• Title/Summary/Keyword: scan blindness

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Scan Blindness Analysis of 1D and 2D Ka-Band Printed Dipole Array Antenna (일차원과 이차원 Ka-대역 프린티드 다이폴 배열 안테나의 스캔 블라인드니스 분석)

  • Koo, Hanni;Song, Sungchan;Nam, Sangwook
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.30 no.3
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    • pp.202-208
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    • 2019
  • In this study, an active element pattern (AEP) of a printed dipole was analyzed in 1D and 2D arrays. First, an AEP of the printed dipole was obtained using the simulation in the 2D infinite array. The scan blindness in the 2D array occurred in the E-plane direction at around ${\pm}36^{\circ}$; however, it was barely observed in the 1D array. To analyze the cause of the scan blindness in the 2D array, the dispersion properties of a unit cell was obtained and compared with the scan blindness by frequency change. The difference between the scan blindness of the 1D and 2D arrays was clarified using the comparison of the Q value in the unit cell in the 1D and 2D arrays. Then, the coupling of the electric field in the E-plane direction was observed when nine elements were separated between the two ports in a linearly arranged dipole structure. Finally, the printed dipole array was fabricated, and an AEP was measured for the $11{\times}1$ and $11{\times}3$ sub arrays. The proposed theory was verified using these observations and by comparison with the simulation results.

Analysis of the Cavity-backed Circular Microstrip Array antenna with Triangular Grid (삼각형 격자 구조를 가지는 Cavity-backed 원형 마이크로스트립 배열 안테나 해석에 관한 연구)

  • 박경빈;정영배;최동혁;박성욱;문영찬;전순익
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.11 no.8
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    • pp.1337-1345
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    • 2000
  • In spite of the advantages of lightweight, low profile, and mass productions, microstrip array antenna has inherently the scan blindness problems in case of wide angle scan. And this scan blindness can be overcome by using cavity-backed microstrip radiator. In this paper, we presented the algorithm of analyzing skewed cavity-backed microstrip array and verified the validity of the proposed numerical results with those of reference papers. Finally, we show the effect of cavity-backed and skewed grid array structure.

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Analysis of the Periodic Microstrip Phased Array Antenna (주기적 마이크로스트립 위상 배열의 특성 해석)

  • 조영수;김동현이상설
    • Proceedings of the IEEK Conference
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    • 1998.10a
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    • pp.335-338
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    • 1998
  • This paper presents calculated results for the infinite phased arrays of the probe-fed rectagualr microstrip patches. A numerical model that is based on a rigorous Green's function and galerkin solutionsis is described. In an arbitrary scan plane, the input impedance and the input reflection coefficient versus the scand angle are calculated. The effects of substrate parameters on the phased arry antenna are considered. The scan blindness phenomenon due to the surface wave is observed and the input impedance bandwidth in the arbitrary scan plane is calculated.

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A Case of Neuroblastoma Presenting with Sudden Blindness (실명을 주소로 한 신경아세포종 1예)

  • Ma, In-Youl;Hah, Jeong-Ok;Kim, Chun-Dong;Lee, Tae-Sook
    • Journal of Yeungnam Medical Science
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    • v.2 no.1
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    • pp.259-264
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    • 1985
  • Neuroblastoma is the most common extracranial solid tumor of childhood which presents various clinical symptoms depending on the primary and metastatic sites. However, it has been rarely reported that sudden onset of blindness was the chief complaint of neuroblastoma. A four years old boy was admitted to the Yeungnam University Hospital with the chief complaint of a sudden onset of blindness due to a distant metastasis of abdominal neuroblastoma to the sphenoid sinus. On admission, both side pupils were dilated without light reflex, fundoscopy showed pale optic disk, electroretinogram was subnormal and visual evoked potential showed no response. The liver was palpable in $3{\frac{1}{2}}$ finger breadth from the right costal margin and adult fist sized mass was palpable in the right flank. Skull X-ray showed destructed sphenoid bone and clinoid process and brain CT scan showed tumor mass in the sphenoid sinus and left orbit. Ultrasonogram and CT scan of the abdomen showed large tumor masses around the right kidney and para-aortic and retropancreatic lymph node. IVP showed displaced right calyceal system with preserved contour. Left supraclavicular lymph node which appeared after admission was biopsied and it showed poorly differentiated neuroblasts. He was treated according to the multiagent chemotherapy schedule for stage IV neuroblastoma patient of children's cancer study group. Abdominal tumor masses and sphenoid sinus mass were markedly reduced after 2 courses of the combination chemotherapy of cyclophosphamide, vincristine, DTIC, adriamycin and VM-26. Eventhough the blindness was not improved, the patient has been in good clinical condition.

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OPTIC NERVE BLINDNESS FOLLOWING MIDFACIAL FRACTURES (중앙 안면부 골절후 발생한 시신경 실명)

  • Lee, Jae Hwy
    • Maxillofacial Plastic and Reconstructive Surgery
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    • v.13 no.3
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    • pp.324-331
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    • 1991
  • Ocular injuries often accompany midfacial trauma Blindness related to indirect optic nerve injury in midfacial fractures is an uncommon and usually permanent complication. Opic nerve blindness is secondary to an indirect optic nerve injury due to the skeletal distortion that occurs in a facial fracture and almost all are caused by frontal, nasoethmoido-frontal or Le Fort III type fractures. When the loss of vision following midfacial fractures is complete and immediate, the prognosis is poor in spite of treatment. Computed tomography revealed compressin of the optic nerve by bony fragments. And so if injury to the optic nerve is suspected, a CT-scan must be performed and massive steroid therapy must be started as soon as possible. Surgery must be performed if there are hematoma or bony fragments injuring the nerve. The following report concerns two patients who suffered immediate and total loss of vision due to a midfacial fracture with no improvement after massive steroid therapy and surgial decompression.

