夜视系统鉴别率测试的新方法

用室内低光照高对比鉴别率取代野外探测目标距离作为衡量夜视系统性能优劣的标准,将给验收工作带来方便。本文给出一种实验室内测试夜视系统鉴别率的方法。文中导出了夜视系统鉴别率的一种新的表达式,从而提出了一种改进后的物理模型及其实验方案。分析表明,采用新方案,即在实验室中人为增加环境照度,由此测得的系统工作鉴别率,用以取代野外探测目标距离,其可信度可望得到明显的提高。     

Ergonomic Analysis of Head‐Mounted Night Vision Goggle Systems in Simulated Ground Operations

This study compared the mounting time and strain on the head‐neck while using an old model (forehead and cheek supported) and a new model (head harness supported) of head‐mounted night vision goggle systems in the postures of standing, sitting, and lying prone. The results showed that effectively reducing the mounting time was attributed to the ease and less time required for length adjustments of the head harness in the new model. The novel device received higher positive subjective ratings for convenience and comfort while wearing than did the old model. Although the weight of the new model was decreased to 0.794 kg and the length was reduced to 0.155 m, the loads on the head‐neck complex remained high. These findings suggest that a rifle should be fitted with the night vision goggle or handheld model to decrease neck‐shoulder workload if the prone position is the most frequent and important posture for soldiers. © 2011 Wiley Periodicals, Inc.     

The impact of night work on psychological well-being

This study tested the efficacy of selected personality, behavioural, and social/organizational variables as predictors of adaptation to night work. Sixty female student nurses were studied during their first IS months of shiftwork. Twenty-two worked on rotating day and afternoon shifts throughout, while the remaining 38 began regular night shifts after six months. Psychological symptoms were measured at baseline (Stage 1), six months (Stage 2) and 15 months (Stage 3). Repeated measures analysis of variance revealed a significant shift group x symptoms interaction (p < 0·05) between Stages 2 and 3. Only the night workers displayed a significant increase (Tukey HSD: p < 0·01) in symptoms between Stages 1 and 3. Multiple regression analysis revealed that neuroticism and perceived work/nonwork conflict predicted symptoms at Stage 2. Night work, social support from supervisors, and morningness were predictors at Stage 3. These results suggest that organisational, behavioural, and physiological factors moderate the impact of night work on psychological well-being, and personality factors do not.     

Adaptation of performance during a week of simulated night work

This study aimed to provide a comparative index of the performance impairment associated with the fatigue levels frequently experienced in workplaces that require night work. To do this, we equated fatigue-related impairment with the impairment resulting from varying levels of alcohol intoxication. Fifteen young individuals participated in two counterbalanced conditions which required them to (1) ‘work’ seven consecutive 8-h night shifts, and (2) consume an alcoholic beverage at hourly intervals until their blood alcohol concentration (BAC) reached 0.10%. In each condition, performance was measured at hourly intervals using a 10-min psychomotor vigilance task (PVT). Analysis indicated that as BAC increased, performance impairment significantly increased. Similarly, response times significantly increased during the first six simulated night-shifts, and lapse frequency significantly increased during the first two shifts. Equating the two conditions indicated that the first simulated night shift was associated with the greatest degree of performance impairment. In general, the impairment at the end of this shift was greater than that observed at a BAC of 0.10%. During the second and third simulated night shifts, the performance impairment was less than on the first night, but greater than that observed at a BAC of 0.05%. For the final four nights, the performance decrements generally did not exceed those observed at a BAC of 0.05%. This suggests that during a week of consecutive night shifts, adaptation of performance occurs.     

Impact of passive cooling techniques on energy demand for residential buildings in a Mediterranean climate

This study presents the thermal analysis of a building prototype, which was designed and built in accordance with energy efficiency measures to improve indoor thermal comfort, particularly in summer. The building prototype is located in Souidania (20 km southwest of Algiers, latitude 36°7N, Longitude 03°2E). The location is characterized by a temperate Mediterranean climate. In order to perform this analysis, various activities are carried out: a series of monitoring campaigns; dynamic simulations with TRNSYS software, calibration of the model with experimental data and comparative study with buildings that use different wall constructions. Based on a validated building thermal model, dynamic analysis is carried out in order to evaluate the impact of thermal mass and of eaves and night ventilation. The results demonstrate that cooling energy demand is more affected by thermal transmittance values than by the envelope thermal mass. A recommended guideline for the optimum overhang length for south-facing windows is proposed. Ultimately, it is found that the combination of both natural ventilation and horizontal shading devices improves thermal comfort for occupants and significantly reduces cooling energy demand.     

