Flux Curves Research Articles

Study of theγ-ray source 1AGL J2022+4032 in the Cygnus region

Identification of gamma-ray-emitting Galactic sources is a long-standing problem in astrophysics. One such source, 1AGL J2022+4032, coincident with the interior of the radio shell of the supernova remnant Gamma Cygni (SNR G78.2+2.1) in the Cygnus Region, has recently been identified by Fermi as a gamma-ray pulsar, LAT PSR J2021+4026. We present long-term observations of 1AGL J2022+4032 with the AGILE gamma-ray telescope, measuring its flux and light curve. We compare the light curve of 1AGL J2022+4032 with that of 1AGL J2021+3652 (PSR J2021+3651), showing that the flux variability of 1AGL J2022+4032 appears to be greater than the level predicted from statistical and systematic effects and producing detailed simulations to estimate the probability of the apparent observed variability. We evaluate the possibility that the gamma-ray emission may be due to the superposition of two or more point sources, some of which may be variable, considering a number of possible counterparts. We consider the possibility of a nearby X-ray quiet microquasar contributing to the flux of 1AGL J2022+4032 to be more likely than the hypotheses of a background blazar or intrinsic gamma-ray variabilty of LAT PSR J2021+4026.

Improved Computation Formula of Thermal Conductivity of Fibrous Porous Materials

For the complexity of convective term, the interior heat transfer is important for the engineering testing of heat conduction of fibrous porous materials. In this paper the heat transfer through the body of fibrous porous materials was simulated with finite volume method. By the simulation, it is found that the total heat flux through the body of fibrous porous materials is a linear function of the thermal conductivity when it is measured by the guarded plate, and some constants in the linear function are related with the thickness and permeability coefficient of the sample. The simulated data are employed to fitting the variation curves of the total heat flux with thermal conductivity, thickness and permeability coefficient, respectively. The improved calculating formula of thermal conductivity for fibrous porous materials is established based on the fitting estimation. Through the experimental, it is demonstrated that the improved calculating formula is more accurate than the original one, which is based on the assumptions of single component continuum material and one dimensional heat transfer.

Boiling regimes in uncoated polydimethylsiloxane microchannels with a fine wire heater

Polydimethylsiloxane (PDMS) is a type of gas permeable media widely used in microfluidic applications. In this work multiphase patterns and boiling curves in PDMS square microchannels were experimentally investigated. Very fine platinum wires with diameter of 50 μm were embedded through the microchannels and serving as heater. The multiphase patterns were visualized by means of high speed CCD camera with microscope. Curves of temperature versus heat flux on the wire heaters were plotted. Based on the evolution of multiphase patterns, five boiling regimes were classified, that is, single phase, bubble formation, slug formation, slug dominated and dry out. Interestingly, the bubbles were generated from the channel walls rather than the heater surface, and so-called “droplets-in-bubble” phenomenon drew attention in which bunches of microdroplets kept forming, growing, and disappearing within the big bubbles. The boiling curves were plotted and compared to boiling in open space and in glass tubes. The heat transfer in the PDMS microchannels got deteriorated when the bubbles formed.

Application of Uintah-MPM to shaped charge jet penetration of aluminum

The capability of the generalized interpolation material point (GIMP) method in simulation of penetration events is investigated. A series of experiments was performed wherein a shaped charge jet penetrates into a stack of aluminum plates. Electronic switches were used to measure the penetration time history. Flash x-ray techniques were used to measure the density, length, radius and velocity of the shaped charge jet. Simulations of the penetration event were performed using the Uintah MPM/GIMP code with several different models of the shaped charge jet being used. The predicted penetration time history for each jet model is compared with the experimentally observed penetration history. It was found that the characteristics of the predicted penetration were dependent on the way that the jet data are translated to a discrete description. The discrete jet descriptions were modified such that the predicted penetration histories fell very close to the range of the experimental data. In comparing the various discrete jet descriptions it was found that the cumulative kinetic energy flux curve represents an important way of characterizing the penetration characteristics of the jet. The GIMP method was found to be well suited for simulation of high rate penetration events.

