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A new concept of magnetic ionic liquid electrospray thruster(ILET) is proposed in this paper. The thruster uses a lower working voltage with the action of an applied magnetic field, and is named as low-voltage ionic liquid electrospray thruster(LV-ILET). A jet needle is used as the emitter and the Helmholtz coil is used to apply an external magnetic field to demonstrate the working principle of the LV-ILET. The experimental results show that the stable working voltage could be reduced to 87% of that in absence of an applied magnetic field. Under the same working voltage, the applied magnetic field can significantly increase the emission current of LV-ILET. Due to the linear relationship between the thrust and the emission current, LV-ILET can either reduce the working voltage or increase the thrust with the help of the applied magnetic field and the magnetization characteristics of the propellant.

Drumsticks (Moringa) have a tremendous potential to solve many issues of the world related to nutrition and general diseases with the support of proper institutions (The authors acknowledge all the respondents, primarily from the marginalised segment of West Bengal, for their valuable time and insights. The authors also acknowledge Professor Lipsa Mohapatra’s efforts regarding data assimilation.). We scanned the literature to understand different benefits of Moringa with a major focus on its nutritional benefits. We analysed the situation of undernutrition in India, strengths and weaknesses of different Moringa-producing organisations across countries, governments’ policies on Moringa production and consumption and interviews with – middle-class/poor rural/semi-urban Indian women through questionnaires. We studied Moringa production and consumption to address the issue of undernutrition and interviewed different government officials who worked in this area. The literature review and empirical evidence collected helped the authors to argue for a holistic, sustainable community-driven organisation that will be deep-rooted with local market networks. This will help in effective Moringa production and consumption in India to address the malnutrition challenges of our country.

THz indicates an electromagnetic wave whose spectrum locates between the microwave and infrared range. In the last two decades the advent of benchtop THz sources filled the so-called ‘THz gap’. The properties of THz radiation such as low photon energy, transparence to it of packaging materials and so on make it suitable for many applications in industrial and scientific fields. In this work we generated intensive broadband THz pulses radiated from femtosecond laser induced plasma via four-wave-mixing process coupling fundamental laser light and its second harmonic. In chapter 1 we generally introduce the principles of THz generation and detection. We also introduce the application of our THz source in static THz time-domain spectroscopy and time-resolved THz spectroscopy. In chapter 2 we present THz generation based on air plasma and THz detection through different methods and sensors, including ZnTe, GaSe, LAPC single crystals and air-based methods. The results show that the detected upper frequency edge with 500 µm ZnTe is limited by the phase mismatch between THz and probe beam. 250 µm ZnTe expands the detected frequency range but the detection efficiency is restricted by phonon absorption at 5.3 THz. GaSe can detect THz up to 30 THz with a deep gap due to phonon mode around 6.5 THz. Another dip around 19.1 THz due to silicon absorption is also found. LAPC is capable of measuring THz up to around 17 THz without gap. The air-based method results in ultra-broadband detection of short unipolar pulses. In chapter 3 we develop a precise contactless micro-distance measurement method based on THz pulses. The resolution of the measurement can achieve 1.5 µm with scanning step equal to 0.01 ps. A comparison between ZnTe detection sensor and air-based sensor indicates that the air-based detection technique has advantages that include the ability to measure smaller distance and the immunity to distortion introduced by vapor absorption in air. We also compare distance measurement with ZnTe in air and in nitrogen. We find that the measurement in nitrogen leads to a more straightforward extraction of the distance as compared to the measurement in air where additional analysis is needed to take into account the coherent oscillations produced by air absorption. In chapter 4 we investigate the mixing behavior of the dielectric function of mixtures of ionic liquids (ILs). In the investigation we measure the cell thickness with the method developed in chapter 3 and detect the THz radiation with electro-optic sampling in a 250 µm ZnTe crystal. The results show that the complex permittivity of ionic mixtures obeys linear mixing law. We also find that all the complex permittivity spectra of mixtures can be simulated with a combination of three oscillators which are assigned to different vibrational modes of the ionic liquids. In chapter 5 we discuss broadband THz time-domain spectroscopy applied to pure imidazolium-based ionic liquids. The broadband THz detection was realized thanks to the use of a LAPC crystal. We find in the absorption spectra of a series of pure ionic liquids clear signatures of both inter- and intra-molecular vibrational modes. This is the first time that inter- and intra-molecular modes of ionic liquids are measured in one shot without combining different techniques. We have assigned these vibrational modes to different processes in ionic liquids. We find an interesting correlation between the specific anion of IL and the peak frequency shift and bandwidth variation observed for the intermolecular absorption band. We discuss these correlations in terms of the ability of the specific anion in forming hydrogen bonds. In chapter 6 we discuss our experiments of THz-pump/second-harmonic-generation in single crystals of quartz. The experiments on quartz show that the second harmonic signal oscillates coherently at several frequencies in the THz frequency range and these oscillations depend on the specific combination of the probe and THz linear polarization, and orientation of quartz axis. We also find that the intensity and bandwidth of the spectrum of second harmonic are enhanced in presence of the THz, i. e., side-bands appears in the second harmonic spectrum.

