Uniform Value Research Articles

Fully Convolutional Network and Visual Saliency-Based Automatic Optic Disc Detection in Retinal Fundus Images.

We present in this paper a novel optic disc detection method based on a fully convolutional network and visual saliency in retinal fundus images. Firstly, we employ the morphological reconstruction-based object detection method to locate the optic disc region roughly. According to the location result, a 400 × 400 image patch that covers the whole optic disc is obtained by cropping the original retinal fundus image. Secondly, the Simple Linear Iterative Cluster approach is utilized to segment such an image patch into many smaller superpixels. Thirdly, each superpixel is assigned a uniform initial saliency value according to the background prior information based on the assumption that the superpixels located on the boundary of the image belong to the background. Meanwhile, we use a pretrained fully convolutional network to extract the deep features from different layers of the network and design the strategy to represent each superpixel by the deep features. Finally, both the background prior information and the deep features are integrated into the single-layer cellular automata framework to gain the accurate optic disc detection result. We utilize the DRISHTI-GS dataset and RIM-ONE r3 dataset to evaluate the performance of our method. The experimental results demonstrate that the proposed method can overcome the influence of intensity inhomogeneity, weak contrast, and the complex surroundings of the optic disc effectively and has superior performance in terms of accuracy and robustness.

DEGRADATION OF SOME POLYSTRENE USING BEETLE LARVAE (TENEBRIO MOLITOR L.)

One alternative to waste processing polystyrene is to use Tenebrio molitor larvae. This study aims to determine the increase in body length and weight, rate of degradation, and value of Waste Reduction Index (WRI) of larvae T. molitor. This study used laboratory experimental using completely randomized design experimental design model (CRD) data analysis with control and 4 feed treatments. Each treatment level was repeated 5 times in order to obtain 25 experimental units. Larvae were reared in a plastic container containing 10 larvae. Each larvae were given bran feed for control and polystrene for treatment, each feed as much as 1 gram. The polystyrene used were food packaging, walls, electronic packaging, and ice boxes. Larvae were measured for length and body weight every 3 days for 30 days. Parameters observed were increase in length and weight of larvae, rate of degradation and WRI values.The highest mean value of increase in larval length on the polystrene wall was 1.69 cm. The lowest value was polystyrene food packaging (1.59 cm). The average weight gain of larvae has a uniform value in the control and treatment of 0.07 gr. The highest degradation rate and WRI values were polystyrene wall and electronic packaging at 0.019 and 0.63%. while the lowest values were polystyrene food packaging at 0.11 and 0.37%.

Optofluidic Platform Based on Liquid Crystals in X-Cut Lithium Niobate: Thresholdless All-Optical Response

In this study, we present a new configuration of the recently reported optofluidic platform exploiting liquid crystals reorientation in lithium niobate channels. In order to avoid the threshold behaviour observed in the optical control of the device, we propose microchannels realized in a x-cut crystal closed by a z-cut crystal on the top. In this way, the light-induced photovoltaic field is not uniform inside the liquid crystal layer and therefore the conditions for a thresholdless reorientation are realized. We performed simulations of the photovoltaic effect based on the well assessed model for Lithium Niobate, showing that not uniform orientation and value of the field should be expected inside the microchannel. In agreement with the re-orientational properties of nematic liquid crystals, experimental data confirm the expected thresholdless behaviour. The observed liquid crystal response exhibits two different regimes and the response time shows an unusual dependence on light intensity, both features indicating the presence of additional photo-induced fields appearing above a light intensity of 107 W/m2.

Effects of beam oscillation modes on microstructure and mechanical properties of laser welded 2060 Al-Li alloy joints

