Longhuan Du

The avian respiratory system, characterized by its caudocranial unidirectional pulmonary airflow, has long fascinated scientists. To date, the mechanisms underlying the unidirectional airflow and the formation of aerodynamic valving, especially the expiratory valve, remain poorly understood. To provide new insights into pulmonary airflow characteristics and to deepen our understanding of the role of aerodynamic valving in generating unidirectional pulmonary airflow, the respiratory tract of a domestic chicken was reconstructed based on CT-scanned data. CFD simulations were performed under various conditions after validation of the numerical model. Flow parameters were analyzed qualitatively and quantitatively during inspiration and expiration phases, respectively. The results showed that the coupled interaction of the distinctive bronchial topology and air-sac pressure conditions preferentially routed inspired air toward the caudal-sac pathways during inspiration. During expiration, aerodynamic valving was primarily associated with a momentum barrier generated by the cranial-sac airstream, which suppressed retrograde caudal-sac airflow through the primary bronchus and redirected it toward the dorsobronchial outlets leading to the physiological paleopulmonic pathway. Moreover, the ‘segmentum accelerans’ structure facilitated the formation of aerodynamic valving, whereas its removal did not abolish major-bronchial flow rectification, although higher air-sac boundary pressures were required during expiration. Finally, fluid density substantially affected inspiratory aerodynamic valving, whereas its effect on the critical pressures associated with expiratory valving remained below 5%.

Airborne diseases pose a significant challenge in intensive livestock farming due to their rapid transmission. Aerosols facilitate the spread of pathogens, introducing external infections to farms and enabling cross-transmission within barns. To address knowledge gaps in aerosol dynamics in animal respiratory tracts and enhance understanding of airborne disease transmission, this study employed CT scanning, 3D printing, and CFD technologies to develop and validate a pig respiratory model. Qualitative and quantitative results from the present study reveal spatiotemporal heterogeneity in aerosol deposition and transmission. Under rest conditions, for aerosols with D ≤ 5.0 μm, 21.1% of inhaled aerosols were deposited in the lung by the end of a respiratory cycle. Doubling the respiratory cycle or the inhalation rate could further increase the penetration ability of small-sized aerosols by approximately 60% to 70%. Moreover, the asymmetric distribution of airflow between the left and right halves of the lower respiratory tract (Q_L/R = 0.89) resulted from the leftward position of the pig’s heart and consequently led to a deposition ratio of about 0.83 between the left and right bronchial airways. These findings provide fundamental scientific data for the development and application of aerosolized vaccines and offer insights into optimizing respiratory intervention strategies.

Piglet diarrhea poses significant economic losses to the pig industry, posing a worldwide challenge that urgently needs to be addressed in pig breeding practices. Porcine rotavirus (PoRV) is an important viral diarrhea pathogen in piglets, with a high incidence rate and a tendency to cause growth retardation. To enhance the sensitivity and specificity of PoRV detection, we sequenced the NSP3 gene of G5 and G9 genotypes of rotavirus A (RVA), enabling simultaneous detection of the two serotypes. Subsequently, we developed a rapid PoRV detection method using a combination of recombinase-aided amplification (RAA) and CRISPR/Cas12a. In this method, Cas12a binds to RAA amplification products, guided by CRISPR-derived RNA (crRNA), which activates its cleavage activity and releases fluorescence by cutting FAM-BHQ-labeled single-stranded DNA (ssDNA). In the optimized reaction system, the recombinant plasmid PoRV can achieve a highly sensitive reaction within 30 min at 37 °C, with a detection limit as low as 2.43 copies/μL, which is ten times higher in sensitivity compared to the qPCR method. Results from specificity testing indicate that no cross-reactivity was observed between the RAA-CRISPR/Cas12a analysis of PoRV and other viral pathogens, including PoRV G3, PoRV G4, porcine epidemic diarrhea virus (PEDV), porcine epidemic diarrhea (PDCoV), and porcine reproductive and respiratory syndrome virus (PRRSV). In the clinical sample detection using the RAA-CRISPR/Cas12a method and qPCR, Cohen’s Kappa value reached as high as 0.952. Furthermore, this approach eliminates the need for large-scale instrumentation, offering a visual result under an ultraviolet lamp through fluorescence signal output.

