Investigation and optimization of the internal cylindrical surface lapping process of 440c steel

A new lapping method is proposed for internal cylindrical surfaces finishing. Regression analysis and artificial neural network (ANN) were used for modeling this lapping process and predicting the effects of parameters of rotational speed of the lapping tool (ω), the length of the lapping tool (L) and difference in external diameter of the lapping tool and internal diameter of the workpiece (D) on the material removal rate (MRR), out-of-cylindricity (C) and surface roughness (Ra) of the lapped holes. Comparison of the results of the regression and ANN models with the values obtained from the experiments indicates that the MRR, Ra and C are more accurately predicted using ANN models. MRR, Ra and C of the lapped holes have been optimized using genetic algorithm (GA) and particle swarm optimization (PSO) algorithm. The results show that the highest MRR, which is equal to 2029 μg/min, has been achieved at ω of 400 rpm, D of 0.1 mm and L of 45 mm. The lowest Ra of the lapped hole is 64 nm which has been obtained at ω of 100 rpm, D of 0.1 mm and L of 20.82 mm. The minimum C of the lapped hole is 3 μm, which was obtained at ω of 212 rpm, D of 0.1 mm and L of 28.3 mm. The most important problem in the lapping process is the low MRR which causes increased cost and production time. Therefore, in the lapping process, the selection of conditions, that in addition to the production of pieces with geometric accuracy and surface roughness needing a high MRR, is very important. In this study, MRR, Ra and cylindricity of the lapped holes was optimized using multi-objective PSO (MOPSO) algorithm and non-dominated sorting genetic algorithm II (NSGA II), and the Pareto optimal solutions were obtained. Comparison of the results obtained from NSGA II and MOPSO shows that both of these algorithms can achieve optimal Pareto front with the same accuracy, but the time required to reach the MOPSO algorithm to the optimal Pareto front is 25 % less than the NSGA II.

     

Interactions of protein levels fed to Holstein cows pre- and postpartum on productive and metabolic responses

The objective of this study was to examine the interaction between levels of dietary crude protein (CP) pre- and postpartum on feed intake, performance, and metabolic status of dairy cows with a 14-d close-up experimental period. Forty multiparous Holstein cows were blocked by expected calving date and previous lactation milk yield at ?14 d relative to expected calving and randomly allocated to receive either a 12.5% CP diet with 3.3% rumen undegraded protein (RUP; 12pre) or a 15.2% CP diet with 5% RUP (15pre) based on dry matter (DM). From d 1 to 21 postpartum, cows within each prepartum group were randomly assigned to receive either a 16.1% CP diet with 4.9% RUP (16post) or a 18.6% CP diet with 6.8% RUP (19post) based on DM. The experiment was conducted as a split-plot design, with CP prepartum being the whole-plot factor and CP postpartum as the subplot factor. Diets were similar in net energy for lactation, and CP levels were increased by replacing grain with a combination of corn gluten meal and fish meal. In prepartum, cows fed the 15pre diet tended to consume more DM than cows fed the 12pre diet (9.65 vs. 9.30 kg/d). Except for blood urea nitrogen (BUN) concentration, no other blood metabolite in prepartum was affected by diets. The interaction between pre- and postpartum CP levels showed that elevating dietary CP from 16post to 19post increased DM intake (15.20 vs. 17.67 kg/d) and milk yield (35.16 vs. 40.26 kg/d) in 12pre cows but not in 15pre cows. Milk fat, protein, and lactose contents were not affected by the interaction between pre- and postpartum CP levels. Feeding 19post compared with 16post increased milk protein (1.28 vs. 1.08 kg/d) and lactose (1.86 vs. 1.61 kg/d) yields in 12pre cows, whereas this effect was not observed in 15pre cows. Milk urea nitrogen was elevated when dietary CP increased from 16post to 19post in 15pre cows (12.98 vs. 14.84 mg/dL) but not in 12pre cows. The concentrations of BUN were greater in 19post cows than in 16post cows for both 12pre (16.31 vs. 13.81 mg/dL) and 15pre (18.44 vs. 14.71 mg/dL) cows. The 19post cows had lower serum fatty acids than 16post cows (0.65 vs. 0.96 mmol/L) in 12pre but not in 15pre. However, a reduction in serum aspartate aminotransferase (AST) concentration was observed in 19post cows compared with 16post cows (68.30 vs. 98.24 U/L) when cows were fed 12pre. For cows fed 15pre, those fed 19post had higher serum AST levels than those fed 16post (86.61 vs. 67.74 U/L) during 21 d of lactation. Body weight and body condition score changes were not affected by interactive effects between pre- and postpartum CP levels, but 19post cows tended (?0.30 vs. ?0.45) to have smaller body condition score losses than 16post cows when fed the 12pre diet. Overall, increasing dietary CP postpartum from 16 to 19% DM improved performance and metabolic status of cows fed 12% CP prepartum. The lack of responses to increased dietary CP postpartum in cows fed 15% CP prepartum suggests that dietary CP postpartum could decrease to 16% DM when cows are fed higher dietary CP prepartum.     