In the present work, laser welding of 2-mm-thick 2060 Al-Li alloy was performed under different beam oscillation modes. Weld seam morphology, microstructure, mechanical properties were compared. The results indicated that joints welded by oscillated laser beam possessed improved collapse, refined grains, higher microhardness and tensile strength. In fusion zone, nondendritic equiaxed grains, parallel dendrite grains and cellular dendrite grains were formed in all welded joints. After applying laser beam oscillation, the collapse decreased from 0.54 mm to 0.1 mm. The maximum tensile strength of welded joint was obtained in the case of ‘8′ shaped laser beam oscillation reaching 338.15 MPa, which was improved by 68% compared with that of joint without oscillation (200.58 MPa). In this case, grain characters and molten pool fluid were studied to reveal the enhancement mechanism of beam oscillation. Enhanced fluid velocity produced with ‘8′ shaped laser oscillation refined grains and more high angle grain boundaries (HAGBs) were formed. The grain size was reduced from 105.27 μm to 89.67 μm in cellular dendrite zone (CDZ). The percentage of HAGBs increased from 65.2% to 75.2%. The refined grains resulted in larger and more uniform microhardness value and better mechanical behavior. Shallower, crystal-sugar shaped dimples were formed in fracture surface obtained by pure laser welding without oscillation while deeper and bigger dimple, including equiaxed dimple and conical dimple were generated in the fracture surfaces of oscillated laser welded joints.

Self-terminating contactless photo-electrochemical (CL-PEC) etching for fabricating highly uniform recessed-gate AlGaN/GaN high-electron-mobility transistors (HEMTs)

Contactless photo-electrochemical (CL-PEC) etching was used to fabricate recessed-gate AlGaN/GaN high-electron-mobility transistors (HEMTs). Self-termination of etching was observed during CL-PEC etching on an AlGaN barrier layer whose residual thickness had a uniform value of 6 nm overall on the same chip. After tetramethylammonium hydroxide post-treatment, the root-mean-square roughness of the etched surface was around 0.4 nm, which had smoothness comparable to that of the unetched surface. Recessed-Schottky HEMTs showed a positive shift in Vth, the suppression of drain leakage currents, and an improvement in the subthreshold-slope value as compared with planar-gate HEMTs. By applying a metal–insulator–semiconductor (MIS)-gate structure, the gate and drain leakage currents were significantly reduced, leading to an increased input dynamic range. Furthermore, the standard deviations (σ) of the Vth of CL-PEC-etched recessed-Schottky HEMTs and recessed-MIS HEMTs were very small, 5.5 and 16.7 mV, respectively. These results showed that the CL-PEC etching process is promising for the fabrication of recessed-gate AlGaN/GaN HEMTs having excellent uniformity for normally-off device operations.

Improving our ability to model crystalline aquifers using field data combined with a regionalized approach for estimating the hydraulic conductivity field

Modelling of heterogeneous aquifers, such as crystalline aquifers, is often difficult and, flow and transport predictions are always uncertain, suffering of our imperfect knowledge of the spatial distribution of aquifer parameters. This paper aims to test the robustness of a first-order hydraulic conductivity map estimated from both a detailed water-table map and hydraulic-conductivity statistics on a granitic watershed in Brittany (57 km2), compare it to local estimates and assess it through various numerical models. Map values range on four orders of magnitude (10-7 to 10-4 m/s, mean: 3.9x10-6 m/s) and their comparison to local estimates from various sources (pumping tests, MRS measurements, streamflow) gives satisfactory results.Four hydraulic conductivity fields were assessed through numerical modelling under steady-state condition. Model 1 used the regionalized hydraulic conductivity field directly, Model 2 used a uniform value (average of Model 1), Model 3 used a hydraulic conductivity field obtained by inverse modelling of the water table and Model 4 used two zones of uniform values based on the analysis of Model 1 and Model 3 fields. Model results were analysed based on their ability to reproduce the observed water-table levels and the groundwater flow directions. Modelled groundwater discharges to streams at sub-catchment scale were compared to spatial streamflow measurements performed during low water condition, which help validating models. The comparison between the fields obtained from Model 3 and that from the regionalized method (Model 1) shows that they are close in terms of mean values and spatial distribution. Model 1 reproduces rather well the water-table map and the groundwater flow directions. Model 2 shows the less good results. Model 4 has led to satisfactory results and shows that the hydraulic conductivity is higher (2.1x10-6 m/s) where the water table is located in the fractured zone, and lower (3.3x10-7 m/s) where it is located in the saprolites (highly weathered rock), which is expected for such aquifer system. Modelled groundwater discharges to streams are comparable in all models to streamflow measurements in most sub-catchments, but the models overestimate them in certain places, mainly because of sub-surface drains in a forest capturing part of the groundwater that can no longer return to streams (drains were not considered in the models).In addition, experiment on a second watershed (40 km2) shows how with much less field data the methodology can already provide interesting information on the hydraulic conductivity field (values and spatial distribution).Results are very encouraging and open up prospects for using quantitative and qualitative information from the mapping of hydraulic conductivity to constrain the spatialization of hydrodynamic parameters on models and thus our ability to model such complex aquifers.

