Elastic lateral-torsional buckling analysis of permanent means of access structure     

Beom-Seon Jang  Ming Ma 《Ocean Engineering》2011,38(10):1114-1122

International Maritime Organization (IMO) adopted a new regulation to request permanent means of access (PMA) for a regular inspection of ship structure. Horizontal platforms for an inspector to walk on should be provided at specified locations. The platform is attached perpendicular to longitudinal bulkheads or side shell like a common longitudinal stiffener. Since the platform is much wider than ordinary stiffeners, a mid-flat-bar is welded in the middle of the platform. The wide platform (i.e. the tall web plate) makes PMA structure prone to lateral torsional buckling prior to overall flexural Euler buckling subjected to axial compression. This study employs the Rayleigh-Ritz method to treat the elastic lateral-torsional buckling of the PMA structure. The deformation of the cross-section can be expressed using six independant parameters. Compared to the previous research for an ordinary stiffened plate (Hughes and Ma, 1996a), two additional parameters are employed to model the deformation of the mid flat bar. This study also proposes a new strain distribution of lateral bending introducing two respective neutral axes for the flange and the mid-flat-bar. Two mathematical models are developed for two cases; one without associated plating, and the other with both the plating and its rotational restraint. In the former, the coupling between the lateral torsional buckling (“tripping”) and the Euler buckling is investigated. In the latter, a plate rotational spring constant is suggested based on extended deformed shape of the plating. For each model, the validity of the proposed method is verified by a comparison with a number of linear buckling analyses carried out using the NASTRAN finite-element program.  相似文献   

The role of mechanical stratigraphy in the lateral variations of thrust development along the central Alberta Foothills,Canada     

Hyunjung Lee  Yirang Jang  Sanghoon Kwon  Myong-Ho Park  Gautam Mitra 《地学前缘(英文版)》2018,9(5):1451-1464

Fold-thrust belts generally exhibit significant variations in structural styles such as differences in thrust geometries and frequencies in imbrication. A natural laboratory of this pattern is preserved in the central Alberta Foothills of the Canadian Rockies, where differences in thrust geometries are represented by the existence vs. non-existence of triangle zones. To seek the factors that make this difference in these regions in terms of structural geometry, stratigraphic thickness variations and mechanical stratigraphy of the sedimentary layers, structural interpretation is conducted based on admissible cross-sections and well log interpretations. In northern region, a backthrust is detached from an incompetent layer(viz.Nomad Unit of the Wapiabi Formation), which gets thinner from the Foothills to the Plains, indicating that it is developed where the shale layers are pinched out where triangle zone is developed. Backthrust is also developed in the southern region, where mechanical strengths of strata(viz. Bearpaw Formation)increase toward the foreland. In the central region, however, only forethrusts are developed along the weak continuous decollement layers(viz. Turner Valley and Brazeau formations), forming an imbricate fan without development of the triangle zone. Incompetent layers such as the top Wapiabi(Nomad),Brazeau(Bearpaw), Coalspur and Paskapoo formations are also pinched out laterally, forming fault glide horizons in different stratigraphic levels in each region. These results indicate that, along the transport direction, triangle zone is developed in relation to the stratigraphic pinch out of the Nomad Unit in the northern region, and is formed associated with the variations in strengths of the layers constituting the Bearpaw Formation in the southern region. It is notable that all the glide horizons are developed along incompetent layers. However, triangle zones are not developed in the areas of continuous stratigraphy of the Nomad Unit, which does not serve as a glide horizon in the central region. This suggests that factors such as stratigraphic thickness changes of incompetent layers and mechanical stratigraphy of the sedimentary layers play an important role in the development of lateral variations in thrust system evolution in terms of triangle zone vs. imbricate fan in the central Alberta Foothills.  相似文献   

Fines adsorption on nanoparticle-coated surface     

Xianglei Zheng  François Perreault  Jaewon Jang 《Acta Geotechnica》2018,13(1):219-226

Fluid flow through porous media is inherently associated with the detachment and migration of fine particles. The migration of fine particles and ensuing clogging is the main reason of flow rate decrease in porous media. Nanoparticle coating can be a promising method to prevent fines’ detachment and migration by changing electrical surface forces between the pore wall surface and the fine particles. In this study, the attraction and adhesion forces of the nanoparticle-coated surface are measured by atomic force microscope. The effect of the nanoparticle coating on the fines adsorption efficiency is then investigated. The results show that there is an increase in the adhesion force on the nanoparticle-coated surface and the significant improvement of the fines adsorption capacity by the nanoparticle coating. The research results are relevant to other research areas whenever migrating fines cause engineering problems.  相似文献   

