基于反射式血管容积波的心理压力测量

由于计算机对人认知与情感方面的利用将有助于未来智能生活的实现,同时研究发现,血液容积脉搏波（photo-plethysmography,简称PPG)信号包含的心脏收缩与血管壁本身压力的效果将有助于对人体心理压力及情感测量的分析,因此介绍了通过利用反射式血氧传感器得到PPG波形,并采用压力血氧反应指数（stress-induced vascular responses index,简称sVRI)模型来分析人体目前的压力值,验证反射式传感器对于人体心理压力测量方面的适用性.实验中不仅比较了传统透射式传感器与反射式传感器在双波长（红光与红外光)正常情况与压力情况下PPG波形的差异,同时也引入了新的波长——绿光,即利用绿光反射式传感器,通过sVRI模型来分析人体的压力值.通过比较与讨论,证明了反射式血氧传感器的适用性.最后,将实验结果与sVRI模型相结合应用于实验鼠标模型中,将反射式传感器所携带的生理信息应用于日常生活中,其佩戴更加舒适以及佩戴位置范围更广的优点适合脉搏检测的高性能医疗保健设备及可穿戴智能设备.     

The Operation of the National Grid System

Abstract

To investigate whether the exercise intensity affects sweating efficiency (η_sw) during exercise under mild environmental conditions, six healthy males, aged 22 ± 2 years, performed three bicycle ergometer exercises at varying intensities (73W: Ex-1, 103W: Ex-2 and 133W: Ex-3) for 40min under the conditions of 25°C room temperature, 50% relative humidity and 0·3-0·4 m s ^?1 wind velocity. Heart rate, oxygen consumption, rectal temperature (T _re), mean skin temperature (T¯ _sk 4 skin sites) and total sweat rate were determined intermittently throughout the experiments. Moreover, heat loss by evaporation (E), radiation (R), convection (C) and η_sw were calculated using the heat balance equations. The findings concerning thermoregulatory parameters under the three experimental conditions were summarized as follows: (1) the higher the exercise intensity, the larger the values of T_re and T¯ _sw at the end of exercise and E, R and C during exercise (2) the mean values ± SE of η_sw were 55·4 ± 5·1, 63·2 ± 5·2 and 58·5 ± 1·9% for Ex-1, Ex-2 and Ex-3, respectively. The results suggest that exercise intensity would have no effect on η_sw in this mild thermal environment.     

智能血氧饱和度监测系统设计与实现

血氧饱和度作为人体重要生理参数,临床需要持续监测.目前的脉搏血氧仪一般选取指尖或耳垂等作为测量部位,采用透射式测量方法,测量时影响正常作息,且无数据存储功能,不便于观察血氧变化趋势.因此,采用反射式测量方式,以ATmega328作为控制和处理核心,交替驱动红光及红外光LED照射手腕,通过测量反射的光强,计算获得血氧饱和度数据.血氧饱和度数据由手环上的蓝牙模块发送至手机APP,完成数据存储和后续数据分析.该仪器具有测量精度高、使用方便、即时测量等特点.     

Assessing corn water stress using spectral reflectance

Multiple remote-sensing techniques have been developed to identify crop-water stress; however, some methods may be difficult for farmers to apply. If spectral reflectance data can be used to monitor crop-water stress, growers could use this information as a quick low-cost guideline for irrigation management, thus helping save water by preventing over-irrigating and achieving desired crop yields. Data was collected in the 2013 growing season near Greeley, Colorado, where drip irrigation was used to irrigate 12 corn (Zea mays L.) treatments with varying water-deficit levels. Ground-based multispectral data were collected and three different vegetation indices were evaluated. These included the normalized difference vegetation index (NDVI), the optimized soil-adjusted vegetation index (OSAVI), and the Green normalized difference vegetation index (GNDVI). The three vegetation indices were compared to water stress as indicated by the stress coefficient (K_s), and water deficit in the root zone was calculated using a soil water balance. To compare the indices to K_s, vegetation ratios were developed from vegetation indices in the process of normalization. Vegetation ratios are defined as the non-stressed vegetation index divided by the stressed vegetation index. Results showed that vegetation ratios were sensitive to water stress as indicated by the good coefficient of determination (R² > 0.46) values and low root mean square error (RMSE < 0.076) values when compared to K_s. To use spectral reflectance to manage crop-water stress, an example irrigation trigger point of 0.93 for the vegetation ratios was determined for a 10–12% loss in yield. These results were validated using data collected from a different field. The performance of the vegetation ratio approach was better than when applied to the main field giving higher goodness of fit values (R² > 0.63), and lower error values (RMSE < 0.043) between K_s and the vegetation indices.     

