• Korean Journal of Microbiology
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• v.29 no.3
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• pp.160-166
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• 1991

The regulatory mechanism of tubercidin biosynthesis in Streptomyces tubercidicus was studied. In a wild type strain, addition of adenine and histidine into the medium decreased the tubercidin production by 60-65% and 40%, respectively. The effects of adenine and histidine were alleviated by the addition of inosine monophosphate and 5-aminoimidazole-4-carboxamide ribotide. The production of tubercidin in S. tubercidicus K115 strain ($ade^{-}$ ) was nearly shut off by histidine. In contrast with K115 strain, adenine inhibited the tubercidin biosynthesis in S. tubercidicus K412 strain ($his^{-}$. In S. tubercidicus F667 strain ($ade^{-}$ , $his^{-}$ ), tubercidin production was increased by adenine and histidine. From the effects of adenine and histidine on tubercidin biosynthesis in S. tubercidicus wild type and mutant strains, it became known that feedback control by adenine and histidine of biosynthetic pathwat for purine ribonucleotide and histidine are involved in the regulation of tubercidin biosynthesis.

• Korean System Dynamics Review
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• v.1 no.1
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• pp.103-131
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• 2000

If a system such as a port has a large boundary and complexity, and the system's substance is considered as a black box, forecast accuracy will be very low. Futhermore various components in a port exert significant influence on each other. To copy with these problem the form of structure models were introduced by using SD method. The Competitive Ports Model had several sub-systems consisting of each Unit Port models, and each Unit Port model was made by quantitative, qualitative factors and their feedback loops. The fact that all components of one port have influence on the components of the other ports should be taken into account to construct Competitive Port Models. However, with the current approach that is impossible, and in this paper therefore, models were simplified by HFP adapted to integrate level variables of unit port models. Although many studies on modelling of port competitive situation have been conducted, both theoretical frame and methodology are still very weak. In this study, a new algorithm called ESD(Extensional System Dynamics) for the evaluation of port competition was presented, and applied to simulate port systems in northeast asia.

• Journal of Sensor Science and Technology
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• v.13 no.3
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• pp.236-243
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• 2004

In this paper, we proposed a brain-computer interface system using EEG signals. It can generate 4 direction command signal from EEG signals captured during imagination of subjects. Bandpass filter used for preprocessing to detect the brain signal, and the power spectrum at a specific frequency domain of the EEG signals for concentration status and non-concentration one is used for feature. In order to generate an adequate signal for controlling the 4 direction movement, we propose a new interface system implemented by using a support vector machine and a time-multiplexing method. Moreover, bio-feed back process and on-line adaptive pattern recognition mechanism are also considered in the proposed system. Computer experimental results show that the proposed method is effective to recognize the non-stational brain wave signal.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.410-413
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• 1988

In this paper, the real-time optical associative memory using multiple hologram which is generated with two angular multiplexed reference beams and Fourier transformed object beam in the $BaTiO_{3}$ crystal based on DFWM mechanism. When one image is recorded in the $BaTiO_{3}$ crystal, complete image can be recalled by 9 % partial input of the stored original image without any additional thresholding and optical feedback process. As an experimental result of multiple Fourier hologram which is recorded with two binary images, OHCHAS and PARKHK, we can obtain complete image recalled by 1/6 partial input of the stored image.

• Journal of Applied Reliability
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• v.13 no.1
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• pp.55-63
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• 2013

For a reliability assessment of large machinery parts, reliable data should be obtained from testing many samples for a long time. However, in case of testing these samples, testing cost is excessive; in case of life test for long time, power consumption is high; and in case of accelerated test by over load, very high cost is required to build the life testing device. Especially it is very frequent that the expensive device's life has ended during a accelerated test by over load. In this study, the design mechanism of the life testing device which excels in energy saving during the reliability test of large machinery parts has been introduced.

