汽车发动机可变式气门驱动机构     

杨军  高吕和 《北京工业职业技术学院学报》2004,3(4):75-78

阐述了配气相位对发动机性能的影响,说明了车用发动机对配气相位的要求及采用可变气门驱动机构的优点.着重介绍了本田公司的可变气门驱动机构VTEC的结构和工作原理.  相似文献   

Attracting solutions in crowdsourcing contests: The role of knowledge distance,identity disclosure,and seeker status     

Patrick Pollok  Dirk Lüttgens  Frank T. Piller 《Research Policy》2019,48(1):98-114

We investigate in the context of crowdsourcing how seekers can increase open innovation performance, measured as received solver attention, by making two strategic decisions: selecting innovation tasks that are well suited for crowdsourcing and choosing between the potentials of status signalling through identity disclosure versus enjoying the benefits of anonymity. Drawing on uncertainty reduction theory, we suggest that a well-articulated problem statement reduces uncertainties of potential solvers and increases their willingness to participate. We argue that the ability of seekers to draft high-quality problem statements depends on the distance between the problem domain and their current knowledge stock. An analysis of 637 crowdsourcing projects finds that problem-seeker knowledge distance and received solver attention are curvilinear related such that moderate levels of knowledge distance maximize solver participation. However, high-status seekers who engage in identity-based status signalling are able to benefit from crowdsourcing across all levels of problem-seeker knowledge distance.  相似文献   

Profile and Motivations of Registered Whole-Body Donors in Turkey: Istanbul University Experience     

İlke Ali Gürses  Ahmet Ertaş  Başak Gürtekin  Osman Coşkun  Mehmet Üzel  Özcan Gayretli  Mehmet Selman Demirci 《Anatomical sciences education》2019,12(4):370-385

Little is known regarding the profiles of whole body donors in Muslim majority countries where donation is scarce. Therefore, this study aims to profile registered donors in Turkey by means of a survey. The explored data could be used to improve ongoing campaign efforts and ethical practices such as commemoration services. Registered donors of the donation programs at the two faculties of medicine of Istanbul University were compared with the national population and a cluster analysis was performed to reveal any concealed sub-groups. Data from 188 respondents were analyzed. The majority of registered donors were married (42%), male (65.4%), aged over 50 years (76%), held a tertiary education degree (49.7%), and were irreligious (58.5%). Cluster analysis revealed two groups with significantly different educational levels, marital statuses, and religious choices. Regarding whether their bodies could be used for education or research, the majority (64.5%) of the respondents left the decision to the anatomy department. Similarly, 73.8% approved indefinite use of their organs, body parts and/or skeletons. The respondents were also willing to share their medical history (94.2%) and personal information (81.6%) if needed. Motivational themes for body donation including usefulness, impermanence, religion, awareness, and kinship were devised after a thematic analysis. Among the respondents, 56.5% were registered organ donors and 63.3% were frequent blood donors. The results of this study provide data that may help revising informed consent forms, developing and implementing thanksgiving ceremonies, and selecting additional targets for supporting body donation campaign activities such as organ and blood donation units.  相似文献   

The link between student-perceived teacher talk and student enjoyment,anxiety and discursive engagement in the classroom     

Gaowei Chen  Jiahong Zhang  Carol K. K. Chan  Sarah Michaels  Lauren B. Resnick  Xiaorui Huang 《British Educational Research Journal》2020,46(3):631-652

This study seeks to understand the emotional connection of teachers' academically productive talk (APT) with student learning from the students' perspective. Using a sample of 2,225 students (N_{7th grade} = 1,146 and N_{8th grade} = 1,079) from 16 middle schools in a city of China, we investigate the relationship between students' perceptions of their teachers’ APT, student emotions (enjoyment and anxiety) and their discursive engagement with others in the mathematics classroom. Results from structural equation modelling and mediation analysis show that after controlling for gender, family resources and mathematics achievement, student-perceived teacher APT was positively associated with their discursive engagement with classmates. Furthermore, student enjoyment and anxiety in class mediated the relationship between student-perceived teacher APT and student discursive engagement with classmates. Multi-group analysis revealed that the model was invariant across genders and grades, indicating that the associations were applicable to male and female students as well as to seventh and eighth graders. These findings shed light on the emotional relationship of teacher APT with the discursive engagement of their students. Although prior research observes a positive relationship between teacher productive classroom talk and student discursive engagement primarily through classroom observations and teacher reflections, this study provides evidence from the students’ perspective and highlights the mediating role of student emotions in the relationship.  相似文献   

