Rectification Process Research Articles

The Turbulent Oscillator: A Mechanism of Low-Frequency Variability of the Wind-Driven Ocean Gyres

Abstract Intrinsic low-frequency variability is studied in the idealized, quasigeostrophic, midlatitude, wind-driven ocean gyres operating at large Reynolds number. A robust decadal variability mode driven by the transient mesoscale eddies is found and analyzed. The variability is a turbulent phenomenon, which is driven by the competition between the eddy rectification process and the potential vorticity anomalies induced by changes of the intergyre transport.

Optimal Molar Fractions of Ternary Zinc-Blende Terahertz Emitters

We report our calculation of optimal molar fractions in various ternary zinc-blende terahertz emitters that can produce terahertz radiation with enhanced powers when the wavelength of the pump laser is changed. While the momentum mismatch between the optical and the terahertz pulses in these non-resonant nonlinear materials was mainly used to understand the spectral and the transient shapes of the generated terahertz waves, the optimal molar fractions in compound semiconductor terahertz emitters were better determined with the full numerical calculations. To demonstrate the output power change and the sensitivity of the calculation, we performed numerical simulations of the optical rectification process during the optical and the terahertz wave propagations. The result suggests that the optimal Cd compositions in Zn1 xCdxTe are x = 0.10 at = 820 nm and x = 0.65 at = 850 nm and that the Te compositions in ZnSe1 xTex are x = 0.6 at = 750 nm and x = 0.95 at = 820 nm. This method could act as a powerful tool to optimally design various zinc-blende semiconductor compounds to generate terahertz waveforms.

TECHNIQUE FOR DEFINITION OF BREAK SIZE OF ROAD COVERING ON THE BRIDGE

The article deals with the submitted photogrammetric method for image rectification to the planar coordinate system. The images are taken by metric digital camera Canon EOS 350D. The camera is calibrated with Technet(Pictran B, D/E) software using the special test‐field for calibration. Calibration parameters are determined to the images rectification process. The images in the planar coordinate system are transformed to 5 control points with the same software. The received results are visible in tables and figures. The transformed, planar images can be applied to research, designing and deformations estimate of engineering constructions.

Remote sensing and modelling of bio-physical distribution patterns at Porcupine and Rockall Bank, Northeast Atlantic

Monthly composites of multi-year sea surface temperature (SST) and chlorophyll-a (Chl- a) have been used in combination with ocean model simulations to study bio-physical distribution patterns at Porcupine and Rockall Bank, two large submarine banks in the Northeast Atlantic in close proximity to the European shelf edge. Seven years (January 1998–December 2004) of remotely sensed data have been collated to create monthly climatological fields and to analyse principal spatio-temporal characteristics. At both banks, a region of cooler SST is found over the summit region compared to warmer waters of the surrounding ocean, less apparent in summer when capped by the seasonal thermocline. Enhanced Chl- a levels are found over both banks with a lifetime partly exceeding the bloom period. At Rockall Bank, both SST and Chl- a signals are more pronounced and persistent showing a 30% increase in annual Chl- a levels over the summit area with an even higher ratio in spring and autumn. A combination of physical processes appears to promote the enhanced productivity over both banks through the generation of a quasi-steady dome of cold, dense water during winter convection and upwelling events. This cold dome is associated with the presence of a retentive circulation based on Taylor cap dynamics and tidal rectification processes. The larger and more persistent enhancement of Chl- a levels over Rockall Bank would appear due to its isolated nature as well as its size. In contrast, Porcupine Bank is partly attached to the Irish shelf edge and exposed to the poleward flowing shelf edge current which may strip passive particles from the central bank region. Satellite derived Chl- a spring/summer distributions over the banks have been used to initialise model simulations of passive tracer dispersion. Timescales for the observed lifetime of the remotely sensed Chl- a patches are consistent with model derived retention timescales and simple scaling for the dispersion of passive biological material over the banks. Surface particle residence times over Rockall Bank are estimated to exceed Porcupine Bank values by a factor of two. Finally, the tidal contribution to individual particle motion is found to be large in some Rockall Bank areas, but less important at Porcupine Bank.

