• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.9
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• pp.687-699
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• 2013

IP-based IP-USN overcomes that disadvantages of verify the existence and geographic limits of the sensor by applying a standard technique called 6LoWPAN. However, in terms of the management and cost, The USN node should work for a long period of time without periodic batter replacement. but this solution is insufficient.In this paper, we configure the node using TI's CC2530 that low-power Soc solution and Contiki OS for optimal low-power operation IP-USN and implement the gateway to support connecting IP networks and Sensor networks. In addition, a system implemented to measure and analyze the energy consumption of an independent power supply to look for ways.

• Journal of Advanced Navigation Technology
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• v.24 no.2
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• pp.61-66
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• 2020

Since the ocean accounts for 70.8 percent of the earth's surface, the success of IoT technology in the marine industry is to collect information from devices placed in a wider range. LPWA is a feature with a wide range of communication and is very suitable for deployment in the ocean. In this paper, the real-sea performance distance experiment was carried out based on Private LoRa, a key technology for executing the electronic phrase real-name system. A private LoRa module based on sx1276 was developed, and Gateway was developed to transfer data received by private LoRa to the server using SKT Cat. M1. After installing gateways at 599 meters above sea level and experimenting with data transmission and reception at 25 km, 40 km and 60 km, we were able to see that the communication success rate was obtained to be 96.1%. 97.1% and 96.2% respectively.

• Journal of Korea Society of Industrial Information Systems
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• v.18 no.2
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• pp.35-40
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• 2013

In this paper, we propose a new image rejection receiver architecture using simultaneously the high-side and low-side injected LO signals. The proposed architecture has a lower noise figure (NF) performance and a higher linearity characteristic than the previous receiver architecture using a single LO signal. Also, the proposed receiver shows a higher IRR performance about 6dB than that of the previous Weaver image rejection architecture even though the same gain and phase errors between I-path and Q-path exist. To verify these characteristics, we derive an IRR formular of the proposed architecture as a function of mismatch parameters. And we demonstrate its formular's usefulness through the system simulation. Therefore, the proposed architecture will be widely used to implement the image rejection receiver due to its higher IRR performance.

• International journal of advanced smart convergence
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• v.7 no.3
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• pp.23-36
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• 2018

In wireless communication, efficient spectrum usage is an issue that has been an attractive research area for many technologies. Recently new technologies innovations allow compact radios to transmit with power efficient communication over very long distances. For example, Low-Power Wide Area Networks (LPWANs) are an attractive emerging platform to connect the Internet-of-Things (IoT). Especially, LoRa is one of LPWAN technologies and considered as an infrastructure solution for IoT. End-devices use LoRa protocol across a single wireless hop to communicate to gateway(s) connected to the internet which acts as a bridge and relays message between these LoRa end-devices to a central network server. The use of the (ISM) spectrum sharing for such long-range networking motivates us to implement spectrum sensing testbed for cognitive radio network based on LoRa and GNU radio. In cognitive radio (CR), secondary users (SUs) are able to sense and use this information to opportunistically access the licensed spectrum band in absence of the primary users (PUs). In general, PUs have not been very receptive of the idea of opportunistic spectrum sharing. That is, CR will harmfully interfere with operations of PUs. Subsequently, there is a need for experimenting with different techniques in a real system. In this paper, we implemented spectrum sensing for cognitive radio networks based on LoRa and GNU Radio, and further analyzed corresponding performances of the implemented systems. The implementation is done using Microchip LoRa evolution kits, USRPs, and GNU radio.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.6
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• pp.34-40
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• 2011

From the present paper researched about the Design of Image Rejection SSB Modulator for X-Band Monopulse RADAR using Waveguide Hybrid Coupler. Generally, SSB modulator mixes IF(RF) and LO signals, and then it converts to RF(IF) frequency band. In this case, in order to transmit one sideband from RF band, SSB modulator is demanded the removal of image and LO signal. The balanced mixer was designed using waveguide hybrid coupler and crystal mixer diode to mix LO and IF signal. And also the IF Amplifier was designed for IF(+) and IF(-) signal generation which have $90^{\circ}$ phase differences which are suitable in two crystal mixer diode inputs. In order to maintain a high electric reliability from high frequency band the waveguide and IF amplifier's case were manufactured with aluminum using deep brazing techniques. The test result of SSB modulator, LO and sideband signal rejection ratio were 14.2dB and 18.5dB respectively.