POLYETHERSULFONE/CELLULOSE CRYSTAL BLEND MEMBRANES AND THEIR ULTRAFILTRATION PERFORMANCE

The casting solution was obtained by blending polyethersulfone ( PES) and cellulose crystal in dimethylacetamide ( DMAC ). PES /cellulose crystal blend membranes were prepared by the immersion precipitation phase inversion process. The effects of cellulose crystal content on the properties of blend membranes were discussed. The pure water flux,rejection ratio,porosity,mean pore size and anti-fouling property were tested in the ultrafiltration equipments. Also,the mechanical properties,thermal stability and morphology were characterized by tensile testing,thermogravimetric analysis ( TGA ) and atomic force microscopy ( AFM). The results showed that at first,the pure water flux of blend membranes was greatly improved with the increasing of cellulose crystal content,but then it decreased to some extent. All the rejection ratios remained at 91% ～ 95% . The tendencies of tensile strength and elongation curses were the same as the one of pure water flux curve. The anti-fouling property of blend membrane had been improved. When the mass fraction of cellulose crystal was 1% ,the pure water flux got to a maximum,813. 3 L·m -2·h -1; porosity was 88. 8% and mean pore size was 70. 9 nm. At the same condition,tensile strength was 7. 25 MPa and elongation was 11. 6% . In addition,fouling degree (FR value) and attenuation coefficient of fouling (m value) were 22. 0% and 35. 8% ,respectively. There were two weight loss stages in the blend membrane,due to thermal degradation of PES and cellulose crystal,respectively. The typical asymmetric membrane structure was displayed in the blend membrane. The surface layer of the blend membrane was dense,and the support layer had larger size pores. Both of them composed the typical asymmetric membrane structure.

Incorporation of conceptual and parametric uncertainty into radionuclide flux estimates from a fractured granite rock mass

Detailed numerical flow and radionuclide simulations are used to predict the flux of radionuclides from three underground nuclear tests located in the Climax granite stock on the Nevada Test Site. The numerical modeling approach consists of both a regional-scale and local-scale flow model. The regional-scale model incorporates conceptual model uncertainty through the inclusion of five models of hydrostratigraphy and five models describing recharge processes for a total of 25 hydrostratigraphic–recharge combinations. Uncertainty from each of the 25 models is propagated to the local-scale model through constant head boundary conditions that transfer hydraulic gradients and flow patterns from each of the model alternatives in the vicinity of the Climax stock, a fluid flux calibration target, and model weights that describe the plausibility of each conceptual model. The local-scale model utilizes an upscaled discrete fracture network methodology where fluid flow and radionuclides are restricted to an interconnected network of fracture zones mapped onto a continuum grid. Standard Monte Carlo techniques are used to generate 200 random fracture zone networks for each of the 25 conceptual models for a total of 5,000 local-scale flow and transport realizations. Parameters of the fracture zone networks are based on statistical analysis of site-specific fracture data, with the exclusion of fracture density, which was calibrated to match the amount of fluid flux simulated through the Climax stock by the regional-scale models. Radionuclide transport is simulated according to a random walk particle method that tracks particle trajectories through the fracture continuum flow fields according to advection, dispersion and diffusional mass exchange between fractures and matrix. The breakthrough of a conservative radionuclide with a long half-life is used to evaluate the influence of conceptual and parametric uncertainty on radionuclide mass flux estimates. The fluid flux calibration target was found to correlate with fracture density, and particle breakthroughs were generally found to increase with increases in fracture density. Boundary conditions extrapolated from the regional-scale model exerted a secondary influence on radionuclide breakthrough for models with equal fracture density. The incorporation of weights into radionuclide flux estimates resulted in both noise about the original (unweighted) mass flux curves and decreases in the variance and expected value of radionuclide mass flux.

