RETRACTED ARTICLE: Search for time variation of the fine-structure constant using [\mathrm{O}_{\mathrm{III}}] emission lines     

Le Duc Thong  Tran Van Hung  Nguyen Thi Thu Huong  Ha Huy Bang 《Astrophysics and Space Science》2012,339(2):405-405

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Hydroclimatic controls on dissolved organic matter (DOM) characteristics and implications for trace metal transport in Hwangryong River Watershed,Korea, during a summer monsoon period     

Ji‐Hyung Park  Ji‐Ho Lee  Seo‐Young Kang  Sei‐Young Kim 《水文研究》2007,21(22):3025-3034

Frequent heavy rainfalls during the East Asian summer monsoon drastically increase water flow and chemical loadings to surface waters. A solid understanding of hydroclimatic controls on watershed biogeochemical processes is crucial for water quality control during the monsoon period. We investigated spatio‐temporal variations in the concentrations and spectroscopic properties of dissolved organic matter (DOM) and the concentrations of trace metals in Hwangryong River, Korea, during a summer period from the relatively dry month of June through the following months with heavy rainfall. DOM and its spectroscopic properties differed spatially along the river, and also depended on storm and flow characteristics around each sampling time. At a headwater stream draining a forested watershed, the concentrations (measured as dissolved organic carbon (DOC)), aromaticity (measured as specific UV absorbance at 254 nm), and fulvic acid‐ and protein‐like fluorescence of DOM were higher in stormflow than in baseflow waters. DOC concentrations and fluorescence intensities increased along the downstream rural and urban sites, in which DOC and fluorescence were not higher in stormflow waters, except for the ‘first flush’ at the urban site. The response of DOM in reservoir waters to monsoon rainfalls differed from that of stream and river waters, as illustrated by storm‐induced increases in DOM aromaticity and fulvic‐like fluorescence, and no significant changes in protein‐like fluorescence. The results suggest that surface water DOM and its spectroscopic properties differentially respond to changes in hydroclimatic conditions, depending on watershed characteristics and the influence of anthropogenic organic matter loadings. DOC concentrations and intensities of spectroscopic parameters were positively correlated with some of the measured trace metals (As, Co, and Fe). Further research will be needed to obtain a better understanding of climate effects on the interaction between DOM and trace metals. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Atmospheres and spectra of strongly magnetized neutron stars   总被引：1，自引：0，他引：1  

Wynn C. G. Ho  Dong Lai 《Monthly notices of the Royal Astronomical Society》2001,327(4):1081-1096

We construct atmosphere models for strongly magnetized neutron stars with surface fields     and effective temperatures     . The atmospheres directly determine the characteristics of thermal emission from isolated neutron stars, including radio pulsars, soft gamma-ray repeaters, and anomalous X-ray pulsars. In our models, the atmosphere is composed of pure hydrogen or helium and is assumed to be fully ionized. The radiative opacities include free–free absorption and scattering by both electrons and ions computed for the two photon polarization modes in the magnetized electron–ion plasma. Since the radiation emerges from deep layers in the atmosphere with     , plasma effects can significantly modify the photon opacities by changing the properties of the polarization modes. In the case where the magnetic field and the surface normal are parallel, we solve the full, angle-dependent, coupled radiative transfer equations for both polarization modes. We also construct atmosphere models for general field orientations based on the diffusion approximation of the transport equations and compare the results with models based on full radiative transport. In general, the emergent thermal radiation exhibits significant deviation from blackbody, with harder spectra at high energies. The spectra also show a broad feature     around the ion cyclotron resonance     , where Z and A are the atomic charge and atomic mass of the ion, respectively; this feature is particularly pronounced when     . Detection of the resonance feature would provide a direct measurement of the surface magnetic fields on magnetars.  相似文献   

Restricted N+1-Body Problem: Existence and Stability Of Relative Equilibria     

D. Bang  B. Elmabsout 《Celestial Mechanics and Dynamical Astronomy》2004,89(4):305-318

We consider n bodies (with equal mass m) disposed at the vertices of a regular n-gon and rotating rigidly around an additional mass m ₀(at its center) with a constant angular velocity (relative equilibrium). In the present paper, we prove results on the existence and on the linear stability of equilibrium positions for a zero-mass particle submitted to the gravitational field generated by the previous system. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Propagation characteristics of historical tsunamis that attacked the east coast of Korea     

