A Comparison of Two Instructional Sequences in an Intelligent Tutoring Program on Multiplicative Concepts and Problem Solving of Students with Mathematics Difficulties

One of the crucial goals of the National Councils of Teachers Mathematics standards (2000) was to have all students, including students with mathematics difficulties (MD), to succeed in establishing a higher-order thinking in mathematic

Interdiffusion Reaction Between Uranium-zirconium And Iron

U-Zr metallic fuels cladded in Fe-alloys are being considered for application in an advanced Sodium-Cooled Fast Reactor (SFR) that can recycle the U-Zr fuels and minimize the long-lived actinide waste. To understand the complex fuel-cladding chemical interaction of the U-Zr metallic fuel with Fe-alloys, a systematic multicomponent diffusion study was carried out using solid-to-solid diffusion couples. The U-10 wt.% Zr vs. pure Fe diffusion couples were assembled and annealed at temperatures, 630, 650 and 680°C for 96 hours. Development of microstructure, phase constituents, and compositions developed during the thermal anneals were examined by scanning electron microscopy, transmission electron microscopy and X-ray energy dispersive spectroscopy. A complex microstructure consisting of several layers that include phases such as U6Fe, UFe2, ZrFe2, α-U, β-U, Zr-precipitates, χ, ε, and λ was observed. Multiphase layers were grouped based on phase constituents and microstructure, and the layer thicknesses were measured to calculate the growth constant and activation energy. The local average compositions through the interaction layer were systematically determined, and employed to construct semi-quantitative diffusion paths on isothermal U-Zr-Fe ternary phase diagrams at respective temperatures. The diffusion paths were examined to qualitatively estimate the diffusional behavior of individual components and their interactions. Furthermore, selected area diffraction analyses were carried out to determine, for the first time, the exact crystal structure and composition of the χ, ε and λ-phases. The χ, ε and λ-phases were identified as Pnma(62) Fe(Zr,U), I4/mcm(140) Fe(Zr,U)2, and I4/mcm(140) U3(Zr,Fe), respectively

Structure analysis of single- and multi-frequency subspace migrations in inverse scattering problems

In this literature, we carefully investigate the structure of single- and multi-frequency imaging functions, that are usually employed in inverse scattering problems. Based on patterns of the singular vectors of the Multi-Static Response (MSR) matrix, we establish a relationship between imaging functions and the Bessel function. This relationship indicates certain properties of imaging functions and the reason behind enhancement in the imaging performance by multiple frequencies. Several numerical simulations with a large amount of noisy data are performed in order to support our investigation.Comment: 11 pages, 10 figure

Relationships of self-identified cold tolerance and cold-induced vasodilatation in the finger

Thermal environments in daily life, such as occupational cold exposure and the use of heating facilities and warm clothing, affect acclimatization to both cold and heat. Also, cold tolerance can be cognized by self-identified evaluation. Thermal life-style during daily life might be one of the factors which affect cold-induced vasodilatation (CIVD) when different degrees of thermal stimuli are considered. Therefore, this study investigated whether or not CIVD response is related to self-identified cold and heat tolerances which is attributable to thermal life-style

Cancer Statistics in Korea: Incidence, Mortality, Survival, and Prevalence in 2008

PURPOSE: This paper overviews the nationwide cancer statistics including incidence, mortality, survival and prevalence, and their trends in Korea based on the year 2008 cancer incidence data. MATERIALS AND METHODS: Incidence data from 1993 to 2008 were obtained from the Korea National Cancer Incidence Database, and the vital status was followed through December 31, 2009. Mortality data from 1983 to 2008 were obtained from the Korea National Statistics Office. Crude rates and age-standardized rates for incidence, mortality, prevalence and relative survival were calculated. RESULTS: There were 178,816 cancer cases and 68,912 cancer deaths observed during year 2008 and 724,663 10-year cancer prevalent cases as of January 1, 2009 in Korea. The incidence rate for all cancer combined showed an annual increase of 3.1% from 1999 to 2008. CONCLUSION: With significantly increasing cancer incidence, Korea faces a large cancer burden and efficient cancer control programs are essential.ope

The Effects Of Cognitive Styles And Stereotype Threat On Cognitive Test Performance

This study examined the difference in cognitive styles between African Americans and Caucasians and how it affected cognitive test scores. This study also sought to detect the interaction of stereotype threat and cognitive style. Study 1 tested whether the cognitive style of field independence/dependence and convergence/divergence mediated the relationship between race and cognitive tests performance. I found support for field independence/dependence as a full mediator; however, I did not find support for convergence/divergence as a mediator. Study 2 sought to replicate Study 1 but add stereotype threat as a possible moderator to the model. I did not find support for the full model but partially replicated the results of Study 1. I discuss the implications of these findings on how to decrease adverse impact on cognitive tests

Phase transformation and growth kinetics in reaction zone between uranium alloy and zirconium diffusion barrier

