• Title/Summary/Keyword: Stray light

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A Coaxial and Off-axial Integrated Three-mirror Optical System with High Resolution and Large Field of View

  • Chen, Zhe;Zhu, Junqing;Peng, Jiantao;Zhang, Xingxiang;Ren, Jianyue
    • Journal of the Optical Society of Korea
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    • v.20 no.1
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    • pp.94-100
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    • 2016
  • A novel optical design for high resolution, large field of view (FOV) and multispectral remote sensing is presented. An f/7.3 Korsch and two f/17.9 Cook three-mirror optical systems are integrated by sharing the primary and secondary mirrors, bias of the FOV, decentering of the apertures and reasonable structure arrangement. The aperture stop of the Korsch system is located on the primary mirror, while those of the Cook systems are on the exit pupils. High resolution image with spectral coverage from visible to near-infrared (NIR) can be acquired through the Korsch system with a focal length of 14 m, while wide-field imaging is accomplished by the two Cook systems whose focal lengths are both 13.24 m. The full FOV is 4°×0.13°, a coverage width of 34.9 km at the altitude of 500 km can then be acquired by push-broom imaging. To facilitate controlling the stray light, the intermediate images and the real exit pupils are spatially available. After optimization, a near diffraction-limited performance and a compact optical package are achieved. The sharing of the on-axis primary and secondary mirrors reduces the cost of fabrication, test, and manufacture effectively. Besides, the two tertiary mirrors of the Cook systems possess the same parameters, further cutting down the cost.

Reliability Assessment against Ultimate Bending Moment of Ships′ Hull Girder (선체의 최종굽힘 모멘트에 대한 신뢰성 검토)

  • Joo-Sung Lee;P.D.C. Yang
    • Journal of the Society of Naval Architects of Korea
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    • v.29 no.1
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    • pp.103-112
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    • 1992
  • The ultimate bending moment of ships is one of the principle strength considered in ship design. Several methods have been proposed to predict the ultimate bending moment and its major part is, in general, predicting the ultimate compressive strength of stiffened panels. In this paper, made is the review on the methods and formulae of predicting the ultimate compressive strength and they are applied to predicting the ultimate bending moment. Safely levels of three bulk carriers have been derived evaluated for two loading conditions, stray, light ship condition and full load condition, and wave bending by Classification Society Rule(ABS, DnV and Lloyd Rule). The present reliability analysis problem is strictly non-linear and the Advanced First-Order Reliability Method has been used. From the results of parametric studies, the methods of predicting the ultimate compressive strength of stiffened panels are compared from the view point of their applicability to the reliability assessment of ships structures. The paper ends wish a brief discussion drawn from the parametric studies and the extension of the study is described.

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Radiative transfer analysis for Amon-Ra instrument

  • Seong, Se-Hyun;Ryu, Dong-Ok;Lee, Jae-Min;Hong, Jin-Suk;Kim, Seong-Hui;Yoon, Jee-Yeon;Park, Won-Hyun;Lee, Han-Shin;Park, Jong-Soo;Yu, Ji-Woong;Kim, Sug-Whan
    • Bulletin of the Korean Space Science Society
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    • 2009.10a
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    • pp.28.4-29
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    • 2009
  • The 'Amon-Ra' instrument of the proposed 'EARTHSHINE' satellite is a dual (i.e. imaging and energy) channel instrument for monitoring the total solar irradiance (TSI) and the Earth's irradiance at around the L1 halo orbit. Earlier studies for this instrument include, but not limited to, design and construction of breadboard Amon-Ra imaging channel, stray light suppression and system performance computation using Integrated Ray Tracing (IRT) technique. The Amon-Ra instrument is required to produce 0.3% in uncertainty for both Sunlight and Earthlight measurement. In this study, we report accurate estimation of the output electric signal derived from the orbital variation of radiant exitance from the Sun and the Earth arriving at the aperture and detector plane of the Amon-Ra. For this, orbital irradiance are computed analytically first and then confirmed by simulation using Integrated Ray Tracing (IRT) model. Specially, the results show the arriving power at the bolometer detector surface is $1.24{\mu}W$ for the Sunlight and $1.28{\mu}W$ for the Earthlight, producing the output signal pulses of 34.31 mV and 35.47 mV respectively. These results demonstrate successfully that the arriving radiative power is well within the bolometer detector dynamic range and, therefore, the proposed detector can be used for the in-orbit measurement sequence. We discuss the computational details and implications as well as the simulation results.