High IIP3 and Low-Noise CMOS Mixer Using Non-linear Feedback Technique

A third-order intermodulation cancelation technique using a non-linear feedback is proposed to design a low-power low-distortion mixer in a 65 nm standard CMOS technology. The IM3 cancelation is achieved by estimating distorting error at a non-linear feedback element and subtracting it from the input. The linearization technique is utilized in the input trans-conductance of the mixer. The circuit functionality is analyzed using Volterra series. The covering frequency range of the mixer is 800 MHz to 5 GHz. The technique increases the input-referred third-order intercept point (IIP3) and input 1 dB compression point to +16.4 dBm and −1.87 dBm, respectively. It obtains a gain of 9 dB and an input-referred noise of 1.84 nV/?{}/\sqrt{}Hz while consumes 8.75 mA from 1.2 V supply. The layout of the mixer occupies 0.315 mm × 0.296 mm of silicon area.     

Characterization of a new shielding rubber for use in neutron–gamma mixed fields

A variety of formulations was investigated for the fabrication of an appropriate shielding rubber to be used in neutron–gamma mixed fields. Having considered the required mechanical properties together with tungsten as the gamma-ray absorbing element, calculations with MCNPX 2.6 code confirmed that the incorporation of 5 weight percentage(wt%) of boron carbide exhibited the best performance as a thermal neutron absorber. A series of both experimental and simulation results are provided for comparison.     

Clock Delayed Domino Logic With Efficient Variable Threshold Voltage Keeper

In this paper, efficient clock delayed domino logic with variable strength voltage keeper is proposed. The variable strength of the keeper is achieved through applying two different body biases to the keeper. The circuits used to generate the body biases are called capacitive body bias generator and cross-coupled capacitive body bias generator. Compared to a previous work, the body bias generator circuits presented in this paper are simpler and do not require double or triple power supply while consuming less area and power. To show the efficiency of the proposed technique, the implementation of a carry generator circuit by the proposed techniques and the previous work are compared. The simulation results for standard CMOS technologies of 0.18 mum and 70 nm show considerable improvements in terms of power and power delay product. In addition, the proposed technique shows much less temperature dependence when compared to that of previous work     

Effects of shortening the close-up period length coupled with increased supply of metabolizable protein on performance and metabolic status of multiparous Holstein cows

