Land Length Research Articles

Modelling land suitability and development potential options for irrigable and rainfed agricultural scenarios in Ethiopia

AbstractDespite being a significant sector in Ethiopia, agriculture is mainly run in rainfed system. However, it is imperative to look for irrigation systems and their suitability to the country's agriculture. The study's objectives were to (1) map areas appropriate for irrigable and rainfed agriculture and examine gaps with current active areas, (2) model possible development for irrigation and rainfed scenarios, and (3) offer evidence‐based decision support for agricultural investment. Land features, agroecology, population density, market accessibility and length of growing seasons were considered as important indicators when determining land suitability for each scenario. Geographically weighted regression was used to model these indicators. The results show that approximately 359,360 (34%) and 13,802 km2 (1.6%) are highly suitable areas for irrigation and rainfed agriculture, respectively. However, Ethiopia's production depends on areas moderately suitable for rainfed agriculture, but these areas are highly suitable for irrigation rather, indicating that it is unfortunate that the areas suitable for irrigation are used for rainfed agriculture so far. In terms of development potential, areas of approximately 71,317 (7%) and 347,435 km2 (33%) had the highest and a high irrigation potential, respectively, while areas with rainfed agriculture had approximately 33,821 (3%) and 105,013 km2 (10%) with the highest and a high development potential, respectively. These analyses suggest that the country has untapped potential for agricultural development in both scenarios, but this remains within the scope identified in this study.

Dynamic Forced Performance of an O-Rings Sealed Squeeze Film Damper Lubricated With a Low Supply Pressure and a Simple Method to Quantify Air Ingestion

Abstract Contemporary squeeze film dampers (SFDs) in air-breathing engines are short in length to limit weight and part count and lubricated with a low feed pressure to reduce oil storage and pumping power. In SFDs, O-rings (ORs) restrict side leakage and increase the viscous damping while a adding a modest centering stiffness. Continuing a long-term project characterizing SFDs for aircraft engines and extending the original work (San Andrés and Rodríguez, 2021, “On the Experimental Dynamic Force Performance of a Squeeze Film Damper Supplied Through a Check Valve and Sealed With O-Rings,” ASME J. Eng. Gas Turb. Power, 143(11), p. 111011) the paper details measurements of the forced performance of an OR sealed damper (OR-SFD) with diameter D = 127 mm, land length L = 0.2 D, and radial clearance c = 0.0022 D. Lubricant ISO VG 2 supplied at 0.69 bar(g) fills an upstream oil plenum and flows into the middle of the land through a single orifice configured with a check valve. Measurements of applied single-frequency dynamic loads, along with the ensuing damper displacements and accelerations serve to identify the parameters of the test structure, ORs, and SFD. The tests encompass centered whirl motions with amplitude r = 0.05–0.45c, and a range of whirl frequencies, ω = 10–130 Hz. Note the squeeze velocity vs = rω reaches 102 mm/s. The ORs force coefficients are nearly invariant with frequency but do depend on the orbit amplitude. The ORs' stiffness (KOR) decreases by 75% as the motion amplitude increases, r → 0.45c, likely due to the large elastic deformations and slow recovery of the ORs material. For small amplitude motions (r/c = 0.05 and 0.10), the ORs damping coefficient (COR) is ∼10% of the overall coefficient for the lubricated system (CL), while for r/c > 0.25, COR ∼ 0.03CL. For small amplitudes of whirl (r ≤ 0.25c), the SFD experimental viscous damping (CSFD) and added mass (MSFD) coefficients, identified over a shorter frequency range (vs<30 mm/s) equal theoretical magnitudes for a fully sealed damper. As the orbit size grows to r = 0.45c MSFD drops nearly by 75% and CSFD decreases by ∼40% due to the onset of both lubricant cavitation and air ingestion occurring for squeeze velocities vs ≥ 24.5 mm/s, as also seen in the recorded dynamic pressures and video recordings of a bubbly mixture leaving the damper. A comprehensive flow model predicts CSFD and MSFD about 8% and 12% larger than the experimentally identified coefficients. A novel approach enables the estimation of the gas volume fraction (GVF) generated in the damper which rapidly increases as vs grows. The simple procedure draws into a deflated balloon the material contents in the squeeze film, weighs the sample, and identifies its volume to produce an estimate of the GVF. The procedure to quantify the GFV will assist in the validation of predictive tools.

