convergence of ANN but also maintaining the fast convergence speed of PSO. The results show that the hybrid algorithm has greater prediction accuracy than those comparing algorithms. High generalization ability was found in the proposed algorithm.

• Earthquakes and Structures
• /
• v.15 no.4
• /
• pp.395-402
• /
• 2018

Floor location of adjacent buildings may be different in terms of height elevation, and thus, the slab may hit on the columns of adjacent insufficiently separated buildings during severe ground motions. Such impacts, often referred to as mid-column pounding, can be catastrophic. Substantial pounding damage or even total collapse of structures was often observed in large amount of adjacent low rise buildings. The research on the mid-column pounding between low rise buildings is in urgency need. In present study, the responses of two adjacent low rise buildings with unequal heights and different dynamic properties have been analyzed. Parametric studies have also been conducted to assess the influence of story height difference, gap distance and input direction of ground motion on the effect of structural pounding response. Another emphasis of this study is to analyze the near-fault effect, which is important for the structures located in the near-fault area. The analysis results show that collisions exhibit significant influence on the local shear force response of the column suffering impact. Because of asymmetric configuration of systems, the structural seismic behavior is distinct by varying the incident directions of the ground motions. Results also show that near-fault earthquakes induced ground motions can cause more significant effect on the pounding responses.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.18 no.2
• /
• pp.31-38
• /
• 2010

Bus manufacturers have tested and studied the dynamic collapse behavior of a bus body structure in rollover since UN ECE established ECE Regulation 66 to provide the requirement for the strength of bus structure. In spite of the costly cycles of practical tests, however, it is still a hard task to meet the rollover regulation by means of local reinforcements in the bus structure. Therefore it is necessary to develop a well designed strategy for the rollover strength implemented in the early stage of vehicle development. In this study, the suitable development method for each design stage from a component to complete body structure was considered to make a well-established development process of a bus body structure for rollover safety. For the efficient approach of the concept design stage, a numerical model based on the plastic hinge theory was used instead of detailed shell models. After setting up the concept design for the component size and geometry, the shell model was used to confirm and optimize the whole structure composition. The process developed in this study was practically used as an effective method to predict the rollover behavior of a new bus body structure.

• Computers and Concrete
• /
• v.1 no.2
• /
• pp.211-226
• /
• 2004

A relatively simple multiple-vertical-line-element macro model has been incorporated into a standard computer code DRAIN-2D. It was used in blind predictions of seismic response of cantilever RC walls subjected to a series of consequent earthquakes on a shaking table. The model was able to predict predominantly flexural response with relative success. It was able to predict the stiffness and the strength of the pre-cracked specimen and time-history response of the highly nonlinear wall as well as to simulate the shift of the neutral axis and corresponding varying axial force in the cantilever wall. However, failing to identify the rupture of some brittle reinforcement in the third test, the model was not able to predict post-critical, near collapse behaviour during the subsequent response to two stronger earthquakes. The analysed macro model seems to be appropriate for global analyses of complex building structures with RC structural walls subjected to moderate/strong earthquakes. However, it cannot, by definition, be used in refined research analyses monitoring local behaviour in the post critical region.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.09a
• /
• pp.677-694
• /
• 2009

While the budget has been allocated more for repairs and reinforcements, casualties are gradually increased due to slope disaster. Slope disaster causes road damaged as well as casualties. It also causes significant social and economic loss. The measurement device, which is installed inside ground of slope like inclinometer, has the high loss rate when slope is being slided. The electric type and the vibrating wire type have low durability because of corrosion. To cover the demerit of the present slope monitoring, the measurement method using the Multi-Antenna GPS has been developed. The Multi-Antenna GPS has been installed in the local slope as the regular monitoring system for slope. Although the initial cost of the Multi-Antenna GPS for installation is high, the additional cost is low. So it is the suitable method for large slope. The regular monitoring system using the Multi-Antenna GPS is the suitable measurement method for watching slope collapse, which is occurred widely, because it is economical, has high durability, and collects data with high resolution.

• Structural Engineering and Mechanics
• /
• v.45 no.6
• /
• pp.803-819
• /
• 2013

This paper addresses two main issues relevant to the structural assessment of buildings subjected to explosions. The first issue regards the robustness evaluation of steel frame structures: a procedure is provided for computing "robustness curves" and it is applied to a 20-storey steel frame building, describing the residual strength of the (blast) damaged structure under different local damage levels. The second issue regards the precise evaluation of blast pressures acting on structural elements using Computational Fluid Dynamic (CFD) techniques. This last aspect is treated with particular reference to gas explosions, focusing on some critical parameters (room congestion, failure of non-structural walls and ignition point location) which influence the development of the explosion. From the analyses, it can be deduced that, at least for the examined cases, the obtained robustness curves provide a suitable tool that can be used for risk management and assessment purposes. Moreover, the variation of relevant CFD analysis outcomes (e.g., pressure) due to the variation of the analysis parameters is found to be significant.

• Journal of the Society of Naval Architects of Korea
• /
• v.48 no.1
• /
• pp.1-7
• /
• 2011

Cavitation is the formation of vapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapor pressure. Various types of cavitations are generated on the propeller blades. As cavity bubbles passing the blade are forced to oscillate in size or shape and come to collapse, they cause very strong local acoustic waves in the fluid and radiate noise. Comparing the Sound Pressure Level(SPL) before and after cavitation, SPL increases 2dB per 1 knot increase in ship speed above the cavitation inception speed(CIS). Consequently, the CIS is an important criteria to design silent propellers. In this work, experimental measurements of radiated noise according to various types of cavitations from the model propeller are carried out in a large cavitation tunnel and their acoustical characteristics are extensively investigated.