• Journal of Electrical Engineering and information Science
• /
• v.2 no.5
• /
• pp.89-99
• /
• 1997

The application for real-time database systems must satisfy timing constraints. Typically the timing constraints are expressed in the form of deadlines which are represented by priorities to e used by schedulers. In any real-time applications, since the system maintains sensitive information to be shared by multiple users with different levels of security clearance, security is another important requirement. As more advanced database systems are being used in applications that need to support timeliness while managing sensitive information, protocols that satisfy both requirements need to be developed. In this appear, we proposed a new priority-driven secure multiversion locking (PSMVL) protocol for real-time secure database systems. The schedules produced by PSMVL are proven to e one-copy serializable. We have also shown tat the protocol eliminates covert channels and priority inversions. The details of the protocol, including the compatibility matrix and the version selection algorithms are presented. the results of the performance comparisons of our protocol with other protocols are described.

• Journal of Korea Multimedia Society
• /
• v.21 no.2
• /
• pp.232-241
• /
• 2018

Operational Transformation (OT) algorithms for real-time collaborative editing systems are becoming increasingly important due to the increased demand for collaborative data processing. The operational transformation algorithm is a technique for real-time concurrency control and consistency maintenance with non-locking technique, and many studies have been conducted to overcome three issues of convergence, causality-prevention, and intention-prevention. However, previous work has the disadvantage of wasting memory by storing all operations that occurred during an edit operation in the history buffer to solve this problem. Therefore, we propose a memory-saving real-time collaborative editing system that maintains a constant memory space and concurrency control through a method of applying the valid-time to each user-generated operation in order to reduce memory waste. This system prevents long-term memory occupation of client-generated operations, thus it reduces the space and time complexity even with low-rate of collaboration work, so that the performance degradation avoids.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.439-440
• /
• 2006

This research proposes a novel method of shape display to present 3-dimensional objects. Shape displays allow us to feel the actual volume of the object, unlike conventional 2D visual displays of 3D objects. The proposed method employs a wire frame structure to present 3D objects. The wire frame is composed of small units driven by shape memory alloy(SMA) actuators. The drive unit is analogous to the agonist-antagonist system of animal musculoskeletal systems, where the SMA actuators serve as agonist and antagonist muscles. The force in the SMA actuator is controlled by electrical current. The drive unit is equipped with the locking mechanism so that it can sustain the external force exerted by the user as well as the own weight of the wire frame structure. By controlling the current into the SMA actuator and locking mechanism, we call control the angle of the drive unit. A chain of drive units enables presentation of 2 dimensional objects. 3 dimensional presentations are possible by collecting the chains of drive units.

• International Journal of Automotive Technology
• /
• v.8 no.2
• /
• pp.185-191
• /
• 2007

The new FMVSS 208, 213, 225 regulations include automatic suppression of airbags to prevent low-risk airbag deployment and the use of child seats with a rigid-bar anchor system. The regulations mean that children must sit in the rear seat, but do not include other specific safety measures for their protection. In the rear, restraint equipment consists of three-point shoulder/lap belts for the outside seats and a static two-point lap belt in the middle, with no additional devices such as pretensioners or load limiters; this is far from optimal for children. This study investigated injury rates using a 3-year-old-child dummy. ECE R44 sled tests used a booster, a speed of 48 km/h, and a 26- to 32-g rectangular deceleration pulse. While seated on a booster, the dummies were restrained by an adult shoulder/lap three-point belt. HIC_15 msec, Chest G and Nij were somewhat lower with an emergency locking retractor (ELR)+pretensioner+load limiter than with only an ELR or with ELR+pretensioner. However, the current seat-belt system results in injury rates that exceed the limit for OOP performance under the new FMVSS 208 regulations.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.5
• /
• pp.82-88
• /
• 2008

This paper proposes a novel method of 2 dimensional shape display. Shape displays allow us to feel tile actual volume of the object, unlike conventional 2D visual displays of 3D objects. The proposed method employs a wireframe structure to present 2D or 3D objects. The wireframe is composed of small units driven by shape memory alloy (SMA) actuators. The drive unit is analogous to the agonist-antagonist system of animal musculoskeletal systems, where the SMA actuators serve as agonist and antagonist muscles. The force in the SMA actuator is controlled by electrical current. The drive unit is equipped with the locking mechanism so that it can sustain the external force exerted by the user as well as the own weight of the wireframe structure. By controlling the current into the SMA actuator and locking mechanism, we can control the angle of the drive unit. A chain of drive units enables presentation of 2 dimensional objects. 3 dimensional presentations are possible by collecting the chains of drive units.

