• Title/Summary/Keyword: Population inversion

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INTENSITY VARIATION OF THE SiO MASER LINE OF LONG PERIOD VARIABLES : MASER PUMPING MECHANISM (장주기 변광성의 SiO 메이저 선 세기 변화 연구 : 메이저 펌핑 기작)

  • Kim, Eun-Hyeok;Lee, Sang-Gak
    • Publications of The Korean Astronomical Society
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    • v.8 no.1
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    • pp.83-104
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    • 1993
  • In principle, both radiation and collision are capable of pumping the SiO masers. In order to check which pumping mechanism is more efficient, we calculated the rate equation for our model including the 3 vibrational slates with 7 rotational states of each vibrational slate. Through solving the radiative transfer equation with the Sovolev approximation, we estimated the line profiles from an expanding envelope for several transitions. It is found that the collision works more efficiently than the radiation for the inversion in excited vibrational stales. However in an expanding envelope model we could not get the strong line intensity as observed one because the population inversion is possible only in a small restricted region. For the enough population inversion to get type observed maser intensity. the number density of SiO and hydrogen molecules should be up to about $2{\times}10^5\;cm^{-3}$ and $1{\times}10^9\;cm^{-3}$, respectively, and the inversion should be occured in the region of no Jess than 11014cm.

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Effects of Pressure Ratio on Population Inversion in a DF Chemical Laser with Concurrent Lasing

  • Park, Jun-Sung;Baek, Seung-Wook
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.287-293
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    • 2004
  • A numerical simulation is presented for investigating the effects of pressure ratio of $D_2$ injector to supersonic nozzle on the population inversion in the DF chemical laser cavity, while a lasing concurrently takes place. The laser beam is generated between the mirrors in the cavity and it is important to obtain stronger population inversion and more uniform distribution of the excited molecules in the laser cavity in order to produce high power laser beam with good quality. In this study, these phenomena are investigated by means of analyzing the distributions of the DF excited molecules and the F atom used as an oxidant, while simultaneously estimating the maximum small signal and saturated gains and power in the DF chemical laser cavity. For the numerical solution, an 11-species (including DF molecules in various excited states of energies), 32-step chemistry model is adopted for the chemical reaction of the DF chemical laser system. The results are discussed by comparison with two $D_2$injector pressure cases; 192 torr and 388.64 torr. Major results reveal that in the resonator, stronger population inversions occur in the all transitions except DF(1)-DF(0), when the $D_2$injection pressure is lower. But, the higher $D_2$injection pressure provides a favorable condition for DF(1)-DF(0) transition to generate the higher power laser beam. In other words, as the pressure of $D_2$injector increases, the maximum small signal gain in the $V_{1-0}$ transition, which is in charge of generating most of laser power, becomes higher. Therefore, the total laser beam power becomes higher.r.

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Effects of Base on Population Inversion in the DF Chemical Laser Cavity (불화중수소 화학레이저 공동 내에서의 분포역전에 대한 기저부의 영향)

  • 박준성;백승욱
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2003.05a
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    • pp.83-86
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    • 2003
  • The chemical laser system makes use of a diffusion type chemical reaction, so a fuel is separated from an oxidant by some gap, which is base in this system. In this study, the effects of base on the population inversion that is one of the most important things in the chemical laser system are numerically investigated. The results are discussed by comparison with three cases of base sizes; 0.4mm, 0.8mm and 1.6mm. Major results reveal that the range of population inversion also increases almost linearly in the transitions; DF$^{(2)}$ -DF$^{(1)}$ and DF$^{(3)}$ -DF$^{(2)}$ as the length of base becomes longer.

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Geoacoustic Parameters Inversion Using Parallel Multi-Population Genetic Algorithm (병렬 다중 개체군 유전 알고리즘을 이용한 지음향 파라미터 역산)

  • Oh Taekhwan;Na Jungyul;Lee Seongwook;Kim Seongil;Park Joung-Soo
    • The Journal of the Acoustical Society of Korea
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    • v.24 no.6
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    • pp.309-316
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    • 2005
  • This paper Presents the geoacoustic inversion with Parallel Multi-Population Genetic Algorithm (PMPGA). This method is the modified form of simple genetic algorithm (SGA), which is devised for complementing the defects of simple genetic algorithm. The light bulb source and vertical line array (VLA) receiver are used for geoacoustic inversion. The results of this study show the geoacoustic Parameters can be estimated by PMPGA and the proposed algorithm is 1.7 times as fast as serial one on an average.

A Cytogenetic Analysis of Inversion as a Type of Structural Chromosome Aberration in Prenatal Diagnosis

  • Hwang, Si-Mok;Kwon, Kyoung-Hun;Jo, Yoon-Kyung;Yoon, Kyung-Ah
    • Biomedical Science Letters
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    • v.15 no.4
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    • pp.363-368
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    • 2009
  • One of the frequent occurrences in rearrangements is chromosome inversion. Pericentric inversion is considered to be the variant of normal karyotype. We investigated the karyotypes of 1195 cases being referred to prenatal diagnosis using standard GTG banding for karyotype preparation. The chromosomal analysis revealed a total of 15 (1.26%) inversions. The characteristics of inversion type [(inv(4), inv(8), inv(9), inv(11)) were investigated on the basis of chromosomal analyses of fetuses and their parents. The results from chromosomal examination of the parents, whose fetuses were diagnosed as inversion, show that either parent might be the carrier. Inversion in human chromosome is commonly seen in normal humans and the frequency estimated to be 1 to 2% in general population and the exact amount of this phenomenon is still unclear. These results indicate that inv(8), inv(9), and inv(11) are phenotypically normal. However these may often cause clinical problems in offspring of the carrier, such as fetal wastage repeated spontaneous abortions and infertility with unknown mechanisms related to sex. We describe an inversion of human chromosome and its clinical correlation with human genetic disease.

