Pulse rate estimation based on facial videos:an evaluation and optimization of the classical methods using both self-constructed and public datasets

Pulse rate is one of the important characteristics of traditional Chinese medicine pulse diagnosis,and it is of great significance for determining the nature of cold and heat in diseases.The prediction of pulse rate based on facial video is an exciting research field for getting palpation information by observation diagnosis.However,most studies focus on optimizing the algorithm based on a small sample of participants without systematically investigating multiple influencing factors.A total of 209 participants and 2,435 facial videos,based on our self-constructed Multi-Scene Sign Dataset and the public datasets,were used to perform a multi-level and multi-factor comprehensive comparison.The effects of different datasets,blood volume pulse signal extraction algorithms,region of interests,time windows,color spaces,pulse rate calculation methods,and video recording scenes were analyzed.Furthermore,we proposed a blood volume pulse signal quality optimization strategy based on the inverse Fourier transform and an improvement strategy for pulse rate estimation based on signal-to-noise ratio threshold sliding.We found that the effects of video estimation of pulse rate in the Multi-Scene Sign Dataset and Pulse Rate Detection Dataset were better than in other datasets.Compared with Fast independent component analysis and Single Channel algorithms,chrominance-based method and plane-orthogonal-to-skin algorithms have a more vital anti-interference ability and higher robustness.The performances of the five-organs fusion area and the full-face area were better than that of single sub-regions,and the fewer motion artifacts and better lighting can improve the precision of pulse rate estimation.

Synchronous measurements of prefrontal activity and pulse rate variability during online video game playing with functional near-infrared spectroscopy

Interactions between the central nervous system(CNS)and autonomic nervous system(ANS)play a crucial role in modulating perception,cognition,and emotion production.Previous studies on CNS–ANS interactions,or heart–brain coupling,have often used heart rate variability(HRV)metrics derived from electrocardiography(ECG)recordings as empirical measurements of sympathetic and parasympathetic activities.Functional near-infrared spectroscopy(fNIRS)is a functional brain imaging modality that is increasingly used in brain and cognition studies.The fNIRS signals contain frequency bands representing both neural activity oscillations and heartbeat rhythms.Therefore,fNIRS data acquired in neuroimaging studies can potentially provide a single-modality approach to measure task-induced responses in the brain and ANS synchronously,allowing analysis of CNS–ANS interactions.In this proof-of-concept study,fNIRS was used to record hemodynamic changes from the foreheads of 20 university students as they each played a round of multiplayer online battle arena(MOBA)game.From the fNIRS recordings,neural and heartbeat frequency bands were extracted to assess prefrontal activities and shortterm pulse rate variability(PRV),an approximation for short-term HRV,respectively.Under the experimental conditions used,fNIRS-derived PRV metrics showed good correlations with ECG-derived HRV golden standards,in terms of absolute measurements and video game playing(VGP)-related changes.It was also observed that,similar to previous studies on physical activity and exercise,the PRV metrics closely related to parasympathetic activities recovered slower than the PRV indicators of sympathetic activities after VGP.It is concluded that it is feasible to use fNIRS to monitor concurrent brain and ANS activations during online VGP,facilitating the understanding of VGP-related heart–brain coupling.

The Change in Pulse Rate and Behavioral Score by Using Video Assisted Induction of Pediatric Anesthesia

Purpose: Objective of this study was to determine whether video assisted anesthesia induction reduced pediatric patients’ stress. Methods: With approval from the local ethics committee and parental informed consent, 75 children undergoing minor surgery were investigated in this prospective observational study. Patients were divided into three groups: group 1 was aged two to three years old, group 2 was aged four to six years old and group 3 was aged from seven to ten years old. The following three characteristics were evaluated: 1) the pulse rate at four points (the ward, the entrance at the operating room, mask notification and the mask fit);2) the behavioral score in the operating room;3) the amount of pain killers after the operation. Results: In group 1 (N = 20), there was a significant difference between the control group and the video assisted group regarding the percentage change in pulse rate based on the children’s ward when the patients looked at the mask. In group 2 (N = 26), there was no significant difference regarding any points. In group 3 (N = 29), there was a significant difference between control and video assisted group regarding the percentage change in pulse rate based on the children’s ward for all points. Also, regarding to the behavioral score, there was a significant difference between the control group and the video assisted group of all ages. However, there was no significant difference regarding the use of NSAIDs in the postoperative period between the control and the video assisted group. Conclusion: These results show that the video assisted anesthesia induction is effective for pediatric patients.

