• Journal of information and communication convergence engineering
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• 제11권1호
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• pp.45-49
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• 2013

A compact radio frequency (RF) bandpass filter (BPF) in low temperature co-fired ceramic (LTCC) is suggested for WiMAX applications. The center frequency ($f_0$) of the BPF is 5.5 GHz and its pass band or 3-dB bandwidth is 700 MHz to cover all the three major bands, low and middle unlicensed national information infrastructure (U-NII; 5.15-5.35 GHz), World Radiocommunication Conference (5.47-5.725 GHz), and upper U-NII/industrial, scientific, and medical (ISM) (5.725-5.85 GHz), for the WiMAX frequency band. A lumped circuit element design-the 5th order capacitively coupled Chebyshev BPF topology-is adopted. In order to design a compact RF BPF, a very thin ($43.18{\mu}m$) ceramic layer is used in LTCC substrate. An interdigital BPF is also designed in silicon substrate to compare the size and performance of the lumped circuit element BPF. Due to the high relative dielectric constant (${\varepsilon}_r$ = 11.9) of the silicon substrate, the quarter-wavelength resonator of the interdigital BPF can be reduced. In comparison to the 5th order interdigital BPF at $f_0$ = 5.5 GHz, the lumped element design is 24% smaller in volume and has 17 and 7 dB better attenuation characteristics at $f_0{\pm}0.75$ GHz.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.191-194
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• 1999

Recently, with the rapid development and demand for compactness of portable communications, the requirement for compact and low-cost filter is increasing. One of the methods for reducing size and cost is to use high dielectric constant and low loss dielectric material in filter. The other is new monoblock dielectric band-pass filter (BPF) which has holes in a single dielectric body without additional coupling elements. This structure effectively reduces the size and cost of the filters. For previous conventional coaxial type dielectric BPF, dielectric substrates were used for coupling between adjacent resonators and additional input and output ports were needed. Coupling between adjacent resonators of monoblock BPF can be otained via electrode pairs. Capacitances of electrode pair structure for coupling are intensively investigated by 3-D FEM. The BPF for PCS has been designed to have a 30 MHz pass-bandwidth with center frequency of 1855 MHz and an attenuation pole at below the passband using a commercial 3-D structure simulator.

• Wind and Structures
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• 제19권4호
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• pp.389-404
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• 2014

The flow characteristics of a circular cylinder surrounded by an outer permeable cylinder were experimentally investigated using Particle Image Velocimetry Technique in deep water flow. In order to consider the effects of diameter and porosity of the outer cylinder on flow structures of the inner cylinder, five different outer cylinder diameters (D=37.5, 52.5, 60, 75 and 90 mm) and eight different porosities (${\beta}$=0.4, 0.5, 0.6, 0.65, 0.7, 0.75, 0.8 and 0.85) were selected. During the experiments, the diameter of inner cylinder was kept constant as d=30 mm. The depth-averaged free-stream velocity was adjusted as U=0.156 m/s, which corresponds to the Reynolds number of Re=5000 based on the inner cylinder diameter. It has been concluded that both the outer permeable cylinder diameter and the porosity have important influences on the attenuation of vortex shedding in the wake region. The presence of outer permeable cylinder decreases the magnitude of Reynolds shear stress and turbulent kinetic energy compared to the bare cylinder case. Moreover, the spectral analysis of vortex shedding frequency has revealed that the dominant frequency of vortex shedding downstream of the cylinder arrangement also reduces substantially due to the weakened Karman shear layer instability.

• Current Optics and Photonics
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• 제3권3호
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• pp.210-214
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• 2019

The allowable path-deviation time of aircraft in a free-space optical communication system has been estimated from various trajectories, using different values of aircraft speeds and turn rates. We assumed the existence of a link between the aircraft and a ground base station. First, the transmitter beam's divergence angle was calculated through two different approaches, one based on a simple optical-link equation, and the other based on an attenuation coefficient. From the calculations, the discrepancy between the two approaches was negligible when the link distance was approximately 110 km, and was under 5% when the link distance ranged from 80 to 140 km. Subsequently, the allowable path-deviation time of the aircraft within the tracking-error tolerance of the system was estimated, using different aircraft speeds, turn rates, and link distances. The results indicated that the allowable path-deviation time was primarily determined by the aircraft's speed and turn rate. For example, the allowable path-deviation time was estimated to be ~3.5 s for an aircraft speed of 166.68 km/h, a turn rate of $90^{\circ}/min$, and a link distance of 100 km. Furthermore, for a constant aircraft speed and turn rate, the path-deviation time was observed to be almost unchanged when the link distance ranged from 80 to 140 km.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1783-1790
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• 2023

