Unwanted Emissions Research Articles

Self-Shielding of X-ray Emission from Ultrafast Laser Processing Due to Geometrical Changes of the Interaction Zone.

Materials processing with ultrashort laser pulses is one of the most important approaches when it comes to machining with very high accuracy. High pulse repetition rates and high average laser power can be used to attain high productivity. By tightly focusing the laser beam, the irradiances on the workpiece can exceed 1013 W/cm2, and thus cause usually unwanted X-ray emission. Pulsed laser processing of micro holes exhibits two typical features: a gradual increase in the irradiated surface within the hole and, with this, a decrease in the local irradiance. This and the shielding by the surrounding material diminishes the amount of ionizing radiation emitted from the process; therefore, both effects lead to a reduction in the potential X-ray exposure of an operator or any nearby person. The present study was performed to quantify this self-shielding of the X-ray emission from laser-drilled micro holes. Percussion drilling in standard air atmosphere was investigated using a laser with a wavelength of 800 nm a pulse duration of 1 ps, a repetition rate of 1 kHz, and with irradiances of up to 1.1·1014 W/cm. The X-ray emission was measured by means of a spectrometer. In addition to the experimental results, we present a model to predict the expected X-ray emission at different angles to the surface. These calculations are based on raytracing simulations to obtain the local irradiance, from which the local X-ray emission inside the holes can be calculated. It was found that the X-ray exposure measured in the surroundings strongly depends on the geometry of the hole and the measuring direction, as predicted by the theoretical model.

Effects of a Nonlinear Boundary Condition on the Steady Aerodynamics of Porous Airfoils

This paper considers the lift coefficient of an airfoil with nonzero prescribed thickness and camber, along with a prescribed porosity distribution in a steady incompressible flow. In similar prior work, considering a Darcy-type porosity condition on the airfoil surface provides a Fredholm integral equation that can be solved exactly for Hölder-continuous porosity distributions. However, the generated lift predicted by the model diverges from the experimental data for porous airfoils with large values of the porosity parameter. This indicates a fundamental characteristic is missing in the mathematical model. Consequently, in this paper, the (linear) Darcy porosity condition is replaced by the (nonlinear) Forchheimer porosity condition. The Forchheimer porosity condition is decomposed into linear sections and furnishes a modified system of Fredholm integral equations, enabling an approximate solution by superposition for Hölder-continuous porosity distributions. The solution is then verified against the SD7003 airfoil results, and the comparison shows better agreement than considering the Darcy porosity condition. The methodology and results presented here may be combined with previous work on the aeroacoustics of porous airfoils with a Forchheimer boundary condition to address the conflicting aims of improving aerodynamic performance while reducing unwanted aeroacoustic emissions.

Aeroacoustic Tonal Noise: Theoretical and Practical Approaches for Flow and Sound Analysis

Aeroacoustic tonal noise, often caused by self-excited flow oscillations, represents a significant challenge in various engineering applications. One prominent example is the cavity tone, responsible for undesirable sound emissions from gaps found on the surfaces of vehicles, door gaps, and pantographs of trains. A similar configuration, known as the edge tone, appears in musical instruments. This paper aims at presenting a comprehensive framework consisting of practical and theoretical tools to analyze these complex flows and the resulting emitted sound. These tools can facilitate the development of mitigation strategies and the optimization of design parameters to minimize unwanted noise emissions.

Stable Spiro‐Linked Terfluorenes with Triphenylamine Pendants as Deep Blue Emitters for Solution‐Processed Organic Light‐Emitting Diodes

