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排序方式: 共有250条查询结果,搜索用时 31 毫秒
21.
Md. Rezaul Hasan Shumon Shamsuddin Ahmed Md. Tasbirul Islam 《Environmental Earth Sciences》2014,72(7):2239-2249
The ever-increasing and rapidly growing volume of waste electrical and electronic equipment has become a serious threat to the environment in many countries. The inevitability of e-waste management and the development of a holistic system to deal with it has become an indispensable socio-economic and environmental issue for the sustainable development of Malaysia. However, no comprehensive research has yet been carried out, and only a few works in a discreet manner have been begun. In view of the above, and as a small endeavor towards achieving the country’s Vision 2020, this study explores the present status and future perspectives of the management of waste electrical and electronic equipment in Malaysia. This article presents an overview of e-waste management practices around the world, including the generation of e-waste, the implementation of management strategies, and collection and recovery activities in Malaysia. It also presents the corresponding responses adopted so far with respect to legislation and other infrastructural development. Finally, through the use of structured and semi-structured interviews, it reveals the barriers and challenges, as well as future perspectives and sustainability issues related to the e-waste management system in this fast developing country. 相似文献
22.
Use of isotopic tracers to characterize the interaction of water components and nitrate contamination in the arid Rasafeh area (Syria) 总被引:1,自引:0,他引:1
Chemical and isotopic data in atmospheric precipitation, surface water, and groundwater in arid Rasafeh area, northeast Syria, are used to clarify the status of groundwater quality, the interaction of water components, groundwater dating, and vulnerability to anthropogenic contamination. Interpretation of chemical data with thermodynamic calculation reveals that the dissolution of evaporate mineral is the main factor of high salinity. The δ18O and δ2H relationships indicate that the groundwater is fed by mixing water from Euphrates River and precipitation and the isotope balance equation were used to estimate the contribution of the Euphrates River to the aquifers recharge. High tritium content, together with high 14C activity in the majority of groundwater samples, indicate shorter residence times and consequently potentially greater recharge. The presence of high nitrate concentration associated with high tritium concentration in both shallow and deep aquifer units indicates the presence of high permeability, so that groundwater is highly susceptible to anthropogenic contamination. Nitrate seems to derive exclusively from the application of N fertilizers. The high nitrate values are characteristic of the areas with intensive agricultural activity, indicating the importance of irrigated return flow on the groundwater. 相似文献
23.
Taskin Kavzoglu Hasan Tonbul Merve Yildiz Erdemir Ismail Colkesen 《Journal of the Indian Society of Remote Sensing》2018,46(8):1297-1306
Object-based image analysis (OBIA) has attained great importance for the delineation of landscape features, particularly with the accessibility to satellite images with high spatial resolution acquired by recent sensors. Statistical parametric classifiers have become ineffective mainly due to their assumption of normal distribution, vast increase in the dimensions of the data and availability of limited ground sample data. Despite pixel-based approaches, OBIA takes semantic information of extracted image objects into consideration, and thus provides more comprehensive image analysis. In this study, Indian Pines hyperspectral data set, which was recorded by the AVIRIS hyperspectral sensor, was used to analyse the effects of high dimensional data with limited ground reference data. To avoid the dimensionality curse, principal component analysis (PCA) and feature selection based on Jeffries–Matusita (JM) distance were utilized. First 19 principal components representing 98.5% of the image were selected using the PCA technique whilst 30 spectral bands of the image were determined using JM distance. Nearest neighbour (NN) and random forest (RF) classifiers were employed to test the performances of pixel- and object-based classification using conventional accuracy metrics. It was found that object-based approach outperformed the traditional pixel-based approach for all cases (up to 18% improvement). Also, the RF classifier produced significantly more accurate results (up to 10%) than the NN classifier. 相似文献
24.
Hasan Md. Khalid Moriom Masuma Shuprio Shariaj Ibna Mizan Younos Tahmina Bintay Chowdhury Md. Arif 《Natural Hazards》2022,111(1):817-849
Natural Hazards - Adequate and effective disaster preparedness in each sector is indispensable to abate disaster impacts and intensify disaster resilience in Bangladesh for achieving sustainable... 相似文献
25.
26.
Hasan Avdan Senay Kayaci Avdan Aysun Akyuz Solen Balman 《Astrophysics and Space Science》2014,352(1):123-128
We report our findings on a new quasi-periodic oscillation (QPO) and a long period from the ultraluminous X-ray source (ULX) X-2 in nearby galaxy NGC 4736 based on the Chandra and XMM-Newton archival data. To examine the timing properties, power density spectra of the source have been obtained using Fast Fourier Transform. Also the spectral parameters of the source have been calculated by obtaining and fitting the energy spectra. Power density spectrum of this source reveals a QPO peak at \(0.73_{-0.14}^{+0.16}~\mathrm{mHz}\) with an fractional rms variability of 16 % using the Chandra data (in the year 2000-lower state of the source). The XMM-Newton data analysis indicates a peak at \(0.53_{-0.35}^{+0.09}~\mathrm{mHz}\) with a fractional rms variation of 5 % (in the year 2006-higher state of the source). These recovered QPOs overlap within errors and may be the same oscillation. In addition, we detect a long periodicity or a QPO in the Chandra data of about (5.2±2.0)×10?5 Hz (~5.4 h) over 3 σ confidence level. If this is a QPO, it is the lowest QPO detected from a ULX. The mass of the compact object in ULX X-2 is estimated using the Eddington luminosity and a disk blackbody model in the range (10–80) M ⊙. 相似文献
27.