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Smart Harness for Preventing Pet Loss Outdoors (실외에서 애완견 분실 방지를 위한 스마트 어깨줄)

  • Lee, Jun-Hyeok;Ruy, Se-Hyun;Lim, Jong-Chan;Chou, Tea-Hyun;Han, Yeong-Oh
    • The Journal of the Korea institute of electronic communication sciences
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    • v.16 no.4
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    • pp.709-718
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    • 2021
  • In this paper, it can be seen that the number of abandoned dogs increases every year through the statistics on the occurrence of abandoned animals. With the goal of reducing the number of stray dogs, a smart pet dog shoulder strap is implemented based on a real-time location tracking system using the ESP32 module and GPS sensor. It is an ESP32 module with a built-in Bluetooth module. It is input to the MCU using various sensors, and finally outputs to a smart-phone application, and communicates through the built-in blue-tooth module. In addition, it uses Neopixels to compensate the weaknesses at night through LED light emission, and automatically sets the warning distance to design a music playback system through the LED flashing effect and MP3 module. In addition, a smart pet dog shoulder strap was designed to help pet dog health care by measuring the moving distance according to the amount of activity through the gyro sensor.

Magneto-Mechano-Triboelectric Generator Enabled by Ferromagnetic-Ferroelectric Composite (강자성-강유전성 복합체를 활용한 자기-기계-마찰전기 변환 발전소자)

  • Yeseul Lim;Geon-Tae Hwang
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.37 no.1
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    • pp.112-117
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    • 2024
  • The Internet of Things (IoT) device is a key component for Industry 4.0, which is the network in homes, factories, buildings, and infrastructures to monitor and control the systems. To demonstrate the IoT network, batteries are widely utilized as power sources, and the batteries inevitably require repeated replacement due to their limited capacity. Magneto-mechano-electric (MME) generators are one of the candidate to develop self-powered IoT systems since MME generators can harvest electricity from stray alternating current (AC) magnetic fields arising from electric power cables. Herein, we report a magneto-mechano-triboelectric generator enabled by a ferromagnetic-ferroelectric composite. In the triboelectric nylon matrix, a ferromagnetic carbonyl iron powder (CIP) was introduced to induce magnetic force near the AC magnetic field for MME harvesting. Additionally, a ferroelectric ceramic powder was also added to the MME composite material to enhance the charge-trapping capability during triboelectric harvesting. The final ferromagnetic-ferroelectric composite-based MME triboelectric harvester can generate an open-circuit voltage and a short-circuit current of 110 V and 8 μA, respectively, which were enough to turn on a light emitting diode (LED) and charge a capacitor. These results verify the feasibility of the MME triboelectric generator for not only harvesting electricity from an AC magnetic field but also for various self-powered IoT applications.

The Detailed Design of the NISS onboard NEXTSat-1

  • Jeong, Woong-Seob;Park, Sung-Joon;Moon, Bongkon;Lee, Dae-Hee;Park, Won-Kee;Lee, Duk-Hang;Ko, Kyeongyeon;Pyo, Jeonghyun;Kim, Il-Joong;Park, Youngsik;Nam, Ukwon;Kim, Minjin;Ko, Jongwan;Im, Myungshin;Lee, Hyung Mok;Lee, Jeong-Eun;Shin, Goo-Hwan;Chae, Jangsoo;Matsumoto, Toshio
    • The Bulletin of The Korean Astronomical Society
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    • v.40 no.2
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    • pp.39.3-40
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    • 2015
  • The NISS (Near-infrared Imaging Spectrometer for Star formation history) onboard NEXTSat-1 is the near-infrared instrument optimized to the first small satellite of NEXTSat series. The capability of both imaging and low spectral resolution spectroscopy in the near-infrared range is a unique function of the NISS. The major scientific mission is to study the cosmic star formation history in local and distant universe. For those purposes, the main targets are nearby galaxies, galaxy clusters, star-forming regions and low background regions. The off-axis optical design of the NISS with two linear variable filters is optimized to have a wide field of view ($2deg.{\times}2deg.$) as well as the wide wavelength range from 0.95 to $3.8{\mu}m$. The mechanical structure is considered to endure the launching condition as well as the space environment. The dewar inside the telescope is designed to operate the infrared detector at 80K stage. From the thermal analysis, we confirmed that the telescope and the dewar can be cooled down to around 200K and 80K, respectively in order to reduce the large amount of thermal noise. The stray light analysis is shown that a light outside a field of view can be reduced below 1%. After the fabrications of the parts of engineering qualification model (EQM), the NSS EQM was successfully assembled and integrated into the satellite. To verify operations of the satellite in space, the space environment tests such as the vibration, shock and thermal-vacuum test were performed. Here, we report the results of the critical design review for the NISS.

