Stirring Period Research Articles

Adsorptive desulfurization of kerosene and diesel oil by Zn impregnated montmorollonite clay

In the present research work, desulfurization of kerosene and diesel oil has been carried out by selective adsorption through metals impregnated montmorollonite clay (MMT). Different metals were impregnated on MMT by wet impregnation method which included Fe, Cr, Ni, Co, Mn, Pb, Zn and Ag. The adsorption study was carried out in batch operation initially for 1h time and at room temperature (25°C). The results show that high desulfurization was brought about by Zn-MMT. In the case of kerosene highest desulfurization of 76% and in the case of diesel maximum desulfurization of 77% was achieved with adsorption through Zn-MMT. Conditions were also optimized for the desulfurization process. Highest yield of desulfurization was obtained at 1-h stirring period, at room temperature (25°C) and using oil to adsorbent ratio of 20:1.5. Under optimized conditions the adsorbent was found to adsorb about 81% of DBT from the model oil containing 1000ppm DBT dissolved in cyclohexane. EDX, Surface characterization and SEM analysis of the adsorbents used in the study were conducted to evaluate their mineralogical nature and textural behavior. Results show that the surface area, pore size and pore volume of the MMT has been found to be increased many fold with Zn impregnation. Also the surface morphology of the MMT has also been improved with Zn impregnation.

Synthesis and Characterization of Hematite Nanoparticles as Active Photocatalyst for Water Splitting Application

This paper highlights on the hydrogen production through photocatalytic activity by using hematite nanoparticles synthesized from self-combustion method based on different stirring period. The morphologies and microstructures of the nanostructures were determined using Field-Emission Scanning Electron Microscope (FESEM), X-Ray Diffractometer (XRD) and Particle Size Analyser (PSA). Besides that, surface area analyser was used to determine the BET surface area of the hematite samples. The hematite nanocatalyst as-synthesized are proven to be rhombohedral crystalline hematite (α-Fe2O3) with particle diameters ranging from 60-140 nm. The BET specific surface area of hematite samples increased from 5.437 to 7.6425 m2/g with increasing stirring period from 1 to 4 weeks. This caused the amount of hydrogen gas produced from photocatalytic water splitting to increase as well.

Mechanical transformation of fullerene (C60) to aqueous nano-C60 (aqu-nC60) in the presence and absence of light

The present study was carried out to evaluate transformation kinetics of derivatized fullerene species by simulating natural aquatic processes, which will help elucidate biological effects of water-stirred nano-C60 (aqu-nC60). Physicochemical analyses of aqu-nC60 included molecular and agglomerate-scale characterization, surface charge analysis through examination of electrophoretic mobility, and chemical composition analysis using spectroscopy. Detailed analysis of aqu-nC60 transformation over a 28-day stirring period in both light and dark conditions indicated aqu-nC60 agglomerate concentrations can be estimated as a time-function using a predictor model (R 2 > 0.99). Number-weighted agglomerate size did not differ significantly over the 28-day stirring period regardless of photocondition, although size distributions were more uniform as stirring time increased. The total number of surface groups identified through XPS indicated increased derivatization as a function of time with additions assigned to mono-oxygenated carbon moieties while the number of di-oxygenated moieties declined. Earlier-phase stirring (t ≤ 14 days) products were shown to contain epoxide surface groups, which were absent in later-phase (t > 14 days) suspensions, suggesting specific pathways to derivatization with preferential mono-oxygenated states. Filter residue, a by-product of the aqu-nC60 synthesis process, demonstrated high hydrophobicity and FTIR spectra similar to underivatized material, suggesting synthesis process inefficiencies.

Influence of final stirring treatment on inclusion number in tool steel

The focus was to study the elimination of non-metallic inclusions during the final part of the ladle refining of tool steel (AISI H13). More specifically, the final stirring treatment in a ladle before casting was modified to study how the number of inclusions could be decreased. The following three stirring treatments were tested: a conventional induction stirring with a 650 A current for 20 min, a short induction stirring with a 650 A current during 10 min, and a combined gas and induction stirring during 20 min (no open eye and a 600 A current). Steel samples were collected from the ladle before and after the final stirring period of the ladle treatment. Thereafter, the numbers of inclusions in steel samples were determined using a light optical microscope based on a classification according to the Swedish standard SS111116 (JK Scale II). Overall, the results showed that a combined gas and induction stirrings was the most efficient way of decreasing the number of DM, DH and DP inclusions. The decrease in the inclusion number in four heats was the following for the different size classes for a combined stirring procedure: 15–40% for DM type inclusions, 30–61% for DH type inclusions and 50–100% for DP inclusions. In addition, it should be mentioned that a stirring practice with induction stirring during 10 min resulted in a 67–100% decrease in the DH type inclusions. However, the results for a combined stirring case for DH type inclusions were more stable than those for a shorter induction stirring time.