This experiment was conducted to compare conventional (CON; 21 d) and shortened (SH; 10 d) close-up period, and evaluate the effect of shortened close-up period combined with feeding different metabolizable protein (MP) levels on dry matter (DM) intake, metabolic status, and performance of dairy cows. Forty-eight multiparous Holstein cows with similar parity, body weight (BW), and previous lactation milk yield were divided into 2 groups. The first group (n = 24) received the far-off diet from ?60 to ?21 d (CON), and the second group (n = 24) received same far-off diet from ?60 to ?10 d (SH) relative to expected parturition. Cows were then moved to individual stalls and randomly allocated to 1 of 3 close-up diets: low MP diet (LMP; MP = 79 g/kg of DM), medium MP diet (MMP; MP = 101 g/kg of DM), or high MP diet (HMP; MP = 118 g/kg of DM). Treatments were used in a 2 × 3 factorial arrangement with 2 lengths of close-up period (CON and SH) and 3 levels of MP (LMP, MMP, and HMP). All diets were fed for ad libitum intake during the close-up period. After calving, all cows received the same fresh cow diet. We found no interaction between close-up period length and MP levels for traits, except for postpartum serum fatty acids and β-hydroxybutyrate (BHB). The concentrations of postpartum serum fatty acids and BHB were higher on LMP than MMP and HMP diets in SH group. The cows of the SH group tended to produce less colostrum in the first milking than cows in CON group. The length of close-up period did not affect pre- and postpartum DM intake or energy balance of cows during the last week of prepartum, but cows of the CON group had greater BW changes during the last 3 wk before parturition than cows in SH group. Cows fed MMP and HMP diets consumed 1.2 and 1 kg more DM than for those fed LMP prepartum, respectively. The concentrations of prepartum BHB and Ca were higher for SH cows than CON group cows. Except for blood urea N concentration, no other blood metabolite in prepartum was affected by dietary MP. We found no effects of close-up period length or MP levels in the close-up diet on urinary pH, purine derivative excretion, and microbial N flow. Postpartum, milk yield was not affected by close-up period length, but cows in CON group tended to have higher 4% fat-corrected milk yield, had higher milk fat content and yield, had greater BW and body condition score loss, and higher energy negative balance than cows in the SH group. Cows fed MMP diet ate 1.8 kg more DM and yielded 3.37 kg more milk than those fed the LMP diet. Milk fat, protein, and lactose content, milk urea N, and somatic cell count were not affected by MP levels, but the yield of milk protein and lactose were higher on MMP diet than on LMP diet. Concentrations of postpartum serum fatty acids and BHB were decreased by shortening the close-up period length, but glucose, cholesterol, and triglyceride were similar between close-up groups. During the postpartum period, serum fatty acids, BHB, aminotransferase, and Ca concentrations were decreased by increasing the MP levels in the close-up diet. It appears from this data set that multiparous cows will benefit from a shortened close-up period, and feeding a moderate MP diet could improve DM intake, milk yield, and metabolic status of periparturient dairy cows.     

Effects of rumen undegradable protein supplementation on productive performance and indicators of protein and energy metabolism in Holstein fresh cows

The objective of this study was to determine the effects of feeding increased dietary crude protein (CP) on productive performance and indicators of protein and energy metabolism during 21 d postpartum. Thirty multiparous Holstein dairy cows were balanced by previous lactation milk yield, body condition score (BCS) at calving, and parity and randomly allocated to 1 of 3 dietary treatments from calving until 21 d postpartum. Dietary treatments were 16.0% CP with 5.0% rumen undegradable protein (RUP) based on dry matter (DM) (16CP), 18.7% CP with 7.0% RUP based on DM (19CP), and 21.4% CP with 9.0% RUP based on DM (21CP). Diets were similar in net energy for lactation (approximately 1.7 Mcal/kg of DM) and CP levels were increased with corn gluten meal and fish meal. Dry matter intake (DMI) was increased by increasing dietary CP levels from 16.0 to 19.0% of DM, but dietary CP beyond 19.0% had no effect on DMI. Milk yields were 4.7 and 6.5 kg/d greater in cows fed the 19CP and 21CP diets versus those fed the 16CP diet, whereas 4% fat-corrected milk was greater for cows fed the 21CP than the 16CP diet (36.0 vs. 31.4 kg/d). Milk protein content and yield, lactose yield, and milk urea nitrogen were elevated by increased dietary CP. Milk lactose content and fat yield were not different among dietary treatments, but milk fat content tended to decline with increasing content of CP in diets. High CP levels increased milk N secretion but decreased milk N efficiency. Apparent digestibility of DM, CP, and neutral detergent fiber was greater on the 19CP and 21CP diets compared with the 16CP diet. Cows fed the 19CP and 21CP diets lost less body condition relative to those fed the 16CP diet over 21 d postpartum. Feeding higher CP levels increased the concentrations of serum albumin, albumin to globulin ratio, and urea nitrogen and decreased aspartate aminotransferase, nonesterified fatty acids, and β-hydroxybutyrate, but had no effect on globulin, glucose, cholesterol, or triacylglycerol. These findings indicated that elevating dietary CP up to 19.0% of DM using RUP supplements improved DMI, productive performance and the indicators of protein and energy metabolism from calving to 21 d postpartum.     