ERGONOMICS RESEARCH SOCIETY THE SOCIETY'S LECTURE, 1964.

Eight male volnntours, aged 20 to 43 yr, participated in a 1 min run to exhaustion. Six of the subjects had experienced work on the treadmill and ran regularly during the year. By means of a preliminary rim a work load was selected for each subject which would produce exhaustion in 60 sec. The speed of the treadmill was 12.8 kph for all runs except one (14.5 kph) and grade varied from 10 to 20%. The warm up consisted of walking 5.6 kph at a 10% grade for min and preceded the rim by 3 or 5 min. Oxygen consumption ([Vdot]o₂), heart rate (HR), and respiration rate (f) were recorded every 15 sec during the run and during the first 30 sec of recovery. Thereafter, recovory measurements were made during progressively longer intervals for a total of 30 min. [Vdot]0₃, during the run with warm up (2.69± 0.39 L) was significantly greater (p<0.05) than without warm up (2.50±0.41 L). Recovory [Vdot]o₃ and total [Vdot]o₂ (run plus recovory) were not significantly different between the warm up and without warm up runs. The results were not different when net [Vdot]o₂ ([Vdot]o₂minus rest [Vdot]o₃) was compared. A significant increase in heart rate was achieved during rutis with warm up compared to no warm up. Respiration rates were also increased with warm up but not significantly. The conclusion was that under the conditions of this study, warm up is of energetic benefit in preparing for a short exhaustive run.     

基于DTW的贝叶斯方法在睡眠和唤醒分类中的应用

许多方便的可穿戴设备被用于医疗用途,如测量心率（HR）、血压和其他信号. 随着睡眠质量监测问题的出现,如何从这些信号中区分睡眠和唤醒状态成为关键问题. 提出了一种基于动态时间规整（DTW）的贝叶斯方法用于睡眠和唤醒分类. 利用心率和血氧饱和度（SpO2）的信号去分析睡眠状态和一些睡眠相关问题. 利用DTW从原始的心率、血氧饱和度信号中提取特征,然后贝叶斯分类方法用于区别睡眠和唤醒状态. 最后,从睡眠心脏健康研究网站收集数据的一个真实案例研究验证了基于DTW的贝叶斯方法的可行性和优势.     

Energy expenditure and clearing snow: a comparison of shovel and snow pusher

In order to assess the energy demands of manual clearing of snow, nine men did snow clearing work for 15 min with a shovel and a snow pusher. The depth of the snowcover was 400–600 mm representing a very heavy snowfall. Heart rate (HR), oxygen consumption ([Vdot]O₂), pulmonary ventilation ( [Vdot]O_E), respiratory exchange ratio (R), and rating of perceived exertion (RPE) were determined during the work tasks. HR, [Vdot]O_E, R, and RPE were not significantly different between the shovel and snow pusher. HR averaged (± SD) 141 ± 20bmin_-1 with the shovel, and 142 ± 19 beats-min_-1 with the snow pusher. [Vdot]O₂was 2·1 ± 0·41 min_-1 (63 ± 12% [Vdot]O₂max) in shovelling and 2·6 ± 0·51 min_-1 (75 ± 14% [Vdot]O₂max) in snow pushing (p< 0·001). In conclusion manual clearing of snow in conditions representing heavy snowfalls was found to be strenuous physical work, not suitable for persons with cardiac risk factors, but which may serve as a mode of physical training in healthy adults.     

