bluuebunny/crossref_metadata_2025 huggingface dataset:
Contact Conditions in 5-Axis-Grinding of Double Curved Surfaces with Toric Grinding Wheels
Authors: Denkena Berend , de Leon Luis , Behrens Leif
Published: August 2010

Five-axis-grinding is a process, which merges high surface quality and high shape accuracy for high precision machining of multiple curved surfaces. Until now, characteristic parameters, which describe the interaction of the grinding tool and the workpiece are not available. In the present paper models for the analytical determination of the contact condition for surface normal grinding of double curved surfaces with toric grinding wheels are introduced to evaluate and configure the machining parameters.
Research on Axisymmetric Free-Form Creation with Rotating Polishing Tool
Authors: Tsubota Shingo , Natsu Wataru
Published: August 2010

The purpose of this research is to establish a way to realize the axisymmetric free-form polishing by controlling the scanning speed of the rotating polishing tool. The scanning speed was determined by comparing the measured result of the polished shape with the target shape. Experiments with the proposed method were carried out and the effectiveness of the method was verified.
Chemical Effect on the Material Removal Rate in the CMP of Silicon Wafers
Authors: Wang Yong Guang , Zhang Liang Chi , Biddut Altabul
Published: August 2010

This paper investigates the effects of some chemical factors on the material removal rate (MRR) in chemo-mechanical polishing (CMP) of Si (100) wafers. The CMP was carried out in alkaline slurry using alumina and ceria particles with hydrogen peroxide. When using the alumina particles, the MRR initially decreases with increasing the slurry pH value until pH = 9. Nevertheless, the application of the ceria particles increases the MRR before the pH of the slurry reaches 10. A higher slurry flow rate brings about a greater MRR.
Laser Assist Powder Jet Deposition
Authors: Yoshihara Nobuhito , Hiromatsu Ryoko , Mizutani Koichi , Yan Ji Wang , Kuriyagawa Tsunemoto
Published: August 2010

Amorphous NiP plate is used as a mold of precision optical parts owing to the superior machinability. In the amorphous NiP plate, some pores, whose diameter is about 100m, are generated occasionally. At present, the amorphous NiP plates with pore are rejected. However, because size of the mold becomes large in recent years, the possibility of pores becomes high. In addition, the cost of the amorphous NiP plate also becomes high. Therefore, reparation method of the pore in the amorphous NiP plate should be developed. In this paper, laser assist powder jet deposition is proposed as a reparation method of the amorphous NiP plate. And fundamental experiments are carried out.
Loading in Grinding: Chemical Reactions in Steels and Stainless Steels
Authors: Badger Jeffrey , Murphy Stuart , O'Donnell Garret E.
Published: August 2010

Loading in grinding – both chemical, in which the grit and the oxidized surface of the workpiece react, and mechanical, in which chips become embedded within the pores of the wheel – causes significant problems such as increased wheel wear, higher grinding temperatures, and poor surface finish. This paper investigates the chemical reactions that occur between the aluminum-oxide abrasive and both steel and stainless steel and their effect on wheel wear and grinding forces. Tests were done on mild steel and stainless steel under dry conditions, with poor and moderate cooling and in the presence of steam. X-ray diffraction was used to measure aluminum deposits on the contact and rear faces of the chip and on the workpiece in regions where cutting was dominant and/or plowing and rubbing were dominant. Normal and tangential forces and wheel wear were measured and loading was quantified visually. Loading in stainless steels was found to occur almost immediately due to the mutual solubility of Cr2O3 and Al2O3 during the rubbing and plowing regimes, but during cutting there was not sufficient time to form an oxide layer. Coolant drastically reduces loading in stainless steel. Steam acts as a catalyst in oxide-layer formation, decreasing loading in regular steels and increasing loading in stainless steels. Wheel wear due to loading was found to be sporadic, with large groups of grits being ripped out of the wheel. Assessing loading via the visual appearance, or “blackness”, of the wheel can lead to incorrect conclusions.
Thrust Force Directional Vibration-Assisted Ductile-Mode Grinding of Single-Crystal Si
Authors: Imai Kenichiro , Hashimoto Hiroshi
Published: August 2010

Under optimum grinding conditions, a constant grinding force is exerted on a workpiece during ductile-mode grinding of BK7 glass. Based on the results, the cutting force, specific grinding energy, and depth of cut for a single grain were calculated. It was found that a single grain was easily removed from the material. However, grinding is impossible because surface burning occurs on the workpiece. In order to avoid burning, a single-crystal silicon wafer (1,0,0) surface was ground with thrust force directional vibration-assisted grinding. The normal grinding force with vibration was comparatively low, but was quite stable. The removal rate was approximately three times greater than that without vibration. The results indicate that the successive abrasive grains of the grinding wheel remove the material intermittently.
Effects of Cutting Parameters on the Transverse Vibration of Diamond Circular Saw Blade
Authors: Fang Huai Ying , Li Yuan , Huang Hui , Xu Xi Peng
Published: August 2010

