Visual attention for solving multiple-choice science problem: An eye-tracking analysis

This study employed an eye-tracking technique to examine students’ visual attention when solving a multiple-choice science problem. Six university students participated in a problem-solving task to predict occurrences of landslide hazards from four images representing four combinations of four factors. Participants’ responses and visual attention were recorded by an eye tracker. Participants were asked to think aloud during the entire task. A 4 (options) × 4 (factors) repeated measures design, two paired t-tests and effect sizes analyses were conducted to compare the fixation duration between chosen and rejected options and between relevant and irrelevant factors. Content analyses were performed to analyze participants’ responses and think aloud protocols and to examine individual’s Hot Zone image. Finally, sequential analysis on fixated LookZones was further utilized to compare the scan patterns between successful and unsuccessful problem solvers. The results showed that, while solving an image-based multiple-choice science problem, students, in general, paid more attention to chosen options than rejected alternatives, and spent more time inspecting relevant factors than irrelevant ones. Additionally, successful problem solvers focused more on relevant factors, while unsuccessful problem solvers experienced difficulties in decoding the problem, in recognizing the relevant factors, and in self-regulating of concentration. Future study can be done to examine the reliability and the usability of providing adaptive instructional scaffoldings for problem solving according to students’ visual attention allocations and transformations in a larger scale. Eye-tracking techniques are suggested to be used to deeply explore the cognitive process during e-learning and be applied to future online assessment systems.     

Ultradrawing properties of ultrahigh‐ molecular‐weight polyethylene/carbon nanotube fibers prepared at various formation temperatures

The influence of formation temperature on the ultradrawing properties of ultrahigh‐molecular‐weight polyethylene/carbon nanotube (UHMWPE/CNT) fiber specimens is investigated. Gel solutions of UHMWPE/CNT with various CNT contents were gel‐spun at the optimum concentration and temperature but were cooled at varying formation temperatures in order to improve the ultradrawing and tensile properties of the UHMWPE/CNT composite fibers. The achievable draw ratio (D_ra) values of UHMWPE/CNT as‐prepared fibers reach a maximum when they are prepared with the optimum CNT content and formation temperature. The D_ra value of UHMWPE/CNT as‐prepared fibers produced using the optimum CNT content and formation temperature is about 33% higher than that of UHMWPE as‐prepared fibers produced using the optimum concentration and formation temperature. The percentage crystallinity (W_c) and melting temperature (T_m) of UHMWPE/CNT as‐prepared fiber specimens increase significantly as the formation temperature increases. In contrast, W_c increases but T_m decreases significantly as the CNT content increases. Dynamic mechanical analysis of UHMWPE and UHMWPE/CNT fiber specimens exhibits particularly high α‐transition and low β‐transition, wherein the peak temperatures of α‐transition and β‐transition increase dramatically as the formation temperature increases and/or CNT content decreases. In order to understand these interesting drawing, thermal and dynamic mechanical properties of the UHMWPE and UHMWPE/CNT as‐prepared fiber specimens, birefringence, morphological and tensile studies of as‐prepared and drawn fibers were carried out. Possible mechanisms accounting for these interesting properties are proposed. Copyright © 2010 Society of Chemical Industry     

42MnVRE非调质钢的研制与应用

在许多领域所用的钢材由于要求进行调质处理，因此工序复杂，成本升高。为此，人们从７０年代开始在不断开发一系列的非调质钢来替代某些调质钢，以达到降低成本的目的。目前，国内的模具、汽车、机械等行业的许多材料是４５调质钢，为减少工序，降低成本，本研究课题旨在...     

A novel single-phase self-regulated self-excited inductiongenerator using a three-phase machine

This paper presents a steady-state analysis of a novel single-phase self-regulated self-excited induction generator which employs a three-phase machine. Performance equations are derived using the method of symmetrical components, while the pattern search method of Hooke and Jeeves is used for the determination of the machine variables. The advantages of the generator include simple circuit configuration, small voltage regulation, good phase balance, and large power output. With an appropriate choice of the series and shunt capacitances, a nearly balanced operating condition can be obtained for a certain load. The theoretical analysis is validated by experiments performed on a small induction machine     

尊重,顺应自然利用·享受自然:温和地区居住建筑节能设计标准编制的技术路线和设计措施

以温和地区气候特征为基础,以人的热舒适度指标为目的,运用建筑气候学原理,从自然生态理念和智慧出发,分析论述了人——气候——建筑的“天人合一”关系,提出了温和地区建筑节能被动式设计的技术路线和设计措施.     

