Instantaneous Removal Research Articles

Drying behaviors of low-rank coal under negative pressure: Kinetics and model

ABSTRACTThe drying behaviors of low-rank coal (LRC) under negative pressure were studied with a vacuum-drying oven under different pressures and temperatures. The results confirmed the feasibility of using the Page model to predict the drying behaviors of LRC under negative pressure. A new ideal radical ball model was proposed to further qualitatively analyze the influences of pressure and temperature on the drying behaviors. Reasoning based on the radical ball model combining the Kelvin formula, Fick’s first law of diffusion, Knudsen’s diffusion law, and transition diffusion region suggests that a higher negative pressure and temperature leads to a higher maximum dehydration rate, that larger pressure and temperature gradients cause smaller critical moisture contents, and that decreases in the drying pressure and increases in the temperature increase the instantaneous removal rate of bound water.

Detection of transience in eroding landscapes

AbstractPast variations in climate and tectonics have led to spatially and temporally varying erosion rates across many landscapes. In this contribution I examine methods for detecting and quantifying the nature and timing of transience in eroding landscapes. At a single location, cosmogenic nuclides can detect the instantaneous removal of material or acceleration of erosion rates over millennial timescales using paired nuclides. Detection is possible only if one of the nuclides has a significantly shorter half‐life than the other. Currently, the only practical way of doing this is to use cosmogenicin situcarbon‐14 (14C) alongside a longer lived nuclide, such as beryllium‐10 (10Be). Hillslope information can complement or be used in lieu of cosmogenic information: in soil mantled landscapes, increased erosion rates can be detected for millennia after the increase by comparing relief and ridgetop curvature. This technique will work as long as the final erosion rate is greater than twice the initial rate. On a landscape scale, transience may be detected based upon disequilibria in channel profiles or ridgetops, but transience can be sensitive to the nature of transient forcing. Where forcing is periodic, landscapes display differing behavior if forcing is driven by changes in base level lowering rates versus changes in the efficiency of either channel or hillslope erosion (e.g. driven by climate change). Oscillations in base level lowering lead to basin averaged erosion rates that reflect a long term average erosion rate despite strong spatial heterogeneity in local erosion rates. This averaging is reflected in10Be concentrations in stream sediments. Changes in hillslope sediment transport coefficients can lead to large fluctuations in basin averaged erosion rates, which again are reflected in10Be concentrations. The variability of erosion rates in landscapes where both the sediment transport and channel erodibility coefficients vary is dominated by changes to the hillslope transport coefficient. Copyright © 2016 John Wiley & Sons, Ltd.

An in situ GISAXS study of selective solvent vapor annealing in thin block copolymer films: Symmetry breaking of in‐plane sphere order upon deswelling

ABSTRACTThin films of asymmetric poly(styrene‐b‐4‐vinylpyridine) (PS‐b‐P4VP) block copolymers are studied by means of in situ grazing‐incidence small‐angle X‐ray scattering (GISAXS) during solvent vapor annealing in tetrahydrofuran, a solvent selective for the PS majority block of the copolymer. Upon swelling, PS‐b‐P4VP block copolymers form hexagonal arrays of spherical P4VP microdomains in a PS matrix in films 7–9 layers thick. Deswelling the films induces a transition from hexagonal to face‐centered orthorhombic (fco) symmetry, which is stable only at ∼7 layers of spherical microdomains. Dry films show co‐existing hexagonal and orthorhombic symmetries when the solvent is removed slowly, whereas instantaneous solvent removal suppresses the fco structure, resulting in films with only hexagonal structure. The in‐plane order of microdomains is significantly deteriorated in dry films independent of the solvent removal rate.Spherical block copolymer microdomains are known to undergo a transition from hexagonal to orthorhombic packing in isothermally annealed thin films when the number of sphere layers is increased from 4 to 5. In this paper, in situ GISAXS experiments reveal that a similar transition occurs during solvent vapor annealing in a selective solvent. Interestingly, the transition from hexagonal to orthorhombic packing of spheres occurs as solvent is removed from a thin block copolymer film. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 331–338

Biodegradation of the herbicide Diuron in a packed bed channel and a double biobarrier with distribution of oxygenated liquid by airlift devices: influence of oxygen limitation