Deformation effects of porosity variation on soil consolidation caused by groundwater table decline   总被引：1，自引：0，他引：1  

Tung-Lin Tsai  Weng-Shin Jang 《Environmental Earth Sciences》2014,72(3):829-838

Soil consolidation has been widely analyzed using the poroelastic theory. As soil consolidation proceeds, porosity variation leads to the changes in hydraulic conductivity, Young’s modulus, and body force. However, the combined deformation effect of porosity variation on soil consolidation is rarely examined. In this study, a poroelastic consolidation model used to simultaneously consider the changes in hydraulic conductivity, Young’s modulus, and body force was developed to investigate the combined deformation effect of porosity variation on soil consolidation caused by groundwater table decline. The results indicate that the deformation effect of porosity variation on soil consolidation is negligible when the body force number is <0.01. For body force numbers >0.01, soil displacement could be overestimated or underestimated if the combined deformation effect of porosity variation is not completely considered. The misestimation of soil displacement increases as the body force number increases. In addition, the combined deformation effect of porosity variation also affects the transmission of pore water pressure. Therefore, it could be concluded that a reliable analysis of soil consolidation must simultaneously account for the variations in hydraulic conductivity, Young’s modulus, and body force.  相似文献   

Correlation of in situ modulus of deformation with degree of weathering, RMR and Q-system     

Seong-Seung Kang  Hyo-Yeol Kim  Bo-An Jang 《Environmental Earth Sciences》2013,69(8):2671-2678

Geotechnical investigation projects in Korea produced data on the in situ modulus of deformation of rock masses (E _M) measured with the borehole test, rock mass rating (RMR), and Q-system. The modulus of deformation of rock masses was correlated with the degree of weathering, RMR, and Q values. Determination of E _M for each degree of weathering allows for the results to be used to classify the degree of weathering or to predict E _M. The relation between E _M and RMR is represented by $ E_{\text{M}} = 10^{{\frac{{{\text{RMR}} - 16}}{50}}} $ , which returns values 2–3 times lower than those reported in previous studies. Despite scatter in the values, due to larger dataset used in this study, the proposed equation may be used to predict the in situ modulus of deformation from RMR values. In addition, the relation between modulus of deformation and Q values is $ E_{\text{M}} = 10^{{0.32{ \log }Q + 0.585}} $ .  相似文献   

Fast Imaging Solar Spectrograph of the 1.6 Meter New Solar Telescope at Big Bear Solar Observatory     

Jongchul Chae  Hyung-Min Park  Kwangsu Ahn  Heesu Yang  Young-Deuk Park  Jakyoung Nah  Bi Ho Jang  Kyung-Suk Cho  Wenda Cao  Philip R. Goode 《Solar physics》2013,288(1):1-22

For high resolution spectral observations of the Sun – particularly its chromosphere, we have developed a dual-band echelle spectrograph named Fast Imaging Solar Spectrograph (FISS), and installed it in a vertical optical table in the Coudé Lab of the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. This instrument can cover any part of the visible and near-infrared spectrum, but it usually records the Hα band and the Ca ii 8542 Å band simultaneously using two CCD cameras, producing data well suited for the study of the structure and dynamics of the chromosphere and filaments/prominences. The instrument does imaging of high quality using a fast scan of the slit across the field of view with the aid of adaptive optics. We describe its design, specifics, and performance as well as data processing  相似文献   

Temperature of Solar Prominences Obtained with the Fast Imaging Solar Spectrograph on the 1.6 m New Solar Telescope at the Big Bear Solar Observatory     

Hyungmin Park  Jongchul Chae  Donguk Song  Ram Ajor Maurya  Heesu Yang  Young-Deuk Park  Bi-Ho Jang  Jakyoung Nah  Kyung-Suk Cho  Yeon-Han Kim  Kwangsu Ahn  Wenda Cao  Philip R. Goode 《Solar physics》2013,288(1):105-116