Solar thermal propulsion is a potential technology in aerospace applications, and it is a significant issue to improve the heat transfer efficiency of the solar thermal thruster. This paper proposes a novel platelet configuration to be used in the heat exchanger core, which is the most important component of solar thermal system. The platelet passage can enhance the heat transfer between the propellant and the hot core heated by the concentrated sunlight. Based on fluid-solid coupled heat transfer method, the paper utilized the platelet heat transfer characteristic to simulate the heat transfer and flow field of the platelet passage.The simulation result shows that the propellant can be heated to the design temperature of 2300K in the platelet passage of the solar thermal propulsion system, and the fluid-solid coupled method can solve the heat transfer in the platelet structure more precisely.

As a heat source capable of producing extremely high temperature, the arc heater developed with the development of ballistic missiles and other spacecraft. With the development of hypersonic vehicles, the requirement of thermal protection performance test on ground simulation equipment is higher and higher, the current and power of arc heater are increasing. The traditional single-electrode arc heater can’t run stably for a long time under large current. In order to improve the operation stability of the arc heater under large current, a multi-electrode technique was developed. In this paper, the effects of parameters such as arc current, gas flow rate and resistance on the current distribution of each sub-electrode of the three-electrode arc heater are studied. The results show that when the arc current is constant, increasing the resistance difference of each sub-electrode is beneficial to the average distribution of current. With the increasing of arc current, the current distribution of each sub-electrode is more uniform. The setting of parameters such as arc current, gas flow rate and resistance has great influence on the distribution of cathode current of multi-electrode arc heater, but little influence on the anode.

A new source of high-power broadband THz radiation has been built in Naples, Italy. The source is based on twocolours mixing of ultrashort femtosecond light pulses. The source can deliver THz frequencies in the range 0.1-30 THz, with pulses of sub-picosecond time duration and having a peak electric field amplitude as high as 1 MV/cm. A characterization of the source is given in this work together with an overview of the preliminary experiments of THzcontrolled excitations in solids.

Experimental investigations were carried out to separate arsenic from contaminated groundwater by using three different types of nanofiltration membranes in a flat sheet cross flow membrane module with a pre-oxidation step for conversion of trivalent arsenic to pentavalent form. KMnO 4 was used as an oxidising agent in the pre-oxidation step. Effects of pressure, iron concentration in groundwater, pH, and pre-oxidation on the performance of the membranes in terms of flux as well as percentage rejection of arsenic were studied. While transmembrane pressure was found to have strong impact on flux and retention of arsenic, pH and pre-oxidation exhibited strong influence on percentage removal of arsenic. Introduction of pre-oxidation step remarkably enhanced arsenic separation in a largely fouling-free membrane module. Overall arsenic removal increased from 50–63% to 97–100% for all the three types of membranes over a transmembrane pressure range of 5–12 kgf/cm 2 on pre-oxidation of trivalent arsenic. With increase in pH from 3 to 10, arsenic rejection increased by 23% for NF-1, 33% for NF-2 and 26% for NF-20 membranes. Polyamide composite nanofiltration membrane fitted in a cross flow membrane module could successfully remove arsenic from contaminated groundwater with a pre-oxidation step.