Dosimetry during adjuvant 131I therapy in patients with differentiated thyroid cancer-clinical implications

The activity of radioiodine (131I) used in adjuvant therapy for thyroid cancer ranges between 30 mCi (1.1 GBq) and 150 mCi (5.5 GBq). Dosimetry based on Marinelli's formula, taking into consideration the absorbed dose in the postoperative tumour bed (D) should systematise the determination of 131I activity. Retrospective analysis of 57 patients with differentiated thyroid cancer (DTC) after thyreidectomy and adjuvant 131I therapy with the fixed activity of 3.7 GBq. In order to calculate D from Marinelli's formula, the authors took into account, among other things, repeated dosimetry measurements (after 6, 24, and 72 h) made during scintigraphy and after administration of the therapeutic activity or radioiodine. In 75% of the patients, the values of D were > 300 Gy (i.e. above the value recommended by current guidelines). In just 16% of the patients, the obtained values fell between 250 and 300 Gy, whereas in 9% of the patients, the value of D was < 250 Gy. The therapy was successful for all the patients (stimulated Tg < 1 ng/ml and 131I uptake < 0.1% in the thyroid bed in follow-up examination). Dosimetry during adjuvant 131I therapy makes it possible to diversify the therapeutic activities of 131I in order to obtain a uniform value of D.

Experimental Analysis of Incipient Motion for Uniform and Graded Sediments

So far, few studies have focused on the concept of critical flow velocity rather than bed shear stress for incipient sediment motion. Moreover, few studies have focused on sediment mixtures (graded sediment) and shape rather than uniform sediment for incipient motion condition. Different experiments were conducted at a hydraulic laboratory at the University of Guilan in 2015 to determine hydraulic parameters on the incipient motion condition. The aim of this study is to conduct a comparison between uniform and graded sediments, and a comparison between round and angular sediments. Experiments included rounded uniform bed sediments of 5.17, 10.35, 14 and 20.7 mm, angular uniform sediment of 10.35 mm, and graded sediment. Results demonstrated that angular sediment has a higher critical shear velocity than rounded sediment for incipient motion. Results also showed that for a given bed sediment, although critical shield stress and relative roughness increased with the bed slope, the particle Froude number (based on critical velocity) decreased. In terms of the sediment mixture, the critical shear stress (Vc*) was higher for the graded sediment than for the three finer uniform sediment sizes. The finer fractions of the mixture have a higher particle Froude number than their corresponding uniform sediment value, while the coarser fractions of the mixture showed a lower stability than their corresponding uniform sediment value. Results demonstrated that the reduction in the particle Froude number was more evident in lower relative roughness conditions. The current study provides a clearer insight into the interaction between initial sediment transport and flow characteristic, especially particle Froude number for incipient motion in natural rivers where stream beds have different gravel size distribution.

Freshwater production by combination of solar still, earth-air heat exchanger and solar chimney for natural air draft