AbstractHerein, we reported new spiro‐linked terfluorenes (TF1 and TF2) as solution‐processible hole‐transporting‐free deep‐blue fluorescent emitters for simple structured organic light‐emitting diodes (OLEDs). They were designed and synthesized by incorporating triphenylamine pendants into the C9 positions of the spiro‐linked terfluorene, resulting in a criss‐cross configuration of the two terfluorene backbones and a highly bulky molecular geometry from the pendant groups. Consequently, TF1 and TF2 exhibited good quality thin films by spin‐coating, stable deep blue emissions with no unwanted long wavelength emission after prolonged thermal annealing and UV exposure, shallow highest occupied molecular orbital energy levels (−5.36–−5.37 eV), decent hole mobilities (1.09–1.23×10−7 cm2 V−1 s−1), and high thermal stability, and effectively employed as non‐doped emissive layers in the OLEDs. Particularly, TF2‐based solution‐processed OLED displayed a bright deep blue emission with superior EL performance (turn‐on voltage (Von) of 3.4 V, external quantum efficiency (EQEmax) of 3.82 %, and luminance efficiency (LEmax) of 5.22 cd A−1). This outstanding EL performance of the non‐doped solution‐processed deep blue OLED could be attributed to the effective molecular design, and this work presented a new approach for constructing effective blue emitters based on oligofluorenes.

Structurally stable but functionally disrupted marine microbial communities under a future climate change scenario: Potential importance for nitrous oxide emissions

The blue mussel Mytilus edulis is a widespread and abundant bivalve species along the North Sea with high economic and ecological importance as an engineer species. The shell of mussels is intensively colonized by microbial organisms that can produce significant quantities of nitrous oxide (N2O), a potent greenhouse gas. To characterize the impacts of climate change on the composition, structure and functioning of microbial biofilms on the shell surface of M. edulis, we experimentally exposed them to orthogonal combinations of increased seawater temperature (20 vs. 23 °C) and decreased pH (8.0 vs. 7.7) for six weeks. We used amplicon sequencing of the 16S rRNA gene to characterize the alpha and beta diversity of microbial communities on the mussel shell. The functioning of microbial biofilms was assessed by measuring aerobic respiration and nitrogen emission rates. We did not report any significant impacts of climate change treatments on the diversity of mussel microbiomes nor on the structure of these communities. Lowered pH and increased temperature had antagonistic effects on the functioning of microbial communities with decreased aerobic respiration and N2O emission rates of microbial biofilms in acidified seawater compared to increased rates in warmer conditions. An overriding impact of acidification over warming was finally observed on N2O emissions when the two factors were combined. Although acidification and warming in combination significantly reduced N2O biofilm emissions, the promotion of aquaculture activities in coastal waters where shellfish do not normally occur at high biomass and density could nonetheless result in unwanted emissions of this greenhouse gas in a near future.

Initial assessment of dioxins polluting the environment outside the sanitary zone of the landfill of production and consumption waste "Lesnaya" (Serpukhov, Moscow region)

Introduction. Landfills of production and consumption waste exist everywhere. Their operation is closely related to unwanted emissions and/or discharges of dioxins. The processes of transfer of these chemicals by air and water flow outside sanitary zones, inclusion in trophic chains, bioaccumulation and overcumulation can contribute to the launch of a toxic process when low subtoxic doses are contained in the medium. It is especially important to take this into account for agro-industrial and residential regions.
 The study aims to assess the dioxin pollution of the environment outside the sanitary zone of the solid waste landfill of production and consumption "Lesnaya" (landfill "Lesnaya") by initial (screening) studies of the expected risk to public health.
 Materials and methods. Experts characterized dioxin contamination by concentrations of compounds toxic to humans in specially prepared samples, as well as indicators of general toxicity (WHO-TEQ 05). The researchers obtained samples from the surface layers of soil and animal carcasses representing successive generations (groupings) of the winter and summer seasons of the natural population of the bank vole (Clethrionomys glareolus). Concentrations of related substances were measured by high-resolution chromatography-mass spectrometry.
 Results. All samples contained dioxins. The good comparability of the profiles of congeners of these substances in soil samples and animal tissues testifies to the general history of their origin, as well as the formation of conditions in the environment for the almost continuous action of small doses of mixtures of these substances on the inhabitants. In soil samples, the values of the WHO-TEQ 05 index were significantly less than the hygienic standard. In animal tissues, concentrations of congeners characterized by pronounced hormone-like toxicity, teratogenic, embryotoxic and carcinogenic properties, primarily 2,3,7,8-tetrachlorodibenzo-p-dioxin, were very high.
 Conclusions. The consequences of prolonged exposure to the local natural population of the bank vole of small doses of dioxins in conditions of environmental pollution outside the sanitary zone of the Lesnaya landfill were characterized by the accumulation in their tissues of toxicants with hormone-like properties capable of triggering the mechanisms of formation and development of the toxic process at any concentrations. The scientific and practical significance of the obtained result is determined by the prospects for creating a methodological technique based on it to solve the problem of initial (screening) assessment of the risk to public health, namely the danger of low concentrations (doses) of dioxins polluting the environment.

