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许多负载型催化剂的活性组分可在载体表面自发分散。当活性组分含量低于其分散阈值时,它在载体表面呈单层但非密置单层分散,逾此阈值时出现晶相。自发分散效应可以称为自发单层分散原理。对自发单层分散原理的实质等问题作了初步探讨。 相似文献
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彭家寅 《内江师范学院学报》2011,26(8):1-5
引入了Q-代数中具有界限的模糊子代数的概念,获得了它的一些相关性质,给出了具有界限的模糊子代数与（∈,∈Vq）-模糊子代数的关系．在Q-代数中,引入了t一蕴含的模糊子代数的概念,讨论了具有界限的模糊子代数与分别基于Gaines—Rescher蕴涵算子、Godel蕴涵算子和Godel蕴涵算子的换质算子的0．5-蕴含的模糊子代数之关系． 相似文献
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Elaine Wilson 《Educational Action Research》2013,21(4):587-612
The development of beginning teachers' practice during a school placement is a multiplicity of mediated interactions between university- and school-based systems. Both systems have the common aim of training effective teachers. However, day-to-day internal institution matters can cause tension between the learning goals set out for the beginning teacher by the university and the schools' drive to ensure maximum student performance in ‘high stake’ national tests. This article reports on an intervention intended to equip beginning teachers with the capacity to learn, through purposive activity, in an authentic classroom environment. The context of the learning was to address the conceptual difficulties that secondary school pupils (aged 11-16) have in understanding scientific concepts within the constraints of a ‘curriculum delivery’ lead culture. The results show that beginning teachers are able to extract principles, which might assist them in new contexts in the future. The interactions which took place during the intervention within a school University Initial Teacher Education and Training partnership were analysed using activity systems. 相似文献
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Dawn Scott 《Journal of sports sciences》2018,36(13):1523-1532
This study examined the utility of a range of approaches used to develop player-dependent speed zones in time-motion analysis (TMA), in determining the dose-response (internal load) of daily football training. Daily external (10 Hz GPS) and internal load (heart rate metrics, ratings of perceived exertion [RPE], wellness ratings) measures were tracked for 22 International women’s football players during a 21-day training camp. High-speed (HSR) and very high speed running (VHSR) were determined according to arbitrary speed thresholds, as well as using a range of different individualization approaches that included the velocities corresponding to the heart rate deflection point, maximal aerobic speed, YYIR1 performance, and maximal sprint speed (MSS). Within-player correlations between the TMA approaches versus internal load measures quantified the dose-response to training. Correlations between HSR and VHSR vs. RPE were large (r = 0.53–0.67), with the exception of VHSR for the MSS technique (moderate; r = 0.44). HSR was very-largely associated with heart rate indices (r = 0.72–0.78), again with the exception of MSS (large; r = 0.60–0.67). Using a range of different fitness characteristics to individualise speed thresholds did not enhance the dose-response determination to daily fluctuations in external load, and was worsened with MSS per se. 相似文献
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彭家寅 《内江师范学院学报》2014,(12):1-8
利用模糊点与模糊集之重于关系,在BL-代数中引入了（∈,∈∨q）-模糊n-重蕴涵滤子的概念,推广了经典的模糊n-重蕴涵滤子,给出了（∈,∈∨q）-模糊n-重蕴涵滤子的一些刻画.研究了（∈,∈∨q）-模糊蕴涵滤子与（∈,∈∨q）-模糊n-重蕴涵滤子的关系、（∈,∈∨q）-模糊n-重蕴涵滤子与（∈,∈∨q）-模糊（n＋1）-重蕴涵滤子的关系.提出门限模糊n-重蕴涵滤子的概念,以此获得了非平凡的经典模糊n-重蕴涵滤子、非平凡的（∈,∈∨q）-模糊n-重蕴涵滤子,研究了门限模糊n-重蕴涵滤子和（∈,∈∨q）-模糊n-重蕴涵滤子的性质. 相似文献
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通过对码本设置阚值的方法来收缩对比度因子,提出了一种新的快速分形图像解码算法.实验结果表明该算法获得了较基本分形算法质量较高的第一次迭代后图像,在图像质量降质较小的情况下较基本分形解码明显地加快了收敛速度,从而可较好地满足需要超高速图像解码的应用场合(如实时视频传输). 相似文献
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Alessandro Fornasiero Aldo Savoldelli Damiano Fruet Gennaro Boccia Barbara Pellegrini Federico Schena 《Journal of sports sciences》2018,36(11):1287-1295
