• Journal of the Optical Society of Korea
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• 제18권1호
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• pp.1-8
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• 2014

Spin reticle infrared seekers have good linearity, and the pulse-modulated reticle seekers have good digital characteristics for anti-jamming processing. A basic design for a spin pulse-modulated reticle is introduced. This design uses the rotating design of the optical system in the spin infrared seekers and an improved design of the reticle in the pulse-modulated seekers. The reticle contains a unique well-designed slit to produce one pulse for each target in the spinning period. The target data will be carried by the unique pulse parameters. A simulation tool is implemented using the MATLAB packages for analyzing and evaluating the new design.

• Investigative Magnetic Resonance Imaging
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• 제20권1호
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• pp.27-35
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• 2016

Purpose: Among RF pulses, a sinc pulse is typically used for slice selection due to its frequency-selective feature. When a sinc pulse is implemented in practice, it needs to be apodized to avoid truncation artifacts at the expense of broadening the transition region of the excited-band profile. Here a sinc pulse tailored by a new apodization function is proposed that produces a sharper transition region with well suppression of truncation artifacts in comparison with conventional tailored sinc pulses. A multiband pulse designed using this newly apodized sinc pulse is also suggested inheriting the better performance of the newly apodized sinc pulse. Materials and Methods: A new apodization function is introduced to taper a sinc pulse, playing a role to slightly shift the first zero-crossing of a tailored sinc pulse from the peak of the main lobe and thereby producing a narrower bandwidth as well as a sharper pass-band in the excitation profile. The newly apodized sinc pulse was also utilized to design a multiband pulse which inherits the performance of its constituent. Performances of the proposed sinc pulse and the multiband pulse generated with it were demonstrated by Bloch simulation and phantom imaging. Results: In both simulations and experiments, the newly apodized sinc pulse yielded a narrower bandwidth and a sharper transition of the pass-band profile with a desirable degree of side-lobe suppression than the commonly used Hanning-windowed sinc pulse. The multiband pulse designed using the newly apodized sinc pulse also showed the better performance in multi-slice excitation than the one designed with the Hanning-windowed sinc pulse. Conclusion: The new tailored sinc pulse proposed here provides a better performance in slice (or slab) selection than conventional tailored sinc pulses. Thanks to the availability of analytical expression, it can also be utilized for multiband pulse design with great flexibility and readiness in implementation, transferring its better performance.

• Journal of Positioning, Navigation, and Timing
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• 제10권2호
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• pp.113-120
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• 2021

The Distance Measuring Equipment (DME) is a ground-based aircraft navigation system and is considered as an infrastructure that ensures resilient aircraft navigation capability during the event of a Global Navigation Satellite System (GNSS) outage. The main problem of DME as a GNSS back up is a poor positioning accuracy that often reaches over 100 m. In this paper, a novel approach of applying deep reinforcement learning to a DME pulse design is introduced to improve the DME distance measuring accuracy. This method is designed to develop multipath-resistant DME pulses that comply with current DME specifications. In the research, a Markov Decision Process (MDP) for DME pulse design is set using pulse shape requirements and a timing error. Based on the designed MDP, we created an Environment called PulseEnv, which allows the agent representing a DME pulse shape to explore continuous space using the Soft Actor Critical (SAC) reinforcement learning algorithm.

• 한국자동차공학회논문집
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• 제9권2호
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• pp.116-129
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• 2001

Traditional occupant analysis has been performed with a pre-determined crash puse which is produced from a test and the involved components are designed based on the analysis resuls. The method has limitations in that the design does not have much freedom. Howrver, if a good crash pulse is proposed, the body structure can be modified to generate the crash pulse. Therefore, it is assumed that the crash pulse can be changed to imptove the occupant crash performance. A preferable crash pulse is determined to minimize the occupant injuty. A constraint is established to keep the phenomena of physics valid. The response surface method(RSM) is adopted for the optimization process. An RSM in a commercial code is utilzed by interfacing with an in-house occupant analysis program called SAFE(Safety Analysis For occupant crash Enviroment). Design of involved components called is carried out through optimization with the RSM. The advantages of the RSM are investigated as opposed to other methods, and the tesults are compared. Also, the design under the new crach pulse is compared with that trom the pre-detetmined pulse.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1297-1300
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• 2008

A conventional linear accelerator system requires a flat-topped pulse with less than ${\pm}$ 0.5% ripple to meet the beam energy spread requirements and to improve pulse efficiency of RF systems. A pulse transformer is one of main determinants on the output pulse voltage shape. The pulse transformer was investigated and analyzed with the pulse response characteristics using a simplified equivalent circuit model. The damping factor ${\sigma}$ must be >0.86 to limit the overshoot to less than 0.5% during the flat-top phase. The low leakage inductance and distributed capacitance are often limiting factors to obtain a fast rise time. These parameters are largely controlled by the physical geometry and winding configuration of the transformer. A rise time can be improved by reducing the number of turns, but it produces larger pulse droop and requires a larger core size. By tradeoffs among these parameters, the high-voltage pulse transformer with a pulse width of 10 ${\mu}s$, a rise time of 0.84 ${\mu}s$, and a pulse droop of 2.9% has been designed and fabricated to drive a klystron which has an output voltage of 284 kV, 30-MW peak and 60-kW average RF output power. This paper describes design optimization of a high-voltage pulse transformer for high-power pulsed applications. The experimental results were analyzed and compared with the design. The design and optimal tuning parameter of the system was identified using the model simulation.

