• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.118-120
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• 2003

PtolemyII의 CSP 도메인은 병렬 시스템을 효과적으로 명세할 수 있는 프로세스 알제브라 언어인 CSP를 구현한 것이다. CCS도 프로세스 알제브라 언어로써 정형적으로 병렬시스템을 명세하고 검증할 수 있다. 이 두 언어는 비슷한 목적으로 가지고 개발되었으나 통신의 세부적인 부분의 개념에 있어서 차이가 존재한다. 특히 CCS 를 기반으로 하여 개발된 ACSR 의 경우 실시간 시스템을 정형적으로 명세하고 검증하기 위해 필요한 시간과 자원의 개념을 추가하였다. 본 논문에서는 ACSR 도메인을 PtolemyII에 구현하기 위한 단계적인 방법으로 CCS와 CSP의 차이점을 밝혀서, 기존의 CSP 도메인의 Rendezvous 알고리즘을 CCS 기반의 통신이 이루어 질 수 있도록 수정하여 PtolemyII에 CCS 도메인을 구현하였다.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10c
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• pp.430-432
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• 1999

인터넷 멀티캐스트 라우팅을 위해 PIM, CBT, DVMR 등의 여러 가지 프로토콜이 연구되고 있다. 본 논문에서는 이와 같은 멀티캐스트 라우팅에서 QoS를 보장하기 위한 새로운 방법을 제시한다. 이 방법은 멀티캐스팅 라우팅의 두가지 접근법 중 공유 트리 접근법에서 지연시간에 대한 QoS를 보장하는 방법으로 PIM-SM을 개선한 형태를 취한다. 동적인 멤버쉽에 의해 주어진 지연시간 상한값을 만족하지 않는 상황이 발생하면 공유 트리의 RP(Rendezvous Point)를 다시 선택하고 트리를 제구성함으로서 QoS를 보장하는 방법을 사용하며, 시뮬레이션을 통해 이 방법의 적절성을 확인하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.12
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• pp.1124-1131
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• 2015

This paper describes a 5-dof ground testbed which emulates micro-gravity environment for developing Rendezvous/docking algorithm of a nano-satellite. The testbed consists of two parts, the low part which eliminates friction force with ground and the upper part which has 3-dof rotational motion with respect to the low part. For Vison-based autonomous navigation algorithm, we use camera, LIDAR and AHRS as sensors and eight cold gas thrusters and three axis directional reaction wheels as actuators. All system software are implemented with C++ based on on-board computer and Linux OS.

• Journal of KIISE:Information Networking
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• v.35 no.4
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• pp.268-281
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• 2008

It is difficult to construct streaming services based on the overlay networks without any loss of scalability. DONet is one of the most representative streaming overlay network protocols without managing any specific structure. Since DONet does not support the nodes on private networks, it can be considered that the performance of the overlay is not the best. Hole Punching is one of the famous techniques participating the nodes on private networks to streaming overlay networks by using a rendezvous server. However, using only a single rendezvous server cannot be suggested in P2P environment, because it can cause problems in terms of scalability and so on. In this paper, we propose DONet-p, an extension of DONet with Distributed Hole Punching techniques. It supports the nodes on private networks without toss of scalability. The experimental results show the better performance and scalability than DONet with a minimum overhead for additional control messages.

• Journal of Astronomy and Space Sciences
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• v.15 no.1
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• pp.235-244
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• 1998

The solutions of orbital maneuver problem using the sliding mode control in the presence of the erath gravitational perturbations is obtained. Especially, the optimization of consuming fuel for maneuver is performed. The impulsive solution to Lambert's problem using the combined equation method to minimize total ${\Delta}V is used for the desired orbit and the maneuver times. Two-step sliding mode control method is introduced for satisfying the boundary conditions of finite-thrust rendezvous problem at the end of maneuver time. Using the new approach to the orbit maneuver problem, two-step sliding mode control, orbit maneuvers are processed. The solutions to a rendezvous using the optimal control are obtained, and they are compared to the results by two-step sliding control.According to the new approach for orbit maneuver, the thrust-coast-thrust type controller is obtained to make satellite to track desired Lambert's orbit, and the total ${\Delta}V$ required for maneuver is resonable in comparison with the impulsive solution to Lambert's problem. The final state variables, also are close to the boundary conditions at the end of maneuver times.