A STUDY OF THE BUILD-UP, INITIATION, AND ACCELERATION OF 2008 APRIL 26 CORONAL MASS EJECTION OBSERVED BYSTEREO

In this paper, we analyze the full evolution, from a few days prior to the eruption to the initiation, and the final acceleration and propagation, of the CME that occurred on 2008 April 26 using the unprecedented high cadence and multi-wavelength observations by STEREO. There existed frequent filament activities and EUV jets prior to the CME eruption for a few days. These activities were probably caused by the magnetic reconnection in the lower atmosphere driven by photospheric convergence motions, which were evident in the sequence of magnetogram images from MDI (Michelson Doppler Imager) onboard SOHO. The slow low-layer magnetic reconnection may be responsible for the storage of magnetic free energy in the corona and the formation of a sigmoidal core field or a flux rope leading to the eventual eruption. The occurrence of EUV brightenings in the sigmoidal core field prior to the rise of the flux rope implies that the eruption was triggered by the inner tether-cutting reconnection, but not the external breakout reconnection. During the period of impulsive acceleration, the time profile of the CME acceleration in the inner corona is found to be consistent with the time profile of the reconnection electric field inferred from the footpoint separation and the RHESSI 15-25 keV HXR flux curve of the associated flare. The full evolution of this CME can be described in four distinct phases: the build-up phase, initiation phase, main acceleration phase, and propagation phase. The physical properties and the transition between these phases are discussed, in an attempt to provide a global picture of CME dynamic evolution.

Imprints of coronal temperature disturbances on type III bursts

The electron temperature Te and ion temperature Ti in the corona vary with time and location, due to transient and persistent activity on the Sun. The effects of spatially localized disturbances in Te and Ti on coronal type III radio bursts are simulated. The disturbances are superimposed on monotonically varying temperature backgrounds and arise from spatially confined solar activity, Qualitatively and quantitatively different imprints are found on the curve of the maximum flux versus frequency of type III bursts, because of the disturbances in Te and Ti. The results indicate that nonthermal coronal type III bursts offer a new tool to probe and distinguish between spatially localized structures of Te and Ti along the paths of type III beams. Furthermore, localized temperature disturbances may be responsible for some fine structures in type III bursts, e.g., striae in type IIIb bursts in the presence of multiple, localized temperature disturbances.

A mathematical model of rat ascending Henle limb. I. Cotransporter function

Kinetic models of Na+-K+-2Cl- costransporter (NKCC2) and K+-Cl- cotransporter (KCC4), two of the key cotransporters of the Henle limb, are fashioned with inclusion of terms representing binding and transport of NH4+. The models are simplified using assumptions of equilibrium ion binding, binding symmetry, and identity of Cl- binding sites. Model parameters are selected to be consistent with flux data from expression of these transporters in oocytes, specifically inwardly directed coupled transport of rubidium. In the analysis of these models, it is found that despite the simplifying assumptions to reduce the number of model parameters, neither model is uniquely determined by the data. For NKCC or KCC there are two- or three-parameter families of "optimal" solutions. As a consequence, one may specify several carrier translocation rates and/or ion affinities before fitting the remaining coefficients to the data, with no loss of fidelity in simulating the experiments. Model calculations suggest that with respect to NKCC2 near its operating point, the curve of ion flux as a function of cell Cl- is steep, and with respect to KCC4, its curve of ion flux as a function of peritubular K+ is also steep. The implication is that the kinetics are suitable for these two transporters in series to act as a sensor for peritubular K+, to modulate AHL Na+ reabsorption, with cytosolic Cl- as the intermediate variable. The models also reveal the potential for luminal NH4+ to be a potent catalyst for NKCC2 Na+ reabsorption, provided suitable exit mechanisms for NH4+ (from cell-to-lumen) are operative. It is found that KCC4 is likely to augment the secretory NH4+ flux, with peritubular NH4+ uptake driven by the cell-to-blood K+ gradient.

Age and Cigarette Smoking are Independently Associated with the Cutaneous Vascular Response to Local Warming

To investigate the relative impacts of age and cigarette smoking on cutaneous blood flow and flow motion. Skin blood flux was measured before and during the hyperaemic response to thermal warming of the skin to 43 degrees C using laser Doppler fluximetry (LDF) in 28 habitual smokers (5.4 [11.4] (median [IQR]) pack years; pack years = packs/day x duration of smoking habit), aged between 18 and 63 years and their age, sex and body mass index. Flow motion was assessed using Fourier analysis of the LDF signal. Mean and total hyperaemic (area under the flux curve, AUC(10)) response during warming were reduced in smokers compared with their non-smoking controls (P<0.05). Attenuation of the response to warming in smokers was associated with a reduction in relative spectral power around 0.01 Hz, reflecting a reduced endothelial/metabolic activity (P<0.04). In regression modelling with AUC(10) as the outcome, and smoking (yes/no), age, sex and BMI, as explanatory variables, age (P<0.0001) and smoking (P=0.018) were independently associated with the hyperaemic response and together accounted for 31% of the variance in AUC(10). Age and smoking are associated with approximately one-third of the variance in the endothelium-associated microvascular vasomotor activity in habitual smokers.

