Hole Ground Research Articles

Chemical and olfactometric inventory of gaseous spot vents in Mt. Amiata volcanic-geothermal area (Italy)

Geothermal areas are typically characterised by the presence of gases and odours in the background atmosphere, stemming from natural emissions and possible mining exploitation of the area. This study presents the first olfactometric investigation of endogenous gas emissions from natural and archaeo-industrial vents in a geothermal area. Mt. Amiata is known for its complex geology and historical cinnabar mining. This study offers an inventory of spot gas emissions, not only in terms of odour and chemical concentration but also including flux data, a ground-breaking achievement in this field. The primary challenge of this investigation was estimating the emitted flow from ground holes or mine entrances, posing the risk of hazardous anoxic conditions. To address this challenge, an innovative and adaptive approach was adopted. The main breakthrough method involved the adaptation of a balometer, typically employed for indoor ventilation systems, to measure the flow of endogenous gases. Field surveys revealed odour concentrations that can exceed 106 of ouE/m3, surpassing industrial emission level considerably. Chemical concentrations, primarily consisted of CO2 (80/90 %v/v) and CH4 (∼10%v/v), providing critical insights into the global warming potential (GWP) associated with natural emissions. Moreover, these spots, often located at ground level and lacking a substantial atmospheric dilution, pose potential risks to nearby individuals, with concentrations of gases such as H2S surpassing safety thresholds. Total emissive flux of the investigated spot vents in the Mt. Amiata area, showed that the emission rate of H2S is notably substantial (55 kg/h), roughly equivalent to emissions from approximately four 20 MW geothermal plants, as along with odour emission rates in the order of 107 ouE/s. Considering the GWP derived from emitted gases, the total inventory assessment of the spot vents resulted in 36 t/h or 23 t/h CO2eq, depending on the time horizon considered (GWP20 or GWP100 respectively).

Edge Hole Effect on Isolation of UWB MIMO RDRA for 5G Outdoor Applications

For 5G sub-6 GHz outdoor applications, a highly isolated two-port rectangular dielectric resonator antenna (RDRA) with UWB MIMO is presented in this research. For isolation enhancement purposes at the lower frequency band (2.27 GHz-2.62 GHz), a longitudinal slot is inserted at the ground plane. For isolation enhancement at the higher frequency band (3.9 GHz-5.73 GHz), an edged hole is inserted in the RDRA. Investigations are conducted on the impacts of slotted ground as well as edged hole radius on isolation. The orthogonal feeding scheme of UWB MIMO RDRA considering both edged hole and slotted ground plane effects are investigated. For the edged hole MIMO RDRA with a slotted ground plane, isolation is better than -24.7 dB at a higher frequency band and is better than -15.5 dB at a lower frequency band. This isolation improvement is explained by the surface current density distribution. The use of an edged hole RDRA and an aperture-coupled orthogonal feeding allows UWB bandwidth and good efficiency performances on the 5G operating bands. To justify the MIMO performance, the envelope correlation coefficient (ECC) and diversity gain (DG) are applied.

Kajian Penggunaan Daun Pisang Kering dalam Pematangan Buah Pisang (Musa Paradisiaca L CV. Kepok) dengan Metode Pemeraman di Lubang Tanah

Purpose: This study aimed to examine the effect of ripening dried banana leaves on ripening bananas and the quality of the fruit produced. Methodology: This research was conducted from May to June 2022 at the Agrotechnology Laboratory and Research and Experimental Garden, University of Bangka Belitung. This study used a completely randomized design with a single-factor form of the addition of dried banana leaves. Results: The test results on day-4 and day-6 showed that the variance had no significant effect on the variables fruit hardness, total dissolved solids, weight loss, and vitamin C. The use of dry banana leaf weights did not accelerate ripening. The ripening of bananas with the three dry banana leaf weight treatments showed fruit ripening on the same day. Limitations: Limited by its small sample size and short storage period. Contribution: This study found that using dried banana leaves to ripen kapok bananas in a ground hole can reduce ripening time, post-harvest loss, and improve fruit quality. This suggests that dried banana leaves can be used as a sustainable and cost-effective method to ripe kapok bananas.

