• Ocean Science Journal
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• v.40 no.2
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• pp.67-78
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• 2005

Complex physical, chemical and biological interactions off the Korean coast created several striking patterns in the phytoplankton blooms, which became conspicuous during the measurements of ocean color from space. This study concentrated on analyzing the spatial and temporal aspects of phytoplankton chlorophyll variability in these areas using an integrated dataset from a Sea-viewing Wide Field-of-view Sensor (SeaWiFS), Advanced Very High Resolution (AVHRR) sensor, and Conductivity Temperature Depth (CTD) sensor. The results showed that chlorophyll concentrations were elevated in coastal and open ocean regions, with strong summer and fall blooms, which appeared to spread out in most of the enclosed bays and neighboring waters due to certain oceanographic processes. The chlorophyll concentration was observed to range between 3 and $54\;mg\;m^{-3}$ inside Jin-hae Bay and adjacent coastal bays and 0.5 and $8\;mg\;m^{-3}$ in the southeast sea offshore waters, this gradual decrease towards oceanic waters suggested physical transports of phytoplankton blooms from the shallow shelves to slope waters through the influence of the Tsushima Warm Current (TWC) along the Tsushima Strait. Horizontal distribution of potential temperature $(\theta)$ and salinity (S) of water off the southeastern coast exhibited cold and low saline surface water $(\theta and warm and high saline subsurface water $({\theta}>12^{\circ}C; S>34.4)$ at 75dBar, corroborating TWC intrusion along the Tsushima Strait. An eastward branch of this current was called the East Korean Warm Current (EKWC), tracked with the help of CTD data and satellite-derived sea surface temperature, which often influenced the dynamics of mesoscale anticyclonic eddy fields off the Korean east coast during the summer season. The process of such mesoscale anticyclonic eddy features might have produced interior upwelling that could have shoaled and steepened the nutricline, enhancing phytoplankton population by advection or diffusion of nutrients in the vicinity of Ulleungdo in the East Sea.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.5
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• pp.469-481
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• 2013

The monitoring of a free surface generated by waterjet cutting technology is very important for an efficient construction process. In this study, experiments using a laser sensor were performed to provide a data processing method and to determine optimized parameters. The experimental parameters here are the angular resolution, measurement distance, and free surface cutting shape. The results show that the monitoring resolution increases with a decrease in the angular resolution and the horizontal measurement distance and with an increase in the cutting (free surface) width. This laser monitoring method can be applied during the measurement of free surface shapes and depths in situ.

• Journal of the Korean Magnetics Society
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• v.22 no.5
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• pp.178-182
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• 2012

This research suggested that the extraction of respiratory rate could be made possible by using frequency analysis in the data process for clip-type pulsimeter equipped with permanent magnet and Hall sensor. The pulse analysis included of cardiac motion information depending on variation of pulse waveforms is investigated by means of Fast Fourier Transformation (FFT). The peaks of FFT spectrums measured at 15, 20, 30, 40, and 50 tempos are coincided to each respiratory rate having 0.125 Hz, 0.16 Hz, 0.25 Hz, 0.33 Hz, and 0.41 Hz, respectively. The FFT spectrum using algorithm for the extraction of respiratory rate showed the best pulse waves measured during 300 s. Based upon these results, the clip-type pulsimeter could extract the effective respiratory rate reflecting physical effects.

• Journal of KIISE:Information Networking
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• v.37 no.5
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• pp.403-408
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• 2010

The sensor nodes can be installed in the environment in which the temperature change is considerable, such as desert, urban, and data center. Particularly, because the output power becomes less than the targeted power if a temperature is increasing, link quality is degraded and packet losses are occurred. In order to compensate the temperature changes, existing schemes detect the change of the link quality between nodes and control transmission power through a series of feedback process. However, these approaches can cause heavy overhead by additional control packets. In this paper, we propose the T2PC(Temperature-aware Transmission Power Control) to keep up the link quality despite temperature variation. At each node, T2PC compensates the attenuated link quality by controlling the transmission power based on the local temperature measurement. In addition, the packet reception ratio can be improved with less control packets than ones required in existing transmission power control methods based on the feedback control.

• Journal of KIBIM
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• v.12 no.4
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• pp.61-69
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• 2022

Earthmoving operations account for approximately 25% of construction cost, generally executed prior to the construction of buildings and structures with heavy equipment. For the successful completion of earthwork projects, it is crucial to constantly monitor earthwork equipment (e.g., trucks), estimate productivity, and optimize the construction process and equipment on a construction site. Traditional methods however require time-consuming and painstaking tasks for the manual observations of the ongoing field operations. This study proposed the use of a GPS sensor embedded in a smartphone for the tracking and visualization of equipment locations, which are in turn used for the estimation and simulation of cycle times and production rates of ongoing earthwork. This approach is implemented into a digital platform enabling real-time data collection and simulation, particularly in a 2D (e.g., maps) or 3D (e.g., point clouds) virtual environment where the spatial and temporal flows of trucks are visualized. In the case study, the digital platform is applied for an earthmoving operation at the site development work of commercial factories. The results demonstrate that the production rates of various equipment usage scenarios (e.g., the different numbers of trucks) can be estimated through simulation, and then, the optimal number of tucks for the equipment fleet can be determined, thus supporting the practical potential of real-time sensing and simulation for onsite equipment management.

