Integrated modelling method of bonding strength and residual life prediction for selective repair structure of aluminium alloy

To accurately describe and predict the overall strength and residual life of selective repair bonded structures, an integrated simulation model of crack propagation including bonding strength is established. Based on two methods, an integrated simulation model including a cohesive zone method model for predicting the residual life of a selective repair structure is established. By comparing the computational efficiency and accuracy of both the stress intensity factor and residual life of selective repair structures using different calculation methods, the modelling scheme is optimised. Based on this optimised scheme, the effect of adhesive thickness on the stress intensity factor and residual life of the repair structure is analysed. FM94 adhesive measuring 0.2–0.4 mm thickness is used to decrease the stress intensity factor and improve the remaining life such that material utilisation efficiency is guaranteed.

Enhanced Leaching of Zinc from Zinc-Containing Metallurgical Residues via Microwave Calcium Activation Pretreatment

Given the shortage of zinc resource, the low utilisation efficiency of secondary zinc resource, and the crucial problem that the synchronous dissolution of zinc from different mineral phases, an activation pretreatment method merged with calcium activation and microwave heating approach was proposed to enhance the zinc leaching from complex encapsulated zinc-containing metallurgical residues (ZMR). Results indicated that under the optimal pretreatment conditions, including microwave activation temperature of 400 °C, CaO addition of 25% and activation time of 20 min, the zinc leaching rate reached 91.67%, which was 3.9% higher than that by conventional roasting pretreatment. Meanwhile, microwave heating presents excellent treatment effects, manifested by the zinc leaching rates, all exceeding that of conventional roasting under the same conditions, while the process temperature is decreased by 200 °C. In addition, XRD and SEM-EDS analysis denoted that microwave calcification pretreatment can effectively promote the transformation of the refractory zinc minerals like Zn2SiO4 and ZnFe2O4 into the easily leachable zinc oxides. The distinctive selective heating characteristics of microwave heating strengthened the dissociation of mineral inclusion, and the generated cracks increased the interfacial reaction area and further enhancing the leaching reaction of zinc from ZMR.

Energy: Protein Ratio in Ruminants: Insights from the Intragastric Infusion Technique

Studies on energy:protein ratio in ruminants are constrained by rumen fermentation since it governs nutrient metabolism and the ratio of energy:protein yielding nutrients available for absorption. By circumventing rumen fermentation, the total intragastric infusion technique (IIT) allowed objective quantification of maintenance energy and protein requirements, volatile fatty acid utilisation efficiency, efficiency of energy utilisation for maintenance (Km) and growth (Kf) and the origin of N retention responses to independent variation of energy and protein intake. This review outlines the key IIT findings and whether they are reflected in current feeding systems with implications for different production systems worldwide. Maintenance energy requirements are similar to those derived from comparative slaughter but maintenance N requirements are significantly lower. No differences in utilisation efficiency exist between acetic, propionic and butyric acids. At low energy intakes, endogenous energy reserves are utilised to retain amino acids and fuel substantial tissue protein gains. The use of fasting metabolism to measure the utilisation of nutritionally balanced diets is questioned since it is a glucose-deficient state. Inter-species differences in glucose metabolism appear to exist, suggesting that glucose requirements may be higher in cattle than sheep. The difficulty in predicting nutrient requirements, particularly protein, with any one technique is highlighted.

Developmental plasticity among strains of the yellow mealworm, Tenebrio molitor L., under dry conditions

Edible insect production relies, among others, on the use of high-quality strains with good productivity characteristics. However, studies on the evaluation of the growth performance of different insect strains are limited. In this framework, the objective of the present study was to evaluate the growth and development under dry conditions of larvae of six Tenebrio molitor strains of different geographical origins, i.e. Greece, Italy, Turkey, Spain and USA, in terms of larval survival and development, as well as feed utilisation efficiency. In light of our results, we report the variable growth performance of different T. molitor strains in the absence of a moisture source. Although no significant differences were shown among the strains tested with regard to the final larval weights and survival rates, there were significant differences in the development time and the growth rate, which may affect the overall efficiency of T. molitor larvae production. Our study aims to highlight the significance of strain for the growth performance and consequently the productivity of T. molitor.

Effects of interspecific competition on crop yield and nitrogen utilisation in maize-soybean intercropping system

Intercropping system plays a crucial role in improving crop yield, nitrogen utilisation efficiency (NUE) and economic benefit. The difference in crop yield and interspecific relationship under different bandwidth and row ratio allocation patterns are still unclear. A field experiment was carried out to explore change regularities between crop yield and interspecific relationships under maize soybean intercropping with different bandwidths and row ratios. The results showed that the yield of intercropped crops was lower than that of the sole crop. The nitrogen accumulation (NA), NUE and nitrogen competition ratio was the highest under the intercropping mode with a bandwidth of 2.0 m, which indicated that this mode was more conducive to the N uptake and utilisation in crops. In all intercropping systems, nitrogen equivalent ratio (NER) and land equivalent ratio (LER) were all greater than one, indicating that intercropping systems were conducive to improving land utilisation efficiency and NUE. Under the same bandwidth pattern, expanding the maize soybean row ratio from 2 : 4 to 3 : 4 was beneficial to the improvement of LER, NER, NUE, crop group yield. In conclusion, it was preferable in the NA, NUE, crop group yield under the system of bandwidth 2.0 m and row ratio 2 : 2, which could be a reference for maize soybean intercropping system.

