Dimensional Correlations Research Articles

Analysis on Resistance Coefficients and Optimization of Structure and Properties of Porous Permeable Refractory

The resistance coefficients through which gas flow permeable refractory are important properties and have great effect on the gas blowing parameters and gas-liquid two phase flowing characteristics in the metallurgy furnace such as ladles, tundish. In this paper, the resistance coefficients were measured according to the Forchheimer’s law. The results show when the gas flow rate is fixed, the viscosity resistance coefficient and inertia resistance coefficient decrease as the apparent porosity and average pore diameter increase. The viscous resistance coefficient is more lager than the inertial resistance coefficient. The resistance coefficients were analyzed by dimensional analysis and the statistical correlations between the resistance coefficients and parameters of porous permeable refractory were got based on the experimental data. In order to get high strength at low resistance coefficients, the raw materials particle degree were adjusted.

Antiferromagnetic correlations near the lower edge of superconducting dome in YBCO6+x

Neutron scattering from high-quality YBCO6.334 single crystals with a Tc of 8.4K shows that there is no coexistence with long-range antiferromagnetic order at this very low, near-critical doping of ∼0.055, in contrast to claims based on local probe techniques. We find that the neutron resonance seen in optimally doped YBCO7 and underdoped YBCO6.5, has undergone large softening and damping. It appears that the overdamped resonance, with a relaxation rate of 2meV, is coupled to a zero-energy central mode that grows with cooling and eventually saturates with no change at or below Tc. Although a similar qualitative behaviour is found for YBCO6.35, our study shows that the central mode is stronger in YBCO6.334 than YBCO6.35. The system remains subcritical with short-ranged three dimensional correlations.

Imaging three dimensional two-particle correlations for heavy-ion reaction studies

We report an extension of the source imaging method for analyzing three-dimensional sources from three-dimensional correlations. Our technique consists of expanding the correlation data and the underlying source function in spherical harmonics and inverting the resulting system of one-dimensional integral equations. With this strategy, we can image the source function quickly, even with the finely binned data sets common in three-dimensional analyses.

Neutron inelastic scattering investigation of the magnetic excitations inCu2Te2O5X2(X=Br,Cl)

Neutron inelastic scattering investigations have been performed on the spin tetrahedral system Cu_2Te_2O_5X_2 (X = Cl, Br). We report the observation of magnetic excitations with a dispersive component in both compounds, associated with the 3D incommensurate magnetic order that develops below $T^{Cl}_{N}$=18.2 K and $T^{Br}_{N}$=11.4 K. The excitation in Cu_2Te_2O_5Cl_2 softens as the temperature approaches $T^{Cl}_{N}$, leaving diffuse quasi-elastic scattering above the transition temperature. In the bromide, the excitations are present well above $T^{Br}_{N}$, which might be attributed to the presence of a degree of low dimensional correlations above $T^{Br}_{N}$ in this compound.

Prediction of Raceway Size in Blast Furnace from Two Dimensional Experimental Correlations

It has been reported in the literature that raceway measurement made during the decreasing gas velocity is relevant to operating blast furnaces. However, no raceway correlation is available for decreasing gas velocity and none of the available correlations either in increasing or decreasing gas velocity take care of frictional properties of the material. Therefore, a systematic experimental study has been carried out on raceway hysteresis. Based on experimental data and using dimensional analysis, two raceway correlations, one each for increasing and decreasing gas velocity, have been developed. Results of these correlations have been compared with the data obtained from literature on the cold models and plant data along with some experimental data. A good agreement exists between the correlations and other data.

