Postural and Muscular Responses While Viewing Different Heights of Screen

This study aimed to examine the effects of visual display terminal (VDT) viewing angle on human postural angle and muscular activity. The participants’ neck, thoracic bending, and trunk inclination angles; and the activity of sternocleidomastoid, trapezius, splenius capitis, and erector spinae at 5 viewing angles (+40°, +20°,0°, –20°, and –40°) of a VDT screen were collected for 1 min. This study showed that neck and thoracic bending angles increased with viewing angle, while viewing angle did not significantly affect trunk inclination angle. In addition, the activity of trapezius and erector spinae increased when viewing a higher or lower VDT screen height compared with viewing a horizontal VDT screen height; however, the activity of splenius capitis decreased with viewing angle.     

Isometric Pull and Push Strengths of Paraplegics in the Workspace: 2. Statistical Analysis of Spatial Factors

The effect of reach levels, horizontal angles, and vertical angles on isometric pull and push strengths of male and female was determined. Highly significant increases in men’s push strength were found between extreme to maximum reaches, and from extreme to normal reaches. However, for women’s push strength, a significant increase was found only between extreme to maximum reach. Significant or highly significant increases were found in men’s and women’s pull strength between the horizontal angle (θ) sagittal through the active shoulder (90°) and other angles (0, 45, and 135°). However, for men’s push strength, highly significant increases were found between the horizontal angle 45° from the frontal plane, and other angles. For women’s push strength, significant or highly significant increases were found between the horizontal angles 0° and angles of 90 and 135°. For men’s and women’s pull strength, significant or highly significant increases were found between the vertical angle (?), 90°, and other angles (–20, 0, and 45°). Similar increases were found for women’s push strength between the 45° angle and other angles. In the design of a workstation for paraplegics that requires pull and push forces, consideration must be given to the spatial factors.     

Flame acceleration in pipes containing bends of different angles

Bend structures are common in process industries. These bends containing three typical angles (90°, obtuse angle and acute angle) are often incorporated into pipes or ducts at different positions. In our experiments, the effect of both the bend angle and bend position on flame acceleration was studied. Flame acceleration in a pipe bend can be divided into three stages. The flame speeds increased before the bend and increased again after decreasing for a short distance in the bend. Flame reversing decreased the flame speeds in the bend and led to additional turbulence, which enhanced flame acceleration after the bend. The flame acceleration in three different pipe bend angles had similar trends. The decreasing amplitude of the flame speed in the bend increased with a decrease in the bend angles. The flame speeds in the bend were ordered such that 52° <90° <145°. However, the maximum flame speeds in the pipe were in the opposite order. Additionally, both the flame speeds in the bends and the maximum flame speeds in the whole pipes increased as the bend’s position away from ignition point increased.     

Response of the buried steel pipeline caused by perilous rock impact: Parametric study

One of threatening buried steel pipeline in bad geological regions is collapsed rock. Buckling behavior of a buried pipeline impacted by a perilous rock with spherical shape was investigated by numerical simulation. Effects of pipeline parameters (internal pressure, wall thickness, diameter, buried depth) and perilous rock parameters (impact velocity, radius, eccentric distance) on deformation, stress and strain of the buried pipeline were discussed. Buckling behaviors of the buried pipeline under transverse and longitudinal inclined impacts also were studied. The results show that cross section shape of the buried pipeline becomes to an oval, then to a peach shape, and finally to a crescent shape or gourd shape in the process of rock’s impact. The deformation process of a buried pipeline can be divided into four stages. They are elastic deformation stage, buckling stage, elastic recovery stage and final deformation stage. Buckling mode of no-pressure pipeline is more serious than the pressure pipeline. The impact dent’s length and depth increase with the decreasing of buried depth, wall thickness and internal pressure. But they increase with the increasing of impact velocity, perilous rock’s radius and pipeline’s diameter. The maximum stress and plastic strain decrease with the increasing of buried depth and wall thickness. Under rock’s eccentric impact, impact dent trends to one side. Stress and plastic deformation decrease with the eccentric distance increases. Under rock’s transverse and longitudinal inclined impacts, cross section shape of the buried pipeline is an oval shape when the incidence angle α ≤ 45°, and there is no plastic deformation. When α > 45°, impact dent appears. Buckling is more serious with the incidence angle increases. Destructive powers of transverse and longitudinal inclined impacts are smaller than the vertical impact.     