ABSTRACT A theoretical study of humidification-dehumidification (HDH) processes inside a system combining a solar still with an earth-air heat exchanger and a solar chimney was introduced. Energy and mass balances in a transient mode for the solar still and the earth-air heat exchanger in addition to the solar chimney were formulated and numerically simulated. The solar radiation heats water in the solar still basin, which in turn warms and humidifies dry air entering the solar still due to the heat and mass transfer into the airstream. When the glass/or the EAHE pipe wall temperatures are lower than or equal to the dew point of the humid air, the vapour condenses and runs down. The results show that the water, the air, and the glass temperatures increase with time to reach their maximum values (66.9 oC,61.8 oC, and 61.24 °C respectively) in June from 15.00 to 16.00. The humidity ratio along with the solar still length increases to reach a uniform value whenever the moist air is saturated. At the same time, the humidity ratio along EAHE decreases due to the condensation of the moisture inside the EAHE pipe. The condensation rate in the EAHE decreases gradually along a pipe length of 70 m until it completely vanishes at the pipe outlet. The hourly condensation rate in the EAHE attaining its maximum value of 49.27 kg/hr. at 14:32 (Basra local time) in June where the solar radiation is at maximum value. Also, the results indicated that the productivity of freshwater in the solar still is strongly affected by the water, air, and glass temperatures. The maximum productivity in the solar still achieved in March was 157 kg/day while it was 369 kg/day in July for the EAHE. The increase of the air velocity increases the productivity in EAHE and decreases it in the solar still. The daily average freshwater production for the system (solar still and the earth-air heat exchanger) throughout the year was found to be 207.44 kg. The thermal efficiency of the system over the interval from 6:00 to 19:00 was found to be 0.23–0.55. The economic evaluation showed that the cost of freshwater production was 0.0282 $/kg. A comparison of the current analysis with other works showed a good agreement.

Numerical study on the supersonic near-wake flow structures of a cylinder at an angle of attack

The supersonic near-wake flow experiment conducted by Dutton on a cylinder with 10 degrees angle of attack was studied numerically with Delayed Detached Eddy Simulation (DDES) method. The wind tunnel test section were included in the geometry model to examine if its omission led to the unsuccessful prediction of several important flow features in previous studies. Flow structures were compared to experiment measurements, Gaitonde's k-ε model results and our previous Monotonically Integrated Large Eddy Simulation (MILES) results. It was revealed that with present geometry model and numerical method, good agreements with wind tunnel experiment result were obtained, including the wave structures, density fields and velocity fields. In particular, the inclusion of wind tunnel test section wall in geometry model reproduces the finite area nozzle exit flow and the expansion wave behind the recirculation zone in the actual experiment setup, which lead to correct prediction of the position of maximum streamwise velocity point. The present simulation also reproduced the uniform pressure profile and value observed in the experiment and the deviation between computation and experiment was within 10%. The flow field data obtained was further analyzed to investigate the vortex surface shape and recirculation region shape in near wake flow with non-zero angle of attack and significant differences were found compared to the zero angle of attack case. The vortex surfaces show a non-axisymmetric slitting movement in the near wake region, which gives an explanation to the non-circular density contour pattern on streamwise flow field slices. The recirculation region shape was identified with zero isosurface of streamwise velocity and was found to be of complex three-dimensional shape with maximum length beside the symmetry plane and a local minimum at windward side of the symmetry plane, which is significantly different from that of zero angle of attack case. The observation that the length of the recirculation zone was greatly reduced on the symmetry plane at non-zero angle of attack in previous study is due to the aforementioned local minimum on the symmetry plane. The reduction of recirculation length is much less if we consider the three-dimensional shape of the region.

Response Surface Methodology to predict the performance and emission characteristics of gas-diesel engine working on producer gases of non-uniform calorific values

Energy generation through gasification technology has received significant attention from policy makers and researchers. To promote government policies on biomass and utilize energy source that are abundantly available in rural areas, suitable technologies must be developed with a focus on popular applications in a place. The biomass in rural areas differs from place to place and they may not generate uniform calorific value (CV) of producer gas (PG). The quality of PG is essential to run engines of power generators with required performance. Hence, in this study, a mathematical investigation was performed on a dual-fuel diesel engine for CV of PG from 3.4 to 6.6 MJ/Nm3. The major objective was to find the impact of the variation in CV of PG from coir pith, rice husk, rubber wood, coconut shell and rubber seed kernel shell on the performance of the engine. Response Surface methodology with suitable tools had been used for developing the model. The model predicted the optimum thermal efficiency, specific energy consumption and diesel replacement rate as 25.8%, 13.95 MJ/kWh and 59.04% respectively while calorific value of PG was 6.57 MJ/Nm3. However, CO and NOx emissions were found increasing with the increase in calorific value of PG.

