The effect of hyperoxia on submaximal exercise with the self-contained breathing apparatus

The effects of hyperoxia on submaximal exercise with the self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed a graded exercise test for the determination of ventilatory threshold (VT) and then a submaximal practice trial with a normoxic gas mixture. The normoxic (20.93 +/- 0.22% O(2); SUB(21)) and hyperoxic (40.18 +/- 0.73% O(2); SUB(40)) submaximal trials were then administered in a random order. All exercise tests were completed on separate days while wearing firefighting gear and the SCBA. Compared with SUB(21), hyperoxia significantly reduced minute ventilation (V(E)), mask pressure (P(mask)), heart rate, blood lactate concentration, perceived exertion, and perceived breathing distress. As expected, hemoglobin saturation remained higher (p < 0.05) during SUB(40). The reductions in both V(E) and P(mask) with hyperoxia imply a reduction in the work of breathing during exercise. Total gas consumption was 10.3 +/- 8.1% lower during SUB(40) when compared to SUB(21), another finding that has significant practical implications for occupational safety.     

The effect of hyperoxia on submaximal exercise with the self-contained breathing apparatus

The e^ffects of hyperoxia on submaximal exercise with the self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed a graded exercise test for the determination of ventilatory threshold (VT) and then a submaximal practice trial with a normoxic gas mixture. The normoxic (20.93 ± 0.22% O₂ ; SUB₂₁) and hyperoxic (40.18 ± 0.73% O₂; SUB₄₀) submaximal trials were then administered in a random order. All exercise tests were completed on separate days while wearing firefighting gear and the SCBA. Compared with SUB₂₁, hyperoxia significantly reduced minute ventilation ([Vdot]_E ), mask pressure (P_mask), heart rate, blood lactate concentration, perceived exertion, and perceived breathing distress. As expected, hemoglobin saturation remained higher (p<0.05) during SUB₄₀. The reductions in both [Vdot]_E and P_mask with hyperoxia imply a reduction in the work of breathing during exercise. Total gas consumption was 10.3 ± 8.1% lower during SUB₄₀ when compared to SUB₂₁, another finding that has significant practical implications for occupational safety.     

The effect of idle time thresholds on computer use time estimations by electronic monitoring

This study examined the effect of idle time setting on the estimation of computer use times by electronic activity monitoring and validated its use by comparing it with video record observations. Twenty-four study subjects were recruited and their work with computers was monitored for 1 h. With the estimates by video record observation as references, the best idle time settings for electronic activity monitoring with the least relative errors were 25, 2.5 and 2.5 s, respectively, for total computer, keyboard and mouse use time estimations. These estimates were highly correlated with the corresponding references (r = 0.918–0.964, p < 0.0001), accompanied by limited mean estimate differences ranging from ?3.0 ± 2.8% to 1.3 ± 1.6%. The estimates by self-report were moderately correlated with the corresponding references (r = 0.387–0.678), with greater mean estimate differences. This study concluded that, for electronic activity monitoring methods, the most appropriate thresholds for idle time setting are 25 s, 2.5 s and 2.5 s for total computer, keyboard and mouse use time estimates, respectively. This method may help evaluate physical work-loading with computer works through a large-scale epidemiological study.     

Effects of the self-contained breathing apparatus and fire protective clothing on maximal oxygen uptake

To examine the effects of firefighting personal protective ensemble (PPE) and self-contained breathing apparatus (SCBA) on exercise performance, 12 males completed two randomly ordered, graded exercise treadmill tests (GXT_PPE and GXT_PT). Maximal oxygen consumption (VO_2max) during GXT_PPE was 17.3% lower than the GXT_PT in regular exercise clothing (43.0 ± 5.7 vs. 52.4 ± 8.5 ml/kg per min, respectively). The lower VO_2max during the PPE condition was significantly related (r = 0.81, p < 0.05) to attenuated peak ventilation (142.8 ± 18.0 vs. 167.1 ± 15.6 l/min), which was attributed to a significant reduction in tidal volume (2.6 ± 10.4 vs. 3.2 ± 0.4 l). Breathing frequency at peak exercise was unchanged (55 ± 7 vs. 53 ± 7 breaths/min). The results of this investigation demonstrate that PPE and the SCBA have a negative impact on VO_2max. These factors must be considered when evaluating aerobic demands of fire suppression work and the fitness levels of firefighters.     

