JaLCDOI 10.18926/15488
フルテキストURL Mem_Fac_Eng_OU_25_1_37.pdf
著者 Bouzidi, Moncef| 古賀 隆治| 和田 修己| 香川 直己| Hai, Xu| 小坂 恵| Sano, Hiroya|
抄録 Is proposed a tunable diode laser absorption spectrometer system which employs a pulsed current to drive the diode laser still implementing a second-harmonic detection methods enhancing a signal to noise up to 104 times that the case without it. This system affords the lead-salt diode laser a higher operating temperature which allows a more compact deep cooling system. A principle is based on employing a gated integrator between the preamplifier and the lock-in amplifier. Investigations are made on the optimum selection of the gating aperture time interval as determined by response time of the infrared detector and the pulse width of the laser driving current.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1990-12-14
25巻
1号
開始ページ 37
終了ページ 50
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307549
JaLCDOI 10.18926/15481
フルテキストURL Mem_Fac_Eng_OU_24_1_81.pdf
著者 和田 修己|
抄録 Are calculated the radiation characteristics of two types of primary-feed waveguides of millimeter wave quasi-optical antennas, which transform circular TE(On) mode into a linearly polarized beam. These antennas are utilized for heating and diagnostics of fusion plasma. Analysis is based on the Huygens-Fresnel principle, which takes the diffraction effect into account. For Convenience in analysis, a feed waveguide is divided into two sections, an uniform waveguide section and a visor section. Assuming that the diameter of the waveguide is several times as large as the wavelength and that the structure of the visor is open, the radiation field is approximated by superposition of direct radiation, and first and second reflection on the visor. Numerical results are presented and compared with experimental results. In these types of waveguides, the shadow section on the visor has a great influence on the radiation field. The results of calculation show that the length of the visor should be longer than that obtained by the geometrical optics, and the longer visor reduces the side-lobe level in the direction of the waveguide axis. The results agree well with those in experiments.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1989-11-29
24巻
1号
開始ページ 81
終了ページ 92
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307974
JaLCDOI 10.18926/15458
フルテキストURL Mem_Fac_Eng_OU_28_2_33.pdf
著者 Wang, Ming| Ahmed, Anis| 和田 修己| 古賀 隆治|
抄録 Proposed here is a convenient optical system to collimate the crescent shaped blue laser beam radiated from a Cerenkov SHG in channel waveguide configuration. This collimation system is consisted of a parabolic mirror and has a very large tolerance to the mirror displacement. The anisotropy of the nonlinear crystal on which the waveguide is fabricated has been taken into account. The optimum mirror location is given to obtain a collimated blue laser beam with an aberration less than 0.07λ. By using an objective lens, the collimated beam can be focused down to a thin beam with the spot size less than 1μm.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1994-03-15
28巻
2号
開始ページ 33
終了ページ 44
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307149
JaLCDOI 10.18926/15439
フルテキストURL Mem_Fac_Eng_OU_26_2_77.pdf
著者 和田 修己| Nakajima Masamitsu|
抄録 This paper describes a method to design an antenna to focus millimeter-wave beam generated by a gyrotron. The antenna, which has been proposed by the authors, consists of a stair-cut circular waveguide and two cylindrical reflectors; one is elliptic and the other is parabolic. Its principle is based on the geometrical optics though slightly modified to consider the diffraction effect. Results of low-power experiments agree well with the design on beam direction, beam width and the position of the focal point. At 35.5 GHz using TE(01) mode, a focused beam with half-power thickness of 13 mm x 10 mm was obtained. This type of antennas find applications to millimeter-wave scattering measurement in fusion plasma research and high- energy-density source for material heating.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1992-03-28
26巻
2号
開始ページ 77
終了ページ 92
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307321
JaLCDOI 10.18926/15419
フルテキストURL Mem_Fac_Eng_OU_29_2_49.pdf
著者 Ahmed, Anis| Taniguchi, Shinji| 和田 修己| Wang, Ming| 古賀 隆治|
抄録 For weakly guiding dielectric waveguides, the eigenmode field distributions are calculated numerically with a simple algorithm. In this numerical method, the transverse sampling space can be chosen arbitrarily, and hence a narrow waveguide can be analyzed. The field satisfying scalar wave equation is expressed by the discrete Fourier transform and the mode eigenvalues and eigenfunctions are calculated by solving an eigenvalue equation numerically. The validity of this method is checked for 2-D waveguides having step and parabolic or square index distributions. It is found that for the well guided TE modes of the slab waveguide, the accuracy of this method is remarkably good, but some discrepancies are found if the mode is near cut off. In the problems where the normalized guide index b is small, caution should be taken in applying the results of this numerical method.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1995-03-27
