Vasodilatation Measurement Using Finger Vascular Images by Near-Infrared Light and Comparison with RH-PAT

Examination of vascular endothelial function can help infer atherosclerosis progression. This study investigated whether vascular visualization by near-infrared (NIR) light can detect vasodilatation after cuff pressure release of the upper arm and what the correlation is between the brightness decrease ratio (R1) corresponding to vasodilation and the reactive hyperemia index (RHI). We obtained finger vascular images of 53 male subjects by photographing NIR light (wavelength 850 nm) transmitted through the middle phalanx of the middle finger with a charge-coupled device camera. The upper arm was compressed for 10 min using a cuff (200 mmHg), and vascular images before and after cuff compression release were obtained. We analyzed the finger vascular images by NIR light and digital pulse volume using endothelial peripheral arterial tonometry (Endo-PAT). We also calculated the average brightness of each vascular image. Using only the data of the ischemic finger, R1 was defined using the average brightness just before cuff release and the minimum average brightness after cuff release. The brightness of vascular images of the ischemic finger decreased after cuff release probably because of vasodilation. We found significant correlation between R1 and the RHI (r = 0.52; P < 0.001). R1 in the lowest RHI quartile was significantly smaller compared to the highest and second-highest RHI quartiles (P < 0.05). Vascular visualization by NIR light can detect vasodilation after cuff release. This is significantly correlated with the RHI on Endo-PAT.

Smooth-Transition Simple Digital PWM Modulator for Four-Switch Buck-Boost Converters

This paper proposes a simple, hardware-efficient digital pulse width modulator for a 4SBB that enables operation in Buck, Boost, and Buck+Boost modes, achieving smooth transitions between the different modes. The proposed modulator is simulated using Simulink and experimentally demonstrated using a 500 W 4SBB converter with 24 V input voltage and 12–36 V output voltage range.

Design of Digital Pulse-Position Modulation System

Pulse-Position Modulation (PPM) is a modulation method that only makes every pulse in the carrier pulse sequence change with time but without changing the shape and amplitude of the pulse signal. In this paper, a PPM system is designed. Firstly, an appropriate mathematical model is established to represent PPM transmission, and the shape of the pulse signal is designed. After that, we write the code and add a white Gaussian noise channel. Then the transmission process is simulated and visualized. At last, the error rate of the scheme is analyzed and discussed through MATLAB simulation then compared with other modulation methods. The goal of this paper is to study PPM by designing a PPM system fully. Besides, our method is compared with other modulation methods to understand the advantages and disadvantages of PPM. This may help other scholars to design and research the PPM system.

Performance Enhancement of DWDM-FSO Optical Fiber Communication Systems Based on Hybrid Modulation Techniques under Atmospheric Turbulence Channel

In this paper, we enhance the performance efficiency of the free-space optical (FSO) communication link using the hybrid on-off keying (OOK) modulation, M-ary digital pulse position modulation (M-ary DPPM), and M-pulse amplitude and position modulation (M-PAPM). This work analyzes and enhances the bit error rate (BER) performance of the moment generating function, modified Chernoff bound, and Gaussian approximation techniques. In the existence of both an amplified spontaneous emission (ASE) noise, atmospheric turbulence (AT) channels, and interchannel crosstalk (ICC), we propose a system model of the passive optical network (PON) wavelength division multiplexing (WDM) technique for a dense WDM (DWDM) based on the hybrid fiber FSO (HFFSO) link. We use eight wavelength channels that have been transmitted at a data rate of 2.5 Gbps over a turbulent HFFSO-DWDM system and PON-FSO optical fiber start from 1550 nm channel spacing in the C-band of 100 GHz. The results demonstrate (2.5 Gbps × 8 channels) 20 Gbit/s-4000 m transmission with favorable performance. In this design, M-ary DPPM-M-PAPM modulation is used to provide extra information bits to increase performance. We also propose to incorporate adaptive optics to mitigate the AT effect and improve the modulation efficiency. We investigate the impact of the turbulence effect on the proposed system performance based on OOK-M ary- PAPM-DPPM modulation as a function of M-ary DPPM-PAPM and other atmospheric parameters. The proposed M-ary hybrid DPPM-M-PAPM solution increases the receiver sensitivity compared to OOK, improves the reliability and achieves a lower power penalty of 0.2–3.0 dB at low coding level (M) 2 in the WDM-FSO systems for the weak turbulence. The OOK/M-ary hybrid DPPM-M-PAPM provides an optical signal-to-noise ratio of about 4–8 dB of the DWDM-HFFSO link for the strong turbulence at a target BER of 10−12. The numerical results indicate that the proposed design can be enhanced with the hybrid OOK/M-DPPM and M-PAPM for DWDM-HFFSO systems. The calculation results show that PAPM-DPPM has increased about 10–11 dB at BER of 10−12 more than the OOK-NRZ approach. The simulation results show that the proposed hybrid optical modulation technique can be used in the DWDM-FSO hybrid links for optical-wireless and fiber-optic communication systems, significantly increasing their efficiency. Finally, the use of the hybrid OOK/M-ary DPPM-M-PAPM modulation schemes is a new technique to reduce the AT, ICC, ASE noise for the DWDM-FSO optical fiber communication systems.

The Design Methodology of Fully Digital Pulse Width Modulation

This paper describes the design methodology and calibration technique for a low-power digital pulse width modulation demodulator to enhance its robustness against the process, voltage, and temperature variations in different process corners, in addition to intra-die variability, which makes it a very good choice for implantable monitoring sensors. Furthermore, the core of the proposed demodulator is fully digital. Thus, along with the proposed design methodology, the proposed demodulator can be simply redesigned in advanced subnanometer CMOS technologies without much difficulty as compared to analog demodulators. The proposed demodulator consists of an envelope detector, a digitizer, a ring oscillator, and a data detector with digital calibration. All the proposed circuits are designed and simulated in the standard 1P9M TSMC’s 40 nm CMOS technology. Simulation results have shown that the circuit is capable of demodulating and recovering data from an input signal with a carrier frequency of 13.56 MHz and a data rate of 143 kB/s with an average power consumption of 5.62 μW.

Coincidence Detection of EELS and EDX Spectral Events in the Electron Microscope

Recent advances in the development of electron and X-ray detectors have opened up the possibility to detect single events from which its time of arrival can be determined with nanosecond resolution. This allows observing time correlations between electrons and X-rays in the transmission electron microscope. In this work, a novel setup is described which measures individual events using a silicon drift detector and digital pulse processor for the X-rays and a Timepix3 detector for the electrons. This setup enables recording time correlation between both event streams while at the same time preserving the complete conventional electron energy loss (EELS) and energy dispersive X-ray (EDX) signal. We show that the added coincidence information improves the sensitivity for detecting trace elements in a matrix as compared to conventional EELS and EDX. Furthermore, the method allows the determination of the collection efficiencies without the use of a reference sample and can subtract the background signal for EELS and EDX without any prior knowledge of the background shape and without pre-edge fitting region. We discuss limitations in time resolution arising due to specificities of the silicon drift detector and discuss ways to further improve this aspect.