50MW级SGT-800型西门子燃气轮机的性能验证

SGT-800是西门子工业透平公司制造的功率最大的工业燃气轮机。2010年推出SGT-800增强型,其额定功率为50.5 MW。为保证产品的质量,对此增强型燃气轮机进行了细致的实验验证,包括零部件级和整机级的验证工作。零部件级试验主要包括第1级静叶和第1级动叶的热动力学性能的验证工作。整机试验包括测试燃气轮机综合性能、压气机性能与转子动态性能、燃烧室的稳定性/排放/热状态、透平性能及其热状态等。测试结果表明,其性能圆满地达到了预期水平。截止2014年4月,首台增强型燃气轮机商业运行的累计等效运行小时数(EOH)已经超过24 000 h。在20 000等效运行小时数之后计划进行的开机检查结果表明,所有部件的状态均达到或预期达到设计寿命。     

COOS: a wave-function based Schrödinger–Poisson solver for ballistic nanotube transistors

This paper gives an in depth overview on a wave-function based simulation framework (called coos) for modeling ballistic nanotube transistors by solving the effective-mass Schrödinger equation. The framework considers non-parabolic electronic band structure effects, band-to-band tunneling as well as a heterojunction-like model for extended contacts to describe the injection and reception of charge carriers into and from the channel. Special emphasis is put on an efficient and reliable numerical implementation. The applicability of the simulation framework and the necessity to include the aforementioned phenomena are shown by comparing simulation results with experimental data of a \(50\hbox { nm}\) long carbon nanotube transistor (cntfet). The intrinsic transit frequencies and the output characteristics for higher drain-source voltages are predicted and analyzed.     

Infrared Decontamination of Oregano: Effects on Bacillus cereus Spores,Water Activity,Color, and Volatile Compounds

Infrared (IR) heating, a novel technology for decontaminating oregano, was evaluated by investigating the reduction of inoculated Bacillus cereus spores and the effect on water activity (a_w), color, and headspace volatile compounds after exposure to IR treatment. Conditioned oregano (a_w 0.88) was IR‐treated in a closed heating unit at 90 and 100 °C for holding times of 2 and 10 min, respectively. The most successful reduction in B. cereus spore numbers (5.6 log units) was achieved after a holding time of 10 min at 90 °C, while treatment at 100 °C for the same time resulted in a lower reduction efficiency (4.7 log units). The lower reduction at 100 °C was probably due to a reduced a_w (a_w 0.76) during IR treatment or possibly to the alteration or loss of volatile compounds possessing antimicrobial properties. The green color of oregano was only slightly affected, while the composition of volatile compounds was clearly altered by IR heating. However, two of the key aroma compounds, carvacrol and thymol, were only slightly affected, compared to the effect on the other studied compounds, indicating that the typical oregano aroma can likely be preserved. In conclusion, IR heating shows potential for the successful decontamination of oregano without severe alteration of its color or the key aroma compounds, carvacrol and thymol.     

The steady-state behavior of multivariate exponentially weighted moving average control charts

Abstract

Multivariate exponentially weighted moving average (MEWMA) charts are popular, handy, and effective procedures to detect distributional changes in a stream of multivariate data. For doing appropriate performance analysis, dealing with the steady-state behavior of the MEWMA statistic is essential. Going beyond early papers, we derive quite accurate approximations of the respective steady-state densities of the MEWMA statistic. It turns out that these densities could be rewritten as the product of two functions depending on one argument only that allows feasible calculation. For proving the related statements, the presentation of the noncentral chi-square density deploying the confluent hypergeometric limit function is applied. Using the new methods it was found that for large dimensions, the steady-state behavior becomes different from what one might expect from the univariate monitoring field. Based on the integral equation driven methods, steady-state and worst-case average run lengths are calculated with higher accuracy than before. Eventually, optimal MEWMA smoothing constants are derived for all considered measures.     

Second-order-based blind signal separation in reverberant environments

The aim of this paper was to provide a derivation to explain the performance of the second-order-based blind signal separation (BSS) in reverberant environments. In particular, the second-order-based BSS algorithm, which exploits non-stationarity of the input signals, is investigated. The derivation provides a quantitative link between the reverberation parameter of the environment with the cost function of the BSS. Importantly, the theoretical finding complements existing literature on the interpretation of BSS and provides incremental insight to its performance.     

Spannungsverteilung bei Transformatorenwicklungen beim Auftreffen einer Stoßwelle mit besonderer Berücksichtigung der zweiten Wicklung

Zusammenfassung Die angegebenen Formeln ermöglichen es, die Spannungsverteilung beim Auftreffen einer Stoßwelle, sowohl für die gestoßene, als auch für die nichtgestoßene Wicklung anzugeben. Vereinfachten Formeln lassen sich nur sehr bedingt anwenden, da zum Teil größere Abweichungen auftreten.Die für die verschiedenen Betriebsfälle abgeleiteten Ausdrucke lassen deutlich den Einfluß der Grenzbedingungen erkennen. Auf die eigentlichen Schwingungsvorgänge wurde nicht eingegangen.     

Die Berechnung der magnetischen Feldstärke bei Transformatorwicklungen

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Zusätzliche Streuung bei Transformatoren

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