Chae Ho Lim  Jae Seok Bae  Jong In Lee  Sung Bum Yoon 《Natural Hazards》2008,47(1):95-118

In this study, a numerical modeling system based on the dispersion–correction finite difference scheme equipped with a grid-nesting scheme is constructed. The model is applied to simulate the propagation of three historical tsunami events that attacked the east coast of Korea. The calculated free-surface displacements for the cases of the 1983 Akita and the 1993 Okushiri tsunamis are compared with the observations at four tidal stations along the east coast of Korea. The comparison shows that the results agree well with the observations. The analyses of the simulated results show that underwater topography, such as submerged rises and ridges, plays an important role in the propagation of tsunamis in this region.  相似文献   

Why are flood and landslide victims less willing to take mitigation measures than the public?     

Shuyeu Lin  Daigee Shaw  Ming-Chou Ho 《Natural Hazards》2008,44(2):305-314

Almost annually, natural hazards such as floods and landslides cause a great deal of financial loss and human suffering in Taiwan. In order to gain a better understanding of disaster preparedness, this paper examines several factors in relation to hazard mitigation behavior: social economic status (education, income), psychological vulnerability (sense of powerless and helpless), risk perception (perceived impact and control) and social trust. The statistical analysis reported here is based on the “2004 National Risk Perception Survey of Floods and Landslides in Taiwan”. The main findings include: (1) in comparison with general public, victims are less willing to adopt risk mitigation measures than the public, even though they perceive larger impacts, worry more about the hazard, and pay more attention to hazard information; (2) trust, risk perception and social economic status are positive predictors for mitigation intentions, whereas psychological vulnerability is a negative predictor; and (3) psychological variables are stronger predictors for mitigation intentions than that of socio-economic variables. In light of these findings, the policy implications and intervention strategy are also discussed.

Shuyeu LinEmail:

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Influence of extractable soil manganese on oxidation capacity of different soils in Korea   总被引：1，自引：0，他引：1  

Chul-Min Chon  Jae Gon Kim  Gyoo Ho Lee  Tack Hyun Kim 《Environmental Geology》2008,55(4):763-773

We examined the relationship between soil oxidation capacity and extractable soil manganese, iron oxides, and other soil properties. The Korean soils examined in this study exhibited low to medium Cr oxidation capacities, oxidizing 0.00–0.47 mmol/kg, except for TG-4 soils, which had the highest capacity for oxidizing added Cr(III) [>1.01 mmol/kg of oxidized Cr(VI)]. TG and US soils, with high Mn contents, had relatively high oxidation capacities. The Mn amounts extracted by dithionite-citrate-bicarbonate (DCB) (Mn^d), NH₂OH·HCl (Mn^h), and hydroquinone (Mn^r) were generally very similar, except for the YS1 soils, and were well correlated. Only small proportions of either total Mn or DCB-extractable Mn were extracted by NH₂OH·HCl and hydroquinone in the YS1 soils, suggesting inclusion of NH₂OH·HCl and hydroquinone-resistant Mn oxides, because these extractants are weaker reductants than DCB. No Cr oxidation test results were closely related to total Mn concentrations, but Mn^d, Mn^h, and Mn^r showed a relatively high correlation with the Cr tests (r = 0.655–0.851; P < 0.01). The concentrations of Mn^d and Mn^h were better correlated with the Cr oxidation tests than was the Mn^r concentration, suggesting that the oxidation capacity of our soil samples can be better explained by Mn^d and Mn^h than by Mn^r. The first component in principal components analysis indicated that extractable soil Mn was a main factor controlling net Cr oxidation in the soils. Total soil Mn, Fe oxides, and the clay fraction are crucial for predicting the mobility of pollutants and heavy metals in soils. The second principal component indicated that the presence of Fe oxides in soils had a significant relationship with the clay fraction and total Mn oxide, and was also related to heavy-metal concentrations (Zn, Cd, and Cu, but not Pb).  相似文献   