Air source heat pump (ASHP) is a good new energy heating system. To explore the effect of ASHP on the production of yellow-feather broiler chicks, 31,500 one-day-old yellow broiler chicks were divided into three chicken houses with the same building structure but different heating methods (ASHP, CCF, CB). During the experiment, the parameters of heating time, temperature uniformity, gas concentration, weight gain, survival rate and production benefit were analyzed and evaluated. Results showed that the difference in NH₃, CO₂, and H₂S concentrations was not significant in all test groups (p > 0.05). Only group II detected the CO gas. In winter and spring, the weight of the chickens in group II were weighed the least at 35 days of age, and were significantly different from the ASHP and CB system (p < 0.05). There was no significant difference in body weight between ASHP and CB (p > 0.05). Group II had the lowest evenness and survival, the slowest warming, the worst uniformity of temperature distribution, and the highest cost. It is concluded that the ASHP was very environmentally friendly and has the highest economy, which is worth promoting and using.

A shed cave structure with a sand cushion is often used as a protective structure for rockfall disasters. Because of the randomness and unpredictability of rockfall disasters, the cushions of shed caves often suffer multiple impacts from rockfalls. Aiming at the problem of multiple impacts of rockfall, this paper uses the three-dimensional discrete element method to study the dynamic response of multiple rockfall impacts on sand cushions from different heights. Before conducting large-scale simulation studies, the input parameters in the numerical model are verified with data from laboratory experiments. Analyzing the simulation results shows that when the same point is impacted multiple times, the maximum impact force and the maximum penetration depth will increase with the number of impacts. According to the numerical results, a calculation formula of the maximum impact force that considers the number of impacts is fitted. At the same time, considering the impact response when the rockfall impacts different positions multiple times, the distance range that the subsequent impact is not affected by the previous impact is given. The significance of studying the multiple impacts of rockfalls is shown by a numerical study of rockfalls impacting a sand cushion multiple times from different heights, and it provides a reference for the design of rockfall disaster-protection structures in practical engineering.

Indoor environmental control is usually applied in poultry farming to ensure optimum growth conditions for birds. However, these control methods represent a considerable share of total energy consumption, and the trend of applying new equipment in the future for precision livestock farming would further increase energy demand, resulting in an increase in greenhouse gas emissions and management costs. Therefore, to ensure optimum efficiency of both energy use and livestock productivity, a customized hourly model was developed in the present study to interpret and analyze the electronically collected data. The modules for estimating indoor gas concentrations were incorporated into the present model, as this has not been properly considered in previous studies. A validation test was performed in a manure-belt layer house using sensors and meters to measure the indoor environmental parameters and energy consumption. The predicted results, including indoor temperature, relative humidity, carbon dioxide and ammonia concentrations, showed good agreement with the measured data, indicating a similar overall trend with acceptable discrepancies. Moreover, the corresponding differences between the measured and simulated energy consumption for heating, tunnel ventilation and base ventilation were 13.7, 7.5, and 0.1%, respectively. The total energy demand estimated by the model showed a limited discrepancy of approximately 10.6% compared with that measured in reality. Although human factors, including inspection, cleaning, vaccination, etc., were not included in the model, the validation results still suggested that the customized model was able to accurately predict the indoor environment and overall energy consumption during poultry farming. The validated model provides a tool for poultry producers to optimize production planning and management strategies, increase the production rate of unit energy consumption and achieve precision livestock farming from an energy consumption standpoint.

There are a large number of natural fractures in shale reservoirs, which create great challenges to hydraulic fracturing. Activating the natural fractures in reservoirs can form a complex fracture network, enhance fracturing effects, and increase shale gas production. Reservoir geological conditions (low in situ stress, natural fracture distribution, and cement strength) and operation parameters (fracturing fluid viscosity and injection rate) have an important influence on fracture network propagation. In this article, a two-dimensional hydraulic fracturing fluid-mechanic coupling numerical model for shale reservoirs with natural fractures was established. Based on the global cohesive zone model, the influence of geological conditions and operation parameters on the propagation of the hydraulic fracture network and fracturing process is investigated. The numerical simulation results show that when the horizontal in situ stress difference, approach angle, and cement strength are low, it is easier to form a complex fracture network. Research on the construction parameters indicated that when the viscosity of the fracturing fluid is low, it is easier to form a complex network of fractures, but the length of the fractures is shorter; in contrast, the fractures are straight and long. In addition, increasing the injection rate is beneficial for increasing the complexity of the fracture network while increasing the initiation pressure and width of the principal fracture reduces the risk of sand plugging. This article also proposes an optimization solution for hydraulic fracturing operations based on numerical simulation results.

