Simulation und Messung der thermischen Behaglichkeit

Vorgestellt wird ein Ansatz, der eine Bewertung der thermischen Behaglichkeit auch unter komplexen, inhomogenen raumklimatischen Verhältnissen unter Berücksichtung der menschlichen Physiologie zulässt. Dabei wird die Strömungssimulation an ein numerisches Modell (UC Berkeley Comfort Model), welches die Thermoregulation des menschlichen Körpers abbildet, gekoppelt. Mit Hilfe der Strömungssimulation können die klimatischen Bedingungen in Räumen detailliert ermittelt werden. Darauf basierend können durch das Thermoregulationsmodell die Temperaturverteilung im menschlichen Körper, die resultierende Wärmeabgabe an die Umgebung sowie die thermische Behaglichkeit bestimmt werden. Beispielhaft wird dieser Ansatz bei der Simulation der thermischen Behaglichkeit sowie des Empfindens bei einer Flächenkühlung angewendet. Simulation and measurement of thermal comfort. An approach is introduced, which enables the assessment of thermal comfort considering the complex and inhomogeneous climatic conditions in buildings as well as the human physiology. Computational fluid dynamic is linked with a numerical model representing the thermophysiological behavior of the human body (UC Berkeley Comfort Model). By dint of CFD, the climatic conditions in buildings are simulated with a detailed resolution. Basing on the simulations, the thermophysiological model is able to determine the temperature distribution of the human body, the heat flux to the environment as well as thermal comfort. The approach is used for the exemplified investigation of thermal comfort and sensation in a room equipped with a radiant cooling floor.     

Herd life,lifetime production,and profitability of Viking Red-sired and Montbéliarde-sired crossbred cows compared with their Holstein herdmates

The first 2 generations from a 3-breed rotation of the Viking Red (VR), Montbéliarde (MO), and Holstein (HO) breeds were compared with their HO herdmates in high-performance commercial herds in Minnesota. The designed study enrolled pure HO females in 2008 to initiate a comparison of 3-breed rotational crossbreds with their HO herdmates. Sires of cows were proven artificial insemination bulls selected for high genetic merit in each of the 3 breeds. The first-generation cows calved for a first time from 2010 to 2014 and had 376 VR × HO and 358 MO × HO crossbreds to compare with their 640 HO herdmates. The second-generation cows calved for a first time from 2012 to 2014 and had 109 VR × MO/HO and 117 MO × VR/HO crossbreds to compare with their 250 HO herdmates. Collection of data ceased on December 31, 2017, and all cows studied had the opportunity for 45 mo in the herd after first calving. Production of milk, fat, and protein (kg) during lifetimes of cows was estimated from test-day observations with best prediction. The lifetime profit function included revenue and cost. Revenue was from production, calves, and slaughter of cull cows. Costs included feed cost during lactation, lactating overhead cost, dry cow cost (including feed cost during dry periods), replacement cost, health treatment cost, insemination cost, fertility hormone cost, pregnancy diagnosis cost, hoof trimming cost, and carcass disposal cost. For individual cows with herd life longer than 45 mo after first calving, survival of cows was projected beyond 45 mo after first calving to estimate herd life, production, and profitability. The 2-breed crossbreds had +158 d longer herd life and the 3-breed crossbreds had +147 d longer herd life compared with their respective HO herdmates. Also, 12.4% of the 2-breed crossbreds died up to 45 mo after first calving compared with 16.3% of their HO herdmates. Furthermore, approximately 29% of both the 2-breed and 3-breed crossbreds lived beyond 45 mo after first calving compared with approximately 18% of their respective HO herdmates. On a lifetime basis, the 2-breed and 3-breed crossbreds provided +$122 and +$134, respectively, more cull cow revenue compared with their HO herdmates. For lifetime replacement cost, the 2-breed crossbreds did not differ from their HO herdmates; however, the 3-breed crossbreds had ?$28 less lifetime replacement cost compared with their HO herdmates because of their younger age at first calving. The combined 2-breed crossbreds had +$0.473 (+13%) more daily profit (ignoring potential differences for feed efficiency) and the combined 3-breed crossbreds had +$0.342 (+9%) more daily profit compared with their respective HO herdmates. This resulted in +$173 more profit/cow annually for the combined 2-breed crossbreds and +$125 more profit/cow annually for the combined 3-breed crossbreds compared with their respective HO herdmates.     

Traffic, transportation, infrastructure and externalities A theoretical framework for a CGE analysis

In Europe traffic congestions make it impossible to estimate travel time. The increasing number of cars calls for a transportation policy towards an improved efficiency of the transportation system. However, extending road infrastructure to reduce the congestion externality implies another type of externality, air pollution. Designing a transportation policy in industrialized countries one has to consider this trade-off. Our objective is to investigate the role of transportation services and their pricces within an interindustry framework. The authority wishes to minimize total cost of production with respect to the provision of infrastructure subject to an emission standard. By omitting a financial constraint to finance infrastructure we determine the size of infrastructure where no congestion occurs. The productivity effect of infrastructure and the cost savings from a dissolved congestion determine the optimal stock of infrastructure. Our congestion index is unity in that case of no financial constraint. If the extension of infrastructure has to be paid for by taxation, we obtain a lower level of infrastructure. In view of the trade-off between the benefit of a productivity gain from a dissolved congestion and the deadweight loss from taxation this lower level of infrastructure will result in an index of congestion higher than unity, implying a negative externality to the economy. Received: June 1996 / Accepted: February 1997     

Temperature reduction due to the application of phase change materials

Overheating is a major problem in many modern buildings due to the utilization of lightweight constructions with low heat storing capacity. A possible answer to this problem is the emplacement of phase change materials (PCM), thereby increasing the thermal mass of a building. These materials change their state of aggregation within a defined temperature range. Useful PCM for buildings show a phase transition from solid to liquid and vice versa. The thermal mass of the materials is increased by the latent heat. A modified gypsum plaster and a salt mixture were chosen as two materials for the study of their impact on room temperature reduction. For realistic investigations, test rooms were erected where measurements were carried out under different conditions such as temporary air change, alternate internal heat gains or clouding. The experimental data was finally reproduced by dint of a mathematical model.     

