• The Journal of the Acoustical Society of Korea
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• v.19 no.2
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• pp.46-53
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• 2000

In coastal bay waters, bubbles are generated by relatively heavy ship-traffic, breaking waves due to man-made structures and biological activities. Therefore, the bubble-generating mechanism as well as the bubble density distribution in the bay are quite different from the open ocean where breaking waves are major contributor for bubble density distribution. High frequency surface-backscattered signals were obtained in the coastal bay waters and they were analyzed to compare with those from the open waters in terms of the sea-surface backscattering strength at various grazing angles, the reverberation characteristics in the sub-surface layer and spectral spreading of the scattered signals. The results show that, the surface scattered signals have an irregular distribution of amplitude in time and the width of the spectral spreading is wider than that of the open sea with rough surface. Furthermore, the amplitude distribution of the reverberation signals is not following the Rayleigh distribution, that is eon to be a typical pattern for the open ocean. The results of our analysis imply that the bubble size and the bubble density in the bay are quite different from those observed in the open waters.

• Journal of Advanced Navigation Technology
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• v.19 no.6
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• pp.558-563
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• 2015

There have recently been various services that use indoor location estimation technologies. Representative methods of location estimation include fingerprinting and triangulation, but they lack accuracy. Various kinds of research which apply existing location estimation methods like AOA, TOA, and TDOA are being done to solve this problem. In this paper, we study the location estimation algorithm based on AOA using a RSSI difference in indoor environments. We assume that there is a single AP with four antennas, and estimate the angle of arrival based on the RSSI value to apply the AOA algorithm. To compensate for RSSI, we use a recursive averaging filter, and use the corrected RSSI and the Pythagorean theorem to estimate the angle of arrival. The results of the experiment, show an error of 18% because of the radiation pattern of the four non-directional antennas arranged at narrow intervals.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.11
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• pp.2379-2384
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• 2010

The reception quality of broadcasting in car radio system may become poor due to the noise such as week signal strength, multipath, Adjacent Channel and so on. To improve this, some european nations and US. serve RDS(Radio Data System) on FM radio, AF(Alternative Frequency) and PI(Programme Identification) code contained information in RDS data are used to switch to the broadcasting having the best reception quality. There are many techniques and studies of maintaining the best reception quality. But many previous techniques are no longer the best way because RF chips are improved every year and noise components can be distinguished in detail. So this research will suggest the best switching technique to maintain the best reception quality.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.7
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• pp.528-537
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• 2014

As the data traffic between ships and a land station continuously increase through the shipbuilding-IT convergence, several wireless communication technologies are being studied to process large amounts of data traffic. In particular, the multi-antenna system is one of the most expected technologies to provide high throughput. This paper proposes an algorithm for the base station to select the ship in consideration of channel characteristics and the transmission angle for a beam of the land station in spatial multiplexing marine communication systems. We increase the system capacity by maximizing the received signal strength of the ship using clustering characteristic of the radio channel. Also, we reduce the time to select the ship by excluding the ship with the large interference between the beams. On our computer simulation, the proposed scheme dramatically reduces the computational complexity with a little sacrifice of the throughput.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.4
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• pp.371-377
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• 2013

Fishing boats more than 5 tons is obliged to VHF DSC by Fishing Vessels Act and Vessel Safety Act. The owner of the fishing vessel is equipped to the automatic position reporting device in accordance with the Notice of the Minister of Land, Transport and Maritime Affairs to regulations, shall be ensure to navigations safety and in order to respond quickly in the event of maritime accidents on fishing vessels. East sea set up to start in 2012, which is now underway the annual install plain to the yellow sea and the south sea for VHF coast stations. It is web-based remote operation of DSC on the remote control and monitoring in Fishery Information Communication Station for the coastal VMS construction project. All fishing vessels is VHF DSC in conjunction with the GPS that location information transmitted to the coast station. automatically by the DSC call. This paper has been studied on the communications coverage set up and traffic operation for realization a roaming service by navigation route tracking and RSSI techniques in parallel algorithm refer to VHF DSC coast stations in east sea.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.837-845
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• 2016

