• 한국통신학회논문지
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• 제14권3호
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• pp.197-206
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• 1989

본 논문에서는 통신 프로토콜의 성능 분석을 위한 개선된 알고리즘을 제안한다. 이는 분산 시스템의 성능을 모델링하고 평가하는데 성공적으로 사용되어져 온 시간을 포함하는 확장된 Timed Petri Net 모델을 분석하는 알고리즘이다. 제안된 알고리즘은 일반적인 Timed Petir Net가 free-chioce 그리고 safe net 이라는 모델링의 제약을 완화하여, 제한적인 병행처리의 모델링을 허용한다. 그리고 Timed Reachability 그래프의 상태공간을 감소시키기 위해, 최다 수행규칙고 동시점화 트랜지션 집합을 이용한다. 알고리즘의 유용성 및 효율성을 보이기 위하여 Timed Reachability 그래프의 구성과 분석과정을 제시하고, 통신 프로토콜에 적용시켰다.

• 한국세라믹학회지
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• 제43권11호
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• pp.734-737
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• 2006

A series of manganite-based superlattices composed of half-metallic $La_{2/3}Sr_{1/3}MnO_3/LaMnO_3$ and insulating LaMnO$_3$ stacking layers were fabricated by employing pulsed laser deposition method. The dc resistivity increased drastically by simply reducing the stacking periodicity. The resistivity enhancement was accompanied by a gradual decrease in the temperature (T$_c$) of the Metal-to-Insulator Transition (MIT). This observation was interpreted as a small decrease in the effective metallic fraction near the percolation threshold. For the stacking periodicity less than a certain critical value, there appeared another transition to an insulating state at temperatures far below T$_c$. This low-temperature transition seems to be closely related to the AF-type (C-type) orbital ordering in newly formed insulating domains.

• Journal of the Korean Physical Society
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• 제73권11호
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• pp.1708-1711
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• 2018

The polycrystalline sample of $Ba_2Co_{1.5}Mg_{0.5}Fe_{11.88}Ga_{0.12}O_{22}$ Y-type hexaferrite, doped with Ga-cation, was prepared by using the solid-state reaction method. The crystalline structure of sample was investigated by x-ray diffractometer (XRD), and the magnetic properties of sample were measured by vibrating sample magnetometer (VSM), and $M{\ddot{o}}ssbauer$ spectrometer. The crystal structure of prepared sample was determined to be rhombohedral with space group R-3m. From the temperature dependence of the magnetization curves under 100 Oe between 4.2 and 740 K, two temperature-dependent magnetic transitions occurred in the $Ba_2Co_{1.5}Mg_{0.5}Fe_{11.88}Ga_{0.12}O_{22}$ sample. $M{\ddot{o}}ssbauer$ spectra of the sample were analyzed at various temperatures ranging from 4.2 to 620 K, and the $Ba_2Co_{1.5}Mg_{0.5}Fe_{11.88}Ga_{0.12}O_{22}$ sample showed abrupt changes in $H_{hf}$ and $E_Q$ at 200 K, indicating the spin transition effect. We have also determined the magnetic transition temperature $T_C$, in addition to the temperature dependent magnetization and ZVC measurements.

• 로봇학회논문지
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• 제14권4호
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• pp.285-292
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• 2019

Path planning is an important problem to solve in robotics and there has been many related studies so far. In the previous research, we proposed the Heterogeneous-Ants-Based Path Planner (HAB-PP) for the global path planning of mobile robots. The conventional path planners using grid map had discrete state transitions that constrain the only movement of an agent to multiples of 45 degrees. The HAB-PP provided the smoother path using the heterogeneous ants unlike the conventional path planners based on Ant Colony Optimization (ACO) algorithm. The planner, however, has the problem that the optimization of the path once found is fast but it takes a lot of time to find the first path to the goal point. Also, the HAB-PP often falls into a local optimum solution. To solve these problems, this paper proposes an improved ant-inspired path planner using the Rapidly-exploring Random Tree-star ($RRT^*$). The key ideas are to use $RRT^*$ as the characteristic of another heterogeneous ant and to share the information for the found path through the pheromone field. The comparative simulations with several scenarios verify the performance of the improved HAB-PP.

• Journal of Power Electronics
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• 제19권2호
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• pp.363-379
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• 2019

Resonant converters have attracted a lot of attention because of their high efficiency due to the soft-switching performance. An isolated high step-up converter with secondary-side resonant loops is proposed and analyzed in this paper. By placing the resonant loops on the secondary side, the current stress for the resonant capacitors is greatly reduced. The power loss caused by the equivalent series resistance of the resonant capacitor is also decreased. Clamp diodes in parallel with the resonant capacitors ensure a unique discontinuous current mode in the converter. Under this mode, the active switches can realize soft-switching during both turn-on and turn-off transitions. Meanwhile, the reverse-recovery problems of diodes are also alleviated by the leakage inductor. The converter is essentially a step-up converter. Therefore, it is helpful for decreasing the transformer turn-ratio when it is applied as a high step-up converter. The steady-state operation principle is analyzed in detail and design considerations are presented in this paper. Theoretical conclusions are verified by experimental results obtained from a 500W prototype with a 35V-42V input and a 400V output.

