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Fundamental Study (fundamental + study)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Internal Noise Coherent Resonance for Mesoscopic Chemical Oscillations: A Fundamental Study

CHEMPHYSCHEM, Issue 7 2006
Zhonghuai Hou
Abstract The effect of internal noise for a mesoscopic chemical oscillator is studied analytically in a parameter region outside, but close to, the supercritical Hopf bifurcation. By normal form calculation and a stochastic averaging procedure, we obtain stochastic differential equations for the oscillation amplitude r and phase , that is solvable. Noise-induced oscillation and internal noise coherent resonance, which has been observed in many numerical experiments, are reproduced well by the theory. [source]

Fundamental study on biomass-fuelled ceramic fuel cell

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 1 2002
B. Zhu
Abstract Recent development in the advanced intermediate temperature (400 to 700°C) ceramic fuel cell (CFC) research brings up feasibility and new opportunity to develop innovative biomass-fuelled CFC technology. This work focuses on fundamentals of the biomass-fuelled CFCs based on available biofuel resources through thermochemical conversion technologies. Both real producer gas from biomass gasification and imitative compounded gas were used as the fuel to operate the CFCs in the biomass CFC testing station. The composition of the fuel gas was varied in a wide range of practices of the present conversion technology both in KTH and Shandong Institute of Technology (SDIT). CFC performances were achieved between 100 and 700 mW cm,2 at 600,800°C corresponding to various gas compositions. A high performance close to 400 mW cm,2 was obtained at 600°C for the gas with the composition of H2 (50 per cent)+CO (15 per cent)+CO2 (15 per cent)+N2 (20 per cent) and more than 600 mW cm,2 for the H2 (55 per cent)+CO (28 per cent)+CO2 (17 per cent) at 700°C. This paper presents the experimental results and discusses the fundamentals and future potentiality on the biomass fuelled CFCs. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Photocrosslinkable Polythiophenes for Efficient, Thermally Stable, Organic Photovoltaics

ADVANCED FUNCTIONAL MATERIALS, Issue 14 2009
Bumjoon J. Kim
Abstract Photocrosslinkable bromine-functionalized poly(3-hexylthiophene) (P3HT-Br) copolymers designed for application in solution-processed organic photovoltaics are prepared by copolymerization of 2-bromo-3-(6-bromohexyl) thiophene and 2-bromo-3-hexylthiophene. The monomer ratio is carefully controlled to achieve a UV photocrosslinkable layer while retaining the ,,, stacking feature of the conjugated polymers. The new materials are used as electron donors in both bulk heterojunction (BHJ) and bilayer type photovoltaic devices. Unlike devices prepared from either P3HT:PCBM blend or P3HT-Br:PCBM blend without UV treatment, photocrosslinked P3HT-Br:PCBM devices are stable even when annealed for two days at the elevated temperature of 150,°C as the nanophase separated morphology of the bulk heterojunction is stabilized as confirmed by optical microscopy and grazing incidence wide angle X-ray scattering (GIWAXS). When applied to solution-processed bilayer devices, the photocrosslinkable materials show high power conversion efficiencies (,2%) and excellent thermal stability (3 days at 150,°C). Such performance, one of the highest obtained for a bilayer device fabricated by solution processing, is achieved as crosslinking does not disturb the ,,, stacking of the polymer as confirmed by GIWAXS measurements. These novel photocrosslinkable materials provide ready access to efficient bilayer devices thus enabling the fundamental study of photophysical characteristics, charge generation, and transport across a well-defined interface. [source]

Existence of a critical carbon number in the aging of a wax-oil gel

AICHE JOURNAL, Issue 9 2001
Probjot Singh
A fundamental study was carried out to understand the aging (or hardening) of the wax-oil gels formed in the subsea pipelines during the flow of crude oil from offshore wells to shore. The aging process is a counterdiffusion phenomenon where there exists a critical carbon number (CCN), and wax molecules with carbon numbers greater than the CCN diffuse into the gel matrices and vice versa. Using a careful analysis of carbon number distributions of gel deposits, collected from a cold finger after various deposition time intervals, the CCN for the wax-oil system was obtained. A mathematical model, based on a modified version of UNIQUAC model, was developed to predict the CCN for wax-oil systems. The size of the interaction units for n-alkanes in the solid-phase UNIQUAC model was found to be a strong function of the mean carbon number in the solid phase. [source]

The effect of gravity on surface temperatures of plant leaves

PLANT CELL & ENVIRONMENT, Issue 4 2003
Y. KITAYA
ABSTRACT A fundamental study was conducted to develop a facility having an adequate air circulation system for growing healthy plants over a long-term under microgravity conditions in space. To clarify the effects of gravity on heat exchange between plant leaves and the ambient air, surface temperatures of sweet potato and barley leaves and replica leaves made of wet paper and copper were evaluated at gravity levels of 0.01, 1.0, 1.5 and 2.0 g for 20 s each during parabolic aeroplane flights. Thermal images were captured using infrared thermography at an air temperature of 26 °C, a relative humidity of 18% and an irradiance of 260 W m,2. Mean leaf temperatures increased by 0.9,1.0 °C with decreasing gravity levels from 1.0 to 0.01 g and decreased by 0.5 °C with increasing gravity levels from 1.0 to 2.0 g. The increase in leaf temperatures was at most 1.9 °C for sweet potato leaves over 20 s as gravity decreased from 1.0 to 0.01 g. The boundary layer conductance to sensible heat exchange decreased by 5% when the gravity decreased from 1.0 to 0.01 g at the air velocity of 0.2 m s,1. The decrease in the boundary layer conductance with decrease in the gravity levels was more significant in a lower air velocity. Heat exchange between leaves and the ambient air was more retarded at lower gravity levels because of less sensible and latent heat transfers with less heat convection. [source]

Effect of sodium chloride on the formation and stability of n-dodecane nanoemulsions by the PIT method

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010
Jeffery Chin Long Liew
Abstract This paper provides a fundamental study of the effect of sodium chloride on the formation and stability of n-dodecane/nonionic surfactant (Brij30)/NaCl nanoemulsions produced by the phase inversion temperature (PIT) method. Nanoemulsions are an emulsion system containing droplets from 20 to 200 nm and widely used in cosmetics and pharmaceutical industries. The PIT method was chosen due to its low energy and surfactant usage to produce the nanoemulsions by heating and quenching an emulsion system. The changes of conductivity with temperatures were continuously monitored to determine phase inversion, and are found to be the same in low surfactant concentrations. PIT point was found to decrease with NaCl concentration especially from 5 to 7 wt% Brij30. At the storage temperature (20 °C), the initial droplet size decreases with NaCl concentration; however, the decrement only occurs from 4 to 7 wt% Brij30 while no nanoemulsions can be produced at 8 wt%. By adding salt, the surfactant concentration needed for the most stable nanoemulsions is reduced to 6 wt% from 7 wt%. Therefore, similar stable nanoemulsions can be produced with less surfactant in a brine system. Furthermore, most of the ageing brine-continuous nanoemulsions could be reproduced to their freshly prepared state by heating process but not for the most stable nanoemulsions. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd. [source]