Double dissociation between first- and second-order processing

To study the difference of sensitivity to luminance- (LM) and contrast-modulated (CM) stimuli, we compared LM and CM detection thresholds in LM- and CM-noise conditions. The results showed a double dissociation (no or little inter-attribute interaction) between the processing of these stimuli, which implies that both stimuli must be processed, at least at some point, by separate mechanisms and that both stimuli are not merged after a rectification process. A second experiment showed that the internal equivalent noise limiting the CM sensitivity was greater than the one limiting the carrier sensitivity, which suggests that the internal noise occurring before the rectification process is not limiting the CM sensitivity. These results support the hypothesis that a suboptimal rectification process partially explains the difference of LM and CM sensitivity.

Terahertz-Pulse Emission Through Laser Excitation of Surface Plasmons in a Metal Grating

The second-order processes of optical-rectification and photoconduction are well known and widely used to produce ultrafast electromagnetic pulses in the terahertz frequency domain. We present a new form of rectification that relies on the excitation of surface plasmons in metal films deposited on a shallow grating. Multiphoton ionization and ponderomotive acceleration of electrons in the enhanced evanescent field of the surface plasmons results in a femtosecond current surge and emission of terahertz electromagnetic radiation. Using gold, this rectification process is third or higher-order in the incident field.

Simulation study on cascaded terahertz pulse generation in electro-optic crystals

We studied cascaded optical rectification processes for intense terahertz (THz) pulse generation in electro-optic crystals using simulations based on one-dimensional coupled propagation equations of THz and optical fields. We found that under ideal conditions of perfect phase matching and no absorption, cascaded optical rectification processes produce intense THz pulses with efficiencies exceeding the Manley-Rowe limit. Large red shifting of the pump light spectrum was observed. Effects of finite optical and THz absorption, phase mismatches, and pulse width were examined using parameters of a ZnTe crystal pumped by 800 nm pulses. THz field enhancement by multiple pulse pumping was also studied.

Precipitation in an AA6111 aluminium alloy and cosmetic corrosion

The near-surface deformed layer on AA6111 automotive closure sheet alloy, generated by mechanical grinding during rectification, has an ultrafine grain microstructure, of 50–150 nm diameter, and a sharp transition with the underlying bulk alloy microstructure. Grinding and heat treatment to simulate rectification and paint baking processes result in the nucleation and growth of ∼20 nm diameter precipitates at grain boundaries within the near-surface deformed layer. High-resolution transmission electron microscopy has shown Q phase precipitates in the deformed layer, giving dramatically increased corrosion susceptibility compared with the bulk microstructure, and this is responsible for the rapid-onset filiform corrosion. Transmission electron microscopy of the corrosion attack showed directly that the mode of corrosion was intergranular and that the Q phase precipitates were preserved after the passage of the corrosion front.

Experimental investigation of mass transfer performance with some random packings for ammonia rectification in ammonia–water absorption refrigeration systems

In ammonia water absorption refrigeration systems (AARS) a high efficiency purification process to remove the water content from the generated vapour is of great importance. One type of equipment to carry out this process is a packed column. Any type of detailed analysis of a packed column requires the calculation of mass transfer coefficients. Therefore, the correlations to obtain these coefficients become an essential tool for an accurate analysis and design of these devices. An experimental facility has been designed and built to analyze the ammonia–water rectification process in packed columns. In this paper a brief description of the experimental facility is given and the variables required to analyze the column performance are explained. An analytical method to determine mass transfer coefficients from the experimental data is developed. Results of mass transfer coefficients for 15 mm glass Raschig rings, 1 2 ″ ceramic Berl saddles and 1 2 ″ ceramic Novalox saddles random packings are reported. The experimental results are compared with different mass transfer correlations proposed in the literature. In the paper corrected correlations are proposed for the packings considered. These correlations could be used to analyze and design a packed column for AARS.

Same calculation efficiency but different internal noise for luminance- and contrast-modulated stimuli detection