Pulsed inductive thruster, which employs pulsed inductive magnetic field to ionize propellant and accelerate a bulk of plasma, is accompanied with complicated phenomena such as plasma physics, magnetohydrodynamics and the strong coupling effect between the drive-circuit and plasma load. Simulations employing a snowplow circuit model or present magnetohydrodynamic model might be insufficient to capture these important phenomena simultaneously and self-consistently. Therefore the validity of currently existing numerical models remain to be verified. In this paper, a novel circuit-coupled magnetohydrodynamic model is proposed. The flow process of the plasma in the acceleration channel and the discharge process of the circuit are solved simultaneously in a bi-directionally coupled method by calculating the voltage drop across the drive-coil according to the drive-coil geometry and the temporal electric field distribution. The magnetohydrodynamic field is solved with Navier-Stokes equations coupled with Maxwell equations, while the plasma thermodynamic parameters and transport parameters are calculated by employing the local thermal equilibrium model. And the circuit process is solved with a set of circuit equations based on Kirchhoff's law. All the physics fields are computed by the finite element method in COMSOL MultiphysicsTM. Numerical simulation for American TRW Inc.'s MK-1 thruster successfully reproduces its working process. The numerical magnetic field distribution in plasma, the time-dependent collective Lorentz force and the specific impulse and efficiency of the thruster under varying working voltages agree well with the corresponding experimental data. Numerical results imply that a compact azimuthal plasma current sheet is established in the initial 1-2 s in the near-face region of the drive-coil. This plasma current sheet, which entrains the majority of the propellant, is excluded and accelerated by the Lorentz force derived from the drive-coil magnetic field. Most of the propellant acceleration is accomplished within the first half period of the circuit current, which is about 7-8 s. Furthermore, the bi-directional coupling effect is quantitatively analyzed with the current model. Numerical results indicate that the coupling plasma load generally tends to increase the effective resistance and reduce the effective inductance of the drive-circuit. Moreover, this effect changes as the plasma structure varies. When the plasma current sheet moves away from the drive-coil, the mutual inductance between plasma load and drive-coil decreases monotonically. That implys that the plasma current sheet decouples gradually from the dirve-circuit in the process. In conclusion, bidirectional coupling effect between plasma load and drive-circuit plays an important role in the operation of the thruster. This model could be used to predict the performances of pulsed inductive thrusters and might be helpful in designing a more effective thruster.

The contamination of groundwater by leached out arsenic has assumed an alarming proportion in several countries. Continued and prolonged ingestion even at a very low level can lead to serious arsenic-related diseases. Strong epidemiological evidence of arsenic carcinogenicity has forced the World Health Organization (WHO) to lower the maximum permissible contaminant limit (MCL) in drinking water to 10 ppb from earlier limit of 50 ppb. This has thrown a big challenge to the scientific community to devise efficient methods to purify contaminated water to such a high level. Though literature abounds in occurrence of groundwater contamination by arsenic and its removal from drinking water by laboratory techniques, millions of people continue to suffer, particularly in the developing countries like India (Bangladesh, West Bengal). Through a comprehensive review of the existing literature on the occurrence, causes, impacts and remedial measures, this article finds out what has gone wrong and what is to be done ...

