• JSTS:Journal of Semiconductor Technology and Science
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• 제17권4호
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• pp.492-498
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• 2017

In this paper, we integrate a divide-by-3 injection-locked frequency divider (ILFD) in CMOS technology with a $0.18-{\mu}m$ BiCMOS process. We propose a self-injection technique that utilizes harmonic conversion to improve the locking range, phase-noise, and input sensitivity simultaneously. The proposed self-injection technique consists of an odd-to-even harmonic converter and a feedback amplifier. This technique offers the advantage of increasing the injection efficiency at even harmonics and thus realizes the low-power implementation of an odd-order division ILFD. The measurement results using the proposed self-injection technique show that the locking range is increased by 47.8% and the phase noise is reduced by 14.7 dBc/Hz at 1-MHz offset frequency with the injection power of -12 dBm. The designed divide-by-3 ILFD occupies $0.048mm^2$ with a power consumption of 18.2-mW from a 1.8-V power supply.

• 한국분무공학회지
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• 제11권3호
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• pp.161-167
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• 2006

As the exhaustion of petroleum resources and air pollution problems are getting serious recently, there are growing interests in premixed diesel engines which have the potential of achieving a more homogeneous mixture near TDC compared to conventional diesel engines. Early studies have shown that the fuel injection frequency and spray angle affected the mixture formation and combustion in a HCCI(Homogeneous Charge Compression Ignition) engine. Therefore, the purpose of this study is to investigate the relationship between combustion and mixture formations by injection timing and frequency using a narrow angle injector, NADI (Narrow Angle Direct Injection). In this study, we found that the fuel injection timing and injection frequency affect the mixture formations and then affect combustion in the HCCI engine.

• 한국전자통신학회논문지
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• 제14권6호
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• pp.1037-1044
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• 2019

본 논문에서는 다중 주파수 발생기의 설계를 위한 단일 인젝션 락킹 현상에 대한 연구를 진행한다. 다중 주파수 발생기 설계를 위하여 인젝션 락킹 현상에 대한 기본적인 이론을 서술하고 이를 토대로 단일 인젝션 락킹 실험에 대하여 서술한다. 실험은 인젝션 신호에 비해 불안정하게 진동하는 발진기에 일정하게 진동하는 안정된 신호인 인젝션 신호를 인가하는 방식으로 진행하였다. 인젝션 신호는 홀렌드 전류원을 사용하고 콜피츠 발진기를 사용하여 회로를 구성하였다. 실험결과 각각의 인젝션 신호(840kHz, 500kHz)를 주입하였을 때 각각의 발진기가 안정하게 진동하는 것을 확인하였다. 위의 단일 인젝션 락킹 실험결과를 통하여 다중 주파수 발생기 설계에 인젝션 락킹 현상을 응용 할 수 있음을 확인하였다.

• The Korean Journal of Physiology and Pharmacology
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• 제20권6호
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• pp.657-667
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• 2016

Critical limb ischemia (CLI) is one of the most severe forms of peripheral artery diseases, but current treatment strategies do not guarantee complete recovery of vascular blood flow or reduce the risk of mortality. Recently, human bone marrow derived mesenchymal stem cells (MSCs) have been reported to have a paracrine influence on angiogenesis in several ischemic diseases. However, little evidence is available regarding optimal cell doses and injection frequencies. Thus, the authors undertook this study to investigate the effects of cell dose and injection frequency on cell survival and paracrine effects. MSCs were injected at $10^6$ or $10^5$ per injection (high and low doses) either once (single injection) or once in two consecutive weeks (double injection) into ischemic legs. Mice were sacrificed 4 weeks after first injection. Angiogenic effects were confirmed in vitro and in vivo, and M2 macrophage infiltration into ischemic tissues and rates of limb salvage were documented. MSCs were found to induce angiogenesis through a paracrine effect in vitro, and were found to survive in ischemic muscle for up to 4 weeks dependent on cell dose and injection frequency. In addition, double high dose and low dose of MSC injections increased vessel formation, and decreased fibrosis volumes and apoptotic cell numbers, whereas a single high dose did not. Our results showed MSCs protect against ischemic injury in a paracrine manner, and suggest that increasing injection frequency is more important than MSC dosage for the treatment CLI.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.437-440
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• 2009

