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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

MR scanner independent 3D B1 field mapping of magnetic resonance spectroscopy RF coils using an automated measurement system / Magnetkameraoberoende bestämning av 3D vektor B1-fält av magnetkameraspolar med ett automatiserat mätsystem

Brandejsky, Vaclav January 2008 (has links)
We developed a method for measurement of the B1+/- fields as an alternative approach to B1+/- fields assessment in MR scanner. Our setup incorporates an industrial coordinate table controlled by a PC-based program, search coils, a two--port vector network analyzer and an analog-to-digital (A/D) card. It is possible to measure in various liquid media (for example in saline solution) to mimic different shapes and dielectric properties of the human body. / Radiofrekventa - spolars känslighetsmönster är viktigt för avbildning med magnetkamera (MRI) och magnetresonansspektroskopi (MRS). Vetskap om RF-spolars känslighet för och förmåga att skapa RF-magnetfält (B1 kan användas för att åstadkomma korrekta excitationsflipvinklar och för att korrigera uppmätta signalstyrkor. Det är också viktigt för att göra MRI och MRS undersökningar snabbare och för att förbättra kvalitén på rekonstruerade bilder. Vi har utvecklat en metod för mätning av B1+ och B1- fält i en testbänk som alternativ till metoder där B1 fältet bestäms inne i magnetkameran. Uppställningen omfattar ett industriellt koordinatbord kontrollerat av PC-baserade program, sökspolar för detektion av B1 fält, en tvåports nätverksanalysator och ett analog till digital omvandlingskort. Mätningen är möjlig att utföra i olika vätskor, exempelvis saltlösning, för att efterlikna olika former och dielektriska egenskaper hos människokroppen.
2

Mercury dimer spectroscopy and an Einstein-Podolsky-Rosen experiment

Qu, Xinmei 15 May 2009 (has links)
The dissociation of a 199Hg2 dimer prepares an entangled state of two spatially separated 199Hg atoms, each with nuclear spin 1/2, and with zero total electron and nuclear spin angular momenta. This is identical to the entangled state of the two spin 1/2 particles in Bohm’s classic version of the EPR gedankenexperiment. An analysis of the rotational structure of the CD=57HCI=0 band of the D3K+ u (1u)HX1Kg + (0+ g ) transition in Hg2 (natural abundance) is presented. The analysis of the fluorescence excitation spectrum using a dye laser gives the values of the constants BCD=57 and BCI=0 for the excited and ground electronic energy states involved in the transition, respectively. To increase the accuracy of the rotational constants and resolve the fine spectrum of the Hg2, a continuously tunable single longitudinal mode laser with ultra-narrow line-width is needed. Measurements using a narrow line-width alexandrite laser had been attempted and the values of BCD=57 and BCI=0 were determined. To improve the quality of the laser beam and hence the precision of the rotational constants, modifications have been made to the cavity of the alexandrite laser. This provides a possibility for further investigation.
3

MR scanner independent 3D B<sub>1</sub> field mapping of magnetic resonance spectroscopy RF coils using an automated measurement system / Magnetkameraoberoende bestämning av 3D vektor B<sub>1</sub>-fält av magnetkameraspolar med ett automatiserat mätsystem

Brandejsky, Vaclav January 2008 (has links)
<p>We developed a method for measurement of the B<sub>1</sub><sup>+/-</sup> fields as an alternative approach to B<sub>1</sub><sup>+/-</sup> fields assessment in MR scanner. Our setup incorporates an industrial coordinate table controlled by a PC-based program, search coils, a two--port vector network analyzer and an analog-to-digital (A/D) card. It is possible to measure in various liquid media (for example in saline solution) to mimic different shapes and dielectric properties of the human body.</p> / <p>Radiofrekventa - spolars känslighetsmönster är viktigt för avbildning med magnetkamera (MRI) och magnetresonansspektroskopi (MRS). Vetskap om RF-spolars känslighet för och förmåga att skapa RF-magnetfält (B<sub>1</sub> kan användas för att åstadkomma korrekta excitationsflipvinklar och för att korrigera uppmätta signalstyrkor. Det är också viktigt för att göra MRI och MRS undersökningar snabbare och för att förbättra kvalitén på rekonstruerade bilder. Vi har utvecklat en metod för mätning av B<sub>1</sub><sup>+</sup> och B<sub>1</sub><sup>-</sup> fält i en testbänk som alternativ till metoder där B<sub>1</sub> fältet bestäms inne i magnetkameran. Uppställningen omfattar ett industriellt koordinatbord kontrollerat av PC-baserade program, sökspolar för detektion av B<sub>1</sub> fält, en tvåports nätverksanalysator och ett analog till digital omvandlingskort. Mätningen är möjlig att utföra i olika vätskor, exempelvis saltlösning, för att efterlikna olika former och dielektriska egenskaper hos människokroppen.</p>
4

A new method for obtaining long optical paths and its use in spectroscopy

Marshall, James Kelso January 1941 (has links)
[No abstract submitted] / Science, Faculty of / Physics and Astronomy, Department of / Graduate
5

Intensity fluctuation spectroscopy with coherent X-rays

Dufresne, Éric January 1995 (has links)
No description available.
6

Spectroscopy of aluminum and copper atom reactions with acetone

Baek, Myung-Gi. January 1993 (has links)
Note:
7

High resolution infrared laser spectroscopy in the solid and gas phases.

