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ABSTRACT A stable passive Q-switched Ytterbium-doped fiber laser (YDFL) operating at 1073-nm region is demonstrated using single-walled carbon-nanotubes (SWCNTs) as a saturable absorber (SA). The SA is prepared using polyvinyl alcohol (PVA) as a host polymer and integrated in the YDFL ring cavity by sandwiching the SWCNT/PVA thin film between two fiber connectors. A stable pulse train is achieved with 17.1-kHz repetition rate, 6.45-μs pulse width, and 3.1-nJ pulse energy at the threshold 980-nm pump power of 95.4 mW. As the pump power increases to 117.5 mW, the pulse train repetition rate also rises to 23.6 kHz. The shortest pulse width of 3.11 μs and pulse energy of 4.4 nJ are achieved at the maximum pump power of 117.5 mW © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1770-1773, 2014 [ABSTRACT FROM AUTHOR]

The fabrication of a silver (Ag) based photodetector on a silicon dioxide/p-silicon (SiO2/p-Si) substrate using direct current (DC) magnetron sputtering is demonstrated. The proposed method deposits a nanoparticle-like Ag thin film that favours the photoconduction mechanism under light illumination at 468 nm and laser illumination at 660 and 980 nm. The thin film is characterized using scanning electron microscope (SEM), energy dispersive x-ray (EDX), x-ray diffraction (XRD), Raman scattering, photoluminescence (PL) and ultraviolet–visible (UV–VIS) analysis. Current–voltage (I–V) analysis and the calculated rectifying ratio (RR) suggests the establishment of good Schottky contacts for incident light/laser at 468, 660 and 980 nm, with good responsivity towards light and laser illumination in the forward and reverse DC bias regions. The responsivity increases as the wavelength decreases from 980 nm → 660 nm → 468 nm, with the highest responsivity of 213.7 mAW−1 at 468 nm indicating better photoconduction at low light powers. [ABSTRACT FROM AUTHOR]

In this work, a passively Q-switched Thulium/Holmium-doped fibre laser (THDFL) using a molybdenum tungsten disulphide (MoWS2) saturable absorber (SA) is proposed and demonstrated. The MoWS2 nanosheets are prepared by hydrothermal exfoliation and then suspended in a polyvinyl alcohol (PVA) thin film host. Q-switching of the THDFL at a maximum 1550 nm pump power of 445.2 mW gives a maximum repetition rate and minimum pulse width of 36.3 kHz and 2.8 µs with a corresponding pulse energy of 86.4 nJ and peak power of 31.1 mW. The MoWS2 based Q-switched THDFL's output has a very high signal-to-noise value of ∼62.2 dB which strongly indicates that the laser is working in a stable operation. To the best of our knowledge, this is the first demonstration of MoWS2 as a passive SA in a THDFL for operation in the 2.0 µm region. The proposed laser would have significant medical and sensing applications, particularly at the biologically active 2.0–2.1 µm regions. [ABSTRACT FROM AUTHOR]

DAS system based on φ-OTDR technique suffers from random noises that affect the signalto-noise-ratio of the extracted signals. This results in high false alarm rate, reducing the capabilities of the systems to detect vibration signals. This paper presented a thorough analysis of a denoising method using discrete wavelet function (DWT). We implemented and compared different mother wavelets such as Symlet 4, Haar, Daubechies 4 (Db4), Biorthogonal 4.4 (Bior4.4), Coiflets 3 (Coif3), Discrete approximation of Meyer wavelet (dmey), Fejér-Korovkin filters 8 (fk8) and Reverse Biorthogonal 6.8 (rbio6.8), using multiple levels of decomposition. Four denoising thresholds, Empirical Bayes, Universal Threshold, Stein's Unbiased Risk Estimation (SURE), and Minimax Estimation (Minimax) were characterized using soft threshold rule. From the results obtained, the combination of the Daubechies 4 wavelet function, level 3 decomposition, SURE denoising threshold with soft threshold rule produces the best denoising performance on the φ-OTDR data. [ABSTRACT FROM AUTHOR]

The phase optical time domain reflectometry (Φ-OTDR) system offers several advantages suitable for distributed acoustic sensing application. It has long sensing range, great antielectromagnetic interference, and high sensitivity towards environmental vibrations. However, as a sensor system, the Φ-OTDR is limited to only collecting environmental vibrations without providing more useful information such as the location and types of events happening around the sensing region. Therefore, it requires an extensive data processing system to distinguish between different events happening within the sensing regions. In this paper, Simple Differential and Normalized Differential method were used to extract perturbation event prior to classification process comprising data organization, features extraction, and classification outcome were implemented. Gammatone Frequency Cepstral Cepstrum were used to handcraft features for classification and were obtained using Gammatone Filter processing. Classification scheme based on Support Vector Machine (SVM) is use as classifier where accuracy score 100%. [ABSTRACT FROM AUTHOR]

