Passive damping concepts for slender columns in space structures

An experimental and theoretical study of three different passive damping concepts is conducted for a slender member with partial rotational end restraints. Over a hundred full-scale natural vibration experiments were conducted to evaluate the effectiveness of mass-string, polyethylene tubing, and chain damping concepts. The damping properties obtained from the experiments were used in the approximate analyses based on the partial differential equation of motion for the problem. The comparison of the experimental and the theoretical deflection-time relations shows that the velocity-dependent damping model used in the theory is adequate. From the experimental results, the effect of end connection friction and induced axial forces on damping is identified. The definition of an efficiency index is proposed based on the damping ratio and the mass of a given passive damping device. Using this definition, the efficiencies of the three damping devices are compared. The polyethylene tubing concept resulted into a low damping efficiency

Stability, vibration and passive damping of partially restrained imperfect columns

A theoretical and experimental study of slender tubular columns for possible use in space structures is conducted in the presence of partial rotational end restraints. Explicit formulas are derived for computing the buckling load and the lowest natural frequency of perfectly straight uniform elastic members with rotational end restraints possessing linear moment-rotation characteristics. An exact solution in the form of a transcendental equation, and a numerical solution using second-order finite-differences are also presented. The presence of an initial imperfection is also incorporated into the numerical procedure. Vibration tests are conducted on an imperfect tubular steel member in the absence of an axial load. A damping concept consisting of a string-mass assembly is explored. Three passive damping configurations involving combinations of three lead shots were investigated. The three lead shot configurations provided considerably greater damping than the single lead shot

Jet Lag From A Physics Point Of View

While the common believe is that dark/light timing causes jet lag, we argue that physics, not the biological clock, may be the main reason for this air travel disorder. We explored the change in voltage in the human brain due to the added voltage induced by flying over the magnetic field of the Earth, and we think that this induced voltage in the brain is significant enough to cause neurological changes that may trigger jet lag or other illnesses

The influence of rumen volatile fatty acids on protein metabolism in growing lambs

The effect of acetic or propionic acid rumen fermentation patterns on whole-body protein turnover, tissue protein synthetic rates and body composition was investigated in growing lambs. Protein turnover was assessed using a continuous intravenous infusion of [2,3-³H]tyrosine and tissue protein fractional synthetic rates (FSR) from the specific activities of plasma free, intracellular free and tissue bound tyrosine. Only the FSR of muscle tissue approached significance. The high FSR in the propionic group was attributed to the high plasma insulin concentration. Values for whole-body protein synthesis, corrected for tyrosine oxidation, were similar to those obtained by summating protein synthesis in individual tissues, confirming that tyrosine oxidation should be measured accurately if reliable whole-body protein synthesis values are required. Tyrosine oxidation and flux were high in the acetic acid group, suggesting that amino acids are used for gluconeogenesis. The high protein turnover rate probably ensures an adequate supply of gluconeogenic amino acids and that the penalty of mobilizing body proteins for gluconeogenic amino acids is minimal. In the propionic acid group, high plasma glucose and insulin concentrations were associated with a low protein turnover rate, high ratio of deposited: synthesized protein and a high body fat content. It is concluded that changing the proportion of ruminal volatile fatty acids influences protein turnover, protein synthesis and the efficiency of protein retention. Such factors probably contribute, indirectly, to the observed differences in body composition

Future Community-Based Ecotourism (CBET) development

Ecotourism is an alternative form of tourism and is usually confused with natural and cultural tourism.CBET is fast becoming a popular biodiversity conservation tool that develops and benefits the local community. Based on the context of conservation theory and practice, Community-Based Ecotourism (CBET) is a form of community-based natural resource management. However, a sustainable CBET development through Community Capacity Building (CCB)programs is not something that it easily achievable. Local community’s capacity varies from one culture to another. It takes a high level of community participation, in order for it to come to a level where the community members themselves are motivated to participate and contribute to the development of the program. This fully qualitative research involved 15 respondents from the community of Kg. Selai, Bekok in Johor, Malaysia. The result show there are five factors that sustained the ecotourism development based for Orang Asli Community in Kg. Selai, namely, existing CBET development, past CBET development, local community participation in planning stage of tourism, local participation in implementation stage of tourism and participation in nature conservation

N=2N=2 quantum chiral superfields and quantum super bundles

We give the superalgebra of $N=2$ chiral (and antichiral) quantum superfields realized as a subalgebra of the quantum supergroup $\mathrm{SL}_q(4|2)$. The multiplication law in the quantum supergroup induces a coaction on the set of chiral superfields. We also realize the quantum deformation of the chiral Minkowski superspace as a quantum principal bundle

Youth Driven Engagement in the Homestay Program

Community-based tourism (CBT) is one of the tourist attracting ways involving local community which aims to develop and to enhance the era as well as to bring renewal to the local community. It includes the involvement of youth. CBT comes in various types and this study was conducted to find how CBT can create youth engagement in the homestay program. There were various factors that motivate youth to participate in homestay program. This study involved one case study of a qualitative study conducted in a district in Sabah, namely in Kundasang. In this study, Mersilou Homestay and Walai Tokou Homestay were chosen to be used as a place of study to review factors youth engagement in the homestay program. Data collection was through interviews in partial structures. Data were analyzed using NviVo 10 software and based on certain themes. The findings shown that there were several factors which drive engagement of youth in the homestay program in terms of interests, income, parental encouragement and comfort working in their own areas. In conclusion, the engagement of youth in the homestay program is based on the factors discovered in the study

Prevalence of Paramphistomum cervi in different sheep breeds of Balochistan (Pakistan)

The prevalence of Paramphistomum cervi infestation in Balochi, Babrik and Harnai sheep breeds from Balochistan (Pakistan) was studied during September to December 2010. For this purpose, rumen of slaughtered sheep in Quetta City and surroundings (n=1,200) were examined. Results showed significant differences (

A process centred virtual approach to support cost estimating along product life cycle

The application of engineering practices and scientific principles to the creation of cost estimates along a product life cycle is one of the basic aspects of Cost Engineering. Cost estimates are used as fundamental criteria to make design decisions in the development stage and also to make business decisions in collaboration between OEMs and their supply chain. The achievement of an estimate requires experience and knowledge of different techniques and methodologies. Key aspects on its creation are the adoption of a cost estimating process, the availability of the needed data and the proper management of the information used during the process. The collaboration between the OEM and its supplier can be facilitated by having a better common understanding of how the cost estimates have been created. The cost estimating process used is then a fundamental piece of trust. In this context, the main purpose of this paper is to present the research conducted in the definition of cost estimating processes and the virtual framework selected. They are the key elements in the development of a prototype set of virtual tools to support the creation of cost estimates, the improvement of competences of the Cost Engineering Community, and the common understanding on cost between OEMs and their supply chain