新型电子束源—虚火花放电室设计

提出一种新型的脉冲线加速器驱动的高功率，强流密度，低发射率，高亮度电子束源－虚火花放电室的初步设计。基于空心阴极效应和虚火花放电经验公式，确定了空心阴极，多隙阴－阳极，取及工作气压范围，最后提出关于虚火花产生高亮度电子束源的总体实验方案。     

Influence of colloidal particle transfer on the quality of self-assembling colloidal photonic crystal under confined condition

The relationship between colloidal particle transfer and the quality of colloidal photonic crystal(CPC) is investigated by comparing colloidal particle self-assembling under the vertical channel(VC) and horizontal channel(HC) conditions.Both the theoretical analyses and the experimental measurements indicate that crystal quality depends on the stability of mass transfer.For the VC,colloidal particle transfer takes place in a stable laminar flow,which is conducive to forming high-quality crystal.In contrast,it happens in an unstable turbulent flow for the HC.Crystals with cracks and an uneven surface formed under the HC condition can be seen from the images of a field emission scanning electron microscope(SEM) and a three-dimensional(3D) laser scanning microscope(LSM),respectively.     

First-principles analysis of the structural,electronic, and elastic properties of cubic organic-inorganic perovskite HC(NH_2)_2PbI_3

The structural, electronic, and elastic properties of cubic HC(NH_2)_2PbI_3 perovskite are investigated by density functional theory using the Tkatchenko–Scheffler pairwise dispersion scheme. Our relaxed lattice parameters are in agreement with experimental data. The hydrogen bonding between NH_2 and I ions is found to have a crucial role in FAPbI_3 stability. The first calculated band structure shows that HC(NH_2)_2PbI_3 has a direct bandgap(1.02 eV) at R-point, lower than the bandgap(1.53 eV) of CH_3NH_3PbI_3. The calculated density of states reveals that the strong hybridization of s(Pb)–p(I) orbital in valence band maximum plays an important role in the structural stability. The photo-generated effective electron mass and hole mass at R-point along the R–Γ and R–M directions are estimated to be smaller: m_e~*= 0.06 m0 and m_h~*= 0.08 m0 respectively, which are consistent with the values experimentally observed from long range photocarrier transport. The elastic properties are also investigated for the first time, which shows that HC(NH_2)_2PbI_3 is mechanically stable and ductile and has weaker strength of the average chemical bond. This work sheds light on the understanding of applications of HC(NH_2)_2PbI_3 as the perovskite in a planar-heterojunction solar cell light absorber fabricated on flexible polymer substrates.     

Formation of PAHs and soot platelets: multiconfiguration theoretical study of the key step in the ring closure–radical breeding polyyne‐based mechanism

Polyynes of general formula H? (C?C? )_nH are known to play a significant role in combustion and pyrolysis, possibly being intermediates in the formation of polycyclic aromatic hydrocarbons (PAHs) and soot. They have also been detected in astrophysical investigations. The key step in the polyyne‐based radical breeding mechanism for PAH growth is a cyclization, put forward by Krestinin, which implies disruption of electron couples, plausibly expected to be energy demanding. We explore the electronic features and energy requirements of such a process by quantum mechanical multiconfiguration methods (CASSCF and CASPT2). The features of the wavefunction are analyzed, and the free energy barriers are estimated over a wide range of temperatures, for three molecular models. The initial radical adduct A, generated by H ^. , HC?C ^. (ethynyl), or HC?C? C ^. H₂ ( propargyl ) addition to butadiyne (BD, HC?C? C?CH), undergoes a cyclization with the generation of two new radical centers. However, in most of the cases, one of these new singly occupied sp² orbitals has some overlap with the unpaired electron lobe already existent in A: some sort of bonding builds up and consequently the triradical character cannot be large. Only one model suggests a possible role of the radical breeding mechanism during combustion. Copyright © 2009 John Wiley & Sons, Ltd.     

