• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권2호
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• pp.611-627
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• 2017

For enhancing the coverage of wireless networks and increasing the spectrum efficiency, small cell networks (SCNs) are considered to be one of the most prospective schemes. Most of the existing literature on resource allocation among non-cooperative small cell base stations (SBSs) has widely drawn close attention and there are only a small number of the cooperative ideas in SCNs. Based on the motivation, we further investigate the cooperative approach, which is formulated as a coalition formation game with power control algorithm (CFG-PC). First, we formulate the downlink sub-channel resource allocation problem in an SCN as a coalition formation game. Pareto order and utilitarian order are applied to form coalitions respectively. Second, to achieve more availability and efficiency power assignment, we expand and solve the power control using particle swarm optimization (PSO). Finally, with our proposed algorithm, each SBS can cooperatively work and eventually converge to a stable SBS partition. As far as the transmit rate of per SBS and the system rate are concerned respectively, simulation results indicate that our proposed CFG-PC has a significant advantage, relative to a classical coalition formation algorithm and the non-cooperative case.

• 한국정보통신학회논문지
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• 제19권11호
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• pp.2554-2561
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• 2015

본 연구에서는 이동 로봇의 군집제어기에 관한 연구로써 구조가 단순한 PID 제어기의 장점을 살리고, 추종 로봇의 동역학 특성에 강인한 성능을 내는 적응 PID 제어기를 제안하고자 한다. 모의실험을 통하여 제안된 적응 PID 제어기가 일반적인 PID 제어기에 비하여 군집 제어에서 추종 로봇의 추종 성능인 일정 거리 와 일정 각도를 잘 유지하며, 추종 로봇의 무게가 변화될 경우에도 잘 추종함을 알 수 있다. 이는 제안된 적응 PID 제어기가 이득을 변화시켜 최적의 성능을 나타냄을 알 수 있다. 이를 통해 제안된 적응 PID 제어기의 성능이 우수함을 검증할 수 있다.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2006년도 PAN PACIFIC CONFERENCE vol.2
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• pp.317-321
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• 2006

The investigation of the formation of organic sulfur compounds (i.e., odor species), mainly methyl mercaptan and demethyl suifide, during kraft pulping has been conducted, in which both hardwood and softwood species were used. It was discovered that there is an organic sulfur compounds formation phase transition point with respect to delignification extent. The transition point occurs at a kappa number of approximately 35 and 20 for softwoods and hardwoods, respectively. The results also showed that both low sulfidity and anthraquinone (AQ) addition are helpful to control the formation of theses organic sulfur compounds during kraft pulping. Whereas Hexenuronic acid (HexA) has contribution to Kappa number, the extended delignification not only lead to low pulp yield, but also be adverse to odor control. A significant in-digester odor reduction can be achieved if the pulping is to be terminated before phase transition point and combined with AQ addition.

• 한국군사과학기술학회지
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• 제25권6호
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• pp.586-595
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• 2022

In this paper, we propose a formation control algorithm for multi-USVs according to COLREGs. First, we applied the Dynamic Window Approach algorithm that can reflect the kinematic characteristics for the path movement of USVs. Then, we propose a virtual structure-based virtual leader-follower method that applies the advantages of leader-follower and virtual structure methods among conventional formation control algorithms for stability. Next, we proposed a collision avoidance algorithm according to all COLREGs when encountering an opposing ship by adding COLREGs situational conditions to the virtual leader, and finally confirmed the feasibility of the proposed method through simulation.

• 한국항공우주학회지
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• 제33권10호
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• pp.51-59
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• 2005

본 논문에서는 위성간 상대 궤도 운동과 최적화 기법에 근거한 다위성체 편대비행 형상 유지에 관한 연구 결과를 제시하였다. 편대를 이루는 위성간의 상대 운동은 궤도 압축 방법을 이용한 닫힌 형태의 궤도 전파기를 이용하여 분석하였고, 최적화 기법을 도입하여 편대 비행 형상을 유지하기 위한 각 위성의 궤도 기동 절차를 설계하였다. 예제로서 원형 편대 비행 제어 문제에 적용하였고 비선형 시뮬레이션 결과를 제시하였다.