The effects of cutting parameters on the transverse vibration of diamond circular saw blade were experimentally investigated. Transverse vibration was online measured by a novel measuring system developed by wireless sensor. Meanwhile, axial force on saw blade was measured by a dynamometer. By the experimental results under different cutting parameters, the time domain characteristics of transverse vibration of saw blade were analyzed, and the relationships between transverse vibration and cutting parameters were also obtained. Axial deformation is greatly influenced by the axial force acting on saw blade.
Improvement in Oxide-Pattern Sizes Controllability on Scanning Probe Nanolithography
Authors: Onuki Teppei , Tokizaki Takashi , Ojima Hirotaka , Shimizu Jun , Zhou Li Bo
Published: August 2010

Pattern size controllability of SPM-based nano-lithography especially in vertical direction was improved using in-situ height and depth measurements at the processed point. The transient oxide growth was monitored by light transmission (depth of the oxide in sample metal surface) and topographical signals measurements obtained from a scanning near-field optical microscope. First, we investigated oxidizing rate limitation on titanium film. At the voltage rise faster than 10 V/sec, the depth growth didn’t follow the voltage change in spite of immediate upheaval growth. This result suggested the rate determining of reactive chemicals transport in the titanium oxide. Next, we discovered improvement in the process stability on intractable materials (e.g. iron group elements or noble metals; manganese in this paper) by using thin cap layer of titanium. As the result, the oxidization reaction progressed moderately due to the facts that the oxide of the cap layer is electrical insulative and restriction of the permeability of the reactive chemicals (ingredients of the oxide) that were electrochemically generated at apex of the probe tip.
New Development of Contact Probe and Methodology
Authors: Kimoto Gunsei , Watanabe Takehiro , Matsusaka Souta , Inoue Akio , Kuroda Takaharu
Published: August 2010

We present a new type of wafer probe card with resin film consisting of two beams. Resin film is embedded on both sides of the probe beam, having a thickness of 4 [μm] and made from polyimide. This proposed probe enables compliant structures with large overdrive to ensure high durability of the structure and controllable scrub motion to assure cleaning process. In this study, Matrix method is introduced for theoretical studies of the probe structure and commercial finite element code is used. Electrical contact resistance is determined by theoretical studies based on Holm's theory and experimentally by　our measurement instrumentation respectively. The structure is proven theoretically to get appropriate scrub motion when it undergoes a large overdrive with preferable exhibited contact force. Moreover, all of these mechanical characteristics can be varied to know the values of the character of probes. The methodology having one of the most preferable characters of the contact-probe had been achieved.
Research on a Helical Drill Point Grinding Machine
Authors: Zou Ping , Yang Xu Lei , Xu Jin Zhong , Tian Wen Yuan , Hu Ming
Published: August 2010

It is necessary to develop drill point grinders in order to improve drilling quality and efficiency. In this paper, a new type of helical drill point grinder is presented. This grinder is mechanically simple, low cost and easy to be used. There are three axis simultaneous motions by means of two cams during helical drill point grinding process. Moreover, the relationships between the helical drill point parameters and helical grinding parameters are derived. As a result, the flank surfaces of helical drill points are described.
Effect of Material Type and Tip Radius of AFM Probes on Nanosheets Groove Machining Accuracy
Authors: Demura Kazuya , Hirose Satoru , Ihara Tohru
Published: August 2010

This paper presents results of groove machining of potassium niobate nanosheets using an atomic force microscope (AFM). Groove machining operations are performed using recently developed diamond coating (DC) and super sharp silicon (sss) probes. The results obtained using these probes are compared to results obtained using a conventional silicon (Si) probe in order to examine the effects of the material type and the tip radius of the AFM probe on groove machining accuracy.
Analysis of Surface Roughness Transformation of Oxide Scale during Hot Steel Manufacturing
Authors: Jiang Zheng Yi , Tang Jian Ning , Tieu A. Kiet , Sun Wei Hua , Wei Dong Bin
Published: August 2010

In this paper, the effects of the surface asperity wavelength, reduction and lubrication (friction) on the surface roughness transformation of the oxide scale have been studied. The simulation results show that the oxide scale surface roughness decreases with an increase of the average asperity wavelength and reduction. The initial surface roughness affects the decrease rate of surface roughness when the reduction increases. The surface roughness of the oxide scale and steel is quite close when the rolling with lubrication and both of them are reduced with reduction, and the surface roughness of the oxide scale is reduced less comparing with that of without lubrication case. The calculated roughness is close to the measured data.
Preparation and Evaluation of Nanocomposite LDPE Films Containing Ag and ZnO for Food-Packaging Applications
Authors: Emamifar Aryou , Kadivar Mahdi , Shahedi Mohammad , Soleimanian-Zad Sabihe
Published: August 2010

Nanocomposite polymer films were produced from composites comprising LDPE /nanosilver and LDPE/nano-ZnO by melt compounding. The mechanical properties of the films prepared were characterized by using stress-strain analysis. Dispersion quality of nanomaterials into the polymer matrix film was monitored using the Transmission Electron Microscopy. The results showed the nanocomposites as possessing lower elongation at break and more antimicrobial activity with the increase of each of nanofillers content.
Research on Vickers Hardness Image Definition Evaluation Function
Authors: Wang Gui Tang , Zhu Jian Lin , Cao Pei Liang , Liu Wen Juan
Published: August 2010

