Circular Trench Research Articles

Environmental and economic impacts of combining backfill materials for novel circular narrow trenches

Over the last few years, several policies and new technological solutions have targeted the construction sector with the aim of reducing the sector's impacts on the environment. Among the different technological advances proposed, the reuse of materials in construction has been reported as a promising solution for an increase in sustainability and circularity. In particular, a type of cities' undergrounds assets for which materials' reuse is being explored are trenches for protecting services (i.e., water and gas transport pipelines, and optic fibre and other telecommunications services). Nonetheless, the economic and environmental benefits and impact of this type of system is still insufficiently quantified. In this research study, the economic and environmental impacts of four scenarios of trenches were assessed by using Life Cycle Costing (LCC) and Life Cycle Assessment (LCA). The four alternatives analysed consisted of: (1) the classical solution; (2) the classical solution with the reuse of soil; (3) the control low-strength material, and (4) the eco-trench. The results allowed concluding that in the eco-trench system, for which all material is reused, the environmental and economic impacts could be reduced by more than 80% and 50%, respectively. A parametric study for which the dimensions of the trenches were varied, permitted to reinforce these results and to quantify the impact's change along with the width and depth of the trench. Overall, this study provides a comprehensive view of the high-impact potential of reusing material for the construction of trenches in cities. The outcomes allow also remarking that the eco-trench system could be an attractive and advantageous solution for urban infrastructure stakeholders, both from an economic and environmental perspective.

β-Ga2O3 junction barrier Schottky diode with NiO p-well floating field rings

Recently, β-Ga2O3, an ultra-wide bandgap semiconductor, has shown great potential to be used in power devices blessed with its unique material properties. For instance, the measured average critical field of the vertical Schottky barrier diode (SBD) based on β-Ga2O3 has reached 5.45 MV/cm, and no device in any material has measured a greater before. However, the high electric field of the β-Ga2O3 SBD makes it challenging to manage the electric field distribution and leakage current. Here, we show β-Ga2O3 junction barrier Schottky diode with NiO p-well floating field rings (FFRs). For the central anode, we filled a circular trench array with NiO to reduce the surface field under the Schottky contact between them to reduce the leakage current of the device. For the anode edge, experimental results have demonstrated that the produced NiO/β-Ga2O3 heterojunction FFRs enable the spreading of the depletion region, thereby mitigating the crowding effect of electric fields at the anode edge. Additionally, simulation results indicated that the p-NiO field plate structure designed at the edges of the rings and central anode can further reduce the electric field. This work verified the feasibility of the heterojunction FFRs in β-Ga2O3 devices based on the experimental findings and provided ideas for managing the electric field of β-Ga2O3 SBD.

Reduction of wind-turbine-generated seismic noise with structural measures

Abstract. Reducing wind turbine noise recorded at seismological stations promises to lower the conflict between renewable energy producers and seismologists. Seismic noise generated by the movement of wind turbines has been shown to travel large distances, affecting seismological stations used for seismic monitoring and/or the detection of seismic events. In this study, we use advanced 3D numerical techniques to study the possibility of using structural changes in the ground on the wave path between the wind turbine and the seismic station in order to reduce or mitigate the noise generated by the wind turbine. Testing a range of structural changes around the foundation of the wind turbine, such as open and filled cavities, we show that we are able to considerably reduce the seismic noise recorded by placing empty circular trenches approx. 10 m away from the wind turbines. We show the expected effects of filling the trenches with water. In addition, we study how relatively simple topographic elevations influence the propagation of the seismic energy generated by wind turbines and find that topography does help to reduce wind-turbine-induced seismic noise.