Improving the waste utilisation efficiency of combined heat and power plants by increasing the performance of dry-ash output units

The study aims to improve the efficiency of waste utilisation from the coal-fired power industry based on an analysis of the dry-ash output unit operating at the Novo-Irkutsk Combined Heat and Power Plant, JSC “Irkutskenergo”. The unit was tested under various operating conditions of steam generating blocks following the standard methods adopted at the enterprise. The tests showed that the station steam generating block No. 3 (with a steam load of 409.2 t/h and an electrostatic precipitator efficiency of 90.46%) provided an ash supply efficiency of 7.10 t/h. When the ash is supplied from the steam generating block No. 4, operating at a steam load of 421.8 t/h and an electrostatic precipitator efficiency of 94.72%, the ash supply efficiency amounts to 9.19 t/h. Under the simultaneous operation of the steam generating blocks No. 3 and 4 at a steam load of 397.6 and 380.7 t/h, respectively, and an electrostatic precipitator efficiency of 90.46 and 94.72%, respectively, the unit efficiency was 14.23 t/h. As a result, limitations in the unit operation were identified. Thus, the airspeed in the pneumatic ash pipeline during ash transporting was 8.0-8.5 m/s, which facilitated the operation of the dry-ash output unit in a pulsed cycle. It was, therefore, recommended to increase the airspeed by accelerating the flow rate through the jet pump or by using a smaller diameter pipe. The conducted analysis showed that the efficiency of the dry-ash output unit depends mainly on the steam capacity of steam generating blocks, as well as on the flue gas cleaning efficiency in the steam generator electrostatic precipitators. The obtained results were used to determine the technical state, efficiency and reliability of the dry-ash output unit of the Novo-Irkutsk Combined Heat and Power Plant.

Productivity, Profitability and Nitrogen Utilisation Efficiency of Two Pasture-Based Milk Production Systems Differing in the Milking Frequency and Feeding Level

The aim of this study was to model the productivity, profitability and the nitrogen (N) utilisation efficiency (NUE) of two spring-calving pasture-based milk production systems differing in milking frequency and intensification levels in New Zealand. For this purpose, physical performance data from a low-intensity production system where cows were milked once per day (OAD-LI) and from a high-intensity production system where cows were milked twice per day (TAD-HI) were employed. OAD-LI cows were milked once-daily with a stocking rate (SR) of 2.1 cows/ha and fed diets with low supplementation (304 kg pasture silage/cow) with applications of 134 kg N fertiliser/ha and TAD-HI cows were milked twice-daily with a SR of 2.8 cows/ha and fed diets of higher supplementation (429 kg pasture silage and 1695 kg concentrate/cow) with applications of 87 kg N fertiliser/ha. The Moorepark Dairy System Model was used to evaluate production, economic performance and N balance on an annual basis. Despite the higher feed costs of TAD-HI as more supplementation was utilised, profitability per hectare was 16% higher because more cows were milked with a higher milk yield per cow (milking frequency) when compared to OAD-LI. At the cow level, the NUE was higher in TAD-HI (30% vs. 27%) reflecting the better balanced diet for energy and crude protein and higher milk yields as a result of milking frequency. At the farm scale the NUE was higher (38% vs. 26%) in the TAD-HI due to the losses associated with the imported feed being excluded and higher N captured in milk. These results suggest that milking frequency, the use of feed supplementation and application of N fertiliser as management tools on grazing dairy systems affect productivity, profitability and N balance. Further studies are required to find optimal stocking rates in combination with the use of supplementary feed and N fertiliser application that maximize milk production and profitability for OAD and TAD milking production systems but minimize N losses.

Proxy Measures and Novel Strategies for Estimating Nitrogen Utilisation Efficiency in Dairy Cattle

The efficiency with which dairy cows convert dietary nitrogen (N) to milk N is generally low (typically 25%). As a result, much of the N consumed is excreted in manure, from which N can be lost to the environment. Therefore there is increasing pressure to reduce N excretion and improve N use efficiency (NUE) on dairy farms. However, assessing N excretion and NUE on farms is difficult, thus the need to develop proximate measures that can provide accurate estimates of nitrogen utilisation. This review examines a number of these proximate measures. While a strong relationship exists between blood urea N and urinary N excretion, blood sampling is an invasive technique unsuitable for regular herd monitoring. Milk urea N (MUN) can be measured non-invasively, and while strong relationships exist between dietary crude protein and MUN, and MUN and urinary N excretion, the technique has limitations. Direct prediction of NUE using mid-infrared analysis of milk has real potential, while techniques such as near-infrared spectroscopy analysis of faeces and manure have received little attention. Similarly, techniques such as nitrogen isotope analysis, nuclear magnetic resonance spectroscopy of urine, and breath ammonia analysis may all offer potential in the future, but much research is still required.