Low Residual Pressure Research Articles

Simultaneous removal of NOx and dust with integrated catalytic filter: Interactions between NH3-SCR and filtration processes

The integrated selective catalytic reduction of nitrogen oxides by NH3 (NH3-SCR) and dust filtration technology can effectively reduce the energy consumption and space of the flue gas purification system. Herein, a novel catalytic filter is fabricated by in situ depositing FeWOx heterogeneous catalyst onto stainless-steel-fiber filter (named as FeWOx/SSFF), which displays excellent deNOx performance (>85 % NOx conversion and 96 % N2 selectivity) with superior H2O and SO2 tolerance, as well as great dedust efficiency (>99.99 % and low residual pressure drop). The suitable oxygen mobility and enhanced charge transfer ability at the crystalline-amorphous interface contribute well to the excellent SCR performance, and the low pressure drop is promoted by the well dispersion of FeWOx species on the SSFF. Notably, a volcanic relationship between dedust process and SCR performance was obtained, due to the boosting of dedust process for the denitrification, which was confirmed by computational fluid dynamics (CFD). Besides, excessive dust-cake could inhibit SCR performance owing to catalytic site being covered by dust particles. Accordingly, SCR process hardly affected dedust efficiency and residual pressure drop. This work reveals the interactions between SCR and dedust processes, and paves a way to design novel catalytic filters for simultaneously removing dust and gas pollutants at practical conditions.

Germanium Nanoparticles Prepared by Laser Ablation in Low Pressure Helium and Nitrogen Atmosphere for Biophotonic Applications.

Due to particular physico-chemical characteristics and prominent optical properties, nanostructured germanium (Ge) appears as a promising material for biomedical applications, but its use in biological systems has been limited so far due to the difficulty of preparation of Ge nanostructures in a pure, uncontaminated state. Here, we explored the fabrication of Ge nanoparticles (NPs) using methods of pulsed laser ablation in ambient gas (He or He-N2 mixtures) maintained at low residual pressures (1–5 Torr). We show that the ablated material can be deposited on a substrate (silicon wafer in our case) to form a nanostructured thin film, which can then be ground in ethanol by ultrasound to form a stable suspension of Ge NPs. It was found that these formed NPs have a wide size dispersion, with sizes between a few nm and hundreds of nm, while a subsequent centrifugation step renders possible the selection of one or another NP size fraction. Structural characterization of NPs showed that they are composed of aggregations of Ge crystals, covered by an oxide shell. Solutions of the prepared NPs exhibited largely dominating photoluminescence (PL) around 450 nm, attributed to defects in the germanium oxide shell, while a separated fraction of relatively small (5–10 nm) NPs exhibited a red-shifted PL band around 725 nm under 633 nm excitation, which could be attributed to quantum confinement effects. It was also found that the formed NPs exhibit high absorption in the visible and near-IR spectral ranges and can be strongly heated under photoexcitation in the region of relative tissue transparency, which opens access to phototherapy functionality. Combining imaging and therapy functionalities in the biological transparency window, laser-synthesized Ge NPs present a novel promising object for cancer theranostics.

Injection and Combustion Analysis of Pure Rapeseed Oil Methyl Ester (RME) in a Pump-Line-Nozzle Fuel Injection System

