• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.2
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• pp.15-22
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• 1998

The effects of shot peening an the fatigue strength are studied in this paper. Applying the multistage shot peening on the material. the relation between the residual stress and fatigue strength compressive is investigated. Observing tensile strength elongation. reduction of area. hardness. and roughness. the results can be summarized as follows ; 1.The change of mechanical properties is small before and after the shot peening is carried out. The change of hardness is also small in high hardness material. 2.The surface roughness does not affect the fatigue strength. but the surface roughness is improved by multi-stage shot peening. 3.The fatigue strength of multi-stage shot peening material is 756MPa and is 1.78 times higher than that of un-peened material. 4.The maximum compressive residual strength of multi-stage shot peening material is -792MPa the fatigue strength seems to be improved by residual stress.

• International Journal of Reliability and Applications
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• v.3 no.3
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• pp.133-145
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• 2002

The traditional methods of evaluating the performance of a network by enumerating all possible states may quickly become computationally prohibitive, since the number of states grows exponentially as the number of components increases. In such cases, enumerating only the most probable states would provide a good approximation. In this paper, we propose a method which efficiently generates upper and lower bounds for coherent performance measures utilizing the most probable states. Compared with Yang and Kubat's method, our procedure significantly reduces the complexity and memory requirement per iteration for computing the bounds and thereby, achieves the given degree of accuracy or the coverage within a shorter time.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.765-770
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• 1999

The purpose of this study is to obtain land classification map by using remotely sensed data; Landsat TM and SPOT panchromatic, and to compare their results with statistical data and digitized coverage from topographic paper map. The classification was conducted by maximum likelihood method with training sets. The best result was obtained from the Landsat TM merged by SPOT Panchromatic, that is, similar with statistical data. This is caused by setting more precise training sets with the enhanced spatial resolution by using SPOT Panchromatic. The classified map may be useful as a fundamental data to estimate pollutant load in regional scale of agricultural watershed.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.191-196
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• 2005

The effects of shot peening on the fatigue strength of SK-5M steel is investigated by experiment. The shot peening process is investigated optimum peening condition by changing impeller speed and exposure time. Bending fatigue test is accomplished to investigate the effect of optimum peening condition on the fatigue characteristics. As exposure time is increased, fatigue life in high stress is increased in early stage, become the maximum from 60 to 100 seconds, and then is decreased. Observing fracture surface through SEM after fatigue test, we can see clear configuration of cracks and peening layer.

• Journal of information and communication convergence engineering
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• v.10 no.3
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• pp.276-283
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• 2012

Nowadays, wireless sensor networks (WSNs) comprise a tremendously growing infrastructure for monitoring the physical or environmental conditions of objects. WSNs pose challenges to mitigating energy dissipation by constructing a reliable and energy saving network. In this paper, we propose a novel network construction and routing method by defining three different duties for sensor nodes, that is, node gateways, cluster heads, and cluster members, and then by applying a hierarchical structure from the sink to the normal sensing nodes. This method provides an efficient rationale to support the maximum coverage, to recover missing data with node mobility, and to reduce overall energy dissipation. All this should lengthen the lifetime of the network significantly.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.3 no.4
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• pp.76-82
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• 2010

For the purpose of controlling the beam tilt angle of the base station sector array antenna, phase shifter is used. Phase angles of this antenna depending on the tilt angles are designed, and the patterns on the vertical and horizontal planes are simulated and analyzed for the evaluation of base station antenna. This analysis is used in the optimal design of base station antenna because of maximum cell coverage and incremented traffic capacity, decreased interference.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.796-800
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• 2011

As the increasing integrity of VLSI, the BIST(Built-In Self Test) is used as an effective method to test chips. Generally the pseudo-random test pattern generation is used for BIST. But it requires too many test patterns when there exist random resistant faults. Therefore we propose a mixed test scheme which applies to the circuit under test, a deterministic test sequence followed by a pseudo-random one. This scheme allows the maximum fault coverage detection to be achieved, furthermore the silicon area overhead of the mixed hardware generator can be reduced.

• Journal of Information Technology Services
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• v.18 no.1
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• pp.141-151
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• 2019

To protect workers from industrial accidents, IoT hazard detection system using LoRa network was designed and fabricated. LoRa networks can operate with low power consumption, wide coverage, and low usage fees. The hazard detection system consists of a sensor unit, a transceiver module, a LoRa base station, ThingPlug, and a monitoring device. We have designed an optimal risk-determining algorithm that can send information quickly in a working environment. As measured by TTA, the implemented system has been found to be able to deliver the worker's location, ambient temperature, and carbon monoxide density to the administrator through the user interface. The implemented system showed a bit rate of 290bps and a maximum application range of 6 km.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.396-404
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• 2021

It is important to verify that the contracted speed-power performance of a ship is satisfied in sea trials. International Organization for Standardization (ISO) has published the procedure for measuring and assessing ship speed during sea trials. The results obtained from actual sea conditions inevitably include various uncertainty factors. In this study, double run tests were performed on one container ship to analyze the uncertainty of sea trial on three maximum continuous rating conditions. The uncertainty factors and scale of uncertainty were examined based on the measured raw data during sea trial. The results indicate that the expanded uncertainty for ideal power performance is approximately ±1.4% at 95% confidence level (coverage factor k = 2) and most of the uncertainty factors were because of the shaft power measurement system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.12
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• pp.4492-4507
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• 2021

In camera sensor networks (CSNs), in order to better identify the point, full-view problem requires capture any facing direction of target (point or intruder), and its coverage prediction and sensor density issues are more complicated. At present, a lot of research supposes that a large number of homogeneous camera sensors are randomly distributed in a bounded square monitoring region to obtain full-view rate which is close to 1. In this paper, we deduce the sensor density prediction model in heterogeneous deployed CSNs with arbitrary full-view rate. Aiming to reduce the influence of boundary effect, we introduce the concepts of expanded monitoring region and maximum detection area. Besides, in order to verify the performance of the proposed sensor density model, we carried out different scenarios in simulation experiments to verify the theoretical results. The simulation results indicate that the proposed model can effectively predict the sensor density with arbitrary full-view rate.