• Journal of Korea Society of Industrial Information Systems
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• v.21 no.6
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• pp.71-80
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• 2016

Along with the increase in the standard of living, the interest and awareness level of the public about environmental issues have also gradually increased. Recently, time spent on indoor activities have increased and the need for awareness and demand on methods in improving the quality of an indoor environment has been recognized. The purpose of this study is to sense the environment information through real-time monitoring of the room environment by using the IoT based technology and to maintain and improve the indoor environment to an appropriate level through the developed interlocking controller device. This provides an automatic control system in improving the indoor environment at home and other small areas like general offices in place of the traditional passive interior environmental improvement actions or large-scale facility control system. A status analysis with the relative reference values of the air quality and CO2, temperature and humidity and illumination and noise was applied through transmitting a control signal to automatic control module in accordance with the nine indoor environment standards set to improve the indoor environment.

• Journal of KIISE
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• v.41 no.11
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• pp.974-981
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• 2014

These days, use of multimedia streaming service and demand of QoS (Quality of Service) improvement have been increased because of development of network. QoS of streaming service is influenced by a jitter, delay, throughput, and loss rate. For guaranteeing these factors which are influencing QoS, the role of transport layer is very important. But existing TCP which is a typical transport layer protocol increases the size of congestion window slowly and decreases the size of a congestion window drastically. These TCP characteristic have a problem which cannot guarantee the QoS of UHD multimedia streaming service. In this paper, we propose a router buffer based congestion control method for improving the QoS of UHD streaming services. Our proposed scheme applies congestion window growth rate differentially according to a degree of congestion for preventing an excess of available bandwidth and maintaining a high bandwidth occupied. Also, our proposed scheme can control the size of congestion window according to a change of delay. After comparing with other congestion control protocols in the jitter, throughput, and loss rate, we found that our proposed scheme can offer a service which is suitable for the UDH streaming service.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.28-35
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• 2017

Recently, conventional hydraulic car lift systems face the technological limitations due to a lack of height control. The demand for height controllability is required in many tasks such as wheel alignment, and requires compensation for the structural deformation of the lift caused by irregular load distribution. In order to resolve this limitation of the conventional car lift, in this work, a new type of a hydraulic vehicle lift using a magneto-rheological (MR) valve system is proposed and analyzed. Firstly, the dynamic model of vehicle lift is formulated to evaluate control performance; subsequently, an MR valve is designed to obtain the desired pressure drop required in the car lift. Next, a proportional-integral-derivative (PID) controller is formulated to achieve accurate control of the lifting height and then computer simulations are undertaken to show accurate height control performances of the proposed new car lift system.

• Transactions on Control, Automation and Systems Engineering
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• v.3 no.3
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• pp.181-189
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• 2001

The software components of embedded control systems get extremely complex as they are designed into distributed systems get extremely complex as they are designed into distributed systems consisting of a large number of inexpensive microcontrollers interconnected by low-bandwidth real-time networks such as the controller area network (CAN). While recently emerging middleware technologies such as CORBA and DCOM address the complexity of distributed programming, they cannot be directly applied to distributed control system design due to their excessive resource demand and inadequate communication models. In this paper, we propose a CORBA-based middleware design for CAN-based distributed embedded control systems. Our design goal is to minimize its resource need and make it support group communication without losing the IDL (interface definition language) level compliance to the OMG standards. To achieve this, we develop a transport protocol on the CAN and a group communication scheme based on the well-known publisher/subscriber model. The protocol effectively realizes subject-based addressing and supports anonymous publisher/subscriber communication. We also customize the method invocation and message passing protocol, referred to as the general inter-ORB protocol (GIOP), of CORBA so that CORBA method invocations are efficiently serviced on a low-bandwidth network such as the CAN. This customization includes packed data encoding and variable-length integer encoding for compact representation of IDL data types. We have implemented our CORBA-based middleware on the mArx real-time operating system we have developed at Seoul National University. Our experiments clearly demonstrate that it is feasible to use CORBA in developing distributed embedded control systems possessing severe resource limitations. Our design clearly demonstrates that it is feasible to use a CORBA-based middleware in developing distributed embedded systems on real-time networks possessing severe resource limitations.

