• Journal of Microbiology and Biotechnology
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• v.14 no.6
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• pp.1327-1332
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• 2004

The hemA gene encoding 5-aminolevulinic acid synthase (ALAS) was cloned from Rhodobacter capsulatus, and its nucleotide sequence was determined. DNA sequencing data revealed one open reading frame coding for a protein with 401 amino acids that displayed high similarity to the amino acid sequences of other known ALASs. The hemA gene was then cloned and expressed under the control of constitutive promotor in E. coli. The recombinant E. coli strain was able to accumulate 5-aminolevulinic acid to 21 mM in the liquid medium supplemented with 45 mM glycine and 120 mM succinate. In addition, a marked effect of the pH of the culture medium on ALA production was observed, and the optimum pH for culture medium was determined to be 5.8-6.3.

• Journal of Powder Materials
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• v.9 no.6
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• pp.422-432
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• 2002

Mechanically driven decomposition of intermetallics during mechanical milling(MM 1 was investigated. This process for Fe-Ce and Fe-Sn system was studied using conventional XRD, DSC, magnetization and alternative current susceptibility measurements. Mechanical alloying and milling form products of the following composition (in sequence of increasing Gecontent): $\alpha$(${\alpha}_1$) bcc solid solution, $\alpha$+$\beta$-phase ($Fe_{2-x}Ge$), $\beta$-phase, $\beta$+FeGe(B20), FeGE(B20), FeGe(B20)+$FeGe_2$,$FeGe_2$,$FeGe_2$+Ge, Ge. Incongruently melting intermetallics $Fe_6Ge_5$ and $Fe_2Ge_3$ decompose under milling. $Fe_6Ge_5$ produces mixture of $\hat{a}$-phase and FeGe(B20), $Fe_2Ge_3$ produces mixture of FeGe(B20) and $FeGe_2$ phases. These facts are in good agreement with the model that implies local melting as a mechanism of new phase for-mation during medchanical alloying. Stability of FeGe(B20) phase, which is also incongruently melting compound, is explained as a result of highest density of this phase in Fe-Ge system. Under mechanical milling (MM) in planetary ball mill, FeSn intermetallic decomposes with formation $Fe_5Sn_3$ and $FeSn_2$ phases, which have the biggest density among the phases of Fe-Sn system. If decomposition degree of FeSn is relatively small(<60%), milled powder shows superparamagnetic behavior at room temperature. For this case, magnetization curves can be fitted by superposition of two Langevin functions. particle sizes for ferromagnetic $Fe_5Sn_3$ phase determined from fitting parameters are in good agreement with crystalline sizes determined from XRD data and remiain approximately chageless during MM. The decomposition of FeSn is attributed to the effects of local temperature and local pressure produced by ball collisions.

• Structural Engineering and Mechanics
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• v.66 no.1
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• pp.45-59
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• 2018

The bi-material elastic system consisting of the pre-stressed hollow cylinder and pre-stresses surrounding infinite elastic medium is considered and it is assumed that the mentioned initial stresses in this system are caused with the compressing or stretching uniformly distributed normal forces acting at infinity in the direction which is parallel to the cylinder's axis. Moreover, it is assumed that on the internal surface of the cylinder the ring load which moves with constant velocity acts and within these frameworks it is required to determine the influence of the aforementioned initial stresses on the critical velocity of the moving load. The corresponding investigations are carried out within the framework of the so-called three-dimensional linearized theory of elastic waves in initially stresses bodies and the axisymmetric stress-strain state case is considered. The "moving coordinate system" method is used and the Fourier transform is employed for solution to the formulated mathematical problem and Fourier transformation of the sought values are determined analytically. However, the originals of those are determined numerically with the use of the Sommerfeld contour method. The critical velocity is determined from the criterion, according to which, the magnitudes of the absolute values of the stresses and displacements caused with the moving load approaches an infinity. Numerical results on the influence of the initial stresses on the critical velocity and interface normal and shear stresses are presented and discussed. In particular, it is established that the initial stretching (compressing) of the constituents of the system under consideration causes a decrease (an increase) in the values of the critical velocity.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.10
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• pp.486-493
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• 2000

This paper presents an application to a multimachine power system of power system stabilizer using revised pole shift adaptive algorithm. Controller parameters are determined by using adaptive control theory in order to maintain optimal operation of generator under the various operating conditions. To determine the optimal parameters of controller and overcome the problem of pole placement algorithm, this paper presents pole shift algorithm revised pole shift factor. Also, the difference between the speed deviation with weighted factor and voltage deviation is used as the input signal of adaptive controller, which provides good damping characteristics. The results tested on a multimachine power system verify that the proposed controller has better dynamic and transient performance than conventional controller.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.4
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• pp.84-94
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• 1991

In order to achieve high accuracy of teaching and increase productivity using industrial robots in polishing process of dies, an off-line task programming system was developed on IBM-PC/386 under WINDOWS 3.0 operating system. The internal structure and the machematical basis of CAMPoli are described. Surface modeling technique of polishing dies with sculptured surfaces is introduced by poing data interpolation methodology through the use of CL-data transmitted from conventional CAM system. Tool selection, polishing speed, polishing pressure and kinds of tool motions can be determined and selected by user specified polishing variables. Task creation and verification of polishing path via computer graphics simulation of polishing tool can be done by the menu- driven function of CAMPoli system. Post-processing module is attached to generate robot language. Some simulation results are provided as verification means of the system.

