Photometry and spectroscopy of Ⅱ Peg,IM Peg and UX Ari     

Ajaz Ahmad Dar  Padmakar Singh Parihar  Manzoor Ahmad Malik 《天文和天体物理学研究(英文版)》2018,(9)

V band photometry of three RS CVn stars, II Peg, IM Peg and UX Ari, is carried out to study the physical properties of these variables. We verified the significant and regular optical photometric variability to be present in all three stars. The strong photometric variability and emission of Hα and Ca II H K using high resolution optical spectroscopy with the Hanle Echelle Spectrograph(HESP),which operates in conjunction with the Himalayan Chandra Telescope, verify the strong chromospheric activity which is present in RS CVn stars. The photometric studies of II Peg, UX Ari and IM Peg were subjected to light curve analysis for spot parameters using a two-starspot model.  相似文献   

Assessing the geoindicators of land degradation in the Kashmir Himalayan region, India     

Sumira Nazir Zaz  Shakil Ahmad Romshoo 《Natural Hazards》2012,64(2):1219-1245

The geoindicators of land degradation such as erosion, vegetation change and wetland loss were identified in the Kashmir Himalayan region using a geospatial model. Geomatics techniques were used to generate information on landuse/landcover, NDVI, slope and the lithological formations that form inputs to map the erosion risk. The results of erosion analysis revealed that 48.27?% of the area is under very high erosion risk. The Middle Himalayan watersheds were found to be under high erosion risk compared to the Greater Himalayan watersheds. Pohru and Doodhganga watersheds of the Middle Himalayas were found to be under very high erosion risk. These two watersheds were studied in detail from 1992 to 2001 for vegetation change and wetland loss. In Pohru watershed, significant change was found in the dense forest with 10?% decrease. Wular lake, an important wetland in the Pohru watershed, has shrunk by 2.7?km² during the last decade. The vegetation change analysis of the Doodhganga watershed revealed that there has been 9.13?% decrease in the forest, 7?% increase in built up and the largest wetland in the Doodhganga, Hokarsar, has reduced by 1.98?km² from 1992 to 2001. Field studies showed that anthropogenic activities and chemically deficit soil (Karewa) along Pir Panjal ranges are the main factors responsible for high land degradation in the area. The assessment of these geoindicators provided valuable information for identifying causes and consequences of the land degradation and thus outlining potential hazard areas and designing remedial measures.  相似文献   

Groundwater aggressiveness assessment according to EN 206-1: data,methods and application on groundwater in the Horna Nitra basin,Slovakia     

M. Fendekova  F. Malik  D. Krcmar  M. Fendek  A. Rohacikova 《Environmental Earth Sciences》2011,64(2):461-470

The history of groundwater aggressiveness evaluation procedures applied in the Slovak Republic is summarized and compared with the newly adopted European technical standard STN EN 206-1. The methodology of data acquiring and processing for groundwater aggressiveness evaluation was proposed. The procedure included basic principles of data mining, requested number of chemical analyses and ways of groundwater aggressiveness assessment. Ways of results interpretation and graphical visualization were proposed, too. The procedure was applied in the area of the Horna Nitra in Slovakia. A total number of 953 groundwater analyses were used to assess the groundwater aggressiveness. The resulting map of zoning comprised eight groundwater aggressiveness zones. Zones with the non-aggressive degree (X0) groundwater to moderately aggressive degree (XA2) were delineated. The aggressiveness was caused mainly by presence of aggressive carbon dioxide (depending on the rock type in the area) and by lowered pH values in association with increased sulfate contents in areas of brown coal mining activities and in heavy industrialized areas. The compilation of a locality map was proposed, where for each municipality type and degree of aggressiveness is assessed. It should serve to local authorities as background information within the decision-making process connected to the permission of construction work.  相似文献   

