Approximating Test Statistics Using Eigenvalue Block Averaging     

Njål Foldnes  Steffen Grønneberg 《Structural equation modeling》2018,25(1):101-114

We introduce and evaluate a new class of approximations to common test statistics in structural equation modeling. Such test statistics asymptotically follow the distribution of a weighted sum of i.i.d. chi-square variates, where the weights are eigenvalues of a certain matrix. The proposed eigenvalue block averaging (EBA) method involves creating blocks of these eigenvalues and replacing them within each block with the block average. The Satorra–Bentler scaling procedure is a special case of this framework, using one single block. The proposed procedure applies also to difference testing among nested models. We investigate the EBA procedure both theoretically in the asymptotic case, and with simulation studies for the finite-sample case, under both maximum likelihood and diagonally weighted least squares estimation. Comparison is made with 3 established approximations: Satorra–Bentler, the scaled and shifted, and the scaled F tests.  相似文献   

Innovation paths and the innovation performance of low-technology firms—An empirical analysis of German industry     

Eva Kirner  Steffen Kinkel  Angela Jaeger 《Research Policy》2009,38(3):447-458

This paper analyses innovation paths and the innovation performance of low-technology firms in comparison to medium- and high-technology firms. Firstly, it shows that low-, medium- and high-technology sectors consist of a considerable mix of low-, medium- and high-technology firms. Thus, it is necessary to look at the firm level when analysing how innovation patterns differ depending on the level of R&D intensity. Secondly, the product and process innovation performance of low-technology firms in German industry is analysed based on data from 1663 firms in the German Manufacturing Survey 2006, applying a set of both product and process related innovation output indicators. The empirical results show that low-technology manufacturing firms lag behind their medium- and high-tech counterparts regarding their product and service innovation performance, to a large degree on purely definitional grounds, but that they seem to perform equally well and in some respects even better at process innovation.  相似文献   

Three-dimensional CoM energetics,pelvis and lower limbs joint kinematics of uphill treadmill running at high speed     

Masamichi Okudaira  Steffen Willwacher  Seita Kuki  Kaito Yamada  Takuya Yoshida  Satoru Tanigawa 《Journal of sports sciences》2020,38(5):518-527

ABSTRACT

The purpose of this study was to investigate the effects of slope on three-dimensional running kinematics at high speed. Thirteen male sprinters ran at high speed (7.5 m/s) on a motorised treadmill in each a level and a 5.0% slope condition. Three-dimensional motion analysis was conducted to compare centre of mass (CoM) energetics, pelvis segment and lower limb joints kinematics. We found that contact time was not affected by the slope, whereas flight time and step length were significantly shorter in uphill compared to level running. Uphill running reduced negative CoM work and increased positive CoM work compared to level running. Ankle, knee and hip joints were more flexed at initial ground contact, but only the knee was more extended at the end of stance in uphill compared to level running. Additionally, the hip joint was more abducted, and the free leg side of the pelvis was more elevated at the end of stance in uphill running. Our results demonstrate that joint motion must be developed from a more flexed/adducted position at initial contact through a greater range of motion compared to level running in order to meet the greater positive CoM work requirements in uphill running at high speed.  相似文献   

Validity of block start performance without arm forces or by kinematics-only methods     

Mitsuo Otsuka  Wolfgang Potthast  Steffen Willwacher  Jan-Peter Goldmann  Toshiyuki Kurihara  Tadao Isaka 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(3):229-244

The purpose of this study was to validate the calculation of reaction time (RT) and normalised power in block starts without considering arm ground reaction forces (GRFs) or using two kinematics-only methods. The RT and normalised power in the action phase were calculated using four different methods: using GRFs of arms and legs by force plates (whole F-based method), which can be regarded as the most valid method, using GRFs of legs captured by force plates (legs F-based method), using position of the centre of mass of the entire body captured by high-speed cameras (whole P-based method), and using only a partial subset of segment position (partial P-based method). Bland–Altman plots demonstrated that the RT of the legs F-based method was not similar to that of the whole F-based method: the mean difference was 7.4 ms and the 95% limits of agreement was?45.1 to 59.8 ms, and it was the least valid method for the calculation among the four methods. In contrast, the normalised power was more valid in the legs F-based method, followed by whole and partial P-based methods. This information will help researchers and practitioners to decide upon their analysis methods when analysing block start performance.  相似文献   

Lower limb joint kinetics in the starting blocks and first stance in athletic sprinting   总被引：1，自引：1，他引：0  

Adam Brazil  Timothy Exell  Cassie Wilson  Steffen Willwacher  Ian Bezodis  Gareth Irwin 《Journal of sports sciences》2017,35(16):1629-1635

The aim of this study was to examine lower limb joint kinetics during the block and first stance phases in athletic sprinting. Ten male sprinters (100 m PB, 10.50 ± 0.27 s) performed maximal sprint starts from blocks. External force (1000 Hz) and three-dimensional kinematics (250 Hz) were recorded in both the block (utilising instrumented starting blocks) and subsequent first stance phases. Ankle, knee and hip resultant joint moment, power and work were calculated at the rear and front leg during the block phase and during first stance using inverse dynamics. Significantly (P < 0.05) greater peak moment, power and work were evident at the knee joint in the front block and during stance compared with the rear block. Ankle joint kinetic data significantly increased during stance compared with the front and rear block. The hip joint dominated leg extensor energy generation in the block phase (rear leg, 61 ± 10%; front leg, 64 ± 8%) but significantly reduced during stance (32 ± 9%), where the ankle contributed most (42 ± 6%). The current study provides novel insight into sprint start biomechanics and the contribution of the lower limb joints towards leg extensor energy generation.  相似文献   