Sub-micrometer pillar formation in fused silica using double-pulse back-surface laser ablation

This work presents an investigation into the characteristics of double-pulse, back-surface ablation of fused silica via the use of a picosecond pulse laser with a wavelength of 532 nm.The processing depth of back-surface ablation was found to be greater than that of front-surface ablation for a given laser power. The processing depth of back-surface ablation was further increased via the use of double-pulse ablation using an appropriate laser fluence combination for the first and second pulse relative to the single-pulse ablation threshold, Fth. Setting the laser fluence of pulses in ascending order (where the first pulse is below Fth and the second pulse is greater than Fth) is found to increase the processing depth. Furthermore, non-trivial features of the processing trace were found; an axisymmetric circular trench with a sub-micrometer scale protrusion at its center was observed in the case of double-pulse, back-surface ablation using laser pulses in an ascending order of laser fluence under certain conditions. The protrusion has a pillar-like shape with a diameter of several hundred nanometers; the pillar-like structure has a height of about 1.3 µm from the trench bottom, and protruded 0.7 µm from the back-surface plane. When the first pulse had a laser fluence of greater than Fth, the protrusion was not present and the shape was similar to that obtained when using a single-pulse ablation.The results of this work show the superiority of double-pulse, back-surface ablation of fused silica compared with the equivalent single-pulse technique in terms of enhanced throughput and the capability to create unique sub-micrometer structures.

Does secretory canal architecture determine the sabotage behaviors of insect folivores?

Insect folivores on plants protected by secretory canals commonly sever leaf veins or cut trenches before feeding beyond the cuts. Previous studies reported that vein cutting occurs when canals have an arborescent arrangement, whereas trenching is found when canals have a net-like arrangement. However, some danaine species, such as the monarch caterpillar, Danaus plexippus, show both behaviors on the same milkweed plant; early instars cut circular trenches and later instars chew furrows in the leaf midrib. This study tests the hypothesis that milkweed canals differ in arrangement at different scales, thus requiring different behaviors from early and late instars. I compared common milkweed, Asclepias syriaca (Apocynaceae) with prickly lettuce, Lactuca serriola (Asteraceae). Leaves were damaged with standard wounds and the response of the laticifers was compared by measuring latex exudate. With L. serriola, severing either the primary or secondary veins failed to reduce latex emission beyond the cuts. The veins and associated laticifers form an interconnected network; plusiine caterpillars on L. serriola disarm the network with a trench. With A. syriaca, transecting the midrib virtually eliminated distal exudation. However, severing a secondary vein caused only a partial reduction. To decrease exudation beyond secondary veins, milkweed insects need either to sever multiple adjacent veins (as shown by Labidomera clivicollis beetles) or to cut a trench (as in early instar danaine larvae). Thus, in both A. syriaca and L. serriola, herbivore behaviors match the laticifer systems as predicted by the hypothesis that canal architecture has a central role in determining behavior.

Corona structures driven by plume–lithosphere interactions and evidence for ongoing plume activity on Venus

In the absence of global plate tectonics, mantle convection and plume–lithosphere interaction are the main drivers of surface deformation on Venus. Among documented tectonic structures, circular volcano-tectonic features known as coronae may be the clearest surface manifestations of mantle plumes and hold clues to the global Venusian tectonic regime. Yet, the exact processes underlying coronae formation and the reasons for their diverse morphologies remain controversial. Here we use three-dimensional thermomechanical numerical simulations of impingement of a thermal mantle plume on the Venusian lithosphere to assess the origin and diversity of large Venusian coronae. The ability of the mantle plume to penetrate into the Venusian lithosphere results in four main outcomes: lithospheric dripping, short-lived subduction, embedded plume and plume underplating. During the first three scenarios, plume penetration and spreading induce crustal thickness variations that eventually lead to a final topographic isostasy-driven topographic inversion from circular trenches surrounding elevated interiors to raised rims surrounding inner depressions, as observed on many Venusian coronae. Different corona structures may represent not only different styles of plume–lithosphere interactions but also different stages in evolution. A morphological analysis of large existing coronae leads to the conclusion that at least 37 large coronae (including the largest Artemis corona) are active, providing evidence for widespread ongoing plume activity on Venus. Thermomechanical modelling shows that the formation and diverse morphologies of coronae on Venus can be explained by interactions between the lithosphere and impinging mantle plumes. Some corona structures are consistent with ongoing plume activity.

