Metagenomic Insight Reveals the Microbial Structure and Function of the Full-Scale Coking Wastewater Treatment System:Gene-Based Nitrogen Removal

Microbial communities play crucial roles in pollutant removal and system stability in biological systems for coking wastewater(CWW)treatment,but a comprehensive understanding of their structure and functions is still lacking.A five month survey of four sequential bioreactors,anoxic 1/oxic 1/anoxic 2/oxic 2(A1/O1/A2/O2),was carried out in a full-scale CWW treatment system in China to elucidate operational performance and microbial ecology.The results showed that A1/O1/A2/O2 had excellent and stable performance for nitrogen removal.Both total nitrogen(TN;(17.38±6.89)mgL1)and ammonium-nitrogen(NH4 t-N;(2.10±1.34)mg·L^(-1))in the final biological effluent satisfied the Chinese national standards for CWW.Integrated analysis of 16S ribosome RNA(rRNA)sequencing and metagenomic sequencing showed that the bacterial communities and metagenomic function profiles of A1 and O1 shared similar functional structures,while those of A2 significantly varied from those of other bioreactors(p<0.05).The results indicated that microbial activity was strongly connected with activated sludge function.Nitrosospira,Nitrosomonas,and SM1A02 were responsible for nitrification during the primary anoxic-oxic(AO)stage and Azoarcus and Thauera acted as important denitrifiers in A2.Nitrogen cycling-related enzymes and genes work in the A1/O1/A2/O2 system.Moreover,the hao genes catalyzing hydroxylamine dehydrogenase(EC 1.7.2.6)and the napA and napB genes catalyzing nitrate reductase(EC 1.9.6.1)played important roles in the nitrification and denitrification processes in the primary and secondary AO stages,respectively.The mixed liquor suspended solids(MLSS)/total solids(TS),TN removal rate(RR),total organic carbon(TOC)(RR),and NH_(4)^(+)t-N(RR)were the most important environmental factors for regulating the structure of core bacterial genera and nitrogen-cycling genes.Proteobacteria were the potential main participants in nitrogen metabolism in the A1/O1/A2/O2 system for CWW treatment.This study provides an original and comprehensive understanding of the microbial community and functions at the gene level,which is crucial for the efficient and stable operation of the full-scale biological process for CWW treatment.

Quantum Spin Liquid Phase in the Shastry–Sutherland Model Detected by an Improved Level Spectroscopic Method

We study the spin-1/2 two-dimensional Shastry–Sutherland spin model by exact diagonalization of clusters with periodic boundary conditions, developing an improved level spectroscopic technique using energy gaps between states with different quantum numbers. The crossing points of some of the relative(composite) gaps have much weaker finite-size drifts than the normally used gaps defined only with respect to the ground state, thus allowing precise determination of quantum critical points even with small clusters. Our results support the picture of a spin liquid phase intervening between the well-known plaquette-singlet and antiferromagnetic ground states, with phase boundaries in almost perfect agreement with a recent density matrix renormalization group study, where much larger cylindrical lattices were used [J. Yang et al., Phys. Rev. B 105, L060409(2022)]. The method of using composite low-energy gaps to reduce scaling corrections has potentially broad applications in numerical studies of quantum critical phenomena.

Increased macrophage inflammation response in pancreatic cancer patients with a diagnosis of Shi-Re