上、下悬窗阻风能力对比研究

环境风会改变排烟窗附近的烟气流向和速度,影响建筑内烟气流动,进而导致建筑自然排烟效率受到影响。采用数值模拟方法,对比研究了排烟窗开启角度和环境风对上、下悬窗阻风能力的影响,分析了不同开窗角度下,悬窗进风量和进风区域随开窗角度和风速的变化规律。结果表明:上、下悬窗相对进风量与开窗角度均成指数关系,但上悬窗阻风能力弱于下悬窗,上悬窗开窗角度大于45°后即失去阻风能力,而下悬窗开窗角度大于75°后才逐渐失去阻风能力,且开窗角度小于30°时,下悬窗至少能比上悬窗多减少50%空气进入室内。上悬窗开窗角度小于56°时,主要进风区域为近窗下侧水平区域;下悬窗开窗角度小于30°时,主要进风区域为窗体两侧及远窗下侧竖直区域,随着开窗角度增大,上、下悬窗主要进风区域均过渡到远窗下侧竖直区域。窗体用于日常通风时建议优选上悬窗。若要用于排烟,则应首选下悬窗,开窗角度15°即可满足阻风要求,若选用上悬窗,开窗角度不宜大于45°。     

Friction measurements on ramps using the Brungraber Mark II slipmeter

It is a common belief that a person is more likely to slip when walking on an inclined surface than when walking on a level surface. Reports of friction measurements were common on horizontal surfaces but were rare on inclined surfaces. A slip measurement device reports different readings on the same surface with different inclined angles if the effect of gravity comes into play. In this study, friction measurements were conducted on the same surface with 0°, 10° and 20° inclined angles under different footwear materials, floors, and surface conditions, using a Brungraber Mark II slipmeter. Statistically significant results were obtained for the measurement results under the inclined angle, footwear material, floor, and surface conditions. A regression model was established to describe the coefficients of friction on ramp floors under footwear material/floor/surface conditions. This model is significant at p < 0.0001 with an R² of 0.87. The cosine function of ramp angle, as suggested in the regression model, was recommended to be used as a correcting factor for friction measurement results using the Brungraber Mark II on ramps to report the corrected friction coefficient of the surfaces.     

AEB effectiveness evaluation based on car-to-cyclist accident reconstructions using video of drive recorder

Objective: Though autonomous emergency braking (AEB) systems for car-to-cyclist collisions have been under development, an estimate of the benefit of AEB systems based on an analysis of accident data is needed for further enhancing their development. Compared to the data available from in-depth accident data files, data provided by drive recorders can be used to reconstruct car-to-cyclist collisions with greater accuracy because the position of cyclists can be observed from the videos. In this study, using data from drive recorders, the performance and limitations of AEB systems were investigated.

Method: Data of drive recorders involving taxi-to-cyclist collisions were collected. Using the images collected from the drive recorders of those taxis, 40 cases of 90° car-to-cyclist intersection collisions were reconstructed using PC-Crash. Then, the collisions were reconstructed again utilizing car models with AEB systems installed while changing the sensor’s field of view (FOV) and the delay time of initiating vehicle deceleration.

Results: The angle of FOV has a significant influence on avoiding car-to-cyclist collisions. Using a 50° FOV with a braking delay time of 0.5?s resulted in avoiding 6 collisions, and using a 90° FOV resulted in avoiding an additional 14 collisions. Even when installing an ideal AEB system providing 360° FOV and no delay time for braking, 8 collisions were not avoided, though the impact velocities were reduced for all of these remaining collisions. These collisions were caused by the cyclists’ sudden appearance in front of cars, and the time-to-collision (TTC) when the cyclists appeared was less than 0.9?s.

Conclusion: The AEB systems were effective for mitigating collisions that occurred due to driver perception delay. Because cyclists have a traveling velocity, a wide-angle FOV is effective for reduction of car-to-cyclist intersection collisions. The reduction of delay time in braking can reduce the number of collisions that are close to the braking performance limit. The collisions that remained even with an ideal AEB system in the PC-Crash simulation indicate that such collisions could still occur for autonomous cars if the traffic environment does not change.     

Presence of scapular dysfunction in dominant shoulder of professional guitar players

Background. Playing guitar can cause adoption of asymmetric postures and affect the shoulder's stability. Objective. To assess the presence of scapular dysfunction in professional guitar players. Method. A lateral scapular slide test was performed at the level of the spine of the scapula and at the inferior angle of the scapula in 20 professional guitar players (age: 18–40 years) and was compared with 20 age-matched non-players at angles of 0°, 45° and 90° of shoulder abduction with both limbs loaded with 0.5-kg weights. Analysis was done by unpaired t test. Results. Scapular dysfunction in guitar players was seen in the form of asymmetric scapula at rest in 25% and dyskinetic scapula in 20% of players. 100% of non-players had normal scapular positioning. Comparison at the level of the spine of the scapula showed no significant difference (p?>?0.05), but the inferior angle showed a significant difference at 0° (1.37?cm), 45° (1.93?cm) and 90° (2.15?cm) which was more in the player's category (p?Conclusion. There exists a marked dysfunction of scapular stabilizers in professional guitar players at the level of the inferior angle of the scapula.     