Improvement of the flocculation process in water treatment by using moringa oleifera seeds extract

Water scarcity encourages researchers to keep working on natural coagulant agents such as Moringa oleifera seed extract, that could be used even in developing countries. With this scope, this investigation is focused on the optimization of certain parameters affecting the use of this coagulant product in the clarification of real surface water. Acidic pH levels seem to enhance the coagulation performance and the turbidity removal increases as the stirring period becomes longer (up to 95% with 40 min). The optimum stirring rate is identified as 80 rpm. Water clarified with this optimum coagulation and flocculation process is turbidity-competitive with other well known coagulants and flocculants and its quality is inside standard ranges for clarified water. No microbial growth is observed within the first 72 hours after the coagulant trials.

Evolvement of soft templates in surfactant/cosurfactant system for shape control of ZnSe nanocrystals

The evolution of soft templates in the synthesis of ZnSe nanocrystals realized through a surfactant/cosurfactant system was investigated and a micelle formation process model was proposed. Through freeze-fracture electron microscopy, it was proven that template micelles were formed in the zinc precursors. Furthermore, it was found that a long stirring period was essential for achieving the lowest energy state of the soft templates which were used for synthesizing monodisperse ZnSe quantum dots.

Influence of SiC Particles Distribution and Their Weight Percentage on 7075 Al Alloy

The stir casting method was used for fabrication of 7075 aluminum alloy with 10 wt.% SiC particles of size 20-40 μm. The research objective of this paper are to achieve uniform distribution of SiC particles in the 7075 aluminum alloy matrix, characterization, and analysis of mechanical properties of composite formed. Experiments were carried out at stirring speeds of 500, 650, 750 rpm, and stirring period of 10 min. Microstructures of aluminum alloy and composites with 5, 10 wt.% SiC reinforcements were examined. The results reveal that composite produced at stirring speed of 650 rpm and stirring time of 10 min has uniform distribution of SiC particles. XRD and EDAX analysis were carried out for 7075 Al alloy and composite with 10 wt.% SiC reinforcement. No adverse reaction was observed in XRD and EDAX of composite with 10 wt.% SiC reinforcement. Tensile strength and hardness increased by 12.74% and 10.48%, respectively, with the increase in percentage of SiC reinforcement from 5 to 15 wt.%.

Emulsification of Top Slags during Argon Stirring through a Porous Plug in the Ladle of Si Deoxidised Carbon Steels

Intensive experiments with 170-t heats of carbon steels in the LD steel plant of Saarstahl AG were performed to study the emulsification of an acid top slag during different stirring conditions in this research project. During ladle treatment samples were taken from steel for the analysis of the composition of the inclusions together with the top slag. Within these investigations gas flow rates and stirring times were systematically varied in order to study their influence on the entrapment of top slag in the steel melt. At the same time a model was developed for the evaluation of the performance of the porous plug with regard to gas flow rate and gas pressure or finally for blockades and leakages. According to the experiments of this project the following results were established. Small top slag particles are discovered nearly in all steel samples together with endogenous SiO2-Al2O3 deoxidation products. But emulsified phases or parts of the top slag generating larger inclusions with a size of 30 – 60 μm show the low melting eutectic composition. On the other hand, this emulsification process leads simultaneously to CaO depletion and SiO2 accumulation of the top slag particularly when a longer stirring period is applied as shown during these experimental trials. The whole process requires low melting top slags and low melting emulsified inclusions in combination with a low viscosity level. To meet the emulsification requirements the gas flow is characterised by high gas flow rates in the order of 30 – 40 STP m3/h and high pressures with 8 – 12 bar indicating a blockade of the porous plug and the existence of a gas jet.

Effects of stirring parameters on rheocast structure of Al–7.1wt.%Si alloy

Abstract In this study, effects of stirring time and stirring speed on the microstructure of semisolid rheocast (SSR) Al–7.1 wt.%Si were examined. The results demonstrated that the non-dendritic structure could be formed by a short stirring period below liquidus temperature and further stirring had little impact on the final morphology of the primary particles. Stirring was shown, however, to affect the average particles size mainly during the initial stages of solidification. Although the average shape factor of primary particles was relatively insensitive to large variations in the stirring speed, higher stirring speeds made the shape and size of the primary particles more uniform. Higher stirring speeds also rendered smaller and more rounded agglomerates of primary particles. The results of two stability models employed suggest that, in general, the primary particles generated in the initial stages of solidification can attain growth stability before pouring and maintain this stability during the secondary cooling stage.

