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Tactile graphics containing only dots have long been widely used. However, tactile graphics containing only dots may be mistaken for braille. This study aimed to investigate the influence of distance between dot pattern and braille in tactile graphics by emboss printing method on the ease of braille identification. Test pieces with varied distance between dot pattern and braille in tactile graphics were created using EDEL software, which is a de facto standard in Japan, and printed using the ESA721 braille printer (JTR Co.). Sighted subjects who were beginner braille readers and subjects with visual impairment who were expert braille readers were asked to identify the test pieces. The results showed that the visually impaired who regularly use tactile charts and braille could identify braille accurately, quickly, and with confidence when the vertical and horizontal distance were 4.7 mm or greater. For novice braille readers, they were able to identify braille accurately, quickly, and confidently when the vertical distance was 5.9 mm or greater and the horizontal distance was 4.7 mm or greater. These results indicate that the novice readers can identify braille correctly, quickly, and confidently when the vertical distance is 5.9 mm or greater and the horizontal distance is 4.7 mm or greater. In addition, test pieces with extended vertical distances were easier to identify than those with extended horizontal distances.

There has been a great demand for flame stability particularly in low-grade residual oil-fired burners. In order to improve the performance of the residual oil burner, it is required to obtain the stable ignition by the swirler devices which create recirculating combustion gas and rotating fuel spray flows. In the present study, a numerical simulation was made on the flow behaviors of air circulation and droplet streamlines for two types of swirlers with different angles of guide vane. A stereo PIV measurement was also made on the velocity distribution of spray droplets. One type of the swirlers is a former type called “Bent plate swirler” with a constant bending angle of the guide vanes. The air after the guide vane expands to the outer circumferencial direction by centrifugal force and the swirling state abruptly declines. Another is a newly developed type “Wing-curved swirler” in which the bending angle of the guide vane becomes deeper from the center to the outer direction. The air flow maintains the swirling force and the recirculation flow is wider than the former “Bent plate swirler”. The Wing-curved swirler with a high swirl force, a swirl number of 2 or more, not only increases the swirl of the sprayed droplet but also lengthens its trajectories. The flame stability was improved by the burner equipped with the developed Wing-curved swirler. The decrease in dust concentration was demonstrated through the residual oil combustion test of the 10 MW actual burner.

Recently, the use of portable terminals with touch screens such as smartphones has spread rapidly. Many users have used these devices to browse the internet or social networking services (SNS). There are many link texts (hyperlinked texts) to navigate between pages or to download files. However, interacting with link text in a portable terminal with a touch screen can often be difficult because link texts that have low text height and narrow space between lines (set by web designers who wanted to display as much information as possible on a screen of limited size) can cause accidental interactions. Many studies have evaluated usability when using portable terminals with touch screens and most of these studies have focused on Button, which is a basic GUI component. In contrast, GUI design approaches for link text have not been received sufficient attention. This study is aimed at evaluating the influence of two factors, namely the text height and the line spacing of link text, on the error rate and pointing time to overcome the usability problems associated with link texts. User experiments on pointing tasks were conducted for seven text heights (1.0, 1.5, 2.0, 2.5, 3.0, 3.5, and 4.0 mm) and five ratios of line spacing to text height (0.1, 0.3, 0.5, 0.7, and 1.0). The result shows that when the text height is 4.0 mm and the ratio of line spacing is 1.0 (the height of touch-sensitive area is 8.0 mm), rapid and accurate pointing the link text can occur. We hope that these findings contribute to an easy-to-use design for link texts.

Acupuncturists determine muscle stiffness by pressing their fingers down. To shorten the palpation time and minimize discomfort to the patient, a good palpation technique is required to determine the stiffness of the patient's muscles with as few presses as possible. However, palpation is dependent on the experience of the practitioner. Therefore, an investigation of human hardness discrimination characteristics is necessary to provide some quantitative guidance. In this study, to determine the relationship between different numbers of presses and the accuracy of discriminating hardness, we investigated the differential threshold of hardness for different numbers of presses (1, 3, or 5). We used 7 elastic test pieces, each with a different Young's modulus, as the presented stimuli. We conducted an experiment using the constant stimuli method to calculate the differential threshold of hardness as an evaluation index of hardness identification. In the experiment, the participants repeatedly pressed for either 1, 3, or 5 sets by using 2 presented stimuli and then distinguished the hardness of the stimuli. The results of the experiment showed that when the pressing forces were 5 and 10 N, as the number of presses decreased, the differential threshold of hardness increased. However, when the pressing force was 15 N, the differential threshold of hardness was small regardless of the number of indentations. This knowledge will be useful for the improvement of the palpation technique in acupuncture schools. For example, the index of the hardness discrimination characteristic used in this study may be used as a quantitative numerical target and for performance evaluation.

