Variation Of Gas Temperature Research Articles

13CO(J = 1–0) On-the-Fly Mapping of the Giant H II Region NGC 604: Variation in Molecular Gas Density and Temperature due to Sequential Star Formation

Abstract We present $^{13}$CO($J$$=$ 1–0) line emission observations with the Nobeyama 45-m telescope toward the giant H II region NGC 604 in the spiral galaxy M 33. We detected $^{13}$CO($J$$=$ 1–0) line emissions in 3 major giant molecular clouds (GMCs) labeled as GMC-A, B, and C beginning at the north. We derived two line intensity ratios, $^{13}$CO($J$$=$ 1–0)$/$$^{12}$CO($J$$=$ 1–0), $R_{13/12}$, and $^{12}$CO($J$$=$ 3–2)$/$$^{12}$CO($J$$=$ 1–0), $R_{31}$, for each GMC at an angular resolution of 25$”$ (100 pc). The averaged values of $R_{13/12}$ and $R_{31}$ are 0.06 and 0.31 within the whole GMC-A, 0.11 and 0.67 within the whole GMC-B, and 0.05 and 0.36 within the whole GMC-C, respectively. In addition, we obtained $R_{13/12}$$=$ 0.09$\ \pm\ $0.02 and $R_{31}$$=$ 0.76$\ \pm\ $0.06 at the $^{12}$CO($J$$=$ 1–0) peak position of the GMC-B. Under the Large Velocity Gradient approximation, we determined a gas density of 2.8 $\times$ 10$^{3}\ $cm$^{-3}$ and a kinetic temperature of 33$^{+9}_{-5}\ $K at the $^{12}$CO($J$$=$ 1–0) peak position of the GMC-B. Moreover, we determined 2.5 $\times$ 10$^{3}\ $cm$^{-3}$ and 25$\ \pm\ $2 K as the averaged values within the whole GMC-B. We concluded that dense molecular gas is formed everywhere in the GMC-B because the derived gas density not only at the peak position of the GMC, but also averaged over the whole GMC, exceeds 10$^{3}\ $cm$^{-3}$. On the other hand, the kinetic temperature averaged over the whole GMC-B, 25 K, is significantly lower than that at the peak position, 33 K. This is because the H II regions are lopsided to the northern part of the GMC-B; thus, OB stars can heat only the northern part, including the $^{12}$CO($J$$=$ 1–0) peak position, of this GMC.

黒鉛炉原子吸光法における測定回数による黒鉛原子化炉の寿命および原子化プロセスへの影響

GF-AAS has been employed for determining several trace impurities in metallic materials. The analytical precision in the continuous analysis tends to worsen due to thermal degradation of the graphite furnace at the atomization stage. Changes of the atomization condition along with increasing the number of measurements were investigated by monitoring the temporal variation in the atomic gas temperature of iron. In a working solution containing low-concentration of acid, the inner wall of the graphite furnace was gradually damaged and then the efficiency for the atomizing process was reduced. In a working solution containing sub-mol/L order of sulfuric acid, thinning or cracking of the graphite furnace progressed more rapidly and the function of it was greatly deteriorated.

Self potential signals preceding variations of fumarole activity at Merapi volcano, Central Java

This paper analyzes simultaneous self-potential and gas temperature variations recorded at Merapi volcano in spring 2011, the dry season shortly after the volcanic crisis 2001. Temporal variations of fumarole gas temperature show characteristic quasi periodic signals at scales 1–8h and amplitudes up to ten degrees. We propose a simple graphical technique combining a wavelet scalogram and a cross-correlation analysis to demonstrate that the variations of gas temperature are systematically preceded by self-potential variations at the same scales. The influence of meteorological variations on these correlated signals can be ruled out. Rather, we suggest them to be related to the magma degassing in the upper conduits of the volcano. We discuss a semi-qualitative model to explain this correlation and the observed phase shift of about two hours.

