• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.6
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• pp.1554-1561
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• 1998

When the superposition of realtime traffic and non-realtime traffic is applied to the ATM network, the successive cell loss(block loss) is more influential on the quality of service (QoS) of two traffic streams than the single loss in case of bursty traffic. Block loss can be identified as an important performance measure because of delay-oriented policy for realtime traffic. In this paper, we consider the system with the two-level overload control reducing of the recurrence of shut-down periods and develop a recursive algorithm to obtain both block loss and cell loss probabilities of both traffic. We can see that it gives the more precise and diverse investigations on performance analysis of queuing strategy.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.11
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• pp.15-22
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• 2008

The cdma2000 1xEV-DO system controls the data rates of mobile terminals based on a binary overload indicator from the base station and a simple probabilistic model. However, this control scheme has difficulty in predicting the future behavior of mobile terminals due to a probabilistic uncertainty and has no reliable means of suppressing the traffic overload, which may result in performance degradation of CDMA systems that have interference-limited capacity. This Paper proposes a new traffic control scheme that controls the data rates of mobile terminals effectively by predicting the future traffic load and adjusting the forward-link control channel. The proposed scheme is analyzed by modeling it as a multi-dimensional Markov process and compared with conventional schemes. The numerical results show that the maximum cell throughput of the proposed scheme is much higher than those of the conventional schemes.

• Journal of Korean Clinical Nursing Research
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• v.27 no.1
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• pp.45-53
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• 2021

Purpose: This study was conducted to assess the factors affecting turnover intention of the nurses working in neonatal intensive care units, including the extent of fatigue, work stresses, and work overload related to infection control. Methods: This was a descriptive correlational study to test factors affecting the turnover intention of the nurses working in neonatal intensive care units. Data was analyzed utilizing descriptive statistics, t-test, One-way ANOVA, Pearsons' Correlation Coefficient, and multiple regressions by using the IBM SPSS Statistics 23.0 Program(IBM Corp., Armonk, NY). Results: The turnover intention of nurses had a positive correlation with the extent of fatigue (r=.54, p<.001), work stress (r=.40, p<.001), and with the work overload (r=.43, p<.001) related to infection control. In addition, factors affecting the turnover intention of nurses included the extent of fatigue (β=.52, p<.001) related to infection control and the number of pediatric patients assigned to each nurse (β=.26, p=.001) and the variances explained by the regression model was 37.0%. Conclusion: It is necessary to establish and implement strategies to lower the extent of fatigue related to infection control by reducing the nurses' workload. Securing additional nurses to ensure an appropriate number of pediatric patients assigned to each nurse, and providing efficient management and available resources to reduce the turnover intention of nurses working in neonatal intensive care units are suggested.

• Fire Science and Engineering
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• v.21 no.4
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• pp.65-71
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• 2007

This paper is studied on a protective control system for electrical fire and electrical faults by using electrical and thermal characteristics of PTC thermistor. The PTC thermistor has characteristic or positive resistivity temperature coefficient according to the temperature variation, which is construction of a regular square and cube demarcation with $BaTiO_3$ Ceramics of positive temperature coefficient. Also PTC thermistor shows the phenomenon which is rapidly increased in the resistivity if the temperature is increased over Curie temperature point. This paper is proposed on a protective control system used PTC thermistor which is protected from electrical fire due to electric short circuit faults or overload faults. Some experimental results of the proposed electric safety control apparatus are confirmed to the validity of the analytical results.

• Journal of applied mathematics & informatics
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• v.12 no.1_2
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• pp.395-408
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• 2003

Common Channel Signaling(CCS) networks need special controls to avoid overload of signaling networks and degradation of call process-ing rate, since they play an important role of controlling communication transfer networks. Congestion control and flow control mechanisms are well described in ITU-T recommendation on Signaling System No.7(SS7). For the practical provisions, however, we need an analysis on the relation among service objects, system requirements and implementation of congestion control algorithms. SS7 provides several options for controlling link congestion in CCS networks. In this paper we give a general queueing model of congestion control algorithm which covers both the international and national options. From the queuing model, we obtain the performance parameters such as throughput, message loss rate and mean delay for the international option. To show the performance of the algorithm, some numerical results are also given.

