Two Analytical Approaches for Solution of Population Balance Equations: Particle Breakage Process

Various particulate systems were modeled by the population balance equation (PBE). However, only few cases of analytical solutions for the breakage process do exist, with most solutions being valid for the batch stirred vessel. The analytical solutions of the PBE for particulate processes under the influence of particle breakage in batch and continuous processes were investigated. Such solutions are obtained from the integro‐differential PBE governing the particle size distribution density function by two analytical approaches: the Adomian decomposition method (ADM) and the homotopy perturbation method (HPM). ADM generates an infinite series which converges uniformly to the exact solution of the problem, while HPM transforms a difficult problem into a simple one which can be easily handled. The results indicate that the two methods can avoid numerical stability problems which often characterize general numerical techniques in this area.     

HYDROMAGNETIC NATURAL CONVECTION OF A BINARY FLUID IN A VERTICAL POROUS ENCLOSURE

An analytical and numerical investigation is conducted to study the effect of an electromagnetic field on natural convection in a vertical rectangular porous cavity saturated with an electrically conducting binary mixture. Uniform heat fluxes are applied to the vertical walls while the horizontal walls are adiabatic. Governing parameters of the problem under study are the thermal Rayleigh R_T, Hartmann number Ha, buoyancy ratio ?, Lewis number Le, and aspect ratio A. An analytical solution, valid for tall enclosures (A > > 1), is derived on the basis of the parallel flow approximation. In the range of the governing parameters considered in this study, a good agreement is found between the analytical predictions and the numerical results obtained by solving the full governing equations.     

Analytical estimate of the heating regime for a recuperative glass-melting furnace

The results of an analytical evaluation of the heat transfer processes in the working space of the furnace are presented. Four atomizers located under the nozzle of the burner are used for heating. The calculations are performed using a three-dimensional heat transfer zonal model for three variants of the thermal load distribution between the atomizers, as well as for heating of the furnace with natural gas (non-luminous flames).     

Determination of Cadmium(II) in Water and Soil Samples after Preconcentration with a New Solid Phase Extractor

Abstract

A new simple and reliable method has been developed to separate and preconcentrate trace cadmium ion from water and soil samples for subsequent measurement by flame atomic absorption spectrometry (FAAS). Cadmium ions adsorbed quantitatively on Amberlyst 36 cation exchange resin were eluted with a 5 mL of 3 mol/L hydrochloric acid solution. Different factors and matrix effects for the preconcentration step were examined. The analytical figures of merit for the determination of cadmium are as follows: analytical detection limit, 0.51 µg/L; precision (RSD), 2.9%; enrichment factor, 200; capacity of resin 192 mg/g. The method was applied for cadmium determination in tap water, natural drinking water, soil, and roadside dust samples. The accuracy of the method is confirmed by analyzing standard reference material (Montana Soil, SRM 2711).     

An efficient green synthesis of quinoxaline derivatives using carbon-doped MoO3–TiO2 as a heterogeneous catalyst

A series of carbon-doped MoO₃–TiO₂ (CMT) material were prepared by sol–gel method. The catalyst prepared has been characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR). The natural wood plant Acacia arabica used as a source for carbon substrate. The effect of variation of wt.% of carbon doping was successfully evaluated for the preparation of quinoxalines by the condensation of benzil and 1,2-diamine under ultra-sonication in EtOH:water (3:1). The merits of the present investigation are extremely short reaction times, mild reaction conditions, excellent yield, simple workup and environmentally benign process.     

Analytical evaluation of six monovarietal virgin olive oils from Northern Tunisia

The characterization of virgin olive oils from six Tunisian cultivars, namely Chétoui, Ain Jarboua, Jarboui, Regregui, Rekhami and Neb Jmel, grown in Nebeur (a region of the Kef) was carried out. These cultivars dominate their natural habitats, but with the exception of the Chétoui cultivar they are only scattered throughout the nation. Several analytical parameters were evaluated; these include quality index, fatty acid composition, chlorophylls, carotenoids, sterols, α‐tocopherol and phenolic compounds. Their relationship with oxidative stability was also tested. The main phenols found were tyrosol, hydroxytyrosol, the dialdehydic form of elenolic acid linked to tyrosol and hydroxytyrosol, oleuropein aglycon and pinoresinol. These phenolic compounds, the colorimetric total phenol content and o‐diphenols showed significant correlations with oxidative stability. Furthermore, most of the analytical parameters of the oils that were determined in this study were greatly influenced by genetic factors (cultivar).     