Structural optimization of slot-die heads with T-shaped cavity for fabrication of large-area OLEDs

With an attempt to achieve highly uniform large-area organic thin films for potential applications in solution-processable organic light-emitting diodes (OLEDs), we have optimized the structure of slot-die heads with T-shaped cavity (manifold) by computational fluid dynamics (CFD) simulation. Depending on the viscosity of coating solutions, the pressure distribution inside the cavity and the velocity distribution at the outlet are analyzed by varying the structure parameters such as the shim thickness, cavity volume (cavity depth, cavity height, cavity width), and land length. From CFD simulation results, we have derived the maximum shim thickness at which the pressure non-uniformity becomes less than 5 %, which can provide a simple and intuitive design guideline. It is addressed that the maximum shim thickness is most affected by the cavity width, followed by the cross-sectional area of the cavity and then the land length. Using the structurally optimized slot-die head, we have carried out slot-die coating of low-viscosity (80 cPs) poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and high-viscosity (4,800 cPs) polydimethylsiloxane (PDMS) and achieved thin films with the thickness non-uniformity less than 10 %. Furthermore, we have successfully fabricated 120 mm × 20 mm OLED devices with the slot-coated conductive PEDOT:PSS layer, exhibiting the luminance of 801 cd/m2 at 6 V.

Glacier Change in the West Kunlun Main Peak Area from 2000 to 2020

Glaciers are sensitive indicators of climate change, and investigation of their dynamics is crucial for ensuring regional ecological security as well as disaster prevention and mitigation measures. Based on Landsat Thematic Mapper (TM)/Enhanced Thematic Mapper Plus (ETM+)/Operational Land Imager (OLI) imagery, the outlines and length of glaciers in the West Kunlun Main Peak Area (WKMPA) during 2000–2020 were obtained by combining a band ratio method with manual interpretation and an automatic extraction method for the glacier centerline, respectively. There were 440 glaciers in the WKMPA in 2020, covering an area of 2964.59 ± 54.87 km2, with an average length of 2916 ± 60 m. The glacier count increased due to division, while the area and length all exhibited a declining trend from 2000 to 2020, at rates of −0.04%·a−1 (24.83 km2) and −0.11%·a−1 (66 m), respectively. Glacier retreat was primarily observed during the early period (2000–2005). Except for glaciers located above an elevation of 6250 m, the glacier area decreased with each altitude interval from 2000 to 2020, and the rate of relative change in glacier area generally decreased with increasing altitude. Moreover, except for a slight increase in north-facing glaciers, the area of glaciers facing other orientations decreased during 2000–2020. The accuracy of the empirical formula fit for glacier length was highly dependent on glacier class, with greater precision observed for smaller glaciers and lower precision for larger valley-basin glaciers due to their complex morphological structures being neglected and only a single quantitative relationship being considered. There was a time lag of 12 years between temperature changes and glacier area response in this region. The mechanism by which glacier division affects glacier change is complex, requiring dissection of multiple factors such as area, length, and terminal elevation before and after division.

Influence of Die Land Length on the Maximum Extrusion Force and Dry Ice Pellets Density in Ram Extrusion Process.