Retardation of grain growth and cavitation by an electric field during superplastic deformation of ultrafine-grained 3Y-TZP at 1,450–1,600 °C

The influence of a continuous dc electric field applied orthogonal to the tensile direction on the flow stress, grain growth, and cavitation during superplastic deformation (SPD) of ultrafine-grained 3Y-TZP at 1,450–1,600 °C was determined. The field gave a significant reduction in the level of the stress-strain curve, and reduced grain growth and cavitation. The decrease in flow stress by the field was attributed mainly to the retardation of grain growth. The decrease in cavitation correlated with the retardation of grain growth and was attributed largely to the reduction in flow stress by the field.     

Predictive optimal management method for the control of polygeneration systems

A predictive optimal control system for micro-cogeneration in domestic applications has been developed. This system aims at integrating stochastic inhabitant behavior and meteorological conditions as well as modelling imprecisions, while defining operation strategies that maximize the efficiency of the system taking into account the performances, the storage capacities and the electricity market opportunities.Numerical data of an average single family house has been taken as case study. The predictive optimal controller uses mixed-integer and linear programming where energy conversion and energy services models are defined as a set of linear constraints. Integer variables model the start-up and shut-down operations as well as the load dependent efficiency of the cogeneration unit. The proposed control system has been validated using more complex building and technology models to asses model inaccuracies. Typical demand profiles for stochastic factors have been used.The system is evaluated in the perspective of its usage in Virtual Power Plants applications.     

Identification and characterization of isomeric intermediates in a catalyst formation reaction by means of speciation analysis using HPLC-ICPMS and HPLC-ESI-MS

Information on chemical speciation is much needed in mechanistic and kinetic studies on catalyst formation processes in pharmaceutical research. Speciation analysis was applied to the identification and quantification of various rhodium species involved in a ligand exchange process leading to formation of catalyst dirhodium(II) tetrakis[methyl 2-oxopyrrolidin-5(S)-carboxylate]. Inductively coupled plasma mass spectrometry (ICPMS) was used as an element-specific detector following species separation by reversed-phase high-performance liquid chromatography (RP-HPLC), and electrospray ionization mass spectrometry (ESI-MS) was used for species identification and confirmation. A novel interface between the HPLC and ICPMS, which consisted of an eluent splitter, a desolvation unit, and the ICPMS built-in peristaltic pump, enabled the use of RP-HPLC with gradient elution and up to 100% organic components in the LC eluent without organic loading in the plasma. A variety of reaction intermediates were identified and quantified along the pathway to formation of the desired product, including isomeric di-, tri-, and tetrasubstituted species previously believed to be absent. This has provided new insights into the mechanism and kinetics of the reaction. The combination of HPLC-ICPMS and HPLC-ESI-MS has proven to be a valuable tool for the investigation of species evolution in catalyst formation process.     

Plastic deformation kinetics of fine-grained MgO in tension

The plastic deformation kinetics of 99.4% MgO (d _o = 5.3 m) was investigated at 1500°–1600°C in uniaxial tension. It was determined that the stress exponent n 1 and the activation energy Q = 204 kJ/mole. Neither the present results on MgO, nor data in the literature on MgO and other oxide ceramics, can be fully explained by the models usually proposed for the plastic deformation of fine-grained oxide ceramics. The present results are however in good agreement with the model for grain boundary diffusion plastic flow recently developed by Kim, Estrin and Bush.     

Contribution of the space charge to the grain boundary energy in yttria-stabilized zirconia

A model based on the effect of a modest applied dc electric field on grain growth is proposed for the contribution of the space charge to the grain boundary (GB) energy in 3 mol % yttria-stabilized zirconia (3 YSZ). The model considers that the total GB energy \( \gamma_{\text{b}}^0 \) (the capillary driving force for grain growth) consists of three major components: (a) \( \gamma_{\text{b}}^\varSigma \) due to the misorientation between neighboring grains, (b) \( \gamma_{\text{b}}^{\text{s}} \) due to the size misfit between the segregated solute and the solvent cations, and (c) \( \gamma_{\text{b}}^{\text{e}} \) the electrostatic (space charge) component, which results from the segregation of the aliovalent yttrium ions to the grain boundaries. The former two components combined comprise 40 % of the total GB energy in 3 YSZ and the electrostatic component 60 %. Based on the model, the calculated magnitudes of the three components were in qualitative accord with theoretical considerations and with values reported in the literature. A reduction in \( \gamma_{\text{b}}^{\text{e}} , \) and in turn in \( \gamma_{\text{b}}^0 , \) results from the bias exerted by the applied field on the space charge potential that occurs with the segregation of the yttrium ions to the grain boundaries. The observed reduction of grain growth in 3 YSZ by an applied electric field is attributed mainly to the reduction in \( \gamma_{\text{b}}^{\text{e}} \) by the field.     

Influence of an external electric field on the microstructure of superplastically deformed 7475 Al

An externally applied electric field retarded strain-enhanced grain growth and promoted dynamic recrystallization during superplastic deformation of 7475 Al. Also, a more extensive dispersoid-free zone was observed in specimens deformed in the electric field, suggesting that the electric field increased the contribution of diffusion creep to superplastic deformation. The electric field promoted the coarsening of dispersoids, especially in the vicinity of the grain boundaries. Possible mechanisms for the observed effects are discussed.