This work suggests an interpretation to the quantitatively higher formation of NOx in a compression ignition (CI) engine when fueled with pure biodiesel (B100). A comparative study about the use of rapeseed oil methyl ester (RME) and diesel fuel mixtures on injection timing, in-chamber pressure, heat release rate, and NOx emissions were carried out using a diesel engine equipped with a pump-line-nozzle injection system. Such engines are still widely adopted mainly in agriculture, as the fleet of agricultural machinery is particularly old (often over 20 years) and the use of biofuels can reduce the environmental footprint of the sector. This work aims to supply some general explanations and figures useful to interpret the phenomena occurring within the fuel line and in the combustion process when using biodiesel, as well as in engines with different construction characteristics and fueling systems. Given the contradictory results available in the literature, the so-called “biodiesel NOx effect” cannot be explained solely by the different physical properties of biodiesel (in particular, a higher bulk modulus). Experimental results show that, with the same pump settings, the start of injection with the RME is slightly advanced while the injection pressure values remain almost the same. With the RME, the pressure in the injection line increases faster due to its greater bulk modulus but the pressure rise starts from a lower residual pressure. The start of combustion takes place earlier, the heat release during the premixed phase is steeper, and a higher peak is reached. The NOx emissions with the RME are at least 9% higher when compared to mineral diesel fuel. The greater amount of the RME injected per cycle compensates for its minor lower heating value, and the brake torque at full load is similar to the two analyzed fuels. Finally, a variation of the pump line timing is evaluated in order to assess the effect of the delay and the advance of the injection on the performance of the engine and on the emissions. A viable and simple solution in the variation of the injection strategy is suggested to counterbalance the biodiesel NOx effect.

Morphology and photoluminescence properties of silicon nanoparticles deposited in helium-nitrogen mixtures maintained at low residual pressures

We elaborated a technique of pulsed laser ablation in gas mixtures (He-N2), maintained under residual pressures of 0.5–5 Torr to deposit silicon (Si)-based nanostructured films on a substrate. We show that the deposited films can exhibit strong photoluminescence (PL) emission with the position of peaks depending on the pressure of ambient gas and the ratio of gases in the mixture. Nanostructured films prepared in pure He gas exhibited a strong band in the infrared range (around 760 nm) and a weak band in the green range (550 nm), which were attributed to quantum-confined excitonic states in small Si nanocrystals and radiative transitions via the localized electronic states in silicon suboxide coating, respectively. In contrast, nanostructured films prepared in He-N2 mixtures exhibited more intense “green-yellow” PL band centered at 580 nm, which was attributed to a radiative recombination in amorphous oxynitride (a-SiNxOy) coating of Si nanocrystals. We also present a detailed analysis of morphology of nanostructures Si-based films prepared by laser ablation. Finally, we show that the nanocrystals can be removed from the substrate and milled by ultrasound to form aqueous solutions of colloidal Si nanopartiles. The fabricated Si-based nanocrystals present a promising object for theranostics, combining imaging functionality based on PL emission and a series of therapy functionalities (photo and radiofrequency hyperthermia, photodynamic therapy).

Strongly temperature-dependent, anomalous secondary electron emission of liquid lithium surfaces exposed to a plasma

• First time reported SEE of a CPS wetted with liquid lithium exposed to a plasma. • Formation and dissolution of a strongly temperature dependent surface oxide film. • SEE values from ~0.5 for clean surfaces to ~2 for heavily oxidized samples. • Exposure to 3 × 10 −7 Torr during one hour increases the SEE to values of about 2. • Annealing at increasing temperatures decreases the SEE to lower values. Electron-induced secondary electron emission (SEE) on a liquid lithium surface confined in a capillary porous system (CPS) and exposed to a plasma is reported for the first time. The liquid lithium surface is exposed to the bombardment of a suprathermal electron flux with energies up 150 eV created in a low pressure He Dc-Glow discharge. Various methods of surface oxidation have been used to reproduce realistic conditions in fusion plasma experiments. Exposure to very low residual gas pressures (around 3 × 10 −7 Torr) is enough to increase the maximum of the SEE to values of about 2. The formation and dissolution of a surface oxide film is strongly temperature dependent and plays an important role in the resulting SEE yield and its time evolution: values have been found to range from ~0.8 for clean surfaces to ~2 for samples that have been heavily oxidized. In the case of O 2 molecule exposure, a clear difference with temperature was observed. The molecular exposure at 330 °C had a much stronger effect on the increase in SEE than the molecular exposure at 220 °C. These results have a direct impact on the development of lithium-based divertor targets in fusion as well as in the understanding of the SEE characteristics of contaminated liquid surfaces, which has never been reported before.

Oxygen Pressure Influence on Properties of Nanocrystalline LiNbO3 Films Grown by Laser Ablation.

