Surface Generation Rate Research Articles

Synergy between fayalite-constituted waste copper smelting slag and hydroxylamine: An efficient combination for construction and application of a surface Fenton system in removal of mining organic pollutants

The growing problem of typical organic pollution in mines, and the effective utilization of increasing mine industrial wastes have been the most challenging issues in the current global situation. In this study, copper smelting slag (CSS), hydroxylamine (HA) and H2O2 were employed to construct an efficient surface heterogeneous catalyst for the degradation of organic pollutants in mines. Fayalite and its ≡Fe were proved, by multiple methods, to be the crucial ferriferous catalyst in the CSS. HA greatly increased the oxidation effectiveness of the CSS from 53.6% to ∼100% by regulating the Fe2+/Fe3+ circulation within the fayalite lattice. Due to the special structural configuration of iron atoms in fayalite, the surface generation rate of •OH catalyzed by CSS was 101-106 times higher than in other iron-bearing minerals. •OH was demonstrated to be the main active radical species, and as an intermediate, O2•- also had a role in the oxidation process. In the presence of low doses of Cr, a synergistic removal of organic pollutants occurred, dominated by the electron transfer. Accordingly, this study proposes both, a new design concept for recycling the industrial solid waste from mines and a new surface catalyst system for the removal of organic pollutants from mining.

INVESTIGATION OF WATERJET EFFLUX NOISE WITH NUMERICAL TECHNIQUES

The URN resulting from a waterjet propulsion (WJP) is to be accurately estimated for stealth considerations. Such WJP systems are designed to operate either with a submerged jet (wet transom) or with a free surface jet (dry transom). The URN due to the operation of WJP system can be broadly categorized as pump noise and nozzle efflux noise. Pump noise includes mainly the cavitation noise and the tonal mechanical/hydrodynamic noise, whereas the nozzle efflux noise is due to jet impact and bubble entrainment. The present study attempts to implement advanced numerical techniques to estimate URN due to the nozzle efflux of a WJP in both wet and dry transom modes. Large Eddy simulations (LES) are carried out to simulate the hydrodynamics of turbulent multiphase flow behind both submerged and free surface water jets. The impact of water jet on free surface and subsequent bubble generation rate is captured using multiphase volume of fluids (VOF) technique. The impact noise is estimated by directly recording the fluctuating acoustic pressure at certain field points during the simulation. A blob detection algorithm is implemented to compute the bubble generation rate. A mathematical model to compute the bubble pulsation noise from bubble generation rate is validated and implemented. The estimated URN levels in wet and dry mode are presented and compared. Key inferences are presented which could be useful in further investigation of URN from water jet of stealth vessels, as well as to investigate bubble noise from propeller cavitation, air lubrication etc.

Origin of the current saturation level of p-doped silicon field emitters

Using p-type semiconductors for field emitters is one simple way to realize an integrated current limiter to improve the lifetime of the cathode. In this work, the origin of the current saturation of p-type silicon emitters is investigated in detail. Single emitters are electrically characterized and compared to simulation results. With a simulation model considering a high surface generation rate and elevated tip temperature, a good agreement to the measured data is found. This observation is supported further by alteration of the surface experimentally. Electrical measurements after different treatments in hydrofluoric acid as well as heated and subsequent operation at room temperature are well explained by the influence of surface generation. Furthermore, it is shown that the field penetration leads to a small voltage drop and a strong geometry-dependent reduction of the field enhancement factor.

Generalized design method of highly-varied-helix end mills for suppression of regenerative chatter in peripheral milling

Peripheral finishing of hardened steel by milling has recently been introduced to the machining field, but often causes severe chatter vibration due to high specific cutting force and low stiffness of slender end mills. It was shown in the previous papers that highly-varied-helix end mills were effective for the suppression of regenerative chatter, and a low radial immersion was applied to avoid the effect of mode coupling. Especially for the highly-varied-helix end mills, it was proved experimentally that they were effective across a wide range of cutting conditions, making it possible for cutting with a relatively large axial depth of cut to be carried out and thus realizing a high surface generation rate in peripheral milling of hard materials. However, the milling tests were carried out under just one specific condition, i.e., tool diameter 8 [mm], projection length 36 [mm], and workpiece of 60 HRC hardened steel, etc., and the helix angles of the tool were varied large enough to suppress regenerative chatter but with no quantitative discussion for their determination. In this paper, a generalized design method for varied-helix end mills to suppress regenerative chatter is proposed. Namely a design index apalim, in which ap is the distance between 2 adjacent regenerative effect cancellation lines and alim is the asymptotic stability limit in the targeted cutting process, is introduced to design the helix angle difference of a tool, and milling experiments are carried out in several conditions to verify the validity of the proposed index.