Effect of Water Conservation Practices and Felling intensity on Growth and Biomass Production of Manvel Bamboo (Dendrocalamus strictus Nees)

A field experiment was conducted at AICRP on Agroforestry, PDKV, College of Agriculture, Nagpur to study the effect of water conservation practices and bamboo felling intensity on production of bamboo and to evaluate suitable combination of water conservation practices and felling intensity on its production. Among the sixteen treatment combinations circular trench (with 1.75 meter diameter, 25 centimeter depth and 60 centimeter width around the bamboo clump.) + 30% felling intensity of bamboo was found best to produce highest biomass 38.13 tons/ha. The Cost Benefit ratio (3.06) and gross monetary gain/ha Rs. 311940 /ha was highest for treatment Circular trench + 30% felling intensity.

The Influence of Anode Trench Geometries on Electrical Properties of AlGaN/GaN Schottky Barrier Diodes

AlGaN/GaN lateral Schottky barrier diodes (SBDs) with three different anode geometries (stripe, circular, and the conventional plane one) and different rows of anode trenches are fabricated and electrically characterized to study the influence of anode trench geometries. The SBDs with anode trenches exhibit the lower on-state resistance (RON) than that with the conventional plane one. It can be explained that the anode trenches made the Schottky metal directly contact to the 2DEG at the sidewall of the AlGaN/GaN interface, removing the AlGaN barrier layer in the conventional plane anode. In addition, the RON of the SBDs with circular trenches is smaller than that of the SBDs with stripe ones. Furthermore, the RON decreases with the increasing rows of anode trenches, which can be attributed to the increased contact area between the Schottky metal and the 2DEG. For the reverse characteristics, the anode trenches do not lead to performance degradation. The fabricated devices exhibit the low reverse current (IR, IR < 1 μA/mm), and the breakdown voltage (VBK) remains unchanged with different anode geometries.

ЕКОЛОГО-ТЕХНОГЕННІ ЗАКОНОМІРНОСТІ ФОРМУВАННЯ РОЗСОЛІВ ДОМБРОВСЬКОГО КАР'ЄРУ

The Dombrovsky quarry, which has been in operation since 1967, is the only one in the world where potash ore has been mined by open-pit method. The article considers the body formation mechanism of water-salt brines in the Dombrovsky quarry and gives a brief overview of the problems due to long-term development of the Kalush-Golynsky potassium salts deposit and waste accumulation in the area of hydraulic geofiltration. Such problems include flooding of the Dombrovsky salt quarry, erosion of salt dumps by precipitation, tailings overflows, pollution of the Quaternary supersalt aquifer and significant water quality deterioration danger in urban water intake, development of salt karst and subsidence of the earth's surface, destruction of engineering structures, residential buildings, etc. Analytical data of water inflows dynamics into the quarry and the increase of the drainage area of the quarry riparian part was analyzed, accompanied by drainage of the circular drainage trench – separation of groundwater level from the bed, the karst formation development on the periphery of the quarry (up to 250–350 m and more), anomalous increase in clay-dust fractions in the quarry wastewater after the flooding 2008 with a simultaneous increase in water inflows. According to the research, we can make a conclusion about the unloading of liquid body filling the quarry in the thickness of the pebble supersalt aquifer, filling karst cavities, erosion of the quarry, increasing the volume of the quarry bowl and the size of the groundwater drainage area of alluvial gravel-sand deposits of Sivka and Lymnutsya. Based on the obtained results, a conclusion was made regarding the threat of the emergency situation development and the deterioration of life safety in areas with disturbed ecological parameters of the geological environment. There is a need for artificial adjustment of the environmental forecast ecological parameters according to monitoring observations

Efficiency analysis of open trench for impact pile driving through a single-variable method