A definition evaluation function is proposed for the Vickers hardness indentation images in this paper. Based on the characteristics of Vickers hardness indentation image, we choose the gradient function as definition evaluation criteria for the image. Because of the advantage of Brenner evaluation function and the image features itself, this paper puts forward a new evaluation function at the idea of Brenner evaluation function, that is not only more suitable for evaluating the Vickers hardness indentation image than Brenner function, but also having the merit of it and becoming more practical according to the experiments.
Study on Automotive Air Conditioner Control System Based on Incremental-PID
Authors: Zhang Jin Dong , Qin Gui He , Xu Bing , Hu Huang Shui , Chen Zhao Xia
Published: August 2010

Perfect automotive air conditioner system can be improved to ensure pleasant air environment in a variety of external conditions, the driver can keep the brain cool, improve work efficiency, reduce fatigue and accidents, and thus guarantees driving safety. Because of the transient nature of automotive air conditioner and systematic non-linear, it is extremely difficult to establish the mathematical model for the system. Generally, to describe the transfer function or the state function of automobile air conditioner accurately is difficult, the control of the system can rarely obtain satisfying results. This article explored the procedures of introducing the digital PID control algorithm into the automotive air conditioner control system, and proposed an automobile air conditioner intelligent control system based on Increment-PID algorithm. Optimized control of automotive air conditioner system can improve its performance.
Effect of Thermal Stimuli on Physical Behaviors of PET/PTT Bicomponent Filament
Authors: Chen Si Hai , Wang Shan Yuan
Published: August 2010

PET/PTT bicomponent filament composed of PTT and PET arranged side-by-side often manifest high curliness after being thermally stimulated at different temperature. In this article, we report an investigation of the effect of thermal stimuli on the performances of PET/PTT bicomponent filament under various temperatures. Both the original and the thermally stimulated ones were characterized by mechanical, thermal, thermo-mechanical and optical methods. The changes of other relevant properties were also discussed.
Numerical and Experimental Investigation into Hot Stamping of High Strength Steel Sheet for Auto B Pillar Reinforced Panel
Authors: Xing Zhong Wen , Cui Jun Jia , Liu Hong Sheng , Li Chun Feng
Published: August 2010

Hot stamping is an innovative way to manufacture complex-shaped components of high strength steel (HSS) sheet with a minimum of springback, meanwhile, it can also obviously improve the tensile strength of the formed parts.The coupled thermo-mechanical FE model for hot stamping of HSS sheet for the B pillar was established by commercial software Pam-stamp. Dynamic explicit module was used to simulate the forming processes under different process parameters. The effects of process parameters on thinning of the blank were studied, the maximum thinning zones of the blank in hot stamping were analyzed. The results show that the thinning rates of the blank increase when the blank holder force(BHF) and friction coefficient increase, the maximum thinning zones appear at the straight wall and corner of the B pillar. The causal of blank thinning during hot stamping was analyzed. Experiments had been conducted with the process parameters obtained by simulation. The experimental and simulation results were in good agreement.
Conductivity Studies of ENR Based Proton Conducting Polymer Electrolytes
Authors: Mohammad S.F. , Idris Razali , Mohamed Nor Sabirin
Published: August 2010

The present study focuses on preparation of ENR-50/PEMA-NH4CF3SO3 proton conducting polymer electrolytes by solution casting technique. Conductivity increases with NH4CF3SO3 concentration up to 40 wt.% but decreases with further increase in salt content. The temperature dependent conductivity study shows that the conductivity-temperature behaviour of ENR-50/PEMA-NH4CF3SO3 electrolytes follows the VTF rule. DSC studies show that the Tg increases with increase in salt content. This means that the increase in conductivity of ENR-50/PEMA-NH4CF3SO3 is incorrelated to the increase of the segmental motion of the host polymer chains but may be attributed to the increase in the concentration and migration rate of charge carriers.
Research on Velocity Influence on Thermal Deformation Field of Heavy Hydrostatic Thrust Bearing
Authors: Yang Xiao Dong , Shao Jun Peng , Xu Xiao Qiu , Wang Yun Fei , Yin Chao , Jiang Hui
Published: August 2010

According to the structure of workbench and base of heavy hydrostatic bearing which is applied in heavy equipment, thermal deformation equations of the structure are deduced and boundary conditions for numerical simulation are established based on thermal elasticity theory. Then thermal deformation of hydrostatic bearing without load is calculated at different velocity. The results indicate that: temperature and velocity impacts a significant influence on thermal deformation of hydrostatic bearing. Thermal deformation increases as the velocity increases; workbench up-warps severely, oil-pad inclines towards outside to a certain extent, which results in the lubrication clearance emerges as wedge-shape deformation. The conclusions from thermal deformation calculation could provide theoretical basis for structure design of hydrostatic bearing and ravel out the thermal deformation problem.
Vegetation structure and potential gross primary productivity of mangroves at Kadolkele in Meegamuwa (Negombo) estuary, Sri Lanka
Authors: Jayakody JMAL , Amarasinghe MD , Pahalawattaarachchi V , De Silva KHWL
Published: August 2010

