• Journal of information and communication convergence engineering
• /
• 제8권6호
• /
• pp.635-639
• /
• 2010

A multi-resonance antenna for wireless communications is reported. By using double inverted-L strips, the antenna demonstrated compact size (15 mm ${\times}$ 14 mm) including the ground, multi-band operation for IEEE 802.11 a/b/g/p applications, and wide bandwidth of 1.7 GHz at 5 GHz band. Good radiation features of omni-directional patterns and 1.98 and 2.29 dBi peak antenna gains for the lower and upper bands, respectively, have been achieved.

• 한국분말재료학회지
• /
• 제9권3호
• /
• pp.153-160
• /
• 2002

A nitrogen gas atomized aluminum powder was consolidated by powder-in sheath rolling method. A pure aluminum tube with outer diameter of 12 mm and wall thickness of 1mm was used as a sheath. The aluminum tube filled with the aluminum powder, first, was cold-rolled to the thickness of 6mm for performing, and then consolidated by the cold rolling and/or subsequent hot rolling at 360, 460 and $560^{\circ}C$. The aluminum powder compact fabricated by the sheath rolling showed high relative density more than 0.96 at any rolling conditions. The 0.2% proof stress increased with increasing hot rolling reduction and hot rolling temperature. Tensile strength was hardly affected by change in the hot rolling reduction, whereas it decreased with increasing hot rolling temperature. The powder compact showed the large elongation when cold rolling or hot rolling reduction was large. It was found that the sheath rolling was an effective method for consolidation of aluminum powder.

• 대한수학회논문집
• /
• 제36권3호
• /
• pp.465-483
• /
• 2021

Let 𝓗(𝔻) be the space of analytic functions on the unit disc 𝔻. Let 𝜓 = (𝜓_j)ⁿ_j=0 and 𝚽 = (𝚽_j)ⁿ_j=0 be such that 𝜓_j, 𝚽_j ∈ 𝓗(𝔻). The linear differential operator is defined by T_𝜓(f) = ∑ⁿ_j=0 𝜓_jf^(j), f ∈ 𝓗(𝔻). We characterize the boundedness and compactness of the difference operator (T_𝜓 - T_𝚽)(f) = ∑ⁿ_j=0 (𝜓_j - 𝚽_j) f^(j) between weighted-type spaces of analytic functions. As applications, we obtained boundedness and compactness of the difference of multiplication operators between weighted-type and Bloch-type spaces. Also, we give examples of unbounded (non compact) differential operators such that their difference is bounded (compact).

• Journal of electromagnetic engineering and science
• /
• 제10권3호
• /
• pp.179-182
• /
• 2010

This paper proposed a novel compact bandpass filter with folded half mode substrate integrated waveguide (FHMSIW) cavities using two-layer printed circuit board(PCB) process. The area of the FHMSIW filter is reduced by nearly 50 % and 75 % compared with half mode substrate integrated waveguide(HMSIW) filter and substrate integrated waveguide(SIW) filter, respectively. A four-pole Chebyshev FHMSIW bandpass filter at C-band has been designed, simulated and fabricated. Measured results are presented and found to agree with the full-wave simulated results by using Ansoft HFSS. The filter shows good performance and compact size.

• 호남수학학술지
• /
• 제32권2호
• /
• pp.255-260
• /
• 2010

Given vectors x and y in a separable complex Hilbert space $\mathcal{H}$, an interpolating operator is a bounded operator A such that Ax = y. In this article, we investigate compact interpolation problems for vectors in a tridiagonal algebra. We show the following : Let Alg$\mathcal{L}$ be a tridiagonal algebra on a separable complex Hilbert space $\mathcal{H}$ and let x = $(x_i)$ and y = $(y_i)$ be vectors in H. Then the following are equivalent: (1) There exists a compact operator A = $(a_{ij})$ in Alg$\mathcal{L}$ such that Ax = y. (2) There is a sequence ${{\alpha}_n}$ in $\mathbb{C}$ such that ${{\alpha}_n}$ converges to zero and for all k ${\in}$ $\mathbb{N}$, $y_1 = {\alpha}_1x_1 + {\alpha}_2x_2$ $y_{2k} = {\alpha}_{4k-1}x_{2k}$ $y_{2k+1}={\alpha}_{4k}x_{2k}+{\alpha}_{4k+1}x_{2k+1}+{\alpha}_{4k+2}+x_{2k+2}$.

• Journal of Positioning, Navigation, and Timing
• /
• 제7권1호
• /
• pp.43-52
• /
• 2018

In recent years, the need of high accuracy navigation for vehicles has increased due to the development of autonomous driving vehicles and increase in land transportation convenience. This study is performed for vehicle users to achieve a performance of centimeter-level positioning accuracy by utilizing Compact Network Real-time Kinematic (RTK) that is applicable as a national-level infrastructure. To this end, medium-baseline RTK was implemented in real time to estimate accurate integer ambiguities between reference stations for reliable generation of Network RTK correction using the linear combination of carrier-phase observations and L1/L2 pseudo-range measurements. The residual tropospheric error was estimated in real time to improve the accuracy of double-differenced integer ambiguity resolution between network configuration reference stations that have at least 30 km or longer baseline distance. In addition, C++ based software was developed to enable real-time generation and broadcasting of Compact Network RTK correction information by utilizing an accurately estimated double-differenced integer ambiguity values. As a result, the horizontal and vertical 95% accuracy was 2.5cm and 5.2cm, respectively, without performance degradation due to user's position change within the network.

