• Journal of the Institute of Electronics and Information Engineers
• /
• v.54 no.6
• /
• pp.3-10
• /
• 2017

In this paper, we have designed a MIMO system using a W-OFDM modulation scheme. And then, we have evaluated and analyzed synchronization performance of the system. In this paper, we have considered Schmidl's method, Minn's method, and Park's method. As simulation results, Schmidl's method has wide plateau of timing metric and Park's method has impulse-shape timing metric. Also, we can confirm that timing metric characteristic of synchronization estimator is not changed by adjusting extension length of W-OFDM system. Because of this, we can confirm that synchronization method of OFDM can be effectively used in MIMO system using W-OFDM modulation.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.21 no.1
• /
• pp.13-20
• /
• 2008

Graded layers in which two different constituent particles are mixed are inserted into functionally graded material such that the volume fractions of constituent particles vary continuously and functionally over the entire material domain. The material properties of this dual-phase graded region, which is essential for the numerical analysis of the thermo-mechanical behavior of FGM, have been predicted by traditional homogenization methods. But, these methods are limited to predict the global equivalent material properties of FGMs because the detailed geometry information such as the particel shape and the dispersion structure is not considered. In this context, this study intends to investigate the characteristics of these homogenization methods through the finite element analysis utilizing the discrete micromechanics models of the graded layer, for various volume fractions and external loading conditions.

• Journal of the Korean Geophysical Society
• /
• v.2 no.1
• /
• pp.57-64
• /
• 1999

To effectively identify near-surface faults with vertical slips from seismic refraction data, the GRM interpretation technique is tested and investigated in terms of various parameters through computer modeling. A characteristic change in shape of the velocity-analysis function near faults is noticed, and a new strategy of `Slope Variation Indicator (SVI)' is developed and tested in this study. The SVI is defined as a first horizontal derivative of the difference of velocity analysis functions for a large XY value and a small one, respectively. As the dip of refractor decreases and as the difference in XY value increases, the peak value of SVI increases and its duration decreases. Consequently, the SVI indicates accurately the location of buried fault in the test models. The SVI is believed to be an efficient tool in seismic refraction method to investigate location and distribution of shallowly buried faults.

• Journal of Convergence for Information Technology
• /
• v.7 no.6
• /
• pp.143-151
• /
• 2017

The generalized Hough transform(GHough) can be used effectively for detecting and extracting an arbitrary-shaped 2-D model in an input image. However, the main drawbacks of the GHough are both heavy computation and an excessive storage requirement. Thus, most of the researches so far have focused on reducing both the time and space requirement of the GHough. But it is still not clear how well their improved algorithms will perform under various noise in an input image. Thus, this paper proposes a new framework that can measure the performance of the GHough quantitatively. For this purpose, we view the GHough as a detector in signal detection theory and the ROC curve will be used to specify the performance of the GHough. Finally, we show that we can evaluate the GHough under various noise conditions in an input image.

• The Korean Journal of Zoology
• /
• v.14 no.4
• /
• pp.181-191
• /
• 1971

In Diplonichus esakii each ovary comprises five telotrophic ovarioles. In the fourth instar, the anterior part of the germarium consists of undifferentiated cells. The middle part contains a spherical trophic and the posterior part comprises young oocytes, followed by the upside downbell shape prefollicular tissue. The bell form is the standard characteristic in this instar larva, and the nutritive cord is found although somewhat indistinctly. In the fifth instar larva, the trophic core is elliptical form, and the oocyte is found at the base of the core. The oocytes are connected with the ocre by the nutritive cord. In the prefollicular tissue are also found some oocytes. In the adult, the vitellarium is filled by the developmental oocytes. The yolk granules inside each oocyte migrate from the base of the follicular epithelial cells to the center of the oocyte. Finally, the ooplasm of the oocyte becomes completely homogeneous. Therefore, according to the advancing of instars the nutritive cord developes completely before the oocyte has chorion and the follicular epithelial cell binucleates. The upper part of the ovariole consists of unchorionated oocytes, and the proximal part comprises chorionated oocytes in the adult.

• Journal of the Korean Magnetics Society
• /
• v.8 no.4
• /
• pp.241-248
• /
• 1998

In accordance with tendency to miniaturization and high frequency operation of electronic products, extensive efforts of miniaturizing magnetic devices such as inductors, transformers and magnetic sensors are being made. In order to study on fabrication and characteristic of micro-magnetic devices, we carried out two sets of experiments. One is to develop a magnetic film that is suitable for high frequency operation, and the other is to develop the fabrication processes for realizing the micro-coil with meander shape. Magnetic films were composed of FeTa(N,C) fabricated by DC magnetron sputtering system. Their microstructures were nanocrystalline structure and magnetic properties showed Bs:13~17 kG, Hc:0.1~0.2 Oe and $\mu$':2000~4000. Cu coil pattern fabricated by selective electroplating process showed good electrical conductivity. In the case of air core inductors, inductance (L) of 50 nH, resonance frequency $(f_R)$ of 700 MHz, and quality factor (Q) of 30 at 200 MHz could be obtained. In the case of close type magnetic inductors, inductance (L) of 150 nH, resonance frequency $(f_R)$ of 100 MHz, and quality factor (Q) of 4 at 10~30 MHz could be obtained.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.13 no.8
• /
• pp.769-776
• /
• 2002

