Bottom Of Column Research Articles

Sequential two-column batch distillation processes for separation of ternary mixture containing three binary minimum boiling point homoazeotropes

Based on the continuous two columns distillation technology, it is difficult to separate the ternary mixture of n-hexane/ethanol/butanone, which contains three binary minimum boiling point homoazeotropes. Through analyzing characteristics of batch distillation and the phase behavior, it is feasible to achieve high purity separation of this kind of complex mixture by two-column batch distillation. Three sequential two-column batch distillation processes including Process A (Double columns with series operation), Process B (Double columns with parallel-then series operation) and Process C (Single column-then double columns process) were designed and analyzed in this work. The processes were evaluated and optimized from the aspects of economy and environment. In terms of economy, environment impacts and operating time, Process B is prior to Process A and Process C. Based on the thermodynamic analysis of the column, the heat integration problem of Process B is considered, which includes a self-preheating scheme at first step, and a heat exchange scheme in which high-pressure column top vapor provide part of the heat to low-pressure column bottom at second step. Compared with the unimproved Process B, the operating cost of the improved Process B can be reduced by 28% and TAC can be reduced by 3% at step 1. The operating cost of the improved Process B can be reduced by 30% at step 2.

Cyclonic eddies in the West Greenland Boundary Current System

AbstractThe boundary current system in the Labrador Sea plays an integral role in modulating convection in the interior basin. Four years of mooring data from the eastern Labrador Sea reveal persistent mesoscale variability in the West Greenland boundary current. Between 2014 and 2018, 197 mid-depth intensified cyclones were identified that passed the array near the 2000 m isobath. In this study, we quantify these features and show that they are the downstream manifestation of Denmark Strait Overflow Water (DSOW) cyclones. A composite cyclone is constructed revealing an average radius of 9 km, maximum azimuthal speed of 24 cm/s, and a core propagation velocity of 27 cm/s. The core propagation velocity is significantly smaller than upstream near Denmark Strait, allowing them to trap more water. The cyclones transport a 200-m thick lens of dense water at the bottom of the water column, and increase the transport of DSOW in the West Greenland boundary current by 17% relative to the background flow. Only a portion of the features generated at Denmark Strait make it to the Labrador Sea, implying that the remainder are shed into the interior Irminger Sea, are retroflected at Cape Farewell, or dissipate. A synoptic shipboard survey east of Cape Farewell, conducted in summer 2020, captured two of these features which shed further light on their structure and timing. This is the first time DSOW cyclones have been observed in the Labrador Sea—a discovery that could have important implications for interior stratification.

Evaluation on influences of inertial mass on seismic responses and structure-soil interactions of pile-soil-piers

This research is to assess the influences of the inertial mass from the girder on the dynamic characteristic, dynamic response, and structure-soil interaction of a pile-soil-pier subsystem in a scale-model of a cable-stayed bridge. Therefore, both connection configurations between the pile-soil-pier and girder, including the sliding and fixed connections, were designed to present various inertial mass from the superstructure delivered to the pile-soil-pier. The pile-soil-pier supported by a 3 × 3 pile-group in mixed soil placed in a shear box was tested using shaking tables. The dynamic characteristics, seismic responses, inertial interactions, and pile group effects of the pile-soil-pier between the sliding and fixed connections were analyzed under three input motions with different shaking amplitudes. These results showed that more inertial mass from the girder significantly increased the reinforcement strain and bending moment at the column bottom and pile top, displacement at the column top, inertial interaction effects, and pile group effects of the pile-soil-pier due to the sliding connection changing to the fixed connection. The inertial mass increment from the girder noticeably decreased the peak accelerations of the column of the pile-soil-pier when subjected to three input motions with different amplitudes. However, the inertial mass insignificantly affected the accelerations of the pile and free-soil. Therefore, the corresponding kinematic interaction effects were almost unaffected by the inertial mass. Additionally, the evident pile group effects were observed in the sliding and fixed connections between the pile-soil-pier and girder. The numerical model could approximately reproduce the macroscopic seismic responses of the pile-soil-piers with sliding and fixed connections and capture the typical response variations induced by the connection configuration change.