Energy conversion devices draw much attention due to their effective usage of energy and resulting decrease in CO2 emissions, which slows down the global warming processes. Fabrication of energy conversion devices based on ferroelectric and piezoelectric lead-free films is complicated due to the difficulties associated with insufficient elaboration of growth methods. Most ferroelectric and piezoelectric materials (LiNbO3, BaTiO3, etc.) are multi-component oxides, which significantly complicates their integration with micro- and nanoelectronic technology. This paper reports the effect of the oxygen pressure on the properties of nanocrystalline lithium niobate (LiNbO3) films grown by pulsed laser deposition on SiO2/Si structures. We theoretically investigated the mechanisms of LiNbO3 dissociation at various oxygen pressures. The results of x-ray photoelectron spectroscopy study have shown that conditions for the formation of LiNbO3 films are created only at an oxygen pressure of 1 × 10−2 Torr. At low residual pressure (1 × 10−5 Torr), a lack of oxygen in the formed films leads to the formation of niobium oxide (Nb2O5) clusters. The presented theoretical and experimental results provide an enhanced understanding of the nanocrystalline LiNbO3 films growth with target parameters using pulsed laser deposition for the implementation of piezoelectric and photoelectric energy converters.

Improving filtration and pulse-jet cleaning performance of metal web filter media by coating with polytetrafluoroethylene microporous membrane

The metal web filter media has been widely used to purify high-temperature exhaust gas because of its good durability and reliability. Although it has fine high-temperature resistance, its filtration efficiency for fine particles is relatively low. In this study, we developed a new type of composite filter of metal web coated with polytetrafluoroethylene (PTFE) membrane, which combined the high-temperature resistance of the metal web filter and the excellent filtration performance of the membrane-coated filter media. The performance parameters of the composite filter, including pressure drop, filtration efficiency, regeneration efficiency, adhesive force, and high-temperature resistance, were investigated experimentally, and compared with those of the metal web filter and polyester fiber coated with PTFE membrane filter. Although the composite filter yielded a higher pressure drop, it exhibited a high particle collection efficiency. At a face velocity of 10.23cm/s, the filtration efficiency of the composite filter was 99.32 %. This was 1.23 and 0.10 % higher than that of the metal web filter and polyester coated with PTFE membrane filter, respectively. In addition, the composite filter has the characteristics of small cake/fabric adhesion force, low residual pressure drop, high regeneration efficiency, and long cleaning interval. The average cleaning interval and residual pressure drop of the composite filter were 421s and 425.0Pa, respectively, whereas those of the metal web filter were 291s and 658.5Pa, respectively; those of the polyester coated with PTFE membrane filter were 415s and 443.2Pa, respectively. Furthermore, the filtration test at high temperatures and thermogravimetric analysis demonstrated that the composite filter has an excellent thermal stability. At a temperature of 260°C, the average dust emission concentration of the polyester coated with PTFE membrane filter was 2.86 times larger than that of the composite filter (0.532mg/m3).

Effect of moisture adsorption on the broadband dielectric response of SiO2-based nanoporous glass

Atmospheric water adsorbed by porous materials may significantly change its electrodynamic response in a wide frequency range. Mechanical and chemical stabilities of silicon dioxide along with a proven manufacturing method of porous SiO2 samples made it convenient for studying the effects of moisture adsorption on various parameters of the porous media. We report the dielectric properties of SiO2-based nanoporous glass in the frequency range of 20 Hz–400 THz at ambient atmospheric conditions and at a low residual pressure of ≤1 mbar. We observed a significant low-frequency dispersion of the complex dielectric permittivity and enhancement of dielectric loss for the porous sample exposed to the ambient moisture. In the terahertz range, the change in dielectric response is smaller and correlates with the moisture saturation of the sample.