Generation of high-current electron beams by a hollow cathode with a ferroelectric plasma source

This paper presents results and analysis of an experimental investigation of the operation of a hollow cathode (HC) with an incorporated ferroelectric plasma source (FPS). It was shown that the use of FPS based on a BaTi solid solution allows one to ignite and to sustain a 10²-10³ A HC discharge with duration of 10^-3-10^-5 s at background pressure of 5 x 10^-3 Pa while keeping the HC design with small dimensions. It was found that the development of the HC discharge is accompanied by formation at the surface of the FPS of dense plasma which serves as a powerful (hundreds of kW) pulsed source of current carrying electrons. Parameters of the HC plasma (radial distribution of the plasma density and temperature and plasma potential) for different discharge current amplitudes and two types of FPS are presented. Application of the FPS as an electron source in a diode under an accelerating pulse 300 kV and pulse duration 400 ns showed that the latter operates in a plasma pre-filled mode with a current amplitude up to 1.6 kA. Parameters of the diode and electron beam for different experimental conditions are presented and discussed.Received: 10 April 2003, Published online: 12 August 2003PACS: 52.50.Dg Plasma sources - 29.25.Bx Electron sources - 52.25.Tx Emission, absorption, and scattering of particles     

Experimental Structures of the Carbon Chains HC(7)N, HC(9)N, and HC(11)N by Isotopic Substitution

The effective structures (r(0)) of the three linear cyanopolyynes HC(7)N, HC(9)N, and HC(11)N have been determined to high accuracy by isotopic substitution, following detection in a supersonic molecular beam with a Fourier transform microwave spectrometer of all of the singly substituted rare isotopic species. For each chain, the lengths of the individual bonds have been determined to an accuracy of 0.001 ? or 0.1% toward the end of the chain and to 0.01 ? or 1.0% toward the center. The experimental structures are in excellent agreement with recent high-level theoretical calculations, or, in the case of HC(11)N, with extrapolation from HC(9)N. The three polyynes studied here represent the largest reactive carbon chain molecules for which accurate structures have been derived empirically. For HC(7)N and HC(9)N, it has been possible to resolve at high-resolution nitrogen hyperfine structure in the lower rotational transitions and determine eQq for all of the singly substituted isotopic species of HC(7)N and for normal HC(9)N. Copyright 2000 Academic Press.     

Application of hierarchical clustering to multi-parametric MR in prostate: Differentiation of tumor and normal tissue with high accuracy

PurposeHierarchical clustering (HC), an unsupervised machine learning (ML) technique, was applied to multi-parametric MR (mp-MR) for prostate cancer (PCa). The aim of this study is to demonstrate HC can diagnose PCa in a straightforward interpretable way, in contrast to deep learning (DL) techniques.MethodsHC was constructed using mp-MR including intravoxel incoherent motion, diffusion kurtosis imaging, and dynamic contrast-enhanced MRI from 40 tumor and normal tissues in peripheral zone (PZ) and 23 tumor and normal tissues in transition zone (TZ). HC model was optimized by assessing the combinations of several dissimilarity and linkage methods. Goodness of HC model was validated by internal methods.ResultsAccuracy for differentiating tumor and normal tissue by optimal HC model was 96.3% in PZ and 97.8% in TZ, comparable to current clinical standards. Relationship between input (DWI and permeability parameters) and output (tumor and normal tissue cluster) was shown by heat maps, consistent with literature.ConclusionHC can accurately differentiate PCa and normal tissue, comparable to state-of-the-art diffusion based parameters. Contrary to DL techniques, HC is an operator-independent ML technique producing results that can be interpreted such that the results can be knowledgeably judged.     

