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21.
Low-energy structures of a hybrid system consisting of a polymer and an attractive nanowire substrate as well as the thermodynamics of the adsorption transition are studied by means of Monte Carlo computer simulations. Depending on structural and energetic properties of the substrate, we find different adsorbed polymer conformations, amongst which are spherical droplets attached to the wire and monolayer tubes surrounding it. We identify adsorption temperatures and the type of the transition between adsorbed and desorbed structures depending on the substrate attraction strength. 相似文献
22.
The use of information technology to enhance teaching and learning processes has been practiced for a number of years now.
However, the rapid growth in the use of the Internet has led to a new dimension in interactive and collaborative learning
anytime and anyplace dynamically. With the explosion of “virtual education initiatives”, the question of the feasibility and
success criteria for such projects quickly arises. To address the question in an organized way, we propose a project assessment
based on critical success factors. Hence, in this article, we draw on a widely recognized critical success factor framework.
We (slightly) adjust the framework to fit the special characteristics of virtual education initiatives, and apply to one case
study, namely the virtual education initiative at the Faculty of Business at the City University of Hong Kong. The results
suggest that the past success of the case is due to the adherence to the large majority of critical success factors. However,
it also outlines some areas of concern. The paper concludes with a discussion on the strength and limitations of virtual learning
environment as well as future directions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
23.
The electrical conductivity in graphite measured normal to the crystallographic c-axis is observed to increase after intercalation with acid molecules which act as acceptors. This behaviour is regarded as the result of ionization of the acid molecule which, in turn, increases the positive current carriers in the host graphite. Since the carrier density depends on the degree of ionization of the acid, it follows that the stronger the acid the greater the increase in carrier concentration, and assuming no adverse mobility effects, the greater the electrical conductivity. The hydrogen fluoride-antimony pentafluoride system produces some of the strongest acid substances known. The experiments described here represent the initial examination of the electrical conductivity resulting from intercalation of this material into graphite. The experiments consisted of intercalating graphite powder with antimony pentafluoride in a copper tube and swaging the sheathed compound into wire. The measured conductivity of the graphite intercalation compound, when the copper conductivity is subtracted out and allowance is made for departure from ideal density, is about 1×106 –1 cm–1. This is approximately 40 times the conductivity of pristine graphite and more than one and a half times the conductivity of pure copper. 相似文献
24.
PTFE (¯M
n=5×106), when heated near the melting temperature (335 to 337 C) while in contact with carbon black, is characterized by an effective viscosity and a thermal stability which are orders of magnitude lower than those found in the absence of the contacting high surface area material. The penetration of the PTFE into the porous carbon black occurs by the spreading of a very thin polymer film followed by a thickening of this film with time at temperature until a limiting concentration is reached. The lower the average molecular weight of the PTFE, the more rapidly it penetrates into the porous material. Similar phenomena have been observed with high molecular weight PTFE heated near the melting temperature while contacting high surface area metal blacks or porous sintered metals. 相似文献
25.
Love John M.; Kisker Ellen Eliason; Ross Christine; Raikes Helen; Constantine Jill; Boller Kimberly; Brooks-Gunn Jeanne; Chazan-Cohen Rachel; Tarullo Louisa Banks; Brady-Smith Christy; Fuligni Allison Sidle; Schochet Peter Z.; Paulsell Diane; Vogel Cheri 《Canadian Metallurgical Quarterly》2005,41(6):885
Early Head Start, a federal program begun in 1995 for low-income pregnant women and families with infants and toddlers, was evaluated through a randomized trial of 3,001 families in 17 programs. Interviews with primary caregivers, child assessments, and observations of parent-child interactions were completed when children were 3 years old. Caregivers were diverse in race-ethnicity, language, and other characteristics. Regression-adjusted impact analyses showed that 3-year-old program children performed better than did control children in cognitive and language development, displayed higher emotional engagement of the parent and sustained attention with play objects, and were lower in aggressive behavior. Compared with controls, Early Head Start parents were more emotionally supportive, provided more language and learning stimulation, read to their children more, and spanked less. The strongest and most numerous impacts were for programs that offered a mix of home-visiting and center-based services and that fully implemented the performance standards early. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
26.
Local-lag and timewarp: providing consistency for replicated continuous applications 总被引:1,自引:0,他引:1
In this paper, we investigate how consistency can be established for replicated applications changing their state in reaction to user-initiated operations as well as the passing of time. Typical examples of these applications are networked computer games and distributed virtual environments. We give a formal definition of the terms consistency and correctness for this application class. Based on these definitions, it is shown that an important tradeoff relationship exists between the responsiveness of the application and the appearance of short-term inconsistencies. We propose to exploit the knowledge of this tradeoff by voluntarily decreasing the responsiveness of the application in order to eliminate short-term inconsistencies. This concept is called local-lag. Furthermore, a timewarp scheme is presented that complements local-lag by guaranteeing consistency and correctness for replicated continuous applications. The computational complexity of the timewarp algorithm is determined in theory and practice by examining a simple networked computer game. The timewarp scheme is then compared to the well-known dead-reckoning approach. It is shown that the choice between both schemes is application-dependent. 相似文献
27.
Pia Stari
Jure Mravlje Miran Mozeti
Rok Zaplotnik Barbara etina Bati
Ita Junkar Katarina Vogel Miku 《International journal of molecular sciences》2022,23(13)
Cold plasma (CP) technology is a technique used to change chemical and morphological characteristics of the surface of various materials. It is a newly emerging technology in agriculture used for seed treatment with the potential of improving seed germination and yield of crops. Wheat seeds were treated with glow (direct) or afterglow (indirect) low-pressure radio-frequency oxygen plasma. Chemical characteristics of the seed surface were evaluated by XPS and FTIR analysis, changes in the morphology of the seed pericarp were analysed by SEM and AFM, and physiological characteristics of the seedlings were determined by germination tests, growth studies, and the evaluation of α-amylase activity. Changes in seed wettability were also studied, mainly in correlation with functionalization of the seed surface and oxidation of lipid molecules. Only prolonged direct CP treatment resulted in altered morphology of the seed pericarp and increased its roughness. The degree of functionalization is more evident in direct compared to indirect CP treatment. CP treatment slowed the germination of seedlings, decreased the activity of α-amylase in seeds after imbibition, and affected the root system of seedlings. 相似文献
28.
Summary Earlier studies on solidification point curves for binary systems of the saturated fatty acids of even-number carbon atom
content have been extended to include the C16 to C24 group. The effect of homology in here beginning to become more obvious than it is in the lower brackets of this series of
compounds in that the three-segment curve which is there a characteristic feature is gradually approaching in form that of
the smooth, continuous type. This phenomenon has been interpreted in the light of a decreasing tendency toward compound-formation.
It has been postulated that one equi-molecular compound is formed between adjacent pairs of fatty acids of even-number carbon
atom content.
This study is being continued in the hope of bringing into the picture acids of higher carbon content than those already studied.
Systems containing the odd-number carbon atom members of this homologous series will also be investigated.
Assistance in the preparation of these materials was furnished by the personnel of Works Projects Administration Official
Project No. 65-1-53-2349. 相似文献
29.
30.
H. A. Schuette H. A. Vogel C. H. Wartinbee 《Journal of the American Oil Chemists' Society》1938,15(2):35-36
Herein reported are the initial results of an attempt to clarify conflicting statements on the nature and composition of alfalfa
seed oil. Its unsaturated acid fraction contains representatives of three common types, linolenic and linoleic acids, neither
of which, apparently, is present there in isomeric form, and oleic acid. The study is being continued. 相似文献