The potential gross primary productivity of the mangrove stands at Kadolkele in Meegamuwa (Negombo) estuary was studied in relation to vegetation structure with a view to understanding the salient structural components that affect functioning of mangrove ecosystems. Structure of mangrove stands under study was characterized with plant species richness, plant (stem) density, frequency of occurrence of constituent species, plant basal area and height. The structural complexity index values calculated from above parameters revealed a statistically significant (p < 0.01) positive relationship with the potential gross primary productivity of the mangrove stands that has been calculated using data on absorption of photosynthetically active radiation (PAR) by the stands that were measured using a light meter with a quantum sensor. Leaf area index (LAI) values were calculated using absorption data and potential gross primary productivity was estimated using an assimilation coefficient. Mean values of structural parameters were used to ordinate the mangrove sites through principal component analysis. Ordination showed a productivity gradient among the mangrove sites where species richness, stem density, plant height and leaf area index were the key factors that affect potential gross primary productivity of mangrove stands.DOI: 10.4038/sljas.v13i0.2209Sri Lanka J. Aquat. Sci. 13 (2008): 95-108
A decadal regional and global trend analysis of the aerosol optical depth using a data-assimilation grade over-water MODIS and Level 2 MISR aerosol products
Authors: Zhang J. , Reid J. S.
Published: August 2010

Abstract. Using the ten-year (2000–2009) DA quality Terra MODIS and MISR aerosol products, as well as 7 years of Aqua MODIS, we studied both regional and global aerosol trends over oceans. This included both natural and data assimilation grade versions of the products. Contrary to some of the previous studies that showed a decreasing trend in aerosol optical depth (AOD) over global oceans, after correcting for what appears to be aerosol signal drift from the radiometric calibration of both MODIS instruments, we found MODIS and MISR agreed on a statistically negligible global trend of 0.0003/per year. Our study also suggests that AODs over the Indian Bay of Bengal, east coast of Asia, and Arabian Sea show statistically significant increasing trends of 0.07, 0.06, and 0.06 per ten years for MODIS, respectively. Similar increasing trends were found from MISR, but with less relative magnitude. These trends reflect respective increases in the optical intensity of aerosol events in each region: anthropogenic aerosols over the east coast of China and Indian Bay of Bengal; and a stronger influence from dust events over the Arabian Sea. Negative AOD trends are found off Central America, the east coast of North America, and the west coast of Africa. However, confidence levels are low in these regions, which indicate that longer periods of observation are necessary to be conclusive.
Observations of ozone production in a dissipating tropical convective cell during TC4
Authors: Morris G. A. , Thompson A. M. , Pickering K. E. , Chen S. , Bucsela E. J. , Kucera P. A.
Published: August 2010

Abstract. From 13 July–9 August 2007, 25 ozonesondes were launched from Las Tablas, Panama as part of the Tropical Composition, Cloud, and Climate Coupling (TC4) mission. On 5 August, a strong convective cell formed in the Gulf of Panama. World Wide Lightning Location Network (WWLLN) data indicated 563 flashes (09:00–17:00 UTC) in the Gulf. NO2 data from the Ozone Monitoring Instrument (OMI) show enhancements, suggesting lightning production of NOx. At 15:05 UTC, an ozonesonde ascended into the southern edge of the now dissipating convective cell as it moved west across the Azuero Peninsula. The balloon oscillated from 2.5–5.1 km five times (15:12–17:00 UTC), providing a unique examination of ozone (O3) photochemistry on the edge of a convective cell. Ozone increased at a rate of ~1.6–4.6 ppbv/hr between the first and last ascent, resulting cell wide in an increase of ~(2.1–2.5)×106 moles of O3. This estimate agrees to within a factor of two of our estimates of photochemical lightning O3 production from the WWLLN flashes, from the radar-inferred lightning flash data, and from the OMI NO2 data (~1.2, ~1.0, and~1.7×106 moles respectively), though all estimates have large uncertainties. Examination of DC-8 in situ and lidar O3 data gathered around the Gulf that day suggests 70–97% of the O3 change occurred in 2.5–5.1 km layer. A photochemical box model initialized with nearby TC4 aircraft trace gas data suggests these O3 production rates are possible with our present understanding of photochemistry.
Tracing the origin of dissolved silicon transferred from various soil-plant systems towards rivers: a review
Authors: Cornelis J.-T. , Delvaux B. , Georg R. B. , Lucas Y. , Ranger J. , Opfergelt S.
Published: August 2010

Abstract. Silicon (Si) released as H4SiO4 by weathering of Si-containing solid phases is partly recycled through vegetation before its land-to-rivers transfer. By accumulating in terrestrial plants to a similar extent as some major macronutrients (0.1–10% Si dry weight), Si becomes largely mobile in the soil-plant system. Litter-fall leads to a substantial reactive biogenic silica pool in soil, which contributes to the release of dissolved Si (DSi) in soil solution. Understanding the biogeochemical cycle of silicon in surface environments and the DSi export from soils into rivers is crucial given that the marine primary bio-productivity depends on the availability of H4SiO4 for phytoplankton that requires Si. Continental fluxes of DSi seem to be deeply influenced by climate (temperature and runoff) as well as soil-vegetation systems. Therefore, continental areas can be characterized by various abilities to transfer DSi from soil-plant systems towards rivers. Here we pay special attention to those processes taking place in soil-plant systems and controlling the Si transfer towards rivers. We aim at identifying relevant geochemical tracers of Si pathways within the soil-plant system to obtain a better understanding of the origin of DSi exported towards rivers. In this review, we compare different soil-plant systems (weathering-unlimited and weathering-limited environments) and the variations of the geochemical tracers (Ge/Si ratios and δ30Si) in DSi outputs.
Rapid changes in ice core gas records – Part 2: Understanding the rapid rise in atmospheric CO2 at the onset of the Bølling/Allerød
Authors: Köhler P. , Knorr G. , Buiron D. , Lourantou A. , Chappellaz J.
Published: August 2010