NUCLEATE POOL BOILING HEAT TRANSFER OF BINARY MIXTURES WITH DIFFERENT BOILING RANGES

The nucleate pool boiling heat transfer data on a smooth flat surface were measured for three binary mixtures of HC600a/HFC134a, HC600a/HC290, and HC600a/HFC23. Much effort was made to investigate the influence of the boiling range on the pool-boiling heat transfer performance. From the experimental results, the HC600a/HFC23 mixture with a wide boiling range showed lower heat transfer coefficients (HTCs) than the mixture with a narrow boiling range such as HC600a/HFC134a and HC600a/HC290 systems. The measured data were also compared with the results predicted by five well-known correlations. It can be found that the average deviation is less than 25% for mixtures with narrow boiling ranges, but a larger deviation for mixtures with wide boiling ranges.     

Scale-up of vortex based hydrodynamic cavitation devices: A case of degradation of di-chloro aniline in water

Hydrodynamic cavitation (HC) is being increasingly used in a wide range of applications. Unlike ultrasonic cavitation, HC is scalable and has been used at large scale industrial applications. However, no information about influence of scale on performance of HC is available in the open literature. In this work, we present for the first time, experimental data on use of HC for degradation of complex organic pollutants in water on four different scales (~200 times scale-up in terms of capacity). Vortex based HC devices offer various advantages like early inception, high cavitational yield and significantly lower propensity to clogging and erosion. We have used vortex based HC devices in this work. 2,4 dichloroaniline (DCA) – an aromatic compound with multiple functional groups was considered as a model pollutant. Degradation of DCA in water was performed using vortex-based HC devices with characteristic throat dimension, d_t as 3, 6, 12 and 38 mm with scale-up of almost 200 time based on the flow rates (1.3 to 247 LPM). Considering the experimental constraints on operating the largest scale HC device, the experimental data is presented here at only one value of pressure drop across HC device (280 kPa). A previously used per-pass degradation model was extended to describe the experimental data for the pollutant used in this study and a generalised form is presented. The degradation performance was found to decrease with increase in the scale and then plateaus. Appropriate correlation was developed based on the experimental data. The developed approach and presented results provide a sound basis and a data set for further development of comprehensive multi-scale modelling of HC devices.     

ANN based modelling of hydrodynamic cavitation processes: Biomass pre-treatment and wastewater treatment

We have developed artificial neural network (ANN) based models for simulating two application examples of hydrodynamic cavitation (HC) namely, biomass pre-treatment to enhance biogas and degradation of organic pollutants in water. The first case reports data on influence of number of passes through HC reactor on bio-methane generation from bagasse. The second case reports data on influence of HC reactor scale on degradation of dichloroaniline (DCA). Similar to most of the HC based applications, the availability of experimental data for these two applications is rather limited. In this work a systematic methodology for developing ANN model is presented. The models were shown to describe the experimental data very well. The ANN models were then evaluated for their ability to interpolate and extrapolate. Despite the limited data, the ANN models were able to simulate and interpolate the data for two very different and complex HC applications very well. The extrapolated results of biomethane generation in terms of number of passes were consistent with the intuitive understanding. The extrapolated results in terms of elapsed time were however not consistent with the intuitive understanding. The ANN model was able to generate intuitively consistent extrapolated results for degradation of DCA in terms of number of passes as well as scale of HC reactor. The results will be useful for developing quantitative models of complex HC applications.     

Oxidation of Sulphur pollutants in model and real fuels using hydrodynamic cavitation

Hydrodynamic Cavitation (HC) offers an attractive platform for intensifying oxidative desulphurization of fuels. In the first part of this work, we present new results on oxidising single ring thiophene in a model fuel over the extended range of volume fraction of organic phase from 2.5 to 80 v/v %. We also present influence of type and scale of HC device on performance of oxidative desulphurization. Further experiments revealed that oxidising radicals generated in-situ by HC alone were not able to oxidise dual ring thiophenes. External catalyst (formic acid) and oxidising agents (hydrogen peroxide, H₂O₂) were therefore used with HC. Based on our prior work with acoustic cavitation (AC), the volumetric ratios for H₂O₂ and formic acid were identified as 0.95 v/v % and 6.25 v/v % respectively. The data of oxidation of dual ring thiophenes with n-dodecane and n-hexane as model fuels and typical transport fuels (diesel, kerosene, and petrol) using these oxidant and catalyst is presented. The observed performance with HC was compared with results obtained from a stirred tank and AC set-up. The presented data indicates that HC is able to intensify oxidation of sulphur species. The presented results provide a sound basis for further developments on HC based oxidative desulphurization processes.     