Surface Generation for Magic-Mirror by End-Milling and Magnetic Polishing with Digitally Functioned CNC Machining Center

This paper describes fabrication of a magic-mirror with an extremely small concavo-convex surface, which is invisible to the naked eye. The magic-mirror was manufactured by end-milling with a machining center on the rear of the workpiece after polishing. Incident light was radiated to the mirror surface and the reflected light was projected on a screen. The tool pass by CNC programming show up as image of magic-mirror on the screen. Analysis of the image on the screen indicated completion rate of magic-mirror surface generation. As some experimental result, the integrated magic-mirror production process on the machining center could be achieved by a novel application of on-machine magnetic abrasive finishing and ball end-milling. Moreover, it was found to possible to fabricate a magic-mirror with satiny and continuous-curvature corrugated surface.

Investigations into abrasive flow finishing of complex workpieces using FEM

Abrasive flow machining (AFM) process provides a high level of surface finish and close tolerances with an economically acceptable rate of surface generation for a wide range of industrial components. It is attempted to analyze the AFM process using finite element method (FEM) for finishing of external surfaces. To study the material removal mechanism of AFM, finite element model of forces acting on a single grain has been developed. Response surface method (RSM) is used to carry out an experimental research to analyze the effect of extrusion pressure and number of cycles on material removal and surface finish. Results obtained from finite element analysis for material removal have been compared with the experimental data obtained during AFM.

Effect of ultrasonic treatment on the generation characteristics of a semiconductor-glass interface

It is demonstrated that the temporal variation of the rate of the surface generation of charge carriers at a semiconductor-glass interface can be determined by measuring the kinetics of capacitance relaxation in the semiconductor-glass-metal structure. Ultrasonic treatment of the semiconductor-glass interface decreases the absolute value of the surface generation rate and modifies its temporal dependence.

The rate of surface generation of charge carriers at the semiconductor-glass interface

A method was proposed that allows to one to determine the temporal dependence of the rate of the surface generation at the semiconductor-insulator interface. It was shown that the rate of surface generation in metal-insulator-semiconductor (MIS) structures made of n-Si covered by a lead-borosilicate glass was a function of time.

SMOLDERING COMBUSTION OF “INCENSE” STICKS—EXPERIMENTS AND MODELING

This paper is concerned with the experimental and modeling studies on the smoldering rates of incense sticks as a function of ambient oxygen fraction in air, the flow velocity and size. The experimental results are obtained both for forward and reverse smolder conditions. The results are explained on the basis of surface combustion due to diffusion of oxygen to the surface by both free and forced convection supporting the heat transfer into the solid by conduction, into the stream by convection and the radiant heat transfer from the surface. The heat release at the surface is controlled by the convective transport of the oxidizer to the surface. To obtain the diffusion rates particularly for the reverse smolder, CFD calculations of fluid flow with along with a passive scalar are needed; these calculations have been made both for forward and reverse smolder. The interesting aspect of the CFD calculations is that while the Nusselt umber for forward smolder shows a clear dependence (Re u = Flow Reynolds Number), the result for reverse smolder shows a peak in the variation with Reynolds number with the values lower than for forward smolder and unsteadiness in the flow beyond a certain flow rate. The results of flow behavior and Nusselt number are used in a simple model for the heat transfer at the smoldering surface to obtain the dependence of the smoldering rate on the diameter of the incense stick, the flow rate of air and the oxygen fraction. The results are presented in terms of a correlation for the non-dimensional smoldering rate with radiant flux from the surface and heat generation rate at the surface. The correlations appear reasonable for both forward and reverse smolder cases.

Finite element analysis of media used in the centrifugal force assisted abrasive flow machining process

Abrasive flow machining (AFM) is a non-conventional finishing process that provides a high level of surface finish and close tolerances with an economically acceptable rate of surface generation for a wide range of industrial components. AFM deburrs and polishes by forcing an abrasive laden media (elastic/viscoelastic polymer) across the workpiece surface. Abrasion occurs only where the media flow is restricted; other areas remain unaffected. One serious limitation of AFM processes is a low material removal rate. An effort has been made towards the performance improvement of this process by applying centrifugal force on the abrasive media using a rotating rod introduced in the workpiece passage. This variant of AFM, called centrifugal force assisted abrasive flow machining (CFAAFM), has been developed. This paper presents finite element modelling (FEM) of a polymer-based non-Newtonian viscoelastic fluid used in the CFAAFM process and the same is used to evaluate the resultant pressure, velocity, and radial stresses during a working cycle. All FEM analyses were performed using a commercial finite element package ANSYS. The results are compared with the data available in the literature, and close agreement has been found between the two.

