共查询到20条相似文献，搜索用时 459 毫秒
1.
V. V. Adushkin P. G. Weidler A. N. Dubovskoi L. M. Pernik S. I. Popel F. Friedrich 《Geology of Ore Deposits》2010,52(5):373-380
The properties of nano- and microparticles (60 nm-200 μm) of the dust formed by mass blasting in the iron ore open pit of
the Lebedinsky Mining and Concentrating Combine have been studied. Data on the morphology of particles, their magnetic properties,
mineralogy, and dimensions have been obtained. Quartz, magnetite, and mica were identified among these particles. The dust
mostly consisted of fragmented iron ore formation from the rock massif involved in the blasting. 相似文献
2.
We use JHKLM photometric data obtained in 1998–2001 to model the dust envelope of the unique object FG Sge, which formed around the star after several consecutive cycles of dust condensation beginning in Autumn 1992. Models with a spherically symmetric, extended envelope consisting of a mixture of spherical particles of amorphous carbon and silicon carbide with an MRN size distribution were fitted to match the mean observed spectral energy distributions of FG Sge during brightness maximum and minimum after 1998 for two values of the luminosity and effective temperature of the central star. The stellar-wind parameters and mass-loss rate have been estimated in each case. The observational data for the brightness maximum and minimum cannot be described by models with a fixed luminosity or fixed distance to the star. This is a consequence of the object’s unusual behavior, with synchronous flux decreases in all the observed bands. The inability of the model to adequately describe the minimum-brightness state is probably associated with the abrupt disruption of the spherical symmetry of the envelope due to the formation of a small, dense dust cloud in the line of sight. 相似文献
3.
Long-term (1984–2008) JHKLM photometry for 254 objects is presented. The observations were carried out in the standard JHKLM photometric system using an original method and a modern IR photometer designed and built at the Sternberg Astronomical Institute.
Our program of studies included searches for and studies of relatively hot circumstellar dust envelopes. The most important
results obtained using these observations include the following. We have detected relatively hot dust envelopes in a number
of objects for the first time, including the RCB star UV Cas, RX Cas, several classical symbiotic stars, etc. A model has
been calculated for the dust envelope of FG Sge, which formed around the star as a result of several successive cycles of
dust condensation beginning in Autumn 1992. Several dust-condensation episodes have been traced in the envelopes of symbiotic
systems (CH Cyg, V1016 Cyg, HM Sge, etc.), as well as the role of the hot component in the formation of the dust envelopes.
We have established from variations of the IR emission that the cool components in the symbiotic novae V1016 Cyg and HM Sge,
and possibly CH Cyg, are Miras. The binarity of V1016 Cyg and HM Sge has also been firmly established. The variability of
a whole series of object has been studied, including the stellar components of close binary systems and several dozen Mira
and semi-regular variables. The ellipsoidality of the components in the RX Cas system (a prototype W Ser star) and the cool
component in the symbiotic systems CI Cyg and BF Cyg has been firmly established. We have obtained the first IR light curve
for the eclipsing system V444 Cyg (WN5+O6), and determined the wavelength dependence of the obtained parameters of the WN5
star. Analysis of the IR light curves of several novae indicate the condensation of dust envelopes in the transition periods
of Cygnus 1992, Aquila 1993, and Aquila 1995. The IR light curve of R CrB has been obtained over a long period and analyzed.