Adequate UV photoemission from Ga2O3/ZnO/Ga2O3 thin film epistructures

Epistructures of Ga2O3/ZnO/Ga2O3 were grown on c-Al2O3 substrate using pulsed laser deposition route. Thickness of ZnO layer varied to form these epistructures were investigated structurally, micro-structurally and optically using respective techniques. The modification made with the epistructures are observed to change the peak position of longitudinal optical phonon plasmon (LPP) i.e. A1(LO) mode of the wurtzite ZnO. The specific mode position observed suggests the presence of optical phonon confinement, defects and impurities present at the interface of the layer with others. However the photoluminescence spectra recorded on these epistructures showed quenching of unwanted visible emissions generally observed in device quality of ZnO and gallium oxide films/crystals is interesting. Further the temperature dependent PL investigations performed on selected specimens confirmed that the donor and acceptor excitonic emissions observed are purely governed by either the electron phonon interactions or due to the lattice dilation and the electron phonon interactions both, depending on the thickness of a sandwiched layer i.e. ZnO. The results observed herewith are encouraging considering use epistructures in thin film form to fabricate UV detectors where cost, repeatability and ease of manufacturing are one of the prerequisites.

Origins of the high-energy electroluminescence peaks in long-wavelength (∼495–685 nm) InGaN light-emitting diodes

We investigate the unexpected high-energy electroluminescence (EL) peaks observed in long-wavelength InGaN light-emitting diodes (LEDs) with ground state emission peaks between ∼495 and 685 nm by studying the EL spectra of LEDs with varying quantum well (QW) thicknesses and indium compositions. In addition to the ground state emission, two high-energy emission peaks were observed in the LEDs with thick QWs and high indium compositions. The less energetic high-energy emission peak (2.4–2.6 eV) is attributed to the optical transitions involving excited states. Factors influencing the excited state transitions, such as the QW thickness and indium compositions, were also examined by simulations to better understand the occurrence of these transitions. The more energetic high-energy emission peak (2.8–3.1 eV) originates from V-defect sidewalls and was verified through micro-photoluminescence measurements. Identification of the high-energy emission peaks is essential as it enables targeted epitaxial or growth optimizations to minimize or eliminate these undesirable emission peaks. This work demonstrates the importance of using thin QWs to suppress the unwanted high-energy emissions due to excited state transitions and V-defect sidewalls for long-wavelength InGaN LEDs.

Reducing unwanted emissions of a wireless power transfer coil by using a parasitic loop element

Reducing unwanted emissions of a wireless power transfer coil by using a parasitic loop element

Toward Efficient Continuous Production of Biodiesel from Brown Grease

An increase in energy consumption and the extended use of nonrenewable fossil fuels raises the need to develop alternative fuels as an energy supply that can protect the environment from unwanted emissions of pollutants. One alternative renewable fuel is biodiesel. Currently, most biodiesel feed sources are edible oils, but using them leads to the dilution of global food sources. The present study aims to find an effective method of biodiesel production using food industry fatty wastes called brown grease (BG). BG contains fats, mainly linoleic and oleic free fatty acids (FFAs), that can serve as raw materials for biodiesel production using esterification reactions. The esterification and transesterification reactions for biodiesel production were studied using commercial FFAs, commercial glyceryl trilinoleate (trilinolein), soybean oil, and BG. The reactions were carried out under ultrasonic activation using BF3 and AlCl3 Lewis acids as catalysts in both free and immobilized forms when immobilization was performed in silica matrices using the sol-gel synthesis route. Biodiesel production was examined in batch and continuous flow reactors. The BF3 catalyst was more efficient at the initial stages of the continuous operation, reaching a maximum conversion of 90%, with a gradual decrease in efficiency after 15 h of the process. The AlCl3 catalyst showed better stability, reaching maximum yields of 97% and maintaining efficiency until the end of the experiment. The proposed method offers an efficient and easy way to produce biodiesel from a variety of lipids sources, including fatty wastes (BG).

