Bilinear Graph Neural Network with Neighbor Interactions

Graph Neural Network (GNN) is a powerful model to learn representations and make predictions on graph data. Existing efforts on GNN have largely defined the graph convolution as a weighted sum of the features of the connected nodes to form the representation of the target node. Nevertheless, the operation of weighted sum assumes the neighbor nodes are independent of each other, and ignores the possible interactions between them. When such interactions exist, such as the co-occurrence of two neighbor nodes is a strong signal of the target node's characteristics, existing GNN models may fail to capture the signal. In this work, we argue the importance of modeling the interactions between neighbor nodes in GNN. We propose a new graph convolution operator, which augments the weighted sum with pairwise interactions of the representations of neighbor nodes. We term this framework as Bilinear Graph Neural Network (BGNN), which improves GNN representation ability with bilinear interactions between neighbor nodes. In particular, we specify two BGNN models named BGCN and BGAT, based on the well-known GCN and GAT, respectively. Empirical results on three public benchmarks of semi-supervised node classification verify the effectiveness of BGNN -- BGCN (BGAT) outperforms GCN (GAT) by 1.6% (1.5%) in classification accuracy.Codes are available at: https://github.com/zhuhm1996/bgnn.Comment: Accepted by IJCAI 2020. SOLE copyright holder is IJCAI (International Joint Conferences on Artificial Intelligence), all rights reserve

Assessment of Tubing Type on Ammonia Gas Adsorption

Different types of tubing and operating conditions may be involved when measuring ammonia (NH3) concentrations and its emissions from animal production facilities. Prices of commercially available tubing vary substantially. A question that has often come up but has not been well investigated is how the tubing type (e.g., PVC vs. FEP) may impact the certainty of NH3 concentration measurement. The study reported here was conducted to address this issue in that it assessed and compared the magnitude of NH3 adsorption to different types of commercially available tubing under conditions that may be present in animal feeding operation (AFO) air emission studies. The types of tubing evaluated were: Teflon® (PFA and FEP tubing), HDPE (clear plastic tubing), and PVC (vinyl tubing). Each tested tubing had a length of 30.5 m (100 ft) and an inside diameter of 6.35 mm (0.25 in.). Five nominal NH3 levels of 10, 20, 40, 80, and 160 ppm, generated with poultry manure, were passed through the tested tubing at an airflow rate of 8 L min-1 (0.28 CFM) for 60 min. Simultaneous measurements of NH3 concentrations at the inlet and outlet of the tested tubing were made with two photoacoustic gas spectrometers (1% repeatability of measured value and 0.2-ppm NH3 detection limit). Although the Teflon tubing had significantly lower NH3 adsorption than the HDPE or PVC tubing, all the tested tubing showed \u3c3% NH3 differences between the inlet and outlet concentrations after the 60-min exposure and mostly \u3c1% for NH3 levels \u3e40 ppm. The results of this study thus suggest that the HDPE and PVC tubing offer viable, more economical air sampling options for AFO NH3 emission studies

Evaluation of Airborne Dust Concentration And Effectiveness of Cooling fan with Spraying Misting Systems in Swine Gestation Houses

Airborne dust in swine houses can cause serious health problems for humans as well as for animals. The aim of this experiment was to evaluate the airborne dust concentration range and effectiveness of cooling fan with spraying misting systems in the gestation houses in the management practices of China. The experiment was implemented in a gestation barn housed 239 gestation pigs in Hebei Province of China. The tests showed that the average airborne dust concentration was about 4.70 ±3.24 mg/m3 in cold weather and 2.18 ±1.61 mg/m3 in warm weather, respectively. The high dust concentration of 17.55 ± 1.18 mg/ m3 in winter and 15.25 ± 1.77 mg/m3 in summer happened in the feeding period. When the misting cooling system with droplet diameter of 20-50µ m turned on, the average airborne dust concentration could be reduced by 75%, from 7.94 ±4.67 mg/m3 to 1.98 ±1.80 mg/m3, during the feeding period

Assessment of In-line Filter Type and Condition on Measurement of Ammonia Concentration

Gas analyzers are commonly protected from impurities in air sampling via use of in-line filters to ensure operational performance and longevity of the instruments. This is especially true for extended period of air monitoring under conditions where airborne dust exists. Prices for commercially available filters vary substantially. A question that has often come up but has not received much investigation is how the filter media type (e.g., paper vs. Teflon) and condition (clean vs. dirty) impact measurement of the gaseous concentration. The study reported here was conducted toward addressing this issue. Specifically, the study assesses the magnitude of ammonia (NH3) adsorption to different types of in-line filters and conditions often used or encountered in air sampling for animal feeding operation air emission studies. The type of filters evaluated in this study included Teflon (most expensive), paper (less expensive), and stand-alone fuel filters, being either clean (new) or dust-laden. Three nominal NH3 levels (20, 45, 90 ppm, generated with poultry manure) coupled with two nominal airflow rates (4 vs. 8 l/min or 8 vs. 16 l/min) through the filters were used in the evaluation. The type of dust used in this study included broiler house dust and starch. Simultaneous measurements of NH3 concentrations before and after the tested filter were made with two photoacoustic gas spectrometers. The results revealed that initial NH3 adsorption was highest for the fuel filter but negligible for the Teflon filters. However, after 30-min exposure the relative NH3 adsorption by the filters were mostly below 1%. During fresh-air purging of the fuel filters laden with broiler house dust, ammonia was initially released but quickly diminished after 15 minutes. Flow rate was inversely related to NH3 adsorption by the filter, particularly dust-laden filters. The result suggest that when used properly, the in-line filters tested in this study (fuel, paper and Teflon) all offer viable options for air emission measurement applications