Teaching a blind student anatomy during the Covid-19 pandemic     

Georga J. Longhurst B.Sc. .  M.Sc.  P.G.Cert.H.B.E.  S.P.Cert.  F.H.E.A. 《Anatomical sciences education》2021,14(5):586-589

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Effects of purposeful soccer heading on circulating small extracellular vesicle concentration and cargo     

Eric R. Muoz  Jaclyn B. Caccese  Brittany E. Wilson  Kyle T. Shuler  Fernando V. Santos  Carolina T. Cabn  John J. Jeka  Dianne Langford  Matthew B. Hudson 《运动与健康科学(英文)》2021,10(2):122

BackgroundConsidering the potential cumulative effects of repetitive head impact (HI) exposure, we need sensitive biomarkers to track short- and long-term effects. Circulating small extracellular vesicles (sEVs) (<200 nm) traffic biological molecules throughout the body and may have diagnostic value as biomarkers for disease. The purpose of this study was to identify the microRNA (miRNA) profile in circulating sEVs derived from human plasma following repetitive HI exposure.MethodsHealthy adult (aged 18–35 years) soccer players were randomly assigned to one of 3 groups: the HI group performed 10 standing headers, the leg impact group performed 10 soccer ball trapping maneuvers over 10 min, and the control group did not participate in any soccer drills. Plasma was collected before testing and 24 h afterward, and sEVs were isolated and characterized via nanoparticle tracking analysis. Next-generation sequencing was utilized to identify candidate miRNAs isolated from sEVs, and candidate microRNAs were analyzed via quantitative polymerase chain reaction. In silico target prediction was performed using TargetScan (Version 7.0; targetscan.org) and miRWalk (http://mirwalk.umm.uni-heidelberg.de/) programs, and target validation was performed using luciferase reporter vectors with a miR-7844-5p mimic in human embryonic kidney (HEK) 293T/17 cells.ResultsPlasma sEV concentration and size were not affected across time and group following repetitive HI exposure. After 24 h, the HI read count from next-generation sequencing showed a 4-fold or greater increase in miR-92b-5p, miR-423-5p, and miR-24-3p and a 3-fold or greater decrease in miR-7844-5p, miR-144-5p, miR-221-5p, and miR-22-3p. Analysis of quantitative polymerase chain reaction revealed that leg impact did not alter the candidate miRNA levels. To our knowledge, miR-7844-5p is a previously unknown miRNA. We identified 8 miR-7844-5p mRNA targets: protein phosphatase 1 regulatory inhibitor subunit 1B (PPP1R1B), LIM and senescent cell antigen-like domains 1 (LIMS1), autophagy-related 12 (ATG12), microtubule-associated protein 1 light chain 3 beta (MAP1LC3B), integrin subunit alpha-1 (ITGA1), mitogen-activated protein kinase 1 (MAPK1), glycogen synthase kinase 3β (GSK3β), and mitogen-activated protein kinase 8 (MAPK8).ConclusionCollectively, these data indicate repetitive HI exposure alters plasma sEV miRNA content, but not sEV size or number. Furthermore, for the first time we demonstrate that previously unknown miR-7844-5p targets mRNAs known to be involved in mitochondrial apoptosis, autophagy regulation, mood disorders, and neurodegenerative disease.  相似文献   

Correlation analysis of performance measures for multi-label classification     

Rafael B. Pereira  Alexandre Plastino  Bianca Zadrozny  Luiz H.C. Merschmann 《Information processing & management》2018,54(3):359-369