Compressible gases transport through porous membrane: A modified dusty gas model

In membrane distillation (MD) and gas permeation (GP) processes, a general equation given by dusty gas model (DGM) is often used for gas flux through porous media. However, several discrepancies were found in fitting experimental data with the DGM equation. An assumption based on the fact that gas is a compressible viscous fluid is introduced in a modified DGM equation (MDGM). Polytropic equation of state is used to estimate the variation of gas temperature along the pores of membrane. The gas temperature influences its viscosity, which affects its flow resistance through membrane. The MDGM equations for single gases are provided by incorporating polytropic equation of state when integrating the differential DGM flux equation. The MDGM for single gases can be used in modeling the inconsistencies in using DGM in literature and it is verified by published experimental data through fitting the distinguished trends under DGM into one line. The MDGM reveals that the temperature may decrease in membrane pores and exit side, and the phase change of vapor may be one of the inducements for pore wetting in MD.

Influence of Gas Supply Mode on CO<sub>2</sub> Hydrate Formation in Water Spraying Reactor

In order to study the influence of gas supply modes on CO2 hydrate formation characteristics, a specific water spray gas hydrate formation apparatus was designed. The gas consumption and temperature variation in the process of CO2 hydrate formation under continuous and oscillating gas supply modes were researched. The experimental results showed that hydrate formation rate in the oscillating gas supply mode was greater than in the continuous gas supply mode, which indicates mass transfer driving force caused by disturbance in oscillating gas supply mode is larger than that of continuous gas supply mode. Additionally, under the same initial pressures and the same gas supplying mode, the lower the initial temperature, the larger the heat transfer drive force, and the faster the hydrate formation rate.

Microwave air plasma source at atmospheric pressure: Experiment and theory

An experimental and theoretical investigation of the axial structure of a surface wave (2.45 GHz) driven atmospheric plasma source in air with a small admixture (1%) of water vapor has been performed. Measurements of the gas temperature and of the intensities of the O(777.4 nm), O(844.6 nm), and O(630 nm) atomic lines and the NO(γ) molecular band versus input power and axial position were carried out. Amplitude and phase sensitive measurements have also been performed to derive the surface wave dispersion characteristics. The experimental results are analyzed in terms of a one-dimensional theoretical model based on a self-consistent treatment of particle kinetics, gas dynamics, and wave electrodynamics. The predicted gas temperature and emission line intensities variations with power and axial position are shown to compare well with experiment. “Hot” excited O atoms (with kinetic energy ∼2 eV) have been detected.

Process simulation of activated carbon production using a rotary kiln

The rotary kiln used for the activation of charcoal is simulated using mass and energy balances to obtain the temperature distributions of environmental gas and solid in the kiln. The computed results are used to find the optimal operation condition. In finding the optimal gas temperature for the reductive gas environment necessary to the charcoal activation, the outcome gives the amount of fuel required and the effects of other operational variables, such as feed and steam rates. While the fuel and feed rates give large variation of gas and solid temperatures, the activation steam and moisture and volatile contents in feed do not affect the temperatures significantly. It was found that the temperature distribution has a similar pattern to that of coal pyrolysis because of the similarity of heat transfer mechanism.

Experimental study of exhaust temperature variation in a homogeneous charge compression ignition engine

Homogeneous charge compression ignition (HCCI) engines have low nitrogen oxide and particulate matter engine-out emissions but have higher unburned hydrocarbon and carbon monoxide emissions than the conventional spark ignition (SI) and diesel engines do. Only for sufficiently high exhaust gas temperatures can an exhaust after-treatment be used; thus a low exhaust gas temperature in certain operating conditions can limit the operating range in HCCI engines. The influences of the engine conditions on the exhaust gas temperature in a single-cylinder experimental engine are investigated at 340 steady state operating points. The variation in the exhaust gas temperature is also studied under transient conditions and during mode switching between SI and HCCI combustion. For the conditions tested, a significant number of data have an exhaust gas temperature below 300°C which is below the light-off temperature of typical catalytic converters on the market. Three different categories of engine variables are recognized and classified by how the exhaust temperature is affected by changing that variable. The first category is defined as the primary variables (e.g. the intake pressure and the fuel octane number) for which the location of ignition timing is the dominant factor in influencing the exhaust temperature. The other groups include compounding variables such as the engine speed and opposing variables such as the intake temperature, the coolant temperature, and the equivalence ratio. In addition, experimental results show that the exhaust temperature for HCCI engines is not strongly dependent on the engine load, unlike that for SI engines where the engine load is a main factor in determining the exhaust temperature.