A new technology in surface finishing: Fluidized bed machining (FBM) of aluminium alloys

This paper deals with the definition of a new finishing process named fluidized bed machining (FBM). Material is removed from the workpiece by an abrasive solid emulsion and air flowing through all the equipment, scratching the surface to be finished. This process is able to produce an accurate surface finishing both on areas inaccessible to traditional methods and complex passages. The application of FBM to sheets and complex shaped components, made from two aluminum alloys, AA 2024 O and AA 2024 T3, with a widespread diffusion in several industrial sectors has been investigated. Experimental tests were performed with the aim of studying mass removal, evolution of surface topography, and process efficiency in terms of improvements in average roughness. The results of experimental tests showed that the surface profile generated and material removal were functions of the processing time, mesh size, type of abrasive, flow speed applied. The results revealed that the efficiency of the process is strongly linked to the mechanical properties of the metal treated. Furthermore, from the surface texture examination, it followed that this technique guarantees good surface finishing without influencing closest geometrical tolerances and with a rate of surface generation for ductile materials being economically acceptable.

Continuously variable mixing-ratio micromixer with elastomer valves

We report a self-contained microfluidic alternate flow injection mixer (AFIM) employing piezoelectrically actuated, PDMS seal-valves to control injection. AFIMs employ pulsatile injection of liquids to enhance interface surface generation. By allowing control of pulse-volume proportionality by variation of the duty-cycle of the valve control signals, continuously variable ratio mixing is achieved without external fluid control components. Mixing is discussed in the context of ‘rate of new surface generation’, thus allowing comparison with laminating mixer designs. The prototype mixer employs a simple micromould fabrication technique to minimize reversible elastomer valve-seal adhesion and hence allow correct valve operation. The resulting device has been characterized over a range of mixing ratios.

Determination of the Minority Carrier Surface Thermogeneration Rate in Metal-Oxide-Semiconductor Structures

A metal-oxide-semiconductor (MOS) structure with the common field electrode insulated from the semiconductor by oxide layers h of different thicknesses allows the surface generation rate of minority charge carriers from current I(t) of nonequilibrium depletion state relaxation to be found. At the same time, it is possible in similar structures to observe the kinematics of electron-hole pair generation at the periphery of the field electrode (the edge generation effect). Measurements performed on an n-Si MOS structure with a stepwise change in oxide layer thickness (h1 = 100 A and h2 = 3200 A) allowed the generation rate at both the initial transient (t ∼ 10−5 s) stage of surface generation (4.34 × 1010 cm−2 s−1) and at the basic extremely slow stage (10.4 cm−2 s−1) to be reliably determined for the first time. The estimated peripheral generation rate of minority charge carriers (holes) was 7.8 × 1011 cm−2 s−1.

Temporal variation of oceanic spreading and crustal production rates during the last 180 My

We present a re-evaluation of seafloor spreading and generation rates, mainly based on a direct measurement of the remaining surfaces of oceanic crust and isochron lengths defined in the most recent isochron maps [J.Y. Royer, R.D. Müller, L.M. Gahagan, L.A. Lawyer, C.L. Mayes, D. Nürnberg, J.G. Sclater, A global isochron chart, Tech. Rep. 117, Austin, Univ. of Tex. Inst. for Geophys., 1992; R.D. Müller, W.R. Roest, J.Y. Royer, L.M. Gahagan, J.G. Sclater, Digital isochrons of the world's ocean floor, J. Geophys. Res., 102 (1997), 3211–3214]. Our evaluation of the amount of oceanic crust per unit age {d A/d t} as a function of age, which can be expressed as d A/d t= C o(1− t/ t m), is in fairly good agreement with previous determinations [J.G. Sclater, B. Parsons, C. Jaupart, Oceans and continents: similarities and differences in the mechanisms of heat loss, J. Geophys. Res., 86 (1981) 11,535–11,552; D.B. Rowley, Rate of plate creation and destruction: 180 Ma to present, Geol. Soc. Amer. Bull., 114 (2002) 927–933], with C o=2.850±0.119 km 2 year −1 and t m=180.2±9.7 Ma. Dividing these d A/d t by the ridge lengths L, defined as the isochron length at each epoch allowed us to compute the evolution of global half-spreading rates. These have been roughly constant at 25.9±3.3 mm year −1 for at least the last 150 Ma. We propose that the global seafloor surface generation rate is roughly constant as well, with a mean half-value of 1.298±0.284 km 2 year −1 and varying ±20% with time. This study corroborates the recent conclusion of Rowley [D.B. Rowley, Rate of plate creation and destruction: 180 Ma to present, Geol. Soc. Amer. Bull., 114 (2002) 927–933], of a constant generation rate since 180 Ma, and completely contradicts the commonly accepted idea of high seafloor spreading and surface generation rates during a large part of the Cretaceous. Combining the oceanic surface generation rates derived here with crustal thicknesses deduced from the chemical composition of old oceanic crusts and seismic measurements [E. Humler, C.H. Langmuir, V. Daux, Depth versus age: new perspectives from the chemical compositions of ancient crust, Earth Planet Sci. Lett., 173 (1999) 7–23], the magmatic flux at young (0–80 Ma) oceanic ridges appears to be about 18.1±3.4 km 3 year −1 and was possibly 15% to 30% higher during the Mesozoic. We propose that mantle temperature variation provides an alternative mechanism to spreading rate for the Cretaceous highstand in sea-level and atmospheric CO 2 generation.

