Real‐time Raman spectroscopic measurement of crystallization kinetics and its effect on the morphology and properties of polyolefin blown films

The nonisothermal crystallization half‐time (t_0.5), defined as the time taken for a polymer film to reach half of its equilibrium crystallinity, was estimated from Raman spectroscopic measurements of crystallinity during blown film extrusion of a linear low‐density polyethylene (LLDPE) and an isotactic polypropylene (i‐PP). The crystalline a‐ and c‐axis orientation of LLDPE and i‐PP films, respectively, increased with decreasing crystallization half‐time. The transverse direction tensile modulus and tear strengths for LLDPE films also increased with decreasing half‐time. However, for i‐PP films, only the transverse direction tear strength increased with decreasing t_0.5, while the machine direction properties did not show a significant dependence on half‐time. Our real‐time Raman spectroscopy studies provide experimental evidence to theories proposed in the literature 1 - 3 with regards to the influence of the nonisothermal crystallization process (along the film axis) on the imparted final film structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1740–1747, 2005     

The aggregation behavior and structure of blends of κ-carrageenan and ε-polylysine hydrochloride

Polypeptides play a key role in improving food quality, and understanding their interactions with polysaccharides would be beneficial to developing new foods. Herein, κ-carrageenan (KC) and ε-polylysine hydrochloride (PLH) were chosen as the model polysaccharide and polypeptide, respectively, to study polysaccharide/polypeptide complexes. The KC/PLH solutions were characterized for turbidity as a function of mass ratio, pH, salts and stirred conditions at 0.5 and 1 mg mL^–1 concentrations. The solutions at a KC/PLH mass ratio of 7:3 have the highest turbidity, and the turbidity is stable in acidic conditions, decreases with increase in pH in alkaline conditions and salt concentration, and increases with increase of stirred time and temperature. The Fourier transform infrared spectra suggest that the amide I band of PLH disappears along with a change in the amide II band upon complexing with KC. These changes further influence the microstructure and reveal a rough, non-uniform and large irregular cavity network structure. Indeed, these observations are intimately associated with the dynamic interactions persistent at the molecular level between the KC and PLH. © 2021 Society of Industrial Chemistry.     

Thermal and catalytic upgrading of a biomass‐derived oil in a dual reaction system

The thermal and catalytic upgrsding of bio‐oil to liquid fuels was studied at atmospheric pressure in a dual reactor system over HZSM‐5, silica‐alumina and a mixed catalyst containing HZSM‐5 and silica‐alumina. This bio‐oil was produced by the rapid thermal processing of the maple wood. In this work, the intent was to improve the catalyst life. Therefore, the first reactor containing no catalyst facilitated thermal cracking of blo‐oil whereas the second reactor containing the desired catalyst upgraded the thermally cracked products. The effects of process variables such as reaction temperature (350°C to 410°C), space velocity (1.8 to 7.2 h^?1) and catalyst type on the amounts and quality of organic liquid product (OLP) were investigated, In the case of HZSM‐5 catalyst, the yield of OLP was maximum at 27.2 wt% whereas the selectivity for aromatic hydrocarbons was maximum at 83 wt%. The selectivities towards aromatics and aliphatic hydrocarbons were highest for mixed and silica‐alumina catalysts, respectively. In all catalyst cases, maximum OLP was produced at an optimum reaction temperature of 370°C in both reactors, and at higher space velocity. The gaseous product consisted of CO and CO₂, and C₁‐C₆ hydrocarbons, which amounted to about 20 to 30 wt% of bio‐oil. The catalysts were deactivated due to coking and were regenerated to achieve their original activity.     