Barium Bismuth Oxide Borate (BBOB) has been synthesized for the first time using solution combustion technique. SEM analysis reveal flower shape of the nanoparticles. The formation of the nanoparticles has been confirmed through XRD & FTIR studies which gives the physical and chemical structure of the novel material. The UV light absorption is observed in the range 200-300 nm. The present study highlights the radiation shielding ability of BBOB for different radiations like X/Gamma rays, Bremsstrauhlung and neutrons. The gamma shielding efficiency is comparable to that of lead in lower energy range and lesser than lead in the higher energy range. The bremsstrauhlung exposure constant is comparably larger for BBOB NPs than that of concrete and steel however it is lesser than that of lead. The beauty of BBOB nanoparticles lies in, high absorption of radiations and low emission of secondary radiations when compared to lead. In addition, the neutron shielding parameters like scattering length, absorption and scattering cross sections of BBOB are found to be much better than lead, steel and concrete. Thus, BBOB nanoparticles are highly efficient in absorbing X/Gamma rays, neutrons and bremsstrauhlung radiations.

• 한국의학물리학회지:의학물리
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• 제14권2호
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• pp.81-89
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• 2003

근접조사용 선원으로 직경이 0.5 mm에 길이 3.5 mm인 Ir-192선원을 고안하고, 선량알고리즘을 개발하였다. 선원을 0.1 mm 두께로 균등분할하고 총 875개의 미소선원으로부터 조직에 도달되는 선량을 계산하고 선량분포를 조사하였다. 선원을 감싸는 캡슐용기의 두께는 0.3 mm이며, 선량기준점인 Ir선원의 Air-kerma strength(S$_{k}$ ) 는 mCi당 4.108U를 얻었으며 선원 측방의 1 cm에서 1.154 Uh$^{-1}$ (1.3167${\times}$$10^{-3}$cGy/mCi-sec)의 조직선량률을 얻었다. Air-kerma strength로부터 조직내 선량률상수(Λ)는 Ir-192에너지 스펙트럼과 실험치인 조직내 산란보정계수를 적용하여 1.154 cGy h$^{-1}$U$^{-1}$ 얻었다. 선량분포의 특성은 선원 축방향으로 56%의 상대선량률을 보였고, 케이블측의 선량감쇠는 50%를 보였다. 마이크로선원의 중심에서 반경 1 cm 주위의 선량분포와 5 cm의 선량분포를 비교한 결과 반경이 큰 경우의 측방선량에 비해 축 방향의 선량이 약 2% 감쇠함을 보았다. 선원자체의 필터효과는 점선원에 비해 88.3%의 선량률을 얻어 약 12%의 감쇠를 보였으며, 캘슐벽의 필터효과는 약 3% 정도로 미미하게 나타났으며 기준점에서 선량필터효과는 약 15.6% 감쇠되는 것으로 나타났다. Ir-192 선원과 같이 에너지가 낮은 선원을 사용하는 경우 선량분포특성에 따라 아프리케이터의 직경을 크게 하여 선원 축 방향의 선량저하를 피할 수 있음을 알 수 있었다.

• 환경정책연구
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• 제9권1호
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• pp.83-107
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• 2010

본 연구의 목적은 빗물저류 및 흡수 등 우수관리를 위해 설치하는 최적관리기법(Best Management Practices: BMPs)의 효율적인 위치 및 분배 정도를 유역단위에서 살펴보는 것이다. 이를 위해 여러 개의 지류유역과 본류유역으로 이루어진 하나의 대유역을 구축한 후 Hydrological Simulation Program Fortran(HSPF)을 이용하여 도시유역 내다양한 규모와 위치의 BMPs 시나리오를 제작/모의하였다. 이때 대유역 내 전체 BMPs 면적은 일정하도록 하였으며, 유역하구의 첨두유량과 이와 관련된 회피비용을 효율성의 지표로 활용하였다. 모의 결과 BMPs가 상류지류 유역들에 분산 입지했을 때 가장 높은 효율을 보였으며, 본류유역을 포함하여 소유역 한 곳에 집중되었을 때 가장 낮은 효율을 보였다. 하지만 본 연구는 BMPs의 위치 및 분배 변수를 제외한 BMPs 설계 및 유지관리, 유역 내 다양한 토양특성등의 기타변수가 통제된 가상유역을 대상으로 진행되었다는 한계를 안고 있다. 따라서 본 연구는 유역관리에서 BMPs위치 및 분배가 유역관리에 중요한 정책변수일 수 있다는 가능성을 제시하는 데 그치고 있으며, 이러한 가능성은 향후 국내유역에 대한 실증적 모의연구를 통해 논의될 수 있을 것이다.

