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排序方式: 共有106条查询结果,搜索用时 31 毫秒
1.
Summary: The influence of number‐average molecular weight ranging from 1.4 · 104 to 1.2 · 106 g/mol on the thermal behaviour of polytetrafluoroethylene (PTFE) has been studied. Samples have been prepared by radiation‐induced degradation of commercial PTFE. The molecular weight has been calculated using end‐group concentration determined by infrared (IR) spectroscopy and 19F solid‐state nuclear magnetic resonance (NMR) spectroscopy. Melting and crystallisation heats were investigated by differential scanning calorimetry (DSC). The results have been discussed with respect to quantitative relationships between number‐average molecular weight and heat of crystallisation of PTFE described in the literature. The molecular weight calculated from Suwa's equation, which is often used in the literature, has been found to be too low.
2.
Maria Augusta de Luca Taís Espíndola Machado Renan Beretta Notti Marly Maldaner Jacobi 《应用聚合物科学杂志》2004,92(2):798-803
Hybrid materials were synthesized from epoxidized (68, 43, or 14%) styrene–butadiene rubber (SBR) and the hydrolysis product of tetraethoxysilane (TEOS) in situ under ultrasonic irradiation. The products were characterized with thermal analysis (differential scanning calorimetry and thermogravimetric analysis), stress–strain tests, scanning electron microscopy (including energy‐dispersive spectrometry), and swelling in tetrahydrofuran and water. The most transparent were those prepared from SBR with the highest degree of epoxidation, whereas those obtained from less epoxidized SBR and with larger amounts of TEOS showed distinct phases that could be considered two hybrid phases (one rich in TEOS and another rich in SBR). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 798–803, 2004 相似文献
3.
Liane Gabor Stefan Leijnen Tiha von Ghyczy 《International Journal of Software and Informatics》2013,7(4):615-627
There are both benefits and drawbacks to cultural diversity. It can lead to friction and exacerbate differences. However, as with biological diversity, cultural diversity is valuable in times of upheaval; if a previously effective solution no longer works, it is good to have alternatives available. What factors give rise to cultural diversity? This paper describes a preliminary investigation of this question using a computational model of cultural evolution. The model is composed of neural network based agents that evolve fitter ideas for actions by (1) inventing new ideas through modification of existing ones, and (2) imitating neighbors'' ideas. Numerical simulations indicate that the diversity of ideas in a population is positively correlated with both the proportion of creators to imitators in the population, and the rate at which creators create. This is the case for both minimum and peak diversity of actions over the duration of a run. 相似文献
4.
A perceived limitation of evolutionary art and design algorithms is that they rely on human intervention; the artist selects
the most aesthetically pleasing variants of one generation to produce the next. This paper discusses how computer generated
art and design can become more creatively human-like with respect to both process and outcome. As an example of a step in
this direction, we present an algorithm that overcomes the above limitation by employing an automatic fitness function. The
goal is to evolve abstract portraits of Darwin, using our 2nd generation fitness function which rewards genomes that not just
produce a likeness of Darwin but exhibit certain strategies characteristic of human artists. We note that in human creativity,
change is less choosing amongst randomly generated variants and more capitalizing on the associative structure of a conceptual
network to hone in on a vision. We discuss how to achieve this fluidity algorithmically.
相似文献
Liane GaboraEmail: |
5.
Roland Vogel Regine Boldt Marijan Vučak Liane Häußler 《Polymer Engineering and Science》2014,54(9):2057-2063
It has been reported in the technical literature that whiskers of rodlike single crystals can be used in order to generate shish‐kebab structures or other different lamellae morphologies during isothermal or dynamic crystallization of sheared or presheared polymer melts. The expected advantage of the changed crystalline structure is a reinforcing effect of the composite. A lot of papers reported about the application of inorganic and organic whiskers such as cellulose and chitin whiskers. This study reports on an attempt to use acicular PCC as appropriate whisker for improving mechanical properties of polypropylene. In this article special attention is given to demonstrate the effect of flow induced crystallization under varying shear conditions in order to improve the mechanical properties. The effects were demonstrated using rheology, thermal analysis, tensile testing, and transmission electron microscopy. POLYM. ENG. SCI., 54:2057–2063, 2014. © 2013 Society of Plastics Engineers 相似文献
6.