Mast Cells and Basophils in the Defense against Ectoparasites: Efficient Degradation of Parasite Anticoagulants by the Connective Tissue Mast Cell Chymases

Ticks, lice, flees, mosquitos, leeches and vampire bats need to prevent the host’s blood coagulation during their feeding process. This is primarily achieved by injecting potent anticoagulant proteins. Basophils frequently accumulate at the site of tick feeding. However, this occurs only after the second encounter with the parasite involving an adaptive immune response and IgE. To study the potential role of basophils and mast cells in the defense against ticks and other ectoparasites, we produced anticoagulant proteins from three blood-feeding animals; tick, mosquito, and leech. We tested these anticoagulant proteins for their sensitivity to inactivation by a panel of hematopoietic serine proteases. The majority of the connective tissue mast cell proteases tested, originating from humans, dogs, rats, hamsters, and opossums, efficiently cleaved these anticoagulant proteins. Interestingly, the mucosal mast cell proteases that contain closely similar cleavage specificity, had little effect on these anticoagulant proteins. Ticks have been shown to produce serpins, serine protease inhibitors, upon a blood meal that efficiently inhibit the human mast cell chymase and cathepsin G, indicating that ticks have developed a strategy to inactivate these proteases. We show here that one of these tick serpins (IRS-2) shows broad activity against the majority of the mast cell chymotryptic enzymes and the neutrophil proteases from human to opossum. However, it had no effect on the mast cell tryptases or the basophil specific protease mMCP-8. The production of anticoagulants, proteases and anti-proteases by the parasite and the host presents a fascinating example of an arms race between the blood-feeding animals and the mammalian immune system with an apparent and potent role of the connective tissue mast cell chymases in the host defense.     

DSP based inverter control for alternate energy systems

This paper presents a DSP based algorithm to control inverters used in interfacing alternate energy systems with the electric utility. Since a constant and ripple free dc bus voltage is not ensured at the output of alternate energy sources, the main aim of the proposed algorithm is to make the output of the inverter immune to the fluctuations in the dc input voltage. In this paper a modified space vector pulse width modulation (SVPWM) technique is proposed which will maintain the quality of the ac output of the inverter, regardless of the ripple present at the inverter input. The principle is explained qualitatively and extensive experiments have been carried out to verify and validate the proposed algorithm. A 16-bit fixed-point C2000 family DSP from Texas Instruments was used as the controller to implement the proposed control algorithm.     

THERMAL STABILITY ANALYSIS OF THE LIQUID PHASE METHANOL SYNTHESIS REACTOR

ABSTRACT

The effect of addition of an inert liquid phase on the rate of heat generation in the catalytic synthesis of methanol from syngas has been studied. Gas compositions typical of product gases from Lurgi and Koppers-Totzek gasifiers, represented by H₂-rich and CO-rich syngas respectively, were used to experimentally verify the “slope” and “dynamic” critria in a three-phase fixed bed recycle reactor. The liquid medium, witco-40 oil, has been effective in controlling the rate of heat generation and in preventing catalyst overheating, signifying that the liquid phase synthesis is thermally far more stable than the vapor phase synthesis. The experimental thermal stability study provides crucial and valuable information in commercializing the liquid phase methanol synthesis process. The current approach of thermal stability analysis does not require any a priori assumption or predetermined reaction kinetics.     

Optimum stand density of Leucaena leucocephala for wood production in Andhra Pradesh, Southern India

Leucaena leucocephala is widely used as raw material for the manufacture of paper and packaging material and in biomass based power plants in the state of Andhra Pradesh, Southern India. Experiments were conducted to study the affect of tree density on the growth, biomass partitioning and wood productivity. Six treatments 1 × 1 m, 1.3 × 1.3 m, 3 × 0.75 m, 3 × 1 m, 5 × 0.8 m and 3 × 2 m corresponding to a tree density of 10,000, 6666, 4444, 3333, 2500 and 1666 were evaluated with leucaena variety K636. At 51 months after planting, spacings significantly influenced tree height, diameter at breast height (DBH), number of branches and biomass partitioning. Wider tree rows resulted in greater tree height and diameter growth resulting in higher per plant productivity. At harvest, 70% of trees in 3 × 2 m attained a diameter of more than 7.5 cm, while 35% of the trees attained the same DBH in 1 × 1 m spacing. Increased spacing levels decreased the relative amount of growth allocated to the bole of the tree. Marketable biomass yield was highest with 1 × 1 m spacing. Spacing of 3 × 0.75 m produced marketable biomass comparable to that of 1 × 1 m and greater proportion of stems with more than 5 cm diameter. Leucaena can be grown at 3 × 0.75 m spacing either for pulpwood or fuelwood depending on the prevailing market prices and demand.     

