Emission Rates Due to Indoor Activities: Indoor Aerosol Model Development,Evaluation, and Applications

This study presents an indoor aerosol model based on size-resolved and multi-compartment approach. The current indoor aerosol model is also developed with a semi-empirical technique to estimate the emission rates due to indoor sources of aerosol particles. We present in this study a methodology to predict and estimate the best-fit input parameters for the current indoor aerosol model. The performance of the current indoor aerosol model in its single-compartment form was evaluated against previously measured indoor-outdoor aerosol data sets from an office room with mechanical ventilation and a family house with natural ventilation. The indoor aerosol model simulations show that the current methodology used to predict the best-fit input parameters to the indoor aerosol model is efficient. As expected, the penetration factor, aerosol particle deposition, and ventilation rate are the most important parameters in the indoor-outdoor relationship of aerosol particles transport. The emission rate analysis showed that fine aerosol particles production was as high as 26 particle/cm ³ s during wood burning in a fireplace. The emission rate was about eight times this value during grilling in a fireplace and sauna heating. Indoor activities take place in another room may significantly increase the aerosol particle concentrations in other rooms in the building. Therefore, it is recommended to use extra air cleaners in houses to reduce the number concentrations of emitted aerosol particles. The quantitative and qualitative results obtained by the current indoor aerosol model in this study are building and condition specific. Applying the current model to a broad range of conditions and previously measured indoor-outdoor aerosol data sets provides better understanding of aerosol particle characteristics indoors, especially regarding the aerosol particles produced during different indoor activities.     

Fostering elementary school students' understanding of simple electricity by combining simulation and laboratory activities

Abstract   Computer simulations and laboratory activities have been traditionally treated as substitute or competing methods in science teaching. The aim of this experimental study was to investigate if it would be more beneficial to combine simulation and laboratory activities than to use them separately in teaching the concepts of simple electricity. Based on their pre-test performances, 66 elementary school students were placed into three different learning environments: computer simulation, laboratory exercise and a simulation–laboratory combination. The results showed that the simulation–laboratory combination environment led to statistically greater learning gains than the use of either simulation or laboratory activities alone, and it also promoted students' conceptual understanding most efficiently. There were no statistical differences between simulation and laboratory environments. The results highlight the benefits of using simulation along with hands-on laboratory activities to promote students' understanding of electricity. A simulation can help students to first understand the theoretical principles of electricity; however, in order to promote conceptual change, it is necessary to challenge further students' intuitive conceptions by demonstrating through testing that the laws and principles that are discovered through a simulation also apply in reality.     

Monitoring environmental performance of the forestry supply chain using RFID

It is estimated that wood raw material worth of approximately €5 billion is wasted annually in Europe. The major reason for this is that the raw material is not used in the most efficient way as information needed regarding the wood raw material is not available throughout the supply chain. An automatic traceability system makes it possible to utilise raw material information efficiently throughout the forestry-wood production chain and to maximize the raw material yield, and to optimise and to monitor the environmental impact, by linking the relevant information to the traced objects. This paper describes novel RFID technology and traceability solutions that have been developed for the wood products industry. RFID-marking connects the physical objects with their database counterparts thus allowing automatic tracing of the objects. The architecture is needed to the dynamic and decentralised nature of the wood industry. The developed novel RFID based technology allows tracing of individual logs from the tree felling to the sawing of the logs at the saw mill. By combining the traceability and process information systems, new methods are enabled for analysing the performance of the supply chain. As an example, the environmental performance of a product can be traced and analysed even on an individual level. This means that not only the performance from the own production of a manufacturer will be accessible, but also the upstream processes that constitute the product value chain and the life cycle performance for the product leaving the manufacturer.     

Knowledge-oriented software engineering process in a multi-cultural context

In software engineering, leading trends can be detected that will affect the characteristic features of a product and its development process. On a product level, the growth of size and complexity is apparent—but on the one hand only. On the other hand, there is also a growing demand for simple and reasonable small software products executed by handheld terminals and smartphones; these applications are in many cases expected to collaborate with databases over the Internet. In addition, different kinds of service concepts (ASP, SaaS) are becoming recognized alternatives to the traditional way of buying software. Increasingly, software products are also distributed in a wide geographical scope to users with different cultural backgrounds and expectations. In software engineering work, as a consequence of this growth in size and complexity, the development work is more and more often distributed. The software business itself is becoming global because of acquisitions, offshoring, and international subcontracting. The globalization of work sets new requirements to the engineering processes: in international teams the organisational and cultural differences of the development subteams have to be recognized. In this paper, the focus is on the software development and its global dimension—especially the roles of multi-cultural and cross-organizational issues in software engineering. Our paper presents the results of the first phase of our three phases research project related to “Culture-Aware Software Engineering.” The main result of the first phase is the multi-cultural software engineering working model introduced in our paper. Culture is seen as one example of the context, i.e. the situation at hand. The concept of culture has also different meanings, which have to be understood in well-organized software engineering. Software engineering work is analyzed as a knowledge creation process, in which both explicit and tacit knowledge are recognized and the transformation between these establishes baselines along the development life cycle.     

