A study for determining the optimum diameter of chopsticks

Chopsticks and knives and forks are fundamental utensils used by Asian and Western-oriented people, respectively, in serving food. Although ergonomics studies on the knife handle have been performed, chopsticks, used by at least 1.5 billion people daily, have seldom been examined by ergonomists. This lack of interest may be attributed to the fact that Occidentals, who tend to give more emphasis on empirical research, do not use chopsticks. Nevertheless, from an ergonomics perspective, chopsticks deserve a systematic study in lieu of the large number of users. This study involves 32 male and female university students who served as the control group. According to these results, the diameter of chopsticks significantly influences `food-pinching' efficiency. Also, the smaller and larger diameters of chopsticks are inferior to those of a medium diameter. In addition, chopsticks with 6 mm diameter are optimum for `food-pinching' efficiency. Subjective preference ranking is also used to cross-validate the above performance measures, with these results confirming the effectiveness of `food-pinching' efficiency measure.Relevance to industryHand tools considered as extensions of human hands, are very important in industry. Chopsticks are one of the simplest and most convenient and efficient hand tools. The result of this study reveals that both the diameter of chopsticks and different sizes of food heavily influenced the `food-pinching' efficiency. Thus, the designers must consider human factors, and ergonomic aspects of the user–tool interface when designing a new hand tool.     

Ergonomics study on the handle length and lift angle for the culinary spatula

The culinary spatula (turning shovel) is one of the most common cooking tools used in the kitchen in Asia. However, the culinary spatula has seldom been ergonomically investigated. When a person uses a spatula to cook food, the operations involve repetitive bent-wrist motions, such as dorsiflexion, palmary flexion, and radial and ulnar deviations. These movements may cause cumulative trauma disorders in the upper extremities, and in particular carpal tunnel syndrome. A poorly designed culinary spatula will be ergonomically inefficient and cause injury to the hand and wrist. The purpose of this study was to investigate the effects of spatula handle length and lift angle on food-frying, food-turning, and food-shoveling performance. Eight female subjects were tested using 16 different culinary spatulas, with four different handle lengths (20, 25, 30 and 35 cm) and four different lift angles (15 degrees, 25 degrees, 35 degrees and 45 ). The criterion measures included cooking performance, and rating of perceived exertion. The subjects ranked their preference after all of the tasks in the tests were completed. The results showed that: (1) The handle length had a significant influence on the cooking performance, and rating of perceived exertion. The optimal handle lengths for frying food, turning food, and shoveling food were 20, 25 and 25 cm, respectively. (2) The lift angle significantly affected the cooking performance, and rating of perceived exertion. The optimal lift angles for frying food, turning food, and shoveling food were 15 degrees, 15 degrees and 25 degrees, respectively. (3) Both the handle length and lift angle had significant effects on subjective preference. For the handle length, the 20 cm length was the best. For the lift angle, the 25 angle was the best. (4) In general, a spatula with a 20 cm handle length and 25 degrees lift angle was the best. A spatula with a 25 cm handle length and 15 lift angle was the second most preferred. (5) However, to prevent subjects from touching the edge of a hot pan, a spatula with a 25 cm handle length and 25 lift angle is suggested.     

An investigation for determining the optimum length of chopsticks

Chopsticks are one of the most simple and popular hand tools ever invented by humans, but have not previously been investigated by ergonomists. Two laboratory studies were conducted in this research, using a randomised complete block design, to evaluate the effects of the length of the chopsticks on the food-serving performance of adults and children. Thirty-one male junior college students and 21 primary school pupils served as subjects for the experiment. The results showed that the food-pinching performance was significantly affected by the length of the chopsticks, and that chopsticks of about 240 and 180 mm long were optimal for adults and pupils, respectively. Based on these findings, the researchers suggested that families with children should provide both 240 and 180 mm long chopsticks. In addition, restaurants could provide 210 mm long chopsticks, considering the trade-offs between ergonomics and cost.     