A new method for calculating saddle seat height with an emphasis on optimal posture based on trigonometric relations

Introduction. Based on the literature, the ergonomic saddle chair provides the most appropriate posture for users. Determination of the seat height is critical to establish the proper posture, carried out using various methods of anthropometry. This study aimed to develop a simple and applied method for determining the saddle seat height with an emphasis on appropriate posture. Methods. In this study, anthropometric dimensions including weight, body height, popliteal height and seat height at 135° knee angle in 150 male and female dentists were measured. In the laboratory, to determine the ‘acetabuloischial number’, 25 male and female natural hip bones were measured. The mean saddle-chair height with knee angle of 135° was then compared by two different methods, field measurement and the new calculation method. Results. The results showed a strong correlation between data gathered from the two different methods, the field measurement and the new calculation method (98%), and Cronbach’s α from the intraclass correlation was equal to 0.994 (p?<?0.05). This indicated that the two methods produced similar results. Conclusion. The new method can be applied to calculate the optimal height of the saddle seat based on body height and popliteal height.     

Readability of Characters on Mobile Phone Liquid Crystal Displays

Subject performance in reading characters on mobile phone liquid crystal displays was researched by using (a) English sentences with 3 or 4 different sizes of characters on 2 types of displays with different resolutions(n = 23; age = 31.0 ± 6.0 years), (b) Japanese characters in 3 different sizes and 2 types of font (n = 98; age = 44.5 ± 18.5 years), and (c) Japanese characters vertically enlarged 1—4 times (n = 120; age = 46.9 ± 18.6 years). Subjective evaluation, reading speed, number of reading errors, and viewing distance were recorded. Readability was higher with higher resolution displays, and with Gothic than with Mincho font in Japanese. Young subjects shortened the viewing distance as characters became smaller, whereas elderly subjects increased the viewing distance irrespective of the size of characters. Characters of 3–5 mm are appropriate for the young but inadequate for the elderly. Readability of Japanese characters improved when they were vertically enlarged to approximately twice the width.     

A Study of Computer-Based Task Performance Under Thermal Stress

A visual-visual dual computer task was designed to test the effect of the thermal environment on dual task performance. The temperatures selected for testing were 20 and 35 °C Wet Bulb Globe Temperature (WBGT). 34 volunteers were randomly assigned to 1 of the 2 temperature conditions. Individual differences in single task performance were controlled by equating the baselines of single task performance. Once individual differences in single task capacity were controlled, statistically significant differences in performance were demonstrated. Mean accuracy was computed over a 1-hr testing period in each temperature condition. Participants’ mean accuracy in the 35° condition (38.18%) was substantially lower than in the 20° condition (50.88%).     

锂离子电池电解液火灾的烟雾探测方法研究

基于散射不对称比的气溶胶识别方法,采用单个入射波长和两个散射角的方式测定了电解液火灾、正庚烷火、棉绳阴燃三种火灾烟雾和D90粉尘的前后向散射不对称比.结果表明,在红外L ED光源作用下,前向散射角为45°和后向散射角为135°时,不同类型气溶胶的散射不对称比的均值和变化率存在差异,这可以用于区分火灾烟雾和干扰气溶胶.此...     

Influence of an oblique path of staircase descent on toe placement and foot clearance

During their commute, pedestrians encounter a variety of staircase designs. One such design is the oblique staircase that allows pedestrians to descend at an angle. The purpose of this study was to assess the influence of an oblique path of descent on heel and toe clearance, and toe placement on a step. Sixteen participants descended a staircase on an angled path at three angles: 0° (perpendicular), 25°, and 45°. Toe placement and foot clearances were compared between the descent angles and feet. An increase in descent angle demonstrated increased clearance of the heel apex compared with straight descent; however, the aspect of the foot closest to the stair changes in angled descent, moving from the apex to the side of the heel. A greater portion of the foot was placed on the stair tread during angled descent. Future work should address the influence of angled descent on fall risk.     

Survey of discomfort glare from the headlamps of cars widely used in Iran

Objective: On 2-lane roads, discomfort glare can cause annoyance, discomfort, inconvenience, stress, and fatigue to drivers, posing a risk of accidents. The aim of this study is to evaluate discomfort glare from the headlamps of cars widely used in Iran.