January 2015 (has links)
本論文旨在利用高分辨激光光譜研究中紅外以及近紅外波段的分子體系。首先在固態氫體系中,我們主要研究其分別位於4 μm 及1.5 μm 的純轉動和振動轉動的W 躍遷(ΔJ=6)。我們搭建了一套全新的差頻激光光譜儀用以研究純轉動的W1(0)躍遷(ΔJ=6);另外振動轉動W₀(0)躍遷(Δv=1,ΔJ=6)則是用到自行搭建的近紅外二極管激光光譜儀。由於激光光譜的分辨率極高,兩種W 躍遷都觀察到晶體場效應導致的三重分裂結構,我們基於定態激子模型還得到了相應的晶體場常數。另外,我們還研究了兩種W 躍遷的線型、頻率與溫度的關係(溫度在3.8 K 至11.8 K 區間),并基於德拜兩能級弛豫模型對此做出解釋,相信主要是由於晶體內聲子散射所引致的。 / 另外我們還研究了三種含過渡金屬元素的氣態雙原子分子,分別是RuC、IrP和IrB。通過聯用激光消融及超聲射流技術,我們研究這些分子體系在近紅外波段的激光誘導熒光光譜。對於RuC 分子,我們記錄了12000 至14000 cm⁻¹ 波段的電子光譜,包擴[附圖]和[附圖]這四個譜帶系統,并分析得到了所有七種同位素分子的各項分子常數。由於極高的分辨率,我們觀察到99RuC 和101RuC 這兩個同位素分子的超精細結構,并得到了它們的[附圖] 這三個電子態的超精細常數。對於IrP 分子,我們在12000 至14000 cm⁻¹ 波段發現了新的電子態躍遷,并得到¹⁹³IrP 和¹⁹¹IrP 這兩種同位素分子的分子常數。對於IrB 分子,我們指認了一個新的電子態躍遷³Δ₃-X³Δ₃,并得到了¹⁹¹Ir¹¹B and ¹⁹³Ir¹¹B 這兩種同位素分子的分子常數。 / This thesis reports the high resolution laser spectroscopic studies of molecular systems in the mid‐ and near‐ infrared regions. In the system of solid parahydrogen, spectrum in the pure rotational and rovibrational W (ΔJ=6) transitions in the 4 μm and 1.5 μm regions respectively have been studied. A high resolution difference frequency laser spectrometer was constructed from scratch for the study of the pure rotational W₀(0) (ΔJ=6) transition, while the rovibrational W₁(0) (Δv=1, ΔJ=6) transition was studied using a home‐built near infrared diode laser spectrometer. The exceedingly high resolution achieved by laser spectroscopy resolved the triplet structure for both transitions due to anisotropic crystal field interactions. Their corresponding crystal field parameters based on the model of localized exciton were determined. In addition, the temperature dependences of line profiles and transition frequencies in the range of 3.8‐11.8 K were also studied for both transitions. These observations were consistent with the Debye’s model for the dephasing of two‐level system by acoustic phonons in the bulk crystal. / Coupled with laser ablation and free jet expansion, high resolution laser induced fluorescence spectroscopy in the near infrared region was applied in the study of three transition metal containing diatomic molecules including RuC, IrP and IrB in the gas phase. For RuC molecule, rotational resolved electronic spectrum have been observed in the range of 12000‐14060 cm⁻¹, covering the [with formula], and the [with formula] band systems. The resolution of our spectrum allowed partially resolved hyperfine structure for both ⁹⁹RuC and ¹°¹RuC isotopes. Accurate molecular constants for all seven RuC isotopic molecules were obtained and hyperfine constants for the [with formula] and states of both ⁹⁹RuC and ¹°¹RuC isotopes were retrieved and analyzed. For IrP molecule, new electronic transition systems were observed in the range of 12000‐14000 cm⁻¹ and the molecular constants for both ¹⁹³IrP and ¹⁹¹IrP isotopes were obtained. For IrB molecule, a new ³Δ₃-X³Δ₃ transition system was identified with the molecular constants of two isotopes ¹⁹¹Ir¹¹B and ¹⁹¹Ir¹¹B derived. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Yang, Mei. / Thesis (Ph.D.) Chinese University of Hong Kong, 2015. / Includes bibliographical references (leaves 82-85). / Abstracts also in Chinese.
8

Appliclation of photoacoustic spectroscopy and photothermal deflectiontechniques to specific liquid and solid samples

黃柏堅, Wong, Pak-kin. January 1994 (has links)
published_or_final_version / Physics / Master / Master of Philosophy
9

INVESTIGATIONS INTO NEW METHODS OF ANALYSIS BY ATOMIC AND MOLECULAR FLUORESCENCE AND FLAME EMISSION

Suddendorf, Ronald Frederick, 1949- January 1976 (has links)
No description available.
10

Development of a model for characterizing pneumatically generated primary aerosols for inductively coupled plasma emission spectrometry

Msimanga, Ntombiyomusa Doris Grissel 05 1900 (has links)
No description available.

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