First-principles study of the lattice dynamics of Sb2S3

We present a lattice dynamics study of orthorhombic antimony sulphide (Sb2S3) obtained using density-functional calculations in conjunction with the supercell force-constant method. The effect of Born effective charges is taken into account using a mixed-space approach, resulting in the splitting of longitudinal and transverse optical (LO-TO) phonon branches near the zone center. Zone-center frequencies agree well with Raman scattering experiments. Due to the slow decay of the interatomic force constants (IFC), a minimal 2x4x2 supercell (Pnma setting) with 320 atoms is crucial for an accurate determination of the dispersion relations. Smaller supercells result in artificial acoustic phonon softening and unphysical lifting of degeneracies along high symmetry directions. We propose a scheme to investigate the convergence of the IFC with respect to the supercell sizes. The phonon softening can be attributed to the periodic images that affect the accuracy of the force constants, and the truncation of long-ranged forces. The commensuration of the q-vectors with the supercell size is crucial to preserve degeneracies in Sb2S3 crystals.Comment: 7 pages 4 figures, 3 table

Computation-Performance Optimization of Convolutional Neural Networks with Redundant Kernel Removal

Deep Convolutional Neural Networks (CNNs) are widely employed in modern computer vision algorithms, where the input image is convolved iteratively by many kernels to extract the knowledge behind it. However, with the depth of convolutional layers getting deeper and deeper in recent years, the enormous computational complexity makes it difficult to be deployed on embedded systems with limited hardware resources. In this paper, we propose two computation-performance optimization methods to reduce the redundant convolution kernels of a CNN with performance and architecture constraints, and apply it to a network for super resolution (SR). Using PSNR drop compared to the original network as the performance criterion, our method can get the optimal PSNR under a certain computation budget constraint. On the other hand, our method is also capable of minimizing the computation required under a given PSNR drop.Comment: This paper was accepted by 2018 The International Symposium on Circuits and Systems (ISCAS

The effects of integrating mobile devices with teaching and learning on students' learning performance: A meta-analysis and research synthesis

AbstractMobile devices such as laptops, personal digital assistants, and mobile phones have become a learning tool with great potential in both classrooms and outdoor learning. Although there have been qualitative analyses of the use of mobile devices in education, systematic quantitative analyses of the effects of mobile-integrated education are lacking. This study performed a meta-analysis and research synthesis of the effects of integrated mobile devices in teaching and learning, in which 110 experimental and quasiexperimental journal articles published during the period 1993–2013 were coded and analyzed. Overall, there was a moderate mean effect size of 0.523 for the application of mobile devices to education. The effect sizes of moderator variables were analyzed and the advantages and disadvantages of mobile learning in different levels of moderator variables were synthesized based on content analyses of individual studies. The results of this study and their implications for both research and practice are discussed

An Empirical Study of the Machine Assembly Efficiency Improvement Based on Lean Six Sigma Technique

Effectively controlling inventory is one of the key factors for small and medium-sized enterprises to make profit. Most small and medium-sized enterprises solve their problems through experience or trial and error, but they are often unable to achieve the desired enterprise performance under limited time and cost. The real case adopted herein covers a manufacturer of optical lens equipment, and the bottleneck is the shortened period of delivery caused by refunded, reduced, and delayed orders due to changes in the market. Under the framework of Lean Six Sigma, this study identified the key factors affecting working hours and product cycle and then formulates strategies to import the actual process. The results show that the inventory turnover rate increases from 20.8% to 41.6%, deriving a financial effect worth of NT$15.57 million. For the practical verification of the case company, Lean Six Sigma really does improve the assembly process efficiency, achieving a result beyond the expected target. With this successful case, this study can be a reference for other firms

Knockdown of PsbO leads to induction of HydA and production of photobiological H2 in the green alga Chlorella sp. DT

Green algae are able to convert solar energy to H2 via the photosynthetic electron transport pathway under certain conditions. Algal hydrogenase (HydA, encoded by HYDA) is in charge of catalyzing the reaction: 2H+ + 2e− ↔ H2 but usually inhibited by O2, a byproduct of photosynthesis. The aim of this study was to knockdown PsbO (encoded by psbO), a subunit concerned with O2 evolution, so that it would lead to HydA induction. The alga, Chlorella sp. DT, was then transformed with short interference RNA antisense-psbO (siRNA-psbO) fragments. The algal mutants were selected by checking for the existence of siRNA-psbO fragments in their genomes and the low amount of PsbO proteins. The HYDA transcription and the HydA expression were observed in the PsbO-knockdown mutants. Under semi-aerobic condition, PsbO-knockdown mutants could photobiologically produce H2 which increased by as much as 10-fold in comparison to the wild type