• Journal of Plant Biology
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• 제14권1호
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• pp.15-23
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• 1971

The productivity of summer phytoplankton communities in Lake Hwajinpo, Lake Yongrang and Lake Changja were studied by measuring vertical variation of chlorophyll a amounts. The author also classified the lake types on the basis of the amount of chlorophyll in the lake water. And in Lake Changja, the seasonal changes of stratification of chlorophyll were studies. In Lake Hwajinpo, the productive structure of the phytoplankton community in summer was found to be L-shaped and of the mesotrophic type. In Lake Yongrang, the productive structure of the phytoplankton community in summer was alo L-shaped and of the mesotrophic type. And maximum chlorophyll layer was near the lake bottom below the compensation depth. In Lake Changja, the structure of phytoplankton community in summer was reversed L-shaped and of the eutrophic type, with the maximum chlorophyll layer just below the surface. The vertical distribution of chlorophyll amounts as a measure of the productive structure almost always formed a stratum distribution except in September and sometimes in May, in Lake Changja. In September homogeneous distribution was observed.

• 한국정보통신학회논문지
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• 제20권7호
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• pp.1221-1228
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• 2016

본 논문에서는 포크 모양의 급전 구조를 갖는 변형된 마름모 슬롯 UWB(Ultra Wide Band) 안테나를 제안하였다. 제안된 안테나는 초광대역 특성을 얻기 위해서 마름모 형태의 슬롯 구조와 포크 모양의 급전 구조로 설계하였다. 변형된 마름모 구조는 기존 마름모 구조에서 상단과 하단 영역이 제거하여 설계하였다. 제안된 안테나는 $34mm(W_1){\times}34mm(L_1){\times}1mm(t)$의 유전율 4.4인 FR-4 유전체 기판 위에 설계되었으며 전체 슬롯 크기는 $30mm(W_2){\times}16.75mm(L_3+L_4)$을 갖도록 설계하였다. 각 파라메타에 대한 시뮬레이션을 진행하여 최적화 수치를 얻었다. 제작 및 측정 결과로부터 제안된 안테나의 반사손실 특성은 3.1 ~ 10.6 GHz UWB 대역에서 -10dB 이하의 값을 갖으며 또한 측정된 이득과 방사패턴 특성 결과를 얻었다.

• Composites Research
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• 제31권5호
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• pp.246-250
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• 2018

본 연구에서는 곡면 복합재 구조물의 모서리에 위치한 결함을 검사하고 가시화하기 위해 제안된 레이저 초음파 기반 회전식 검사 기법을 소개한다. 모서리 부위에 결함이 위치한 L 형 복합재 구조물을 레이저 초음파 기반 회전식 검사 기법을 이용하여 검사하였다. L 형 시편은 층간분리 손상을 모사하기 위해 각기 다른 세 가지 깊이에 위치한 인공 결함을 포함하고 있다. 모든 인공 결함이 각각의 위치한 깊이에 따라 다른 시간대에 선명하게 탐지되었다. 검사결과는 제안된 방법이 어떠한 특별한 도구 없이도 곡면 복합재 구조물의 모서리 부위의 검사에 적합하다는 것을 보여준다.

• Journal of electromagnetic engineering and science
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• 제17권1호
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• pp.1-8
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• 2017

This paper introduces a technique to obtain the broadband characteristics of circularly polarized antennas using an L-shaped probe. A waveguide antenna is suitable for obtaining high gain and handling convenience in some applications; however, the asymmetrical structure of the L-shaped probe results in cross-polarization and frequency dependence on the field distribution of higher-order modes (HOM). In addition to the basic characteristics of a waveguide antenna with an L-shaped probe, the author discusses some techniques to reduce the HOM and cross-polarization. As a result, the 3-dB axial ratio (AR) is obtained with the fundamental mode even when the frequency is expanded to the region for HOM of TM. This reduction is mainly due to the cutoff structure to the TM mode around the short wall of the waveguide. Furthermore, some aperture modification techniques can reduce the cross-polarization in a wide range of angles in the radiation pattern. Such techniques and their mechanisms are discussed in this paper. The obtained performance shows that the proposed antennas have a wide range of angles of 3-dB AR in the radiation pattern, broadband characteristics in impedance and AR, and low variation in group velocity.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.616-618
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• 2016

TCAD 시뮬레이션을 이용하여 터널링 전계효과 트랜지스터(Tunnel Field-Effect Transistor; TFET) 구조에 따른 특성을 조사하였다. Single-Gate TFET, Double-Gate TFET, Pocket TFET, L-shaped TFET 구조 중에서 Pocket TFET와 L-shaped TFET이 on-current와 subthreshold swing에서 가장 좋은 성능을 보였다. 본 논문은 터널링 전계효과 트랜지스터의 새로운 구조에 대한 가이드라인을 제시하고자 한다.