Thermal Transport Analysis of Injected Flow through Combined Rib and Metal Foam in Converging Channels with Application in Electronics Hotspot Removal

The development of miniaturized and more powerful electronic devices and microprocessors has resulted in high heat generation and temperature values in these components. That affects the performance, reliability and lifespan of the devices. In addition, more local hot spots are generated in the components that require even more attention to prevent stress failure and fatigue. As such, the employment of advanced electronics cooling systems is very essential to keep the temperature below the safe temperature. In this work, innovative cooling systems are developed and analyzed employing jet impingement technology, high conductive metal foam, rib structured target surfaces, confined non-uniform small-scale channel, and conductive heat spreader plate. The base of the foam-filled cooling channel is subject to a uniform high heat flux value resembling the electronics device to be cooled. For numerical modeling of thermal transport through foam filled region, the local thermal non-equilibrium model in porous media is utilized resulting in two energy equations for solid and fluid phases. For better understanding of flow and thermal characteristics of jet impingement through the combination of metal foam and rib structured surfaces in confined channels, several effective parameters are studied such as slot and circular jet impingements, the shape and orientation of the ribs, impinging jet velocity, applied heat flux and the thickness of conductive heat spreader plate for hotspot removal. The results show that the fully foam filled channel provides a more efficient cooling in comparison with partially foam filled channel. Furthermore, the results indicate the advantage of utilization of ribs at the stagnation region of the impinging jet, for local thermal treatment of hotspots. The perpendicular cuboid ribs placed at the stagnation zone of the coolant jet impingement provide 13% increase in maximum local Nusselt number while the increase in the pressure drop and required pumping power are as small as 4.2%. Doubling the velocity would result in 35.3% increase in the maximum local Nusselt number, 180% increase in the pressure drop and 460.7% increase in the required pumping power. An increase in the thickness of the conductive heat spreader plate increases the base local temperature but improves local temperature uniformity.

Prevention, precaution and resilience: Are they worth the cost?

The assumption that risk, represented as an expected value of the loss could be implied to be a measure of safety, in a cost benefit analysis, is firmly entrenched in economic risk analysis. However, this does not mean that without a marker, the value of a loss, can be established with any necessary level of certainty to make such a cost balancing act ethically possible. The appropriateness of using the Value of a Statistical Life (VOSL) at all in a safety analysis, is a matter of perspective, which renders attempts to establish a uniform value of a statistical life questionable. This makes it questionable whether decisions from which values for a VOSL were evaluated, really were based on consideration of saving lives, or whether other arguments, such as available budget, were much more dominant. Ethical considerations do not seem to be in the frame of corporate risk management, where loss-of-life catastrophes appear to be simply the cost of doing business. Because there is no real basis for any estimate of the value of a statistical life, the values employed in cost-benefit analyses therefore only seem to serve the purpose of dissembling, concealing that the decision is taken on grounds other than saving human lives, or even that potential harm to humans was not even considered. The strict meaning given to resilience as at most to make a plan for recovery and see if we can live with the consequences, seems just another step towards putting the economy before people.

Deflection test and modal analysis of lightweight timber floors

In order to meet the objective requirements of the safety and comfort of the modern lightweight timber floors, and strengthen the research on the coupling performance of the lightweight timber floors vibration characteristics and the building comfort, this article discusses the floor of a two-story prefabricated lightweight timber building demonstration house. In this paper, the floor structure of a two-story light-weight wooden house has been carried out on structural calculation modal and experimental modal, static uniform load and concentrated load deflection value testing. The evaluation of the deflection value of the floor structure, the mode shape, the coupling of the fundamental frequency mode parameters, and the vibration comfort were also studied. The results show that the fundamental frequency simulation value, one-way modal test value and two-way modal test value of the floor structure all meet the requirements of BS-6472 (BS6472-1:2008). That is, the floor structure is not lower than 8 Hz design requirements, and meets the frequency of BS-6472(BS6472-1:2008). The weighted root mean square acceleration is lower than the requirement of 0.45 m/s2; the first three natural frequencies of the floor structure calculated by the finite element simulation are 16.413, 31.847 and 48.921 Hz, and the fundamental frequency mode is the bending vibration in the length and width directions. The second order is the bending mode in the length direction, and the third order is the bending mode in the width direction. The fundamental frequency of the two-way modal test of the floor structure is the first-order bending mode in the X direction; and the second-order natural frequency is the second-order bending vibration shape in the X direction. when the uniform load is mainly the weight of floor own, the simulated maximum deflection value is 1.0658 mm; the simulation is performed according to the standard value of 0.566 kN/m for the uniform load of the floor design, and the simulation is the largest. The maximum deflection value of the simulated floor is 1.47383 mm at its midpoint, which meets the requirements of National Building Code of Canada-2015 (NBCC). The maximum deflection limit of the light wood structure floor system is lower than 3 m and the maximum deflection limit is 2 mm; the six deflection value test lines simulated under a concentrated load of 1 kN all present a parabolic distribution and are symmetrical. The above results has engineering application value for promoting the research on the vibration characteristics of the fabricated lightweight timber floors structure and its optimization design.