Objective:Traditional Chinese medicine(TCM)is a comprehensive system of medical practice.ZHENG(also known as syndrome differentiation)is the essence of TCM;however,its molecular basis remains unknown.This study evaluated the molecular basis of Shi-Re ZHENG in patients with pancreatic cancer.Methods:A total of 144 patients with pathologically-confirmed locally advanced or metastatic pancreatic ductal adenocarcinoma(PDAC)were retrospectively recruited between June 2015 and February 2016.Two cohorts,including the discovery cohort(n=60)and validation cohort(n=84),were included in this study.QPlex multiplex array and an enzyme-linked immunosorbent assay were used to evaluate serum inflammatory cytokine levels of pancreatic cancer patients with different TCM ZHENG.Receiver operating characteristic(ROC)curve analysis was used to evaluate the importance of the systemic inflammation response index(SIRI)in the detection of Shi-Re ZHENG.Results:Shi-Re ZHENG patients exhibited a different expression pattern of cytokines,including interleukin(IL)-6,IL-8,chemokine(C-C motif)ligand 18(CCL18),and C-reactive protein,than patients with other ZHENG diagnoses.M2-like macrophage-related inflammatory cytokines,such as IL-10,CCL17,and CCL22,were increased in Shi-Re ZHENG compared with non-Shi-Re ZHENG patients.The SIRI score was significantly increased in Shi-Re ZHENG compared with non-Shi-Re ZHENG patients(P<0.001).ROC analysis revealed that SIRI had a diagnostic value for Shi-Re ZHENG both in the discovery cohort(area under the curve[AUC]=0.833,95%confidence interval[CI]=0.709–0.957)and validation cohort(AUC=0.810,95%CI=0.716–0.905).Additionally,pancreatic cancer patients with Shi-Re ZHENG had a significantly shorter survival time than non-Shi-Re ZHENG(P=0.002).Conclusion:Shi-Re pancreatic cancer patients are characterized by an increased macrophage inflammation response,which may contribute to a poorer prognosis when compared to those with other ZHENG diagnoses.

Radical innovation breakthroughs of biodegradation of plastics by insects:history,present and future perspectives

Insects damaging and penetrating plastic packaged materials has been reported since the 1950s.Radical innovation breakthroughs of plastic biodegradation have been initiated since the discovery of biodegradation of plastics by Tenebrio molitor larvae in 2015 followed by Galleria mellonella in 2017.Here we review updated studies on the insect-mediated biodegradation of plastics.Plastic biodegradation by insect larvae,mainly by some species of darkling beetles(Tenebrionidae)and pyralid moths(Pyralidae)is currently a highly active and potentially transformative area of research.Over the past eight years,publications have increased explosively,including discoveries of the ability of different insect species to biodegrade plastics,biodegradation performance,and the contribution of host and microbiomes,impacts of polymer types and their physic-chemical properties,and responsible enzymes secreted by the host and gut microbes.To date,almost all major plastics including polyethylene(PE),polypropylene(PP),polyvinyl chloride(PVC),polyethylene terephthalate(PET),polyurethane(PUR),and polystyrene(PS)can be biodegraded by T.molitor and ten other insect species representing the Tenebrionidae and Pyralidae families.The biodegradation processes are symbiotic reactions or performed by synergistic efforts of both host and gut-microbes to rapidly depolymerize and biodegrade plastics with hourly half-lives.The digestive ezymens and bioreagents screted by the insects play an essential role in plasatic biodegradation in certain species of Tenebrionidae and Pyralidae families.New research on the insect itself,gut microbiomes,transcriptomes,proteomes and metabolomes has evaluated the mechanisms of plastic biodegradation in insects.We conclude this review by discussing future research perspectives on insect-mediated biodegradation of plastics.

La^(3+)@BC500-S_(2)O_(8)^(2−)system for removal of sulfonamide antibiotics in water

Sulfonamide antibiotics(SAs)widely used have potentially negative effects on human beings and ecosystems.Adsorption and advanced oxidation methods have been exten-sively applied in SAs wastewater treatment.In this study,compared with Al^(3+)@BC500 and Fe^(3+)@BC500,La^(3+)@BC500 for activating persulfate(S2O82−)had the best effect removal per-formance of sulfadiazine(SDZ)and sulfamethoxazole(SMX).Morphology,acidity,oxygen-containing functional groups,and loading of La^(3+)@BC500 were analyzed by techniques,in-cluding EA,BET,XRD,XPS,FT-IR.XRD results show that with the increase of La^(3+)loading,the surface characteristics of biochar gradually changed from CaCO_(3)to LaCO_(3)OH.Through EPR technology,it is proved that LaCO_(3)OH on the surface of La^(3+)@BC500 can not only acti-vate S2O82−to generate SO_(4)^(−)•,but also to produce•OH.In the optimization experiment,the optimal dosage of La^(3+)is between 0.05 and 0.2(mol/L)/g.SDZ had a good removal effect at pH(5-9),but SMX had a good removal effect only at pH=3.Zeta potential also proves that the material is more stable under acidic conditions.The removal process of SDZ is more in accord with pseudo-first-order kinetics(R^(2)=0.9869),while SMX is more in line with pseudo-second order kinetics(R^(2)=0.9926).