• Journal of the Daesoon Academy of Sciences
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• v.19
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• pp.81-98
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• 2005

Nepal's role in the expansion of Mahayana Buddhism beyond the Himalaya is very significant. Nepal became the center of Mahayana Buddhism after the Muslim invasion of Nalanda Mahavihara in the 1199 A.D., which she maintained almost for 300 years. During this period, Nepal had produced a large number of profound Buddhist scholars. Most of them were the teachers of eminent Tibetan Buddhists. Some of the Nepalese Gurus also has continued lineage in Tibet until now. During that time, every Tibetan had desire to go to Nepal for higher Buddhist learning. As a matter of fact, many Tibetans made arduous journey across the Himalaya to fulfill the dream. Tibetan studied various forms of tantra, precepts, logic, doctrine, Sutra, Sadhana, Doha, Charyagiti, meditation etc. under direct supervision of Nepalese teachers. Great Tibetan scholars such as Marpa, Rwa Lo, Chag Lo, Khon phu ba, Klog Lo, Gos Lo, and others were the product of Nepal's scholarly tradition. They have significant place in the history of Tibet. Nepalese scholars also frequently visited Tibet where they taught Buddhism in various monasteries. They also had major role in propagating tantra in Tibet. Tibetans firmly believe that it is not possible to attain enlightenment without practicing tantra. The contribution of Nepalese scholars was so profound that Tibet produced many eminent scholars who developed scholastic tradition in Tibet. But after 14th century, Nepal's scholarly tradition ceased to continue. Then after, Tibetans started to call them 'the dull'.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.12
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• pp.1189-1193
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• 2010

Mobility management is one of the most important research issues in 6LoWPAN, Since the IP-WSN application domain is expanded to real-time applications such as healthcare and surveillance systems, a fast and seamless handover becomes an important criterion in 6LoWPAN. However, a draft of IETF 6LoWPAN WG for mobility support does not decrease handover delay. Although LoWMob supports a fast intra-PAN handover. it can be supported when the infrastructure node has the location information of the other nodes in the mobile node's moving direction. In this paper, we propose a fast and seamless mobility protocol to support intra-PAN handover, named intra-MARIO. In intra-MARIO, a parent node of the mobile node preconfigures its handover to the PAN when the parent node detects its movement, thereby reducing the handover delay. Since intra-MARIO also supports route optimization, the mobile node can communicate with its corresponding nodes through the optimal route. In this paper, we analysis the signaling cost and evaluates that the handover can be completed in 20ms by simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.1070-1088
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• 2017

Recently, the applications of Internet of Things (IoTs) are growing rapidly. Wireless Sensor Network (WSN) becomes an emerging technology to provide the low power wireless connectivity for IoTs. The IPv6 over low-power wireless personal area networks (6LoWPAN) has been proposed by IETF, which gives each WSN device an IPv6 address to connect with the Internet. The transmission congestion in IoTs could be a problem when a large numbers of sensors are deployed in the field. Therefore, it is important to consider whether the WSN devices have be completely integrated into the Internet with proper quality of service (QoS) requirements. The Software Defined Network (SDN) is a new architecture of network decoupling the data and control planes, and using the logical centralized control to manage the forwarding issues in large-scale networks. In this research, the SDN-based 6LoWPAN Border Router (6LBR) is proposed to integrate the transmission from WSNs to Internet. The proposed SDN-based 6LBR communicating between WSNs and the Internet will bring forward the requirements of end-to-end QoS with bandwidth guarantee. Based on our experimental results, we have observed that the selected 6LoWPAN traffic flows achieve lower packet loss rate in the Internet. Therefore, the 6LoWPAN traffic flows classified by SDN-based 6LBR can be reserved for the required bandwidth in the Internet to meet the QoS requirements.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.2
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• pp.169-179
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• 1999

In this paper, a GaAs MESFET single-ended resistive mixer with high linearity and isolation is designed. The bias voltage of this mixer is applied only gate of GaAs MESFET to use the channel resistance. The LO is applied the gate and the RF is applied the drain through 7-pole hairpin bandpass filter to obtain the proper isolation thru LO-RF. The IF is extracted from the source with short circuit and lowpass filter. Using extracted equivalent circuits for LO and RF, conversion loss is calculated and compared with result of harmonic balance analysis. Measured conversion loss of this S-band down converter mixer is 8.2~10.5dB by considering the measured 3.0~3.4dB RF 7-pole hairpin bandpass filter loss and IP3in is 26.5dBm at Vg=-0.85~-1.0V in distortion performance.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.2
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• pp.133-140
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• 2015

Purpose: It was investigated whether two different stabilization designs of toric contact lenses changed the rotational axis and degree of toric lenses according to body posture and gaze direction in the present study. Methods: Toric soft contact lenses with Lo-Torque$^{TM}$ design and ASD design (accelerated stabilized design) were fitted on 52 eyes aged in 20s-30s. Then, rotational degree was measured at the five gaze directions including front gaze and the lying position. Results: When gazing the front and vertical directions in the upright posture, lens was much rotated to nasal side for the Lo-Torque$^{TM}$ design and temporal side for the ASD design. When gazing horizontal direction, both design lenses were rotated against to the gaze direction. Rotation degree was the smallest at superior direction gaze and the largest at nasal gaze. In case of the rotation degree less than $5^{\circ}$, Lo-Torque$^{TM}$ design was more frequent when gazing front and vertical directions, and ASD design was more frequent when gazing horizontal direction. In addition, the lens with Lo-Torque$^{TM}$ design was lesser rotation degree than with ASD design immediately after lying. On the other hand, the lens with ASD design was lesser rotation degree than with Lo-Torque$^{TM}$ design 1 minute later after lying. Conclusions: This study confirmed that axis rotation of the lens induced by gaze direction and posture was different according to axis stabilization design during wearing toric soft contact lens.