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排序方式: 共有1474条查询结果,搜索用时 15 毫秒
941.
Tomasz Majchrzak Wojciech Wojnowski Tomasz Dymerski Jacek Gębicki Jacek Namieśnik 《Food Analytical Methods》2018,11(12):3417-3424
The change of concentration of various volatiles generated during frying may be an indicator of oil quality. Chemical compounds such as aldehydes, ketones, alcohols and carboxyl acids are the products of oxidation during thermal degradation of edible oils. Shown in this work is a complementary use of GC×GC-TOFMS and PTR-MS for the detection and determination of quality indicators of rapeseed oil. The former technique was used for the identification of potential markers and the latter for their quantitative determination. As a result of the GC×GC analysis, it was determined that 2-pentanone, heptane, octane, 1-heptanol and nonanal can be considered indicators of thermal degradation of rapeseed oil. Using PTR-MS, it was possible to monitor the concentration of these volatile indicators in real time. Based on the results of the analysis and of the reference method, it was concluded that 1-heptanol is best suited for the role of a quality indicator of thermal degradation of rapeseed oil. 相似文献
942.
The influence of aggregate type on the physical and mechanical properties of high‐performance concrete subjected to high temperature
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This paper presents the results of an experimental study on the behaviour of high‐performance concretes after high temperature exposure. The high temperature exposure is related to the potential risk of fire, and mechanical properties analysis is needed afterwards to assess the residual strength of the material. The results presented in the paper show the properties evolution of four concretes made with four different aggregate types: basalt, granite, dolomite and riverbed gravel. The mix compositions allow comparisons, because the cement paste and mortar compositions and their volumes remain the same for all the four concretes. Moreover, the aggregate particle size distribution was chosen to be quasi identical so that this factor does not affect the concrete behaviour. The decrease of tensile strength value with the increase of temperature is more pronounced than compressive strength reduction thus, the exponential and power function equations were proposed to describe ftT–fcT relationship. The change of modulus of elasticity in relative values is similar, although the initial values of modulus are different and correspond to the aggregate type. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
943.
944.
Ming Zhou Gregoire Allaire Gengdong Cheng Jianbin Du Matthew Gilbert Xu Guo James Guest Raphael Haftka Alicia Kim Thomas Lewinski Kurt Maute Julian Norato Niels Olhoff Glaucio H Paulino Tomasz Sokol Michael Wang Ren-Jye Yang Byeng Dong Youn 《Structural and Multidisciplinary Optimization》2016,54(5):1107-1111
945.
Wiesław Wócik Bronisław Jańczuk Tomasz Białopiotrowicz 《Petroleum Science and Technology》2013,31(2):117-135
Abstract Aggregative flotation tests of gas-flaming coal were carried out in a laboratory flotation machine and a flotation column. Aggregation of coal feeds was carried out using as a collector unemulsified and emulsified kerosene at dosages of 130 and 10 kg/t, respectively. The results of the aggregative flotation showed that it is possible to beneficate gas-flaming coal at a huge dosage of the collector, the flotation response of which is very low. Preemulsification of kerosene caused a distinct decrease of its consumption. The efficiency of aggregative flotation of coal was higher in the flotation machine; however, the flotation selectivity of the finest feeds (?0.13 and ?0.23 mm) in the column was a little better. The influence of the size of coal grains on coal recovery and ash reduction both in the flotation machine and flotation column was interpreted as dependent on the decrease of the contact plane of aggregates formed by coal grains with air bubbles and on the size of these aggregates. 相似文献
946.
ND++ – an extended IPv6 Neighbor Discovery protocol for enhanced stateless address autoconfiguration in MANETs
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Monika Grajzer Tomasz Żernicki Mariusz Głąbowski 《International Journal of Communication Systems》2014,27(10):2269-2288
Recent trends in information and communications technologies are oriented toward the design of the Future Internet and the Internet of Things. While IPv6‐based mobile ad hoc networks (MANETs) are emerging as an important building block of these new technologies, it is necessary to come up with adequate self‐configuration capabilities allowing for seamless and automated configuration of addresses in mobile environment. The mechanisms of stateless address autoconfiguration proposed for IPv6 networks are supposed to automate some configuration steps; however, they would need to be aligned with the requirements imposed by MANET networks. Therefore, in this article, we present Neighbor Discovery ++ – an extended IPv6 Neighbor Discovery protocol for enhanced duplicate address detection in MANETs, which provides increased coverage of network nodes, while minimizing protocol overhead. It exploits efficient flooding mechanism on the basis of the multipoint relay concept, which makes it an interesting approach also for large‐scale networks. Trials performed on the designated real‐world testbed platform indicate that ND++ is a promising solution to support efficient address autoconfiguration in MANETs. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
947.