A review of CFD simulation in pressure driven membrane with fouling model and anti-fouling strategy

Pressure-driven membrane filtration systems are widely utilized in wastewater treatment,desalination,and water reclamation and have received extensive attention from researchers.Computational fluid dynamics(CFD)offers a convenient approach for conducting mechanistic studies of flow and mass transfer characteristics in pressure-driven systems.As a signature phenomenon in membrane systems,the concentration polarization that accompanies the permeation process is a key factor in membrane performance degradation and membrane fouling intensification.Multiple fouling models(scaling,biofouling and colloidal particle fouling)based on CFD theory have been constructed,and considerable research has been conducted.Several representative antifouling strategies with special simulation methods,including patterned membranes,vibration membranes,rotation membranes,and pulsatile flows,have also been discussed.Future studies should focus on refining fouling models while considering local hydrodynamic characteristics;experimental observation tools focusing on the internal structure of inhomogeneous fouling layers;techno-economic model of antifouling strategies such as vibrational,rotational and pulsatile flows;and unfavorable hydraulic phenomena induced by rapidly changing flows in simulations.

Purple acid phosphatase promoted hydrolysis of organophosphate pesticides in microalgae

When organophosphate pesticides(OPs)are not used and handled in accordance with the current rules and standards,it results in serious threats to the aquatic environment and human health.Phaeodactylum tricornutum is a prospective microalgae-based system for pollutant removal and carbon sequestration.Genetically engineered P.tricornutum,designated as the OE line(endogenously expressing purple acid phosphatase 1[PAP1]),can utilize organic phosphorus for cellular metabolism.However,the competencies and mechanisms of the microalgae-based system(namely the OE line of P.tricornutum)for metabolizing OPs remain to be addressed.In this study,the OE line exhibited the effective biodegradation competencies of 72.12%and 68.2%for 30 mg L^(-1)of dichlorvos and 50 mg L^(-1)of glyphosate,accompanied by synergistic accumulations of biomass(0.91 and 0.95 g L^(-1))and lipids(32.71%and 32.08%),respectively.Furthermore,the biodiesel properties of the lipids from the OE line manifested a high potential as an alternative feedstock for microalgae-based biofuel production.A plausible mechanism of OPs biodegraded by overexpressed PAP1 is that sufficient inorganic P for adenosine triphosphate and concurrent carbon flux for the reduced form of nicotinamide adenine dinucleotide phosphate biosynthesis,which improved the OP tolerance and biodegradation competencies by regulating the antioxidant system,delaying programmed cell death and accumulating lipids via the upregulation of related genes.To sum up,this study demonstrates a potential strategy using a genetically engineered strain of P.tricornutum to remove high concentrations of OPs with the simultaneous production of biomass and biofuels,which might provide novel insights for microalgae-based pollutant biodegradation.