Working gas temperature and pressure changes for microscale thermal creep-driven flow caused by discontinuous wall temperatures

Microscale temperature gradient-driven (thermal creep/transpiration) gas flows have attracted significant interest during the past decade. For free molecular and transitional conditions, applying temperature gradients to a flow channel's walls induces the thermal creep effect. This results in a working gas flowing through the channel from cold to hot, which is generally accompanied by a rising pressure from cold to hot in the channel. Working gas temperature and pressure distributions can vary significantly, depending on a flow channel's configuration and wall temperature distribution. Understanding working gas temperature excursions, both increases and decreases, is essential to ensure the effective use of thermal creep flows in microscale applications. In this study, the characterizations of working gas temperature variations, due to both temperature discontinuities and more gradual changes, on a variety of flow channel walls, were systematically investigated using the direct simulation Monte Carlo (DSMC) method. A micro/meso-scale pump, the Knudsen compressor, was chosen to illustrate the importance of controlling working gas temperature in thermal creep-driven flows. Gas pressure and temperature variations, through several Knudsen compressor stage configurations, were studied to determine the most advantageous flow phenomena for the efficient operation of Knudsen compressors.

LIFETIME OF THE EMBEDDED PHASE OF LOW-MASS STAR FORMATION AND THE ENVELOPE DEPLETION RATES

Motivated by a considerable scatter in the observationally inferred lifetimes of the embedded phase of star formation, we study the duration of the Class 0 and Class I phases in upper-mass brown dwarfs and low-mass stars using numerical hydrodynamics simulations of the gravitational collapse of a large sample of cloud cores. We resolve the formation of a star/disk/envelope system and extend our numerical simulations to the late accretion phase when the envelope is nearly totally depleted of matter. We adopted a classification scheme of Andre et al. and calculate the lifetimes of the Class 0 and Class I phases (\tau_C0 and \tau_CI, respectively) based on the mass remaining in the envelope. When cloud cores with various rotation rates, masses, and sizes (but identical otherwise) are considered, our modeling reveals a sub-linear correlation between the Class 0 lifetimes and stellar masses in the Class 0 phase with the least-squares fit exponent m=0.8 \pm 0.05. The corresponding correlation between the Class I lifetimes and stellar masses in the Class I is super-linear with m=1.2 \pm 0.05. If a wider sample of cloud cores is considered, which includes possible variations in the initial gas temperature, cloud core truncation radii, density enhancement amplitudes, initial gas density and angular velocity profiles, and magnetic fields, then the corresponding exponents may decrease by as much as 0.3. The duration of the Class I phase is found to be longer than that of the Class~0 phase in most models, with a mean ratio \tau_CI / \tau_C0 \approx 1.5--2. A notable exception are YSOs that form from cloud cores with large initial density enhancements, in which case \tau_C0 may be greater than \tau_CI. Moreover, the upper-mass (>= 1.0 Msun) cloud cores with frozen-in magnetic fields and high cloud core rotation rates may have the \tau_CI / \tau_C0 ratios as large as 3.0--4.0. (Abdridged).