A revised mineral dust emission scheme in GEOS-Chem: improvements in dust simulations over China

Abstract. Mineral dust plays a significant role in climate change and air quality, but large uncertainties remain in terms of dust emission prediction. In this study, we improved treatment of the dust emission process in a global 3-D chemical transport model (GEOS-Chem v12.6.0), by incorporating the geographical variation of aerodynamic roughness length (Z0), smooth roughness length (Z0s) and soil texture and by introducing the Owen effect and the formulation of the sandblasting efficiency α by Lu and Shao (1999). To investigate the impact of the modifications incorporated in the model, several sensitivity simulations were performed for a severe dust storm during 27 March to 2 April 2015 over northern China. Results show that simulated threshold friction velocity is very sensitive to the updated Z0 and Z0s field, with the relative difference ranging from 10 % to 60 % compared to the original model with a uniform value. The inclusion of the Owen effect leads to an increase in surface friction velocity, which mainly occurs in the arid and semi-arid regions of northwest China. The substitution of a fixed value of α assumed in the original scheme with one varying with friction velocity and soil texture based on observations reduces α by 50 % on average, especially over regions with sand texture. Comparisons of sensitivity simulations and measurements show that the revised scheme with the implementation of updates provides more realistic threshold friction velocities and PM10 mass concentrations. The performance of the improved model has been evaluated against surface PM10 observations as well as MODIS aerosol optical depth (AOD) values, showing that the spatial and temporal variation of mineral dust are better captured by the revised scheme. Due to the inclusion of the improvement, average PM10 concentrations at observational sites are more comparable to the observations, and the average mean bias (MB) and normalized mean bias (NMB) values are reduced from −196.29 µg m−3 and −52.79 % to −47.72 µg m−3 and −22.46 % respectively. Our study suggests that the erodibility factor, sandblasting efficiency and soil-related properties which are simply assumed in the empirical scheme may lack a physical mechanism and spatial–temporal representativeness. Further study and measurements should be conducted to obtain a more realistic and detailed map of these parameters in order to improve dust representation in the model.

Fractional-atom search algorithm-based deep recurrent neural network for cancer classification

Deep learning has been paid great attention in several fields for the good reason, and their results achieved were not before possible. In deep learning, the models are trained based on huge labelled dataset and the neural network architectures consist of several layers. Still, the methods suffer to achieve expected higher performance and introduce poor classification accuracy. Towards improving the classification performance, this paper introduces the deep learning networks for the cancer classification application. The main aim is to develop the optimized model for classification application. Accordingly, the input data is pre-processed using Log transformation for converting the data to its uniform value range. Then, the feature selection is done based on Wrapper approach to select the important features for classifying the cancer. Once the features are selected, the cancer classification is performed using Deep Recurrent Neural Network (Deep RNN), which is trained by the proposed Fractional-Atom Search Algorithm (Fractional-ASO). The Fractional-ASO is designed by integrating Fractional Calculus with Atom Search Optimization (ASO). The performance of the Fractional-ASO-based Deep RNN is evaluated in terms of accuracy, True Positive Rate (TPR) and True Negative Rate (TNR). The proposed Fractional-ASO -based Deep RNN method achieves the maximal accuracy of 92.87%, maximal TPR of 92.87%, and the maximal TNR of 93.48% using colon dataset.