The ground vibrations during pile driving operation have a drastic potential to undermine the surrounding structures both in land and reclaimed land. Particularly, reclaimed land necessitates ample application of pile driving due to the weak land condition. To prevent the structural damage, attenuation of the ground vibrations to an allowable level through active isolation of circular open trench is the scope of this study. In this research, finite element simulations of continuous impact pile driving process from the ground surface was executed with particular attention to the pile-soil interaction, and thereby, the efficiency of open trench application in attenuation of the unsafe distance of different structures was surveyed using the vibration sensitivity degree. Regarding the crucial parameters of an open trench (depth, width, and location), it was concluded that a sufficient high depth can attenuate the unsafe distance up to 68%, the trench width variations are less effective, and an average pile-trench distance is the most efficient option. The excavation volume was also concluded as another crucial parameter in open trench design which takes all three parameters into account. The trench depth equal to the pile’s maximum critical depth of vibration was inferred for an optimum design.

Feeding behaviour of chrysomelid leaf beetles Aplosonyx chalybaeus (Hope) and A. scutellatus (Baly)

Two chrysomelid leaf beetles, Aplosonyx chalybaeus (Hope) and A. scutellatus (Baly) (Galerucinae: Chrysomelidae) are endemic to the northeast Indian hills and adjoining areas where their host plant, Colocasia esculenta (L.) Schott originated. This study brings out the feeding behaviour of these. The univoltine life cycle of these beetle is in close synchrony with the phenology of their host plant C. esculenta. The creamy white ‘caterpillar-like’ grubs from first to the fourth instar feed gregariously inside the long petioles and sometimes enter the underground tubers. The final instar grubs invariably bore into the tuber and feed inside. Due to the feeding and movements of a group of 15–20 grubs, the internal starchy contents of the tuber get loosened. The final instar make vigourous churning movements within the tuber and this often leads to the starchy contents become a thick viscous milky fluid. Thus the final instar grubs live in a fluid environment till they get dispersed for pupation underground. The adult beetles exhibit leaf trenching behaviour to drain off the milky latex from the leaf canals before feeding. The feeding results in circular or elongated holes in the leaf. The beetle feeds the leaf at a very early stage of trenching. Lack of turgor pressure in the leaf veins could be the reason for early discontinuance of trenching on severed leaf. Time taken to make circular trench and feeding hole on the leaves and the area of leaf consumed by adults is discussed.

A Tellurium Oxide Microcavity Resonator Sensor Integrated On-Chip with a Silicon Waveguide

We report on thermal and evanescent field sensing from a tellurium oxide optical microcavity resonator on a silicon photonics platform. The on-chip resonator structure is fabricated using silicon-photonics-compatible processing steps and consists of a silicon-on-insulator waveguide next to a circular trench that is coated in a tellurium oxide film. We characterize the device’s sensitivity by both changing the temperature and coating water over the chip and measuring the corresponding shift in the cavity resonance wavelength for different tellurium oxide film thicknesses. We obtain a thermal sensitivity of up to 47 pm/°C and a limit of detection of 2.2 × 10−3 RIU for a device with an evanescent field sensitivity of 10.6 nm/RIU. These results demonstrate a promising approach to integrating tellurium oxide and other novel microcavity materials into silicon microphotonic circuits for new sensing applications.

A test of tree protection zones: Responses of Quercus virginiana Mill trees to root severance treatments