The management of waste materials, particularly non-biodegradable substances such as plastics and composites, is an increasingly pressing issue. Energy efficiency in industrial processes is crucial throughout their life cycle, including the handling of materials such as carbon dioxide (CO2), which has a significant environmental impact. This study focuses on the conversion of solid CO2 into pellets using ram extrusion, a widely used technique. The length of the die land (DL) in this process plays a critical role in determining the maximum extrusion force and the density of dry ice pellets. However, the influence of DL length on the characteristics of dry ice snow, known as compressed carbon dioxide (CCD), remains understudied. To address this research gap, the authors conducted experimental trials using a customized ram extrusion setup, varying the DL length while keeping the other parameters constant. The results demonstrate a substantial correlation between DL length and both the maximum extrusion force and dry ice pellets density. Increasing the DL length leads to a decreased extrusion force and optimized pellet density. These findings provide valuable insights for optimizing the ram extrusion process of dry ice pellets and improving waste management, energy efficiency, and product quality in industries utilizing this technique.

Effects of non-native Salmo trutta and multiscale habitat factors on native fishes in the Driftless Area

We collected fishes and habitat data at 138 streams to evaluate the effects of introduced brown trout ( Salmo trutta) and habitat conditions on occurrence, detection, abundance, and size structure of sculpin ( Cottus spp.), longnose dace ( Rhinichthys cataractae), and southern redbelly dace ( Chrosomus erythrogaster) in the Driftless Area, USA. Sculpin detection decreased with increasing stream velocity, whereas southern redbelly dace detection increased with stream depth. Sculpin occupancy declined with increasing stream temperature and velocity and increased with increasing forested land, boulder substrate, and brown trout length and abundance. Longnose and southern redbelly dace occupancy and abundance declined with increasing brown trout abundance and occupancy increased with stream temperature. Longnose dace occupancy also increased with increasing stream temperature and cobble substrate and declined with increasing elevation. Native fish size structure was unrelated to brown trout presence. Our results suggest that effects of brown trout are not ubiquitous across native fishes and depend on abiotic conditions and species-specific habitat requirements, highlighting the need to consider both biotic and abiotic conditions when balancing native species conservation with introduced sportfish management.

RATE ANALYSIS OF SOIL EROSION USING UNIVERSAL SOIL LOSS EQUATION (USLE) METHOD IN JENEBERANG WATERSHED

Erosion in a watershed is a complex phenomenon that affects the quality of land resources due to either natural or human influence. The purpose of this study to determine the rate of erosion in the Jeneberang watershed and produce a recommendation of soil conservation to reduce the rate of erosion. This study uses some parameter maps, such as Rain Erosivitas Index (R) map, Land Erodibility Index (K) map, Length and Slopes Declivity Factor (LS) map, and Plants Management Factor and Soil Conservation (CP). All parameters were analysed using USLE map to determine the rate of erosion. The analysis results the rate of erosion by USLE method indicates the hazard level of the erosion in the Jeneberang watershed are dominantly at the very low levels with an area 55.068,39 ha or 71.6% of the research area. However, the erosion in the study area can not be ignored because there is a very high level of danger to the extensive erosion 11.681,55 or 15% of the research area. Therefore, generated a recommendation of soil conservation by soil cover planting and terrace construction repairs. By this conservation recommendation, the area with a high level of the rate of erosion reduce in the amount of 10,6%.

Die Design for Extrusion Process of Titanium Seamless Tube Using Finite Element Analysis

In this paper, the extrusion process of titanium seamless tubes was studied using several finite element (FE) analyses. First, the finite element result was compared with experimental extrusion data acquired to validate the current analysis. Then, the effect of design parameters of the die shape was numerically analyzed using commercial FE software, Forge NxT, for the metal forming process. Elastic FE analyses were also conducted for dies to analyze the maximum principal stress that affects the early fracture of dies during the extrusion process and the maximum von Mises stress that causes the severe deformation of dies. Consequently, the effect of the corner radius at the exit and land length on the extrusion load and die stress is negligible compared to that of the corner radius at the entrance and die angle. Finally, we suggested a die angle of 60° and a corner radius at the die entrance between 10 and 15 mm as an optimal design for the current extrusion process.

