• 제목/요약/키워드: moon phase changes

검색결과 123건 처리시간 0.031초

넓은 공극 범위에서도 안정된 소프트 스위칭 동작 가능한 개선된 무선 전력 충전 시스템 (An Improved Wireless Power Charging System Capable of Stable Soft-Switching Operation Even in Wide Air Gaps)

  • 우정원;문유진;김은수
    • 전력전자학회논문지
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    • 제27권3호
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    • pp.180-191
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    • 2022
  • In this paper, a single-stage alternating current (AC)-DC converter is proposed for the automated-guided vehicle wireless charging system. The proposed converter is capable of soft-switching under all input voltage (VAC: 220 Vrms ± 10%), load conditions (0-1 kW), and air gap changes (40-60 mm) by phase control at a fixed switching frequency. In addition, controlling a wide output voltage (Vo: 39~54 VDC) is possible by varying the link voltage and improving the input power factor and the total harmonic distortion factor. Experimental results were verified by making a prototype of a 1-kW wireless power charging system that operates with robustness to changes in air gaps.

회수 Cyclotol의 비군사화를 위한 소각공정 (Incineration for Demilitarization of Waste Cyclotol)

  • 이시황;백승원;문일;박정수;김현수;오민
    • 한국군사과학기술학회지
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    • 제19권4호
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    • pp.545-550
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    • 2016
  • Demilitarization involves the disposal and recovery of obsolete explosives or ammunition. Cyclotol has been used as a military explosive along with RDX and HMX. A limited number of processes exist for safe disposal due to their sensitivity to thermal shock. Rotary kilns are widely used for thermal decomposition in many countries due to cost effectiveness and simplicity compared with supercritical oxidation. Phase change as well as condensed phase reactions(CPRs) and gas phase reactions(GPRs) with rates described by the Arrhenius equation of cyclotol has been considered in this work. Changes in gas fraction, reaction rate and mass of explosives were predicted at 490, 505 and 575 K. A maximum temperature of 2062 K has been predicted within the reactor at an initial temperature of 575 K due to GPRs. From this research, Thermal decomposition in the rotary kiln is plausible for demilitarization.

월경통 환자의 월경주기에 따른 심박변이도(Heart Rate Variability) 차이에 대한 고찰 (Effects of Menstrual Cycle on Heart Rate Variability in Dysmenorrhea Patients)

  • 김은숙;문승준;조한백;임은미;고성규;조정훈
    • 대한한방부인과학회지
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    • 제23권2호
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    • pp.124-130
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    • 2010
  • Purpose: The aim of the study was to investigate menstrual cycle phase differences in Heart Rate Variability(HRV) in dysmenorrhea patients. Methods: 16 dysmenorrhea patients were enrolled. The severity of dysmenorrhea was measured by Visual Analog Scale(VAS). Recordings for HRV analysis were obtained during the two phases of the menstrual cycle (follicular phase 4~10 days and luteal phase 18~23 days from the start of bleeding). Results: No measure of HRV was significantly different between two menstrual cycle phases. Conclusion: We concluded that menstrual cycle was not significantly associated with changes in autonomic nervous system as measured by HRV in dysmenorrhea patients.

주기 회전하는 원형주상체 주위 유동장의 수치 시뮬레이션 (Numerical simulation on laminar flow past an oscillating circular cylinder)

  • 문진국;박종천;전호환
    • 한국해양공학회:학술대회논문집
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    • 한국해양공학회 2004년도 학술대회지
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    • pp.210-211
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    • 2004
  • The effect of oscillating on the unsteady laminar flow past a circular cylinder is numerically investigated in the present study. Our study is to analyze the vortex formation behind a circular cylinder for different rotary oscillation conditions. And then we are study to portray the unsteady dynamics of wake flows. We decide lock-on region by observing the phase switching phenomena We classify the vortex formation patterns in the primary lock-on region The present study is to identify the quasi-periodic state around lock-on region. At the boundary between lock-on and non-lock-on the shedding frequency is bifurcated. After the bifurcation, one frequency follow the forcing frequency ($S_f$) and the other returns to the natural shedding frequency ($St_0$). In the quasi-periodic state, the variation of magnitudes and relevant phase changes of $C_L$ with forcing phase are examined.