Long-term creep of polyphenylene sulfide (PPS) subjected to complex thermal histories: The effects of nonisothermal physical aging

The long-term viscoelastic behavior of polymeric materials used below the glass transition temperature (T_g) is greatly affected by physical aging. In contrast to isothermal physical aging, long-term response under nonisothermal history has received far less attention. This paper reports experimental results and analytical methods of long-term creep behavior of polyphenylene sulfide (PPS) subjected to complex thermal histories in a temperature range below T_g. To characterize the effects of aging, creep tests were performed using a dynamic mechanical analyzer (DMA). Besides the long-term data, short-term creep tests in identical thermal conditions were also analyzed; these were utilized with effective time theory to predict long-term response under both isothermal and nonisothermal temperature histories. The long-term compliance after a series of temperature changes was predicted by the effective time theory using the KAHR-a_te model to obtain nonisothermal physical aging shift factors. Comparison of theoretical predictions with experimental data shows good agreement for various thermal histories.     

Artificial and natural weathering of ABS

Acrylonitrile‐butadiene‐styrene (ABS) is a complex copolymer with exceptional importance in technological applications. However, ABS is known to present a high susceptibility to weathering when exposed to UV radiation in the presence of oxygen. In this work, photodegradation of ABS was studied under natural and accelerated conditions. Exposed samples were removed periodically and characterized by several analytical techniques. During both types of weathering chemical modifications occurs mainly at the surface, which affects considerable the optical, mechanical, and rheological properties. The results obtained evidence that during accelerated weathering the formation rate of photodegradation products is higher when compared to natural weathering results. However, chain scission occurs mainly along natural conditions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Comparison of Sampling Methods for Carbonaceous Aerosols in Ambient Air

Measurement methods for fine particle carbon were compared under field sampling conditions. Sampling methods included filtration, impaction, and adsorption-corrected filtration. Systems were operated side-by-side for nine consecutive days in the Los Angeles Basin. Analytical methods were compared separately. For organic carbon and total carbon, ambient measurements showed greater variability than could be accounted for by differences in analytical methods, and these differences are attributed to sampling methodology. The highest reported concentrations were obtained by quartz filter sampling; the lowest were from the sum of the impactor stages (excluding the quartz afterfilters). Positive artifact from the adsorption of gaseous vapors on quartz fiber filters was significant. However, correction for vapor adsorption by subtraction of the carbon value on the second of two filters in series did not completely eliminate the dependence of the apparent total aerosol carbon concentration on filter face velocity or sample duration     

New Bioactive Oxylipins Formed by Non-Enzymatic Free-Radical-Catalyzed Pathways: the Phytoprostanes

In animals and plants, fatty acids with at least three double bonds can be oxidized to prostaglandin-like compounds via enzymatic and non-enzymatic pathways. The most common fatty acid precursor in mammals is arachidonic acid (C20:4) (AA) which can be converted through the cyclooxygenase pathway to a series of prostaglandins (PG). Non-enzymatic cyclization of arachidonate yields a series of isoprostanes (IsoP) which comprises all PG (minor compounds) as well as PG isomers that cannot be formed enzymatically. In contrast, in plants, α-linolenic acid (C18:3) (ALA) is the most common substrate for the allene oxide synthase pathway leading to the jasmonate (JA) family of lipid mediators. Non-enzymatic oxidation of linolenate leads to a series of C18-IsoPs termed dinor IsoP or phytoprostanes (PP). PP structurally resemble JA but cannot be formed enzymatically. We will give an overview of the biological activity of the different classes of PP and also discuss their analytical applications and the strategies developed so far for the total synthesis of PP, depending on the synthetic approaches according to the targets and which key steps serve to access the natural products.     