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The Analysis and Implementation of Cavity-backed Circular Microstrip Patch Antenna (원형 공진기 구조 마이크로스트립 안테나 해석 및 구현 방법 연구)

  • Park, Gyeong-Bin;Jeong, Yeong-Bae;Choe, Dong-Hyeok;Park, Seong-Ok;Mun, Yeong-Chan;Jeon, Sun-Ik
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.37 no.12
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    • pp.1-8
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    • 2000
  • The analysis of cavity-backed circular microstrip antenna is performed, based on the method of moments, and verified with experimental results. The proposed algorithm was used to analyze the return loss and radiation characteristics of antenna by the variation of each associated parameter. This result was used to provide the optimum design guideline. Finally active reflection coefficient of infinite cavity-backed microstrip away was calculated to show the effect of suppressing surface wave to eliminate scan blindness.

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Radiator Design Method considering Wide-Angle Beam Steering Characteristics of AESA Radar (AESA 레이더 광각 빔조향 특성을 고려한 복사소자 설계 기법)

  • Kim, Young-Wan;Chae, Hee-Duck;An, Se-Hwan;Joo, Ji-Han
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.22 no.5
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    • pp.87-92
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    • 2022
  • In this paper, a study was conducted on the design of an array element that can be applied to the AESA radar for seeker. An antenna for application to AESA radar should choose an optimal radiation element to be applied to an array antenna in order to secure electronical beam steering characteristics, and consider beam steering characteristics when designing. In particular, in order to satisfy the wide-angle beam steering characteristics, the wide-angle impedance matching technique should be used to minimize the scan blindness region that may occur during wide-angle steering. As such, securing the stability of system operation is becoming an important design consideration for AESA radar. In this paper, WAIM is applied to the end of the radiation element to improve the characteristics of the radiation element applied to the AESA radar antenna device, and the change in the performance of the active reflection coefficient, which is a stable operation index of the system, is reviewed. The final performance result verified the validity of the proposed method by mathematically synthesizing the simulation data.

Intraorbital Encephalocele Presenting with Exophthalmos and Orbital Dystopia : CT and MRI Findings

  • Asil, Kiyasettin;Gunduz, Yasemin;Yaldiz, Can;Aksoy, Yakup Ersel
    • Journal of Korean Neurosurgical Society
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    • v.57 no.1
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    • pp.58-60
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    • 2015
  • A 15-year-old female patient with progressive pulsatile exophthalmos caused by intraorbital encephalocele was evaluated with computed tomography (CT) and magnetic resonance imaging (MRI) in our clinic. She had no history of trauma or reconstructive surgery. When she was a little girl, she had undergone surgery for congenital glaucoma on the right eye. On the three-dimensional image of CT, a hypoplasic bone defect was observed in the greater wing of the right sphenoid bone. MRI and CT scan showed herniation through this defect of the arachnoid membrane and protruded cerebral tissue into the right orbita. Intraorbital encephalocele is an important entity that can cause pulsatile exophthalmos and blindness.

Analysis and Implementation of the Stacked Cavity-Backed Circular Microstrip Patch Antenna (적층형 Cavity-Backed 원형 마이크로스트립 안테나 해석 및 구현에 관한 연구)

  • 박경빈;정영배;최동혁;박성욱;문영찬;전순익
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.11 no.1
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    • pp.37-45
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    • 2000
  • Though microstrip antenna has several advantages, it makes engineers struggle against the difficulties of narrow bandwidth and scan-blindness with probe-feeding and array configuration. To overcome these disadvantages, stacked patch and cavity-backed structure had been proposed. But this structure can not be analyzed easily because we have no concrete means to analyze it. So the algorithm to analyze the structure should be established to make it useful. This paper explained the algorithm of moment method to analyze the structure and verified it by comparing the calculated and measured results.

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An Extra-adrenal Pheochromocytoma Presenting with Spontaneous Intracerebral Hematoma

  • Park, Seong-Keun;Lee, Jung-Kil;Kim, Jae-Hyoo;Kim, Soo-Han
    • Journal of Korean Neurosurgical Society
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    • v.38 no.1
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    • pp.61-64
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    • 2005
  • We report a 18-year-old man, who has been taking antihypertensive medication for 1month in a local clinic, presented with a sudden onset headache followed by left blindness. He experienced palpitation and chest discomfort during physical exertion since 2years before admission, but unfortunately has been ignored. Brain CT showed intracerebral hemorrhage in the left temporoparietal area, but cerebral angiogram and magnetic resonance image revealed no vascular anomaly. He was managed conservatively, and headache and visual loss were improved over time. Subsequently, on the evaluation of hypertension, he was diagnosed as having extra-adrenal pheochromocytoma on left paraaortic area from the results of endocrinological evaluations, abdominal CT scan, and $^{131}I$-MIBG scintigraphy.