Manifold‐Based 3D Face Caricature Generation with Individualized Facial Feature Extraction

Caricature is an interesting art to express exaggerated views of different persons and things through drawing. The face caricature is popular and widely used for different applications. To do this, we have to properly extract unique/specialized features of a person's face. A person's facial feature not only depends on his/her natural appearance, but also the associated expression style. Therefore, we would like to extract the neutural facial features and personal expression style for different applicaions. In this paper, we represent the 3D neutral face models in BU–3DFE database by sparse signal decomposition in the training phase. With this decomposition, the sparse training data can be used for robust linear subspace modeling of public faces. For an input 3D face model, we fit the model and decompose the 3D model geometry into a neutral face and the expression deformation separately. The neutral geomertry can be further decomposed into public face and individualized facial feature. We exaggerate the facial features and the expressions by estimating the probability on the corresponding manifold. The public face, the exaggerated facial features and the exaggerated expression are combined to synthesize a 3D caricature for a 3D face model. The proposed algorithm is automatic and can effectively extract the individualized facial features from an input 3D face model to create 3D face caricature.     

On uniform integrability and asymptotically risk-efficient sequential estimation

In the theory of asymptotically risk-efficient sequential estimation, one encounters uniform integrability of both positive and negative powers of stopping rules and moment convergence of randomly stopped statistics. We describe a simple approach to obtain these uniform integrability and moment convergence results, not only in the classical setting of i.i.d. observations but also for much more general stochastic sequences. We also use this approach to establish asymptotic risk efficiency of sequential estimators of means of stochastic sequences and to derive asymptotic approximations for the mean squared errors of ratio estimators.     

Determination of Uniformity of Filter Deposits

Certain measurement techniques (such as the asbestos method using phase contrast microscopy) require uniform deposits of the sample on a filter. The asbestos fiber analytical methods require such uniform deposition because the analysis only observes small, randomly chosen locations on the filter. In this study, a vibrating orifice monodisperse aerosol generator was used to generate methylene blue particles. The aerosols were dried by filtered compressed air and then neutralized by inducing a charge on the droplet stream that emerged from the vibrating orifice. An Aerodynamic Particle Sizer was used to measure the number concentration and size distribution of the generated aerosol particles. Meanwhile, the filter deposits were examined via image processing, combined with statistical methods for defining uniformity. In order to better define uniformity and make the indicator more universal, the uniformity was defined as the exponential of the negative CV (coefficient of variation) value which was a transformation for easily understanding the uniformity of the filter deposits. The experimental results demonstrated that, when aerosol counting was performed, the equal area approach was superior to the equivalent distance approach.     

CO2 Capture by Liquid Solvents and their Regeneration by Thermal Decomposition of the Solid Carbonated Derivatives

The chemical capture of CO₂ by either aqueous Na₂CO₃ and K₂CO₃ or nonaqueous solutions of the amines 2‐amino‐2‐methyl‐1‐propanol (AMP) or piperazine (PZ) is described. The captured CO₂ is stored as solid NaHCO₃, KHCO₃, and AMP or PZ carbamates. Solid NaHCO₃ and KHCO₃ are decomposed at 200 °C and 250 °C, respectively, to regenerate the carbonates for their reuse. In the experiments with AMP or PZ, the solid carbamates are decomposed at 80 °C–110 °C to regenerate the free amines. The absence of water in the desorption‐regeneration step is intriguing and could have the potential of reducing one of the major disadvantages of aqueous absorbents, namely the energy cost of the regeneration step and amine degradation, yet preserving the efficiency of the absorption in the liquid phase.     

水泥生产工艺与混凝土耐久性的关系

1 影响混凝土耐久性的因素 水泥是混凝土的一种重要原料,它的性能对混凝土性能有十分重要的影响.混凝土诸多性能中耐久性非常重要,如果混凝土结构物没有达到预期使用年限而过早地被破坏,不但经济损失巨大而且危及人们的安全.黄士元等[1]将混凝土破坏的原因分为四大类:①磨损;②物理因素的破坏;③化学作用的破坏;④钢筋锈蚀造成的破坏.