In this work, we report the effect of four-wave mixing (FWM) in MoTe2 deposited on a side-polished fibre (SPF). The MoTe2 layer has a nonlinear coefficient of 17.368 W−1 km−1 at 1550 nm, while the coated SPF has a conversion efficiency of – 38 dB and output tuning range of 5 nm. The generated idlers from the induced FWM effect were observed to be highly stable with minimal peak fluctuations and only minor changes in their measured conversion efficiency. The proposed MoTe2 based SPF is thus a suitable device for inducing the FWM effect in an optical fibre laser cavity and could also serve to induce other non-linear optical effects for use in optical communications networks. [ABSTRACT FROM AUTHOR]

Background: The association between increased arterial stiffness and Left ventricular (LV) diastolic dysfunction (DD) has been well characterized, suggesting a close interaction between the arterial system and the left ventricle. Aortic pulse-wave velocity (PWV) is a measure of aortic stiffness, and it has an established prognostic role in cardiovascular diseases and in the general population. Aim: Evaluation of aortic PWV assessed by echocardiography as a new diagnostic parameter for LV DD by correlation with current echocardiographic LV DD indices, and also evaluation of aortic PWV prognostic value in patients with DD by correlation with Brain natriuretic peptide (BNP). Methods: This study was conducted at Ain-Shams and Helwan University hospitals from December 2017 to December 2018. It included 100 subjects aged from 55 to 60 years; they were divided into two groups, 1st group (case group): 80 patients with asymptomatic LV DD with preserved ejection fraction ≥ 50%, 2nd group (control group): 20 patients with normal diastolic function. All patients were subjected to full history and thorough physical examination. BNP, ECG and full echocardiography with assessment of aortic PWV were done. Results: A total of 100 patients were enrolled, 38 (47.5%) males in case group vs. 9 (45%) in control group. Hypertension, diabetes and dyslipidemia were significantly higher in case vs. control (P-values: <0.001, 0.005, 0.002 respectively). Aortic PWV has significant positive correlation with both age and body mass index (r=0.422, r=0.847 respectively with P<0.001 for both). Aortic PWV has significant positive correlation with E/e' (r=0.957, P<0.001), tricuspid regurge velocity (r=0.941, P<0.001), and left atrial volume index (r=0.947, P<0.001), but it has significant negative correlation with septal e' (r=-0.970, P<0.001) and lateral e' (r=-0.932, P<0.001). Aortic PWV has significant positive correlation with plasma BNP level (r=0.958, P <0.001). Aortic PWV was significantly higher in case vs. control group with mean values (15.50±1.32 vs. 10.11±0.78 m/s respectively; P<0.001). The area under the ROC curve for aortic PWV to detect DD was 0.86 (95% CI, 0.76-0.98; P<0.001) and the optimal cutoff point of 12.5 m/s produced 92.3% sensitivity and 75.0% specificity (the positive and negative predictive values were 93.5 and 72.7%, respectively with an accuracy of 89.0%). Conclusion: Echocardiographic assessment of aortic PWV appears not only to be a highly sensitive, reliable, easy, rapid and practical parameter for LV DD detection but also has a promising prognostic value in patients with LV DD. [ABSTRACT FROM AUTHOR]

A C-band mode-locked fibre laser incorporating a boron nitride-doped graphene oxide (BN-GO)-based saturable absorber (SA) is proposed and demonstrated. The SA is fabricated by depositing multiple layers of synthesized BN-GO nanoparticles onto the polished surface of a side-polished fibre, which is then inserted into an erbium-doped fibre laser cavity to generate the desired pulsed output. The strong nonlinear optical response and light absorption of the BN-GO nanoparticles induces the generation of a highly stable mode-locked pulse at 1567.32 nm with visible Kelly’s sidebands. The pulses have a measured repetition rate of 13.56 MHz and a pulse width of 1.18 ps at the maximum pump power of 280.5 mW. The pulses have a frequency signal-to-noise ratio of ∼53 dB, indicating a highly stable output. The proposed laser would find significant telecommunications applications, particularly for dense wavelength division multiplexing systems. [ABSTRACT FROM AUTHOR]