A suite of best management practice documents (BMPs) providing procedures to protect trees are available around the world. An underpinning component of these texts is the provision of a tree protection zone (TPZ), the purpose of which is to define an area of ground surrounding the tree to be excluded from development activities. TPZs 12 times the trunk diameter are common in BMPs, however, the principles of the TPZ have not been extensively tested. The objective of this study was to test the suitability of TPZs by monitoring the responses of trees to different root removal treatments. Mature Quercus virginiana Mill trees (n = 18) were exposed to five root pruning treatments consisting of a circular trench around each tree. Trenches were established with radial offsets from the tree base between 3 and 15 times the trunk diameter in increments of three, plus control. Roots were severed manually, and their diameters measured to obtain a total cross-sectional area of severed roots, which were expressed as ratios of whole trunk cross-sectional areas (Ar(1)) as well as conductive sapwood areas (As(1)). Ar and As ratios were regressed against physiological (predawn leaf water potential (Ψ), stomatal conductance (gs) and chlorophyll fluorescence) and growth (trunk diameter, shoot extension and specific leaf area) responses. Ar(1) was a significant predictor of Ψ (p < 0.0001), trunk diameter growth (p ≤ 0.01), specific leaf area (p ≤ 0.001) and shoot extension (p ≤ 0.001), although model strength varied (R2 = 0.75, 0.47, 0.57, 0.58 respectively). Significant (p ≤ 0.05) differences were observed in Ψ between control trees and all treatments except 15 × . Growth responses were affected for one or more treatments between 3x and 9 × . The results reveal that a TPZ defined by 12 times the trunk diameter was insufficient to adequately avoid short-term physiological perturbations in Quercus virginiana.

Prediction of surface topography due to finite pixel spacing in focused ion beam milling of circular holes and trenches

Successful implementation of focused ion beam technologies in fabrication of practically important structures, including circular holes and trenches requires evaluating the ion dose delivered to the specimen by the beam and subsequently predicting the formed topography. In this article, the analytical expressions for the ion dose are obtained in polar coordinates using Bessel functions. These expressions can be transformed into relatively straightforward formulas useful in many applications. On the basis of the expressions derived, the surface shape of structures under consideration is analytically described if constant sputtering yield conditions are realized throughout the milling process. For practically relevant structure preparation, when the distance between neighboring beam stops is less than approximately two beam diameters, it was established that the mean depth and the peak-to-valley surface roughness can be evaluated by simple formulas. The outcomes of theoretical findings are confirmed by the comparison with the numerically obtained results and experimental data retrieved from the fabricated circular holes.

Chemical Imprinting of Crystalline Silicon with Catalytic Metal Stamp in Etch Bath.

Conventional lithography using photons and electrons continues to evolve to scale down three-dimensional nanoscale patterns, but the complexity of technology and equipment is increasing due to diffraction and scattering problems. Physical contact lithography methods, such as nanoimprint and soft lithography, have been developed as an alternative technique. These techniques imprint predefined structures on a stamp to the polymer resist and use the polymer resist as a mask to dry etch the nanostructure on the substrate. In this study, we introduce a method of chemically imprinting crystalline silicon (Si) with a catalytic stamp to enable the direct etching of the Si without using a polymer mask. A metal catalyst is deposited on the predefined structure of the stamp. The stamp physically contacts the Si in the etching bath, and metal-assisted chemical etching occurs on the semiconductor surface. Since the metal catalyst is mounted on a stamp, it can be used repeatedly. This is a technology that combines conventional lithography and etching without using a polymer resist. This technology not only produced nano/microscale arrays of circular and square holes and trench structures but also successfully produced complex eagle-shaped structures that contained such structures.

Destabilisation of nanoporous membranes through GB grooving and grain growth

We have used a phase field model to study destabilization of cylindrical pores in a polycrystalline membrane; a key feature in the model is that it incorporates surface diffusion as the mechanism for mass transport. Using a model system in which a cylindrical pore runs through a material in which all the grain boundaries (GBs) are perpendicular to the pore axis, we identify two elementary mechanisms for pore failure. The first one is based just on grain boundary (GB) grooving, which causes a circular trench at the groove, and a constriction of the pore on either side of the GB; as the groove deepens, the constriction narrows, and eventually closes the pore. Pore closure through this mechanism is possible only when the grain size exceeds a critical size (below which the open pore surface acquires an inverse-bamboo morphology), and therefore, it is controlled by grain growth kinetics. In the second mechanism, the groove profiles of unequal sized grains is such that the curvature differences trigger a coarsening-like process in which atoms from the surface of smaller grains are transported to that of larger grains, causing an ever-narrowing constriction there. A simplified model that incorporates these two mechanisms acting in parallel is used to rationalize our observations of pore failure in polycrystalline systems.