There is no consensus on whether luminance-modulated (LM) and contrast-modulated (CM) stimuli are processed by common or separate mechanisms. To investigate this, the sensitivity variations to these stimuli are generally compared as a function of different parameters (e.g., sensitivity as a function of the spatial or temporal window sizes) and similar properties have been observed. The present study targets the sensitivity difference between LM and CM stimuli processing. Therefore, instead of studying the variation of sensitivity in different conditions, we propose to decompose the sensitivities in internal equivalent noise (IEN) and calculation efficiency (CE) to evaluate at which processing level the two mechanisms differ. For each stimulus type, the IEN and CE of four observers were evaluated using three different carriers (plaid, checkerboard, and binary noise). No significant CE differences were noted in all six conditions (3 carriers x 2 modulation types), but important differences were found between the IEN of the two stimulus types. These data support the hypothesis that the two pathways are initially separate and that the two stimuli may be treated by common mechanisms at a later processing stage. Based on ideal observer analysis, pre-rectification internal noise could explain the difference of IEN between LM and CM stimuli detection when using binary noise as a carrier but not when using a plaid or a checkerboard. We conclude that a suboptimal rectification process causes higher IEN for CM stimuli detection compared with LM stimuli detection and that the intrinsic noise of the binary carrier had a greater impact on the IEN than the suboptimal rectification.

Automated flame rectification process planning system in shipbuilding based on artificial intelligence

Distortion is a crucial problem with all welded fabrications in shipbuilding. Flame rectification is one of the most time-consuming processes. At present, it is still an experience-relying and manual operation. Because of lack in uniform flame rectification process, production has poor stability and productivity varies greatly among operators. In this paper, three typical kinds of welding components are chosen as study objects to generate the process planning of manual flame rectification automatically by artificial intelligence (AI) technology. In addition, we may also attain appropriate process parameters based on the model of neural network. A prototype system of automated flame rectification process planning is built. The system has been tested on actual components, and the results were found to be quite accurate and efficiency. Meanwhile, it establishes the fundament for the automation of flame rectification process.

AUTOMATED METHOD OF FLAME RECTIFICATION PROCESS OF WELDING DISTORTION FOR MEDIATE STEEL PLATE AND SYSTEM IN SHIPBUILDING

The welding is one of the most important and prevalent processes for shipbuilding. So welding distortion is inevitable and rectification becomes important task. Aiming at the situation of manual operation in flame rectification, prototype is developed to realize automation of flame rectification process, three kinds of typical welding components are chosen as objects to establish automatically standard flame rectification process by logic reasoning. In addition, appropriate process parameters are obtained based on neural network. An example is implemented to attain approving rectification result. It indicates that the system can improve the efficiency of flame rectification and stability of rectification quality. As a result, the fundament for automation of flame rectification process is established.

The role of distillation on the quality of tequila

SummaryThe role of a batch rectification on the quality of tequila, a traditional Mexican beverage, was studied. It was shown that the official tequila standard composition, particularly the size of the slop cuts and the correct balance of flavour constituents, can be determined by monitoring the concentration of the regulated compounds (ethanol, methanol, higher alcohols, ethyl acetate, acetaldehyde and furfural) throughout the rectification process. It was found that these regulated compounds are produced over the same time scales when either stainless steel or copper alembics are used. When distillations were done in copper alembics, however, it was found that the copper content of the rectified product exceeded the amount permitted in the official tequila standards. Finally, we report a comparison of sensory properties of tequila distillates obtained in both copper and stainless steel alembics.

An integrated description of terahertz generation through optical rectification, charge transfer, and current surge

Ultrafast terahertz pulses can be generated through a number of processes such as optical rectification in an electro-optic crystal, a current surge in a biased photoconductive antenna, or charge transfer in aligned molecules. It will be shown that all these rectification processes can be described by a single analytical formula in the frequency domain. A recipe is given for the quick calculation of terahertz waveforms generated through any rectification process and detected through electro-optic sampling. This theory is compared with experimentally measured terahertz waveforms.

Transport properties of nanopores in electrolyte solutions: the diffusional model and surface currents

Ion transport through single-cation selective nanopores in thin polymer foils is examined experimentally and described by a diffusional model based on the reduction of the three-dimensional Smoluchowski equation into a one-dimensional equation of Fick–Jacobs type. The model enables semi-quantitative predictions of the transport properties of nanopores of various shapes and surface charge properties even when bulk electrolyte values of various parameters are used. The experimental conductivity data clearly indicate the presence of a surface current component not described by the bulk-type diffusion. The values of the measured surface conductivities depend, among others, on the properties of the channel's internal surface. These surface currents play a substantial role in the rectification processes and are partially responsible for the high-cation selectivity of nanopores.Both theory and electrolytic conductivity measurements show that asymmetric nanopores partially rectify the current with a preferential direction of cation flow from a pore of high surface charge density towards a pore of low surface charge density and/or from the narrow towards the wide opening of the pore.

