• 상하수도학회지
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• 제28권1호
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• pp.1-11
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• 2014

The water distribution system should be invariably operated on continuous pattern for 24 hours a day. Occasionally, it is not practically possible to operate for 24 hours due to water shortage or financial constraints. Therefore an intermittent water supply is unavoidable in water shortage area and developing countries. But the intermittent water supply can introduce large pressure forces and rapid fluid accelerations into a water supply network. These disturbances may result in new pipe failure, leakage and secondary contamination. This paper proposed an improvement methodology to prevent the disturbances by intermittent water supply. For the study, the hydraulic variation of intermittent flow in water distribution system was measured and analyzed in the field by comparing with simulation of hydraulic model. Installations of control valves such as, pressure reducing and sustaining and air valves were employed for pressure and flow control. The effectiveness of the methods are presented by comparing hydraulic conditions before and after introducing the proposed solutions.

• 드라이브 ㆍ 컨트롤
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• 제11권4호
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• pp.53-60
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• 2014

This paper proposes a control scheme to reduce the power consumption of a variable displacement swash-plate type piston pump supplying oil to a valve-controlled hydraulic cylinder at constant pressure. Whenever flow rate demand was absent, the swash plate angle and the pump speed were changed to the minimum values required to compensate for the internal leakage flow. In response to command signals, the pump speed was changed in proportion to the absolute mean value of the speed component for position commands. At the same time, a pressure regulator was activated to maintain constant system pressure by precisely adjusting the pump speed with the swash plate angle fixed at the maximum. The conventional system consisting of a pressure-compensated variable displacement type pump is driven at a constant speed of 1,800rpm. By comparison, computer simulation and experimental results showed that idling power at stand-by status could be reduced by up to 70% by reducing the pump speed from 1,800rpm to 300rpm and the swash plate angle to the minimum.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권1호
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• pp.58-64
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• 2013

In this paper, two new flip-flop circuits with PCRAM latches that are FF-1 and FF-2, respectively, are proposed not to waste leakage during sleep time. Unlike the FF-1 circuit that has a normal PCRAM latch, the FF-2 circuit has a selective write latch that can reduce the switching activity in writing operation to save switching power at sleep-in moment. Moreover, a sequential sleep-in control is proposed to reduce the rush current peak that is observed at the sleep-in moment. From the simulation of storing '000000' to the PCRAM latch, we could verify that the proposed FF-1 and FF-2 consume smaller power than the conventional 45-nm FF if the sleep time is longer than $465{\mu}s$ and $95{\mu}s$, respectively, at $125^{\circ}C$. For the rush current peak, the sequential sleep-in control could reduce the current peak as much as 77%.

• 한국군사과학기술학회지
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• 제24권2호
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• pp.219-227
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• 2021

In the present study, the effect of command signals of the flow control valve on performance of underwater discharge systems using a linear pump was investigated numerically. For that, the improved mathematical model was developed. The improvement is to calculate the flow leakage between the water cylinder and the piston. Also the model of the hydraulic cylinder is simplified. To validate the improved model, calculation results were compared with experiment results. The results of the study is as follows: Double ramp command signals of the flow control valve had an advantage over single ramp signals. The parametric study on the effect of double ramp command signals on performance of the system was performed. In case of using double ramp signals, the maximum acceleration of the underwater vehicle was reduced by approximately 50 % compared with using single ramp signals.

• 한국안전학회지
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• 제36권4호
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• pp.1-11
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• 2021

Piping systems comprising pumps and valves are essential in the power plant, oil, and defense industry. Their purpose includes a stable supply of the working fluid or ensuring the target system's safe operation. However, piping system accidents due to leakage of toxic substances, explosions, and natural disasters are prevalent In addition, with the limited maintenance personnel, it becomes difficult to detect, isolate, and reconfigure the damage of the piping system and recover the unaffected area. An autonomous recovery piping system can play a vital role under such circumstances. The autonomous recovery algorithms for the piping system can be divided into low-pressure control algorithms, hydraulic resistance control algorithms, and flow inventory control algorithms. All three methods include autonomous opening/closing logic to isolate damaged areas and recovery the unaffected area of piping systems. However, because each algorithm has its strength and weakness, appropriate application considering the overall design, vital components, and operating conditions is crucial. In this regard, preliminary research on algorithm's working principle, its design procedures, and expected damage scenarios should be accomplished. This study examines the characteristics of algorithms, the design procedure, and working logic. Advantages and disadvantages are also analyzed through simulation results for a simplified piping system.

• 생물환경조절학회지
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• 제2권1호
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• pp.27-36
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• 1993

Carbon dioxide enrichment for greenhouse crops has generally been a standard commercial practice for many years. Vegetable crops such as tomato, cucumber, and lettuce respond positively to the $CO_2$ enrichment. But improper $CO_2$ enrichment leads to physiological damage and economical loss. This study was carried out to develop a $CO_2$ concentration control algorithm considering growth stage and efficiency. The measurand was $CO_2$ consumption rate and top fresh weight that represents growth stage. The weight of top fresh lettuce as a whole in the tray was measured through a non-destructive method. The demand in $CO_2$ concentration according to growth stage was investigated. The results are summarized as follows. 1. The $CO_2$ consumption rate could be measured within the error of $\pm$ 15.4mg$CO_2$/hr in the range of $CO_2$ concentration of 500-1500ppm. 2. The weight of top fresh lettuce could be measured within the error $\pm$ 4.3g in the range of 0-1400g. 3. The $CO_2$ control model developed could determine an economical $CO_2$ supply rate considering $CO_2$ consumption rate and leakage rate. 4. The $CO_2$ control algorithm based on the control model was composed of feedforward control for maintaining a stable $CO_2$ concentration level, and feedback control with $CO_2$ consumption rate and top fresh weight for adapting to the change in $CO_2$ demand by growth stage. 5. For the performance test with the developed control algorithm on lettuce the decrease in $CO_2$ supply rate was obtained without a significant decrease in top fresh weight.

