A review of topic modeling methods

Topic modeling is a popular analytical tool for evaluating data. Numerous methods of topic modeling have been developed which consider many kinds of relationships and restrictions within datasets; however, these methods are not frequently employed. Instead many researchers gravitate to Latent Dirichlet Analysis, which although flexible and adaptive, is not always suited for modeling more complex data relationships. We present different topic modeling approaches capable of dealing with correlation between topics, the changes of topics over time, as well as the ability to handle short texts such as encountered in social media or sparse text data. We also briefly review the algorithms which are used to optimize and infer parameters in topic modeling, which is essential to producing meaningful results regardless of method. We believe this review will encourage more diversity when performing topic modeling and help determine what topic modeling method best suits the user needs.     

Automatic playlist generation based on tracking user’s listening habits

Algorithms for automatic playlist generation solve the problem of tedious and time consuming manual selection of musical playlists. These algorithms generate playlists according to the user’s music preferences of the moment. The user describes his preferences either by manually inputting a couple of example songs, or by defining constraints for the choice of music. The approaches to automatic playlist generation up to now were based on examining the metadata attached to the music pieces. Some of them took also the listening history into account. But anyway, a heavy accent has been put on the metadata, while the listening history, if it was used at all, had a minor role. Missings and errors in metadata frequently appear, especially when the music is acquired from the Internet. When the metadata is missing or wrong, the approaches proposed so far cannot work. Besides, entering constraints for the playlist generation can be a difficult activity. In our approach we ignored the metadata and focused on examining the listening habits. We developed two simple algorithms that track the listening habits and form a listener model—a profile of listening habits. The listener model is then used for automatic playlist generation. We developed a simple media player which tracks the listening habits and generates playlists according to the listener model. We tried the solution with a group of users. The experiment was not a successful one, but it threw some new light on the relationship between the listening habits and playlist generation.     

NUMERICAL ANALYSIS OF THE EFFECTS OF LOCAL HYDRODYNAMICS ON MASS TRANSFER IN HETEROGENEOUS POROUS MEDIA

Many engineering problems require the estimation of mass transfer coefficients in porous materials. In heterogeneous materials or in cases where mass transfer sites are not spatially uniform, empirical equations for mass transfer coefficients vary widely, and the origin of these differences is not well understood. In this article, we use a stochastic algorithm to model mass transfer from single particles in a two-dimensional heterogeneous packed bed. The computed mass transfer coefficients are used to generate a distribution of local Peclet numbers in the bed. Detailed hydrodynamics are then used to interpret variations in the local Peclet number. The results show clear relationships between pore structure, streamline patterns, and mass transfer rates.     

The impact of presentation graphics on students’ experience in the classroom

To investigate the benefits and perceived effectiveness of instructional technology, students enrolled in several courses were compared on student evaluations of instruction, grades and an attitudinal questionnaire. The instructors of the courses taught the same course across two successive semesters, using traditional “chalk-and-talk” methods the first semester, and PowerPoint the next; all other techniques (e.g., exams, lecture material) were held constant. Results suggest that organization and clarity, entertainment and interest, professor likeability, and good professor behaviors were enhanced with PowerPoint although final grades were not.     

Radiation-laminar free convection in a square duct with specular reflection by absorbing-emitting medium

The purpose of this work is to study the effects of specularly reflecting wall under the combined radiative and laminar free convective heat transfer in an infinite square duct. An absorbing and emitting gray medium is enclosed by the opaque and diffusely emitting walls. The walls may reflect diffusely or specularly. Boussinesq approximation is used for the buoyancy term. The radiative heat transfer is evaluated using the direct discrete ordinates method. The parameters under considerations are Rayleigh number, conduction to radiation parameter, optical thickness, wall emissivity and reflection mode. The differences caused by the reflection mode on the stream line, and temperature distribution and wall heat fluxes are studied. Some differences are observed for the categories mentioned above if the order of the conduction to radiation parameter is less than order of 10^-3 for the range of Rayleigh number studied. The differences at the side wall heat flux distributions are observed as long as the medium is optically thin. As the top wall emissivity decreases, the differences between these two modes are increased. As the optical thickness decreases at the fixed wall emissivity, the differences also increase. The difference of the streamlines or the temperature contours is not as distinct as the side wall heat flux distributions. The specular reflection may alter the fluid motion.     

覆膜滤料的滤尘性能测试方法研究

由于覆膜滤料的结构和性能有别于普通滤料，因而普通滤料的滤尘性能测试方法不完全适用于覆滤料。本文作者在总结实践经验的基础上，提出了在覆膜滤料的滤尘性能测试中应注意的一些问题和应增加的测试项目。     

低铁耗条件下转炉高碳低磷工艺实践与应用

对转炉炼钢实现低铁耗和高碳低磷工艺进行了分析，介绍了南钢公司转炉炼钢实践低铁耗条件下高碳低磷工艺的具体应用措施。     

日本锰质合金生产与锰矿石的消耗

本文全面介绍了日本近年特别是1990年锰矿石进口量和锰铁合金的生产情况。同时还介绍了锰质合金、电解金属锰和电解二氧化锰的进出口情况。日本1990年进口锰矿石143万t,高碳锰铁4.6万t,中、低碳锰铁0.3万t,硅锰21.8t。还列出了进口矿石和硬质合金来源国数量。此外,还介绍了日本重点锰质合金厂的产品。     

HDPE装置超负荷低能耗生产方案的设计与实施

本文介绍大庆ＨＤＰＥ装置提高生产能力及产品质量的方法。通过采用釜外络合催化剂新技术和提浆液浓度可将ＨＤＰＥ装置聚合釜单釜的生产能力由４．７５ｔ／ｈ提高到５．０ｔ／ｈ，各项能耗下降，收到了增产降耗的显著效果，并使产品质量，产量，品种，能耗，物耗，环保６项指标全部达到了设计要求。     

基于MSP430F413 MCU的IC卡煤气表的设计与实现

提出了以TI公司MSP430系列MCU为基础的IC卡煤气表的设计思想，给出了总体设计，硬件电路设计，软件流程设计及主要模块的编程框架，讨论了低功耗问题。同时，对IC卡煤气表设计中一些应注意的问题也进行了简要的阐述。