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Progress Report on NISS onboard NEXTSat-1

  • Jeong, Woong-Seob;Park, Sung-Joon;Park, Kwijong;Moon, Bongkon;Lee, Dae-Hee;Pyo, Jeonghyun;Park, Youngsik;Kim, Il-Joong;Park, Won-Kee;Lee, Duk-Hang;Park, Chan;Ko, Kyeongyeon;Nam, Ukwon;Han, Wonyong;Im, Myungshin;Lee, Hyung Mok;Lee, Jeong-Eun;Shin, Goo-Hwan;Chae, Jangsoo;Matsumoto, Toshio
    • The Bulletin of The Korean Astronomical Society
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    • v.39 no.1
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    • pp.49.1-49.1
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    • 2014
  • The NISS (Near-infrared Imaging Spectrometer for Star formation history) onboard NEXTSat-1 is the near-infrared instrument onboard NEXTSat-1 which is being developed by KASI. The imaging low-resolution spectroscopic observation in the near-infrared range for nearby galaxies, low background regions, star-forming regions and so on will be performed on orbit. After the System Requirement Review, the optical design is changed from on-axis to the off-axis telescope which has a wide field of view (2 deg. ${\times}$ 2 deg.) as well as the wide wavelength range from 0.95 to $3.8{\mu}m$. The mechanical structure is considered to endure the launching condition as well as the space environment. The design of relay optics is optimized to maintain the uniform optical performance in the required wavelength range. The stray light analysis is being made to evade a light outside a field of view. The dewar is designed to operate the infrared detector at 80K stage. From the thermal analysis, we confirmed that the telescope can be cooled down to around 200K in order to reduce the large amount of thermal noise. Here, we report the current status of the NISS development.

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Conceptual Design Study of NISS onboard NEXTSat-1

  • Jeong, Woong-Seob;Park, Sung-Joon;Park, Kwijong;Lee, Dae-Hee;Moon, Bongkon;Pyo, Jeonghyun;Park, Youngsik;Kim, Il-Joong;Park, Won-Kee;Lee, Duk-Hang;Park, Chan;Ko, Kyeongyeon;Nam, Ukwon;Han, Wonyong;Im, Myungshin;Lee, Hyung Mok;Lee, Jeong-Eun;Shin, Goo-Hwan;Chae, Jangsoo
    • The Bulletin of The Korean Astronomical Society
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    • v.38 no.2
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    • pp.82.2-82.2
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    • 2013
  • The NISS (Near-infrared Imaging Spectrometer for Star formation history) onboard NEXTSat-1 is being developed by KASI. The NISS will perform the imaging low-resolution spectroscopic observation in the near-infrared range for nearby galaxies, low background regions, starforming regions and so on. The off-axis reflecting telescope with a wide field of view (2 deg. ${\times}$ 2 deg.) will be operated in the wavelength range from 0.95 to $3.8{\mu}m$. In order to reduce thermal noise, a telescope and a HgCdTe infrared sensor will be cooled down to 200K and 80K, respectively. To evade a stray light outside a field of view and use limited space efficiently, the NISS adopted the off-axis reflective optical system. The primary and secondary mirrors, optomechanical part and mechanical structure were designed to use the same material. It will lessen the degradation of optical performance due to a thermal variation. The purpose of NISS is the observation of cosmic near-infrared background in the wide wavelength range as well as the detection of near-infrared spectral lines in nearby galaxies, cluster of galaxies and star forming regions. It will give us less biased information on the star formation history. In addition, we will demonstrate the space technologies related to the development of the Korea's leading near-infrared instrument for the future large infrared telescope, SPICA.

