• Radiation Oncology Journal
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• v.9 no.2
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• pp.343-350
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• 1991

The quasi-conformation therapy was performed to get a homogeneous dose distributions for irregeular shaped tumor lesion by using the arc moving beam and beam modifying filter which was made by cerrobend alloy($\rho$=9.4 g/cc) metal. In our dose calcuation programme, it was fundmentally based on Clarkson's method to calcuate the irregular multi-step block field in rotation therapy. In this study, the expected relative depth doses under multipartial attenuator agree well with measured data at same plane. The results of comparison the dose computation with that of TLD measurement are very closed within ${\pm}5\%$ uncertainties in the irradiation to phantom with quasi-comformation method. And it has shown that irregular typed multi-step filter can be applied to quasi-conformation therapy in high energy radiation plannings.

• Journal of Korean Society of Water and Wastewater
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• v.16 no.6
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• pp.670-678
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• 2002

Since Korean government imposed a stricter regulation on effluent T-N and T-P concentrations from wastewater treatment plant, a new process has to be developed to meet these rules and this process should remove T-N and T-P, economically, from weak wastewater that is typical for Korea's combined sewer system sewage. In this study, a computer simulator, BioWin from EnviroSim, Inc. was used. Three processes - A2/O, Modified Johannesburg, UCT- had been simulated under same operational conditions and a new process - Parallel BNR Process - had been developed based on these simulation results. The Parallel BNR process consists of two rows of reactors: One row has anaerobic and aerobic reactors in series, and the other row has RAS anoxic1 and RAS anoxic2 reactors in series. In order to ensure anaerobic state in anaerobic tank, a part of influent is fed to RAS anoxic1 tank in second row. This process had been simulated under same conditions of other three processes and the simulation results were compared. The results showed that three existing processes could not perform biological phosphorus removal when the average influent was fed at any operation temperatures. However, the Parallel BNR process was found that biological phosphorus removal could be performed when both design and average influent were fed at any operation temperatures. This process showed the T-N concentration in effluent had a maximum value of 15mg/L when design influent was fed at $13^{\circ}C$ and a minimum value of 14mg/L when average influent was fed at $20^{\circ}C$. Also, T-P concentrations had a maximum value of 1.3mg/L when average influent was fed at $20^{\circ}C$ and a minimum value of 1.1mg/L when design influent was fed at $13^{\circ}C$. Based on these results, we found that this process can remove nitrogen and phosphorus biologically under any operational conditions.

• The Journal of the Korea Contents Association
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• v.17 no.5
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• pp.317-325
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• 2017

There has been a growing interest in programming education recently. However, to use most programming languages the corresponding compiler and IDE have to be installed on computers. To tackle this issue, though there developed several web-based programming environment including Eclipse Che and JDOODLE, most of them does not support GUI nor Korean programming languages. This paper proposes a web-based programming environment called Bombart, which supports Saesark, a Korean programming language, with GUI output. It also supports a console-based input and output. To support both kinds of interfaces, two compiling subsystems are designed and implemented. To test the effectiveness of the GUI support of Bombart, all the Java tutorial codes on GUI are translated into Saesark and executed on top of Bombart. According to this test, 81.42% of codes can be successfully converted and executed.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10a
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• pp.238-243
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• 2006

휴대용 단말기의 보급과 인터넷 및 무선 네트워크의 발달로 사용자들이 사용하는 개별 장치들이 보편화되어 있으며, 이들을 서로 유기적으로 엮은 서비스가 등장하고 있다. 본 논문에서는 이러한 서비스의 한 종류로 U-Kiosk의 개념을 소개한다. U-Kiosk는 Kiosk 단말장치나 공용 PC를 사용자 개인의 PC처럼 사용할 수 있도록 하여 이들의 리소스를 직접 제어할 수 있는 기능을 제공한다. 이것을 실현하기 위한 방안으로 본 논문에서는 공용 PC에서 개인 PC의 바탕화면 설정을 포함해 모든 자원을 직접 사용할 수 있도록 하는 부분을 구현하고 설명을 하였으며, 인증 과정에서 사용자의 개입을 최소한으로 줄이는 방법에 대해서 소개한다. 이를 위하여 초소형 보안 단말기인 PANDA를 사용하였으며, Zigbee 통신을 사용하여 사용자의 위치정보를 파악하여 자동으로 인증을 하도록 하는 Transient Authentication의 개념을 도입하였다. 두 컴퓨터 간의 원격 접속을 위해서는 VNC를 이용하여 구현하였으며, 사용자가 공용 PC로부터 일정 거리 안에 있을 경우, 자동으로 원격 접속이 이루어지고, 공용 PC로부터 멀어질 경우 자동으로 접속이 종료되도록 구현하였다. 이를 기반으로 제안하는 U-Kiosk의 개념에 맞는 테스트 베드를 구축 하였다. 이는 UFC Project$^{2)}$의 일부로서 차후 완벽한 인증 인프라를 구축하여 보다 안정적이고 사용하기 편리한 U-Kiosk의 구현에 초석이 될 것이다.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.11
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• pp.581-591
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• 2001