Kasprzyk I Grinn-Gofroń A Strzelczak A Wolski T 《The Science of the total environment》2011,409(5):949-956
Ganoderma spores are one of the most airspora abundant taxa in many regions of the world, and are considered to be important allergens. The aerobiology of Ganoderma basidiospores in two cities in Poland was examined using the volumetric method, (Burkard and Lanzonii Spore Traps), from selected days in 2004, 2005 and 2006. Spores of Ganoderma were present in the atmosphere from June to November, with peak concentrations generally occurring from late July to mid-October. ANN (artificial neural network) and MRT (multivariate regression trees), models indicated that atmospheric phenomenon, hour and relative humidity were the most important variables influencing spore content. The remaining variables (air temperature, dew point, air pressure, wind speed and wind direction), also contributed to the high network performance, (ratio above 1), but their impact was less distinct. Those results are consistent with the Spearman's rank correlation analysis. 相似文献
948.
Delgado J Barba-Brioso C Nieto JM Boski T 《The Science of the total environment》2011,409(19):3666-3679
Recent studies have demonstrated that the Guadiana Estuary contains metal concentrations in excess of background values. Therefore, this work aims to document the potential environmental hazards associated with the availability of these metals in this environment of high ecological value. Mineralogical analysis shows that the sediments are composed mainly of quartz, albite, and clay minerals (illite, smectite, kaolinite, and vermiculite) along with several small, reactive compounds (including soluble sulphated salts, Fe-Mn oxyhydroxides, organic matter, and pyrite) capable of retaining metals, which can be subsequently released, causing environmental degradation. BCR sequential extraction shows that As, Cd, Cu, Mn, Pb, and Zn present mobile fractions with respect to the total metal content (41, 100, 57, 53, 70, and 69%, respectively) in any of the described reactive phases (F1 + F2 + F3).Calculated environmental risk indices demonstrate moderate to considerable ecological risk for almost the entire estuary, associated mainly with acid mine drainage from the nearby Iberian Pyrite Belt. In addition, the indices highlight several zones of extremely high risk, which are related to industrial and urban dumps in the vicinity of the estuary and to heavy traffic on the international bridge. 相似文献
949.
Agnieszka Matuszewska Beata Nowak Anna Nikodem Anna Merwid-Ld Benita Wiatrak Tomasz Tomkalski Diana Jdrzejuk Ewa Szelg Tomasz Sozaski Maciej Danielewski Paulina Jawie Ireneusz Ceremuga Marta Szandruk-Bender Marek Bolanowski Jarosaw Filipiak Adam Szelg 《International journal of molecular sciences》2021,22(13)
Bone structure abnormalities are increasingly observed in patients chronically treated with antiepileptic drugs (AEDs). The majority of the available data concern older conventional AEDs, while the amount of information regarding newer AEDs, including stiripentol, is limited. The aim of the study was to assess the effect of stiripentol on bones. For 24 weeks, male Wistar rats, received 0.9% sodium chloride (control group) or stiripentol (200 mg/kg/day) (STP group). In the 16th week of the study, we detected lower serum PINP levels in the STP group compared to the control group. In the 24th week, a statistically significant lower 1,25-dihydroxyvitamin D3 level, higher inorganic phosphate level and higher neutrophil gelatinase-associated lipocalin (NGAL) levels in serum were found in the STP group compared to the control. Micro X-ray computed tomography of the tibias demonstrated lower bone volume fraction, lower trabecular thickness, higher trabecular pattern factor and a higher structure model index in the stiripentol group. Considering the results of this experiment on rats which suggests that long-term administration of stiripentol may impair the cancellous bone microarchitecture, further prospective human studies seem to be justified. However, monitoring plasma vitamin D, calcium, inorganic phosphate and kidney function in patients on long-term stiripentol therapy may be suggested. 相似文献
950.
In the work a conception of a miniature, orbitron ion vacuum micropump for an integration with vacuum MEMS devices is presented. It is made of silicon and glass using microengineering technology. The main part of the device is a lateral field-emission source of electrons, which has been fabricated on oxidized silicon wafer. Both, cold cathode and anode of the source are made of thin gold layer using only one photolithography process. Fabrication process and the preliminary results of electrical tests of the field-emission electron source are presented. Experimental studies have shown its good emission parameters: a low threshold voltage (over a dozen Volts), a high electron current (from tens to several hundred micro amperes), and field enhancement coefficient from 107 to 108 cm−1. These results are promising and give possibility to fabricate orbitron micropump as an integrated part of vacuum MEMS. 相似文献