<正>("美无非是一个关于幸福的承诺"——司汤达,《论爱情》,第17章,1822年)对于建筑界的大奖——普利茨克奖在2017年花落RCR建筑事务所的消息,世界各地的出版物不约而同地评论:实乃意外。此前,媒体大多预测着一个闪亮的大师名号摘得荣耀,却只获知了一个干巴巴的首字母缩略词——RCR——一个低调的加泰罗尼亚建筑事务所。该事务所由三名建筑师所组成:拉法尔·阿兰达(Rafael Aranda). 相似文献
7.
Thomsen C Knutsen HK Liane VH Frøshaug M Kvalem HE Haugen M Meltzer HM Alexander J Becher G 《Molecular nutrition & food research》2008,52(2):228-237
Very high concentrations of polybrominated diphenyl ethers (PBDE) have been reported in fish from Lake Mj?sa in Norway. This study was performed to examine the serum concentrations of PBDE and hexabromocyclododecane (HBCD) in consumers of fish from this lake and to investigate possible relationships between serum concentrations, self-reported fish intake and calculated total dietary PBDE exposure. Serum concentrations of the sum of the seven PBDE (BDE-28, 47, 99, 100, 153, 154 and 183) were significantly higher than those of a reference group of Norwegians eating only food with background levels of contamination (medians: 18 ng/g lipids men, 8.4 ng/g lipids women). The median dietary intake of Sum 7 PBDE was 2549 ng/day (30 ng/kg body weight/day), the highest dietary intake of PBDE reported. The contribution from fish caught from the contaminated lake comprised 98.7% of the total dietary exposure. For men, serum levels of PBDE were strongly correlated with the calculated dietary exposure, except for BDE-209. This suggests that sources other than the diet are important for human BDE-209 exposure. The median serum HBCD concentration was 4.1 and 2.6 ng/g lipids for men and women, respectively, and was also found to be associated with consumption of fish from Lake Mj?sa. 相似文献
8.
Ana Julia Dal Forno Fernando Augusto Pereira Fernando Antonio Forcellini Liane M. Kipper 《The International Journal of Advanced Manufacturing Technology》2014,72(5-8):779-790
Value stream mapping (VSM) is an important tool of the lean approach and is used to identify value-adding activities and those considered wasteful of materials and the flow of information and people. However, when not applied correctly, VSM can complicate the identification of waste, lead to misinterpretations and assessment mistakes, and undermine the implementation of future improvements. The purpose of this paper is to investigate the main difficulties and limitations encountered during the construction of current state maps, analysis of the associated causes, and pointing out of guidelines to facilitate the use of VSM to map processes. To do so, a search and evaluation of papers in journals, conferences, theses, and dissertations was conducted, and the articles were categorized according to the field of application (factory floor, supply chain, product development and services) and approach (theoretical or practical). In conclusion, this paper criticizes some ways that VSM has been used, observing that important constraints created by its application must be considered and that when used incorrectly, the tool can lead to mistakes that can cause problems instead of benefits. Considering the problems identified, the paper suggests future works for improving the use of VSM for mapping processes. 相似文献
9.
Comeau Liane; Cormier Pierre; Grandmaison éric; Lacroix Diane 《Canadian Metallurgical Quarterly》1999,91(1):29
English-speaking children (N?=?122) in French immersion classes participated in a 1-year longitudinal study of the relation between phonological awareness and reading achievement in both languages. Participants were administered measures of word decoding and of phonological awareness in French and in English as well as measures of cognitive ability, speeded naming, and pseudoword repetition in English only. The relation of phonological awareness in French to reading achievement in each of the languages was equivalent to that in English. These relations remained significant after partialing out the influences of speeded naming and pseudoword repetition. Phonological awareness in both languages was specifically associated with 1-year increments in decoding skill in French. These findings support the transfer of phonological awareness skills across alphabetic languages. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
Summary New aromatic polymers containing formamidine groups were prepared by high temperature solution polycondensation of triethyl orthoformate with various aromatic diamines. The resulting polyformamidines were characterized by elemental analysis, IR' and 1H NMR spectroscopy, viscosity measurements, thermogravimetry, DSC- and WAXS measurements. With few exceptions aromatic polyformamidines show excellent solubility in polar solvents and strong acids, but they were gradually decomposed in extended contact with moisture. Polyformamidines containing rigid para structures are well crystallizing materials, which was proved by WAXS investigations. Glass transition temperatures in the range of 62 – 163°C were observed for semicrystalline or amorphous polymers. All aromatic polyformamidines are thermally stable in nitrogen up to 300°C. 相似文献