Two-zone Method Research Articles

Study on milling behavior of TiAlN coated tool with variable distribution density micro-texture

Considering that after milling titanium alloy with a ball-end milling cutter, the wear degree of different areas of the rake face is different, which indicates that the tool-chip contact conditions in this area are different, and then the micro-texture action mode is different. To improve the effect of micro-texture, this paper establishes a mathematical distribution model of variable distribution density micro-texture based on the two-zone method, builds a variable distribution density micro-texture ball-end milling titanium alloy test platform, studies the influence of variable density micro-texture parameters on tool milling behavior, and optimizes the parameters based on the improved particle swarm optimization algorithm. The results show that the micro-texture with variable distribution density has a positive effect on the milling behavior of the tool. The micro-texture parameters of the stickiness area have the greatest influence on the milling behavior of the tool. A texture parameter is optimized, and the overall milling behavior of the variable density micro-texture TiAlN coated milling cutter is optimal. This study provides a theoretical basis for the design and preparation of variable distribution density micro-textured tools. Highlights Based on the two-zone method, the mathematical distribution model of the variable distribution density micro-texture of the rake face of the tool is constructed. The influence mechanism of micro-texture parameters on the milling behavior of a ball-end milling cutter is explored. The multi-objective optimization of the variable density micro-texture parameters was carried out, and the optimal parameter combination was obtained. It is verified that the variable distribution density of the micro-texture has a positive effect on the cutting performance of the tool.

Approximate Thermal Calculation of the Superheated Steam Condenser of Heat Pumps

A comparative analysis of the methods of approximate thermal calculation of the superheated steam condenser of the steam compression heat pump of the heat supply system is presented. The working substance of the heat pump and the condensing steam is the refrigerant R410a. When the single-zone method is applied, the condenser is calculated by one area with the inclusion of the heat of overheating in the heat of condensation and the use of the overheating coefficient. The two-zone method assumes the calculation of the condenser in two separate areas, viz. the cooling of superheated steam and its actual condensation. The approbation was carried out during a numerical study of a condenser of a low-temperature heat pump system for heating and hot water supply, with a heat exchange surface in the form of a spiral coil pipe in a pipe immersed in a heated liquid. In the first approach, the flow rate and temperature of the heated water are limited by the saturation temperature of the condensing refrigerant, regardless of the flow pattern of the working media. The method of two-zone calculation of the superheated steam condenser with a counter-current or cross-counter-current flow scheme of working media makes it possible to obtain real results of the temperature of the heated water that exceeds the temperature of the saturated refrigerant vapor, taking into account the flow rate of the heated water. In this case, the wall temperature in the cooling area is higher than the saturation temperature, and during condensation it is lower, which further confirms the adequacy of the presented technique. The use of a two-zone technique with a separate averaging of the physical properties of the working media in the areas of superheated steam and condensation cooling, as well as temperature pressures, provides a more accurate value of the heat exchange surface, which in the case under consideration is reduced to 20%. Based on the conducted studies, it is recommended to use a two-zone technique that makes it possible to obtain reliable data on the parameters of the superheated steam condenser.

A hybrid performance prediction method for centrifugal compressors based on single-zone and two-zone models

High-accuracy models are essential for rapid performance estimations and reliable parameter refinements during the preliminary design of centrifugal compressors. In this paper, a hybrid performance prediction method is proposed by combining the loss models of the single-zone method and the division idea of the two-zone method. Physically-based loss models are adopted for the jet zone analysis in substitute of the empirical parameters in the two-zone method. Two additional parameters are introduced for the wake zone analysis to implicitly evaluate the loss not fully understood in the single-zone method. For these two-zone parameters, prediction models are proposed by first analyzing the dominant factors from one-dimensional level and then extracting the coefficients from diverse datasets with statistical techniques. The hybrid method is validated on four centrifugal compressors with flow coefficients ranging from 0.09 to 0.58 and pressure ratios up to 8.5. The results show that, compared with the single-zone and two-zone methods, the hybrid method provides more reliable performance predictions with higher accuracy in the whole operating range.