We observed solar prominences with the Fast Imaging Solar Spectrograph (FISS) at the Big Bear Solar Observatory on 30 June 2010 and 15 August 2011. To determine the temperature of the prominence material, we applied a nonlinear least-squares fitting of the radiative transfer model. From the Doppler broadening of the Hα and Ca ii lines, we determined the temperature and nonthermal velocity separately. The ranges of temperature and nonthermal velocity were 4000?–?20?000 K and 4?–?11 km?s^?1. We also found that the temperature varied much from point to point within one prominence.  相似文献   

Comparison of Cone Model Parameters for Halo Coronal Mass Ejections     

Hyeonock Na  Y.-J. Moon  Soojeong Jang  Kyoung-Sun Lee  Hae-Yeon Kim 《Solar physics》2013,288(1):313-329

Halo coronal mass ejections (HCMEs) are a major cause of geomagnetic storms, hence their three-dimensional structures are important for space weather. We compare three cone models: an elliptical-cone model, an ice-cream-cone model, and an asymmetric-cone model. These models allow us to determine three-dimensional parameters of HCMEs such as radial speed, angular width, and the angle [γ] between sky plane and cone axis. We compare these parameters obtained from three models using 62 HCMEs observed by SOHO/LASCO from 2001 to 2002. Then we obtain the root-mean-square (RMS) error between the highest measured projection speeds and their calculated projection speeds from the cone models. As a result, we find that the radial speeds obtained from the models are well correlated with one another (R > 0.8). The correlation coefficients between angular widths range from 0.1 to 0.48 and those between γ-values range from ?0.08 to 0.47, which is much smaller than expected. The reason may be the different assumptions and methods. The RMS errors between the highest measured projection speeds and the highest estimated projection speeds of the elliptical-cone model, the ice-cream-cone model, and the asymmetric-cone model are 376 km?s^?1, 169 km?s^?1, and 152 km?s^?1. We obtain the correlation coefficients between the location from the models and the flare location (R > 0.45). Finally, we discuss strengths and weaknesses of these models in terms of space-weather application.  相似文献   

Flood risk assessment using regional regression analysis   总被引：2，自引：0，他引：2  

Young-Oh Kim  Seung Beom Seo  Ock-Jae Jang 《Natural Hazards》2012,63(2):1203-1217

This study aimed to create a flood risk map for ungauged regions, which have limited flood damage data and other relevant data. The fact that there is a shortage of data that are critical for the establishment of a flood assessment and mitigation plan is not surprising even in developed countries like South Korea. To address this problem, the regional regression concept in statistical hydrology was introduced to the flood risk assessment field in this study, and it was framed with a series of two regression functions: flood damage and regional coefficients. As the second regression function utilizes the local socioeconomic variables, the resulting flood risk map can reflect the spatial characteristics well. The proposed methodology was applied to create flood risk maps for the three metropolitan areas in South Korea. The comparison of the proposed methodology with the existing methods revealed that only the proposed methodology can produce a statistically meaningful flood risk map based on a recent major flood in 2001.  相似文献   

Tintinnid species as biological indicators for monitoring intrusion of the warm oceanic waters into Korean coastal waters   总被引：2，自引：0，他引：2  

Young-Ok Kim  Kyoungsoon Shin  Pung-Guk Jang  Hyun-Woo Choi  Jae-Hoon Noh  Eun-Jin Yang  Eung Kim  Dongchull Jeon 《Ocean Science Journal》2012,47(3):161-172

This study examined seasonal and annual occurrences of warm oceanic tintinnid species in southern Korea coastal waters. The indicative species of tintinnids was monitored using three approaches: monitoring from cruises traveling from the warm pool in the western North Pacific to the Korea Strait; biweekly or monthly monitoring in the Korea Strait; and daily monitoring in the nearshore water. Annual pulses of warm oceanic indicator species were regularly observed in the Korea Strait. In September 2008 recorded a maximum species number of warm water indicators, a representative species for warm oceanic waters, Climacocylis scalaroides was simultaneously detected in the nearshore water as well as the Korea Strait. The result indicates that the greater warm water extension into Korean coastal areas was in September 2008. Sharp declines in species diversity were observed in the transitional area between neritic and Kuroshio zone in East China Sea (ECS). Epiplocyloides reticulata, reported previously as a Kuroshio indicator, was considered an ECS indicator species, as it was undetected in the western North Pacific central zone but was found abundantly in the ECS. Tintinnid species can be used as biological indicators to detect the inflow of warm oceanic waters into Korean coastal waters.  相似文献