Helmet design to facilitate thermoneutrality during forest harvesting

The purpose of this investigation was to evaluate the ventilatory characteristics of vented and non-vented helmets for use in forestry harvesting operations. A ventilation index developed by Birnbaum and Crockford (1978) was used to determine the ventilation capacity of twelve helmets varying in design and presence, location, and dimension of vents. Helmets with top vents had higher ventilation indices than non-vented, side and side/top-vented helmets. Ten physically fit men participated in a maximal oxygen consumption test and four trials wearing a non-vented, round-side-vented, round-top-vented or rectangulartop-vented helmet. Trials simulated typical summer environmental conditions (28°C, 80% rh) and physiological work loads (40% V O 2 max) experienced during forest harvesting in New Zealand. The temperature and humidity under the helmet was typically lowest when the helmet with the largest vented area (288 mm 2) in the crown was worn, although physiological responses (temperatures at the tympanum, ear and scalp; humidity at the centre of the helmet) of the participants to wearing the helmets differed significantly during some rest periods only. Top-vented helmets (in this experiment measured 288 mm 2) should be worn to minimize temperature and humidity of the head during forest harvesting operations.     

基于智能视频图像分析的安全帽识别

为解决石油行业工作现场人员不佩戴安全帽的情况,避免因违规操作或违反规定,造成不必要的伤亡,提出一套基于施工现场安防监控系统的智能安全帽检测系统。设计一套综合利用安全帽的颜色、轮廓,以及多层神经网络分类建立的统计模型,对是否佩戴安全帽进行检测。结合实例,验证了算法的有效性和系统的可行性。实例结果表明,该系统能很好检测出现场没佩戴安全帽的人员,一定程度上杜绝了安全隐患,减少了事故的发生。     

Ergonomics evaluation of modified industrial helmets for use in tropical environments

Hotness, weight, fitting problems etc., have been found to be the chief causes of the unpopularity of industrial safety helmets in tropical environments in developing countries (DC). Some selected safety helmets manufactured in industrialized countries (IC) were modified to provide extra head ventilation and to reduce weight, in order to make them more acceptable to users in hot environments. The modified helmets were subjected to ergonomics evaluation both objectively and subjectively in the laboratory (in simulated tropical conditions) as well as in the field situation. There was evidence that white helmets had some advantages in comfort, viz. reduction of hotness, compared to the other colours, e.g. red, green etc., when worn in the presence of radiant heat in the laboratory. Ventilation holes provided at the top of the shell seemed to reduce the greenhouse effect within the helmet shell which therefore felt less uncomfortable than a fully covered helmet. Even with a small reduction of weight, such as 45 g in helmets weighing about 350g, the difference in weight was perceived by the wearers. In adapting helmets made in IC for use in tropical climates, head ventilation and low weight perception are important aspects in comfort which need to be considered. In addition to low cost, a harness material suitable for sweat absorption is required. Adjustability and sizing to fit 90% of the user population also needs to be considered in the design and manufacture of safety helmets for people in DC.     

Comparisons between Shikoro-type helmet with no hood and typical fire protective helmets with hood in a hot and humid environment

The purpose of this study was to evaluate physiological and subjective responses while wearing the Shikoro-type helmet for firefighters when compared to typical helmets. Eight firefighters conducted a 30-min exercise at a 5 km h^?1 in three helmet conditions at an air temperature of 32 °C with 70%RH. The results showed that no significant differences in rectal, mean skin temperature and physiological strain index among the three conditions were found during exercise and recovery. Skin temperatures on the cheek, ear and neck during exercise were significantly lower for the Shikoro-type condition (p < 0.05), but forehead temperature was greater for the Shikoro-type helmet when compared to the other conditions (p < 0.05). Statistical differences in thermal sensation and thermal comfort for overall and local body regions were not found among the three conditions. These results imply that the Shikoro-type helmet had local advantages in reducing skin temperatures on the face and neck.

Practitioner Summary: Firefighters wear their helmet with its hood to protect the head and neck but a Shikoro type helmet has no fire protective hood. This study aimed to evaluate the comfort function of Shikoro helmet along with typical helmets. The results demonstrated thermal benefits of the Shikoro helmet on the head.     