• Geomechanics and Engineering
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• 제30권4호
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• pp.393-399
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• 2022

The Segregation Potential (SP) is one of the most widely used predictors of frost heave in cold regions. Laboratory step-freezing tests determining a representative SP at the onset of the formation of the last ice lens (near the thermal steady state condition) can predict susceptibility to frost heave. Previous work has proposed empirical semi-log fitting for determination of the representative SP and applied it to several fine-grained soils, but considering only frost-susceptible soils. The presence of fines in coarse-grained soil affects frost susceptibility. Therefore, it is required to evaluate the applicability of the empirical semi-log fitting for both frost-susceptible and non-frost-susceptible soils with fines content. This paper reports laboratory frost heave tests for fines contents of 5%-70%. The frost susceptibility of soil mixtures composed of sand and silt was classified by the representative SP, and the suitability of the empirical semi-log fitting method was assessed. Combining semi-log fitting with simple laboratory frost heave testing using a temperature-controllable cell is shown to be suitable for both frost-susceptible and non-frost-susceptible soils. In addition, initially non-frost-susceptible soil became frost susceptible at a 10%-20% weight fraction of fines. This threshold fines content matched well with transitions in the engineering characteristics of both the unfrozen and frozen soil mixtures.

• Journal of Korean Vacuum Science & Technology
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• 제6권1호
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• pp.12-15
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• 2002

The physical properties, including magneto-optical and transport ones, of Ni$_2$MnG$_2$ alloy in the martensitic and austenitic states were investigated. The dependence of the temperature coefficient of resistivity on temperature shows kinks at the structural and ferro-para magnetic transitions. Electron-magnon and electron-phonon scattering are analyzed to be the dominant scattering mechanisms of the Ni$_2$MnG$_2$ alloy in the martensitic and austenitic states, respectively. The experimental real parts of the off-diagonal components of the dielectric function present two sharp peaks, one at 1.9 eV and the other at 3.2 eV, and a broad shoulder at 3.5 eV, all are identified by the band-structure calculations. These peak positions are coincident with those in the corresponding optical-conductivity spectrum, which is thought to originate from the single-spin state in Ni$_2$MnG$_2$ alloy.

• Elastomers and Composites
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• 제37권4호
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• pp.234-243
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• 2002

A general scheme of a rubber structure is proposed. Using the thermomechanical method(TMA), some changes in the molecular and topological structures for uncured and cured, and unfilled and filled rubbers during processing are shown. In our investigations as region it is understood a complex structure, which is expressed at the thermomechanical curve(TMC) as a zone differed from others in thermal expansion properties. This zone is between the noticed temperatures of relaxation transitions, usually on the level like those determined by DMTA at 1Hz. These regions, which shares, are not stable, and differ in molecular-weight distribution(MWD) of chain fragments between the junctions. Differences in dynamics of the formation of the molecular and topological structures of a vulcanizate are dependent on the rubber formulation, mixing technology and curing time. Some of characteristics of these regions correlate with mechanical properties of vulcanizates what is shown for NR rubbers containing ENR or CPE as a polymeric additive. It is well known that the state of order influences diffusivity of low-molecular substances into the polymer matrix. Because of this, the two topological amorphous regions should influence the distribution of the ingredients and resulting in rubber compounds' heterogeneity, and related properties of cured rubber. Investigation of this problem is expected to be, in the future, one of the essential factors in determining further improvement of polymeric materials properties by compounding with additives and in reprocessing of rubber scrap.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권1호
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• pp.64-88
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• 2024

Security and reliability are the utmost importance facts in intelligent networked vehicles. Stochastic Petri Net and Z (SPZN) as an excellent formal verification tool for modeling concurrent systems, can effectively handles concurrent operations within a system, establishes relationships among components, and conducts verification and reasoning to ensure the system's safety and reliability in practical applications. However, the application of a system with numerous nodes to Petri Net often leads to the issue of state explosion. To tackle these challenges, a refinement and abstraction method based on SPZN is proposed in this paper. This approach can not only refine and abstract the Stochastic Petri Net but also establish a corresponding relationship with the Z language. In determining the implementation rate of transitions in Stochastic Petri Net, we employ the interval average and weighted average method, which significantly reduces the time and space complexity compared to alternative techniques and is suitable for expert systems at various levels. This reduction facilitates subsequent comprehensive system analysis and module analysis. Furthermore, by analyzing the properties of Markov Chain isomorphism in the case study, recommendations for minimizing system risks in the application of intelligent parking within the intelligent networked vehicle system can be put forward.

• 드라이브 ㆍ 컨트롤
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• 제21권3호
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• pp.36-45
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• 2024

Collaborative robots, designed for direct interaction with humans have limited adaptability to environmental changes. This study addresses this limitation by implementing a barista robot system using AI technology. To overcome limitations of traditional collaborative robots, a model that applies a real-time object detection algorithm to a 6-degree-of-freedom robot arm to recognize and control the position of random cups is proposed. A coffee ordering application is developed, allowing users to place orders through the app, which the robot arm then automatically prepares. The system is connected to ROS via TCP/IP socket communication, performing various tasks through state transitions and gripper control. Experimental results confirmed that the barista robot could autonomously handle processes of ordering, preparing, and serving coffee.