• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.334-341
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• 2016

In this paper, the study of a waveguide aperture-coupled feed-structured antenna has been conducted for the purpose of applying it to a wireless back-haul system sufficient for high-capacity gigabits-per-second data rates. For this study, a $32{\times}32$ waveguide slot sub-array antenna with a corporate-feed structure was designed and produced. Also, this antenna is used at 57 GHz to 66 GHz in the V-band. The construction of the antenna is a laminated form with radiating parts (outer groove and slot, cavity), a coupled aperture, and feeds in each. The antenna was designed with HFSS, which is based on 3D-FEM, produced with aluminum processed by a precision-controlled milling machine, and assembled after a silver-plating process. The measurement result from analysis of the characteristics of the antenna shows that return loss is less than -12 dB, VSWR < 2.0, and a wide bandwidth ranges up to 16%. An overall first side lobe level is less than -12.3 dB, and a 3 dB beam width is narrow at about $1.85^{\circ}$. Also, antenna gain is 38.5 dBi, offering high efficiency exceeding 90%.

• Korean Journal of Cognitive Science
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• v.17 no.2
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• pp.75-102
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• 2006

Three experiments were conducted using a verification task to examine good and poor readers' generation of causal inferences(with because sentences) and contrastive inferences(with although sentences). The unfamiliar, critical verification statement was either explicitly mentioned or was implied. In Experiment 1, both good and poor readers responded accurately to the critical statement, suggesting that both groups had the linguistic knowledge necessary to the required inferences. Differences were found, however, in the groups' verification latencies. Poor, but not good, readers responded faster to explicit than to implicit verification statements for both because and although sentences. In Experiment 2, poor readers were induced to generate causal inferences for the because experimental sentences by including fillers that were apparently counterfactual unless a causal inference was made. In Experiment 3, poor readers were induced to generate contrastive inferences for the although sentences by including fillers that could only be resolved by making a contrastive inference. Verification latencies for the critical statements showed that poor readers made causal inferences in Experiment 2 and contrastive inferences in Experiment 3 doting comprehension. These results were discussed in terms of context effect: Specific encoding operations performed on anomaly backgrounded in another passage would form part of the context that guides the ongoing activity in processing potentially relevant subsequent text.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.3
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• pp.313-318
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• 2018

A coaxial band rejection filter is designed and fabricated for a beam interacting cavity. The proposed filter has a quarter wavelength choke for the dominant mode of the cavity. The equivalent circuit of the coaxial band rejection filter is presented and the ABCD parameter os each part is derived to obtain the ABCD parameter of the entire filter. The scattering matrix was obtained from the ABCD matrix and the was simulated by MATLAB using the obtained scattering matrix. The coaxial band rejection filter structure was simulated using HFSS, and the results confirmed the simulation using the equivalent circuit was useful. The designed coaxial band rejection filter was fabricated with 6-1/8 flange. The fabricated filter was measured using a transition from 6-1/8 flange to N-type flange. The insertion loss of the fabricated filter is greater than 25 dB in the dominant mode of the cavity and less than 0.25 dB in the first higher order mode. The measurement results are in good agreement with the simulated results and meet the design specification.

• Progress in Medical Physics
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• v.11 no.2
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• pp.91-99
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• 2000

This is a preliminary study for developing the method of the dose reconstruction in the patients, irradiated by mega-voltage photon beams from the linear accelerator, using the transit dose distributions. In this study we present the method of three-dimensional dose reconstruction and evaluate the method by computer simulation. To acquire the dose distributions in the patients (or phantoms) we first calculate the differences between the doses at the arbitrary points in the patients and the doses at the corresponding points where the transit doses are measured. Then, we can get the dose in the patients from the measured transit dose and the calculated value of the difference. The dose differences are calculated by applying the inverse square law and using the linear attenuation coefficient. The scatter to primary dose ratios, which are calculated by the Monte Carlo program using the CT data of the patient (or phantoms), are also used in the calculations. For the evaluation of this method we used various kinds of homogeneous and inhomogeneous phantoms and calculated the transit dose distributions with the Monte Carlo program. From the distributions we reconstructed the dose distributions in the phantom. We used mono-energy Photon beam of 1.5MeV and Monte Carlo program EGS4. The comparison between the dose distributions reconstructed using the method and the distributions calculated by the Monte Carlo program was done. They agreed within errors of -4%∼+2%. This method can be used to predict the dose distributions in the patient