Intensifying extraction of biomolecules from macroalgae using vortex based hydrodynamic cavitation device

Macroalgae have a tremendous potential to become an important renewable resource for valuable biomolecules and chemicals. New and improved ways of cell disruption and of enhancing rate as well as yield of extraction of valuable products from macroalgae are needed to fully realise this potential. In this work, hydrodynamic cavitation (HC) was used for intensifying rate and yield of extraction of phycoerythrin, proteins and carbohydrates from marine macroalgae Palmaria palmata. We use vortex-based HC devices which do not use small restrictions like orifice-based HC devices or moving parts like rotor–stator based HC devices. A bench scale setup with a nominal slurry flow rate of 20 LPM was established. Dried and powdered macroalgae was used. Influence of key operating parameters like pressure drop and number of passes on extraction performance (the rate and yield) was measured. A simple, yet effective model was developed and used for interpreting and describing experimental data. The results indicate that there exists an optimum pressure drop across the device at which extraction performance is maximum. The extraction performance with HC was found to be significantly better than the stirred vessels. HC has resulted in 2 to 20 times improvement in the rate of extraction of phycoerythrin (R-PE), proteins and carbohydrates. Based on the results obtained in this work, pressure drop of 200 kPa and number of passes through the HC devices of about 100 were found to be most effective for HC-assisted intensified extraction from macroalgae. The presented results and model will be useful for harnessing vortex-based HC devices for intensifying the extraction of valuable products from macroalgae.     

Investigation of Binding Properties of Umbelliferone (7Hydroxycoumarin) to Lysozyme

The binding interaction of lysozyme and umbelliferone (7hydroxcoumarin, 7HC) was investigated by UV–vis absorption and fluorescence quenching. It was obtained from fluorescence spectra that the fluorescence quenching of lysozyme by 7HC was probably a result of the formation of lysozyme-7HC complex and binding parameters were determined according to the Stern-Volmer equation. The effects of various common metal ions on the binding were also studied. The thermodynamic parameters were calculated at different temperatures which indicated that hydrophobic interaction. The binding distance (r) between the donor (lysozyme) and the acceptor (7HC) was 3.81 nm based on the Förster theory of non-radioactive resonance energy transfer.     

Hydrodynamic cavitation as a novel approach for pretreatment of oily wastewater for anaerobic co-digestion with waste activated sludge

Application of hydrodynamic cavitation (HC) was investigated with the objective of biogas production enhancement from co-digestion of oily wastewater (OWW) and waste activated sludge (WAS). Initially, the effect of HC on the OWW was evaluated in terms of energy consumption and turbidity increase. Then, several mixtures of OWW (with and without HC pretreatment) and WAS with the same concentration of total volatile solid were prepared as a substrate for co-digestion. Following, several batch co-digestion trials were conducted. To compare the biogas production, a number of digestion trials were also conducted with a mono substrate (OWW or WAS alone). The best operating condition of HC was achieved in the shortest retention time (7.5 min) with the application of 3 mm diameter orifice and maximum pump rotational speed. Biogas production from all co-digestion reactors was higher than the WAS mono substrate reactors. Moreover, biogas production had a direct relationship with OWW ratio and no major inhibition was observed in any of the reactors. The biogas production was also enhanced by HC pretreatment and almost all of the reactors with HC pretreatment had higher reaction rates than the reactors without pretreatment.     