This work examines the performance of the Cu2SnS3 (CTS) solar cells using the solar cell capacitance simulator (SCAPS) approach. The performance of the CTS solar cell was evaluated in terms of , , fill factor and efficiency. The structural parameter variation of CTS solar cell has been studied in terms of buffer and absorber layer thickness, bandgap, effect of temperature on total efficiency of the solar cell. Increasing the thickness of the CdS buffer layer decreases the efficiency of the simulated solar cell. A significant increase in the efficiency of the solar cell to 20.36% was obtained with a simulated buffer layer thickness to 10nm. In terms of the CTS absorber layer thickness, the efficiency of the solar cell increases by increasing the thickness of absorber layer. By setting the thickness of CTS to 4.0m, the efficiency obtained is 20.36%. It is observed that an increase in the bandgap can enhance the efficiency of the solar cell. In the performed simulation, an 0.9eV bandgap resulted in a 11.58% cell efficiency and a 1.25eV bandgap resulted in 21.96% cell efficiency. In terms of temperature, the efficiency of 20.36% was obtained at 300K, and as the temperature increases, cell efficiency will decrease. [ABSTRACT FROM AUTHOR]

This paper demonstrates the use of a tapered fibre in generating a highly stable and tunable dual-wavelength fibre laser. By unique arrangement of polarization controller, adjustable spacing range between 0.94 and 3.32 nm and side mode suppression ratio (SMSR) up to 50 dB were recorded. The results were achieved at laser pump power of 94.7 mW. The inter-modal interference is achieved through the use of a non-adiabatic tapered fibre, made by a systematic flame brushing technique. The tapered fibre suppresses the mode competition in the 3-m erbium-doped fibre (EDF) gain medium. Over 60 min, the laser exhibited very high stability with acceptable peak power and SMSR. The proposed EDF laser operates from 1556.71 to 1562.13 nm range. [ABSTRACT FROM PUBLISHER]

In this paper, a microfibre polarizer based on graphene oxide (GO) is proposed and demonstrated. A microfibre was coated with GO using the drop-casting technique. The extinction ratio (ER) has been measured at wideband range of 1310, 1460, 1550 and 1600 nm. The highest ER obtained in this experiment was 37.0 dB measured at 1480 nm wavelength. The result has been achieved with a GO coating thickness of 24 μm and coating length of 12 mm. This work demonstrates a polarizing effect of GO-coated microfibre. [ABSTRACT FROM AUTHOR]

Yaw stability control systemplays a significant role in vehicle lateral dynamics in order to improve the vehicle handling and stability performances. However, not many researches have been focused on the transient performances improvement of vehicle yaw rate and sideslip tracking control. This paper reviews the vital elements for control system design of an active yaw stability control system; the vehicle dynamic models, control objectives, active chassis control, and control strategies with the focus on identifying suitable criteria for improved transient performances. Each element is discussed and compared in terms of their underlying theory, strengths, weaknesses, and applicability. Based on this, we conclude that the sliding mode control with nonlinear sliding surface based on composite nonlinear feedback is a potential control strategy for improving the transient performances of yaw rate and sideslip tracking control. [ABSTRACT FROM AUTHOR]

A novel frequency and pattern reconfigurable Yagi antenna is proposed. The antenna is formed by a driver, a reflector and two directors. The introduction of switches using a PIN diode at the arms of the driver element produces three switchable frequencies at 1.25 GHz, 1.85 GHz and 2.45 GHz. By controlling the switches at the directors and reflector, the radiation pattern can be configured to near omni-directional pattern or directional pattern at those three frequencies. Simulated and measured results are used to demonstrate the performance of the antenna. The simulated and measured return losses and the radiation patterns, are presented and compared. It was found that the gain of the antenna increases from 3.3 dB to 5 dB in a directional pattern, when compared to the near omni-directional pattern. [ABSTRACT FROM AUTHOR]

We demonstrate a simple, compact and low cost Q-switched erbium-doped fiber laser (EDFL) using single-wall carbon nanotubes (CNTs) as a saturable absorber for possible applications in metrology, sensing, and medical diagnostics. The EDFL operates at around 1560nm with repetition rates of 16.1 kHz and 6.4 kHz with saturable absorbers SA1 and SA2 at a pump power of 120mW. The absorbers are constructed by optically driven deposition and normal deposition techniques. It is observed that the optical deposition method produces a Q-switched EDFL with a lower threshold of 70mW and better Q-switching performance compared to that of the normal deposition method. The EDFL also has pulse energy of 90.3 nJ and pulse width of 11.6 μs at 120mW pump power. [ABSTRACT FROM AUTHOR]