Directly silica bonded analytical reagents: synthesis of 2-mercaptobenzothiazole–silica gel and its application as a new sorbent for preconcentration and determination of silver ion using solid-phase extraction method

A new and efficient method is described for the easy synthesis of directly bonded 2-mercaptobenzothiazole–silica gel. This new bonded analytical reagent is used as an effective sorbent for the solid-phase extraction of silver ion from aqueous solutions. Conditions for effective adsorption of trace levels of silver ion concentration are optimized with respect to different experimental parameters in column process. Sodium thiosulfate solution could efficiently elute the adsorbed silver ion from the surface of the sorbent which then was determined by atomic absorption spectroscopy (AAS). Common coexisting ions did not interfere with the separation and determination. The preconcentration factor is 300 (1 ml elution volume) for a 300 ml sample volume. The sorbent exhibited excellent stability and its sorption capacity under optimum conditions has been found to be 343 μg of silver per gram of sorbent. The relative standard deviation under optimum conditions is 2.04% (n=7). Accuracy of the method was estimated by using test samples of natural water spiked with different amounts of silver ion. The method is simple and inexpensive.     

HEAT TRANSFER TO NON-NEWTONIAN LIQUIDS FLOWING THROUGH HORIZONTAL TUBES

Experimental and analytical investigation of heat transfer to single phase flow of pseudoplastic fluids under constant heat flux condition was carried out. Experimental data for laminar flow heat transfer in the thermally developing region over a wide range of rheological properties ( n from 0.54 to 0.84 and K from 0.07 to 2.41 Nsⁿ/m²) in 0.028 and 0.057 m diameter pipes were collected. Enhancement in heat transfer rate due to natural convection and temperature dependent rheotogy was observed. The temperature dependent viscosity effect is a function of flow behavior index and it contributes more towards heat transfer enhancement than natural convection does. A correlation (confidence level ±15%) for the entire set of data is also presented.     

Process effects on activated carbon performance and analytical methods used for low level mercury removal in natural gas applications

Type HGR^® activated carbon is frequently employed to protect aluminum heat exchangers in liquefying natural gas. Residual mercury levels in the treated gas are frequently at or near the limits of detection, challenging the analytical methods employed. Additionally, process variables and variations in the testing environment can affect the analytical procedures used to measure low levels of mercury. This paper will describe the analytical procedures used to routinely measure mercury levels to below 0.01 μg/Nm³ under challenging process and field conditions. The impact of process variables on adsorbent performance will also be described.     

NATURAL CONVECTION OF A BINARY MIXTURE IN A VERTICAL CLOSED ANNULUS

This article reports an analytical and numerical study of natural convection of a binary mixture within a vertical closed annulus. Neumann boundary conditions for temperature are applied to the vertical walls of the enclosure, while the short walls are insulated. The solutal buoyancy forces are assumed to be induced either by the imposition of constant fluxes of mass on the vertical walls (double-diffusive convection, a = 0) or by temperature gradients (Soret effect, a = 1). The governing parameters for the problem are the thermal Rayleigh number R_T, Prandtl number Pr, Lewis number Le, buoyancy ratio ?, aspect ratio A, constant a, and curvature parameter η. An analytical solution, based on the assumption of parallel flow over a large portion of enclosure, is derived. Numerical confirmation of the analytical results is also presented.     