Characteristics of the plasma discharge generated in dielectric capillary at atmospheric pressure

An atmospheric-pressure argon plasma discharge with a length of 63 cm is generated in a quartz capillary by using a pair of hollow needle electrodes. The discharge mode transition from abnormal glow to arc is investigated by means of electrical measurement and optical emission spectroscopy. The effects of the distance between two needle electrodes and the operating frequency of power supply on the voltage-current characteristics are discussed. The plasma electron density was estimated to be the order of 1014 cm-3 in the arc discharge. Moreover, the variation of gas temperature with the applied voltage is also studied, which is closely associated with the power dissipation. Furthermore, in measuring the oxygen atoms generated in argon/oxygen arc plasma discharge by optical actinometry, we found that the amount of oxygen atoms almost does not change with the rise of oxygen concentration.

Degradation Process of Graphite Furnace Estimated from the Atomic Gas Temperature of Iron in Graphite Furnace Atomic Absorption Spectrometry

GF-AAS has been employed for determining several trace impurities in metallic materials. The analytical precision in the continuous analysis tends to worsen due to thermal degradation of the graphite furnace at the atomization stage. Changes of the atomization condition along with increasing the number of measurements were investigated by monitoring the temporal variation in the atomic gas temperature of iron. In a working solution containing low-concentration of acid, the inner wall of the graphite furnace was gradually damaged and then the efficiency for the atomizing process was reduced. In a working solution containing sub-mol/L order of sulfuric acid, thinning or cracking of the graphite furnace progressed more rapidly and the function of it was greatly deteriorated.

Analysis of Effect of Gas Temperature on Cooling Stave of Blast Furnace

In order to study the effect of gas temperature variation on cooling stave, temperature, stress and displacement distributions of cooling stave were analyzed respectively when gas temperature inside blast furnace increases from 1000 to 1600 °C. The results show that the temperature field on cold side is under control of cooling pipes and hardly changes when gas temperature increases. The temperature gradient and change rate with time near hot sides are greater than those in other regions and the later can reach 100 °C/s. The stress intensity near middle area of hot surface is up to 400 MPa and that's why there are lots of cracks at this place. The edge of stave is bent to cold side and middle regions between fixed bolts and pin moves to hot side. The displacement around fixed pin is smaller but larger on the edge and the maximum is located on hot side of top surface. The maximum displacement in z direction is about 4 mm and 3 mm in y direction. If the expansion coefficient of packing layer is 1/4, the thickness of packing layer between the cooling staves is 32 mm and 24 mm between sides up and down.

MICROMEGAS chambers for hadronic calorimetry at a future linear collider

Prototypes of MICROMEGAS chambers, using bulk technology and analog readout, with 1 × 1 cm2 readout segmentation have been built and tested. Measurements in Ar/iC4H10 (95/5) and Ar/CO2 (80/20) are reported. The dependency of the prototypes gas gain versus pressure, gas temperature and amplification gap thickness variations has been measured with an 55Fe source and a method for temperature and pressure correction of data is presented. A stack of four chambers has been tested in 200 GeV/c and 7 GeV/c muon and pion beams respectively. Measurements of response uniformity, detection efficiency and hit multiplicity are reported. A bulk MICROMEGAS prototype with embedded digital readout electronics has been assembled and tested. The chamber's layout and first results are presented.

Modeling Catalytic Combustion of Methane During the Warm-Up Period of the Converter

Modeling for hydrocarbon methane was carried out during the warm-up period. A one-dimensional model based on its catalytic combustion reaction was formed. The mass and energy balance equations derived for the gas and the solid phase are a set of partial differential equations. All these equations are solved using Backward Implicit Scheme. The variation of gas concentration, temperature and solid temperature along the length of the converter during the warm-up period was analysed. Also, the effects on time while changing various parameters—like inlet gas temperature, catalyst loading, surface area, and converter length—for methane conversion, were studied.

Temporal Variation in Gas Temperature at the Atomization Stage in Several Types of Graphite Furnaces for Atomic Absorption Spectrometry

In order to compare and evaluate the atomization process occurring in several types of graphite furnaces for atomic absorption spectrometry, the authors estimated temporal variations in the gas temperature by using a two-line method under the assumption of a Bolzmann distribution. The atomization furnaces employed were a graphite tube, a graphite tube coated with pyrolitic carbon, a graphite tube with a platform and a graphite cup. Differences in the temporal variation in the gas temperature among these graphite furnaces were observed.