Biosorption of clofibric acid and carbamazepine in aqueous solution by agricultural waste rice straw

Due to their widespread use, clofibric acid （CA） and carbamazepine （CBZ） have been frequently detected simultaneously at relatively high concentrations in aquatic environments. In this study, agricultural waste rice straw was employed as a potentially low-cost, effective and easy-to-operate biosorbent （RSB） to remove CA and CBZ. The adsorption of both pharmaceuticals followed pseudo second-order kinetics, and intraparticle diffusion was an important rate-limiting step. The adsorption isotherms of both drugs were fit well with Freundlich model. The adsorption of CA onto RSB was exothermic and was more likely to be dominated by physical processes, while the adsorption of CBZ was endothermic. Solution pH was determined to be the most important factor for CA adsorption, such that the adsorption capacity of CA onto RSB increased with the decline of solution pH. In the lower range of solution pH below 3. l, the CA removal efficiency was enhanced with the increase of biosorbent dosage. The CBZ removal efficiency was enhanced with the increase of RSB dosage without pH control. The maximum adsorption capacities were 126.3 mg/g for CA and 40.0 mg/g for CBZ.

Pb(Ⅱ) removal from water using Fe-coated bamboo charcoal with the assistance of microwaves

Bamboo charcoal（BC） was used as starting material to prepare iron-modified bamboo charcoal（Fe-MBC） by its impregnation in FeCl 3 and HNO 3 solutions simultaneously,followed by microwave heating.The material can be used as an adsorbent for Pb（Ⅱ） contaminants removal in water.The composites were prepared with Fe molar concentration of 0.5,1.0 and 2.0 mol/L and characterized by means of N 2 adsorption-desorption isotherms,X-ray diffraction spectroscopy（XRD）,scanning electron microscopy coupled with energy dispersive X-ray spectrometry（SEM-EDS）,Fourier transform infrared（FT-IR） and point of zero charge（pH pzc） measurements.Nitrogen adsorption analyses showed that the BET specific surface area and total pore volume increased with iron impregnation.The adsorbent with Fe molar concentration of 2 mol/L（2Fe-MBC） exhibited the highest surface area and produced the best pore structure.The Pb（Ⅱ） adsorption process of 2Fe-MBC and BC were evaluated in batch experiments and 2Fe-MBC showed an excellent adsorption capability for removal Pb（Ⅱ）.The adsorption of Pb（Ⅱ） strongly depended on solution pH,with maximum values at pH 5.0.The ionic strength had a significant effect on the adsorption at pH 〈 6.0.The adsorption isotherms followed the Langmuir isotherm model well,and the maximum adsorption capacity for Pb（Ⅱ） was 200.38 mg/g for 2Fe-MBC.The adsorption processes were well fitted by a pseudo second-order kinetic model.Thermodynamic parameters showed that the adsorption of Pb（Ⅱ） onto Fe-MBC was feasible,spontaneous,and exothermic under the studied conditions,and the ion exchange mechanism played an significant role.These results have important implications for the design of low-cost and effective adsorbents in the removal of Pb（Ⅱ） from wastewater.

Toripalimab plus chemotherapy as second-line treatment in previously EGFR-TKI treated patients with EGFR-mutant-advanced NSCLC:a multicenter phase-II trial

This multicenter phase-II trial aimed to investigate the efficacy,safety,and predictive biomarkers of toripalimab plus chemotherapy as second-line treatment in patients with EGFR-mutant-advanced NSCLC.Patients who failed from first-line EGFR-TKIs and did not harbor T790M mutation were enrolled.Toripalimab plus carboplatin and pemetrexed were administrated every three weeks for up to six cycles,followed by the maintenance of toripalimab and pemetrexed.The primary endpoint was objective-response rate(ORR).Integrated biomarker analysis of PD-L1 expression,tumor mutational burden(TMB),CD8+tumor-infiltrating lymphocyte(TIL)density,whole-exome,and transcriptome sequencing on tumor biopsies were also conducted.Forty patients were enrolled with an overall ORR of 50.0%and disease-control rate(DCR)of 87.5%.The median progression free survival(PFS)and overall survival were 7.0 and 23.5 months,respectively.The most common treatment-related adverse effects were leukopenia,neutropenia,anemia,ALT/AST elevation,and nausea.Biomarker analysis showed that none of PD-L1 expression,TMB level,and CD8+TIL density could serve as a predictive biomarker.Integrated analysis of whole-exome and transcriptome sequencing data revealed that patients with DSPP mutation had a decreased M2 macrophage infiltration and associated with longer PFS than those of wild type.Toripalimab plus chemotherapy showed a promising anti-tumor activity with acceptable safety profiles as the second-line setting in patients with EGFR-mutant NSCLC.DSPP mutation might serve as a potential biomarker for this combination.A phase-III trial to compare toripalimab versus placebo in combination with chemotherapy in this setting is ongoing(NCT03924050).