Effects of the self-contained breathing apparatus and fire protective clothing on maximal oxygen uptake

To examine the effects of firefighting personal protective ensemble (PPE) and self-contained breathing apparatus (SCBA) on exercise performance, 12 males completed two randomly ordered, graded exercise treadmill tests (GXTPPE and GXTPT). Maximal oxygen consumption (VO2max) during GXTPPE was 17.3% lower than the GXTPT in regular exercise clothing (43.0 +/- 5.7 vs. 52.4 +/- 8.5 ml/kg per min, respectively). The lower VO2max during the PPE condition was significantly related (r = 0.81, p < 0.05) to attenuated peak ventilation (142.8 +/- 18.0 vs. 167.1 +/- 15.6 l/min), which was attributed to a significant reduction in tidal volume (2.6 +/- 10.4 vs. 3.2 +/- 0.4 l). Breathing frequency at peak exercise was unchanged (55 +/- 7 vs. 53 +/- 7 breaths/min). The results of this investigation demonstrate that PPE and the SCBA have a negative impact on VO2max. These factors must be considered when evaluating aerobic demands of fire suppression work and the fitness levels of firefighters.     

The effect of aerodynamic handlebars on oxygen consumption while cycling at a constant speed

Abstract

In this study, the oxygen consumption ([Vdot]O₂) of bicycling was measured at a fixed speed (40 km·h^?1on level terrain, with normal and aerodynamic handlebars using a Douglas bag collection system. Eleven elite (USCF category I or 2) men cyclists age 24 to 40 years (X¯=28·5, SD±4·6) performed four consecutive (two with each bar in alternating order) steady state rides at 40 km· h^?1over a 4 km flat course (same direction each trial). Expired gases were collected in a 1501 Douglas bag attached to a following vehicle during the last 45 s (approx. 0·5 km) of each trial. A repeated measures analysis of variance revealed a significant (p<0·02) handlebar effect. Specifically, [Vdot]O₂was 2% lower under the aerodynamic handlebar treatment (X¯=4·26, SD±0·36 1 min^?1when compared with that of the normal handlebar treatment (X¯=4·34, SD±0·35 1 min^?1The results of this study demonstrate that the reported aerodynamic advantage of the aerodynamic handlebars produces a small but significant reduction in the [Vdot]O₂of bicycling at 40 km·h^?1     

气压变化对极限电流型氧传感器输出特性的影响

对气压变化对极限电流型氧传感器扩散机理的影响进行了研究。实验中将扩散孔径为30μm的极限电流型氧传感器先后放置在不同气压环境中进行了电学性能测试。实验结果显示:在常压下该氧传感器的极限电流IL与氧浓度的对数表达式ln(1-XO2)具有很好的线性关系,呈现正常扩散模型的特征。但在低气压环境下,该传感器的极限电流IL受气压P的影响,并呈现Knudsen模型的某些特征。     

沉积氧气压力对纳米晶硅光致发光的影响

用脉冲激光（Nd：YAG激光）沉积技术在硅基上沉积富硅SiO2薄腊（SiOx，x〈2），沉积时氧气压力分别为1．33，2．66，3．99，5．32，6．65，7．98Pa，膜的厚度约为300nm。随后，在氩（Ar）气中1000℃的温度下对沉积的SiOx薄膜进行热退火处理30min，使在SiO2薄膜中生长出硅纳米晶。用光谱分析仪分析其在室温下的光致发光（PL）光谱时发现，随着沉积氧气压力的增强，峰值波长在减小（即蓝移），表明纳米晶硅颗粒在减小；同时，在本研究中的制作条件下，PL强度与沉积氧气压力有较强的依存关系，在2．66-3．99Pa的氧气压力条件下沉积制作的试样，得到最大的PL强度。     

The effects of spatial configuration on relative translation gain thresholds in redirected walking

Virtual Reality - In this study, we explore how spatial configurations can be reflected in determining the threshold range of Relative Translation Gains (RTGs), a translation gain-based Redirected...     

