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.     

Effect of different coagulants on the isoflavone levels and physical properties of prepared firm tofu

The objective of this study was to understand the effect of different coagulants in their ability to retain isoflavones in prepared firm tofu. Harovinton beans were processed to obtain soymilk and a specific amount of this soymilk was coagulated using different types of coagulants for the preparation of tofu. A reversed phase high performance liquid chromatographic method was used for determining the concentration of isoflavones in tofu and whey. Quality parameters such as the texture, color and moisture of tofu, prepared from different coagulants were also determined in this study. Tofus coagulated with different coagulants were found to contain different amounts of isoflavones. Calcium sulfate was found to be the most suitable coagulant for tofu making in terms of its high yield, retention of maximum amount of isoflavones and in obtaining a firm, but not hard texture of tofu.     

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.     

Advances in a-Si:H/c-Si heterojunction solar cell fabrication and characterization

Our progress in amorphous/crystalline silicon (a-Si:H/c-Si) heterojunction solar cell technology and current understanding of fundamental device physics are presented. In a-Si:H/c-Si cells, device performance is strongly dependent on the quality of the a-Si:H/c-Si heterojunction. Four topics are crucial to minimize recombination at the junction and thereby maximize cell efficiency: wet-chemical pre-treatment of the c-Si surface prior to a-Si:H deposition; optimum a-Si:H doping; thermal and plasma post-treatments of the a-Si:H/c-Si structure. By optimizing these aspects using specifically developed characterization methods, we were able to realize (n)a-Si:H/(p)c-Si and (p)a-Si:H/(n)c-Si cells with up to 18.5% and 19.8% efficiency, respectively.     

Hydrodynamic parameters of mesh fillers relevant to miniature regenerative cryocoolers

Directional hydrodynamic parameters of two fine-mesh porous materials that are suitable for miniature regenerative cryocoolers were studied under steady and oscillating flows of helium. These materials included stacked discs of #635 stainless steel (wire diameter of 20.3 μm) and #325 phosphor bronze (wire diameter of 35.6 μm) wire mesh screens, which are among the commercially available fillers for use in small-scale regenerators and heat exchangers, respectively. Experiments were performed in test sections in which pressure variations across these fillers, in the axial and lateral (radial) directions, were measured under steady and oscillatory flows. The directional permeability and Forchheimer’s inertial coefficient were then obtained by using a Computational Fluid Dynamics (CFD)-assisted method. The oscillatory flow experiments covered a frequency range of 50–200 Hz. The results confirmed the importance of anisotropy in the mesh screen fillers, and indicated differences between the directional hydrodynamic resistance parameters for steady and oscillating flow regimes.     

Prediction of response during interferon alfa 2b therapy in chronic hepatitis C patients using viral and biochemical characteristics: a comparison

Patients with chronic hepatitis C (n = 103) were treated for 24 weeks with interferon alfa 2b and followed up for 24 weeks after cessation of therapy (week 48). When hepatitis C virus (HCV) RNA at week 48 was used to assess interferon response, 15 (14.6%) were virological complete responders, and all have remained HCV RNA negative for a mean of 3 years. At week 48, 3 of 15 virological complete responders had elevated alanine transaminase (ALT) values. When serum ALT level was used at week 48 to determine response to interferon, 20 (19.4%) were biochemical complete responders. However, 8 of the 20 patients with normal ALT levels were HCV RNA positive at week 48, and 7 of these individuals have had a recurrence of elevated ALT levels within 3 years after cessation of treatment. These findings indicate that measurement of HCV RNA was more accurate than ALT in determining true responses to interferon therapy. Identification of nonresponders early during the course of interferon treatment showed that an elevated ALT level at week 12 was 92% predictive (odds ratio 3.7) but misidentified 33% (5 of 15) of the patients who were virological complete responders at week 48. In contrast, a positive HCV RNA at week 12 of treatment was 98% predictive (odds ratio 35.5) and misidentified only 6.7% (1 of 15) of the virological complete responders. Thus, positive HCV RNA at week 12 of therapy was more accurate in identifying eventual virological nonresponders than measurement of ALT at this time. Termination of interferon therapy in patients who were HCV RNA positive at week 12 would result in a 27% reduction in the direct medical costs and keep patients from undergoing unnecessary treatment. Therefore, testing for HCV RNA at week 12 to identify nonresponders and then discontinuing their treatment is practical, cost-efficient and beneficial both to patients and to third-party payers.