Yield Control of Chemically‐Synthesized Magnetite Nanoparticles

Magnetic Fe3O4 nanoparticles have generated a vast amount of interest as they bridge the gap between the atomic and microscopic world. Below a certain size (<15 nm), these particles display a novel phenomenon known as superparamagnetism in which they can be magnetized and demagnetized rapidly with the aid of an external magnetic field. Thus, they have potential applications such as targeted drug delivery, hyperthermia, etc. in the biomedical field. Yield control is essential if these particles are to be used for diverse applications on a large scale. In this study, Fe3O4 have been prepared using the standard co‐precipitation of Fe2+ and Fe3+ with an alkaline base. Three synthesis parameters, namely the stirring rate, stirring period and the reaction temperature were varied to study their effects on the yield of the nanoparticles.

Characterization of Chemically Prepared Magnetite Nanoparticles

Magnetite (Fe3O4) nanoparticles are being extensively researched as potential building blocks for nanoscaled structures, devices and systems. They exhibit many unique properties due to their dimension that lies in the mesoscopic scale (in between atomic scale and microscopic scale). In addition, it is possible to fine tune the properties of magnetite particles prepared by wet chemical techniques simply by varying the synthesis parameters. Thus, they are widely considered for various applications in fields such as electronics, optoelectronics, biomedicine and medical diagnostics. However, in order to be widely utilized for biomedical and commercial applications, these particles have to be produced at a large scale with low cost, high yield and high reproducibility. Moreover, the particles have to possess uniform properties and narrow size distribution. In this paper, Fe3O4 nanoparticles are prepared under non‐oxidized environment using co‐precipitation of Fe2+ and Fe3+ with an alkaline base. The effect of preparation variables, such as the stirring rate, stirring period and reaction temperature, on the properties of the nanoparticles are compared using TEM, VSM and XRD.

Environmental factors which influence the sink of silica in the limnetic system of the large monomictic Lake Biwa and its watershed in Japan

Dissolved silica (DSi) and its associated biological and physicochemical factors were measured in Lake Biwa, Japan and its watershed from 2002 to 2003 in order to clarify seasonal variations in the magnitude of the sink of silica and the factors that influence it within the limnetic system. Consequently, it is concluded that Lake Biwa is a noticeable body of water where a massive sink of silica is caused. Calculated silica sedimentation in Lake Biwa was 2.0 × 107 kg Si year−1 (7.1 × 108 mol Si year−1) which is equivalent to about 80% of the annual inflow discharge of DSi to Lake Biwa. The magnitude of the sink varies seasonally by increasing in the winter holomictic stirring period, since it is greatly affected by the species composition of phytoplankton, the load of phosphorus and the condition of stratification. It seems reasonable to suppose that the DSi in Lake Biwa is removed mainly by biological processes, i.e., the assimilation of DSi by large centric diatoms and its accumulation in their frustules. Such silica sinks occur naturally in deeper stagnant waters, providing extended water residence time and supplying a certain amount of nutrients. These findings indicate that an increase in nutrient loads and abundance of stagnant water due to the construction of large dams lead to an expansion in the magnitude of the silica sink in a limnetic system.

Most relevant mechanisms of inclusion growth in an induction–stirred ladle

The purpose of this study has been to theoretically evaluate which inclusion growth mechanisms are important in an inductively stirred ladle. This has been done using data from a computational fluid dynamics model of a real ladle. The data was utilized as the input to the different collision equations. It was concluded that diffusion of oxygen and deoxidant to the inclusion surface, diffusion coalescence and Brownian motion collisions contribute very little to growth of inclusions during the stirring period in the ladle. This was in accordance with earlier findings in the literature. This study also showed that laminar shear collisions could be excluded from a growth model. The major growth mechanism is turbulent collisions. It was also shown that a 700–A stirring current leads to more growth due to turbulent collisions than a 500–A stirring current. The importance of a correct value of the collision efficiency coefficient for turbulent collisions was pointed out. If a large difference in inclusion size exists then collisions due to difference in buoyancy (Stokes collisions) also need to be considered in a growth model. Finally, it is concluded that the variation in fluid flow and turbulent properties in different parts of the ladle should be incorporated into a growth model, since it can affect average turbulent collision volumes by 25–30%.

