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Estimating failure probabilities of engineering systems is an important problem in many engineering fields. In this work we consider such problems where the failure probability is extremely small (e.g. ≤ 10 − 10 ). In this case, standard Monte Carlo methods are not feasible due to the extraordinarily large number of samples required. To address these problems, we propose an algorithm that combines the main ideas of two very powerful failure probability estimation approaches: the subset simulation (SS) and the multicanonical Monte Carlo (MMC) methods. Unlike the standard MMC which samples in the entire domain of the input parameter in each iteration, the proposed subset MMC algorithm adaptively performs MMC simulations in a subset of the state space, which improves the sampling efficiency. With numerical examples we demonstrate that the proposed method is significantly more efficient than both of the SS and the MMC methods. Moreover, like the standard MMC, the proposed algorithm can reconstruct the complete distribution function of the parameter of interest and thus can provide more information than just the failure probabilities of the systems. [ABSTRACT FROM AUTHOR]

Abstract: There are wide ranges of lutein and β-carotene in Chinese kale. This work assessed the capability of near-infrared reflectance spectroscopy (NIRS) to predict the contents of lutein and β-carotene in Chinese kale against HPLC analysis. Compared to other regression methods, the regression of modified partial least squares with math treatments of 2,4,4,1 (where the first number of 2 represents the second derivative of log1/R, the second of 4 is the gap in data points over which the derivative is calculated, the third and fourth numbers refer to the number of data points used in the first and second smoothing, respectively) showed the best results. The calibration equations of lutein and β-carotene were characterized by the coefficients of determination (RSQ) of 0.983 and 0.982 and standard error of 0.056 and 0.131mgg−1 DW, respectively. In cross-validation, high 1 minus variance ratio (1−VR) of 0.955 and 0.966 and standard error of 0.092 and 0.179mgg−1 DW for lutein and β-carotene were obtained, respectively. In external validations, the RSQ were 0.926 and 0.875 with standard error of 0.131 and 0.367mgg−1 DW, respectively. These results showed that NIRS could be used for the determination of carotenoids in Chinese kale. [Copyright &y& Elsevier]

The optical polarization properties of AlGaN/AlN conventional rectangular shaped and triangular shaped quantum wells (QWs) were investigated using the modified theoretical model based on the effective mass equation. The calculated results show that there is more emission component with TE polarization from triangular shaped QWs than that from conventional QWs for same peak emission wavelength, which is beneficial to the surface emission of Al-rich AlGaN-based light-emitting diodes (LEDs). Furthermore, the AlGaN/AlN triangular shaped QWs have shorter critical wavelength for polarization switching between dominant TE and TM emissions than conventional QWs. This is because that valence subband structure changes for the special band edge potential in AlGaN/AlN triangular shaped QWs. So, the polarization control to enhance the surface emission of DUV AlGaN-based LEDs can be realized by using triangular shaped QWs structure. [ABSTRACT FROM AUTHOR]

The application of anaerobic ammonium oxidation (Anammox) technology in low-strength wastewater treatment still faces difficult in-situ start-ups and unstable operations. Sponge-iron sludge (R1) was used as a novel inoculum to provide a promising solution. Conventional activated sludge (R0) was used as the control. However, little is known about the feasibility and performance during the start-up and operation of Anammox combined with biological iron and iron bacteria in an iron sludge system. Anammox was successfully started both in R1 (87 days) and R0 (89 days) with a low-strength influent (with a nitrogen loading rate (NLR) of 43.64 ± 0.41 g N/(m3⋅d)). During long-term operation, the R0 nevertheless produced higher nitrates (9.7 ± 0.1 mg/L) than expected. In contrast, R1 presented no excess nitrate production (2.1 ± 0.06 mg/L). The total inorganic nitrogen (TIN) removal efficiency increased from 78.2 ± 7.1% in R0 to 86.1 ± 4.3% in R1. The iron sludge in R1 was divided equally into three parts and three different nitrogen-feeding methods were used over the 34 days of operation, as follows: first using a mixture of ammonium (27.15 ± 1.0 mg/L) and nitrite (32.7 ± 1.7 mg/L), then only ammonium (27.15 ± 1.0 mg/L) and lastly only nitrite (32.7 ± 1.7 mg/L) as the influent. R1 was a coupled system composed of Anammox, Feammox, and NO x −-dependent Fe(II) oxidation (NDFO). The contribution of Feammox and NDFO to TIN removal was 27.1 ± 1.2% and 31.9 ± 0.7%. However, Anammox was the primary nitrogen transformation pathway. X-ray diffraction (XRD) analysis shows that iron hydroxide (Fe(OH) 3) and iron oxide hydroxide (FeOOH) were generated in R1. The produced Fe(OH) 3 and FeOOH were capable of participating in Feammox and formed a Fe(II)/Fe(III) cycle which further removed nitrogen. Therefore, a highly stable and impressive nitrogen removal performance was demonstrated in the iron sludge Anammox system under the cooperation of biological iron and iron bacteria. The study considered the enrichment of norank_c_ OM190 , Desulfuromonas , and Thiobacillus and their contribution to the Anammox, Feammox, and NDFO processes, respectively. This study provides a new perspective for the start-up and stable operation of low-strength wastewater Anammox engineering applications. [Display omitted] • The sponge-iron sludge system (R1) showed the efficient and stable removal of TIN. • Cooperation of iron and iron bacteria was key to ensure the success of R1. • R1 was a coupled system composed of Anammox, Feammox and NDFO. • Anammox was the primary nitrogen transformation pathway. [ABSTRACT FROM AUTHOR]

The impact of strain on optical polarization of c-plane Al 0.37 Ga 0.63 N/Al 0.5 Ga 0.5 N multiple quantum wells (QWs) has been studied by the polarized photoluminescence spectroscopy at room temperature. By adopting multiple alternation cycles of low- and high-temperature growth, the strain state of AlN template can be modulated. With increasing in-plane compressive strain of QWs layers, the polarization degree can be enhanced from 41.5% to 61.9%. Furthermore, the strain dependence of the polarization degree has been confirmed by the numerical simulation based on k·p method, revealing the dominant role of energy level shift and wavefunction overlap. It is found that the relative position of the three valence subbands is responsible for the steep increase of the polarization at smaller strain, while the wavefunction overlap induced by piezoelectric effect modulates the optical polarization at larger strain. These results are of great importance in the design and analysis of AlGaN based ultraviolet light emitting devices. • The influence of strain on optical polarization was studied in c-plane AlGaN QWs. • The strain state of AlN template was modulated, achieving the prominent enhancement of TE mode emission. • The numerical simulation based on k·p methodconfirms the dominant role of energy level shift and wavefunction overlap. [ABSTRACT FROM AUTHOR]