With the detailed consideration of electrochemical reactions and collision relations, a direct numerical simulation model of helicon plasma discharge with three-dimensional fluid-dynamic equations is proposed in the present work. It can improve the precision of results and widen the model applicability by discarding the small perturbation theory in previous helicon models which are partially analytical in essence. Under the assumption of weak ionization, the Maxwell equations coupled with the plasma parameters are directly solved in the whole computational domain. Thus the energy deposited from electromagnetic wave to plasma can be then easily calculated. The values of plasma parameters which include electron density, mean electron energy and heavy species density are obtained by solving a set of drift-diffusion equations. Meanwhile, seven kinds of chemical reactions in the plasma and two kinds of surface reactions on the wall are taken into account. All of the partial differential equations are solved by the finite element solver of COMSOL MultiphysicsTM with the full coupled method.#br#The results of numerical cases employing argon as the working medium show that there exists a sharp density jump from a low to high value as the radiofrequency power is raised. The density jump phenomenon is in accordance with the experimental results of Toki (Toki K, Shinohara S, Tanikawa T, Shamrai K P 2006 Thin Solid Films 506-507 597) and Chen (Chen F F 2007 Plasma Sources Sci. Technol. 16 593). The electron temperature decreases with an increase of the gas pressure, which is similar to Toki's (Toki K, Shinohara S, Tanikawa T, Shamrai K P 2006 Thin Solid Films 506-507 597) measurement by a RF compensation probe. In comparison with the classical sheath theory, the simulation result demonstrates that the distribution of parameters such as particle number density, the Deby length, electric potential and electron temperature can be solved exactly. In addition, the phenomenon of low-field density peak in helicon discharge was studied in the work. Previous research by Chen (Chen F F 2003 Phys. Plasmas 10 2586) suggests that this peak is caused by constructive interference from the reflected wave. The effect of length of the discharge chamber on the relation of electron density and background magnetic field is investigated numerically. The results validate the mechanism of wave interference reflected by endplates of the discharge chamber. Furthermore, the time-averaged magnetic energy density has more than one peak on the axial direction. Comparing the distribution of the magnetic energy density to that of the dimensionless amplitude of the helicon wave and the TG wave in the one-dimensional undamped condition, it found that the length of peak to peak of the helicon wave is just as twice as that of the magnetic energy density, which indicates that the substance of wave interference is involved in the standing wave generated by the helicon wave and its reflected wave from endplates.

For laser ablation propulsion, the shielding effect of ablation plume on the incident laser is an essential factor affecting the propulsion performance. When the polymer doped metal is utilized as the propellant, the shielding effect would be more significant because the metal dopant is easily ionized. In order to study the shielding effect of ablation plume on the incident laser energy, a laser ablation model with taking into account the plume expansion, ionization and the shielding effect is built in the present work. For the polyoxymethylene doped aluminum particles irradiated by a laser with a fluence of 3-40 J/cm2, the specific impulse of laser ablation is calculated, and the consistency of the numerical results with the experimental data demonstrates the availability of the model. Furthermore, the effects of both the incompletely decomposed polymer chains and the plasma induced by laser ablation on the incident laser are considered. The time variations of electron number density distribution under different laser fluences are calculated based on the laser induced ionization model. Subsequently, the absorption coefficient distributions and the time variations of shielding coefficient under different laser fluences are obtained. The results show that at a low laser fluence (5 J/cm2), the electron number density is small, so the plume shielding effect is dominated by the laser energy absorption of the small polymer chains which are not completely decomposed. While at a high laser fluence (20 J/cm2), small polymer chains are almost completely decomposed into atoms even plasma, hence the shielding effect is dominated by the plasma since the electron number density in the plume increases up to 1020 m-3, and the complicated characteristic in the time variation of shielding coefficient appears. The quantitative analysis results obtained in the present work can be helpful for optimizing the performances of laser ablation propulsion.

The contents of tellurium in Chinese soils are investigated. The distributive character in different soil types in 34 provinces (cities) is studied. Some conclusions can be obtained based on these results.

Helicon discharges have attracted great attention in the electric propulsion community in recent years. To acquire the equilibrium properties, a self-consistent model is developed, which combines the helicon/Trivelpiece—Gould (TG) waves-plasma interaction mechanism and the plasma flow theory under the confinement of the magnetic field. The calculations reproduce the central peak density phenomenon observed in the experiments. The results show that when operating in the wave coupling mode, high magnetic field strength B0 results in the deviation of the central density versus B0 from the linear relationship, while the density rise becomes flatter as the radiofrequency (rf) input power Prf grows, and the electron temperature Te radial profile is mainly determined by the characteristic of the rf energy deposition. The model could provide suggestions in choosing the B0 and Prf for medium power helicon thrusters.