• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.143-152
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• 1998

In this paper, we present the performances of a Doppler system using single channel RF(Radio Frequency) sampling. This technique consists of undersampling the ultrasonic blood backscattered RF signal on a single channel. Conventional undersampling method in Doppler imaging system have to use a minimum of two identical parallel demodulation channels to reconstruct the multigate analytic Doppler signal. However, this system suffers from hardware complexity and problem of unbalance(gain and phase) between the channels. In order to reduce these problems, we have realized a multigate pulsed Doppler system using undersampling on a single channel, It requires sampling frequency at $4f_o$(where $f_o$ is the center frequency of the transducer) and 12bits A/D converter. The proposed " single-Channel RF Sampling" method aims to decrease the required sampling frequency proportionally to $4f_o$/(2k+1). To show the influence of the factor k on the measurements, we have compared the velocity profiles obtained in vitro and in vivo for different intersequence delays time (k=0 to 10). We have used a 4MHz center frequency transducer and a Phantom Doppler system with a laminar stationary flow. The axial and volumetric velocity profiles in the vessel have been computed according to factor k and have been compared. The influence of the angle between the ultrasonic beam and the flow axis direction, and the fluid viscosity on the velocity profiles obtained for different values of k factor is presented. For experiment in vivo on the carotid, we have used a data acquisition system with a sampling frequency of 20MHz and a dynamic range of 12bits. We have compared the axial velocity profiles in systole and diastole phase obtained for single channel RF sampling factor.ng factor.

• Journal of the Korea Society of Computer and Information
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• v.18 no.11
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• pp.87-97
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• 2013

In the RFID system, multiple tags respond in the process of identifying multiple tags in the reader's interrogation zone, resulting in collisions. Tag collision occurs when two or more tags respond to one reader, so that the reader cannot identify any tags. These collisions make it hard for the reader to identify all tags within the interrogation zone and delays the identifying time. In some cases, the reader cannot identify any tags. The reader needs the anti-collision algorithm which can quickly identify all the tags in the interrogation zone. The proposed algorithm efficiently divides tag groups through an efficient separation to respond, preventing collisions. Moreover, the proposed algorithm identifies tags without checking all the bits in the tags. The prediction with efficient separation reduces the number of the requests from the reader.

• Journal of the Korean Geophysical Society
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• v.4 no.1
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• pp.21-33
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• 2001

Simultaneous inversion of first-arrivals of local earthquakes recorded by the Korea Meteorological Administration(KMA) seismograph network from 1991 to 1998 is made to derive 1D crustal velocity structure of the Korean peninsula. Twenty-nine events with 178 observations are used in the inversion. Average crustal P-wave velocity turns out to be about 6.3 km/sec, and crustal thickness and upper mantle P-wave velocity are estimated as 33 km and 7.9 km/sec, respectively. Results of inversion indicate the possibility of the low velocity layer in the lower crust. Joint inversion is applied to estimate hypocenters, station delays, and velocities simultaneously. Relative station corrections for 11 stations range from zero to about 1.2 sec. Analysis of the synthetic data shows that estimates of hypocenter locations and station corrections as well as averaged crustal structure are reliable for the given data set..

• BMB Reports
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• v.52 no.11
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• pp.653-658
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• 2019

MYB-type transcription factors (TFs) play important roles in plant growth and development, and in the rapid responses to unfavorable environmental conditions. We recently reported the isolation and characterization of a rice (Oryza sativa) MYB TF, OsMYB102, which is involved in the regulation of leaf senescence by downregulating abscisic acid (ABA) biosynthesis and the downstream signaling response. Based on the similarities of their sequences and expression patterns, OsMYB102 appears to be a homolog of the Arabidopsis thaliana AtMYB44 TF. Since AtMYB44 is a key regulator of leaf senescence and abiotic stress responses, it is important to examine whether AtMYB44 homologs in other plants also act similarly. Here, we generated transgenic Arabidopsis plants expressing OsMYB102 (OsMYB102-OX). The OsMYB102-OX plants showed a delayed senescence phenotype during dark incubation and were more susceptible to salt and drought stresses, considerably similar to Arabidopsis plants overexpressing AtMYB44. Real-time quantitative PCR (RT-qPCR) revealed that, in addition to known senescence-associated genes, genes encoding the ABA catabolic enzymes AtCYP707A3 and AtCYP707A4 were also significantly upregulated in OsMYB102-OX, leading to a significant decrease in ABA accumulation. Furthermore, protoplast transient expression and chromatin immunoprecipitation assays revealed that OsMYB102 directly activated AtCYP707A3 expression. Based on our findings, it is probable that the regulatory functions of AtMYB44 homologs in plants are highly conserved and they have vital roles in leaf senescence and the abiotic stress responses.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.12
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• pp.311-318
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• 2021

With the rapid development of the Internet of Things(IoT) technology recently, multi-access edge computing(MEC) is emerged as a next-generation technology for real-time and high-performance services. High mobility of users between MECs with limited service areas is considered one of the issues in the MEC environment. In this paper, we consider a vehicle edge computing(VEC) environment which has a high mobility, and propose a task migration algorithm to decide whether or not to migrate and where to migrate using DQN, as a reinforcement learning method. The objective of the proposed algorithm is to improve the system throughput while satisfying QoS(Quality of Service) requirements by minimizing the difference between queueing delays in vehicle edge computing servers(VECSs). The results show that compared to other algorithms, the proposed algorithm achieves approximately 14-49% better QoS satisfaction and approximately 14-38% lower service blocking rate.