The relationship between physical activity,fitness, physical complaints and BMI in German adults – results of a longitudinal study     

Susanne A. Tittlbach  Darko Jekauc  Steffen C. E. Schmidt  Alexander Woll  Klaus Bös 《European Journal of Sport Science》2017,17(8):1090-1099

Objectives: This study’s aims were to describe the development of physical activity, physical fitness (PF), subjective (physical complaints (PC)) and objective (Body mass index (BMI)) health measures and to examine the relationship between the development trajectories. In addition, the study also aimed to assess the influence of sociodemographic determinants (age, sex, socioeconomic status (SES)) in German adults over a period of 18 years. Methods: The longitudinal study population comprises of 721 men and women, aged 33–76 years over the study period. There was self-report of physical activity and PC and testing of physical fitness and BMI in each study year (1992, 1997, 2002 and 2010). Latent growth curve models were used to analyse the development. Results: Physical activity slightly increased while fitness, PC and BMI worsened over the course of 18 years. Sex, age and SES play important roles concerning physical activity, fitness and health. Several integrative associations could be detected between physical activity, fitness, PC and BMI as well as their trajectories. In particular, high initial levels of physical activity and fitness protect from high PC and BMI.The slope of physical activity was not significantly associated with slopes of fitness, PC and BMI. However, increase of fitness resulted in decrease of PC. Conclusions: A general positive development regarding the amount of physical activity could be detected. However, if it is only an unsystematic increase of physical activity, this is not in itself enough to achieve health benefits. The strengthening of fitness should be focused when increasing physical activity, since only then a health benefit is possible.  相似文献   

An Attachment Model of University Connectedness     

Steffen Wilson  Jonathan Gore 《Journal of Experimental Education》2013,81(2):178-198

Students with high levels of connectedness to the university have been found to be more likely to complete their college degree than are students with low levels of university connectedness. This study examined the role of parental and peer attachment as distal predictors of school connectedness. As predicted, it was found that attachment style to parents predicted attachment style to peers. An avoidant attachment style to peers predicted negative perceptions of peer support and support services. An anxious attachment style to peers predicted negative perceptions of faculty support. Perceptions of peer support, support services, and faculty support then predicted feelings of connectedness to the university. Classroom comfort also predicted university connectedness, although it was not found to be related to attachment style to parents or peers. Implications for college students and college/university administrators are discussed.  相似文献   

From the open road to the high seas? Piracy,damnation and resistance in academic consumption of publishing     

Armin Beverungen  Steffen Böhm 《普罗米修斯》2013,31(3):241-247

Armin Beverungen conducts research on how universities retain their charitable status in a market environment, and on the teaching of ethics in business schools. Steffen Böhm has a particular interest in the economics and management of sustainability. He has also founded an open access journal and an open access press, MayFlyBooks. Christopher Land works on artists and the management of their creativity.  相似文献   

Evaluating an Automatically Scorable, Open-Ended Response Type for Measuring Mathematical Reasoning in Computer-Adaptive Tests     

Randy Elliot Bennett  Manfred Steffen  Mark Kevin Singley  Mary Morley  Daniel Jacquemin 《Journal of Educational Measurement》1997,34(2):162-176

The first generation of computer-based tests depends largely on multiple-choice items and constructed-response questions that can be scored through literal matches with a key. This study evaluated scoring accuracy and item functioning for an open-ended response type where correct answers, posed as mathematical expressions, can take many different surface forms. Items were administered to 1,864 participants in field trials of a new admissions test for quantitatively oriented graduate programs. Results showed automatic scoring to approximate the accuracy of multiple-choice scanning, with all processing errors stemming from examinees improperly entering responses. In addition, the items functioned similarly in difficulty, item-total relations, and male-female performance differences to other response types being considered for the measure.  相似文献   

The role of socioeconomic background and prior achievement for students’ perception of teacher support     

Cansu Atlay  Nicole Tieben  Benjamin Fauth  Steffen Hillmert 《British Journal of Sociology of Education》2019,40(7):970-991

Abstract

Building on the sociological work by Lareau, this study examined the association between students’ socioeconomic background, prior achievement and the perception of teacher support within the classroom. We expected that students from higher socioeconomic backgrounds would be more critical about the support they receive in the classroom and rate their teachers more negatively, while those with higher prior achievement would perceive teacher support more positively. Multilevel models confirmed that there is a negative association between wealth and students’ perception of two dimensions of teacher support, and a negative association between parental educational attainment and one dimension of teacher support. Our findings were in line with the ‘sense of entitlement’ theory by Lareau. Having higher prior achievement was associated with a more positive perception of teacher support, but did not seem to interact with socioeconomic background.  相似文献