基于荧光猝灭原理的溶解氧浓度检测系统的设计

介绍了荧光猝灭原理,设计了一种基于荧光猝灭原理的溶解氧浓度测量系统,解释了系统检测原理,给出了系统结构图及关键部分的电路设计.最后给出了相关的实验结果并进行了分析.实验表明,系统测量精度为0.01 mg/L,响应时间少于30ms,具有较好的响应速度、精度以及稳定性.     

中心氧配比对GE气化炉内冷态流场分布影响的数值模拟研究

以三通道雾化喷嘴GE水煤浆气化炉为研究对象,应用Fluent软件分别对中心氧体积分数为14%,16%,18%和20%时气化炉内三维冷态流场进行了仿真模拟,考察不同中心氧配比对气化炉内流场分布、颗粒浓度分布和颗粒停留时间的影响。采用标准κ-ε模型描述气相湍流流动,通过SIMPLE算法求解压力速度耦合方程:采用DPM模型描述气体和颗粒相耦合,用随机轨道模型追踪水煤浆颗粒的运动。模拟结果表明:相对于其他3种情况,当中心氧体积分数为16%时,气化炉内流场分布最为合理,颗粒浓度分布最为均匀,颗粒停留时间最长。该分析结果可为实际气化炉的操作参数优化提供指导。     

Evaluating mobile apps for breathing training: The effectiveness of visualization

Deep and slow breathing exercises can be an effective adjunct in the treatment of stress, anxiety, post-traumatic stress disorder, chronic pain and depression. Breathing techniques are traditionally learned in courses with trainers and/or with materials such as audio CDs for home practice. Recently, mobile apps have been proposed as novel breathing training tools, but to the best of our knowledge no research has focused on their evaluation so far. In this paper, we study three different designs for breathing training apps. The first employs audio instructions as in traditional training based on audio CDs, while the other two include visualizations of the breathing process, representative of those employed in current breathing training apps. We carry out a thorough analysis, focusing on users’ physiological parameters as well as subjective perception. One visualization produces better results both objectively (measured deepness of breath) and subjectively (users’ preferences and perceived effectiveness) than the more traditional audio-only design. This indicates that a visualization can contribute to the effectiveness of breathing training apps. We discuss which features could have allowed one visualization (but not the other) to obtain better results than traditional audio-only instructions.     

Effect of wearing personal protective clothing and self-contained breathing apparatus on heart rate, temperature and oxygen consumption during stepping exercise and live fire training exercises

Fire fighter breathing apparatus instructors (BAIs) must possess the ability to respond to both the extrinsic stress of a high temperature environment and the intrinsic stress from wearing personal protective equipment (PPE) and self-contained breathing apparatus (SCBA), repeatedly and regularly, whilst training recruits in live fire training exercises (LFTEs). There are few previous investigations on BAIs in hot environments such as LFTEs, since the main research focus has been on regular fire fighters undertaking exercises in temperate or fire conditions at a moderate to high exercise intensity. In this study, the intrinsic cardiovascular stress effects of wearing PPE + SCBA were first investigated using a step test whilst wearing gym kit (control), weighted gym kit (a rucksack weighted to the equivalent of PPE + SCBA) and full PPE + SCBA (weight plus the effects of protective clothing). The extrinsic effects of the very hot environment were investigated in BIAs in LFTEs compared to mock fire training exercises (MFTEs), where the fire was not ignited. There was an increase in heart rate due to the modest workload imposed on the BAIs through carrying out the MFTEs (25.0 (18.7)%) compared to resting. However, when exposed to fire during the LFTEs, heat storage appears to be significant as the heart rate increased by up to 39.8 (+/-20.1)% over that of the mock LFTEs at temperate conditions. Thus, being able to dissipate heat from the PPE is particularly important in reducing the cardiovascular responses for BAIs during LFTEs.     