• 한국산업정보학회논문지
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• 제24권5호
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• pp.115-120
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• 2019

본 논문에서는 이동 구간 입자 군집 최적화 (Receding horizon particle swarm optimization; RHPSO) 알고리즘 기반 다개체 로봇 편대 제어 알고리즘의 통계적 성능 분석 결과를 제시한다. 다개체 로봇의 편대 제어 문제는 로봇 간 충돌 회피를 고려할 경우, 구속 조건이 있는 비선형 최적화 문제로 정의될 수 있다. 일반적으로 구속 조건이 있는 비선형 최적화 문제는 최적해를 찾는데 많은 시간이 걸리는 문제점이 있다. 이동 구간 입자 군집 최적화 알고리즘은 로봇 편대 제어의 최적화 문제에 대한 준최적해를 빠르게 찾기 위해 제안된 알고리즘이다. 이동 구간 입자 군집 최적화 알고리즘은 알고리즘에 사용되는 후보해의 개수와 세대 수가 증가함에 따라 계산 복잡도가 증가한다. 따라서 최소의 후보해와 세대 수만으로 실시간 제어에 사용될 수 있는 준최적해를 찾는 것이 중요하다. 본 논문에서는 이동 구간 입자 군집 최적화 알고리즘의 후보해의 수와 세대 수에 따른 제어 오차를 비교하였다. 다양한 조건의 시뮬레이션 실험을 통해서 통계적으로 결과를 분석하고, 허용 가능한 편대 오차 범위 내에서 이동 구간 입자 군집 최적화 알고리즘의 최소 후보해의 수와 세대 수를 도출한다.

• Imaging Science in Dentistry
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• 제34권3호
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• pp.137-144
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• 2004

Purpose: To investigate the effects of low dose irradiation on the calcium content and calcific nodule formation of the MC3T3-El osteoblastic cell line. Materials and Methods: Cells were irradiated with a single dose of 0.2, 0.4 and 0.6 Gy at a dose rate of 5.38 Gy/min using Cs-137 irradiator. After irradiation, the calcium content and calcific nodule formation were examined on the 1st, 2nd, 3rd and 4th week. Results: We did not find any significant difference of total calcium content after irradiation of 0.2, 0.4 and 0.6 Gy when compared with the unirradiated control group. There was no significant difference of total calcium content between 0.2, 0.4 and 0.6 Gy irradiated groups. We found an increased tendency of the calcific nodule formation after irradiation of 0.2, 0.4 and 0.6 Gy when compared with the unirradiated control group without significant difference of calcific nodule formation between 0.2, 0.4 and 0.6 Gy irradiated groups. Conclusion : The results showed an increased tendency of the calcific nodule formation after low dose irradiation. However, this tendency did not increase with the increase of irradiation dose.

• Geomechanics and Engineering
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• 제23권2호
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• pp.127-137
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• 2020

To study the reverse fault formation process and the stress evolution feature, a simulation test system of reverse fault formation is developed based on the analysis of reverse fault formation mechanism. The system mainly consists of simulation laboratory module, operation console and horizontal loading control system, and data monitoring system. It can represent the fault formation process, induce fault crack initiation and simulate faults of different throws. Simulation tests on reverse fault formation process are conducted by using the simulation test system: horizontal loading is added to one side of the model. the bottom rock layer cracks under the effect of the induction device. The crack dip angle is about 29°. A reverse fault is formed with the expansion of the crack dip angle towards the upper right along the fracture surface and the slippage of the hanging wall over the foot wall. Its formation process unfolds five stages: compressive deformation of rock, local crack initiation, reverse fault penetration, slippage of the hanging wall over the foot wall and compaction of fault plane. There is residual structural stress inside rock after fault formation. The study methods and results have guiding and referential significance for further study on reverse fault formation mechanism and rock stress evolution.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2475-2480
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• 2003

A control system design based on coupled nonlinear oscillators (CNOs) for a self-organized swarm system is presented. In this scheme, agents self-organize to flock and arrange group formations through attractive and repulsive forces among themselves using CNOs. Virtual agents are also used to create richer group formation patterns. The objective of the swarm control in this paper is to follow a moving target with a final group formation in the shortest possible time despite some obstacles. The simulation results have shown that the proposed scheme can effectively construct a self-organized multi-agent swarm system capable of group formation and group immigration despite the emergence of obstacles.

• Journal of Astronomy and Space Sciences
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• 제25권3호
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• pp.255-266
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• 2008

The current paper presents application of a new analytic solution in general relative motion to spacecraft formation flying in an elliptic orbit. The calculus of variations is used to analytically find optimal trajectories and controls for the given problem. The inverse of the fundamental matrix associated with the dynamic equations is not required for the solution in the current study. It is verified that the optimal thrust vector is a function of the fundamental matrix of the given state equations. The cost function and the state vector during the reconfiguration can be analytically obtained as well. The results predict the form of optimal solutions in advance without having to solve the problem. Numerical simulation shows the brevity and the accuracy of the general analytic solutions developed in the current paper.