Reciprocal tutoring using cognitive tools

Abstract Reciprocal tutoring, where peers take turns to tutor each other, is an interesting style of social learning. In the Reciprocal Tutoring System (RTS), three computational cognitive tools were designed to facilitate reciprocal tutoring of Lisp programming on the network. The first is a Petal-style of code–chunk interface, with which a tutee can enter Lisp code without making syntactic errors. The second tool is Diagnosis-Hint Tree, with which a tutor can diagnose and comment on the errors in the tutee's program. The third one is a list of dialogue templates, with which the tutee and the tutor can communicate during the tutoring process. A three-phase experiment was conducted, with each phase using different cognitive tools. In addition, with the help of the cognitive tools, RTS provides a virtual learning companion that can play tutor or tutee. Evaluation results reveal both the strengths and weaknesses of peer-based learning and intelligent tutoring, with supports of different cognitive tools. Peer-based learning supported by cognitive tools is a practical and attractive alternative to intelligent tutoring systems. Exactly which type of tutor is preferred depends on the tutee's cognitive, communication, and emotional needs in the tutorial context.     

Electron trap generation in high-/spl kappa/ gate stacks by constant voltage stress

Positive bias constant voltage stress combined with charge pumping (CP) measurements were applied to study trap generation phenomena in SiO/sub 2//HfO/sub 2//TiN stacks. Using gate stacks with varying thicknesses of the interfacial SiO/sub 2/ layer (IL) or high-/spl kappa/ layer and analysis for frequency-dependent CP data developed to address trap depth profiling, the authors have determined that the defect generation in the stress voltage range of practical importance occurs primarily within the IL on as-grown "precursor" defects most likely caused by the overlaying HfO/sub 2/ layer. The generated traps can be passivated by a forming gas or nitrogen (N/sub 2/) anneal, whereas a postanneal stress reactivates these defects. The results obtained identify the IL as one of the major targets for reliability improvement of high-/spl kappa/ stacks.     

Spatial Distributions of Trapping Centers in HfO2/SiO2 Gate Stack

An analysis methodology for charge pumping (CP) measurements was developed and applied to extract spatial distributions of traps in SiO ₂/HfO₂ gate stacks. This analysis indicates that the traps accessible by CP measurements in the frequency range down to a few kilohertz are located primarily within the SiO₂ layer and HfO₂/SiO₂ interface region. The trap density in the SiO₂ layer increases closer to the high-kappa dielectric, while the trap spatial profile as a function of the distance from the high-kappa film was found to be dependent on high-kappa film characteristics. These results point to interactions with the high-kappa dielectric as a cause of trap generation in the interfacial SiO₂ layer     

The effect of orifice lead cutting edge distance and fluid viscosity on jet performance in high-velocity waterjet cutting systems

This paper uses numerical methods to discuss the influence of different designs of orifice geometries on the coherence of waterjets for cutting accurately in high velocity waterjet systems. Firstly, the numerical inner flow fields of standard waterjets, including orifice housings and cutting heads, are set up. Then, we infer the government equations for computational requirements. Finally, according to the specific conditions, the influences on velocity distributions of waterjets are simulated. In addition to water, fluids of different viscosities and densities (the SAE 10W engine oil and glycerin) are used to expand the relationships of the velocity field and coherence in high velocity waterjets . The above-mentioned results not only contribute to understanding the lead cutting distance of the orifice, which must be controlled under 3 μm, but also this study finds that the laminar flows of the waterjets are more coherent than the turbulent flows of the waterjets.     

Obfuscation for object‐oriented programs: dismantling instance methods

Code obfuscation can help software developers protect technological secrets. Code readability is greatly enhanced with object‐oriented technology that represents dynamic binding using instance method invocation. Therefore, dismantling instance methods is proposed in this paper as a critical obfuscating technique for object‐oriented programs. The interception classes are interpolated first into the project. The static images and the up forwarders are then created. For each virtual function system and each interface function system, a respective dispatching function is set up. By properly arranging the class identifiers and binding identifiers, the switch statement in the dispatching function can be compiled into constant‐time low‐level code. After using dispatching functions to simulate virtual function system or interface function system invocations, all original instance methods in the project will be removed. Interception functions and export functions are indispensable in supporting the operation of callback methods. A prototype of our obfuscation system was implemented and successfully tested on some practical scale applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Extraction of the Threshold-Voltage Shift by the Single-Pulse Technique

Methods for extracting threshold-voltage shift (DeltaV_th) in high-kappa transistors using the single-pulse drain current-gate voltage (I_d-V_g) technique were compared with respect to their accuracies and limitations. It is concluded that an accurate estimation of the (DeltaV_th) caused by charge trapping in high-kappa dielectrics can be obtained from the hysteresis of the pulsed (I_d-V_g) curve with proper calibration of the pulse measurement to account for the propagation delay. The (DeltaV_th) extraction that is based on the decrease of drain current during a pulse tends to underestimate charge trapping for higher pulse amplitudes.     

