허니콤 코어에 적용된 비발디 안테나의 방사 특성 분석

장우혁,노정언,김천곤 한국복합재료학회 2024 Composites research Vol.37 No.1

Numerous studies have explored structural antennas for integrating advanced wireless systems into aircraft without altering their external form. However, most of the research on structural antennas uses patch antennas, characterized by limitations such as narrow frequency bands and low directivity. In contrast, the Vivaldi antenna, widely used in the wireless applications, has the advantages of a wide frequency band and directivity. Nevertheless, it has been difficult to apply it to aircraft due to the direction of radiation. In this study, we try to solve this problem by applying the antenna patch on the honeycomb wall in order to apply the Vivaldi antenna on the aircraft. The effect of the honeycomb structure on the antenna radiation performance was analyzed and the potential of the honeycomb Vivaldi antenna was verified through the simulation.

초등학교 저학년 아동을 대상으로 한 피젯 스피너 훈련이 손 기능과글씨쓰기 명료도에 미치는 영향

장우혁,완창연,어석진,서창훈,이동형 대한작업치료학회 2018 대한작업치료학회지 Vol.26 No.4

Objective : The purpose of this study was to investigate the effects of fidget spinner training on the hand functionand handwriting legibility of lower grade elementary school studens. Methods : This study randomly assigned a study group of 12 children and control group of 12 children from 24children in grade 1 and 2 (ages 7 through 8), whose are dominantly right handed. The study used was a pre-postprocess. The intervention was conducted only on the study group twice a week for 5 weeks and for 40 minutesper session, for a total of ten sessions. The measuring instruments used to compare the hand functions andhandwriting legibility were the Jebsen-Taylor Hand Function Test, Grip Strength Test, and Legibility Test. Thedata analysis used a Wilcoxon signed rank, Mann-Whitney U and Chi-Square cross analysis. Results : The fidget spinner training showed significant improvement in the study group’s hand function(grip strengthand handwriting legibility) and a significant difference was shown between the control and study groups. Conclusion : This study confirmed the value and utility of a fidget spinner as a tool for improving the hand functionand handwriting legibility of elementary school students in lower grades. Future studies are expected to verify theeffectiveness of the fidget spinner training based on the present study. 목적 : 본 연구는 피젯 스피너를 활용하여 초등학교 저학년 아동의 손 기능과 글씨쓰기 명료도에 미치는 영향을 알아보고자 하였다. 연구방법 : 본 연구는 일반아동 중 우세손이 우측인 1~2학년(만 7~8세) 아동 24명을 대상으로 실험군 12명,대조군 12명으로 무작위 분류하여 실시하였다. 연구 설계는 사전-사후 설계이다. 중재는 실험군 아동들에게만 실시하였으며, 5주간, 주 2회, 1회 당 40분씩 총 10회기로 진행하였다. 측정도구로는 중재 전, 후의손 기능과 글씨쓰기 명료도의 비교를 위하여 젭슨-테일러 손 기능 검사(Jebsen-Taylor Hand FunctionTest; JHFT)와 장악력 검사(Grip Strength Test; GST) 그리고 명료도 검사(Legibility Test; LT)를 사용하였다. 자료 분석은 Wilcoxon signed rank 검정과 Mann-Whitney U 검정, 그리고 교차분석의 카이제곱 검정을 사용하였다. 결과 : 피젯 스피너 훈련은 실험군의 손 기능과 장악력, 글씨쓰기 명료도에 유의한 향상을 보였으며, 실험군과 대조군 사이의 유의한 차이를 보였다. 결론 : 본 연구는 초등학교 저학년 아동의 손 기능과 글씨쓰기 명료도를 효과적으로 향상시키는 도구로써피젯 스피너의 가치 및 효용성을 확인하였다. 이에 향후 연구에서는 본 연구를 토대로 피젯 스피너 훈련의 효과를 검증하는 다양한 연구가 이어지길 기대한다.

