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1.
Recognition of the major scattering sources on complex targets based on the high frequency radar cross section integrated calculation technique 总被引：1，自引：0，他引：1
Based on the high frequency (HF) integrated radar cross section (RCS) calculation approach, a technique of detecting major
scattering source is developed by using an appropriate arithmetic for scattering distribution and scattering source detection.
For the perfect adaptability to targets and the HF of the HF integrated RCS calculation platform, this technique is suitable
to solve large complex targets and has lower requirement to the target modeling. A comparison with the result of 2-D radar
imaging confirms the accuracy and reliability of this technique in recognition of the major scattering source on complex targets.
This technique provides the foundation for rapid integrated evaluation of the scattering performance and 3-D scattering model
reconstruction of large complex targets.
Project supported by the National Natural Science Foundation of China (Grant No.90305026) 相似文献
2.
为了提高时域有限差分法的计算精度,以二维金属圆柱散射为例,研究了在各向异性完全匹配层(UPML)吸收条件下,改变总场-散射场的输出及吸收边界时误差的变化规律。比较了UPML与二阶Mur吸收边界条件下的误差。同时发现,可采用迭代步数相差半个周期的双站雷达散射截面(RCS)的平均来减小误差,也可采用距离为半个波长的两个输出边界得到RCS的平均来减小误差。 相似文献
3.
Buckling design of large steel silos with various slendernesses 总被引：1，自引：0，他引：1
Large steel silos are typical kinds of thin-walled structure which are widely used for storing huge quantities of granular solids in industry and agriculture. In the present analyses, the buckling design of large steel silos subject to Eurocode-specified solid pressure is demonstrated. The finite element model is established using the commercial general purpose computer package ANSYS. Six types of buckling analyses are carried out for the geometrically perfect and imperfect models with and without consideration of material plasticity. The load cases of concentric discharge, discharge patch load, large eccentricity discharge, and large eccentricity filling are considered. The buckling behavior of six example steel silos with capacities of 30 000–60 000 m3 is investigated. The silos’ slenderness ranges from 4.77 to 0.35, comprising very slender, slender, intermediate slender, squat, and retaining silos. The index called the ratio of capacity to steel consumption (RCS) is initially defined in the paper, which provides an effective measure for the economical design of steel silos. It is validated that the RCS index increases rapidly with the decrease of silo slenderness, and the storage efficiency of steel silo improved greatly as the slenderness changes from slender silo to retaining silo. The effects of patch load reveal that the buckling modes in the case of discharge patch load are very different from those of silos under concentric solid pressure, and the effect is unfavorable for buckling resistance of all levels of slenderness of the example silos, but contributes a small decrease to the RCS index (less than 10%). The buckling deformations from both the linear and nonlinear buckling analyses in large eccentric discharge are strongly asymmetrical arising from the circumferential and meridional non-uniform distribution of the solid pressures. The buckling is mainly governed by the non-uniform distribution of the solid pressure other than other influential factors such as the weld imperfection, geometrical and material nonlinearity, compared with the load case of concentric discharge. The RCS index of example silos under large eccentric discharge is reduced substantially, and is approximately half that of silos under concentric discharge. The linear and nonlinear buckling deformations in large eccentric filling are also asymmetrical, deviating from the center to the side where the most friction locates to the highest wall contact. The RCS index of example silos under large eccentric filling is also reduced substantially, and is approximately 70% that of silos under concentric discharge. This reveals that the large eccentricity both in discharging and filling could result in a strong decrease of storage efficiency of steel silos. 相似文献
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Betsy Ng C.K. John Wang W.C. Liu 《International Journal of Research & Method in Education》2017,40(1):91-107
The motivated strategies for learning questionnaire (MSLQ) is widely used as a self-report instrument to assess students’ motivation and self-regulation. This study utilized the MSLQ Junior High to examine the motivational beliefs and self-regulation of secondary school students (Grades 8 and 9) from Singapore. The instrument was slightly modified and administered to students (N?=?610) in mathematics and science classes. In the first sample, 314 students completed the MSLQ Junior High while a second sample of 296 students completed the revised MSLQ Junior High. Using a congeneric approach of confirmatory factor analysis (CFA), the five-factor measurement model was determined with the first sample. This measurement model was further supported using a second sample and its goodness-of-fit indices were compared with other CFA models. Statistical findings showed that the five-factor structure of the revised MSLQ Junior High had a good model fit. The present study contributes a novel methodological approach by investigating the parsimony confirmatory factor structure of the revised MSLQ Junior High in local academic contexts. 相似文献
6.
