Perceived intragroup homogeneity in minority-majority contexts.

Examined how the factors relative in-group size and relative outgroup size (i.e., minority vs. nonminority) affect the perception of in-group and out-group homogeneity. On the basis of social identity theory, we hypothesized that (a) members of minorities would perceive the in-group as more homogeneous than the out-group, whereas members of nonminorities would perceive the reverse; (b) this effect would be strongest on dimensions most strongly correlated with the social categorization; and (c) members of minorities would identify more strongly with their in-group than would members of nonminorities. 192 13–15 yr olds participated in the experiment. On the presumed basis of a perceptual task, approximately half were randomly allocated to minimal social categories, which differed in perceived size relative to an out-group (which also differed in perceived size). They were asked to estimate the homogeneity of the two groups on a number of dimensional attributes. The remaining (control) subjects gave similar estimates under identical conditions, except that they were not allocated to a category. The data confirmed all but the second hypothesis, which was only partially supported. The results were interpreted in terms of social identification processed. Results tend to rule out alternative explanations in terms of an inverse relation between group size and perceived group homogeneity, rating extremity, and in-group favoritism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dreidimensionale,turbulente Strömungs-und Mischungsgradberechnung mit dem PISO-Algorithmus

Zusammenfassung Die numerische Berechnung von turbulenten Str?mungen, sei es isotherm oder mit chemischer Reaktion und W?rmefreisetzung, kann infolge der st?ndigen Fortschritte auf Seiten der Hardware-Entwicklung, auf immer weiteren Anwendungsgebieten eingesetzt werden. Im vorliegenden Fall handelt es sich um ein Programmpaket (COMPAC-3D), welches für die dreidimensionale Simulation der Str?mung und W?rmefreisetzung in Dampferzeugerfeuerungen konzipiert wurde. Hierbei kommt ein neuer Gleichungsl?sungs-und Bilanzierungsalgorithmus zum Einsatz, welcher es gestattet, Parameterstudient mit wesentlich geringerem Rechenzeitaufwand durchzuführen. Dieser Algorithmus wird im folgenden beschrieben. Anhand eines klassischen Testbeispiels, n?mlich der horizontalen Eindüsung in eine vertikale Hauptstr?mung, werden die Simulationsergebnisse mit Me?werten und Ergebnissen aus Rechenl?ufen mit dem Programmpaket PHOENICS verglichen.     

Small thermophotovoltaic prototype systems

In an earlier paper we reported on a small grid-connected thermophotovoltaic (TPV) system consisting of an ytterbia mantle emitter and silicon solar cells with 16% efficiency (under solar irradiance in standard test conditions, STCs). The emitter was heated up using a butane burner with a rated thermal power of 1.35 kW (referring to the lower heating value). This system produced an electrical output of 15 W, which corresponds to a thermal to electric (direct current) conversion efficiency of 1.1%. In the interim, further progress has been made, and significantly higher efficiencies have been achieved. The most important development steps are: (1) the infrared radiation-absorbing water filter between emitter and silicon cells (to protect the cells against overheating and against contact with flue gasses) has been replaced by a suitable glass tube. By doing this, it has been possible to prevent losses of convertible radiation in water. (2) Cell cooling has been significantly improved, in order to reduce cell temperature, and therefore increase conversion efficiency. (3) The shape of the emitter has been changed from spherical to a quasi-cylindrical geometry, in order to obtain a more homogeneous irradiation of the cells. (4) The metallic burner tube, on which the ytterbia emitter was fixed in the initial prototypes, has been replaced by a heat-resistant metallic rod, carrying ceramic discs as emitter holders. This has prevented the oxidation and clogging of the perforated burner tube. (5) Larger reflectors have been used to reduce losses in useful infrared radiation. (6) Smaller cells have been used, to reduce electrical series resistance losses. Applying all these improvements to the basic 1.35 kW prototype, we attained a system efficiency of 1.5%. By using preheated air for combustion (at approximately 370 °C), 1.8% was achieved. In a subsequent step, a photocell generator was constructed, consisting of high-efficiency silicon cells (21% STC efficiency). In this generator, the spaces between the cells were minimized, in order to achieve as high an active cell area as possible, while simultaneously reducing radiation losses. This new system has produced an electrical output of 48 W, corresponding to a system efficiency of 2.4%. This is the highest-ever-reported value in a silicon-cell-based TPV system using ytterbia mantle emitters. An efficiency of 2.8% was achieved by using preheated air (at approximately 500 °C). An electronic control unit (fabricated of components with low power consumption, and including a battery store) was developed, in order to make the TPV system self-powered. This unit controls the magnetic gas supply valve between gas supply cylinder and burner as well as the high-voltage ignition electrodes. Both the control unit’s own power consumption and the battery-charging power are supplied directly by the TPV generator. A small commercial inverter is used to transfer excess power to the 230 V grid.     

Pyrolysis-field ionization mass spectrometry of modified bagasse fractions

The fractions obtained from bagasse after activation with 17.5% NaOH, alternative alkylation with quarternary ammonium groups and extraction with 80% ethanol, water and 5% NaOH, were analyzed using pyrolysis-field ionization mass spectrometry (Py-FIMS). The proposed degradation products from lignin were mostly symmetric fragments containing two aromatic rings while the compounds formed from polysaccharides were the result of dehydration reactions. From the temperature-resolved Py-FIMS it could be seen that ethanol-lignin starts to degrade at temperatures lower than 180°C before the degradation of the hemicellulose fraction. The lignin markers are eliminated from hemicellulose fractions before the polysaccharide gasification starts. The quarternary ammonium groups are cleaved from the fractions at temperatures lower than 200°C.     

Zehn weitere Briefe zwischen K.E. v. Baer und L.F. und R. Froriep aus den Jahren 1825–1851

Following the publication of 7 letters from Baer to the Frorieps by H.E. Müller-Dietz inNTM N.S. 1 (1993), 2 further letters from Baer and 8 from the Frorieps are published. A curious technical problem in the presentation of the journalNotizen published by Froriep in his Landes-industriecomptoir in Weimar is discussed at length. Froriep recommends his son Robert, to whom Baer sends several enquiries and commissions, which Robert deals with carefully (1831 in Jena, 1849 in Paris). Robert explains in great detail his intention to leave Jena for Berlin in 1831. After his father's death in 1847 he returns to take charge of the Landesindustriecomptoir and begins to cooperate with the newly founded Russian Geographic Society as publisher on behalf of the Society. But about 1850 the cooperation is discontinued by the Russians, and Froriep, who is in economic difficulties, asks Baer (who lives and works in St. Petersburg) urgently (but in vain) to help him with the Society.     

Sizing and characterization of ultrasonic indications using imaging techniques

For discontinuity analysis more and more sophisticated methods are used in the nuclear industry. The rapid development of computer technology offers the possibility to use imaging techniques. Instead of specialized focusing transducers the more flexible synthetic focusing techniques can be used. Presupposing that the material is ultrasonically isotropic and homogeneous, imaging techniques make it possible to visualize the reflectivity of the volume to be tested.Siemens developed the high speed holographic instrument Holo 3000 in cooperation with the University of Bochum. In this paper the method of Broad Band Holography is presented in the context of other imaging techniques.Different filtering methods have been investigated in order to achieve highest resolution and best signal to noise ratio with a given dataset. Different transducers respective wave modes have been applied to austenitic welds and claddings. The reconstructed image was evaluated using image processing techniques in order to investigate the possibilities to produce results easier to be quantifed than the original reconstruction.The results presented show a reliable expert tool for analysis measurements which also can be used for flaw detection.