Effect of External Fields on the Electronic and Optical Properties in ZnTe/CdSe and CdSe/ZnTe Spherical Quantum Dots

A theoretical analysis was conducted to examine the electronic and optical properties of a confined electron and a hole in a type-II core-shell spherical quantum dot composed of CdSe/ZnTe and ZnTe/CdSe. The Schrödinger equation for the electron and the hole was numerically solved using COMSOL-Multiphysics software in the 2D axisymmetric module, which employs the finite element method under the effective mass approximation. A Fortran code was utilized to calculate excitonic energy, specifically designed to solve the Coulomb integral. The calculations encompassed variations in the inner radius (R1), as well as variations in the electric (Fz) and magnetic (B) fields along the z-axis. The absorption coefficients were determined for transitions between the hole and electron ground states, considering z-polarized incident radiation. Including a magnetic field increases the transition energy, consequently causing the absorption peaks to shift toward the blue region of the spectrum. On the other hand, the electric field decreased the overlap of the electron and hole wavefunctions. As a result, the amplitude of the absorption peaks decreased with an increase in the electric field.

Theoretical and Experimental Studies on Material Gain for Wide Polar InGaN Quantum Well‐Mechanism Leading to Electric Field Screening and Lasing

AbstractThe width of polar InGaN quantum wells (QWs) is usually limited to a few nanometers to ensure a sufficient overlap between the wave functions of the ground electron and hole state. This paper presents the results of material gain measurements for thin (2.6 nm), wide (10.4 nm), and extremely wide (25 nm) InGaN QWs. The comparison of experimental data with theoretical predictions allows for correlation of the current density with the carrier concentration, which contributes to the positive material gain, and determination of the coefficients in the standard ABC model. It is shown that the mechanism in wide and narrow polar QWs that leads to electric field screening and lasing is different. For wide QWs, the optical transitions between excited states become dominant in the gain spectrum. The reason for such a gain mechanism is the built‐in electric field, which must first be screened. The ground electron and hole states play a very important role in the screening; however, their contribution to the material gain and lasing in wide QWs is very weak.

Enhancement of Single‐Photon Purity and Coherence of III‐Nitride Quantum Dot with Polarization‐Controlled Quasi‐Resonant Excitation (Small 5/2023)

Quantum Dots The quantum dot embedded in the nanowire is excited by the quasi-resonant excitation laser, which generates electron and hole in the excited states of the conduction and valence bands, respectively. After relaxation of each electron and hole, a single photon is emitted by the recombination of the ground state electron and hole. The polarization of the emitted photon is perpendicular to the axis of the nanowire. More details can be found in article number 2205229 by Yong-Hoon Cho and co-workers.

GaN field-effect transistor with efficient heat dissipation on Si substrate

A simple design of a GaN field-effect transistor on a Si substrate with efficient heat removal through polydiamond layers formed on the walls of grounding holes is proposed. According to calculations, as a result of the introduction of such a heat sink with the same average distance between the gate sections, the maximum temperature in the channel of the GaN transistor on the Si substrate decreases significantly and becomes comparable to the maximum temperature in the channel of the GaN transistor on the SiC substrate.. Keywords: GaN FET, ground hole, channel temperature, polydiamond.

Энергетический спектр и волновые функции дырок в 2D-сверхрешетках из квантовых проволок (GaAs/AlAs)

A numerical analysis of the hole energy spectrum and wave functions in a 2D (GaAs/AlAs) quantum wire (QWr) superlattice (SL) with arbitrary cross-section is presented. The intricate fourfold degenerate nature of valence band Г8 of the given materials is taken into account. The presented approach is based on a modified effective mass method, wherein the microscopic structure of the heterostructure and hole kp-interaction in the valence band are considered. It is shown that the solution of this problem in a k-representation is reduced to an eigenvalue problem for a matrix Hamiltonian. Superlattices of quantum wires with different cross-sections (square, circle, ellipse, and ring) are considered as an example. The influence of superlattice parameters on the hole energy spectrum is studied. Anti-crossing effects in the hole dispersion law are observed. For the hole ground and excited states, the wave function spatial distribution in the plane perpendicular to the QWr axis is also studied.

Importance of core and shell sizes in the localization of the electron and hole in the formation of type I or type II excitons in spherical CdSe/ZnTe and CdSe/CdTe quantum dots.

Semiconductor core/shell quantum dots represent a promising class of nanostructure that can provide new techniques of control for performing the electronic and optical properties. Through each combination formed by the core and the shell radii and the confinement effect, the trapped charge carries behave differently, which obviously has a direct effect on the semiconductor properties. Studying the behavior of charge carriers is one of the most important steps in understanding the semiconductor performance when it undergoes certain conditions, which inevitably can offer other benefits for various applications. The electron and hole localizations strongly depend on core and shell sizes, but determining these limit sizes has not been sufficiently discussed in the literature. This paper gives a detailed theoretical study describing the three cases of electron and hole positions in two different type II core/shell quantum dots, CdSe/ZnTe and CdSe/CdTe considering the core and shell sizes. Our numerical calculations show that two significant critical radii of the core allow to switch between the exciton type I and type II quasi-particle. As a function of the shell thickness, the ground state energy of the electron is found to be higher when the core radius is small; contrariwise, the hole ground state energy remains smaller. Afterward, these specific variations influence the ground state binding energy of the correlated electron–hole quasi-particle (exciton), leading to a particular behavior of this energy as a function of the core and shell sizes.