Aplikasi Model Rusle untuk Estimasi Kehilangan Tanah Bagian Hulu di Sub Das Garang, Jawa Tengah

The Garang watershed is one of the main rivers passing through Semarang City, Central Java. Garang uptream is mostly a buffer zone and a catchment area for the water and soil resources conservation of Semarang City and surroundings. This research is located in the upstream Garang watershed, with the aim of knowing the level of erosion or soil loss tolerance due to land use change.The erosion model is specific to sheet erosion which modeled with RUSLE (Revised Universal Soil Loss Equation) method. The data used are (R) ground rainfall from 7 hydrological stations for 10 years, (K) soil types derived from land form interpretation, (LS) length and slope from SRTM radar data, (CP) conservation and land cover derived using a multispectral supervised classification (maximum likelihood). The quality of modeling is maintained through validation of input data, such as the normal ratio method and consistency test of rain data, soil texture and color surveys for soil data, confusion matrices for land cover and slope validation.The research results of the upstream Garang watershed area of 1191,56 hectares (14.14%), the erosion that occurred was still below the allowable erosion limit, while the area of 7.232,67 hectares (85.86%) was erosion that occurred above the allowable erosion value. The average soil loss is 222 tonnes / ha / year with the potential for soil loss up to 39,236 tonnes per year or soil loss thickness of 3.8 cm. Even though it is within the threshold, this must be controlled considering the importance of the upstream Garang watershed, whose land cover has begun to change its function to agriculture and plantations on sloping land.

Influence of Manufacturing Parameters and Post Processing on the Electrical Conductivity of Extrusion-Based 3D Printed Nanocomposite Parts.

The influence of manufacturing parameters of filament extrusion and extrusion-based Additive Manufacturing (AM), as well as different post processing techniques, on the electrical conductivity of 3D printed parts of graphene nanoplatelets (GNP)-reinforced acrylonitrile butadiene styrene (ABS) has been analyzed. The key role of the manufacturing parameters to obtain electrically conductive filaments and 3D printed parts has been demonstrated. Results have shown that an increase in extrusion speed, as well as lower land lengths, induces higher extrudate swelling, with the consequent reduction of the electrical conductivity. Additionally, filaments with lower diameter values, which result in a higher surface-to-cross-section ratio, have considerably lower electrical conductivities. These factors tune the values of the volume and surface electrical conductivity between 10−4–100 S/m and 10−8–10−3 S/sq, respectively. The volume and surface electrical conductivity considerably diminished after 3D printing. They increased when using higher printing layer thickness and width and were ranging between 10−7–10−4 S/m and 10−8–10−5 S/sq, respectively. This is attributed to the higher cross section area of the individual printed lines. The effect of different post processing (acetone vapor polishing, plasma and neosanding, which is a novel finishing process) on 3D printed parts in morphology and surface electrical conductivity was also analyzed.

Effects of die land length and geometry on curvature and effective strain of profiles produced by a novel sideways extrusion process

Abstract In the present investigation, effects of length and geometry of die land/bearing on curved profiles/sections produced by a novel process, differential velocity sideways extrusion (DVSE), were studied through physical experiments using plasticine as a model material and finite element modelling. Profile curvature decreases as die land length increases due to its negative influence on exit velocity gradient, and a straight profile is extruded when the ratio of die land length to die orifice diameter exceeds a critical value l 0 which increases as extrusion ratio λ increases and extrusion velocity ratio v 2 / v 1 decreases. Generally, effective strain level of the extrudate slightly increases as the die land length increases. Larger die land length increases the frictional areas between extrudate surface layers and die land (and mandrel for tube extrusion), generating zone of shear along the profile edge and thus increases surface layer effective strain. As a result, the strain homogeneity over the cross-section or wall thickness (for tube extrusion) is decreased. Compared with a sharp die land/container transition corner, a chamfered or radiused die land transition corner leads to an increased curvature due to the decreased effective land length, while it decreases overall effective strain level in the cross-section and strain homogeneity as a result of lower effective strain rate across the deforming region. A sharp die land transition corner is recommended for achieving a relatively large and homogenous effective strain in the cross-section.