• 천문학회보
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• 제42권1호
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• pp.55.1-55.1
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• 2017

A number of recent studies have claimed that the double red clump observed in the Milky Way bulge is a consequence of an X-shaped structure. In particular, Ness & Lang (2016) report a direct detection of a faint X-shaped structure in the bulge from the residual map of the Wide-Field Infrared Survey Explorer (WISE) image. Here we show, however, that their result is seriously affected by a bulge model subtracted from the original image. When a boxy bulge model is subtracted, instead of a simple exponential bulge model as has been done by Ness & Lang, we find that most of the X-shaped structure in the residuals disappears. Furthermore, even if real, the stellar density in the claimed X-shaped structure appears to be too low to be observed as a strong double red clump at $l=0^{\circ}$

• 한국전자파학회논문지
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• 제15권10호
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• pp.938-943
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• 2004

본 논문에서는 CPW에 식각된 T자형 DGS를 제안하고 전송이론을 이용하여 전파 방사를 포함한 손실률, BW(3-dB fractional bandwidth) 등을 closed-form 형태의 수식으로 유도하고 이의 영향에 대해 분석한다. 제안된 T자형 DGS 구조는 기존의 아령형 DGS 구조보다 약 5.5배정도 큰 커패시턴스(C) 조절 특성을 가진다. 또 DGS 등가회로의 R, L, C값과 손실률, BW, 저지대역 공진 각주파수($\omega_0$)의 상관관계를 정량적으로 이끌어낸다.

• International Journal of Internet, Broadcasting and Communication
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• 제12권1호
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• pp.37-44
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• 2020

In this paper, we proposed a compact printed monopole antenna with an inverted L-shaped slot for dual-band operations. Two operating frequency bands are achieved with the use of an inverted L-shaped slot etched on the radiating strip for bandwidth enhancement and a defected ground structure for return loss improvement in the higher frequency band. The measured results showthat the proposed antenna has impedance bandwidths (S₁₁< -10 dB) of 270 MHz (1.81-2.08 GHz) and 340 MHz (2.36-2.70 GHz), covering the required bandwidths for PCS (1850.5-1989.5 MHz), CDMA 2000 (1850-1990 MHz), TD-SCDMA (1880-2025 MHz) and 2.4 GHz WLAN (2400-2484 MHz). The measured return loss of the proposed antenna has a good value of approximately 27.2 dB at 2.4 GHz WLAN. The antenna's peak gains also have a high value of 1.92 dBi at 2 GHz and 2.12 dBi at 2.45 GHz. The proposed antenna shows omnidirectional radiation patterns over the entire frequency range of interest.

• 한국기계가공학회지
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• 제20권11호
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• pp.52-59
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• 2021

Titanium alloy (Ti-alloy) is widely used as a material for core parts of aircraft structures and engines that require both lightweight and heat-resistant properties owing to their high specific stiffness. Most parts used in aircraft have I-, L-, and H-shaped thin-walled structures for weight reduction. It is difficult to machine thin-walled structures owing to vibrations and deformations during machining. In particular, cutting tool damage occurs in the corners of thin-walled structures owing to the rapid increase in cutting force and vibration, and machining quality deteriorates because of deep tool marks on machined surfaces. In this study, milling experiments were performed to derive an effective method for machining a L-shaped thin-walled structure with Ti-alloy (Ti-6Al-4V). Three types of machining experiment were performed. The surface quality, tool wear, cutting force, and vibration were analyzed comprehensively, and an effective machining method in terms of tool life and machining quality was derived.

• Earthquakes and Structures
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• 제16권1호
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• pp.97-107
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• 2019

The frame structures investigated in this paper is composed of Concrete encased columns with L-shaped steel section and steel beams. The seismic behavior of this structural system is studied through experimental and numerical studies. A 2-bay, 3-story and 1/3 scaled frame specimen is tested under constant axial loading and cyclic lateral loading applied on the column top. The load-displacement hysteretic loops, ductility, energy dissipation, stiffness and strength degradation are investigated. A typical failure mode is observed in the test, and the experimental results show that this type of framed structure exhibit a high strength with good ductility and energy dissipation capacity. Furthermore, finite element analysis software Perform-3D was conducted to simulate the behavior of the frame. The calculating results agreed with the test ones well. Further analysis is conducted to investigate the effects of parameters including concrete strength, column axial compressive force and steel ratio on the seismic performance indexes, such as the elastic stiffness, the maximum strength, the ductility coefficient, the strength and stiffness degradation, and the equivalent viscous damping ratio. It can be concluded that with the axial compression ratio increasing, the load carrying capacity and ductility decreased. The load carrying capacity and ductility increased when increasing the steel ratio. Increasing the concrete grade can improve the ultimate bearing capacity of the structure, but the ductility of structure decreases slightly.