基于Maxwell方程的一阶状态矢量微分方程描述，从基本的差分原理出发，利用矩阵运算的特点，该文导出了各向异性材料中的时域有限差分（FDTD）迭代公式。通过对各向同性介质球雷达散射截面（RCS）的计算，验证了本算法的正确性。在此基础上计算了各向异性材料涂覆立方体的RCS，得到了一些有益的结论。 相似文献
7.
Peter Zeegers 《高等教育研究与发展》2002,21(1):73-92
The Biggs' Study Process Questionnaire (SPQ), an instrument for the evaluation of student learning in higher education, was revised over a three-year period with over 2500 tertiary students. The original instrument structure of 42 items in 6 sub-scales was maintained with each item being subject to revision and assessed for internal consistency and appropriateness through a sequence of trial and retrial. The final version consists of 8 original items and 34 revised items. This version was evaluated with 996 students, at first-year and third-year level, through the use of confirmatory factor analysis using AMOS. The two models having the best fit to the data are represented by the original six sub-scale model which loads onto two higher order factors, a deep approach and a surface approach to learning, or a seven sub-scale version which loads on the same two higher order factors. Evidence is presented as to the preference of the latter model. 相似文献
8.
Yu Luo Wen-long Li Wen-hua Huang Xue-hua Liu Yan-gang Song Hai-bin Qu 《Journal of Zhejiang University. Science. B》2017,18(5):383-392
A near infrared spectroscopy (NIRS) approach was established for quality control of the alcohol precipitation liquid in the manufacture of Codonopsis Radix. By applying NIRS with multivariate analysis, it was possible to build variation into the calibration sample set, and the Plackett-Burman design, Box-Behnken design, and a concentrating-diluting method were used to obtain the sample set covered with sufficient fluctuation of process parameters and extended concentration information. NIR data were calibrated to predict the four quality indicators using partial least squares regression (PLSR). In the four calibration models, the root mean squares errors of prediction (RMSEPs) were 1.22 μg/ml, 10.5 μg/ml, 1.43 μg/ml, and 0.433% for lobetyolin, total flavonoids, pigments, and total solid contents, respectively. The results indicated that multi-components quantification of the alcohol precipitation liquid of Codonopsis Radix could be achieved with an NIRS-based method, which offers a useful tool for real-time release testing (RTRT) of intermediates in the manufacture of Codonopsis Radix. 相似文献
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Melita Puklek Levpu&#x;
ek Candido J. Ingls Juan C. Marzo Jose M. García‐Fernndez 《Psychology in the schools》2015,52(9):860-873
The purpose of this study was to examine the reliability and validity of the School Anxiety Inventory (SAI) using a sample of 646 Slovenian adolescents (48% boys), ranging in age from 12 to 19 years. Single confirmatory factor analyses replicated the correlated four‐factor structure of scores on the SAI for anxiety‐provoking school situations (Anxiety about School Failure and Punishment, Anxiety about Aggression, Anxiety about Social Evaluation, and Anxiety about Academic Evaluation), and the three‐factor structure of the anxiety response systems (Physiological Anxiety, Cognitive Anxiety, and Behavioral Anxiety). Equality of factor structures was compared using multigroup confirmatory factor analyses. Measurement invariance for the four‐ and three‐factor models was obtained across gender and school‐level samples. The scores of the instrument showed high internal reliability and adequate test–retest reliability. The concurrent validity of the SAI scores was also examined through its relationship with the Social Anxiety Scale for Adolescents (SASA) scores and the Questionnaire about Interpersonal Difficulties for Adolescents (QIDA) scores. Correlations of the SAI scores with scores on the SASA and the QIDA were of low to moderate effect sizes. 相似文献
11.