Assessment of In-Line Dust Filter Type and Condition on Ammonia Adsorption

Gas analyzers are commonly protected from impurities in air sampling via use of in-line dust filters to ensure operational performance and longevity of the instruments. This is especially true with extended periods of air quality monitoring in dusty environments. Prices for commercially available filters and monitoring needs vary considerably. A question that has often come up but has not received much investigation is how the filter media types (e.g., paper vs. Teflon) and operational conditions (clean vs. dirty) impact the integrity of gaseous concentration measurement. The study reported here was conducted toward addressing this issue. Specifically, the study assessed the magnitude of ammonia (NH3) adsorption for several types of in-line filters and conditions often used or encountered in animal feeding operation air emission studies, namely, Teflon (most expensive), paper (least expensive), and stand-alone automobile fuel filters, being either clean (new) or dust-laden. Three nominal NH3 levels (20, 45, or 90 ppm, generated with poultry manure) coupled with two nominal airflow rates (4 vs. 8 L/min or 8 vs. 16 L/min) through the filters were used in the evaluation. The types of dust used in the study included corn starch and broiler-house dust. Simultaneous measurements of NH3 concentrations before and after the tested filter were made with two photoacoustic gas spectrometers. The results revealed that NH3 adsorption was highest for the fuel filter initially but negligible for the Teflon filters. However, after 30 min exposure, relative NH3 adsorption by the filters mostly fell below 1%. The higher flow rate led to significantly lower relative NH3 adsorption for both the fuel and paper filters (P \u3c 0.001) but made no difference for the Teflon filters (P = 0.31 to 0.49). During fresh-air purging of the fuel filters laden with broiler-house dust, NH3 was initially released but diminished after 15 min. The results suggest that when used properly (e.g., proper flow rate), the in-line dust filters tested in this study (fuel, paper, and Teflon) offer viable, performance-based options for air emissions (especially NH3) measurement applications

Ammonia and greenhouse gas emissions from co-composting of dead hens with manure as affected by forced aeration rate

The effect of ventilation rate (VR) on ammonia (NH3) and greenhouse gas (GHG) emissions from composting piles of dead hens mixed with hen manure was quantified by measuring the gaseous concentrations and airflow rate through the compost bins. Three VR levels of 0.9, 0.7 and 0.5 m³/hr/bin (equivalent to the air exchanges per hour of 0.9, 0.7 and 0.5) were evaluated, each with three replicates. The compost piles were turned once (on day 58) during the 11-wk composting period. Gaseous concentrations of the inlet and exhaust air of the compost bins were measured using a multi-gas infrared photoacoustic analyzer coupled with a multi-channel sampler; VR was measured with a flow meter; and the emission rate (ER) of each gas was computed from the VR and the gas concentration. Decomposition of the carcass over the 11-wk composting period was found to be greater than 88%, as assessed by the reduction in carcass mass. NH3 ER was relatively stable when the compost pile was at high temperatures (~60?). Sharp increase in carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions occurred quickly after construction of the compost pile. VR was found to significantly affect NH3, CO2 and CH4 emissions (p less than 0.05). Specifically, cumulative emissions per kg of initial co-compost matter for the three VR of 0.9, 0.7 and 0.5 m³/hr/bin were, respectively, 2.4, 2.0 and 1.2 g NH3; 78, 66 and 42 g CO2; 120, 90 and 52 mg CH4; and 6.4, 6.1 and 5.1 mg N2O. Hence, the study results suggest that the rate of forced aeration can be adjusted to reduce NH3 and GHG emissions from animal mortality compositing

Ammonia and Greenhouse Gas Emissions from Co-Composting of Dead Hens with Manure as Affected by Forced Aeration Rate

The effect of ventilation rate (VR) on ammonia and greenhouse gas emissions from co-composting dead hens mixed with hen manure was quantified. Three VR levels of 0.9, 0.7, and 0.5 m3 h-1 were evaluated. Gaseous concentrations were measured using a multi-gas infrared photoacoustic analyzer, VR was measured with flowmeters, and the gas emission rate was computed from the VR and gas concentration. Decomposition of the carcasses over the 11-week composting period was greater than 88%. VR was found to significantly affect NH3, CO2, and CH4 emissions (p \u3c 0.05). Specifically, cumulative emissions per kg of initial matter for VR of 0.9, 0.7, and 0.5 m3 h-1 were, respectively, 2.4, 2.0, and 1.2 g NH3; 78, 66, and 42 g CO2; 120, 90, and 52 mg CH4; and 6.4, 6.1, and 5.1 mg N2O. Hence, the study results suggest that the ventilation rate can be adjusted to reduce NH3 and GHG emissions from animal mortality compositing

