• Journal of Power Electronics
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• 제10권6호
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• pp.604-610
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• 2010

Experiments in electrical engineering should mirror the key components of successful research and development: Understand the basic theory needed, test the resulting concepts by simulation and verify these, finally, in the experiment. For optimal learning outcome continuous monitoring of the progress of each individual student is necessary, immediately repeating those subjects which have not been learned successfully. Classically, this is the task of the teacher. In case of remote-controlled experiments this monitoring process and the repetition of subjects should be automated for optimal learning outcome. This paper describes a remote-controlled experiment combining theory, simulation and the experiment itself with an automated monitoring process. Only the evaluation of the experimental results and their comparison to the simulation results has to be checked by a teacher. This paper describes the details of the educational structure for a remote-controlled experiment introducing active filtering of harmonics. For better understanding the content of the learning material (theory and simulation) as well as the results of the experiment and the underlying booking system are shortly presented.

• 대한원격탐사학회지
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• 제20권1호
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• pp.47-55
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• 2004

We have constructed a level-1 processor to generate brightness temperatures using the direct-broadcast data from the passive microwave radiometer onboard Aqua satellite. Although 50-minute half-orbit data, called a granule, are being routinely produced by global data centers, to our knowledge, this is the first attempt to process 10-minute long direct-broadcast (DB) data. We found that the processor designed for a granule needs modification to apply to the DB data. The modification includes the correction to path number, the selection of land mask and the manipulation of dummy scans. Pixel-to-pixel comparison with a reference indicates the difference in brightness temperature of about 0.2 K rms and less than 0.05 K mean. The difference comes from the different length of data between 50-minute granule and about 10-minute DB data. In detail, due to the short data length, DB data do not always have correct cold sky mirror count. The DB processing system is automated to enable the near-real time generation of brightness temperatures within 5 minutes after downlink. Through this work, we would be able to enhance the use of AMSR-E data, thus serving the objective of direct-broadcast.

• 한국음향학회지
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• 제38권5호
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• pp.587-592
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• 2019

수중음향통신에서 다중경로로 인한 인접 심볼 간 간섭은 통신 성능을 저하시킨다. 인접 심볼 간 간섭의 영향을 최소화하여 수중음향통신 성능을 향상시키기 위해 다이버시티 기법을 사용한다. 본 논문에서는 공간 다이버시티와 시간 다이버시티의 결합을 통해 수중음향통신 성능이 개선됨을 보인다. 시공간 다이버시티를 통해 제한적인 배열에서 수중통신 시스템의 효율성을 증대시켰다. 또한 2018년 10월 한국의 동쪽 해역에서 수행한 BLAC18(Biomimetic Long range Acoustic Communication 18) 실험 데이터와 비교하여 이를 검증하였다.

• 한국융합학회논문지
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• 제10권2호
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• pp.175-182
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• 2019

한국과 중국은 다른 어떤 사회보다도 유사한 문화적 이념체계의 지배하에 놓여있던 사회라고 할 수 있다. 유교적 가부장제가 바로 그것으로 한국은 자본주의, 중국은 사회주의와 결합되면서 생겨나는 문제들을 안고 있다 할 것이다. 이렇게 볼 때 사회주의로 전환되기 전까지 중국여성들의 신여성으로서의 경험은 한국사회에 나타나는 여성문제의 본질을 규명하는데 귀중한 비교 문화적 시각을 제공한다고 볼 수 있다. 이에 본 논문은 1920년대 신문학 운동 시기에 등장한 이래 역사의 주요 시기마다 문학작품을 통해 여성에 대한 선진적 담론을 이끌어냈던 중국의 걸출한 작가이자 여성주의의 대변인이었던 딩링(丁玲)에 주목하고자 한다. 특히 초기 대표작인 <소피여사의 일기(莎菲女士的日記)>와 해방구 옌안에서 발표한 <3.8절 유감(三八節有感)>을 중심으로 격동의 중국 현대사를 관통했던 그녀의 삶과 문학의 변화추이를 고찰함으로서 오늘날의 여성주의를 다시 돌아보고자 한다.

• Current Optics and Photonics
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• 제6권6호
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• pp.627-633
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• 2022

To realize uniform side pumping of solar lasers and improve their output power, a solar concentrating system based on off-axis parabolic mirrors is proposed. Four identical off-axis parabolic mirrors with focal length of 1,000 mm are toroidally arranged as the primary concentrator. Four two-dimensional compound parabolic concentrators (2D-CPCs) are designed as a secondary concentrator to further compress the focused spot induced by the parabolic mirrors, and the focused light is then homogenized by four rectangular diffusers and provides uniform pumping for a laser-crystal rod to achieve solar laser emission. Simulation results show that the solar power received by the laser rod, uniformity of the light spot, and output power of the solar laser are 7,872.7 W, 98%, and 351.8 W respectively. This uniform pumping configuration and concentrator design thus provide a new means for developing high-power side-pumped solid-state solar lasers.

• Journal of Astronomy and Space Sciences
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• 제40권4호
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• pp.237-245
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• 2023

Laser communication has been considered as a novel method for earth observation satellites with generation of high data volume. It offers faster data transmission speeds compared to conventional radio frequency (RF) communication due to the short wavelength and narrow beam divergence. However, laser beams are refracted due to atmospheric turbulence between the ground and the satellite. Refracted laser beams, upon reaching the receiver, result in angle-of-arrival (AoA) fluctuation, inducing image dancing and wavefront distortion. These phenomena hinder signal acquisition and lead to signal loss in the course of laser communication. So, precise alignment between the transmitter and receiver is essential to guarantee effective and reliable laser communication, which is achieved by pointing, acquisition, and tracking (PAT) system. In this study, we simulate the effectiveness of tip/tilt compensation for more efficient laser communication in the satellite-ground downlink. By compensating for low-order terms using tip/tilt mirror, we verify the alleviation of AoA fluctuations under both weak and strong atmospheric turbulence conditions. And the performance of tip/tilt correction is analyzed in terms of the AoA fluctuation and collected power on the detector.