• Journal of Information Technology Applications and Management
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• 제26권6호
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• pp.103-117
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• 2019

Demand for high power motors is rapidly increasing as the 4th industry and convergence technology has recently emerged. In order to produce high-strength permanent magnets, the magnets used for magnetization have been increased from DC 300V in the 1970s to DC 2.5kV in the 2010s, Up to DC 10kV in the 2030s, It is expected that higher voltage will be used to magnetize. However, in the case of a magnetizer using an existing electric signal control device, it is necessary to use a control device with a high-voltage insulation function in case a high voltage used for magnetization is leaked to the control device. If a short circuit accident occurs, the controller must be shut down and serious problems such as excessive repair costs arise. In this study, a control system adopting optical communication method instead of electric signal control method is proposed to prevent leakage currents in high-voltage magnetizer. We design a transmitter(Tx) and a receiver(Rx) device for the optical communication control device and implemented a prototype connecting the optical cable. In order to demonstrate the utility of high-voltage magnetizer using the optical communication control device, we analyzed the initial cost and the yearly cost for the years to analyze the net present value. As a result, In the case of the low-voltage magnetizer, the electric signal control method cost less, As the operating voltage of the magnetizer becomes higher. It is confirmed that it takes less cost when the optical communication control device is used.

• 한국정보통신학회논문지
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• 제14권12호
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• pp.2657-2662
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• 2010

모바일 기기 기반의 제어시스템에서 정보 해킹과 유출에 대비한 보안기능의 적용이 요구되고 있다. 이를 위한 보안 기술로서 가장 일반적인 방법은 암호와 인증이다. 본 연구에서는 보안 기능이 취약한 모바일 기기 기반의 제어 시스템에 있어서 효율적인 인증 방식 중 하나인 CBC-MAC (Cipher Block Chaining-Message Authentication Code)을 사용하여 외부의 공격으로부터 정보를 보호하는 CBC-MAC 기반의 보안 모바일기기 제어시스템 (SMIV: Secure Mobile in Vehicle)을 제안한다. CBC-MAC 은 송신측과 수신측에 비밀 키를 공유함으로써 전송된 정보가 변경되지 않고 본래의 정보임을 보증하는 방식이다. 제안 시스템의 검증을 위하여 모바일 기기 제어 시스템의 H/W 및 S/W를 구현하고 CBC-MAC 인증 방식을 적용하였다. 기존 연구에서는 모바일 기기를 이용한 제어시스템에서 보안성보다는 개선된 제어 방식이 주로 보고되고 있다. 본 연구에서는 모바일 기기를 이용한 제어시스템에서 보안성을 제고한 모바일 기기 제어시스템을 제안하며 이러한 보안 제어 시스템은 향후 모바일 기기를 이용한 각종 제어 시스템 설계 및 구축에 유용하게 사용될 것이다.

• 정보보호학회논문지
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• 제25권2호
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• pp.343-361
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• 2015

국내 금융권은 은행창구를 통해 전통적 수신, 여신 상품을 판매하던 구조에서 금융 소비채널의 변화 및 금융상품의 패러다임 변화를 겪으며 무한경쟁시대로 진입하고 있다. 이에 따라, 금융서비스의 개인화는 점점 가속화되고 있으며, 금융 관련 개인정보의 가치는 더욱 높아지고 있다. 2014년 카드사 정보유출사고에서 보았듯이, 대부분의 대형 금융관련 정보유출 사고는 해당 정보에 접근 권한을 가진 인력에 의해 발생한다. 따라서, 이러한 대량의 금융 관련 개인정보에 접근 권한이 있는 인력에 대한 기존의 정보 접근 통제정책 적용기준에 문제는 없는지 확인해 볼 필요가 있으며, 보안사고의 위험도에 영향을 미치는 요인에 따라 정보 접근 통제정책을 보완할 필요가 있다. 본 논문에서는 직무상 대량의 금융 정보에 접근 권한이 필요한 금융IT인력에 대해 직무, 직책 및 접근 정보의 민감도를 기준으로 보안사고의 위험도 측정에 필요한 영향 요인이 무엇인지 양적분석을 수행하고, 분석결과를 반영한 정보 접근 통제정책을 실무적 사례에 적용해 봄으로써 금융IT인력의 보안사고 위험도를 최소화할 수 있는 방안을 제시한다.

• 제어로봇시스템학회논문지
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• 제22권9호
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• pp.766-772
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• 2016

Recent advances in networking and computers, especially internet of things (IoT) technologies, have improved the quality of home life and industrial sites. However, the security vulnerability of IoT technologies causes life-threatening issues and information leakage concerns. Studies regarding security algorithms are being conducted. In this paper, we proposed SEED algorithms based on one time passwords (OTPs). The specified server sent time data to the client every 10 seconds. The client changed the security key using time data and generated a ciphertext by combining the changed security key and the matrix. We applied the SEED algorithms with enhanced security to Linux-based embedded boards and android smart phones, then conducted a door lock control experiment (door lock & unlock). In this process, the power consumed for decryption was measured. The power consumption of the OTP-based algorithm was measured as 0.405-0.465W. The OTP-based algorithm didn't show any difference from the existing SEED algorithms, but showed a better performance than the existing algorithms.