Model and Experimental Verification of the Dynamic Forced Performance of a Tightly Sealed Squeeze Film Damper Supplied With a Bubbly Mixture

Abstract Practice and experiments with squeeze film dampers (SFDs) sealed with piston rings (PRs) show the lubricant exits through the PR slit, i.e., the gap made by the PR abutted ends when installed, forced as a jet during the portion of a rotor whirl cycle generating a positive squeeze film pressure. In the other portion of a whirl cycle, a subambient dynamic pressure ingests air into the film that mixes with the lubricant to produce a bubbly mixture. To reduce persistent air ingestion, commercial air breathing engines utilizing PRSFDs demand of a sufficiently large lubricant supply pressure (Ps), and hence a larger flow rate that is proportional to the journal squeeze velocity (vs = amplitude r × frequency of motion ω). The stringent requirement clearly limits the applicability and usefulness of SFDs. This paper presents a computational physics model for a sealed-end SFD operating with a mixture and delivers predictions benchmarked against profuse laboratory test data. The model implements a Reynolds equation adapted for a homogeneous bubbly mixture, includes temporal fluid inertia effects, and uses physics-based inlet and outlet lubricant conditions through feed holes and PR slit, respectively. In the experiments for model validation, a SFD damper, 127 mm in diameter D, film land length L = 25.4 mm (L/D = 0.2), and radial clearance c = 0.371 mm, is supplied with an air in ISO VG2 oil bubbly mixture of known gas volume fraction (GVF), zero (pure oil) to 50% in steps of 10%. The mixture supply pressure varies from Ps = 2.06 bar-g (30 psig) to 6.20 bar-g (90 psig). Located in grooves at the top and bottom of the journal, a PR and an O-ring (OR) seal the film land. The OR does not allow any oil leakage or air ingestion; hence, the supplied mixture discharges through the PR slit into a vessel submerged within a large volume of lubricant. Dynamic load tests with a single frequency ω, varying from 10 Hz to 60 Hz, produce circular centered orbits (CCO) with amplitude r = 0.2c. The measurements record the exerted forces and journal motions and an analysis delivers force coefficients, damping and inertia, representative of the exerted frequency range. The model predicts the pressure field and evolution of the GVF within the film land and, in a simulated process replicating the experimental procedure, delivers representative force coefficients. For all Ps conditions, both predictions and tests show the SFD added mass coefficients significantly decrease as the inlet GVF (βs) increases. The experimentally derived damping coefficients do not show a significant change, except for tests with the largest concentration of air (βs = 0.5). The predicted damping differs by 10% with the test derived coefficient which does not readily decrease as the inlet GVF (βs) increases. The added mass coefficients, test and predicted, decrease with βs, both being impervious to the magnitude of supply pressure. The test PRSFD shows a quadrature stiffness due to the sliding friction between the PR being pushed against the journal. An increase in supply pressure exacerbates this unique stiffness that may impair the action of the squeeze film to dissipate mechanical energy. The comprehensive test results, first of their kind, demonstrate that accurate modeling of SFDs operating with air ingestion remains difficult as the flow process and the paths of its major components (air and liquid) are rather complex.

Unravel the landscape and pulses of cycling activities from a dockless bike-sharing system