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ADVANTAGES OF USING ARTIFICIAL NEURAL NETWORKS CALIBRATION TECHNIQUES TO NEAR-INFRARED AGRICULTURAL DATA

  • Buchmann, Nils-Bo;Ian A.Cowe
    • Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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    • 2001.06a
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    • pp.1032-1032
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    • 2001
  • Artificial Neural Network (ANN) calibration techniques have been used commercially for agricultural applications since the mid-nineties. Global models, based on transmission data from 850 to 1050 nm, are used routinely to measure protein and moisture in wheat and barley and also moisture in triticale, rye, and oats. These models are currently used commercially in approx. 15 countries throughout the world. Results concerning earlier European ANN models are being published elsewhere. Some of the findings from that study will be discussed here. ANN models have also been developed for coarsely ground samples of compound feed and feed ingredients, again measured in transmission mode from 850 to 1050 nm. The performance of models for pig- and poultry feed will be discussed briefly. These models were developed from a very large data set (more than 20,000 records), and cover a very broad range of finished products. The prediction curves are linear over the entire range for protein, fat moisture, fibre, and starch (measured only on poultry feed), and accuracy is in line with the performance of smaller models based on Partial Least Squares (PLS). A simple bias adjustment is sufficient for calibration transfer across instruments. Recently, we have investigated the possible use of ANN for a different type of NIR spectrometer, based on reflectance data from 1100 to 2500 nm. In one study, based on data for protein, fat, and moisture measured on unground compound feed samples, dedicated ANN models for specific product classes (cattle feed, pig feed, broiler feed, and layers feed) gave moderately better Standard Errors of Prediction (SEP) compared to modified PLS (MPLS). However, if the four product classes were combined into one general calibration model, the performance of the ANN model deteriorated only slightly compared to the class-specific models, while the SEP values for the MPLS predictions doubled. Brix value in molasses is a measure of sugar content. Even with a huge dataset, PLS models were not sufficiently accurate for commercial use. In contrast an ANN model based on the same data improved the accuracy considerably and straightened out non-linearity in the prediction plot. The work of Mr. David Funk (GIPSA, U. S. Department of Agriculture) who has studied the influence of various types of spectral distortions on ANN- and PLS models, thereby providing comparative information on the robustness of these models towards instrument differences, will be discussed. This study was based on data from different classes of North American wheat measured in transmission from 850 to 1050 nm. The distortions studied included the effect of absorbance offset pathlength variation, presence of stray light bandwidth, and wavelength stretch and offset (either individually or combined). It was shown that a global ANN model was much less sensitive to most perturbations than class-specific GIPSA PLS calibrations. It is concluded that ANN models based on large data sets offer substantial advantages over PLS models with respect to accuracy, range of materials that can be handled by a single calibration, stability, transferability, and sensitivity to perturbations.

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MEMS Fabrication of Microchannel with Poly-Si Layer for Application to Microchip Electrophoresis (마이크로 칩 전기영동에 응용하기 위한 다결정 실리콘 층이 형성된 마이크로 채널의 MEMS 가공 제작)

  • Kim, Tae-Ha;Kim, Da-Young;Chun, Myung-Suk;Lee, Sang-Soon
    • Korean Chemical Engineering Research
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    • v.44 no.5
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    • pp.513-519
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    • 2006
  • We developed two kinds of the microchip for application to electrophoresis based on both glass and quartz employing the MEMS fabrications. The poly-Si layer deposited onto the bonding interface apart from channel regions can play a role as the optical slit cutting off the stray light in order to concentrate the UV ray, from which it is possible to improve the signal-to-noise (S/N) ratio of the detection on a chip. In the glass chip, the deposited poly-Si layer had an important function of the etch mask and provided the bonding surface properly enabling the anodic bonding. The glass wafer including more impurities than quartz one results in the higher surface roughness of the channel wall, which affects subsequently on the microflow behavior of the sample solutions. In order to solve this problem, we prepared here the mixed etchant consisting HF and $NH_4F$ solutions, by which the surface roughness was reduced. Both the shape and the dimension of each channel were observed, and the electroosmotic flow velocities were measured as 0.5 mm/s for quartz and 0.36 mm/s for glass channel by implementing the microchip electrophoresis. Applying the optical slit with poly-Si layer provides that the S/N ratio of the peak is increased as ca. 2 times for quartz chip and ca. 3 times for glass chip. The maximum UV absorbance is also enhanced with ca. 1.6 and 1.7 times, respectively.