Investigation of geological conditions beyond the excavation face using a MSP boring data monitoring system

Pre-investigation of geological conditions beyond the excavation face is crucial for assessment of safety and design in underground construction. This study developed a boring data monitoring system equipped for a multi-setting smart-investigation of the ground and pre-large hole boring (MSP) machine that typically drills a horizontal distance of 50 m to reduce blast-induced vibration. The monitoring system was applied to the tunnel construction site, which drills 40 m with the MSP method to investigate the geological conditions ahead of the excavation face. In addition, the analysis results of the boring data were compared with the observed images taken inside the holes, using a borehole alignment tracking and ground exploration system. The analysis of the boring data indicated rapid changes in pressure and boring speed with changes in geological conditions. Furthermore, the ground conditions ahead of the excavation face can be classified into three stages based on the boring pressure and speed variations. Therefore, these boring data can be the basis for predicting the geological conditions beyond the excavation face without additional effort and processes, and can help in ensuring the safety and efficiency of tunnel construction projects.

Applied Geophysics for Managed Aquifer Recharge.

Increasing water stress and decreasing supplies caused by growth and climate variability have expanded demand for managed aquifer recharge (MAR) projects to provide water supply resilience. Some of the most important factors in determining the performance of a MAR project include site selection, subsurface hydrogeologic characteristics and associated properties of the storage zone. Costs for invasive subsurface investigations to address these factors have slowly increased over the past two decades, with drilling costs increasing dramatically by as much as 30% or more since COVID-19 hit, a result of supply chain issues, steel prices, and manpower challenges. This paper provides a high-level review of major geophysical methods that have become more mainstream over the past decade or two to supplement invasive subsurface investigations and are very cost effective when compared to drilling boreholes and installing wells, which provide only point data. The more commonly used surface geophysical methods include ground-based and airborne time-domain electromagnetic methods (TEM), electrical resistivity, and seismic reflection. Airborne TEM methods (AEM) collect data very quickly, avoiding ground-based access constraints, and land-based methods are especially efficient using towed arrays. Electrical resistivity measurements provide resolution comparable to TEM but require more time than towed methods. Seismic reflection surveys are more expensive than other methods but typically have a much greater depth of penetration and can provide high resolution information on aquifer geometry, geology, and faults. Borehole geophysics is one of the more common methods used in MAR, providing near hole formation data and ground truths surface geophysics.

Prediction of Vertical Alignment of the MSP Borehole using Artificial Neural Network

The multi-setting smart-investigation of the ground and pre-large hole boring method (MSP) has been widely used to secure a free face to effectively reduce the peak particle velocity (PPV) at tunnel construction. MSP generally involves drilling a 50-m borehole in the sub-horizontal direction using a 0.9-ton hammer bit at the end of MSP rod. As the borehole length increases, the hammer bit begins to vertically sag as a result of its heavy weight. If the alignment of the borehole diverges from its intended target, borehole reconstruction is inevitable, which leads to extensive time delays and extra costs. Though the borehole height is a crucial factor in determining whether reconstruction is required, there is currently no quantitative method to predict the vertical alignment of the borehole. We gathered 2,630 datasets from 13 tunnel construction sites where MSP had been applied, and developed a prediction model about the borehole height using artificial neural networks. In testing with 25% of those datasets, the mean absolute error was 0.008 m and the coefficient of determination between the measured and predicted values was 0.9998. The prediction model demonstrated good agreement with the actual measurements and can contribute to preventing unnecessary reconstruction events.

Antibonding ground states in crystal phase quantum dots

Atomistic approaches enable computational studies ofnanostructures with unusual properties. Here, the authors showthat the indium phosphate zinc-blende section embedded in a wurtzitenanowire, thus forming so-called crystal phase quantum dots, mayexhibit a rare antibonding hole ground state. The authors also findthat even a small lattice mismatch at the wurtzite/zinc-blendeinterface can profoundly mix the lowest hole states, resulting inunusual double-peak features in the excitonic optical spectra. Furtherresearch is, however, needed to determine strained band offsets inpolytype homostructures, allowing for better agreement betweenexperiment and theory.

