Detection of Nonlinear Behavior in Voltage Source Converter Control in Wind Farms Based on Higher-Order Spectral Analysis

In recent years, the sub-synchronous oscillation (SSO) accidents caused by wind power have received extensive attention. A method is needed to distinguish if nonlinear behavior exists in the recorded equal-amplitude accident waveforms, so that different methods can be adopted to analyze the mechanism of the oscillation. The theory of higher-order statistics (HOS) has become a powerful tool for detection of nonlinear behavior (DNB) in production quality control since 1960s. However, HOS analysis has been applied in mechanical condition monitoring and fault diagnosis, even after being introduced into the power system and wind farms. This paper focuses on the voltage source converter (VSC) control systems in wind farms and tries to detect the nonlinear behavior caused by the bilateral or unilateral saturation hard limits based on HOS analysis. First, the traditional describing function is extended to obtain more frequency domain information, and hereby the harmonic characteristics of bilateral and the unilateral saturation hard limit are studied. Then the bispectrum and trispectrum are introduced as HOS, which are extended into bicoherence and tricoherence spectrums to eliminate the effects from linear parts in the VSC control system. The effectiveness of DNB and classification based on HOS is strictly proved and its detailed calculation and estimation process is illustrated. Finally, the proposed method is demonstrated and further discussed through simulation results

Expanding non-axisymmetric beams in spherical coordinates with cylindrical wave spectrum decomposition

Description of structured beams in spherical coordinates is critical in studying the interaction between beams and spherical particles. The work extends the cylindrical wave spectrum decomposition (CWSD) method to non-axisymmetric beams, applied herein to the elliptical Gaussian beam, cosine Gauss beam and Hermite-Gauss beam as examples. It is shown that for these beams the beam shape coefficients (BSCs) can be expressed in one dimensional integrations and hence numerical calculations can be performed very efficiently. The beam fields reproduced by using these BSCs show satisfactory faithfulness to the rigorous expression of the given fields. Typically, the difference between them is less than 10−8

Ionizing Radiation Reduces TKI Resistance Caused by T790M Mutation in NSCLC Cell Lines

Background and objective Epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI), which targets EGFR, plays an important role in non-small cell lung cancer (NSCLC) treatment. Patients with somatic activating mutations in the EGFR gene exhibit significant initial response but eventually develop resistance to TKI. The second mutation (T790M) of the EGFR gene is the possible main cause of drug resistance. The aim of this study is to investigate the effect of ionizing radiation on EGFR-TKI resistance caused by T790M mutation in NSCLC cell lines. Methods We selected H1975 and H3255 as research subjects and tested the mutation states by real-time PCR analysis. Radiosensitivity was determined by clone-forming test, and drug resistance was detected in different groups by MTT assay. Results H1975 is an EGFR double mutant (L858R plus T790M), whereas H3255 is an EGFR single mutant (L858R). The cell survival fractions of H1975 and H3255 did not vary in different treatment groups (P=0.952). Thus, T790M mutation did not affect the radiosensitivity of NSCLC cell lines. The IC50 of H1975 in the 2.5 Gy group [(0.678; 2±0.373) μmol/L] was statistically significant compared with that in the 0 Gy normal control group [(3.520±0.821) μmol/L] (P=0.008). The drug tolerance of the H1975 cell line by 89.5 dropped to 39.2 times. Conclusion Ionizing radiation can reduce TKI resistance caused by T790M mutation in NSCLC cell lines. Our results provide a research basis for future in vivo and clinical studies. Radiotherapy combined with EGFR-TKI treatment can be a promising strategy to overcome T790M-mediated drug resistance

Friction Performance of Aluminum-Silicon Alloy Cylinder Liner after Chemical Etching and Laser Finishing

In order to enhance the surface friction performance of the aluminum-silicon (Al-Si) alloy cylinder liner, chemical etching and laser finishing techniques are applied to improve the friction performance. The cylinder liner samples are worn against a Cr-Al2O3 coated piston ring by a reciprocating sliding tribotester. The friction coefficient and weight loss are measured to determine the friction performance; a stress contact model is developed to ascertain the wear mechanism. The results show that the optimal etching time is 2 min for the chemical etching treatment and the optimal laser power is 1000 W for the laser finishing treatment. The chemical etching removes the surface aluminum layer and exposes the silicon on the surface, thereby avoiding metal-to-metal contact. The laser finishing results in the protrusion and rounded edges of the silicon particles, which decreases the stress concentration. The laser finishing results in better friction performance of aluminum-silicon alloy cylinder liner than the chemical etching

