Session-based Recommendation with User Cold-Start Problem Using Markov Chain Model & Incremental Learning

Session-based recommendation has become a hot topic of intelligent system in recent years. As a sub-field of Recommending System, the session-based recommendation studies the sequential relationship of data in user's usage sessions. In some applications, the recommending system should focus more on the personalized usage feature in order to make better recommendations. This thesis analyzed the statistics of user's usage sessions and proposed the Statistics Enhanced FPMC algorithm to enhance the personalized usage pattern of users to improve the recommending performance of recommender system for in-vehicle infotainment system and APP manage system application. The proposed algorithm also addressed the user cold-start problem by incremental learning with a knowledge distillation method to alleviate the catastrophic forgetting problem. The user cold-start problem is defined as making recommendations to new users under cold-start conditions. While the usage data becomes available for new users, the model can continue to be updated to improve recommending performance.MSEElectrical Engineering, College of Engineering & Computer ScienceUniversity of Michigan-Dearbornhttp://deepblue.lib.umich.edu/bitstream/2027.42/167350/1/Zhengru Li - Final Thesis.pd

Numerical Study of the Interaction between Level Ice and Wind Turbine Tower for Estimation of Ice Crushing Loads on Structure

In this paper, the interaction between level ice and wind turbine tower is simulated by the explicit nonlinear code LS-DYNA. The isotropic elasto-plastic material model is used for the level ice, in which ice crushing failure is considered. The effects of ice mesh size and ice failure strain on ice forces are investigated. The results indicate that these parameters have a significant effect on the ice crushing loads. To validate and benchmark the numerical simulations, experimental data on level ice-wind turbine tower interactions are used. First, the failure strains of the ice models with different mesh sizes are calibrated using the measured maximum ice force from one test. Next, the calibrated ice models with different mesh sizes are applied for other tests, and the simulated results are compared to corresponding model test data. The effects of the impact speed and the size of wind turbine tower on the comparison between the simulated and measured results are studied. The comparison results show that the numerical simulations can capture the trend of the ice loads with the impact speed and the size of wind turbine tower. When a mesh size of ice model is 1.5 times the ice thickness, the simulations can give more accurate estimations in terms of maximum ice loads for all tests, i.e., good agreement between the simulated and measured results is achieved

Facile Construction of Bi₂Sn₂O₇/g-C₃N₄ Heterojunction with Enhanced Photocatalytic Degradation of Norfloxacin

To mitigate antibiotic residues in the water environment, Bi2Sn2O7/g-C3N4 (BSCN) heterojunction was fabricated by a facile ultrasound-assisted hydrothermal method. The microstructure, morphology, and optical properties of Bi2Sn2O7/g-C3N4 heterojunction was studied by XRD, FTIR, XPS, SEM, TEM, UV–Vis DRS, and PL. The degradation rate of 20 mg/L norfloxacin (NOR) under visible light for 3 h was adopted as one of the indexes to evaluate the photocatalytic performance of Bi2Sn2O7/g-C3N4 heterojunction. Embellished with 20% Bi2Sn2O7 (BSO), the Bi2Sn2O7/g-C3N4 heterojunction decomposed 94% NOR in the experimental solution, which was 2.35 and 3.03 times as much as pristine g-C3N4 and bare Bi2Sn2O7, respectively. In addition, the Bi2Sn2O7/g-C3N4 heterojunction still eliminated 89% of NOR after five cycles, portending outstanding stability and cyclability of photocatalytic activity. A possible photocatalytic mechanism of Bi2Sn2O7/g-C3N4 heterojunction for NOR degradation is proposed

Numerical Study of the Interaction between Level Ice and Wind Turbine Tower for Estimation of Ice Crushing Loads on Structure

In this paper, the interaction between level ice and wind turbine tower is simulated by the explicit nonlinear code LS-DYNA. The isotropic elasto-plastic material model is used for the level ice, in which ice crushing failure is considered. The effects of ice mesh size and ice failure strain on ice forces are investigated. The results indicate that these parameters have a significant effect on the ice crushing loads. To validate and benchmark the numerical simulations, experimental data on level ice-wind turbine tower interactions are used. First, the failure strains of the ice models with different mesh sizes are calibrated using the measured maximum ice force from one test. Next, the calibrated ice models with different mesh sizes are applied for other tests, and the simulated results are compared to corresponding model test data. The effects of the impact speed and the size of wind turbine tower on the comparison between the simulated and measured results are studied. The comparison results show that the numerical simulations can capture the trend of the ice loads with the impact speed and the size of wind turbine tower. When a mesh size of ice model is 1.5 times the ice thickness, the simulations can give more accurate estimations in terms of maximum ice loads for all tests, i.e., good agreement between the simulated and measured results is achieved

Photocatalytic degradation of gaseous toluene over ZnAl(2)O(4) prepared by different methods: A comparative study