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.19-24
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• 2021

The low normal zone propagation velocity (NZPV) of high-temperature superconducting (HTS) tape leads to a quench protection problem in HTS magnet applications. To overcome this limitation, various studies were conducted on HTS coils without turn-to-turn insulation (NI coils) that can achieve self-protection. On the other hand, NI coils have some disadvantages such as slow charging and discharging time. Previously, the HTS coils with turn-to-turn insulation (INS coils) were operated in power supply (PS) driven mode, which requires physical contact with the external PS at room-temperature, not in persistent current mode. When a quench occurs in INS coils, the low NZPV delays quench detection and protection, thereby damaging the coils. However, the rotary HTS flux pump supplies the DC voltage to the superconducting circuit with INS coils in a non-contact manner, which causes the INS coils to operate in a persistent current mode, while enabling quench protection. In this paper, a new protection characteristic of HTS coils is investigated with INS coils charging through the rotary HTS flux pump. To experimentally verify the quench protection characteristic of the INS coil, we investigated the current magnitude of the superconducting circuit through a quench, which was intentionally generated by thermal disturbances in the INS coil under charging or steady state. Our results confirmed the protection characteristic of INS coils using a rotary HTS flux pump.

• Smart Media Journal
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• v.8 no.3
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• pp.41-46
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• 2019

In a MMORPG, a typical application of virtual environment systems, it is a common desire to play in a more realistic environment. However, it is very difficult to provide a latency-free virtual environment to a large user base, mainly due to the fact that the real environment must be configured on multiple servers rather than on single server and that data must be shared on the real server when users move from one region to another. Experiencing response delays continuously in the process of information synchronization between servers greatly deteriorates the degree of immersion. In order to solve this problem, it is necessary to minimize the response delay occurring in the information synchronization process between the servers. In this paper, we propose Migration Agent for efficient information synchronization between field servers providing information of virtual environment and minimizing response delay between Field Server and PC(Player Character) and implement it in cloud computing network. In the proposed system, CPU utilization of field server increased by 6 ~ 13%, and response time decreased by 5 ~ 10 seconds over the existing system in 70,000 ~ 90,000 PCs

• Nuclear Engineering and Technology
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• v.51 no.6
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• pp.1514-1524
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• 2019

Hydrogen-steam gas mixture may be injected into containment with flow regime varying both spatially and transiently due to wall effect and pressure difference between primary loop and containment in severe accidents induced by loss of coolant accident. Preliminary CFD analysis is conducted to gain information about the helium flow regime transition process from jet to buoyancy plume for forthcoming experimental study. Physical models of impinging jet and wall condensation are validated using separated effect experimental data, firstly. Then helium transportation is analyzed with the effect of jet momentum, buoyancy and wall cooling discussed. Result shows that helium distribution is totally dominated by impinging jet in the beginning, high concentration appears near gas source and wall where jet momentum is strong. With the jet weakening, stable light gas layer without recirculating eddy is established by buoyancy. Transient reversed helium distribution appears due to natural convection resulted from wall cooling, which delays the stratification. It is necessary to concern about hydrogen accumulation in lower space under the containment external cooling strategy. From the perspective of experiment design, measurement point should be set at the height of connecting pipe and near the wall for stratification stability criterion and impinging jet modelling validation.

• Journal of the Korea Convergence Society
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• v.13 no.3
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• pp.43-54
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• 2022

Simultaneous translation is online decoding to translates with only subsentence. The goal of simultaneous translation research is to improve translation performance against delay. For this reason, most studies find trade-off performance between delays. We studied the experiments of the fixed policy-based simultaneous translation in Korean. Our experiments suggest that Korean tokenization causes many fragments, resulting in delay compared to other languages. We suggest follow-up studies such as n-gram tokenization to solve the problems.

• Journal of Navigation and Port Research
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• v.46 no.3
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• pp.236-242
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• 2022

Busan Port is operated separately by a number of terminal operators, resulting in a large number of ITT (Inter-Terminal Transportation) volumes. The occurrence of ITT volume causes various problems such as additional transportation cost, empty truck trips, truck delays and terminal congestion, weakening Busan Port's competitiveness. Among them, the empty truck trip problem is a representative factor, that exacerbates the cost problem of the ITT operation at Busan Port. But the ITT backhaul rate at Busan Port remains low. To strengthen the transhipment competitiveness of Busan Port, it is necessary to increase the ITT backhaul rate. In this paper, to improve ITT backhaul rate, we present a mathematical model for maximizing backhaul transport using buffer space. And we analyzed the improving effects of backhaul transport using buffer space through experiments based on actual operating data.