Electrical properties of metal-dysprosium oxide-gadolinium oxide-silicon structures

We have studied the electrical properties of aluminum-dysprosium oxide-gadolinium oxide-silicon (Al-Dy2O3-Gd2O3-Si) structures. The conductivity of these metal-insulator-semiconductor (MIS) structures is satisfactorily described by the Poole-Frenkel mechanism. The density of surface states determined by the method of capacitance-voltage characteristics is 5.6×1011 cm−2. The surface generation rate and lifetime of the minority charge carriers determined using the Zerbst method fall within 47–67 cm/s and 0.3–0.6 μs, respectively. The structures studied are promising materials for MIS varactors with a high capacity variation coefficient.

Prediction of regenerative chatter by modelling and analysis of high-speed milling

High-speed milling is widely used in the manufacturing industry. For the efficiency of the milling process, high demands on the material removal rate and the surface generation rate are posed. The process parameters, determining these two rates, are restricted by the occurrence of regenerative chatter. Chatter is an undesired instability phenomenon, which causes both a reduced product quality and rapid tool wear. In this paper, the milling process is modelled, based on dedicated experiments on both the material behaviour of the workpiece material and the machine dynamics. These experiments show that both the material properties and the machine dynamics are dependent on the spindle speed. Furthermore, a method for the prediction of the chatter boundaries is proposed and applied in order to predict the chatter boundaries as a function of process parameters, such as spindle speed and depth-of-cut, for spindle speed varying material and machine parameters. Finally, experiments are performed to estimate these chatter boundaries in practice. The modelled chatter boundaries are compared to the experimental results in order to validate the model and the stability analysis.

The effect of ultrasonic treatment on the generation characteristics of a Si-SiO2 interface

We have studied the effect of ultrasonic treatment on the generation characteristics of a silicon-silicon dioxide (Si-SiO2) interface obtained by thermal oxidation of the surface of silicon. The ultrasonic treatment leads to a decrease in the surface generation rate and an increase in the generation lifetime of minority charge carriers. These effects are related to a transformation of the defect structure of a transition layer at the Si-SiO2 interface and in the adjacent region of silicon.

Effect of germanium on redistribution of boron and phosphorus during thermal oxidation of silicon

The diffusion–segregation redistribution of B and P impurities during thermal oxidation of Ge-containing Si has been simulated. In all probability, Ge affects the diffusion of B and P via bulk recombination of self-interstitials (SI) on Ge centres, rather than through a decrease in the rate of surface generation of SI in thermal oxidation. The Ge-induced retardation of the oxidation-enhanced diffusion of B and P in Si and redistribution of the B and P impurities at the SiO2/Si interface are described. The parameters of SI bulk recombination on Ge-related centres are found and an increase in the segregation coefficient of B in the SiO2–Si system in the presence of Ge is revealed by comparing the calculated and experimental concentration distributions.

Effect of the Nickel Impurity on the Rate of Surface Generation of Charge Carriers at the Si–SiO 2 Interface

The effect of the nickel impurity on the generation characteristics of the Si–SiO2 interface is investigated by the method of isothermal capacitance relaxation. It is demonstrated that doping by the nickel impurity increases the rate of surface generation of charge carriers and the spread of this parameter from structure to structure. The effects observed are associated with the existence of defect-impurity complexes formed in doped structures as a result of interaction of impurity clusters (precipitates) with native defects in the transition layer at the Si–SiO2 interface.

Modeling of material removal and surface roughness in abrasive flow machining process

Abrasive flow machining process provides a high level of surface finish and close tolerances with an economically acceptable rate of surface generation for a wide range of industrial components. This paper deals with the theoretical investigations into the mechanism of abrasive flow machining (AFM) process. A finite element model is developed for the flow of media during AFM and the same is used to evaluate the stresses and forces developed during the process. Theoretical analysis to estimate the material removal and surface roughness obtained during AFM is also proposed. The theoretical results are compared with the experimental data available in the literature, and they are found to agree well.