Oestrogen receptor β5 and epidermal growth factor receptor synergistically promote lung cancer progression

Oestrogen receptor beta (ERβ) and epidermal growth factor receptor (EGFR) pathway can synergistically promote the proliferation, invasion, and metastasis of non-small-cell lung cancer (NSCLC) cells. ERβ has five subtypes, and the selective splicing of exon 8 in ERβ5 transcription translational phase makes its biological function different from other subtypes. The following study investigates whether ERβ5 interacts with EGFR pathway in lung cancer. Briefly, we found that the overexpression of ERβ5 and EGFR is associated with poor prognosis and decreased overall survival in NSCLC patients. Furthermore, the effects of ERβ5 and EGFR on cell biological behaviour were investigated in vitro. These results indicated that the combination of ERβ5 and EGF induces cell proliferation and invasion, while the combination of ERβ5 and Gefitinib (EGFR inhibitors, Gef) induces cell apoptosis and promotes cell mitosis in A549 cell line. In addition, the combination of ERβ5 and EGF increases the expression of ERβ5, EGFR, and p-ERK1/2 in lung cancer cells. To sum up, the obtained results suggest that ERβ5 and EGFR synergistically promote the progression of lung cancer by activating MEK/ERK signalling pathway, which provides a theoretical basis for more accurate combined targeted therapy

Anti-Wear Property of Aluminum–Silicon Alloy Treated by Chemical Etching, Mechanical Honing and Laser Finishing

To enhance the anti-wear property of aluminum–silicon (Al–Si) alloy, three processing technologies—chemical etching, mechanical honing and laser finishing—were compared in terms of their effects on anti-wear performance. The treated Al–Si alloy cylinder liner samples were worn against a piston ring by a reciprocating sliding tribotester; the anti-wear performance was represented by the friction coefficient and wear loss; and the wear mechanism was determined by establishing stress contact models. The results showed that the best time for both the chemical etching and mechanical honing treatments was 2 min, and the optimal laser power was 1000 W for the laser finishing treatment. The three processing technologies could all remove the aluminum layer and make the silicon protrude on the surface to avoid the plastic flow of aluminum during the friction process. The laser finishing could not only protrude the silicon particle but also make its edge rounded and smooth, which decreased the stress concentration. Therefore, the Al–Si alloy cylinder liner treated with laser finishing had the best anti-wear performance

Preliminary Effect of Cyberknife Radiosurgery in the Treatment of 31 Patients with Advanced Non-small Cell Lung Cancer

Background and objective Recently, Cyberknife is a new flame-less stereotactic radiation therapy technology, which has several advantages, such as large dose, high precision and minimizing exposure to the surrounding normal tissue or adjacent vital structures, so it is successful in the treatment of non-small cell lung cancer (NSCLC). The aim of this study is to determine the effectiveness and safety of robotic stereotactic radiotherapy-Cyberknife with image guidance and realtime respiratory tracking against clinical stage III-IV peripheral NSCLC. Methods A review of treatment details and outcomes for 31 patients, with 34 tumors with histologically proven cancers treated by Cyberknife at the CyberKnife Center of Nanjing general hospital of Nanjing military command between March 2009 and March 2010 is presented. Of the 31patients, 15 were adenocarcinoma and 12 were squamous cell cancer. Twenty-eight patients received other forms of antineoplastic therapy such as chemotherapy. A total dose of 36 Gy-60 Gy was prescribed to the 65%-85% isodose line and given in two to five fractions in less than 1 week using the CyberKnife radiosurgery system. CT scans were performed after one-two months, then patients were followed every 3 months. Results Two patients had complete radiographic responses, 16 patients showed PRs, 7 patients showed SDs. Two patients showed PRs (reduction in tumor size), but developed distant metastases. Response rate was 58% and disease control rate was 81%. All patients tolerated the radiosurgery well, fatigue being the main side effect. No grade 4 or above toxicity was encountered. Conclusion In this small cohort of patients with advanced peripheral NSCLC, Cyberknife seems to be a safe and has good therapeutic effects with slight adverse reaction, but long time follow-up is necessary to evaluate the survival data and late toxicity