Kit Ling Lau 《Educational Research and Evaluation》2013,19(5):489-509
The purpose of the study is to construct and validate a Chinese self-regulated learning (SRL)-based reading instruction questionnaire (CSRIQ) and to examine the relationship between Chinese reading instruction and Hong Kong students' reading development from the SRL perspective. A total of 339 Grade 10 students completed the initial CSRIQ in Study 1. Exploratory factor analysis and reliability analyses were used to assess the psychometric quality of the questionnaire, and the original CSRIQ subscales were then revised. Study 2 comprised 1,121 Grade 10 students. The factor structure of the revised CSRIQ was supported by the findings of confirmatory factor analysis. The findings of structural equation modelling indicated significant relations between SRL-based instruction and various reading-related variables. Among the four aspects of instruction, teacher support was the most positive factor facilitating Chinese students' reading development, whereas student autonomy seemed less favourable. Cultural and curricula factors affecting Chinese reading instruction in Hong Kong were discussed. 相似文献
12.
Previous research on professional certification has primarily focused on graduate certificates in intensive care nursing, writing certificates for practitioners, maintenance of certification in radiation oncology, and the certification of teachers and surgeons. Research on certification in the domain of business and management from an attitudinal?Cbehavioral approach has been lacking. Social psychological theories provide potentially useful tools for explaining how attitudes, intentions, and behaviors are changed. The current study compared four intention-based models??the theory of planned behavior, the theory of self-regulation (TSR), the revised TSR (in which desire is a partial mediator), and the other revised TSR (in which desire is a full mediator)??in terms of their ability to predict the intentions of business and management students to obtain certification in their fields. Participants were drawn from the southern, middle, and northern areas of Taiwan. A structural equation model applied to a sample of 273 undergraduates demonstrated that attitudes, subjective norms, perceived behavioral controls, desires, intentions, and behaviors were associated with certification in business and management domains. The explanatory power of the revised TSR in which desire was a full mediator was superior to that of the competing models. Implications and future directions are discussed. 相似文献
13.
The Nonverbal Literacy Assessment (NVLA) is a literacy assessment designed for students with significant intellectual disabilities. The 218‐item test was initially examined using confirmatory factor analysis. This method showed that the test worked as expected, but the items loaded onto a single factor. This article uses item response theory to investigate the NVLA using Rasch models. First, we reduced the number of items using a unidimensional model, which resulted in high levels of test reliability despite decreasing the number of questions, providing the same information about student abilities in less time. Second, the multidimensional analysis indicated that it is possible to view the NVLA as a test with four dimensions, resulting in more detailed information about student abilities. Finally, we combined these approaches to obtain both specificity and brevity, with a four‐dimensional model using 133 items from the original NVLA. 相似文献
14.