Optimizing a novel PPG sensor patch via optical simulations towards accurate heart rates

This study proposes the design and optimization of the flexible OLED–OPD photoplethysmography (PPG) sensor patch to estimate the long time continuous heart rate. Using optical simulation, the distance between OLED–OPD and the aperture area of the OLED–OPD has been optimized to enhance the AC/DC ratio of the receive PPG signal. The optical simulation incorporates an empirical optical skin model. All the patches incorporate green OLED@525 nm wavelength and red OLED@630 nm wavelength. Simulation results show that the optimized AC/DC ratio of the cross-type patch for the green and the red OLED is 2.16% and 6.25%, respectively. Similarly, the optimized AC/DC ratio of the square-type patch for the green, and the red OLED is 9.6% and 5.8%, respectively. Experiment results show that the received PPG signal AC/DC ratio for the square type and cross-type are 2%@green OLED and 4.5% @green OLED, respectively. Also, the AC/DC ratio of the received PPG signal from the square type and cross-type are 1.4%@red OLED and 1.1%@red OLED, respectively. The AC/DC ratio is reduced because the skin and blood itself act as a lossy medium so that the DC signal increased more; as a result, the overall AC/DC ratio decrease. The best design of the optical patch is the square-type OPD patch due to the wide area of the OPD. The OLED drive current ranges between 0.1 and 0.4 mA. The average OPD current is 800 nA. The flexibility of the design PPG sensor patch is 130°. The non-invasive square-type PPG sensor patch is applied to the wrist artery of 40 subjects for sensing the PPG pulsation of the blood vessel. The heart rate measurement accuracy is 95%, whereas the standard error rate is 0.37 ± 1.96 bpm, respectively.

     

Ergonomics diary

Physiological, perceptual and physical responses to a typical circuit weight-training (CWT) regimen were recorded in two studies. The aims were to assess the intensity of exercise during CWT; and to determine whether physical responses as evaluated by spinal shrinkage were related to physiological and perceptual responses to CWT. In the first study (n = 10) heart rate (HR), oxygen consumption (VO), ventilation (VE), blood lactate (La) and perceived exertion (RPE) were measured in response to CWT. Mean ( ± SD) time to complete three circuits of CWT was 17.8 (± 1-4) min. The HR max, VO₂max and peak La, measured first during an incremental treadmill test, were 195 (±13) beats.min ^?159-7 (±4-8) ml.kg^?1.min^?1 and 14-3 (±3-5) mM respectively. Mean HR and vO₂ during CWT were 69% and 50% of the respective maximal values. The HR-VO₂ ratio observed on the treadmill was elevated during CWT, with VO₂ being lowered relative to HR. Mean VE and La values were 52-7 (± 14-5) l.min^?1 and 6-9 ( ± 3-6) mM. The effect of the same CWT regimen on spinal loading as indicated by change in stature (shrinkage) was investigated in a second study (n = 8). The mean ( ± SD) time taken to complete the circuit was 17-4 ( ± 1-3) min. Mean shrinkage due to CWT (2-5 ± 1 -5?mm) was unrelated to the time taken to complete the circuits, to HR, RPE or to low back pain ratings (p > 0-05). Observations suggest that CWT as represented in these studies engages anaerobic as well as aerobic mechanisms but the exercise intensity may not provide sufficient stimulation for aerobic training. The physical load on the spine indicated by spinal shrinkage was not related to the physiological or perceptual strain.     

The physical strain of dairy farming

The aim of this study was to estimate the physical stress and strain in dairy farming, using ambulatory heart rate and oxygen consumption measurements. The rate of perceived exertion was estimated with Borg scale. The maximal oxygen consumption was measured in the laboratory. The study group consisted of eight male and 15 female farmers. The handling of feed and manure was the heaviest work task in dairy farming. The aerobic capacity ([Vdot]O₂ max) of female farmers (26 ± 3 ml/min/kg) was below average, and their work required over 50% of [Vdot]0₂ max during most of the tasks. The [Vdot]0₂ max of male fanners (32±10 ml/min/kg) was moderate, and most work tasks required below 50% of [Vdot]0₂ max. The mean heart rate in dairy farming tasks was 99 beats min^-1 in men and 116 beats min^-1 in women. However, according to the rate of perceived exertion, the men experienced the same work tasks as subjectively more heavy than did the women. The physical strain of female farmers in dairy farming seems to be too high because of heavy work tasks and relatively low [Vdot]0₂ max of women. Special attention should be paid to these factors in the occupational health services for farmers.     

