Automated impact device with non-synchronous impacts: a practical solution for modal testing during operation     

Zhi Chao Ong  Hong Cheet Lim  Anders Brandt 《浙江大学学报(A卷英文版)》2018,19(6):452-460

Previous study has shown that synchronization of phases between impacts and the cyclic load component should be avoided to improve the effectiveness of operational modal testing, i.e. impact-synchronous modal analysis in obtaining a cleaner frequency response function (FRF) estimation with fewer number of averages. However, avoiding the phase synchronization effect is rarely achievable with the current manual impact hammer because of the lack of control of the impact timing. We investigate how to improve FRF estimation in the presence of harmonic disturbances, such as those present in operating rotating machines. An auto impact device is therefore introduced to replace the manual impact hammer. This device ensures that impact intervals can be applied at non-synchronous instances with respect to the harmonic disturbance. We demonstrate that this new device is a viable option for operational modal testing. It allows significant improvement in FRF estimation and shows good correlation of modal extraction data with benchmark experimental modal analysis results.  相似文献   

Robust mixed H2/H∞ model predictive control for Markov jump systems with partially uncertain transition probabilities     

Yueyuan Zhang  Cheng-Chew Lim  Fei Liu 《Journal of The Franklin Institute》2018,355(8):3423-3437

This paper addresses the control problem for a class of discrete-time Markov jump linear systems with partially unknown transition probabilities using model predictive controller subject to external disturbances and input constraints. Our focus is on the design of a model predictive controller to stabilize the system with a given mixed H₂/H_∞ performance index. Sufficient conditions are derived in terms of a set of linear matrix inequalities. Examples are presented to demonstrate the effectiveness of the proposed controller design method.  相似文献   

Pre-movement and during-movement visual search behaviours vary depending on expertise and anxiety levels in ten-pin bowling     

Wan Xiu Goh  Bernice H. Y. Lim  Matthew James Wylde  Michele Macnaughton  Jia Yi Chow 《Journal of sports sciences》2018,36(18):2076-2086

This study investigated the pre-movement and during-movement visual search behaviour (VSB) and quiet eye (QE) of 11 elite versus 10 sub-elite ten-pin bowlers, performing under high-anxiety and low-anxiety conditions. Pre-movement and independent of expertise, bowlers had more fixations and directed them to more locations when performing under high-anxiety compared with low-anxiety. Elite bowlers fixated at more locations closer to the pins in pre-movement than during-movement, with pre-movement QE occurring mostly at the breakpoint and middle arrows. During movement however, bowlers fixated closer to the foul-line at the middle and right dots and arrows, with during-movement-QE occurring at the middle dots and right arrows. Elite bowlers recorded longer QE durations during-movement rather than pre-movement, albeit a later onset during the longish five-step approach prior to ball release compared with sub-elite bowlers. Our results suggest that QE during-movement instead of pre-movement could be more pertinent in differentiating expertise during sporting tasks with a long movement phase and far-aiming target. The relevance of pre-movement or movement-QE in characterising expertise and performance could therefore be sport-dependent. This should be considered when investigating skilled action and developing training programs for skill acquisition.  相似文献   

The effects of part-task and whole-task instructional approaches on acquisition and transfer of a complex cognitive skill     

Jung Lim  Robert A. Reiser  Zane Olina 《Educational technology research and development : ETR & D》2009,57(1):61-77

This study was designed to investigate the effects of two instructional approaches (whole-task versus part-task) and two levels of learner prior knowledge (lower versus higher) on learner acquisition and transfer of a complex cognitive skill. Participants were 51 undergraduate pre-service teachers. In the part-task condition, a complex skill (preparing a grade book using Excel) was decomposed into a series of smaller tasks, each of which was demonstrated and practiced separately. In the whole-task condition, which was based on the 4C/ID-model (van Merriënboer 1997), learners were exposed to the entire complex skill from the beginning of the instruction and were required to practice performing a series of whole tasks throughout the unit. Results indicated that the whole-task group performed significantly better than the part-task group on a skill acquisition test and a transfer test. Possible reasons for these findings and suggestions for future research are discussed.  相似文献   

Unpacking the hidden efficacies of learning in productive failure     

David Hung  Victor Chen  Seo Hong Lim 《Learning Inquiry》2009,3(1):1-19

This paper describes a framework for learning where learners undergo experimentations with the phenomena at hand according to progressive and staged goals. Bowling is used as a case study in this paper. The premise for experimentations is that learners can experience hidden efficacies, including the formation of “bad habits.” A distinction is made between productivity in learning and performance in terms of learning outcomes. In other words, productivity in learning may not necessarily manifest in successful performance, hence the term productive failure. To emphasize the need for self-regulation during problem-solving process, we discuss the movements within the productive–unproductive and success–failure dimensions through three-staged self-regulatory processes and draw implications to learning and instruction.  相似文献   

