Horizontal Zone Research Articles

In Search of an Alternative Solar Grade Silicon Production By Electrochemical Reduction of SiO2

Silicon plays an important role in fabrication of solar cells and solar chips. Metallurgical grade silicon (98 to 99 % Si) demands further purification such as zone refining [1, 2], metallothermic reduction [3] and Siemens process [4] to convert it to solar grade. A promising method, based on direct electrochemical reduction of oxides by FFC Cambridge Process [5], was adopted to form silicon from porous SiO2 pellets in molten CaCl2 and CaCl2–NaCl salt mixture [6]. The contamination of silicon powder by iron and nickel originating from stainless steel cathode was reported to disqualify the product from solar applications. SiO2 pellets, sintered at 1300oC for 4 hours, were sandwiched between pure silicon wafer plates to minimize contamination of silicon. The promising results indicated a potential alternative method of direct solar grade silicon production for expanding solar energy industry. [1] P.R. Mei, S.P.Moreira, E.Cardoso, A.D.S.Cortes, F.C.Marques, “Purification of metallurgical silicon by horizontal zone melting”, Sol. Energ. Mat. Sol., 98 (2012), 233-239. [2] P. Siffert, E.F. Krimmel, eds. Silicon: Evolution and future of a technology. Berlin,Springer (2004). [3] K. Yasuda, T.H. Okabe, “Solar-grade silicon production by metallothermic reduction”, JOM,62 (12) (2010), 94-101. [4] Siemens & Halske: BRD Patents 1.102.117 and 1.140.1594 filed 1954, issued 1956 [5] G.Z. Chen, D. J. Fray, T. W. Farthing, “Direct Electrochemical Reduction of Titanium Dioxide to Titanium in Molten Calcium Chloride”, Nature, 407 (2000), 361-364. [6] E. Ergül, İ. Karakaya, M. Erdoğan, “Electrochemical decomposition of SiO2 pellets to form silicon in molten salts” Journal of Alloys and Compounds, 509 (2011), 899-903.

Hypereutectic Al2O3/YAG/ZrO2 In Situ Composite Prepared by Horizontal Laser Zone Melting

Abstract Al2O3/YAG/ZrO2 eutectic in situ composite has now been considered as the new generation of high-temperature structural material due to its excellent performance even close to its melting point. In this work, hypereutectic Al2O3/YAG/ZrO2 in situ composite is manufactured by the horizontal laser zone melting technique. The relationship between the solidification microstructure and the solidification parameters is studied. The minimum lamellar spacing is as finer as 0.20 μm when the laser scanning rate is 800 μm/s. Compared with eutectic Al2O3/YAG/ZrO2, hypereutectic exhibits more regular and finer microstructure at the similar conditions. Meanwhile, it is found that the lamellar spacing remains almost as constant at a certain high solidification velocity. The maximum hardness and fracture toughness are 15.9 GPa and 4.2 MPa · m1/2, respectively.

Surface morphological features of fiber laser cutting of AA2219 aluminum alloy

High-power fiber laser cutting of AA2219 aluminum alloy was studied. The cutting surface morphologies were examined by optical stereoscopic microscope, and the characteristic sizes were measured by a Vernier caliper. The results showed that the cutting surface was grouped into three zones featured by different striation patterns from the upper to the bottom, which are horizontal striation zone at the upper, vertical striation zone at the middle, and oblique striation zone at the lower. The oblique striation zone was the roughest zone. An optimal range of laser line energy to get an accepted cutting surface both with a small fraction of oblique striation zone and less dross was found, which was determined as 25–35 J/mm. The formation mechanisms of surface features were summarized by the interaction between the gas flow inside the cut and the forces exerted on the molten pool.