Analysis of the periodicity of voltage versus applied flux curves of planar andthree-dimensional SQUIDs in the presence of coupling inhomogeneity

Coupling inhomogeneities in the Josephson junctions of planar0-SQUIDsand π-SQUIDs and of three-dimensional SQUIDs are considered. Starting from the properties ofplanar SQUIDs, it is shown that slight non-homogeneous couplings of the twelve junctionsin three-dimensional superconducting interferometers do not affect the periodicityproperties of voltage versus applied flux curves. The results are obtained by applying arigorous and general analytic approach to planar and three-dimensional superconductingdevices.

Numerical Modeling of the AC Limiting Properties of Insulated, Conduction Cooled ${\hbox {MgB}}_{2}$ Strands

It is known that MgB2-based strands may be used in fault current limiters as a low-cost alternative to high-temperature YBCO coated conductors. Numerical modeling of the ac limiting properties of MgB2 strands with Kapton insulation and conduction cooling have been performed using a finite element method. Two 2D ac Poisson equations, one for calculating the electric field and one for determining the heat transfer were solved simultaneously with input parameters taken from experimental results. As boundary conditions, we took the full non-linear curve of the heat flux into a cryocooler cold head as well as heat radiation from the free surfaces of the wire. The influence of different values and durations of fault electric fields were studied and the maximum temperatures, limiting currents and recovery times were calculated. Obtained results may be useful for understanding the behavior of different kinds of MgB2 multifilamentary wires under conditions encountered in fault current limiter devices.

Experimental study of atomization effects on two-phase pulse detonation engines

This article presents some results dealing with effects of atomizer types on mean droplet size and pulse detonation engine (PDE) performance. The plain-orifice injector and twin-fluid air-assist atomizer were located at the head-end of a PDE mockup to inject gasoline, which was used as the liquid fuel. A particle size meter based on laser light scattering was employed to measure mean droplet size. The curves of mean droplet size versus gasoline flux and gasoline/air ratio are obtained. The twin-fluid air-assist atomizer can produce much smaller mean droplet size than the plain-orifice injector. The air was injected into the mixing chamber through tangential ports that gave the fuel a high angular velocity, thereby creating smaller droplets. To observe the effect of gasoline droplet size on PDE, the proof-of-principle experiments of PDE were carried out. The experimental results indicated that the equivalence ratio lower limits decreased and the upper limits increased as the gasoline droplet size decreased when air-assist atomizer was used instead of plain-orifice injector. That meant the equivalence ratio limits turned wide as the gasoline droplet size decreased. Meanwhile, the optimum equivalence ratio decreased as the gasoline droplet size decreased. The smaller the droplet size, the lower the optimum equivalence ratio required to stabilize detonation. As the operation frequency increased, the equivalence ratio limit became narrow and the difference of optimum equivalence ratio between the air-assist atomizer and the plain-orifice injector decreased. Furthermore, droplet size of liquid fuel had a considerable effect on the wave speed. The wave speed increased as the gasoline droplet size decreased, while still being lower than the gas-phase Chapman—Jouguet detonation velocity.