Organizational and cultural factors affecting international transfer of training     

Doo H. Lim 《Performance Improvement》1999,38(3):30-36

  相似文献   

Brain simulation and personhood: a concern with the Human Brain Project     

Daniel Lim 《Ethics and Information Technology》2014,16(2):77-89

The Human Brain Project (HBP) is a massive interdisciplinary project involving hundreds of researchers across more than eighty institutions that seeks to leverage cutting edge information and communication technologies to create a multi-level brain simulation platform (BSP). My worry is that some brain models running on the BSP will be persons. If this is right then not only will the in silico experiments the HBP envisions being carried on the BSP be unethical the mere termination of certain brain models running on the BSP will be unethical. To assess the possible personhood of certain brain simulations I consider John Searle’s critique of strong AI. In arguing that Searle’s critique fails I conclude that the HBP must tread carefully and devise strict rules on how research using the BSP ought to proceed.  相似文献   

Student experiences of assessment in two problem‐based dental curricula: Adelaide and Dublin     

Tracey Winning  Elaine Lim  Grant Townsend 《Assessment & Evaluation in Higher Education》2005,30(5):489-505

Dental students in third (n?=?35) and fifth years (n?=?50) at Adelaide and Trinity College Dental Schools were surveyed about their experiences of assessment and their perceptions of the importance of particular aspects of assessment. Students reported on their assessment experience within their programmes by describing a critical assessment incident and their response to it, and also rated assessment purposes and features using a 5‐point Likert scale of relative importance. The students described a range of assessment methods, including group assignments, vivas, laboratory assessment, and problem‐based learning tutorials, but written examinations/tests and clinical assessment were discussed most frequently. Negative assessment experiences were commonly noted. The two most frequently raised issues were lack of congruence between student and staff perceptions of performance, and not receiving adequate feedback. There were no significant differences between years or schools in students’ ratings of the importance of assessment purposes. Overall, the students rated the provision of feedback on learning and motivation for learning as the most important purposes (>?80%). Patient‐based scenarios were rated as the most important method for judging students’ learning (>?90%), whilst group‐work tasks were rated of little importance. Overall, students rated clear requirements and feedback as the most important characteristics for positive assessment outcomes. Students’ ratings of assessment purposes, characteristics and methods closely matched the features of good assessment practice found in the literature. However, their assessment experiences indicate the need for review of assessment in both schools, particularly related to student–staff expectations of performance levels, and the provision of feedback.  相似文献   

Effective integration of ICT in Singapore schools: pedagogical and policy implications   总被引：2，自引：0，他引：2  

Cher Ping Lim 《Educational technology research and development : ETR & D》2007,55(1):83-116

This paper examines and analyses where and how information and communication technologies (ICT) are integrated in Singapore schools to engage students in higher-order thinking activities. Taking the activity system as a unit of analysis, the study documents the actual processes and sociocultural elements that engage students in higher-order thinking. By employing methods such as observations, focus group discussions with students, and face-to-face interviews with teachers, ICT-coordinators and principals, an account of how the activity systems within and between classrooms, and the schools are generated. Based on the analysis of the data from 10 schools, issues in the learning environment are discussed: Necessary (classroom management and orienting activities) and sufficient conditions (scaffolding activities and supporting school policies) for effective ICT integration in the classroom. The account also highlights the constraints of time and lack of knowledge and experience in the contexts that the teachers are working under, and how these constraints are addressed by supporting school policies in the larger sociocultural setting of the school. This account provides a sample of pedagogical and sociocultural issues that are discussed over the course and at the end of the project. Like a good guidebook, the study sensitizes the audience to what is likely to happen given a particular objective, constraint, or design.  相似文献   

Provision of early field experiences for teacher candidates in Singapore and how it can contribute to teacher resilience and retention     

Pak Tee Ng  Kam Ming Lim  Ee Ling Low  Chenri Hui 《Teacher Development》2018,22(5):632-650

While teacher retention is a pressing issue for many jurisdictions, Singapore has a relatively low teacher attrition rate. Drawing on the experiences of student teachers from the sole institute for pre-service teacher education in Singapore, this article argues that it is important to expose teacher candidates to a substantial period of school experience as part of the teacher recruitment process. Before they are officially enrolled into pre-service teacher education, the Ministry of Education in Singapore requires all teacher candidates in the Postgraduate Diploma of Education program to go through a compulsory school stint. The authors' research findings show that this exposure to the realities and complexities of teaching can be an important contributor to teacher retention in terms of assessing and promoting teacher candidates’ resilient qualities, such as passion for teaching, self-efficacy beliefs, and positive emotion. In other words, early field experiences can help teacher candidates understand themselves as teachers and assess their own suitability for a teaching career. This study sheds new light on the policies and practices of teacher retention and teacher recruitment strategies.  相似文献