Abstract. During the last glacial/interglacial transition the Earth's climate underwent rapid changes around 14.6 kyr ago. Temperature proxies from ice cores revealed the onset of the Bølling/Allerød (B/A) warm period in the north and the start of the Antarctic Cold Reversal in the south. Furthermore, the B/A is accompanied by a rapid sea level rise of about 20 m during meltwater pulse (MWP) 1A, whose exact timing is matter of current debate. In situ measured CO2 in the EPICA Dome C (EDC) ice core also revealed a remarkable jump of 10±1 ppmv in 230 yr at the same time. Allowing for the age distribution of CO2 in firn we here show, that atmospheric CO2 rose by 20–35 ppmv in less than 200 yr, which is a factor of 2–3.5 larger than the CO2 signal recorded in situ in EDC. Based on the estimated airborne fraction of 0.17 of CO2 we infer that 125 Pg of carbon need to be released to the atmosphere to produce such a peak. Most of the carbon might have been activated as consequence of continental shelf flooding during MWP-1A. This impact of rapid sea level rise on atmospheric CO2 distinguishes the B/A from other Dansgaard/Oeschger events of the last 60 kyr, potentially defining the point of no return during the last deglaciation.
A comparison of basal reflectivity and ice velocity in East Antarctica
Authors: Jacobel R. W. , Lapo K. E. , Stamp J. R. , Youngblood B. W. , Welch B. C. , Bamber J. L.
Published: August 2010

Abstract. Ground-based radio echo sounding data acquired along the 1700 km US-ITASE traverse have been used to determine ice attenuation and relative basal reflectivity across the major catchments funneling ice from East Antarctica to the Ross Ice Shelf. We find that basal reflectivity varies locally by up to 40 dB which we interpret as due to changes in the phase state at the bed. Some, though not all, areas of high local reflectivity are observed to have flat-lying bed reflections indicative of sub-glacial lakes. We compare basal reflectivity to ice balance velocity and find a general association of higher flow speeds with high radar reflection strength. This set of observations from two independent remotely sensed geophysical data sets extends the range of field observations to the interior of East Antarctica and confirms the importance of basal lubrication on modulating the ice dynamics of the largest ice sheet on the planet.
An energy-conserving model of freezing variably-saturated soil
Authors: Dall'Amico M. , Endrizzi S. , Gruber S. , Rigon R.
Published: August 2010

Abstract. In this paper we provide a method for solving the energy equation in freezing soil. The solver is linked with the solution of Richards equation, and therefore able to approximate water movement near the liquid-solid phase transition. The equations show non-linear characteristics causing oscillatory behavior in the solution close to the phase transition, when normal methods of iterative integration, as Newton or Picard, are used. Thus, a globally convergent Newton method has been implemented to achieve convergence. The method is tested by comparison with an analytical solution to the Stefan problem and by comparison with experimental data derived from literature.
Experimental Control Study of Biomass for Continuous Saccharomyces cerevisiae Fermentation
Authors: Anweiler D.D. , Dlugan A.B. , Hill G.A. , Rohanl S.
Published: August 2010

Using a novel, continuous flow‐cell mounted in a spectrophotometer, various digital control algorithms have been experimentally investigated to control biomass concentration within a turbidostat. The manipulated variable was a stream of pure, sterile water while disturbances were generated in the glucose feed stream.

Biomass concentration was found to be related to the controlled variable by a simple first order relation with maximum least squares parameter deviations of 20% when subjected to a variety of disturbances. After two trial and error attempts, the PI algorithm was found to be poorly tuned and gave unstable and oscillatory control. Using the process reaction curve results, the Dahlin's method was found to be an excellent tool for tuning the PI algorithm and gave good to excellent control for each of two adjustments of its tuning parameter. The IMC algorithm was also successfully used to control biomass but it was necessary to adjust the sampling time up from 5 seconds to 5 minutes to overcome the instability problems generated by the sensitivity of its tuning parameter at low sampling times.

Finally, it is shown that a mechanistic model employing Ghose growth biokinetics for Saccharomyces cerevisiae simulated the controlled, transient nature of the bioreactors with a good degree of accuracy.
Effect of Superficial Gas Velocity on Bubble Size, Terminal Bubble Rise Velocity and Gas Hold‐up in Bubble Columns
Authors: Jamialahmadi M. , Müuller‐Steinhagen H.
Published: August 2010

