Exploiting Causal Independence in Bayesian Network Inference

A new method is proposed for exploiting causal independencies in exact Bayesian network inference. A Bayesian network can be viewed as representing a factorization of a joint probability into the multiplication of a set of conditional probabilities. We present a notion of causal independence that enables one to further factorize the conditional probabilities into a combination of even smaller factors and consequently obtain a finer-grain factorization of the joint probability. The new formulation of causal independence lets us specify the conditional probability of a variable given its parents in terms of an associative and commutative operator, such as ``or'', ``sum'' or ``max'', on the contribution of each parent. We start with a simple algorithm VE for Bayesian network inference that, given evidence and a query variable, uses the factorization to find the posterior distribution of the query. We show how this algorithm can be extended to exploit causal independence. Empirical studies, based on the CPCS networks for medical diagnosis, show that this method is more efficient than previous methods and allows for inference in larger networks than previous algorithms.Comment: See http://www.jair.org/ for any accompanying file

Creating Value for Competitive Advantage in Supply Chain Relationships: The Case of the Sri Lankan Tea Industry

The declining competitiveness of the Sri Lankan tea industry is an example of shifting competitive advantage in agribusiness. This research uses a case study approach to identify the specific role of information and communication on exporter/importer relationships within the tea supply chain, and the impact on value addition, channel member performance and competitive advantage in the Sri Lankan tea industry. The main primary data collection was conducted through thirty face-to-face executive interviews in Sri Lanka using an extensive semi-structured interview guide. Analyses of the information from the interviews were qualitative in nature. Results demonstrated how good information and communication between exporters and importers promote joint decision making, commitment and loyalty. In turn these affect relationship quality in respect of concepts such as trust, commitment, satisfaction and opportunism. Relationship quality was also shown to have impacts on value creation. Results indicated that this approach leads to inimitable strategic advantages for supply chain players whereby it is difficult for competitors to duplicate such relationships.Agribusiness, Industrial Organization,

Responding to Sexual Discrimination: The effects of societal versus self-blame

While self-blame has been considered to be a useful coping tool for victims, its benefits within the context of group discrimination are equivocal. The present research hypothesized that women encouraged to engage in self-blame for sex discrimination would be more likely to endorse accepting their situation or endorse the use of individual, normative actions. In contrast, women encouraged to engage in societal blame for sex discrimination would be more likely to participate in non-normative actions aimed at enhancing the status of the group as a whole. Female students in Canada were subjected to a situation of discrimination and were encouraged to blame either themselves or social discrimination. They were then given the opportunity to respond to the discrimination by endorsing various actions. A profile analysis of the endorsed actions indicated that women encouraged to blame themselves were most likely to endorse accepting their situation, while women encouraged to blame society endorsed non-normative individual confrontation

Development and flight tests of a gyro-less wing leveler and directional autopilot

A gyro-less wing leveler and directional autopilot were developed and flight tested in a single-engine light airplane. The primary purpose of the project was to develop a simple, reliable, low-cost stability augmentation and autopilot system for light aircraft. The wing leveler used a fluidic inertial rate sensor, electronic signal processing circuitry, and vacuum operated servos. A strap-down magnetic heading reference of simple design provided the wing leveler with directional autopilot capability. Flight tests indicated that the performance of the gyro-less wing leveler was equal to that of a commercial wing leveler using a gyroscopic rate sensor. Drift-free, long-term, heading-hold capability of the magnetic heading reference was demonstrated

Analysing Linkages between Strategy, Performance, Management Structure and Culture in the Spanish Fresh Produce Industry

This article reports the results of an industry-level study that seeks to identify empirical regularities between firm strategy, management style, organisational structure and performance in the Spanish fresh fruit and vegetable (fresh produce) industry using strategic group analysis. Groups were formed from key dimensions reflecting firms' strategic orientations. Performance levels did not differ systematically between strategic groups, but performance was found to be influenced by the alignment between entrepreneurial culture and organisational structure. A move towards greater flexibility and/or adopting an entrepreneurial style are both likely to contribute to an improvement in the overall performance of the firm.Strategic groups, Business strategy, Management structure, Fresh, Agribusiness, Crop Production/Industries,

Miniature spectrally selective dosimeter

A miniature spectrally selective dosimeter capable of measuring selected bandwidths of radiation exposure on small mobile areas is described. This is achieved by the combination of photovoltaic detectors, electrochemical integrators (E-cells) and filters in a small compact case which can be easily attached in close proximity to and substantially parallel to the surface being measured. In one embodiment two photovoltaic detectors, two E-cells, and three filters are packaged in a small case with attaching means consisting of a safety pin. In another embodiment, two detectors, one E-cell, three filters are packaged in a small case with attaching means consisting of a clip to clip over a side piece of an eye glass frame

Reducing Polarization Mode Dispersion With Controlled Polarization Rotations

One of the fundamental limitations to high bit rate, long distance, telecommunication in optical fibers is Polarization Mode Dispersion (PMD). Here we introduce a conceptually new method to reduce PMD in optical fibers by carrying out controlled rotations of polarization at predetermined locations along the fiber. The distance between these controlled polarization rotations must be less than both the beat length and the mode coupling length of the fiber. This method can also be combined with the method in which the fiber is spun while it drawn. The incidence of imperfections on the efficiency of the method is analysed.Comment: 4 page