이슈분석 : 인도 세무당국, 외국 기업에 과세 강화 -조세 회피로 간주하는 범위 넓힐 예정

장우혁 포스코경영연구원 2011 CHINDIA Plus Vol.61 No.-

만성 단안 일광망막병증 1 예

장우혁 영남대학교 의과대학 2007 Yeungnam University Journal of Medicine Vol.24 No.2

일광망막병증은 드물지만 일반적으로 잘 알려진 황반질환이며 이는 직접적인 태양 관찰로 인해 일어난다. 21세 남자가 단안 망원경을 이용하여 좌안으로 약 30초간 태양을 관찰하고 약 48시간 후 시력저하와 중심암점을 호소하였다. 그로부터 약 8개월 후 중심시력은 1.0에서 0.1로 저하되었고 안저검사에서 황백색의 점상 침착물이 관찰되었고 형광안저 촬영에서 망막 색소상피의 결손으로 인한 창문 결손이 좌안 중심와에 나타났다. 시야검사에서는 중심 암점이 괸찰되었고 시력저하는 빛에 노출된 후 1년이 지난 후에도 지속되었다. Solar retinopathy is a rare but well-recognized clinical entity of macular damage, caused by viewing a solar eclipse or direct sun gazing. A 21-year-old man gazed at the sun for approximately thirty seconds at noon using a monocular telescope with his left eye. Forty-eight hours after sun gazing, the patient experienced symptoms uf blurred vision and central scotoma in the left eye. Eieht months after sun gazing, the visual acuity decreased from 1.0 to 0.1 in the left eye and the fundus examination showed a round, yellowish-white discoid lesion at the left fovea. Fluorescein angiography showed an early window defect in the fovea of the left eye, that persisted without size change during the late phase resulting from atrophy uf the retinal pigment cpithelium. A small, central scotoma of the left eye was also found in the visual field test. The visual acuity was unchanged at the end of a one-year follow-up period.

Pronunciation Errors and Strategies by Korean L2 learners of Mongolian

장우혁 한국몽골학회 2014 몽골학 Vol.0 No.36

The main purpose of this paper is to offer a typological observation ofpossible errors in the pronunciation of Mongolian sounds by Koreanlearners of Mongolian. It is examined that pronunciation errors are mainlyattributed to different phonemic inventories and phonological featuresbetween the Korean language (native language) and the Mongolianlanguage (target language). According to contrastive analysis, Mongolianvoiced and palatalized stops are the most difficult sounds for Koreanlearners to acquire because there is no corresponding segments in Korean. With regard to laryngeal features, Korean obstruents are contrastivedepending on the markedness of Glottal Width (GW) whereas Mongolianobstruents are marked with either Glottal Width (GW) or Glottal Tension(GT). Thus, Mongolian laryngeal system is more complicated than Koreanone. This may induce Korean learners to have difficulty in learningMongolian obstruents. In addition to the segmental differences betweenthe two languages, suprasegmental factors, such as syllable types andvowel length, can prevent Korean learners from acquiring the pronunciationof Mongolian sounds. For example, Mongolian allows a consonant clusterin coda position, which may lead Korean learners to insert epentheicvowels in between adjacent consonants. In Mongolian, vowel length is adistinctive feature to distinguish long vowels from short ones. However,the distinction between long and short vowels is insignificant in Korean. This paper also addresses that the Grammar-Translation method and Audio-lingual method that are popular in teaching foreign languages donot help Korean learners learn how to pronounce Mongolian phonemes. An alternative teaching method, the Silent Way seems to have benefitedmost by associating sounds with certain symbols, which allows Koreanlearners to facilitate an insight into Mongolian phonemes.

Carbon-Fiber-Stitched Substrate in Coaxial-Fed-Patch-Antenna for Removing Hole in Feeder