Simultaneous multiple-fracture treatments in horizontal wellbores have become one of the key methods for economically and efficiently developing oil and gas resources in unconventional reservoirs. However, field data show that some perforation clusters have difficulty propagating fractures due to the internal mechanism of competing initiation and propagation among the fractures. In this paper, the physical mechanisms that influence simultaneous multiple-fracture initiation and propagation are investigated, and the effects of engineering parameters and in situ conditions on the nonuniform development of multiple fractures are discussed. A 3D fracture propagation model was established with ABAQUS to show the influence of the stress shadow effects and dynamic partitioning of the flow rate by simulating the propagation of multiple competing fractures generated in the perforation clusters. Based on the results of these simulations, simultaneous flow in multiple fractures can propagate evenly. Through adjusting the number of perforations in each cluster or the perforation diameter, the effect of the stress shadow can be significantly reduced by increasing the perforation friction, and the factors that affect the development of multiple fractures are changed, from the stress shadow effect to the dynamic partitioning of the flow rate. When the stress shadow effect is dominant, increasing the fracturing fluid viscosity promotes the uniform development of multiple fractures and increases the fracture width. When the dynamic partitioning of the flow rate is dominant, increasing the injection rate greatly affects the uniform development of multiple fractures.

The main advantage of having livestock, for example, the laying hens, in a controlled environment is that the optimum growth conditions can be achieved with accuracy. The indoor air temperature, humidity, gases concentration, etc., would significantly affect the animal performance, thus should be maintained within an acceptable range. In order to achieve the goals of precision poultry farming, various models have been developed by researchers all over the world to estimate the hourly indoor environmental parameters so as to provide decision suggestions. However, a key parameter of hourly manure area in the poultry house was missing in the literature to predict the ammonia emission using the recently developed mechanistic model. Therefore, in order to fill the gap of the understanding of hourly manure coverage proportion and area on the manure belt, experimental measurements were performed in the present study using laying hens from 10 weeks age to 30 weeks age. For each test, six polypropylene (pp) plates were applied to collect the manure dropped by the birds every hour, and photographs of the plates were taken at the same time using a pre-fixed camera. Binary images were then produced based on the color pictures to determine the object coverage proportion. It was demonstrated that for laying hens of stocking density around 14 birds/m², the manure coverage proportion at the 24th hour after the most recent manure removal was about 60%, while the value was approximately 82% at the 48th hour. Meanwhile, for laying hens at different ages, the hourly increment of manure coverage proportion showed a similar pattern with four distinct stages within 48 h. The statistical analyses demonstrated no significant correlation between the hourly increment of manure weight and the hourly increment of manure coverage proportion. Finally, prediction models for estimating the hourly manure coverage proportion on the manure belt in typical laying hen houses were provided.

The aim of the study was to compere the effects of using air energy heat pump, flue heating and water heating as brood heating system on brood production of yellow-feathered broilers. In the experiment, three heating methods were used to heat chicks, and the parameters such as heating time, temperature uniformity, concentration of poisonous and harmful gases in the house, chick weight gain, mortality rate and production benefit were compered and analyzed. The results showed as follows: 1. There was no significant difference in NH3 and H2S concentration among the three groups (P > 0.05). The CO2 concentration in the flue group was significantly higher than that in the other two groups (P < 0.01), and there was no significant difference in CO2 concentration between the other two groups (P >0.05). 2. The body weight of chickens in the flue group at 30 days of age was the lowest, which was significantly different from that in the other two groups (P < 0.01); The air energy heat pump group had significant difference with coal fired boiler group (P < 0.05), the uniformity and survival rate of flue group were the lowest, and the air energy heat pump group had the best; 3. The temperature rise of honeycomb flue was the slowest, the temperature distribution uniformity was the worst, and the cost was the highest; The heating rate of coal-fired boiler was faster than that of flue, and the temperature distribution uniformity was better, and the cost was lower. The heating rate of air energy heat pump was the fastest, and the temperature distribution uniformity was better, and the operating cost was the lowest. 4. The air energy heat pump group has higher investment in the early stage, better use effect, better production performance of brood, long service life and lower brood cost.