Experimental analysis of thermal power plant operating Efficiency Improvements

Boiler efficiency "The percentage of the total suction heating value of the output steam to the total supply heating value." The main objective of thermal power plants is to meet the energy needs of the market and meet these requirements; Factories need technical availability with parts reliability and maintenance strategies. The current energy situation in India strongly supports the economic security, stability and future development of the country and the social and economic well-being of the people, all of which depend on the wise use of available domestic resources and imported energy. Increasing energy demand. Our future lies in taking extreme measures to combat energy waste caused by the use of inadequate equipment and poor work practices. The industrial and commercial sector of any economy is its pillar. Since they are the main energy users and are few in number, they are easy to approach and target. Thus, they offer a significant opportunity to save considerable energy in their operations by implementing appropriate energy efficiency measures. However, we must not forget that this is a nursery school for developing energy efficient skills as a nation. Moreover, it should not be forgotten that innovation is the key to growth and success. Therefore, we as a nation must think ahead and quickly to utilize the alternative energy sources that exist in our country to utilize our conventional energy sources and use innovative technologies. It is true that boilers are highly desirable for efficient operation / reducing production costs, saving energy and reducing unwanted emissions. If possible, immediate replacement of inefficient boilers should be considered. Here is a review of the following aspects: · Basic Priority Boiler Efficiency and Area Management · Estimate the energy performance of earth boilers and calculate the efficiency. · Factors affecting boiler efficiency · Identification and rational use of alternative renewable energy sources It contains relevant theoretical material and information and is a practical guide for students to identify and implement energy efficiency and savings opportunities in steam boilers. Our project is concerned with determining the current operating efficiency of boilers and calculating the main losses of boilers in thermal power plants. Then determine the reason for the decline in productivity. It also improves boiler efficiency. Boilers are widely used in power generation, chemical and processing industries. This project attempts to explore available methods to maintain and improve boiler efficiency.

Electrified CO2 valorization driven by direct Joule heating of catalytic cellular substrates

The growing environmental concerns have driven catalytic CO2 valorization as a forward-looking solution to mitigate the carbon footprint of valuable chemical products. CO2 conversion processes into synthesis gas, such as CO2 reforming of methane (CRM) or reverse water–gas shift (RWGS), may have a strategic role for the future sustainable production of chemicals and energy carriers. However, fuel combustion to supply the heat of the associated endothermic reactions would result in unwanted CO2 emissions, frustrating the overall objective. Electrification of the endothermic processes may represent the technological solution to such an issue. Here we report a promising approach for the direct electrification of the CO2 reforming of methane (eCRM) and reverse water–gas shift (eRWGS) processes in washcoated structured reactors. We employ catalytically activated open-cell foams that provide optimal heat and mass transfer properties and serve as Joule heating substrates for the catalytic conversion of CO2 via reaction with methane or hydrogen. The proposed reactor system with Joule-heated Rh/Al2O3-coated foam exhibited excellent catalytic and electrical stability for more than 75 h, operating up to 800 °C and approaching equilibrium conversion at high space velocity, i.e., GHSV of 600 and 100 kNl/kgcat/h for eRWGS and eCRM, respectively. Such a reactor concept has potential to ensure remarkably low specific energy demand for CO2 valorization. Assuming an optimized process configuration approx. 0.7 kWh/Nm3CO2 is calculated for eRWGS. By replacing fuel combustion with Joule heating driven by renewable electricity, the electrified CO2 valorization processes provide an important approach for dealing with the intermittent nature of renewable sources by storing the energy in chemicals with a low carbon footprint.