IR observations of the nova-like variable V4334 Sgr have been carried out over four years, over which the star passed through
four stages during its motion along its post-AGB evolutionary track; the star’s bolometric flux and optical depth of its dust
envelope have been estimated, and the structure and mass of the dust layer determined. We have analyzed the IR variability
of the symbiotic star V407 Cyg over 14 years, and found its cool component to be a Mira with a period of 745 days. The observed
pulsations and trend are associated with the luminosity and temperature variations of the Mira, as well as the optical depth
of the dust envelope. The size of the dust grains and mass-loss rate of the Mira have been determined. We have obtained JHKL light curves for the Seyfert galaxy NGC 4151 over 23 years. The IR brightness of the galaxy grew from 1985 through 1996 (by
∼0.9
m
at 1.25 μm, ∼1
m
at 1.65 μm, ∼1.1
m
at 2.2 μm, and ∼1.3
m
at 3.5 μm), while the galaxy simultaneously reddened. The “cool” variable source in NGC 4151 was still in the active state
in 1998, although its luminosity had decreased by approximately 15%–20%. If the “cool” component of the variable source in
this galaxy is a dust envelope heated by the central “hot” source, it should be optically thin to the radiation of this source:
its mean optical depth is in the range 0.05–0.15. Emission from dust particles heated to temperatures of 600–800 K was observed
in the near IR at a distance of several parsecs from the nucleus during the period of activity in 1995–1998; the inferred
mass of emitting dust was 5–20 M
⊙. In 1994–2003, we observed a tendency for NGC 4151 to become bluer at 1.25–1.65 μm while simultaneously reddening at 2.2–3.5
μm. Beginning in Autumn 2000, the galaxy began to emerge from a minimum, which lasted from March 2000 through April 2001 in
the IR; a flare of the galactic nucleus was observed and followed in detail in the IR in this same period. We confirm the
IR variability of the nucleus of the Seyfert galaxy NGC 1068, which can be located in various stages of activity. The variability
of NGC 1068 is associated with a complex source. A periodic component has been detected in the J brightness variations of the oxygen Mira V2108 Oph; we have shown that this star is immersed in a fairly dense dust envelope,
and have calculated amodel for this envelope. We have calculated an (axially symmetrical) dust-envelope model for the carbon
semi-regular variable RWLMi with a density distribution characteristic for the “superwind” stage. This envelope model is able
to reproduce the observed fluxes over the entire observable spectrum, and displays a good agreement with the observational
data. The three hot supergiants V482 Cas, QZ Sge, and HD 338926 may be variable in the IR. Long-term photometry of eight planetary
nebulae in the near IR (1.25–5 μm) has enabled us to firmly establish the IR brightness and color variability of these nebulae
on time scales from several tens of days to six-to-eight years. We have analyzed long-term JK photometry of the X-ray binary Cyg X-1 (V1357 Cyg). Periodicity with a characteristic time scale of ∼11.5 years is visible
in the JK brightness variations of Cyg X-1 in 1984–2007, possibly due to periodic variations of the temperature, radius and luminosity
of the optical component of the binary with P ∼11.5 yr. Fourteen-year IR light curves of five RV Tau stars (R Sge, RV Tau, AC Her, V Vul, and R Sct) and the yellow supergiant
and protoplanetary-nebula candidate V1027 Cyg have been analyzed. A spherically symmetrical dust-envelope model has been calculated
for V1027 Cyg. 相似文献
4.
Identifying the spatial extent of volcanic ash clouds in the atmosphere and forecasting their direction and speed of movement has important implications for the safety of the aviation industry, community preparedness and disaster response at ground level. Nine regional Volcanic Ash Advisory Centres were established worldwide to detect, track and forecast the movement of volcanic ash clouds and provide advice to en route aircraft and other aviation assets potentially exposed to the hazards of volcanic ash. In the absence of timely ground observations, an ability to promptly detect the presence and distribution of volcanic ash generated by an eruption and predict the spatial and temporal dispersion of the resulting volcanic cloud is critical. This process relies greatly on the heavily manual task of monitoring remotely sensed satellite imagery and estimating the eruption source parameters (e.g. mass loading and plume height) needed to run dispersion models. An approach for automating the quick and efficient processing of next generation satellite imagery (big data) as it is generated, for the presence of volcanic clouds, without any constraint on the meteorological conditions, (i.e. obscuration by meteorological cloud) would be an asset to efforts in this space. An automated statistics and physics-based algorithm, the Automated Probabilistic Eruption Surveillance algorithm is presented here for auto-detecting volcanic clouds in satellite imagery and distinguishing them from meteorological cloud in near real time. Coupled with a gravity current model of early cloud growth, which uses the area of the volcanic cloud as the basis for mass measurements, the mass flux of particles into the volcanic cloud is estimated as a function of time, thus quantitatively characterising the evolution of the eruption, and allowing for rapid estimation of source parameters used in volcanic ash transport and dispersion models.
相似文献5.
D. A. Mendis 《Journal of Earth System Science》1984,93(3):177-188
Recent spacecraft observations of the Saturnian and Jovian ring systems have highlighted a plethora of interesting new phenomena
associated with those regions containing fine (micron and sub-micron sized) dust. Recognizing that these dust grains, by virtue
of being immersed within the planetary magnetospheres, are electrostatically charged to the point that they experience comparable
gravitational and electric forces, a new “gravito-electrodynamic” theory has been developed to describe their dynamics. This
theory has been successful in explaining all these phenomena in a systematic way. In this review, the basic model and its
range of validity are outlined, and its application to the Saturnian and Jovian ring systems are discussed. 相似文献
6.