The recent boom of sharing economy along with its technological underpinnings have brought new opportunities to urban transport ecosystems. Today, a new mobility option that provides station-less bike rental services is emerging. While previous studies mainly focus on analyzing station-based systems, little is known about how this new mobility service is used in cities. This research proposes an analytical framework to unravel the landscape and pulses of cycling activities from a dockless bike-sharing system. Using a four-month GPS dataset collected from a major bike-sharing operator in Singapore, we reconstruct the temporal usage patterns of shared bikes at different places and apply an eigendecomposition approach to uncover their hidden structures. Several key built environment indicators are then derived and correlated with bicycle usage patterns. According to the analysis results, cycling activities on weekdays possess a variety of temporal profiles at both trip origins and destinations, highlighting substantial variations of bicycle usage across urban locations. Strikingly, a significant proportion of these variations is explained by the cycling activeness in the early morning. On weekends, the overall variations are much smaller, indicating a more uniform distribution of temporal patterns across the city. The correlation analysis reveals the role of shared bikes in facilitating the first- and last-mile trips, while the contribution of the latter (last-mile) is observed to a limited extent. Some built environment indicators, such as residential density, commercial density, and number of road intersections, are correlated with the temporal usage patterns. While others, such as land use mixture and length of cycling path, seem to have less impact. The study demonstrates the effectiveness of eigendecomposition for uncovering the system dynamics. The workflow developed in this research can be applied in other cities to understand this new-generation system as well as the implications for urban design and transport planning.

Effect of die pockets on the extruded products in Multi-hole Extrusion Process: A finite element simulation study.

Multi-hole extrusion process uses a die with more than one orifice through which the billet material is allowed to flow under compressive load. This process is suitable for obtaining many extruded parts of different shapes and sizes (automobile parts and components for medical devices) from a same billet material. The extrusion load, quality of the extruded parts depend on many process parameters like extrusion ratio, billet length, location of orifices or holes on the die, die land length, die design, lubrication and extrusion speed. During design of a multi-hole die, each hole shape and the profile of the hole are mainly considered. In that context, the die pockets play a major role in the extrusion process. The pockets of different geometry and shape are provided at the entry side of the die, through which the work material flows and subsequently pass through the die land region. The properly designed die pockets help in reducing extrusion load and produces parts with less variation in length. In the present finite element study, 2-hole, 3-hole and 4-hole dies have been used to extrude a billet material of 20 mm length and 20 mm diameter at a extrusion speed of 1 mm/min. This low extrusion speed does not put any strain rate effect in the extrusion process. The FE package DEFORM 3D has been used for this study. The diameter of each hole is 3 mm and the pockets of diameter 6 mm and depths of 3, 4, 5, 6, 7 and 8 mm are used. The billet material of lead alloy is used for understanding the process in both simulation and experiments. The detailed study on the extruded product lengths, mean stress on the product and the effective strain are studied. From the study it is observed that optimum pocket geometry for a particular die provides least variation in the product length, mean stress (compressive) and an in-depth focus on the deformation behavior (effective strain study). The study will help in selecting an optimum die design for obtaining high productivity with better quality products.

Experimental Force Coefficients for Two Sealed Ends Squeeze Film Dampers (Piston Rings and O-Rings): An Assessment of Their Similarities and Differences