• The KIPS Transactions:PartC
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• v.10C no.1
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• pp.11-16
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• 2003

This paper implements Multiple User Authentication System to which the system authenticating with password only has been upgraded. The 4-staged authentication including user ID, password, smart card and access control information, etc. is used at the suggested Multiple User Authentication System. The user authentication system that this paper suggests has been developed based on SecuROS/FreeBSD with the function of access control added to FreeBSD kernel. It provides both the function to limit accost range to the system to each user and the function to check that when inputting important information the demand is the one if the system ; thus, the reliability becomes increased. In the SecuROS/FreeBSD system, MAC and RBAC are being used. So, in the case of users accessing to the system, the Information about the policies of MAC and RBAC to which users would access is used in the authentication. At the time, the access to system if permitted only when the access control information that users demanded satisfies all the access control rules which have been defined In the system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.257-258
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• 2015

Korean power consumption of the electrical supply problems due to excess demand is repeated every year, the interest in energy increasing social and personal cost has been subject to the number of ways to reduce this cost increases. Automatic doors and automatic door installation market is increasing every year and frequently, when used in general commercial and communal porch consumption based on average 300 times a day power is 70[W] degree is a monthly average usage is about 50.4[KW]. The level can not ignore the power consumption due to switching frequency is large. In this paper, by converting the energy to be discarded in the automatic doors to the inverter and the regenerative energy and to develop control systems for power regeneration to reduce the power consumption by utilizing automatic contact auxiliary power.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.6B
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• pp.553-562
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• 2003

Supporting QoS (Quality of Service) for the multimedia applications becomes an important issue as the demand of multimedia applications increases. Thus, it is necessary for the application layer to have an efficient congestion control algorithm, which can support the multimedia applications' QoS requirements. In this paper, we propose a new application layer congestion control algorithm, called RRC-OTT (Receiver-based Rate Control with One-way Trip Time). RRC-OTT algorithm differs from the previously proposed algorithms in that the receiver takes the responsibility of the network congestion control. Thus, RRC-OTT algorithm can not only precisely estimate the network congestion using OTT (one-way Trip Time), but reduce the work load from the sender (e.g., the web server). Our simulation study shows that RRC-OTT algorithm can maintain the comparable link utilization to the previously proposed algorithms and keep the packet jitter low, which thus can help enhance the quality of multimedia applications.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.2
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• pp.131-136
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• 2021

A DC motor is an important driving source used in a wide range along with an induction motor. Although the structure is complex and has disadvantages in terms of maintenance, most of the demands are given to induction motors as a power source in the industry today, but due to its excellent control performance, DC motors are constantly being used as small-sized control motors. In addition, DC motors with a structure capable of high-power and high-efficiency operation are being developed with the development of magnetic materials as a structure capable of using a permanent magnet in a armature. In addition, the configuration of the controller is simpler than that of an induction motor using an inverter, and the demand for a DC motor is still not negligible, so it is still occupied as an important power source. Considering these trends, this paper attempts to investigate the control performance of DC motors through hardware implementation such as modeling through simulation, PWM generation circuit and electric motor circuit using EPLD, and PI control using processor.

• Plant Journal
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• v.18 no.4
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• pp.66-72
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• 2023

In order to respond to the demand for flexible operation of thermal power generation, development of natural sliding pressure operation that minimizes throttle loss by opening the turbine control valve 100% and maximize power generation efficiency in conjunction with ESS in order to quickly respond to fluctuations in the system frequency is required. The logic development of natural sliding pressure operation with ESS was developed to modify the existing logic at the power plant's top-level control logic such as the unit master, the boiler master and the turbine master. Cooperative control algorithms that complement the advantages and disadvantages of ESS operation (quick response, limited capacity) and power plant operation (slow response, continuous operation) not only improve efficiency when applied to actual power plants, but also respond quickly and flexibly to load demands to ensure system stability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1781-1791
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• 2013

The present study was intended to measure the level of psychosocial stress and fatigue symptom according to the various characteristics such as sociodemographic, health-related, job-related, job stress factors, and psychosocial factors among nurses working at ward and operating room in university hospitals, and to reveal the relation between these factors and psychosocial stress and fatigue symptom. The self-administered questionnaires were given to 220 nurses working at ward, and 147 nurses working at operating room in 4 participating hospitals located in Daejeon City during the period from July 1st to Aug 31st, 2012. As a results, the factors related to the psychosocial stress of nurses working at ward were age, subjective health status, job career, satisfaction of work, fit to the job, job demand, job control, coworker support, self-esteem, locus of control, type A behavior pattern. In operating room, there were age, sleep hours, subjective health status, job career, physical burden of work, satisfaction of work, fit to the job, consider quitting the job, job demand, job control, type A behavior pattern. The factors related to the fatigue symptoms of nurses working at ward were age, leisure time, subjective health status, satisfaction of work, consider quitting the job, job demand, locus of control, type A behavior pattern. In operating room, there were age, subjective health status, physical burden of work, supervisor support, coworker support, locus of control. Based on the study results, we suggest that the factors related to psychosocial stress and fatigue symptom of nurses were different from working station. We need development and application of programs to keep under management psychosocial stress and fatigue symptom.