Providing a customer with tailored location-based services (LBSs) is a fundamental problem. For location-estimation techniques with radio-based measurements, LBS applications are widely available for mobile devices (MDs), such as smartphones, enabling users to run multi-task applications. LBS information not only enables obtaining the current location of an MD but also provides real-time push-pull communication service. For indoor environments, localization technologies based on radio frequency (RF) pattern-matching approaches are accurate and commonly used. However, to survey radio information for pattern-matching approaches, a considerable amount of time and work is spent in indoor environments. Consequently, in order to reduce the system-deployment cost and computing complexity, this article proposes an indoor positioning approach, which involves using Asus Xtion to facilitate capturing RF signals during an offline site survey. The depth information obtained using Asus Xtion is utilized to estimate the locations and predict the received signal strength (RF information) at uncertain locations. The proposed approach effectively reduces not only the time and work costs but also the computing complexity involved in determining the orientation and RF during the online positioning phase by estimating the user's location by using a smartphone. The experimental results demonstrated that more than 78% of time was saved, and the number of samples acquired using the proposed method during the offline phase was twice as much as that acquired using the conventional method. For the online phase, the location estimates have error distances of less than 2.67 m. Therefore, the proposed approach is beneficial for use in various LBS applications.

• Journal of KIISE
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• v.42 no.6
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• pp.807-816
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• 2015

The Internet of Things (IoT) has recently been showered with much attention worldwide. Various kinds of devices, communicating with each other in the IoT, demand multiple communication technologies to coexist. In this environment, mobile devices may utilize the vertical handover between different wireless radio interfaces such as Wi-Fi and Bluetooth, for efficient data transfer. In this paper, an IoT broker is implemented to support the vertical handover, which can also support and manage heterogeneous devices and communication interfaces. The handover is activated based on RSSI, Link Quality values, and real time traffic. The experimental results show that the proposed handover system substantially improves QoS in Bluetooth and reduces power consumption in mobile devices as compared with a system using only Wi-Fi.

• Microbiology and Biotechnology Letters
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• v.47 no.4
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• pp.662-666
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• 2019

In this study, the NABH558 gene expression system was constructed to efficiently produce neoagarobiose hydrolase (NABH) in Saccharomyces cerevisiae strain. The ADH1 and GAL10 promoters of the pAMFα-NABH and pGMFα-NABH plasmids were examined to determine the suitable promoter for the NABH558 gene expression, respectively. The effect of promoter and carbon sources on NABH558 gene expression was investigated by transforming each plasmid into the S. cerevisiae 2805 strain. The NABH activity in the 2805/pAMFα-NABH strain was 0.069 unit/ml/DCW in YPD medium, whereas that in the 2805/pGMFα-NABH strain was similar (0.02-0.027 unit/ml/DCW) irrespective of the medium composition. The higher NABH activity in the YPD medium was due to the increased NABH558 gene transcription. NABH produced in the recombinant strains could degrade agarose to galactose and AHG. This indicated that ADH1 promoter was a more optimal promoter for the expression of NABH558 gene than the GAL10 promoter. The NABH activity induced by the ADH1 promoter was about 3-fold higher than that induced by the GAL10 promoter.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.7
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• pp.2414-2434
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• 2015

Among numerous localization schemes proposed specifically for Wireless Sensor Network (WSN), the range-free localization algorithms based on the received signal strength indication (RSSI) have attracted considerable research interest for their simplicity and low cost. As a typical range-free algorithm, Approximate Point In Triangulation test (APIT) suffers from significant estimation errors due to its theoretical defects and RSSI inaccuracy. To address these problems, a novel localization method called FIAPIT, which is a combination of an improved APIT (IAPIT) and a fuzzy logic system, is proposed. The proposed IAPIT addresses the theoretical defects of APIT in near (it's defined as a point adjacent to a sensor is closer to three vertexes of a triangle area where the sensor resides simultaneously) and far (the opposite case of the near case) cases partly. To compensate for negative effects of RSSI inaccuracy, a fuzzy system, whose logic inference is based on IAPIT, is applied. Finally, the sensor's coordinates are estimated as the weighted average of centers of gravity (COGs) of triangles' intersection areas. Each COG has a different weight inferred by FIAPIT. Numerical simulations were performed to compare four algorithms with varying system parameters. The results show that IAPIT corrects the defects of APIT when adjacent nodes are enough, and FIAPIT is better than others when RSSI is inaccuracy.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.3
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• pp.331-339
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• 2016

Real time location (RTL) system which can control the safety of laborers in the underground space is developed in this study. This innovative system can monitor the location and history of movement of multiple laborers in real time. To accommodate constrains of the underground space, the system is portable and composed with low-battery mode. Since conventional method to detect the location of laborer with radio signal strength indicator (RSSI) contains high errors, new measurement system using accelerometers and correction method are suggested in this study. Field test is performed to validate the developed system. The error for moving laborer was 0.4 m and for non-moving laborers was 0.2 m. Thus, it is found that the new RTL system can be used to monitor the location of laborers in the underground construction space.