• 제어로봇시스템학회:학술대회논문집
• /
• 1997.10a
• /
• pp.640-643
• /
• 1997

This paper describes speed controller of a induction motor for electric vehicles using PLL and Fuzzy logic. The proposed system is combined precise speed control of PLL and robust, fast speed control of Fuzzy logic. The motor speed is adaptively incremented or decremented toward the PLL locking range by the Fuzzy logic using information of sampled speed errors and then is maintained accurately by PLL. The results of experiment show excellence of proposed system and that the proposed system is appropriates to control the speed of induction motor for electric vehicles.

• Proceedings of the IEEK Conference
• /
• 2002.07a
• /
• pp.540-541
• /
• 2002

In this paper, the performance of upidirectional and hi-directional regenerative erbium-doped fiber amplifier (EDFA) is compared. The systems are operating above laser oscillation threshold. The experimental results show that the unidirectional regenerative EDFA has a better performance than the hi-directional.

• Asia pacific journal of information systems
• /
• v.5 no.1
• /
• pp.219-235
• /
• 1995

Complexity of some problems often transcends the problem solving capability of human individuals. As such, we cannot but take a collaborative approach to those complex problems. Collaboration while using computing systems can take place through shared objects. However, current commercial DBMSs do not provide a satisfactory control for concurrent access to objects shared by collaborators. A new concurrency control scheme is proposed which will help a group of people work in a more collaborative and natural way. The idea of softlock is refined into three different kinds of softlocks and the roles of collaborators are taken into account in the proposal of the new scheme. Although these softlocks are illustrated together with read/write hardlocks in this paper, the use of softlocks can be extended to be exploited with other kinds of hardlocks, for example, of granularity locking.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.11
• /
• pp.1623-1630
• /
• 2010

In this study, effective forming methods for reducing the roll-over of a sector tooth, which is a main component of an automotive seat recliner, are proposed. Due to the large amount of roll-over, accurate contact between the inner gear of a sector tooth and the outer gear of a pawl tooth cannot be normally achieved; thus sensitivity and safety for the passengers decrease. To overcome the aforementioned drawback, we investigated the effect of flowcontrol forming methods involving local embossing die, coining punch, and VIC (Variable Inverse Clearance) on the roll-over depth by FE-analysis and an experiment. The results of a fine-blanking experiment for verifying the proposed methods showed that VIC type is decidedly superior from the aspects of reduction of roll-over and tool strength of the sector tooth.

• Korean Institute of Interior Design Journal
• /
• v.17 no.5
• /
• pp.61-71
• /
• 2008

The study alms to seek a plan of applying the digital technology to housing for the elderly. The purpose of the study was to grasp the needs of the aged on 30 types of digital systems in housing. The subjects were 120 persons aged of more than 60 years and lived in Busan. Data were collected by the individual interview. The following results were drawn from this study. First, the needs of the aged on the digital systems categorized as safe and security, control of indoor environment, and housework support were very high and should be provided at first. Second, the necessary types of digital systems which should be provided to the digital home for the elderly were digital systems for heating control, health checking, sensing of fire and gas leak, and house cleaning. Also, the basic types of digital systems were ones for invasion and burglarproof, emergency, air cleaning, automatic facet, door locking, and waste collecting. Third, the Income and usage level of digital equipment of the aged influenced to the floods of the aged on the digital system. Therefore, in addition to the necessary and basic types of digital systems mentioned above, the income and usage level of digital equipment should be considered in planning the digital home for the elderly.