Massively Parallel Ray Tracing Algorithm Using GPU

Ray tracing is a technique for generating an image by tracing the path of light through pixels in an image plane and simulating the effects of high-quality global illumination at a heavy computational cost. Because of the high computation complexity, it can't reach the requirement of real-time rendering. The emergence of many-core architectures, makes it possible to reduce significantly the running time of ray tracing algorithm by employing the powerful ability of floating point computation. In this paper, a new GPU implementation and optimization of the ray tracing to accelerate the rendering process is presented

MANAGEMENT PERSPECTIVES ON THE IMPACTS OF NAFTA ON THE U.S. TEXTILE AND APPAREL INDUSTRIES

The NAFTA has brought profound changes to the U.S. textile and apparel industries, which have been interdependent with those in Mexico and Canada. A nationwide textile and apparel business survey has unveiled the management's perspectives on pros and cons of the NAFTA to the development and prosperity of the two industries.International Relations/Trade,

Mandarin Chinese Heritage Language Maintenance among Mandarin-English Bi/multilingual Children in Saskatchewan

So far, there have been no significant studies in Canada or Saskatchewan that examine sociolinguistic factors (such as language attitude, language use, and language exposure) as well as a factor of age vis-à-vis heritage (Mandarin) language proficiency among Mandarin-English bi/multilingual children. Mandarin has prestige in China as the language of education and government, and the number of Mandarin speakers in Canada is increasing. However, more people in Saskatchewan speak Cantonese and Chinese dialects other than Mandarin. Thus, this study examines the Mandarin language proficiency of the bi/multilingual children from Chinese-speaking immigrant families in Saskatchewan, a province with a small demographic group of Mandarin language speakers and very little support for its maintenance as compared with other provinces, such as British Columbia and Ontario. In addition, this study explores what sociolinguistic factors contribute to Chinese immigrant children’s language proficiency in these settings. The relationship between language proficiency and sociolinguistic factors was investigated via the framework of Variationist Sociolinguistics. An audio-recorded narrative task was adopted to assess bi/multilingual (Saskatchewan) and monolingual (in China) children’s oral Mandarin language proficiency. Objective linguistic proficiency parameters (vocabulary size, syntactic complexity, and fluency) were extracted from the sound records and compared bi/multilingual and monolingual children. Questionnaires and interviews were conducted to assess parents’ and children’s language attitudes and language use, and the children’s language exposure in the home and social domains. Finally, statistical relationships were performed between contextual sociolinguistic factors and language proficiency parameters. This study has shown that bi/multilingual children are overall successful in learning and maintaining Mandarin as a heritage language in Saskatchewan. While some of the critical results suggest that attending community-run Chinese heritage language schools plays an essential role in learning Mandarin, the most crucial indicator of Mandarin heritage language acquisition and maintenance is the positive attitudes of the parents towards the Mandarin as a heritage language. Of equal (if not greater) importance are their efforts to create a supportive and consistent home language environment, and to provide sufficient and varied (in terms of quality and quantity) Mandarin language input within the home and family. Since the Mandarin language is core to Chinese culture, this research offers recommendations to the Ministry of Education, Public School Boards, and the University of Saskatchewan and Regina to promote Mandarin as a foreign language and as a heritage language. This would contribute to sound bilingualism among Mandarin heritage speakers and facilitate heritage language learning, acquisition, maintenance, and development

Optimizing Hartree-Fock orbitals by the density-matrix renormalization group

We have proposed a density-matrix renormalization group (DMRG) scheme to optimize the one-electron basis states of molecules. It improves significantly the accuracy and efficiency of the DMRG in the study of quantum chemistry or other many-fermion system with nonlocal interactions. For a water molecule, we find that the ground state energy obtained by the DMRG with only 61 optimized orbitals already reaches the accuracy of best quantum Monte Carlo calculation with 92 orbitals.Comment: published version, 4 pages, 4 figure

Development of analytical systems and monitoring of VOCs emissions during polymer processing

A method using direct flame ionization detector (FID) measurement was developed to study total volatile organic compounds (VOCs) emissions during thermal degradation of polymers. This was used to estimate organic emissions from both virgin polymer resins and commingled plastics. The effects of process parameters, i. e., temperature, heating rate and residence time, were also studied. Significant VOCs emissions were observed at normal processing temperatures, particularly from recycled polymers. Each polymer showed a distinct evolution pattern during its thermal degradation. Kinetics of VOCs emissions were also studied using a non-isothermal technique. The kinetic parameters were in agreement with data from the literature. Polypropylene, as a commodity recyclable thermoplastic, was studied in this research to evaluate the potential environmental impact resulting from VOCs emitted during multiple melt reprocessing. Unstabilized and stabilized PP homopolymers, referred to as U-PP and S-PP, were used to simulate recycled materials prone to degradation. They were evaluated for total VOCs emissions generated during multiple melt reprocessing by injection molding and extrusion respectively. Results show that the maximum amount of total VOCs from each cycle (up to six cycles for extrusion and up to ten for injection molding) did not significantly change, while the cumulative VOCs increased with increasing processing cycle for both materials. A good correlation was obtained between the cumulative VOCs increase and the Melt Flow Index increase for the U-PP, and the MW decrease for the S-PP. Reprocessing in all cases was accompanied by decreases in molecular weight and melt viscosity as a result of thermo-oxidative degradation. Corresponding structural changes were investigated using FTIR, and the data showed increases in carbonyl content and degree of unsaturation with the increase of processing cycle number. At equivalent cycle numbers, degradation appeared to be more severe for the extruded material in spite of the longer oxidative induction time of the as received pellets used in extrusion. The onset and type of structural changes was shown to depend on cycle number and reprocessing method. A simulation study was also performed by multiple heating and cooling of a single U-PP sample under static conditions, and under different gaseous atmospheres. The results indicate that the actual reprocessing conditions generated emissions whose levels, and rate of generation were closer to a mild thermo-oxidative degradation rather than a pure thermal one. Continuous nonmethane organic carbon (C-NMOC) analysis was considered to be a more accurate and on-line method for monitoring emissions during polymer processing. An improved version of the C-NMOC system was developed in this research. A multibed microtrap was developed to prevent the breakthrough of small molecules such as propane and methanol. Two novel sampling configurations were also developed, and were referred to as sequential valve with backflushed microtrap (SV-BM) and multiinjection sequential valve with backflushed microtrap (MSV-BM). By combining the multi-bed microtrap with the SV-BM and MSV-BM configurations, ideal performances were obtained in terms of linearity, reproducibility of multiple injections and separation of background gases. Both small molecules and large molecules could be effectively collected and desorbed with the optimized microtrap