遗传算法与人工神经网络在流体机械研究领域中的应用     

周淑娟 《廊坊师范学院学报(自然科学版)》2011,11(2):40-43

神经网络能精确地对复杂问题进行预测,但易受训练过度的影响且训练速度慢。遗传算法是一种全局优化搜索算法,这种方法的要求是拟合度函数必须收敛于最小误差,这为具体的实现方案留下了许多自由空间。将遗传算法与神经网络结合起来使用可以在较高的层次上提高模型的可理解性。  相似文献   

What characterizes children nominated as gifted by teachers? A closer consideration of working memory and intelligence     

Jessica Kornmann  Ingo Zettler  Yvonne Kammerer  Peter Gerjets  Ulrich Trautwein 《High Ability Studies》2015,26(1):75-92

Teacher nominations are often used in school settings to identify gifted children. However, although high intelligence is part of almost all definitions of giftedness, prior research has consistently shown that not all children nominated as gifted by teachers have high intelligence. In order to further understand the characteristics of these students, we herein explore the role of another cognitive construct, namely working memory (WM). In a sample comprising N = 81 fourth graders, both WM and intelligence showed the same predictive value for characterizing teacher-nominated gifted children, pointing to the importance of the thus-far-unattended WM for characterizing these students.  相似文献   

Antiracism defined as equitable sociocultural interactions in prekindergarten: Classroom racial composition makes a difference     

Stephanie M. Curenton  Shana E. Rochester  Jacqueline Sims  Nneka Ibekwe-Okafor  Iheoma U. Iruka  Arlene G. García-Miranda  Jessica Whittaker 《Child development》2022,93(3):681-698

This study used secondary data from the My Teaching Partner-Math/Science 2013–2016 randomized control trial to explore whether equitable sociocultural classroom interactions (see Curenton et al., 2019) were associated with the skills of 105 four- and five-year-olds (52% boys; drawn from 20 unique video recordings of preschool teachers/classrooms; 43% were Black, Latine, Asian, or other racially marginalized learners). Equitable interactions predicted children's skills with effect sizes ranging from small (0.01–0.44) to large (1.00). Moderation analyses revealed that when classrooms had more racially marginalized learners, teachers’ use of equitable disciplinary and personalized learning practices were associated with higher executive functioning gains across prekindergarten. Findings illustrate how classroom composition can be a key indicator between equitable classroom interactions and young children's early skills.  相似文献   

External quality assessment for the RIA of thyroid related hormones: Second phase     

Ajay Kumar  D. H. Shah  M. G. R. Rajan  U. R. Thakare  S. M. Sharma 《Indian journal of clinical biochemistry : IJCB》1992,7(2):159-164

An external quality assessment was conducted to assess the performance of various laboratories for RIA of thhyroid related hormones in two phases. In the first phase thirty five laboratories participated. At the end of first phase a meeting cum workshop was organised to discuss the results of first phase, difficultires faced by the participants and pinpoint the short oming. A second phase was then initiated with an objective of improvement in the performance, if any, where twelve samples from four pools were distributed to twenty four laboratories who participated for the second phase. The overall return of the results increased significantly from 71.8% (1586/2208) for the first phase to 92.4% (732/792) for the second phase. The inter laboratory %CV for T₃, T₄ and TSH were lower during the second phase (30.6%, 19.0% and 31.6% respectively) as compared to those observed during first phase (36.3%, 22.7% and 52.8% respectively). Similarly, there was an improvement in reproducibility of ALTM as %CV for T₃, T₄ and TSH decreased from 6.0%, 9.8% and 13.4% respectively to 4.5%, 4.6% and 8.5% respectively. The individual performances of the participating laboratories viz. bias, variability of bias and imprecision also showed a trend towards improvement as percent laboratories having desirable or acceptable results for T₃, T₄ and TSH increased from 10.7%, 60.7% and 0.0% respectively to 20.8%, 66.7% and 22.2% respectively. External quality assessment thus appears to be beneficial in assessing the performane of a laboratory in comfparison with other laboratories and indeed helps in improving the performance.  相似文献   

Bond graphs for thermal energy transport and entropy flow     

Jean U. Thoma 《Journal of The Franklin Institute》1971

The transport of thermal energy in thermodynamics is described as the product of entropy flow and of the absolute temperature, in analogy to the volume flow and pressure in oil hydraulics and to electric charge flow (= current) and voltage in electronics. Bond graphs are shown to be especially suitable to describe the splitting of applied thermal energy into internal energy and external mechanical work. Transformers and the 0- and 1-junctions of Paynter can illustrate various entropy flow processes, including Carnot engines and heat exchangers. Entropy flow in heat conduction is distinguished from entropy convection, or transport by moving mass, where the entropy/temperature characteristic or equation of state is important. Irreversibilities are represented by impedance transformers reducing temperature and increasing entropy flow but conserving power.  相似文献   

Feasibility of determination of fertile period in Indian women based on urinary hormone estimations     