Влияние конструктивных решений на формирование кривой усталости боковых рам тележек грузовых вагонов

Fatigue resistance is the main parameter of the quality of cast parts. Fatigue tests allow evaluating performance of designs, feasibility of introducing structural changes, efficiency of used in the manufacture parts of technological solutions. The analysis of the results of fatigue tests of the side frames of different manufacturers is made. The main places of destruction were determined and defects in the centers of origin of the fatigue cracks were systematized. The parameters of fatigue curves (m - exponent equation, ρ - correlation coefficient), as well as limits of endurance and resistance to fatigue safety factor n were calculated in the article. In some cases, the value of the index m greatly exceeds the average level of the entire test volume. Test results of three batches of the side frames with high values of m and n were reviewed. The first batch of the side frames is represented by the base case. Analysis of the fracture of surfaces showed the presence of damage with high operating time of parts without casting defects. Also, there is destruction of parts with low operating time with presence of numerous casting defects. This indicates instability of manufacturing techniques of parts during its development in the enterprise. Side frames in the second batch are reinforced in the zone of internal angle of pedestal jaw opening by introducing additional edge, increasing the height of the vertical walls in 1.2 times and the wall thickness in 1.25 times. Efforts of pedestal opening led to a peak stresses in the lower and diagonal tension members, side frames divided into two groups of parts with different levels of damage. As a result - the formation of the fatigue curve with the magnitude | m | = 17. Side frames of third batch are an option of enhancing inner angle of pedestal opening by increasing the height of the vertical walls in 1.2 times and the thickness of the horizontal zone in 1.3 times. The rigidity of reinforced zone (pedestal opening) has led to an increase in stress in a neighbor zone - diagonal tension member. As a result, obtaining fatigue of the curve with the magnitude | m | = 25. Formation of zones with different levels of stress state distorts results of fatigue tests of the side frames, unreasonably increases the value of index m, and hence index n. When receiving m in absolute value over 10 an analysis of zones of destruction with establishing reasons behind this increase should be made as well.

Partition and growth of convection patterns in Poiseuille-Rayleigh-Bnard flow

The natural phenomena which we are familiar with, such as the convections in reservoir, ocean, atmosphere, etc., all occur in nonequilibrium open systems away from heat equilibria. The Poiseuille-Rayleigh-Bnard flow in a horizontal fluid layer heated from below has always been a typical experimental system for studying the nonlinear problem and the pattern formation. The experimental system can be accurately described by the full hydrodynamic equations. Therefore, the researches of the convection spatiotemporal structure, stability and the nonlinear dynamics by using the Poiseuille-Rayleigh-Bnard flow model possess certain representative and theoretical significance and practical value. So far, the investigation on the Poiseuille-Rayleigh-Bnard flow in a horizontal layer heated from below has concentrated mainly on the stability and made remarkable progress. However, a partition of convection pattern and growths of different patterns in the Poiseuille-Rayleigh-Bnard flow have been seldom studied in theory. By using a two-dimensional numerical simulation of the fully hydrodynamic equations in this paper, the research is conducted on the partition of convection pattern, growth and the effects of horizontal flow on the characteristic parameters of different patterns in the Poiseuille-Rayleigh-Bnard flow in a rectangular at an aspect ratio of 10. The SIMPLE algorithm is used to numerically simulate the two-dimensional fully hydrodynamic equations. The basic equations are solved in primitive variables in two-dimensional staggered grids with a uniform spatial resolution based on the control volume method. The power law scheme is used to treat the convective-diffusive terms in the discrete formulation. Results show that a flow zone is divided into three zones by the upper and lower critical Reynolds numbers Reu and Rel, i.e., traveling wave zone, localized traveling wave zone, and horizontal flow zone, where each of the Rel and Reu is a function of reduced Rayleigh number r and increases with increasing r. In the growth stage of the convection pattern, the growth processes of three kinds of patterns with time are different, but the convection rolls all start to grow from the downstream. The variations of characteristic parameters with time are also different, with maximum vertical velocity wmax and Nusselt number Nu of traveling wave and localized traveling wave entering into the stable stage of the cycle variation after the exponential growth stage, and the wmax and Nu of horizontal flow pattern decrease down to a stable constant after slow increase. The values of wmax and Nu of three types of patterns decrease with increasing Reynold number Re, with different laws being in the different pattern areas. In this paper, formulas for computing the Rel and Reu varying with r and formulas for computing the wmax and Nu varying with Re in different convection patterns are suggested.