Thermal detection of ESR on spin-polarized hydrogen: Study of surface recombination

We introduce a new method for the detection of electron-spin resonance in spin-polarized atomic hydrogen gas (H). Instead of observing the microwave power absorbed in the ESR transition, we monitor the recombination heat deposited by ESR-induced spin-up atoms (H) onto a liquid-helium coated carbon bolometer. The signal from this sensor reproduces well the ESR absorption lineshape registered by our 128 GHz homodyne spectrometer. Using the recombination detection we have achieved a density detection limit of n=3·10¹⁰ atoms/cm³ for 0.2 nW microwave power incident on the resonant cavity at the temperature T=150 mK. We have studied the decay rate of recombination heat absorbed by the bolometer after an ESR excitation pulse and the dependence of this rate on T, n and nuclear polarization of the H sample. The bolometer signal is found to be related mainly to second-order H + H recombination to ortho-H₂ on the surfaces of the sample cell. From the signals we have determined the rate constant K _bc ^c =3.2(5)·10^–5T cm²/s·K^–1/2 in the interval from T=250 to 425 mK in a field of 4.5 T.     

A new class of upper bounds on the log partition function

We introduce a new class of upper bounds on the log partition function of a Markov random field (MRF). This quantity plays an important role in various contexts, including approximating marginal distributions, parameter estimation, combinatorial enumeration, statistical decision theory, and large-deviations bounds. Our derivation is based on concepts from convex duality and information geometry: in particular, it exploits mixtures of distributions in the exponential domain, and the Legendre mapping between exponential and mean parameters. In the special case of convex combinations of tree-structured distributions, we obtain a family of variational problems, similar to the Bethe variational problem, but distinguished by the following desirable properties: i) they are convex, and have a unique global optimum; and ii) the optimum gives an upper bound on the log partition function. This optimum is defined by stationary conditions very similar to those defining fixed points of the sum-product algorithm, or more generally, any local optimum of the Bethe variational problem. As with sum-product fixed points, the elements of the optimizing argument can be used as approximations to the marginals of the original model. The analysis extends naturally to convex combinations of hypertree-structured distributions, thereby establishing links to Kikuchi approximations and variants.     

Plutonium in the air in Kurchatov, Kazakhstan

Weekly air samples of 25000 m(3) volume were taken with two air samplers over a period of one year in 2000-2001 in the town of Kurchatov in Kazakhstan. For another three-month period in 2001, the samplers were run in the city of Astana, about 500 km west of Kurchatov. (137)Cs, Pu and U concentrations were determined from the filters. Pu activities in Kurchatov varied in a 100-fold range; median (239,240)Pu activities were 100 nBq/m(3) and (238)Pu activities 34 nBq/m(3). The corresponding values for Astana were considerably lower: 29 and 9 nBq/m(3), respectively, and in half of the filters the (238)Pu activity was below the detection limit. Plutonium concentration correlated with the amount of dust retained on the filters only at the highest dust loads. Also no correlation between wind speed and the plutonium activity in the filters was observed. Thus, resuspension does not seem to be the mechanism responsible for the airborne plutonium. No clear seasonal variation of Pu air concentration was observed, though levels were somewhat elevated in February to April. There was no correlation between the plutonium and (137)Cs concentrations. In most of the filters the cesium concentration was below the detection limit, but in those filters where it could be detected the cesium concentration was practically constant at 3.9+/-1.6 microBq/m(3). Dose estimation for the inhalation of the airborne plutonium gave a low value of 0.018 microSv/a for the inhabitants in Kurchatov, which is about a thousand times lower than the dose caused by the naturally occurring (210)Po. Air parcel trajectory analysis indicated that the observed Pu activities in the air could not unambiguously be attributed to the most contaminated areas at the Semipalatinsk Test Site.     

Electromagnetic Gaussian beam beyond the paraxial regime

A modified electromagnetic beam technique is derived analytically from the asymptotic field expressions for the quasi-optical, millimeter-wave, plane polarized Laguerre-Gaussian modes of arbitrary order. The method makes use of the paraxial-wave formulas only, yet it accurately gives the full electric field vector at any point far beyond the conventional Gaussian beam regime. The technique is assessed numerically against the exact Green's function results     

Size and composition of airborne particles from pavement wear, tires, and traction sanding

Mineral matter is an important component of airborne particles in urban areas. In northern cities of the world, mineral matter dominates PM10 during spring because of enhanced road abrasion caused by the use of antiskid methods, including studded tires and traction sanding. In this study, factors that affect formation of abrasion components of springtime road dust were assessed. Effects of traction sanding and tires on concentrations, mass size distribution, and composition of the particles were studied in a test facility. Lowest particle concentrations were observed in tests without traction sanding. The concentrations increased when traction sand was introduced and continued to increase as a function of the amount of aggregate dispersed. Emissions were additionally affected by type of tire, properties of traction sand aggregate, and driving speed. Aggregates with high fragmentation resistance and coarse grain size distribution had the lowest emissions. Over 90% of PM10 was mineral particles. Mineralogy of the dust and source apportionment showed that they originated from both traction sand and pavement aggregates. The remaining portion was mostly carbonaceous and originated from tires and road bitumen. Mass size distributions were dominated by coarse particles. Contribution of fine and submicron size ranges were approximately 15 and 10% in PM10, respectively.