Improving surface integrity in finish machining of Inconel 718 alloy using intelligent systems

In machining of hard materials, surface integrity is one of the major customer requirements which comprise the study of the changes induced to the workpiece. Surface roughness and residual stress are often considered as the most significant indications of surface integrity. Inducing tensile residual stress during the machining processes is a critical problem which should be avoided or minimized to obtain better service quality and component life. This problem becomes more evident in the presence of rough machined surface because fatigue life of manufactured components might be decreased significantly. Inconel 718 superalloy is one of the hard materials used extensively in the aerospace industries. It is prone to tensile residual stress in machined surface. Thus, controlling and optimizing residual stress and surface roughness in machining of Inconel 718 are so needed. Intelligent techniques based on the predictive and optimization models can be used efficiently for this purpose. In this study, the optimal machining parameters including cutting speed, depth of cut, and feed rate were accessed by intelligent systems to evaluate the state of residual stress and surface roughness in finish turning of Inconel 718. The results of experiments and analyses indicated that implemented techniques in this work provided a robust framework for improving surface integrity in machining of Inconel 718 alloy. It was shown that cutting speed has more effect on surface integrity than other investigated parameters. Also, depth of cut and feed rate were found in the moderate range to obtain satisfactory state of tensile residual stress and surface roughness.     

Characterization of 1050Al/Al3Ni/ZrO2 hybrid surface composites fabricated by friction stir processing

Al/Al₃Ni and Al/nano-ZrO₂ mono and Al/Al₃Ni/ZrO₂ hybrid composites were produced by one- and four-pass friction stir processing (FSP). Then, the microstructure, hardness, and wear performance of the surface composites were evaluated. Results showed that the incorporation of Ni particles into the Al surface and their in situ reaction with the substrate resulted in the development of Al₃Ni particles in the stir zone. The formation mechanism of these particles was deeply studied from both thermodynamics and kinetics aspects. Similarly, the four-pass FSP led to the distribution of ZrO₂ nanoparticles and the formation of Al/ZrO₂ composites. With the addition of both Ni and ZrO₂ particles, a hybrid Al/Al₃Ni/ZrO₂ composite was produced. This caused a 60% improvement in hardness and a 35% improvement in wear resistance of Al substrate. In the case of monolithic composites, both abrasion and adhesion were responsible for the material removal during the wear test, whereas adhesion was specified as the dominant wear mechanism in the hybrid composite.     

Analytical modeling of work hardening of duplex steel alloys in the milling process

Severe plastic deformation in cutting operations such as milling might change mechanical properties (especially the strength and hardness) of the machined surface and its underlying layers. This phenomenon called work hardening and reduces machinability. This study presents an analytical solution to calculate the work hardening of the upper layers of the workpiece in the milling process of 2205 duplex stainless steel. In this regard, the stresses in the cutting regions are calculated to find the stress and temperature fields in the workpiece. Then the strain and strain rate values are calculated for each point of the surface and subsurface layers using the determined stress field. Finally, the Johnson-Cook material model is used to calculate flow stress and work hardening. Experimental results of the different machining conditions have been used to validate the proposed model. However, comparisons of subsurface microhardness and resultant cutting force obtained by an analytical model with experimental tests showed that the model properly predicts the amount of work hardening.