장우혁,김솔,노정언,최주성,차지훈,김천곤 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.2

There are many studies about using structural antennas for aircrafts; these structures have disadvantages such as being thick or requiring complex manufacturing processes. In this study, we propose using a carbon-fiber-stitched substrate for designing a micro-strip-patch antenna without the defect of having a hole for the feeder. We constructed an antenna without increased thickness or a complicated manufacturing process, using a carbon-fiber feeder. The effect of the carbon-fiber feeder on the antenna was confirmed by simulation, revealing that the antenna performance hardly changed when the radius of the feeder was 0.6 mm, which was the same as that of the feeder of the connector; similarly, the resistivity of the feeder was like that of the carbon fiber. If the radius of feeder was not 0.6 mm, there would be a loss due to the outgoing power. It has been, however, confirmed that the carbon-fiber feeder could be used as an antenna feeder via additional impedance matching. To reduce the outgoing power loss, the antenna performance was measured again after performing additional impedance matching. The antenna with the carbon-fiber feeder had a reflection loss of − 19.3 dB at 9.11 GHz and a maximum gain of 4.7 dBi. Therefore, it was verified that the carbon-fiber stitched substrate could be used for the coaxial-fed patch antenna, also eliminating the defects of the feeding line.

몽골인 영어 학습자의 영어 유성성에 따른 모음 길이 차이의 인식에 있어서 제1언어의 음운적 특성이 미치는 영향

장우혁 한국몽골학회 2024 몽골학 Vol.- No.78

본 연구의 목적은 영어를 배우는 몽골인 학습자들이 영어 단어의 어말에 나타나는 유성음과 무성음의 차이를 인식할 수 있는지를 조사하는 것이다. 영어에서는 모음의 길이가 뒤따르는 자음의 유성성 여부에 따라 달라지며, 이는 단순한 음향적 특성을 넘어 중요한 음운현상이다. 영어의 유성음은 어말에서 무성음으로 발음되어 유·무성의 대립이 중화되기 때문에, 어말 자음보다는 선행 모음의 길이 차이가 단어 인식에 더 중요한 단서가 된다. 몽골어에서는 모음의 길이 차이가 음운적 대립으로 나타나기 때문에, 모음 길이가 몽골어 음운 체계에서 중요한 자질이 된다. 본 연구에서 25명의 몽골인 영어 학습자와 25명의 영어 원어민을 대상으로 두 가지 음성 인식 과제를 실시한 결과, AX-변별 과제에서는 몽골어 학습자들이 영어 원어민과 유사한 성과를 보였으나, 식별 과제에서는 낮은 성과를 보였다. 이는 몽골어 학습자들이 영어에서 유성음에 의해 조건화된 선행 모음의 길이에 대해서 제대로 습득하지 못했음을 시사한다. 결과적으로, 이러한 실험 결과는 L1의 음운적 특징이 L2의 음소를 구별하는데 도움이 될 수는 있지만, L2의 정확한 음소를 인식하기 위해서는 L2의 음운현상을 이해하는 것이 필수적임을 보여준다. The main purpose of this study is to determine whether Mongolian learners of English as a second language can perceive English minimal pairs that shows voicing contrast in word-final positions. In English, the length of the preceding vowel changes depending on the presence or absence of voicing in the following consonant, which is understood as a significant phonological phenomenon in English. Given that voiced sounds become voiceless at the end of words, voicing contrast is neutralized. Therefore, the difference in the length of the preceding vowel is a more important perceptual cue than word-final voicing contrast in English. Noticing that Mongolian vowels have a phonemic contrast between short and long vowels, we realize that vowel length is a phonological feature in Mongolian. In terms of second language acquisition, it can be predicted that Mongolian learners will easily acquire English vowel length difference due to the fact that vowel length is a phonological feature in L1 grammar. In this study, I conducted two types of speech perception tasks with 25 Mongolian participants as an experimental group and 25 native speakers of English as a control group: AX-discrimination and identification tasks. In the AX-discrimination task, Mongolian participants performed as well as native English speakers, which seems to support the positive transfer effect of L1 grammar on L2 perception. On the contrary, Mongolian participants showed much poorer performance than English speakers in identifying the corresponding word that they listened to from a series of minimal pairs. It can be assumed that Mongolian learners did not learn voicing-conditioned vowel length in English. Crucial to the findings of the study is that learners need to understand phonological phenomena in L2 in order to correctly perceive L2 phonemes even though L1 phonological features can be helpful in distinguishing phonetic differences in L2.

