Longitudinal Temperature Variation Research Articles

Carrier density non-pinning at stripe edges and widened lateral far field due to longitudinal temperature variation in broad-area high power diode lasers

Broad area lasers operating at high power with improved beam quality are needed in many applications. In typical high-power diode lasers with asymmetric facet coating, it is observed that the carrier density fails to completely pin above threshold with significant levels of lateral carrier accumulation (LCA) at the front facet stripe edges. Systematic experimental data are presented to quantify such non-pinning and its effect on lateral far field in multiple diode lasers with varying longitudinal temperature variation (LTV) using spontaneous emission imaging. LTV is quantified and correlated with the carrier accumulation and its dependence on facet reflectivity and cavity length. Results of measurements under continuous wave (CW) and quasi-CW conditions are used to regulate the level of heating and, hence, to isolate the contribution of LTV and optical field profile. Conventional long resonator asymmetric-coated devices show a twofold increase in LCA from threshold to 10 A current at the front stripe edge, but LCA varies less than 20% for lower facet asymmetry or short resonators. Similarly, strong temperature driven far field broadening is observed for conventional long-resonator asymmetric-coated devices (3°–4° variation with temperature at 10 A), which is strongly reduced for lower facet asymmetry or short resonators (<1° at 10 A).

Experimental Study on Freezing Front Model of Alpine Tunnel under Wind Field

In order to study the freezing front characteristics of alpine tunnels under the condition of wind flow field and relying on the Osaka Mountain tunnel in Qinghai Province, the physical model test of an alpine tunnel was built. By using the Surfer software combined with the laboratory test data, the radial and longitudinal temperature variation trends of the tunnel were obtained, and the overall temperature vector graph of the tunnel was simulated; the radial and longitudinal evolutionary laws of a freezing front in an alpine tunnel under airflow conditions were systematically analyzed, and the radial and longitudinal governing equations of a freezing front in the tunnel model under airflow conditions were proposed. The results show that: With the decrease of the test air temperature, the thermonuclear area in the surrounding rock gradually shrinks, the frozen area of surrounding rock at the bottom of the arch gradually increases, and the frozen area of surrounding rock at the top of the arch gradually expands to the interior of the mountain. The influence degree of ventilation on the longitudinal and radial temperature distribution of the tunnel is obvious, and the greater the wind speed, the greater the influence degree. In particular, the fluctuation range of the longitudinal temperature distribution of the tunnel is more extensive under the influence of ventilation. The freezing front distance in the inverted arch area is the largest, and the expansion distance of the freezing front in the wall foot area is obviously higher than that in the vault; the variation of the longitudinal freezing front at different positions of the tunnel shows parabolic attenuation and with an increase in tunnel depth, the trend of freezing front gradually eases and becomes stable and disappears; the three radial regions of the freezing front and the longitudinal quadratic parabola governing equations can predict the specific distribution characteristics of the freezing front at different depths of the tunnel.

Monitoring of Longitudinal Temperature Variation in Tunnel in Cold Region

Based on the high-altitude cold area super-long railway tunnel-Dangjinshan tunnel as the background, this paper studies the temperature distribution and its variation rule in the tunnel through the method of field measurement and theoretical analysis, and obtains the variation rule of tunnel temperature under different temperature conditions at the entrance, as well as the location of 0°C point from the entrance of the tunnel. The conclusions obtained in this paper can be applied to the study of tunnel anti-frost heaving technology and have reference value for the construction of tunnels in cold areas under similar conditions.

Mantle-induced temperature anomalies do not reach the inner core boundary

SUMMARY Temperature anomalies in Earth’s liquid core reflect the vigour of convection and the nature and extent of thermal core–mantle coupling. Numerical simulations suggest that longitudinal temperature anomalies forced by lateral heat flow variations at the core–mantle boundary (CMB) can greatly exceed the anomalies that arise in homogeneous convection (i.e. with no boundary forcing) and may even penetrate all the way to the inner core boundary. However, it is not clear whether these simulations access the relevant regime for convection in Earth’s core, which is characterized by rapid rotation (low Ekman number E) and strong driving (high Rayleigh number Ra). We access this regime using numerical simulations of non-magnetic rotating convection with imposed heat flow variations at the outer boundary (OB) and investigate the amplitude and spatial pattern of thermal anomalies, focusing on the inner and outer boundaries. The 108 simulations cover the parameter range 10−4 ≤ E ≤ 10−6 and Ra = 1−800 times the critical value. At each Ra and E we consider two heat flow patterns—one derived from seismic tomography and the hemispheric $Y_1^1$ spherical harmonic pattern—with amplitudes measured by the parameter q⋆ = 2.3, 5 as well as the case of homogeneous convection. At the OB the forcing produces strong longitudinal temperature variations that peak in the equatorial region. Scaling relations suggest that the longitudinal variations are weakly dependent on E and Ra and are much stronger than in homogeneous convection, reaching O(1) K at core conditions if q⋆ ≈ 35. At the inner boundary, latitudinal and longitudinal temperature variations depend weakly on Ra and q⋆ and decrease strongly with E, becoming practically indistinguishable between homogeneous and heterogeneous cases at E = 10−6. Interpreted at core conditions our results suggest that heat flow variations on the CMB are unlikely to explain the large-scale variations observed by seismology at the top of the inner core.