The Importance of Food Pulses in Benthic-Pelagic Coupling Processes of Passive Suspension Feeders

Benthic-pelagic coupling processes and the quantity of carbon transferred from the water column to the benthic suspension feeders need multiple intensive sampling approaches where several environmental variables and benthos performance are quantified. Here, activity, dietary composition, and capture rates of three Mediterranean gorgonians (Paramuricea clavata, Eunicella singularis, and Leptogorgia sarmentosa) were assessed in an intensive cycle considering different variables such as the seston concentration and quality (e.g., carbon, nitrogen, and zooplankton), the colony branch patterns, and the energetic input of the single species (i.e., mixotrophic and heterotrophic). The three species showed clear differences in their impact on the seston concentration. Paramuricea clavata, the most densely distributed, showed a greater impact on the near bottom water column seston. The lowest impact of E. singularis on the seston could be explained by its mixotrophy and colony branching pattern. Leptogorgia sarmentosa had a similar impact as E. singularis, having a much more complex branching pattern and more than an order of magnitude smaller number of colonies per meter square than the other two octocorals. The amount of carbon ingested in the peaks of the capture rates in the three species may cover a non-neglectable proportion of the potential carbon fluxes.

Eutrophication effects on CH4 and CO2 fluxes in a highly urbanized tropical reservoir (Southeast, Brazil).

Shallow urban polluted reservoirs at tropical regions can be hotspots for CO2 and CH4 emissions. In this study, we investigated the relationships between eutrophication and GHG emissions in a highly urbanized tropical reservoir in São Paulo Metropolitan Area (Brazil). CO2 and CH4 fluxes and limnological variables (water and sediment) were collected at three sampling stations classified as hypereutrophic and eutrophic. Analysis of variance (ANOVA) and the principal component analysis (PCA) determined the most significant parameters to CO2 and CH4 fluxes. ANOVA showed significant differences of CO2 and CH4 fluxes between sampling stations with different trophic state. The hypereutrophic station showed higher mean fluxes for both CO2 and CH4 (5.43 ± 1.04 and 0.325 ± 0.167 g m-2 d-1, respectively) than the eutrophic stations (3.36 ± 0.54 and 0.060 ± 0.005 g m-2 d-1). The PCA showed a strong relationship between nutrients in the water column (surface and bottom) and GHG fluxes. We concluded that GHG fluxes were higher whenever the trophic state increases as observed previously in temperate and tropical reservoirs. High concentrations of nutrients in the water column in the studied area support the high production of autotrophic biomass that, when sedimented, ends up serving as organic matter for CH4 producers. These outcomes reinforce the necessity of water quality improvement and eutrophication mitigation in highly urbanized reservoirs in tropical regions.

Experimental Study on Distillation Column Parameters for Liquefaction Device of Low Concentration Coalbed Methane

The input-output ratio and comprehensive energy consumption of low concentration coalbed methane cryogenic liquefaction devices are determined by the process parameters in control of the distillation column. In order to accurately control the actual operation process of the distillation column, the effect of the operating temperature of the distillation column on the liquefaction performance of a cold box was studied experimentally, and the optimal control parameters of the distillation column were obtained. The results show that the recovery rate of methane decreases with the increase in temperature at the top of the distillation column, and when this temperature is higher than −178 °C, the methane recovery rate drops sharply to below 90%. When the temperature at the bottom of the distillation column rises from −154 °C to −142.7 °C, the purity of LNG products is improved, and when this temperature is increased to −143.5 °C, the purity of products at the bottom of the distillation column reaches the standard, and can be stored safely. In actual operation, the evaporation temperature at the bottom of the column should not be higher than −140 °C. In the process of industrial plant design, measures should be taken to reduce the interaction of the temperature regulation at the top and bottom of the distillation column. When selecting the refrigerant circulation compressor, the leakage of the refrigerant should be considered to maintain the operating pressure of the refrigeration cycle.