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A Study on the Satellite Launch Vehicle Separation Detection Interface to Improve the Reliability of the Launch and Early Operation Phase

  • Lee, Nayoung;Kwon, Dong-young;Jeon, Hyeon-Jin;Jeon, Moon-Jin;Cheon, Yee-Jin
    • 항공우주시스템공학회지
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    • 제15권4호
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    • pp.57-63
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    • 2021
  • The launch vehicle (LV) separation detection interface of the satellite, which is designed to initiate the launch and early operation phase (LEOP) for S-band data transmission and the solar array deployment after the LV separation, is one of the hazard items at the launch site. Therefore, this interface should satisfy the single-fault tolerance requirement for the range safety. In this paper, we discuss the LV separation detection interfaces for two different satellite launch configurations and propose a method to guarantee for the satellite to start the LEOP even under the emergency case such as a partial separation from the LV. Furthermore, the proposed method meets the range safety requirement of the launch site. As this method only changes the external harness configuration of the satellite, it increases the reliability of the satellite early operation without any modification of the existing internal logics to detect the separation event.

압력용기용 Ni-Mo-Cr계 고강도 저합금강의 합금원소 함량 변화에 따른 미세조직학적 특성변화의 열역학 계산 및 평가 (Thermodynamic Calculation and Observation of Microstructural Change in Ni-Mo-Cr High Strength Low Alloy RPV Steels with Alloying Elements)

  • 박상규;김민철;이봉상;위당문
    • 대한금속재료학회지
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    • 제46권12호
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    • pp.771-779
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    • 2008
  • An effective way of increasing the strength and fracture toughness of reactor pressure vessel steels is to change the material specification from that of Mn-Mo-Ni low alloy steel(SA508 Gr.3) to Ni-Mo-Cr low alloy steel(SA508 Gr.4N). In this study, we evaluate the effects of alloying elements on the microstructural characteristics of Ni-Mo-Cr low alloy steel. The changes in the stable phase of the SA508 Gr.4N low alloy steel with alloying elements were evaluated by means of a thermodynamic calculation conducted with the software ThermoCalc. The changes were then compared with the observed microstructural results. The calculation of Ni-Mo-Cr low alloy steels confirms that the ferrite formation temperature decreases as the Ni content increases because of the austenite stabilization effect. Consequently, in the microscopic observation, the lath martensitic structure becomes finer as the Ni content increases. However, Ni does not affect the carbide phases such as $M_{23}C_6 $ and $M_7C_3$. When the Cr content decreases, the carbide phases become unstable and carbide coarsening can be observed. With an increase in the Mo content, the $M_2C$ phase becomes stable instead of the $M_7C_3$ phase. This behavior is also observed in TEM. From the calculation results and the observation results of the microstructure, the thermodynamic calculation can be used to predict the precipitation behavior.

A High-Efficiency High-Power Step-Up Converter with Low Ripple Content

  • Kang Jeong-il;Roh Chung-Wook;Moon Gun-Woo;Youn Myung-Joong
    • 전력전자학회:학술대회논문집
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    • 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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    • pp.708-712
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    • 2001
  • A new phase-shifted parallel-input/series-output (PI SO) dual inductor-fed push-pull converter for high-power step­up applications is proposed. This converter is operated at a constant duty cycle and employs an auxiliary circuit to control the output voltage with a phase-shift between the two modules. It features a voltage conversion characteristic which is linear to changes in the control input, and high step-up ratio with a greatly reduced switch turn-off stress resulting in a significant increase in the converter efficiency. It also shows a low ripple content and low root-mean-square (RMS) current in the output capacitor. The operational principle is analyzed and a comparative analysis with the conventional pulse-width-modulated (PWM) PISO dual inductor-fed push-pull converter is presented. A 50kHz, 800W, 350Vdc prototype with an input of 20-32Vdc has also been constructed to validate the proposed converter. The proposed converter compares favorably with the conventional counterpart and is considered well suited to high-power step-up applications.