The 3+1 spacetime split is used in a preliminary investigation of waves propagating in a medium of isothermal plasma in the vicinity of event horizon of Reissner-Nordström planar analogue. The general relativistic magnetohydrodynamic equations for isothermal have been investigated there. The dispersion relations are obtained by using linear perturbation and Fourier analyze techniques for non-rotating and rotating, non-magnetized and magnetized environment. The wave number, phase velocity, group velocity etc. are shown to discuss the nature of the waves. 相似文献
28.
S. Turck-Chièze P. Lamy C. Carr P. H. Carton A. Chevalier I. Dandouras J. M. Defise S. Dewitte T. Dudok de Wit J. P. Halain S. Hasan J. F. Hochedez T. Horbury P. Levacher M. Meissonier N. Murphy P. Rochus A. Ruzmaikin W. Schmutz G. Thuillier S. Vivès 《Experimental Astronomy》2009,23(3):1017-1055
The DynaMICCS mission is designed to probe and understand the dynamics of crucial regions of the Sun that determine solar
variability, including the previously unexplored inner core, the radiative/convective zone interface layers, the photosphere/chromosphere
layers and the low corona. The mission delivers data and knowledge that no other known mission provides for understanding
space weather and space climate and for advancing stellar physics (internal dynamics) and fundamental physics (neutrino properties,
atomic physics, gravitational moments...). The science objectives are achieved using Doppler and magnetic measurements of
the solar surface, helioseismic and coronographic measurements, solar irradiance at different wavelengths and in-situ measurements
of plasma/energetic particles/magnetic fields. The DynaMICCS payload uses an original concept studied by Thalès Alenia Space
in the framework of the CNES call for formation flying missions: an external occultation of the solar light is obtained by
putting an occulter spacecraft 150 m (or more) in front of a second spacecraft. The occulter spacecraft, a LEO platform of
the mini sat class, e.g. PROTEUS, type carries the helioseismic and irradiance instruments and the formation flying technologies.
The latter spacecraft of the same type carries a visible and infrared coronagraph for a unique observation of the solar corona
and instrumentation for the study of the solar wind and imagers. This mission must guarantee long (one 11-year solar cycle)
and continuous observations (duty cycle > 94%) of signals that can be very weak (the gravity mode detection supposes the measurement
of velocity smaller than 1 mm/s). This assumes no interruption in observation and very stable thermal conditions. The preferred
orbit therefore is the L1 orbit, which fits these requirements very well and is also an attractive environment for the spacecraft
due to its low radiation and low perturbation (solar pressure) environment. This mission is secured by instrumental R and
D activities during the present and coming years. Some prototypes of different instruments are already built (GOLFNG, SDM)
and the performances will be checked before launch on the ground or in space through planned missions of CNES and PROBA ESA
missions (PICARD, LYRA, maybe ASPIICS). 相似文献
29.
In this paper, using 2MASS photometry, we study the structural and dynamical properties of four young star clusters viz. King 16, NGC 1931, NGC 637 and NGC 189. For the clusters King 16, NGC 1931, NGC 637 and NGC 189, we obtain the limiting radii of 7′, 12′, 6′ and 5′ which correspond to linear radii of 3.6 pc, 8.85 pc, 3.96 pc and 2.8 pc respectively. The reddening values E(B?V) obtained for the clusters are 0.85, 0.65–0.85, 0.6 and 0.53 and their true distances are 1786 pc, 3062 pc, 2270 pc and 912 pc respectively. Ages of the clusters are 6 Myr, 4 Myr, 4 Myr and 10 Myr respectively. We compare their structures, luminosity functions and mass functions (φ(M)=dN/dM ∝ M ?(1+χ)) to the parameter τ=t age /t relax to study the star formation process and the dynamical evolution of these clusters. We find that, for our sample, mass seggregation is observed in clusters or their cores only when the ages of the clusters are comparable to their relaxation times (τ≥1). These results suggest mass seggregation due to dynamical effects. The values of χ, which characterize the overall mass functions for the clusters are 0.96±0.11, 1.16±0.18, 0.55±0.14 and 0.66±0.31 respectively. The change in χ as a function of radius is a good indicator of the dynamical state of clusters. 相似文献
30.
Water resources in semi-arid regions like the Mediterranean Basin are highly vulnerable because of the high variability of weather systems. Additionally, climate change is altering the timing and pattern of water availability in a region where growing populations are placing extra demands on water supplies. Importantly, how reservoirs and dams have an influence on the amount of water resources available is poorly quantified. Therefore, we examine the impact of reservoirs on water resources together with the impact of climate change in a semi-arid Mediterranean catchment. We simulated the Susurluk basin (23.779-km2) using the Soil and Water Assessment Tool (SWAT) model. We generate results for with (RSV) and without reservoirs (WRSV) scenarios. We run simulations for current and future conditions using dynamically downscaled outputs of the MPI-ESM-MR general circulation model under two greenhouse gas relative concentration pathways (RCPs) in order to reveal the coupled effect of reservoir and climate impacts. Water resources were then converted to their usages – blue water (water in aquifers and rivers), green water storage (water in the soil) and green water flow (water losses by evaporation and transpiration). The results demonstrate that all water resources except green water flow are projected to decrease under all RCPs compared to the reference period, both long-term and at seasonal scales. However, while water scarcity is expected in the future, reservoir storage is shown to be adequate to overcome this problem. Nevertheless, reservoirs reduce the availability of water, particularly in soil moisture stores, which increases the potential for drought by reducing streamflow. Furthermore, reservoirs cause water losses through evaporation from their open surfaces. We conclude that pressures to protect society from economic damage by building reservoirs have a strong impact on the fluxes of watersheds. This is additional to the effect of climate change on water resources. 相似文献