Computing depth maps from descent images

In the exploration of the planets of our solar system, images taken during a lander's descent to the surface of a planet provide a critical link between orbital images and surface images. The descent images not only allow us to locate the landing site in a global coordinate frame, but they also provide progressively higher-resolution maps for mission planning. This paper addresses the generation of depth maps from the descent images. Our approach has two steps, motion refinement and depth recovery. During motion refinement, we use an initial motion estimate in order to avoid the intrinsic motion ambiguity. The objective of the motion-refinement step is to adjust the motion parameters such that the reprojection error is minimized. The depth-recovery step correlates adjacent frames to match pixels for triangulation. Due to the descending motion, the conventional rectification process is replaced by a set of anti-aliasing image warpings corresponding to a set of virtual parallel planes. We demonstrate experimental results on synthetic and real descent images.

A new coarse-to-fine rectification algorithm for airborne push-broom hyperspectral images

Rectification for airborne push-broom hyperspectral images is an indispensable and important task in registration procedure. In this paper, a coarse-to-fine rectification algorithm is proposed. In the coarse rectification process, the data provided by the Positioning and Orientation System (POS) is used in a model of direct georeference position to adjust the displacement of each line of images. In the fine rectification step, polynomial model is applied to realize that the geometric relationships of all the pixels in raw image space are same to those in the reference image. Experiments show that the fine rectified images are satisfying, and our rectification algorithm is very effective.

A work study of the CAD/CAM method and conventional manual method in the fabrication of spinal orthoses for patients with adolescent idiopathic scoliosis

A study was conducted to compare the CAD/CAM method with the conventional manual method in fabrication of spinal orthoses for patients with adolescent idiopathic scoliosis. Ten subjects were recruited for this study. Efficiency analyses of the two methods were performed from cast filling/ digitization process to completion of cast/image rectification. The dimensional changes of the casts/ models rectified by the two cast rectification methods were also investigated. The results demonstrated that the CAD/CAM method was faster than the conventional manual method in the studied processes. The mean rectification time of the CAD/CAM method was shorter than that of the conventional manual method by 108.3 min (63.5%). This indicated that the CAD/CAM method took about 1/3 of the time of the conventional manual to finish cast rectification. In the comparison of cast/image dimensional differences between the conventional manual method and the CAD/CAM method, five major dimensions in each of the five rectified regions namely the axilla, thoracic, lumbar, abdominal and pelvic regions were involved. There were no significant dimensional differences (p < 0.05) in 19 out of the 25 studied dimensions. This study demonstrated that the CAD/CAM system could save the time in the rectification process and offer a relatively high resemblance in cast rectification as compared with the conventional manual method.

Relief effects on aerial photos geometric correction

Aerial photos are the best support to detect changes in the landscape over the time, particularly when associated with GIS based analyses. Since all metrics calculated on a landscape (from area coverage by vegetation classes to patches shape and size) are sensible to geometric distortions, the geometric correction of aerial photos is due to allow a realistic multi-temporal study. In this paper the mostly used methods of rectification were applied to aerial photos of different terrain types, with respect to their roughness (a flat area, a hilly area and a volcanic area), aiming to test residuals in x and y axes, under different conditions of terrain roughness. Polynomial functions confirmed their power in rectification process only in case of flat areas, with an increase of the error with more rugged terrains; on the contrary, orthorectification assured great results for all terrain types.

Development of an integrated CAD–FEA process for below-knee prosthetic sockets

Computer-aided design and manufacturing has been successfully used in prosthetic applications since 1980s. It simplifies the socket rectification process and improves reproducibility but does not introduce any new principle into socket design. Integrating finite element analysis to CAD will provide a more objective assessment of socket fit and improve the chance of a successful first fitting. Current study aims to establish a finite element model generation technique directly from geometrical information of commercial prosthetic CAD workstation. A program developed in-house automatically performs meshing of the stump geometry and assigns suitable material properties, load and boundary conditions to the model. The model was validated by comparing predicted pressure with experimentally measured values for one amputee subject. The predicted pressure distribution has an root-mean-square error of 8.8 kPa compared to experimental values at 10%, 25% and 50% of the gait cycle. Current method was able to develop a finite element model to predict interface pressure reasonably well and can be integrated with prosthetic CAD system to provide quantitative feedback to the prosthetist in an automated process.