• Toxicological Research
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• v.31 no.4
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• pp.347-354
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• 2015

Excess manganese (Mn) is neurotoxic. Increased manganese stores in the brain are associated with a number of behavioral problems, including motor dysfunction, memory loss and psychiatric disorders. We previously showed that the transport and neurotoxicity of manganese after intranasal instillation of the metal are altered in Hfe-deficient mice, a mouse model of the iron overload disorder hereditary hemochromatosis (HH). However, it is not fully understood whether loss of Hfe function modifies Mn neurotoxicity after ingestion. To investigate the role of Hfe in oral Mn toxicity, we exposed Hfe-knockout ($Hfe^{-/-}$) and their control wild-type ($Hfe^{+/+}$) mice to $MnCl_2$ in drinking water (5 mg/mL) for 5 weeks. Motor coordination and spatial memory capacity were determined by the rotarod test and the Barnes maze test, respectively. Brain and liver metal levels were analyzed by inductively coupled plasma mass spectrometry. Compared with the water-drinking group, mice drinking Mn significantly increased Mn concentrations in the liver and brain of both genotypes. Mn exposure decreased iron levels in the liver, but not in the brain. Neither Mn nor Hfe deficiency altered tissue concentrations of copper or zinc. The rotarod test showed that Mn exposure decreased motor skills in $Hfe^{+/+}$ mice, but not in $Hfe^{-/-}$ mice (p = 0.023). In the Barns maze test, latency to find the target hole was not altered in Mn-exposed $Hfe^{+/+}$ compared with water-drinking $Hfe^{+/+}$ mice. However, Mn-exposed $Hfe^{-/-}$ mice spent more time to find the target hole than Mn-drinking $Hfe^{+/+}$ mice (p = 0.028). These data indicate that loss of Hfe function impairs spatial memory upon Mn exposure in drinking water. Our results suggest that individuals with hemochromatosis could be more vulnerable to memory deficits induced by Mn ingestion from our environment. The pathophysiological role of HFE in manganese neurotoxicity should be carefully examined in patients with HFE-associated hemochromatosis and other iron overload disorders.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.10
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• pp.1328-1336
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• 2014

This paper proposes Power System Health Index(PSHI) newly. The paper describes several kind of power system health indices based on two main categories, which are adequacy and security. In adequacy, four kinds of health indices of Frequency, Voltage, Reserve(Operating Reserve Power and Frequency Regulation Reserve Power) and Overload of lines and transformers are proposed. In security, four kinds of health indices of Voltage(154kV, 345kV and 765kV), Overload of lines and transformers, Power flow constraint among areas and SPS are proposed. All indices are mapped with three domains, which are indicated as Health, Margin and Risk, defined with expert interview. While domains of health, margin and risk is defined similar with the conventional well being analysis of power system. The criterion of the domains is proposed using an interview with expert operators and practical reliability codes in Korea. The several kinds of health index functions, which are linear ratio, piecewise linear ration and reverse ratio function etc. are developed in this paper. It will be expected that the developed health indices can help operators to control power system more successfully and also prevent power system from accident as like as black out in future because operator can make a decision immediately based on more easily visual information of system conditions from too much indices acquisition of complex power system.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.1
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• pp.23-33
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• 2002

A hysteresis control is widely used to control output current of inverter. A hysteresis bandwidth is affected by system parameters such as source voltage, device on/off time, load inductance and resistance. The frequency limiter is used to protect switching devices overload. In the conventional hysteresis controller, a lock-out circuit with D-latch and timer is used to device protection circuit. But switching delay time and harmonic components are appeared in output current. In this paper the performance of lock-out circuit is tested, and new circuit for switching device fault protection is proposed ad it's performance is simulated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2535-2542
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• 2000

The regulator system has been modeled and combined to a swashplate type axial piston pump. Linear approximation has been performed for nonlinear coefficient terms of an axial piston pump-regulator model without significantly affecting accuracy. Based on the mathematical model of an axial piston pump-regulator system, a couple of characteristic curves of negative flow control and horsepower control are drawn, which show a good correlation with those of experimental results. So the simplified axial piston pump-regulator model in this paper is expected to be utilized not only for the design and analysis of hydraulic circuit of excavator but also for prevention of engine overload.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.3
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• pp.1523-1545
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• 2019

Cloud computing is now a widespread and economical option when data owners need to outsource or share their data. Designing secure and efficient data access control mechanism is one of the most challenging issues in cloud storage service. Anonymous broadcast encryption is a promising solution for its advantages in the respects of computation cost and communication overload. We bring forward an efficient anonymous identity-based broadcast encryption construction combined its application to the data access control mechanism in cloud storage service. The lengths for public parameters, user private key and ciphertext in the proposed scheme are all constant. Compared with the existing schemes, in terms of encrypting and decrypting computation cost, the construction of our scheme is more efficient. Furthermore, the proposed scheme is proved to achieve adaptive security against chosen-ciphertext attack adversaries in the standard model. Therefore, the proposed scheme is feasible for the system of data access control in cloud storage service.