A modified linear extrapolation approach towards red edge position detection and stress monitoring of wheat crop using hyperspectral data

The inflection point of spectral reflectance of crop in the red edge region (680–780 nm) is termed as the red edge position (REP), which is sensitive to crop biochemical and biophysical parameters. We propose a technique for automatic detection of four dynamic wavebands, i.e. two in the far-red and two in the near-infrared (NIR) region from hyperspectral data, for REP estimation using the linear extrapolation method. A field experiment was conducted at the SHIATS Farm, Allahabad, India, with four levels of nitrogen and irrigation treatments to assess the sensitivity of REP towards crop stress. A correlation analysis was carried out between REPs and different biophysical parameters, such as leaf area index (LAI) and chlorophyll content index (CCI), recorded in each plot at 50, 70, and 90 days after sowing of wheat crop under the field experiment. The inter-comparison among different REP extraction techniques revealed that the proposed technique, i.e. the modified linear extrapolation (MLE) method, has a better ability to distinguish different crop stress conditions. REPs extracted using the MLE technique showed high correlations with a wide range of LAI, CCI, and LAI × CCI, being comparable with results obtained using the traditional linear extrapolation and polynomial fitting techniques. The behaviour of the new techniques was found to be stable at both narrower and broader bandwidth, i.e. 2 and 10 nm. A new red-edge-based index, i.e. area under REP (A_REP), was used to detect the cumulative stress over wheat crop by utilizing the REP and its rate of change information at different crop growth stages. A high coefficient of determination (R² = 0.89) was found between A_REP and dry grain yield (Q ha^?1) up to 50 Q ha^?1 of wheat crop, whereas, beyond this range the relationship was found to be diminishing.     

Increased variation of the response index of nociception during noxious stimulation in patients during general anaesthesia

Objective

Analgesia is an important part of general anaesthesia, but no direct indicators of nociceptive-anti-nociceptive balance have been validated in detail. The Response Index of Nociception (RN) is a multiparameter approach which combines photoplethysmographic waveform (PPG), State Entropy (SE), Response Entropy (RE), and heart rate variability (HRV). We aimed at evaluating RN during general anaesthesia; especially we wanted to compare pre- and post-index values of certain noxious stimuli to the average index values. Our assumption was that RN could be a useful indicator of nociceptive-anti-nociceptive balance during the surgery.

Methods

Sixty women undergoing gynaecological or breast surgery participated in the study. All patients had elective surgery and anaesthesia was maintained with propofol-remifentanil target controlled infusion. Neuromuscular blocking agent rocuronium was used at the beginning of the surgery. Electrocardiography (ECG), photoplethysmography (PPG) and electroencelophalography (EEG) were registered and extracted off-line. An index, reflecting amplitude and frequency of occurrence of abrupt increases (“peaks”) in the RN was evaluated during surgery in general and around occurrences of predefined noxious stimuli in particular.

Results

Fifty-four patients were eligible for analysis. Patient movement was associated with increased index values, both before and after the event. Post-event values of the index for intubation and skin incision were higher than its intra-surgery baseline, while pre-event values remained unchanged.

Conclusion

Changes in RN can be used to detect noxious stimuli during surgery. RN also predicted movement in our patients under propofol-remifentanil anaesthesia.     

Hyperoxia improves maximal exercise with the self-contained breathing apparatus (SCBA)

The effects of hyperoxia on maximal exercise while breathing from a self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed three graded exercise tests (GXT) for the assessment of maximal oxygen uptake (Vdot;O _2max): two with 20.95 ± 0.28% O₂ and the third (GXT₄₀) while breathing hyperoxia (40.64 ± 1.29% O₂). No significant differences were found between the two normoxic tests, except for a 16W increase in maximal power output (PO_max) in the second trial (GXT₂₁). Compared to GXT₂₁, hyperoxia significantly increased Vdot;O _2max and PO_max by 10.0 ± 3.8% and 10.2 ± 7.1%, respectively. This was likely due to an increase in O₂ delivery as suggested by the significantly higher oxyhemoglobin saturation. The increase in Vdot;O _2max with hyperoxia was similar to the increase in carbon dioxide production (9.3 ± 6.5%). No other significant differences were found at maximal exercise. However, at the intensity that elicited Vdot;O _2max in GXT₂₁, pulmonary ventilation and SCBA mask pressure were significantly lower during GXT₄₀, suggesting a decrease in the work of breathing. These findings could have significant implications for occupations that involve heavy work with SCBA.     

