1,721,427 research outputs found
Speaking characters in Possessing the Secret of Joy
Full text linkThis paper is a study of Alice Walker’s Possessing the Secret of Joy in light of Julia Kristeva’s speaking subject. This novel deals with the issue of circumcision and its negative psychological effects on a woman’s mind. Moreover, it criticises female genital mutilation. In this novel, each character expresses his/her feelings, thoughts and emotions about female circumcision. In Julia Kristeva’s view, the speaking subject does not have a fixed identity but is in the process of being. The speaking subject's identity is shaped through using language and interaction with other people. This article applies Kristeva’s notion of the subject in process to Walker’s Possessing the Secret of Joy and primarily indicates Tashi’s opinion of circumcision. The findings of this study demonstrate that, through sisterhood, women can achieve their goal which is to abolish female circumcision. It indicates that although women are oppressed in African patriarchal societies, they can improve their life through sisterhood. It advises future female generations to stand up for their rights and reject the circumcision which hurts women physically and psychologically
Cultural identity in K. S. Maniam's Ratnamuni
Full text linkIn his fiction, the Malaysian-Indian author, K. S. Maniam depicts the identity and culture of Malaysian-Indian. This is shaped with a collection of materials that are vital to keep the trace of ancestral identification marks, of retaining the status of being Indian, even though the land they live in is not India. In the new land the Indian community invests its new narrative of existence with a power structure to support the Diasporic Indian “self”. In Maniam’s reconstruction of the Indian immigrant experience in Malaysia, there are the difficulties that the community faced when trying to recreate this world. Maniam depicts the rites of the complicated cultural issues in a Diasporic Indian community. In his reconstruction of the Indian immigrant experience of Malaya, One can see these previously peripheral characters as the agents of the Diasporic identity that the present day Malaysian-Indian has inherited. The passage of such identity formation, however, is demonstrated to be filled with the many snares of both colonial and postcolonial experiences. The present study examines Maniam’s short story, Ratnamuni, from a Diaspora perspective. This study shows the way in which Maniam symbolically depicts the culture of a nation in Diaspora
Two-photon absorption laser induced fluorescence (TALIF) of neutral xenon in a Hall Effect thruster plasma
Full text link2021 Fall.Includes bibliographical references.This work presents measurements of ground state neutral xenon in the plume of a 1.5 kW Hall Effect thruster (HET) using two-photon absorption laser induced fluorescence (TALIF). Neutral xenon particles in the thruster plasma play an important role in ionization processes, overall energy conversion, and life-limiting interactions with surrounding wall materials in the thruster. Therefore, a detailed understanding of the neutral particle dynamics within the plume is desired. The TALIF diagnostic technique allows for laser induced excitation of xenon from its ground state using commercially available laser systems at accessible ultraviolet wavelengths (~222 nm). The signal collected from fluorescence of the excited atoms can be used to determine the local neutral density. We present a demonstration of TALIF first in a barium oxide (BaO) hollow cathode plume at varying radial positions, then in an HET plume at varying axial positions using fiber coupled collection optics with a spatial resolution of 3.14 mm2. The detection limit of the TALIF measurement system 2.1 cm downstream of the thruster face was estimated to be 8 x 1017 m-3 as determined by comparison to a known reference signal. The ability to analyze ionization and thermal characteristics using these results is also discussed
Gas temperature measurements from ps-TALIF in highly collisional plasmas
No full textInternational audienceIn this work, we present a straightforward approach to retrieve gas temperatures directly from the effective lifetime τH of the ps-laser excited species measured with picosecond Two Photon Absorption Laser Induced Fluorescence (ps-TALIF). This approach allows for simultaneous measurements of absolute atom densities and gas temperatures performed in moderate-pressure reactive plasmas using an advanced ps-TALIF diagnostic and has been demonstrated for highly collisional hydrogen microplasmas. Furthermore, this methodology was applied to obtain a 2D distribution of gas temperature and H-atom densities in the downstream region of the microplasma discharge
Quantitative fs-TALIF in high-pressure NRP discharges: calibration using VUV absorption spectroscopy
No full textInternational audienceAbstract This work presents a femtosecond two-photon absorption laser-induced fluorescence (fs-TALIF) diagnostic for measuring ground-state atomic nitrogen in nanosecond repetitively pulsed (NRP) discharges. Absolute atom density is obtained from the TALIF signal via a novel calibration technique based on one-photon direct absorption measurements performed in a low-pressure DC discharge. The Vacuum Ultraviolet (VUV) measurements were done at the Soleil synchrotron facility using the high-resolution Fourier-transform spectrometer (minimum linewidth Δ ν ~ = 0.08 cm −1 ). The main goal of this work was to develop a quench-free diagnostic technique, which would allow measurements at elevated pressures with high spatial and temporal resolution. Here fs-TALIF measurements of N( 4 S) are demonstrated in the NRP post-discharge between 1–500 μ s after the nanosecond high-voltage pulse. A maximum number density of N-atoms of 5 × 10 16 cm −3 was measured at 1 μ s after the pulse when the discharge was operated at 1 bar in pure nitrogen. This corresponds to a dissociation fraction of ∼0.1%. The fs-TALIF technique at high laser intensity regime (>1 TW cm −2 ) calibrated using VUV absorption was compared with the fs-TALIF at low laser intensity regime (<100 MW cm −2 ) calibrated via the well-established non-saturated TALIF technique using krypton as an etalon gas. It was found that the two measurements of N( 4 S) in the NRP post-discharge agree within a factor of 3. Importantly, the limit of detection of the fs-TALIF at high laser intensity regime was determined to be n N ( S 4 ) ∼ 1 0 12 c m − 3 . This is approximately one order of magnitude better than previously reported by ns-TALIF in low-pressure discharges