Hardness identification is one of the most important tactile senses in humans. People use their hands in various ways to identify the hardness of an object. For example, acupuncturists identify stiffness in a muscle by pressing down with their forefinger held flat over the affected area. However, experimental evidence for the role of the pressing method in the identification of an object's hardness even when the same finger is used has not been shown yet. In this fundamental study, we investigated the differential threshold of hardness for different finger postures of pressing (pressing down with one's forefinger held “flat” or “vertically”) to determine the relationship between the different finger postures of pressing and hardness identification. We used seven elastic test pieces, each with a different Young's modulus, as the presented stimuli. We conducted an experiment using the constant method to calculate the differential threshold of hardness as a measure of hardness identification. The results showed that the differential threshold of hardness was higher when pressing down with a forefinger held “flat” than when pressing down “vertically” with the same force. This finding will be useful in evaluating the tactile identification of hardness in acupuncturists.

Tactile characters aid in providing information to visually impaired persons. The Japanese Standards Association enacted basic design methods for embossed tactile patterns in March 2011. However, data on the appropriate size of tactile alphabets are not necessarily enough available. The purpose of this study was to evaluate the influence of the size of a tactile alphabet on identification and to investigate the perceptible size for people without rich tactile experiences. The participants of this study were 15 young people and 15 old people who were unfamiliar with tactile characters intended for visually impaired people. They were asked to discriminate tactile alphabets of six different sizes by using their forefingers without the aid of eyesight. The results showed that the younger and older participants were able to discriminate the presented stimuli faster and more accurately as the stimulus size was increased. Concretely, when the size was 28 mm, each participants regardless of young or older groups could identify the tactile character accurately and quickly. In addition, a trend was seen in that the older group needed larger tactile alphabet sizes than the younger group. We determined the relationship between the tactile alphabet size and discrimination ability of younger and older people without rich tactile experiences.

Tactile guide maps are well-known information support tools for visually impaired people. In a tactile guide map, area information is expressed by use of raised dot patterns and raised boundary lines. Tactile guide map designers must place spaces between these raised dot patterns and raised boundary lines so that tactile guide map users can easily identify the lines. However, there is a lack of quantitative data on the perceptibility of tactile guide map lines. In this study, we investigated the influence of the spaces between the raised dot patterns and raised boundary lines on the perceptibility of the tactile guide map lines. We made test pieces with seven different dot distances for dot patterns and five different space distances. The participants included 40 sighted people (20 younger and 20 older ones) as tactile guide map beginner users. The participants were asked to identify the direction of a line, which could be horizontal, vertical, diagonally left up, or diagonally right up. Based on these results, we found that the raised boundary lines were highly easy to identify when the distance between the raised dot patterns and raised boundary lines was greater than 5 mm. This knowledge will be helpful for tactile guide map designers.

Identification of the hardness of an object in a human hand is different according to the hardness of the object. For example, chiropractors identify stiffness in the muscle by using their thumb, which can press more forcefully than the forefinger. However, it has not been shown experimentally if the characteristics of hardness discriminability are different according to fingers. In this study, to clarify the relation between different fingers pressing elastic objects and the characteristics of hardness discriminability, we investigated the differential threshold of hardness using the forefinger and thumb. Additionally, the influence of press force and press displacement on the characteristics of hardness discriminability was clarified. We used 7 elastic test pieces with different Young’s moduli as the presented stimuli. We also used the test pieces with hardness sensation judged as ‘hard’ in our previous research. We conducted the experiment using the constant stimuli method to calculate differential threshold of hardness as one evaluation index of hardness discriminability when using the forefinger and thumb. The results of this experiment showed that the hardness discriminability of the thumb was better than that of the forefinger. In addition, these results suggested that press displacement but not press force should be used to estimate the hardness discriminability and that the thumb is better than the forefinger to discriminate the displacement. These findings clarify the mechanism underlying hardness discriminability in the human hand.

Braille is a well-known communication tool for the visually impaired. In recent years, as a result of advances in Braille printing technology, the use of transparent resinous ultraviolet cured type (TRUCT) Braille has spread rapidly. As one of the most popular Braille printing technologies, the screen printing method is applied for printing TRUCT Braille. However, the screen printing method produces TRUCT Braille prints of poor quality. In this study, in order to improve the printing quality, we created a device for printing TRUCT Braille. Additionally, we evaluated TRUCT Braille readability for Braille beginner readers by focusing on horizontal and vertical Braille dot distances using our created device. From this study, we found that it was easy to print TRUCT Braille using our device. Braille beginner readers found it easy to read TRUCT Braille with adequate horizontal and vertical Braille dot distances. These findings support the use of TRUCT Braille for new Braille beginner textbooks, as well as for printing Braille signs in public facilities.