• Journal of the Korea Society for Simulation
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• v.17 no.4
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• pp.191-198
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• 2008

6LoWPAN (IPv6 Low-power Wireless Personal Area Network) is IPv6 packets transmission technology at Sensor network over the IEEE 802.15.4 Standard MAC and Physical layer. Adaptation layer between IP layer and MAC layer performs fragmentation and reassembly of packet for transmit IPv6 packets. RFC4944, IETF 6LoWPAN WG standard document define packet fragmentation and reassembly. In this paper, we propose the 6PASim (6LoWPAN Packet Simulator) to perform IPv6 packet fragmentation and reassembly for performance evaluation. The 6PASim consist of two parts. One is Packet_Transmit_module that makes IEEE 802.15.4 frames the IPv6 packet from upper layer, and transmit its. and the another is Packet_Receive_module that reassembles transferred frames and completes original IPv6 packets. we can evaluate frame transmit rate and amount of control message through 6PASim. The result of simulation shows the SRM (Selective Retransmission Method) scheme provider better performance than IRM (Immediate Retransmission Method) scheme.

• Corrosion Science and Technology
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• v.11 no.3
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• pp.96-102
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• 2012

Outer diameter stress corrosion cracking (ODSCC) has occurred for Alloy 600 (Ni 75 wt%, Cr 15 wt%, Fe 10 wt%) as a heat exchanger tube of the steam generator (SG) in nuclear power plants (NPP) during long term operation. Among many causes for SCC, lead (Pb) is known to be one of the most deleterious species in the secondary system. In the present work, the oxide formed on Alloy 600 was characterized as a function of the PbO content in 0.1 M NaOH at $315^{\circ}C$ by using an electrochemical impedance spectroscopy (EIS), a transmission electron microscopy (TEM), equipped with an energy dispersive x-ray spectroscopy (EDS). The oxide property was analyzed in view of SCC susceptibility.

• Korean Journal of Optics and Photonics
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• v.18 no.6
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• pp.441-446
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• 2007

Outcoupling efficiency of the OLED device is improved by incorporating both a microlens array and a diffractive grating pattern. The microlens array improves the light transmission at the interface of glass and air, and the diffractive grating outcouples the guided mode propagating at the waveguide, which consists of ITO and organic layers. By using the PDMS soft mold imprinting method, the microlens array is fabricated on the glass substrate. The diffractive grating pattern is directly fabricated on the ITO surface by using laser interferometry. A microlens array with a diameter of $10{\mu}m$ improves the light coupling efficiency by 22%. The diffractive grating made of TSMR photoresist enhances the luminance power efficiency by 41% at a current density of $20mA/cm^2$.

• Korean Journal of Optics and Photonics
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• v.22 no.4
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• pp.179-183
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• 2011

An external cavity laser operating at near infrared wavelength is demonstrated by incorporating polymer waveguide Bragg reflectors. 3rd order Bragg grating and oversized rip waveguide structure were designed by using the effective index method and the transmission matrix method. The polymer waveguide was fabricated using polymer materials with refractive indices of 1.462 and 1.435 for the core and the cladding layers, respectively. The external feedback laser with 875-nm Bragg grating exhibits single mode lasing located at 850-nm wavelength with an output power of 0 dBm, a 20-dB bandwidth of 0.2 nm and a side mode suppression ratio of 40 dB.

• Journal of Digital Convergence
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• v.13 no.7
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• pp.207-212
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• 2015

The sensor network that is component of the Internet of Things require a lot of research to select the best route to send information to the anchor node, to collect a number of environment and cost efficient for communication between the sensor life. On the sensor network in one of the components of IOT's environment, sensor nodes are an extension device with low power low capacity. For routing method for data transmission between the sensor nodes, the connection between the anchor and the node must be accurate with in adjacent areas relatively. Localization CA (Centroid Algorithm) is often used although an error frequently occurs. In this paper, we propose a range-free localization method between sensor nodes based on the Radical Line in order to solve this problem.

