Seongil Lee

Power-aware optimal checkpoint intervals for mobile consumer devices

It is highly desired to employ a checkpoint and rollback scheme on a mobile consumer device for fault tolerance, because spatial fault-tolerant schemes such as hardware replications cannot be used. We can reduce the loss of computation of a process in the presence of failures by periodically saving the processs state on stable storage as a checkpoint and rolling back to the latest checkpoint when a failure has occurred. However, a mobile consumer device is not considered to have sufficiently large and stable storage to store its checkpoint data. Therefore, a remote checkpoint technique is preferred in wireless environments in which the checkpoint data of a mobile device is kept in a remote checkpoint server instead of the mobile device. Dense checkpoints incur frequent wireless transmissions whereas coarse checkpoints increase the loss of computation. Many checkpoint research papers have tried to minimize the expected execution time. However, an effective solution which minimizes the energy expenditure should be also provided, because battery power is one of the most critical resources of a mobile device. In this paper, we propose the energy-aware optimal checkpoint interval in wireless remote checkpoint environments. We develop a stochastic model with Markov chain and then derive the optimal value. For the practical evaluation, we conducted not only analytical estimation and simulation but also experimental measurements by implementing on a real test-bed.1.

Usability evaluation of Korean e-government portal

This paper reports the results of an evaluative study of the Korean e-Government portal from the usability perspectives, using a common set of performance metrics from user participation. For fourteen civil affairs service sites, 51 participants performed usability tests and post-test interviews. The results showed that even though the e-Government services are fairly attainable, it takes too many steps and long time for users to complete the given tasks. The overall success rate to complete the tasks on e-Government was 0.69 and it took more than 4 minutes and 12 page navigations on average to complete simple transactions. A strong digital divide could be observed in the use of e-Government services in that the users with different vocations and ages resulted in difference in perceived usability and actual performance. Results suggest that not only are there wide variations in the usability for the services provided, but that significant work still needs to be undertaken in order to make the services of the e-Government more usable, particularly for the older users.

A Pair of Wireless Braille-Based Chording Gloves

Since input devices for desktop computers are inconvenient to use in a mobile working environment, other small input devices have been proposed. Few of them, however, are for visually impaired people. This paper proposes a pair of wireless Braille-based chording gloves as an input device to use in a mobile working environment for visually impaired people. Its keys are mounted on the fingers and its chording method is similar to that of a Braille keyboard. Since Braille has been efficiently devised to represent many language characters, numbers, and symbols including mathematical and musical notations, the proposed chording gloves will be also used for visually non-impaired people. IrDA (Infrared Data Association) and RF (Radio Frequency) wireless modules are designed and implemented to make the proposed chording gloves wireless.

Accessibility evaluation of Korean e-government

This paper aims to discover to what extent web accessibility is considered by the e-Governments of Korea. Accessibility of the e-Government of Korea was evaluated using Web diagnostic engines that check the compliance level of Web sites to the W3C guidelines. The accessibility of the e-Government was at a lower level, complying to only 10% of the priority 1 checkpoints. This means that lack of coherent government policy for web accessibility causes lack of providing standard e-Government services for the part of the population with special needs.

A study on usability of human-robot interaction using a mobile computer and a human interface device

A variety of devices are used for robot control such as personal computers or other human interface devices, haptic devices, and so on. However, sometimes it is not easy to select a device which fits the specific character of varied kinds of robots while at the same time increasing the users convenience. Under these circumstances, in this study, we have tried to measure user convenience. We tried to understand the characteristics of several devices used to achieve human robot interaction by using each of these devices that could be used with a personal computer: We used a button type device, a joystick, a driving device which consisted of a handle and pedals, and a motion-based human interface device including an acceleration sensor.

Enabling a gesture-based numeric input on mobile phones

We designed a gesture-based numeric input scheme using a mobile phone equipped with an acceleration sensor. In the suggested scheme, users could key in numbers with a gesture input, instead of a traditional numeric keypad input. The numeric codes are expressed in certain series of gestures with a mobile phone, including tapping, flipping, and shaking. The scheme developed in this study is an activity-recognition-based system by which gestures are categorized through a preprocessing and a probabilistic inference model we developed. The people with visual disabilities who cannot see the screen can take advantage of the proposed scheme to enter numeric codes on most of currently available touch-based smart phones.

Chording as a Text Entry Method in Mobile Phones

A chording input method on mobile phones, using two thumbs simultaneously, was examined. This paper addresses advantages and disadvantages in chording applied to text input and control using keypads of mobile phones. Chording can be a good input and control method in that it can provide more options with limited number of keys, and that it can provide mobile users with extended usability and functionality. The chording input method on a mobile keypad showed comparable performances in choice reaction times and error rates with conventional single keying method, even though certain chording seemed to cause troubles in finger coordination, resulting in longer reaction times and more errors.

Energy-aware checkpoint intervals in error-prone mobile networks

Checkpoint and rollback scheme can be a good choice on a mobile device for the fault tolerant computing. Since the battery power is one of the most critical resources of a mobile device, it is very important to know the optimal checkpoint interval that minimizes the energy expenditure. In this paper, we propose a method for determining the optimal checkpoint interval that minimizes the energy expenditure in wireless remote checkpoint environments by considering failures both on the system and the wireless link of a mobile device. To evaluate the proposed solution, we conducted performance analysis and simulations.

A customized mouse for people with physical disabilities

In a rapidly growing information-oriented society, people with disabilities are faced with serious inconveniences in accessing products due to the increasingly complicated use of technology-oriented but poorly designed devices. To solve these problems, we designed a customized computer input device (mouse) to be used by physically impaired people. The users performed better with the customized computer mouse than with the traditional computer mouse.

Mapping User Accessibility Needs Systematically to Universal Design Principles

In a rapidly growing information-oriented society, people with disabilities and older people are faced with serious inconveniences in accessing IT products due to complicated use of technologies and poorly designed interfaces. To solve the problems, it is required for designers and engineers to find out and understand user needs, and then to figure out the functionalities and design characteristics to meet the needs. Figuring out the Engineering Characteristics (EC) of products from user needs for people with disabilities and older people who have problems using main stream products due to limited accessibility would take great efforts and time. We merged two important concepts of product design for people with disabilities and older people, accessibility and universal design, using an engineering design framework of QFD (Quality Function Deployment) to provide engineers and designers with a systematic methodology for universal product design. We adapted a technical report from the ISO/IEC JTC1 Special Working Group on Accessibility (SWG-A), the Information Technology --- Accessibility Considerations for People with Disabilities --- Part 1: User Needs Summary (ISO/IEC PDTR 99999-1), and mapped the detailed user accessibility needs to the guidelines of 7 universal design principles which are widely accepted. We explained how a process model was built for mapping relationship between the guidelines and user accessibility needs, and extracting the critical engineering characteristics for IT product design based on these two models. A model House of Quality(HOQ) was built for such procedures.