A shirt containing multistage phase change material and active cooling components was associated with increased exercise capacity in a hot,humid environment

Recent advances in clothing design include the incorporation of phase change materials (PCM) and other active cooling components (ACC) to provide better body heat dissipation. The purpose of this study was to determine the effect of wearing a shirt containing multistage PCM/ACC on exercise capacity at low (5.0), moderate–high (7.5) and extreme (9.0) levels of the physiological strain index (PSI). Fourteen individuals tested two shirts (control vs. cooling) during 45-min of interval running in a hot, humid (35 ± 1 °C; 55 ± 6% RH) environment. The cooling shirt resulted in an 8% improvement in exercise capacity at a PSI of 7.5 (p < 0.05). The observed increase in exercise capacity would likely translate to a significant improvement in exercise performance. More research is needed to determine a best practice approach for the use of cooling clothing as a counter to exercise-induced heat exposure.

Practitioner Summary: In this report, we demonstrate that when forced to exercise in a hot, humid environment, an individual’s exercise capacity may increase by as much as 8% when wearing a shirt composed of multistage phase change material and active cooling components.     

Real-time core body temperature estimation from heart rate for first responders wearing different levels of personal protective equipment

First responders often wear personal protective equipment (PPE) for protection from on-the-job hazards. While PPE ensembles offer individuals protection, they limit one's ability to thermoregulate, and can place the wearer in danger of heat exhaustion and higher cardiac stress. Automatically monitoring thermal–work strain is one means to manage these risks, but measuring core body temperature (T_c) has proved problematic. An algorithm that estimates T_c from sequential measures of heart rate (HR) was compared to the observed T_c from 27 US soldiers participating in three different chemical/biological training events (45–90 min duration) while wearing PPE. Hotter participants (higher T_c) averaged (HRs) of 140 bpm and reached T_c around 39°C. Overall the algorithm had a small bias (0.02°C) and root mean square error (0.21°C). Limits of agreement (LoA ± 0.48°C) were similar to comparisons of T_c measured by oesophageal and rectal probes. The algorithm shows promise for use in real-time monitoring of encapsulated first responders.     

Sublimation enthalpies of terbium and lutetium triiodides and formation enthalpies of their monomer and dimer molecules

The sublimation of terbium and lutetium triiodides was studied by Knudsen effusion mass spectrometry. The temperature dependencies of partial vapor pressures [atm] of the monomer and dimer molecules were determined as: lnp(TbI₃) = – (31.74 ± 0.24)× 10³/T + (21.43 ± 0.29) for 743–906 K; lnp(Tb₂I₆) = – (38.66 ± 0.38)× 10³/T + (25.63 ± 0.46) for 786–906 K; lnp(LuI₃) = – (31.48 ± 0.25)× 10³/T + (22.28 ± 0.30) for 721–951 K; and lnp(Lu₂I₆) = – (36.95 ± 0.37)× 10³/T + (25.21 ± 0.43) for 796–950 K. On the basis of a joint analysis of all literature data, the sublimation enthalpies [kJ mol^–1] at 298.15 K are recommended as 281 ± 3 (TbI₃), 346 ± 30 (Tb₂I₆), 279 ± 12 (LuI₃), and 340 ± 30 (Lu₂I₆). The standard formation enthalpies [kJ mol^–1] of the gaseous species at 298.15 K are –343 ± 4 (TbI₃), –902 ± 30 (Tb₂I₆),–326 ± 12 (LuI₃), and –870 ± 30 (Lu₂I₆).     

