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。     

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。     

Improving fit of bicycle helmet liners using 3D anthropometric data

3D anthropometry has provided much-needed information about the size and shape of the head, which can be used to improve the fit of protective helmets. In this study, a new 3D head scan sizing method was implemented in a reverse engineering approach for bicycle helmet liner dimensioning. The inside liner of a commercially available helmet was modified to improve the fit for a selected size group of 30 participants. The fit of the standard and new liner were assessed and compared, using the Helmet Fit Index (HFI). The HFI scores showed a significant improvement of overall fit (Difference: 11.32 ± 7.82 (μ ± SD), p < 0.0005) and for each of five defined regions of the liner inside surface. The presented methodology for dimensioning helmet liners based on 3D anthropometry proved effective, resulting in improved fit for the end users.     

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.     

Binaural helmet: improving speech recognition in noise with spatialized sound

This study assessed the effects of spatialized sound presentation on a listener's ability to monitor target (T) messages in the presence of competing (C) messages and high-level (110 dB[A]) background noise (BGN). In a simulated military environment, 8 participants wore two-channel, active noise reduction (ANR) equipped helmets and listened to combinations of T and C messages (89 dB[A] at the ear). T messages were presented synchronously with 0, 1, 2, and 3 C messages in four listening modes: (a) BGN + diotic, (b) BGN + dichotic, (c) BGN + spatial audio, and (d) quiet + spatial audio. Best overall performance occurred in the spatialized modes (c and d) and poorest in the diotic mode (a). As expected, speech recognition was better in quiet than in BGN when multiple C messages were present. Findings indicate that message spatialization in acoustic space improves auditory performance during times of heavy message competition, even in high-level noise. The proposed technology has numerous applications, such as multichannel communications in tactical operations centers, monitoring of complex security systems, and air traffic control.     

Shortcomings and user requirements associated with cricket helmets currently in use: A study on features for safety and usability

Wearing helmets has reduced the risk of head and facial injury among cricketers. Yet, design gaps are present in the cricket helmets currently being used. The aim of this research was to identify the shortcomings and user requirements pertinent to safety and usability of cricket helmets. The objectives were to explore the design criteria and the drawbacks of state-of-the-art cricket helmets, to identify user requirements for design and to analyse them. To collect data, a three-faceted approach, i.e. a literature review (n = 58), a video-based accident analysis (n = 24) and a user study (n = 42), was used. A frequency analysis technique based on the constant comparative method was used to identify and prioritize the shortcomings and user requirements. Findings from the three approaches were then triangulated to confirm the shortcomings and user requirements. Results revealed that poor fit, inadequate impact attenuation capacity and thermal discomfort are the main categories of shortcomings in the cricket helmets. Research on multi-objective optimisation of features for better fit, impact attenuation and thermal comfort (FIT) is suggested as future work.     

The effect of an optimised helmet fit on neck load and neck pain during military helicopter flights

The main purpose of this study was to improve the helmet fit of military helicopter aircrew members and evaluate its effect on the experienced helmet stability (helmet gliding), neck load, neck pain, hot spots (pressure points), irritation/distraction, and overall helmet comfort during night flights. A within-subject design was used over a three-month period that consisted of two consecutive interventions of optimising the fit of the aircrew's helmets: 1) a new helmet fit using a renewed protocol and 2) replacement of a thermoplastic inner liner with a viscoelastic foam inner liner. A total of 18 pilots and loadmasters rated the outcome measures using the Visual Analogue Scales immediately after their night flights, for three night flights in total per measurement period. The optimised helmet fit resulted in a significant decrease in the experienced helmet gliding, neck load and pressure points, a decrease trend in the experienced neck pain and irritation/distraction, and a significant increase in the experienced overall helmet comfort during flight. These results demonstrate the importance of achieving an optimised helmet fit for military helicopter aircrew and that an optimised helmet fit might have implications for both health and safety concerns.     