The 266-nm ultraviolet-beam generation of all-fiberized super-large-mode-area narrow-linewidth nanosecond amplifier with tunable pulse width and repetition rate

We report on a compact, stable, all-fiberized narrow-linewidth(0.045 nm) pulsed laser source emitting laser beam with a wavelength of 266 nm, and tunable pulse width and repetition rate. The system is based on all-fiberized nanosecond amplifier architecture, which consists of Yb-doped fiber preamplifiers and a super-large-mode-area Yb-doped fiber power amplifier. The fiber amplifier with a core of 50 μm is used to raise the threshold of the stimulated Brillouin scattering(SBS) effect and to obtain high output power and single pulse energy. Using lithium triborate(LBO) crystal and betabarium borate(BBO) crystal for realizing the second-harmonic generation(SHG) and fourth-harmonic generation(FHG),we achieve 17 μJ(1.73 W) and 0.66 μJ(66 mW), respectively, at wavelengths of 532 nm and 266 nm and a repetition rate of 100 kHz with pulse width of 4 ns. This source has great potential applications in fluorescence research and solar-blind ultraviolet optical communication.

All-fiberized very-large-mode-area Yb-doped fiber based high-peak-power narrow-linewidth nanosecond amplifier with tunable pulse width and repetition rate

We demonstrate an all-fiberized narrow-linewidth nanosecond amplifier with high peak power,tunable pulse width,and repetition rate.A fiber-coupled narrow-linewidth laser diode operating at 1064.1 nm is employed as the seed source,which is gain-switched to generate nanosecond pulses with tunable pulse widths of 1-200 ns and tunable repetition rates of10 Hz-100 kHz.By utilizing a very-large-mode-area Yb-doped fiber with a core diameter of 50 μm in the power amplifier,thresholds of the stimulated Brillouin scattering at different pulse widths and repetition rates are increased.The maximum average power reaches 30.8 W at the pulse width of 4 ns and a repetition rate of 100 kHz,corresponding to an optical-tooptical conversion efficiency of ~55.2%.Pulse energy and peak power are calculated to be 0.2 mJ and 50 kW,respectively,which are limited by stimulated Brillouin scattering.The 3-dB spectral linewidth remains around 0.05 nm during the power scaling process.The stimulated Brillouin scattering limited output powers at different pulse widths and repetition rates are investigated.Peak power of 47.5 kW(0.19 mJ) is obtained for the 4 ns pulses at a repetition rate of 50 kHz,which is nearly the same as that of 4 ns pulses at 100 kHz.When the pulse width of the seed source is increased to 8 ns,peak powers/pulse energies are decreased to 19.6 kW/0.11 mJ and 13.3 kW/0.08 mJ at repetition rates of 50 kHz and 100 kHz,respectively.

Characterization of zirconium thin films deposited by pulsed laser deposition

Zirconium （Zr） thin films deposited on Si （100） by pulsed laser deposition （PLD） at different pulse repetition rates are investigated. The deposited Zr films exhibit a polycrystalline structure, and the X-ray diffraction （XRD） patterns of the films show the α Zr phase. Due to the morphology variation of the target and the laser-plasma interaction, the deposition rate significantly decreases from 0.0431 A/pulse at 2 Hz to 0.0189A/pulse at 20 Hz. The presence of droplets on the surface of the deposited film, which is one of the main disadvantages of the PLD, is observed at various pulse repetition rates. Statistical results show that the dimension and the density of the droplets increase with an increasing pulse repetition rate. We find that the source of droplets is the liquid layer formed under the target surface. The dense nanoparticles covered on the film surface are observed through atomic force microscopy （AFM）. The root mean square （RMS） roughness caused by valleys and islands on the film surface initially increases and then decreases with the increasing pulse repetition rate. The results of our investigation will be useful to optimize the synthesis conditions of the Zr films.

