Investigation of bio-aerosol dispersion in a tunnel-ventilated poultry house

Bio-aerosol concentrations in poultry houses must be controlled to provide adequate air quality for both birds and workers. High concentrations of airborne bio-aerosols would affect the environmental sustainability of the production and create environmental hazards to the surroundings via the ventilation systems. Previous studies demonstrate that several factors including the age of the birds, the housing configuration, the humidity and temperature would strongly affect the indoor concentration of bio-aerosols. However, limited studies are performed in the literature to investigate the bio-aerosol dispersion pattern inside poultry buildings. In order to fill a gap of the understanding of the bio-aerosol dispersion behavior, experimental measurements of the indoor bio-aerosol distribution are performed in a tunnel-ventilated poultry house in this paper. Meanwhile a three-dimensional computational fluid dynamics (CFD) model is built and validated to further investigate the effect of flow pattern, turbulence and vortex on the dispersion and deposition of the bio-aerosols. Furthermore, bio-aerosols with various diameters are also examined in the CFD model. It is found that higher concentrations of bio-aerosols are detected at the rear part of the house and strong turbulent flow resulting from the ventilation inlets enhances the diffusion and dispersion of bio-aerosols. Local vortex or disturbed flow is responsible for higher local concentration due to the re-suspension of settled bio-aerosols, which suggests that careful attentions should be paid to these locations during cleaning and disinfection. Results from present study contribute to the optimization of design and operation of the poultry houses from the standing point of reducing airborne bio-aerosol concentrations

Computational Fluid Dynamics aided investigation and optimization of a tunnel-ventilated poultry house in China

Ventilation system is crucial for poultry houses to control the indoor climate and air quality. The tunnel ventilation system is widely applied for large-scale poultry buildings in China but only limited scientific researches regarding the flow pattern, temperature distribution and design criteria are available in the literature. Thanks to the fast development of computer technology, Computational Fluid Dynamics (CFD) techniques were used in present study to investigate the indoor air movement, air temperature and relatively humidity. A three-dimensional CFD model was built according to the real dimensions of a laying hen house and the model was validated by comparing the simulation results with the field measurements at 30 positions. Meanwhile, statistical analysis was performed to determine the differences between different boundary conditions regarding the agreement between measured and CFD simulated results. Optimization of air inlet configurations was performed by using the validated CFD model and it was found that the uniformity of indoor air movement could prevent excessive local convective heat losses and reduce the temperature at the end of the house. Furthermore, the air inlets placed at the middle of the side wall could significantly reduce the high temperature expected at the end of the building without using extra energy, which is especially important for large-scale poultry farms with long buildings. The performance of side-wall windows was also examined and preliminary guidance was provided to effectively regulate the indoor climate by using these windows with the help of environmental monitoring systems. The present study contributes to the understanding and design of the tunnel ventilation system used in poultry houses

Coupled Effect of Curing Temperature and Moisture on THM Behavior of Cemented Paste Backfill

Cemented paste backfill (CPB), a mixture of tailings, binder, and water, is widely and continually utilized in underground mines for subsidence control and disposal of surface hazardous waste discharge. The mechanical strength of CPB, which is the key for the backfill structure to play the role of supporting overlying roof and controlling subsidence, is governed by complex factors (thermal, hydraulic, and mechanical loads), particularly strongly affected by the environmental conditions, such as ambient temperature and humidity. Thus, it is crucial to understand and assess the response of CPB subjected to the loads mentioned above, so as to better ascertain its performance and obtain a cost-effective, safe, and stable CPB structure. Accordingly, a coupled THM model is developed to describe and analyze the performance of CPB. Comparisons between model simulation and experiment data prove the capability of the developed model in predicting the evolutions of temperature and internal relative humidity, as well as stress-strain relation of CPB. The obtained results indicate that all these properties are significantly affected by ambient humidity and temperature

The ‘magic of filter’ effect: Examining value co-destruction of social media photos in destination marketing