A comparison of circadian rhythms in work performance between physically active and inactive subjects

This study compared circadian rhythms in physiological, subjective, and performance measures between groups exhibiting different levels of habitual physical activity. Fourteen male subjects, aged 19–29 years, were assigned to a physically active (group I, n=7) or a physically inactive (group II,n= 7) group on the basis of leisure–time physical activity. Rectal temperature, oral temperature, resting pulse rate, subjective arousal and sleepiness were measured at 02:00,06:00, 10:00, 14:00, 18:00 and 22:00 in a counter–balanced sequence for each subject. Whole–body flexibility, back and leg strength, grip strength (right and left), flight time in a vertical jump, PWC₁₅₀ and self–chosen work–rate were also recorded at each time point. At least 8h separated each test session. Subjects avoided exercise 48h prior to, and during the experiment. Data were subjected to the group cosinor method. Group I evidenced 1·5–2·5 times greater rhythm amplitudes than Group II for oral temperature, subjective arousal, sleepiness, flexibility, left and right grip strength, submaximal heart rate, and self–chosen work–rate (p<0·05). Oral temperature and arousal for Group I were lower than Group II only at 06:00. Early morning troughs in most of the performance measures were significantly greater for Group I (p<005). The groups did not differ with respect to phasing of the rhythms (p<005). These results confirm with physical performance measures that rhythm amplitudes are higher for physically fit subjects. This could be attributed to greater early–morning troughs in the measures for active individuals. Since the subjects were sedentary immediately prior to testing, it is plausible that these findings are training effects of physical activity.     

断夜处理天数对延迟甘蔗开花的影响

对早花甘蔗亲本进行同一光照强度不同持续天数的断夜处理,研究断夜天数对甘蔗开花的影响和不同品系对断夜天数反应的差异.参试品种在8月下旬至9月中旬间断夜15天和26天处理的开花高峰期分别比自然光照处理的延迟20天和30天左右,增加断夜天数对推迟甘蔗始花期和降低抽穗率有明显的影响,但不同品系对断夜天数的反应,特别是在开花持续期和终花期方面,存在较大的差异.在实际应用中,宜根据不同品系的特性确定适宜的断夜处理天数.     

广州地区室内氡、(气土)浓度随季节及昼夜变化规律的探讨

本文报道1984年7月至1985年6月间在本院实验室内测定的氡、(气土)浓度随季节和昼夜变化的情况。结果表明氡浓度的昼夜变化为早晨6—7时较高,下午1—3时较低,最高与最低值之比达3—4倍,接近日平均水平的时间为上午8—11时;氡、(气土)浓度随季节的变化规律相似,都是冬季(1—3月)较高,夏季(6—9月)较低,氡、(气土)月平均浓度的最高和最低值之比,分别为7.0和5.0倍,春(4—5月)、秋季(10—12月)的氡,(气土)浓度都分别与其年平均水平接近。     

Eyepiece focus and vergence/accommodation conflict: Implications for night‐vision devices

Abstract— Aviation increasingly conducts night operations using night‐vision devices. However, design of some aspects may limit performance. As pointed out by Kotulak, vergence/accommodation mismatch in NVDs, usually due to eyepiece focus misadjustments, is sometimes a source of visual acuity (VA) decrement. The increased separation between sensors, existing in some binocular helmetmounted displays, was also identified to be potentially responsible for decreased VA at short distances. Based upon knowledge pertaining to vergence and accommodation, a study was performed to better understand the problem of dissociation accommodation/convergence. Different conditions of interocular separation and viewing distances were used. Twelve subjects participated and were asked to resolve Landolt C charts using night‐vision goggles. The results show that, with the eyepiece focus fixed at 10 m, the decrease in VA is roughly proportional to the interocular separation, when looking at short distances. A fixed eyepiece focus at 4 m considerably reduces the conflict and results in improved VA. An additional experiment was conducted to investigate the effect of fixing the objective lenses focus at infinity. With this setting, the decrease in VA at a short distance was such that effects of the mismatch accommodation/convergence are no longer apparent regardless of the interocular separation.     

Performance of a heat pipe assisted night sky radiative cooler

A passive radiative cooling system was designed, constructed and tested under clear skies. This refrigerator operates by losing heat to the night sky through infrared (i.r.) radiation emission. It consists of a radiator, an array of heat pipe elements and a cold chamber. The heat pipe elements are so arranged that they act as thermal diodes, transferring heat from the cold chamber to the radiator. Performance tests show that the system has a cooling capacity of 628 kJ/m² per night with a sky coefficient of performance of 0.26. The lowest temperature attained in the cold chamber was 12.8°C for an ambient temperature of 20°C. The overall results indicate that the system has a great potential for providing a cold storage facility in developing countries and in remote areas.