• ETRI Journal
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• 제42권4호
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• pp.575-584
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• 2020

Electromagnetic (EM) waves used to send signals under seawater are normally restricted to low frequencies (f) because of sudden exponential increases of attenuation (𝛼) at higher f. The mathematics of EM wave propagation in seawater demonstrate dependence on relative permeability (𝜇_r), relative permittivity (𝜀_r), conductivity (𝜎), and f of transmission. Estimation of 𝜀_r and 𝜎 based on the W. Ellison interpolation model was performed for averaged real-time data of temperature (T) and salinity (S) from 1955 to 2012 for all oceans with 41 088 latitude/longitude points and 101 depth points up to 5500 m. Estimation of parameters such as real and imaginary parts of 𝜀_r, 𝜀_r', 𝜀_r", 𝜎, loss tangent (tan 𝛿), propagation velocity (V_p), phase constant (𝛽), and α contributes to absorption loss (L_a) for seawater channels carried out by using normal distribution fit in the 3 GHz-40 GHz f range. We also estimated total path loss (L_PL) in seawater for given transmission power P_t and antenna (dipole) gain. MATLAB is the simulation tool used for analysis.

• Restorative Dentistry and Endodontics
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• 제41권3호
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• pp.202-209
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• 2016

Objectives: The purpose of this study was to investigate the involvement of TRPA1 in the cinnamaldehyde-induced pulpal blood flow (PBF) change in the feline dental pulp. Materials and Methods: Mandibles of eight cats were immobilized and PBF was monitored with a laser Doppler flowmetry at the mandibular canine tooth. To evaluate the effect of cinnamaldehyde on PBF, cinnamaldehyde was injected into the pulp through the lingual artery at a constant rate for 60 seconds. As a control, a mixture of 70% ethanol and 30% dimethyl sulfoxide (DMSO, vehicle) was used. To evaluate the involvement of transient receptor potential ankyrin 1 (TRPA1) in PBF change, AP18, a specific TRPA1 antagonist, was applied into the pulp through the Class V dentinal cavity followed by cinnamaldehyde-administration 3 minutes later. The paired variables of experimental data were statistically analyzed using paired t-test. A p value of less than 0.05 was considered as statistically significant. Results: Administration of cinnamaldehyde (0.5 mg/kg, intra-arterial [i.a.]) induced significant increases in PBF (p < 0.05). While administration of a TRPA1 antagonist, AP18 (2.5 - 3.0 mM, into the dentinal cavity [i.c.]) caused insignificant change of PBF (p > 0.05), administration of cinnamaldehyde (0.5 mg/kg, i.a.) following the application of AP18 (2.5 - 3.0 mM, i.c.) resulted in an attenuation of PBF increase from the control level (p < 0.05). As a result, a TRPA1 antagonist, AP18 effectively inhibited the vasodilative effect of cinnamaldehyde (p < 0.05). Conclusions: The result of the present study provided a functional evidence that TRPA1 is involved in the mechanism of cinnamaldehyde-induced vasodilation in the feline dental pulp.

• 센서학회지
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• 제11권5호
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• pp.273-278
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• 2002

광섬유의 침입 감지기능을 개발하기 위하여 다중모드 GRIN(graded-Index) 광섬유의 휨에 의한 광섬유내의 광전파 특성변화를 고찰하였다. 다중모드 CRIN 광섬유의 data파는 기본(fundamental) 모드로, 침입 감시용 감시파는 높은 차수의 모드로 동시에 전파 되게 하고, 광섬유의 휨(bending)에 의한 데이타 유출시도는 높은 차수 모드의 감시파의 감쇠를 가져오고, 결국 수신측의 경보를 작동하도록 한다. 또한 일정한 곡률반경으로 감겨진 광섬유에 기본 모드만 선별적으로 주입된 경우에 있어서, 다중모드 GRIN 광섬유 내에서의 광파의 전파과정을 이론적으로 해석하고, 광섬유가 휘게 피는 경우 여러 모드 사이에 결합(coupling)이 생겨나게 되는데, 광섬유가 감겨진 곡률반경을 변경해가면서 결합되는 기본모드의 power 변화를 수치해석을 이용한 프로그램 시뮬레이션을 통하여 조사하였다. 이 연구결과는 광섬유의 휨에 의하여 방출되는 데이타 도청 및 침입자 감지에 다중모드 GRIN 광섬유 활용 가능성과 광섬유의 곡률반경이 1cm 정도가지는 Asawa-Taylor의 모델[4]이 정당함을 보였다.