The Effect of Simultaneously Developing Flow on Heat Transfer in Rectangular Tubes

A study of heat transfer in simultaneously developing flow through rectangular tubes is presented in this article. Heat transfer coefficients were measured for three different tube sizes and shapes (D h = 2.21 mm, f = 0.050; D h = 3.02 mm, f = 0.108; and D h = 1.74 mm, f = 0.029), which correspond to typical dimensions used in automotive heat exchangers. For each of these tubes, several different tube lengths were tested to measure the effect of developing flow on the Nusselt number. The results demonstrate that developing flow enhances Nusselt numbers, especially for short tubes. For the geometry range studied, the effect of aspect ratio was not very significant. Heat transfer correlations that accounted for the effects of Reynolds number (118 < Re < 10,671) Prandtl number (6.48 < Pr < 16.20), and bulk-to-wall property variations (0.243 < w b / w w < 0.630), and geometric features such as tube length, hydraulic diameter, and aspect ratio, were developed from the data.     

Prioritizing Groundwater Monitoring in Data Sparse Regions using Atanassov Intuitionistic Fuzzy Sets (A-IFS)

Water quality index (WQI) is a single measure that is commonly used to prioritize water wells and manage groundwater resources. WQI is pragmatic as it combines several water quality parameters into a single index. However, the process of aggregation is imprecise and suffers from uncertainties in measurements and subjective specification of weights. The goal of this study is to demonstrate how Atanassov’s Intuitionistic Fuzzy Sets (A-IFS) can be used to aggregate water quality parameters into a composite index to rank and prioritize groundwater wells. The A-IFS weighted geometric mean (A-IFS-WGM) method and the A-IFS based Technique for Order of Preference by Similarity to Ideal Solution (A-IFS-TOPSIS) using Euclidean (A-IFS-TOPSIS-E) and Hamming (A-IFS-TOPSIS-H) are introduced and illustrated to prioritize and rank water supply wells in a fast growing yet poorly studied area in Guntur, Andhra Pradesh, India. The concept of A-IFS entropy is also presented to directly ascertain weights from the data. This objective selection of weights from the data eliminates the subjectivity and difficulties associated with assigning relative importance to different water quality parameters. The results of the study indicate that the weights obtained using the entropy methods are consistent with the geochemical characteristics of the regional aquifer. The A-IFS-WGM method is more sensitive to weights compared to the A-IFS-TOPSIS methods which are influenced to a larger extent by the membership and non-membership values (ratings). Special consideration must be placed on ascribing the hesitation margin of the decision maker and identifying the membership values for non-preference as the methods exhibit greater sensitivity to these factors. The developed methods provide pragmatic data-driven approaches to prioritize and rank groundwater wells within a monitoring network.     

Condensation on a spray of water drops: A cell model study-I. Flow description

A unit cylinder cell model with a body-fitted coordinate system is employed to analyze the hydrodynamics and heat transfer associated with steam condensation on a spray of equal sized water droplets. The droplets are assumed to be moving in the intermediate Reynolds number regime, Re_g = O(100). The distance between neighboring droplet centers is allowed to be arbitrary in the plane of motion, but the droplets are assumed to be uniformly spaced in the plane perpendicular to the direction of motion. Furthermore, once a particular configuration of the droplets is set, the subsequent spacings between the droplet centers in that configuration are taken to remain constant during the entire condensation process. The formulation entails a simultaneous numerical solution of the quasi-steady elliptic partial differential equations that describe the flow field in both the dispersed and continuous phases in each cell. In part 1 of this study, the results for the velocity, surface pressure and drag are presented. In part II of this study, the results for the condensation induced velocities, surface shear stress, the Nusselt number and the Sherwood number are provided. In both parts of the study, the interactions between neighboring drops have been examined.