Testing collapse models with levitated nanoparticles: Detection challenge

We consider a nanoparticle levitated in a Paul trap in ultrahigh cryogenic vacuum, and look for the conditions which allow for a stringent noninterferometric test of spontaneous collapse models. In particular we compare different possible techniques to detect the particle motion. Key conditions which need to be achieved are extremely low residual pressure and the ability to detect the particle at ultralow power. We compare three different detection approaches based respectively on a optical cavity, optical tweezer and a electrical readout, and for each one we assess advantages, drawbacks and technical challenges.

Filtration Performance Characteristics of Sticky Aerosol Using Calcium Hydroxide

This study examined the performance of removing aerosol upon a flow rate variable by agglomerating sticky aerosol with calcium hydroxide and removing cohesive aerosol through an experimental apparatus, simulating an actual painting booth. As a result of examining the performance of the filter by fixing the paint spray quantity, the calcium hydroxide input and the filtration area under variable flow rates of 5, 10, and 15 Nm3/min, we confirmed that the filter performance has long average aerosol removing intervals at the 5 Nm3/min flow rate. At the 5 Nm3/min flow rate, there is a low residual pressure drop trend and high fractional collection efficiency, and a high level of total collection efficiency is maintained at 99.42%. When the flow rate is less than 5 Nm3/min, the aerosol settling and experimentation was impossible. With this research, the optimal conditions for the use of sticky aerosol have been examined.

Deflation behavior and related safety assessment of an air-supported membrane structure

As a large span structure that might serve many occupants, the deflation behavior of an air-supported membrane structure under emergency deflation is of critical importance for safety assessment on occupants' evacuation but has received few studies. This paper presents experimental field tests and numerical simulations on deflation behaviors of a real-life air-supported membrane structure. A numerical model is employed in deflation simulation which considers tension-only membrane based on the vector form intrinsic finite element method for membrane motion analysis and pressure change due to air loss in deflation according to the classic thermodynamics. The correctness and the applicability of the model are verified by good correlation of prediction in response of pressure, displacement, and wrinkling formation and development of the structure with those measured and observed in deflation tests. The study shows that the structure in emergency deflation will lose its high pressure quickly first, and then sustain deflating under low residual pressure for a long time. The model is further used in parametrical analysis on factors that affect deflation progress and a complete deflation simulation to predict the whole collapse process, which is accordingly characterized by two typical phases, the tender deflation stage and the severe deflation stage. In tender stage the structure holds a relatively plump form, while in the severe stage the structure bears low decreasing residual pressure, membrane losses most tension stress so that many elements wrinkle and the structure experiences instability. Due to wrinkling, the residual pressure is found to approximately balance with its vertical loads. As a result, the feasible method proposed based on the residual pressure in deflation is very simple and reliable to predict the deflation duration and evaluate maximum escape area for deflation assessment of the studied structure.

Influence of an Added Fraction of Hygroscopic Salt Particles on the Operating Behavior of Surface Filters for Dust Separation

AbstractAn innovative approach to manipulating the operating behavior of surface filters for dust separation by raw gas conditioning using hygroscopic salt particles is described. The basis for a targeted manipulation of the operating behavior of surface filters is the fact that a favorable performance adjusts itself at long cycle times. These are obtained by a slow increase in pressure drop during the filtration phase and by a low residual pressure drop after the regeneration. Technically, such states can be realized by so‐called raw gas conditioning. The deliquescence and efflorescence properties of hygroscopic salt particles can be considered as possibilities for the formation of solid bridges between dust particles in the dust cake. With this concept, a flexible and targeted strengthening of the cohesion in the dust cake without an accompanying modification of the adhesion between the cake layer and the filter medium is theoretically possible.

Beam transport and space charge compensation strategies (invited).

The transport of intense ion beams is affected by the collective behavior of this kind of multi-particle and multi-species system. The space charge expressed by the generalized perveance dominates the dynamical process of thermalisation, which leads to emittance growth. To prevent changes of intrinsic beam properties and to reduce the intensity dependent focusing forces, space charge compensation seems to be an adequate solution. In the case of positively charged ion beams, electrons produced by residual gas ionization and secondary electrons provide the space charge compensation. The influence of the compensation particles on the beam transport and the local degree of space charge compensation is given by different beam properties as well as the ion beam optics. Especially for highly charged ion beams, space charge compensation in combination with poor vacuum conditions leads to recombination processes and therefore increased beam losses. Strategies for providing a compensation-electron reservoir at very low residual gas pressures will be discussed.