• Journal of the Korea Computer Industry Society
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• v.3 no.9
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• pp.1235-1244
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• 2002

This paper proposes a group key management protocol for a secure of all the multicast user in PIM-SM multicast group communication. With prosed architect, subgroups for multicast secure group management will be divided by RP (Rendezvous-Point) unit and each RP has a subgroup manager. Each subgroup manager gives a secure key to it's own transmitter md the transmitter compress the data with it's own secure key from the subgroup manager. Before the transmitter send the data to receiver, the transmitter prepare to encrypt a user's service by sending a encryption key to the receiver though the secure channel, after choking the user's validity through the secure channel. As the transmitter sending a data after then, the architecture is designed that the receiver will decode the received data with the transmitter's group key. As a result, the transmitting time is shortened because there is no need to data translation by group key on data sending and the data transmition is possible without new key distribution at path change to SPT (Shortest Path Tree) of the router characteristic. Additionally, the whole architecture size is samller than the other multicast secure architecture by using the conventional PIM-SIM routing structure without any additional equipment.

• Journal of Trauma and Injury
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• v.31 no.2
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• pp.103-106
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• 2018

Fat embolism refers to the presence of fat droplets within the peripheral and lung microcirculation with or without clinical sequelae. However, early diagnosis of fat embolism is very difficult because the embolism usually does not show at the computed tomography as a large fat complex within vessels. Forty-eight-year-old male with pedestrian traffic accident ransferred from a local hospital by helicopter to the regional trauma center by two flight surgeons on board. At the rendezvous point, he had suffered with dyspnea without any airway obstruction sign with 90% of oxygen saturation from pulse oximetry with giving 15 L of oxygen by a reserve bag mask. The patient was intubated at the rendezvous point. The secondary survey of the patient revealed multiple pelvic bone fracture with sacrum fracture, right femur shaft fracture and right tibia head fracture. Abdominal computed tomography was performed in 191 minutes after the injury and fat embolism with Hounsfield unit of -86 in his right common iliac vein was identified. Here is a very rare case that mass of fat embolism was shown within common iliac vein detected in computed tomography. Early detection of the fat embolus and early stabilization of the fractures are essential to the prevention of sequelae such as cerebral fat embolism.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.153-164
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• 2010

In this paper, we propose a multi-channel MAC protocol to improve the channel efficiency and network performance in wireless ad hoc networks. There are two main problems encountered in designing multi-channel MAC protocols. The first problem is the rendezvous problem and the second is multi-channel hidden node problem. In order to solve these problems, most of previous researches that have considered multi-channel MAC protocols use a common control channel to exchange control packets. However, they have a bottleneck problem at common control channel as increasing the number of data channels. The proposed MAC protocol solves the multi-channel hidden node problem using a TDMA scheme and increases the network throughput because transmitting and receiving data at the same time is possible. Also, since there is no common control channel, the network does not suffer from the common control channel saturation problem. Moreover, it achieves energy savings by allowing nodes that are not involved in communication to go into sleep mode. Simulation results show that the proposed MAC protocol improves the network throughput and channel efficiency and provides energy savings.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1B
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• pp.45-54
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• 2003

In the Protocol-Independent Multicast Sparse Mode(PIM-SM), we need a careful selection scheme for the Rendezvous Point(RP) which influences much on the QoS due to the delay among multicast group members and packet loss The QoS based RP selection schemes choose RPs which satisfy the restriction conditions such as bandwidth, delay, and other QoS parameters In this paper, we propose a new RP selection scheme which is a variation of the group-based RP selection scheme The new algorithm, MCT(Maximum Cross Tree), is implemented by taking advantages of the topology-based selection scheme and the group-based selection scheme as well In order to verify the proposed algorithm, we first measure the multicast traffic data of the Virtual Conference System implemented on the IPv6 network via KOREN, then expand the results to two types of network models and analyze the performance by computer simulation.

• The KIPS Transactions:PartC
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• v.10C no.6
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• pp.809-814
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• 2003

The multicast transmitting the real-time data to groups may easily have many attacks from abnormal attacks because it has many links as compared to the unicast. The existing group key management architectures for preventing these problems are designed for protocols suitable for a large scale. Thus these architectures applied to a small scale routing protocols may have many overheads with key distribution and a constant core tree. Therefore this paper proposes a groups key management protocol for a secure multicast in PIM-SM multicast group communication. The proposed method divide multicast groups with RO(Rendezvous-Point), and subgroup key managers are established in each RP and can be transmitted groups keys between senders and receivers, so the security cannel is set up for secure data transfer, And this does not have needs of the data translation for group keys and the new key distribution for path change. As a result of this, the data transmission time can be reduced.