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Strong Accretion Shock Waves in Cluster Outskirts and Possibility of Cosmic-Ray Population Inversion

  • Hong, Sungwook E.;Ryu, Dongsu;Kang, Hyesung
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.2
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    • pp.72.2-72.2
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    • 2012
  • We analyzed the properties of shock waves in galaxy clusters, by using the data of simulations for the large-scale structure of the universe with the spatial resolution of up to 25 kpc/h. In a substantial fraction of clusters, we found that strong shocks with Mach number of several or larger exist in outskirts within the virial radius. They are produced by the accretion of warm gas flowing from filaments to clusters, and generate large cosmic-ray fluxes. The cosmic rays advect into cluster cores, but may temporally induce the population inversion, that is, larger population at larger radius, suggested by recent radio and ${\gamma}$-ray observations.

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Meteorological Factors Affecting Winter Particulate Air Pollution in Ulaanbaatar from 2008 to 2016

  • Wang, Minrui;Kai, Kenji;Sugimoto, Nobuo;Enkhmaa, Sarangerel
    • Asian Journal of Atmospheric Environment
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    • v.12 no.3
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    • pp.244-254
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    • 2018
  • Ulaanbaatar, the capital of Mongolia, is subject to high levels of atmospheric pollution during winter, which severely threatens the health of the population. By analyzing surface meteorological data, ground-based LIDAR data, and radiosonde data collected from 2008 to 2016, we studied seasonal variations in particulate matter (PM) concentration, visibility, relative humidity, temperature inversion layer thickness, and temperature inversion intensity. PM concentrations started to exceed the 24-h average standard ($50{\mu}g/m^3$) in mid-October and peaked from December to January. Visibility showed a significant negative correlation with PM concentration. Relative humidity was within the range of 60-80% when there were high PM concentrations. Both temperature inversion layer thickness and intensity reached maxima in January and showed similar seasonal variations with respect to PM concentration. The monthly average temperature inversion intensity showed a strong positive correlation with the monthly average $PM_{2.5}$ concentration. Furthermore, the temperature inversion layer thickness exceeded 500 m in midwinter and overlaid the weak mixed layer during daytime. Radiative cooling enhanced by the basin-like terrain led to a stable urban atmosphere, which strengthened particulate air pollution.

Cytogenetic Study in 535 Couples with Recurrent Spontaneous Abortions in Korea (한국에서 반복 자연유산을 하는 535쌍의 부부에 있어서의 세포 유전학적 연구)

  • Hwang, Han Sung;Yang, Eun Suk;Hong, Won Ki;Kim, Mi Soon;Yang, Young Ho
    • Clinical and Experimental Reproductive Medicine
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    • v.32 no.2
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    • pp.113-119
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    • 2005
  • Objective: The purposes of this study were to investigate the types and the incidences of chromosomal abnormalities, and to provide an explanation for the genetic causations of recurrent spontaneous abortions in Korean population. Methods: Cytogenetic studies were carried out in 535 couples with at least two spontaneous first trimester abortions from January 1981 to December 2003. For karyotype analysis, we used modified Moorhead method by Giemsa staining and Giemsa-Trypsin-Giemsa banding Results: The overall incidence of chromosome abnormality was 32 out of 535 cases (5.98%). There were 25 cases (4.67%) of translocation and 7 cases (1.31%) of inversion. In translocation, 5 cases (0.93%) of Robertsonian translocation and 20 cases (3.74%) of reciprocal translocation were observed. In inversion, 6 cases (1.12%) of inversion of chromosome 9 and one case (0.19%) of inversion of chromosome 18 were found. Conclusion: In this study, overall chromosomal abnormality rate in couples with recurrent spontaneous abortions is much higher than that in the general population. So, chromosomal analysis should be offered for the prognostic information in genetic counseling such as prenatal diagnosis in couples with repetitive reproductive failure.

The Schema Extraction Method for GA Preserving Diversity of the Distributions in Population (개체 분포의 다양성을 유지시키는 GA를 위한 스키마 추출 기법)

  • Jo, Yong-Gun;Jang, Sung-Hwan;Hoon Kang
    • Proceedings of the Korean Institute of Intelligent Systems Conference
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    • 2000.05a
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    • pp.232-235
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    • 2000
  • In this paper, we introduce a new genetic reordering operator based on the concept of schema to solve the Traveling Salesman Problem(TSP). Because TSP is a well-known combinatorial optimization problem and belongs to a NP-complete problem, there is a huge solution space to be searched. For robustness to local minima, the operator separates selected strings into two parts to reduce the destructive probability of good building blocks. And it applies inversion to the schema part to prevent the premature convergence. At the same time, it searches new spaces of solutions. In addition, we have the non-schema part to be applied to inversion as well as for robustness to local minima. By doing so, we can preserve diversity of the distributions in population and make GA be adaptive to the dynamic environment.

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