Role of homogeneous distribution of SiC reinforcement on the characteristics of stir casted Al–SiC composites

Stir casting process is very popular for the fabrication of particle reinforced metal matrix composites. However, achieving a homogenous distribution of the reinforcement particles is very challenging, which directly affect the final mechanical performances. In this research, a detailed investigation was conducted to obtain a superior synthesis of Al–SiC composite materials and to detect the effect of SiC particles distribution on the mechanical characteristic of the stir casted Al matrix composites using glycerol–water based model. The glycerol–water based model study displays the impacts of viscosity of Al melt (1.04–1.24 mPa.s), impeller position (10–50%), stirring speed (100–300 rpm) and blade angle (0–90°) on the vortex height, dispersion time, settling time and clustering of particles. The results of the experiments using glycerol–water based model, 45° blade angles, impeller position of 40% from the base, stirring speed of 250 rpm showed the best uniform distribution of reinforcement particles. Confirmation experiments were carried out by fabricating Al–SiC PRMMC based on three different viscosities (1.04, 1.13, and 1.24 mPa.s) of Al melt and considering other parameters as constant. Fabricated Al–SiC samples were analysed by Scanning Electron Microscope (SEM) and mechanical testing such as tensile, hardness and wear tests. Based on the confirmation results, the viscosity of 1.13 mPa.s for Al melt (at 750 °C) resulted in uniform distribution of SiC particles, which enhanced the tensile strength by 4%, wear resistance by 21%, and led to a uniform hardness value of 47 VHN throughout the composites.

A Comprehensive Review of Specific Yield in Land Surface and Groundwater Studies

AbstractSpecific yield is a key parameter for estimating water table depth in land surface models, which can strongly modulate the interaction between soil moisture and groundwater and further affect the water budget between the land surface and the atmosphere. The error in water table simulation comes mainly from the uncertainty in determining the specific yield. The determination of specific yield in land surface models is simplified, and a uniform empirical constant value of specific yield is generally used in global simulations, especially for deep aquifers, for its convenience. However, a uniform fixed value is insufficient for worldwide aquifers with diverse environments. Before estimating specific yields for global aquifers in Earth system simulations, a comprehensive understanding of the specific yield and comparison of current determination methods are required. This study provides a comprehensive review of the literature focusing on different concepts of the specific yield, complex variabilities, and various determination methods. Specifically, we detail the distinction and interconversion of different subconcepts that are used to reflect the influence of different factors on the specific yield and are likely to confuse scholars; present the representative comparisons of previous estimated specific yields using different methods, and summarize the applicabilities and limitations of these methods, indicating directions for their future improvement.

Simulasi Penempatan Rorak Sebagai Bentuk Pengoptimalan Konservasi Air

Trenching is a form of soil and water conservation engineering that is commonly used and is known to be effective in controlling runoff and increasing water content in the root zone of plants. There are various configurations of trench placement in the field and this study aims to simulate the placement of trench by comparing the three trench configurations to find out which configuration is most effective in capturing surface runoff. The simulation is carried out by calculating the catchment capacity of surface runoff under different rainfall intensity conditions and runoff coefficients in the three trench configurations that have different catchment areas. From the calculation, it is known that configuration 3 in optimal conditions has a comparative advantage of 41.67% - 68.80% (compared to configuration 1) and 27.78% - 52.83% (compared to configuration 2). Meanwhile, configuration 2 has a comparative advantage of 13.89% - 16.06% when compared to configuration 1. From the calculation it is also known that there are conditions where the three configurations will produce a uniform value so that there will be no comparative advantage between the three configurations. This condition is generally above the rain intensity of 50 mm per hour and the runoff coefficient is above 0.45.&#x0D;

Modelling of shrinkage formation in casting by the phase field method

Most commercial softwares simulating casting process use a scalar field to quantify the shrinkage on final parts. The repartition of this scalar is used to localize shrinkage in the part. In this work, the objective is to use a new approach to predict morphological information about size and shape of shrinkage: the phase field method. This method is based on a parameter order defining the alternating zones metal/gas. Starting with a uniform unit value of this scalar, the phase field equation is modified with a nucleation process predicting the growth of the air phase into the metal one still liquid. The coupling with the Navier-Stokes equation brings up some interesting non-dimensional parameters that affect shrinkage morphology. This is what we have tried to analyse after proposing the modified phase fields formalism. Even if we are not yet in the predictive stage, we present in the end of this paper a numerical/experimental comparison showing the potentiality of the developed approach.