• 한국의상디자인학회지
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• 제26권2호
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• pp.15-32
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• 2024

Modern fashion manifests in forms that mirror the diverse lifestyles and personalities of consumers. It transcends mere aesthetic designs and embodyies practicality. There is a preference for comfortable, highly functional attire, leaning towards easy wear. Casual wear, in particular, embraces a sense of freedom not found in standard business attire. It seeks a comfortable, natural silhouette through tactile fabrics rather than sportswear. Loose, drop shoulder sleeves enhance comfort and mobility and often become key elements in casual wear designs. Given that clothing must balance aesthetics with functionality, especially across various activities, it is natural to prioritize functional design. Research on patterns suited for dynamic conditions is imperative. The rise of drop shoulder styles necessitates the development of corresponding sleeve patterns. It is crucial to differentiate pattern drafting methods due to the resulting silhouette variations. This study aims to categorize drop shoulder pattern drafting techniques based on shoulder extension and angle dimensions. Each method will be examined, and drop shoulder sleeve patterns and wear forms will be studied using a 3D virtual system. This research holds significance in providing valuable insights and foundational data for designing diverse drop shoulder sleeve patterns, contributing to their practical development and advancement.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권2호
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• pp.210-215
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• 2017

We have developed the neuromorphic system that can work with the four-terminal Si-based synaptic devices and verified the operation of the system using simulation tool and printed-circuit-board (PCB). The symmetrical current mirrors connected to the n-channel and p-channel synaptic devices constitute the synaptic integration part to express the excitation and the inhibition mechanism of neurons, respectively. The number and the weight of the synaptic devices affect the amount of the current reproduced from the current mirror. The double-stage inverters controlling delay time and the NMOS with large threshold voltage ($V_T$) constitute the action-potential generation part. The generated action-potential is transmitted to next neuron and simultaneously returned to the back gate of the synaptic device for changing its weight based on spike-timing-dependent-plasticity (STDP).

• 항공우주시스템공학회지
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• 제12권3호
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• pp.9-17
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• 2018

지구 관측용 소형 위성카메라의 경우, 중대형 위성에 비해 상대적으로 약한 구조 안정성으로 인해 열악한 발사환경 및 우주환경에서 광부품의 정렬오차가 발생하기 쉽다. 발생한 정렬오차는 위성카메라의 광학 성능 저하를 유발시킨다. 본 연구에서는 소형 위성 카메라의 정렬오차를 보상하기 위하여 3축 포커스 메커니즘을 제안하였다. 이 메커니즘은 3개의 압전 작동기로 구성되어 x-축, y-축 틸트 및 디스페이스(De-space) 보정을 수행할 수 있다. 포커스 메커니즘의 설계 요구조건은 슈미트-카세그레인(Schmidt-Cassegrain) 타입의 목표 광학계 설계에서 도출되었다. 부경 정렬오차 보상을 위하여 부 반사경의 뒤에 포커스 메커니즘을 부착하여 부경의 3축 운동을 제어하였다. 이 때 파면오차로 인한 광학 성능 저하를 최소화하기 위한 플렉셔를 Box-Behnken 실험계획법을 통하여 설계하였으며, ANSYS를 이용하여 파면오차 해석을 수행하였다. 제작된 포커스 메커니즘은 작동기의 수학적 모델링, PID 제어기 설계, 서보 제어실험을 통해 서보성능을 검증하였다.

• 천문학논총
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• 제15권spc2호
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• pp.21-25
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• 2000

The ionosphere, the atmosphere of the earth ionized by solar radiations, has been strongly varied with solar activity. The ionosphere varies with the solar cycle, the seasons, the latitudes and during any given day. Radio wave propagation through or in the ionosphere is affected by ionospheric condition so that one needs to consider its effects on operating communication systems normally. For examples, sporadic E may form at any time. It occurs at altitudes between 90 to 140 km (in the E region), and may be spread over a large area or be confined to a small region. Sometimes the sporadic E layer works as a mirror so that the communication signal does not reach the receiver. And radiation from the Sun during large solar flares causes increased ionization in the D region which results in greater absorption of HF radio waves. This phenomenon is called short wave fade-outs. If the flare is large enough, the whole of the HF spectrum can be rendered unusable for a period of time. Due to events on the Sun, sometimes the Earth's magnetic field becomes disturbed. The geomagnetic field and the ionosphere are linked in complex ways and a disturbance in the geomagnetic field can often cause a disturbance in the F region of the ionosphere. An enhancement will not usually concern the HF communicator, but the depression may cause frequencies normally used for communication to be too high with the result that the wave penetrates the ionosphere. Ionospheric storms can occur throughout the solar cycle and are related to coronal mass ejections (CMEs) and coronal holes on the Sun. Except the above mentioned phenomena, there are a lot of things to affect the radio communication. Nowadays, radio technique for probing the terrestrial ionosphere has a tendency to use satellite system such as GPS. To get more accurate information about the variation of the ionospheric electron density, a TEC measurement system is necessary so RRL will operate the system in the near future.