From agricultural soils, where the herbicide Diuron has been frequently applied, a microbial community capable of degrading Diuron and 3,4-dichloroaniline was obtained. The volumetric rates and degradation efficiencies of Diuron and 3,4-DCA were evaluated in two distinct biofilm reactors, which differ in their operating conditions. One is a horizontal fixed bed reactor; plug-flow operated (PF-PBC) with severe limitation of oxygen. In this reactor, the air was supplied to an equalizer reservoir at the start of the PF-PBC reactor. The other is a compartmentalized aerobic biobarrier with internal recirculation of liquid aerated through airlift devices (ALB), continuously or intermittently operated. Both reactors were inoculated with a microbial community capable of degrading Diuron, isolated from a sugarcane field. In the oxygen-limited PF-PBC reactor, 3,4-DCA accumulation was detected, mainly in the middle zone of the packed channel. On the contrary, in the fully aerobic ALB reactor, minimal accumulation of catabolic byproducts was detected, and high Diuron removal efficiencies and removal rates were obtained when it was continuously operated in steady-state conditions. Additionally, the influence of oxygen limitation on the kinetic behavior of the PF-PBC reactor was determined, and a method to estimate the local removal rates of Diuron RV,CD along the plug-flow channel is described. It was observed that the local values of the instantaneous removal rate of Diuron dCD/dt are high in the aerobic region of the PF-PBC reactor; but, suddenly decay in the reactor zones limited by dissolved oxygen.

Lightning strike thermal damage model for glass fiber reinforced polymer matrix composites and its application to wind turbine blades

A physics-based model describing the thermal interaction between a lightning channel and a composite structure has been developed. The model includes: (i) spatial and temporal evolution of the lightning channel as a function of the electric current waveform; (ii) temporary and spatially non-uniform heat flux generated at the composite structure, where the heat flux is an explicit function of the electric current waveform and the instant lightning channel radius; (iii) nonlinear transient heat transfer problem formulation for layered anisotropic composites that accounts for temperature-dependent material properties, a moving boundary of the expanding lightning channel, and phase transition moving boundary associated with instantaneous material removal due to sublimation. The model is applied for evaluation of thermal damage of the tip glass fiber reinforced polymer matrix composite panel of the Sandia 100-meter All-glass Baseline Wind Turbine Blade (SNL 100-00) subjected to lightning strike.

Progressive collapse resisting capacity of reinforced concrete load bearing wall structures

Reinforced concrete (RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the “load factor” parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.

Dynamic Performance of Flush End-Plate Beam-Column Connections and Design Applications in Progressive Collapse

An experimental program was conducted in this study to investigate the dynamic behavior of flush end plate steel beam-column cruciform connections following instantaneous removal of a central supporting column. The dynamic tests were performed by using a quick-release mechanism to simulate sudden column-removal scenarios. In the test program, the geometries of the flush end-plate connections remained unchanged but subjected to five different magnitudes of uniformly distributed load. Another five quasi-static tests were also carried out for comparison with the dynamic response and investigation of the dynamic increase factors (DIF). Test results showed that the release-time durations of the column support force were approximately 30 ms for all five dynamic tests. For the same initial applied dead loads, the maximum dynamic displacement was significantly increased compared to the corresponding quasi-static displacement. In order to observe the full dynamic performance of the tested connection until final failure, a general-purpose finite-element software was used to conduct the three-dimensional numerical simulations. Comparison results showed that the numerical model could accurately simulate the monotonic quasi-static test results and the dynamic test results under sudden column removal. Subsequently, a series of parametric studies was conducted to investigate the connection behavior considering the load-release time, different loading methods, and the magnitude of uniform distributed load. By comparing the full dynamic response of the flush end-plate connection with its corresponding quasi-static response, both the displacement-based DIF and force-based DIF could be respectively determined. The paper also addresses which DIF is more appropriate for the design of structures to resist progressive collapse.

Investigations of nonlinear dynamic performance of top-and-seat with web angle connections subjected to sudden column removal

It is well known that progressive collapse is a complicated dynamic process with geometry and material nonlinearities. Sudden column removal scenario is a simple yet effective method for analysis and design of structures to mitigate progressive collapse. The main objective of this study is to investigate the dynamic performance of top-and-seat with web angle (TSWA) steel beam–column connections under progressive collapse condition. This type of connection represents typical bolted cleat connections with excellent ductility. Each specimen consisted of two adjoining beams pinned at the far ends and connected to a middle column stub. Five dynamic tests for the TSWA connections subjected to sudden removal of the middle columns were conducted in Nanyang Technological University. Another five corresponding static tests were also carried out for comparison with the dynamic behaviour. Test results showed that the release-time durations of the column support force were around 30ms for all the five dynamic tests. Transient dynamic responses with free vibrations were observed for the connections following instantaneous removal of the middle columns. The maximum dynamic displacement was significantly increased compared to the static connection response. In addition, numerical simulations were also conducted using the general-purpose finite element software ABAQUS. The three-dimensional finite element model was validated by comparing the simulation results against the test data. Parametric studies were carried out to investigate the full dynamic connection performance and its structural resistance under push-down analysis to simulate progressive collapse. By comparing the full dynamic response with its corresponding quasi-static response, both the displacement-based dynamic increase factor (DIF) and force-based DIF were investigated, respectively. The paper ends with some discussions on practical applications of displacement-based DIF and force-based DIF.