Effect of wearing personal protective clothing and self-contained breathing apparatus on heart rate,temperature and oxygen consumption during stepping exercise and live fire training exercises

Fire fighter breathing apparatus instructors (BAIs) must possess the ability to respond to both the extrinsic stress of a high temperature environment and the intrinsic stress from wearing personal protective equipment (PPE) and self-contained breathing apparatus (SCBA), repeatedly and regularly, whilst training recruits in live fire training exercises (LFTEs). There are few previous investigations on BAIs in hot environments such as LFTEs, since the main research focus has been on regular fire fighters undertaking exercises in temperate or fire conditions at a moderate to high exercise intensity. In this study, the intrinsic cardiovascular stress effects of wearing PPE + SCBA were first investigated using a step test whilst wearing gym kit (control), weighted gym kit (a rucksack weighted to the equivalent of PPE + SCBA) and full PPE + SCBA (weight plus the effects of protective clothing). The extrinsic effects of the very hot environment were investigated in BIAs in LFTEs compared to mock fire training exercises (MFTEs), where the fire was not ignited. There was an increase in heart rate due to the modest workload imposed on the BAIs through carrying out the MFTEs (25.0 (18.7)%) compared to resting. However, when exposed to fire during the LFTEs, heat storage appears to be significant as the heart rate increased by up to 39.8 (±20.1)% over that of the mock LFTEs at temperate conditions. Thus, being able to dissipate heat from the PPE is particularly important in reducing the cardiovascular responses for BAIs during LFTEs.     

虚拟现实中手重映射的偏移检测阈值研究

针对虚拟现实交互（virtual reality interaction,VRI）中环境限制导致使用手的操作效率较低的问题,提出了虚拟现实中手重映射的固定偏移检测阈值估计方法以提高使用手的操作效率,该方法从人的心理感知出发,引入心理测量函数计算出偏移检测阈值从而提升交互体验。首先,根据双选择强制选择（two alternative forced choice,2AFC）理论设计实验,记录被试者使用不同偏移的虚拟手完成目标抓取任务过程中的感觉差异作为评价标准,同时记录被试者完成任务的时间,根据心理测量函数（Quickpsy）对感觉差异进行计算,估计重映射交互的检测阈值;通过协方差确定虚拟手偏移量超过阈值后的方向、幅度和轴向及其相互作用是影响触碰任务性能的显著因素,若在阈值范围内,上述因素就不再影响任务性能;最后,以某VR（virtual reality,虚拟现实）医院物资智能配送系统为例验证所提方法的可行性。研究结果表明,适当的偏移缩短了用户完成触碰任务的时间,能够在提升交互效率的同时降低传统偏移量计算方法对VR的交互保真度的影响。     

氧分子在镍钛合金(100)表面吸附行为的研究

NiTi形状记忆合金作为一种广泛使用的生物医学材料，表面形成的氧化膜是其具有良好生物相容性的基础。氧分子在NiTi合金表面的吸附是其形成氧化膜的关键，应用离散变分Xα方法，首次对O2分子在B2结构NiTi(100)表面的吸附过程进行了理论研究，分别计算了在两种不同的O2分子吸附方式中Ti-O原子间的键级和电荷分布。结果表明：O2分子垂直接近NiTi(100)表面对其发生吸附更为有利。在吸附过程中，O2分子中只有一个氧原子被其最近邻的一个表面铁原子所吸附，而合金中其它表面原子及体相原子的电子结构没有变化。Mulliken集居数及局域态密度分析表明，吸附过程中铁原子与氧原子之间的相互作用主要是由2p(O)电子和4s，4p(Ti)电子贡献。