High-frequency induction is an efficient way to heat mold surface by electromagnetic induction in a non-contact manner. Thanks to its capability of rapid heating and cooling of mold surface, it has been recently applied to the injection molding. The present study applies the high-frequency induction heating for elimination of weldlines in an injection-molded plastic part. To eliminate weldlines, the mold temperature of the corresponding weld locations should be maintained higher than the glass transition temperature of the resin material. Through experiments, the maximum temperature of $143^{\circ}C$ is obtained on the mold surface around the elliptic coil, while the temperature of the mold plate is lower than $60^{\circ}C$. An injection molding experiment is then performed with the aid of induction heating, and the effect of induction heating conditions on the surface appearance of the weldline is investigated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.144-146
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• 2007

High frequency voltage signal injection have been widely used but they have some problems like over current protection. High frequency current signal injection and feedback control are more stable than voltage signal injection. In this paper, high frequency current controller for self-sensing and parameter estimation of induction motors is presented.

• 전력전자학회논문지
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• 제23권2호
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• pp.139-146
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• 2018

This work puts forward a theoretical analysis on position estimation performance of interior permanent magnet synchronous motor (IPMSM) according to the injection frequency in carrier-based sensorless operation. The effects of spatial harmonics on inductance and voltage distortion due to the nonideal characteristics of IPMSM and inverter are examined as factors influencing the position estimation performance. Furthermore, the position estimation performance is analyzed by calculating the current at the switching instant in several operating conditions. In summary, the half switching frequency injection is more robust to the nonideal characteristics of IPMSM, especially with light load condition. The validity of the analysis is verified by the simulation and experimental results.

• 전기학회논문지
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• 제62권12호
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• pp.1700-1705
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• 2013

A second harmonic millimeter wave oscillator utilizing sub-harmonic injection-synchronization is presented. A 8.7GHz oscillator with MES-FET is designed, and is driven as a harmonic output oscillator at 17.4GHz by means of sub-harmonic injection-synchronization. The oscillator operates as a multiplier as well as a oscillator in this scheme. Adopting this method, a high sable, high frequency millimeter wave source is obtainable even though self-oscillating frequency of an oscillator is relatively low. The range of injection-synchronization is about 26MHz, and is proportional to the input sub-harmonic power. The spectrum analysis of the 2nd harmonic output frequency shows remarkably decreased the phase noise level.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.293-296
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• 2007

호주국립대학의 T3 자유충격파관을 이용하여, 마하수 3.7의 유입 유동에 대해 비분사유동, 공동이전 경사분사유동, 공동내부 평행분사유동, 공동내부 역분사유동에 대해 주파수를 확인하고, 공동 유동 특성을 살펴보았다. 비분사유동은 고조파 형태의 주파수가 나타나지 않았으나 10 kHz 부근에서 비교적 큰 압력 스펙트럼이 나타났다. 공동 이전 경사분사는 공동의 앞전에서 박리되는 전단층의 두께를 증가시켜 공동 뒷전에서 발생하는 유동의 진동 현상을 현저히 감소시켰다. 공동 내부 평행분사는 공동의 뒷전에 분사 유동이 직접 부딪히게 되고, 공동의 진동 현상을 오히려 증가시켰다.

• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1515-1527
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• 2018

This paper presents a sensorless speed control of IPMSM (Interior Permanent Magnet Synchronous Motor) using the high-frequency (HF) square wave injection method. In the proposed HF pulsating square wave injection method, injection voltage is applied into the estimated d-axis of rotor and high-frequency induced q-axis current is considered to estimate the rotor position. Conventional square wave injection methods may need complex demodulation process to find rotor position, while in the proposed method, an easy demodulation process based on the rising-falling edge of the injected voltage and carrier induced q-axis current is implemented, which needs less processing time and improves control bandwidth. Unlike some saliency-based sensorless methods, the proposed method uses maximum torque per ampere (MTPA) strategy, instead of zero d-axis command current strategy, to improve control performance. Furthermore, this paper directly uses resultant d-axis current to detect the magnet polarity and eliminates the need to add an extra pulse injection for magnet polarity detection. As experimental results show, the proposed method can quickly find initial rotor position and MTPA strategy helps to improve the control performance. The effectiveness of the proposed method and all theoretical concepts are verified by mathematical equations, simulation, and experimental tests.