The seated man (Homo Sedens) the seated work position. Theory and practice

Modern furniture in schools, factories and offices is constructed in such a way that no one can use it properly. Each day people sit for many hours hunched over their tables in postures extremely harmful to the back. No one should be surprised that more than half of the population today is complaining of backache. In no other field of human activity is a similar gap between theory and reality found. A closer study of 'normal' sitting postures will explain why nobody is able to sit in the 'ideal' position. First of all, the eye in this position is at a distance of 50-60 cm from the book or working material and the axis of vision is horizontal. In addition, this posture requires at least 90 degrees flexion of the hip joint, yet the normal human being can only bend 60 degrees . A considerably better sitting posture can be obtained if the table is tilted about 10 degrees . In this way the book is brought closer and at a better angle to the eye. The worst bending of the neck is thus avoided. Furthermore, the seat can, with advantage, be tilted 20 degrees forward to reduce the flexion of the lumbar region. By both these means the extra 30 degrees flexion, which is the most strenuous part of flexion, is avoided.     

Chemical characterisation of CTC black tea of northeast India: correlation of quality parameters with tea tasters' evaluation

BACKGROUND: Consumers have different regional perceptions of tea quality. Objective evaluation based on biochemical data for different regions has been needed for a long time. Biochemical factors regulating this variation would help to remove regional disparities. This study was undertaken on CTC (crust, tear and curl) black tea to generate the biochemical data responsible for quality along with tea tasters' evaluation of three geographical regions of northeast India and to determine the reason for the variation. RESULTS: Brahmaputra valley teas had highest theaflavin (TF), thearubigin (TR), brightness (BR) and total colour (TC) and low crude fibre content (CFC) and total polyphenol (TPP). Brahmaputra valley and Dooars region teas showed high total soluble solid (TSS). Barak valley teas had highest CFC and low TSS, caffeine (CA), TF, TR and TC. Dooars region teas had high CA and TPP and low BR. Dooars region and Barak valley teas contained higher levels of residual catechin than Brahmaputra valley teas. CONCLUSION: Overall quality as evaluated by tea tasters was found to be highest for Brahmaputra valley teas followed by Dooars region and Barak valley teas. This high evaluation can be attributed to higher levels of TF, TR, BR and TSS. Barak valley and Dooars region teas contained high residual catechin, indicating limitation in oxidation during processing. Copyright © 2009 Society of Chemical Industry     

Dynamic Effect of Soil-Tunnel Interface Under Dynamic Loading

Soil Mechanics and Foundation Engineering - The resilience of the Daikai subway station during the Kobe earthquake is taken as a case study of tunnel endurance at various points under different...     

Interpenetrating polymer networks of photocrosslinkable cellulose derivatives

A series of interpenetrating polymer networks has been prepared from two cellulose derivatives, one of which contains cinnamate groups and the other containing randomly substituted cinnamate and allyl groups. The latter derivative forms a crosslinked network in less than 5 min on exposure to ultraviolet radiation and can be used to make amorphous interpenetrating polymer networks containing 50% by weight loading level of crosslinked vinyl polymers. The syntheses of both derivatives and the thermal properties and film morphologies of their interpenetrating polymer networks are discussed. © 1996 John Wiley & Sons, Inc.     

Electron microscopy of shock deformation in alumina

Shock recovered samples of a coarse grain (10 μm), high density (>99.9% theoretical) alumina from asymmetric impact tests conducted at 6.5 GPa (e.g. 3.2 times its Hugoniot Elastic Limit) in a single stage gas gun and characterized by X-ray diffractometry, scanning and field emission scanning electron microscopy, and transmission electron microscopy showed prolific presence of reduced crystallite size, higher average microstrain, grain localized micro/nano-scale deformations, micro-cleavages, grain-boundary microcracks, micro-wing crack formation, extensive shear induced deformations and fractures localized at grains, grain boundaries and triple grain junctions, grain localized entanglement of dislocations and their pile up impeded at grain boundaries. A new qualitative model based on micro-shear and micro-twist induced deformation and fracture in single and/or multiple planes in suitably oriented grain and/or grain assembly was developed to explain the experimentally observed damage evolution process.     