7.
We describe the formation of carbon dust in binary systems with hot components as a result of the collisions of clouds in a two-phase stellar-wind model. Calculations are made for the well studied system WR 140. The collisions lead to the formation of composite clouds and shock waves, with the temperature at the shock front equal to about 3×108 K along both sides of the interface boundary. During isobaric deexcitation to (0.5–0.7)×104 K, the cloud density increases by a factor of several thousand; its thickness in the direction of the shock decreases by the same factor. After deexcitation, the hydrogen inside the composite cloud is in its atomic state, while the carbon remains ionized. The deexcitation is followed by expansion of the cloud, which moves away from both stars. During the first 106 s, its thickness remains relatively small, so that the expansion is one-dimensional. The radiation field inside the cloud decays, resulting in the recombination of the carbon. Further expansion of the cloud leads to adiabatic cooling, and the formation of dust particles becomes possible. After the dimensions of the cloud have become roughly the same in all directions, its expansion is isotropic, so that it becomes transparent within approximately 106 s, and the dust is heated to (1.0–1.4)×103 K, observed as an IR “lare.” The time required for the cloud to move from the exciting star and heat the dust is comparable to the observed delay in the increased IR emission relative to the time of periastron. 相似文献
8.
Considering different mechanical cutting tools for excavation of rock, drilling and blasting is said to be inexpensive and
at the same time most acceptable and compatible to any geo-excavation condition. Depending upon strength properties of in-situ
rock mass, characteristics of joint pattern and required quality of blasting, control blasting techniques viz., pre-split
and smooth blasting are commonly implemented to achieve an undamaged periphery rock-wall. To minimize magnitude of damage
or overbreak, the paper emphasized that in-situ stresses and re-distribution of stresses during the process of excavation
should be considered prior to selection of explosive parameters and implementation of any suitable blast pattern. Rock structure
being not massive in nature, the paper firstly explains the influence of discontinuities and design parameters on smooth-wall
blasting. Considering the empirical equations for estimation of stress wave’s magnitude and its attenuation characteristics
through transmitting medium, the paper has put forward a mathematical model for smooth blasting pattern. The model firstly
illustrates that rock burden for each hole should be sub-divided into thin micro strips/slabs to understand the characteristics
of wave transmission through the medium and lastly with the help of beam theory of structural dynamics have put forward a
mathematical model to analyze and design an effective smooth blasting pattern to achieve an undamaged periphery rock-wall. 相似文献
9.
A dispersion relation has been obtained for waves propagating in an inhomogeneous gas with viscosity and gravity in the direction
of the density gradient. It has been shown that a stationary distribution of isothermal gas is unstable under gravitational—convective
perturbations. It is suggested that the initialand boundary-value problems of the non-stationary dynamics of an isothermal
gas with gravity but without viscosity are incorrect and require regularization, for example, by adding viscosity. The presence
of viscosity does not prevent the development of the Jeans long-wave instability. Numerical experiments based on a fully three-dimensional,
non-stationary numerical code have demonstrated the development of a collapse inside an isothermal cloud. 相似文献
10.
A Non-Ideal Detonation Model for Evaluating the Performance of Explosives in Rock Blasting 总被引：1，自引：0，他引：1
S. Esen 《Rock Mechanics and Rock Engineering》2008,41(3):467-497
Summary A new model to predict the non-ideal detonation behaviour of commercial explosives in rock blasting is presented. The model
combines the slightly divergent flow theory, polytropic equation of state, simple pressure-dependent rate law and statistical
expressions to model the effect of confinement on detonation. The model has been designated as DeNE, an acronym for the Detonics
of Non-ideal Explosives. It is aimed at predicting the detonation state and subsequent rarefaction (Taylor) wave to provide
the pressure history for different explosive, rock type and blasthole diameter combinations. It enables the prediction and
comparison of the performance of commercial explosives in different blasting environments. The unconfined detonation velocity
data has been obtained from the testing of six commercial explosives to calibrate DeNE. A detailed sensitivity analysis has
been conducted to evaluate the model. The model has been validated using the results of hydrocodes as well as measured and
published in-hole detonation velocity data.
Author’s address: Sedat Esen, Metso Minerals Process Technology (Asia-Pacific), Unit 1, 8–10 Chapman Place, Eagle Farm, Qld
4009, Australia 相似文献
11.