Dispersion Stability of Multi-walled CNTs in the Presence of Amphiphilic Macromolecules and Their CNT/PMMA Nancomposites

장우혁,조희경,정인우 한국고분자학회 2006 한국고분자학회 학술대회 연구논문 초록집 Vol.2006 No.4

The Dispersion Stability of Multi-Walled Carbon Nanotubes in the Presence of Poly(styrene/α-methyl styrene/ acrylic acid) Random Terpolymer

장우혁,정인우,심상은,최순자 한국고분자학회 2006 Macromolecular Research Vol.14 No.5

Aqueous dispersions of pristine and functionalized (COOH- and NH2-) multi-walled, carbon nanotubes (MWNTs) were prepared by using three types of surfactants: sodium dodecyl sulfate (SDS, anionic), PEO-PPO-PEO (Pluronic P84, non-ionic), and poly(styrene/α-methyl styrene/acrylic acid) random terpolymer, i.e., alkali-soluble resin (ASR). The aggregate size, ζ-potential, and storage stability of the MWNT aqueous dispersions were investigated by using dynamic light scattering and the turbidity method at room temperature. The exfoliation of the MWNT aggregates was determined by a UV-visible spectrophotometer and the morphology of the surfactant-coated MWNTs was observed by transmission electron microscopy (TEM). In all cases, ASR showed better dispersion stability with the smallest aggregate size, compared with the other surfactants, because of its unique molecular structure, i.e., randomly incorporated carboxylic acid groups and planar phenyl groups that can be irreversibly and effectively adsorbed on the MWNT surface. A predominantly-exfoliated morphology of MWNTs was observed in the presence of ASR from the strong intensity of the UV-vis spectrum at 263nm.

Modified Hausdorff 거리 척도를 이용한 기하 특징점 위치 기반 정량적 필적 감정 방법

장우혁,김세희,김윤경,이의철 사단법인 인문사회과학기술융합학회 2018 예술인문사회융합멀티미디어논문지 Vol.8 No.2

본인 인증 및 범죄 증거 분석 등의 분야에서 생체인식 기술의 활용 범위가 넓어지고 있다. 필적은 행동 기반 생체인식으로 활용될 수 있는 수단이다. 필적 감정은 두 문서에 기재된 글씨를 비교하여 동일인에 의해 작성되었는지를 판별하는 기술이다. 필적 감정 전문가는 필획, 필압, 기하학적 특징의 유사성을 종합적으로 고려하여 결정한다. 하지만, 각자의 기준이 다르고, 어떠한 특징을 기준으로 판단하는지에 대한 근거가 모호하여 감정 결과를 신뢰할 수가 없다. 따라서, 법정에서 증거력을 인정되지 못한다. 본 논문에서는 동일한 단어를 필기한 두 이미지를 비교하기 위해, 이진화, 라벨링, 사이즈 필터링, 세선화와 같은 디지털 영상처리 과정을 거쳐 필획의 분기점 과 끝점 및 코너점을 검출한다. 검출된 특징 중 인접하여 나타나는 중복 요소를 제거하여 최종 특징을 선정한다. 서로 다른 영상 크기를 정규화하기 위해 특징점의 좌표 값은 배율을 곱하는 과정을 거쳤다. 검출된 특징점 집합들 사이의 비교는 modified Hausdorff 거리 척도를 통해 수행한다. 동일인 및 타인 간 비교과정을 통해 성능을 분석함으로써, 객관적인 필적 감정의 가능성을 확인하였다. The scope of application of biometrics technology is expanding in the areas of identity verification and crime analysis. Handwriting is a means to be used as behavioral biometrics. Handwriting verification is a technique of comparing characters written in two documents to determine whether they were created by the same person. The handwriting verification expert determines the similarity of the marking, the pressure, and the geometric features in a comprehensive manner. However, it is not possible to trust verification results because the basis of each criterion is different and ambiguous to define. Therefore, the verification result as evidence is not acceptable in court. To solve the problems, we use geometric features such as bifuaction, ending, and corner points which were extracted by some digital image processing such as binarization, component labeling, size filtering, and thinning in order to compare two handwritings. The final features are selected by eliminating adjacent points. In order to normalize different image sizes, the coordinate values ​​of the feature points are multiplied by the magnification factor. Comparisons between detected feature point sets are performed through measuring the modified Hausdorff distance. By analyzing the performance through genuine and imposter matching, we confirmed the feasibility of objective handwriting verification.