A New Varactor-Tuned 5.8 GHz Dielectric Resonator Band-Stop Filter for ITS and C-V2X Coexistence with Vehicular DSRC

In this paper, we introduce an electronically tuneable band-stop filter based on a dielectric resonator, along with its design principles and equivalent circuit model aimed at the coexistence of intelligent transport systems (ITS) and cellular vehicle-to-everything (C-V2X) communications operating at 5.9 GHz, with the widely spread vehicular dedicated short range communications (DSRC) at 5.8 GHz. The proposed architecture involves a dielectric resonator coupled via a microstrip transmission line to a planar ring resonator. The resonance is electronically tuned by varying the bias voltage of a varactor diode placed in the ring. This design is analyzed theoretically and experimentally. For validation, a filter operating at 5.8 GHz was designed. The prototype is capable of enhancing coexistence exhibiting to features. First, when inserted into the ITS transmitter chain, it reduces unwanted transmitter emissions in the out-of-band spectrum occupied by the DSRC carriers in the 5.8 GHz frequency band of at least 25 dB, with a minimal insertion loss at 5. 9 GHz of 1.6 dB; secondly, when inserted in the ITS receiver chain, it exhibits high linearity that prevents the generation of intermodulation products falling into the filter pass band. The prototype features more than 21 dBm of third-order input intercept points, and a tuning range of 26 MHz while maintaining a minimal loaded Q factor of 93. The prototype is discussed regarding the detailed equivalent circuit parameter extraction and their dependency upon the control voltage.

Effect of different-sized bulking agents on nitrification process during food waste digestate composting

ABSTRACT Food waste digestate (FWD) disposal is a serious bottleneck in anaerobic digestion plants to achieve a circular bioeconomy. FWD could be recycled into nitrogen-rich compost; however, the co-composting process optimisation along with bulking agents is required to reduce nitrogen loss and unwanted gaseous emissions. In the present study, two different-sized bulking agents, namely, wood shaving (WS) and fine sawdust (FS), were used to investigate their impact on FWD composting performance along with the nitrogen dynamics. The mixing of FWD with different bulking agents altered the physiochemical characteristics of composting matrix and the effective composting performance was observed through reduced ammonium nitrogen and increased seed germination index during 28 days of composting. The carbon loss of 19–22% through CO2 emission indicated similar carbon mineralisation with both types of sawdust; however, the nitrogen transformation pathways were different. Only WS treatment demonstrated the nitrification process, whereas the nitrogen loss was higher with FS. A total nitrogen loss of ∼15% was observed in treatments with FS, whereas WS treatments displayed a nitrogen loss of 12%. The outcome of the present study could significantly contribute to the practical aspect of the FWD composting operation with the promotion of the bio-recycling economy.

Ion Exchange in Natural Clinoptilolite: Aspects Related to Its Structure and Applications

Clinoptilolite is one of the most common, widespread and abundant zeolites in nature. Its availability, low cost, and outstanding ion exchange properties make clinoptilolite an excellent candidate for both direct use and various modifications to create new low-cost functional materials for sustainable development. Specific applications in which clinoptilolite is already being used include water treatment and heavy metal ion removal, agricultural purposes, storage and conversion of unwanted gaseous emissions into the atmosphere, production of catalysts and photocatalysts, bioactive materials, and a number of others. Unlike some other zeolites, clinoptilolite is difficult to synthesize, which is why most publications refer to this zeolite in its natural form, either directly from the deposit or after applying various processes to this mineral to improve its properties. Among the modification methods used, ion exchange stands out. This review is devoted to the study of ion exchange processes in natural clinoptilolite with two goals: first, as its strategic property for use in processes in which cation exchange is fundamentally necessary; second, as a way to modify it to create composite materials with predetermined desired properties.

A review of zirconia oxygen, NOx, and mixed potential gas sensors – History and current trends

Zirconia-based electrochemical sensors have revolutionized oxygen monitoring and combustion control. These robust, solid-state devices are found in virtually every internal combustion engine today providing feedback information for tight air to fuel ratio control thus minimizing unwanted emissions and improving engine efficiency. Variations on the sensor design and operational mode enable the measurement of nitrogen oxides to part per million levels, providing control information for exhaust after-treatment systems. Emerging designs include the development of "gas analyzers on a chip" capable of monitoring oxygen, carbon monoxide, nitrogen oxides, ammonia and hydrocarbons. • Zirconia based electrochemical gas sensors can detect wide variety of pollutants. • Potentiometric, amperometric, impedance-based, and pulsed polarization methods are reviewed. • Modeling of sensor behavior can predict sensor response. • Machine learning techniques can be applied for sensor signal decoding.