Evaporative heat transfer characteristics of industrial safety helmets

Thermal discomfort is one of the major complaints from the wearers of industrial safety helmets. While studies have been reported on dry heat transfer (conduction, convection and radiation) in safety helmets, the investigation of wet heat dissipating (evaporation) properties has not been found in the literature. To evaluate experimentally the evaporative heat transfer characteristics of industrial safety helmets, a method was developed to simulate sweating of a human head on a thermal head manikin, and to use this manikin to assess the wet heat transfer of five industrial safety helmets. A thermal head manikin was covered with a form-fitting cotton stocking to simulate 'skin'. The skin was wetted with distilled water to simulate 'sweating'. A form-fitting perforated polyethylene film was used to cover the wetted stocking to control the skin wettedness at two levels, 0.64 and 1.0. Experiments were conducted in a climatic chamber, under the following conditions: the ambient temperature = head manikin surface temperature = 34 +/- 0.5 degrees C; ambient relative humidity 30% and 60%. Also, the effects of wind and a simulated solar heat load were investigated. The five helmets showed statistically significant difference in evaporative heat transfer under the experimental conditions. Skin wettedness, ambient humidity, wind and solar heat showed significant effects on evaporative heat transfer. These effects were different for the different helmets.     

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.     

融合环境特征与改进YOLOv4的安全帽佩戴检测

目的 在施工现场，安全帽是最为常见和实用的个人防护用具，能够有效防止和减轻意外带来的头部伤害。但在施工现场的安全帽佩戴检测任务中，经常出现难以检测到小目标，或因为复杂多变的环境因素导致检测准确率降低等情况。针对这些问题，提出一种融合环境特征与改进YOLOv4（you only look once version 4）的安全帽佩戴检测方法。方法 为补充卷积池化等过程中丢失的特征，在保证YOLOv4得到的3种不同大小的输出特征图与原图经过特征提取得到的特征图感受野一致的情况下，将两者相加，融合高低层特征，捕捉更多细节信息；对融合后的特征图采用3×3卷积操作，以减小特征图融合后的混叠效应，保证特征稳定性；为适应施工现场的各种环境，利用多种数据增强方式进行环境模拟，并采用对抗训练方法增强模型的泛化能力和鲁棒性。结果 提出的改进YOLOv4方法在开源安全帽佩戴检测数据集（safety helmet wearing dataset，SHWD）上进行测试，平均精度均值（mean average precision，mAP）达到91.55%，较当前流行的几种目标检测算法性能有所提升，其中相比于YOLOv4，mAP提高了5.2%。此外，改进YOLOv4方法在融合环境特征进行数据增强后，mAP提高了4.27%，在各种真实环境条件下进行测试时都有较稳定的表现。结论 提出的融合环境特征与改进YOLOv4的安全帽佩戴检测方法，以改进模型和数据增强的方式提升模型准确率、泛化能力和鲁棒性，为安全帽佩戴检测提供了有效保障。     

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MobileNet-SSD的安全帽佩戴检测算法

针对真实场景下安全帽佩戴检测面临的背景复杂、干扰性强、待检测目标较小等问题,在SSD算法的基础上,提出改进的MobileNet-SSD算法。通过引入轻量型网络MobileNet并构建MobileNet-SSD算法提高检测速度,采用迁移学习策略克服模型训练困难问题。从施工相关视频中获取真实环境下的安全帽样本构建样本集,以解决当前安全帽数据集规模较小、网络难以充分拟合特征的问题。实验结果表明,MobileNet-SSD算法在损失很小精度的情况下,相较于SSD算法,检测速度提高了10.2倍。     

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...     