Heat loss variations of full-face motorcycle helmets

Heat loss of 27 full-face motorcycle helmets was studied using a thermal manikin headform. The headform was electrically heated and positioned at the exit of a wind tunnel, so that the air stream flowed onto its front side. All helmets were measured in three sessions in which all the vents were opened or closed consecutively in random order. Average heat loss was calculated from a steady state period, under controlled environmental conditions of 22±0.05 °C, 50±1% RH and 50.4±1.1 km h⁻¹ (14.0±0.3 m s⁻¹) wind speed. The results show large variations in heat loss among the different helmets, ranging from 0 to 4 W for the scalp section of the headform and 8 to 18 W for the face section of the headform. Opening all the vents showed an increase in heat loss of more than 1 W (2 W) for four (two) helmets in the scalp section and six (one) helmets in the face section. These levels of heat transfer have been shown to be the thresholds for human sensitivity in scalp and face sections. Furthermore, helmet construction features which could be identified as important for heat loss of motorcycle helmets were identified.     

基于YOLO的安全帽检测方法

安全帽作为作业工人最基本的个体防护装备,对作业人员的生命安全具有重要意义.但是部分作业人员安全意识缺乏,不佩戴安全帽行为时常发生.本文聚焦于复杂场景下对工作人员是否佩戴安全帽的实时检测.YOLO （You Only Look Once）是当前最为先进的实时目标检测算法,在检测精度和速度上都取得了良好的效果,将YOLO应用于安全帽检测.针对未佩戴安全帽单类检测问题,修改分类器,将输出修改为18维度的张量.基于YOLOv3在ImageNet上的预训练模型,对实际场景下采集到的2010张样本进行标注并训练,根据损失函数和IOU曲线对模型进行优化调参,最终得到最优的安全帽检测模型.实验结果表明,在2000张图片测试集上取得了98.7%的准确率,在无GPU环境下平均检测速度达到了35 fps,满足实时性的检测要求,验证了基于YOLOv3安全帽检测方法的有效性.     

改进YOLOv3的安全帽佩戴检测方法

在生产和作业场地中，工人由于不佩戴安全帽而引发的安全事故时有发生。为了降低由于未佩戴安全帽而引发的安全事故发生率，提出了一种基于改进YOLO v3算法的安全帽佩戴检测方法。通过采用图像金字塔结构获取不同尺度的特征图，用于位置和类别预测；使用施工现场出入口监控视频作为数据集进行目标框维度聚类，确定目标框参数；在训练迭代过程中改变输入图像的尺寸，增加模型对尺度的适应性。理论分析和实验结果表明，在安全帽佩戴检测任务中，mAP（Mean Average Precision）达到了92.13%，检测速率提高到62?f/s，其检测准确率与检测速率相较于YOLO v3均略有提高，所提算法不仅满足安全帽佩戴检测中检测任务的实时性，同时具有较高的检测准确率。     

The effect of a helmet on cognitive performance is,at worst,marginal: A controlled laboratory study

The present study looked at the effect of a helmet on cognitive performance under demanding conditions, so that small effects would become more detectible. Nineteen participants underwent 30 min of continuous visual vigilance, tracking, and auditory vigilance (VTT + AVT), while seated in a warm environment (27.2 (±0.6) °C, humidity 41 (±1)%, and 0.5 (±0.1) m s⁻¹ wind speed). The participants wore a helmet in one session and no helmet in the other, in random order. Comfort and temperature perception were measured at the end of each session. Helmet-wearing was associated with reduced comfort (p = 0.001) and increased temperature perception (p < 0.001), compared to not wearing a helmet. Just one out of nine cognitive parameters showed a significant effect of helmet-wearing (p = .032), disappearing in a post-hoc comparison. These results resolve previous disparate studies to suggest that, although helmets can be uncomfortable, any effect of wearing a helmet on cognitive performance is at worst marginal.     

基于改进YOLOv5的安全帽佩戴检测算法

针对现有安全帽佩戴检测干扰性强、检测精度低等问题,提出一种基于改进YOLOv5的安全帽检测新算法。首先,针对安全帽尺寸不一的问题,使用K-Means++算法重新设计先验框尺寸并将其匹配到相应的特征层;其次,在特征提取网络中引入多光谱通道注意力模块,使网络能够自主学习每个通道的权重,增强特征间的信息传播,从而加强网络对前景和背景的辨别能力;最后,在训练迭代过程中随机输入不同尺寸的图像,以此增强算法的泛化能力。实验结果表明,在自制安全帽佩戴检测数据集上,所提算法的均值平均精度（mAP）达到96.0%,而对佩戴安全帽的工人的平均精度（AP）达到96.7%,对未佩戴安全帽的工人的AP达到95.2%,相较于YOLOv5算法,该算法对佩戴安全帽的平均检测准确率提升了3.4个百分点,满足施工场景下安全帽佩戴检测的准确率要求。     