Design of Online Vitals Monitor by Integrating Big Data and IoT

In this work,we design a multisensory IoT-based online vitals monitor(hereinafter referred to as the VITALS)to sense four bedside physiological parameters including pulse(heart)rate,body temperature,blood pressure,and periph-eral oxygen saturation.Then,the proposed system constantly transfers these signals to the analytics system which aids in enhancing diagnostics at an earlier stage as well as monitoring after recovery.The core hardware of the VITALS includes commercial off-the-shelf sensing devices/medical equipment,a powerful microcontroller,a reliable wireless communication module,and a big data analytics system.It extracts human vital signs in a pre-programmed interval of 30 min and sends them to big data analytics system through the WiFi module for further analysis.We use Apache Kafka(to gather live data streams from connected sen-sors),Apache Spark(to categorize the patient vitals and notify the medical pro-fessionals while identifying abnormalities in physiological parameters),Hadoop Distributed File System(HDFS)(to archive data streams for further analysis and long-term storage),Spark SQL,Hive and Matplotlib(to support caregivers to access/visualize appropriate information from collected data streams and to explore/understand the health status of the individuals).In addition,we develop a mobile application to send statistical graphs to doctors and patients to enable them to monitor health conditions remotely.Our proposed system is implemented on three patients for 7 days to check the effectiveness of sensing,data processing,and data transmission mechanisms.To validate the system accuracy,we compare the data values collected from established sensors with the measured readouts using a commercial healthcare monitor,the Welch Allyn®Spot Check.Our pro-posed system provides improved care solutions,especially for those whose access to care services is limited.

Short mid-infrared watt-level all-fiber nonlinear pulse compressor above 100-MHz pulse repetition rate

We firstly report a 2-μm all-fiber nonlinear pulse compressor based on two pieces of normal dispersion fiber(NDF),which enables a high-power scaling ability of watt-level and a high pulse compression ratio of 13.7.With the NDFbased all-fiber nonlinear pulse compressor,the 450-fs laser pulses with a repetition rate of 101.4 MHz are compressed to 35.1 fs,corresponding to a 5.2 optical oscillation cycle at the 2-μm wavelength region.The output average power reaches 1.28 W,which is believed to be the highest value never achieved from the previous 2-μm all-fiber nonlinear pulse compressors with a high pulse repetition rate above 100 MHz.The dynamic evolution of the ultrafast pulse inside the all-fiber nonlinear pulse compressor is numerically analyzed,matching well with the experimental results.

Effects of urban street trees on human thermal comfort and physiological indices: a case study in Changchun city, China

Planting trees along urban streets is one of the most important strategies to improve the urban thermal environment.However,the net impacts of urban street trees on human thermal comfort and physiological parameters are still less clear.On three similar east-west orientated streets with different degrees of tree cover-low(13%),medium(35%),and high(75%),urban microclimatic parameters and human physiological indices for six male students were simultaneously measured on three cloudless days in summer 2018.The results show that the differences in tree cover were predominant in influencing urban thermal environment and comfort.The street with the highest tree cover had significantly lower physiological equivalent temperature(PET) and more comfortable than the other two streets.The frequency of strong heat stress(PET> 35℃) was 64%,11 %,and 0%,respectively,for streets with low,medium,and high tree cover.For the six male university students,human physiological indices varied greatly across the three streets with different tree cover.Systolic blood pressure,diastolic blood pressure,and pulse rate increased with decreasing tree cover.The results also suggest that urban thermal environment and comfort had considerable impact on human physiological parameters.Our study provides reasons for urban planners to plant trees along streets to improve the thermal environment and promote urban sustainability.

The adaptive value of increasing pulse repetition rate during hunting by echolocating bats

During hunting, bats of suborder Microchiropetra emit intense ultrasonic pulses and analyze the weak returning echoes with their highly developed auditory system to extract the information about insects or obstacles. These bats progressively shorten the duration, lower the frequency, decrease the intensity and increase the repetition rate of emitted pulses as they search, approach, and finally intercept insects or negotiate obstacles. This dynamic variation in multiple parameters of emitted pulses predicts that analysis of an echo parameter by the bat would be inevitably affected by other co-varying echo parameters. The progressive increase in the pulse repetition rate throughout the entire course of hunting would presumably enable the bat to extract maximal information from the increasing number of echoes about the rapid changes in the target or obstacle position for successful hunting. However, the increase in pulse repetition rate may make it difficult to produce intense short pulse at high repetition rate at the end of long-held breath. The increase in pulse repetition rate may also make it difficult to produce high frequency pulse due to the inability of the bat laryngeal muscles to reach its full extent of each contraction and relaxation cycle at a high repetition rate. In addition, the increase in pulse repetition rate increases the minimum threshold （i.e. decrease auditory sensitivity） and the response latency of auditory neurons. In spite of these seemingly physiological disadvantages in pulse emission and auditory sensitivity, these bats do progressively increase pulse repetition rate throughout a target approaching sequence. Then, what is the adaptive value of increasing pulse repetition rate during echolocation？ What are the underlying mechanisms for obtaining maximal information about the target features during increasing pulse repetition rate？ This article reviews the electrophysiological studies of the effect of pulse repetition rate on multiple- parametric selectivity of neurons in the central nucleus of the inferior colliculus of the big brown bat, Eptesicusfuscus using single repetitive sound pulses and temporally patterned trains of sound pulses. These studies show that increasing pulse repetition rate improves multiple-parametric selectivity of inferior collicular neurons. Conceivably, this improvement of multiple-parametric selectivity of collicular neurons with increasing pulse repetition rate may serve as the underlying mechanisms for obtaining maximal information about the prey features for successful hunting by bats.