29巻
2号
開始ページ 49
終了ページ 55
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307858
JaLCDOI 10.18926/15416
フルテキストURL Mem_Fac_Eng_OU_26_1_43.pdf
著者 Bouzidi, Moncef| 古賀 隆治| 和田 修己| 香川 直己| Hai Xu| 小坂 恵| Sano HIroya|
抄録 A numerical technique called as "adjoint spectrum" has been proposed by the authors in a previous work. Two applications of it are presented here. It is demonstrated that by generalizing the aspect of adjoint spectrum it becomes possible to measure densities of mixed gases simultaneously. An experimental proof of this has been carried on and simultaneous measurement of densities of both methane and dinitrogen oxide was realized. On the other hand, it is also reported that frequency shifting of spectra, which is a cause of error in spectrometric measurements, can be corrected by exploiting the adjoint spectrum technique in connection with the Taylor expansion. Numerical examples showing the success of this method are reported as well.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1991-11-30
26巻
1号
開始ページ 43
終了ページ 49
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307796
JaLCDOI 10.18926/15392
フルテキストURL Mem_Fac_Eng_OU_27_1_45.pdf
著者 香川 直己| 和田 修己| Hai, Xu| 古賀 隆治| Sano, Hiroya| Inubushi, Kazuyuki|
抄録 A prototype device based on the tunable diode laser absorption spectrometry was constructed and the atmospheric methane concentration near the terrain in a rice paddy field was measured. An open optical path of 50 m length was employed along with a PbSnTe diode laser. Diurnal change of methane density with 30 seconds temporal resolution was recorded associated with meteorological parameters. A feasibility was proven for a practical application for in situ study of atmospheric methane.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1992-11-25
27巻
1号
開始ページ 45
終了ページ 53
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307877
JaLCDOI 10.18926/15384
フルテキストURL Mem_Fac_Eng_OU_30_1_99.pdf
著者 Wang, Ming| 和田 修己| 古賀 隆治|
抄録 A cylindric mirror was used, in place of a parabolic mirror, to collimate the crescent blue laser beam radiated from the Cerenkov SHG in channel waveguide configuration. The cylindric mirror radius is requested to be twice the focal length of the parabolic mirror. The focusing effect of the cylindric mirror in collimation can be compensated by slightly lifting the mirror in its normal direction. Under the condition that the mirror was declined by 5.56° and lifted by 25 μm, we got the collimated beam with divergence angle less than 1.3 mrad. In the focusing experiment, the collimated beam was focused with spotsize of 1.8 μm. The details on the analysis and experiment are reported.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 1995-12-28
30巻
1号
開始ページ 99
終了ページ 110
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307418
JaLCDOI 10.18926/15360
フルテキストURL Mem_Fac_Eng_OU_34_27.pdf
著者 Wei, He| 古賀 隆治| 五百旗頭 健吾| 和田 修己| 豊田 啓孝|
抄録 In spring of 1998, Asian dust was observed with a Mie LIDAR in Okayama University, which can measure depolarization ratio. Three events of intense Asian dust were occurred in the period and medially detailed structure of atmosphere was found after examining records. Asian dust was distinguished from water droplets and the possibility to study three dimensional dynamic structure of atmosphere were demonstrated.
キーワード Mie lidar Asian dust (KOSA) depolarization ratio backscattering ratio range normalized
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 2000-03-27
34巻
1-2号
開始ページ 27
終了ページ 37
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002307539
JaLCDOI 10.18926/14158
フルテキストURL Mem_Fac_Eng_39_1_93.pdf
著者 五百旗頭 健吾| 豊田 啓孝| 和田 修己| 古賀 隆治|
抄録 The optical properties of clouds were measured with a polarization Mie lidar during April, 2004 and investigated to categorize the particles detected by the lidar. The cloud layers were categorized into five types according to the depolarization ratios, as follows: (I) constant and small (less than 5%); increasing with height (II) nearly from 0% and (III) from about 50%; (IV) large and varying with the backscattering coefficient; and (V) sharply decreasing. This categorization of clouds enabled us to separate aerosols from clouds in a lidar signal. Comparison of the backscattering coefficients between clouds of types (I) and (II) suggested that the depolarization ratio induced by multiple scattering in dense clouds does not depend on the particle density. Estimation of the particle phase for the five cloud categories was also examined.
出版物タイトル Memoirs of the Faculty of Engineering, Okayama University
発行日 2005-01
39巻
1号
開始ページ 93
終了ページ 101
ISSN 0475-0071
言語 English
論文のバージョン publisher
NAID 120002308479