Methods: The discomfort glare of new vehicles including Pride Saba model GTX, Pride Model 131SL, Samand Soren, Peugeot 405, Megane, and Peugeot Pars was examined at distances of 5 to 100 m at a background luminance of 50 cd/m² (late twilight/early dawn lighting) and 1 cd/m² (nighttime) using Schmidt-Clausen and Bindels model and de Boer's subjective scale.

Results: According to the de Boer scale, at a background luminance of 50 cd/m², the discomfort glare for all studied vehicles was between 1.98 and 4.05 in high-beam mode and between 3.5 and 5.4 in low-beam mode. At a background luminance of 1 cd/m², discomfort glare was between 0.41 and 2.48 in high-beam mode and between 1.93 and 3.84 in low-beam mode. In high-beam mode, the average levels of discomfort glare of these vehicles gradually increased when the distance between cars was reduced by up to about 20 m. In low-beam mode, there was no discomfort glare up to a vehicle distance of 40 m. In addition, at an angle of 1.15°–5.73° between the line of sight and light of vehicles in high-beam mode, the level of discomfort glare was increased, but at an angle of 5.73°–22.9° the level of discomfort glare was reduced. In low-beam mode at an angle of 2.86°–22.9°, the level of discomfort glare was almost identical. The results show that in high-beam mode and with a 100-m distance between vehicles as well as in low-beam mode at intervals of less than 40 m between cars, discomfort glare is created.

Conclusion: It can be concluded that by providing solutions such as installing road lighting system, an increase in luminance of roads, separating or widening road lanes, increasing the lateral distance between vehicles, and increasing the angle between lighted vehicles and drivers can noticeably reduce discomfort glare.     

顺层或逆层岩质急倾斜边坡坡角的确定

为了解当岩体具有急倾斜构造和水平裂隙发育时,由该岩体形成顺层和逆层边坡情况下,不同坡角对该边坡稳定性的影响,使用基于颗粒流理论的PFC3D进行了模拟。利用PFC3D中的JSET和Bonds模拟了非连续性和连续性的岩体构造形式。构建了坡角为40°、50°、60°、70°和80°的顺层和逆层边坡,并对边坡稳定性进行了模拟。模拟结果表明,岩层的重力作用在逆层时有利于岩体外倾,顺层时抑制外倾。相同坡角时顺层较逆层更为稳定。大变形裂隙区的出现位置与岩体构造有很大关系。提出的修建边坡坡角建议为顺层时坡角不应大于60°,逆层时坡角不应大于50°。     

Explosion parameters of wood chip-derived syngas in air

The wood gasification process poses serious concerns about the risk of explosion. The design of prevention and mitigation measures requires the knowledge of safety parameters, such as the maximum explosion pressure, the maximum rate of pressure rise and the gas deflagration index, K_G, at standard ambient temperature (25 °C) and pressure (1 bar) conditions. However, the analysis at specific process conditions is strongly recommended, as the explosion behavior of gas mixtures may be completely different.In the work presented in this paper, the explosion behavior of mixtures with composition representative of wood chip-derived syngas (CO/H₂/CH₄/CO₂/N₂ mixtures with and without H₂O) was experimentally studied in a closed combustion chamber. Experiments were run at two temperatures, 300 °C and 10 °C, and at atmospheric pressure. Test conditions were requested by the safety engineering designer of an existing industrial-scale wood gasification plant. In order to identify the specific fuel–air ratios to be analyzed, thus reducing the number of experimental tests, a preliminary thermo-kinetic study was performed.Results have shown that the mixtures investigated can be classified as low-reactivity mixtures, the higher value of K_G found (∼36 bar m/s) being much lower than the K_G value of methane (55 bar m/s @ 25 °C).     