Effect of dilution rate on dynamic and steady-state biofilm characteristics during phenol biodegradation by immobilized Pseudomonas desmolyticum cells in a pulsed plate bioreactor

Pulsed plate bioreactor （PPBR） is a biofilm reactor which has been proven to be very efficient in phenol biodegradation. The present paper reports the studies on the effect of dilution rate on the physical, chemical and morphological characteristics of biofilms formed by the cells of Pseudomonas desmolyticum on granular activated carbon （GAC） in PPBR during biodegradation of phenol. The percentage degradation of phenol decreased from 99% to 73% with an increase in dilution rate from 0.33 h^-1 to 0.99 h^-1 showing that residence time in the reactor governs the phenol removal efficiency rather than the external mass transfer limitations. Lower dilution rates favor higher production of biomass, extracellular polymeric substances （EPS） as well as the protein, carbohydrate and humic substances content of EPS. Increase in dilution rate leads to decrease in biofilm thickness, biofilm dry density, and attached dry biomass, transforming the biofilm from dense, smooth compact structure to a rough and patchy structure. Thus, the performance of PPBR in terms of dynamic and steady-state biofilm characteristics associated with phenol biodegradation is a strong function of dilution rate. Operation of PPBR at lower dilution rates is recommended for continuous biological treatment of wastewaters for phenol removal.

A compact Tirsapphire femtosecond pulse amplifier without stretcher at high repetition rate

We report a simple approach to amplify Ti:sapphire femtosecond pulses to moderate energy levels by a chirped regenerative amplifier. The seed pulses are broaden naturally because of the material dispersion of system components in regenerative cavity. The off-focusing Ti:sapphire crystal avoids effectively the optical damage. It sustains amplification over a wavelength range from 775 nm to more than 810 nm with a birefringent filter and an oscillation bandwidth of 7.7 nm, and produces 2.1 ps chirped output pulse energy of 100 uJ at 1.1-mJ pumping energy. This system shows good performances in stability and efficiency with the benefits of two thin-film polarizers and TEMoo mode pumping laser.

PIPBQ Effect Aware SER Analysis for Combinational Logic Circuits

Technology scaling results in the propagation-induced pulse broadening and quenching（PIPBQ） effect become more noticeable.In order to effectively evaluate the soft error rate for combinational logic circuits,a soft error rate analysis approach considering the PIPBQ effect is proposed.As different original pulse propagating through logic gate cells,pulse broadening and quenching are measured by HSPICE.After that,electrical effect look-up tables（EELUTs） for logic gate cells are created to evaluate the PIPBQ effect.Sensitized paths are accurately retrieved by the proposed re-convergence aware sensitized path search algorithm.Further,by propagating pulses on these paths to simulate fault injection,the PIPBQ effect on these paths can be quantified by EELUTs.As a result,the soft error rate of circuits can be effectively computed by the proposed technique.Simulation results verify the soft error rate improvement comparing with the PIPBQ-not-aware method.

Eye-safe,single-frequency pulsed all-fiber laser for Doppler wind lidar

A single-frequency pulsed erbium-doped fiber （EDF） laser with master-oscillator power-amplifier configuration at 1 533 nm is developed. A short-cavity, erbium-doped phosphate glass fiber laser is utilized as a seeder laser with a linewidth of 5 kHz and power of 40 mW. The seeder laser is modulated to be a pulse laser with a repetition rate of 10 kHz and pulse duration of 500 ns. The amplifier consists of two pre-amplifiers and one main amplifier. The detailed characteristics of the spectrum and linewidth of the amplifiers are presented. A pulse energy of 116 μJ and a linewidth of 1.1 MHz are obtained. This laser can be a candidate transmitter for an all-fiber Doppler wind lidar in the boundary layer.