Ionizational mechanism of heterogeneous chemiluminescence excitation. I

The kinetics and steady characteristics of the heterogeneous chemiluminescence (HC) of crystals is considered for an ionizational mechanism of excitation as a function of the sample temperature and the concentration of atoms and molecules of the exciting gas. The characteristic differences from the corresponding dependences for a direct mechanism of HC excitation are found (HC is luminescence due to the transformation of energy liberated in exothermic events of heterogeneous chemical reaction at the surface of solids into the energy of superequilibrium radiation of a solid).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 80–86, April, 1979.     

Hydrodynamic cavitation efficiently inactivates potato virus Y in water

Waterborne plant viruses can destroy entire crops, leading not only to high financial losses but also to food shortages. Potato virus Y (PVY) is the most important potato viral pathogen that can also affect other valuable crops. Recently, it has been confirmed that this virus is capable of infecting host plants via water, emphasizing the relevance of using proper strategies to treat recycled water in order to prevent the spread of the infectious agents. Emerging environmentally friendly methods such as hydrodynamic cavitation (HC) provide a great alternative for treating recycled water used for irrigation. In the experiments conducted in this study, laboratory HC based on Venturi constriction with a sample volume of 1 L was used to treat water samples spiked with purified PVY virions. The ability of the virus to infect plants was abolished after 500 HC passes, corresponding to 50 min of treatment under pressure difference of 7 bar. In some cases, shorter treatments of 125 or 250 passes were also sufficient for virus inactivation. The HC treatment disrupted the integrity of viral particles, which also led to a minor damage of viral RNA. Reactive species, including singlet oxygen, hydroxyl radicals, and hydrogen peroxide, were not primarily responsible for PVY inactivation during HC treatment, suggesting that mechanical effects are likely the driving force of virus inactivation. This pioneering study, the first to investigate eukaryotic virus inactivation by HC, will inspire additional research in this field enabling further improvement of HC as a water decontamination technology.     

Degradation of 2,4-dinitrophenol using a combination of hydrodynamic cavitation,chemical and advanced oxidation processes

In the present work, degradation of 2,4-dinitrophenol (DNP), a persistent organic contaminant with high toxicity and very low biodegradability has been investigated using combination of hydrodynamic cavitation (HC) and chemical/advanced oxidation. The cavitating conditions have been generated using orifice plate as a cavitating device. Initially, the optimization of basic operating parameters have been done by performing experiments over varying inlet pressure (over the range of 3–6 bar), temperature (30 °C, 35 °C and 40 °C) and solution pH (over the range of 3–11). Subsequently, combined treatment strategies have been investigated for process intensification of the degradation process. The effect of HC combined with chemical oxidation processes such as hydrogen peroxide (HC/H₂O₂), ferrous activated persulfate (HC/Na₂S₂O₈/FeSO₄) and HC coupled with advanced oxidation processes such as conventional Fenton (HC/FeSO₄/H₂O₂), advanced Fenton (HC/Fe/H₂O₂) and Fenton-like process (HC/CuO/H₂O₂) on the extent of degradation of DNP have also been investigated at optimized conditions of pH 4, temperature of 35 °C and inlet pressure of 4 bar. Kinetic study revealed that degradation of DNP fitted first order kinetics for all the approaches under investigation. Complete degradation with maximum rate of DNP degradation has been observed for the combined HC/Fenton process. The energy consumption analysis for hydrodynamic cavitation based process has been done on the basis of cavitational yield. Degradation intermediates have also been identified and quantified in the current work. The synergistic index calculated for all the combined processes indicates HC/Fenton process is more feasible than the combination of HC with other Fenton like processes.     