Towards calibration of picosecond O-TALIF
No full textInternational audienceExperimental procedure of obtaining the Xe/O two-photon absorption cross-section ratio is discussed for nanosecond and picosecond TALIF experiments. The same nanosecond capillary discharge with 100% oxygen dissociation at 30 mbar pressure is used as a source of O-atoms
Femtosecond TALIF for atomic radical detection at high pressure and cell calibration developments
No full textInternational audienceTwo-photon Absorption Laser Induced Fluorescence (TALIF) enables in situ, high space-and time-resolved measurements of atomic species, such as O, H, N, C, F.• Conventional ns-TALIF, operating in the quadratic regime, has several limitations• i) two-photon absorption cross sections are known within ~50% ,• ii) the quenching rates on which the TALIF signal depends may be difficult to measure in highly collisional plasmas, even with the use of streak cameras , • iii) several non-quadratic phenomena become significant as the laser intensity increases (focused ns, ps, fs laser intensities may reach hundreds of GW/cm² to PW/cm²) • In this work, we follow the path set in [1,2] and present the results of VUV-absorption absolute calibration of the fs-TALIF diagnostic.</div
Implementation of TALIF on negative ion sources for the determination of the properties of atomic hydrogen
Full text linkThe production of negative hydrogen ions in a negative ion source used for future neutral beam injection systems in nuclear fusion is closely tied to the density and energy distribution function (EDF) of neutral hydrogen atoms in the plasma in negative ion sources. In this work, a diagnostic (two-photon absorption laser induced fluorescence, TALIF) is installed at a negative ion source which can determine both density and EDF of H atoms in the relevant plasma region. In an intermediate step, TALIF is set up at a reference plasma source for characterization and first measurements. The gained knowledge is then used for the installation of TALIF at the negative ion source at the test stand BATMAN Upgrade where the very first TALIF measurements at such an ion source are performed
Ground-State Atomic Nitrogen Measurements using fs-TALIF in High-Pressure NRP Discharges
No full textInternational audienceMeasurements of ground state atomic nitrogen inside of a nanosecond repetitively pulsed (NRP) discharge operating at pressures between 0.1-5 bar are performed using a femtosecond two-photon absorption laser induced fluorescence (fs-TALIF) technique. The main goal of this work is to develop a quench-free diagnostic technique which would allow measurements at elevated pressures with high spatial and temporal resolution. Quantitative information is extracted from the TALIF signal via a novel calibration technique based on direct absorption measurements performed in a low-pressure DC discharge. The VUV measurements were done at the Soleil synchrotron facility using their unique high-resolution Fourier-transform spectrometer (⁄ =). During this preliminary work, fs-TALIF measurements of N(4 S) are demonstrated in the post-discharge of the NRP between 1-500 µs after the nanosecond pulse. A maximum number density of N-atoms of × was measured at 1 µs after the pulse when the discharge was operated at 1 bar in pure nitrogen. Importantly, the limit of detection of the fs-TALIF technique was determined to be ()~. This is approximately two orders of magnitude lower than previously reported by ns-TALIF
Time-selective TALIF spectroscopy of atomic oxygen applied to an atmospheric pressure argon plasma jet
No full textTwo-photon laser excitation diagnostics is applied to characterize the atomic oxygen production in an atmospheric pressure Ar+O-2% plasma jet. The plasma jet device is driven by a 13.56-MHz radio-frequency power supply. It is found that in addition to the fast decaying two-photon absorption laser-induced fluorescence (TALIF), unexpected emissions from excited atomic argon and oxygen species with a long decay time are existent in TALIF processes. This phenomenon is believed to be common in TALIF diagnostics of atomic oxygen, especially in high-pressure plasmas because of intense collisional energy transfer processes. In order to avoid the influence of extra emissions on TALIF performance, time-selective detection is utilized to capture the pure atomic oxygen fluorescence through nanosecond imaging for characterizing the spatial distribution of O atoms in the plasma effluent. An approximate method for the absolute density calibration based on the atomic oxygen fluorescence in the open air, due to the laser-induced photodissociation of O-2 molecules, is applied to the TALIF signal from a plasma jet. The 2-D spatial distributions of the ground state density of atomic oxygen are built in the plasma effluent under different O-2 contents. With the increase in O-2 admixtures, the generation of atomic oxygen is constricted to the plasma core area close to the gas outlet, and a maximum O density is obtained with 0.3% O-2 in the core area
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