Comparison of Two Laboratory Methods for Measuring Soil Critical Temperature

Abstract Coupled heat and moisture transfer above a critical temperature is important in various geothermal applications (e.g., geothermal heat exchangers, buried power cables, and energy piles) because of its impact on nonsteady soil thermal properties. In this study, temperature and moisture content of seven sandy soils were measured using two laboratory approaches—vertical and radial—to evaluate the critical temperatures. The vertical approach measured temperature and moisture data from top to bottom of a soil column, and the radial method obtained the measurements from center to outside of the specimen. To validate the test results, computational modeling was also carried out in MATLAB. Although the results obtained from radial testing included rapid changes in temperature gradients near the boundaries between dry and wet zones, ambiguous temperature profiles (i.e., gradual gradients over the entire range) were observed in vertical testing possibly because of horizontal boundary heat losses. In contrast to the gradual temperature gradients, moisture content profiles showed significant variations near the transitional regime, thus the critical temperatures were determined based on both temperature and moisture profiles. Average critical temperature for seven soils was 45.8°C, and the critical temperature was dependent on the void ratio. As void ratio decreased, critical temperature increased with a corresponding decrease in the size of the dry zone. The critical temperatures obtained from radial testing were higher (up to 5.2°C higher) and took more time to reach steady-state condition (up to 9 h longer) than those obtained from vertical testing. Because there are limited data and methodology in published studies that discuss a standard methodology to measure soil critical temperature, a consistent, universally accepted, procedural-based method is needed for the measurement or determination of the critical temperature.

Micro-vibrational erythrocyte sedimentation rate (ESR) for sensitive measurement of erythrocyte aggregation

The erythrocyte sedimentation rate (ESR) can act as a useful index of nonspecific disease activity in the diagnosis of inflammatory conditions. However, there are several drawbacks, including long time measurement. To promote ESR tendency, a micro-vibrational erythrocyte sedimentation rate (MV-ESR) was proposed. By controlling the profile of injecting flow rate into blood sample, air between the syringe pump and bottom of blood column was compressed and released. Micro-vibration (MV) is simple reciprocating flow including motion in both positive and negative directions in a line. It is determined as the edge of the interface between top of blood column and air is pinned under the pressure wave. From that, shear rate generated by determined MV is from 0 to 10–2 (s−1) in this study. Extremely low shear conditions may enhance the probability of erythrocyte aggregation formation. During measurement, a meniscus of separated plasma and sedimented erythrocytes was recorded using a camera. For validation of the proposed MV-ESR method, the effects of hematocrit as well as the frequency and amplitude of flow in the sedimentation tube were investigated. To quantify the enhancement of MV-ESR, the area of relative gradient (ARG) based on a relative gradient of 1 was used. When MV with a maximum flow rate of 1 mL/min and a period of 100 ms was produced until 15 min, MV-ESR exhibited the best performance. Then, the proposed technique was used to diagnose the ESR difference between a normal and periodontitis patient. The characteristic time (λESR), indicating the degree completion of the erythrocyte sedimentation, of the periodontitis patients was lower than that of the control. Based on the experimental demonstrations, λESR of the MV-ESR method has significant potential in the diagnosis of inflammatory conditions and prognosis of non-inflammatory conditions.

Trace Metal Contamination Impacts Predicted Functions More Than Structure of Marine Prokaryotic Biofilm Communities in an Anthropized Coastal Area.

Trace metal (TM) contamination in marine coastal areas is a worldwide threat for aquatic communities. However, little is known about the influence of a multi-chemical contamination on both marine biofilm communities’ structure and functioning. To determine how TM contamination potentially impacted microbial biofilms’ structure and their functions, polycarbonate (PC) plates were immerged in both surface and bottom of the seawater column, at five sites, along strong TM contamination gradients, in Toulon Bay. The PC plates were incubated during 4 weeks to enable colonization by biofilm-forming microorganisms on artificial surfaces. Biofilms from the PC plates, as well as surrounding seawaters, were collected and analyzed by 16S rRNA amplicon gene sequencing to describe prokaryotic community diversity, structure and functions, and to determine the relationships between bacterioplankton and biofilm communities. Our results showed that prokaryotic biofilm structure was not significantly affected by the measured environmental variables, while the functional profiles of biofilms were significantly impacted by Cu, Mn, Zn, and salinity. Biofilms from the contaminated sites were dominated by tolerant taxa to contaminants and specialized hydrocarbon-degrading microorganisms. Functions related to major xenobiotics biodegradation and metabolism, such as methane metabolism, degradation of aromatic compounds, and benzoate degradation, as well as functions involved in quorum sensing signaling, extracellular polymeric substances (EPS) matrix, and biofilm formation were significantly over-represented in the contaminated site relative to the uncontaminated one. Taken together, our results suggest that biofilms may be able to survive to strong multi-chemical contamination because of the presence of tolerant taxa in biofilms, as well as the functional responses of biofilm communities. Moreover, biofilm communities exhibited significant variations of structure and functional profiles along the seawater column, potentially explained by the contribution of taxa from surrounding sediments. Finally, we found that both structure and functions were significantly distinct between the biofilm and bacterioplankton, highlighting major differences between the both lifestyles, and the divergence of their responses facing to a multi-chemical contamination.