Squeeze film dampers (SFDs) in aircraft engines effectively aid to reduce rotor motion amplitudes, in particular when traversing a critical speed, and help to alleviate rotor whirl instabilities. The current work is a long-term endeavor focused on quantifying the dynamic force performance of practical SFDs, exploring novel design damper configurations, and producing physically sound predictive SFD models validated by experimental data. Piston rings (PRs) and O-rings (ORs), commonly used as end seals in SFDs for commercial and military gas turbine engines, respectively, amplify viscous damping in a short physical length and while operating with a modicum of lubricant flow. This paper presents experimental force coefficients (damping and inertia) for two identical geometry SFDs with end seals, one configuration hosts PRs, and the other one ORs. The test rig comprises a stationary journal and bearing cartridge (BC) hosting the SFD and supported on four elastic rods to emulate a squirrel cage. The damper film land length, diameter, and clearance are L = 25.4 mm, D = 5L, and c = 0.373 mm (D/c = 340), respectively. A supply feeds ISO VG 2 oil to the film land at its middle plane through either one hole or three holes, 2.5 mm in diameter, 120 deg apart. In the PRSFD, the lubricant exits through the slit opening at the ring butted ends. The ORs suppress oil leakage; hence, lubricant evacuates through a 1 mm hole at ¼ L near one journal end. The ORs when installed add significant stiffness and damping to the test structure. The ORSFD produces 20% more damping than the PRSFD, whereas both sealed ends SFDs show similar size added mass. For oil supplied at 0.69 bar(g) through a single orifice produces larger damping, 60–80% more than when the damper operates with three oil feedholes. A computational model reproducing the test conditions delivers force coefficients in agreement with the test data. Archival literature calls for measurement of a single pressure signal to estimate SFD reaction forces. For circular centered orbits (CCOs), the dynamic pressure field, in the absence of any geometrical asymmetry or feed/discharge oil condition, “rotates” around the bearing with a speed equal to the whirl frequency. The paper presents force coefficients estimated from (a) measurements of the applied forces and ensuing displacements, and (b) the dynamic pressure recorded at a fixed angular location and “integrated” over the journal surface. The first method delivers a damping coefficient that is large even with lubricant supplied at a low oil supply pressure whereas the inertia coefficient increases steadily with feed pressure. Predictions show good agreement with the test results from measured forces and displacements, in particular the added mass. On the other hand, identified damping and inertia coefficients from dynamic pressures show a marked difference from one pressure sensor to another, and vastly disagreeing with test results from the first method or predictions. The rationale for the discrepancy relies on local distortions in the dynamic pressure fields that show zones of oil vapor cavitation at a near zero absolute pressure and/or with air ingestion producing high frequency spikes from bubble collapsing; both phenomena depend on the magnitude of the oil supply pressure. An increase in lubricant supply pressure suppresses both oil vapor cavitation and air ingestion, which produces an increase of both damping and inertia force coefficients. No prior art compares the performance of a PRSFD vis-à-vis that of an ORSFD. Supplying lubricant with a large enough pressure (flow rate) is crucial to avoid the pervasiveness of air ingestion. Last, the discussion on force coefficients obtained from two distinct methods questions the use of an oversimplifying assumption; the dynamic pressure field is not invariant in a rotating coordinate frame.

FACTORS AFFECTING THE FLOATING AQUATIC FEED PELLETS QUALITY

Production of high quality floating aquatic feed has in recent years accounted more than 65% of the market needs of fish feed. Most of fish feed factories have tended to develop their production lines by adding extrusion units to produce floating fish feed after increasing demand from farmers for this type of feed for many reasons, such as :the high conversion rates than sinking feed , decreased the consumed amounts of fish feed in aquaculture farms about 30%,easy to follow the fish vitality during feeding process and reduced the chances of infection by fish diseases. The parameters under studied were water addition site (just pre-conditioner- just extruder barrel zones -pre-conditioner and extruder barrel zones), extruder screw configurations profile (high configuration shear, medium configuration shear and low configuration shear) and drying cooling process after extrusion (cooling only and drying with cooling). Steam percentage of (13%) added into the pre-conditioner for all study treatments as constant parameters. The floating die specifications of the extruder were L/D ratio of 30:1, land length diameter of 2.5 mm and the die consists of 10 holes each outer diameter of 2.5mm. The optimum running parameters for proceeds floating aquatic feed were water addition into both pre-conditioner and extruder barrel zones (9%PC+5%EX), high shear screw configurations profile, and drying process for 10.5 min at air temperature of 210oC with cooling process for 5.5 min. The result of extruder performance and floating pellets quality measurements for these parameters were, extruder production rate of 196.6 kg/h, extruder specific mechanical energy (SME) of 130.7 kJ/kg, floating pellets bulk density of 332.9 kg/m3, final product pellets expansion ratio of 2.28, and floating pellets water stability of 100% after 33 h in water.

Finite Element Analysis and Experimental Study on Forward, Backward and Forward-backward Multi-hole Extrusion Process

The present work investigates the multi-hole extrusion process. Forward, backward and forward-backward multi-hole extrusions have been carried out to determine the extrusion load and variation of extruded product lengths. The process parameters like extrusion speed and die land lengths are considered. The extrusion load depends on the extrusion speed. The friction conditions and the ironing effect also affect the extrusion load. The variations of extruded product lengths depend on the die land length. The 5-hole die and 9-hole dies exhibits different material flow behavior and due to which the load and product lengths vary. The finite element analysis also shows a good agreement in results of experiments.