Three-dimensional assessment of pedicular screws in thoracic and lumbar fractures using free-hand technique: a single-surgeon experience

Introduction Several sophisticated image-guided modalities have been developed to improve the accuracy of screw placement; however, such modalities may increase healthcare costs and radiation exposure to the patient, and the clinical efficacy compared with traditional techniques may be questionable. Globally, the free-hand technique of pedicle screw placement was found to be a reliable and safe method with low rates of complications and to be potentially more cost-effective than other sophisticated techniques in treating several spinal disorders. Aim The aim of this work was to assess the accuracy and safety of free-hand pedicle screw placement in thoracic and lumbar fractures using minimal image exposure. Materials and methods This is a prospective radiographic review of thoracic and lumbar pedicle screws inserted in patients suffering from unstable fractures. All of the procedures were performed by a single consultant spine surgeon. Screws were inserted at one side and then intraoperative lateral imaging was used to check the level and verify the position of the screws. The same procedure was repeated on the other side. The vertebral bodies were divided into three equidistant horizontal zones (A, B, and C). Positioning of the screw tips was regarded as ideal when located in zones A and B. Multislice computed tomography was used to assess the accuracy. Results There were 669 pedicle screws inserted in 88 consecutive cases from T3 to L5, with a mean of 7.6 screws. The overall number of misplaced screws was nine (1.3%). Intraoperative revision was made in 16 (seven cases, 2.4%) screws. No intraoperative or immediate postoperative complication occurred due to screw placement. Conclusion Minimal revision rate was noticed, and only two lateral images were needed in most of the cases. This is quite important in developing countries, where an image intensifier serves more than one room.

Metabolism-Induced CaCO3 Biomineralization During Reactive Transport in a Micromodel: Implications for Porosity Alteration.

The ability of Pseudomonas stutzeri strain DCP-Ps1 to drive CaCO3 biomineralization has been investigated in a microfluidic flowcell (i.e., micromodel) that simulates subsurface porous media. Results indicate that CaCO3 precipitation occurs during NO3(-) reduction with a maximum saturation index (SIcalcite) of ∼1.56, but not when NO3(-) was removed, inactive biomass remained, and pH and alkalinity were adjusted to SIcalcite ∼ 1.56. CaCO3 precipitation was promoted by metabolically active cultures of strain DCP-Ps1, which at similar values of SIcalcite, have a more negative surface charge than inactive strain DCP-Ps1. A two-stage NO3(-) reduction (NO3(-) → NO2(-) → N2) pore-scale reactive transport model was used to evaluate denitrification kinetics, which was observed in the micromodel as upper (NO3(-) reduction) and lower (NO2(-) reduction) horizontal zones of biomass growth with CaCO3 precipitation exclusively in the lower zone. Model results are consistent with two biomass growth regions and indicate that precipitation occurred in the lower zone because the largest increase in pH and alkalinity is associated with NO2(-) reduction. CaCO3 precipitates typically occupied the entire vertical depth of pores and impacted porosity, permeability, and flow. This study provides a framework for incorporating microbial activity in biogeochemistry models, which often base biomineralization only on SI (caused by biotic or abiotic reactions) and, thereby, underpredict the extent of this complex process. These results have wide-ranging implications for understanding reactive transport in relevance to groundwater remediation, CO2 sequestration, and enhanced oil recovery.