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2000.11a
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• pp.17-17
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• 2000

탄소섬유/에폭시 적충복합재는 경량성 및 비강도, 비강성이 우수해 최근 들어 항공기, 자동차, 우주선 등에 대한 적용이 급속도로 증가하고 있다. 그러나 적충복합재 구조물에 있어 최대 약점 중 하나는 적충된 면이 서로 떨어지는 충간분리가 발생 할 수 있다는 것이다. 본 논문에서는 탄소섬유/에폭시 적충복합재의 파괴특성을 향상시키기 위해 프리프레그 (prepreg)를 이온빔으로 표면처리하는 방법에 대해 연구하였다. 즉 프리프레그를 $Ar^+$ 이온도 움반응법에 의해 표면처리 하였으며 이를 적용, 열림모드 파괴특성을 검토하였다. 즉 표준 프리프레그와 표면처리 된 프리프레그를 이용 $0^{\circ}$ 단일방향 DCB(Double Cantilever Beam) 시편을 제작하였으며, 각각의 경우에 대하여 파괴시험을 수행하였다. 파괴시험으로부터 파괴 저항곡선(R-곡선)을 결정하여 이를 비교 검토함으로서 프리프레그의 표면처리가 파괴특성에 미치는 영향을 해석하였다. 본 연구를 통해 얻어진 결과를 요약하면 다음과 같다. 첫째, 층간분리 길이가 동일한 경우 표면처리한 경우의 컴플라이언스가 표면처리 하지 않은 경우에 비해 작게 나타남을 알 수 있었다. 둘째, 파괴하중 값은 컴플라이언스와 반대현상을 나타낸다. 즉 표면처리한 경우의 파괴하중 이 표면처리 하지 않은 경우에 비해 크게 나타남을 알 수 있었다. 셋째, 표면처리 한 시편의 경우 R-곡선이 향상됨을 알 수 있었다. 즉 표면처리 한 경우의 열림모드 파괴이성, $G_{Ic}$ 값은 표준 시편의 값보다 24% 높았다. 이는 프리프레그의 표면처리 가 충과 충간의 접착강도를 증가시키고 또한 탄소섬유와 에폭시 간의 계면력을 증가시킨데 기인하는 것으로 사려된다.되었으며, duty-on 시간의 증가에 따라 $Cr_2N$ 상의 형성이 점점 많아져 80% duty-on 시간 경우에는 거의 CrN과 $Cr_2N$ 상이 공존하는 것으로 나타났다. 또한 duty-on 시간이 증가할수록 회절피크의 세기가 증가하여 결정화가 더 많이 진행되어짐을 알 수 있었다. 마찬가지로 바이어스 펄스이 주파수에 다른 결정성의 변화도 펄스의 주파수가 증가할수록 박막이 결정성이 좋아지고 $Cr_2N$ 상이 쉽게 형성되었다. 증착 진공도에 따른 결정성은 상대적으로 질소의 농도가 높은 낮은 진공도에서는 CrN 상이 주로 형성되었으며, 반대로 높은 진공도에서는 $Cr_2N$ 상이 많이 만들어졌다. 즉 $1.3{\times}10^{-2}Torr$의 증착 진공도에서는 CrN 상만이 보이는 반면 $9.0{\tiems}1-^{-2}Torr$ 진공도에서부터 $Cr_2N$ 상이 형성되기 시작하여 $5.0{\tiems}10^{-2}Torr$ 진공도에서는 두개의 상이 혼재되어 있음을 알 수 있었다. 박막의 내마모성을 조사한 결과 CrN 박막의 마찰 계수는 초기에 급격하게 증가한 후 0.5에서 0.6 사이의 값으로 큰 변화를 보이지 않았으며, $Cr_2N$ 박막도 비슷한 거동을 보였다.차 이, 목적의 차이, 그리고 환경의 의미의 차이에 따라 경관의 미학적 평가가 달라진 것으로 나타났다.corner$적 의도에 의한 경관구성의 일면을 확인할수 있지만 엄밀히 생각하여 보면 이러한 예의 경우도 최락의 총체적인 외형은 마찬가지로 $\ulcorner$순응$\lr