The study of structural system dynamic problems by recursive estimation method

This paper presents the recursion-relation algorithm to determine the input forces of beam structures and the individual node displacement. The system state equations of the beam structures are based on the average acceleration method, and a dynamic beam matrix equation is constructed by using the finite element method. Implementation of this method involves handling various systems' parameters such as the measurement noise, the modeling error, and the external disturbance. The Kalman filter is used to predict the applied forces and adjusted at each time step according to the measured dynamic response data of structures. The estimator employs a recursive least-squares algorithm to compute the magnitudes of the impulsive loads. The accuracy of the present method is demonstrated by the numerical simulations for loads applied along the axis of a beam on different time frames.     

Preparation and characterizations of tantalum pentoxide (Ta2O5) nanoparticles and UV‐curable Ta2O5‐acrylic nanocomposites

Tantalum pentoxide (Ta₂O₅) nanoparticles with the sizes in the range of 20–50 nm were prepared via a chemical route in which the oleic acid (OLEA) was adopted as the surfactant for the synthesis process. X‐ray diffraction (XRD) revealed the as‐synthesized Ta₂O₅ transforms from amorphous to hexagonal and orthorhombic structures at the temperatures of 700°C and 750°C, respectively, illustrating the suppression of recrystallization temperature of Ta₂O₅ due to the particle size reduction. UV‐curable nanocomposites containing the Ta₂O₅ nanoparticles and acrylic matrix were also prepared. Thermogravimetry analysis (TGA) found an about 10–20°C improvement on the 5% weight‐loss thermal decomposition temperatures (T_ds). Dielectric measurement showed that the dielectric constant of nanocomposite increases with the increase in the filler loading without severe deterioration of dielectric loss. The increment of dielectric constants was ascribed to the addition of high‐dielectric inorganic fillers as well as the presence of interfacial polarization at the organic/inorganic interfaces. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Characterizations of UV‐curable montmorillonite/epoxy nanocomposites prepared by a hybrid of chemical dispersion and planetary mechanical milling process

Ammonium salt, [2‐(methacyloyloxy)ethyl] trimethylammonium methyl sulfate (MAOTMA), was adopted to modify montmorillonite (MMT) via the cationic exchange process in an acidic environment and a successful enlargement of MMT lamellar spacing from 1.18 to 1.39 nm was identified by x‐ray diffraction and Fourier‐transform infrared spectroscopy. Accordingly, UV‐curable epoxy nanocomposite resins containing various amounts of MAOTMA‐modified MMT were prepared with the aid of a planetary mechanical milling process. Transmission electron microscopy revealed a uniform dispersion of exfoliated MMT lamella in epoxy matrix, leading to the distinct improvements on thermal stability and thermal expansion property of nanocomposite samples. Calcium (Ca) test indicated that the good dispersion of MMT fillers in polymer effectively suppresses the moisture permeation in sample matrix. More than twofold increment on retention time of 5% Ca hydrolysis and 20% improvement on the permeation kinetic parameters were observed in the nanocomposite sample containing 8 wt % MMT in comparison with the pristine epoxy sample. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A 2-Opt based differential evolution for global optimization

Differential evolution (DE) is a simple and effective global optimization algorithm. It has been successfully applied to solve a wide range of real-world optimization problems. However, DE has shown some weaknesses, especially the long computational times because of its stochastic nature. This drawback sometimes limits its application to optimization problems. Therefore we propose the 2-Opt based DE (2-Opt DE) which is inspired by 2-Opt algorithms to accelerate DE. The novel mutation schemes of 2-Opt DE, DE/2-Opt/1 and DE/2-Opt/2 are substituted for mutation schemes of the original DE namely DE/rand/1 and DE/rand/2. We also provide a comparison of 2-Opt DE to DE. A comprehensive set of 19 benchmark functions is employed for experimental verification. The experimental results confirm that 2-Opt DE outperforms the original DE in terms of solution accuracy and convergence speed.