LONG-TERM VARIABILITY OF RADIO-BRIGHT BL LACERTAE OBJECTS

Radio-bright BL Lacertae objects (BLOs) are typically very variable and exhibit prominent flaring. We use a sample of 24 BLOs, regularly monitored at Metsähovi Radio Observatory, to get a clear idea of their flaring behavior in the radio domain and to find possible commonalities in their variability patterns. Our goal was to compare the results given by computational timescales and the observed variability parameters determined directly from the flux curves. Also, we wanted to find out if the BLO flares adhere to the generalized shock model, which gives a schematic explanation for the physical process giving rise to the variability. We use long-term monitoring data from 4.8, 8, 14.5, 22, 37, 90, and 230 GHz, obtained mainly from the University of Michigan and Metsähovi Radio Observatories. The structure function, discrete correlation function, and Lomb–Scargle periodogram timescales, calculated in a previous study, are analyzed in more detail. Also, we determine flare durations, rise and decay times, and absolute and relative peak fluxes from the monitoring data. We find that radio-bright BLOs demonstrate a wide range of variability behavior, and few common denominators can be found. BLOs include sources with fast and strong variability, such as OJ 287, PKS 1749+096, and BL Lac, but also sources with more rolling fluctuations such as PKS 0735+178. The most extreme flares can last for up to 13 years or have peak fluxes of approximately 12 Jy in the observer's frame. When the Doppler boosting effect is taken into account, the peak flux of a flare does not depend on the duration of the flare. A rough analysis of the time lags and peak flux evolution indicates that, typically, BLO flares in the mm–cm wavelengths are high peaking, i.e., are in the adiabatic stage. Thus, the results concur with the generalized shock model, which assigns shocks traveling in the jet as the main cause for active galactic nucleus variability. Comparing the computational timescales and the parameters obtained from the flux curve analysis (i.e., rise and decay times and intervals of the flares) reveals that they do have a significant correlation, albeit with large scatter.

GALEX Ultraviolet Observations of Stellar Variability in the Hyades and Pleiades Clusters

ABSTRACTWe present GALEX near-ultraviolet (NUV: 1750–2750 Å) and far-ultraviolet (FUV: 1350–1750 Å) imaging observations of two 1.2° diameter fields in the Hyades and Pleiades open clusters in order to detect possible UV variability of the member stars. We have performed a detailed software search for short-term UV flux variability during these observations of the ∼400 sources detected in each of the Hyades and Pleiades fields to identify flarelike (dMe) stellar objects. This search resulted in the detection of 16 UV variable sources, of which 13 can be directly associated with probable M-type stars. The other UV sources are G-type stars and one newly discovered RR Lyrae star, USNOB1.0 1069–0046050, of period 0.624 day and distance ∼4.5 to 7 kpc. Light curves of photon flux versus time are shown for seven flare events recorded on six probable dMe stars. UV energies for these flares span the range 2 × 1027 to 5 × 1029 erg, with a corresponding variability change of ΔNUV = 1.82 mag. Only one of these flare events (on the star Cl* Melotte 25 LH129) can definitely be associated with an origin on a member of the Hyades cluster itself. Finally, many of our M-type candidates show long periods of enhanced UV activity but without the associated rapid increase in flux that is normally associated with a flare event. However, the total UV energy output during such periods of increased activity is greater than that of many short-term UV flares. These intervals of enhanced low-level UV activity concur with the idea that, even in quiescence, the UV emission from dMe stars may be related to a superposition of many small flare events possessing a wide range of energies.

MEASUREMENTS OF HEAT LOSSEST DURING SOLIDIFICATION OF LIGHT MEALS

This paper describes the application of a new in-cavity thermal measurement method to determine the heat flux and calculate heat losses during high pressure die casting of aluminium A380 alloy and the magnesium alloy AZ91-D. Thermal management of the die is a critical concern in high pressure die casting and the development of microstructures after solidification. Detailed measurements were performed using infra-red probes linked to pyrometric chains and thermocouple arrays that accurately determine both casting and die surface temperatures enabling the determination of heat flux densities and interfacial heat transfer coefficients and the rapid evolution of these values with time during high pressure die casting of these alloys. The energy losses during the spray cycle can then be determined by integrating the heat flux curves for the duration of the spray application. The significance of the findings presented in this investigation arise from the uniqueness of the measurement methods applied to the determination of heat flux during the high pressure die casting of both magnesium and aluminium alloys. In particular the detailed knowledge of the thermal characteristics occurring at the cavity fill stages of the die casting process achieved through the selection of an array of fine rapid-response thermocouples integrated in one sensor along with the light pipe/pyrometric chain have enabled the accurate measurement of both the die and metal surface temperatures through the entire die casting cycle enabling the calculation of heat losses during solidification and processing.