Synthesis and characterization of intercalated few-layer graphenes

Toward achieving room-temperature superconductivity, FeCl3-intercalated few-layer graphenes (FeCl3-FLGs) and Ca-intercalated few-layer graphenes (Ca-FLGs) were synthesized. FeCl3-FLGs were synthesized by the two-zone method and Ca-FLGs were synthesized using Ca–Li alloy. The Raman spectra of the FeCl3-FLGs showed a lower-intensity peak at 1607 cm−1 than that of the corresponding bare G. The peak at 1607 cm−1 suggested that the sample was stage 4–5 FeCl3-FLGs. The room-temperature electrical resistivity of FeCl3-FLGs was 2.65 × 10−5 Ω·m, which linearly decreased with decreasing temperature with a marked change occurring at approximately 200 K. From a XRD pattern of Ca-FLGs, we concluded that Ca is intercalated in FLGs. The room-temperature resistivity of Ca-FLGs was 3.45 × 10−5 Ω·m, which increased with decreasing temperature.

Polycrystal Synthesis and Single Crystal Growth of PbI<sub>2</sub>

High-pure and single-phase PbI2 polycrystal was synthesized by Pb and I elements (99.9999%) according to the stoichiometry of PbI2 with excess of 0.3% Pb through modified two-zone vapor-transporting method (MTVM). The synthesis reaction was carried in a special quartz ampoule to prevent the ampoule exploding by controlling the temperature. With presynthesized polycrystal, an integral PbI2 single crystal with 15 mm in diameter and 25 mm in length was grown by vertical Bridgman method (VBM). The as-grown crystal was characterized by X-ray diffraction (XRD), ZC36 megger and Infrared (IR) spectrophotometers. XRD analysis indicated the structure of PbI2 crystal is 2H with hexagonal space group of , the lattice constants of a and c are 0.4560 nm and 0.6979 nm, respectively. The IR transmittance of a sample of 2.5 mm thickness is about 40% in the range from 4000 to 400 cm-1. Resistivity of the crystal is about 1013 Ωcm magnitude. These results demonstrate that the quality of the as-grown crystal is high enough for applications of room temperature nuclear radiation detectors.

An extension of the two-zone method for evaluating a fission gas release under an irradiation-induced resolution flux

This paper describes an extension of the adaptive two-zone method whose accuracy is substantially enhanced when compared to the original formulation by Matthews and Wood. A diffusive problem under the presence of an irradiation-induced resolution flux is evaluated by applying a variational principle to the diffusion equation. Prior to a gas saturation in the grain boundaries, a constraint associated with a gas balance is added to the variational equation. The spherical grain is divided into two regions whose interface is relocated as the ratio of the number of gas atoms within a grain to that generated. The distribution of the gas concentration is calculated over the grain. During the calculations, the number of degrees of freedoms is reduced to provide a profile which decreases monotonically along the radius. Numerical verifications show that the present approach is viable in computing a gas release accurately and efficiently in fuel performance codes.

A two-zone method with an enhanced accuracy for a numerical solution of the diffusion equation

A variational principle is applied to the diffusion equation to numerically obtain the fission gas release from a spherical grain. The two-zone method, originally proposed by Matthews and Wood, is modified to overcome its insufficient accuracy for a low release. The results of the variational approaches are examined by observing the gas concentration along the grain radius. At the early stage, the concentration near the grain boundary is higher than that at the inner points of the grain in the cases of the two-zone method as well as the finite element analysis with the number of the elements at as many as 10. The accuracy of the two-zone method is considerably enhanced by relocating the nodal points of the two zones. The trial functions are derived as a function of the released fraction. During the calculations, the number of degrees of freedom needs to be reduced to guarantee physically admissible concentration profiles. Numerical verifications are performed extensively. By taking a computational time comparable to the algorithm by Forsberg and Massih, the present method provides a solution with reasonable accuracy in the whole range of the released fraction.

Correlation Effects in Two-Electron Model Atoms in Intense Laser Fields

We report an efficient implementation of a spatial two-zone method for solving Schr\"odinger's equation numerically, using a canonical basis set decomposition, and also its application to two-electron wave functions in a study of double multiphoton ionization. We make the first calculation of the time-dependent degree of electron correlation for this poorly understood process. Our results show a particularly sensitive window of intensities coinciding exactly with the well-known ``knee'' regime in ion-count data.

Techniques for the Preparation of Metal Chloride- and Alkali Metal-GICS.

For preparation of metal chloride- and alkali metal-graphite intercalation compounds (GICs), the two-zone method is usually employed. When the experiments are carried out, however, some difficulties should be considered: e. g. corrosive chlorine gas is essential to the two-zone reactor for the greater part of metal chloride-GICs and alkalimetals are reactive with atmospheric moisture. In this report we present some useful techniques for the effective andless dangerous preparation of metal chloride- and alkali metal-GICs.