Liposome Delivery Systems Containing Ibuprofen

AbstractMultilamellar liposome vescicles containing ibuprofen were successfully prepared by hydrating the lipids in the presence of organic solvent. The effects of varying the ratio of lipid to drug; the filter size; and the stirring period during hydration of the dried lipids layer were evaluated. Liposomes sample prepared by using a ratio of 3 lipid: 1 drug gave the highest entrapment efficiency of the drug and released all the drug over 12 hours of testing dissolution. Also the dissolution data showed that the drug release from large liposomes (5.0 μm) was 65.7% after 12 hours; 62.6% from medium size (0.8 pm) and 46.6% from small size liposomes (0.22 μm). Additionally, the increase of the stirring period during hydration of the dried lipid layer with the aqueous phase increased the release of the drug from the liposomes.

Upgrading of Anaerobic Digestion Processes for Night Soil

The upgrading of night soil anaerobic digestion processes was studied by field investigation of the performance of anaerobic digesters in existing night soil treatment plants and by serai-continuous experiments with bench-scale digesters. Both the average monthly amount of collected night soil fed to a digester and the concentration of volatile solids in night soil increased in winter. A good correlation was found to exist between gas production and digestion temperature. The COD removal rate in the first digester was markedly higher than that in the second digester. The stirring period in the first digester in one plant differs from that in the other plant. Stirring the first digester for too long a period reduces the rate of COD removal by the second digester in the two-stage anaerobic digestion process. The first digester should be stirred for more than one hour per day in order to promote gas production. Gas production and CODCr removal rate in the second digester were hardly affected by reductions in retention time ranging from 15 days to 5 days. As night soil contains a large amount of cellulose and other refractory organics, some kind of pretreatment of the night soil fed to the digester may be necessary for the promotion of acidogenesis in the two-phase anaerobic digestion process.

Determination of selenium(IV) in seawater by gas chromatography after coprecipitation with hydrous iron(III) oxide

Selenium(IV) concentration in seawater was determined by gas chromatography with electron capture detection after coprecipitation with hydrous iron(III) oxide. Quantitative precipitation of Se(IV) was obtained at pH 5.0. Following a brief, 15 min, stirring and setting period, the coprecipitate was filtered and dissolved in hydrochloric acid. Selenium was derivatized to 5-nitroplazselenol, extracted into toluene and introduced into the chromatograph. The detection limit was 1 pg injected or 5 ng of Se/L of seawater using a 200-mL sample. The precision was 6% at the 0.025 ..mu..g of Se/L level.

鋳片最終凝固位置近傍の電磁攪拌効果

It is commonly observed that severe V-channel segregates are associated with the equiaxed zone in the central region of a strand. This type of segregation may deteriorate the product qualities especially for sour gas service. The modification of V-segregates is found to be attained by electromagnetic stirring at the final stage of solidification. The laboratory scale stirring experiments have been carried out in order to eliminate V-segregation and the following results have been obtained.1) V-segregation streaks can be eliminated by linear or rotary type stirrer at the final stage of solidification.2) The upward flow of molten steel at the solidification front which may prevent the inter-dendritic liquid flow toward the bottom is effective.3) In the case of stirring by rotary type stirrer, adequate amount of fine equiaxed crystals is necessary. Alternating stirring at the final stage of solidification may prevent coagulation of equiaxed crystals and modify the packing of them.4) It was found that only weak stirring is enough.5) It is important to time the stirring to the progress of solidification. Optimum stirring period should be aimed at right after the precipitation of crystals, fraction of solid equals to 0.1 at the center of a strand.

Henry VIII and Scotland

Henry VIII was a great king, and great things were done in his day. The story of his reign has been told by more than one famous historian, and in that story Scotland, as a rule, plays only a small part. Generally she appears as the ally of France used to embarrass England from time to time, as a sort of Highland dirk threatening the back of stout King Hal as he faced south—a dirk little used in fact, and in use very ineffective; witness Flodden and Solway Moss! If we may judge by the standard histories, Scotland had little to do with the action and the movement of a stirring period.

The Late Captain Cameron

CAPTAIN VERNEY LOVETT CAMERON, C.B., R.N., died very suddenly, in his fiftieth year, on March 26, in consequence of being thrown from his horse while returning from a day's stag-hunting. His name is associated with the most stirring period of modern inland exploration in Africa. In 1871 Mr. H. M. Stanley met and relieved Livingstone at Ujiji, and on returning to the east coast met the Livingstone relief expedition of the Royal Geographical Society, the leader of which, believing his work to be forestalled, declined to proceed, and broke up his caravan. Lieutenant Cameron had for some time been anxious to explore Africa, and had been one of the unsuccessful applicants for the command of the abortive expedition. On its collapse he submitted proposals for the exploration of the Victoria Nyanza and of east equatorial Africa to the Royal Geographical Society, and in 1872 he was entrusted with a new Livingstone relief expedition, which was to proceed from the east coast, while another expedition, under Lieutenant Grandy, pushed its way up the Congo.