Psychophysical evaluation of diameter and angle of container handles

The objectives of this study were, firstly, to apply an efficient approach to assess both optimal handle diameter and angle by subjective perception of heaviness, and secondly, to evaluate one-hand power grip on alternative container handles, using weight discrimination as a criterion. Twelve student subjects (six males and six females) participated in the four experiments designed in this study. Six handle diameters (25.4 mm (1″), 31.8 mm (1.25″), 38.1 mm (1.5″), 44.5 mm (1.75″), 50.8 mm (2″) and 57.2 mm (2.25″)) and six handle angles (radial 20° (R20), radial 10° (R10), neutral (NO), ulnar 10° (U10), ulnar 20° (U20) and ulnar 30° (U30)) were evaluated. The results indicated that the containers were perceived less heavy when handle diameter was about 51 mm (2″) and handle angle was about neutral position. Further, insignificant influences of handle diameter and handle angle on human's ability to discriminate weight difference were found when the standard weight was 8.2 kg.Relevance to industryThe results of this study can be applied to handle design in manual material handling tasks.     

The pincer chopsticks: the investigation of a new utensil in pinching function

The manipulation of chopsticks requires skillful motions of fingers. Therefore, it would be difficult to manipulate chopsticks for people with hand dysfunction. We designed a simple and convenient utensil, the pincer chopsticks, to simulate the pincers-pinching operation of traditional chopsticks. To compare the performance of the new device with that of traditional chopsticks and spoons, 32 volunteers applied these utensils to pick up four kinds of food with either hand. For dominant hands, the manipulation time of both pincer and traditional chopsticks was shorter than that of spoons, while using pincer chopsticks with non-dominant hands revealed the best performance among the three experimental utensils for users without experience. In this study, the newly designed pincer chopsticks demonstrated advantages for operation and performance. It has the potential to benefit patients with impaired hands.     

Evaluation of recessed and bar handles of freezer door in refrigerator

Design components of handles can affect the physical demands on users and their satisfaction. However, few studies have evaluated the physical usability of different handle configurations in refrigerators. The objective of this study was to evaluate the effect of the handle height, clearance, embossing, and users’ stature on their physical demands and satisfaction with two different handle types. Twenty‐eight participants were recruited, and several design components, including the handle type (recessed, bar), height (620 and 680 mm), clearance (0, 3, 5, and 7 mm), embossing (with and without), and users’ stature (short, medium, and tall) were investigated. Regardless of handle type, higher handle (680 mm) exhibited a lower flexion angle and flexion moments of the hips and back compared with lower handle (620 mm), and participants expressed greater satisfaction with embossed handles when using the recessed handle. Handle height and comfortable grip configuration were the primary components that affected physical usability. The results could be useful in designing and improving refrigerator handles.     

Choice of handle characteristics for pistol grip power tools

The optimal surface material and cross-section of power tool handles are not sufficiently described in ergonomic literature. The objective of the present study was to increase knowledge in these matters. The handle of four similar drilling machines were covered with rubber with different hardness. The preferences and forearm muscle electric activity (12 male and 12 female subjects) as well as the vibration level (6 male subjects) when using these drilling machines were assessed. The results showed that foam rubber on the handle is a more preferable covering material compared to harder rubber and it does not increase the muscular activity. Foam rubber on the handle may also to some extent attenuate vibrations.

Furthermore preferred width and thickness of handles for drilling machines were evaluated by letting 12 male and 12 female subjects perform three tasks: (a) choosing handle width (free choice) and ranking handle thickness (3 alternatives), (b) ranking handle width (3 alternatives), (c) making a handle out of hand putty (free choice). The subjects hand size (hand length, functional grip diameter and hand volume) were also measured and compared to their preferences. The results showed that the most commonly used handle cross-section size (50×35 mm) is an acceptable compromise in terms of preferences. The measured hand size measures had low correlation with preferred handle width/circumference.

Relevance to industry

Information concerning the design of handles for power tools is essential for tool designers.     

An auxiliary device for chopsticks operation to improve the food-serving performance

Chopsticks are popular dining utensils in many Asian countries. It is well recognized that the pincers-pinching mode has been recommended for chopsticks operation for Chinese dining. The objective of this study was to propose an auxiliary device for transferring the subjects who had experienced scissors pinching to that of pincers pinching. A total of 30 male university students who used scissors pinching daily were recruited for the experiment. Subjects were requested to perform four simulated food-serving tasks under four different pinching stages. An additional testing was also performed for validation purpose. Results showed that the subjects had a better performance of food serving by the pincers-pinching method than by the scissors-pinching method, after familiarizing themselves with pincers pinching with the assistance of an auxiliary for 1 h. Because of the relatively shorter transferring time (1 h), the subjects still evaluated scissors pinching as their preferable ones. We suggested that this new auxiliary device could be used to teach or correct the chopsticks operation of people who are na?ve/children and are interested in chopsticks use or experienced in chopsticks scissors pinching.     