Resistance of Flat-Plate Buildings against Progressive Collapse. II: System Response

AbstractUsing a macromodeling approach and alternate path method, dynamic and static analyses are performed to assess the progressive collapse resistance of a multistory reinforced concrete flat-plate building lacking structural integrity reinforcement in the slabs. Two loading scenarios, instantaneous removal of an exterior column and interior column, are considered. The dynamic analyses examine the potential of progressive collapse of the building, the dynamic demands on global and local nonlinear deformations, the effects of strain rate in materials, and the development of compressive membrane action. The effectiveness of an energy-based nonlinear static analysis procedure is examined for equivalently estimating the peak dynamic global and local responses caused by sudden column removal. The analyses indicate that older flat-plate buildings are vulnerable to progressive collapse; the combined effects from strain rate and compressive membrane action can significantly increase punching resistance; energy...

Conditional possibility of spacecraft propulsion at superluminal speeds

The concept at hand deals primarily with the application of the conditional replacement technique (CRT) (Pais, 1991) to Special Relativity Theory. It is observed that under certain physical conditions, the singularity expressed by the relativistic stretch factor 'gamma' as the spacecraft's speed (v) approaches the speed of light (c), is no longer present in the physical picture. This involves the instantaneous removal of energy-mass from the system (spacecraft) when the spacecraft's speed reaches v = c/2. Hence under such conditions, faster than light spacecraft propulsion, is feasible. The original concept at hand does not violate the Special Theory of Relativity, it rather builds on its foundations.

Cirrus and water vapour transport in the tropical tropopause layer – Part 2: Roles of ice nucleation and sedimentation, cloud dynamics, and moisture conditions

Abstract. A high-resolution, two-dimensional numerical model is used to study the moisture redistribution following homogeneous ice nucleation induced by Kelvin waves in the tropical tropopause layer (TTL). We compare results for dry/moist initial conditions and three levels of complexity for the representation of cloud processes: complete microphysics and cloud radiative effects, likewise but without radiative effects, and instantaneous removal of moisture in excess of saturation upon nucleation. Cloud evolution and moisture redistribution are found to be sensitive to initial conditions and cloud processes. Ice sedimentation leads to a downward flux of water, whereas the cloud radiative heating induces upward advection of the cloudy air. The latter results in an upward (downward) flux of water vapour if the cloudy air is moister (drier) than the environment, which is typically when the environment is subsaturated (supersaturated). Only a fraction (~25% or less) of the cloud experiences nucleation. Post-nucleation processes (ice depositional growth, sedimentation, and sublimation) are important to cloud morphology, and both dehydrated and hydrated layers may be indicators of TTL cirrus occurrence. The calculation with instantaneous removal of moisture not only misses the hydration but also underestimates dehydration due to (i) nucleation before reaching the minimum saturation mixing ratio, and (ii) lack of moisture removal from sedimenting ice particles below the nucleation level. The sensitivity to initial conditions and cloud processes suggests that it is difficult to reach generic, quantitative estimates of cloud-induced moisture redistribution on the basis of case-by-case calculations.

Erratum to: Numerical study of a chemical method applied to instantaneous heat removal under high heat flux

Erratum to: Numerical study of a chemical method applied to instantaneous heat removal under high heat flux

Interpreting aerosol lifetimes using the GEOS-Chem model and constraints from radionuclide measurements