In many important application domains, such as text categorization, scene classification, biomolecular analysis and medical diagnosis, examples are naturally associated with more than one class label, giving rise to multi-label classification problems. This fact has led, in recent years, to a substantial amount of research in multi-label classification. In order to evaluate and compare multi-label classifiers, researchers have adapted evaluation measures from the single-label paradigm, like Precision and Recall; and also have developed many different measures specifically for the multi-label paradigm, like Hamming Loss and Subset Accuracy. However, these evaluation measures have been used arbitrarily in multi-label classification experiments, without an objective analysis of correlation or bias. This can lead to misleading conclusions, as the experimental results may appear to favor a specific behavior depending on the subset of measures chosen. Also, as different papers in the area currently employ distinct subsets of measures, it is difficult to compare results across papers. In this work, we provide a thorough analysis of multi-label evaluation measures, and we give concrete suggestions for researchers to make an informed decision when choosing evaluation measures for multi-label classification.  相似文献   

No public value without a valued public     

Bettina Lis  Heinz-Werner Nienstedt  Christoph Günster 《媒体管理杂志》2018,20(1):25-50

This study aims to enlighten the controversial discussion about the term public value in an innovative way. Instead of normative pronouncements and paternalistic posits, this study combines a theoretical, literature-based conception with an empirical quantitative approach. For this, the key term, public value, is split into its constituent parts of customer value and citizen value and is transformed into measurable attributes. By means of a choice-based conjoint analysis on panel data for Germany and the United Kingdom, we explore which performance attributes of public service broadcasters are the most important. Based on the results, we create a conception of public value from the perspective of the license fee payers as the main stakeholder of public service broadcasters. Our findings may unlock existing potential to increase our understanding of what is meant by the term public value.  相似文献   

Outdoor life,nature experience,and sports in Norway: tensions and dilemmas in the preservation and use of urban forest     

Kirsti Pedersen Gurholt  Trygve B. Broch 《Sport in Society》2019,22(4):573-588

Abstract

How should contemporary societies promote physical activity in nature and preservation of the natural environment? Outdoor life occupies a central and contested position on this question in the Nordic countries. In Norway, a 1957 Act of Parliament took a major step by guaranteeing free public access to both public and private uncultivated land. This article explores the media debate that raged in 2008–2009, when the national government proposed new legislation intended to promote outdoor life, sport, nature experience and urban forest preservation around Oslo, Norway’s capital. Applying narrative and discourse methodologies, this case study reveals how the media debate evolved from an initial cacophony of voices into a schism between advocates of nature preservation and advocates of sport. The controversy explored here is increasingly relevant throughout all of Europe: how to encourage urban active living, sustainable recreation and democratic citizenship that embody distinct social practices, identities, emotional bonds and symbolic meaning.  相似文献   

Cut points of the Actigraph GT9X for moderate and vigorous intensity physical activity at four different wear locations     

Matthew B. Rhudy  Scott B. Dreisbach  Matthew D. Moran  Marissa J. Ruggiero  Praveen Veerabhadrappa 《Journal of sports sciences》2020,38(5):503-510

ABSTRACT

Accelerometer cut points are an important consideration for distinguishing the intensity of activity into categories such as moderate and vigorous. It is well-established in the literature that these cut points depend on a variety of factors, including age group, device, and wear location. The Actigraph GT9X is a newer model accelerometer that is used for physical activity research, but existing cut points for this device are limited since it is a newer device. Furthermore, there is not existing data on cut points for the GT9X at the ankle or foot locations, which offers some potential benefit for activities that do not involve arm and/or core motion. A total of N = 44 adults completed a four-stage treadmill protocol while wearing Actigraph GT9X sensors at four different locations: foot, ankle, wrist, and hip. Metabolic Equivalent of Task (MET) levels assessed by indirect calorimetry along with Receiver Operating Characteristic (ROC) curves were used to establish cut points for moderate and vigorous intensity for each wear location of the GT9X. Area under the ROC curves indicated high discrimination accuracy for each case.  相似文献