The Analysis for Crystallization of Sn-Pb Alloys Using Acoustic Emission Testing about Wind Turbine Root Materials

Regular researches of system Sn-Pb alloys with use AE are carried out in various crystallization conditions. In the given researches the technique has been used, which allow to divide the signals radiated with plastic deformation and crack's formation and development from each process. In the metals and alloys majority radiation of AE signals begins in the middle of crystallization's area and comes to an end at the moment of the crystallization termination However in a number of materials AE signals have been registered below an excess point on a cooling curve in a firm condition. Essential influence of small impurity on AE feature and is revealed at crystallization AE character with crystallization of pure metals is defined by a kind of a crystal lattice. Linear dependence total AE from cooling rate is established Influence of superfluous and low residual pressure on AE character established with crystallization.

Implementation of a novel hydrogen direct-injection concept in single and multi-cylinder engines: CFD, experimental and engine powertrain design studies

A novel low-pressure hydrogen direct-injection system, characterised by low storage residual pressure and simple mechanical solutions, has been implemented in single and multi-cylinder engines. Based on two-step operation, this system keeps hydrogen metering apart from injection. The first step relates to the system with constant H2 flow rate and variable opening duration. The second step is characterised by variable H2 flow rate and constant angular duration. A prototype has been realised modifying a single-cylinder production engine, following the results of a wide CFD activity during which in-cylinder hydrogen injection and mixing phases have been simulated to investigate how valve and seat-valve geometries affect mixing characteristics. The prototype engine ran properly at full load, without pre-ignition, knocking or roughness even with stoichiometric or slightly rich mixtures, providing higher maximum power than with gasoline. At part load the engine worked correctly even with very lean mixtures. Current research is directed to explore the feasibility of applying the two-step injection concept in a multi-cylinder engine. The CFD analysis together with the design study aimed to integrate the injection system in the engine powertrain are shown and discussed.

Botulinum toxin treatment for oropharyngeal dysphagia in patients with stroke

In a previous pilot study, we demonstrated that a single injection of botulinum toxin A (BTX-A) in the cricopharyngeus muscle is effective in patients with neurologic dysphagia with upper esophageal sphincter (UES) opening dysfunction and presence of some pharyngeal contraction (>25mmHg). The aim of this study was to confirm the long-lasting efficacy of this procedure after stroke. We prospectively studied 23 patients with stroke for at least 6months before administration of a BTX-A injection. Baseline diagnosis of UES opening dysfunction and presence of some pharyngeal contraction were assessed by videofluoroscopy (VFS) and esophageal manometry (EM). Clinical and VFS follow-up was made at 3weeks and 3, 6, and 12months postinjection. Eighteen patients (78%) were fed by gastrostomy tube prior to treatment. Videofluoroscopy showed UES relaxation impairment, residue in pyriform sinuses, and aspiration in all cases. After BTX-A, the number of patients with aspiration and pharyngeal residue decreased to 52% and 70%, respectively (p<0.05 for both); residue was severe in only 4%. Esophageal manometry showed a mean pharyngeal amplitude 66.8mmHg (range: 25-120mmHg). We observed a significant improvement in feeding mode during follow-up: after 3months, 70% of patients were eating exclusively by mouth. Lower residual pressure and minor pharyngeal delay time at baseline were all predictive factors for treatment effectiveness. A single injection of BTX-A is efficacious for a period of at least 12months in improving oropharyngeal dysphagia in stroke patients with UES opening dysfunction and some pharyngeal contraction (>25mmHg).

When do residual gas electrons destabilize an ion beam?

