• Journal of Communications and Networks
• /
• v.11 no.4
• /
• pp.375-383
• /
• 2009

The WiMedia alliance has specified a distributed medium access control (WiMedia MAC) protocol based on ultra wideband (UWB) for high data rate WPANs (HR-WPANs). The merits of WiMedia MAC such as distributed nature and high data rate make it a favorite candidate in HR-WPAN. Although QoS parameters such as the range of service rates are provided to a traffic stream, the WiMedia MAC is not able to use the QoS parameters and to determine or adjust a service rate using the QoS parameters for the traffic stream. In this paper, we propose a fair and adaptive resource allocation method that allocates time slots to isochronous streams according to QoS parameters and the current traffic load condition in a fully distributed manner. Although the traffic load condition changes, each device independently recognizes the changes and calculates fair and maximum allowable service rates for traffic streams. From the numerical and simulation results, it is proved that the proposed method achieves high capacity of traffic streams and fair QoS provisioning under various traffic load condition.

• Journal of Positioning, Navigation, and Timing
• /
• v.7 no.2
• /
• pp.91-103
• /
• 2018

Conventional inertial measurement units cannot be used in the spinning vehicle with high rotation rate due to gyro's narrow operation range. By the way, angular acceleration can be measured using the accelerometer array distributed in the vehicle. This paper derives a mechanization for the gyro-free INS in the navigation frame, and proposes a gyro-free INS algorithm based on the derived mechanization. In addition, the proposed algorithm is used to estimate angular velocity, attitude, velocity, and position of a spinning vehicle with high rotation rate. A MATLAB-based software platform is configured in order to show validation of the proposed algorithm. The reference trajectory of a spinning vehicle at 3 round per second, 30 round per second are set up, and the outputs of accelerometer are generated when triads of accelerometer are located at the origin and all the axes. Navigation results of the proposed algorithm for the generated output are presented. The results show that the proposed navigation algorithm can be applied to the spinning vehicle with high rotation rate.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.392-392
• /
• 2010

In this study, high-speed chemical dry thinning process of Si wafer and evolution of surface roughness were investigated. Direct injection of NO gas into the reactor during the supply of F radicals from $NF_3$ remote plasmas was very effective in increasing the Si thinning rate due to the NO-induced enhancement of surface reaction but thinned Si surface became roughened significantly. Addition of Ar gas, together with NO gas, decreased root mean square (RMS) surface roughness of thinned Si wafer significantly. The process regime for the thinning rate enhancement with reduced surface roughness was extended at higher Ar gas flow rate. Si wafer thinning rate as high as $22.8\;{\mu}m/min$ and root-mean-squared (RMS) surface roughness as small as 0.75 nm could be obtained. It is expected that high-speed chemical dry thinning process has possibility of application to ultra-thin Si wafer thinning with no mechanical damage.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.14 no.3
• /
• pp.125-135
• /
• 2004

IEEE 802.15.3 High Rate WPAN is a mechanism for wireless home network such as PDAs, digital video camcoder, etc. While symmetric keys are used for MAC layer security, the process of establishing a secure membership or a secure relationship is outside of the scope of the standard. In addition, to prepare for ubiquitous environment in the near future, it is important to study the process of establishing a secure relationship between DEVs in different dependent piconets. This paper propose a secure model and a process of establishing a secure relationship using PKI without a ousted certificate authority.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.16 no.3
• /
• pp.423-428
• /
• 2021

The performance of wind profilers were evaluated in Bukgangneung and Changwon, where both wind profilers and radiosonde are being operated. From December 2019 to November 2020, the acquisition rate of wind speed data by altitude and month was investigated and compared with the wind speed of radiosonde. The acquisition rate of normal data increased at the minimal observable altitude, and then decreased again from 2 km or more at the two observation sites. The acquisition rate was high in summer (June, July, August), and low in winter (December, January, February). The results compared with radiosonde showed high correlation of 0.9 in the high mode and 0.8 in the low mode.