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Determination of volatile compounds by headspace-solid phase microextraction - gas chromatography / mass spectrometry: Quality evaluation of Fuji apple

  • Lee, Yun-Yeol;Jeong, Moon-Cheol;Jang, Hae Won
    • 분석과학
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    • 제30권2호
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    • pp.68-74
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    • 2017
  • The volatile components in 'Fuji' apple were effectively determined by a headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). A total of 48 volatile components were identified and tentatively characterized based on National Institute of Standards and Technology (NIST) MS spectra library and the Kovats GC retention index I (RI). The harvested Fuji apples were divided into two groups: 1-methylcyclopropene (1-MCP) treated and non-treated (control) samples for finding important indicators between two groups. The major volatile components of both apples were 2-methylbutyl acetate, hexyl acetate, butyl 2-methylbutanoate, hexyl butanoate, hexyl 2-methylbutanoate, hexyl hexanoate and farnesene. No significant differences of these major compounds between 1-MCP treated and non-treated apples were observed during 1 month storage. Interestingly, the amount of off-flavors, including 1-butanol and butyl butanoate, in 1-MCP treated apples decreased over 5 months, and then increased after 7 months. However, non-treated apples did not show significant changes for off-flavors during 7 month storage (p<0.05). The non-treated apples also contained the higher levels of two off-flavors than 1-MCP treated apples. These two compounds, 1-butanol and butyl butanoate, can be used as quality indicators for the quality evaluation of Fuji apple.

돼지 난소내 과립세포의 염색질이상응축과 여포액내 스테로이드호르몬의 농도 변화와의 상관관계 (The Relationship Between the Pyknosis of Granulosa Cell and the Change of Steroid Concentration in Porcine Ovarian Follicles)

  • 이창주;윤용달;김종흡;김문규
    • Clinical and Experimental Reproductive Medicine
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    • 제16권1호
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    • pp.35-40
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    • 1989
  • In order to study the follicular atretic mechanism in mammalian ovary, the relationship between pyknotic index (PI) of granulosa cells and the steroid concentrations in the follicular fluid of atretic follicle was investigated. Follicles were isolated from porcine ovary according to their sizes and the reproductive phases. Steroid concentrations were quantified by high-performance liquid chromatography. As PI increased, the concentration of progesterone was significantly increased(p<0.05), whereas testosterone and estradiol showed no significant changes in their concentration. As follicular size was increased, PI of follicular GC in the luteal phase was increased significantly(p<0.05) and the molar ratio of progesterone to testosterone was increased in the follicles of follicular phase. It can be concluded that progesterone accumulated in the follicular fluid as atresia of the follicles was progressed, and that PI of granulosa cells could be used as one of convenient and pratical criteria for the identification of follicular atresia.

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TIME/FREQUENCY ANALYSIS OF TERRESTRIAL IMPACT CRATER RECORDS

  • Chang Heon-Young
    • Journal of Astronomy and Space Sciences
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    • 제23권3호
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    • pp.199-208
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    • 2006
  • The terrestrial impact cratering record recently has been examined in the time domain by Chang & Moon (2005). It was found that the ${\sim}26$ Myr periodicity in the impact cratering rate exists over the last ${\sim}250$ Myrs. Such a periodicity can be found regardless of the lower limit of the diameter up to D ${\sim}35km$. It immediately called pros and cons. The aim of this paper is two-fold: (1) to test if reported periodicities can be obtained with an independent method, (2) to see, as attempted earlier, if the phase is modulated. To achieve these goals we employ the time/frequency analysis and for the first time apply this method to the terrestrial impact cratering records. We have confirmed that without exceptions noticeable peaks appear around ${\sim}25$ Myr, corresponding to a frequency of ${\sim}0.04(Myr)^{-1}$. We also find periodicities in the data base including small impact craters, which are longer. Though the time/frequency analysis allows us to observe directly phase variations, we cannot find any indications of such changes. Instead, modes display slow variations of power in time. The time/frequency analysis shows a nonstationary behavior of the modes. The power can grow from just above the noise level and then decrease back to its initial level in a time of order of 10 Myrs.