Design and Realization of GaN Trench Junction-Barrier-Schottky-Diodes

We present the design principle and experimental demonstrations of GaN trench junction-barrier-Schottky-diodes(trench JBSDs), where the Schottky contact within the patterned trenches is at the same plane as the adjacent p-n junctions. Assisted by the TCAD simulations, the leakage current reduction mechanism is identified as the reduced surface field (RESURF) effect due to the barrier-height difference between the p-n junction and Schottky junction. Design space for the width of stripe-shaped trenches is found to be $ for a drift layer doping level of $10^{15} \sim 10^{16}$ cm $^{-3}$ , while for circular trenches, the size requirement is relaxed. In the fabricated devices with 1– $4~\mu \text{m}$ diameter circular trenches, about 20 times reduction in the reverse leakage is observed with a characteristic shift in the turn-on voltage, which are signatures of the trench JBSD with desired RESURF. The experimental observations are in excellent agreement with the simulation results. This JBSD design shows promising potential in further improving the performance of Schottky-based GaN power devices without the need for ion-implantation or material regrowth.

GEOMETRIC PROBABILITY MODELS TO ANALYZE STRATEGIES FOR FINDING A BURIED CABLE

Different strategies can be used to find a straight cable buried underground. The original problem considered by Faber et al. focused on a telephone company that wishes to dig a trench to locate a straight cable. The cable is known to pass within a given distance, a, from a marker erected above the putative location of the cable. Faber et al. showed that the shortest simply connected curve guaranteed to find the cable is a U-shaped curve whose length is about 18% less than that of a circular trench of radius a. This problem can be regarded as minimizing the maximum length that a trench digger must dig. In reality, once the cable is found, digging can stop. So far, however, no attempt has been made to evaluate the trench shape on characteristics other than the maximum trench length. In this paper, we present geometric probability models to analytically derive the distribution of trench length and calculate the expected value and variance for both the short-length (U-shaped) trench and a circular trench. Our main result is that the expected digging length is about 5% less for the circular trench than for the U-shaped trench.

The erosion groove effects on RF planar magnetron sputtering

Magnetron sputtering erodes the target non-uniformly, leading to the formation of a circular deep trench called groove, which will have a direct effect on plasma and thin film deposition properties. These effects are highlighted by measurements of the electrical parameters and the deposition rate. Moreover, the measurements of the discharge electrical equivalent plasma impedance indicate clearly, that the occurrence of the target erosion effects is related to the ion sheath thickness formed in front of the eroded target groove. The effects of the eroded target, on discharge parameters, appear from a certain pressure transition range (0.1–0.5Pa). The eroded target lowers the self-bias voltage by 50%, reduces the deposition rate by almost 40% and increases the ion current density at the substrate. The use of an eroded target improves the plasma confinement, and the electrical equivalent impedance becomes less capacitive and more resistive. Our results show that measuring the plasma impedance might be used as a tool for monitoring the groove formation.

Design criteria for XeF2 enabled deterministic transformation of bulk silicon (100) into flexible silicon layer

Isotropic etching of bulk silicon (100) using Xenon Difluoride (XeF2) gas presents a unique opportunity to undercut and release ultra-thin flexible silicon layers with pre-fabricated state-of-the-art Complementary Metal Oxide Semiconductor (CMOS) electronics. In this work, we present design criteria and mechanism with a comprehensive mathematical model for this method. We consider various trench geometries and parametrize important metrics such as etch time, number of cycles and area efficiency in terms of the trench diameter and spacing so that optimization can be done for specific applications. From our theoretical analysis, we conclude that a honeycomb-inspired hexagonal distribution of trenches can produce the most efficient release of ultra-thin flexible silicon layers in terms of the number of etch cycles, while a rectangular distribution of circular trenches provides the most area efficient design. The theoretical results are verified by fabricating and releasing (varying sizes) flexible silicon layers. We observe uniform translation of design criteria into practice for etch distances and number of etch cycles, using reaction efficiency as a fitting parameter.