Cold Spray Deposition of Freestanding Inconel Samples and Comparative Analysis with Selective Laser Melting

Cold spray offers the possibility of obtaining almost zero-porosity buildups with no theoretical limit to the thickness. Moreover, cold spray can eliminate particle melting, evaporation, crystallization, grain growth, unwanted oxidation, undesirable phases and thermally induced tensile residual stresses. Such characteristics can boost its potential to be used as an additive manufacturing technique. Indeed, deposition via cold spray is recently finding its path toward fabrication of freeform components since it can address the common challenges of powder-bed additive manufacturing techniques including major size constraints, deposition rate limitations and high process temperature. Herein, we prepared nickel-based superalloy Inconel 718 samples with cold spray technique and compared them with similar samples fabricated by selective laser melting method. The samples fabricated using both methods were characterized in terms of mechanical strength, microstructural and porosity characteristics, Vickers microhardness and residual stresses distribution. Different heat treatment cycles were applied to the cold-sprayed samples in order to enhance their mechanical characteristics. The obtained data confirm that cold spray technique can be used as a complementary additive manufacturing method for fabrication of high-quality freestanding components where higher deposition rate, larger final size and lower fabrication temperatures are desired.     

Acid resistance of polyester-impregnated modified cement mortar

The influence of distilled water and sulphuric acid solutions on the physico-mechanical properties of neat and modified cement mortar has been investigated. The samples were immersed in distilled water, and different concentrations of sulphuric acid ranged from 5–15% by vol for immersion times from 1 to 120 days. The effect on the loss of weight, compressive strength, apparent porosity, water absorption, IR, and SEM were studied. The results indicate that the compressive strength and loss of weight decrease, whereas the apparent porosity and water absorption increase with immersion time and acid concentration. These are probably due to partial dissolution of the set cement. IR spectra and SEM studies showed significant changes in some absorption bands and the appearances of new voids of the neat and composite mortars after being immersed in H₂SO₄ solutions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 685–693, 1999     

PREDICTION OF MOLAR VOLUMES, VAPOR PRESSURES AND SUPERCRITICAL SOLUBILITIES OF ALKANES BY EQUATIONS OF STATE

A generalized cubic equation of state which can represent all the cubic equations is introduced and thermodynamic property relations for it are presented. Five cubic equations of states with respective mixing rules are used to predict molar volumes and vapor pressures of pure alkanes (from methane till n-tritriacontane) and solubilities of solid wax components (high molecular weight alkanes) in supercritical solvents. They are the RK (Redlich-Kwong), MMM (Mohsennia-Modarress-Mansoori), RM (Riazi-Mansoori), PR (Peng-Robinson), and SRK (Soave-Redlich-Kwon) equations of state. The experimental data necessary to compare the equations of state are taken from the literature. It is demonstrated that the SRK equation of state is more accurate for predicting vapor pressures of alkanes. The RM equation of state is shown to be more accurate for predicting molar volumes of saturated and sub-cooled liquid alkanes as well as molar volumes of alkanes in their supercritical condition. For the solubility of wax components in supercritical solvents it is shown that the MMM equation of state gives the least AAD% for the 270 data points of 10 binary systems studied consisting of a high molecular weight alkane and supercritical ethane and carbon dioxide.     

Modelling Energy Dissipation Over Stepped-gabion Weirs by Artificial Intelligence

The hydraulics of energy dissipation over stepped-gabion weirs is investigated by carrying out a series of laboratory experiments, building models to explain the experimental data, and testing their robustness by using the data reported by other researchers. The experiments comprise: six different stepped-gabion weirs tested in a horizontal laboratory flume, a wide range of discharge values, two weir slopes (V:H): 1:1 and 1:2, and gabion filling material gravel size (porosity equal to 38 %, 40 % and 42 %). These experimental setups were selected to ensure the development of both the nappe and skimming flow regimes within the measured dataset. The models developed for computing energy dissipation over stepped-gabion weirs comprise: multiple regression equations based on dimensional analysis theory, Artificial Neural Network (ANN) and Gene Expression Programming (GEP). The analysis shows that the measured data capture both flow regimes and the transition in between them and above all, and by using all of the data, it may be possible to identify the range of each regime. Energy dissipation modelled by the ANN formulation is successful and may be recommended for reliable estimates but those by GEP and regression analysis can still serve for rough-and-ready estimates in engineering applications.     