• Korean Journal of Materials Research
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• v.22 no.11
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• pp.636-641
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• 2012

In this study, we have investigated highly efficient nanoscale surface corrugated light emitting diodes (LEDs) for the enhancement of light extraction efficiency (LEE) of nitride semiconductor LEDs. Nanoscale indium tin oxide (ITO) surface corrugations are fabricated by using the conformal nanoimprint technique; it was possible to observe an enhancement of LEE for the ITO surface corrugated LEDs. By incorporating this novel method, we determined that the total output power of the surface corrugated LEDs were enhanced by 45.6% for patterned sapphire substrate LEDs and by 41.9% for flat c-plane substrate LEDs. The enhancement of LEE through nanoscale surface corrugations was studied using 3-dimensional Finite Different Time Domain (FDTD) calculation. From the FDTD calculations, we were able to separate the light extraction from the top and bottom sides of device. This process revealed that light extraction from the top and bottom sides of a device strongly depends on the substrate and the surface corrugation. We found that enhanced LEE could be understood through the mechanism of enhanced light transmission due to refractive index matching and the increase of light scattering from the corrugated surface. LEE calculations for the encapsulated LEDs devices also revealed that low LEE enhancement is expected after encapsulation due to the reduction of the refractive index contrast.

• Journal of the Korean Magnetics Society
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• v.25 no.1
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• pp.22-26
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• 2015

In this paper, a magneto-inductive wave generated in a chain of LC resonators fabricated with Ni-Zn ferrite cores and chip capacitors is presented. RF signal propagates to neighbor resonator one by one as a consequence of the magnetical coupling between two resonators in the device. The magnetical coupling is due to the mutual inductances along the chain of resonators. So, the signal amplitude (${\approx}$ coupling intensity) is dependent of the mutual inductance which can be adjusted by applied magnetic field. In order to demonstrate the device, some experiments have been carried out systemically. The transmission characteristics of a magneto-inductive wave could be controlled by applied external magnetic field. The device composed of 5 resonators; the center frequencies were estimated to be 32 MHz and 38 MHz with the external magnetic flux density of 75 Oe and 222 Oe, respectively. We expect that the reported results could open a promising way to a high variety of applications in one- and two-dimensional functional devices, such as transducers, delay lines, power dividers and couplers.

• Journal of Distribution Science
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• v.1 no.1
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• pp.1-24
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• 1999

CALS/EC is about doing business electronically. It is based on the electronic processing and transmission of data, including text, sound and video. It encompasses many diverse activities including electronic trading of goods and services, online delivery of digital content, electronic fund transfers, electronic share trading, electronic bills of lading, commercial auctions, collaborative design and engineering, online sourcing, public procuremet, direct consumer marketing, and after-sales service. It involves both products(e.g. consumer goods, specialised medical equipment) and services(e.g. information services, financial and legal services); traditional activities(e.g. healthcare, education) and new activities (e.g. virtual malls). CALS/EC will be emerging to replace and substitute the role of the conventional market. By changing and eliminating some processes of the transactions, the electronic market and the electronic commerce will redistribute the power and hence the benefits of the market activities. Traditional way of doing business may enter into the new electronic market because the role and function of trust and established reputation will be reinforced in the electronic market. The CALS/EC through the Internet has been in the spotlight in the shopping behavior of the consumers. Accordingly Corporates are trying to adapt themselves to those rapidly changing environments being affected by the Internet. Among others, particularly to be noted is the CALS/EC between corporations and consumers whose potential growth can be considered very substantial. This report, focusing on the introduction of CALS/EC for the logistics of SMEs, will allow us to prepare more efficiently for the coming 21st Century. It is obvious that CALS/EC is fast becoming the useful way of exchanging not only information but products in business between firm-to-firm and firm-to-customer.

• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.6
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• pp.698-703
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• 2003

This paper presents analog secure communication system about safe speech transmission using chaotic signals. We applied various conditions that happen in actuality communication environment modifying chaotic synchronization and chaotic communication schemes and analyzed restoration performance of speech signal to computer simulation. In transmitter, we made the chaotic masking signal which is added voice signal to chaotic signal using PC(Pecora ＆ Carroll) and SFB(self-feedback) control techniques and transmitted encryption signal to noisy communication channel And in order to calculate the degree of restoration performance, we proposed the definition of analog average power of recovered error signals in receiver chaotic system. The simulation results show that feedback control techniques can certify that restoration performance is superior to quantitative data than PC method about masking degree, susceptibility of parameters and channel noise. We experimentally computed the table of relation of parameter fluxion to restoration error rate which is applied the encryption key values to the chaotic secure communication.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.165-172
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• 2012

Integrated-optic asymmetric Mach-Zehnder interferometer at $1.3{\mu}m$ wavelength and segmented electrode structure were designed and fabricated as a sensing part for the electric-field measurement system. The device was simulated based on the BPM software and fabricated utilizing Ti-diffused $LiNbO_3$ channel optical waveguides and lumped-type electrodes. Almost half-maximum power transmission was observed for asymmetric interferometers with ${\pi}/2$ intrinsic phase difference. Expected experimental measurements were observed for 1KHz electrical signal bandwidth.