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291.
Gongjun Xu Chun Wang Zhuoran Shang 《The British journal of mathematical and statistical psychology》2016,69(3):291-315
There has recently been much interest in computerized adaptive testing (CAT) for cognitive diagnosis. While there exist various item selection criteria and different asymptotically optimal designs, these are mostly constructed based on the asymptotic theory assuming the test length goes to infinity. In practice, with limited test lengths, the desired asymptotic optimality may not always apply, and there are few studies in the literature concerning the optimal design of finite items. Related questions, such as how many items we need in order to be able to identify the attribute pattern of an examinee and what types of initial items provide the optimal classification results, are still open. This paper aims to answer these questions by providing non‐asymptotic theory of the optimal selection of initial items in cognitive diagnostic CAT. In particular, for the optimal design, we provide necessary and sufficient conditions for the Q ‐matrix structure of the initial items. The theoretical development is suitable for a general family of cognitive diagnostic models. The results not only provide a guideline for the design of optimal item selection procedures, but also may be applied to guide item bank construction. 相似文献
292.
Tungsten (W) is cited as a candidate first-wall material in fusion reactors owing to its outstanding thermal properties and erosion resistance. An important issue is that the energetic isotopes of hydrogen, tritium (T) and deuterium (D) and helium (He) particles damage the surface of W in fusion reactors. He particles cause more notable damage than D or T because the binding energy of defects and He is larger than that of defects and D or T. In this study, well-annealed W specimens were implanted with 5 keV He ions at room temperature and irradiation dosages of 1.0 × 1020 and 2.5 × 1021 ions/m2. Then, thermal desorption spectroscopy analysis was performed by heating the samples to 1973 K at a ramping rate of 0.5 K/s. Thermal desorption of He in the sample irradiated with a low dosage occurred at 1400 and 1960 K, whereas that in the sample irradiated with a high dosage occurred at 740, 1050 and 1500 K. According to the microstructures observed using transmission electron microscopy, both peaks in the former case were attributed to He de-trapping from irradiation to nduced helium-vacancy clusters of different sizes, whereas the peaks in the latter case were attributed to He de-trapping from surface defects, irradiation-induced dislocation loops and tiny helium-vacancy clusters, respectively. 相似文献
293.
C. Liu;X. Qin;B. Liu;X. Xu;A. Deng;Y. Zhang;Z. Zhang;W. Zhang; 《British journal of psychology (London, England : 1953)》2024,75(4):1055-1062
A pectin lyase gene pnlzj5b from Aspergillus niger ZJ5 was identified and overexpressed successfully in Pichia pastoris. Recombinant PNLZJ5B exhibited high activity towards citrus pectin (150 U ml−1). Through further codon optimization, the expression efficiency of PNLZJ5B in P. pastoris increased to 3·5-fold (532/150 U ml−1). PNLZJ5B was purified by ultrafiltration, anion exchange and gel chromatography. It showed optimal activity and good stability at 58°C and pH 4·5. PNLZJ5B activity improved with increasing degrees of methyl esterification of pectin. The Km and Vmax values were 0·81 mg ml−1 and 372·8 μmol min−1 mg−1, respectively. In addition, PNLZJ5B effectively decreased the viscosity of apple juice. Compared with commercial pectin lyase, PNLZJ5B obtained a higher juice volume. These favourable enzymatic properties of PNLZJ5B show potential utility in juice-processing applications and other food-related fields. 相似文献
294.
Chun Wang Gongjun Xu 《The British journal of mathematical and statistical psychology》2015,68(3):456-477
In real testing, examinees may manifest different types of test‐taking behaviours. In this paper we focus on two types that appear to be among the more frequently occurring behaviours – solution behaviour and rapid guessing behaviour. Rapid guessing usually happens in high‐stakes tests when there is insufficient time, and in low‐stakes tests when there is lack of effort. These two qualitatively different test‐taking behaviours, if ignored, will lead to violation of the local independence assumption and, as a result, yield biased item/person parameter estimation. We propose a mixture hierarchical model to account for differences among item responses and response time patterns arising from these two behaviours. The model is also able to identify the specific behaviour an examinee engages in when answering an item. A Monte Carlo expectation maximization algorithm is proposed for model calibration. A simulation study shows that the new model yields more accurate item and person parameter estimates than a non‐mixture model when the data indeed come from two types of behaviour. The model also fits real, high‐stakes test data better than a non‐mixture model, and therefore the new model can better identify the underlying test‐taking behaviour an examinee engages in on a certain item. 相似文献
295.
L. Song X.J. Xu C. Peng Y.L. Wang Y.F. Liang S.L. Shang 《Philosophical Magazine Letters》2015,95(2):85-91
Microstructure and deformation mechanisms at a nanoindentation in the lamellar colony of high Nb containing TiAl alloy have been studied using the focused ion beam and the transmission electron microscopy. Considerable deformation twins are observed around the nanoindentation, and a strain gradient is generated. A continuous change in the bending angle of the lamellar structure can be derived, and a strain-induced grain refinement process is observed as various active deformations split the γ grains into subgrains. In addition to all possible deformation mechanisms (ordinary dislocation, super-dislocation and deformation twining) activated due to the heavy plastic deformation, a 6-layer hexagonal (6H) long-period stacking ordered structure is identified for the first time near the contact zone and is thought to be closely related to the glide of partial dislocations. 相似文献
296.
