Children's conceptions of the gaseous state, prior to teaching

1986 ◽  
Vol 8 (4) ◽  
pp. 413-425 ◽  
Author(s):  
Marie‐Geneviève Séré
Keyword(s):  
Gaseous State ◽  
Children’S Conceptions

Children's Conceptions of Intelligence in France and Mexico

2012 ◽  
Author(s):  
Elisa Gruillen Gutierrez ◽  
Annamaria Lammel
Keyword(s):  
Children’S Conceptions

Young children’s conceptions of morality in a South African context

2021 ◽  
Vol 31 (1) ◽  
pp. 69-75
Author(s):  
Melanie Y. Martin ◽  
Nithi Muthukrishna ◽  
Gugulethu M. Hlatshwayo
Keyword(s):  
South African ◽  
South African Context ◽  
African Context ◽  
Children’S Conceptions

LPG Synthesis from Syngas over Cu/ZnO-Pd-β Catalysts Prepared by Ultrasonic Spray Pyrolysis

2015 ◽  
Vol 659 ◽  
pp. 252-256
Author(s):  
Sudarat Chaiwatyothin ◽  
Wittawat Ratanathavorn ◽  
Tharapong Vitidsant ◽  
Prasert Reubroycharoen
Keyword(s):  
Spray Pyrolysis ◽  
Fixed Bed ◽  
Ultrasonic Spray Pyrolysis ◽  
Product Distribution ◽  
Fixed Bed Reactor ◽  
Spherical Particles ◽  
Gaseous State ◽  
X Ray ◽  
Ultrasonic Spray ◽  
Co Conversion

Synthesis of nanoCu/ZnO catalyst for LPG production was prepared by ultrasonic spray pyrolysis (USP). Hollow spherical particles were obtained by USP technique using an aqueous solution of Cu (NO3)3.6H2O and Zn (NO3)3.3H2O with different concentration of 0.05, 0.1 and 0.5 molar under the pyrolysis temperatures of 600, 700 and 800°C. Mists of the solution were generated from the precursor solution by ultra sonic vibrators at frequency of ~1.7 MHz. The physicochemical properties of catalysts were characterized by X-ray diffraction, temperature-programmed reduction, scanning electron microscope, nitrogen adsorption-desorption, and energy dispersive X-ray spectrometer. The results showed that increasing in precursor concentration resulted in a large particle and particles size distributed in a range of 0.63-1.21 μm. Particles prepared at pyrolysis temperature 700°C exhibited homogeneous in size and shape compared to other temperature. The catalytic activity of nanoCu/ZnO-Pd-β catalysts was performed in a fixed-bed reactor for synthesizing LPG. The reaction took place at 260°C, 3.0 MPa, and the ratio of H2/CO = 2/1. All the products from the reactor were in gaseous state, and analyzed by on-line gas chromatography. The results showed that %CO conversion was high but decreased rapidly with increasing reaction time. Cu/ZnO catalyst prepared by co-precipitation gave higher %CO conversion than that prepared by ultrasonic spray pyrolysis. Moreover, hydrocarbon product distribution for Cu/ZnO catalyst produced at concentration 0.1 M 700°C by ultrasonic spray pyrolysis gave the highest LPG selectivity.

Nanocrystalline Mg-based hydrides for hydrogen storage

2001 ◽  
Vol 676 ◽  
Author(s):  
W. Oelerich ◽  
T. Klassen ◽  
R. Bormann
Keyword(s):  
Hydrogen Storage ◽  
Mobile Applications ◽  
Research Effort ◽  
Metal Hydrides ◽  
Clean Energy ◽  
High Energy ◽  
Sorption Kinetics ◽  
Desorption Kinetics ◽  
Gaseous State ◽  
Sorption Behaviour

ABSTRACTHydrogen is the ideal means of energy storage for transportation and conversion of energy in a comprehensive clean-energy concept. However, appropriate storage facilities, both for stationary and for mobile applications, are complicated, because of the very low boiling point of hydrogen (20.4 K at 1 atm) and its low density in the gaseous state (90 g/m3). Furthermore, the storage of hydrogen in liquid or gaseous form imposes safety problems, in particular for mobile applications, e.g. the future zero-emission vehicle. Metal hydrides are a safe alternative for H-storage and, in addition, have a high volumetric energy density that is about 60% higher than that of liquid hydrogen. Mg hydride has a high storage capacity by weight and is therefore favoured for automotive applications. However, so far light metal hydrides have not been considered competitive because of their rather sluggish sorption kinetics. Filling a tank could take several hours. Moreover, the hydrogen desorption temperature of about 300 °C is rather high for most applications. A breakthrough in hydrogen storage technology was achieved by preparing nanocrystalline hydrides using high-energy ball milling. These new materials show very fast aband desorption kinetics within few minutes, thus qualifying lightweight Mg-based hydrides for storage application. In this paper recent detailed results on the sorption behaviour of nanocrystalline Mg and Mg-based alloys are presented. In a following research effort the sorption kinetics of nanocrystalline Mg has been further enhanced by catalyst additions. Furthermore, different transition metals have been added to Mg to achieve a thermodynamic destabilisation of the hydride, thus lowering the desorption temperatures to about 230 °C. The newly developed materials are currently being tested in prototype storage tanks.

Epistemic modality in French children's discourse:to be sureornot to be sure?

1992 ◽  
Vol 19 (2) ◽  
pp. 389-413 ◽  
Author(s):  
Dominique Bassano ◽  
Maya Hickmann ◽  
Christian Champaud
Keyword(s):  
Epistemic Modality ◽  
Verbal Interactions ◽  
Epistemic Attitude ◽  
Developmental Progression ◽  
Subsequent Interview ◽  
Target Speaker ◽  
Children’S Conceptions

ABSTRACTThis study focuses on the development of epistemic modality, with particular attention to how French children evaluate the conditions of use for modal expressions marking certainty and uncertainty. Sixty children aged four, six and eight were shown films involving verbal interactions in which a target speaker accused another of having performed a deed. The analysis examine children's responses during a subsequent interview in which they were asked to attribute an epistemic attitude of certainty/uncertainty to the target speaker as a function of three factors: (a) whether he had witnessed the deed; (b) whether his accusation was modalized by the verbcroire(‘think/believe’); and (c) whether the accusation was true or false. The results show that the four-and six-year-olds attribute certainty more often than the eight-year-olds. This dissymmetry is accompanied by a developmental progression in children's conceptions of these modal categories, which change from a ‘realistic’ conception (mainly based on truth/falsity) at four years to an increasingly metalinguistic and relativized conception thereafter.

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