Meena Desai  U. M. Donde  M. Ikram Khatkhatay 《Indian journal of clinical biochemistry : IJCB》2001,16(1):127-131

Baseline data available on the excretory profiles of estrone giucuronide (E₁G), pregnanediol glucuronide (PdG) and luteinising hormone (LH) on human menstrual cycles (n=104) was retrospectively analysed for identifying the limits of fertile period (FP) to be used as natural method of family planning. The limits of fertile period are suggested based on centile distribution of E₁G and PdG levels during defined phase of menstrual cycle. Two approaches, which do not involve any mathematical calculation are suggested. In approach A, fertile period is said to have started when E₁G value of 35 ng/ml is reached and is said to have ended when the PdG value of 2 μg/ml on two consecutive days is obtained. The criteria were applied to 30 test cycles in whom authentic fertile period was identified based on excretory profiles of E₁G, PdG and LH throughout the menstrual cycles. When approach A was followed the authentic fertile period was covered in 27 cycles giving an accuracy of 90% with a mean fertile period length of 9.11+1.9 days. In approach B, the cut off limit of E₁G value was increased to 55 ng/ml in order to reduce the days of abstinence. Though the length of the fertile period was reduced to 7.2+1.5 days the accuracy of the approach was 66.6%. Thus the approach A which has accuracy of 90% may appeal to determined couples who wish to practice family planning by periodic abstinence or restrict the use of barrier methods.  相似文献   

Do central examinations lead to greater grading comparability? A study of frame-of-reference effects on the University entrance qualification in Germany     

Marko Neumann  Ulrich Trautwein  Gabriel Nagy 《Studies in Educational Evaluation》2011,37(4):206-217

In Germany, the Abitur grades awarded at the end of upper secondary education are critical in the allocation of sought-after university places. Drawing on a representative sample of 3526 grade 13 Abitur students in the German state of Baden-Württemberg, this article examines whether and to what extent grading is affected by the mean achievement of the school serving as frame of reference (“group-referenced grading”), and to what extent this influence differs for coursework and examination grades in mathematics and English as a foreign language. Overall, the results indicate that the higher level of standardization of the central Abitur examinations makes examination grades less susceptible to frame-of-reference effects than are coursework grades.  相似文献   

Hopf bifurcation and synchronization of a five-dimensional self-exciting homopolar disc dynamo using a new fuzzy disturbance-observer-based terminal sliding mode control     

Zhouchao Wei  Amin Yousefpour  Hadi Jahanshahi  Uǧur Erkin Kocamaz  Irene Moroz 《Journal of The Franklin Institute》2021,358(1):814-833

Having found hidden hyperchaos in a 5D self-exciting homopolar disc dynamo, we study the existence of a Hopf bifurcation, which leads to unstable limit cycles bifurcating from a stable equilibrium. Hidden chaos with only stable equilibria can be observed from the Hopf bifurcation: a typical way to enable hidden attractors to be located. We then provide a new fuzzy controller, and a fast fuzzy disturbance observer, based on terminal sliding mode control for synchronization of the hyperchaotic system. Fuzzy inference is considered to weaken the chattering phenomena. Using Lyapunov stability theory, the stability of the closed-loop system is proved. Finally, simulations of synchronization are illustrated to show the efficient performance of the designed control method via external disturbances and dynamic uncertainties.  相似文献   

Neuromuscular control and running economy is preserved in elite international triathletes after cycling     

Bonacci J  Saunders PU  Alexander M  Blanch P  Vicenzino B 《Sports biomechanics / International Society of Biomechanics in Sports》2011,10(1):59-71

Running is the most important discipline for Olympic triathlon success. However, cycling impairs running muscle recruitment and performance in some highly trained triathletes; though it is not known if this occurs in elite international triathletes. The purpose of this study was to investigate the effect of cycling in two different protocols on running economy and neuromuscular control in elite international triathletes. Muscle recruitment and sagittal plane joint angles of the left lower extremity and running economy were compared between control (no preceding cycle) and transition (preceded by cycling) runs for two different cycle protocols (20-minute low-intensity and 50-minute high-intensity cycles) in seven elite international triathletes. Muscle recruitment and joint angles were not different between control and transition runs for either cycle protocols. Running economy was also not different between control and transition runs for the low-intensity (62.4 +/- 4.5 vs. 62.1 +/- 4.0 ml/min/kg, p > 0.05) and high-intensity (63.4 +/- 3.5 vs. 63.3 +/- 4.3 ml/min/kg, p > 0.05) cycle protocols. The results of this study demonstrate that both low- and high-intensity cycles do not adversely influence neuromuscular control and running economy in elite international triathletes.  相似文献   

Algorithmic thinking development through physical computing activities with Arduino in STEM education     

Sarı  Uğur  Pektaş  Hüseyin Miraç  Şen  Ömer Faruk  Çelik  Harun 《Education and Information Technologies》2022,27(5):6669-6689

Education and Information Technologies - The need to benefit from information technologies in the twenty-first century digital age is increasing in all economies to overcome problems and...  相似文献