Temperature renormalization of the magnetic excitations in S = 1/2 KCuCl3

A complete temperature characterization of the spin dynamics in the unconventional S =1/2 antiferromagnet KCuCl3 is presented from single crystal inelastic neutron scattering studies. KCuCl3 features a quantum disordered singlet ground state with a finite spin gap to triplet excitations of dimer origin. Three dimensional magnetic correlations support the dispersive propagation of the excitations in the whole reciprocal space. Upon increasing the temperature, a renormalization in the energy, in the intensity and in the damping rate of the triplet modes is reported. The experimental observations can be described within the framework of a selfconsistent dimer RPA theory, with no free parameters. The driving mechanism behind the model is the thermally activated decrease of the occupation difference n 0 - n 1 between singlet and triplet dimer states. This is the expression of kinematic constraints which are of minor importance for classical magnons in Neel ordered antiferromagnets. Implications for the temperature dependence of macroscopic quantities are discussed.

Correlations and Néel Order of Randomly Diluted Quantum Spin Ladders

We present a Monte Carlo study of the correlation length $\xi$ of randomly diluted antiferromagnetic Heisenberg ladders, composed of two spin--1/2 chains. For weak and intermediate inter--chain couplings, $J_{\bot}/J \leq 1$, we find an enhancement of correlations that is strongest for a fraction $z^* \approx J_{\bot}/(8J)$ of dilutants. We are able to access the experimentally relevant low--temperature regime, $T/J \approx 1/500$, and find that the recently inferred N\'eel temperature of $Sr(Cu_{1-z}Zn_z)_2O_3$ corresponds to a curve of constant correlation length $\xi \approx 18$ of the single diluted ladder with $J_{\bot}/J \alt 1/2$. The primary reason for the N\'eel ordering is argued to be a strong enhancement of two--dimensional correlations due to a Cu--Sr--Cu exchange coupling of $\approx 10 meV$ in the stacking direction of the ladders.

7th order acoustic speaker

A loudspeaker system has specific exterior dimensions and specific interior dimensional correlations which has at least a first electroacoustical transducer having a vibratable diaphragm for converting an input electrical signal into a corresponding acoustic output signal. A speaker enclosure is divided into at least first, second and third subchambers by at least first and second dividing walls. The first dividing wall supports and coacts with the first electrical transducer to bound the first and second subchambers. At least a first passive radiator intercouples the first and third subchambers. At least a second passive radiator intercouples at least one of the second and third subchambers with the region outside the enclosure. Each passive radiator is characterized by acoustic mass, and each subchamber is characterized by acoustic compliance. The acoustic mass and acoustic compliances coact to establish at least three spaced frequencies in the passband of the loudspeaker system at which the deflection characteristic of the vibratable diaphragm as a function of frequency has a minimum value.

Mass transfer coefficient in stirred tank reactors for xanthan gum solutions

The oxygen transfer rate in Newtonian and non-Newtonian fluids in a stirred tank reactor (STR) of 20 l of operating volume has been studied. The volumetric mass transfer coefficient, k L a, has been measured by a dynamic technique in solutions of xanthan gum for a wide interval of operational conditions. This coefficient has been determined changing many variables, such as the superficial gas velocity ( V s), the stirred speed ( N) or the power input by unit of volume ( P V ). Also, the properties of the liquid phase, mainly the rheologic properties of the liquid, as well as the geometry of the stirrer, have been studied considering the effect of the number and type of stirrers (paddle or turbine), the number of blades of the stirrers and the sparger type (ring and disk). The k L a values are dramatically affected by the viscosity of the liquid; to take into account this effect, the rheology of the system has been described using both the Ostwald-de Waele and the Casson models. Dimensional correlations — as a function of the operational conditions—have been obtained, and also dimensionless equations — expressing the Sherwood number as a potential function of the Reynolds, Aireation and Weber numbers—have been determined for several stirrer types.

Effect of particle density on heat and mass transfer during fluidized bed sublimation

The transfer of heat and mass between a large sublimable object and a sand fluidized bed is studied in terms of both particle size and object diameter. Convective and conductive components are identified and dimensional correlations are proposed to predict them. New data are then compared with the results previously obtained with beds of lighter particles such as non-absorbent molecular sieves. The significant differences are discussed and correlations are proposed that underline the effect of particle density.

Examination of the relationship between true halo and halo error in performance ratings.

