Semisupervised learning of hierarchical latent trait models for data visualization

Recently, we have developed the hierarchical Generative Topographic Mapping (HGTM), an interactive method for visualization of large high-dimensional real-valued data sets. In this paper, we propose a more general visualization system by extending HGTM in three ways, which allows the user to visualize a wider range of data sets and better support the model development process. 1) We integrate HGTM with noise models from the exponential family of distributions. The basic building block is the Latent Trait Model (LTM). This enables us to visualize data of inherently discrete nature, e.g., collections of documents, in a hierarchical manner. 2) We give the user a choice of initializing the child plots of the current plot in either interactive, or automatic mode. In the interactive mode, the user selects "regions of interest," whereas in the automatic mode, an unsupervised minimum message length (MML)-inspired construction of a mixture of LTMs is employed. The unsupervised construction is particularly useful when high-level plots are covered with dense clusters of highly overlapping data projections, making it difficult to use the interactive mode. Such a situation often arises when visualizing large data sets. 3) We derive general formulas for magnification factors in latent trait models. Magnification factors are a useful tool to improve our understanding of the visualization plots, since they can highlight the boundaries between data clusters. We illustrate our approach on a toy example and evaluate it on three more complex real data sets. © 2005 IEEE.

Economic efficiency of mobile latent heat storages

In a pilot project an optimized mobile latent heat storage based on a system available on the market has been tested at Fraunhofer Institute for Environmental, Safety and Energy Technology. Initially trials were conducted with the aim of optimizing the process of charging and discharging. A specifically constructed test rig at the incineration trials centre at the institute allowed charging and discharging procedures of the mobile latent heat storage with adjustable parameters. In addition an evaluation model was constructed to further optimize the heat exchanger systems. In conclusion the prototype of the mobile latent heat storage was tested in practical operation. The economic and technical feasibility of heat transportation was shown if not utilized waste heat is available. © 2014 The Authors.

How good are citizen weather stations? Addressing a biased opinion

The UK is home to a dense network of Citizen Weather Stations (CWS) primarily set up by members of the public. The majority of these stations record air temperature, relative humidity and precipitation, amongst other variables, at sub-hourly intervals. This high resolution network could have benefits in many applications, but only if the data quality is well characterised. Here we present results from an intercomparison field study, in which popular CWS models were tested against Met Office standard equipment. The study identifies some common instrumental biases and their dependencies, which will help us to quantify and correct such biases from the CWS network.

Many Facet, Common Latent Trait Polytomous IRT Model and EM Algorithm

2000 Mathematics Subject Classification: 91E45.

Anisotropic opinion dynamics

We consider the process of opinion formation in a society of interacting agents, where there is a set B of socially accepted rules. In this scenario, we observed that agents, represented by simple feed-forward, adaptive neural networks, may have a conservative attitude (mostly in agreement with B) or liberal attitude (mostly in agreement with neighboring agents) depending on how much their opinions are influenced by their peers. The topology of the network representing the interaction of the society's members is determined by a graph, where the agents' properties are defined over the vertexes and the interagent interactions are defined over the bonds. The adaptability of the agents allows us to model the formation of opinions as an online learning process, where agents learn continuously as new information becomes available to the whole society (online learning). Through the application of statistical mechanics techniques we deduced a set of differential equations describing the dynamics of the system. We observed that by slowly varying the average peer influence in such a way that the agents attitude changes from conservative to liberal and back, the average social opinion develops a hysteresis cycle. Such hysteretic behavior disappears when the variance of the social influence distribution is large enough. In all the cases studied, the change from conservative to liberal behavior is characterized by the emergence of conservative clusters, i.e., a closed knitted set of society members that follow a leader who agrees with the social status quo when the rule B is challenged.

Semi-supervised Gaussian process latent variable model with pairwise constraints

In machine learning, Gaussian process latent variable model (GP-LVM) has been extensively applied in the field of unsupervised dimensionality reduction. When some supervised information, e.g., pairwise constraints or labels of the data, is available, the traditional GP-LVM cannot directly utilize such supervised information to improve the performance of dimensionality reduction. In this case, it is necessary to modify the traditional GP-LVM to make it capable of handing the supervised or semi-supervised learning tasks. For this purpose, we propose a new semi-supervised GP-LVM framework under the pairwise constraints. Through transferring the pairwise constraints in the observed space to the latent space, the constrained priori information on the latent variables can be obtained. Under this constrained priori, the latent variables are optimized by the maximum a posteriori (MAP) algorithm. The effectiveness of the proposed algorithm is demonstrated with experiments on a variety of data sets. © 2010 Elsevier B.V.