Critical review of perovskites-based advanced oxidation processes for wastewater treatment: Operational parameters, reaction mechanisms,and prospects

In the field of advanced oxidation processes(AOPs) of wastewater, many materials can be used as heterogeneous catalysts. The role of these catalysts is to activate oxidants and generate reactive oxygen species(ROS) to decompose refractory pollutants. Perovskite oxide, an emerging catalyst in the field of AOPs, has been extensively studied in wastewater treatment. Nevertheless, the application of perovskite in AOP systems still faces some problems, such as leaching of metal ions, a small surface area, a low number of active sites, etc. Herein, this critical review comparatively examines the activation mechanisms of peroxymonosulfate, hydrogen peroxide, and peroxydisulfate. Furthermore, the formation pathways of oxidizing species based on recent advances in experimental and theoretical studies were evaluated. In addition, the impacts of water parameters and constituents such as initial p H, oxidant concentration, catalyst dosage,natural organic matter, halide, phosphate, and carbonate were discussed. Finally, a critical discussion and prospects of mechanism exploration and possible materials development are proposed to confront the existing challenges in the application of perovskite oxides in AOPs.

Technologies for pollutant removal and resource recovery from blackwater:a review

Blackwater(BW),consisting of feces,urine,flushing water and toilet paper,makes up an important portion of domestic wastewater.The improper disposal of BW may lead to environmental pollution and disease transmission,threatening the sustainabie development of the world.Rich in nutrients and organic matter,BW could be treated for resource recovery and reuse through various approaches.Aimed at providing guidance for the future development of BW treatment and resource recovery,this paper presented a literature review of BWs produced in different countries and types of toilets,including their physiochemical characteristics,and current treatment and resource recovery strategies.The degradation and utilization of carbon(C),nitrogen(N)and phosphorus(P)within BW are underlined.The performance of different systems was classified and summarized.Among all the treating systems,biological and ecological systems have been long and widely applied for BW treatment,showing their universality and operability in nutrients and energy recovery,but they are either slow or ineffective in removal of some refractory pollutants.Novel processes,especially advanced oxidation processes(AOPs),are becoming increasingly extensively studied in BW treatment because of their high efficiency,especially for the removal of micropollutants and pathogens.This review could serve as an instructive guidance for the design and optimization of BW treatment technologies,aiming to help in the fulfilment of sustainable human excreta management.

Carbamazepine degradation by heterogeneous activation of peroxymonosulfate with lanthanum cobaltite perovskite:Performance,mechanism and toxicity

The widely used carbamazepine(CBZ)is one of the most persistent pharmaceuticals and suffers insufficient removal efficiency by conventional wastewater treatment.A synthesized Co-based perovskite(LaCoO3)was used to activate peroxymonosulfate(PMS)in order to degrade CBZ.Results showed that LaCoO3 exhibited an excellent performance in PMS activation and CBZ degradation at neutral pH,with low cobalt leaching.The results of FT-IR and XPS verified the high structurally and chemically stability of LaCoO3 in PMS activation.Electron spin resonance(ESR)analysis suggested the generation of radical species,such as sulfate radicals(SO4·-)and hydroxyl radicals(·OH).Radical quenching experiments further revealed the responsibility of SO4·-as the dominant oxidant for CBZ oxidation.Ten products were detected via the oxidation of CBZ,with the olefinic double bond attacked by SO4·-as the initial step.Hydroxylation,hydrolysis,cyclization and dehydration were involved along the transformation of CBZ.The toxicity of CBZ solution was significantly reduced after treating by PMS/LaCoO3.