Anneke D. M. Haddad Mengran Xu Sophie Raeder Jennifer Y. F. Lau 《Cognition & emotion》2013,27(5):914-922
Common and persistent fears may emerge through learning mechanisms such as fear conditioning and generalisation. Although there have been extensive studies of these learning processes in healthy but also psychiatric samples, many of the tasks used to produce conditioning and assess generalisation either use painful and aversive stimuli as the unconditioned stimuli (UCS), or suffer from poor belongingness between the conditioned stimuli and the UCS. Here, we present novel data from a paradigm designed to examine fear conditioning and generalisation in healthy individuals. Two female faces served as conditioned threat cue (CS+) and conditioned safety cue (CS?) respectively. The CS+ was paired repeatedly with a fearful, screaming face (unconditioned stimulus). Generalisation included intermediate faces which varied in their similarity to the CS+ and CS?. We measured eyeblink startle reflex and self-reported ratings. Acquired fear of the CS+ generalised to intermediate stimuli in proportion to their perceptual similarity to the CS+. Our findings demonstrate how fears of new individuals may develop based on resemblance to others with whom an individual has had negative experiences. The paradigm offers new opportunities for probing the role of generalisation in the emergence of common and persistent fears. 相似文献
297.
Weerasak Chonchaiya Twila Tardif Xiaoqin Mai Lin Xu Mingyan Li Niko Kaciroti Paul R. Kileny Jie Shao Betsy Lozoff 《Developmental science》2013,16(2):159-172
Auditory processing capabilities at the subcortical level have been hypothesized to impact an individual's development of both language and reading abilities. The present study examined whether auditory processing capabilities relate to language development in healthy 9‐month‐old infants. Participants were 71 infants (31 boys and 40 girls) with both Auditory Brainstem Response (ABR) and language assessments. At 6 weeks and/or 9 months of age, the infants underwent ABR testing using both a standard hearing screening protocol with 30 dB clicks and a second protocol using click pairs separated by 8, 16, and 64‐ms intervals presented at 80 dB. We evaluated the effects of interval duration on ABR latency and amplitude elicited by the second click. At 9 months, language development was assessed via parent report on the Chinese Communicative Development Inventory ‐ Putonghua version (CCDI‐P). Wave V latency z‐scores of the 64‐ms condition at 6 weeks showed strong direct relationships with Wave V latency in the same condition at 9 months. More importantly, shorter Wave V latencies at 9 months showed strong relationships with the CCDI‐P composite consisting of phrases understood, gestures, and words produced. Likewise, infants who had greater decreases in Wave V latencies from 6 weeks to 9 months had higher CCDI‐P composite scores. Females had higher language development scores and shorter Wave V latencies at both ages than males. Interestingly, when the ABR Wave V latencies at both ages were taken into account, the direct effects of gender on language disappeared. In conclusion, these results support the importance of low‐level auditory processing capabilities for early language acquisition in a population of typically developing young infants. Moreover, the auditory brainstem response in this paradigm shows promise as an electrophysiological marker to predict individual differences in language development in young children. 相似文献
298.
Although a large body of research has documented country‐of‐origin effects, very few works have inquired systematic differences in the content of national stereotypes that shape attitudes toward foreign products and their manufacturers. Drawing from the stereotype content model, the authors propose that the often ignored warmth dimension of the origin country is as important as (sometimes more important than) the well‐studied competence dimension in certain situations. As shown in two studies, perceived warmth of the origin country predicts purchase intention in normal situations as well as after product failure. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
299.
AMT（Autobiographical Memory Test）主要用于测量自传体记忆的概括性和具体性特征,已经被诸多研究者所采用,然而关于测验方法的具体问题鲜有研究,其中测验的关键部分线索词的选择和匹配更没有设计较严谨的量化研究。目的：分析与自传体记忆相关的线索词的多种维度,并通过统计指标的计算选取多种维度上最为匹配的线索词,形成中文版的AMT测验材料。方法：采用专家评定法,选取差异系数（cv）作为线索词的计算指标,并设计了差异系数的函数公式,把维度作为参数来计算情绪词的多维参数的函数值,最终作为线索词选择的依据。结果：依据每个词汇的差异系数函数值选择了三个维度上最为匹配的词汇,得到了以15个中文线索词为测验材料的AMT测验工具。 相似文献
300.
Drawing on the social information process perspective, we hypothesized that transformational leadership fosters psychological safety climate leading to enhanced individual-level creative process engagement. Furthermore, psychological safety climate was hypothesized to strengthen the relationship between creative process engagement and employee creativity. The hypothesized model was tested with data obtained from a sample of 358 employees and their supervisors from two organizations in the People’s Republic of China. Results of hierarchical linear modeling analysis revealed that transformational leadership influenced creative process engagement via psychological safety climate. Furthermore, psychological safety climate moderated the creative process engagement–creativity relationship such that the relationship was stronger in groups with high rather than low psychological safety climate. 相似文献