阐述了采用控制爆破技术在复杂环境下拆除大型基坑内钢筋混凝土支撑的方法。在特殊的环境条件下进行支撑爆破时,采用预先切断振源、减少单段起爆药量的防震方法以及搭建防护棚的方法,可以有效控制爆破振动、飞石、扬尘对周围的影响。实践证明,采用控制爆破技术拆除大型基坑内钢筋混凝土支撑是安全、高效的。 相似文献
12.
We present a numerical method and the URAN(IA) computer code for two-dimensional, axially symmetric radiative-transfer computations in molecular lines and spectral modeling. The algorithm is based on Monte Carlo computations of the mean radiation intensity and Accelerated Λ Iterations (ALI) to provide self-consistency between the radiation field and molecular excitation. The code is applied to the structure and kinematic properties of the starless core L1544, which is often considered to be the collapsing core of a molecular cloud. This object has been well studied, but none of the one-dimensional models obtained earlier has been able to provide a self-consistent picture of its structure and kinematics. We show that the spectral features of L1544 can be reproduced in a two-dimensional model in which the cloud has an axial ratio of 2: 1, a mean velocity of contraction (collapse) of Vr～50 m/s, and a rotational velocity of up to V φ ～ 200 m/s. We construct the model of L1544 based on a continuous transition from an initially homogeneous cloud to the observed configuration. The velocity of the contraction is appreciably lower than is predicted by one-dimensional dynamical models. We discuss the problems of interpreting observed molecular-line profiles and prospects for developing self-consistent models for the chemical and dynamical evolution of molecular clouds. 相似文献
13.
R. R. Yadav Dilip Kumar Jaiswal Hareesh Kumar Yadav Gulrana 《Environmental Earth Sciences》2012,65(3):849-859
A three-dimensional model for non-reactive solute transport in physically homogeneous subsurface porous media is presented.
The model involves solution of the advection-dispersion equation, which additionally considered temporally dependent dispersion.
The model also account for a uniform flow field, first-order decay which is inversely proportional to the dispersion coefficient
and retardation factor. Porous media with semi-infinite domain is considered. Initially, the space domain is not solute free.
Analytical solutions are obtained for uniform and varying pulse-type input source conditions. The governing solute transport
equation is solved analytically by employing Laplace transformation technique (LTT). The solutions are illustrated and the
behavior of solute transport may be observed for different values of retardation factor, for which simpler models that account
for solute adsorption through a retardation factor may yield a misleading assessment of solute transport in ‘‘hydrologically
sensitive’’ subsurface environments. 相似文献
14.
粉尘释放和沉积机制的研究进展 总被引：3，自引：1，他引：2
风蚀地表释放的粉尘气溶胶在其输送和沉积过程中产生的直接和间接环境效应促进了对其释放和沉积机制的研究.随着土壤风蚀研究的发展,对粉尘释放机制有了较为深入地研究,从简单的经验方程模型发展到目前考虑粉尘释放微观过程的具有清晰物理机制的释放模型,并在大尺度沙尘预报研究中得到了广泛应用.粉尘沉积主要集中于对干沉积和云下清除过程的研究,而对云内清除过程认识不足.简要回顾了粉尘释放和沉积机制研究的发展历史,系统地评述了研究的现状,提出了粉尘释放和沉积模拟研究中存在的问题和今后的发展趋势. 相似文献
15.
16.
According to World Meteorological Organization report in 2015, the southwest of Iran has become one of the dust sources in the region. And the objective of this research is to study the dust storms originating in this region. For this purpose, based on the weather data of 14 stations, the dust storms of the region were investigated, and the dust storm of February 7, 2015, was selected due to its very high concentration of dust particles (66 times the normal values). For the analysis of source areas and storm paths, the FNL data was used. The regional models of Navy Aerosol Analysis and Prediction System (NAAPS), Barcelona Supercomputing Centre-Dust Regional Atmospheric Model 8b (DREAM 8b), Non-hydrostatic Multiscale Model Barcelona Supercomputing Center (NMMB/BSC), and hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) were used to study and analyze the selected storm. The results showed that the dust event in February 8, 2016, has been the result of the polar front jet stream (PJF) caused by western immigrant system that had been over the Sahara in Africa, the deserts of Iraq, Syria, Saudi Arabia, and finally southwest of Iran in making the extreme dust event. According to the Moderate Resolution Imaging Spectroradiometer data and point models of NAAPS, optical depth was very high. The DREAM 8b and NMMB/BSC models confirmed the impact of the local factors and closeness to the dust source regions. The backward tracking of the model with the HYSPLIT model showed three tracks transporting the dust particles to the region. This software also showed that the dust particles occupied an atmospheric tunnel of 1.5 km in diameter. 相似文献
17.
