• Korean Journal of Materials Research
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• v.23 no.5
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• pp.293-298
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• 2013

In this study, an HP-mod. type(KHR-45A), which is used as a heater tube material in the pyrolysis process, was evaluated for its carburizing properties. It was confirmed from the microstructural observation of the tubes that the volume fraction of carbide increased and that the coarsening of Cr-carbide generated as a degree of carburization increased. The depth of the hardened layer, which is similar to the thickness of the carburized region of each specimen, due to carburization is confirmed by measurement of the micro-Vickers hardness of the cross section tube, which thickness is similar to that of the carburized region of each specimen. Two types of chromium carbides were identified from the EBSD (electron back-scattered diffraction) image and the EDS (energy-dispersive spectroscopy) analysis: Cr-rich $M_{23}C_6$ in the outer region and Cr-rich $M_7C_3$ in the inner region of tubes. The EDS analysis revealed a correlation between the ferromagnetic behavior of the tubes and the chromium depletion in the matrix. The chromium depletion in the austenite matrix is the main cause of the magnetization of the carburized tube. The method used currently for the measurement of the carburization of the tubes is confirmed; carburizing evaluation is useful for magnetic flux density measurement. The volume fraction of the carbide increased as the measuring point moved into the carburized side; this was determined from the calculation of the volume fraction in the cross-section image of the tubes. These results are similar to the trends of carburization measurement when those trends were evaluated by measurement of the magnetic flux density.

• International Journal of Highway Engineering
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• v.19 no.2
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• pp.67-74
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• 2017

PURPOSES : The objective of this study is to ascertain the curing period of cementless cold central plant recycled asphalt base-layer, using mechanical analyses and specimen quality tests on the field. METHODS : Cold central plant recycled asphalt base-layer mixture was produced in the plant from reclaimed asphalt, natural aggregate, filler for the cold mix, and the modified emulsion AP using asphalt mix design and plant mix design. In order to examine the applicability of the curing period during the field test, the international standards for the possibility of core extraction and the degree of compaction and LFWD deflection were analyzed. Moreover, Marshall stability test, porosity test, and indirect tensile strength test were performed on the specimens of asphalt mix and plant mix design. RESULTS : The plant production process and compaction method of cementless cold central plant recycled asphalt base-layer were established, and the applicability of the optical moisture content for producing the mixture was verified through the field test. In addition, it was determined that the core extraction method of the conventional international curing standard was insufficient to ensure performance, and the LFWD test demonstrated that the deflection converges after a two-day curing. However, the back-calculation analysis reveals that a three-day curing is satisfactory, resulting in a general level of performance of dense asphalt base-layer. Moreover, from the result of the specimen quality test of the asphalt mix design and plant mix design according to the curing period, it was determined that the qualities satisfied both domestic and international standards, after a two-day curing. However, it was determined that the strength and stiffness after three-day curing are higher than those after a two-day curing by approximately 3.5 % and 20 %, respectively. CONCLUSIONS:A three-day curing period is proposed for the cementless cold central plant recycled asphalt base-layer; this curing period can be demonstrated to retain the modulus of asphalt-base layer in the field and ensure stable quality characteristics.

• Journal of the Korea Society of Computer and Information
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• v.15 no.2
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• pp.147-154
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• 2010

This paper suggests new route plan cost calculation and cost-effective route plan algorithm and architecture for the new city traffic information system when it is operated nationwide. New algorithm and architecture estimates cost with traffic speeds which is supported for all different lanes, stratifies logical layer which process different levels' traffic information with diverse traffic patterns and provides different traffic information in the few levels. Also suggested new algorithm supports drivers' customized traffic information through both-way communications and plans routes effectively based on the distance between drivers' start position and destination and different levels which start and end position located. It proposes additional research items and requirement for integration between different cities' traffic information system which the national police agency invested and led.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.16 no.2
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• pp.75-81
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• 1983

The studies on the age determination of the spottybelly greenling, Agrammus agrammus, caught in the shore of Tongbaeksom were done by the articulative fossae of the vertebra through a stero-dissecting microscope. For determining annunli the vertebra had been cleaved lengthwise in the dorsoventral direction. Half of the vertebra had been fixed on Canada balsam with the flat side directed upwards. The alternation of two zones on the vertebra was observed. One is wide and light-colored, and the other is narrow and dark-colored. The annual layer, where the dark-colored zone shifts to the light-colored one, was appeared extending from July to August once a year. Study of the growth of A. agrammus was carried out by the method of back calculation from the vertebra.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.5
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• pp.90-99
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• 1984

A onetimensional distribution of the temperature and the heat source in the SOI (silicon-on-insulator) multi-layer structure illuminated by tungsten lamps from both sides was obtained by solving the heat equation in steady state on a finite difference grid using successive over-relaxation method. The heat source distribution was obtained by considering such features as spectral components of the light source, multiple reflection at the internal interfaces, temperature and frequency dependence of the light absorption coefficient, etc. The front and back surface temperatures, which are boundary conditions for the heat equation, were derived from a requirement that they satisfy the radiation conditions. The radiation flux as well as the conduction flux was considered in modelling the thermal behaviour at the internal interfaces. Since the temperature and the heat source profiles are strongly dependent upon each other, the calculation of each profile was iterated using the updated profile of the other until they are consistent with each other. The experimental temperature at the front surface of the wafer as measured by Pyrometer was about 1200$^{\circ}$K, while the simulated temperature was 1120$^{\circ}$K.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.1
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• pp.36-46
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• 2013