Nitrifying population dynamics in a redox stratified membrane biofilm reactor(RSMBR)for treating ammonium-rich wastewater

Nitrogen removal performance and nitrifyingpopulation dynamics were investigated in a redox stratifiedmembrane biofilm reactor(RSMBR)under oxygen limitedcondition to treat ammonium-rich wastewater.When theNH_(4)^(+)-N loading rate increased from 11.1±1.0 to 37:2±3:2 gNH_(4)^(+)-N·m^(-2)·d^(-1),the nitrogen removal inthe RSMBR system increased from 18.0±9.6 mgN·d^(-1)to 128.9±61.7 mgN·d^(-1).Shortcut nitrogen removal wasachieved with nitrite accumulation of about22:3±5:3 mgNO_(2)^(-)-N·L-1.Confocal micrographsshowed the stratified distributions of nitrifiers anddenitrifiers in the membrane aerated biofilms(MABs)atday 120,i.e.,ammonia and nitrite oxidizing bacteria(AOBand NOB)were dominant in the region adjacent to themembrane,while heterotrophic bacteria propagated at thetop of the biofilm.Real-time qPCR results showed that theabundance of amoA gene was two orders of magnitudehigher than the abundance of nxrA gene in the MABs.However,the nxrA gene was always detected during theoperation time,which indicates the difficulty of completewashout of NOB in MABs.The growth of heterotrophicbacteria compromised the dominance of nitrifiers inbiofilm communities,but it enhanced the denitrificationperformance of the RSMBR system.Applying a highammonia loading together with oxygen limitation wasfound to be an effective way to start nitrite accumulation inMABs,but other approaches were needed to sustain orimprove the extent of nitritation in nitrogen conversion inMABs.

Effect of nitrate concentration on filamentous bulking under low level of dissolved oxygen in an airlift inner circular anoxic-aerobic incorporate reactor

This laboratory research investigated a possible cause of filamentous bulking under low level of dissolved oxygen conditions （dissolved oxygen value in aerobic zone maintained between 0.6-0.8 mgO2 /L） in an airlift inner-circular anoxic-aerobic reactor. During the operating period, it was observed that low nitrate concentrations affected sludge volume index significantly. Unlike the existing hypothesis, the batch tests indicated that filamentous bacteria （mainly Thiothrix sp.） could store nitrate temporarily under carbon restricted conditions. When nitrate concentration was below 4 mg/L, low levels of carbon substrates and dissolved oxygen in the aerobic zone stimulated the nitrate-storing capacity of filaments. When filamentous bacteria riched in nitrate reached the anoxic zone, where they were exposed to high levels of carbon but limited nitrate, they underwent denitrification. However, when nonfilamentous bacteria were exposed to similar conditions, denitrification was restrained due to their intrinsic nitrate limitation. Hence, in order to avoid filamentous bulking, the nitrate concentration in the return sludge （from aerobic zone to the anoxic zone） should be above 4 mg/L, or alternatively, the nitrate load in the anoxic zone should be kept at levels above 2.7 mg NO-3N/g SS.

Characteristics of pellets with immobilized activated sludge and its performance in increasing nitrification in sequencing batch reactors at low temperatures

Immobilized pellets obtained by means of entrapping activated sludge in waterborne polyurethane were successfully adapted in ammonium（NH4^＋–N）synthetic wastewater.Its physicochemical characteristics were determined using scanning electron microscope,pyrosequencing,and microelectrodes,and its influence on the nitrification process in sequencing batch reactors（SBRs）at low temperatures was evaluated.A large number of rod-shaped bacteria were observed on the surface of the immobilized pellet,in which Rudaea spp.（Xanthomonadaceae family）was an important bacterial component（23.44% of the total bacteria）.The oxygen uptake rate of immobilized pellets reached 240.83±15.59 mg O2/（L·hr）,and the oxygen was primarily consumed by the bacteria on the pellet surfaces（0–600μm）.The dosing of the pellets（30 m L/L）into an SBR significantly improved the nitrification efficiency at low temperatures of 7–11℃,achieving an average NH4^＋–N removal of 84.09%,which is higher than the removal of 67.46% observed for the control group.

