• IEMEK Journal of Embedded Systems and Applications
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• v.5 no.3
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• pp.128-135
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• 2010

Recently complexity of embedded software cause to be used real-time operating system (RTOS) to implement various functions in the embedded system. And also, according to requirement of complex functions in embedded systems, the number as well as complexity of tasks get increased continuously. In case that many tasks collaborated in a microprocessor, context switching time between tasks is a overhead waisting a CPU resource. Therefore the time of task context switching is an important factor that affects performance of RTOS. In this paper, we concentrate on the improvement of task context switch for reducing overhead and achieving fast response time in RTOS. To achieve these goal, we suggest multiple register files and task context switching algorithm. By reducing the context switch overhead, we try to ease scheduling and assure fast response times in multitasking environment. As a result, the context switch overhead decreased by 8~16% depend on the number of register files, and some task set which are not schedulable with single register file are schedulable due to that decrease with multiple register files.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.165-167
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• 2000

This paper presents the influence of the lightning overvoltage and the shielding effects of overhead grounding wire on the DC railway system. Modeling of Railway system is established in ATPDraw to perform simulation. The result of simulation reveals that the shielding effects of overhead grounding wire has over 90% than the case which has not it. Therefore it is evaluated that overhead grounding wire should be installed in the DC railway line.

• ETRI Journal
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• v.42 no.3
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• pp.388-398
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• 2020

We herein propose a heuristic redundancy selection algorithm that combines resubmission, replication, and checkpointing redundancies to reduce the resiliency overhead in fault-tolerant workflow scheduling. The appropriate combination of these redundancies for workflow tasks is obtained in two consecutive phases. First, to compute the replication vector (number of task replicas), we apportion the set of provisioned resources among concurrently executing tasks according to their needs. Subsequently, we obtain the optimal checkpointing interval for each task as a function of the number of replicas and characteristics of tasks and computational environment. We formulate the problem of obtaining the optimal checkpointing interval for replicated tasks in situations where checkpoint files can be exchanged among computational resources. The results of our simulation experiments, on both randomly generated workflow graphs and real-world applications, demonstrated that both the proposed replication vector computation algorithm and the proposed checkpointing scheme reduced the resiliency overhead.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.824-828
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• 2007

With increasing interest in the reduction of cost for operation and maintenance of overhead catenary system, various methods of condition monitoring have been developed and used in with high-speed analysis and advanced image processing techniques. This study utilizes a high-speed camera as inspecting system to measure the wear, stagger, hight and arc extinguishing test of overhead catenary system. All measuring image were captured by a high speed CMOS camera with PCI express output, which can acquire up to 1000 frames per second with the resolution 1024 × 1280 pixels. Line type laser source with a power equal to 300 mW and the National Instrument LabVIEW (8.0) based on vision acquisition software have been used in application programming interface for image acquisition, display, and storage. The proposed high-speed camera system is finally applied to measure the overhead catenary system showing promising on-field applications

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.2
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• pp.12-17
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• 2006

This study uses a characteristic function to explain correlations between the objective function and design variables. For the use, structural analysis and buckling analysis are carried out. the dimensional change of an original overhead crane is made based on the table of orthogonal array. For two functions or more, the effectiveness of design change can be evaluated in accordance with change in design parameters. Also, the overhead crane's weight is reduced by up to 10.55 percent while its structural stability maintained.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.3
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• pp.281-285
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• 2007

Facilities of electric railway should be maintained only at night and it is necessary to maintain by human power because facilities are installed at a high place. This paper presents the development and application of a real-time data acquisition system for the characteristics measurement of overhead contact wires in electric railway. The system is designed to perform in the telemetry environments that developed to store data by wireless in a live wire state of 25 kV power source. The field test results show that the proposed technique and the developed system can be practically applied to measure characteristics of temperature, displacement, and strain on overhead contact lines.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.3231-3244
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• 2016

As processor design has been transiting from homogeneous multicore processor to heterogeneous multicore processor, traditional Amdahl's law cannot meet the new challenges for asymmetric multicore system. In order to further investigate the impact factors related to the Overhead of Data Preparation (ODP) for Asymmetric multicore systems, we evaluate an asymmetric multicore system built with CPU-GPU by measuring the overheads of memory transfer, computing kernel, cache missing and synchronization. This paper demonstrates that decreasing the overhead of data preparation is a promising approach to improve the whole performance of heterogeneous system.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.800-802
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• 1997

After flashover occurs on the overhead distribution line by lighting strokes(direct or induced), the power frequency arc current continues. If lightning flashover occurs on the overhead lines using covered conductors, the power frequency art current with fixed path overheats the conductor, and arc fusion fault can be occurred. There are two categories protecting or reducing methods of arc fusion faults caused by lightning stokes. - Reducing lightning flashover rate : G/W, LA, etc. - Protection by AFPD(Arc Fusion Protection Device) : power follow current interruption. This paper presents lightning surge phenomena on overhead distribution lines and protecting performance of arc fusion Protection devices to the lightning strokes nearby overhead line.

• Proceedings of the KSR Conference
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• 1999.05a
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• pp.151-158
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• 1999

In this study, we developed the simulation program of an overhead catenary-pantograph system, The overhead catenary is modeled with point mass and the pantograph is replaced with 3 d. o. f. model which is composed of mass, spring and damper. Using the developed program, we analyzed the static structure of the overhead catenary and the dynamic characteristics of an overhead catenary-pantograph system such as uplift displacement of contact wire and contact force. we compared the analysis results with the results of GASENDO software developed at RTRI in Japan. The behaviors of uplift displacement of contact wire and contact force were similar with the results of GASENDO software.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1468-1474
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• 2001

In this paper, a new fuzzy-logic anti-swing control scheme is proposed for a three-dimensional overhead crane. The proposed control consists of a position servo control and a fuzzy-logic control. The position servo control is used to control the trolley position and rope length, and the fuzzy-logic control is used to suppress load swing. The proposed control guarantees not only prompt suppression of load swing but also accurate control of trolley position and rope length for the simultaneous travel, traverse, and hoisting motions of the crane. The effectiveness of the proposed control is shown by experiments with a prototype three-dimensional overhead crane.