The development of a " green" treatment process for typical indoor pollutants such as toluene is greatly desirable. In this study, ZnAlO nanoparticles were prepared via three different routes, i.e., solvothermal, citrate precursor and hydrothermal methods. Their structural properties were systematically investigated by X-ray powder diffraction (XRD), scanning electronic microscopy (SEM), energy-dispersive X-ray spectra (EDX), Brunauer-Emmett-Teller (BET), UV-vis diffuse reflectance spectroscopy (DRS), and Fourier transform infrared spectroscopy (FT-IR) techniques. The photo-induced charge separation in the samples was demonstrated by surface photovoltage (SPV) measurement. The photocatalytic performances of the ZnAlO samples and nanostructured TiO samples were comparatively studied by the degradation of gaseous toluene under UV lamp irradiation in in situ FTIR reactor. The results indicated that the sample synthesized by facile solvothermal method exhibited about 90% photocatalytic efficiency of toluene. The toluene was mineralized into carbon dioxide and water as the major species. The photocatalytic oxidation of gaseous pollutant over UV-illuminated ZnAlO is a promising technique for air purification

Pricing Model for Earthquake CAT Bonds

Conference Name:2nd International Conference on Business Intelligence and Financial Engineering. Conference Address: Beijing, PEOPLES R CHINA. Time:JUL 24-26, 2009.Catastrophe bond (CAT bond) is one of the most active instruments to transfer catastrophic risk into the capital market around the whole world. And the pricing theories are developed recently. For earthquake disaster, a pricing model, base on engineering seismic risk assessment, is given. The occurring probability of a defined earthquake catastrophe, estimated by seismic risk assessment method, is adopted as an input. Some factors, like yields and proportion of reinvestment, principal protected ratio, issuance fee, circulation, maturity period, claim payments of insurers and reinsurers, are designed. The cash flows of earthquake insurance premium in complete and incomplete markets are described by Geometric Brownian Motion and Jump-Diffusion processes respectively. The annual coupon rate of a CAT bond is calculated under the equilibrium between the incomes of investors and issuers. The feasibility of the model is represented by a production

Ultrasound-Assisted Hydrothermal Synthesis of SrSnO₃/g-C₃N₄ Heterojunction with Enhanced Photocatalytic Performance for Ciprofloxacin under Visible Light

In this work, an SrSnO3/g-C3N4 heterojunction with different dosage of SrSnO3 was fabricated by an ultrasound-assisted hydrothermal approach and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible diffuse reflectance spectra (UV-Vis DRS), and photoluminescence spectroscopy (PL). Ciprofloxacin was adopted to assess the degradation performance, and the sample combined with 40% SrSnO3 eliminated 93% of ciprofloxacin (20 mg/L) within 3 h under visible light, which is 6.6 and 1.7 times greater than for SrSnO3 and g-C3N4, respectively. Furthermore, 85% CIP was extinguished after five cycles of a photocatalytic process. Ultimately, a possible photocatalytic mechanism was dissected

Fabrication of La2O3/g-C3N4 Heterojunction with Enhanced Photocatalytic Performance of Tetracycline Hydrochloride

In this study, La2O3/g-C3N4 heterojunction photocatalysts doped with different dosages of La2O3 were constructed by a facile ultrasound-assisted calcination approach. The as-prepared photocatalysts were characterized by XRD, FTIR, FESEM, TEM, XPS, PL and DRS to verify the composite photocatalysts’ purity and to investigate their structural, morphological and elemental composition, and their energy band. According to the results, a type of pure rod–sheet-shaped, heterostructured nanoparticle was successfully obtained. Decorated with 10% La2O3, 2 g/L of the composite sample had a 93% degradation rate for 20 mg/L tetracycline hydrochloride within 2 h under visible light at a pH of 7. After four successive photocatalytic runs, satisfactory stability and reusability was exhibited, with 70% of the tetracycline hydrochloride being removed in the final experiment. Electrons (e−), photogenerated holes (h+), superoxide radical anions (·O2−) and hydroxyl radicals (·OH) were the fundamental active species during the photocatalytic process and were investigated via quenching experiments. Furthermore, possible photocatalytic mechanisms were analyzed in this work

A parametric study on the final blade installation process for monopile wind turbines under rough environmental conditions

Single blade installation is a method for installing wind turbine blades. If a jack-up vessel is used during an o shore installation, the wind turbine blade is mainly subjected to wind loads and experiences resonant motions, and the monopile is subjected to wave-induced vibrations. The blade mating process can be challenging if large relative motions occur between the blade root and the monopile top. This study numerically models a blade installation system that consists of a pre-installed monopile and nacelle assembly, and a 5 MW blade with tugger lines. By analyzing the blade-root and the hub motion radii from time-domain simulations, we evaluate the effects of mean wind speed, wind turbulence, significant wave height, wave spectrum peak period, wind-wave misalignment, and water depth on the blade installation. For the alignment phase, the blade-root motion is critical, especially when the mean wind speed and turbulence are high. The hub motion can be important when the monopile resonant responses are prominent. The relative in-plane motions rather than the hub or the blade motion alone should be considered during the assessment. For the mating phase, the high-frequency components of the responses are important in general. Because of the dominant flange-hole motions at the monopile top, an increase in water depth reduces the success rate of mating