• Journal of Power Electronics
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• v.16 no.1
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• pp.329-339
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• 2016

Owing to mismatched feeder impedances in an islanded microgrid, the conventional droop control method typically results in errors in reactive power sharing among distributed generation (DG) units. In this study, an improved droop control strategy based on secondary voltage control is proposed to enhance the reactive power sharing accuracy in an islanded microgrid. In a DG local controller, an integral term is introduced into the voltage droop function, in which the voltage compensation signal from the secondary voltage control is utilized as the common reactive power reference for each DG unit. Therefore, accurate reactive power sharing can be realized without any power information exchange among DG units or between DG units and the central controller. Meanwhile, the voltage deviation in the microgrid common bus is removed. Communication in the proposed strategy is simple to implement because the information of the voltage compensation signal is broadcasted from the central controller to each DG unit. The reactive power sharing accuracy is also not sensitive to time-delay mismatch in the communication channels. Simulation and experimental results are provided to validate the effectiveness of the proposed method.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.3
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• pp.223-230
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• 1999

A conventional sliding mode control approach is often impractical or difficult when it is applied to high order process b because the number of tuning parameters in the sliding mode controller increases with the order of the plant. C Camacho(l996) proposed a design method of a fixed structure sliding mode controller based on a first order plus dead t time approximation to the higher-order process. But, his method has such problems as chattering, over‘shoot, and c command following due to the Taylor the approximation en‘ors for the time delay term of the first order model. In this p paper, a new design technique for a sliding mode controller based on the modified Taylor approximation considered a w weight is developed to improve the Camacho's problems.

• Journal of Information Science Theory and Practice
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• v.3 no.2
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• pp.16-30
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• 2015

The term megajournal is used to describe publication platforms, like PLOS ONE, that claim to incorporate peer review processes and web technologies that allow fast review and publishing. These platforms also publish without the constraints of periodic issues and instead publish daily. We conducted a yearlong bibliometric profile of a sample of articles published in the first several months after the launch of PeerJ, a peer reviewed, open access publishing platform in the medical and biological sciences. The profile included a study of author characteristics, peer review characteristics, usage and social metrics, and a citation analysis. We found that about 43% of the articles are collaborated on by authors from different nations. Publication delay averaged 68 days, based on the median. Almost 74% of the articles were coauthored by males and females, but less than a third were first authored by females. Usage and social metrics tended to be high after publication but declined sharply over the course of a year. Citations increased as social metrics declined. Google Scholar and Scopus citation counts were highly correlated after the first year of data collection (Spearman rho = 0.86). An analysis of reference lists indicated that articles tended to include unique journal titles. The purpose of the study is not to generalize to other journals but to chart the origin of PeerJ in order to compare to future analyses of other megajournals, which may play increasingly substantial roles in science communication.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.2
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• pp.582-596
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• 2019

Considering that the existing Long Term Evolution is not suitable for the fast and frequent handovers of high-speed trains, this paper proposes a relay-assisted handover mechanism to solve the problems of long handover authentication time and vulnerable to security attacks. It can achieve mutual authentication for train-ground wireless communication, and data transmission is consistent with one-time pad at the same time. The security analysis, efficiency analysis and simulation results show that the proposed mechanism not only realizes the forward security and resists many common attacks, but also effectively reduces the computational overhead of train antenna during the secure handover process. When the running speed of a train is lower than 500km/h, the handover delay is generally lower than 50ms and the handover outage probability is less than 1.8%. When the running speed of a train is 350km/h, the throughput is higher than 16.4mbps in the process of handover. Therefore, the secure handover mechanism can improve the handover performance of high-speed trains.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.4
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• pp.79-88
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• 2020

Hypergolic propellants have been widely used for space propulsion systems based their long-term storability and high ignition reliability. Since conventional hypergolic propellants are highly toxic and carcinogenic, handling and operating costs are significant. To overcome the drawbacks, numerous studies have been actively performed to develope new hypergolic propellants, ensuring that the combinations are high performance, low toxicity and low environmental impact. In the present study, a comprehensive survey was conducted to summarize the research and development of green hypergolic propellants involving hydrogen peroxide, nitric acid, and ionic liquids.

• Journal of Dental Anesthesia and Pain Medicine
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• v.22 no.3
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• pp.233-237
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• 2022

Postpolio syndrome (PPS) is widely known to manifest as muscle weakness in patients affected by poliomyelitis in early childhood. This is caused by the long-term overwork of motor nerves regenerated from surviving nerve cells. We report a characteristic delay in recovery from muscle relaxation after administering rocuronium to a patient with PPS under general anesthesia with desflurane. A 59-year-old woman was scheduled to undergo surgical debridement for jaw osteonecrosis. She had a history of poliomyelitis at the age of 2 years, and was diagnosed with PPS at the age of 51 years. General anesthesia was induced with 80 mg propofol, 50 ㎍ fentanyl, and 30 mg (0.69 mg/kg) rocuronium, and maintained with desflurane and remifentanil. The durations of train-of-four (TOF) count 0 and 1 were 96 and 37 min, respectively. Five minutes after discontinuing desflurane, the TOF count was 4. Three minutes after administering 200 mg sugammadex, the TOF ratio was 0.83, and the tracheal tube was subsequently removed. In summary, the effect of a single dose of rocuronium on twitch in TOF monitoring was significantly prolonged in a patient with PPS, which may have been exacerbated by desflurane.