Pyroelectric thin-film sensor array

Pyroelectric thin-film point detectors and 1 × 12 arrays have been fabricated and characterized. They consist of sol-gel-deposited PZT thin-film elements on micromachined Si₃N₄/SiO₂ membranes. The measured current and voltage response as a function of modulation frequency of a 1 × 12 array element is compared with finite-element calculations. Voltage responsivities of almost 3000 V W⁻¹ in vacuum and 800 V W⁻¹ in air have been achieved for 0.4 mm × 0.9 mm elements. Some point detectors have been completely packaged and correct operation in a movement detection system has been demonstrated.     

Ergonomics in sickle operation

Sickle operation in harvesting has been analysed with reference to design features of nine different types of sickles, and field and laboratory based investigations on biomechanical stresses and physiological valuation on six farmers. It has been indicated that the blade geometry contributes significantly to human performance and there is ample scope for further design optimisation. The suggested modifications are: (i) sickle weight - 200 g; (ii) total length of sickle - 33 cm; (iii) handle length - 11 cm; (iv) handle diameter - 3 c cm; (v) radius of blade curvature - 15 cm; (vi) blade concavity - 5 cm; (vii) serrated sickle: tooth pitch - 0.20 cm and tooth angle - 60 degrees; (viii) ratio of the length of cutting surface to chord length - 1.20.     

Effect of scribe‐wheel dimensions on the cutting of AMLCD glass substrate

Abstract— The scribe‐and‐break method for glass cutting is widely used to separate individual liquid‐crystal‐display (LCD) panels from a larger motherglass substrate cell. Optimum glass‐scribing conditions including scribe‐wheel dimensions, scribing load, scribing speed, etc., have been determined based on practical manufacturing experience. However, there has been no systematic study to determine the scribing conditions necessary to avoid stray breakage. In this paper, the influence of the scribe‐wheel angle and diameter upon the scribing and breaking of an active‐matrix liquid‐crystal‐display (AMLCD) glass substrate, Corning Code1737F glass, was experimentally investigated for the case of simple single‐glass‐sheet separation. It was determined that an equation including the factors of scribe‐wheel tip angle and diameter can be used to predict median crack depth as a function of scribe load. It was further found that the breaking force of the scribed sheet was strongly influenced by the residual stress created during scribing. A wheel having a 130° tip angle and 4‐mm diameter demonstrated the best results for sheet separation in terms of the lowest breaking force without lateral crack propagation. In addition, increasing the time interval between scribing and separating was found to result in an increase in the breaking force required to separate the glass substrate.     

Factors affecting minimum push and pull forces of manual carts.

The minimum forces needed to manually push or pull a 4-wheel cart of differing weights with similar wheel sizes from a stationary state were measured on four floor materials under different conditions of wheel width, diameter, and orientation. Cart load was increased from 0 to 181.4 kg in increments of 36.3 kg. The floor materials were smooth concrete, tile, asphalt, and industrial carpet. Two wheel widths were tested: 25 and 38 mm. Wheel diameters were 51, 102, and 153 mm. Wheel orientation was tested at four levels: F0R0 (all four wheels aligned in the forward direction), F0R90 (the two front wheels, the wheels furthest from the cart handle, aligned in the forward direction and the two rear wheels, the wheels closest to the cart handle, aligned at 90 degrees to the forward direction), F90R0 (the two front wheels aligned at 90 degrees to the forward direction and the two rear wheels aligned in the forward direction), and F90R90 (all four wheels aligned at 90 degrees to the forward direction). Wheel width did not have a significant effect on the minimum push/pull forces. The minimum push/pull forces were linearly proportional to cart weight, and inversely proportional to wheel diameter. The coefficients of rolling friction were estimated as 2.2, 2.4, 3.3, and 4.5 mm for hard rubber wheels rolling on smooth concrete, tile, asphalt, and industrial carpet floors, respectively. The effect of wheel orientation was not consistent over the tested conditions, but, in general, the smallest minimum push/pull forces were measured with all four wheels aligned in the forward direction, whereas the largest minimum push/pull forces were measured when all four wheels were aligned at 90 degrees to the forward direction. There was no significant difference between the push and pull forces when all four wheels were aligned in the forward direction.     