MASS-TRANSFER FLOW IN A PARALLEL-PLATE CHANNEL WITH PERMEABLE BARRIERS INSERTED FOR COUNTERCURRENT MULTI-PASS OPERATIONS

The mass-transfer flow of a multi-pass counterflow laminar mass exchanger by inserting three permeable barriers with external refluxes was investigated theoretically, and the mathematical formulation was developed as well. With the use of an orthogonal expansion technique and the eigenfunction expanding in power series, the analytical solutions were obtained for finding the outlet concentration and mass transfer efficiency. The influences of the design parameters, the channel thickness ratio (β) and barrier characteristics (γ), and the operating parameters, the mass-transfer Graetz number (Gz _m ) and recycle ratio (R), are examined. Theoretical predictions of the new multi-pass operations are compared with those in the single- (without the permeable barrier inserted) and double-pass operations under the same working dimensions and represented graphically. The results show that the influences of the recycle ratio and channel thickness ratio in the present device with external refluxes are dominant in low and high mass-transfer Graetz number regions, respectively. Therefore, an optimal economic feasibility of multi-pass mass exchangers was found when the recycle ratio and channel thickness ratio are suitably selected under the operating conditions of interest.     

ICP-AES分析低合金钢中的Mn、Mo、V、Ni、Al、Cu、Cr元素

用等离子发射光谱法测定低合金钢中的Mn、Mo、V、Ni、Al、Cu、Cr元素,试样用HNO3和HCl在加热条件下分解,经过系列试验,选择仪器的工作条件,进行测定,建立了一套分析方法,经对照分析,分析结果令人满意。本方法快速准确,精密度良好,完全可以满足生产需要。     

ZCP—AES分析低合金钢中的Mn、Mo、V、Ni、Al、Cu、Cr元素

用等离子发射光谱法测定低合金钢中的Mn、Mo、V、Ni、Al、Cu、Cr元素，试样用HNO，和HCl在加热条件下分解，经过系列试验，选择仪器的工作条件，进行测定，建立了一套分析方法，经对照分析，分析结果令人满意。本方法快速准确，精密度良好，完全可以满足生产需要。     

Effect of functionalized multiwalled carbon nanotubes on weather degradation and corrosion of waterborne polyurethane coatings

A series of waterborne polyurethane/functionalized multiwalled carbon nanotube (WBPU/f-MWCNT) nanocomposite dispersions was prepared using three defined concentrations of 0.5, 1.0 and 2.0 wt% carboxyl functionalized multiwalled carbon nanotubes (f-MWCNTs). All dispersions were coated on mild steel and exposed under natural weather condition for a maximum of 365 days. Both exposed and unexposed coatings were characterized by potentiodynamic polarization (PDP) and X-ray photoelectron spectroscopy (XPS) analyses. The pristine WBPU coating showed slight degradation and corrosion protection. Inclusion of a higher content of f-MWCNTs significantly improved both the degradation and corrosion protection efficiencies of the coatings. Maximal degradation and corrosion protection was observed when 2.0 wt% f-MWCNT was mixed with WBPU for all of the coatings.     

Effects of jackfruit waste flour on the properties of poly(vinyl alcohol) film

A series of biodegradable polymer films based on poly(vinyl alcohol) (PVOH) and jackfruit waste flour (JWF) was prepared in the presence of water and glycerol and cast by a solution casting method. The JWF was introduced as a promoter of biodegradability. The blended films were evaluated for their tensile properties, water absorption, water vapor transmission rate (WVTR), and degradation behavior under different environmental conditions such as natural weathering and natural soil. The tensile strength (1.7–6.4 MPa) and elongation at break (13–108%) of the PVOH/JWF films were lower than those of unfilled PVOH film (26MPa and 238%). However, the Young's modulus values (157–196 MPa) of the PVOH/JWF films were higher than that of unfilled PVOH film (137 MPa). The PVOH/JWF blended films showed higher water absorption and WVTR, which increased with increasing JWF content. Biodegradability tests revealed that the presence of JWF stimulated the degradation rate and caused the weight loss and reduction in tensile properties of the PVOH/JWF blended films. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

ICP—AES法测定巴氏合金中杂质

用等离子发射光谱法测定巴氏合金中杂质元素,试样用硫酸和硫酸氢钾在高温下分解,经过系列试验,选择仪器的工作条件,进行测定,建立了一套分析方法,经标钢分析,分析结果令人满意。本方法快速准确,精密度良好,完全可以满足生产需要。