Influence of Seat Properties on Occupant Dynamics in Severe Rear Crashes

Seat performance in retaining an occupant, transferring energy, and controlling neck responses is often questioned after severe rear crashes when fatal or disabling injury occur. It is argued that a stiffer seat would have improved occupant kinematics. However, there are many factors in occupant interactions with the seat. This study evaluates four different seat types in 26 and 32 mph (42 and 51 km/h), rear crash delta Vs. Two seats were yielding with k = 20 kN/m occupant load per displacement. One represented a 1970s yielding seat with j = 3.4°/kN frame rotation per occupant load, and 3 kN maximum load (660 Nm moment), and the other a high retention seat phased into production since 1997 with j = 1.4°/kN, and 10 kN maximum load (2200 Nm). Two seats were stiff with k = 40 kN/m. One represented a 1990s foreign benchmark with j = 1.8°/kN and a 7.7 kN maximum load (1700 Nm), and the other an all belts to seat (ABTS) with j = 1.0°/kN and 20 kN maximum load (4400 Nm). The crash was a constant acceleration of 11.8 g, or 14.5 g for 100 ms. Occupant interactions with the seat were modeled using a torso mass, flexible neck and head mass. By analysis of the equations of motion, the initial change in seatback angle (Δθ) is proportional to jk(y ? x), the product jk and the differential motion between the vehicle (seat cushion) and occupant. The transition from 1970s–80s yielding seats to stronger seats of the 1990s involved an increase in k stiffness; however, the jk property did not change as frame structures became stronger. The yielding seats of the 1970s had jk = 68°/m, while the stiff foreign benchmark seat had jk = 72°/m. The foreign benchmark rotated about the same as the 1970s seat up to 50 ms in the severe rear crashes. While it was substantially stronger, it produced higher loads on the occupant, and the higher loads increased seatback rotations and neck responses. The ABTS seat had the lowest rotations but also caused high neck responses because of the greater loads on the torso. Neck displacement (d) is initially proportional to (k/m_T) ∫∫ y, seat stiffness times the second integral of vehicle displacement divided by torso mass. As seat stiffness increases, head-torso acceleration, velocity, and neck displacement increase. This study shows that the jk seat property determines the initial seatback rotation in rear crashes. If a stronger seat has a higher stiffness, it rotates at higher loads on the occupant, reducing the overall benefit of the stronger frame, while increasing neck responses related to whiplash or neck extension prior to subsequent impacts. The aim of seat designs should be to reduce jk, provide pocketing of the pelvis, and give head-neck support for the best protection in severe rear crashes. For low-speed crashes, a low k is important to reduce early neck responses related to whiplash.     

同忻井田地应力测量与回采巷道稳定性研究

为保证同忻煤矿安全、高效开采,采用应力解除法对大同矿区同忻井田3-5#煤层的地应力场进行了测量,结合理论分析、数值模拟与现场监测,分析了在该类型应力场中不同巷道布置方向与巷道围岩稳定性之间的关系。测得同忻井田最大主应力为20.42 MPa,方位角为245.18°,确定了同忻井田地应力场属于σHv型。理论计算和数值模拟的结果表明,有利于回采巷道稳定性的布置方向为与最大水平主应力方向成30°,并采用巷道顶板离层监测仪对其进行了验证。     

Assessment of cervical range of motion,cervical core strength and scapular dyskinesia in violin players

Background. Playing the violin can lead to asymmetric postures which can affect the cervical range of motion, cervical core strength and scapular stability. Objective. The objective of the study was to assess the cervical range of motion, cervical core strength and scapular dyskinesia in violin players and non-players of the same age group. Methods. An inclinometer was used to assess the cervical range of motion, pressure biofeedback was used to assess cervical core strength and scapular dyskinesia was also assessed in 30 professional violin players (18–40 years) compared with 30 age-matched non-players. Analysis was done using an unpaired t test. Results. Significant change was seen with respect to extension (p?=?0.051), cervical core strength (p?=?0.005), right (Rt) superior angle 0° (p?=?0.004), Rt superior angle 45° (p?=?0.015) and Rt inferior angle 90° (p?=?0.013). Conclusion. This study shows a significant difference in extension range of motion and cervical core strength of violin players. Also, there was scapular dyskinesia seen at 0° and 45° right-side superior angle of the scapula and 90° right-side inferior angle of the scapula.     

Posture and belt fit in reclined passenger seats

Abstract

Objective: Highly reclined postures may be common among passengers in future automated vehicles. A laboratory study was conducted to address the need for posture and belt fit in these seating configurations.

Methods: In a laboratory vehicle mockup, the postures of 24 men and women with a wide range of body size were measured in a typical front vehicle seat at seat back angles of 23°, 33°, 43°, and 53°. Data were gathered with and without a sitter-adjusted headrest. Posture was characterized by the locations of skeletal joint centers estimated from digitized surface landmarks.

Results: Regression analysis demonstrated that the pelvis rotated rearward and lumbar spine flexion decreased with increasing recline. The lap portion of the 3-point belt was more rearward relative to the pelvis in more-reclined postures, and the torso portion crossed the clavicle closer to the midline of the body. Regression equations were developed to predict posture and belt fit variables as a function of passenger characteristics, seat back angle, and the use of the headrest.

Conclusions: Spine posture changes as the torso reclines in an automotive seat, and belt fit is altered by the change in posture. The results can be used to accurately position crash test dummies and computation human models and to guide the design of belt restraints.