Characteristics of dynamic membrane filtration:structure,operation mechanisms,and cost analysis

Dynamic membrane technology represents a promising substitution for conventional membrane bioreactor system,which owns the merits of flexible and comparably cheap materials,easy for backwash,good antifouling property,etc.It has been over half a century since the principle of dynamic membranes was first reported,whereas the development and popularization are still limited.This paper makes a review on characteristics of dynamic membranes,including development and application,mechanism,structure and materials,operation conditions,membrane fouling,dynamic membrane cleaning,and cost analysis,attempting to give clues on promotions and perspectives exhibited of this technology.

Zero-valent iron doped carbons readily developed from sewage sludge for lead removal from aqueous solution

Low-cost but high-efficiency composites of iron-containing porous carbons were prepared using sewage sludge and ferric salts as raw materials. Unlike previous time- and energy-consuming manufacturing procedures, this study shows that pyrolyzing a mixture of sludge and ferric salt can produce suitable composites for lead adsorption. The specific surface area, the total pore volume and the average pore width of the optimal composite were 321 m^2/g, 0.25 cm^3/g, and 3.17 nm, respectively. X-ray diffraction analysis indicated that ferric salt favored the formation of metallic iron, while Fourier transform infrared spectroscopy revealed the formation of hydroxyl and carboxylic groups. The result of batch tests indicated that the adsorption capacity of carbons activated with ferric salt could be as high as 128.9 mg/g, while that of carbons without activation was 79.1 mg/g. The new manufacturing procedure used in this study could save at least 19.5 k J of energy per gram of activated carbon.

Influence of the Maximum Blur Radius on Depth Sensor Based on Liquid Crystal Lens

This paper describes how the maximum blur radius affects the depth results by depth from the defocus(DFD)method based on liquid crystal(LC)lens.Boundary frequency is determined by the maximum blur radius.It is found that if the maximum blur radius used in the calculation is larger than the real value,the depth resolution obtained is reduced;on the other hand,if one smaller than the real value is used,the depth resolution in the middle range of the scene is increased,but errors occur in the near and far planes.Using the maximum blur radius close to the real one results in the best depth results.

Localization and characterization of intermittent pollutant source in buildings with ventilation systems:Development and validation of an inverse model

Terrorist attacks through building ventilation systems are becoming an increasing concern.In case pollutants are intentionally released in a building with mechanical ventilation systems,it is critical to localize the source and characterize its releasing curve.Previous inverse modeling studies have adopted the adjoint probability method to identify the source location and used the Tikhonov regularization method to determine the source releasing profile,but the selection of the prediction model and determination of the regularization parameter remain challenging.These limitations can affect the identification accuracy and prolong the computational time required.To address the difficulties in solving the inverse problems,this work proposed a Markov-chain-oriented inverse approach to identify the temporal release rate and location of a pollutant source in buildings with ventilation systems and validated it in an experimental chamber.In the modified Markov chain,the source term was discrete by each time step,and the pollutant distribution was directly calculated with no iterations.The forward Markov chain was reversed to characterize the intermittently releasing profile by introducing the Tikhonov regularization method,while the regularized parameter was determined by an automatic iterative discrepancy method.The source location was further estimated by adopting the Bayes inference.With chamber experiments,the effectiveness of the proposed inverse model was validated,and the impact of the sensor performance,quantity and placement,as well as pollutant releasing curves on the identification accuracy of the source intensity was explicitly discussed.Results showed that the inverse model can identify the intermittent releasing rate efficiently and promptly,and the identification error for pollutant releasing curves with complex waveforms is about 20%.