The aims of the study were to describe the physiological profile of a 65-km (4000-m cumulative elevation gain) running mountain ultra-marathon (MUM) and to identify predictors of MUM performance. Twenty-three amateur trail-runners performed anthropometric evaluations and an uphill graded exercise test (GXT) for VO2max, ventilatory thresholds (VTs), power outputs (PMax, PVTs) and heart rate response (HRmax, HR@VTs). Heart rate (HR) was monitored during the race and intensity was expressed as: Zone I (VT2) for exercise load calculation (training impulse, TRIMP). Mean race intensity was 77.1%±4.4% of HRmax distributed as: 85.7%±19.4% Zone I, 13.9%±18.6% Zone II, 0.4%±0.9% Zone III. Exercise load was 766±110 TRIMP units. Race time (11.8±1.6h) was negatively correlated with VO2max (r = ?0.66, P <0.001) and PMax (r = ?0.73, P <0.001), resulting these variables determinant in predicting MUM performance, whereas exercise thresholds did not improve performance prediction. Laboratory variables explained only 59% of race time variance, underlining the multi-factorial character of MUM performance. Our results support the idea that VT1 represents a boundary of tolerable intensity in this kind of events, where exercise load is extremely high. This information can be helpful in identifying optimal pacing strategies to complete such extremely demanding MUMs. 相似文献
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Leonardo A. Pasqua Salomão Bueno Guilherme G. Artioli Antônio H. Lancha JR. Monique Matsuda Mônica V. Marquezini 《Journal of sports sciences》2016,34(2):163-170
The purpose of this study was to verify the association between ACTN3 polymorphism and physiological parameters related to endurance performance. A total of 150 healthy male volunteers performed a maximal incremental running test to determine the speeds corresponding to ventilatory threshold (VT) and respiratory compensation point (RCP). Participants were genotyped and divided into terciles based on the analysed variables. Genotype frequencies were compared through χ2 test between lower and higher terciles, with the lowest or highest values of each analysed variable. ACTN3 XX genotype was over-represented in higher tercile for VT and RCP. Odds ratio also showed significantly higher chances of XX individuals to be in higher tercile compared to RR (7.3) and RR + RX (3.5) for VT and compared to RR genotype (8.1) and RR + RX (3.4) for RCP. Thus, XX individuals could attain the VT and RCP at higher speeds, suggesting that they are able to sustain higher running speeds in lower exercise intensity domains. It could result in higher lipid acids oxidation, saving muscle glycogen and delaying the fatigue during prolonged exercises, which could be the advantage mechanism of this genotype to endurance performance. 相似文献
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《The Journal of educational research》2012,105(3):194-201
ABSTRACT Many educational policymakers consider attendance as a tool to induce learning. Researchers also agree that attendance has a positive effect on learning; however, there are few empirical studies that measure the nature and significance of that effect. The authors analyzed the effect of class attendance on academic performance and evaluated the existence and importance of a minimum attendance requirement. Using student data from a sample of public primary schools in Chile, and considering for endogeneity and sample selection bias, they found two important results. First, attendance had a relevant and statistically significant effect on educational performance. Second, the existence of a threshold was identified, but educational performance did not continue to decrease after a certain number of absences, which seems to contradict policies that have a minimum attendance requirement. 相似文献