• Nuclear Engineering and Technology
• /
• 제55권8호
• /
• pp.2873-2878
• /
• 2023

The purpose of this study is to perform radiation monitoring by acquiring gamma images and real-time optical images for ^99mTc vial source using charge couple device (CCD) cameras equipped with the proposed compact gamma camera. The compact gamma camera measures 86×65×78.5 mm³ and weighs 934 g. It is equipped with a metal 3D printed diverging collimator manufactured in a 45 field of view (FOV) to detect the location of the source. The circuit's system uses system-on-chip (SoC) and field-programmable-gate-array (FPGA) to establish a good connection between hardware and software. In detection modules, the photodetector (multi-pixel photon counters) is tiled at 8×8 to expand the activation area and improve sensitivity. The gadolinium aluminium gallium garnet (GAGG) measuring 0.5×0.5×3.5 mm³ was arranged in 38×38 arrays. Intrinsic and extrinsic performance tests such as energy spectrum, uniformity, and system sensitivity for other radioisotopes, and sensitivity evaluation at edges within FOV were conducted. The compact gamma camera can be mounted on unmanned equipment such as drones and robots that require miniaturization and light weight, so a wide range of applications in various fields are possible.

• 대한기계학회논문집
• /
• 제10권6호
• /
• pp.937-946
• /
• 1986

본 논문에서는 이와 같은 점을 고려하여 두께가 얇은 평면응력 상태의 CT 시 험편을 이용하여 W와 z의 변화에 따른 파괴인성치와 J저항곡선의 거동 및 크랙성장을 고려한 J적분식도 검토하였다. 또한, 재료를 변형경화 재료로 가정하고 HRR 응력변 형율장의 특성을 이용하여 컴퓨터 프로그램을 작성하여 J적분을 구한 후 실험치와 상 호 비교 검토하였다. 이 때 사용한 입력자료는 실험치의 그것과 동일하게 하였다.

• 한국태양에너지학회 논문집
• /
• 제31권4호
• /
• pp.9-18
• /
• 2011

This study assessed the performance of a compact heat exchanger with staggered tube banks for recuperation of high temperature exhaust thermal energy for SOFC fuel cell system. The compact heat exchanger in this study is two pass system which consists of $315{\times}202.5{\times}48.5mm^3$ and 132 tubes of $6.0mm{\Phi}$ for each heat exchanger. From experiments of the 2 pass heat exchanger system, air temperature was increased from $60{\sim}85^{\circ}C$ to $402{\sim}482^{\circ}C$ while gas temperature was decreased from $600^{\circ}C$ to $305{\sim}402^{\circ}C$ according to mass flow rates of 3.9~7.8 g/s. The experimental heat transfer rates of the heat exchanger were compared with CFD numerical solutions with the conventional ${\xi}-NTU$ method. From the comparisons, the following conclusions were obtained. For the heat exchanger system, the relative errors of heat transfer rate by CFD solution were from 7.1 to 27%, and those by ${\xi}-NTU$ method were from 0.6% to 21% compared with experimental data. From the comparisons, it can be said that both of CFD and ${\xi}-NTU$ method almost simulated to experimental data except specific conditions. Pressure drops through air tubes and gas passages were calculated with both of the CFD computation and head loss equations. The differences between them were from 14 to 22%.

• 한국분말재료학회지
• /
• 제4권2호
• /
• pp.113-121
• /
• 1997

The densification of the compacts of Co+32%Cr+20%W+l.5%C, Co+32%Cr+20%W+3.0%C and Co+32%Cr+20%W+4.5%C sintered under $H_2$ gas or vacuum was investigated. The effect of V and B addition on the densification was also investigated. The densification of these compacts were always incomplete regardless of sintering atmosphere, temperature and time. The amounts of oxygen and carbon in compacts sintered in $H_2$ for 3.6ks at 1523K were 0.105~0.160 mass% and 0.33~0.89 mass%, respectively. And those in vacuum were 0.028~0.032% and 0.957~4.08%, respectively. Relative density(Ds) of Co+29%Cr+17%W+3.0%C compact containing 6%V and Co+32%Cr+20%W+2.97%C compact containing 0.03%B were 99 and 100%, respectively, indicating complete densification by solid phase sintering. Victors hardness of sintered compacts containing 6%V or 0.03%B were 632 and 568, showing 50~60% increase in comparison to those without V or B. These results can be explained in terms of oxidation/reduction of oxides and equilibrium pressure of CO in isolated pore, instead of presence of liquid formation and grain boundary separation from pores due to large grain growth.