针对轻量化网络的安全帽检测方法

变电站内电气设备数量众多,在工人进行现场作业时需要对工人佩戴安全帽进行监测。由于机器学习的安全帽佩戴检测方法常常出现漏检和误检的情况,为提高对安全帽佩戴识别的准确率,同时加快识别速度,提出了一种基于YOLOv5s的轻量化卷积神经网络模型。通过引入RepVGG模块对网络主干进行轻量化,在网络后处理阶段通过Soft-NMS降低遮挡目标漏检率,以Mixup数据增强来扩充数据集,建立样本之间的线性关系,提升训练模型泛化性能,最后进行消融实验。实验结果表明,改进的模型的均值平均精度(mAP)达到80.4%,推理速度达到了83.3 f/s,为变电站安全帽佩戴检测提供了有效参考。     

The effects of helmet design and bowling speed on indices of stress in cricket batting

Abstract

Elite cricketers believe that the use of helmets may help to reduce anxiety when facing fast bowling although they risk visual impairment in time-stressed circumstances. This study aimed to determine the effects of helmet design and bowling speed on heart rate (HR), anxiety arid batting performance.

Elite batsman (n=12) faced 20 deliveries from a bowling machine at slow (21 m s^?1) and fast (42ms^?1 ) speeds under three different headgear conditions— helmet with bars, visorless helmet and no-helmet. State measures of anxiety were taken before and after each batting condition by questionnaire. Heart rate (HR) was monitored throughout the test session. Batting performance was filmed and rated for quality by expert coaches on the basis of bat contact, foot movement, element of attack and timing.

Repeated measures analysis of variance revealed no significant differences in HR or performance between helmet conditions. Batting performance was significantly better against slow bowling than fast (p<0·01) and no significant differences were found for HR between the bowling speeds. No significant correlations were found between HR, performance and state anxiety scores but there was a significant negative relationship between perceived quality of performance and post-batting A-state (r= ?0·62; p<0·05) in the barred helmet condition only.

It is concluded that elite cricketers experienced little change in the level of performance-related anxiety when wearing helmets of varying designs, even when faced with bowling of considerable speed. There was no evidence of performance decrements when wearing helmets with bars and visors which suggests that the use of maximum protection against the possibility of facial damage does not seriously affect the batsman's ability to track and play the ball.     

引入注意力机制的YOLOv5安全帽佩戴检测方法

对于钢铁制造业、煤矿行业及建筑行业等高危行业来说,施工过程中佩戴安全帽是避免受伤的有效途径之一.针对目前安全帽佩戴检测模型在复杂环境下对小目标和密集目标存在误检和漏检等问题,提出一种改进YOLOv5的目标检测方法来对安全帽的佩戴进行检测.在YOLOv5的主干网络中添加坐标注意力机制(coordinate attenti...     

FPN-CenterNet安全帽佩戴检测算法

安全帽作为施工场所工人的安全保障,佩戴与否影响着工人的生命安全。在佩戴检测方面引入深度学习可以高效地提醒工人佩戴安全帽。但由于施工图像中安全帽的图像过小,CenterNet表现得并不好。因此针对这个情况,提出了FPN-CenterNet框架;使用ACNet非对称卷积核来对主干网络的特征提取进行增强;使用DIoU损失函数来优化边框预测的准确度。最终修改的算法相较于原始的CenterNet算法mAP提升了4.99个百分点,在GTX GeForce 1050的GPU上的FPS达到25.81。实验结果表明修改之后的算法在安全帽佩戴检测上有良好的准确性和效率。     

基于YOLOv3的安全帽佩戴检测方法研究

在大型锅炉、钢铁和其他制造业工厂中,正确佩戴安全帽是进入现场的前提.但是在现实场景中,由于各种原因,工人伤亡事故中没有正确佩戴安全帽而导致的事故占比一直较高.为了减少该类事故的发生,对深度学习、人工智能展开了研究,采用了卷积神经网络的方法.首先,对相关数据集标定,将数据集总体分为三种类别,针对标定好的数据,使用迁移学习...     