U-10wt.%Mo (U10Mo) alloy as a part of monolithic fuel system is being developed under Material Management and Minimization Reactor Conversion (MMMRC) program, tasked with replacing high-enriched uranium (HEU) fuel with low-enriched uranium (LEU) fuel in civilian research and test reactors. Use of U10Mo fuel alloy entails a Zr diffusion barrier to avoid the undesirable interdiffusion and reactions between the U10Mo and Al-alloy cladding. To better understand the interaction between these fuel system constituents, microstructural development and diffusion kinetics in U-Mo-Zr, U-Zr and fuel plate assembly processed by co-rolling and hot isostatic pressing (HIP) were investigated using a variety of analytical techniques accompanying scanning electron microscopy and transmission electron microscopy. Phase constituents, microstructure and diffusion kinetics between U10Mo and Zr were examined using solid-to-solid diffusion couples annealed at 650 °C for 240, 480 and 720 hours. Concentration profiles were mapped as diffusion paths on the isothermal ternary phase diagram. Within the diffusion zone, single-phase layers of (γU,βZr) were observed along with a discontinuous layer of Mo2Zr between the βZr and βU layers. In the vicinity of Mo2Zr phase, islands of αZr phase were also found. In addition, acicular αZr and U6Zr3Mo phases were observed within the γU(Mo). Growth rate of the interdiffusion-reaction zone was determined to be 1.81 × 10-15 m2/sec at 650 °C, however with an assumption of a certain incubation period. Investigation for interdiffusion and reaction between U and Zr were carried out using solidto-solid diffusion couples annealed at 580, 650, 680 and 710 °C. The interdiffusion and reaction layer consisted of αU containing Zr acicular precipitate, α’ (oC4-variant) and (γU,βZr) solid solution at 650, 680 and 710 °C. The δ-UZr2 phase, instead of (γU,βZr) solid solution phase, was observed in the couple annealed at 580 °C. The interdiffusion fluxes and coefficients were determined for the αU, (γU,βZr) and δ-UZr2 (580 C only) phases using both Sauer-Freise and Boltzmann-Matano analyses. For the α’-phase with negligible concentration gradient, integrated interdiffusion coefficients were determined via Wagner method. Marker plane was found in (γU,βZr) (cI2) solid solution from the couples annealed at 650, 680 and 710 °C and δ-UZr2 from the couple at 580 °C. Intrinsic diffusion coefficients at the compositions corresponding to the marker plane were determined based on Heumann analysis: U intrinsically diffused an order magnitude faster than Zr. Arrhenius temperature-dependence, Darken relation, and comparison to existing literature data demonstrated consistency in results. Monolithic fuel plate assembly was fabricated by sequential process of (1) co-rolling to laminate the Zr barrier onto the U10Mo fuel alloy and (2) HIP to encase the fuel laminated with Zr, within the Al-alloy 6061 (AA6061). In this study, HIP process was carried out as functions of temperature (520, 540, 560 and 580 °C for 90 minutes), time (45, 60, 90, 180 and 345 minutes at 560 °C) with ramp-cool rate (35, 70 and 280 °C/hour). At the interface between the U10Mo and Zr, following the co-rolling, the UZr2 phase was observed to develop adjacent to Zr, and the αU phase was found between the UZr2 and U10Mo. Mo2Zr was found as precipitates mostly within the αU phase. Observable growth due to HIP was only observed for the (Al,Si)3Zr phase found at the Zr/AA6061 interface, however, with a large activation energy of 457 kJ/mol. Decomposition of γU into αU and γ’ was observed in the U10Mo alloy. The volume fraction of α and γ’ increased as the HIP temperature and ramp-cool rate decreased. The UC-UO2 inclusions within the U10Mo fuel alloy were observed, but the volume percent of the UC-UO2 inclusions within the U10Mo alloy, ranging from approximately 0.5 to 1.8, did not change as functions of HIP temperature and holding time. However, the inclusions located near the surface of the U10Mo alloy, were frequently observed to interfere the uniformity of interdiffusion and reaction between the U10Mo alloy and Zr diffusion barrier. The regions of limited interaction between the U10Mo and Zr barrier associated with UC-UO2 inclusions decreased with an increase in HIP temperature, however no significant trend was observed with an increase in HIP duration at 560 °C

Value Creation' Through Mathematical Modeling: Students' Mathematics Dispositions and Identities Developed in a Learning Community

This study examines how mathematical modeling activities within a collaborative group impact students' `value creation' through mathematics. Creating `value' in this study means to apply one's knowledge in a way that benefits the individual and society, and the notion of `value' was adopted from Makiguchi's theory of `value creation' (1930/1989). With a unified framework of Makiguchi's theory of `value', mathematical disposition, and identity, the study identified three aspects of value-beauty, gains, and social good-using observable evidence of mathematical disposition, identity, and sense of community. Sixty students who enrolled in a college algebra course participated in the study. The results showed significant changes in students' mathematics dispositions after engaging in the modeling activities. Analyses of students' written responses and interview data demonstrated that the modeling tasks associated with students' personal data and social interactions within a group contributed to students' developing their identity as doers of mathematics and creating social value. The instructional model aimed to balance the cognitive aspect and the affective skills of learning mathematics in a way that would allow students to connect mathematical concepts to their personal lives and social lives. As a result of the analysis of this study, there emerged a holistic view of the classroom as it reflects the Makiguchi's educational philosophy. Lastly, implications of this study for research and teaching are discussed