• Journal of the Korea Institute of Military Science and Technology
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• v.26 no.3
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• pp.214-226
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• 2023

A transfer alignment is used to initialize, align, and calibrate a SINS(Slave INS) using a MINS(Master INS) in motion. This paper presents an airborne transfer alignment with velocity and azimuth matching to estimate inertial sensor biases under the wing flexure influence. This study also considers the lever arm, time delay and relative orientation between MINS and SINS. The traditional transfer alignment only uses velocity matching. In contrast, this paper utilizes the azimuth matching to prevent divergence of the azimuth when the aircraft is stationary or quasi-stationary since the azimuth is less affected by the wing flexibility. The performance of the proposed Kalman filter is analyzed using two factors; one is the estimation performance of gyroscope and accelerometer bias and the other is comparing aircraft dynamics and attitude covariance. The performance of the proposed filter is verified using a long term flight test. The test results show that the proposed scheme can be effectively applied to various platforms that require airborne transfer alignment.

• Clinical and Experimental Pediatrics
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• v.48 no.9
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• pp.924-928
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• 2005

Purpose : Treatment efficacy for children with speech and language delay has been the subject of considerable debate in recent years. We evaluated the clinical features of children with delayed speech and language and their prognoses according to their etiologies after 6 months of speech and language therapy. Methods : From January, 2000 to March, 2004, we retrospectively reviewed 56 children with speech and language delay who were administered speech and language therapy for 6 months in Uijongbu St. Mary's Hospital. Results : Of 56 cases, the proportion of developmental language disorder was 66.1 percent, structural malformation 19.6 percent, mental retardation 12.5 percent, hearing defect 1.8 percent. The ratio of male to female was 4.6 : 1 and the most frequent age group was over 47 months. The mean age of first spontaneous words with useful meaning was 15.9 months. The mean gestational age of the subjects was 39.8 weeks. The proportion of full-term infants was 96.4 percent and of premature infants was 3.6 percent. As for the birth order, the proportion of the first baby was 51.8 percent, the one of second babies it was 42.9 percent, and percent of third babies it was 7.1 percent. After 6 months of language intervention, 32.4 percent of patients with developmental language disorder showed normal linguistic development. All the patients with mental retardation showed sustained language and speech delay. As for the patients with structural malformations, five out of 11 patients showed normal linguistic development. Conclusion : The relatively advanced old age of majority of participants in this study suggests the necessity of screening test for language delay in this local community.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.3
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• pp.8-15
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• 2010

Due to the increasing demand of network convergence, in future, hybrid/integrated satellite and terrestrial systems will play an important role. In that case, compatibilities between the satellite and terrestrial systems are very important for efficiency of the systems. 3GPP Long Term Evolution (LTE) is one of the most powerful candidates of the 4G system Therefore, in this paper, we introduce the design of interleaver for mobile satellite system based 3GPP LTE specification. The 4G system including the LTE specification adopted adaptive modulation and coding (AMC) schemes for efficient usage of resources, and the updating interval of resource allocation is an order of msec. However, because of the long round trip delay of satellite systems, we cannot employ the same AMC scheme specified for the terrestrial system, and thus it cannot effectively counteract to short term fadings. Therefore, in order to overcome these problems, we propose an interleaver scheme combined with AMC. We present the interleaγer design results considering mobile satellite system based on the LTE and analyze the simulation results.

• Journal of Bio-Environment Control
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• v.20 no.4
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• pp.304-310
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• 2011

To evaluate the effect of curing treatment using a newly developed simplified curing unit (SCU) on the physicochemical quality of stored sweet potatoes was investigated for six months. The SCU consisting of a heater, an air circulation fan, exhaust fans, and a humidifying duct was installed in a cold storage room where the harvested sweet potatoes were stacked. During the six days of curing treatment, air temperature and relative humidity in the storage room were set at $32^{\circ}C$ and 90%, respectively. Physical and chemical properties of sweet potatoes were measured at 1-month intervals from the first day of storage. McKinney index showing the incidence and severity of decay was 0.83% in the curing treatment, while that of untreated control was 5.08% over the same storing period. Firmness, soluble solids content, and dry matter content in the cured sweet potatoes were greater than those of untreated control. Moreover, the changes of skin color in uncured potatoes occurred rapidly than cured one which showed delay of skin discoloration during the long-term storage. Results suggest that the SCU treatment improves the physicochemical quality of stored sweet potatoes and extends their storability. Therefore, the SCU can be effectively used for curing treatment of sweet potatoes with a relatively low cost.