Joule heating effect of electroosmosis in a finite-length microchannel made of different materials

This paper presents a numerical analysis of Joule heating effect of electroosmosis in a finite-length microchannel made of the glass and polydimethylsiloxane (PDMS) polymer. The Poisson-Boltzmann equation of electric double layer, the Navier-Stokes equation of liquid flow, and the liquid-solid coupled heat transfer equation are solved to investigate temperature behaviors of electroosmosis in a two-dimensional microchannel. The feedback effect of temperature variation on liquid properties (dielectric constant, viscosity, and thermal and electric conductivities) is taken into account. Numerical results indicate that there exists a heat developing length near the channel inlet where the flow velocity, temperature, pressure, and electric field rapidly vary and then approach to a steady state after the heat developing length, which may occupy a considerable portion of the microchannel in cases of thick chip and high electric field. The liquid temperature of steady state increases with the increase of the applied electric field, channel width, and chip thickness. The temperature on a PDMS wall is higher than that on a glass wall due to the difference of heat conductivities of materials. Temperature variations are found in the both longitudinal and transverse directions of the microchannel. The increase of the temperature on the wall decreases the charge density of the electric double layer. The longitudinal temperature variation induces a pressure gradient and changes the behavior of the electric field in the microchannel. The inflow liquid temperature does not change the liquid temperature of steady state and the heat developing length.

Fiber Heat Transfer Element for Modeling the Thermal Response of Structures in Fire

This paper introduces a novel type of heat transfer finite element that can be used to model the three-dimensional thermal response of structural beams and columns subjected to elevated temperatures associated with fire. The element is a three-node heat transfer element that uses a fiber discretization to account for both transverse and longitudinal temperature variations in a structural member. This fiber heat transfer element is purposely formulated to be compatible with any fiber beam-column finite element in a sequentially coupled thermal-mechanical analysis of a structural frame subjected to fire. The element is implemented in ABAQUS using a user-defined element subroutine. To demonstrate the capabilities of the fiber heat transfer element, analyses are performed on members with various types of thermal boundary conditions. Results indicate that the fiber heat transfer element offers excellent accuracy with minimal computational expense, making the fiber heat transfer element a valuable tool for modeling the behavior of frame structures in fire.

Longitudinal variability of mesospheric temperatures during equinox at middle and high latitudes

Airglow emission and temperature observations by the wind imaging interferometer (WINDII) on the upper atmosphere research satellite (UARS) and ground-based stations revealed a rapid 2-day rise in the nighttime emission rate in springtime followed by a subsequent decrease in the magnitude, which was termed ‘springtime transition’. A rapid temperature enhancement was also revealed in the average annual temperature at 87 km height, employing observations from 1991 to 1997 and more recent temperature data from 1998 to 1999. Large amplitude perturbations in mesospheric Na-lidar and OH rotational temperatures at 87 km around the autumnal equinox at mid-latitudes were also reported. Recently it has been suggested that the observed fall perturbation is a signature of mesospheric planetary waves of zonal wavenumber 1 (hereafter a wave 1) in the Northern hemisphere. The current study extends earlier work on mesospheric temperatures from the WINDII/UARS experiment and complementary ground-based observations to examine global spatial and temporal characteristics of the equinox transition at 87 km height. A 7-year climatology at middle and high latitudes, 40–60°N is presented revealing a V-shaped signature of temperature decrease with amplitude of ∼25 K below the annual mean and a duration of 3–4 weeks depending on the year, following fall equinox (Day 257–284). Satellite and ground-based temperature observations were successfully combined to infer tidal information, a key to the interpretation of the results obtained. After accounting for the diurnal tidal perturbation a distinct planetary wave structure was revealed at latitudes from 45°N to 65°N. Longitudinal temperature variations show a drop at 140–180°E on Day 264 at 50°N which extends to at least 60°N accompanied by wave signatures. Spectral analysis indicated planetary waves with waves 1 and 2 planetary perturbations maximizing on Day 263–265 (September 20–22). Various waveforms were also identified (waves 3–6) from which a waveform with a wavenumber 4 appeared to be the third most persistent wave signature during the period with a period of about 4 days. The spectral analysis also revealed a depressed planetary wave activity following fall equinox. It is concluded that the observed temperature perturbation is the likely result of in situ generated gravity waves at 87 km superposed on the planetary wave 1 propagating upwards from below enhanced by the reversal of zonal mean wind flow at equinox.

