Forbidden induced subgraphs and the price of connectivity for feedback vertex set.

Let fvs(G) and cfvs(G) denote the cardinalities of a minimum feedback vertex set and a minimum connected feedback vertex set of a graph G, respectively. For a graph class G, the price of connectivity for feedback vertex set (poc-fvs) for G is defined as the maximum ratio cfvs(G)/fvs(G) over all connected graphs G in G. It is known that the poc-fvs for general graphs is unbounded. We study the poc-fvs for graph classes defined by a finite family H of forbidden induced subgraphs. We characterize exactly those finite families H for which the poc-fvs for H-free graphs is bounded by a constant. Prior to our work, such a result was only known for the case where |H|=1

A Prototype for the PASS Permanent All Sky Survey

A prototype system for the Permanent All Sky Survey (PASS) project is presented. PASS is a continuous photometric survey of the entire celestial sphere with a high temporal resolution. Its major objectives are the detection of all giant-planet transits (with periods up to some weeks) across stars up to mag 10.5, and to deliver continuously photometry that is useful for the study of any variable stars. The prototype is based on CCD cameras with short focal length optics on a fixed mount. A small dome to house it at Teide Observatory, Tenerife, is currently being constructed. A placement at the antarctic Dome C is also being considered. The prototype will be used for a feasibility study of PASS, to define the best observing strategies, and to perform a detailed characterization of the capabilities and scope of the survey. Afterwards, a first partial sky surveying will be started with it. That first survey may be able to detect transiting planets during its first few hundred hours of operation. It will also deliver a data set around which software modules dealing with the various scientific objectives of PASS will be developed. The PASS project is still in its early phase and teams interested in specific scientific objectives, in providing technical expertise, or in participating with own observations are invited to collaborate.Comment: Accepted for Astronomische Nachrichten (special issue for 3rd Potsdam Thinkshop 'Robotic Astronomy' in July 2004). 4 pages, 4 fig

optimized low pressure solar dec with zeolite based adsorption

Abstract This paper presents a new concept of hybrid/natural air conditioning system with a high level of architectural integration. A solar DEC (Desiccant Evaporative Cooling) open cycle with very low pressure drops, drastically reduces the electricity consumption for driving fans. The supply air is dehumidified by an innovative zeolite coated adsorption bed and cooled indirectly by an evaporative cooler, through a low pressure drop heat exchanger. The adsorption bed is a finned coil heat exchanger coated with a SAPO-34 zeolite layer realizing both heat and mass transfer in one component. Low thermal grade heat is used to regenerate the adsorbent material, showing high compatibility with low temperature solar systems such as flat plate or evacuated tubes solar collectors. Experimental data have been used for validating a CFD model of the coated coil. The possibility to remove the adsorption heat during dehumidification reduces the air temperature with a positive effect on cooling power

Influence of occupants’ behavior on indoor CO2 concentration of a naturally ventilated multifamily building in Porto, Portugal

Adequate supply of fresh air is essential to provide a healthy, safe and comfortable indoor environment in buildings. Currently, the majority of the residential buildings in mild climate European countries, such as Portugal or Spain, remain naturally ventilated. This fact has raised concerns in the building sector regarding the indoor air quality present in these buildings as fresh air supply mostly relies on occupants? window opening behavior and personal habits, which can vary significantly from one apartment to the next. In this context, this work presents the indoor CO2 concentration levels registered during more than one year in the bedrooms and living rooms of eight apartments of a naturally ventilated residential building located in Porto, Portugal. Monitored CO2 concentrations confirmed relevant periods of time with inadequate indoor air quality, exhibiting great variations between apartments. Differential occupants? window opening behavior, personal habits as well as presence of internal CO2 sources (e.g. smokers) were stated as the major reasons behind these wide discrepancies. Results suggest that, in some situations, implementation of mechanical ventilation systems in residential contexts should be promoted in order to guarantee adequate IAQ at all times and regardless of outdoor weather conditions or occupants? window opening behavior. info:eu-repo/semantics/publishedVersio

Factors influencing engineering students for choosing techno-entrepreneurship as a career: An implication for better learning

Techno-entrepreneurship is critical to the growth of society as a useful technique for overcoming youth unemployment. However, the growth of techno-entrepreneurship has been limited with the end outcome being less than satisfying. Hence, the purpose of this study was to determine the factors that influence the possibility of choosing techno-entrepreneurship as a profession among engineering students in the Philippines. There were 200 engineering students selected by stratified random sampling and the significance of the factors was then determined using Pearson correlation analysis. Based on the findings, students’ likelihood of choosing techno-entrepreneurship as a career was not influenced by their equipment availability but by their e-commerce experience, geographical location, and internet ability. This implies the need for academic personnel and instructors teaching techno-entrepreneurship courses to guarantee students have relevant technopreneur knowledge, skills, and competencies that value students’ creativity and innovation to encourage techno-entrepreneurship as a profession