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New lumped-mass-stick model based on modal characteristics of structures: development and application to a nuclear containment building

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Earthquake engineering and engineering Vibration 2013年第2期12卷 307-317页

作者： Hwasung Roh Huseok Lee Jong Seh Lee department of civil engineering Chonbuk National University department of civil and Environmental engineering Hanyang University

In this study, a new lumped-mass-stick model （LMSM） is developed based on the modal characteristics of a structure such as eigenvalues and eigenvectors. The simplified model, named the ＂frequency adaptive lumped-massstick model,＂ hasonly a small number of stick elements and nodes to provide the same natural frequencies of the structure and is applied to a nuclear containment building. To investigate the numerical performance of the LMSM, a time history analysis is carried out on both the LMSM and the finite element model （FEM） for a nuclear containment building. A comparison of the results shows that the dynamic responses of the LMSM in terms of displacement and acceleration are almost identical to those of the FEM. In addition, the results in terms of floor response spectra at certain elevations are also in good agreement.

关键词： new lumped-mass-stick model frequency adaptive nuclear containment buildings seismic response floor response spectrum

An Assessment and Identification of Avalanche Hazard Sites in Uri Sector and its Surroundings on Himalayan Mountain

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Journal of Mountain Science 2015年第6期12卷 1499-1510页

作者： A.S.MOHAMMED Abdul Athick Hasan Raja NAQVI Zikra FIRDOUSE department of geomatics engineering (School of engineering) Adama Science & Technology University department of Aerospace engineering School of Engineering and Technology Jain University

Avalanches are one of the most natural hazard in the mountain areas and therefore, identification of avalanche hazard is necessary for planning future development activities. The study area falls under the international boundary region which generally covered by the snow(38%) on high altitude regions of the western part of Himalayas. Avalanches are triggered in study area during snowfall resulting in loss of human life, property and moreover the transportation and communication affected by the debris which ultimately delays the relief measures. Therefore in this study three major causative parameters i.e terrain, ground cover and meteorological have been incorporated for the identification of avalanche hazard zones(AHZ) by integrating Analytical Hierarchical Process(AHP) method in Geographical Information System(GIS). In the first part of study, avalanche sites have been identified by the criteria related to terrain(slope, aspect and curvature) and ground cover. Weights and ratings to these causative factors and their cumulative effects have been assigned on the basis of experience and knowledge of field. In the second part of the study, single point interpolation and Inverse Distance Weighted(IDW) method has been employed as only one weather station falls in study area. Accordingly, it has been performed to generate the meteorological parameter maps(viz. air temperature and relative humidity) from the field observatories and Automatic Weather Stations(AWS) located at Baaj OP in Uri sector. Finally, the meteorological parameter maps were superimposed on the terrain-based avalanche hazard thematic layers to identify the dynamic avalanche hazard sites. Conventional weighted approach and Analytical Hierarchical Process(AHP) method have been implemented for the identification of AHZ that shows approximately 55% area under maximum hazard zone. Further, the results were validated by overlapping the existing registered avalanche sites. The sites were identified through fie

关键词： Snow Digital Elevation Model(DEM) Meteorology Analytical Hierarchical Process(AHP) Avalanche hazard Uri sector

Effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete

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International Journal of Minerals,Metallurgy and Materials 2013年第2期20卷 205-213页

作者： Fareed Ahmed Memon Muhd Fadhil Nuruddin Nasir Shafiq department of civil engineering Faculty of EngineeringUniversiti Teknologi PETRONAS department of civil engineering Faculty of EngineeringMehran University of Engineering and Technology

The effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete （SCGC） was investigated in this paper. The work focused on the concrete mixes with a fixed water-to-geopolymer solid （W/Gs） ratio of 0.33 by mass and a constant total binder content of 400 kg/m3. The mass fractions of silica fume that replaced fly ash in this research were 0wt%, 5wt%, 10wt%, and 15wt%. The workability-related fresh properties of SCGC were assessed through slump flow, V-funnel, and L-box test methods. Hardened concrete tests were limited to compressive, splitting tensile and flexural strengths, all of which were measured at the age of 1, 7, and 28 d after 48-h oven curing. The results indicate that the addition of silica fume as a partial replacement of fly ash results in the loss of workability; nevertheless, the mechanical properties of hardened SCGC are significantly improved by incorporating silica fume, especially up to 10wt%. Applying this percentage of silica fume results in 4.3% reduction in the slump flow; however, it increases the compressive strength by 6.9%, tensile strength by 12.8% and flexural strength by 11.5%.