The natural angle between the hand and handle and the effect of handle orientation on wrist radial/ulnar deviation during maximal push exertions

The purpose of this experiment was to quantify the natural angle between the hand and a handle, and to investigate three design factors: handle rotation, handle tilt and between-handle width on the natural angle as well as resultant wrist radial/ulnar deviation (‘RUD’) for pushing tasks. Photographs taken of the right upper limb of 31 participants (14 women and 17 men) performing maximal seated push exertions on different handles were analysed. Natural hand/handle angle and RUD were assessed. It was found that all of the three design factors significantly affected natural handle angle and wrist RUD, but participant gender did not. The natural angle between the hand and the cylindrical handle was 65 ± 7°. Wrist deviation was reduced for handles that were rotated 0° (horizontal) and at the narrow width (31 cm). Handles that were tilted forward 15° reduced radial deviation consistently (12–13°) across handle conditions.

Practitioner summary: Manual materials handling (MMH) tasks involving pushing have been related to increased risk of musculoskeletal injury. This study shows that handle orientation influences hand and wrist posture during pushing, and suggests that the design of push handles on carts and other MMH aids can be improved by adjusting their orientation to fit the natural interface between the hand and handle.     

Measurement of coupling forces at the power tool handle-hand interface

This study explored a low-cost system for measurement of coupling forces imposed by the hand on a handle under static and dynamic conditions, and its feasibility for applications to hand-held power tools. The properties of thin-film, flexible and trim-able resistive sensors (FlexiForce) were explored in view of their applicability for measurements of the hand-handle interface forces. The sensors showed very good linearity, while considerable differences were evident in the sensitivity amongst different sensors. The appropriate locations of the sensors on the handle surface were subsequently determined on the basis of the hand-handle geometry and reported force distributions. The validity of the measurement system was investigated for measuring the hand grip and push forces with eight subjects grasping five different stationary instrumented handles (cylindrical: 32, 38 and 43 mm diameter; and elliptical: 32 × 38 and 38 × 44 mm) considering two different positions of the sensors on the handle. The validity of the measurement system was also investigated under vibration for the 38 and 43 mm diameter cylindrical handles. The results showed good linearity and repeatability of the sensors for all subjects and handles under static as well as vibration conditions, while the sensors' outputs differed for each handle. The feasibility of the measurement system was also examined for measurements of hand forces on a power chisel hammer handle. The evaluations were conducted with three subjects grasping the power chisel handle under stationary as well as vibrating conditions, and different combinations of hand grip, push and coupling forces. The measurements revealed very good correlations between the hand forces estimated from the FlexiForce sensors and the reference values for the stationary as well as the vibrating tool.Relevance to industryThe measurement of hand-handle interface forces is vital for assessing the hand-transmitted vibration exposure and musculoskeletal loads. The low cost and flexible sensors, proposed in the study, could be conveniently applied to the curved surfaces of real power tool handles in the field to measure hand grip and push forces, and the forces exerted on the palm and the fingers. The most significant benefits of the sensors lie with its minimal cost and applicability to the real tool handles.     

Balance with the interactive size effects of display,target, and key spacing in tablet tapping,dragging, and typing tasks

This study aimed to expand the current demonstration of display size effects from pointing tasks to dragging and tap‐typing tasks to investigate the effects of influential factors on the performance of touchscreen tablets. From 7‐ to 11‐in. displays, the index of difficulty was kept constant by increasing the target amplitudes and widths (6.0–9.5 mm) proportionally, and the key spacing were, respectively, 13.5 × 7.3–21.5 × 11.5 mm with 0‐mm key gaps. The results demonstrated that simple task types (complexities) reinforced the display size effects and that the effects interacted with target sizes (including amplitude/width scaling) and key spacing to reflect increasing efficiency and usability with increasing sizes. Gender effects were only significant in subjective assessments. Display sizes approaching 10 in., target sizes not less than 7 mm (optimal 9–10 mm) and key spacing larger than 17.5 mm induced the effects of motor scale (the scale of the upper limb joint coordination) and interacted with one another to result in the optimal performance and usability.     