Component contribution of personal protective equipment to the alleviation of physiological strain in firefighters during work and recovery

The purpose of this study was to investigate the components contributions of personal protective equipment on physiological strain in firefighters during exercise and recovery. Eight firefighters participated in trials in which various combinations of personal protective equipment components weighing from 1.3 to 15.1 kg were worn. The results showed that rectal temperature, changes in rectal temperature, mean skin temperature, heart rate, oxygen consumption and blood lactate concentration were smaller in conditions without boots (no-boots) than in other conditions with no helmet, gloves or self-contained breathing apparatus (P < 0.05). Increases in rectal temperature per unit mass of personal protective equipment were approximately twice as small in no-boots condition as the other conditions. These results suggest that the reduction of the boots' mass might be more efficient to alleviate heat strain of firefighters wearing personal protective equipment, rather than the reduction of the mass of self-contained breathing apparatus, helmet or gloves.     

Sound localisation ability of soldiers wearing infantry ACH and PASGT helmets

Helmets provide soldiers with ballistic and fragmentation protection but impair auditory spatial processing. Missed auditory information can be fatal for a soldier; therefore, helmet design requires compromise between protection and optimal acoustics. Twelve soldiers localised two sound signals presented from six azimuth angles and three levels of elevation presented at two intensity levels and with three background noises. Each participant completed the task while wearing no helmet and with two U.S. Army infantry helmets – the Personnel Armor System for Ground Troops (PASGT) helmet and the Advanced Combat Helmet (ACH). Results showed a significant effect of helmet type on the size of both azimuth and elevation error. The effects of level, background noise, azimuth and elevation were found to be significant. There was no effect of sound signal type. As hypothesised, localisation accuracy was greatest when soldiers did not wear helmet, followed by the ACH. Performance was worst with the PASGT helmet.     

一种上下文信息融合的安全帽识别算法

为了预防人员防护缺失导致的生产事故,着力探究复杂施工场景下人员安全帽佩戴情况的智能化识别。在一阶段目标检测算法的基础上,针对安全帽识别问题中的小目标和安全帽纹理信息缺失的问题,提出提取并融合上下文信息,以增强模型的表征学习能力。首先,为解决特征鉴别力不足的问题,提出局部上下文感知模块和全局上下文融合模块。局部上下文感知模块能够融合人体头部信息和安全帽信息获取具有鉴别力的特征表示;全局上下文融合模块将高层的语义信息与浅层特征融合,提升浅层特征的抽象能力。其次,为了解决小目标识别问题,提出使用多个不同的目标检测模块分别识别不同大小的目标。在构建的复杂施工场景下的安全帽识别数据集上的实验结果表明：提出的2个模块将mAP提高了11.46个百分点,安全帽识别的平均精度提高了10.55个百分点。本文提出的方法具有速度快、精度高的特点,为智慧工地提供了有效的技术解决方案。     

Heart rate strain in cable hauler choker setters in New Zealand logging operations.

This study examined the physical strain experienced by cable hauler choker setters, and the applicability of heart rate indices for measuring physical strain in commercial forest harvesting operations in New Zealand. The heart rate of four choker setters were recorded continuously throughout the working day and applied to heart rate indices. Based on the relative heart rate at work (%HRR), ratio of working heart rate to resting heart rate and 50% level indices, the mean working heart rate (HRw) of 106 bt. min(-1) +/- 6.9 (mean +/- SD) placed choker setting in the moderate workload category. The specific tasks of line shifts (120.3 +/- 4.8 bt. min(-1)), hooking up drags (118.8 +/- 6.6 bt. min(-1)) and uphill travel (126.1 +/- 12.9 bt. min(-1)), imposed the most severe workloads on the choker setters. This research also demonstrated that heart rate indices could be used as an effective means of determining the physiological strain of subjects working in New Zealand's commercial forest harvesting operations.     

改进目标检测算法在变电站内安全管控的应用

变电站作为电力系统中重要一环,保证变电站作业人员的安全是至关重要的。为了自动检测作业人员是否正确穿着工作服佩戴安全帽,提出一种基于Transformer自注意力编码特征融合轻量级的目标检测网络。通过采用轻量级的主干网络提取特征,注意力机制融合多尺度特征。提出了质量焦点损失方法,改善目标检测模型训练和测试阶段推理过程不一致问题。同时,采集并标注变电站场景下人员工作服安全帽数据5?200张。将提出的轻量级目标模型在自制的工作服安全帽数据集上训练,并在测试集上验证,该目标检测方法识别mAP达44.6%,AP50达79.5%,达到117 FPS。