Land snails benefit from human alterations in rural landscapes and habitats

AbstractMetapopulation functioning in the context of landscape and habitat structure is generally well understood. However, in human‐transformed landscapes, human disturbance may affect not only a species of interest but also biotic interactions in which that species is engaged, which has been rarely studied at multiple spatial scales. We tested (1) the associations between local (habitat and micro‐habitat) and landscape factors and the occurrence and abundance of the land snail Cepaea nemoralis and two of its predators (thrushes and mice); and (2) the hypothesis that human disturbances modify associations between C. nemoralis and its predators. We surveyed snail colonies in rural landscapes of Poland. Generalized linear mixed models were used to test the stated hypotheses. At the landscape scale, the occurrence of C. nemoralis colonies was positively related to the cover of suitable habitats, fallow/waste land, and road length in the surrounding landscape. Bird predator abundance was positively correlated with the occurrence of snail colonies, mostly at sites with a high human impact, and was negatively correlated with snail abundance at sites with low human disturbance. Snail occurrence and abundance at the micro‐habitat scale were positively correlated with variables describing the proximity of shelter and humidity. Avian predation pressure was negatively correlated with forest and settlement cover, whereas rodent predation pressure was positively associated with snail abundance and was negatively correlated with bird abundance. Human disturbance at the habitat and landscape scales benefited C. nemoralis through the creation of suitable habitats and scaling down of avian predation pressure. Conditions related to shelter and humidity were linked to the distribution and abundance of snails at the micro‐habitat scale.

Travelled Distance Estimation for GPS-Based Round Trips Car-Sharing Use Case

Traditional travel survey methods have been widely used for collecting information about urban mobility although Global Position System (GPS) has become an automatic option for collecting more precise data of the households since mid-1990s. Many studies on mobility patterns have focused on the GPS advantages leaving aside its issues such as the quality of the data collected. However, when it comes to extract the frequency of the trips and travelled distance, this technology faces some gaps due to the related issues such as signal reception and time-to-first-fix location that turns out in missing observations and respectively unrecognised or over-segmented trips. In this study, we focus on two aspects of GPS data for a car-mode, (i) measurement of the gaps in the travelled distance and (ii) estimation of the travelled distance and the factors that influence the GPS gaps. To asses that, GPS tracks are compared to a ground truth source. Additionally, the trips are analysed based on the land use (e.g. urban and rural areas) and length (e.g. short, medium and long trips). Results from 170 participants and more than a year of GPStracking show that around 9 % of the travelled distance is not captured by GPS and it affects more short trips than long ones. Moreover, we validate the importance of the time spent on the user activity and the land use as factors that influence the gaps in GPS.

Chip inward curl and its influence on dimensional accuracy in groove cutting with a novel restricted contact tool

Tool geometry has a significant influence on cutting force, cutting temperature, and surface quality. Restricted contact tools show good advantages in reducing cutting force, decreasing temperature, and improving surface quality. In this article, a new pattern of chip curl, “chip inward curl,” and its influence on dimensional accuracy were investigated using a novel restricted contact tool when cutting grooves. This novel restricted contact tool has symmetrical tool/chip contact length which varies along the main cutting edge and has a smaller tool land length in the middle of the rake face. In order to analyze the chip inward curl and its influence on dimensional accuracy with this novel restricted contact tool, a theoretical method to predict the chip back-flow angle using a slip-line model taking into consideration of cutting tool edge was proposed. Dimensional accuracy of the grooves achieved by this novel restricted contact tool in groove cutting tests was investigated and compared with those cut by a conventional flat-faced tool. Also, three-dimensional finite element models were developed to analyze the chip back-flow angle and chip inward curl. Results indicate that this new type of restricted contact tool has significant advantages in the control of chip curl and obtains better dimensional accuracy in groove cutting.