Integrated range comparison for data-parallel compilation systems

A major difficulty in restructuring compilation, and in parallel programming in general, is how to compare parallel performance over a range of system and problem sizes. Execution time varies with system and problem size and an initially fast implementation may become slow when system and problem size scale up. This paper introduces the concept of range comparison. Unlike conventional execution time comparison in which performance is compared for a particular system and problem size, range comparison compares the performance of programs over a range of ensemble and problem sizes via scalability and performance crossing point analysis. A novel algorithm is developed to predict the crossing point automatically. The correctness of the algorithm is proven and a methodology is developed to integrate range comparison into restructuring compilations for data-parallel programming. A preliminary prototype of the methodology is implemented and tested under Vienna Fortran Compilation System. Experimental results demonstrate that range comparison is feasible and effective. It is an important asset for program evaluation, restructuring compilation, and parallel programming     

Evaluation of thermal and evaporative resistances in cricket helmets using a sweating manikin

The main objective of this study is to establish an approach for measuring the dry and evaporative heat dissipation cricket helmets. A range of cricket helmets has been tested using a sweating manikin within a controlled climatic chamber. The thermal manikin experiments were conducted in two stages, namely the (i) dry test and (ii) wet test. The ambient air temperature for the dry tests was controlled to ∼23 °C, and the mean skin temperatures averaged ∼35 °C. The thermal insulation value measured for the manikin with helmet ensemble ranged from 1.0 to 1.2 clo. The results showed that among the five cricket helmets, the Masuri helmet offered slightly more thermal insulation while the Elite helmet offered the least. However, under the dry laboratory conditions and with minimal air movement (air velocity = 0.08 ± 0.01 ms⁻¹), small differences exist between the thermal resistance values for the tested helmets. The wet tests were conducted in an isothermal condition, with an ambient and skin mean temperatures averaged ∼35 °C, the evaporative resistance, R_et, varied between 36 and 60 m² Pa W⁻¹. These large variations in evaporative heat dissipation values are due to the presence of a thick layer of comfort lining in certain helmet designs. This finding suggests that the type and design of padding may influence the rate of evaporative heat dissipation from the head and face; hence the type of material and thickness of the padding is critical for the effectiveness of evaporative heat loss and comfort of the wearer. Issues for further investigations in field trials are discussed.     

The elastic stability of square perforated plates

A direct matrix method of analysis for the buckling loads on structures, which had already been proven on various structural forms, is applied to the examination of the stability of flat square plates with central square perforations. The results for a variety of boundary conditions are presented for a range of hole to plate size from 0 to 0.8. The method generally shows trends which are different to those predicted by other numerical methods, particularly over the range of the larger hole sizes. Possible reasons for these differences are suggested, but further work to obtain definitive results is clearly needed by all investigators.     

Modal Locomotion: Animating Virtual Characters with Natural Vibrations

We present a general method to intuitively create a wide range of locomotion controllers for 3D legged characters. The key of our approach is the assumption that efficient locomotion can exploit the natural vibration modes of the body, where these modes are related to morphological parameters such as the shape, size, mass, and joint stiffness. The vibration modes are computed for a mechanical model of any 3D character with rigid bones, elastic joints, and additional constraints as desired. A small number of vibration modes can be selected with respect to their relevance to locomotion patterns and combined into a compact controller driven by very few parameters. We show that these controllers can be used in dynamic simulations of simple creatures, and for kinematic animations of more complex creatures of a variety of shapes and sizes.     

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.     

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 degrees C, 80% rh) and physiological work loads (40% VO(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.     

Queueing analysis of manufacturing systems with set ups

A manufacturing system with one server (machine), two classes of jobs, finite buffer sizes, and non-negligible set-up times is analysed. A cycling service discipline with a ’wait and see‘ set-up policy is invoked by the server. The state of the machine, whether in set up or in processing, is explicitly considered in the model. Utilization, mean queue length, and cycle time are derived using markovian analysis, first under a fixed lot size environment and then with random lot sizes. With lot sizes fixed, increasing arrival rates, set-up times, and service times generally increase the utilization, cycle time, and queue lengths. When lot sizes are random, there are negligible variations in the cycle time result, with somewhat smaller queue lengths compared to the fixed lot size case. An approximate mean value analysis is also developed and results are compared to those of the markovian analysis. Numerical studies show the robustness of the mean value analysis for most of the system parameters tested.