• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.807-808
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• 2010

To insert payload to the orbit over the 200km-altitude using launch vehicle which has 300sec the Isp, multi staging technique for launch is necessary. The range between the sea-level to the transfer orbit about 200~250km is for operation of 1st and 2nd rocket engines and the higher altitude is for propulsion system of the acceleration block and satellite. The upper stage rocket engine should have the high technology for entering the payload into the orbit precisely more than the performance for high thrust level. With this investigation of the upper stage rocket engines which have been used, we want to understand their development trend and prospect which is going to be references for the development of ours.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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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.

• Journal of Aerospace System Engineering
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• v.11 no.6
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• pp.76-83
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• 2017

The MIL-STD-1553 standard has been used for over 40 years as a data bus technology for high-reliability mobile systems. However, 1 Mbps transmission speed is absolutely insufficient to implement sensor data convergence, which is an essential requirement of modern aerospace systems. In this paper, we analyze the hierarchical structure of the MIL-STD-1553B version specification and describe several methods to increase the transmission speed without losing the advantages of the existing MIL-STD-1553 bus. In addition, we analyzed the R & D cases of the high-speed MIL-STD-1553 technology, which have been conducted in leading aerospace countries.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.1
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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.

• Biomedical Science Letters
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• v.27 no.3
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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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• v.13 no.3
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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.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.6
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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.

• Journal of the Korea Safety Management & Science
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• v.23 no.4
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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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• v.46 no.2
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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.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1990.10a
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• pp.294-298
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• 1990