Study on the longitudinal nonlinear seismic behavior of the arch bridge with steel tubular frame without inner filling

The dynamic analysis model of a typical cantilever hollow steel tubular skeleton arch bridge in the western high-intensity region is established to obtain the longitudinal nonlinear seismic performance of the bridge. By combining the N-F 2-D yield surface of each key fiber section of a bridge, the critical section state of a bridge under the action of E2 rare intensity earthquake is evaluated and described, and the overall seismic performance of the structure is evaluated. The research results show that: The results show that the damaged part of the structure under the longitudinal and vertical seismic action is mostly the bottom of the upper arch column, and the upper arch column closer to the arch is more likely to be damaged, which is the weak part of the structure.

Effectiveness of the Size of Organic Matter Used in the Reclamation of Saline Sodic Soil

A laboratory experiment was conducted to evaluate the efficiency of (FYM) and gypsum in the reclamation of a saline sodic soil using leaching columns. Soil samples were collected from South Port Said Regional Research Station, Port Said Governorate, and Egypt at summer season 2019. Gypsum, (FYM) applied in 3 sizes, in 2 methods, soaking or mixing. The leachate samples were collected at the bottom of soil columns. The samples were analyzed for EC, pH, Na, ESP, T.P and H.C. The results of leaching increased in EC and Na compared with control. The all treatments revealed more pronounced decreased in pH compared to the control. Data showed that applications of soil amendments decreased soil pH and EC an ESP but there is an increase in the values of soil T.P and H.C.A field experiment was conducted in winter seasons 2019/2020 at the same soil. Results indicated that the highest values of H.C, T.P, by applying (FYM) at soft size with gypsum treatment compared to control and other treatments, on the other hand this treatment induced the lowest values of soil pH, EC and ESP. it can be concluded that combination of (FYM) + gypsum proved to be the best soil amendment for reducing soil EC, pH, ESP and improving T.P, H.C and A.W.

Progressive collapse of multistory 3D reinforced concrete frame structures after the loss of an edge column

Due to the frequent occurrence of natural disasters and terrorist attacks, research on resisting progressive collapse has attracted increasing attention from the engineering and academic communities. Numerous experimental studies conducted in recent decades have focussed on single-story 3D structures; however, there are many differences between single-story 3D structures and multistory 3D frames due to spatial effects. Therefore, a 1-bay-by-2-bay two-story reinforced concrete (RC) frame with the loss of one edge column was constructed, tested and analysed in this study. The collapse phenomena, load–displacement curves, lateral displacements and axial load distributions were recorded and discussed. Furthermore, the effect of the slab on the progressive collapse resistance of the multistory 3D frame without one bottom edge column was investigated using ABAQUS software. Moreover, a previously presented dynamic resistance model was modified in this article, and the contributions of the beams and slabs to the progressive collapse resistance of the multistory 3D frame were theoretically analysed. The slabs and beams in these frames could contribute approximately 1/3 and 2/3 of the load resistance, respectively.

