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1.
Charles A. White John F. Kennedy Anna Lombard Valeria Rossetti 《Polymer International》1985,17(4):327-329
The oligosaccharide component compositions of a series of non-reducing oligosaccharides extracted from the roots of Arnica montana L. has been determined by gel permeation chromatography (g.p.c.). The range of oligosaccharides present was found to extend beyond the octasaccharide previously reported. with 16% to 19% of the oligosaccharides having a degree of polymerisation of between 11 and 19 and almost 3% having a degree of polymerisation greater than 20. The chromatographic behaviour of this series of oligosaccharides is compared with that observed for series of D-gluco-oligosaccharides. 相似文献
2.
3.
This essay examines a politically engaged research genre, which follows the biography of the author who founded two journals: one on mathematical models published in English (Quality and Quantity) and one on politically committed social and economic research published in Italian (Inchiesta). The research considered focuses on Italy in the 1950s, the research by Lazarsfeld in Vienna in the 1920s and in the United States in the 1950s and 1960s, and post-1968 politically committed research in Italy. The analysis of such politically committed types of research (all very different from one another in terms of the interpretative model of reality, the methods used and the relations with the tendering party and the people observed) allows one to understand how this kind of research can be performed with very different methods—all of which do, however, seek to modify reality on the grounds of the research results. The metaphor of the crystal and the flame presented by Italo Calvino in order to classify facts and ideas and styles and feelings can also be used to visualise the polarity (and the difficulty/impossibility of contact) that has always been present in sociology between two different tendencies: towards a discipline that offers the most abstract and objective interpretative model of reality possible with the use of mathematical models (the crystal), and, instead, towards a discipline in which an interpretative model of reality is central, one that produces a social change and in which the qualitative and quantitative methods utilised are at the service of this change (the flame). This polarity thus allows us to separate first and foremost all the politically committed research performed by others for different purposes (market research, research to verify some theoretical hypotheses, etc.) but the same polarity also lies within the politically committed research. We can, indeed, identify a type of politically committed research in an area that has, at one extreme, research tending towards the utmost objectivity and scientific quality of the results and where the co-ordinators try to have all the information on the subjects maintaining the greatest possible distance (the subjects must not know they are being observed); at the other extreme, there is a type of research in which the coordinator completely involves the subjects in the gathering of information that will serve to realise a piece of research whose political aims are explicitly shared. For the identification of a sufficiently articulated typology it has been important to consider five dimensions of politically committed research: (a) the characteristics of the research coordinator (his/her belonging to the type and the academic/non-academic professional status) and his/her interpretative model of reality (b) some general characteristics of the research (the tender and funding, the topic choice, the aims, the contributions to the sociological theory, the duration); (c) the research coordinators relations with the political actors (the intensity of the relations, the political use of the research); (d) the relations of the research co-ordinator with the research subjects; (e) the methodological choices (the basic strategies, the methods used, the use of mathematical procedures). The research that exemplifies this typology is all politically committed to the left and was realised in different times and contexts. I start by considering a kind of politically engaged research (co-research) that appeared in Italy in the 1950s; I then analyse two types of politically engaged research realised in Austria at the end of the 1920s and one in the United States in the 1950s; there then follow two kinds of research realised in the 1960s and 1970s in the United States and a further two kinds realised in Italy in the 1970s and early 1980s. In order to have other kinds of research please refer to the two Journals of which I am the editor: one is an English language journal of mathematical models (Quality and Quantity, International Journal of Methodology, founded in 1966 and published today by Kluwer of Amsterdam), and a politically engaged review (Inchiesta, founded in 1971 and still published today by Dedalo of Bari). 相似文献
4.
Cathodic material La1.0Sr1.0FeO4+δ for an intermediate temperature solid oxide fuel cell (IT-SOFC) was prepared via the glycine-nitrate process and characterized
by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM). XRD results
showed that no reaction occurred between the La1.0Sr1.0FeO4+δ electrode and Sm0.2Ce0.8O1.9 (SDC) electrolyte at 1000 °C. SEM results showed that the electrode formed good contact with the SDC electrolyte after sintering
at 1000 °C for 2 h. The electrochemical properties of La1.0Sr1.0FeO4+δ were measured using electrochemical impedance spectroscopy (EIS) and steady state polarization measurement. At 700 °C, the
polarization resistance was about 3.90 Ωcm2, and the lowest polarization overpotential was 57 mV at a current density of 55 mA cm−2. 相似文献
5.
