Ahyoung Kim

Responses to Failure as Influenced by Task Attribution, Outcome Attribution, and Failure Tolerance

AbstractThe effects of two levels of task attribution (self-selected and other-imposed) and three levels of outcome attribution (ability, strategy, and effort) were examined with the use of a situational description about “Greg,” a Navy recruit who received an unsatisfactory mid-term training report. Navy recruits in their final 2 weeks of military training served as subjects. They were asked to predict, under one of six experimental conditions, the feelings and behavior of Greg as well as the support he was likely to receive from fellow recruits and commanding officers. A measure of failure tolerance was also administered to subjects. Outcome attribution was found to be a more powerful determinant of responses to failure than was task attribution. Consistent with previous findings, these data suggest that strategy attributions generally lead to more constructive responses to failure than do effort and ability attributions. However, this pattern of findings is evidenced only under the self-selected task a...

Electrogyration effect in a chiral bent-core molecular system

The linear electrogyration effect is observed in the crystallike B4 phase of a mixture of chiral and achiral bent-core mesogens. A large birefringent monodomain with a single sense of chirality was selected for experiment. Upon application of a modulating electric field to the sample cell, a strong modulation of refractive index was observed. Analysis showed that both the linear electro-optic and the linear electrogyration effect are responsible for the index modulation with the latter being dominant. The effective electro-optic coefficient was measured to be reff=21.6 pm/V at 488 nm.

Control of self-collimated Bloch waves by partially flat equifrequency contours in photonic crystals

Self-collimation effects in photonic crystals are generally investigated by employing flat equifrequency contours. Here we report, based on a partially flat equifrequency contour inducing two different group velocity vectors, the simultaneous excitation of dual self-collimated beams and the selective excitation of either of them by varying the incident angle or the width of an input Gaussian beam. With combination of the finite-difference time-domain simulation and the Fourier analysis as well as the wave vector diagram, we analyze the refractive behaviors of these self-collimated Bloch waves.

Characterization of electro-optic properties of self-assembled monolayer by attenuated total reflection

The electro-optic (E-O) effect was investigated in a self-assembled monolayer by use of the attenuated total reflection technique. The self-assembled monolayer was composed of a pair of layers, cationic polymer with hemicyanine pendent group and anionic molecule. The surface plasmon resonance spectroscopy enabled the determination of the anisotropic dielectric constants and the thickness of each organic layer. A linear change in the modulation of the reflection curve upon application of a modulating electric field was observed, which is from the E-O response of polar-ordered hemicyanine pendent group.

ELECTRO-OPTIC AND ELECTRO-GYRATION EFFECTS IN CHIRAL MOLECULAR SYSTEMS

The linear electro-optic (EO) and electro-gyration (EG) effects are studied in an optically active material systems including Bi12SiO20 (BSO) oxide and bent-core liquid crystals. In an isotropic BSO sample, the breaking of intrinsic centro-symmetry allowed the EO modulation of the refractive index. In a mixture of bent-shaped liquid crystalline molecules having both optical activity and birefringence, the observed intensity modulation is investigated, which is related to the nonlinear optical responses of both the optical rotatory power and the birefringence. Both the linear EO and EG effects are understood in terms of the superposition principle of linear and circular birefringences.

An improvement on local FDR analysis applied to functional MRI data.

BACKGROUND Discovering effective connectivity between brain regions gained a lot of attention recently. A vector autoregressive model is a simple and flexible approach for exploratory structural modeling where the involvement of a large number of brain regions is crucial to avoid confounding. The non-zero coefficients of the VAR model are interpreted as actual effective connectivity between brain regions. Thus methods for a higher correct discovery rate are crucial for neuroscience. NEW METHOD We propose an improved version of the FDR analysis procedure which would be more suitable to fMRI data. The estimates of the VAR coefficients are often not symmetric about 0 with non-zero modes. In this case, we suggest to estimate the null distribution of the estimates which is assumed symmetric about 0 in two steps: use one side of the estimates and then both sides under some condition. RESULTS A theoretical argument is provided for the proposed procedure with a theorem and two types of experiments are made. In a simulation experiment, we show via ROC curves improvement over previous methods. We apply the proposed method to analyze real fMRI data with results interpreted in the language of cognitive neuroscience. COMPARISON WITH EXISTING METHOD(S) The proposed method outperforms the standard method in the simulation experiment with a VAR model of dimension up to 100 over a wide range of sample sizes. The improvement is made in the context of the true positive rate and performance consistency. CONCLUSIONS The proposed method is more appropriate for analyzing fMRI data with VAR models when the estimates of the VAR coefficients are not symmetric about 0 and have non-zero modes.

A longitudinal study of the development of rational number concepts and strategies in the middle grades

The purpose of this project was to trace longitudinal changes in rational number knowledge and proportional reasoning among middle-school students; exposing barriers or detours in their journey toward rational number understanding. One hundred two children were interviewed over the course of the study. Children were interviewed once every 3 weeks (approximately nine times per year per child). At the same time, children’s classes were observed approximately twice per week for the duration of the 20-month study. As a result, parallels between classroom instruction and students’ individual problem-solving strategies were developed, providing implications for curriculum, teaching, and individualized instruction. A Hierarchical Linear Model was used to describe the overall change in students’ thinking across the study, and sample students were compared to their (inter)national peers on rational number items from TIMSS and NAEP. Students entered the middle grades with a large repertoire of strategies for making sense of rational number problems. However, by the end of the eighth grade, students’ strategies tended to narrow and focus on inefficient understandings. Results show that instructional focus on Part/Whole fractions, in particular, hampered students’ ability to reason about ratio, rates, and proportional reasoning. The use of large-scale secondary data with which to compare results from this more modest study enhanced the ability of the researchers to make statistical claims about the generalizability of patterns uncovered in children’s fraction and proportional reasoning strategies.

A Three-Step Approach to Factor Analysis on Data of Multiple Testlets

A testlet consists of a text and several items following it. It is often observed that a test consists of multiple testlets. The items within a testlet are more interrelated than they are with other items in the test. In this note, we attempt to show how to estimate common factors in the data of multiple testlets. We start our argument from the rationale of common factor analysis on each testlet. However, we treat the effect of a testlet on the item scores within the testlet as the method effect. If we are able to remove the method effect from subjects’ response data, then we can apply ordinary factor analysis on the residualized scores that remain after partialing out the method effect. Application of our approach is also demonstrated.

Optical characteristics of self-assembled ultrathin films of tetra-copperphthalocyanine by attenuated total reflection

Abstract Multilayer thin films consisting of alternate layer-pairs of cationic macrocycles (tetra-copperphthalocyanine) and anionic macromolecules (polyethylenimine) were fabricated on thin silver film using alternate electrostatic self-assembly technique. The optical properties of the film were characterized by uv-vis absorption spectra and attenuated total reflection measurements. From the data analysis based on the multilayer reflection theory, it was shown that the ultra thin films were successfully fabricated by self-assembly technique with the mean layer-pairs thickness of 25 Å. Moreover, especially for tetra-copperphthalocyanine layer, we obtained the anisotropy in dielectric constants with respect to the surface normal, indicating anisotropic orientation of the tetra-copperphthalocyanine molecules on the polyethylenimine layer.