Stimulated Brillouin scattering threshold dependent on temporal characteristics in a kilowatt-peak-power,single-frequency nanosecond pulsed fiber amplifier

The stimulated Brillouin scattering （SBS） threshold affected by repetition rate and pulse duration in a single- frequency nanosecond pulsed fiber amplifier is studied. The experimental results demonstrate that the SBS threshold can be improved either by reducing the repetition rate or by narrowing the pulse duration; however, the average power may be limited in some cases. Otherwise, two evaluation methods for the SBS threshold in the fiber amplifier are compared and discussed, aiming to obtain a more accurate description for the SBS threshold in our single-frequency amplifier system.

Diode-pumped Nd:YLF slab master oscillator power amplifier laser system with 655 m J output at 50 Hz repetition rate

A laser-diode-pumped high-pulse-energy Nd：LiYF4 master oscillator power amplifier 1053 nm laser system is demonstrated. We design a home-made pump module to homogenize the pump intensity through the ray tracing method. To increase the extraction efficiency, the pre-amplifier adopts a double-pass amplification structure. At a repetition rate of 50 Hz, 655 mJ pulse energy and 12.9 ns pulse width of 1053 nm laser is obtained from the master oscillator power amplifier system. The corresponding peak power is 51 MW. The optical-to-optical efficiency of the system is about 9.7%.

All-fiber cascaded ytterbium-doped nanosecond pulsed amplifier

A cascaded ytterbium-doped all-fiber master oscillator power amplifier（MOPA） with 1064-nm pulsed laser is demonstrated,and it can produce up to 20-W average power and 0.1-mJ pulse energy at tunable repetition rates from 10 to 200 kHz.Two main difficulties of the all-fiber configuration are overcome：all fiber isolator and mode field adapter between single mode fiber（SMF） and double cladding fiber（DCF）. Gain saturation and nonlinear effect are analyzed theoretically,and the possibility of further power-scaling of this cascade scheme is predicted.

Electro-optically Q-switched high-repetition-rate1.73 μm optical parametric oscillator

We demonstrate a potassium titanyl phosphate-based optical parametric oscillator （OPO） emitting at 1729 nm. A maximum output power of 1,56 W at 1729.4 nm is obtained with an original fundamental laser power of 5.48 W. The pulse with a pulse duration of 11.22 ns exceeds 3 mJ at a 500 Hz repetition rate. To our knowledge this is the highest energy output of an OPO laser emitting around 1.73 μm operating at a 100 Hz order of magnitude. This laser is primarily used for bond-selective imaging of deep tissue, a promising way for diagnosing vulnerable plaques in live patients.

Conductively cooled 1-kHz single-frequency Nd:YAG laser for remote sensing

A conductively cooled, laser diode （LD） end-pumped, injection-seeded single-frequency Nd：YAG laser is designed and implemented. The laser is capable of producing an 8-mJ Q-switched pulse with a ll-ns pulse width at 1 064 nm and at a pulse repetition rate of 1 000 Hz. At the maximum output energy of 8 m J, the frequency jitter is less than 3.5 MHz （root mean square （RMS）） over two minutes, and the linewidth is around 54.2 MHz. The M2 of the laser beam is approximately 1.30 in both horizontal and vertical direc- tions. The optimized ramp-fire technique is applied to build reliable single longitudinal mode oscillating.

Compact and high-energy diode-side-pumped Q-switched Nd:YAG slab laser system for space application

We develop a compact and high-energy Nd：YAG slab laser system consisting of an oscillator and an amplifier for space applications. The oscillator is a diode-side-pumped electro-optically Q-switched slab laser with a cross-Porro resonator. The KD＊P Pockels cell with a low driving voltage of 950 V is used to polarization output coupling. The amplifier is a Nd：YAG zigzag slab pumped at bounces. The maximum output pulse energy of 341 m3 with 13 ns pulse duration is obtained from the system at the repetition rate of 20 Hz and the beam quality factors are M2=3.1 and M2=3.5. The beam pointing stabilities of the laser system are 3.05μrad in the X-direction and 3.99 grad in the Y-direction, respectively.