The purpose of this study was to test competing theories regarding the relationship between true halo (actual dimensional correlations) and halo rater error (effects of raters' general impressions on specific ratee qualities) at both the individual and group level of analysis. Consistent with the prevailing general impression model of halo rater error, results at both the individual and group level analyses indicated a null (vs. positive or negative) true halo-halo rater error relationship. Results support the ideas that (a) the influence of raters' general impressions is homogeneous across rating dimensions despite wide variability in levels of true halo; (b) in assigning ratings, raters rely both on recalled observations of actual ratee behaviors and on general impressions of ratees in assigning dimensional ratings; and (c) these 2 processes occur independently of one another.

Agreement between self-report and semi-structured interviewing in the assessment of personality disorders

This paper presents the results of a study comparing two instruments for the assessment of personality disorders according to the DSM-III-R and the ICD-10 classification systems: the International Personality Disorder Examination (IPDE), a semi-structured clinical interview, and the “Questionnaire on Personality Traits” (VKP), a self-report questionnaire. IPDE interviews and VKP self-reports were administered to 108 psychiatric patients and ‘normals’. The VKP appeared to overestimate the prevalence of personality disorders when compared with the IPDE: prevalence of personality disorders is about 2.5 times higher when assessed by self-report than by interview. The mean Kappas for DSM and ICD disorders were low, respectively 0.25 and 0.26. These mean Kappas were only calculated if a positive DSM and ICD disorder base rate is at least 5%. The sensitivity of the VKP is 100% for eight of the 22 disorders. For 15 out of 22 disorders, the specificity of the VKP is reasonable to high (⩾ 0.80). The probable and positive diagnoses of the VKP cover 87% of the positive IPDE diagnoses. On the dimensional level high correlations were found between similar scales of the IPDE and the VKP, and low correlations between scales that measure different concepts, pointing to reasonable convergent and discriminant validity. Based on the results of this study it is concluded that the VKP is a suitable screening instrument for most DSM-III-R and ICD-10 personality disorders.

Hole Doping Effect on 2D Spin Correlations in La2NiO4+δ

Quasielastic neutron scattering experiments from La 2 NiO 4+δ revealed a substantial hole doping effect on the 2 dimensional spin correlations. Thermal evolution of correlation length clearly shows the reduction of the exchange stiffness constant by hole doping, which is in marked contrast to that of La 2 CuO 4+δ . The present result is reflected by the hole character in La 2 NiO 4+δ , which is different from that in the cuprate.

EXPERIMENTAL STUDY OF A GLAZED SOLAR COLLECTOR/REGENERATOR OPERATED UNDER A HUMID CLIMATE

The performance of a glazed solar collector/regenerator (C/R) for an open-cycle absorption solar cooling system using aqueous lithium chloride solution as the working fluid was tested at Kaohsiung, Taiwan under a humid climate. The results indicate that the peak system efficiency is 15.2% and the day-average efficiency is 14.1%. The effects of parameters on the C/R performance are studied, and the non dimensional correlations for heat and mass transfer were given.

Effective surface heat transfer coefficients encountered in air blast freezing of single plastic wrapped whole turkey

The surface heat transfer coefficients during air blast freezing of single plastic overwrapped turkey were estimated under conditions encountered in commercial practice. Whole turkey was approximated by a hallow sphere. A numerical method based on enthalpy formulation was used to simulate the freezing process. A series of experiments were conducted to obtain the temperature profiles during air blast freezing. The experimental and simulated temperature histories were compared using a sum of error squares technique to estimate surface heat transfer coefficients. The results were presented as dimensional and non-dimensional correlations. An approximate analytical method based on Plank's equation was extended to predict freezing times of hollow spherical shape. The effects of air temperature, air humidity and plastic wrap on the surface heat transfer coefficient were analysed. Parametric effects on surface heat transfer coefficients and freezing times were studied.

