Novel control strategy for the global model of wind turbine

This paper presents a new nonlinear control for the overall model of a three-blade horizontal axis variable speed wind turbine (VSWT) including mechanical and electrical parts, with the aim of improving its performance and making it more profitable. The proposed control is an extension of the classical sliding mode control (SMC) by converting its sliding surface into a sliding sector. The classical SMC approach is widely used for nonlinear systems due to its stability against parameter variation, it is robustness against modeling uncertainties, its good results against external disturbances, and its ease of implementation in real time. Unfortunately, the SMC has a major drawback related to the chattering phenomenon. This phenomenon is due to the utility of a higher switching gain in the case of large uncertainties, it causes high-frequency oscillations once the sliding regime is reached, and it can cause a loss of accuracy by influencing the input control variables. This is the reason that aims to develop a new control law to eliminate the chattering and to guarantee stability, which is demonstrated by the Lyapunov theory. The effectiveness of the developed control is compared with the SMC and is illustrated by numerical simulations using MATLAB toolboxes

PREDICTIONS OF CRITICAL GAS RATES IN HORIZONTAL AND DEVIATED WELLS

The author’s intent through this work is to shed light on the current methods of predicting the onsets of liquid loading and to clarify that there is a difference in critical gas rate predictions between horizontal and vertical wells. A new model that predicts the critical gas rates for horizontal and deviated wells is presented. Literature data comprised of 69 horizontal and deviated wells reported in various studies in addition to experimental data from two horizontal wells are used to test the accuracy of the model and compare it to currently available models. Results using literature data show that the new model is capable of predicting the critical gas flow rates in horizontal wells within 15.7% of the actual values, a 2–6% improvement over the currently available horizontal well models, and 8–20% improvement over the currently available vertical well models. Results from the experiment tend to support the finding from literature comparison with a deviation of 5% from actual observed rates, an 18-24% improvement over the current horizontal well models, and 23-35% improvement over the current vertical well models. The New model yield best results for rates less than 10,000 Mscf/d and BUR’s between 4 and 30o/100 ft. The Conventional models (such as the Turner and Coleman) are not suitable for usage in horizontal wells and should only be used for vertical wells. The new model accounts for the effect of geometry on flow especially particle impact with the flow conduit wall as a result of change in geometry present in horizontal wells. When this effect is accounted for, as in the new model, the estimation of the critical gas rate is more accurate and yields optimized production performance from horizontal wells

Cellular Responses to Anthracyclines Identify Ku70, a DNA Repair Factor that Changes Compartment and Remains Stable in Leukemic Cells

Anthracyclines such as doxorubicin and daunorubicin are anticancer drugs that act by damaging the DNA and used for treating a variety of cancers including adult acute myeloid leukemia.  To date, nearly 50 % of acute myeloid leukemia patients show resistance to anthracyclines although the cause is not known.  We first investigate if there is a relationship between the expression level of 23 DNA repair genes in three leukemic cell lines (KG-1, HL-60 and Mono-Mac1) and cellular responses to anthracyclines.  We observed that the DNA repair genes were all downregulated in these cell lines following exposure to doxorubicin.  Further analysis revealed that the general downregulation of the genes was linked to a substantial decrease in the recovery of total RNA raising the possibility that assessment of total RNA, and not specific gene or set of genes, can be used as a simple indicator of cellular responses to anthracyclines.  Furthermore, examination of total protein extracts derived from these cell lines revealed for the first time that Ku70 is a key protein that remained stable, while the majority of proteins were loss, upon anthracycline treatment.  Importantly, Ku70 redistributes from the cytoplasm to the nucleoli in a time-dependent manner in response to anthracycline exposure.  We propose that Ku70 redistribution might play a vital role in predicting cellular response to anthracycline and promoting cell death

Numerical simulation of solar cells besed CZTS buffer layer (ZnO1-XSX) using SCAPS-1D software

Cds buffer layer has many advantages such as large bandgap, and the carrier density. Otherwise, the presence of cadmium is an inconvenient. Research work, are shifted on the possibility of replacing CdS by a buffer layer devoid of cadmium. This manuscript presents the numerical study, using SCAPS-1D program, the effects of sulfur content in the buffer layer Zn (O,S) on the electrical parameters of the solar cell ZnO: Al / i-ZnO / Zn (O, S) / CZTS /. Changes in the band gap and electron affinity of Zn (O, S) were calculated from the law of Vegard. The numerical results of the thickness of the absorbent layer CZTS equal to 2.5μm, show that from the sulfur content equals to 45% we can find the same results with CdS, an efficiency varies slightly, about 19%.Keywords: CZTS; ZnO1-xSx; CdS; SCAPS; Solar cell