Changes in depositional paleoenvironment of black shales in the Permian Irati Formation (Paraná Basin, Brazil): Geochemical evidence and aromatic biomarkers

Physicochemical changes that occurred during deposition of Irati black shales were investigated via outcrop samples collected in the northeastern and central-eastern Paraná Basin. Various traditional geochemical indicators were used, in addition to newly detected biomarkers: C32 lanostane, simonellite, sempervirane, and C32–C35 benzohopanes. Bulk geochemistry parameters, mineralogy, and conventional saturated biomarkers, such as tetracyclic polyprenoids (TPPs), reflect restricted and hypersaline marine deposition with freshwater input and increased terrigenous contribution toward the top of the studied outcrops. This led to stratification of the water column, establishing euxinic conditions in the photic zone and reducing conditions at the bottom of the water column, which enhanced preservation of organic matter. Principal component and hierarchical cluster analyses were performed to group the samples according to their similar geochemical characteristics: prevailing marine environment (basal outcrop samples) and higher freshwater inflow with greater terrigenous contribution (top outcrop samples). These geochemical observations were corroborated by aromatic biomarkers such as triaromatic steroids, trimethylnaphthalenes, simonellite, and sempervirane. The aryl isoprenoid ratio (AIR) indicates persistence of photic zone euxinia (PZE) during Irati black shale deposition. The presence of C32 lanostane and C32–C35 benzohopanes is directly related to the hypersaline depositional environment of the analyzed samples. Finally, the C32-33/C32-35 benzohopane ratio is proposed as a thermal maturity proxy because variations in the ratio can be linked to the presence of a diabase sill and temperature catalyst minerals near one of the outcrops.

Effects of clay in a sandy soil on saturated/unsaturated pore water flow and dissolved chloride transport from road salt applications.

Saturated/unsaturated pore water flow induced by rainwater infiltration in a soil column composed of a mixture of Toyoura sand and a small amount of clay (kaolin minerals) and the rinsing rate (mass transfer) of dissolved NaCl accumulated in the pore system from previous road salt application were investigated by experiments and simulations. Experiments were conducted with variable kaolin minerals mass contents (mixing ratios) in the soil columns. Measured saturated hydraulic conductivity (Ks) diminished with increased clay contents, i.e., Ks=0.00771, 0.00560, 0.00536, 0.00519, and 0.00314 cm s-1, for clay contents = 0.2, 0.5, 1, 2, and 5%, respectively. Experimental NaCl concentrations in the effluent from the bottom of the soil columns were about constant for times t ≈ 800, 1200, 1300, 1400, and 3400 s from the beginning of a rinsing experiment for the clay contents = 0.2, 0.5, 1, 2, and 5%, respectively. These NaCl concentrations then decreased with time quickly, and finally, approached zero. The presented model can reproduce experimental time variations of NaCl concentration in the effluent from the soil column reliably. Simulated salt mass left in the soil column with time also matches the experimental results for the clay contents = 0.2 and 0.5%. An inconsistency between simulated and experimental salt mass left in the soil columns becomes more significant as the clay content increases. These results suggest that the soil-water retention curve for the pure Toyoura sand can be applied to the soil column composed of kaolin minerals/Toyoura sand mixture when the clay content is small, i.e., less than 1%. Prediction of rinsing process becomes more difficult with increased clay content. However, the time required to remove saline water from the soil column to less than 1% of its initial value simulated by the model agrees closely with experimental results of 1000, 1500, 1700, 2100, and 5400 s, respectively.

Recovery of high-purity NO2 and SO2 products from iron-ore sintering flue gas by distillation: process design, optimization and analysis

High-purity NO2 and SO2 have significant economic values and are widely used in many fields. The large amounts of NO2 and SO2 in industrial flue gases are worthy of recovery for environmental protection and economic benefits. In this work, a dual-column distillation separation process was proposed to further separate and upgrade NO2 and SO2 following a flue gas adsorption capture process. The feasibility of distillation separation of NO2/SO2 from the desorbed gas, and the advantage of liquid-phase feeding way over gas-phase counterpart in terms of lower energy consumption (1286.39 kW) were demonstrated. Key process parameters such as the number of total stages, the feed stage number, the mole flow rate at bottom of column, the reflux ratio and operating pressure for the two columns (15, 6, 16.66 kmol/h, 0.16, 4 bar; 21, 10, 4.43 kmol/h, 0.50, 1 bar) were determined. Heat and mass transfers along the column height as well as the process robustness against feed composition fluctuation indicate its applicability for practical operation and adaptation to industrial needs. An economic analysis shows a significant annual revenue of 14,333.52 thousand USD based on high-purity (>99.5%) SO2 and NO2 products recovered from a typical scale (~1000,000 m3/h) of iron-ore sintering flue gas, not only offsetting the total operating cost of the entire adsorption capture-distillation recovery process but also generating net profit.

