• Smart Structures and Systems
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• v.30 no.5
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• pp.433-446
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• 2022

Despite efforts to reduce unexpected accidents at confined construction sites, choking accidents continue to occur. Because of the poorly ventilated atmosphere, particularly in long, confined underground spaces, workers are subject to dangerous working conditions despite the use of artificial ventilation. Moreover, the traditional monitoring methods of using portable gas detectors place safety inspectors in direct contact with hazardous conditions. In this study, a long-range (LoRa)-based wireless safety monitoring system that features the network organization, fault-tolerant, power management, and a graphical user interface (GUI) was developed for underground construction sites. The LoRa wireless data communication system was adopted to detect hazardous gases and oxygen deficiency within a confined underground space with adjustable communication range and low power consumption. Fault tolerance based on the mapping information of the entire wireless sensor network was particularly implemented to ensure the reliable operation of the monitoring system. Moreover, a sleep mode was implemented for the efficient power management. The GUI was also developed to control the entire safety-monitoring system and to manage the measured data. The developed safety-monitoring system was validated in an indoor testing and at two full-scale water pipeline construction sites.

• KSBB Journal
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• v.21 no.5
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• pp.325-330
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• 2006

This study presents the characterization of an integrated portable microfluidic electrical detection system for fast and low volume immunoassay using polystyrene microbead, which are used as immobilization surfaces. In our chip, a filtration method using the microbead was adopted for sample immobilization and immunogold silver staining(IGSS) was used to increase the electrical signal. The chip is composed of an inexpensive and biocompatible Polydimethylsiloxane(PDMS) layer and Pyrex glass substrate. Platinum microelectrodes for electric signal detection were fabricated on the substrate and microchannel and pillar-type microfilters were formed in the PDMS layer. With a fabricated chip, we reacted antigen and antibody according to the procedures. Then, silver enhancer was injected to increase the size of nanogold particles tagged with the second antibody. As a result, microbeads were connected to each other and formed an electrical bridge between microelectrodes. Resistance measured through the electrodes showed a difference of two orders of magnitude between specific and nonspecific immuno-reactions. The detection limit was 10 ng/ml. The developed immunoassay chip reduced the total analysis time from 3 hours to 50 min. Fast and low-volume biochemical analysis has been successfully achieved with the developed microfilter and immuno-sensor chip, which is integrated to the microfluidic system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.7
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• pp.1364-1370
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• 2017

This paper proposes a method that automatically sets profile schedule context-based mobile phone by collecting the user's external situation based on the GPS sensor and accelerometer built into the smartphone and interacting with the data in the user's schedule to minimize the user's handset handling. However, real-time data collection in mobile phones causes energy shortage in the device due to battery consumption. In other words, a service control method is explained in a way that can efficiently handle resource consumption because accessing a measurement device such as GPS and other sensors may increase power consumption of the portable device. Therefore, effective data sharing for context awareness to reduce weekly schedules and smartphone mode has improved energy efficiency in sensing for data collection. The user can use the context more effectively by providing environmental adaptability for various situations such as the end user's local context and smartphone force control.

• Journal of the Korean Institute of Gas
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• v.18 no.3
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• pp.1-12
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• 2014

In this paper, we developed an explosion proof type and portable combustible gas leak detector and proposed an algorithm to improve the accuracy for measuring gaseous concentrations. The nation's first we developed an infrared gas leak detector with explosion proof standard(Ex d ib) and improved measuring accuracy by using linearization recursion equation and 2nd Lagrange interpolation polynomial. Together, we advanced their performances and added their easy functions after investigating field demands. To compare our and other company's detectors, we performed measurement tests with eight standard gases made by Korea Gas Safety Corporation. We demonstrated the excellence of our instruments in measuring accuracy other than detecters through experimental results.

• Journal of Sensor Science and Technology
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• v.17 no.2
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• pp.87-94
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• 2008

Blood pressure (BP), one of the most important vital signs, is used to identify an emergency state and reflects the blood flow characteristics of the cardiovascular system. The conventional noninvasive method of measuring BP is inconvenient because patients must wear a cuff on their arm and the measurement process takes time. This paper proposes an algorithm for estimating the BP using the pulse transit time (PTT) of the photoplethysmography (PPG) and pressure pulse from finger at the same time as a more convenient way to measure the BP. After recording the electrocardiogram (ECG), measuring the pressure pulse, and performing PPG, we calculated the PTT from the acquired signals. Then, we used a multiple regression analysis to measure the systolic and diastolic BP indirectly. Comparing the BP measured indirectly using the proposed algorithm and the real BP measured with a sphygmomanometer, the systolic pressure had a mean error of ${\pm}3.240$ mmHg and a standard deviation of 2.530 mmHg, while the diastolic pressure had a satisfactory result, i.e., a mean error of ${\pm}1.807$ mmHg and a standard deviation of 1.396 mmHg. These results are more superior than existing method estimating blood pressure using the one PTT and satisfy the ANSI/AAMI regulations for certifying a sphygmomanometer i.e., the measurement error should be within a mean error of ${\pm}5$ mmHg and a standard deviation of 8 mmHg. These results suggest the possibility of applying our method to a portable, long-term BP monitoring system.