关键词： geopolymer concrete silica fume fresh properties compressive strength tensile strength flexural strength

Interpretation of electrochemical impedance spectroscopy(EIS) circuit model for soils

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Journal of Central South University 2015年第11期22卷 4318-4328页

作者：韩鹏举张亚芬陈幼佳白晓红 department of civil engineering Taiyuan University of Technology department of civil engineering The Penn State University

Based on three different kinds of conductive paths in microstructure of soil and theory of electrochemical impedance spectroscopy(EIS), an integrated equivalent circuit model and impedance formula for soils were proposed, which contain 6 meaningful resistance and reactance parameters. Considering the conductive properties of soils and dispersion effects, mathematical equations for impedance under various circuit models were deduced and studied. The mathematical expression presents two semicircles for theoretical EIS Nyquist spectrum, in which the center of one semicircle is degraded to simply the equivalent model. Based on the measured parameters of EIS Nyquist spectrum, meaningful soil parameters can easily be determined. Additionally, EIS was used to investigate the soil properties with different water contents along with the mathematical relationships and mechanism between the physical parameters and water content. Magnitude of the impedance decreases with the increase of testing frequency and water content for Bode graphs. The proposed model would help us to better understand the soil microstructure and properties and offer more reasonable explanations for EIS spectra.

关键词： soil electrochemical impedance spectroscopy(EIS) e

Dynamic earth pressure on rigid retaining walls induced by a neighboring machine foundation,by the meshless local Petrov-Galerkin method

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Earthquake engineering and engineering Vibration 2015年第4期14卷 647-661页

作者： Mehdi Veiskarami Arash Bahar Erfan Zandi Lak Geotechnical engineering Division Department of Civil EngineeringUniversity of Guilan department of civil and Environmental engineering School of Engineering No.1Shiraz University Structural engineering Division Department of Civil EngineeringUniversity of Guilan

Dynamic earth pressure induced by machine foundations on a neighboring retaining wall is analyzed with emphasis on factors which control the intensity and location of the design forces. The meshless local Petrov-Galerkin (MLPG) method is used to analyze the problem for a variety of retaining wall and machine foundation geometries. The soil medium is assumed to be homogeneous and visco-elastic. The machine foundation is idealized as a harmonic sinusoidal dynamic force often encountered in practice. A number of analyses have been made to reveal the effect of the loading frequency, the location and size of the foundation and the soil shear wave velocity on the distribution and magnitude of the dynamic earth pressure. Results indicate that there is a critical frequency and a critical location for which the passive pressure takes the maxima in the entire duration of the dynamic load.

关键词： MLPG retaining wall dynamic loading visco-elastic soil machine foundation

A remote sensing-based agricultural drought indicator and its implementation over a semi-arid region, Jordan

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Journal of Arid Land 2017年第3期9卷 319-330页

作者： Khaled HAZAYMEH Quazi K HASSAN department of geomatics engineering Schulich School of Engineering University of Calgary department of Geography Faculty of Arts Yarmouk University

The objective of the study was to develop a remote sensing （i.e., Landsat-8 and MODIS）-based agricultural drought indicator （ADI） at 30-m spatial resolution and 8-day temporal resolution and also to evaluate its performance over a heterogeneous agriculture dominant semi-arid region in Jordan. Firstly, we used principal component analysis （PCA） to evaluate the correlations among six commonly used remote sensing-derived agricultural drought related variables. The variables included normalized difference water index （NDWI）, normalized difference vegetation index （NDVI）, visible and shortwave drought index （VSDI）, normalized multiband drought index （NMDI）, moisture stress index （MSI）, and land surface temperature （LST）. Secondly, we integrated the relatively less correlated variables （that were found to be NDWI, VSDI, and LST） to generate four agricultural drought categories/conditions （i.e., wet, mild drought, moderate drought, and severe drought）. Finally, we evaluated the ADI maps against a set of 8-day ground-based standardized precipitation index values （i.e., SPI-I, SPI-2, ..., SPLS） by use of confusion matrices and observed the best results for SPI-4 （i.e., overall accuracy and Kappa-values were 83% and 76%, respectively） and SPI-5 （i.e., overall accuracy and Kappa-values were 85% and 78%, respectively）. The results demonstrated that the method would be valuable for monitoring agricultural drought conditions in semi-arid regions at both a reasonably high spatial resolution （i.e., 30-m） and a short time period （i.e., 8-day）.

关键词： spatio-temporal image fusion model (STI-FM) land surface temperature (LST) surface reflectance standardizedprecipitation index (SPI) Landsat-8 MODIS

Reliability of GPS/GNSS-based positioning in a forestry environment

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Journal of Forestry Research 2017年第3期28卷 605-614页

作者： R.Cuneyt Erenoglu department of geomatics engineering Canakkale Onsekiz Mart University17100 CanakkaleTurkey

The critical environment is one of the main insufficient to positioning. Geodetic observing systems such as the global positioning system （GPS） and the global navigation satellite systems （GNSS） are routinely used to estimate the contaminating effects by critical environment. In an effort to define the accuracy and reliability of GPS/ GNSS positioning, we investigated the data having con- taminating effects due to forestry environment. Some reliability criteria and geometric concepts were defined and then examined by them. Two sets of data were collected in open sky and closed canopy separately. The analysis of the observed data was performed using the reliability criteria and geometric concepts. The accuracy and reliability of positioning strongly depended on the canopy ratio and satellite availability. The minimum detectable error on baseline was estimated about 2.5 mm under closed canopy. The number of observable satellites and minimal detectable errors were computed for each epoch. The minimal biases on estimated baselines, bias-to-noise ratios for estimating baseline components and probability of success of the integer ambiguity solution were defined in case of forest canopy. Finally, geometric quality could be achieved using the factors of dilution of precision. Thus, the presented accuracy and reliability concepts fulfill the requirement proposed by the global geodetic observing system in forest environment.