This paper proposes the design of broadband spiral antenna for a potable non-linear junction detector (NLJD) system. To realize the broadband antenna design, it was considered optimization of the number of spiral turns by iteration calculation. Ground plane with the Archimedean spiral slit to keep the same current distribution between radiating plane and ground is considered for circular polarization design. In order to realize high directivity and high gain of the proposed antenna, the cavity wall and the metal cap which is located on back of ground plane were also considered in design. Measurement results of return loss were agreed well with VSWR 2:1 at interested frequency band among 2.4 to 2.44 GHz, 4.84 to 4.92 GHz and 7.28 to 7.36 GHz. Measured axial ratio was observed 3 dB below and showed reasonable agreement with simulation results. Characteristics of the RHCP(Right Hand Circular Polarization) with the measured gain of 6.8 dBi above at interested frequency band were also observed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1212-1217
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• 2004

The main back-bone operation in elliptic curve cryptosystems is scalar point multiplication. The most frequently used method implementing the scalar point multiplication, which is performed in the upper level of GF multiplication and GF division, has been the double-and-add algorithm, which is recently challenged by NAF(Non-Adjacent Format) algorithm. In this paper, we propose a more efficient and novel scalar multiplication method than existing double-and-add by applying redundant receding which originates from radix-4 Booth's algorithm. After deriving the novel quad-and-add algorithm, we created a new operation, named point quadruple, and verified with real application calculation to utilize it. Derived numerical expressions were verified using both C programs and HDL (Hardware Description Language) in real applications. Proposed method of elliptic curve scalar point multiplication can be utilized in many elliptic curve security applications for handling efficient and fast calculations.

• Korean Journal of Optics and Photonics
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• v.16 no.2
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• pp.113-120
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• 2005

Luminous efficiency and uniformity in a LCD-BLU are mainly determined by fine scattering patterns formed on the light guide panel. We propose a novel fabrication method of 3-dimensional scattered patterns based on anisotropic etching of silicon wafers. Micro-pyramid patterns with 70.5 degree apex-angle and micro-prism patterns with 109.4 degree apex-angle can be self-constructed by the wet, anisotropic etching of (100) and (110) silicon wafers, respectively, and those patterns are easily duplicated by the PDMS replica process. Experimental results on spatial and angular distributions of irradiation from the light guide panel with the micro-pyramid patterns were very consistent with the calculation results. Surface roughness of the silicon-based micro-patterns is free from any artificial defects since the micro-patterns are inherently formed with silicon crystal surfaces. Therefore, we expect that the silicon based micro-patterning process makes it possible to fabricate perfect 3-dimensional micro-structures with crystal surface and apex angles, which may guarantee mass-reproduction of the light guide panels in LCD-BLU.

• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.149-158
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• 2006

We have analyzed various tolerances of the multi-configurative microscopic system for inspecting the wire-bonding of a reed frame by using the Gaussian bracket method and the equivalent lens method. The tolerances for the curvature and the thickness, which are axial symmetric tolerances, are given by varying the back focal length within a fecal depth under diffraction-limited conditions. Moreover, by using the trial and error method, the axial non-symmetric tolerances for decenter and tilt are established by assigning the 5% variation of MTF(modulation transfer function) at the spatial frequency of 50 lp/mm and at the field angle of 0.7 field. As the tolerances with the most probable distribution are distributed within the range of the decay rate of less than 5% independent of the probability distribution of tolerances, we can achieve completely the desired design performances of the multi-configurative microscopic system by using the various ranges of these tolerances.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1778-1790
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• 2018

Based on the requirements and characteristics of multi-zone autonomous decision-making in modern power system, fully distributed computing methods are needed to optimize the economic dispatch (ED) problem coordination of multi-regional power system on the basis of constructing decomposition and interaction mechanism. In this paper, four fully distributed methods based on alternating direction method of multipliers (ADMM) are used for solving the ED problem in distributed manner. By duplicating variables, the 2-block classical ADMM can be directly used to solve ED problem fully distributed. The second method is employing ADMM to solve the dual problem of ED in fully distributed manner. N-block methods based on ADMM including Alternating Direction Method with Gaussian back substitution (ADM_G) and Exchange ADMM (E_ADMM) are employed also. These two methods all can solve ED problem in distributed manner. However, the former one cannot be carried out in parallel. In this paper, four fully distributed methods solve the ED problem in distributed collaborative manner. And we also discussed the difference of four algorithms from the aspects of algorithm convergence, calculation speed and parameter change. Some simulation results are reported to test the performance of these distributed algorithms in serial and parallel.