Behavior of splice connection during transfer of vertical load in full-scale corner-supported modular building

Splice connection, comprised of splice plates and slip-critical high strength bolts, is an efficient and convenient connecting technique for modular buildings. Previous investigations on this splice connection were mainly conducted based on tests of substructures, which may not reveal the real connection behavior in the whole modular building. To fill this research gap, this paper presents a comprehensive research on a full-scale corner-supported modular building assembled with splice connections. Behavior of the splice connection during the transfer of vertical load in the full-scale modular building is analyzed in details with combined experimental and numerical techniques. Test results showed that no unfavorable phenomenon was caused by the proposed splice connection before the global buckling of the module column. Based on the validated numerical model, a three-stage behavior during the entire loading process is found for the splice connection. The involvement of splice connection in the transfer of vertical load is negligible in the first stage while the splice connection provides sufficient constraint for the second-order moment at the bottom of module column in the second stage. The localized deformation and obvious formation of gap are found in the third stage. However, the analysis on the full-range bolt pre-tension force of the bolt group indicates that the origin of such negative phenomenon is located after the global buckling, which will not affect design on the vertical-load transfer performance of the module column. The sensitivity of connection behavior to the values of initial imperfections are also investigated by the parametric study. It is found that the proposed splice connection has a satisfactory tolerance for extreme initial imperfections. A transitional initial imperfection is further proposed, which may be used as an important reference for the practical control on the initial imperfection.

Seismic Behavior of RC Bridge Piers Locally Replaced with SFRC‐FA Subjected to Torsion Combined with Axial Compression

Under complex seismic forces, the failure characteristics of the plastic hinge region at the bottom of the pier column and the methods improving the ductility have attracted extensive attention. In this study, steel fiber‐reinforced concrete with fine aggregate (SFRC‐FA) was applied to locally replace the conventional concrete in the potential plastic hinge region at the bottom of the pier column. Five SFRC‐FA pier column specimens with different stirrup ratios and different replacement lengths and one conventional reinforced concrete pier column specimen were produced. Using the seismic behavior tests under the combined bending‐shear‐torsion‐axial force, the failure mode, torsional bearing capacity, energy dissipation, and the torsional plastic hinges of the pier columns were investigated. In addition, an equation for calculating the torsional bearing capacity of the new composite pier columns was proposed. The results showed that (1) compared with the reinforced concrete pier column, the plastic hinge was shifted from the bottom of the pier column to the middle of the height of the pier column due to the application of SFRC‐FA at the bottom of the pier column, which improved the torsional bearing capacity; (2) the effect of reducing the stirrup ratio of the SFRC‐FA replacement region on the torsional bearing capacity, cracking mode, energy dissipation, and ductility was not obvious; (3) the accuracy of the new equation based on the space truss model proposed in this article was verified by comparison with the experiments of this study and other researches.

CH<sub>4</sub> variation and main influencing factors of bottom water column in the middle section of Three Gorges Reservoir