• Journal of IKEEE
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• v.5 no.1 s.8
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• pp.35-42
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• 2001

This paper deals with an architecture of network-based control system using the CAN(Controller Area Network) protocol and its traffic analysis. It is difficult to determine an optimal network-based control architecture for a specific AGV(Autonomous Guided Vehicle) system with a manipulator arm. The fixed number of periodic messages to be occurred is pre-defined in the system. To determine whether the proposed system architecture is effective or not, we perform traffic analysis for the real-time communication of all messages. Through simulations, the range of transmission speed is found satisfying required conditions and the permissible number of additional sensors is investigated for improving the system performance, when the sampling periods of analog sensors are determined under fixed condition that the transmission speed is over 500Kbps.

• Water Engineering Research
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• v.4 no.1
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• pp.1-17
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• 2003

A mathematical model was developed to simulate the performance of a prototype wind-powered reverse osmosis desalination system. The model consists of two sub-models operated in a series. The first sub-model is the wind-energy conversion sub-model, which has wind energy and feed water as its input and pressurized feed water as its output. The second sub-model is a reverse osmosis (RO) process sub-model, with pressurized feed water as its input and the flow and salinity of the product water or permeate as its output. Model coefficients were determined based on field experiments of a prototype wind powered RO desalination system of the University of Hawaii, from June to December 2001. The mathematical model developed by this study predicts the performance of wind-powered RO desalination systems under different design conditions. The system optimization is achieved using a linear programming approach. Based on the results of system optimization, a design guide is prepared, which can be used by both manufacturer and end-user of the wind-driven reverse osmosis system.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.1159-1165
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• 2011

Telemetry techniques of rats have been used for assessing safety pharmacology of drugs and chemicals. Biological signals including blood pressure and heart rate measured under anesthesia were significantly different from those obtained under normal conditions. The stress of restraint in awake animals can also affect the accuracy of physiological evaluation. This paper details the surgery required to allow key cardiovascular parameters to be determined. The telemetric measurement of cardiovascular parameters such as blood pressure, heart rate, electrocardiograph(ECG) established. We carried out the continuous monitoring of cardiovascular parameters using the telemetry system in F344 rats. During the measurement, no significant changes were observed in the heart rate and blood pressure. ECG signals and body temperature were also constant during the measurement of biological signals. With the results of this study, we conclude that this telemetry system can be applied usefully for the assesment of biological parameters in the rats.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.2
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• pp.185-191
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• 2000

The safety problem of aged tunnels has been emphasized. For the effective maintenance, site inspection of tunnel structures and surrounding grounds are required periodically. Also, the determination of safety of tunnels is not a simple problem. So the role experienced engineer in the maintenance is very important and development of an expert system that can perform as the engineers, has been needed. In this study, from the results of numerical analysis in several case, new precision inspection rules which can substitute actual numerical analysis are determined by a commercial program FLAC and regression analysis under various parameters such as material property, lining thickness, overburden and laterial coefficients. They are added to the knowledge base to determine safety of tunnel lining. To verify the expert system, the results are compared with an existing tunnel diagnosis report. It can be concluded that the new rule are well represented the actual numerical analysis under various site conditions. Therefore it is expected that the systematic management for effective maintenance of tunnel structure will be possible.

• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.60-72
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• 2019

The air-cooled passive decay heat removal system (APDHR) was proposed to provide the ultimate heat sink for non-LOCA accidents. The APDHR is a modified one of Passive Auxiliary Feed-water system (PAFS) installed in APR+. The PAFS has a heat exchanger in the Passive Condensate Cooling Tank (PCCT) and can remove decay heat for 8 h. After that, the heat transfer rate through the PAFS drastically decreases because the heat transfer condition changes from water to air. The APDHR with a vertical heat exchanger in PCCT will be able to remove the decay heat by air if it has sufficient natural convection in PCCT. We conducted the thermal-hydraulic simulation by the MARS code to investigate the behavior of the APR + selected as a reference plant for the simulation. The simulation contains two phases based on water depletion: the early phase and the late phase. In the early phase, the volume of water in PCCT was determined to avoid the water depletion in three days after shutdown. In the late phase, when the number of the HXs is greater than 4089 per PCCT, the MARS simulation confirmed the long-term cooling by air is possible under extended Station Blackout (SBO).