Assessing the Accuracy of GIS-Based Analytical Hierarchy Process for Watershed Prioritization; Gorganrood River Basin,Iran

Watershed prioritization based on the natural and anthropogenic factors involves by locating the critical areas of flood hazard, which cause socio-economic and environmental consequences to take up mitigation activities on priority basis. The pair-wise comparisons of natural and anthropogenic factors is a bit problematic, because these two mentioned factors are different from typology view point. In order to assess flood hazard potential by using (1) only natural factors (FHPNF), (2) only anthropogenic factors (FHPAF), and (3) ensemble the obtained sub-watersheds priorities from natural and anthropogenic factors , the coupling of the Analytical Hierarchy Process (AHP) and Geographical Information Systems (GIS) were applied the Gorganrood river basin of Iran. Each effective factor was assigned to appropriate weight based on Saaty’s 9 point scale and the obtained weights were normalized through the Eigenvector method. By using the Weighted Linear Combination (WLC), two flood hazard potential indexes were defined separately for anthropogenic and natural factors. Finally, both indices values were combined to determine sub-watersheds priority. For the validation of the predictions, the Receiver Operating Characteristic (ROC) curve and historical data of flash flood events were used. According to the results of ROC curves, the FHPNF and FHPAF maps showed a reasonable good performance in watershed prioritization with area under ROC curve (AUC) values of 76.1 and 79.5 %, respectively. In addition, these results imply that one and two sub-watersheds fall under very high and high priority, respectively. The results of this study act as guidelines for managers and planners to determine sub-watersheds priority and rational management of watersheds based on both natural and anthropogenic components.     

Effect of Various On-Farm Water Management Scenarios on Equity and Productivity in Irrigation Networks

This research investigated the optimum on-farm water management methods for a summer crop (Maize). Water equity and productivity were optimized simultaneously by using genetic algorithms in Doroodzan Irrigation Network. Increase in water reduction fraction (WRF) (0.0 to 0.8) has the incremental effect on water equity (on average 19.4 %), however by increasing WRF, water productivity initially increased (on average 25.3 % at WRF?=?0.4) and then decreased. With increasing irrigation application efficiency (E_a) (40 to 90 %), the values of water equity and productivity increased by on average 52.8 and 91.5 %, respectively. Increment of conveyance efficiency of channels (E_c) (70 to 90 %) resulted in minimum incremental effect on water equity and productivity (on average 18.5 and 11.9 %, respectively). Furthermore, the values of performance measure decreased from wet water year to drought water year. Tape irrigation system was considered as the best choice at low quantities of WRF (<=0.4), however for higher values of WRF (>?=?0.6), sprinkler irrigation system was considered as the best choice for achieving higher values of water equity and productivity. Meanwhile, when equity and productivity were considered together for a specific method of deficit irrigation scheduling, under specified quantity of irrigation water, with increasing equity the water productivity reduction was negligible.     

Exploring Regional Profile of Drought History- a New Procedure to Characterize and Evaluate Multi-Scaler Drought Indices Under Spatial Poisson Log-Normal Model

Water Resources Management - Drought is recurrently occurring in many parts of the globe. In contrast to other natural hazards, drought has complex climatic characteristics. Several environmental...     

Optimizing Approach of Water Allocation to Off-Takes During Reduced Flows

Multi-objective optimization models with an index were developed based on farmers’ preferences, local requirements, supplies available at the head of the canal, system losses, crop demand about different growth stages, and field soil moisture balance. The models were applied using linear programming. The Model 1 determines the cropping pattern by maximizing net economic benefits using a monthly basis lumped volume available at the head of the canal and is set to the minimum and maximum area constraints along with the constraint of minimum main crop area. The areas for different crops given by the first model form input for the Model 2. The other inputs of Model 2 included periodic supply available at the head of the primary canal (7-day period in this study), root growth depth, demand, and soil moisture constants. The Model 2 optimizes the sum of relative yields of all the crops and provide the irrigation levels of various crops for specified periods. Finally, the distributed area and irrigation levels determined by Model 2 are used in conjunction with the losses to decide flow rates of off takes. The complete program was implemented in the West branch irrigated area of Mirpurkhas subdivision. The results showed that the resources were allocated to off-takes in a competitive and conflict-free manner.

     

试论改造沙苑新模式:引洛淤灌

从沙苑成因出发 ,回顾了解放后改造沙苑模式的建立与发展 ,对历来改造模式的利弊进行了分析 ,提出了以引洛淤灌改良土壤为中心的改造沙苑新模式 ,论述了该模式的可行性 ,得出了新模式是解决阻碍沙苑农业发展的风沙和干旱两大问题的最佳途径     

The role of coal in energy production—Consumption and sustainable development of Turkey

Energy is one of the indispensable factors regarding the assurance of social prosperity and economic development of a country. The developing countries struggle to obtain energy sources reliable in the long term to complete their economic development, and the developed countries struggle to get them to keep their present prosperity levels. Coal seems to continue its indispensable position among the other energy sources for many years because of its production in more than 50 countries, the least effect it has from the price fluctuation and its usage lifespan of more than 200 years. The countries that are aware of it have investments in mining fields in the countries rich in coal reserves, and they continue investing considerable amount of money.