Abstract. Aerosol removal processes control global aerosol abundance, but the rate of that removal remains uncertain. A recent study of aerosol-bound radionuclide measurements after the Fukushima Daiichi nuclear power plant accident documents 137Cs removal (e-folding) times of 10.0–13.9 days, suggesting that mean aerosol lifetimes in the range of 3–7 days in global models might be too short by a factor of two. In this study, we attribute this discrepancy to differences between the e-folding and mean aerosol lifetimes. We implement a simulation of 137Cs and 133Xe into the GEOS-Chem chemical transport model and examine the removal rates for the Fukushima case. We find a general consistency between modelled and measured e-folding times. The simulated 137Cs global burden e-folding time is about 14 days. However, the simulated mean lifetime of aerosol-bound 137Cs over a 6-month post-accident period is only 1.8 days. We find that the mean lifetime depends strongly on the removal rates in the first few days after emissions, before the aerosols leave the boundary layer and are transported to altitudes and latitudes where lifetimes with respect to wet removal are longer by a few orders of magnitude. We present sensitivity simulations that demonstrate the influence of differences in altitude and location of the radionuclides on the mean lifetime. Global mean lifetimes are shown to strongly depend on the altitude of injection. The global mean 137Cs lifetime is more than one order of magnitude greater for the injection at 7 km than into the boundary layer above the Fukushima site. Instantaneous removal rates are slower during the first few days after the emissions for a free tropospheric versus boundary layer injection and this strongly controls the mean lifetimes. Global mean aerosol lifetimes for the GEOS-Chem model are 3–6 days, which is longer than that for the 137Cs injected at the Fukushima site (likely due to precipitation shortly after Fukushima emissions), but similar to the mean lifetime of 3.9 days for the 137Cs emissions injected with a uniform spread through the model's Northern Hemisphere boundary layer. Simulated e-folding times were insensitive to emission parameters (altitude, location, and time), suggesting that these measurement-based e-folding times provide arobust constraint on simulated e-folding times. Despite the reasonable global mean agreement of GEOS-Chem with measurement e-folding times, site by site comparisons yield differences of up to a factor of two, which suggest possible deficiencies in either the model transport, removal processes or the representation of 137Cs removal, particularly in the tropics and at high latitudes. There is an ongoing need to develop constraints on aerosol lifetimes, but these measurement-based constraints must be carefully interpreted given the sensitivity of mean lifetimes and e-folding times to both mixing and removal processes.

Effect of Hydraulic Retention Time and Wastewater Temperature on Treatment Efficiency of Upflow Anaerobic Filter Treating Campus Domestic Wastewater

The study examined the removal efficiency of upflow anaerobic filter reactor fed continuously with campus domestic wastewater at different hydraulic retention time and wastewater temperature. The reactor was filled with non woven filter materials and operated at hydraulic retention time ranging from 1 to 6 days and wastewater temperature ranging from 20 to 30C. At that operating condition, the result revealed no significant difference for Carbonaceous (COD) and nutrients materials except there was significant production of gas. The result revealed that increase in HRT and wastewater temperature improves removal performance of the reactor. The overall reactor removal efficiency for COD, TN, NH₄⁺-N, NO₃^-N and TP concentration were 51, 22, 21, 28 and 10% and 61 35, 37, 49 and 27% in the anaerobic and anoxic columns, respectively. The experimental system was capable of instantaneous removal of the carbonaceous, nitrogenous and phosphorous compounds.

Neural Correlates of Illusory Line Motion

Illusory line motion (ILM) refers to a motion illusion in which a flash at one end of a bar prior to the bar's instantaneous presentation or removal results in the percept of motion. While some theories attribute the origin of ILM to attention or early perceptual mechanisms, others have proposed that ILM results from impletion mechanisms that reinterpret the static bar as one in motion. The current functional magnetic resonance imaging study examined participants while they made decisions about the direction of motion in which a bar appeared to be removed. Preceding the instantaneous removal of the bar with a flash at one end resulted in a motion percept away from the flash. If this flash and the bar's removal overlapped in time, it appeared that the bar was removed towards the flash (reverse ILM). Independent of the motion type, brain responses indicated activations in areas associated with motion (MT+), endogenous and exogenous attention (intraparietal sulcus, frontal eye fields, and ventral frontal cortex), and response selection (ACC). ILM was associated with lower percept scores and higher activations in ACC relative to real motion, but no differences in shape-selective areas emerged. This pattern of brain activation is consistent with the attentional gradient model or bottom-up accounts of ILM in preference to impletion.

Progressive collapse testing and analysis of a steel frame building

A steel frame building was tested by physically removing four first story columns from one of the perimeter frames prior to building's scheduled demolition. The purpose of the field experiment was to simulate sudden column loss in buildings that may cause progressive collapse. Another objective was to investigate the load redistribution within the building after each column removal. The measured experimental data and observed performance of the building was valuable because it is very difficult and cost-prohibitive to build and test three-dimensional full-scale building specimens in the laboratory. Generally, the design code requirements prescribe simplified analysis procedures involving instantaneous removal of certain critical columns in a building. Design methodologies and simplified analysis procedures recommended in the design guidelines were also evaluated using the experimental data. In this study, two and three-dimensional models of the building were developed and analyzed to simulate the progressive collapse response. The effectiveness of the analysis procedures was evaluated by comparing with the experimental data.