Linking magma transport structures at Kīlauea volcano

AbstractIdentifying magma pathways is important for understanding and interpreting volcanic signals. At Kīlauea volcano, seismicity illuminates subsurface plumbing, but the broad spectrum of seismic phenomena hampers event identification. Discrete, long‐period (LP) events dominate the shallow (5–10 km) plumbing, and deep (40+ km) tremor has been observed offshore. However, our inability to routinely identify these events limits their utility in tracking ascending magma. Using envelope cross‐correlation, we systematically catalog non‐earthquake seismicity between 2008 and 2014. We find that the LPs and deep tremor are spatially distinct, separated by the 15–25 km deep, horizontal mantle fault zone (MFZ). Our search corroborates previous observations, but we find broader band (0.5–20 Hz) tremor comprising collocated earthquakes and reinterpret the deep tremor as earthquake swarms in a volume surrounding and responding to magma intruding from the mantle plume beneath the MFZ. We propose that the overlying MFZ promotes lateral magma transport, linking this deep intrusion with Kīlauea's shallow magma plumbing.

Polyphase deformation and metamorphism of the Cuiabá group in the Poconé region (MT), Paraguay Fold and Thrust Belt: kinematic and tectonic implications

Several deformation models have been proposed for the Paraguay Belt, which primarily differ in the number of phases of deformation, direction of vergence and tectonic style. Structural features presented in this work indicate that the tectonics was dominated by low dip thrust sheets in an initial phase, followed by two progressive deformation phases. The first phase of deformation is characterized by a slate cleavage and axial plane of isoclinal recumbent folds with a NE axial direction, with a recrystallization of the minerals in the greenschist facies associated with horizontal shear zones with a top-to-the-SE sense of movement. The second stage shows vergence towards the NW, characterized by crenulation cleavage axial plane to F2 open folds over S0 and S1, locally associated with reverse faults. The third phase of deformation is characterized by subvertical faults and fractures with a NW direction showing sinistral movement, which are commonly filled by quartz veins. The collection of tectonic structures and metamorphic paragenesis described indicate that the most intense deformation at the deeper crustal level, greenschistfacies, occurred during F1, which accommodated significant crustal shortening through isoclinal recumbent folds and shear zones with low dip angles and hangwall movement to the SE, in a thin-skinned tectonic regime. The F2 deformation phase was less intense and had a brittle to ductile behavior that accommodated a slight shortening through normal open subvertical folds, and reverse faults developed in shallower crustal level, with vergence towards the Amazonian Craton. The third phase was less pervasive, and the shortening was accommodated by relief subvertical sinistral faults.

A Comparative Analysis of the Performance of a Grid-Connected Photovoltaic System Based on Low- and High-Frequency Solar Data

The performance of solar photovoltaic (PV) systems has been widely investigated based on the low-frequency data such as hourly or daily solar data. However, its short-term performance monitored at high frequency has been relatively less studied. This paper presents the short-term performance of a grid-connected solar photovoltaic (PV) system monitored at 1-min interval from July 1, 2010 to June 30, 2011 and compares with the daily performance. The summary results based on mean, standard deviation, and coefficient of variation (CV) are presented. The results indicate that the yearly means of the minutely array output power and the minutely global horizontal irradiance (GHI) in a typical day are bell-shaped. The CV pattern of the minutely array output power appears to be U-shaped while the CV pattern of the minutely GHI is varying within a horizontal zone of [0, 5%]. More importantly, the minutely data reveal that the output power responds nonlinearly to changes in solar irradiance while the hourly data conventionally used suggest a linear relationship between them. A piecewise quadratic model was built to fit the nonlinear relationship between array output power and GHI based on the minutely data. The model was proved to be accurate with high value of R2 and validated by the measured data.