Role of choline formate ionic liquid in the polymerization of vinyl and methacrylic monomers

Polymerizations of vinyl and methacrylate monomers (2‐hydroxyethyl methacrylate, styrene, and methyl methacrylate) were carried out in a choline formate ionic liquid at room temperature without the addition of peroxide‐based initiators. Choline formate acted as both an initiator and a solvent and produced high‐molecular‐weight polymers. Gel permeation chromatography and electron paramagnetic resonance measurements indicated that the polymerizations predominantly occurred by a free‐radical mechanism. This method of polymerization provides an alternate route to eliminate the use of toxic initiators and solvents. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Studies on the engineering properties of LCP‐Vectra B 950/PP blends with the variations of EAA content

Polypropylene (PP) was melt blended with Vectra B‐950 [a thermotropic liquid crystalline polymer (LCP)], in a single screw extruder in presence of different doses of ethylene acrylic acid (EAA) copolymer, as modifier. The effect of incorporation in different proportions of EAA at a fixed dose of 5% LCP, on mechanical, thermal, morphological, and rheological properties of such blends was studied and the same were compared with that of pure PP and amongst themselves. Mechanical analysis (tensile properties) of the prepared blends exhibited improvements in ultimate tensile strength (UTS), modulus, toughness, hardness, and impact strength of PP matrix with the incorporation of EAA. The improvement in mechanical properties is associated with the formation of LCP fibrils as evidenced by scanning electron microscopy (SEM). A strong interaction through H‐bonding between the segments of Vectra B‐950 and EAA was established by FTIR study. Differential scanning calorimetry (DSC) studies indicated substantial increase in melting point of the blends, and thermogravimetric analysis (TGA) showed that the thermal stability of PP was improved with the addition of LCP and EAA. Rheological properties showed that LCP and EAA drop down the melt viscosity of PP and thus facilitate processibility of blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A Three-Phase AC-to-DC Power Transistor Converter-Controlled DC Motor Drive

A three-phase ac-to-dc power transistor converter that is suitable for speed control of a dc motor and for a variable dc power supply is investigated. The availability of power transistors of fairly high power rating has made the task of ac-to-dc conversion relatively easy due to simplification of the converter circuit configuration. The external performance characteristics of the power transistor converter-controlled separately excited dc motor are obtained by employing the equal pulsewidth modulation (EPWM) control technique with 18 pulses per half-cycle of the supply voltage and are verified experimentally. There is good agreement between experimental and theoretical results. The external performance is also evaluated under constant torque operation. The use of inductance-capacitance (LC) filters for reducing the effect of predominant supply harmonics is briefly discussed. Experimental oscillograms of some typical waveforms are illustrated to verify the basic principles of operation.     

Sequential mixing as effective method in the reduction of percolation threshold of multiwall carbon nanotube in poly(methyl methacrylate)/high‐density poly(ethylene)/MWCNT nanocomposites

This work demonstrates sequential heating protocol to be an effective method in the reduction of percolation threshold of multiwall carbon nanotube (MWCNT) in (70/30 w/w) poly(methyl methacrylate) (PMMA)/high‐density poly(ethylene) (HDPE)/MWCNT nanocomposites. Here, the percolation threshold (P_c) value was reduced to 0.08 wt % of MWCNT, which is the lowest among the ever reported values of P_c for the PMMA system. Moreover, a co‐continuous morphology of the minor HDPE phase was evident throughout the major PMMA phase in a highly asymmetric composition (70/30 w/w) of the blend constituents. The AC conductivity as well as the dielectric permittivity values were increased with increase in loading of MWCNT in the nanocomposites. The detailed analysis of electrical and morphological properties is discussed in depth in the article. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40235.     

Green microalga Chlorella vulgaris as a potential feedstock for biodiesel

BACKGROUND: A major bottleneck in microalgal biodiesel production is lipid content, which is often low in microalgal species. The present study examines Chlorella vulgaris as a potential feedstock for biodiesel by identifying and evaluating the relationships between the critical variables that enhance the lipid yield, and characterizes the biodiesel produced for various properties. RESULTS: Factors affecting lipid accumulation in a green microalga, Chlorella vulgaris were examined. Multifactor optimization raised the lipid pool to 55% dry cell weight against 9% control. When C. vulgaris cells pre‐grown in glucose (0.7%)‐supplemented medium were transferred to the optimized condition at the second stage, the lipid yield was boosted to 1974 mg L^?1, a value almost 20‐fold higher than for the control. The transesterified C. vulgaris oil showed the presence of ～82% saturated fatty acids, with palmitate and stearate as major components, thus highlighting the oxidative stability of C. vulgaris biodiesel. The fuel properties (density, viscosity, acid value, iodine value, calorific value, cetane index, ash and water contents) are comparable with the international (ASTM and EN) and Indian (IS) biodiesel standards. CONCLUSION: C. vulgaris biomass with 55% lipid content and adequate fuel properties is potentially a renewable feedstock for biodiesel. Copyright © 2011 Society of Chemical Industry