Variational Monte Carlo study of gapless spin liquid in the spin-1/21/2 XXZ antiferromagnetic model on the kagome lattice

By using the variational Monte Carlo technique, we study the spin-$1/2$ XXZ antiferromagnetic model (with easy-plane anisotropy) on the kagome lattice. A class of Gutzwiller projected fermionic states with a spin Jastrow factor is considered to describe either spin liquids (with $U(1)$ or $Z_2$ symmetry) or magnetically ordered phases (with ${\bf q}=(0,0)$ or ${\bf q}=(4\pi/3,0)$). We find that the magnetic states are not stable in the thermodynamic limit. Moreover, there is no energy gain to break the gauge symmetry from $U(1)$ to $Z_2$ within the spin-liquid states, as previously found in the Heisenberg model. The best variational wave function is therefore the $U(1)$ Dirac state, supplemented by the spin Jastrow factor. Furthermore, a vanishing $S=2$ spin gap is obtained at the variational level, in the whole regime from the $XY$ to the Heisenberg model.Comment: 7 pages, 7 figure

HOW TO IMPROVE THE HACCP SYSTEM IN AN INTERNATIONAL TOURIST HOTEL GROUP? CAUSE-AND -EFFECT ANALYSIS AND PDCA APPLICATION

The aim of this study is to discuss not only what the difficulties are to be confronted when a HACCP is introduced into international tourist hotels, but also how to apply effective solutions to overcome these crucial issues.  In-depth interviews were applied in this study to analyze the case of Taiwan’s X international tourist hotels. Based on the outcomes of interviews, a fish-bone diagram was carried out to analyze the practical difficulties encountered in implementing the HACCP system. Next, with the results of the cause and effect analysis, strategies for different problems were developed according to the interviewee’s points of view. PDCA analysis is used repeatedly to develop strategies and recommendations. In comparison to current literature that only provides piecemeal exploration of the difficulties of introducing the HACCP system and the effectiveness of implementing HACCP, this study takes an entire system view into consideration and enables further practical analysis and solutions.

APPLIED STUDY OF BIRCH PULP BLEACHING USING DIMETHYLDIOXIRANE TO OBTAIN ACETATE-GRADE PULP

As a pulp bleaching agent, dimethyldioxirane (DMD) is effective and selective. In this study, it was employed as a delignifying agent or as an activating agent for hydrogen peroxide treatment in bleaching acetate-grade pulp. Brightness, kappa number, degree of polymerization (DP), and alpha-cellulose content were evaluated to determine the optimal charges of DMD: 2.5% AO, and 4% HSO5-, respectively. Results from the totally chlorine-free (TCF) sequences MEQMPA, MEpQMPA, and OQMPA suggested that DMD is both effective and selective as a delignifying agent but not as a brightening agent as compared to oxygen. And in a long sequence for the bleaching of dissolving pulp, acid treatment can be used in two approaches: to remove the metal ions without washing before the chelation stage, and to reduce hemicellulose and ash in the final stage

A Study on the Design Thinking and Drawing of the Concept Development

This study was aim to examine the cognitive progress of graphic design involved in concept development. The results show that: (1) Cognitive progress can be observed from the design thinking and drawing patterns that emerge in designing works. The thinking activity was distinguished into general, experiential and evaluating thoughts, whereas drawing activity was categorized into graphic drawing and word description. (2) On the whole, more time was spent on general thought, less on experiential thought, and the least on evaluating thought. (3) There were three stages of concept development. General thought occurs more frequent in the initial stage while picture sketch takes place more frequent in the middle and final stages. In the other words, the process of the concept development was filled up via the concepts formed at first stage and translated into idea sketches at the next two stages