• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.807-808
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• 2010

비추력이 300초 정도 되는 발사체로 고도 200km 이상의 궤도에 페이로드를 진입시키기 위해서는 2단 이상의 단 구성이 필요하다. 전이궤도인 고도 200~250km 까지는 1단과 2단 로켓 엔진의 작동 영역이고 그 이상은 최상단 가속블록과 인공위성의 추진기관이 작동하는 영역이다. 최상단의 엔진은 페이로드를 목표한 궤도에 정확하게 투입시키기 위해 높은 추력은 아니지만 정밀한 제어를 필요로 한다. 현재 운용 중인 상단 엔진에 대한 조사와 정리를 통하여 개발 동향을 파악하고 향후 우리의 고성능 상단 엔진을 개발하는데 참고하고자 한다.

• 천문학회보
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• 제37권2호
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• pp.228.1-228.1
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• 2012

Digital waveform generation technology for SAR payload can be divided into DDS(Direct Digital Synthesizer) method and Memory Mapped(M/M) method. DDS is the single chip which consists of the Sine Table, NCO(Numerically Controlled Oscillator), DAC, and so on. DDS method is a very simple method because the circuit configuration is not complex but has a disadvantage that can not control phase and amplitude easily by using NCO. M/M method has the complexity of the circuit configuration because it requires the memories which stores the waveforms, the control circuits, and DAC. And this method should apply the high interface technology for being compatible with the wide bandwidth of the digital signal and has the difficulty for PCB design because the number of the signal lines should be increased according to the number of the data bits for DAC. Although it has several disadvantages, this method has the capability of pre-distortion function which can compensate the phase and amplitude characteristics of the system and also has an excellent advantage to make any arbitrary waveform, so this method is considered as an important technology with DDS method. This research describes the technological trends of the waveform generator for the SAR payload and analyzes the characteristics of the technology.

• 항공우주시스템공학회지
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• 제11권6호
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• pp.76-83
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• 2017

MIL-STD-1553 버스 표준은 40여 년 동안 고 신뢰성 이동체 시스템의 데이터버스 기술로 많이 사용되어 왔다. 하지만 현대 최신의 항공우주시스템의 필수 요구사항인 센서 데이터 융합을 구현하기 위해서는 1 Mbps 전송속도는 절대적으로 부족하다. 본 논문에서는 MIL-STD-1553B 버전 규격을 중심으로 계층구조로 분석하여 기존 MIL-STD-1553 버스의 장점을 잃지 않으며 전송속도를 높이기 위한 방안을 기술하였다. 또한 항공우주 선도국가에서 수행된 고속 MIL-STD-1553 버스 기술에 대한 연구개발 사례를 분석하였으며 이를 구현하기 위해 사용된 핵심기술을 분석하였다.

• 한국소음진동공학회논문집
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• 제24권1호
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• pp.5-13
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• 2014

Number of components and payload systems installed in satellites were found to be exposed to various disturbance sources such as the reaction wheel assembly, the control moment gyro, coolers, and others. A micro-level of vibration can introduce jitter problems into an optical payload system and cause significant degradation of the image quality. Moreover, the prediction of on-orbit vibration effects on the performance of optical payloads during the development process is always important. However, analyzing interactions between subsystems and predicting the vibration level of the payloads is extremely difficult. Therefore, this paper describes the analytical and experimental approach to microvibration effects on satellite optical payload performance with integrated jitter analysis frame-work, microvibration emulator and satellite structure testbed.

• 대한의생명과학회지
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• 제27권3호
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• pp.121-133
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• 2021

Antibody-drug conjugates (ADCs) are drawing much interest due to its great potential to be one of the important options in cancer treatments. ADCs are acting like a magic bullet which delivers cytotoxic drugs specifically to cancerous cells throughout the body, thus attacks these cells, while not harming healthy cells. ADCs are complex molecules that are composed of an antibody having targeting capability and linked-payload or cytotoxic drug killing cancerous cells. The key factors of the success in the development of ADC are selection of appropriate antibody, cytotoxic payload and linker for conjugation. Recently there was considerable progress in ADCs development, and a large number of ADCs gained US FDA approval. About 80 new ADCs are under active clinical studies. In this review we present a brief introduction of the US-FDA approved ADCs and global situation in the clinical studies of ADC pipelines. We address an overview on each component of an ADC design such as target antigens, payloads, linkers, conjugation methods, drug antibody ratio. In addition, we discuss on the trend of ADC market where global big pharmas and domestic biopharmaceutical companies are competing to develop safer and more effective ADCs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권3호
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• pp.1284-1297
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• 2019

The network environment is presently becoming very increased. Accordingly, the study of traffic classification for network management is becoming difficult. Automatic signature extraction system is a hot topic in the field of traffic classification research. However, existing automatic payload signature generation systems suffer problems such as semi-automatic system, generating of disposable signatures, generating of false-positive signatures and signatures are not kept up to date. Therefore, we provide a fully automatic signature update system that automatically performs all the processes, such as traffic collection, signature generation, signature management and signature verification. The step of traffic collection automatically collects ground-truth traffic through the traffic measurement agent (TMA) and traffic management server (TMS). The step of signature management removes unnecessary signatures. The step of signature generation generates new signatures. Finally, the step of signature verification removes the false-positive signatures. The proposed system can solve the problems of existing systems. The result of this system to a campus network showed that, in the case of four applications, high recall values and low false-positive rates can be maintained.

• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.542-550
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• 2021

As the application of multirotor grows, the demands for multirotor that can fly longer and load more are increasing. Hydrogen has a high energy density, so it can satisfy these demands when used in multirotor. In order to design hydrogen fueled multirotor that satisfies the desired flight time and payload, it is important to calculate the specifications of a fuel cell, battery, and hydrogen storage system. This paper contains detailed information on various energy systems used in multirotor and fuel cell powered multirotor research trends. This study proposed a sizing calculation method that meets the target flight time and payload using thrust and power equations. It has been explained how the two equations derive the particular specifications. The specifications of the multirotor were derived by assuming a payload of 50 kg and a flight time of 1 hour. In addition, the effects of the values of the fuel cell, hydrogen storage system, and motor propeller were analyzed.

• 대한안전경영과학회지
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• 제23권4호
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• pp.93-104
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• 2021

In this paper, we propose a method for diagnosing overload and working load of collaborative robots through performance analysis of machine learning algorithms. To this end, an experiment was conducted to perform pick & place operation while changing the payload weight of a cooperative robot with a payload capacity of 10 kg. In this experiment, motor torque, position, and speed data generated from the robot controller were collected, and as a result of t-test and f-test, different characteristics were found for each weight based on a payload of 10 kg. In addition, to predict overload and working load from the collected data, machine learning algorithms such as Neural Network, Decision Tree, Random Forest, and Gradient Boosting models were used for experiments. As a result of the experiment, the neural network with more than 99.6% of explanatory power showed the best performance in prediction and classification. The practical contribution of the proposed study is that it suggests a method to collect data required for analysis from the robot without attaching additional sensors to the collaborative robot and the usefulness of a machine learning algorithm for diagnosing robot overload and working load.

• ETRI Journal
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• 제46권2호
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• pp.323-332
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• 2024

Receiver and transmitter monolithic microwave integrated circuit (MMIC) multifunction chips (MFCs) for active phased-array antennas for Ka-band satellite communication (SATCOM) terminals have been designed and fabricated using a 0.15-㎛ GaAs pseudomorphic high-electron mobility transistor (pHEMT) process. The MFCs consist of four-channel radio frequency (RF) paths and a 4:1 combiner. Each channel provides several functions such as signal amplification, 6-bit phase shifting, and 5-bit attenuation with a 44-bit serial-to-parallel converter (SPC). RF pads are implemented on the bottom side of the chip to remove the parasitic inductance induced by wire bonding. The area of the fabricated chips is 5.2 mm × 4.2 mm. The receiver chip exhibits a gain of 18 dB and a noise figure of 2.0 dB over a frequency range from 17 GHz to 21 GHz with a low direct current (DC) power of 0.36 W. The transmitter chip provides a gain of 20 dB and a 1-dB gain compression point (P1dB) of 18.4 dBm over a frequency range from 28 GHz to 31 GHz with a low DC power of 0.85 W. The P1dB can be increased to 20.6 dBm at a higher bias of +4.5 V.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권6호
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• pp.1619-1637
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• 2024

In today's highly digitized landscape, securing digital communication is paramount due to threats like hacking, unauthorized data access, and network policy violations. The response to these challenges has been the development of cryptography applications, though many existing techniques face issues of complexity, efficiency, and limitations. Notably, sophisticated intruders can easily discern encrypted data during transmission, casting doubt on overall security. In contrast to encryption, steganography offers the unique advantage of concealing data without easy detection, although it, too, grapples with challenges. The primary hurdles in image steganography revolve around the quality and payload capacity of the cover image, which are persistently compromised. This article introduces a pioneering approach that integrates image steganography and encryption, presenting the BitPatternStego method. This novel technique addresses prevalent issues in image steganography, such as stego-image quality and payload, by concealing secret data within image pixels with identical bit patterns as their characters. Consequently, concerns regarding the quality and payload capacity of steganographic images become obsolete. Moreover, the BitPatternStego method boasts the capability to generate millions of keys for the same secret message, offering a robust and versatile solution to the evolving landscape of digital security challenges.