• Journal of the Korean Society of Radiology
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• v.16 no.7
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• pp.851-856
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• 2022

The purpose of this study is to confirm the effect of reducing the surface dose around the radiation field in breast cancer radiotherapy using the Field-in-Field (FIF) technique. X-ray was exposed from a linear accelerator (Linac) was used for irradiation, and the surface dose was measured with a glass dosimeter. The source-to-surface distance (SSD) was 90 cm, the field size is 10 × 10 cm², and the X-ray energy was 6 MV and 10 MV, respectively. The surface dose of the FIF was compared with the dose measured in the physical wedge (PW) and dynamic wedge (DW). Wedge angles of 15° and 30° were used in the PW and DW, respectively. Surface dose was measured at 1 cm, 3 cm, and 5 cm from the center of the field size, respectively. According to the results, FIF showed lower surface dose compared to PW and DW regardless of the energy of the X-ray beam, wedge angle, and dose measurement point. Since FIF could reduce the radiation dose in periphery of the field size in breast cancer treatment, it is expected to be able to reduce the secondary damage caused by the radiation beam as well as to obtain a uniform dose distribution on the target.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.9 s.339
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• pp.97-100
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• 2005

An orthogonal antenna is presented for reader application of radio frequency identification (RFID) at 433 MHz. Two 1x2 sub-arrays are orthogonally placed on a ground plane and two different feeding networks are applied to control horizontal and vertical radiation current flows for each sub-array, respectively. Inverted-F structures are used as radiation elements and can generate two linear polarizations by relative current distribution of radiators forming sub-arrays. Antenna gains are 2.7 and 0.4 dBi and isolation between two input ports is less than 25dB.

• Radiation Oncology Journal
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• v.16 no.2
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• pp.195-202
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• 1998

Purpose : In order to obtain basic data for treatment plan in radiosurgery, we measured small fields of 6 MV X-rays and compared the measured data with our Monte Carlo simulations for the small fields. Materials and Methods : The small fields of 1.0, 2.0 and 3.0 cm in diameter were used in this study. Percentage depth dose (PDD) and beam Profiles of those fields were measured and calculated. A small semiconductor detector, water phantoms, and a remote control system were used for the measurement Monte Carlo simulations were Performed using the EGS4 code with the input data prepared for the energy distribution of 6 MV X-rays, beam divergence, circular fields and the geometry of the water phantoms. Results : In the case of PDD values, the calculated values were lower than the measured values for all fields and depths, with the differences being 0.3 to 5.7% at the depths of 20 to 20.0 cm and 0.0 to 8.9% at the surface regions. As a result of the analysis of beam profiles for all field sizes at a depth of loom in water phantom, the measured 90% dose widths were in good agreement with the calculated values, however, the calculated Penumbra radii were 0.1 cm shorter than measured values. Conclusion : The measured PDDs and beam profiles agreement with the Monte Carlo calculations approximately. However, it is different when it comes to calculations in the area of phantom surface and penumbra because the Monte Carlo calculations were performed under the simplified geometries. Therefore, we have to study how to include the actual geometries and more precise data for the field area in Monte Carlo calculations. The Monte Carlo calculations will be used as a useful tool for the very complicated conditions in measurement and verification.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.4
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• pp.318-327
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• 2017