Progressive Collapse Assessment of RC Structures under Instantaneous and Gradual Removal of Columns

The subject of progressive collapse assessment in RC structures has been concerned in various studies. In contrast, most of these studies have attended to a scenario in which an instantaneous removal of a column due to unexpected impact or explosion has occurred. The present study addresses progressive collapse in RC structures resulting from both instantaneous and gradual removal of columns. The scenario for a gradual removal is the result of slow decreasing strength due to fire propagation in a specific zone of structure which is partially fire-proved. A five-story building model was selected as a case study for which the nonlinear model is later developed. Vertical displacement in the upper node of the removed column, redistribution of forces after removing the column, plastic deformations in adjoining elements, and the stress imposed on the sections of the beams adjacent to the removed column in both instantaneous and gradual cases are studied.

Onyx embolization using dual-lumen balloon catheter: Initial experience and technical note

Onyx as an embolization agent for the management of vascular malformation is well established. We report our initial experience with dimethyl-sulphoxide (DMSO) compatible double lumen balloon catheters used for Onyx embolization. Between December 2011 and March 2013, we treated 22patients aged between 1.5 to 70years with two types of DMSO compatible dual-lumen balloon catheters (Scepter C and Ascent) to treat dural arteriovenous fistulas, brain arteriovenous malformation (AVM) with dural feeders, mandibular, facial, lingual, vertebral and paravertebral AVMs. The catheter has good navigability, compliant balloon on inflation formed a "plug" that has more resistance than Onyx plug enhancing better penetration. During injection, the balloon remained stable without spontaneous deflation or rupture and withstood the pressure build-up well. The retrieval of the catheter in most cases took less than a minute (19/28) while in five, it was less than five minutes and in the remaining four, it was longer that includes a trapped catheter on prolonged attempted retrieval resulted in an epidural hematoma, requiring emergent surgical evacuation. The fluoroscopy time is reduced, as we do not form a proximal onyx plug, the injection time is shorter along with easy and instantaneous removal of the catheter after balloon deflation in most cases. Dual-lumen balloon catheter Onyx embolization is a safe and effective technique. Currently, an important tool to circumvent some of the shortcomings associated with Onyx embolization. The catheter has good navigability, the balloon has stability, tolerance, enhances penetrability. It is easy to retrieve the microcatheter. With the experience gained, and with more compliant balloon catheters available, this technique can be applied to cerebral vessels in near future.

Experimental and analytical progressive collapse assessment of a steel frame building

A field experiment and numerical simulations were performed to investigate the progressive collapse potential of an existing steel frame building. Four first-story columns were physically removed from the building to understand the subsequent load redistribution within the building. Experimental data from the field tests were used to compare and verify the computational models and simulations. Due to the scarcity of data from full-scale tests, the experimental data produced during this research is a valuable addition to the state of knowledge on progressive collapse of buildings. The progressive collapse design guidelines typically recommend simplified analysis procedures involving instantaneous removal of specified critical columns in a building. This paper investigates the effectiveness of such commonly used progressive collapse evaluation and design methodologies through numerical simulation and experimental data.

Numerical study of a chemical method applied to instantaneous heat removal under high heat flux

In this study, a method of chemical cooling is put forward, that is, C–CO2 endothermic reaction is applied to instantaneous heat removal under high heat flux. A method in which theoretical research is in combination with numerical simulation is used to study C–CO2 endothermic reaction. In comparison with the theoretically computational results, numerical code is validated. A high heat flux of 500 W/cm2 is applied to the research of the heat dissipation characteristics of C–CO2 endothermic reaction. The theoretical calculation results show that, under a certain temperature and pressure condition, the C–CO2 chemical endothermic reaction could remove heat from the system promptly; the product CO could be used as a supplementary medium of power source for cycling. Compared with water phase change, the C–CO2 endothermic reaction appears to have stronger heat removal ability. “Species Transport” module in FLUENT was adopted to simulate the reaction. Under the same temperature and pressure condition, the numerical simulation results are found to be well congruous with theoretical results. The C–CO2 endothermic reaction could make a high temperature in the reaction system due to a high heat flux reduce to a low temperature (below zero) promptly. The heat removal and reaction time are in consistence with theoretical calculation.