We consider some problems of remote file accesses of multiple clients in mobile computing environments. In this environment, user mobility affects file access latency. Mobile hosts have severe resource constraints in terms of limited size of non-volatile storage. Thus, the burden of computation and communication load raise file access latency. In this paper, we propose a scheme for reducing the file access latency through the file migration. The objective is to minimize of file accesses for all mobile hosts which delivering the file to clients as quickly as possible. We develope an on-demand scheme which determines when the file server should migrate files to another server, or when it should transfer files to mobile hosts. Using simulation, we examine the effects which parameters such as file access frequency, file size, mobility rate have on file system access latency. Through simulation results, we show that our proposed migration scheme is effective in reducing the access latency on the requested file of a mobile host with high access rate and low mobility.

• KIPS Transactions on Computer and Communication Systems
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• v.1 no.1
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• pp.29-34
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• 2012

Wireless multicast service can be used for video streaming service to save the network resources by sending the same popular multimedia contents to a group of users at once. For better multimedia streaming multicast service, we propose a quality-aware rate adaptation (QARA) scheme for scalable video multicast in rate adaptive wireless networks. In QARA, transmission rate is determined depending on the content's type and users' channel conditions. First, the base layer is transmitted by a low rate for high reliability. That means we provide basic service quality to all users. On the contrary, the transmission rate for enhancement layer is adapted by using channel condition feedback from a randomly selected node. So, the enhancement layer frames in a multimedia content is sent with various transmission rates. Therefore, each node can be provided with differentiated quality services. Consequently, QARA is capable of serving heterogeneous population of mobile nodes. Moreover, it can utilize network resources more efficiently. Our simulation results show that QARA outperforms utilization of the available transmission rate and reduces the data transmission time.

• The KIPS Transactions:PartC
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• v.11C no.5
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• pp.645-652
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• 2004

In this paper, we aggregate multi-links information between boundary nodes using the line segment scheme that aggregates topology in-formation within PG referring bandwidth and delay parameter. The proposed scheme can search multi-links efficiently using the depth priority method based on hop count instead of searching all links. To do this, we propose a modified line segment algorithm using two line segment method that represents two points which consist of delay-bandwidth pair to reduce topology information and provide a flexibility to the multi pie-links aggregation. And we apply it to current star topology aggregation. To evaluate performance of the proposed scheme, we compare/analyze the current method with the proposed scheme with respect to call success rate, access time and crankback rate. Through the simulation result analysis, the proposed star topology aggregation scheme presents the better performance than existing scheme.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.11
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• pp.549-560
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• 2001

Cluster system provides attractive scalability in terms of compution power and memory size. With the advances in high speed computer network technology, cluster systems are becoming increasingly competitive compared to expensive MPPs (massively parallel processors). Load balancing is very important issue since an inappropriate scheduling of tasks cannot exploit the true potential of the system and can offset the gain from parallelization. In parallel processing program, it is difficult to predict the load of each task before running the program. Furthermore, tasks are interdependent each other in many ways. The dynamic load balancing algorithm, which evaluates each processor's load in runtime, partitions each task into the appropriate granularity and assigns them to processors in proportion to their performance in cluster systems. However, if the communication cost between processing nodes is expensive, it is not efficient for all nodes to attend load balancing process. In this paper, we restrict a processor that attend load balancing by the communication cost and the deviation of its load from the average. We simulate various models of the cluster system with parameters such as communication cost, node number, and range of workload value to compare existing load balancing methods with the proposed dynamic algorithms.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.5
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• pp.591-597
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• 2007

In swarm robot systems, each robot must behaves by itself according to the its states and environments, and if necessary, must cooperates with other robots in order to carry out a given task. Therefore it is essential that each robot has both learning and evolution ability to adapt the dynamic environments. In this paper, the new polygon based Q-learning algorithm and distributed genetic algorithms are proposed for behavior learning and evolution of collective autonomous mobile robots. And by distributed genetic algorithm exchanging the chromosome acquired under different environments by communication each robot can improve its behavior ability Specially, in order to improve the performance of evolution, selective crossover using the characteristic of reinforcement learning is adopted in this paper. we verify the effectiveness of the proposed method by applying it to cooperative search problem.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.5
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• pp.648-653
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• 2007

Researches on artificial emotion which generates emotion artificially from various external excitations imitating human emotion has been initiated in recent years. But the conventional studies in which the emotion state is changed exponentially or linearly by external emotion excitation have a drawback that the variation of emotion state is changed rapidly and abruptly. In this paper, we propose an artificial emotion generation model which reflects not only strength and frequency of external emotion excitations but also period of it in the emotion state and represents the emotion state with a sigmoid curve w.r.t. time. And we propose an artificial emotion system which generates emotion at the situation of no external emotional excitations through recollection of past emotional excitations, and show its effectiveness through computer simulation results.