Effective surface heat transfer coefficients encountered in air blast freezing of whole chicken and chicken parts, individually and in packages

The surface heat transfer coefficients encountered in air blast freezing of plastic wrapped whole chicken, traypacks of chicken parrts and boxed chicken parts were determined during this study. Freezing of these items was simulated using a numerical method based on enthalpy formulation. A series of experiments were conducted using poultry packages at three different air blast velocities. The experimental temperature histories were compared with simulated temperature histories to estimate surface heat transfer coefficients. The results were presented as dimensional and non-dimensional correlations. Approximate analytical methods based on Plank's equation were developed to predict freezing times.

Two and three dimensional gamma ray correlations in rotational nuclei

Several new methods for the study of nuclear structure at low temperature are reviewed. The methods analyze the fluctuations of the intensity of Eγ1 · Eγ2 spectra, and the shape and width Γrot of the correlated patterns with different characteristics of the rotational motion in cold and warm nuclei. New results are given for the rotational damping width, and the number of 2-step-paths below and above U0 ≈ 800 keV, considered to be the energy of the borderline between undamped and damped rotational motion. The rotational damping width Γrot is studied as function of rotational frequency for selected regions of entry states in 163Tm , and found to be rather constant ≈ 80 keV, significantly smaller than current theoretical predictions. The fluctuation analysis supports the damping picture in general, and confirms that a strong branching of the transition strength for each step in the E2 cascades exists at high spin. This can be taken as evidence for damping of the rotational motion in warm nuclei.

A mathematical model of mixing and polymerization in a semibatch stirred‐tank reactor

AbstractEffects of mixing on number‐ and weight‐average degree of polymerization in free radical homopolymerization in solution in a semibatch stirred tank‐reactor have been modeled by use of the “partially segregated feed” model of Villermaux (1989) and the lumped kinetic treatment of addition polymerization. Mixing conditions are described in terms of the dimensionless time constants θM and θX for convective and diffusive mixing, respectively. Results show that DPn is relatively insensitive, while DPw is highly sensitive to mixing conditions. Comparison with ideal mixing results shows that polydispersity (DPw/DPn) can rise greatly as mixing becomes increasingly nonideal, depending on the value of dimensionless flow rate and dimensionless initiator rate constant. Time constants of the mixing model need to be expressed as dimensional correlations before the proposed polymerization model can be compared to experimental measurements. The model may be adapted to melt polymerization in nonideal CSTR such as LDPE.

Improving the statistical accuracy of dimensional analysis correlations for precise coefficient estimation and optimal design of experiments

Two main problems arise in the computation of coefficients in dimensional analysis correlations. The first is connected with the possible inadequacy of the usual power law [1]. The second is the lack of statistical consistency brought about by the usual computational methods based on linear least squares. This problem has been recently tackled by Li and Lee. [2] In this paper we propose a general, statistically sound framework for correct coefficient determination and optimal design of experiments.

133Cs NMR study of the ferroelectric and antiferroelectric transitions in CsH2PO4

Abstract Pressure and temperature effects on the one dimensional (1D) and higher-dimensionality correlations associated with the ferroelectric (FE) and antiferroelectric (AFE) phase transitions in cesium dihydrogen phosphate were studied using 133Cs nuclear magnetic resonance at 6.5 MHz. The spin-latticerelaxation time T1 was measured at temperatures down to the FE Curie point TC at pressures of 1 bar and at 1.5 and 3.0 kbar, down to the triple point Tt = 124.6 K at 3.3 kbar, and down to the AFE Neel point TN at 3.6 kbar. Far from the transition T1 decreases exponentially with decreasing temperature due to 1D fluctuations associated with the Jb interactions in disordered hydrogen-bonded chains running along the b axis. As temperature is decreased further, T1 decreases linearly as the JC interaction between hydrogen-bonded chains in b-c planes becomes important. From these results the pressure dependences of Jb, JC and the interplanar interaction Ja were calculated. At 3.3 kbar Ja changes sign, so the stacking of ordered planes becomes AFE rather than FE. At pressures above about 9 kbar, where the interaction JC extrapolates to zero, a new AFE phase is predicted in which each b-axis chain is oriented AFE with respect to nearest neighbors in both the a and c directions.