Analysis of Increasing Thickening Capacity of Inclined Thickener by Use of Vertical and Inclined Solid Flux Curves

垂直および傾斜固体流束曲線を用いて，連続傾斜シックナーでの処理量の増加の理論的解析を行った．種々の濃度の炭酸カルシウムスラリーを用いて，垂直管内回分沈降および傾斜管内回分沈降実験を行い，垂直および傾斜固体流束曲線を得た．上部傾斜板下に生成するくさび形の清澄水を考えたモデルによって，垂直沈降速度と傾斜沈降速度の差異を説明することができた．この垂直および傾斜固体流束曲線を用いて，定常状態での臨界負荷操作における連続傾斜シックナーの処理量の増加を図解法により予測することができた．この解析法から予測される処理量の増加と炭酸カルシウムスラリーを用いた実験から求められる処理量の増加は，ほぼ一致した．したがって，この手法が連続傾斜シックナーの解析に利用できることが示され，任意の初期高さの傾斜シックナーでの処理量の増加を図的に算出することが可能となった．

高感度磁束密度計によるステンレス鋼の損傷評価

Various stainless steels were investigated to examine the new NDE technique. The new NDE technique did not depend on either magnetization or demagnetization of materials. The magnetic flux caused by stress concentration in stainless steels was examined with the ultra sensitive magnetic flux density meter. Tensile and biaxial fatigue tests were conducted to observe the magnetic flux leakage. Results from biaxial fatigue tests indicated that the measured magnetic flux curves had local periodical cycles with global increasing tendencies. The defect evaluation would be possible by comparing the flux density value at the stress concentration regions with that of other areas.

Numerical Simulation of Unsteady Discharge Flow with Fluctuation in Positive Discharge Blower

The operating performance of positive discharge blower is markedly influenced by the pulsation of the discharge flow, but difficult to be measured with experimental methods. The internal and discharge flow of positive discharge blower with involute type three-lobe are numerically investigated, both in air cooling and countercurrent cooling conditions by means of computational fluid dynamics (CFD). The unsteady compressible flow equations are solved using RNG κ-e turbulent model. The finite difference method and the second order upwind difference scheme are applied into discrete equations. In the numerical simulation, the dynamic mesh techniques are used to approach the rotating displacement of cell cubage and the alterability of inlet, outlet flow area. The non-uniform mesh is applied to the rotor-stator coupled area. The reliability of the numerical method is verified by simulating the inner flow and comparing with the semi-empirical theory. The flow flux curves and the distributing of velocity vector showed obvious vortex motion in all the discharge process, both in air cooling and countercurrent cooling conditions. These vortexes with different positions, intension and numbers at different rotating angles have remarkable influences on the discharge flux. For air cooling, the vortex produced a second pulsation with big-amplitude in a cycle, and led to the early appearance of maximum of backflow. For countercurrent cooling, the frequency of pulsation increased due to the pre-inflow, but the backflow at the outlet is prevented, also the pulsation strength has greatly decreased.

Microcalorimetric Investigation on Effects of LaIII on Metabolic Activity of Mitochondria Isolated from Hybrid Rice

Rare earth elements (REEs) have beneficial influence on plant growth and are widely used in agriculture practice, but little is known about the behavior of the REEs in mitochondria of plant cell. Thermogenic metabolic curves were determined by the ampoule method at 303 K using a TAM air isothermal microcalorimeter in mitochondria isolated from hybrid rice Liangyoupeijiu (Oryza sativa L.), and the effect of La(III) on its mitochondrial metabolism was investigated. From the obtained heat flux curves, the crucial parameters including as activity recovery rate constant (k) and maximum heat power (P(max)) were determined. Application of La(3+) in concentrations ranging from 0 to 120 microg/ml significantly increased k and P(max) values with the high point reaching 346 and 222% of the control, respectively. Concentrations from 140-150 microg/ml had the opposite effect. These results were consistent with previous reports on the effects of REEs on plant growth. It was concluded that the La-induced change of mitochondrial metabolic activity is a possible mechanism by which La(III) ions influences hybrid rice growth.