It is important to have a reliable estimate of bubble size, terminal bubble rise velocity and gas hold‐up in bubble columns, since these parameters are directly related to the transfer coefficients and the transfer area. Mean bubble diameters have been measured as a function of the superficial gas velocity in air‐water systems. In the bubbly flow regime, the bubble size is a strong function of the orifice diameter and the wettability of the gas distributor and a weak function of superficial gas velocity. In the turbulent churn flow regime this functionality is reversed and the bubble diameter becomes a strong function of the superficial gas velocity. A correlation is presented which covers both regimes. The terminal bubble rise velocity was measured as a function of the bubble size and the results were compared with correlations recommended in the literature. Finally, the gas hold‐up was measured over a wide range of superficial gas velocities. The results were compared with a variety of empirical and theoretical correlations. New equations are presented which predict gas hold‐up of the air‐water system with good accuracy.
The Nature of Pores in the Skin Layer of Polymeric Reverse Osmosis/Ultrafiltration Membranes
Authors: Wood Hal , Sourirajan S.
Published: August 2010

It is assumed that a linear polymer solution may be represented as a suspension of impermeable macromolecule spheres. In the film‐forming procedure, spheres at the interface form a monolayer and then partially coalesce with each other. Their size, disposition and degree of coagulation are dependent on the casting composition and subsequent film‐forming procedure.

This ‘interstitial void model’ is applied to Reverse Osmosis (RO) / Ultrafiltration (UF) films. Results indicate that an RO membrane skin layer is at least one monolayer thickness of predominantly close‐packed partially coalesced macromolecule spheres. Variations in the casting conditions influence the surface morphology and may cause defects in the monolayer, comparable to voids formed by the surrounding of four or more spheres.

The interstitial void model verifies the existence of a bimodal distribution of pores on the skin layer of polymeric RO/UF membranes. The general RO membrane fabrication requirements are that the casting macromolecules be small and packed closely together at the interface during the membrane forming procedure.
Optimum Flotation Conditions for Al‐Jalamid Phosphate Rock
Authors: Al‐Fariss Tariq F. , Ozbelge H.O. , Abdulrazik A.M.
Published: August 2010

This study is concerned with the beneficiation by flotation of carbonate‐rich phosphate rock from the Al‐Jalamid region of northern Saudi Arabia. Flotation of carbonate‐rich phosphate rock has been the subject of intensive research in recent years due to the depletion of deposits rich in silica. A flotation method called ‘short conditioning’ has been defined by the authors for the Al‐Jalamid rock. The optimization parameters are identified and optimum conditions are found for the highest CaO separation efficiency from the phosphate concentrate.

The most important optimization parameters investigated were pulp density, pH of the pulp, collector quantity, depressor quantity and flotation time.

The optimum conditions determined from the experimental work are: pulp density: 10.61% solid (w/w); pH of the pulp: 6.47; collector quantity: 1.64 g kg−1 of rock; depressor quantity: 20.36 g kg−1 of rock; and flotation time: 3.03 minutes.
Development of Solutions to Two‐Resistance Mass Transport Models Based on External and Pore Diffusion. Part I: Theoretical Development
Authors: Mckay Gordon , Al‐Duri Bushra , Mckee Stephen
Published: August 2010

A two‐resistance mass transfer model has been developed to describe the adsorption of various pollutants onto adsorbents in batch adsorbers. The mechanism is based on external liquid‐phase mass transfer and pore‐diffusion controlling internal mass transport. A previous analytical modef−1 was developed for a pseudo‐irreversible isotherm, but it was only applicable to systems in which operating lines and tie lines terminated on the isotherm monolayer. The application of the original model has been extended by incorporating several curve fitting equations into the analysis and differentiating them, thus enabling mass transfer coefficients to be predicted for operating lines over the whole range of the equilibrium isotherm. A comparison of the curve fitting equations was made to test which, if any, gave the 'best‐fit' to experimental data.
Some Design Aspects of Aromatic Polyamide Reverse‐Osmosis Membranes
Authors: Wood Hal , Sourirajan S.
Published: August 2010

Linear‐polymer solutions are comparable to a suspension of macromolecule spheres. Macromolecules concentrate at the interface during the membrane‐forming procedure. They coalesce with each other sufficiently for the surface to become a sheet of interconnected macromolecules. Interstitial voids are formed whose magnitude is dependent on the size and packing arrangement of the macromolecules, and is also influenced by the extent of coalescence occurring in the interstitial voids. A subsequent gelation procedure renders the macromolecules paracrystalline. During operation, the membrane allows permeation of solution components primarily through the interstitial voids. Membrane design requires the ability to predict membrane performance from the precursor casting conditions. This paper illustrates the practical utility of the interstitial void model for membrane design purposes. Some design aspects are presented for various reverse‐osmosis membranes made from an aromatic polyamide polymer.
Multicomponent Distillation Column Design: A Semi‐rigorous Approach
Authors: Maiti S.N. , Ganguly S. , Das A. K. , Saraf D. N.
Published: August 2010

A new semi‐rigorous approach for the design and simulation of multicomponent distillation columns is presented which combines a rigorous Naphtali‐Sandholm algorithm with Edmister's shortcut method. The column is assumed to comprise of single and multi‐tray units with the number of trays inside the multi‐tray unit treated as an iterative variable. The assumption of linear variation of flows inside a multi‐tray unit made by earlier workers (which often lead to convergence difficulties or erroneous results) has been replaced with a more rigorous calculation procedure. Examples are presented to demonstrate the usefulness of the new method for both design and simulation calculations. The semi‐rigorous model equations can be solved directly to obtain a reasonably accurate and practical design, whereas most other available methods require repeated calculations. Computer memory requirement is drastically reduced in this semi‐rigorous formulation as compared to rigorous methods.
The Measurement of High Pressure Vapour‐Liquid‐Equilibria: Part II: Static Methods
Authors: Raal J. D. , Mühlbauer A. L.
Published: August 2010

Static equilibrium cells in a variety of configurations have been widely used for high pressure VLE measurement. The method can be divided into analytical procedures where both vapour and liquid compositions are sampled and measured, and the synthetic method for which no sampling of the phases is required. Where the isobars and isotherms have large gradients the synthetic method is the least accurate of the two methods. For mixtures with more than two components the information obtainable by the non‐analytical method is limited. Attempts to combine features of the analytical and non‐analytical method in a single cell are also described.