Zonal stratification and geographic clustering of a species-rich chironomid community in freshwater coastal rock pools

Chironomidae are typically abundant in freshwater habitats and can be good indicators of ecological health. Coastal rock pools of barrier islands were sampled to determine how communities varied spatially between two horizontal zones, defined by wave disturbance and distance from shore, and from island-to-island. Pupal exuviae were collected monthly from pool surfaces to assess species composition, true community richness, and alpha and beta diversity. Cluster analyses were used to determine geographic community variation. A majority of species were rare, while three species dominated relative abundances. Zonal differences were significant, diversity was greater in near-shore pools overall, and few species occurred in both zones. Communities were more species-rich than expected based on prior studies in similar habitats. Community clusters were not strongly differentiated but suggested increased dispersal challenges at wider gaps between islands. Higher diversity near the shore and geographic clustering of communities are important to consider when planning for remediation activities following pollution events such as ship groundings or oil spills. In general, baseline coastal studies and conservation planning should consider aquatic invertebrates when pool habitats are present.

Evaluation of electrical impedance ratio measurements in accuracy of electronic apex locators.

ObjectivesThe aim of this paper was evaluating the ratios of electrical impedance measurements reported in previous studies through a correlation analysis in order to explicit it as the contributing factor to the accuracy of electronic apex locator (EAL).Materials and MethodsThe literature regarding electrical property measurements of EALs was screened using Medline and Embase. All data acquired were plotted to identify correlations between impedance and log-scaled frequency. The accuracy of the impedance ratio method used to detect the apical constriction (APC) in most EALs was evaluated using linear ramp function fitting. Changes of impedance ratios for various frequencies were evaluated for a variety of file positions.ResultsAmong the ten papers selected in the search process, the first-order equations between log-scaled frequency and impedance were in the negative direction. When the model for the ratios was assumed to be a linear ramp function, the ratio values decreased if the file went deeper and the average ratio values of the left and right horizontal zones were significantly different in 8 out of 9 studies. The APC was located within the interval of linear relation between the left and right horizontal zones of the linear ramp model.ConclusionsUsing the ratio method, the APC was located within a linear interval. Therefore, using the impedance ratio between electrical impedance measurements at different frequencies was a robust method for detection of the APC.

A simple technique to synthesise vertically aligned boron nitride nanosheets at 1200°C

In order to make the synthesis of boron nitride nanosheets (BNNS) easier and safe, a very simple technique is introduced in the present study. In this technique BNNS are synthesised in a conventional horizontal dual zone quartz tube furnace at 1200°C. Field emission scanning electron microscopy image shows the morphology of synthesised BNNS like spread out cotton packs. Transmission electron microscopy (TEM) images show highly crystalline nature of synthesised nanosheets of boron nitride with an interlayer spacing of 0.34 nm. Raman spectrum shows a major peak at 1366 (cm−1) that corresponds to E2g mode of h-BN. X-ray photon spectroscopy survey shows B 1s (at 191 eV) and N 1s (at 398 eV) peaks that verify the boron and nitrogen contents in synthesised nanosheets.

Numerical Simulation and Design Optimization Research of Slope Ratio and Platforms Influence on a High Rock Cut Slope Engineering Stability

According to the rock high-cut slope excavation engineering practice of a substation in Jiangxi, with the goals of stable and economic rational slope design, numerical simulation research of the slope ratio and unloading platform and design optimization work was carried out. The slope safety factor, displacement and plastic zone distribution changes of different slope ratio and platform setting programs were obtained. The results show that:(1) the adjustment of the slope ratio and platform can significantly affect the slope displacement and plastic zone distribution, reasonable slope ratio and platform can reduce the horizontal displacement and plastic zone of slope, increase the safety factor and stability;(2) the slope monitoring results show that numerical simulation optimization design is feasible, and the excavation slope maintain security and stability during the construction period, and economic benefit has been obtained. The research conclusions can provide technical support for the engineering design, and reference for design and research of high-cut slope excavation engineering with similar conditions in that region.

Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate.

Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm2 using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si.