• Journal of Software Assessment and Valuation
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• v.16 no.2
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• pp.127-133
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• 2020

As the usages of artificial intelligence is increased, the demand to algorithms for small portable devices increases. Also as the embedded system becomes high-performance, it is possible to implement algorithms for high-speed computation and machine learning as well as operating systems. As the machine learning algorithms process repetitive calculations, it depend on the cloud environment by network connection. For an stand alone system, low power consumption and fast execution by optimized algorithm are required. In this study, for the purpose of smart control, an energy measurement sensor is connected to an embedded system, and a real-time monitoring system is implemented to store measurement information as a database. Continuously measured and stored data is applied to a learning algorithm, which can be utilized for optimal power control, and a system interfacing various sensors required for energy measurement was constructed.

• Tunnel and Underground Space
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• v.34 no.2
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• pp.154-168
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• 2024

The Tunnel Boring Machine (TBM) disc cutter is subjected to wear and damage during the rock excavation process, and the worn disc cutter should be replaced on time. The manual inspection by workers is generally required to determine the disc cutter replacement. In this case, the workers are exposed to dangerous environments, and the measurements are sometimes inaccurate. In this study, we developed a technology that measures the disc cutter wear in real time. From a series of laboratory tests, a magnetic sensor was selected as the wear sensor, and the real-time disc cutter measurement system was developed integrating wireless communication modules, power supply and data processing board. In addition, the measurement system was verified in actual TBM excavation circumstances. As a result, it was confirmed that the accuracy and stability of the system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.497-500
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• 2010

Wireless sensor network is the system for data collection and data process between many nodes. For this work, Synchronization of operation execution and ordering many events are needed. Reference the external time information is the most accurate way to have same time information for all nodes but it's hard to apply these to sensor network. So there are many study of time synchronization there are many error occurred when the time synchronization is executed in the sensor network and minimizing these errors is important. In this paper, we propose how to minimize errors using several time stamp information exchanging when the network is initialized. When the big difference is occurred between receive time and send time in the node communication(cause of traffic overhead and etc), it shows big error of time correction and transfer delay time. but it's hard to detect these errors when it exchanges time stamp information just one time. so we try to reduce these errors using the median value of transfer delay and time correction value with many times of time stamp information exchange.

• The Journal of the Korea Contents Association
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• v.9 no.9
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• pp.31-40
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• 2009

What are important in wireless sensor networks are reliable data transmission, energy efficiency of each node, and the maximization of network life through the distribution of load among the nodes. The present study proposed DSPR, a dynamic unique path routing machanism that considered these requirements in wireless sensor networks. In DSPR, data is transmitted through a dynamic unique path, which has the least cost calculated with the number of hops from each node to the sink, and the average remaining energy. At that time, each node monitors its transmission process and if a node detects route damage it changes the route dynamically, referring to the cost table, and by doing so, it enhances the reliability of the network and distributes energy consumption evenly among the nodes. In addition, when the network topology is changed, only the part related to the change is restructured dynamically instead of restructuring the entire network, and the life of the network is extended by inhibiting unnecessary energy consumption in each node as much as possible. In the results of our experiment, the proposed DSPR increased network life by minimizing energy consumption of the nodes and improved the reliability and energy efficiency of the network.

• Journal of Sensor Science and Technology
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• v.23 no.6
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• pp.377-382
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• 2014

Detecting and segmenting diffuse targets in laser ranging data is a critical problem for tactical reconnaissance. In this study, we propose a new method that facilitates the characterization of diffuse irregularly shaped objects using "spin images," i.e., local 2D histograms of laser returns oriented in 3D space, and a clustering process. The proposed "cluster-based spin imaging" method resolves the problem of using standard spin images for diffuse targets and it eliminates much of the computational complexity that characterizes the production of conventional spin images. The direct processing of pre-segmented laser points, including internal points that penetrate through a diffuse object's topmost surfaces, avoids some of the requirements of the approach used at present for spin image generation, while it also greatly reduces the high computational time overheads incurred by searches to find correlated images. We employed 3D airborne range data over forested terrain to demonstrate the effectiveness of this method in discriminating the different geometric structures of individual tree clusters. Our experiments showed that cluster-based spin images have the potential to separate classes in terms of different ages and portions of tree crowns.