The difficulty of sampling from a high pressure space without serious disturbance of the equilibrium, and the problem of homogenization of a vapourised liquid sample are reviewed. A static jet mixer for vapourized liquid‐sample homogenization is described. A new static equilibrium cell design is proposed in which the liquid level is made visible by internal mechanical adjustment, and multiple liquid‐phases can be sampled using a single sampling valve without disturbing equilibrium. A mechanism for producing a small continuous flow of liquid through a sample valve by use of the internal stirrer is a novel idea, and is also described.
High‐Temperature Selective Membranes for Hydrogen Separation
Authors: Gobina E. , Hughes R. , Monaghan D. , Arnell D.
Published: August 2010

Palladium‐silver alloy films (5‐8 μm) were deposited onto porous ‘Vycor’ glass tubes by the process of magnetron sputtering. The films were characterised by electron probe microanalysis (EPMA), scanning electron microscopy (SEM), relative light transmission and electrical resistivity respectively. A membrane reactor capable of operating at high temperatures (573‐773K) was used to study the permeability characteristics of the membranes in relation to hydrogen gas from a 60% H2 40% N2 feed gas mixture. The membranes were found to be 100% selective for hydrogen with adequate permeation flux. A limiting purge rate of 500 cm3 (STP)/min was found to be sufficient to double the hydrogen permeation rate for a total feedrate of 350 cm3(STP)/min.
A New Technique for the Determination of Overall Mass‐transfer Coefficients in Continuous Dialyzers
Authors: Ǒzdural A. R.
Published: August 2010

A mass transfer model has been developed to describe the dialysis of solutes in continuous dialyzers. The model is based on recycle systems, and yields a new technique for the calculation of overall mass‐transfer coefficients. The permeability of a Cuprophane PT‐150 membrane to NaCl solutions was determined. Sherwood numbers describing mass‐transfer resistance in the fluid adjacent to the membrane were determined, and presented as a function of the corresponding Reynolds and Schmidt numbers.
Acceleration of Potassium Permanganate Electrochemical Reactions with Orthogonal Magnetic Fields
Authors: Evers S. , Simandl J.
Published: August 2010

Experiments were conducted to examine the effect of orthogonal magnetic fields upon the kinetics of potassium permanganate electrochemical reactions. Magnetic field strengths of up to 15 kGauss were applied to a thin cell, with electrodes connected to a constant voltage source. The results indicated that the presence of a magnetic field accelerated the global reaction kinetics.
Structural Features of Activated Carbon Produced From Oil Sands Coke
Authors: Dippanfilo R. , Egiebor N. O.
Published: August 2010

The physical and structural properties of oil sands coke were investigated in an attempt to produce activated carbon from this material via steam activation. Although the activation process resulted in over 60 wt. % burnoff from the starting raw coke, the particle size distribution of the activated coke was similar or slightly larger than that of the raw coke. The changes in bulk density with activation showed a linear decrease with activation, thus indicating that the mass losses occurred mainly in the interior of the coke particles. Absolute density measurements showed an increasing trend with activation between a mass burnoff of 35 wt.% and 50 wt.%., which is consistent with a modification in the amorphous structure within the coke matrix. Scanning electron microscopic examination of the structural features of the activated coke revealed hollow spherical particles composed of concentric layers of carbonaceous matter with void volumes between the layers. The formation of the concentric layers promotes the activation process, thus enhancing internal surface area development.
Selective Permeation of Vanadium(V) and Chromium(VI) through Anion Exchange and Supported Liquid Membranes
Authors: Kojima T. , Yagi S. , Nishijima K. , Matsukata M.
Published: August 2010

Selective permeation of vanadium(V) and chromium(VI) using three types of membrane systems was studied. The first was an anion exchange membrane, the second and third were supported liquid membranes containing either a tertiary amine or a quaternary ammonium salt. The membrane was sandwiched between two glass cells. One cell was filled with a solution of identical concentrations of vanadium(V) and chromium(VI), and the other cell contained sodium hydroxide solution. The permeation rates of vanadium(V) and chromium(VI) were measured from the concentration change in the solution on the recovery side of the membrane. The selectivity of vanadium(V) over chromium(VI) was defined as the ratio of their rates. The selectivity of vanadium(V) over chromium(VI) was as high as 10 for pH of feed phase between 8 and 10 when using the quaternary ammonium salt and much better than these for the other membranes with an alkaline feed phase, which was used to simulate of the effluent from leaching of the heavy oil combustion ash and other wastes containing vanadium.
Multi‐Stage Flash Desalination Process: A Thermal Analysis
Authors: El‐Dessouky Hisham , Shaban Habib I. , Al‐Ramadan Hamida
Published: August 2010

Multi‐Stage Flash (MSF) desalination processes play a vital role in the provision of fresh water in many areas of the World, particularly in the Arab Gulf countries. This paper describes a steady‐state mathematical model developed to analyze the MSF water desalination process. Relations between parameters controlling the product water cost (e.g. thermal performance ratio, specific heat transfer surface area, and specific flow rate of cooling water and recirculated brine) to other operating and design variables are established. These relations can be used to design new plants or to analyze existing units.