Ion-Acoustic Wave Generation by Two Kinetic Alfvén Waves and Particle Heating     

M. Malik  R. P. Sharma  H. D. Singh 《Solar physics》2007,241(2):317-328

In this paper we have investigated the beat wave excitation of an ion-acoustic wave at the difference frequency of two kinetic (or shear) Alfvén waves propagating in a magnetized plasma with β<1 (β=8π n _e0 T _e/B ₀ ² , where n _e0 is the unperturbed electron number density, T _e is the electron temperature, and B ₀ is the external magnetic field). On account of the interaction between two kinetic Alfvén waves of frequencies ω ₁ and ω ₂, the ponderomotive force at the difference frequency ω ₁−ω ₂ leads to the generation of an ion-acoustic wave. Also because of the filamentation of the Alfvén waves, magnetic-field-aligned density dips are observed. In this paper we propose that the ion-acoustic wave generated by this mechanism may be one of the possible mechanisms for the heating and acceleration of solar wind particles.  相似文献   

A framework to quantify uncertainties of seafloor backscatter from swath mapping echosounders     

Mashkoor Malik  Xavier Lurton  Larry Mayer 《Marine Geophysical Researches》2018,39(1-2):151-168

Multibeam echosounders (MBES) have become a widely used acoustic remote sensing tool to map and study the seafloor, providing co-located bathymetry and seafloor backscatter. Although the uncertainty associated with MBES-derived bathymetric data has been studied extensively, the question of backscatter uncertainty has been addressed only minimally and hinders the quantitative use of MBES seafloor backscatter. This paper explores approaches to identifying uncertainty sources associated with MBES-derived backscatter measurements. The major sources of uncertainty are catalogued and the magnitudes of their relative contributions to the backscatter uncertainty budget are evaluated. These major uncertainty sources include seafloor insonified area (1–3 dB), absorption coefficient (up to >?6 dB), random fluctuations in echo level (5.5 dB for a Rayleigh distribution), and sonar calibration (device dependent). The magnitudes of these uncertainty sources vary based on how these effects are compensated for during data acquisition and processing. Various cases (no compensation, partial compensation and full compensation) for seafloor insonified area, transmission losses and random fluctuations were modeled to estimate their uncertainties in different scenarios. Uncertainty related to the seafloor insonified area can be reduced significantly by accounting for seafloor slope during backscatter processing while transmission losses can be constrained by collecting full water column absorption coefficient profiles (temperature and salinity profiles). To reduce random fluctuations to below 1 dB, at least 20 samples are recommended to be used while computing mean values. The estimation of uncertainty in backscatter measurements is constrained by the fact that not all instrumental components are characterized and documented sufficiently for commercially available MBES. Further involvement from manufacturers in providing this essential information is critically required.  相似文献   

Dating of small gully formation and establishing erosion rates in old gullies under forest by means of anatomical changes in exposed tree roots (Southern Poland)     

Ireneusz Malik   《Geomorphology》2008,93(3-4):421-436

Small gullies occur in forested gully systems on the undulating loess plateau in southern Poland. The old gully hillslopes are mainly covered with 200-year old beech trees in contrast with the surface of the summit plateau, which is cultivated agricultural land. Beech roots are exposed in the gullies through erosion. Wood vessels in the root tree rings divide into early wood and late wood and, after the roots are exposed, start to make fewer vessels. These anatomical changes in root tree rings allow us to date erosion episodes.Small gullies form in a different manner on the valley floor and on hillslopes. In valley bottoms, erosion features are often formed at some distance from one another, and in time small gullies combine to form a single, longer one. Depending on local conditions, such as the hillslope profile, hillslopes may exhibit headward erosion or may be eroded downwards. Hilllope gullies may be transformed into side valleys as a result of gradual widening and deepening.Dating the exposure of roots indicates that small gullies had already formed in the valley system by 1949. Intensive gully erosion was recorded between 1984 and 2002, during intense precipitation in 1984 and, of particular note, during the extraordinary flood of 1997 which affected all of Central Europe. The mean rate of small gully erosion in the old gully system studied is 0.63 m/year. On hillslopes the mean gully erosion rate is 0.21–0.52 m/year, and on the valley bottoms 0.18–1.98 m/year. High bottom erosion rates resulted from the emergence of long gullies during the erosion episodes in 1984 and 1997. Sheet flow in valley floors intensifies at times of heavy rainfall which causes long gullies to form.Taking into account the fact that conditions favoured erosion, the rate at which the old gullies under forest were transformed should be considered slow. New side gullies form slowly within the valley and it appears that if erosion progressed at the rate observed, new side valleys would take a few hundred years to form.  相似文献   