关键词： Accuracy Canopy Forestry GPS/GNSS Reliability

Carbon stock estimation by dual-polarized synthetic aperture radar (SAR) and forest inventory data in a Mediterranean forest landscape

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Journal of Forestry Research 2022年第3期33卷 827-838页

作者： Can Vatandaşlar Saygin Abdikan department of Forest engineering Artvin Coruh University08100ArtvinTurkey department of geomatics engineering Hacettepe University06800AnkaraTurkey

Forest ecosystems play a crucial role in mitigating global climate change by forming massive carbon sinks. Their carbon stocks and stock changes need to be quantified for carbon budget balancing and international reporting schemes. However, direct sampling and biomass weighing may not always be possible for quantification studies conducted in large forests. In these cases, indirect methods that use forest inventory information combined with remote sensing data can be beneficial. Synthetic aperture radar (SAR) images offer numerous opportunities to researchers as freely distributed remote sensing data. This study aims to estimate the amount of total carbon stock (TCS) in forested lands of the Kizildag Forest Enterprise. To this end, the actual storage capacities of five carbon pools, i.e. above- and below-ground, deadwood, litter, and soil, were calculated using the indirect method based on ground measurements of 264 forest inventory plots. They were then associated with the backscattered values from Sentinel-1 and ALOS-2 PALSAR-2 data in a Geographical Information System (GIS). Finally, TCS was separately modelled and mapped. The best regression model was developed using the HH polarization of ALOS-2 PALSAR-2 with an adjusted R^(2) of 0.78 (p < 0.05). According to the model, the estimated TCS was about 2 Mt for the entire forest, with an average carbon storage of 133 t ha^(−1). The map showed that the distribution of TCS was heterogenic across the study area. Carbon hotspots were mostly composed of pure stands of Anatolian black pine and mixed, over-mature stands of Lebanese cedar and Taurus fir. It was concluded that the total carbon stocks of forest ecosystems could be estimated using appropriate SAR images at acceptable accuracy levels for forestry purposes. The use of additional ancillary data may provide more delicate and reliable estimations in the future. Given the implications of this study, the spatiotemporal dynamics of carbon can be effectively controlled

关键词： Carbon storage Aboveground carbon Soil-bound carbon Forest biomass Synthetic aperture radar(SAR)

Determination of Helmert transformation parameters for continuous GNSS networks:a case study of the Géoazur GNSS network

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Geo-Spatial Information Science 2023年第1期26卷 125-138页

作者： Dinh Trong Tran Jean-Mathieu Nocquet Ngoc Dung Luong Dinh Huy Nguyen department of Geodesy and geomatics engineering Hanoi University of Civil EngineeringHanoiVietnam UniversitéCôte d’Azur CNRSObservatoire de la Côte d’AzurIRDValbonneFrance

In this paper,we propose an approach to determine seven parameters of the Helmert transfor-mation by transforming the coordinates of a continuous GNSS network from the World Geodetic System 1984(WGS84)to the International Terrestrial Reference *** includes(1)convert-ing the coordinates of common points from the global coordinate system to the local coordinate system,(2)identifying and eliminating outliers by the Dikin estimator,and(3)estimating seven parameters of the Helmert transformation by least squares(LS)estimation with the“clean”data(*** removed).Herein,the local coordinate system provides a platform to separate points’horizontal and vertical ***,the Dikin estimator identifies and eliminates outliers in the horizontal or vertical component *** is significant because common points in a continuous GNSS network may contain *** proposed approach is tested with the Géoazur GNSS network with the results showing that the Dikin estimator detects outliers at 6 out of 18 common points,among which three points are found with outliers in the vertical compo-nent ***,instead of eliminating all coordinate components of these six common points,we only eliminate all coordinate components of three common points and only the vertical component of another three common ***,the classical LS estimation is applied to“clean”data to estimate seven parameters of the Helmert transformation with a significant accuracy *** Dikin estimator’s results are compared to those of other robust estimators of Huber and Theil-Sen,which shows that the Dikin estimator performs ***,the weighted total least-squares estimation is implemented to assess the accuracy of the LS estimation with the same *** inter-comparison of the seven estimated parameters and their standard deviations shows a small difference at a few per million levels(E-6).

关键词： Continuous GNSS tectonic geodesy Dikin estimation Helmert transformation