A kockázat mint látens fogalom (Risk - A latent concept)

A kockázat statisztikai értelemben közvetlenül nem mérhető, azaz látens fogalom éppen úgy, mint a gazdasági fejlettség, a szervezettség vagy az intelligencia. Mi bennünk a közös? A kockázat is komplex fogalom, több mérhető tényezőt foglal magában, és bár sok tényezőjét mérjük, fel sem tételezzük, hogy pontos eredményt kapunk. Ebben a megközelítésben az elemző kezdettől fogva tudja, hogy hiányos az ismerete. Ezt Bélyácz [2011[ nyomán úgy is megfogalmazhatjuk: „A statisztikusok tudják, hogy valamit éppen nem tudnak.” / === / From statistical point of view risk, like economic development is a latent concept. Typically there is no one number which can explicitly estimate or project risk. Variance is used as a proxy in finance to measure risk. Other professions are using other concepts for risk. Underwriting is the most important step in insurance business to analyse exposure. Actuaries evaluate average claim size and the probability of claim to calculate risk. Bayesian credibility can be used to calculate insurance premium combining frequencies and empirical knowledge, as a prior. Different types of risks can be classified into a risk matrix to separate insurable risk. Only this category can be analysed by multivariate statistical methods, which are based on statistical data. Sample size and frequency of events are relevant not only in insurance, but in pension and investment decisions as well.

Framing infectious diseases and U.S. public opinion

The United States has been increasingly concerned with the transnational threat posed by infectious diseases. Effective policy implementation to contain the spread of these diseases requires active engagement and support of the American public. To influence American public opinion and enlist support for related domestic and foreign policies, both domestic agencies and international organizations have framed infectious diseases as security threats, human rights disasters, economic risks, and as medical dangers. This study investigates whether American attitudes and opinions about infectious diseases are influenced by how the issue is framed. It also asks which issue frame has been most influential in shaping public opinion about global infectious diseases when people are exposed to multiple frames. The impact of media frames on public perception of infectious diseases is examined through content analysis of newspaper reports. Stories on SARS, avian flu, and HIV/AIDS were sampled from coverage in The New York Times and The Washington Post between 1999 and 2007. Surveys of public opinion on infectious diseases in the same time period were also drawn from databases like Health Poll Search and iPoll. Statistical analysis tests the relationship between media framing of diseases and changes in public opinion. Results indicate that no one frame was persuasive across all diseases. The economic frame had a significant effect on public opinion about SARS, as did the biomedical frame in the case of avian flu. Both the security and human rights frames affected opinion and increased public support for policies intended to prevent or treat HIV/AIDS. The findings also address the debate on the role and importance of domestic public opinion as a factor in domestic and foreign policy decisions of governments in an increasingly interconnected world. The public is able to make reasonable evaluations of the frames and the domestic and foreign policy issues emphasized in the frames.

Controls on sensible heat and latent energy fluxes from a short-hydroperiod Florida Everglades marsh

Little is known of energy balance in low latitude wetlands where there is a year-round growing season and a climate best defined by wet and dry seasons. The Florida Everglades is a highly managed and extensive subtropical wetland that exerts a substantial influence on the hydrology and climate of the south Florida region. However, the effects of seasonality and active water management on energy balance in the Everglades ecosystem are poorly understood. An eddy covariance and micrometeorological tower was established in a short-hydroperiod Everglades marsh to examine the dominant environmental controls on sensible heat (H) and latent energy (LE) fluxes, as well as the effects of seasonality on these parameters. Seasonality differentially affected H and LE fluxes in this marsh, such that H was principally dominant in the dry season and LE was strongly dominant in the wet season. The Bowen ratio was high for much of the dry season (1.5–2.4), but relatively low (H and LE fluxes across nearly all seasons and years (). However, the 2009 dry season LE data were not consistent with this relationship () because of low seasonal variation in LE following a prolonged end to the previous wet season. In addition to net radiation, H and LE fluxes were significantly related to soil volumetric water content (VWC), water depth, air temperature, and occasionally vapor pressure deficit. Given that VWC and water depth were determined in part by water management decisions, it is clear that human actions have the ability to influence the mode of energy dissipation from this ecosystem. Impending modifications to water management under the Comprehensive Everglades Restoration Plan may shift the dominant turbulent flux from this ecosystem further toward LE, and this change will likely affect local hydrology and climate.