Excessive filter processing of social media photos may cause viewers to question the authenticity of the photos. From the value co-destruction perspective, this research examines the effect of photo filtering on consumer perceptions. Study 1 ran content analysis of 2035 social media user posts and identified that destination marketing failure caused by filtered photos is a process involving tourists\u27 negative emotions and multi-stakeholder (including platform, travel blogger, and destination) value co-destruction, represented by a chain relationship mechanism of “stimulation of filtered photos → negative emotions of tourists → failure of destination marketing.” Study 2 applied an experimental design and found that filtered photos have a significant effect on tourists\u27 negative emotions, which play a complete mediating role in the relationship between filtered photos and value co-destruction of destination marketing. Additionally, the moderating effect of tourists’ aesthetic and authenticity pursuit in the influence mechanism was partially verified. Theoretical and practical implications are discussed

Construction and verification of an environment and energy prediction model for Controlled Environment Housing

In order to satisfy the healthy growth and performance of livestock and poultry, a large amount of energy is often consumed in the production process of modern livestock and poultry breeding, which is used for automatic feeding management and regulation of breeding environment. In this study, based on the ISO 13790 5R1C equivalent resistance capacitance network computing model, using the henhouse heat balance, water balance, balance of gas (ammonia, carbon dioxide concentration) principle, we developed a simple closed loop control henhouse environment and energy consumption prediction model, Through on-site validation tests, the results show that the model is reliable, and it can assist the farmer for breeding planning, house-design process and increase environmental control and energy management efficiency

Space-time block coded rectangular differential spatial modulation: system design and performance analysis

In this paper, a novel scheme dubbed space-time block coded rectangular differential spatial modulation (STBC-RDSM) is proposed for multiple-input and multiple-out (MIMO) systems, which combines space-time block coding (STBC) and rectangular differential spatial modulation (RDSM) to reap their respective benefits while avoiding the drawbacks of conventional differential spatial modulation (DSM) systems. More specifically, in the proposed STBC-RDSM scheme, information bits are conveyed via the rectangular differentially encoded antenna index matrices, as well as the STBC blocks. Furthermore, a low-complexity detection scheme is proposed. Our simulation results demonstrate that STBC-RDSM outperforms its conventional DSM counterparts in various spectral efficiencies. Finally, a closed-form union bound on the bit error rate (BER) is derived and validated by our simulation results

Space-time/frequency line coded OFDM : system design and practical implementation

In this paper, we investigate a class of new multiple-input multiple-output (MIMO) transmission schemes, dubbed space time line code (STLC), in the context of different mobility situations. We extend its original structure into space and frequency domains and propose a novel frequency line code (SFLC) for combining with orthogonal frequency division multiplexing (OFDM) in order to achieve potential diversity gains in time-varying multipath fading channels. Specifically, at the transmitter, the STLC/SFLC-OFDM scheme exploits the channel state information (CSI) to linearly encode successive modulated symbols in the time/frequency domain to achieve full diversity gain. At the receiver, it can retrieve the transmit symbols without full CSI, thanks to its special structure. We analyse the impact of time-variant channels to STLC and SFLC to show the expected performance degradation in practical channel, especially in the case of different mobile speeds. Our analysis and simulations show that the BER performance degrades with increasing correlation coefficient, which makes STLC-OFDM more robust in channels with abundant multipath spread, and SFLC-OFDM more robust in channels with high mobility speed. Meanwhile, a guideline is provided for switching when the communication environment changes. Finally, we carry out the practical implementation of STLC-OFDM and SFLC-OFDM schemes and characterize their performance with both computer simulations and an experimental testbed.Published versio

Development and Validation of an Energy Consumption Model for Animal Houses Achieving Precision Livestock Farming

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

Determination on Outdoor Stocking Density of Free-range Broilerin Different Ecosystems Based on Nitrogen Cycling

The free-range broiler production is an effective combination of ecological and economic benefits. However, excessive stocking will inevitably lead to a variety of negative effects, such as the destruction of vegetation, the hardening and even acidification of soil. It is very important to determine the reasonable stocking density for free-range broiler. In this paper, the outdoor feeding density of free-range broiler in different stocking ecosystems based on the nitrogen cycling was proposed combination of theoretical derivation and investigation and research, and proved the correctness of the research idea and density parameters through empirical research, which provided the key technical parameters for scientific guidance of free range chicken production