• Journal of Biosystems Engineering
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• v.34 no.6
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• pp.462-469
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• 2009

The aim of this study was to develop a portable electronic nose system for freshness measurement of stored pork. An electronic nose system was constructed using seven different MOS sensor array. To determine the quality change of pork with storage time, the samples were divided into ten groups in terms of storage time with an increment of 2 day up to 19 storage days. GC-MS, total bacteria's count (TBC), thiobarbituric acid reactive substance (TBARS), and pH analyses as well as the analysis of the electronic nose system measurement were performed to monitor the freshness change of the samples. To investigate the performance of the electronic nose system for detecting the change of freshness of pork, the acquired signal values of the system were compared with those of GC-MS, TBC, TBARS, and pH analysis values. According to principal component analysis (PCA) and linear discriminant analysis (LDA) with the signals of the electronic nose system for the pork samples, the sample groups were clearly separated into two groups of 1-9 days and 11-19 days, and four groups of 1-3 days, 5-9 days, 11 days, and 13-19 days respectively. The results show that the electronic nose system has potential for evaluating freshness of pork.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.6
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• pp.65-73
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• 2012

Wrist wearable device for the measurement of pulse rate, ECG, and activity during normal daily life, which could be used for the continuous monitoring and remote transmission of acquired data, was developed. Pressure sensor, device attached electrodes, and 3-degree accelerometer were used. Analysis algorithm and firmware program were established for providing diagnostic information for the users. Results of this study, possible for the management of health report and transmission of the results through bluetooth by wearing simple personal wrist device, could be used for the development of portable device in the u-healthcare environment.

• Journal of Sensor Science and Technology
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• v.12 no.6
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• pp.258-264
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• 2003

The present paper studies how to calibrate hydrometer using image process. The method aligns particular scales of hydrometer selected for calibrating the hydrometer with the horizontal plane of the reference liquid automatically without man's operation. Major parts composing the system are CCD camera, frame grabber, stepping motor and image process program. The image process program is composed of a part that locates the meniscus and aligns it with a scale and a part that controls the step motor. To verify the performance of the developed method, this study compares the meniscus and scale observed directly with the naked eye with the result of calibration by the manual calibration method. The differences between the corrections were less than $0.004\;kg/m^3$ with uncertainty of $0.06\;kg/m^3$. These showed that the calibration results of the developed hydrometer calibration using image process nearly equal to manual method.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.10
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• pp.35-42
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• 2011

WPAN(Wireless Personal Area Network) have many advantages such as using low power and cheap price, small size. So it is recently increasing application range such as personal portable device, home network and sensor network so and on. IEEE 802.15.3 basically has the point to point or peer to peer UM(Usage Model). But using devises that need data transmission is increasing in the house and office. Therefor UM of point to multipoint is proposed. In this paper, I proposed Multicast ACK mechanism on the point to multipoint UM. So it is able to transfer data to multiple devices as this Multicast transfer method at a time. Thus, throughput performance is improved. But the problem that increases data transfer delay is appeared because of adding Multicast ACK traffic. We compared the performance between standard and proposed mechanism through a numerical analysis.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1246-1247
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• 2008

With recent advanced in portable electric devices, wireless sensor, MEMS and bio-Mechanics device, the new typed power supply, not conventional battery but self-powered energy source is needed. Particularly, the system that harvests from their environments are interests for use in self powered devices. For very low powered devices, environmental energy may be enough to use power source. Therefore, in other to made piezoelectric energy harvesting device, PMN-PZT thick film was formed by the screen printing method on the Ag/Pd coated alumina substrate. The layer was 8 layers and slurry where a-terpineol, ethycellulose, ferro B-75001 as Vehicle, PMN-PZT powder used are fabricated by ball mill. The output power quality was be also investigated by changing the load resistance, weight and frequency. The made piezoelectric energy harvesting device was resulted from the conditions of 33$k{\Omega}$, 0.25g, 197Hz respectively. The thick film was prepared at the condition of 2.75Vrms, and its power was 230${\mu} W$ and its thickness was 56${mu}m$. The piezoelectric energy harvesting device output voltage was increased, when the load weight, load resistance was increasing and resonance frequency was diminishing. The other side, resonance frequency was diminished, when the weight was increasing. And output power was continuously it changed by load resistance, output voltage, weight and resonance frequency.