Two-Zone Convective Scaling of Diffusion in Complex Terrain

A “two-zone” convective scaling equation is developed that allows for a step change in scaling parameters. The results of the Lompoc Valley Diffusion Experiment, conducted at coastal site in California under variable cloud cover, are compared to the two-zone model and five other parameterizations obtained from the literature. The two-zone method is shown to unambiguously select appropriate convective scaling parameters for the partially cloud-covered cases. Its accuracy is comparable to a statistical approach that relies on in situ turbulence measurements and a Lagrangian time scale derived from the data. While the two-zone method works for maximum concentration predictions at any downwind distance, all models underpredict plume width and crosswind-integrated concentration measured at long ranges. It is speculated that the observed enhancement is due to near-surface topographic flows that spread the plume at the surface but maintain centerline concentration.

Bi-intercalation process of high stage metal chloride-graphite intercalation compounds

Stage-4 AlCl3-GIC prepared by the standard two-zone method were oxidized galvanostatically in H2SO4. The X-ray diffraction data indicate the stepwise intercalation of H2SO4 into host graphite and no formation of the GBC is observed, whereas AlCl3 is deintercalated in an early step of the reaction. In the case of the stage-4 MoCl5-GIC, the galvanostatic oxidation caused the stepwise bi-intercalation of H2SO4 into the host GIC as well as the displacement of MoCl5 by H2SO4.Alternatively, AlCl3 vapour was allowed to react with stage-3 FeCl3-GIC. The competition between the displacement reaction of FeCl3 by AlCl3 and the stepwise bi-intercalation of AlCl3 into the stage-3 FeCl3-GIC was observed.The bi-intercalation process of such a high stage GIC is explained with a schematic chemical potential diagram, comparing the bi-intercalation into stage-2 GIC.

Electrochemical preparation of the graphite bi-intercalation compound with H 2SO 4 and FeCl 3

Stage- n FeCl 3-GICs ( n = 2,3) prepared in the standard two-zone method were oxidized galvanostatically in H 2SO 4. The electrode potential vs. electric quantity curves observed during the treatment and the X-ray powder patterns of the products showed clearly the intercalation of H 2SO 4 into FeQ 3-GICs and the formation of the graphite bi-intercalation compounds (GBCs) of FeCl 3 and H 2SO 4. The c axis repeat distance I c of the GBCs, 17.38Å, from the stage-2 FeCl 3-GIC was equal to the sum of those of FeCl 3-GIC, 9.38Å, and of H 2SO 4-GIC, 8.00Å. From the stage-3 FeCl 3-GIC the compound with I c of 25.38Å ( = 9.38Å + 8.00Å + 8.00Å), through the intermediate with I c of 20.73Å ( = 9.38Å + 3.35Å + 8.00Å). The electrochemical reduction of these GBCs suggested that the intercalation of H 2SO 4 into FeCl 3-GICs is reversible.

Electrochemical preparation of metal chloride-sulfuric acid-graphite bi-intercalation compound

Stage-2 metal chloride-GICs (metal chloride: AlCl3, BiCl3 and CuCl2) prepared in the standard two-zone method were oxidized galvanostatically in H2SO4.The electrode potential vs. electric quantity curves observed during the electrochemical treatment and the X-ray powder patterns of the products showed clearly the intercalation of H2SO4 into metal chloride-GICs and the formation of the graphite biintercalation compounds (GBCs) of metal chloride and H2SO4.The c axis repeat distance Ic of the GBCs was equal to the sum of those of metal chloride-GIG and of H2SO4-GIC.

Cesium and bromine doping into hexagonal boron nitride

Using a two-zone method, the possible formation of an intercalation compound of hexagonal boron nitride (BN) with Cs and Br2 was investigated. Only a few percent weight increase was observed by doping BN with Cs and Br2. The electron paramagnetic resonance (EPR) signal was significantly modified by Cs doping, which is attributed to the reaction between the Cs atoms and spin resonance centers (N vacancies) in BN; no change in the EPR spectra was observed with Br2 doping. However, the deep blue colored Cs-BN complex reported by Mugiya and co-workers was not obtained with the two-zone method. Though no evidence of systematic intercalation reaction in BN was observed in contrast to graphite host materials, intercalation islands induced by the introduction of Cs atoms were suggested by the transmission electron microscopy (TEM) observations.