Roohollah Sadeghi Ali Mohebbi Mehdi Baniasadi 《International Journal of Mineral Processing》2011,98(1-2):55-65
In this study, a computational fluid dynamics (CFD) modeling accompanied by experimental field measurements has been applied to study the behavior of aqueous–organic dispersion on the performance of the launder of the settler of the copper solvent extraction plant at the Sarcheshmeh copper complex, Iran. Fluid flow field has been calculated by solving the continuity and Navier Stokes equations along with the standard k-ε turbulence model. The simulation results have been compared with the field measurements data to check the accuracy of the CFD work. The effects of picket fence on the launder performance and pressure drop over the picket fences in the launder have been investigated. The model predicts that by setting the picket fences, flow pattern becomes uniform, and turbulent eddies disappear. The results also show that by installing two picket fences without dam in the launder, the phase separation is improved and the performance of the launder is optimized. 相似文献
18.
Our analysis of JHKLM photometric data obtained in 1978–2003 for the CH Cyg system shows that the “local” dust envelope that formed in the system in 1986 and reached its highest column density in 1996 had largely dispersed by mid-2001, so that the observed brightness of the system’s red giant has returned to its pre-1985 level. The giant’s spectral type varied in the range M6.5–M7.5 in 2001–2003. The optical depth of the dust envelope at 1.25 µm was τ(J)≈0.83 near JD 2450090. The increase in the dust envelope’s optical depth was approximately a factor of 2.3 slower than the decrease. The envelope of CH Cyg can be pictured as a “stationary” dust cloud with an optical depth at λ=1.25 µm of ～0.4 and a dust-grain temperature of ～750–800 K. There was probably an injection of matter into this cloud toward the end of 1985, initiating the condensation of dust grains. The optical depth began to increase and, by 1991, the dust envelope was transformed from a cloud into a local, almost spherically-symmetric envelope with a grain temperature of 750–800 K. Its optical depth reached its maximum in 1996, after which the local envelope began to disperse, becoming a cloud again by 2001. The detected 4000-day variability of the JHK brightness of CH Cyg is in good agreement with a model with an eclipsing binary consisting of two cool giants with effective temperatures differing by approximately 100 K, a luminosity ratio of L(M7)/L(M6)～6.8, and a radius ratio of R(M7)/R(M6)～3.6. The orbital ephemeris is given by JD (Min I)=2444180+4000E. 相似文献
19.
穿层抽放是一些高突矿井常用的瓦斯治理手段,在穿层抽放时采用爆破技术已被证明具有良好的抽放效果。以重庆市南桐矿穿层爆破为背景,建立了穿层深孔爆破数学模型;利用数值计算和现场实测抽放数据相结合的方法,分别研究了各爆破孔、控制孔动应力的变化以及爆破应力场强度与抽放效果的关系。研究结果表明,穿层抽放的特点决定了爆破孔与抽放孔的布孔方式。由于炮孔斜穿煤层,煤层各断面动应力场分布极不均匀,药包中心控制孔所受动应力为控制孔中最大。在南桐矿薄煤层试验条件下,药包长度为3.2 m的爆破孔平均破坏半径为0.57 m,较其他两排炮孔大20%以上。炮孔中药包长度是影响瓦斯抽放量的重要因素。爆破孔的平均单孔抽放量较控制孔高55%,爆破钻场较非爆破钻场平均单孔流量大49%。 相似文献
20.
Chiara Biscarini 《Landslides》2010,7(2):117-124
This paper describes the application of detailed computational fluid dynamics (CFD) to simulate the formation and propagation
of waves generated by the impact of landslide material with water. The problem is schematised as a multiphase–multicomponent
fluid flow: compressible air, water and transported alluvial material. The landslide simulation is performed by means of a
hybrid approach: as a rigid solid body slipping down along an inclined slope until it starts penetrating the water body. The
CFD model solves the Navier–Stokes equations with the RNG k-ɛ turbulence closure scheme and the volume of fluid multiphase
method, which maintains the interface as a sharp front. The governing equations are solved using the commercial CFD code,
FLUENT. The computed results are compared with experimental data reported in the literature. The model is then applied to
simulate the 1958 Lituya bay Tsunami event with a 2D a simplified geometry and the results are compared to others found in
literature. 相似文献