It is essential for the near-field receiving measurement to make beam pattern and check the performance of a active phased array antenna system. Also, we could obtain compensation value for mono-pulse function through the near-field receive test, however, if the radar has many frequency channel, the test would take long time and hard effort. So it is needed that frequency channels are selected for measurement and calculates the values for other frequency channels to improve efficiency in development and manufacture. In this case, the phase variations in sum and del channels would be checked. The phase measurement includes un-linear characteristic because of wrapping effect. Generally, radars have similar path length in sum and del channel, but if a radar has a electrical length gap between sum and del channel, errors could occur by phase's wrapping effect. In this paper, the interpolation method's error caused by electrical length gap is checked and the effective method for frequency channel selection to avoid wrapping effect is introduced.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.132-132
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• 2012

압력 $10^{-9}$ Torr 이하의 초고진공(ultrahigh vacuum) 영역에서의 압력 측정에는 수 mA의 열전자로 잔류 가스를 이온화시켜 그 이온 전류를 측정하는 이온게이지를 주로 사용한다. 압력이 $10^{-12}$ Torr영역 이하인 극고진공(extreme high vacuum: XHV) 영역에 진입하면, ESD (electron stimulated desorption) 효과 등에 의한 이온 게이지 자체의 가스방출률이 커져 정확한 압력 측정이 곤란해 진다. 극고진공 영역에서 이온 게이지는 수 와트(W) 이상의 전력을 사용하여 수 mA의 열전자를 방출시키나, 신호인 이온 전류의 양은 1pA 이하이기 때문에 열전자에 의해 발생되는 백그라운드 전류에 묻혀 신호 전류가 측정되지 않는다고 할 수 있다. 100 nm 이하의 곡률을 가진 뾰족한 금속 탐침에 강한 전기장을 걸어주면 고체 내부의 전자가 터널링 효과에 의해 진공 중으로 방출되며, 이를 전계방출(Field Electron Emission) 효과라 부른다. 전계 방출 전류량은 탐침 표면의 일함수에 의존하며, 일함수가 클수록 지수함수 적으로 감소한다. 금속 표면에 진공 중의 잔류 가스가 부착하면 일함수가 증가한다. 가열에 의해 전계방출 탐침의 표면을 세정한 후에 전자 빔을 방출 시키면, 표면에 가스 분자가 흡착하여 방출 전류량은 점점 감소한다. 감소 속도는 압력에 비례하며, W(310) 탐침의 경우 $10^{-10}$ Torr 영역에서는 수분만에 최초 전류값의 1% 이하로 감소한다. 전계방출 전류의 감소속도가 압력에 비례하는 현상을 이용하여 압력을 측정하였다. Extractor Ionization Gauge 측정값 $5{\times}10^{-12}-3{\times}10^{-10}$ Torr의 범위에서 (111) 방향으로 정렬된 텅스텐 단결정 탐침을 사용하여 방출전류의 로그값을 시간의 함수로 semilog그래프를 그리면, 그래프는 직선을 그리며 그 기울기가 압력에 비례함을 알 수 있었다. 기울기 값과 게이지 측정값은 $10^{-11}{\sim}10^{-10}$ Torr 영역에서 거의 완벽한 비례관계를 보여주었으나, $10^{-12}$ Torr 영역에서 게이지 측정값은 기울기 값에서 추출한 압력치보다 높은 값을 보여주었으며, 이는 게이지 백그라운드 전류에 의한 차이라고 생각된다. W (310) 탐침의 방출전류는 그 감소속도가 W (111) 탐침과 마찬가지로 압력에 비례하였으나, 전류-시간 그래프는 가열 세정 직후에 전류가 거의 감소하지 않는 $2{\times}10^{-10}$ Torr에서 약 10분간 지속되는 '안정 영역'이 존재함을 보여주었다. '안정 영역'은 $10^{-11}$ Torr 영역에서는 수십분, $10^{-12}$ Torr 영역에서는 수시간 이상으로 증가하였다. 초-극고진공 영역에서의 잔류가스 주성분인 수소에서 물, 일산화탄소등의 가스로 바뀌면 '안정 영역'은 사라졌고, 이는 '안정 영역'이 수소 흡착에 의해서만 나타나는 고유 현상임을 말해준다.