The model assumes the practical case of constant heat‐transfer surface area per stage in each section. It considered the variation of water physical properties with temperature and salt concentration, the effect of fouling factors, and the presence of non‐condensable gases on the overall heat‐transfer coefficients, and variations in stage flash down and thermodynamic loss from stage to stage. The model also takes into consideration the heat transfer losses from the stages to the surrounding and through rejection of the noncondensable gases. The results obtained from the developed model are compared with data from six different MSF plants, and good agreement is obtained.
Mathematical Modeling of the Prereduction Process of Iron Ore in a Circulating Fluidized Bed
Authors: Hahn Y. B. , Im Y. H. , Kim K. J. , Park D. G. , Lee I. O. , Nam I. S. , Chang K. S.
Published: August 2010

A mathematical model has been developed to describe the various subprocesses occurring in a circulating fluidized bed (CFB) used for pre‐reduction of iron ore particles in the smelting reduction iron‐making process. The model incorporates hydrodynamics, iron reduction kinetics, and heat and mass transfer. One of the key features is the inclusion of a wall‐to‐bed heat transfer model to describe the heat transfer phenomena occurring in the CFB. The predicted and measured heat transfer coefficients showed a minima in the lower part of the bed due to the irregular up‐and‐down movement of ore particles. The model predictions of the reduction degree of iron oxides based on shrinking‐unreacted‐core chemical reaction control mode showed satisfactory overall agreement with measured data. The performance of the CFB reactor has been tested extensively in terms of gas oxidation degree, inlet temperature, particle size and mean particle residence time. It was confirmed that the reduction degree is significantly affected by gas oxidation degree, wall temperature and particle size.
On‐Line Inferential Models in Nonlinear Multivariate Control Applications
Authors: Ansari R. M. , Tadé M. O.
Published: August 2010

On‐line product quality measurements suffer from excessive time delays and sampling intervals which limit their effectiveness as inputs for automatic control. Inferential models which are based on fast and continuously available temperature, pressure and flow measurements reduce the negative impact of the sample intervals and time delays with minimum compromise on accuracy. The resulting continuous and fast response keeps the product qualities on specifications and minimizes the quality giveaway. This paper highlights the development aspects of correlations, use of inferential models in both open and closed loop environments, laboratory update mechanism, operators acceptance and benefits of inferential models and their use as a controlled variable in nonlinear multivariable control applications.
Generating Operating Command Sequences for the Regulation of Complex Chemical Processes Using Artificial Intelligence Techniques
Authors: Roach J. R. , O'Neill B. K. , Strimaitis P. J.
Published: August 2010

Complex processing plants are operated (and for that matter designed) by individuals who cannot always envisage in sufficient detail the longer‐range consequences of their current actions. This is particularly the case where interactions can occur between sequential operating modes of a plant. Given that the desired outcome is the achievement of the overall process goals safely and efficiently, it is worthwhile considering the factors which can mitigate against the achievement of these aims and how they can be avoided. This study describes methods which can be used to help develop safer and more efficient plant operation by the use of the computer to devise operating command sequences which achieve consecutive sets of process goals subject to a variety of constraints (e.g. the avoidance of unsafe states). The operating command sequences are required to be generated in the form of a sequence of valve operations. A catalyst‐regeneration plant example originally devised by Rivas and Rudd (1974) is presented.
Peat for Environmental Applications: A Review
Authors: Mckay G.
Published: August 2010

Peat occurs abundantly in nature in various forms. Its chemical composition varies widely with geographical region, age and within individual deposits due to the chemical reactions resulting in its formation. However, it is now realized that the basic chemical and physical properties of most peats are beneficial to sorption and ion exchange processes. The potential range of environmental uses for peat described in this paper vary from the treatment of oil spills and textile effluents to VOC removal and metalion removal from waste streams.
Development of a Particle‐Bubble Collision Model for Flotation columns
Authors: Egiebor N. O. , Zhou Z. A. , Nyavor K.
Published: August 2010

Particle‐bubble collisions in bubble swarm systems have been modelled based on previous work on single bubble systems and bubbly flow characterization. This approach relates the overall collision probability to bubble and particle sizes, gas holdup, column height, and other operating parameters, thus providing a theoretical basis for column design and analysis of particle collection in flotation columns. The simulated results indicate that the existing collision models based on single bubble systems cannot be accurately applied to actual flotation columns for analysis of the particle‐bubble collision process. This is mainly due to the effect of gas holdup, bubble interaction, and multi‐layers of bubbles in a swarm. For column flotation of fine particles under normal operating conditions, a recovery zone of about 10 meters is sufficient to ensure that the collision probability approaches unity. For bigger particles, higher gas holdups, and smaller bubble sizes, much shorter recovery zone heights can be used to achieve the same high collision probability.