• 한국항공우주학회지
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• 제45권10호
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• pp.872-880
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• 2017

일반적으로 추력기는 on/off 제어 방식을 이용한다. Bang-Bang Control, PWM(Pulse Width Modulator), PWPF(Pulse Width Pulse Frequency) 등이 그 방법으로 많이 이용되고 있다. PWPF를 설계할 때 파라미터($K_m$, ${\tau}$, $U_{on}$, $U_{off}$, $U_m$)를 잘못 선정하면 위상 지연, 연료 낭비, 수명 감소 등이 발생한다. 그러므로 파라미터가 시스템 성능에 미치는 영향을 분석하고 적절한 파라미터를 선정하여야 한다. 본 논문은 정적 해석을 수행하여 PWPF 파라미터 설계방안을 제시하였으며, 동적 분석 및 시뮬레이션을 수행하여 설계변수에 미치는 상호 영향을 분석하였다.

• International Journal of Aeronautical and Space Sciences
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• 제15권2호
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• pp.205-211
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• 2014

The design parameters to affect the cooling capacity of a cryocooler were examined with the application of numerical modeling to optimize an inertance pulse tube cryocooler. This modeling includes the regenerator, pulse tube, inertance tube, gas reservoir, and heat exchangers. One-dimensional modeling on strings of acoustic and thermoacoustic elements was applied to compare the design parameters. The diameter and length of the pulse tube can significantly affect the cooling capacity and efficiency. The aftercooler was optimized by maintaining a certain size. The efficiency also improved as the length of inertance tube and volume of gas reservoir are increased. It was confirmed that effective design parameters are critical to the performance of an inertance pulse tube cryocooler considering the comparison of the dimensions of each part to optimize its cooling power and efficiency.

• Journal of Power Electronics
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• 제6권3호
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• pp.214-225
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• 2006

The design and performance analysis of a reduced rating autotransformer based thirty-pulse AC-DC converter is carried out for feeding a vector controlled induction motor drive (VCIMD). The configuration of the proposed autotransformer consists of only two single phase transformers, with their windings connected in a T-shape, resulting in simplicity in design, manufacturing and in a reduction in magnetics rating. The design procedure of the autotransformer along with the newly designed interphase transformer is presented. The proposed configuration has flexibility in varying the transformer output voltage ratios as required. The design of the autotransformer can be modified for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. The proposed thirty-pulse AC-DC converter is capable of suppressing less than $29^{th}$ harmonics in the supply current. The power factor is also improved to near unity in the wide operating range of the drive. A comparison of different power quality indices at AC mains and DC bus is demonstrated in a conventional 6-pulse AC-DC converter and the proposed AC-DC converter feeding a VCIMD. A laboratory prototype of the proposed autotransformer based 30-pulse AC-DC converter was developed with test results validating the proposed design and system.

• 한국통신학회논문지
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• 제19권1호
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• pp.1-9
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• 1994

In general, when IIR digital filter are designed from analog filters, the bilinera transformation and the impluse invariant tramsformation are commonly used. It is known, however, that high frequency response of digital filters designed by these transformations can not be well approximated to the sampled analog signals. In this paper, the symbol pulse invariant transformation is analyzed theoretically so that the symbol pulse invariant transformation which was originally application to a rectangular pulse is newly applied to double rate pulse signals and generic shape pulse signals. Also, the relation of spectra between a transfer function of digital filter and one of analog filter is considered. Further, we apply to design the digital high pass filters using the symbol pulse invariant transformation method.

• Journal of Communications and Networks
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• 제5권4호
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• pp.328-343
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• 2003

Orthogonal pulse-shape modulation using Hermite pulses for ultra-wideband communications is reviewed. Closedform expressions of cross-correlations among Hermite pulses and their corresponding transmit and receive waveforms are provided. These show that the pulses lose orthogonality at the receiver in the presence of differentiating antennas. Using these expressions, an algebraic model is established based on the projections of distorted receive waveforms onto the orthonormal basis given by the set of normalized orthogonal Hermite pulses. Using this new matrix model, a number of pulse-shape modulation schemes are analyzed and a novel orthogonal design is proposed. In the proposed orthogonal design, transmit waveforms are constructed as combinations of elementary Hermites with weighting coefficients derived by employing the Gram-Schmidt (QR) factorization of the differentiating distortion model’s matrix. The design ensures orthogonality of the vectors at the output of the receiver bank of correlators, without requiring compensation for the distortion introduced by the antennas. In addition, a new set of elementary Hermite Pulses is proposed which further enhances the performance of the new design while enabling a simplified hardware implementation.