• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.10
• /
• pp.2006-2013
• /
• 2015

In this paper we propose a multi-protocol gateway system based on low power wireless communications. The proposed multi-protocol gateway system was designed to allow real-time monitoring and control of the on-site situation through wired and wireless networks by gathering information for streetlight power control and environmental monitoring. The sensing data using multi-sensors with composite processing that selectively used wired or wireless communication (e.g., CDMA, Ethernet (TCP/IP), GPS, etc.) were designed to act as intermediaries that transmitted to the main server through ZigBee. Inaddition, they were designed by separating a CPU board and baseboard to ensure low maintenance cost and ease of hardware replacement. The proposed multi-protocol gateway system's power, impact, continuous operation stability, and immunity test results obtained a normal operation success rate of over 95% and normal continuous operation results. Moreover, in the voltage drop test, instantaneous immunity test, and conductive RF electromagnetic field immunity test, it obtained an average rating result of "A".

• Journal of Korean Society of Disaster and Security
• /
• v.14 no.1
• /
• pp.9-21
• /
• 2021

Recently, the importance of eco-friendly power generation facility using renewable energy has newly appeared. Hydropower plant is a very important source of electricity generation and supply which is very important to secure safety because it is commonly connected with multi facility and operated on a large scale. In this study, a scenario-based analysis method was suggested to assess vulnerability of a penstock system caused by water hammer commonly occurred in the operation of hydropower plants. A hypothetical hydropower plant was used to demonstrate the applicability of a transient analysis model. In order to verify reliability of the model, the prediction of pressure behaviors were compared with the results of commercial model (SIMSEN) and measured data, then a real hydroelectric power plant was applied to develop all potential water hammer scenarios during the actual operation. The scenario-based simulation and vulnerability assessment for water hammer in the penstock system were performed with internal and external load conditions. The simulation results indicated that the vulnerability of a penstock system was varied with the operating conditions of hydropower facilities and significantly affected by load combination consisting of different load scenarios. The proposed numerical method could be an useful tool for the vulnerabilityty assessment of the hydropower plants due to water hammer.

• Journal of the Society of Naval Architects of Korea
• /
• v.49 no.3
• /
• pp.273-279
• /
• 2012

The concept of the Mobile Harbor had been made recently as a kind of feeder vehicle to transfer a certain amount of container boxes (i.e. 250 TEU at a time) from main ocean container vessels over 5,000 TEU capacity to the container terminal on land. In a harbor a short distance apart from the land, the container loading/unloading operation has to be performed on the main deck of the Mobile Harbor using the container cranes in the state of side-by-side mooring with protection of fenders and robot arms in the gap. Even under the ocean condition of the sea state class 2 or 3, the operation has to be confirmed to be safely performed. In this situation, the floating bodies considering the multiple-body interaction effect also has to be examined whether they might behave safely or not. Especially, this study focuses on the dynamic behavior of the Mobile harbor when a container box is hanged on the crane and the impact load due to the slewing motion is imposed in a certain sea state. The motion response should be controlled within the motion level to assure the safe operation.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.6 no.3
• /
• pp.71-76
• /
• 2007

The fatalities of pedestrian account for about 40.0% of all fatalities in Korea 2005. Vehicle-Pedestrian accident generates trajectory of pedestrian. In pedestrian involved accident, the most important data to inspect accident is throw distance of pedestrian. The throw distance of pedestrian can be influenced by many variables. The variables that influence trajectory of pedestrian can be classified into vehicular factors, pedestrian factors, and road factors. Vehicular factors are the frontal shape of vehicle, impact speed of vehicle, the offset of impact point. Many studies have been done about the relation between impact speed and throw distance of pedestrian. But the influence of the offset of impact point was neglected. The influence of the offset of impact point was analyzed by Working Model, and the trajectory of pedestrian, dynamic characteristics of multi-body were analyzed by PC-CRASH, a kinetic analysis program for a traffic accident. Based on the results, the increase of offset reduced the throw distance of pedestrian. However box type vehicle just like bus, the offset of impact point did not influence the throw distance of pedestrian considerably.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.9
• /
• pp.995-1000
• /
• 2016

The maximum cross-correntropy (MCC) algorithm with a set of random symbols keeps its optimum weights undisturbed from impulsive noise unlike MSE-based algorithms and its main factor has been known to be the input magnitude controller (IMC) that adjusts the input intensity according to error power. In this paper, a normalization of the step size of the MCC algorithm by the power of IMC output is proposed. The IMC output power is tracked recursively through a single-pole low-pass filter. In the simulation under impulsive noise with two different multipath channels, the steady state MSE and convergence speed of the proposed algorithm is found to be enhanced by about 1 dB and 500 samples, respectively, compared to the conventional MCC algorithm.