• Smart Structures and Systems
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• v.7 no.3
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• pp.199-211
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• 2011

Using computational modeling, we design a pair of biomimetic microcapsules that exploit chemical mechanisms to communicate and alter their local environment. As a result, these synthetic objects can undergo autonomous, directed motion. In the simulations, signaling microcapsules release "agonist" particles, while target microcapsules release "antagonist" particles and the permeabilities of both capsule types depend on the local particle concentration in the surrounding solution. Additionally, the released nanoscopic particles can bind to the underlying substrate and thereby create adhesion gradients that propel the microcapsules to move. Hydrodynamic interactions and the feedback mechanism provided by the dissolved particles are both necessary to achieve the cooperative behavior exhibited by these microcapsules. Our model provides a platform for integrating both the spatial and temporal behavior of assemblies of "artificial cells", and allows us to design a rich variety of structures capable of exhibiting complex dynamics. Due to the cell-like attributes of polymeric microcapsules and polymersomes, material systems are available for realizing our predictions.

• Smart Structures and Systems
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• v.6 no.3
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• pp.211-223
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• 2010

Accurate sensing of mechanical strains in civil structures is critical for optimizing structure reliability and lifetime. For instance, combined with intelligent control systems, electromechanical sensor output feedback has the potential to be employed for nondestructive damage evaluation. Application of Ionic Polymer Transducers (IPTs) represents a relatively new sensing approach with more than an order of magnitude higher sensitivity than traditional piezoelectric sensors. The primary reason this sensor has not been widely used to date is an inadequate understanding of the physics responsible for IPT sensing. This paper presents models and experiments defending the hypothesis of a streaming potential sensing mechanism.

• Journal of the Korean Operations Research and Management Science Society
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• v.28 no.2
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• pp.1-15
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• 2003

This paper presents a new evolutionary algorithm to solve complex multi-level integration problems, which is called multi-level symbiotic evolutionary algorithm (MEA). The MEA uses an efficient feedback mechanism to flow evolution information between and within levels, to enhance parallel search capability, and to improve convergence speed and population diversity. To show the MEA's applicability, It is applied to the integrated planning of production and distribution in supply chain management. The encoding and decoding methods are devised for the integrated problem. A set of experiments has been carried out, and the results are reported. The superiority of the algorithm's performance is demonstrated through experiments.

• Journal of KSNVE
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• v.2 no.1
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• pp.49-59
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• 1992

The motion analysis of a translation device driven by a piezoelectric actuator is performed to identify the mechanics of impact drive mechanism and to find the maximum speed waveform. The translation device is modeled as a semidefinite two-degree-of-freedom system. The motion analysis includes effects of friction force between moving mass and contact surface, dynamics of voltage amplifier and piezoelectric elements, and hysteresis of piezoelectric actuator. Base on the model, simulation studies are carried out and then compared with experimental results. It is found that the error between moving distances obtained by analysis and experiment is less than 15% and that the actual motion of moving mass is well predicted by the analytical work, finally, precision positioning experiments are carried out by using a proximity sensor as a feedback sensor. Position control of moving mass is initiated by the maximum speed waveform and finely tuned by the scaled down waveform so that accurate positioning is accomplished within the resolution of the sensor.

• Annual Conference of KIPS
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• 2000.10b
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• pp.1013-1016
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• 2000

기존의 end-to-end 방식에서는 네트워크 내부에서 혼잡(congestion)이 발생했을 경우 각 endpoint에서 즉시 알아 낼 수 없기 때문에 일정시간 동안 수신된 packet의 순서에 대한 정보로 혼잡이 발생했는지에 대해 추론하는 것이다. 따라서 네트워크 내부에서 직접적으로 정보를 얻거나 처리를 해 줄 수 있다면 기존 방식보다 처리율이 향상될 것이다. 본 논문에서는 Active Network 메커니즘을 이용하여 라우터를 구성하고 관련 모의실험결과를 보인다. 이를 통해서 기존의 방식보다 향상된 혼잡제어를 제시한다.