A two‐dimensional model with input parameters from a general circulation model: Ozone sensitivity to different formulations for the longitudinal temperature variation

Net heating and temperature derived from the middle atmospheric version of the National Center for Atmospheric Research's Community Climate Model (MA CCM2) history tapes are used to evaluate three different approaches to account for zonal temperature asymmetries in the calculation of gas phase and heterogeneous chemical reaction rate constants and polar stratospheric cloud (PSC) surface area in a two‐dimensional chemistry transport model (2‐D CTM). The first method uses the daily (and monthly) averaged three‐dimensional (3‐D) temperature distribution derived from the MA CCM2 to calculate chemical and heterogeneous reaction rates at each 3‐D grid point, followed by zonal averaging (pseudo‐3‐D method). The second method uses 3‐D daily temperature statistics from the MA CCM2 to calculate the monthly averaged probability function (stochastic approach). The third method is based on a planetary wave superposition on the zonally averaged temperature (wave approach). The sensitivity of the gas phase reactions to the longitudinal temperature asymmetry is small, while the sensitivity of the heterogeneous reaction rates is comparable to the ozone response to aircraft emissions. All three methods of accounting for longitude temperature asymmetry give similar PSC morphologies in the southern hemisphere, in good agreement with climatological data and independent model calculations. In the northern hemisphere, where the CCM2 winter temperatures at high latitudes are known to be warmer than those observed, the PSCs predicted by the pseudo‐3‐D and wave methods are much scarcer than those observed or calculated by other authors using climatological temperatures. For the same reason, all other methods employed in the present study failed to predict any PSCs in the northern hemisphere.

Thermal and Heat Transfer Characteristics of Cannonsville Reservoir

ABSTRACT Observations of the spatial and temporal distribution of temperature in Cannonsville Reservoir over the 1988–1995 period are reviewed, with emphasis on 1994 and 1995. The dominant spatial variations in temperature are in the vertical direction (thermal stratification), with modest spatial variations along the longitudinal axes of the basin. Longitudinal temperature variations were greatest in the spring, with shallow, upstream waters being warmer than at deeper sites downstream near the dam. Diurnal temperature variations of the surface waters of the reservoir were generally less than 2 °C. The variations of temperature of two major reservoir tributaries are also documented. The tributaries are generally warmer than reservoir surface waters in spring, but are cooler through most of the summer and the fall. Diurnal fluctuations in tributary temperature may be significant, with day-night changes as large as 15 °C observed for Trout Creek. A reservoir heat budget calculation for 1995 indicates that inflow/outflow and water surface heat transfer are both important in affecting temperature variations of the reservoir. Direct measurements of incident solar radiation at the reservoir site for a single year allowed calibration of a predictive relationship that may be used in hydrothermal modeling. Estimation of empirical coefficients in predictive expressions for other components of water surface heat transfer was performed using the net water surface heat transfer computed from the heat budget. The implications of these findings for predictive hydrothermal modeling of the reservoir are discussed.

Free convection analysis of a window cavity and its longitudinal temperature profile

Window condensation in dwellings and offices can be very troublesome. It not only obstructs the view through the windows, but also runs off, accelerating the deterioration of paintwork, frames and furniture. In the present article, measurements and modelling techniques have been used to study the longitudinal temperature variation of double-glazed windows. It has been shown, herein, that the above temperature variation is primarily due to the buoyancy driven flow of gas within the sealed enclosure. This flow of gas alternates between the heated inward and cooled outward panes. The present work provides a physical model which can be used to calculate, with precision, the temperatures along the height of double-glazed windows. This method may be a prerequisite for the quantification of condensation, so commonly encountered in the European and North American climates.

