National Taiwan University of Science and Technology

About: National Taiwan University of Science and Technology is a education organization based out in Taipei, Taipei, Taiwan. It is known for research contribution in the topics: Fuzzy logic & Control theory. The organization has 16288 authors who have published 21577 publications receiving 426294 citations. The organization is also known as: Taiwan Tech & Taiwantech.

Transitional Markov Chain Monte Carlo Method for Bayesian Model Updating, Model Class Selection, and Model Averaging

Abstract: This paper presents a newly developed simulation-based approach for Bayesian model updating, model class selection, and model averaging called the transitional Markov chain Monte Carlo (TMCMC) approach. The idea behind TMCMC is to avoid the problem of sampling from difficult target probability density functions (PDFs) but sampling from a series of intermediate PDFs that converge to the target PDF and are easier to sample. The TMCMC approach is motivated by the adaptive Metropolis–Hastings method developed by Beck and Au in 2002 and is based on Markov chain Monte Carlo. It is shown that TMCMC is able to draw samples from some difficult PDFs (e.g., multimodal PDFs, very peaked PDFs, and PDFs with flat manifold). The TMCMC approach can also estimate evidence of the chosen probabilistic model class conditioning on the measured data, a key component for Bayesian model class selection and model averaging. Three examples are used to demonstrate the effectiveness of the TMCMC approach in Bayesian model updating, ...

Electrical Transport Properties of Single-Layer WS2

Abstract: We report on the fabrication of field-effect transistors based on single layers and bilayers of the semiconductor WS2 and the investigation of their electronic transport properties. We find that the doping level strongly depends on the device environment and that long in situ annealing drastically improves the contact transparency, allowing four-terminal measurements to be performed and the pristine properties of the material to be recovered. Our devices show n-type behavior with a high room temperature on/off current ratio of similar to 10(6). They show clear metallic behavior at high charge carrier densities and mobilities as high as similar to 140 cm(2)/(V s) at low temperatures (above 300 cm(2)/(V s) in the case of bilayers). In the insulating regime, the devices exhibit variable range hopping, with a localization length of about 2 nm that starts to increase as the Fermi level enters the conduction band. The promising electronic properties of WS2, comparable to those of single layer MoS2 and WSe2, together with its strong spin-orbit coupling, make it interesting for future applications in electronic, optical, and valleytronic devices.

Cross-Linking with Diamine Monomers To Prepare Composite Graphene Oxide-Framework Membranes with Varying d-Spacing

Abstract: Three diamine monomers (ethylenediamine, butylenediamine, and p-phenylenediamine) were selected for cross-linking graphene oxide (GO) to prepare composite graphene oxide-framework (GOF) membranes through filtration using a pressure-assisted self-assembly technique. The membranes were applied to separate an ethanol–water mixture by pervaporation. Unmodified GO comprised only hydrogen bonds and π–π interactions, but after cross-linking it with a diamine, attenuated total reflectance–Fourier transform infrared and X-ray photoelectron spectroscopy demonstrated that the diamine was chemically bonded both to GO and the membrane support. Moreover, GO hydrophilicity was substantially altered; water contact angle increased from 24.4° to 80.6° (from cross-linking with an aliphatic structure of diamine to cross-linking with an aromatic structure). Results of X-ray diffraction showed that d-spacing in GOF layers varied from 10.4 to 8.7 A. For GOFs presoaked in 90 wt % ethanol–water, covalent bonds between the layer a...

Study of increasing lipid production from fresh water microalgae Chlorella vulgaris

Abstract: Study of increasing lipid production from fresh water microalgae Chlorella vulgaris was conducted by investigating several important factors such as the effect of CO 2 concentration, nitrogen depletion and harvesting time as well as the method of extraction. The drying temperature during lipid extraction from algal biomass was found to affect not only the lipid composition but also lipid content. Drying at very low temperature under vacuum gave the best result but drying at 60 °C still retained the composition of lipid while total lipid content decreased only slightly. Drying at higher temperature decreased the content of triacylglyceride (TG). As long as enough pulverization was applied to dried algal sample, ultrasonication gave no effect whether on lipid content or on extraction time. In addition to the increase of total lipid content in microalgal cells as a result of cultivating in nitrogen depletion media, it was found that changing from normal nutrient to nitrogen depletion media will gradually change the lipid composition from free fatty acid-rich lipid to lipid mostly contained TG. Since higher lipid content was obtained when the growth was very slow due to nitrogen starvation, compromising between lipid content and harvesting time should be taken in order to obtain higher values of both the lipid content and lipid productivity. As the growth was much enhanced by increasing CO 2 concentration, CO 2 concentration played an important role in the increase of lipid productivity. At low until moderate CO 2 concentration, the highest lipid productivity could be obtained during N depletion which could surpassed the productivity during normal nutrition. At high-CO 2 concentration, harvesting at the end of linear phase during normal nutrition gave the highest lipid productivity. However, by reducing the incubation time of N depletion, higher lipid content as well as higher lipid productivity may still be achieved under this condition.