Rietveld and pair distribution function study of Hägg carbide using synchrotron X‐ray diffraction

Fischer–Tropsch (FT) synthesis is an important process in the manufacturing of hydrocarbons and oxygenated hydrocarbons from mixtures of carbon monoxide and hydrogen (syngas). The reduced iron catalyst reacts with carbon monoxide and hydrogen to form bulk Fe₅C₂ Hägg carbide (χ‐HC) during FT synthesis. Arguably, χ‐HC is the predominant catalyst phase present in the working iron catalyst. Deactivation of the working catalyst can be due to oxidation of χ‐HC to iron oxide, a step‐wise decarburization to cementite (θ‐Fe₃C), carbon formation or sintering with accompanying loss of catalytic performance. It is therefore critical to determine the precise crystal structure of χ‐HC for the understanding of the synthesis process and for comparison with the first‐principles ab initio modelling. Here the results of high‐resolution synchrotron X‐ray powder diffraction data are reported. The atomic arrangement of χ‐HC was confirmed by Rietveld refinement and subsequent real‐space modelling of the pair distribution function (PDF) obtained from direct Fourier transformation. The Rietveld and PDF results of χ‐HC correspond well with that of a pseudo‐monoclinic phase of space group Pī [a = 11.5661 (6) Å, b = 4.5709 (1) Å, c = 5.0611 (2) Å, α = 89.990 (5)°, β = 97.753 (4)°, γ = 90.195 (4)°], where the Fe atoms are located in three distorted prismatic trigonal and one octahedral arrangement around the central C atoms. The Fe atoms are distorted from the prismatic trigonal arrangement in the monoclinic structure by the change in C atom location in the structure.     

Degradation of reactive orange 4 dye using hydrodynamic cavitation based hybrid techniques

In the present work, degradation of reactive orange 4 dye (RO4) has been investigated using hydrodynamic cavitation (HC) and in combination with other AOP’s. In the hybrid techniques, combination of hydrodynamic cavitation and other oxidizing agents such as H₂O₂ and ozone have been used to get the enhanced degradation efficiency through HC device. The hydrodynamic cavitation was first optimized in terms of different operating parameters such as operating inlet pressure, cavitation number and pH of the operating medium to get the maximum degradation of RO4. Following the optimization of HC parameters, the degradation of RO4 was carried out using the combination of HC with H₂O₂ and ozone. It has been found that the efficiency of the HC can be improved significantly by combining it with H₂O₂ and ozone. The mineralization rate of RO4 increases considerably with 14.67% mineralization taking place using HC alone increases to 31.90% by combining it with H₂O₂ and further increases to 76.25% through the combination of HC and ozone. The synergetic coefficient of greater than one for the hybrid processes of HC + H₂O₂ and HC + Ozone has suggested that the combination of HC with other oxidizing agents is better than the individual processes for the degradation of dye effluent containing RO4. The combination of HC with ozone proves to be the most energy efficient method for the degradation of RO4 as compared to HC alone and the hybrid process of HC and H₂O₂.     

Hydrodynamic cavitation degradation of Rhodamine B assisted by Fe3+-doped TiO2: Mechanisms,geometric and operation parameters

In this paper, a novel method, hydrodynamic cavitation (HC) combined with Fe³⁺-doped TiO₂, for the degradation of organic pollutants in aqueous solution is reported. The venturi tubes with different geometric parameters (size, shape and half divergent angle) are designed to obtain a strong HC effect. The structure, morphology and chemical composition of prepared Fe³⁺-doped TiO₂ as catalyst are characterized via using XRD, SEM, TEM, XPS, UV-vis DRS and PL methods. The effects of added TiO₂ (heat-treated at different temperatures for different times) and Fe³⁺-doped TiO₂ (with different mole ratios of Fe and Ti) on the HC catalytic degradation of RhB are discussed. The influences of operation parameters including inlet pressure, initial RhB concentration and operating temperature on the HC catalytic degradation of RhB are studied by Box-Behnken design (BBD) and response surface methodology (RSM). Under 3.0 bar inlet pressure for 10 mg/L initial concentration of RhB solution at 40 °C operating temperature in the presence of Fe³⁺-doped TiO₂ with 0.05:1.00 M ratio of Fe and Ti, the best HC degradation ratio can be obtained (91.11%). Furthermore, a possible mechanism of HC degradation of organic pollutants in the presence of Fe³⁺-doped TiO₂ is proposed. Perhaps, this study may provide a feasible method for a large-scale treatment of dye wastewater.