In this paper, we propose uniform slot width bow-tie-shaped meander slot antenna for 5 GHz application. The conventional bow-tie slot antenna has broadband characteristic, however, its size is large. Meanwhile, the meander slot antenna has small size, but it has quite narrow bandwidth. The proposed antenna geometry is a variation of the meander slot antenna incorporating bow-tie shape to realize miniaturized antenna having relatively large bandwidth. Simulated results show that with the same slot width and total slot length, the bandwidth of the proposed antenna is 3 times wider than that of meander slot antenna, and its resonant frequency is 3.01 GHz lower than that of the equal size(H x V) bow-tie slot antenna, and measured results show that the bandwidth of proposed antenna is 218 MHz(5.142 GHz ~ 5.360 GHz) which satisfy the required bandwidth from 5.15 GHz to 5.35 GHz.

• Journal of electromagnetic engineering and science
• /
• v.14 no.3
• /
• pp.284-292
• /
• 2014

This paper presents a characteristic evaluation of commercial gallium nitride (GaN) transistors having two different gate-lengths of $0.4-{\mu}m$ and $0.25-{\mu}m$ in the design of a class-S power amplifier (PA). Class-S PA is operated by a random pulse-width input signal from band-pass delta-sigma modulation and has to deal with harmonics that consider quantization noise. Although a transistor having a short gate-length has an advantage of efficient operation at higher frequency for harmonics of the pulse signal, several problems can arise, such as the cost and export license of a $0.25-{\mu}m$ transistor. The possibility of using a $0.4-{\mu}m$ transistor on a class-S PA at 955 MHz is evaluated by comparing the frequency characteristics of GaN transistors having two different gate-lengths and extracting the intrinsic parameters as a shape of the simplified switch-based model. In addition, the effectiveness of the switch model is evaluated by currentmode class-D (CMCD) simulation. Finally, device characteristics are compared in terms of current-mode class-S PA. The analyses of the CMCD PA reveal that although the efficiency of $0.4-{\mu}m$ transistor decreases more as the operating frequency increases from 955 MHz to 3,500 MHz due to the efficiency limitation at the higher frequency region, it shows similar power and efficiency of 41.6 dBm and 49%, respectively, at 955 MHz when compared to the $0.25-{\mu}m$ transistor.

• Journal of the Korean Ceramic Society
• /
• v.53 no.5
• /
• pp.529-534
• /
• 2016

Nanocrystalline powder of zirconia stabilized with 8 mol% yttria (YSZ) has been synthesized through oxalate process using $ZrOCl_2{\cdot}8H_2O$ and $Y(NO_3)_3{\cdot}6H_2O$ as starting materials. Understanding of the characteristic changes of YSZ powder as a function of processing conditions is crucial in developing dense and porous microstructures required for fuel cell applications. In this research, microstructure change, surface area, particle shape and particle size were measured as a function of different processing conditions such as calcination temperature, stirring speed and concentration of starting materials. The resultant crystallite sizes were calculated by XRD-LB (X-Ray Diffraction Line-Broadening) method, BET method, and morphology of the crystal was observed in TEM and FE-SEM. The TEM examination showed that the powder synthesized with 0.7 M of YSZ concentration had a spherical morphology with sizes ranging from 20 to 40 nm. However, the powder was gradually aggregated above 1.0 M of YSZ concentration with the aggregation being intensified as the YSZ concentration was increased.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.29 no.1
• /
• pp.32-40
• /
• 2001

The purpose of designing Haebaragi park, legally designated as children park, is to make a place for children including residents performing outdoor recreation, various social interactions, and cultural activities. Design concept for space plan have twofold; the one is a positive and creative playing space and facilities for children, escaped from a monotonous playground, and the other is a cultural and social space for neighboring communities. The site having the area of 1,316.7 square meters, located in Nowon-Dong, Buk-Gu, Daegu metropolitan City, is just like a vest pocket park. The adjacent area had been developed a slum area with mixed ad visually conflicting land use patterns and low income groups. The children and residents living in the area do not have any public space suitable for playing and/or rest. After analyzing such locational characteristic as accessibility, land use of the communities, and potentials for park development, and such design concept as arrangement of facilities, efficient use of site, and functional allocation of park space, We have mad a plan for composition of spaces for various activities, provision of facilities based on estimation of user-demand and activities, and planting. In the design process, we have tried to harmonize functional spaces with facilities, and to organize all the functions as a whole. To improve urbanity and aesthetic shape of park design, we have introduced a central plaza, design of a pave floor, a torrent, large trees for shade, colonnades and so on. From this design project, we can develop the site as a children park for increasing creativities and various playing opportunities, and as a resident space for rest, cultural activities. In the future, it is required that many attempt to design and develop urban small space as a park for children and residents.