Physical properties of vapour grown indium monotelluride platelets

Indium monotelluride (InTe) crystals were grown from vapour phase under different temperature gradients by employing physical vapour deposition (PVD) method. The morphology of these crystals such as whiskers, needles, platelets etc., strongly depends on the temperature distribution in the horizontal dual zone furnace. InTe platelets were deposited by setting the temperature of the charge (TC) and growth (TS) zones at 1073K and 773K (ΔT=300K), respectively, for different growth periods (24h, 48 h, 72h and 96h). The surface growth features have been analyzed by scanning electron microscopes, which indicate layer growth mechanism for all the crystals. Various crystals grown under ΔT=200K and 300K (retaining TS invariant) were examined by X-ray diffraction and elemental analysis. InTe samples exhibited consistent lattice parameters, density and atomic percentage, establishing stoichiometry and chemical homogeneity. The results obtained for Seebeck coefficient, electrical conductivity, power factor, dislocation density and microhardness are found to be reproducible as well. The vapour deposited InTe platelets are mechanically stable and possess high value of TEP, which ensure their practical application in thermoelectric power generation.

Deep heterogeneity of the stress state in the horizontal shear zones

The formation structures of brittle destruction in a rock layer above an active strike-slip fault in the crystalline basement is studied. The problem is analyzed from the standpoint of loading history, when after the stage of pure gravitational loading, an additional strain state of uniform horizontal shear of both the layer and underlying basement develops, which is further followed by a vertically nonuniform shear caused by the activation of the deep fault. For the studied object, irreversible fracture deformations on macro- and microlevels arise as early as the initial stage of loading under the action of gravitational stresses. These deformations continue evolving on the megascopic level in the course of horizontal shearing that is quasi-uniform both along the depth and laterally. The final formation of the structural ensemble occurs after a long stage of horizontal displacement of the blocks of the crystalline basement—the stage of localized shear. The theoretical analysis of the evolution of the stress state and morphology of the failure structures established the presence of numerous fractures with the normal dip-slip components in the intermediate-depth part of the rock mass, which are formed at the stages of uniform and localized horizontal shearing. The fractures with a strike-slip component mainly arise in the upper and near-axial deep parts of the section.

Argon Blowing Technology Using in the LF Refining

The process of LF Refining is introduced in this paper. Because the LF ladle furnace has the advantages are widely used and developed in many companies. The argon is blown into the ladle, so the purpose of refining is achieved. The argon stirring can accelerate the chemical reaction between slag and steel. In the circulation process, large inclusion and deoxidation product in the lower region transfer into the slag. The material transfer between steel and slag can be accelerated. At the same time, argon stirring can make molten steel composition and temperature uniformity. Thus, the ladle of blowing argon can be roughly divided into three important flow region has been introduced. Two-phase region, the top horizontal flow zone and recirculation zone exists in the ladle.

Flow dynamics through a submerged bridge opening with overtopping

ABSTRACTThis paper reports the results of detailed numerical simulations of the flow over a submerged bridge. The method of Large Eddy Simulation (LES) is applied, which allows elucidation of the instantaneous flow and accurate quantification of its turbulence statistics. The in-house LES code employs a free surface algorithm based on the Level Set Method (LSM) to determine the complex water surface profile over the bridge, which is validated with data from a physical model of the bridge under analogous flow conditions. Numerically predicted water surface profiles show good agreement with measured data. The water surface resembles that of the flow over a broad-crested weir with a plunging nappe and a standing wave downstream of the bridge. The mean flow is characterized by a multitude of complex flow features including horizontal recirculation zones upstream and downstream of the bridge abutment and vertical recirculation zones of the separated plunging flow. The latter influences significantly the near-bed turbulence and the bed shear stress.

Research Status of Physical Simulation on LF Furnace Refining Ladle

The research status of physical simulation on LF furnace refining ladle is introduced in this paper.Since 1970, the research on the gas-liquid two-phase region has begun. The ladle of blowing argon can be roughly divided into three important flow region has been introduced. Two-phase region, the top horizontal flow zone and recirculation zone exists in the ladle.The establishment of physical model should include similarity principle and flow field measurement technique