Emissions of Greenhouse Gases from a Typical Chinese Swine Farrowing Barn

Emissions of greenhouse gases (GHGs) from animal feeding operations to the atmosphere are of environmental importance and concerns because of their impact on global warming. Gaseous concentrations and emission rates (ERs) of animal facilities can be affected by the animal production stages, animal species, dietary nutrition, housing types, manure handling schemes, and environmental conditions. This article reports ERs of methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) for a typical, naturally ventilated 24-crate swine farrowing barn located in suburban Beijing, China, that was monitored over one-year period. The measurements were made at bi-monthly intervals (i.e., six measurement episodes total), with each measurement episode covering three consecutive days. Gaseous concentrations were monitored at bi-hourly intervals throughout each 3-day measurement episode. The ventilation rate of the barn was estimated using the CO2 mass balance method. The GHG concentrations and ERs of the farrowing barn showed diurnal and seasonal variations. Specifically, the concentrations (monthly mean ±SD, mg m-3) ranged from 2.3 (±0.3) to 9.3 (±2) for CH4, from 0.6 (±0.02) to 1.2 (±0.16) for N2O, and from 1,370 (±163) to 11,100 (±950) for CO2, with the higher levels occurring in January and the lower levels in July. The specific ER ranged from 95.2 to 261.8 mg h-1 pig-1 for CH4, from 6.4 to 12.9 mg h-1 pig-1 for N2O, and from 122.9 to 127.3 g h-1 pig-1 for CO2. On the basis of per animal unit (1 AU = 500 kg live body mass), the average daily ERs of the farrowing barn were 9.6 ±3.6 g AU-1 d-1 for CH4, 0.54 ±0.15 g AU-1 d-1 for N2O, and 7.5±0.1 kg AU-1 d-1 for CO2. Results of the GHG ERs from this study differ markedly from the limited literature data collected primarily under European production systems and conditions. Results of the current study provide some baseline data on GHG ERs for swine farrowing operations, thus contributing to development or improvement of GHG emission inventory under the Chinese livestock production conditions

Ammonia and Greenhouse Gas Emissions from Biogas Digester Effluent Stored at Different Depths

Carbonaceous and nitrogenous gases are produced during storage of livestock manure, with the magnitude of production being affected by the chemical properties of the manure and the physical conditions of storage. This lab-scale study quantifies the emission rates of ammonia (NH3), nitric oxide (NO), and greenhouse gases (GHG), i.e., methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O), from biogas digester effluent (BDE) stored at different depths of 1.0, 1.5, and 2.0 m in dynamic emission vessels (DEVs). The selected storage depths were reflective of the typical depth range of on-farm BDE storage in China. The static storage was held at a relatively constant media temperature of 15°C and an air exchange rate of 11.5 air changes per hour (ACH) for 78 days. Each depth regimen was replicated four times using four DEVs (12 DEVs total). The results showed that the mean (±SE) daily gaseous emission rates per volume of BDE stored at 1.0, 1.5, and 2.0 m depths, in g gas m-3 d-1, were, respectively, 9.1 (±0.7), 10.1 (±0.6), and 10.1 (±0.4) for CH4 (p = 0.39); 38.0 (±2.2), 34.5 (±1.3), and 30.7 (±0.6) for CO2 (p \u3c 0.05); 1.9 (±0.11), 1.3 (±0.08), and 0.9 (±0.03) for NH3 (p \u3c 0.05); and 6.7 (±0.5) × 10-3, 5.0 (±0.8) × 10-3, and 3.4 (±0.2) × 10-3 for N2O (p \u3c 0.05). Nitric oxide (NO) emissions were negligible. The overall GHG (CH4 + N2O + CO2) emissions were dominated by CH4, which accounted for more than 85% of the CO2-equivalent emissions for all three storage depths. The CH4 emissions peaked during the early storage period, with the first 20-day cumulative emissions accounting for 56% to 58% of the total 78-day storage emissions. The results reveal that storage of BDE at 2.0 m depth yielded lower CO2, NH3, and N2O emission rates but similar CH4 emission rates compared to the 1.0 and 1.5 m depths

Temporal Variation of Greenhouse Gas Emission in Gestation Swine Building

The objective of this study was to examine the temporal variation of greenhouse gas (GHG) concentration in the swine building over both daily and seasonal basis. The air samples were collected every one hour continuously for three days during summer and spring, and analyzed by gas chromatography (GC). Barn temperature was collected and the management practices were also noted. Results showed that methane (CH4) and carbon dioxide (CO2) concentration was related to the internal temperature and ventilation. Daily CH4 and CO2 concentrations varied more during cold weather than warmer weather; nighttime GHG concentration in the gestation building was higher than daytime because of the low air exchange. Average CH4 concentration in the gestation building was 16.67 + 9.88 ppm in spring and 9.25 + 7.64 ppm in summer. Average CO2 concentrations were 2361.65 + 960.96 ppm in spring and 1134.96 + 373.53 ppm in summer