Cardiorespiratory responses of firefighters to a computerized fire strategies and tactics drill during physical activity

Firefighters are subjected to a combination of physical and mental challenges in the course of their occupational responsibilities. However, due to the ecological factors involved with firefighting, it makes it extremely difficult to examine physiological and psychological changes that occur as a result of these combined challenges. The purpose of this study was to examine the efficacy of a computer-based Fire Strategies and Tactics Drill (FSTD) in eliciting psychological and physiological measures of stress in professional firefighters. In one session, participants exercised at 60% VO_2max for 37 min (exercise alone condition, EAC), and in the other session the firefighter exercised for an equal amount of time and responded to the FSTD (dual challenge condition; DCC) while exercising. Cardiorespiratory (heart rate [HR], respiration rate [RR], minute ventilation [V_E], oxygen consumption [VO₂], ventilatory efficiency [V_E/VO₂], and respiratory exchange ratio [RER]) and psychometric measures (State Anxiety Inventory [SAI] and Ratings of Perceived Exertion [RPE]) were obtained throughout the experimental protocols. The NASA Task Load Index was used to assess perceived physical and mental load during each condition. The results demonstrated that the participants perceived overall workload to be higher in the DCC. Repeated measures ANOVAs revealed no differences between the EAC and DCC for VO₂ or RER, but the DCC did elicit significantly greater elevations in HR, RR, V_E, and V_E/VO₂ compared to the EAC. These results suggest that the FSTD utilized in this study provides an effective method for examining the physiological and psychological responses of firefighters in a research laboratory environment.     

Reliability of the finite element method for calculating free edge stresses in composite laminates

The edge-stress problem for a [±45]_s graphite/epoxy laminate was examined in detail. A review of the literature on this problem showed that the interlaminar normal stress σ_z distributions along the interface between the +45° and -45° plies, obtained by various investigators, disagreed in magnitude and sign. In particular, a finite difference solution and a perturbation solution predicted a tensile σ_z, whereas the finite element methods predicted a compressive stress. Since a stress singularity exists at the intersection of the interface and the free edge, the differences in magnitude of the peak stress were expected, but not the difference in the sign.This paper investigates the reliability of the displacement-formulated finite element method in analyzing the edge-stress problem. Analyses of two well-known elasticity problems, one involving a stress discontinuity and one a singularity, showed that the finite element analysis yields accurate stress distributions everywhere except in two elements closest to the stress discontinuity or singularity. Stress distributions for a [±45]_s laminate showed the same behavior near the singularity as found in the well-known problems with exact solutions. The displacementformulated finite element method, therefore, appears to be a highly accurate technique for calculating interlaminar stresses in composite laminates. The disagreement among the numerical methods was attributed to the unsymmetric stress tensor at the singularity.     

Nonlinear analysis of edge effects in angle-ply laminates

An initial stress iteration method using a quasi-three-dimensional finite element has been developed for the nonlinear analysis of Carbon Fibre Reinforced Plastic (CFRP) laminates subjected to a uniform inplane load. Linear and nonlinear analyses of the free edge problem were carried out for the [0/90]_s, and [ ± 45]_s laminates with and without resin layers included between plies of laminae. The nonlinear results show that the peak shear stress in the [0/90]_s laminate and all the stress components in the [±45], laminates are reduced. A maximum strain failure criterion was used and failure modes were predicted.     

Development of a High-Resolution Human-Specific Breath Gas Sensor for Survivor Detection in Disaster Zones

This paper presents a new type of ultrasonic gas molecule concentration sensor for rescue robotics. This device can measure the change of gas concentration with a sampling rate of over 400 kHz. The performance is evaluated by measuring the CO₂ concentration in human respiration gas. The experiments show that the proposed sensor could detect a difference between 5% CO₂-containing air, humidified air and dry air with over 50 dB signal-to-noise, which are the main components of our respiration gas. Another important result was that our sensor could give information about the 'dead space', which is distributed from the lungs to the mouth. The 'dead space' could not be detected by previously proposed commercially distributed gas sensors because of the time needed to analyze the gas. We verified the distance dependency of the respiration detection in a open space that was considered for use for finding survivors. These results make the proposed sensor especially applicable for finding survivors in disaster zones.