Performance of Weibull function as a diameter distribution model for <Emphasis Type="Italic">Pinus thunbergii</Emphasis> stands in the eastern coast of South Korea     

Azyleah Cañizares Abino  Sung Yong Kim  Roscinto Ian Canicosa Lumbres  Mi Na Jang  Ho Joong Youn  Ki Hyung Park  Young Jin Lee 《山地科学学报》2016,13(5):822-830

This study was carried out to determine the performance of percentile-based Weibull diameter distribution model for Pinus thunbergii stands thriving along the eastern coast of South Korea. The parameter recovery technique was used to estimate the three parameters of the Weibull model. The analysis demonstrated satisfactory results based on the following test statistics for the principal percentile models: fit index (FI) range from 0.501 (minimum diameter) to 0.932 (50th diameter percentiles) and root mean square error (RMSE) range from 0.112 (quadratic mean diameter) to 3.572 (minimum diameter). The developed model was further evaluated by determining the mean bias (ē) in trees per ha (TPH) for each diameter class, and the results showed highest over-prediction in the 20 cm, and under-prediction in the 16 cm and 24 cm diameter classes. The goodness of fit tested by Kolmogorov-Smirnov (KS) test showed no significant differences (p>0.05) between the observed and predicted diameter distributions for almost all plots. Using site index and aboveground biomass (AGB) models developed for P. thunbergii in South Korea, a model to predict the AGB per ha for each diameter class and subsequently the total AGB of the stand was created. An application guide was also created, which will serve as a decision-support tool for forest managers in quantifying the future total AGB in P. thunbergii stands located in the eastern coast of South Korea and, subsequently, the quantification of potential carbon stocks aside from being a vital input in designing efficient management and protection strategies for these stands.  相似文献   

Spatial prediction of rainfall-induced shallow landslides using hybrid integration approach of Least-Squares Support Vector Machines and differential evolution optimization: a case study in Central Vietnam     

Dieu Tien Bui  Binh Thai Pham  Quoc Phi Nguyen  Nhat-Duc Hoang 《International Journal of Digital Earth》2016,9(11):1077-1097

This study represents a hybrid intelligence approach based on the differential evolution optimization and Least-Squares Support Vector Machines for shallow landslide prediction, named as DE–LSSVM_SLP. The LSSVM is used to establish a landslide prediction model whereas the DE is adopted to search the optimal tuning parameters of the LSSVM model. In this research, a GIS database with 129 historical landslide records in the Quy Hop area (Central Vietnam) has been collected to establish the hybrid model. The receiver operating characteristic (ROC) curve and area under the curve (AUC) were used to assess the performance of the newly constructed model. Experimental results show that the proposed model has high performances with approximately 82% of AUCs on both training and validating datasets. The model’s results were compared with those obtained from other methods, Support Vector Machines, Multilayer Perceptron Neural Networks, and J48 Decision Trees. The result comparison demonstrates that the DE–LSSVM_SLP deems best suited for the dataset at hand; therefore, the proposed model can be a promising tool for spatial prediction of rainfall-induced shallow landslides for the study area.  相似文献   

Adaptive GPS/INS integration for relative navigation   总被引：1，自引：0，他引：1  

Je Young Lee  Hee Sung Kim  Kwang Ho Choi  Joonhoo Lim  Sebum Chun  Hyung Keun Lee 《GPS Solutions》2016,20(1):63-75

Relative navigation based on GPS receivers and inertial measurement units is required in many applications including formation flying, collision avoidance, cooperative positioning, and accident monitoring. Since sensors are mounted on different vehicles which are moving independently, sensor errors are more variable in relative navigation than in single-vehicle navigation due to different vehicle dynamics and signal environments. In order to improve the robustness against sensor error variability in relative navigation, we present an efficient adaptive GPS/INS integration method. In the proposed method, the covariances of GPS and inertial measurements are estimated separately by the innovations of two fundamentally different filters. One is the position-domain carrier-smoothed-code filter and the other is the velocity-aided Kalman filter. By the proposed two-filter adaptive estimation method, the covariance estimation of the two sensors can be isolated effectively since each filter estimates its own measurement noise. Simulation and experimental results demonstrate that the proposed method improves relative navigation accuracy by appropriate noise covariance estimation.  相似文献