• Journal of Practical Agriculture & Fisheries Research
• /
• v.21 no.2
• /
• pp.77-86
• /
• 2019

To determine none top soil covering in rice seedling nursery method for the sparse machine transplanting, four different sowing methods were tested. Shoot and root length, fresh weight, leaf number and color using leaf color chart(LCC) and SPAD were collected as the data comparison of methods. The seedling height showed the highest growth according to the conventional (230g seed rate of pre-emerged seeds and top-soil covering) > high sowing density 1 (290g seed rate of pre-emerged seeds and top-soil covering) ≥ high sowing density 2(290g seed rate of pre-emerged seeds and none top-soil covering) > high sowing density 3(290g seed rate of iron-coated seeds and none top-soil covering). There was any statistical difference between groups in root length, leaf number, LCC, and SPAD values. Thus, a high sowing density of 290g for rice nursery seedling box was recommended to the sparse machine transplanting in rice cultivation with the none top-soil covering method, enabling convenient handling in transportation and machine transplanting work.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.21 no.4
• /
• pp.543-558
• /
• 2023

Currently, Japan is undertaking a nationwide project to measure and map radioactive contamination around Fukushima, as part of the efforts to restore normalcy following the nuclear accident. The Japan Atomic Energy Agency (JAEA) manages the Fukushima Environmental Safety Center, located approximately 20 km north of the Fukushima Daiichi nuclear power plant in Minamisōma City, Fukushima Prefecture. In collaboration with the JAEA, this study involved conducting comparison experiments and analyses with radiation detectors in high radiation environments, a challenging task in Korean environments. Environmental radiation surveys were conducted using three types of detectors: CZT, NaI(Tl), and LaBr₃(Ce), across two contaminated areas. Dose rate values were converted using dose rate conversion factors for each detector type, and dose rate maps were subsequently created and compared. The detectors yielded similar results, demonstrating their feasibility and reliability in high radiation environments. The findings of this study are expected to be a crucial reference for enhancing the verification and supplementation of procedures and methods in future radiation measurements and mobile surveys in high-radiation environments, using these three types of radiation instruments.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.44 no.6 s.360
• /
• pp.77-82
• /
• 2007

In the existing frame-layer rate control for H.264, buffer status and content complexity are used improperly, causing quality fluctuations of high-motion video at low bit rates and high frame rates (under 19.2 kbps at 30 fps). We propose an enhanced H.264 frame-layer rate control scheme to obtain steady video quality and stable buffer management. Experimental results showed that the proposed scheme performed better than existing schemes.

• Journal of Distribution Science
• /
• v.16 no.12
• /
• pp.13-21
• /
• 2018

Purpose - Because it is not possible to assess the quality of service products before experiencing them, one feature of a service product is quality uncertainty; hence consumers may react sensitively to pricing. It is necessary to investigate how different pricing strategies affect consumer purchase intention depending on the level of service quality uncertainty. Research design, data, and methodology - The authors have investigated the potential impact of the level of service quality uncertainty, price discount rate and presentation method on consumer purchase intention. A play was selected as an experimental stimulus, and Vietnamese consumers were surveyed to verify the hypotheses. Results - When uncertainty regarding service quality is low, consumer purchase intention is higher when the price discount rate is high or when the price is low. When uncertainty regarding service quality is high, if the normal price, discount rate, and discounted price are presented simultaneously, consumer purchase intention is higher when the price discount rate is low, but when only the discounted price is presented, purchase intention is higher when the price discount rate is high. Conclusions - The results of this study can provide valuable practical implications for pricing for service products with quality uncertainty.

• Transactions of Materials Processing
• /
• v.7 no.5
• /
• pp.450-458
• /
• 1998

The high temperature deformation behavior of Al 5083 alloy has been studied in the temperature range of 350 to 520 ${\circ}C$ and strain rate range of 0.2 to 3.0/sec by torsion test. The strain rate sensitivity(m) of the material was evaluated and used for estabilishing power dissipation maps following the dynamic material model. These maps show the variation of efficiency of power dissipation(${\eta}$=2m/(2m+1)) with temperature and strain rate. Hot restoration of dynamic recrystallization (DRX) was analyzed from the flow curve, deformed microstructure, and processing maps during hot deformation. Also, the effect of deformation strain on the efficiency of power dissipation of the alloy was analysed using the processing maps. Moreover relationship between the hot-ductility and efficiency of power dissipation of the alloy depending on thmperature and strain rate was studied using the Zener-Hollomon parameter(Z=${\varepsilon}$exp(Q/RT) It is found that the maximum efficiency of power dissipation for DRX in Al 5083 alloy is about 74.6 pct at the strain of 0.2. The strain rate and temperature at which the efficiency peak occurred in the DRX domain is found to be ∼0.1/sec and ∼450${\circ}C$ respectively.