Observations and Analysis of Longitudinal Thermal Waves on Jupiter

We analyze the properties of wave-like longitudinal temperature variations in Jupiter's upper troposphere and stratosphere, as revealed using thermal infrared (IR) ground-based observations taken yearly during the 1989–1993 period. These thermal waves are apparently the same as the “slowly moving thermal features” identified in Voyager data. We conclude that they are ubiquitous at near-equatorial latitudes on Jupiter, and have a spatial scale which typically spans wavenumber ≊2 to ≊15. Their stratospheric (20 mbar) temperature amplitude, from 7.8 μm data, is approximately a factor of 3 larger than their amplitude in the upper troposphere (≊0.3 bars), as revealed using 18 μm data. These amplitudes are consistent with the ρ −1/2growth expected for a vertically propagating Rossby wave. The phase at the two levels is the same to within 5° of longitude. The temperature wave is not advected by the zonal winds, having a phase velocity of ≊5 m sec −1in system III, but the temperature amplitude can decay on time scales ≊10 5sec. Imaging of the thermal waves shows that they are extended in latitude to a greater extent than the belt/zone structure, or the zonal wind jets. An apparently related wave is seen in broad-bandwidth (7–13 μm) IR observations which are sensitive to clouds and aerosols. This structure is advected by the zonal wind, indicating that some cloud or aerosol component shares the wave-like structure and spatial scale of the temperature wave. We interpret these waves as stationary Rossby waves, represented by small latitude excursions in the streamlines of the zonal winds. The latitude excursions could be produced by either deep structure, or by the global effect of vortices such as the Great Red Spot. In either case, temperature fluctuations are produced via “vortex stretching.” We calculate the required magnitude of the latitude excursions in the zonal winds to be ≊1° in order to produce the observed temperature amplitudes. This is a subarcsec scale for Earth-based observations, but might be detectable using observations from the Hubble space telescope.

Mapping flowfields with a heated wire and an infrared imaging system

IR imaging system measurements of longitudinal temperature variations created in wakes, jet flows, etc. by an electrically heated wire can furnish indications of air velocity distributions through Nusselt number correlations. These correlations can either account for, or minimize and neglect, wire conduction and radiation effects under steady state conditions. The IR imaging system whose experimental use is presently evaluated employs an InSb detector sensitive to 3.5-5.6-micron IR emissions.

Automatic cross-wall temperature monitor for coke ovens

A system has been devised for the automatic measurement of the temperature of coke as it is ejected from an oven following carbonisation. It gives information on both the vertical and longitudinal temperature variations within the oven, and the measurements can be related to the positions of individual flues within the heating walls.

The surface layer of the eastern North Pacific in winter

Analyses of hydrographic data from a single winter cruise and of 29 years of climatological surface temperature data are used to describe some horizontal and vertical properties (and their interrelations) of a large‐scale longitudinal temperature maximum in the eastern North Pacific. The climatological surface temperature data for individual monthly means at 35° and 40°N from 1947 to 1975 show that (1) the position of the permanent large‐scale temperature maximum at 35°N in the eastern Pacific almost always lies to the west of that of the corresponding maximum at 40°N, and the average angle counterclockwise from the east of the line connecting the two maxima is about 40° and (2) a positive correlation exists between the temperature and east‐west scales of the longitudinal temperature variation at 40°N. Both results agree with preliminary analyses based on long‐term averages of monthly mean temperatures (Kenyon, 1977a). The hydrographic data from March and April 1976 along 35°N show that both the depth scale and the east‐west scale associated with the temperature maximum in the eastern Pacific can be related to the surface layer thickness and are about 100 m and 4000 km, respectively. The surface layer thickness, defined by a temperature‐salinity relation, is relatively large (small) when the surface temperature is relatively high (low), a relation which holds for the large‐scale horizontal variability in the eastern Pacific as well as for the smaller‐scale (500 km) variability in the western Pacific. The hydrographic data at 35°N show also that the maximum surface temperature in the eastern Pacific is significantly west of the maximum surface layer thickness. Beneath the maximum surface layer temperature, where the vertical temperature gradient is large, the isotherms slope downward from west to east. The geostrophic surface velocity relative to 250 dbar, where the isotherms are nearly level, has a northward component in a broad region surrounding the surface temperature maximum. The hydrographic data strengthen the interpretation that the longitudinal surface temperature maximum is predominantly associated with horizontal advection in the surface layer, which has a significant northward component, and is the surface expression of a mechanism of net poleward heat transport in the eastern Pacific.

Gas Flow In Window Enclosures And Its Effect On Temperature Distribution

Continuing demand for tightening of building regulations with respect to energy efficiency has led to the increased use of double-glazed windows. However, even with the use of low emissivity coatings and inert gas infill the glass window is by far the thermally weak element in the buildings' fabric. In the present article measurements and modelling techniques have been used to study the longitudinal temperature variation along the inward facing glass pane of a double-glazed window. It has been shown herein that the above temperature variation is primarily due to the buoyancy driven flow of gas within the sealed enclosure which alternates between the heated inward and cooled outward panes. This work will be a prerequisite for quantification of the condensation problem so commonly encountered in the European and North American climates.