Experimentally-Verified Modeling of InGaAs Quantum Dots.

We develop a model of an epitaxial self-organized InGaAs quantum dot buried in GaAs, which takes into account experimentally determined indium distribution inside the QD, its geometry and crystallography. The problem of solid mechanics was solved to determine the stress-strain field. Then, the parameters of the electron and hole ground states were evaluated by solving the problem of the quantum mechanics on the same mesh. The results of calculations appeared to be reasonably well consistent with experimentally recorded optical emission spectra for the QDs in the same sample. The experimentally-verified modeling reveals a bagel-like shape of the hole wave function at the ground state, which should considerably impact the optical and magnetic properties of the QDs. Such shape of the wave function is beyond the predictions of simplified models with uniform indium distribution.

The biocatalytic activity of the “lantern-like” binuclear copper complex with trisulfide bridges mimicking SOD metallo-proteins

Through a redox process, an in situ transformation of propylthiouracil led to the formation of a trisulfur ligand that coordinates Cu(II) ion forming a lantern-like binuclear copper(II) complex [Cu2(ptu-S-ptu)2]. The complex was characterized by elemental analysis, spectroscopic techniques (FTIR, UV–Vis, EPR, and Hirshfeld surfaces analyses.), single-crystal X-Ray analysis, and its optimized molecular structure was obtained by DFT calculations. It crystallizes as a twin in the space group P-1, with two different, though closely related, centrosymmetric binuclear complexes per unit cell. The (ptu-S-ptu)2− thiouracil rings are nearly perpendicular to each other and their N and O atoms equatorially cis-coordinate the two copper ions in a two-fold Cu-OCN-Cu bridging mode. The four-fold bridging configuration is completed by another (ptu-S-ptu)2− ligand, inversion-related through the middle of the Cu…Cu contact. The elongated octahedral coordination around each copper is completed by the linking S-atom of the ligand at the axial position. The crystallographic results point to a copper d(x2-y2) d-orbital for the electron (or hole) ground state and optimal overlap of this orbital with molecular electronic path bridging the two metal atoms, hence indicating a relatively large antiferromagnetic coupling between them. The designed complex behaves as a promiscuous promising catalyst. It possesses intrinsic peroxidase-like activity catalyzing phenol red bromination in the presence of H2O2 at room temperature, and the oxidation of pyrogallol, and behaves as a superoxide dismutase (SOD) mimic compound acting on superoxide anion. Additionally, insights into their reactivity are analyzed by comparison with a family of other sulfur-containing copper(II) metal complexes in an attempt to explain the differences in catalytic properties and to determine the structural properties that affect the reactivity with substrates. Albumin interactions studies are also incorporated.

Quantum Dot Acceptors in Two-Dimensional Epitaxially Fused PbSe Quantum Dot Superlattices.

Oriented attachment of colloidal quantum dots allows the growth of two-dimensional crystals by design, which could have striking electronic properties upon progress on manipulating their conductivity. Here, we explore the origin of doping in square and epitaxially fused PbSe quantum dot superlattices with low-temperature scanning tunneling microscopy and spectroscopy. Probing the density of states of numerous individual quantum dots reveals an electronic coupling between the hole ground states of the quantum dots. Moreover, a small amount of quantum dots shows a reproducible deep level in the band gap, which is not caused by structural defects in the connections but arises from unpassivated sites at the {111} facets. Based on semiconductor statistics, these distinct defective quantum dots, randomly distributed in the superlattice, trap electrons, releasing a concentration of free holes, which is intimately related to the interdot electronic coupling. They act as acceptor quantum dots in the host quantum dot lattice, mimicking the role of dopant atoms in a semiconductor crystal.

Material Gain in Polar GaInN and AlGaN Quantum Wells: How to Overcome the ‘Dead’ Width for Light Emitters in These QW Systems?

<bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Polar GaInN and AlGaN quantum wells (QWs) are widely used in light emitting diodes and laser diodes (LDs). However, the widths of such QWs are usually limited to a few nanometers in order to ensure a sufficiently large overlap between the wave functions of the ground electron and the ground hole state. By increasing the QW width we enter the area of ‘dead’ width where, the overlap of the electron and hole wave functions decreases almost to zero and the luminescence efficiency drastically deteriorates. Therefore, it is assumed that wide QWs are not suitable for light emitters and very wide (8-15 nm) QWs are not considered as a promising gain medium for LDs. Hence such QWs are very rarely studied both experimentally and theoretically. In this work the material gain is calculated for Ga_0.8In_0.2N/GaN and Al_0.8Ga_0.2N/AlN QWs with a width varying in the range of 2-15 nm. We observed that the material gain at fixed carrier concentration for these QWs drops to zero with the increase in the QW width and reaches negative values in the width range of ∼4-8 nm even for high carrier concentrations, but after exceeding a certain width to ∼8-12 nm it begins to increase rapidly and reaches the values greater than those observed for narrow QWs. This phenomenon is related to the screening of the built-in electric field by carriers, which is easier for wide QWs, and the reduction of the distance between the energy levels for electrons and holes. For the latter reason, optical transitions between higher energy states make a very significant contribution to the positive material gain</b> .

Stemming and best practice in the mining industry: A literature review

In 2015, after amendments to the explosives regulations, stemming became a mandatory activity for all South African mining operations. There are, however, circumstances in which it is thought stemming has an adverse impact on the blasting outcome. Some of these circumstances include blasting in hot holes, in reactive ground, or when blasting a pre-split. In order to determine when stemming is necessary, its role in the control of adverse blasting phenomena and impact on explosive performance were reviewed. Stemming was found to play a significant role in the fragmentation process and burden movement. Additionally, stemming significantly influences the control of flyrock, air-blast, and toxic fume generation. The review of the literature indicates some motivation for not using stemming for pre-split, trim, hot hole, and reactive ground blasting, provided the benefits associated with not stemming the holes outweigh the risks of stemming them. Best practice for stemming from the literature indicates a stemming length of 0.7 x burden is best for larger hole diameters, and 20 to 30 x 0 for smaller hole diameters. Crushed aggregate appears to be the most effective stemming material. The South African explosives regulations pertaining to stemming were found to be consistent with those of Australia and the USA.

Insecticide Resistance Variation among Three Culex pipiens (Diptera: Culicidae) Populations in Egypt

Several studies have reported on insecticide resistance in mosquitoes; however, there is a lack of information about the resistance of Culex pipiens in Egypt. This study was conducted to investigate insecticide resistance status in three Cx. pipiens populations. These populations were collected from two rural breeding sites and one urban site in Egypt. Al-Beshlawy drainage canal and El-Khartoum irrigation ditch were selected to represent rural sites in Giza and Beheira governorates, respectively. One man-made ground hole was selected in Tanta, Gharbia Governorate, as an urban breeding site. Insecticide residues were analysed in water samples collected from the three breeding sites. Four insecticides, malathion chlorpyrifos, deltamethrin and fipronil, were tested against Cx. pipiens third-instar larvae of three field populations and one insecticide-susceptible (reference) population. Four insecticide residues and one additive (piperonyl butoxide) were detected; only malathion and piperonyl butoxide concentrations exhibited significant differences among all breeding sites. The level of malathion residue in the Giza breeding site was significantly higher than those in the Gharbia and Beheira breeding sites. According to the lethal concentrations (LC50) of the applied insecticides, the susceptibility of Cx. pipiens third-instar larvae to different insecticides demonstrated the order fipronil > chlorpyrifos > deltamethrin > malathion. Variations in the percentage mortality of Cx. pipiens were observed following malathion application between the Gharbia population and with both Giza and Beheira populations. Culex pipiens populations exhibited low resistance to most tested insecticides; however, the populations of Giza and Beheira exhibited moderate resistance to malathion. The variation in the resistance of Cx. pipiens populations to malathion could provide new information about the intraspecific variation among some mosquito populations in Egypt.

Tuning electronic structures and optical properties in CdSe/CdS Dot-in-rod colloidal nanostructures: Atomistic tight-binding theory

Using the atomistic tight-binding theory, in this study, the electronic structures and optical properties of CdSe/CdS dot-in-rod nanocrystals are modified by engineering the core and rod diameters. The ground electron states favor an s-like orbital, while the ground hole states are formed by light hole-like characteristics. The quantum confinement effect is attributed to the reduction in excitonic band gaps as the core and rod diameters increase. Changing the core and rod sizes produces excitonic band gaps across the visible light spectra. The highest oscillation strength, excitonic-binding energy, and dark-bright excitonic splitting are witnessed at a 3.0 nm CdSe core diameter. The oscillation strength, excitonic-binding energy, and dark-bright excitonic splitting decrease as the CdS rod diameters increase. This study highlights the importance of theoretically understanding and controlling the active materials’ structural parameters in optoelectronic technology.