• Applied Chemistry for Engineering
• /
• v.24 no.2
• /
• pp.214-218
• /
• 2013

Nylon66/multi-walled carbon nano tube (MWCNT) composites were fabricated by twin screw extruder. The contents of MWCNT were 1, 3, 5, and 7 wt%. Thermal properties, dispersion, rheological and impact properties were measured by DSC, TGA, X-ray diffraction (XRD), SEM, Dynamic rheometer, and Izod impact tester. The effect of MWCNT on the non-isothermal crystallization of Nylon66 was confirmed by DSC. The complex viscosity at low frequency and the shear thinning tendency of the composites increased with MWCNT content. An increase in the elasticity was confirmed from the decrease in the slop of G'-G" plot. Izod impact strengths of the composites were analyzed as a measure of mechanical properties, which indicated that the composites exhibit a 60% enhancement for the impact strength when 3 wt% MWCNT was added. The dispersion of MWCNT within Nylon66/MWCNT composites was also checked by SEM.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.8 no.6
• /
• pp.923-931
• /
• 2013

RFID (Radio Frequency Identification), which is a kind of the electronic tag, is a wireless access device using the radio frequency for recognizing the ID information. It has a variety of application such as the bus card, gate access card, distribution industry, and management of construction materials. The performance and size of RFID depend on the penetrability, recognition ratio, memory size, multi tag recognition, external pollution dust, and exterior impact, and RFID requires the packaging to protect itself considered above factors. Recently, RFID is diversely employed to effectively manage construction materials and the RFID packaging, which is robust to the external impact, is required to attach RFID on construction materials. In this paper, we propose the construction material RFID packaging designed to be robust for the external impact and to be practicable for change of the broken RFID. For the change of RFID, we separate the cast and body of the packaging. Also, we present the detail drawing for the proposed construction material RFID packaging and implement the performance evaluation of the packaging manufactured using 3D printer.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.28 no.2
• /
• pp.144-150
• /
• 2008

In this study, the PVDF (polyvinylidene fluoride) piero-film sensor was applied to measure the internal quality of apple. The developed sensor detected the response signal through apple after mechanical impact on the surface of apple. The acoustical parameters at time domain such as rise time (RT), ring down count (RC), energy (EN), event duration (ED) and peak amplitude (PA) and acoustical parameter at frequency domain such as spectral density (SE) were analyzed. The size of waveform decreased as storage time of apple increased. The frequency at maximum magnitude was shifted to lower frequency band according to the storage time. The acoustical parameters showed strong relationship with storage time. The multiple linear regression equation was developed to estimate storage time of apple using the acoustical parameters at time domain and its coefficient of determination was 0.97. The internal quality of apple according to storage time is predictable using developed PVDF sensor and acoustical parameters defined in this study.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.11a
• /
• pp.177-180
• /
• 2010

Two-stage light gas gun, sorted with Ballistic Range System, is used to research spray characteristics of supersonic liquid jets. When high pressure tube was pressurized to the 135 bar, diaphragm films which composed with OHP film are ruptured. Expansion gases accelerate a projectile approximately 250 m/s at the exit of pump tube. And accelerated projectile collides with liquid storage part and liquid jets were injected into supersonic conditions. Supersonic liquid jets show the multiple jets and generate shockwave at the forward region of jets. Supersonic liquid jets of speed and shockwave angle have different value at each case. Supersonic liquid jets with minimum velocities are injected with M=1.53 at the geometry condition of L/d=23.8.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.9
• /
• pp.234-242
• /
• 2018

This descriptive study aims to examine the factors that influence nursing students' adaptation to clinical practice. Data was collected from 180 nursing students between April 26 and May 4, 2018. A self-reporting questionnaire was employed, which comprised of 17 questions regarding transition shock, 24 questions about social support, two questions regarding the levels of preparedness for clinical practice, and 14 questions about the degree of adaptation to clinical practice. Collected data was analyzed using t-test, one-way analysis of variance, and stepwise multiple regression, as well as by calculating the Pearson correlation coefficient. Subjects' degree of adaptation to clinical practice had a negative correlation with their transition shock. The degree of adaptation had a positive correlation with the levels of preparedness for clinical practice (r = 0.35) and the sub-variables of social support in the domains of friends (r = 0.24), parents (r = 0.32), and professors (r = 0.38). The smaller the transition shock (B = -0.409) and the greater the levels of preparedness (B = 0.766), professorial support (B = 0.228), and parental support (B = 0.163), the higher the degree of adaptation to clinical practice. Transition shock had the greatest influence on the degree of adaptation to clinical practice felt by subjects, followed by their level of preparedness for clinical practice and professorial support. Hence, to increase the degree of adaptation to clinical practice, not only should individual nursing students be better prepared to conduct clinical practice and professors provide greater support, but also there needs to be measures implemented to reduce transition shock.