甲烷（CH₄）是一种重要的温室气体，对全球气候变化有不可忽视的影响.三峡水库是中国最大的水库，其潜在的CH₄释放近年来备受关注.然而，此地区现存研究主要集中于水-气界面通量观测，对库底沉积物同底层水体CH₄浓度变化之间关系的认知仍然欠缺.为探究三峡水库泥沙主要沉降淤积的中段区域库底水体CH₄浓度变化及其主要影响因素，本研究于2017年8月-2018年11月在涪陵南沱镇、忠县石宝寨、万州小周镇采集库底上覆水体和底泥样本，并结合三峡水库调度运行特征进行分析.结果表明，三峡水库中段库底上覆水CH₄浓度范围为0.02~0.91 μmol/L，二氧化碳（CO₂）浓度范围为0.006~0.105 mmol/L，沉积物有机碳含量范围为7~90 g/kg，总氮含量范围为0.27~45.6 g/kg.另外，三峡水库低水位运行时期（5—9月），上游及陆源输入大量异源性有机碳是该时期三峡库中段底部CH₄积累的充分条件.在水库高水位运行时期（10月-次年4月），水位与径流变化对三峡水库中段底部CH₄的影响并不明显，库底自源性有机质相对比重有所增加，温度是该时期影响水库底层水体CH₄浓度分布的主要水环境因素.;Methane (CH₄) is an important greenhouse gas contributing to global climate change. The Three Gorges Reservoir (TGR) is the largest reservoir in China and has been receiving concerns for its potential CH₄ emissions during the past decades. However, the current research in the TGR mainly focuses on the observation of water-air interface fluxes, the knowledge of relationship between bottom sediments in the reservoir and CH₄ concentrations variation of the bottom water column is still lacking. To explore CH₄ concentrations variation and main influencing factors of the bottom water column in the middle section of TGR, this study collects overlying water and sediment of the bottom respectively at Nanling Town of Fuling, Shibaozhai of Zhongxian and Xiaozhou Town of Wanzhou in the middle section of the TGR during August 2017 and November 2018, and analyzing the data combined with reservoir operation characteristics. The results indicate that CH₄ concentrations in the overlying water of the bottom ranges from 0.02 μmol/L to 0.91 μmol/L, carbon dioxide (CO₂) ranges from 0.006 mmol/L to 0.105 mmol/L, the organic carbon (OC) content in the sediment ranges from 7 g/kg to 90 g/kg, and total nitrogen ranges from 0.27 g/kg to 45.6 g/kg. During the low water level period of the TGR (May to September), a large amount of allochthonous OC input from upstream and terrestrial sources is a sufficient condition for CH₄ accumulation of the bottom in the middle section of the TGR. During the high water level period (October to April of the following year), water level and runoff variations have no obvious effect on CH₄ of the bottom in the middle section of the TGR, the relative proportion of autochthonous organic matter of the bottom in the reservoir is increased, and temperature is the main aquatic environmental factor that affected the CH₄ distribution.

Simulation application of ALC external wall panel on rigid column frame brace system

Taking a building under construction as an example, based on ABAQUS software, studies the failure mode, hysteretic curve, displacement ductility and energy consumption capacity of ALC external wall panel under three working conditions of assembled stiffened column frame brace system, assembled frame system and cast-in-place frame system.The simulation results show that:1.Under the action of low cycle load, the assembled stiffened column frame support system has no damage,the maximum stress value is 6.98 MPa, which is located at the position of steel plate at the column bottom; 2.Under the condition of ALC hanging wall plate, the structure ductility is better; 3.Part of the energy consumption is borne by the light material hanging wall plate, and the stiffened column frame support system has higher energy consumption capacity.The assembled ALC external wall panel based on the rigid column frame support system has better mechanical performance, can significantly improve the energy consumption capacity of the overall structure, and has high construction feasibility,economy and engineering application value.

Evapotranspiration estimation in rain gardens using soil moisture sensors

AbstractRain gardens are increasing in use as the shift from gray to green infrastructure continues. Water that enters a rain garden is removed by three mechanisms: overflow to an outlet, percolation to the underlying soil, and evapotranspiration (ET) to the atmosphere. Despite the importance of ET in aiding a rain garden to recover void space during the time between storm events, it is not often measured or calculated because it is so difficult to do so. This paper explores the use of soil moisture sensors to estimate ET, since they are relatively inexpensive to purchase and install. Three rain garden weighing lysimeters in Villanova, PA, were used for this study. Over a 3‐yr study period daily ET was calculated each dry day and summed during the time in between storm events >25 mm. The cumulative changes of soil moisture readings during the interevent time at three depths were compared with the concurrent cumulative changes in the lysimeter weight readings. Cumulative soil moisture change was found to be strongly correlated to the cumulative ET for the different lysimeter media and drainage types. Using the two soil moisture sensors at the top and bottom of the soil column provided a similar result to using all soil moisture reading depths. The best single soil moisture reading depth was at the bottom of the lysimeter. The ET estimates via soil moisture tracking performed similar to uncalibrated potential ET estimates, but not as well as calibrated ET estimates.