Michael J. Lichtenstein Steven V. Owen Cheryl L. Blalock Yan Liu Kacy A. Ramirez Linda A. Pruski Carolyn E. Marshall Mary Anne Toepperwein 《科学教学研究杂志》2008,45(5):600-616
The central purposes of this study were to review the development and evolution of the Scientific Attitude Inventory (SAI) and then reevaluate the psychometric properties of the revised form of the SAI, the Scientific Attitude Inventory II (SAI‐II). The SAI‐II was administered to a convenience sample of 543 middle and high school students from five teachers in four schools in four school districts in San Antonio, Texas, at the beginning of the 2004–2005 school year. Confirmatory factor analysis on the full data set failed to support the existence of a 12‐factor structure (as proposed by the scale developers) or a one‐factor structure. The data were then randomly divided into exploratory [exploratory factor analysis (EFA)] validation and confirmatory [confirmatory factor analysis (CFA)] cross‐validation sets. Exploratory and confirmatory models yielded a three‐factor solution that did not fit the data well [χ2 (321) = 646, p < .001; RMSEA = .061 (.90 CI = .054–.068); and CFI = .81]. The three factors were labeled “Science is About Understanding and Explaining” (13 items), “Science is Rigid” (6 items), and “I Want to Be a Scientist” (8 items). The α‐coefficients for these three factors ranged from 0.59 to 0.85. Whether these identified subscales are valid will require independent investigation. In this sample, and consistent with prior publications, the SAI‐II in its current form did not have satisfactory psychometric properties and cannot be recommended for further use. © 2008 Wiley Periodicals, Inc. J Res Sci Teach 45: 600–616, 2008 相似文献
15.
The development and validation of a new and unique learning climate instrument, the Sports Class Environment Scale (SCES),
was the focus of this study. We began with a consolidation of the dimensions and items of the Perceived Motivational Climate
in Sport Questionnaire–2 and the Classroom Environment Scale. Field-testing of the SCES involved 204 competitive gymnasts
from six metropolitan and four regional competitive gymnastics clubs in Queensland, Australia. Exploratory factor analysis
provided a revised SCES with five scales labelled Task Involvement & Improvement, Ego Involvement & Mistakes, Coach–Athlete
Communication, Effort, Order & Organisation, and Affiliation. Using scales of the revised SCES as dependent variables, multivariate
analyses of variance were conducted to compare club types, genders and competitive levels. Effective measurement of sports
class learning climates using the SCES could lead to a greater understanding of effective sports classes, and of coach and
athlete behaviours in those classes, and provide a first step in monitoring sports class learning climates. 相似文献
16.
John L. Nietfeld Sara J. Finney Gregg Schraw Matthew T. McCrudden 《Contemporary educational psychology》2007
This study tested four theoretical models in terms of their fit with demands placed on our cognitive system by traditional tests of cognitive ability. We did so by administering seven tests of cognitive ability known to require varying types of processing demands to a large group of college undergraduates (N = 193). We compared the models using confirmatory factor analyses, including those based upon a unitary factor, speed and capacity, crystallized and fluid intelligence, and verbal and spatial ability. The crystallized/fluid model provided the best fit with the data. This finding is consistent with previous research. Implications for education and future research are discussed. 相似文献
17.
张世龙 《南通职业大学学报》2021,(1):63-67
利用Excel对空气质量国控点与自建点的"两尘四气"浓度日平均数据进行透视分析,得到二者相对应的变化趋势,发现大部分数据波动比较大;再利用SPSS对"两尘四气"数据与风速、压强、降水量、温度、湿度的相关性进行分析,结果表明,PM2.5、PM10与湿度呈中度相关,SO2与风速、湿度基本不相关;最后以自建点整点时刻"两尘四气"的平均数据与国控点数据的差值为因变量,风速、压强、降水量、温度、湿度为自变量,用MATLAB进行多元线性回归,建立自建点数据的矫正模型,模型校验效果达到预期。 相似文献
18.
研究了一种循环中和-分段沉淀处理酸性含铁废水的方法,使用该方法可以提高氢氧化铁沉淀渣的总铁品位,降低碱用量。某工业废水经4次循环处理,总铁含量达61.1%,达到铁矿石冶炼的工业品位. 相似文献
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张北试区降水规律与防沙尘暴对策 总被引：1，自引：0，他引：1
谷茂 《深圳职业技术学院学报》2002,1(1):1-6
本文明确了以张北为代表的坝上地区年降水量分布符合正态分布,其长期变化趋势存在20年的周期,有89.97％的年份年降水量≥300mm;月降水量高度集中且变异系数小,一年中70％的降水量集中在6、7、8三个月。在明确降水规律的基础上提出5项防沙尘暴对策。 相似文献