The social loafing paradigm was used to test the contribution of self-evaluation to goal-setting effects. If, as E. Locke and G. Latham (1990) argued, goals lead to improved performance because they serve as standards for self-evaluation, eliminating the opportunity for experimenter evaluation should not reduce performance. Results suggest that when the goal is seen as informative, the prospect of self-evaluation may contribute to goal-setting effects. However, the results also suggest that when goals are seen as too stringent or too lenient, it is concern over evaluation by an external source, not self, that motivates performance. Implications of these findings for E. Locke and G. Latham's (1990) theory of goal setting and general theories of self-evaluation are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
Regularities of sintering compacted SiO2 powder under the action of a CO2-laser are studied by experiment. Features are considered for rebuilding the structure of a powder body (particle regrouping, formation of interparticle contacts, joining of particles into conglomerates, evolution of the porous structure) in different stages of sintering (with different laser irradiation duration). Sintering is accomplished by a liquid-phase mechanism (by melting particles and joining solid unmelted cores by the liquid phase formed). The results obtained may be used for developing laser sintering methods for ceramic powders. 相似文献
In this article, the syntheses and attempts at synthesis for the preparation of gem-dinitrodiols and their derivatives are outlined. The three gem-dinitrodiols described are 2,2-dinitropropane-1,3-diol, 3,3-dinitropentane-1,5-diol, and 4,4-dinitroheptane-1,7-diol. The nitrooxy, azido, and azidoacetoxy derivatives of the latter were prepared and are compared to derivatives of the first, which were presented in a previous article. The tedious and expensive synthesis of pentanediol precluded its use as an intermediate. Only one compound both had excellent glass transition temperature and was thermally stable. This compound was 4,4-dinitro-1,7-diazidoheptane. 相似文献
Hybrid polymeric inlays, patterned by nanoimprint lithography, are used to rapidly mass replicate pillar‐like nanostructures by injection moulding. This is difficult to achieve with traditional nickel inlays due to the rapid heat transfer of the metal, which results in premature cooling of the molten polymer and improper filling of nanoscale features. Using hybrid inlays, nanopillars can reliably be stretched by up to 40% of their designed height by adjusting moulding parameters. Hybrid inlays display longevity of more than 2000 cycles and can rapidly be fabricated to firmly establish injection moulding as an exceptionally useful tool for the high volume prototyping and production of nanopatterned polymeric devices.
Selectivity estimation of a boolean query based on frequent itemsets can be solved by describing the problem by a linear program. However, the number of variables in the equations is exponential, rendering the approach tractable only for small-dimensional cases. One natural approach would be to project the data to the variables occurring in the query. This can, however, change the outcome of the linear program.We introduce the concept of safe sets: projecting the data to a safe set does not change the outcome of the linear program. We characterise safe sets using graph theoretic concepts and give an algorithm for finding minimal safe sets containing given attributes. We describe a heuristic algorithm for finding almost-safe sets given a size restriction, and show empirically that these sets outperform the trivial projection.We also show a connection between safe sets and Markov Random Fields and use it to furtherreduce the number of variables in the linear program, given some regularity assumptions on the frequent itemsets. 相似文献
Summary High cadmium and nickel contents in sunflower kernels intended for human consumption are reported.The cadmium contents of 55 samples from North America and Europe were 0.25-0.69 mg/kg with averages from different countries of 0.32-0.54 mg/kg. The contents in kernels from bird seeds (i.e. animal feed) from China and Egypt were much lower.The cadmium content of sunflower kernels for human consumption might pose a risk to human health. Danish authorities recommend the Danish consumers do not eat large amounts of sunflower kernels for a long period of time.The nickel contents of 25 of the samples of kernels for human consumption were 2.3--5.3 mg/kg. This is comparable with that found in different kinds of nuts with high nickel contents.
Hoher Gehalt von Cadmium und Nickel in Sonnenblumenkernen
Zusammenfassung Es wurde der Gehalt von Cadmium und Nickel in Sonnenblumenkernen untersucht. In 55 Proben aus Nord-Amerika und Europa war der Cadmiumgehalt durchschnittlich 0,32-0,54 mg/kg. Der Gehalt in Sonnenblumenkernen aus China und Ägypten - als Vogelfutter vorgesehen - war viel niedriger. Der Gehalt von Cadmium in diesem Lebensmittel kann ein Gesundheitsrisiko sein. Die Behörde in Dänemark empfiehlt daher den Verzehr größerer Mengen von Sonnenblumenkernen über längere Zeit zu vermeiden. Der Gehalt von Nickel in 25 Proben von Sonnenblumenkernen - als Lebensmittel vorgesehen- war 2,5-5,3 mg/kg. Dieser Inhalt ist vergleichbar dem hohen Nickelgehalt verschiedener Nüsse.