A simulated study on the effects of information volume on traffic signs, viewing strategies and sign familiarity upon driver''s visual search performance

A two-stage simulation experiment was conducted to investigate the effect of information volume on traffic regulatory/road direction signs, drivers’ viewing strategies and sign familiarity on performance in visual search. In Stage I experiment, the amount of information on a total of 187 traffic regulatory and 1272 road direction signs was calculated and divided into five information levels using cluster analysis. In Stage II experiment, 24 subjects participated in a 2 (familiarity)×5 (information volume level)×2 (viewing strategy) mixed factorial experiment. Each subject was required to perform a visual search task and a question-and-answer (Q&A) task. Visual search time and number of correct responses collected serve as the objective dependent variables. Subjective workload related to time stress and visual effort was gathered through a modified three-point rating. Results show that information volume on traffic signs had significant impact on drivers’ visual search performance. Generally, the greater the amount of information, the slower the drivers in visual search are. However, while drivers had the highest accuracy rate in remembering purely pictorial traffic signs, these signs within the smallest information volume level required a relatively longer search time. Different viewing strategies also led to different performances. The back-and-forth strategy yielded better search performance than the fixed strategy. Subjective workload evaluation indicates that drivers with less sign familiarity will be under greater time/visual pressures. Guidelines for designing for traffic signs or in-vehicle signing systems are provided.

Relevance to industry

This study calculated the amount of information on traffic signs and compared the effects of different information volume on drivers’ visual search performance. The results can provide guidelines for traffic sign designers to help decide on the presentation format for in-vehicle signing information systems.     

Effect of different handgrip angles on work distribution during hand cycling at submaximal power levels

The effect of different handle angles on work distribution during hand cycling was determined. Able-bodied subjects performed hand cycling at 20% of maximum power level (mean (SD) power level: 90.0 (25.8) W) at a cadence of 70 rpm using handle angles of ±30°, ±15° and 0°. The handle angle had a significant effect on work during the pull down (p < 0.001) and lift up (p = 0.005) sector, whereby the highest work was performed with handle angles of +30° and ?15° respectively. The cycle sector had a significant effect on work (p < 0.001) and significantly (p = 0.002) higher work was performed in the pull down sector (25% higher than mean work over one cycle) as compared to the lift up sector (30% lower than mean work over one cycle). Therefore, a fixed handle angle of +30° is suggested to be optimal for power generation. The results of this study help to optimise the handbike–user interface. A more pronated handle angle compared to the one conventionally used was found to improve the performance of hand cycling and thereby the mobility of disabled people.     

Vacuum fluorescent displays: from single digits to colour TV

Physical principles and operational characteristics of various vacuum fluorescent displays are outlined. A VFD history and details of construction are also given. Displays of various resolutions for different applications are described up to a 256 × 256 dot matrix unit. Uniform brightness and precise switching operation are realized using improved anode and grid electrode construction, anode baseplate processing, and grid configuration and its fixing processes. A scrolling VFD and a MOS FET switching array VFD are introduced. The latter uses an integrated circuit of 241 × 246 elements to produce a picture 23 × 23 mm. Prospects for the development of VFDs are given in conclusion.     

The effect of handle design on upper extremity posture and muscle activity during a pouring task

In this study, the effect of container handle parameters on shoulder and upper limb muscle activity and joint posture during a pouring task is investigated. Results indicated that a low handle position and a vertical handle slope minimised the loading of the shoulder muscles. A high and sloped handle minimised the muscle activity and wrist deviation of the lower arm. The effects of diameter were not significant for most dependent variables during the lifting phase of the task; however, beneficial effects were seen with the smallest handle diameter during the pouring phase. A trade-off existed between the shoulder and the hand/wrist posture with the different handles. The findings of significance with relatively small effect size suggest a high sensitivity of the system to any changes. In the real world, speed, space and work conditions are important factors that influence how a task is performed. This emphasises the importance of proper handle design.

Practitioner Summary: In this study, the effect of container handle design on the muscle activity and postures of the upper extremity during a pouring task were analyzed using the experimental data collected from electromyography and motion tracking systems. The low handle height and vertical handle slope design yielded the lowest shoulder muscle activity.     

The effect of display movement angle,indicator type and display location on control/display stereotype strength

Abstract

Much research on stereotype strength relating display and control movements for displays moving in the vertical or horizontal directions has been reported. Here we report effects of display movement angle, where the display moves at angles (relative to the vertical) of between 0° and 180°. The experiment used six different controls, four display locations relative to the operator and three types of indicator. Indicator types were included because of the strong effects of the ‘scale-side principle’ that are variable with display angle. A directional indicator had higher stereotype strength than a neutral indicator, and showed an apparent reversal in control/display stereotype direction beyond an angle of 90°. However, with a neutral indicator this control reversal was not present.

Practitioner Summary: The effects of display moving at angles other than the four cardinal directions, types of control, location of display and types of indicator are investigated. Indicator types (directional and neutral) have an effect on stereotype strength and may cause an apparent control reversal with change of display movement angle.