Lan American Coups: Have They Vanished or Taken New Shapes?

In the following pages, three well-known Latinoamericanists share their views on the current prospects for coups in Latin America. They are: Rut Diamint of the University Torcuatto de Tella in Buenos Aires, Argentina; Pablo Policzer of the University of Calgary in Canada; and Michael Shifter of the Inter-American Dialogue in Washington, DC. Each looks at the potential for coups from different perspectives but, all three come to similar conclusions. That is, that despite substantial gains in democracy, the threat of coups in Latin America remains latent. The authors agree that democracy is growing in the region. Opinion surveys such as the Americas Barometer consistently show that citizens in Latin America have gradually incorporated democracy as part of their core value system. Yet, the authors argue convincingly that Latin America faces new types of interruptions to its democratic process that should be considered coups, even if not following the traditional style of military coup that predominated in the past. Situations that have taken place in Peru, Ecuador, Nicaragua, Honduras and other countries serve to illustrate the new trends. More specifically, Professor Diamint argues that in Latin America a culture of intolerance, demonization of the opposition, and the utilization of any method to achieve power prevails. In a region with a very high threshold of violence, governments fail to set an example of establishing a culture of debate, consensus, and transparency. This culture is inclined to uncontrollable political expressions, preferring confrontational means to resolve conflict. Within this scenario, “messianic” solutions are promoted and coups cannot be discarded as an option that would never transpire. Professor Policzer looks more closely to the constitutional loopholes that allow for a transformation of limited into absolute power. He argues that coups can be constitutional or unconstitutional, and that a constitutional coup can occur when violations to democracy actually stem from the constitutions themselves. In Honduras, for example specific provisions in the Constitution itself created conditions for a constitutional crisis; similar provisions have also led to constitutional authoritarianism in Venezuela and other countries. Dr. Policzer stresses that when a head of state or the military take absolute power, even temporarily, based on provisions in their constitutions; they are in essence staging a constitutional coup. These blind spots in constitutions, he argues, may be more serious threat to democracy than that of traditional coups. Lastly, Dr. Shifter argues that some kind of coup should be expected in Latin America in coming years, not only because fundamental institutions remain weak in some countries, but because the regional political environment is less prepared to respond effectively to transgressions than it was a few years ago. The good news, however, is that only a handful of countries, show no interest in governing. The bad news is that in those few countries where situations are indeed shaky, they are also in some cases aggravated by rising food and fuel prices, and spreading criminality, which pose serious risks to the rule of law and democratic governance.

In My Opinion: Michael E. Hurst: July 8, 1931 - March 22, 2001

My reflections of Michael E. Hurst are a much more modest enterprise than a memoir or biography. My portrait of him will only portray the images I observed and remember: As he was an adult when I met him, it is far from a complete picture of him. I was his academic dean, fellow professor, and friend. While fame has eluded most people I know. Hurst was the exception: everyone in the food service industry knew him.

In My Opinion.. Legend in his Time: Lendal H. Kotschevar

Lednal H. Kotschevar is a pioneer in the food service industry. His life spans that of the 20th century and his influence in the hospitality discipline molded its growth and its directions.

In My Opinion: Skill Development Key to Managerial Success

The professional success of future hospitality graduates will require that they have gone beyond the acquisition of contemporary industry knowledge and training in current best practices. Increasingly relevant hospitality education will emphasize skill development. Managerial thinking and renewal skills will be especially useful in an industry which is constantly changing.

In My Opinion… Good Intentions Don't Count

While simple guest surveys can be poorly constructed with little negative consequences, often surveys are used in making important policy decisions. Researchers and policy makers must carefully construct their research instruments in order to avoid biases which may result in muddled or incorrect responses. The authors review the process of creating, administering, and analyzing surveys with an eye toward reducing survey bias to a minimum. Reliable results require a rigorous and careful approach when creating and using instruments.