本文介绍了一个基于AT89S52的振动数据采集系统。该系统用单片机控制891型拾振器对结构振动信号进行采集,并将采集到的数据经过处理,通过串口发送到PC机。文中对系统的硬件组成结构予以详细介绍,并给出了软件流程。 相似文献
6.
7.
S. P. Tobin G. N. Pultz E. E. Krueger M. Kestigian K. K. Wong P. W. Norton 《Journal of Electronic Materials》1993,22(8):907-914
The field and temperature dependence of the Hall coefficient has been used to simultaneously extract information about the
p and n layers in very long wave length infrared P/n HgCdTe heterojunctions. The field dependence allows the effects of high
mobility electrons to be separated from those of low mobility holes. The higher the magnetic field, the higher the sensitivity
to the parameters of the P layer. For a maximum magnetic field of 8000 gauss, the hole sheet concentration must be at least
five times the electron sheet concentration to obtain accurate results for the P layer. This criterion is satisfied for typical
liquid phase epitaxy (LPE) heterostructures. The analysis determines the hole sheet resistance (concentration times mobility),
rather than the hole concentration or mobility separately. Independent knowledge of the P layer thickness and the relationship
between hole concentration and resistivity are needed to convert the Hall measurement results to hole concentrations. Analysis
of the field-dependent Hall data is complicated by the finding that at least three electrons of different mobilities are needed
to fit the field dependence of the Hall coefficient in n-type LPE HgCdTe layers. These results are consistent with previous
conclusions that electrons with different mobilities are needed to model bulk n-HgCdTe, and with a range of mobilities in
the graded composition interface between the LPE layer and CdTe substrate. Consistent results are obtained for the concentrations
and mobilities of the three types of electrons in the n-HgCdTe layer with and without the P layer present. N and P type carrier
concentrations are also consistent with dopant concentrations measured by secondary ion mass spectroscopy. 相似文献
8.
Wayne Wolf 《Journal of Electronic Testing》1997,11(3):211-225
Previous work in automata theory has shown how to eliminate sequential redundancy from networks of FSMs by finding sequences of inputs and outputs which are never communicated between components of the network. This paper shows that behavior automata—finite-state machines whose inputs and outputs are incompletely scheduled—exhibit similar properties. Using the behavior FSM (BFSM) as a model for scheduling, we show how to identify and eliminate both input and output scheduling dont-cares. When a scheduling dont-care is eliminated from a network of BFSMs, the register-transfer implementation is guaranteed not to suffer from the corresponding dont-care sequence. A definition of scheduling dont-cares improves our understanding of the foundations of high-level synthesis and the relationship between high-level and sequential optimization. In practice, scheduling dont-care elimination is a powerful tool for eliminating redundancy early in the design process. 相似文献
9.
10.
Janet E. Hails Stuart J.C. Irvine David J. Cole-Hamilton Jean Giess Michael R. Houlton Andrew Graham 《Journal of Electronic Materials》2008,37(9):1291-1302
Acceptor doping of many II–VI compound semiconductors has proved problematic and doping of epitaxial mercury cadmium telluride
(MCT, Hg1−x
Cd
x
Te) with arsenic is no exception. High-temperature (>400°C) anneals followed by a lower temperature mercury-rich vacancy-filling
anneal are frequently required to activate the dopant. The model frequently used to explain p-type doping with arsenic invokes an amphoteric nature of group V atoms in the II–VI lattice. This requires that group VI
substitution with arsenic only occurs under mercury-rich conditions either during growth or the subsequent annealing and involves
site switching of the As. However, there are inconsistencies in the amphoteric model and unexplained experimental observations,
including arsenic which is 100% active as grown by metalorganic vapor-phase epitaxy (MOVPE). A new model, based on hydrogen
passivation of the arsenic, is therefore proposed. 相似文献