Full Steam Ahead for Chemical Power

Alternatives to fossil fuels are continuously being researched to provide energy and avoid unwanted toxic emissions. Andrew Smith looks at how waste heat is providing an alternative power source for industrial pumps.

Electrically‐Driven Photonic Crystal Lasers with Ultra‐low Threshold

AbstractLight sources with ultra‐low energy consumption and high performance are required to realize optical interconnects for on‐chip communication. Photonic crystal (PhC) nanocavity lasers are one of the most promising candidates for this role. In this work, a continuous‐wave PhC nanolaser with an ultra‐low threshold current of 10.2 µA emitting at 1540 nm and operated at room temperature is demonstrated. The lasers are InP‐based bonded on silicon (Si), and comprise a buried heterostructure active region and lateral p–i–n junction, feature CMOS‐compatible drive voltage, and exhibit low self‐heating. Carrier leakage is a fundamental limitation of the lateral pumping scheme that is identified as unwanted spontaneous emission from the InP p–i interface, limiting the injection efficiency to 3% which further decreases at higher current. The effect of fabrication disorder and p‐doping absorption on the Q‐factor is studied experimentally showing that p‐doping limits the Q‐factor to 8000, with a p‐doping absorption coefficient of 120 cm−1.

Application of Field Olfactometry to Monitor the Odour Impact of a Municipal Sewage System

Odorant emissions are associated with, among other things, wastewater transport in sewer networks; they contribute to air pollution and result in complaints from residents living close to emission sources. The critical location in terms of the formation of unpleasant odour compounds is the pressure line that connects the pumping station and the expansion well; this is where they are released into the atmosphere. This paper presents comprehensive results of olfactometric and chromatographic tests in the Polish city of Białystok using portable devices that allow for multiple determinations and instant results. The study attempts to investigate the relationship between odour and odorant concentrations and check the suitability of field olfactometry as a tool for the ongoing monitoring of the emission of noxious odours and for verifying complaints submitted by residents. Statistical analysis shows a very high correlation coefficient between cod and the concentrations of individual odorants, ranging from 0.82 to 0.91. This olfactometric research, mainly conducted in situ, can be an appropriate method for the ad hoc monitoring of processes in sewage networks. This method allows the detection of unwanted emissions of odours at individual points in the network in concentrations that are not detected by standard sensors but that nevertheless cause odour nuisances, complaints, and social conflict. The research results provide evidence in favour of the energetic usage of wastewater, which is in line with circular economy conception, since odour nuisance is one of its indicators.

Assessment of using solid residues of fish for treating soil by the biosolarization technique as an alternative to soil fumigation

Organic food-waste is an ever growing environmental, economic, and social problem. One way to address this problem is to find new ways to valorise food waste in a circular economical manner. In this study, the concept of separating food from waste at its source in eateries was applied to obtain separated fish waste residues from the general waste of our university's canteen. This study is the first known attempt to use separated fish residues as soil amendments for soil biosolarization (SBS), a soil treatment method which is an environment-friendly alternative to chemical fumigation of soil. In this study a unique laboratory simulation system was used which mimics the conditions of field temperature, monitors the soil respiration and the follows the temporal profile of emitted volatile organic compounds. The fish waste residues were used as soil amendment in 2% wt. and the results showed elevated levels of aerobic soil respiration without unwanted CH4 emission. A different profile of volatile organic compounds (VOCs) was also identified in the soils treated with fish residues. The profile of volatiles found in the soil with fish residues included changes in the amounts of compounds such as: Dimethylsulfide, Methanethiol and C9-aldehydes that have been found to supress soilborne plant pathogens. This is the first indication that VOCs can be used as indicators for the SBS process. Greenhouse studies and analyses of soils treated by fish residues showed no soil residual phytotoxicity affecting later growth of lettuce seedlings while not hindering the herbicidal effect of SBS on unwanted Bidens (Bidens pilosa) weeds. These results indicate that fish waste residues can be used as a soil amendment in the SBS process.