Neat fuel influence on biodiesel blend emissions

The emissions of oxides of nitrogen (NO x) from biodiesel blended fuels reported in the literature vary from an NO x increase to an NO x decrease relative to the neat petroleum diesel fuel (PDF). To explain these NO x differences, three PDFs with varying fuel properties were admixed with a neat soy-derived biodiesel at 10 per cent and 20 per cent volume ratios and evaluated using a heavy-duty diesel engine exercised over transient and steady-state cycles. The PDFs with ‘low’ and ‘medium’ cetane numbers led to a change in combustion phasing when blended with the neat biodiesel, resulting in reduced NO x emissions at low engine power. The B100 blended with the ‘high’-cetane-number PDF showed minimal change in combustion phasing and resulted in an NO x increase at all engine loads. The derived peak in-cylinder gas temperature variation correlated with the brake-specific NO x emissions indicating that the thermal NO x formation responds to the addition of biodiesel. The biodiesel blends had an NO x—particulate matter trade-off, also suggesting a thermal NO x effect. The increase in NO x emissions of the biodiesel blends also had a strong correlation with the level of saturated hydrocarbons at high engine power.

Spectral analysis for gravitational constant measurements

Spectral analysis has been carried out for time series of gravitational constant measurements. Latent periodicities have been revealed, testifying to an influence of microseisms, non-equilibrium rarefied gas flows and temperature variations on the results of measurements.

Influence of EGR unequal distribution from cylinder to cylinder on NO x–PM trade-off of a HSDI automotive Diesel engine

The influence of cylinder-to-cylinder variation in EGR distribution on the NO x–PM trade-off (while varying EGR rate) is studied on an automotive high-speed direct injection Diesel engine. Experiments have been conducted on an engine test bench with and without air-EGR mixer and demonstrate that variations in cylinder-to-cylinder EGR distribution results in a deteriorated NO x–PM trade-off (increased NO x emissions level at a given PM emissions level, or increased PM emissions level at a given NO x emissions level) compared to the well mixed configuration with equal EGR rate for all the cylinders. A qualitative study as well an original experiment is conducted to explain this emissions increase induced by unequal distribution of EGR. When recirculating hot exhaust gases, the emissions increase is due to cylinder-to-cylinder variations in intake gas composition and temperature.

Temporal Variations in Gas Temperature in an Atomization Stage of Cadmium and Tellurium Evaluated by Using the Two-line Method in Graphite Furnace Atomic Absorption Spectrometry

In order to discuss the atomization process of an analyte element occurring in a graphite furnace for atomic absorption spectrometry, we measured variations in the characteristic temperature with the progress of an atomization stage, by using a two-line method under the assumption of a Boltzmann distribution. For this purpose, iron was chosen as the analyte element. Also, the atomic absorption of two iron atomic lines, Fe I 372.0 nm and Fe I 373.7 nm, was simultaneously monitored as a probe for the temperature determination. This method enables variations in the gas temperature to be directly traced, yielding a temperature distribution closely related to the diffusion behavior of the probe element in the furnace. This temperature variation was very different from the furnace wall temperatures, which were monitored in conventional temperature control for atomic absorption spectrometry. Correlations between the gas temperature and the charring/atomizing temperatures in the heating program of the furnace were investigated. The atomization of cadmium and tellurium was also investigated by a comparison between the gas temperature with the wall temperature of the furnace. The atomic absorption of cadmium or tellurium appeared to be apart from the absorption of iron while the gas temperature was still low. Therefore, the analyte atoms could be atomized through direct contact with the wall of the graphite furnace, which has a much higher temperature compared to the gas atmosphere during atomization. Their atomization would be caused by conductive heating from the furnace wall rather than by radiant heating in the furnace.