Search engine For Twitter sentiment analysis

textThe purpose of sentiment analysis is to determine the attitude of a writer or a speaker with respect to some topic or his feeling in a document. Thanks to the rise of social media, nowadays there are numerous data generated by users. Mining and categorizing these data will not only bring profits for companies, but also benefit the nation. Sentiment analysis not only enables business decision makers to better understand customers' behaviors, but also allows customers to know how the public feel about a product before purchasing. On the other hand, the aggregation of emotions will effectively measure the public response toward an event or news. For example, the level of distress and sadness will increase significantly after terror attacks or natural disaster. In our project, we are going to build a search engine that allows users to check the sentiment of his query. Some of previous researches on classifying sentiment of messages on micro-blogging services like Twitter have tried to solve this problem but they have ignored neutral tweets, which will result in problematic results (12). Our sentiment analysis will also be based on tweets collected from twitter, since twitter can offer sufficient and real-time corpora for analysis. We will preprocess each tweet in the training set and label it as positive, negative or neutral. As we use words in the tweet as the feature for our model, different features will be used. We will show that accuracy achieved by different machine learning algorithms (Naïve Bayes, Maximum Entropy) can be improved with a feature vector obtained by using bigrams (5). In our practice, we find that Naive Bayes has better performance than Maximum Entropy.Statistic

Flocculation in the Scheldt Estuary: a case study of intertidal mudflats

The flocculation mechanism dominates the fate of suspended matter in the estuarine environment. As it modifies the texture of suspended matter, flocculation thus affects suspended matter's transport and deposition. In order to understand the complexity of the flocculation mechanism, a case study was performed on two intertidal mudflats in the Scheldt estuary, a freshwater and a brackish water one. A one-year biweekly survey investigated the seasonal variation of flocculation, physical properties of suspended matter, organic matter content and suspended matter deposition in the intertidal area. The flocculation study includes floc’s shape, sphericity and microfabric, which properties are believed to be significant in the suspended matter transport processes in the estuary. This study shows that floc size as well as floc sphericity positively correlates with the change of organic matter. Moreover, it reveals that with increasing organic matter floc expands in a three-dimensional way. It is observed that relatively dense, small and elongated flocs appear in winter and spring periods, while loose, large and spherical flocs occur in summer time. The study also reveals that suspended matter transported as dense and fine-to-medium sand-sized flocs have a greater effect on its short-term deposition than loose and medium-to-coarse sand-sized flocs. As the measured suspended matter deposition is much higher in winter-spring than in summer time, it is deducted here that highly concentrated and relatively dense flocs contribute to fast deposition during winter and spring periods resulting in a compact layer, while loosely formed flocs likely lead to an easier erodible layer in summer time. This study concludes that floc density is a more determining parameter in suspended matter’s transport processes than floc size

Gear ratio optimization of one- and two-speed transmissions for fully-electric vehicles

Currently, electric vehicles use a transmission with a single-speed fixed gear ratio optimized for performance. This work features the development of a framework to optimize the gear ratio for a given vehicle design, motor efficiency map, motor noise spectrum, and transmission noise spectrum. The framework provides a methodology for designing the optimization problem to be solved using derivative-free optimization methods. As electric vehicles become increasingly prevalent in the global automotive market, the need to develop multi-speed transmissions to provide a competitive edge against other electric vehicles. This work also explores the optimization of gear ratios for a two-speed transmission and identifies a corresponding switching point to switch between the two ratios. Using the same methodology, the optimization problem is formatted such that derivative-free optimization methods can be used to solve the optimization problem quickly and efficiently. Utilizing the framework developed, the program was able to identify an optimal gear ratio for a single-speed transmission in about half the time it took a brute-force search method to the same. The two-speed optimization process completed about 50 times faster than the brute force search. In both cases, the result returned by the optimization process was compared against the brute force search result to confirm global optimality. The single-speed gear ratio optimization, the two-speed gear ratio optimization, and the two-speed switching point optimization reliably located a global optimum.Mechanical Engineerin

Stellar adiabatic mass loss model and applications

Roche-lobe overflow and common envelope evolution are very important in binary evolution, which is believed to be the main evolutionary channel to hot subdwarf stars. The details of these processes are difficult to model, but adiabatic expansion provides an excellent approximation to the structure of a donor star undergoing dynamical time scale mass transfer. We can use this model to study the responses of stars of various masses and evolutionary stages as potential donor stars, with the urgent goal of obtaining more accurate stability criteria for dynamical mass transfer in binary population synthesis studies. As examples, we describe here several models with the initial masses equal to 1 Msun and 10 Msun, and identify potential limitations to the use of our results for giant-branch stars.Comment: 7 pages, 5 figures,Accepted for publication in AP&SS, Special issue Hot Sub-dwarf Stars, in Han Z., Jeffery S., Podsiadlowski Ph. ed

Magnetic and pair correlations of the Hubbard model with next-nearest-neighbor hopping

A combination of analytical approaches and quantum Monte Carlo simulations is used to study both magnetic and pairing correlations for a version of the Hubbard model that includes second-neighbor hopping $t^{\prime }=-0.35t$ as a model for high-temperature superconductors. Magnetic properties are analyzed using the Two-Particle Self-Consistent approach. The maximum in magnetic susceptibility as a function of doping appears both at finite $$ and at $t^{\prime }=0$ but for two totally different physical reasons. When $t^{\prime }=0$, it is induced by antiferromagnetic correlations while at $t^{\prime }=-0.35t$ it is a band structure effect amplified by interactions. Finally, pairing fluctuations are compared with $$-matrix results to disentangle the effects of van Hove singularity and of nesting on superconducting correlations. The addition of antiferromagnetic fluctuations increases slightly the $d$-wave superconducting correlations despite the presence of a van Hove singularity which tends to decrease them in the repulsive model. Some aspects of the phase diagram and some subtleties of finite-size scaling in Monte Carlo simulations, such as inverted finite-size dependence, are also discussed.Comment: Revtex, 8 pages + 15 uuencoded postcript figure

Water wave propagation and scattering over topographical bottoms

Here I present a general formulation of water wave propagation and scattering over topographical bottoms. A simple equation is found and is compared with existing theories. As an application, the theory is extended to the case of water waves in a column with many cylindrical steps

Theoretical analysis of the focusing of acoustic waves by two-dimensional sonic crystals

Motivated by a recent experiment on acoustic lenses, we perform numerical calculations based on a multiple scattering technique to investigate the focusing of acoustic waves with sonic crystals formed by rigid cylinders in air. The focusing effects for crystals of various shapes are examined. The dependance of the focusing length on the filling factor is also studied. It is observed that both the shape and filling factor play a crucial role in controlling the focusing. Furthermore, the robustness of the focusing against disorders is studied. The results show that the sensitivity of the focusing behavior depends on the strength of positional disorders. The theoretical results compare favorably with the experimental observations, reported by Cervera, et al. (Phys. Rev. Lett. 88, 023902 (2002)).Comment: 8 figure