Potential Risk Assessment of Metal Consumption in Food Crops Irrigated with Wastewater          下载免费PDF全文

Muhammad U. Khan  Said Muhammad  Riffat N. Malik 《洁净——土壤、空气、水》2014,42(10):1415-1422

  相似文献   

Coupling between landslides and eroding stream channels reconstructed from spruce tree rings (examples from the Carpathians and Sudetes – Central Europe)          下载免费PDF全文

Małgorzata Wistuba  Ireneusz Malik  Krzysztof Wójcicki  Patrycja Michałowicz 《地球表面变化过程与地形》2015,40(3):293-312

The analysis of the positive feedback between landslides and erosion requires determination of the precise temporal and spatial relations between events of colluvium delivery and fluvial erosion. In our study we use decennial datasets on the occurrence of landsliding and erosion achieved through dendrochronological methods. Four sites covering areas of landslide slopes and adjacent valley floors with stream channels were studied. Landsliding on slopes was dated from the tree‐ring eccentricity developed in stems tilted due to bedrock instability. Erosion in channels was dated using the wood anatomy of roots exposed by erosion of the soil cover. Analysis of the temporal relations between dated landsliding, erosion and precipitation record has revealed that two types of repeating sequences can be observed: (1) rainfall → landsliding → erosion; (2) rainfall → erosion → landsliding. These sequences are an indication of the occurrence of slope‐channel positive feedback in the sites studied. In the first type, landsliding triggered by rainfall delivers colluvia into the valley floor and causes its narrowing, which in turn causes increased erosion. In the second type erosion triggered by rainfall disturbs the slope equilibrium and causes landsliding. Landsliding and erosion, once triggered by precipitation, can occur alternately in years with average precipitation and reinforce one another. Bidirectional coupling between landsliding and channel erosion was shown notably through the effects of channel shifting and forced sinuosity and by increased erosion of the slopes opposite the active landslides. Observations also suggest that the repetition of sequences described over longer periods of time can lead to a general widening of the valley floor at the expense of slopes and to a gradual change of the valley cross‐profile from narrow, V‐shaped into a wide flat‐bottomed. Thus landsliding–erosion coupling/positive feedback was recognized as an important factor shaping hillslope–valley topography of the mid‐mountain areas studied. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

End bearing capacity comparison of screw pile with straight pipe pile under similar ground conditions     

Adnan Anwar Malik  Jiro Kuwano  Shinya Tachibana  Tadashi Maejima 《Acta Geotechnica》2017,12(2):415-428

In the present study, the end bearing capacity of screw and straight pipe pile under similar pile tip area and ground conditions were investigated. The effect of increasing overburden pressure was also considered in this research. Pile load tests on close-ended screw and straight pipe piles were conducted in the small scale. Dry Toyoura sand was used to develop the model ground. The sand was compacted at relative density of 70, 80 and 92 %. It was observed that in case of straight pipe pile, load settlement curve plunges downward without increase in load around settlement equals to 10 % of pile tip diameter, whereas in case of screw pile, the load settlement curve plunges around settlement equals to 15 % of pile tip diameter. Moreover, the screw piles having helix-to-shaft diameter ratio 2–4.1 showed 2–12 times higher end bearing capacity than straight pipe piles with similar pile shaft diameter. It was also observed from the test results that the end bearing capacity of single-helix screw pile was in average 16.25 % less than straight pipe pile with similar pile tip area and ground conditions irrespective of the effect of increasing overburden pressure.  相似文献   

Nonlinear waves in superposed fluids     

R. Kant  S. K. Malik 《Astrophysics and Space Science》1982,86(2):345-360

A weakly nonlinear theory of wave propagation in superposed fluids in the presence of magnetic fields is presented in this paper. We derive the equations governing the evolution of the amplitude of the progressive as well as the standing waves. It is demonstrated that the waves can be unstable against modulation in the presence of the magnetic fields. We also obtain the nonlinear cut off wave number which separates the region of stability from instability.  相似文献