The stability of coasting ion beams against residual gas electrons accumulating in the beam potential is studied. We analyze the instability threshold intensities for ion beams of different charge state and mass using the linear centroid theory. Numerical simulations are used to study the thresholds for realistic transverse beam distributions. The effect of Coulomb collisions between beam ions and electrons is analyzed analytically and numerically using the Langevin equations. We show that at low residual gas pressures Coulomb collisions limit the neutralization degree of the ion beam to values below the instability threshold.

Investigating the surface of particles of ultradispersed copper powders obtained by gas-phase condensation

Ultradispersed powders of metal copper obtained by evaporation-condensation technology are investigated. It is shown that, depending on the evaporation rate, various dispersities and degrees of agglomeration of copper powders are attained with the conservation of the weight fraction of copper in them no lower than 99.0%. It is established using the XPES method that a 5- to 6-nm-thick CuO layer (on the surface of which there is a Cu2O layer up to 1 nm thick) is always present on the surface of Cu particles of all powders under consideration. It is assumed that, because of a low residual air pressure in industrial installations, the surface layer of copper oxidizes to the lower oxide Cu2O during the evaporation of metal, while oxide CuO is formed as a result of the decomposition of Cu2O during the condensation of copper particles. The smaller the particle size of the powder is, the higher the content of oxides is.

Internal anal sphincter relaxation associated with bisacodyl‐induced colonic high amplitude propagating contractions in children with constipation: a colo‐anal reflex?

Describe the association of internal anal sphincter (IAS) relaxation with colonic high- amplitude peristaltic contractions (HAPCs). Retrospective review of colon manometry tracings of children with constipation to determine the IAS relaxation characteristics associated with HAPC's (HAPC-IASR) events and compare them to the those seen during the performance of the anorectal manometry (ARMRAIR) events. A total of 70 HAPC- IASRs were observed in 15 patients, 65 after bisacodyl, two during fasting and three after a meal. In 64% of events, the IAS relaxation started when the HAPC reached left colon and in 36% as proximal as the hepatic flexure. High- amplitude peristaltic contraction propagation seems to be important in HAPC-IASR characteristics; those propagating distal to sigmoid colon demonstrated larger and longer IAS relaxation as well as lower residual pressure, but equivalent resting pressure compared with HAPC's ending proximal to sigmoid colon. Although IAS resting pressure was comparable for ARM-RAIRs and HAPC-IASRs, the duration and magnitude of anal relaxation was higher, and the anal residual pressure was lower in HAPC-IASRs. We demonstrated that IAS relaxation in constipated children is associated with HAPCs migrating in the proximal and distal colon; in most cases, starting when peristalsis is migrating through left colon and in an important proportion while migrating proximally. We also demonstrated that HAPC-IASRs are different from ARM-RAIRs suggesting a neurally mediated reflex. Finally, the IAS relaxation characteristics are highly dependent on the degree of propagation of HAPCs, which could have important implications in the understanding of defecation disorders.

Effect of peroral endoscopic myotomy on esophageal manometry in patients with achalasia

Objective To determine the effect of peroral endoscopic myotomy （POEM） on esophageal manometry in patients with aehalasia. Methods Esophageal manometric data of 3 patients with aehala- sia before and after POEM was retrospectively analyzed. Results The post-POEM lower esophageal sphincter pressure （LESP） and upper esophageal sphincter residual pressure （UESRP） were significantly lower than those of before （ P 〈 0. 05 ）. The average post-POEM lower esophageal sphincter residual pressure （LESRP） decreased （P 〉 0. 05 ）, with significant decrease to normal level in 2 patients and almost unchanged （above normal） in the other. The esophageal aperistalsis remained after POEM in all 3 patients. The lower esophageal sphincter relaxing rate （LESRR） remained lower than normal after POEM as before. The average upper esophgeal sphincter pressure （UESP） decreased after POEM without statistical significance. Conclusion POEM can improve the outcomes of esophageal manometry in patients with aehalasia in the short term. Key words: Esophageal aehalasia; Esophageal manometery; Peroral endoscopic myotomy